Influencia de la carga de los depósitos en la generación de fallas de atajo durante la inversión de una cuenca extensional: El caso de la cuenca de Abanico (Eoceno-Oligoceno), Andes de Chile central (33°- 35°S).

Abstract

The current paper analyzes the evolution of the Abanico Basin, in the Chilean Principal Cordillera in central Chile (33º-35ºS). According to previous studies, the basin has been affected by two main deformational episodes: the first, related to extension, and the second, to partial basin inversion. Deposits of the Abanico Formation, Eocene-Oligocene, and the Farellones Formation, Early-Middle Miocene, represent these two deformational episodes, respectively. Studies of the basin deposits and the structural features show that the basin was asymmetric and that it developed two main depocenters. The eastern depocenter is deeper and was controlled by a west-dipping fault system (El Diablo Fault System) that formed its eastern border. We propose that the geometry of the basin and the magnitude of inversion were strongly influenced by the load generated by the thick volcanic and volcaniclastic pile that accumulated in the eastern depocenter. Through analogue modeling, we interpret that the Aconcagua fold-thrust belt was triggered at ~16 Ma by a shortcut thrust rooted in the El Diablo Fault System, which during inversion was blocked because of the high load exerted by the deposits of the Abanico and Farellones formations. In addition, the stratified Mesozoic succession that formed the eastern border of the basin allowed the propagation of the shortcut thrust along the ductile Oxfordian gypsum layer. This would have determined the east vergence of the fold-thrust belt. On the western side of the basin, the absence of weak layers prevented development of a west-vergent fold-thrust belt.

Diversity of volcanism and evidence of discrete eruption centres in the Miocene Andes of Central Chile

“…This unit is characterized by 2.5 km thick of lava ows, lava breccias, pyroclastic deposits and domes with basaltic to rhyolitic compositions (Nyström et al 2003). Rivano et al (1990) divided the formation into three main members; the lower member, related with predominantly pyroclastic rocks with interbedded layers of lacustrine sediments, the middle member composed predominantly by a sequence of andesitic-basaltic lavas, and the upper member formed by both ma c and felsic lavas and domes. Some thick ash ow deposits from the base, cut locally by N-S faults, were described and interpreted as caldera related ignimbrites (Rivano 1990;Thiele et al 1991;Elgueta et al 1999;Nyström et al 2003).…”

“…Miocene volcanic and volcaniclastic rocks, in the western Andean Cordillera to the east of Santiago in Central Chile (Fig. 1), have been generally included in a single volcanic unit (Farellones Formation Beccar 1983; Vergara et al 1988;Rivano et al 1990; Thiele et al 1991;Nyström et al 2003;Muñoz et al 2006)), with unconformably overlies the volcanic Eocene-Oligocene Abanico Formation. Even if several studies describe the petrology, geochemistry and geochronology of the two no studies has been carried out in order to locate and characterize individual volcanic centres within the volcanic sequences.…”

“…1] Mentions to Miocene eruptive centres can be found in (1) Thomas (1953), who stated that the lavas and tuffs of Farellones came from discrete volcanic centres and recognized a ssure vent. ; (2) Beccar (1983) indicated that the La Parva, Colorado, and El Pintor hills are sections of an eroded Miocene volcanic centre; (3) Rivano (1990) also suggested that the peaks of "La Parva" and "El Pintor" were a deeply eroded stratovolcano; and nally (4) Thiele et al (1991) described the Farellones Formation as a sequence of lavas and ash deposits with the uppermost member being a series of domes, laccoliths, considered to be remnants of stratovolcanoes. Later works (e.g., Nyström et al 2003;Muñoz-Gómez et al 2006; Piquer et al 2010;Piquer 2015) focused on the geochemistry and structural characterization but an analysis of physical volcanology in the area has been lacking.…”

Neogene erosion of the Andean Cordillera in the flat-slab segment as indicated by petrography and whole-rock geochemistry from the Manantiales Foreland Basin (32°–32°30′S)

“…1a) in the Early Miocene were uplifted through a tectonic inversion (e.g., Charrier et al, 2012). This deformation probably propagated to the east during the Early to Late Miocene (e.g., Charrier et al, 2002;Giambiagi et al, 2003a;Fock et al, 2006;Muñoz Sáez et al, 2014) up to the Frontal Cordillera (Fig. 1b).…”

Study of Natural Hazards in the Upper Part of the Mapocho River Basin, Metropolitan Region of Chile, Using Satellite Imagery

“…The Central Andes range of Chile is geologically characterized by the presence of stratified, sedimentary, volcanic, and volcanoclastic rocks that date from between the Eocene and middle Miocene [1]. Among the most essential structural traits are the North to South Olivares River Fault, to the west the Dominion of the Abanico basin and, to the East, the Dominion of the Faja Plegada and Corrida of Aconcagua [2,3].…”