The southern Andes are regarded as a typical subduction orogen formed by oblique plate convergence. Despite decades of studies, there is considerable uncertainty as to how deformation is kinematically partitioned in the upper plate. Using scaled analogue experiments modelling, we test the concept of dextral transpression for this orogen. We advocate that the GPS velocity field portrays interseismic deformation related to deformation of strong crust north, and weak crust south, of 37°S. Contrary to the popular hypotheses that the Liquiñe-Ofqui Fault Zone, a prominent intra-arc deformation zone, takes up most of the plate boundary-parallel dextral strike-slip, we find that dextral transpression affects the entire model orogen through tectonic segmentation of crust.
Moreover, prominent, regularly spaced sinistral oblique-slip thrust faults, interpreted as antithetic Riedel shears, developed spontaneously in all of our experiments and call into question the general believe that their NW-striking natural equivalents formed from pre-Andean discontinuities. Our experiments prompt us to reconsider the apparently well-established geodynamic concept that strain and margin-parallel displacement is localized on a few margin-parallel faults in the southern Andes.
This data set includes 40 videos (+ 1 image) depicting the surface evolution of 39 experiments on crustal extension, as well as 4D CT imagery (figures and videos) of 6 of these experiments. The experiments examined the influence of the method for driving extension (foam base, rubber base, plate base or conveyor base) for localization of deformation in overlying layers of brittle-only and brittle-viscous materials representing the earth’s crust. All experiments were performed at the Tectonic Modelling Laboratory of the University of Bern. Detailed descriptions of the experiments and monitoring techniques can be found in Zwaan et al. (2019) to which these data are supplementary material.All experiments were monitored with top view photographs (SLR camera Nikon D-100 6.1 MPx). The photograph time steps depend on the applied extension velocity, but are generally 1 or 2 min. Six experiments were also monitored with an X-Ray computed tomography technique using a 64 slice Siemens Somatom Definition AS X-ray CT-scanner (Zwaan et al., 2016) with varying time intervals (5-30 min). CT-data was analyzed with the software OsiriX (Pixmeo SARL).
Tracking the evolution of the deformational energy budget within accretionary systems provides insight into the driving mechanisms that control fault development. To quantify the impact of these mechanisms on overall system efficiency, we estimate energy budget components as the first thrust fault pair develops in dry-sand accretion analogue experiments.This data set includes photos taken and forces measured in four experiments performed at Université de Cergy-Pontoise in October-November 2016. The experiments are described in McBeck et al. (submitted).The data are organized into 5 main folders, with the following contents:1) E373_photos: Contains 3 subfolders: droit_RDY, gauche_RDY, haut_RDY. Each subfolder contains images taken at 1 second intervals throughout experiment. droit_RDY, gauche_RDY, and haut_RDY contain photos of the right, left, and top of the sandpack.2) E374_photos: Same organization and contents of folder E373_photos3) E375_photos: Same organization and contents of folder E373_photos4) E376_photos: Same organization and contents of folder E373_photos5) forces: Contains text files that list the normal force against the backwall (N) and total applied normal displacement to the backwall (mm) in the second and first columns, respectively. The filename indicates which experiment the text file describes.