Abstracts
Abstract
The late Wisconsinan deglaciation of the Riding Mountain Uplands was associated with the Lockhart Phase of glacial Lake Agassiz (11,600-10,800 B.P.). During the waning stages of the Falconer ice advance (post 11,400 B.P.) a large area of glacial ice stagnated on the Riding Mountain Uplands. Subsequent downwasting generated a drainage network consisting of several superglacial lakes, spillways and meltwater channels. Many of these glacial rivers eroded their ice beds and incised into the substratum. Glaciofluvial sediments were deposited as sandurs, eskers and kames. Subaqueous fans were deposited in the superglacial lakes and a major delta was built into the north end of glacial Lake Hind. During this time an advance of the Valley River Sublobe created the Mears kame moraine.
Following this advance. Northeastern ice (the Assiniboine Sublobe) retreated from the Rivers - Rapid City Endmoraine to the Brookdale position. As downwasting of the stagnant ice on the uplands continued, the superglacial lakes drained and an entrenched drainage system developed on the stagnant ice moraine complex.
RESUME
La deglaciation du Wisconsinien tardif du plateau de Riding Mountain 6tait associ£e a la phase Lockhart du lac glaciaire Agassiz (11,600-10,800 B.P.). A la fin de l'avanc£e glaciaire Falconer (apres 11.400B.P.), une vaste Itendue de glace est reside stagnante sur le plateau de Riding Mountain. L'ablation subsdquente a laisse' un rdseau de drainage composd de plusieurs lacs supraglaciaires ainsi que des canaux de d£bordement et de fonte. Plusieurs de ces rivieres glaciaires ont 6rod£ leur lit de glace et le substrat. Les sediments fluvio-glaciaires ont €l€ d£pos€s sous forme de sandurs, d'eskers et de kames. Des cones subaqueux ont 6l6 d£pos£s dans les lacs supraglaciaires et un delta important a 6t6 formd a l'extremite' nord du lac glaciaire Hind. Pendant ce temps, une avancde du lobe secondaire de la riviere Valley a ct66 la moraine a kames Mears.
Apres cette avancle, la partie nord-est du glacier (le lobe secondaire Assiniboine) a recul£, depuis la moraine frontale de Rivers - Rapid City jusqu'a la position de Brookdale. Pendant l'ablation du glacier stagnant sur le plateau, les lacs supraglaciaires se sont drained et un r£seau de drainage encaiss6 s'est ddveloppe' sur le complexe de moraine associd au glacier stagnant.
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