Shallow Stratigraphy, Structure, and Modern Depositional Processes along Margins of Small Detached Carbonate Platforms in an Active Tectonic Setting

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The Nicaraguan Rise is a major structural/tectonic feature, consisting of detached carbonate platforms, that separates the southwestern and northwestern basins of the Caribbean Sea. During research cruises in March-April 1987 and May 1988, a large data set was collected that includes single-channel seismic reflection profiling data, bottom samples, SCUBA diver observations, remote operated vehicle and bottom camera pigment data. In their first two years of research, Hine and Hallock- Muller have discovered corresponding east-west gradients in platform depth (average bank top depth increases east to west), sediment facies (gradients from chlorozoan to chloralgal sediment types), benthic communities (algal-sponge dominance increases to the west), and biotic pigment concentrations (doubling east to west). Documentation of these gradients has important implications for understanding carbonate platform drownings in the geologic record. In addition, their seismic reflection data have provided new insights concerning the infilling of seaways, erosion/deposition on carbonate slopes, and tectonic influences on carbonate bank development. They have also discovered the first Halimeda bioherms to be described from the Caribbean. About two thirds of the data remain to be analyzed. This renewal grant will enable completion of this project examining processes controlling deposition on an important, but poorly known system of modern carbonate platforms.