Research Symposium

BIO

Rachelle Brouillette is a second-year junior at Florida State University, majoring in Environmental Science and Policy. Rachelle is currently working in the Atwood Lab, assisting her mentor, Neda Mobasher, in developing coral-based paleoclimate reconstructions in the tropical Pacific. She is passionate about understanding environmental issues and the relationship between science and governmental policy. After graduation, Rachelle plans to enter the workforce and pursue a career where she can contribute to environmental sustainability and responsible resource management.

Rapid-screen 14C age distributions of coral fossils from Floreana, Española, and Isla Gardner in the Galápagos Islands

Abstract

Scleractinian “stony” corals provide a detailed record of past climate and ocean conditions because of their well-preserved skeletal structure, in which geochemical variations reflect changes in their environmental conditions. Corals from the eastern equatorial Pacific are especially beneficial in reconstructing past climate and can be used to understand how climate variability has evolved over the mid-to-late Holocene, 0-5,000 years before present (BP). This study presents a range and distribution of rapid-screen 14C ages for corals from Floreana, Española, and Isla Gardner to better understand the availability of coral fossils in the southernmost Galápagos Islands.

Approximately 50 corals were analyzed to reconstruct their geologic ages and spatial distribution throughout the Galápagos Islands. Coral chips were drilled, cleaned, and ground into a fine powder using a mortar and pestle on a clean, aluminum-foil-covered surface. Prepared samples were run on an accelerated mass spectrometer at the Keck Carbon Cycle AMS Facility (KCCAMS) at UC-Irvine, then sent for X-ray diffraction to determine the percentage of calcite in the coral skeleton. Raw 14C ages were calibrated in the CALIB 14C Calibration Program to the marine20 calibration curve. Floreana corals were calibrated to a median probability age between 0 to 4,000 BP, Española corals between 0 to 3,000 BP, and Isla Gardner corals between 2,000 to 3,000 BP. Mapping the distributions presented in this research can help accurately pinpoint areas for generating climate reconstructions and increase understanding of the age baseline for available coral fossils in the Galápagos Islands.

Keywords: coral, fossil, geochemistry, age dating, ocean, radiocarbon