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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. 21×5 km), deep (373 m), and asymmetric basin to the east; 2. an E-W trending (44×3 km), shallower (150 m) central sub-basin; and 3. a smaller (3.5×1.3 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. 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: 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: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS); Italia Fil: Menichetti, Marco. Università di Urbino; Italia Fil: Lippai, Horacio Francisco. 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: Waldmann, Nicolás. University of Haifa; Israel Fil: Darbo, Alexia. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS); Italia Fil: Baradello, Luca. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS); 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: 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; Argentina Fil: 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; Argentina Fil: 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; Argentina

The geothermal area of Rio Valdez is located in the central portion of the Isla Grande de Tierra del Fuego (South Argentina), ten kilometers south of the southeastern sector of the Fagnano Lake. It consists of a series of thermal springs with low discharge rates (≤1L/s) and temperatures in the range of 20-33°C distributed in an area of

Una nuova datazione U-Pb sugli zirconi che provengono da un campione riolitico dall’area delle terme di Rio Valdez permette integrare temporaneamente le rocce vulcaniche delle Andes Fueginos con la evoluzione del bacino di Rocas Verdes. Le età concordanti ottenute delle 11 zirconi analizzati danno un range compreso tra 155-170 Ma, posizionando la roccia nel Giurassico Medio a Superiore. Il resto dei risultati, discordanti, sono stati tracciati su un grafico di concordia, in cui la intercetta inferiore indica un età di cristallizzazione di 163.9 ± 3.6 Ma. In un contesto regionale, questa età conferma l’ipotesi di apertura da SE a NW del bacino marginale di Rocas Verdes, e potrebbe rappresentare un magmatismo precedente alla generazione di crosta quasi-oceanica. Inoltre, non e stata riconosciuta una relazione con la migrazione a SW del magmatismo acido Giurassico. Fil: Palotti, Priscila Fiorella. Università di Urbino Carlo Bó. Dipartimento di Scienze della Terra, della Vita e dell'Ambiente; Italia Fil: Menichetti, Marco. Università di Urbino Carlo Bó. Dipartimento di Scienze della Terra, della Vita e dell'Ambiente; 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: 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

Two ERT (Electrical Resistivity Tomography) profiles were conducted at the eastern head of Lago Fagnano within the main deformation zone of the Magallanes-Fagnano Transform fault system (MFS) which represents the onland boundary between the SouthAmerica and Scotia plates. Results from the inversion models have provided new evidence of the presence and location at shallow depths of some strands of the MFS. Tomographic models showed significant resistivity contrasts across the inferred fault zones in the subsurface. The combination of ERT, geomorphic and outcrop structural data allowed us to interpret the stepped southwards subsidence of Tertiary and Quaternary units within the studied area. The Holocene development and evolution of a shallow deltaic basin at the mouth of Río Turbio, the eastern tributary of Lago Fagnano, was also interpreted from electrical imaging. 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: Santomauro, Melina. 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. Istituto Di Scienze Della Terra; 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: Lodolo, Emanuele. Istituto Nazionale Di Oceanografia E Di Geofisica Speri; Italia Fil: Remesal, Marcela Beatriz. 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: Lippai, Horacio Francisco. 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: Hormaechea, José Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; 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

The North Scotia Ridge (NSR) is the submerged morpho-structural expression of the Scotia plate northern edge. It is constituted by the Tierra del Fuego continental margin, isla de Los Estados, Burdwood (BB), Davis and Aurora banks, and the Georgias islands shelf (Parker et al., 1996; Barker, 2001; Giner-Robles et al., 2003; Pandey et al., 2010). About 40 Ma these blocks were grouped forming a continental link between Tierra del Fuego and Antarctica. Afterwards, with the development of the Scotia plate, the blocks drifted towards the east to their actual position (Barker, 2001; Pandey et al., 2010). Several authors have established that the actual movement of the South America - Scotia plate boundary is left-lateral (Forsyth, 1975; Pelayo and Wiens, 1989; Giner-Robles et al., 2003; Thomas et al., 2003; Smalley et al., 2007). In the Tierra del Fuego region, the plate boundary is represented by a mostly transtensional fault system known as Magallanes-Fagnano (Lodolo et al., 2002, 2003, 2006, Tassone et al., 2008; Menichetti et al., 2008). Towards east, the boundary is located in the Malvinas trough, at the north of the BB and it would be transpressive (Cunningham et al., 1998; Giner-Robles et al., 2003; Bry et al., 2004). The change of the tectonic regime (transtensional to the W to transpressional to the E) would occur at 63.5 ºW (Lodolo et al., 2003; Yagupsky et al., 2003). As part of a study of the evolution of the SW Atlantic continental margin, we analyze and describe the morpho-structure of the western sector of the North Scotia Ridge. Fil: Esteban, Federico Damián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Tassone, Alejandro Alberto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lodolo, E.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Menichetti, M.. Università di Urbino; Italia

Dai depositi lacustri della Tierra del Fuego e della Patagonia meridionale si possono ricostruire le variazioni climatiche e gli ambienti del passato. Recenti campagne geofisiche e geologiche rivelano come la coltre di ghiaccio che un tempo copriva buona parte di questo settore meridionale dell’America del Sud, abbia subito una serie di avanzamenti e ritiri a partire dall’Ultimo Massimo Glaciale. Queste dinamiche sono ricostruibili sia attraverso le geometrie delle sequenze sedimentarie, sia attraverso le geometrie delle sequenze sedimentarie, sia attraverso approfondite analisi geochimiche e mineralogiche condotte su carote prelevate dal fondo dei laghi. Fil: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Baradello, L.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Caffau, M.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Grossi, M.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Lippai, Horacio Francisco. 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. Università di Urbino; Italia

With the aim of studying the tectonic evolution of the Fueguian Andes,the magnetic susceptibility tensor was measured on sample rocks of the Lemaire and Yahgán Fms outcrop in the area between Paso Garibaldi and Canal Beagle in Tierra del Fuego. In the northern area the orientations of the K1 axis of the magnetic fabric shows a dominant directions N-S that can be correlated to the tectonic transport. In the south from Carbajal valley to Canal Beagle, the orientations are roughly E-W that are linked to the morphostructural lineations associated with a the strike-slip faults. The good correspondence between the magnetic anisotropy axis K3 and the rock foliation, permit to assign to a tectonic origin of the magnetic fabric. 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: 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. 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: Rapalini, Augusto Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina Fil: Lippai, Horacio Francisco. 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

A synthesis of the structural geology of the Tierra del Fuego Island, which integrates a new data set derived from field surveys and literature data of the last few years, is here presented. The main geological features of the region developed during the Mesozoic-Cenozoic Andean orogenic cycle that started in the Middle to Late Jurassic with a back-arc extension, crustal stretching and widespread volcanism, related to the break-up of Gondwanaland. An extensional fault system deriving from the mechanical and thermal subsidence led the evolution of the Rocas Verdes marginal basin, which hosts the upper Jurassic volcanoclastic rocks, the lower Cretaceous turbiditic sequences and few isolated elongated ophiolitic complexes. From the Late Cretaceous onward, the orogenic cycle of the Fuegian Andes continued with the shortening and inversion of the back-arc margin through horizontal contraction and crustal thickening. The uplift of the Cordillera, the emplacement of plutonic rocks, and the intracontinental polyphase deformation resulted from thick-skinned tectonics. The thrust system developed from its deeper roots, where the Palaeozoic basement was involved in compressional deformation, and propagated to the shallower stratigraphic levels of the northward verging Magallanes fold-and-thrust belt. The Magallanes foreland basin developed in front of the orogenic wedge that records at least four syntectonic angular unconformities from Late Cretaceous to Lower Miocene. During the Late Cretaceous Andean compression, three distinct phases of penetrative ductile deformation defined by low-greenschist facies assemblages took place, both in the basement and in the cover units. These deformations are related to a single metamorphic event with foliation development, as observed from microscopic analysis of the schist in the Ushuaia area. The first foliation S1 is preserved either as relic sericite microfolds between microlithons of the dominant S2, or as early refolded veins of recrystallized quartz. The S2 foliation is defined by oriented white mica. The crenulation of S2, which is related to D3 and occurs in most strained zones, becomes a pressure solution S3 spaced foliation, lined by opaque minerals. From the Palaeogene to the present, EW sinistral wrench tectonics affected the region as a component of the relative motion between South America and the Antarctic Peninsula. This strike-slip activity is well documented from the Carbajal valley to the Canal de Beagle region south of the Magallanes-Fagnano transform fault system. Restraining bends and overlapping step-over geometry characterize few sectors of the strike-slip faults with pop-ups, pressure ridges and uplifted slivers of crust. Releasing step-over along the transform fault system, both in on-shore and off-shore zones, formed several elongated pull-apart basins with many tens of km in length and a few km in width. The Lago Fagnano represents the main morphotectonic expression of this structural setting. A N-S geological cross-section through the Fuegian Andes synthesizes all the geological and geophysical data. The major stacks of internal thick-skinned basement involved in the thrusting are high-grade Upper Palaeozoic to Lower Tertiary metamorphic rocks. The geometry of the thrust complex is an upright, south plunging monocline of moderately tilted sedimentary cover strata, as well as related thrusts, faults and chevron folds involving the Upper Jurassic and Cretaceous rocks. The orogenic shortening of the Fuegian Andes, including the Cordillera and the Magallanes fold-and-thrust belt, reaches few hundred kilometres with a left-lateral wrenching component of many tens of meters. The Tierra del Fuego Island is characterized by low magnitude (M

We present a revised tectonic interpretation (from ∼28 Ma to 3.2 Ma) of the western sector of the Scotia Sea, incorporating new multichannel seismic reflection profiles and magnetic anomaly identifications for the continental margin off the Tierra del Fuego Island, and available complementary data for the conjugate margin of the northwestern flank of the South Scotia Ridge. Seismic profiles show a remarkable diversity of the pair of conjugate passive margins of the western Scotia Sea in both their morphology and structural framework. The Tierra del Fuego continental margin can be related to a classic rifted passive margin, while the southwestern margin of the Scotia Sea is characterized by steep slopes mostly generated by subvertical faults that abruptly separate the continental crust of the South Scotia Ridge from the oceanic crust of the western Scotia Sea. This structural difference was caused by intense strike-slip tectonism, mostly concentrated along the modern South Scotia Ridge since the early development of the western Scotia Sea. We find evidence for a previously unrecognized magnetic anomaly 10 (∼28 Ma) at the foot of the Tierra del Fuego continental margin; the same anomaly is present at the conjugate northern flank of the South Scotia Ridge. The timing of events leading to the earliest development of the western Scotia Sea, which determined the opening of the Drake Passage is important because this gateway opening had a profound effect on global circulation and climate. The thickness and the distribution of the sedimentary cover overall in the abyssal plain off the two western Scotia Sea margins is different. This is due to the different regimes of the bottom-current flows which affected the western Scotia Sea, both in the past and in the present time. Fil: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Donda, Federica. 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 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.