台湾地区上下第三系界线划分的孢粉学证据

PHOSPHATIC STROMATOLITE BIOHERMS AND ASSOCIATED MICROBIAL FOSSILS FROM THE SINIAN DOUSHANTUO FORMATION, CENTRAL GUIZHOU,SOUTH CHINA

通过对台湾中部南投县国姓地区北港溪剖面的孢粉样品分析，结合已有的台湾北部基隆地区万里－大武仑露头剖面的孢粉资料，认为台湾地区上下第三系界线置于炭寮地层与十四股层（南投）或公馆凝灰岩与木山层（基隆）之间较为合理。其孢粉组合特征，反映出古气候由晚渐新世以含桤木粉松粉孢粉组合为特征的寒冷潮湿的北亚热带型向早中新世以含榆科栎属孢粉组合为特征的温暖湿润的南亚热带型过渡趋势。由于南海北部大陆架北坡的珠海组、涠洲组、陵水组和尚村组孢粉组合均以含有丰富（或显著）的桤木粉Ａｌｎｉｐｏｌｅｎｉｔｅｓ和松粉Ｐｉｎｕｓｐｏｌｅｎｉｔｅｓ为主要特征。

The phosphate bearing strata containing phosphatic stromatolite bioherms of the Sinian Doushantuo Formation are mainly distributed in Wenquan,Shabatu and Maluping mining areas of central Guizhou.In these bioherms,there are numerous columnar stromatolites which can be classified into three forms,namely, Gymnosolen sp., Inzeria sp.and an unnamed form.These phosphatic stromatolites often contain abundant well preserved microfossils and small numbers of microfossil like objects.Each morphologically distinct stromatolite form was found to have a unique microbial composition or stromatolite microcommunitie.The present data suggest the existence of different small scale environmental conditions in three mining areas during formation of stromatolite bioherms.Environmental fluctuation may well have affected the composition of microcommunities.Changes in microfossils within phosphatic stromatolites possibly reflect changes in the original microcommunities,and in some instances,such changes happened to have taken place simultaneously with changes in environment and gross morphology of individul stromatolites.