The Quaternary history of Fuego-Patagonia

Abstract

Tierra del Fuego and Patagonia are geographically so closely related that they can he called Fuego-Patagonia. Its two main units are the Andes and the region of the mesetas to the east of them. As a result of the predominantly westerly winds, the rainfall and the forests are concentrated in the Andes whereas in the region of the mesetas and the plains there are steppes and semideserts. The boundary between them seems to be a zone of struggle between the forest and the steppe. Its past oscillations can be studied against the background of palaeogeographic evolution especially since the last ice age. The stratigraphy of bogs and alluvial clays provides most important evidence on this topic. Tierra del Fuego is especially suitable as a study area since bogs are present all over the main island. In order to separate the ice ages with certainty, and thus to find out how many ice ages there were in Fuego-Patagonia, I looked for organic interglacial layers. Those found are the only ones so far recorded in South America. The southernmost is on the east coast of Tierra del Fuego in a till cliff facing the Atlantic Ocean, about 20 km from the Viamonte estancia (figure 26). The peat is, according to a dating at the Yale Geochronometric Laboratory, over 41000 years old. Its macro- and microscopic plant remains reflect a richer flora than the present one.