ISOTOPIC AND SEDIMENTOLOGICAL EVIDENCE FOR SEA ICE CONDITIONS AND PALEOCEANOGRAPHY IN LAST 15,000 YEARS ON THE BEAUFORT SEA SLOPE AND AMUNDSEN GULF, CANADA

Foraminiferal data from a core on the Beaufort Slope at 1087m water depth (core 750) and a core in the Amundsen Gulf at 442m water depth (core 124) have been compared in a previous paper in regards to foraminiferal assemblages an their relationship to paleo-sea ice conditions. In this paper we examine other proxies: carbon and oxygen stable isotopes from both planktic and benthic foraminifera and sedimentological markers from clays and coarse fractions of the IRD that were identified but not studied previously. Site 750 is particularly sensitive to paleo-ice cover because it rests beneath the present margin of the permanent Arctic ice pack. In the Holocene section of the core (except the very surface) there is little carbonate and therefore no isotopic data could be obtained but starting at 120cm and extending down to 380cm there is strong evidence of IRD and with it, many calcareous foraminifera, both planktic and benthic, allowing us to obtain both a surface and bottom water signal. BThis unit is dated from ~11,500 cal BP to over 13,000 cal BP. Below this unit IRD disappears as do the calcareous foraminifera. Oxygen isotopes in the IRD unit were uniformly high for the benthic species (>+4.0‰), and lower and more variable for the planktics (-+0.5 to almost +3.0‰ ). Site 124 in the Amundsen Gulf also has an IRD-rich unit similar to that in core 750 and the paleo-magnetic data suggest that it has a similar source as well as a similar age (~12,000 cal BP). This location is very close to the former glacial margin in the Gulf. Benthic foram isotope data indicate bottom water conditions similar to site 750 which is interesting because this core is in only 442m of water and from an enclosed gulf. The commencement of ice rafting can only occur if the ice pack starts to move to allow glacial calving and iceberg movement so the date of ~13,000calBP marks the beginning of deglaciation in the Amundsen Gulf and the Beaufort Sea. These new data combined with the previous foraminiferal assemblage data make it possible to reconstruct bottom and surface water conditions both before and during ice break-up as well as suggest what sea ice conditions were throughout the Holocene and before. The date of 13,000 calBP also pre-dates ages from the adjacent landmass for commencement of deglaciation in this part of the Arctic