526 O. H. HERSHEY TERTIARY AND QUATERNARY GEOLOGY 



On a rock bench 125 feet above the river at the mouth of Pine Creek 

 a thin sheet of light brown sandy silt has scattered over it many cobbles 

 and small boulders up to 2 feet in length of quartzite and igneous rocks, 

 including the varieties of granite and basic crystallines usual to the 200- 

 foot terrace. An 8-inch boulder is of fine-grained gneiss. The bouldery 

 deposit extends up the slope back of the rock bench to at least 50 feet 

 above it. Igneous material constitutes at least 25 per cent of all cobbles 

 and boulders over 3 inches in diameter. Xo fine gravel appears. 



The old river valley between Pine Creek and Kingston is about 500 

 yards wide. The northern part of its floor is a shallow U-shaped trough 

 about 400 feet wide, under which there is a bed of argillaceous material 

 abounding in rock fragments of all sizes up to small boulders. Most of 

 them are of local material, largely Cataldo quartzite,^ in an angular and 

 subangular condition. There are some water-worn boulders and cobbles 

 of quartzite, but the most characteristic portion of the material is the 

 igneous rocks. Various varieties of granite and diorite are common. 

 There are basic crj^stallines, fine-grained gneisses, and pegmatites. Many 

 of the well rounded, dark gray quartzite pebbles have probably come with 

 the igneous rocks. When I first discovered this deposit in the summer 

 of 1909, I was impressed by its having some glacial characteristics, and 

 I even thought I found traces of glacial striation on some of the sub- 

 angular rock fragments. In fact on my last visit I found a 2i/^-inch 

 quartzite fragment apparently faceted and scratched on two sides and 

 less clear scratches on other pebbles. However, as they occur on the 

 slope of an old railway cut now used for a wagon road, I am willing to 

 ignore these apparently glacially striated stones. 



In a 20-foot cut the boulder clay is underlaid by a succession of thin 

 beds of horizontally stratified fine argillaceous sand and silt of blue 

 gray, reddish brown, 3'ellowish brown, and white colors. This I believe 

 belongs to the deep valley filling. On tlie south of the valley several 

 nearly flat-topped ridges of Prichard slate are crossed by a gentle de- 

 pression. They probably represent the rock bench under the south por- 



3 The term "Cataldo quartzite" is temporarily applied to a member of the Belt series 

 of formations, which was not recognized by Ransome and Calkins in their report on the 

 Coeur d'Alene district, as it is apparently poorly represented in that district. It consists 

 chiefly of heavy beds, in part cross-bedded, of lilac-colored medium-srnined quartzite. 

 differing in appearance from any quartzite above the Prichard. With this are beds of 

 greenish, finer-grained sericitic rock. Its thickness is at least 1.000 feet. It evidently 

 underlies the Prichard slate. Beginning a little above the mouth of Pine Creek, it is 

 exposed over a great area, thence nearly to the station of Rose Lake. It also occurs 

 near the town of Tekoa. in Washington, and it is my impression that it will be found 

 generally along the border of the Arclvean gneisses and granites, it being apparently the 

 basal member of the Belt series: it probably corresponds to the Creston quartzite of 

 Daly. Its outcrops have a light gray color and it gives rise to a stony sterile soil. 



