eotlich.] SWEETWATER REGION RESUME. 117 



crossed in the region of its lowest depression by a chain of lnetaniorphic 

 origin. This chain, so far as the evidence collected permits ns to speak, 

 is the direct result of an extensive upheaval along a curved line trend- 

 ing from north to south, southeast, and east. It seems surprising at 

 first that neither the older schists nor the prozoic granites are brought 

 to the surface by this extensive action. We must take into considera- 

 tion, however, the thickness of the youngest metamorphic series, as ex- 

 hibited farther northwest, and it will be ajrparent that, unless consider- 

 able variations of the vertical dimensions occurred within a compara- 

 tively short distance, the older series must remain hidden. Upon recog- 

 nizing the structure of the hills formed by this southeasterly outcrop of 

 metamorphics, we find in them a strati graphical arrangement analogous 

 to that of the Wind River Eange. Here, as there, we have a predomi- 

 nance of the one side of the anticlinal fold. In other words, the axis of 

 upheaval does not stand vertical. This fact is shown not only by the 

 non-appearance of the repetition of strata on its opposite side, but is in- 

 dicated by the shape of the area of the metamorphics. Essentially this 

 forms a wedge, showing that the force applied was not an equal one at 

 all points. Were it so, then the outcrop would essentially represent a 

 symmetrical figure. 



A second disturbance of metamorphic rocks is due to the more easterly 

 anticlinal upheaval. In this instance the prozoic granites appear to 

 Lave been affected somewhat thereby. Along a definite line — one coin- 

 ciding with the longitudinal axis of the fold, we observe an exposure of 

 metamorpliic beds which have undoubtedly been raised from their nor- 

 mal position by some locally-acting cause. This fold again may be 

 traced farther to the southeast, forming a curve nearly parallel with the 

 first one. Where appearing in an unmistakable manner at the surface, 

 we find it to be analogous in direction, form, and results with the former. 

 Reconstructing, then, a surface-picture of the region of the Sweetwater 

 prior to the invasion by Tertiary waters, we obtain a result totally differ- 

 ing from that presented to-day. Instead of a general slope to the east- 

 ward we find that the region now occupied by the valley was cut by two 

 ridges trending obliquely across it. Of these the western one was the 

 higher. For some distance near the line now occupied by the river 

 existed the divide from which the drainage flowed to the northwest and 

 south. Farther downstream this line shifted toward the southeast and 

 the drainage was mainly to the north. Bare and rugged, as to-day, the 

 Granite Hills rose high above the surrounding country, never, probably, 

 having been entirely under water. This distribution of drainage ac- 

 counts for the primary erosion we find both to the north and south of 

 the Sweetwater region, more particularly in the former direction. The 

 dividing line was, in all probability, the eastward extension of the axis 

 along which the Wind Eiver Eange was elevated. Thus prepared, hav- 

 ing much of the sedimentary material removed by erosion, the successive 

 valleys were ready to receive the influx of Tertiary waters. The analogy 

 of the deposits with those found on Wind Eiver indicate that a former 

 connection between the two may have existed. They furthermore sub- 

 stantiate the conclusions drawn from purely stratigraphical occurrences, 

 that the main drainage-connection of this region was to the north and 

 northeast. 



So far as the classification of the metamorphics is concerned, which 

 here enter into consideration, we may refer them to the Huronian system. 



With regard to sedimentary formations, we may say that their appear- 

 ance, which in some instances seems contradictory, is fully explained 

 by the movements in which the older rocks have participated. When 



