SALIENT FEATURES OF THE GEOLOGY OF OREGON 109 



these seas. In California this boreal sea followed the warmer one 

 of the Middle Jurassic, in which reef-building corals abounded. 



It is not unlikely that minor diastrophic movements intervened 

 between the close of the Galice and the opening of the Dothan- 

 Franciscan time. During this succeeding epoch sediments accumu- 

 lated in a basin in part coextensive with that of the Galice. Some 

 of these were terrestrial deposits developed under arid conditions, 

 while others point to the not infrequent recurrence of marine 

 conditions. That the climate was more humid and warmer during 

 at least' a part of this epoch seems to be vouched for by the remark- 

 able flora obtained from Nichols, Douglas County, Oregon, which 

 includes cycads, ferns, ginkgoes, and conifers. This remarkable 

 flora is said to be the richest of that obtained from any Mesozoic 

 locality. 



This period of sedimentation was followed by a great mountain- 

 building epoch at or near the close of the Jurassic, resulting in the 

 uplift of the Sierra, Klamath, and Blue mountains to greater alti- 

 tudes than they had yet attained. These movements resulted in 

 folding and faulting of the strata involved, and were accompanied, 

 if not caused, by the intrusion of the Siskiyou tonolite batholith, 

 and other types of igneous rock in the southwest, giving the main 

 structural features to the Klamath Mountains as well as greatly 

 metamorphosing many of the rocks involved. 



In eastern Oregon "after the deposition of the Trias followed 

 another and more extensive uplift, probably the same which 

 affected the whole of the Pacific slope. Both the Triassic and Paleo- 

 zoic series were folded .... the Trias were violently compressed 

 in the area now occupied by the Wallowa Mountains. The uplift 

 was accompanied by very extensive intrusions of granular rocks. "^ 

 Thus the Blue Mountains in late Jurassic and Cretaceous times 

 must have been a range of imposing height having a general east- 

 ward and westward trend. 



The principal metallic deposits of southwestern and northeastern 

 Oregon are genetically related to these igneous intrusives. The 

 earlier epoch of mineralization occurring in the Paleozoic was of 



^ W. Lindgren, U. S. Geol. Surv., 22d Ann. Rept., p. 596. 



