Clay mineral analysis of sediments from the Amundsen Sea

The Amundsen Sea embayment is a probable site for the initiation of a future collapse of the West Antarctic Ice Sheet. This paper contributes to a better understanding of the transport pathways of subglacial sediments into this embayment at present and during the last glacial period. It discusses the clay mineral composition of sediment samples taken from the seafloor surface and marine cores in order to decipher spatial and temporal changes in the sediment provenance. The most striking feature in the presentday clay mineral distribution is the high concentration of kaolinite, which is mainly supplied by the Thwaites Glacier system and indicates the presence of hitherto unknown kaolinite-bearing sedimentary strata in the hinterland, probably in the Byrd Subglacial Basin. The main illite input is via the Pine Island Glacier. Smectite originates from the erosion of volcanic rocks in Ellsworth Land and western Marie Byrd Land. The clay mineral assemblages in diamictons deposited during the last glacial period are distinctly different from those in corresponding surface sediments. This relationship indicates that glacial sediment sources were different from modern ones, which could reflect changes in the catchment areas of the glaciers and ice streams.

阿蒙森海凹陷（Amundsen Sea embayment）是未来西南极冰盖（West Antarctic Ice Sheet）发生崩塌的潜在起始区域。本研究旨在增进对当前及末次冰期（last glacial period）期间，冰下沉积物（subglacial sediments）向该海凹陷输运路径的认识。研究通过分析采自海底表层（seafloor surface）与深海岩芯（marine cores）的沉积物样品的黏土矿物（clay mineral）组成，以解析沉积物物源（sediment provenance）的时空变化特征。现今黏土矿物分布最显著的特征为高浓度高岭石（kaolinite），其主要由思韦茨冰川（Thwaites Glacier）系统供给，这表明其腹地（大概率位于伯德冰下盆地（Byrd Subglacial Basin）内）存在此前未被发现的含高岭石沉积地层。伊利石（illite）的主要输入路径为派恩岛冰川（Pine Island Glacier）。蒙脱石（Smectite）源自埃尔斯沃思地（Ellsworth Land）与玛丽·伯德地（Marie Byrd Land）西部火山岩的侵蚀作用。末次冰期沉积的混杂沉积物（diamictons）中的黏土矿物组合与同期表层沉积物存在显著差异。这种差异表明，冰期沉积物源与现代沉积物源存在显著不同，这或可反映冰川及冰流汇水区的变化。