Mineralogy, grain size composition, bulk carbonate isotopic ratios and ages of ODP Site 182-1128 sediments@en

This report presents mineralogic and geochemical data from Ocean Drilling Program Leg 182 Site 1128 in the Great Australian Bight. Clay mineralogy is dominated by mixed-layer illite-smectite, followed by minor amounts of kaolinite and illite, with intervals of pure smectite. Carbonate mineralogy is exclusively low-Mg calcite, except for one interval of dolomite in lower Oligocene sediments. Carbonate increases significantly in upper Eocene sediments, decreases through the lower Oligocene, then increases again in the Neogene. Quartz is present as a minor component that covaries inversely with carbonate. High-resolution sampling associated with Chron 13 normal (early Oligocene) reveals high-frequency (~23 k.y.) fluctuations in clay mineralogy and carbonate abundance and a positive oxygen and carbon isotope excursion (in bulk carbonates) related to Antarctic glaciation.本报告收录了澳大利亚大湾（Great Australian Bight）海域大洋钻探计划（Ocean Drilling Program, ODP）第182航次1128站位的矿物学与地球化学数据。该站位的黏土矿物组合以混层伊利石-蒙脱石为主，其次含少量高岭石与伊利石，局部层段发育纯蒙脱石。碳酸盐矿物组成几乎均为低镁方解石，仅渐新世下部沉积物中存在一层白云石。碳酸盐含量在始新世上部沉积物中显著升高，渐新世下部逐步降低，至新近纪时期再度回升。石英作为次要组分存在，其含量与碳酸盐含量呈负相关变化。针对早渐新世13号正常地磁极性带（Chron 13）开展的高分辨率采样分析显示，黏土矿物组合与碳酸盐丰度呈现出约23千年的高频波动，且伴随与南极冰川作用相关的全岩碳酸盐氧、碳同位素正偏移事件。