New biostratigraphic and chemostratigraphic data from the Ediacaran Doushantuo Formation in intra-shelf and upper slope facies of the Yangtze platform: Implications for biozonation of acanthomorphic acritarchs in South China
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Carbon isotopic and microfossil records of the Doushantuo Formation in South China provide a valuable window onto major perturbations of the Ediacaran carbon cycle and the evolution of morphologically complex acanthomorphic acritarchs. Both records exhibit significant geographic heterogeneity related to environmental, taphonomic, and diagenetic variations. Absolute δ13Ccarb values vary by as much as 10‰ between sections of the Doushantuo Formation. The geographic and stratigraphic distribution of microfossils in the Doushantuo Formation is controlled by the occurrence of early diagenetic cherts and phosphorites that preserve microfossils. Early diagenetic cherts of the Doushantuo Formation have been investigated extensively at intra-shelf sections around the Huangling anticline but have been poorly documented elsewhere in South China. Here we present new petrographic and micropaleontological data from three Doushantuo sections to the south of the Huangling anticline, including the Wangzishi and Huangjiaping sections representing intra-shelf settings, as well as the Siduping section representing an upper slope setting. We also present δ13Ccarb data from Wangzishi. Petrographic observations indicate that some chert nodules at Siduping were formed in situ, whereas others were reworked and probably transported from the outer shelf along with olistostromes. Integrated lithostratigraphic and chemostratigraphic correlations suggest that the fossiliferous intervals at the three studied sections belong to the lower Doushantuo Formation. The new micropaleontological data extend the geographic range of Ediacaran acanthomorphs and suggest that elements of the Tanarium conoideum–Hocosphaeridium scaberfacium–Hocosphaeridium anozos biozone recognized in the upper Doushantuo Formation around the Huangling anticline, specifically Hocosphaeridium anozos and Urasphaera nupta, are also present in the lower Doushantuo Formation at the Siduping section. The data suggest that the first appearance of Hocosphaeridium anozos may be in the δ13Ccarb chemostratigraphic feature EP1 and it is necessary to revise the acritarch biozonation developed in the Yangtze Gorges area. This study highlights the importance of integrating δ13Ccarb chemostratigraphic and acritarch biostratigraphic data from multiple facies to develop Ediacaran acanthomorph biozonation in South China and beyond. © 2017 Elsevier B.V.
Hawkins, A. D.,
New biostratigraphic and chemostratigraphic data from the Ediacaran Doushantuo Formation in intra-shelf and upper slope facies of the Yangtze platform: Implications for biozonation of acanthomorphic acritarchs in South China.
Precambrian Research, 300