An introduction to the geology of Tierra del Fuego

DÍAZ BALOCCHI, LUIS; CAO, SEBASTIÁN JOSÉ; BEDOYA AGUDELO, ÉRIKA LORENA

Geological Resources of Tierra del Fuego

Springer

Año: 2021; p. 1 - 17

Tierra del Fuego is an island located at the southern tip of South America. It is one of the southernmost emerged lands on Earth, except for Antarctica. Its position is significant in terms of geologic environments both in the past and present times. During the Middle Jurassic, southern South America was exposed to regional extension and volcanism, associated to the breakup of Gondwana supercontinent. In the Early Cretaceous, the Rocas Verdes back-arc basin (which included oceanic floor expansion) was developed. Contractional tectonics started in the Late Cretaceous, closing the back-arc basin and initiating the Andean orogeny. The crustal thickening led to the formation of the Austral (Magallanes) foreland basin. From the Late Cretaceous to the Eocene the Fuegian Andes went through a counterclockwise rotation that generated the bending of the South America-Antarctica connection and formed an orocline. Crustal extension responsible for the rupture of the continental bridge started at the Eocene and implied the relative displacement of South America to the north and Antarctica to the South. The contraction in the Fuegian Andes ended during the Miocene. Later, they were affected by a strike-slip faulting regime associated with transcurrence that started in the late Miocene. Nowadays, the island is placed over the South American and Scotia plates, separated by the Magallanes Fagnano transform boundary (tectonically active) and is encircled by the Andes range to the west and south. Through the late Cenozoic, diverse agents sculpted the relief of Tierra del Fuego, mainly triggered by tectonic, climatic and eustatic action. Since the Late Miocene, the climate of southern South America entered the glacial cycles that are still active. Ice sheets covered the highest mountains in the southwestern portion of the island and fed four main ice lobes that occupied valleys in the lowlands. Late Pleistocene and Holocene glaciers were restricted to the higher and southern zones. Coastal landscapes of the island expose evidences of the oscillation of sea level through the late Cenozoic. Neotectonics related to the Magallanes-Fagnano Transform System is playing an important role in the landscape development in the central region.