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The Changing Proglacial Environment of the Casement Glacier, Glacier Bay, Alaska

1965; Wiley; Issue: 36 Linguagem: Inglês

10.2307/621457

1475-5661

Robert Price,

Polar Research and Ecology

The glacier has an area of fifty to sixty square miles with extensive neve basins between 3000 and 5000 feet. The Casement Glacier has retreated north-eastward from Muir Inlet where it joined the Muir Glacier at the beginning of the present century, and northward from the shores of Adams Inlet where it once joined the Adams Inlet Glacier. Apart from the Klotz Hills (Fig. 2) in the south, and the area to the north of Forest Creek in the north, the area between Muir Inlet and the present ice margin consists entirely of glacial and fluvioglacial deposits. It is this area of approximately fifteen square miles that will be considered in this paper. A thick gravel deposit that has been shown to be Hypsithermal in age1 forms a steep scarp (Fig. 3) behind a series of gravel fans along the east shore of Muir Inlet. This steep scarp, which is generally thirty to sixty feet high, is backed by a more gentle slope rising to a northsouth trending ridge generally between 200 and 300 feet in altitude. To the east of this ridge the topography is irregular but has a general slope down to about 130 feet at the present ice margin. Several large meltwater channels have been cut through the main north-south ridge. Except for the most northerly of the channels, which is now occupied by a relatively small stream named Forest Creek, the channels are not occupied by streams. All the meltwaters flowing off the south-eastern part of the Casement Glacier now enter an arm of Adams Inlet which will be referred to in this paper as Seal Inlet. The glacial chronology since the retreat of the Wisconsin Age glaciers in Glacier Bay is well known. R. P. Goldthwait,2 using thirty-six radiocarbon dates, was able to date the deposits accumulated during the Hypsithermal period and the events of the Little Ice Age glaciation. He established that by 7500 years B.P., the Wisconsin Age glaciers had withdrawn farther than those existing at present. He also stated that gravel and lacustrine deposits filled the upper bays to present sea-level about 7000 years ago and reached Ioo metres above present sea-level between 1700 and 2500 years ago. The southward expansion of glaciers now referred to as the Little Ice Age began as early as 2735 B.P. These advancing glaciers eroded the outwash that accumulated during the Hypsithermal period, removing most of it from the middle of the valleys and streamlining those deposits that occurred in protected localities. During this period of glacier expansion, a silty grey till was laid down on top of the Hypsithermal deposits to a