Search

Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of

Context. Hydrated minerals, such as phyllosilicates, on asteroids can provide constraints on the temperature or compositional distribution of the early Solar System. Previous studies pointed out the possibility that absorption in the near-ultraviolet (NUV, 0.35–0.5 μm) wavelength region is a proxy for hydrated minerals in primitive asteroids. However, the radial distribution of the NUV absorption among primitive asteroids was not revisited after the Eight Color Asteroid Survey (ECAS). Aims. Our objectives are first to evaluate the possibility of using the NUV absorption as diagnostics of hydrated minerals based on the recent datasets of primitive asteroids and hydrated carbonaceous chondrites, and second to investigate the reflectance spectrophotometry of the primitive asteroids in the NUV as functions of heliocentric distance and size. Methods. The NUV and visible reflectance spectrophotometry of more than 9000 primitive asteroids was investigated using two spectrophotometric surveys, ECAS and the Sloan Digital Sky Survey (SDSS), which cover wavelengths down to 0.32 μm and 0.36 μm, respectively. We classified asteroids from the main asteroid belt, the Cybele and Hilda zones, and Jupiter Trojans based on Tholen’s taxonomy and described the statistical distribution of primitive asteroid types. We also examined the relationship of the NUV, 0.7 μm, and 2.7 μm absorptions among primitive asteroids and hydrous carbonaceous chondrites CI and CM. Results. We find strong correlations between the NUV and the OH-band (2.7 μm) absorptions for primitive asteroids and hydrated meteorites, suggesting the NUV absorption can be indicative of hydrated silicates. Moreover, there is a great difference in the NUV absorption between the large asteroids (diameter d > 50 km) and small asteroids (d < 10 km) in the taxonomic distribution. The taxonomic distribution of asteroids differs between the inner main belt and middle-outer main belt. Notably, the C types are dominating large members through the main belt and the F types are dominating small asteroids of the inner main belt. The asteroids beyond the main belt consist mostly of P and D types, although P types are common everywhere in the main belt. The peculiar distribution of F types might indicate a different formation reservoir or a displacement process of F types in the early Solar System. The strongest absorptions of the NUV and 0.7 μm band were observed in G types, which likely comprise CM-like Fe-rich phyllosilicates. On the other hand, according to a recent sample return from an F-type asteroid (162173) Ryugu, the F types with the OH-band at 2.7 μm and the shallow NUV absorption could comprise CI-like Mg-rich phyllosilicates.

Lago Argentino hosts a series of calving glaciers originating from the Southern Patagonian Icefield, the largest temperate ice cap of the southern hemisphere. Brazo Rico and Brazo Sur are two basins located in the southern part of Lago Argentino, where a series of high-resolution seismic profiles have allowed reconstruction of its depositional setting and sedimentary architecture, and to produce the following maps: top of the acoustic basement, top of the glacial sequence, and thickness of the glacio-lacustrine deposits. Data reveal the role of basement highs in the complex dynamic behavior of the two main glaciers, Perito Moreno and Frías glaciers, which fluctuated along Brazo Rico and Brazo Sur since the end of the Last Glacial Maximum. Their advances and retreats are testified by the presence of several moraine fronts buried beneath a generally undisturbed, glacio-lacustrine and lacustrine sequence, which records the depositional history of the southern arms of Lago Argentino. Fil: Lozano, Jorge Gabriel. 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: Donda, Federica. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Bran, Donaldo Mauricio. 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: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Baradello, Luca. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Romeo, Roberto. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Vilas, Juan Francisco A.. 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: Grossi, Maurizio. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Tassone, Alejandro Alberto. 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 outer Fuegian fold and thrust belt is the deformed sector of the Austral-Magallanes Basin, which underwent a contractional phase since the Late Cretaceous and a strike-slip phase during the Neogene. The area hosts two Neogene basins (Yehuin and Chepelmut) which have been mainly developed by the influence of wrench deformation, and were subsequently modified by glacial activity of the Ewan and Fuego glacier lobes of the Fagnano palaeoglacier. Geophysical surveys using Electrical Resistivity Tomography, onland shallow seismic surveys, and magnetometry, have been combined with outcrop analysis and deep seismic lines to recognize both shallow and intermediate deep structures related to the lacustrine basins. Four sets of faults with different deformation history were involved in the basin genesis. Comparison with the Deseado Fault Zone indicates similarities of the structural features between the two zones. The stress field interpreted as responsible for the origin of the studied basins is analogous to the one in the Deseado valley, located in the western Tierra del Fuego. Therefore, a transcurrent fault zone, here named Yehuin–Chepelmut Fault Zone, is proposed as part of the diffuse boundary between South America and Scotia plates.

Lago Argentino hosts various calving glaciers, including the famous Perito Moreno. Although the onland Holocene glacier dynamics is rather well constrained, the paleoenvironments developed in association with a retreating ice front remain largely unknown. A detailed analysis of high-resolution seismic reflection profiles acquired in the southern arms of Lago Argentino has allowed the identification of several unconformities within the lacustrine sedimentary infill. Four seismostratigraphic sequences have been identified in Brazo Rico and three in Brazo Sur. These sequences are separated by three erosive unconformities in Brazo Rico and two in Brazo Sur, and reflect the sedimentation of a pre-Holocene deep basin in a proglacial lake. The older unconformities are associated with instability events within the basin which triggered several mass movements, possibly related to enhanced seismic activity. The younger erosive unconformities were correlated with the “Pearson 1a/Frias 1 advance”, the major glacier advance in the Holocene of the Lago Argentino Basin. This research highlights the importance of studying the glaciolacustrine sediments, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the factors controlling glacier dynamics in the basin and reconstructing the deglacial landscape of the area.

A cartografia social (CS) tem se configurado como uma importante metodologia participativa para o engajamento político e social de comunidades tradicionais e grupos sociais fragilizados social e economicamente. Na luta pelo território e sua defesa, um processo de CS configura-se como instrumento de produção de conhecimento e mobilização. Tal potencial tem fomentado a incorporação desta metodologia em processos formativos, devido as suas contribuições reais à Geografia Escolar (GE). Neste artigo, objetiva-se problematizar as aproximações entre este tipo de cartografia com a escola, dando enfoque para as contribuições que levem à compreensão do espaço geográfico por crianças e jovens escolares. Os posicionamentos se apoiam na literatura sobre CS, Cartografia e na GE. Como resultados apresentam-se, sumariamente, alguns cuidados a serem observados pelo professor de geografia quando este estiver usando essa metodologia para fins pedagógicos. Dentre estes estão: compreender os princípios da cartografia social; a adequação ao nível de ensino; intencionalidade pedagógica definida; estar aberto ao inesperado; a valorização dos saberes dos escolares, objetivos e subjetivos; o investimento na dialogicidade, criatividade e ludicidade; valorizar a escala local contextualizada em relação às demais dimensões nacional e global; e a compreensão do processo e divulgação do produto (fascículo), com textos, imagens e mapa situacional; Isto posto como forma de engajamento político, proposições e encaminhamentos junto à comunidade. PALAVRAS-CHAVE Cartografia Social. Geografia Escolar. Crianças e Jovens Escolares. SOCIAL CARTOGRAPHY AND SCHOLAR GEOGRAPHY: approaches and possibilities ABSTRACT The social cartography (SC) has been set as an important participative methodology for the social and political engagement of traditional communities and social groups weakened social and economically. In the struggle for the territory and in its defense, a process of SC set itself as knowledge production tool and mobilization. This potential has promoted the incorporation of this methodology on formative processes, due to their real contributions for scholar geography. In this paper, the aim is to problematize the approaches between this kind of cartography with the school, giving focus to the contributions that lead to an understanding of the geographic space by the children and the young people students. The positions are supported by the literature about SC and the scholar geography. The results are showed, summarily, some thoughts to be observed by the geography teacher when he is using this methodology for educational purposes. Among them are: to comprehend the social cartography principles; the adaptation to the learning level; pedagogical intentionality defined; be open to the unexpected; the valorization of the subjective and objective knowledge from the school; the investment in the degree of dialogue [dialogicidade], creativity, and playfulness; to value the contextualized local scale in relation to the other dimensions national and global; and the process comprehension and dissemination of the product (fascicle), with texts, images and the situational map; This put as a way of political engagement, propositions and issues forwards at the community. KEYWORDS Social Cartography. Scholar Geography. Children and young. People students. ISSN: 2236-3904REVISTA BRASILEIRA DE EDUCAÇÃO EM GEOGRAFIA - RBEGwww.revistaedugeo.com.br - revistaedugeo@revistaedugeo.com.br

The social cartography (SC) has been set as an important participative methodology for the social and political engagement of traditional communities and social groups weakened social and economically. In the struggle for the territory and in its defense, a process of SC set itself as knowledge production tool and mobilization. This potential has promoted the incorporation of this methodology on formative processes, due to their real contributions for scholar geography. In this paper, the aim is to problematize the approaches between this kind of cartography with the school, giving focus to the contributions that lead to an understanding of the geographic space by the children and the young people students. The positions are supported by the literature about SC and the scholar geography. The results are showed, summarily, some thoughts to be observed by the geography teacher when he is using this methodology for educational purposes. Among them are: to comprehend the social cartography principles; the adaptation to the learning level; pedagogical intentionality defined; be open to the unexpected; the valorization of the subjective and objective knowledge from the school; the investment in the degree of dialogue [dialogicidade], creativity, and playfulness; to value the contextualized local scale in relation to the other dimensions national and global; and the process comprehension and dissemination of the product (fascicle), with texts, images and the situational map; This put as a way of political engagement, propositions and issues forwards at the community. / A cartografia social (CS) tem se configurado como uma importante metodologia participativa para o engajamento político e social de comunidades tradicionais e grupos sociais fragilizados social e economicamente. Na luta pelo território e sua defesa, um processo de CS configura-se como instrumento de produção de conhecimento e mobilização. Tal potencial tem fomentado a incorporação desta metodologia em processos formativos, devido as suas contribuições reais à Geografia Escolar (GE). Neste artigo, objetiva-se problematizar as aproximações entre este tipo de cartografia com a escola, dando enfoque para as contribuições que levem à compreensão do espaço geográfico por crianças e jovens escolares. Os posicionamentos se apoiam na literatura sobre CS, Cartografia e na GE. Como resultados apresentam-se, sumariamente, alguns cuidados a serem observados pelo professor de geografia quando este estiver usando essa metodologia para fins pedagógicos. Dentre estes estão: compreender os princípios da cartografia social; a adequação ao nível de ensino; intencionalidade pedagógica definida; estar aberto ao inesperado; a valorização dos saberes dos escolares, objetivos e subjetivos; o investimento na dialogicidade, criatividade e ludicidade; valorizar a escala local contextualizada em relação às demais dimensões nacional e global; e a compreensão do processo e divulgação do produto (fascículo), com textos, imagens e mapa situacional; Isto posto como forma de engajamento político, proposições e encaminhamentos junto à comunidade.

We investigated the immunomodulatory, antiparasitic and cardioprotective effects of a sesquiterpene lactone (SL) administered alone or combined with benznidazole (Bz), in a murine model of Chagas’ disease by in vitro and in vivo assays. Antiparasitic and cytotoxic potential of tagitinin C (SL) and Bz were tested in vitro against T. cruzi epimastigotes and cardiomyocytes. Swiss mice challenged with T. cruzi were also treated for 20 days with tagitinin C (10 mg/kg) alone and combined with Bz (100 mg/kg). Tagitinin C exhibited a higher antiparasitic (IC50: 1.15 µM) and cytotoxic (CC50 at 6.54 µM) potential than Bz (IC50: 35.81 µM and CC50: 713.5 µM, respectively). When combined, these drugs presented an addictive interaction, determining complete suppression of parasitemia and parasitological cure in all infected mice (100%) compared to those receiving Bz alone (70%). Anti-T. cruzi immunoglobulin G, and pro-inflammatory cytokines IFN-γ and TNF-α levels were reduced in animals treated with tagitinin C combined with Bz, while IL-10 production was unaffected. Heart inflammation was undetectable in 90% of the animals receiving this combination, while only 50% of the animals receiving Bz alone showed no evidence of myocarditis. Together, our findings indicated that the combination of tagitinin C and Bz exerts potent antiparasitic, immunomodulatory and cardioprotective effects. Due to the remarkable suppression of parasitemia and high parasitological cure, this combination was superior to Bz monotherapy, indicating a high potential for the treatment of Chagas’s disease.

In the southern Central Andes, the Andean foreland was deformed due to Neogene shallowing of the Nazca slab beneath the South America plate. In this 27-33° S Pampean flat-slab segment, the N-trending Argentine Precordillera transpressional fold-and-thrust belt and the Sierras Pampeanas broken foreland developed as a consequence of inward migration of the orogenic front. At 28° S, a NNE-trending westward-dipping, thick Neogene synorogenic sequence is exposed in the Sierra de los Colorados, which shares deformation features of the Precordillera and the Sierras Pampeanas. Integration of new structural and kinematic data and available structural, kinematic, geophysical and palaeomagnetic information allows consideration of the Sierra de los Colorados area as part of the northern sector of the Precordillera during the middle Neogene. At c. 9 Ma, basement block exhumation started with the uplift of the Sierra de Umango-Espinal that was triggered by deformation along the NE-trending Tucumán oblique belt. This stage marked the beginning of compartmentalization of the incipiently deformed Vinchina foreland. Since c. 6.8-6.1 Ma, basement block uplift linked to the Miranda-Chepes and Valle Fértil NNW-trending sinistral transpressional belts, as well as kinking of the Neogene sequence by localized WNW-striking cross-strike structures, resulted in multiple segmentation that produced a complex mosaic of basement-block pieces. The overprint of these regional, basement-involved, oblique, brittle-ductile transpressional and cross-strike megazones could be related to high interplate coupling. Localized mechanical and rheological changes introduced by magmatism favoured this thick-skinned deformation overprint. Fil: Japas, Maria Silvia. 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: Re, Guillermo Hector. 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: Oriolo, Sebastián. Universität Göttingen; Alemania Fil: Vilas, Juan Francisco A.. 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

Although renin-angiotensin system (RAS) imbalance is manifested in cardiomyopathies with different etiologies, the impact of RAS effectors on Chagas cardiomyopathy and skeletal myositis is poorly understood. Given that diminazene aceturate (DMZ) shares trypanocidal, angiotensin-converting enzyme 2 (ACE2) and angiotensin-(1–7) stimulatory effects, we investigated the impact of DMZ on cardiomyocytes infection in vitro, renin-angiotensin system, Chagas cardiomyopathy and skeletal myositis in vivo. Cardiomyocytes and T. cruzi were used to evaluate DMZ toxicity in vitro. The impact of 20-days DMZ treatment (1 mg/kg) was also investigated in uninfected and T. cruzi-infected mice as follows: control uninfected and untreated, uninfected treated with DMZ, infected untreated and infected treated with DMZ. DMZ had low toxicity on cardiomyocytes, induced dose-dependent antiparasitic activity on T. cruzi trypomastigotes, and reduced parasite load but not infection rates in cardiomyocytes. DMZ increased ACE2 activity and angiotensin-(1–7) plasma levels but exerted no interference on angiotensin-converting enzyme (ACE) activity, ACE, ACE2 and angiotensin II levels in uninfected and infected mice. DMZ treatment also reduced IFN-γ and IL-2 circulating levels but was ineffective in attenuating parasitemia, MCP-1, IL-10, anti-T. cruzi IgG, nitrite/nitrate and malondialdehyde production, myocarditis and skeletal myositis compared to infected untreated animals. As the antiparasitic effect of DMZ in vitro did not manifest in vivo, this drug exhibited limited relevance to the treatment of Chagas disease. Although DMZ is effective in upregulating angiotensin-(1–7) levels, this molecule does not act as a potent modulator of T. cruzi infection, which can establish heart and skeletal muscle parasitism, lipid oxidation and inflammatory damage, even in the presence of high concentrations of this RAS effector.

The southern foothills of the Fuegian Andes are bounded by the Beagle Channel (BC), a conspicuous E-W longitudinal basin, controlled by a large transcurrent fault system, which extends from the Atlantic to the Pacific Ocean. The northern shore of the Beagle Channel’s central segment is characterized by several E-W oriented valleys, parallel to the main basin, which are interspersed with a series of oblique NW trending lineaments that extend across the mountain belt. A geoelectrical survey was carried out in order to investigate the shallow architecture of such sets of linear morphologies. The principal E-W lineament system was characterized by conspicuous sub-vertical resistivity contrasts, interpreted as fractured zones associated with fault strands of the main strike-slip Beagle Channel system, whereas the oblique NW-SE trending set of lineaments revealed slightly different resistivity patterns, with vertical displacements and less abrupt contrasts. These resistivity patterns, in combination with the widespread occurrence of normal faulting in the area, allowed to infer an extensional control over the oblique depressions. These morphological features were related to oblique transverse faults that segment two sub parallel E-W fault systems. The oblique faults were probably developed along inherited structural anisotropies and can be extended well beyond the BC shoreline to the NW. Both geophysical and field evidence suggest a post-glacial deformation along the area. La cordillera Fueguina está limitada al sur por el canal de Beagle, una gran fosa longitudinal que se extiende desde el océano Atlántico al este, hasta el Pacífico al oeste y está desarrollada sobre un sistema de fallamiento regional transcurrente. La costa norte del segmento central del Canal está caracterizada por la intersección de valles paralelos a la fosa principal con una serie de lineamientos morfológicos oblicuos de orientación NW-SE, los cuales se extienden a través del sistema montañoso. Se llevó a cabo un relevamiento de Tomografía de Resistividad Eléctrica con el objetivo de investigar la arquitectura somera de los diferentes juegos de lineamientos observados en el sector y dilucidar el control estructural que determina su geometría. Los resultados muestran que el sistema de lineamientos E-W está caracterizado por un patrón de resistividades con marcados contrastes de disposición subvertical interpretadas como zonas de fractura asociadas al fallamiento de rumbo del canal de Beagle. Por otro lado, los lineamientos NW poseen un patrón de resistividades distinto, que exhibe contrastes menos marcados además de notorios desplazamientos en la vertical de los dominios resistivos. Considerando conjuntamente los patrones de resistividad con la presencia de fallas normales en el área, se deduce la existencia de un control extensional sobre el juego de lineamientos oblicuo, el cual ha sido interpretado como un sistema de fallas transversas que segmenta dos sistemas de fallas E-W subparalelos. Asimismo, evidencias geofísicas y de campo revelan la ocurrencia de deformación posglacial en el área. Fil: Bran, Donaldo Mauricio. 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: Tassone, Alejandro Alberto. 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: Menichetti, Marco. Universita di Urbino Campus Scientifico E. Matte; Italia Fil: Cerredo, Maria Elena. 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: Lozano, Jorge Gabriel. 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: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Vilas, Juan Francisco A.. 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

El lago Yehuin, una cuenca elongada de rumbo ONO-ESE localizada en la faja plegada y corrida externa de los Andes Fueguinos, ocupa una depresión compartimentada originada a lo largo de un segmento del sistema de fallas sinistrales del lago Deseado. Este trabajo describe un primer relevamiento geofísico llevado a cabo en el lago. Los datos de sísmica monocanal de alta resolución, integrados con información geológica de los alrededores del lago Yehuin, permitieron: (i) producir un mapa de la batimetría completa del lago, (ii) reconstruir la superficie del basamento del lago, y (iii) analizar la geometría, distribución y espesor del relleno sedimentario. Se reconocieron dos subcuencas dentro del lago Yehuin: una subcuenca oeste de 7,5 km de largo, con una profundidad máxima de 118 m; una subcuenca este de 7,2 km de largo y una profundidad máxima de 80 m. Ambas subcuencas están limitadas por un conjunto de fallas normales que cortan a una serie de corrimientos de vergencia NE. Se identificaron tres unidades sismo-estratigráficas en el registro sísmico: (1) una unidad inferior con geometría acuñada interpretada como depósitos de remoción en masa; (2) una unidad intermedia gruesa (de hasta 120 m) de origen glaciolacustre e irregularmente distribuida en la cuenca del lago; (3) una unidad superior lacustre delgada (

Lago Chepelmut is a relatively small lake in size, of ellipsoidal shape, located in the outer fold-and-thrust belt of the Fuegian Andes (southernmost South America). High-resolution single-channel seismic profiles, integrated with geological information in the surrounding area, have allowed to reconstruct for the first time a bathymetric map of the lake and the architecture, distribution and thickness of the sedimentary cover. Two main seismic units were identified in the seismic records: (i) a Lower Unit of glacial nature, likely associated to the Last Glacial Maximum (LGM), and irregularly distributed through the basin, and (ii) an Upper Unit of lacustrine origin which drapes the entire basin. Submerged moraine deposits within the lake were also found from seismic data, and correlated with moraine arcs widespread distributed in the surroundings of the basin. These morphologies represent the recessional deposits left by the Ewan glacier lobe, one of the easternmost fronts of the Tierra del Fuego glaciers during the LGM. The lacustrine sedimentary record shows that the lake level was not constant through the recent history of the lake. Moreover, data analysis has shown that there is also an important structural component that has conditioned the evolution of the basin, in addition to that linked to glacial activity. Fil: Lozano, Jorge Gabriel. 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: Tassone, Alejandro Alberto. 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: Bran, Donaldo Mauricio. 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: Lodolo, Emanuele. Istituto Nazionale Di Oceanografia E Di Geofisica Sperimentale; Fil: Menichetti, Marco. Università di Urbino; Italia Fil: Cerredo, Maria Elena. 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: Esteban, Federico Damián. 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: Ormazabal, Juan Pablo. 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: Isola, José Ignacio. 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: Baradello, Luca. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Vilas, Juan Francisco A.. 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

Purpose: To conduct a biophysical analysis of the factors associated with front-crawl performance at moderate and severe swimming intensities, represented by anaerobic-threshold (vAnT) and maximal-oxygen-uptake (vVO2max) velocities. Methods: Ten high-level swimmers performed 2 intermittent incremental tests of 7 × 200 and 12 × 25 m (through a system of underwater push-off pads) to assess vAnT, and vVO2max, and power output. The 1st protocol was videotaped (3D reconstruction) for kinematic analysis to assess stroke frequency (SF), stroke length (SL), propelling effciency (ηP), and index of coordination (IdC). VO2 was measured and capillary blood samples (lactate concentrations) were collected, enabling computation of metabolic power. The 2nd protocol allowed calculating mechanical power and performance effciency from the ratio of mechanical to metabolic power. Results: Neither vAnT nor vVO2max was explained by SF (0.56 ± 0.06 vs 0.68 ± 0.06 Hz), SL (2.29 ± 0.21 vs 2.06 ± 0.20 m), ηP (0.38 ± 0.02 vs 0.36 ± 0.03), IdC (-12.14 ± 5.24 vs-9.61 ± 5.49), or metabolic-power (1063.00 ± 122.90 vs 1338.18 ± 127.40 W) variability. vVO2max was explained by power to overcome drag (r =.77, P ≤.05) and ηP (r =.72, P ≤.05), in contrast with the nonassociation between these parameters and vAnT; both velocities were well related (r =.62, P ≤.05). Conclusions: The biomechanical parameters, coordination, and metabolic power seemed not to be performance discriminative at either intensity. However, the increase in power to overcome drag, for the less metabolic input, should be the focus of any intervention that aims to improve performance at severe swimming intensity. This is also true for moderate intensities, as vAnT and vVO2max are proportional to each other. © 2017 Human Kinetics, Inc.

A paleomagnetic study from the earliest Paleocene Cerros de Montecristo Quartz Monzonite and its Jurassic to uppermost Cretaceous host rock (northern Chile, ∼22°S) provided high-temperature, high-coercivity magnetizations of dominantly reversed polarity. The remanences of the tilted host rock gave a negative fold-test and are indistinguishable from the remanences found in the pluton, indicating that the uppermost Cretaceous rocks underwent deformation before intrusion of the earliest Paleocene pluton, thus documenting a K-T deformation at the locality. Although this deformation may be another product of typical subduction-related noncollisional tectonics in the Central Andes, an alternative hypothesis, permitted by plate reconstructions, is that the event was associated with collision of an oceanic plate boundary. This latter hypothesis may also provide a context for several other tectonic events from northern Chile to the Patagonian Andes, wherein deformation would the consequence of a southward migrating triple junction between the latest Maastrichtian and Early Eocene. Fil: Somoza, Ruben. 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: Tomlinson, A. J.. Servicio Nacional de Geologia y Mineria; Chile Fil: Caffe, Pablo Jorge. 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: Vilas, Juan Francisco A.. 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

An anisotropy of magnetic susceptibility (AMS) transect was carried out across the Fuegian Andes, in Argentina, withthe aim of studying its tectonic evolution. Two-hundred and forty oriented samples were collected from 27 sites distributed between the Paso Garibaldi to the north and the Canal Beagle to the south. The study was restricted to the Upper Jurassic Lemaire Formation, with a single site located in the Lower Cretaceous Yahgán Formation. Stu-died rocks comprised basaltic, andesitic, volcaniclastic and sedimentary rocks affected by low-grade metamorphism. AMS measurements were complemented with thin section analyses of representative samples in order to characterize the microstructures and metamorphic assemblages. In general, the magnetic fabric shows dominantoblate shapes and a large variation in the anisotropy degree from 1.04 up to 2. The anomalously high values were observed to be associa-ted to growth of secondary pyrrhotite, which was identified by rock magnetic tests. Magnetic foliation was generally consistent with slaty cleaveage as observed in the field, confirming the tectonic origin of the magnetic fabric. Three geographic domains were distinguished in the study región on the basis of the pattern of the AMS axes distribution. In the northern domain, from Paso Garibaldi to Valle Carbajal, the orientation of the máximum susceptibility axis (κ1), or magnetic lineation, is N-S to NE-SW with modérate plunge towards the S-SW and coincides with previous determination of mineral lineations associated with the Andean deformation and very low grade metamorphism. The magnetic fabric pattern can be correlated with the main deformational phase responsible for the development of slaty cleavage (main Andean deformational phase) and the tectonic transport due to progression of the Fuegian fold and thrust belt in the Late Cretaceous. A different character is shown along the Valle Carbajal domain, where subvertical E-W magnetic foliation planes and roughly E-W to ESE-WNW subhorizontal magnetic lineations are more difficult to correlate with the main folding phase and suggest its relation to an E-W, possibly localized, strike-slip regime during the main deformational and metamorphic phase. The magnetic fabrics in the third domain, cióse to the Canal Beagle, displays a more heterogeneous character with both E-W and N-S striking foliations; in this case a population of subhorizontal E-W magnetic lineation (κ1) suggests the existence of a significant component of strike-slip deformation.Se presentan los resultados de una transecta de Anisotropía de Susceptibilidad Magnética (ASM) realizada en los Andes Fueguinos, Argentina. Se midieron 240 muestras orientadas provenientes de 27 sitios de muestreo distribuidos entre Paso Garibaldi, al norte y el Canal Beagle al sur. El muestreo se focalizó esencialmente en la Formación Lemaire del Jurásico Superior, con un único sitio en la Formación Yahgán del Cretácico inferior. Las litologías estudiadas incluyen basaltos, andesitas y rocas volcanoclásticas y sedimentarias afectadas por metamorfismo de bajo grado. Las mediciones de fábrica magnética se complementaron con el estudio microscópico de muestras representativas con el propósito de caracterizar las microestructuras y las asociaciones metamórficas. La fábrica magnética está dominada por formas obladas y presenta una gran variación en el grado de anisotropía (1,04-2). Los mayores valores de anisotropía están asociados a la presencia de pirrotina secundaria, identificada por medio de ensayos magnéticos. La foliación magnética muestra muy buena correspondencia con el clivaje medido en campo, confirmando el origen tectónico de la fábrica magnética. Los modelos de distribución de los ejes de ASM permitieron distinguir tres dominios geográficos. El dominio septentrional, entre Paso Garibaldi y Valle Carbajal, presenta lineaciones magnéticas (κ1) de orientación N-S aNE-SW con buzamiento moderado hacia el S-SW, coincidente con determinaciones previas de lineaciones minerales asociadas con la deformación andina. Este diseño de fábrica magnética se vincula a la fase de deformación principal responsable del desarrollo del clivaje pizarreño y de la faja plegada y corrida Fueguina en el Cretácico Tardío. Un segundo dominio corresponde al Valle Carbajal, caracterizado por foliaciones magnéticas E-W, subverticales y lineaciones magnéticas E-W (a ESE-WNW) subhorizontales que se interpretan como vinculados a regímenes localizados de transcurrencia. La fábrica magnética en el tercer dominio, en la zona del Canal Beagle, presenta un carácter más heterogéneo con foliaciones de orientación tanto E-W como N-S; la presencia de una población de lineaciones magnéticas subhorizontales de rumbo E-W sugiere la existencia de un componente de rumbo significativo.

Adenoid cystic carcinoma is a frequently occurring malignant salivary gland neoplasm. We studied the induction of protease activity by the laminin-derived peptide, SIKVAV, in cells (CAC2) derived from this neoplasm. Laminin alpha1 and matrix metalloproteinases (MMPs) 2 and 9 were immunolocalized in adenoid cystic carcinoma cells in vivo and in vitro. CAC2 cells cultured on SIKVAV showed a dose-dependent increase of MMP9 as detected by zymography and colocalization of alpha3 and alpha6 integrins. Small interfering RNA (siRNA) knockdown of integrin expression in CAC2 cells resulted in decreased adhesion to the peptide. SIKVAV affinity chromatography and immunoblot analysis showed that alpha3, alpha6, and beta1 integrins were eluted from the SIKVAV column, which was confirmed by mass spectrometry and a solid-phase binding assay. Small interfering RNA experiments also showed that these integrins, through extracellular signal-regulated kinase (ERK) 1/2 signaling, regulate MMP secretion induced by SIKVAV in CAC2 cells. We propose that SIKVAV increases protease activity of a human salivary gland adenoid cystic carcinoma cell line through alpha3beta1 and alpha6beta1 integrins and the ERK 1/2 signaling pathway.

SUMMARY Detailed palaeomagnetic studies of Late Palaeozoic rocks exposed in the UspallataCalingasta Valley region, located at about 32"s 69.5"W in the Argentine Andean Chain, have been recently accomplished. Previous results are discussed in Valencio & Vilas (1985) and Rapalini et al. (1989). The most recent studies were carried out mainly on the thick sequences of late Early Permian to Late Permian rhyolites and ignimbrites assigned to the Tambillos and Horcajo Formations. Both formations yielded palaeomagnetic pole positions (P15: 319.6"E, 78.9"S7 N = 16, k = 33.5, AgS = 6.5" and P17: 264.8"E, 72.4"S, N = 26, k = 6.4, Ag5 = 12", respectively) concordant with the Late-Palaeozoic path of South America. Preliminary palaeomagnetic results from the Middle Carboniferous Hoyada Verde Formation, exposed in the same region, suggest that these rocks carry a synfolding magnetization acquired during the Late Carboniferous, as the palaeomagnetic pole position computed from partially corrected remanence directions (C6: 356.2"E, 41.9"S, D1 = 8.3", 02 = 6.0") agrees with the Late Carboniferous poles from cratonic areas of South America. This concordant position of C6 definitely rules out the possibility of a Late Palaeozoic allochthony of this section of the Argentine Andean Chain. The discordant positions previously found in Late Carboniferous and early Early Permian rocks of this region are interpreted as caused by large clockwise crustal block rotations that occurred not later than the late Early Permian. A tectonic model is proposed to explain these rotations which suggests that they were associated with strike-slip displacements parallel to the western continental margin of South America caused by an oblique subduction of the Proto-Pacific Plate during the Early Permian. Many tectonic and geologic observations fit this model. The concordant position of C6 also suggests that a complex pattern of crustal block rotations should have developed in this continental margin. Other palaeomagnetic data suggest that similar rotations may have taken place in other areas of the Argentine Andean Chain in the Early Permian.

Late Cenozoic volcanic rocks outcrop in the northern Patagonia Extrandina. Lava flows, characterized as olivine and alkaline basalts, belong to intraplate volcanism. We report paleomagnetic and rock-magnetic studies carried out on Late Cenozoic basalts belonging to the Cráter, Mojón and Moreniyeu Formations. The paleomagnetic sampling comprised 75 sites in lava flows and dikes from the Cráter Formation, three sites in a lava flow from the Mojón Formation and three sites in a lava flow from the Moreniyeu Formation. Alternating field (AF) and thermal detailed demagnetization techniques were used. Most of the samples have a viscous component. The AF procedure was more effective than thermal demagnetization in destroying viscous components and in defining the characteristic remanent magnetizations. Demagnetization curves and rock-magnetic studies suggest that the main remanence carrier is Ti-poor magnetite. Radiometric K-Ar ages were performed on these basalts. The radiometric ages are 0.8±0.1 Ma from outcrops located at Cerro Fermín and 1.9±0.4 Ma from outcrops at Cerro Negro, both at the Cráter Formation. These ages suggest an early-middle Pleistocene age for the lava flows from Cerro Fermín, and a late Pliocene to early Pleistocene age for the Cerro Negro lava flows. Based on the magnetic polarity temporal scale, the Cerro Fermín lava flows have registered the beginning of the Brunhes Chron, while the Cerro Negro basalts could have been extruded during the Olduvai Subchron. The K-Ar radiometric age of the Moreniyeu Formation (1.6±0.2 Ma) suggests an early Pleistocene age for this lava flow. The reverse polarity of its virtual geomagnetic poles (VGPs) is in agreement with the predominant one during the Matuyama Chron and suggests that the Moreniyeu Formation constitutes another volcanic event clearly separate from those of the Cráter Formation. The K-Ar radiometric age of the Mojón Formation (3.3±0.4 Ma) locates it in the middle Pliocene. The VGP polarity would be correlated with some reverse subchron located in Gauss Chron or with the end of the Gilbert Chron. The petrographical and geochemical similarities between the studied basalt and the Somuncura plateau basalts (late Oligocene-early Miocene, located northern and eastern of the study area), together with the time lapsed among between the Mojón and Cráter basalt extrusion suggest the presence in the area of a temporarily extensive thermal anomalies.

Paleomagnetic studies carried out on six cores from the bottom sediments from lake El Trebol, South Argentina are described. Measurements of directions declination and inclination (D and I) and intensity of natural remanent magnetisation (NRM), magnetic susceptibility at low and high frequency (specific, X and volumetric, k), isothermal remanent magnetisation (IRM), saturation isothermal remanent magnetisation (SIRM), back field and anhysteric remanent magnetisation (ARM) were carried out. Stability of the NRM was investigated by alternating-field demagnetisation. Rock magnetic studies suggest that the main carriers of magnetisation are ferrimagnetic minerals, predominantly pseudo single domain magnetite. Records of NRM and k show a good correlation with the sedimentological description, and also with those of shorter cores previously studied. The tephra layers were identified from the lithologic profiles and also from the magnetic susceptibility logs. Due to their different chronological meaning and their rather bad behaviour as magnetic recorder, these layers were removed from the sequence and the gaps that were produced along the profiles by the removal were closed, obtaining a shortened depth. Radiocarbon age estimates from these cores and from earlier studies allow us to construct a paleosecular variation (PSV) record for the past 24,000 years. These results show good correlation with the previous one. The spectrum obtained from spectral analysis shows major peaks at periodicities of about 1150, 1500, 2490, 3630, 5240 and 11,810 years. Both clockwise and counterclockwise precession of the geomagnetic vector is evident from analysis of the Bauer plots, with a preponderance of clockwise movement.

Geophysical and geological field surveys carried out in the central and eastern part of the Argentinean Tierra del Fuego Island on the Magallanes–Fagnano fault system (MFS) delineate its main structural features and tectonic setting. Gravity and magnetic data provide critical information for those areas lacking good exposures and support a present-day transtensional tectonic regime for the MFS. In the surveyed area, the MFS segments have a clear morphological expression and are associated with localized gravity minima interpreted as pull-apart basins. In the southeastern corner of Lago Fagnano, the magnetic data suggest a prominent crystalline body in the subsurface, partially exposed in Cerro Hewhoepen. The shape and position of this intrusive body suggest that its emplacement was localized in a releasing bend. Two-dimensional density modeling along a 40 km long N–S section east of Lago Fagnano suggests a deep duplex similar to that exposed in the western part of the island. The obtained model, combined with available surface data, implies the subsurface configuration of geological units and structures, in which the structure of the deep duplex is similar to that exposed in the western part of the Island. The model indicates the southward deepening of the basement from 5 to 7 km and provides further support for the piston shape of the Hewhoepen intrusive.

Paleomagnetic and sedimentological studies carried out on four cores, about 11 m long, from the bottom sediments of Escondido Lake (southwestern Argentina) are described. This lake is geologically related to the set of lakes of glacial origin located in western Patagonia. Using several magnetic studies, the predominance of pseudo-single/single domain magnetite as main carrier, as well as an increase of concentration and grain size with depth was determined. The pairs of magnetic susceptibility and intensity of remanent magnetization profiles show a good correlation with the sedimentological macroscopic descriptions, and also with those of shorter cores previously studied. The stability of the natural remanent magnetization was investigated by alternating-field demagnetization. Within-lake correlation was based on lithology, magnetic susceptibility and intensity of remanent magnetization, because the patterns of these parameters showed similarity for every core. Radiocarbon dating suggests higher deposition rates during the early stage of the lacustrine basin (Late Pleistocene). The transfer function depth–age also allowed constructing a secular variation record from south Argentina for the past 19,000 years. The declination and inclination logs show some anomalous directions at about 18,000 calibrated years.

Lago Fagnano, an E-W elongated basin located in the central part of Isla Grande de Tierra del Fuego, occupies a structural depression originated along a segment of the Magallanes-Fagnano fault system. Its evolution was mostly conditioned by tectonic processes, and later was affected by glacial and glacio-lacustrine depositional events. New high-resolution single-channel seismic data, integrated with previous seismic profiles, and geological information acquired in the surroundings of the Lago Fagnano, allows us reconstructing the basement surface of the lake, and the geometry, distribution, and thickness of the glacial and glacio-lacustrine sequences. We recognized three main sub-basins within the Lago Fagnano: 1. a medium-size (ca. 21x5 km), deep (373 m), and asymmetric basin to the east; 2. an E-W trending (44x3 km), shallower (150 m) central sub-basin; and 3. a smaller (3.5x1.3 km), shallow (128 m) sub-basin to the west. The isopach sediment map shows that the most pronounced deposition occurred along the E-W axis of the lake, with a gradual increase in thickness towards east (from 100 to 150 m). The glacial deposits are widespread along the basin. The lacustrine sediments are preferentially localized along the E-W axis of the lake filling topographic lows. The shape of the sub-basins and their location in relation with the Magallanes-Fagnano fault system, along with the distribution, geometry, and thickness of the sedimentary units, show that the general morphology of the Lago Fagnano was mostly controlled by pre-existing and syntectonic features. Based on the structural data observed in the outcrops around the Lago Fagnano and the geophysical data, we proposed that the lake is composed by 4 amalgamated pull-apart sub-basins. El lago Fagnano, una cuenca elongada E-W en la parte central de la isla Grande de Tierra del Fuego, ocupa una depresión estructural originada a lo largo de un segmento del sistema de fallas Magallanes-Fagnano. Su evolución estuvo principalmente condicionada por procesos tectónicos y, luego, fue afectada por eventos deposicionales glaciales y glaciolacustres. Nueva sísmica monocanal de alta resolución, integrada con perfiles sísmicos previos e información geológica adquirida en los alrededores del lago Fagnano, nos permite reconstruir la superficie del basamento del lago, y las geometrías y espesores de las secuencias glaciales y glaciolacustres. Reconocimos tres subcuencas principales dentro del Lago Fagnano: 1. una subcuenca asimétrica profunda (373 m) de tamaño medio (ca. 21x5 km) en el este; 2. una gran subcuenca central (44x3 km) más somera (150 m); y 3. una pequeña subcuenca occidental (3,5x1,3 km) somera (128 m). El mapa isopáquico muestra que los mayores depósitos se localizan a lo largo del eje E-W del lago, con un incremento gradual del espesor hacia el este (de 100 a 150 m). Los depósitos glaciales están ampliamente distribuidos a lo largo de la cuenca. Los sedimentos lacustres están preferentemente localizados a lo largo del eje E-W rellenando los bajos topográficos. La forma de las subcuencas y su localización en relación con el Sistema de Fallas Magallanes-Fagnano, junto con la distribución, geometría y espesor sedimentario de las unidades sedimentarias, muestra que la morfología general del lago Fagnano estuvo principalmente controlada por características tectónicas preexistentes y por fallas sintectónicas. Basándonos en los datos estructurales en los alrededores del lago Fagnano y en los datos geofísicos, proponemos que el lago está compuesto por 4 subcuencas de 'pull aparts' amalgamadas.

Anisotropy of magnetic susceptibility (AMS) provides a statistically robust technique to characterize the fabrics of deposits of pyroclastic density currents (PDCs). AMS fabrics in two types of pyroclastic deposits (small-volume phreatomagmatic currents in the Hopi Buttes volcanic field, Arizona, USA, and large-volume caldera-forming currents, Caviahue Caldera, Neuquén, Argentina) show similar patterns. Near the vent and in areas of high topographical roughness, AMS depositional fabrics are poorly grouped, with weak lineations and foliations. In a densely welded proximal ignimbrite, this fabric is overprinted by a foliation formed as the rock compacted and deformed. Medial deposits have moderate-strong AMS lineations and foliations. The most distal deposits have strong foliations but weak lineations. Based on these facies and existing models for pyroclastic density currents, deposition in the medial areas occurs from the strongly sheared, high-particle-concentration base of a density-stratified current. In proximal areas and where topography mixes this denser base upwards into the current, deposition occurs rapidly from a current with little uniformity to the shear, in which particles fall and collide in a chaotic fashion. Distal deposits are emplaced by a slowing or stalled current so that the dominant particle motion is vertical, leading to weak lineation and strong foliation. Fil: Ort, M. H.. Northern Arizona University; Estados Unidos Fil: Newkirk, T.. University of British Columbia; Canadá Fil: Vilas, Juan Francisco A.. 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: Vazquez, J. A.. United States Geological Survey; Estados Unidos

Data from paleomagnetic and sedimentological studies carried out on four cores from the bottom sediments of Lake Moreno (southern Argentina) were integrated with data obtained by Creer et al., Geophys. J. R. Astron. Soc., 74 (1983), 109 . Within-lake correlations are based on the magnetic susceptibility and intensity of remanent magnetization. The individual measurements were stacked and transformed to a time-scale to produce type-curves. The secular variation of the geomagnetic field was studied using spectral analysis and precession analysis of the magnetic vector. The spectrum obtained from spectral analysis shows major peaks at periodicities of about 1500, 2400, 3300, and 6200 yr for inclination data and major peaks at periodicities of about 1200, 2300, and 3500 yr for declination data. In order to test the stability of the obtained periodicities, spectral analysis was applied to every 6000 yr time span at intervals of 500 yr for both records. Both clockwise and counterclockwise precession of the geomagnetic vector is evident from analysis of the VGP path plots, with a preponderance of clockwise.

Summary Regional type curves depicting secular variations in declination and inclination through the last 6700 calendar years constructed for southwestern Argentina (about 41°S, 71°30′W) by stacking palaeomagnetic data derived from lake sediment cores are described and analysed. The data consist of records from four lakes which have been previously studied (El Trebol, Brazo Campanario, Moreno and Escondido), and are here integrated. Within-lake correlation was based on magnetic susceptibility (χ) and intensity of the natural remanent magnetization (NRM). Interlake correlation was derived from declination and inclination patterns and a set of radiocarbon age determinations. The secular variation (SV) of the geomagnetic field was studied using spectral analysis and precession analysis of the magnetic vector. The spectrum obtained from spectral analysis of declination (D) and inclination (I) at the same time shows major peaks at periodicities of about 3400, 1600 and 1200 yr for both parameters. In order to test the stability of the periodicities obtained, spectral analysis has been applied to every 3500-yr time span at intervals of 500 yr for both records. Patterns of circularity during the last 6700 yr appear to recur with a near constant interval of about 2000 yr. Both open and closed loops are associated with clockwise and counter-clockwise circularity.