Abstract: Modeling of listric fault/rollover systems

MAUDUIT, T., J.P. BRUN, G. GUERIN, H. LECANU and S. RAILLARD

We present a series of experiments on brittle-ductile models designed to simulate salt tectonics in gravity gliding environments such as those occurring on passive margins. Models consist of a basal layer of Newtonian silicone putty representing a salt decollement, overlain by a layer of dry sand representing the sedimentary overburden. To simulate synkinematic sedimentation sand is poured on model surface at regular time intervals during deformation.

Listric faults/rollovers systems which commonly develop in thin skinned extension can be either synthetic or antithetic with respect to the regional sense of displacement. The experiments show that the commonly accepted kinematic model of a listric fault does not apply to either of these situations. A reappraisal of the kinematic significance of listric faults/rollover systems is therefore proposed.

Various modes of initiation, amplification and decay of listric fault/rollover systems are identified in the experiments. Major growth faults are generally unsteady, leading to shape irregularities of the rollover base and variations in dihedral angle between layering and the brittle/ductile interface. Models also document various modes of three dimensional relationships between neighboring listric faults: lateral changes in vergency (antithetic vs. synthetic), cross cutting relationships, symmetric and asymmetric turtle backs.

Model results are compared with seismic sections from the Gulf of Guinea. Finally, the relevance of analytical and experimental models postulating an initial and permanent curvature of listric faults is questioned.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria