Sedimentary record of the last glaciation of the Bellingshausen Sea, West Antarctica

Upper Quaternary marine sediments recovered from the West Antarctic continental margin are characterized by a distinct lithological succession allowing the reconstruction of past environmental changes. Massive, homogenous diamictons were deposited elsewhere on the margin during the last glacial period, when grounded ice masses advanced across the shelf. Sedimentological investigations using a multi-proxy approach and examination of the margin topography suggest that during this time a deformation till and subsequently a glaciomarine till were deposited on the shelf, while glaciogenic debris flows were deposited on the slope and rise. The comparison of the clay mineral assemblages in the matrix of the diamictons with clay mineral assemblages of potential source areas reveals distinct pathways of grounded ice flow on the shelf. Lithogenic sandy muds overlying the diamictons were deposited by meltwater flows and/or marine currents on the shelf, and by turbidity currents and marine currents on the slope and rise, respectively. The sedimentation of the sandy muds denotes a deglaciation stage, when grounded ice started to retreat from the shelf, but semi-permanent sea-ice coverage still hampered biological productivity. Bioturbated, foraminifer-bearing sediments were deposited in a glaciomarine setting during the present interglacial period, when sea-ice cover was only seasonally present and a marine current related to the southern boundary of the Antarctic Circumpolar Current winnowed the seafloor on the outer shelf, slope and rise.

从西南极大陆边缘获取的上第四纪海相沉积物，以独特的岩性演替序列为典型特征，可用于重建古环境变化。末次冰期期间，当接地冰体大规模推进覆盖陆架时，该边缘的其他区域沉积了块状均质混杂堆积（diamictons）。通过多代用指标方法开展的沉积学调查以及对该边缘地形的解析表明，此时期陆架上先后沉积了变形碛与冰海碛，而陆坡与陆隆区域则沉积了冰成因碎屑流。将混杂堆积基质中的黏土矿物组合与潜在物源区的黏土矿物组合进行对比，可明确陆架上接地冰体流动的具体路径。覆于混杂堆积之上的陆源砂质泥质沉积物，分别由陆架上的融水径流及/或海流、陆坡与陆隆上的浊流与海流沉积形成。该套砂质泥质沉积物的沉积代表了冰消期阶段——此时接地冰体开始从陆架后撤，但半永久性海冰覆盖仍阻碍了生物生产力。当前间冰期期间，海冰仅季节性出现，与南极绕极流（Antarctic Circumpolar Current）南界相关的海流对外陆架、陆坡与陆隆区域的海底进行了淘洗，此时期的冰海相环境中沉积了受生物扰动的含孔虫沉积物。