South Dakota School of Mines 53 



to suggest the latter idea were Dr. Theodore Fuchs of Germany 

 snd Prof. Cope. More recently Mr. O. A. Peterson has em- 

 phasized the latter view as a result of the finding of numerous 

 iossils of burrowing rodents within the corkscrews.* In con- 

 clusion it may be said that no single suggestion as to the manner 

 of origin seems as yet to cover all the varied features and un- 

 certainty must needs linger until the discovery of some 

 form or relationship that retains the unmistable key to the 

 explanation. 



MANNER OF DEPOSITION. 



Geologists who first studied the badland formations of the 

 western plains early formulated the theory that the deposits 

 were collected by streams from the highlands of the Rocky 

 Mountains and the Black Hills and were laid down as sediment 

 in great fresh water lakes. These lakes were thought to have 

 varied in position and extent in the different periods of time 

 during which the several formations were being deposited. They 

 were believed in general to have had their origin in certain 

 ■structural changes, either a slight depression along the western 

 side or the elevation of some drainage barrier on the east, and 

 to have been obliterated by the development of new drainage 

 channels accompanied possibly by general uplift, and by the 

 progressive aridity of the climate. 



More recently doubts began to be entertained as to the 

 accuracy of this attractive lacustrine theory, more detailed study 

 <lisclosing many facts at variance with the usual conditions of 

 lake deposition, both with reference to the physical character of 

 the deposits and to the nature, condition, and distribution of the 

 fossil remains found in them. There now seems to be abundant 

 evidence for the belief that the deposits were of combined 

 lagoon, fluviatile, flood-plain, and possibly eolian origin instead 

 of having been laid down over the bottoms of great and con- 

 tinuous bodies of standing water as was first supposed. 



The lacustrine theory originated in the earlier accepted 

 idea that all horizontally-bedded sedimentary rocks were depos- 

 ited in bodies of comparatively still water, either marine, brack- 

 ish, or fresh. It was believed that the fine-grained banded 

 clays were deposited in the quiet deeper waters of the lake, that 

 the sandstones and conglomerates were deposited along* the 



* Peterson, O. A. Description of New Rodents and OikSteussion 

 of the Origin of Daemonelix. Carnegie Mus. Mem., Vol. 2, 1905, pp. 

 139-202, pis. 17-21. 



