Abstract: Influence and Control of Basement Faults on Development of Salt Structures: A Model Approach

Hemin Koyi, Kenneth Petersen

Scaled centrifuged models are prepared to investigate the relation between basement faults and the development of salt structures. The models are based on interpreted seismic profiles and intend to simulate the diapiric structures in the Danish basin. The models consisted of a viscous layer simulating rock salt, overlain by layers of cohesive sand that simulate brittle failure in natural overburdens. In plan view, model diapirs are localized as two dimensional structures along faults in the overburden that collapsed due to basement fault movement. With further burial some of the diapirs surfaced, a few were trapped beneath the competent Cretaceous units and others were starved due to lack of supply from below. In section, model diapirs are asymmetric and are rooted on the tip of the f ults or located on the footwall blocks. The discrete basement faults cause a wider area of deformation in the overburden where the diapirs eventually rise. Even those model diapirs that were not located on faults were triggered by differential loading and collapsing of the overburden caused by rotation of the basement blocks.

Model results support the hypothesis that basement faults trigger the growth of many salt diapirs in the Danish basin. The models suggest that the presence of fewer salt structures in the northern than the southern part of the basin is due to differential subsidence and flow of buoyant material from north to south where they rise diapirically. In general, the model results illustrate that basement faults influence diapirs by accumulating buoyant material in half-grabens and introducing a slope and steps at the base of the buoyant layer, weakening its overburden and causing differential loading and compaction. Similar relationships are expected to be recognized in different sedimentary basins including the Gulf of Mexico.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994