OSTRACODA FROM A NEW FOSSIL LOCALITY IN THE PANAMA CANAL ZONE: A PRELIMINARY REPORT

Persistent environmental changes greatly impact marine communities, as demonstrated both from modern cases and those documented in the fossil record. Prior work has shown the uplift of the Panama isthmus in the Miocene epoch triggered global climatic disturbances that influenced tropical fauna. Tropical fossil Ostracoda are particularly useful to gauge the effects of such paleoclimatic changes because extant species prefer to inhabit a specific range of environmental conditions. Despite their research applications in paleoecology, research on fossil Ostracoda in the Neogene of Panama has remained sporadic.

The Culebra Formation is comprised of a transgressive-regressive marine sequence that preserves intertidal to upper bathyal paleoenvironments of the early Miocene epoch. We report a previously undocumented invertebrate locality of the Culebra Formation, and the fossil ostracode assemblage preserved therein. Sediment samples were processed, picked, and sorted, and representative individuals were imaged using a Zeiss EVO 40 Scanning Electron Microscope. An exploratory study of the fauna present indicates this locality was a near-shore marine environment containing a diversity of not only ostracodes, but also bivalves, gastropods, and foraminifera.

Based on the taxonomic assemblage and the valve:carapace ratio, the assemblage is a low-to-moderate energy thanatocoenosis, making it a fairly reliable indicator of the life environment during the time of deposition. Phytal-dwelling genera Loxoconcha sp. and Cytheropteron sp. dominate the fossil ostracode assemblage; however, the outer-neritic/upper-bathyal taxon Bradleya sp. is additionally featured. Preliminary results suggest the paleoenvironment experienced localized upwelling, notably during a time of significant regional tectonic activity. Further analysis of the microfossil taxa is underway, in order to elucidate the paleoenvironmental conditions present at the time of deposition. Funding for this research is from PCP PIRE, supported by the NSF grant 0966884 (OISE, EAR, DRL).