Introduction

Abstract

This first chapter, as well as outlining the purpose of this book, introduces the regional framework of the basin, i.e. the Argentinian Extra-Andean Patagonia—the territory in which the San Jorge Gulf Basin occurs—its geographical location, extension and physical borders . The main geomorphological units are described, together with aspects of the landscape formation and the hydrography . The latter is characterized by its , perennial nature , the nival or pluvio-nival regime of the main rivers , and the fact that they lose water to groundwater, a situation that also occurs in lakes and dams . The lithology of the surface geology is very diverse, with ages ranging from the Proterozoic to the Cenozoic : Tertiary clastic and pyroclastic deposits predominate, followed by Cretaceous sedimentary rocks and Jurassic–Cretaceous igneous rocks . The hydrogeology is mainly conditioned by the climate . There are post-Jurassic aquifers of interest that occur in porous media , as well as deep aquifers occurring in fissured media . Brackish to saline groundwater prevails, with the occurrence of fresh groundwater in the local arid climate being due to particular recharge mechanisms. Its use is restricted and mainly reserved for domestic supply . Hydrocarbon production and metal mining use large volumes, though it is water of lower quality. Such economic activities have displaced the original primary activity, which was sheep farming.