Document generated on 10/05/2021 2:08 a.m. Géographie physique et Quaternaire The Early Wisconsinan History of the Laurentide Ice Sheet L’évolution de la calotte glaciaire laurentidienne au Wisconsinien inférieur Geschichte der laurentischen Eisdecke im frühen glazialen Wisconsin Jean-Serge Vincent and Victor K. Prest La calotte glaciaire laurentidienne Article abstract The Laurentide Ice Sheet The identification, particularly at the periphery of the ice sheet, of glacigenic Volume 41, Number 2, 1987 sediments thought to postdate nonglacial sediments or paleosols regarded as having been laid down sometime during the Sangamonian Interglaciation URI: https://id.erudit.org/iderudit/032679ar (stage 5) and thought to predate nonglacial sediments or soils reckoned to be of DOI: https://doi.org/10.7202/032679ar Middle Wisconsinan age (stage 3), has led numerous authors to propose that the Laurentide Ice Sheet initially grew during the Sangamonian and/or the Early Wisconsinan (stage 4). The evidence for the beginning of the See table of contents Wisconsinan ice sheet in various areas of Canada and the northern United States is briefly reviewed. The general absence of sound geochronometric frameworks for potential Sangamonian or Early Wisconsinan glacial deposits Publisher(s) has led to a situation where in most areas it can be argued, depending on one's interpretation, that ice completely inundated or was completely absent at that Les Presses de l'Université de Montréal time. On the premise (perhaps false) that Laurentide Ice was in fact extensive during the Early Wisconsinan, a map showing maximum possible ice extent, as ISSN put forward by some authors is presented and the glacigenic units possibly 0705-7199 (print) recording the ice advance are shown in a correlation chart. This post 1492-143X (digital) Sangamonian sensu stricto (substage 5e) -pre Middle Wisconsinan limit of ice extent is generally more extensive than the Late Wisconsinan (stage 2) limit. The geometry of the ice sheet margin and scanty available information on Explore this journal direction of ice movements indicate that this assumed Early Wisconsinan ice likely developed in a very similar manner to that of the Late Wisconsinan ice complex. A hypothetical growth model of the Laurentide Ice Sheet, following Cite this article the last interglaciation is also proposed. Vincent, J.-S. & Prest, V. K. (1987). The Early Wisconsinan History of the Laurentide Ice Sheet. Géographie physique et Quaternaire, 41(2), 199–213. https://doi.org/10.7202/032679ar Tous droits réservés © Les Presses de l'Université de Montréal, 1987 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, 1987, vol. XLI, n° 2, p. 199-213, 4 fig. THE EARLY WISCONSINAN HISTORY OF THE LAURENTIDE ICE SHEET* Jean-Serge VINCENT and Victor K. PREST, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8. ABSTRACT The identification, particularly RÉSUMÉ L'évolution de la calotte glaciaire ZUSAMMENFASSUNG Geschichte der at the periphery of the ice sheet, of glacigenic laurentidienne au Wisconsinien inférieur. laurentischen Eisdecke im frùhen glazialen sediments thought to postdate nonglacial L'identification, surtout en périphérie de l'in­ Wisconsin. Zahlreiche Autoren sind zu der sediments or paleosols regarded as having landsis, de dépôts glaciaires que l'on croit Annahme gekommen, dap die laurentische been laid down sometime during the San­ postérieurs à la mise en place de sédiments Eisdecke wàhrend des Sangamoniums und/ gamonian Interglaciation (stage 5) and non glaciaires ou de paléosols datant de I1In- oder des frùhen glazialen Wisconsin (Phase thought to predate nonglacial sediments or terglaciaire sangamonien (phase 5) et an­ 4) zu wachsen anting. Dièse Annahme stùtzt soils reckoned to be of Middle Wisconsinan térieurs aux sédiments non glaciaires ou des sich auf die Identifizierung glacialer Sedi- age (stage 3), has led numerous authors to sols mis en place au Wisconsinien moyen mente, die man fur alter als nichtglaziale propose that the Laurentide Ice Sheet initially (phase 3) a amené de nombreux chercheurs Sedimente oder Paleobôden halt, die ihrer- grew during the Sangamonian and/or the Early à supposer que la calotte laurentidienne s'est seits irgendwann wàhrend der Intergtazialzeit Wisconsinan (stage 4). The evidence for the d'abord développée au Sangamonien ou au des Sangamoniums (Phase 5) abgelagert beginning of the Wisconsinan ice sheet in Wisconsinien inférieur (phase 4). On passe worden sind und vermutlich nichtglazialen various areas of Canada and the northern en revue les différentes preuves associées Sedimenten oder Bôden, die der mittleren United States is briefly reviewed. The general au début de la formation de la calotte glaciaire glazialen Wisconsin-Zeit (Phase 3) zugeord- absence of sound geochronometric frame­ wisconsinienne recueillies au Canada et au net werden, vorausgehen. Die Belege fur den works for potential Sangamonian or Early nord des États-Unis. En l'absence quasi gé­ Beginn der Wisconsin-Eisdecke in verschie- Wisconsinan glacial deposits has led to a néralisée de données géochronométriques denen Gebieten Kanadas und der nôrdlichen situation where in most areas it can be argued, sûres pour déterminer l'âge des dépôts gla­ Vereinigten Staaten wird kurz zusammen- depending on one's interpretation, that ice ciaires datant probablement du Sangamonien gefapt. Das volkommene Fehlen eines ges- completely inundated or was completely ab­ ou du Wisconsinien inférieur, on peut aussi icherten geo-chronometrischen Gerùsts fur sent at that time. On the premise (perhaps bien supposer, pour une période donnée, que môgliche glaziale Ablagerungen im Sanga- false) that Laurentide Ice was in fact extensive les glaces ont entièrement envahi une région monium oder frùhen glazialen Wisconsin during the Early Wisconsinan, a map showing ou en étaient tout à fait absentes. En tenant fùhrte dazu, dap in den meisten Gebieten je maximum possible ice extent, as put forward pour acquis (?) que la calotte laurentidienne nach Interpretationsweise das Eis in jener by some authors is presented and the gla­ était en fait très étendue au Wisconsinien Zeit entweder vollstândig ùberflutete oder gar cigenic units possibly recording the ice inférieur, on présente une carte montrant son nicht vorhanden war. Ausgehend von der advance are shown in a correlation chart. étendue maximale et un tableau de corrélation (vielleicht falschen) Prâmisse, dap sich das This post Sangamonian sensu stricto entre les unités glaciaires. Les glaciers pos­ laurentische Eis tatsâchlich wàhrend des frù­ (substage 5e) -pre Middle Wisconsinan limit térieurs au Sangamonien sensu stricto (sous- hen glazialen Wisconsin ausdehnte, wird eine of ice extent is generally more extensive than phase 5e) et antérieurs au Wisconsinien Karte mit der môglichen maximalen Eisaus- the Late Wisconsinan (stage 2) limit. The ge­ moyen sont généralement plus étendues dehnung gezeigt, entsprechend der Annahme ometry of the ice sheet margin and scanty qu'au Wisconsinien supérieur (phase 2). La einiger Autoren; und in einer dazu in Verbin- available information on direction of ice géométrie de la marge glaciaire et les dung stehenden Ùbersicht werden die gla­ movements indicate that this assumed Early quelques données sur la direction de l'écou­ zialen Einheiten gezeigt, die den vermutlichen Wisconsinan ice likely developed in a very lement montrent que les inlandsis du Wis­ Eisvorstop dokumentieren. Dièse Grenze der similar manner to that of the Late Wisconsinan consinien inférieur et du Wisconsinien Eisausdehnung im Postsangamonium sensu ice complex. A hypothetical growth model of supérieur se sont développés de façon si­ stricto (Unterphase 5e) vor dem mittleren the Laurentide Ice Sheet, following the last milaire. On présente enfin un modèle hy­ glazialen Wisconsin ist im Allgemeinen aus- interglaciation is also proposed. pothétique de croissance de la calotte gedehnter als die Grenze im spâten glazialen laurentidienne après le dernier interglaciaire. Wisconsin (Phase 2). Die Géométrie des Eisdeckenrands und ungenùgende zugân- gliche Informationen ùber die Richtung der Eisbewegungen zeigen, dap dieses vermu­ tlich aus dem frùhen glazialen Wisconsin stammende Eis môglicherweise sich àhnlich entwickelte wie die Eisdecke des spâten gla­ zialen Wisconsin. Auperdem wird ein hy- pothetisches Wachstumsmodell der laurentischen Eisdecke nach der letzten In- terglazialzeit vorgestellt. * Geological Survey of Canada Contribution 33186 200 J.-S. VINCENT and V. K. PREST INTRODUCTION for one view point at the expense of another. The documents only serve to illustrate a view point. The location of sites The continental evidence for the beginning of the Laurentide mentioned in the text is shown on Figure 1 and numbers in Ice Sheet1 sometime during the Sangamonian (marine oxygen brackets throughout the paper refer to this figure. isotope stage 5) or Early Wisconsinan (stage 4) and before the Middle Wisconsinan (stage 3) is the subject of this paper. This evidence comes mainly from the