The marine stratigraphic record in the northwestern South China Sea provides an excellent case for understanding the provenance and sedimentary evolution of the marginal sea. However, considerable uncertainty exists in unraveling the geochemical record since the Oligocene due, in part, to a lack of systematic measurements of the sediments. In this study, the major and trace elements of sedimentary rocks from the northern Yinggehai-Song Hong Basin were analyzed to ascertain the provenance and reconstruct the sedimentary evolution in the northwestern South China Sea. The chondrite-normalized rare earth element (REE) patterns show fractionation between light REEs (LREEs) and heavy REEs (HREEs) with significant negative Eu anomalies (Eu/Eu* = 0.59–1.10), combining with discriminant function analysis, implies that the sediments were predominantly eroded from granitic rocks, which are mostly felsic igneous materials. The relatively high index of chemical variability (ICV) values (1.30–3.54) and low chemical index of alteration (CIA) values (36.2–61.5) indicate that these sediments are immature and might have experienced weak to intermediate chemical weathering during transportation and deposition. The geochemical data also show that the Red River catchment was the primary source region for the northern Yinggehai-Song Hong Basin since the late Oligocene. The variations in the element contents and ratios are consistent with the multi-stage tectonic activities of the basin and the provenance shift caused by the recombination of the Red River system in different sedimentary periods.

南海西北部的海相地层记录为了解边缘海的物源和沉积演化提供了极好的案例。然而，在解释渐新世以来的地球化学记录方面存在相当大的不确定性，部分原因是缺乏对沉积物的系统测量。本研究通过分析莺歌海-宋洪盆地北部沉积岩的主量元素和微量元素，确定南海西北部的物源并重建沉积演化。球粒陨石归一化稀土元素 (REE) 模式显示轻稀土 (LREE) 和重稀土 (HREE) 之间的分馏具有显着的负 Eu 异常 (Eu/Eu* = 0.59–1.10)，结合判别函数分析，这意味着沉积物主要是由花岗岩侵蚀而成，花岗岩主要是长英质火成岩材料。相对较高的化学变异指数 (ICV) 值 (1.30–3.54) 和较低的化学蚀变指数 (CIA) 值 (36.2–61.5) 表明这些沉积物不成熟，可能在运输和沉积过程中经历了弱到中等的化学风化. 地球化学资料还表明，晚渐新世以来，红河流域是莺歌海-宋洪盆地北部的主要生源区。元素含量和比例的变化与盆地的多期构造活动和不同沉积时期红河水系重组引起的物源转移相一致。相对较高的化学变异指数 (ICV) 值 (1.30–3.54) 和较低的化学蚀变指数 (CIA) 值 (36.2–61.5) 表明这些沉积物不成熟，可能在运输和沉积过程中经历了弱到中等的化学风化. 地球化学资料还表明，晚渐新世以来，红河流域是莺歌海-宋洪盆地北部的主要生源区。元素含量和比例的变化与盆地的多期构造活动和不同沉积时期红河水系重组引起的物源转移相一致。相对较高的化学变异指数 (ICV) 值 (1.30–3.54) 和较低的化学蚀变指数 (CIA) 值 (36.2–61.5) 表明这些沉积物不成熟，可能在运输和沉积过程中经历了弱到中等的化学风化. 地球化学资料还表明，晚渐新世以来，红河流域是莺歌海-宋洪盆地北部的主要生源区。元素含量和比例的变化与盆地的多期构造活动和不同沉积时期红河水系重组引起的物源转移相一致。5) 表明这些沉积物是不成熟的，可能在运输和沉积过程中经历了弱到中等的化学风化。地球化学资料还表明，晚渐新世以来，红河流域是莺歌海-宋洪盆地北部的主要生源区。元素含量和比例的变化与盆地的多期构造活动和不同沉积时期红河水系重组引起的物源转移相一致。5) 表明这些沉积物是不成熟的，可能在运输和沉积过程中经历了弱到中等的化学风化。地球化学资料还表明，晚渐新世以来，红河流域是莺歌海-宋洪盆地北部的主要生源区。元素含量和比例的变化与盆地的多期构造活动和不同沉积时期红河水系重组引起的物源转移相一致。