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The Andes offer a distinctive example of the intricate interplay among climate, tectonics, and surface processes. This is exemplified by the mountain range's north-south orientation, which contrasts with the prevailing east-west wind direction. This interplay controls the uplift evolution of the broken foreland and thus the sediment transfer and erosion from mountain ranges to their forelands. The Neuquén Andes is a peculiar segment of the southern Central Andes, registering dramatic North-South variabilities in elevation, climate, and tectonic intensities established during the Neogene and Quaternary. In this study, we aimed to identify the tectono-stratigraphic evidence of the Neogene to Quaternary evolution of paleo-environments and drainage networks in the intramountainous basin of Pampa de Agua Amarga in the broken foreland of the southern Neuquén Andes of Argentina. Starting with a non-depositional and/or erosional phase during the Paleogene, the Pampa de Agua Amarga Basin underwent several phases of syn-orogenic sedimentation in the late Oligocene to early Miocene. The basin gradually shifted from a lacustrine to an alluvial depositional environment, with alluvial deposits becoming dominant in the mid-Miocene and fluvial deposits dominating in the Pliocene. A significant event occurred during the late Pliocene to early Pleistocene when coarse fluvial deposits were deposited, marking the last aggradation phase. In the early Pleistocene, the onset of incision triggered the drainage system to cut through the downstream topographic barrier. The excavation of the basin was abrupt, as evidenced by a mid-Pleistocene stepped fluvial terrace and alluvial fan that filled a large canyon across the southern end of the downstream topographic barrier. The study confirms the regional trend that Miocene basin infill is related to dry climate and high tectonic uplift, which overwhelmed the erosive power of the drainage network. The lowering of tectonic uplift intensity in the southern Neuquén Basin during the Plio-Pleistocene, along with sudden fluctuations in the global colder and wetter climate, ultimately led to the excavation of the intramountainous basin. The Westerlies Wind Belts generate high precipitation rates in the southern Neuquén Andean Cordillera, feeding the Negro River catchment in the retroarc Andean broken foreland. Consequently, the erosive power of the Negro River catchment overcame the declining tectonic uplift, causing significant erosion of the entire broken foreland and Cordillera of the southern Neuquén Andes. Conversely, more intense tectonic uplifts in the northern Neuquén Andes built a more effective orographic barriers that limited precipitation rates of both the Westerlies Wind Belt and South America Summer Monsoon, and preserved the intramountainous basins and mountain interior from erosion. • Tectono-sedimentary analyze of an intramountainous basin in the South Neuquén Andes. • Neogene coarsening-up sequence due to a dry and warm climate and intense shortening. • Pleistocene basin excavation due to lower shortening and colder and wetter climate. • Pleistocene significant erosion and sedimentary transfer in the South Neuquén Andes. • Opposite tectonic, climate and thus basins' evolution in the North Neuquén Andes. [ABSTRACT FROM AUTHOR]

A morphostructural analysi s of a Pliocene flood basalt forma-tion in the southern Neuquén basin (40°S) shows evidence of contractional deformation less than 3.5 Ma ago. This forma-tion exhibits a general dip towards the south-east, with relict outcrops located 100 m higher than the main source volcano, which suggests a local tilting of the lava flow. This tilt has been brought about by Plio-Quaternary reactivation of the eastern border of the Sanico Massif along two thrusts that offset the lava flow. Another long-wavelength bulge in the southern part of the lava flow unit indicates a possible Pliocene uplift of the North Patagonian Massif. These results provide new evidence of continuing shortening in the Neuquén basin during the Plio-Quaternary, challenging the hypothesis that an extensional regime has existed since the end of the Miocene in this basin. [ABSTRACT FROM AUTHOR]

Although the Neuquén basin in Argentina forms a key transitional domain between the south-central Andes and the Patagonian Andes, its Cenozoic history is poorly documented. We focus on the sedimentologic and tectonic evolution of the southern part of this basin, at 39-40°30′S, based on study of 14 sedimentary sections. We provide evidence that this basin underwent alternating erosion and deposition of reworked volcaniclastic material in continental and fluvial settings during the Neogene. In particular, basement uplift of the Sañico Massif, due to Late Miocene-Pliocene intensification of tectonic activity, led to sediment partitioning in the basin. During this interval, sedimentation was restricted to the internal domain and the Collon Cura basin evolved towards an endorheic intermontane basin. From stratigraphic interpretation, this basin remained isolated 7-11 Myr. Nevertheless, ephemeral gateways seem to have existed, because we observe a thin succession downstream of the Sañico Massif contemporaneous with the Collon Cura basin-fill sequence. Comparisons of stratigraphic, paleoenvironmental and tectonic features of the southern Neuquén basin with other foreland basins of South America allow us to classify it as a broken foreland with the development of an intermontane basin from Late Miocene to Late Pliocene. This implies a thick-skinned structural style for this basin, with reactivation of basement faults responsible for exhumation of the Sañico Massif. Comparison of several broken forelands of South America allows us to propose two categories of intermontane basins according to their structural setting: subsiding or uplifted basins, which has strong implications on their excavation histories. [ABSTRACT FROM AUTHOR]