524 O. H. HERSHEY TERTIARY AND QUATERNARY GEOLOGY 



grate northward. This might have been due to a progressive northward 

 tilting of the country, but I believe it had a dilt'erent cause. In the 

 vicinity of Kello'gg the mountains on the south of the valley are much 

 higher and more abrupt than those on the north. As a consequence the 

 debris that worked do^^ai from them and the gravel deposits that came 

 out of the gulches were much stronger than those from the north and 

 forced the river toward the north. It is significant that up and down 

 the valley where this distinction between opposite sides of the valley 

 breaks down the terrace remnants are no longer practically confined to 

 the south side. 



Terraces east of Kellogg Region 



The 600-foot terrace is represented by graA^el at an elevation of 700 

 feet above the river on the first ridge east of Big Creek, a small remnant 

 on the next ridge east, and a gravel deposit at 650 feet a little over a 

 mile east of the mouth of Big Creek. A small area of gravel on the 

 ridge west of Two-mile Creek, at an elevation of 500 feet above the river, 

 is probably a remnant of the deposit under the terrace. One and one- 

 half miles east of Osburn the old valley is obstructed by a gravel de- 

 posit at least several hundred feet thick, compelling the river to pass 

 through a short section of new valley on the south. It reaches 550 feet 

 above the river. There is much fine gravel and near the highest point 

 an excavation shows yellow and buff sand. Xo boulders of granite or 

 other igneous rocks were seen in connection with the deposit. Though 

 much eroded, the gravel was not cut down enough to permit the 200- 

 foot terrace level to pass through the old valley. The great width of the 

 present valley at Osburn is due to the fact that there the old and new 

 valleys coincide. 



Remnants of the 200-foot terrace occur at 350 feet above tlie river on 

 the first ridge east of Big Creek, at 300 feet on the west side of Terror 

 Gulch, and at 300 feet in a gently rolling gravel flat on the east side of 

 Terror Gulch. No boulders of granite or other igneous and metamor- 

 phic rocks were observed in connection with them. This is especially 

 remarkable in the case of the last remnant, Avhicli is of sufficient extent 

 to be occupied by a farm, whose broad fields and piles of boulders along 

 the fences make conditions unusually favorable for observation. It is 

 evident that the granite boulders on the 200-foot terrace terminate about 

 a mile east of Kellogg, and that they were not derived from some point 

 up the valley. This makes their presence more remarkable. 



The 1,150-foot terrace stage may be represented by an extensive gravel 

 deposit, reaching an elevation of 1,250 feet above the river about 1% 



