| 广西渐新世宁明组三种植物碳同位素与古气候分析 |
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| 引用本文： | 王秋军,郑军,孙柏年,马福军,王振,王万梅.广西渐新世宁明组三种植物碳同位素与古气候分析[J].沉积学报,2020,38(2):358-366. |
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| 作者姓名： | 王秋军 郑军 孙柏年 马福军 王振 王万梅 |
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| 作者单位： | 1.贵州大学资源与环境工程学院，贵州省古生物研究中心，贵阳 550000 |
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| 基金项目： | 国家自然科学基金项目31860050贵州省古生物研究中心建设基金QianKHZ(2014)4003贵州省科技计划项目QianKHZ(2017)5788贵州师范学院科研基金项目2015BS014贵州大学引进人才科研项目201535 |
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| 摘 要： | 渐新世代表地球一个早期的“冰室”期，是地球气候演化和生物演替过程中一段特殊的时期。渐新世植物化石的碳同位素可为研究该时期的古气候提供依据。对广西渐新世宁明组三种植物及其最近现生亲缘种的碳同位素进行分析，化石种Buxus ningmingensis，Chuniophoenix slenderifolia和Cephalotaxus ningmingensis的碳同位素组成（δ13C）分别为-29.0‰，-28.3‰，-28.0‰；碳同位素分馏（Δ13C）分别为23.48‰，22.74‰，22.43‰；叶内细胞间和外界大气的CO2分压比（C植物/C空气）分别为0.84，0.81，0.80；水分利用效率（WUE）分别为42.63μmol CO2/mol H2O，51.56μmol CO2/mol H2O，55.38 μmol CO2/mol H2O。其对应的最近现生亲缘种（NLRs）的δ13C分别为-27.9‰，-29.7‰，-28.8‰；Δ13C分别为20.47‰，22.36‰，21.42‰；C植物/C空气分别为0.71，0.79，0.75；WUE分别为72.22 μmol CO2/mol H2O，51.28μmol CO2/mol H2O，61.76 μmol CO2/mol H2O。化石种δ13C值均落在现代C3植物相应的数值范围内，其Δ13C和C植物/C空气均高于相应的NLRs数值；而Buxus ningmingensis和Cephalotaxus ningmingensis的WUE低于相应的NLRs数值；其中Chuniophoenix slenderifolia的WUE稍高于相应的最近现生亲缘种C. hainanensis，推测可能与其NLR标本的母本植物生长在水源充足、空气潮湿的湖溪边湿地环境有关。基于Δ13C、C植物/C空气和WUE结果，推测化石种可能生活在一种比现在更为温暖湿润的气候环境中；化石种及同层位化石的古气候重建支持了当前古气候分析结果。
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| 关 键 词： | 碳同位素 古气候 植物化石 渐新世 宁明组 |
| 收稿时间： | 2018-10-06 |
Carbon Isotope and Paleoclimatic Implications of Three Plants from the Oligocene Ningming Formation,Guangxi |
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| Institution: | 1.Guizhou Research Centre for Palaeontology & College of Resources and Environmental Engineering, Guizhou University, Guiyang 550000, China2.School of Earth Sciences, Lanzhou University, Lanzhou 730000, China3.School of Geography and Resources, Guizhou Education University, Guiyang 550000, China |
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| Abstract: | The Oligocene represented an early "icehouse" epoch and is a significant period in which global climates and organisms had pronounced evolutions. Carbon isotope data for plant fossils from the Oligocene strata records the evolution of contemporaneous climates. Three plants from the Oligocene Ningming Formation in Guangxi were selected for carbon isotope analysis, along with their nearest living relatives (NLRs). The carbon isotope composition (δ13C) values of the fossil plants Buxus ningmingensis, Chuniophoenix slenderifolia and Cephalotaxus ningmingensis were -29.0‰, -28.3‰, -28.0‰, with carbon isotope discrimination (Δ13C) values 23.48‰, 22.74‰, 22.43‰ and Cplant/Cair ratios (intra-leaf CO2: atmospheric CO2) 0.84, 0.81, 0.80. Their water-use efficiency (WUE) were 42.63 μmol CO2/mol H2O, 51.56 μmol CO2/mol H2O, 55.38 μmol CO2/mol H2O. δ13C values of their NLRs were -27.9‰, -29.7‰, -28.8‰, with Δ13C values 20.47‰, 22.36‰, 21.42‰, Cplant/Cair ratios 0.71, 0.79, 0.75 and WUE 72.22 μmol CO2/mol H2O, 51.28 μmol CO2/mol H2O, 61.76 μmol CO2/mol H2O. The carbon isotope analysis shows that δ13C values of the three fossil plants were within the range of δ13C of extant C3 plants, and their Δ13C and Cplant/Cair also showed higher values than their NLRs. The WUE values of Buxus ningmingensis and Cephalotaxus ningmingensis were lower than their NLRs; WUE of Chuniophoenix slenderifolia is slightly higher than its NLR (C. hainanensis), which may have grown in a wetland environment alongside a small stream or lake. The δ13C, Cplant/Cair and WUE values all suggest that the fossil plants may have lived in a warmer and wetter climate. This is supported by paleoclimatic reconstruction based on the three fossil taxa and other plant fossils from the same horizon. |
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