The chronology of the Last Glacial Maximum and deglacial events in central Argentine Patagonia

Andrew S. Hein, Nicholas R. J. Hulton, Tibor J. Dunai, David Sugden, Michael R. Kaplan, Sheng Xu

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Abstract

This paper evaluates the chronology of the last glacial cycle and deglaciation in the Lago Pueyrredon valley of central Patagonia, 47.5 degrees S, Argentina. The valley was a major outlet of the former Patagonian Ice Sheet and the moraines that record its fluctuations are an important proxy record of climate change in southern South America. Such moraines are well-preserved in the Lago Pueyrredon valley owing in part to the semi-arid environment east of the mountain front. Here, we provide the first direct chronology for the age of the "Rio Blanco" moraine system by utilizing cosmogenic-nuclide surface exposure ages. Boulders on the moraines give Be-10 exposure ages that indicate the Last Glacial Maximum (LGM) maximum extent occurred by 27-25 ka. Subsequent advances occurred at 23-22 ka, 20-18 ka, and ca. 18-17 ka. Initial deglaciation began after ca. 18-17 ka and was interrupted as evidenced by the Lago Columna moraines up-valley. Subsequently the outlet glaciers occupying both the Lago Pueyrredon basin (Chilean name: Lago Cochrane) and the Lago Buenos Aires basin (Chilean name: Lago General Carrera) to the north, rapidly retreated more than 80 km at around 16.5-15 ka. The timing of the LGM maximum extent and the onset of deglaciation occurred broadly synchronously throughout Patagonia. Deglaciation resulted in a series of interconnected glacier-dammed lakes in the region that initially drained toward the Atlantic Ocean and later drained to the Pacific Ocean as a consequence of disintegrating ice in the Andes.

Original languageEnglish
Pages (from-to)1212-1227
Number of pages16
JournalQuaternary Science Reviews
Volume29
Issue number9-10
DOIs
Publication statusPublished - May 2010

Keywords

  • SOUTHERN SOUTH-AMERICA
  • LAGO BUENOS-AIRES
  • COSMOGENIC NUCLIDE CHRONOLOGY
  • CHILEAN LAKE DISTRICT
  • HOLOCENE TRANSITION
  • ABRUPT VEGETATION
  • TAITAO PENINSULA
  • PRODUCTION-RATES
  • CENTRAL STRAIT
  • EXPOSURE AGES

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