The Shinumo Area. 505 



fragments of chert of the same character as that contained in 

 the overlying limestones. The whole is cemented with the red 

 mud. The conglomerate is very little indurated in this local- 

 ity. Although the contact of the diorite with the mica-schists 

 in the underlying Vishnu is not two hundred yards distant, 

 there is not a fragment of the mica-schist to be observed in the 

 conglomerate. 



In the Asbestos Canyon, four miles to the west of the East 

 Wash, the underlying rocks are mica schists and veins of 

 quartz and pegmatite. Here the Vishnu schist is scarcely 

 weathered at all below the unconformity. The overlying 

 conglomerate is 6 feet thick and consists of angular fragments 

 of the underlying mica-schists, fragments of pegmatitic feldspar 

 and vein quartz, and the arkose cement described above. The 

 degree of induration is here very great, and the rock fractures 

 across the grains like a hard, dense quartzite. This is due to 

 the fact that the lower contact of the diabase sill lies only 150 

 feet above this basal conglomerate in the Asbestos Canyon, 

 while in the locality in the East Wash it lies 550 feet above. 



Two important features characterize the basal conglomerate 

 of the Unkar in the Shinumo area ; the arkose nature, and the 

 lack of sorting and transportation of the component frag- 

 ments. 



Second Memher. — Calcareous Shales and Limestone. The 

 section was measured on the west side of the canyon of 

 the East Wash. This and all the following sections read from 

 the base upward, a. 1 being the bottom bed, overlain by a. 2, 

 etc. 



Character Thickness 



a. Basal white limestone. 



1. White, nodular, cherty limestone. The chert 

 occurs in nodules with a roughly concentric 

 structure somewhat suggestive of the structure 



of Cryptozoon 1' 6" 



2. White, cherty limestone carrying the chert in 

 thin parallel bands which are etched out by the 

 weather on the cross sections. The surface of 

 each chert layer shows polygonal cracks sugges- 

 tive of sun-cracks in shale. This structure 

 belongs to each separate chert layer and is not 

 a columnar structure. The weathered surfaces 

 of these chert layers are dotted with small cubic 

 depressions which were apparently formed by 

 the leaching out of some mineral of a cubic 



habit . 4' 6" 



Total 6' 



