ISSN:
1573-0417
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Geologie und Paläontologie
Notizen:
Abstract Glacial Lake Hind was a 4000 km2 ice-marginal lake which formed in southwestern Manitoba during the last deglaciation. It received meltwater from western Manitoba, Saskatchewan, and North Dakota via at least 10 channels, and discharged into glacial Lake Agassiz through the Pembina Spillway. During the early stage of deglaciation in southwestern Manitoba, part of the glacial Lake Hind basin was occupied by glacial Lake Souris which extended into the area from North Dakota. Sediments in the Lake Hind basin consist of deltaic gravels, lacustrine sand, and clayey silt. Much of the uppermost lacustrine sand in the central part of the basin has been reworked into aeolian dunes. No beaches have been recognized in the basin. Around the margins, clayey silt occurs up to a modern elevation of 457 m, and fluvio-deltaic gravels occur at 434–462 m. There are a total of 12 deltas, which can be divided into 3 groups based on elevation of their surfaces: (1) above 450 m along the eastern edge of the basin and in the narrow southern end; (2) between 450 and 442 m at the western edge of the basin; and (3) below 442 m. The earliest stage of glacial Lake Hind began shortly after 12 ka, as a small lake formed between the Souris and Red River lobes in southwestern Manitoba. Two deltas at an elevation of 450 were formed in this lake. At the same time, the Souris Lobe retreated far enough to allow glacial Lake Souris to expand farther north along the western side of the basin from North Dakota into what was to become glacial Lake Hind. Three deltas were built at an elevation above 460 m in the Canadian part of this proglacial lake. Continued ice retreat allowed the merger of glacial Lake Souris with the interlobate glacial Lake Hind to the east. Subsequent erosion of the outlet to the Pembina Spillway allowed waters in the glacial Lake Hind basin to become isolated from glacial Lake Souris, and a new level of glacial Lake Hind was established at 442 m, with 5 deltas built at this level by meltwater runoff from the west. Next, a catastrophic flood from the Moose Mountain uplands in southeastern Saskatchewan flowed through the Souris River valley to glacial Lake Souris, spilling into Lake Hind and depositing another delta. This resulted in further incision of the outlet (Pembina Spillway). A second flood through the Souris Spillway from glacial Lake Regina further eroded the outlet; most of glacial Lake Hind was drained at this time except for the deeper northern part. Coarse gravel was deposited by this flood, which differs from previous flood gravel because it is massive and contains less shale.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1007904824169
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