QUATERNARY DEPOSITS 249 



terraces composed of coarse subangular lava detritus. These appear to 

 be referable to the early Pleistocene. 



TRAVERTINE OR CALCAREOUS SPRING DEPOSITS 



There are noted on the geological map, at the south end of the Clayton 

 Valley playa and at other points, small masses of travertine, presumably 

 formed largely in recent time. Some of them are, however, so inter- 

 bedded with sandstones of the Esmeralda formation — for example, the 

 mass one mile west of Cave spring — as to suggest a contemporaneous 

 origin with the inclosing sandstone, and such masses may be of Tertiary 

 age. 



PLAYA DEPOSITS 



The playa deposits comprise two areas in Fish Lake valley, one in 

 Clayton valley, and one in Big Smoky valley, locally known as the San 

 Antonio marsh. All of the playas in Fish Lake valley within the quad- 

 rangle contain borax salts and have been worked for borax. Over many 

 square miles the Big Smoky playa shows a thin white coating which 

 consists largely of chloride of sodium. Over other portions of the valleys 

 are deposits of other salts, such as sulphate of soda, which are ordinarily 

 termed alkali. 



SAND DUNES 



At the south end of Clayton valley is a considerable group of hills 

 composed entirely of wind-blown sand. This is said to contain a small 

 amount of gold distributed through it. These dunes appear to have been 

 formed by an eddy in the air currents, which seems permanently to exist 

 at this point. They shift about from year to year to a certain extent, 

 but on the whole remain essentially at their present location. There are 

 also low hillocks of sand near the San Antonio marsh in Big Smoky 

 valley and in Fish Lake valley. 



RECENT DETRITAL FANS 



The latest of the alluvial fans, formed largely by the rearrangement 

 of the materials of older fans, undoubtedly belong to Eecent time. 



Granular igneous Eocks 



GRANITE AND SYENITE 



Under this heading are described granitic rocks which are much later 

 in age than the granites and gneisses of the pre-Cambrian complex. 



The granite and syenite series comprises granolites nearly all of which 

 are rich in alkali-feldspar. 



