514 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



Besides the Green River and Thompson Plateaus, there are the Ham's 

 Fork Plateau and the Bear Lake Plateau, all of which will be hereafter 

 described in detail. 



Mountains. — The mountains of the district have in general the char- 

 acter of short, isolated ranges. The Bear River Range, extending south 

 from the Great Bend of Bear River, is the longest within our district 

 (having a length of 60 miles), and stretches some distance south of our 

 line to join the Wahsatch Range. The Wind River Range occupies a 

 small portion of our area in the northeast corner. 



On the west side of Green River Basin are the Wyoming Mountains, 

 and west of them the Salt River Range. Although short, these are 

 important ranges. The Wyoming Range ends at the head of La Barge 

 Creek, but the line of uplift is continued southward in the Absaroka 

 Ridges. The Salt River and Wyoming Ranges both have north and 

 south trends. West of the Salt River Range we have no mountains until 

 we reach the Portneuf Range. The northern end of the Preuss Range, 

 it is true, extends northward between the east and south forks of the 

 Blackfoot, but the mountainous character is here nearly lost. Besides 

 this, there are only comparatively low ridges and isolated groups of 

 hills in the northern part of the district between the Salt River Range 

 and the Portneuf Range. West of the Portneuf is a range to which 

 we gave the name " Bannack." It extends southward, of very unequal 

 height, to the head of the Malade Valley. Opposite the southern end 

 of this range, at the head of Marsh Creek Valley, the Malade Range 

 begins. This range consists really of two groups, the ends of which 

 overlap each other. The southern one ends just north of the " Gates " 

 of Bear River, and on the south side, some distance from the river, is the 

 northern end of the Wahsatch Range. A few degrees south of east 

 from the Portneuf Range is a group of hills, some of which attain the 

 dignity of mountains. They are north of Cache Valley, lying between 

 Marsh Creek Valley and Bear River. They will be described as the 

 southern extension of the Portneuf Range. 



On both the eastern and western edges of the Bear Lake Plateau 

 erosion has removed the plateau character, and there are hills and ridges 

 with north and south trends. This is more noticeable toward the north- 

 ern end of the plateau. The hills on the east have been named the 

 Boundary Hills, as the boundary line separating Wyoming and Idaho 

 crosses them, following aiDproximately their trend. 



Following the strike of the beds on the west side of the plateau, north- 

 ward across Bear River, we find the ridges soon rising into a range, the 

 culminating peaks of which are found in Mount Preuss and the neigh- 

 boring mountains. Farther north the strike of the beds seems to turn 

 somewhat to the westward, and a number of ridges branch from the 

 range and are seen as spurs separating the branches of the Blackfoot 

 River. 



North of Bear River Valley is Sublette Range, between Smith's Fork 

 and Thomas Fork. The strata composing these hills or mountains pass 

 under Bear River Valley as we follow the strike southward. 



The western edge of the Ham's Fork Plateau is bordered by a line of hills 

 with a north and south trend. They stand on the east side of Rock 

 Creek 'and die out to the northward, where a second range, that marks 

 the west side of Rock Creek, becomes the most prominent. The latter 

 range begins in a plateau-remnant in the angle of Twin and Rock Creeks, 

 and extends northward on the west side of Rock Creek and the east 

 side of Smith's Fork, until it loses the character of a distinct range in 

 the group of high mountains that connect the Salt River Range, the 



