rEALE.| INTRODUCTION — MOUNTAINS VALLEYS. 515 



Wyoming' Range, and the Absaroka Ridge. This range really joins the 

 latter, for the drainage of Smitli's Forlv and Labarge Creek separates 

 them both from the two ranges that lii; to the northward. 



The monntains about the sources of tlie Labarge and Smith's Fork 

 are Aiery irregular topograpbically. Tlio drainage flows sometimes with 

 the strilio of the rocks and sometimes cuts across at right angles, so that 

 there appears to l)e no system either in the drainage or the mountains, 

 except that the strike of the rocks is ap])roximately north and south, 

 and where erosion has not worn down the beds the ranges have trends 

 corresponding to this strike. 



With the exception of the Wind River Range, the mountains of the 

 district belong to the Wahsatch system. 



V{(Uei/fi. — Owing to the isolated character of the mountain ranges, we 

 have numerous valleys l.ving between them. In addition to the river 

 valleys, or those due to the erosive action of the rivers, there are wider 

 areas which corresiwnd to the parks of Colorado. The impression made 

 upon the mind as these broad valleys are seen from the mountains is 

 that they must once have been occupied by lakes above which many of 

 the smaller groups of mountains must have lisen as island masses at 

 least when the lakes were at their highest level. These vaUeys form 

 some of the I'ichest agricidtural areas in the district. The principal ones 

 are Ham's Fork Basin, Salt River Yalley, Bear River Valley, Bear Lake 

 Valley, Soda Spring Valley, Hollow Hand, Basalt Valley, Upper Port- 

 neuf Valley, Lower Portneuf Valley, Marsh Creek Valley, Malade Valley, 

 Cache Valley, and Gentile Valley. Of these Cache Valley is the most 

 celebrated, having been settled many years ago by the Mormons. It is 

 now well cultivated and has many flourishing towns. Bear Lake Valley 

 is also comparatively well settled, although it does not appear to be as 

 favorably adapted for agricultural purposes as Cache Valley. Basalt 

 Valley and the " Hollow Hand " are floored with basalt which came 

 from craters that still exist in the region. All of these valleys will be 

 treated of in detail in subsequent portions of this report and in the report 

 of Mr. Gannett. 



GEOLOGICAL FORMATIONS. 



With the exception of the limited granitic areas along the western 

 slopes of the Wind River Mountains in the northeastern corner of the 

 district, and the prominent basaltic flow^s filling the valleys in the Black- 

 foot and Up])er Portneuf regions, the rocks of the district are sediment- 

 ary. The following list gives aU that are found in our district : 



Archaean Metamorphic. 



Silurian 1 



Carboniferous 



Jura-Trias jT"^«^'^- 



) Jurassic o,,. , 



Cretaceous )> Sedunentary. 



Post-Cretaceous ? Laramie Group 



Tertiary • 



Quaternary ^ 



Basalt Volcanic. 



These will be considered in detail in the succeeding chapters, when 

 the subdivision and thicknesses will be enumerated. 



