Evolution of a fringing coral reef margin during the Mid-Pleistocene Transition: Results of the Dominican Republic Drilling Project

A sequence stratigraphic model has been developed for a seven-core transect across a series of coastal limestone terraces exposed on the southern coast of the Dominican Republic. Combined, these cores provide a near continuous record of fringing-reef development and margin evolution over the past 1.6 m.y. This period encompasses the transition from an obliquity-dominated climate regime (40 k.y. cycles) to a high-amplitude eccentricity-dominated regime (100 k.y.) following the Mid-Pleistocene climate transition. Furthermore, the cores span two major ecological transitions in the predominant reef-building coral fauna, which appear to be associated with the Marine Isotope Stage (MIS)-11 and MIS-31 super-interglacials, two of the longest and warmest interglacial periods over the past 2 m.y. Combined, the Dominican Republic cores provide an ideal setting to assess how the timing and amplitude of sea-level change can influence facies distributions both laterally and vertically across the margin. The sequence stratigraphic model for the cores is based on integrated chronostratigraphic tools including U-series dating, paleomagnetism, strontium isotopes, nannofossils, and lithostratigraphic and biofacies distributions. We have constrained ages from ca. 1.6 Ma to ca. 125 ka (the last interglacial). We constrain the regional extinction and ecological decline of the dominant reef coral genera Stylophora (and other extinct taxa) to near the MIS-31 highstand event. Correlation of the sequences in the youngest and most seaward cores (Core 4 and Core 5) has provided grounds for interpreting reef morphology and architectural evolution from the shelf through the slope and basin for the past ∼800 k.y. The higher amplitude (100 k.y.) cycles resulted in rapidly prograding, well-developed, Acropora-dominated reefal facies. Significant depositional changes are also associated with the extensive shelf flooding of MIS-11, a higher highstand. Reef development in the shallow shelf waters resulted in more carbonate production, steeper slopes, and significant carbonate “highstand shedding” into the forereef.