NEW TAXA OF LATE CRETACEOUS (MAASTRICHTIAN) MARINE OSTRACODES FROM JAMAICA AND THEIR PALEOBIOGEOGRAPHIC RELATIONSHIPS TO THE SURROUNDING REGIONS

Twenty-four new species and three new genera of Late Cretaceous (Maastrichtian) marine ostracodes were described from Jamaica. Thirty-five samples were collected from five Cretaceous inliers, which include the central, northern and western parts of the island. The best preserved specimens were collected from the Guinea Corn Formation of the Central Inlier. These twenty-four new species were recognized out of thirty-two identified taxa, indicating a high degree of endemism. Whereas some ostracode taxa, such as the genera Cytherella, Bairdia, Krithe and Paracypris, are nearly ubiquitous, many ornamented taxa lived only in shallow water; for these taxa, deep water was a barrier to migration, thus resulting in provincial distributions. The purpose of this study was to determine endemism of the ostracode faunas and its relation to the geologic evolution of the Caribbean region.

Ostracodes collected from the Ocozocoautla Formation (Maastrichtian) of Mexico are similar to those of Jamaica, although the poor preservation of the Mexican samples makes determination uncertain at the species level. Common shallow-water taxa occurring in both Jamaica and Mexico include species of Buntonia and Ayselgulina and the new genus Spinicytheridea. None of these genera occur in coeval deposits of North America, whereas many genera of North America, including Fissocarinocythere, Antibythocypris, Ascetoleberis, and Bicornicythereis, among many others, do not occur outside of the North American Gulf Coastal Plain (NAGCP).

Paleobiogeographically, these distributions indicate that ostracode faunas in Jamaica and Mexico were in good genetic communication, but communication with those of the NAGCP was more tenuous. This observation indicates that, during the Late Cretaceous, Jamaica was close to Mexico, if not in shallow-water continuity. Translation of Jamaica from Mexican proximity to its present relative position was accomplished by a well-known mechanism: movement along the Cayman Trough. Complex left-lateral movement and spreading in the Cayman structure initiated during the Eocene and has translated Jamaica approximately 1500 kilometers to its present relative position.