534 



THE CRETACEOUS PERIOD 



chemical changes in sediments perhaps as the result of "decomposi- 

 tion of the organic matter contained in the foraminiferal shells. 



The subdivisions now generally recognized are the following, 

 commencing with the lowest: i. Matawan formation; 2. Monmouth 

 formation; 3. Rancocas formation; 4. Manasquan formation. These 

 formations are not all continuous throughout the coastal region, 

 and all the formations show notable variations when traced along 

 their strikes. Their aggregate thickness nowhere exceeds a few 

 hundred feet. 



Eastern Gulf border. The outcrop of the Cretaceous formations 

 of the eastern Gulf states is shown in Fig. 452. Near the Missis- 



Fig. 452. Map showing the positions of the several members of the Comanchean 

 and Cretaceous systems in Alabama and adjacent states. C, Tuscaloosa series 

 (Comanchean); Ke, Eutaw formation; Ks, Selma chalk; Kr, Ripley formation; 

 Tr, Tertiary. (After Smith.) 



sippi, the belt of outcrops extends northward to Kentucky. Meager 

 remnants (outliers) are found even north of the Ohio, in southern 

 Illinois. 



In Alabama, where the Gulf Coast part of the system is best 

 known, there are three principal divisions: the Eutaw below 



