Controls on the Precipitation of Early Diagenetic Calcite, Dolomite and Siderite Concretions in Complex Depositional Sequences
Published:January 01, 1985
C. D. Curtis, M. L. Coleman, 1985. "Controls on the Precipitation of Early Diagenetic Calcite, Dolomite and Siderite Concretions in Complex Depositional Sequences", Roles of Organic Matter in Sediment Diagenesis, Donald L. Gautier
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Carbonate concretions occur commonly in organic-rich clastic sediments of ancient coastal floodplains and deltas. They consist of calcite, dolomite, or siderite or combinations of these. The influence of marine, mixed or non-marine depositional waters is seen in early cements; solute sources from decomposition of unstable detrital minerals become more important in later diagenesis.
The mineralogy and chemistry of early cements are dependent on dissolved sulphate concentrations and processes which affect them (notably depositional water composition, microbial sulphate reduction and mixing with waters of different origin). Calcite precipitates from marine-influenced pore waters rich in dissolved sulphate, dolomite from similar waters depleted in sulphate and siderite from meteorically-derived pore waters.
Systematic compositional variations with depth of precipitation are preserved both within and between siderite concretions. Earliest cements have higher Mn/Fe, Fe/Mg and δ13C values: all decline in later cements. These trends are linked with solute supply for cations and microbial metabolism for bicarbonate.
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Roles of Organic Matter in Sediment Diagenesis
This volume is the direct result of an SEPM Research Conference held in October 1983 at Lost Valley Ranch, Colorado. The goal of the volume is to bring attention of the sedimentological community the importance of interaction of organic compounds with the inorganic sedimentary system and the degree to which organic compounds drive diagenetic systems. This volume comprises 16 reports illustrative of the scope and direction of current research in sedimentological and geochemical studies of organic/inorganic interaction.