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



HIGH ROCK CANON EXPOSURES. 



About thirty miles southwest of Virgin Valley a number of 

 exposures were found to contain a fauna similar to that of the 

 Virgin Valley Beds. The localities at which collections were 

 made ai*e near High Rock Canon and Little High Rock Canon 

 (see pi. 1 ) . 



The beds in which the mammalian remains were obtained con- 

 sist of ashy or tufaceous materials resembling some of the ex- 

 posures in Virgin Valley. The region bordering the valley in 

 which the mammal beds appear is largely lava-covered, and 

 according to Heindl and Furlong the fossil beds appear to dip 

 under the lavas at some localities. Whether the apparent posi- 

 tion of the lava over the mammal beds is an original strati- 

 graphic relation is uncertain, as there is considerable faulting 

 in this region. The nature of the lavas here is not certainly 

 known, but a rhyolite seems to form the greater part of the out- 

 crops. A further study of this region is desirable. 



During the period in which the Virgin Valley Beds were 

 being deposited there was probably more or less accumulation of 

 similar materials over a wide area in this region. The deposits 

 laid down at this time may have formed extensive continuous 

 sheets in some localities. .In this particular place accumulation 

 may have taken place in small separated basins formed through 

 faulting. 



PHYSICAL CONDITIONS OBTAINING DURING DEPOSITION OP 

 VIRGIN VALLEY AND THOUSAND CREEK BEDS. 



The sedimentary deposits, and the fossil remains which have 

 been found in them at Virgin Valley, show that there was some 

 variation in the physical conditions obtaining in this region 

 in late Tertiary time. During the deposition of a portion 

 of the lower beds in Virgin Valley, swampy or moist ground 

 covered a considerable area, and thin lignitic deposits were 

 formed. Particularly during the deposition of the middle 

 portion of the Virgin Valley Beds, there was a partial forestation 

 of the region, as is evidenced by the abundant petrified remains 

 of large trees preserved in these strata. The mammalian fauna 



