MARTDiE.] GEOLOGY STEATIGEAPHY OF THE EAST SLOPE. 147 



parallel lines ; but if the anticlinal dipped norths the beds would mantle 

 around its northern end in curves, with their convexity or apices directed 

 northward, the beds dipping from it northeast and west, with a northern 

 dipping synclinal would have the curved outcrops i^ointing south, but 

 dipping northward and inward from all sides. Anticlinals are indicated 

 by dot and dash lines, synclinals by three dot and space lines, the arrow- 

 heads indicating the direction of the inclination of their axes. It is by 

 no means claimed that the map represents with perfect accuracy the 

 geology throughout ; it is simply a means of putting together before the 

 eye the observations recorded, and to show, only so far as these indicate, 

 the broader ideas of the structure of the mass. Long study will be 

 required to unravel completely the structure of these rocks, and much 

 that is here inferred may finally have to be modified. The portions 

 represented with least certainty on the map will be mentioned in the fol- 

 lowing brief and hurried description : 



The portion of the region under consideration whose structure was 

 probably most clearly made out is that lying south of South Clear Creek, 

 and having Mount Evans as its great culminating mass. This mountain 

 was approached from the upper branches of Bear Creek, on its northeast 

 side, and for eight miles near the summit no evidence of structure what- 

 ever was obtained, the great massive bosses of rock being often sculptured 

 into dome-like forms, with profound gorges and amphitheaters, all com- 

 posed of normal granites, both coarse and fine, some containing much 

 mica, others with but little, in small, scattered flakes. The different 

 granites were not observed to occur in zones, as if once bedded, but not 

 enough was seen of the mass to say that they did not so occur. As will 

 be seen later, the mass is probably all metamorphic, and a more extended 

 examination of it would probably have developed many evidences 

 of a former structure throughout it. These granites seem to occupy as 

 low a geological position as any rocks observed anywhere in the mount- 

 ains. At the northeast the high ridge rising opposite the mountain 

 from the other side of Bear Creek, and between the latter and Clear 

 Creek, and which culminates in The Chief, is composed of well-bedded 

 schistose rocks, all striking about northwest-southeast, and dipping from 

 25^ to 60"^ to the northeast. The Chief itself, and ridges running from 

 it to the southeast, are composed of very irregular and contorted dirty- 

 red and white-banded schists, often granitiferous, which compose a con- 

 siderable thickness of the formation above. Below, on the southwestern 

 face of The Chief, and extending southeastward, is a well-defined bedded 

 zone of fine, handsome, light-gray granite, with small scattered mica- 

 flakes many hundred feet thick, and in turn underlaid by a still greater 

 thickness of more evenly and flner-banded schists than above the granite, 

 inclined to steel-gray in color, with some irregular schists. The edges 

 of these form the lower southern elopes of the hills, their bases being 

 followed quite closely by the valleys of the main streams, which seem 

 to indicate a well-defined and regular line of demarkation between this 

 plainly bedded series, above on the northeast, and the underlying struc- 

 tureless granites rising in the great slopes of Evans. The impression 

 thus first received is that here are two difl'erent and distinct rock forma- 

 tions. The heavier dashed line upon the map here shows the limit of 

 the granites as it follows one of the principal northern forks of Bear 

 Kiver, gradually bending eastward, and indicating, with other strikes 

 observed in the schists above, a flat synclinal, with its axis dipping north- 

 ward. The dotted extension of this horizon southeastward is but ap- 

 proximate, and will be referred to later, while the extension westward is 

 wholly inferred from the observation farther to the northwest, and was 



