2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 10
Presentation Time: 10:45 AM

Biogeographic Comparisons of Neogene Benthic Foraminifera of Venezuela, Panama and Ecuador

SMITH, Carly J., Department of Earth Sciences, Florida International University, Miami, FL 33199, COLLINS, Laurel S., Dept. of Earth and Environment, and Dept. of Biological Sciences, Florida International University, Miami, FL 33199, JARAMILLO, Carlos, Center for Tropical Paleoecology and Archeology, Smithsonian Tropical Research Institute, Balboa, Ancon, 0843-03092, Panama and QUIROZ, Luis I., Department of Geological Sciences, University of Saskatchewan, Saskatoon, S7N 5E2, Canada, carly.smith@fiu.edu

Upper Miocene to Pliocene shallow-water benthic foraminiferal assemblages from Venezuela, Panama, and Ecuador are compared to assess the effects of the constricting Central American Seaway on Caribbean and tropical Eastern Pacific biotas. Before the completion of the Panama land bridge, shallow-water marine environments and their faunas on either side of the Isthmus were more similar than they are today. The prediction is that the gradual separation of Caribbean and tropical Eastern Pacific waters resulted in the progressive differentiation of the two faunas. While uplift from the collision of the Panama arc with South America began to affect deep-sea circulation by the upper Middle Miocene, and complete deep-water cutoff is generally dated to ~8 Ma, the timing of surface-water changes and the resulting divergence of Pacific and Caribbean neritic faunas remains unclear. The present study uses Upper Miocene and middle Pliocene benthic foraminifera from inner to outer neritic (<200m) deposits of northwestern Venezuela, Caribbean and Pacific Panama, and coastal Ecuador. The relationships between the assemblages are measured using similarity indices such as Simpson's and Jaccard's. As an additional characteristic of assemblages, the diversity of each sample is measured using Fisher's alpha. Assemblages deposited shortly before and after the ~8 Ma deep-water cutoff are compared, as well as those deposited during seaway closure, at ~3.5 Ma.