WebThe formation is composed of marine deposits of the generally retreating phase (hemi-cycle) of the Greenhorn cycle of the Western Interior Seaway, which followed the advancing phase of the same cycle that formed the underlying Graneros Shale … WebThe Niobrara Formation / ˌ n aɪ. ə ˈ b r ær ə /, also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago …

U.S. DEPARTMENT OF THE INTERIOR U.S.

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. See more The formation was named for the Greenhorn Station on Greenhorn Creek in Colorado in 1896 by Grove Karl Gilbert; and it is the namesake of the Greenhorn Marine Cycle of the Cretaceous Western Interior Seaway. … See more The formation is recognized for its sequence of index fossils, including oysters, Ammonoidea, Belemnitida, and Inoceramidae. • Ammonoidea and Belemnitida were common, free-swimming pelagic predators, reflecting abundant … See more The Greenhorn Formation is characterized as shale to chalky shale, light bluish-gray in color, with rhythmically repeating beds of chalk or limestone … See more • Earth sciences portal • Paleontology portal • Dinosaurs portal • Cretaceous portal See more WebGreenhorn Formation and Graneros Shale (Turonian and Cenomanian) at surface, covers 3 % of this area Limited to northeastern area. Chinle Group (Upper to middle Triassic) at surface, covers 3 % of this area dicks north dartmouth

Geologic units in Hutchinson county, South Dakota - USGS

WebOct 11, 2011 · Less extensive disconformities are within the Greenhorn Formation, the Niobrara Formation, and the Pierre Shale. Citation Information Contact Geology, Minerals, Energy, and Geophysics Science Center Building 19, 350 N. Akron Rd. P.O. Box 158 Moffett Field, CA 94035 United States WebNov 18, 2024 · Named as top formation of Lower Cretaceous series, top of Lower Cretaceous. Formerly called "formation No. 3" (Meek and Hayden, 1857). Type not designated. Named for Niobrara River, Knox Co, NE in Salina basin, where formation forms 90-100 ft cliffs near mouth along Missouri River. WebRaton Formation (Paleocene and upper Cretaceous) at surface, covers < 0.1 % of this area. Distal sandstones, mudstones, and coal beds in eastern Raton Basin. Middle barren zone laterally equivalent to Poison Canyon Formation. K/T boundary discontinuously exposed about 100 m above basal conglomerate in area southwest of Raton. dicks northborough