384 University of California Publications in Geology [Vol. 13 



extruded anterior to the uplift of the present mountain range with 

 the attendant deposition of fanglomerates along its flanks. On the 

 other hand, it is younger than the Hathaway formation, which is late 

 Pliocene or early Quaternary. Therefore it is probable that the basalt 

 is of early Quaternary age. 



Quaternary Fanglomerates 



The basalts are the youngest rocks of general distribution in the 

 region. Some time after their extrusion the present mountains began 

 to rise between faults along the north and south sides, and with this 

 uplift streams began to rapidly dissect the mass and bring down great 

 quantities of debris. In discussing the physiography we have seen 

 that in an arid climate this material is characteristic, the bulk of it 

 being coarse and angular. In some cases, however, small perennial 

 streams contribute to them and beds of pebbles, so rounded as to be 

 termed "stream conglomerates," are often present. 



Alluvial fans are still being deposited along both the north and 

 south sides of the range, but quite distinct from these are older 

 deposits of similar nature. Since these were deposited during an 

 uplift of the region and were themselves subject to movement, they 

 contain unconformities. During the uplift there were definite halting 

 periods and probably also changes in the humidity of the region. 

 These periods and changes are evidenced partly in the physiography 

 and partly in the deposits of fanglomerate. 



It is impossible to correlate all the different fanglomerates at any 

 one place with those of another, but in some cases there is strongly 

 suggestive evidence of identity or equivalence. They are considered 

 Quaternary in age, for the general conditons under which they were 

 deposited still exist. Present information justifies a partial classifi- 

 cation and naming of these formations, as appears in the following 

 descriptions. 



Deep Canon fanglomerate. — On both sides of Deep Canon the 

 basalt is overlain by fanglomerate and both have been warped and 

 faulted together. Across their upturned and eroded edges later fan- 

 glomerate has been deposited. The older detritus greatly resembles 

 the Hathaway formation which underlies the basalt. While the bulk 

 of the Hathaway is rather fine for fanglomerate, in this vicinity the 

 upper portion, that immediately below the basalt, is rather coarse. 



The detrital rocks above and below the basalt are similar in that 

 they consist largely of angixlar and subangular boulders derived from 



