Publications
Deformation during passive diapirism: implications for salt-flank traps. M. Rowan, K. Giles, T. Lawton & R. Ratliff, 2003 Geological Society of London, 6th Petroleum Geology Conference: North West Europe & Global Perspectives
Deformation around salt diapirs is commonly attributed to drag folding in shear zones that accommodate relative rise of diapirs and subsidence of adjacent strata. However, a drag model cannot account for strata that are folded beyond the dip of the diapir edge, nor does it explain the lack of deformation observed around some parts of many diapirs. Instead, the deformation is caused by near-surface drape folding of a thin, onlapping stratal wedge that forms a bathymetric scarp over the diapir edge. Drape folding can produce near-diapir geometries in which strata range from undeformed to severely overturned with 90-degree unconformities. The amount of bed upturn, angular truncation, and stratal thinning depends largely on the width of the bathymetric halo extending beyond the diapir. This, in turn, is primarily a function of the interplay between salt-rise rates and episodic sedimentation, which results in fluctuating bathymetric relief. Coeval shortening produces a broader, but less intense, deformation zone. The new model has important implications for diapir-flank exploration and production. Trap geometries are controlled by the degree of deformation, and the thinning or pinchout of reservoir sands is a function of the varying bathymetric relief. The unconformities are zones of concentrated slip similar to faults and may thus serve as local pressure seals. Finally, radial faults are a three-dimensional consequence of drape folding, and their distribution depends on the amount of folding and the plan-view curvature of the diapir edge.
