云南罗平生物群产出层位沉积微相及其化石富集规律

Microfacies and enrichment pattern of fossils in the fossiliferous beds of Luoping Biota,Yunnan Province

云南罗平上石坎剖面是产出罗平生物群的代表性剖面。参考Wilson的标准微相模式,从产化石层位识别出6种沉积微相:灰泥灰岩、生屑粒泥灰岩、粪球粒-生屑泥灰岩、纹层状泥晶灰岩、生屑泥粒灰岩和砾屑灰岩。通过在化石采掘现场对化石富集层位的统计,将产化石层位细分为生物群上层段UFH(Upper Fossil Horizon)和生物群下层段LFH(Lower Fossil Horizon),并进一步探讨了每个层段中沉积微相与化石富集规律的关系,发现化石富集程度高的层段主要发育灰泥灰岩、生屑粒泥灰岩、粪球粒-生屑泥灰岩、纹层状泥晶灰岩等4种沉积微相。这种沉积微相组合主要发育在深水、低能的台内盆地环境中,环境水体的滞留、缺氧给生物埋藏提供了良好的条件。

Shangshikan stratigraphic section in Luoping of Yunnan Province is a representative fossiliferous bed that produced Luoping Biota.According to the standard microfacies model put forward by Wilson（1975）,the authors recognized six types of microfacies,i.e.,marlite,bioclastic wackestone,pelleted-bioclastic marlite,laminated micrite,bioclastic packstone and calcirudite,in the fossiliferous bed of Shangshikan section.The fossiliferous bed can be subdivided into two horizons： the Upper Fossil Horizon（UFH） and the Lower Fossil Horizon（LFH）.The relationship between microfacies and fossil enrichment in each fossiliferous horizon was further studied.The result reveals that four kinds of microfacies are mainly developed in the fossil-enriched horizons,comprising marlite,bioclastic wackestone,pelleted-bioclastic marlite and laminated micrite,whose assemblage always occurs in the deep,low-energy intra-platform basin.The water in this environment implies a high anoxic and retained condition,This study shows that this intra-platform basin is highly anoxic and retained,which is suitable for the preservation of fossils.