廖梦娜^1,,,
于革^2,,,
桂峰³
1. 浙江师范大学化学与生命科学学院, 浙江 金华 321004
2. 中国科学院南京地理与湖泊研究所, 湖泊与环境国家重点实验室, 江苏 南京 210008
3. 浙江海洋大学海洋科学与技术学院, 浙江 舟山 316000

基金项目: 国家重点研发计划项目（批准号：2017YFC0405205）资助


详细信息

作者简介: 廖梦娜, 女, 30岁, 讲师, 自然地理学专业, E-mail:mnliao@zjnu.edu.cn

通讯作者: 廖梦娜, E-mail:mnliao@zjnu.edu.cn; 于革, E-mail:geyu@niglas.ac.cn

中图分类号: P534.63⁺1, P737.12⁺1, Q915.81

收稿日期:2017-09-22
修回日期:2017-12-20
刊出日期:2018-05-30

Paleoecological records of transgressions in Core YZ07 from Changjiang River delta-radial sand ridges of the South Yellow Sea since the Late Pleistocene

Liao Mengna^1,,,
Yu Ge^2,,,
Gui Feng³
1. College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, Zhejiang
2. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, Jiangsu
3. Marine Science and Technology College, Zhejiang Ocean University, Zhoushan 316000, Zhejiang


More Information

Corresponding authors: Liao Mengna,E-mail:mnliao@zjnu.edu.cn ; Yu Ge,E-mail:geyu@niglas.ac.cn

MSC: P534.63⁺1, P737.12⁺1, Q915.81

--> Received Date: 22 September 2017
Revised Date: 20 December 2017
Publish Date: 30 May 2018


摘要
摘要:相对海平面变化对河口海岸的生态环境影响重大。长江三角洲地区不稳定的构造运动以及沉积物的持续堆积作用叠加在气候控制的全球海平面变化之上，引起了复杂的相对海平面变化过程，因此，长江沿海地区晚更新世以来的相对海平面变化问题仍存在较大争论。文章以取自长江三角洲和南黄海辐射沙脊群交界处的YZ07钻孔记录为载体，通过分析该钻孔硅藻和有孔虫化石记录，试图从古生态学角度探究长江沿海地区晚更新世以来的海侵过程。YZ07钻孔硅藻和有孔虫记录显示该区域在MIS 3晚期和MIS 1早-中期发生了海侵。其中，有孔虫丰度、异地属种比例、列式壳类的比例等特征指示MIS 1高海面时期比MIS 3晚期海侵时的相对海平面更高，并且两次海侵过程中潮流作用影响强烈。硅藻群落组合整体表现为Cyclotella stylorum-Cyclotella striata-Paralia sulcata，指示了滨岸-潮间带沉积环境，其中暖水种（Actinoptychus annulata、Actinoptychus mammifer、Coscinodiscus blanda、Coscinodiscus nodulifer、Thalassiosira nitzschioides）和一些指示种（Xanthiopyxis、Thalassiosira oestrupii）在MIS 1早-中期的增加或出现反映了更为温暖的海水环境，可能与东黄海暖流系统的形成演化有关。MIS 1最大海侵后，沉积物粒度、有孔虫和硅藻的丰度和保存情况均反映出潮流影响的减弱以及相对海平面的下降。此外，在MIS 1海退地层中发现的硅藻富集层（34.95 m处）可能指示一次风暴潮事件。
关键词: 晚更新世/
长江三角洲/
辐射沙脊群/
海侵/
硅藻/
有孔虫

Abstract:Relative sea-level change has great impacts on the ecological environments in estuarine and coastal areas. The unstable tectonic movement and continuous sediment accumulation superimposed on the climate-mediated sea level change leads to complicated relative sea-level change in the China's east coast. Up till now, how the relative sea-level change in this region since the Late Pleistocene is still in debate. We therefore used the diatom and foraminifera records of core YZ07 from the tidal flat of Dongzao Harbor, Jiangsu Province, to discuss this question. Core chronology was established by accelerator mass spectrometry(AMS) ¹⁴C and Optically Stimulated Luminescence(OSL) dating methods. Core YZ07(32.114°N, 121.479°E) was extracted from the tidal flat of Dongzao Harbor, Jiangsu Province. It lies at the transition between the Changjiang River delta and radial sand ridges of the South Yellow Sea. This area is highly sensitive to relative sea-level change due to the strong influences from tidal currents and river hydrology. Core YZ07 is 143.44 m long and the coring recovery rate reaches to 95.6%. This study focused on the upper 52 m of this core where we have established a robust chronology. The chronology shows the absence of(Marine Isotope Stage) MIS 2 in this core. From the evidence of lithology, we speculated that the sediments deposited during this period had been eroded during the Last Deglaciation when transgression happened, which is similar to many other records from this region. Fossil diatom and foraminifera were not preserved very well in the sediments. We found mechanical crushing as the most important factor controlling the preservation of these fossil records. Chemical erosion also has influence on the fossil diatoms. However, these records can still reflect relative sea-level changes because diatom and foraminifera species can only survive in some specific habitats. In Core YZ07, abundance and species of both diatom and foraminifera records showed two transgressions happened during late MIS 3 and early-middle MIS 1. Changes in foraminifera abundance, ratios of allochthonous taxa, porcellaneous and agglutinated tests reflected strong impact of tidal dynamics on sedimentary process during the transgressions, and indicated higher relative sea level in early-middle MIS 1 than in late MIS 3. Diatom record with relative high abundance occurred between 40~52 m along the core profile. The composition of Cyclotella stylorum-Cyclotella striata-Paralia sulcata in the sediments indicated a littoral-intertidal sedimentary environment during the transgressions. Changes in warm-water species(Actinoptychus annulata, Actinoptychus mammifer, Coscinodiscus blanda, Coscinodiscus nodulifer and Thalassiosira nitzschioides) and indicator species(Xanthiopyxis and Thalassiosira oestrupii) reflected a warmer marine environment during the MIS 1 transgression. This may be due to formation and evolution of the modern warm current system in the East China Sea and the Yellow Sea since the Last Deglaciation. Diatom abundance above ca.40 m is very low and the valves are highly broken. Sedimentary facies in this section revealed a transition from middle to high tidal flats, and the upward-fining grain size indicated a gradually weakened sedimentary process and lower relative sea level. A distinct layer with high diatom abundance was identified at a depth of 34.95 m. Considering specific geomorphology and strong influence of tidal wave and currents on sedimentary environment in this region, this layer may be a mark of huge storm surge, although lacking an obvious strata sequence of storm deposits. Micropaleontological records from Core YZ07 indicate two transgressions during the late MIS 3 and early-mid MIS 1, and the latter is stronger than the former. Although this study region has been subsiding consistently since the Late Quaternary, the shoreline retreated and showed a declining sea level. This because the containable space decreased since the mid-MIS 1 due to huge sediment discharge from the Changjiang River.
Key words:Late Pleistocene/
Changjiang River delta/
the radial sand ridges of South Yellow Sea/
transgression/
diatom/
foraminifera



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