鄂尔多斯盆地早-中侏罗世植物多样性演替及古气候演变

Early-Middle Jurassic (Toarcian to Aalenian-Bajocian) was the time of significant change of global palaeoclimate. Studing plant diversity succession and climatic evolution during this period will provide reference for us to understand the climate today and predict future climate change. The Ordos Basin consists of a continuous and well-exposed Early-Middle Jurassic strata (Fuxian and Yan’an Formation). The Early-Middle Jurassic strata which contains major fossil-bearing beds and diverse fossil plants is a natural archives for studying the Early-Middle Jurassic plant diversity succession and climatic evolution. Further study based upon phytomorphology and phytoanatomy of Early-Middle Jurassic fossil plants can greatly contribute to understand their systematic position. On this basis, statistical analysis (e.g., Floral Gradient and Rarefaction) will be applied in order to summarize the Early-Middle Jurassic plant diversity succession on the high precision stratigraphic framework. Along with consideration the global climate change of warming to cooling during the Early-Middle Jurassic period, the responses of plants to the climate change will be summarized. Meanwhile, this work will provide a detail palaeobotanic evidence for the reconstruction of palaeoclimate and help studying the co-evolution between plant and environment during the Jurassic.

早-中侏罗世（Toarcian期到Aalenian-Bajocian期）全球气候发生重大变化，研究该时期植物多样性演替及古气候演变为我们了解现在和推测未来气候变化提供科学依据。鄂尔多斯盆地早-中侏罗世地层（富县组和延安组）沉积连续，序列清晰，化石层较多，植物多样性丰富，是研究植物多样性演替和气候演变的天然档案馆。本项研究拟对该地区早-中侏罗世植物化石开展形态学和解剖学相结合的系统分类学研究，精确植物化石系统分类位置；运用“植物群梯度”（Floral Gradient）和“稀疏分析”（Rarefaction）等统计分析方法，结合高精度地层框架，查明植物类群纵向上多样性演替规律；结合早-中侏罗世全球由热变凉的气候变化背景，揭示该地区植物对全球气候变化的响应。该项研究不仅为研究区侏罗纪古气候重建提供详实的古植物学证据，而且为研究该地质时期植物与环境的协同演化关系提供重要科学依据。

早-中侏罗世全球气候发生重大变化，陆地生态系统如何响应仍不清楚。鄂尔多斯盆地早-中侏罗世地层连续，植物化石丰富，是研究该科学问题的天然档案馆。本项目综合运用地层学、古植物学、统计分析学在鄂尔多斯盆地富县组-延安组的连续剖面上开展早-中侏罗世植物多样性演替与古气候演变研究。结果表明：1）富县组植物化石20属28种，延安组植物化石26属40种，主要由苔藓类、石松类、楔叶类、真蕨类、种子蕨类、苏铁类、银杏类、茨康类和松柏类组成。2）早侏罗世晚期富县组植物群真蕨纲和银杏纲大量减少，含双扇蕨科和马通蕨科等喜热植物；而中侏罗世早期延安组植物群真蕨纲和银杏纲繁盛，松柏纲无具鳞状叶分子，含苔类植物。富县组孢粉植物群以裸子植物花粉占优势，蕨类植物孢子次之，含丰富的Classopollis为特点，而延安组孢粉植物群以蕨类植物孢子含量为主，裸子植物花粉次之，Classopollis含量大量降低为特点。3）运用银杏类植物化石气孔参数法参数法恢复中侏罗世古大气CO2浓度为939±99ppmv，高于现代大气CO2浓度，低于侏罗纪其它时期，代表该时期变得更为温凉。4）富县组植物群（含孢粉）代表了炎热干旱气候而延安组植物群（含孢粉）代表了温暖湿润气候，体现了研究区植物化石对早-中侏罗世全球由热变凉气候变化的响应。