Sand dispersal in the southeastern Austral Basin, Tierra del Fuego, Argentina: Outcrop insights from Eocene channeled turbidite systems

Abstract

We made a detailed facies analysis of well exposed Eocene foredeep and wedge-top successions in the SE Austral Basin of eastern Tierra del Fuego, Argentina, contributing to a better understanding of its patterns of sand dispersal. The analysis reveals that these successions constitute portions of turbidite systems with recurrent facies associations, interpreted as channel, channel-margin and levée depositional elements. The channel facies, paleocurrents and interpreted paleogeography suggest that the studied successions form the transfer zone of the turbidite systems that fed the foreland basin. We hypothesize that the SE Austral Basin, which forms the transition between the Austral and Malvinas Basins, acted as an east-west conduit for sediments sourced at the Fuegian Andes and transported to a deeper depositional zone in the SW Malvinas Basin. The fill of the channels in the transfer zone involved a large amount of turbidity flows, which in addition to the evidence of levée confinement in the studied deposits suggests that the sandier portion of the flows was able to reach the depositional zone, were mostly unconfined (sheeted) sand bodies may have formed. In addition, overbank sand bodies were deposited within the transfer zone, associated to processes of flow overspill. Both types of sand bodies constitute potential reservoirs in this hydrocarbon producing basin, implying that the Eocene SE Austral Basin, and the ultimate zone of deposition in the SW Malvinas Basin may constitute major prospects for hydrocarbon exploration. The proposed model define a new perspective for future research on the sedimentologic and stratigraphic evolution of the SE portion of the Austral Basin.