THE CRETACEOUS PERIOD 



237 



European 



Danian. 

 Senonian. 



Turonian. 

 Oenomanian. 



{ Albian. 



Aptian. 

 Barremian. 



Neocomian. 



North Atlantic 

 Coastal Plain 



Manasquan. 

 Rancocas. 

 Monmouth. 

 Matawan. 



Magothy. 



Raritan. 



{unconformity) 

 Patapsco. 



Arundel. 



Patuxent. 



Alabama 



(Absent) . 



Selma-Ripley. 



Eutaw. 

 Tuscaloosa. 



{unconformity) 

 (Absent). 



Lower 

 Cretaceous. 



Texas 



Navarro. 



Taylor. 



Austin. 

 Eagle Ford. 

 Woodbine. 



Washita. 

 Fredericks- 

 burg. 



Trinity. 



Western 

 Interior 



Laramie. 

 Montana. 



Colorado. 

 Dakota. 



Kootenai. 

 Morrison. 



California 



Chico. 



{unconformity) 

 Horsetown. 



Knoxville 

 (Probably) 

 partly Ju- 

 rassic) . 



Virginia, 1 these rocks are seen to form a narrow outcropping belt 

 at the western margin of the Atlantic Coastal Plain from New 

 Jersey to Alabama. Passing eastward from the exposed belt, well 

 borings show that much at least of the whole Coastal Plain is under- 

 lain with Lower Cretaceous rocks. " The sediments (of the Coastal 

 Plain) in general form a series of thin sheets which are inclined 

 seaward (Fig. 155), so that successively later formations are en- 

 countered in a journey from the inland border of the region 

 toward the Coast" (W. B. Clark). 



As the map shows, the most extensive surface distribution of 

 Lower Cretaceous rocks is in Mexico and Texas. Here, too, in 

 passing toward the (Gulf) Coast these strata are known to be 

 extensively developed under cover of later formations. In general, 

 therefore, the actual extent of Lower Cretaceous strata in the 

 Atlantic and Gulf Coastal Plain is much greater than the surface 

 exposures. 



Several small areas are known in the western United States in 

 the Rocky Mountains and in the Coast Range of northern Cali- 

 fornia. Large surface areas occur in British Columbia and Alaska. 

 In most of these western regions the Lower Cretaceous strata are 

 notably folded or tilted, so that their full extent is not shown by 

 the outcrops. 



1 In this part of Virginia the Lower Cretaceous strata are completely con- 

 cealed under Tertiary strata. 



