teale.I INTRODUCTION MOUNTAINS VALLEYS. 515 



Wyoming Range, and the Absaroka Ridge; This range really joins the 

 latter, for the drainage of Smith's Fork and Labarge Creek separates 

 tliem both from the two ranges that he to the northward. 



The mountains about the sources of the Labarge and Smith's Fork 

 are very irregular topographically. The drainage flows sometimes with 

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

 there appears to be no system either in the drainage or the mountains, 

 except that the strike of the rocks is approximately 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. 



Valley s. — Owing to the isolated character of the mountain ranges, we 

 have numerous valleys lying between them. In addition to the river 

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

 areas which correspond 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 risen as island masses at 

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

 some of the richest agricultural areas in the district. The principal ones 

 are Ham's Fork Basin, Salt River Valley, 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 m subsequent portions of this report and in the report 

 of Mr. Oanuett. 



GEOLOGICAL FORMATIONS. 



With the exception of the limited granitic areas along the western 

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

 district, and the prominent basaltic flows filling the valleys in the Black- 

 fopt and Upper Portneuf regions, the rocks of the district are sediment- 

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



Archaean Metamorphic. 



Silurian "i 



Carboniferous. 



i 1 



Jura-Trias { T 



I Jurassic. 



Sedimentary. 



Cretaceous 



Post-Cretaceous ? Laramie Group 



Tertiary 



Quaternary ^ 



Basalt «. Volcanic. 



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

 the subdivision and thicknesses will be enumerated. 



