MARVKE] GEOLOGY STRATIGRAPHY OF THE EAST SLOPE. 149 



Toward Georgetown the scliistose-gneisses stand for the most part very 

 nearly vertical, with many faults. At one point near Silver Plume, a 

 small hill on the north side of the valley showed an abrupt synclinal 

 structure, a fault apparently passing directly through the axis. About 

 as far below Georgetown as the Terrible mine is above it, a rock on the 

 west side of the valley, and forming a little promontory at the junction 

 of a side stream, shows the same hard, structureless porphyritic granite 

 as at the Terrible mine, with some abrupt lines of demarkation between 

 it and the adjacent schistose-gneisses, but also presenting some examples 

 of more gradual transition than elsewhere, and deserving of more care- 

 ful study than the time allowed. This porphyritic granite impressed me 

 as being more probably an eruptive mass occupying an anticlinal axis 

 than one metamorphism in situ, though it may not have come from afar, 

 nor from rocks of an origin dissimilar from that of its present com- 

 panions. The dip on the southeast side of this anticlinal must become 

 reversed in rising up against the Evans mass, forming a synclinal be- 

 tween the Gray's Peak anticlinal and Mount Evans, but as this region 

 was not directly entered, it was not observed, and is not indicated on 

 the map. 



Eeturning to the irregular schists of The Chief lying on the Mount 

 Evans granites, and following them eastward, they maintain their char- 

 acters for some distance, but with increasing granite characters, until 

 they appear to cross Bear Creek and merge into a granite country. The 

 hills are less high and sharp than before and rise from a more uniform 

 plateau-like surface, with southern sides almost always steep and almost 

 invariably steeper than their massive northern slopes. The rock gen- 

 erally appears to be a reddish granite, with tabular trimmed feldspar 

 crystals, and small scattered mica flakes ; yet remnants of structure are 

 very numerous and can be found in almost every hill. Patches of the 

 dirty-red and white-contorted schists, similar to those of The Chief, occur, 

 apparently indicating approximately the same horizon. linear the bor- 

 der of the range, and approaching the sedimentaries, schists predomin- 

 ate, a line of white quartzite outcrops being observed at one point ex- 

 tending for a little distance. All the rocks still uniformly incline to the 

 north, or else east and west, and none to the south. A most decided 

 unanimity exists among the very numerous recorded strikes and dips 

 observed in the granites, which is confirmed by the adjacent schists, in 

 indicating a series of minor folds with axes dipping northward, some 

 quite abrupt, as shown upon the map. Though concealed by the sedi- 

 mentaries, the last-observed rocks on the extreme border of the archsean 

 rocks seem to indicate that the general strike has swung from southeast 

 to northeast, as if the border was near the principal and northward dip- 

 ping-axis of a great synclinal — the compliment of the main Evans an- 

 ticlinal, with the rocks within it crumpled into minor folds just as the 

 similar wrinkles exist on the Evans fold. The more southern rocks here 

 are the most metamorphosed, and in tracing them toward Mount Evans 

 evidences of structure become less and less marked until they become 

 so diificult to find in the red and gray granites, that the latter become 

 practically structureless. While the higher mountain-mass beyond may 

 hereafter be found to be partially exotic in character, yet here, upon its 

 southeastern extension, its rocks are certainly clearly metamorphic. It 

 is at points here that an approximate parallelism of the tabular feld- 

 spar crystals to the bedding was first observed, though it is a character 

 that readily became lost in a wholly fortuitous arrangement of the com- 

 ponents of the granite. Large inclosed schistose masses, with most 

 gradual transitions along their borders into the surrounding granites, to 



