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

梅尔维尔湖位于高度动态的前劳伦泰德冰盖（LIS）的东南边缘附近。在湖的最上层约10米的沉积物序列中，记录了大约10000 cal. y BP的冰期后历史。然而，由于总沉积物填充物超过300-400米，其中很大一部分是分层良好的，因此，该湖可能拥有一个很好的长期记录，可以追溯到远超过最后一次冰期的时间。在去年夏天进行的RV Maria S. Merian探险MSM84期间，我们收集了一系列沉积物岩心以及密集的水声数据网格。岩心的第一个数据与沉积物回声测深数据相结合，揭示了5个地震和岩性单元：(I)冰期后沉积物，（II）脱冰沉积物，（III）推测是在梅尔维尔湖作为冰下湖泊持续存在的时期沉积的沉积物，（IV）可能是在MIS5、MIS4或MIS3早期的无冰阶段沉积的冰下湖泊沉积物下面的层状良好的沉积物。在这些单元下面，确定了基岩(V)。我们的核心穿透了第一至第二单元和第三单元的上部。我们建议研究全新世和去冰期序列，以重建各自的古气候条件和冰川退缩的历史。此外，冰下湖及其沉积物将被表征并测试其敏感性和记录古气候变化的能力。对于沉积物岩心，在选定沉积物序列取样之前，将进行CT扫描、物理性质测量和XRF扫描等非破坏性高分辨率分析。通过使用MICADAS系统对不同沉积物成分进行AMS 14c定年，并在u型通道上进行古地磁测量，获得了时间控制。将TIC、TOC、粒度、XRD和WD-XRF等无损分析与破坏性分析相结合，重建古气候和古环境变化。重点放在允许重建LIS动态的代理的开发上。如果梅尔维尔湖的沉积物能被证明保存着远超过全新世的古气候档案，那么这个地点将成为未来联合两栖iodp - icdp钻井项目的主要目标，该项目旨在重建过去的LIS盛衰。

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.