Lake Melville sediments: A window to the pre-Holocene glacial history of the Laurentide Ice Sheet (Acronym: MELSED)

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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. y BP 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. During RV Maria S. Merian expedition MSM84 that took place last summer, we collected a series of sediment cores along with a dense grid of hydroacoustic data. First data from the cores in concert with the sediment echosounder data reveal five seismic and lithological units: (I) postglacial sediments, (II) deglacial sediments, (III) sediments that were presumably deposited during a phase when Lake Melville persisted as subglacial lake below the LIS, (IV) well-layered sediments below the subglacial-lake sediments possibly deposited during a previous ice-free phase, possibly of MIS5, MIS4, or early MIS3 age. Below these units, bedrock (V) was identified. Our cores penetrated through units I to II and into the uppermost part of III. We propose to investigate the Holocene and deglacial sequence to reconstruct the respective paleoclimate conditions and the history of the LIS retreat. In addition, the subglacial lake and its deposits will be characterized and tested for their sensitivity and ability to record paleoclimate change. On the sediment cores, non-destructive, high-resolution analyses like CT scanning, physical property measurements and XRF scanning will be performed prior to 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. Using a 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 joint amphibious IODP-ICDP-drilling project with the aim to reconstruct the past waxing and waning of the LIS.