WP a Le ie or cap te geen ee nn 
a 5h ee inet tt 8): ee ee, oe 5 ae ben Tes a Hy 
: one . Swigh i i. A Me RE ty 2 eS wit Wii 
' a : ar ” + 36" a? Tina? Br: 
. * rw 
. 7 Bo bs 
‘ s 7 ie 
(228 
2 ae ‘ 
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ee 
74 '  B. N. A. BOUNDARY COMMISSION. en 
‘ee 
in correspondence with the increased quantity of calcareous matter a 
other rocks. EB ae 
165. Red beds overlying the Carboniferous limestone are frequently ae 
found in the western territories. Some of them, from their fossils, are 
certainly Jurassic, while others are Triassic, or perhaps Permian. They — 
have been already more than once referred to. Near the head waters of 
the Cheyenne River, in some localities, between the Carboniferous lime- 
stone and the supposed Jurassic red beds, they attain a considerable thick- 
ness, and hold gypsum,* the accumulation of which implies conditions 
similar to those causing the briny lakes, shown to have existed after the 
deposition of the great limestone in the Boundary sections. Near the head — 
of Wind River, the Carboniferous rocks are followed in ascending order | 
by 150 feet of arenaceous beds, and greyish, ash-coloured sandy clays; then 
by a great series of reddish, purplish, yellowish, and grey beds, sand- 
stones, flaggy ‘limestones and marls. Ripple-marked surfaces are com- 
. mon, and organic remains prove the rocks to be Jurassic. : 
; 166. Of the mountains about the sources of the Missouri, the Big 
Horn, and Wind River ranges, Dr. Hayden wri “A series of arena- 
ceous beds, which we have called the red arenaceous deposits, or Triassic, 
form one of the most conspicuous features of the geology along the flanks 
r of both sides of the principal ranges of mountains, and are almost always 
} | present.” They are “ sometimes called saliferous or gypsum-bearing beds, 
| from the fact that they contain both salt and gypsum, the latter mineral 
oftentimes in great quantity.” A portion of these red beds is believed to 
be Triassic, but above them lies a series of marls, or arenaceous marls, of 
light or ashen grey colour, with Jurassic fossils.f 


167. Though the absence of fossils in the rocks of the mountains 
near the forty-ninth parallel, wherever I have examined them, pre- 
cludes the fixing of their horizons by paleontological evidence, it seems 
possible to correlate them lithologically and stratigraphically with 
: similar beds in other and better known regions of the west. This means 
| of correlation appears to be a pretty reliable one, from the great general — 
: constancy in succession and character of the stratified rocks of the interior 
. and western part of the continent. 
c 168. On comparing the sections, it would hardly seem to admit of 
| * Geological Report Yellowstone and Missouri Expedition., p. 76. t Ibid., pp. 82-83. 
; t U.S. Geol. Surv. Territ. 1857-59., pp. 112-113. 


appears to be wanting in the Uinta section, but its introduction would be Bar ; ‘ 
