RIVER TERRACES AND GLACIAL SERIES 45 I 



overlying deposits. A little farther west it is exposed along the 

 bank for several hundred feet and has a thickness of 6 to 8 feet, 

 with the bottom not seen. It is partially indurated so as to 

 resist erosion well. It is without any apparent stratification and 

 its general appearance is that typical of the ground moraine of 

 a glacier. The included pebbles are partly subangular and 

 partly well rounded. There are faint traces of striation. No 

 serpentine is present, consequently the deposit must be referred 

 to an early stage of the Cohnrad Gulch glacier, a stage appar- 

 ently closely preceding the maximum extension of the Brown's 

 Gulch glacier and certainly long preceding the stage which 

 formed the moraine over the stratified fine gravel and silt. 



We will return our attention again to the vicinity of the gorge 

 at the head of the old Salmon valley. At Cooper's saw-mill, 

 which is just below the gorge, there is the first of a series of 

 remnants of a terrace which extends down the valley, with a 

 level at first about 50 feet above the river, but gradually decreas- 

 ing to 30 feet. It is, at the saw-mill, a rock bench covered with 

 gravel and bowlders. The canyon trenched below it is compar- 

 able with that developed in the rock platform above the gorge, 

 and I consider this level to represent the closing stages of gla- 

 ciation in the broad valley above the gorge. The rock bench 

 rapidly descends below the river level and thence the terrace 

 remnants appear to be built entirely, displaying nothing but 

 gravel and bowlders in the bank. This deposit partially filled a 

 rather wide trench excavated by the river into the earlier glacial 

 deposits and the lake deposit of fine gravel and sand. In the 

 vicinity of Conzetti's mine there are several flat-topped remnants 

 of this terrace which lie 30 feet above the river and which formed 

 part of the valley floor at a time long succeeding the Brown's 

 Gulch maximum glaciation ; Conzetti is probably in part work- 

 ing this deposit in his hydraulic mine. Unfortunately, between 

 here and the lower old channel remnants farther down the river, 

 there are no more remnants of this late Wisconsin terrace; but 

 it is safe to say that it is not older than Channel D and not 

 newer than Channel E. 



On the northern side of the valley, above the saw-mill just 



