Document generated on 09/23/2021 9:47 a.m. Géographie physique et Quaternaire Postglacial Isobases from Northern Ellesmere Island and Greenland: New Data Isobases postglaciaires du nord de l’île d’Ellesmere et du Groenland : nouvelles données Postglaziale Isobasen vom Norden der Ellesmere-lnsel und Grönland: neue Daten John England and Jan Bednarski Volume 40, Number 3, 1986 Article abstract Over seventy new 14C dates on former relative sea levels from Hall Land, URI: https://id.erudit.org/iderudit/032650ar northwest Greenland, and Clements Markham Inlet, northern Ellesmere DOI: https://doi.org/10.7202/032650ar Island, are combined with previous data to revise the regional isobases for this area. These isobases show : 1) a centre of maximum postglacial emergence See table of contents over northwest Greenland extending to; 2) an intervening cell of lower emergence over northeast Ellesmere Island which was isostatically-dominated by the Greenland Ice Sheet; in turn, extending to 3) a higher centre of Publisher(s) emergence over the Grant Land Mountains, northernmost Ellesmere Island, associated with the independent history of local ice caps there. Radiocarbon Les Presses de l'Université de Montréal dates from raised marine shorelines show a 2000 year lag between glacial unloading on northwest Greenland and northernmost Ellesmere Island. This ISSN lag in glacioisostatic adjustments suggests a considerable range in the glacier response times and/or glacioclimatic regimes in this area. Throughout the area 0705-7199 (print) the last ice limit was ca. 5-60 km beyond present ice margins. Maximum 1492-143X (digital) emergence at these ice limits is marked by shorelines built into a full glacial sea which range from 124 m asl in Clements Markham Inlet to 150 m asl in Hall Explore this journal Land. This indicates that similar emergence (120-150 m) in other areas does not necessarily require the removal of entire ice sheets although this has been commonly assumed in the literature. The geophysical implications of this Cite this article warrant consideration. England, J. & Bednarski, J. (1986). Postglacial Isobases from Northern Ellesmere Island and Greenland: New Data. Géographie physique et Quaternaire, 40(3), 299–305. https://doi.org/10.7202/032650ar Tous droits réservés © Les Presses de l'Université de Montréal, 1986 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, 1986, vol. XL, n° 3, p. 299-305, 7 fig., 1 tabl. POSTGLACIAL ISOBASES FROM NORTHERN ELLESMERE ISLAND AND GREENLAND: NEW DATA John ENGLAND and Jan BEDNARSKI, respectively Department of Geography, University of Alberta, Edmonton, Alberta T6G 2H4 and Department of Geography, Trent University, Peterborough, Ontario K9J 7B8. ABSTRACT Over seventy new '4C dates RÉSUMÉ Isobases postglaciaires du nord AUSAMMENFASSUNG Postglaziale Iso- on former relative sea levels from Hall Land, de l'île d'Ellesmere et du Groenland: nou­ basen vom Norden der Ellesmere-lnsel und northwest Greenland, and Clements Markham velles données. Plus de 70 nouvelles data­ Grônland: neue Daten. Ùber 70 neue '4C Inlet, northern Ellesmere Island, are combined tions au radiocarbone effectuées sur d'anciens Daten ùberfrùhere relative Meeresspiegel von with previous data to revise the regional iso­ niveaux marins, sur la terre de Hall (nord- Hall Land, Nordwest-Grônland und der bases for this area. These isobases show : ouest du Groenland) et dans la baie de Cle­ Clements Markham Bucht, nôrdliche Elles­ 1 ) a centre of maximum postglacial emerg­ ments Markham (nord de l'île d'Ellesmere), mere-lnsel, werden mit schon vorhandenen ence over northwest Greenland extending to; ont été associées aux données déjà recueillies Daten kombiniert, um die regionalen Isobasen 2) an intervening cell of lower emergence over et permettent de réviser les isobases de la fur dieses Gebiet zu revidieren. Dièse Isoba­ northeast Ellesmere Island which was isos- région. Celles-ci révèlent: 1)un centre sen zeigen : 1 ) ein Zentrum des maximalen tatically-dominated by the Greenland Ice d'émersion postglaciaire maximale au nord- postglazialen Auftauchens ùber Nordwest- Sheet; in turn, extending to 3) a higher centre ouest du Groenland qui s'étend jusqu'à 2) un Grônland, welches sich ausdehnt zu 2) einem of emergence over the Grant Land Mountains, compartiment de faible relèvement dans le dazwischenliegenden Gelàndeabschnitt mit northernmost Ellesmere Island, associated nord-est de l'île d'Ellesmere, couvert par l'in­ niedrigerem Auftauchen ùber dem Nordosten with the independent history of local ice caps landsis du Groenland qui s'étendait jusqu'à der Ellesmere-lnsel, welcher isostatisch durch there. Radiocarbon dates from raised marine 3) un centre d'émersion plus importante à die Grônland Eiskappe dominiert wurde; shorelines show a 2000 year lag between l'endroit des Grant Land Mountains, à l'ex­ welcher seinerseits sich zu 3) einem hôheren glacial unloading on northwest Greenland and trême nord de l'île d'Ellesmere, associée à Auftauchzentrum ùber den Grant Land northernmost Ellesmere Island. This lag in révolution des calottes glaciaires locales. La Mountains ausdehnte, im àuBersten Norden glacioisostatic adjustments suggests a con­ datation au radiocarbone de lignes de rivage der Ellesmere-lnsel, das mit der unabhângi- siderable range in the glacier response times soulevées révèle un décalage de 2000 ans gen Geschichte der dortigen lokalen Eis- and/or glacioclimatic regimes in this area. entre le retrait glaciaire qu'a connu l'extrême kappen in Verbindung gebracht wird. Throughout the area the last ice limit was ca. nord d'Ellesmere et celui qu'a connu le nord- Radiokarbon-Daten der gehobenen marinen 5-60 km beyond present ice margins. Maxi­ ouest du Groenland. Ce décalage entre les Kùstenlinien zeigen einen Zeitunterschied von mum emergence at these ice limits is marked rajustements glacioisostatiques laisse entre­ 2000 Jahren zwischen dem glazialen Rùckzug by shorelines built into a full glacial sea which voir une grande variation dans le temps de im Nordwesten von Grônland und dem im range from 124 m asl in Clements Markham réaction du glacier et dans les régimes gla- àuBersten Norden der Ellesmere-lnsel. Dieser Inlet to 150 m asl in Hall Land. This indicates cioclimatiques de la région. Partout la dernière Zeitunterschied in den glazialisostatischen that similar emergence (120-150 m) in other limite glaciaire se situe de 40 à 60 km au- Anpassungen IaBt eine erhebliche Schwan- areas does not necessarily require the removal delà des marges glaciaires actuelles. kung in der Reaktionszeit des Gletschers und/ of entire ice sheets although this has been L'émersion maximale près de cette limite est oder glazialklimatischen Systemen in diesem commonly assumed in the literature. The marquée par des lignes de rivage construites Gebiet vermuten. In diesem ganzen Gebiet geophysical implications of this warrant en pleine mer glaciaire, qui vont de 124 m ging die âuBerste Eisgrenze etwa 40-60 km consideration. anm, dans la baie de Clements Markham, à ùber die heitigen Eisgrenzen hinaus. Das 150 m anm, sur la terre de Hall. Ceci révèle maximale Auftauchen an diesen Eisgrenzen qu'ailleurs une emersion de cet ordre, soit ist durch Kùstenlinien markiert, die in ein voiles de 120 à 150 m, ne suppose pas nécessai­ glaziales Eismeer hineingebaut sind und rement le retrait de toute la calotte glaciaire, welche von 124 m ùber dem Meeresspiegel in bien que cette idée soit généralement ac­ der Bucht von Clements Markham bis zu ceptée. Les conséquences géophysiques qui 150 m ùber dem Meeresspiegel in Hall Land en découlent exigent désormais qu'on en reichen. Das zeigt, daB ein vergleichbares tienne compte. Auftauchen (120-150 m) in anderen Gebieten nicht unbedingt den Rùckzug der ganzen Eiskappen erfordert, auch wenn dies allge- mein in der Fachliteratur angenommen wurde. 300 J. ENGLAND and J. BEDNARSKI INTRODUCTION equilibrium has been attained and it does not include restrained rebound before déglaciation. The amount of postglacial emergence is commonly thought to reflect the magnitude of a former ice load and regional Conversely, WEIDICK (1976) took a similar data base isobases drawn on postglacial shorelines are used to infer along Nares Strait and contoured it to indicate maximum the pattern of the ice cover (cf. ANDREWS, 1968, 1970). In emergence extending from Hall Land to Ellesmere Island via Arctic Canada, BLAKE (1970) reported a ridge of greatest the central part of the strait (Fig. 2b). In both cases (ENGLAND, Holocene emergence running from Bathurst Island to Eureka 1976a; WEIDICK, 1976) the isobases increase in value Sound. From this he concluded that an "lnnuitian Ice Sheet" southward from the Lincoln Sea, toward northern Ellesmere inundated the eastern Queen Elizabeth Islands during the Island and northwest Greenland (Fig. 1). Moreover, both sets last glaciation when it presumably coalesced with the Greenland of isobases extend smoothly from northernmost Greenland Ice Sheet in Nares Strait and the Laurentide Ice Sheet in to Ellesmere Island where they trend obliquely across the Lancaster Sound (Fig. 1). WALCOTT (1970) also contoured northern coast towards the west. The overall difference between a ridge of maximum emergence extending from near Bathurst the two reconstructions is due to the sparsity of control points, Island, across Ellesmere Island, to northwest Greenland which for example ENGLAND (1976a) had only two sites on the he named the 'lnnuitian Uplift*. entire north coast of Ellesmere Island. Because of this shortage of data PATERSON (1977) noted that different authors could ENGLAND (1976a, 1982) on the other hand, interpreted provide different interpretations and he also questioned whether this emergence data in a different manner.