Abstract This field guide provides an opportunity to examine the central Andes between 31° and 32°S latitude in a segment characterized by flat-slab subduction. The field trip road was chosen to observe the westernmost contact between the basement uplift of Sierras Pampeanas and Precordillera, the early Paleozoic stratigraphy, and the Andean structure of the Precordillera, as well as a complete section of the Frontal and Principal Cordilleras in Argentina and Chile. The trip ends in the Coastal Cordillera along the Pacific margin. This road log discusses a complete early and late Paleozoic history of the central Andes with their typical Famatinian and Gondwanan orogenic rocks and the accretionary evolution of the Pacific margin at these latitudes. Superimposed on this framework, the structure of the Andes is viewed through the examination of the Precordillera and the Aconcagua fold-and-thrust belts, together with the observation of the Andean volcanic history, will allow reconstructing the shallowing of the subduction zone through the Neogene and the final formation of the Pampean flat-slab.

Abstract The South American record of remagnetizations is linked to specific events of its tectonic history stretching back to Precambrian times. At the Ediacaran–Cambrian time interval (570–500 Ma), the final stages of the western Gondwana assemblage led to remagnetization of Neoproterozoic carbonates within the São Francisco–Congo Craton and at the border of the Amazon Craton, along the Araguaia–Paraguay–Pampean Belt. From the late Permian to early Triassic, the San Rafaelic orogeny and the emplacement of the Choiyoi magmatic province was responsible for widespread remagnetizations in Argentina and Uruguay. Cretaceous remagnetization has also been documented in Brazil and interpreted to result from magmatism and fault reactivations linked to the opening of the South Atlantic Ocean. We present a review of these widespread remagnetization events principally based on palaeomagnetic data and, when available, on rock magnetic and radiogenic isotope age data. This study gives an overview of the geographical distribution of the remagnetization events in South America, and provides important clues to better understand the geodynamic evolution of the South American plate at these times. In addition, magnetic mineralogy data for the different case studies presented here constrain the physical–chemical mechanisms that led to partial or total resetting of magnetic remanences in sedimentary rocks.

Abstract Early Paleozoic rocks are widespread, superbly exposed, and reach several thousand metres thick in southern South America. A largely quadripartite geotectonic subdivision of this huge area encompasses: (1) intracratonic basins forming the sedimentary cover of the Amazonian craton (Brazilian collage); (2) a clastic platform surrounding the Amazonian craton and the Pampia Terrane (Sierras Subandinas and Cordillera Oriental); (3) subduction-related parautochthonous volcanic arcs and associated volcano-sedimentary basins (Puna–Famatina arc); and (4) crustal fragments accreted to the proto-Andean margin of Gondwana (e.g. Cuyania Terrane). In this context, disparity in the geodynamic histories, preserved record and geological knowledge are remarkable. Biostratigraphical frameworks allow the recognition of global chronostratigraphical Ordovician subdivisions with fairly good resolution in the Early and Middle Ordovician of the Precordillera and the Early Ordovician of the Cordillera Oriental of Argentina. In Sierras Subandinas and Cordillera Oriental of Bolivia the Ordovician statigraphy is almost complete, although these extensive regions are still poorly known. In addition, trilobite-rich assemblages from the Cordillera Oriental and brachiopod-rich ones from Precordillera and Famatina offer a remarkable template for dissecting regionally different scenarios underlying Ordovician diversifications. Overall, a more complete knowledge of this key area of Gondwana will certainly enhance our understanding of the global dynamics during the Ordovician.