HR: 14:00h
AN: GC53A-03 INVITED     [Abstracts]
TI: High Resolution Fossil Chironomid Records From Lake Mascardi (41§S) During The Late Glacial: Additional Evidence Of The Huelmo/Mascardi Cold Reversal Event.
AU: * Massaferro, J
EM: julm@nhm.ac.uk
AF: CRUB, Universidad del Comahue, Quintral s/n, Bariloche, RN 8400 Argentina
AB: Despite the increasing number of palaeoclimatic studies from southern South America (Hajdas et al.,2004) there are still unresolved questions concerning the synchrony of climatic events between the northern and southern hemisphere and the extent of climate variability in the south. In particular, there is conflicting evidence about whether or not the Younger Dryas (YD) cold period, which is well-known from the North Atlantic region, was also evident in southern South America. So far, most of the evidence for climate change for these mid-latitude South American regions has been derived from glacial, pollen and beetle records but in an attempt to resolve these questions I have used chironomid midges as an independent proxy in one of the few studies of its kind in Patagonia. This study shows a high resolution chironomid stratigraphy, covering the Late Glacial cooling and early Holocene (between 15,000 and 11,000 cal yr BP) in Lake Mascardi, Argentina. An intensive radiocarbon chronology allowed to pinpoint the onset and timing of cold and warm episodes and to establish comparisons between previous multiproxy studies developed in the lake. The dynamics of the chironomid fauna of Lake Mascardi shows a cyclical pattern which appears to be linked to cold/warm climatic changes. Changes in chironomid assemblages indicated that a climatic cooling did occur during the YD and agreed with the Late Glacial scenario proposed by Hajdas et al. (2004). Based in a refined chronology, their results show the Huelmo/Mascardi Cold Reversal (HMCR) that encompasses the YD and a transition period, between 13,500 and 13,200 cal yr BP, preceding the onset of the YD event. The outstanding correlation between Hajdas' chronology and the chironomid results allowed to determine the exact phasing of cold/warm events confirming the HMCR between 13,300 and 11,500 cal yr BP (11,400-10,200 14C yr BP) as well as other short term climate oscillations occurred at Lake Mascardi. Hajdas, I., Bonani, G., Moreno, P.I., Ariztegui, D., 2003. Precise radiocarbon dating of Late-Glacial cooling in mid-latitude South America. Quaternary Research 59, 70- 78.
DE: 1620 Climate dynamics (3309)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting