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- Title
The late Quaternary stratigraphic record northwest of Montréal: regional ice-sheet dynamics, ice-stream activity, and early deglacial events.
- Authors
Ross, Martin; Parent, Michel; Benjumea, Beatriz; Hunter, James
- Abstract
The Quaternary sediments of previously unstudied buried valleys and sections near Montréal are analyzed and other sites are revisited to further develop the stratigraphic framework of the St. Lawrence Lowland and to establish regional glacial and deglacial models. The southwest-trending buried valleys were investigated by stratigraphic drilling and high-resolution seismic profiling. The Quaternary succession consists, from base to top, of proximal glaciolacustrine sediments, two superposed till sheets (Argenteuil and Oka tills) of inferred Late Wisconsinan age, and Champlain Sea sediments. The glacial sediments of this sequence record an ice advance toward south (Argenteuil Till) followed by an abrupt ice-flow shift toward the southwest (Oka Till). Compositional and geomorphic data indicate that Oka Till is ubiquitous and is associated with a regional set of glacial landforms. The analysis of a regional digital elevation model in combination with published ice-flow indicators shows convergent flow patterns from the Ottawa-Montréal-Adirondack regions toward the Lake Ontario basin. Landforms produced by the inferred ice stream are locally crosscut by southwardtrending ice-flow features. Hence southward flow in the upper St. Lawrence Valley seemingly took place in two distinct contexts: (1) during full glacial conditions, as ice margins stood at or near the late glacial maximum limits, and (2) during late deglaciation, as a post-ice stream reequilibration mechanism. Early deglacial events in the study area were also characterized by subglacial meltwater channelling and erosion along the valleys, subaquatic outwash deposition in glacial Lake Candona, and rapid infill of the valleys during the early stages of the ensuing Champlain Sea.
- Subjects
GREAT Lakes (North America); OKA (Quebec); ARGENTEUIL (Quebec : County); GEOMORPHOLOGY; GLACIAL landforms; LANDFORMS; VALLEYS; GLACIAL lakes; EROSION; SEDIMENTATION &; deposition
- Publication
Canadian Journal of Earth Sciences, 2006, Vol 43, Issue 4, p461
- ISSN
0008-4077
- Publication type
Article
- DOI
10.1139/E05-118