Resumen de Tesis Doctoral: Sismoestratigrafía y evolución tectonosedimentaria del Margen Continental Norcatalán (Mediterráneo Occidental, NE de España) durante el Cenozoico

The integrated analysis of the onshore and offshore geological record in the Northern Catalan continental margin allows to establish the major factors which controlled its Cenozoic upbuilding and evolution. The structural processes, which took place along successive tectonic stages, together with the coeval vertical movements and eustatic variations were critical for the generation of major erosion and sedimentation areas. All these factors as a whole, controlled the accommodation and the sedimentary supply throughout the margin upbuilding and resulted in its sedimentary architecture. Two sectors (Northern and a Southern) have been defined for the studied area, upon the basis of differences in their structure and sedimentary record. The main Eastern Pyrenean Paleogene contractive structures (axial zone antiformal stack, Figueres - Montgrí thrustsheet, Vallfogona thrust) and their coeval foreland basin were traced in the offshore areas, as far as the shelf edge. Extensional structures occur related to two major fault systems, which strike NE-SW to NNE-SSW and NW-SE and later shaped the divergent Catalan continental margin. The NE-SW fault system would have originated during a Late Oligocene-Earlier Miocene faulting stage, which would have resulted in most of the recorded crustal extension and thinning. The NW-SE faults have been at least partially active as strike-slip faults during the Paleogene, with displacements which are difficult to precise. However, these faults behaved as normal faults during Middle Miocene to Quaternary and though they display less important displacements than those of the NE-SW system, they are closely related to extensive volcanic activity, which suggests its connection with the lower lithosphere. The Cenozoic stratigr a p hy records the successive influence of sedimentary and erosive processes related to 1) the upbuilding of the Pyrenean orogene and the evolution of its foreland basin; 2) the activity of the NE-SW to NNE-SSW fault system as well as the lithospheric uplifting related to the NW Mediterranean rifting and 3) the later thermal subsidence of the continental margin developed during the Middle Miocene-Quaternary, which was opposite to the isostatic rebound of the Pyrenees and its foreland. Changes of sea level, together with other environmental factors, have extensively controlled the present architecture of the submerged margin since Late Miocene. On the basis of the predominance of one or more of those factors, the Cenozoic record of the North-Catalan margin has been split into two, upper and lower parts. The lower part is composed by four tectonostratigraphic units (seismic units 1 to 4), related to the main tectonic events. The upper part is made up by two depositional supersequences (units 5 and 6), which are controlled by changes in sea level and environmental factors. Tectonostratigraphic units are as follows: Unit 1: syntectonic and coeval to the compression which gave rise to the Pyrenees. Corresponding sediments are those deposited in the foreland basin. Unit 2: syntectonic in relation to the NE-SW structures. Sediments belonging to Subunit 2a are synrift, while those of Subunit 2b belong to the late rifting stage. Deposits of Unit 3 in the Southern zone are postrift while in the Northern zone they are associated to the valley infill during lithospheric uplifting related to Oligocene rift generation and possibly to the beginning of NW-SE fault system activity. Unit 4 in the Southern sector shows the evidences of the ceasing of the extensional process, while in the Northern sector, sediments are syntectonic with the starting or persistence of the NW-SE system activity. The two upper supersequences (Units 5 and 6) consist of sequences 5.1 and 5.2 (3rd order), 6.1 (3rd order) 6.2 (5th order) and sequences 6.3 and 6.4 (7th order). During their development, the margin underwent alternatively regressions (seq. 5.2, 6.2, 6.3 ), transgressions (seq. 5.1, 6.3, 6.4) and aggradation (6.2). The occurrence and development of the different sedimentary bodies and depositional systems forming the sedimentary system tracts in both the Northern and Southern sectors was related to eustatic variation and environmental factors, resulting in different arrangements among the sedimentary system tracts identified within each sequence. Eight arrangements have been defined and a certain pattern can be recognized for their areal distribution when comparing Northern with Southern sectors. The conspicuous difference between the volumes of sediments supplied during different periods at the Northern and Southern sectors, and the tectonic control due to Pre-Neogene and Pre-Pliocene structure on later sedimentary infill are remarkable features of the studied zone. The accumulation of Miocene to Quaternary sediments related to the more widespread subsidence stage at the continental margin was modified by the generation of local depocenters resulting from the excavation of topographical depressions and the more or less simultaneous activity of the NW-SE faults. Some of these low laying zones were superimposed and thus accentuated pre-existing contractive Paleogene depressions. In some cases this fact controlled the development of significant de-pocenters as well as the location of some conspicuous Neogene and Recent submarine canyons at the continental margin. These c a nyons have played a relevant role from north to south as sedimentary traps and barriers. At a former stage, essentially pre-Pliocene, the main sedimentary trap would have been the L’ Escala paleocanyon, while during Pliocene and Quaternary the La Fonera canyo n would act as the main sediment barrier. The Cap de Creus canyon originated during the Quaternary, acting as a trap. The relationship of some of these canyons with sedimentary processes and onshore depositional systems can be observed at the whole system of L’ Escala canyon, with its head inside the emerged continent (Fluvia river basin), its transport segment and its accumulation system at the base-of-slope

Resumen de Tesis Doctoral: Sismoestratigrafía y evolución tectonosedimentaria del Margen Continental Norcatalán (Mediterráneo Occidental, NE de España) durante el Cenozoico

The integrated analysis of the onshore and offshore geological record in the Northern Catalan continental margin allows to establish the major factors which controlled its Cenozoic upbuilding and evolution. The structural processes, which took place along successive tectonic stages, together with the coeval vertical movements and eustatic variations were critical for the generation of major erosion and sedimentation areas. All these factors as a whole, controlled the accommodation and the sedimentary supply throughout the margin upbuilding and resulted in its sedimentary architecture. Two sectors (Northern and a Southern) have been defined for the studied area, upon the basis of differences in their structure and sedimentary record. The main Eastern Pyrenean Paleogene contractive structures (axial zone antiformal stack, Figueres - Montgrí thrustsheet, Vallfogona thrust) and their coeval foreland basin were traced in the offshore areas, as far as the shelf edge. Extensional structures occur related to two major fault systems, which strike NE-SW to NNE-SSW and NW-SE and later shaped the divergent Catalan continental margin. The NE-SW fault system would have originated during a Late Oligocene-Earlier Miocene faulting stage, which would have resulted in most of the recorded crustal extension and thinning. The NW-SE faults have been at least partially active as strike-slip faults during the Paleogene, with displacements which are difficult to precise. However, these faults behaved as normal faults during Middle Miocene to Quaternary and though they display less important displacements than those of the NE-SW system, they are closely related to extensive volcanic activity, which suggests its connection with the lower lithosphere. The Cenozoic stratigr a p hy records the successive influence of sedimentary and erosive processes related to 1) the upbuilding of the Pyrenean orogene and the evolution of its foreland basin; 2) the activity of the NE-SW to NNE-SSW fault system as well as the lithospheric uplifting related to the NW Mediterranean rifting and 3) the later thermal subsidence of the continental margin developed during the Middle Miocene-Quaternary, which was opposite to the isostatic rebound of the Pyrenees and its foreland. Changes of sea level, together with other environmental factors, have extensively controlled the present architecture of the submerged margin since Late Miocene. On the basis of the predominance of one or more of those factors, the Cenozoic record of the North-Catalan margin has been split into two, upper and lower parts. The lower part is composed by four tectonostratigraphic units (seismic units 1 to 4), related to the main tectonic events. The upper part is made up by two depositional supersequences (units 5 and 6), which are controlled by changes in sea level and environmental factors. Tectonostratigraphic units are as follows: Unit 1: syntectonic and coeval to the compression which gave rise to the Pyrenees. Corresponding sediments are those deposited in the foreland basin. Unit 2: syntectonic in relation to the NE-SW structures. Sediments belonging to Subunit 2a are synrift, while those of Subunit 2b belong to the late rifting stage. Deposits of Unit 3 in the Southern zone are postrift while in the Northern zone they are associated to the valley infill during lithospheric uplifting related to Oligocene rift generation and possibly to the beginning of NW-SE fault system activity. Unit 4 in the Southern sector shows the evidences of the ceasing of the extensional process, while in the Northern sector, sediments are syntectonic with the starting or persistence of the NW-SE system activity. The two upper supersequences (Units 5 and 6) consist of sequences 5.1 and 5.2 (3rd order), 6.1 (3rd order) 6.2 (5th order) and sequences 6.3 and 6.4 (7th order). During their development, the margin underwent alternatively regressions (seq. 5.2, 6.2, 6.3 ), transgressions (seq. 5.1, 6.3, 6.4) and aggradation (6.2). The occurrence and development of the different sedimentary bodies and depositional systems forming the sedimentary system tracts in both the Northern and Southern sectors was related to eustatic variation and environmental factors, resulting in different arrangements among the sedimentary system tracts identified within each sequence. Eight arrangements have been defined and a certain pattern can be recognized for their areal distribution when comparing Northern with Southern sectors. The conspicuous difference between the volumes of sediments supplied during different periods at the Northern and Southern sectors, and the tectonic control due to Pre-Neogene and Pre-Pliocene structure on later sedimentary infill are remarkable features of the studied zone. The accumulation of Miocene to Quaternary sediments related to the more widespread subsidence stage at the continental margin was modified by the generation of local depocenters resulting from the excavation of topographical depressions and the more or less simultaneous activity of the NW-SE faults. Some of these low laying zones were superimposed and thus accentuated pre-existing contractive Paleogene depressions. In some cases this fact controlled the development of significant de-pocenters as well as the location of some conspicuous Neogene and Recent submarine canyons at the continental margin. These c a nyons have played a relevant role from north to south as sedimentary traps and barriers. At a former stage, essentially pre-Pliocene, the main sedimentary trap would have been the L’ Escala paleocanyon, while during Pliocene and Quaternary the La Fonera canyo n would act as the main sediment barrier. The Cap de Creus canyon originated during the Quaternary, acting as a trap. The relationship of some of these canyons with sedimentary processes and onshore depositional systems can be observed at the whole system of L’ Escala canyon, with its head inside the emerged continent (Fluvia river basin), its transport segment and its accumulation system at the base-of-slope

Morpho-sedimentary features of the south-western Scotia Sea

Fil: Rovira, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Tassone, Alejandro Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Esteban, Federico Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Evolución del sector septentrional del margen continental catalán durante el Cenozoico

Preliminary integrative analysis of the geological record in the onshore and offshore areas of the Northern Catalan continental margin, enable one to trace as far as the shelf edge, the main Eastem Pyrenean Paleogene contractive structures (axial zone antiformal stack, Figueres-Montgrí thrust-sheet, Vallfogona thrust) and their coeval foreland basin. These structures are cut by two major, NE-SW to NNE-SSW and NW-SE oriented, extensional fault systems. The activity of the NE-SW to NNE-SSW fault system (mainly Late Oligocene-earliest Miocene in age) would have resulted in most of the crustal extension and thinning recorded in this extensional margin of the Valencia Trough. On the other side the NW-SE faults were at least partially active as strike-slip faults during the Paleogene, with displacements which are difficult to be precised. Nevertheless these faults were mainly normal faults during Middle Miocene to Quatemary. Although the faults display minor slips than those of NE-SW orientation, they are closely related to a noticeable alkaline volcanic activity which denote they reach the lower litosphere. The Cenozoic stratigraphy in the Northern Catalan continental margin records and was influenced succesively by: 1) the Paleogene (Paleocene-Early Oligocene) upbuilding of the Pyrenean orogen and the evolution of its foreland basin; 2: the activity of the Late Oligocene-Early Miocene NE-SW to NNE-SSW faults and coeval lithospheric uplifting, both related to the the NW Mediterranean rifting; and 3: the later thermal subsidence of the continental margin developed during the Middle Miocene-Quaternary and which was opposite to the isostatic rebound of the Pyrenees and its southern foreland. Middle Miocene to Quaternary sedimentation related to the resulting total subsidence of the continental margin was modified by the generation of local depocenters. These depocenters resulted from the excavation of topographical depressions and the more or less simultaneous activity of the NW-SE faults. Some of these low lying zones were superimposed and accentuated pre-existing contractive Paleogene depressions. In some cases this fact controlled the develoment of significative Late Neogene depocenters and the location in the continental margin of some conspicuous Neogene and recent submanne canyons

Gravity map of the Isla Grande de Tierra del Fuego, and morphology of Lago Fagnano

A complete Bouguer gravity map of the central-eastern part of the Isla Grande de Tierra del Fuego, and a general bathymetric chart of the Lago Fagnano have been realized, on the basis of a series of field geophysical surveys carried out on the Island since 1998. The regional gravity anomaly trend onshore shows a progressive negative gradient from N to S. Distinct, broadly E-W-trending gravity minima are superimposed on this regional negative gradient. They follow the main trace of the Magallanes-Fagnano fault system, which represents the western segment of the left-lateral South America-Scotia transform plate boundary. The gravity minima reflect the presence in the subsurface of restricted and elongated basins developed within the principal displacement zone of the fault system. A relative positive gravity maximum is located just at the SE corner of the Lago Fagnano, and represents the response of a partially exposed crystalline body, occupying an area 3 x 3 km wide. A 2D vertical crustal model has been constructed, combining gravity data inversion and geological information available for the central-eastern region of Lago Fagnano. The bathymetric map of the Lago Fagnano delineates the main morphological features of this 110-km-long, 7-km-wide lake, the largest of Isla Grande. The floor is divided into distinct parts, which suggests that the basin is composed of different sub-basins. In most areas, the basin floor is highly asymmetric in shape, with flat depocentral areas. The most pronounced asymmetry of the basin is seen in the eastern end of the lake, where there is also the deepest depression. The steeper slope of the basin, along the northern shore of the Lago Fagnano, also coincides with the most pronounced regional topographic gradient. The general gravimetric and morphological features of the investigated region are here discussed.Fil: Lodolo, Emanuele. No especifíca;Fil: Lippai, Horacio Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; ArgentinaFil: Tassone, Alejandro Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; ArgentinaFil: Zanolla, Marianela. No especifíca;Fil: Menichetti, Marco. Università Degli Studi Di Urbino Carlo Bo; ItaliaFil: Hormaechea, José Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

The submerged footprint of Perito Moreno glacier

Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of Perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the Perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the Canal de Los Témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of the “Herminita advance” identified and dated onland. We interpret these bedforms as the evidence of the most pronounced advance of Perito Moreno glacier during the mid-Holocene cooling event that characterized this sector of the Southern Hemisphere. This study highlights the importance of subaqueous glacial bedforms, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of glaciers like Perito Moreno that in a warming climate are relatively stable.Fil: Lodolo, Emanuele. Istituto Nazionale di Oceanografa e di Geofsica Sperimentale ; ItaliaFil: Donda, Federica. Istituto Nazionale di Oceanografa e di Geofsica Sperimentale ; ItaliaFil: 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; ArgentinaFil: Baradello, Luca. Istituto Nazionale di Oceanografa e di Geofsica Sperimentale ; ItaliaFil: Romeo, Roberto. Istituto Nazionale di Oceanografa e di Geofsica Sperimentale; ItaliaFil: 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; ArgentinaFil: 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; Argentin

Erosional and depositional contourite features at the transition between the western Scotia Sea and southern South Atlantic Ocean: links with regional water-mass circulation since the Middle Miocene

The aim of the present study was to characterise the morpho-sedimentary features and main stratigraphic stacking pattern off the Tierra del Fuego continental margin, the north-western sector of the Scotia Sea abyssal plain (Yaghan Basin) and the Malvinas/Falkland depression, based on single- and multi-channel seismic profiles. Distinct contourite features were identified within the sedimentary record from the Middle Miocene onwards. Each major drift developed in a water depth range coincident with a particular water mass, contourite terraces on top of some of these drifts being associated with interfaces between water masses. Two major palaeoceanographic changes were identified. One took place in the Middle Miocene with the onset of Antarctic Intermediate Water flow and the enhancement of Circumpolar Deep Water (CDW) flow, coevally with the onset of Weddell Sea Deep Water flow in the Scotia Sea. Another palaeoceanographic change occurred on the abyssal plain of the Yaghan Basin in the Late Miocene as a consequence of the onset of Southeast Pacific Deep Water flow and its complex interaction with the lower branch of the CDW. Interestingly, these two periods of change in bottom currents are coincident with regional tectonic episodes, as well as climate and Antarctic ice sheet oscillations. The results convincingly demonstrate that the identification of contourite features on the present-day seafloor and within the sedimentary record is the key for decoding the circulation of water masses in the past. Nevertheless, further detailed studies, especially the recovery of drill cores, are necessary to establish a more robust chronology of the evolutionary stages at the transition between the western Scotia Sea and the southern South Atlantic Ocean.Fil: Pérez, Lara F.. Instituto Andaluz de Ciencias de la Tierra; España. Geological Survey of Denmark and Greenland; DinamarcaFil: Hernández Molina, F. Javier. Royal Holloway University of London; Reino UnidoFil: 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; ArgentinaFil: 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; ArgentinaFil: Piola, Alberto Ricardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maldonado, Andrés. Instituto Andaluz de Ciencias de la Tierra; EspañaFil: Preu, Benedict. Chevron North Sea; Reino UnidoFil: Violante, Roberto Antonio. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Itali

Origen y evolución del lago Yehuin (isla Grande de Tierra del Fuego, Argentina): resultados de un relevamiento geofísico

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 (<10 m) que cubre la cuenca entera. El lago Yehuin se considera una cuenca neógena e origen tectónico que fue luego afectada por depositación glaciaria y glaciolacustre. Se han interpretado morenas sumergidas dentro del lago Yehuin que se correlacionan con los arcos morrénicos en tierra y permiten completar el camino recesivo de los lóbulos de hielo Ewan y Fuego. Se propone un fuerte control estructural no solo para la formación del lago Yehuin, sino también para las rutas generales de los brazos norte del Paleoglaciar Fagnano.Lago Yehuin, a WNW-ESE elongated basin located in the outer fold-and-thrust belt of the Fuegian Andes, occupies a compartmented structural depression originated along a segment of the left-lateral Lago Deseado fault system. This paper describes the first geophysical survey performed within the lake. New acquired high-resolution single-channel seismic data, integrated with geological information in the surroundings of the Lago Yehuin, allowed to: (i) produce a complete bathymetric map of the lake, (ii) reconstruct the basement surface of the lake, and (iii) analyze the geometry, distribution, and thickness of the sedimentary infill. Two sub-basins were recognized within Lago Yehuin: A western sub-basin, 7.5 km long, with a maximum depth of 118 m; an eastern sub-basin, 7.2 km long with a maximum depth of 80 m. Both sub-basins are limited by a set of normal faults which overprint NE-verging thrusts. Three seismo-stratigraphic units have been identified in the seismic records: (1) a lower unit with wedged geometry interpreted as a mass flow deposits; (2) a thick (up to 120 m) intermediate unit of glacio-lacustrine nature and irregularly distributed in the Yehuin basin; (3) a thin (generally <10 m) upper lacustrine unit which drapes the entire basin. Lago Yehuin is considered a Neogene basin generated by strike-slip tectonics that was later affected by glacial and glacio-lacustrine deposition. Interpreted submerged ridge moraines within Lago Yehuin are correlated with onland moraine arcs built by the complete recessional paths of Fuego and Ewan ice lobes. A significant structural control is proposed not only for the formation of Lago Yehuin, but also for the general paths of the northern arms of the Fagnano palaeo-glacier.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; ArgentinaFil: 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; ArgentinaFil: Lodolo, Emanuele. Istituto Nazionale Di Oceanografia E Di Geofisica Sperimentale;Fil: Menichetti, Marco. Universita Degli Studi Di Urbino Carlo Bo;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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: Baradello, Luca. Instituto Nazionale di Oceanografia e di Geofísica Sperimentale; ItaliaFil: 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; Argentin

Glacial-related morphology and sedimentary setting of a high-latitude lacustrine basin: The Lago Chepelmut (Tierra del Fuego, Argentina)

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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: Lodolo, Emanuele. Istituto Nazionale Di Oceanografia E Di Geofisica Sperimentale;Fil: Menichetti, Marco. Università di Urbino; ItaliaFil: 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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: Baradello, Luca. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; ItaliaFil: 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; Argentin

Gateways and climate: The Drake Passage opening

The Oligocene opening of the Drake Passage between the southern tip of South America and the Antarctic Peninsula, and the subsequent evolution of the Scotia plate, have definitively separated Antarctica from the other continental masses, and have created conditions for the development of the Antarctic Circumpolar Current. This annular water flow has had a profound influence on the global climate system because it has allowed the free transfer of water masses between the Pacific and Atlantic Oceans at mid to high southerly latitudes. The comparative seismic analysis of the passive margins of the western sector of the Scotia plate, represented by the Tierra del Fuego continental margin to the north, and by the Terror Rise to the south, has shown significant morphological and structural similarities between these two margins, supporting the interpretation that they were conjugate before the Drake Passage opened. Moreover, the identification of the oldest magnetic anomalies present at the base of the two margin pairs, corresponding to about 32 million years ago, has allowed the reconstruction, through time, of the relative positions of the two continental margins, and to constrain the events that occurred immediately after the break-up and opening of the Drake Passage. These timings correlate with events seen in the oxygen isotope record from benthic foraminera, and support the view that the Drake Passage opening was the trigger for abrupt Eocene-Oligocene climate deterioration and the growth of extensive ice sheets on the Antarctic continent.Fil: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; ItaliaFil: 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. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentin