102 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



to the eastward, we meet witli the first extensive outcrops on the north 

 side of these hills, at the locality which is cut by Section YII. Eesting 

 upon a narrow band of granite, the red quartzites stand nearly vertical, 

 decreasing slightly in dip as they continue southward. Near a small creek 

 in that region they have been raised to an elevation of about 500 feet, 

 forming a prominent hill. To this region tliek thickness is about 400 

 feet. As in the ^dcinity of the mountains, so here Ave observe a number 

 of variations in the quartzites. Generally they show a rusty red color, 

 occasionally deepening into a dark brown. Near the top some hghter 

 strata occur, of pink, yellow, and white color. From there they do not 

 appear again in the hiUs until we reach Elkhorn Gap. 



Near the western termination of the Granite Hills a prominent anti- 

 clinal upheaval is observed in the sedimentary beds just north of the 

 Sweetwater plateau. Its continuation extends toward the southeast. 

 South of the i^oint where the disturbed beds join the plateau edge, a 

 small caiion is formed, through which the river finds its way. The walls 

 of this are composed mainly of Potsdam quartzite. Although the rent 

 does not occur exactly on the vertical axis of the anticlinal which reaches 

 this region from Sheep Mountain, I am inclined to ascribe its formation 

 to this cause. It is apparent that the strata here, which dii3 at angles 

 varying from 15° to 20° to the north and northeast, form the northern 

 side of the anticlinal, which in the sections has been marked A. For a 

 short distance only are the quartzites here exposed, disappearing under 

 the beds of the Sweetwater Group. 



Directly east of Elkhorn Gap, on the north side of the hills, we find 

 a rather extensive outcrop of the same strata. Eising at first appa- 

 rently directly out of the Tertiary beds adjoining, we soon find the cause 

 of their elevated position by examining the country a very short dis- 

 tance farther east. Dipping toward the northeast at an angle of 80° to 

 85°, the quartzites form sharp, prominent hills. We find them resting 

 upon metamorphic granites, which gradually increase in height and area 

 toward the east. Near the centre of the hill the granite is once more 

 covered by Tertiary beds, but the quartzites remain exposed. Enormous 

 masses of glacial drift render it imi^ossible to foUow the line of outcrop, 

 but the recurrence of the Potsdam quartzites only a short distance west 

 of Whiskey Gap proves the underground connection. Throughout the 

 entire line they stand nearly on end, evidently havmg been pushed up 

 with great violence. 



East of Whiskey Gap, we find the continuation of the series, flanking 

 the Seminole Mountains on the north side. Crossing Muddy Creek, we 

 notice a narrow line of red quartzites, trending approximately east and 

 west. They stand vertically or dip at a very steep angle to the south. 

 The same granite which has produced their elevation near Sweetwater 

 Gap now apj)ears in the same relative position. It forces the quartzites 

 liigh uj) into the Seminole Hills, making up almost the entire eastern 

 slope. 



Caleiferous Group. 



At the most westerly outcrops of the Potsdam quartzites the caleifer- 

 ous series has shrunk to a minimum. Farther east it is represented by 

 a series of gray and yellow dolomites, partly arenaceous, which are of 

 very little importance, however. In stratigraphical arrajigement and in 

 participation in folds and plications, the beds of this series are thor- 

 oughly conformable with those underlying. 



In the two Silurian Groups but very few fossils were found through- 

 out this region. Lingula occurs in the quartzites, and a number of poorly. 



