Sedimentology and history of deglaciation in the Dryden, Ontario are, and their bearing on the history of Lake Agassiz
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Date
1991
Authors
Warman, Timothy A.
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Abstract
The goals of this study were to determine the nature of unconsolidated sediments in the area, to determine the sedimentary processes responsible for these deposits, and to then re-examine the deglaciation history of the area, including the history of Lake Agassiz. It has been recognized that moraines in the Dryden area are composed of sorted and stratified materials displaying abundant sedimentary structures indicating deposition by flowing water. This differs significantly from the composition implied by most moraine models which tend to envisage moraines as being composed mainly of unstratified, unsorted "till", which has been piled up at a stationary ice margin by slumping, bulldozing, and/or glaciotectonic thrusting. Thus, a careful examination of the moraines in the area (the Eagle- Finlayson and Hartman moraines) was undertaken. The relationship between the large, coarse-grained end moraines, and the finer, rhythmically-laminated sediments (rhythmites) associated with them was also examined. These rhythmites had previously been studied by Rittenhouse (1933, 1934), and interpreted as varves. Varve chronologies based on this interpretation have been devised not only for the Dryden area, but for other locations in northwestem Ontario...