104 



TITANOTHEBES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



White River group * * * Wliite and light drab clays, 

 with some beds sandstone, and local layers limestone. Fossils: 

 Oreodon, Titanotherium, Choeropotamus, Rhinoceros, Anchithe- 

 rium, Hyaenodon, Machairodus, Trionyx, Testudo, Helix, 

 Planorbis, Limnaea, petrified wood, &c., &o. All extinct. No 

 brackish- water or marine remains * * * I^OOO feet or 

 more * * * Badlands of White River; under the Loup 

 River beds, on Niobrara, and across the country to the Platte. 

 * * * Miocene. 



This original definition appears to include all that 

 has been determined subsequently and mapped by 

 the United States Geological Survey (Darton, 1905) 

 under three formations, namely, Chadron, Brule, and 

 Arikaree, as shown in the accompanying illustration 



east. This fact is significant. It would appear, as 

 stated at the beginning of this chapter, that sedimen- 

 tation in this region was suspended after Denver, 

 Lance, and Fort Union time. The Eocene gradients 

 were so high that there were long periods of erosion, 

 during which large areas of Upper Cretaceous beds 

 were laid bare in the region that now includes North 

 and South Dakota, western Nebraska, and Colorado, 

 so that the lowest Oligocene sediments of the White 

 River group, composing the Titanotherium zone 

 (Chadron A), lie in gentle valleys of ancient formation 

 that range in age from the Algonkian to the Denver 

 formation and Dawson arkose. In Hayden's typical 



Figure 71. — Map showing tributaries of Cheyenne River, S. Dak., from the southeast and tlie type locality 

 (X) of the " Titanotherium beds" of Hayden (Chadron formation), on Bear Creek; also principal collecting 

 ground of Hatcher (dotted area) , the chief fossiliferous area in the Big Badlands 



(fig. 69). Meek and Hayden did not, however, specif- 

 ically define the upper limit of theii' White River group, 

 and all the fossils listed by them as characteristic 

 of the White River group apparently came from beds 

 now classified as Oligocene. The name White River 

 group has therefore for years been restricted to the 

 beds of Oligocene age (Brule and Chadron formations). 

 This great flood-plain deposition was preceded by 

 a long period of erosion in Eocene time. No sedi- 

 ments of Wasatch, Bridger, or Uinta age have been 

 found on the Plains east of the Front Range of the 

 Rocky Mountains, except in a small area of Huerfano 

 sediment which lies within a mountain basin farther 



locality of the White River group — the Mauvaises 

 Terres of early explorers — the Big Badlands between 

 the Cheyenne and the White River of South Dakota — 

 the underlying beds are composed entirely of the 

 Pierre (Upper Cretaceous). At some places (Loomis, 

 1904.1, p. 432) the rivers depositing the Titanotherium- 

 bearing beds washed out along theu" banks masses of 

 the Pierre shale that contained characteristic Pierre 

 fossils — Baculites and the bones of Cretaceous rep- 

 tiles — and redeposited them in Oligocene sediments. 

 On this level, the gently undulating surface of the 

 Pierre, east of the Rocky Mountains and the Black 

 Hills, meandered broad, sluggish streams, whose chan- 



