A new SIMS zircon U–Pb date from the Ediacaran Doushantuo Formation: age constraint on the Weng'an biota

• Published in: Geological magazine Vol. 154; no. 6; pp. 1193 - 1201
• Main Authors: ZHOU, CHUANMING, LI, XIAN-HUA, XIAO, SHUHAI, LAN, ZHONGWU, OUYANG, QING, GUAN, CHENGGUO, CHEN, ZHE
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.11.2017
• Subjects: absolute age; Acanthomorpha; acritarchs; Algae; Asia; biostratigraphy; Biota; China; correlation; dates; Doushantuo Formation; Ecosystems; Ediacaran; Eukaryotes; Far East; Fossils; Geochronology; Geochronometry; Geologists; Geology; Glaciation; Glaciology; Hubei China; ion probe data; Lagerstatten; Lead; lithostratigraphy; mass spectra; microfossils; Microorganisms; Neoproterozoic; nesosilicates; Original Articles; orthosilicates; Paleontology; palynomorphs; phosphatization; Phosphorite; Precambrian; problematic fossils; problematic microfossils; Proterozoic; Radiometric dating; sedimentary rocks; silicates; Sinian; spectra; Stratigraphy; Thalli; U/Pb; upper Precambrian; Weng'an biota; Yichang China; Zhangcunping China; Zircon; zircon group; China; Zhangcunping; lithostratigraphic and biostratigraphic correlation; phosphatized Lagerstätte; tuffaceous bed; South China
• ISSN: 0016-7568; 1469-5081
• DOI: 10.1017/S0016756816001175

As a well-known phosphatized Lagerstätte, the Ediacaran Weng'an biota in central Guizhou Province of South China contains diverse acanthomorphic acritarchs, algal thalli, tubular microfossils as well as various spheroidal fossils. These fossils provide crucial palaeontological evidence for the radiation of multicellular eukaryotes after the termination of the Neoproterozoic global glaciation. While the Weng'an biota is generally considered as early Ediacaran in age on the basis of phosphorite Pb–Pb isochron ages ranging from 572 Ma to 599 Ma, the reliability and accuracy of these age data have been questioned and some geologists have proposed that the Weng'an biota may be younger than 580 Ma instead. Here we report a SIMS zircon U–Pb age of 609 ± 5 Ma for a tuffaceous bed immediately above the upper phosphorite unit in the Doushantuo Formation at Zhangcunping, Yichang, South China. Litho-, bio- and chemostratigraphic correlations suggest that the upper phosphorite unit at Zhangcunping can be well correlated with the upper phosphorite unit at Weng'an, which is the main horizon of the Weng'an biota. We therefore conclude that the Weng'an biota could be as old as 609 ± 5 Ma.