Mkkriam.] 



fohti Day Basin. 



295 



At most John Day localities, including Bridge Creek, Turtle 

 Cove, and the entire region of the North Fork, the uppermost beds 

 in the section are buff, tufaceous, or ashy deposits, sometimes with 

 sand and gravels near the top. These beds show a thickness of at 

 least 300 to 400 feet, and perhaps much more in some localities. 

 They are usually harder and are generally exposed as steeper 

 bluffs than the strata of the lower divisions. The steepness of the 

 bluffs is sometimes partly due to the fact that they are protected 

 by the lavas above, but even where there is no protective covering 

 they tend to assume the same erosion forms. 



In the North Fork region, at Monument and Hamilton, red and 

 pinkish beds, resembling the Lower John Day somewhat in color, 

 are found next to and grading into the uppermost division. It is 

 quite certain that some of these exposures at Monument are really 

 Upper John Day, and a close examination shows the rock to be 

 lithologically different from the typical basal shales. At Hamilton 

 a considerable thickness of red beds, looking at a distance much 

 like the typical lower division, was seen to be apparently immedi- 

 ately below the upper beds. It was not possible to examine the 

 exposures and it is not known whether the middle division is miss- 

 ing here or whether the beds are Upper John Day similar to the 

 red phase at Monument. 



This division contains the only typical sands and gravels in the 

 John Day and the only known remains of fresh-water mollusca 

 occur here. Fxcepting a single leaf, the only plant remains known 

 to occur in the series are in the upper division. 



While it has not been possible for the writer to draw sharp 

 lines between the divisions discussed, the lithologic characters are 

 in general sufficiently well marked so that one is enabled to deter- 

 mine the horizon in the series to which beds in question belong. 



Palceontdlogic Classification. — -That the fauna of the John Day 

 region changed considerably during the period of deposition of this 

 series has already been shown by Wortman,* who has proposed a 

 division of the series on a palaeontological basis into lower or 

 Diceratherium beds and upper or Merycochcerus beds. Wortman 



* Extinct Camelida; of N. America, Bull. Am. Mus. , V. 10, p. 120. 



