大兴安岭中段晚二叠世林西组介形虫化石及环境意义

晚二叠世-中三叠世在中亚造山带东段构造演化过程中是承上启下的关键地质时期，所以晚二叠世林西组沉积环境对研究古亚洲洋闭合这一重大问题具有重要意义。大兴安岭地区晚二叠世林西组曾有双壳、叶肢介、植物及孢粉化石记录，但鲜有介形虫化石报道。在大兴安岭中段林西组研究中首次发现介形虫化石，经初步研究，主要分子有Kemeroviana，Volganella，Iniella，Qitaina，Darwinuloides，Palaeocypridopsis，Tomiella，Darwinula和Urumqiella等，暂划为Volganella-Kemeroviana组合，其时代为晚二叠世。与俄罗斯地台晚二叠世介形虫化石群关系较为密切，部分属种曾见于我国新疆准噶尔盆地和塔里木盆地。从介形虫化石组合特征和保存特点来看，其生存环境为淡水湖泊，故认为这一地区的林西组为陆相沉积。

New Discovery of Ostracods of Upper Permian Linxi Formation in Central Da Hinggan Mountains and Its Significance

The Late Permian to Middle Triassic is an important tectonic evolution period in the eastern segment of the Central Asia orogenic belt, which is related to the final closure of the Paleo-Asian Ocean and the sharp changes of the sedimentary environment. The well exposed Upper Permian Linxi Formation recorded the evolution history of the Da Hinggan Mountains. The fossils, including sporopollen, conchostracan, bivalves, and megaplants, are found in the Upper Permian Linxi Formation in the southern Da Hinggan Mountains, however only bivalves and a few megaplants are found in the central Da Hinggan Mountains. A total of nine genera ostracods Kemeroviana,Volganella,Iniella,Qitaina,Darwinuloides,Palaeocypridopsis,Tomiella,Darwinula and Urumqiella are found for the first time in the central Da Hinggan Mountains. The paleo-zoogeography of the ostracods assemblage is closely related to those Late Permian ostracods assemblages, which are widely distributed in Russian platform. The evidences of the fossil assemblages and their preservation suggest that Linxi Formation was deposited in a continental lacustrine environment.