EDITORIAL 7 l 



the lower end being much the wider. The dominant formation enter- 

 ing into the structure of this region is Tertiary ; but this rests nearly 

 horizontally upon a very uneven floor of older rocks, which in the 

 central portion have been exposed and suffered extensive erosion. 

 From the rim the slopes are very steep throughout, seldom being less 

 than 1 5 to 20 and usually much higher and in many instances 

 from 28 to 34 . Occasionally there are vertical walls of the Tertiary 

 rocks from 100 to 200 feet, carved in the most unusual manner and 

 often cut with deep, narrow, dry gorges. Capping the highest Tertiary 

 escarpments there is a heavy conglomerate of unknown age ; beneath 

 this are the Titanotherium beds which have a thickness of about 600 

 feet, and in local depressions in the Cretaceous series underlying this 

 region there is a third series of Tertiary beds, composed of variegated 

 clays and sands that is in all probability Eocene. Along the Platte 

 River all of the Tertiary rocks have been removed and along the Laramie 

 Mountains there are exposed in natural order, Cretaceous, Jurassic, 

 Triassic, Carboniferous, Cambrian, and Archean as one ascends the 

 range. Along the Tertiary escarpments are numerous stunted pines 

 {Pinus flexlis) whose roots are exposed from one to eight feet which 

 signifies very rapid erosion. This erosion has been very general and 

 data that will aid us in determining the age of Bates' Hole are well in 

 hand. Illustrated with lantern slides. 



A Geological Section through the John Day Basin. By John C . 

 Merriam, Berkeley, Cal. 



The John Day River and its tributaries have exposed in the erosion 

 of their canyons about ten thousand feet of strata, giving a full series 

 of formations from Lower Cretaceous to Quaternary. 



The oldest rocks in this region, which are known to the writer, are 

 a series of altered sedimentaries in the northeastern part of the basin. 

 They are pretty certainly of pre-Cretaceous age and are underlain by 

 quartz diorite x which is presumably intruded into them. 



On Bridge Creek, near Mitchell, a great thickness of Cretaceous is 

 exposed. The lower 2000 to 3000 feet of this section are typical 

 Knoxville. The upper 1000 to 2000 feet are Chico. 



Resting upon the Chico, near Mitchell, also showing typical expo- 

 sures at Clarno's Ferry, is a presumably Eocene formation to which the 

 name Clarno is given. This formation is made up entirely of tuffs, 



1 Determined by Frank C. Calkins. 



