MOOK, STUDY OF THE MORRISON FORMATION 57 



vary much in their occurrence. They are usually more or less argil- 

 laceous. "The relative amount and position of sandstones, shale and 

 limestones at any one point is no indication that a similar relation will 

 be found at any other point. There is no abrupt lateral change, but the 

 various beds blend into each other or pinch out laterally in a gradual 

 though somewhat rapid manner, so that, while no sudden change is seen, 

 a comparison of sections a few miles apart may show a total change in 

 kind and relation of materials" (Lee, 1901. 7 ; 1902, 5). Dinosaur bones 



Fig. 16. — The "Nipple," looking went from Garden Park, Colorado. 



This view is in the opposite direction from that in flg. 12. The section shown in flg. 13 



was taken in this cliff. 



were found at many horizons. Some of these have been identified by 

 Barnum Brown as Morosaurus and Diplodocus. 



The Bed Beds, Morrison and "Dakota" all have the appearance of being 

 conformable, though critical examination has shown that there is evidence 

 in favor of concluding that there is a stratigraphical break both above 

 and below the formation. There is distinct evidence of erosion at the 

 surface of the Morrison, below the "Dakota (Purgatoire), in the presence 

 of undulations in the line of contact with the "Dakota" (Purgatoire). 



The Morrison lies on beds of gypsiun in these localities. This gypsum 



