A new constrain on the central Andean rotation pattern from paleomagnetic studies in the southern Subandes of Bolivia

CALVAGNO, J.M.; GALLO, L.C.; TOMEZZOLI R.N.; CRISTALLINI, E.O.; DALENZ FARJAT A.; HERNÁNDEZ R.M.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020

0895-9811

Ninety-nine (99) specimens from the southern of Bolivia were measured for paleomagnetic and anisotropy of magnetic susceptibility (AMS) studies in order to assess vertical axis rotation in a poorly studied area. Due to the presence of polarity reversals it was possible to perform a reversal test that provided evidence of a reliable paleomagnetic record interpreted to be primary. In an area where vertical axis rotations are a principal component of deformation we have developed a nonparametric approach for the determination of tectonic rotations. We calculated a paleomagnetic pole for Miocene from Tariquia Formation (Lat.= 78.4º S, Long.= 113.1º E, A95= 3.5º) and from our results, rotations around vertical axes, commonly sought around the Arica-Santa Cruz bend were ruled out. From the integration of paleomagnetic and AMS results, it was seen that the magnetic lineation lies within the bedding plane, consistent with early stages of layer parallel shortening, but it is not parallel to the axis of the fold. In concomitance with paleomagnetic results, this allow us to argue that a local change in the azimuth of the structures at this latitude could be the consequence of a grow control due an asymmetric or heterogeneous basement and/or exogenous agents like differences in erosion along the course of the structures during the evolution of the Bolivian fold and thrust belt.