Geologic Unit: Ogallala

Usage:

Ogallala Formation (CO*,KS*,NE*,NM*,OK*,SD*,TX*,WY*)
Ogallala Group (NE,SD, and WY-local)
Misspelled Ogalalla in some early reports.

Subunits:

GROUP STATUS (alphabetical): Ash Hollow Formation (NE,SD), Box Butte Formation (NE), Olcott Formation (NE), Runningwater Formation (NE, and WY-local), Sand Canyon beds [informal] (NE-local), Sheep Creek Formation (NE, and WY-local), Snake Creek Formation (NE-local), Thin Elk Formation (SD), Valentine Formation (NE,SD).
FORMATION STATUS (alphabetical): Bridwell Member (TX), Calvert Ash Bed (KS-local), Couch Member (TX), Dellvale Ash Bed (KS-local), Edson local fauna (informal) (KS-local), Fort Wallace Ash Bed (KS-local), Rawlins Ash Bed (KS), Reager Ash Bed (KS), Reamsville Ash Bed (KS), Rhinoceros Hill local fauna (informal) (KS-local), Woodhouse Clay [unranked] (KS-local), Wray Channel Beds (CO).

Geologic age:

late Tertiary (Miocene to Pliocene)*

Type section, locality, area and/or origin of name:

Named from exposures around Ogallala (correct spelling), located along South Platte River, [Ogallala quadrangle, scale 1:125,000], Keith Co., western NE (Darton, 1898).
Type section: on Feldt Ranch, in SE/4 sec. 33, T. 14 N., R. 38 W., 2 mi east and 0.5 mi north of town of Ogallala, [Ogallala 7.5-min quadrangle], Keith Co., western NE (Hesse, 1935).

AAPG geologic province:

Anadarko basin*
Central Kansas uplift*
Chadron arch*
Denver basin*
Las Animas arch*
Palo Duro basin*
Permian basin*
Powder River basin*
Salina basin*
Sierra Grande uplift*
Sioux uplift*
Wind River basin*