Vol. 6] Merriam: Virgin Valley and Thousand Creek. 



41 



ment along the east side of Thousand Creek Ridge in post-Mesa 

 Basalt time, earthquakes of considerable violence probably 

 occurred. 



Suggestions of a stage during which considerable volumes of 

 sediment may have accumulated in the valley before it had 



Fig. 4. — A portion of the mesa south of Virgin Valley. Antelope Butte, a 

 prominent dome of rhyolite in the background, rises above the level floor of basalt. 

 The circular lake in the foreground is surrounded by steep walls of basalt. 



attained as much as one-half , of its present depth are offered 

 by a bed of gravel and boulders which covers the top of a 

 prominent ridge in the angle between the drainage of Virgin 

 Creek and Beet Creek (pi. 8). At this point the top of the 

 spur running out from the sharp eastern point of the mesa is 

 covered with at least fifty feet of coarse gravel and boulders. 

 Farther east Mr. Heindl measured a section of this gravel 

 one hundred and twenty feet thick. At some points near the 

 east end of the ridge these gravels are interbedded with strata 

 which appear like a part of the Virgin Valley Formation. Along 

 a large portion of the north side of this ridge the contact 

 between the gravel and the underlying Virgin Valley Beds is 



