The Zitai Formation in South China: unique deeper-water marine red beds in terms of lithology, distribution and δ13Ccarb chemostratigraphy

Abstract

During the EarlyöMiddle Ordovician characteristic red carbonate beds, i.e., the Zitai Formation and its coeval units, developed in the deeper-water marine setting of the Yangtze Platform, South China. The temporal and spatial distribution of these reddish limestones is discussed based on published data and our own observations and analyses. The red limestones formed along the margin of the Yangtze Platform on a carbonate ramp during six stages. The different stages, (0) early Fl3 and before, (1) middle to late Fl3, (2) early Dp1, (3) middle to late Dp1, (4) Dp2, and (5) Dp3 to early Dw1, are associated with regional sea-level changes and tectonic movements. Several positive shifts in the δ13Ccarb record occur in the succession beneath the red beds. Their formation presumably was induced by a global transgression in association with the drowning of the Yangtze Platform. Better ventilation and oxygenation of sediments on the platform are also indicated by the marine red beds and together intensified the Great Ordovician Biodiversification Event. Other factors such as iron presumably play a significant role in controlling occurrences and distribution of the red limestone beds.