Holocene rainfall variability in southern Chile: a marine record of latitudinal shifts of the Southern Westerlies

Geochemical and clay mineral parameters of a high accumulation marine sedim ent core from the Chilean continental slope (41 degreesS) provide a 7700 yr record of rainfall variability in southern Chile related to the position o f the Southern Westerlies. We especially use the iron content, measured wit h a time-resolution of ca. 10 yr on average, of C-14- accelerator mass spec trometry dated marine sediments as a proxy for the relative input of iron-p oor Coastal Range and iron-rich Andean source rocks. Variations in this inp ut are most likely induced by rainfall changes in the continental hinterlan d of the core position. Based on these interpretations, we find a pronounce d rainfall variability on multi-centennial to millennial time-scales, super imposed on generally more arid conditions during the middle Holocene (7700 to 4000 cal yr B.P.) compared to the late Holocene (4000 to present). This variability and thus changes in the position of the Southern Westerlies are first compared to regional terrestrial paleoclimate data-sets from central and southern Chile. In order to derive possible wider implications and for cing mechanisms of the Holocene latitudinal shifts of the Southern Westerli es, we then compare our data to ice-core records from both tropical South A merica and coastal Antarctica. These records show similar bands of variabil ity centered at ca. 900 and 1500 yr. Comparisons of band pass filters sugge st a close connection of shifts of the Southern Westerlies to changes withi n the tropical climate system. The correlation to climate conditions in coa stal Antarctica shows a more complicated picture with a phase shift at the beginning of the late Holocene coinciding with the onset of the modern stat e of El Nino-Southern Oscillation system. The presented data provide furthe r evidence that the well known millennial-scale climate variability during the last glacial continued throughout the Holocene. (C) 2001 Elsevier Scien ce B.V. All rights reserved.