434 New York State Museum 



place in narrow strips along the present California coast 

 area and along the present coast from British Columbia 

 northwards into Alaska. The Upper Cretaceous was a 

 time of great subsidence. The sea spread over the coas- 

 tal plains of the Atlantic and Gulf states and portions of 

 the Pacific coast were submerged. An inland sea of great 

 size covered the central part of North America for some 

 time and extended from the Gulf of Mexico to the Arc- 

 tic. During the Mesozoic era most of the eastern part 

 of the United States was undergoing erosion which re- 

 sulted in the reduction of the country to a more or less 

 perfect peneplane, known as the Cretaceous peneplane 

 because it was best developed in that period. 



Cretaceous deposits in New York State occur on Long 

 Island and Staten Island. The nonmarine Lower Cre- 

 taceous beds (Potomac) are found only along the north- 

 western border of Long Island and were deposited when 

 slight subsidence produced low-lying flats. Reelevation 

 and erosion were followed by the Upper Cretaceous sub- 

 sidence of the coastal plain area, permitting marine de- 

 position in a shallow sea. This subsidence included most 

 of Long and Staten Islands. These Cretaceous deposits 

 (Raritan formation of New Jersey etc.) are largely char- 

 acterized by plant remains, some of which are illustrated 

 in figure 62. 



The closing stages of the Upper Cretaceous are marked 

 by great crustal disturbances which resulted in great 

 mountain building from Alaska to the southern end of 

 South America. The Rocky mountains were formed, 

 also the Wasatch and Uinta mountains. North America 

 became practically dry land and the Atlantic and Pacific 

 coasts extended farther out than in Tertiary time fol- 

 lowing. 



