Paleoenvironmental inferences based on fossil chironomids during the last glacial/interglacial transition in northwest

MASSAFERRO, J. Y MORENO, P.I.

Chile

Congreso; III Reunion Binacional de Ecologia; 2007

SOCECOL/ASAE

The origin of millennial scale climate events in the Southern Hemisphere during the Late glacial/interglacial transition (LGIT) still remains a major debate in paleoclimatic investigations. Different hypotheses, relying on different lines of evidence, point variously to the northern Hemisphere leading the southern Hemisphere and vice versa, or to synchrony between hemispheres.  The inconsistencies between these interpretations continue to make the presence of the YD (ACR) cooling signal in South America, a controversial topic. To date, most of the evidence for climate change in southern South America has been derived from glacial, pollen and beetle records. In recent years chironomid midges have emerged as a powerful independent proxy indicator of climate change. Existing studies on chironomids in the southern Hemisphere (Massaferro & Vandergoes, 2007) appear to indicate climate changes during the LGIT. Several pollen records from Argentinean and Chilean lakes bear no evidence of a reversal during the Late Glacial period (Bennett et al. 2000; Markgraf, 1993). In contrast, other sites in Patagonia show pollen changes  assemblages at the end of the Lateglacial that have been interpreted as a response to climatic cooling (Haydas et al., 2003; Heusser, 2003) between 11,300 and 9,400 yr BP.             In this study we compare high resolution pollen and chironomid records from western Patagonia to address differences in the existing paleoreconstructions from southern South America. This multi-proxy approach can contribute substantially to produce more robust interpretations of climate change.   Bennett et al. 2000. Science 290, 325– 328. Hajdas, I., et al. 2003. Quat. Res.59, 70– 78. Heusser, 2003 Developments in Quaternary Science 3: 1-240 Markgraf, 1993 Quaternary Science Reviews 12: 351-355. Massaferro & Vandergoes,  2006. Encyclopedia of Quat  Sci. MS 287.