Geologic units in Sebastian county, Arkansas

McAlester Formation (Middle Pennsylvanian- Des Moinesian) at surface, covers 46 % of this area

McAlester Formation

Atoka Formation - Upper part (Middle Pennsylvanian- Atokan) at surface, covers 20 % of this area

Atoka Formation - Upper part

Savanna Formation (Late Pennsylvanian- Des Moinesian) at surface, covers 11 % of this area

Savanna Formation

Harthshorne Sandstone (Middle Pennsylvanian- Des Moinesian) at surface, covers 10 % of this area

Harthshorne Sandstone

Atoka Formation - Middle part (Middle Pennsylvanian- Atokan) at surface, covers 7 % of this area

Atoka Formation - Middle part

Alluvium (Holocene) at surface, covers 3 % of this area

Alluvial deposits of present streams

Atoka Formation - Lower part (Middle Pennsylvanian- Atokan) at surface, covers 1 % of this area

Atoka Formation - Lower part

Terrace deposits (Late Pleistocene) at surface, covers 0.9 % of this area

Alluvial deposits on one or more terrace levels

Atoka Formation, undivided (Middle Pennsylvanian- Atokan) at surface, covers 0.5 % of this area

Atoka Formation, undivided

Alluvium (Holocene) at surface, covers < 0.1 % of this area

WOODWARD- Lenticular and interfingering deposits of gravel, sand, silt, and clay. Generally light-tan to gray. Thickness along major streams ranges up to 100 feet and probably averages 40 feet; along minor streams the thickness ranges up to 45 feet and probably averages 20 feet. ENID- Sand, silt, clay, and locally gravel. Maximum thickness ranges from 30 to 80 feet (9 to 24 m) along major streams and from 0 to 60 feet (0 to 18 m) along minor streams. TULSA- Gravel, sand, silt, and clay. TULSA- Gravel, sand, silt, and clay. OKLAHOMA CITY- Sand, silt, clay, and lenticular beds of gravel. Thickness ranges from about 30 to 100 feet and probably averages about 50 feet along major streams. Along minor streams, thickness ranges from a few feet to about 50 feet and probably averages about 25 feet. LAWTON- Sand, clay, and gravel as much as 50 feet (15 m) thick; Shown only along major streams and tributaries. ARDMORE-SHERMAN- Gravel, sand, silt, and clay, including low terraces; thickness, about 25 to 100 feet. McALESTER TEXARKANA- Gravel, sand, silt, and clay, including low terraces about 30 feet above channels; thickness, about 50 feet along Little River and 110 feet along Red River.