104 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



latter was seen only from a distance, but it is probably similar to the 

 country to the west of the Gunnison, near its mouth, the streams prob- 

 ably cutting through to the Triassic*? red sandstones. On the Un- 

 compahgre the terrace is about one hundred feet high. 



On the south side of the Gunnison below the mouth of the TJncom- 

 pahgre, are three terraces. The first is 100 feet above the level of the 

 river, the second 150 feet, and the third 200 feet. 



Below the junction of the Uncompahgre, the Gunnison keeps a course 

 a few degrees south of west, until it reaches the mouth of Roubideau's 

 Creek, nearly five miles below. Here it enters the lower canon. Above 

 Eoubideau's Creek the valley is very wide, averaging about two miles. 

 The immediate river-bottom is also broad and overgrown with cotton- 

 woods and low brush. There are numerous sloughs along the course of 

 the river, and the fall per mile is very small. The river winds slug- 

 gishly in curves that sometimes seem to approach circles. 



On the north side are terraces which soon form low hills or buttes 

 reaching almost to the mesa. The edge of the mesa stands boldly out, 

 like the edge of a fortification-wall. Its slopes are well timbered. The 

 buttes below, extending toward the river, are composed of yellow, gray, 

 and whitish strata, the weathering of which gives a most curious appear- 

 ance to the landscape. On the south side, as I have already said, there 

 are terraces extending southward toward the Uncompahgre Moun- 

 tains. 



The caiion which commences at the mouth of Eoubideau's Creek, ex- 

 tends almost to the mouth of the Gunnison. It is, therefore, about 32 

 miles in length, in an air-line. By the Ute Indians it is called Unaiceep 

 or Eed Caiion,* from the deep-red sandstones that are exposed at va- 

 rious points along its course. In the caiion the river winds considerably, 

 and has in places meadows and even groves of cottonwood fringing it. 

 It is not very rapid, the fall per mile being about eight feet. Although 

 in an air-line the caiion is 32 mile's long, the length of the river is about 

 forty-five miles, or perhaps a little more, if we allow for all the smaller 

 curves. The course of the river at first for ten miles is north 60° west. It 

 then flows due north for about three miles, when it turns, taking a course 

 to the northwest, which it keeps generally for nearly fifteen miles, when 

 it again bends to the vvest and gradually curves back again to its mouth 

 in the Grand. 



The walls of the caiion often rise abruptly from the water's edge in 

 sheer precipices, while in others there is a narrow strip between the river 

 and the edge of the bluffs. The latter are better preserved on the eastern 

 side, as the course of the river is nearly at right angles to the dip, which 

 is approximately to the eastward, really a few degrees north of east. 



At the mouth of Eoubideau's Creek the walls are only 200 feet high, 

 while at station 60 they are 663 feet high on the eastern side, and much 

 higher opposite. This probably increases slightly as we go down-stream, 

 but it can scarcely reach a thousand feet at any point. 



At first the river merely cuts through the sandstones and shales of 

 the Dakota group (Cretaceous No. 1), as shown in a section of the 

 bluffs given in another portion of the report. 



As we go down, the river gradually cuts through the base of No. 1 

 into the Jurassic shales and limestones ; and finally, below station 62, 

 the red sandstones (Triassic ?) appear beneath the shales. 



Fig. 3, Plate IX, represents a section across the Gunnison through 

 station 60 eastward to the mesa terminating the plateau divide. It will 



* Vide Pacific Railroad Report, vol. II, page 57. 



