Late Wisconsinan Buildup and Wastage of the Innuitian Ice Sheet Across Southern Ellesmere Island, Nunavut1

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Late Wisconsinan buildup and wastage of the Innuitian Ice Sheet across southern Ellesmere Island, Nunavut1

John H. England, Nigel Atkinson, Arthur S. Dyke, David J.A. Evans, and Marek Zreda

Abstract: During the Late Wisconsinan, a precursor of the Prince of Wales Icefield, southern Ellesmere Island, formed a prodigious ice divide of the Innuitian Ice Sheet. Initial buildup occurred after 19 ka BP, when the icefield advanced west (inland) across Makinson Inlet from margins similar to present. Subsequent reversal of flow to the east required ice divide migration to the west onto a plateau that is largely ice-free today. From this divide, a trunk glacier flowed eastward through Makinson Inlet to join the Smith Sound Ice Stream en route to nothern Baffin Bay. Westward flow from this divide filled Baumann Fiord, depositing a granite dispersal train that extends a further 600 km across the archipelago to the polar continental shelf. Deglaciation of most of Makinson Inlet occurred catastrophically at -9.3 ka BP, forming a calving bay that thinned the Innuitian divide, thereby triggering deglaciation of most of Baumann Fiord by 8.5 ka BP. Ninety 14C dates on Holocene shells and driftwood constrain deglacial isochrones and postglacial emergence curves on opposite sides of the former Innuitian divide. Isobases drawn on the 8 ka BP shoreline rise northwest towards Eureka Sound, the axis of maximum former ice thickness. Ice margins on Ellesmere Island were similar to present from -50–19 ka BP (spanning marine isotope stages 3 and 2). However, significant regional variation in ice extent during this interval is recorded by ice rafting from the Laurentide Ice Sheet into Baffin Bay. Later buildup of the Innuitian Ice Sheet occurred during the low global sea level that defines the last glacial maximum (18 ka BP). We also suggest that the Innuitian Ice Sheet was influenced by the buttressing and subsequent removal of the Greenland Ice Sheet along eastern Ellesmere Island.

Résumé : Au cours du Wisconsinien tardif,61 un précurseur du champ de glace Prince de Galles, île d’Ellesmere Sud, a formé un gigantesque partage glaciaire de l’inlandsis innuitien. L’accumulation initiale a eu lieu plus tard que 19 ka avant notre ère, lorsque les champs de glace ont avancé vers l’ouest (vers l’intérieur des terres), par-dessus le passage de Makinson, à partir de bordures semblables à celles du présent. Un renversement subséquent de l’écoulement vers l’est a poussé la migration de la ligne de partage glaciaire vers l’ouest, sur un plateau généralement libre de glace de nos jours. De cette ligne de partage glaciaire, un glacier principal s’écoulait vers l’est par le passage de Makinson pour rejoindre le courant glaciaire du détroit de Smith se dirigeant vers la baie de Baffin Nord. L’écoulement vers l’ouest à partir de cette ligne de partage glaciaire a rempli le fjord de Baumann, déposant une traînée de blocs glaciaires de granite qui s’étend sur plus de 600 km à travers l’archipel jusqu’à la plate-forme continentale polaire. La déglaciation de la plus grande partie du passage de Makinson a eu lieu de façon catastrophique vers ~9,3 ka avant le présent, formant une baie de vêlage qui a aminci la ligne de partage glaciaire innuitienne, déclenchant ainsi la déglaciation de la plus grande partie du fjord de Baumann vers 8,5 ka avant le présent. Quatre-vingt-dix datations au 14C sur des coquillages holocènes et du bois de grève limitent les courbes isochrones de déglaciation et de l’émergence post-glaciaire de part et d’autre de l’ancienne ligne de partage innuitienne. Les isobases tracées sur le rivage de 8 ka avant le présent s’élèvent au nord-ouest, vers le détroit d’Eureka, l’axe de l’épaisseur maximale antérieure de la glace. Les limites glaciaires sur l’île d’Ellesmere de ~50–19 ka avant le présent (chevauchant les étapes 3 et 2 des isotopes marins) étaient semblables aux limites actuelles. Toutefois, des variations régionales importantes dans l’étendue de la glace durant cet intervalle sont enregistrées par le transport de la glace de l’inlandsis laurentidien dans la baie de Baffin. Une croissance tardive de l’inlandsis innuitien a eu lieu au cours du bas niveau global de la mer qui définit le dernier maximum glaciaire (18 ka

Received 17 January 2003. Accepted 21 August 2003. Published on the NRC Research Press Web site at http://cjes.nrc.ca on 3 February 2004. Paper handled by Associate Editor C.R. Burn. J.H. England2 and N. Atkinson. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada. A.S. Dyke. Terrain Sciences Division, Geological Survey of Canada, 601 Booth Street, Ottawa ON K1A 0E4, Canada. D.J.A. Evans. Department of Geography and Topographic Sciences, University of Glasgow, Glasgow, G12 8QQ, Scotland. M. Zreda. Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721, U.S.A. 1Polar Continental Shelf Project (PCSP) Contribution 01003. 2Corresponding author (e-mail: [email protected]).

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avant le présent). Nous suggérons aussi que l’inlandsis innuitien ait été influencé par les contreforts de l’inlandsis du Groenland le long de l’île d’Ellesmere Est et de son retrait subséquent.

[Traduit par la Rédaction] England et al.

Background on the IIS Introduction The IIS consisted of alpine and lowland sectors. Ice in the Here we discuss Late Wisconsinan glaciation and Holocene alpine sector dispersed radially from the highlands of Axel sea-level change across an east–west transect (200 km) of Heiberg and Ellesmere islands, filling a central inter-island southern Ellesmere Island (Fig. 1). This field area is important basin (Fig. 1). Ice in the central basin thickened to ≥1km to the glacial history of the Queen Elizabeth Islands (QEI) (Ó Cofaigh et al. 2000) with flow diverging southward through because physiography and climate combined to make it a Eureka Sound to Norwegian Bay and northward through prodigious centre of ice dispersal within the former Innuitian Nansen Sound to the Arctic Ocean (Bednarski 1998). Postglacial Ice Sheet (IIS; Blake 1970, 1972). Although a consensus emergence within the basin exceeds 140 m (Blake 1970; now favours the existence of the IIS during the last glacial Hodgson 1985; Bell 1996), the highest in the QEI, and has maximum (LGM; Bednarski 1998; England 1998, 1999; Dyke long been interpreted as the axis of maximum former ice 1999), outstanding questions remain concerning its geometry, sheet thickness (Blake 1970; Walcott 1972). Southwest of ice flow pattern, extent, and chronology. This paper focuses Eureka Sound, this axis extends across Norwegian Bay to on the buildup and dynamics of the main divide of the the marine channels of the central Arctic islands, where it southeast IIS during the LGM, as well as on the subsequent trends east–west, marking the former divide of the lowland wastage of this ice sheet and its glacioisostatic effects. We sector of the IIS (Fig. 1; Dyke 1998, 1999; Lamoureux and report that the former IIS divide on southern Ellesmere Island England 2000). was oriented north–south, occupying plateaus close to the modern drainage divide separating Makinson Inlet and Baumann Geology and physiography Fiord that is largely ice-free today. To the west of this divide, Innuitian ice advanced across an open landscape The landscape of southern Ellesmere Island descends from leading into Baumann and Bay fiords that provided unim- east to west, reflecting the regional geology. The highest terrain peded passage across the Arctic Archipelago, likely reaching (-1200 m asl (above sea level)) underlies the Canadian Shield, the continental shelf of the Arctic Ocean Basin. To the east, which is composed of granite, gneiss, and metasediments Innuitian ice advanced through Makinson Inlet, entering the (Frisch 1988) largely obscured by the modern Prince of Wales Smith Sound Ice Stream that was dominated by Greenland Icefield (-14,000 km2; Figs. 1, 2). Outer Makinson Inlet is ice flowing southward from Nares Strait to Baffin Bay (Blake incised through the Canadian Shield and is characterized by 1992a, 1993; Blake et al. 1996). Prior to the last buildup of a precipitous coastline with tidewater glaciers. This area has the IIS, numerous 14C dates record a prolonged interval the highest precipitation in the QEI (Koerner 1977; Maxwell (-50–19 ka BP) during which the Ellesmere Island icefields, 1981) and lies adjacent to the North Water polynya in northern including those adjacent to northern Baffin Bay, had margins Baffin Bay. similar to present. This interval spans marine isotope stage 3 Along its western flank, the Shield is overlain by undeformed and extends into stage 2, with ice buildup coinciding with a Paleozoic carbonate rocks of the Arctic Platform (Fig. 1). period of low global sea level (-18 ka BP; Clark and Mix Around inner Makinson Inlet, these rocks form a dissected 2000). plateau (<400 m asl) sloping westward to Vendom Fiord Our reconstruction is based on widespread geomorphic (Figs. 1, 2). Between inner Vendom Fiord and Makinson Inlet, and geologic evidence mapped across southern Ellesmere Island. the plateau rises to intercept the modern equilibrium line altitude Twenty-seven 14C dates, using accelerator mass spectrometry (ELA, -750 m asl; Miller et al. 1975), supporting small ice (AMS), on subtill organics and ice-transported shells constrain caps. Here the carbonate rocks are folded, defining the the chronology of ice buildup. Another 90 14C dates obtained Franklinian mobile belt which continues to the west (Trettin on Holocene shells and driftwood collected from raised marine 1987). North of Baumann Fiord, Svendsen Peninsula is char- shorelines provide a chronology of subsequent ice retreat. acterized by alpine topography, whereas to the south, on Dated shorelines are also used to establish postglacial emergence Bjorne Peninsula (3500 km2), isolated mountains (<600 m curves on opposite sides of the former IIS divide and to asl) occur within an expansive lowland (<150 m asl). The draw postglacial isobases for 8 ka BP. These data are relevant base of Bjorne Peninsula is flanked by the Schei Syncline to geophysical modelling used to reconfigure the IIS during (700 m asl) and the northern margin of Sydkap Ice Cap the LGM (Tushingham and Peltier 1991; Peltier 1996). This (>1000 m asl, Figs. 1, 2). paper contributes to our understanding of high-latitude ice Baumann Fiord and Makinson Inlet converge from opposite sheet dynamics adjacent to Baffin Bay and the Arctic Ocean coasts, reducing Ellesmere Island to a stem of land only Basin, where the relationship between marine sedimentation 25 km wide (Figs. 1, 2). Baumann Fiord is -100 km long, and the terrestrial record warrants elaboration (Bischof and 15–20 km wide, and 200–400 m deep, and recurves northward Darby 1999). The interaction of the Greenland and Innuitian into Vendom Fiord (75 km long and <100 m deep). Makinson ice sheets during the LGM is also relevant to the dating of Inlet extends 90 km inland from Smith Bay (adjoining northern paleo-ice-core records from this region. Baffin Bay). Outer Makinson Inlet is 8 km wide and up to

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Fig. 1. Regional map of the Queen Elizabeth Islands and the adjacent coast of Greenland. Contemporary ice caps are shaded. Field area on southern Ellesmere Island is enclosed by the rectangle. Bedrock geology within the rectangle is illustrated to the left. Fd. Fiord; P.B., Piliravijuk Bay.

500 m deep, whereas its inner half is shallow (<100 m) and papers predating our field work. We summarize their obser- narrow (in places -1 km). The entire north shore of Makinson vations and interpretations first for Makinson Inlet, then for Inlet is bordered by the Prince of Wales Icefield, whereas the Baumann and Vendom fiords. inner south shore, including Piliravijuk Bay, is characterized by Near Makinson Inlet, radiocarbon dates (AMS) on subtill low, ice-free terrain (Figs. 2, 3). Piliravijuk Bay branches to organic deposits (peat with twigs, sedges, moss) record a the SW where it divides into “north” and “south” arms (informal non-glacial interval spanning at least 20 to 43 ka BP (Blake names used in text). 1992b, Fig. 4A). In outer Makinson Inlet, streamlined bedforms, striae, and carbonate erratics on the Precambrian Shield of Previous research Bowman Island (Blake 1993) record vigorous, eastward ice flow towards Baffin Bay. Blake used the elevation of carbonate Hodgson (1973, 1985) and Blake (1992b, 1993) wrote salient erratics on the island’s summit (-570 m asl) to calculate a

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Fig. 2. LANDSAT 7 image showing physiography of southern Ellesmere Island and principal place names used in text. Modern drainage divide on uplands between Makinson Inlet and Vendom Fiord is shown by a dashed, white line which divides field area into its eastern and western sectors. P.B., Piliravijuk Bay.

minimum former ice thickness of 1200 m (based on water from eastern Ellesmere Island. The northern dispersal train fol- depth of ≤600 m). The freshness of these erosional landforms, lows Bay Fiord (Fig. 1; Bell 1996), whereas the southern dis- and low amino acid ratios on shells collected from adjacent persal train follows Trold and Vendom fiords. The trajectory of till, indicated passage of late Wisconsinan ice (Blake 1993, the southern dispersal train records its deflection towards Fig. 4A). During deglaciation of Makinson Inlet, Hodgson Bjorne Peninsula by local ice caps occupying Raanes Peninsula (1985, p. 361) noted that ice margins “did not retreat towards, (Ó Cofaigh et al. 2000). Deglaciation of Raanes Peninsula or even parallel to, the present ice caps, but westward, towards involved a two-step process starting -9 ka BP. Initially, marine- a divide that bears only a few small glaciers today”. Radio- based ice broke up rapidly in Eureka Sound and adjoining carbon dates on marine shells indicated that deglaciation fiords. This was followed by the stabilization of land-based progressed rapidly from the outer coast of southeastern ice at fiord heads where a prominent “drift belt” was deposited Ellesmere Island (9.3 ka BP at Clarence Head, Fig. 1) to (Hodgson 1985). Subsequently, ice on Raanes Peninsula inner Makinson Inlet (9.3 ka BP, Hook Glacier) after which retreated either radially towards local upland divides or east- retreat slowed, reaching inland of the fiord head by 7.3 ka BP ward to the Prince of Wales Icefield. Prior to this study, (Blake 1993). Associated marine limits reach 80–120 m asl Holocene 14C dates were unavailable for Bjorne Peninsula. throughout the inlet (Hodgson 1985; Blake 1993). A postglacial There, marine limit reaches >110 m asl but declines to emergence curve from Piliravijuk Bay is similar to other -70 m asl at the head of Vendom Fiord where shells date emergence curves reported from Arctic Canada — the only 7.0 ka BP (Hodgson 1973, 1985). Postglacial isobases drawn exception being a small transgression at -5.5 ka BP (Blake across SW Ellesmere Island reach 140 m asl north of 1993). Baumann Fiord, along southern Eureka Sound (Ó Cofaigh Prior to this study, fewer observations concerning late 1999). Quaternary glaciation and sea-level change were available from Baumann and Vendom fiords (Hodgson 1973, 1985). Field observations North of Baumann Fiord, Bell (1996) and Ó Cofaigh et al. (2000) identified two granite dispersal trains deposited during The field area is partitioned into eastern and western sectors, the LGM by westward-flowing ice entering Eureka Sound located on opposite sides of the drainage divide between

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Fig. 3. Physiography of Makinson Inlet. (A) View east out of Makinson Inlet from surface of granite felsenmeer (-640 m asl) at junction with Piliravijuk Bay. Note steep-sided Bowman Island and precipitous highlands along fiord that typifies the Precambrian Shield. (B) View southeast across inner Makinson Inlet. Lower terrain surrounding Hook Glacier is the dissected plateau underlain by Paleozoic carbonate of the Arctic Platform. Higher terrain on horizon is the Precambrian Shield underlying the Prince of Wales Icefield.

Makinson Inlet and Vendom Fiord. Field results are presented Inlet where limestone erratics rest on granite felsenmeer. first for the eastern sector, then for the western sector. Available Farther out Makinson Inlet, Blake (1993) observed Paleozoic radiocarbon dates are listed in Tables 1 and 2. carbonate erratics on Bowman Island (Figs. 1–3, 6), origi- nating at least 35 km up-fiord (Blake 1978). We revisited Erratics and ice-flow indicators Bowman Island to collect shell fragments from till for AMS dating in order to further constrain the age of ice advance. Eastern sector Granite erratics from the Precambrian Shield occur through- Western sector out the eastern sector. They have been transported westward Granite erratics are widespread within till resting on carbonate onto the Paleozoic sedimentary terrain forming the watershed bedrock along Vendom and Stenkul fiords and on southern (770 m asl) between Vendom Fiord and Makinson Inlet. Svendsen Peninsula (up to 615 m asl, Fig. 5B). However, Granite erratics also occur southwest of Piliravijuk Bay on granite erratics were not observed elsewhere on Svendsen the plateau (Fig. 5A); however, they are sparse in this direction. Peninsula, or on southern Raanes Peninsula (Fig. 1; Ó Cofaigh Shelly till and glaciofluvial gravel both containing granite et al. 2000). Granite erratics are widespread on Bjorne erratics also occur on Swinnerton Peninsula. Peninsula, where till blankets occur to > 400 m asl and Paleozoic erratics and striae also record an eastward ice commonly contain fragmented shells several kilometres flow out of the inlet, across the Precambrian Shield. For inland of Baumann Fiord (Figs. 1, 5B). On southern Bjorne example, Blake (1993) reported striated dolomite above 300 m Peninsula, granite erratics are supplanted by carbonates asl on the east and west ends of Swinnerton Peninsula, both transported northward from Schei Syncline by a precursor to sets indicating ice flow towards Makinson Inlet (Fig. 5A). the Sydkap Ice Cap. This eastward flow is also recorded at higher elevations Other ice-flow indicators (striae and bedforms) are rare in (680 m asl) at the junction of Piliravijuk Bay and Makinson the western sector because of poor preservation on carbonate

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Fig. 4. Distribution of pre-Holocene radiocarbon dates (ka BP) discussed in text. Site numbers (in brackets) and dates correspond to those in Table 1. Eastern (A) and western (B) field areas.

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England et al. 45 ) ) ) b b b (1979) Hodgson (1973) This paper This paper This paper This paper This paper Blake (1988) Blake (1988) Blake (1988) Blake (1988) Blake (1992 Blake (1992 Hodgson (1973) Blake and Matthews Blake (1983) This paper This paper This paper Blake (1992 This paper This paper Blake (1988) This paper This paper Dyck and Fyles (1964) Ó Cofaigh et al. (2000) Hodgson (1985) ′′ ′′ ′′ ′′ ′′ ′′ ′′ 8, p.16) states that the wood 54 54 30 17 48 17 17 410 years was applied. ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ! 82°13 81°30 86°46 81°27 80°17 85°30 81°45 81°45 81°45 81°45 81°45 81°45 82°15 81°37 81°37 82°03 87°45 82°01 82°03 81°23 81°45 80°17 80°17 86°46 81°40 87°24 85°45 olded rocks of the Eureka Sound For- erator mass spectrometry (AMS) whereas ries”) and Hodgson (1985). The remains of ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′′ 20 22 52 22 50 05 05 44 5 44 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ey are subtill fossils. 20 77°31 63 78°02 90 77°47 ≥ ≤ Related RSL (m asl) Lat. N Long. W References ≥ 25‰ and a reservoir correction of ! C= 20 13 42 ? 77°19.2 140140 NA132 NA140 77°49.8 NA 77°49.8 NA 77°49.8 77°49.8 140140 NA NA 77°49.8 77°49.8 400400 NA NA 77°41.4 77°41.5 240 ? 77°20 240105130 ?130 ? ? NA 77°20 77°19 77°18 77°49.8 ------Sample elevation (m asl) ------Subtill organics Subtill organics Subtill organics Subtill organics Subtill organics Subtill organics BeachDeltaic 5 gravel ? 63 78°05 c c c d c c c d 30 000 45 000 Peaty soil ≥ Age (years BP)>52 Enclosing 000 material ≥ Peat >39 000 31 100±480 35 260±78034 310±610 Beach Shelly till 29 800±220 Surface35 310±400>33 000 Till 90 Marine silt30 100±750 ? Gravelly silt 77°20 191 67 103–108 ? ? 78°10 77°29 sp. 41 260±400and Marine silt sp. >38 000 and sp. 32 500±1580 Lacustrine sediments ? 24 840±160 Till blanket (?) 36 550±420 Till blanket sp. sp. Salix Salix Salix Salix Salix Salix giganteum Betula Betula Material Calliergon Peat H. arctica M. truncata H. arctica H. arctica H. arctica M. truncata H. arctica H. arctica b a b Laboratory dating No. C dates. Samples of marine shells were corrected for isotopic fractionation to a base of 14 Pre-Holocene radiocarbon dates (see Fig. 4 for site locations). Fd., Fiord; Lat., latitude; long., longitude; NA, Not applicable; RSL, relative sea level. Laboratory designations: GSC, Geological Survey of Canada;Several TO, additional IsoTrace “old” Laboratory; dates AA, on Univeristy peat of occur Arizona. in TO this and area AA and samples are were discussedSeveral dated by dates by Blake on accel and wood Matthews from (1979), the Blake head (1983, of p. Vendom 28–29, Fd. “Makinson are Inlet > Peat 30 Se ka BP. In reference to GSC-1942 (>23 ka BP, not listed in Table), Hodgson (in Lowdon and Blake, 197 These samples constitute part of a series of old peat dates from a site 16 km north of the head of Makinson Inlet (N. Arm). These dated deposits occur over f Note: a b c d GSC designations are conventional several species of beetles in GSC-3607-2 indicates a climate warmer than present and the occurance of these samples beneath boulders suggests that th mation and are discussed in Blake (1988). Table 1. SiteMakinson Location Inlet 1a N. Arm,1b E.2 N. Arm,3 E. Hook4a Glacier, S. lobe Inner4b Piliravijuk Bay, Glacier N. 7A-45 Glacier 7A-454c GSC-2677 AA-23631 TO-1135a Glacier 7A-454d GSC-3607-2 Inner Driftwood Piliravijuk Bay, N. Central Wood; Piliravijuk5b GSC-3364-2 Bay, N.6 GSC-3828 TO-9496 Central GSC-3364 Wood Piliravijuk (twigs)7 45 Bay, 700±2600 N. Central8 GSC-3421 Piliravijuk Wood; Bay, Surface, TO-9497 N. ice-thrust Central Wood; 9a >40 silt Piliravijuk 000 Bay, N. Glacier9b AA-23621 7A-45 Wood; W. Bowman9c AA-23618 I. W. Bowman10 I. W. Bowman4e I. Central Piliravijuk4f Bay, N. Glacier 7A-45 GSC-2687Baumann GSC-134 Fiord Glacier and 7A-45 AA-23635 tributaries 11 TO-944712 Wood; Vendom TO-9448 Fd. Shell13 head fragment Outer Baumann14a Fd., Unknown N. TO-1300 Outer Baumann14b 32 Fd., 170±480 Outer W. Unknown Baumann TO-2690 Fd.,15 W. Outer Baumann TO-5602 Fd., Till16 W. GSC-1789 Sedge GSC-6469 Inner 22 Baumann 830±40017 Fd., TO-9486 Sedge S Inner 19 Baumann 130±370 Fd., TO-9485 W. Driftwood Vendom Till Fd. head Till Shell TO-9498 fragment GSC-2700 20 Shell 240±310 fragment >36 000 19 33 790±300 460±380 Shell 32 fragment GSC-1832 670±310 242 Till Till 32 070±290 Wood; ? 242 Till 242 ? 77°15 ? 175 77°15 175 77°15 ? 209 ? ? 77°49 77°49 77°15 “resembled material found in…possible Beaufort Formation age sediments of central Ellesmere Island”.

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Fig. 5. Glacial geomorphology and granite erratic distribution across the field area. Eastern (A) and western (B) field areas. In B, note granite-free area on western Svendsen Peninsula ascribed to exclusion of granite-bearing ice by local ice cap.

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Fig. 6. (A) Oblique aerial view looking east across Bowman Island, Peninsula. A shell fragment from the east end of the peninsula outer Makinson Inlet. Note prominent lower bench on middle dated 34.3 ka BP (site 7, Fig. 4A), whereas two fragments right side of island (white arrow) where photo B was taken. Ice collected 15 km to the west yielded ages of 36.6 and 24.8 ka flow out of the inlet heavily eroded the island and deposited BP (site 5, Fig. 4A, and Table 1). Elsewhere, carbonate till carbonate erratics on its summit (>500 m asl, Blake 1993). containing erratic shells is widespread below -250 m asl on (B) Roche moutonnée eroded on quarried granite gneiss, Bowman glacially abraded bedrock of Bowman Island (Fig. 6). Three Island, by ice flowing from right to left. Person circled for scale. fragments from this till yielded AMS ages of 19.1, 22.8, and Carbonate till at this site contains shells dated 19.1, 22.8, and 32.2 ka BP (site 9, Fig. 4A, and Table 1). 32.2 ka BP (site 9, Table 1). Western sector Subtill organic deposits have not been reported from Bjorne and Svendsen peninsulas. Two allochthonous pieces of wood collected by Hodgson (1973) from raised marine deposits at the head of Vendom Fiord dated > 30 ka BP and > 36 ka BP (sites 11 and 17, respectively, Fig. 4B). Hodgson suggested that these samples may have originated from the late Tertiary Beaufort Formation that is both wood-bearing and widespread on central Ellesmere Island. To date, the only sediment of known pre-Holocene age occurs on northern Bjorne Peninsula, where abundant shells eroding from marine silt (67 m asl) dated > 33 ka BP (site 13, Fig. 4B). Three AMS 14C dates were obtained on individual shell fragments collected from till above marine limit along Baumann Fiord. Along the outer west shore, two fragments dated 33.5 and 32.7 ka BP (site 14, Table 1). A third fragment, collected up-fiord, dated 32.1 ka BP (site 15, Fig. 4B). In the same vicinity, Hodgson (1985) reported shells dated 30.1 ka BP (site 16, Fig. 4B).

Lateral meltwater channels and gradient of marine limit Lateral meltwater channels are widespread in the field area (Fig. 5) and are commonly nested in the direction of ice retreat (Dyke 1993). These channels have been mapped from aerial photographs (in stereo) onto topographic maps (1 : 250 000), then plotted at publication scale (Fig. 5). The lowermost channels terminate at Holocene marine limit, and therefore must date from deglaciation. Although some meltwater channels may have formed earlier (i.e., during ice buildup or pre-Late Wisconsinan glaciations), none are clearly discordant with those that formed during early Holocene deglaciation. bedrock and weakly lithified sandstone. Striae aligned with Baumann Fiord occur on Hoved Island (at 132 m asl) and Eastern sector eastern Svendsen Peninsula (at 600 m asl, Fig. 5B). Striae Lateral meltwater channels display two patterns of ice retreat were also observed above the south shore of Grytte Bay, in the field area. One set of channels that is not widespread oriented east–west, perpendicular to its eastern shore (Fig. 5B). records the northward retreat of trunk ice from inner Makinson Elsewhere, striae are commonly parallel to valleys entering Inlet (Fig. 5A; cf., Hodgson 1985). The former trunk-ice margin is prominently displayed by a fiord-parallel canyon, fiords, e.g., at the heads of Trold and Svarte fiords and - entering Jaeger Bay (Fig. 5B; Ó Cofaigh et al. 2000). cut in bedrock, 2 km northwest of Polynya Bluff (Fig. 5A). The mouth of the canyon is occupied by an ice-fed delta Ice buildup marking marine limit at 88 m asl (Fig. 7D). Meltwater channels on the plateau to the west descend towards Makinson Inlet Eastern sector and record the separation and inland retreat of local ice caps Pre-Holocene radiocarbon dates (27) are listed in Table 1, adjacent to the canyon. with corresponding site locations shown in Fig. 4A. Subtill The second pattern of lateral meltwater channels records organic deposits, apart from those reported by Blake (1982, widespread ice retreat in tributary valleys at right angles to 1992b) were not observed during this study. The youngest of Makinson Inlet and Piliravijuk Bay (Fig. 5A). This pattern is these samples is 19.8 ka BP (site 4, Fig. 4A). well developed along the inner west shore of Makinson Inlet, Six shell samples were collected and dated from till above as well as in valleys draining southeast into Piliravijuk Bay. marine limit. Each date was based on an individual shell The retreat of glaciers at right angles to the inlet is also recorded fragment to avoid a blended age. Three of these samples by former piedmont lobes that deposited thick (>30 m) were recovered from granite-bearing till on Swinnerton glaciomarine outwash dipping up-inlet (west) on Ujuk Island

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Fig. 7. Elevation of marine limit (m asl) across the field area. Eastern (A) and western (B) field areas. In A, note general decline of marine limit from east to west along Makinson Inlet, and from south to north along Vendom Fiord. In B, note decline in marine limit from west to east.

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Fig. 8. Examples of deglacial sea level in the field area. (A) Ice-fed delta (62 m above sea level (asl)) at the head of Vendom Fiord (seen lower right). Shells dated 6.9 ka BP (TO-9879) collected from bottomset mud, distal to this delta, provide a minimum age for local deglaciation and the 62 m relative sea level. Note proximity of the Prince of Wales Icefield (right background) and the lateral meltwater channels eroded during its retreat (barbed arrows). (B) Oblique view north across deglacial delta inland (southwest) of Piliravijuk Bay (south arm). Two shell dates were obtained at this site (8.4 and 8.6 ka BP, AA-23611 and AA-23612, respectively; site 7, Fig. 9A, and Table 2). (C) View overlooking surface of marine limit delta (72 m asl), north of Split Lake, -15 km north of the head of Makinson Inlet (site 24, Fig. 9A). H. arctica collected in this vicinity (not shown) from silt and clay at 36 m asl provide a minimum age for the delta (7.3 ka BP, GSC-1972; Blake 1993). Delta foreset beds are highlighted by dashed lines. (D) View north towards interior of Makinson Inlet, -2 km west of Polynya Bluff. Sinuous arrow outlines terminus of fiord-parallel canyon cut along former margin of retreating trunk glacier occupying Makinson Inlet. Canyon ends at 88 m marine limit delta dated at least 8.0 ka BP based on shells in exposed bottomsets (site 16, Fig. 9A).

and on the north shore of the inlet where outwash rises to Peninsula and Hoved Island (Fig. 5B). On Bjorne Peninsula, marine limit (103 m asl, Fig. 7A). abundant meltwater channels occur below 250 m asl, and Marine limit was not observed along the steep coastline of display a radial pattern extending into interior valleys, at outer Makinson Inlet. However, fossiliferous Gilbert-type deltas right angles to the coast (Fig. 5B). The lowest channels are are widespread throughout much of the inner inlet and often associated with small moraines and terminate at deltas Piliravijuk Bay (Figs. 7, 8). Collectively, marine limit is marking marine limit. In contrast to Baumann Fiord, lateral highest (-105 m asl) in central Makinson Inlet and lowers meltwater channels recording trunk ice retreat are widespread progressively northward along inner Makinson Inlet (to 72 m asl, in the narrow tributary fiords (e.g., Svarte and Vendom fiords). Fig. 7A) and southward along Piliravijuk Bay (82–95 m asl, Farther inland, lateral meltwater channels nested towards the Fig. 7A). Prince of Wales Icefield and Sydkap Ice Cap show increasing topographic control as remnant glaciers on Svendsen and Western sector Bjorne peninsulas thinned and separated. The uppermost lateral meltwater channels that rim Svendsen Marine limit in the western sector descends progressively and Bjorne peninsulas (-350 and 270 m asl, respectively) from west to east. The highest marine limit measured (135 m descend towards Baumann Fiord (Fig. 5B). Occasional, coast- asl, as shown in Fig. 7B) occurs on northern Bjorne Peninsula parallel channels record the retreat of trunk ice from Baumann (Fig. 7B). Towards central Baumann Fiord, marine limit Fiord. The trunk glacier margin in central Baumann Fiord is descends to -105 m asl and, farther east, to -75 m asl at the recorded by a morainal bank deposited between Svendsen heads of Sor, Stenkul, and Vendom fiords (Fig. 7B). These

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50 Can. J. Earth Sci. Vol. 41, 2004

elevations are similar to marine limit inland of Makinson Inlet (103 m asl) containing shells dated 8.8 ka BP (site 3). Ice and Piliravijuk Bay (Fig. 7A). persisted later inland of Piliravijuk Bay’s north arm, where an ice-fed delta (72 m asl) dated 8.1 ka BP (site 6). Age of marine limit There are -90 Holocene radiocarbon dates from Makinson Western sector Inlet and Baumann Fiord, two-thirds of them introduced in Radiocarbon dates on marine shells from outer Baumann this paper (Table 2). The dates considered pertinent to the Fiord indicate that marine limit was established by 8.8 ka BP deglacial chronology are shown in Figs. 9A and 9B. We exclude (sites 37 and 39, respectively, Fig. 9B, and Table 2). In central from this analysis age determinations on Portlandia arctica Baumann Fiord, the age of marine limit decreases to 8.2 ka BP (see the following subsection). (site 50). Inland of Baumann Fiord, the sea had reached the head of Stenkul Fiord by 7.9 ka BP (site 55). Marine limit Portlandia problem dates are younger still along the south shore of Vendom Portlandia arctica is an infaunal bivalve that commonly Fiord (7.6–7.0 ka BP; sites 58–62). constitutes a pioneer species in deglacial environments in Arctic Canada. Radiocarbon dates on P. arctica collected Holocene emergence curves from deglacial sediments in both the eastern and western sectors are systematically older than dates on other mollusk Eastern sector species from the same sediments. In the eastern sector, a In central Makinson Inlet, 14 radiocarbon dates are available on shorelines ranging from marine limit (-107 m asl) to just date of 9.3 ka BP (GSC-3180, Blake 1993) was obtained on - P. arctica collected from silt (65 m asl) near Hook Glacier above high tide ( 4 m asl, Fig. 10A, and Table 3). Most of (site 11b, Table 2). A sample of Hiatella arctica collected these samples come from Swinnerton Peninsula along an from silt (71 m asl) at the same coordinates dated 8.4 ka BP isobase (northeast–southwest) defined by two driftwood samples (AA-23628, site 11a, Table 2) and this age corresponds with (25 km apart) of similar age (4.9 ka BP) and elevation (23 m a similar marine limit dated nearby (site 9, Fig. 9A). P. arctica asl; sites 30c and 32, Table 3). The older dates (8–9 ka BP) was also collected on Swinnerton Peninsula (-20 km to the were obtained on marine shells within deglacial beaches or south) from glaciomarine mud (68 m asl; site 1, Fig. 9A). deltas. All younger dates are on driftwood from raised beaches. P. arctica from this mud yielded ages of 9.6 and 9.5 ka BP We use nine new control points to construct our emergence (AA-23620 and TO-9487), whereas an H. arctica valve from curve which supplements a previous curve for the same area the same sample dated 9.0 ka BP (-500 14C years younger, (Blake 1993; Fig. 10A). This curve shows continuous emergence TO-9488, sites 1a, 1b, 1c, respectively, Table 2). during the past 9 ka BP, with a half-life of 1500 years. The In the western sector, the oldest Holocene date was again one outlier in the Makinson Inlet data (Fig. 10A) was obtained obtained on P. arctica collected on northern Bjorne Peninsula on driftwood embedded in a raised beach at 45 m dated (9.4 ka BP, CAMS-61418, site 37, Fig. 9B, and Table 2). 6.0 ka BP (site 29, Table 3). Why this sample plots > 10 m H. arctica and M. truncata from the same sample dated above the curve is unknown, but it may have been transported 14 above its contemporaneous sea level (by sea-ice push?) or it 600 C years younger (8.8 ka BP, GSC-6410, Table 2). 14 Another sample of P. arctica (the next oldest sample along is the result of an incorrect C age determination. Baumann Fiord) was collected at a depth of6minalake Western sector sediment core on Hoved Island (9.3 ka BP, TO-4757, site 38, Nine dated samples were selected around Schei Point, Fig. 9B; from Smith 1998). H. arctica and M. truncata collected northern Bjorne Peninsula, extending from marine limit nearby, and within5mofmarine limit (103–108 m asl), (-133 m asl) to -6 m asl (Fig. 10B, Table 3). Driftwood dated 1100 14C years younger (8.2 ka BP, Beta-116771, site was not found in this area. However, shells (in growth position) 50, Fig. 9B, and Table 2). Collectively, these and other 14C occurred not only in deglacial sediments but also in Gilbert-type comparisons indicate that dates on P. arctica are significantly deltas at intermediate and low elevations. The availability of older than those on accompanying species where the substrate deltas on Bjorne Peninsula spanning a wide range of elevation is calcareous. These age differences are much larger than the is exceptional for Ellesmere Island, likely because of the local standard errors on these dates. Similar inter-species age availability of erodible Sverdrup Basin rocks that have supplied differences are widespread throughout the QEI and are sediment throughout the Holocene. The sites selected for the discussed elsewhere (England et al. 2003). Schei Point emergence curve fall along a common isobase, Eastern sector assuming an orientation (northeast–southwest), similar to those drawn for neighbouring parts of Ellesmere Island (Blake The older deglacial dates (9.0–9.2 ka BP) occur in central 1975; England 1976; Ó Cofaigh 1998). Our curve indicates Makinson Inlet and along the north shore of Piliravijuk Bay continuous, ongoing emergence since deglaciation with a (Fig. 9A), where marine limit is ≥ 105 m asl. North of this half-life of 1500 years (Fig. 10B). locality, dates on marine limit (9.0–7.6 ka BP) record subsequent ice retreat and the re-entry of the sea that had reached inland of Split Lake by 7.3 ka BP (site 24). Interpretation East of Piliravijuk Bay, the retreat of a valley glacier from Makinson Inlet towards Manson Icefield is marked by an Ice buildup ice-contact delta at 107 m asl dated 8.7 ka BP (site 4, Fig. 9A). Late Wisconsinan buildup of a precursor of the Prince of At this time, trunk ice had retreated at least 3 km inland of Wales Icefield is constrained by subtill organic detritus dated Piliravijuk Bay’s south arm, recorded by an ice-contact delta as young as 19.8 ka BP (TO-2690; Blake 1992b). This site

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England et al. 51

Fig. 9. Distribution of Holocene radiocarbon dates (ka BP) related to deglaciation discussed in text. Site numbers (in brackets) and dates correspond to those in Table 2. Eastern (A) and western (B) field areas.

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52 Can. J. Earth Sci. Vol. 41, 2004 This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper Blake (1993) This paper Lowdon and Blake (1978) This paper This paper This paper Lowdon and Blake (1979) Lowdon and Blake (1979) This paper This paper Blake (1983) This paper This paper This paper This paper Lowdon and Blake (1979) This paper Lowdon and Blake (1978) this paper Blake (1981) Dyck and Fyles (1964) ′′ ′′ ′′ ′′ ′ ′ ′ ′ ′ ′ 02 11 52 08 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 82°15 82°04 81°34 82°25 81°43 81°43.3 81°51 81°56 81°58 81°30 81°33 81°32 82°15 82°25 81°33 82°03 82°05 82°03 81°33 82°03 80°52 81°27 81°34 82°08.5 82°01 81°17.4 81°17.5 81°47.5 81°25 81°56 81°32 82°14 82°01 81°32 81°50 81°34 81°44.5 81°50 ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ 30 ′ ′ ′ ′ ′ ′ ′ 30 30 31 09 20 17 20 40 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 87 77°07 93 77°32 115 77°23 102 77°20 107 77°23 107 77°15 7272 77°19 77° 19 84 77°17 105 77°30.6 7287 77°50 77°34 103 77°10 ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ ≤ 91 77°19 81 77°31 82– 82 77°07 82 77°19.4 42103103 77°19 77°25.6 77°25.6 47 77°48.3 Related RSL (m asl) Lat. N Long. W References - ≥ ≤ ≥ ≥ ≤ ≤ ≥ - 5838 >58– >38405840 >40 77°19 >58– >409671 77°19 >96– 77°19 82 5858 >58– >58– 70 8667 77°09 87 77°34 84 >8456 77°19 >56– 82 4275 >42 8842 77°19 77°31 50 >503236 77°31 >32–<94 >36– 77°09 71 >71–<93 77°32 10 65 >65– 51 78 77°36 Sample elevation (m asl) ------<81 - - - gravel gravel glaciomarine silt gravel sand gravel Age (years BP) Enclosing material 9600±65 Rhythmites9270±110 Marine silt 58 65 <115 >65– 77°23 9470±709340±70 Rhythmites Rhythmites 9190±709150±60 Silt9020±60 and sand Rhythmites 8930±100 Rhythmites 8780±80 Clayey silt Foreset8710±70 86 sand and 8630±65 Delta8620±65 face Marine8600±65 >96– sand Bottomset8550±70 sand Beach Foreset sand and <82 8360±65 Silt 938140±608090±80 95 Bedded sand Bedded sand 77°18 8540±708540±70 Surface Silt8260±60 Bottomset sand 8090±708090±100 77 Surface 8000±65 Stoney silt 7930±60 Bottomset silt 102 Ice-thrust 7920±1107910±70 Stony silt 7840±65 Foreset gravel 77°12 Foreset7780±65 sand and Bottomset7740±120 silt 27 and 7690±65 Stoney silt Foreset7620±60 sand and 7590±60 Bottomset7310±80 silt Massive7220±75 sand Clayey silt Rhythmites <25 83 27 >27– 77°40 ? 8440±75 Marine silt b b Material P. arctica P. arctica P. arctica H. arctica P. arctica H. arctica H. arctica H. arctica M. truncata M. truncata M. calcarea H. arctica M. truncata M. truncata P. arctica H. arctica P. arctica M. truncata H. arctica H. arctica H. arctica H. arctica M. truncata M. calcarea M. truncata Salix H. arctica H. arctica M. truncata H. arctica H. arctica H. arctica M. truncata H. arctica H. arctica a AA-23634 Laboratory dating No. Holocene Radiocarbon Dates (see Fig. 9 for site locations). 1a1b Outer N. Arm, W.2a Outer N. Arm, W. Inner Piliravijuk Bay, N.2b2c Inner Piliravijuk Beta-111699 AA-23620 Bay, N.1c Inner Piliravijuk TO-9487 Bay, N.2d Outer TO-9999 N. Arm, W.3 Inner Piliravijuk TO-224 Bay, N. Inner Piliravijuk Bay,4 S. GSC-2519 5 TO-9488 Central Makinson TO-9997 7a Inlet, S. Outer Piliravijuk8 Bay, Inner N. Piliravijuk Bay, S.9 Outer AA-23619 Piliravijuk Bay, N. Hook AA-23612 Glacier, N. lobe AA-23617 TO-9998 7b Inner Piliravijuk Bay, S.6a AA-23611 6b Inner Piliravijuk Bay, N. Inner Piliravijuk Bay, N. AA-23633 Beta-119914 Table 2. Site Location Makinson Inlet 11b S. lobe, Hook Glacier GSC-3180 1013b Outer Piliravijuk11a Bay, Inner N. Piliravijuk Bay, S. S. lobe, AA-23622 Hook Glacier12 TO-9873 13a Inner Piliravijuk Bay, Inner N. AA-23628 Piliravijuk Bay, S. AA-23632 14 GSC-146 IF15a Inner Piliravijuk16 Bay, Inner N. Piliravijuk shell Bay, fragments N.17 Polynia GSC-2692 Bluff GSC-2701 Hook IF Glacier, S.15b lobe18a Inner Piliravijuk 8200±220 Bay, N.18b Outer N. AA-23630A Arm, Raised E. Outer beach GSC-2712 N. Arm, AA-23616 E.19 Central N. Arm,20 W. TO-9874 7321 Hook AA-23623 Glacier, S. lobe Inner N. Arm,22a AA-23629 W. >73– 23 Inner N. TO-9875 Arm, W.24 Inner Piliravijuk25 Bay, S. N. of AA-23615 26 Split Lake Hook Glacier, AA-23610 27 N. lobe N. AA-23613 of Fiord head N. of Split Lake AA-23626 GSC-1972 GSC-3783 GSC-3688 Peat Driftwood 6260±60 6450±70 Marine mud — 47 ? NA 77°49.8

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England et al. 53 (1996) This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper Dyck et al. (1965) This paper Lowdon and Blake (1978) Smith (1998) This paper Blake (1993) This paper Blake (1993) Blake (1993) This paper Blake (1993) Blake (1993) Blake (1988) McNeely and Atkinson This paper Ó Cofaigh et al. (2000) This paper This paper This paper This paper This paper This paper Ó Cofaigh et al. (2000) Ó Cofaigh et al. (2000) Blake (1993) ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ c 00 34 52 34 50 14 12 10 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 87°31 86°49 81°56 80°55 81°33 80°55 80°55 86°49 84°37 87°39 81°35 81°34 86°47 85°52 85°31 81°23 85°06 85°05 82°10 81°20 82°11 82°11 81°20 82°10 82°10 82°10 82°10 83°52 86°14 85°28 85°60 86°17 84°38 84°51 85°08 83°27 87°27 86°40 ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ c 30 04 20 30 30 30 04 40 46 50 30 54 45 40 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 133 77°50 123 78°06 96 77°56 ≤ ≤ ≤ 32 77°34 121 77°49 23 77°19 334532 77°17 31 77°26 16 77°19 23 77°19 21 77°40 21 77°26 19.5 77°19 15 77°19 8.5 77°19 5.3 77°15 7.5 77°15 4 77°19 77°15 77°19 121 77°49 10987 77°46 77°32 113 77°49 30 77°18 ! Related RSL (m asl) Lat. N Long. W References ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ 90 103 77°32 32 > 3 >34 77°18 95 88 >88– 101 104 77°36 23 115 121 77°48 - ! - - - - 133 >133–<143 78°06 Sample elevation (m asl) - - - f ice-moulded bedrock Age (years BP) Enclosing material 9370±409270±80 Marine silt Lake core 113 8180±50 Upper beaches 4540±70 Raised beach 10 >10 77°19 8800±90 Marine silt8725±65 Surface overlying 113 8660±70 Marine8650±120 silt8530±80 Marine sand 8480±140 Marine8360±60 silt Surface8340±50 123 Marine8380±100 silt Marine sand Sand and silt >123– 8110±708000±70 116 Bottomset8050±70 silt 82 Marine8020±60 87 silt >116– Bottomset7900±70 silt Beach 118 Bottomset 77 beds 61 65 107 77°42 <75 102 113 85 77 77°34 77°34 77°16 77°20 8750±100 Surface8660±70 132 Raised beach gravel >132–<142 128 78°07 >128–<138 78°08 e , b b H. arctica M. trucata Material B. mysticetus P. arctica P. arctica M. truncata H. arctica H. arctica H. arctica, M. truncata H. arctica H. arctica H. arctica H. arctica M.truncata H. arctica, M. trucata H. arctica, M. truncata H. arctica H.arctica H. arctica H. arctica, M. trucata H. arctica, M. truncata a O-8148 Laboratory dating No. Beta-111695 Driftwood 5700±60 Marine siltBeta-111694 Driftwood 28 3900±70CAMS-61418 Surface GSC-6410 GSC-6028 ). continued ( Mouth of Baumann Fd., N. Outer Blind Fd. TO-5862 d d Table 2 Site Location 2829 Outer Piliravijuk30a Bay, N. Outer N.31 Arm, Inner E. Piliravijuk GSC-1817 Bay, N.30b Central Piliravijuk22b Bay, Inner N. Piliravijuk GSC-2713 Bay, Driftwood N.30c Inner N. Arm, W.32 Inner AA-23625 GSC-3703 Piliravijuk Driftwood Bay, N.30d Outer N.30e Arm, Inner E. Piliravijuk Driftwood GSC-2705 Driftwood Bay, N.33 Inner Piliravijuk AA-23614 Bay, N.30f 6100±90 GSC-2651 Central Driftwood Piliravijuk35a Bay, Inner N. GSC-3411 Piliravijuk Bay, Driftwood N.36 5930±60 Central AA-23624 Beach Makinson gravel T Driftwood Inlet, S.35b GSC-3456 Central Driftwood Piliravijuk 5950±65 Beach30g Beta-111693 Bay, 5630±70 Central shingle N. Makinson Driftwood Inlet, S. Inner Piliravijuk Driftwood Bay, Driftwood Raised N. Raised Beta-111689 beach35c 4900±60 32.7 beach30h Central 5270±65 GSC-5055 Makinson Driftwood 32 Inlet, Beach S. 4600±60 Inner PiliravijukBaumann Bay, N. Fiord 4590±90 Beta-111772 Surface and Driftwood tributaries 45 37a 30.5 4870±65 Beach gravel GSC-1836 Driftwood38 Mouth Beach 4000±60 of 4480±60 gravel Baumann Fd.,37b Raised S. beach Lake 1, Driftwood Hoved Mouth Raised 3250±70 I. Beach of beach gravel Baumann Fd.,39 S. 21 16 Raised 21 2880±60 beach 23 40 2830±50 15 Beach TO-4757 19.5 shingle Outer Trold Fd. Raised 2060±50 beach41 8.5 Raised42 beach N. Bjorne 4.6 43 Pen.44 AA-23583 7.5 N. Bjorne45 Pen. Central Baumann46 Fd., E. Outer Baumann47 Fd. Outer Beta-111682 Baumann TO-9483 48 Fd., W. Outer Baumann49 Fd., W. Inner Baumann GSC-6412 50 Beta-111681 Fd., GSC-244 N. Troll Fd.51 Beta-116131 Hoved I.52 Beta-111705 Mouth of53 Svarte Fd., Hoved W. I.54 Inner Baumann55 Fd., Beta-111678 S. N. Bjorne Pen. Head of Stenkul Fd. Beta-111703 Beta-116773 Beta-116771 shell fragment Beta-111697 Beta-111679 TO-9484 8190±50 Stony silt

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54 Can. J. Earth Sci. Vol. 41, 2004 C= 13 nd, Dyke, , which routinely This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper Hodgson (1973) This paper Lowdon and Blake (1978) This paper P. arctica ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ 39 57 07 01 17 00 46 06 36 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 87°00 87°11 86°50 86°54 86°38 86°26 86°50 86°38 82°31 86°53 86°48 82°10 83°17 82°06 82°14 ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ a. TO and AA samples were dated by accelera- 56 30 30 10 30 49 35 26 36 40 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 74 77°54 ≤ 7372 77°48 77°50 534832 78°07 35 77°51 18 77°52 19 77°50 9 77°49 77°52 77°51 Related RSL (m asl) Lat. N Long. W References ≥ ≥ >61– ≥ ≥ ≥ ≤ ≤ ≤ ≤ 5215 >52 62 78°04 78°03 - - Sample elevation (m asl) C dates. Samples of marine shells were corrected for isotopic fractionation to a base of 14 Massive stony muds 58 dated 9370 BP (site 37a). The 8.2 ka BP date is given precedence over the date on Age (years BP) Enclosing material 7870±707750±80 Delta7560±80 sand Stony7370±80 sand7010±80 Marine6980±90 silt Surface 6880±60 Marine6830±80 silt 70–73 Stony6750±60 70–72 silt Foreset6200±80 sand Foreset 554430±60 sand Stony4420±80 silt Sand3980±100 53 84 Foreset2790±70 sand Bottomset 32–36 sand2670±60 27–31 Bottomset sand Foreset sand 28–32 77°33 16 8–12 16–18 0.5 24 6.5 2 77°52 77°52 P. arctica , on S. Swinnerton Pen. (Lowdon and Blake 1978). This would put the sample in Piliravijuk Bay. Given the reported longi- ′ . The driftwood at site 30 h from the head of Piliravijuk Bay indicates a longitude corresponding to inner Baumann Fd. (>40 km to the ′ Material A. borealis A. borealis H. arctica, M. trucata H. arctica, M. trucata H. arctica H. arctica H. arctica M. truncata A. borealis M. truncata A. borealis H. arctica M. truncata H. arctica H. arctica a 410 years was applied. Laboratory dating No. ! from the Candian Arctic commonly show systematically greater ages than accompanying shells of different species when these samples are dated (Engla relates to marine limit adjacent to the lake where P. arctica ). H. arctica concluded ( Fd., Fiord; Lat., latitude; long., longitude; NA, Not applicable; Pen., Peninsula; RSL, relative sea level. Laboratory designations: Beta, Beta Analytic, Miami, Florida; GSC, Geological SurveyRadiocarbon of dates Canada; on TO, IsoTrace Laboratory; AA, Univeristy of Arizon Only the oldest deglacial dates are presented. For a full listing of available dates, see Ó Cofaigh et al. (2000). The latitude for the driftwood sample at site 28 is reported to beThis 77°17 date on This sample was recovered from the basal sediments of a 6-m-long lake core from a 26-m-deep isolation basin. Note: a b c d e f 25‰ and a reservoir correction of ! and McNeely, in preparation); hence, the younger dates from this site are given preference. tor mass spectrometry (AMS). Beta-116131 and Beta-116773 are AMS dates, all others are conventional exceeds the age of other species in the same sample. tude, it is morewest); likely this that must the be sample in is error, located hence closer the to sample 77°19 is included in the site 30 series. Table 2 Site Location 5657 N. Bjorne58 Pen. N. Bjorne59 Pen. Inner Vendom Fd.,60 E. Outer Vendom Fd.,61 E. Head of62 Vendom Fd. Head Beta-111684 of GSC-6483 63 Vendom Fd. Head Beta-111685 of GSC-6464 64 Vendom Fd. N. Bjorne GSC-1858 65 Pen. N. Bjorne GSC-1957 66 Pen. N. Bjorne TO-9879 67 Pen. N. Bjorne68 Pen. N. Bjorne69 Pen. N. Bjorne GSC-6498 70 Pen. N. Bjorne GSC-6502 Pen. N. Bjorne GSC-6501 Pen. GSC-6499 GSC-6407 GSC-6406 GSC-6404 GSC-6503

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England et al. 55

occurs north of the head of Makinson Inlet (near Glacier 7A-45, glaciers are uncommon bordering the wider and deeper parts Fig. 4A) and records ice-free conditions from at least 43– of Baumann Fiord and outer Makinson Inlet. Their scarcity 20 ka BP (Blake 1992b). It is also known that the sea occupied along Baumann Fiord is attributed to the occupation of its Makinson Inlet during this interval based on AMS dates on coastlines by tributary ice debouching from Bjorne and redeposited shells in till that span 19.1 to 36.6 ka BP (sites 9 Svendsen Peninsula as the marine-based trunk glacier retreated, and 5, respectively, Fig. 4A). Furthermore, shells within granitic thereby precluding the formation of coast-parallel channels. till overlying Paleozoic bedrock require a westward advance In outer Makinson Inlet, the modern coastline is steep and of Prince of Wales Icefield onto Swinnerton Peninsula no heavily glacierized; hence, the lack of coast-parallel channels earlier than 24.8 ka BP (site 5, Fig. 4A), from an ice margin suggests that either (1) the adjacent Prince of Wales and similar to present. Granite erratics are more abundant in the Manson icefields remained in contact with the trunk ice during northern part of the eastern sector, indicating that Vendom its retreat, or (2) coast-parallel channels were formed and Fiord was the primary recipient of westward outflow from they have been subsequently overridden by the late Holocene the central Prince of Wales Icefield. In contrast, fewer granite readvance of these icefields (see below). In both sectors, erratics around Piliravijuk Bay suggest that during ice buildup, where the fiords are narrower (<5 km) and shallower, lateral the primary outflow from the Manson Icefield was not west- meltwater channels recording trunk ice retreat are well ward, but rather northward into Makinson Inlet or eastward developed (i.e., Vendom Fiord and inner Makinson Inlet). into Baffin Bay. In these settings, the ice bordering the fiords withdrew si- The subsequent transport of carbonate erratics eastward multaneously, allowing drainage along the flanks of the trunk through Makinson Inlet and across Bowman Island records a glaciers to erode lateral channels. Following trunk ice retreat, reversal in the direction of ice flow (from -west to northeast). lateral meltwater channels formed throughout the field area This flow reversal signals a migration of the ice divide, from at right angles to the fiords, recording widespread radial re- its initial, near-modern configuration to a position over the treat of land-based ice (Figs. 5A, 5B). carbonate plateau to the west (-750 m asl), between Makinson Using the configuration of lateral meltwater channels (Fig. 5), Inlet and Vendom Fiord. Striae on Swinnerton Peninsula, together with the available 14C dates on marine limit landforms oriented towards Makinson Inlet (Blake 1993; Fig. 5A), are contacting them (Figs. 7 and 9, respectively), isochrones of consistent with this divide position. The continuation of this ice retreat are drawn for Makinson Inlet and Baumann Fiord ice flow out of the inlet eroded streamlined bedforms on (Fig. 11). In the wider, outer parts of both fiords, the isochrones Bowman Island (Blake 1993) and redeposited shells as young form prominent embayments that record the more rapid breakup as 19.1 and 22. 8 ka BP (site 9, Figs. 4A, 6, and Table 1). It of trunk glaciers relative to the retreat of ice on adjacent is unknown when the proposed ice divide migration was land. For example, the isobase embayment in Makinson Inlet completed, establishing this sector of the IIS; however, it shows that the sea had penetrated to the head of Piliravijuk must postdate the youngest, ice-transported shells (19.1 ka BP). Bay (north arm) by 9.2 ka BP (site 2b, Table 2). The rate of The westward migration of the local IIS divide, to a position retreat to this position is unknown because of the current between Makinson Inlet and Vendom Fiord, was likely lack of dates from the outer part of the inlet. However, a date accompanied by a similar westward migration of its divide of 9.3 ka BP (GSC-3183, Lowdon and Blake 1981) obtained on highlands to the north and south. North of Vendom Fiord, on shells at Clarence Head, 120 km to the east on Smith this would place the divide close to the modern margin of Sound (Fig. 1), provides a similar, minimum age for marine the Prince of Wales Icefield, where thick (>10 m), granite- limit in central Makinson Inlet. These dates suggest that the bearing Tertiary gravel is plentiful on Braskeruds Plain (Fig. 1; breakup of ice westward from Baffin Bay may have been Hodgson 1985). Such a westward migration of the divide catastrophic. After 9.2 ka BP, the rate of trunk glacier retreat would have enhanced ice flow through Vendom Fiord, allowing through inner Makinson Inlet slowed to -3 km/century based granite-bearing ice to override eastern Svendsen Peninsula on the difference between the establishment of marine limit en route to Baumann Fiord (Figs. 1, 5B; Ó Cofaigh et al. 2000). on northern Swinnerton Peninsula (9.0 ka BP, site 1, Fig. 9A) The absence of granite erratics on the higher (≥1000 m and north of Split Lake, -55 km away (7.3 ka BP, site 24, asl), western half of Svendsen Peninsula is interpreted to be Fig. 9A). This retreat rate differs from that proposed by a record of their exclusion by radial outflow from a local ice Blake (1993, 1.8–2.1 km/century) because his calculation divide. A similar explanation was proposed for the lack of used the date (9.2 ka BP) on P. arctica at Hook Glacier, inner granite erratics on Raanes Peninsula to the northwest which Makinson Inlet, that we regard as anomalously old. In Baumann bifurcates their distribution into northern and southern dispersal Fiord, trunk ice retreated from the fiord mouth at 8.8 ka BP, trains (Ó Cofaigh et al. 2000, their fig. 11). The local ice forming a deep embayment by 8.0 ka BP (Fig. 11). By mass on western Svendsen Peninsula would have deflected 7.6 ka BP, glaciers were close to the heads of Vendom and the southern granite dispersal train across Baumann Fiord Stenkul fiords (Fig. 11), indicating a retreat rate averaging and onto Bjorne Peninsula where granite erratics are abundant -10 km/century. (Fig. 5B). The youngest shell date on till currently available As proposed by Hodgson (1985), most of the ice retreating from Bjorne Peninsula is 32.1 ka BP (TO-9498; site 16, up Makinson Inlet continued to recede to the west, obliquely Fig. 4B, Table 1); however, this is superceded by the date away from the modern margin of the Prince of Wales Icefield (19.8 ka BP) on subtill organics adjacent to the Prince of (Fig. 11). This retreat left remnant ice on the plateau separating Wales Icefield 100 km to the northeast (site 4, Fig. 4A). Vendom Fiord from Makinson Inlet, close to the proposed local divide of the IIS during the LGM. The remnant ice on Deglaciation and pattern of isochrones the plateau continued to join the Prince of Wales Icefield Lateral meltwater channels marking the retreat of trunk and the Sydkap Ice Cap until at least 8 ka BP, and possibly

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Fig. 10. Holocene emergence curves from Makinson Inlet (A) with a response time (half-life) of 1500 years. Zreda and and Schei Point (B). Data from Table 3. Drinkard (1998) constructed a similar emergence curve for the same locality in Makinson Inlet based on cosmogenic surface exposure dating (36Cl) of raised beaches, which showed a half-life of 2000 years. Analyses of emergence curves from North America indicated that those associated with the former IIS have a response time of -2 ka at its centre, decreasing to -1 ka BP at its margin (Dyke and Peltier 2000). Our curves suggest a shorter response time towards the former centre of the IIS and no apparent dissimilarity as one moves closer to its former margin. For example, despite its location -120 km down-isobase from the axis of the Innuitian uplift, the Makinson Inlet curve has the same half-life as the Bjorne Peninsula (Schei Point) curve (Fig. 10). We do not know whether the half-life of the Makinson Inlet curve has been influenced by the regrowth of Prince of Wales Ice- field (Koerner 1977), even though Dyke (1998) reported no discernible effect of Neoglacial expansion of the Devon Is- land Ice Cap on postglacial emergence curves in that area. Whether the Makinson Inlet curve contains glacioisostatic effects from the preceding retreat of the Smith Sound Ice Stream is also unknown.

Discussion

Cape Storm Nonglacial Interval Numerous AMS dates on individual shell fragments collected from till and outwash along eastern Ellesmere Island range from 19.0 to 50.2 ka BP (see compilation, Table 1, England et al. 2000). We report 11 new age determinations ranging from 19.1 to 36.6 ka BP on ice-transported shells across southern Ellesmere Island which span a similar interval as as late as 7.6 ka BP when ice still reached tidewater in both subtill terrestrial organics north of Makinson Inlet (20–43 ka BP; inner Vendon Fiord and Makinson Inlet (Fig. 11). Along Blake 1982). To the southwest of Makinson Inlet (150 km), both the Prince of Wales and Manson icefields, the isochrones Blake (1992b) further reported mid-Wisconsinan, subtill marine extend an unknown distance inside modern margins which sand containing shells, macroalgae, and a bird sternum that have since readvanced to their 8–9 ka BP positions (Fig. 11). he assigned to the Cape Storm Nonglacial Interval (-35–50 ka In Makinson Inlet and adjacent parts of southeastern Ellesmere BP). Given the increasing number of dates along eastern Island, Blake (1975, 1981) also reported the readvance of Ellesmere Island that record reduced ice extent from 19 to glaciers across late Holocene alluvial fans, and elsewhere, 35 ka BP, we propose that the Cape Storm Nonglacial Interval into valleys where sediments from former proglacial lakes be extended to include all such deposits, hence increasing its are radiocarbon dated at -1kaBP. range from -50 to 19 ka BP. Here we use the term nonglacial to signify an extent of glaciers in the eastern QEI that is similar Postglacial isobases and emergence curves to present. The Cape Storm Nonglacial Interval broadly spans Postglacial isobases are drawn on the 8 ka BP shoreline marine isotope stage 3 and into stage 2 (Waelbroeck et al. throughout Makinson Inlet and Baumann Fiord and these 2002). However, significant regional variation in ice extent observations are extended to adjoining control points published during this interval is indicated by the persistence of the for Raanes Peninsula and southern Eureka Sound (Ó Cofaigh Laurentide Ice Sheet (LIS), which reportedly deposited three 1998), southern Ellesmere Island (Blake 1975), and Devon to six layers of ice-rafted detrital carbonate (DC) in northern Island (Dyke 1998). Collectively, the 8 ka BP isobases are and central Baffin Bay (Andrews et al. 1998). These DC layers oriented NE-SW and rise westward across Makinson Inlet are attributed to the rapid retreat of ice streams, possibly towards outer Baumann Fiord and southern Eureka Sound triggered by the advection of Atlantic Water into Baffin Bay (Fig. 12). This pattern adds support for a broad ridge of (Hiscott et al. 1989). maximum emergence (-100 m asl since 8 ka BP) extending through Eureka Sound and corresponds to previous recon- Greenland trigger for IIS dynamics (alpine sector) structions of the Innuitian uplift (Fig. 10; Blake 1970; Both the buildup and wastage of the eastern sector of the Walcott 1972; Ó Cofaigh 1998). To the east, the isobases IIS appear to be linked to its coalescence with, and subsequent descend towards northern Smith Sound where they cross to decoupling from, the Greenland Ice Sheet (GIS). England Greenland, recurving southward along its west coast. (1999) noted that granite erratics are widespread along the The two relative sea-level curves from Makinson Inlet and northeast coast of Ellesmere Island, recording occupation by Bjorne Peninsula show continuous emergence since deglaciation Greenland ice (to ≤ 760 m asl). Farther south, Greenland

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England et al. 57 c d This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper This paper Blake (1993) This paper Blake (1993) Blake (1988) Blake (1993) Lowdon and Blake (1978) 25‰ and a reservoir correc- ! ′′ ′′ ′′ ′′ ′′ ′′ C= 13 14 39 57 01 06 00 36 12 00 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ a-116131 and Beta-116773 samples were 87°39 87°00 87°11 86°50 86°38 86°53 86°50 86°48 82°25 86°47 81°33 80°52 81°27 82°14 87°31 80°55 80°55 81°2082°10 81°20 This paper 82°10 82°10 82°10 83°52 ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ ′′ 46 56 30 30 30 36 35 40 30 54 30 30 30 ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ ′ 133 77°50 107105 77°23 77°15 8472 77°17 77°19 ≤ ≤ ≤ ≤ ≤ 1137372 77°49 4835 77°48 77°50 19 77°51 6.5 77°50 77°52 77°52 45232321 77°26 19.5 77°19 77°26 77°19 77°19 5.34 77°19 77°19 158.5 77°15 77°15 ≥ ≥ ≥ ≥ ≤ ≤ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ ≥ Related RSL (m asl) Lat. N Long. W References 115 121 77°48 5896 >68– 56 >96– 58 >56– 23 >58– 4 ------Sample elevation (m asl) 18 km to east, down-isobase from other samples in this table. - Enclosing material 8660±708650±120 Marine silt8020±60 Marine sand 7870±70 Beach7750±80 Delta 123 sand6830±80 Stony sand6200±80 Foreset sand4430±60 >123– Stony 70–73 silt 113 3980±100 Sand 70–72 2790±70 32–36 Bottomset sand Bottomset 8–12 sand 28–32 9020±60 0.5 8710±70 Rhythmites 16–188600±65 Delta face 8260±60 Beach 248090±80 Bottomset sand Bedded sand 77°52 93 95 77°18 Age (years BP) C dates. Samples of marine shells were corrected for isotopic fractionation to a base of 14 H. arctica H. arctica H. arctica A. borealis A. borealis M. truncata M. truncata A. borealis M. truncata H. arctica H. arctica M. truncata H. arctica H. arctica H. arctica Material b Laboratory dating No. Beta-111693Beta-111689 Driftwood Driftwood 4000±60 3250±70 Raised beach Raised beach 15 8.5 e e Radiocarbon dates for relative sea-level change (see Fig. 10). 410 years was applied. Lat., latitude; long., longitude; Pen., Peninsula; RSL, relative sea level. Location ! a Site numbers coincide withLaboratory those designations: in Beta, Table Beta 2 Analytic; and GSC, Fig. Geological 9. Survey of Canada; TO, IsoTrace Laboratory;One AA, other Univeristy age of assessment Arizona. on TO, this AA, sample and was Bet similar in age (see TO-23, in Blake 1993). Blake (1993, Table 2) lists additional radiocarbonThis dates site not occurs used 3 here km because to of east the of uncertain Piliravijuk designation Bay, of on relative south sea shore level. of Makinson Inlet, hence Note: a b c d e tion of dated by accelerator mass spectrometry (AMS), all others are conventional Table 3. Site Schei Point 4143 N. Bjorne54 Pen. N. Bjorne56 Pen. N. Bjorne57 Pen. N. Bjorne63 Pen. N. Bjorne65 Pen. N. Bjorne66 TO-9483 Pen. N. Bjorne68 GSC-6412 Pen. N. Bjorne69 TO-9484 Pen. N. Bjorne GSC-6483 Pen.Makinson N. Inlet Bjorne GSC-6464 Pen.1c GSC-6498 4 GSC-6501 Outer8 N. Arm, GSC-6499 W.12 Central Makinson GSC-6406 Inlet, S.6b Outer Piliravijuk GSC-6404 Bay, Inner AA-23634 N. Piliravijuk29 Bay, N. Inner Piliravijuk30c TO-9488 AA-23617 Bay, N. Outer AA-23632 N.32 Arm, Inner E. Piliravijuk Bay, Beta-119914 30d N. Outer N.30f Inner Arm, Piliravijuk E. GSC-2705 Bay,35a N. Inner Piliravijuk Bay,35b N. Central AA-23625 Driftwood GSC-2651 Makinson Inlet,30g S. Central Makinson GSC-3456 Inlet,30h S. Inner Driftwood AA-23624 Driftwood 4900±60 Piliravijuk Bay, N. Inner Piliravijuk Driftwood Bay, Beach N. Driftwood 5950±65 4600±60 GSC-5055 GSC-1836 4480±60 Raised Beach beach 4870±65 gravel Driftwood Beach Driftwood gravel Raised 45 beach 21 2880±60 2060±50 19.5 Beach 23 shingle Raised beach 4.6

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Fig. 11. Isochrones (ka BP) showing sequential retreat of Late Wisconsinan ice westward through Makinson Inlet and southeastward through Baumann Fiord. Note prominent embayments in the isochrones in both fiords relative to the more stable ice on adjacent land. Retreat is earliest in Makinson Inlet serving to lower the IIS divide to the west. This diminished ice supply to Baumann Fiord where retreat quickly ensued. Isochrones around the head of Makinson Inlet and Piliravijuk Bay extend inside the modern margins of the Prince of Wales and Manson icefields (see text). Pen., Peninsula.

Fig. 12. Isobases drawn on 8 ka BP shoreline across southern Ellesmere Island. Isobases rise northwest to Eureka Sound and decline southeast en route to northwestern Greenland, where they form an embayment over Smith Sound.

erratics become intermittent, restricted to coastal sites between blocked the outflow of Innuitian trunk glaciers at the mouths the mouths of Ellesmere Island fiords. At these localities, of their fiords. This buttressing would have allowed the Innuitian Ellesmere Island trunk glaciers still lacked the size and through- trunk glaciers to backfill their fiords and, as Greenland and put to keep Greenland ice offshore. Around Cape Herschel Innuitian margins thickened, establish the Smith Sound Ice (Fig. 1), Blake (1977) reported Greenland erratics on Pim Island, Stream, which flowed southward to Baffin Bay (Blake 1992a). immediately seaward of the Ellesmere Island coast, recording Based on the youngest, ice-transported shells in Princess Greenland ice at least 1200 m thick. Consequently, the arrival Marie Bay and Makinson Inlet, this buttressing did not occur of Greenland ice along most of eastern Ellesmere Island until after 19 ka BP. Growth of the IIS after 19 ka BP is

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England et al. 59

significantly out of phase with both the LIS and the GIS the growth of this part of the IIS was delayed to within 1000 which attained their maximum configuration -18 ka BP (based 14C years of the LGM (-18 14C ka BP, Clark and Mix 2000), on a period of low global sea level, Clark and Mix 2000, by which time the LIS, and likely the GIS, had already reached Dyke et al. 2002). Therefore, the buttressing and eustatic their maximum extent. sea-level lowering acted in concert to promote westward Ice-transported shells and granite erratics deposited through- advance of Innuitian ice through the marine channels of the out inner Makinson Inlet demonstrate an initial ice flow archipelago. from divides located to the north and east, similar to the During backfilling of the Ellesmere Island fiords, the Innuitian modern Prince of Wales Icefield. The arrival of Greenland ice divide, initially near that of the modern Prince of Wales ice along eastern Ellesmere Island reinforced Innuitian ice Icefield, shifted westward onto the plateau between Makinson buildup by diminishing eastward drainage of trunk glaciers Inlet and Vendom Fiord. This migration of the divide strength- into Nares Strait and Smith Sound. This promoted backfilling ened outflow towards the open terrain of Baumann and Vendom of these fiords, as well as thickening and westward migration fiords. Opposing flow on the east side of this divide would of the local Innuitian ice divide onto uplands separating have been weaker because the ice surface gradient was lower Makinson Inlet and Baumann Fiord. This ice divide migration as the result of coalescence with pervasive Greenland ice in strengthened the westward flow of granite-bearing ice through Smith Sound. Consequently, not only did Greenland ice play Vendom and Baumann fiords, en route to Norwegian Bay, a pivotal role in filling the east Ellesmere Island fiords, it and ultimately to the polar continental shelf of the western also strengthened the westward migration of the local Innuitian archipelago. This ice divide migration is consistent with east- ice divide. Currently, we do not have evidence that Greenland ward flow out Makinson Inlet, recorded by carbonate-bearing ice ever thickened sufficiently to flow westward through till and streamlined bedforms on the Precambrian Shield. Makinson Inlet and into Baumann Fiord. During the early Holocene, deglaciation across the archi- Blake et al. (1996) discussed the extent of the Smith Sound pelago was triggered by increased solar insolation and eustatic Ice Stream during the LGM, suggesting that it may have sea-level rise. However, on southern Ellesmere Island, ice reached the Carey Øer, 150 km SE of Makinson Inlet (Fig. 1). retreat was enhanced by the decoupling of Innuitian and Conversely, Funder and Hansen (1996) place the LGM limit Greenland ice. We propose that retreat of the Smith Sound north of Makinson Inlet. We suggest that a deglacial date of Ice Stream unblocked the mouth of Makinson Inlet by 9.3 ka ≥ 9.3 ka BP at Clarence Head (Fig. 1; Blake 1993) is congruent BP, triggering the rapid retreat of its trunk glacier to mid-fiord with the unblocking of Makinson Inlet by the Smith Sound by 9.2 ka BP. The resulting calving bay promoted thinning Ice Stream that occasioned the abrupt evacuation of its trunk of the Innuitian divide to the west, thereby diminishing supply glacier by 9.2 ka BP. The draw-down of ice from the inlet is to the Baumann Fiord trunk glacier, which retreated rapidly consistent with the pervasive streamlined bedforms noted on soon afterward (8.8 ka BP). The heads of Makinson Inlet Bowman Island (Fig. 6). This evacuation would have had the and Baumann Fiord were ice-free by 7.6 ka BP. In outer additional effect of lowering the Innuitian divide, diminishing Makinson Inlet, the 9 ka BP isochrone extends well inside its opposing outflow to Baumann Fiord and Norwegian Bay. the contemporary margin of the Prince of Wales Icefield, This sequence of deglaciation is supported by our radiocarbon which cross-cuts late Holocene shorelines, recording a Neo- chronology across the field area. Deglaciation of Norwegian glacial readvance. Postglacial isobases drawn on the 8 ka BP Bay and southern Eureka Sound occurred close to 9 ka BP, shoreline are oriented northeast–southwest and rise across and, by 8.8 ka BP, the sea had entered the mouth of Baumann the field area to Eureka Sound, which marks the axis of the Fiord, reaching the centre of the fiord by 8.2 ka BP (Fig. 11). Innuitian uplift. Lower isobases in outer Makinson Inlet extend This deglacial chronology suggests that ice retreat on both across northern Smith Sound to join the Greenland uplift. sides of the local IIS divide was enhanced by the sequential Postglacial emergence curves from Makinson Inlet and outer decoupling of Greenland and Innuitian ice. Similar ice- Baumann Fiord show continuous and ongoing emergence buttressing may have played an important role in the wastage, (up to 130 m asl) that display a half-life of -1500 years. and possibly buildup, elsewhere in the archipelago. For example, the northward retreat of the Smith Sound Ice Stream led to the decanting of eastern Ellesmere Island trunk glaciers from Acknowledgments their fiords. However, it is widely recognized that the retreat of the IIS during the early Holocene was forced predominately This research was funded by the Natural Sciences and by high ablation rates caused by increased solar insolation Engineering Research Council of Canada (research grant (Koerner and Fisher 1989) and by eustatic sea-level rise A6680 to J. England) and Canadian Circumpolar Institute (Fairbanks 1989). (University of Alberta, Edmonton, Alberta). Logistical support was provided by the Polar Continental Shelf Project, Natural Resources Canada. Radiocarbon dates were provided by Conclusions IsoTrace Laboratory, University of Toronto, Toronto, Ontario; the Geological Survey of Canada (GSC), Ottawa, Ontario; AMS radiocarbon dates (ranging from 19 to -50 ka BP) and the University of Arizona, Tucson, Arizona. Field assistance obtained on subtill organics and ice-transported shells on was provided by Murray Unick and Kareen Erbe in 1997 southern Ellesmere Island are assigned to the Cape Storm and by Michelle Laurie in 1999. Colm Ó Cofaigh and Kim Nonglacial Interval during which ice margins were similar to Jardine, then of the University of Alberta, also contributed to modern. Buildup of a precursor to the Prince of Wales Icefield the 1997 fieldwork. Kenna Wilke, University of Alberta, occurred after 19 ka BP, inundating the entire landscape diligently collated the radiocarbon tables. Formal reviews by surrounding Makinson Inlet and Baumann Fiord. Consequently, R. M. Koerner (GSC, Ottawa) and Julie Brigham-Grette (Uni-

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versity of Massachusetts, Amherst, Massachusetts) helped to Dyke, A.S. 1993. Landscapes of cold-centred late Wisconsinan ice clarify and improve the manuscript. We also acknowledge caps, Arctic Canada. Progress in Physical Geography, 71: 223–247. the internal review by Weston Blake Jr. on behalf of the Terrain Dyke, A.S. 1998. Holocene delevelling of Devon Island, Arctic Sciences Division (GSC, Ottawa). Canada: implications for ice sheet geometry and crustal response. Canadian Journal of Earth Sciences, 35: 885–904. References Dyke, A.S. 1999. The last glacial maximum and the deglaciation of Devon Island: support for an Innuitian Ice Sheet. Quaternary Andrews, J.T., Kirby, M.E., Aksu, A., Barber, D.C., and Meese, D. Science Reviews, 18: 393–420. 1998. Late Quaternary detrital carbonate (DC-) layers in Baffin Dyke, A.S., and Peltier, W.R. 2000. 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