辽西晚侏罗世义县期植物群性质、时代及气候

迄今为止 ,在辽西义县—北票地区的义县期植物群中 ,已发现有 72个属的近 14 0个种 ,它们分别属于苔藓类、石松类、有节类、真蕨类、苏铁类、本内苏铁类、银杏类、茨康类、松柏类、买麻藤类及被子植物类等 11个类群。根据植物群性质、组合特征、各已知属种的时代分布、群落演替规律以及同期植物群对比 ,表明义县期植物群的时代最可能为晚侏罗世的最晚期。通过植物各大类群的生态及属种成分分析 ,认为义县期植物群应属于欧洲—中国古植物地理区的东亚省。按照无机界 (含化石的沉积层 )及有机界 (植物群本身 )所指示的生存环境 ,可以推测义县期植物群是生长在半干旱至半潮湿或季节性干旱的亚热带或亚热带至暖温带的气候环境中

CHARACTERISTICS, AGE AND CLIMATE OF LATE JURASSIC YIXIANIAN FLORA FROM WESTERN LIAONING

Western Liaoning is one of a few typical areas in China where continental Late Jurassic volcanic rocks are well developed, which have been called Yixian Stage consisting of the Laogonggou Bed, intermediate basic volcanic rocks, Yenangou Bed, intermediate basic volcanic rocks, Zhuanchengzi Bed, intermediate basic volcanic rocks, Dakangbu Bed, intermediate volcanic rocks, Zhujiagou Bed and intermediate acid volcanic rocks (upward),but not including Jingangshan Bed. Excepting that Zhujiagou Bed, all sedimentary interbeds include mostly fossil plants, especially abundant in Zhuanchengzi Bed from Yixian and Jianshangou Bed from Beipiao. The Yixianian flora includes about 140 species belonging to 72 genera. According to the comprehensive study of various groups of plant assemblages and the comparison of identical flora, it seems that the Yixianian flora is probably of Late Jurassic Tithonian age. In general, the Late Jurassic Yixianian flora in Western Liaoning is supposed to be a flora characterized by the xeric conifers of Cherolepidiaceae, Bennettitales and Gnelales, and was growing under seasonal arid or semi arid climate around a lake bank or at the slope of hills near headwaters. The flourishing flora co existed with fauna to form a complete and characteristic Late Jurassic ecosystem with a peculiar Eastern Asia Province aspect of the Euro Sinian Region.