【作者】 吴靖宇；

【导师】 王永栋； 孙柏年；

【作者基本信息】 兰州大学 ， 古生物学与地层学， 2009， 博士

【摘要】 滇西地处横断山系的南部、青藏高原的东南缘，新近纪以来受喜马拉雅强烈构造运动的影响，形成了复杂的地形地貌、独特的植被景观和立体的气候特征。滇西地区不仅拥有复杂的植被类型和丰富的植物资源，而且是我国乃至全球新生代植物化石保存最好的地区之一。研究滇西地区的新生代植物，尤其是新近纪植物的发展和演化，不仅可以为了解我国植物的多样性提供资料，而且可以从中提取古气候、古环境数据，进而为研究青藏高原隆升时期的气候环境演变提供古植物学证据。本文通过叶结构与角质层微细构造特征相结合，对腾冲地区团田盆地上新世芒棒组植物化石进行了分类鉴定。目前鉴定的化石植物共有：裸子植物1科1属1种，被子植物化石20科28属36种。从植物的组合面貌来看，团田植物群以盛产大型常绿阔叶植物为主，气候类型为热带至亚热带气候。解剖学和同位素地球化学研究表明，叶片面积、表皮细胞壁的弯曲程度等形态特征，气孔密度、气孔指数以及角质层的δ¹³C值可以用于辨别化石植物叶片的古生态类型。化石和现生植物的表皮和碳同位素特征显示，金缕梅科马蹄荷属（Exbucklandia）植物的阴叶相对于阳叶有以下特点：较大的叶片面积、较弯曲的表皮细胞壁、较小的气孔密度和气孔指数，以及较低的δ¹³C值等特征；此外，阳叶具有优先保存为化石的埋藏学特点。通过气孔比率法重建地史时期的大气CO₂浓度，是当前古植物学领域的重要课题。本文利用10种化石植物及其现存最近亲缘种的气孔比率，恢复出团田晚上新世的古大气CO₂浓度值在387.5-466.5 ppmv之间，平均值为433.4 ppmv，明显较当前的水平要高。通过共存因子分析法，取团田植物群37个化石种的最近亲缘种的气候因子的共存区间，定量重建了团田晚上新世的古气候特征：年均温为16.4-19.8℃，最热月平均气温21.3-25.1℃，最冷月平均气温10.8-14.6℃，气温年较差11.3-16.3℃，年均降水量1225.7-1638.3 mm，年均相对湿度75-82％。同时对腾冲中新世南林组、剑川中新世双河组以及洱源晚上新世三营组三个植物群的植物大化石进行了古气候共存分析，并与团田晚上新世植物群古气候数据进行了对比。结果表明，滇西地区新近纪以来的古气候演变存在以下趋势：中新世至晚上新世，滇西地区的古气候条件基本未变，或仅有微小变化；晚上新世之后，腾冲以及洱源地区气温下降幅度均较大，气候迅速变冷。更多还原

【Abstract】 West Yunnan lies in the South of Hengduan Mountains and Southeast edge of theQinghai-Tibetan Plateau. It has been affected by the Himalayan tectonic movement sincethe Neogene, which has formed a complicated physiognomy, peculiar vegetation andtridimensional climate. The various vegetation conditions, abundant modern plantresources and plentiful Cenozoic fossil plants of West Yunnan can provide us goodmaterials for the studies of the plant diversity and paleoenvironmental evolvement. What isremarkable that the Neogene fossil plants from West Yunnan will greatly help us tounderstand the uplift and paleoclimatic evolvement of the Qinghai-Tibet Plateau.The combination of the leaf architectural and cuticular characters, will improve thereliability of the identification of fossil plants. Based on leaf architecture and cuticularanalysis, 1 gymnosperm species and total 36 angiosperm species which belong to 20families and 28 genera have been identified from the Pliocene Mangbang Formation ofTuantian Basin. The plant fossil assemblage shows that the Pliocene Tuantian flora ismainly composed of evergreen broad-leaved trees and living under a tropical or subtropicalclimatic condition.The evidences of anatomy and isotope geochemistry have proved that the leaf area,undulated degree of epidermal cell anticline, stomatal density and stomatal index, andδ¹³Cvalue can be regard as good indicators for the distinguish of sun and shade morphotypes offossil leaves. The cuticular and carbon isotope characters of fossil and modern leaves ofExbucklandia （Hamamelidaceae） show that the shade ecotype leaves usually possessbigger laminas, more undulated epidermal cell anticlines, and lower stomatal density,stomatal index andδ¹³C values. In addition, the present study also indicates that the sunleaves usually tend to be fossilized preferentially relative to the shade ecotypes.Reconstruct the paleoatmospheric CO₂ concentration of the geological history is animportance issue for palaeobotanical and paleoenvironmental research. In present study,the method of Stomatal Ratio on the 10 fossil plant species from the Pliocene Tuantianflora and their nearest living relatives are utilized to reconstruct the paleoatmospheric CO₂ concentration. The values of paleoatmospheric CO₂ concentration during the Late Pliocenein Tuantian Basin is range of 387.5-466.5 ppmv, and the mean value is 433.4 ppmv, whichis evidently higher than that of current levels.The paleoclimatic parameters were quantitatively reconstructed based on theCoexistence Approach of the NLRs of 37 fossil species from Tuantian flora. The resultsshow that the Pliocene paleoclimate of Tuantian Basin is characterized by the mean annualtemperature （MAT） 21.3-25.1℃, mean temperature of the warmest month （WMT）21.3-25.1℃, mean temperature of the coldest month （CMT） 10.8-14.6℃, difference intemperature between the coldest and warmest month （DT） 11.3-16.3℃, mean annualprecipitation （MAP） 1225.7-1638.3 mm, and relative humidity （RH） 75-82%. Thepaleoclimates of the Miocene Nanlin Formation of Tengchong, Miocene ShuangheFormation of Jianchuan and Pliocene Sanying Formation of Eryuan were as well asanalyzed by the Coexistence Approach. Comparing the paleoclimatic data of thesemacrofossil floras, the conclusion can be inferred that the areas of West Yunnan had notoccurred remarkable climatic changes from the Miocene to Late Pliocene, however, thetemperatures of Tengchong and Eryuan had declined quickly since the Late Pliocene.更多还原