THE MID CENOZOIC CARBONATE PLATFORM OF THE NICARAGUAN RISE: IMPORTANCE OF CARBONATE PRODUCTIVITY, VOLCANISM AND TECTONICS

Carbonate platforms developed progressively on shallow-water blocks during the mid Paleocene-mid Eocene across the Nicaragua Rise as volcanism related to subduction of Proto-Caribbean oceanic crust ceased and an east-west strike-slip boundary developed along the northern margin of the Caribbean Plate. These carbonate platforms were dominated by foraminiferal and algal communities with corals and molluscs locally accounting for carbonate production. Platform margins were dominated by extensive Lepidocyclina-Miogypsina grainstones and packstones which passed into the platform interiors into miliolid dominated micrites, wackestone and even grainstones. The platforms were extinguished in the mid Miocene by the Caribbean carbonate crash. These extensive carbonate platforms have previously been associated with a tectonic quiescent phase in the geological evolution of Jamaica (and the Nicaragua Rise) with the implication that tectonic quiescence allowed the developed of extensive carbonate factories.

My work has mapped out the facies patterns associated with these carbonate platforms throughout the Paleocene to Miocene interval. The patterns that emerge are those of repeated angular unconformities that remove 100s of metres of section and syn‑sedimentary faults within the platform that were active during deposition. Deep-water sediments (chalks) surrounding the platform also saw the influx of thick units of turbidites and mass-flow deposits (olistostromes) separated by thick sequences of chalks with a few thin turbidites. The turbidites and mass flow deposits correspond with the unconformities on the platform (as far as can be determined). In eastern Jamaica, the carbonates onlap onto Cretaceous basement in multiple areas indicating tectonic uplift, erosion and subsidence.