Geochemical Calibration of Modern Isopora and Acropora Corals from the Great Barrier Reef and Application to IODP Leg 325 Fossil Corals

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In 2010, Integrated Ocean Drilling Project Leg 325 (IODP325) cored drowned fossil reefs off the Great Barrier Reef with the objective of collecting fossil corals that would yield information about past sea levels, ocean temperatures, and ocean chemistry. Massive coral colonies up to ~40 cm in length were the main types of coral recovered during IODP325 with ages spanning the last glacial maximum to the earliest part of the modern warm period (~30,000 to 10,000 years B.P.). Today these corals (Isopora and Acropora species) grow in relatively high-energy environments but little is known about their potential to support paleoceanographic reconstructions since these genera have not been previously used for this purpose. To address this issue and fully utilize the collected coral cores, this research is designed to develop sampling protocols and calibrations between modern oceanographic temperature and salinity data and skeletal oxygen isotopes and strontium/calcium in modern Isopora and Acropora corals from the Great Barrier Reef. Previously collected modern Isopora and Acropora corals from Heron Island, Myrmidon Reef and New Guinea will be analyzed. In the second part of this work the developed calibrations and sampling protocols will be applied to the fossil corals collected as part of IODP325 to generate more accurate temperature and salinity reconstructions. Because the geochemistry of Isopora and Acropora corals has not been previously calibrated against modern data, this project will directly assist all researchers using IODP325 fossil corals working to answer questions about sea level and sea surface temperature in the climatically important Western Pacific Warm Pool. This work will also provide a sound basis for comparisons with analogous studies using other corals in other localities and habitats (e.g., IODP Leg 310 in Tahiti). The project will support a female graduate student at the Lamont-Doherty Earth Observatory.