ALBERT

Description: Along the West Greenland continental margin adjoining Baffin Bay, bathymetric data show a series of large submarine fans located at the mouths of cross-shelf troughs. One of these fans, termed here ‘Uummannaq Fan’, is a trough-mouth fan built largely by debris delivered from a fast-flowing outlet of the Greenland Ice Sheet during past glacial maxima. Cores from this fan provide the first information on glacimarine sedimentary facies within a major West Greenland trough-mouth fan and on the nature of Late Weichselian–Holocene glacigenic sediment delivery to this region of the Baffin Bay margin. Glacigenic debris flows deposited on the upper slope and extending to at least 1800 m water depth in front of the trough-mouth are related to the remobilization of subglacial debris that was delivered onto the upper slope at times when an ice stream was positioned at the shelf edge. In contrast, sedimentary facies from the northern sector of the fan are characterized by hemipelagic and ice-rafted sediments and turbidites; glacigenic debris flows are notably absent in cores from this region. Quantitative X-ray diffraction studies of the 〈2-mm sediment fraction indicate that the bulk of the sediment in the fan is derived from Uummannaq Trough but there are distinct intervals when sediment from northern Baffin Bay sources dominates, especially on the northern limit of the fan. These data demonstrate considerable variation in the nature of sediment delivery across the Uummannaq Fan when the Greenland Ice Sheet was at the shelf edge. They highlight the variability of glacimarine depositional processes operating on trough-mouth fans on high-latitude continental margins during the last glacial maximum and indicate that glacigenic debris flows are just one of a number of mechanisms by which such large depocentres form. Copyright © 2012 John Wiley & Sons, Ltd.

Description: Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250 km seaward from the mouth of Cumberland Sound, and 400 km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from ∼10 to 58 ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the 〈 2-mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite-rich sediments from Baffin Bay, calcite-rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H-0 (Younger Dryas), whereas Hudson Strait was the source during H-events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H-events, thus both leading and lagging Hudson Strait-sourced H-events. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT A suite of cores from the North-West Iceland and East Greenland shelves sampled fossiliferous or unfossiliferous basal glacial diamictons. Radiocarbon dates above the diamictons are similar on both shelves, but the value of the ocean reservoir correction, Δ R , is unknown. Deglaciation occurred either ∼16 or 14 cal ka BP depending on the choice of Δ R . The ice sheets were behind the present coastline by 12.2 cal ka BP. We examine seven cores that record the glacial/deglacial transition and present new data on the sea-ice biomarkers IP 25 and C 25:2 from four of the cores plus data on ice-rafted debris counts, grain-size spectra, δ 18 O on the near-surface planktonic foraminifera Neogloboquadrina pachyderma (s), foraminifera assemblages, and quartz percentage. IP 25 concentrations are markedly higher for the East Greenland sites, while they are frequently below the limit of quantification off Iceland, observations that parallel the wt% quartz in the sediments. The δ 18 O N. pachyderma (s) data show a strong gradient across Denmark Strait with lighter δ 18 O values towards the East Greenland shelf indicative of a large freshwater flux. The presence of the chilled Atlantic Water benthic foraminifera, Cassidulina neoteretis indicates that rapid ice sheet retreat was associated with ocean forcing, combined with other factors.