Estilos estructurales del sector sur de la Sierra de Moreno de la Cordillera de Domeyko en el norte de Chile
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2023
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
La configuración geológica-estructural de la Sierra de Moreno en la Cordillera de Domeyko, se ha
vinculado tradicionalmente a un estilo estructural de tipo rumbo-deslizante (strike-slip)
transpresivo, en donde las estructuras observadas en superficie responden a esfuerzos oblicuos a
un margen continental N-S. Sin embargo, no hay evidencias típicas de este estilo estructural (e.j.
estructuras de flor positiva) en el área de estudio. Por el contrario, se observan estilos estructurales
del tipo cabalgamientos y repeticiones de secuencias estratigráficas que son difíciles de explicar a
través de esfuerzos transpresivos. Este trabajo recopila la información estructural y estratigráfica
que se tiene del sector sur de la Sierra de Moreno, y se elaboran modelos cinemáticos 2-D (de tipo
forward) para reconstruir su configuración actual. Los resultados obtenidos muestran una
combinación de estilos estructurales de escama gruesa y escama delgada, que responden a dos
mecanismos tectónicos. El primer mecanismo corresponde a la inversión tectónica de una cuenca
de hemigraben, en la cual se depositaron secuencias sedimentarias marinas y continentales
Jurásicas de syn-rift (Fm. Quehuita), las cuales se encuentran deformadas en forma de fajas corridas
y plegadas. Este mecanismo está representado por la Falla Barrera, una falla normal lístrica,
parcialmente invertida de primer orden convergencia al oeste nucleada en basamento cristalino
Paleozoico. El segundo mecanismo tectónico corresponde al empuje del basamento sobre las
unidades Jurásicas. Este mecanismo está representado por la Falla Sierra de Moreno, una falla
inversa de primer orden de tipo “By-pass” convergencia al oeste, de la cual despega una falla
sintética de tipo “Short-cut” de segundo orden, que deforma internamente la Fm. Quehuita sin
exponerse en superficie. Estos dos mecanismos parecen haber trabajado de forma conjunta en el
Cretácico Superior, durante el cambio de régimen extensivo a compresivo en las cuencas de trasarco, en la evolución de los Andes Centrales.
The structural configuration of the Sierra de Moreno in the Cordillera de Domeyko has traditionally been related to transpressive and strike-slip deformation; however, there is no sufficient evidence of this structural style (positive flower structures) at the study area. On the contrary, the main structural styles consist of thrust faults and other contractional structures associated. This work compiles previous stratigraphic and structural information from the southern sector of the Sierra de Moreno to development a series of forward-type 2-D kinematic models, in order to reproduce its present-day configuration. The results obtained in this study showed that the structures in the region response to a mix of thick-skinned and thin-skinned structural styles associated with two tectonic mechanisms. The first one corresponds to a tectonic inversion of a Jurassic half-graben structure where initially syn-rift marine and continental sedimentary sequences (Fm. Quehuita) were deposited, and then were shortened and involved in a fold-and-thrust belt. This mechanism is evidenced by the Barrera Fault, a west-verging and partially inverted, and basement rooted normal fault. The second mechanism consist in the propagation of basement-involved thrust faults. This is evidenced by the Sierra de Moreno Fault, a west-verging reverse fault of type "By-pass" from which a blind second-order synthetic "Short-cut" fault detaches. The last deforms internally the Quehuita strata. These two mechanisms could have worked together in the Late Cretaceous, during the change from extensive to compressive regime in the forearc basins, in the evolution of the Central Andes.
The structural configuration of the Sierra de Moreno in the Cordillera de Domeyko has traditionally been related to transpressive and strike-slip deformation; however, there is no sufficient evidence of this structural style (positive flower structures) at the study area. On the contrary, the main structural styles consist of thrust faults and other contractional structures associated. This work compiles previous stratigraphic and structural information from the southern sector of the Sierra de Moreno to development a series of forward-type 2-D kinematic models, in order to reproduce its present-day configuration. The results obtained in this study showed that the structures in the region response to a mix of thick-skinned and thin-skinned structural styles associated with two tectonic mechanisms. The first one corresponds to a tectonic inversion of a Jurassic half-graben structure where initially syn-rift marine and continental sedimentary sequences (Fm. Quehuita) were deposited, and then were shortened and involved in a fold-and-thrust belt. This mechanism is evidenced by the Barrera Fault, a west-verging and partially inverted, and basement rooted normal fault. The second mechanism consist in the propagation of basement-involved thrust faults. This is evidenced by the Sierra de Moreno Fault, a west-verging reverse fault of type "By-pass" from which a blind second-order synthetic "Short-cut" fault detaches. The last deforms internally the Quehuita strata. These two mechanisms could have worked together in the Late Cretaceous, during the change from extensive to compressive regime in the forearc basins, in the evolution of the Central Andes.
Notas
Tesis (Geólogo)
Palabras clave
Geología Estructural, Estratigrafía, Chile, Zona Norte