726 



JAMES H. GARDNER 



San Juan Basin were deposited. Tiie uplift in the San Juan Moun- 

 tains of southwestern Colorado at the close of the "Laramie" folded 

 the Cretaceous sediments steeply along its flanks, but at some distance 

 from them the sedimentary rocks were only slightly disturbed and 

 possibly at no great elevation above tide. While local deposition 

 was in process at this time in certain regions near the mountains, 

 the elevated sedimentaries over other, perhaps extensive, areas were 



Fig. 8. — Shale in the Wasatch formation, six miles southwest of Gallina, New 

 Mexico, similar in appearance to the Nacimiento, but usually more highly variegated. 



being reduced to base-level. By the beginning of Puerco time an 

 extensive gently sloping plane had been produced over which broad 

 streams flowed quietly to the sea, depositing sediment in shallow 

 lakes and lagoons along their courses and at times shifting in position 

 or overflowing and commingling with each other. Such a theory 

 seems to explain the nature of the deposits as well as the conditions 

 suitable to the fauna. In order to account for the thickness of the 

 sediments deposited in this manner it seems necessary to assume 

 that a slow submergence of the land kept equal pace with deposition. 



