Orogenic shortening and the origin of the Patagonian orocline (56° S.Lat)

Kraemer, Pablo

doi:10.1016/s0895-9811(02)00132-3

Cited by 102 publications

(114 citation statements)

References 31 publications

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“…However, this argument does not appear to be supported by comparative regional shortening estimates: the estimated TFB shortening range is between 30 km (Álvarez-Marrón et al, 1993) and 50 km (Rojas and Mpodozis, 2006) (see also Kley et al, 1999;Kraemer, 2003) in Chile and ~45 km in eastern Argentine Tierra del Fuego (Torres Carbonell, 2010). Taking into account differences in balancing techniques and inherent assumptions for each case, this difference along the TFB (5 to 15 km) is not significant on a regional scale of analysis.…”

Section: Discussionmentioning

confidence: 99%

“…The structures at the leading edge of this belt involve strata from the Upper Cretaceous to Neogene infill of the Austral (Magallanes) foreland basin (Olivero and Malumián, 2008;, an important hydrocarbon source in southernmost South America (Rossello et al, 2008). Many previous structural studies assessed the TFB on a regional scale (e.g., 1:500,000), providing cross sections focusing on the general structural style (e.g., Álvarez-Marrón et al, 1993;Kraemer, 2003;Rojas and Mpodozis, 2006;Ghiglione et al, 2010). Although the TFB front overlaps with the zone of hydrocarbon exploration in the Austral basin (Robbiano et al, 1996;Rossello et al, 2008), published studies on its detailed geometry are sparse.…”

Section: Introductionmentioning

confidence: 99%

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Evaluación de variaciones en el grado de deformación y el estilo estructural a lo largo del frente de la faja corrida y plegada Fueguina, Argentina.

Carbonell

Dimieri

Olivero

2013

Andgeo

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ABSTRACT. The Fuegian thrust-fold belt (TFB) forms the thin-skinned outer wedge of the Andes in Tierra del Fuego. Using subsurface and outcrop data from two areas (Western and Eastern) of the TFB front in Argentina we aimed to verify and characterize the apparent structural variations along the strike. Both areas reveal pro-and retro-vergent faultrelated folds detached at similar horizons, with a youngest early to middle (?) Miocene deformation age. However, the Western Area has gentle, large-wavelength folds whereas the Eastern Area is characterized by a very tight structural geometry, with closer fold geometries. This difference manifests itself in the shortening of analogous structures: below 5.5% in the west as against ~22% in the Eastern Area. Our findings verify structural style variations along the strike and suggest that the Eastern Area endured higher strain. We evaluate two possible causes of this strain gradient, assuming homogeneous regional shortening: (i) lateral rheological variations at the base of the thrust wedge, namely the occurrence of more competent beds which would have restrained the propagation of the detachment toward the east; and (ii) the effect of strong buttressing in the eastern TFB exerted by the Río Chico arch basement promontory during deformation. Published results, together with our current subsurface and outcrop data, rule out significant rheological gradients in a preferred direction along the TFB. On the other hand, we present evidence of the nucleation of frontal thrusts above basement steps at the Río Chico arch western margin, which comprise local buttresses. We speculate that this buttressing was mantained along the TFB front and is enhanced toward the east, where forward TFB propagation was hindered due to the southern projection of the Río Chico promontory. This would explain the higher strain and more complex structural style in the Eastern Area. 439Torres Carbonell et al. / Andean Geology 40 (3): 438-457, 2013 RESUMEN. Evaluación de variaciones en el grado de deformación y el estilo estructural a lo largo del frente de la faja corrida y plegada Fueguina, Argentina. La faja corrida y plegada Fueguina (FCP) comprende el cinturón de piel fina en el antepaís de los Andes en Tierra del Fuego. Con la finalidad de verificar y caracterizar posibles variaciones estructurales a lo largo del frente de la FCP en Argentina, hemos analizado datos de subsuelo y superficie en dos áreas (occidental y oriental). Ambas revelan pliegues relacionados con fallas, tanto provergentes como retrovergentes, que despegan en niveles similares, y tienen una edad mínima miocena temprana a media (?). Sin embargo, en el área occidental el plegamiento es suave y de alta longitud de onda mientras que en el área oriental la estructura es muy apretada, con pliegues más cerrados. Esta diferencia se manifiesta al comparar el acortamiento en estructuras análogas: menor a 5,5% en el oeste contra ~22% en el área oriental. Por lo tanto, queda verificada la existencia de variaciones en el estilo estructur...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluación de variaciones en el grado de deformación y el estilo estructural a lo largo del frente de la faja corrida y plegada Fueguina, Argentina.

Carbonell

Dimieri

Olivero

2013

Andgeo

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“…These upper amphibolite facies rocks occur exclusively north of the Beagle Channel in Cordillera Darwin. We test the hypothesis that the metamorphic rocks, and structures preserved within them, record the south directed subduction (present coordinates) of the basaltic floor of the Rocas Verdes basin and adjacent continental crust beneath an early Andean arc active during basin closure [Dalziel, 1981;Cunningham, 1995;Kraemer, 2003]. Testing this hypothesis is important because similar mechanisms involving continental underthrusting have been proposed to explain how crustal shortening and uplift are accommodated in other orogens, including beneath Tibet [Tilmann et al, 2003], New Zealand [Stern et al, 2002], and the central Andes [Allmendinger et al, 1997;Beck and Zandt, 2002;Sobolev and Babeyko, 2005].…”

Section: Introductionmentioning

confidence: 99%

Continental underthrusting and obduction during the Cretaceous closure of the Rocas Verdes rift basin, Cordillera Darwin, Patagonian Andes

et al. 2010

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The Patagonian Andes record a period of Cretaceous‐Neogene orogenesis that began with the compressional inversion of a Late Jurassic rift called the Rocas Verdes basin. Detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of ∼148 Ma, suggesting that the basin opened approximately simultaneously along its length during the Late Jurassic. Structural data and U‐Pb isotopic ages on zircon from granite plutons near the Beagle Channel (55°S) show that basin inversion involved two stages of shortening separated by tens of millions of years. An initial stage created a small (∼60 km wide) thrust wedge that placed the basaltic floor of the Rocas Verdes basin on top of adjacent continental crust prior to ∼86 Ma. Structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in Cordillera Darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of ∼35 km beneath a coeval volcanic arc. A subsequent stage of out‐of‐sequence thrusting, culminating in the Paleogene, shortened basement and Upper Jurassic igneous rock in the internal part of the belt by at least ∼50 km, forming a bivergent thrust wedge. This latter period coincided with the exhumation of rocks in Cordillera Darwin and expansion of the fold‐thrust belt into the Magallanes foreland basin. This orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi‐oceanic rift basin.

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“…A major tectonic event was the widespread extensional regime in the Late Jurassic that led to formation of the Rocas Verdes marginal basin (RVB) along the southern Patagonian and Fuegian continental margin (Dalziel et al, 1974;Suárez and Pettigrew, 1976;Hanson and Wilson, 1991;Calderón et al, 2007). In the Late Cretaceous, compression in the Pacific margin of the South American plate led to the closure and inversion of the basin and the development of the Andean orogen with its associated fold-and-thrust belt (Dalziel et al, 1974;Wilson, 1991;Bruhn, 1979;Nelson et al, 1980;Diraison et al, 2000;Kraemer, 2003;Menichetti et al, 2008). Since the Paleocene, in correspondence with the expansion of the Weddell Sea between South America and Antarctica, the formation of the small Scotia plate produced a strike-slip tectonic regime along the Fuegian Andes (Cunningham, 1993(Cunningham, , 1995.…”

Section: Geological Framework Of the Southernmost Andesmentioning

confidence: 99%

Fabrica Magnetica y Microestructuras a traves de los Andes de Tierra del Fuego, Argentina.

Esteban

Tassone

Menichetti

et al. 2011

Andgeo

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ABSTRACT. An 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 (k 1 ), 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 (k 1 ) suggests the existence of a significant component of strike-slip deformation. Keywords: AMS, Microstructures, Mesozoic, Andean tectonics, Tierra del Fuego, Argentina. 65 Esteban et al./ Andean Geology 38 (1): 64-81, 2011 RESUMEN. Fábrica Magnética y Microestructuras a través de los Andes de Tierra del Fuego, Argentina.Se presentan los resultados de una transecta de Anisotropía de Susceptibilidad Magnética (ASM) realizada en los Andes Fueguinos, Argentina. Se midieron 240 muestras orientadas provenientes de 27 sitios de muestreo distribuidos entre Paso Garibaldi, al norte y el Canal Beagle al su...

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Orogenic shortening and the origin of the Patagonian orocline (56° S.Lat)

Cited by 102 publications

References 31 publications

Evaluación de variaciones en el grado de deformación y el estilo estructural a lo largo del frente de la faja corrida y plegada Fueguina, Argentina.

Evaluación de variaciones en el grado de deformación y el estilo estructural a lo largo del frente de la faja corrida y plegada Fueguina, Argentina.

Continental underthrusting and obduction during the Cretaceous closure of the Rocas Verdes rift basin, Cordillera Darwin, Patagonian Andes

Fabrica Magnetica y Microestructuras a traves de los Andes de Tierra del Fuego, Argentina.

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