@article{SchildgenvanderBeekD'Arcyetal.2022, author = {Schildgen, Taylor F. and van der Beek, Peter A. and D'Arcy, Mitch and Roda-Boluda, Duna N. and Orr, Elizabeth N. and Wittmann, Hella}, title = {Quantifying drainage-divide migration from orographic rainfall over geologic timescales}, series = {Earth \& planetary science letters}, volume = {579}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2021.117345}, pages = {13}, year = {2022}, abstract = {Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Aconquija, on the eastern side of the southern Central Andes, northwest Argentina, is undergoing active westward drainage-divide migration. The mountain range has been subjected to steep rock trajectories and pronounced orographic rainfall for the last several million years, presenting an ideal setting for using low-temperature thermochronometric data to explore its topographic evolution. We perform three-dimensional thermal-kinematic modeling of previously published thermochronometric data spanning the windward and leeward sides of the range to explore the most likely structural and topographic evolution of the range. We find that the data can be explained by scenarios involving drainage-divide migration alone, or by scenarios that also involve changes in the structures that have accommodated deformation through time. By combining new Be-10-derived catchment-average denudation rates with geomorphic constraints on probable fault activity, we conclude that the evolution of the range was likely dominated by west-vergent faulting on a high-angle reverse fault underlying the range, together with westward drainage-divide migration at a rate of several km per million years. Our findings place new constraints on the magnitudes and rates of drainage-divide migration in real landscapes, quantify the effects of orographic rainfall and erosion on the topographic evolution of a mountain range, and highlight the importance of considering drainage-divide migration when interpreting thermochronometer age patterns.}, language = {en} } @article{OrtizSaezAlvaradoetal.2022, author = {Ortiz, Gustavo and Saez, Mauro and Alvarado, Patricia and Rivas, Carolina and Garc{\´i}a, V{\´i}ctor Hugo and Alonso, Ricardo and Zullo, Fernando Morales}, title = {Seismotectonic characterization of the 1948 (M-W 6.9) Anta earthquake Santa Barbara System, central Andes broken foreland of northwestern Argentina}, series = {Journal of South American earth sciences}, volume = {116}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2022.103822}, pages = {15}, year = {2022}, abstract = {The region of the Andean back-arc of northwestern Argentina has been struck by several magnitude >= 6 crustal earthquakes since the first historically recorded event in 1692. One of these events corresponds to the Anta earthquake on 25 August 1948, with epicenter in the Santa Barbara System causing three deaths and severe damage in Salta and Jujuy provinces with maximum Modified Mercalli seismic intensities (MMI) of IX. We collected and digitized analog seismograms of this earthquake from worldwide seismic observatories in order to perform first-motion analysis and modeling of long-period teleseismic P-waveforms. Our results indicate a simple seismic source of M0 = 2.85 x 1019 N m consistent with a moment magnitude Mw = 6.9. We have also tested for the focal depth determining a shallow source at 8 km with a reverse focal mechanism solution with a minor dextral strike-slip component (strike 20 degrees, dip 30 degrees, rake 120 degrees) from the best fit of waveforms. Using magnitude size empirical relationships, the comparison of the obtained Mw 6.9 magnitude value and the ca. 10,000 km2 area of MMI >= IX from our seismic intensity map, which was obtained from newspaper and many historical reports, indicates a rupture length of 42 +/- 8 km for the Anta earthquake. We show our results in a 3D geological model around the epicentral area, which integrates modern seismicity, geological data, and information of a previously studied east-west cross section located a few kilometers south of the 1948 epicenter. The integration of all available information provides evidence of the re-activation of the Pie de la Sierra del Gallo fault during the 1948 Mw 6.9 shallow earthquake; this thrust fault bounds the Santa Barbara System along its western foothill.}, language = {en} } @article{LiuSobolevBabeykoetal.2022, author = {Liu, Sibiao and Sobolev, Stephan and Babeyko, Andrey and Pons, Micha{\"e}l}, title = {Controls of the foreland deformation pattern in the orogen-foreland shortening system}, series = {Tectonics}, volume = {41}, journal = {Tectonics}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1029/2021TC007121}, pages = {18}, year = {2022}, abstract = {Controls on the deformation pattern (shortening mode and tectonic style) of orogenic forelands during lithospheric shortening remain poorly understood. Here, we use high-resolution 2D thermomechanical models to demonstrate that orogenic crustal thickness and foreland lithospheric thickness significantly control the shortening mode in the foreland. Pure-shear shortening occurs when the orogenic crust is not thicker than the foreland crust or thick, but the foreland lithosphere is thin (<70-80 km, as in the Puna foreland case). Conversely, simple-shear shortening, characterized by foreland underthrusting beneath the orogen, arises when the orogenic crust is much thicker. This thickened crust results in high gravitational potential energy in the orogen, which triggers the migration of deformation to the foreland under further shortening. Our models present fully thick-skinned, fully thin-skinned, and intermediate tectonic styles in the foreland. The first tectonics forms in a pure-shear shortening mode whereas the others require a simple-shear mode and the presence of thick (>similar to 4 km) sediments that are mechanically weak (friction coefficient