The Paleocene-Miocene of Península Mitre: foredeep and wedge-top of the Austral Basin, Tierra del Fuego, Argentina.

Abstract

The orogenic margin of the Austral-Malvinas foreland basin system is formed by a marine succession exposed at northern Península Mitre, composed of 550 m of the late Paleocene-early Eocene foredeep, and more than 2,900 m of the late middle Eocene-?Miocene María Luisa wedge-top sub-basin. The succession is subdivided in the following formations: La Barca (100 m, upper Paleocene), Punta Noguera (450 m, lower Eocene), Leticia (30 m, upper middle Eocene), Cerro Colorado (935 m, upper middle Eocene-upper Eocene), Puesto José (nom. nov., 1,600 m, Oligocene) and Malengüena (nom. nov., 216 m, ?Miocene). The foraminiferal content of the Malengüena Formation is distinguished by the dominance of Globocassidulina cf. brocha, and by its particular preservation, features not previously recognized in the Argentinean part of the Austral Basin. Syntectonic unconformities are recognized between the Paleocene-Eocene boundary and the middle Eocene, related to regional orogenesis; in the uppermost Eocene-lowermost Oligocene, locally related to the Campo del Medio anticline; in the ‘mid’ Oligocene, associated with the Malengüena backthrust; and in the ?lower Miocene, related to deep structures of the thrust-fold belt.