SEDIMENTOLOGY, STRATIGRAPHY AND CHEMOSTRATIGRAPHY OF EOCENE-MIOCENE CARBONATE SUCCESSIONS IN THE WESTERN CARIBBEAN: THE SWANSWICK AND SOMERSET FORMATIONS, JAMAICA

Eocene-Miocene shallow marine carbonates have become major oil and gas reservoir targets along the Circum-Caribbean. The Eocene-Miocene carbonate record from Jamaica may constitute an important frontier for the exploration of fossil fuels. Here, we present sedimentologic, stratigraphic, petrographic and chemostratigraphic information for the Eocene-Miocene carbonate record from the North Coast Belt and the Wagwater Trough in Jamaica, where their age, depositional environment, and paragenetic history were constrained.

Shallow marine heterozoan carbonates predominated along the Wagwater Trough during the Middle-Late Eocene, while deep heterozoan carbonate successions prevailed along the North Coast Belt. Photozoan and heterozoan carbonates occurred in the Early Oligocene followed by a carbonate depositional hiatus that took place between the Early and Late Oligocene. This regional hiatus has been observed in other Circum-Caribbean basins, i.e. the Nicaraguan Rise, the San Jacinto Basin, Colombia, the Alta and Baja Guajira basins, the Falcon Basin, Venezuela. A new period of heterozoan carbonate deposition began during the Late Oligocene when a major transgression occurred. A new increase in relative sea level occurred during the Early Miocene followed by an important red algae deposition.

Changes in carbonate factories follow sea level changes and likely nutrient and sunlight changes over time. The heterozoan and photozoan define the porosity before diagenetic processes. In heterozoan carbonates, the main components are red algae and benthic foraminifera and they present high porosity, while photozoans are mainly formed of micrite, corals and planktonic foraminifera and show relatively lower porosity. The data we present here does not support the carbonate factory-porosity relationship, but instead suggests a correlation between burial diagenesis and porosity. The major factor creating porosity is observed as dolomitization as lime mud shrank into smaller dolomite crystals with accompanying dissolution. Another diagenetic process, micritization, is the primary cause of low porosities.