四川省壤塘县金木达晚三叠世深水沉积中的遗迹化石及沉积环境分析

四川壤塘金木达日基沟晚三叠世地层中首次发现了大量的遗迹化石,经鉴定有 38个遗迹属、6 3个遗迹种。根据不同遗迹属在不同层位的相对丰度,建立了 5个遗迹组合 全部遗迹组合均属于Nereites遗迹相。同时应用遗迹化石的生态习性分类、特征遗迹化石和遗迹相来进行沉积环境的分析,认为金木达晚三叠世中晚期的沉积环境经历了大陆斜坡下部-深海盆地边缘-大陆斜坡中下部-深海盆地-大陆斜坡下部的演变。

Late Triassic Deep Water Trace Fossils and Their Sedimentary Environment in the Jinmuda,Rangtang,Sichuan

The study area,Jinmuda,Rangtang county, Sichuan province is located in the southeast of Aba Mass. During the early period of Late Triassic, deep water detrital sediments, which can be divided into Zhuwo Formation and Xinduqiao Formation, deposited in this area.The area is one part of Songpan-Ganze trough. For the first time,plenty of trace fossils have been discovered in Late Triassic Zhuwo Formation and Xind uqiao Formation in Riji Gully of Jinmuda area. After determination, these trace fossils have been classified into 38 ichnogenera and 63 ichnospecies.Most of them belong to deep water trace fossil. According to their composition, the relative abundance in different stratigraphic horizons and distribution features, five ich- noassemblages have been established, namely (1) Helminthopsis-Paleodictyon ichnoassemblage, (2) Paleodictyon-Neonereites ichnoassemblage, (3) Megagrapton-Imponoglyphus ichnoassemblage, (4) Paleodictyon -Phycosiphon ichnoassemblage, (5) Megagrapton-Helminthoida ichnoassemblage. Based on detailed study it,turns out that all these five ichnoassemblages belong to Nereites ichnofacies.