FKDucn.] EAST OF WIND EIVEE EANGE CARBONIFEROUS. 79 



disappears under the Tertiary beds of the Sweetwater Group. Toward 

 the north it can he traced between the eastern end of the Carboniferous 

 limestones and the western edge of the Mesozoic red beds. Similar in 

 lithologica! constitution, it closely follows the outlines produced by ero- 

 sion in tbe latter. Subjected to the same effects, these two groups show 

 a similarity of weathering and of type of removal that renders the Per- 

 mian liable at many places to be overlooked. Northward a thinning 

 out of its strata may be observed $ but it continues uubrokenly through 

 our district to the forty-third parallel. At such points where the Car- 

 boniferous strata have been brought to the surface we observe the Per- 

 mian strata in the same relative position to them as they are on Twin 

 Creek. As a rule they have permitted the formation of depressions run- 

 ning parallel with the strike of the strata. In order to make clear the 

 stratigraphical arrangement of Pakeozoic strata along a hue from the 

 Wind River Mountains to Sheep Mountain, a section is here introduced. 

 It will explain more readily than can be done by words the relative po- 

 sitions of the groups that have been treated of above. 



The annexed section (Section I) runs from the Wind River Range to 

 Sheep Mountain in a direction nearly east. In the western portion of 

 the section the arrangement of prepaheozoic rocks is represented. Upon 

 the prozoic granite (a) rest the oldest metamorphic schists (b). These 

 contain the metalliferous veins, which are indicated. Above the schists 

 we find the granites (c) of the main chain. The schists forming the 

 steep eastern slope (bb) are given. Metamorphic granite (d) forms 

 the chain of foot-hills. Descending with this we reach the Potsdam 

 sandstone (e) directly overlying it. A pinching out of the calciferous 

 series (/) has been represented by the two converging lines. Above this we 

 find the series of Subcarboniferous strata (g) occupying the western base 

 of the outlying third chaiu. Massive beds of Carboniferous blue lime- 

 stones (/<) make up the main portions of the hill and slope eastward to- 

 wards the younger sedimentary region. At the eastern edge of the ex- 

 posure of this group we find the Permian strata (i). Above them the 

 Red Beds (A). Thus far the dip has been a steady easterly one, its angles 

 being indicated on the drawing. 



By following the line showing the upper termination of Permian beds 

 (?) we will find that the easterly dip gradually diminishes, farther on is 

 entirely obliterated, and then turns into a westerly one. We have, then, 

 the formation of a synclinal fold within this group. On the line of our 

 section the beds are broken off and no connection exists at that point 

 with those farther east. Tracing in a similar manner the flexures of the 

 massive blue limestone (/?), we find that the same conditions exist here. 

 When we reach the Subcarboniferous strata (//), we are enabled to form the 

 connection to the east. In that direction a sharp anticlinal axis succeeds 

 the synclinal fold, carrying the strata up to considerable elevation. The 

 culmination of the latter is reached on the summit of Sheep Mountain. 

 From there the beds fall off toward both west and east. On the latter 

 side we find the counterpart of what was seen from the base of the third 

 chain toward the east. Superimposed upon the Permian are a number 

 of Mesozoic formations, which will be considered further on. Through- 

 out this entire section the various beds show a remarkable uniformity of 

 thickness and lithological character. They are entirely conformable and 

 show no disturbances of continuity. Viewing the elevation of Sheep 

 Mountain, we see that thereby an S-shaped flexure. of a considerable 

 thickness of strata has been produced. From evidence obtained in the 

 vicinity, we are enabled to say that the Potsdam sandstones are prob- 

 are probably to be found directiy underlying the Subcarboniferous group 

 at Sheep Mountain. 



