TRANSPORTED CORAL ASSOCIATIONS IN THE UPPER BATHYAL BOWDEN FORMATION, LATE PLIOCENE, JAMAICA

Shallow water corals are often found in transported fossil associations in deep water slope deposits. Indeed, collections of reef corals from deep water deposits of the Dominican Republic, Jamaica and elsewhere have played an important part in our understanding of the stratigraphic and geographic ranges of Neogene – Recent Caribbean corals. These transported corals are generally more easily collected and better preserved than in situ associations locked in reefal limestone. Despite their frequency, little is known about the possible controls on variability in these coral slope deposits. The present work examines multiple transported coral faunas in the Late Pliocene Bowden Formation to focus on how lithologic, paleoenvironmental and taphonomic factors influence species richness, diversity and the paleoecologic structure of these coral associations.

The Bowden Formation is a planktonic foraminiferal marl deposited in upper bathyal depths with scattered shelly units rich in transported shallow water invertebrates. In the most famous of these shell beds from the south east coast of Jamaica, some 600 species of molluscs and 24 coral species have been collected from an outcrop <8 m across. Shallow water corals are also found in distinct shell beds at other sites where the Bowden is exposed on the north and south coast of Jamaica. These sites were sampled extensively and analyzed using presence-absence as well as relative abundance data.

The entire coral fauna of the Bowden Formation samples a large proportion of the total standing diversity of the Caribbean Pliocene. There is, however, significant variability between sites in richness, diversity and composition. Q mode ordination of sites compared with their lithologic and taphonomic characteristics suggests that richness and diversity of these coral associations are largely controlled by the extent and complexity of the transported shell concentrations. Differences in species composition between sites are related to the relative abundance of free-living species versus attached massive or ramose forms. Free-living species dominate transported associations off the broader more siliciclastic-rich southern island shelf while more ‘reefal’ hard bottom adapted taxa dominate associations transported off the narrower northern shelf.