ksdlich.] SWEETWATER DRAINAGE TRIAS. 107 



the Dakota sandstones. The line n o has been drawn to indicate the 

 possible limits of the lnetainorphic granite (b). North of the sedi- 

 mentary formations the section contains a body of granite (a) which does 

 not appear on the surface along that line, but crops out, holding the 

 same relative position only a very short distance farther west. 



This section presents the most interesting case of plication which we 

 observed in our district. I attribute it to the influence of the anticlinal 

 upheaval which has previously been alluded to, and is marked B on the 

 sections. The character of this section is in perfect accordance with the 

 dynamic manifestations which we are accustomed to see in this region, 

 and fully coincides in structure with the "oval quaquaversals" so fre- 

 eaiently exhibited in this section of country. The overturn of the strata 

 is an interesting and important feature. It is very much to be regretted 

 that the thick Tertiary beds to the north prevent any outcrops in that 

 direction, because the position of the Palaeozoic groups there must neces- 

 sarily afford a large amount of information upon the nature and extent 

 of the forces which produced these and other plications. 



On the Sweetwater Hills the Triassic beds are exposed again a short 

 distance west of Whiskey Gap. They there retain the same relative 

 position as heretofore. 



At Whiskey Gap we find the continuation of the Triassic beds. They 

 appear along a hue curving first north, then east, and finally southeast. 

 A prominent bluff is formed by the superimposed Jurassic atrata, below 

 which the "red beds" form a steep northerly slope, bare of vegetation. 

 An excellent opportunity was here afforded to search the strata for fos- 

 sils, but all our effort in that direction resulted merely in obtaining 

 some fucoidal plates which were very poorly preserved. At this locality 

 the division between the lower red shales and sandstones and the 

 upper lighter ones is very marked. The latter group contains white, 

 yellow, and pink sandstones, heavily bedded and interstratified with 

 thin layers of pink and light-green shales. Below that follows the 

 series of massive, highly argillaceous red sandstones. These overlie 

 thick beds of bright red shale, containing interstiata of yellow, pink, 

 white, and bluish dolomites. Yarying from 2 inches to 2 feet in thick- 

 ness, these hard beds produce slight terraces in the slopes occupied by 

 the shales. 



In every respect, except in the absence of fossils, the red beds of this 

 region closely resemble the Keuper Group of the South European Trias. 

 The " marnes irisees" of the French and "fiunte MergeV of German geol- 

 ogists agree closely. Although this group in Europe shows a great 

 paucity of fossUs, some typical genera occur which we fail to find in 

 what we regard as the Triassic beds of the Bocky Mountains. The 

 thickness of the formation east of Whiskey Gap may be regarded as 

 very near 1,000 feet. 



Curving with the Palaeozoic series, the red beds sweep around the 

 western base of the Seminole Bulls, and disappear altogether from the 

 northern slope. Skirting the border of the hills on the south side, they 

 gradually sink down and disappear in the vicinity of Sandy Creek Pass. 

 There some slight local disturbances, probably nothing more than unim- 

 portant faults, have caused a change of the dip, which is generally to 

 the southward. 



JURA. 



Yarying but slightly in character from the Jurassic beds east of the 

 Wind Biver Bange, we find the same formation exposed on the Sweet- 

 water drainage. Essentially the arrangement of strata is the same, 



