PEALE.] DESCRIPTIVE GEOLOGY — JOHN DAY's EIVER. 545 



west side of tlie river, where tliey form gray and reddish bkiffs as far 

 north as the abrupt westward turn in the river. 



Foiu^ or five miles northwest of Station 53 the Wyoming Eange is cut 

 by a stream flowing a few degrees south of west. From the mouth of 

 this creek the course of John Day's Eiver is west for about a mile and 

 a half, when it turns northwest, a course that it holds to its mouth. On 

 the north side of this tributary stream a good section of the strata is 

 seen, as viewed from Station 53. Toward the east, the limestones, the 

 basset edges of which face the Green Eiver Basin, are seen dipping a 

 little south of west 35°. Above the limestones are red sandstones and 

 quartzites, and still higher lighter colored red sandstones, inclining 

 about ^5° in the same direction. Above the latter are the gray lime- 

 stones and shales, in which the angle is from 20° to 25°. The entire 

 thickness of the beds is between 9,000 feet and 10,000 feet. 



The foUowing section agrees with the section given in the illustration : 



Section JVo. 12. 



Feet. 



Or.-rUr^r^-fc^r'r.T.a !• YbUow limestoncs aiid quartzites \ r> iaa 



L-arDonuerons ^2. Blue limestones somewhat laminatecl near tlie top . . 5 '^'^^^ 



i 3,« 



rr • ■ 9 J 3. Eeddisli sandstones and quartzites, lieM colored near 



T"^««i«- j tliebase .^ > 3,600 



i.4. Eed sandstones. 



{5. Gray and blue limestones ^ 

 6, Bluish and gray limestones, with shales and sand- 

 stones near the top. (Beds of section at McDou- 

 gal's Creek come in this section here) } 3, 300 



( 7.' Sandstones and shales, gray and greenish . 



Cretaceous? < 8. l^ellow sandy shales? 



( 9. Variegated reddish and grayish shales 



9,000 



It is probable that a careful detailed examination of these beds would 

 determine the presence of the whole Cretaceous series to the top of the 

 Fox Hills Group. The section given above is only general, and the thick- 

 nesses are approximate. They are obtained by taking the dip of 35° for 

 the limestones, 25° for the red beds, and 20° for the Jurassic strata. Tak- 

 ing the average dip at 25° for aU, we get a thickness of 8,000 instead of 

 9,000 feet. 



The western side of the valley of John Day's Eiver is a high plateau 

 of Cretaceous (f) rocks. It is from two to four miles in width, and 

 slopes gently from the Salt Eiver Mountains to a bluff facing the river 

 bottom. This bluff is from 400 to 600 feet in height ia the upper part 

 of the valley, and increases to about 800 feet above the mouth of 

 McDougal's Creek. In this portion the plateau is much cut up by the 

 branches of the river. 



SALT KIVEE EANGE. 



This range is one of the most comiDlicated within the limits of the 

 district, especially towards the southern end, where it merges into the 

 commencement of the ridges that continue southward from this range 

 and the Wyoming Eange. Geologically, the direct southern prolonga- 

 tion of the Salt Eiver Eange is found in the range that forms the divide 

 between the tributaries of Bear Eiver and Smith's Fork and the branches 

 of Ham's Fork. The Salt Eiver Eange proper, from Smith's Fork north- 

 ward, has a length in our district of about 35 miles. It probably ex- 

 tends 5 or 6 miles farther to the Canon of Snake Eiver. It is rough 

 and rugged, but not hea^saly timbered. There is but one pass across it, 

 35 G s 



