ST.JOHH.] MESOZOIC AREAS TEIASSIC. 493 



include iu the latter the deposits here referred to, which embrace a thick- 

 ness of about 2,000 feet, the depositions of the period underwent marked 

 chanj>e in their lithological api^earance and the nature of the comjio- 

 nents — indeed to such an extent as to render the term red beds of no de- 

 scriptive significance in this quarter. The appearance i)resented by the 

 horizon here alluded to is shown in the section across this ridge at a 

 point but a short distance north of our southern boundary, a description 

 of which has been given iu a preceding page. 



A few miles to the north, however, in the vicinity of Station IV, there 

 occurs a set of red sandstone strata and deep-red arenaceous shales, 

 underlaid by a heavy ledge of coarse, conglomeritic, quartzitic reel sand- 

 stone, which, lithologically, bears marked resemblance to portions of the 

 '' red bed " series. But the details of the structural complications ac- 

 companying these deposits at the latter locality have not been suffi- 

 ciently investigated to warrant a more definite statement of their strati- 

 graphical relations than that based upon lithological resemblances. And, 

 so far as lithological appearances may be relied, upon, the reddish sand- 

 stones to the southwest and northwest of Higham's Peak (Station Y) 

 might be compared witli the Triassic " red beds," only these deposits oc- 

 cur outside of and apparentty overlying a belt of limestones whose fos- 

 sils are probably allied to Jurassic forms. Hence, in regard to the 

 horizons of this period in the southwest portion of the distri(5t, I can 

 speak with any degree of confidence only of the section above mentioned, 

 which crosses this ridge near our south line, and where the " red beds," 

 as such, are scarcely recognizable lithologically. 



The examinations in these deposits in the basin ridges west of John 

 Gray's Lake merely recognized their i)resence as heavy beds of red sand- 

 stones and sandy shales, while in the vicinity of the Blackfoot Eange 

 only remnants of the formation were met Tvith. But in the Caribou 

 Eange the Triassic deposits are developed under their ordinary phases, 

 and, as seen along the northeast flank of the range, they may attain an 

 average thickness. In this quarter it was found to be in many instances 

 difficult to distingaiish between these de])Osits and a series of red sand- 

 stones and shales which belong to a later formation, overlying or inter- 

 bedded with limestones containing Jiu'assic fossils. Such is the case iu 

 the mountain block between Fall Creek and Pyramid Creek, and, unless 

 these deposits reach an enormous vertical thickness at this locality, it 

 may be questioned whether the red sandstone forming the crest of Sta- 

 tion XXV ridge is not a member of the Jiu'assic rather than of the Trias. 

 To the northwest of the latter point the space occupied by these de- 

 posits probably does not exceed 1,500 feet, and it may not be above 

 1,000 feet. Above the latter locality the Trias gradually declines in the 

 present mountain border, being confined to a narrow strij^ adjacent the 

 valley and not well exposed at the points visited south of McCoy Creek ; 

 this, of course, assuming that the rusty -red sandstones and shales and 

 intercalated limestones at the latter locality and vicinity pertain to the 

 Jurassic. Eocks of this age were not recognized, iu the wider belt extend- 

 ing over across to the southwest base of the range at anj' part within 

 our territory. 



The Trias is much more prominently displaj^ed in the Snake Eiver 

 Eange, and may be traced for miles by its color characters, its outcrop 

 forming a narrow belt of variable width, extending from the Pierre's 

 Mountains in the northwest to the low mountains south of Teton Pass, 

 whence they probably extend dowTi to the Snake Eiver in the vicinity 

 of the upper entrance to the Grand Canon. In the immediate vicinity 

 of Station XL this horizon is well exposed, consisting of heavy deposits 



