THE NEOGENE PLATE TECTONIC HISTORY OF THE SOUTHERN CENTRAL AMERICA CONVERGENT MARGIN AND ITS IMPACT ON UPPER PLATE DEFORMATION AND VOLCANISM

New plate reconstructions for the Cocos and Nazca plates constrain the tectonic and volcanic evolution of the southern Central American subduction zone from Late Miocene to Recent. The reconstructions highlight three important events in the Neogene history of this margin: 1) the coeval development of the Panama Triple Junction with the initiation of oblique subduction of the Nazca plate at ~8.5 Ma; 2) the initiation of seamount and rough crust subduction beginning at ~3-4 Ma; and 3) Cocos Ridge subduction from ~2-3 Ma. A comparison of these events with independent geologic, geomorphic, volcanic, and stratigraphic datasets reveals that the timing, rates and origin of subducting crust directly impacted the Neogene growth of upper (Caribbean) plate deformation and volcanism in southern Central America. The reconstructions constrain the timing, geometry and causes of a number of significant tectonic and volcanic processes, including rapid Plio-Quaternary arc-forearc contraction due to Cocos Ridge subduction, the detachment of the Panama microplate at ~1-3 Ma, and the cessation of mantle-wedge-derived volcanism across ~300 km of the subduction zone in the Late Miocene.