EXDLicH.] S^VEETWATER DEAIXAGE PERMIAN. 105 



tained at all, are derived from the red color of the Triassic Group. While 

 discussing" this, a se(;tion will be given Avhich cuts this region. 



Directly east of Whiskey Gap the Carboniferous Group reaches the 

 greatest development and most prominent position iu our ilistnct. 

 Standing on end, or showing a dip of 80° to 85° to the south and south- 

 Avest, the strata are first found low down, biit soon make a turn to the 

 southeast and occupy the summit of the hills. Their mode of weath- 

 ering and the position of the strata give the Seminole Hills a very 

 characteristic api)earance. The white, blue, and yellow dolomites and 

 limestones of the Carboniferous formation jiroduce high, almost vertical, 

 v.'alls, separated by narrow gullies which are filled Avith loose debris, 

 Ectaining a strike a httle south of east, Ave follow the Carboniferous 

 Group throughout the Senunole Hills to Sandy Creek Pass. IJetaining 

 a A'ciy steep so^ltheliy dij), it is gradually crowded toward that direction 

 by the increasing bulk of the granites directly to the north. Inclining 

 with the strata, but diminishing in dip, are younger sedimentary beds. 



Wherever we find the Carboniferous Group represented in the region 

 to Avhifh this chapter is dcA^oted, Ave found that the hmestones were 

 thoroughly impregnated Avith siliceous matter. As in the Wind Eiver 

 district, so here too, there are a lumiber of varieties of quartz to be seen, 

 occurring in the form of concretions, geodes, and small seams. All the 

 fossils, Avhich are the same as those found to the northeast, are silicified 

 and A'ery poorly ])reserved. Crinoids make an excei)tion as to their com- 

 X)osition. In the Seminole Hills the thickness of the Carboniferous Group 

 api)ears to be about 2,100 to 2,200 feet, perhaps a httle more. The posi- 

 tion it occux)ies renders it difficult to make an accurate estimate. 



Fermian Grouj). 



x\bout this gToup but A'cry little is to be said. It is analogous to the 

 occurrence on Twin Creek, Avhich has been described in the preceding 

 chapter. On the upper portions of the SweetAvater it is entirely hidden 

 by Teitiary beds, and first appears in the Sweetwater Hills. In connection 

 with the Carbonifercms outcrop shoAvn in Section XI the Permian strata 

 are found in the h)AV A'allcy dhectly Avest of the main mass of limestones. 

 At that point they are composed of gray, greenish, and pink sandstones, 

 with some shales, and shoAV indistinct remains of plants. I did not suc- 

 ceed, nuich to my regret, in obtainhig even a single specimen that could be 

 identified. Here the thickness of tlie group is rendered doubtful by the 

 du-ect suiK'rposition of beds belonging to the Sweetwater Grouji. Farther 

 east the P(.'rmian occupies a position directly aboA^e the blue limest^mes, 

 as heretofore, and takes part in all the llexures and pUcations4hat liaA'e 

 been described as occiu-ring in connection therewith. A maximum thick- 

 ness of neaily 300 feet is reached at some of the more easterly localities. 

 Farther Avest the thickness diminishes to less than 200 feet. 



MESOZOIC rOEMATIOKS. 



TRIAS. 



Traveling doA\Tistream in the Sweetwater region, we meet Avith the 

 first outcrop of Triassic beds at the Avestern end of the SweetAvater Hills. 

 There they are overlying Carboniferous strata conformably, but soon dis- 

 appear, sinking down low toward the east, Avhile westward they are 

 covered by Teitiary beds. As usual, they sIioav the typical red sand- 

 stones and shales, amounting iu thickness to about GOO feet. From Section 



