2006 Philadelphia Annual Meeting (22–25 October 2006)

Paper No. 8
Presentation Time: 9:55 AM


SCOTT, David B., Department of Earth Sciences, Dalhousie University, Halifax, NS B3H 4J1, SCHELL, Trecia, Department of Earth Science, Dalhousie Univ, Halifax, NS B3H 3J5, Canada and ROCHON, Andre, Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310, allée des Ursulines, Rimouski, QC G5L 3A1, Canada, dbscott@dal.ca

The continuing problem of sea-ice deterioration in the Arctic Ocean can only be assessed by examining prehistoric sea-ice records from the Arctic. Here we present results from a core that was collected in the Beaufort Sea on the upper slope of the western McKenzie Shelf at 1000m water depth at the mid-point between the Mckenzie Trough (a high sed.-rate location) and the Amundsen Gulf (a low sed.-rate area). The 5.8m core contains a 15,000 year record including glaciation, the onset of deglaciation and the Holocene interglacial. Pb210 dating indicates that there is an accelerated rate of sedimentation in the last 100yr (10-15cm), which may be capturing the global warming of the late Holocene. The upper 3cm of this core has a typical slope foraminiferal fauna with mixed deep-sea Arctic forms as well as some upper slope ice edge forms (Islandiella teretis). This fauna is followed by complete disappearance of calcareous species replaced low numbers of agglutinated foraminifera in the middle of the core, suggesting high continued organic input. This may have caused dissolution of most calcareous foraminifera. Some tintinnids occur which indicate freshwater input from the Mckenzie Shelf. Abruptly, at 140cm core depth, a more typical (for the central Arctic) deep-sea fauna occurs which may be the earliest Holocene; Oridorsalis umbonatus makes its last appearance until the surface sediments. This fauna is mixed with abundant planktonic foraminifera and typical Arctic benthic species but O. umbonatus is diminished very quickly below this level as ice rafted sediments appear, probably coming from icebergs originating in the Amundsen Gulf. Below the last ice rafting at 15,000 ybp (380cm in the core) there is a signal that suggests massive transport from the shelf to the 1000m site as the sedimentation increases and foraminifera are highly diluted. The lowest unit suggests massive sediment transport during a lowered glacial sea level coming from the Mckenzie Shelf. For the first time we have timing from before late Wisconsinan deglaciation through to the Present from a slope environment in the Western Canadian Arctic. These data indicate that icebergs continued to be important sediment transport mechanisms through the early Holocene but also that sea-ice cover is diminishing through most of the late Holocene.