Late Quaternary terrigenous sedimentation in the Western Arctic Ocean as exemplied by a sedimentary record from the Alpha Ridge

Abstract

Terrigenous components in sediment core B84A from the Alpha Ridge, Western Arctic Ocean, havebeen investigated to reconstruct Mid to Late Quaternary variations in sedimentation, provenance, and relatedclimate changes. The core stratigraphy, evaluated by a combination of variations in Mn content, color cycles,foraminiferal abundance, and lithological correlation, extends back to estimated Marine Isotope Stage 12. TwelveIce Rafted Detritus (IRD, >250 μm) events were identifld and interpreted to mostly occur during deglaciation.The Canadian Arctic, which was covered by ice sheets during glacial periods, is suggested to be the major sourceregion. The IRD events likely indicate the collapses of ice sheets, possibly in response to abrupt climate changes.Grain size analysis of B84A indicates sedimentologically sensitive components in core B84A in the 4-9 μm and19-53 μm silt subfractions, which are inferred to be mainly transported by currents and sea ice, respectively. Downcore variability of these two fractions may indicate changes in ice drift and current strength. In accordance withprevious studies in the central Arctic Ocean, the average sedimentation rate in core B84A is about 0.4 cm•a -1 .Compared with the relatively high sedimentation rates on the margins, sedimentation in the central Arctic Oceanis limited by sea ice cover and the correspondingly low bioproductivity, as well as the long distance from sourceregions of terrigenous sediment.