Past sedimentation rates and environments of the Mendeleev Rise inferred from Sr isotope and δ18O chemostratigraphy of its Late Cenozoic sediments

Resumo

Multiproxy investigation of sediment core AF-0731 from the Mendeleev Rise revealed several epochs of high bioproductivity corresponding to climate amelioration and surface water mass warming in the Arctic. During these periods, sediments became enriched in carbonate microfossils as well as in coarsegrained ice- and iceberg-rafted debris (IRD) that precipitated from melting sea ice and icebergs. Variability in the δ¹⁸О composition of planktic foraminifers also reflects glacial-interglacial periodicity. Low δ¹⁸О values correspond to glacial epochs and, especially, glacial terminations with strong meltwater inputs. Increased δ¹⁸О values characterize interglacial epochs of sea-level rise and growing salinity due to enhanced water exchange with neighboring oceans. The ⁸⁷Sr/⁸⁶Sr ratio was measured in foraminifers from basal core layers, and their SIS-age was estimated at 670 + 50 ka. Sedimentation rates at AF-0731 core site on the Mendeleev Rise varied between 0.4 and 0.6 cm/kyr.