THE CRETACEOUS PERIOD. 161 



Chi co is wanting where the Lower Cretaceous is present. 1 In British 

 Columbia, the Shastan period seems to have been inaugurated by 

 subsidence, but as the period progressed the area of land increased 

 till the sea failed to cover the Cordilleran belt. 2 Formations younger 

 than the Dakota are not known in British Columbia between the Coast 

 range and the Selkirks, 3 but along the coast there are formations cor- 

 related with the Colorado and Montana. Upper Cretaceous formations 

 are also known in western Alaska. 4 In Vancouver Island, the Chico 

 is reported to be coal-bearing. 



The relations between the Chico beds and the Cretaceous formations 

 of the interior have not been determined but the remaining portions 



Fig. 402. — Section showing the position of the Cretaceous beds in western Oregon. 

 Mg, meta-gabbro of unknown age; sp, serpentine; as, amphibolite schist; Jr, 

 Jurassic (?); Km (Myrtle formation), Cretaceous, and Kmw, lentils of limestone 

 in the Myrtle formation; Eu (Umpqua formation), Eocene; Ed, Eocene diabase. 

 (Diller, Roseburg, Ore., folio, U. S. Geol. Surv.) 



of the former do not appear to represent the latest part of the system. 

 The region may have emerged before the closing stages of the period, 

 or the beds then deposited may have been removed by erosion. 



Climate. — The climate of North America during the Cretaceous 

 period seems to have been uniform and warm throughout a great range 

 of latitude. In Greenland, Alaska, and Spitzbergen, the climatic 

 conditions seem to have been similar to those in Virginia. Toward 

 the close of the period, however, the climate seems to have been cooler, 

 for the Laramie flora is a temperate, rather than a tropical one. 



Close of the Period. 



The Cretaceous period is commonly said to have been brought to 

 a close by a series of disturbances on a scale which had not been equaled 

 since the close of the Paleozoic era, and perhaps not since the close 

 of the Algonkian. These changes furnish the basis for the classifi- 

 cation which makes the close of the Cretaceous not the close of a 



1 Roseburg, Ore., folio, U. S. Geol. Surv. 



2 Dawson, loe. cit. 



3 Dawson, BuU. Geol. Soc. Am., Vol. XII, p. 77. 

 4 Schrader, Bull. Geol. Soc. of Am., Vol. XIII, p. 247. 



