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Sangamon and Pre-Sangamon Interglaciations in the Hudson Bay Document generated on 09/28/2021 12:36 a.m. Géographie physique et Quaternaire Sangamon and Pre-Sangamon Interglaciations in the Hudson Bay Lowlands of Manitoba Les interglaciations du Sangamonien et du pré-Sangamonien dans les basses terres hudsoniennes du Manitoba Interglaziale des Sangamonium und Präsangamonium im Tiefland der Hudson Bay Lynda A. Dredge, Alan V. Morgan and Erik Nielsen The Last? Interglaciation in Canada Article abstract Le dernier (?) interglaciaire au Canada The manuscript documents voluminous new and published stratigraphie and Volume 44, Number 3, 1990 paléontologie data from a region unique in North America, and possibly the world, in that it has abundant natural exposures recording a long and URI: https://id.erudit.org/iderudit/032833ar consistent succession of Quaternary tills and fossiliferous intertill sediments. DOI: https://doi.org/10.7202/032833ar Two major non-glacial intervals have been recognized under tills. Various non-glacial sediments have been correlated using their stratigraphie position, pollen analysis, and beetle assemblages, and are found to be equivalent to the See table of contents Missinaibi Formation in Ontario. Non-finite high pressure radiocarbon dates, and aspartic acid ratios on wood suggest that the uppermost and most prevalent interval is of Sangamonian age. The Sangamonian record begins and Publisher(s) ends with cool intervals, separated by a warmer period when climates were similar to or slightly warmer than present, and when the northern treeline was Les Presses de l'Université de Montréal near its present position. The interval began with a high glacioisostatic sea, which regressed to levels below present Hudson Bay datum. The Sundance ISSN paleosol and silt beds below the Amery till relate to an earlier interglaciation 0705-7199 (print) characterized by cool tundra conditions. As an analogue for predicting future 1492-143X (digital) global change, the record preserved in the Hudson Bay Lowlands is second to none: additional intensive research is strongly recommended. Explore this journal Cite this article Dredge, L. A., Morgan, A. V. & Nielsen, E. (1990). Sangamon and Pre-Sangamon Interglaciations in the Hudson Bay Lowlands of Manitoba. Géographie physique et Quaternaire, 44(3), 319–336. https://doi.org/10.7202/032833ar Tous droits réservés © Les Presses de l'Université de Montréal, 1990 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire. 1990. vol. 44. n 3, p. 319-336. 17 fig., 3 tabl. SANGAMON AND PRE-SANGAMON INTERGLACIATIONS IN THE HUDSON BAY LOWLANDS OF MANITOBA* Lynda A. DREDGE, Alan V. MORGAN and Erik NIELSEN, respectively Geological Survey of Canada, 601 Booth Street, Ottawa. Ontario K1A 0E8; Department of Earth Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1; Manitoba Department of Energy and Mines, 535-330 Graham Avenue, Winnipeg, Manitoba R3C 4E3. ABSTRACT The manuscript documents RÉSUMÉ Les interglaciations du Sangamo­ ZUSAMMENFASSUNG Interglaziale des voluminous new and published stratigraphie nien et du pré-Sangamonien dans les basses Sangamonium und Pràsangamonium im and paléontologie data from a region unique terres hudsoniennes du Manitoba. L'article Tiefland der Hudson Bay. Der Artikel enthàlt in North America, and possibly the world, in renferme une très grande quantité de données umfangreiche neue und schon publizierte stra- that it has abundant natural exposures record­ stratigraphiques et paléontologiques inédites tigraphische und palàontologische Daten ùber ing a long and consistent succession of ou déjà publiées sur une région unique en eine einzigartige Gegend in Nordamerika und Quaternary tills and fossiliferous intertill sed­ Amérique du Nord, voire dans le monde, en môglicherweise in der ganzen Welt: dies iments. Two major non-glacial intervals have raison des nombreux affleurements naturels wegen ihrer zahlreichen natùrlichen been recognized under tills. Various non- qu'elle renferme et qui témoignent d'une Aufschlùsse, die eine lange und bestândige glacial sediments have been correlated using longue succession continue de tills quater­ Folge von Quaternâr-Grundmorànen und fos- their stratigraphie position, pollen analysis, naires et d'intertills fossilifères. On a reconnu silhaltigen Zwischentill-Sedimenten belegen. and beetle assemblages, and are found to be deux intervalles non glaciaires sous les tills. Zwei grôssere nichtglaziale Intervalle wurden equivalent to the Missinaibi Formation in Sur la base de leur position stratigraphique, unter den Grundmoranen festgestellt. Ontario. Non-finite high pressure radiocarbon de l'analyse pollinique et des assemblages de Verschiedene nichtglaziale Sedimente wur­ dates, and aspartic acid ratios on wood sug­ coléoptères, on a corrélé les divers sédiments den mittels ihrer stratigraphischen Position, gest that the uppermost and most prevalent non glaciaires à la Formation de Missinaibi, Pollen-Analyse und Kâfer-Ansammlungen mit interval is of Sangamonian age. The en Ontario. Les datations au radiocarbone der Missinaibi Formation in Ontario korreliert, Sangamonian record begins and ends with obtenues à haute pression et les taux d'acide mit der sie ùbereinstimmen. Nicht begrenzte, cool intervals, separated by a warmer period aspartique sur bois laissent voir que l'intervalle unter Hochdruck gewonnene Radiokarbon- when climates were similar to or slightly supérieur dominant date du Sangamonien. Le Daten und der Anteil aspartischer Sâure auf warmer than present, and when the northern début et la fin du Sangamonien étaient des HoIz lassen darauf schliessen, dass das treeline was near its present position. The intervalles froids séparés par une période plus oberste und beherrschende Intervall aus dem interval began with a high glacioisostatic sea, chaude pendant laquelle le climat était aussi Sangamonium stammt. Der sangamonische which regressed to levels below present chaud ou un peu plus que maintenant et que Beleg beginnt und endet mit kalten Hudson Bay datum. The Sundance paleosol la limite des arbres était à peu près à la même Zwischenzeiten, unterbrochen durch eine wâr- and silt beds below the Amery till relate to an latitude. Le début de l'intervalle a été marqué mere Période, wâhrend der das Klima àhnlich earlier interglaciation characterized by cool par la présence d'une mer glacioisostatique, oder etwas warmer als das gegenwàrtige war tundra conditions. As an analogue for predict­ qui a par la suite régressé à des niveaux infé­ und die nôrdliche Baumgrenze sich in der ing future global change, the record preserved rieurs au niveau actuel de la baie d'Hudson. Nàhe ihrer heutigen Position befand. Das in the Hudson Bay Lowlands is second to Le paléosol de Sundance et les lits de silt Intervall begann mit einem hohen glazioisos- none: additional intensive research is strongly sous-jacents au till d'Amery datent d'une inter­ tatischen Meer. welches auf niedrigere recommended. glaciation antérieure caractérisée par un cli­ Niveaus als das heutige Hudson Bay-Datum mat froid de toundra. Comme point de com­ zurùckging. Der Palâoboden von Sundance paraison à l'étude des changements à und die Schlammbetten unter der Amery- l'échelle du globe, les données préservées Grundmoràne gehôren zu einem friiheren dans les basses terres de la baie d'Hudson Interglazial, welches durch kùhle Tundra- sont uniques: on doit donc y effectuer des Bedingungen gekennzeichnet ist. AIs recherches intensives. Vergleichsbasis fur die Voraussage einer kùnftigen weltweiten Verânderung ist der im Tiefland der Hudson Bay erhaltene Beleg von einzigartigem Wert: zusàtzliche intensive Forschung wird nachdrùcklich empfohlen. * Geological Survey of Canada Contribution No. 48688 Manuscrit reçu le 30 janvier 1989: manuscrit révisé accepté le 25 septembre 1989 320 L. A. DREDGE, A. V. MORGAN and E. NIELSEN INTRODUCTION the coast, and scattered stunted trees. The tundra areas farther south are covered with thick bog deposits containing abundant In recent years, predicting global change has become quantities of ground ice forming polygons (Fig. 3). The surface increasingly important for long term environmental planning. vegetation there is a lichen-heath association, with scattered Since we presently live part way through an interglaciation alders, tamarack and spruce. An open forest-tundra transition which began more than 10,000 years ago, a first step towards zone runs diagonally from northwest to southeast across the predicting future change is to examine the course of previous region (Fig. 4). The boreal forest consists of stands of black interglacial intervals and evaluate the present against them. spruce (Fig. 5) with a Ledum-Sphagnum-Vaccinium ground This paper explores the range of climatic and environmental cover. Tamarack, birch, sedge, alder and grasses are also conditions experienced in mid-Canada during the last intergla­ common in wet areas. ciation. The thick Quaternary sequences exposed along rivers in the Hudson Bay Lowlands of Manitoba provide a long record of waxing and waning ice sheets, and climatic changes. STRATIGRAPHIC FRAMEWORK
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