| XU Hong,ZHAO Xinwei,EBERLI G. P.,LIU Xinyu,ZHU Yurui,CAI Ying,LUO Wei,YAN Guijing,ZHANG Bolin,WEI Kai,SHI Jian. 2015. Biogenic carbonate formation and sedimentation in the Xisha Islands: evidences from living Halimeda. Acta Oceanologica Sinica, 34(4):62－73 |
| Biogenic carbonate formation and sedimentation in the Xisha Islands: evidences from living Halimeda |
| 西沙群岛生物碳酸盐的成因和沉积:来自活体仙掌藻的证据 |
| Received:June 01, 2014 Revised:September 29, 2014 |
| DOI：10.1007/s13131-015-0584-0 |
| Key words:Xisha Islands Halimeda composition of biogenic carbonate 14C accelerator mass spectrometry dating segment aragonite raphide trace elements |
| 中文关键词: 西沙群岛 仙掌藻 生物沉积碳酸盐组分 14C加速器质谱定年 节片文石针晶 微量元素 |
| 基金项目: |
| Author Name | Affiliation | E-mail | | XU Hong | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China | qdxhong@163.com | | ZHAO Xinwei | School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China | | | EBERLI G. P. | Comparative Sedimentology Laboratory, University of Miami, Miami 33149, USA | | | LIU Xinyu | Zhanjiang Branch of China National Offshore Oil Corporation (CNOOC) Limited, Zhanjiang 524057, China | | | ZHU Yurui | College of Energy Resouces, Chengdu University of Technology, Chengdu 610059, China | | | CAI Ying | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China | | | LUO Wei | Zhanjiang Branch of China National Offshore Oil Corporation (CNOOC) Limited, Zhanjiang 524057, China | | | YAN Guijing | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China | | | ZHANG Bolin | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China
College of Energy Resouces, Chengdu University of Technology, Chengdu 610059, China | | | WEI Kai | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China | | | SHI Jian | Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao 266071, China | |
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| Abstract: |
| A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems: the depleted atoll system and growth atoll system; the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected, the isotopic ages of 14C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60-100 g/m2; the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium (Te), rhodium (Rh) and strontium. It is believed that the Halimeda grow slowly, including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration. |
| 中文摘要: |
| 披露新近海岛调查发现结果,分类西沙群岛宣德环礁/永乐环礁分别为亏损型环礁体系和成长型环礁体系;指出几个面积减小的沙洲对于最大岛屿面积不过2.13 km2,最低海拔高度1.4 m的西沙群岛是不可承受之痛.本文通过针对性的西沙石岛老龙头破浪带海域仙掌藻生态特征调查,发现采集到白色与绿色两类活体仙掌藻,14C同位素年龄27年和55年,主要形成提供团块、节片、砂、沙和灰泥五种碳酸盐组分,能够在礁区环境长久提供生物沉积碳酸盐沉积物主要是仙掌藻节片,年单位面积生产力60-100 g/m2;分析了仙掌藻显微结构构造的特征,都在皮层、髓部及孢囊沉积富集文石针晶碳酸盐,普遍含有常量元素C、O、Ca、Cl、Mg、K、Na、S、Al,富集某些微量元素如碲(Te)、铑(Rh)和锶（Sr）.认为仙掌藻包括礁区珊瑚造礁生物群落成长成熟缓慢,具有环境修复能力但时间长,需要立法科学保护西沙海洋生态及其造礁生物群落生态、海岛环境多样性和脆弱性.指出在全球气候变暖海平面升高背景下,大量仙掌藻在老龙头海域的发现,对于宣德环礁亏损型环礁体系沙洲的自然增长,具有重要意义,而仙掌藻节片即是地质条件下能够大量保存、且能被鉴定到属种的化石仙掌藻原形,曾在西琛1井中新世被大量发现.因此,仙掌藻沉积碳酸盐特征和机制的研究,对于南海生物礁形成、建设及油气勘探,都具有重要价值. |
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