WYOMING FORMATION. 53 



The lower division. AltllOUgh tile contact lletWeell llle A l'( '] II '.'1 1 1 and the 



Trias occurs al a constantly varying horizon in both formations, the 

 lower 5 to 20 feel of the Red Beds is nearly everywhere composed of 

 coarse, sufeangular fragments of the adjacent granite, gneiss, or schists, 

 with a small admixture of their derived sand, which shades in places to a 

 red arenaceous mud. The materials are usually hut loosely agglomerated, 

 yel instances arc frequent where the liner and less-worn ddbris is com- 

 pacted to a ruck so hard that, with the same mineralogical constitution, it 

 closely resembles the underlying granite, their dividing line being very 

 difficult to determine. Cross-bedding is developed at the base of this 

 layer, while in its upper portion evidences of eddying shore currents exist 

 in heavy deposits of pebbles in deep-wom depressions in the beds fix-si 

 laid down. 



Succeeding this layer is a series of heavily bedded sandstones and 

 grits, with small local bodies of arenaceous shale. The normal thickness 



of this series is aboul L,200 feet. The color varies from prevailing red to 

 gray, according as the chief constituent of the rock is red feldspar or 

 quartz. A very fine-grained, deep-red, shaly sediment, approaching mud 

 in consistency, contains also a considerable per cent of black and white 

 mica. Iron oxide is generally present and assists in the coloring, particu- 

 larly in the more shah" varieties. 



The lower 200 feet of sediments are generally coarser and less compact 

 than those overlying. Cross-bedding is a marked feature from base to 

 summit. 



The foregoing \«-<\> pass liv a broad transitional zone of lighter-red 

 and more quartzose sandstones to the upper member of the division, a 

 heavy bed of cream-white sandstones from 200 to 400 feet thick. From 

 its color thi> sandstone has become known as the "Creamy sandstone." It 

 usually forms a well-marked ridge from 50 to 100 feel high along the 



middle of the valley of Triassic rocks. In the lower half it is somewhat 



more friable, and consequently more frequently eroded, than in the upper. 

 It is also occasionally tinged a faint red, in irregular patches. Two -mail 

 bands of dark-brown, quartzose limestone, from 2 to 8 feet thick, are 

 usually present — one near the base, the other 40 feet up. The intervening 



