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North Carolina State Library ( f t jleigh NORTH CAROLINA DEPARTMENT OF CONSERVATION AND DEVELOPMENT William P. Saunders, Director fo _ %* DIVISION OF MINERAL RESOURCES Jasper L. Stuckey, State Geologist BULLETIN NUMBER 71 EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad RALEIGH 1958 Norffe Carolir* St** NORTH CAROLINA DEPARTMENT OF CONSERVATION AND DEVELOPMENT William P. Saunders, Director DIVISION OF MINERAL RESOURCES Jasper L. Stuckey, State Geologist BULLETIN NUMBER 71 EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad RALEIGH 1958 MEMBERS OF THE BOARD OF CONSERVATION AND DEVELOPMENT GOVERNOR LUTHER H. HODGES, Chairman Raleigh MILES J. SMITH, First Vice Chairman Salisbury WALTER J. DAMTOFT, Second Vice Chairman Canton CHARLES S. ALLEN ..__„___ Durham W. B. AUSTIN Jefferson F. J. BOLING Siler City H. C. BUCHAN, JR North Wilkesboro SCROOP W. ENLOE, JR Spruce Pine VOIT GILMORE Southern Pines R. M. HANES Winston-Salem LEO H. HARVEY Kinston CHARLES H. JENKINS - __..._...Ahoskie AMOS R. KEARNS High Point H. C. KENNETT Durham R.W.MARTIN Raleigh CECIL MORRIS Atlantic HUGH M. MORTON Wilmington W. EUGENE SIMMONS Tarboro T.MAX WATSON Spindale LETTER OF TRANSMITTAL Raleigh, North Carolina February 4, 1958 To His Excellency, HONORABLE LUTHER H. HODGES Governor of North Carolina Sir: I have the honor to submit herewith manuscript for publication as Bulletin No. 71, "Explanatory Text for Geologic Map of North Carolina". This text is an essential part of the new geologic map of North Carolina. The new geologic map and this explanatory text contain a summary of the best information pres-ently available on the geology of North Carolina. This information should be of real value to mining companies and individuals interested in the geology and mineral resources of the State. Respectfully submitted, WILLIAM P. SAUNDERS Director CONTENTS Page Abstract 7 Introduction 8 Acknowledgments 8 Map units 9 Dependability of the map 10 Structure and metamorphism 11 Description of rock units 12 Introduction 12 Igneous and metamorphic rocks 12 Gneisses and schists^ 12 Precambrian ( ?) 12 Mica gneiss 12 Mica schist 13 Hornblende gneiss 14 Granite gneisses 15 Precambrian ( ?) 15 Unnamed granite gneiss 15 Granite gneiss complex 16 Henderson granite gneiss 16 Cranberry granite gneiss 17 Blowing Rock gneiss 18 Max Patch granite gneiss 18 Beech granite gneiss 19 Granites and mafic igneous rocks 19 Paleozoic ( ?) 19 Dunite 19 Granite 20 Syenite 22 Mount Airy granite 22 Diorite-gabbro 23 Paleozoic 23 Toluca quartz monzonite 23 Cherryville quartz monzonite 24 Whiteside granite 24 Alaskite 24 CONTENTS—Continued Page Triassic ( ?) 25 Bakersville gabbro __ 25 Diabase dikes 25 Metavolcanic rocks 26 Precambrian or Lower Paleozoic ( ?) 26 Carolina Slate Belt 26 Felsic volcanics 27 Mafic volcanics 28 Bedded argillites (volcanic slate) 28 Upper Precambrian 29 Grandfather Mountain window 29 Linville metadiabase 29 Montezuma schist 29 Flattop schist 30 Metarhyolite 30 Mount Rodgers volcanic group 30 Metasedimentary rocks 30 Upper Precambrian (?) or Lower Paleozoic (?) 30 Stokes County and Kings Mountain belt 30 Kings Mountain group 30 Lower Cambrian ( ?) 31 Brevard belt 31 Brevard schist 31 Murphy belt 31 Brasstown schist 31 Valleytown formation 32 Andrews schist-Murphy marble 32 Sedimentary rocks 32 Upper Precambrian 32 Ocoee series 32 Snowbird formation • 34 Great Smoky conglomerate 35 Nantahala slate 36 Sandsuck shale 37 Undifferentiated 37 CONTENTS—Continued Paye Cambrian 37 Lower Cambrian 37 Unicoi formation 38 Hampton formation 39 Erwin formation 39 Shady dolomite 39 Rome formation 40 Triassic 40 Upper Triassic '_ 40 Pekin formation 41 Cumnock formation 41 Sanford formation 41 Undifferentiated 41 Coastal Plain _ 43 Cretaceous 43 Upper Cretaceous 43 Tuscaloosa formation 43 Black Creek formation 44 Pee Dee formation 44 Tertiary 44 Eocene (Middle and Upper) 44 Castle Hayne limestone 44 Miocene (Upper) 45 Yorktown formation 45 Quaternary 46 Pleistocene and Recent 46 Undifferentiated 46 References cited 48 ILLUSTRATIONS Figure 1. Generalized geologic cross-section from Wilson, N. C. to Cape Hatteras, N. C opposite page 47 State Library EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad ABSTRACT A new geologic map of North Carolina, compiled from all available sources, is presented herewith. The accompanying text describes the rock units shown on the map. The classification of rock units is based more on rock type than age relations. However, where possible formation names and age relations were used. The rocks were divided into the following four groups: Igneous and Metamorphic Rocks, Metavolcanic Rocks, Metasedimentary Rocks and Sedimen-tary Rocks. Included in the Igneous and Metamorphic Rocks are gneisses and schists, granite gneisses, and granites and mafic igneous rocks. The gneisses and schists occur mostly in the upper Piedmont and Blue Ridge regions of the State and are presumably the oldest rocks present. With one exception, the granite gneisses are restricted to the Blue Ridge region and probably represent ancient igneous and sedimentary rocks that have been highly metamorphosed. The granites and mafic igneous rocks occur throughout the Piedmont and Blue Ridge regions, but are most abundant in the Piedmont. Included in this group are a wide variety of rock types that vary greatly in age, but all appear to be of igneous origin. Metavolcanic Rocks occur in three distinct areas. The Carolina Slate belt occupies the largest area and is present in two separate but parallel belts. The main belt lies across the central part of the State in a northeast-southwest direction, and the second belt occurs along the western edge of the Coastal Plain. The Grandfather Mountain window is the second area of metavolcanic rocks, and it lies partly in the Blue Ridge and partly in the Piedmont Plateau in Avery, Watauga, Caldwell, Burke and McDow-ell Counties. Third is the Mount Rodgers volcanic group which occupies a relatively small area in the northwest corner of Ashe County. The Carolina Slate belt consists of volcanic-sedimentary formations, composed of slates, breccias, tuffs and flows. These rocks vary from acid, or rhyolitic, to basic, or andesitic, in composition and generally have a well developed cleavage. Rocks in the Grandfather Mountain window include schists, altered basalt and amygdaloidal basalt, metadiabase, and metarhyo-lite. The Mount Rodgers volcanic group is composed mostly of metarhyolite, including both tuffs and flows. Rocks more or less metamorphosed but retaining enough of their original characteristics to indi-cate that they were sediments are classed as Metasedimentary Rocks. These rocks occur in four areas, commonly referred to as the Stokes County area, the Kings Mountain area, the Brevard area, and the Murphy area. The rocks in the Stokes County and Kings Mountain areas are much alike and are com-posed mostly of quartzite, schist, conglomerate and marble. These two areas are classed as the Stokes County and Kings Mountain belt. The other two areas are classed as the Brevard belt and the Murphy belt, and they are composed mostly of schists with lesser amounts of marble. The oldest Sedimentary Rocks occur along the western edge of the State. These rocks belong to the Ocoee series and form much of the rugged topography in the Great Smoky Mountains. The Ocoee series is a very thick sequence of detrital rocks of graywacke type that rest unconformably on the older gneisses and granite gneisses. The Ocoee series is classed as Upper Precambrian in age. Overlying the Ocoee series is a sequence of somewhat better sorted detrital rocks called the Chilhowee group that are classed as Lower Cambrian in age. The Shady dolomite conformably overlies the Chilhowee group and is overlain by the Rome formation. Both of these formations are classed as Lower Cambrian. Triassic sedimentary rocks occupy two belts in North Carolina. The Deep River belt, the largest, lies along the eastern edge of the Piedmont Plateau and extends from Anson County on the southwest to near Oxford, Granville County, on the northeast. The Dan River belt lies in the north central part of the Piedmont Plateau and extends from Davie and Yadkin Counties across Stokes and Rockingham Counties into Virginia. The rocks of the two belts are very similar and consist of red, brown, purple and gray claystone, shale, sandstone, conglomerate and fanglomerate, and some coal. The eastern one half of the State is underlain by sedimentary deposits that range from Upper Cretaceous to Recent in age. These sediments are commonly referred to as the Coastal Plain deposits and consist largely of unconsolidated sediments that include gravels, sands, clays, limestone and marls. The deposits of the Coastal Plain form a wedge-shaped block of sediments that increases in thickness from a feather edge along its western border to approximately 10,000 feet at Cape Hatteras. The sedi-ments rest unconformably on crystalline rocks of Precambrian (?) age. INTRODUCTION A new geologic map of North Carolina, compiled from all available sources and supplemented by several months of fieldwork, is presented here-with. The accompanying text describes the rock units shown on the map and indicates briefly the importance of the units and their mineral deposits. Prior to the preparation of the present map, the only geologic map of the State of North Caro-lina was one prepared by W. C. Kerr and pub-lished as a part of his Geology of North Carolina, Volume I, 1875. This map was revised slightly by J. A. Holmes in 1887 and published as a part of Ores of North Carolina by W. C. Kerr and G. B. Hanna (1893). Modifications of these maps, geologic maps of portions of the State found in various state reports, geologic folios and other reports of the U. S. Geological Survey, and a black and white map of North Carolina modified from the Geologic Map of the United States by the U. S. Geological Survey, 1932, served as a basis for interpreting the geology of North Carolina until the present map was compiled. ACKNOWLEDGEMENTS The geologic map of North Carolina presented herewith is a compilation from all available sources, published and unpublished. It is supple-mented by several months of fieldwork, during which time areas of the State not previously cov-ered were mapped on a reconnaissance basis, and other areas were checked for accuracy of mapping and to harmonize older maps. In addition to in-formation obtained from older reports and from geologists who have had experience in the State in recent years, many others gave freely of their time and knowledge in making the present map possible. Thanks are gratefully expressed to all who aided in the project, and where possible, indebtedness for particular information is ex-pressed below. An apology is hereby expressed to any who have been overlooked. First, thanks should be given to Luther H. Hodges, Governor of North Carolina, who became interested in the project and made funds avail-able for the necessary fieldwork and for compiling and publishing the map. Without his interest and enthusiastic support the map could not have been made available at the present time. To Thomas B. Nolan, Director of the U. S. Geo-logical Survey, and many members of the staff of that agency, thanks are gratefully extended. The U. S. Geological Survey cooperated informally by making available unpublished geologic maps of portions of the State, authorizing members of its staff to evaluate much of the material used, and furnishing the new base map on which the geology was compiled and published. Robert A. Laurence served as representative of the Survey in furnish-ing unpublished material and gave valuable assist-ance and advice on the map. Philip B. King re-viewed the manuscript of the Piedmont and Moun-tain areas of the State and made many valuable suggestions. Jarvis B. Hadley edited the geology of the Great Smoky Mountains area and furnished valuable information on adjacent areas. W. C. Overstreet, A. A. Stromquist, and Phil Choquette contributed valuable data on the Central Piedmont region. H. M. Bannerman, C. A. Anderson, R. H. Lyddan, Harold Williams, J. P. Alders, and G. M. Fitzgerald furnished valuable information as to available maps and procedures to be used in the preparation of the map. The geology of the Coastal Plain is based on recent work of H. E. LeGrand and P. M. Brown. Robert L. Moravetz and his associates in the Office of Publications of the Survey gave valuable instructions on the prep-aration of the final manuscript and did photo-graphic work that greatly reduced hand labor. The 8 Committee on Geologic Names checked the legend and approved the names and ages of many of the rock units and formations used on the map. To make the map possible several areas in the State not previously mapped were mapped on a reconnaissance basis specifically for the project. R. J. Council and C. M. Llewellyn, Jr., mapped Alleghany, Wilkes, Surry, Yadkin, and parts of Ashe and Caldwell Counties. D. B. Sterrett aided Councill and Llewellyn and also mapped Alexan-der County. V. I. Mann and S. S. Alexander map-ped Franklin, Warren, and parts of Vance, Hen-derson, Buncombe, and McDowell Counties and checked several areas in the western part of the State. W, A. White and E. C. Brett mapped Dur-ham, Orange, and parts of Person and Granville Counties. R. L. Ingram and O. B. Eckhoff mapped Union, Stanly, and parts of Anson and Montgom-ery Counties. S. D. Heron, Jr., and W. D. Reves mapped Richmond and parts of Anson, Harnett, Lee, Moore, Montgomery, and Randolph Counties. J. M. Parker III and J. F. Conley mapped parts of Granville, Wake, Harnett, Moore, Lee, and Chat-ham Counties. J. L. Stuckey and S. G. Conrad mapped parts of Johnston, Wake, Harnett, Chat-ham, and Randolph Counties. S. D. Broadhurst checked several areas and made valuable contribu-tinons to the project. T. L. Kesler, chief geologist of Foote Mineral Company, made available to the project the results of his mapping in the Kings Mountain district and offered valuable suggestions on other areas. In addition to field mapping, the men mentioned above, as well as E. Willard Berry, G. R. McCarthy, W. H. Wheeler, and E. L. Miller, Jr., gave valuable aid and criticism while the map was being compiled. MAP UNITS A geologic map is no better than the rock units or formations used. The map presented is not a final summary of the geology of North Carolina but a progress report in which an attempt has been made to present the best information avail-able. To give meaning to the map units, more description is needed than can be presented in a conventional map explanation. To meet this need, the following descriptive text has been pre-pared to indicate the relative dependability of the map and point out areas where more work is most urgently needed. There are enough such areas to keep many geologists busy for a long time, and it is hoped that this map will serve as a stimulus and framework for increased geologic mapping in North Carolina. Since the present map is based on fieldwork that is not sufficiently detailed to warrant a complete revision of nomenclature, an attempt has been made to show detail where detail exists and only generalized units where information is lacking. As a result, standardized units and names already in use and approved by the Committee on Geologic Names of the U. S. Geological Survey have been used wherever possible instead of introducing new ones. Not all rock unit and formation names found in the literature are retained on the present map. In that portion of the Piedmont and Appalachian regions covered by various folios and unpublished maps of the U. S. Geological Survey are large areas which were mapped as Carolina gneiss and Roan gneiss. The formation names Carolina gneiss and Roan gneiss are no longer accepted by the U. S. Geological Survey and are not used on the present map. Many of the rocks classed as Carolina gneiss and Roan gneiss in older reports are shown as mica gneiss, mica schist, and horn-blende gneiss on the present map. The same procedure was followed in the Caro-lina Slate Belt of the Lower Piedmont. Prior to the preparation of the present map, two methods of classifying rock units in that belt had been employed. Laney (1910), Pogue (1910), and Stuckey (1928) mapped areas in the Carolina Slate Belt and classed the rocks as acid volcanic fragmental and flow materials, basic volcanic fragmental and flow materials, and bedded slate. Laney (1917) used the names Virgilina green-stone, Aaron slate, Hyco quartz porphyry, and Goshen schist for the volcanics in the Virgilina district. For the preparation of the present map it was not possible to do enough detailed fieldwork to apply these formation names to the whole slate belt ; instead, the rock-unit names Felsic volcanics, Mafic volcanics and Bedded argillites (volcanic slate) were used, as these units are more easily recognized throughout the belt. The Coastal Plain is doubtless the best mapped part of the State, and the formation names in com-mon use there have been retained with few changes. In areas of the State, chiefly the Pied-mont Plateau, where only limited mapping had been done previous to the preparation of the pres-ent map, rock units were set up and names most descriptive of these units were used. 9 DEPENDABILITY OF THE MAP In the order of dependability the Coastal Plain is probably the best mapped part of the State. This is true with respect to the formations estab-lished and their age relations, but some of them vary in thickness from place to place, and it is not always easy to determine the exact limits of sur-face exposures. The region west of longitude 81° 30' is the next best mapped part of the State, but here variations in metamorphism and complex structure make detail mapping difficult. East of longitude 81° 30' and west of the western limits of the Coastal Plain less detailed work has been done, and the map is less complete. These three areas are discussed below in the order of depend-ability. The first detailed map of the Coastal Plain was prepared by Clarke et al. (1912). In that report Stephenson considered the oldest Cretaceous rocks in North Carolina to be Lower Cretaceous and classed them as Patuxent in age. In the same report Miller considered the Trent formation to be Eocene and older than the Castle Hayne lime-stone. Cooke (1926) reclassified the Patuxent as the equivalent of the Tuscaloosa of Upper Creta-ceous age, and Kellum (1926) placed the Trent formation in the Miocene. In subsequent years other changes were proposed by different geolo-gists. Berry (1947) compiled a geologic map of the Coastal Plain from all available sources, which has served until the present time. LeGrand and Brown (1955) revised the geologic map of the Coastal Plain and combined the Trent formation with the Castle Hayne limestone. The present map contains all the formations in the Coastal Plain that are approved by the U. S. Geological Survey. Considerable mapping has been done in the region west of longitude 81° 30', but all the earlier work was highly generalized. Kerr (1875) divid-ed the rocks of the region into three units, which he classed as Lower Laurentian, Upper Lauren-tian, and Huronian. The lower Laurentian cor-responds to Paleozoic (?) granites of the present map ; the Upper Laurentian corresponds to granite gneisses and gneisses and schists of the present map; and the Huronian corresponds to metavol-canics and sedimentary rocks older than Triassic of the present map. Holmes (1893 see Kerr and Hanna 1893) used essentially the same classifica-tion employed by Kerr but considered the three units to be Archean in age. Pratt and Lewis (1905) classed the gneisses, schists, granites, diorite, and other crystalline rocks of the region as Precambrian in age and the conglomerates, quartzites, slates, etc., ac Ocoee of Cambrian age. They considered the peridotites, dunites, and related rocks as probably early Paleo-zoic in age. During a period beginning in 1888 and ending about 1912, the U. S. Geological Survey mapped the region being considered, except Polk and parts of Henderson and Cleveland Counties, on 30-min-ute quadrangles. Nine of these were published as folios, and five were not published. The nine pub-lished folios are: Keith (1895, Knoxville f. 16; 1903, Cranberry f. 90; 1904, Asheville f. 116; 1905, Mount Mitchell f. 124; 1907a, Nantahala f. 143 ; 1907b, Pisgah f. 147 ; 1907c, Roan Mountain f. 151) , LaForge and Phalen (1913, Ellijay f . 187) , and Keith and Sterrett (1931, Gaffney-Kings Mountain f. 222). The five unpublished maps were: Keith (Cowee q. and Mt. Guyot q.) ; Keith and Sterrett (Morganton q. and Lincolnton q.) ; and Keith and Hayes (Murphy q.). The areal geologic map of the Cowee, Mt. Guyot, Morganton, and Murphy quadrangles were revised by Philip B. King and placed on open file by the U. S. Geo-logical Survey and were available for use during the preparation of the present map. In recent years, considerable mapping has been done in the region by the U. S. Geological Survey and the Tennessee Valley Authority, independent-ly, and by the State of North Carolina in coopera-tion with these agencies. Philip B. King, Jarvis B. Hadley, and others of the U. S. Geological Sur-vey mapped the Great Smoky Mountains and vicinity, and R. G. Yates, W. R. Griffitts, and W. C. Overstreet of the same agency mapped the Shelby quadrangle and adjacent areas. The U. S. Geological Survey in cooperation with the State of North Carolina carried out extensive mapping of mica mines in the area during World War II; and under the same program J. C. Olsen (1944) prepared a map of a part of the Spruce Pine dis-trict, E. N. Cameron (1951) prepared a map of a part of the Bryson City district, and J. M. Parker III (1952) prepared a map covering the geology and structure of a part of the Spruce Pine district. More recently, Kulp, Brobst et al. (unpublished) completed a geologic map of the Spruce Pine dis-trict covering some 250 square miles. Geologists of the Tennessee Valley Authority, including Charles E. Hunter, Sam D. Broadhurst, and E. C. Van Horn, did extensive geological work 10 in the region prior to 1941. Under cooperation between the Tennessee Valley Authority and the State of North Carolina, E. C. Van Horn (1948) prepared a geologic map of the Murphy Marble Belt, and S. S. Oriel (1950) prepared a geologic map of the Hot Springs area. Under the same cooperative agreement a number of other reports on mineral resources were prepared, chief of which were by Hunter, et al. (1942) , Murdock and Hunter (1946), Hunter and Hash (1949), Hash and Van Horn (1951), and Broadhurst and Hash (1953). All of these, and other reports not men-tioned here, were freely drawn upon in compiling the map of the region west of longitude 81° 30'. When compilation of the present map was be-gun, less detailed mapping had been done between longitude 81° 30' and the western limits of the Coastal Plain than in any other part of the State. Laney (1910 and 1917), Pogue (1910), and Stuckey (1928) had prepared maps of a part of the Carolina Slate Belt. Stone (1912), Campbell (1923), and Reinemund (1955) had prepared maps of the Dan River and Deep River Coal Fields. Keith and Sterrett (1931) had mapped a part of Cleveland County, and Overstreet et al. (1953) had prepared a preliminary map of the Lincoln-ton quadrangle. J. M. Parker III, under a coop-erative agreement between the U. S. Geological Survey and the State of North Carolina, had just completed a map, not yet published, of the Hamme Tungsten district covering parts of Granville and Vance Counties. These and a number of maps covering 50 to 100 square miles each, which had been prepared by graduate students in connection with theses problems, represented the only de-tailed mapping in the region. Considerable mapping, however, had been done on a reconnaissance basis in connection with a cooperative project between the U. S. Geological Survey and the State of North Carolina for the study of ground water in the State. Mundorff (1946) prepared a geologic map of the Halifax area covering Nash, parts of Halifax, Northamp-ton, and Wilson Counties in the Piedmont. Mun-dorff (1948) prepared a similar map of the Greensboro area covering Alamance, Caswell, Guilford, Rockingham, Forsyth, and Stokes Coun-ties. LeGrand and Mundorff (1952) prepared the same sort of map of the Charlotte area covering Cabarrus, Mecklenburg, Gaston, Lincoln, Cleve-land, Rutherford, and Polk Counties. LeGrand (1954) prepared a similar map of the Statesville area covering Alexander, Catawba, Iredell, Davie, Rowan, and Davidson Counties. The maps listed plus the new mapping in the areas referred to under acknowledgments above served as the basis for compiling the present map of the State. Every possible precaution was taken to make the best possible use of the available data, but it should be pointed out that the map appears much more accurate than it actually is. No one is so well aware of its weak points and imperfec-tions as the compilers are. A general precaution is issued to all users not to consider it a finished map, but a summation of the best information at present available on the geology of North Carolina. STRUCTURE AND METAMORPHISM In an area as complex in geology as that found in the Piedmont and Mountain regions of North Carolina, structural features and metamorphism of the rock units present many major problems. After giving much thought to the structural fea-tures of the rocks in the Piedmont and Mountain regions of the State and discussing the subject with many people who are more or less familiar with the region, it was decided that enough de-tailed information is not available to produce structure sections of real value. It was also de-cided that enough information is not available to warrant any detailed discussion of faulting, fold-ing, metamorphism, unconformities, and facies changes. As a result, metamorphism is not dis-cussed as such, and the only structural features shown on the map are a few faults of regional significance. The U. S. Geological Survey is now engaged in the detailed mapping of a strip from the western edge of the Cumberland Plateau, across the Appa-lachian Mountains, the Piedmont Plateau, and the Coastal Plain. This strip is expected to cross a part of North Carolina. Perhaps, when it is com-pleted, a revised map of North Carolina will be prepared which will contain more information on structure and metamorphism than is now avail-able. Structural features in the Coastal Plain are less complicated than in the Piedmont and Mountain regions. The formations generally strike north-east- southwest and dip gently a few feet per mile to the southeast. No faults or folds of any significance have been found in the region. A geologic cross-section across the Coastal Plain 11 with considerable subsurface data, obtained from deep-well records, is presented below. DESCRIPTION OF ROCK UNITS INTRODUCTION In the explanation listed on the map and dis-cussed below, a three-fold grouping of rock units has been used. First, the rock units have been grouped as sedimentary rocks, metasedimentary and metavolcanic rocks, and igneous and meta-morphic rocks. Igneous and metamorphic rocks have been grouped together because some of the units used have characteristics of both igneous and metamorphic rocks. Second, an attempt has been made to group the rock units in the explana-tion according to their geographic distribution in the State. Third, as far as possible the sequence in the explanation represents the stratigraphic position of the rock units in the earth's crust. This is thought to be correct for the sedimentary rocks; however, in the case of metasedimentary rocks, metavolcanic rocks, and igneous and meta-morphic rocks, the sequence in the explanation may not represent the true stratigraphic position. For example, the rock units used in the metavolcanic rocks of the Carolina Slate Belt are interbedded and, as a result, are not distinctly different in age. The exact ages of most of the granites listed as Paleozoic (?) and Paleozoic are not known, and as a result some may be the exact stratigraphic equivalents of others. The same holds true for the granite gneisses, as Eckelman and Kulp (1956) classed the Cranberry granite gneiss and the Hen-derson granite gneiss as stratigraphically equiva-lent. Finally, the exact ages of the gneisses and schists are not known, and it is quite probable that the units used contain materials differing greatly in ages. IGNEOUS AND METAMORPHIC ROCKS The gneisses, schists, and granite gneisses, list-ed as Precambrian( ?) , present a major problem in age classification. Many of these units in the Blue Ridge area, according to King (personal communication), are unconformable below Lower Cambrian and Upper Precambrian units and should be classed as Precambrian without the query. However, the difficulty comes in going southeast from the Blue Ridge area where similar units have no certain stratigraphic relations to the Cambrian or Upper Precambrian. The result is that Precambrian (?) looks incongruous in the Blue Ridge area where these rocks are in contact with Upper Precambrian and Lower Cambrian, but is well justified in the southeast. No simple solution could be found for the problem, and it has been left for map users to draw their own con-clusions. GNEISSES AND SCHISTS PRECAMBRIAN(P) The three units—Mica gneiss, Mica schist, and Hornblende gneiss—used in this grouping repre-sent essentially Carolina gneiss and Roan gneiss in the areas mapped by Keith and similar mate-rials outside these areas. The formation names Carolina gneiss and Roan gneiss are no longer accepted by the U. S. Geological Survey and are not used on the present map. The three units as presently constituted are too complex in compo-sition to be given formation names, and it was thought best to use the rock-unit names, Mica gneiss, Mica schist, and Hornblende gneiss. Mica Gneiss (mgn) The Mica gneiss unit, as mapped, occurs over a wider area and probably underlies more square miles of the State than any other formation on the map. It is especially abundant in the Blue Ridge region and the western part of the Piedmont Plateau where it covers large areas. It is less abundant in the central part of the Piedmont Pla-teau but is common along the eastern part of that area. In the Blue Ridge and upper Piedmont areas, the Mica gneiss unit consists largely of Carolina gneiss as mapped by Keith (1903, 1904, 1905, 1907a, 1907b, 19007c, and 1931). In other parts of the State the Mica gneiss unit is in all respects comparable to that in the areas mapped by Keith. The Mica gneiss unit consists of an immense series of mica gneiss, mica schist, and fine gran-itoid layers in which mica gneiss predominates. Most of these are light to dark gray in color, weathering to dull gray, greenish gray, or yellow. Varying amounts of garnet gneiss, garnet schist, kyanite gneiss, granite gneiss, hornblende gneiss, and crystalline limestone or marble are present in the unit at many localities. There are also in-cluded in the Mica gneiss unit younger bodies of 12 granite, diorite, and dikes and lenses of pegmatite too small or not well enough known to show on the map. Mica gneiss, which is the chief component of the Mica gneiss unit, is composed chiefly of quartz and feldspar with varying amounts of mica, both biotite and muscovite, with biotite predomi-nating in many localities. Much of the Mica gneiss unit is doubtless metamorphosed sedimentary ma-terial, while some of it resembles granite gneiss and may well represent granite that has been strongly metamorphosed. Rock of this type has been quarried extensively around Asheville, Bun-combe County; Hickory, Catawba County; Hen-derson, Vance County ; and Raleigh, Wake County. This material was used in the construction of the present State Capitol in Raleigh, which was erect-ed between 1830 and 1835. Bands and lenses of mica schist, usually fine-grained and composed of quartz, muscovite, a little biotite, and very little feldspar are common in the Mica gneiss unit. Closely associated with the mica schist bands and lenses are extensive bands and zones of garnet gneiss, garnet schist, and kyanite gneiss. The garnet and kyanite gneisses and schists are too widespread to describe in detail here. Some of the better known garnet areas are near Marshall, Madison County; on Sugar Loaf Mountain near Willetts, the Savannah mine on the headwaters of Betty Creek, and the Presley mine near Speedwell in the upper Tuckaseegee valley, all in Jackson County; and on Shooting Creek, Clay County. An important belt of kyanite gneiss, six to eight miles wide, extends along the line of the Black and Great Craggy Mountains from Swannanoa, Buncombe County, to Bakersville, Mitchell County. The kyanite crystals vary in length from a fraction of an inch to three or four inches but average less than an inch. On weath-ered surfaces, they often stand out in relief, giv-ing the rock a porphyritic appearance. Small gar-nets are often associated with the kyanite gneiss. At many places throughout the Mica gneiss unit there are thin, interbedded layers of hornblende gneiss and schist, too small to show on the map. These are in all respects similar to the Horn-blende gneiss unit described below. Bodies of crystalline limestone or marble are present at many localities in the Mica gneiss unit. The more important of these occur near Marshall, Madison County; south of Bakersville, Mitchell County ; eight miles northwest of Winston-Salem, Forsyth County; and near Germanton, Stokes County. Included in the Mica gneiss unit at many places are dikes and lenses of pegmatite which are dis-tinctly younger than the enclosing rock. These vary in thickness from a few inches to as much as 200 feet (Olson, 1946, p. 7) and are equally vari-able in length. Most of the kaolin and feldspar produced in North Carolina prior to 1945 came from pegmatite bodies. Throughout the history of mica mining in the State pegmatites have been, and still are, the chief source of sheet mica. A wide variety of commercially less important min-erals are present in the dikes, and Olson (1944, p. 26) stated, "At least 44 different minerals have been reported from the Spruce Pine pegmatites." Spodumene-bearing pegmatites, which are the chief source of lithium in the United States, are abundant in the Mica gneiss unit south of Lincoln-ton in the Kings Mountain district. The Mica gneiss is deeply weathered in most places and is covered with a thick layer of resi-dual clay. As a result, fresh outcrops and ledges of solid rock are seldom seen except along streams, on steep slopes, and in the more mountainous areas. The residual clay contains fragments and layers of schist, quartz, mica, and gneiss. The cover of soil on the thick mantle of residual clay and weathered rock is usually light and thin. Mica Schist (msh) The Mica schist unit occurs most abundantly along the western border of the Piedmont Plateau, just east of the Blue Ridge Mountains, and extends intermittently completely across the State. In the vicinity of Kings Mountain and around Gastonia there are fairly large areas of mica schist, and smaller areas are widespread throughout the Pied-mont Plateau. The main occurrences of this unit along the western border of the Piedmont Plateau, the area around Gastonia, and the areas through-out the lower Piedmont are essentially mica schist of the Carolina gneiss as mapped on the various folios of the U. S. Geological Survey. North of the Yadkin River, the Mica schist unit consists principally of a thinly foliated muscovite-sericite schist. This unit also includes bands and zones of muscovite-biotite schist and some areas of mica gneiss, partly altered to mica schist. In-jections of granite, too small to show on the map, are also common east of the Blue Ridge, and small amounts of hornblende gneiss and schist are pres-ent at many places in the unit. At many places, the Mica schist contains varying amounts of gar- 13 net, sillimanite, kyanite, magnetite, ilmenite, and pyrite. South of the Yadkin River, the Mica schist unit consists basically of biotite schist. Three varie-ties of biotite schist are common, namely, biotite schist, biotite-muscovite schist, and sillimanite-biotite schist. All gradations exist among the three varieties. The sillimanite schist is in all places more contorted and sheared than the other varieties. A number of accessory minerals, in-cluding garnet, graphite, chlorite, and pyrite are present in the Mica schist unit. Pegmatites and narrow quartz veins occur throughout the mica schist. The pegmatites in general average less than a foot in thickness and rarely exceed four feet in length. Locally, they make up as much as one-half of the sillimanite-biotite schist. Over-street and Griffitts (1955, pp. 551-556) gave an excellent description of the Mica schist unit and related rock units and discussed their mineral content in some detail. Bands and zones of hornblende gneiss and horn-blende schist, most of which are too small to show on the map, are common throughout the Mica schist unit. These hornblende rocks are generally of simple mineral composition and locally may con-tain varying amounts of garnet. Many bodies of foliated to massive granite, too small to show on the map, are present in the unit. The Mica schist around Gastonia and in the other areas of the Piedmont Plateau to the east and northeast is essentially a fine-grained rock composed chiefly of quartz, muscovite and sericite mica. At places, the rock is a quartz-biotite schist, while at others it becomes a quartz-sericite, chlorite schist. The Mica schist evidently resulted from the metamorphism of sedimentary rocks that varied greatly in character from place to place. Weathering has been extensive, and outcrops of fresh rock are seldom seen except along streams and on steep slopes. The thick layer of residuum consists of clay mixed with fragments and layers of schist, quartz, and mica. The clay varies from yellow to dark red in color depending on the amount of biotite in the schist. The soil cover is usually light and thin. Hornblende Gneiss (hgn) The Hornblende gneiss unit is most abundant in the mountain region west of the Blue Ridge and north and northeast of Asheville. Several small areas occur west of the Blue Ridge in Clay and Macon Counties. In and parallel to the east side of the Blue Ridge small areas occur almost com-pletely across the State. In the central part of the upper Piedmont, in the general vicinity of Hickory and Statesville, there are some relatively large areas. Smaller areas occur along the east-ern edge of the Piedmont Plateau, particularly in Wake County. The Hornblende gneiss unit consists essentially of Roan gneiss as mapped and defined by Keith (1903). The type locality of the Roan gneiss is Roan Mountain, which lies along the North Caro-lina- Tennessee line and extends southward into Mitchell County, North Carolina. Keith (1903) stated, "The Roan gneiss appears to cut the Caro-lina gneiss, but the contacts are so much metamor-phosed that the fact cannot be proved." He con-sidered the Roan gneiss as chiefly diorite and smaller amounts of gabbro, which had been in-truded into older rocks and metamorphosed to hornblende gneiss and hornblende schist. In recent years considerable attention has been given to Roan gneiss, as mapped and defined by Keith, and much of it is no longer considered to be of igneous origin. Kesler (1944, 1955) pointed out that bodies of hornblende gneiss in the Kings Mountain district (See Kings Mountain group be-low, p. 31) are metamorphosed, calcareous sedi-ments. Parker (1952, p. 8) described the relation of the hornblende gneiss to the mica gneiss in the Spruce Pine district and concluded that certain thin, interbedded hornblende gneisses and actino-lite- tremolite rocks may have been impure dolo-mitic limestones. He added: "The mafic min-eralogic composition, however, coupled with the conformable relations to mica gneiss, has led most workers to believe that the ordinary hornblende rocks are metamorphosed mafic volcanic extru-sives, and perhaps, in part at least, are conform-able intrusive sills," and concluded, "Perhaps some of the hornblendic rocks are sedimentary in origin and some are igneous." Brobst (unpublished) concluded that the Roan-type rocks (hornblende gneiss) are of sedimen-tary origin and stated, "The hornblende rocks, therefore, may represent the metamorphosed equivalent of impure carbonate layers in the sedi-mentary sequence." Overstreet and Griffitts (1955, p. 553) considered the hornblende gneiss between Kings Mountain and Marion, North Caro-lina, to be in part of igneous and in part of sedi-mentary origin. 14 The Hornblende gneiss unit consists essentially of hornblende gneiss and hornblende schist layers that vary from a fraction of an inch to many feet in thickness. The thin layers of hornblende gneiss and hornblende schist are interbedded with thin layers of mica gneiss and mica schist to the extent that portions of the Hornblende gneiss unit con-tains considerable mica gneiss and mica schist, and in the same way portions of the Mica gneiss unit and portions of the Mica schist unit contain considerable amounts of hornblende gneiss and hornblende schist. The hornblendic rocks of the Hornblende gneiss unit include distinctly banded gneisses consisting of alternating layers of hornblende and feldspar, schistose rocks consisting almost entirely of coarse to fine hornblende needles, and nearly massive am-phibolites that lack distinct foliation. The gneisses and schists are black to dark green and grade into one another by feldspar content. Quartz, feld-spar, and hornblende are the chief minerals pres-ent, but varying amounts of biotite and chlorite are present at places. Garnet is less abundant than in the Mica gneiss and Mica schist but at places becomes an impor-tant constituent of the Hornblende gneiss. Peg-matite dikes, some of which have furnished con-siderable amounts of feldspar and mica, are pres-ent at many places in the unit. Numerous bodies of soapstone and talcose schist are associated with the Hornblende gneiss unit especially in the Spruce Pine district. These bodies, which vary from five to 25 feet in thickness and consist of talc, soap-stone, actinolite, biotite, chlorite, and vermiculite, appear to have been formed locally by secondary hydrothermal alteration of the hornblende gneiss. In the more mountainous areas, the Hornblende gneiss often crops out as ledges and bold ridges, but at lower elevations it usually occupies broad, flat areas or lower ground. It weathers readily and is usually covered with a thick layer of resi-dual clay mixed with rock fragments. This clay has a strong, dark-red color and is covered with a rich, fertile soil. intruded by a number of rocks which he classed as granites and granite gneisses (all highly meta-morphosed) and named in various areas Cran-berry granite, Henderson granite, Max Patch granite, and Beech granite. One unit, the Blow-ing Rock gneiss, he did not definitely class as a granite, even though he considered it intrusive into the older gneisses and the Cranberry gran-ite. Little has been published on these rocks since the work of Keith, but a number of workers in the area have made observations that caused them to doubt the validity of classing these units as either intrusive in origin or true granites in composition. This is true especially of the Cran-berry and Henderson granites. Brobst (unpub-lished) listed and described the Cranberry granite as Cranberry gneiss. He discussed specifically some layers, typical of the Cranberry gneiss, which are interbedded with other metamorphic rocks along the northwest and east borders of the Bakersville-Plumtree area, Avery County, close to the contact of the large body of Cranberry gneiss that surrounds that part of the Spruce Pine district on three sides (Kulp and Brobst, 1956). Eckelman and Kulp (1956) considered the Cran-berry and Henderson granites to be metasedimen-tary in origin and stratigraphically equivalent. During the preparation of the present map it was not possible to restudy these units in detail. As a result, in the areas covered by published folios these units are shown as nearly as possible as originally mapped. Outside the areas covered by published folios, it is doubtful if the units cor-respond in all details to those in the areas covered by published maps. In view of the diversity of materials in the units and the intense metamorph-ism which has altered them, it was decided, after discussing the problem with a number of workers who have made observations in the field, to add the word gneiss to each unit originally classed as granite. As a result, each of these units originally classed as granite becomes a granite gneiss on the present map. GRANITE GNEISSES PRECAMBRIAN(P) Along the western edge of the Piedmont Pla-teau and throughout much of the Blue Ridge Mountains area, according to Keith (see reference above), the older gneisses and schists have been Unnamed Granite Gneiss (gru) In Jackson, Haywood, and Swain Counties, west and north of Sylva, are areas of Unnamed granite gneiss. J. B. Hadley, on a map of the Great Smoky Mountains area furnished for use in the prepara-tion of the present map, designated these rocks as granite gneiss without formation or unit names or 15 age designations. Hadley et al. (1955, p. 402) classed these rocks as Max Patch and Cranberry as mapped by Keith (1904) and described them as medium to very coarse genissic granites, gen-erally gray but locally pink in color and containing minor amounts of leucogranite, amphibolite, peg-matite, and much blue quartz. Cameron (1951, p. 10) described one of these areas near Bryson City in some detail. He classed the rocks of the area as granitic gneisses and de-scribed them as predominantly fine- to coarse-grained leucocratic and mesocratic gneisses, vary-ing in composition from granitic to granodioritic with well developed foliation and lineation. He stated that the granite gneisses are cut by dikes of fine-grained granite and by dikes of medium-gray granite porphyry. Granite Gneiss Complex (gnc) Beginning a few miles northeast of Morganton and extending in a southwest direction across Burke, McDowell, Rutherford, and Polk Counties is an area underlain with rocks classed as Granite gneiss complex on the present map. About half of this area, in Burke and McDowell Counties, extending to latitude 35° 30' N. and longitude 82° W. in Rutherford County, was mapped by Keith on the Morganton quadrangle, which was not pub-lished. He made field surveys in the Morganton quadrangle in the years 1896, 1899, 1900, 1901, and 1907 and was aided by D. B. Sterrett during the last year. Traverse sheets available in the U. S. Geological Survey files show complete cover-age of the quadrangle. Based on these surveys, Philip B. King edited a geologic map of the Mor-ganton quadrangle, which appears to be a general-ization by Keith of a more detailed map not at present available. The central part of the Morganton quadrangle, as edited by King, is underlain with a rock unit 5 to 15 miles wide which is classed as "Cranberry, Henderson (and other?) granites (Archean) (in-cludes small areas of Roan gneiss)." Small areas of the same unit are shown in the southeast corner of the Morganton 30' quadrangle and in the Shelby 15' quadrangle. Rocks of this unit in Cleveland, Lincoln and Burke Counties were named Toluca quartz monzonite and classed as Ordovician in age by Griffitts and Overstreet (1952). The main area of Granite gneiss complex ex-tends southwest from the Morganton quadrangle across Rutherford County and well into Polk County. LeGrand and Mundorff (1952) mapped this unit in Rutherford County as mica schist and granite with schist predominant, and hornblende gneiss and granite interlain, and in Polk County as granite gneiss interlain with hornblende gneiss, and hornblende gneiss and granite interlain. Attempts were made to harmonize the mapping done by LeGrand and Mundorff in Rutherford and Polk Counties with that done by Keith in the Mor-ganton quadrangle. Attempts were also made to determine if the granitic material in the Granite gneiss complex as shown on the present map could be correlated with the granitic rocks in the south-east corner of the Morganton quadrangle and the northeast corner of the Shelby quadrangle, which Griffitts and Overstreet designated as Toluca quartz monzonite of Ordovician age. The problem was not fully recognized until com-pilation of the map was well underway, and time was not available to work out all the details. Two field parties, working independently, spent several days in the area and decided that the materials mapped by LeGrand and Mundorff in Polk and Rutherford Counties and by Keith in the Morgan-ton quadrangle are essentially the same. It was decided that in the time available no correlation could be made between the granites in the area and the Toluca quartz monzonite to the east and southeast. The rock unit shown on the present map as Granite gneiss complex contains mica gneiss, mica schist, and hornblende gneiss similar to that in the gneisses and schists described above. In addi-tion it contains granite gneiss similar to Hender-son granite gneiss, and Cranberry granite gneiss and also younger granite. Henderson Granite Gneiss (hgg) The Henderson granite gneiss unit on the pres-ent map is essentially Henderson granite as origi-nally named and described by Keith (1905) and further described (1907b). The Henderson gran-ite as mapped by Keith is not shown in contact with Cranberry granite at any place on his maps. On the present map the main area of Henderson granite gneiss begins near Marion, McDowell County, and continues southwest to the South Carolina line. West of Marion, a narrow band continues northeast along the west side of the Shady dolomite and Erwin formation to the limits of the Mount Mitchell quadrangle. Recently, Eck-elman and Kulp (1956) extended this band north- 16 east to near Linville Falls, McDowell County, where it makes contact with what they considered the southern extension of Cranberry granite as mapped by Keith in the Cranberry folio. They considered the Cranberry granite and the Hender-son granite to be metasedimentary in origin and stratigraphically equivalent. Keith (1905, p. 4) stated that the Henderson granite extended eastward into the Morganton quadrangle. A large area in the Morganton quad-rangle (discussed above under Granite gneiss complex) was mapped as Cranberry, Henderson (and other?) granites No age relations are shown between Cranberry and Henderson granites on the Morganton quadrangle, but in the legend on the Mount Mitchell folio, Keith placed Henderson granite above Cranberry granite. The exact origin and age of the Henderson granite is un-known. The Henderson granite gneiss, whatever its origin and age, is composed essentially of rocks with a pronounced gneissoid structure. Min-eralogically, the rock consists of orthoclase, pla-gioclase, quartz, muscovite, and biotite, named in the order of their abundance. Biotite varies a great deal in amount but is usually subordinate. The gneiss is usually gray in color but becomes lighter on weathering. Porphyritic crystals of feldspar are a prominent feature of the gneiss, and at many places it is a typical augen gneiss. The porphyritic varieties are not limited to any particular areas or positions in the gneiss but are generally irregularly distributed through it. Por-phyritic varieties of the gneiss grade into even-grained varieties, and the two varieties may be seen in a single exposure. Even-grained varieties of the gneiss are subordinate in amount to the porphyritic varieties. The rocks of this unit have been greatly changed by metamorphism. In areas where the finer grained beds did not contain porphyritic crystals of feldspar, the rock has been metamorphosed into gneisses and schists similar to those of the Mica gneiss and Mica schist units. Areas of mica gneiss, mica schist, and hornblende gneiss, too small to show on the map, are included at many places in the Henderson granite gneiss. Weathering of the Henderson granite gneiss varies greatly, and as a result the rock produces a varying landscape with strong cliffs and ridges in places and broad, flat areas in others. The Henderson granite gneiss has not been much used, but it offers an important source of dimension and crushed stone. Cranberry Granite Gneiss (cgn) The Cranberry granite gneiss unit on the pres-ent map consists essentially of Cranberry granite as originally named and described by Keith (1903), and further described (1904, 1905, and 1907c). The name Cranberry granite was first given to well developed exposures at Cranberry, Mitchell County, now Avery County. The rela-tions of the Cranberry granite gneiss to the Hen-derson granite gneiss have been discussed above under Henderson granite gneiss. Keith (references listed above) considered the Cranberry granite as igneous in origin, Archean in age, and intrusive into elder formations. He described it as granite of varying texture and color, and schists and granitoid gneisses derived from granite. Included were small or local beds of schistose basalt, diorite, hornblende gneiss, and pegmatite. As pointed out above, a number of workers in the area have made observations that caused them to doubt the validity of classifying the Cranberry granite as either intrusive in origin or a true gran-ite in composition. Brobst (unpublished) describ-ed the unit as Cranberry gneiss, consisting of white to gray gneisses, composed chiefly of micro-cline, sodic plagioclase, and quartz, and stated that in some layers biotite, muscovite, and rarely horn-blende may be present in amounts in excess of ten percent. He described the texture as cataclastic, with rounded and fractured porphyroblasts of microcline or plagioclase from three millimeters to one centimeter across the longest dimension. The Cranberry granite gneiss unit occurs as strips and patches in the Mountain region along the northwest border of the State. These begin about the latitude of Asheville in Haywood and Madison Counties and continue northeast to the Virginia line. The strips and patches which make up the unit have an elongation which conforms in general with the northeast-southwest trend of the mountains. The Cranberry granite gneiss, whatever its origin, is essentially a gneiss, which grades at places into schist. Logs of cores from 12 drill holes, varying in length from 400 to 1250 feet, which were drilled at the Cranberry iron mine in the type locality of the Cranberry granite in 1943- 1944, were examined during the preparation of 17 this report. These logs, which were prepared by competent geologists, show the rock to be a typical gneiss. In addition to gneiss, narrow bands' of hornblende gneiss, chlorite schist, and pegmatite were occasionally shown near the iron-ore veins. Some of the gneiss in the area is coarse-grained, but much of it is medium-grained and uniform in texture. In color, it varies from light to dark gray. In general, the Cranberry granite gneiss is a medium-grained, even-textured rock that varies from light to dark gray in color. It is composed of quartz, orthoclase, plagioclase, muscovite, bio-tite, and occasionally hornblende. In some areas the rock is more or less porphyritic, and in some places it has a marked red appearance due to the presence of red feldspar. The gneiss contains many small areas of mica gneiss, mica schist, horn-blende gneiss, schistose basalt, diorite, metadia-base, metarhyolite, and pegmatite. The Cranberry granite gneiss has been used to a limited extent for chimneys, foundations, and bridge piers, but no major quarrying operations have developed. The rock withstands weathering quite well in natural exposures. It takes a good polish and should make an attractive building stone. Quarry sites for crushed stone are avail-able at many places. Perhaps the most important mineral deposits associated with the Cranberry granite gneiss are the magnetic iron ores near Cranberry, Avery County. The magnetite deposits, while surrounded by the Cranberry granite gneiss, did not originate with the gneiss. According to Bayley (1923) the iron ore was brought up by pegmatites and depos-ited in the gneiss. These iron-ore bodies have been of interest for more than a hundred years. Sys-tematic mining was carried on intermittently be-tween 1880 and 1928, and some 2,250,000 tons of crude ore, which produced some 1,500,000 tons of shipping ore containing 42 to 46 per cent iron, were mined. Blowing Rock Gneiss (brgn) The main area of Blowing Rock gneiss is a wedge-shaped body beginning a few miles north of Blowing Rock, Watauga County, extending southward almost completely across Caldwell County and coming to a point at its southern end. A small area is shown near Creston, Ashe County. Keith (1903) named the unit Blowing Rock gneiss because it is well developed near the town of Blowing Rock. He classed it as an igneous rock, intrusive into Cranberry granite and older forma-tions and described it as chiefly dark, coarse, por-phyritic gneiss. The unit consists of two varieties, one contain-ing large porphyritic crystals of orthoclase feld-spar embedded in a groundmass of quartz, feld-spar, biotite, and muscovite, and the other con-sisting of the same minerals in grains of uniform size. The porphyritic crystals vary in length from three inches down to one-quarter of an inch and are frequently twinned. Many layers of fine-grained, black and gray schist are present in the unit. Biotite is so abundant that both varieties of the rock have a rather dark-gray color. The unit as a whole has been so much altered by fold-ing and metamorphism that while some of it is gneissoid, much of it is distinctly schistose. The rocks weather slowly, and outcrops are abundant, as in the Blue Ridge near Blowing Rock and south of Boone. Complete weathering produces a reddish-yellow clay, which is usually covered with light, well drained, fertile soil. The Blowing Rock gneiss has been used locally to a limited extent, but its importance as a build-ing stone has not been realized. The formation contains material suitable for ornamental and building uses that can be obtained in great abund-ance. Max Patch Granite Gneiss (mpgn) Max Patch granite gneiss consists entirely of Max Patch granite as mapped by Keith (1904 and 1905) . It was named for Max Patch Mountain in Madison County, North Carolina, which may be considered the type locality. In North Carolina the unit is limited to Haywood and Madison Coun-ties, with small extensions in Cocke and Unicoi Counties, Tennessee. Keith classed the unit as almost wholly coarse grained, in places porphy-ritic and in places of uniform grain. It is com-posed of orthoclase, plagioclase, quartz, biotite, and a little muscovite. At many places crystals of orthoclase feldspar more than an inch long are present. The porphyritic variety is dull white to light gray in color, while the even-grained variety is darker in color due to the biotite present. An-other variety of considerable extent is a coarse red granite which gets its color from the red feld-spar present. The red feldspars are often par-tially altered to epidote, giving the rock an at-tractive color. In places the feldspar has been 18 so far replaced by epidote that this mineral com-poses one-third to one-half of the bulk of the rock. The unit has been so completely metamorphosed that most of it has a gneissic to schistose struc-ture, and little, if any, true granite remains un-altered. The porphyritic variety of the unit has been altered to augen gneiss, while the even-grained variety has been altered to gneiss or schist. Weathering reduces the surface of the unit slowly, and as a result it commonly occupies higher elevations and steep slopes. Complete decay re-sults in a reddish or brownish clay of no great depth. Where soils accumulate on gentle slopes, they are rich and fertile. Mineral deposits are scarce in the Max Patch granite gneiss. A few small pegmatites near Lemon Gap, Madison County, contain small amounts of radioactive minerals. Some of the red feldspars, partly altered to epidote, make beautiful polished specimens, but the rocks of the unit have not become important as building materials. Beech Granite Gneiss (bgn) Beech granite gneiss consists of Beech granite as mapped by Keith (1903, 1905, and 1907c) and named for Beech Mountain, Avery County, where it is best developed. The largest area lies in and around Beech Mountain in Avery County, and extends westward into Carter County, Tennessee. Three other small areas are shown on the map, one around Blowing Rock in Watauga and Cald-well Counties, another west of Roan Mountain, Mitchell County, and extending into Carter Coun-ty, Tennessee, and a third in the western part of Yancey County, extending into Unicoi County, Tennessee. The unit consists of three varieties of granite gneiss. One is a coarse-grained, usually porphy-ritic rock, another is medium to fine grained, while the third is a coarse, red variety. In the porhy-ritic variety, crystals of orthoclase feldspar as much as two inches in length are often present. The chief minerals present in the unit are ortho-clase and plagioclase feldspar, quartz, biotite, and a little muscovite. The porphyritic variety is dull white to light gray in color, the medium- to fine-grained variety is darker in color due to the pres-ence of biotite mica, while the red variety gets its color from many pink or red feldspar crystals present. The unit has been greatly changed by meta-morphism. The mineral composition is essentially that of a granite, but the rocks composing the unit have a decided gneissic structure often becoming schistose with an increase of mica. The rocks of this unit are not too readily attacked by weather-ing and usually underlie higher ground. On complete weathering they produce a thin, brown-ish clay containing much sand. On gentle slopes where soils develop, they are strong and fertile. Mineral deposits are not known to occur in the Beech granite gneiss. The unit contains rock varieties that should make excellent building and crushed stone, but due mainly to location, they have not been developed. GRANITES AND MAFIC IGNEOUS ROCKS Rocks of definite igneous origin that have under-gone varying amounts of metamorphism and pos-sess textures ranging from massive to gneissic are classed as Paleozoic (?), Paleozoic, and Trias-sic(?) on the present map. The units classed as Paleozoic (?) could probably be classed as Paleo-zoic without the query, as most of them, except the dunites, have been considered for years as late Carboniferous in age and were shown on the 1932 Geologic Map of the United States as Carbonifer-ous ( ?) . However, little has been done to prove or disprove this classification since 1932, and it was thought best to show them on the present map as Paleozoic (?). PALEOZOIC?) There are five rock units in this group, four of which consist of granite, syenite, and diorite-gabbro. The fifth is classed as dunite and con-sists essentially of peridotite and pyroxenite, part-ly altered to talc, soapstone, and serpentine. The positions of these units in the column is arbitrary. Dunite (du) Dunite bodies are most abundant in the Blue Ridge Mountains where more than 250 outcrops occur in a northeast-southwest trending belt ap-proximately 175 miles long. A few small bodies occur in the western half of the Piedmont Plateau, but the most important bodies outside the Blue Ridge Mountains are found in the northern part of Wake County. Only a few of the larger bodies in the Blue Ridge Mountains and those in Wake County are shown on the map. In the mountains 19 the bodies vary greatly in size. The smallest, near Otto, contains 1500 square feet, while the largest, near Swannanoa in Buncombe County, is four miles long with a maximum width of nearly one mile. One of the most interesting is a ring dike near Webster, Jackson County, with a major axis six miles long and a minor axis about four miles long. In Wake County the deposits vary in length from a few hundred feet to nearly two miles. The age of the dunites is not definitely estab-lished. Keith (folios listed above) classed the dunites as Archean in age. He considered them intrusive into and closely related to the Roan gneiss but older than Cranberry and other gran-ites which he classed as Archean in age. Pratt and Lewis (1905, p. 159) suggested that they may have been formed during the Taconic revolution at the end of the Ordovician period. Parker (1952), Probst (unpublished) and King (1955) classed the dunites as Paleozoic in age. The dunites consist chiefly of peridotite and pyroxenite, in part altered to talc, soapstone, and serpentine. Some deposits consist almost entirely of olivine, and some contain small amounts of pyroxene minerals, but most of them have been altered extensively by metamorphism and hydra-tion. Many of the deposits in their present state consist of talc, soapstone, serpentine, asbestos, chlorite, vermiculite, and varying amounts of car-bonate. Unlike most metamorphosed rocks they show only minor schistosity. Amphibole minerals, such as tremolite and actinolite, often form bunches and radiating clusters in soapstone. The dunites in general weather slowly and often stand out as hills and ledges with much barren rock exposed at the surface. Final decay leaves a stiff yellow clay of little depth, and soils derived from this clay are of no value. Many of the de-posits, particularly in the Blue Ridge Mountains, are covered sparsely with a stunted vegetation. The dunites contain a wide variety of minerals that have been of interest at different times for many years. Many of the deposits contain varying amounts of chromite; and, while the production has been limited, much prospecting has been car-ried out for this mineral. At a few places, especially near Webster and Democrat, nickel sili-cate veins are conspicuous in the dunite, and con-siderable prospecting was carried out for nickel at Webster more than fifty years ago. The dunites contain varying amounts of corundum. Between 1871 and 1905, North Carolina was an important producer of corundum, most of which came from dunites. Talc and soapstone, associated with the dunites, have been of interest for many years, and small amounts have been produced. The most important period of activity was during World War II, when considerable amounts of ground talc and crayons were produced around Marshall, Mad-ison County. In recent years, considerable inter-est has developed in the olivine associated with the dunites. Hunter (1941) described some twenty-five deposits in the Blue Ridge Mountains that contain 230 million tons of high-grade olivine and more than one billion tons of partly altered olivine. Varying amounts of vermiculite are as-sociated with some of the dunites, and vermiculite production, which began in North Carolina in 1933, has continued intermittently since that time. Granite (gr) The rocks included in this unit are abundant along the western edge of the Coastal Plain and throughout the Piedmont Plateau. They were divided into three belts by Watson and Laney (1906), as follows: (1) Eastern Piedmont and Western Coastal Plain Belt ; (2) Central Piedmont Belt (Carolina Igneous Belt) ; and (3) Western Piedmont Belt. The rocks of the three belts are essentially gran-ite according to the commonly accepted meaning of the term. They consist in general of quartz, orthoclase, plagioclase, biotite, a little muscovite, and varying amounts of accessory minerals, such as chlorite, epidote, titanite, zircon, and mag-netite. On the basis of accessory minerals, varie-ties such as biotite granite and biotite-hornblende granite may be recognized. Councill (1954), on the basis of microscopic studies of the feldspars present, pointed out that in addition to granite, granodiorite is present, and quartz monzonite is common. He stated: "Many of the so-called granites of North Carolina approach more closely the mineral composition of granodiorite and/or quartz monzonite than normal granite." Each of the three belts listed above contains distinctive granites that seem to justify a brief description. The western boundary of the Eastern Piedmont and Western Coastal Plain Belt is formed by sedi-mentary rocks of Triassic age. In general the granites of this belt are massive, even-granular rocks, that show little effects of metamorphism. Jointing is common but not excessive at any place. 20 The textures present are chiefly medium to coarse grained. Porphyritic texture, though not abund-ant, is present at many localities, while fine-grained texture is seldom found. Two basic colors, one a light to medium gray and the other light to medium pink, sometimes approaching red, predominate. Outcrops, while not abundant, are common throughout the belt. Along stream val-leys, outcrops form elongated masses and ledges ; while in rolling topography, large boulders are often found. Away from streams in relatively flat topography, flat to dome-shaped masses often oc-cur. Where it has not been removed by erosion, the granites are covered with a residuum varying from a few inches to as much as 25 to 40 feet thick. This residuum varies in color from buff, yellow, and red to reddish-brown, depending on the weathering of the underlying granite. The granites of the Central Piedmont Belt (Carolina Igneous Belt) occupy a region several miles wide in the central part of the Piedmont Plateau. In this belt bodies of granite, varying greatly in shape and size, have intruded older rocks. On the basis of work by Mundorff (1948) and LeGrand and Mundorff (1952), the granites of this belt can be divided into three distinct geo-graphic areas. In one area, the granite, which Mundorff (1948) mapped as Sheared granite, crops out as an irreg-ular and interrupted zone across northern Ran-dolph County, southeastern Guilford County, most of Alamance County, the southeastern corner of Caswell County, and into central Person County. The granite is most commonly a coarse-grained rock of light-pink color, composed chiefly of ortho-clase, plagioclase, quartz, and biotite. At a few places, it is light gray and medium grained, with plagioclase as the chief feldspar. The granite is badly crushed and broken with the development of a schistose or gneissic structure. Basic dikes that vary from green to brown in color occur nearly everywhere in the granite in great numbers. Rarely does an outcrop of 200 to 300 feet of granite fail to expose one or more dikes, and at many places 10 to 12 dikes cut a granite body of that size. The dikes are more numerous and closely spaced along the margins of the granite. In some marginal exposures dike material is more abundant than granite. The dikes are fine grained, schistose in structure, and com-posed chiefly of chlorite, biotite, plagioclase, and augite. The granites of this area were intruded into basic volcanic rocks, largely of andesitic ori-gin. Councill (1954, p. 56) described these gran-ites as containing inclusions of basic volcanic rocks, probably of andesitic composition. It is probable that the dikes described above are in part dikes and in part inclusions from the basic vol-canic rocks into which the granite was intruded. In the second area, the granite, which Mundorff (1948) mapped as Porphyritic granite, crops out as irregularly shaped masses and elongated bodies in the southeastern corner of Rockingham County, across northwestern Guilford County, and in the southeastern half of Forsyth County. The granite in this area is coarse grained to porphyritic in tex-ture and usually medium gray in color. Porphy-ritic crystals of orthoclase feldspar up to eight inches in length have been observed in this granite. The groundmass consists of feldspar, quartz, and biotite. At many places dikes and fingers of granite can be seen cutting the surrounding gneiss and schists parallel to the regional strike. The granites have intruded these rocks much more complexly than could be shown on the map. Ex-cept for gneissic structure around the margins of the bodies, which was probably inherited from the gneisses and schists into which the granite was intruded, no effects of shearing or metamorphism are present. In the third area, the granite, which LeGrand and Mundorff (1952) and LeGrand (1954) map-ped as Granite and Granite-diorite complex, be-gins about the Forsyth-Davidson county line, lies west of the Gold Hill fault, and continues south-west to the South Carolina line. Mundorff and LeGrand mapped the rocks of this area as Granite ; Granite and diorite, granite predominant; and Diorite and granite, diorite predominant. On the present map, the first two of these have been com-bined in one unit, Granite. The diorite and gran-ite, diorite predominant unit has been included in the Diorite-gabbro unit, which is discussed as a separate unit. In using this subdivision, the boundaries between the Granite unit and the Dio-rite- gabbro unit are necessarily somewhat indef-inite. In this area granite occurs in some places as distinct bodies and in other places interlayered with diorite. Large bodies composed essentially of granite, occur in northern Davidson and eastern Davie Counties, in Rowan County, and in southern Iredell and Catawba Counties. Large areas of granite-diorite complex, in which granite predom-inates and which are shown as granite, occur in Davidson, Davie, Rowan, Cabarrus, Mecklenburg, and eastern Gaston and Lincoln Counties. In the 21 granite-diorite complex, the relations of the gran-ite and diorite are uncertain. At many places, relations suggest that granite has intruded dio-rite, while at others it appears that diorite has intruded granite. In western Gaston and Lincoln Counties, granite has been intruded into gneisses and schists, forming a complex. Where granite predominates, this complex has been mapped as Granite. As a result, considerable gneiss and schist are included in the granites in Gaston and Lincoln Counties. The granites of this area vary from fine grained, through medium grained to porphyritic in texture, with medium-grained and porphyritic texture pre-dominating. Porphyritic granites are common along the western part of the area in Gaston, Ire-dell, Rowan, and Davie Counties and northwest of Concord, Cabarrus County. The other granites of the area vary from medium to fine-grained in texture, with medium-grained texture predomi-nating. Outcrops are common and vary from large boulders to flat-surface areas. Colors vary from almost white through various shades of gray and pink to almost red. Minerals present consist of orthoclase, plagioclase, quartz, biotite, musco-vite, and various accessory minerals. Where gran-ite is associated with diorite, hornblende often occurs in the granite. Jointing is widespread but not excessive at any place in these rocks. The larger bodies, composed essentially of granite, show little metamorphism, but where granite has been intruded into gneisses and schists and in the granite diorite complexities, gneissic structure is often found. The rocks of this area react readily to the forces of weathering, and as a result the residuum varies in thickness from a few inches to many feet. The residuum covering the granites varies from buff through yellow to reddish-brown in color, while that covering the granite-diorite complex is much darker in color. The granites of the Western Piedmont Belt con-sist of numerous bodies of varying size and shape lying between the Central Piedmont Belt and the Blue Ridge, exclusive of the Mount Airy granite in northern Surry County. The granite in north-ern Stokes and eastern Surry Counties are largely porphyritic. The others are medium to fine grain-ed, with medium-grained rocks predominating. Most of these rocks may be classed as biotite granite, since biotite is common in all the outcrops. They are composed of orthoclase, plagioclase, quartz, biotite, a little muscovite, and minor ac-cessory minerals. They vary from massive gran-ite, showing no metamorphism, as in Stone Moun-tain, Wilkes County, to gneissic and schistose rock, where granites have been intruded into gneisses and schists. Outcrops are in the form of boulders and flat-surface exposures. Stone Mountain in northern Wilkes County, is a barren, granite monadnock, 500 to 600 feet high and measuring three to four miles in circumference at the base. The residuum in the various areas is similar in composition and color and equally as thick as that found in other granite regions of the State. The rocks of the Granite unit as a whole have intruded a wide variety of older rocks. As a result, many small bodies and lenses of these older rocks, chiefly in the form of gneisses, schists, and meta-morphosed volcanics, are included in the Granite unit. The rocks of this unit contain quartz veins, pegmatite dikes, and dikes of granite, quartz por-phry, aplite, diorite, gabbro, and diabase, which vary in amounts and sizes from place to place. Mineral deposits as such are not abundant in the Granite unit, but the granites of the unit are the basis of an important quarrying industry. Quar-ries too numerous to discuss here, but which have been described by Councill (1954) , are widespread throughout the unit and furnish a large produc-tion of dimension and crushed granite. Syenite (sy) The only discrete body of syenite in the State is a ring dike, approximately 22 miles in circum-ference, located in the west-central part of Cabar-rus County, LeGrand and Mundorff (1952). The outcrop of this syenite body varies in width from a few hundred feet at its southern limits to more than a mile along its western border, where it is crossed by Rocky River. The Syenite is more re-sistant to erosion than the surrounding rocks and stands out strongly in relief. The area of outcrop is generally marked by large boulders and pedistal rocks. The rock is an augite-syenite, composed largely of bluish-gray feldspar and augite. It is uniformly of coarse texture and massive in struc-ture showing no effects of metamorphism. The absence of a fine-grained matrix permits the sye-nite to disintegrate into a residual granular ma-terial that makes excellent road metal. Mount Airy Granite (mag) The name, Mount Airy Granite, is introduced by the writers for a body of granite approximately eight miles long and four miles wide, which is 22 located around Mount Airy in northeastern Surry County. Much of the granite in this area is deeply weathered and covered with a thick layer of resi-dumm. The most important outcrop is located one mile north of Mount Airy, where a body of fresh granite more than five thousand feet long occupies the crest of a prominent hill. The rock is a very light gray, nearly white, biotite granite of medium texture, composed of orthoclase, plagioclase, quartz, biotite, and minor amounts of apatite, zir-con, muscovite, chlorite, and epidote. On the basis of the feldspar content, it is best classed as a quartz monzonite. The rock contains no injurious minerals and is free of joints and the effects of metamorphism. Quarrying was started at Mount Airy in 1890 and has continued uninterrupted since that time. Over the years, the quality and attractiveness of the rock has made Mount Airy granite a popular building stone. The absence of joints and lack of metamorphism have made pos-sible the production of dimension stone of almost any desired size. The rock is used extensively for the construction of mausoleums, bridges, statues, and as architectural stone and curbing. Large amounts of crushed stone are produced also. Diorite-Gabbro (digb) Rock of the Diorite-gabbro unit are confined largely to the Central Piedmont Plateau, where they are associated with granites of the Central Piedmont Belt (the Carolina Igneous Belt), dis-cussed above. They are most abundant west of the Gold Hill fault and south of Forsyth and Yad-kin Counties, but a few small bodies are found in southeastern Guilford County, southern Caswell and Person Counties, and in the northeastern cor-ners of Person and Granville Counties. The rocks of this unit range locally from diorite to gabbro but, as a whole, are intermediate between true dio-rite and gabbro. Some rocks consisting of diorite and granite, diorite predominating, are included in the unit. Areas of relatively true diorite and gabbro have been designated on the map, but most of the rock is shown as Diorite-gabbro. Bodies of almost normal diorite occur in southeastern Guil-ford, southern Caswell, and Person Counties. Bodies of nearly normal gabbro are found in northeastern Granville and Person Counties, in-side the syenite ring dike in Cabarrus County, and from a short distance north of Barber south to Bear Poplar in Rowan County. The Diorite-gab-bro is a coarse-textured rock that is distinctly massive and not closely jointed. It is composed chiefly of hornblende or pyroxene, plagioclase, and varying amounts of quartz and accessory min-erals. In some places it is exposed as rounded boulders or flat outcrops that are not much weath-ered, but in most places it is deeply weathered, and covered with a thick layer of soil that is deep red or brown and relatively fertile. At sev-eral places, both on interstream areas and along valleys, shallow depressions resembling sinks in limestone are present. These appear to be the result of weathering and solution of the Diorite-gabbro. PALEOZOIC The four units in this group have been studied and described by Olson (1944) , Griffitts and Over-street (1952), Parker (1952), and Overstreet and Griffitts (1955) and classed as Paleozoic. These workers did not agree completely as to the position the units occupy in the Paleozoic, but they were in agreement in classing them as Paleozoic in age. Two of these, Toluca quartz monzonite and Cherryville quartz monzonite, consist in part of Whiteside granite as mapped by Keith and Sterrett (1931). ToSuca Quartz Monzonite (tqm) Toluca quartz monzonite consists of numerous bodies of varying shape and size, occupying a belt extending across central and western Cleveland County, western Lincoln County, and into southern Burke County. It was named by Griffitts and Overstreet (1952) for the town of Toluca in the western edge of Lincoln County. Individual bod-ies vary from a few inches to several thousand feet thick and from a few feet to ten miles long. In general, these are parallel to the foliation of the mica gneiss into which they were intruded but occasionally cross it. Outcrops are not abundant as the rock is deeply weathered and underlies broad areas of light-gray soil. Toluca quartz monzonite is typically a medium gray, moderately gneissic rock. Usually, the smaller bodies are more strongly foliated than the larger, which, while gneissic throughout, are more strongly fol-iated near the margins. Chief minerals are oligo-clase, microcline, orthoclase, quartz, and biotite. Minor amounts of garnet and muscovite and small amounts of apatite, zircon, ilmenite, and monazite are present. The rock is characterized by a wide variation in texture and composition. The texture 23 is everywhere gneissic, but the size, shape, and arrangement of the grains vary widely. Monazite-bearing pegmatites genetically associ-ated with the quartz monzonite inject it and occur parallel to the foliation of the surrounding gneiss. These dikes vary from a few inches to several feet in thickness and often attain lengths of several iiundred feet. Overstreet and Griffitts (1955, p. 556) classed the Toluca quartz monzonite as early Ordovician in age. Cherryville Quartz Monzonite (cqm) Cherryville quartz monzonite occupies a broad belt across eastern Cleveland, western Gaston, and central Lincoln Counties. The unit was named by Griffitts and Overstreet (1952) for Cherryville, Gaston County. Outcrops are not abundant as the rock underlies thick layers of light-gray soil. South of Cherryville, the belt is parallel to the structure of the older rocks, but north of Cherry-ville, it bends eastward and crosses the structures of the older rocks. The Cherryville quartz mon-zonite contains many inclusions of country rock. It is essentially a gray, even-grained, massive to slightly gneissic rock, consisting chiefly of two varieties, one containing muscovite and biotite and the other containing muscovite but no biotite. It is, in general, a medium-grained rock, composed of oligoclase, microcline, quartz, muscovite, and biotite, with minor amounts of zircon, ilmenite, and apatite. Overstreet and Griffitts (1955, p. 556) classed the Cherryville quartz monzonite as probably Devonian in age. Two major varieties of pegmatite dikes, spod-umene- bearing and mica-bearing, are related to the Cherryville quartz monzonite. Spodumene-bearing pegmatites are restricted to the tin-spod-umene belt that lies along the east side of the Cherryville quartz monzonite bodies. These dikes are most commonly in gneiss, but some extend into the quartz monzonite bodies. These dikes vary from zoned and nongneissic, north of Kings Moun-tain, to gneissic and nonzoned, south of Kings Mountain. Mica-bearing pegmatites that are well zoned occur in the northern part of the Lincolnton and Shelby quadrangles. These form dikes that cross the foliation of the enclosing gneiss and also the Toluca quarts monzonite. Whiteside Granite (wg) The Whiteside granite unit on the present map is essentially Whiteside granite as originally nam- 24 ed and described by Keith (1907b) . It was named for the cliffs of Whiteside Mountain, Jackson County, where it is well developed. On the pres-ent map, it is shown as several areas of varying sizes and shapes, along the southern boundary of the State in Henderson, Transylvania, and Macon Counties. The granite is a light-gray, even-grain-ed, massive rock, composed of orthoclase, plagio-clase, quartz, muscovite, biotite, and minor amounts of magnetite, ilmenite, and garnet. Bio-tite varies in amount and is often absent. The granite was injected into older rocks, parallel to their foliation, and often contains inclusions of gneiss and schist. Two varieties were described by Keith. One is fine to medium grained and massive, the other contains a decided flow banding. Outcrops vary with topography, and much of the granite is covered with thick layers of light red to yellowish soil mixed with sand. ABaskite (a!) The Alaskite unit consists essentially of a coarse-grained pegmatitic granite that crops out near Spruce Pine, Mitchell County, as a number of bodies varying greatly in size and shape. The rock, which has been of interest to miners in the Spruce Pine district for several years, was desig-nated by Hunter (1940) as alaskite. It consists essentially of oligoclase, quartz, microcline, and muscovite, listed in the order of abundance. Dark-colored minerals are almost absent, but small amounts of biotite and garnet occur at places near inclusions or contacts with country rock and are apparently products of contamination. The rock is not true alaskite, but the name is so well estab-lished in the Spruce Pine district that it is used here. The alaskite masses are granitoid in tex-ture and uniform in grain size and mineral con-tent. Much of the rock is sufficiently coarse-grained to be called pegmatite, but its uniformity and wide extent make the name Alaskite appro-priate. The alaskite bodies contain many inclu-sions of gneiss and schist near their margins, but internally they are relatively free of such. Alas-kite bodies containing inclusions of gneiss and schist often grade into gneiss and schist, contain-ing numerous bands and lenses of alaskite. Most inclusions, as well as alaskite bands and lenses, are parallel to one another and to the foliation of the country rock. Pegmatites occur in all parts of the alaskite, but the average size and number is greater near the margins of the alaskite bodies. The pegmatites in alaskite and in the surrounding gneisses and schists are important sources of mica, feldspar, kaolin, and other minerals, for the production of which the Spruce Pine district is widely recogniz-ed. Sheet mica is obtained almost exclusively from pegmatites. For many years, feldspar and kaolin were produced from fresh and weathered pegmatites. As the demands for these minerals increased, attention was directed to alaskite, and it is now the chief source of feldspar, kaolin, and flake, or scrap, mica. Large bodies of unaltered alaskite serve as a source of feldspar by flotation. In many places, the alaskite is deeply weathered, often to depths approximating a hundred feet. Many of these weathered deposits are rich in kaolin and contains considerable flake mica. Most of the kaolin and a large part of the flake mica produced in the State are being obtained from weathered alaskite. Economically, Alaskite is one of the most important rock units shown on the present map. TRSASSICC?) Two units, Bakersville gabbro and Diabase dikes, are shown as Triassic(?) on the present map. Diabase dikes have been considered of pos-sible Triassic age for many years and probably should be classed as Triassic without the query; however, there is some question as to the exact age of the Bakersville gabbro. Keith (1903) first named this unit and described it in the text as Juratrias(?) but showed it in the legend on the geologic map as Juratrias without the query. The unit has received considerable attention in recent years, but its exact age is still in doubt. Kulp and Brobst (unpublished) showed Bakersville gabbro on an unpublished geologic map of the Spruce Pine district as Devonian. Brobst (1955, pp. 584- 585) described the unit briefly and pointed out that it is considered younger than the alaskite and pegmatites. As to age, he stated, "The Bakersville might have been emplaced between the late Ordo-vician .or early Silurian and the Triassic." The Committee on Geologic Names of the U. S. Geo-logical Survey recommends Triassic (?) for the Bakersville gabbro, and it is so shown on the present map. Bakersville Gabbro ("Rg) Bakersville gabbro outcrops are shown on the map near Bakersville, Mitchell County, and south and west of Elk Park and Cranberry, Avery County. The major outcrop near Bakersville is roughly triangular in shape, with a maximum length of five miles and a maximum width near the base of the triangle of about three miles. The outcrop near Elk Park and Cranberry is about two miles long and one mile wide. A number of out-crops too small to be shown on the map are found in the general area. Keith (1903) named the unit for Bakersville, Mitchell County, and described it briefly. It is a dense, hard, unmetamorphosed rock, nearly black when fresh but becoming red-dish brown on weathering. It is composed chiefly of plagioclase, hornblende, and pyroxene in crys-tals of medium size, with small amounts of mag-netite, epidote, and garnet as accessory minerals. The texture is usually massive and granular but occasionally becomes aplitic. Outcrops consist of spheroidal masses and boulders mixed in a dark-brown clay. Diabase Dikes (lid) Diabase dikes of probable Triassic are widely distributed throughout the Piedmont and Moun-tain regions of North Carolina. They are most abundant in and adjacent to sedimentary rocks of Triassic age along the eastern and central Pied-mont region, but become less common in the west-ern Piedmont and are found sparingly in the Blue Ridge region. They also occur frequently along the western edge of the Coastal Plain where pre- Triassic rocks are not covered by younger sedi-ments. Because of the wide distribution and limited area of outcrop, Diabase dikes are shown in only two localities on the map. One of these is the Deep River basin in Chatham, Lee, and Moore Counties, and the other is an unusually long dike northeast of Morganton, Burke County. In the Deep River basin, according to Reinemund (1955), who gave an excellent description of the diabase intrusives in that basin, dikes, sills, and sill-like masses occupy about four percent of the Triassic rocks. Diabase dikes in the Deep River basin vary in width from less than an inch to 320 feet and in length from a few feet to nearly seven miles. Most dikes in the area are between 20 and 75 feet wide and are fairly constant in width for several thousand feet of length. Sills and sill-like intrusives of diabase are abundant in the Deep River basin Triassic sediments and range in thick-ness up to 400 feet. In the Morganton area, an unusual diabase dike extends in a northwest-south-east direction with minor interruptions for nearly twenty miles. 25 The diabase intrusives are massive, crystal-line, unmetamorphosed rock that varies in color from dark gray, grayish black to nearly black. The minerals and textures present are those commonly found in normal diabase, except some of the larger sills which more nearly ap-proach gabbro in composition. In general, the dikes form low ridges and divides, but in the Deep River basin, they are an important influence on drainage patterns. The direction of flow of sev-eral streams in the area is determined in part by the trends of the dikes. Many springs occur along these dikes, and it has been learned from experience that water-well sites located near dikes are more likely to furnish good yields. Outcrops are common in the form of boulders, which were produced by spheroidal weathering along the joints in the rock. Two types of soil, one a brown or grayish-brown, silty loam and the other a dark red to brownish-red heavy clay loam, occur over areas of diabase. Both soil types are underlain with yellow to dark red, sticky clays. METAVOLCANIC ROCKS Metavolcanic rocks occur in three distinct geo-graphic areas in North Carolina. First and most important is the Carolina Slate Belt which actually consists of two belts, one lying across the central part of the State, and the other lying along the eastern edge of the Piedmont Plateau and western edge of the Coastal Plain. Second is the Grand-father Mountain Window, which lies partly in the Blue Ridge area and partly in the Piedmont Pla-teau in Avery, Watauga, Caldwell, Burke, and Mc- Dowell Counties. Third is a relatively small area known as the Mount Rogers volcanic group which lies in the northwestern corner of Ashe County. PRECAMBRIAN OR LOWER PALEOZOICt?) CAROLINA SLATE BELT Rocks of the Carolina Slate Belt, because of their complex character and well defined cleavage, have been called slates. Actually, they consist of volcanic-sedimentary formations, composed of slates, breccias, tuffs, and flows. The flows are interbedded with the breccias and tuffs, while the tuffs pass gradationally into slates. These rocks vary from acid or rhyolitic to basic or andesitic in composition and generally have a well developed cleavage, which gives them a slaty appearance. Rocks of the Carolina Slate Belt series actually form two belts in the State. The first and most important of these, and the one which Olmstead (1825) first called the Great Slate Formation, crosses the central part of the State in a northeast direction from Anson and Union Counties on the south to Granville and Person Counties on the north. This belt varies in width from 25 to 60 miles and consists of metavolcanic rocks intruded at many places by younger granites, described above. The second belt, in which metavolcanic rocks are exposed as irregular bodies of varying size and shape, lies along the eastern edge of the Piedmont Plateau and western edge of the Coastal Plain. This belt, in which Kerr (1875, p. 131) first recognized rocks similar to those of the Great Slate Formation of Olmstead, begins in Richmond County on the south, varies greatly in width, and continues in a northeast direction to Northampton County on the north. Olmstead (1825), Emmons (1856), and Kerr (1875) considered the rocks of the slate belt as sedimentary in origin but described them as slates, containing beds of porphyry, hone or whetstone slate, breccia, and conglomerate. Emmons (1856) placed the rocks in the Taconic System, while Kerr (1875) classed them as Huronian in age, which, according to his geologic column, is a division of the Archean. Williams (1894) recognized for the first time the presence of volcanic rocks in the slates. He described exposures of volcanic flows, breccias, and tuffs, which had been sheared into slates by dynamic metamorphism. Nitze and Hanna (1896) recognized volcanic rocks in the slate belt and considered the Bedded argillites (volcanic slate) of the present map as younger than the volcanics and called them Monroe slates. It is now recognized that the Monroe slates repre-sent a better bedded, less metamorphosed portion of the slate-belt rocks. Following the work of Williams (1894) , reports by Laney (1910 and 1917), Pogue (1910), and Stuckey (1928) emphasized the importance of volcanic rocks in the slate belt but did not over-look entirely the presence of sedimentary material. These authors considered the rocks of the slate belt to be largely of volcanic derivation but recog-nized the presence of considerable sedimentary (nonvolcanic) material and classed the whole se-ries as laid down by sedimentary processes. Mapping carried out for the compilation of the present map tended to verify the above findings. Rocks which may be classed as flows, breccias, 26 tuffs, and shales or slates were found to be present. All of these, except flows, contain considerable amounts of nonvolcanic materials. The flows, breccias, tuffs, and slates are all interbedded and do not occupy any definite stratigraphic positions in the series. The flows vary from rhyolite, through andesite, to basalt. The rhyolites and andesites vary from fine grained to coarsely por-phyritic, while the basalts are often amygdaloidal. The breccias vary from rhyolitic to andesitic in composition and in size from an inch to nearly a foot in diameter. The fragments of the breccias are, in turn, fragmental, apparently of a pyro-clastic origin. Some of the fragments in the breccias are sharply angular, while many are rounded, indicating transportation and deposition. The tuffs are generally of acid composition and composed of fragments less than an inch in diam-eter. These fragments, which vary from angular to rounded, are embedded in much fine-grained material apparently of nonvolcanic origin. Be-ginning at Siler City, Chatham County, and con-tinuing southwest for 15 to 20 miles are several beds of quartz conglomerate, varying in width from a few inches to 250 feet and of unknown length. The quartz pebbles are less than an inch in diameter and well rounded, further indicating sedimentary processes. The shales or slates, which are generally well bedded, are composed of fine-grained volcanic material and much land waste. Finally, much of the finer material in the breccias, tuffs, and portions of the shales or slates strongly resembles metasiltstone and metagraywacke of some of the metagraywacke rocks in other areas, further indicating sedimentary origin. In view of the above facts, there is a strong trend on the part of some workers to drop the term metavolcanic and use one that defines the rock more nearly as sediments. That idea was considered for the present map but was discarded in favor of metavolcanics, since the rocks of the slate belt are largely of volcanic origin, and the terminology has been in the literature for more than sixty years. No fossils have been discovered in the slate belt, and the age of the rocks is not known. For many years they were classed as Precambrian, while in recent years there has been a trend towards classing them as lower Paleozoic. On the present map, they are classed as Precambrian or Lower Paleozoic (?). They have been divided into three units, Felsic volcanics, Mafic volcanics, and Bed-ded argillites (volcanic slate). Felsic Volcanics (fvs) Rocks of the Felsic volcanics unit occupy about half of the Carolina Slate Belt in the central part of the State and are the only rocks shown in that portion of the belt lying along the eastern part of the Piedmont Plateau and western part of the Coastal Plain. In the central part of the State, rocks of the Felsic volcanics unit occupy much of the eastern part of the Carolina Slate Belt north-east of Anson, Richmond, and Stanly Counties. The rocks of the Felsic volcanics unit are com-posed largely of materials of volcanic flow or frag-mental origin. The flows are essentially rhyolite, while the fragmental materials vary from rhyo-litic to dacitic in composition. The fragmental rocks consist of breccia and coarse and fine tuff, with coarse and fine tuff making up the greater portion of the unit. Lenses of bedded slate and mafic volcanics, too small to show on the map, are present in this unit. The rhyolite occurs as narrow bands and lenses interbedded with the breccia and tuff. It is dense and indistinctly porphyritic with a dark gray to bluish color, and, on fresh surfaces, shows a greasy luster. Flow lines are often present and are best seen on weathered surfaces, while amygdaloidal structure is also present. In porphyritic speci-mens the minerals are plagioclase, orthoclase, and quartz. None of the rhyolite outcrops show any effects of metamorphism. The fragmental rocks consist of breccia and coarse and fine tuff. The coarse tuff predominates and contains the breccia and fine tuff as interbed-ded bands and lenses. The fragments composing these rocks are angular to well rounded and vary in size from nearly a foot to a fraction of an inch in diameter. The larger fragments are internally fragmental, while the finer material grades into Bedded argillites (volcanic slate) . At places, within a few inches, fine fragmental rock grades into a rock showing bedding planes. When freshly broken, the rock proves to be made up of quartz and feldspar grains and rock fragments, some of which show a flow structure, set in a dense bluish or greenish groundmass. In general, the rocks of this unit have a light gray to greenish color. In the central part of the State, the rocks of the Felsic volcanics unit vary from massive to schistose. At places, the fragmental texture of the rock may be seen, but much of the rock has been strongly metamorphosed and possesses a well denned slaty cleavage that strikes northeast- 27 southwest and dips to the northwest in the south-ern part of the area and to the southeast in the northern part. The felsic volcanics weather to a light gray soil usually underlain by yellow to light-red clay. The layer of soil and clay is usually thick, and outcrops of fresh rock are not abund-ant. Along the eastern part of the Piedmont Plateau and western edge of the Coastal Plain, all the raetavolcanics of the Carolina Slate Belt are shown as the Felsic volcanics unit on the present map. The rocks are deeply weathered and covered by a thick layer of soil. As a result, outcrops of fresh rock are scarce, and mapping is difficult. Mun-dorff (1946) showed these rocks on the legend of his map as Slates, schists, and metamorphosed volcanics. He considered the series as metamor-phosed sedimentary and igneous rocks, including lavas, tuffs, and breccias. He did not mention rhyolite or rocks of a mafic character but did refer to a coarse breccia near Roanoke Rapids. In the course of fieldwork for the present map no rhyo-lite was seen, but small amounts of breccia and in one or two places small outcrops of mafic volcanics too small to show on the present map, were ob-served. In general, the rocks of this area consist of coarse to fine tuff and bedded slate, with which bodies of gneiss and schist are present in many places. The tuffs and bedded slates are present throughout the area in about equal amounts. In some places, bedded slate predominates, and in others tuffs predominate. These rocks are usually altered near igneous intrusions to garnetiferous mica schist, mica hornblende schist, or biotite schist. Some bodies of gneiss and schist not ap-parently related to igneous intrusives are present and probably represent metamorphosed nonvol-canic sediments. Six miles west of Smithfield, Johnston County, on the east side of U. S. High-way 70, is a large outcrop that resembles quartzite and contains kyanite crystals. It may be siliceous sediment metamorphosed to quartzite, or it may be a silicified tuff. Similar outcrops, except for the kyanite, are found north of Princeton in the eastern part of Johnston County. The bedded slates are dark blue to greenish gray when fresh and become various shades of yellow and red when weathered, while the tuffs, gneisses, and schists are generally gray, yellow, or brown. All these rocks have been moderately metamorphosed and contain a cleavage that strikes northeast and stands nearly vertical. Mafic Volcanics (mvs) Rocks of the Mafic volcanics unit are shown on the present map only in the northern two-thirds of Carolina Slate Belt in the central part of the State. They are scattered throughout the area but are more abundant along the western side. The rocks of this unit consist largely of flows and fragmental materials of volcanic origin. The flows vary from andesite to basalt, while the frag-mentals are generally andesitic in composition. Lenses of bedded slate and felsic volcanics, too small to show on the map, are present in this unit. The andesite and basalt occur as narrow bands and lenses interbedded with the fragmentals. The andesite is dark green in color, usually massive or fine grained, but occasionally coarsely porphyritic. A coarse porphyritic variety, with hornblende crystals up to two inches long, occurs in western Randolph County. The basalt is dark to nearly black and often amygdaloidal. Both the andesite and basalt are characterized by the lack of a well defined cleavage. Minerals present consist of epidote, plagioclase, quartz, secondary calcite, and iron oxides. Epidote is the most abundant min-eral present, giving the rock its green color. The fragmentals consist of breccias and tuffs of andesitic composition, often intermixed with much fine-grained material. In places these rocks are fine grained and lack the fragmental appearance. In such areas, one of which may be seen along U. S. Highway 64 for a mile west of Haw River, the rock strongly resembles a graywacke. The breccias and tuffs contain much epidote and often have a greenish color. Other colors vary from dark gray to nearly black. In addition to epidote, plagioclase, and quartz, secondary calcite and iron oxides are present. The mafic fragmentals are not as strongly metamorphosed as the felsic frag-mentals but contain a cleavage that strikes north-east and dips to the northwest in the southern part of the area and to the southeast in the northern part. These rocks are usually covered with a thick layer of dark-red residuum. Bedded Argillifes (Volcanic Slate) (ar) Bedded argillites (volcanic slate), commonly re-ferred to as slate, bedded slate, or volcanic slate, occur in the southern part of the Carolina Slate Belt in the central part of the State and extend north as far as the central part of Davidson and Randolph Counties. A few small areas are shown on the east side of the belt in Montgomery, Moore, 28 and Chatham Counties. There are also some small areas east of the Jonesboro fault in Anson and Richmond Counties. The unit as shown on the map is chiefly bedded argillites or bedded slate, but many lenses of felsic and mafic volcanics, too small to show on the map, are included. The Bedded argillites (volcanic slate) consist chiefly of dark-colored or bluish shales or slates, which are usually massive and thick bedded. However, the beds occasionally show very .finely marked bedding planes. Contacts between the slates and the tuffs are usually grada-tional, and often a single hand specimen will show gradation from a bedded slate to a fine-grained tuff. Much of the slate is massive and jointed, showing little effects of metamorphism, while in other places it has been strongly metamorphosed and shows a well defined, slaty cleavage. The cleavage, or schistosity, does not in most places correspond to the bedding planes of the rock. In places, especially near igneous intrusive and min-eralized zones, the slate is highly silicified and often resembles a chert. The slates are deeply weathered, and good outcrops of fresh rock are seldom seen. In general, they are covered with a thick layer of residuum, which consists of light soil on top and yellowish, decomposed slate be-neath. The rocks of the Carolina Slate Belt have fur-nished mineral resources of considerable impor-tance for many years. Between 1800 and 1860, the slate belt produced important amounts of gold. Gold mining is no longer important, but many quartz veins in the area contain varying amounts of silver, lead, zinc, and copper. The production of these metals has never been large, but the veins continue to attract the attention of individuals and mining companies. Important deposits of pyrophyllite occur in Moore, Randolph, Alamance, Orange, and Granville Counties, from which large amounts of pyrophyllite are being mined. The Bedded argillites (volcanic slate) are deeply weathered in many places to clay and shale, suitable for the manufacture of clay prod-ucts. Brick and tile are being produced in large amounts from these materials. Lightweight ag-gregate is being produced in Stanly County from semiweathered slate. Rocks of the Carolina Slate Belt were first used for building purposes at Hills-boro in colonial days. More recently, both felsic and mafic volcanics were quarried near Hillsboro and used in the construction of the buildings on the West Campus of Duke University. Bedded slate is being quarried in southern Davidson County and southern Montgomery County and used as building stone and flagstone. When fresh and unweathered, the bedded slate makes an ex-cellent crushed stone, and large amounts are be-ing produced. Upper Precambrian grandfather mountain window The Grandfather Mountain window area is nearly surrounded by the Grandfather Mountain fault and lies partly in the Blue Ridge and partly in the Piedmont Plateau in Avery, Watauga, Cald-well, Burke, and McDowell Counties. Keith (1903) mapped and described four units in that area, as follows : Linville metadiabase, Montezuma schist, Flattop schist, and Metarhyolite. His names and descriptions have been retained on the present map. Linville Metadiabase (Imd) Linville metadiabase occurs as irregular out-crops associated with Montezuma schist, Flattop schist, Cambrian quartzite, and as narrow bands in Cranberry granite gneiss. It occurs as flows, which came up through cracks in older rocks, such as those now filled with metadiabase in the Cran-berry granite. The metadiabase contains plagio-clase, largely altered to epidote, chlorite, and quartz. Other original minerals, olivine and augite, are largely replaced by hornblende, epidote, and chlorite. Epidote sometimes occurs as grains and masses as much as six inches in diameter. The rock has been much metamorphosed, but at places its original character is retained. It is generally of a dull-yellowish color, due to epidote, chlorite, and hornblende. The metadiabase weathers read-ily and usually is covered by a thick layer of dark-red and brown clay. Montezuma Schist (mtsh) The Montezuma schist consists of fine-grained epidotic and chloritic schists and amygdaloidal beds and is rather uniform in appearance. Orig-inally it was probably a basalt, but it has been so completely metamorphosed that only a few traces of flow banding remain. Amygdaloidal beds are the commonest evidence of its original nature. The color of the rock when fresh is bluish black, gray, or green, becoming more green and yellowish green on weathering. The chief min- 29 erals are chlorite and feldspar in abundance and muscovite, epidote, and quartz in small amounts. The schists weather slowly and usually form high ledges and cliffs, while the amygdaloidal beds weather more readily and are covered with thick clay of yellow or red color. Flattop Schist (fsh) This unit, named for Flattop Mountain, Watau-ga County, consists of black, dark-blue, bluish-green, and greenish-gray schists, which weather to a yellow or greenish-gray color. The schist is commonly banded. The bands, which are seldom more than half an inch thick, consist of quartz and feldspar grains of varying size, and the rock strongly resembles a sandy slate of sedimentary origin. Where not banded, the schist contains pyrophyritic crystals of feldspar and amygdules, indicating that it is volcanic in origin. Originally, the rock was probably a lava flow, but it has been strongly metamorphosed, and most of the original minerals have been replaced by secondary quartz, feldspar, and mica. The Flattop schist resists decay and forms ridges and mountains. Final decay produces a reddish, sandy clay. Metarhyolite (mry) This unit consists mainly of fine metarhyolite but occasionally contains layers which show por-phyritic crystals of feldspar and quartz. When fresh, the rock is dark blue, dark gray, and bluish black; but, when weathered, it becomes dull yel-low and yellowish gray. It occurs as intrusive sheets and dikes in older rocks and as surface flows. The unit has been greatly metamorphosed, but flow banding and amygdules are occasionally poorly preserved. The rocks of this unit vary from rhyolite, little altered, to a well defined schist, depending on the original nature of the rocks and the amount of metamorphism. These rocks weather slowly, but final decay produces a thin layer of fine yellow and red clay. MOUNT ROGERS VOLCANIC GROUP (mr) The Mount Rogers volcanic group, named by Stose and Stose (1944, pp. 410-411) for Mount Rogers, the highest point in Virginia, underlies a small area in the northwest corner of Ashe County, North Carolina, adjacent to Tennessee and Virginia. Jonas and Stose (1939, pp. 590- 591) and Rogers (1953, p. 23) have summarized very well the characteristics of the group. The 30 unit consists of purplish and greenish metavol-canic rocks, chiefy metarhyolite, but apparently contains tuffs as well as flows. The rock has been strongly metamorphosed and possesses a slaty cleavage. Some of it is good slate; but, despite the foliation, much of the rock forms massive ledges and blocks. The foliation of the more mas-sive rock is interrupted by small, irregular masses of quartz, while the slaty rock commonly contains small, very thin lenses of chlorite and epidote. Interbedded with the volcanic rocks are layers of conglomerate, graywacke, and nonvolcanic silty shale or slate. The rocks of the group often crop out in large masses, and at places in Tennessee and Virginia, they form high, rough mountains. They weather to a thin, very strong, light soil. METASEDIMENTARY ROCKS Rocks more or less metamorphosed but retaining enough of their original characteristics to indicate that they were originally sediments are classed as metasedimentary rocks on the present map. They occur in four areas, commonly known as the Kings Mountain area, the Stokes County area, the Brevard area, and the Murphy area. The rocks in the Stokes County area and the Kings Mountain area appear to be much alike and stratigraphically equivalent. On the present map, these two areas are classed as the Stokes County and Kings Moun-tain Belt, while the other two are classed as the Brevard Belt and the Murphy Belt. The ages of the rocks in these three belts are not definitely known, but it is assumed that their position in the explanation is essentially correct. Upper precambrian(?) or lower paleozoic?) stokes county and kings mountain belt Kings Mountain Group (kmg) The rocks of this unit fall into two natural groups, one of which consists of highly siliceous rock, while the other consists largely of calcareous rock. The siliceous group consists in the Kings Mountain part of the belt, of slate, rhyolite, vol-canics, quartzite, and conglomerate, and, in the Stokes County part of the belt, of mica schist, quartz mica schist, and quartzite. In the Kings Mountain area, the slates and phyllites are essen-tially sericitic schist. Pyroclastic textures are not abundant but are common enough to indicate that volcanics make up an important part of the group. Quartzite and conglomerate are present in beds that crop out prominently at many places. In the Stokes County area, the chief rocks are quartzite, mica schist, and quartz mica schist, apparently interbedded. At a few places in the Stokes County area is found a flexible sandstone, consisting of fine, interlocking quartz grains and mica flakes. Throughout the Stokes County and Kings Moun-tain Belt, the siliceous rocks form the higher ele-vations and prominent ridges, often called moun-tains. The calcareous group is confined largely to the Kings Mountain part of the belt and consists of crystalline limestone, dolomite, and calcareous metashales. In the southern part of Catawba County and the northern part of Lincoln County, interesting amounts of hornblende gneiss are found, apparently interbedded with quartzite, that probably represent metamorphosed calcareous shales. One important body of crystalline lime-stone occurs near Siloam, Yadkin County, in the Stokes County part of the belt. Other limestone bodies, mentioned above, occur in mica gneiss along the southern border of the belt in Yadkin and Stokes Counties, that may or may not belong in this group. The limestone and dolomite of the belt have been quarried intermittently for years, and a large quarry is in operation near Kings Mountain. The quartzite in the Kings Mountain part of the belt contains interesting amounts of kyanite, but it has not been mined in North Carolina. LOWER CAMBRIAN(?) BREVARD BELT Brevard Schist (bv) The Brevard Belt begins in North Carolina at the state line, southwest of Brevard, for which it was named by Keith (1907b), crosses Transyl-vania, Henderson, and Buncombe Counties, and ends in McDowell County, a short distance north-west of Old Fort. The Brevard schist, the only unit in this belt, consists mainly of schist and slate. Schist, which predominates, is of a dark-bluish- black, bluish-black, black, or dark-gray color. Lenses of limestone, varying from a few hundred feet to more than a mile in length and up to 250 feet in thickness, are scattered widely throughout the belt. Thin layers of quartzite and conglomerate are occasionally found. Graphite is widely disseminated as small flakes through large masses of the rock and occasionally forms lenses that are graphite schist. The schists are composed of quartz and muscovite, through which are scat-tered numerous small grains of iron oxides, while garnets are occasionally found. The slates are essentially clay slates. The rocks are all essen-tially fine grained except for occasional layers of quartzite and conglomerate. Some years ago graphite was produced from the northern part of the belt, west of Old Fort but none has been mined in recent years. Considerable amounts of crystalline limestone have been pro-duced for lime, agricultural lime, and aggregate near Fletcher, Henderson County. At the present time, crushed stone for aggregate is the chief ma-terial being produced. Near Etowah, Henderson County, a clay slate weathered to a shale is being used for the manufacture of brick. MURPHY BELT Rocks of the Murphy belt occur in the southwest corner of the State, where Keith (1907a) mapped a synclinal structure and named the following formations: Tusquitee quartzite, Brasstown schist, Valleytown formation, Murphy marble, An-drews schist, and Nottely quartzite. The Tusqui-tee quartzite and Nottely quartzite could not be shown on the present map due to the limited area each covers. They are much alike and consist essentially of v/hite quartzite. On the present map the Brasstown schist and Valleytown formation are shown as separate units, while the Murphy marble and Andrews schist are combined as one unit due to the limited area each covers. Brasstown Schist (bt) The Brasstown schist consists of schists and slates more or less banded. The greater part of the formation consists of banded ottrelite schist, but some of it is banded slate with little or no ottrelite. All the rocks are dark colored and vary from dark blue or bluish black to dark gray. They are usually marked by a fine banding of light and dark-gray colors. The light layers are often sili-ceous and sometimes grade through sandy slate into sandstone. The slates are argillaceous, while the schists are more siliceous. The most outstand-ing mineral is ottrelite of dull-bluish or greenish-gray color, but varying amounts of garnet and staurolite are present at many places. The rocks 31 weather to thin, yellow and brown clay soils of poor fertility. Valleyfrown Formation (vfr) The rocks of the Valleytown formation vary widely from place to place but consist mainly of mica schist and fine-banded gneiss. However, in many areas, mica slate, argillaceous slate, gray-wacke, feldspathic sandstone, and occasionally beds of coarse quartzite are present. These rocks are usually dark colored, varying from dark gray to grayish black. In most of the rocks the min-erals that can be identified in hand specimens are quartz and mica in the mica schist and feldspar and quartz in the feldspathic sandstone ; however, bands of ottrelite schist and garnet schist are often present. The rocks of this unit are resistant to weathering and stand up as knobs and ridges. Final decay produces a thin soil, full of rock frag-ments, which is of little value. Andrews schist—Murphy Marble (ma) Because of limited areal extent, the Murphy marble and Andrews schist have been combined into one unit on the present map. The Murphy marble is found in two areas, one along the Nan-tahala and Valley Rivers in Swain and Cherokee Counties, and the other along Peachtree and Little Brasstown Creeks in Cherokee County. The rock consists entirely of marble, rather fine grained but completely crystalline. The predominant color is white, but a large part of the marble is dark gray or blue, and many layers consists of banded or mottled blue and white. In the Red Marble Gap some of the layers have a rose-pink color. Van Horn (1948 pp. 12-13) established a zoning or stratigraphic sequence in the marble, based on color and secondary minerals. The Murphy mar-ble passes by gradation into the Andrews schist and often contains bands of schist. Other than crystals of calcite and dolomite, the marble con-tains mica, quartz, garnet, and ottrelite along gradational zones and talc and tremolite at many places. Much of the marble underlies low ground and is covered with stream deposits of sand and gravel. The Andrews schist consists essentially of thin beds of calcareous schist of relatively light-gray color. It is characterized by a large number of ottrelite cyrstals, which lie at right angles to the bedding. Muscovite and biotite occur frequently, lie parallel to the bedding, and are the chief cause of the schistose planes in the rock. The Andrews schist weathers readily and usually underlies low ground. It is usually covered wit ha residual, micaceous clay, that grades downward into fresh rock. The Murphy marble is an attractive rock, and over the years considerable dimension and crushed stone have been produced from it. Building, mon-umental, and crushed stone are being produced near Marble, Cherokee County, and crushed aggre-gate and agricultural limestone are being produced near Hewitts, Swain County. A white, fine-grain-ed dolomite, occupying the approximate center of the marble, often contains deposits of high-grade talc. This talc has been mined for years and is presently being produced about one mile south-west of Murphy. Iron ore in the form of limonite occurs at many places, usually associated with the Andrews schist. Production was carried on for many years with maximum development and min-ing taking place between 1917 and 1920. No pro-duction has been made since 1921. SEDIMENTARY ROCKS Upper precambrian OCOEE SERIES Along the western boundary of the State, in Cherokee, Graham, Swain, Haywood, and Madi-son Counties and smaller areas in Clay, Jackson, and Mitchell Counties, occurs a thick sequence of clastic, nonfossiliferous sedimentary rocks. These rocks were named the Ocoee conglomerate and slates by Safford (1856) from the exposures along the Ocoee River between Parksville and Ducktown, Tennessee. Keith (1895, 1896, 1904, and 1907c) mapped and named a number of forma-tions within the series ; however, his formations differed considerably from one folio to another. Rodgers (1953), in his compilation of a geologic map of East Tennesse
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Title | Explanatory text for geologic map of North Carolina |
Creator |
Stuckey, Jasper L. (Jasper Leonidas), 1891-1979. |
Contributor |
Conrad, Stephen G. North Carolina. Division of Mineral Resources. |
Date | 1958 |
Subjects | Geology--North Carolina--Maps |
Place |
North Carolina, United States |
Time Period |
(1954-1971) Civil Rights era (1945-1989) Post War/Cold War period |
Publisher | North Carolina, Dept. of Conservation and Development, Division of Mineral Resources |
Agency-Current |
North Carolina Department of Environmental Quality |
Rights | State Document see http://digital.ncdcr.gov/u?/p249901coll22,63754 |
Physical Characteristics | 51 p. : map ; 28 cm. 1 folded map in pocket. |
Collection | North Carolina State Documents Collection. State Library of North Carolina |
Type | text |
Language | English |
Format | Bulletins |
Digital Characteristics-A | 3956 KB; 60 p. |
Series | Bulletin (North Carolina. Division of Mineral Resources) ; no. 71. |
Serial Title | North Carolina Geological Survey bulletin |
Digital Collection | North Carolina Digital State Documents Collection |
Digital Format | application/pdf |
Audience | All |
Pres File Name-M | pubs_geology_explanatorytextgeologic1958.pdf |
Pres Local File Path-M | \Preservation_content\StatePubs\pubs_geology\images_master\ |
Full Text | North Carolina State Library ( f t jleigh NORTH CAROLINA DEPARTMENT OF CONSERVATION AND DEVELOPMENT William P. Saunders, Director fo _ %* DIVISION OF MINERAL RESOURCES Jasper L. Stuckey, State Geologist BULLETIN NUMBER 71 EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad RALEIGH 1958 Norffe Carolir* St** NORTH CAROLINA DEPARTMENT OF CONSERVATION AND DEVELOPMENT William P. Saunders, Director DIVISION OF MINERAL RESOURCES Jasper L. Stuckey, State Geologist BULLETIN NUMBER 71 EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad RALEIGH 1958 MEMBERS OF THE BOARD OF CONSERVATION AND DEVELOPMENT GOVERNOR LUTHER H. HODGES, Chairman Raleigh MILES J. SMITH, First Vice Chairman Salisbury WALTER J. DAMTOFT, Second Vice Chairman Canton CHARLES S. ALLEN ..__„___ Durham W. B. AUSTIN Jefferson F. J. BOLING Siler City H. C. BUCHAN, JR North Wilkesboro SCROOP W. ENLOE, JR Spruce Pine VOIT GILMORE Southern Pines R. M. HANES Winston-Salem LEO H. HARVEY Kinston CHARLES H. JENKINS - __..._...Ahoskie AMOS R. KEARNS High Point H. C. KENNETT Durham R.W.MARTIN Raleigh CECIL MORRIS Atlantic HUGH M. MORTON Wilmington W. EUGENE SIMMONS Tarboro T.MAX WATSON Spindale LETTER OF TRANSMITTAL Raleigh, North Carolina February 4, 1958 To His Excellency, HONORABLE LUTHER H. HODGES Governor of North Carolina Sir: I have the honor to submit herewith manuscript for publication as Bulletin No. 71, "Explanatory Text for Geologic Map of North Carolina". This text is an essential part of the new geologic map of North Carolina. The new geologic map and this explanatory text contain a summary of the best information pres-ently available on the geology of North Carolina. This information should be of real value to mining companies and individuals interested in the geology and mineral resources of the State. Respectfully submitted, WILLIAM P. SAUNDERS Director CONTENTS Page Abstract 7 Introduction 8 Acknowledgments 8 Map units 9 Dependability of the map 10 Structure and metamorphism 11 Description of rock units 12 Introduction 12 Igneous and metamorphic rocks 12 Gneisses and schists^ 12 Precambrian ( ?) 12 Mica gneiss 12 Mica schist 13 Hornblende gneiss 14 Granite gneisses 15 Precambrian ( ?) 15 Unnamed granite gneiss 15 Granite gneiss complex 16 Henderson granite gneiss 16 Cranberry granite gneiss 17 Blowing Rock gneiss 18 Max Patch granite gneiss 18 Beech granite gneiss 19 Granites and mafic igneous rocks 19 Paleozoic ( ?) 19 Dunite 19 Granite 20 Syenite 22 Mount Airy granite 22 Diorite-gabbro 23 Paleozoic 23 Toluca quartz monzonite 23 Cherryville quartz monzonite 24 Whiteside granite 24 Alaskite 24 CONTENTS—Continued Page Triassic ( ?) 25 Bakersville gabbro __ 25 Diabase dikes 25 Metavolcanic rocks 26 Precambrian or Lower Paleozoic ( ?) 26 Carolina Slate Belt 26 Felsic volcanics 27 Mafic volcanics 28 Bedded argillites (volcanic slate) 28 Upper Precambrian 29 Grandfather Mountain window 29 Linville metadiabase 29 Montezuma schist 29 Flattop schist 30 Metarhyolite 30 Mount Rodgers volcanic group 30 Metasedimentary rocks 30 Upper Precambrian (?) or Lower Paleozoic (?) 30 Stokes County and Kings Mountain belt 30 Kings Mountain group 30 Lower Cambrian ( ?) 31 Brevard belt 31 Brevard schist 31 Murphy belt 31 Brasstown schist 31 Valleytown formation 32 Andrews schist-Murphy marble 32 Sedimentary rocks 32 Upper Precambrian 32 Ocoee series 32 Snowbird formation • 34 Great Smoky conglomerate 35 Nantahala slate 36 Sandsuck shale 37 Undifferentiated 37 CONTENTS—Continued Paye Cambrian 37 Lower Cambrian 37 Unicoi formation 38 Hampton formation 39 Erwin formation 39 Shady dolomite 39 Rome formation 40 Triassic 40 Upper Triassic '_ 40 Pekin formation 41 Cumnock formation 41 Sanford formation 41 Undifferentiated 41 Coastal Plain _ 43 Cretaceous 43 Upper Cretaceous 43 Tuscaloosa formation 43 Black Creek formation 44 Pee Dee formation 44 Tertiary 44 Eocene (Middle and Upper) 44 Castle Hayne limestone 44 Miocene (Upper) 45 Yorktown formation 45 Quaternary 46 Pleistocene and Recent 46 Undifferentiated 46 References cited 48 ILLUSTRATIONS Figure 1. Generalized geologic cross-section from Wilson, N. C. to Cape Hatteras, N. C opposite page 47 State Library EXPLANATORY TEXT FOR GEOLOGIC MAP OF NORTH CAROLINA By Jasper L. Stuckey and Stephen G. Conrad ABSTRACT A new geologic map of North Carolina, compiled from all available sources, is presented herewith. The accompanying text describes the rock units shown on the map. The classification of rock units is based more on rock type than age relations. However, where possible formation names and age relations were used. The rocks were divided into the following four groups: Igneous and Metamorphic Rocks, Metavolcanic Rocks, Metasedimentary Rocks and Sedimen-tary Rocks. Included in the Igneous and Metamorphic Rocks are gneisses and schists, granite gneisses, and granites and mafic igneous rocks. The gneisses and schists occur mostly in the upper Piedmont and Blue Ridge regions of the State and are presumably the oldest rocks present. With one exception, the granite gneisses are restricted to the Blue Ridge region and probably represent ancient igneous and sedimentary rocks that have been highly metamorphosed. The granites and mafic igneous rocks occur throughout the Piedmont and Blue Ridge regions, but are most abundant in the Piedmont. Included in this group are a wide variety of rock types that vary greatly in age, but all appear to be of igneous origin. Metavolcanic Rocks occur in three distinct areas. The Carolina Slate belt occupies the largest area and is present in two separate but parallel belts. The main belt lies across the central part of the State in a northeast-southwest direction, and the second belt occurs along the western edge of the Coastal Plain. The Grandfather Mountain window is the second area of metavolcanic rocks, and it lies partly in the Blue Ridge and partly in the Piedmont Plateau in Avery, Watauga, Caldwell, Burke and McDow-ell Counties. Third is the Mount Rodgers volcanic group which occupies a relatively small area in the northwest corner of Ashe County. The Carolina Slate belt consists of volcanic-sedimentary formations, composed of slates, breccias, tuffs and flows. These rocks vary from acid, or rhyolitic, to basic, or andesitic, in composition and generally have a well developed cleavage. Rocks in the Grandfather Mountain window include schists, altered basalt and amygdaloidal basalt, metadiabase, and metarhyo-lite. The Mount Rodgers volcanic group is composed mostly of metarhyolite, including both tuffs and flows. Rocks more or less metamorphosed but retaining enough of their original characteristics to indi-cate that they were sediments are classed as Metasedimentary Rocks. These rocks occur in four areas, commonly referred to as the Stokes County area, the Kings Mountain area, the Brevard area, and the Murphy area. The rocks in the Stokes County and Kings Mountain areas are much alike and are com-posed mostly of quartzite, schist, conglomerate and marble. These two areas are classed as the Stokes County and Kings Mountain belt. The other two areas are classed as the Brevard belt and the Murphy belt, and they are composed mostly of schists with lesser amounts of marble. The oldest Sedimentary Rocks occur along the western edge of the State. These rocks belong to the Ocoee series and form much of the rugged topography in the Great Smoky Mountains. The Ocoee series is a very thick sequence of detrital rocks of graywacke type that rest unconformably on the older gneisses and granite gneisses. The Ocoee series is classed as Upper Precambrian in age. Overlying the Ocoee series is a sequence of somewhat better sorted detrital rocks called the Chilhowee group that are classed as Lower Cambrian in age. The Shady dolomite conformably overlies the Chilhowee group and is overlain by the Rome formation. Both of these formations are classed as Lower Cambrian. Triassic sedimentary rocks occupy two belts in North Carolina. The Deep River belt, the largest, lies along the eastern edge of the Piedmont Plateau and extends from Anson County on the southwest to near Oxford, Granville County, on the northeast. The Dan River belt lies in the north central part of the Piedmont Plateau and extends from Davie and Yadkin Counties across Stokes and Rockingham Counties into Virginia. The rocks of the two belts are very similar and consist of red, brown, purple and gray claystone, shale, sandstone, conglomerate and fanglomerate, and some coal. The eastern one half of the State is underlain by sedimentary deposits that range from Upper Cretaceous to Recent in age. These sediments are commonly referred to as the Coastal Plain deposits and consist largely of unconsolidated sediments that include gravels, sands, clays, limestone and marls. The deposits of the Coastal Plain form a wedge-shaped block of sediments that increases in thickness from a feather edge along its western border to approximately 10,000 feet at Cape Hatteras. The sedi-ments rest unconformably on crystalline rocks of Precambrian (?) age. INTRODUCTION A new geologic map of North Carolina, compiled from all available sources and supplemented by several months of fieldwork, is presented here-with. The accompanying text describes the rock units shown on the map and indicates briefly the importance of the units and their mineral deposits. Prior to the preparation of the present map, the only geologic map of the State of North Caro-lina was one prepared by W. C. Kerr and pub-lished as a part of his Geology of North Carolina, Volume I, 1875. This map was revised slightly by J. A. Holmes in 1887 and published as a part of Ores of North Carolina by W. C. Kerr and G. B. Hanna (1893). Modifications of these maps, geologic maps of portions of the State found in various state reports, geologic folios and other reports of the U. S. Geological Survey, and a black and white map of North Carolina modified from the Geologic Map of the United States by the U. S. Geological Survey, 1932, served as a basis for interpreting the geology of North Carolina until the present map was compiled. ACKNOWLEDGEMENTS The geologic map of North Carolina presented herewith is a compilation from all available sources, published and unpublished. It is supple-mented by several months of fieldwork, during which time areas of the State not previously cov-ered were mapped on a reconnaissance basis, and other areas were checked for accuracy of mapping and to harmonize older maps. In addition to in-formation obtained from older reports and from geologists who have had experience in the State in recent years, many others gave freely of their time and knowledge in making the present map possible. Thanks are gratefully expressed to all who aided in the project, and where possible, indebtedness for particular information is ex-pressed below. An apology is hereby expressed to any who have been overlooked. First, thanks should be given to Luther H. Hodges, Governor of North Carolina, who became interested in the project and made funds avail-able for the necessary fieldwork and for compiling and publishing the map. Without his interest and enthusiastic support the map could not have been made available at the present time. To Thomas B. Nolan, Director of the U. S. Geo-logical Survey, and many members of the staff of that agency, thanks are gratefully extended. The U. S. Geological Survey cooperated informally by making available unpublished geologic maps of portions of the State, authorizing members of its staff to evaluate much of the material used, and furnishing the new base map on which the geology was compiled and published. Robert A. Laurence served as representative of the Survey in furnish-ing unpublished material and gave valuable assist-ance and advice on the map. Philip B. King re-viewed the manuscript of the Piedmont and Moun-tain areas of the State and made many valuable suggestions. Jarvis B. Hadley edited the geology of the Great Smoky Mountains area and furnished valuable information on adjacent areas. W. C. Overstreet, A. A. Stromquist, and Phil Choquette contributed valuable data on the Central Piedmont region. H. M. Bannerman, C. A. Anderson, R. H. Lyddan, Harold Williams, J. P. Alders, and G. M. Fitzgerald furnished valuable information as to available maps and procedures to be used in the preparation of the map. The geology of the Coastal Plain is based on recent work of H. E. LeGrand and P. M. Brown. Robert L. Moravetz and his associates in the Office of Publications of the Survey gave valuable instructions on the prep-aration of the final manuscript and did photo-graphic work that greatly reduced hand labor. The 8 Committee on Geologic Names checked the legend and approved the names and ages of many of the rock units and formations used on the map. To make the map possible several areas in the State not previously mapped were mapped on a reconnaissance basis specifically for the project. R. J. Council and C. M. Llewellyn, Jr., mapped Alleghany, Wilkes, Surry, Yadkin, and parts of Ashe and Caldwell Counties. D. B. Sterrett aided Councill and Llewellyn and also mapped Alexan-der County. V. I. Mann and S. S. Alexander map-ped Franklin, Warren, and parts of Vance, Hen-derson, Buncombe, and McDowell Counties and checked several areas in the western part of the State. W, A. White and E. C. Brett mapped Dur-ham, Orange, and parts of Person and Granville Counties. R. L. Ingram and O. B. Eckhoff mapped Union, Stanly, and parts of Anson and Montgom-ery Counties. S. D. Heron, Jr., and W. D. Reves mapped Richmond and parts of Anson, Harnett, Lee, Moore, Montgomery, and Randolph Counties. J. M. Parker III and J. F. Conley mapped parts of Granville, Wake, Harnett, Moore, Lee, and Chat-ham Counties. J. L. Stuckey and S. G. Conrad mapped parts of Johnston, Wake, Harnett, Chat-ham, and Randolph Counties. S. D. Broadhurst checked several areas and made valuable contribu-tinons to the project. T. L. Kesler, chief geologist of Foote Mineral Company, made available to the project the results of his mapping in the Kings Mountain district and offered valuable suggestions on other areas. In addition to field mapping, the men mentioned above, as well as E. Willard Berry, G. R. McCarthy, W. H. Wheeler, and E. L. Miller, Jr., gave valuable aid and criticism while the map was being compiled. MAP UNITS A geologic map is no better than the rock units or formations used. The map presented is not a final summary of the geology of North Carolina but a progress report in which an attempt has been made to present the best information avail-able. To give meaning to the map units, more description is needed than can be presented in a conventional map explanation. To meet this need, the following descriptive text has been pre-pared to indicate the relative dependability of the map and point out areas where more work is most urgently needed. There are enough such areas to keep many geologists busy for a long time, and it is hoped that this map will serve as a stimulus and framework for increased geologic mapping in North Carolina. Since the present map is based on fieldwork that is not sufficiently detailed to warrant a complete revision of nomenclature, an attempt has been made to show detail where detail exists and only generalized units where information is lacking. As a result, standardized units and names already in use and approved by the Committee on Geologic Names of the U. S. Geological Survey have been used wherever possible instead of introducing new ones. Not all rock unit and formation names found in the literature are retained on the present map. In that portion of the Piedmont and Appalachian regions covered by various folios and unpublished maps of the U. S. Geological Survey are large areas which were mapped as Carolina gneiss and Roan gneiss. The formation names Carolina gneiss and Roan gneiss are no longer accepted by the U. S. Geological Survey and are not used on the present map. Many of the rocks classed as Carolina gneiss and Roan gneiss in older reports are shown as mica gneiss, mica schist, and horn-blende gneiss on the present map. The same procedure was followed in the Caro-lina Slate Belt of the Lower Piedmont. Prior to the preparation of the present map, two methods of classifying rock units in that belt had been employed. Laney (1910), Pogue (1910), and Stuckey (1928) mapped areas in the Carolina Slate Belt and classed the rocks as acid volcanic fragmental and flow materials, basic volcanic fragmental and flow materials, and bedded slate. Laney (1917) used the names Virgilina green-stone, Aaron slate, Hyco quartz porphyry, and Goshen schist for the volcanics in the Virgilina district. For the preparation of the present map it was not possible to do enough detailed fieldwork to apply these formation names to the whole slate belt ; instead, the rock-unit names Felsic volcanics, Mafic volcanics and Bedded argillites (volcanic slate) were used, as these units are more easily recognized throughout the belt. The Coastal Plain is doubtless the best mapped part of the State, and the formation names in com-mon use there have been retained with few changes. In areas of the State, chiefly the Pied-mont Plateau, where only limited mapping had been done previous to the preparation of the pres-ent map, rock units were set up and names most descriptive of these units were used. 9 DEPENDABILITY OF THE MAP In the order of dependability the Coastal Plain is probably the best mapped part of the State. This is true with respect to the formations estab-lished and their age relations, but some of them vary in thickness from place to place, and it is not always easy to determine the exact limits of sur-face exposures. The region west of longitude 81° 30' is the next best mapped part of the State, but here variations in metamorphism and complex structure make detail mapping difficult. East of longitude 81° 30' and west of the western limits of the Coastal Plain less detailed work has been done, and the map is less complete. These three areas are discussed below in the order of depend-ability. The first detailed map of the Coastal Plain was prepared by Clarke et al. (1912). In that report Stephenson considered the oldest Cretaceous rocks in North Carolina to be Lower Cretaceous and classed them as Patuxent in age. In the same report Miller considered the Trent formation to be Eocene and older than the Castle Hayne lime-stone. Cooke (1926) reclassified the Patuxent as the equivalent of the Tuscaloosa of Upper Creta-ceous age, and Kellum (1926) placed the Trent formation in the Miocene. In subsequent years other changes were proposed by different geolo-gists. Berry (1947) compiled a geologic map of the Coastal Plain from all available sources, which has served until the present time. LeGrand and Brown (1955) revised the geologic map of the Coastal Plain and combined the Trent formation with the Castle Hayne limestone. The present map contains all the formations in the Coastal Plain that are approved by the U. S. Geological Survey. Considerable mapping has been done in the region west of longitude 81° 30', but all the earlier work was highly generalized. Kerr (1875) divid-ed the rocks of the region into three units, which he classed as Lower Laurentian, Upper Lauren-tian, and Huronian. The lower Laurentian cor-responds to Paleozoic (?) granites of the present map ; the Upper Laurentian corresponds to granite gneisses and gneisses and schists of the present map; and the Huronian corresponds to metavol-canics and sedimentary rocks older than Triassic of the present map. Holmes (1893 see Kerr and Hanna 1893) used essentially the same classifica-tion employed by Kerr but considered the three units to be Archean in age. Pratt and Lewis (1905) classed the gneisses, schists, granites, diorite, and other crystalline rocks of the region as Precambrian in age and the conglomerates, quartzites, slates, etc., ac Ocoee of Cambrian age. They considered the peridotites, dunites, and related rocks as probably early Paleo-zoic in age. During a period beginning in 1888 and ending about 1912, the U. S. Geological Survey mapped the region being considered, except Polk and parts of Henderson and Cleveland Counties, on 30-min-ute quadrangles. Nine of these were published as folios, and five were not published. The nine pub-lished folios are: Keith (1895, Knoxville f. 16; 1903, Cranberry f. 90; 1904, Asheville f. 116; 1905, Mount Mitchell f. 124; 1907a, Nantahala f. 143 ; 1907b, Pisgah f. 147 ; 1907c, Roan Mountain f. 151) , LaForge and Phalen (1913, Ellijay f . 187) , and Keith and Sterrett (1931, Gaffney-Kings Mountain f. 222). The five unpublished maps were: Keith (Cowee q. and Mt. Guyot q.) ; Keith and Sterrett (Morganton q. and Lincolnton q.) ; and Keith and Hayes (Murphy q.). The areal geologic map of the Cowee, Mt. Guyot, Morganton, and Murphy quadrangles were revised by Philip B. King and placed on open file by the U. S. Geo-logical Survey and were available for use during the preparation of the present map. In recent years, considerable mapping has been done in the region by the U. S. Geological Survey and the Tennessee Valley Authority, independent-ly, and by the State of North Carolina in coopera-tion with these agencies. Philip B. King, Jarvis B. Hadley, and others of the U. S. Geological Sur-vey mapped the Great Smoky Mountains and vicinity, and R. G. Yates, W. R. Griffitts, and W. C. Overstreet of the same agency mapped the Shelby quadrangle and adjacent areas. The U. S. Geological Survey in cooperation with the State of North Carolina carried out extensive mapping of mica mines in the area during World War II; and under the same program J. C. Olsen (1944) prepared a map of a part of the Spruce Pine dis-trict, E. N. Cameron (1951) prepared a map of a part of the Bryson City district, and J. M. Parker III (1952) prepared a map covering the geology and structure of a part of the Spruce Pine district. More recently, Kulp, Brobst et al. (unpublished) completed a geologic map of the Spruce Pine dis-trict covering some 250 square miles. Geologists of the Tennessee Valley Authority, including Charles E. Hunter, Sam D. Broadhurst, and E. C. Van Horn, did extensive geological work 10 in the region prior to 1941. Under cooperation between the Tennessee Valley Authority and the State of North Carolina, E. C. Van Horn (1948) prepared a geologic map of the Murphy Marble Belt, and S. S. Oriel (1950) prepared a geologic map of the Hot Springs area. Under the same cooperative agreement a number of other reports on mineral resources were prepared, chief of which were by Hunter, et al. (1942) , Murdock and Hunter (1946), Hunter and Hash (1949), Hash and Van Horn (1951), and Broadhurst and Hash (1953). All of these, and other reports not men-tioned here, were freely drawn upon in compiling the map of the region west of longitude 81° 30'. When compilation of the present map was be-gun, less detailed mapping had been done between longitude 81° 30' and the western limits of the Coastal Plain than in any other part of the State. Laney (1910 and 1917), Pogue (1910), and Stuckey (1928) had prepared maps of a part of the Carolina Slate Belt. Stone (1912), Campbell (1923), and Reinemund (1955) had prepared maps of the Dan River and Deep River Coal Fields. Keith and Sterrett (1931) had mapped a part of Cleveland County, and Overstreet et al. (1953) had prepared a preliminary map of the Lincoln-ton quadrangle. J. M. Parker III, under a coop-erative agreement between the U. S. Geological Survey and the State of North Carolina, had just completed a map, not yet published, of the Hamme Tungsten district covering parts of Granville and Vance Counties. These and a number of maps covering 50 to 100 square miles each, which had been prepared by graduate students in connection with theses problems, represented the only de-tailed mapping in the region. Considerable mapping, however, had been done on a reconnaissance basis in connection with a cooperative project between the U. S. Geological Survey and the State of North Carolina for the study of ground water in the State. Mundorff (1946) prepared a geologic map of the Halifax area covering Nash, parts of Halifax, Northamp-ton, and Wilson Counties in the Piedmont. Mun-dorff (1948) prepared a similar map of the Greensboro area covering Alamance, Caswell, Guilford, Rockingham, Forsyth, and Stokes Coun-ties. LeGrand and Mundorff (1952) prepared the same sort of map of the Charlotte area covering Cabarrus, Mecklenburg, Gaston, Lincoln, Cleve-land, Rutherford, and Polk Counties. LeGrand (1954) prepared a similar map of the Statesville area covering Alexander, Catawba, Iredell, Davie, Rowan, and Davidson Counties. The maps listed plus the new mapping in the areas referred to under acknowledgments above served as the basis for compiling the present map of the State. Every possible precaution was taken to make the best possible use of the available data, but it should be pointed out that the map appears much more accurate than it actually is. No one is so well aware of its weak points and imperfec-tions as the compilers are. A general precaution is issued to all users not to consider it a finished map, but a summation of the best information at present available on the geology of North Carolina. STRUCTURE AND METAMORPHISM In an area as complex in geology as that found in the Piedmont and Mountain regions of North Carolina, structural features and metamorphism of the rock units present many major problems. After giving much thought to the structural fea-tures of the rocks in the Piedmont and Mountain regions of the State and discussing the subject with many people who are more or less familiar with the region, it was decided that enough de-tailed information is not available to produce structure sections of real value. It was also de-cided that enough information is not available to warrant any detailed discussion of faulting, fold-ing, metamorphism, unconformities, and facies changes. As a result, metamorphism is not dis-cussed as such, and the only structural features shown on the map are a few faults of regional significance. The U. S. Geological Survey is now engaged in the detailed mapping of a strip from the western edge of the Cumberland Plateau, across the Appa-lachian Mountains, the Piedmont Plateau, and the Coastal Plain. This strip is expected to cross a part of North Carolina. Perhaps, when it is com-pleted, a revised map of North Carolina will be prepared which will contain more information on structure and metamorphism than is now avail-able. Structural features in the Coastal Plain are less complicated than in the Piedmont and Mountain regions. The formations generally strike north-east- southwest and dip gently a few feet per mile to the southeast. No faults or folds of any significance have been found in the region. A geologic cross-section across the Coastal Plain 11 with considerable subsurface data, obtained from deep-well records, is presented below. DESCRIPTION OF ROCK UNITS INTRODUCTION In the explanation listed on the map and dis-cussed below, a three-fold grouping of rock units has been used. First, the rock units have been grouped as sedimentary rocks, metasedimentary and metavolcanic rocks, and igneous and meta-morphic rocks. Igneous and metamorphic rocks have been grouped together because some of the units used have characteristics of both igneous and metamorphic rocks. Second, an attempt has been made to group the rock units in the explana-tion according to their geographic distribution in the State. Third, as far as possible the sequence in the explanation represents the stratigraphic position of the rock units in the earth's crust. This is thought to be correct for the sedimentary rocks; however, in the case of metasedimentary rocks, metavolcanic rocks, and igneous and meta-morphic rocks, the sequence in the explanation may not represent the true stratigraphic position. For example, the rock units used in the metavolcanic rocks of the Carolina Slate Belt are interbedded and, as a result, are not distinctly different in age. The exact ages of most of the granites listed as Paleozoic (?) and Paleozoic are not known, and as a result some may be the exact stratigraphic equivalents of others. The same holds true for the granite gneisses, as Eckelman and Kulp (1956) classed the Cranberry granite gneiss and the Hen-derson granite gneiss as stratigraphically equiva-lent. Finally, the exact ages of the gneisses and schists are not known, and it is quite probable that the units used contain materials differing greatly in ages. IGNEOUS AND METAMORPHIC ROCKS The gneisses, schists, and granite gneisses, list-ed as Precambrian( ?) , present a major problem in age classification. Many of these units in the Blue Ridge area, according to King (personal communication), are unconformable below Lower Cambrian and Upper Precambrian units and should be classed as Precambrian without the query. However, the difficulty comes in going southeast from the Blue Ridge area where similar units have no certain stratigraphic relations to the Cambrian or Upper Precambrian. The result is that Precambrian (?) looks incongruous in the Blue Ridge area where these rocks are in contact with Upper Precambrian and Lower Cambrian, but is well justified in the southeast. No simple solution could be found for the problem, and it has been left for map users to draw their own con-clusions. GNEISSES AND SCHISTS PRECAMBRIAN(P) The three units—Mica gneiss, Mica schist, and Hornblende gneiss—used in this grouping repre-sent essentially Carolina gneiss and Roan gneiss in the areas mapped by Keith and similar mate-rials outside these areas. The formation names Carolina gneiss and Roan gneiss are no longer accepted by the U. S. Geological Survey and are not used on the present map. The three units as presently constituted are too complex in compo-sition to be given formation names, and it was thought best to use the rock-unit names, Mica gneiss, Mica schist, and Hornblende gneiss. Mica Gneiss (mgn) The Mica gneiss unit, as mapped, occurs over a wider area and probably underlies more square miles of the State than any other formation on the map. It is especially abundant in the Blue Ridge region and the western part of the Piedmont Plateau where it covers large areas. It is less abundant in the central part of the Piedmont Pla-teau but is common along the eastern part of that area. In the Blue Ridge and upper Piedmont areas, the Mica gneiss unit consists largely of Carolina gneiss as mapped by Keith (1903, 1904, 1905, 1907a, 1907b, 19007c, and 1931). In other parts of the State the Mica gneiss unit is in all respects comparable to that in the areas mapped by Keith. The Mica gneiss unit consists of an immense series of mica gneiss, mica schist, and fine gran-itoid layers in which mica gneiss predominates. Most of these are light to dark gray in color, weathering to dull gray, greenish gray, or yellow. Varying amounts of garnet gneiss, garnet schist, kyanite gneiss, granite gneiss, hornblende gneiss, and crystalline limestone or marble are present in the unit at many localities. There are also in-cluded in the Mica gneiss unit younger bodies of 12 granite, diorite, and dikes and lenses of pegmatite too small or not well enough known to show on the map. Mica gneiss, which is the chief component of the Mica gneiss unit, is composed chiefly of quartz and feldspar with varying amounts of mica, both biotite and muscovite, with biotite predomi-nating in many localities. Much of the Mica gneiss unit is doubtless metamorphosed sedimentary ma-terial, while some of it resembles granite gneiss and may well represent granite that has been strongly metamorphosed. Rock of this type has been quarried extensively around Asheville, Bun-combe County; Hickory, Catawba County; Hen-derson, Vance County ; and Raleigh, Wake County. This material was used in the construction of the present State Capitol in Raleigh, which was erect-ed between 1830 and 1835. Bands and lenses of mica schist, usually fine-grained and composed of quartz, muscovite, a little biotite, and very little feldspar are common in the Mica gneiss unit. Closely associated with the mica schist bands and lenses are extensive bands and zones of garnet gneiss, garnet schist, and kyanite gneiss. The garnet and kyanite gneisses and schists are too widespread to describe in detail here. Some of the better known garnet areas are near Marshall, Madison County; on Sugar Loaf Mountain near Willetts, the Savannah mine on the headwaters of Betty Creek, and the Presley mine near Speedwell in the upper Tuckaseegee valley, all in Jackson County; and on Shooting Creek, Clay County. An important belt of kyanite gneiss, six to eight miles wide, extends along the line of the Black and Great Craggy Mountains from Swannanoa, Buncombe County, to Bakersville, Mitchell County. The kyanite crystals vary in length from a fraction of an inch to three or four inches but average less than an inch. On weath-ered surfaces, they often stand out in relief, giv-ing the rock a porphyritic appearance. Small gar-nets are often associated with the kyanite gneiss. At many places throughout the Mica gneiss unit there are thin, interbedded layers of hornblende gneiss and schist, too small to show on the map. These are in all respects similar to the Horn-blende gneiss unit described below. Bodies of crystalline limestone or marble are present at many localities in the Mica gneiss unit. The more important of these occur near Marshall, Madison County; south of Bakersville, Mitchell County ; eight miles northwest of Winston-Salem, Forsyth County; and near Germanton, Stokes County. Included in the Mica gneiss unit at many places are dikes and lenses of pegmatite which are dis-tinctly younger than the enclosing rock. These vary in thickness from a few inches to as much as 200 feet (Olson, 1946, p. 7) and are equally vari-able in length. Most of the kaolin and feldspar produced in North Carolina prior to 1945 came from pegmatite bodies. Throughout the history of mica mining in the State pegmatites have been, and still are, the chief source of sheet mica. A wide variety of commercially less important min-erals are present in the dikes, and Olson (1944, p. 26) stated, "At least 44 different minerals have been reported from the Spruce Pine pegmatites." Spodumene-bearing pegmatites, which are the chief source of lithium in the United States, are abundant in the Mica gneiss unit south of Lincoln-ton in the Kings Mountain district. The Mica gneiss is deeply weathered in most places and is covered with a thick layer of resi-dual clay. As a result, fresh outcrops and ledges of solid rock are seldom seen except along streams, on steep slopes, and in the more mountainous areas. The residual clay contains fragments and layers of schist, quartz, mica, and gneiss. The cover of soil on the thick mantle of residual clay and weathered rock is usually light and thin. Mica Schist (msh) The Mica schist unit occurs most abundantly along the western border of the Piedmont Plateau, just east of the Blue Ridge Mountains, and extends intermittently completely across the State. In the vicinity of Kings Mountain and around Gastonia there are fairly large areas of mica schist, and smaller areas are widespread throughout the Pied-mont Plateau. The main occurrences of this unit along the western border of the Piedmont Plateau, the area around Gastonia, and the areas through-out the lower Piedmont are essentially mica schist of the Carolina gneiss as mapped on the various folios of the U. S. Geological Survey. North of the Yadkin River, the Mica schist unit consists principally of a thinly foliated muscovite-sericite schist. This unit also includes bands and zones of muscovite-biotite schist and some areas of mica gneiss, partly altered to mica schist. In-jections of granite, too small to show on the map, are also common east of the Blue Ridge, and small amounts of hornblende gneiss and schist are pres-ent at many places in the unit. At many places, the Mica schist contains varying amounts of gar- 13 net, sillimanite, kyanite, magnetite, ilmenite, and pyrite. South of the Yadkin River, the Mica schist unit consists basically of biotite schist. Three varie-ties of biotite schist are common, namely, biotite schist, biotite-muscovite schist, and sillimanite-biotite schist. All gradations exist among the three varieties. The sillimanite schist is in all places more contorted and sheared than the other varieties. A number of accessory minerals, in-cluding garnet, graphite, chlorite, and pyrite are present in the Mica schist unit. Pegmatites and narrow quartz veins occur throughout the mica schist. The pegmatites in general average less than a foot in thickness and rarely exceed four feet in length. Locally, they make up as much as one-half of the sillimanite-biotite schist. Over-street and Griffitts (1955, pp. 551-556) gave an excellent description of the Mica schist unit and related rock units and discussed their mineral content in some detail. Bands and zones of hornblende gneiss and horn-blende schist, most of which are too small to show on the map, are common throughout the Mica schist unit. These hornblende rocks are generally of simple mineral composition and locally may con-tain varying amounts of garnet. Many bodies of foliated to massive granite, too small to show on the map, are present in the unit. The Mica schist around Gastonia and in the other areas of the Piedmont Plateau to the east and northeast is essentially a fine-grained rock composed chiefly of quartz, muscovite and sericite mica. At places, the rock is a quartz-biotite schist, while at others it becomes a quartz-sericite, chlorite schist. The Mica schist evidently resulted from the metamorphism of sedimentary rocks that varied greatly in character from place to place. Weathering has been extensive, and outcrops of fresh rock are seldom seen except along streams and on steep slopes. The thick layer of residuum consists of clay mixed with fragments and layers of schist, quartz, and mica. The clay varies from yellow to dark red in color depending on the amount of biotite in the schist. The soil cover is usually light and thin. Hornblende Gneiss (hgn) The Hornblende gneiss unit is most abundant in the mountain region west of the Blue Ridge and north and northeast of Asheville. Several small areas occur west of the Blue Ridge in Clay and Macon Counties. In and parallel to the east side of the Blue Ridge small areas occur almost com-pletely across the State. In the central part of the upper Piedmont, in the general vicinity of Hickory and Statesville, there are some relatively large areas. Smaller areas occur along the east-ern edge of the Piedmont Plateau, particularly in Wake County. The Hornblende gneiss unit consists essentially of Roan gneiss as mapped and defined by Keith (1903). The type locality of the Roan gneiss is Roan Mountain, which lies along the North Caro-lina- Tennessee line and extends southward into Mitchell County, North Carolina. Keith (1903) stated, "The Roan gneiss appears to cut the Caro-lina gneiss, but the contacts are so much metamor-phosed that the fact cannot be proved." He con-sidered the Roan gneiss as chiefly diorite and smaller amounts of gabbro, which had been in-truded into older rocks and metamorphosed to hornblende gneiss and hornblende schist. In recent years considerable attention has been given to Roan gneiss, as mapped and defined by Keith, and much of it is no longer considered to be of igneous origin. Kesler (1944, 1955) pointed out that bodies of hornblende gneiss in the Kings Mountain district (See Kings Mountain group be-low, p. 31) are metamorphosed, calcareous sedi-ments. Parker (1952, p. 8) described the relation of the hornblende gneiss to the mica gneiss in the Spruce Pine district and concluded that certain thin, interbedded hornblende gneisses and actino-lite- tremolite rocks may have been impure dolo-mitic limestones. He added: "The mafic min-eralogic composition, however, coupled with the conformable relations to mica gneiss, has led most workers to believe that the ordinary hornblende rocks are metamorphosed mafic volcanic extru-sives, and perhaps, in part at least, are conform-able intrusive sills," and concluded, "Perhaps some of the hornblendic rocks are sedimentary in origin and some are igneous." Brobst (unpublished) concluded that the Roan-type rocks (hornblende gneiss) are of sedimen-tary origin and stated, "The hornblende rocks, therefore, may represent the metamorphosed equivalent of impure carbonate layers in the sedi-mentary sequence." Overstreet and Griffitts (1955, p. 553) considered the hornblende gneiss between Kings Mountain and Marion, North Caro-lina, to be in part of igneous and in part of sedi-mentary origin. 14 The Hornblende gneiss unit consists essentially of hornblende gneiss and hornblende schist layers that vary from a fraction of an inch to many feet in thickness. The thin layers of hornblende gneiss and hornblende schist are interbedded with thin layers of mica gneiss and mica schist to the extent that portions of the Hornblende gneiss unit con-tains considerable mica gneiss and mica schist, and in the same way portions of the Mica gneiss unit and portions of the Mica schist unit contain considerable amounts of hornblende gneiss and hornblende schist. The hornblendic rocks of the Hornblende gneiss unit include distinctly banded gneisses consisting of alternating layers of hornblende and feldspar, schistose rocks consisting almost entirely of coarse to fine hornblende needles, and nearly massive am-phibolites that lack distinct foliation. The gneisses and schists are black to dark green and grade into one another by feldspar content. Quartz, feld-spar, and hornblende are the chief minerals pres-ent, but varying amounts of biotite and chlorite are present at places. Garnet is less abundant than in the Mica gneiss and Mica schist but at places becomes an impor-tant constituent of the Hornblende gneiss. Peg-matite dikes, some of which have furnished con-siderable amounts of feldspar and mica, are pres-ent at many places in the unit. Numerous bodies of soapstone and talcose schist are associated with the Hornblende gneiss unit especially in the Spruce Pine district. These bodies, which vary from five to 25 feet in thickness and consist of talc, soap-stone, actinolite, biotite, chlorite, and vermiculite, appear to have been formed locally by secondary hydrothermal alteration of the hornblende gneiss. In the more mountainous areas, the Hornblende gneiss often crops out as ledges and bold ridges, but at lower elevations it usually occupies broad, flat areas or lower ground. It weathers readily and is usually covered with a thick layer of resi-dual clay mixed with rock fragments. This clay has a strong, dark-red color and is covered with a rich, fertile soil. intruded by a number of rocks which he classed as granites and granite gneisses (all highly meta-morphosed) and named in various areas Cran-berry granite, Henderson granite, Max Patch granite, and Beech granite. One unit, the Blow-ing Rock gneiss, he did not definitely class as a granite, even though he considered it intrusive into the older gneisses and the Cranberry gran-ite. Little has been published on these rocks since the work of Keith, but a number of workers in the area have made observations that caused them to doubt the validity of classing these units as either intrusive in origin or true granites in composition. This is true especially of the Cran-berry and Henderson granites. Brobst (unpub-lished) listed and described the Cranberry granite as Cranberry gneiss. He discussed specifically some layers, typical of the Cranberry gneiss, which are interbedded with other metamorphic rocks along the northwest and east borders of the Bakersville-Plumtree area, Avery County, close to the contact of the large body of Cranberry gneiss that surrounds that part of the Spruce Pine district on three sides (Kulp and Brobst, 1956). Eckelman and Kulp (1956) considered the Cran-berry and Henderson granites to be metasedimen-tary in origin and stratigraphically equivalent. During the preparation of the present map it was not possible to restudy these units in detail. As a result, in the areas covered by published folios these units are shown as nearly as possible as originally mapped. Outside the areas covered by published folios, it is doubtful if the units cor-respond in all details to those in the areas covered by published maps. In view of the diversity of materials in the units and the intense metamorph-ism which has altered them, it was decided, after discussing the problem with a number of workers who have made observations in the field, to add the word gneiss to each unit originally classed as granite. As a result, each of these units originally classed as granite becomes a granite gneiss on the present map. GRANITE GNEISSES PRECAMBRIAN(P) Along the western edge of the Piedmont Pla-teau and throughout much of the Blue Ridge Mountains area, according to Keith (see reference above), the older gneisses and schists have been Unnamed Granite Gneiss (gru) In Jackson, Haywood, and Swain Counties, west and north of Sylva, are areas of Unnamed granite gneiss. J. B. Hadley, on a map of the Great Smoky Mountains area furnished for use in the prepara-tion of the present map, designated these rocks as granite gneiss without formation or unit names or 15 age designations. Hadley et al. (1955, p. 402) classed these rocks as Max Patch and Cranberry as mapped by Keith (1904) and described them as medium to very coarse genissic granites, gen-erally gray but locally pink in color and containing minor amounts of leucogranite, amphibolite, peg-matite, and much blue quartz. Cameron (1951, p. 10) described one of these areas near Bryson City in some detail. He classed the rocks of the area as granitic gneisses and de-scribed them as predominantly fine- to coarse-grained leucocratic and mesocratic gneisses, vary-ing in composition from granitic to granodioritic with well developed foliation and lineation. He stated that the granite gneisses are cut by dikes of fine-grained granite and by dikes of medium-gray granite porphyry. Granite Gneiss Complex (gnc) Beginning a few miles northeast of Morganton and extending in a southwest direction across Burke, McDowell, Rutherford, and Polk Counties is an area underlain with rocks classed as Granite gneiss complex on the present map. About half of this area, in Burke and McDowell Counties, extending to latitude 35° 30' N. and longitude 82° W. in Rutherford County, was mapped by Keith on the Morganton quadrangle, which was not pub-lished. He made field surveys in the Morganton quadrangle in the years 1896, 1899, 1900, 1901, and 1907 and was aided by D. B. Sterrett during the last year. Traverse sheets available in the U. S. Geological Survey files show complete cover-age of the quadrangle. Based on these surveys, Philip B. King edited a geologic map of the Mor-ganton quadrangle, which appears to be a general-ization by Keith of a more detailed map not at present available. The central part of the Morganton quadrangle, as edited by King, is underlain with a rock unit 5 to 15 miles wide which is classed as "Cranberry, Henderson (and other?) granites (Archean) (in-cludes small areas of Roan gneiss)." Small areas of the same unit are shown in the southeast corner of the Morganton 30' quadrangle and in the Shelby 15' quadrangle. Rocks of this unit in Cleveland, Lincoln and Burke Counties were named Toluca quartz monzonite and classed as Ordovician in age by Griffitts and Overstreet (1952). The main area of Granite gneiss complex ex-tends southwest from the Morganton quadrangle across Rutherford County and well into Polk County. LeGrand and Mundorff (1952) mapped this unit in Rutherford County as mica schist and granite with schist predominant, and hornblende gneiss and granite interlain, and in Polk County as granite gneiss interlain with hornblende gneiss, and hornblende gneiss and granite interlain. Attempts were made to harmonize the mapping done by LeGrand and Mundorff in Rutherford and Polk Counties with that done by Keith in the Mor-ganton quadrangle. Attempts were also made to determine if the granitic material in the Granite gneiss complex as shown on the present map could be correlated with the granitic rocks in the south-east corner of the Morganton quadrangle and the northeast corner of the Shelby quadrangle, which Griffitts and Overstreet designated as Toluca quartz monzonite of Ordovician age. The problem was not fully recognized until com-pilation of the map was well underway, and time was not available to work out all the details. Two field parties, working independently, spent several days in the area and decided that the materials mapped by LeGrand and Mundorff in Polk and Rutherford Counties and by Keith in the Morgan-ton quadrangle are essentially the same. It was decided that in the time available no correlation could be made between the granites in the area and the Toluca quartz monzonite to the east and southeast. The rock unit shown on the present map as Granite gneiss complex contains mica gneiss, mica schist, and hornblende gneiss similar to that in the gneisses and schists described above. In addi-tion it contains granite gneiss similar to Hender-son granite gneiss, and Cranberry granite gneiss and also younger granite. Henderson Granite Gneiss (hgg) The Henderson granite gneiss unit on the pres-ent map is essentially Henderson granite as origi-nally named and described by Keith (1905) and further described (1907b). The Henderson gran-ite as mapped by Keith is not shown in contact with Cranberry granite at any place on his maps. On the present map the main area of Henderson granite gneiss begins near Marion, McDowell County, and continues southwest to the South Carolina line. West of Marion, a narrow band continues northeast along the west side of the Shady dolomite and Erwin formation to the limits of the Mount Mitchell quadrangle. Recently, Eck-elman and Kulp (1956) extended this band north- 16 east to near Linville Falls, McDowell County, where it makes contact with what they considered the southern extension of Cranberry granite as mapped by Keith in the Cranberry folio. They considered the Cranberry granite and the Hender-son granite to be metasedimentary in origin and stratigraphically equivalent. Keith (1905, p. 4) stated that the Henderson granite extended eastward into the Morganton quadrangle. A large area in the Morganton quad-rangle (discussed above under Granite gneiss complex) was mapped as Cranberry, Henderson (and other?) granites No age relations are shown between Cranberry and Henderson granites on the Morganton quadrangle, but in the legend on the Mount Mitchell folio, Keith placed Henderson granite above Cranberry granite. The exact origin and age of the Henderson granite is un-known. The Henderson granite gneiss, whatever its origin and age, is composed essentially of rocks with a pronounced gneissoid structure. Min-eralogically, the rock consists of orthoclase, pla-gioclase, quartz, muscovite, and biotite, named in the order of their abundance. Biotite varies a great deal in amount but is usually subordinate. The gneiss is usually gray in color but becomes lighter on weathering. Porphyritic crystals of feldspar are a prominent feature of the gneiss, and at many places it is a typical augen gneiss. The porphyritic varieties are not limited to any particular areas or positions in the gneiss but are generally irregularly distributed through it. Por-phyritic varieties of the gneiss grade into even-grained varieties, and the two varieties may be seen in a single exposure. Even-grained varieties of the gneiss are subordinate in amount to the porphyritic varieties. The rocks of this unit have been greatly changed by metamorphism. In areas where the finer grained beds did not contain porphyritic crystals of feldspar, the rock has been metamorphosed into gneisses and schists similar to those of the Mica gneiss and Mica schist units. Areas of mica gneiss, mica schist, and hornblende gneiss, too small to show on the map, are included at many places in the Henderson granite gneiss. Weathering of the Henderson granite gneiss varies greatly, and as a result the rock produces a varying landscape with strong cliffs and ridges in places and broad, flat areas in others. The Henderson granite gneiss has not been much used, but it offers an important source of dimension and crushed stone. Cranberry Granite Gneiss (cgn) The Cranberry granite gneiss unit on the pres-ent map consists essentially of Cranberry granite as originally named and described by Keith (1903), and further described (1904, 1905, and 1907c). The name Cranberry granite was first given to well developed exposures at Cranberry, Mitchell County, now Avery County. The rela-tions of the Cranberry granite gneiss to the Hen-derson granite gneiss have been discussed above under Henderson granite gneiss. Keith (references listed above) considered the Cranberry granite as igneous in origin, Archean in age, and intrusive into elder formations. He described it as granite of varying texture and color, and schists and granitoid gneisses derived from granite. Included were small or local beds of schistose basalt, diorite, hornblende gneiss, and pegmatite. As pointed out above, a number of workers in the area have made observations that caused them to doubt the validity of classifying the Cranberry granite as either intrusive in origin or a true gran-ite in composition. Brobst (unpublished) describ-ed the unit as Cranberry gneiss, consisting of white to gray gneisses, composed chiefly of micro-cline, sodic plagioclase, and quartz, and stated that in some layers biotite, muscovite, and rarely horn-blende may be present in amounts in excess of ten percent. He described the texture as cataclastic, with rounded and fractured porphyroblasts of microcline or plagioclase from three millimeters to one centimeter across the longest dimension. The Cranberry granite gneiss unit occurs as strips and patches in the Mountain region along the northwest border of the State. These begin about the latitude of Asheville in Haywood and Madison Counties and continue northeast to the Virginia line. The strips and patches which make up the unit have an elongation which conforms in general with the northeast-southwest trend of the mountains. The Cranberry granite gneiss, whatever its origin, is essentially a gneiss, which grades at places into schist. Logs of cores from 12 drill holes, varying in length from 400 to 1250 feet, which were drilled at the Cranberry iron mine in the type locality of the Cranberry granite in 1943- 1944, were examined during the preparation of 17 this report. These logs, which were prepared by competent geologists, show the rock to be a typical gneiss. In addition to gneiss, narrow bands' of hornblende gneiss, chlorite schist, and pegmatite were occasionally shown near the iron-ore veins. Some of the gneiss in the area is coarse-grained, but much of it is medium-grained and uniform in texture. In color, it varies from light to dark gray. In general, the Cranberry granite gneiss is a medium-grained, even-textured rock that varies from light to dark gray in color. It is composed of quartz, orthoclase, plagioclase, muscovite, bio-tite, and occasionally hornblende. In some areas the rock is more or less porphyritic, and in some places it has a marked red appearance due to the presence of red feldspar. The gneiss contains many small areas of mica gneiss, mica schist, horn-blende gneiss, schistose basalt, diorite, metadia-base, metarhyolite, and pegmatite. The Cranberry granite gneiss has been used to a limited extent for chimneys, foundations, and bridge piers, but no major quarrying operations have developed. The rock withstands weathering quite well in natural exposures. It takes a good polish and should make an attractive building stone. Quarry sites for crushed stone are avail-able at many places. Perhaps the most important mineral deposits associated with the Cranberry granite gneiss are the magnetic iron ores near Cranberry, Avery County. The magnetite deposits, while surrounded by the Cranberry granite gneiss, did not originate with the gneiss. According to Bayley (1923) the iron ore was brought up by pegmatites and depos-ited in the gneiss. These iron-ore bodies have been of interest for more than a hundred years. Sys-tematic mining was carried on intermittently be-tween 1880 and 1928, and some 2,250,000 tons of crude ore, which produced some 1,500,000 tons of shipping ore containing 42 to 46 per cent iron, were mined. Blowing Rock Gneiss (brgn) The main area of Blowing Rock gneiss is a wedge-shaped body beginning a few miles north of Blowing Rock, Watauga County, extending southward almost completely across Caldwell County and coming to a point at its southern end. A small area is shown near Creston, Ashe County. Keith (1903) named the unit Blowing Rock gneiss because it is well developed near the town of Blowing Rock. He classed it as an igneous rock, intrusive into Cranberry granite and older forma-tions and described it as chiefly dark, coarse, por-phyritic gneiss. The unit consists of two varieties, one contain-ing large porphyritic crystals of orthoclase feld-spar embedded in a groundmass of quartz, feld-spar, biotite, and muscovite, and the other con-sisting of the same minerals in grains of uniform size. The porphyritic crystals vary in length from three inches down to one-quarter of an inch and are frequently twinned. Many layers of fine-grained, black and gray schist are present in the unit. Biotite is so abundant that both varieties of the rock have a rather dark-gray color. The unit as a whole has been so much altered by fold-ing and metamorphism that while some of it is gneissoid, much of it is distinctly schistose. The rocks weather slowly, and outcrops are abundant, as in the Blue Ridge near Blowing Rock and south of Boone. Complete weathering produces a reddish-yellow clay, which is usually covered with light, well drained, fertile soil. The Blowing Rock gneiss has been used locally to a limited extent, but its importance as a build-ing stone has not been realized. The formation contains material suitable for ornamental and building uses that can be obtained in great abund-ance. Max Patch Granite Gneiss (mpgn) Max Patch granite gneiss consists entirely of Max Patch granite as mapped by Keith (1904 and 1905) . It was named for Max Patch Mountain in Madison County, North Carolina, which may be considered the type locality. In North Carolina the unit is limited to Haywood and Madison Coun-ties, with small extensions in Cocke and Unicoi Counties, Tennessee. Keith classed the unit as almost wholly coarse grained, in places porphy-ritic and in places of uniform grain. It is com-posed of orthoclase, plagioclase, quartz, biotite, and a little muscovite. At many places crystals of orthoclase feldspar more than an inch long are present. The porphyritic variety is dull white to light gray in color, while the even-grained variety is darker in color due to the biotite present. An-other variety of considerable extent is a coarse red granite which gets its color from the red feld-spar present. The red feldspars are often par-tially altered to epidote, giving the rock an at-tractive color. In places the feldspar has been 18 so far replaced by epidote that this mineral com-poses one-third to one-half of the bulk of the rock. The unit has been so completely metamorphosed that most of it has a gneissic to schistose struc-ture, and little, if any, true granite remains un-altered. The porphyritic variety of the unit has been altered to augen gneiss, while the even-grained variety has been altered to gneiss or schist. Weathering reduces the surface of the unit slowly, and as a result it commonly occupies higher elevations and steep slopes. Complete decay re-sults in a reddish or brownish clay of no great depth. Where soils accumulate on gentle slopes, they are rich and fertile. Mineral deposits are scarce in the Max Patch granite gneiss. A few small pegmatites near Lemon Gap, Madison County, contain small amounts of radioactive minerals. Some of the red feldspars, partly altered to epidote, make beautiful polished specimens, but the rocks of the unit have not become important as building materials. Beech Granite Gneiss (bgn) Beech granite gneiss consists of Beech granite as mapped by Keith (1903, 1905, and 1907c) and named for Beech Mountain, Avery County, where it is best developed. The largest area lies in and around Beech Mountain in Avery County, and extends westward into Carter County, Tennessee. Three other small areas are shown on the map, one around Blowing Rock in Watauga and Cald-well Counties, another west of Roan Mountain, Mitchell County, and extending into Carter Coun-ty, Tennessee, and a third in the western part of Yancey County, extending into Unicoi County, Tennessee. The unit consists of three varieties of granite gneiss. One is a coarse-grained, usually porphy-ritic rock, another is medium to fine grained, while the third is a coarse, red variety. In the porhy-ritic variety, crystals of orthoclase feldspar as much as two inches in length are often present. The chief minerals present in the unit are ortho-clase and plagioclase feldspar, quartz, biotite, and a little muscovite. The porphyritic variety is dull white to light gray in color, the medium- to fine-grained variety is darker in color due to the pres-ence of biotite mica, while the red variety gets its color from many pink or red feldspar crystals present. The unit has been greatly changed by meta-morphism. The mineral composition is essentially that of a granite, but the rocks composing the unit have a decided gneissic structure often becoming schistose with an increase of mica. The rocks of this unit are not too readily attacked by weather-ing and usually underlie higher ground. On complete weathering they produce a thin, brown-ish clay containing much sand. On gentle slopes where soils develop, they are strong and fertile. Mineral deposits are not known to occur in the Beech granite gneiss. The unit contains rock varieties that should make excellent building and crushed stone, but due mainly to location, they have not been developed. GRANITES AND MAFIC IGNEOUS ROCKS Rocks of definite igneous origin that have under-gone varying amounts of metamorphism and pos-sess textures ranging from massive to gneissic are classed as Paleozoic (?), Paleozoic, and Trias-sic(?) on the present map. The units classed as Paleozoic (?) could probably be classed as Paleo-zoic without the query, as most of them, except the dunites, have been considered for years as late Carboniferous in age and were shown on the 1932 Geologic Map of the United States as Carbonifer-ous ( ?) . However, little has been done to prove or disprove this classification since 1932, and it was thought best to show them on the present map as Paleozoic (?). PALEOZOIC?) There are five rock units in this group, four of which consist of granite, syenite, and diorite-gabbro. The fifth is classed as dunite and con-sists essentially of peridotite and pyroxenite, part-ly altered to talc, soapstone, and serpentine. The positions of these units in the column is arbitrary. Dunite (du) Dunite bodies are most abundant in the Blue Ridge Mountains where more than 250 outcrops occur in a northeast-southwest trending belt ap-proximately 175 miles long. A few small bodies occur in the western half of the Piedmont Plateau, but the most important bodies outside the Blue Ridge Mountains are found in the northern part of Wake County. Only a few of the larger bodies in the Blue Ridge Mountains and those in Wake County are shown on the map. In the mountains 19 the bodies vary greatly in size. The smallest, near Otto, contains 1500 square feet, while the largest, near Swannanoa in Buncombe County, is four miles long with a maximum width of nearly one mile. One of the most interesting is a ring dike near Webster, Jackson County, with a major axis six miles long and a minor axis about four miles long. In Wake County the deposits vary in length from a few hundred feet to nearly two miles. The age of the dunites is not definitely estab-lished. Keith (folios listed above) classed the dunites as Archean in age. He considered them intrusive into and closely related to the Roan gneiss but older than Cranberry and other gran-ites which he classed as Archean in age. Pratt and Lewis (1905, p. 159) suggested that they may have been formed during the Taconic revolution at the end of the Ordovician period. Parker (1952), Probst (unpublished) and King (1955) classed the dunites as Paleozoic in age. The dunites consist chiefly of peridotite and pyroxenite, in part altered to talc, soapstone, and serpentine. Some deposits consist almost entirely of olivine, and some contain small amounts of pyroxene minerals, but most of them have been altered extensively by metamorphism and hydra-tion. Many of the deposits in their present state consist of talc, soapstone, serpentine, asbestos, chlorite, vermiculite, and varying amounts of car-bonate. Unlike most metamorphosed rocks they show only minor schistosity. Amphibole minerals, such as tremolite and actinolite, often form bunches and radiating clusters in soapstone. The dunites in general weather slowly and often stand out as hills and ledges with much barren rock exposed at the surface. Final decay leaves a stiff yellow clay of little depth, and soils derived from this clay are of no value. Many of the de-posits, particularly in the Blue Ridge Mountains, are covered sparsely with a stunted vegetation. The dunites contain a wide variety of minerals that have been of interest at different times for many years. Many of the deposits contain varying amounts of chromite; and, while the production has been limited, much prospecting has been car-ried out for this mineral. At a few places, especially near Webster and Democrat, nickel sili-cate veins are conspicuous in the dunite, and con-siderable prospecting was carried out for nickel at Webster more than fifty years ago. The dunites contain varying amounts of corundum. Between 1871 and 1905, North Carolina was an important producer of corundum, most of which came from dunites. Talc and soapstone, associated with the dunites, have been of interest for many years, and small amounts have been produced. The most important period of activity was during World War II, when considerable amounts of ground talc and crayons were produced around Marshall, Mad-ison County. In recent years, considerable inter-est has developed in the olivine associated with the dunites. Hunter (1941) described some twenty-five deposits in the Blue Ridge Mountains that contain 230 million tons of high-grade olivine and more than one billion tons of partly altered olivine. Varying amounts of vermiculite are as-sociated with some of the dunites, and vermiculite production, which began in North Carolina in 1933, has continued intermittently since that time. Granite (gr) The rocks included in this unit are abundant along the western edge of the Coastal Plain and throughout the Piedmont Plateau. They were divided into three belts by Watson and Laney (1906), as follows: (1) Eastern Piedmont and Western Coastal Plain Belt ; (2) Central Piedmont Belt (Carolina Igneous Belt) ; and (3) Western Piedmont Belt. The rocks of the three belts are essentially gran-ite according to the commonly accepted meaning of the term. They consist in general of quartz, orthoclase, plagioclase, biotite, a little muscovite, and varying amounts of accessory minerals, such as chlorite, epidote, titanite, zircon, and mag-netite. On the basis of accessory minerals, varie-ties such as biotite granite and biotite-hornblende granite may be recognized. Councill (1954), on the basis of microscopic studies of the feldspars present, pointed out that in addition to granite, granodiorite is present, and quartz monzonite is common. He stated: "Many of the so-called granites of North Carolina approach more closely the mineral composition of granodiorite and/or quartz monzonite than normal granite." Each of the three belts listed above contains distinctive granites that seem to justify a brief description. The western boundary of the Eastern Piedmont and Western Coastal Plain Belt is formed by sedi-mentary rocks of Triassic age. In general the granites of this belt are massive, even-granular rocks, that show little effects of metamorphism. Jointing is common but not excessive at any place. 20 The textures present are chiefly medium to coarse grained. Porphyritic texture, though not abund-ant, is present at many localities, while fine-grained texture is seldom found. Two basic colors, one a light to medium gray and the other light to medium pink, sometimes approaching red, predominate. Outcrops, while not abundant, are common throughout the belt. Along stream val-leys, outcrops form elongated masses and ledges ; while in rolling topography, large boulders are often found. Away from streams in relatively flat topography, flat to dome-shaped masses often oc-cur. Where it has not been removed by erosion, the granites are covered with a residuum varying from a few inches to as much as 25 to 40 feet thick. This residuum varies in color from buff, yellow, and red to reddish-brown, depending on the weathering of the underlying granite. The granites of the Central Piedmont Belt (Carolina Igneous Belt) occupy a region several miles wide in the central part of the Piedmont Plateau. In this belt bodies of granite, varying greatly in shape and size, have intruded older rocks. On the basis of work by Mundorff (1948) and LeGrand and Mundorff (1952), the granites of this belt can be divided into three distinct geo-graphic areas. In one area, the granite, which Mundorff (1948) mapped as Sheared granite, crops out as an irreg-ular and interrupted zone across northern Ran-dolph County, southeastern Guilford County, most of Alamance County, the southeastern corner of Caswell County, and into central Person County. The granite is most commonly a coarse-grained rock of light-pink color, composed chiefly of ortho-clase, plagioclase, quartz, and biotite. At a few places, it is light gray and medium grained, with plagioclase as the chief feldspar. The granite is badly crushed and broken with the development of a schistose or gneissic structure. Basic dikes that vary from green to brown in color occur nearly everywhere in the granite in great numbers. Rarely does an outcrop of 200 to 300 feet of granite fail to expose one or more dikes, and at many places 10 to 12 dikes cut a granite body of that size. The dikes are more numerous and closely spaced along the margins of the granite. In some marginal exposures dike material is more abundant than granite. The dikes are fine grained, schistose in structure, and com-posed chiefly of chlorite, biotite, plagioclase, and augite. The granites of this area were intruded into basic volcanic rocks, largely of andesitic ori-gin. Councill (1954, p. 56) described these gran-ites as containing inclusions of basic volcanic rocks, probably of andesitic composition. It is probable that the dikes described above are in part dikes and in part inclusions from the basic vol-canic rocks into which the granite was intruded. In the second area, the granite, which Mundorff (1948) mapped as Porphyritic granite, crops out as irregularly shaped masses and elongated bodies in the southeastern corner of Rockingham County, across northwestern Guilford County, and in the southeastern half of Forsyth County. The granite in this area is coarse grained to porphyritic in tex-ture and usually medium gray in color. Porphy-ritic crystals of orthoclase feldspar up to eight inches in length have been observed in this granite. The groundmass consists of feldspar, quartz, and biotite. At many places dikes and fingers of granite can be seen cutting the surrounding gneiss and schists parallel to the regional strike. The granites have intruded these rocks much more complexly than could be shown on the map. Ex-cept for gneissic structure around the margins of the bodies, which was probably inherited from the gneisses and schists into which the granite was intruded, no effects of shearing or metamorphism are present. In the third area, the granite, which LeGrand and Mundorff (1952) and LeGrand (1954) map-ped as Granite and Granite-diorite complex, be-gins about the Forsyth-Davidson county line, lies west of the Gold Hill fault, and continues south-west to the South Carolina line. Mundorff and LeGrand mapped the rocks of this area as Granite ; Granite and diorite, granite predominant; and Diorite and granite, diorite predominant. On the present map, the first two of these have been com-bined in one unit, Granite. The diorite and gran-ite, diorite predominant unit has been included in the Diorite-gabbro unit, which is discussed as a separate unit. In using this subdivision, the boundaries between the Granite unit and the Dio-rite- gabbro unit are necessarily somewhat indef-inite. In this area granite occurs in some places as distinct bodies and in other places interlayered with diorite. Large bodies composed essentially of granite, occur in northern Davidson and eastern Davie Counties, in Rowan County, and in southern Iredell and Catawba Counties. Large areas of granite-diorite complex, in which granite predom-inates and which are shown as granite, occur in Davidson, Davie, Rowan, Cabarrus, Mecklenburg, and eastern Gaston and Lincoln Counties. In the 21 granite-diorite complex, the relations of the gran-ite and diorite are uncertain. At many places, relations suggest that granite has intruded dio-rite, while at others it appears that diorite has intruded granite. In western Gaston and Lincoln Counties, granite has been intruded into gneisses and schists, forming a complex. Where granite predominates, this complex has been mapped as Granite. As a result, considerable gneiss and schist are included in the granites in Gaston and Lincoln Counties. The granites of this area vary from fine grained, through medium grained to porphyritic in texture, with medium-grained and porphyritic texture pre-dominating. Porphyritic granites are common along the western part of the area in Gaston, Ire-dell, Rowan, and Davie Counties and northwest of Concord, Cabarrus County. The other granites of the area vary from medium to fine-grained in texture, with medium-grained texture predomi-nating. Outcrops are common and vary from large boulders to flat-surface areas. Colors vary from almost white through various shades of gray and pink to almost red. Minerals present consist of orthoclase, plagioclase, quartz, biotite, musco-vite, and various accessory minerals. Where gran-ite is associated with diorite, hornblende often occurs in the granite. Jointing is widespread but not excessive at any place in these rocks. The larger bodies, composed essentially of granite, show little metamorphism, but where granite has been intruded into gneisses and schists and in the granite diorite complexities, gneissic structure is often found. The rocks of this area react readily to the forces of weathering, and as a result the residuum varies in thickness from a few inches to many feet. The residuum covering the granites varies from buff through yellow to reddish-brown in color, while that covering the granite-diorite complex is much darker in color. The granites of the Western Piedmont Belt con-sist of numerous bodies of varying size and shape lying between the Central Piedmont Belt and the Blue Ridge, exclusive of the Mount Airy granite in northern Surry County. The granite in north-ern Stokes and eastern Surry Counties are largely porphyritic. The others are medium to fine grain-ed, with medium-grained rocks predominating. Most of these rocks may be classed as biotite granite, since biotite is common in all the outcrops. They are composed of orthoclase, plagioclase, quartz, biotite, a little muscovite, and minor ac-cessory minerals. They vary from massive gran-ite, showing no metamorphism, as in Stone Moun-tain, Wilkes County, to gneissic and schistose rock, where granites have been intruded into gneisses and schists. Outcrops are in the form of boulders and flat-surface exposures. Stone Mountain in northern Wilkes County, is a barren, granite monadnock, 500 to 600 feet high and measuring three to four miles in circumference at the base. The residuum in the various areas is similar in composition and color and equally as thick as that found in other granite regions of the State. The rocks of the Granite unit as a whole have intruded a wide variety of older rocks. As a result, many small bodies and lenses of these older rocks, chiefly in the form of gneisses, schists, and meta-morphosed volcanics, are included in the Granite unit. The rocks of this unit contain quartz veins, pegmatite dikes, and dikes of granite, quartz por-phry, aplite, diorite, gabbro, and diabase, which vary in amounts and sizes from place to place. Mineral deposits as such are not abundant in the Granite unit, but the granites of the unit are the basis of an important quarrying industry. Quar-ries too numerous to discuss here, but which have been described by Councill (1954) , are widespread throughout the unit and furnish a large produc-tion of dimension and crushed granite. Syenite (sy) The only discrete body of syenite in the State is a ring dike, approximately 22 miles in circum-ference, located in the west-central part of Cabar-rus County, LeGrand and Mundorff (1952). The outcrop of this syenite body varies in width from a few hundred feet at its southern limits to more than a mile along its western border, where it is crossed by Rocky River. The Syenite is more re-sistant to erosion than the surrounding rocks and stands out strongly in relief. The area of outcrop is generally marked by large boulders and pedistal rocks. The rock is an augite-syenite, composed largely of bluish-gray feldspar and augite. It is uniformly of coarse texture and massive in struc-ture showing no effects of metamorphism. The absence of a fine-grained matrix permits the sye-nite to disintegrate into a residual granular ma-terial that makes excellent road metal. Mount Airy Granite (mag) The name, Mount Airy Granite, is introduced by the writers for a body of granite approximately eight miles long and four miles wide, which is 22 located around Mount Airy in northeastern Surry County. Much of the granite in this area is deeply weathered and covered with a thick layer of resi-dumm. The most important outcrop is located one mile north of Mount Airy, where a body of fresh granite more than five thousand feet long occupies the crest of a prominent hill. The rock is a very light gray, nearly white, biotite granite of medium texture, composed of orthoclase, plagioclase, quartz, biotite, and minor amounts of apatite, zir-con, muscovite, chlorite, and epidote. On the basis of the feldspar content, it is best classed as a quartz monzonite. The rock contains no injurious minerals and is free of joints and the effects of metamorphism. Quarrying was started at Mount Airy in 1890 and has continued uninterrupted since that time. Over the years, the quality and attractiveness of the rock has made Mount Airy granite a popular building stone. The absence of joints and lack of metamorphism have made pos-sible the production of dimension stone of almost any desired size. The rock is used extensively for the construction of mausoleums, bridges, statues, and as architectural stone and curbing. Large amounts of crushed stone are produced also. Diorite-Gabbro (digb) Rock of the Diorite-gabbro unit are confined largely to the Central Piedmont Plateau, where they are associated with granites of the Central Piedmont Belt (the Carolina Igneous Belt), dis-cussed above. They are most abundant west of the Gold Hill fault and south of Forsyth and Yad-kin Counties, but a few small bodies are found in southeastern Guilford County, southern Caswell and Person Counties, and in the northeastern cor-ners of Person and Granville Counties. The rocks of this unit range locally from diorite to gabbro but, as a whole, are intermediate between true dio-rite and gabbro. Some rocks consisting of diorite and granite, diorite predominating, are included in the unit. Areas of relatively true diorite and gabbro have been designated on the map, but most of the rock is shown as Diorite-gabbro. Bodies of almost normal diorite occur in southeastern Guil-ford, southern Caswell, and Person Counties. Bodies of nearly normal gabbro are found in northeastern Granville and Person Counties, in-side the syenite ring dike in Cabarrus County, and from a short distance north of Barber south to Bear Poplar in Rowan County. The Diorite-gab-bro is a coarse-textured rock that is distinctly massive and not closely jointed. It is composed chiefly of hornblende or pyroxene, plagioclase, and varying amounts of quartz and accessory min-erals. In some places it is exposed as rounded boulders or flat outcrops that are not much weath-ered, but in most places it is deeply weathered, and covered with a thick layer of soil that is deep red or brown and relatively fertile. At sev-eral places, both on interstream areas and along valleys, shallow depressions resembling sinks in limestone are present. These appear to be the result of weathering and solution of the Diorite-gabbro. PALEOZOIC The four units in this group have been studied and described by Olson (1944) , Griffitts and Over-street (1952), Parker (1952), and Overstreet and Griffitts (1955) and classed as Paleozoic. These workers did not agree completely as to the position the units occupy in the Paleozoic, but they were in agreement in classing them as Paleozoic in age. Two of these, Toluca quartz monzonite and Cherryville quartz monzonite, consist in part of Whiteside granite as mapped by Keith and Sterrett (1931). ToSuca Quartz Monzonite (tqm) Toluca quartz monzonite consists of numerous bodies of varying shape and size, occupying a belt extending across central and western Cleveland County, western Lincoln County, and into southern Burke County. It was named by Griffitts and Overstreet (1952) for the town of Toluca in the western edge of Lincoln County. Individual bod-ies vary from a few inches to several thousand feet thick and from a few feet to ten miles long. In general, these are parallel to the foliation of the mica gneiss into which they were intruded but occasionally cross it. Outcrops are not abundant as the rock is deeply weathered and underlies broad areas of light-gray soil. Toluca quartz monzonite is typically a medium gray, moderately gneissic rock. Usually, the smaller bodies are more strongly foliated than the larger, which, while gneissic throughout, are more strongly fol-iated near the margins. Chief minerals are oligo-clase, microcline, orthoclase, quartz, and biotite. Minor amounts of garnet and muscovite and small amounts of apatite, zircon, ilmenite, and monazite are present. The rock is characterized by a wide variation in texture and composition. The texture 23 is everywhere gneissic, but the size, shape, and arrangement of the grains vary widely. Monazite-bearing pegmatites genetically associ-ated with the quartz monzonite inject it and occur parallel to the foliation of the surrounding gneiss. These dikes vary from a few inches to several feet in thickness and often attain lengths of several iiundred feet. Overstreet and Griffitts (1955, p. 556) classed the Toluca quartz monzonite as early Ordovician in age. Cherryville Quartz Monzonite (cqm) Cherryville quartz monzonite occupies a broad belt across eastern Cleveland, western Gaston, and central Lincoln Counties. The unit was named by Griffitts and Overstreet (1952) for Cherryville, Gaston County. Outcrops are not abundant as the rock underlies thick layers of light-gray soil. South of Cherryville, the belt is parallel to the structure of the older rocks, but north of Cherry-ville, it bends eastward and crosses the structures of the older rocks. The Cherryville quartz mon-zonite contains many inclusions of country rock. It is essentially a gray, even-grained, massive to slightly gneissic rock, consisting chiefly of two varieties, one containing muscovite and biotite and the other containing muscovite but no biotite. It is, in general, a medium-grained rock, composed of oligoclase, microcline, quartz, muscovite, and biotite, with minor amounts of zircon, ilmenite, and apatite. Overstreet and Griffitts (1955, p. 556) classed the Cherryville quartz monzonite as probably Devonian in age. Two major varieties of pegmatite dikes, spod-umene- bearing and mica-bearing, are related to the Cherryville quartz monzonite. Spodumene-bearing pegmatites are restricted to the tin-spod-umene belt that lies along the east side of the Cherryville quartz monzonite bodies. These dikes are most commonly in gneiss, but some extend into the quartz monzonite bodies. These dikes vary from zoned and nongneissic, north of Kings Moun-tain, to gneissic and nonzoned, south of Kings Mountain. Mica-bearing pegmatites that are well zoned occur in the northern part of the Lincolnton and Shelby quadrangles. These form dikes that cross the foliation of the enclosing gneiss and also the Toluca quarts monzonite. Whiteside Granite (wg) The Whiteside granite unit on the present map is essentially Whiteside granite as originally nam- 24 ed and described by Keith (1907b) . It was named for the cliffs of Whiteside Mountain, Jackson County, where it is well developed. On the pres-ent map, it is shown as several areas of varying sizes and shapes, along the southern boundary of the State in Henderson, Transylvania, and Macon Counties. The granite is a light-gray, even-grain-ed, massive rock, composed of orthoclase, plagio-clase, quartz, muscovite, biotite, and minor amounts of magnetite, ilmenite, and garnet. Bio-tite varies in amount and is often absent. The granite was injected into older rocks, parallel to their foliation, and often contains inclusions of gneiss and schist. Two varieties were described by Keith. One is fine to medium grained and massive, the other contains a decided flow banding. Outcrops vary with topography, and much of the granite is covered with thick layers of light red to yellowish soil mixed with sand. ABaskite (a!) The Alaskite unit consists essentially of a coarse-grained pegmatitic granite that crops out near Spruce Pine, Mitchell County, as a number of bodies varying greatly in size and shape. The rock, which has been of interest to miners in the Spruce Pine district for several years, was desig-nated by Hunter (1940) as alaskite. It consists essentially of oligoclase, quartz, microcline, and muscovite, listed in the order of abundance. Dark-colored minerals are almost absent, but small amounts of biotite and garnet occur at places near inclusions or contacts with country rock and are apparently products of contamination. The rock is not true alaskite, but the name is so well estab-lished in the Spruce Pine district that it is used here. The alaskite masses are granitoid in tex-ture and uniform in grain size and mineral con-tent. Much of the rock is sufficiently coarse-grained to be called pegmatite, but its uniformity and wide extent make the name Alaskite appro-priate. The alaskite bodies contain many inclu-sions of gneiss and schist near their margins, but internally they are relatively free of such. Alas-kite bodies containing inclusions of gneiss and schist often grade into gneiss and schist, contain-ing numerous bands and lenses of alaskite. Most inclusions, as well as alaskite bands and lenses, are parallel to one another and to the foliation of the country rock. Pegmatites occur in all parts of the alaskite, but the average size and number is greater near the margins of the alaskite bodies. The pegmatites in alaskite and in the surrounding gneisses and schists are important sources of mica, feldspar, kaolin, and other minerals, for the production of which the Spruce Pine district is widely recogniz-ed. Sheet mica is obtained almost exclusively from pegmatites. For many years, feldspar and kaolin were produced from fresh and weathered pegmatites. As the demands for these minerals increased, attention was directed to alaskite, and it is now the chief source of feldspar, kaolin, and flake, or scrap, mica. Large bodies of unaltered alaskite serve as a source of feldspar by flotation. In many places, the alaskite is deeply weathered, often to depths approximating a hundred feet. Many of these weathered deposits are rich in kaolin and contains considerable flake mica. Most of the kaolin and a large part of the flake mica produced in the State are being obtained from weathered alaskite. Economically, Alaskite is one of the most important rock units shown on the present map. TRSASSICC?) Two units, Bakersville gabbro and Diabase dikes, are shown as Triassic(?) on the present map. Diabase dikes have been considered of pos-sible Triassic age for many years and probably should be classed as Triassic without the query; however, there is some question as to the exact age of the Bakersville gabbro. Keith (1903) first named this unit and described it in the text as Juratrias(?) but showed it in the legend on the geologic map as Juratrias without the query. The unit has received considerable attention in recent years, but its exact age is still in doubt. Kulp and Brobst (unpublished) showed Bakersville gabbro on an unpublished geologic map of the Spruce Pine district as Devonian. Brobst (1955, pp. 584- 585) described the unit briefly and pointed out that it is considered younger than the alaskite and pegmatites. As to age, he stated, "The Bakersville might have been emplaced between the late Ordo-vician .or early Silurian and the Triassic." The Committee on Geologic Names of the U. S. Geo-logical Survey recommends Triassic (?) for the Bakersville gabbro, and it is so shown on the present map. Bakersville Gabbro ("Rg) Bakersville gabbro outcrops are shown on the map near Bakersville, Mitchell County, and south and west of Elk Park and Cranberry, Avery County. The major outcrop near Bakersville is roughly triangular in shape, with a maximum length of five miles and a maximum width near the base of the triangle of about three miles. The outcrop near Elk Park and Cranberry is about two miles long and one mile wide. A number of out-crops too small to be shown on the map are found in the general area. Keith (1903) named the unit for Bakersville, Mitchell County, and described it briefly. It is a dense, hard, unmetamorphosed rock, nearly black when fresh but becoming red-dish brown on weathering. It is composed chiefly of plagioclase, hornblende, and pyroxene in crys-tals of medium size, with small amounts of mag-netite, epidote, and garnet as accessory minerals. The texture is usually massive and granular but occasionally becomes aplitic. Outcrops consist of spheroidal masses and boulders mixed in a dark-brown clay. Diabase Dikes (lid) Diabase dikes of probable Triassic are widely distributed throughout the Piedmont and Moun-tain regions of North Carolina. They are most abundant in and adjacent to sedimentary rocks of Triassic age along the eastern and central Pied-mont region, but become less common in the west-ern Piedmont and are found sparingly in the Blue Ridge region. They also occur frequently along the western edge of the Coastal Plain where pre- Triassic rocks are not covered by younger sedi-ments. Because of the wide distribution and limited area of outcrop, Diabase dikes are shown in only two localities on the map. One of these is the Deep River basin in Chatham, Lee, and Moore Counties, and the other is an unusually long dike northeast of Morganton, Burke County. In the Deep River basin, according to Reinemund (1955), who gave an excellent description of the diabase intrusives in that basin, dikes, sills, and sill-like masses occupy about four percent of the Triassic rocks. Diabase dikes in the Deep River basin vary in width from less than an inch to 320 feet and in length from a few feet to nearly seven miles. Most dikes in the area are between 20 and 75 feet wide and are fairly constant in width for several thousand feet of length. Sills and sill-like intrusives of diabase are abundant in the Deep River basin Triassic sediments and range in thick-ness up to 400 feet. In the Morganton area, an unusual diabase dike extends in a northwest-south-east direction with minor interruptions for nearly twenty miles. 25 The diabase intrusives are massive, crystal-line, unmetamorphosed rock that varies in color from dark gray, grayish black to nearly black. The minerals and textures present are those commonly found in normal diabase, except some of the larger sills which more nearly ap-proach gabbro in composition. In general, the dikes form low ridges and divides, but in the Deep River basin, they are an important influence on drainage patterns. The direction of flow of sev-eral streams in the area is determined in part by the trends of the dikes. Many springs occur along these dikes, and it has been learned from experience that water-well sites located near dikes are more likely to furnish good yields. Outcrops are common in the form of boulders, which were produced by spheroidal weathering along the joints in the rock. Two types of soil, one a brown or grayish-brown, silty loam and the other a dark red to brownish-red heavy clay loam, occur over areas of diabase. Both soil types are underlain with yellow to dark red, sticky clays. METAVOLCANIC ROCKS Metavolcanic rocks occur in three distinct geo-graphic areas in North Carolina. First and most important is the Carolina Slate Belt which actually consists of two belts, one lying across the central part of the State, and the other lying along the eastern edge of the Piedmont Plateau and western edge of the Coastal Plain. Second is the Grand-father Mountain Window, which lies partly in the Blue Ridge area and partly in the Piedmont Pla-teau in Avery, Watauga, Caldwell, Burke, and Mc- Dowell Counties. Third is a relatively small area known as the Mount Rogers volcanic group which lies in the northwestern corner of Ashe County. PRECAMBRIAN OR LOWER PALEOZOICt?) CAROLINA SLATE BELT Rocks of the Carolina Slate Belt, because of their complex character and well defined cleavage, have been called slates. Actually, they consist of volcanic-sedimentary formations, composed of slates, breccias, tuffs, and flows. The flows are interbedded with the breccias and tuffs, while the tuffs pass gradationally into slates. These rocks vary from acid or rhyolitic to basic or andesitic in composition and generally have a well developed cleavage, which gives them a slaty appearance. Rocks of the Carolina Slate Belt series actually form two belts in the State. The first and most important of these, and the one which Olmstead (1825) first called the Great Slate Formation, crosses the central part of the State in a northeast direction from Anson and Union Counties on the south to Granville and Person Counties on the north. This belt varies in width from 25 to 60 miles and consists of metavolcanic rocks intruded at many places by younger granites, described above. The second belt, in which metavolcanic rocks are exposed as irregular bodies of varying size and shape, lies along the eastern edge of the Piedmont Plateau and western edge of the Coastal Plain. This belt, in which Kerr (1875, p. 131) first recognized rocks similar to those of the Great Slate Formation of Olmstead, begins in Richmond County on the south, varies greatly in width, and continues in a northeast direction to Northampton County on the north. Olmstead (1825), Emmons (1856), and Kerr (1875) considered the rocks of the slate belt as sedimentary in origin but described them as slates, containing beds of porphyry, hone or whetstone slate, breccia, and conglomerate. Emmons (1856) placed the rocks in the Taconic System, while Kerr (1875) classed them as Huronian in age, which, according to his geologic column, is a division of the Archean. Williams (1894) recognized for the first time the presence of volcanic rocks in the slates. He described exposures of volcanic flows, breccias, and tuffs, which had been sheared into slates by dynamic metamorphism. Nitze and Hanna (1896) recognized volcanic rocks in the slate belt and considered the Bedded argillites (volcanic slate) of the present map as younger than the volcanics and called them Monroe slates. It is now recognized that the Monroe slates repre-sent a better bedded, less metamorphosed portion of the slate-belt rocks. Following the work of Williams (1894) , reports by Laney (1910 and 1917), Pogue (1910), and Stuckey (1928) emphasized the importance of volcanic rocks in the slate belt but did not over-look entirely the presence of sedimentary material. These authors considered the rocks of the slate belt to be largely of volcanic derivation but recog-nized the presence of considerable sedimentary (nonvolcanic) material and classed the whole se-ries as laid down by sedimentary processes. Mapping carried out for the compilation of the present map tended to verify the above findings. Rocks which may be classed as flows, breccias, 26 tuffs, and shales or slates were found to be present. All of these, except flows, contain considerable amounts of nonvolcanic materials. The flows, breccias, tuffs, and slates are all interbedded and do not occupy any definite stratigraphic positions in the series. The flows vary from rhyolite, through andesite, to basalt. The rhyolites and andesites vary from fine grained to coarsely por-phyritic, while the basalts are often amygdaloidal. The breccias vary from rhyolitic to andesitic in composition and in size from an inch to nearly a foot in diameter. The fragments of the breccias are, in turn, fragmental, apparently of a pyro-clastic origin. Some of the fragments in the breccias are sharply angular, while many are rounded, indicating transportation and deposition. The tuffs are generally of acid composition and composed of fragments less than an inch in diam-eter. These fragments, which vary from angular to rounded, are embedded in much fine-grained material apparently of nonvolcanic origin. Be-ginning at Siler City, Chatham County, and con-tinuing southwest for 15 to 20 miles are several beds of quartz conglomerate, varying in width from a few inches to 250 feet and of unknown length. The quartz pebbles are less than an inch in diameter and well rounded, further indicating sedimentary processes. The shales or slates, which are generally well bedded, are composed of fine-grained volcanic material and much land waste. Finally, much of the finer material in the breccias, tuffs, and portions of the shales or slates strongly resembles metasiltstone and metagraywacke of some of the metagraywacke rocks in other areas, further indicating sedimentary origin. In view of the above facts, there is a strong trend on the part of some workers to drop the term metavolcanic and use one that defines the rock more nearly as sediments. That idea was considered for the present map but was discarded in favor of metavolcanics, since the rocks of the slate belt are largely of volcanic origin, and the terminology has been in the literature for more than sixty years. No fossils have been discovered in the slate belt, and the age of the rocks is not known. For many years they were classed as Precambrian, while in recent years there has been a trend towards classing them as lower Paleozoic. On the present map, they are classed as Precambrian or Lower Paleozoic (?). They have been divided into three units, Felsic volcanics, Mafic volcanics, and Bed-ded argillites (volcanic slate). Felsic Volcanics (fvs) Rocks of the Felsic volcanics unit occupy about half of the Carolina Slate Belt in the central part of the State and are the only rocks shown in that portion of the belt lying along the eastern part of the Piedmont Plateau and western part of the Coastal Plain. In the central part of the State, rocks of the Felsic volcanics unit occupy much of the eastern part of the Carolina Slate Belt north-east of Anson, Richmond, and Stanly Counties. The rocks of the Felsic volcanics unit are com-posed largely of materials of volcanic flow or frag-mental origin. The flows are essentially rhyolite, while the fragmental materials vary from rhyo-litic to dacitic in composition. The fragmental rocks consist of breccia and coarse and fine tuff, with coarse and fine tuff making up the greater portion of the unit. Lenses of bedded slate and mafic volcanics, too small to show on the map, are present in this unit. The rhyolite occurs as narrow bands and lenses interbedded with the breccia and tuff. It is dense and indistinctly porphyritic with a dark gray to bluish color, and, on fresh surfaces, shows a greasy luster. Flow lines are often present and are best seen on weathered surfaces, while amygdaloidal structure is also present. In porphyritic speci-mens the minerals are plagioclase, orthoclase, and quartz. None of the rhyolite outcrops show any effects of metamorphism. The fragmental rocks consist of breccia and coarse and fine tuff. The coarse tuff predominates and contains the breccia and fine tuff as interbed-ded bands and lenses. The fragments composing these rocks are angular to well rounded and vary in size from nearly a foot to a fraction of an inch in diameter. The larger fragments are internally fragmental, while the finer material grades into Bedded argillites (volcanic slate) . At places, within a few inches, fine fragmental rock grades into a rock showing bedding planes. When freshly broken, the rock proves to be made up of quartz and feldspar grains and rock fragments, some of which show a flow structure, set in a dense bluish or greenish groundmass. In general, the rocks of this unit have a light gray to greenish color. In the central part of the State, the rocks of the Felsic volcanics unit vary from massive to schistose. At places, the fragmental texture of the rock may be seen, but much of the rock has been strongly metamorphosed and possesses a well denned slaty cleavage that strikes northeast- 27 southwest and dips to the northwest in the south-ern part of the area and to the southeast in the northern part. The felsic volcanics weather to a light gray soil usually underlain by yellow to light-red clay. The layer of soil and clay is usually thick, and outcrops of fresh rock are not abund-ant. Along the eastern part of the Piedmont Plateau and western edge of the Coastal Plain, all the raetavolcanics of the Carolina Slate Belt are shown as the Felsic volcanics unit on the present map. The rocks are deeply weathered and covered by a thick layer of soil. As a result, outcrops of fresh rock are scarce, and mapping is difficult. Mun-dorff (1946) showed these rocks on the legend of his map as Slates, schists, and metamorphosed volcanics. He considered the series as metamor-phosed sedimentary and igneous rocks, including lavas, tuffs, and breccias. He did not mention rhyolite or rocks of a mafic character but did refer to a coarse breccia near Roanoke Rapids. In the course of fieldwork for the present map no rhyo-lite was seen, but small amounts of breccia and in one or two places small outcrops of mafic volcanics too small to show on the present map, were ob-served. In general, the rocks of this area consist of coarse to fine tuff and bedded slate, with which bodies of gneiss and schist are present in many places. The tuffs and bedded slates are present throughout the area in about equal amounts. In some places, bedded slate predominates, and in others tuffs predominate. These rocks are usually altered near igneous intrusions to garnetiferous mica schist, mica hornblende schist, or biotite schist. Some bodies of gneiss and schist not ap-parently related to igneous intrusives are present and probably represent metamorphosed nonvol-canic sediments. Six miles west of Smithfield, Johnston County, on the east side of U. S. High-way 70, is a large outcrop that resembles quartzite and contains kyanite crystals. It may be siliceous sediment metamorphosed to quartzite, or it may be a silicified tuff. Similar outcrops, except for the kyanite, are found north of Princeton in the eastern part of Johnston County. The bedded slates are dark blue to greenish gray when fresh and become various shades of yellow and red when weathered, while the tuffs, gneisses, and schists are generally gray, yellow, or brown. All these rocks have been moderately metamorphosed and contain a cleavage that strikes northeast and stands nearly vertical. Mafic Volcanics (mvs) Rocks of the Mafic volcanics unit are shown on the present map only in the northern two-thirds of Carolina Slate Belt in the central part of the State. They are scattered throughout the area but are more abundant along the western side. The rocks of this unit consist largely of flows and fragmental materials of volcanic origin. The flows vary from andesite to basalt, while the frag-mentals are generally andesitic in composition. Lenses of bedded slate and felsic volcanics, too small to show on the map, are present in this unit. The andesite and basalt occur as narrow bands and lenses interbedded with the fragmentals. The andesite is dark green in color, usually massive or fine grained, but occasionally coarsely porphyritic. A coarse porphyritic variety, with hornblende crystals up to two inches long, occurs in western Randolph County. The basalt is dark to nearly black and often amygdaloidal. Both the andesite and basalt are characterized by the lack of a well defined cleavage. Minerals present consist of epidote, plagioclase, quartz, secondary calcite, and iron oxides. Epidote is the most abundant min-eral present, giving the rock its green color. The fragmentals consist of breccias and tuffs of andesitic composition, often intermixed with much fine-grained material. In places these rocks are fine grained and lack the fragmental appearance. In such areas, one of which may be seen along U. S. Highway 64 for a mile west of Haw River, the rock strongly resembles a graywacke. The breccias and tuffs contain much epidote and often have a greenish color. Other colors vary from dark gray to nearly black. In addition to epidote, plagioclase, and quartz, secondary calcite and iron oxides are present. The mafic fragmentals are not as strongly metamorphosed as the felsic frag-mentals but contain a cleavage that strikes north-east and dips to the northwest in the southern part of the area and to the southeast in the northern part. These rocks are usually covered with a thick layer of dark-red residuum. Bedded Argillifes (Volcanic Slate) (ar) Bedded argillites (volcanic slate), commonly re-ferred to as slate, bedded slate, or volcanic slate, occur in the southern part of the Carolina Slate Belt in the central part of the State and extend north as far as the central part of Davidson and Randolph Counties. A few small areas are shown on the east side of the belt in Montgomery, Moore, 28 and Chatham Counties. There are also some small areas east of the Jonesboro fault in Anson and Richmond Counties. The unit as shown on the map is chiefly bedded argillites or bedded slate, but many lenses of felsic and mafic volcanics, too small to show on the map, are included. The Bedded argillites (volcanic slate) consist chiefly of dark-colored or bluish shales or slates, which are usually massive and thick bedded. However, the beds occasionally show very .finely marked bedding planes. Contacts between the slates and the tuffs are usually grada-tional, and often a single hand specimen will show gradation from a bedded slate to a fine-grained tuff. Much of the slate is massive and jointed, showing little effects of metamorphism, while in other places it has been strongly metamorphosed and shows a well defined, slaty cleavage. The cleavage, or schistosity, does not in most places correspond to the bedding planes of the rock. In places, especially near igneous intrusive and min-eralized zones, the slate is highly silicified and often resembles a chert. The slates are deeply weathered, and good outcrops of fresh rock are seldom seen. In general, they are covered with a thick layer of residuum, which consists of light soil on top and yellowish, decomposed slate be-neath. The rocks of the Carolina Slate Belt have fur-nished mineral resources of considerable impor-tance for many years. Between 1800 and 1860, the slate belt produced important amounts of gold. Gold mining is no longer important, but many quartz veins in the area contain varying amounts of silver, lead, zinc, and copper. The production of these metals has never been large, but the veins continue to attract the attention of individuals and mining companies. Important deposits of pyrophyllite occur in Moore, Randolph, Alamance, Orange, and Granville Counties, from which large amounts of pyrophyllite are being mined. The Bedded argillites (volcanic slate) are deeply weathered in many places to clay and shale, suitable for the manufacture of clay prod-ucts. Brick and tile are being produced in large amounts from these materials. Lightweight ag-gregate is being produced in Stanly County from semiweathered slate. Rocks of the Carolina Slate Belt were first used for building purposes at Hills-boro in colonial days. More recently, both felsic and mafic volcanics were quarried near Hillsboro and used in the construction of the buildings on the West Campus of Duke University. Bedded slate is being quarried in southern Davidson County and southern Montgomery County and used as building stone and flagstone. When fresh and unweathered, the bedded slate makes an ex-cellent crushed stone, and large amounts are be-ing produced. Upper Precambrian grandfather mountain window The Grandfather Mountain window area is nearly surrounded by the Grandfather Mountain fault and lies partly in the Blue Ridge and partly in the Piedmont Plateau in Avery, Watauga, Cald-well, Burke, and McDowell Counties. Keith (1903) mapped and described four units in that area, as follows : Linville metadiabase, Montezuma schist, Flattop schist, and Metarhyolite. His names and descriptions have been retained on the present map. Linville Metadiabase (Imd) Linville metadiabase occurs as irregular out-crops associated with Montezuma schist, Flattop schist, Cambrian quartzite, and as narrow bands in Cranberry granite gneiss. It occurs as flows, which came up through cracks in older rocks, such as those now filled with metadiabase in the Cran-berry granite. The metadiabase contains plagio-clase, largely altered to epidote, chlorite, and quartz. Other original minerals, olivine and augite, are largely replaced by hornblende, epidote, and chlorite. Epidote sometimes occurs as grains and masses as much as six inches in diameter. The rock has been much metamorphosed, but at places its original character is retained. It is generally of a dull-yellowish color, due to epidote, chlorite, and hornblende. The metadiabase weathers read-ily and usually is covered by a thick layer of dark-red and brown clay. Montezuma Schist (mtsh) The Montezuma schist consists of fine-grained epidotic and chloritic schists and amygdaloidal beds and is rather uniform in appearance. Orig-inally it was probably a basalt, but it has been so completely metamorphosed that only a few traces of flow banding remain. Amygdaloidal beds are the commonest evidence of its original nature. The color of the rock when fresh is bluish black, gray, or green, becoming more green and yellowish green on weathering. The chief min- 29 erals are chlorite and feldspar in abundance and muscovite, epidote, and quartz in small amounts. The schists weather slowly and usually form high ledges and cliffs, while the amygdaloidal beds weather more readily and are covered with thick clay of yellow or red color. Flattop Schist (fsh) This unit, named for Flattop Mountain, Watau-ga County, consists of black, dark-blue, bluish-green, and greenish-gray schists, which weather to a yellow or greenish-gray color. The schist is commonly banded. The bands, which are seldom more than half an inch thick, consist of quartz and feldspar grains of varying size, and the rock strongly resembles a sandy slate of sedimentary origin. Where not banded, the schist contains pyrophyritic crystals of feldspar and amygdules, indicating that it is volcanic in origin. Originally, the rock was probably a lava flow, but it has been strongly metamorphosed, and most of the original minerals have been replaced by secondary quartz, feldspar, and mica. The Flattop schist resists decay and forms ridges and mountains. Final decay produces a reddish, sandy clay. Metarhyolite (mry) This unit consists mainly of fine metarhyolite but occasionally contains layers which show por-phyritic crystals of feldspar and quartz. When fresh, the rock is dark blue, dark gray, and bluish black; but, when weathered, it becomes dull yel-low and yellowish gray. It occurs as intrusive sheets and dikes in older rocks and as surface flows. The unit has been greatly metamorphosed, but flow banding and amygdules are occasionally poorly preserved. The rocks of this unit vary from rhyolite, little altered, to a well defined schist, depending on the original nature of the rocks and the amount of metamorphism. These rocks weather slowly, but final decay produces a thin layer of fine yellow and red clay. MOUNT ROGERS VOLCANIC GROUP (mr) The Mount Rogers volcanic group, named by Stose and Stose (1944, pp. 410-411) for Mount Rogers, the highest point in Virginia, underlies a small area in the northwest corner of Ashe County, North Carolina, adjacent to Tennessee and Virginia. Jonas and Stose (1939, pp. 590- 591) and Rogers (1953, p. 23) have summarized very well the characteristics of the group. The 30 unit consists of purplish and greenish metavol-canic rocks, chiefy metarhyolite, but apparently contains tuffs as well as flows. The rock has been strongly metamorphosed and possesses a slaty cleavage. Some of it is good slate; but, despite the foliation, much of the rock forms massive ledges and blocks. The foliation of the more mas-sive rock is interrupted by small, irregular masses of quartz, while the slaty rock commonly contains small, very thin lenses of chlorite and epidote. Interbedded with the volcanic rocks are layers of conglomerate, graywacke, and nonvolcanic silty shale or slate. The rocks of the group often crop out in large masses, and at places in Tennessee and Virginia, they form high, rough mountains. They weather to a thin, very strong, light soil. METASEDIMENTARY ROCKS Rocks more or less metamorphosed but retaining enough of their original characteristics to indicate that they were originally sediments are classed as metasedimentary rocks on the present map. They occur in four areas, commonly known as the Kings Mountain area, the Stokes County area, the Brevard area, and the Murphy area. The rocks in the Stokes County area and the Kings Mountain area appear to be much alike and stratigraphically equivalent. On the present map, these two areas are classed as the Stokes County and Kings Moun-tain Belt, while the other two are classed as the Brevard Belt and the Murphy Belt. The ages of the rocks in these three belts are not definitely known, but it is assumed that their position in the explanation is essentially correct. Upper precambrian(?) or lower paleozoic?) stokes county and kings mountain belt Kings Mountain Group (kmg) The rocks of this unit fall into two natural groups, one of which consists of highly siliceous rock, while the other consists largely of calcareous rock. The siliceous group consists in the Kings Mountain part of the belt, of slate, rhyolite, vol-canics, quartzite, and conglomerate, and, in the Stokes County part of the belt, of mica schist, quartz mica schist, and quartzite. In the Kings Mountain area, the slates and phyllites are essen-tially sericitic schist. Pyroclastic textures are not abundant but are common enough to indicate that volcanics make up an important part of the group. Quartzite and conglomerate are present in beds that crop out prominently at many places. In the Stokes County area, the chief rocks are quartzite, mica schist, and quartz mica schist, apparently interbedded. At a few places in the Stokes County area is found a flexible sandstone, consisting of fine, interlocking quartz grains and mica flakes. Throughout the Stokes County and Kings Moun-tain Belt, the siliceous rocks form the higher ele-vations and prominent ridges, often called moun-tains. The calcareous group is confined largely to the Kings Mountain part of the belt and consists of crystalline limestone, dolomite, and calcareous metashales. In the southern part of Catawba County and the northern part of Lincoln County, interesting amounts of hornblende gneiss are found, apparently interbedded with quartzite, that probably represent metamorphosed calcareous shales. One important body of crystalline lime-stone occurs near Siloam, Yadkin County, in the Stokes County part of the belt. Other limestone bodies, mentioned above, occur in mica gneiss along the southern border of the belt in Yadkin and Stokes Counties, that may or may not belong in this group. The limestone and dolomite of the belt have been quarried intermittently for years, and a large quarry is in operation near Kings Mountain. The quartzite in the Kings Mountain part of the belt contains interesting amounts of kyanite, but it has not been mined in North Carolina. LOWER CAMBRIAN(?) BREVARD BELT Brevard Schist (bv) The Brevard Belt begins in North Carolina at the state line, southwest of Brevard, for which it was named by Keith (1907b), crosses Transyl-vania, Henderson, and Buncombe Counties, and ends in McDowell County, a short distance north-west of Old Fort. The Brevard schist, the only unit in this belt, consists mainly of schist and slate. Schist, which predominates, is of a dark-bluish- black, bluish-black, black, or dark-gray color. Lenses of limestone, varying from a few hundred feet to more than a mile in length and up to 250 feet in thickness, are scattered widely throughout the belt. Thin layers of quartzite and conglomerate are occasionally found. Graphite is widely disseminated as small flakes through large masses of the rock and occasionally forms lenses that are graphite schist. The schists are composed of quartz and muscovite, through which are scat-tered numerous small grains of iron oxides, while garnets are occasionally found. The slates are essentially clay slates. The rocks are all essen-tially fine grained except for occasional layers of quartzite and conglomerate. Some years ago graphite was produced from the northern part of the belt, west of Old Fort but none has been mined in recent years. Considerable amounts of crystalline limestone have been pro-duced for lime, agricultural lime, and aggregate near Fletcher, Henderson County. At the present time, crushed stone for aggregate is the chief ma-terial being produced. Near Etowah, Henderson County, a clay slate weathered to a shale is being used for the manufacture of brick. MURPHY BELT Rocks of the Murphy belt occur in the southwest corner of the State, where Keith (1907a) mapped a synclinal structure and named the following formations: Tusquitee quartzite, Brasstown schist, Valleytown formation, Murphy marble, An-drews schist, and Nottely quartzite. The Tusqui-tee quartzite and Nottely quartzite could not be shown on the present map due to the limited area each covers. They are much alike and consist essentially of v/hite quartzite. On the present map the Brasstown schist and Valleytown formation are shown as separate units, while the Murphy marble and Andrews schist are combined as one unit due to the limited area each covers. Brasstown Schist (bt) The Brasstown schist consists of schists and slates more or less banded. The greater part of the formation consists of banded ottrelite schist, but some of it is banded slate with little or no ottrelite. All the rocks are dark colored and vary from dark blue or bluish black to dark gray. They are usually marked by a fine banding of light and dark-gray colors. The light layers are often sili-ceous and sometimes grade through sandy slate into sandstone. The slates are argillaceous, while the schists are more siliceous. The most outstand-ing mineral is ottrelite of dull-bluish or greenish-gray color, but varying amounts of garnet and staurolite are present at many places. The rocks 31 weather to thin, yellow and brown clay soils of poor fertility. Valleyfrown Formation (vfr) The rocks of the Valleytown formation vary widely from place to place but consist mainly of mica schist and fine-banded gneiss. However, in many areas, mica slate, argillaceous slate, gray-wacke, feldspathic sandstone, and occasionally beds of coarse quartzite are present. These rocks are usually dark colored, varying from dark gray to grayish black. In most of the rocks the min-erals that can be identified in hand specimens are quartz and mica in the mica schist and feldspar and quartz in the feldspathic sandstone ; however, bands of ottrelite schist and garnet schist are often present. The rocks of this unit are resistant to weathering and stand up as knobs and ridges. Final decay produces a thin soil, full of rock frag-ments, which is of little value. Andrews schist—Murphy Marble (ma) Because of limited areal extent, the Murphy marble and Andrews schist have been combined into one unit on the present map. The Murphy marble is found in two areas, one along the Nan-tahala and Valley Rivers in Swain and Cherokee Counties, and the other along Peachtree and Little Brasstown Creeks in Cherokee County. The rock consists entirely of marble, rather fine grained but completely crystalline. The predominant color is white, but a large part of the marble is dark gray or blue, and many layers consists of banded or mottled blue and white. In the Red Marble Gap some of the layers have a rose-pink color. Van Horn (1948 pp. 12-13) established a zoning or stratigraphic sequence in the marble, based on color and secondary minerals. The Murphy mar-ble passes by gradation into the Andrews schist and often contains bands of schist. Other than crystals of calcite and dolomite, the marble con-tains mica, quartz, garnet, and ottrelite along gradational zones and talc and tremolite at many places. Much of the marble underlies low ground and is covered with stream deposits of sand and gravel. The Andrews schist consists essentially of thin beds of calcareous schist of relatively light-gray color. It is characterized by a large number of ottrelite cyrstals, which lie at right angles to the bedding. Muscovite and biotite occur frequently, lie parallel to the bedding, and are the chief cause of the schistose planes in the rock. The Andrews schist weathers readily and usually underlies low ground. It is usually covered wit ha residual, micaceous clay, that grades downward into fresh rock. The Murphy marble is an attractive rock, and over the years considerable dimension and crushed stone have been produced from it. Building, mon-umental, and crushed stone are being produced near Marble, Cherokee County, and crushed aggre-gate and agricultural limestone are being produced near Hewitts, Swain County. A white, fine-grain-ed dolomite, occupying the approximate center of the marble, often contains deposits of high-grade talc. This talc has been mined for years and is presently being produced about one mile south-west of Murphy. Iron ore in the form of limonite occurs at many places, usually associated with the Andrews schist. Production was carried on for many years with maximum development and min-ing taking place between 1917 and 1920. No pro-duction has been made since 1921. SEDIMENTARY ROCKS Upper precambrian OCOEE SERIES Along the western boundary of the State, in Cherokee, Graham, Swain, Haywood, and Madi-son Counties and smaller areas in Clay, Jackson, and Mitchell Counties, occurs a thick sequence of clastic, nonfossiliferous sedimentary rocks. These rocks were named the Ocoee conglomerate and slates by Safford (1856) from the exposures along the Ocoee River between Parksville and Ducktown, Tennessee. Keith (1895, 1896, 1904, and 1907c) mapped and named a number of forma-tions within the series ; however, his formations differed considerably from one folio to another. Rodgers (1953), in his compilation of a geologic map of East Tennesse |
OCLC Number-Original | 4201730; 2306506 |
OCLC number | 4201730; 2306506 |
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