Stratigraphy, sedimentology, and isotopic geochemistry of Australian Neoproterozoic postglacial cap dolostones; deglaciation, delta 13 C excursions, and carbonate precipitation

作者：M. J. Kennedy · 发表于：Journal of Sedimentary Research · 年份：1996 · DOI：10.2110/jsr.66.1050 · 被引用次数：309 · 研究领域：Geology and Paleoclimatology Research、Paleontology and Stratigraphy of Fossils、Marine Biology and Ecology Research

Abstract Thin (< 15 m) laterally persistent carbonate units cap glacial deposits in Neoproterozoic successions (1000-544 Ma) on almost every continent. Because these enigmatic carbonate units are typically isolated within siliciclastic successions, recurrently overlie successive glacigenic units, and define one of the most pronounced delta 13 C excursions in the geologic record, they are interpreted to record a brief postglacial anomaly in ocean chemistry. In Australia, the Marinoan (Varanger equivalent nearly equal 600 Ma) cap dolostone units exhibit many of the characteristics displayed by such deposits elsewhere around the globe, including fine-grained dolomitic mineralogy, lateral persistence at basinal scales, thin laminae, graded beds, intervals with abundant marine cements, crystal fans, and a distinctive negative delta 13 C isotopic signature of up to -5 per thousand PDB. On the basis of these features, the Australian examples are interpreted here to be deeper-water deposits (below storm wave base) resulting from an anomalous flux of inorganic carbonate to the sea floor during postglacial transgression. Detailed isotopic analysis of Australian cap dolostones indicates delta 13 C values ranging from -1 per thousand to -5 per thousand and generally becoming more depleted in 13 C upsection. Trace-element data indicate some diagenetic stabilization, but textural evidence and the presence of similar profiles in different basins argue against a pervasive recrystallization e...