248 HISTORICAL GEOLOGY 



accumulation of materials in the marine waters which then occu- 

 pied the sites of the present Great Valley and Coast Range of 

 California. According to Bailey Willis, "a bold peninsula devel- 

 oped from Oregon south to Santa Barbara (California) " during 

 Lower Cretaceous time, as shown on the map Fig. 150, but accord- 

 ing to certain others marine waters spread over most of the Coast 

 Range district during both Lower and Upper Cretaceous times. 



Fig. 152 



Typical exposure of Upper Cretaceous (Selma) chalk in Alabama. (After 



L. W. Stephenson, U. S. Geological Survey, Prof. Paper 81.) 



In British Columbia and Alaska the presence of marine strata 

 proves the existence of sea water over the areas indicated on the 

 accompanying maps, though the coal beds show that great swamps 

 or lagoons must have existed locally. 



Close of the Period in the West (Rocky Mountain Revolu- 

 tion). — The close of the Cretaceous period, or, what is the same 

 thing, the close of the Mesozoic era, was marked by one of the most 

 profound and widespread physical disturbances in the history of 



