TEALE.] AREA B — GRAND RIVER VALLEY BOOK gIjIFFS. 173 



from the Grand at the mouth of Muddy Creek. South of this is the 

 Dome Plateau, named from the domed shape of the country. 



From the foot of the hogbacks there is a gradual swell, covered for 

 some distance with a portion of the Jurassic. This, however, soon dis- 

 appears, and the upper part of the Trias (?) forms the surface, reaching to 

 the edge of the cliffs overlooking the Valle Colorado of Grand River. A 

 section of the beds in these cliffs at station 12 was given in the Report 

 for 1875, p. 83. 



^ In the western part of Grand River Valley there are three streams, 

 Muddy, Alkali, and Desert Creeks, rising in the Book Cliffs. The names 

 were given as an indication of the kind of country through which they 

 flow. 



Muddy Creek rises in the cliffs outside of the" district. Like the others 

 in Grand River Valley, the course of this stream can be traced by the 

 line of sage-brush along its gulley. In the cliffs it probably has running 

 water, and near its mouth we saw several pools of alkaline water. 



Alkali Creek we found entirely destitute of water, and it is probably 

 only in the spring that it is a running stream. The bed of Desert Creek 

 contained a trickling stream at the entrance to the cliffs, but it soon dis- 

 appeared in the clayey deposits of the valley. On the way across the 

 valley to the exit of Desert Creek, we crossed a low mesa about half way 

 from the Grand to the cliffs. This mesa, not a hundred feet high, is 

 capped with a sandstone which had a dip of 1'^ or 2° toward the cliffs. 



Grand River Valley is a valley of erosion determined first, perhaps, by 

 the fold resulting from the upheaval of the Uncompahgre Plateau. An 

 immense amount of material must have been removed to form the trough 

 that we now see extending along the Uncompahgre, Gunnison, and 

 Grand Rivers to the Green. We leave the Grand just as it enters the 

 great cafion-country so characteristic of the great Colorado River of the 

 West. 



As has already been stated, the valley is not adapted for agricultural 

 l)urposes, and much less for grazing, unless there should be a change 

 of climate. Traces of a poor quality of coal are found at several places 

 in the sandstones at the summit of the hogbacks along the Grand, but 

 it is of no economic importance. Gypsum is found in the Jurassic 

 shales, and also in the Colorado Cretaceous, but as far as seen, not in 

 beds, nor as large deposits. 



EOAN OR BOOK CLIFFS. 



The cliffs that overlook the Grand River Valley are divided into two 

 portions, the Roan or Book Cliffs, overlooking the western part, and the 

 Little Book Cliffs, overlooking the eastern part, extending from Hog- 

 back Canon of Grand River to Salt Creek. The name Roan is given on 

 account of the color, and the name Book Cliff's from the resemblance of 

 their edges to those of a bound book. The summit of the cliff's forms 

 the southern edge of the Roan or Book Plateau, which extends north- 

 ward, forming the district investigated by Dr. Endlich. In this direc- 

 iion the streams flow in the direction of the dip of the rocks, and the 

 country is not so rugged as that on the south. North of the bend of 

 Grand River is the basin drained by Salt Creek, which has its sources 

 about 10 or 18 miles north of the northern edge of Grand River Valley, 

 while the other streams have a much shorter course in the cliffs. The 

 edge of the cliff's is the divide between the drainage of Grand River and 

 that which flows to White River. From Bitter-water Creek this divide 

 has a nearly due east and west direction until the head of the first 



