Configuración estructural de la vertiente occidental del Altiplano entre los 21°00' - 21°15', región de Tarapacá, Chile
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2017
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es
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Universidad Andrés Bello
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Resumen
El alzamiento y acortamiento del borde occidental del Altiplano entre los 21°S – 22°S ha sido explicado como una consecuencia de la actividad de un conjunto de fallas inversas con vergencia occidental y oriental, alto ángulo y orientación N-S a NNE-SSW denominadas Sistema de Fallas de Sierra de Moreno (SFSM). El SFSM alza el Basamento de la Cuenca de Tarapacá por sobre su cobertura Jurásico – Cretácica Inferior la cual conforma un cinturón plegado (CPSM) de similar orientación. La cobertura Oligo – Neógena, que constituye la Cuenca de la Pampa del Tamarugal (CPT), sobreyace en discordancia angular a todas las estructuras.
Sin embargo, no se han establecido relaciones genéticas entre las asociaciones estructurales descritas ni tampoco se ha identificado su presencia bajo la cobertura Oligo – Neógena. Mediante un análisis estructural descriptivo junto con la cuantificación del acortamiento y alzamiento, este trabajo propone la arquitectura actual de la Precordillera y Depresión Central.
Se define un estilo estructural de piel gruesa para la vertiente occidental del Orógeno Andino en esta latitud. La asociación estructural de la Depresión Central está compuesta por una falla normal invertida de vergencia occidental, fallas de atajo, estructuras pop – up, cabalgamientos fuera de secuencia y fallas de paso. Estas estructuras están relacionadas espacialmente con altos topográficos locales. Por otro lado, en la Precordillera, fallas inversas de bajo a alto ángulo que comprometen basamento, están involucradas en la generación de pliegues asimétricos, cerrados a abiertos, con planos axiales subverticales buzantes al este y localmente volcados. Relaciones de corte con intrusivos y arquitectura depositacional sintectónica facultan fechar la edad de la deformación en el Cretácico Tardío. Estas estructuras generan un acortamiento promedio de 4Kms en equivalente al 20% y un máximo de 5Kms equivalente al 37%, junto con un alzamiento promedio de 4 Km.
The elevation and shortening of the western edge of the Altiplano between 21 ° S - 22 ° S has been explained as a product of the activity of a set of reverse faults with western and eastern vergence, high angle and orientation NS to NNE - SSW denominated System Of Fault de Sierra de Moreno (SFSM). The SFSM increases the Basin of the Tarapacá Basin over its Jurassic - Lower Cretaceous age coverage, which forms a folded belt (CPSM) of similar orientation. The Oligo - Neógene cover, which constitutes the Tamarugal Pampa Basin (TPB), overlaps in angular discordance to all structures. However, no relationships have been established between the described structural associations neither their presence it has been identified under Oligo - Neogene coverage. Throughout a descriptive structural analysis along with the quantification of shortening and uprising, this work proposes the current architecture of the Precordillera and Central Depression. A thick skin structural style is defined for the western slope of the Andean Orogen at this latitude. The structural association of the Central Depression is composed of a normal inverted fault of western vergence, shortcut faults; pop - up structures, out - of - sequence ridges and step failures. These structures are especially related to high local topographies. On the other hand, in the Precordillera low-tohigh-angle inverse faults involving basement are involved in the generation of asymmetric folds, closed to open with sub vertical axial plots to the east and locally overturned. Cutting relationships between intrusive and CSPM stratified rocks, with the identification of the syntectonic depositional architecture make it possible to date the age of the deformation in the Late Cretaceous. These structures generate an average shortening of 4 km in equivalent to 20% and a maximum of 5 km equivalent to 37%, together with an average rise of 4 km.
The elevation and shortening of the western edge of the Altiplano between 21 ° S - 22 ° S has been explained as a product of the activity of a set of reverse faults with western and eastern vergence, high angle and orientation NS to NNE - SSW denominated System Of Fault de Sierra de Moreno (SFSM). The SFSM increases the Basin of the Tarapacá Basin over its Jurassic - Lower Cretaceous age coverage, which forms a folded belt (CPSM) of similar orientation. The Oligo - Neógene cover, which constitutes the Tamarugal Pampa Basin (TPB), overlaps in angular discordance to all structures. However, no relationships have been established between the described structural associations neither their presence it has been identified under Oligo - Neogene coverage. Throughout a descriptive structural analysis along with the quantification of shortening and uprising, this work proposes the current architecture of the Precordillera and Central Depression. A thick skin structural style is defined for the western slope of the Andean Orogen at this latitude. The structural association of the Central Depression is composed of a normal inverted fault of western vergence, shortcut faults; pop - up structures, out - of - sequence ridges and step failures. These structures are especially related to high local topographies. On the other hand, in the Precordillera low-tohigh-angle inverse faults involving basement are involved in the generation of asymmetric folds, closed to open with sub vertical axial plots to the east and locally overturned. Cutting relationships between intrusive and CSPM stratified rocks, with the identification of the syntectonic depositional architecture make it possible to date the age of the deformation in the Late Cretaceous. These structures generate an average shortening of 4 km in equivalent to 20% and a maximum of 5 km equivalent to 37%, together with an average rise of 4 km.
Notas
Tesis (Geología)
Palabras clave
Cuencas Hidrográficas (Estructura), Corteza Terrestre, Geomorfología, Chile