A Geological Heritage Itinerary Across the Andes in the Isla Grande de Tierra del Fuego

This chapter presents a strategy for disseminating some of the most important characteristics of the geological heritage of the Isla Grande de Tierra del Fuego. First, the geodiversity elements are related to the major morpho-structural episodes during the geological history of the Isla Grande, from the Jurassic—lower Cretaceous back-arc extension, through Andean compression that progressed diachronically from the SW Andean cordilleran belt (late Cretaceous) toward the NE Magallanes fold-and-thrust belt and Magallanes foreland basin (early Cenozoic) to final Cenozoic-to-recent sinistral transcurrent fault tectonic regime. Next, the didactic and geotouristic potential of a selection of localities is evaluated using different geoheritage criteria. We discuss the geological heritage potential of localities along the Canal Beagle as the low-grade metamorphic rocks at bahía Lapataia (W of Ushuaia), the older rock outcrops of the Isla Grande. To the NE, going from Ushuaia though Paso Garibaldi we found the meta-volcanoclastic rocks of Lemaire and Yahgán Fms., temoins of the volcano-sedimentary processes in the Jurassic-lower Cretaceous back-arc Rocas Verdes basin. The Yahgán Fm. rocks are seen deformed in Mount Olivia slope, a magnificent example of the Andean compressional episode. As examples of the Andean plutonic intrusives we discuss the geopotential of the diorite-syenite plutonic complex of Cerro Jeu-Jepén, near Tolhuin at eastern tip of Lago Fagnano and the ultramafics outcrops at Estancia Túnel, intruded in Yahgán rocks, with its contact metamorphic aureole and located in the N shore of Canal Beagle. Some examples of recent processes as the glaciofluvial and the seismically related deposits are analyzed near the E end of Lago Fagnano. Also, of recent glacial origin are the large erratic blocks of Punta Sinai and the placer type heavy mineral (including gold) deposits on the N coast of San Sebastián Bay, at the NE tip of Isla Grande.