This study represents an important first step in constructing the chronostratigraphic framework needed for regional correlation and environmental interpretation for shallow marine benthic communities in the tropical Western Atlantic between 6 and 1 Ma. The research provides a stratigraphic and environmental framework for evaluating faunal turnover and community change. It addresses questions including: (1) if/how did reef communities change over time during an episode of turnover which shaped the development of modern Caribbean reef ecosystems, and (2) if/how were these changes related to changes in the environment.
New data on benthic foraminifera are being combined with information on sedimentary features to interpret depositional environments. The resulting stratigraphic and environmental framework is used to assess patterns of temporal and spatial variation in both reef coral and free-living coral communities and their environmental correlates. The project also explores the relationship between community change, speciation, and extinction in order to better understand the ecological processes involved as new species were added to communities and extinct species were removed.
Shallow marine benthic communities in the area were profoundly altered by biotic turnover associated with the closure of the Central American isthmus and the onset of Northern hemisphere glaciation. Changes in taxonomic composition and community structure are well documented in corals and mollusks and in many other marine organisms. These events were responsible for shaping the composition and structure of modern-day shallow benthic communities in the Caribbean region. The causes of turnover are controversial and poorly understood, in part because most evolutionary studies are not performed within the context of a rigorous stratigraphic and environmental framework. High-resolution chronostratigraphy is needed for determining the timing of evolutionary events, and for reconstructing regional changes in ocean circulation and sea level that affected environmental factors such as nutrients and temperature. As part of this work, the group is revising the systematics of one of the most important ecological dominants, the Stylophora, which became extinct in the Caribbean at the end of the turnover.
By adding new data types to the Neogene Marine b(I)ota of Tropical America (NMITA) taxonomic database at the University of Iowa and linking NMITA with CHRONOS, the project provides information to the paleontological community. Specifically, the team are developing an integrated chronostratigraphic model for a classic, richly fossiliferous sequence extending from ~6-3 Ma, the Cibao Valley of the northern Dominican Republic. The sequence contains more first occurrences of reef corals than any other known Caribbean sequence (37 of the 91 recorded species first occur) and is therefore critical for understanding speciation events during turnover.
