RIVER TERRACES AND GLACIAL SERIES 437 



FROM BIG BEND BASIN TO COOPER'S MINE. 



Between the Big Bend and Little South Fork creeks, there 

 are several marked remnants of the main channel (Channel C), 

 crossing points on the inner side of curves in a new course of 

 the river. The local alluvium which was deeply piled over the 

 regular river deposit, displaced the river repeatedly and com- 

 pelled it to take a somewhat serpentine course. Consequently 

 the new canyon is not everywhere directly under the old. 



At the upper end of Big Bend basin, Channel C has a height 

 above the river of only 50 feet, but is clearly seen to be the same 

 level as the 75-foot channel at the lower end of the basin. Small 

 remnants of this 50-foot channel occur on each rock point on 

 the south side of the river for some distance upstream. Below 

 them there is a long narrow bench of the 15-foot channel 

 (Channel D). On the first prominent point on the north side, 

 the main channel is 50 feet above the river, but at 70 feet there 

 is another channel (Channel B). Both of them were buried 

 under the stratified local debris, the lower the deeper. On 

 the same point occurs a marked remnant of the 15-foot channel, 

 which was not buried under local debris. 



The next point on the south of the river has a marked rem- 

 nant of the main old channel whose floor is here 55 feet above the 

 river. There is a distinct outer rim. The new canyon is 75 feet 

 (minimum) in depth. Over the old channel gravel there is at 

 least 40 feet of local stratified alluvial debris (including that of 

 the Crosby Creek fan) . There is also a remnant of the higher 

 channel. 



The next point on the north side of the river has a narrow 

 remnant of the old channel system. It is about 50 feet above the 

 river and is distinctly higher than the main channel remnants 

 on the south points both above and below this point. Hence 

 it represents Channel B. There is not much local debris left 

 over it. 



The next point on the south side of the river, which is a 

 short distance below Little South Fork Creek, has an important 

 remnant of Channel C. Its rock floor is 75 feet above the river, 

 it has a distinct outer rim, and the new channel has been cut 



