sT.joiLX.] GROS VENTRE RANGE. 451 



To tlie northeast of Station XLYI, in tlie opposite face of the deep 

 broad ^orge in that direction, the strata, Carbon ilerons, form a low arch. 

 Folhnvin^- along this high ridge, ^vhich is apparently the same that 

 forms the north tiank of the range along the south side of the mountain 

 course of Gros Ventre Eiver, to a point about east-southeast of XLVI, 

 the escarpments delining tlie deep drainage channels reveal at intervals 

 magnificent sections of the sedimentaries incoiniection with a remarkably 

 uniform uplift which appears to hold about the same magnitude through- 

 out the extent indicated, as seen from Station XLIV. Along the south 

 or soutlnvest Hank of this told the strata plunge steeply, in places vertical, 

 elsewhere flagging gigantic ridges. But in the op])osite slope the same 

 deposits dip much more gently in the direction of the Gros Ventre Val- 

 ley, and appear to be faced with an extensive development of "red 

 beds," whose edges often appear in the crests of the huge ridge, which 

 shows in places the whole Pala?ozoic series, even the Archa'an nucleus 

 appearing in low outliers in the bottom of the intermoutaue valley. 



The northwestern terminus of this anticlinal fold, or such as the erosion 

 of Jackson's Basin has determined it to be, apparently lies to the south 

 of the debouchnre of the Gros Ventre Eiver, where its appearance will 

 be described in connection with the notice of the observations in the 

 vicinity of Station XLVI. In this part of the range the lower interme- 

 diate ridges to the eastward are mainly made up of the Silurian limestones 

 and quartzite. The former show the rusty weathered exposures so 

 characteristic of the Quebec Group beds in the Teton Monntains, while 

 the su])erimposed niagnesian limestones are accompanied by overlying 

 red-stained limestones with shaly partings so frequently associated with 

 the exposures of the Niagara and the inferior member of the Carbonif- 

 erous in the same region. These strata dip gently to the east or north- 

 eastward off the crest of the uplift, whose axis at one i)oint cidminates 

 near the pi"esent summit of Station XLIV. 



Towards the southeast these beds gently rise, where they appear low 

 on the slope descending from a still more lofty and rugged Archtean 

 peak some live miles about south-southeast of Station XLIV. A very 

 iiTCgular deej) saddle connects this peak with XLIV, which bears for 

 a part of the way a covering of Silurian beds dipping quite steeply south 

 or southeastAvard, in which dii'ection they are followed by the Car- 

 boniferous limestones, and in the extremely broken region still beyond, 

 stretching across what has the appearance of a profound narrow valley 

 which here intersects the mountains, an enormous development of pale 

 and deep-red strata occiu's, the structural featiu'es of which, however, 

 it was impossible satisfactorily to make out. 



On the northeast tlanlc of this high iVi*ch?ean peak an interesting flexure 

 in the Primordial nisty buft" beds is finely displayed, the imcleal rocks 

 sliowing all the peculiar featmes of weathering characteristic of the 

 Archaean series. This latter fold is in line Avith the above peak and 

 Station XLIV, and doubtless pertains to the same general uplift. The 

 Station XLIV uplift dift'ers from that previouslj^ mentioned a few miles 

 to the northeast, and Avitli which it is probably more or less i>arall('l, in 

 the less regular distribution of the forces that (;aused the disturbance, 

 and which, but for the immense erosion which has bared its real <diar- 

 acter, might be mistaken for so many local quaquaversals or a bulging 

 of the sedimentary beds. While, indeed, a section carried along the 

 saddle from one peak to the other represents a broad synclinal depression 

 filled with sedimentary deposits, a transverse section across the saddle 

 ridge also reveals its antichnal stnicture, and at the same time its probable 

 intimate relations to the culminating peaks which mark the sites of the 



