GLACIATION IK DEER CREEK VALLEY, MONTANA 519 



and ridges that attain altitudes of about 6,000 feet liave cirques and 

 often tarns on their northern and eastern sides. The main glacier in 

 Canyon Creek Valley had a leng-th of about 5 miles, as indicated by 

 Calkins' map, and one nearly as long occupied the valley at the head of 

 the Saint Regis River in Montana ; a portion of it flowed through a pass 

 into the Coeur d'Alene Basin. There appear to be no prominent terraces 

 of extra-glacial material leading down the valleys from the glacial de- 

 posits. The disappearance of the small alpine glaciers has been quite 

 recent, as the postglacial erosion has been insignificant near the head of 

 the valleys. Although I am not able to state so from observation, it is 

 doubtless true that the deposits include the products of the two glacial 

 stages recognized in the Deer Creek Valley in Montana. The most con- 

 spicuous feature of these late glaciations is their confinement to rela- 

 tively high altitudes. Xo mountain whose altitude does not exceed 

 5,500 feet gave rise to a glacier, and Calkins has not mapped any glacial 

 deposit below 3,200 feet. 



Kellogg System of River Terraces 

 in general 



The vicinity of Kellogg, in the valley of the South Fork of the Coeur 

 d'Alene River, has the most complete system of river terrace remnants 

 in the Coeur d'Alene district. Moreover, the w^riter has resided at Kel- 

 logg for over two years and has had opportunity, in connection with 

 other work, to study these terraces in considerable detail; for these rea- 

 sons they will be first described and then the terrace system traced up 

 and down the valley. 



MODERN ALLUVIUM 



From the mouth of Milo Creek at Kellogg west for about 3I/2 miles 

 the floor of the valley averages about 800 yards wide. Before being 

 largely buried under tailings from the concentrating mills of the great 

 lead mines of the district, the floodplain was apparently a bed of moder- 

 ately coarse gravel overlaid by several feet of dark brown sandy silt. 

 The coarsest gravel along the present channel has few boulders 12 inches 

 in diameter. Igneous material is very inconspicuous, probably not ex- 

 ceeding 1 per cent of the gravel. I suppose the depth of the alluvium 

 to be not more than 20 to 50 feet. The fall of the valley is about 30 

 feet per mile near Kellogg. 



THIRTY-FOOT TERRACE 



This terrace is developed along the south side of the valley from near 

 the mouth of Milo Creek to near the mouth of Deadwood Creek, a dis- 

 XXXVII— Bull. Geol. Soc. Am., Vol. 23, 1911 



