ENuucii.] EAST OF WIND EIVER RANGE — TRIAS. 81 



Within our district the Triassic beds have reached a good development 

 and are exposed very frequently. One of the best known occurrences 

 east of the Wind Kiver Eange is that of lied Canon. If we stand on 

 Twin Peak and look towards the northeast, we will have before us a 

 gradiuil slope down to the narrow valley of Beep Creek. Eising imme- 

 diately upon the eastern bank of this small stream Ave see a steep red 

 wall, continuing for the distance of several miles. The remarkable bril- 

 lian(5y of color renders it a very striking feature of the landscape. An 

 examination of this wall \Aall reveal the fact that it is comjjosed almost 

 entirely of bright red shales and sandstones. Near the base of the series 

 we lind red sandstones, highly argillaceous and rather thiidy bedded. 

 A little higher up the strata grow thicker and somewhat coarser. They 

 are separated from each other by thin layers of very fine-grained shale. 

 Thus far we have seen about the lower third of the group. Above that 

 thick beds of red shale set in, weathering in characteristic forms. Numer- 

 ous vertical seams aid the progress of erosion. Near the top of these 

 shales we find thin beds of sandstone, more or less coarse grained, usu- 

 ally red, but sometunes x>ink and white. Throughout the shales Ave meet 

 with narroAV " ledges " composed of very compact gray and yellow dolo- 

 mite. Small cavities and seams in them are lined by crystals of the 

 same mineral. AboA^e the shales and thinly bedded sandstones, we 

 again obserA^e massiA^e strata of the latter. Shales close the group. 

 Both near the base and the top, isolated layers of pink and Avhite sand- 

 stones may be noticed. As a rule, we may accept two horizons for 

 coarse-grained sandstones, although they are essentially a local product. 

 Near the base, and again in tbe upper third of the series, they are found. 

 The thickness of the Triassic beds at this locality may be regarded as 

 about 800 feet. 



In this region, as well as elsewhere within our district, we find the- 

 Eed Beds du'ectly OA^erljing the Permian strata, and covered by Jm^assic 

 limestones. From the section previously given, it wiU be seen that the 

 Triiissic beds (A") are perfectly conformable Avith both under and overly- 

 ing groups. Following the outcrop southward from Eed Canon, we 

 find that the red sandstones and shales retain a prominent position luitiL 

 closely approaching the Sweetwater group. There the southAvesterly 

 direction of the anticlinal axis causes a j)reponderance of paljeozoic 

 rocks, the greater portion of the younger groups disappears, and the Eed 

 Beds are crowded mto a narroAv si>ace. Finally they disappear under 

 the Tertiary strata, not again to be exiiosed until many miles farther to 

 the eastward. North of Eed Caflon the Triassic strata first make a tiu'n, 

 which brings them high up on the eastern slope of the third cham. 

 Eeceding again they form a series of blufis along the base of this chain 

 until they pass beyond the limits of our district. So far as the out-crops 

 have been described the strata have a general dip east and northeast,, 

 amountmg to 32° to 30°. At the highest point reached by them this 

 angle is somewhat increased. 



We find that along this line of exposure the Triassic strata presents 

 but a small area. Eapidly remoA^ed by erosion on the west -side, they are 

 coA'ered by younger formations a short distance eastward. Eeverting 

 again to Section I, it Avill be seen that the Eed Beds form prominent blufis 

 on either side of Sheep Mountain. On the east side they present a 

 steep, quadrich'ciilar Avail similar to that on Deep Creek. From there- 

 southward the blutt-line folloAvs the strike of the Carboniferous lime- 

 stones, until finally both are lost under the beds of the SweetAvater 

 Group. North of Sheep Mountain we find different conditions,, hoAvever. 

 A thickening of the entire series is noticeable, Avliich reaches OA'er 1,000 

 feet. Following doAvn TAvin Creek to its j unction with the Little Popo-Agie, 

 6 a S 



