Pollen distribution in marine surface sediments from Chilean Patagonia

Southern South America is the only mid-to high-latitude continental landmass in the southern hemisphere and therefore represents one of the key areas to recover terrestrial records for the study of past and future climate variability at these latitudes. During cruise MD/159 of R/V Marion Dufresne, cores were taken off the Chilean coast from 40 to 55°S in the open ocean and the fjords. Pollen spectra of 32 core top samples illustrate the relationships between pollen distribution in the sampled marine sediments and their transport from the vegetation onshore. Pollen concentrations show two distinct gradients: (1) a north to south gradient controlled by latitudinal vegetation changes and by westerly winds, and (2) from the fjords to the open ocean, a gradient clearly controlled by wind, fluvial inputs and pollen diagenesis linked to the distance from the coast and water-depth. The distribution of pollen percentages in these marine surface sediment samples reflects the local vegetation from the nearby continental area. Consequently pollen analyses from older sediments in these marine cores will be reliable tools to reconstruct past vegetational changes.