276 



University of California. 



[Vol. 2. 



whole country has since been deeply buried by successive overflows 

 of volcanic rock. It is only where the latter have been washed 

 away that the lake deposits can be examined. The discovery and 

 first explorations in this basin were made by Rev. Thomas Condon, 

 the present state geologist of Oregon. The typical localities of 

 this Miocene basin are along the John Day River, and this name 

 may very properly be used to designate the lake basin. The strata 

 in this basin are more or less inclined and of great thickness. One 

 section near the John Day River, examined by the writer in 187 1 

 and again in 1873, seems to indicate a thickness of not less than 

 5,000 feet. The upper beds alone of this series correspond to the 

 deposits in the White River basin. The lower portion also is clearly 

 Miocene, as shown by its vertebrate fauna, which differs in many 

 respects from that above. Beneath these strata are seen, at a few 

 localities, the Eocene beds containing fossil plants mentioned 

 above. They are more highly inclined than the Miocene beds, 

 and some of them show that they have been subjected to heat. 

 The inferior strata elsewhere are Mesozoic, and apparently Cretace- 

 ous. Above the Miocene strata Pliocene beds are seen in a few 

 places, but basalt covers nearly all." 



In this account we find the name "John Day" first used for 

 the principal fossil beds of the basin. The relation of this horizon 

 to the great lava beds is also correctly stated, though it is not 

 quite clear whether he considered the Pliocene as also covered by 

 the basalt flows. The Pliocene referred to is pretty certainly the 

 Mascall beds. It is known that Marsh camped near the typical 

 exposure of this formation and did some collecting in it. To what 

 Marsh referred in his statement concerning Eocene and Cretaceous 

 it is not certain. He has, however, correctly described the strati- 

 graphic sequence. 



In 1880 Prof. E. D. Cope* published the following statement 

 concerning the geology of the John Day country: — 



"The regions of the John Day River and Blue Mountains 

 furnish sections of the formations of central Oregon. Above the 

 Loup Fork or Upper Miocene there is a lava outflow, which has 



*Cope Proc. Am. Phil. Soc, 1S80, p. 61. 



