112 WARREN DUPRE SMITH AND EARL L. PACKARD 



California, yet apparently deficient in diatamaceous and radiolarian 

 remains which are associated with the petroliferous deposits of that 

 state. Volcanic activity then became the dominant feature of the 

 period. Olivine basalts, issuing from fissures and vents along the 

 axis of the present Cascades and throughout eastern Oregon, 

 formed vast floods of lava, which rose high upon the flanks of the 

 Blue Mountains. These flows were intermittent, as is attested 

 by interbedded lateritic deposits, frequently containing petrified 

 wood. This epoch of volcanic activity came to a close in middle 

 Miocene time. In the John Day region these lavas were flexed, 

 faulted, and partially eroded before the deposition of the middle 

 Miocene Mascall in structural or erosional basins. Along the axis 

 of the present Cascades these flows were thrown into an ante- 

 chnorum now exposed within the gorge of the Columbia. This 

 epoch of deformation was of more than state-wide significance, 

 being recognized in Washington and California. 



The upper Miocene record of Oregon west of the Cascades is 

 read mainly in the details of the later history of the then pene- 

 plained Klamath region. The marine epoch of Empire time is now 

 thought to be early Pliocene. The upper Miocene floras of adjoin- 

 ing states and that of the eastern Oregon Mascall indicate a moist, 

 warm, temperate climate, in which the camel, the horse, the an- 

 cient bear, and the proboscidians thrived. By the close of the 

 Miocene, movements again interrupted the sedimentation in the 

 John Day region, which deformed the Mascall beds. Upon their 

 eroded edges were deposited gravels, tuffs, and flows of the early 

 Pliocene. 



Other local lake and flood plain deposits of later Phocene age 

 occur nearer the Idaho line, giving evidence of the formation of 

 structural basins or changes in drainage as yet but imperfectly 

 deciphered. A depression of a narrow strip paralleling the present 

 shore fine developed along the coast in early Pliocene and received 

 the marine sediments of the Empire. The fauna of this sea indi- 

 cates a cooler climate. This marine epoch was brought to a close 

 by the epeirogenic movements which elevated the entire coast, 

 producing the gentle folds now found in the Empire, probably the 

 faulting and warping of the Klamath peneplain, and perhaps the 



