Geologic units in Macon county, Alabama

Tuscaloosa Group undifferentiated (Cretaceous) at surface, covers 30 % of this area

Light-gray to moderate-reddish-orange clayey, gravelly fine to very coarse sand; massive mottled sandy clay; local wood and leaf beds; and thin beds of indurated sandstone. Gravel consists mainly of quartz and quartzite and range in size from very fine pebbles to large cobbles. Mapped eats of the Tallapoosa River.

Eutaw Formation (Cretaceous) at surface, covers 24 % 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.

Alluvial, coastal and low terrace deposits (Holocene) at surface, covers 23 % 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.

Selma Group; Blufftown Formation (Cretaceous) at surface, covers 15 % of this area

The Blufftown extends from the Chattahoochee River Valley westward into central Russell County where it is divided into two westward-extending tongues by an eastward-extending tongue of the Mooreville Chalk. In the Chattahoochee River Valley the Blufftown is mainly glauconitic calcareous fine sand, micaceous clay and marl, fossiliferous clay, gray calcareous fossiliferous sandstone, and carbonaceous clay and silt. To the west the lower tongue of the Blufftown is gravelly sand, glauconitic sand, calcareous clay, and sandy clay and merges with the lower part of the Mooreville Chalk in southwestern Macon County. The upper tongue is mainly calcareous sandy clay and micaceous silty fine sand with thin layers of limestone and sandstone. The upper tongue merges with the Mooreville Chalk and the lower part of the Demopolis Chalk in western Bullock County.

Selma Group; Mooreville Chalk (Cretaceous) at surface, covers 7 % of this area

Yellowish-gray to olive-gray compact fossiliferous clayey chalk and chalky marl. The unconformable contact at the base is characterized by a bed of glauconitic, chalky sand containing phosphate pellets and molds of fossils. The Arcola Limestone Member at the top consists of two to four beds of light-gray brittle, dense, fossiliferous limestone seperated by beds of light-gray to pale-olive calcareous clay.

Opelika Complex; Bottle Granite (Precambrian to Paleozoic) at surface, covers 0.7 % of this area

Leucocratic, fine to medium-grained, well-foliated quartz monzonite to granite; locally porphyritic.

Opelika Complex; Loachapoka Schist (Precambrian to Paleozoic) at surface, covers 0.4 % of this area

Muscovite-quartz schist; locally contains biotite-garnet-muscovite schist, many layers conatin sillimanite (northeast of Mount Jefferson, Lee County); kyanite (west of Mount Jefferson); locally muscovite-rich schist and quartzite common.

Pine Mountain Group; Manchester Schist (Precambrian to Paleozoic) at surface, covers 0.2 % of this area

Interlayered muscovite-quartz schist and quartzite, locally contains garnet, sillimanite and graphite; commonly intensely shared.

Dadeville Complex; Ropes Creek Amphibolite (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

Layered and massive amphibolite; locally includes hornblende migmatite and ultramafic pods.

Opelika Complex; Auburn Gneiss, Unnamed unit (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

Unnamed unit comprised of masses of medium- to coarse-grained muscovite-biotite schist, locally garnetiferous; grades into oa.

Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

Blastomylonite, mylonite gneiss, locally includes mylonite schist and mylonite quartzite in Towaliga fault zone.

Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones (Precambrian to Paleozoic) at surface, covers < 0.1 % of this area

Mylonite and blastomylonite; contains minor ultramylonite, mylonite schist, and mylonite gneiss.