| 黔西南郭家湾地区中三叠世坡段组幻龙化石埋藏环境 ——来自碳酸盐岩岩相与碳、氧同位素的指示 |
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| 引用本文： | 向坤鹏,贺永忠,赵磊,安亚运,盘应娟,何犇,刘奎勇.黔西南郭家湾地区中三叠世坡段组幻龙化石埋藏环境 ——来自碳酸盐岩岩相与碳、氧同位素的指示[J].沉积学报,2019,37(5):957-967. |
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| 作者姓名： | 向坤鹏 贺永忠 赵磊 安亚运 盘应娟 何犇 刘奎勇 |
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| 作者单位： | 贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081;贵州省地质调查院,贵阳,550081 |
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| 基金项目： | 贵州省地质矿产勘查开发局科研项目（QDKKH[2017]28）；贵州省科技计划项目（黔科合平台[2018]5626）；中国地质调查局项目（DD20 160020） |
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| 摘 要： | 为详细刻画黔西南郭家湾一带中三叠世安尼期幻龙化石的埋藏环境，对所属地层坡段组进行岩相和碳、氧同位素分析。结果显示该组属于开阔台地、台地边缘礁和礁缘斜坡亚相，包含五种沉积微相类型。全岩碳氧同位素分析结果显示，δ18OPDB值为-6.28‰~-2.11‰，平均值为-4.36‰；δ13CPDB值为+0.50‰~+2.86‰，平均值为1.58‰，与黔西南及邻区同期地层碳氧同位素组成一致。获得古海水温度为16℃~20℃，盐度为125.77~131.62，指示为正常温暖的海相沉积环境。淡水的加入是导致δ13CPDB和δ18OPDB在化石层显示轻微负偏的主要原因。综合分析还原化石的埋藏活动表明:地震活动导致碳酸盐岩台地局部地层失稳，形成含大量幻龙骨骼的碎屑流最终于礁缘斜坡地带发生卸载，形成异地埋藏化石层。研究结果为进行黔西南及邻区三叠纪化石群特异埋藏分析提供资料。
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| 关 键 词： | 岩相分析 碳氧同位素 安尼期 地震 郭家湾剖面 |
| 收稿时间： | 2018-09-13 |
The Burial Environment of Nothosaurs in the Middle Triassic Pod-uan Formation,Guojiawan,Southwest of Guizhou: Implications from carbonate lithofacies and carbon and oxygen isotopes |
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| Institution: | Guizhou Geological Survey, Guiyang 550081, China |
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| Abstract: | The burial paleoenvironment of Nothosaurs during the Anisian Stage of the Poduan Formation,Guojiawan area,southwest of Guizhou province,is chacterized in detail. Analysis of carbon and oxygen isotopes in the lithofacies showed that the Poduan Formation consisted of an open platform and a platform-edge reef. The reef edge slope subfacies comprises five sedimentary microfacies types. Whole rock isotope analysis revealed a δ18O(PDB) value of -6.28‰ to -2.11‰,averaging 4.36‰;the δ13C(PDB) was +0.50‰ to +2.86‰,at an average of 1.58‰. Both values are consistent with the carbon and oxygen isotopic composition in southwestern Guizhou province and adjacent region during the Anisian Stage. The study showed that the ancient seawater temperature was 16℃ to 20℃,and the salinity was between 125.77 and 131.62,indicating a normal warm marine environment. The slight negative deviation of the δ13C(PDB) and δ18O(PDB) was caused by the mingling of fresh water with the seawater. Based on a comprehensive analysis,the following burial process of the Nothosaur is proposed. Earthquakes led to local instability of the carbonate platform,causing a debris flow. This is evident from the large number of Nothosaur bones deposited on the reef edge slope,ultimately forming the present-day fossil bed. This study provides more information for the analysis of Triassic biota in southwestern Guizhou province and adjacent areas. |
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