496 PROCEEDINGS OF THE ALBANY MEETING 



from 6 to 10 miles into Carbon county and from 20 to 25 miles into Natrona county. 

 The bottom of this depression is 800 feet below the rim near the head and over 

 1,700 feet below it near the Platte river. The drainage is practically confined to 

 Camp creek, which rises at the southern end of the hole, but which affords water 

 for only a portion of the year, and Bates creek, which rises in the Laramie moun- 

 tains and furnishes quite a stream. The country about this area is comparatively 

 level, but to the eastward only a few miles rise the Laramie mountains, and to the 

 westward the Indian grove and other ranges, which are made up of Mesozoic, 

 Paleozoic, and Archean rocks. In length Bates hole varies from 25 to 35 miles, 

 and in width from G to 12 miles, the lower end being much the wider. The domi- 

 nant formation entering into the structure of this region is Tertiary, but this rests 

 nearly horizontally on 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 15 to 20 degrees and 

 usually much higher, and in many instances from 28 to 34 degrees. 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 [Pinns flexlis) whose roots are exposed from 1 to 8 feet, which signifies very 

 rapid erosion. This erosion has been very general, and data which will aid us in 

 determining the age of Bates hole are well in hand. 



GEOLOGICAL SECTION THROUGH JOHN DAY BASIN* 

 BY J. C. MEKRIAM 



lAbstractl 



The John Day river and its tributaries have exposed in the erosion of their can- 

 yons about 10,000 feet of strata, giving a full series of formations from Lower Cre- 

 taceous 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 cer- 

 tainly of pre-Cretaceous age and are underlain by quartz diorite,t which is presum- 

 ably intruded into them. 



On Bridge creek, near Mitchell, a great thickness of Cretaceous is exposed. The 

 lower 2,000 to 3,000 feet of this section are typical Knoxville. The upper 1,000 to 

 2,000 feet are Chico. 



Resting upon the Chico, near Mitchell, also showing typical exposures at Clarnos 

 ferry, is a presumably Eocene formation, to which the name Clarno is given. This 



*Tlie paper was illustrated with lantern slides showing the principal formations and their rela- 

 tions to each other, 

 t Determined by Frank C. Calkins. 



