Three Balanced Cross Sections Using LOCACE Program

S. Triboulet, J. F. Ballard

The LOCACE program has been used to balance three cross sections. The first one is the result of experimental modeling in a compressive regime. The two others are cross sections from two different overthrust belt frontal zones, constructed with geologic and seismic data. In both regions major distensive or transtensive events occurred before the thrusting.

Our study shows that the balancing technique includes four steps. (1) Analysis of the assumptions on which the section restoration is based. We show, for example, that, with no knowledge on the amount of transverse displacement in the foreland, it is better to make a hypothesis on the original bending of the frontal thrust fault than on the lack of deformation in the foreland. (2) Analysis of the assumptions on which the geologic interpretation is based. (3) A test of the coherence of the section, taking into account admissible geometries of the restored section and admissible mechanisms going from the restored section to the deformed one. (4) Modification of the restored section, taking into account regional data. This step lets us go further into the interpretation, giving details o the relative location of paleofaults and facies variations in the deformed state.

The interactivity of LOCACE allows us to go as far as possible with these steps. This leads to more constraint and to more accurate and predictive geologic sections in structurally complex regions.

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