Quantifying frictional variations and erosion in the Mexican fold-thrust belt

The impact of frictional crustal heterogeneities and surface processes on the evolution of the ancient thin-skinned Mexican fold-and-thrust belt (MFTB) is investigated and quantified using numerical finite-element simulations. These simulations explore the evolution, total shortening, and structural styles of deforming orogenic wedges. The models include spatial lateral variations in the internal friction, and the topographic erodibility (K), using the power law incision rule. The MFTB exhibits paleogeographical elements manifested as lateral facies changes across two platforms units and two sedimentary basins that show different degrees of deformation. The observed kinematics of the MFTB requires, based on the parameters considered in this study, a rheologically heterogeneous crust, with at least laterally varying internal friction. Yet only limited syntectonic and post-tectonic erosion are necessary to explain the geometries and internal total shortening constrained by field observations and interpretations. Application of the analytical and homogeneous critical Coulomb wedge (CCW) theory to the MFTB closely predicts the external wedge geometry but fails to predict the observed shortening of the individual litho-tectonic units and structural styles.