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



35 



The section of the formation immediately above the dark 

 red horizon is distinguished by a brownish-yellow coloration 

 over a considerable part of the valley. The same general horizon 

 is apparently represented by a grayish or buff phase in many 

 places. 



In that portion of the section above the red beds, at some 

 localities in the yellow phase and at others either below or 

 above it, there are considerable thicknesses of thinly-bedded, 

 highly carbonaceous shales which may contain numerous lignitic 

 layers (pis. 6 and 7). The shales are largely clay and ash, but 

 may be diatomaceous. The lignitic seams are very numerous in 

 some of the sections, as on the south side of the valley of Beet 

 Creek. They have usually a thickness of only an inch or two. 

 Prospecting for coal has been carried on in this portion of the 

 series but no deposits of economic value have yet been dis- 

 covered. 



A number of fossil leaves were obtained in the section on 

 Beet Creek. It has been found very difficult to transport speci- 

 mens owing to the friable nature of the rock, and only a few 

 species have been obtained for study. 



At one locality of the middle beds in Virgin Valley opal 

 specimens of some commercial value are found. The opals 

 occur largely in cracks or cavities in the typical fossil-bearing 

 beds of this horizon. 



The deposits of that portion of the Virgin Valley represented 

 by the yellow beds and the carbonaceous strata were certainly 

 in part laid down in water. The diatomaceous beds are of 

 aqueous origin, and some of the gray clayey strata which are 

 found to contain fish-bones in considerable numbers must also 

 have been formed in water. The shales with numerous lignitic 

 seams are evidently swamp or lake deposits in a large part. 



That portion of the Virgin Valley Beds above the yellow and 

 the carbonaceous phase of the formation constitutes the largest 

 part of the series of beds exposed. It is made up almost entirely 

 of white to buff or cream-colored ash and tuff. Some strata are 

 almost pure, sharp-edged ash which has been but little worked 

 over. In other beds, the glass is much decomposed and the 

 material has apparently been worked over considerably. There 



