广西中泥盆世腕足动物空间分布及古环境意义

SPATIAL DISTRIBUTION OF MIDDLE DEVONIAN BRACHIOPODS FROM GUANGXI,SOUTH CHINA AND ITS ENVIRONMENTAL IMPLICATIONS

统计广西中泥盆世不同沉积相区二十条剖面的腕足动物化石记录共计13目45科69属167种,其中Eifelian期47属73种,Givetian期32属100种。对不同级别分类单元的多样性分析表明,从Eifelian期到Givetian期,不仅腕足动物各个目的组成及多样性结构有明显改变,而且各个时期不同沉积环境下的腕足动物多样性也有明显差异,主要表现近岸和远岸环境下多样性较低,而浅海碳酸盐岩台地环境多样性较高。该多样性的空间分布特征与通过样本聚类分析识别出的腕足动物分布范围具有显著一致性。这一结果,清晰地表明腕足动物多样性分布与岩相和沉积环境分布存在一定联系。

Middle Devonian brachiopods are widely distributed in Guangxi Province of South China.167 species in 69 genera belonging to 45 families have been recorded in 20 investigated Middle Devonian sections.Biostratigraphically,73 species in 47 genera occur in the Eifelian Stage,and 100 species in 32 genera in the Givetian Stage.Cluster analyses based on the generic data from each locality within these stages indicate that brachiopod diversities and abundance also vary in different depositional environments.The faunas are highly diversified in carbonate shelf environments and are chara-cterized by having a large number of endemic taxa in central Guangxi.In contrast,those brachiopod faunas from clastic,onshore settings in the East and in offshore settings with siliceous lithofacies in West Guangxi have low diversities and are usually dominated by only one or a few genera.The spatial distribution of these different brachiopod associations strongly suggests that brachiopod diversities in the Middle Devonian of Guangxi were related largely to depositional environments.