Earliest diagenesis in scleractinian coral skeletons: implications for palaeoclimate-sensitive geochemical archives |
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Authors: | Luke D Nothdurft Gregory E Webb |
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Institution: | (1) School of Natural Resource Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia |
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Abstract: | Live-collected samples of four common reef-building coral genera (Acropora, Pocillopora, Goniastrea, Porites) from subtidal and intertidal settings of Heron Reef, Great Barrier Reef, show extensive early marine diagenesis where parts
of the coralla less than 3 years old contain abundant macro- and microborings and aragonite, high-Mg calcite, low-Mg calcite,
and brucite cements. Many types of cement are associated directly with microendoliths and endobionts that inhabit parts of
the corallum recently abandoned by coral polyps. The occurrence of cements that generally do not precipitate in normal shallow
seawater (e.g., brucite, low-Mg calcite) highlights the importance of microenvironments in coral diagenesis. Cements precipitated
in microenvironments may not reflect ambient seawater chemistry. Hence, geochemical sampling of these cements will contaminate
trace-element and stable-isotope inventories used for palaeoclimate and dating analysis. Thus, great care must be taken in
vetting samples for both bulk and microanalysis of geochemistry. Visual inspection using scanning electron microscopy may
be required for vetting in many cases. |
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Keywords: | Early diagenesis Scleractinia Coral Palaeoclimate Porites Cementation Bioerosion |
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