1912] 



Baker: Western El Paso Range 



129 



south as the north foot of the El Paso Range. The alluvial 

 material is indistinguishable in texture, structure, and composi- 

 tion from the granite arkoses of the Rosamond series, and at 

 places at the foot of the north flank of the El Paso Range it is 

 difficult to distinguish alluvium from Rosamond. It is the prob- 

 lem of distinguishing residual soil or mantle rock from trans- 

 ported alluvium of the same nature in a region where both are 

 present. The alluvium has been dissected by the shallow valleys 

 of the upper tributaries of Red Rock Canon and Last Chance 

 Gulch, and where the contact between it and the underlying 

 Rosamond is exposed by such dissection it is seen that the 

 alluvium mantles an even surface bevelling the edges of the 

 upturned Rosamond. 



Structure 



The main exposures of the Rosamond series are in the north- 

 ern more gentle flank of the El Paso Range. The strata dip 

 northwestward at an average angle of 15 degrees. The strike, 

 which is approximately N 25° E in the middle portion of the 

 exposure, curves in a southward direction near the west end 

 of the range. On the south flank of the range were noted two 

 small exposures of the Rosamond series, one on the east wall of 

 Red Rock Canon near its mouth and the other in the low-lying 

 area just north of Kane ' ' dry lake, ' ' some eight or ten miles east 

 of Red Rock Canon. These two isolated exposures have the same 

 general dip and strike as the main exposures on the north flank. 



The lower Rosamond (the strata below the basalt flows) is 

 cut by several normal strike faults with displacements up to 

 fifty feet in amount. 



The south flank has a much steeper profile than the north 

 flank. The base of the south front of the range is a nearly 

 straight line and there are no shoulders projecting out from the 

 main mountain mass into the basin area. The stream courses of 

 the south flank are steep and narrow and, with the exception 

 of Red Rock Canon and Last Chance Gulch, exhibit lack of 

 topographic conformity with the wide broad basin of Kane "dry 

 lake" (pi. 8, fig. 1). From physiographic evidence alone one 

 would come to the conclusion that the Kane Lake basin was a 



