Timing of the termination of Sturtian glaciation: SIMS U-Pb zircon dating from South China

Radiometric calibration of the Cryogenian glaciations is critical in understanding the nature of the climatic, geochemical and biological events in the Cryogenian period. However, the timing of termination of the Sturtian glaciation remains unsettled. Here we carried out new SIMS U-Pb zircon dating from two tuff layers at the non-glacial Datangpo Formation at the Jiangjunshan section in Guizhou, South China. The SIMS U-Pb zircon analyses yield U-Pb concordia ages of 659.3 +/- 2.4 Ma and 657.3 +/- 3.2 Ma for the two tuff layers, respectively. The age of 659.3 +/- 2A Ma obtained from the tuff layer occurring at the boundary between Sturtian diamictites and the non-glacial Datangpo Formation is regarded as the best age estimate for the termination of Sturtian glaciation in South China. This new U-Pb age is well consistent with those from the previous studies, suggesting a globally synchronous termination of the Sturtian glaciation at ca. 659 Ma. The onset of the Marinoan glaciation has been estimated to occur at ca. 649 Ma, based on the radiometric age obtained in this study and previous cyclostratigraphic results. Thus it is argued that the Marinoan glaciation was a long-lived glaciation and spanned approximately 14 million years.