Catastrophic slab loss in southwestern Pangea preserved in the mantle and igneous record

The Choiyoi Magmatic Province represents a major episode of silicic magmatism in southwestern Pangea in the mid-Permian-Triassic, the origin of which remains intensely debated. Here, we integrate plate-kinematic reconstructions and the lower mantle slab record beneath southwestern Pangea that provide clues on late Paleozoic-Mesozoic subducting slab configurations. Also, we compile geochronological information and analyze geochemical data using tectono-magmatic discrimination diagrams. We demonstrate that this magmatic event resulted from a large-scale slab loss. This is supported by a paleogeographic coincidence between a reconstructed 2,800-3,000-km-wide slab gap and the Choiyoi Magmatic Province and geochemical data indicating a slab break-off fingerprint in the latter. The slab break-off event is compatible with Permian paleogeographic modifications in southwestern Pangea. These findings render the Choiyoi Magmatic Province the oldest example of a geophysically constrained slab loss event and open new avenues to assess the geodynamic setting of silicic large igneous provinces back to the late Paleozoic.Fil: Gianni, Guido Martin. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Navarrete Granzotto, César Rodrigo. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Transient plate contraction between two simultaneous slab windows: Insights from Paleogene tectonics of the Patagonian Andes

Plate kinematic reconstructions show that the Farallon-Phoenix (Aluk) spreading center subducted under South America sometime between the Late Cretaceous and the Paleogene periods. Geological studies have supported a ridge-trench interaction in Patagonia during Paleocene to Eocene times mostly based on the documentation of slab window magmatism and Andean arc-quiescence. However, a revision of most recent works dealing with the Paleogene tectonic evolution of Central Patagonia between 39 °S to 50 °S highlights inconsistencies in this model. Particularly, the existence of two discrete areas with simultaneous slab window-related magmatism separated by a sector with plate-wide contraction, along with a spatio-temporal mismatch between magmatism location and ridge kinematics, preclude a single ridge-trench interaction. With the purpose to better understand this complex tectonic setting, we integrated this updated geological evolution into a plate kinematic model. We propose that the oblique collision of a segmented Farallon-Phoenix/Aluk mid-ocean ridge would explain the latitudinally variable tectonomagmatic evolution of Patagonia during early Paleogene times. Finally, this work adds resolution to geodynamic processes in active margins where complex midocean ridge-trench interactions take place.Fil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Pesce, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Soler, Santiago Rubén. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentin

Surface and mantle records reveal an ancient slab tear beneath Gondwana

Vertical slab-tearing has been widely reported in modern convergent settings profoundly influencing subduction and mantle dynamics. However, evaluating a similar impact in ancient convergent settings, where oceanic plates have been subducted and the geological record is limited, remains challenging. In this study, we correlate the lower mantle structure, which retained the past subduction configuration, with the upper-plate geological record to show a deep slab rupture interpreted as a large-scale tearing event in the early Mesozoic beneath southwestern Gondwana. For this purpose, we integrated geochronological and geological datasets with P-wave global seismic tomography and plate-kinematic reconstructions. The development of a Late Triassic-Early Jurassic slab-tearing episode supports (i) a slab gap at lower mantle depths, (ii) a contrasting spatiotemporal magmatic evolution, (iii) a lull in arc activity, and (iv) intraplate extension and magmatism in the Neuquén and Colorado basins. This finding not only has implications for identifying past examples of a fundamental process that shapes subduction zones, but also illustrates an additional mechanism to trigger slab-tearing in which plate rupture is caused by opposite rotation of slab segments.Fil: Gianni, Guido Martin. 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 Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Navarrete Granzotto, César Rodrigo. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Spagnotto, Silvana Liz. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentin

Effective elastic thickness in the Central Andes. Correlation to orogenic deformation styles and lower crust high-gravity anomaly

Global studies have assessed the importance of elastic thickness (Te) on orogenic evolution, showing that the style and nature of upper crustal shortening are influenced by the inherited lithospheric strength. Thus, pioneer works have identified that the upper crustal deformation style in the easternmost sector of the Central Andes in South America are related to the elastic thickness (Te). There, the thick-skinned and pure-shear style of Santa Bárbara system was initially related to the existence of low Te values. In contrast, the thin-skinned and simple-shear style of deformation in the Subandean system involves high Te values. However, more recent Te studies in the Central Andes present conflicting results which lead to question this straightforward relation. Results from these studies show a strong dependence on the applied methodology hampering the general understanding of the lithospheric thermo-mechanical state of the Central Andes. To contribute to this issue, we perform a high-resolution Te map, using forward modeling by solving flexural equation of infinite plate model in two dimensions. To achieve this, the crust-mantle interface was calculated using a high-resolution gravity anomaly dataset which combines satellite and terrestrial data, and an average density contrast. Additionally, the gravity anomaly and the foreland basin depth in the Central Andes were best predicted by considering that lower crustal rocks fill the space deflected downward in the plate model. The obtained Te values show an inverse correlation with previous heat flow studies, and a strong spatial correlation with the styles and mechanisms of deformation in the easternmost sector of the Central Andes. In the Santa Bárbara system Te values less than 10 km predominate, whereas in the Subandean system high Te values were observed. Such high values correlate with the orogenic curvature and with an shallower gravity Moho zone, which breaks the regional trend of the Central Andes. This shallower gravity Moho is linked to a high-gravity anomaly located in the east part of the Eastern Cordillera and Subandean system. These results are also correlated with a high-velocity zone in the upper mantle previously found by receiver functions studies. This correlation could indicate changes in the properties of the lower crustal rocks that justify the shallower gravity Moho zone and explain in part the highest Te values.Fil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lupari, Marianela Nadia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sanchez, Marcos Ariel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soler, Santiago Rubén. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Quaternary tectonics at the Andean backarc at the latitude of the Tromen volcano (37°S)

Estudios recientes focalizados en las vecindades del volcán Tromen, en el norte de la provincia de Neuquén, indican la presencia de estructuras afectando rocas de edad cuaternaria. En particular, un análisis detallado del flanco occidental del volcán Tromen muestra amplias zonas de deformación neotectónica, de las cuales sólo habían sido reconocidos sus sectores frontales. Se detallan geometría y mecanismos asociados a las principales estructuras cuaternarias a través de los dos valles principales que afectan este flanco volcánico. La coexistencia de estructuras neotectónicas contraccionales y distensivas es descripta como un rasgo distintivo. Así, el campo de esfuerzos asociado a este conjunto de estructuras es discutido: Mientras algunos estudios previos puntualizan que la deformación sería de carácter contraccional, otros apuntan a un régimen predominantemente distensivo. Finalmente, se plantea una alternativa que reconcilia ambos modelos en base a los nuevos datos.Recent studies focalized in the vicinity of the Tromen volcano, in the northern Neuquén province, indicate the presence of Quaternary structures. In particular, a detailed analysis on its western volcanic flank shows broad neotectonic deformational zones, whose only frontal sector had been previously recognized. Geometry and associated mechanisms are described for these, through the two main incisions that are developed on the volcanic flank. The coexistence between contractional and extensional neotectonic structures is described as a distinctive feature and consequently the related stress field is discussed. While some studies had argued that young deformation in the area would be predominantly contractional, others indicated that it would be mainly extensional. Finally, an alternative reconciling both models is put forward based on the new data.Fil: Gianni, Guido Martin. 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 ; ArgentinaFil: Sagripanti, Lucía. 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 ; ArgentinaFil: Folguera Telichevsky, Andres. 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 ; ArgentinaFil: Spagnuolo, Mauro Gabriel. 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 ; ArgentinaFil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Magnetic characterization of a retroarc extensional basin: The Loncopué Trough

The Loncopué Trough is a Pliocene to Quaternary extensional basin developed over the hinterland area of the Southern Central Andes. This basin is bounded by two neotectonic extensional fault systems delimiting a narrow topographic low. Previous studies have mostly focused on structural and geochemical aspects of this feature. However, geophysical surveys, aimed to unravel deep structure beneath a thick-younger than 5 My volcanic coverage, are scarce and based their interpretations on low resolution data sets. In this study, we collected new aeromagnetic data with the objective of characterizing the magnetic properties of the crust in the Loncopué Through and nearby zones. Additionally, we analyze the spatial relation between geological structures, volcanic fields and magnetic data. In order to highlight the boundaries of the magnetic sources and calculate the basement depth, we applied derivative techniques and the source parameter imaging. Also, we estimated an effective susceptibility model using the Magnetization Vector Inversion method, which takes into account the combined effects of remanence and induced magnetization. To determine the thermal structure of the area, we calculated the Curie depth points through the spectral analysis technique. From the analysis of magnetic data we were able to characterize the main structures and lineaments associated with this retroarc extensional trough. Notably, only the Loncopué eastern fault system seems to be a crustal-scale tectonic feature, while E-W-, ENE- and ESE-trending lineaments are interpreted as relatively minor structures segmenting the basement. Finally, our susceptibility model, together with the analysis of the Curie point, revealed potential magmatic/hydrothermal reservoirs in the Copahue volcano, and the Codihue and Cajón de Almanza regions that could be connected at depth forming a regional magmatic body.Fil: Pesce, Agustina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Gimenez, Mario Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Folguera Telichevsky, Andres. 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"; ArgentinaFil: Martínez, Myriam Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentin

The passage of the Farallon-Aluk spreading ridge along the Andean margin

Plate reconstructions show that the Farallon-Aluk mid-ocean ridge interacted with the Andean marginat 30°S by ~80 Ma and then moved southwards. This process influenced the marginproducing contrasts in the magmatic evolution. At 35º30?S, the Late Cretaceous-Paleocene LosAngeles Unit (67 Ma; Fennell et al., in press), developed with a tholeiitic to alkalinesignature, and Sr-Nd isotopic trends similar to OIB magmatism (Iannelli et al., 2018). The coevalPlan de Los Yeuques Formation (34º30?S, Muñoz et al., 2018) and Naunauco Group (37-38ºS,Zamora Valcarce et al., 2006) show calc-alkaline signatures with arc-like trends. By Eocenetimes the Farallon-Aluk ridge reached the 42°S. Its influence is seen when comparing arc-likePVNM (37-38°S; Llambías and Rapela 1989) with the alkaline-like Pilcaniyeu Belt (40-42°S;Aragón et al. 2011). The segmented configuration of this spreading ridge would have favored thedevelopment of diachronic slab windows and the upwelling of more enriched mantle. This couldexplain the geochemical signatures and distribution of magmatism. A recent methodologycombining plate reconstructions and seismic tomography supports the past existence of thisprocess.Fil: Iannelli, Sofía B.. 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"; ArgentinaFil: Litvak, Vanesa D.. 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"; ArgentinaFil: Gianni, Guido Martin. 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"; ArgentinaFil: Fernández Paz, Lucía. 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"; ArgentinaFil: Folguera Telichevsky, Andres. 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"; Argentina8th International Symposium on Andean GeodynamicsQuitoEcuadorInstituto GeofísicoEscuela Politécnica NacionalFrench Institut de Recherche pour le Développemen

Oligocene to present shallow subduction beneath the southern Puna plateau

The southern Puna plateau is a conspicuous example of a high-elevation orogenic plateau in a non-collisional setting. This orogenic sector is currently located above an anomalously shallow subduction segment, in which timing and relation to upper-plate tectonics have been widely overlooked. This subduction segment, here referred to as the southern Puna shallow subduction (SPSS), is characterized by a ~200 km wide shallow area located at ~300 km from the trench at a depth of ~100–120 km and dipping 10–12° to the east. To determine the onset of the SPSS and its link to the tectonic and magmatic activity in this region, we analyzed the tectonomagmatic record of the southern Puna plateau from preexisting datasets. Also, we present a new approach based on global subduction data that provides a straightforward methodology to extract potential paleo-slab angles from the bedrock arc record. This analysis reveals that a pronounced eastward arc-front migration and magmatic broadening took place at ~26 Ma and was preceded by ~4 Ma of reduced magmatic activity, which we link to the inception of the SPSS. As expected in shallow subduction settings, a change to basement-cored distributed deformation south of 25°S in the southern Puna plateau coincides with the beginning of shallow subduction. Also, the SPSS is coincident with the enigmatic post-Eocene intraplate deformation of the Otumpa Hills located at ~950 km from the trench. We suggest that this succession of events is not fortuitous and that the development of the SPSS impacted directly the overriding plate since the Oligocene contributing to the building of one of the largest topographies (>3 km) and thickest orogenic crusts (~70–60 km) on Earth. The shallow subduction would have acted jointly with Cenozoic changes in plate kinematics and climate enhancing Andean orogenesis at studied latitudes.Fil: Gianni, Guido Martin. 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"; ArgentinaFil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Pesce, Agustina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Lupari, Marianela Nadia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: González, Marcelo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: 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; Argentin

Constraints on the Neogene growth of the central Patagonian Andes at the latitude of the Chile triple junction (45–47°S) using U/Pb geochronology in synorogenic strata

Desertification of Central Patagonia began between ~14–12 Ma and therefore was not directly connected to the opening of the Drake Passage and initial conformation of the Antarctica ice cap in early Miocene times. Local processes, in particular the uplift of the Southern Andes, seem to have played a major role in climatic and biotic changes. We studied synorogenic strata filling a partly cannibalized foredeep between ~45° and 47°S at the latitudes of the Chile triple juction. Older synorogenic successions have yielded 18.7–16.4 Ma (U-Pb) in the western sector of the North Patagonian Cordillera corresponding to Meseta Guadal, Jeinemeni and Alto de Río Cisnes sections. This uplift was partly contemporaneous with broken foreland deformation associated with the San Bernardo fold belt to the east at 17.7–15 Ma. Younger synorogenic successions of 13.5 Ma (U-Pb), associated with a short pulse of major uplift that gave way to deposition of a thick conglomeratic succession, and subsequently finer-grained deposits of 12.3 Ma, are on the eastern Andean front in the Chalía and Guenguell sections, implying a retraction in orogenic activity, and out-of-sequence growth of the Patagonian Cordillera. Consequently, contractional deformation in this area ended after ~12 Ma, sealed by the extrusion of extensive alkali flood basalts, indicating that Neogene shortening only lasted ~6 My, ending around 6 My before the subduction of the Chile Ridge at the latitudes of Central Patagonia and 4.5 My before subduction at the southern tip of South America.Fil: Folguera Telichevsky, Andres. 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"; ArgentinaFil: Encinas, Alfonso. Universidad de Concepción; ChileFil: Echaurren Gonzalez, Andres. 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"; ArgentinaFil: Gianni, Guido Martin. 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 Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Orts, Darío Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Valencia, Víctor. Washington State University; Estados UnidosFil: Carrasco, Gabriel. Servicios Científicos Educativos y Turismo Científico Chile; Chil

Deformation evidences on the glacier sediments from the northernmost El Bolsón valley, Northpatagonian Andes

Sobre el faldeo nororiental del cerro Negro, en el extremo norte del valle de El Bolsón, en la Cordillera Patagónica de Río Negro, un corte de ruta expone un afloramiento de depósitos glaciarios de aproximadamente 400 metros de longitud. En dicha localidad se observaron una serie de rasgos deformacionales cuya descripción y análisis son objeto de este trabajo. A través de la confección de una serie de secciones y perfiles sedimentarios se interpretaron los depósitos y las estructuras como glaciotectónicas, producto de los esfuerzos que produce el movimiento glaciar, restando una investigación más exhaustiva para descartar su eventual conexión con procesos neotectónicos. Siendo así, la vergencia de las fallas y de los plegamientos observados permitió definir un avance de la masa glaciar desde el norte, siendo un aporte más para estudiar la dirección del flujo de hielo en este sector de los Andes durante el Último Máximo Glaciar. Además, se reconocieron dos pulsos de avance de los glaciares, el primero de los cuales puede no haber guardado expresión geomorfológica tras haber sido sobre cabalgado por el pulso posterior.On the northeast face of Cerro Negro, in the northern extreme of the El Bolsón valley in the Patagonian Cordillera of Río Negro, a road cut left an outcrop of around 400-meters length of glacigenic deposits. In thislocation, some deformational features were observed, whose description and analysis are objects of this work. Through the development of a series of sedimentary sections and profiles, the observed structures were interpreted as glaciotectonic in origin, resulting from the stresses applied from the movement of glaciers. However, still remain further research to be done in order to discard their potential connection with neotectonic processes. The folding direction indicates an advance from north to south, providing useful information on the study of ice flow direction in this Andean region during the Last Glacial Maximum. Moreover, two glacial advances were recognized, the first one having probably no geomorphological expression as it was overthrusted by a latter glacial advance.Fil: Colavitto, Bruno. 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"; ArgentinaFil: Gianni, Guido Martin. 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"; ArgentinaFil: Tobal, Jonathan Elías. 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"; ArgentinaFil: Folguera Telichevsky, Andres. 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"; Argentin