Palaeomagnetic data from the Precordillera fold and thrust belt constraining Neogene foreland evolution of the Pampean flat-slab segment (Central Andes, Argentina)

Abstract

Available and new palaeomagnetic data reveal transpressional deformation in the Argentine Precordillera fold and thrust belt contemporaneous with Juan Fernández ridge subduction. Localized changes in the orientation of palaeomagnetic directions indicate a vertical axis rotation pattern linked to local, oblique brittle-ductile shear zones that overprint the regional structure. The nearly homogeneous clockwise block rotation pattern from Western-Central Precordillera shows localized rotation nulls along NNW-trending left-lateral oblique belts, revealing that overprinting anticlockwise tectonic rotations could have balanced previous clockwise rotations. Conversely, clockwise rotations in Eastern Precordillera are only localized in the vicinity of these NNW-trending structures, and are controlled by rigid block rotations linked to basement-involved deformation.These results combined with available regional palaeomagnetic data in the forearc would indicate a regional bending of the upper plate margin between 27° S and 33° S that seems to be related to the subduction of the Juan Fernández aseismic ridge.

Faulting and erosion in the Argentine Precordillera during changes in subduction regime: Reconciling bedrock cooling and detrital records

“…The synchroneity between deformation and erosion along the tectonically active boundaries of the Precordillera (this study), and flattening of the Nazca plate beneath the region (Kay et al, 2005;Ramos et al, 2002) suggest that erosional processes responded to deformation and changes in stress conditions in the foreland region. Notably, deformation styles within these margins of the Precordillera depart from purely orthogonal deformation and exhibit sinistral transpression (in the west) and strike-slip faulting and involvement of basement structures (in the east) that may be a manifestation of stresses transferred to the upper plate by flat slab subduction (e.g., Japas et al, 2015;Siame et al, 2005).…”

Basement-involved deformation overprinting thin-skinned deformation in the Pampean flat-slab segment of the southern Central Andes, Argentina

“…Ph.D. thesis, Univ. de Buenos Aires, 2008; Japas et al 2015). Clockwise rotation at the base of the Neogene sequence in the Sierra de los Colorados was considered by Aubry et al (1996) as the consequence of tectonic activity of the NE-striking Tucumán Zone.…”

“…Regional NNW- and NNE-trending structures comprise transpressional brittle–ductile shear zones (Ré, Japas & Barredo, 2001; Cortés & Cegarra, 2004; Japas & Ré, 2012 a, b ; Oriolo et al 2014; Japas et al 2015; Fig. 1c).…”

“…A Late Pliocene basement-involved oblique brittle–ductile shear zone was recognized in the northern sector of the thin-skinned Western and Central Precordillera, the Rodeo–Talacasto belt, based on vertical axis rotation data and structures (Japas et al 2015). This late, NNW–SSE-trending left-lateral structure overprinted the regional Miocene N–S / NNE–SSW-trending, dextral transpressional fabric representative of the Central Andes Rotation Pattern (CARP of Somoza, Singer & Coira, 1996).…”

Introduction: Palaeomagnetism in fold and thrust belts: new perspectives

“…The second part of the volume presents a suite of papers focused on different structural and tectonic problems in the Andes, Pyrenees, the Iberian Range, the Alps and Anatolia. Rapalini et al (2015) show new data focused on unravelling the primary or secondary nature of the Patagonian orocline, Japas et al (2015) discuss Neogene rotations measured in the Andean Precordillera fold and thrust belt. Oliva-Urcia et al (2015) present a new magnetostratigraphic section from the southwestern portion of the Pyrenean main thrust that allows for both the refinement of the chronostratigraphy of the region and dating of primary folding and thrusting events.…”