142 GEOLOGICAL SURVEY OF THE TEREITORIES. 



from otlier regious, indicate it, but the evidence exists to show that an 

 enormous amount of material has actually been removed from the ancient 

 surface to bring to light the rocks as now exposed. The caQon-cutting 

 and surface-erosion of the present has only been in progress since the 

 latestuplift — x^robablyinearly Tertiary times — and is almost as nothingin 

 amount, so far as themetamorphics are concerned, compared with erosions 

 in the distant past. Eegarding as still correct the evidence from within 

 the district in question, the whole region, except, perhaps, its extreme 

 southwestern portion, stood above the ocean-level at least just previous 

 to the deposition of the Triassic sandstones, and probably did so all 

 during Paleozic time, and if the erosion then approximated in rapidity 

 to the erosion of the present time, in such a long interval it must have 

 been enormous. That the erosion was by no means gentle is evidenced 

 by the almost universal coarseness of the adjacent derived sediments, 

 the amount of which themselves attest and measure the amount of ma- 

 terial removed from off the adjacent archsean areas. The " overlap" 

 and shelving-oft" of the lower Triassic sandstones all along the east bor- 

 der of the range show a gradual encroachment of the shore-line, a win- 

 ning of the laud by the sea, effected by the slow degradation of the land 

 by erosion. How far and rapidly this extended cannot be told, but all 

 of what is now the Middle Park, and probably much farther up on the 

 range, had, by Cretaceous times, succumbed to this degrading and sea- 

 encroachmg process. And yet adjacent land must have existed, as the 

 marked coarseness of some of the Lignitic (Eocene?) beds indicate, com- 

 posed, as they are, of granitic debris, and the complemental and actual 

 evidence exists in part in the archsean rocks themselves. Looking at 

 those that are only now ex^josed to view, some of the lower horizons 

 showing near the center of the range lie many thousands of feet in geo- 

 logical antecedence below the upper exjoosed portions, and how much 

 the latter may have been below the surface that existed when meta- 

 morphism was in progress, is an unrevealed story, the evidence being 

 hid beneath the ruins of the rocks themselves in the debris that now 

 forms the sedimentary rocks of the plains, but which, as said before, 

 show that much more has been removed than now exposed. Thus the 

 thickness to which the archsean rocks were piled up strata upon strata, 

 before even their own debris was worked over into the more modern 

 rocks, must be recorded by thousands of feet, if not by miles. Thus 

 deeply buried beneath the surface, heat from below must have gradually 

 invaded the mass, and have played an important part in its meta- 

 morphism. That depth, and hence, probably, heat, was a factor, seems 

 indicated by the fact that in a general way the largest and most struc- 

 tureless masses occupy the lowest geological positions, while the less 

 generally metamorphosed regions lie higher up in the exposed series. 

 Some profound plications have occurred in the mass, the strata, generally 

 beiughighly inclined, and the resistance to this folding, in friction, crush- 

 ing, and motion, must have added much heat to the invading earth-heat 

 following upon the accumulation of the strata. For the metamorphism 

 itself is ancient, the debris of the already metamorphosed rock being 

 frequent in the derived sedimentaries, and I think evidence may be 

 found to show that it probably continued, if it was not most active, 

 during the earlier foldings of the series. The intensity of this heat can 

 hardly be stated. It was not necessarily of that temperature that would 

 be required to melt the granites as they now stand, for the presence of 

 saline waters may have so acted as to have assisted the heat in inducing 

 plasticity or liquidity, to produce a state of '■'' aqueo-igneous fusion'''' without 

 the actual temperature being very great. How far such action really 



