Geologic units in Cleburne county, Alabama

Additional scientific data in this geographic area

Talladega Group; Lay Dam Formation (Silurian?-Devonian) at surface, covers 37 % of this area

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).

Heflin Phyllite (Cambrian?) at surface, covers 22 % of this area

Grayish-green, medium-gray, and medium-bluish-gray calcareous sandy metasiltstone interbedded with minor greenish-gray fine to coarse-grained metasandstone and rare thin lenses of calcite and dolomite marble; an interval of greenish-gray to dark-gray phyllitic quartzite or quartz-pebble metaconglomerate is locally present near the base. The Heflin underlies the Lay Dam Formation and overlies the rocks tentatively identified as the Chilhowee Group undifferentiated.

Wedowee Group; Wedowee Group undifferentiated (Precambrian to Paleozoic) at surface, covers 8 % of this area

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.

Ketchepedrakee Amphibolite (Precambrian to Paleozoic) at surface, covers 7 % of this area

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.

Poe Bridge Mountain Group (Precambrian to Paleozoic) at surface, covers 6 % of this area

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.

Weisner and Wilson Ridge Formations undifferentiated (Cambrian) at surface, covers 5 % of this area

Interbedded quartzose to slightly feldspathic sandstone and laterally continous conglomerate in ledge-forming units seperated by greenish-gray silty mudstone.

Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian) at surface, covers 5 % of this area

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.

Chilhowee Group undifferentiated (Cambrian) at surface, covers 4 % of this area

Light to medium-gray arkose, arkosic conglomerate, and discontinous mudstone overlain by greenish-gray mudstone with minor siltstone and sandstone; dominantly light-gray pebbly quartzose sandstone in upper part.

Poe Bridge Mountain Group; Roscoelite-graphite quartz schist and graphitic quartzite (Precambrian to Paleozoic) at surface, covers 3 % of this area

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.

Shady Dolomite (Cambrian) at surface, covers 2 % of this area

Bluish-gray or pale-yellowish-gray thick-bedded siliceous dolomite; characterized by coarsely crystalline porous chert.

Hillabee Greenstone (Paleozoic) at surface, covers 1 % of this area

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

Nichols Formation (Cambrian) at surface, covers 0.5 % of this area

Massive to laminated greenish-gray and black micaceous mudstone containing minor interbeds of siltstone and very fine-grained sandstone.

Talladega Group; Cheaha Quartzite Member of Lay Dam Formation (Silurian?-Devonian) at surface, covers 0.3 % of this area

White to light-gray medium to coarse-grained arkosic quartzite and metaconglomerate.

Knox Group undifferentiated in part (Ordovician-Cambrian) at surface, covers 0.2 % of this area

Light-gray to light-brown locally sandy dolomite, dolomitic limestone, and limestone; characterized by abundant light-colored chert.

Mad Indian Group (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

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.

Poe Bridge Mountain Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

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.

Rome Formation (Cambrian) at surface, covers < 0.1 % of this area

Variegated thinly interbedded mudstone, shale, siltstone, and sandstone; limestone and dolomite occur locally. Quartzose sandstone commonly present near top of formation.

Conasauga Formation (Cambrian) at surface, covers < 0.1 % of this area

Light to dark-gray finely to coarsely crystalline, medium to thick-bedded dolomite containing minor greenish-gray shale and light-bluish-gray chert. In the Columbiana area of Shelby County, the Conasauga is dominated by thin to medium-bedded, dark-gray dolomitic limestone and minor dark-gray shale. In Bibb County and southwestern Shelby County, the Conasauga consists of medium-bluish-gray fine-grained, thin-bedded argillaceous limestone and interbedded dark-gray shale. In the eastern Valley and Ridge the lower part includes dark-green to pale-olive fossiliferous shale with a few dark-gray limestone interbeds.

Cochran Formation (Cambrian) at surface, covers < 0.1 % of this area

Poorly sorted arkosic sandstone and conglomerate containing interbedded greenish-gray siltstone and mudstone. The Cochran Formation is exposed only in northeastern Calhoun and northwestern Cleburne Counties.

Phyllite and Quartzite (Precambrian-Paleozoic) at surface, covers < 0.1 % of this area

Phyllite and Quartzite

Phyllite undifferentiated (Precambrian-Paleozoic) at surface, covers < 0.1 % of this area

Phyllite undifferentiated

Beaverdam Amphibolite (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

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.

Newala Limestone (Ordovician) at surface, covers < 0.1 % of this area

Newala Limestone

Chickamauga Group; Middle Ordovician rocks; Rockmart Slate (Middle Ordovician) at surface, covers < 0.1 % of this area

Chickamauga Group; Middle Ordovician rocks; Rockmart Slate

Frog Mountain (Devonian) at surface, covers < 0.1 % of this area

Frog Mountain

Knox Group undifferentiated (Ordovician-Cambrian) at surface, covers < 0.1 % of this area

Knox Group undifferentiated