华南古、中生代之交牙形石原位氧同位素分析及其古气候重建

The proposed study aims to re-sample systematically several raltively better studied,conodont-enriched Permian-Triassic boundary sections in South China such as Meishan of Zhejiang, Guandao of Guizhou, Zuodeng of Guangxi, Xiakou of Hubei, and Chaohu of Anhui. The newly obtained conodonts as well as these previously obtained specimens will be ultilized to undertake oxygen isotopic analysis of apatites. Unlike the previous approaches, this study attempts to conduct the high-resolution, in situ analysis of conodont oxygen isotopes at mm-scale using the Cameca IMS-1280 techniques and methodology. Paleoclimatic change over the Paleozoic-Mesozoic transition is anticipated to be revealed on the basis of paleotemperature changes derived from oxygen isotope excursions of conodont apatites. This study therefore is able to determine the relationships between temporature change and biotic crisis during this critical period. In addition, the selected sections represent sedimentation in various environmental settings. Thus, various oxygenic isotopes and oceanic geochemical conditions derived from conodont apatites of different environmental settings are greatly helpful in exploitting the possible causes triggerring the biotic mass extinction and delayed recovery during the Paleozoic-Mesozoic transition. The proposed project therefore enhances Chinese study profile and leadership in the studies on the Permian-Triassic mass extinction worldwide.

本项目拟对华南几个研究程度较高并富含牙形石化石的二叠-三叠系界线地质剖面如安徽巢湖平顶山、贵州关刀、广西作登、湖北大峡口及浙江煤山等剖面进行系统地采集牙形石化石样品，并充分利用已获得的牙形石标本,依托Cameca IMS-1280离子探针技术和实验方法对牙形石微区原位氧同位素组成进行系统测量并开展高分辨率牙形石原位氧同位素分析研究。该研究有望首次建立不同相区古、中生代之交及早三叠世牙形石原位氧同位素组成变化模式与古海洋化学、古气候变化以及主要生物事件之间的对应关系；通过氧同位素恢复晚二叠世至整个早三叠世的古温度变化趋势、时限和幅度，从而揭示古生代末生物大灭绝事件及其之后生物的滞后复苏与古温度和古海洋化学变化的内在联系，为查明引起二叠纪末生物大灭绝的元凶提供新的研究思路，加强了我国在世界范围内在二叠纪-三叠纪之交群集大灭绝事件这一热点研究中的领先地位。

研究了中-下扬子地区（如浙江煤山剖面、安徽巢湖剖面和宜昌峡口剖面）以及南盘江盆地地区（如广西作登剖面和太平剖面）一系列代表性剖面的牙形石生物地层，系统的利用牙形石化石，依托Cameca SIMS-1280离子探针技术和实验方法对获得的P/T附近和早三叠世的牙形石进行分析测试和结果分析。同时，利用激光拉曼、LA-ICP-MS和XRD等技术对牙形石所受成岩作用影响程度进行了指标性评价，对牙形石不同部位（牙尖、牙冠和牙基）氧同位素比值做了对比分析。牙形石成岩作用的分析为获取准确可靠的牙形石氧同位素数据以及古温度的重建提供了技术支持。通过一系列晚二叠-中三叠剖面的牙形石生物地层研究，建立了精确的时间地层框架，高分辨率地牙形石原位氧同位素以及古温度演变曲线。探讨了早三叠世生物缓慢复苏的模式和原因，以及气候的变化与生物多样性和生态系统的崩塌或重建之间的关系。这一研究为深入研究全球古生代末生物大灭绝及其后生物复苏过程、时限与环境气候变化之间的联系提供了重要依据，为今后围绕古-中生代之交大灭绝的研究提供了重要参考资料。