Late Quaternary chronostratigraphic framework of deep Baffin Bay glaciomarine sediments from high-resolution paleomagnetic data

Abstract

The late Quaternary Baffin Bay sediments provide exclusive records of Greenland, Innuitian and Laurentide ice sheet margin activities, as well as information about the Arctic and northern Atlantic ocean linkages through the Canadian Arctic Archipelago. Because of specific oceanographic conditions, foraminiferal δ 18 O-stratigraphies and radiocarbon ages fail to provide reliable chronologies. Here we propose an original chronostratigraphy spanning the last glacial cycle based on high-resolution paleomagnetic investigations on a 741-cm long core (HU2008-029-016PC) raised from the deep central Baffin Bay, near ODP site 645. Two major difficulties were encountered: (1) the high-frequency occurrence of rapidly deposited layers related to short ice sheet margin events (e.g., ice surges), and (2) the magnetic grain size variability. Physical and magnetic mineralogical properties were used to screen out unreliable magnetic sediment layers. The obtained relative paleointensity (RPI) proxy matches reference paleomagnetic stacks and regional records. Moreover, the resulting record depicts two major excursions which were assigned to the Laschamp and the Norwegian-Greenland-Sea events. It has thus been possible to derive a robust 115ka chronology for the cored sequence. We concluded that even under such a dynamic sedimentary regime, magnetic properties of the sediments can provide a reliable chronostratigraphy, together with information on sedimentary processes. © 2012 American Geophysical Union. All Rights Reserved.