Sedimentary environment and formation mechanism of the mud deposit in the central South Yellow Sea during the past 40kyr
Sedimentary environment and formation mechanism of the mud deposit in the central South Yellow Sea during the past 40kyr
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DOI：
10.1016/j.margeo.2013.11.008
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发表时间：
2014
期刊：
影响因子：
2.9
通讯作者：
Yonghong Wang;Guangxue Li;Weiguo Zhang;P. Dong
中科院分区：
文献类型：
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作者：
Yonghong Wang;Guangxue Li;Weiguo Zhang;P. Dong
通过对YS01A型新岩心的粒度、沉积物密度、化学特征、磁学性质和AMS14C年龄的分析，结合其他已有的岩心资料，研究了南黄海中部中国近40年来的沉积环境和形成机制。结果表明，该40áKYR期间存在4个沉积剖面，包括两个海相剖面(A和C)和两个陆相/潮间带剖面(B和D)。D剖面的沉积指标显示该剖面风化侵蚀强烈，形成时间早于40ákyr。相比之下，B断面的沉积环境更湿、更暖，风化侵蚀不如D断面，A、C断面的沉积表明海平面上升的影响，C断面的沉积是在气候比A断面湿润得多的时候沉积的。气候和当地水动力的变化造成了两个海洋断面不同的沉积物特征。研究发现，这些河流输入的泥沙仅占南黄海中部和东南部两个泥沙沉积的48%左右。沉积物的另一个主要来源是来自黄海的海床侵蚀、再悬浮和再沉积，其次是生物成因和成岩作用，通过对比YS01a岩心A和C剖面的沉积特征，为了解泥质沉积物的形成和来源提供了独特的机会。研究发现，泥沙沉积的形成与黄海暖流没有直接关系，只是改变了全新世以来A剖面泥沙沉积的性质，带来了大量的有机质和更细的颗粒。然而，在这一地区形成的冷水团是重要的，因为它有助于在两个海洋区段捕获更多和更细的颗粒。上升流通常发生在50ám水深附近，这是两个相反的水流的交界处，形成了最厚的沉淀层。研究还证实，南黄海中部泥沙沉积的形成主要是由大陆架上的潮流引起的。
Sedimentary environment and formation mechanism of the mud deposit in the central South Yellow Sea of China during the last 40ákyr are studied based on the analysis of particle size, sediment density, chemical features, magnetic properties and AMS14C ages of a new core YS01A together with other available core data. The results show that there exist four sedimentary sections during this 40ákyr period, including two marine sections (A and C) and two terrestrial/intertidal sections (B and D). Sedimentary indexes of section D, which were formed before 40ákyr, show that strong weathering and erosion occurred in this section. In contrast, sedimentary environment of section B was wetter and warmer and weathering and erosion were not as strong as in section D. Marine deposits in both sections A and C indicated the effects of sea level rise and section C was deposited when the climate was much wetter than in section A. Variations of climate and local hydrodynamics created different sediment features of two marine sections.From the estimated river discharges of the Huanghe, Changjiang and relevant Korean rivers and calculation of mud deposit volumes of section A during the past 9.7ákyr, it is found that the sediment inputs from these river sources can only account for about 48% of sediments in the two mud deposits of the central and southeastern South Yellow Sea. The other main source of sediments is identified to be the seabed erosion, resuspension and redeposition from the Yellow Sea and, to a lesser extent, from the biogenesis and diagenesis.It provides a unique opportunity of understanding the formation and source of mud deposits by comparing the sedimentary properties of sections A and C in core YS01A. It is found that formation of mud deposits is not related directly to the Yellow Sea Warm Current, which only changed the sediment properties of mud deposits in section A since it formed from Holocene by bringing a large amount of organic mass and finer particles. However, cold water mass developed in this area is important as it helped to trap more and finer particles in the two marine sections. Upwelling usually occurs around 50ám bathymetry which is at the juncture of two opposite water currents and has induced the thickest sediment layer. This study also confirmed that formation of the mud deposit in the central South Yellow Sea is caused mainly by the tidal currents on the continental shelves.