Neogene Deep-Water Dolomite from the Florida-Bahamas Platform
Published:January 01, 1988
Henry T. Mullins, George R. Dix, Anne F. Gardulski, Lynton S. Land, 1988. "Neogene Deep-Water Dolomite from the Florida-Bahamas Platform", Sedimentology and Geochemistry of Dolostones, Vijai Shukla, Paul A. Baker
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Authigenic calcian dolomite is a common but rarely abundant (≤20%) component of Neogene deep-water (475-2,767 m) carbonates peripheral to the Florida-Bahamas Platform. Dolomite concentrations as high as 57% of the carbonate fraction occur in the Miocene of west Florida, however, and as much as 86% dolomite has been found in a hardground from the Bahamas.
Dolomite occurs principally as pore-filling euhedral rhombs (5–20 μm) that precipitated in situ, as well as by replacement of calcite at disconformities. Stable isotope ratios (oxygen and carbon) suggest dolomite precipitation from deep, cold, seawater-derived fluids, and trace-element (Sr) concentrations suggest strontium-rich aragonitic(?) precursors. Preliminary 87Sr/86Sr data suggest substantial lag times for dolomite precipitation and contamination by "old" strontium.
Because of the high diagenetic potential of periplatform carbonates, Bahamian deep-water dolomites appear to be a natural consequence of shallow subsurface (<60 m) burial diagenesis. In contrast, carbonate ramp slope sediments from west Florida, which have a much lower initial diagenetic potential, are punctuated by discrete concentrations of authigenic dolomite, which may represent paleoceanographically controlled dolomite "events." Overall, our data indicate that deep-water dolomite has had little difficulty in precipitating from normal marine-derived fluids.
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Sedimentology and Geochemistry of Dolostones
Sedimentology and Geochemistry of Dolostones - The need has always existed for understanding the processes of dolomitization and the origin of thick sequences of dolostones. This need becomes even more critical because pre-Cretaceous dolostones commonly host economically important deposits of natural resources and fossil fuels. This publication was derived from an SEPM Research Symposium held in Raleigh, North Carolina, on September, 1986. The volume attempts to answer the questions: How have the concepts and models presented in other publications been applied to sedimentary dolomites, Have we gained new insights and awareness into the processes of dolomitization, and many others. The principal message of this publication is, whereas enormous progress has been made in dolostone research since 1965, the subject is ripe for further study.