Geologic units in Talladega county, Alabama

Additional scientific data in this geographic area

Knox Group undifferentiated in part (Ordovician-Cambrian) at surface, covers 49 % of this area

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

Talladega Group; Lay Dam Formation (Silurian?-Devonian) at surface, covers 20 % 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).

Conasauga Formation (Cambrian) at surface, covers 5 % 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.

Rome Formation (Cambrian) at surface, covers 4 % of this area

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

Kahatchee Mountain Group; Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers 4 % of this area

Grayish-green to black micaceous, partly carbonaceous to graphitic slate and metasiltstone containing interbedded light-gray to light-brown fine to coarse-grained metasandstone.

Parkwood Formation and Floyd Shale undifferentiated (Pennsylvanian-Mississippian) at surface, covers 3 % of this area

Parkwood Formation -- Interbedded medium to dark-gray shale and light to medium-gray sandstone; locally contains dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal. Floyd Shale -- Dark-gray shale, sideritic in part; thin beds of sandstone, limestone and chert are locally present; beds of partly bioclastic, partly argillaceous limestone are abundant in parts of Calhoun and Cherokee Counties.

Heflin Phyllite (Cambrian?) at surface, covers 2 % 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.

Chilhowee Group undifferentiated (Cambrian) at surface, covers 2 % 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.

Sylacauga Marble Group; Gooch Branch Chert (Cambrian?-Ordovician?) at surface, covers 2 % of this area

Light-gray to light-brown dolomite marble associated with abundant light-gray to white massive to moderately foliated metachert.

Sylacauga Marble Group; Jumbo Dolomite (Cambrian?-Ordovician?) at surface, covers 2 % of this area

Light to medium-gray thin to thick-bedded dolomite marble; contains intraclast-bearing dolomite, locally sandy in middle part.

Sylacauga Marble Group; Fayetteville Phyllite (Cambrian?-Ordovician?) at surface, covers 1 % of this area

Dusky-red and medium-gray phyllite and slate interlayered with light-brown to light-gray feldspathic metasiltstone, fine-grained metasandstone and dolomite marble.

Shady Dolomite (Cambrian) at surface, covers 1 % of this area

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

Sylacauga Marble Group; Shelvin Rock Church Formation (Cambrian?-Ordovician?) at surface, covers 0.8 % of this area

Moderate-pink to light-gray calcite and locally dolomite marble.

Weisner and Wilson Ridge Formations undifferentiated (Cambrian) at surface, covers 0.8 % of this area

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

Conasauga Formation, lower unnamed shale facies (Cambrian) at surface, covers 0.6 % of this area

Lower unnamed shale facies in eastern Valley and Ridge consists of dark-green to pale-olive fossiliferous shale with a few dark-gray limestone interbeds.

Sylacauga Marble Group; Gantts Quarry Formation (Cambrian?-Ordovician?) at surface, covers 0.6 % of this area

White and pale-blue to light-gray calcite marble locally containing interlayered dolomite marble and thin phyllite layers.

Hillabee Greenstone (Paleozoic) at surface, covers 0.5 % of this area

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

Newala Limestone (Ordovician) at surface, covers 0.4 % of this area

Light to dark-gray thick-bedded micritic and peloidal limestone and minor dolomite.

Tuscumbia Limestone and Fort Payne Chert undifferentiated (Mississippian) at surface, covers 0.4 % of this area

Tuscumbia Limestone -- light to dark-gray fossiliferous and oolitic partly argillaceous and cherty limestone. Apparently present only along part of the northwest limb of the Coosa synclinorium. Fort Payne Chert -- dark-gray to light-gray limestone with abundant irregular light-gray chert nodules and beds. Commonly present below the Fort Payne is greenish-gray to grayish-red phosphatic shale (Maury Formation) which is mapped with the Tuscumbia Limestone and Fort Payne Chert undifferentiated.

Kahatchee Mountain Group; Kalona Quartzite Member of Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers 0.3 % of this area

Light-brown to light-gray coarse-grained, feldspathic quartzite and metaconglomerate in lower part of Wash Creek Slate.

Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian) at surface, covers 0.3 % 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.

Talladega Group; Cheaha Quartzite Member of Lay Dam Formation (Silurian?-Devonian) at surface, covers 0.2 % of this area

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

Metaclastic rocks of unknown affinity (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

In the area south of Talladega, Talladega County, the unit includes greenish-gray chlorite-sericite phyllite; in small area south of Childersburg the unit consists of greenish-gray chlorite-sericite phyllite and slate locally containing interbeds of metagraywacke; and in the area east of Columbiana, Shelby County, the unit includes dark-greenish-gray slate and metasiltstone containing interbedded coarse-grained to conglomerate quartzite.

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

White to light-bluish-gray medium to coarse-grained, locally conglomeratic thick-bedded quartzose sandstone. Possible Devonian fossils.

Athens Shale (Ordovician) at surface, covers < 0.1 % of this area

Black graptolitic shale, locally contains interbedded dark-gray limestone.

Hillabee Greenstone, unnamed dacite unit (Paleozoic) at surface, covers < 0.1 % of this area

Unnamed unit comprised of masses of well-foliated quartz dacite.

Poe Bridge Mountain Group (Precambrian to Paleozoic) at surface, covers < 0.1 % 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.

Ketchepedrakee Amphibolite (Precambrian to Paleozoic) at surface, covers < 0.1 % 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; Garnet quartzite (garnetite) and garnitiferous altered mafic rock (Precambrian to Paleozoic) at surface, covers < 0.1 % 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.