Late Quaternary glacial history and meltwater discharges along the Northeastern Newfoundland Shelf

Abstract

The geomorphology of the Eastern Canadian margin has been shaped by glacial processes during the Quaternary. Many studies have focused on the ice-sediment pathway through Hudson Strait to reconstruct the dynamics of the Laurentide Ice Sheet, and as a consequence, little is known on its marginal ice domes. Here we reconstruct the dynamics of two trough mouth fans (TMFs) offshore NE Newfoundland using sediment cores and radiocarbon ages supported by very high resolution seismic reflection profiles. These two TMFs, namely Notre Dame and Hawke, are fed by two glacial troughs incised in the bedrock. The TMFs show a complete sedimentary sequence from 30 ka BP to the beginning of the Holocene. The sampled sedimentary record on the upper slope extends back to a thick Heinrich event 3 (H3) deposit that corresponds to the end of the maximum extent of the Newfoundland ice dome. Above H3, a thick succession of turbidite deposits (>10 m) observed in both TMFs is correlated with periods of major meltwater supply from 28–29 to 17 ka BP. Our results show that the Last Glacial Maximum (LGM) period was characterized by major input of meltwater events stemming from the Newfoundland dome. The presence of H1 (∼17 ka BP) coincide with the end of the turbidite activity which is replaced by an open-water environment characterized by hemipelagic sediments rich in ice-rafted debris. The proglacial muddy sediment older than 13.3 ka BP on the shelf shows that ice was not grounded after H1, suggesting a very rapid retreat of the ice on the Newfoundland shelf after 17 ka BP.

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…Furthermore, have been able to identify at least two sources for the Heinrich layers in the Labrador Sea based on source rock signatures. The complex internal structure of Heinrich events as well as the variability in the sediment source (Tripsanas and Piper, 2008b;Rashid et al, 2012;Roger et al, 2013) indicates a complex series of ice stream catchments and tributary redistribution for each event, which is consistent with the activation of a number of different ice streams (see Section 2.2).…”

“…Dispersed drop clasts and pellets within the turbidite layers suggest that ice calving occurred at the same time as meltwater supply. High resolution sedimentary records from the Bay of Biscay also show a similar pattern for meltwater events, with turbidites attributed to meltwater during warm periods, and IRD beds topping the turbidites during cold periods (Zaragosi et al, 2006;Toucanne et al, 2009;Roger et al, 2013). Thus, Heinrich events appear to involve seasonal meltwater discharge and iceberg calving, similar to that seen at modern glacier outlets.…”

“…Additional work is required to determine the average duration of a couplet, but it is likely that they are annual (T and P = turbidites and meltwater plume deposits; IRD = ice rafted debris; cp = couplet). Roger et al (2013). Different coloured bars for meltwater production emphasise that each source has a distinctive detrital petrology.…”

“…These are recorded in turbidite records, particularly in the North Sea fan, the Orphan Basin, and the Laurentian fan, where thick sequences of turbidites were interrupted every 1-2 ka by hemipelagic sediments (Lekens et al, 2006;Piper et al, 2007;Tripsanas and Piper, 2008b;Roger et al, 2013). Recent work, however, suggests that the existence of individual D-O oscillations does not rely upon meltwater outputs to force them, but may arise from self-sustained nonlinear oscillations of the coupled atmosphereocean-sea ice system that are 'kicked' into action by preceding Heinrich events (Peltier and Vettoretti, 2014).…”

“…The amount of meltwater increased toward the LGM, with a climax from 15 to 28 ka ( Figure 11) (Lekens et al, 2006;Haapaniemi et al, 2010; 26 Roger et al, 2013). Where ice persisted, sedimentation rates remained high until the beginning of the Holocene .…”