Geologic Map of Georgia -- Blue Ridge and Piedmont


Georgia Geologic Survey
1977

David E. Lawton


Blue Ridge and Piedmont Geologic Map (ca. 90kb)



Blue Ridge and Piedmont Crystalline Rocks

(No stratigraphic order implied)

Granite symbol GRANITE Includes those units which are granitic in composition and texture and units of mixed lithology which are composed predominantly of granite.
Granite Gneiss symbol GRANITE GNEISS Includes all strongly banded metamorphic units of granitic composition whether of igneous or sedimentary origin.
Biotite Gneiss symbol BIOTITE GNEISS Includes units of metamorphic rock displaying gneissic banding, strong foliation, and relatively high biotite-mica content. Also includes those mixed lithologies which are predominantly biotite gneiss.
Quartzite symbol QUARTZITES Includes those units which are composed predominantly of metasandstone. Also mixed lithologies in which quartzite predominates.
Metagraywacke symbol METAGRAYWACKE Includes metagraywackes with lesser units of mica schist, quartzite, amphibolite and conglomerate.
Mica Schist symbol MICA SCHIST Includes a wide variety of mica schists containing biotite and/or muscovite with lesser units of graphite schist, gneisses, and amphibolites.
Aluminous Schist symbol ALUMINOUS SCHISTS Includes those mica schist units which contain a moderate to large percentage of aluminosilicate minerals such as garnet, kyanite, sillimanite, and staurolite. Also includes mixed lithologies in which the aluminous schists predominate.
Pelitic/Calcareous symbol PELITIC AND CALCAREOUS ROCKS Includes calcareous schists, metagraywackes, metaconglomerates, metasandstones, and marble.
Phyllite symbol PHYLLITIC ROCKS Includes meta-argillites, phyllites, graphitic phyllites and similar very fine-grained rocks of lower metamorphic grade.
Mafic Gneiss symbol MAFIC GNEISS Includes a wide variety of metamorphic rocks, (composed largely of iron-magnesium silicates) such as amphibolite, homblende gneiss, and mafic hornfels. Also includes mixed lithologies composed predominantly of these rock types.
Mafic Schist symbol SCHISTOSE MAFIC ROCKS Includes schistose units composed predominantly of various mafic minerals including chlorite, tremolite, actinolite, and hornblende.
Mafic/Ultramafic symbol ULTRAMAFIC-MAFIC ROCKS Includes gabbros, serpentinites, diabase, and undifferentiated ultramafics. The generally northwest trending diabase dikes are indicated by thin green lines.
Metavolcanic symbol METAVOLCANIC ROCKS Includes metavolcanic rocks of mafic to felsic composition; locally includes meta-argillites, phyllites, and schists.


Map and legend are reproduced from Geologic Map of Georgia, 1977 (1:2,000,000), compiled by David E. Lawton, available from Georgia Geologic Survey.

This map and the larger (1:500,000) 1976 Geologic Map of Georgia were compiled when the ideas of plate tectonics were relatively new and their implications for Georgia geology were not well understood. See reading list for more recent interpretations.