TITLES A^'D ABSTRACTS OF PAPERS 193 



to the indications of the relative length of Tertiary time. Smith was of the 

 opinion that observations in the tropics indicated that the Tertiary was shorter 

 than ordinarily considered. Clark held that a study of the Pacific Coast strati- 

 graphic column indicated that the Tertiary is very long, representing a real 

 era rather than simply a period. 



SYMPOSIUM ON PROBLEMS OF THE NORTH PACIFIC OCEAN 



The meeting adjourned at 11.25 a. m., after decision that no afternoon 

 meeting should be held, so that the members might have an opportimity 

 to attend the symposium on "Problems of the North Pacific Ocean/' held 

 under the auspices of the Western Society of Naturalists. 



Session of Friday, June 20 



The meeting was called to order at 9.50 a. m. by the temporary chair- 

 man. The following papers were presented : 



STRUCTURE OF THE COAST RANGES OF CALIFORNIA 

 BY BAILEY WILLIS 



{Abstract) 



According to the interpretation here presented, the typical structure of the 

 Coast Ranges and of the Sierra Nevada is the rotated mountain block. The 

 block commonly presents a long slope, which is a more or less steeply tilted 

 surfac*e of erosion, often a peneplain. Tilting is an effect of rotation of the 

 block on a curved under surface. The rotation is a movement which may be 

 described as a highly inclined upthrust fault and which is an effect of com- 

 pression due to horizontal pressure. The paper describes specific cases and 

 indicates that the upthrust fault in fact frequently exists where normal faults 

 have been assumed. 



Discussion 



Discussion by W. D. Smith in relation to tidal stress, by Buell on the mag- 

 nitude of the movements, by Louderback in regard to the apparent lack of 

 correspondence between actual observations on schistosity and lava occur- 

 rences with the tlieoretical deductions. Clark discussed the relation to the 

 thrusting along the Great Valley of California and several miles to the west. 

 He (juestioned how this was possible with faulting as explained by the author 

 and also in(|uired concerning the Santa Lucia thrust. The author replied, 

 exjjlaining the relationship of this theory to the various other phenomena 

 mentioned. 



At 11.05 the meeting adjourned to permit the members to take part in 

 the meeting of the Seismological Society of America. 



XIII— Blll. Geol. Soc. Am., Vol. 31, 1919 



