Evidence for a recent (0.65 Ma) formation of the Isthmus of Panama

Abstract

Leonidas Brikiatis

The exact age of the final formation of the Isthmus of Panama is a critical reference point for oceanographic, climatic, biogeographic, and evolutionary hypotheses. The prevailing interpretation of geotectonic evidence is that the isthmus was completed between 12 Ma and 3 Ma, and an age of 3–4 Ma has been used as a benchmark in hundreds of studies over the past 30 years. Phylogeographic data indicate the existence of marine connections across the isthmus much more recently, however. Here, using the most updated data available, I reconsider the geological arguments invoked to conclude the age of 3–4 Ma and show that, in fact, this age is not supported by the current geological knowledge. Rather, recent geotectonic evidence, in conjunction with multiple lines of indirect phylogeographic, biostratigraphic, oceanographic, and paleoclimatic indications, suggests that as many as four transisthmian seaways persisted until as recently as the onset of the Middle Pleistocene (~0.65 Ma). The concurrence of the final formation of the Isthmus of Panama with the mid-Pleistocene Transition of glacial/interglacial periodicity suggests a tight relationship between these events. Unusual and contrasting climate phenomena, including the “900-Ka (cold) event” and the “greening” of South Greenland during the MIS 22 glacial maximum, can be explained by this palaeogeographical and palaeoceonographical scenario.

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