Article

Deciphering patterns of postglacial sea level at the junction of the Laurentide and Innuitian Ice Sheets, western Canadian High Arctic

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Recent sampling of deglacial and postglacial raised marine sediments across Melville and Eglinton islands in the western Canadian High Arctic yielded over 200 new radiocarbon dates on molluscs, driftwood and other organic materials. From this database, eight relative sea-level curves and an isobase map for the 9.5 cal ka BP shoreline were constructed. The forms, chronology and pattern of the relative sea-level curves across the study area reflect the complex glacial history of this region, including the asynchronous retreat of the formerly coalescent Laurentide and Innuitian Ice Sheets. Zone I relative sea-level curves, which show continuous emergence to present, were observed in areas closer to greater Last Glacial Maximum ice sheet loading; at more distal sites, transitional Zone I/II curves display emergence followed by submergence in the mid- to late-Holocene (still ongoing) related to forebulge migration and collapse. An independent record of late Holocene submergence is provided by radiocarbon-dated driftwood, which is accumulating at modern sea level due to re-deposition during transgression. Geomorphic evidence of submergence at the modern coastline is widespread but does not distinguish areas that experienced a late Holocene lowstand and subsequent transgression from those that are currently at their lowstand. Of special interest are the relative sea-level histories of two areas that experienced earlier deglaciation by the Laurentide Ice Sheet, while remaining in the peripheral depression of the more stable and adjacent Innuitian Ice Sheet The flat-topped relative sea-level curves from these sites appear to record unusually slow rates of glacioisostatic emergence for similar to 1500 years immediately following deglaciation. The relative sea-level data presented in this paper provide important comparisons for sea level models, which have been shown to fit poorly with previously published data from this region.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The reality of sequences, systems tracts, and depositional systems at sub-seismic scales has become evident with the advances in high-resolution sequence stratigraphy (e.g., Tesson et al., 1990Tesson et al., , 2000Lobo et al., 2004;Amorosi et al., 2005Amorosi et al., , 2009Amorosi et al., , 2017Bassetti et al., 2008;Catuneanu and Zecchin, 2013;Nanson et al., 2013;Zecchin and Catuneanu, 2013, 2015, 2017Nixon et al., 2014;Magalhaes et al., 2015;Zecchin et al., , 2017aAinsworth et al., 2017Ainsworth et al., , 2018Pellegrini et al., 2017Pellegrini et al., , 2018Catuneanu, 2019). The improvements in stratigraphic resolution also demonstrated that unconformities may form over a wide range of scales, both below and above the seismic resolution, and therefore, unconformity-bounded units are not restricted to the scales of seismic stratigraphy (e.g., Miall, 2015;Strasser, 2016Strasser, , 2018. ...
... Stratigraphic stacking patterns refer to a stratal architecture that involves changes in systems tracts and component depositional systems. The minimum timescales required to form a depositional system are commonly within a range of 10 2 -10 3 yrs, as indicated by simulation models and highresolution studies (e.g., Bridge and Leeder, 1979;Amorosi et al., 2009Amorosi et al., , 2017Nanson et al., 2013;Nixon et al., 2014;Miall, 2015;Pellegrini et al., 2018). Changes in relative sea level, energy flux, sediment supply, and shoreline trajectory occur at all scales, and may accompany the formation of both sedimentological and stratigraphic cycles. ...
... The scale-independent nature of sequences and component systems tracts and depositional systems has become evident with the increase in the resolution of stratigraphic studies (e.g., Amorosi et al., 2005Amorosi et al., , 2009Amorosi et al., , 2017Bassetti et al., 2008;Mawson and Tucker, 2009;Nanson et al., 2013;Nixon et al., 2014;Magalhaes et al., 2015;Ainsworth et al., 2017;Pellegrini et al., 2017Pellegrini et al., , 2018Zecchin et al., 2017a,b;Figs. 13 and 14). ...
... Proglacial deltas and fan deltas are widespread features of glaciated terrain and particularly typical of ice-free fjord-head and side-entry settings in the Arctic (Syvitski et al., 1987;Syvitski and Hein, 1991;Lønne and Nemec, 2004;Forbes, 2011). Raised proglacial deltas are frequently the most prominent indicators of the postglacial marine limit (e.g., Dyke, 1979;Nixon et al., 2014). Proglacial fjord-head deltas commonly develop under conditions of early rapid uplift following ice recession and multiple terrace levels can develop (Church, 1972). ...
... The associated rivers drain low-relief (150 m) drainage basins of 161 and 54 km 2 , respectively. The surficial material is sparsely vegetated, weathered, poorly cemented to unlithified Mesozoic sand and shale (Harrison et al., 2015), mantled by a thin and discontinuous veneer of postglacial marine mud and locally thicker deltaic deposits up to the marine limit at 64 m elevation, dating no later than 11.6 ka (Nixon et al., 2014). ...
... The postglacial emergence is reasonably well defined and appears to have been anomalously linear since 9 ka (Forbes et al., 1986;Nixon et al., 2014). From an elevation of 30 m about 9 ka, RSL fell to 20 m ~6 ka (the highest terrace in Fig. 10), 4 m ~2 ka, and 2 m ~1000 years ago. ...
Chapter
Deltas and estuaries in high latitudes have many features in common with river-mouth systems everywhere. In addition, they share a suite of polar characteristics driving distinctly Arctic processes and outcomes. Various forms of ice (including ground ice, river and sea ice, glacial ice, and snow) are the primary distinguishing factors, but extreme seasonality and the near-absence of trees are also important. The glacial legacy is a key influence, through sediment supply, affecting delta growth and survival, and glacial-isostatic crustal motion, leading to both falling and rising relative sea levels. High-latitude amplification of climate warming is causing dramatic losses of sea ice, land-based ice, and ice shelves, and accelerating coastal erosion. Moreover, Arctic deltas and estuaries (including ice shelves) provide critical ecosystem services, are responding to global climate forcing, and serve as sentinel systems for detection and tracking of climate warming effects at high latitudes. © 2019 Crown
... 13,14,48). The stacking patterns relevant to sequence stratigraphy are observed at scales that afford the development of coastal depositional systems (i.e., building blocks of systems tracts: deltas vs. estuaries, or prograding strandplains vs. backstepping lagoon-barrier island systems), which commonly require minimum 10 2 -10 3 years (e.g., Amorosi et al., 2009Amorosi et al., , 2017Nixon et al., 2014;Pellegrini et al., 2017;Fig. 48). ...
... Stratigraphic stacking patterns refer to a stratal architecture that involves changes in systems tracts and component depositional systems. The minimum timescales required to form a depositional system are commonly within a range of 10 2 -10 3 yrs., as indicated by simulation models and high-resolution studies (e.g., Bridge and Leeder, 1979;Amorosi et al., 2009Amorosi et al., , 2017Nanson et al., 2013;Nixon et al., 2014;Miall, 2015;Pellegrini et al., 2017). Changes in relative sea level, energy flux, sediment supply, and shoreline trajectory occur at all scales, starting with the scale of tidal and fairweather-storm cycles, and may accompany the formation of both sedimentological and stratigraphic cycles. ...
... The scale-independent nature of sequences and component systems tracts and depositional systems has become evident with the increase in the resolution of stratigraphic studies (e.g., Amorosi et al., 2005Amorosi et al., , 2009Amorosi et al., , 2017Nanson et al., 2013;Nixon et al., 2014;Magalhaes et al., 2015;Ainsworth et al., 2017;Zecchin et al., 2017a,b;Figs. 58, 61). ...
... The development of stratigraphic stacking patterns that define systems tracts in both downstream-and upstream-controlled settings requires, typically, timescales of minimum 10 2 -10 3 years (e.g., Amorosi et al., 2005;Bridge and Leeder, 1979;Miall, 2015;Nanson et al., 2013;Nixon et al., 2014;Fig. 17). ...
... Stratigraphic stacking patterns refer to a stratal architecture that involves changes in systems tracts and component depositional systems. The minimum timescales required to form a depositional system are commonly within a range of 10 2 -10 3 years, as indicated by simulation models and high-resolution studies (e.g., Amorosi et al., 2005;Bridge and Leeder, 1979;Miall, 2015;Nanson et al., 2013;Nixon et al., 2014). Changes in relative sea level, energy flux, sediment supply, and shoreline trajectory occur at all scales, starting with the scale of tidal and fairweather-storm cycles, and may accompany the formation of both sedimentological and stratigraphic cycles. ...
... 2004; Magalhaes et al., 2015;Miall, 2015;Nanson et al., 2013;Nixon et al., 2014;Tesson et al., 1990Tesson et al., , 2000Zecchin et al., 2017a,b), which defines the scope of high-resolution sequence stratigraphy (Fig. 17). The stacking pattern of high-frequency sequences defines systems tracts, and component depositional systems, of higher hierarchical ranks in lower resolution studies (Figs. 15 and 16). ...
... The reality of sequences, systems tracts, and depositional systems at sub-seismic scales has become evident with the advances in high-resolution sequence stratigraphy (e.g., Tesson et al., 1990Tesson et al., , 2000Lobo et al., 2004;Amorosi et al., 2005Amorosi et al., , 2009Amorosi et al., , 2017Bassetti et al., 2008;Catuneanu and Zecchin, 2013;Nanson et al., 2013;Zecchin and Catuneanu, 2013, 2015, 2017Nixon et al., 2014;Magalhaes et al., 2015;Zecchin et al., , 2017aAinsworth et al., 2017Ainsworth et al., , 2018Pellegrini et al., 2017Pellegrini et al., , 2018Catuneanu, 2019a,b). The improvements in stratigraphic resolution also demonstrated that unconformities may form over a wide range of scales, both below and above the seismic resolution, and therefore, unconformity-bounded units are not restricted to the scales of seismic stratigraphy (e.g., Miall, 2015;Strasser, 2016, 2018. ...
... The scale-independent nature of sequences and component systems tracts and depositional systems has become evident with the increase in the resolution of stratigraphic studies (e.g., Amorosi et al., 2005Amorosi et al., , 2009Amorosi et al., , 2017Bassetti et al., 2008;Mawson and Tucker, 2009;Nanson et al., 2013;Nixon et al., 2014;Magalhaes et al., 2015;Ainsworth et al., 2017;Pellegrini et al., 2017Pellegrini et al., , 2018Zecchin et al., 2017a,b;Catuneanu, 2019b). Seismic stratigraphy imposed, by default, a minimum scale to the concepts of sequence, systems tract, and depositional system, which had to exceed the vertical seismic resolution (i.e., 10 1 m in the 1970s). ...
Article
Confusions between methodology and modeling created a false premise to question the ‘future of sequence stratigraphy’. In reality, the future is already here in terms of a standard methodology. Despite the variability of the stratigraphic architecture, there are only a few stacking patterns that are diagnostic to the definition of stratal units and bounding surfaces, which can be observed at all stratigraphic scales. The identification of the diagnostic stacking patterns, at scales defined by the purpose of the study or by the resolution of the data available, provides the guiding principle of the sequence stratigraphic methodology. The modeling of the possible controls on sequence development plays no role in the methodological workflow, and can continue indefinitely after the construction of a sequence stratigraphic framework. Therefore, it is important to separate methodology from modeling in sequence stratigraphy. The standard methodology does not prevent future developments in the field of stratigraphic modeling. Uncalibrated modeling can ‘demonstrate’ any stratigraphic scenario, whether realistic or not. While the methodology evolved from a model-driven to a data-driven approach, uncalibrated modeling has become the new ‘triumph of interpretation over facts and common sense’. The latest trend in forward modeling is the shift from an overemphasis on accommodation to an overemphasis on sediment supply, to the point that all aspects of the stratigraphic architecture are explained by variations in sediment supply or even solely by autocyclicity. In reality, it is always a combination of accommodation and sedimentation, and both elements of this ‘dual control’ contribute in discernible ways to the architecture and makeup of the sequence stratigraphic framework. The methodology does not require an interpretation of the underlying controls on accommodation and sedimentation, but only the observation of stratal stacking patterns and stratigraphic relationships that result from their interplay. Muddling the distinction between methodology and modeling leads to unnecessary confusion and a reversal of the progress made in the development of sequence stratigraphy as a data-driven methodology.
... m (Collingwood et al., 2014). Localities below the Holocene marine limit (~60-70 m asl) are usually characterised by higher silt and ground-ice contents than areas above the marine limit (Barnett et al., 1977;Nixon et al., 2014). ...
... Owing to limited mapping of the surficial geology in this area, elevation was used to delimit the marine limit as a proxy for low-elevation fine-grained sediments (Barnett et al., 1977). The presence of marine clay is an important control over disturbance occurrence, with 91 per cent of disturbances occurring below the marine limit (~60-70 m asl) (Nixon et al., 2014). ...
Article
Modelling the susceptibility of permafrost slopes to disturbance can identify areas at risk to future disturbance and result in safer infrastructure and resource development in the Arctic. In this study, we use terrain attributes derived from a digital elevation model, an inventory of permafrost slope disturbances known as active-layer detachments (ALDs) and generalised additive modelling to produce a map of permafrost slope disturbance susceptibility for an area on northern Melville Island, in the Canadian High Arctic. By examining terrain variables and their relative importance, we identified factors important for initiating slope disturbance. The model was calibrated and validated using 70 and 30 per cent of a data-set of 760 mapped ALDs, including disturbed and randomised undisturbed samples. The generalised additive model calibrated and validated very well, with areas under the receiver operating characteristic curve of 0.89 and 0.81, respectively, demonstrating its effectiveness at predicting disturbed and undisturbed samples. ALDs were most likely to occur below the marine limit on slope angles between 3 and 10° and in areas with low values of potential incoming solar radiation (north-facing slopes).
... This is in part because many Arctic coasts are emergent, with relict shorelines raised above present sea level, and in part because the technology to map submerged coastal geomorphic features has not been widely deployed until recently (Hughes Clarke et al. 2015). Some evidence of lower postglacial RSL has been observed along the eastern, southeastern, and northwestern fringes of the former LIS, within the glacial-isostatic zones of submergence (e.g., Nixon et al. 2014). These include submerged wave-cut terraces, deltas, beach ridges, incised bedrock, barrier platforms, flooded estuaries and salt marshes, and flooded isolated basins (e.g., England and Andrews 1973;Shaw and Forbes 1995;Forbes et al. 1995Forbes et al. , 2014Bell et al. 2003;Shaw 2005;Billy et al. 2018). ...
Article
Full-text available
This study investigates the postglacial sea-level history of eastern Cumberland Peninsula, a region of Baffin Island, Nunavut where submerged terraces were documented in the 1970s. The gradient in elevation of emerged postglacial marine-limit deltas and fiord-head moraines led Dyke (1979) to propose a conceptual model for continuous postglacial submergence of the eastern peninsula. Multibeam mapping over the past decade has revealed eight unequivocal submerged deltas at 19-45 m below [present] sea level (bsl) and other relict shore-zone landforms (boulder barricade, spits, and sill platform) at 16-51 m bsl. Over a distance of 115 km from Qikiqtarjuaq to Cape Dyer, the submerged coastal features increase in depth toward the east, with a slope (0.36 m/km), somewhat less than that of the marine-limit shoreline previously documented (0.58-0.62 m/km). The submerged ice-proximal deltas, deglacial ice limits, and radiocarbon ages constrain the postglacial lowstand between 9.9 and 1.4 ka cal BP. The glacial-isostatic model ICE-7G_NA (VM7) (Peltier 2020) computes a lowstand relative sea level at 8.0 ka, the depth of which increases eastward at 0.28 m/km. The difference between observed and model-derived lowstand depths ranges from 1 m in the west to 10 m in the east and the predicted tilt is significantly less than observed (p=0.0008). The model results, emerging data on Holocene glacial re-advances on eastern Baffin Island, and evidence for proglacial delta formation point to a Cockburn (9.5-8.2 ka) age for the lowstand, most likely later in this range. This study confirms the 1970s conceptual model of postglacial submergence in outer Cumberland Peninsula and provides field evidence for further refinement of glacial-isostatic adjustment models.
... Data from 913 driftwood samples previously collected throughout the western Arctic coastline and covering the Holocene was collated from a range of previous studies [Allard and Tremblay, 1983;Atkinson and England, 2004;Bednarski, 1984;Bennike, 2004;Bennike and Weidick, 2001;Birkenmajer and Olsson, 1970;Blake, 1961aBlake, , 1961bBlake, , 1970Blake, , 1989Blake, , 1972Blake, , 1974Blake, , 1975Blake, , 1983Blake, , 1986Blake, , 1987Blake, , 1993Bondevik et al., 1995;Broecker and Olson, 1959;Crary, 1960;Dibner, 1965;Dyke, 1979Dyke, , 1984Dyke, , 1993Dyke, , 1998Dyke and Morris, 1990;Dyke and Savelle, 2000, 2003, 2009Dyke et al., 1989Dyke et al., , 1991Dyke et al., , 1996Dyke et al., , 2011England, 1976aEngland, , 1976bEngland, , 1978England, , 1983England, , 1985England, , 1990England et al., 1978England et al., , 2017Evans, 1988Evans, , 1990Evans and England, 1992;Forman, 1990;Forman and Ingolfsson, 2000;Forman et al., 1996Forman et al., , 1997Forman et al., , 1999aForman et al., , 1999bFunder et al., 2011;Glazovskiy et al., 1992;Grosswald, 1963;Grosswald et al., 1973;H€ aggblom, 1982;Hattersley-Smith et al., 1969;Henoch, 1964;Hillaire-Marcel, 1976;Hjort, 1997;Hodgson, 1992;Hodgson et al., 1991;Hoppe et al., 1969;Ives et al., 1964;Johansen, 1998;Knuth, 1967;Kovaleva, 1974;Landvik and Salvigsen, 1987;Landvik et al., 2001;Lemmen, 1988;Lowdon and Blake, 1973, 1979Lubinski, 1998;Lubinski et al., 1999;Marthinussen, 1962;McLaren and Barnett, 1978;McNeely, 2005McNeely, , 2006McNeely and McCuaig, 1991;Mielke and Long, 1969;Naslund et al., 1994;Nixon et al., 2014Nixon et al., , 2016Nydal, 1960;O Cofaigh, 1999;Olson and Broecker, 1959;Preston et al., 1955;Salvigsen and Osterholm, 1982;Salvigsen, 1978Salvigsen, , 1984Salvigsen and Mangerud, 1991;Salvigsen and Nydal, 1981;Schledermann, 1978;Sharpe, 1992;Stewart and England, 1983;St-Hillaire-Gravel et al., 2015;Taylor, 1975;Trautman, 1963;Wagner et al., 2010;Washburn, 1962;Webber et al., 1970;Weidick, 1972Weidick, , 1975Weidick, , 1977Weihe, 1996;Zale and Brydsten, 1993;Zeeberg et al., 2001] (also see supporting information Table S1). ...
Article
Full-text available
The collation of 913 driftwood samples from across the western Arctic, with spatiotemporal distribution and available provenance data, enabled the production of a high-resolution proxy-based reconstruction of Holocene Arctic Ocean surface current and sea ice dynamics. Regionally bounded, driftwood-based sea ice reconstructions studies suggest spatiotemporally complex past Arctic sea ice extent and movement; however, a large-scale compilation of Holocene Arctic driftwood has not previously been developed. Sparse driftwood in the early Holocene (≥8.2 cal ka B.P.) deglacial period was followed by increased driftwood deposition in the warmer mid-Holocene (8.2–4.2 cal ka B.P.); characterized by an enhanced Transpolar Drift (TPD) ∼7 cal ka B.P., leading to sea ice loss through the Fram Strait. Driftwood incursion peaks show spatial E-W progression from the Eurasian Archipelagos to Greenland and the Canadian Arctic Archipelago, suggesting a progressive shift in the orientation of the TPD on centennial-millennial time scales and intermediate phases in the Arctic Oscillation. Late Holocene cooling (≤4.2 cal ka B.P.) is indicated by increased influx of probably North American Picea via a strengthened Beaufort Gyre (BG) which enhanced sea ice recirculation, starting in the western Arctic and progressing eastward. In recent millennia (<2 cal ka B.P.), a more variable driftwood record alternates between BG and TPD dominance on centennial time scales. To further constrain a spatiotemporal reconstruction of variations in Holocene ocean current and sea ice dynamics, a more definitive determination of driftwood provenance is recommended to build upon the current framework, such as through radiogenic isotope tracing and aDNA analysis.
... However, relative sea level rise is not necessarily universal, and where coastal uplift is occurring significantly, the sediment transport pathways may be very different. For example, parts of the Canadian Archipelago and the Baffin Shelf continue to experience uplift (Nixon et al. 2014), with rates estimated at 3-7 mm a −1 (Sella et al. 2007). In Hudson Bay, a shelf sea slightly south of the Archipelago, exceptional rates of falling relative sea level, especially in the southern portion (rates of almost 12 mm a −1 ), appear to support uncommonly large resuspension and lateral transport rates, which consequently affect the sediment budget for the Bay (Kuzyk et al. 2009). ...
Article
The sediments of the pan-Arctic shelves contribute an important component to the Arctic Ocean ecosystem by providing a habitat for biota (benthos), a repository for organic and inorganic non-conservative substances entering or produced within the ocean, a reactor and source of transformed substances back to the water column, and a mechanism of burial. Sediments interact with ice, ocean, and the surrounding land over a wide range of space and time scales. We discuss the vulnerability of shelf sediment to changes in (i) organic carbon sources, (ii) pathways of sediment and organic carbon supply, and (iii) physical and biogeochemical alteration (diagenesis). Sedimentary environments of the shelves and basins are likely to exhibit a wide variance in their response to global change because of their wide variation in sediment sources, processes, and metabolic conditions. In particular, the Chukchi and Barents shelves are dominated by inflowing waters from oceans to the south, whereas the interior shelves are more closely tied to terrigenous sources due to river inflow and coastal erosion.
... 31.1b). The area was entirely covered by the Laurentide Ice Sheet (LIS) during the Late-Wisconsinan (Nixon et al. 2013). By 14 ka cal BP, the retreat of the LIS margin led to the marine invasion, which reached areas today located at ~75 m asl. ...
Chapter
East Lake, located at Cape Bounty (Melville Island, Canadian High Arctic), was mapped using a high-resolution swath bathymetric sonar and a 12 kHz sub-bottom profiler, allowing for the first time the imaging of widespread occurrence of mass movement deposits (MMDs) in a Canadian High Arctic Lake. Mass movements occurred mostly on steep slopes located away from deltaic sedimentation. The marine to lacustrine transition in the sediment favours the generation of mass movements where the underlying massive mud appears to act as a gliding surface for the overlying varved deposits. Based on acoustic stratigraphy, we have identified at least two distinct events that triggered failures in the lake during the last 2000 years. The synchronicity of multiple failures and their widespread distribution suggest a seismic origin that could be related to the nearby Gustaf-Lougheed Arch seismic zone. Further sedimentological investigations on the MMDs are however required to confirm their age and origin.
... In this case, the MFS and the BSFR would coincide (Fig. 11A). Another peculiar situation is associated with a progressive decrease of the isostatic rebound to a rate that is lower than that of the glacio-eustatic sea-level rise (e.g., Dyke and Peltier, 2000;Nixon et al., 2014); in that case, FSST shallow-water deposition related to isostatic rebound may pass later to LST, and even TST plus HST deposition, resulting in two high-frequency sequences, separated by an isostatic-related SU, composing a larger eustatic-related sequence (Fig. 11B). ...
Chapter
Eastern Canada was almost completely glaciated from four major and several lesser ice centres on multiple occasions during the Quaternary. Most of the geomorphology relates to Marine Isotope Stage 2. Areas of resistant bedrock are dominated by glacial erosional features, such as roches mountonées. Glacial depositional landforms are prominent in southern Ontario, Québec, and the Maritime provinces. In Arctic Canada, glaciation had lesser effects on geomorphology, with the exception of the mountainous areas of Baffin and Ellesmere islands. Glacial retreat exposed the isostatically depressed coastlines to marine incursions. Champlain Sea glacimarine sediments cover the St. Lawrence and Ottawa Valleys. In the Great Lakes Lowlands and southern Canadian Shield, blockage of northward and eastward drainage led to the formation of successions of proglacial lakes and other paraglacial landforms during the transition from MIS 2 to the Holocene.
Article
Fifty-six new radiocarbon dates from driftwood (mainly Larix, Picea and Populus spp.) collected from the modern and raised shorelines of Melville and Eglinton islands (western Canadian High Arctic) are presented and compared to other driftwood collections from the Canadian Arctic Archipelago (CAA) and Greenland. By documenting the species (provenance) and spatio-temporal distribution of driftwood at various sites across the Arctic, regional characterizations of former sea-ice conditions and changes in Arctic Ocean circulation patterns may be deduced. The earliest postglacial invasion of the Canadian Arctic Archipelago by driftwood is recorded on central Melville Island at c. 11 cal. ka BP, suggesting that the modern circulation pattern of Arctic Ocean surface water southeast through the archipelago was established >1000 years earlier than previously proposed. Throughout most of the Holocene until c. 1.0 cal. ka BP, the rate of driftwood delivery to the western Arctic islands was low (~1 recorded stranding event per 200 years) and intermittent, with the longest break in the record occurring between c. 3.0 and 5.0 cal. ka BP. This 2000-year hiatus is attributed to a period of colder temperatures causing severe sea-ice conditions and effectively making the coasts of the western Arctic islands inaccessible. After c. 1.0 cal. ka BP, driftwood incursion increased to maximum Holocene levels (~1 recorded stranding event every 20 years). Driftwood identified to the genus level as Larix that was delivered at this time suggests that the Trans Polar Drift current was regularly in its most southwestern position, related to a dominantly positive Arctic Oscillation mode. The Little Ice Age appears to have had little impact on driftwood entry to the western Canadian Arctic Archipelago, indeed the general abundance in the latest Holocene may record infrequent landfast sea ice.
Article
Full-text available
The post-glacial sea-level history is complex, dominated by the effects of an ice-marginal crustal forebulge produced by isostatic deformation of the lithosphere. Marine fossils found above present sea-level can be 14C dated, and examination of the temporal and geographical distribution of these 14C dates in combination with geomorphological indicators of past sea-levels indicates regional trends of relative sea-level change. For most of the island (apart from the Northern Peninsula) no samples have been recovered that date younger than 8000 BP, suggesting that sea-level lay below the present one in these areas for the last 8000 years. Over most of Newfoundland, following deglaciation, sea-level fell to below present levels, and subsequently rose to the modern level. Mapping the time at which sea-level fell below the present level allows estimation of the rate of northerly migration and collapse of the forebulge at between 4.5 and 11 km/100 years; this is considerably faster than previous estimates. -from Author
Article
Full-text available
Emerged shorelines are few and poorly defined on Prince Patrick and Brock islands. The sparse radiocarbon dates show emergence of only 10 m through the Holocene on the Arctic Ocean coast, increasing to 20 m 100 km to the east. Hence, from Brock Island, representative of westernmost coasts, the sea level curve since the latest Pleistocene has a very low gradient, whereas on eastern Prince Patrick Island the curve takes the more typical exponential form. A decline in isobases towards the west is thus registered. Drowned estuaries, breached lakes, and coastal barriers, particularly in southwest Prince Patrick Island, suggest that the sea is now transgressing at a rate that decreases towards the north end of the island, hence there is also a component of tilt to the south. Delevelling is assumed to result from undefined ice loads, but may have a tectonic component. The sole prominent raised marine deposit is a ridge probably built in a period of more mobile sea ice, possibly at a time of stable or slightly rising sea level in the middle or early Holocene. It winds discontinuously along several hundred of kilometres of the shores of the Arctic Ocean and connecting channels, declining to the south.
Article
Full-text available
Marine molluscs, including bivalves, gastropods and scaphopods, were recovered by dredging at depths of 3 - 82 m in Expedition Fiord, Axel Heiberg Island, Canada. Cluster analysis, based on presence/absence data at 27 stations, defined two mollusc associations within the fiord. A Portlandia-Thyasira association, characterized by the abundance of Portlandia arctica and Thyasira gouldi, inhabits silty clay substrates at depths of 32 - 82 m throughout the fiord. An Astarte association, characterized by the abundance of Astarte borealis and Astarte warhami, inhabits sandy mud substrates at depths of 3 - 32 m in the middle and outer fiord. The absence of this mollusc association at the fiord head suggests that the suspension-feeding molluscs that const itute this association, such as Astarte, Hiatella, Mya and Trichotropis, are intolerant of the lowered salinities and high suspended- sediment concentrations created by the discharge of Expedition River into the fiord-head environment. The Expedition Fiord molluscan fauna is compared to the molluscan fauna recorded in Jørgen Brønlund Fjord, Greenland. In the latter fiord, shallow- water (5 - 19 m) molluscan faunas are characterized by the abundance of Portlandia arctica and Hiatella arctica, while deep-water (22 - 48 m) faunas are characterized by the abundance of Thyasira dunbari. Molluscs recovered live in both of these fiords are distributed widely in high-latitude fiord and continental shelf environments.
Article
Full-text available
An extended form of the correspondence principle is employed to determine directly the quasi-static deformation of viscoelastic earth models by mass loads applied to the surface. The stress-strain relation employed is that appropriate to a Maxwell medium. Most emphasis is placed on the discussion of spherically stratified self-gravitating earth models, although some consideration is given to the uniform elastic half space and to the uniform viscous sphere, since they determine certain limiting behaviors that are useful for interpretation and proper normalization of the general problem. Laplace transform domain solutions are obtained in the form of ‘s spectra’ of a set of viscoelastic Love numbers. These Love numbers are defined in analogy with the equivalent elastic problem. An efficient technique is described for the inversion of these s spectra, and this technique is employed to produce sets of time dependent Love numbers for a series of illustrative earth models. These sets of time dependent Love numbers are combined to produce Green functions for the surface mass load boundary value problem. Through these impulse response functions, which are obtained for radial displacement, gravity anomaly, and tilt, a brief discussion is given of the approach to isostatic equilibrium. The response of the earth to an arbitrary quasi-static surface loading may be determined by evaluating a space-time convolution integral over the loaded region using these response functions.
Article
Full-text available
This paper presents relative sea-level curves from Amund and Ellef Ringnes islands, northwest Queen Elizabeth Islands. These curves are of exponential form and record continuous, ongoing Holocene emergence, although northwest Ellef Ringnes Island is experiencing a late Holocene transgression. Isobases drawn on postglacial shorelines rise southeastward towards an uplift centre in Norwegian Bay. These suggest the Ringnes Islands occupied the northwest radius of the Innuitian uplift, which is congruent with glacial geological evidence suggesting parts of the Ringnes Islands were covered by the Late Wisconsinan Innuitian Ice Sheet. The isobases provide a provisional reconstruction of glacioisostatic recovery within the northwest Innuitian uplift. Their pattern supports earlier reconstructions that maximum Late Wisconsinan ice thickness occurred across Norwegian Bay, marking the position of an ice divide, which is consistent with ice-flow features on Amund Ringnes Island. They record the diminishing thickness of the Innuitian Ice Sheet from Norwegian Bay to the Arctic Ocean. The absence of an isobase embayment across the Ringnes Islands suggests a relatively uniform ice load across both islands and Hassel and Massey sounds. Parallel isobases across Peary Channel indicate this ice load extended beyond Massey Sound, although their northward deflection suggests an increasing influence of the former Axel Heiberg Island ice load.
Article
Full-text available
Relative sea level in coastal regions of Newfoundland fell from late-glacial maximum levels to postglacial minima in several phases: (i) an early period of high relative sea level, when Late Wisconsinan ice was at the coast and discharging meltwater plumes into the ocean; (ii) a period of rapidly falling relative sea level, during which glaciers retreated inland; and (iii) a period without glacier ice, during which relative sea level continued to fall, but at decreasing rates. Falling relative sea level caused fluvial incision of glacial deposits in some coastal embayments, and culminated with the construction of lowstand marine deltas. These deltas were submerged during the subsequent Holocene transgression. Seismic reflection data from selected deltas show that they comprise wedges of sediment with prograded, seaward-dipping, foreset-style internal reflections. The depth of the relative sea-level lowstand varies spatially, and it was diachronous. It occurred relatively early and deep in peripheral regions (i.e., farther from the centre of the island), but was later and shallower landward, and close to its northern limits. Approximate ages of the lowstand are 9.5 +/- 1 ka in the St. George's Bay - Port au Port region, just over 8.6 ka in Hamilton Sound, before 7.0 ka at Swift Current, 8.7 ka at Connoire Bay, just over 8.2 ka in Bay d'Espoir, and ca. 6.5 ka on the Great Northern Peninsula. The relative sea-level minima range down to at least -30 m, and form a concentric pattern around central Newfoundland, similar to the pattern of raised marine limits.
Article
Full-text available
New radiocarbon-dated cores obtained by Vibracorers in the western Gulf of Maine confirm that a short-lived, relative sea-level lowstand of ˜-55 m occurred at 11 10.5 ka. These cores and younger salt-marsh data also reveal that rates of transgression varied throughout the Holocene, probably due to local variations in glacial isostasy. The isostatic component is resolved by subtracting published approximations of eustatic sea level from our well-determined observations of local relative sea level. A large peak in the isostatic curve coincides with the lowstand and is interpreted as a forebulge 20 25 m in amplitude. Forebulge migration is estimated at 7 11 km/100 yr, based on the timing of lowstands across the region.
Article
Full-text available
For more than four decades, the reporting of 14C dates on marine molluscs from Arctic Canada has been notable for the lack of consistently applied marine reservoir corrections. We propose that the common approach of reporting Canadian Arctic marine 14C dates using presumed time-invariant reservoir corrections be abandoned in favour of calibration of 14C dates, using the current standard protocol. This approach best facilitates inter- and intra-regional correlation, and correlation with other geochronometers. In order to enable the consistent calibration of marine 14C dates from Arctic Canada, we analysed a 14C database of 108 marine mollusc samples collected live between 1894 and 1956, and determined regional reservoir offset values (ΔR) for eight oceanographically distinct regions. The following new ΔR values should be used for 14C calibration: NW Canadian Arctic Archipelago, 335 ± 85 yrs; Foxe Basin, 310 ± 90 yrs; NE Baffin Island, 220 ± 20 yrs; SE Baffin Island, 150 ± 60 yrs; Hudson Strait, 65 ± 60 yrs; Ungava Bay, 145 ± 95 yrs; Hudson Bay, 110 ± 65 yrs; and James Bay, 365 ± 115 yrs.
Article
Full-text available
Key Words glacial isostasy, mantle viscosity, ice-age ice sheets, paleotopography s Abstract The 100 kyr quasiperiodic variation of continental ice cover, which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of Earth history, has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n-body effects in the Solar System on the geometry of Earth's orbit around the Sun. The impacts of the changing surface ice load upon both Earth's shape and gravitational field, as well as upon sea-level history, have come to be measurable using a variety of geological and geophysical techniques. These observations are invertible to obtain useful information on both the internal vis-coelastic structure of the solid Earth and on the detailed spatiotemporal characteristics of glaciation history. This review focuses upon the most recent advances that have been achieved in each of these areas, advances that have proven to be central to the construction of the refined model of the global process of glacial isostatic adjustment, denoted ICE-5G (VM2). A significant test of this new global model will be provided by the global measurement of the time dependence of the gravity field of the planet that will be delivered by the GRACE satellite system that is now in space.
Article
25 ¹⁴C dates from the coast of Melville Island show that there has been up to 100m of Holocene emergence. The Winter Harbour moraine on the S coast is thought to mark the maximum northward advance of the Laurentice Ice. However, emergence for this area appears to be essentially complete, whereas the NE coast is still recovering at a rate of approximately 0.35 cm/yr. Ice cover in the region to the NE must, therefore, have been thicker and/or lasted longer than in the peripheral areas of the Laurentide Ice, lending support to the concept of an Innuitian Ice Sheet, rather than local ice masses over the central Queen Elizabeth Islands. This ice sheet may have had a thermal regime below the pressure melting point, thus depriving the ice of much of its erosive and depositional capabilities, but with a sufficient mass to account for the observed pattern of emergence. -from Authors
Article
Both the 2-L counter, described in GSC I, and the 5-L counter (GSC IV) were operated routinely during the past year. Approximately one-half of the determinations reported here were obtained from each counter. The 5-L counter was operated mainly at 1 atm. For more than a year, age calculations have been carried out monthly by an I.B.M. 1620 computer. If the background, standard, and sample counts during a month conform to statistical laws, they are entered on sheets together with their respective counting times and sample identifications and sent to the computing center for processing.
Article
Both the 2-L counter, described in GSC I, and the 5-L counter (GSC IV) were operated routinely during the past year. Approximately half of the determinations reported here were obtained from each counter. The 5-L counter was operated mainly at 1 atm.
Article
Prince Patrick and Eglinton islands have a polar desert climate and a landscape of coastal plains and dissected plateaux with limited vegetation cover. Use of a properly damped surveyor's compass is possible, however, magnetic declination changes markedly over short distances and large temporal variations are present. Bedrock of the report area is divisible into four major successions. These include: 1) 14 to 18 km of Proterozoic(?) and/or older bedrock above the Mohorovicí Discontinuity; 2) 10 to 14 km of thermally overmature but variably tectonized ("Franklinian") strata that range from Vendian(?) at the base through Upper Devonian at the top; 3) less than 1 km grading to more than 7 km of thermally mature and immature, relatively undeformed Carboniferous through Lower Cretaceous strata of the Sverdrup Basin, including up to 2 km of Middle Jurassic through Upper Cretaceous strata preserved in four peripheral basins and numerous small grabens; and 4) 70 m to more than 600 m of unconsolidated Pliocene sand, gravel, and peat, and related seismically defined Neogene strata of the Arctic Continental Terrace Wedge. The Franklinian succession is further subdivided into siliciclastic rocks of the Devonian clastic wedge (up to 6000 m thick), subsurface Lower Devonian and older strata of the Prince Patrick Platform, and correlative seismically defined deep-water strata of Canrobert Trough. A thrust-fold belt imaged seismically in the northeast is continuous with folds known at the surface on northwestern Melville Island, and folded Devonian strata are everywhere separated from Carboniferous and younger rocks by a profound angular unconformity. Other lower Paleozoic folds extend under southwestern Prince Patrick Island. A Carboniferous rift system located under the Sverdrup Basin margin has developed on the eroded roots of the Paleozoic fold belt. The rift formed in the Early Carboniferous (Serpukhovian), expanded to the southwest during the later Carboniferous, and was partly inverted during the Early Permian. Mid-Permian through early Middle Jurassic was a time of passive subsidence and progressive basin expansion toward the southwest. During Sverdrup Basin subsidence, four intracratonic basins, separated by Devonian "basement" highs, developed to the southwest between Middle Jurassic and Late Cretaceous time. An array of northerly trending horsts and grabens also developed during this time, part of a rift system that provides a geological record of the early development of the Arctic Ocean basin. Potential exists for far-travelled hydrocarbons within the Permo-Carboniferous and Jurassic-Cretaceous rift systems and in stratigraphic traps on the margins of the Mesozoic basins. Subbituminous coal seams to 1.5 m occur in Lower Cretaceous strata, and deposits of manganese carbonate are widespread in Campanian sandstone of Eglinton Island.
Article
This paper is a reconstruction of postglacial relative sea level change and shoreline delevelling in southern Eureka Sound, High Arctic Canada. Postglacial emergence of up to 150 m is recorded in this area by raised marine deltas, beaches and washing limits that date from the early Holocene. Marine limit is metachronous and formed successively with glacier retreat. Marked contrasts in the form of relative sea level curves and rate of initial emergence are recorded from the study area. In Blind Fiord, relative sea level fell continuously following deglaciation. Initial emergence was characterised by rates of ≥5 m/century. This contrasts with curves from Starfish and Irene bays, where the rate of initial emergence was ≤1 m/century. Isobases drawn on the 8.5 ka shoreline for greater Eureka Sound demonstrate that a cell of highest emergence (≥130 m asl) extends along the length of the channel, and closes in the vicinity of the entrance to Norwegian Bay. This pattern confirms a distinct loading centre over Eureka Sound during the Last Glacial Maximum, and is compatible with independent glacial geological evidence indicating that the thickest ice was centred over the channel during the Late Wisconsinan.
Article
An investigation of Holocene relative sea level (RSL) changes in Disko Bugt has been carried out with the purpose of reconstructing, with a good resolution in time and space, the Holocene RSL changes of a smaller part of GreenLand, and thereby to allow testing of modern models for RSL changes in Greenland. This paper summarises the results of the investigation. The Holocene marine limit in Disko Bugt has been mapped, four RSL curves representing the Early-Middle Holocene emergence of different parts of Disko Bugt have been constructed, and attempts have been made to reconstruct the Late Holocene RSL changes within the region. Important conclusions are: 1. The rate of Early-Middle Holocene relative land rise increases towards the margin of the Greenland Ice Sheet. 2. RSL reached present sea level earlier in areas close to the Greenland Ice Sheet than in areas at greater distances from the Greenland Ice Sheet. 3. RSL fell below present sea level between 2 and 4 ka BP. 4. Submergence has occurred since ca. 1 ka BP.
Article
An introduction to the extensive Quaternary data base which currently exists and to the geophysical models which have been developed to interpret these data; it is clear that an active interplay between theory and observation is desirable. The Quaternary geological data can be brought to bear upon several vital geodynamic issues, including the question of the variation of mantle viscosity with depth, the question of the thickness of the continental lithosphere, and the question of the nature of the discontinuities in elastic parameters which are observed seismically to occur at depths of 420 and 670 km in the earth. Much of the data set is now amenable to direct quantitative interpretation through application of the gravitationally self-consistent model for deglaciation induced relative sea level change. -from Authors
Article
From 7.0 ka to the present, radiocarbon dates on wood and salt marsh peats provide a relatively precise sea-level curve. During the period 4.2-1.5 ka, sea-level rose at 1.22 m/1000 yr. Before that period, it may have risen more than twice as fast. After 1.5 ka, it slowed to half the mid-late Holocene rate. Recent tide-gauge records show an acceleration in rate to 2-3 mm/yr for the past 40 yr. Releveling, tide gauges, and other evidence suggest that the coast is being warped downward to the east, possibly due to non-glacially induced neotectonics. -from Authors
Article
Local postglacial isobases are constructed over northeastern Ellesmere Island and Polaris Promontory, northwestern Greenland, for 7500 and 6000 BP. Both sets of isobases demonstrate a strong upward displacement extending from northeastern Ellesmere Island toward the Greenland Ice Sheet. This reflects two conditions: (1) the glacioisostatic dominance, but not coverage, of the Greenland Ice Sheet over northeastern Ellesmere Island and (2) an accompanying, restricted advance of the northern Ellesmere Island ice sheet during the last glaciation. Regional isobases are also constructed over the Queen Elizabeth Islands and the adjacent Greenland coast. These isobases provisionally indicate that the Queen Elizabeth Islands contribute to the westward extension of the Greenland isobases. This ridge of uplift was produced by the combined glacioisostatic depressions from the ice sheets over the Queen Elizabeth Islands and Greenland. These ice sheets, however, are not considered to have been convergent during the last glaciation. Three postglacial uplift curves from northeastern Ellesmere Island more closely parallel the general decay curves characteristic of the central and southern Canadian Arctic than do previously constructed uplift curves from northern Ellesmere Island.
Article
Age determinations on marine mollusks indicate that the northwestern part of Jones Sound became open to the sea more than 9000 conventional radiocarbon years ago. The presence of postglacial marine features at elevations of up to 130 m near Cape Storm, Ellesmere Island, shows that a significant thickness of glacier ice was present in this area, and the differential uplift of pumice and other materials associated with raised beaches provides convincing evidence that the former ice cover was thicker to the west and to the north. Numerous cross-checks have shown that in such an Arctic environment the organic (collagen) fraction of whale bones gives reliable results, as opposed to the bone apatite fraction, which commonly yields ages that are too young. Marine mollusks also are reliable for 14C age determinations, and the evidence available from areas of carbonate rocks in the Queen Elizabeth Islands suggests that the ages of marine mollusks are no more than 350 years older than the ages of contemporaneous terrestrial plants. Near Cape Storm over fifty 14C age determinations on driftwood, whale bone, and marine mollusks have permitted the construction of a curve showing the pattern of emergence over the past 9000 to 9500 years. Emergence between 9000 and 8000 years ago proceeded at a rate of 7 m/century, and over one-half of the total emergence (70 m out of 130 m) since the initial incursion of the sea took place during this interval. By 6500 to 4500 years ago emergence had slowed to 0.8 m/century, and for the last 2400 years it has averaged <0.3 m/century. The age determinations are sufficiently numerous and closely-spaced, especially between 6500 and 4400 years B. P., to indicate that fluctuations of sea level have not exceeded amplitudes of 2 m or periods >500 years. The concentration of the pumice and the nature of the features associated with it suggest that its deposition may be related to: 1) a eustatic rise close to 5000 years ago; 2) a period of more open water, when wave action and storm surges would have been more effective; 3) a combination of these two factors. The formation of the strandline where the pumice occurs is not believed to be related to a slowing-down or cessation of uplift due to the thickening of ice caps and glaciers.
Article
We investigated a hypersaline, seasonally isolated marine basin (SIMB) in the Canadian High Arctic to elucidate the role of brine rejection, tidal forcing, and groundwater input over the formation of hypersalinity. Analyses of physical parameters and seasonal sampling of ionic and isotopic composition were carried out on a coastal basin near Shellabear Point, Melville Island, Northwest Territories (75°N, 113°W). Observations reveal daily and seasonal variability in the water column due to a seasonal tidal connection during the ice-free season, which lasts substantially longer than the period of freshwater inflow from the catchment. An ice formation model of the volume of brine rejected from surface ice formed from marine water indicates that rapid saline enrichment of the basin due to ice formation is possible from tidally replenished marine water, and that the current hypersalinity may have formed in less than a decade. Modeled isotopic composition of brines are consistent with observations and provide an alternative to freshwater isotopic dilution suggested by other workers. A tidal connection is a critical consideration in lake evolution, and many hypersaline polar lakes could have developed their current chemical composition before full marine isolation. By contrast, in some coastal lakes, marine stratification caused by ice shelves before isolation provides a setting for minimal brine formation and subsequent meromictic conditions to develop. Hence, the marine setting at the time of isolation represents a key factor in explaining divergent lake chemical evolution in the High Arctic.
Article
We present results from an investigation of relative sea-level changes in the Qaqortoq area in south Greenland from c.11 000 cal. yr BP to the present. Isolation and transgression sequences from six lakes and two tidal basins have been identified using stratigraphical analyses, magnetic susceptibility, XRF and macrofossil analyses. Macrofossils and bulk sediments have been dated by AMS radiocarbon dating. Maximum and minimum altitudes for relative sea level are provided from two deglaciation and marine lagoon sequences. Initially, relative sea level fell rapidly and reached present-day level at ˜9000 cal. yr BP and continued falling until at least 8800 cal. yr BP. Between 8000 and 6000 cal. yr BP, sea level reached its lowest level of around 6–8 m below highest astronomical tide (h.a.t.). At around 3750 cal. yr BP, sea level has reached above 2.7 m below h.a.t. and continued to rise slowly, reaching the present-day level between ˜2000 cal. yr BP and the present. As in the Nanortalik area further south, initial isostatic rebound caused rapid isolation of low elevation basins in the Qaqortoq area. Distinct isolation contacts in the sediments are observed. The late Holocene transgression is less well defined and occurred over a longer time interval. The late Holocene sea-level rise implies reloading by advancing glaciers superimposed on the isostatic signal from the North American Ice Sheet. One consequence of this transgression is that settlements of Palaeo-Eskimo cultures from ˜4000 cal. yr BP may have been transgressed by the sea.
Article
Throughout northern Canada, live-collected, pre-bomb, deposit-feeding marine molluscs from calcareous sedi- ments yield greater apparent radiocarbon ages than do suspension feeders. We explore the size of this effect in a set of 57 paired datings of deposit feeders, mainly Portlandia arctica, and suspension feeders, mainly Hiatella arctica and Mya truncata, collected from both calcareous and non-calcareous Holocene sediments. Deposit feeders from calcareous sediments are older than their suspension-feeding counterparts by as much as 2240􏰀130 14C years. This is attributed to the uptake of ‘old’ bicarbonate derived from calcareous bedrock. The age discrepancy between suspension and deposit feeders in calcareous terrain is non-systematic in space and time, thereby invalidating the application of a correction. In contrast, the age comparisons are concordant at sites located on the Precambrian Shield. In terrestrial environments underlain by carbonate, previous acceptance of dates on deposit feeders led to erroneous interpretations of deglaciation and relative sea-level history, in both the North American and the Eurasian Arctic. This has prompted several researchers to exclude deposit feeders from their late Quaternary reconstructions. The same chronological problem of deposit-feeding molluscs now needs to be more widely acknowledged by the marine community.
Article
Late Wisconsinan age glacial landforms and deposits indicate that an ice shelf of at least 60,000 km2 flowed northwestward into Viscount Melville Sound, probably from the M'Clintock Dome of the Laurentide Ice Sheet. The ice shelf overlapped coastal areas and laid Winter Harbour Till up to 125 m above present sea level on the southern coast of Melville Island, to 135 m on Byam Martin Island, to possibly 90 m on the northeast tip of Banks Island, and to 150 m on the north coast of Victoria Island. The contemporary sea level was 50 to 100 m higher than present (it now rises eastward). A maximum age of 10,340 ± 150 yr B.P. for the till, and thus the ice-shelf advance, is provided by shells in marine sediments which underlie it, whereas a minimum age of 9880 ± 150 yr B.P. is provided by overlying shells that postdate the ice advance. The major advance of shelf ice into Viscount Melville Sound may be the result of the rapid disintegration of the M'Clintock Dome while the climate ameliorated in the western Arctic.
Article
The raised beaches and deltas of Devon Island contain an abundance of dateable materials. A large set of radiocarbon dates (228), 154 of which are new, are used to construct relative sea level curves and isobase maps for the island. The best materials for this purpose are driftwood logs (61 dates) and bowhead whale bones (74 dates) from raised beaches and mollusc shells from marine-limit deltas (20 dates) or from altitudes close to marine limit (14 dates). During the last glacial maximum, the island is thought to have lain beneath the southeastern flank of the Innuitian Ice Sheet. The relative sea level history is congruent with that inferred ice configuration. The island spans half the ice sheet width. Relative sea level curves are of simple exponential form, except near the glacial limit where an early Holocene emergence proceeded to a middle Holocene lowstand below present sea level, which was followed by submergence attending the passage of the crustal forebulge. The response times of relative sea level curves and of crustal uplift decrease from the uplift centre toward the limit of loading, but the change appears strongest near the limit. The Innuitian uplift is separated from the Laurentide uplift to the south by a strong isobase embayment over Lancaster Sound. Hence, ice load irregularities with wavelengths of about 100 km were large enough to leave an isostatic thumbprint in this region of the continent. The apparent absence of a similar embayment over Jones Sound probably indicates a greater Late Wisconsinan ice load there, or a thicker crust than in Lancaster Sound.
Article
During the last glacial maximum of east-central Ellesmere Island, trunk glaciers inundated the landscape, entering the Smith Sound Ice Stream. Accelerator mass spectrometry (AMS) dates on individual shell fragments in till indicate that the ice advanced after 19 ka BP. The geomorphic and sedimentary signatures left by the trunk glaciers indicate that the glaciers were polythermal. The configuration and chronology of this ice is relevant to the reconstruction of ice core records from northwestern Greenland, the history of iceberg rafting of clastic sediments to northern Baffin Bay, the reopening of the seaway between the Arctic Ocean and Baffin Bay, and the regional variability of arctic paleoenvironments. Deglaciation began with the separation of Ellesmere Island and Greenland ice at fiord mouths ∼8-8.5 ka BP. Ice reached fiord heads between 6.5 and 4.4 ka BP. Trunk glacier retreat from the fiords of east-central Ellesmere Island occurred up to 3000 years later than in west coast fiords. This later retreat was favoured by (1) impoundment by the Smith Sound Ice Stream in Kane Basin until ∼8.5 ka BP, which moderated the impact of high summer melt recorded in nearby ice cores between ∼11.5 and 8.5 ka BP; (2) the shallow bathymetry and narrowness (<2 km) of the east coast fiords, which lowered calving rates following separation of Innuitian and Greenland ice; and (3) the likelihood of higher precipitation along east Ellesmere Island. Glaciers throughout the field area readvanced during the late Holocene. The greater advance of coastal glaciers is attributed to their proximity to the North Water polynya in Baffin Bay.
Article
For the past half-century, reconstructions of North American ice cover during the Last Glacial Maximum have shown ice-free land distal to the Laurentide Ice Sheet, primarily on Melville and Banks islands in the western Canadian Arctic Archipelago. Both islands reputedly preserve at the surface multiple Laurentide till sheets, together with associated marine and lacustrine deposits, recording as many as three pre-Late Wisconsinan glaciations. The northwest corner of Banks Island was purportedly never glaciated and is trimmed by the oldest and most extensive glaciation (Banks Glaciation) considered to be of Matuyama age (>780 ka BP). Inside the limit of Banks Glaciation, younger till sheets are ascribed to the Thomsen Glaciation (pre-Sangamonian) and the Amundsen Glaciation (Early Wisconsinan Stade). The view that the western Canadian Arctic Archipelago remained largely ice-free during the Late Wisconsinan is reinforced by a recent report of two woolly mammoth fragments collected on Banks and Melville islands, both dated to ∼22 ka BP. These dates imply that these islands constitute the northeast extremity of Beringia.
Article
More than 130 new radiocarbon dates form the basis for 14 emergence curves for Prince of Wales and adjacent smaller islands. These curves and 14 additional curves from a large surrounding area are the primary basis for a set of central Arctic isobase maps. During and just after deglaciation the Boothia Arch was reactivated, producing 60-120m of relief on the regionally elevated 9.3 ka shoreline. This deformation could have the form of a symmetrical ridge or a ridge with a fault zone on its western side. The ridge is flanked on the west by a large isobase plateau where the emerged 9.3 ka shoreline has little gradient. The 8 ka and younger shorelines are not affected by the Boothia Arch, but the Prince of Wales Island isobase plateau persisted as the predominant regional isobase feature throughout postglacial time. The emergence history of Prince of Wales Island since 8 ka can be described by a single exponential least squares regression curve based entirely on 41 driftwood dates. Addition of two select shell dates produces a curve for the area of earliest deglaciation at about 11 ka. The half-response time - the time during which one half of remaining emergence is accomplished - is 2000 years. -from Authors
Article
Approximately 90% of Canada's ocean coastline is affected by seasonal or multiyear sea ice and winter ice develops on most lakes. Recent studies of ice effects in the shore zone have included investigations of ice-congested and protected shores in the north-west Canadian Arctic Archipelago, processes involved in the construction by ice of large shore ridges in the same region, direct ice scour and enhanced hydrodynamic scour in the presence of ice (strudel scour and ice wallow), particularly as potential hazards to buried pipelines in the Beaufort Sea, and the dynamics of boulder-strewn tidal flats and boulder barricades in eastern Canada. The extent and frequency of shore nourishment by ice and details of the processes involved, including die relative importance of ride-up versus pile-up, remain important research questions. Reports emphasizing the contribution of ice rafting to shoreface retreat along the Alaskan coast of the Beaufort Sea suggest the need for quantitative studies of this phenomenon in Canada, in particular with respect to prodelta sedimentation at the mouth of the Mackenzie River. The coastal zone in the Beaufort Sea is particularly sensitive to climate change through effects on thermokarst processes, rising sea level, the relation between ice cover and wave energy through fetch limitation, and potential changes involving ice dynamics and freeze-up processes.
Article
Substantial postglacial emergence (up to 150m) characterizes the Canadian High Arctic following the last glacial maximum. Across northern Ellesmere Island, rapid emergence is not observed during the early stages of deglaciation as it is in other parts of Arctic Canada. Rather, the curves show an interval of slow emergence (c. 1 m per century) during initial ice retreat. This is attributed to a slow rate of glacial rebound that was countered by a similar rate of eustatic sea-level rise. Normally, isobases drawn on postglacial shorelines define broad cells of uplift that mimic centres of former maximum ice thickness. However, isobases on the 8 ka sp shoreline, surveyed throughout northern Ellesmere Island, indicate more complex patterns of crustal uplift that seem incongruent with reported ice thicknesses. On west-central Ellesmere Island, the isobases (110-150 m asl) trace a plunging ridge, aligned with geological structure, across an area considered to have had minimal ice cover during the last glacial maximum. The ridge may record an important structural influence associated with the geologically youthful Sverdrup Basin. Collectively, this evidence cautions against the view that postglacial emergence has a universally, predictable signature solely portraying former ice loads.
Article
Eleven paleogeographic maps and a summary ice retreat map outline the history of advance, retreat, and readvances of the Laurentide Ice Sheet along with associated changes in proglacial drainage and relative sea level oscillations for Late Wisconsinan and Holocene times. The text outlines pertinent chronological control and discusses the paleoglaciology of the ice sheet, with attention to location and migration of ice divides, their attendant domes and saddles, and to ice streams, ice shelves, and mechanisms of deglaciation. -from Authors
Article
Dark brown pumice has been discovered recently on raised beaches of Ellesmere and Devon Islands, and in archeological sites on Baffin Island. It is similar in appearance and chemical composition to pumice associated with raised marine features throughout northern Europe, especially along the coasts of Norway and Spitsbergen. The source area for the pumice is uncertain, but Iceland is a good possibility.Radiocarbon dates on driftwood and whale bones imbedded in beaches at the "pumice level", as well as at higher and lower elevations, indicate that the pumice arrived approximately 5000 years ago.The pumice serves as a time-line and provides a means of correlating widely-separated marine features. Because these features now occur at different elevations, the amount and direction of tilt can be calculated. Also, former ice centers can be delineated, as the areas which have undergone the greatest uplift are those where the ice cover was once thickest. In Arctic Canada the "pumice level" rises westward along Jones Sound—from 16.5 m a.s.l. at the mouth of South Cape Fiord, Ellesmere Island, to 24.0 m at the eastern tip of Colin Archer Peninsula, Devon Island, ca. 130 km away. It also rises northwestward toward the head of South Cape Fiord.The Jones Sound information, plus radiocarbon dates from elsewhere in the Queen Elizabeth Islands indicating the approximate position of the shoreline at the same time, shows that there is a region in the eastern and central part of the archipelago where >25 m of uplift has occurred during the last 5000 years. This region, including considerable areas that are now sea, is believed to have been covered by a major ice sheet during the last glaciation.
Article
Moraines and meltwater channels mark the limit of the last glaciation that interfingered with the sea around the perimeter of Greely Fiord and its tributaries. The extent of this ice advance was dictated predominantly by its proximity to the sea. Consequently, the large tidewater glaciers at the fiord heads today were so constrained by calving that they advanced only 5-10 km. Similarly, grounding-line deposits from widespread plateau ice caps also terminate just below marine limit. The most extensive outlet glaciers, which advanced 20-35 km beyond present margins, are simply those that had access to the most extensive terrain above marine limit, ie, the NW margin of the Agassiz Ice Cap. The modest extent of the last ice limit encircling Greely Fiord, together with its occupancy by the full glacial sea, is fully compatible with the paleogeography previously reported from NE Ellesmere Island and NW Greenland. Furthermore, this data base provides a reinterpretation of a 500 km transect previously reported along west-central Ellesmere Island to the south and affirms that the Innuitian Ice Sheet, defined sensu stricto for the last glaciation, is supplanted by the full glacial Innuitian Sea, which penetrated the Queen Elizabeth Islands, constraining the last ice limit. -from Author
Article
During the last glaciation an ice-free corridor existed between the northeast Ellesmere Island and northwest Greenland ice sheets. This corridor constituted a peripheral depression in which the marine limit marks the uppermost extent of a full glacial sea. The full glacial sea is characterized by (1) 14C dates on in situ marine shells that predate initial emergence (unloading) followed by (2) synchronous emergence from the marine limit throughout the peripheral depression. Relative sea-level curves from the full glacial sea confirm previous morphostratigraphic and glacioisostatic evidence for limited ice extent during the last glaciation. These curves also document the history of glacial unloading and the form of the relative sea-level curve that one would theoretically expect in the peripheral depression. The form of the curves presented here is unlike any other published emergence curves from arctic Canada or from Fennoscandia.The relative sea-level curves for northeast Ellesmere Island show three segments: (1) an interval of stable relative sea level (isostatic equilibrium) at the marine limit between at least 11 000 and 8000 BP; (2) an interval of slow emergence from 8000 to 6200 BP during which northeast Ellesmere Island ice slowly retreated; and (3) an interval of rapid emergence, caused by rapid glacial unloading, after 6200 BP when a prominent amelioration was in progress. These relative sea-level curves are discussed in relation to other paleoclimatic changes and the deglacial history of northwest Greenland. These curves are of regional importance in that they provide a new means of distinguishing between areas that were ice covered and ice free during the last glaciation.
Article
Despite the widespread occurrence of gravel barriers on mid- to high-latitude coasts, understanding of their stability and relationship to gravel deposits on the inner continental shelf remains rudimentary. On sand-dominated coasts subject to rising relative sea level, barrier overstepping has been postulated as a mechanism for preservation of beach deposits on the shelf, but direct observation of overstepping events has been lacking. Observations at a site on the Atlantic coast of Canada reveal migration of a gravel barrier at 8 m a−1 landward over back-barrier mud, following abandonment of part of the barrier volume on the shoreface. This provides clear evidence for overstepping and suggests that it may play a role in the formation of inner-shelf gravel deposits. Integrity of the migrating (stretching) barrier depends on continued sediment supply from the headland source to a connecting ridge, which must become progressively longer as the landward displacement of the barrier increases.
Article
Distribution sampling from sequences of radiocarbon ages is used to obtain confidence intervals for intermediate age estimates, sediment deposition times, and thence pollen deposition rates. Three types of age-depth model are explored by this approach, and it is demonstrated that the choice of model has implications for confidence intervals on the results. Line-fitting of polynomials by least- squares will produce narrower confidence intervals than interpolation models. It is shown that radiocarbon ages should be evenly spaced, and that results towards the ends of sequences have wider confidence intervals. Of the total width of confidence intervals for pollen deposition rates, up to half may be due to the uncertainties associated with the sediment deposition time, even in uniform sediment. The importance of including confidence intervals of all values as an essential part of the presentation of palaeoecological data is stressed.
Article
Glacial erratics collected on Melville Island, western Canadian Arctic Archipelago, were analyzed to determine their mainland provenance, thereby constraining their long-distance transport by the Laurentide Ice Sheet. These erratics can be broadly subdivided into three main lithologies: granite (n = 15), quartzite (n = 7), and diabase-diorite (n = 3). The granite erratics are most distinctive from a provenance perspective and can be further subdivided into three geochemical groups based on their potassium content: (1) a high-K2O group (K2O> 4.0 wt.%), (2) an intermediate-K2O group (K2O between 2.0 and 4.0 wt.%), and (3) a low-K2O group (K2O< 2.0 wt.%). In situ thin section laser ablation inductively coupled plasma mass spectrometer U-Pb zircon ages obtained for eight granite erratics yielded both Archean (2575 Ma) and a range of Paleoproterozoic (2472-1778 Ma) crystallization ages. In addition, three overprint ages were identified at 1.90, 1.84, and ~1.0 Ga. The most compelling constraint for a northward regional ice flow originating on the mainland are two high-precision conventional U-Pb zircon ages of 1969.5± 1.0 and 2472.3± 0.5 Ma, indicating that these granite erratics must have been derived from the 2.0-1.9 Ga Taltson-Thelon Orogen and the nearby 2.5-2.4 Ga Queen Maud Block, respectively. These granite-dominated terranes are located 600km due south and southeast of the collection area on Melville Island. Although it is unknown whether the final deposition of these erratics on Melville Island involved transport by one or more glaciations, it is apparent that this ice flow cannot be accommodated by the proposed north-south axis of the M'Clintock Ice Divide, the primary topographic feature of the northwestern Laurentide Ice Sheet during the last glacial maximum. The transport of erratics reported here would have required a former ice divide oriented east-west over the mainland, close to that proposed for the Ancestral Keewatin Divide. An east-west ice divide in this region is consistent with previously reported ice-flow indicators that document northward flow from the mainland and recent thermomechanically coupled ice-sheet numerical modeling that indicates former maximum ice thickness on the mainland immediately south of Melville Island.Des blocs erratiques recueillis sur l'île Melville, dans l'archipel arctique canadien, ont été analysés afin de déterminer leur provenance des régions continentales, encadrant ainsi leur transport sur de longues distances par l'Inlandsis laurentidien. Ces blocs erratiques peuvent être subdivisés selon trois principales lithologies : granite (n = 15), quartzite (n= 7) et diabase-diorite (n = 3). Les erratiques de granite sont les plus distinctifs du point de vue de la provenance et ils peuvent être subdivisés de nouveau en trois groupes géochimiques basés sur leur contenu en potassium : (1) un groupe à teneur élevée en K2O (K2O> 4,0 % poids), (2) un groupe à teneur intermédiaire en K2O (K2O entre 4,0 et 2,0 % poids) et (3) un groupe à faible teneur en K2O (K2O< 2,0 % poids). Des âges U-Pb in situ déterminés sur des zircons en lame mince par analyse à couplage inductif et spectrométrie de masse avec ablation au laser (LA-ICP-MS) de huit blocs erratiques de granite ont donné des âges de cristallisation archéens (2575 Ma) et paléoprotérozoïques (2472-1778 Ma). De plus, trois âges de surimpression ont été identifiés à 1,90, 1,84, et ~1,0 Ga. La contrainte la plus convaincante pour un écoulement régional de la glace vers le nord à partir du continent a été la détermination de deux âges conventionnels U-Pb de grande précision sur des zircons, soit 1969,5± 1,0 et 2472,3± 0,5 Ma, indiquant que ces blocs erratiques de granite doivent provenir respectivement de l'orogène Taltson-Thelon (2,0-1,9 Ga) et du bloc Queen Maud (2,5-2,4 Ga) avoisinant. Ces terrains dominés par des granites sont situés à 600km franc sud et sud-est du secteur de collecte sur l'île Melville.
Article
The island of Newfoundland, Canada, is situated close to the former margins of the Laurentide ice sheet. The post-glacial sea-level history is complex, dominated by the effects of an ice-marginal crustal forebulge produced by isostatic deformation of the lithosphere. Marine fossils found above present sea-level can be 14C dated, and examination of the temporal and geographical distribution of these 14C dates in combination with geomorphological indicators of past sea-levels indicates regional trends of relative sea-level change. For most of the island (apart from the Northern Peninsula) no samples have been recovered that date younger than 8000 BP. suggesting that sea-level lay below the present one in these areas for the last 8000 years. The same areas commonly show geomorphological evidence for stands of sea-level both above and below present sea-level. This evidence is interpreted as showing that over most of Newfoundland, following deglaciation, sea-level fell to below present levels, and subsequently rose to the modern level. Exceptions to this pattern are the north of the Northern Peninsula, which shows a history of continuous emergence, or a more complex pattern of sea-levels falling below present, subsequently rising above present, and currently falling; and the northeast Avalon Peninsula, which may have had sea-levels below present throughout post glacial times. This pattern of relative sea-level change is interpreted as being mostly due to isostatic recovery, with the main factor being northerly migration of the forebulge. Mapping the time at which sea-level fell below the present level allows estimation of the rate of northerly migration and collapse of the forebulge at between 4.5 and 11 km/100 years; this is considerably faster than previous estimates.
Article
The IPCC Fourth Assessment Report (AR4) stated that global sea level rose by about 120 m between the Last Glacial Maximum (LGM) and 3–2 ka and did not rise again until the late 19th century. A review of relevant literature demonstrates that the rise may have been larger (by 10–15 m), that the timing of stabilisation is poorly constrained (within the last 7 ka BP), and that the onset of modern rates of sea-level rise is not synchronous and uniform across the globe. The LGM lowstand as defined in the AR4 is based on the ‘classic’ Barbados sea-level history, but the sea-level curve from this island may not be an accurate ‘eustatic’ approximation if glacial isostatic adjustment (GIA) processes were significant, as suggested by various authors. The Barbados sea-level curve revealed the existence of meltwater pulse (MWP) 1a at around 14 000 cal. a BP. Questions about the source and causal mechanism of MWP 1a are still being explored by field scientists and GIA modellers. These problems have direct relevance for contemporary measurements of ice mass changes, because space geodetic measurements rely on information provided by GIA models to separate land motion from ice mass changes. Global patterns of Holocene sea-level change are controlled by regional sea-level variability, not only through isostatic and tectonic processes, but also through steric effects, longer-wavelength gravitational changes produced by changing ice–ocean mass flux and hemispheric-scale perturbations in the Earth's rotation. ‘Eustasy’ is therefore merely a concept, not a measurable quantity. Constraining the late Holocene ice melt contribution to global sea-level rise and determining regional sea-level rise patterns in the 18th and 19th centuries are important future tasks for sea-level scientists; these will establish the baseline contributions to 20th- and 21st-century sea-level rise and will help to determine the causes of modern rates of sea-level rise. Constraining historical sea-level accelerations and short-term ice-mass flux will aid models of ice-sheet dynamics and help to reduce current uncertainties in future sea-level predictions. The AR4 shows that regional sea-level variability is clearly present in sea-level change patterns for the past 50 a and an important challenge for the next IPCC assessment is to incorporate this variability into regional future sea-level rise scenarios. Copyright © 2009 John Wiley & Sons, Ltd.
Article
Along the northern coasts of Ellesmere Island, at least two glaciations are recognized on the basis of morphostratigraphy. The early Holocene ice limit lay only 5 to 60 km beyond present glaciers due to constraints imposed by aridity and calving. This limited ice advance likely extended beyond any Wisconsinan glacial limit. Marine limits established during, retreat from the last glacial maximum reach 148 m a.s.l. In contrast, earlier, more extensive glaciations inundated the coastlines and are associated with former relative sea levels now reaching 286 m a.s.l. Correlation of these pre-Wisconsinan glaciations is based upon amino acid ratios. However, this approach is severely limited by slow rates of racemization, a lack of in situ samples, and complex thermal histories owing to multiple transgressions. Models favoring extensive regional glaciation of northern Ellesmere Island and Greenland must include a glacioclimatic scenario recognizing the constraint that aridity places on glaciation. We suggest that the large ice volume associated with the oldest recognized glaciation relates to a period of reduced sea-ice cover, possibly >400,000 BP, and may correlate with an interglacial stage of the marine oxygen isotope record.
Article
1] For the 1955 –2003 period, the thermal expansion of the 0 – 700 m layer of the World Ocean contributed approximately 0.33 mm/year to global sea level rise. About half of this thermosteric trend is due to warming of the Atlantic Ocean. Approximately one third of the total thermosteric rise is due to the warming of the Pacific Ocean. For the period of available TOPEX/Poseidon (T/P) satellite altimetry data (1993 – 2003), the linear trend of thermosteric sea level (0 – 700 m) is 1.23 mm/year, 60% of which is due to the trends in the Pacific Ocean. For the 0– 3000 m layer of the entire World Ocean, the linear trend of thermosteric sea level is 0.40 mm/year for 1955 – 1959 through 1994 – 1998. For the 50°S–65°N region that we previously reported (Antonov et al., 2002) which was characterized by a 0.50 mm/year trend for 1955 –1959 through 1992 – 1996, our new estimate is 0.47 mm/year for this same period. Citation: Antonov, J.
Article
The extent and origin of Quarternary glaciers in the Queen Elizabeth Islands of Arctic Canada, especially during the Last Glacial Maximum (LGM), has been debated for well over a century. No consensus has yet emerged and the spectrum of interpretations within the last decade is the broadest ever. The glacial geology of Devon Island strongly supports the Late Wisconsinan Innuitian Ice Sheet hypothesis. During LGM, the southeastern part of the Queen Elizabeth Islands was covered by an ice sheet flowing from a centre, or a divide centrally located, in the archipelago. Another ice divide extended from the centre across Devon Island. Flow from the Innuitian centre and convergent flow from Devon Island, and probably also from Cornwallis and Bathurst Islands, sustained an ice stream in Wellington Channel. Ice was locally advancing to its LGM limit about 23 ka BP. Recession in the vicinity of the present coastline was underway by 10 ka BP and final ice remnants west of the present Devon Ice Cap vanished about 8 ka BP. The island bears the same two-part landscape zonation as do other islands and peninsulas in the region. These reflect a cold-based core and warm-based periphery at LGM.
Article
After ~ 11,000 years of glacio-isostatically induced forced regression, geomorphological evidence indicates that the coastline of eastern Melville Island, western Canadian Arctic Archipelago, is now being transgressed. Recently developed coastal features associated with this transgression include: drowned gullies and small estuaries, barriers and lagoons, barrier islands, erosional notches, backstepping beaches, and drowned tundra vegetation and vehicle tracks dating from the 1970s. We mainly attribute this relative sea-level rise to the eastward migration of a peripheral crustal forebulge. Furthermore, the reported transgression also includes a component from recent eustatic sea-level rise during the 20th century. Recent earthquakes recorded in the Gustav-Lougheed Arch Seismic Zone located in Byam Martin Channel, 70 km east of Melville Island, suggest that neotectonics could also be involved in local relative sea-level adjustments. Other factors associated with global warming, especially the formation of an earlier shore-ice lead coupled with increased storm activity might also be responsible for some of the coastal changes. Our study indicates that the current zero isobase, separating areas of net transgression from those of net regression, is now located off the east coast of the island. Our field observations support recent glacio-isostatic modelling that shows the island is presently undergoing a transgression.