THE CRETACEOUS PERIOD. 



141 



and Mississippi to western Tennessee and Kentucky on the west and 

 north. If any of the formations once had greater extension to the 

 northward, as is probable, they have been removed by erosion. 



The system is best known in Alabama l where three principal divi- 

 sions are recognized; the Eutaw below (mainly clays and sands, some 



Fig. 389. — Map showing the positions of the several members of the Cretaceous sys- 

 tem in Alabama and adjacent states. C, Tuscaloosa series; Ke, Eutaw formation; 

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



greensand, 300 feet), the Selma Chalk (Rotten limestone, 1000 feet) 

 in the middle, and the 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. Either the area where the Cretaceous formations of the 

 Gulf region are exposed emerged from the sea before the end of the 

 period, or the youngest beds have been removed by erosion from the 

 area where the system is exposed. 



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, Geol- 

 ogy of Mississippi, 1860. 



