National Geographic : 1892 May 15
Evidence of non-Glaciation. 157 much as it appears at present, only somewhat larger, its waters being held by the dam of silt which had been laid down in front of the ice. Having in mind the conclusions of Dawson, McConnell and Russell as to the northern limit of glaciation in the Yukon basin, evidence on that point was carefully sought in the plateau region southwest of Selkirk. For the first one hundred and twenty five miles the evidence was wholly negative. No sign of glaci ation was seen, and this too in a country well calculated to retain the marks of ice action. The stream gravels consist of a very small number of rock species, and on following a stream to its head the source of each was usually found, showing that no foreign material had been brought into their basins: While in general the surface contours are smooth and flowing, this is the result of long-continued subaerial rock disintegration, and gen erally the surface rock is deeply buried beneath great accumu lations of fragmental debris, though occasional sharp pinnacles and towers of rock project from the smooth talus slopes. Had this region been subjected to the action of an ice sheet during the glacial epoch, not only would the greater part of the rock debris have been removed but the projecting pinnacles would have been planed down to rounded knobs which would still retain polished and striated surfaces. Where Nisling river was crossed its broad valley is filled with a deposit of coarse gravel and bowlders, and from their great quantity and variety it was inferred that the stream had its source in a drift-covered region. The first undoubted evidence of ice, however, was found on the divide between Nisling and Kluantu rivers, where the northern edge of a sheet of bowlder clay was passed. From this point southward the character of the surface suffers a marked change. It is no longer composed of the fragments of one or two kinds of rock occurring in place near at hand, but rather of many varieties confusedly mingled with clay and sand. The drainage system is imperfectly adjusted to the topographic surface, so that wide valleys carry small streams, and large streams like the Kluantu and Donjek flow, for considerable distances at least, through narrow valleys. The ice which has left its records in this sheet of bowlder clay was probably a confluent glacier formed by streams coming from the south through narrow valleys now occupied by Kluantu and Donjek rivers. These valleys do not appear to have been 22-NAT. GEOG. MAO., VOL. IV, 1892.
1893 Feb 08
1892 Mar 31