io8 WARREN DUPRE SMITH AND EARL L. PACKARD 



conditions in Oregon, yet judging from other evidences these seas 

 elsewhere teemed with corals, indicating tropical conditions. By 

 Carboniferous time this, or a later sea in which crinoids lived, also 

 covered a portion of the Blue Mountains of northeastern Oregon, 

 which approximately marks the easternmost extension of that arm 

 of the sea. The presence of tuffs and vesicular lava in the south- 

 west gives a glimpse of volcanic activity upon the adjacent land 

 mass. 



Continental movements culminating in the Appalachian revolu- 

 tion caused a general retreat of the oceans to the outer edges of the 

 continental shelf. In Oregon the Paleozoic sediments of both the 

 southwest and northeast were uplifted, folded, and somewhat meta- 

 morphosed, though the principal orogenic movements of the 

 Klamath region may have occurred later. 



A long erosion interval followed, longer perhaps in the southwest 

 than in the Wallowa Mountain region, for there the record of a 

 shallow, oscillating sea, with a shore line not far to the southeast, 

 is found in the Eagle Creek series of Triassic age. The meager 

 fauna suggests little of the probable mild climate that prevailed. 



During the Triassic and the earlier Jurassic the Klamath region 

 of California and Oregon was probably land, and is thought by 

 Diller to have been the scene of vigorous volcanic activity, the 

 record of which is still seen in California along the southern margin 

 of that land mass. If an early Mesozoic sea ever covered that 

 region its record is yet to be discovered. 



A few lower marine Jurassic fossils from the southwestern 

 flank of the Blue Mountains is the only record of the Jurassic of 

 eastern Oregon. This sea, skirting the slowly rising Blue Moun- 

 tains probably did not extend far into Idaho, and it may have 

 received the sediments from a great westward-flowing stream occu- 

 pying the Snake River valley of Idaho. 



Late in the Jurassic an epoch of sedimentation, known as the 

 Galice, was again initiated in southwestern Oregon by the develop 

 ment of a basin in which diverse marine and possibly terrestrial 

 beds accumulated. The meager fauna from these or even later 

 Jurassic beds in Oregon tells little of the probable boreal aspect of 



