南海东沙海域末次冰期异常沉积事件与水合物分解

陈芳; 庄畅; 张光学; 陆红锋; 段虓; 周洋; 苏新; 吴聪; 刘广虎

doi:10.3799/dqkx.2014.144

南海东沙海域末次冰期异常沉积事件与水合物分解

doi: 10.3799/dqkx.2014.144

陈芳^{1, 2,},
庄畅^{1, 2},
张光学^{1, 2},
陆红锋^{1, 2},
段虓^{1, 2},
周洋^{1, 2},
苏新³,
吴聪^{1, 2},
刘广虎^{1, 2}

1.
国土资源部海底矿产资源重点实验室, 广东广州 510075
2.
广州海洋地质调查局, 广东广州 510075
3.
中国地质大学海洋学院, 北京 100083

基金项目:

国家自然科学基金项目 41372012

国家重点基础发展研究规划项目 2009CB219502

国家专项项目课题 GZH2011003050602

详细信息

作者简介:
陈芳(1966-), 女, 教授级高级工程师, 主要从事微体古生物学和水合物研究.E-mail: zhchenfang66@21cn.com

中图分类号: P67
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- 被引次数: 0
出版历程
- 收稿日期: 2014-04-03
- 刊出日期: 2014-11-01

Abnormal Sedimentary Events and Gas Hydrate Dissociation in Dongsha Area of the South China Sea during Last Glacial Period

Chen Fang^{1, 2
,},
Zhuang Chang^{1, 2},
Zhang Guangxue^{1, 2},
Lu Hongfeng^{1, 2},
Duan Xiao^{1, 2},
Zhou Yang^{1, 2},
Su Xin³,
Wu Cong^{1, 2},
Liu Guanghu^{1, 2}

1.
Key Laboratory of Marine Mineral Resources, Ministry of Land and Resources, Guangzhou 510075, China
2.
Guangzhou Marine Geological Survey, Guangzhou 510075, China
3.
School of Ocean Sciences, China University of Geosciences, Beijing 100083, China

摘要

摘要: 对南海东沙海域陆坡区973-3柱状样开展沉积学和年代学、有孔虫同位素和壳体B/Ca比值、碳酸钙和黄铁矿含量的分析, 发现该岩芯浮游有孔虫Globigerinoides ruber和底栖有孔虫Uvigerina peregrina的δ¹³C在末次冰期同时在多个层位发生负偏, 最大负偏达-2.03‰; 有孔虫δ¹³C负偏层位环境[CO₃^2-]浓度相对偏低; 负偏层位同时出现大量黄铁矿, 最高含量达17%.在负偏层位以下沉积的碳酸盐溶解作用强烈, CaCO₃含量最低, 沉积物颜色偏深.究其成因与水合物分解关系较大.甲烷渗漏事件发生在末次冰期, 说明末次冰期的海平面下降是水合物分解的主要诱因.根据有孔虫δ¹³C负偏的次数和程度推断至少发生过4次甲烷渗漏, 渗漏的强度基本相当.
- 水合物分解 /
- δ¹³C负偏 /
- CaCO₃溶解 /
- 末次冰期 /
- 东沙陆坡 /
- 海洋地质
Abstract: Core 973-3 is located at the potential gas hydrate area on the slope within Dongsha area of the South China Sea, with the water depth of 1026m. According to the sedimentology, chronology, isotope and B/Ca ratio of the foraminiferal tests, carbonate and pyrite content, the light δ¹³C values of planktonic Globigerinoides ruber and benthic Uvigerina peregrine are found in several core layers with the most negative value of -2.03‰. In the δ¹³C distinctly depleted layers, the concentration of environmental [CO₃^2-] is relatively low, and the pyrites are abundant up to 17%, which indicates abnormal seepage of methane. Below the δ¹³C depleted layers, the carbonate intensely dissolves, and its content decreases to the bottom. It suggests that it has probably been caused by the gas hydrate dissociation. The seepage and anaerobic oxidation of methane resulted from the dissociation and release of gas hydrates is the primary reason of the depleted δ¹³C values of foraminiferal tests, carbonate dissolution and the deposits of enormous pyrites. Methane release events occurred in the last glacial period, which implies that the descending sea level induced the gas hydrate dissociation. According to the δ¹³C depleted record of foraminiferas, it is concluded that there were at least four times release events of methane, and their intensities were almost at the same level.
- gas hydrate dissociation /
- depleted δ¹³C /
- carbonate dissolution /
- last glacial period /
- Dongsha slope /
- marine geology

HTML全文

图 1 东沙海域研究站位位置

Fig. 1. Location of studied piston core in Dongsha area

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图 2 973-3柱状样岩性与沉积特征

Fig. 2. Lithology and sedimentary features of 973-3PC

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图 3 973-3柱状样地层划分

Fig. 3. Stratigraphic division of 973-3PC

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图 4 973-3柱状样浮游有孔虫G.ruber和底栖有孔虫U.peregrina碳同位素特征

Fig. 4. Planktonic and benthic foraminifera carbon isotope records of 973-3PC

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图 7 973-3柱状样异常沉积事件与水合物的分解过程示意

Fig. 7. Abnormal sedimentary events and gas hydrates dissociation process from 973-3PC

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图 5 973-3柱状样粗组分含量变化曲线与组成(显微镜照片)

Fig. 5. Coarse fraction content (%) and its components (micro-photos) of 973-3PC

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图 6 973-3柱状样黄铁矿含量变化及其显微镜照片

Fig. 6. Content of pyrite of 973-3PC

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图 8 973-3柱状样990cm处褐红色粗组分XRD成分分析结果

Fig. 8. The XRD component analysis of coarse fraction from 973-3PC(990cm)

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图 9 973-3柱状样有孔虫δ¹³C负偏层位(690~695cm，770~775cm)的壳体扫描电镜照片

Fig. 9. SEM images of foraminifera U. peregrina (a) and G. ruber (b, c, d) which δ¹³C depletion

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表 1 973-3柱状样AMS¹⁴C测年结果

Table 1. AMS¹⁴C dating results of 973-3PC

样品深度(cm)	样品性质	δ¹³C(‰)	¹⁴C测试结果(aBP)	δ¹³C同位素分馏校正	¹⁴C校正年代(aBP, 1σ)
50~55	G.ruber+G.sacculifer	2.01	3335±45	3781±45	4138±48
100~105	G.ruber+G.sacculifer	1.38	4415±40	4850±40	5600±17
226~231	G.ruber+G.sacculifer	2.28	10270±80	10721±80	12773±63
239~243	G.ruber+G.sacculifer	2.11	12230±60	12678±60	14976±134
274~279	G.ruber+G.sacculifer	-1.97	26850±180	27229±180	27229±180
282~285	G.ruber+G.sacculifer	1.66	26370±200	26810±200	26810±200
400~405	G.ruber+G.sacculifer	2.04	38520±310	38967±310	38967±310
500~505	G.ruber+G.sacculifer	0.44	40960±340	41379±340	41379±340
600~605	G.ruber+G.sacculifer	-1.30	29520±190	29910±190	29910±190
700~705	G.ruber+G.sacculifer	-0.84	42210±360	42608±360	42608±360

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