412 proceedings: geological society 



U. S. Geol. Survey Water-Supply Paper 425), and most of the present 

 paper is based on an automobile reconnaissance that the writer made 

 with him in the region through which the abandoned channel passes. 



The region is underlain, for the most part, by Yakima basalt. Where 

 the diverted waters reached the monoclinal fold in the basalt that causes 

 the descent into Quincy Valley they apparently formed a cataract, 

 which retreated about 17 miles, cutting through the basalt a gorge 

 several hundred feet deep. The ancient falls resemble Niagara Falls 

 in consisting of two parts separated by an island corresponding to Goat 

 Island. A short distance down stream there is a similar island past 

 which the falls had retreated a little earlier in their history. The 

 ancient falls, which may be called ''Grand Falls," as they occur in 

 Grand Coulee, were somewhat wider and higher than Niagara Falls. 

 As an agent of erosion, the Pleistocene Columbia had two great ad- 

 vantages over the present Niagara: (1) It fluctuated much more and 

 in heavy floods probably carried at least three times as much water as 

 the maximum of the modern Niagara. (2) It was much better provided 

 with tools for erosion than the Niagara, as is impressively shown by the 

 great quantity of large boulders in the glacial outwash below the mouth 

 of the gorge. Although the basalt through which Grand Falls retreated 

 was more difficult to excavate than the rocks through which Niagara 

 Falls are retreating, less time was probably required to make this 

 retreat of 17 miles than for Niagara Falls to make its retreat of only 7 

 miles. At the mouth of the gorge the ancient river discharged, in the 

 early part of its history, into a lake which occupied Quincy Valley, as 

 is indicated by the topography, by fossiliferous stratified deposits, by 

 erratic glacial boulders of granite and quartzite which must have been 

 carried to their present positions by icebergs, and by two ancient water 

 falls along the present gorge of Columbia River obviously caused by the 

 overflow of the lake. 



An interesting story of postglacial erosion and deformation is told by 

 the well-developed terraces of the Columbia, which are related in vari- 

 ous ways to the glacial features. 



The 326th meeting was held in the lecture room of the Cosmos Club 

 on March 13, 1918. 



REGUL*AR PROGRAM 



Kirk Bryan: Classification of springs. (Illustrated.) No abstract. 



Arthur J. Collier: A formation hitherto unaccounted for in North 

 Dakota. (Illustrated.) In the collection of photographs made by 

 A. L. Beekly in the Culbertson lignite field, there are several very good 

 views of filled valleys in which the filling is being eroded by the present 

 streams which flow through them in narrow canyons or gullies. No 

 statement of the materials or agents filling these valleys is given, and 

 one is left to infer that it is alluvium deposited at some old level of 

 Missouri River. 



