黑龙江依兰始新世植物群的研究

本文报道了黑龙江依兰煤矿早第三系始新统达连河组的上、下两个层位所产的植物化石的区系组成及植物群特征：一个系产于煤层下部的砂页岩中的植物群A，另一个是产于煤层上部油页岩中的植物群B。植物组合共计35科49属52种，其中有蕨类植物2种，裸子植物10种，被子植物40种，其中包括1个新种。对其进行区系成分和叶相分析表明，A段植物群的古植被为北亚热带常绿阔叶和落叶阔叶混生林；B段植物群的古植被为暖温带落叶阔叶林。通过与邻近地区的国内外相应植物群比较及植物群的属种地史分布分析，确定A段植物群的时代为早始新世，B段植物群的时代很可能为晚始新世。两个层位间植物群区系成分的变化，表明始新世我国东北地区发生了较明显的气温下降过程，即古气候发生了由亚热带向暖温带的变化。

A STUDY ON THE EOCENE FLORA IN YILAN COUNTY, HEILONGJIANG

This paper reports the fossil flora in the Yilan Coal Mine, Heilongjiang Province. The Paleogene flora of the Dalianhe formation includes two groups according to their geology column;one (flora A) is from sand-shale above the lower coal seams and the other (flora B) is from oil shale above the upper coal beds. The flora contains two species of pteridophytes, 10 species of gymnosperms and over 40 species of angiosperms including 1 new species and 10 uncertain species, assigned to 49 genera and 35 families. The analysis of the floristic composition and their foliar physiognomy showes that the flora A consists of elements in evergreen broad-leaved and deciduous broad-leaved forests indicating its subtropical feature, whereas the flora B consists of elements in deciduous broad-leaved forests indicating a warm-temperate feature. Compared to the Paleogene floras of Northeastern Asia and North America, the flora A is assigned to the early Eocene, and the flora B to the late Eocene. These results seem to indicate that in the Eocene, paleoclimatic decline took place in Northeast China.