588 REPORT UNITED STATES GEOLOGICAL SURVEY. 



Group is not seen north of Swan Creek. On the west side of the southern 

 extremity of the lake, Mr. Mushbach made two stations on a smallhog- 

 back-like ridge, in which a conglomeritic qxiartzite outcrops with eastern 



dips. Near the mouth of Swan Greek similar qnartzites were seen by 

 him, with eastern dips, while in the range to the westward the dip is to 

 the west. There is here, therefore, an anticlinal, the northern extension 

 of an anticlinal that lies beneath the Bear River plateau, or perhaps the 

 eastern portion of the very broad anticlinal that lies west of it, as shown 

 on the maps of the Fortieth Parallel Survey. The latter fold, however, 

 probably becomes narrower as it extends to the north. 



This anticlinal near Swan Creek is the same one referred to by Dr. 

 Hay den in the report for 1871 (p. 157), when he says: "The beds of 

 quartzite incline like a steep roof from the west side of the mountain, 

 forming a wall very near the road. The inclination of the quartzites 

 was 60°, while all along the sides of the mountains the basset ridges of 

 the strata are shown inclining in an opposite direction 10° to 15°." The 

 lake is probably underlaid by at least one anticlinal fold. We have seen 

 that the ridges south of Station 100 run out under the lake. Quartzites 

 are the prevailing rocks in the foothills on the west side of the lake, and 

 they come down close to the lake, forming rounded ridges, between 

 which there are numerous rapid and clear streams. 



From the north end of the lake the valley on the west side widens, 

 and west of the marsh it is from two to three miles to the edge of the hills. 

 Northwest of the town of Paris outcrops of white beds are seen on the 

 lower hills. Station 115 was also located on similar hills in which white 

 limestones and sandstones outcrop. Remnants of similar beds are also 

 seen on the hills to the westward of the station. They are so like the 

 beds seen in various portions of Cache Valley that they have been col- 

 ored as representing the same formation, viz, Pliocene Tertiary. Back 

 of Montpelier, on the east side of the valley, limestones are seen with a dip 

 to the westward. They come up over the ridge and are probably of 

 Jurassic age. A little farther south an outcrop of white sandstone was 

 noted, probably Pliocene? The valley here is very broad and covered 

 with a local drift. This drift extends along the valley of the Bear as far 

 as Soda Springs. The Pliocene beds are probably present on both sides 

 of the valley as far as Twin Creek. The latter stream drains the west-' 

 ern slopes of the Preuss Eange. It has a broad meadow T -like valley, in 

 which Georgetown is located. The southwest spurs of the Preuss Range 

 are probably composed of Jurassic rocks, although the Carboniferous 

 may show in some of the deeper gorges. Back of Bennington Dr. Hay- 

 den made the following section in 1871 : * 



Top. Feet. 



1. Massive yellowish-gray, hard, and quite pure limestone 200 



2. Hard, tough, bluish or steel gray, calcareous rand, with all the peculiar mark- 



ings of a shallow mud-deposit, in layers from an inch to.two feet in thickness 

 and. very regular 300 



Total 500 



I think there is very little doubt of the Jurassic age of these beds, as 

 they appear to correspond closely to the beds observed in the Aspen 

 Ridge, which continues the folds to the northwest. 



Just north of Georgetown there are several buttes in which white 

 sandstones and conglomerates outcrop. These I have referred to the 

 Pliocene. The valley of Bear River between Georgetown and Soda 

 Springs was not passed over by me, but there is no doubt as to its being 



* Report U. S. Geol. Survey for 1871, 1872, p. 155. 



