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在云南省腾冲县上新统芒棒组发现了保存较好的被子植物化石密脉鹅耳枥Carpinus m io-fangianaHu et Chaney。该种化石曾在我国山东山旺组有过报道,当前化石在叶形及叶脉特征上都和山旺的标本非常相似。进一步分析了化石叶片的角质层微细构造特征,并结合叶结构分析提高了对化石植物分类鉴定的准确性。基于化石Carpinusm iofangiana与现生植物Carpinus fangiana在生态环境及其结构特征上的相似性,将Carpinus fangiana作为化石的现生对应种进行对比,并统计二者的气孔密度和气孔指数,用气孔比率的方法推测上新世的大气CO2浓度为464×10-6,基本上与Berner全球碳平衡模型GEOCARB III中CO2浓度变化曲线上的数值一致,说明C.m iofangiana叶片可以作为古大气CO2浓度变化的生物指标。最后通过化石和现生叶片角质层的对比分析推断滇西地区上新世时气候比现在温暖湿润。
Carpinus m io-fangiana Hu Cha et al., A well-preserved angiosperm fossil carinius, was found in the Upper Xuanmangbang Formation in Tengchong County, Yunnan Province. This kind of fossil was reported in Shandong Shanwang Formation in Shandong Province. At present, the fossils are very similar to the specimens of Shanwang in leaf shape and vein characteristics. The microstructural features of the stratum corneum of fossil leaves were further analyzed, and the accuracy of classification and identification of fossil plants was improved by combining the leaf structure analysis. Based on the similar ecological and structural characteristics of the carpinus fangiana and the carpinus fangiana, Carpinus fangiana was used as a living fossil of fossils, and the stomatal density and stomatal index of both were calculated. The stomatal ratio The results suggest that the atmospheric CO2 concentration in the Pliocene was 464 × 10-6, which is basically consistent with that on the CO2 concentration curve of Berner’s global carbon balance model GEOCARB III, which indicates that Cm iofangiana can be used as a biological indicator of CO2 concentration in paleoenvironment . Finally, the comparative analysis of the stratum fission of fossils and present-day leaves suggests that the climate is warm and humid in the Pliocene in western Yunnan.