THE CORAL CLADOCORA CAESPITOSA AS A HIGH RESOLUTION PALAEOCLIMATE ARCHIVE
High resolution proxy data (stable isotopes, trace elements) from coral skeletons is an established method to reconstruct seawater growth temperatures for palaeoenvironmental studies. In this work the temperate, colonial, Mediterranean scleractinian coral Cladocora caespitosa was investigated. First modern Adriatic corals from Mljet (Croatia) where growth temperatures were known were studied. A clear sinusoidal cyclicity is present in both the δ18O and trace element (Sr, Mg, U, etc.) composition of the modern coral skeletons. Cyclicity approximately matches the number of seasonal growth band pairs in each corallite, implying a genetic link between these cycles and factors that determine seasonal growth band development, in this case mainly water temperature. It is found that C. caespitosa do not calcify in equilibrium with seawater in respect to any of the proxies analysed. Much intra-site variation is observed in trace element composition between coral colonies so this is not useful for production of a reliable palaeothermometer. For δ18O and Δ47 however, the offset, from what would be expected for aragonite precipitated in equilibrium with water, appears constant and so it was possible to derive a species-specific δ18O-temperature calibration equation, although more work needs to be done on Δ47. The δ18O-temperature calibration equation was applied to well-preserved corals collected from late Pleistocene deposits, MIS 1, 5, 7, in central Greece. The fossils contain ‘similar to modern’ δ18O values and variability in all proxies preserving growth environment seasonal signatures. MIS 5e, which has the best supporting contextual palaeoclimatic information, was found to be the warmest period studied with a lower than modern seasonal temperature range. The Early-Mid Holocene probably Sam Royle Abstract iii experienced the coolest temperatures while conditions in MIS 7a/c were probably the wettest with most freshwater input into the Gulf.
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