Geologic units in Warren county, North Carolina

Mica Schist (Cambrian/Late Proterozoic) at surface, covers 50 % of this area

Contains garnet, staurolite, kyanite, or sillimanite; includes lenses and layers of quartz schist, micaceous quartzite, biotite gneiss, amphibolite, and phyllite.

Biotite Gneiss and Schist (Cambrian/Late Proterozoic) at surface, covers 25 % of this area

Inequigranular and megacrystic; in places contains garnet; interlayered and gradational with mica schist and amphibolite; includes small masses of granitic rock.

Granitic Rock (Permian/Pennsylvanian) at surface, covers 16 % of this area

Megacrystic to equigranular. Castalia and Wilton intrusives.

Foliated to Massive Granitic Rock (Permian/Pennsylvanian) at surface, covers 5 % of this area

Megacrystic to equigranular. Rolesville suite, Wise and Lemon Springs (?) intrusives.

Felsic Mica Gneiss (Cambrian/Late Proterozoic) at surface, covers 2 % of this area

Interlayered with graphitic mica schist and mica-garnet schist, commonly with kyanite; minor hornblende gneiss.

Amphibolite (Cambrian/Late Proterozoic) at surface, covers 0.9 % of this area

Metamorphosed mafic extrusive and intrusive rock; includes hornblende gneiss, thin layers of mica schist, and small nonlayered masses of metadiorite and metagabbro.

Foliated to Massive Granitic Rock (Permian/Pennsylvanian) at surface, covers 0.5 % of this area

Megacrystic to equigranular. Butterwood Creek intrusive and Rocky Mount intrusive suite.

Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic) at surface, covers 0.4 % of this area

Bedding plane and axial-planar cleavage common; interbedded with metasandstone, meta-conglomerate, and metavolcanic rock.

Metamorphosed Granitic Rock (Cambrian/Late Proterozoic) at surface, covers 0.3 % of this area

Megacrystic, well foliated, locally contains hornblende; Vance County suite and Buckhorn granite.

Biotite Gneiss (Proterozoic) at surface, covers 0.3 % of this area

Light-gray, medium- to coarse grained, compositionally-layered and locally migmatitic rocks, include interlayered biotite gneiss, muscovite-biotite gneiss, muscovite-biotite schist, and sillimanite-mica schist; also includes minor interlayers and lenses of granitic gneiss, biotite-amphibole gneiss, amphibolite, garnet-mica schist, calc-silicate granofels, and rare ultramafic rocks. This unit correlates with Raleigh belt rocks in North Carolina (Parker, 1979; Geologic Map of North Carolina, 1985).

Terrace Deposits and Upland Sediment (Tertiary) at surface, covers 0.2 % of this area

Gravel, clayey sand, and sand, minor iron-oxide cemented sandstone.

Biotite-Muscovite Granite (Proterozoic) at surface, covers 0.2 % of this area

Light-gray, fine- to coarse grained, muscovite-biotite granite, biotite-muscovite granite, and leucogranite with accessory garnet. The granite is undated but interpreted as part of the Pennsylvanian-Permian suite of granites, and considered as part of the Wise pluton, which can be traced into North Carolina (McSween and others, 1991).

Mylonite, Mylonite Gneiss, and Cataclastic Rocks (Proterozoic - Paleozoic ?) at surface, covers < 0.1 % of this area

Mylonite. Includes protomylonite, mylonite, ultramylonite, and cataclastic rocks. Lithology highly variable, depending on the nature of the parent rock, and on intensive parameters and history of deformation. In most mapped belts of mylonite and cataclastic rock (my), tectonized rocks anastomose around lenses of less-deformed or undeformed rock. In the Blue Ridge, some of these lenses are large enough to show at 1:500,000 scale. In many places mylonitic and cataclastic rocks are gradational into less deformed or undeformed adjacent rocks, and location of contacts between tectonized rocks (my) and adjacent units is approximate or arbitrary. These boundaries are indicated on the map by color-color joins with superimposed shear pattern. Most mapped belts of mylonite represent fault zones with multiple movement histories. In the Blue Ridge, Paleozoic age contractional deformation fabrics are superimposed on Late Precambrian extensional fabrics (Simpson and Kalaghan, 1989; Bailey and Simpson, 1993). Many Piedmont mylonite zones contain dextral-transpressional kinematic indicators that formed during Late Paleozoic collision al tectonics (Bobyarchick and Glover, 1979; Gates and others, 1986). Paleozoic and older faults were reactivated in many places to form extensional faults during the Mesozoic (Bobyarchick and Glover, 1979).

Buggs Island Pluton (Mississippian Pennsylvanian) at surface, covers < 0.1 % of this area

Light-gray, medium- to coarse grained, massive to strongly foliated biotite-muscovite granite. The name first appears in the literature as the Buggs Island granite gneiss (Kish and Fullagar, 1978); those workers report an Rb-Sr whole-rock age of 314±16 Ma.

Porphyroblastic Biotite Granite (Proterozoic) at surface, covers < 0.1 % of this area

Light-gray, medium to coarse-grained, compositionally layered, well-foliated, commonly lineated gneiss composed of metamorphosed granite, leucogranite, and granodiorite, which locally contains feldspar megacrysts. This unit includes the granite at Lawrenceville; the rocks are variably mylonitic and lineated along the Lake Gordon mylonite zone near Kenbridge (Horton and others, 1993).