Formation conditions of Ediacaran–Cambrian cherts in South China: Implications for marine redox conditions and paleoecology

•The cherts in the slope and basin setting were strongly affected by hydrothermal activities.•The oxygen isotope value of paleo-seawater was assessed during the early Cambrian.•The paleo-seawater temperature presented an obvious gradient trend in South China.•There existed an oxygen minimum zone (OMZ) during the shelf and slope transition.•Biological reproduction was closely related to seawater temperature and oxic environment.