Continental slope sedimentation adjacent to an ice-margin. II. Glaciomarine depositional facies on labrador slope and glacial cycles

摘要: Eight depositional facies have been identified in Labrador Slope and Basin cores on the basis of sedimentary structures textures. These are combined into three genetic groups: (1) hemipelagic HI with ice-rafted debris (IRD) H without IRD (with a thickness about 53% total core length); (2) debris-flow D (7%) turbidite (34%) T (thin, fine-grained bodyspill turbidites), TH (headspill turbidites) TI (turbidites interlayered laminae IRD); (3) contourite (<3%) nepheloid-layer deposits (3%) C N. The latter characteristic proximal Heinrich layers. intercanyon regions slope mainly covered by sediment intercalated spillover turbidites. canyons, if filled, contain dominant sediment-delivery transport mechanisms change from vertical settling bedload glacial stream-discharge upper to down-slope mass-flow processes, which predominate over along-slope processes lower rise. Up 15 lithostratigraphic units differentiated cores, based recognition various combinations 8 types short-distance correlations AMS 14C-dated intervals. Very dark muds low detrital carbonate content, little debris, degree bioturbation abundant sinistral-coiling, cold-water foraminifera (Facies 3,5,7,9,11 13) tentatively ascribed tunes Mid-to Late Wisconsinan glaciation extensive seasonal sea-ice cover Sea. Turbidites cannot be related specific phases cycle result largely redeposition mid-slope sediments. Ice-rafted dispersed nepheloid-flow or as separate between thin mud-turbidites short-lived events during times partial ice-cap collapse, but not restricted these events. youngest sediments, were deposited since early part marine oxygenisotope stage 2 (<32 ka) correlate chronologically lithologically adjacent shelf, rise basin oldest 14C date 54,530 ± 2090 yr B.P. was obtained for unit 1112 boundary at 1008 cm subsurface depth 90-26.