Geologic units in Chilton county, Alabama

Tuscaloosa Group; Coker Formation (Cretaceous) at surface, covers 36 % of this area

Light-colored micaceous very fine to medium sand, cross-bedded sand, varicolored micaceous clay, and a few thin gravel beds containing quartz and chert pebbles. Beds of thinly laminated finely glauconitic very fine to fine sand, silt and dark-gray carbonaceous clay (Eoline Member) occur locally in the lower part in western AL. Locally quartz and chert gravels at the base of the formation range in size from very fine pebbles to large cobbles. In southeastern Elmore County the formation includes marine sediments consisting of glauconitic, fossiliferous, quartzose fine to medium sand and medium-gray carbonaceous silty clay. Not mapped east of the Tallapoosa River.

Tuscaloosa Group; Gordo Formation (Cretaceous) at surface, covers 17 % of this area

Massive beds of cross-bedded sand, gravelly sand, and lenticular beds of locally carbonaceous partly mottled moderate-red and pale-red-purple clay; lower part is predominantly a gravelly sand consisting chiefly of chert and quartz pebbles. Not mapped east of the Tallapooza River.

Alluvial, coastal and low terrace deposits (Holocene) at surface, covers 7 % of this area

Varicolored fine to coarse quartz sand containing clay lenses and gravel in places. Gravel composed of quartz and chert pebbles and assorted metmorphic and igneous rock fragments in streams near the Piedmont. In areas of the Valley and Ridge province gravel composed of angular to subrounded chert, quartz, and quartzite pebbles. Coastal deposits include fine to medium quartz sand with shell fragments and accessory heavy minerals along Gulf beaches and fine to medium quartz sand, silt, clay, peat, mud and ooze in the Mississippi Sound, Little Lagoon, bays, lakes, streams, and estuaries.

Higgins Ferry Group (Precambrian to Paleozoic) at surface, covers 4 % of this area

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.

Higgins Ferry Group; Roscoelite-graphite-quartz schist and graphitic quartzite (Precambrian to Paleozoic) at surface, covers 4 % of this area

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

Eutaw Formation (Cretaceous) at surface, covers 4 % of this area

Light-greenish-gray to yellowish-gray cross-bedded, well-sorted, micaceous, fine to medium quartz sand that is fossiliferous and glauconitic in part and contains beds of greenish-gray micaceous, silty clay and medium-dark-gray carbonaceous clay. Light-gray glauconitic fossiliferous sand, thin beds of sandstone, and massive accumulations of fossil oyster shells occur locally in the upper part of the formation in western AL (Tombigbee Sand Member). In eastern AL thin to thick-bedded accumulations of the fossil oyster Ostrea cretacea Morton occur throughout much of the formation.

Kahatchee Mountain Group; Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers 3 % 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.

Talladega Group; Lay Dam Formation, unnamed diamictite facies (Silurian?-Devonian) at surface, covers 3 % of this area

Unnamed diamictite facies of Lay Day Formation in Coosa and Chilton Counties consists of cobbles and boulders of carbonate, pelitic rocks, quartzite, chert, felsic plutonic rocks, and gneiss in a metagraywacke matrix.

Kahatchee Mountain Group; Waxahatchee Slate (Precambrian?-Cambrian?) at surface, covers 3 % of this area

Dark-gray to grayish-green thin-bedded, micaceous metasiltstone, slate, and fine-grained quartzite.

Kahatchee Mountain Group; Stumps Creek Formation (Precambrian?-Cambrian?) at surface, covers 3 % of this area

Grayish-green micaceous metasiltstone and minor phyllite; grayish-green fine to medium-grained pyritic metasandstone in middle to upper part.

Wedowee Group; Wedowee Group undifferentiated (Precambrian to Paleozoic) at surface, covers 2 % 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.

Talladega Group; Lay Dam Formation (Silurian?-Devonian) at surface, covers 2 % 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).

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.

Kahatchee Mountain Group; Kalona Quartzite Member of Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers 1 % of this area

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

Chepultepec and Copper Ridge Dolomites undifferentiated (Ordovician-Cambrian) at surface, covers 1 % of this area

Light-gray to dark-bluish-gray thick-bedded dolomite and interbedded light-gray limestone; includes abundant chert.

Parkwood Formation and Floyd Shale undifferentiated (Pennsylvanian-Mississippian) at surface, covers 1 % 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.

Kahatchee Mountain Group; Brewer Phyllite (Precambrian?-Cambrian?) at surface, covers 1 % of this area

Dusky-red micaceous slate and phyllite, locally containing interbedded micaceous arkosic quartzite and metasiltstone; locally at the base is interbedded calcite and dolomite marble.

Talladega Group; Butting Ram Sandstone (Silurian?-Devonian) at surface, covers 0.8 % of this area

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

Mitchell Dam Amphibolite (Precambrian to Paleozoic) at surface, covers 0.8 % of this area

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.

Newala Limestone (Ordovician) at surface, covers 0.8 % of this area

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

Talladega Group; No name on map (Silurian?-Devonian) at surface, covers 0.7 % of this area

Fossiliferous chert facies in vicinity of Jemison, Chilton County, contains marine invertabrate fossils of early to Middle Devonian age.

Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian) at surface, covers 0.7 % 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.

Newala and Longview Limestones undifferentiated (Ordovician) at surface, covers 0.3 % of this area

Light to dark-grey thick-bedded limestone and dolomite, cherty in part.

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

Higgins Ferry Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock.

Hatchet Creek Group; Pinchoulee Gneiss (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

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

Longview Limestone (Ordovician) at surface, covers 0.2 % of this area

Longview Limestone - light to medium-gray thick-bedded cherty limestone and dolomite, locally sandy.

Talladega Group; Miller Mill Quartzite Member of the Lay Dam Formation (Silurian?-Devonian) at surface, covers 0.1 % of this area

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

Athens Shale and Lenoir Limestone undifferentiated (Ordovician) at surface, covers 0.1 % of this area

Athens Shale -- black graptolitic shale, locally contains interbedded dark-gray limestone. Lenoir Limestone -- dark-gray medium to thick-bedded argillaceous limestone; locally contains an interval of fenestral mudstone at the base (Mosheim Limestone Member).

Sylacauga Marble Group; Jumbo Dolomite (Cambrian?-Ordovician?) at surface, covers 0.1 % of this area

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

High terrace deposits (Pleistocene) at surface, covers 0.1 % of this area

Varicolored lenticular beds of poorly sorted sand, ferruginous sand, silt, clay, and gravelly sand. Sand consists primarily of very fine to very coarse poorly sorted quartz grains; gravel composed of quartz, quartzite, and chert pebbles.

Kahatchee Mountain Group; Sawyer Limestone Member of Brewer Phyllite (Precambrian?-Cambrian?) at surface, covers 0.1 % of this area

Light to medium-gray argillaceous, silty to siliceous calcite and dolomite marble interbedded with phyllite and quartzite, locally cherty.

Tuscumbia Limestone and Fort Payne Chert undifferentiated (Mississippian) at surface, covers < 0.1 % 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.

Bibb Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Dark-gray thick-bedded siliceous dolomite; characterized by locally abundant chert containing irregular cavities.

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

Leucocratic granite, granodiorite, and trondhjemite; locally well foliated, numerous pegmatites. Includes unnamed granitoids in Chilton County.

Ketona Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Light to medium-gray thick-bedded coarsely crystalline dolomite.

Brierfield Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Medium to dark-bluish-gray thick-bedded siliceous dolomite; characterized by locally abundant chert with irregular cavities.