Roughly 15 to 3 million years ago the Central American Isthmus formed between North and South America resulting in a dramatic transformation of Caribbean marine biota. The exact cause for these faunal changes is not well understood since the formation of the Isthmus changed several ocean characteristics at the same time, including temperature, salinity, and turbidity. The goal of this project was to reconstruct sea surface temperatures at a seasonal resolution for a time interval just prior to final closure of the Isthmus in order to better understand how seasonal temperature change was related to this faunal turnover.
The oxygen isotopic composition of marine carbonates is controlled by water temperature, AND Corals are particularly useful since they can provide a record with seasonal resolution due to the presence of annual growth bands. Several corals from the ~5 million-year-old Gurabo formation, Dominican Republic , were collected in June 2003. All samples were examined for signs of diagenetic alteration, and one sample of Goniopora hilli was shown to be pristine. This coral was slabbed and sampled at high resolution (~20 analyses per annual growth band) for stable isotopic analysis. These data reveal a sinuisoid pattern in both oxygen and carbon isotopic values formed by seasonal variability in water temperature and the carbon isotopic values of dissolved inorganic carbon.
Stephanie Penn, ’05 Alameda , CA
Majors: Geology and Art
Sponsor: Rhawn Denniston