WHITE MOUNTAIN EEGION. ll>7 



latter rock stretching' down ou both the north and south sides of the nioiui- 

 taiu to Spring Valley. Patches of quartzite resting upon the limestone on 

 the summit give sti'atigraphieal evidence of the age of the beds. It is proba- 

 ble that the quartzite passed over the top of the limestone, east of the 

 mountain, and that the patches of the former, found near the summit, are 

 mere relics of erosion. As regards stratigraphic position of beds, we have 

 here conditions neai-ly identical to those in the Fish Creek Mountains. 

 Characteristic Pogonip fossils, sufficient to determine the position of the 

 beds, have been secured from a number of localities, proving the age of the 

 limestone, while the beds forming the summit have furnished a typical 

 fixuna of the upper portions of this horizon. About 800 feet below the tup 

 of the mountain and not far from the same distance below the quartzite 

 bodies an interesting grouping of fossils occurs, and immediately beneath 

 the quartzite on the summit the Receptaculites beds are well shown. The 

 student of structural geology in this region owes much to the genus Recep- 

 tacuUtes, which is very abundant within a restricted vertical range. A list 

 of the principal groupings of fossils collected on White i\Iountain will be 

 found on page 52. 



South of White Mountain, and separated from it by a belt of Eureka 

 quartzite not over 1,000 feet in width, an irregular shaped body of lime- 

 stone is exposed from beneath the quartzite. If any evidence of its age is 

 needed beyond its stratigraphical position, it will be found in the typical 

 Pogonip fossils which occur scattered throughout the beds which, like the 

 con-esponding beds on the east slope of White Mountain, possess a south- 

 east dip and a northeast and southwest strike. This limestone, like the 

 main body, is nearly everywhere encircled by the quartzite, the only ex- 

 ception being on the south side, where it abuts against the Nevada lime- 

 stone, which forms a part of the east ridge of Atrypa Peak. I'he two 

 limestone bodies are unconformable, of different lithological character, and 

 dip in opposite direction. 



North of White Mountain the Eureka quartzite terminates abruptly 

 against the Prospect Peak fault, the Cambrian and Silurian quartzites 

 being placed in juxtaposition. These quartzites resemble each other 

 closely in their upper strata, being simply indm'ated sandstones, and it is 



