PEALE.] AREA B GRAND RIVER VALLEY. 171 



arroyas or gullies in the soft soil. Salt Creek was the only one that car- 

 ried any water when we crossed them. Desert Creek had a small stream 

 at the edge of the valley close to the foot of the cliffs, but the water, 

 which was alkaline, soon disappeared. The formation forming the floor 

 of the valley is the Middle Cretaceous or Colorado group, the dip of the 

 beds being away from the river. 



Between the mouth of the Gunnison and Station 4 a wide alkali flat ex- 

 tends from the foot of the Little Book Clifi^s to Grand River. The latter 

 stream comes from a deep cafion (named Hogback Canon) cut through 

 the Little Book Cliffs, and flows almost directly west across Grand River 

 Yalley nearly at right angles to its course. On the south side of tbe 

 river, the shales of the Colorado group are seen dipping 2° or 3° in the 

 bluff, which is about 200 feet high. 



After the Gunnison joins the Grand the latter takes the course fol- 

 lowed by the former above its mouth, and hugs the lower or southern 

 side of the valley. South of the river is a low hogback ridge of Dakota 

 sandstones, dipping toward the northeast. On these sandstones rest 

 remnants of the shales. The Dakota group crosses to the north side 

 southwest of Station 4, at the point where the wagon-road leaves the 

 river, and soon rises into a ridge of about 300 feet, on which Station 5 

 was located. 



Station 4 was on a remnant of a former level of the valley, a yellow- 

 topped butte underlaid by black argillaceous shales (probably Creta- 

 ceous No. 2). 



Station No. 5 was on the edge of the canon of the Grand. The river 

 is in the upper part of the Red Beds, above which is the following sec- 

 tion : 



Base. Feet 



1. White sandstones with thin bands of limestone ) oq 



2. Greenish shales ) 



3. White sandstones . . 71 



4. Variegated shales and marls reddish and greenish 70 



5. Yellowish white sandstone, rather massive 88 



309 

 The thicknesses were measured by angles, taken with the gradienter. 

 Layers Nos. 4 and 5, and perhaps No. 3, belong to the Dakota group, 

 while the remainder of the section is referable to the Jurassic, the de- 

 crease in thickness from that in the southern area being probably due 

 to the presence in this region of limestones. 



Station 6 was located on a mesa of Dakota sandstones. The dip here 

 is not great, although it increases a little as we go north from the 

 station, and the sandstones disappear beneath the Colorado shales. 

 Salt Creek flows into the Grand at the head of the bend. From this 

 bend to Station 8 the river is in a narrow caiion cut in the Red Beds. 

 These are seen on the south side of the river rising to the south in the 

 Uucompahgre Plateau. Opposite Station 7 several buttes are seen 

 which have cappings of Jurassic shales. On the north side of the river 

 tbe Jurassic forms most of the surface, although there is one area be- 

 tween Stations 7 and 8 where it has been removed. The following sec- 

 tion was obtained here : 



Top. Feet. 



1. Massive sandstone, general color light red, white on top 150 



2. Red laminated sandstones and shales 100 



3. Massive sandstone, deep red in places and light red in others. . . 200 



450 



