| Titre | Does the Qeovik Silt on the Labrador Shelf host deposits of Lake Agassiz outburst floods that led to the 8.2 cal Ka cold event? |
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| Auteur | Lewis, C F M ;
Mcdonald, K; Piper, D J W; Sonnichsen, G V; Miller, A A
L |
| Source | L'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 33, 2008 p. 97 |
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| Année | 2008 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20070604 |
| Réunion | Joint Meeting of the Geological Association of Canada, Mineralogical Association of Canada, Society of Economic Geologists and the Society for Geology Applied to Mineral Deposits; Quebec City; CA; mai
26-28, 2008 |
| Document | publication en série |
| Lang. | anglais |
| Media | papier |
| Province | Région extracotière de l'est |
| Région | Labrador Shelf |
| Sujets | lacs glaciaires; dépôts de lacs glaciaires; sediments lacustres; inondations; silts; géologie des dépôts meubles/géomorphologie; Cénozoïque; Quaternaire |
| Programme | Les géosciences à l'appui de la gestion des océans Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières |
| Diffusé | 2008 01 01 |
| Résumé | (disponible en anglais seulement)
A Quaternary stratigraphic framework for the Labrador Shelf, established in 1986, consists of Lower and Upper Tills, Qeovik Silt, and surficial units Makkaq
Clay, Sioraq Sand, and Sioraq Silt and Gravel. The sandy Qeovik Silt (QS) is characterized by relatively high carbonate content, both as sand-sized lithic grains and as finer particles which were interpreted as glacial erosional products transported
by ice rafting, mainly from a glacial ice margin near the mouth of Hudson Strait. The QS age was estimated at 20 ka to 8 ka.
New data from seismic profiles, piston cores, and improved radiocarbon dating, together with advances in
understanding deglacial ice margin positions and ice dam failures of ice-impounded glacial lakes allow more detailed insight into the origin and mechanisms for QS DC delivery. Also, finds of correlative beds rich in detrital carbonate (DC) with
distinct foraminiferal faunas indicating reduced-salinity waters on the Northeast Newfoundland Shelf (NENS) add to the new understanding. The new information reinforces the interpretation that the QS DC originated from glacial erosion of the
limestone and dolomite bedrock underlying Hudson Bay, Foxe Basin and Hudson Strait. However, its deposition was mainly limited to the period 10 ka to 6 ka. In addition to ice-rafting, the DC sediments were likely carried in freshwater-influenced
plumes southward over the Shelf by the Labrador Current. Correlations to known deglacial events suggest that QS DC originated mainly with the Gold Cove (~9.9 ka) and Noble Inlet (~8.7 ka) advances of ice across eastern Hudson Strait. Rapid subglacial
drainage of impounded water behind the latter advance may have enhanced sediment-entrained outflow. Thick deposition followed from glacial Lake Agassiz outburst floods via Hudson Bay about 7.7 ka. The uppermost DC deposition resulted from
deglaciation of Foxe Basin and enhancement of circulation of Arctic Ocean water through the Basin and Hudson Strait. Sand-sized DC deposition on the northern Labrador Shelf and correlative DC deposition to the south on NENS imply that the Agassiz
discharge was a major contributor of sediment to the QS by both ice-rafting and plume transportation. The Agassiz-influenced, reduced-salinity water, indicated by benthonic foraminifera, probably continued southward in the Labrador Current to mix and
be transported in the North Atlantic Current system, contributing to suppression of thermohaline circulation in the Nordic Seas, and initiation of the 8.2 cal ka cold event around the North Atlantic Ocean. |
| GEOSCAN ID | 224901 |
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