peale.] GEOLOGY LOWEE CANON OF GUNNISON RIVER. 105 



be seen that there is a gentle slope from the edge of the canon, and that 

 from the edge of the mesa there is another slope, thus forming a valley 

 between the two points. This valley is filled with Cretaceous sand- 

 stones, shales, and marls, which, on the east side, form mesa-like 

 buttes. 



There are five streams joining the Gunnison from the east in the canon. 

 The largest is Kahnah Creek. Most of the creeks cut deep canons as 

 they join the river. It will be seen, on referring to the illustration 

 (Fig. 2, Plate IX), that there is a dip at right angles to the stream, and 

 that thisisthegreatest at the river, anddecreases as we goaway in either 

 direction. At the point where the section was made, the dip is only about 

 5°. Farther north, on the south side of the Grand, the angle is from 15° 

 to 20°, decreasing as we go westward or south westward to about 5°, and 

 also decreasing as we go toward the east. There is therefore here a 

 monoclinal fold, the axis of which has a direction about northwest, the 

 dip being to northeast. At station 60, the fold is very gentle; but, as 

 we have seen, to the north it is much steeper, and probably still far- 

 ther it may become a fault. 



Fig. 1, Plate IX, represents a profile of this fold as far north as we 

 could see it from the mouth of the Gunnisou. It will be in oue of the 

 districts during the next season, when it will be thoroughly investi- 

 gated. 



This canon of the Gunnison seems, therefore, to have been outlined by 

 a fissure in the rocks caused by their folding; otherwise it would seem 

 most natural for the river to have cut its way through the soft strata 

 that lie between the edge of the canon and the basaltic-capped mesa. 



The country to the southwest rises into a broad plateau, beyond which 

 we conld see the peaks of the Sierra la Sal. Ked sandstones seem to 

 form the basis of this plateau, which is-ent into profound caiions by the 

 branches joining the Gunnison on the southwest side. Tbis will be in 

 the field of explorations next season, and I therefore only refer to it 

 Liere. 



The bluffs of the Gunnison as we approach the Grand again fall off, 

 and do not exceed 150 feet in height. A section at this point will be 

 found elsewhere, with a description of the beds forming it. 



