ABSTRACTS OF PAPERS 135 



Discussion 



I'rofessor Louderback poiuted out that while all recognized the desirability 

 (if uniformity, the dithculty was in agreeing on any uniform system. The 

 system i)roiJOsed by the athor is not strictly a jjeti-ologic system, but a tiekl 

 flassiticatiou, and the question arises as to wliether such classification is to be 

 complete in itself or shall simply attempt to approximate a more refined classi- 

 fication, which latter shall determine the definitions. In the former case the 

 names used by author might each ha\e two definitions, thus perpetuating con- 

 fusion. In the latter case the field classification would be merely approximate 

 and temporary until more accurate determination could be made. It was also 

 pointed out that the strict use of the author's tables would yield results at 

 \ariance with the standard nomenclature based on microscopic and chemical 

 analysis. Tlie great bulk of the andesitcs — the augite andesites, for example — 

 would by the table be placed among the basalts. The table uses physical 

 characteristics for major groups, but uses names based on field occurrence, 

 and instances were cited of common western types where volcanic fiows would 

 be called intrusives and vice versa. Agreement was bad with the author that 

 an oversimplified system, such as has been presented by certain American 

 petrographers for field u.ses, is of no practical value. It slurs over important 

 distinctions which can usually easily be made. 



The meeting adjourned for the day at 4.15 p. m. 



Sessiof of Friday, May 33. 



The meeting was called to order at 9.55 a. m. by the chairman, Presi- 

 dent Branner, and the scientific program was continued as follows : 



GEOLOaiC STRUCTURE IN WESTERN WASHINGTON 

 BY CHARLES E. WEAVER 



i Abstract) 



The geologic structure in western Washington consists of three nearly par- 

 allel predominant upwarps and three intervening downfolds extending from 

 the Cascade Mountains to tlie Pacific Ocean. Major and minor anticlinal and 

 synclinal folds have been developed parallel and ti-ansverse to these. The pre- 

 dominating trend of all folds in the western half of the State and on Van- 

 couver Island is approximately north 60° west. The minor folds on tlie flanks 

 of the major folds are nearly north and .south. The iiiKiation of movements 

 producing such strucliire appears to have been al or near (lie dose of (be 

 Juras.sic. It was intensified toward the close of ibc Tertiary. 



Presented uithouL Jioles and illusiniird l.v si iml uml niiips. 



