Greenhorn Limestone

Greenhorn Limestone
Stratigraphic range: Cenomanian-Turonian, around 94.3–89.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
The Jetmore Chalk Member of the Greenhorn Formation in Kansas.
Type	Formation
Unit of	Colorado Group (lower), Benton Formation/Group, Mancos Shale (lower), or Cody Shale
Sub-units	Colorado members: Bridge Creek Limestone Hartland Shale Lincoln Limestone Kansas members: Pfeifer Shale (with Fencepost ls) Jetmore Chalk Hartland Shale Lincoln Limestone
Underlies	Carlile Shale
Overlies	Graneros Shale
Lithology
Primary	Shale to chalky shale Limestone, chalk to marl
Other	bentonite
Location
Coordinates	38°16′37″N 104°42′47″W / 38.277°N 104.713°W / 38.277; -104.713
Region	mid-continental
Country	United States
Type section
Named for	Greenhorn Station, 14 mi south of Pueblo, CO, and for Greenhorn Creek[1]
Named by	Grove Karl Gilbert
Year defined	1896[2]
Greenhorn Limestone (the United States) Show map of the United States Greenhorn Limestone (Colorado) Show map of Colorado

The Greenhorn Limestone or Greenhorn Formation is a geologic formation in the Great Plains Region of the United States, dating to the Cenomanian and Turonian ages of the Late Cretaceous period. The formation gives its name to the Greenhorn cycle of the Western Interior Seaway.