Late Quaternary sedimentation in Kejser Franz Joseph Fjord and the continental margin of East Greenland

Abstract

The marine sedimentary record in Kejser Franz Joseph Fjord and on the East Greenland continental margin contains a history of Late Quaternary glaciation and sedimentation. Evidence suggests that a middle-shelf moraine represents the maximum shelfward extent of the Greenland Ice Sheet during the last glacial maximum. On the upper slope, coarse-grained sediments are derived from the release of significant quantities of iceberg-rafted debris (IRD) and subsequent remobilization by subaqueous mass-flows. The middle-lower slope is characterized by hemipelagic sedimentation with lower quantities of IRD (dropstone mud and sandy mud), punctuated episodically by deposition of diamicton and graded sand/gravel facies by subaqueous debris flows and turbidity currents derived from the mass failure of upper slope sediments. The downslope decrease of IRD reflects either the action of the East Greenland Current (EGC) confining icebergs to the upper slope, or to the more ice-proximal setting of the upper slope relative to the LGM ice margin. Sediment gravity flows on the slope are likely to have fed into the East Greenland channel system, contributing to its formation in conjunction with the cascade of dense brines down the slope following sea-ice formation across the shelf.Deglaciation commenced after 15 300 14C years BP, as indicated by meltwater-derived light oxygen isotope ratios. An abrupt decrease in both IRD deposition and delivery of coarse-grained debris to the slope at this time supports ice recession, with icebergs confined to the shelf by the EGC. Glacier ice had abandoned the middle shelf before 13 000 14C years Bp with ice loss through iceberg calving and deposition of diamicton. Continued retreat of glacier-ice from the inner shelf and through the fjord is marked by a transition from subglacial till/bedrock in acoustic records, to ice-proximal meltwaterderived laminated mud to ice-distal bioturbated mud. Ice abandoned the inner shelf before 9100 14C years BP and probably stabilized in Fosters Bugt at 10 000 14C years BP. Distinct oxygen isotope minima on the inner shelf indicate meltwater production during ice retreat. The outer fjord was free of ice before 744014C years BP. Glacier retreat through the mid-outer fjord was punctuated by topographically-controlled stillstands where iceproximal sediment was fed into fjord basins. The dominance of fine-grained, commonly laminated facies during deglaciation supports ablation-controlled, ice-mass loss.Glacimarine sedimentation within the Holocene middle-outer fjord system is dominated by sediment gravity flow and suspension settling from meltwater plumes. Suspension sediments comprise mainly mud facies indicating significant meltwater-deposition that overwhelms debris release from icebergs in this East Greenland fjord system. The relatively widespread occurrence of fine-grained lithofacies in East Greenland fjords suggests that meltwater sedimentation can be significant in polar glacimarine environments. The icedistal continental margin is characterized by meltwater sedim...

Simulation of the Greenland Ice Sheet over two glacial–interglacial cycles: investigating a sub-ice- shelf melt parameterization and relative sea level forcing in an ice-sheet–ice-shelf model

“…1), and reaching the PD margin by 7.4 ka BP (red star, Fig. 1) (Cofaigh et al, 2004;Evans et al, 2002). Along the SE margin, the retreat from the outer to inner shelf is highly asynchronous, retreating from the outer Kangerdlugssuaq Trough at ∼ 17.8 ka BP (dark blue triangle, Fig.…”

Unraveling Sediment Transport Along Glaciated Margins (the Northwestern Nordic Seas) Using Quantitative X-Ray Diffraction of Bulk (< 2mm) Sediment

“…4) (Evans et al, 2002). If sea ice were the pervasive sediment transport medium then the influence of the local glacier sources should be small.…”

Submarine landforms and shallow acoustic stratigraphy of a 400 km-long fjord-shelf-slope transect, Kangerlussuaq margin, East Greenland

“…Secondly, there is still some doubt as to which parts of the East Greenland margin experienced ice-sheet growth to the continental shelf edge at the Last Glacial Maximum (LGM) (Mienert et al, 1992;Funder and Hansen, 1996;Roberts et al, 2008) and diagnostic submarine glacial landforms should assist in resolving this question (e.g. Evans et al, 2002;Evans et al, 2009). Thirdly, Kangerlussuaq Fjord and the cross-shelf trough that extends across the shelf beyond the fjord mouth are, in part at least, deep enough to have avoided major reworking of sea floor geomorphology and shallow stratigraphy by the action of deep-keeled icebergs (Syvitski et al, 2001).…”