Listric extensional fault systems ‐ results of analogue model experiments

Abstract

Analogue models are a powerful tool for investigating progressive deformation in extensional fault systems. This paper presents exciting new insights into the progressive evolution of hanging wall structures in listric extensional terranes. Analogue models, scaled to simulate deformation in a sedimentary sequence, were constructed for simple listric and ramp/flat listric extensional detachments. For each detachment geometry homogeneous sand, sand/mica and sand/clay models were used to simulate respectively, deformation of isotropic sediments, of anisotropic sediments and of sedimentary sequences with competency contrasts.Roll-over anticlines with geometrically necessary crestal collapse graben structures are characteristic of the steepening-upwards segments of listric extensional fault systems in all of our models. With progressive deformation, crestal collapse grabens show hanging wall nucleation of new faults. Variations in graben size, amount of fault rotation and throw, are dependent on detachment curvature and amount of extension. Individual faults and associated fault blocks may significantly change shape during extension. Complex and apparently conjugate fault arrays are the result of superposition of successive crestal collapse grabens.Ramp/flat listric extensional fault systems are characterized by a roll-over anticline and a crestal collapse graben system associated with each steepening-upwards segment of the detachment and a ramp zone consisting of a hanging wall syncline and a complex deformation zone with local reverse faults. The roll-over anticlines and crestal collapse graben are similar in geometry to those formed in simple listric extensional systems.The models demonstrate that the geometry of the detachments exerts a fundamental control on the evolution of hanging wall structures. Analysis of particle displacement paths for these experiments provides new insights into the mechanical development of roll-over anticlines. Two general models for deformation a b o 4 simple listric and ramp/flat listric extensional detachments have been erected.

Tectonics of complex crater formation as revealed by the Haughton impact structure, Devon Island, Canadian High Arctic

“…Antithetic faults dip in the opposite direction to major listric faults and eliminate the gaps that would otherwise be produced by displacements on curved surfaces (e.g., Davis and Reynolds 1996). Such faults, along with crestal collapse grabens and rollover anticlines, are ubiquitous in extensional terrains where listric faulting predominates (e.g., Stewart 1972;Wernicke and Burchfield 1982;Ellis and McClay 1988). The presence of such features at Haughton suggests, therefore, that some of the outward-dipping faults are antithetic faults that formed as a consequence of the collapse of the transient cavity walls along major, inward-dipping listric faults.…”

Localization of listric faults at thrust fault ramps beneath the Great Salt Lake Basin, Utah: Evidence from seismic imaging and finite element modeling

“…Seismic and geological interpretations suggest that the thrust ramps controlled the location and the nature (synthetic) of the younger normal faults. Several workers [e.g., Ellis and McClay, 1988;Melosh and Williams, 1989] also have shown that extension along a primary normal fault (planar or curviplanar) results in additional secondary normal faults which generally are antithetic to the primary fault. In order to understand how initial normal slip along preexisting thrust ramps causes synthetic normal faults, a finite element approach was adopted.…”

Mechanisms for folding of high-grade rocks in extensional tectonic settings

“…Such rollover or fault-bend folds have been created in sandbox experiments (e.g. Cooke and Harris, 1987;Ellis and McClay, 1988;McClay, 1989) and modelled kinematically (Braun et al, 1994). The style of folds above a listric normal fault may vary significantly (Fig.…”