The White River Group of northwestern Nebraska: Stratigraphic revisions, correlations, and paleopedology

Revised lithologic correlations between type areas of the White River Group in Nebraska and South Dakota have resulted in a new lithostratigraphy for the lower part of the White River Group. The following pedostratigraphic and lithostratigraphic units, from oldest to youngest, are newly recognized in northwestern Nebraska and can be correlated with units in the Big Badlands of South Dakota: the Yellow Mounds Paleosol Equivalent, Interior and Weta Paleosol Equivalents, Chamberlain Pass Formation, and Peanut Peak Member of the Chadron Formation. The term Interior Paleosol Complex for the brightly colored zone at the base of the White River Group in northwestern Nebraska is abandoned in favor of a two-part division. The lower part is related to the Yellow Mounds Paleosol Series of South Dakota, which represents the pedogenically modified Cretaceous Pierre Shale. The upper part of this Complex is composed of the unconformably overlying, pedogenically modified overbank mudstone facies of the Chamberlain Pass Formation (which contains the Interior and Weta Paleosol Series in South Dakota). Greenish-white channel sandstones at the base of the White River Group in Nebraska (previously correlated with the Ahearn Member of the Chadron Formation in South Dakota) are here correlated with the channel sandstone facies of the Chamberlain Pass Formation in South Dakota. The Chamberlain Pass Formation is unconformably overlain by the Chadron Formation in South Dakota and Nebraska. Unlike the threefold division of the Chadron Formation into the Ahearn, Crazy Johnson, and Peanut Peak Members in South Dakota, only the bluish green, hummocky-weathering mudstones of the Peanut Peak Member are present in northwestern Nebraska. The remainder of the Chadron Formation in northwestern Nebraska, the Chadron B and Chadron C , is included within the newly defined Big Cottonwood Creek Member. The contact between the Peanut Peak and Big Cottonwood Creek Members of the Chadron Formation in northwestern Nebraska is intertonguing, except where strata of the Big Cottonwood Creek Member fill depressions and minor valleys in the Peanut Peak Member