ABSTRACTS OF PAPERS PRESENTED 75 



NOTES ON THE PREOLACIAL GEOLOGY OF THE PUGET SOUND BASIN 



BY CHARLES E. WEAVER 



In the absence of the author the following papers were read by title : 



GEOLOGICAL RECONNAISSANCE OF NORTHEASTERN NICARAGUA 

 BY OSCAR H. HERS HEY 



SOME TERTIARY AND QUATERNARY GEOLOGY OF WESTERN MONTANA, 

 NORTHERN IDAHO, AND EASTERN WASHINGTON 



BY OSCAR H. HEBSHEY 



(Ahstract) 



Evidences of two stages of glaciation in Deer Creek Valley, Montana, are 

 given and brief reference is made to the latest glaciation in the Coeur d'Alene 

 Mountains of Idaho. A sj'stem of river terraces distributed for 80 miles along 

 the valley of the South Fork of the Coeur d'Alene River is described in detail. 

 The 1,150-foot terrace is probably early Miocene in age, but merely marks a 

 vicissitude in the erosion of a valley 4,000 feet deep. In Middle Miocene time 

 the Columbia River lava obstructed the valley and produced a lake in which 

 were deposited white and variegated silts and the delta gravels of the river, 

 filling the old valley 500 feet deep, to the level of the 600-foot terrace. A new 

 valley 400 feet deep, partly on a new course, was trenched in early Quaternary 

 time down to the 200-foot terrace. A remarkable distribution of granitic and 

 gneissic boulders on this terrace is attributed to icebergs in a lake produced 

 by the glacial damming of the valley at some point not determined ; this is 

 considered evidence of very early glaciation somewhere in northern Idaho. 

 The CO-foot terrace is a gravel-capped rock bench, but the 30-foot terrace was 

 built by the river and is tentatively correlated with the first glacial stage in 

 Deer Creek Valley. Physiographic features of the Clearwater region and the 

 lake plateau of eastern Washington are discussed, and Coeur d'Alene Lake and 

 the Post and Spokane falls are explained as the result of the deposition of 

 glacial overwash gravels in the broad Spokane Valley during the last glacial 

 stage. 



The meeting adjourned at 5.30 p. m. 



During the session Mr. Wilkie, of Palo Alto, exhibited a collection of 

 California tourmalines, benitoites, etcetera, in room 27, South Hall. 



Register of the Berkeley Meeting 



FELLOWS 



F. M. AxDERsox G. D. Louderback 



H. Foster Baix R. H. Loughridge 



A. J. Collier J. C. Merriam 



A. S. Eakle H. F. Reid 



E. W. Hilgard W. S. Tangier Smith 



A. C. Lawsox J. A. Taff 



