Geological aspects and evolution of the Patagonian continental margin

Abstract

The Patagonian continental margin records some of the tectonic, sedimentary, climatic, and oceanographic events that participated in the evolution of the Patagonian and south-western Atlantic regions. Those records are essential for fully understanding the geology and biodiversity of Patagonia. Regional geotectonic and morphosedimentary features are characterized by different types of continental margins (passive, transcurrent, and transpressive). In each of them the constituent features (shelf, slope, and rise) acquire particular morphological and sedimentary configurations. Characteristics of the sedimentary sequences and the limiting discontinuities document the different evolutive stages of the margin and intervening major processes. The regional tectonic, palaeoclimatic, and palaeoceanographic events that occurred after the break-up of Gondwana until the Quaternary, which conditioned the morphosedimentary characteristics, are analysed and described here. It is concluded that the region evolved in three major stages, according to the predominance of different factors: (1) a stage dominated by endogene factors, which occurred in Mesozoic times, when the major processes at work were plate tectonics and oceanic opening; (2) a transitional stage, which occurred in the lower Tertiary, when the proto-Atlantic Ocean evolved towards an open sea, and climatic and oceanographic factors became at least as important as tectonic factors; and (3) a stage dominated by exogene factors, which occurred in post-Oligocene times, when the Atlantic Ocean was definitively installed and the circulation of oceanic currents influenced the characteristics of the sedimentary environmentsthis stage ended in the Quaternary when glacioeustatic fluctuations imprinted the present morphosedimentary configuration.