210 University of California Publications. [Geology 



The affinities of this fauna with that known from Virgin 

 Valley are close enough to indicate that the beds near High Rock 

 Canon probably represent the same epoch as the mammal beds of 

 Virgin Valley. 



FAUNA OF THE THOUSAND CREEK BEDS 



Occurrence and Composition. — The beds at Thousand Creek 

 stretch over a territory many miles in extent, but the sections 

 examined thus far are not more than a few hundred feet in thick- 

 ness. The basal strata have not been seen in these exposures. 

 As these beds seem to extend a considerable distance to the north 

 beyond the farthest point thus far examined, it is possible that 

 still lower horizons may yet be found. 



The nature of the formation does not vary greatly throughout 

 the region as a whole, and the strata are generally horizontal or 

 only slightly inclined. There are a few well-marked beds which 

 with careful work might be traced and mapped for a considerable 

 distance. A sharply defined stratum of white to gray ash in the 

 northern part of the basin resembles an ash layer at the southern 

 end of the field so closely as to suggest their representing the 

 same horizon. 



Around the border of the Thousand Creek Flats there are 

 several terraces evidently formed in late Pleistocene time. The 

 possibility of Pleistocene deposits occurring on these terraces and 

 being confused with an older formation was considered in the 

 field. With the exception of one or two cases, which are especi- 

 ally considered under the discussion of the fauna, the exposures 

 in which collections were obtained could not be separated from 

 the pre-Pleistocene formation here referred to as the Thousand 

 Creek Beds. 



Mammalian fossils have been found in most of the exposures 

 in this region, though they are comparatively rare at some places. 

 A complete list of the species from the localities about the Thou- 

 sand Creek Basin is as follows : 



