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Sangamonian and early Wisconsinan events in the St. Lawrence lowland and Appalachians of southern Quebec, Canada

Lamothe, M. et Parent, M. et Shilts, W.W. (1992). Sangamonian and early Wisconsinan events in the St. Lawrence lowland and Appalachians of southern Quebec, Canada. Special Paper of the Geological Society of America , 270 . pp. 171-184.

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In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited the Levrard Till. This glacial event, known as the Nicolet Stade, is tentatively correlated with marine oxygen-isotope stage 4. Radiocarbon and thermoluminescence ages bracket the Nicolet Stade between 90 and 70 ka. This advance was preceded and followed by periods of free drainage during which were deposited the Lotbiniere Sand and St. Pierre Sediments, two nonglacial units dated at or beyond the limit of the radiocarbon method. Available evidence suggests that the Deschaillons Varves were deposited ca. 80 ka in a large glacial lake that was impounded in front of the Laurentide Ice Sheet as it advanced up the St. Lawrence Valley. In the Appalachian Uplands, fluvial and lacustrine sediments of the Massawippi Formation were probably deposited at the end of the Sangamonian Interglacial. These sediments underlie the Chaudiere Till, a unit in which the occurrence of distinctive lithological indicators is taken as evidence that a regional episode of westward to southwestward ice flow prevailed at the onset of the last glaciation. The proposed paleogeographic reconstruction suggests that the development of an independent ice cap in the northeastern Appalachians played a key role during the early part of the Wisconsinan Glaciation in southern Quebec. This independent ice mass flowed southwestward across the Appalachian Uplands of southern Quebec and eventually coalesced with the Laurentide Ice Sheet, which was advancing up the St. Lawrence Valley.

Type de document: Article scientifique
Statut du texte intégral: Autre
Mots-clés libres: St. Lawrence Lowlands, Wisconsinan, Levrard Till, Nicolet Stade, Glacial event, Radiocarbon and thermoluminescence ages, Lotbiniere Sand, St. Pierre Sediments, Deschaillons varves, Laurentide Ice Sheet, Appalachian uplands, Sediments of the Massawippi Formation, Sangamonian interglacial, Chaudiere Till, Lithological indicators, Glaciation, Paleogeographic reconstruction
Sujets: 2. Milieu physique > 2.1. Géologie
2. Milieu physique > 2.4. Hydrologie
8. Impacts et monitoring > 8.1. Qualité de l’eau
Date de dépôt: 14 août 2016 13:33
Dernière modification: 14 août 2016 13:33

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