Retreat of Wisconsin and Recent Ice in North America

Prest, V K

doi:10.4095/109206

Cited by 188 publications

(98 citation statements)

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“…3g des mêmes auteurs). Un âge approximatif de 9 500 à 9 000 ans avant l'actuel peut être attribué à cette déglaciation, d'après la carte des isochrones de PREST (1969). Toutefois, en se fondant sur la chronologie varvaire de ANTEVS (1925) et de HARDY (1976 et en connaissant l'âge de la vidange du lac Ojibway (HARDY, 1976), il est possible d'affirmer que la déglacia-tion de la région étudiée s'est effectuée il y a à peu près 9 000 ans.…”

Section: Contexte Paleogeographiqueunclassified

Histoire postglaciaire de la végétation au sud du lac Abitibi, Ontario et Québec

Richard

2011

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Les lacs Yelle et Clo, situés à environ 10 km au sud du lac Abitibi, ont respectivement livré des séquences continues de sédiments depuis la déglaciation de la région, vers 9 000 BP, et le retrait du lac proglaciaire Ojibway, vers 7 900 BP jusqu’à l’actuel. L’interprétation des diagrammes polliniques révèle que la rive sud du lac Ojibway était occupée, vers 8 900 BP, par une forêt ouverte dominée par l’épinette noire (Picea mariana), dans laquelle le tremble (Populus tremuloides) et le pin gris (Pinus divaricata) jouaient un rôle important. Ce type de paysage s’est maintenu durant environ 1 000 ans dans les collines alors insulaires entourant le lac Yelle, pendant que le niveau du lac Ojibway passait de 355 à 280 m. Lors de la vidange du lac Ojibway, la colonisation végétale des basses terres s’est effectuée rapidement. De 7 900 à 7 200 ans BP, la forêt appartenait déjà au domaine de la sapinière à bouleau blanc, occupant les stations mésiques, mais l’épinette noire et le tremble étaient abondants, de même que le pin gris. De 7 200 à 6 000 BP, la végétation a atteint un maximum de diversité et de thermophilie. Le pin blanc (Pinus strobus) s’est installé, surtout dans les collines et sur les stations xériques. Entre 6 000 et 3 250 BP, le genévrier (Juniperus) est devenu beaucoup plus abondant. Depuis 3 250 ans BP, la forêt s’est refermée, et l’épinette noire et le pin gris ont progressé, aux dépens du pin blanc notamment. La sapinière à bouleau blanc, sur stations moyennes, s’est toujours maintenue au sein du paysage et, malgré des différences, révolution de la végétation a été synchrone entre les deux sites depuis 7 900 ans BP.Complete sequences of sediments representing the time since ice retreat (ca. 9,000 BP) and drainage of proglacial Lake Ojibway (ca. 7,900 BP) have been recovered from Lake Yelle and Lake Clo, two lakes, in a region about 10 km south of lake Abitibi. The interpretation of the pollen diagrams lead to the reconstruction of an open forest dominated by black spruce (Picea mariana), with abundant aspen (Populus tremuloides) and jack pine (Pinus divaricata), at the southern shore of lake Ojibway around 8,900 BP. This type of vegetation lasted about 1 000 years on the islands formed at that time by the hills around Lake Yelle, while the level of Lake Ojibway's level fell from 355 to 280 m. The forest vegetation migrated rapidly into the lowlands after the drainage of the proglacial lake. From 7,900 to 7,200 years BP, the forest was a balsam fir — white birch community, on the mesic sites, but black spruce and jack pine were abundant. From 7,200 to 6,000 BP, the vegetation was at its maximum diversity and thermophily. White pine (Pinus strobus) migrated into the area, especially on hills and on xeric sites. Between 6,000 and 3,250 BP, juniper (Juniperus) became more abundant, the forest canopy being still open. Since 3,250 BP, the forest cover has closed and black spruce and jack pine have increased at the expense of white pine, in particular. The balsam fir-white birch community, on the mesic sites...

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Section: Contexte Paleogeographiqueunclassified

Histoire postglaciaire de la végétation au sud du lac Abitibi, Ontario et Québec

Richard

2011

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“…With the déglaciation of the St. Lawrence Valley, probably involving a relatively long and complex response over about 1000 years between 12,800 and 11,700 BP (RICHARD, 1975;LASALLE and ELSON, 1975), and the collapse of the Hudson Bay center, the Laurentide Ice Sheet was centered over Labrador (IVES, 1960). A final date for the disappearance of the ice in the vicinity of Schefferville is not known with any certainty (BRYSON ef al., 1969;PREST, 1969;MORRISON, 1969), but probably occurred close to 6000 BP.…”

Section: Deglacial Historymentioning

confidence: 99%

“…Dramatic events characterize the period about 8000 radiocarbon years ago (based on dates on marine shells). These have now been discussed by several workers (ANDREWS and FALCONER, 1969;FALCONER ef al., 1965;BLAKE, 1966;PREST, 1970;SKINNER, 1974;ANDREWS and PELTIER, 1976). However, the rapid clearing of ice between Hudson Strait and James Bay about 8000 BP does mean that over this immense distance the marine limit is essentially isochronous.…”

Section: Relative Sea Level Movements Since 8000 Bpmentioning

confidence: 99%

“…By 6000 BP Hudson Bay was completely deglaciated and most workers infer that residual, stagnant ice masses may have been in the final stages of disintegration in central Labrador (BRYSON ef al., 1969;PREST, 1969). Thus, by 6000 BP all the coastline of Québec and Nouveau-Québec was ice free, and, in addition, the ice sheet had now cleared from Southampton Island (BIRD, 1970) and Foxe Basin (BLAKE, 1966;ANDREWS, 1970b).…”

Section: Relative Sea Level Movements Since 6000 Bpmentioning

confidence: 99%

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The observed postglacial recovery of Québec and Nouveau-Québec Since 12,000 BP

Andrews

Tyler

2011

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Radiocarbon dated relative sea levels, the tilts of proglacial lake shorelines and raised marine shorelines, the directions of the tilt of these features, and postglacial delevelling are used to construct six isobase maps showing relative sea level movements over the last 12,000, 10,000, 8000, 4000, and 2000 years, No map has more than 30 control points and usually there are only 12 "good" points controlling the isobase patterns. Each map shows the relationship of the isobases to the current ice sheet extent. Along the southern margin of the Laurentide Ice Sheet, the maximum postglacial emergence has been quite uniform with the 240 to 200 m isobase always close to the ice margin. Along the northeastern margin of the ice sheet, the postglacial emergence at the retreating ice edge was closer to 100 m. Equidistant diagrams are drawn along planes southeast from southern Hudson Bay and eastward from Southampton Island. If these diagrams are compared on a Shoreline Relation Diagram, the two profiles appear similar and compare moderately well with a theoretical SR Diagram published in 1969. The isobases show a major uplift center located around the area of James Bay and southern Hudson Bay where a maximum emergence of nearly 300 m occured in the last 7500 years. High marine limits southwest of Ungava Bay need to be dated because if they date close to 8000 BP as we suggest, then more emergence is suggested for the region southwest of Ungava Bay than we currently allow for.

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“…One model proposes that Bathurst Island lay beneath the south-central part of an lnnuitian Ice Sheet, which is thought to have covered all or most of the islands north of Parry Channel (Blake, 1970;Prest, 1969;McLaren and Barnett, 1978;Mayewski et al, 1981); the other model proposes that Bathurst Island, along with Melville, Cornwallis, Devon, Ellesmere and Axel Heiberg islands, supported large local ice caps that were partly coalescent (England, 1976;England and Bednarski, 1989;Dyke and Prest, 1987).…”

Section: Incongruous Crustal Deformation Patternsmentioning

confidence: 99%

Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

Dyke¹

2007

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Lowther and Griffith islands, in the centre of Parry Channel, were overrun by the Laurentide Ice Sheet early in the last glaciation. Northeastward Laurentide ice flow persisted across at least Lowther Island until early Holocene déglaciation. Well constrained postglacial emergence curves for the islands confirm a southward dip of raised shorelines, contrary to the dip expected from the ice load configuration. This and previously reported incongruities may indicate regionally extensive tectonic complications of postglacial rebound aligned with major structural elements in the central Canadian Arctic Islands.Les îles Lowther et Griffith, situées au centre du chenal de Parry, ont été recouvertes par l'Inlandsis laurentidien tôt au cours de la dernière glaciation. Un écoulement glaciaire vers le nord-ouest a persisté à l'île Lowther, tout au moins, jusqu'à la déglaciation au début de l'Holocène. Les courbes d'émersion bien identifiées de l'île confirment une inclinaison des plages soulevées vers le sud, contrairement à l'inclinaison prévue à partir de la configuration de la charge glaciaire. Ce fait ainsi que d'autres anomalies déjà signalées pourraient indiquer des complications d'ordre tectonique à l'échelle régionale au moment du relèvement isostatique postglaciaire correspondant aux principaux éléments structuraux des îles du centre de l'Arctique canadien.Die im Zentrum des Parry-Kanals gelegenen Insein Lowther und Griffith wurden zu Beginn der letzten Vereisung durch die laurentidische Eisdecke bedeckt. Der laurentidische EisfluB in Richtung Nordosten hat zumindest ùber die Insel Lowther hinweg bis zur frùhen Holozan-Enteisung gedauert. Die deutlich erkennbaren postglazialen Auftauchkurven der Insein bestâtigen eine Neigung der angehobenen Kùstenlinien nach Sùden, entgegen der Neigung, die man entsprechend der Eismassenkonfiguration erwartet hàtte. Dies und zuvor schon aufgezeigte Anomalien kônnten auf regional extensive tektonische Komplikationen beim postglazialen isostatischen Rùckprall hinweisen, entsprechend den wichtigsten strukturellen Elementen der Insein im Zentrum der kana-dischen Arktis

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Retreat of Wisconsin and Recent Ice in North America

Cited by 188 publications

References 0 publications

Histoire postglaciaire de la végétation au sud du lac Abitibi, Ontario et Québec

Histoire postglaciaire de la végétation au sud du lac Abitibi, Ontario et Québec

The observed postglacial recovery of Québec and Nouveau-Québec Since 12,000 BP

Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

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