LARGER FORAMINIFERA FROM THE PLATFORM MARGIN OF JAMAICA DURING THE EOCENE

During the Paleogene the Nicaragua Rise saw the development of extensive carbonate platforms that today are only exposed at surface in Jamaica. However, faults associated with the tectonic uplift of Jamaica have largely obliterated the original platform margins with shallow-water deposits faulted against deep-water deposits. In this presentation we report on an Eocene platform margin that is preserved on the northern part of the largest platform that developed in central Jamaica. In this location the platform margin is preserved with the platform margin deposits prograding over the slope deposits. The platform margin is represented by extensive carbonate sand banks (foraminiferal grainstones and packstones) dominated by foraminifers and algal oncoids. The foraminiferal assemblages are characterized by typical Eocene shelf margin taxa including various species of lepidocyclinids (Lepidocyclina pustulosa, L. macdonaldi, Pliolepidina tobleri), nummulitids (Nummulites striatoretciulatus, Operculinoides floridensis) as well as forms such as Fabiania cubensis. Locally red algae become important sediment producers. The platform margin deposits prograde across slope deposits that dip at about 30° towards the basin and consist of fine grained packstones with benthic foraminiferal tempestites derived from the platform margin. The slope deposits show erosive slump scars suggesting repeated slope failures. This exposure allows a detailed understanding of the microfacies changes across an Eocene platform in the Caribbean.