18 FOSSIL FLORA OF THE JOHN DAY BASIN, OREGON, [bull. 20]. 



JOHN DAY SERIES. 



Resting- diroctly upon and apparently conformable with the Clarno 

 formation iy a thick scries of regularly stratitied sediments now 

 widelj^ known as the John Day beds. This series of beds is found 

 quite generally throughout the basin, and represents what was called 

 b}^ Marsh the deposits of the John Day Lake. The beds are made 

 up almost entirely of ashy or tufaceous materials, with occasionally, 

 toward the top, some 100 or 200 feet of a harder, blocky tuff. 



The erosion forms and coloration of the John Day strata are quite characteristic 

 when compared with those of other formations in the basin. In general the beds are 

 colored various shades of red, green, blue, or yellow. In some cases they are white 

 or gray. As will be shown later, the coloration is an important character in distin- 

 guishing the subdivisions of the system. The beds are usually quite soft and dis- 

 integrate very rapidly, forming a layer of mud several inches thick over a large part 

 of the exposed surface. A moderately heavy rain starts the nuid almost in streams. « 



The thickness of the John Day series north of the southern portion of 

 the Blue Mountains i,s placed bj^Dr. Merriam between 1,500 and 2,000 

 feet, while to the south, in the vicinity of Logan Butte, it is estimated 

 to be between 3,000 and tt.OOi) feet. 



The John Day series is divided by Dr. Merriam into a lower, middle, 

 and upper division The lower division, having an estimated thick- 

 ness of 250 or 300 feet, consists of — 



highly colored shale which breaks down readily, forming characteristic mud-covered 

 domes. These beds are in the main a deep red, with occasional alternating strata of 

 buff or white ash. At Bridge Creek alternating beds of red, white, and green, 

 occurring in a group of typical hills of this division, form a striking feature of the 

 landscape, the colored strata making sharply-defined rings about the hills. ^ 



The middle division, having a thickness of from 500 to possibly 800 

 or 1,000 feet- 

 consists of drab to bluish-green beds, sometimes forming rounded hills, but more 

 frequently exposed as steep, pinnacled, and ribbed bluffs. <• 



The uppermost beds, showing a thickness of 300 or 400 feet, or in 

 some cases of somewhat more, are — 



buff, tufaceous, or ashy deposits, sometimes with sand and gravels near the top. 

 .... They are usually harder and are generally exposed as steeper bluffs than the 

 strata of the lower divisions.^ 



The lower division of the John Day series is practically barren of 

 fossils of all kinds, while the middle and upper divisions have fur- 

 nished a very extensive fauna. The only plant remains, with possibly 

 a single exception, are found in the upper division, and even here they 

 consist of only four or live species. The locality is 3i miles south of 

 Lone Rock. 



aMerriam, op. cit., p. 292. b Idem, p. 293. c Idem, p. 294. didem, p. 395. 



