Asymmetrical turbid surface-plume deposition near ice-outlets of the Pleistocene Laurentide ice sheet in the Labrador Sea

 Ice-sheet drainage of glacial detritus into the sea involves size fractionation by ice-margin winnowing on a giant scale caused by the lower density of meltwater entering cold seawater. Despite its load of suspended sediment, the fresh water rises to or stays at the sea surface forming turbid surface plumes, whereas the coarse-grained sediment forms bed load. On the Labrador Slope south of the Hudson Strait turbid plumes were supplied by meltwater from the Pleistocene ice sheet (LIS). Sediments with the seismic characteristics of plume deposits occur in a 200-km-long slope sector up to 130 km seawards from the strait. The widespread distribution of these deposits is attributed to entrainment of the surface plumes by the south-flowing Labrador Current and suppressed flocculation due to the high detrital carbonate-content of the suspended sediment. Deposits with typical characteristics of surface plume deposits have been recovered within 20 km from former ice margin south of or in front of outlets, but not north of outlets. They consist of 1 to 2-cm-thick alternations of fine sandy silt/coarse silt layers with finer-grained clayey silt/silty clay, and for brevity are called plumites.

Authors and Affiliations

1. Department of Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada H3A 2A7, , , , , , CA

   Reinhard Hesse & Saeed Khodabakhsh

2. IFREMER DRO-GM, Laboratoire Environments Sedimentaires, BP 70, F-29280 Plouzané, France, , , , , , FR

   Ingo Klaucke

3. Lamont-Doherty Earth Observatory of Columbia University, Palisades, N.Y. 10964-8000, USA, , , , , , US

   William B. F. Ryan

Received: 6 August 1996/Revision received: 21 January 1997

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