In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate (i.e., thickness and composition of the rock units) and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29°–39°S). Here, the subduction angle increases from subhorizontal (5°) north of 33°S to steep (~30°) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive thermal modeling. We found that the orogen is overall warmer than the forearc and the foreland and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (<50 km depth). Specific conditions are present where the oceanic slab is relatively shallow (<85 km depth) and the radiogenic crust is thin. This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50 km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening.

In the orogen-foreland shortening system, pure-and simple-shear are two common shortening modes in foreland deformation belts. The pure-shear shortening mode is characterized by a vertically quasi-homogeneous thickening of the foreland crust. In contrast, the foreland lithosphere underthrusts beneath the orogen along a low-angle detachment fault in the simple-shear mode. During shortening, crustal-scale deformation in the foreland forms either shallow thin-skinned, or deep thick-skinned tectonics (e.g., Dahlen, 1990;Lacombe & Bellahsen, 2016;Pfiffner, 2017). In the former, the sedimentary cover overlies the almost undeformed basement along a shallow décollement fault, while faults reach down into the basement in the latter. These different foreland deformation patterns (i.e., shortening mode and tectonic style) are generally found in natural orogens, for example, in the Central-Southern Andes (e.g.,

In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29°–39°S). Here, the subduction angle increases from subhorizontal (5°) north of 33°S, to steep (~30°) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive modeling. We found that the orogen is overall warmer than the forearc and the foreland, and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (< 50 km depth). Specific conditions are present where the oceanic slab is relatively shallow (< 85 km depth) and the radiogenic crust is thin, This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50 km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening.

In the orogen-foreland shortening system, pure-and simple-shear are two common shortening modes in foreland deformation belts. The pure-shear shortening mode is characterized by a vertically quasi-homogeneous thickening of the foreland crust. In contrast, the foreland lithosphere underthrusts beneath the orogen along a low-angle detachment fault in the simple-shear mode. During shortening, crustal-scale deformation in the foreland forms either shallow thin-skinned, or deep thick-skinned tectonics (e.g., Dahlen, 1990;Lacombe & Bellahsen, 2016;Pfiffner, 2017). In the former, the sedimentary cover overlies the almost undeformed basement along a shallow décollement fault, while faults reach down into the basement in the latter. These different foreland deformation patterns (i.e., shortening mode and tectonic style) are generally found in natural orogens, for example, in the Central-Southern Andes (e.g.,

In the orogen-foreland shortening system, pure-and simple-shear are two common shortening modes in foreland deformation belts. The pure-shear shortening mode is characterized by a vertically quasi-homogeneous thickening of the foreland crust. In contrast, the foreland lithosphere underthrusts beneath the orogen along a low-angle detachment fault in the simple-shear mode. During shortening, crustal-scale deformation in the foreland forms either shallow thin-skinned, or deep thick-skinned tectonics (e.g., Dahlen, 1990;Lacombe & Bellahsen, 2016;Pfiffner, 2017). In the former, the sedimentary cover overlies the almost undeformed basement along a shallow décollement fault, while faults reach down into the basement in the latter. These different foreland deformation patterns (i.e., shortening mode and tectonic style) are generally found in natural orogens, for example, in the Central-Southern Andes (e.g.,

The formation of the Central Andes dates back to ~ 50 Ma, but its most pronounced phase, including the growth of the Altiplano-Puna Plateau and pulsatile tectonic shortening phases, occurred within the last 25 Ma. The reason for this evolution remains unexplained. Using geodynamic numerical modeling we infer that the primary cause of the pulses of tectonic shortening and growth of Central Andes is the changing geometry of the subducted Nazca plate, and particularly the steepening of the mid-mantle slab segment which results in a slowing down of the trench retreat and subsequent shortening of the advancing South America plate. This steepening rst happens after the end of the at slab episode at ~ 25 Ma, and later during the buckling and stagnation of the slab in the mantle transition zone. The Intensity of the shortening events is enhanced by the processes that mechanically weaken the lithosphere of the South America plate, which were suggested in previous studies. These processes include delamination of the mantle lithosphere and weakening of the foreland sediments. Our new modeling results are consistent with the timing and amplitude of the deformation from geological data in the Central Andes at the Altiplano latitude.

&lt;p&gt;The Sierras Pampeanas (29 - 35&amp;#176;S) located south of the Altiplano-Puna plateau above the Chilean subduction zone, consist of uplifted foreland basement blocks that are an expression of the eastward propagation of compresive deformation. Their presence is one of the most enigmatic features of the Andes. The formation of these ranges is considered an end member of the thick-skinned foreland deformation style, which involves the deformation of the sedimentary cover and the crystalline basement. At 33&amp;#176;S, the onset of compression occurs at 22Ma, and the change between thin and thick skinned deformation style at 16Ma. However, the mechanism responsible for this evolution remains controversial. Two main hypotheses have been proposed to explain this evolution. The first one atributes the change in foreland deformation style to the setting of the Pampean flat slab at 12 Ma, which is contemporanous to the southward migration and subduction of the Juan Fernandez hotspot ridge at 33S. Alternatively, it has been proposed that the reactivation of pre-existing structures inherited from pre-Neogen tectonic events could better explain the onset of deformation about 10 Ma before the arrival of the flat-slab. To resolve this controversial debate, we have developed a data-driven 3D geodynamic model using the FEM geodynamic code ASPECT. We incorporated the present-day geometrical and thermal configuration of the southern central Andes and the flat-slab from previous models. This approach allowed us to study the structural and thermomechanical factors responsible for the location of deformation in the Sierras Pampeanas (e.g., topography, temperature and composition, strength of the lithosphere and velocity of the plates).&amp;#160; Moreover, &amp;#160;we investigated the role of the geometry of the Nazca plate on the foreland deformation, and proposed a new mechanism (&quot;flat slab conveyor)&quot; that reconciles the timing of the main geological events (onset of shortening, change in tectonics style of deformation of the foreland, growth of the topography, cessation of volcanic activity, uplift of the basement, and propagation of the deformation). This work expands our understanding of how plates interact at convergent boundaries, in particular at the subduction zones, and how and where deformation is expressed at the surface of the the upper continental plate.&lt;/p&gt;

The formation of the Central Andes dates back to ~50 Ma, but its most pronounced phase, including the growth of the Altiplano-Puna Plateau and pulsatile tectonic shortening phases, occurred within the last 25 Ma. The reason for this evolution remains unexplained. Using geodynamic numerical modeling we infer that the primary cause of the pulses of tectonic shortening and growth of Central Andes is the changing geometry of the subducted Nazca plate, and particularly the steepening of the mid-mantle slab segment which results in a slowing down of the trench retreat and subsequent shortening of the advancing South America plate. This steepening first happens after the end of the flat slab episode at ~25 Ma, and later during the buckling and stagnation of the slab in the mantle transition zone. The Intensity of the shortening events is enhanced by the processes that mechanically weaken the lithosphere of the South America plate, which were suggested in previous studies. These processes include delamination of the mantle lithosphere and weakening of the foreland sediments. Our new modeling results are consistent with the timing and amplitude of the deformation from geological data in the Central Andes at the Altiplano latitude.