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Located in the centre of the Argentinean Patagonia between 46° and 49°S, the Deseado Region represents the foreland domain of the Southern Patagonian Andes. Its geology is characterized by thick Mesozoic sequences which, at its eastern sector, present a Mesozoic and Cenozoic geologic evolution which has been strongly determined by the development o...
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... Verdes veins, Gutiérrez, 2005;Dietrich et al., 2005; and Cerro León- Tranquilo-Pingüino, Jovic et al., 2006). The analysis of several mineralized systems from various loca- tions, such as the ones observed at La Reconquista (LR), El Tranquilo (ET) and Cerro Vanguardia (CV), allows us (Table 1) (Fig. 7). The outcropping veins present a complex geologic structure in which we have been able to recognize: a) fault breccias and fault gouges; b) hydraulic breccias filled with quartz, barite and Mn-oxides; c) massive quartz and barite veins; d) sub-parallel thin veins of quartz and barite; e) stockworks of quartz and barite; f) jogs of barite, and g) areas of siliceous replacement of the host rock. ...
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... Changes in the temperature field of rocks can reflect the distribution and activity of heat sources in the crust, revealing the dynamic processes in the deep underground, especially in the study of tectonic belts, volcanic belts, and regions with heat flow anomalies [5,6]. Accurate prediction of the rock temperature field can better understand the interaction between tectonic changes and thermodynamic processes, providing a reliable theoretical basis for geological disaster prediction, resource exploration, and energy development [7][8][9][10][11][12][13]. More importantly, the study of rock temperature response provides an important research window for revealing the evolution of deep underground materials, the relationship between thermodynamic and mechanical processes, and the long-term dynamics of crustal evolution. ...
... Raimondo et al. 2014). En este contexto, aquí presentamos nuevos datos que sostienen el desarrollo de un orógeno intracontinental y su cuenca sedimentaria asociada en el centro del Macizo del Deseado, el cual ha sido generado por una respuesta de campo lejano debido al ridge-push de cuencas oceánicas periféricas (Giacosa et al. 2010;Perez Frasette et al. 2024). A fin de caracterizar este sistema orogénico, se llevó a cabo un relevamiento de campo y se confeccionó un mapa geológico-estructural de detalle. ...
... Debido a esto y como ha sido previamente indicado (e.g. Giacosa et al. 2010), se interpreta que esta discordancia angular fue generada por un evento contraccional ocurrido entre el Jurásico tardío y el Cretácico temprano. A partir de la interpretación de las líneas sísmicas, se observa que los reflectores correspondientes al Complejo Volcánico Bahía Laura han sido depositados en depocentros extensionales de tipo graben y hemi-graben. ...
... Estas observaciones concuerdan con trabajos previos que han mostrado un control extensional en la depositación del Complejo Volcánico Bahía Laura y un posterior evento de inversión tectónica (e.g. Giacosa et al. 2010). Por otro lado, los depocentros de la Formación Bajo Grande muestran una migración con respecto a los depocentros del Complejo Volcánico Bahía Laura, desarrollándose siempre a los lados de las estructuras generadas por la inversión tectónica antes mencionada. ...
El paradigma de la tectónica de placas ha logrado explicar de manera exitosa los mecanismos
que gobiernan los procesos de orogénesis en márgenes convergentes. Orógenos de tipo
andino, de tipo alpino y de arco de islas han sido ampliamente estudiados en los últimos años.
Estos sistemas son capaces de generar cadenas montañosas de cientos de kilómetros
cuadrados de extensión debido al apilamiento cortical causado por la convergencia de las
placas (e.g. Frish et al. 2011). Además, los sistemas orogénicos de márgenes convergentes
pueden generar cuencas sedimentarias en respuesta al levantamiento. En consecuencia,
muchas de las variables que controlan la evolución de estas cuencas (e.g. subsidencia, zonas
de aporte, tasa de erosión/sedimentación) son sensibles al proceso de levantamiento. (e.g.
Allen y Allen 2013). Por otro lado, procesos de orogénesis han sido identificados en sectores
de intraplaca (e.g. Raimondo et al. 2014). Se ha mostrado que los esfuerzos generados en
márgenes tanto convergentes como divergentes pueden propagarse cientos de kilómetros a
través de la litósfera mediante un mecanismo llamado respuesta de campo lejano (far-field
response; e.g. Raimondo et al. 2014). Por lo tanto, fuerzas de ridge-push, de slab-pull, de
colisión, o de drag-basal generadas en márgenes activos pueden ser transmitidas hasta
nuclearse en sectores específicos de intraplaca y construir relieve (e.g. Raimondo et al. 2014).
En este contexto, aquí presentamos nuevos datos que sostienen el desarrollo de un orógeno
intracontinental y su cuenca sedimentaria asociada en el centro del Macizo del Deseado, el
cual ha sido generado por una respuesta de campo lejano debido al ridge-push de cuencas
oceánicas periféricas (Giacosa et al. 2010; Perez Frasette et al. 2024).
A fin de caracterizar este sistema orogénico, se llevó a cabo un relevamiento de campo y se
confeccionó un mapa geológico-estructural de detalle. Se abarcó un área de ~280 km² en las
inmediaciones de las estancias Las Mercedes y Sierras Blancas. Se identificaron las unidades
estratigráficas aflorantes y se adquirieron datos estructurales (inclinación y dirección de
inclinación de capas). Además, se complemento está información con la interpretación de
líneas sísmicas 2D.
Del análisis de superficie se observa que las unidades más antiguas reconocidas forman parte
del Complejo Volcánico Bahía Laura, el cual está compuesto por rocas volcánicas y
volcaniclásticas de edad jurásica temprana a tardía. Apoya sobre estas secuencias la
Formación Bajo Grande, datada recientemente en ~140 Ma (Perez Frasette et al. 2024) e
integrada principalmente por rocas sedimentarias continentales. Por último, el Grupo Baqueró
(Cretácico temprano), compuesto por tobas de ceniza y paleosuelos, cubierto por el basalto
Las Mercedes (Cretácico tardío-Paleoceno), completan la estratigrafía. Desde el punto de
vista estructural, el Complejo Volcánico Bahía Laura y la Formación Bajo Grande se
encuentran basculados, con valores de inclinación por debajo de los 25º y con direcciones de
inclinación variables. Por otro lado, el Grupo Baqueró y el basalto Las Mercedes se presentan en posición horizontal a sub-horizontal, encontrándose en una relación de discordancia
angular con respecto a las unidades subyacentes. Debido a esto y como ha sido previamente
indicado (e.g. Giacosa et al. 2010), se interpreta que esta discordancia angular fue generada
por un evento contraccional ocurrido entre el Jurásico tardío y el Cretácico temprano.
A partir de la interpretación de las líneas sísmicas, se observa que los reflectores
correspondientes al Complejo Volcánico Bahía Laura han sido depositados en depocentros
extensionales de tipo graben y hemi-graben. Por lo tanto, se interpreta al Complejo Volcánico
Bahía Laura como depósitos de syn-rift, con algunos posibles niveles de post-rift. Además,
estos depocentros presentan una geometría en arpón, lo cual sugiere que las fallas normales
han sufrido un proceso de inversión tectónica positiva, generando, entre otras estructuras,
plegamientos con longitudes de onda que varían de 1 a 5 km. Estas observaciones
concuerdan con trabajos previos que han mostrado un control extensional en la depositación
del Complejo Volcánico Bahía Laura y un posterior evento de inversión tectónica (e.g. Giacosa
et al. 2010).
Por otro lado, los depocentros de la Formación Bajo Grande muestran una migración con
respecto a los depocentros del Complejo Volcánico Bahía Laura, desarrollándose siempre a
los lados de las estructuras generadas por la inversión tectónica antes mencionada. Además,
los depósitos de estas cubetas poseen internamente geometrías acuñadas hacia las fallas
invertidas, junto con discordancias progresivas internas que generan múltiples relaciones de
on-lap. Esta configuración permite sugerir que estos depocentros han sido generados por el
proceso de inversión tectónica, siendo la Formación Bajo Grande una unidad de syn-inversión.
En conclusión, se confirma la existencia de un evento de inversión tectónica positiva para el
sector central del Macizo del Deseado, el cual habría ocurrido entre el Jurásico Tardío y el
Cretácico Temprano (Perez Frasette et al. 2024). Este episodio pudo haberse desencadenado
por una respuesta de campo lejano (e.g. Giacosa et al. 2010), originando un orógeno de
intraplaca. Además, se habría generado una cuenca sedimentaria de syn-inversion asociada
a este sistema orogénico, en la cual la Formación Bajo Grande se depositó sincrónicamente
con el crecimiento de este orógeno de intraplaca (Perez Frasette et al. 2024).
... Likewise, in southern Patagonia, in the Deseado Massif, other studies indicate a tectonic evolution in the same direction, with sinistral strike-slip faults (e.g. Reimer et al. 1996 ;Giacosa et al. 2010 ; Fig. 11 d). Therefore, when combining the structural evidence described to the north and south of the studied area, the difference in the shear direction of the structures is notable. ...
In this study, we present the results of palaeomagnetic research conducted on Jurassic units of the Cañadón Asfalto Basin (CAB) in Patagonia, formed during Gondwana breakup. This basin is a key locality for understanding intraplate deformation within Patagonia during the Jurassic. The nature of this basin has been a subject of debate, based on the dynamics of the blocks that constitute its depocentres. In this context, the palaeomagnetic study of the Jurassic units of this basin provides a unique methodology to characterize the tectonic motions of its crustal blocks during its formation and development. To achieve this, we collected 350 samples from 53 sites in the sedimentary units of Las Leoneras (ca. 189 Ma) and Cañadón Calcáreo Formations (ca. 160–157 Ma), as well as the volcanic Lonco Trapial Group (ca. 185–172 Ma). The palaeomagnetic results from the sedimentary units show a regional remagnetization due to hydrothermal activity that obliterated the original remanence and overprinted a new one, simultaneously imprinting a secondary remanence in the volcanic units of the Lonco Trapial Group. When comparing the direction of the palaeomagnetic pole obtained from the remagnetized units with respect to average poles of equivalent ages, it is observed that the remagnetization must have occurred during the Late Jurassic (ca. 145 Ma). The age range in which this process occurred (Oxfordian to Aptian) and the direction of the calculated pole dispute a monster polar shift postulated for Late Jurassic to Early Cretaceous times. In addition, the primary magnetization recorded in the units of the Lonco Trapial Group indicates a counterclockwise rotation of the studied crustal blocks between 21° and 11°, which, in line with previous studies, refutes large-scale dextral motion along the Gastre Fault System since the Jurassic. Similar counterclockwise rotations of equivalent magnitudes are found along the units overlying the Palaeozoic Central Patagonian Igneous–Metamorphic Belt, which represents the opposite shear sense compared to the Jurassic units beyond this belt. This is interpreted as a reactivation of the Palaeozoic belt structures in the opposite sense, from transpressive during the Palaeozoic to transtensive during the Mesozoic.
... This unit extends through a large area of platforms and volcanoes in the foreland region of the Patagonian Andes between 46°S and 49°S, and belongs to the Deseado Massif located in Southern Patagonia, Santa Cruz Province, Argentina (De Giusto et al. 1980;Andreis 2002;Giacosa et al. 2002;Panza and Franchi 2002;Panza and Haller 2002;Malumian and Nañez 2002;Nullo and Combina 2002;Rabassa et al. 2010). Throughout the Mesozoic, the tectonic and structural evolution of the Deseado Massif was related to the breakup of Gondwana, the opening of the southern Atlantic Ocean, and the subduction process initiated in the western margin of southern South America (Echavarría et al. 2005;Giacosa et al. 2010). In this scenario for the Middle Jurassic, an intense extensional tectonics zone originated in the back-arc of the Andean subduction (Pankhurst et al. 1998;Riley et al. 2001), related by fissure volcanism and predominating flows of lava during the Middle-Late Jurassic times. ...
Preservation of arthropod cuticles is of paramount importance for taphonomic interpretations in which the fossil record of the chitin-protein complex is considered a key molecular signature of the group studied. In this work, different specimens of clam shrimps and their surrounding sedimentary matrix recovered from four localities of the La Matilde Formation (Patagonia, Argentina) were chemically analyzed for the first time by Laser-induced breakdown spectroscopy (LIBS) and RAMAN spectroscopic techniques. The spectral data recorded from the fossils were processed and analyzed through multivariate statistics, including Principal Component Analysis (PCA), Nonmetric Multidimensional Scaling (NMDS), and Analysis of Similarities (ANOSIM). The correlation between the different colorations featured by the specimens and the atomic chemical composition of their carapaces was systematically investigated to gain a better understanding of the fossilization processes together with more detailed interpretations. We found that the carapaces featuring a yellow-brown color exhibited a similar chemical profile with iron predominance, while those with the same color as the sedimentary matrix presented a distinctive composition. Considering the volcanic influence to which the different localities studied and carapaces were exposed, we propose that the clam shrimps from the four localities were preserved in at least three ways, namely, (1) pyritization; (2) admixed preservation; and (3) impression, each with distinctive characteristics of the taphonomic processes involved. Overall, results obtained provide useful information to achieve a more comprehensive knowledge about the taphonomy of fossils in a Jurassic lacustrine paleo-environment, as the La Matilde Formation.
... Geological investigations conducted in Patagonia over recent decades have unveiled a complex tectonic history encompassing multiple extensional episodes that formed large basins, alongside notable contractional events that resulted in the tectonic inversion of preexisting faults (e.g., Giacosa et al., 2010;Navarrete et al., 2018). However, large areas remain unexplored, and their geological history is elusive. ...
... Furthermore, these studies identified four deformation phases during the Phanerozoic, of which two phases were extensional and generated intracratonic rift systems. The first event occurred during the Late Permian-Early Triassic and was controlled by N-S and NE normal faults; which was followed by a second extensional episode, which formed NW and NE faults during the Jurassic (e.g., Giacosa et al., 2010 Navarrete et al., 2023). Then, two contractional events occurred, during the Early Cretaceous and the Miocene. ...
... Then, two contractional events occurred, during the Early Cretaceous and the Miocene. According to Giacosa et al. (2010), the Early Cretaceous shortening event, which is recorded in several sectors of the Deseado Massif, caused the inversion of the previous extensional structures. Additionally, Micucci et al. (2011) presented evidence supporting the presence of the Early Cretaceous and Miocene shortening episodes in the offshore San Julián basin (Fig. 1), located to the east of the Deseado Massif in the Argentine marine platform. ...
In recent years, multiple Mesozoic episodes of crustal shortening and extension have been documented throughout Patagonia. These findings unveil a complex history of regional intraplate tectonic deformation. Nevertheless, there are numerous sectors in this vast region that have yet to undergo in-depth tectonic investigations, and hence aspects of its evolutionary history remain elusive. We present herein a comprehensive dataset comprising geophysical data (2D seismic lines), field data (detailed geological mapping and lithofacies analysis), and U-Pb geochronological data (LA-ICP-MS and SHRIMP zircon ages) from a key region in southern Patagonia, known as the Bajo Grande area, located in the center of the Deseado Massif. The datasets support the hypothesis of a Late Jurassic(?) to Early Cretaceous shortening event that led to the tectonic inversion of former Jurassic (or may be older) extensional depocenters. This episode promoted the syn-inversion (syn-orogenic) deposition of Late Jurassic(?)-Early Cretaceous (140 ± 3 Ma) epiclastic and pyroclastic rocks within NNE-striking depocenters. These rocks are part of the Bajo Grande Formation, representing one of the oldest documented syn-orogenic sequences in southern Patagonia. This shortening event may have been triggered by a far-field response to the opening of the Rocas Verdes basin and to the rift-drift transition of the South-Atlantic Ocean.
... The Patagonian region is a natural laboratory for studying intraplate deformation events since multiple Paleozoic, Mesozoic, and Cenozoic extensional and shortening episodes have been recorded (e.g., Uliana et al., 1985;Homovc et al., 1995;Giacosa et al., 2010;Bilmes et al., 2013;Figari et al., 2015;Gianni et al., 2015;Savignano et al., 2016;Suárez et al., 2019;Navarrete et al., 2015;2019a;2019b;Bucher et al., 2019;López et al., 2019;Benedini et al., 2022 and references therein). The existence of multiple extensional-related depocenters throughout the region has led to the traditional view of the entire Triassic-Jurassic period as an extensional phase in southwestern Gondwana, which predates the supercontinent breakup (e.g., Uliana et al., 1985;Homovc and Constantini, 2001;Franzese and Spalletti, 2001;Mpodozis and Ramos, 2008;Giacosa et al., 2010;Figari et al., 2015;González et al., 2016). ...
... The Patagonian region is a natural laboratory for studying intraplate deformation events since multiple Paleozoic, Mesozoic, and Cenozoic extensional and shortening episodes have been recorded (e.g., Uliana et al., 1985;Homovc et al., 1995;Giacosa et al., 2010;Bilmes et al., 2013;Figari et al., 2015;Gianni et al., 2015;Savignano et al., 2016;Suárez et al., 2019;Navarrete et al., 2015;2019a;2019b;Bucher et al., 2019;López et al., 2019;Benedini et al., 2022 and references therein). The existence of multiple extensional-related depocenters throughout the region has led to the traditional view of the entire Triassic-Jurassic period as an extensional phase in southwestern Gondwana, which predates the supercontinent breakup (e.g., Uliana et al., 1985;Homovc and Constantini, 2001;Franzese and Spalletti, 2001;Mpodozis and Ramos, 2008;Giacosa et al., 2010;Figari et al., 2015;González et al., 2016). However, recent studies conducted in northern, southern, and western Patagonia, as well as the formerly contiguous Antarctic Peninsula, have provided evidence of a significant Late Triassic shortening event (e.g., Suárez et al., 2019;Navarrete et al., 2019a;Riley et al., 2020;Bastías-Silva et al., 2020;González et al., 2021). ...
... In the Deseado Massif, the Jurassic volcanic rocks of this SLIP are referred to as the Bahía Laura Volcanic Complex (Sruoga et al., 2008 and references therein), which includes the Bajo Pobre, Cerro León, Chon Aike, and La Matilde formations. Following this, a shortening event occurred in southern Patagonia during the Late Jurassic and earliest Cretaceous (Giacosa et al., 2010;Perez Frasette et al., 2022). This event was accompanied by the syn-orogenic deposition (Perez Frasette et al., 2023) of the Bajo Grande Formation (Lesta, 1969). ...
Previous tectonic studies have indicated that the peri-cratonic lithosphere, located away from continental margins, is sensitive to far-field stresses propagating from active plate margins, which induce variable deformation. In order to gain a better understanding of potential intraplate tectonic events associated with the geodynamic evolution of the active margin of southwestern Gondwana, we conducted a tectono-sedimentary study of the Permian-Jurassic volcano-sedimentary record in the Deseado Massif, located in southern Patagonia. Our multidisciplinary analysis includes detailed geological mapping of an area of approximately 150 km2, structural analysis, geoelectric tomography, 2D seismic data, new geochronological dating, petrographic studies, and stratigraphic loggings of the volcano-sedimentary basin record. This comprehensive data set has allowed us to establish the tectonic, sedimentary, and magmatic evolution of the eastern Deseado Massif. Specifically, we have identified major normal faults associated with the syn-extensional deposition of late Permian and Jurassic sedimentary and volcanic rocks, as well as the Late Triassic emplacement of intermediate and felsic intrusive bodies. Additionally, interspersed large-scale shortening events were recognized, which induced positive tectonic inversion events in the region, recording contrasting stress fields during the analyzed lapse. Based on this, six major intraplate tectonomagmatic events were defined: (i) a potential post-Devonian pre-late Permian exhumation of the Neoproterozoic-early Paleozoic igneous-metamorphic basement, which we tentatively link to the Gondwanide orogeny; (ii) intraplate extension in the Late Permian (255±4 Ma) related to the deposition of the Dos Hermanos Member of the La Golondrina Formation; (iii) Late Triassic (231±3 Ma) intrusion of andesitic bodies, tentatively linked to the inland migration of arc magmatism associated with the South Gondwana flat slab; (iv) subsequent Late Triassic positive tectonic inversion of Permian extensional faults caused by a large-scale contractional event linked to the South Gondwana flat slab; (v) the extension-related emplacement and deposition of Early-Middle Jurassic (176±3 Ma; 172±4 Ma) sedimentary (lacustrine and fan deltas-related deposits), pyroclastic rocks (ignimbrites and ash tuffs), and lavas (lava domes and dykes) related to the Chon Aike silicic large igneous province; and (vi) poorly-constrained post-Middle Jurassic positive tectonic inversion of Jurassic faults. Therefore, we suggest that the geological events preserved in the Deseado Massif provide a key deformational record of the distal effects associated with ancient geodynamic processes that occurred along the southwestern active margin of Gondwana.
... Keywords: Epithermal, steam heated waters, Deseado Massif, FWHM index INTRODUCCIÓN El proyecto minero La Josefina se ubica en el centro de la provincia de Santa Cruz, Argentina, en el Macizo del Deseado (Fig. 1). Fue caracterizado como un depósito epitermal de Au y Ag (Moreira 2005) y se encuentra alojado en una secuencia volcánica del Jurásico Medio a Tardío de composición intermedia a félsica y firma calcoalcalina (Giacosa et al. 2010) que conforman las formaciones Chon Aike y Bajo Pobre (Fig. 1). Estas formaciones se vinculan genéticamente al mega-evento volcánico que ocurrió en Patagonia y Península Antártica y que dio origen a la Provincia Ígnea Chon Aike (Pankhurst et al. 1998, Pankhurst et al. 2000, Riley et al. 2001. ...
... También hay prospectos epitermales hospedados en rocas sedimentarias y metamórficas más antiguas (Jovic et al. 2011). La actividad volcánica en el Macizo del Deseado y los numerosos depósitos epitermales espacialmente relacionados están controlados por fallas regionales de rumbo NO a ONO producto de un régimen extensional de dirección NE y por fallas menores con orientación NE a EO (Echavarría et al. 2005, Giacosa et al. 2010, Páez et al. 2016. Sin embargo, las variaciones locales son comunes y la orientación de algunos sistemas de fallas pueden diferir de las anteriores (p. ...
La Veta Norte forma parte del sistema de vetas epitermales de baja a intermedia sulfuración del proyecto La Josefina, localizado en el Macizo del Deseado, provincia de Santa Cruz, Argentina y se aloja en rocas volcánicas jurásicas de la Formación Chon Aike. Las descripciones macroscópicas y microscópicas, análisis de difractometría de rayos X y microscopía electrónica de barrido en muestras de testigo corona, permitieron caracterizar las litologías hospedantes y la mineralogía de la alteración hidrotermal asociada a la Veta Norte. Las texturas, las relaciones de corte y las condiciones de estabilidad de los minerales identificados, permitieron establecer una secuencia paragenética con cuatro estadios. En el estadio 1 (E1) la interacción de las rocas volcánicas con fluidos hidrotermales de pH neutro a débilmente alcalino y temperaturas entre ~ 210° y 300°C generó en los alrededores de la veta una alteración representada por clorita, pirita, cuarzo y adularia. Durante el estadio 2 (E2) un leve descenso del pH (entre 5 y 6) y de la temperatura de los fluidos (entre ~ 150° y 250°C) generó condiciones favorables para la formación de illita, illita-esmectita, cuarzo y sulfuros. En el estadio 3 (E3), y a partir de aguas calentadas por vapor, se formó caolinita + calcedonia a temperaturas <190°C y pH ácido. Posteriormente a la actividad hidrotermal, la incursión de aguas meteóricas desestabilizó los minerales previos y se formaron óxidos e hidróxidos de Fe y Mn y carbonatos de Cu, característicos de la alteración supergénica (E4). Caolinita presenta cristalinidad alta en todas las rocas estudiadas, con aumento de la misma en los sectores próximos a la Veta Norte. Illita no es un buen indicador de paleoconductos ya que no presenta una variación clara de su cristalinidad respecto a la estructura mineralizada.
... The initiation of the Cretaceous cooling phase at ~120 Ma as shown by models FRO1-LGC2-JK1 ( Fig. 5), could be explained by a proposed shallow subduction phase linked to an eastward arc expansion in Patagonia at 46° -48° S, that would have taken place between ~121-117 Ma and 84-82 Ma (Gianni et al., 2018). As a result, coupling between the Aluk-South America plates increased, promoting intraplate shortening reported east of the study area in the Deseado Massif ( Fig. 1) after the Barremian-Aptian (Giacosa et al., 2010;Gianni et al., 2018) and in the San Bernardo FTB (Fig. 1) ...
The Southern Patagonian Andes at the latitude of the Chile Triple junction in Argentina and Chile (46°–47.5°S) are the object of an ongoing discussion regarding their orogenic evolution in terms of tectonic crustal thickening and exhumation. Recent works point to an Early Cretaceous onset of shortening according to observations in foreland sequences. The ensuing Cenozoic thermal history of the region was influenced by increased shortening, oceanic‐ridge collision and formation of asthenospheric windows in a dynamic subduction setting. Furthermore, the onset of Patagonian glaciations after 7 Ma added increased complexities to the analysis of the main drivers of crustal cooling in this region. We applied zircon (U‐Th)/He and apatite fission track thermochronometry, and inverse thermal modeling to unravel the thermal history throughout different structural domains of the Patagonian Andes. New thermochronological data and thermal models showed a previously unrecognized set of Cretaceous cooling ages (120‐80 Ma) toward the foreland, that we relate to the onset of contraction during initial tectonic inversion. Toward the hinterland, Cenozoic cooling ages predominate, and are related to Oligocene‐Miocene contraction in response to increased subduction velocities. Based on the regional distribution of thermochronological ages and on results from thermal modeling, a resetting of the zircon (U‐Th)/He and apatite fission track systems in response to crustal heating related to the formation of an asthenospheric window after 16 Ma appears unlikely. After 7 Ma cooling rates increased in response to enhanced glacial erosion.
... The Late Jurassic deposits from Patagonia were subsequently overlain, but not deeply buried, by Cretaceous and Cenozoic continental and marine successions (Giacosa et al., 2010) and then unearthed with minimal structural disturbance (Guido and Campbell, 2011). This is consistent with the values obtained from the majority of the biomarker ratios and the alkylnaphthalenes, but less consistent with the thermally mature signature derived from the other aromatic parameters and from a few of the biomarkers. ...
Gas chromatography–mass spectrometry was applied to samples collected from an exceptionally well-preserved Late Jurassic (∼150 Ma) sinter complex of the Claudia palaeo-geothermal field, Deseado Massif geological province, Argentinean Patagonia, which, despite its age, has never been deeply buried. Results indicate that the distal sinter apron has a much higher preservation potential for indigenous organic matter (OM) than the more proximal (vent area) facies of this palaeo-geothermal field. Specifically, homohopane ratios show that the OM of the proximal apron is of mixed thermal maturities and is in low abundance. In contrast, the OM extracted from the distal apron contains highly abundant, thermally immature biomarkers, the presence of which are consistent with the lower original fluid temperatures of the distal spring facies. Moreover, despite indications of the presence of some thermally mature aromatic compounds, hopane and sterane ratios confirm that the distal apron samples are extremely thermally immature and thereby constitute an area of exceptional molecular preservation. From an astrobiological viewpoint, these results suggest that silica sinter can preserve abundant organics over millions of years in palaeoenvironmentally conducive settings, and that sample-site selection within a hot spring facies-model framework may be critical in the successful search for ancient extra-terrestrial life.
... The San Jorge Basin (Figs. 1 and 2) is a broadly E-W elongated, on-shore-offshore basin related to extensional processes, while the Patagonia region experienced mostly shortening during the Mesozoic-Cenozoic (e.g., Folguera et al., 2020). This extension basin is bounded by the igneous-metamorphic province known as the Deseado Massif in the south (e.g., Giacosa et al., 2010), the North Patagonian Massif in the north, and the San Bernardo FTB in the northwest. The latter consists of Mesozoic sedimentary successions originally deposited in grabens that formed during the break-up of the Gondwana paleocontinent (Fitzgerald et al., 1990;Mpodozis and Ramos, 2008;Figari et al., 2016) and have been episodically deformed since the late Early Cretaceous (Homovc et al., 1995;Gianni et al., 2015a). ...
... The first shortening event in the Patagonian Andes started during the late Early Cretaceous and persisted to the middle Eocene. This phase has been evidenced by angular unconformities recognized between Aptian and Albian deposits (Giacosa et al., 2010), growth-strata observed in coeval Upper Cretaceous and Paleogene deposits (Navarrete et al., 2016;Gianni et al., 2017), and thermochronological data (Savignano et al., 2016;Genge et al., 2021b; among others) both along the Cordillera and in the broken foreland. This deformation period is followed by a neutral tectonic regime across the retroarc region coeval with a regional subsidence reported from the late Eocene to the middle Miocene through the entire Patagonian foreland (Bechis et al., 2014;Echaurren et al., 2016;Fernández Paz et al., 2018). ...
The evolution of central Patagonia is associated with episodic shortening and extension that have greatly affected the topography of the Cordillera and intraplate belt. The San Jorge Basin is a site of sediment accumulation in the foreland that is surrounded by igneous and broken foreland relief. The latter originated from episodic deformation and reactivation of inherited structures associated with a period of slab shallowing that allowed the far-field transmission of Andean stresses to the foreland. Thus, due to of its location, the San Jorge Basin provides an exceptional opportunity to study the denudation of both Cordilleran and intraplate topography during the Cenozoic, particularly during the late Eocene–early Miocene interval of mild deformation. In this study, we use a single-grain geochronological approach combining apatite fission tracks and UPb dating on apatite, along with maximum deposition ages obtained from UPb zircon dating for Neogene foreland basin deposits, to distinguish between two distinctive sediment source regions in central Patagonia during the Cenozoic, despite the persistent volcanic signal. A compilation of previously published cooling ages combined with our new data define: (i) a dominant local source from the northern broken foreland from the late Eocene until the early Miocene; and (ii) a widespread source in the Cordillera during the Miocene based on a very uniform thermochronological signal observed throughout the entire foreland. Therefore, this study provides new insights into the variation of in sediment sourcing in the central Patagonian foreland. This variation is primarily controlled by the decrease of post-orogenic erosional processes during a period of relative tectonic quiescence following the highly active Early Cretaceous–middle Eocene time interval.
