Diagenesis and Porosity Modification in Acropora Palmata, Pleistocene Of Barbados, West Indies

Abstract

ABSTRACT The uplifted coral reefs of Barbados have served as an excellent natural laboratory for the study of porosity changes and diagenesis in Pleistocene and Holocene carbonate material. The mineralogy and petrography of a single coral species, Acropora palmata, was examined in detail. Post-depositional modifications of the coral skeleton included entrapment of lime sand and mud, precipitation of void-filling aragonite needles in the marine environment, solution of the coral, alteration from aragonite to calcite skeletal mineralogy and the precipitation of calcite cement. The precipitation of calcite cement is volumetrically the most important porosity alteration in the history of these corals. The source of this void filling cement is shown to be the excess material remaining after the volume solution of aragonite skeleton and reprecipitation of calcite when the coral skeleton equilibrates mineralogically to the subaerial environment. It has become apparent from this study that a varied suite of rocks may result from the differential effects of the few processes mentioned above.