海进体系域碳氧同位素地球化学响应——以黔西南地区三叠系为例 |
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引用本文: | 李荣西,;魏家庸,;肖家飞,;王兴理,;Lehrmann DJ. 海进体系域碳氧同位素地球化学响应——以黔西南地区三叠系为例[J]. 西安地质学院学报, 2007, 0(1): 1-5 |
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作者姓名: | 李荣西, 魏家庸, 肖家飞, 王兴理, Lehrmann DJ |
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作者单位: | [1]长安大学地球科学与国土资源学院,陕西西安710054; [2]中国科学院地球化学研究所,贵州贵阳550002; [3]威斯康星大学奥什科什分校地质系,奥什科什,WI 54901,美国 |
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基金项目: | 国家自然科学基金项目(40173005)参加野外工作的有美国堪萨斯大学Paul Enos教授、中国科学院地球化学研究所杨卫东和郭庆军研究员等,谨此致谢. |
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摘 要: | 层序地层研究表明,位于扬子地块西南缘的黔西南地区在中三叠世末期(相当于Ladinian-Carnian期)出现了一次与全球同步的大规模海侵,形成了一个向上变深的碳酸盐岩台地淹没沉积层序。垄头组顶部和竹竿坡组分别是海进体系域(TST)的下、上部分。碳、氧同位素研究表明,垄头组顶部自下而上δ(^18O)持续增大,而δ(^13 C)先逐渐增大,后在顶部界面附近快速下降,反映了垄头组顶部在暴露环境下氧化作用的结果。竹竿坡组δ(^13 C)自下而上逐渐增大,δ(^13 C)总体呈现逐渐减小趋势,反映了海平面变化特征。研究认为,海进体系域的δ(^13 C)和δ(^18 O)演化不但反映了海平面和沉积环境变化,同时对密集段(CS)、层序界面和古暴露面等也有很好的识别作用,在层序地层研究中具有重要的意义。
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关 键 词: | 碳同位素 氧同位素 层序地层 三叠系 黔西南 |
Response of Carbon and Oxygen Isotopic Geochemistry to Transgressive Systems Tract: An Example From Triassic Stratigraphy in Southwestern Guizhou Province |
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Affiliation: | LI Rong-xi , WEI Jia-yong , XIAO Jia-fei , WANG Xing-li , Lehrmann D J (1. School of Earth Sciences and Resources Management, Chang'an University, Xi' an 710054, Shaanxi, China; 2. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, Guizhou , China ; 3. Department of Geology, University of Wisconsin-Oshkosh, Oshkosh WI 54901, USA) |
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Abstract: | There was a large regression of sea-level in the Later Middle Triassic in Yangtze Block (the famous Ladinia large regression in China). But a large transgression of sea-level took place synchronously with the global sea-level changes in the southwest corner of Yangtze Block at the southwest region of Guizhou Province during the same period. The Yangtze carbonate platform was drawn and a transgressive sequence was formed during that time. The transgressive systems tract (TST) comprised the top section of Longtou Formation and Zhuganpo Formation. Studies to the variations of δ(^13 C) and δ(^18 O) of the TST show that the δ(^18 O) of Longtou Formation increased upward while the δ(^13 C)increased in lower part but decreased abruptly at the top, which reflects the diagenetic alteration to the top of Longtou Formation due to exposure under continental weathering environment. The δ(^13 C) increasing significantly while the δ(^18 O) decreasing gradually upward within Zhuganpo Formation indicates a major sea-level rise. The δ(^13 C) and δ(^18 O) values of TST reflect sea level fluctuation and paleoenvironment changes. The condensed section (CS) and the strata boundary can be reflected with carbon and oxygen isotopic composition. |
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Keywords: | Carbon isotope Oxygen isotope transgressive systems tract (TST) Triassic Period Southwestarea of Guizhou Province |
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