Kinematic modelling of extensional fault-propagation folding

Many studies have shown that in extensional basins discrete faulting at dep th is commonly linked to more distributed deformation, in particular foldin g, at higher levels. Such extensional fault-propagation folds are particula rly common where there is a distinct mechanical contrast between faulted ba sement and sedimentary cover. Outcrop and analogue modelling studies indica te that such folds form as upward widening zones of distributed deformation (monoclines) above discrete faults at depth. With increasing displacement (strain) the folds are cut by faults as they propagate upwards into the cov er. To date, however, there has been little investigation into the kinemati cs of linked basement faulting and extensional fault-propagation folding. H ere we present a two-dimensional kinematic model of linked basement faultin g and fault-propagation folding which is based upon trishear. The model all ows investigation of the influence of shear zone geometry and the rate of f ault propagation upon the style of folds and the strains associated with th em. The evolution of linked basement faulting and folding predicted by the model is compared in detail to that observed in an analogue model. The kine matic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.