Geologic Unit: Niobrara

Usage:

Niobrara Formation (MN*,MT*)
Niobrara Formation of Colorado Group (CO*,KS*,NE*,NM*,ND*,SD*,WY*)
Niobrara Shale of Colorado Group (MT*,ND*)
Niobrara Chalk of Colorado Group (KS*)
Niobrara Marl of Colorado Group (SD)
Niobrara Marl (SD)
Niobrara Limestone (recognized locally in CO*,SD*,WY*)
Niobrara Member of Cody Shale (MT*,WY*)
Niobrara Member of Colorado Shale (MT*)
Niobrara Member of Mancos Shale (CO*,NM*)

Subunits:

(alphabetical): Fort Hays Limestone Member (CO*,KS*,NE*,NM*,SD*,WY), Smoky Hill Chalk Member (CO*,KS*,NE*,SD*) or Smoky Hill Marl Member (CO*,NM*) or Smoky Hill Member (WY) or Smoky Hill Shale Member (CO*,NE*,NM*).

Geologic age:

Late Cretaceous (Turonian to Campanian)*

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

Named from cliff exposures along Missouri River near mouth of Niobrara River, [approx. Lat. 42 deg. 46 min. 00 sec. N., Long. 98 deg. 03 min. 00 sec. W., Niobrara 7.5-min quadrangle], Knox Co., northeastern NE (Meek and Hayden, 1862; US geologic names lexicons, USGS Bull. 896, 1200).

AAPG geologic province:

Central Montana uplift*
Denver basin*
Iowa shelf*
Las Vegas-Raton basin*
North Park basin*
Powder River basin*
Salina basin*
San Juan basin*
Sioux uplift*
Williston basin*