Stratigraphic, Sequence Stratigraphic and Chronostratigraphic Studies of Marine Authigenesis
2000. "Stratigraphic, Sequence Stratigraphic and Chronostratigraphic Studies of Marine Authigenesis", Marine Authigenesis: From Global to Microbial, Craig R. Glenn, Liliane Prévôt-Lucas, Jacques Lucas
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Early diagenetic minerals are common within mudstone-dominated shallow marine sediments. However, our understanding of how these early diagenetic assemblages vary in a spatial and temporal sense across sedimentary basins is poorly developed. Such an appreciation is important, as early diagenetic mineral assemblages show a clear relationship with stratigraphic architecture and stratal surfaces.
In this study we present integrated stratigraphic and geochemical data for four differently aged mudstone-dominalcd successions (the Lower Jurassic Scunthorpe and Brant Mudstone Formations of eastern England, the Lower Jurassic Cleveland Ironstone Formation of eastern England, the Triassic Westbury Formation of South West England, and the Upper Cretaceous Mesaverde Group of Book Cliffs, Utah). Both spatial and temporal variability in early diagenetic mineral assemblages can be recognized in these successions, taking the form of ooidal ironstones, phosphates (apatite-rich units and bone-beds), concretionary carbonates, and pyritic mudstones. These variations are interpreted to result from spatial and temporal variations in physical and gcochemical conditions in the sediments close to the sediment-water interface. Specifically, the physical and geochemical conditions required for the formation of these cemented units occur at key stratal surfaces (marine flooding surfaces, maximum flooding surfaces, and down-dip equivalents of sequence boundaries).
The physical conditions that occur at sequence boundaries (low accommodation, high energy, and frequent sediment reworking) can lead to (he predominance of suboxic diagenesis and the formation of berthierine- and siderite-rich ooidal ironstones. Conditions of low net sediment accumulation and oxic/suboxic diagenesis upon major transgressive surfaces and maximum flooding surfaces leads to the formation of phosphate-rich units. Breaks in sediment accumulation at marine flooding surfaces lead to enhanced early diagenesis and the formation of laterally extensive carbonate cements and concretionary horizons. Sulfide-dominated early diagenesis (that dominated by sulfate reduction) is predominant during “normal” periods of shallow marine sedimentation and appears to mark the bulk of sediments within systems tracts. This study emphasizes the importance of integrating stratigraphic and geochemical data in developing quantitative and predictive models for early diagenesis.
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Marine Authigenesis: From Global to Microbial
This volume is a collection of 33 state-of-the-art papers focusing on various aspects of authigenic and diagenetic marine minerals and related global elemental cycling. The commingling of the various studies of authigenic minerals in this volume, including the most recent advances in knowledge concerning the occurrence and origins of phosphorites, glauconites, dolomites, siderites, manganese-iron associations, barites, ironstones, and other marine chemical sediments/sedimentary rocks of early authigenic/diagenetic origin, is partly the result of the increasing awareness that there are many overlaps, even direct co-associations, between different authigenic minerals, both in time, space, and genesis. Taken together, this compilation represents a holistic approach towards marine authigenesis that considers the integrated whole more than the simple sum of its parts.