ABSTRACT Uplift of the central Andes during the Miocene was followed by large-scale reorganization of Atlantic-draining rivers in Argentine Patagonia. Here, we document the abandonment of one large river in the late Pliocene and the establishment of the modern drainage in the Early Pleistocene. A chronology for these events is provided by 40 Ar/ 39 Ar ages on basalt flows. Remnants of the Pliocene paleovalley system are well preserved in the Lago Cardiel–Gobernador Gregores area, where they are eroded into flat-lying basalt flows dated from ca. 13.9 Ma to 8.6 Ma. Younger basalts that erupted onto the abandoned floor of the paleovalley are as young as 3.7 Ma. Abandonment of the Pliocene paleovalley and establishment of the modern Río Chico and Río Shehuen catchments happened near the close of the Pliocene when Andean glaciers incised the east-sloping pediment on which the late Miocene drainage was established. Lago Cardiel sits within a large endorheic basin that is inset into the late Pliocene paleovalley. The basin began to develop just before 4 Ma, after the paleovalley was abandoned. It became larger and deeper during the Pleistocene due to mass movements along its margins, deflation of the basin floor during times when Lago Cardiel was dry or nearly dry, and possibly lowering along bounding faults. The Pliocene–Pleistocene landscape and drainage changes that we have documented are not unique to the Lago Cardiel–Gobernador Gregores area; similar changes are apparent elsewhere in Patagonia east of the crest of the Andes.

Abstract The Timor Orogen comprises the island of Timor, a narrow offshore area to the north and a wider offshore fold-and-thrust belt to the south. This orogen formed by jamming and subsequent collision of the Banda Sea subduction system by the Australian Plate. The BandaSeis seismic survey has revealed excellent images of the deep-water fold-and-thrust belt. Seismic interpretation of the dataset demonstrated structural and tectonic features not previously described, including regional geological features on the Australian continental crust and two regional NE–SW sinistral strike-slip faults, and a prominent Middle Permian palaeogeographical high (Timor Plateau). Moreover, since the Middle–Late Triassic and Middle Jurassic, the two NE-trending strike-slip faults governed the formation of the West Timor and Cova-Lima sub-basins. The location along the Australian margin plays a dominant role in controlling the structural style and shaping of the Timor Orogen. Vertical loading and the southerly motion of the orogenic wedge are the main driving forces responsible for its building, illustrating a thin-skinned tectonic framework. Thrust faults nucleate in a forward-breaking sequence in the motion of thrust transport, with younger thrusts developing in front of older thrusts. Most of the collisional deformation has been classified into two styles: shallow thin-skinned and deep-seated deformation.