42 THE WHITE RIVER BADLANDS 



from 250 to 300 feet. The stratigraphy in Pine Kidge dif- 

 fers in some important respects lithologically from that of 

 the Big Badlands and the exact equivalent there of the 

 Oreodon beds does not yet seem clear. 



The Protoceras Beds. The Protoceras beds, earlier con- 

 sidered as part of the Oreodon beds, were first differen- 

 tiated by J. L. Wortman as a result of field work done 

 during the summer of 1892 for the American Museum of 

 Natural History. The name is derived from the character- 

 istic and highly interesting extinct animal, the Protoceras, 

 which occurs in the sandstones of these beds in considerable 

 abundance. 



Lithologically the beds are made up of isolated patches 

 of coarse, lenticular sandstones, fine-grained clays, and 

 nodular layers. The sandstones occur in different levels and 

 are usually fossiliferous. They are seldom continuous for 

 any great distance and often change abruptly into fine- 

 grained barren clays. Immediately overlying the sand- 

 stones there is a pinkish colored nodule-bearing clay, con- 

 taining abundant remains of Lepthauchenia and other forms, 

 hence the name Leptauchenia zone often used in connection 

 with these beds. The Protoceras beds have been clearly 

 differentiated only in the Big Badlands. Elsewhere the 

 lithologic conditions do not generally serve to indicate their 

 presence, hence if they occur outside of the Big Badlands, 

 the determination of their areal distribution must in a large 

 measure await the study of the paleontologist. The total 

 thickness of the beds, including with them the Leptauchenia 

 clays, is approximately 150 to 175 feet. 

 LOWER MIOCENE 

 The Arikaree Formation 



The Arikaree formation, first designated as such by 

 Darton, receives its name from the Arikaree Indians, who 

 were at one time identified with the area in which it is most 

 largely developed. Its greatest development is in Pine 

 Ridge and southward. It is of Lower Miocene age and lies 

 uncomformably on the Brule and in places overlaps the 

 margins of that formation. 



The Arikaree is largely a soft sandstone, varying in 

 color from white to light gray. Calcareous concretions 

 occur throughout the formation in abundance. They are 

 usually of cylindrical form and are often more or less con- 



