Geochemistry of Quaternary sediments in the northwestern South China Sea: Sediment provenance and mid-Pleistocene transition

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology Pub Date : 2024-08-22 DOI:10.1016/j.margeo.2024.107371

Xubiao Li , Jiawang Ge , Xiaoming Zhao , Kun Qi , Brian G. Jones , Xiaoyu Fang

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引用次数: 0

Abstract

The Quaternary sediments in the northwestern South China Sea (NW-SCS) provide valuable information about provenance, climate and sea level changes. However, the correlation between the geochemical records in marine sediments and these influencing factors remains less understood in the NW-SCS. Two wells penetrated Quaternary sediments on the shelf and shelf margin of the NW-SCS and provide an excellent dataset. In this study, the major, trace, and rare earth elements in the sediments were analyzed to reveal the Quaternary provenance changes that correlate with the climatic Middle Pleistocene transition (MPT). These results indicate that the core sediments were mainly derived from felsic source rocks and the degree of chemical weathering in the source areas is relatively low (CIA averaged at 58). The Quaternary provenance of the NW-SCS did not undergo significant changes, recording mixed sedimentation from the Red River, Hainan Island, and central Vietnamese sources. The felsic source rocks and negative Eu anomaly indicated the shelf area received sediments primarily from the Red River and Hainan Island. However, a positive Eu anomaly on the shelf margin suggests additional contributions from mafic rocks sourced from central Vietnam. During the MPT (1.3–1.4 to 0.8–0.9 Ma), the dominant periodicity of climate cycles changed from a 40 kyr obliquity cycle to a 100 kyr eccentricity cycle; the cooling climate led to a slight weaking in chemical weathering and a minor decrease in sediment supply from terrestrial sources. After the MPT, the mixed sourced sediments in the shelf and shelf margin areas of the NW-SCS likely suffered from multiple hydrodynamic forces under the influence of the Pleistocene high-frequency and high-amplitude sea level fluctuations. These climate induced changes led to significant fluctuations in element content that provide new insights into Quaternary sources and climatic events in the NW-SCS.

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中国南海西北部第四纪沉积物的地球化学：沉积物产地与更新世中期过渡

中国南海西北部的第四纪沉积物提供了有关产地、气候和海平面变化的宝贵信息。然而，在中国南海西北部，海洋沉积物中的地球化学记录与这些影响因素之间的相关性仍然不太清楚。西北太平洋大陆架和大陆架边缘的两口井穿透了第四纪沉积物，提供了极好的数据集。本研究对沉积物中的主要、痕量和稀土元素进行了分析，以揭示与中更新世气候转变（MPT）相关的第四纪出处变化。这些结果表明，岩芯沉积物主要来自长英质源岩，源区的化学风化程度相对较低（CIA 平均值为 58）。西南大陆架西北部的第四纪成因没有发生重大变化，记录了来自红河、海南岛和越南中部的混合沉积。长石源岩和负欧氏异常表明大陆架地区的沉积物主要来自红河和海南岛。然而，陆架边缘的正欧姆异常表明，还有来自越南中部的黑云母岩。在大跃进期间（1.3-1.4 至 0.8-0.9 Ma），气候周期的主要周期从 40 kyr 的斜率周期变为 100 kyr 的偏心率周期；气候变冷导致化学风化作用略有减弱，来自陆地的沉积物供应略有减少。MPT之后，在更新世高频率、高振幅海平面波动的影响下，西北-南大陆架陆架和陆架边缘地区的混合来源沉积物可能遭受了多种流体动力的影响。这些由气候引起的变化导致了元素含量的显著波动，为了解西北-南中国海的第四纪来源和气候事件提供了新的视角。

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来源期刊

Marine Geology 地学-地球科学综合

CiteScore

6.10

自引率

6.90%

发文量

175

审稿时长

21.9 weeks

期刊介绍： Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.