. Bulletin of the Geological Society of America. Geology. 546 PRE-WISCOXSIN GLACIAL DRIFT IX MONTANA »<« siderable interval elapsed between the exposure of the mountain drift on the recession of the fronts of the mountain glaciers and the deposition of the overlapping drift by the continental ice-sheet, and he also stated that the lack of modification by erosion of the surface of the moraines corresponded as evidence of relative recency of deposition with that of the moraines of the late Wisconsin drift of the Mississippi Valley. Cal- houn and we also were therefore led to the conclusion th
. Bulletin of the Geological Society of America. Geology. 546 PRE-WISCOXSIN GLACIAL DRIFT IX MONTANA »<« siderable interval elapsed between the exposure of the mountain drift on the recession of the fronts of the mountain glaciers and the deposition of the overlapping drift by the continental ice-sheet, and he also stated that the lack of modification by erosion of the surface of the moraines corresponded as evidence of relative recency of deposition with that of the moraines of the late Wisconsin drift of the Mississippi Valley. Cal- houn and we also were therefore led to the conclusion that drift of the mountain glaciers deposited in the valleys near and south of the Interna- tional Boundary should be referred to the Wisconsin stage of glaciation, and that the same is true of the overlap- ping drift of the continental ice-sheet. AYe think this deduction applies also at least as far north as the valley of Oldman Creek, where the mountain drift is not confined to the valleys, but spreads over the intervening undulating areas, where erosion has left no remnants of the Black- foot peneplain. This overlap was observed by us on South Fork of Oldman Eiver west of Pincher, Alberta (township 7 north, range 21 west), and on Drywood Fork of AVaterton Eiver (township 4 north, range 30 west), and it was also observed by Calhoun and by us both on Belly Eiver (township 2 north, range 28 west) west of Mountainview, Alberta, and on Saint Mary Eiver near the International Boun- dary and some miles to the northward. In the last two situations the two drifts are exposed near the levels of the present streams and at elevations of more than feet lower than the nearest pre-TVis- consin drift-capped remnants of the Blackfoot peneplain but a few miles awav. From this relation it is clear that the deposition of the imbricated drift in the valleys post-dated that of the drift on the high-level tracts by a long interval, during which the valleys were deepened hundreds of feet. It
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