LEWIS G. WESTGATE 



which formerly occupied the valley of Lake Creek. This paper 

 describes the topographic features of the basin of Lake Creek and 

 of the neighboring part of the Arkansas valley, and treats of the 

 preglacial topography of the region, the topographic effects produced 

 by Pleistocene glaciation, and postglacial changes. 



PREGLACIAL TOPOGRAPHY OF THE UPPER ARKANSAS 



All of the larger tributary valleys of the Arkansas on the west, and 

 some of those about Leadville on the east, were occupied by valley 

 glaciers during Pleistocene time, while the other tributary valleys 



V/sxA BewUer moraine. 

 \///\ Laier mora\-ne 

 GotIic** g*mvel-s 



\ .'-; v] LaJer gravels 



[V^TI Scatfer 

 P.*»"» | Lief gVa-ve-lJ 



Fig. i. — Map of the Twin Lakes area. 



and the main valley were free of ice. It is thus possible to compare 

 the glaciated and non-glaciated areas, and to determine what features 

 are due to stream-erosion in preglacial time, and to contrast that 

 topography with that which has been changed by glacial action. 



Fig. 2 will make clear the main elements of preglacial form along 

 the Arkansas. The river flows in a narrow interglacial valley cut 

 300 to 400 feet into the granite. From the edge of this inner valley 

 on the east a terrace (BC), from one-half to a mile in width, rises at 

 an angle of 5 to the foothills of the Park Range. This terrace is 

 cut in granite, and while now somewhat dissected, is evidently a 



