Surtseyan tuff cones of the Bano Nuevo Volcanic Complex erupted in shallow marine water during the waning stage of the Aisen Basin, the northern part of the Austral Basin of the Central Patagonian Cordillera. This volcanic complex was emplaced within the Hauterivian to early Aptian Apeleg Formation, the youngest sedimentary unit of this basin, whilst the sediments were still wet. Three new Ar/Ar dates (amphibole) and one U-Pb SHRIMP date (zircon) from this complex yielded concordant early Aptian ages of 122-121 Ma. These data agree with the contact relationships between the Apeleg Formation and the tuff cones. These dates also agree with those of early Aptian ammonites collected from the Apeleg Formation 100 km south of the study area, which represent the youngest fossils identified in this unit. Aptian to Albian subaerial volcanic rocks of the Divisadero Group, paraconformably overlie the Apeleg Formation. The emplacement of the Bano Nuevo Volcanic Complex pre-dates the disappearance of the Aisen Basin. (C) 2009 Elsevier Ltd. All rights reserved.