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Along the western slope of the Central Andes in the southernmost part of the Pampean flat-slab subduction zone segment (∼33°S), crustal Quaternary west-vergent reverse faults are found, but little is known about them. To better understand and characterize these faults, grouped as the Cariño Botado thrust fault system (CBF), we undertook a multidisciplinary study focused on remote sensing and field geomorphic and geologic mapping, sedimentary relationships, and fault characterization. Optically Stimulated Luminescence (OSL) and U Pb dating samples were obtained from faulted deposits to constrain the timing of fault motion. We combined the mapping, fault relationship descriptions, and age control to understand this system better and quantify tectonic rates here for the first time. The main CBF is best expressed with Late-Cenozoic hanging wall fault rocks over thrusting Quaternary coarse-grained alluvial fan deposits, and the fault zone is found over a large area and with an altered fault zone (∼0.5–2 km wide). The principal reverse fault segment of the CBF is well exposed in creeks, with an average dip of 40°E and an associated vertical throw (up to the east) of the hanging wall from ∼3.2 m up to ∼30 m. Five OSL samples, taken from tilted and untilted alluvial fan deposits adjacent to the CBF's main fault, yielded ages between 2.5 ± 0.2 ka and 9.0 ± 0.7 ka, supporting Holocene activity and ∼4.9 m of fault slip in the last ∼8.7 ka. Ninety-nine detrital zircons from fluvial terrace deposits in the study area were dated using U Pb ICPMS, giving mainly Oligo-Miocene ages. The youngest ages of detrital zircons are Quaternary (n = 3; ∼0.9–4.4 Ma), which indicates that CBF activity could have started as early as ∼0.9 Ma producing an accumulated hanging wall uplift of ∼130 m. The alignment of the fault profiles, creek and river knickpoints, and alluvial and fluvial deposits allows the most recent activity of the main CBF to be traced between 5 km and up to 15 km along the fault trace. Based on fault length, slip characteristics, and earthquake scaling relationships, earthquakes up to Mw 7.5 could be associated with the fault. Because of the clear relationship between the river incision, distribution of fluvial terraces, variation in sinuosity and stream power, and the location of the faults, we suggest that the tectonic uplift controls the hanging wall fluvial incision from ∼0.9 Ma to the present. The Quaternary (at least 0.9 Ma to present) active CBF shares geometric, structural, and rupture timing similarities with the nearby better-characterized San Ramón Fault system. The latter is located ∼50 km to the south along the eastern border of Santiago, the capital city of Chile. Both fault systems share a comparable morpho-structural setting with a consistent average N-S trend. Significant seismic hazard is associated with both the CBF and the San Ramon System, which may be linked structurally and temporally regarding previous surface ruptures and major earthquakes, and therefore remain important research targets. • Tectonic geomorphology of a west-vergent thrust at a flat-slab of the Andes • Studies fault exposures, uplifted terraces, and tilted alluvial fan deposits • Fault activity dated by OSL and U Pb applied to geomorphic markers • Space-time similarities between the San Ramón and Cariño Botado faults • Cariño Botado faults suggests a possible seismic hazard of up to Mw 7.5. [ABSTRACT FROM AUTHOR]

Andean fold-and-thrust belts (FTBs) in the western border of South America show important along-strike variations in their structural style (thin- or thick-skinned) and shortening magnitudes, among others. These variations can arise from multiple factors, such as depth-to-detachment, geometry, and thickness of underlying basins, structural highs, the competence of the units involved in deformation, pre-orogenic structure of the basement, the rheological state of the upper crust or latitudinal gradients in shortening, among others. We carry out a set of new analogue models to understand how two of these factors affect the development and the geometry of the thrust systems within the Andean Principal Cordillera and adjacent fold-and-thrust belts at 32°-34°S (La Ramada and Aconcagua FTBs). In this contribution, we present the results of analogue modeling of doubly-vergent thrust systems with a built-in heterogeneity that allow us to evaluate the influence of differential shortening and presence of competent blocks (of relatively higher cohesion) in the generation, evolution, and structural setting of Andean FTBs. We highlight that despite the similar pattern of differential shortening in the models, the presence of the competent block has a significant influence on the structural configuration and leads to greater topographic uplift. Differential shortening plays a role in accommodating deformation, but when a competent block is present, the faults bounding the block control the deformation, producing a notable curvature of the FTBs. Summarizing, the presence of a competent block significantly influences the structural configuration within a doubly-vergent thrust system, emphasizing the role of inherited architecture in the orogenic growth of the Southern Central Andes. • Analogue models were carried out to assess the impact of differential shortening and competent blocks on FTB formation. • We ran a series of models to establish comparisons with the Principal Cordillera and neighboring FTBs in the Central Andes. • We recognize that pre-orogenic architecture controls the structural development of the Southern Central Andes. • We recognize that competent blocks within a doubly-vergent wedge induces the generation of curved thrust systems. • We propose that differential shortening and competent blocks exert critical control on obliquity andmcurvatures of structures. [ABSTRACT FROM AUTHOR]