SHRIMPIIU-Pb Zircon Date from the Nanhuan Datangpo Formation in Songtao County, Guizhou Province

Abstract

The reported new U-Pb age by sensitive high-resolution ion microprobe on zircon (SHRIMP II) was obtained from a tuff sample at the basal Datangpo Formation in the Hishuixi manganese ore in Songtao County, Guizhou Province, South China. Twenty-four spots of zircons were analyzed and a weighted mean 206Pb/ 238U age of 667.3±9.9 Ma (MSWD=1.6) was given. This age is quite similar to that reported in Geology by Zhou Chuanming et al., which gives a U-Pb zircon age of 662.9±4.3 Ma (MSWD=1.24) from a tuffaceous bed in the lower part of the Datangpo Formation at the Zhailanggou section, Songtao County (Chuanming Zhou et al., 2004). Both of them form a robust age constraint on the timing of the Datangpo interglacial period. It also provides a maximum age constraint for the Nantuo (Mrinoan) glaciation. Together with other new isotopic ages in recent years, the new age suggests that the Nantuo glaciation is equivalent to the Mrinoan glaciation, which occurred at 660～630 Ma and the earlier glaciation is equivalent to the Sturtian glaciation, which occurred at 750～670 Ma.