江西玉山古城一带早、中奥陶世笔石地层

Early-Middle Ordovician graptolite beds of Guchen, Yushan county, Jiangxi

江西玉山北部古城—带奥陶纪地层剖面完整,化石丰富。其中,早奥陶世宁国组与中奥陶世胡乐组属于深水笔石页岩相沉积,含笔石丰富,是我国笔石序列完整的剖面之一。陈旭、韩乃仁(1964),陈旭、杨达铨(1988)先后做了笔石带的划分工作。 古城陈家坞(印渚埠组顶部至胡乐组)剖面,厚86m。逐层采集化石114层。

The Ordovician sequence at Guchen in Yushan County can be summarized as follows; Middle Ordovi-cian Hule Formation (Dicranograptus sinensis Zone, Ncmagraptus gracilis Zone and Giossograptus hincsii Zone), Lower Ordovician Ningkuo Formation (Didyinagra plus jtangxiemis Zone, Pterograptus clegans Zons, Ntcholsonograptus jasdculatus Zone, Did y mo gr opt us cllesae Zone, Glyptograptus austrodcntatus Zone, Cardiograptus ampins Zone, Oncograptus ma gnus Zone, Isograptus victor tae Zone, Azygograptus sttccicus Zone, Didymograpius dejlcxus Zone, Didymograptus protohijidus Zone, Acrograptus filiformis Zone and Etagraptus approximatus Zone), Lower Ordovician Yinchupu Formation (Adclograptus-Clonograptus Zone).The graptolues of Yushan, belonging biogeograpbically and biostratigraphically to the Jiangnan Region.This graptolite subtype is essentially similar to the Pearl River graptolite subtype, belonging to the graptolite fauna of the Pacific type.Among them important and abundant genera and species are: Tctragrapius jruncosns, Isograptus, Oncograptus, Cardiograptus, Paraglossograptus, Sinograptids Pterograptus etc.In the area neighbouring the graptolite fauna of the Yangtzi subtype, there are often a few elements of the Atlantic type, such as Acrograptus, Dtdymograptus dcflcxus, Azygograptus, Didymograpttts murchisom.Graptolite fauna of this subtype seems 10 be akin to that found in Taimyr (USSR), Argentina, Newfounland and Central-Western Australia, belonging also to graptolite fauna of mixed or transitional-type.