Beschreibung
Lake Melville is located close to the southeastern rim of the highly dynamic former Laurentide Ice Sheet (LIS). In the uppermost approximately 10 m of the lake’s sediment sequence, the post-glacial history of the LIS back to ca. 10000 cal. yBP is archived. With a total sediment infill of more than 300-400 m, of which a large portion is well-layered, however, the lake potentially holds an excellent long-term record that might reach back well beyond the last glaciation. The lake probably was a subglacial lake during most of this time and it is currently unknown whether several glacial/interglacial cycles are archived in its sediments. In the context of a planned ICDP drilling project, this project will investigate a) if the sediment record of Lake Melville reaches back in time beyond the last deglaciation, and b) how paleoclimate and paleoenvironmental changes are recorded in the sediments even if they were deposited subglacially. To answer these questions, the combination of a high-resolution hydroacoustic survey with high-resolution techniques of sediment analyses will be applied. During RV Maria S. Merian expedition MerMet 17-49 scheduled for June/July 2019, a dense grid of Parasound and seismic profiles will be collected. Sediment cores will be retrieved a) at sites that allow the detailed characterization of the Holocene sediment infill and b) at sites that allow a penetration into deeper/older sediment layers due to a reduced or missing Holocene sediment cover. On the sediment cores, non-destructive, high-resolution analyses like CT scanning, MSCL measurements and XRF scanning will be performed before contiguous sampling of selected sediment sequences. Chronological control is gained through AMS 14C-dating of different sediment components with the MICADAS system and paleomagnetic measurements performed on U-channels. With the combination of non-destructive with destructive analyses like TIC, TOC, grain-size, XRD and WD-XRF determinations, a reconstruction of paleoclimate and paleoenvironmental changes will be achieved. A focus is placed on the development of proxies that allow the reconstruction of LIS dynamics. If Lake Melville sediments could be shown to hold a paleoclimate archive reaching back well beyond the Holocene, this site would be a prime target for a future ICDP project (possibly ICDP-IODP “amphibious”-type) with the aim to reconstruct the past waxing and waning of the LIS.