PRE-WISCONSIN GLACIAL DRIFT OF GLACIER PARK 731 



exists in the area east of the mountains, but farther from the base of the 

 range than Mr. Alrlen has yet worked? 



May not tlie Blackfoot peneplain pass under the older glacial drift, as 

 described by Mr. Alden? 



Are the older glacial deposits described in this paper on the highest mesas 

 bordering the range, or are there still higher levels where there may be gravel 

 deposits, sometimes referred to as "high-level gravels?" 



Are the older glacial deiwsits associated with the modern canyon in such a 

 way as to indicate that the ice which left them moved down these troughs? 



SOME GLACIAL DEPOSITS EAST OF CODY, WYOMING, AND THEIR RELATION 

 TO THE PLEISTOCENE EROSIONAL HISTORY OF THE ROCKY MOUNTAIN 

 REGION 



BY WM. J. SINCLAIR 



(Abstract) 



Twelve miles east of Cody, Wyoming, in the Eocene Bad Lands in the vicin- 

 ity of McCulloch Peak, angular blocks of Paleozoic limestone occur at eleva- 

 tions of 6,000 feet al)Ove sea, either on the crests of narrow ridges separating 

 deep valleys cut in the Bad Land clays or on terraces several hundred feet 

 above the Shoshone River. No other rocks than limestone have been seen in 

 these high-level deposits, but at lower levels abundant pebbles and boulders 

 of andesite may be found, all of which are water-worn, while the high-level 

 material is highly angular, the only sign of abrasion being the pitted surface 

 produced by the solvent action of rain water. Corals and br^^ozoa frequently 

 appear in relief on the rain-etched surfaces. Individual fragments vary in 

 size from a few inches or less to blocks (5 by 8 by -t or 5 feet. The source of 

 the limestone is. undoubtedly, the Paleozoic formations of the mountains to the 

 west of Cody. Glacial ice is the only known agent capable of transporting 

 blocks of the size indicated. If the.y have been transported by ice, 1,200 feet 

 or more of canyon cutting has intervened since their deposition, for they are 

 stranded on narrow divides and comb ridges at least that high above the 

 Shoshone River. If they are to be correlated with the first glacial advance 

 in the Rocky ^Mountain region, much of the deep dissection of such inter- 

 montane troughs as the Bighorn Basin must be regarded as an event of 

 Pleistocene time. 



Prof. W. W. Atwood: It appears from Mr. Sinclair's presentation that he 

 has secured some very important evidence on the recent physiographic his- 

 tory of the Rocky Mountains of Wyoming. I should like to ask him two 

 questions: How far away from the range are the large boulders which he 

 attributes to glacial origin? Are the deposits which he describes opposite 

 the present canyon in the mountains to the west? 



Dr. SiNcr^iR, in reply to the foregoing and to questions put by Prof. W. M. 

 Davis, said: The limestone boulders are twelve miles east of Cody, opposite 

 the mouth of Shoshone Canyon. I doubt if boulders were transported down 

 a hypothetical slope as sketched by the President on the black-board, but they 

 seem to have b( en carried across the Eocene filling of the basin to the east of 

 the mountains previous to the dissection of the basin deposits. 

 LI— Bull. Geol. Soc. Am., Vol. 23, 1911 



