Miocene to Recent tephrostratigraphy offshore Central America: Evolution, Provenance and Cyclicities

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IODP Expeditions 334 and 344 offshore Costa Rica recovered sediments with numerous marine tephras down to the middle Miocene. Together with the marine tephras of former DSDP and ODP cruises offshore Central America as well as correlative Neogene tephras from on-land an overwhelming data set of major and partly trace elements has been acquired in the last 16 months (995 marine tephras, 282 field tephras). This facilitated first correlation between drill Legs, sites and Holes as well as on-shore tephras. Compilation of data showed that temporal and spatial changes in the marine and on-land tephras occur along the Central American Volcanic Arc (CAVA) within the Neogene, that Cocos Ridge subduction took place at least before 1.8 Ma and is probably accompanied by subduction of Galapgos-like crust in N-Costa Rica before, influencing the arc volcanism in this segment. Furthermore, there is indeed a significant contribution of an explosive phase from the Galapagos Hot Spot within the Miocene marine sediments on the Cocos Ridge. Using our data set we are also able to find hidden volcanic centres along the CAVA and there is the possibility that the longevity of existing volcanic complexes exceed our actual knowledge by far. Referring to our analysed data there are also reasonable evidences for cyclic abundance of explosive volcanism at the CAVA. The detailed elaboration on these topics, together with remaining analysis of trace elements and determination of ages, will lead to a complete tephrochronostratigraphic framework for the Neogen explosive volcanism of Central America and highlight the compositional and temporal relationships between subduction input and arc output along the whole Neogene Central American Volcanic Arc.