%0 Journal Article
%T Evolution of ice-dammed proglacial lakes in ¨²ltima Esperanza, Chile: implications from the late-glacial R1 eruption of Recl¨²s volcano, Andean Austral Volcanic Zone Evoluci¨®n de lagos proglaciales embalsados por hielo en ¨²ltima Esperanza, Chile: Implicancias de la explosi¨®n volc¨¢nica tardiglacial R1 del volc¨¢n Recl¨²s, Zona Volc¨¢nica Austral Andina
%A Charles R Stern
%A Patricio I Moreno
%A Rodrigo Villa-Mart¨ªnez
%A Esteban A Sagredo
%J Andean Geology
%D 2011
%I Servicio Nacional de Geolog¨ªa y Miner¨ªa (SERNAGEOMIN)
%X Newly described outerops, excavations and sediment cores from the region of ¨²ltima Esperanza, Magallanes, contain tephra derived from the large late-glacial explosive Rl eruption of the Recl¨²s 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¡À240 14C yrs BP), and volume, to >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¨®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¨ªnsula Antonio Varas west of Seno Ultima Esperanza, to-150 m a.s.l. aroundLago Sof¨ªa, 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¨ªa 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¡À180 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 <80 m a.s.l. at the time of this eruption. The original lake may have drained to this level across the low elevation pass between Fiordo Obstrucci¨®n and Seno Skyring, and subsequently into Seno Otway and the Pacific Ocean, when Canal Jer¨®nimo opened up prior to the Rl eruption. Another suite of cores, from the Eberhard site, ind¨ªcate that the lake persisted at >70 m a.s.l. until 12.8 cal kyrs BP (10,695¡À40 14C yrs BP). However, a 14.2 cal kyrs BP (12,125¡À85 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¨ªnsula 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
%K ¨²ltimo M¨¢ximo Glacial
%K Tefra
%K Lagos proglaciales
%K Terrazas glaciolacustres
%K Rebote isost¨¢ticoposglaciales
%K Mylodon
%K Chil
%K Last Glacial Maximum
%K Tephra
%K Ice-dammed proglacial lakes
%K Lake terraces
%K Post-glacial isostatic rebound
%K Mylodon
%K Chile
%U http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062011000100005