THE CRETACEOUS PERIOD 



745 



seaward at a low angle. Near the Mississippi, the belt of their 

 exposure extends northward to Kentucky. If any of the forma- 

 tions once had greater extensions to the northward, as is probable, 

 they have been worn away except for possible meager remnants, 

 not certainly identified. 



Fig. 505. Map showing the positions of the several members of the Co- 

 manchean and Cretaceous systems in Alabama and adjacent states. 

 C, Tusealoosa series (Comanchean) ; Ke, Eutaw formation; Ks, Selma 

 chalk; Kr, Ripley formation; Tr, Tertiary. (After Smith.) 



In Alabama/ where the system is best known, there are three 

 mncipal divisions : the Eutaw below (mainly clays and sands, some 

 greensand, 300 feet), the Selma Chalk (Rotten limestone, 1,000 feet) 

 in the middle, and Ripley (mainly sand, 200-500 feet) above. The 

 Eutaw is believed to be the equivalent of the Matawan formation 

 of the Atlantic coast, and the Ripley is thought to be older than 

 the Rancocas. 



1 For an account of the Cretaceous of Alabama, see Smith, Report of the 

 Alabama Survey for 1894. See also Safford, Geology of Tennessee, 1869, 

 and Hilgard, Geology of Mississippi, 1860. 



