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

Abstract

New paleomagnetic data from the Coastal Cordillera‐Precordillera boundary area of northern Chile, east of Copiapó, between 26°00′S and 28°00′S are reported. Early Cretaceous to earliest Paleocene volcanics and sediments are nearly completely remagnetized, the remagnetization typically being carried by both magnetite and hematite. In a small minority of sites a pretilting remanence is retained, however, both pretilting and posttilting remanences yield similar directions. These remanences plus primary remanences from Paleocene intrusions indicate a significant >35° rotation of the whole area, in agreement with previous results from the region. The data suggest that the whole of this part of the Andean fore arc has undergone a substantial, regionally coherent, clockwise rotation. This rotation, it is argued, is in response to rapid and highly oblique Nazca–South American plate convergence in the period ∼60–45 Ma prior to later Incaic deformation in the east of the study area. In the east, heterogeneous rotations associated with the Domeyko Fault System are interpreted as being superimposed on this regional rotation resulting in a highly variable and localized pattern of rotations in the vicinity of the main structures comprising the fault system itself.

The Lautaro Basin: A record of inversion tectonics in northern Chile

“…Structural studies carried out in several morphostructural units along northern Chile, such as the thick-skinned, inverted Cordillera de Do meyko and the Coastal Cordillera, have traditionally emphasized motion along major N-S fault systems. In the other hand, the Paleogene deformation is more widely distributed across the Andes of northern Chile (Arriagada et al, 2000(Arriagada et al, , 2003(Arriagada et al, , 2006bTaylor et al, 2007). Eocene-Oligocene deformation was accompanied by tectonic shortening, mountain uplift and significant clockwise block rota tions (e.g., Hartley et al, 1992;Riley et al, 1993;Forsythe and Chisholm, 1994;Randall et al, 1996;Taylor et al, 1998;Arriagada et al, 2000;Somoza and Tomlinson, 2002;Arriagada et al, 2003Arriagada et al, , 2006bArriagada et al, , 2008.…”

Paleomagnetic evidence of earliest Paleocene deformation in Calama (∼22°S), northern Chile: Andean-type or ridge-collision tectonics?

“…Regional mapping indicates this deformation can be traced through much of the Central Depression from south of El Salvador (27 ) to nearly the latitude of Antofagasta (24 ) (Cornejo et al, 2003;Espinoza et al, 2009). Still farther south, near Copiapo (27 30 0 S), Taylor et al (2007) found that uppermost Cretaceous to lowermost Paleocene rocks of the Hornitos Formation, with UePb zircon ages between 66.9 Ma and 65.2 Ma (Arévalo, 2005a, b;Maksaev et al, 2009), were deformed before the intrusion of Early Paleocene plutons with 64e59 Ma 40 Ar/ 39 Ar and KeAr ages (Arévalo, 2005a, b;Taylor et al, 2007).…”

Tectonic rotations and internal structure of Eocene plutons in Chuquicamata, northern Chile

“…Our understanding of the spatial distribution and timing of the CARP has improved in recent years (e.g. Arriagada et al, 2000Arriagada et al, , 2003Randall et al, 1996Randall et al, , 2001Roperch et al, 2000Roperch et al, , 2006Roperch et al, , 2011Rousse et al, 2003;Somoza and Tomlinson, 2002;Somoza et al, 1999;Taylor et al, 2007). In particular, the timing of rotations in northern Chile has been constrained by Somoza and Tomlinson (2002), who showed the presence of unrotated lower Miocene strata that unconformably lie on rotated Cretaceous rocks.…”