High-resolution biostratigraphic and chemostratigraphic data from the Chenjiayuanzi section of the Doushantuo Formation in the Yangtze Gorges area, South China: Implication for subdivision and global correlation of the Ediacaran System

Abstract

Intensive investigations on the Doushantuo Formation of South China have greatly advanced our understanding of the evolution of multicellular life and the atmospheric–oceanic system during the Ediacaran Period. Particularly, the well-established carbon isotope profile and rich acritarch microfossils from the composite carbonate and shale successions of the Yangtze Gorges area provide potential for chronostratigraphic subdivision and global correlation of the Ediacaran System. Here we present high-resolution biostratigraphic and carbon isotope data from a well exposed section: the Chenjiayuanzi section in the Yangtze Gorges area. The bio- and chemostratigraphic data confirm the presence of three distinct negative and two positive δ13C excursions, and two characteristic assemblages of acanthomorphic acritarchs: the lower Tianzhushania spinosa assemblage, and upper Hocosphaeridium scaberfacium – Hocosphaeridium anozos (=Tanarium conoideum Tanarium anozos in Liu et al., 2013) assemblage within the Doushantuo Formation. The results demonstrate the clear stratigraphic relationship between the acritarch assemblages and carbon isotope excursions of the Doushantuo Formation, and that the last occurrence of acanthomorphic acritarchs in the Chenjiayuanzi section represents the last occurrence datum found so far in the Yangtze Gorges of South China. Four stratigraphic markers are suggested here for defining chronostratigraphic boundaries of the Ediacaran System based on bio- and chemostratigraphy combined with intra- and interbasinal correlation. In particular, the base of the most significant and distinctive carbon isotope excursion (DOUNCE) at the top of the Doushantuo Formation, which is equivalent to the Shuram/Wonoka event elsewhere, shows potential to be a marker to define the series (Lower and Upper) boundary of the Ediacaran System, because it also marks the extinction of the Ediacaran acanthomorphic acritarchs.