18 GEOLOGICAL SURVEY OF THE TERRITORIES. 



raiig'o of monntains, wliicli we call the Wahsatcli Ean<?e, was orij2:inally 

 a complete anticlinal fol<l, then it forms a line illustration of the erosive 

 effects of water in comi)aratively modern .^eolo^ical times, which for so 

 great a distance has swept away the entire half of the range. We may 

 alsosai)i)ose that beneath the great thickness of snperlicial deposits which 

 com])ose the terraces, the etlges of the strata which form the west side of 

 the fold now exist, dipping beneath the valley, but rising again on the side 

 of someotherfoid in thebasin as Antelope Island, &c. If our suppositions 

 are true, the next question that at once arises in the mind would be as to 

 the cause of this tremendous erosion. We have neither space nor time, 

 even if we had all the facts, to discuss this most interesting ])roblem in 

 the present report, but we promise our readers to recur to it again at 

 sx)me future time. We may, however, supi)0se that the Wahsatch Range 

 formed the eastern shore of the great inland sea which, at a compara- 

 tively modern geological period, covered the entire basin. How great a 

 depth it ever attained it is dilticult now to determine, but at some i)eriod 

 its waters must have reached high upon the sides of the loftiest ranges, 

 so that they ai)peared scattered here and there as islands projecting 

 above the surrounding waters. It is probable that during the gradual 

 decrease of the waters of this lake the greater portion of the erosion of 

 the caiions was performed. Up the valleys of all the little streams that 

 lead into Salt Lake are the terraces and peculiar lake-deposits, showing 

 that the lake- waters extended far up beyond the wall-like shores. It is 

 altogether probable, from the proofs which are found everywhere in 

 these valleys, that tliere were continued oscillations in the depth of the 

 lake-waters, a rise and fall, and long periods when the waters would 

 remain at a hxed level. If we take the })osition that the present resuJts 

 of erosion have all been brought about b.\ the slow destruction of the 

 rock- materials by water, and that this t'ovce is produced by the agita- 

 tion of the waters beating upon the shores, then we may supi)ose that 

 the winds from the west and southwest prevailed an<l gave to the waters 

 the force that slowly produced the erosive results that we now see on 

 the east and iiortheast sides of the valley. Other causes may have 

 united in producing" these results, which we hope to present at some 

 other time. 



From Salt Lake Valley the Snake Elver division of the survey pro- 

 ceeded northward, by way of the i)aralk*l valley, to the valley of Snake 

 Eiver near Fort Hall. In my report for jl871, I recorded most of our 

 observations on this route, and now refer the reader to the moR-e com- 

 plete account of Professor Bradley in this report. 



xVs we proceed northward toward the divide between the waters of 

 the basin and Snake Eiver, the quartzites seem to diminish and the cal- 

 careous beds to increase, and the conditions seem to have been more 

 favorable for the preser\'ation of organic remains. The Carboniferous 

 limestones seem to be well developed, and charged in some places with 

 characteristic fossils. On the divide between Eoss Fork and Lincoln 

 Valh\v, near Fort Hall, Professor Bradley obtained a stray mass of 

 lim,eston(', in which was crowded together a mass of minute fossils, nearly 

 forty species, many of them identical Avith species found at Spergen Hill, 

 Indiaiui. (See Catalogue of Fossils, by Mr. Meek.) This is certaiidy a 

 most important discovery, extending the existence of this formation 

 very much farther west than it had ever been known before. Previous 

 to this time not a single species of this group had been found west of 

 Iowa or Missouri. It indicates that quite probably, if the great mass of 

 Paleozoic roolvs of the \Vest could be examined in detail, they might be 

 separated into numerous subdivisions, as we find them where they have 



