Biogeographic effects of the closing Central American Seaway on benthic Foraminifera of Venezuela

Abstract

Studies of the effects of the Central American Seaway's closure on microfossil taxa and stable isotopes of foraminifera previously addressed the timing of emplacement of the Caribbean-tropical eastern Pacific sill, changes in marine nutrients, evolutionary and paleobiogeographic events associated with closure, and rates of uplift in Central America. However, there have been no quantitative studies of the transisthmian divergence of whole biotas. Here we assess biogeographic effects of the closing Central American Seaway by comparing middle Miocene to Pliocene, neritic benthic foraminiferal assemblages from Falcon State, Venezuela, to those of coeval deposits with similar paleoenvironments from Panama, Costa Rica, and Ecuador. Benthic foraminiferal assemblages from the Urumaco, Codore, Caujarao, and La Vela formations of Venezuela's central coast were compared to other Caribbean and tropical eastern Pacific assemblages with Simpson's, Dice, and Jaccard similarity coefficients. Results of the Simpson's Coefficient indicate that the Caribbean inner neritic faunas of Venezuela, Costa Rica, and Panama became significantly more similar from the late Miocene to Pliocene, as mixing with Pacific waters was reduced and modern oceanic conditions of the Caribbean Sea were established.