Abstract This final chapter is designed primarily for the foreign visitor to Chile who wishes to gain a broad overview of the field geology and scenery of central and northern Chile. We hope that it will also aid an appreciation of the nature of human interaction with this climatically and topographically challenging area, from the early settlers to the modern mining industry. This is a traverse along and across one of the world’s classic compressional ocean–continent subduction zones, where strong coupling between the oceanic and continental plates is linked to active mountain building, dramatic scenery, and frequent earthquake and volcanic activity. The drive moves north from Santiago, which lies in the forearc Central Valley west of the South American Southern Volcanic Zone, into one of the flat-slab Andean segments. Within this flat-slab zone we divert east to describe a west-to-east across-strike traverse from the coast into the High Andes where, because of the low dip of the subducting plate, volcanoes are absent (Chapters 4 and 5). Returning to the coast, the drive continues north into the latitude of the South American Central Volcanic Zone, with its superbly developed line of modern volcanoes in the hyperarid high Atacama Desert. A second west-to-east traverse from the coast to these volcanoes illustrates how the modern continental forearc region is segmented into a series of mountain belts and intervening basins, each with its own distinctive scenery and geology. Additional details on the rock units and places visited, and the tectonic settings of ancient and modern

Abstract This chapter examines the main characteristics of surface waters and groundwater deposits in Chile. The extreme variations in Chilean climate are reflected directly by huge differences in hydrological conditions, from the deserts of the north to the temperate rainforests of the south. The mountainous geomorphology, the presence of major basins, and the influence of the Pacific Ocean and the South Pole on oceanic currents and air masses, all also affect water distribution across the country. Anthropogenic demand for water resources, mostly for municipal wastewater, industry and agriculture, has created pollution problems that are currently being dealt with by application of new environmental legislation. Such problems are particularly acute in the north, where scarce water deposits, already commonly contaminated by naturally occurring metalliferous deposits, have been affected by extensive mining operations. In the centre of the country, where most of the population lives, the main challenges to a high quality water supply have been more associated with treating municipal wastewater. Further south, threats to clean water resources are often associated with effluents from cellulose plants and aquaculture. The striking variations in Chilean climate from north to south, and therefore water supply, stem mainly from geographic location, topography and atmospheric circulation. The importance of geographic location derives from the position of the country along the southwestern side of the South American continent, with a corresponding strong influence from the Pacific Ocean and the South Pole. Movements of Antarctic and Subantarctic water currents and masses of polar air affect the whole country. Similarly,

Abstract We combine geomorphological analysis of palaeosurfaces and U–Pb zircon geochronology of overlying tuffs to reconstruct the Neogene landscape evolution in north-central Chile (28–32°S). Prior to the Early Miocene, a pediplain dominated the landscape of the present-day Coastal Cordillera. The pediplain was offset during the Early (Middle?) Miocene, leading to uplift of the present-day eastern Coastal Cordillera and to the formation of a secondary topographic front. During the Late Miocene, the entire Coastal Cordillera was uplifted, with resulting deposition taking place within river valleys similar to those of the present day. A new pediplain developed on top of these deposits between the Early to Middle Pleistocene and was finally uplifted post-500 ka. These three major uplift stages correlate with episodes of increased deformation widely recognized throughout the Central Andes, starting after a Late Oligocene–Early Miocene episode of increased plate convergence. North of 30°S, the previous palaeotopography along the western Coastal Cordillera probably influenced Neogene landscape evolution. The presence of an inherited palaeotopography together with a strong decrease of precipitation to the north of 30°S would have determined differences in landscape development between this area and the area to the south of 30°S since the Early Miocene.

Abstract In this classic segment, many tectonic processes, like flat-subduction, terrane accretion and steepening of the subduction, among others, provide a robust framework for their understanding. Five orogenic cycles, with variations in location and type of magmatism, tectonic regimes and development of different accretionary prisms, show a complex evolution. Accretion of a continental terrane in the Pampean cycle exhumed lower to middle crust in Early Cambrian. The Ordovician magmatic arc, associated metamorphism and foreland basin formation characterized the Famatinian cycle. In Late Devonian, the collision of Chilenia and associated high-pressure/low-temperature metamorphism contrasts with the late Palaeozoic accretionary prisms. Contractional deformation in Early to Middle Permian was followed by extension and rhyolitic (Choiyoi) magmatism. Triassic to earliest Jurassic rifting was followed by subduction and extension, dominated by Pacific marine ingressions, during Jurassic and Early Cretaceous. The Late Cretaceous was characterized by uplift and exhumation of the Andean Cordillera. An Atlantic ingression occurred in latest Cretaceous. Cenozoic contraction and uplift pulses alternate with Oligocene extension. Late Cenozoic subduction was characterized by the Pampean flat-subduction, the clockwise block tectonic rotations in the normal subduction segments and the magmatism in Payenia. These processes provide evidence that the Andean tectonic model is far from a straightforward geological evolution.