Latest Pleistocene and Holocene glacier fluctuations in southernmost Tierra del Fuego, Argentina

• Autores: Menounos, Brian; Clague, John J.; Osborn, Gerald; Thompson Davis, P.; Ponce, Juan Federico; Goehring, Brent; Maurer, Malyssa; Rabassa, Jorge Oscar; Coronato, Andrea Maria Josefa; Marr, Rob
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Late Pleistocene; Holocene; Cirques; Tierra del Fuego; Glacier Fluctuations; Patagonia; Surface Exposure Dating; Tephrochronology
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27–12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38–12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52–17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5–12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9–11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96–7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96–7.34 ka and 5.29–5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to those of the Little Ice Age shortly before 5.29–5.05 ka.
Fil: Menounos, Brian. University of Northern British Columbia; Canadá
Fil: Clague, John J.. University Fraser Simon; Canadá
Fil: Osborn, Gerald. University of Calgary; Canadá
Fil: Thompson Davis, P.. Bentley University; Estados Unidos
Fil: Ponce, Juan Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina
Fil: Goehring, Brent. Purdue University; Estados Unidos
Fil: Maurer, Malyssa. University of Northern British Columbia; Canadá
Fil: Rabassa, Jorge Oscar. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina
Fil: Coronato, Andrea Maria Josefa. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina
Fil: Marr, Rob. University Fraser Simon; Canadá