1875.] ^^ * [Stevenson. 



Colorado Springs, they form a perfect and imperceptible transition from 

 the Sandstone No. 3, downward to undisputed Cretaceous. With possi- 

 bly one exception, the Lignitic and Cretaceous series are everywhere per- 

 fectly conformable. Mr. Marvine found distinct unconformability between 

 them in Middle Park near Mt. Bross ; but this must be quite local, for 

 Dr. Hayden states respecting Middle Park, in the same vicinity , that the 

 Tertiary rocks are found in great thickness and perfectly conformable to 

 the underlying Cretaceous. At many localities east from the mountains 

 a conglomerate occurs resting unconformably upon the lignitic rocks. 



About twenty miles south from Cheyenne, this group is exposed. The 

 Cretaceous passes up imperceptibly into the fucoidal sandstone, which is 

 ninety-five feet thick. At a few feet above the sandstone is a coal-bed, 

 four to six feet thick, roofed by clay, containing an oyster like 0. subtri- 

 gonalis. On Boulder Creek, the same Ostrea is found above the coal. 

 Near Golden, the sandstone is separated from the Cretaceous beds by 

 only a few inches of clay, and contains dicotyledonous leaves along 

 with Halymenites major. Near Colorado Springs this rock contains a 

 a variable seam of coal, and affords the fucoid and dicotyledonous leaves. 

 Below it are layers of clay and shale, yielding Baculites with other Cre- 

 taceous forms, and passing downward into Cretaceous dark shales. 



In the vicinity of Canon City, on the Arkansas, the succession is clearly 

 shown. The dark Cretaceous shales gradually merge into a mass of 

 clay and argillaceous sandstones which passes upward imperceptibly into 

 the fucoidal sandstone. In the upper portion of this loose-grained rock 

 there are many impressions of fucoids and, in some of the more compact 

 layers, indefinite impressions of mollusca. In the upper portion of the 

 clay-beds Dr. Hayden found an imperfect Inoceramus. From this locality 

 southward, the sandstone is easily followed, standing out like a wall for 

 long distances. Near Trinidad, on the Purgatory River, Mr. Lesquereux 

 found it 200 feet thick, resting on the dark shales of the Middle Creta- 

 ceous. On Raton Creek it is 178 feet, resting on the Cretaceous shales, 

 and overlaid by 300 feet of coal-bearing rocks. On Yermejo Creek, the 

 sandstone contains three thin seams of coal. At Caiion City it contains 

 certainly two. 



Respecting the relations of the Cretaceous and the Lignitic Group, east 

 from the mountains. Dr. Hayden says, "These black shales pass gradu- 

 ally up into rusty arenaceous clays, which characterize No. 5 ; and No. 5 

 passes up into the Lignite Tertiary beds, where they can be seen in con- 

 tact, without any well-defined line of separation that I could ever dis- 

 cover."* 



In its southern extension and near the mountains the fucoidal sand- 

 stone is for the most part of a texture unfavorable to the preservation of 

 organic remains and seldom contains any other than very rude specimens 

 of fucoids. Dr. Hayden states, that he has searched it over an area of 

 many miles, but has succeeded in finding no fossils excepting "one 



* Reprint of Reports, p. 121. 



