Astronomical tuning and magnetostratigraphy of Neogene biogenic reefs in Xisha Islands, South China Sea  

作　　者：Liang Yi Zhimin Jian Xinyu Liu Youhua Zhu Daojun Zhang Zhenfeng Wang Chenglong Deng 

机构地区：[1]State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China [2]Laboratory for Marine Geology. Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China [3]China National Offshore Oil Corporation Ltd., Zhanjiang Branch, Zhanjiang 524057, China [4]Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology. Chinese Academy of Sciences, Nanjing 210008, China [5]State Key Laboratory of Lithospheric Evolution. Institute of Geology and Geophysics. Chinese Academy of Sciences, Beijing 100029, China [6]Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China [7]University of Chinese Academy of Sciences. Beijing 100049, China

出　　处：《Science Bulletin》2018年第9期564-573,共10页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China(41630965,41690112 and 41621004);the National Programme on Global Change and Air–Sea Interaction of China(GASI–GEOGE–04);the Fundamental Research Funds for the Central Universities

摘　　要：Biogenic reefs are one of two major depositional types in the South China Sea, and are constructed by coral, algae and bryozoa. The West Pacific is a major area of biogenic reef development and plays a critical role in the global carbon cycle. However, the lack of geochronological studies in previous works inhibits our understanding of their contributions. Herein, we conduct a cyclostratigraphic and magnetostratigraphic study on Neogene biogenic reefs using the XK–1 core that was drilled at the Shidao Island,Xisha(Paracel) Islands. The main findings of this study are:(1) the establishment of reliable magentostratigraphy for Ledong, Huangliu, Meishan and Sanya Formations;(2) the magnetic susceptibility variation can be inferred as growth index and tuned to the 405–ka long eccentricity cycle;(3) the astronomical geochronology suggests that the bottom ages for Ledong, Yinggehai, Huangliu, Meishan,and Sanya Formations are 2.2 Ma, 5.7 Ma, 10.4 Ma, 16.6 Ma, and 24.3 Ma, respectively; and (4) Earth's eccentricity and obliquity played predominant roles in biogenic reef establishment on orbital to tectonic timescales. Thus, the reported geochronology offers an opportunity to test the contributions of various factors and hypothesize their roles in the global carbon cycle in future.Biogenic reefs are one of two major depositional types in the South China Sea, and are constructed by coral, algae and bryozoa. The West Pacific is a major area of biogenic reef development and plays a critical role in the global carbon cycle. However, the lack of geochronological studies in previous works inhibits our understanding of their contributions. Herein, we conduct a cyclostratigraphic and magnetostrati- graphic study on Neogene biogenic reefs using the XK-1 core that was drilled at the Shidao Island, Xisha （Paracel） Islands. The main findings of this study are： （1） the establishment of reliable magen- tostratigraphy for Ledong, Huangliu, Meishan and Sanya Formations; （2） the magnetic susceptibility variation can be inferred as growth index and tuned to the 405-ka long eccentricity cycle; （3） the astronomical geochronology suggests that the bottom ages for Ledong, Yinggehai, Huangliu, Meishan, and Sanya Formations are 2.2 Ma, 5.7 Ma, 10.4 Ma, 16.6 Ma, and 24.3 Ma, respectively; and （4） Earth＇s eccentricity and obliquity played predominant roles in biogenic reef establishment on orbital to tectonic timescales. Thus, the reported geochronology offers an opportunity to test the contributions of various factors and hypothesize their roles in the global carbon cycle in future.

关 键 词：Astronomical tuning Magentostratigraphy Magnetic susceptibility Biogenic reefs Neogene South China Sea 

分 类 号：P539.3[天文地球—古生物学与地层学] P736.2[天文地球—地质学]