Papers by Nemesio Heredia Carballo
Geogaceta, 2023
This paper describes three different Fe-Mn ore-types found in Cuera Range (Cantabrian Mountains, ... more This paper describes three different Fe-Mn ore-types found in Cuera Range (Cantabrian Mountains, NW Spain): Sedimentary (Carboniferous), low-temperature hydrothermal (early Permian) and karstic supergene (Quaternary). Relationships between these ore-types have been analyzed, finding that they follow a temporary evolutive path: firstly, sedimentary ores were formed. Secondly, Fe- Mn was remobilized by a hydrothermal event and, eventually, Fe- Mn was reconcentrated by recent karstic processes.
Journal of South American Earth Sciences
In the southern part of the Andean Cordillera and nearby areas of its foreland, located in the Bo... more In the southern part of the Andean Cordillera and nearby areas of its foreland, located in the Bolivian, Chilean and Argentinian territory, there are Paleozoic basement relicts of variable extension, which formed part of the W and SW margin of Gondwana. This basement has been involved in orogenic events prior to the Andean orogeny (active from the Cretaceous to the present), some of which starts in the Neo- proterozoic or reach the beginning of the Mesozoic. During the Paleozoic and according to Heredia et al. (2016, 2018), a set of continental frag- ments of variable extent and allochtony was successively accreted to the Gondwana margin, resulting in six Paleozoic orogenies of different temporal and spatial extension: Pampean (Ediacaran-early Cambrian), Famatinian (Middle Ordovician-Silurian), Ocloyic (Middle Ordovician-Devonian), Chanic (Middle Devonian-early Carboniferous), Gondwanan (Middle Devonian-middle Permian) and Tabarin (late Permian-Triassic). All these orogenies culminate with collisional events, with the exception of the Tabarin and the Gondwanan north of 39◦ S that are subduction-related. The random distribution of Paleozoic outcrops along this segment of the Andes and the unclear separation between Paleozoic and Andean orogenic events did not facilitate the establishment of a coherent model of geodynamic evolution. In the last 30 years (1993–2023), the Paleo- Andes Group has worked to characterize these Paleozoic orogenic events and to propose a geodynamic model for the Paleozoic evolution of the Chilean-Argentinian Andes, south of 21◦ S, and including the Antarctic Peninsula. The PaleoAndes Group was constituted by researchers of the Insti- tuto Geolo ́gico y Minero de Espan ̃a (IGME-CSIC), the Servicio Geolo ́gico y Minero Argentino (SEGEMAR), the University of Barcelona (UB) and the University of Oviedo (UNIOVI), institutions that led the research projects developed in these last 30 years. In these projects have also participated the Geosciences Barcelona (GEO3BCN–CSIC) and the Rey Juan Carlos University (URJC) from Spain, the national universities of La Plata, La Patagonia-San Juan Bosco, Rio Negro, Salta, Comahue, San Juan, the Consejo Nacional de Investigaciones Científicas y T ́ecnicas (CONICET) and the Instituto Anta ́rtico Argentino (IAA) from Argentina and the universities of Chile, Andr ́es Bello and Desarrollo from Chile. The first works of the PaleoAndes Group in the Paleozoic basement of the Andes begin in the context of the project “Programa Nacional de Cartas Geolo ́gicas de la República Argentina”, lead by the SEGEMAR and IGME and supported by the Agencia Espan ̃ola de Cooperacio ́n Inter- nacional (AECI) between 1993 and 1997 (Areas 1, 6 and 16 in Fig. 1) and also in 2015 (Area 20, Tierra del Fuego, in Fig. 1A). Between 1998 and 2000 the University of Barcelona joined the works on the Paleozoic basement of the Andes, leading the TRANSCUYO Project (PB98-1189) (Fig. 1A). During 2001–2003 the IGME lead the TABARIN Project (REN2000-2959-E/ANT) in which the study of the Paleozoic basement of the northern Antarctic Peninsula were included (Fig. 1B). The next works of this Group in the Paleozoic basement of the Andes were developed be- tween 2003 and 2015 and already included the University of Oviedo. These projects were supported by the Spanish I + D + i Plan and FEDER Founds of the EU and are from oldest to newest: the INVERANDES (BTE 2002-04316-C03), PALEOANDES I & II (CGL 2006-12415-CO3/BTE and CGL 2009-13706-CO3) and TORANDES (CGL 2012-38396-C03). Finally, during 2017 and 2020 SEGEMAR and IGME lead the MISAC Project (CANOA2722) (Fig. 1A) supported by an agreement between both institutions. As results of these research projects, the members of the PaleoAndes Group are authors of several articles and book chapters on the Paleozoic basement of the Andean Cordillera. The main publications of this research group are collected in Heredia et al. (2016, 2018a, b) and Serra-Varela et al. (2022). Previously to this Special Volume the PaleoAndes Group has pub- lished two other special volumes dedicated to the Andes, entitled respectively: “Geology of the Argentinian-Chilean Central Andes” (Busquets et al., 1997), edited by Acta Geolo ́gica Hisp ́anica (now Geo- logica Acta) and “Palaeozoic geodynamics of the southwestern margin of Gondwana: controls on the present architecture of the Argentinian-Chilean Andes” (Colombo et al., 2014), edited by the Journal of Iberian Geology. The present Special Volume “The Paleozoic evolution of the Andes and its foreland” publish the last data of the TORANDES project and also include contributions of other authors that work in the same or close areas of the PaleoAndes Group (Fig. 2). This volume also represents a tribute to Ferra ́n Colombo Pin ̃ol, Pere Busquets i Buezo (University of Barcelona) and Isabel Mendez Bedia (University of Oviedo) (Fig. 3), recently retired, and coordinators respectively of the sedimentological, stratigraphic and…
Journal of South American Earth Sciences
The Paleozoic pre-Carboniferous rocks of the San Rafael Block, located to the east of the Los Rey... more The Paleozoic pre-Carboniferous rocks of the San Rafael Block, located to the east of the Los Reyunos Gondwanan Thrust, show Chanic structures (Late Devonian–early Carboniferous) with east vergence, which were generated in the absence of metamorphism. This Paleozoic succession is unconformably located on the basement of Cuyania. The rocks, located to the west of the Los Reyunos Thrust, were deformed by two fold episodes, the first and main (D1) west verging, developed under low to very low-grade metamorphic conditions, and the second (D2) east verging and mainly developed near Los Reyunos reservoir. Therefore, the Los Reyunos Thrust must be considered a reactivation of a Chanic structure during the Gondwanan Orogeny (late Carboniferous–early Permian). The ancient Chanic thrust could be responsible for the overlay of the hinterland of the western branch of the Chanic Orogen on the foreland of its eastern branch, at the end of the collision between the Cuyania and Chilenia subplates. The results of this work have been related to those of nearby areas located to the north and west, which has allowed the elaboration of a model that explains the characteristics of the Chanic Orogen in this area. During the Carboniferous, the Los Reyunos thrust was reactivated as a normal fault, facilitating the sedimentation of carboniferous rocks thousands of meters thick in its hanging wall and later, during the Gondwanan deformation, it underwent a tectonic inversion. During the Andean cycle, the Permian–Triassic beds of the Choiyoi Group were deposited in relation to NW–SE trending normal faults, giving rise to rollover structures. Finally, during the Cenozoic, Andean compression gave rise to the formation of an open antiform, in whose core is the Mesoproterozoic–Paleozoic basement of the San Rafael Block.
Journal of South American Earth Sciences
During the late Carboniferous–middle Permian, the basement of the Chilean Coastal Cordillera was ... more During the late Carboniferous–middle Permian, the basement of the Chilean Coastal Cordillera was deformed by the Gondwanan Orogeny, developed by the subduction of the Paleo-Pacific plate under Gondwana from the early Carboniferous. In the Maule sector (35.4°S), the following metamorphic rock units are distinguished: (i) Western Series, formed by metapelites, metabasites, metacherts, metaconglomerates, and marbles, mixed in a subduction channel, with probably ages between the Cambrian and the Carboniferous; (ii) Eastern Series, consisting of metasediments of a fore-arc basin, Carboniferous in age. In the Eastern Series two units are recognized in terms of lithology and deformation style: the Eastern Pelitic Series and the Eastern Sandy Series. Three Gondwanan deformation episodes have been distinguished, affecting both series unequaly. In the Western Series, D1 structures consist of a foliation (S1) developed under high-pressure and low-temperature conditions, while in the Eastern Series it comprises tight east-verging folds, with the associated S1 developed under low PT metamorphic conditions (greenschist facies). D2 structures are only present in the Western Series and Eastern Pelitic Series and represents the exhumation of the accretionary prism and its emplacement to the east over the fore-arc basin, with the development of east-verging recumbent folds and a thick shear-zone. Difficulties in the propagation of the deformation by the presence of the Coastal Batholith to the east led to the development of the D3 deformation event, only well developed in the Eastern Sandy Series, and represented by the Los Tablones Back-thrust and associated folds, as well as N–S open right folds formed under low PT metamorphic conditions.
Geotemas ( Madrid ), 2016
Resumen: En el basamento paleozoico pre-carbonífero del Bloque San Rafael, las rocas situadas al ... more Resumen: En el basamento paleozoico pre-carbonífero del Bloque San Rafael, las rocas situadas al este del Cabalgamiento Gondwánico de Los Reyunos muestran estructuras chánicas vergentes al este y generadas en ausencia de metamorfismo, mientras las situadas al oeste de dicho accidente fueron deformadas en condiciones metamórficas de bajo grado por dos sistemas de pliegues, el primero de los cuales es, por lo general, vergente al oeste. Por esta razón el Cabalgamiento de Los Reyunos debe interpretarse como una reactivación de una estructura chánica. Este último sería el responsable de la superposición de la rama occidental del Orógeno Chánico sobre la rama Oriental del mismo, producida como consecuencia de la colisión entre Chilenia y Cuyania. Palabras clave: Bloque San Rafael, Andes, Basamento Paleozoico, deformación chánica, deformación gondwánica. Abstract: In the pre-Carboniferous Paleozoic basement of the San Rafael block, rocks located east of Los Reyunos Gondwanan thrust show chanic late-Carboniferous east-vergent structures and were generated in the absence of metamorphism. The rocks located west of Los Reyunos thrust were deformed by two sets of folds, the first usually west-vergent, under low grade metamorphic conditions. That is why the Reyunos thrust must be considered a reactivated chanic structure. Such chanic old thrust could be responsible for the superposition of the western branch of Chanic Orogen over its eastern branch which was produced as a consequence of the Chilenia-Cuyania collision.
Geotemas ( Madrid ), 2016
Resumen: La sucesión pre-carbonífera del Complejo Guarguaraz consta de tres unidades metamórficas... more Resumen: La sucesión pre-carbonífera del Complejo Guarguaraz consta de tres unidades metamórficas que se encuentran deformadas por estructuras pertenecientes a tres episodios de deformación chánicos. El primer episodio (D1) está representado por pliegues de pequeño tamaño, acostados y vergentes al NO, a los que se asocia un clivaje (S1) desarrollado parcialmente en condiciones metamórficas de alta presión. Durante el segundo evento de deformación (D2) tiene lugar la exhumación de parte de las rocas del complejo mediante el emplazamiento del cabalgamiento de La Yesera, vergente al NO y en relación con el cual se desarrolla un tren de pliegues apretados a los que se asocia una esquistosidad de crenulación (S2). Las paragénesis minerales y las relaciones cristalización-deformación indican que este evento tuvo lugar en condiciones metamórficas de descenso de presión, coherente con dicha exhumación. El tercer episodio de deformación (D3) se caracteriza por pliegues suaves de dirección variable que deforman las estructuras previas. Palabras clave:Andes, Cordillera Frontal, Complejo Guarguaraz, deformación chánica, basamento paleozoico. Abstract: Pre-Carboniferous series in the Guarguaraz Complex are formed by three metamorphic units, deformed during three deformation episodes belonging to the Chanic orogeny. The first episode is represented by little, recumbent and NO verging folds, with an associated cleavage (S1) partially developed under HP metamorphic conditions. During the second deformation event (D2), the emplacement of the NO verging La Yesera thrust produced the exhumation of a part of the rocks of the complex. NO verging folds and S2 crenulation cleavage formed associated to the thrust. Mineral assemblages and crystallization-deformation relationships indicate that D2 event took place in descent pressure metamorphic conditions, which is coherent with said exhumation.
Asociación Geológica Argentina, 2017
This article presents a historiographical update on Coímbre Cave, known up to the present for its... more This article presents a historiographical update on Coímbre Cave, known up to the present for its important cave art collection, together with the information available to date from the digs conducted in 2008, enabling the documentation of a valuable Magdalenian site, which is currently being excavated and whose early results we present in this article.
Trabajos de Geologia, 2015
Introducción La Zona Cantábrica (ZC) constituye la zona externa de la Cordillera Varisca del NO d... more Introducción La Zona Cantábrica (ZC) constituye la zona externa de la Cordillera Varisca del NO de la Península Ibérica [1]. Su estructura actual es el resultado de la superposición de las orogenias varisca y alpina, entre las que se intercaló una tectónica extensional durante los tiempos mesozoicos. No obstante, la deformación alpina [2] produjo esencialmente un levantamiento del basamento paleozoico y la reactivación de las estructuras previas, por lo que la gran mayoría de las estructuras actualmente visibles en la ZC tuvieron su origen en la deformación varisca. Esta deformación tuvo lugar en condiciones superficiales, con poca deformación interna; se trata de una tectónica de piel fina (thin-skinned), con el principal nivel de despegue situado en la base de una formación carbonatada del Cámbrico inferior-medio (Fm. Láncara) [3] (Fig. 1), aunque existen otros niveles de despegue a diferentes alturas de la sucesión estratigráfica. La estructura varisca de la ZC ha sido descrita en diversos trabajos de síntesis [3, 4] y en otros de carácter más local, por lo que aquí no vamos a insistir en ello. El objetivo central de la excursión es el reconocimiento de las estructuras características de la deformación varisca en las regiones orientales de la ZC, particularmente en las denominadas regiones del Esla, Ponga y Picos de Europa (Fig. 1). La sucesión estratigráfica tiene un carácter preorogénico desde el Cámbrico al Devónico Superior y es sinorogénica en tiempos carboníferos [5, 6]. Los nombres de las formaciones que se mencionan en las paradas de esta guía aparecen en la leyenda de la figura 1. Las paradas, cuya situación se muestra en la figura 1 y en kmz, persiguen un doble objetivo: la mayoría ilustran la geometría de cabalgamientos individuales o de asociaciones de cabalgamientos, incluyendo la visita a varios dúplex, mientras en algún caso se muestra la geometría de los pliegues asociados a cabalgamientos, particularmente los generados en las rampas de bloque superior.
Global and Planetary Change, 2021
In the northern Iberian Peninsula, the Pyrenean-Cantabrian orogenic belt extends E-W for ca. 1000... more In the northern Iberian Peninsula, the Pyrenean-Cantabrian orogenic belt extends E-W for ca. 1000 km between the Atlantic Ocean and Mediterranean Sea. This orogen developed from the collision between Iberia and Eurasia, mainly in Cenozoic times. Lower-middle Permian sediments crop out in small, elongated basins traditionally considered independent from each other due to misinterpretations on incomplete lithostratigraphic data and scarce radiometric ages. Here, we integrate detailed stratigraphic, sedimentary, tectonic, paleosol and magmatic data from well-dated lithostratigraphic units. Our data reveal a similar geodynamic evolution across the Pyrenean-Cantabrian Ranges at the end of the Variscan cycle. Lower-middle Permian basins started their development under an extensional regime related to the end of the Variscan Belt collapse, which stars in late Carboniferous times in the Variscan hinterland. This orogenic collapse transitioned to Pangea breakup at the middle Permian times in the study region. Sedimentation occurred as three main tectono-sedimentary extensional phases. A first phase (Asselian-Sakmarian), which may have even started at the end of the Carboniferous (Gzhelian) in some sections, is mainly represented by alluvial sedimentation associated with calc-alkaline magmatism. A second stage (late Artinskian-early Kungurian), represented by alluvial, lacustrine and palustrine sediments with intercalations of calc-alkaline volcanic beds, shows a clear upward aridification trend probably related to the late Paleozoic icehouse-greenhouse transition. The third and final stage (Wordian-Capitanian) comprised of alluvial deposits with intercalations of alkaline and mafic beds, rarely deposited in the Cantabrian Mountains, and underwent significant pre-and Early Mesozoic erosion in some segments of the Pyrenees. This third stage can be related to a transition towards the Pangea Supercontinent breakup, not generalized until the Early/Middle Triassic at this latitude because the extensional process stopped about 10 Myr (Pyrenees) to 30 Myr (Cantabrian Mountains).
Journal of Structural Geology, 2021
Abstract The role of inherited weaknesses in metamorphic basements with respect to the geometry a... more Abstract The role of inherited weaknesses in metamorphic basements with respect to the geometry and tectonic evolution of subsequent orogens formation forms a cornerstone of structural reconstructions, especially in non-inverted orogens with old Variscan basements. In this study, we analyse the geometry, kinematics, and tectonic evolution of the complex western termination of the Alpine Pyrenean–Cantabrian orogen using an integrated approach based on analogue modelling, constrained by structural mapping and geochronology, to provide new insights into the role of pre-existing structures and the shift in the orientation of the stress field. Our results demonstrate that pre-existing structures are necessary to explain the complex western termination, which does not follow the same tectonic architecture as the rest of the orogen. The reason for this is the different orientation of the pre-existing Variscan structures in this area, which do not follow the general E–W trend. These western structures (including NNE–SSW and NW–SE strike-slip fault systems and a greater number of E–W thrusts) accommodate the shortening, but have a less favourable orientation. The reactivation of the NNE–SSW strike-slip faults and the southern E–W thrusts in the recent stages indicates a late intraplate tectonic regime, mainly following the shift of the Shmax (from N–S to NNW–SSE) which occurred when the convergence between the Iberian, Eurasian, and African plates changed.
Andean Geology, 2018
In San Martín de los Andes area (Argentinian Patagonia) the Palaeozoic basement consists of metam... more In San Martín de los Andes area (Argentinian Patagonia) the Palaeozoic basement consists of metamorphic and plutonic rocks. The metamorphic rocks include strongly deformed schists, gneisses and migmatites. Their geochemical and petrographic characteristics suggest that the protholith could have been a sequence of pelites and greywackes. Detrital zircon analysis (U-Pb Q-ICP-LA-MS) yielded a maximum depositional age of 501±14 Ma (Series 3 Cambrian) for this sedimentary protolith. Metasedimentary rocks are affected by a regional foliation defined by the minerals of the metamorphic peak. This is a S2 foliation, since relics of a former foliation are present in some samples. This regional foliation is locally affected by open folds that develop an incipient crenulation cleavage (S3). The high-grade metamorphism includes partial melting processes, where the incipient segregates intrude parallel to the regional foliation and also cut it in presence of abundant melt. Zircons from anatectic ...
Gold is a mineral very appreciated by most civilizations and gold deposits arouse the interest of... more Gold is a mineral very appreciated by most civilizations and gold deposits arouse the interest of both the students and the general public. The Roman mine of Las Médulas, declared World Heritage Site by UNESCO and its surroundings areas are an exceptional site, not only by the quality of its outcrops, which allow teaching geological lithologies and processes, but also because they are associated with an important archaeological site. Taking advantage of the infrastructure and interest already existing on this site, we can explain the geology of the region that often has not been sufficiently highlighted. This site offers a great educational resource to explain the genesis of the NW Iberian Peninsula Mountains and the alluvial fan sediments. In addition, the anthropic impact on the landscape and the importance of the natural resources management can be discussed. The mountains and sedimentation that filled the depression of El Bierzo are the result of tectonic activity (since the Oli...
Geologica Acta
El Bierzo Tertiary sub-basin (Oligocene–Miocene, NW Spain) is a small remnant of the western Duer... more El Bierzo Tertiary sub-basin (Oligocene–Miocene, NW Spain) is a small remnant of the western Duero Basin, a nonmarine broken foreland basin developed in front of the Cantabrian Mountains (Pyrenean orogen). The alluvial infill of El Bierzo Tertiary sub-basin consists of a coarsening-upward succession from fluvial (Toral Formation) to alluvial-fan deposits (Las Médulas Formation) and reflects the uplift of the Cantabrian Mountains, in the north, and then of the related Galaico-Leoneses Mountains, in the south. These alluvial deposits show signs of having been laid down mainly by catastrophic flows (flood-dominated systems) and consist of three main depositional elements, namely, flood-plain fines, and lobe and channel conglomerates and sandstones. The vertical stacking patterns of these deposits and their relationships to the Alpine structures permit to unravel the tectonosedimentary evolution of the basin. The alluvial-plain element is the main constituent of a wide unconfined alluvi...
Palaeozoic rocks of the Choapa Metamorphic Complex (ChMC) (metabasites, gneisses and quartz-schis... more Palaeozoic rocks of the Choapa Metamorphic Complex (ChMC) (metabasites, gneisses and quartz-schists) and sedimentary and meta-sedimentary rocks of the Arrayán and Huentelauquén formations crop out to the North of Los Vilos. Near Huentelauquén, the ChMC has been affected by three deformation episodes related to the Gondwanan Orogenic Cycle. The first episode (D1) is represented by a foliation (S1) formed under HP-LT metamorphic conditions and preserved in syn-D2 garnet and albite porphyroblasts. A generalized crenulation cleavage (S2) was developed during the second deformation episode (D2) characterised by decompression. This episode is responsible for the exhumation of the ChMC, accommodated by east-directed thrusts overlying the ChMC on the Arrayán Fm., producing more than 20 km shortening. The third deformation episode (D3) is represented by a west-verging kilometric-scale anticline, with a thrust in its reverse limb. Minor folds and crenulations are also associated to D3. D3 str...
Las provincias geologicas del noroeste argentino Puna, Cordillera Oriental y Sierras Subandinas-s... more Las provincias geologicas del noroeste argentino Puna, Cordillera Oriental y Sierras Subandinas-sistema de Santa Barbara integran partes de una faja plegada y fallada ubicada en el retroarco del orogeno andino. Con el objetivo identificar los rasgos estructurales principales resultantes de la contraccion andina y de analizar la transicion de estilos estructurales entre estas unidades, en este trabajo se presenta una transecta regional del noroeste argentino entre los paralelos 23oS y 24oS resultante de la union de tres secciones geologicas. El estilo estructural general de esta region corresponde a estructuras vergentes tanto al este como al oeste producidas por la inversion tectonica durante la compresion andina de antiguos sistemas de rift de edad cretacica y ordovicica.
RESUMEN. La deformación compresiva cenozoica estructuró la vertiente argentina de los Andes Nordp... more RESUMEN. La deformación compresiva cenozoica estructuró la vertiente argentina de los Andes Nordpatagónicos como una faja plegada y corrida con corrimientos de vergencia este y retrocorrimientos. El sector ubicado al oeste de 71º 15´O está caracterizado por la presencia de sistemas de retrocorrimientos, que en su interacción con los corrimientos vergentes hacia el este, conforman zonas triangulares. Los dos sistemas de retrocorrimientos más importantes estructuraron los cordones Piltriquitrón (2.284 m) y Serrucho (2.120 m) respectivamente. En el primero se reconocen tres retrocorrimientos importantes con zonas de intensa deformación, en tanto que la estructura del segundo consiste en al menos dos retrocorrimientos de rumbo norte que forman la gran escarpa occidental del cordón. Como consecuencia de la interacción entre corrimientos y retrocorrimientos, las sedimentitas del valle de El Bolsón se estructuraron como un gran sinclinal de arrastre de rumbo norte. En ambos casos estas estructuras exponen rocas ígneo-metamórficas del basamento premesozoico. El diseño cartográfico sugiere el enraizamiento en profundidad de ambos sistemas con el corrimiento Ventana-Catedral, la estructura regional que limita los sectores oeste y este de la faja plegada y corrida. Se interpreta que la estructuración descripta podría representar en profundidad un modelo de zona triangular de piel gruesa, y que su localización estaría relacionada con la inversión tectónica cenozoica de fallas normales mesozoicas, las que controlaron la distribución paleogeográfica de los depósitos volcano-sedimentarios jurásicos de la región.
Uploads
Papers by Nemesio Heredia Carballo
Metamorphic basement rocks of San Martín de los Andes area comprise schists, gneisses and migmatites. They are intruded by Devonian granitoids that cut the metamorphic internal structure of these rocks. This basement belongs to a pre-Gondwanan cycle and its regional extension in the Nordpatagonian Andes is unknown. Petrographic analysis and pseudosections allowed us to determine physical parameters in order to characterize the metamorphic conditions. P-T conditions for migmatites range between 710° and 740°C below 0.44GPa. These conditions correspond to a low pressure – high temperature (LP-HT) metamorphism between amphibolite and granulite facies. Considering its metamorphic characteristics and age (pre-Devonian), no equivalent rocks have yet been found in nearby areas with outcrops of pre-Andine basement.
During the late Neoproterozoic and Paleozoic, the Argentinean-Chilean Andes and, since the late Paleozoic, the
Antarctic Peninsula formed part of the southwestern margin of Gondwana. During this long period of the geological
time, a set of continetal fragments of variable size and allochtonie was successively accreted to that margin. This
process, coupled with the development of several subductive systems, resulted in six Paleozoic orogenies, which
have different temporal and spatial extensions: Pampean (Neoproterozoic-early Cambrian), Famatinian (Middle Ordovician-
Silurian), Ocloyic (Middle Ordovician-Devonian), Chanic (Middle Devonian-early Carboniferous), Gondwanan
(Middle Devonian-middle Permian) and Tabarin (late Permian-Triassic). All these orogenies had a collisional
character, with the exception of the Tabarin and a part of the Gondwanan orogenies that are subduction-related.