Vol. G I Merriam: Virgin V 'alley and Thousand Creek. 223 



Valley section seems to be separated from the middle zone by an 

 unconformity below the rhyolitic gravels lends some support to 

 this view. If, as seems to be the case, the unconformity below 

 the rhyolitic gravels in Virgin Valley is not due to accumulation 

 during the cutting of the present valley ; and if this uncon- 

 formity is not a purely local discordance due to extraordinary 

 stream action in Virgin Valley time, then there is reason to con- 

 sider the Virgin Valley as divisible into two periods of sedi- 

 mentation which may have been separated by a considerable 

 epoch of erosion. 



The Thousand Creek Beds may correspond to that portion 

 of the Virgin Valley series above the unconformity. Also if 

 the unconformity should appear to be between typical Virgin 

 Valley Beds and gravels laid down in the course of the cutting 

 of the valley, the gravels may correspond to some phase of the 

 Thousand Creek Beds. So far as these possibilities are con- 

 cerned, it is important to know if a fauna similar to that of 

 Thousand Creek can be obtained in the uppermost portion of the 

 section of Virgin Valley. As yet nothing characteristic of 

 either the Virgin Valley or the Thousand Creek faunal phase 

 has been obtained from this portion of the section. The only 

 suggestion of evidence has come through the examination of a 

 number of the low hills in Virgin Valley which seem to be formed 

 by slides which have come down from the summit of the mesa. 

 In this locality mastodon remains seem more abundant than in 

 other places in Virgin Valley, and the only specimen represent- 

 ing a very large feline was found here. At Thousand Creek, 

 mastodon remains are more abundant than at Virgin Valley, and 

 remains of very large felines are well known. 



In order to come to an entirely clear understanding of the 

 true stratigraphic relations of the Virgin Valley and Thousand 

 Creek beds it will be necessary to make a farther examination 

 of the geology of this region. Such evidence as will make per- 

 fectly clear the relation of the biologic succession to the series 

 of events in the physical history of this region is much to be 

 desired, as the final understanding of either the biological or 

 the physical history of the Pacific Coast region can be accom- 

 plished only by utilizing all evidence which can be obtained. A 



