NITRATE PEOSPECTS IN THE AMAEGOSA VALLEY. 



GEOLOGY. 



The exposed rocks of the region seem to belong to two series only. 

 Below is a series of limestones, schists, and quartzites, probably of 

 Cambrian age, and much folded and faulted. 



Lying unconformably on these are gravels, sands, and clays of very 

 variable character and usually only slightly indurated. (See fig. 1.) 

 Some of the gravels are cemented by calcium carbonate into a sort of 

 conglomerate resembling some of the " caliches " of Arizona and 

 Texas. Not infrequently the clays are slightly saline, and thin inter- 

 calated layers of gypsum are frequent. Near Morrison's ranch 

 gypsum layers up to 18 inches in thickness are intercalated with the 

 clays, and are mined for plaster. The gravel-sand-clay series is be- 

 lieved to be of Tertiary age, though its exact correlation remains 

 uncertain. No fossils were found. 



FIG. 1. Tertiary ( ?) gravels resting on Cambrian ( ?) basement, near Morrisons Siding. 



This Tertiary (?) series has also suffered a great deal of movement 

 and is now found dipping variously and with a very complex struc- 

 ture, still almost entirely unknown. Since (or during) its disturb- 

 ance it has been much eroded by the Amargosa and its tributaries, 

 very largely obscuring its original distribution and its relations with 

 the Cambrian (?) basement. (See fig. 2.) 



Gravels and sands of present or very recent age occasionally overlie 

 it, with an erosional unconformity between. 



GEOLOGICAL, HISTORY. 



As the writer interprets the history in the light of the meager 

 data now available, it indicates an original uplift which can not 

 be exactly dated, but was certainly Post-Cambrian, followed by a 



