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 

 b}/ 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 sandj'; 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. 



