THE MORRISON FORMATION OF COLORADO 35 I 



case in the typical Red Beds along the mountains. The strati- 

 graphic position of the shale formation is between the Dakota 

 and the Red Beds. In this respect its position is identical with 

 that of the Morrison. 



b. In lithological character, the shale closely resembles the 

 Morrison, which, in its typical areas 1 , is composed of soft, varie- 

 gated clay, containing more or less sandstone and limestone. A 

 comparison of the shale formation with the typical Morrison of 

 Colorado shows a striking resemblance. There is a somewhat 

 greater proportion of clay than in the Morrison, as would natu- 

 rally be expected so far from the mountain area, which was 

 probably a part of the feeding ground at that time. A com- 

 parison of the Morrison (Como) of Wyoming reveals a still 

 closer resemblance, if, indeed, it cannot be called identity. One 

 who is familiar with the Morrison and has studied the shales of 

 southeastern Colorado finds a striking likeness between the two 

 in material structure and general aspect. 



c. The Morrison is notable chiefly for the great Dinosaurs 

 found in its beds, and they are not found in the Dakota above 

 nor in the Red Beds beneath. The bones found in the shales 

 near Plum Canyon are similar in size, texture, and general aspect 

 to the characteristic Dinosaurs of the Morrison formation. 

 Although none of these bones have yet been studied by a pale- 

 ontologist, there is little doubt that they are Dinosaur bones, 

 and if Dinosaurs occur between the Dakota and the Red Beds, 

 the presumption is that the formation containing them is an 

 equivalent of the Morrison. 



The shales found in the Canyon of the Cimarron perhaps 

 deserve separate discussion. Near the southern boundary of 

 Colorado is the divide between the Cimarron and Purgatory 

 rivers. On this divide, a distance of nearly thirty miles, no 

 stream, so far as observed, cuts through the Dakota. At the top 

 of this divide is an extensive mesa capped by flows of basalt and 



J See U. S. Geol. Surv., Monograph XXVII, Geology of the Denver Basin, p. 52; 

 also W. N. L03AN, Kas. Univ. Quarterly, 1900 — "The Stratigraphy and Invertebrate 

 Kaunas of the JurassL Formation in the Freeze-Out Hills of Wyoming," pp. 113- 11 5. 



