Sedimentology and palaeoenvironment of the Pliocene Bowden Formation, southeast Jamaica

The Pliocene Bowden Formation of southeast Jamaica, estimated to be at least 150 m in thickness, is composed of three lithofacies herein termed the conglomerate/sandstone, marlstone, and micritic limestone lithofacies. Six measured sections, encompassing approximately 70 m of strata, indicate that these lithofacies represent 11%, 87% and 2%, respectively, of the formation. The conglomerate/sandstone lithofacies is interpreted as a product of sediment gravity flows, more specifically turbidites, and constitutes an integral component of the Bowden shell bed that occurs near the base of the sequence. The marlstone lithofacies is interpreted as a product of pelagic and hemipelagic deposition from low density turbidity currents, or possibly even bottom water nepheloid layers, and the micritic limestone lithofacies as selectively cemented carbonate-rich nodules and horizons within the marlstone lithofacies. Marlstones are characterised by abundant ichnofaunas which collectively are indicative of more or less stable ecological systems in hydrodynamically low-energy, deep-water environments. Together with sedimentological data, this suggests the Bowden Formation to have been deposited in a deep-water environment, below storm wave base, that possibly deepened upwards. We speculate that the most likely palaeoenvironment was not too dissimilar to the present-day Yallahs Basin of southern coastal Jamaica.