Paired 未³⁴S data from carbonate-associated sulfate and chromium-reducible sulfur across the traditional Lower-Middle Cambrian boundary of W-Gondwana

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• 作者：Thomas Wotte^a ; ^{thomas.wotte@uni-muenster.de} ; Harald Strauss^a ; Artur Fugmann^a ; Dieter Garbe-Sch&ouml ; nberg^b
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2012
• 期刊代码：27_00167037
• 类别：ear
• 出版时间：15 May, 2012
• 卷：85
• 期：Complete
• 页码：228-253
• 文件大小：2143 K

摘要

In this study, we present the first high-resolution data from coupled 未³⁴S analyses of carbonate-associated sulfate (CAS) and chromium-reducible sulfur (CRS) from three Lower-Middle Cambrian sections in western Gondwana. CAS and CRS were extracted and analyzed from marine dolostone, limestone, and nodular limestone from Spanish and French successions. In parallel, carbonate samples were also analyzed for 未¹³Cb>carbb>, 未¹⁸Ob>carbb>, and major/trace element concentrations (Ca, Fe, Mg, Mn, Sr). 未³⁴Sb>CASb> values vary between 17.6鈥?and 33.2鈥? with a maximum CAS concentration of ca. 900 ppm. 未³⁴Sb>CRSb> data show a similar broad range between 鈭?.1鈥?and 29.7鈥? with maximal CRS contents up to ca. 3700 ppm. Notably, there is little stratigraphic variation in the 未³⁴Sb>CASb> data in each of the sections confounding inter-basinal chemostratigraphic correlations. Nonetheless, the absolute differences in 未³⁴Sb>CASb> between sections as well as variations in CAS and CRS concentrations are attributed to paleoenvironmental differences between proximal and distal parts of the carbonate ramp, as well as effects of subaerial exposure and riverine input. Thus, the generated 未³⁴Sb>CASb> data deliver not only valuable paleoecological and paleoenvironmental information, they also illustrate a heterogeneity in the seawater sulfate sulfur isotopic composition of the western Gondwanan ocean. Consequently, the lack of correlation between our Gondwanan 未³⁴Sb>CASb> data and time equivalent sections of Laurentia and Siberia is probably not only caused by the absence of an internationally accepted biostratigraphic correlation, but rather supports the view that sulfate was non-conservative anion in seawater during the Cambrian Period.