Fossil Record 18(2): 105-117, doi: 10.5194/fr-18-105-2015
Chemo- and biostratigraphy of the Gaojiashan section (northern Yangtze platform, South China): a new Pc-C boundary section
expand article infoA. Gamper, U. Struck, F. Ohnemueller§, C. Heubeck|, S. Hohl
‡ Museum für Naturkunde Berlin, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany§ Department of Geosciences and MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str., 28359 Bremen, Germany| Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74–100, 12249 Berlin, Germany¶ Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74-100, 12249 Berlin, Germany
Open Access
Abstract
The widespread, terminal Ediacaran Dengying Formation (~ 551–~ 542 Ma)of South China hosts one of the most prominentnegative carbonate carbon isotope excursions in Earth's history and thusbears on the correlation of the Precambrian–Cambrian boundary worldwide. Thedominantly carbonate strata of the Dengying Formation are largely studiedfor their unique preservation of its terminal Ediacaran fauna but theirgeochemical context is poorly known. This study presents the firsthigh-resolution stable isotope record (δ13C, δ18O)of calcareous siliciclastic shallow-water deposits of theGaojiashan section (Shaanxi Province). The section includes (in ascendingorder) the Algal Dolomite Member, the Gaojiashan Member and the BeiwanMember of the Dengying Formation. Our data record a major δ13Ccarb negative excursion to −6 ‰ in theuppermost Gaojiashan Member which is comparable in shape and magnitude tothe global Precambrian–Cambrian boundary negative δ13Cexcursion. Our data set is consistent with a "shallow-water anoxia"scenario which is thought to contribute to the "Cambrian explosion". Thestratigraphic occurrence of Cloudina and a large negative δ13Cexcursion suggest that the Precambrian–Cambrian boundary is located near thetop of the Gaojiashan Member and, consequently, that overlying carbonatesand dolomites of the Beiwan Member are of earliest Cambrian age. Thus theGaojiashan section may represent a new shallow-water section spanning thePrecambrian–Cambrian boundary. Although bio- and chemostratigraphic datasupport this novel interpretation, we cannot exclude the possibility that thekey excursions may represent a local perturbation indicating arestricted-basin environment.