The Island of Tierra del Fuego, at the southernmost extreme of Patagonia, is located in one of the most extensively glaciated areas of the Southern Hemisphere outside Antarctica during the late Pleistocene. The Lago Fagnano region, at ∼54°30′S and ∼68°W, has experienced several phases of glacier growth and retreat since the Last Glacial Maximum (LGM). We illustrate these phases using combined geomorphological, geophysical and coring surveys in Lago Fagnano itself, a ∼105 km-long, E-W-oriented glacio-tectonic basin. We identify and map a complex set of submerged frontal, central and lateral moraines covered by lacustrine sediments using seismic stratigraphic analysis of multi-channel profiles imaging the sub-lake floor. We then combine these geophysical data with field observations and regional maps of similar structures around the lake to reconstruct the spatial behavior of the Fagnano paleo-glacier since the LGM. We interpret the preserved frontal moraines as having formed during at least 20 re-advance stages of the glacier within a long-term deglaciation interval post-LGM. Preliminary tephrochronological dating of a ∼7.5 m long core indicates a step-wise deglaciation pattern comprising a final glacier re-advance stage at ∼11.2 ka BP.
Bibliographical noteFunding Information:
Robert Dunbar of Stanford and Christopher Moy of USGS Woods Hole Science Center are gratefully acknowledged for the invaluable help they provided in the field and for many long and fruitful scientific discussions. We thank Steffen Saustrup and Mark Wiederspahn of the Institute for Geophysics, and David Mucciarone of Stanford, for technical assistance during all aspects of the field work. Stanford University (Dunbar) supplied the R/V Neecho. This research also benefited from constructive discussions with Jan Mangerud from the University of Bergen and Mortaza Pirouz from the University of Geneva. The logistical help and hospitality of Alejandro, Maria Elena and Gabriel Echeverría from Bahía Torito on Lago Fagnano are kindly acknowledged. Centro Austral de Investigaciones Científicas (CADIC), located in Ushuaia, supplied housing and logistical support during the 2005 and 2006 field seasons. This work is part of the project Environmental Changes Down-South (ENDS) supported by the Swiss National Science Foundation , grants 200021-100668/1 and 200020-111928/1 (to Ariztegui and Anselmetti). We also acknowledge support from the U.S. National Science Foundation (to Dunbar) and the Joint Oceanographic Institutions, Inc. and National Geographic Society , grant CRE 7705-04 (both to Austin).
ASJC Scopus subject areas
- Global and Planetary Change
- Ecology, Evolution, Behavior and Systematics