3-D Restoration of Salt Diapir: Application to La Popa Basin (Mexico)
Restoration methods have long been used as validation techniques and as tools to understand the structural evolution of geological models. Primarily applied in cross-sections, extended to maps, and finally to volumes, they help quantify the degree of deformation in geological units. Restorations are also very helpful for checking the coherency of the structural model, evaluating the degree of extension or compression, and analyzing the migration of depocenters. Restoration techniques applied to salt tectonics suffer from at least three significant problems that are linked to simplifying assumptions needed for the restoration. The first problem is the fully 3-D nature of the deformation around salt bodies. The assumption of plane strain that simplifies 2-D restorations cannot be applied to salt systems, as movement in and out of a 2-D section is the rule, rather than the exception. The second problem is that elasticity is the only material behavior currently suitable for this process, while salt is a viscous material, and the surrounding sediments are plastic. This can be a serious limitation on using these restorations to make quantitative predictions of stress and strain. The third problem is the presence of significant unconformities and halokinetic sequences around the margins of salt bodies. The topology of these features may change through time, which in turn interferes with the proper restoration of the stratigraphic units.
Our approach to 3-D salt body restoration avoids several of these problems by using a multi-surface restoration technique. It is similar to 2-D restoration algorithms that do not incorporate material behavior, but is compatible with the 3-D nature of the deformation and allows for the changing topology of the unconformities at each step of restoration. This technique is based on the conservation of apparent thicknesses between stratigraphic layers and an isoparametric restoration process of each horizon. This method also preserves fault-horizon contacts and salt-horizon interfaces. We have applied this technique to the El Papalote diapir in La Popa Basin, northeastern Mexico. It helps validate several structural interpretations of the geology in the area, in particular the shape of the basement surface.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009