56 GEOLOGY OF THE DENVEE BASEST. 



features are especially well seen along Beai' Creek. A heavy-bedded, 

 fine-grained sandstone occasionally appears in this series, notably in the 

 vicinity of Turkey ( 'reek. 



At 150 or 200 feet below the top of the Trias the strata become more 

 clayey and take on a variety of irregularly distributed bright colors — gray, 

 yellow, green, pink, and lilac. In tins /.one gypsum and brown earthy 

 limestones are common. The gypsum occurs either in small local bodies 

 of lenticular shape or in crystals uniformly disseminated through the claw 

 The limestones are also lenticular, but in bodies greatly attenuated and 

 rarely over 6 feet thick; they are especially developed about 4<> feel below 

 the capping sandstone of the formation. The larger bodies of gypsum 

 occur in connection with the limestone. About this horizon is also found 

 at .Morrison and at Deer Creek, though not observed elsewhere, a thin band 

 of sandstone carrying liner or coarser particles of a white and red jasper- 

 like material. 



The Trias closes with a sandstone from 15 to 25 feet thick, usually 

 fine-grained, and composed of quartz, with a small quantity of mica and 

 feldspar, the lower portion slightly calcareous. The sandstone is either 

 compact and massive, when it is adapted for building purposes, or thin- 

 bedded and friable, with a tendency to become shaly. The lower 8 feet is 

 usually brown; the middle 1<> or 15 feet, pink: the tipper 4 feet, brown. 

 The entire bed is often delicately cross-bedded and ripple-marked. Rolled 

 particles of clay are occasionally present, which, by weathering out, leave 

 a pitted surface. both the under and upper surfaces of the bed are sharply 

 divided from the shalv strata adjoining, hut the upper surface is especially 

 Well defined, and at Morrison is somewhat undulating — apparently the line 

 of an unconformity, or at least of interrupted deposition. 



CORRELATION. 



The Weil beds, wherever present in the West, constitute a prominent 

 feature in the scenery, on account of their color and persistent lithological 

 characteristics. They were regarded as Triassic by the earliest geological 

 explorers, because they were locally found between horizons characterized 

 b\ well-defined Jurassic fauna above and an Upper Carboniferous fauna 

 below. As exploration extended, it was found that on the western flanks 



