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At the east of the Ventana Ranges, Buenos Aires, Argentina, outcrops the Carboniferous-Permian Pillahuincó Group (Sauce Grande, Piedra Azul, Bonete and Tunas Formation). We carried out an Anisotropy of Magnetic Susceptibility (AMS) study on Sauce Grande, Piedra Azul and Bonete Formation that displays ellipsoids with constant Kmax axes trending NW-SE, parallel to the fold axes. The Kmin axes are orientated in the NE-SW quadrants, oscillating from horizontal (base of the sequence-western) to vertical (top of the sequence-eastern) positions, showing a change from tectonic to almost sedimentary fabric. This is in concordance with the type and direction of foliation measured in petrographic thin sections which is continuous and penetrative to the base and spaced and less developed to the top. We integrated this study with previous Tunas Formation results (Permian). Similar changes in the AMS pattern (tectonic to sedimentary fabric), as well as other characteristics such as the paleo-environmental and sharp curvature in the apparent polar wander path of Gondwana marks a new threshold in the evolution of the basin. Those changes along the Pillahuincó deposition indicate two different spasms in the tectonic deformation that according to the ages of the rocks are 300-290 Ma (Sauce Grande to Bonete Formation deposition) and 290-276 Ma (Tunas Formation deposition). This Carboniferous-Permian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpreted as the result of rearrangements of the microplates that collided previously with Gondwana, and latitudinal movements of Gondwana toward north and Laurentia toward south to reach the Triassic Pangea.

At the east of the Ventana Ranges, Buenos Aires, Argentina, outcrops the Carboniferous-Permian Pillahuincó Group (Sauce Grande, Piedra Azul, Bonete and Tunas Formation). We carried out an Anisotropy of Magnetic Susceptibility (AMS) study on Sauce Grande, Piedra Azul and Bonete Formation that displays ellipsoids with constant Kmax axes trending NW–SE, parallel to the fold axes. The Kmin axes are orientated in the NE–SW quadrants, oscillating from horizontal (base of the sequence-western) to vertical (top of the sequence-eastern) positions, showing a change from tectonic to almost sedimentary fabric. This is in concordance with the type and direction of foliation measured in petrographic thin sections which is continuous and penetrative to the base and spaced and less developed to the top. We integrated this study with previous Tunas Formation results (Permian). Similar changes in the AMS pattern (tectonic to sedimentary fabric), as well as other characteristics such as the paleo-environmental and sharp curvature in the apparent polar wander path of Gondwana, marks a new threshold in the evolution of the basin. Those changes along the Pillahuincó deposition indicate two different spasm in the tectonic deformation that according to the ages of the rocks are 300–290 Ma (Sauce Grande to Bonete Formation deposition) and 290–276 Ma (Tunas Formation deposition). This Carboniferous-Permian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpreted as the result of rearrangements of the microplates that collided previously with Gondwana, and latitudinal movements of Gondwana toward north and Laurentia toward south to reach the Triassic Pangea. Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. LA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina Fil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina Fil: Fortunatti, Natalia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina Fil: Cesaretti, Nora Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina Fil: Febbo, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina Fil: Calvagno, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina

Fil: Galetto, Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Universidad de Buenos Aires, Ciudad Universitaria. Buenos Aires, Argentina,. Fil: Georgieva, Viktoria. Universidad Austral de Chile, Instituto de Ciencias de la Tierra/Instituto de Ciencias Físicas y Matemáticas. Valdivia, Chile. Fil: García, Victor Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Institut für Geowissenschaften, Universität Potsdam, Potsdam-Golm. Germany. Fil: Zattin, Massimiliano. Department of Geosciences, University of Padova. Padova, Italy. Fil: Sobel, Edward. Institut für Geowissenschaften, Universität Potsdam. Potsdam-Golm, Germany. Fil: Glodny, Johannes. GFZ German Research Centre for Geosciences. Potsdam, Germany. Fil: Bordese, Sofía. Laboratorio de Termocronología La.Te. Andes S.A. Vaqueros, Argentina. Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Laboratorio de Termocronología La.Te. Andes S.A. Vaqueros, Argentina. Fil: Bechis, Florencia. Universidad Nacional de Río Negro. Río Negro, Argentina. Fil: Caselli, Alberto. Universidad Nacional de Río Negro. Río Negro, Argentina. Fil: Becchio, Raúl. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Universidad Nacional de Salta. Salta, Argentina. The integration of inverse thermal history modeling of new geochronological data with structural analyses from the western flank of the Domuyo volcano (∼36°30′S) allows us to propose a detailed cooling history of a key region in the Southern Andes. The Domuyo area is located in the northwestern part of the Chos Malal fold-and-thrust belt in the back-arc of the Southern Andes. Despite extensive geological investigations in this region, details about the early stages of Andean deformation remain poorly understood. The present study focuses on the interpretation and integration of new U-Pb, fission track, and (U-Th-Sm)/He data constraining the Cretaceous to Paleogene exhumation history of the Southern Andes at these latitudes. The results indicate two main episodes of rapid cooling during Albian-Campanian and Eocene times that can be related to exhumation driven by two main contractional pulses. The first event promoted basement cooling/exhumation associated with the uplift and erosion of a broad N-S striking antiform; whereas the Eocene episode triggered the inversion of the preexisting N-S striking Manchana Covunco normal fault and the deformation of the Mesozoic sedimentary cover. The two orogenic phases are separated by a potential period of orogenic quiescence during the Paleocene. These new insights highlight the importance of the initial compressional stages of mountain building in the Southern Andes at these latitudes. .

Fil: Gómez, Ricardo. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina. Fil: Galetto, Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). CONICET-IDEAN, Universidad de Buenos Aires. Argentina. Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Laboratorio de Termocronología (LaTe Andes). Argentina. Fil: Tunik, Maisa. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina. Fil: Casadio, Silvio. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina. Fil: Parada, Martin. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina. Fil: Lothari, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Laboratorio de Termocronología (LaTe Andes). Argentina. The combination of detrital low-temperature thermochronology with previous U–Pb geochronology, petrological and sedimentological analyses, has proven to be a valuable approach to constrain the provenance of non-marine Lower to Upper Cretaceous synorogenic deposits in the northern Neuquén Basin. This work focuses on the study of the Diamante Formation, a fluvial succession that represents the first synorogenic products of the Andean foreland basin at 34–35°S. The results indicate that the deposition of the Diamante Formation occurred simultaneously with the existence of an active western volcanic arc during the onset of the foreland basin. The facies associations evidence the transition between the backarc and the foreland basin stages as well as the inception of fluvial sedimentation in the foredeep. Petrographic analyses, together with changes in the paleocurrents and the record of limestone clasts suggest a regional detrital source shift. Apatite fission-track analyses (AFT) of a sample collected from the lower part of the Diamante Formation indicate an Albian central cooling age. This sample also evidences a remarkable presence of angular apatite and zircon crystals with subordinated rounded and subangular grains. Zircon fission-track analyses (ZFT) of a sample from the upper part of the Diamante Formation yield two discrete populations of cooling ages, both reflecting source-cooling during the Late Jurassic (∼161 Ma) and the Permian (∼265 Ma). Finally, a comparison between the AFT and the U–Pb maximum depositional zircon-age reveals a short lag time (ca. 3 ma), likely related to the rapid magmatic cooling of a coeval volcanic source at ∼110 Ma (Albian). .

The evolution of fold and thrust belts requires time data restrictions to determine the rates related to the interaction of surface and subsurface processes and to quantify the time relationship between the components of the petroleum system: reservoir, seal, source rock and trap. The sub-Andean fold-and-thrust belt in the Bolivian territory in general, and the regional transect that links the structures of Curuyuqui-Carohuaicho-Tatarenda-Borebigua-Charagua and Mandeyapecua in particular, constitutes a complex multi-variable system in which the definition of time-Temperature (t-T) trajectories has led to new suitable structural and stratigraphic conclusions. The integration of multiple thermochronological-geochronological systems (Apatite Fission Track, Apatite (U-Th-Sm)/He and UPb SHRIMP on zircon) and the existing surface and subsurface geological constraints made it possible to develop a chrono-kinematic characterization of fault-related anticlines, defining their formation chronology, structural growth rate and link between them in the study area. Furthermore, it was also possible to perform a quantitative analysis of the subsidence-burial and exhumation-erosion phenomena that occurred from the deposition of Silurian-Devonian source rocks to the present time, providing relevant determinations to the modeling of the Oil & Gas system. Fil: Hernandez, Juan I.. Geomap S.a.; Argentina Fil: Hernández, Roberto M.. Geomap S.a.; Argentina Fil: Dalenz Farjat, Alejandra. Geomap S.a.; Argentina Fil: Cristallini, Ernesto Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Modelado Geológico; Argentina Fil: Alvarez, Luis A.. Geomap S.a.; Argentina Fil: Dellmans, Luis M.. Geomap S.a.; Argentina Fil: Costilla, Marcos Roberto. Geomap S.a.; Argentina Fil: Alvarez, Andres F.. Geomap S.a.; Argentina Fil: Becchio, Raul Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina Fil: Bordese, Sofia. lA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina Fil: Arzadún, Guadalupe. lA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Guibaldo, Cristina. lA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina Fil: Glasmacher, Ulrich A.. Ruprecht Karls Universitat Heidelberg; Alemania Fil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Stockli, Daniel F.. University of Texas; Estados Unidos Fil: Fuentes, Facundo. YPF - Tecnología; Argentina Fil: Soria Galvarro, Jaime. YPF - Tecnología; Argentina Fil: Rosales, Adolfo. YPF - Tecnología; Argentina Fil: Dzelalija, Francisco. YPF - Tecnología; Argentina Fil: Haring, Claudio. YPF - Tecnología; Argentina

Anisotropy of magnetic susceptibility (AMS) has been used as an important tool to study magnetic fabrics and as a basis of interpretation of depositional conditions and post-depositional processes in sedimentary successions. This contribution presents results of standard AMS and magnetic mineralogy analysis performed in core samples from the PANG 0003 well, located at the Claromeco Basin, Buenos Aires province, Argentina. The sedimentary sequence analyzed has been assigned to the Tunas Formation (Permian), upper Pillahuinco Group, southwestern of the Gondwana boundary. Additionally, obtained results were compared with previous Tunas Formation outcrop data at the Sierras Australes and Claromeco Basin area. Measured AMS parameters vary with depth, reflecting changes in postdepositional conditions such as mechanical compaction and the influence of tectonic stress. Analyses of the mean magnetic susceptibility, thermomagnetic properties and petrographic studies indicate that paramagnetic minerals as Fe-phyllosilicates are the main contributors for the AMS of this sequence. Obtained AMS parameters are mainly characterized by triaxial to oblate AMS ellipsoids and shortening directions (Kmin) with a tendency to cluster in vertical positions, parallel to the bedding plane poles, assigned to sedimentary or weak deformed magnetic fabrics. By contrast, toward the base of the sequence, strongly oblate AMS ellipsoid shapes and Kmin axes that migrate to horizontal positions indicate a high deformation degree product of tectonic stress. The presented results are consistent with geological, AMS and paleomagnetic data from Tunas Formation outcrops and confirm that deformation degree was gradually attenuated upwards in the sequence, to the younger strata and toward the foreland Claromeco basin. The study of AMS parameters and magnetic mineralogy have proven to be important tools to interpret the processes that acted during the burial history of Tunas Formation, increasing the knowledge about the evolution of the Claromeco Basin.

The Sierras Australes fold and thrust belt (Buenos Aires Province, Argentina) was in the southwestern Gondwanaland margin during the Paleozoic. The Tunas Formation (Permian) is exposed along the eastern part of it and continues eastward beneath the Claromeco Basin. Anisotropy of magnetic susceptibility (AMS) and compaction studies are described and compared with previous paleomagnetic studies with the aim of determining direction and magnitude of the main stresses acting during the sedimentation of the Tunas Formation. The anisotropy ellipsoids are triaxial with oblate or prolate shapes, reflecting different stages of layer parallel shortening during the evolution of the basin. Kmax axes trend NW-SE, parallel to the fold axes, while Kmin move from a horizontal (base) to a vertical orientation at the top of the succession, showing a change from a tectonic to almost a sedimentary fabric. The magnitude of anisotropy and compaction degree decreases toward the top of the succession. The AMS results are consistent with the outcrop structural observations and the compaction and paleomagnetic data. Regional pattern indicates a compression from the SW along this part of Gondwana, with a migration of the orogenic front and attenuation toward the NE in the foreland basin during the Upper Paleozoic. This deformation, locally assigned to the San Rafael noncollisional orogenic phase, is the result of the latitudinal movements toward the Equator of Gondwana (southern plates) and Laurentia (northern plates) during the Permian. This movement is the result of a rearrangement of the microplates that collided with Gondwana during the Late Devonian, to configure Pangea during the Triassic.

The Andes at ~31°-32°S lie above the Chilean-Pampean flat slab zone (~27–33°S), where several morphostructural units developed resulting in a large orogenic width. The core of the Andes is composed of the La Ramada fold-and-thrust belt in Principal Cordillera and the basement blocks of Frontal Cordillera. While rock uplift of these blocks has been broadly constrained to the middle Miocene based on structural and provenance studies, thermochronologic approaches with the potential to directly constrain the timing and amount of exhumation have not been exploited until recently. Apatite fission track data from a ~1 km vertical profile collected within the Carboniferous Pico Los Sapos Batholith in the High Andes at 31.5°S places some constraints on the thermal evolution of the region since the Paleocene. The age-elevation profile combined with inverse thermal modeling and previous AHe thermochronology, indicates an episodic cooling/exhumation history. Rocks cooled rapidly in the early Cenozoic (ca. 65-55 Ma), followed by a period of relative thermal and tectonic stability when residence in an apatite partial annealing zone (PAZ) from at least ~52 Ma to ca.15 Ma, followed by final rapid cooling beginning ca. 15 Ma. We interpret early Cenozoic and middle Miocene rapid cooling events as to be related to erosional exhumation during Andean contractional phases, associated with thrust activity along the Mondaquita Fault. The age-elevation profile is partially duplicated, with upper samples being offset ~500 m due to back-thrusting since the late Miocene. The preservation of part of an exhumed PAZ indicates 3–5 km of exhumation since the onset of rapid cooling/exhumation at ~15 Ma. Although evidence for an early Cenozoic compressional phase in the High Andes at this latitude is scarce, the occurrence of a regional K-T (~65 Ma) unconformity supports our results. The Eocene Inca phase, registered north of 30°S, on the other hand, is not shown in our thermochronological data, suggesting that this tectonic phase did not affect the core of the Andes south of this latitude. Independent geological evidence both from the hinterland (structural, geochemical and thermochronological analyses) and foreland (provenance studies) corroborate our findings of a middle Miocene deformational event in the core of the Andes at 31.5°S. Fil: Lossada, Ana Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Suriano, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Giambiagi, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Fitzgerald, Paul G.. Syracuse University; Estados Unidos Fil: Hoke, Gregory. Syracuse University; Estados Unidos Fil: Mescua, Jose Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Tedesco, Ana. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; Argentina Fil: Arzadún, Guadalupe. lA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Bordese, Sofía. lA - Te Andes S.A. Laboratorio de Termocronología de Los Andes; Argentina

A long-standing debate regarding the configuration of Pangea during the Late Paleozoic has been going on among the paleomagnetic community concerning the validity of one of two significantly different Pangea reconstructions (Pangea A vs Pangea B) since the proposal of Pangea B. Although, Pangea B avoids any continental overlap marring classical Pangea A configuration (Wegener's type), it requires a Carboniferous-Permian megashear of up to 1500 km to achieve the pre-Jurassic configuration. The existence of this megashear is controversial and has led to a wide range of hypotheses, in order to avoid Pangea A continental overlaps and consequently the need for major intra-Pangea movements and to accommodate the paleomagnetic database within a Pangea A reconstruction. We present paleomagnetic results from Permian volcanic rocks of the El Centinela, La Pampa, Argentina. Undeformed volcanic rocks are not affected by any inclination bias and are, therefore, ideal to test different paleogeographic models. The presence of two different paleopole positions, at the base and the top of the same stratigraphic sequence, makes this location optimal to constrain the track of the Gondwana's path during the Late Paleozoic, which shows the transition from Pangea B during the Carboniferous-Permian, to Pangea A at the Permian - Triassic boundary. Fil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina Fil: Tickyj, Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina Fil: Rapalini, Augusto Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina Fil: Gallo, Leandro César. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina Fil: Cristallini, Ernesto Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Chemale, Farid. Universidade do Vale do Rio dos Sinos; Brasil

Pyroclastic levels are descripted in Sierras Australes outcrops and Claromeco Basin sub-surface records, interbedded with mudrocks and coal beds in the base of the Tunas Formation sequence that correspond to the Permian South West margin of Gondwana. The pyroclastic levels classify as fine tuff. SHRIMP zircon ages obtained are 291.7 ± 2.9 Ma in the outcrop and 295.5 ± 8.0 Ma in the subsurface. These ages are consistent with other zircon SHRIMP ages of other outcrops tuff of the Tunas Formation, with Permian flora, and with tuff ages of correlated Gondwana areas, in the Paraná, Karoo and Paganzo basins. These data, in addition with other geological evidences, support a tectonically active and changing environment during the Permian of Gondwana. The ages allowed calculating a northward latitudinal speed of 2.7 cm/year for Gondwana during the Permian. This latitudinal movement is explained as the consequence of the final coupling of several continental microplates, gradually amalgamated from the southern margins of Gondwana and from the northern of Laurentia to configure the final Pangea during the Triassic. Since the main accretions in the southwestern margin of Gondwana could have started during the Devonian - Carboniferous, this Permian orogeny (San Rafael Orogenic Phase in Argentina) would be representing the post - collisional deformation, with a peak of compression in the Early Permian that was attenuating towards the foreland during the Late Permian - Early Triassic. With these results, it is also possible to constraint the age of the upper Paleozoic glaciation up to 295, previous to the deposition of the Tunas Formation in the Sauce Grande Formation. Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. La.Te. Andes; Argentina Fil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina Fil: Ferreira Da Trindade, Ricardo Ivan. Universidade de Sao Paulo; Brasil Fil: Gallo, Leandro César. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina Fil: Cesaretti, Nora Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentina Fil: Calvagno, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina

The anisotropy of magnetic susceptibility (AMS) is an effective tool to measure the rock petrofabric and it allow analyzing the tectonic stress. The southwest boundary of Gondwana in South America is the counter-part of the Cape fold belt of South Africa and its geological evolution is still a subject of debate. Samples of different localities of this sector were analyzed with the AMS technique, from Buenos Aires, La Pampa and Mendoza province. For rocks of Permian age, there is a clear regional magnetic signature indicating a NW-SE elongation direction and a NE-SW shortening. The ASM patterns obtained in the oldest rocks are complex, probably as the result of stress interference in the magnitudes, space and time with different pulses of the orogenic activity developed from the Middle Devonian to the Permian. In the southwest of Gondwana, small continental plates were accreted to the main continent mass during the Middle Devonian. The Permian deformation has been interpreted as the consequence of a paleogeographic re-organization of Gondwana that moves to lowest latitudes to makes the Pangea continent during the Triassic. This younger deformation evidences an orogenic front migration and attenuation to the foreland basin.

The PANG0001 well, situated in the Claromecó Basin, Argentina, involves rocks that belong to the Tunas Formation [29], Permian of Gondwana. It is composed of fine to medium sandstones intercalating with black and green mudrocks and three coal seams up to 3 m thick. In the coals, a petrographic analysis was carried out to analyze the depositional environment and the diagenesis level reached by the Tunas Formation. The coals are composed of mono-maceral bands of Collotelinite and Gelinite, from the Vitrinite Group, or Fusinite, from the Inertinite Group. They were deposited in a wet swampy forest with rises and decreases of the phreatic level. The presence of inertinite or charcoal evidence the occurrence of palaeo-fires during the Permian. The vitrinite reflectance values are between 1.3% and 2.38%. The coals classify as semiantracitic to low volatile bituminous, with 10 to 25% of volatile matter. The vitrinite reflectance values indicate temperatures between 140 °C and 190 °C. The Tunas Formation reaches the oil to methane gas window, into a catagenesis to metagenesis range related to the organic matter diagenesis. Coal petrography is a good method for the environment and diagenesis analyses applied to the Tunas Formation. Fil: Arzadún, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentina Fil: Cisternas, María Eugenia. Universidad de Concepción; Chile Fil: Cesaretti, Nora Noemi. Universidad Nacional del Sur. Departamento de Geología; Argentina Fil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina