EDITORIAL 73 



The Geology of the Great Basin in Eastern California and South- 

 western Nevada. By H. W. Turner, San Francisco, Cal. 



The ridges of the western edge of the Great Basin in Nevada and 

 eastern California are usually very complex in structure and composition. 

 They comprise sediments of Paleozoic and . Jura-Trias age much dis- 

 turbed at some points by intrusions of granolites. In Tertiary time 

 there were extensive lakes, and contemporaneous with these lakes and 

 also later are lavas and tuffs in large amounts, chiefly rhyolites, andes- 

 ites, and basalts. 



The formation of the ranges, or at least their latest uplifts, date 

 from the late Tertiary and post-Tertiary time. 



They were elevated along normal faults, the valleys being in part 

 subsided areas, often of the nature of rock basins, whose rims are com- 

 posed of rocks older than the desert detritus. 



There are some gneisses pretty certainly of pre-Cambrian age. 

 These gneisses underlie Lower Cambrian sediments rich in fossil 

 remains at some points. There is an extensive chert series containig 

 abundant graptolites supposed to be of Lower Silurian age. There 

 are Lower Trias beds in the Inyo Range and Jurassic limestone in the 

 Pilot Mountains. 



The Tertiary lake beds contain abundant plant, molluscan, and fish 

 remains. 



The paper was illustrated with lantern slides. 



Notes on the Geology of the Three Sisters, Oregon. By H. W. Fair- 

 banks, Berkeley, Cal. 



The Three Sisters form a group of volcanic peaks upon the summit 

 of the Cascade Range in central Oregon. They rise to a height of 

 about ten thousand feet, and are quite similar in many respects to the 

 other great volcanic peaks which mark the crest of the Cascade Range 

 through Oregon and Washington. 



This group of peaks is marked by the presence of a glacier nearly 

 three miles long and half a mile wide. 



To the north of the peaks recent volcanic activity is indicated by 

 extensive flows of basic lavas. Volcanic eruptions have occurred since 

 the glacial period, as shown by the relation of the lavas to the grooved 

 and polished surfaces. A volcanic cone upon the North Sister lies in 

 the path of the present glacier. 



Illustrated by lantern slides. 



