6 



TITANOTHEEES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



or more" of Hayden's section. It therefore appears 

 that Hayden's description of the White River group 

 conforms with the accompanying panoramic section 

 of the Oligocene and lower Miocene exposed on the 

 south side of White River, South Dakota, shown in 



of his 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). 



DISCOVERY OF THE TITANOTHEEES OF 

 THE PLAINS 



At the base of this great section lies 

 the Titanotherium zone, or " Titano- 

 therium beds" of the Hayden-Leidy 

 memoirs, fully described in Chapter II, 

 composed in part of clays, in part of 

 river-channel sandstones, in which 

 titanothere remains are extraordi- 

 narily abundant. 



The northern borders of this wonder- 

 ful region appear to have been first 

 explored around Bear Creek, a dry 

 tributary on the south side of Cheyenne 

 River, from which Thaddeus A. Cul- 

 bertson brought back the first collection 

 of fossils in 1850. From these expo- 

 sures of the Titanotherium. and Oreodon 

 life zones were obtained the greater 

 part of Leidy's types, which are de-c 

 scribed in Chapter III. The Brule and 

 Arikaree formations, which overlie the 

 Chadron, belong to a period succeed- 

 ing the titanothere epoch, with which 

 this monograph closes. 



The physiography of this ancient 

 flood-plain region — its broad level 

 stretches, its meandering rivers, its 

 fringing river-border forests, its distant 

 mountains and active volcanic peaks — 

 as restored from our present knowledge 

 of its fauna and flora, is described in 

 Chapter II. It forms a wide contrast 

 to the mountain-basin region, in the 

 heart of which lie the Wind River de- 

 posits, described by Hayden in 1862. 



DISCOVERY OF THE MOUNTAIN - BASIN 

 ENVIRONMENT OF THE TITANOTHEEES 



As the entire lower Oligocene history 

 Figure 7 —Panoramic section of the Big Badlands of South Dakota, looking of the titanotheres is recorded chiefly 

 southeastward across Cheyenne and White Rivers to Porcupine Butte 



This section of the ancient flood-plain sediments now expoi^ed cuts through five great life zones — the 

 Titanotherium, Oreodon, Leptauchenia, Promenjcochoerus, and Merycochoerus zones. It includes also four 

 ancient river-channel sandstones and conglomerates— the •'Titanotherium sandstones," " Metamynodon 

 sandstones," "Protoceras sandstones," and " Fromcrycochoerus sandstones" — each of which includes a 

 more or less distinct river-border and forest fauna. (See map, fig. 69, vicinity of section B.) 



Figure 7, as sketched under the direction of Osborn 

 for the United States Geological Survey in 1909. 

 (Osborn and Matthew, 1909.321.) Hayden did not, 

 however, specifically define the upper limit of his 

 group, and all the fossils listed by him as characteristic 



in the Great Plains region east of the 

 Front Range of the Rocky Mountains, 

 so their entne Eocene history is 

 recorded almost exclusively in the 

 mountain -basin region west of the 

 Front Range, in western Wyoming, northwestern 

 Colorado, and northeastern Utah. The interpreta- 

 tion of these remnants of the great Eocene sediments 

 (given in Chapter II) involves far more difficult 

 problems and has required more prolonged and in- 



