184 CAKHONIKKKOUS KOKMATIONS AND FAUNAS OF COLORADO. 



ill till' upper part. Tlir Ihickiicss varies from 500 to ;-),000 i'eot, but is j^-cncniliy 

 .soiiu'what under 1,500 IVet. The forinatioii is separable about midway into a lower 

 di\isioii of soft, frial)le eonglomeratcs and coarse sandstones, with few shales, and 

 an upper one of shales, with some prominent sandstone bands, narrow beds of 

 limestone, and small local deposits of gypsum. The lower 5 to 20 feet of the lied 

 Reds is nearly everywhere composed of coarse, suViangular fragments of the adjacent 

 g-ranites, gneisses, and schists, with a small admi.xture of their derived sand, which 

 shades in places to a red, arenaceous mud. Succeeding this formation is a series of 

 heavily bedded sandstones and grits, with small local beds of arenaceous shale. The 

 normal thickness is about 1,200 feet. The color varies from prevailing red to gra}', 

 according as the chief constituent of the rock is red feldspar or quartz. The lower 

 200 feet of sediments are generally coarser and less compact than those overl^'ing. 

 These pass, by a liroad transitional zone of lighter red sandstones, to the upper mem- 

 ber of the lower division, a bed of creamy white sandstone from 200 to -±00 feet 

 thick. It contains impure limestones and some conglomeratic la3'ers. The lower 

 half of the upper division consists of bright brick-red arenaceous shales and sand- 

 stones, with important intercalations of limestone. The strata above the limestone 

 series become more and more arenaceous, though still retaining in large degree 

 their shaly nature. At 150 or 200 feet below the top of the Trias the strata become 

 more claye}^ and take on a variety of irregularl};- distributed bright colors — graj', 

 j-ellow, red, green, pink, and lilac. In this zone gypsum and brown earthy lime- 

 stones are common. The Trias usually closes with a sandstone from 15 to 25 feet 

 thick. The Wyoming formation is overlaid by the Morrison formation, the former 

 being assigned to the Triassic and the latter to the Jurassic period. The Wyoming- 

 is supposed to overlie the Fountain formation, by which name Cross designates the 

 lower portion of the Red Beds in the Pikes Peak quadrangle, but it has suggested 

 itself to me that probablj' a part of the Wyoming formation may locally be equiva- 

 lent to the Maroon. The great variability of the lower member, the lower half of 

 which i-anges from 270 feet to 2,000 feet, might be taken as evidence that at the 

 points of greatest thickness the lowest beds belong to a different and older formation. 

 The lithology of the lower division is not unlike that of the Maroon, while it is only 

 the upper division which is described as being brick red. Emmons offers a similar 

 suggestion on page 19 of the monograph. No fossils were found in the Wyoming 

 formation and the evidence for assigning it to the Trias is more or less unsatisfac- 

 tory. In the Morrison, however, remains of Jurassic dinosaurs occur. 



In a paper read before the Geological Society of America, but never published, 

 save by abstract, N. H. Darton recognizes in the fine section at Morrison a limestone 

 which he identifies with the Minnekahta limestone of the Black Hills, "having," he 

 says, '"precisely similar stratigraphic relations in the Eed Beds and containing some 



