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Six gravity cores (GC) and four sea-floor drill rig (MeBo) cores from water depths of ~18001400 m have been successfully collected off the outer Disko Bay fan in eastern CentralBaffinBay during the research expedition MSM111 in 2022. These sediment cores provide an up to 125m long (MeBo 14, 20 and 23) record potentially reflecting the late- and mid-Pleistocene dynamics of the Western Greenland ice sheet. Besides the presence of a few turbiditic sequences a continuous sedimentation is well supported by the parasound seismostratigraphy as well as by lithostratigraphic log correlation based on X-ray Fluorescence (XRF) and magnetic susceptibility (MS). Establishing a chronostratigraphy of the Baffin Bay glaciomarine sediments is, however, challenging as e.g., carbonate dissolution impedes reliable foraminiferal 18O stratigraphy. Here, we present our preliminary chronostratigraphic framework established by combining three stratigraphic tools: radiocarbon ages, relative paleointensity (RPI), and characteristic basin-wide detrital carbonate layers (BBDCs). BBDCs represent periods of elevated terrigenous deposition in response to increased meltwater discharge that can be well identified by XRF Ca/Ti. The GC 1222 and MeBo 1420 cores contain rhythmic alterations between sandy-rich detrital carbonate layers and clayish layers, which are clearly represented by Ca/Ti and MS data. Intriguingly, these cyclic alterations also display significant correlation with marine isotope stages (MIS), where higher Ca/Ti and MS values correspond to warmer periods. We thus estimated that our 125-m composite core lasts until MIS 16 or ~700ka. This long duration is also partly supported by our RPI data from MeBo 2023. Nevertheless, two major difficulties were encountered: (1) RPI data of GC2421 do not reveal an unambiguous match with global RPI reference stacks and/or regionally established RPI records, probably due to condensed sedimentation of these two deeper gravity cores; and (2) recurring BBDCs of the studied cores can be interpreted as high-frequency events reflecting the intrinsic dynamics of the North American Arctic-ice sheet complex, or, alternatively as glacial-interglacial cycles.In order to solve the current chronostratigraphy controversy between a Late Pleistocene age or of deeper mid-Pleistocene age, further carbon-14 ages from the condensed GC24 and collect RPI data from the more expanded MeBo 14 will be obtained.
Zhang et al. (Fri,) studied this question.