The Sedimentary Characters And Carbon Isotope Chemostratigraphy Of The Gaojiashan Biota In Southern Shaanxi, China

The Ediacaran Biota, known as the earliest and reliable metazoan, provids indispensable evidence for the study of early life. The Gaojiashan biota is of the Late Ediacaran in age and typically yields Nama-type fossils, and differs a great deal with the word-wide Ediacaran-type biotas in taphonomic feature. Therefore, the study of sedimentary environment of the Gaojiashan Biota can provide new clues and perspectives for the taphonomy of Ediacaran-type biotas. Unfortunately, biostratigraphy, a principle tool for subdivision and correlation of richly fossiliferous Phanerozoic strata, is of limited usefulness in developing a global time scale for the Ediacaran System, the difficulties being related to the low species diversity, taxonomic uncertainty, and the sporadic and endemic palaeogeographic distribution of Ediacaran fossils. Thus, a critical task of establishing a high resolution, globally applicable Ediacaran chemostratigraphy has become the primary objective of the International Subcommission on Neoproterozoic Stratigraphy of the ICS. However, chemostratigraphy of the Gaojiashan Biota is of relatively weak and still waiting to be corroborated.The purpose of this paper, therefore, will focus on the sedimentary facies and paleoenvironment as well as carbon isotope stratigraphy of the Gaojiasha Biota, with particular references to the sedimentary, petrological (8 reference sections) andδ¹³C chemostratigraphy correlation of different sections (19 reference sections) in South China. The sedimentary environments of the Gaojiashan Biota are elaborated mainly based on the different features of storm deposits. A compositeδ¹³C profile of the Dengying Formation in South China is provided and carbon isotopic oscillations from Gaojiashan section are correlated with the reference curves for South China. In addition, Small Shell Fossils from the Early Cambiran Kuanchuanpu Formation are rectified, including 14 genuses, 22 species, and two sedimentary models of the Kuanchuanpu Biota are reconstructed.