urbidites in the Lower Triassic Xikou Formation in Southwestern Fujian, South China

Li Peijun; Hou Quanlin; Li Jiliang; Sun Shu

The sedimentological research on the Lower Triassic Xikou Formation in southwestern Fujiandemonstrated that the rocks are mainly composed of deep-water turbidites, in which 5 facies and 7 sub-facies are recognized on the basis of lithology, textures and structures of the rocks,i.e.(1) conglomeratefacies;(2) sandstone facies;(3) sandstone-mudstone facies;(4) siltstone-mudstone facies;(5) graded siltymudstone facies.These facies consist of 5 facies associations that are formed in upper-fan, mid-fan andlower-fan environments, respectively.According to the characteristics of the turbidites, the turbiditefan in the study area is inferred to an elongate fan which is mainly formed in a stable tectonic setting,such as passive continental margin.Trace fossils contained in the rocks, such as Pasichnia, Grazing traces and some horizontal traces,indicated that they once lived in a bathyal-abyssal environment.The paleocurrent directions derivedfrom the sole marks and cross-beddings are toward to southeast after rotation correction.The spatialdistribution of the facies associations, paleocurrent data and distribution of the trace fossils all suggestedthat the continental slope was once dipped toward to the southeast at that time.The tectonic setting of the sedimentary basin was interpreted as passive continental margin based onthe geochemical composition analysis of the sandstone

1Institute of Remote Sensing and Geographic Information System,Peking University,Beijing,100871,China;

2 Institute of Geology,Chinese Academy of Sciences,Beijing,Beijing,100029,China

Received Date: 1996-09-24

Publish Date: 1997-12-10

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Abstract: The sedimentological research on the Lower Triassic Xikou Formation in southwestern Fujiandemonstrated that the rocks are mainly composed of deep-water turbidites, in which 5 facies and 7 sub-facies are recognized on the basis of lithology, textures and structures of the rocks,i.e.(1) conglomeratefacies;(2) sandstone facies;(3) sandstone-mudstone facies;(4) siltstone-mudstone facies;(5) graded siltymudstone facies.These facies consist of 5 facies associations that are formed in upper-fan, mid-fan andlower-fan environments, respectively.According to the characteristics of the turbidites, the turbiditefan in the study area is inferred to an elongate fan which is mainly formed in a stable tectonic setting,such as passive continental margin.Trace fossils contained in the rocks, such as Pasichnia, Grazing traces and some horizontal traces,indicated that they once lived in a bathyal-abyssal environment.The paleocurrent directions derivedfrom the sole marks and cross-beddings are toward to southeast after rotation correction.The spatialdistribution of the facies associations, paleocurrent data and distribution of the trace fossils all suggestedthat the continental slope was once dipped toward to the southeast at that time.The tectonic setting of the sedimentary basin was interpreted as passive continental margin based onthe geochemical composition analysis of the sandstone

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urbidites in the Lower Triassic Xikou Formation in Southwestern Fujian, South China

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