13 research outputs found
The central Fuegian fold and thrust belt in Tierra del Fuego: Strike‐slip tectonics superimposed onto compressional deformation
No full textThe boundary between South America and Scotia plates was established during Neogene times when a wrench tectonic regime was developed along the central area of Tierra del Fuego. This boundary includes the Magallanes–Fagnano fault system: a regional diffuse deformation zone, which involves the development of the satellite Yehuin–Chepelmut fault zone and a series of pull-apart basins overprinting the Fuegian fold and thrust belt. The analysis of regional seismic lines allowed to reconstruct and recognize the structure of the external fold and thrust belt. The interpreted structures were integrated into a regional transect and a 3D block diagram that display the different structural domains and, mainly, the wrench deformation associated with the Magallanes–Fagnano fault system. Geophysical data from gravity and magnetic anomaly maps provided further support for the location and development of the pull-apart basins along the plate boundary. The deformation of the external fold and thrust belt is characterized by an imbricated fan system with a Paleogene detachment surface, which was later cut across by the Yehuin–Chepelmut fault zone and the Magallanes–Fagnano fault system.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. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; ArgentinaFil: Bran, Donaldo Mauricio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. 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: Peroni, Javier Ignacio. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lodolo, Emanuele. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; ItaliaFil: Menichetti, Marco. Università Degli Studi Di Urbino Carlo Bo; ItaliaFil: Cerredo, Maria Elena. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. 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. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. 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
Magnetic fabric and microstructures across the Andes ofTierra del Fuego, Argentina
No full textAn anisotropy of magnetic susceptibility (AMS) transect was carried out across the Fuegian Andes, in Argentina, with the 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. Studied 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 dominant oblate shapes and a large variation in the anisotropy degree from 1.04 up to 2. The anomalously high values were observed to be associated 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 region 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 maximum susceptibility axis (k1), or magnetic lineation, is N-S to NE-SW with moderate 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, close 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 (k1) suggests the existence of a significant component of strike-slip deformation
Shallow architecture of Fuegian Andes lineaments based on Electrical Resistivity Tomography (ERT). Evidences of transverse extensional faulting in the central Beagle Channel area
No full textThe 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
Fragmenta chorologica occidentalia, Lichenes, 5590-5649
No full text[Inicio] 5590. Aspicilia bricconensis Hue
Hs, *Luco: A Fonsagrada, Sierra del Muradal,
29TPH5075, 1111 m, sobre pizarra, 30-VII-1988,
C. P. Valcárcel, SANT-Lich. 7864. 1.* cita para
Galicia.
5591. Aspicilia caesiocinerea (Nyl. ex Malbr.)
Arnold
Hs, *Luco: A Fonsagrada, Cerredo, 29TPH5172,
1000 m, sobre pizarra, 5-11-1987, C. P. Valcárcel,
SANT-Lich. 7865. [...]Dirección General de Investigación Científica y Técnica | Ref. PB92-0518-C02-0
Temporal and spatial evolution of the Somún Curá Magmatic Province, Northern Extra-Andean Patagonia, Argentina
No full textThe Somún Curá Magmatic Province (SCMP) is a Cenozoic volcanic region comprised by several basaltic fields and large central volcanoes located at the Northern Extra-Andean Patagonia, Argentina. The principal volcanic sequences were erupted between the late Eocene and late Miocene, forming the Meseta de Somún Curá, which covers ~30,000 km2 between 40°30′-43°20′S and 65°50′-69°20′W, involving around 1 to 2 × 103 km3 of mafic lavas, and about half that volume of intermediate to silicic lava-pyroclastic associations. The SCMP developed in a back-arc to intraplate tectonic setting over the North Patagonian Massif (NPM), at the time of two major geodynamic events at the western margin of South America: the consumption of the Aluk and the break-up of the Farallón oceanic plates. The magmatism at the studied area is represented by eight volcanic complexes, the Somún Curá Formation flood basalts, and other units related to minor volcanic fields or polygenetic centres. These sequences share intricate stratigraphic relations, which hinder the evolution of the SCMP. To address this issue, an updated compilation of geochronological determinations for the Meseta de Somún Curá region is provided. Its integrated analysis, together with stratigraphic information, allowed the identification of periods of preferential volcanic emission, after which seven constructional phases between late Eocene and late Miocene are proposed. Within these phases, seven pulses of magmatic activity are interpreted for the volcanic complexes emplaced in this area (~38-37 Ma, ~32.5–31 Ma, ~29.5–28 Ma, ~26-24 Ma, ~21–18.5, ~18-15 Ma and ~10.5 Ma), together with four pulses of effusion of flood basalts, represented by the Somún Curá Formation (~32 Ma, ~27-26 Ma, ~26-25 Ma, and ~21.5 Ma). The superposition and recurrence of the magmatic pulses associated with the volcanic complexes and the Somún Curá Formation argue against the application of a "pre-plateau", "plateau" and "post-plateau" scheme, which is revised. The largest volumes of magma associated with the Somún Curá Formation and the volcanic complexes were extruded during the late Oligocene and the early Miocene, respectively. The area of emplacement of the Somún Curá Formation changed over time, defining a roughly counter-clockwise spatial and temporal pattern, starting from the southwest. The magmatic activity recorded by the volcanic complexes from late Eocene to middle Oligocene seems to have concentrated alternatively along NW-SE and NE-SW corridors, and along a N–S belt to the west during the early Miocene. This systematic organization could be related to the reactivation of previous structures, triggered by the kinematic changes in the convergence vector between the Farallón-Nazca Plates and the South American Plate.Fil: Cordenons, Pablo Damián. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; ArgentinaFil: 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; ArgentinaFil: Salani, Flavia Maria. 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: Cerredo, María 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; Argentin
Origin and evolution of lago Yehuin (Tierra del Fuego, Argentina): Results from a geophysical survey
No full textLago 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 seismostratigraphic
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
Petrología del complejo volcánico Barril Niyeu (Mioceno inferior), Patagonia Argentina
No full textEl plateau volcánico oligoceno de Somún Curá, en el norte de la Patagonia extraandina de Argentina, está compuesto principalmente por basaltos afíricos de olivino, alcalinos a transicionales, que cubren un área de ~25,000 km2. Se distinguen varios eventos post-plateau del Mioceno que originaron grandes centros bimodales y volúmenes menores provenientes de volcanes monogenéticos. Uno de los complejos post-plateau más grandes es el Complejo Volcánico Barril Niyeu (CVBN), conformado por una secuencia de rocas lávicas y piroclásticas asociadas a por lo menos cinco calderas de varios kilómetros de diámetro. Dataciones K/Ar sobre roca total (20.6±0.4 Ma y 18.7±0.4 Ma) acotan la actividad del CVBN al Mioceno temprano. La facies lávica y piroclástica de traquitas predomina en la base de la secuencia y las composiciones basálticas en la parte superior. La facies piroclástica está integrada por flujos piroclásticos y depósitos de caída de composición ácida y depósitos de tipo estromboliano subordinados. Toda la serie tiene tendencia alcalina y presenta un gap composicional de 52 a 67% SiO2. Los datos geoquímicos e isotópicos (Sr, Nd) indican que las rocas del CVBN están relacionadas genéticamente por procesos cristal-líquido, esencialmente de fusión parcial y cristalización fraccionada. Según el modelado geoquímico, el basalto más primitivo de la serie (Mg# = 66; Ni = 160 ppm; Cr = 290 ppm) habría derivado de la fusión parcial (8–10%) de una fuente peridotítica granatífera. Las interrelaciones de elementos de alto potencial iónico (Th/Yb, Ta/Yb) indican un ambiente de intraplaca, y las relaciones LILE/REE (Ba/ La) una contribución subordinada de componentes de zona de subducción. Las relaciones Rb/Nb y las concentraciones de Th en algunos basaltos podrían ser el resultado de asimilación de rocas corticales. En general, la composición isotópica de los basaltos sugiere una fuente mantélica empobrecida (DM) con contribuciones subordinadas de manto enriquecido de tipo 1 (EM1). El magmatismo oligo-mioceno de Somún Curá es atribuido a un proceso de delaminación litosférica disparado por perturbaciones gravitacionales durante la reorganización de placas en el borde Pacífico de la placa Sudamericana, con contribución subordinada de una placa oceánica desprendida (Aluk?)
Petrología del complejo volcánico Barril Niyeu (Mioceno inferior), Patagonia Argentina
No full textThe Oligocene Somún Curá plateau is the largest volcanic field in the northern extra-andean
Patagonia of Argentina. It is mostly composed of alkaline to transitional aphyric olivine basalts that
cover a sub-circular area of ~25,000 km2. Several early Miocene post-plateau volcanic events resulted in
small monogenetic centres and large bimodal complexes. The Barril Niyeu Volcanic Complex (BNVC) is one of the largest post-plateau bimodal centres built through several stages of eruptive activity outpoured
from at least five vents (presently cauldrons) of distinct trachyte/rhyolite and basaltic compositions. New
whole rock K/Ar dating of early trachyte (20.6±0.4 Ma) and late basaltic (18.7±0.4 Ma) rocks constrain
the time span of the BNVC activity within 2-2.5 My. The earliest eruptive stage of the BNVC produced
viscous trachyte lava restricted to the volcanic centre, followed by two explosive eruptive episodes of
dominant intermediate to acid composition: The first episode produced air-fall, mainly plinian (lesser
strombolian) and pyroclastic flow deposits and the second was dominated by ignimbritic pyroclastic flows.
Basaltic lava, minor breccia and spatter cone deposits dominate the final stage. The magmatic series
of the BNVC involves basaltic/trachybasaltic and trachyte/rhyolite compositions, with a characteristic
gap in the 52-67% SiO2 range. Transitional olivine basalt is the most primitive rock of the series
(Mg# = 66; Ni = 160 ppm; Cr = 290 ppm) and shows a chemical composition compatible with a liquid that
evolved through the crystal fractionation of a basaltic magma derived from partial melting (8-10%) of a
lherzolithic source. Major and trace element contents and element ratios suggest differentiation through
crystal fractionation from an olivine basaltic magma. Intraplate-like Th/Yb, and Ta/Yb ratios characterize
basalts, whereas high LILE/REE (Ba/La) ratios suggest the contribution of a subordinated subduction
zone component. In addition, Rb/Nb ratios along with a relative Th enrichment in some basalt suggest
assimilation of upper crustal rocks. Isotopic compositions (Sr-Nd) of BNVC basalts suggest a source from
a depleted mantle and minor contribution of EM1 melts. Somún Curá magmatism is attributed to a process
of lithospheric delamination associated with gravitational disturbances during plate reorganization,
with subordinated contributions from detached segments of a foundered subducted slab (Aluk plate?).El plateau volcánico oligoceno de Somún Curá, en el norte de la Patagonia extraandina de
Argentina, está compuesto principalmente por basaltos afíricos de olivino, alcalinos a transicionales, que
cubren un área de ~25,000 km2. Se distinguen varios eventos post-plateau del Mioceno que originaron
grandes centros bimodales y volúmenes menores provenientes de volcanes monogenéticos. Uno de los
complejos post-plateau más grandes es el Complejo Volcánico Barril Niyeu (CVBN), conformado por una
secuencia de rocas lávicas y piroclásticas asociadas a por lo menos cinco calderas de varios kilómetros de
diámetro. Dataciones K/Ar sobre roca total (20.6±0.4 Ma y 18.7±0.4 Ma) acotan la actividad del CVBN
al Mioceno temprano. La facies lávica y piroclástica de traquitas predomina en la base de la secuencia
y las composiciones basálticas en la parte superior. La facies piroclástica está integrada por flujos
piroclásticos y depósitos de caída de composición ácida y depósitos de tipo estromboliano subordinados.
Toda la serie tiene tendencia alcalina y presenta un gap composicional de 52 a 67% SiO2. Los datos
geoquímicos e isotópicos (Sr, Nd) indican que las rocas del CVBN están relacionadas genéticamente por
procesos cristal-líquido, esencialmente de fusión parcial y cristalización fraccionada. Según el modelado
geoquímico, el basalto más primitivo de la serie (Mg# = 66; Ni = 160 ppm; Cr = 290 ppm) habría derivado
de la fusión parcial (8-10%) de una fuente peridotítica granatífera. Las interrelaciones de elementos de
alto potencial iónico (Th/Yb, Ta/Yb) indican un ambiente de intraplaca, y las relaciones LILE/REE (Ba/
La) una contribución subordinada de componentes de zona de subducción. Las relaciones Rb/Nb y las
concentraciones de Th en algunos basaltos podrían ser el resultado de asimilación de rocas corticales.
En general, la composición isotópica de los basaltos sugiere una fuente mantélica empobrecida (DM)
con contribuciones subordinadas de manto enriquecido de tipo 1 (EM1). El magmatismo oligo-mioceno
de Somún Curá es atribuido a un proceso de delaminación litosférica disparado por perturbaciones
gravitacionales durante la reorganización de placas en el borde Pacífico de la placa Sudamericana, con
contribución subordinada de una placa oceánica desprendida (Aluk?)
Structure, seismostratigraphy, and tectonic evolution of Lago Roca (Southern Patagonia, Argentina)
No full textLago Roca is a NE–SW elongated lacustrine body located to the south of Lago Argentino, the largest lake of the UNESCO ‘Los Glaciares’ National Park. An extensive high-resolution seismic survey carried out within the Lago Roca, integrated with geological information gathered in the area, have allowed to produce: (a) a complete bathymetric map of the lake; (b) a basement topography map and a structural map; and (c) an analysis of the geometry, distribution, and thickness of the sedimentary infill. Two sub-basins were recognized in Lago Roca, separated by a central basement high that shows a pop-up structure. The northern and southern margins of the lake basement are bounded by NE–SW trending strike-slip faults that constitute subsidiary faults strands of the regional structural lineament known as the ‘Lago Argentino transfer fault’. The shallow, low magnitude seismicity recorded in the area supports the interpretation that this fault segment is active at the present. The relative motion along the fault led to the deformation of the sedimentary infill of the lake, which was also affected by several subsidiary normal faults oriented parallel to the Lago Argentino transfer fault. Data show the peculiar asymmetry in the sedimentary filling of Lago Roca, typical of those of pull-apart basins generated along transform margins. A simplified model for the evolution of Lago Roca is also here proposed, based on the analysed data and the regional tectonic background.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: Gutierrez, Yasmin Soledad. 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; 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: 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: 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
Shallow architecture of Fuegian Andes lineaments based on Electrical Resistivity Tomography (ERT) : Evidences of transverse extensional faulting in the central Beagle Channel area
No full textThe 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 are
