PHYSICAL MODELING OF OVERBURDEN DEFORMATION AROUND SALT DIAPIRS

Salt diapirs produce highly complex deformation patterns in the surrounding overburden which are difficult to image seismically or model numerically. To further the understanding of deformation around salt structures we have used physical models with brittle granular overburdens, and simulated sedimentation accompanying diapiric rise. Rigid linear indenters produce a crestal horst above the indentor with two flanking graben. Large amounts of indentation produce predominantly reverse faults along the margins of the diapir and extensional faults over the crest. In contrast hemispherical indenters produced inward-dipping concentric reverse faults. Forefully intruded polymer diapirs produce a narrow crestal graben above the diapir crest. Downbuilt polymer diapirs produce extensional faults on the flanks of the diapirs which offset the diapir walls. No clear secondary rim synclines were developed as polymer is withdrawn evenly from the whole of the polymer layer across the model. Strong and anisotropic layered overburden were simulated using cohesive clay and mica respectively. Detachments were formed along mica layers which suppressed faults with large throws. Cohesive layer deformation began with tensile fractures, permitting rotation of fractured rafts around the sides of the diapir. These progressively slip off the crest and create large gaps in the stratigraphy.