黄河和长江碎屑物质扩散研究——来自江苏沙脊物源示踪的约束

研究源-汇系统对于理解岩石风化、河流输砂、泥砂沉积以及陆地和海洋沉积过程具有重要意义。我国江苏省东海岸具有丰富的沉积物供应,在某些沿海地段形成了一系列沙脊,是进行沉积物源-汇过程研究的理想沉积记录之一。但目前对其物源区来自哪里还未达成共识。我们利用已发表的碎屑锆石U-Pb年龄和钾长石Pb同位素数据,结合江苏沙脊及其周缘区域的数据结果,详细厘定江苏沙脊的物源区,并运用蒙特卡罗反演模型定量评估江苏沙脊潜在物源区对其物质贡献率。结果表明江苏沙脊北部的碎屑物质主要受大别山(45%)和鲁中山区(24%)的共同影响;黄河(29%)、古黄河(27%)和长江(25%)的碎屑物质对江苏沙脊中部的物质组成起重要影响。江苏沙脊南部的物源主要来自长江(68%)。江苏沙脊的出现得益于黄河和长江这样的大陆尺度的大河搬运了丰富的碎屑物质到下游,南黄海西海岸的平坦地貌有利于保存这些碎屑物质,末次冰期后东亚陆架海动力过程(潮汐、海浪和沿岸流等)持续对其改造,这体现了河流-海洋在塑造河口-海岸地貌中的交互作用。

Detrital Material Diffusion in the Yellow River and Yangtze River: Constraints of Provenance Tracing for the Sand Ridges in Jiangsu Province

The study of source-sink systems is important for understanding rock weathering, fluvial sand transport, mud and sand deposition, and terrestrial and marine sedimentary processes. The east coast of Jiangsu Province, which has an abundant sediment supply and a series of sand ridges in some coastal areas, comprises an ideal sedimentary record for studying the sediment source-sink process. However, there is no consensus on the provenance of these sand ridges. Based on previously published data on the U-Pb age of detrital zircon and Pb isotope composition of K-feldspar, we determined the provenance of the Jiangsu Sand Ridges in detail, using the Monte Carlo inversion model to quantitatively assess the contribution rates of the provenances to the material of the Jiangsu Sand Ridges. The results showed that the clastic material in the northern part of the sand ridge was mainly influenced by the Dabie(45%) and Luzhong Mountains(24%). The detrital materials from the Yellow River(29%), ancient Yellow River(27%), and Yangtze River(25%) had an important influence on the composition of the central Jiangsu Sand Ridges. The provenance of the southern part of the sand ridge in Jiangsu Province was mainly the Yangtze River(68%). The emergence of the Jiangsu Sand Ridges was due to the transportation of large amounts of detritus to the downstream by the large continental-scale Yellow River and Yangtze River. The flat landform on the west coast of the South Yellow Sea was conducive to the preservation of these detrital materials, and the East Asian shelf sea dynamic processes (tides, waves, and coastal currents) continued to transform the sand ridge after the last glacial age. This process reflects river-ocean interactions in shaping estuarine-coastal landscapes.