黔西滇东地区晚二叠世大灭绝后植物的残存与复苏机制研究

The Latest Permian Mass Extinction (LPME) event, the most severe biocrisis of the Phanerozoic, marked the collapse of marine and terrestrial ecosystems on a world-wide scale. Locally, about 95% of peat-forming plants became extinct and the number of families of higher land plants has drastically declined in this biocrisis. .Recently developed botanical and palynological records from the Upper Permian to Lower Triassic have provided a better understanding of the mechanism and dynamic of floral turnover across the Permian-Triassic Boundary (PTB). Land vegetation, as one highly sensitive index to environmental change, is one of the most useful proxies for analyzing the patterns of biotic extinction, survival and recovery during this critical period of Earth life. .Western Guizhou and eastern Yunnan (WGEY) region records are not only the best exposed and most continuous marine PTB successions in the world, but also many well-exposed, continuous PTB successions of terrestrial-marine transition and terrestrial facies. After a decade effort, biostratigraphy, chemostratigraphy and geochronology of the non-marine P-Tr successions from the WGEY region have been much better studied. Abundant and diverse floras in study area provide an excellent plant record revealing the extinction, survival and recovery patterns and evolutionary dynamics of floras across the PTB. Accordingly, this study aims to summarize the well-preserved palaeofloras from three best studied terrestrial PTB sections, namely Chahe, Jiucaichong and Guangbachong, and three key terrestrial-marine transitional PTB sections, namely Mide, Tucheng and Kele. .Based on recently published data and newly obtained materials from the WGEY, the contents of the study include: 1) Morphology and Taxonomy — establishing Early Triassic the floral community structure according to the leaf (including phyllotaxy, shape and veining etc.), the microstructures of in situ and dispersed fossil cuticles, anatomical structure of fossil woods, the Mega- and Microspores. 2) Paleoecology — combining sedimentology, floral taphonomy and other marine fauna (mainly ostracoda and conchostracan), discussing its ecological habit, habitat. 3) Paleoclimate — mixing foliar physiognomy, stomatal index of fossil plants and C, S, O isotope, explanating the climatic change related with the recovery of the paleofloras during the Permian and Triassic transition..The purposes of this study is to evaluate extinction, survival and recovery as well as evolutionary dynamic of those paleofloras (including macro- and microfloras) after the PTB crisis on land in WGEY.

黔西滇东地区发育的从海相到海陆过渡相再到陆相二叠纪-三叠纪界线剖面具有地层出露完整，沉积连续，动、植物化石丰富等优势，是解决由海到陆生物地层划分对比、研究植物群演替的关键地区。基于该地区陆相岔河剖面、韭菜冲剖面和官坝冲剖面，海陆过渡相密德剖面、土城剖面和可乐剖面早三叠世印度期地层中发现的大量保存精美的植物化石新材料，利用其保存的植物叶片（营养叶、生殖叶、叶序、叶形和叶脉等）、解剖结构（角质层和木化石）和繁殖器官（大、小孢子）等特征，开展植物形态分类、植物组合特性和植物群落结构研究；结合伴生的动物化石（主要是叶肢介和介形虫）、植物埋藏特征、沉积环境和同位素地球化学分析，探讨它们的生态习性及其生存环境；挖掘非海相区二叠纪—三叠纪重大突变期生物和环境事件信息，建立该时期陆地植物灭绝、残存和复苏的模式，解决早三叠世早期陆地植物残存、复苏的原因及其动力机制，为当今脆弱的生态系管理提供启示。

围绕着黔西滇东地区晚二叠世大灭绝后植物的残存与复苏机制这一主题开展了近四年的研究工作，针对项目设计的主研究区（黔西滇东）的7条主干剖面和两大辅助研究区（华北和新疆）开展了10余次野外工作，共采集到植物大化石2580余块，微体化石350余块，地化及岩石样品1500余件。基于上述材料的分析研究，本项目取得以下显著成果：（1）对黔西滇东晚二叠世大灭绝时期的植物化石的形态特征、解剖结构、繁殖器官等进行研究，建立了黔西滇东早三叠世非海相植物化石组合与群落，并分析其生态习性和埋藏特征。（2）结合海陆过渡相和陆相地层中伴生的动物化石（叶肢介、介形虫、双壳等），对比分析华南、华北该时期的海陆过渡相混生生物群的形态学、生态学和埋藏学等特征，指示大灭绝时期非海相生物的生存环境特征；（3）总结华南地区在晚二叠世大灭绝时期的五个植物群属种数量的变化，归纳出华南地区陆地植物在二叠纪-三叠纪之交的灭绝、残存和复苏模式。（4）利用松柏类植物化石保存的角质层进行气孔指数、碳氧同位素分析测试，认为在晚二叠世长兴期至早三叠世印度期古大气CO2浓度在300-500ppm之间，温度为22℃-25℃之间；（5）运用汞元素浓度及同位素限定了华南地区和新疆地区陆相沉积物的火山记录的时限以及来源，认为陆相地层中的火山活动和生物灭绝有很好的对应，同时，火山活动引起陆地风化作用加强对陆地生物和海洋环境的影响不容忽视。（6）从晚二叠世长兴期植物危机期（以宣威及大隆组中华夏植物群分子为典型）、早三叠世最早期植物残存期（以卡以头组底部残存华夏植物群分子与早三叠世机会分子脊囊混生为特征）、早三叠世中晚期植物多样性复苏（代表分子为飞仙关组与岭文组中的裸子植物分子）、早三叠世晚期后植物的数量复苏即全面复苏（巴东组内植物分子延续早三叠世植物群特征且出现二叠-三叠植物危机后的首次煤层）。发表了14篇SCI论文和两篇国内核心及三篇科普文章，培养博士生3名、硕士生3名及博士后2人。

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