Les étapes de la déglaciation dans le nord de la Gaspésie (Québec) : les marges glaciaires des dryas ancien et récent

• Published in: Géographie physique et Quaternaire
• Main Authors: Hétu, Bernard, Gray, James T.
• Format: Text
• Language: French
• Published: Les Presses de l'Université de Montréal 2000
• Subjects: Goldthwait; Renard; Ice cap; Newfoundland
• Online Access: http://id.erudit.org/iderudit/004831ar; https://doi.org/10.7202/004831ar

Mapping and 14 C dating of quaternary deposits and landforms of deeply incised coastal valleys, over a 100 km stretch between Cap-au-Renard and Petite-Vallée along the northern coastline of the Gaspé Peninsula, permit a detailed reconstruction of Late Wisconsin deglaciation. During the glacial maximum these coastal valleys were occupied by glacier tongues which flowed out to the Gulf of St Lawrence from an ice-cap developed on the high and intermediate level plateaux in the interior of the Gaspé Peninsula. Initial deglaciation of the coast occurred towards 13 300 yrs BP, but massive ice contact marine deltas at or close to the mouths of four valleys between 12 300 and 11 800 yrs BP, are indicative of a long period of stability of glacier fronts in contact with the postglacial Goldthwait Sea. Meanwhile small catchment basins at the head of tributary gullies on the flanks of these valleys were occupied by cirque glaciers, some of which remained active until at least 10 000 14C yrs BP. At Anse Pleureuse and Grande Vallée, a second generation of ice-contact marine deltas, indicates a later pause during ice retreat, between 11 000 and 10 000 yrs BP. The two major pauses during ice front retreat, indicated by such deposits coincide with the Older and the Younger Dryas cold phases. Correlations with late glacial readvances recognised elsewhere in the Laurentian axis between the Great Lakes and Newfoundland, and with amphi-Atlantic oscillations suggest that secular climatic change was responsible for both events. Une cartographie morphosédimentologique des vallées comprises entre Cap-au-Renard et Petite-Vallée, complétée par des levés stratigraphiques et plusieurs datations au 14 C et au SMA inédites, ont permis de reconstituer en détail les étapes de la déglaciation wisconsinienne dans le nord de la Gaspésie. Durant le pléniglaciaire wisconsinien, la partie orientale de la Gaspésie était occupée par une calotte glaciaire régionale à écoulement radial. La déglaciation s'amorce le long du littoral peu avant 13 300 BP. ...