CGRG Bibliography of Canadian Geomorphology
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Author : Lamarche, L.; Lamothe, M.; Bondue, V.; and Roy, A.G.
Date : 2006.
Title : Dating Holocene sediments and landforms using luminescence and radiocarbon: a tool for deciphering the recent evolution of the St. Lawrence River drainage system.
Publication : Joint Annual Meeting of the Geological Association of Canada and the Mineralogical Association of Canada. University of Quebec in Montreal (UQAM) May 14-17, 2006.
Issue :
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Abstract
The St. Lawrence River is an important drainage route for eastern North American fresh waters. Following Late Pleistocene deglaciation and the Champlain Sea event, several fluctuations in base level have fine-tuned the evolution of the ancestral St. Lawrence. These fluctuations are hereby dated using K-feldspar infrared stimulated luminescence (IRSL) and radiocarbon. The accuracy of the individual IRSL dates was achieved by properly correcting for thermal transfer and anomalous fading. For each site investigated, statistical approaches in equivalent dose data have been used to establish which age model, the central or the minimum model, would be appropriate to define the “true” depositional age. The chronology of the succession of regional lake levels is based on careful mapping and dating of the regional dunes, beaches and deltaic sediments. A relative time-space evolution history could be drawn, from ca. 10,000 years to the present time period, from which several major fluctuations could be documented. The three most conspicuous terraces, known as Rigaud, Montréal and Saint-Barthélémy, represent Early Holocene relative stabilization, and they may result from a combination of erosional features (e.g. stratigraphical discontinuities and sediment cohesiveness) and regional sediment input from up river lake discharges. The location of the modern Saint-Lawrence River channel seems to have been established in Middle Holocene time, its base level having dropped through vertical incision by about 15 m until present day. An unexpected finding, from the ages cluster diagram, is that there have been times in the recent past (ca. 1,000 to 4,000 years BP) when the river level was lower or at the same elevation as today. Indeed, distinctive sedimentary environments that prevailed about 2000 years ago are best analog to what is expected for the evolution of the St. Lawrence tributaries over the next century.
Bibliography of Canadian Geomorphology