闽西南地区早三叠世溪口组浊流沉积

闽西南地区的早三叠世溪口组主要由深水浊流沉积组成，可以识别出５个相类型:砾岩相、砂岩相、砂岩－泥岩相、粉砂岩－泥岩相、具粒序的粉砂质泥岩相。它们可组成５个相组合，分别形成于浊积扇的上扇、中扇和下扇环境。相组合的空间展布、古水流以及遗迹化石的分布均一致表明，当时的大陆坡倾向南东。砂岩的地球化学成分反映其构造背景为被动大陆边缘.

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

The sedimentological research on the Lower Triassic Xikou Formation in southwestern Fujian demonstrated that the rocks are mainly composed of deep water turbidites, in which 5 facies and 7 subfacies are recognized on the basis of lithology, textures and structures of the rocks,i.e.(1)conglomerate facies;(2)sandstone facies;(3)sandstone mudstone facies;(4)siltstone mudstone facies;(5)graded silty mudstone facies. These facies consist of 5 facies associations that are formed in upper fan, mid fan and lower fan environments, respectively. According to the characteristics of the turbidites, the turbidite fan 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 derived from the sole marks and cross beddings are toward to southeast after rotation correction. The spatial distribution of the facies associations, paleocurrent data and distribution of the trace fossils all suggested that 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 on the geochemical composition analysis of the sandstone.