332 University of California Publications in Geology [Vol. 7 



plied. When the range is composed chiefly of volcanic rocks 

 the fanglomerate may resemble an agglomerate. These distinc- 

 tions are, however, matters for petrographical description rather 

 than for a, special varietal nomenclature. 



Other varieties are based upon the degree of induration and 

 the nature of the cementing material. The fanglomerates now 

 in process of accumulation in Nevada, Utah, and California are 

 usually incoherent or but feebly cemented ; but in parts of 

 Arizona, New Mexico and over a large part of Mexico, the 

 embankments of fanglomerate are to a varying depth strongly 

 cemented by carbonate of lime. The process of cementation is 

 now in progress on a vast scale and proceeds as fast as the 

 detritus accumulates. This cemented detritus forms one of the 

 numerous kinds of deposits called in Spanish countries caliche. 

 This variety of fanglomerate has an additional geological interest 

 in that it constitutes a continental deposit at the local base level 

 of arid erosion, which is in a large measure resistant to erosion, 

 when, in the course of time, the base level is lowered. It is little 

 affected by structural planes, such as joints and bedding, and is 

 thus not so susceptible to disintegration as the rocks from which 

 it is derived. Neither is it susceptible to waste by aeolian 

 ablation. The cementing carbonate of lime though occupying 

 the spaces between the rock fragments is practically syngenetic 

 with their accumulation. 



A genetically distinct process of cementation is similar to that 

 which indurates ordinary sedimentary rocks and which is 

 apparently conditioned by the burial of the strata by later 

 deposits. In this way sands are converted into hard sandstones 

 and quartzite. Similarly the incoherent materials of an alluvial 

 fan may in the course of time be so strongly cemented that 

 when broken by a blow the fracture will traverse the constituent 

 fragments rather than pass around them. This is the case with 

 the fanglomerate of Battle Mountain. 



Geological Significance of the Battle Mountain Fanglomerate. 

 Apart from its interest as a type of sedimentary rock the fan- 

 glomerate of Battle Mountain is significant of the existence of 

 conditions in the far past similar to those which prevail in the 

 Great Basin today. Those conditions are bold relief and aridity. 



