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Glaciations in the Magellan Straits and Tierra del Fuego, southernmost South America

2004; Elsevier BV; Linguagem: Inglês

10.1016/s1571-0866(04)80110-6

2212-1161

Andrea Coronato, Andrés Meglioli, Jorge Rabassa,

Climate change and permafrost

This chapter reviews that the landscape morphology of the southernmost end of South America shows many erosional and depositional features of glacial origin. Many of these features are related to ancient glaciations, although most of them represent the more recent Quaternary glacial events. In all cases, the glaciers that formed this landscape were derived from the mountain ice sheet of the Darwin Cordillera, from which ice tongues emerged in all directions. The genesis of the various ice lobes depended upon the ice thickness in each glacial episode and the underlying superficial relief. According to the regional morphology and stratigraphy, the formation of the different ice lobes would have been physically defined from the older to the younger glaciations in a progressive succession. As indicated in the map, the Sierra de los Frailes glaciation would have expanded over a vast extension, between the Rio Gallegos valley and Central Tierra del Fuego. The existence of an ancient glaciation, named the Rio Grande Glaciation, has been interpreted from the observation of scattered erratic boulders along the Rio Grande valley and neighbouring areas and more, a few tens of kilometres further north in the Rio Chico valley. This area belongs to a large basin that drains the western and central portions of Tierra del Fuego toward the Atlantic ocean. Moreover, this area received the outwash discharge of the glaciers occupying the Carmen Sylva and Beauvoir ranges during the Pleistocene. The region adjacent to the Atlantic coast in southeastern Tierra del Fuego is shown in the map as covered by "undifferentiated drifts" because the till deposits observed in various positions along the mountain valleys have not been studied in detail.