格陵蘭外海羅蒙諾索夫海脊上獨特灰色沉積層之來源探討

Abstract

The sediment deposited in the Arctic Ocean is transported by sea ice and icebergs, which are controlled by the Arctic surface circulations. Several cores from the central Arctic, the Lomonosov Ridge north of Greenland and the Morris Jesup Rise contain a distinct grayish, ice rafted debris (IRD)-rich, layer with some specific features: a sharp lower boundary, relatively low content of manganese, and a lack of bioturbation. Heavy minerals from these layers were analyzed primarily by Electron Probe X-Ray Microanalyzer (EPMA) and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) to establish the prominent provenance areas. The provenance variations can show the paleo-distribution and transport pathways of sea ice and icebergs and even indicate the origin of some abrupt glacial events. Initial results suggest that the majority of the grains in the gray layer originated from a limited area near the Putorana Basalt Plateau. We therefore hypothesize that this gray layer is related to an abrupt ice dammed lake drainage from northern Siberia, tentatively dated to around the boundary between MIS 4 and 3 based on all available chronostratigraphic data points and the correlation of distinct geochemical and sedimentological features: variation in Mn, bulk density, bioturbation and abundance of planktonic and benthic foraminifera; including published data and measured data in this study.