CORAL COMMUNITIES IN THE LATEST MAASTRICHTIAN OF JAMAICA

Recent mapping and stratigraphic work in the Jamaican Cretaceous has revealed thick successions with rich coral and rudist assemblages dating from the latest Maastrichtian (66.7-65.8 ma). This provides an excellent opportunity to examine the structure and diversity of Caribbean coral communities immediately prior to the K-T boundary.

In the present study, we analysed results from detailed sampling of three Cretaceous inliers in Jamaica (Central, Marchmont and Maldon) with more than 1350 identified scleractinian and octocoral specimens from 47 sample sites. A total of 59 species from 39 genera were recognized. Bulk collections (441 specimens) from a single biostromal unit in the Guinea Corn Formation of the Central Inlier yielded 35 species from 28 genera.

Compared to 60 well-sampled reef faunas from the Caribbean Cenozoic, our Maastrichtian taxonomic richness is relatively high. Richness in the extensively sampled biostrome in the Guinea Corn Formation is comparable to that in similarly well-sampled ‘reefal' units in the Jamaican late Oligocene and Plio-Pleistocene, times of high coral diversity in the Caribbean. Branched and massive coral growth forms are common in the Maastrichtian assemblages, though plate-shaped and laminar forms are rare. The scarcity of platy corals along with the general lack of reef growth fabric at our sample sites is likely related to unfavourable muddy environments common in the Jamaican Cretaceous.

Thus, in overall species richness and ecological diversity our latest Maastrichtian assemblages are comparable to diverse faunas from the later Cenozoic of the Caribbean. They contrast sharply with the Jamaican early Cenozoic record. Only five coral species are known from the Jamaican Paleocene; only two Maastrichtian species are found in younger Jamaican sediments.