Evolution of ice-dammed proglacial lakes in 迆ltima Esperanza, Chile: implications from the late-glacial R1 eruption of Recl迆s volcano, Andean Austral Volcanic Zone Evoluci車n de lagos proglaciales embalsados por hielo en 迆ltima Esperanza, Chile: Implicancias de la explosi車n volc芍nica tardiglacial R1 del volc芍n Recl迆s, Zona Volc芍nica Austral Andina

作者：Charles R Stern; Patricio I Moreno; Rodrigo Villa Martinez; Esteban A Sagredo

来源：Andean Geology, 2011.

• ultimo Maximo Glacial
• Tefra
• Lagos proglaciales
• Terrazas glaciolacustres
• Rebote isostaticoposglaciales
• Mylodon
• Chil
• Last Glacial Maximum
• Tephra
• Ice-dammed proglacial lakes
• Lake terraces
• Post-glacial isostatic rebound
• Mylodon
• Chile

Newly described outerops, excavations and sediment cores from the region of 迆ltima Esperanza, Magallanes, contain tephra derived from the large late-glacial explosive Rl eruption of the Recl迆s volcano in the Andean Austral Volcanic Zone. New radiocarbon dates associated to these deposits refine previous estimates of the age, to 14.9 cal kyrs BP (12,670㊣240 14C yrs BP), and volume, to %26gt;5 km3, of this tephra. The geographic and stratigraphic distribution of Rl also place constraints on the evolution of the ice-dammed proglacial lake that existed east of the cordillera in this area between the termination of the Last Glacial Maximum (LGM) and the Holocene. This proglacial lake generated wave-cut terraces, and also caves, such as the Cueva de Milod車n, along the highest prominent terrace. The current elevation of these terraces depends on the total amount of post-glacial isostatic rebound, which is unknown. Due to differential rebound, the highest prominent lake terraces decrease in height from west-to-east, from -170 m a.s.l. on Pen赤nsula Antonio Varas west of Seno Ultima Esperanza, to-150 m a.s.l. aroundLago Sof赤a, anddownto-125 m a.s.l. along their easternmost margin. The presence of thick deposits of Rl tephra in some of the caves around Lago Sof赤a implies that the proglacial lake had already dropped below its highest level prior to the time of this eruption, and, in fact, even earlier, prior to 16.1 cal kyrs BP (13,560㊣180 14C yrs BP), when land mammals first oceupied these caves. The depositional environment of Rl in a core from Dumestre bog suggests that the lake level was in fact 70 m a.s.l. until 12.8 cal kyrs BP (10,695㊣40 14C yrs BP). However, a 14.2 cal kyrs BP (12,125㊣85 14C yrs BF) Mylodon pelvis from a nearby site, located at only -7 m a.s.l., suggests that the lake could have emptied, for at least a brief period, to this low level at this time. This latter datum, combined with the lack of any prominent terraces between the highest ones (170-125 m a.s.l.) and much lower ones (at only 30 m a.s.l. on Pen赤nsula Antonio Varas and 20 m a.s.l. along the coast north and south of Puerto Natales), suggests abrupt changes in the lake level after the Rl eruption. The likely mechanism for producing