68 
The American Geologist. 
February, 1896 
flows. These are probably 1,000 feet or more in thickness and 
extend over a considerable area between the El Paso range and 
the Sierra Nevadas. On the north and northeast they pass 
beneath Salt Wells valley and the wash from the Sierra Neva- 
das. They are finely exposed in Red Rock canon and about 
Black mountain, the highest peak of the district. The Red 
Rock canon beds have been described by Gilbert,* who also 
gives a cross-section sketch. The beds are tilted northward 
at an angle of 15-20 degrees. Remnants of strata of about 
the same degree of consolidation appear on the south side of 
the El Paso range and dip in the same direction. This seems 
to indicate a tilting en mass of the range and adjoining coun¬ 
try. 
A seam of coal fourteen inches thick and inclosed between 
clay strata has been found southeast of Black mountain 
occupying a position apparently below the tuffs. Impressions 
of leaves occur in the clay immediately above the seam of 
coal. They were submitted to Dr. F. H. Knowlton who says; 
“ I have looked over the three small fragments of fossil plants 
from the Mojave desert with the following result: Two 
species are represented, /Sapinches affinis Newb., and Anemia 
suhcretacea (Sap.) Ett. and Gard. The question at issue is 
the age of the deposits. Of course the material is hardly 
sufficient to warrant speaking with positiveness, but this can 
be said with reasonable certainty. The plants indicate a 
Tertiary age beyond doubt, and they seem to belong to the 
Eocene. Both species have quite a wide distribution geogra¬ 
phically and are confined, with several unimportant excep¬ 
tions, to the Eocene.” This occurrence is very interesting 
because of its remoteness from any other known Eocene, and as 
giving a clue to the conditions existing in this section during 
the early Tertiary. 
Although Gilbert says that the upper portion of the Red 
Rock canon beds cannot be separated from the detrital slope 
of the Sierra Nevadas there can be no question but that they 
are much older, and were deposited under water. Black 
mountain seems to have been the pivotal point of disturbance. 
Finely stratified tuffs are exposed in the canons and on its 
*Geographical Sur. West of the 100th Meridian, vol. in, p. 142. 
