湖北宜昌黄花场早奥陶世疑源类的新类型

NNEW FORMS OF ACRITARCHS FROM EARLY ORDOVICIAN SEDIMENTS IN YICHANG, HUBEI ,CHINA

该文报道了湖北宜昌黄花场下奥陶统大湾组下段的疑源类（海洋微体浮游植物化石）新类型，描述和建立３新属：Ｐａｐｉｌｌｉｆｅｒｕｍｇｅｎ．ｎｏｖ．，１ｇｅｎ．ｎｏｖ．和Ｙｉｃｈａｎｇｉａｇｅｎ．ｎｏｖ．；２新种：Ｐａｐｉｌｌｉｆｅｒｕｍｉｒｒｅｇｕｌａｒｅｇｅｎ。ｅｔｓｐ．ｎｏｖ．，Ｙｉｃｈａｎｇｉａｂｉｐｏｒｏｓａｇｅｎ；ｅｔｓｐ。ｎｏｖ。及重新修改和组合的３属、种：Ｐａｐｉｌｌｉｆｅｒｕｍｒｈａｂｄｏｃｌａｄｉｕｍ（Ｌｕ）ｃｏｍｂ．ｅｔｅｍｅｎｄ．ｎｏｖ．，Ｐ。ｓｔｒｉａｔｕｍ（Ｌｕ）ｃｏｍｂ．ｅｔｅｍｅｎｄ。ｎｏｖ。和Ｓｔｅｌｏｍｏｒｐｈａｅｒｃｈｕｎｅｎｓｉｓ（Ｆａｎｇ）ｃｏｍｂ；ｅｔｅｍｅｎｄ．ｎｏｖ．这些疑源类新类型目前仅见于我国西南的部分地区的早奥陶世地层。它们为探讨早奥陶世海洋微体浮游植物的区域分布及扬子地台的古地理位置，提供了重要的证据．

The new acritarch forms dealt with in this paper are obtained from the lower part of the lower Ordovician Dawan Formation in Huanghuachang Section of Yichang ,Hubei. Three new genera, Papilliferum gen. nov., Stelomorpha gen. nov. and Yichangia gen. nov., and 2 new species,Papilliferum irregulare gen. et sp. nov. and Yichangia biporosa gen. et sp. nov.,are described. In addition,the diagnoses of three forms, Aremoricanium erchunensis Fang, Gorgonisphaeridium rhabdocladium Lu and G. striatum Lu, reported previously by Fang Xiao-si (1986) and Lu Li-chang (1987)are emended, with the three forms separately combined into Stelomorpha erchunensis (Fang) comb. et emend. nov., Papilliferum rhabdocladium (Lu)comb. et emend. nov. and P. striatum(Lu)comb. et emend. nov.The acritarch assemblage from the lower part of the Dawan Formation indicates their deposition in about the Arenigian period,which is consistent with the time line defined by graptolites, conodonts, etc. Based on the present data,three new acritarch genera are onlyknown from the Early Ordovician sediments of Southwest China. Undoubtedly,they are ofsignificance in discussing the microphytoplanktonic distribution and paleogeographic position of the Yangtze Platform during the Early Ordovician episode.