Abstract
Sandbox experiments with different boundary conditions demonstrate that antiformal stacks result from a forward-breaking thrust sequence. An obstacle blocks forward thrust propagation and transfers the deformation back to the hinterland in a previously formed true duplex. In the hinterland, continued shortening causes faults to merge toward the tectonic transport direction until the older thrusts override the younger thrusts. In experiments using thin sand layers or high basal friction, shortening is accommodated by a cyclic process of thrusting, back rotation of the newly formed thrust combined with strong vertical strain, and nucleation of a new thrust. Continuous deformation produces an antiformal stack through progressive convergence of branch lines.
Highlights
Physical modelling has been used with success to investigate the mechanical and kinematic evolution of structures and deformational systems
We have introduced some variables concerning the geometry of pre-existing basement structures, initial sand layer thickness and basal friction
Several conclusions may be drawn with respect to development of antiformal stacks: (1) Antiformal stacks form when there is an impediment to the progressive evolution of a forwardbreaking thrust system
Summary
Physical modelling has been used with success to investigate the mechanical and kinematic evolution of structures and deformational systems. Davis et al (1983) and Dahlen et al (1984) have proposed the critical taper model based on mathematical calculations and demonstrated its validity using sandbox modelling. Marshak et al (1992) have discussed the formation of curved thrust belts using analogue models. McClay & Ellis (1987), McClay (1990) and McClay & Scott (1991) have presented scaled sandbox models of extensional structures to illustrate the tectonic evolution of sedimentary basins. Thrust system geometries were described by Bally et al (1966), Dahlstrom (1969) and Boyer & Elliott (1982). Boyer & Elliott (1982) published a Thrust system geometries were described by Bally et al (1966), Dahlstrom (1969) and Boyer & Elliott (1982). Boyer & Elliott (1982) published a
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