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

Geologic units in Shelby county, Alabama

[Additional scientific data in this geographic area]

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

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

Weisner and Wilson Ridge Formations undifferentiated -- interbedded quartzose to slightly feldspathic sandstone and laterally continous conglomerate in ledge-forming units separated by greenish-gray silty mudstone.

Lithology: sandstone; conglomerate; mudstone

Longview Limestone (Ordovician) at surface, covers 1 % of this area

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

Lithology: limestone; dolostone (dolomite)

Little Oak and Lenoir Limestones undifferentiated (Ordovician) at surface, covers 0.8 % of this area

Little Oak and Lenoir Limestones undifferentiated - dark-gray argillaceous, fossiliferous medium to thick-bedded limestone; locally contains rare chert in upper part and an interval of fenestral mudstone in lower part (Mosheim Limestone Member of the Lenoir Limestone). Between Siluria and Pelham in Shelby County, the Little Oak and Lenoir Limestones are separated by a tongue of the Athens Shale.

Lithology: limestone; mudstone; chert

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

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

Lithology: dolostone (dolomite)

Rome Formation (Cambrian) at surface, covers 2 % 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)

Newala Limestone (Ordovician) at surface, covers 9 % of this area

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

Lithology: limestone; dolostone (dolomite)

Parkwood Formation (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.

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

Athens Shale (Ordovician) at surface, covers 1 % of this area

Athens Shale - black graptolitic shale, locally contains interbedded dark-gray limestone.

Lithology: black shale; limestone

Athens Shale and Lenoir Limestone undifferentiated (Ordovician) at surface, covers 0.4 % 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 0.7 % 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 5 % 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

Kahatchee Mountain Group; Brewer Phyllite (Precambrian?-Cambrian?) at surface, covers 0.3 % of this area

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

Lithology: slate; phyllite; quartzite; metasedimentary rock; marble

Kahatchee Mountain Group; Waxahatchee Slate (Precambrian?-Cambrian?) at surface, covers 7 % of this area

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

Lithology: metasedimentary rock; slate; quartzite

Knox Group undifferentiated (Ordovician-Cambrian) at surface, covers 6 % of this area

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

Lithology: dolostone (dolomite); limestone; chert

Kahatchee Mountain Group; Stumps Creek Formation (Precambrian?-Cambrian?) at surface, covers 0.3 % of this area

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

Lithology: phyllite; metasedimentary rock

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

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

Lithology: dolostone (dolomite); chert

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

Little Oak Limestone - dark-gray medium to thick-bedded fossiliferous, argillaceous to silty limestone containing chert nodules. Locally includes thin beds of bentonite in the upper part.

Lithology: limestone; chert; bentonite

Newala and Longview Limestones undifferentiated (Ordovician) at surface, covers 0.4 % of this area

Newala and Longview Limestones undifferentiated - light to dark-grey thick-bedded limestone and dolomite, cherty in part.

Lithology: limestone; dolostone (dolomite); chert

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 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 21 % 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

Kahatchee Mountain Group; Sawyer Limestone Member of Brewer Phyllite (Precambrian?-Cambrian?) at surface, covers 0.2 % of this area

Sawyer Limestone Member of Brewer Phyllite - light to medium-gray argillaceous, silty to siliceous calcite and dolomite marble interbedded with phyllite and quartzite, locally cherty.

Lithology: marble; phyllite; quartzite

Pottsville Formation (lower part) (Pennsylvanian) at surface, covers 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

Brierfield Dolomite (Cambrian) at surface, covers 1 % 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

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

Metaclastic rocks of unknown affinity - 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.

Lithology: phyllite; slate; metasedimentary rock; quartzite

Parkwood Formation and Floyd Shale undifferentiated (Pennsylvanian-Mississippian) at surface, covers 23 % 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

Tuscaloosa Group; Coker Formation (Cretaceous) at surface, covers < 0.1 % 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