166 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



The rocks at first are the Dakota sandstones, which are rapidly cut 

 throng'b, Jura and Trias showing a short distance below Naturita 

 Creek. 



Naturita Creelc rises on the northern and northwestern slopes of Lone 

 Cone. The various small streams unite to form two branches, which 

 soon join, and the stream thus formed flows nearly due north for about 

 eight miles, when it turns nearly west, gradually turning to a north- 

 west course. 



The sources are in a beautiful park-like country underlaid with the 

 Middle Cretaceous shales, which are soon cut through, exposing the Da- 

 kota group, the sandstones of which form the caiiou walls to the mouth. 

 The caiiou becomes shallower as we go down the stream. Southwest of 

 Station 4 it is about 500 feet deep, and at the mouth only some 200 

 to 300 feet. There is a narrow valley bordering the stream in this 

 lower portion of its course. There is running water in it, probably, 

 throughout the entire year. Below the bend are two unimportant 

 branches that rise in the low divide separating Naturita Creek from Basin 

 Creek. . The creek was named from the abundance of the Spanish 

 bayonet-plants {Tucda angusUfolia)^ which the Indians call Naturita (the 

 Spanish name). When we were iu this region the plant was in fruit, 

 and the Utes were gathering and drying it. 



Basin Creek joins the San Miguel a few miles below the bend below 

 Naturita Creek. It rises in the rolling mesa country northwest of Lone 

 Cone, and flows northwestward across the Basin Plateau to within six 

 miles of its mouth, when it turns abruptly at right angles and flows 

 northeast to the Miguel, cutting across an anticlinal fold and a synclinal 

 depression, with a fault on the east side. In the Basin Plateau the 

 stream keeps near the eastern side of a synclinal depression, which is 

 occupied by the Cretaceous shales. In this part of its course the stream 

 is dry during the summer. Near the head, ijools of alkali-water were 

 found in September. From the Basin Plateau it turns at right angles 

 and plunges into a canon cutting across an anticlinal fold, in the centre 

 of which the Eed Beds (Trias 1) are exposed. In this caiiou the stream 

 has running water, which sinks again when it emerges into the synclinal 

 valley east of the fold. On the east side of this synclinal depression of 

 Cretaceous shales, there is a fault with the down-throw on the west. 

 This fault will be described under the head of Paradox Valley. Basin 

 Creek cuts across this fault, and joins the San Miguel a short distance 

 beyond. 



Southwest of Basin Creek, the first creek of any importance is Disap- 

 pointment Greek. In midsummer, water is found in it only in holes, it 

 joins the Dolores on the southwest side of Saucer Valley. 



KIO DOLORES. 



The reports for 1875 describe the upper and lower parts of the Dolores. 

 There was left undescribed, however, a gap of unexplored country 

 through which the Dolores flows. 



On the eastern side of the Great Sage Pla'n the general course of the 

 Dolores is a few degrees west of north. It zigzags somewhat, flowing 

 sometimes with the dip of the rocks and at others with the strike. It is in 

 deep caiion for the most part in the Eed Beds. On both sides of the 

 river the beds dip to the eastward or northeast, and are capped with 

 Jurassic (?) shales and Dakota sandstones and shales. On the west the 

 country rises to the Great Sage Plain, which stretches away to the 

 westward and south west ward. This region was visited by Mr. Holmes, 



