\Tkrriam.] 



John Day Basin. 



299 



the highest beds of the series. At another locality, some miles 

 east of this point, numerous thrusts are beautifully shown in cliff 

 sections. Along the North Fork two systems of fractures were 

 noticed. One trends north and south and the other appears to 

 cross it at nearly a right angle. 



As has already been indicated, the series is evidently uncon- 

 formable upon the Clarno. 



In the whole of the region occupied by John Day north of the 

 southern range of the Blue Mountains, it is covered by the Colum- 

 bian lavas, being accessible only in the deep canons, where it lias 

 been exposed by extensive stream corrasion. At every locality in 

 the basin where the series can be seen, its relations to the overlying 

 formations are beautifully shown. In several places, notably at 

 Sheep Rock in the upper end of Turtle Cove, and on the main river 

 below Spray, residual hills in the middle of the valley are capped 

 by portions of the lower flows, which have served to protect the 

 softer beds beneath. 



The Columbia lavas are in some places seen to be decidedly 

 non-conformable to the John Day. Near Haystack the fossil beds 

 form a fairly sharp anticline below lavas which are almost horizon- 

 tal. At Clarno's Ferry lava flows are seen at one locality to rest 

 upon the middle beds, the typical upper division being absent. 



At many points where the contacts of Columbia lava and John 

 Day were examined, fossil wood was found to be abundant. In 

 one place at the lower end of Turtle Cove, where there was much 

 petrified wood at the contact, branches of trees were found pushed 

 up into the lava beds. Some of these stems showed an interesting 

 mode of preservation, being unaltered charcoal on the outside, 

 while the interior was petrified. 



Evidently the John Day had been slightly crumpled, had suf- 

 fered erosion for a considerable period, and was at least partially 

 covered by forest when the first lava floods were poured out. 



Mode of Deposition. — The John Day beds have generally been 

 considered as entirely of lacustrine origin, and probably a part of 

 the series has been formed in that way. There are, however, cer- 

 tain peculiarities about a considerable portion of the section which 

 it is difficult to explain by this theory. 



