Oligocene Series undifferentiated

Descriptions of the units of the Oligocene Series follow in descending order. Paynes Hammock Sand - locally fossiliferous, calcareous, argillaceous medium to coarse sand; pale-blue-green clay; and thin-bedded sandy limestone; exposed at Paynes Hammock and at St. Stephens. Chickasawhay Limestone - white to yellowish-gray fossiliferous, glauconitic limestone and soft marl. Byram Formation includes three members in descending order: Bucatunna Clay Member - dark, bentonitic, carbonaceous, sparsely fossiliferous clay and greyish-yellow sand; unnamed marl member - light-grey to yellowish-grey sandy, glauconitic , fossiliferous marl; Glendon Limestone Member - irregularly indurated coquinoid and crystalline limestone, weathering to indurated rock containing large tubular cavities, locally known as 'horsebone'. Marianna Limestone - white to yellowish-grey soft, porous, very fossiliferous limestone. Forest Hill sand - dark-greenish-grey carbonaceous clay with lenses of glauconitic fossiliferous sand; extends eastward from MS into Choctaw, Clarke and Washington Counties. Red Bluff Clay - greenish-gray calcareous clay locally containing selenite crystals, yellowish-grey glauconitic, fossiliferous limestone; and light-gray silty clay with interbeds of sand (Forest Hill equivalent); from Tombigbee River eastward grades into glauconitic fossiliferous limestone equivalent to the Bumpnose Limestone. Bumpnose Limestone - very light-gray to yellowish-gray chalky, subcoquinoid, glauconitic, argillaceous, fossiliferous limestone; intertongues with Red Bluff Clay in vicinity of the Alabama River and is readily differentiated eastward from the Sepulga River.
State Alabama
Name Oligocene Series undifferentiated
Geologic age Oligocene
Lithologic constituents
Major
Sedimentary > Carbonate > Limestonewhite to yellowish-gray fossiliferous, glauconitic limestone, thin-bedded sandy limestone, irregularly indurated coquinoid and crystalline limestone
Minor
Unconsolidated > Fine-detrital > Claydark, bentonitic, carbonaceous, sparsely fossiliferous clay
Unconsolidated > Coarse-detrital > Sandlocally fossiliferous, calcareous, argillaceous medium to coarse sand; lenses of glauconitic fossiliferous sand.
Incidental
Sedimentary > Clastic > Mudstone > Claystone > Bentonitedark, bentonitic, carbonaceous, sparsely fossiliferous clay
Unconsolidated > Marllight-grey to yellowish-grey sandy, glauconitic , fossiliferous marl;
Unconsolidated > Fine-detrital > Silt
References

Szabo, M.W., Osborne, E.W., Copeland, C.W. Jr., and Neathery, T.L., 1988, Geologic Map of Alabama, Geological Survey of Alabama Special Map 220, scale 1:250,000.

NGMDB product
Counties Choctaw - Clarke - Conecuh - Covington - Escambia - Geneva - Monroe - Washington