Paleocommunity Replacements of Benthic Brachiopod in the Middle-Upper Devonian in the Longmenshan Area, Southwestern Chi

Twelve paleocommunities dominated by benthic brachiopod are recognized in the Givetian-Frasnian stages of the Devonian in the Longmenshan area, southwestern China, in which two kinds of brachiopod community replacement are classified. One is the abrupt replacement, represented by abrupt alternation between the Leiorhynchus community and Zhonghuacoelia-Striatopugnax community in the Frasnian Tuqiaozi Formation. The other is the gradual one, developed in the Givetian Guanwushan Formation, which had been completed by the shift of the Independatrypa lemma-Uncinulus heterocostellis-Emanuella takwanensis community via the Sinospongophyllum irregulare-Pseudomicroplasma fongi community to the Clathrocoilona spissa-Hexagonaria composite reef community. According to analyses of the paleocommunities, either the abrupt or gradual paleocommunity replacement of the Middle-Upper Devonian in the Longmenshan area is suggested as a response to the 5th-order sea level fluctuation due to the replacements of the paleocommunities in a tracts-system of depositional sequence. It is supposed that changes of paleocommunity diversity,one of the results of paleocommunity replacement, are depended on the range and magnitude of sea level fluctuation, but there is not a linear relationship between them. Furthermore, a suggestion is proposed that the concept of paleocommunity succession seem to be abandoned in the paleocommunity analysis because it almost never be practiced to recover the information of community succession in the geological record at present.

作 者： Chen Yuanren Li Xianghui   作者單位： Chen Yuanren(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059)

Li Xianghui(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059;State Key Laboratory of Oil-Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059) 

刊 名： 地質學報（英文版）  SCI 英文刊名： ACTA GEOLOGICA SINICA  年，卷(期)： 2005 79(3)  分類號： P5  關鍵詞： community replacement   brachiopod   benthic paleocommunity   sea level fluctuation   Middle Devonian   Upper Deovnian   Longmenshan   Sichuan