102 



ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



sections. The Rustler limestone lies upon an eroded surface of the Delaware 

 limestone and very probably this eroded surface was at one time covered 

 by Capitan limestone. 



Fig. 3. — Map showing Beede's idea on the paleogeography of red beds in 

 the southern part of the Plains Province (after Beede). 



In his Review of the Geology of Texas, Udden^ describes the formations 

 concerned as follows: 



"Delaware Mountain Formation. 



"This formation is composed of an alternation of gray and bluish limestone 

 with white and brown sandstone. At the lower part is a blue-black thin-bedded 

 limestone, shaly in part. The base is not exposed. Toward the north of the 

 Delaware Mountains the formation becomes more sandy; toward the south the 

 limestone increases in amount. In the Apache Mountains the formations consist 

 entirely of massive whitish-gray limestone. As the base of the formation is 

 unknown, the entire thickness can not be determined, but is at least 2,200 feet. 

 The Delaware formation forms a broad zone composing the Delaware, the 



^ Udden, J. A., Bull. University of Texas No. 44, p. 54, 1916. 



