Paleomagnetically defined rotations from the Precordillera of northern Chile: Evidence of localized in situ fault‐controlled rotations

Implications for crustal rotation and tectonic evolution in the central Andes fore arc: New paleomagnetic results from the Copiapó region of northern Chile, 26°–28°S

“…The reference poles for South America have been widely discussed in recent years with several sets produced based on differing methodologies and criteria [Beck, 1999;Besse and Courtillot, 2002;Lamb and Randall, 2001;Randall et al, 2001]. We tested all four reference pole data sets plus an unpublished one (R. Somoza, personal communication, 2001) and found that the choice of reference poles does not significantly alter the calculated expected declinations and inclinations nor subsequently derived rotations in this study.…”

“…[36] Around the DFS the pattern of rotations is very heterogeneous with much localized variation in the recorded rotations ranging from clockwise 76 ± 18°to counterclockwise À7 ± 22° [Arriagada et al, 2006;Fernández et al, 2000;Randall et al, 2001;Riley et al, 1993] (Table 3 and Figures 1 and 2). East of the DFS, data are limited and ambiguous as to whether the rotations decrease rapidly or whether the results from this part of the area are also highly variable.…”

“…The study area lies at the southern limit of the Central Valley between 26.5 and 27.5°S and east of the city of Copiapó (Figures 2 and 3). Our study seeks to determine the relationship between the large rotations recorded in the Coastal Cordillera and the more variable rotations recorded in the Precordillera from around the Domeyko Fault System [Arriagada et al, 2006;Randall et al, 2001;Riley et al, 1993].…”

“…R is the calculated rotation compared to the appropriate reference 5 Ma synthetic poles from Besse and Courtillot [2002] and its associated error [Demarest, 1983]. Sources of data are 1, Arriagada et al [2006]; 2, Riley et al [1993]; 3, Randall et al [2001]; 4, Randall et al [1996]; 5, Forsythe et al [1987];6, Taylor et al [1996]. sinistral faults and lineaments which could have accommodated clockwise rotation during margin normal contraction [Abels and Bischoff, 1999;Forsythe and Chisholm, 1994;Grocott and Taylor, 2002;Randall et al, 1996;Taylor et al, 1998].…”

Influencia de un bloque rigido en un sistema de fallas de rumbo: modelamiento análogo

“…La historia cinemática de este sistema de fallas es compleja, con evidencias de fallamiento de rumbo inicial dextral y de una inversión de éste a sinistral (Reutter et al, 1991(Reutter et al, , 1996Tomlinson, 1997a y b;Maksaev y Zentilli, 1999), y fallamiento inverso en algún momento de la evolución de la deformación (Amilibia et al, 2000;McInnes et al, 1999), con un desplazamiento total de rumbo sinistral estimado en 25 a 35 km en el caso de la falla Oeste (Reutter et al, 1996;Tomlinson y Blanco, 1997a, b;Campbell et al, 2006). Estudios paleomagnéticos han demostrado rotaciones horarias de hasta 40º en rocas del Mesozoico y Paleógeno a lo largo de la cordillera de Domeyko (Randall et al, 2001;Arriagada et al, 2006). La larga evolución de los procesos de deformación ha otorgado una geometría propia de sistemas de fallas de rumbo, con el desarrollo de múltiples estructuras rotacionales, fallas paralelas y de conexión entre ellas, fallas de tipo cola de caballo, fallas inversas, entre otras, descritos en diversos mapas geológicos y estructurales de la región (e.g., Mpodozis et al, 1993).…”