Scientists interested in global climate change have increasingly turned to proxy climate records provided by stable isotopic and elemental analyses of massive coral skeletons. Because of their relatively slow growth rate (mm per year), long life spans (centuries) and accretionary mode of growth, the skeletons of corals with massive colony growth forms can potentially record sea surface temperature and salinity changes at many temporal scales. Moreover, geochemical analyses of coral skeletal material are often the only proxy climate record available from low latitudes.
The last interglacial (Sangamon, oxygen isotope substage 5e) was a time of rapid and pronounced climate change. The purpose of this project is to determine whether seasonal and/or decadal scale cyclic changes in sea surface temperatures occurred during the interval. Four specimens of the coral Montastraea annularis were collected from a fossil reef exposed adjacent to the northern barrier reef tract in Belize, C.A. U-series dates obtained using alpha spectrometry have indicated a last interglacial age for the reef assemblage. From each coral, a representative 20-year interval was sampled by obtaining four samples per annual growth band. A total of 320 samples (4 corals x 20 annual growth bands x 4 samples/growth band) are currently undergoing stable isotopic (delta 18O) and elemental (Sr/Ca) analyses. We hope to be able to detect high-resolution seasonal and decadal climate cycles, and compare our results to a companion study of modern specimens of Montastraea collected offshore from the Pleistocene locality.
Jill Leonard, ’03 Blue Grass, IA
Majors: Geology, Environmental Studies
Sponsor: Benjamin Greenstein