CGRG Bibliography of Canadian Geomorphology
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Author : Evans, D.J.A.
Date : 1994
Title : The stratigraphy and sedimentary structures associated with complex subglacial thermal regimes at the southwestern margin of the Laurentide Ice Sheet, southern Alberta, Canada.
Publication : Formation and Deformation of Glacial Deposits. Edited by: W.P. Warren and D.G. Croot. A.A.Balkema, Rotterdam, Netherlands.
Issue :
Page(s) : 203-220
Abstract
Complex stratigraphic sequences in the cliffs of One Tree Creek, southern Alberta reveal seven lithofacies associations (LFA's) which have been disturbed by two generations of glacitectonics. LFA's 1 and 2 (preglacial fluvial and lacustrine sediments), LFA 3 (grey till) and LFA 4 (supraglacial sediments) were all disturbed by the first generation glacitectonic event which terminated when either ice or a deforming till layer truncated the contorted sediments. Above the erosional contact formed at the end of the first generation glacitectonic event, a lodgement till forms the base of LFA 5 which grades upwards into a gravitationally deformed melange of debris flow, fluvial and subaqueous origin (subglacial cavity fills). LFA 6 is a diamicton which records the glacial molding of pre-existing material followed by melt-out. A prominent erosional contact separating LFA's 5 and 6 suggests renewed contact of the glacier with its bed after a period of decoupling. Second generation glacitectonics acted to disturb LEA's 2, 3, 4 and 5 after renewed ice/till coupling which was a response to renewed fast glacier flow or surging. The LFA's and glacitectonic structures in the One Tree Creek sections are related to sediment properties which were in turn related to the discontinuous permafrost and proglacial lakes overrun by the ice sheet and to chancing subglacial thermal regimes. Subglacial cavity fills and the second generation glacitectonics may relate to periods when large amounts of meltwater were being generated regionally by the ice sheet. Many ice thrust terrains are cross-cut by subglacial meltwater channels, indicating that they date to initial ice advance. Shifting reservoirs of subglacial meltwater may have had profound effects on the distribution of both fluviglacially and glacially derived flutings. The initiation of one of the processes of subglacial tunnel valley cutting (piping), cavity filling, ice streaming/till deformation and a glacier surging in one area would have brought about a chain reaction elsewhere.
Bibliography of Canadian Geomorphology