Provenance shift of the abyssal plains in the Southwest sub-basin of the South China Sea at ∼ 8 Ma: Tectonics & climate changes implication

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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Abstract

Tectonic processes and climatic changes are recognized as two major drivers of erosion along the southeastern margin of the Tibetan Plateau and consequently are the main factors controlling depositional patterns along the margins of the South China Sea. However, the role of tectonics and climate in governing the types and patterns of sedimentation in the abyssal plains is relatively little known. The results of International Ocean Discovery Program (IODP) drilling in the abyssal plains of the Southwest sub-basin of the South China Sea show that the multi-trace element and rare earth element (REE) character of sediments older than ∼8 Ma are in disorder. εNd(0) and 87Sr/86Sr values exhibit large fluctuations, which implies temporally variable sediment sources during the early post-spreading stage of the South China Sea. High εNd(0) and low 87Sr/86Sr values and abundant Cenozoic (13–35 Ma) zircon grains in the sediments suggest relatively juvenile sources for their origins, such as the Cagayan Ridge and Palawan Block in the south before ∼8 Ma. Multi-trace element and REE patterns of sediments younger than ∼8 Ma are more uniform. Low εNd(0) and high 87Sr/86Sr values of the sediments indicate that more continentally-derived sediments were transported to the abyssal plain. Coastal rivers in SE Vietnam, and the Mekong and Red Rivers in the west gradually became the major detrital sources of abyssal sediments in the Southwest sub-basin after ∼8 Ma. The switching of the sediment sources from the south to the west is consistent with the progressive uplift of the Vietnamese Central Highlands (VCH) and the SE Tibetan Plateau margin during the Late Miocene. The strengthened summer monsoon since ∼5 Ma affected not only the marginal basins, but also the deep abyssal basins. We argue that the regional tectonics shaped and controlled the shift of provenance and sediment routing system, whereas the East Asian monsoon affected the sediment flux to the abyssal plains of the Southwest sub-basin in the South China Sea.

南海西南次盆地深海平原在 ∼ 8 Ma 的成因转变:构造和气候变化的影响
构造过程和气候变化被认为是青藏高原东南边缘侵蚀的两个主要驱动因素,因此也是控制中国南海边缘沉积模式的主要因素。然而,人们对构造和气候在控制深海平原沉积类型和模式方面的作用却知之甚少。国际大洋发现计划(IODP)在南海西南次盆地深海平原的钻探结果表明,年龄大于 8 Ma 的沉积物的多痕量元素和稀土元素特征紊乱,εNd(0)和 Sr/Sr 值波动较大,这意味着南海后展布早期沉积物来源存在时间上的变化。沉积物中的高εNd(0)值和低Sr/Sr值以及丰富的新生代(13-35 Ma)锆石颗粒表明沉积物的来源相对较新,如8 Ma以前的卡加延海岭和南部的巴拉望地块。年龄小于 ∼8 Ma 的沉积物的多痕量元素和 REE 模式较为一致。沉积物的低εNd(0)值和高Sr/Sr值表明更多的大陆沉积物被搬运到深海平原。越南东南部的沿海河流以及西部的湄公河和红河在 ∼8 Ma 之后逐渐成为西南亚盆地深海沉积物的主要碎屑源。沉积物来源由南向西的转变与晚中新世时期越南中部高原和青藏高原东南缘的逐渐隆升相一致。5Ma以下夏季季风的加强不仅影响了边缘盆地,也影响了深渊盆地。我们认为,区域构造塑造并控制了产地和沉积物流向系统的变化,而东亚季风则影响了沉积物流向南海西南次盆地的深海平原。
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来源期刊
Marine Geology
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.
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