Evidence for meltwater drainage via the St. Lawrence River Valley in marine cores from the Laurentian Channel at the time of the Younger Dryas

Levac, Elisabeth; Lewis, Michael J.; Stretch, Vanessa; Duchesne, Katie; Neulieb, Thomas

doi:10.1016/j.gloplacha.2015.04.002

Cited by 18 publications

(16 citation statements)

References 112 publications

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“…; Levac et al . ; Rémillard et al . ), the mineralogical, geochemical, grain‐size, magnetic and spectral reflectance results obtained for each sediment core are presented by geographical location as follows:…”

Section: Resultsmentioning

confidence: 99%

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Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Casse

Montero‐Serrano

St‐Onge

2017

Boreas

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Onge, G. 2017 (July): Influence of the Laurentide Ice Sheet and relative sea-level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation.Physical properties, grain size, bulk mineralogy, elemental geochemistry and magnetic parameters of three sediment piston cores recovered in the Laurentian Channel from its head to its mouth were investigated to reconstruct changes in detrital sediment provenance and transport related to climate variability since the last deglaciation. The comparison of the detrital proxies indicates the succession of two sedimentary regimes in the Estuary and Gulf of St. Lawrence (EGSL) during the Holocene, which are associated with the melting history of the Laurentide Ice Sheet (LIS) and relative sea-level changes. During the early Holocene (10-8.5 cal. ka BP), high sedimentation rates together with mineralogical, geochemical and magnetic signatures indicate that sedimentation in the EGSL was mainly controlled by meltwater discharges from the local retreat of the southeastern margin of the LIS on the Canadian Shield. At this time, sediment-laden meltwater plumes caused the accumulation of fine-grained sediments in the ice-distal zones. Since the mid-Holocene, postglacial movements of the continental crust, related to the withdrawal of the LIS (c. 6 cal. ka BP), have triggered significant variations in relative sea level (RSL) in the EGSL. The significant correlation between the RSL curves and the mineralogical, geochemical, magnetic and grain-size data suggest that the RSL was the dominant force acting on the sedimentary dynamics of the EGSL during the mid-to-late Holocene. Beyond 6 cal. ka BP, characteristic mineralogical, geochemical, magnetic signatures and diffuse spectral reflectance data suggest that the Canadian Maritime Provinces and western Newfoundland coast are the primary sources for detrital sediments in the Gulf of St. Lawrence, with the Canadian Shield acting as a secondary source. Conversely, in the lower St. Lawrence Estuary, detrital sediments are mainly supplied by the Canadian Shield province. Finally, our results suggest that the modern sedimentation regime in the EGSL was established during the mid-Holocene.

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Section: Resultsmentioning

confidence: 99%

“…; Levac et al . ). Indeed, modifications in deglacial meltwater inputs via the St. Lawrence drainage system as the southern LIS margin retreated caused abrupt changes in sedimentation rates in the EGSL, with rates higher than ~30 m ka −1 during the initial deglaciation and lower rates (~40–67 cm ka −1 ) during the early to late Holocene (e.g.…”

mentioning

confidence: 97%

Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Casse

Montero‐Serrano

St‐Onge

2017

Boreas

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“…Recent research suggests that meltwater from Lake Agassiz could have had an ice-free route to the North Atlantic at the time of the YD initiation (Leydet et al, 2018), revising earlier ice sheet reconstructions suggesting that the Laurentide Ice Sheet blocked the most obvious meltwater pathways to the North Atlantic (Lowell et al, 2005). Although direct evidence that a meltwater pulse occurred along this route immediately preceding the YD's onset is limited, some sediment core evidence suggesting that floods through the St Lawrence Valley coincided with the YD initiation does exist (Levac et al, 2015;Rayburn et al, 2011). A northward meltwater flow path along the MacKenzie Valley to the Arctic Ocean is also possible (Murton et al, 2010;Not and Hillaire-Marcel, 2012;Tarasov and Peltier, 2005).…”

Section: Compatibility With Other Hypothesesmentioning

confidence: 89%

“…The freshwater pulse may have followed another route to the ocean, and other research has proposed the Mackenzie Valley (Condron and Winsor, 2012;Murton et al, 2010) as a possible alternative and the Fennoscandian Ice Sheet as an alternate source . Very recent surface exposure ages suggest that the route to the North Atlantic from Lake Agassiz was indeed free of ice before the YD initiation (Leydet et al, 2018), coinciding with evidence of freshening of the Gulf of St Lawrence (Levac et al, 2015), illustrating that meltwater could indeed have followed the St Lawrence Valley route to the North Atlantic. Nevertheless, the issue concerning the routing of a meltwater pulse illustrates a key uncertainty inherent in the meltwater pulse hypothesis.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

2018

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Abstract. The Younger Dryas is considered the archetypal millennial-scale climate change event, and identifying its cause is fundamental for thoroughly understanding climate systematics during deglaciations. However, the mechanisms responsible for its initiation remain elusive, and both of the most researched triggers (a meltwater pulse or a bolide impact) are controversial. Here, we consider the problem from a different perspective and explore a hypothesis that Younger Dryas climate shifts were catalysed by the unusually sulfurrich 12.880 ± 0.040 ka BP eruption of the Laacher See volcano (Germany). We use the most recent chronology for the GISP2 ice core ion dataset from the Greenland ice sheet to identify a large volcanic sulfur spike coincident with both the Laacher See eruption and the onset of Younger Dryasrelated cooling in Greenland (i.e. the most recent abrupt Greenland millennial-scale cooling event, the Greenland Stadial 1, GS-1). Previously published lake sediment and stalagmite records confirm that the eruption's timing was indistinguishable from the onset of cooling across the North Atlantic but that it preceded westerly wind repositioning over central Europe by ∼ 200 years. We suggest that the initial short-lived volcanic sulfate aerosol cooling was amplified by ocean circulation shifts and/or sea ice expansion, gradually cooling the North Atlantic region and incrementally shifting the midlatitude westerlies to the south. The aerosol-related cooling probably only lasted 1-3 years, and the majority of Younger Dryas-related cooling may have been due to the seaice-ocean circulation positive feedback, which was particularly effective during the intermediate ice volume conditions characteristic of ∼ 13 ka BP. We conclude that the large and sulfur-rich Laacher See eruption should be considered a viable trigger for the Younger Dryas. However, future studies should prioritise climate modelling of high-latitude volcanism during deglacial boundary conditions in order to test the hypothesis proposed here.

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“…The best current chronology indicates that water from the Lake Agassiz subbasin first flowed east to the newly ice-free Saint Lawrence (Broecker et al, 1989;Carlson et al, 2007a;Carlson and Clark, 2012;Breckenridge, 2015;Levac et al, 2015;Leydet, 2016), though this rerouting did not produce any significant drawdown of the lake level. Starting at 12.18 ± 0.48 ka, outflow from the Lake Agassiz subbasin was rerouted to the northwest towards the Mackenzie River (Andrews and Dunhill, 2004;Carlson et al, 2007a;Breckenridge, 2015).…”

Section: Drainage Histories By Rivermentioning

confidence: 96%

Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

Wickert

2016

Earth Surf. Dynam.

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Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins -the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

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Evidence for meltwater drainage via the St. Lawrence River Valley in marine cores from the Laurentian Channel at the time of the Younger Dryas

Cited by 18 publications

References 112 publications

Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

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