North Dakota Stratigraphy Bison bison ROCK ROCK UNIT COLUMN PERIOD EPOCH AGES MILLIONS OF YEARS AGO Common Name: Holocene Oahe .01 American bison Coleharbor Pleistocene QUATERNARY Classification: 1.8 Pliocene Unnamed 5 Miocene Class: Mammalia 25 Arikaree Order: Artiodactyla Family: Bovidae Brule Oligocene 38 South Heart Description: Chadron Chalky Buttes Bison bison, the American bison, lives in North Dakota today but Camels Butte Eocene Golden was much more abundant in the past. Two hundred years ago, 55 Valley Bear Den Lewis and Clark recorded huge herds of bison in North Dakota. Sentinel Bison are large animals, the males are up to about 10 feet long and Butte TERTIARY weight as much as 1800 pounds. Bison live in herds and mostly eat grass. They have a keen sense of smell and have excellent eyesight. Bison bison date back to about 5,000 years ago. The Bullion species has likely lived in North Dakota that long. Bison fossils, Paleocene Creek skulls and skeletal bones, are abundant in North Dakota and have been found throughout the state. Slope Cannonball Ludlow 65 Hell Creek Fox Hills ACEOUS Pierre CRET 84 Niobrara Carlile Carbonate Calcareous Shale Claystone/Shale Siltstone Sandstone Sand & Gravel Bison herd along the Missouri River north of Bismarck with the Mudstone Lignite Glacial Drift Lewis and Clark expedition in boats on the river in 1804. Painting by, and courtesy of, Vern Erickson. Locations where fossils have been found ND State Fossil Collection Prehistoric Life of ND Map North Dakota Geological Survey Home Page.