Tectonomorphic and kinematic characterization of Neogene deformation in the southern Central Andes (23˚-28˚S, NW Argentina)

Abstract

<p>This thesis focuses on the tectonomorphologic evolution of the Central Andean Puna Plateau and its eastern foreland. The collective findings of fault-slip and tectonomorphic analyes help in understanding the mechanical behavior of non-collisional orogens at convergent plate boundaries and result in an improved Neogene tectonic record of the Central Andes.</p> <p>Fault-slip analysis indicates Neogene WNW-ESE horizontal shortening of the thickened crust of the Puna Plateau and Eastern Cordillera and simultaneous lateral gravitational spreading. The less thickened of Pampean Ranges continue to undergo horizontal shortening only. The importance of N-S extension in the kinematics of elevated parts of the Central Andes is underscored by the strike-slip components on prominent dip-slip faults. Strain axis configurations in the southern Central Andes are generally controlled by (1) overall WNW-ESE horizontal shortening imposed by plate convergence and (2) differences in crustal thickness, i.e., gravitational potential energy. Therefore, a geodynamic interpretations in which still increasing elevation and crustal thickness significantly influence upper-crustal kinematics of the southern Central Andes is suggested.</p> <p>To allow regional-scale tectonomorphic studies, including Valley-Width-to-Valley-Height (Vf) ratio and the Transverse-Topographic-Symmetry (T-) factor, an Esri ArcGIS compatible software tool was developed. This Geographical Information System (GIS)-based tool, was coded in Python to enable conversion to other ArcGIS versions. This herein presented first version of the tool is fully functioning and drastically reduces the otherwise long processing times.</p> <p>A qualitative main basin symmetry description, Mountain-Front-Sinuosity (Smf) indices, and Vf-ratios of second-order drainage basins, indicate ubiquitous Quaternary deformation on reverse and thrust faults in the southern Central Andes. The recorded Quaternary deformation strongly influences Quaternary landform development, as shown by main drainage basin asymmetries and second-order drainage basins shapes. However, non-systematic T-factor distribution for second-order basins indicates that basin asymmetry is subject to litholigcal variations.</p>