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

Geologic units in Bibb county, Alabama

Kahatchee Mountain Group; Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers < 0.1 % of this area

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

Lithology: slate; metasedimentary rock

Tuscumbia Limestone and Fort Payne Chert undivided (Mississippian) at surface, covers 0.2 % of this area

Tuscumbia Limestone and Fort Payne Chert undivided - Tuscumbia Limestone -- light-gray partly oolitic limestone; very coarse bioclastic crinoidal limestone common; light-gray chert nodules and concretions locally abundant. Fort Payne Chert -- very light to light-olive-gray, thin to thick-bedded fine to coarse-grained bioclastic (abundant pelmatozoans) limestone containing abundant nodules, lenses and beds of light to dark-grey chert. Upper part of formation locally consists of light-bluish-gray laminated siltstone containing vugs lined or filled with quartz and scattered throughout the formation are interbeds of medium to greenish-gray shale, shaly limestone and siltstone. Lenses of dark-gray siliceous shale occur locally at the base of the Fort Payne in Wills Valley. Commonly present below the Fort Payne is a ligh-olive-gray claystone or shale (Maury Formation) which is mapped with the Fort Payne. The Tuscumbia and Fort Payne are undifferentiated in Murphrees and Wills Valleys.

Lithology: limestone; chert; siltstone; shale; claystone

Bibb Dolomite (Cambrian) at surface, covers 0.5 % of this area

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

Lithology: dolostone (dolomite); chert

Pottsville Formation (upper part) (Pennsylvanian) at surface, covers 15 % of this area

Pottsville Formation (upper part) - Interbedded dark-gray shale, siltstone, medium-gray sandstone, and coal in cyclic sequences. The members present in the Cahaba synclinorium in descending order include: the Straven Conglomerate Member, Rocky Ridge Sandstone Member, and Chestnut Sandstone Member. The members present in the Coosa synclinorium in descending order include: Straight Ridge Sandstone Member and Wolf Ridge Sandstone Member.

Lithology: shale; siltstone; sandstone; coal

Pottsville Formation (lower part) (Pennsylvanian) at surface, covers 0.7 % of this area

Pottsville Formation (lower part) - Light-gray thick-bedded to massive pebbly quartzose sandstone, containing varying amounts of interbedded dark-gray shale, siltstone, and thin discontinuos coal. In both the Cahaba and Coosa synclinoria the members in descending order include: the Pine Sandstone Member and the Shades Sandstone Member. Top of unit is mapped at top of Pine Sandstone Member.

Lithology: sandstone; shale; siltstone; coal

Kahatchee Mountain Group; Kalona Quartzite Member of Wash Creek Slate (Precambrian?-Cambrian?) at surface, covers < 0.1 % of this area

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

Lithology: quartzite; meta-conglomerate

Parkwood Formation and Floyd Shale undifferentiated (Pennsylvanian-Mississippian) at surface, covers 0.3 % of this area

Parkwood Formation and Floyd Shale undifferentiated - 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.

Lithology: shale; sandstone; mudstone; limestone; chert; mixed clastic/coal; clay or mud

Talladega Group; Lay Dam Formation (Silurian?-Devonian) at surface, covers < 0.1 % 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

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

Copper Ridge Dolomite - light-gray finely to coarsely crystalline, thick-bedded siliceous dolomite; characterized by abundant stromatolitic chert. Mapped seperately only in the Birmingham anticlinorium where overlying units within the Knox Group are absent beneath the post-Knox unconformity.

Lithology: dolostone (dolomite); chert

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

Chickamauga Limestone - Medium to dark-gray thick to thin-bedded partly argillaceous, locally fossiliferous limestone. Restricted to the western part of the Valley and Ridge province and Murphrees Valley and Wills Valley anticlines. Locally includes a thin interval of Attalla Chert Conglomerate Member at base. Attalla Chert Conglomerate - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized matrix; thin beds of gray-green or dusky-red shale common at base.

Lithology: limestone; conglomerate; chert; shale; dolostone (dolomite); quartzite

Tuscaloosa Group; Coker Formation (Cretaceous) at surface, covers 49 % of this area

Coker Formation - (Tuscaloosa Group), 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.

Lithology: sand; clay or mud; silt; gravel; chert

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

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

Lithology: dolostone (dolomite); chert

Tuscaloosa Group; Gordo Formation (Cretaceous) at surface, covers 12 % of this area

Gordo Formation - (Tuscaloosa Group), 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.

Lithology: sand; clay or mud; gravel; chert

Eutaw Formation (Cretaceous) at surface, covers 0.4 % of this area

Eutaw Formation - 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.

Lithology: sand; clay or mud; sandstone;

Red Mountain Formation (Silurian) at surface, covers 0.2 % of this area

Red Mountain Formation - Interbedded yellowish-gray to moderate-red sandstone, siltstone and shale; greenish-gray to moderate-red fossiliferous partly silty and sandy limestone; few thin hematitic beds.

Lithology: sandstone; shale; siltstone; limestone

Longview Limestone (Ordovician) at surface, covers 0.7 % of this area

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

Lithology: limestone; dolostone (dolomite)

Alluvial, coastal and low terrace deposits (Holocene) at surface, covers 8 % of this area

Alluvial, coastal and low terrace deposits - 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.

Lithology: beach sand; alluvium

Chepultepec and Copper Ridge Dolomites undifferentiated (Ordovician-Cambrian) at surface, covers 5 % of this area

Chepultepec and Copper Ridge Dolomites undifferentiated - Light-gray to dark-bluish-gray thick-bedded dolomite and interbedded light-gray limestone; includes abundant chert.

Lithology: dolostone (dolomite); limestone; chert

Athens Shale and Lenoir Limestone undifferentiated (Ordovician) at surface, covers 0.8 % of this area

Athens Shale and Lenoir Limestone undifferentiated - 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).

Lithology: shale; limestone; mudstone

Conasauga Formation (Cambrian) at surface, covers 0.6 % of this area

Conasauga Formation - Medium-bluish-gray fine-grained, thin-bedded argillaceous limestone and interbedded dark-gray shale in varying proportions.

Lithology: limestone; shale

Floyd Shale (Mississippian) at surface, covers 0.3 % of this area

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.

Lithology: shale; sandstone; limestone; chert

Newala Limestone (Ordovician) at surface, covers 0.9 % of this area

Newala Limestone - light to dark-gray thick-bedded micritic and peloidal limestone and minor dolomite.

Lithology: limestone; dolostone (dolomite)

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

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

Lithology: mudstone; shale; siltstone; sandstone; limestone; dolostone (dolomite)

Ketona Dolomite (Cambrian) at surface, covers 0.6 % of this area

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

Lithology: dolostone (dolomite)

Parkwood Formation (Pennsylvanian-Mississippian) at surface, covers 1.0 % 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.

Lithology: shale; sandstone; mudstone; limestone; clay or mud; mixed clastic/coal