Millenial-Scale Records of ENSO and Intense Caribbean Hurricanes

Jeffrey Donnelly, Marine Chemistry and Geochemistry Department, WHOI

In order to reconstruct the history of intense tropical cyclone activity from St. Kitts and the terrestrial sediment flux record (i.e. ENSO) from Panama we will collect a series of sediment cores from each of the proposed sites using a vibracore rig. The Liquid Jungle Lab provides an ideal staging area from which to conduct our field work in Panama and the Munson Landing craft will provide access to the sites.  Hurricane and terrestrial runoff deposits will be identified, mapped, and dated. Cores will be returned to WHOI, photographed, x-radiographed, and analyzed for grain size, and organic and inorganic carbon.

In addition to the standard sedimentological techniques mentioned above, chemical scanning of cores using the newly acquired ITRAX X-ray fluorescence (XRF) scanner will provide data for determining the source of the both terrestrial and marine allocthonous material deposited in the lagoons and mangrove swamps. The XRF core scanner obtains a non-destructive characterization of the bulk chemical composition (from Al to U) as well as a density profile for the sediments using digital X-ray radiography, both at a spatial resolution as low as 200 μm. XRF analysis of cores from Vieques revealed distinctive chemical signatures for both terrestrial and marine inputs (Woodruff and Donnelly, unpublished data). For example dramatic increases in Ti and Fe are associated with terrestrial runoff events and increased Ca and Sr concentrations are indicative of marine sourced sediment transported to the lagoon. Therefore, the XRF scanner should provide high-resolution geochemical records of both hurricane-induced deposits in the St. Kitts lagoons, as well as fluctuations in terrestrial sediment input into the Panamanian mangrove swamps.