华南阿伦尼格世几丁虫生物地层与古生物地理

ARENIGIAN CHITINOZOAN BIOSTRATIGRAPHY AND PALAEOBIOGEOGRAPHY IN SOUTH CHINA

本文系统介绍了湖北宜昌黄花场及浙江常山黄泥塘剖面Arenig统几了虫分布发育规律,指出华南地区Arenig统的几丁虫自下而上可划分为:Conochitina symmetrica,Eremochiti-na baculata, Eremochitina brevis-Conochitina, pirum, Rhabdochitina turgida等生物带.讨论了华南地区这一时期几丁虫的古生物地理特征,认为华南地区在Arenig世早期与北冈瓦纳大区同期几丁虫面貌相似;中晚期则与其它古生物门类一样,更相似于波罗的海板块同期几丁虫组合面貌。

Systematic study of Arenigian chitinozoans, graptolites and conodonts collected from two important Ordovician sections at Huanghuachang, Yichang, W. Hubei, and Huangnitang, Changshan, W. Zhejiang, and correlation with relevant chitinozoans reported from other sections in S. China show that 5 chitinozoan biozones, C. symmetrical E. baculata, E. brevis-C. langei, C. pirum and R. turgida biozones, can be recognized in ascending order. The strati-graphic range of each biozone, its assemblage characteristic and relationship with graptolite and conodont biozones and equivalent chitinozoan biozones in other areas of the world are discussed. It is found that the base of R. turgida biozone basically coincides with the FAD of Undulo-graptus austrodentatus at the Huangnitang section, while the latter has been suggested as a mark to define the base of the revised merged 'Llanvirn-Llandeilo' Series at this boundary stratotype candidate section.In contrast with other benthonic and planktic faunas in S. China, the Early Arenig chitinozoans there, which are characterized by the existence of E. baculata, E. brevis, L. obeligis and J. vulgaris, has a close biogeographical affinity with those on the northern margin of Gond-wana, but the occurrence of large amount of C. cucumis, C. davaherculi and R. turgida in the Middle-Late Arenig strata in S. China, along with a great deal of conodonts, cephalopods, graptolites of cool-water type, indicates a closer biogeographic affinity of South China with the Baltic realm during that time even though a few typical elements such as S. oblonga, of the N. Gond-wana realm were present in the strata. It may be inferred that the South China plate migrated gradually from the middle-low latitudes in the initial Arenig stage to the middle latitudes in the southern hemisphere equivalent to those of the Baltic Sea plate during the Mid-Late Arenig. The occurrence of several chitinozoan elements of the N. Gondwana realm in the S. China plate was likely to be related to the cool currents from south to north.