Modificacion estructural de un sistema acrecional del Paleozoico tardio en el centro-norte de Chile (34°-35°S), durante deformacion posacrecional.
Structural overprint of a late Paleozoic accretionary system in north-central Chile (34°-35°S) during post-accretional deformation.
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Willner, Arne P. | |
| dc.creator | Richter, Peter P. | |
| dc.creator | Ring, Uwe | |
| dc.date | 2010-07-01 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V36n1-a02 | |
| dc.identifier | 10.5027/andgeoV36n1-a02 | |
| dc.description | En la Cordillera de la Costa de Chile, de 36° a 35°S, se encuentra expuesta la arquitectura coherentemente preservada de un prisma de acrecion del Paleozoico tardio, en cercana vecindad a un area entre los 34° y 35°S, donde el mismo esta fuertemente modificado por procesos postacrecionales. Estudiando las desviaciones de la arquitectura original, en esta region pueden ser perfectamente distinguidas estructuras sin- y post acrecionales. Al sur de los 35° se observa un contacto transicional entre dos unidades mayores, el cual refleja un cambio continuo en el modo de acrecion de la cuna acrecional antes de -305 Ma: las metagrauvacas estructuralmente suprayacentes de las series orientales muestran estructuras tipicas de una acrecion frontal, pliegues chevron subverticales de planos de estratificacion con una foliacion de plano axial S . Con el aumento de la deformacion finita hacia su base, se desarrollan pliegues abiertos F2 asociados con una foliacion S , la cual se va tornando cada vez mas achatada y subhorizontal. En las series occidentales estructuralmente subyacentes, S2 es la foliacion de transposicion penetrativa que afecta a las metagrauvacas derivadas de un continente e intercalaciones de metabasitas de origen oceanico. Las estructuras fueron formadas durante acrecion basal. Esta evolucion principal del sistema acrecionario pone firmes restricciones sobre la arquitectura original, tambien en regiones donde este fue destruido luego de la acrecion. La acrecion finalizo cerca de los 225 Ma, cuando ocurrio un cambio mayor en las condiciones geodinamicas hacia un regimen ex-tensional. Aunque el desarrollo del margen en el centro de Chile esta ampliamente caracterizado por extension durante el Mesozoico y Cenozoico, dos episodios pronunciados que involucran acortamiento del antearco afectaron las series orientales al norte de 35°S: 1. Las expresiones de actividad de deslizamiento de rumbo durante el Jurasico son planos empinados de foliacion penetrativa S2, rotacion local de la lineacion de estiramiento L2 a una direccion norte-sur, ple-gamiento apretado vertical de la foliacion principal y replegamiento alrededor de ejes empinados, con zonas de cizalla verticales, semifragiles y sinistrales asociadas. 2. La falla inversa Pichilemu-Vichuquen, levemente sinistral, en el limite entre ambas unidades, es una prominente estructura fragil formada hace cerca de 100 Ma, concomitante con el cierre de cuencas y aceleracion de la exhumacion en el antearco. Estructuras compresivas similares ocurren a lo largo de la costa hacia el norte, donde ambas unidades desaparecieron parcialmente por subduccion, probablemente durante estos eventos de deformacion. La transicion entre sistemas acrecionales casi sin afectar y sistemas afectados, parcialmente subductados al norte, ocurre a los 35°S. | es-ES |
| dc.description | In the Coastal Cordillera of central Chile a coherently preserved architecture of a late Paleozoic accretionary prism is exposed at 36°-35°S in cióse spatial association with a neighbouring área at 34°-35°S, where it is strongly modified by post-accretional processes. Syn- and post-accretional struetures can be distinguished relatively easily in this región studying the deviations from the original architecture. South of 35°S a transitional contact between two major units is observed, which reflects a continuous change of the mode of accretion in the accretionary wedge before -305 Ma: the structurally overlying metagreywacke of the Eastern Series exhibits struetures typical of frontal accretion, Le., subvertical chevron folds of bedding planes with an axial-plane foliation Sr With increasing finite strain structurally downwards, open F2 folds develop associated with a S2-foliation which becomes gradually flattened as it rotates into a subhorizontal orientation. S2 is the penetrative transposition foliation in the structurally underlying Western Series. It affeets the continent-derived metagreywacke series as well as metabasite intercalations of oceanic origin and was formed during basal accretion. This principal evolution of the accretionary system places firm constraints on the original architecture also in regions where it was destructed after accretion. Accretion ceased at -225 Ma, when a major tectonic change from a convergent to an extensional/strike-slip regime oceurred. Although the development of the margin in central Chile is largely characterized by extensión during Mesozoic and Cenozoic times, two pronounced episodes involving shortening of the forearc particularly affected the Western Series north of 35°S: 1. Expressions of strike-slip activity during Jurassic times involve local steepening of the originally flat S2-foliation planes, local rotation of the stretching lineation L2 into the N-S direction, tight upright folding of the S2 foliation and refolding about steep axes with associated vertical cataclastic left-lateral shear zones. 2. The left-lateral reverse Pichilemu-Vichuquén fault at the boundary between both units is a prominent brittle structure that formed at -100 Ma concomitant with basin closure and acceleration of exhumation rates in the forearc. Similar contractional struetures oceur along the coast further north, where both units partly disappeared by subduction erosión most likely during these deformation episodes. The transition between nearly unaffected accretion systems in the south and disrupted and partly subducted ones in the north oceurs at 35°S. | en-US |
| dc.format | application/pdf | |
| dc.format | text/html | |
| dc.language | eng | |
| dc.publisher | Servicio Nacional de Geología y Minería | en-US |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V36n1-a02/803 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V36n1-a02/html | |
| dc.source | Andean Geology; Vol 36, No 1 (2009); 17-36 | es-ES |
| dc.source | Andean Geology; Vol 36, No 1 (2009); 17-36 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Modificacion estructural de un sistema acrecional del Paleozoico tardio en el centro-norte de Chile (34°-35°S), durante deformacion posacrecional. | es-ES |
| dc.title | Structural overprint of a late Paleozoic accretionary system in north-central Chile (34°-35°S) during post-accretional deformation. | en-US |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
This item appears in the following Collection(s)
-
Andean Geology
[0-9]{4}