STRATIGRAPHY AND DISTRIBUTION OF THE COASTAL GROUP, ST. ELIZABETH PARISH, SOUTHWESTERN JAMAICA

This contribution examines the characteristics and ages of sedimentary units in the Coastal Group located along the southwestern Jamaica coast between Great Pedro Bluff and Fort Charles Bay in southwestern St. Elizabeth Parish. The coastline is characterized by laterally discontinuous low cliff exposures, separated by modern beach deposits and tectonically raised shore platforms composed of the White Limestone Group (mid-Eocene to mid-Miocene) and coral rudstone to floatstone and calcareous sandstone of the Coastal Group (late Pleistocene). Electron-Spin Resonance spectroscopy conducted on corals collected from a coral rudstone to floatstone facies yielded an estimated age of 120 ka. The coral facies may be assigned to the Falmouth Formation, and it has been confirmed to have been deposited within the MIS 5e (132 ka – 115 ka). However, the other units within the Coastal Group likely are diachronous. Significant amounts of sand and silt components are present throughout the Coastal Group exposures. These vertical exposures cannot be a standard for determining relative mean sea level (RMSL) as they have been tectonically disturbed and the upper surface of the coral facies may have been eroded below cross-bedded sandstones. Due to the widespread variability of sedimentary units both locally and longshore, assignment of existing stratigraphic nomenclature of the Coastal Group to these formations is difficult. While these exposures in southwestern Jamaica cannot serve as a proxy for correlation of MIS 5e strata due to tectonism and siliciclastic influxes, they provide an example of the potential for accelerated sea-level rise with current trends in climate changes.