152 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



and there in Four-Mile Creek as striking south of east and dipping 

 northward. Eunning from Gold Hill eastward would thus appear to be 

 an eastward dipping synclinal axis, the included surface-rock seeming 

 to be a coarse gray and reddish gneissic granite, some of it containing 

 considerable mica, but much of it, like most of the granites north, hav- 

 ing but little mica, and that in small and scattered flakes. This syncli- 

 nal may be the eastern extremity of the fold that was stated to flex, the 

 great north-south anticlinal of the main range near Arapaho Peak, 

 flattening the axis toward the north. The schists running southeast 

 from near Gold Hill seem to continue on westward in a pretty well de- 

 fined zone with some small but obvious north-south folds, as indicated 

 on the map, but with general northern dip. A northwest extension of 

 schists, with south dip, as if the east-west synclinal extended through 

 here westward, does not appear fi?om the few and imperfect observations 

 made in this direction to exist here, indicating that a fault must be re- 

 sorted to to explain the curious outcrop that the map indicates. South 

 of these schists there seems to be shown a pretty sharp line of demarka- 

 tion between them and a coarse granite region across which the North 

 and the Lower Middle Boulder Creeks cut their impressive caiions. 

 Along the caGon of the latter a very few imperfect east- west strikes, 

 with steep north dip, seemed indicated, which lower down, near the 

 sandstones, swing southward. South of here, between the Middle and 

 South Boulder Creeks, though no direct strikes were observed, yet the 

 different granites were plainly arranged in zones trending about north 

 and south, but running more southwest in following them southward. 

 Near the mouth of the South Boulder Canon, and resting on these zoned 

 but otherwise structureless granitps, the quartzites first appear in force, 

 with a south-southwest strike, and dip of 60° to the southeast. Though 

 mostly quite pure, yet these quartzites may be traced into siliceous 

 schists and are associated with mica schists and gneisses. The above- 

 described structural relations would seem to indicate that these quartz- 

 ites were the stratigraphical equivalent of the Four-Mile schist zone, 

 though here by no means so far metamorphosed, and that could the cov- 

 ering sandstones at the east be stripped off, the two might be traced 

 out till they unite and become continuous. The quartzite ridges are 

 well marked, and near the southern end the rocks appeared to show as 

 if folded upon themselves into a sharp synclinal, the east side being 

 thrown even beyond the vertical, and if this is so it may be the north- 

 ern prolongation of the flatter synclinal that appears east of The Chief, 

 as indicated on the map, but this is very uncertain. Attention has 

 already been called to the sharp fold near Idaho, and forming the north- 

 east corner of the greater Evans fold. The region lying directly be- 

 tween Idaho and Central was not passed over, but at Central the rocks 

 indicated a sharp fold similar to that at Idaho, and in view of the per- 

 sistence of the fold south of Idaho it would seem to be the northern ex- 

 tension of the same, as likewise shown on the map. It would then pass 

 on northward and be lost in the structureless granites below the quartzite. 

 These here form the bulky mass of Ralston Butte. The granites here 

 are not red, but gray, the feldspar being mostly a clear, translucent 

 white, and the rock very coarse-grained and exceedingly handsome. 

 Still one or two small isolated gneissic patches were observed. If the 

 stratigraphy is here indicated by the dotted lines this granite area must 

 represent much fattened strata in order to widen out the formation as 

 it appears to do, yet all the observations made near its edges were of 

 steep dipping rocks. The relations, however, all through here are not 

 so clear as it could be wished. In the region near Ralston and Clear 



