HR: 10:50h
AN: PP12A-03 INVITED     [Abstracts]
TI: Glacial Lake Outflow via the St. Lawrence Pathway Prior to the Champlain Sea Invasion and During the Younger Dryas
AU: * Occhietti, S
EM: glypto@videotron.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Anderson, T W
EM: twa@magma.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Karrow, P F
EM: pfkarrow@sciborg.uwaterloo.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Lewis, M C
EM: lewis.bowerman@ns.sympatico.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Mott, R J
EM: rjmott@NRCan.gc.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Parent, M
EM: miparent@nrcan.gc.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Richard, P J
EM: Pierre.Richard@UMontreal.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Rodrigues, C G
EM: ma01x@sympatico.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AU: Stea, R
EM: rrstea@gov.ns.ca
AF: Laboratoire Jacques Rousseau Geographie Universite de Montreal, CP 6128 Centre-ville, Montreal, QC H3C 3J7 Canada
AB: When the Laurentide Ice Sheet receded north of the Adirondacks, Glacial Lake Frontenac overflowed to Glacial Lake Vermont (Coveville phase)-Albany. The water level of Lake Frontenac fell by about 90 m, as a result of the drawdown, glacio-isostatic rebound and outflow of Lake Vermont-Albany through the Hudson Valley to the North Atlantic Ocean. Lake level stabilized to form the Belleville, Upper Fort-Ann, post-Sherbrooke phase of glacial lakes post-Iroquois, Vermont and Memphremagog, respectively. Initially, the confluent fresh-water body extended from the Lake Ontario basin into the upper St. Lawrence Valley, Lake Champlain basin and along the Appalachian piedmont. The outlet of the lake was the Upper Fort-Ann sill, along the Hudson pathway (Lake Albany). The expansion of the lake was time transgressive and related to the regional ice retreat. As the lake expanded across the lowlands, into the Ottawa and central St. Lawrence valleys, and along the Appalachian piedmont, its level fell by about 20 m, from the Belleville to the Trenton strandlines on the western side of the Adirondacks, and about 26 m (Rayburn, 2004) from the Upper to the Lower Fort-Ann strandlines in the Lake Champlain basin. The extent of the lake during its final stage is estimated at about 30,000 km². Varves deposited in the deeper parts of the lake are characterized by the ostracode Candona subtriangulata. Varve counts from several reference sections provide an approximate duration for the glaciolacustrine phase in different parts of the lowlands. They range from about 50 to 30 yr in the lower Ottawa Valley, where the estimated depth was 180 to 200 m, about 100 yr along the Appalachian piedmont and, tentatively, to more than 160 yr in the Lake Champlain basin (Rayburn et al., 2005). The lake overflowed/drained suddenly to the east, toward the western arm of the Goldthwait Sea, in the Estuary and Gulf of St. Lawrence, and hence into the North Atlantic Ocean. During this event, the water level fell by about 50 to 40 m to the highest strandline of the Champlain Sea. The timing and volume of this fresh-water discharge are quantified to allow assessment of its potential impact on the thermohaline circulation of the North Atlantic Ocean, and whether it could have triggered the cold Younger Dryas episode. The overflow occurred within a one-year span between 11.2 and 10.9 ¹⁴C ka BP or 13.2 and 12.85 cal ka BP, close to the onset of the Younger Dryas cold interval. The total freshwater outflow through the St. Lawrence pathway comprised the one-year overflow phase (about 1500 km³), an early mixing phase of fresh and marine waters in the Champlain Sea domain (about 400 km³ for several years), a rapid collapse of the ice margin in the lowlands during about 250 yr and, during the Younger Dryas, several outburst floods from glacial Lake Algonquin into the Champlain Sea through the middle Ottawa Valley.
DE: 0720 Glaciers
DE: 0746 Lakes (9345)
DE: 4901 Abrupt/rapid climate change (1605)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005