Cordilleran-type Mountain building and subduction geometry: insights from the Peruvian Andean orogenic segment

Mountain building in Cordilleran-type orogens, such as the Andes, is controlled by complex interactions between subduction dynamics, crustal and lithospheric deformation, and climatic influences. However, the mechanisms linking these processes to the orogen's structural evolution remain poorly understood, particularly in regions influenced by variations in crustal thickness, plate heterogeneities, and mantle dynamics. This PhD thesis examines the impact of the Nazca Ridge on the tectonic and thermal evolution of the Peruvian Andean margin. The Nazca Ridge is an aseismic ridge formed in the early Cenozoic at the Pacific-Farallon/Nazca spreading centre that has been subducting beneath South America since 11 Ma, significantly influencing the geodynamics of the Peruvian forearc system and the South American Plate. Through integrated large-scale and local-scale investigations, this research reconstructs the lithospheric structure and deformation patterns associated with Nazca Ridge subduction. The study is organized around a multidisciplinary approach that begins by constructing a balanced and restored cross-section along the Peruvian margin using surface geological and geophysical data, delineating the crustal structure to a depth of approximately 130 km. This structural framework serves as the basis for developing a 2D geothermal model to analyse the thermal configuration of the overriding plate. Building on this, a forward gravity modelling technique is employed to refine the initial framework, generating a detailed density model that captures the complex lithosphere and crustal geometries associated with the subducting Nazca Ridge. Subsequently, the geothermal model is enhanced, and a 2D finite element analysis is conducted to simulate stress accumulation and megathrust deformation, providing a clearer picture of the mechanical behaviour of the overriding plate. Additionally, the geological structures and stratigraphic framework of the East Pisco Basin are mapped in detail, shedding light on the tectono-sedimentary evolution of the forearc region. The results underscore the significant impact of Nazca Ridge subduction on the tectonic evolution of the Peruvian margin, driving changes in thermal structure, stress distribution, and forearc basin development. This comprehensive approach offers new perspectives on the geodynamic processes shaping the Peruvian forearc and serves as a reference for understanding similar tectonic interactions in other convergent margin settings.