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Mineral Resources > Online Spatial Data > Geology > by state > Alabama Geology

Geologic units in Clay county, Alabama

[Additional scientific data in this geographic area]

Hillabee Greenstone (Paleozoic) at surface, covers 4 % of this area

Hillabee Greenstone - pale-green to light-olive-brown massive, fine-grained greenstone interbedded locally with well-foliated mafic phyllite.

Lithology: greenstone; phyllite

Higgins Ferry Group (Precambrian to Paleozoic) at surface, covers 0.5 % of this area

Higgins Ferry Group - thinly layered coarse to fine-grained biotite-feldspar-quartz gneiss, sericite-feldspar-muscovite schist, +/- biotite +/- garnet-muscovite schist, and biotite-garnet feldspathic gneiss; locally common pegmatites.

Lithology: felsic gneiss; mica schist; pegmatite

Wedowee Group; Hackneyville Schist (Precambrian to Paleozoic) at surface, covers 10 % of this area

Hackneyville Schist - medium to coarse-grained quartz-plagioclase +/- almandine +/- kyanite +/- biotite-muscovite schist, graphite-muscovite-quartz schist, and quartzite containing biotite. Large porphyroblasts of muscovite, andalusite and/or chiastrolite common. Rocks in the areas between Goodwater in Coosa County and Millerville in Clay County that are here assigned to the Hackneyville Schist also have been interpreted as part of the Higgins Ferry Group.

Lithology: schist; quartzite

Talladega Group; No name on map (Silurian?-Devonian) at surface, covers 0.9 % of this area

No name on map - fossiliferous chert facies in vicinity of Jemison, Chilton County, contains marine invertabrate fossils of early to Middle Devonian age.

Lithology: chert

Poe Bridge Mountain Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock (Precambrian to Paleozoic) at surface, covers 2 % of this area

Poe Bridge Mountain Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.

Lithology: quartzite; mafic metavolcanic rock

Ketchepedrakee Amphibolite (Precambrian to Paleozoic) at surface, covers 5 % of this area

Ketchepedrakee Amphibolite - dark-green to black fine to coarse-grained, layered to massive amphibolite mixed with zones of chlorite actinolite schist, includes all amphibolite associated with the Poe Bridge Mountain Group.

Lithology: amphibolite; schist

Hatchet Creek Group; Pinchoulee Gneiss (Precambrian to Paleozoic) at surface, covers 0.3 % of this area

Pinchoulee Gneiss - medium to fine-grained migmatitic, locally garnetiferous biotite-feldspar gneiss, commonly saturated with granitic pods.

Lithology: felsic gneiss; granite

Higgins Ferry Group; Roscoelite-graphite-quartz schist and graphitic quartzite (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

Higgins Ferry Group; Roscoelite-graphite-quartz schist and graphitic quartzite

Lithology: schist; quartzite

Talladega Group; Cheaha Quartzite Member of Lay Dam Formation (Silurian?-Devonian) at surface, covers 2 % of this area

Cheaha Quartzite Member of Lay Dam Formation - white to light-gray medium to coarse-grained arkosic quartzite and metaconglomerate.

Lithology: quartzite; meta-conglomerate

Talladega Group; Lay Dam Formation (Silurian?-Devonian) at surface, covers 18 % of this area

Lay Dam Formation (Talladega Group) - interbedded dark-green phyllite, medium-gray to light-brown and black metasiltstone, dark-green feldspathic metagraywacke, and light-gray and dark-gray medium to coarse-grained arkosic quartzite and metaconglomerate; graphitic phyllite common in upper part. In Cleburne and Calhoun Counties, rocks mapped as the Lay Dam include the Abel Gap Formation of Bearce (1973) and consist of interbedded greenish-gray metasiltstone and quartzite, black phyllitic metasiltstone, medium-gray to greenish-gray arkosic quartzite, and dark-gray pyritic quartzite. In Clay Chounty the upper part of the Lay Dam includes black graphitic sericite phyllite and slate reportedly containing plant fossils (Erin Slate Member).

Lithology: phyllite; metasedimentary rock; quartzite; slate; meta-conglomerate

Ultramafic rock (Precambrian to Paleozoic) at surface, covers 0.1 % of this area

Ultramafic rock - ultramafic pods and sheets, principally enstatite-hypersthene pyroxenite with hornblende and actinolite alteration assemblages.

Lithology: pyroxenite

Wedowee Group; Cornhouse Schist (Precambrian to Paleozoic) at surface, covers 1 % of this area

Cornhouse Schist - medium to coarse-grained multiply foliated +/- plagioclase +/- garnet-biotite-muscovite-quartz schist interlayed with chlorite-biotite-garnet schist, typically mylonitic.

Lithology: schist

Elkahatchee Quartz Diorite Gneiss (Precambrian to Paleozoic) at surface, covers 1 % of this area

Elkahatchee Quartz Diorite Gneiss - mesocratic to melanocratic, fine to coarse-grained, massive to strongly foliated, locally sheared quartz diorite gneiss.

Lithology: orthogneiss

Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian) at surface, covers 6 % of this area

Jemison Chert and Chulafinnee Schist undifferentiated - grayish-white to yellowish-orange massive, thick-bedded, fine-grained, locally argillaceous, locally fossiliferous metachert and light to dark-greenish-gray fine to medium-grained fissile quartz-sericite-chlorite phyllite and schist which locally includes thin chlorite phyllite and quartzose phyllite beds.

Lithology: schist; phyllite; metasedimentary rock

Almond Trondhjemite (Precambrian to Paleozoic) at surface, covers 0.3 % of this area

Almond Trondhjemite - leucocratic, fine to medium-grained, locally foliated trondhjemite containing abundant muscovite and locally biotite and epidote.

Lithology: trondhjemite

Rockford Granite (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

Rockford Granite - leucocratic granite, granodiorite, and trondhjemite; locally well foliated, numerous pegmatites. Includes unnamed granitoids in Chilton County.

Lithology: granite; granodiorite; trondhjemite; pegmatite

Mitchell Dam Amphibolite (Precambrian to Paleozoic) at surface, covers 0.1 % of this area

Mitchell Dam Amphibolite - dark-green to black fine to coarse-grained, thin-layered to massive hornblende-actinolite amphibolite; includes all amphibolite associated with the Higgins Ferry and Hatchet Creek Groups.

Lithology: amphibolite

Wedowee Group; Wedowee Group undifferentiated (Precambrian to Paleozoic) at surface, covers 11 % of this area

Wedowee Group undifferentiated - Wedowee Group undifferentiated includes the Cragford Phyllite and Cutnose Gneiss. Cragford Phyllite -- interbedded fine-grained graphite-chlorite-sericite schist and phyllite, garnet-sericite schist and phyllite, graphite-quartz-sericite phyllite, locally feldspathic biotite gneiss, calc-silicate rock, and quartzite. Cutnose Gneiss -- cyclically interbedded fine-grained quartz-biotite feldspathic gneiss, graphite-chlorite-sericite schist, locally thin interbeds of graphite-quartz-sericite phyllite, and quartzite. Rocks in the area northeast of Clanton in Chilton and Coosa Counties that are here assigned to the Wedowee Group also have been interpreted as part of the Higgins Ferry Group.

Lithology: schist; phyllite; felsic gneiss; quartzite; calc-silicate rock

Beaverdam Amphibolite (Precambrian to Paleozoic) at surface, covers 0.3 % of this area

Beaverdam Amphibolite - dark-green to dark-gray hornblende amphibolite, extensively sheared and folded, and locally retrograded to actinolite-tremolite-chlorite schist. Includes all amphibolite associated with the Wedowee Group.

Lithology: amphibolite; schist

Mad Indian Group; Irregular zones of sericite-quartz schist (Precambrian to Paleozoic) at surface, covers 2 % of this area

Mad Indian Group; Irregular zones of sericite-quartz schist - irregular zones of sericite-quartz schist (+/- garnet) containing finely disseminated graphite, possibly infolded Wedowee Group equivalents. Both mi and migr extensively cut by feldspathic dikes and pegmatites.

Lithology: schist; pegmatite

Poe Bridge Mountain Group (Precambrian to Paleozoic) at surface, covers 5 % of this area

Poe Bridge Mountain Group - coarse to fine-grained feldspathic graphite schist, +/- staurolite +/- kyanite +/- sillimanite-muscovite-biotite schist, and garnet-biotite-muscovite schist, and gneiss; locally common pegmatites. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.

Lithology: mica schist; gneiss; pegmatite

Hillabee Greenstone, unnamed dacite unit (Paleozoic) at surface, covers 0.7 % of this area

Hillabee Greenstone, unnamed dacite unit - unnamed unit comprised of masses of well-foliated quartz dacite.

Lithology: dacite

Talladega Group; Butting Ram Sandstone (Silurian?-Devonian) at surface, covers 0.1 % of this area

Butting Ram Sandstone - white to light-bluish-gray medium to coarse-grained, locally conglomeratic thick-bedded quartzose sandstone. Possible Devonian fossils.

Lithology: sandstone; conglomerate

Poe Bridge Mountain Group; Roscoelite-graphite quartz schist and graphitic quartzite (Precambrian to Paleozoic) at surface, covers 5 % of this area

Poe Bridge Mountain Group; Roscoelite-graphite quartz schist and graphitic quartzite. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.

Lithology: schist; quartzite

Mad Indian Group (Precambrian to Paleozoic) at surface, covers 19 % of this area

Mad Indian Group - fine-grained feldspathic biotite gneiss; medium to coarse-grained muscovite-biotite-garnet schist; locally kyanite and sillimanite. Many of the schists have been retrograded to chlorite-garnet-quartz-sericite schist. Both mi and migr extensively cut by feldspathic dikes and pegmatites.

Lithology: felsic gneiss; schist; pegmatite

Bluff Springs Granite (Precambrian to Paleozoic) at surface, covers 5 % of this area

Bluff Springs Granite - leucocratic quartz diorite (tonalite) to quartz monzonite or trondhjemite, locally foliated.

Lithology: tonalite; quartz monzonite; trondhjemite