ssdlich.] SWEETWATER DRAINAGE PERMIAN. 105 



tamed at all, are derived from tlie red color of tlie Triassic Group. "While 

 discussing this, a section will he given which cuts this region. 



Directly east of Whiskey Gap the Carboniferous Group reaches the 

 greatest development and most prominent position in our district.* 

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

 west, the strata are first found low down, but soon make a turn to the 

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

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

 characteristic appearance. The white, blue, and yellow dolomites and 

 limestones of the Carboniferous formation produce high, almost vertical, 

 walls, separated by narrow gullies which are filled with loose debris. 

 Retaining a strike a little south of east, we follow the Carboniferous 

 Group throughout the Seminole Hills to Sandy Creek Pass. Ketaining 

 a very steep southerly dip, 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 hi the region 

 to which this chapter is devoted, we found that the limestones were 

 thoroughly impregnated with siliceous matter. As in the W'ind Eiver 

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

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

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

 and very poorly preserved. Crinoids make an exception as to their com- 

 position. In the Seminole Hills the thickness of the Carboniferous Group 

 appears to be about 2,100 to 2,200 feet, perhaps a little more. The posi- 

 tion it occupies renders it difficult to make an accurate estimate. 



Permian Group. 



About this group but very little is to be said. It is analogous to the 

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

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

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

 with the Carboniferous outcrop shown in Section XI the Permian strata 

 are found in the low valley directly west of the main mass of limestones. 

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

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

 ceed, much to my regret, in obtaining even a single specimen that could be 

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

 direct superposition of beds belonging to the Sweetwater Group. Farther 

 east the Permian occupies a position directly above the blue limestones, 

 as heretofore, and takes part in all the flexures and plications that have 

 been described as occiuring hi connection therewith. A maximum thick- 

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

 Farther west the thickness diminishes to less than 200 feet. 



MESOZOIC FOBMATKMS. 



TRIAS. 



Traveling downstream in the Sweetwater region, we meet with the 

 first outcrop of Triassic beds at the western end of the Sweetwater Hills. 

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

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

 covered by Tertiary beds. As usual, they show the typical red sand- 

 stones and shales, amounting in thickness to* about 600 feet. From Section 



