204 



University of California Publications. [Geology 



FAUNA OF THE VIRGIN VALLEY BEDS 



Occurrence and Composition. — The section exposed in Virgin 

 Valley has been more or less arbitrarily subdivided as follows : 



Upper Zone. White to buff beds. Ashes and ) 



-,• , > Upper Virgin Valley? 



diatomaceous beds. \ 



Unconformity?" 



Middle Zone. Gray to yellow and brown shales 

 and clays. Carbonaceous shales, 

 lignites, diatomaceous beds. 



^ Lower Virgin Valley ? 



Lower Zone. White to green, purple, and red 

 clays and ashes. 



The zones as indicated above are not sharply defined, but 

 where the attempt has been made to trace them they seem to be 

 fairly persistent. Careful mapping of these horizons throughout 

 the valley is desirable. 



No mammalian remains have been found in Virgin Valley in 

 characteristic beds of the lower zone, and only imperfect frag- 

 ments were found in that portion of the section above the 

 horizon at which an unconformity appears between the rhyolitic 

 gravels and the underlying fine-grained beds. 



Locality 1065, on the south side of the valley of Virgin Creek, 

 the original locality at which mammalian fossils were found by 

 McGrhee, is immediately below the carbonaceous shales of the 

 middle division ; while locality 1091 on the west side of Beet 

 Creek is a considerable distance above the carbonaceous shales. 

 Most of the other localities at which collections have been made 

 in Virgin Valley would probably fall within the limits of vertical 

 range marked by these two localities. Mapping of the faunal 

 and lithologic zones of the Virgin Valley Beds will probably show 

 that the principal fossil horizons fall within a zone only a few 

 hundred feet in thickness situated near the middle of the section. 

 Other fossiliferous beds are naturally to be expected both above 

 and below this horizon. 



The complete list of mammalian species obtained from all of 

 the localities in the Virgin Valley Beds is as follows : 



* Merriam, J. C, op. cit., part I, pp. 36, 43, and pi. 8. 



