KELLOGG SYStEJM OF RIVER TERRACES 523 



the old channel was filled to a depth of 500 feet. The characteristic 

 feature of the deposit is its relative fineness, there being much rather 

 fine well-worn gravel and much sand. The oUl channel, whose floor, at 

 Kellogg was about 100 feet above the present river level, emerges into 

 the present river valley on the western side of the Kellogg cemetery. 

 On the south side of the deep channel a much shallower channel was 

 eroded in the bedrock and filled with gravel. A small remnant of this 

 deposit caps a knoll on the ridge immediately east of Government Gulch 

 at the same altitude as the Page ranch. In fact the 600-foot terrace 

 marks the floor of the valley at the completion of the deep valley filling. 



ELEVEN-HUNDRED-AND-FIFTY-FOOT TERRACE 



The chief remnant of this terrace is on a narrow spur between Milo 

 and Elk creeks, about a mile south of Kellogg. In a flat of several acres 

 extent the gravel may be 50 or 100 feet deep. It is relatively coarse and 

 abounds in cobbles. This terrace is the highest of the Kellogg system, 

 and probably represents a valley floor that was broader than in any sub- 

 sequent stage and was bordered by high mountains, not much less rugged 

 than at the present day. 



- Calkins has pointed out that the general uniformity of elevation of 

 the high ridges of the Coeur d'Alene Mountains suggests a dissected 

 peneplain at about 6,000 feet of altitude, but I do not consider the evi- 

 dence to be sufficiently strong to be worthy of confidence. The South 

 Fork of the Coeur d'Alene Eiver excavated at Kellogg a valley about 

 4,000 feet deep. The 1,150-foot terrace marks a local vicissitude in the 

 deepening of this valley and, has no particular significance otherwise. 

 Then the river aggraded this deep valley until it was filled with gravel, 

 sand, and silt to a depth of 500 feet. The valley Avas then much wider 

 than at any subsequent stage and the river flowed near its northern side. 

 A change in conditions caused it to actively erode the valley floor. East 

 of Kellogg as far as Big Creek the new channel is largely cut in Prichard 

 slate and indicates considerable age for the 600-foot terrace. "When the 

 new valley had been cut down 400 to 450 feet, it was floored by a rela- 

 tively coarse alluvium 30 to 40 feet thick. Then the boulders of granite 

 and other igneous rocks were introduced and scattered over the valley 

 floor. After that the river deepened the new valley 250 to 350 feet, 

 partly in gravel but chiefly in Prichard slate. It then aggraded the 

 valley to a height about 30 feet above the present river level, then nearly 

 removed this new filling and finally deposited the Modern alluvium. 



It is to be noted that the river tended to cut each canyon beneath the 

 northern portion of the floor of the next higher canyon — that is, to mi- 



