The history of the southern central Andes, including the world's second largest plateau and adjacent intermontane basins and ranges of the Eastern Cordillera and the northern Sierras Pampeanas of Argentina and Bolivia, impressively documents the effects of tectonics and topography on atmospheric circulation patterns, the development of orographic barriers, and their influence on erosion and landscape evolution at various timescales. Protracted aridity in the orogen interior has facilitated the creation and maintenance of the Puna-Altiplano plateau. Contraction and range uplift, filling of basins, and possibly wholesale uplift of the plateau increased gravitational stresses in the orogen interior, which caused the eastward migration of deformation into the foreland and successive aridification. The uplift of the Andean orogen has also had a far-reaching influence on atmospheric and moisture-transport patterns in South America. This is documented by the onset of humid climate conditions on the eastern side of the Andes in late Miocene time, which was coupled with the establishment of dramatic precipitation gradients perpendicular to the orogen, and changes in tectonic processes in the Andean orogenic wedge.

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[1] The northwest Argentine Andes constitute a premier natural laboratory to assess the complex interactions between isolated uplifts, orographic precipitation gradients, and related erosion and sedimentation patterns. Here we present new stratigraphic observations and age information from intermontane basin sediments to elucidate the Neogene to Quaternary shortening history and associated sediment dynamics of the broken Salta foreland. This part of the Andean orogen, which comprises an array of basement-cored range uplifts, is located at ∼25°S and lies to the east of the arid intraorogenic Altiplano/Puna plateau. In the Salta foreland, spatially and temporally disparate range uplift along steeply dipping inherited faults has resulted in foreland compartmentalization with steep basin-tobasin precipitation gradients. Sediment architecture and facies associations record a three-phase (∼10, ∼5, and <2 Ma), east directed, yet unsystematic evolution of shortening, foreland fragmentation, and ensuing changes in precipitation and sediment transport. The provenance signatures of these deposits reflect the trapping of sediments in the intermontane basins of the Andean hinterland, as well as the evolution of a severed fluvial network. Present-day moisture supply to the hinterland is determined by range relief and basin elevation. The conspiring effects of range uplift and low rainfall help the entrapment and long-term storage of sediments, ultimately raising basin elevation in the hinterland, which may amplify aridification in the orogen interior. Citation: Hain, M. P.,

An array of 74 seismological stations was deployed in the Argentine Puna and adjacent regions for a period of two years. The aim is to investigate the seismic structure in the crust and upper mantle in order to address fundamental questions regarding the processes that form, modify and destroy continental lithosphere and control lithospheric dynamics in this part of the Central Andes. This portion of the Central Andes is an ideal locale to address these questions given that there is geologic evidence that there has been recent lower crustal and mantle lithospheric delamination. 2We performed a teleseismic P wave tomography study using seismic events at both teleseismic

The intermontane Quebrada de Humahuaca Basin (Humahuaca Basin) in the Eastern Cordillera of the southern Central Andes of NW Argentina (23°-24°S) records the evolution of a formerly contiguous foreland-basin setting to an intermontane depositional environment during the late stages of Cenozoic Andean mountain building. This basin has been and continues to be subject to shortening and surface uplift, which has resulted in the establishment of an orographic barrier for easterly sourced moisture-bearing winds along its eastern margin, followed by leeward aridification. We present new U-Pb zircon ages and palaeocurrent reconstructions suggesting that from at least 6 Ma until 4.2 Ma, the Humahuaca Basin was an integral part of a largely contiguous depositional system that became progressively decoupled from the foreland as deformation migrated eastward. The Humahuaca Basin experienced multiple cycles of severed hydrological conditions and subsequent re-captured drainage, fluvial connectivity with the foreland and sediment evacuation. Depositional and structural relationships among faults, regional unconformities and deformed landforms reveal a general pattern of intrabasin deformation that appears to be associated with different cycles of alluviation and basin excavation in which deformation is focused on basin-internal structures during or subsequent to phases of large-scale sediment removal.