st. johx.] BUFFALO FOEK EEGION. 465 



side of the stream, in which a thickness of a couple of hundred feet of 

 yellowish and drab arenaceous clays and sandstones outcrop, passing 

 under the above deposits, and which belong to the series included in 

 the section in the outlying slopes south of Station XLVIIL The gen- 

 eral similarity of the heavy drab deposits in the crest of the ridge with 

 those in Mount Leidy, strongly suggests their probable stratigraphic 

 identity, and to which belongs the remnant capping Station XL VIII. 



To the left of the above mountain is seen another high, massive sum- 

 mit forming the divide a few miles to the west, the eastern face of which 

 is broken down in cliffs of dark, rusty -weathered strata inclining gently 

 west or southwestward, the nature of which could not be satisfactorily 

 made out at this distance. From the low Tertiary uplands south of 

 Buffalo Fork the southern aspect of the latter mountain is rounded, dis- 

 playing brownish, earthy-looking deposits. From this point of view the 

 mountain is seen to form one of the heights of the divide, in a depression 

 of which between this and the first-mentioned ridge appear more dis- 

 tant mountain-crests to the north, bearing reddish-brown ledges, and 

 which may belong to the volcanic-crowned ridges found by Professor 

 Bradley on the northern edge of this divide at the head of Coulter's 

 Creek. In the latter quarter he observed the prevalence of" gray tra- 

 chytic lavas and red basalt" and " rapidly-disintegrating volcanic rocks, 

 mostly conglomerates of trachytic porphyry, obsidian, &c," the latter 

 evidently belonging to the volcanic series which is so largely developed 

 in the watershed farther east. Light-grayish deposits, probably sand- 

 stones, are exposed in the summits of the more massive and mountain- 

 ous portion of the divide still to the west, where then outcropping edges, 

 facing the south, are nearly horizontal. Farther on, the mountain-crest 

 shows similar light-grayish strata inchned gently in the direction of 

 Jackson's Basin, and just beyond they again rise to the westward, 

 forming a shallow synclinal in the vicinity of the elevated summit which 

 marks the angle at the point where the divide trends round more to the 

 north. 



Throughout this portion of the divide there are no evidences of great 

 disturbance, the dips apparently not exceeding 15°, and generally much 

 less. But farther north, where the ridge sinks beneath the volcanic 

 plateau of the lake region in its northwestern flank, opposite the conflu- 

 ence of Lake Fork and the Snake, the sedimentary deposits rise at a 

 steep angle to the northwest, bringing to view a belt of Palaeozoic in the- 

 foot of the mountain. The latter is described by Professor Bradley, from 

 observations made by Mr. Taggart, as follows :* "At the base lie about 

 200 feet of white and light-gray quartzites, overlaid by from 500 to 600 

 feet of light-drab and dark-gray limestones, and about 100 feet of gray 

 sandstones, followed by heavy beds of red, shaly sandstones, apparently 

 the same as those seen higher up the river. I am not satisfied as to the 

 age of either the limestone or the quartzite " [colored on the map accom- 

 panying the report, Quebec and Potsdam]. " The ridge is capped by- 

 beds of porphyritic trachytes, having a dip of about 30° to the south- 

 east, while the limestones beneath dip about 40° in the same direction,, 

 showing that their tilting commenced before the deposition of the tra- 

 chytes." About seven miles above the mouth of Lake Fork, Professor 

 Bradley notes the occurrence of "red, shaly sandstones, containing no> 

 fossils beyond indistinct fucoidal markings, which, are referred with 

 doubt to the Triassic period. The gray beds of the lower part of the* 

 series make their appearance in the lower end of the canon." These de- 



* U. S. Geol. Survey of the Territories, 1872, p. 259. 

 30 GS 



