Morphology and surface texture of quartz grains from ODP Site 105-645

The shapes and surface textures of sand-sized quartz grains from the sediments cored at Site 645 in southern Baffin Bay during ODP Leg 105 were studied to characterize the terrigenous materials and the settling processes involved in the deposition of these sediments. Here, we show a homogeneous sand fraction that results from mixing grains from various provenances. The characteristics inherited from terrestrial processes (varying degrees of wear; fluviatile, aeolian, and diagenetic features) dominate the characteristics that result from evolution in a high-energy marine environment. Thus, the influence of the last stage of sedimentation in a deep-marine environment was difficult to distinguish. However, fluctuations in the relative proportions of particular features reveal that the terrigenous material derived from sedimentary formations of Baffin Island and East Greenland or from direct abrasion of the crystalline shield, which changed through time as the dominant settling processes evolved. In particular, this study confirms the onset of major ice rafting as old as late Miocene.

本研究针对大洋钻探计划（Ocean Drilling Program, ODP）第105航次在巴芬湾南部645站位获取的沉积岩芯中的砂级石英颗粒形态与表面纹理展开分析，旨在明确该沉积物的陆源物质组成及其沉积沉降过程。研究结果表明，本次分析的均一砂粒级组分来源于多物源区颗粒的混合。源自陆表作用的特征（包括不同程度的磨蚀痕迹、河流及风成成因特征与成岩特征），主导了该颗粒在高能海洋环境中演化所形成的特征。因此，深海环境沉积末期的作用影响难以被区分辨识。但特定特征的相对占比波动表明，源自巴芬岛与东格陵兰沉积地层，或直接来源于结晶基底磨蚀的陆源物质，会随着主导沉降过程的演化而随时间发生变化。尤为重要的是，本研究证实大规模冰筏搬运作用最早可追溯至晚中新世时期。