Chadron Formation

Geology

Group: White River

Members: unnamed (66), Ahearn (3), Big Cottonwood Creek (8), Chalky Buttes (1), Crazy Johnson (2), Peanut Peak (6), upper (1), Yoder (1)

Lithologies: not reported (35), "siliciclastic" (8), claystone (1), siltstone (2), sandstone (2), marl (1), "limestone" (1), "volcaniclastic" (1), tuff (1)

Paleoenvironments: terrestrial indet. (76), fluvial indet. (4), "channel" (1), wet floodplain (1), fluvial-lacustrine indet. (5), lacustrine indet. (1)

Age range: Chadronian or 37.20000 to 33.90000 Ma
Collections

Time interval Ma Country or state Original ID and collection number
Chadronian37.2 - 33.9USA (Montana) (16990 181607)
Chadronian37.2 - 33.9USA (Colorado) (99642)
Chadronian37.2 - 33.9USA (Wyoming) (16892 16933 16942 16971 16972 16973 16980 17045 181578 181579 181597 181598 181601 181602 181604 181612 181613 199544 232921)
Chadronian37.2 - 33.9USA (Nebraska) (16895 16917 16918 16930 16940 16941 16970 16975 16985 16995 17000 17014 17018 17026 17031 17033 17037 17038 99591 99593 99595 99641 179707 179708 179709 179710 181603 181605 181614 186971 186972 223995 223996 223997 223998 223999 224000)
Chadronian37.2 - 33.9USA (South Dakota) (13097 16885 16899 16900 16910 16913 16936 16937 16938 16967 16978 17006 17007 17012 17013 17021 74636 83881 99707 99708 99709 99711 99855 168799 191398 197281)
Chadronian37.2 - 33.9USA (North Dakota) (16991)
Chadronian - Orellan37.2 - 33.3USA (Nebraska) (186970)
Late/Upper Chadronian - Orellan37.2 - 33.3USA (Nebraska) (230806)