page_title: Greenhorn Limestone
hierarchical_section_title: Greenhorn Limestone
caption_attribution_description: English: Jetmore Chalk member of the Greenhorn Limestone in Ellis County, Kansas.
context_page_description: The Greenhorn Limestone or Greenhorn Formation is a geologic formation in the Great Plains Region of the United States. It preserves fossils dating back to the Cenomanian and Turonian of the Late Cretaceous period.
  The formation was named for the Greenhorn Station on Greenhorn Creek in Colorado in 1896 by Grove Karl Gilbert; and it is the eponym of the Greenhorn Marine Cycle of the Cretaceous Western Interior Seaway. With the underlying Graneros Shale, it records the progressive stage of Greenhorn Marine Cycle while the overlying Carlile Shale records the regressive stage.
  The unit under that name is recognized in the Great Plains Region from Minnesota and Iowa to New Mexico to Montana and the Dakotas.
  In much of Alberta and Saskatchewan, the "Second White-Specked Shale" contains limy equivalents of the Greenhorn.
  In Kansas, the Greenhorn Formation is divided into the Lincoln Limestone, Hartland Shale, Jetmore Chalk, and Pfeifer shale members, each noted by changes in chalkiness and limestone rhythmite patterns. In Colorado and western Kansas Hydrocarbon exploration, the divisions are Lincoln Limestone, Hartford Shale, and Bridge Creek Limestone.
context_section_description: The Greenhorn Limestone or Greenhorn Formation is a geologic formation in the Great Plains Region of the United States. It preserves fossils dating back to the Cenomanian and Turonian of the Late Cretaceous period.
  The formation was named for the Greenhorn Station on Greenhorn Creek in Colorado in 1896 by Grove Karl Gilbert; and it is the eponym of the Greenhorn Marine Cycle of the Cretaceous Western Interior Seaway. With the underlying Graneros Shale, it records the progressive stage of Greenhorn Marine Cycle while the overlying Carlile Shale records the regressive stage.
  The unit under that name is recognized in the Great Plains Region from Minnesota and Iowa to New Mexico to Montana and the Dakotas.
  In much of Alberta and Saskatchewan, the "Second White-Specked Shale" contains limy equivalents of the Greenhorn.
  In Kansas, the Greenhorn Formation is divided into the (lowest) Lincoln Limestone, Hartland Shale, Jetmore Chalk, and (highest) Pfeifer shale members, each noted by changes in chalkiness and limestone rhythmite patterns. In Colorado and western Kansas Hydrocarbon exploration, the divisions are Lincoln Limestone, Hartford Shale, and Bridge Creek Limestone. In other states, where the formation is less developed, the unit is not subdivided and is named the Greenhorn Limestone, as a formation or as a member of another formation, e.g., Cody Shale.
caption: The Jetmore Chalk Member of the Greenhorn Formation in Kansas.
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