Scaled Sandbox Models of Growth-Faulting Processes: Mechanisms, Evolution and 3-D Geometry of Listric Normal Growth Faults

Bruno Vendeville, Jean-Claude Chermette, Bernard Colletta, Peter Cobbold

The northwest and southeast Mediterranean margins display spectacular gravity-related synsedimentary normal faults which affect Pliocene-Quaternary sediments above an evaporitic Messinian decollement layer. As in other growth-faulted terranes, Mediterranean growth faults are highly listric and sole out at depth within the basal salt layer. Faults tend to form in domains of seaward-verging fault planes which bound tilted blocks showing fan-shaped layering of Pliocene-Quaternary deposits.

Several physical experiments have been designed to examine the structural evolution of growth-faulted terranes, the 3-D geometry of structures, and the interaction between faulting, sedimentation, and salt diapirism. Models have been scaled in terms of densities, viscosities, lengths, and gravitational forces with respect to natural data from the deep Rhone delta area. A basal layer of perfectly ductile silicone putty models the Messinian salt and deforms gravitationally by downslope spreading-gliding above a low-dipping planar base. Sand layers are deposited at regular time intervals on the top surface of the model and simulate sedimentation of an idealized brittle Pliocene-Quaternary sequence.

Models emphasize that sedimentation rate strongly controls the shape, curvature, location, and evolution of normal growth faults. Experiments also suggest that listric growth-fault curvature is partly due to interaction between block rotation, sedimentation, and upward propagation of a fault plane during burial. Comparison of our results with seismic data from the deep Rhone delta and other growth-faulted regions can provide useful insights on growth-fault kinematics and 3-D geometry, which are critical in petroleum exploration.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.