【作者】 张鹏；

【导师】 解三平；

【作者基本信息】 兰州大学 ， 地质学， 2022， 硕士

【摘要】 青藏高原作为北半球新生代植物区系成分交换的十字路口,一直以来是古生物和古气候研究的热点地区。在前人对青藏高原东北缘动植物化石研究的基础上,本文对产自高原东北缘乌兰盆地中新统油砂山组木贼及腹足化石开展了研究,并探讨了它们的地质意义。通过当前化石标本与现生类群和相关化石在形态上的综合对比研究,本文共鉴定和描述了动植物化石3属4新种。木贼化石共鉴定出1属2新种:乌兰木贼(Equisetum wulanensis Zhang et Xie sp.nov.)和柯柯木贼(Equisetum kekeensis Zhang et Xie sp.nov.)。腹足化石共计鉴定出2属2新种:海西旋螺(Gyraulus haixiensis Zhang et Xie sp.nov.)和圆锥钻螺(Opeas conicus Zhang et Xie sp.nov.)。本文木贼块茎化石为该类群在乌兰盆地中新统的首次发现。结合已发现的木贼块茎化石,本文对地质历史时期的木贼块茎化石记录进行归纳总结,其形态学演化规律为:从白垩纪至今,木贼块茎形态种类趋于减少和单一。对木贼单个节上块茎体积及表面积进行统计,其规律为:白垩纪至渐新世、中新世再至现今,块茎体积及表面积经历先变大后变小的过程。对旋螺属及钻螺属的化石记录进行统计,探讨其生物地理学意义。对木贼及腹足绘制出复原素描图,以恢复其在地质历史时期的形态。对乌兰植物群植物化石的现存最近亲缘种进行共存分析,重建乌兰盆地中新世古海拔,结果为:乌兰盆地中新世古海拔不超过1680 m;并重建乌兰盆地中新世古气候,结果为:乌兰盆地中新世年平均气温为13.3-19.1℃,最热月均温为22.2-23.7℃,最冷月均温为3.6-10.0℃,年平均降水量为999-1736 mm。各项数据均比乌兰现代数据要高,表明乌兰地区中新世时期为温暖湿润的亚热带气候,与现今乌兰寒冷干旱的环境截然不同。究其原因,可能是鄂拉山脉抬升、新生代全球气候变冷和青藏高原隆升共同作用的结果。本文最后结合化石证据,对乌兰盆地中新世古生态环境进行了恢复,恢复后的乌兰盆地中新世古生态环境为动植物种类繁多、气候温暖湿润的亚热带气候。更多还原

【Abstract】 As the Cenozoic crossroads of floristic component exchange in the Northern Hemisphere,the Qinghai-Tibet Plateau has become a hottest region in the study of paleontology and paleoclimate.On the basis of previous studies on animal and plant fossils in the northeast margin of the QinghaiTibet Plateau,this paper studies the Equisetum and gastropod fossils from the Miocene Youshashan Formation in the Wulan basin in the northeast margin of the plateau,and discusses their geological significance.Through the comprehensive comparative study on the morphology of current fossil specimens,living groups and related fossils,the animal and plant fossils identified in this paper belong to 3 genera and 4 new species.There are 1 genus and 2 new species of Equisetum-wulanensis Zhang et Xie sp.nov.and Equisetum kekeensis Zhang et Xie sp.nov.Two genera and two new species were identified in Gastropoda,which are Gyralus haixiensis Zhang et Xie sp.nov.and Opeas conicus Zhang et Xie sp.nov.The tuber fossils in this paper are representative of the first occurrence of Equisetum from the Miocene of the Wulan basin so far.The fossil records of Equisetum tubers in the geological historical period are summarized and illustrated.It is found that the morphological types of Equisetum tubers tend to be reduced from the Cretaceous to the present.The statistics of tuber volume and surface area on a single node of Equisetum are as follows: from Cretaceous via Oligocene and Miocene to now,the tuber volume and surface area experienced the process of first increasing and then decreasing.This paper also investigates on the fossil records of Spirulina and Spirulina,and discusses their biogeographic significance.On the basis of fossil materials,the sketches of Miocene Equisetum and gastropods are reconstructed.Based on the coexistence analysis of the Nearest living Relatives of angiosperms in Wulan flora,the Miocene paleoelevation of Wulan basin is reconstructed,and the result is that the Miocene paleoelevation of Wulan basin does not exceed 1680 m;the Miocene paleoclimate in Wulan basin is reconstructed as follows: the annual average temperature is 13.3-19.1 ℃,the average temperature in the hottest month is 22.2-23.7 ℃,the average temperature in the coldest month is 3.6-10.0 ℃,and the annual average precipitation is 999-1736 mm.This data is much higher than the modern corresponding parameters of the Wulan Basin,indicating a warm and humid subtropical climate in Wulan area during Miocene,which is in contrast to the cold and arid environment in Wulan today.The contrasting climates may be as a synactic result of the global cooling,uplift of ELA mountainsand and the uplift of the Qinghai-Tibet Plateau in the Cenozoic.Finally,combined with fossil evidence,the scenario of Miocene paleoecological environment in the Wulan basin is figured out.The restored Miocene paleoecological environment of Wulan basin is a subtropical climate with a wide variety of animals and plants and a warm and humid climate.更多还原