Resumen
The supplementary material presented herein furnishes detailed information on the methods and parameters employed in obtaining the results delineated in the main article. Specifically, the ensuing information provides an elaborate description of the principles applied in stress inversion (Text S1), conveyed through a table detailing the parameters of stress tensors (Table S1, uploaded as separate file), which specifies the fault-slip data stations, from which the stress tensor was obtained, a figure illustrating calculations of average horizontal stress directions (Figure S1.1), several figures showing field evidence of cross-cutting relationship between the structures used to obtain the stress tensor (Figure S1.2, S1.3, S1.4 and S1.5), and field-measured fault data (Data Set S1, uploaded as separate file). The kinematic parameters used at each stage of the forward modeling process are described in Text S2, in conjunction with the modeling stages depicted in Figure S2. Lastly, Text S3 outlines the methodology and equipment utilized in acquiring U-Pb ages. Data set S3 (uploaded as separate file) encapsulates the analytical results of LA-ICP-MS U-Pb analysis.
Métodos
The slip sense was identified using the standard kinematic indicators described in previous studies (e.g., Petit, 1987; Tchalenko, 1970; Wilcox et al., 1973; Allmendinger, 1989; Doblas, 1998). The reduced stress tensor inversion analysis was accomplished using the TENSOR program (Delvaux and Sperner, 2003) in order to determine the paleo-stress field acting since the late Oligocene until Pliocene times. The software separates homogeneous subsets composed by families of fault-slip data (Angelier, 1994) that are mechanically compatible with a common stress ellipsoid. We characterize each stress regime, associated with each subset, with the best fit of stress parameters: the stress axes σ1≥σ2≥σ3 defining the stress ellipsoid, and the stress regime parameter R´(R), where R = (σ2 − σ3) / (σ1 − σ3) and ranges between 0 and 1. In an extensional regime R´ =R, in a strike-slip regimes R´=2 - R, and in a compressive regime R’=2 + R, (Delvaux et al., 1997; Delvaux and Sperner, 2003). The separation of each set is done with Right Dihedron and Rotational Optimization methods (Angelier and Mechler 1977; Angelier, 1994; Dunne and Hancock 1994; Delvaux and Sperner, 2003). We made a first separation using the Right Dihedron method to obtain subsets where the population of faults are mechanically compatible with a low range of σ1 and σ3 possible orientations. The counting deviation parameter improves the Right Dihedron method because it helps to estimate the degree of compatibility of data into a particular subset. The homogeneity of the data that compose a subset can be observed in the standard deviation of the countain deviation parameter, which means that as a smaller standard deviation is obtained, the compatibility is better. The separation consists in removing fault-slip data with a highest misfit angle, until the subset of data gets a misfit angle < ~30°, which is calculated as a function of the best fit of the stress parameters (σ1, σ2, σ3 and R´) for each stress solution. Then each subset is analyzed using the Rotational Optimization where the stress parameters are rotated until the deviation angle (α) is less than 30°. After the first stress tensor was obtained, the process is repeated with the residual of original data. Considering careful field observations that can help to identify more than one event, using cross-cutting relations between the faults (Figures S1.2, S1.3, S1.4 and S1.4), we discuss the reduced stress tensors and their relation with the tectonic events documented in the area that would explain the obtained paleostress results. The definition (thrust-faulting, strike-slip, and normal faulting regimes) and quality of the reduced tensors are reported using the criteria established by the World Stress Map Project (Heidbach et al., 2016).