Fossil chironomids from Lake Mascardi (41ºS) during the Late Glacial/Holocene transition: more evidence of the Huelmo/Mascardi Cold Reversal Event (HMCR).

MASSAFERRO, J

Cordoba

Congreso; Holocene Environmental Catastrophes In South America: From The Lowlands to The Andes; 2005

ICGP 490-ICSU

There is conflicting evidence concerning the extent and timing of late-Quaternary climate variability in southern South America and how this may be linked to climate change in the Northern Hemisphere. In particular, there are still unresolved questions about the existence of the YD cold period in South America, which is well-known from the North Atlantic region [1, 2, 3, 5, 6, 7]. In recent years chironomid midges have emerged as a powerful independent proxy indicator of climate change. Studies in North America and Europe have shown that the distribution and abundance of chironomids are strongly influenced by air and water temperature, and low-error models have been developed to infer mean July air and surface water temperatures from fossil chironomid assemblages [4, 8, 9]. 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 climate changes.  Changes in chironomid assemblages provided evidence that a climatic cooling did occur during the YDC and agreed with the Late Glacial scenario proposed by Hajdas et al. (2004). Based in a refined chronology, their results show HMCR encompasses the YD and a transition preceding the YD event between 13,500 and 13,200 cal yr BP. An almost perfect correlation between Hajdas´ chronology and the chironomid results of the present study 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.