Hyper extended rifted margins: A computational procedure for a stretching-thinning factor estimation

• Published in: Tectonophysics 2021-10, Vol.817, p.229065, Article 229065
• Main Authors: Ibañez, J.P., Muller, A.L., Santi, M.
• Format: Article
• Language: English
• Subjects: Algorithms; Analysis; Beta factor; Concretions; Configurations; Conservation; Constitutive models; Crustal stretching; Crusts; Deformation; Deformation effects; Estimation; Evolution; Finite element method; Geodynamic analysis; Geological faults; Kinematic modeling; Kinematics; Mathematical analysis; Mathematical models; Procedures; Rift margin; Shear; Shear deformation; Slip; Stretching; Thinning; Uplift
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2021.229065

Crustal extension mechanisms control rifted margin formation. During these extensional processes, the crust stretches and thins following both non-uniform and non-symmetric patterns. The modeling of main features of these processes is a relevant issue, as well as its quantification by the calculation of the stretching-thinning factors along the margins. This work presents a computational procedure for reproducing the crustal extension process due to Andersonian faulting and estimating the evolution of its extension-thinning factors. This procedure uses an algorithm based on geological hypotheses, geodynamic analysis results and kinematic relationships. The algorithm applies pure-shear extension, where stretching and thinning are based on Andersonian faulting formation. It is supposed to be applied in two-layer (upper/lower) crust configurations in two ways: a) including a new active fault; b) reactivating a previously activated fault. Kinematic relationships consider area conservation for the upper crust. The first step is the application of a crustal extension increment. This increment activates the faulting by simple shear in the upper crust and induces plastic distributed pure-shear deformation in the lower crust. This double effect generates a local thinning of both upper and lower crusts. Slip-in-fault also occurs as part of the thinning deformation. Additionally, a geodynamic analysis was carried out with an in-house developed system, based on the Finite Element Method. Coupled with advanced constitutive models, this approach is useful to reproduce stress-strain-temperature evolution during the crustal extension. Geodynamic analysis guided the definition of some improved kinematic relationships for the proposed procedure: a variable thinning zone, nonlinear thinning configurations, a variable slip/extension ratio, a shoulder uplift and out-of-section fault pivot. The procedure was applied to reproduce part of a crustal stretch of a hyper extended margin due to Andersonian faulting, estimating its thinning and extension factors. The results show that this procedure is able to qualitatively reproduce crustal extensional configurations. •Numerical procedure based on the kinematic-geodynamic coupled approach.•Kinematic model for estimation of stretching-thinning factors in rifted margins.•Margin hyper-extension combining Andersonian faulting and basal detachment.•Quantification of West Iberia margin hyper-extension.