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Palinspastic restoration of the Cerro Mocho cross section, starting at the Neuquén basin synrift stage (Late Triassic to Early Jurassic times) (d), and following with Late Cretaceous tectonic inversion (c), Late Oligocene to Early Miocene early extensional relaxation (b), and Early Pliocene to Quaternary late extensional relaxation (after Late Miocene tectonic inversion) (a).
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The Andean orogenic front between 38 and 39 degrees S is formed by extensional structures delimiting the Loncopue trough. These structures are superimposed to Late Cretaceous-Late Miocene compressive structures that formed the Agrio fold and thrust belt. Gravity data, and limited borehole and seismic data complimented with previous field studies we...
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Lithospheric-scale fault systems control the large-scale permeability in the Earth’s crust and lithospheric mantle, and its proper recognition is fundamental to understand the geometry and distribution of mineral deposits, volcanic and plutonic complexes and geothermal systems. However, their manifestations at the current surface can be very subtle...
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... Gravity data extracted from global geopotential models provide an invaluable tool for regional-scale tectonic-geophysical analysis achieving homogeneous data coverage in those areas where ground gravity data maintain a skewed and dispersed distribution. The Residual Bouguer anomalies analysis based on different filtering techniques in the space domain (Bandpass and Butterworth) allows for defining the spatial continuity of blind structures (Pacino, 2007;Rojas Vera et al., 2010;Rivas et al., 2021). The geophysical and geological analyses would confirm the existence of blind structures limiting and controlling tectonic depressions and basement highs. ...
This work describes new evidence of N–S and oblique trending surface and blind structures in the La Cantera-Gualilán tectonic depression in the Central Precordillera, San Juan Province, Argentina. Two main N–S Quaternary thrusts cross longitudinally the valley located ∼60 km west of San Juan city (30° 50′- 31° 17′ S and 68° 55′- 69° 05′ W). One of them is located in the eastern piedmont of the Sierra de La Invernada (San Juan Fault) and the other in the western piedmont of the Sierra de La Cantera (La Cantera Fault System), although the northward continuation of this structure has not yet been confirmed.
Besides, a smooth water divide or “portezuelo” controlled by an oblique transpressive structure (Divisadero Coba Rubia Fault) separates two N–S elongated river basins with opposite water flow directions. One of these is the Gualilán River, which flows from south to north, and the other corresponds to the La Cantera River, running from north to south.
In the present work, we describe some new natural exposures and subtle geomorphological evidence of Quaternary structures identified in the Gualilán-La Cantera tectonic depression. We also use regional and local gravity data to analyze and interpret gravity anomalies related to these surface or blind active structures. Then, based on our geologic and geophysical interpretations, we infer the presence of several, buried cross-strike structures with NW and NE trends, one of them coincident with the drainage divide between the Gualilán and La Cantera opposite river basins, possibly related to the Coba Rubia Fault. Also, we suggest the northward continuation of the La Cantera Fault System (LCFS) as a buried structure in coincidence with the Gualilán River alluvial plain. In this sense, the gravity response of the basement and these river sub-basins shows a close relationship with the surface and subsurface structures. We propose that the oblique structures could represent pre-existing crustal fabrics reactivated during the Andean orogeny, segmenting the N–S Precordillera fold and thrust belt system. Finally, according to the analyzed neotectonic and gravimetric features, we consider the La Cantera-Gualilán Valley as a potentially seismogenic source in this intraplate portion of the Andean Precordillera, crossed by several N–S and oblique surficial and buried/blind active structures. These tectonic features could play a significant role in a regional seismic hazard assessment.
... Verduzco et al. (2004) suggested the effective use of the total horizontal derivative of tilt angle (HGTA), which is, by far, the most widely used edge detection algorithm. In order to decipher the basement discontinuities and main sedimentary depocenters, Vera et al. (2010) used the HGTA method and suggested that the method enhances the maximum horizontal gradients in low wavelength anomalies. Pinto and Vidotti (2019) applied the HGTA method over gravity and magnetic data to delineate the tectonic framework of the Paran a basin, South America. ...
Edge detection is one of the most commonly used interpretation techniques applied to potential data for detecting subsurface susceptibility/density discontinuities. Several edge detection techniques utilize the first, second, or even third-order gradients of the magnetic field to delineate the susceptibility contrasting zones. A new filter called Balanced Horizontal Gradient (BHG) filter is designed for enhancing the edges of the subsurface bodies that overcomes the limitations of the conventional filters. The BHG filter is based on the arctangent function of derivatives of horizontal gradients. The main advantage of the proposed filter is that it seems to detect all the source edges with no false edges generated around the true edges and effectively balances the edges arising from the shallow and deep-seated sources. We applied the filter on the aeromagnetic data from central India and identified the extensions of the Godavari rift and central Indian shear underneath the Deccan volcanic province.
... Particularly, a relevant Pliocene-Quaternary activity is focused on the Loncopué Trough (Fig. 1B). This is a narrow, N-S topographic depression of 200 km in length located between the 36 • 30 ′ and 39 • S and limited by the Agrio fold and thrust belt to the east and the volcanic arc to the west Rojas Vera et al., 2010Folguera et al., 2011;Pesce et al., 2019). The basal volcanosedimentary infill of the axial part of the depression starts in the early Pliocene (Cola de Zorro Formation), followed by silicic distal pyroclastic sequences associated with the development of a series of calderas in the west during Pleistocene times, and the posterior emplacement of a basaltic cover in the western sector (Rojas Vera et al., 2014;Pesce et al., 2019). ...
Monogenetic volcanoes are among the most common volcanic landforms on Earth. The morphology and distribution of small volcanoes can provide important information about eruption dynamics and tectonics. The Southern Volcanic Zone of the Andes (CSVZ) comprises one of the most active magmatic regions on Earth. Characterized by the presence of polygenetic volcanoes and calderas in a complex tectonic setting, this region also hosts hundreds of small, back-arc monogenetic volcanoes. In this contribution, we apply a Geographic Information System (GIS) that combines imagery data and digital elevation models to establish the first comprehensive dataset of monogenetic volcanoes in the CSVZ (38°to 40°S), exploring their eruption dynamics and relationship to tectonic and structural processes. Combining spatial analysis and geomorphological observations, we identify the presence of 335 monogenetic volcanoes distributed into nine clusters, now grouped in the Zapala Volcanic Field (ZVF). The ZVF is marked by the predominance of cinder cones (80%) followed by phreatomagmatic volcanoes (20%), suggesting some influence of external water in the eruption dynamics. Generally, monogenetic vents present a clear association with local and regional lineaments, suggesting a strong structural control on the occurrence of the monogenetic deposits. The higher vent densities are observed in the southern Loncopué Though, an important extensional feature related to tearing of the subducted Nazca plate underneath the South American Plate. Morphometric parameters of cinder cones indicate variable stress orientations in the CSVZ that possibly results from the oblique tectonics in the region. From north to south, the maximum principal stress rotates from NE-SW to E-W and becomes progressively less constrained as it distances from the current magmatic arc. Based on the relative ages, we map the evolution of monogenetic volcanism through time. Our results suggest a waning in the monogenetic activity in ZVF over time. When compared to monogenetic fields in the Central Andes, the ZVF is marked by higher vent densities and number phreatomagmatic landforms, with the absence of lava domes. This ultimately reflects the contrasting crustal structure and climate conditions of these two regions.
... The Agrio FTB extends from the 38°50′ to 37°35′ S and is characterized by two sectors with different structural styles (Vergani et al., 1995;Zamora Valcarce et al., 2007;Zapata & Folguera, 2005). To the west, the inner sector shows basement deformation and tectonic inversion of previous extensional (Triassic) structures Rojas Vera et al., 2010). The outer sector is dominated by thin-skinned deformation showing basal detachments within Jurassic and Lower Cretaceous evaporites and marine shales with a general deformation sense to the east and several west-verging backthrusts (Rojas Vera et al., 2015;Zamora Valcarce et al., 2011). ...
The Vaca Muerta Formation (Tithonian–early Valanginian) is the main source rock in the Neuquén Basin and the most important unconventional shale resource in South America. In the present study, organic geochemistry, electron microscopy and basin and petroleum system modelling (BPSM) were combined to evaluate source rock properties and related processes along a transect from the early oil (east) to the dry gas (west) window. The unit is characterised by high present‐day (1–8% average) and original (2–16% average) total organic carbon contents, which increase toward the base of the unit and toward basinal (west) settings. Scanning electron microscopy shows that organic pores derived from the transformation of type II kerogen. Isolated bubble pores are typical of the oil window, whereas bubble and densely distributed spongy pores occur in the gas stage, indicating that the maturity gradient exerts strong control on organic porosity. Organic geochemistry, pressure and porosity data were incorporated into a 2‐D basin petroleum system model that includes the sequential restoration of tectonic events and calculation of compaction trends, kerogen transformation, hydrocarbon generation and estimation of pore pressure through geologic time. The W–E regional model extends from the Agrio Fold and Thrust Belts to the basin border and allows us to evaluate the relationship between thermal maturity and timing of hydrocarbon generation from highly deformed (west) to undeformed (east) regions. Modelling results show a clear decrease of maturity and OM transformation toward the eastern basin margin. Maximum hydrocarbon generation occurred in the inner sectors of the belt, at ~120 Ma; long before the first Andean compression phase, which started during the Late Cretaceous (~70 Ma). Miocene compression (15 to 7 Ma) promoted tectonic uplift of the inner and outer sectors of the belt associated with a reduction of thermal stress and kerogen cracking, as well as massive loss of retained fluids and a decrease in pore pressure. The organic matter transformation impacted (1) the magnitude of effective porosity associated with organic porosity development, and (2) the magnitude and distribution of pore pressure within the unit controlled by hydrocarbon generation and compaction disequilibrium. BPSM shows a progressive increase in effective porosity from the top to the base and toward the west region related to the original organic carbon content and maturity increasing along the same trend. Overpressure intervals with high organic carbon contents are the most prone to develop organic pores. The latter represent favorable sites for the storage of hydrocarbons in the Vaca Muerta Formation.
... Airborne and land-based gravity data sets are used to delineate density distributions within the earth and one of their common applications has been to investigate the basement architecture beneath fold and thrust belts (e.g., Ali et al., 2009;Ayarza et al., 2005;Snyder & Barazangi, 1986;Vera et al., 2010). A merged data set comprising the highest resolution Bouguer corrected gravity data available across this area of PNG is shown in Figure 7c. ...
The Papuan Fold and Thrust Belt (PFTB) in Papua New Guinea is actively forming within a complex tectonic setting at the boundary of the obliquely converging Australian and Pacific plates. The tectonic setting and inaccessibility of the PFTB make it one of the least well‐understood fold and thrust belts on Earth. On February 25, 2018, a Mw 7.5 earthquake occurred within the PFTB, triggering an aftershock sequence which included five events ≥Mw 6. In this study, we combine seismological, GPS and remote sensing observations to investigate the spatiotemporal distribution of crustal deformation during these events. All earthquakes ≥Mw 6 were related to reverse offset on northeast‐dipping fault planes and five out of the six, including the mainshock, were associated with midcrustal focal depths (∼15–30 km). During the sequence, the PFTB underwent up to 1.2 m of uplift and ground deformation occurred over 7,500 km². Combining these observations with our geological knowledge of this convergent margin highlights the primary control of the northern Australian passive margin on PFTB structural style. We propose that the earthquake sequence was related to tectonic inversion on a hidden extensional fault system beneath the PFTB and lateral variations along this fault zone had significant influence on the complex distribution of ground deformation. It follows that this fault system has had an important control on the evolution of variable structural styles within the PFTB. This study highlights the complexity that can characterize the evolution and structural style of fold and thrust belts.
... North of 39 • S the interaction is more complex due to the anomalous amplitude of the Valdivia FZ fault system and the obliquity of the Mocha FZ (Folguera and Ramos, 2009). This configuration affects the development of post-Oligocene contractional and extensional structures within these deformational belts as in the Neuquén Precordillera (Zamora-Valcarce et al., 2006;Cobbold and Rossello, 2003;Folguera et al., 2010Folguera et al., , 2012Rojas-Vera et al., 2010;Garcia-Morabito et al., 2011;Sagripanti et al., 2015). Associated with this retroarc deformational belts, a series of Neogene foreland basins, such as the Santa Cruz, Río Mayo, Collón Curá, Ñ irihuau, and restricted depocenters within the Neuquén Basin was developed ( Fig. 12; see also Bilmes et al., 2013). ...
A set of fracture zones left by transform faults segmenting the active Chile Ridge that separates the Nazca and Antarctica Plates has been subducting beneath western Patagonia in the last 18 Myr. The subduction direction of these fractures zones has remained almost unaltered during this time lapse since these intersected the Chilean trench. In this context, the analyzed Patagonian sector is associated with the subduction of a highly buoyant oceanic floor due to its relatively young age that contrasts with the ocean floor bathymetry to the north where oceanic crust gets progressively older up to the Eocene and consequently isostatically subsides. Short-term elastic deformational patterns associated with the earthquake cycle have been linked to this segmentation imposed by subducting fracture zones in previous works. Similarly, this work explores the relationship between long-term topography, seismicity, gravity, and magnetic anomalies as a proxy for upper crustal structure, deformation, exhumation, and consequently surface geology segmented nature associated with this pattern of oceanic fracture zones. Through these analyses, we have identified a series of ENE structural trends or lineaments across the continental crust that could be directly related to the segmented mechanical behavior of the plate interface and enhanced by particular climatic and tectonic history of the Patagonian region. These evidences could contribute to the understanding of how fracture zones can control, to a certain extent, the segmented nature of the upper plate in a subduction setting.
... Particularmente, la Fosa de Loncopué constituye una depresión plio-cuaternaria que marca el límite de la vertiente oriental de la Cordillera Principal . Estudios recientes han demostrado que este bajo estructural coincide con una serie de depocentros profundos que alcanzan miles de metros de espesor (Rojas Vera et al., 2010). ...
... Cabe destacar que los valores elevados de COT se reconocen en la sección basal de GS2, tanto en lo que hace al hemiciclo transgresivo, como a la parte inferior del hemiciclo regresivo. Estos depósitos se corresponden con un La columna estratigráfica Cerro Mulichinco se encuentra localizada en la denominada Fosa de Loncopué, uno de los depocentros más profundos de la Cuenca Neuquina (RojasVera et al., 2010). Esta región limita al oeste con el valle del río Agrio, sobre el cual afloran depósitos lacustres de la Formación Tordillo. ...
The Vaca Muerta Formation is a fine-grained marine stratigraphic unit accumulated during the Late Jurassic-Early Cretaceous in the Neuquén Basin, Argentina. This contribution presents a sedimentological and stratigraphic analysis of Vaca Muerta´s shales emerged from the integration of regional and detailed outcrop research and subsurface data gathered from the study of different well cores.
The fieldwork comprised, on the one hand, the description of 7 stratigraphic sections of the Early Tithonian-Early Valanginian interval widely distributed across the western region of the Neuquén province and southern Mendoza province. The sedimentological and sequence-stratigraphic analysis of the different stratigraphic sections allowed integrating them into a regional N-S oriented correlation panel covering an area of 340 km. Five composite depositional sequences were recognized (GS1-GS5). They represent the evolution of a complex mixed shelf/ramp depositional system comprising from basinal/slope facies (central area) to ramp (northern area) and mixed-shelf to continental deposits (southern area). Depositional sequences are represented by thin, organic-rich (up to 10 % TOC), mudstone dominated transgressive cycles, whereas regressive cycles are commonly thicker and mainly composed of organic-lean, carbonate and mixed (carbonate/siliciclastic) facies.
On the other hand, aiming at studying the transport and accumulation processes of Vaca Muerta´s organic-rich shales, hand specimen samples of early-diagenetic carbonate concretions were collected from the organic-rich basal condensed section deposited in basinal settings. Concretion samples were thoroughly examined (mm- μm scale) integrating the observation of macroscopic polished samples, thin sections and scanning-electron microscope analyses. The evidence found inside concretions suggest an origin related to muddy underflows, possibly triggered by slope failures on the western margin of the basin. The bedload and suspended-load transport of mud within these muddy underflows would have resulted in the accumulation of graded event mudstone beds exhibiting ripple lamination. Petrographic analysis demonstrates that muddy underflows would have been important mechanisms for reworking the seafloor and redistributing mud in basinal settings. Furthermore, muddy underflows would have been effective processes for organic matter concentration in organic-rich mudstone strata (up to ≈ 6 % TOC).
The subsurface studies comprised the sedimentological analysis of seven well cores of the Vaca Muerta Formation, representing a total core data of 387 m. The descriptive facies analysis at centimeter scale allowed the recognition of a distally steepened mixed ramp system. Sediment delivery to basinal settings was mainly controlled by muddy underflows triggered by different mechanisms. Deposition from muddy underflows would have interacted with fallout processes from buoyant plumes and marine snow from the water column. The stacking pattern of the studied core deposits shows ≈ 0.5 to 3 m-thick parasequences building up prograding/retrograding parasequence sets of high-order depositional cycles (10-20 m thick).
... Cordillera/Central Depression and in the Malargüe fold-and-thrust belt also suggest a late Cretaceous (~100 Ma) onset of shortening in this part of the Andes (Horton, 2018b and references therein) (Fig. 3C). However, the formation of several basins filled by volcanosedimentary deposits in the late Eocene to the Oligocene (~37-23 Ma) document large-scale extension and crustal thinning in this region, similar to the setting at 30°S (Jordan et al., 2001b;Charrier et al., 2002;Ramos and Folguera, 2005;Burns et al., 2006;Folguera et al., 2010;Rojas Vera et al., 2010;Horton et al., 2016;Horton et al., 2018b). Shortening finally resumed in the latest Oligocene by tectonic inversion of the former extensional basins (Godoy et al., 1999;Charrier et al., 2002). ...
... Cordillera/Central Depression and in the Malargüe fold-and-thrust belt also suggest a late Cretaceous (~100 Ma) onset of shortening in this part of the Andes (Horton, 2018b and references therein) (Fig. 3C). However, the formation of several basins filled by volcanosedimentary deposits in the late Eocene to the Oligocene (~37-23 Ma) document large-scale extension and crustal thinning in this region, similar to the setting at 30°S (Jordan et al., 2001b;Charrier et al., 2002;Ramos and Folguera, 2005;Burns et al., 2006;Folguera et al., 2010;Rojas Vera et al., 2010;Horton et al., 2016;Horton et al., 2018b). Shortening finally resumed in the latest Oligocene by tectonic inversion of the former extensional basins (Godoy et al., 1999;Charrier et al., 2002). ...
The Central Andes between 18°S and 36°S latitude strike north-south for 2000 km along the Chilean subduction margin, cross several climate zones from hyperarid to humid and exhibit mean elevations in excess of 4000 m.a.s.l. Here, we investigate the relationships between tectonics, climate and exhumation by inverting low-temperature thermochronological data compiled from the literature (824 ages from 549 samples) and new data (238 ages from 146 samples) to quantify the exhumation rate history of the Central Andes since 80 Ma. Our inferred exhumation rates west of the drainage divide and between 18 and 32°S did not exceed 0.25 km/Ma. Such low exhumation rates are consistent with low shortening rates and arid conditions in this region. Local pulses of exhumation occurred only during the Eocene as response to active deformation and during the Miocene, probably as response to uplift of the western Andean slope. East of the drainage divide between 18 and 28°S, the observed exhumation pattern reflects the onset and eastward propagation of deformation. Here, exhumation occurred locally since the middle-to-late Eocene in the Eastern Cordillera and the Altiplano-Puna and subsequently affected larger parts of these regions and the north-western Sierra Pampeanas during the Oligocene. In the early Miocene (~20 Ma), the Interandean zone started exhuming and at 12-10 Ma exhumation propagated into the Subandean zone. Enhanced shortening rates and intensified precipitation along the eastern deformation front associated with the onset of the South American Monsoon led to increased exhumation rates in the eastern Interandean and the Subandean zones in the Plio-Pleistocene (0.6 km/Ma). Higher Pleistocene exhumation rates are also observed in the northern Sierra Pampeanas (1.5 km/Ma) that can be related to rock uplift along steep reverse faults coupled with high precipitation. South of 32°S on the western side, exhumation rates in the Principal Cordillera increased from ca. 0.25 km/Ma in the Miocene to rates locally exceeding 2 km/Ma in the Pleistocene. Whereas the tectonic regime in the southern Principal Cordillera remained unchanged since the late Miocene, these higher rates are likely associated with enhanced erosion resulting from intensified Pleistocene precipitation and glacial growth in this region, reinforced by isostatic rock uplift and active tectonics. Our study shows that the onset of exhumation correlates mainly with the initiation of horizontal shortening and crustal thickening, whereas the magnitude of exhumation is largely set by the amount of precipitation and glacial erosion and by the style of deformation, which is controlled by inherited structures and the amount of sediments in the foreland.
... During the late Miocene, a compressional regime triggered by a slab shallowing event caused the inversion of the extensional basins, the expansion of arc magmatism, and consequently the uplift of the frontal sector of the Principal Cordillera and the San Rafael Block Silvestro and Atencio, 2009;Rojas Vera et al., 2010;Turienzo, 2010;Giambiagi et al., 2012;Turienzo et al., 2012;Litvak et al., 2015). This slab shallowing event has been recently connected to the potential subduction of the ancient Payenia plume (Gianni et al., 2017). ...
... The latest Oligocene-early Miocene volcanic sequences were associated with the broad extensional basins induced by the rapid and orthogonal subduction of the Nazca plate and the steepening of the subducted slab (Muñoz et al., 2000;Jordan et al., 2001;Kay et al., 2006;Fennell et al., 2018). In particular, the initial infill lower section of the volcanosedimentary Cura Mallín basin (27-20 Ma; 36-38 • S) developed during this period under control of extensional structures (Figures 1, 3), composed of pyroclastic deposits, lava flows, and interbedded lacustrine and delta facies (Suárez and Emparán, 1995;Jordan et al., 2001;Radic et al., 2002;Burns et al., 2006;Kay et al., 2006;Melnick et al., 2006;Folguera et al., 2010;Rojas Vera et al., 2010). To the west, the coeval Coastal Magmatic Belt developed with a predominant tholeiitic composition and variable geochemical signatures similar to the SVZ (Southern Volcanic Zone) (López-Escobar and Vergara, 1997;Muñoz et al., 2000). ...
Since the initial proposal of the past existence of a southward-directed mid-ocean ridge–subduction interaction in the Andes during Late Cretaceous–Paleogene times, several studies have been devoted to uncover the tectonomagmatic evidence of this process. The collision of a spreading ridge against a subduction margin provokes important tectonomagmatic changes, including, between them, variations in arc-related magmatic activity and in the plate-margin stress regime. However, the cryptic nature of the geological record often hampers assessing the influence and along-strike evolution of this process. In this study, we integrate new isotopic data with previous field and geochemical data on Andean arc-related magmatism, together with seismic tomography to track the main tectonic changes that affected the Andes between 35° and 42°S from Latest Cretaceous to early Miocene times. In particular, we carry out a new tomotectonic analysis combining the regional bedrock record of the Late Cretaceous–early Miocene arc with upper–lower mantle seismic tomography. This analysis allowed us to unravel the main geodynamic changes that affected the Andean active-margin when the Farallon–Aluk spreading ridge was subducting. Besides, new isotopic analyses reveal the variable nature of the mantle source that fed the Late Cretaceous–early Miocene arc. Hence, the integration of geological, geochemical, and geophysical data, together with new isotopic data studying the geochemical composition of the main Andean arc-related magmatic units in three main periods – (1) Latest Cretaceous–early Paleocene, (2) Early Paleocene–late Eocene, and (3) Late Eocene–early Miocene – allow us to understand with an unprecedented detail the geochemical and spatiotemporal evolution of the passage of this spreading ridge along the Andean margin.
... This is produced by a geodynamic scale process occurring at the mantle transition zone (i.e. the effect of the slab pull force), whose impact in the surface is reflected by the accelerated retreat of the trench hinge (Fig. 5a). Retreating subduction zones are characterized by back-arc extension and space creation in the overriding plate (Waschbusch and Beaumont 1996), in agreement with the basin shown in the model and the presence of normal faulting associated with synextensional deposition in the late Oligocene to early Miocene intra-arc basins (Jordan et al. 2001;Charrier et al. 2002;Folguera et al. 2010;Rojas Vera et al. 2010;Garcia Morabito and Ramos 2012;Ramos et al. 2014;Jara and Charrier 2014). Furthermore, the mafic flood devoid of subduction-related components recorded in the present retroarc zone (Fig. 5a) provides evidence for the presence of back-arc mantle being injected far east of the . ...
Geological observations in the Neuquén Basin indicate a Late Oligocene to Early Miocene episode of extension followed by an abrupt shift towards regional compression. However, the reasons behind this brief extensional episode and the Oligo-Miocene tectonic mode switch are not fully understood. Through the aid of numerical modelling, it has been shown that after a period of limited subduction in Early Palaeogene times, the penetration of Nazca’s slab tip into the mantle transition zone in Late Oligocene times resulted in the renewal of effective subduction due to the effect of the slab pull force. This renewed subduction consists of an initial stage of higher trench hinge retreat and steep slab dips, leading to extension and mantelic upwelling processes east of the trench. Then, the natural evolution of the slab produces a deceleration of roll-back and shallowing of the subduction angle once it reaches the lower mantle, resulting in horizontal shortening. These results indicate that the effect of the slab pull force is a potential responsible for the Oligo-Miocene tectonic mode switch, causing the opening of a series of intra-arc basins and widespread magmatism partially devoid of arc-like components followed by an increasing influence of the slab in the magmatic arc and the final closure of the Neuquén Basin.
