Cenozoic History of Paleo-Currents through the Central American Seaway: Insights from Deep Sea Sediments and Outcrops in Panama

Abstract:

Paleontologic, oceanographic, and ecologic studies suggest gradual shoaling of the Central American Seaway between ~15 to 2 Ma that caused a stepwise shutdown of deep, intermediate, and shallow water exchange between the Pacific Ocean and Caribbean Sea. This diminishing communication has been further associated with changes in surface and deep ocean currents, atmospheric flow, and ultimately regional and global climate. Recent studies of the Isthmus of Panama’s exhumation history, palm phylogenies, and fossil/molecularly derived migration rates, however, suggest that the isthmus may have risen much earlier. An earlier rise scenario would call into question many accepted consequences of this gateway event under the ‘Panama Hypothesis,’ including strengthened thermohaline circulation, North Atlantic Deep Water production, the onset of Northern Hemisphere glaciation, and the Great American Biotic Interchange. Despite considerable research on the Neogene, few paleoceanographic studies have directly examined long-term changes in the adjacent oceans over the Cenozoic to evaluate the potential for earlier events in the closure history of the seaway. In this study, we extend records of bottom water circulation reconstructed from the Nd-isotopes of fish teeth from several Caribbean International Ocean Discovery Program sediment cores (ODP Sites 998, 999, 1000). These reconstructions clearly depict an increase in Pacific volcanism throughout the Cenozoic and sustained transport of Pacific waters into the Caribbean basin from ~50 to 9 Ma, although there appear to be interesting complexities within the Caribbean basin itself. We also present preliminary investigations into the potential of Nd-isotopic analyses on fossil fish teeth recovered from outcrops and exposures of marine strata across Panama to further elucidate the regional dynamics and shoaling history of the Central American Seaway.