South Dakota School of Mines 21 



Tiundreds of miles north and south along the eastern slopes of 

 the Rocky Mountain front. Their original plainsward exten- 

 sion is not always well defined but in South Dakota they 

 reached eastward to near the James river valley. Of the Black 

 Hills proper only the highest portions seem to have remained 

 uncovered. Apparently from these restricted areas as well as 

 from the far greater Rocky Mountain region detrital materials 

 had opportunity throughout the period to add their volume to 

 the deposits of the bordering lowlands. Later this vast series 

 of sediments was elevated and gradually trenched by innumer- 

 able streams and most of the material has been washed away. 

 Along the Little Missouri river only a few isolated buttes and 

 tables such as Castle Rock, Haystack Butte, Deers Ears, Slim 

 Buttes, Short Pine Hills, Long Pine Hills, and Cave Hills, 

 made up partially or wholly of badland materials, remain to in- 

 dicate the enormous erosion that has taken place. 



The most important and best connected tracts are south- 

 east, south, and southwest of the Black Hills but areas of no 

 mean significance occur in many places within the Hills them- 

 selves. In the Northern Hills there are many isolated areas 

 -mostly small and irregular and generally lying upon or near the 

 highest shoulders of the more important mountain masses. 

 The most extensive are those of the Bear Lodge range where 

 north and west of Warren Peaks the deposits cap several of the 

 ridges and gently sloping tables to a height of nearly 6,000 

 feet. The highest of these are more than 2,500 feet higher than 

 the highest points in the Badlands betw r een Cheyenne river 

 and White river. In addition to the Bear Lodge tracts three 

 small areas are found near Missouri Buttes, a half dozen or 

 more between Nigger Hill and Beulah, one at Maitland, another 

 between Maitland and Spearfish, and two at Lead. 



Farther south the Black Hills are more intimately connected 

 with the formations. Within the higher areas here the deposits 

 are not abundant, being confined chiefly to small areas near 

 Argyle, Minnekahta, and Custer, but between Rapid City and 

 Buffalo Gap they cover large portions of the foothills and in 

 places extend outward almost without break to the great area 

 beyond the Cheyenne river. In addition to this the high tables 

 in the Big Badlands and the infacing escarpment of Pine Ridge 

 proclaim clearly enough their former Black Hills- ward extension. 



The locality of chiefest interest is near the southeastern 

 border of the Black Hills between the White and Cheyenne 

 rivers. This is known as the Big Badlands and is the area 



