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UNIVERSIDAD ANDRÉS BELLO Facultad De Ingeniería Escuela De Geología ANÁLISIS TECTÓNICO-ESTRUCTURAL DEL ANTE ARCO CHILENO (

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UNIVERSIDAD ANDRÉS BELLO Facultad De Ingeniería Escuela De Geología ANÁLISIS TECTÓNICO-ESTRUCTURAL DEL ANTE ARCO CHILENO ( UNIVERSIDAD ANDRÉS BELLO Facultad de Ingeniería Escuela de Geología ANÁLISIS TECTÓNICO-ESTRUCTURAL DEL ANTE ARCO CHILENO (OFFSHORE) ENTRE LOS 28,5°-37,5°S: EFECTOS DE LA SUBDUCCIÓN EN MORFO- ESTRUCTURAS SUBMARINAS. Tesis para optar al título de Geólogo Autor: Pablo Sebastián González Godoy Profesor guía Dr. Cristian Rodrigo Ramírez Viña del Mar, 2020. RESUMEN El comportamiento del ante arco chileno en su segmento offshore ha sido motivo de una gran cantidad de estudios durante los últimos 30 años. Este trabajo se basa en una nueva interpretación de antecedentes geofísicos previamente publicados en conjunto con una mejora de grillas batimétricas con la finalidad de entregar nuevas improntas sobre el comportamiento morfoestructural del ante arco en su segmento offshore (28.5°S – 37.5°S). Las líneas sísmicas y batimetrías analizadas en este trabajo permiten identificar que las cuencas de ante arco se ubican principalmente en la zona del talud medio superior y se encuentran limitadas en su borde occidental por un arco exterior alzado. Este rasgo morfológico es de principal interés ya que representa el límite para el transporte de sedimentos hacia la trinchera, sino también, para el comportamiento estructural del talud, el cual presenta estructuras con rumbos paralelos a la trinchera (desviaciones de hasta 20°) y manteos en dirección W para el segmento al occidente del arco exterior y en dirección E para el segmento al oriente del arco exterior. Los perfiles sísmicos de velocidad demuestran que la presencia del arco exterior coincide con un contacto entre dos capas de distintas velocidades reconocidas como un paleo-prisma de acreción y el basamento continental rígido. Esta zona a su vez alberga la mayor cantidad de sismicidad ocurrida durante los últimos 20 años. Evidencias de movimientos transcurrentes pueden ser identificados en la cinemática de dos de los terremotos más grandes ocurridos en los últimos 60 años y también en los arreglos estructurales presentados en las líneas sísmicas al sur de la cuenca de Valparaíso. De esta manera, se sugiere que, la presencia de una estructura tipo sliver pone en contacto el paleo-prisma de acreción y el basamento continental y puede que sea un factor importante en la evolución morfológica del ante arco, en conjunto con los procesos de acreción/erosión que dominan la subducción del margen chileno. ABSTRAC The behavior of the Chilean Fore arc in its offshore segment has been the subject of a large number of studies during the last 30 years. This work is based on a new interpretation of previously published geophysical antecedents together with an improvement of bathymetric grids in order to provide new imprints on the morpho - structural behavior of the ante arch in its offshore segment (28.5 ° S - 37.5 ° S) The seismic lines and bathymetries analyzed in this work allow us to identify that the Fore arc basins are located mainly in the upper - middle slope area and are limited on their western edge by a raised outer arc high. This morphological feature is of primary interest since it represents the limit for the transport of sediments towards the trench, but also for the structural behavior of the slope, which presents structures with strike parallel to the trench (deviations of up to 20 °) and dips with west direction for the occidental segment of the outer arc high and in the east direction for the oriental segment of the outer arc high. The seismic velocity profiles demonstrate that the presence of the outer arc coincides with a contact between two layers of different velocities recognized as a paleo-accretionary prism and the rigid continental basement. This area in turn is home to the highest amount of seismicity that has occurred in the last 20 years. Evidence of strike-slip movements can be identified in the kinematics of two of the largest earthquakes in the past 60 years and also in the structural arrangements presented on the seismic lines south of the Valparaíso basin. In this way, it is suggested that the presence of a sliver-type structure brings the paleo- accretionary prism and the continental basement into contact and may be an important factor in the morphological evolution of the fore arc, together with the accretion/ erosion processes that dominate the subduction of the Chilean margin. AGRADECIMIENTOS Primero que todo, quiero dar gracias a mis padres por su paciencia y amor incondicional, por brindarme la oportunidad de estudiar la carrera que amo y por sobre todo por ser los mejores profesores que la vida me pudo entregar. Quiero agradecer a mis hermanas por orientarme en este proceso tan largo y complejo que ha sido la tesis, entregándome la sabiduría necesaria desde sus propias experiencias para superar esto, no solo desde lo académico, sino también desde lo emocional. Como no agradecer a el mejor compañero que la vida me pudo entregar, mi maravilloso Antu, mi eterno cachorro, amigo y hermano que ha estado conmigo en las buenas, en las malas y en las peores. A la pequeña Miel por llegar a alegrar nuestras vidas con su gigantesco amor y sus locuras. Sin ustedes mi vida no sería nada. En segundo lugar, quiero agradecer a mis amigos Daniel Gómez, Matías Fernández, Nicolas Saavedra, Tomas Zapatta, Nicolas Valenzuela, Juan Pablo Garay y Fernando Marín por ser el mejor grupo humano que la universidad me pudo entregar, amigos desde antes de comenzar las clases con ese mítico partido de futbol en donde solo llegamos nosotros y en donde no tengo duda la amistad perdurara por siempre. Mención especial para todos aquellos que se sumaron durante este largo camino, Jaime, Stefano, Alvar, Joaquín, Marce, Valeria, Paula Otárola, Paula Villar y a todos mis compañeros de generación por sus consejos, discusiones, apoyo y locuras. A los profesores Sergio Calderón, Ximena Contardo, Camilo Palape y Harry Esterio por sus amplias charlas sobre geología y la vida compartidas durante las salidas a terreno, por enseñarme la importancia de la constancia, la responsabilidad y la consciencia de nuestro rol como profesionales para con la sociedad, de todos ustedes rescato las mejores enseñanzas y experiencias durante mi formación. Al profe Cristian por su paciencia y disposición a siempre colaborar con esta investigación. Finalmente quiero reflexionar sobre lo afortunado que soy de tener un grupo humano maravilloso que me rodea y me apoya, este proceso ha sido muy difícil desde lo personal, sin ustedes nada de esto habría sido posible. Ahora comienza el verdadero reto y sé que siempre podre contar con ustedes, así como ustedes conmigo, gracias totales.. ÍNDICE Capítulo 1............................................................................................................................................... 1 1.1 Presentación del problema ................................................................................................... 1 1.2 Objetivos ............................................................................................................................... 4 1.2.1 Objetivo general ...............................................................................................4 1.2.2 Objetivos específicos .......................................................................................4 1.3 Hipótesis................................................................................................................................ 4 Capítulo 2............................................................................................................................................... 5 2.1 MARCO TEÓRICO ................................................................................................................ 5 2.1.1 Marco Geotectónico .........................................................................................5 2.1.2 Marco Geológico ............................................................................................ 12 2.1.3 Estilos de cuencas ......................................................................................... 22 2.1.4 Procesos tectónicos ....................................................................................... 28 2.1.5 Segmentación del ante arco ......................................................................... 34 3 METODOLOGIA ......................................................................................................................... 37 4 RESULTADOS ............................................................................................................................ 40 4.1 Interpretación batimétrica .................................................................................................... 40 4.2 Análisis estructural de líneas sísmicas .............................................................................. 44 4.3 Estructuras del ante arco (offshore) ................................................................................... 61 4.4 Rasgos Morfológicos ........................................................................................................... 68 4.5 Antecedentes sísmicos ............................................................................................................ 75 5 DISCUSIÓN ................................................................................................................................. 77 5.1 Clasificación de cuencas submarinas ................................................................................ 77 5.2 Configuración estructural del ante arco (offshore) ...........................................................
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