(Table T1) Geochemical composition of ODP Site 184-1143 late Pliocene sediments

Pliocene core intervals from Ocean Drilling Program Site 1143 located in the southern part of the South China Sea were measured for their major and minor element composition at ~2-k.y. resolution. Changes in sediment composition parallel glacial-interglacial changes as indicated by the corresponding oxygen isotope record of benthic foraminifers. Carbonate contents are lower during glacial stages and higher during interglacial stages. This is attributed to dilution by a higher contribution of terrigenous detrital matter during glacial intervals and to enhanced biological productivity during interglacials as indicated by enrichments in barium. The terrigenous detrital matter fraction shows small but distinct changes in composition. These variations may be explained by multiple processes, including changes in provenance and weathering caused by monsoonal climate variability and sea level fluctuations. Gradual or long-term changes in sediment composition also occur during the investigated interval. There is a shift toward lower TiO2 (carbonate-free basis; cfb) values at around 2.9 Ma and an increase in Al2O3 (cfb) variations at around 2.55 Ma. These changes can be explained in both cases by an increasing contribution from the Mekong River, delivering material with low TiO2 (cfb)/Al2O3 (cfb) ratios, followed by a gradual increase in weathering, causing higher Al2O3 (cfb) (probably reflecting kaolinite) contents. Both may be the result of an enhanced summer monsoon. The manganese and phosphate geochemistry of Site 1143 sediments seem to be strongly dominated by biological productivity and a high burial flux of carbonate, which acts as an adsorbing agent and/or substrate. During strong interglacials and corresponding times of enhanced productivity, Mn may be remobilized from continental margin sediments deposited within an oxygen minimum zone and subsequently exported into the pelagic region, where it oxidizes and settles to form Mn-enriched layers in the sediment.采集自南海南部的大洋钻探计划（Ocean Drilling Program）1143站位的上新世岩心段，以约2千年的分辨率对其常量与微量元素组成开展了测试分析。沉积物组成的变化与冰期-间冰期旋回变化一致，该结论可通过底栖有孔虫的对应氧同位素记录得到验证。冰期阶段碳酸盐含量较低，间冰期阶段则较高。该现象可归因于冰期时段陆源碎屑物质输入占比更高带来的稀释作用，以及间冰期生物生产力提升——该结论可通过钡元素富集得到佐证。陆源碎屑组分的组成虽存在小幅变化，但特征显著。这些组分变化可通过多种过程加以解释，其中包括季风气候波动与海平面升降引发的物源变化与风化作用改变。在所研究的时段内，沉积物组成同样存在渐进式或长期的演化趋势。约2.9 Ma时，TiO₂（无碳酸盐基准，carbonate-free basis，缩写cfb）含量出现降低趋势；约2.55 Ma时，Al₂O₃（cfb）的波动幅度有所增大。上述两种变化均可通过湄公河输入贡献占比的提升得到解释：湄公河所携带的物质具有较低的TiO₂(cfb)/Al₂O₃(cfb)比值；随后风化作用逐渐增强，使得Al₂O₃(cfb)含量升高（该指标或可反映高岭石的富集情况）。上述两种过程均可能与夏季风增强有关。1143站位沉积物中的锰与磷地球化学特征，似乎主要受控于生物生产力与高埋藏通量的碳酸盐——碳酸盐可作为吸附剂与/或沉积底物。在强间冰期以及对应生物生产力提升的时段，锰可从氧最低带内沉积的大陆边缘沉积物中被活化迁移，随后被搬运至远洋区域，在该处发生氧化并沉降，最终在沉积物中形成富锰层。