FOSSIL ECHINODERMS OF THE UPPER PLIOCENE HOPEGATE FORMATION OF NORTH CENTRAL JAMAICA

Jamaican Pliocene echinoderms remain poorly known. The most diverse fauna is from the Upper Pliocene Bowden Formation, a siliciclastic unit deposited in a deeper water island shelf setting below storm wave base, perhaps 100-200 m water depth. The Bowden Formation has yielded an allochthonous accumulation of ossicles of asteroids and a basket star, and the spines, test fragments and rare tests of eight species of echinoid. However, almost nothing can be said regarding paleoecology for these mainly(?) derived fossils.

The Hopegate Formation of northern central Jamaica is an Upper Pliocene raised reef. It is particularly well exposed as a 5 km cliffline between Discovery Bay and Rio Bueno on the north coast. New and extensive exposures of the Hopegate Formation have become available since 2002 as the main north coast road has been re-engineered in central north Jamaica. The Hopegate Formation is well-lithified and largely dolomitized, and has thus discouraged close paleontological investigation; it has not yielded echinoids until now.

At least five echinoid taxa are now known from the Hopegate Formation: a cidaroid, probably Eucidaris sp.; Echinometra sp.; a small regular echinoid sp. indeterminate; Schizaster sp.; and Brissus sp. Those genera that can be identified are typical of modern shallow water environments of the Caribbean. With the exception of Brissus, these nominal genera have also been identified from the Bowden Formation and is also similar to that of the Sangamonian (oxygen isotope stage 5e) raised reef of the Falmouth Formation, which rests unconformably on the Hopegate Formation.

Although the Bowden Formation has yielded numerous fragmentary echinoderm specimens, mainly picked from bulk samples, these fragments are commonly well preserved. In contrast, the Hopegate Formation has yielded only rare echinoid tests and rarer fragments. Although preserved as tests, preservation of these specimens is poor. This research is supported by National Geographic Society grant #7278-02.