Sediments, sedimentation rates, and environments, southeast Baffin Shelf and northwest Labrador Sea, 8–26 ka

Abstract

Ten 14C-dated cores are described from the Labrador Sea, continental slope, and Hatton and Resolution basins on the southeast Baffin Shelf. Based on sharply defined detrital carbonate layers in the Labrador Sea cores, we propose that the Laurentide Ice Sheet reached the shelf break at both 20 and 15 14C ka (24.3 and 18.2 sidereal ka) and contributed significant sediment to the northwest Labrador Sea both times; the flux was ± 720 kg/(m2∙ka) during these periods of maximum ice extent. The Laurentide Ice Sheet retreated from its 15 ka position at the shelf break to the inner shelf between 14 and 12 14C ka. Ice-proximal conditions, recognized by relatively light δ18O on near-surface planktonic foraminifera, high detrital carbonate, and benthic foraminiferal faunas (dominated by Elphidium excavatum forma clavata; Cassidulina reniforme), prevailed until at least 10 14C ka. The ice readvanced toward Resolution Basin and across part of Hatton Basin at 11 14C ka. Accelerator mass spectrometry dates on core tops indicate that deposition on the shelf virtually ceased by 7 ka and was very low in the northwest Labrador Sea throughout the Holocene. Downcore accelerator mass spectrometry dates indicate that during deglaciation, the loci of depocentres shifted in response to changes in the position of the ice margin. On the southeast Baffin Island shelf net sediment fluxes at the sea floor reached values of over 3000 kg/(m2∙ka) between 12 and 10 14C ka, of which nearly half was detrital carbonate, principally calcite.

Late Quaternary stratigraphy, chronology, and depositional processes on the slope of S.E. Baffin Island, detrital carbonate and Heinrich events: Implications for onshore glacial history

“…Dates from the tops of three piston cores are around 10 ka (Table I); the trigger weight (tw) core of HU87-009 has a date of 10,670 ± 90 (Table I) at 105 cm, and the tw and pc sections can be matched from that depth to the top of both (Tedesco, 1993). Although some sediment was probably lost in the coring operations the results are similar to core top dates from the shelf east of Hudson Strait where sedimentation ceased about 8 ka once the LIS had retreated into Hudson Bay (Andrews et al, 1994b(Andrews et al, , 1995b. The abrupt decrease in the rate of sediment accumulation is due to sediment trapping in new basins within the continental margin (e.g.…”

“…8B) suggests significant variability in sediment grainsize and/or mineralogy. Intervals of low magnetic susceptibility coincide with intervals of increased sand and, based on previous studies (Andrews et al, 1994b), imply that these episodes are also ones of increased detrital carbonate input. Thus HU75-060 records possibly four (4) DC-events; the first occurred sometime before 43.2 ka (Fig.…”

“…The increase in kaolinite may be a tracer for the Cretaceous outcrop on the floor of Cumberland Sound (Jennings, 1989(Jennings, , 1993Jennings et al, 1996). Later work suggested that there were two sources for DC-events in the region: the first is dominated by calcite and appears to have a source in Hudson Strait; the other is dominated by dolomite with potential sources in Cumberland Sound and/or Baffin Bay (Andrews, 1993;Andrews et al, 1989Andrews et al, , 1994bAndrews et al, , 1995aJennings, 1993).…”

“…The abrupt decrease in the rate of sediment accumulation is due to sediment trapping in new basins within the continental margin (e.g. Cumberland Sound) (Andrews et al, 1994b;Jennings, 1993).…”

Magnetic properties and paleointensity records frome late quaternary Labrador sea sediments =

“…High detrital carbonate has been shown to be associated with deposits from Hudson Strait (Josenhans et al 1985 and may indicate periods when the ice sheet in this region reached the outer shelf (Andrews et al, 1994b). We postulate that the ice surges which produced the IRD in P-094, P-013 and in correlative North Atlantic Heinrich layers also triggered turbiditic flows down the NAMOC.…”