90 GEOLOGICAL SURVEY OF THE TERRITORIES. 



hills are capped with basalt. The elevation of station 24 is 10,642 feet, 

 and station 25, 9,031 feet. There is but little timber here, the summits 

 being grassy and park-like. In some few places there are pines, but 

 cottonwoods are more abundant. In the hills east of station 24, and on 

 the lower slope, there is scrub-oak (Quercus alba) in abundance. The 

 small creeks rising in the Cretaceous shales we generally found strongly 

 impregnated with alkali. 



The western branch of the creek referred to above, heads in beautiful 

 meadows. Its course here is nearly due west. After flowing in this 

 direction for five miles it turns and flows to the northwest, gradually 

 crossing to the western side of a low, broad anticlinal. The strata on 

 the east incline 5° to the northeast, and on the opposite side from 5° 

 to 10° in the opposite direction. Beyond, the beds probably become 

 horizontal, as seen in the high white cliffs east of station No. 48, on 

 the edge of the plateau. 



In looking down upon this valley from the hills bordering it, it ap- 

 pears more open than it really is, for we find that it has numerous hills 

 or buttes in which the sandstones, outcrop. They are gray, chocolate- 

 colored, and greenish. We were not able to visit them, but noted them 

 from the stations on the east side and from the plateau. 



We were not on the Grand River in this valley nor on North Mam 

 Creek, which joins it above the canon. North Mam Creek flows along 

 the eastern edge of the plateau from which some of its branches are de- 

 rived. Its general course is north 15° east. 



The branches of the Grand from the south in the canon valley north 

 of the plateau are all small and unimportant, simply draining the pla- 

 teau. The next branch of importance is Plateau Creek flowing into the 

 Grand 50 or 60 miles below the head of the canon. It is a stream of con- 

 siderable size, deriving its water principally from the mesa divide on the 

 south, the branches heading in the plateau of station 48, carrying water 

 only in the spring and early summer. 



There are two principal streams uniting to form the creek, one (/ 

 creek, map E), having its sources opposite those of the northern branches 

 of the North Fork of the Gunnison, and the other (g creek, map E), rising 

 more to the north and eastward, opposite the head of North Mam Creek. 

 The branch first mentioned is the largest. Its course is generally north. 

 A few miles above its mouth, however, it turns abruptly and flows west- 

 ward, parallel to the other branch, leaving a flat-topped terrace between. 

 It rises on the divide, in beautiful park-like meadows, among low hills 

 whose 1 rounded outlines are covered with groves of quaking aspens whose 

 foliage in the fall of the year is of a rich golden hue, contrasting boldly 

 with the dark green of the pines found on the higher points. These 

 groves abound in game, and are favorite hunting-grounds of the Indians. 

 We found their trails leading in almost every direction. Near the head 

 of the creek are outcrops of soft shaly beds covered in some places with 

 basalt which forms rough points reaching above the general level. In 

 the valleys the soil is made of the debris from the shales mingled with 

 pebbles from the erosion of the basaltic layer which once formed a 

 capping to the plateau. Scattered over it are chips of chalcedony and 

 agate. The sedimentary beds are nearly horizontal. As we go down 

 the valley we find the creek cutting deeper and deeper into the soft 

 strata, leaving high terraces between the branches. Between camp 44 

 and camp 45 the river falls 2,583 feet, which is about 200 feet per mile. 

 In the lower part of the valley there are outcrops of soft gray sand- 

 stones. The terraces are partially covered with scrub-oak, which make 

 traveling somewhat difficult. The other branch has a much more open 



