HYDROGRAPHIC CONDITIONS IN THE SEVERAL EPOCHS 



29 



near Fairburn, along Battle creek and Lame Johnny creek, and doubtless 

 at other points. Traces of these gravelly deposits are found below the 

 Titanotherium beds along Indian draw and at other points. 



During the Miocene, including the Oligocene, it has been commonly 

 believed that a large freshwater lake crossed the state from north to south, 

 east of the Black hills. This lake lay nearer the Black hills during the 

 White River stage and shifted toward the east during the Loup Fork 



Later Paleozoic. 



Figure 1. — Hydrographic Conditions of South Dakota for the Epochs indicated. 



stage. Later investigations have made it certain that much of the mate- 

 rial was deposited by rivers in their valleys and deltas, particularly in 

 the" vicinity of the Black hills. Some also have the idea that eolian 

 deposits form a large portion of these beds. There can be little doubt, 

 however, considering the topographic relations, that extensive lakes 

 occupied much of the region, if not so extensively as formerly thought. 



