600 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



tween it and Nortli Creek. The latter stream flows to the northward 

 with a course a little east of north, while Bloomington Creek flows 

 directly eastward. The station is located on a dark-drab almost black 

 limestone, which rests on a white quartzite. In the limestone I noted 

 Za'plirentis and crinoidal markings. These limestones dipped gently to 

 the eastward, becoming flat and again rising gently with a dip to the 

 westward. They appeared to be a remnant left in a synclinal that was 

 very shallow. They appear to outcrop on a mountain at the pass near 

 the head of the creek, and there dip 25^ to the eastward, or perhaps a 

 little south of east. A little east of south from the station, on the other 

 side of the creek, the underlying quartzites dip 5° to the westward. 

 Below the quartzites are limestones, and below the latter dark quartzites 

 generally of a reddish hue. The latter beds, a couple of miles northeast 

 of the station, dip 20° to the westward. On Station 112, which is 16 

 miles further south and a couple of miles to the eastward, the dip is also 

 west 5° to 10°. The latter station is on quartzite and below it are blue 

 limestones. These westward-dipx)ing beds are the western members of 

 the anticlinal of Swan Creek. The eastern side has been so eroded that 

 only occasionally can it be seen. It appears, therefore, that the syn- 

 clinal east of Station 111 becomes i^rominent as we iDroceed northward and. 

 forms the principal portion of the range. At the north the quartzites 

 appear to pass beneath the Pliocene deposits, north of which the geol- 

 ogy has not been very closely studied on the south side of the Bear. 

 North of the river, however, we have Jurassic limestones entering into 

 the folds of the Carboniferous. Nothing can be x^redicated of this north- 

 ern portion of the range until after it is visited and investigated. While 

 the topography of this portion of the range was worked I was obliged to 

 work the region of the southern branches of the Blackfoot which was 

 much complicated geologically. At Sheep rock the limestones are prob- 

 ably Carboniferous. Station 91, which was the most northern station 

 made by Mr. Gannett, had outcrops of massive light-colored limestone 

 without fossils. On 95 quartzites outcrop, but of what age I cannot 

 say, as no fossils were brought in. 



Eeturning again to the southern portion of the range, we see that on 

 our south line the range consists of a synclinal on the west of Carbon- 

 iferous rock. Then follows an anticlinal of Silurian ; next a synclinal, 

 on the eastern side of which the Carboniferous appears again at Station 

 111. Then another anticlinal fold is noted, which is concealed west of 

 Bear Lake by the unconformable Wahsatch beds. South of our district 

 the range is much simpler, consisting of only one broad anticlinal, with 

 a secondary fold developing on the west side. This is the western syn- 

 clinal we have noted. Followed to the north it broadens? as the beds 

 rise, and finally disappears, while the eastern synclinal forms the main 

 portion of the range. • 



GENTILE VALLEY. 



Gentile Valley lies west of the northern end of the Bear Eiver Eange 

 and directly south of Basalt Yalley. It is about 16 miles in length, and 

 about 4 miles in width at the lower end. Bear Eiver enters the valley 

 flowing south along the western edge of the basalt flow, which ends in 

 a tongue-like projection. The river-bottom is broad and meadow-like, 

 often marshy, and the stream is very sluggish. A trij) of a day's dura- 

 tion was made into the valley from Mink Creek and two stations located. 

 One {ci) was located at the mouth of Trout Creek, and another (&) on the 

 west side of the Bear south of Collier's Creek. Station a was located on 

 soft, sandy, and marly beds, which were so broken down that a section 



