522 O. H. HERSHEY TERTIARY AND QUATERNARY GEOLOGY 



and 150 feet deep. This is cut through the gravel into the Prichard 

 slate. 



The gravel terrace on which the Kellogg cemetery is situated is 250 

 to 300 feet above the river and its surface slopes 5 degrees toward the 

 north. There is apparently a distinct channel in the bedrock under the 

 terrace; it is separated from the present river channel by a ridge of 

 Prichard slate. This slate rim-rock ridge, cut by numerous transverse 

 gulches and canyons, is present between the old and new channels for 

 about 2^2 miles east from the cemetery. The original filling of tlie old 

 channel by river gravel apparently long preceded the development of 

 the 200,foot terrace. An important remnant of the latter, occupied 

 by a ranch about a mile above Kellogg, has a granite boulder nearly 3 

 feet long, several smaller granite boulders and cobbles of several varie- 

 ties of granitic rocks. They have an altitude of about 300 feet above the 

 river or 2,650 above the sea. A small remnant of the gravel of the 200- 

 foot terrace occurs on the north side of the valley at Kellogg. 



This terrace certainly presents some interesting problems, the chief 

 of which are the origin and mode of transportation of the granite 

 boulders; but we must get acquainted with more facts concerning the 

 terraces of the region before we can discuss them. 



SIX-HUNDRED-FOOT TERRACE 



The principal remnant of this terrace, about 600 yards long, parallel 

 to the valley, and 300 yards wide, is occupied by the Page ranch, imme- 

 diately west of the valley of Milo Creek. The surface is quite undulat- 

 ing because of much erosion, but the unconsolidated material in the 

 small ridges is at least 40 to 50 feet thick. The water-worn boulders 

 that weather out around the borders of the terrace are chiefly of local 

 quartzites and no granite or other igneous rocks have been seen among 

 them. My impression is that the lower part of the deposit is very coarse 

 and includes boulders 3 feet in length. Elsewhere the gravel of this 

 terrace is inclined to be relatively fine, and probably the boulder deposit 

 under the Page ranch was formed near the mouth of a tributary valley. 

 It is a characteristic of this terrace that its inner border is usually ob- 

 scured by debris from the neighboring mountain slopes. 



The nearly even crested ridge at the surface of the deposit in the old 

 buried channel east of Elk Creek Valley is 50 feet higher than the Page 

 ranch. The corresponding ridge over the gravel in the old channel im- 

 mediately west of the canyon of Big Creek has a flat of considerable 

 extent at a level of about 550 feet above the river, but the highest por- 

 tion of the deposit is 700 feet above the river. I agree with Calkins that 



