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Analogue Modelling of Inverted Domino-Style Basement Fault Systems


Inversion of pre-existing extensional fault systems is common in rifts and passive margins and significantly influences the development of hydrocarbon traps. Scaled two-dimensional sandbox models were used to investigate the geometric, kinematic and strain evolution of inversion structures developed above reactivated domino-style basement fault systems. Progressive model deformation was monitored using high-resolution time-lapse photography and digital image correlation (DIC) techniques. The resultant detailed strain and particle displacement analyses highlighted reactivated fault evolution as well as hangingwall deformation patterns and enabled the development of new evolutionary models for inverted basement-involved extensional faults. Inversion of domino-style fault systems produced characteristic syn-rift harpoon geometries, asymmetric contractional fault-propagation folds and footwall shortcut faults as the basement faults were progressively back-rotated. The pre-existing extensional fault architectures, basement fault geometries, and the relative hangingwall and footwall block rotations exerted fundamental controls on the inversion styles. The model results compare well with natural examples of inversion structures associated with reactivated domino-style fault systems observed in seismic data. DIC strain monitoring illustrated complex vertical fault segmentation and linkage during inversion as the major faults were reactivated and strain was progressively transferred onto footwall shortcut faults. The mechanical stratigraphy of the cover sequences strongly influenced fold and fracture development and the propagation, vertical linkage, and strain histories of the reactivated faults. Detailed particle displacement analysis indicated that progressive hangingwall deformation during extension and inversion was dominated by a significant component of rotation. Hangingwall shear angle varied according to the relative rotations of the hangingwall and footwall blocks and progressively decreased during inversion as the basement faults were back-rotated. This has important implications for the methodologies used to restore balanced cross-sections involving inversion of rotational basement fault systems. Comparative geomechanically-based restorations of inverted domino-style faults, which incorporated internal deformation of the basement, showed similar deformation mechanisms to the analogue models.