Song, Tengfei; Hillaire-Marcel, Claude; de Vernal, Anne et Liu, Yanguang
(2023).
« A resilient ice cover over the southernmost Mendeleev Ridge during the
late Quaternary ».
Boreas(12632).
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Résumé
The presence of a late Quaternary ice sheet/ice shelf over the East Siberian Sea has been proposed in several papers. Here, we further document its duration/resilience based on the sedimentary, bulk mineralogical, and geochemical (organic matter content and its stable isotopic composition, U-Th series) properties of a core raised from the southernmost Mendeleev Ridge. The chronostratigraphy of the studied core was mainly built from the 230Th excess (230Thxs) distribution and decay downcore. At the core-top, peaking 230Thxs values during the early MIS 3 and mid-MIS1 encompassing anMIS2 hiatus were observed. As documented in several papers, these peaks suggest seasonally openice conditions overproximal continental shelves. Below, the interval spanning MIS4 and possibly MIS5d records major ice-rafting events illustrated byoverall high coarse-fraction contents. Underlying MIS 5e, down to MIS 11, the sediment depicts relatively low sand (1.7-2.5 dw%), high clay (33.5-4.7 dw%), and very low organic carbon
(0.10-0.06 dw%) contents, and low d13Corg values (-24.3 -0.9&). This section is interpreted as recording fine sediment transport by deep currents and/or meltwater plumes below a resilient ice cover, only interrupted by a few short-duration events. These events include (i) detrital carbonate pulses assigned to deglacial events along the NW
Laurentide Ice Sheet margin (Termination (T) III), and (ii) intervals with some planktonic foraminifer occurrences, likely relating to their advection fromopen areas of the Arctic Ocean(MIS5e, 9 and 11). All Terminations, but TII and the early MIS 3, show peaking Mn/Al values linked to the submergence of Arctic shelves under a rising sea level.We conclude that the resilient ice cover, likely an ice shelf, has been present over the southern Mendeleev Ridge during most of the interval after the Mid-Pleistocene Transition and was favoured by the low summer insolation of the MIS 14 to 10 interval.
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