Geologic map of the North Carolina portion of the John H. Kerr Dam 7.5-minute quadrangle, Warren and Vance Counties, North Carolina

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF LAND RESOURCES NORTH CAROLINA GEOLOGICAL SURVEY JAMES D. SIMONS, DIRECTOR AND STATE GEOLOGIST This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program OPEN FILE REPORT 2010-01 78° 22' 30" 78° 15' 00" 36° 37' 30" 36° 30' 00" \3>i жЙшАйР ft V. X ; D - ni ■Щ'?' у ■'BURG СО, ГЩщ& СО ■■ 7 MCsc. CZvbm ZPmi CZvbm i ZPwms ZPmi ZPwms iZvbm CZvbm John U. Keir Reservoir MCSC 74 MCsc ZPwms MCsc -,-©£• f 81 MCsc / ZPwms MCsc 78 36° 37' 30" 36°30' 00" 78° 22' 30" 78° 15' 00" Description of Map Units Qal Qal - Quaternary alluvium: Unconsolidated, poorly sorted and poorly stratified tan to light gray stream deposits of gravel, sand, silt, and clay. Jd - Diabase dikes: Steeply dipping to vertical, gray to blue-black, slightly to severely weathered, fine to medium crystalline, locally porphyritic plagioclase diabase that may be olivine-bearing. MCsc MCsc - Cataclasitic fault zone: Silicified and highly fractured zone containing mm to cm scale silicified angular clasts. Extensional veins of rhombohedral quartz prisms and local epidote common. Silicified and epidotized clasts of granitic gneiss locally preserved. Considered to be Mesozoic or Cenozoic in age. Rocks of Unclear Affinity ZPum - Ultramafic rocks: Hypermelanocratic to melanocratic (Cl greater than 65), green to black-green interlayers of massive, coarse-grained actinolite talc schist and medium-grained metagabbro. Locally associated with epidote-quartz rock. Appears as a large enclave in biotite granite. ZPpg - Porphyroclastic plagioclase biotite hornblende gneiss: Mesocratic (CI-35-45), black-gray to blue-gray, medium grained to porphyroclastic gneiss. Biotite and hornblende define a foliation associated with mm-scale plagioclase and quartz compositional layers and larger plagioclase porphyroclasts. Grain size variations in part due to mylonitic overprint. ZPfg - Felsic Gneiss: Leucocratic (Cl less than 5-10), orange-gray and white-tan. dominantly very fine to fine grained, well foliated, white mica quartzofeldspathic gneiss. Minor compositional layers vary in biotite and white mica content in chiefly a microcline. plagioclase. and quartz matrix. Mylonitic and ultramylonitic overprint obscure protolith relationships. ZPfg ZPpg ZPwms - White mica ± sillimanite ± garnet ± chlorite schist: Medium-fine to medium crystalline, gray to gray-tan. strongly foliated and iineated white mica + sillimanite + garnet schist. Medium crystalline, strongly foliated and Iineated. green-gray, white mica + chlorite ± sillimanite ± garnet schist. Sillimanite is prismatic and occurs along the foliation plane. Contact with ZPfg is often transitional. Flattened and rotated quartz and feldspar aggregates commonly occur as porphyroclastic minerals forming composite S-C surfaces and C’ foliations defined by white mica. Often intruded by pegmatitic to coarsely crystalline, porphyroclastic white mica ± biotite + quartz + feldspar gneissic metagranitoid sills that are locally migmatitic and often intruded along the foliation plane. Raleigh Terrane Pgi - Foliated granitic mylonitic gneiss: Leucocratic (Cl less than 1 0-15), pink-tan and white-gray-tan, dominantly fine- to medium-grained, well foliated and Iineated. white mica ± biotite granitic gneiss. Some domains vary in biotite and white mica content in chiefly a pink -white microcline. plagioclase. and quartz matrix and may represent earlier enclaves or later intrusive granitoids. Mylonitic and ultramylonitic overprint obscures contact relationships. Flattened and rotated K-feldspar porphyroclasts form composite S-C surfaces and C-shear bands. Intruded by multiple generations of white to pink-gray-white pegmatitic quartz + K-feldspar dikes and sills. Locally contains amphibolite, hornblende gneiss, and biotite schist enclaves. pgi ZPwms Pg2 - Foliated granitic rocks 2: Medium to coarsely crystalline and often megacrystic. porphyroclastic, strongly foliated, blue-gray to gray-tan. leucocratic to mesocratic, locally compositionally layered biotite ± white mica + K-feldspar gneiss. Commonly protomylonitic to mylonitic and ultramylonitic. Pg3 Pgr - Foliated granitic rocks 3: Medium crystalline, tan-gray to blue-gray, leucocratic to mesocratic. well foliated biotite + white mica metagranitoid and white mica ± biotite ± garnet leucocratic metagranitoid. Commonly protomylonitic to mylonitic and porphyroclastic. Also includes mylonitized pegmatitic to coarsely crystalline, porphyroclastic white mica ± biotite + quartz + feldspar metagranitoid sills that are locally migmatitic and often intruded along the foliation plane. eZfgf CZfgf - Foliated felsic gneiss: Leucocratic (Cl less than 2). dark to light pink-red-orange, fine- to coarse-grained felsic protomylonitic, mylonitic, and ultramylonitic granitic gneiss. Variably foliated and Iineated, and locally contains relict red-orange K-feldspar porphyroclasts and pegmatitic K-feldspar and quartz layers and boudins. Form resistant lakeside outcrops and cobble and boulder fields that are highly fractured. Outcrops are reminiscent of the Ruin Creek Gneiss or Falls Leucogneiss. ZPahg ZPahg - Amphibolite and hornblende gneiss: Mesocratic (Cl-50), blue-green-white to gray-green, foliated and Iineated, medium-grained compositional layers of more mesocratic amphibolite and less mesocratic hornblende gneiss. Occur as local outcrops in Pgi interpreted to be enclaves. ZPbs ZPbs - Biotite schist: Silver-gray to silver-black, fine to medium grained, compositionally layered, and well foliated and Iineated. White mica, biotite. quartz, and plagioclase define a lepidioblastic matrix for local garnet porphyroblasts several mm in diameter. Occurs as elongate selvages and enclaves in Pgi. Pg: and Pg3. ZPmi - Mixed suite of meta-intrusive rocks: Melanocratic to mesocratic, and locally leucocratic, variably grained sized exposures gneiss and subordinate schist depending upon the presence of mafic, intermediate, or felsic metaplutonic rocks. Local outcrops of biotite schist are interlayered with dark green-black, fine- to medium¬ grained biotite hornblende metagabbroic gneiss that are crosscut by blue-gray to green-black, fine- to medium¬ grained metadiorite. Both rock types are locally crosscut by layers of fine- to medium-grained leucocratic metagranitoid having variable feldspar and biotite percentage. Outcrops are reminiscent of the Raleigh Gneiss. Carolina Terrane CZvbm - Chlorite-white mica phyllonite, mylonite, and ultramylonite: Light greenish-gray to dark green, foliated and Iineated phyllitic rocks derived primarily from recrystallized metamorphosed tonalite and granite of the Vance County pluton. Includes chlorite and sericite protomylonite through ultramylonite and phyllonite that form in distinctive relict igneous and high strain compositional layers. Iron and manganese oxide commonly coat fractured and foliated surfaces. Flattened and rotated polycrystalline aggregates of plagioclase and quartz common as porphyroclastic minerals that form composite S-C and C' foliations. Quartz, feldspar, chlorite, and white mica contribute to a mineral aggregate, mineral stretch, and slickenline lineation. White mica and chlorite form conspicuous asymmetric fish structures ranging from mm to meters in scale. 6Zvbm ZPmi eZvpg CZvpg - Vance County porphyritic granite: Leucocratic (Cl less than 5), white to white-tan to white-gray, medium-grained to porphyritic. Locally contains sparse biotite and commonly porphyritic quartz phenocrysts ranging up to 5-7 mm. Lakeshore boulder fields and saprolite outcrops are common on Henderson Point. Biotite-free to biotite-bearing outcrops generally have a highly fractured, then crystalloblastic protomylonitic to ultramylonitic or phyllonitic microstructure, grading eastward into the Nutbush Creek fault zone. Highly fractured and mylonitic outcrops also form resistant hillside and lakeside outcrops, and cobble and boulder fields. SZvt CZvt - Vance County tonalite: Mesocratic (Cl greater than 1 0-20), intermediate gray-blue-green, and coarse¬ grained metamorphosed biotite ± hornblende tonalite and minor granodiorite. Commonly forms medium- to coarse-grained boulder outcrops. Granular saprolite and saprock lakeshore exposures display a reddish salt-and- pepper appearance, and horizons of pure magnetite are common. Biotite phenocrysts ± mm-scale prismatic hornblende join rounded to tabular, saussaritized and sericitized pale green plagioclase and gray to distinctly cobalt-blue quartz phenocrysts and give fresh outcrops a gray-blue-green tint. Locally contains foliated and unfoliated enclaves of fine-grained chlorite phy llite, metagabbro. and metadiorite. Cut by mm- to meter-scale metamorphosed trondhjemite, monzonite, and granodiorite dikes. EXPLANATION OF MAP SYMBOLS CONTACTS lithologic contacts - dashed where inferred, dotted where concealed Qal contact faults - Dashed where inferred, dotted where concealed. Arrows indicate relative motion. In cross section. T indicates movement toward the viewer, A indicates movement away from the viewer. diabase dikes - Solid where location known, dashed where inferred, dotted where concealed Carolina Terrane Raleigh Terrane Rocks of Unclear Affinity EAST WEST Dodson Creek Fault Zone Nutbush Creek Fault Zone Lake Gordon Fault Zone ZPwms * UTM GRID AND 1981 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET SCALE 1:24 000 1 0.5 0 1,000 500 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 111 I I И I — I I — H Feet 1 _ 05 _ 0 _ 1 I — I I — I I — I I — I I — I I 1 Kilometers CONTOUR INTERVAL 10 FEET 1 3 Miles This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program, award number G09AC00183. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. Base topographic map is a digital raster graphic image of the John H. Kerr Dam 7.5-minute quadrangle (1981), North Carolina State Plane NAD 83 meters coordinate system. Disclaimer: This Open-File report is preliminary and has not been reviewed for conformity with the North Carolina Geological Survey editorial standards or with the North American Stratigraphic Code. Further revisions or corrections to this preliminary map may occur prior to its release as a North Carolina Geological Survey map. LINEAR FEATURES Bearing and plunge of mesoscale fold hinge "\ Bearing and plunge of crenulation lineation 26 \ Bearing and plunge of slickenline Bearing and plunge of mineral rod or aggregate lineation PLANAR FEATURES Observation sites are centered on the strike bar or are at the intersection point of multiple symbols. Planar feature symbols may be combined with linear features. 55 / X Strike and dip of inclined early 6V Strike and dip of inclined S-C shear strain foliation (Srs) у / fracture surface Strike and dip of inclined undifferentiated X Strike of vertical X shear strain foliation (Src) fracture surface У Strike of vertical undifferentiated 7V Strike and dip of X shear strain foliation (Src) X slickenline surface 72 Strike and dip of inclined late 7V Strike and dip of axial surface / C shear band foliation (Src1) / of mesoscale fold X Strike of vertical late C X Strike of vertical axial surface shear band foliation (Src1) of mesoscale fold V Strike and dip of inclined foliation in enclave 62y Strike and dip of kink band У Strike and dip of diabase dike, X Strike of vertical kink band granitic dike or quartz vein © Observation station location У Strike of vertical diabase dike. /• granitic dike or quartz vein • Diabase station location GEOLOGIC MAP OF THE NORTH CAROLINA PORTION OF THE JOHN H. KERR DAM 7.5-MINUTE QUADRANGLE, WARREN AND VANCE COUNTIES, NORTH CAROLINA By David E. Blake, Christopher L. Buford, Adam G. Schronce and David T. Hill Digital representation by Michael A. Medina and Heather D. Hanna 2010 Scan with smartphone for link to GeoPDF of map. Third party App required. Z О о сл О -а гч Z г ГЧ я гч ■V О 73 Н N» Р 9 о X я гч 73 73 а ;-4 i/i Z С н гч о с Z о г гч