658 T. W. STANTON 



The colors of the shales and marls are greenish-gray, purplish, maroon 

 and red, very irregularly distributed, while the sandstones are usually 

 gray, sometimes weathering brown or with small brown spots. The 

 limestones are gray, in some cases weathering with a reddish tinge. 

 The general appearance of the formation is remarkably uniform 

 over large areas, and yet the individual elements are so variable that 

 no two detailed sections are exact duplicates of each other. The 

 total thickness is seldom more than 200 feet, though it is possibly 

 more than 400 feet at Canyon City. 



Stratigraphically the Morrison is always rather closely associated 

 with the Dakota formation. When the huge Morrison dinosaur 

 bones were first discovered it was announced that they came from 

 the Dakota, and after it was learned that they really came from a 

 lower horizon it was generally believed for many years that there 

 was no unconformity nor visible stratigraphic break between the 

 two formations. Through the work of Ward, Jenney, and Darton 

 in the area north of Colorado the Lakota and Fuson formations 

 have been recognized between the true Dakota and the Morrison 

 and referred to the Lower Cretaceous. I shall presently show that 

 in southern Colorado, New Mexico, and Oklahoma the .so-called 

 Dakota should also be divided because it includes a marine Lower 

 Cretaceous horizon. It is nevertheless true that the base of the Dakota 

 is usually not more than 100 to 200 feet above the top of the Mor- 

 rison, and it is often less than that. Darton has recognized a general 

 unconformity at the top of the Morrison in Colorado and eastern 

 Wyoming, but he believes that the interval represented by it is unim- 

 portant. The base of the restricted Dakota also rests on an uneven 

 surface wherever the actual contact has been seen. 



While the Morrison formation is thus almost invariably accom- 

 panied by the Dakota, the converse is not true; for the Dakota has 

 a much wider distribution to the east and southeast, and, in the 

 typical Dakota area extending southwesterly from the Missouri 

 River in eastern Nebraska to the Arkansas in Kansas, the Morrison 

 formation does not occur. The Dakota is fairly well recognized 

 in northern Texas near Denison, where it rests on the Comanche 

 series, here developed to a thickness of several hundred feet. This 

 area was doubtless originally continuous with the Cretaceous in 



