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首页> 外文期刊>Journal of Asian earth sciences >Depositional sequences of the Mekong river delta and adjacent shelf over the past 140 kyr, southern Vietnam
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Depositional sequences of the Mekong river delta and adjacent shelf over the past 140 kyr, southern Vietnam

机译：湄公河三角洲和邻近架子的沉积序列在过去的140 kyr，越南南部

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摘要

Two 40 m-long sediment cores BL01 and SC02 were drilled in the lower Mekong River Delta plain and compared to high-resolution seismic profiles from the adjacent shelf documenting the presence of two depositional sequences (SQ1, SQ2) for the past 140 kyr. SQ2 is a fourth-order sequence and covers a complete sea-level cycle of 120 kyr. SQ1 is a fifth-order sequence comprising a sea-level half cycle in the past 20 kyr. These two sequences are bounded by the sequence boundaries (SB1, SB2) and the topographic surface. The transgressive systems tract (TST2) of SQ2 was probably formed during the sea-level rise from the Marine Isotope Stage (MIS) 6 lowstand to the MIS 5e highstand, indicated by riverine-estuarine and shallow-marine sediments. The regressive systems tract (RST2) of SQ2 corresponds to the sea-level lowering from MIS 5e to 3 with deltaic and alluvial plain sediments prevailing. These sediments were then gradually exposed to tropical subaerial processes to generate the formation of patchy reddish-orange stiff sandy silt and clay. The overlaying sequence SQ1 contains the lowstand systems tract (LST1), TST1, and RST1. LST1 consists of deltaic sediments at the shelf edge deposited during the MIS 2 sea-level low-stand. TST1 includes retrograding-fluvial, estuarine, and shallow-marine sediments deposited during the deglacial sea-level rise 19-8 cal kyr BP and the maximum flooding period 8-6 cal kyr BP before the advance of the modern Mekong River Delta. RST1 comprises the modern delta-facies association formed during the past 8 kyr and is restricted to the water depth of 25 m.
机译：在湄公河下河达达拉平原中钻了两种40米长的沉积物芯BL01和SC02，并与来自相邻货架的高分辨率地震曲线，记录了过去140 kyr的两种沉积序列（SQ1，SQ2）的存在。 SQ2是四阶序列，涵盖120 kyr的完整海平周期。 SQ1是5阶序列，包括过去20 kyr的海平半周期。这两个序列由序列边界（SB1，SB2）和地形表面限制。在海上同位素阶段（MIS）6对MIS 5E高层的海平面上升期间，SQ2的近次SQ2的越野（TST2）在MIS 5E高层期间形成，由河流 - 河口和浅海沉积物表明。 SQ2的回归系统道（RST2）对应于从MIS 5E降低到3的海平面，并具有较为普通的普通沉积物。然后将这些沉积物逐渐暴露于热带的子系统方法中，以产生斑块红橙色硬沙淤泥和粘土的形成。覆盖序列SQ1包含低通位系统散（LST1），TST1和RST1。 LST1由在MIS 2海平面低位期间沉积的搁板边缘处的Deltaic沉积物组成。 TST1包括逆行 - 氟，河口和浅海洋沉积物，沉积在临时海平面上升19-8克拉尔BP和现代湄公河三角洲之前的最大洪水期限8-6 Cal Kyr BP。 RST1包括在过去的8kyr期间形成的现代化三角形关联，并限制在水深25米。

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