580 REPORT UNITED STATES GEOLOGICAL SURVEY. 



topography indicates thatifcis tlie same fold sIlowti in the Carboniferous 

 limestones east of Eock Creek. Here, however, the red sandstones 

 (probably Trias) form the surface of the fold. Station 42 is a little to 

 the west of it. 



East of tlie ridge is a synclinal depression, the centre of Avhich is occu- 

 pied by gray beds identical with the limestones seen in the bluff on the 

 west side of the Lake Fork. They are continuous mth them a few miles 

 to the northward, where the anticlinal ridge is loAver, and the fold in 

 the Jurassic preserved. I am unable to say how far south this synclinal 

 depression continues. It appears to narrow very rapidly, and probably 

 soon dies out, leaving the red beds to form a broad anticlinal. The 

 latter rise from beneath the gray limestones and form the summit of the 

 range to the eastward. The eastern face of this range, as we saw when 

 describing the head of La Barge Creek, is composed of Carboniferous 

 limestones, presenting a bluif face toward the valley of the La Barge. 



JSTorth of Station 43 is a beautiful emerald lake (Lake Alice), which 

 has apparently no outlet. It has been formed by a landslide at the 

 mouth of the gorge separating the station hill from the one north. 

 Whatever outlet there is, must be beneath the mass of earth that has 

 dammed up the stream that once occupied this gorge. The lake has no 

 beach. It is five miles long and less than three-quarters of a mile in 

 width at the widest x^ortion. The fold of Station 43 is probably the 

 southern continuation of the western fold of the Salt Elver Eange. 

 Between the two points, however, the reddish shales that lie above the 

 Jurassic limestones outcrop and form the surface. Tlie eastern fold of the 

 range also begins a short distance north of this point, the red beds rising 

 from beneath the gray limestones. The Avhole region is so comijlicated 

 that I can only present the most general features. The investigation of 

 these folds will well repay the student of geology, and before coloring 

 the final map of the region I hope to be able to revisit it. 



The Lake Branch, as we have seen, has its valley cut almost entirely 

 in Jurassic rocks, and flows south in a monoclinal valley. The main 

 branch has an almost parallel course, rising however, some miles farther 

 north, viz, between the head of La Barge Creek and the extreme source 

 of Salt Eiver. The upper course of the river is in the variegated beds 

 that lie just above the Jurassic limestones. Near the junction with the 

 other fork it is in the shales and sandstones that lie above tlie conglom- 

 erate, layer K"o. 6 of Section 25. The section west of Smith's Fork will 

 be given subsequently, when considering the Sublette Eange and the 

 region of Thomas' Fork, 



The valley of Smith's Fork above the bend has but little available 

 agricultural land. The mountains at the head of its various branches 

 are well timbered with pines. The lower valley merges into that of Bear 

 Eiver, and is meadow-like and well grassed, although somewhat high 

 for general agricultural purposes. Some of the settlers seem to think, 

 however, that there has been some change in the climate since the first 

 settlement of this region. 'No accurate observations have been made, 

 and it is probably only an opinion, with very little fact for a foundation. 



SUBLETTE RANGE. 



The Sublette Eange is a short range of rather rounded form, risuig 

 2,000 to 3,000 feet above Bear Eiver on the east side, extending north 

 between Smith's Fork and Thomas' Fork. The total length of the range 

 is about twenty-one miles. It is divided into two portions by a branch of 

 Thomas' Fork. The northern portion was not visited by us j butjudg- 



