EXTENSIONAL FAULT SYSTEMS IN SEDIMENTARY BASINS - A REVIEW OF ANALOG MODEL STUDIES

Scaled analogue models have provided graphic new insights into the progressive development of extensional fault systems. This paper reviews recent results of an on-going analogue modelling programme and compares the structural styles in the models with examples of natural extensional fault systems. Four fundamental model styles, scaled to simulate deformation in brittle sedimentary rocks in the upper 10 km of the crust, are reviewed. Extension above a basal detachment which undergoes stretching over a limited are produces an asymmetric rift graben bounded by planar faults and in which the internal deformation is accommodated by rotational domino faults. These experimental results are directly comparable to structures found in intracontinental rifts. Extension above a basal detechment which undergoes extension under the whole model and which has no constraints at the ends produces domino-style fault arrays in the pre-rift sequence and listric growth faults in the syn-rift sequence. These results compare with highly extended rift basins and terranes such as the Basin and Range Province, USA. Extension above a simple listric fault produces a characteristic hangingwall roll-over and crestal collapse graben system. At high values of extension, superposed crestal collapse grabens occur and a fan of listric growth faults is developed. These structures bear striking similarities to growth faults in progradational delta systems. Ramp-flat listric extensional fault systems using sand-mica models produce a characteristic family of structures with an upper roll-over crestal collapse system, a ramp syncline and reverse fault/fold zone and a lower roll-over crestal collapse system. An example of a ramp-flat fault system from the Gulf Coast, USA, is presented as a comparison with the analogue model results. Preliminary results of three-dimensional extensional model experiments are presented to illustrate the complexities in such fault systems. In all of the experimental models, it is found that the geometry of the underlying detachment system exerts fundamental control on structures produced in the hangingwall. The analogue models illustrated in this review provide valid geometric and kinematic templates for the progressive evolution of extensional fault systems in sedimentary basins. © 1990.