520 REPORT UNITED STATES GEOLOGICAL SURVEY. 



partly in craters in the Blackfoot Valley, and partly in some craters just 

 north of the bend, where the Bear passes out into the valley. The north 

 end of the Bear River Mountains terminates in Slice]) Bock. North of 

 the bend the mountains consist of isolated hills and ridges of Carbonif- 

 erous and Jurassic rocks with basalt-covered valleys between them. ( 5ar- 

 boniferous and Jurassic rocks also occur east and northeast of the bend, 

 and in this region there are several interesting i'olds. From Soda Springs 

 we followed up Bear Biver, passing through Georgetown, Bennington, 

 and Montpelier. 



Above Bennington the valley of Bear Biver is wide, and, as the lake 

 is approached, becomes fiat and marshy. This portion of the valley is 

 well settled, and the farmers appear to be doing well. The great objec- 

 tion appears to be the elevation of the valley, which is probably the cause 

 of the frosts late in the spring and early in the fall. This portion of the 

 valley is, however, better off in this respect than the Upper Bear Biver 

 Valley. In the latter, near the mouth of Smith's Fork, about July 1, 

 when we were there, there were heavy frosts nearly every night. In 

 order to keep cattle successfully through the winter, one of the farmers 

 living in the settlement at the mouth of Smith's Fork told me it requires 

 them to put up one and a half tons per head. He also informed me that 

 the weather we were then experiencing was exceptional. All these val- 

 leys, however, are excellent summer ranges. Near Montpelier, and on 

 the west side of Bear Lake, the crops of wheat were large and the settle- 

 ments all seemed to be in a prosperous condition. At one place I was 

 shown some apples that grew there in 1877, but fruit crops in this region 

 are generally understood to be precarious. 



At the south end of Bear Marsh, Bear Biver emerges from the marsh 

 into which it entered after coming from a canon a few miles north of 

 Bear Lake. This canon begins a short distance below Thomas Fork. 

 Sublette's road, which we had been following from Soda Springs, crosses 

 the hills north of the canon, sometimes coming down to the river's edge. 

 At several points there are broad alluvial bottoms, especially as the 

 mouth of Thomas Fork is approached. Between Thomas Fork and 

 Smith's Fork the valley narrows, but south of the latter again expands. 

 Beyond the alluvial bottom, which immediately borders the river, there 

 is a wide drift-covered valley, bordered on the east by hills which soon 

 develop into mountains toward the north. Formations from the Carbon- 

 iferous to the Wasatch Tertiary are represented, the latter resting on the 

 upturned edges of the older rocks near the south line of the district. On 

 the west side, also, the same unconformability is noticed, the variegated 

 sandstones and conglomerates extending farther to the north than on the 

 east, and forming the Bear Lake Plateau, which is really the northern 

 extension of the eastern side of the Bear Biver Plateau mapped by the 

 survey of the fortieth parallel. On the west side of the plateau, erosion 

 " has left a range of hills that are about 1,500 feet above the level of the 

 lake. There is a steep descent to the edge of the lake which leaves but 

 a narrow beach margin. We crossed the Bear Lake Plateau a few miles 

 north of our south line, reaching the south end of Bear Lake at Lake 

 Town. The western shore of the lake was then followed and the eastern 

 edge of the Bear Biver Mountains worked up. West of Paris, a town 

 a few miles northwest of the lake, we crossed the Bear Biver Range to 

 the head of Mink Creek, a branch of Bear Biver. 



The Bear Biver Mountains are composed of Silurian and Carboniferous 

 rocks, mainly quartzites and limestones. Between Bear Lake and 

 Cache Valley there is a rather broad synclinal fold complicated by 

 secondary folds, and this has resulted in breaking the Bear Biver Moun- 



