LATEE TEETIARY (MIOCENE AND PLIOCENE). 827 



fragments of bones and teeth, which probably represent forms similar to those in the beds 

 immediately below. 



Rhyolite flows are found toward the lower part of the Middle John Day at Bridge Creek, 

 near the top of this diyision in Turtle Cove, and overlying what is probably Middle John Day 

 on Pine Creek, about 3 miles northwest of Spanish Gulch. 



The tuffs and ashes seem in some cases to have been worked over somewhat by air or water. 

 At other points beds many feet thick have apparently been deposited directly, without much if 

 any working over by either wind or water. 



The source of the ash and tuff is as yet unknown. It probably came from vents not very 

 distant from this basin of deposition. 



Excepting the beds of sand and gravel near the top of the sectign, the stratification through- 

 out the whole thickness of the John Day is very regular. Numerous beds of almost pure ash 

 or tuff compose uniform, hard, and prominent layers, between which in the softer beds the 

 regular deposition of thin layers is plainly indicated by delicate variations in color. Nodular 

 layers, possibly produced in part by contained organic remains, are not infrequent in some 

 localities, and small nodules are usually scattered through a large part of the Middle John Day. 



Without having accurately measured the John Day section, the writer would not be willing 

 to consider the exposures north of the southern range of mountains as representing a thickness 

 much greater than 2,000 feet. Perhaps it is not more than 1,500 feet thick. At Sheep Rock, 

 near Picture Gorge, the whole section is shown rather sharply tilted, and all but the lower 

 division would be included in the column between the cap rock and the level of the river. At 

 Bridge Creek, also, the section includes the whole of the series. It may reach a thickness some- 

 what over 2,000 feet at that locality. 



********* 



Wherever the John Day is well exposed in the central and western portion of the basin, 

 it seems to be divisible into three stages, which have been designated" the Lower, Middle, and 

 Upper John Day. 



The lower division consists usually 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 the typical hills of this division, form a striking feature 

 of the landscape, the colored strata making sharply defined rings about the hills. At Clarno's 

 Ferry numerous alternations of contorted and faulted red and white beds are splendidly exposed 

 in prominent hills at the bottom of the section. 



The beds of this group appear usually to show more deformation than those higher up in 

 the series. This may be due in part to their being softer and having offered less resistance to 

 disturbances than the more rigid strata above them. 



The Lower John Day is almost barren of fossil remains at all points where it was visited 

 and has never, so far as can be discovered, furnished many good specimens. Diligent search 

 by the writer at several localities has been rewarded by the discovery of two or three fragments 

 of rhinoceros teeth. An Oreodon skull was found at this horizon, many years ago, by Mr. L. S. 

 Davis, but definite information regarding it is not now obtainable. 



The lower division was estimated to be 250 to 300 feet thick at Clamo's Ferry. Its maxi- 

 mum thickness will probably exceed that limit. It is not impossible that the Lower John Day 

 will some time be found to be separated by an unconformity from the middle division. Such 

 fossil remains as have so far been found in it indicate, however, that it belongs to the John Day 

 series. 



The middle portion of the John Day section at Bridge Creek, Clarno's Ferry, and Turtle 

 Cove consists of drab to bluish-green beds, sometimes forming rounded hUls but more frequently 



a Merriam, J. C, Science, new ser., vol. 11, Feb., 1900, p. 219. 



