FKDUcii.] EAST OF WIND EIVER RANGE CARBONIFEROUS. 79 



disappears under tlie Tertiary beds of the Sweetwater Group. Toward 

 the north it can be traced between the eastern end of the Carboniferons 

 limestones and tlie western edge of the Mesozoic red beds. Siniihir in 

 lithok)gical constitution, it closely follows the outlines produced by ero- 

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

 a simihirity of weatliering 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 unbrokenly 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 tliem 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 Pahieozoic strata along a line from the 

 Wind Eiver IMountains 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 liaA'e been treated of above. 



The annexed section (Section I) runs from the Wind Eiver Eange to 

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

 the section the arrangement of prepahieozoic rocks is represented. Upon 

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

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

 we lind the granites (e) of the main chain. The schists forming the 

 steep eastern slo]ie {bb) are given. Metamoii)hic granite {(1) forms 

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

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

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

 lind the series of Subcarboniferous strata- {{j) occupying the western base 

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

 stones {h) 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 Ave lind the Permian strata (/). AboA'e them the 

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

 being indicated on the drawing. 



By folloAving the line showing the upper termination of Permian beds 

 (/.) we will lind that the easterly di^i gradually diminishes, farther on is 

 entirely obliterated, and then turns into a westerly one. We haA'e, then, 

 the formation of a spiclinal fold Avithin this group. On the line of our 

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

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

 massive blue limestone (//), Ave lind that the same conditions exist here. 

 When Ave reach the Subcarboniferous strata (r/), Ave 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 

 cuhnination of the latter is reached on the summit of Sheep ]Mountain. 

 From there the beds tall off toward both AA'est and east. On the latter 

 side Ave lind the counterpart of AAiiat Avas seen from the base of the third 

 chain toward the east. Superim])osed upon the Permian are a number 

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

 out this entire section the Aarious beds show a remarkable unilbrmity of 

 thickness and lithological character. They are entu*ely conformable and 

 shoAV no distiu-bances of continuity. Viewing the elcA'ation of Sheep 

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

 thickness of strata has been produced. From eA'idence obtained in the 

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

 are probably to be foimd directly underlying the Subcarboniferous grouj) 

 at Sheep Mountain. 



