Age determination and geochemistry of sediment core KK9601@en

A light, mining drill rig deployed from the stern of a research vessel has been used to carry out shallow drilling in 212 m water depth on the continental shelf in the eastern Weddell Sea. Penetration was 15 m below the seabed with 18% recovery in the 31 hours available for the experiment. The recovered glacigenic sediments are predominantly volcanic material of basaltic and andesitic composition with petrological characteristics and age similar to the continental flood basalts exposed in Vestfjella, about 130 km upstream from the drill site. The sediments include a reworked marine Miocene diatom flora. The material documents oscillations of the East Antarctic Ice Sheet over the past 30 ka. The lowermost diamicton probably represents a deformation till, and the grounding line retreated past the drill site 30 km from the shelf edge about 30 kyr BP. A readvance occurred during the Late Wisconsin Glacial Maximum. Assuming a reservoir correction of 1300 yr, marine conditions existed at the site between 10.1-7 kyr BP, and later at least between 2.8 and 2.5 kyr BP. The stratigraphy at the site has been disturbed by iceberg ploughing and/or contact between the ice shelf and the sea floor during local advances after 2.5 kyr BP.本研究依托科考船船尾部署的轻型钻探钻机，在威德尔海东部大陆架212米水深海域开展了浅层钻探（shallow drilling）作业。本次实验总耗时31小时，最终钻探贯入海底（seabed）以下15米，岩心回收率为18%。回收的冰成沉积物（glacigenic sediments）以玄武质、安山质火山物质为主，其岩石学特征与年代学属性均与钻探点上游约130公里处维斯特费拉（Vestfjella）出露的大陆溢流玄武岩（continental flood basalts）高度相似。沉积物中包含经再改造的中新世海洋硅藻群（marine Miocene diatom flora）。该钻探物质记录了过去30千年（ka）间东南极冰盖（East Antarctic Ice Sheet）的振荡演化过程。最底部的混杂堆积（diamicton）大概率为变形冰碛（deformation till）；约30千年BP时，冰架接地线（grounding line）从距离陆架边缘30公里的位置后退并越过钻探点位。晚威斯康星冰盛期（Late Wisconsin Glacial Maximum）发生了冰进事件。假设储层校正（reservoir correction）值为1300年，则该点位在10.1~7千年前存在海洋环境，且至少在2.8~2.5千年前也曾处于海洋环境。2.5千年后的局部冰进过程中，冰山犁蚀（iceberg ploughing）及/或冰架（ice shelf）与海底接触作用扰动了该点位的地层序列（stratigraphy）。