山东莱阳盆地下白垩统植物化石系统学与古环境研究

The Cretaceous is an important "greenhouse climate" period. During this period, significant changes occurred in the aspects of global environment, climate and vegetation. Accordingly, a comprehensive study on the Cretaceous plant fossils has a constructive meaning for understanding the terrestrial ecosystem, palaeoenvironment and palaeoclimate of this stage. The Laiyang Basin is located on the north side of the Sulu orogenic belt. A set of lacustrine-dominated strata were developed in this area. Abundant plant fossils have been discovered, whereas some of them are poorly studied. This project will carry through a cross-study of morphology, anatomy, geochemistry and mathematical statistics on the fossil plants from the Lower Cretaceous Laiyang Formation. Based on the comprehensive study on the morphological features and microstructures of vegetative and reproductive organs, the fossil plants are accurately identified. The palaeovegetation composition during the strong uplift of the Sulu orogenic belt is ascertained and the ancient vegetation landscape is recovered. In addition, the paleoatmospheric CO2 concentrations of the Early Cretaceous are reconstructed by using the stomatal parameters and stable carbon isotope composition of Coniferopsida plant fossils from Laiyang Formation. The palaeoclimate and the response to the global green-house climate during the Early Cretaceous in the study area are analyzed comprehensively, which has important guiding significance for predicting the trend of global climate change in future.

白垩纪作为重要的“温室气候”时期，全球环境、气候及植物面貌发生了较大地变化。因此，研究白垩纪的植物化石，对全面了解及认识该时期的陆地生态环境具有重要意义。莱阳盆地位于苏鲁造山带北侧，盆地内发育一套以湖相为主的地层，所含植物化石丰富，但研究程度较为薄弱。本项目以该区下白垩统莱阳组的植物化石为研究对象，采用详细的古植物形态学、解剖学、地球化学以及数理统计等多学科交叉的方法，通过对化石植物营养器官和繁殖器官的宏观和微观特征的分析，对化石进行准确的分类鉴定。查明在苏鲁造山带强烈隆升时期，研究区内早白垩世植物群组合特征及古植被面貌。同时利用松柏类植物化石气孔参数以及稳定碳同位素组成，定量重建莱阳盆地早白垩世古大气 CO2 浓度范围，综合探讨莱阳地区早白垩世早期的古气候环境以及对早白垩世全球温室气候的响应，对预测未来全球气候变化的趋势具有重要的指导意义。

早白垩世是全球开始进入典型温室气候的关键时期，全球环境、气候及植物面貌发生了较大地变化。因此，研究早白垩世植物化石，对全面了解及认识该时期的陆地生态环境具有重要意义。本项目以山东莱阳盆地下白垩统莱阳组的植物化石为研究材料，通过形态学和解剖学方法获得植物化石上记录的古环境信息。利用柏科植物Cupressinocladus和掌鳞杉科植物Brachyphyllum 叶片角质层气孔参数，根据气孔比率法、碳同位素模型和光合气体交换模型三种代理方法，对莱阳地区早白垩世Hauterivian–Barremian古大气CO2浓度进行重建。结果表明莱阳盆地早白垩世早期Hauterivian–Barremian大气CO2浓度为 202-1106 ppmv，相对偏低，且在各重建指标恢复的误差范围之内。此外对掌鳞杉科雌性繁殖器官化石Pararaucaria进行了详细的系统发育分析，表明Pararaucaria与Araucaria具有同源性。同时结合掌鳞杉科其他繁殖器官化石记录及地理分布进行分析，得出Pararaucaria可能适应生长于半干旱地区。同时，在项目的支持下，对酒西盆地下白垩统赤金堡组和下沟组孢粉组合进行了详细研究，为开展我国早白垩世气候环境区域性对比具有重要意义。