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This project is focused on collecting marine Late Cretaceous ostracodes from the greater Antillean region in order to contribute to understanding the complex plate tectonic evolution of the region. Ostracodes are particularly suited for this kind of work because of their provinciality; that is, deep water is a barrier to migration for many types of ostracodes, and thus regions now separated by deep water but containing the same shallow water ostracode species indicate the possibility that the regions were once connected. Alternatively, regions now adjacent to each other that contain different shallow water ostracode species could have formed separately and later come together due to plate tectonic movements. These concepts are being explored for the Caribbean and Gulf of Mexico regions.

This past year, funding from the ACS PRF grant was provided to hire our last geology major, Bradley Arnett, who worked on the project for eight months. Bradley took part in all aspects of the research, from assisting in the field in Mexico, washing the samples, and picking and sorting the specimens. Bradley was also the first author of an abstract on preliminary results of the research and gave a presentation at the Annual Meeting of the Alabama Academy of Science. Bradley is now working as a geologist for a private mining company.

Great effort was devoted this year on obtaining excellent specimens from the samples that were collected in Jamaica the previous year. The late Maastrichtian samples from Jamaica generally contain an abundant and diverse ostracode fauna. The preservation and condition of the microfossils is not great in most of the samples for a variety of reasons, including recrystallization, pyritization and encrustation of calcareous material. After an initial picking of all the thirty-five samples, the samples with the best preservation were reprocessed extensively, including two or three rewashings and several-hour treatments in an ultrasonic bath. Ultimately, specimens in excellent condition were obtained, often displaying beautiful external ornamentation. The University of North Alabama recently (April, 2010) acquired a new Zeiss EVO MA10 scanning electron microscope, which has greatly increased the productivity of imaging the specimens. So far, more than 7100 ostracodes have been picked from the Jamaican and Mexican samples, including at least 28 species and three new genera. Most of these species have now been imaged.

It has been known for several years that some fossil groups with provincial distributions occur in Jamaica and in Chiapas, Mexico, including “larger” foraminifera, decapod crustaceans, and corals. These fossil associations suggest the possibility of a similar distribution with regard to the ostracodes. Most of the fossils from the Late Cretaceous of Chiapas are from the Ocozocoautla Formation. Last November, therefore, my student Bradley Arnett and I traveled to Tuxtla-Gutierrez, Chiapas, Mexico, to collect from the Ocozocoautla. Under the guidance of Gerardo F. Carbot and Marco Antonio Coutiño of the Museo de Paleontología “Elliseo Palacios Aguilera” in Tuxtla-Gutierrez, five samples were collected from this formation and have yielded almost 1100 ostracodes. Among the specimens are species similar or identical to several species from Jamaica, including members of an as-yet undescribed genus.

Significantly, there is a mechanism that can account for this paleobiogeographic distribution. According to several sources, Jamaica was adjacent to southern Mexico during the Late Cretaceous. Beginning in the Eocene, the Cayman Trough became an active spreading center connected by two left-lateral transform faults. Based on magnetic anomalies and calculated rates of plate motion, lateral movement along this structure is on the order of 1100 km, which is enough to move Jamaica from southern Mexico to its present location immediately south of the Cayman Trough.

Another critical location from which to collect samples in the Caribbean is in Cuba. Several years ago (2002), the author collected samples from the Late Cretaceous of Cuba and many of the ostracodes seemed to be endemic. It now appears that some of those species also occur in Jamaica. That initial reconnaissance work yielded only two samples with ostracodes. Plans are now being finalized to travel to Cuba this November to collect more samples from the fruitful localities previously sampled, in addition to sites unpublished in a doctoral thesis, with field assistance from Manuel Iturralde-Vinent and Leidy Menendez of the Museo Nacional de Historia Natural in Havana. As part of this effort, a student will be hired this fall to assemble a GIS database on the geology of Cuba. This will include scanning in the many-sheeted 1:250,000 geologic map of Cuba (which the author has) and compositing the raster images into a single database tied to regional or global geographic coordinates. The same geographic coordinate system will be used for the Jamaican and Cuban geologic maps so they can be compared directly.

A field trip to Honduras was made this past June in an effort to determine whether the latest Cretaceous ostracode faunas of that country were similar to those in Chiapas and in Jamaica. This trip was made under the guidance of Dr. Robert Rogers of the California State University at Stanislaus. The ages of the marine units in Honduras are not known precisely due to the paucity of paleontological studies. During the course of the field work, echinoids were discovered that were identified by Dr. Andrew Smith of the British Natural History Museum as Washitaster wenoensis of late Albian age. This was unfortunate, as the samples collected in Honduras (some of which include a depauperate ostracode fauna) are much older than the samples from the Caribbean and cannot be used as a paleobiogeographic comparison.

In all, several thousand ostracodes have been picked from the Jamaican and Mexican samples, and many more should be extracted from samples to be collected in Cuba. These samples have yielded many new species and new general of shallow marine ostracodes. The taxonomic, paleobiogeographic, plate tectonic, and evolutionary significance of these faunas will yield years of fruitful research.