This project will fill a key temporal gap (1.8-0.4 Ma) in the evolutionary/ecological transition to modern Caribbean reefs. Reefs in the Pliocene are well documented, as are those from the later Pleistocene (0.4 Ma) to Recent. What is missing, is a record that bridges this critical gap: the final stage of a regional faunal extinction event. With this terminal evolutionary event came a change in the way reefs build their framework, the way corals are zoned, the rate of coral growth, and thus the way they respond to high-frequency sea level fluctuations and other climatic changes. To address this data gap we have identified a coral-rich section along the southern coast of the Dominican Republic that records the missing transition from Sylophora dominated reefs to Acropora dominated reefs in a series of step-like coastal terraces.
An integrated model of fringing reef development will be generated for the early/middle Pleistocene that includes the controlling factors of climate change, sea level, tectonics, antecedent topography, and the maximum growth rate of dominant reef builders. A sequence stratigraphic model will be developed for a seven core transect of the Pleistocene reef deposits on the southern coast of the Dominican Republic. Age determinations will be based on strontium isotopes, magnetostratigraphy, and radiometric dating. Once dated, these cores will be used to calculate accretion and progradation, and reconstruct fringing reef zonation and facies geometries both vertically and perpendicular to the coast. These data will allow us to pinpoint the terminal stage of faunal turnover, evaluate the ecological and environmental factors that gave rise to this transition, and determine the impact on fringing reef development, including changes in reef initiation, vertical accretion, progradation, and development of backreef lagoons and foreslope reefs.
Results from this project will provide the missing stratigraphic and environmental framework to evaluate the final stage of Plio-Pleistocene faunal turnover, and the rise of modern Caribbean reefs. It addresses questions including: (1) how did reef communities change during an episode of turnover and biodiversity loss which shaped the development of modern Caribbean reef ecosystems, (2) how did climate change and global high-amplitude sea level changes influence this ecological transition, and (3) what impact did ecological and environmental changes have on the fundamental shift in morphology to fringing reef terraces. Results will contribute to conservation measures and predictive models to determine how threatened coral reef ecosystems around the world might respond to ecologic collapse, climate change and global sea level rise. To promote international outreach, and broaden participation in the project, a collaboration will be established with the Universidad Autónoma de Santo Domingo (UASD), and the Dirección General de MinerÃa. To facilitate future access and use to the geoscience community, all taxonomic and chronostratigraphic information will be added to the Neogene Marine Biota of Tropical America webpage (NMITA).
