First SHRIMP Zircon U-Pb Dating Constraints for the Ediacaran Wenghui Biota

The Ediacaran Period records a significant turning point in the evolution of life on Earth, witnessing the rise to ecological dominance of macroscopic tissue-grade organisms. The Wenghui biota from the Doushantuo Formation of South China hosts abundant multicellular algal macrofossils and problematica, some of which might be closely related to taxa from classic Late Ediacaran assemblages from South Australia and the White Sea biota of Russia. However, a lack of well-resolved isotopic age estimates has hampered efforts to constrain the timing of appearance of the Wenghui biota, obfuscating its significance to our understanding of Ediacaran macroevolution in the aftermath of the Snowball Earth events. Here, we present the first SHRIMP zircon U-Pb dating results for samples obtained from a laminated tuff ash layer at the base of the Wenghui biota in the Doushantuo Formation, Jiangkou County, Tongren City, Guizhou Province, China. Our analyses yield an age of 595.4 ± 5.3 Ma for the first appearance of Wenghui biota, suggesting that its appearance postdated that of the Lantian and Weng ' an biotas, but preceded that of the Miaohe biota.These newly obtained age proxies offer an independent test of previous isotopic estimates for the age of the Wenghui biota, providing new chronostratigraphic evidence to map the succession of Ediacaran fossil assemblages on the Yangtze Platform during the Doushantuo interval. These data suggest that the Lantian, Weng ' an, Wenghui, and Miaohe biotas may record a sequence of biotic assemblages attesting to successive phases in the radiation of Ediacaran macroscopic organisms,particularly macroalgae.