Precipitation of Trace Elements and Stable Isotopes in Reef Corals: a Process Study of Species, Growth Rate, and Diagnetic Influence

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Of all the mineral phases found in the marine environment, carbonates of various biological origins have proven to be the richest repository of paleoceanographic/paleoclimatic information. Two classes of chemical indicators, stable isotopes and trace elements, have been developed in two principal host phases, foraminiferal calcite and coral aragonite. As biological systems, however, foraminifera and reef corals are capable of leaving metabolic imprints on top of chemical signals which record environmental change. The nature of these imprints must be understood to accurately reconstruct oceanic conditions during Earth's history. Over the last several decades, a process framework has evolved to permit the interpretation of such signals in ancient foraminifera. The intent of this proposal is to initiate a similar framework for metal incorporation by corals. 4 fundamental process issues and their effect on metal (including Cd, Mn, Pb, V, Ba, U) and isotopic precipitation (18O and 13C) will be addressed in this work: (1) growth rate, (2) species variability, (3) reef spatial variability, and (4) digenetic influences on thousand year timescales, taking advantage of existing samples and the ease of cross dating short growth intervals within specimens from a single reef to form detailed comparisons. This approach offers many advantages to a difficult and costly culturing study. Numerous species collected live from Pacific, Atlantic, and Caribbean sites will form the sample basis. The diagenesis study component will utilize precisely dated (U-Th) materials from Barbados to address the feasibility of interpreting Pleistocene trace metal records in fossil corals.