Lower Permian Taiyuan Formation Storm Deposit And Associated Ichnofossils Characteristics In Northwestern Henan And Southeastern Shanxi Area

The Lower Permian Taiyuan Formation is well exposed in Jiaozuo area located in northwest Henan Province and Fucheng area located in southeast Shanxi Province. Based on the detail observation and description of these typical outcrops, microscopic analysis of the tempestites and synthetical research of storm deposit structures, sedimentary sequences and fossil-bearing characteristics, this paper summarizes the composition and distribution law of the storm deposit types associated with ichnofossils in the Lower Permian Taiyuan Formation of this study area, chiefly results have been obtained as follows:(1) Trace fossils were preserved in the carbonate rocks of the lower permian Taiyuan Formation are 11 ichnogenera, including: Zoophycos, Palaeophycus, Nereites, Chondrites, Planolites, Palaeophycus, Helminthopsis, Teichichnus, Rhizocorallium, Thalassinoides, Ophiomorpha and so on.(2) The vertical sedimentary sequences of the Taiyuan Formation storm deposits can be divided into 7 types according to the change characters of lithology and fossils from bottom to top, i. e.,Type I consists of the erosion surface, shelly lags and fine-silty crystal limestone and micrite containing ichnofossil Thalassinoides and Zoophycos;Type Ⅱ is composed of the erosion surface, shelly lags, lamination beds and ichnofossil-bearing fine-silty crystal limestone, common ichnofossils are Palaeophycus and Zoophycos;TypeⅢ is made up of the erosion surface, shelly lags, graded bed and ichnofossil-bearing fine-silty crystal limeston or micrite associated with Planolites and Helminthopsis;TypeⅣ and TypeⅡ are similar in vertical sedimentary sequence, but TypeⅣ contains trace fossils as Ophiomorpha and Rhizocorallium in the limestone layer, so, both difference is very apparent;TypeⅤ is constituted by the erosion surface, shelly lags, lamination beds, strong bioturbated beds and ichnofossil-bearing micrite bed, in which trace fossil common is Zoophycos, and associated with Teichichnus;TypeⅥ consists mainly of the erosion surface, shelly lags and strong bioturbated beds,mostly containing Zoophycos;TypeⅦ is composed of the erosion surface, shelly lags and ichnofossil-bearing micrite layer, which trace fossils are characterized by Chondrites with Nereites.(3) Base on the lithologic characteristics, sedimentary structures, fossil features, sedimentary sequences, the above-mentioned 7 type of storm deposits can be explained to form in the three facies belts, namely, the bay-lagoon(TypeⅠ), intertidal- subtidal shallow(TypeⅡ, TypeⅢ) and subtidal open carbonate platform(TypeⅣ, TypeⅤ, TypeⅥ, Type Ⅶ),meantime, the sedimentary environment model of the storm deposits sequence types in the Taiyuan Formation of this study area was draw out. This result provides the important information of event deposits and ichnofossils to reconstruct the Early Permian palaeogeography and analyze the Early Permian paleoenvironments in Taihang tectonic area.