Chronology of the last glaciation in central strait of magellan and bahía inútil, southernmost south america

• Published in: Geografiska annaler. Series A, Physical geography Vol. 87; no. 2; pp. 289 - 312
• Main Authors: Mcculloch, R.D., Fogwill, C.J., Sugden, D.E., Bentley, M.J., Kubik, P.W.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Taylor & Francis 01.06.2005; Blackwell Publishing Ltd; Swedish Society for Anthropology and Geography
• Subjects: Boulders; Glacial lakes; Glacial landforms; Glacial retreat; Glaciers; Moraines; Peat; Proglacial lakes; Radiocarbon; Tephra
• ISSN: 0435-3676; 1468-0459
• DOI: 10.1111/j.0435-3676.2005.00260.x

Glacier fluctuations in the Strait of Magellan tell of the climatic changes that affected southern latitudes at c. 53-55°S during the Last Glacial Maximum (LGM) and Late-glacial/Holocene transition. Here we present a revised chronology based on cosmogenic isotope analysis, 14 C assays, amino acid racemisation and tephrochronology. We unpick the effect of bedrock-derived lignite which has affected many 14 C dates in the past and synthesise new and revised dates that constrain five glacier advances (A to E). Advance A is prior to the LGM. LGM is represented by Advance B that reached and largely formed the arcuate peninsula Juan Mazia. Carbon-14and 10 Be dating show it occurred after 31 250 cal yrs BP and culminated at 25 200-23 100 cal yrs BP and was then followed by the slightly less extensive advance C sometime before 22 400-20 300 cal yrs BP. This pattern of an early maximum is found elsewhere in South America and more widely. Stage D, considerably less extensive, culminated sometime before 17 700-17 600 cal yrs BP and was followed by rapid and widespread glacier retreat. Advance E, which dammed a lake, spanned 15 500-11770 cal yrs BP. This latter advance overlaps the Bølling-Allerød interstadials and the glacier retreat occurs during the peak of the Younger Dryas stadial in the northern hemisphere. However, the stage E advance coincides with the Antarctic Cold Reversal (c. 14800-12700 cal yrs BP) and may indicate that some millennial-scale climatic fluctuations in the Late-glacial period are out of phase between the northern and southern hemispheres.