During the Cretaceous Period 209 



terrestrial, and the fossils have correspondingly been em- 

 phasized. Broadly speaking the lowest or Wealden and 

 the Neocomian beds of Central Europe, that seem exactly 

 to correspond with the Comanchean and Dakota beds of 

 North America, are largely freshwater, and often show 

 direct continuity with the Purbeck or Upper Jurassic below. 

 The Greensand-Gaults of England, the Aptian-Cenomanian 

 of France, the Flammenmergel and Lower Planer of 

 Germany, and the Benton-Niobrara-Pierre-Foxhill groups 

 of North America are wholly or largely marine. The Chalk 

 strata of England, the Turonian-Senonian of France, and 

 the Middle-Upper Planer of Germany are probably inferior 

 in position to the Laramie of North America, though in 

 saying this the writer does not forget the controversies over 

 the age of the last. These strata are either balanced be- 

 tween freshwater and marine beds, or somewhat preponde- 

 rate toward the latter. The chart on p. 211 sets forth the 

 supposed correlation relation. 



Two important and fundamental changes were largely 

 consummated during this period, and undoubtedly affected 

 organisms powerfully. First: during the Lower Cretace- 

 ous period in South Africa and in western America great 

 volcanic activity proceeded, but this was, so to speak, the 

 prelude to greatly more catastrophic action during the Later 

 Cretaceous in India, in South Africa, and in Western 

 America. Thus the enormous deposits of volcanic rock in 

 the Deccan, that are 4,000 feet to 6,000 feet thick, cover 

 an area of at least 200,000 square miles. The "Laramide" 

 rocks of Dana cover a large part of Western America and 

 indicate tremendous volcanic action. 



Regarding this entire area Geikie (/ill: 1374) says: 

 "At the close of the Jurassic period, the first great up- 

 heavals took place. Two lofty ranges of mountains — the 

 Sierra Nevada (now with summits more than 14,000 feet 

 high) and the Wasatch — 400 miles apart, were pushed up 

 from the great subsiding area. These movements were 

 followed by a prolonged subsidence, during which Cretace- 

 ous sediments accumulated over the Rocky Mountain region 

 to a depth of 9000 feet or more. Then came another vast 

 uplift, whereby the Cretaceous sediments were elevated 



