REEF CORAL ASSEMBLAGES OF THE MIOCENE TO PLIOCENE OF THE NORTHERN DOMINICAN REPUBLIC

Assemblages of reef corals from the Late Miocene to early Late Pliocene of the Northern Dominican Republic were statistically analyzed to document patterns of change during the period of high generic and species origination leading up to the Late Pliocene Caribbean-wide episode of accelerated faunal turnover. The sections analyzed were part of a thick sedimentary wedge (as much or more than 1000 m thick) that prograded north forming a thin shelf and slope along a narrow eastward-opening trough located north of the rapidly uplifting Cordillera Central. Exposures are located along five rivers of the Cibao Valley: the Rio Gurabo, Rio Cana, Rio Mao, Rio Amina and Rio Yaque del Norte. Stratigraphic variations in coral occurrences were determined from over 2,900 coral samples collected by haphazardly extracting well-preserved material from the surface of the outcrop. Sampling therefore was roughly representative of species composition, but not of abundance. Analysis of occurrence data was performed using average linkage clustering, nonmetric multidimensional scaling and Jaccard’s similarity coefficients. At the coarsest level assemblages can be categorized as either grassflat communities (>35% free-living taxa) or mixed-shape communities (<29% free-living taxa). Grassflat and mixed-shape communities are stratigraphically scattered throughout the section, reflecting variations in facies rather than the evolution of communities. To more accurately characterize the mixed shape coral communities in three areas of exceptional reef development, twenty-six 40 m point intercept transects were additionally collected. This data allows characterization of pre-turnover coral reef zonation patterns and provides insights into the ecological role of several dominant pre-turnover taxa.