Abstract:

The terrigenous components in sediment core B84A from the Alpha Ridge, western Arctic Ocean have been investigated to reconstruct the late Quaternary history of the Ice Rafted Detritus (IRD) events, variations of the sedimentation, source regions and climate changes. The core stratigraphy is established by a combination of variations in Mn content, color cycles and foraminiferal abundance. The core extends back to Marine Isotope Stage (MIS) 12.The 12 IRD (>250 μm) events in core B84A are identified; they are assumed to mostly occur during the deglacial periods. The Canadian Arctic Archipelago is suggested to be the source region. These IRD events indicate the collapse of Canadian Arctic ice sheet and drastic climate change. The environmental sensitive components in core B84A are in the silt fractions: 4~9 μm and 19~53 μm, which are mainly transported by sea ice rafting and currents. The two fractions vary asymmetrically and provide indications of current strength. In accordance with previous studies surrounding Alpha Ridge region, the average of sedimentation rate in core B84A is about 0.39 cm/ka. Compared to the high sedimentation rate in the marginal area, the sedimentation rate in the central Arctic Ocean is limited by the sea ice cover and related low bioproductivity, and low terrigenous input due to the relatively long distance transportation from the source region.

Key words: IRD event, terrigenous component, sedimentation rate, Arctic Ocean, Alpha Ridge, Quaternary