Linked detachment folds, thrust faults, and salt diapirs: Observations and analog models

Abstract

Contractional deformation in salt-bearing rifted- and convergent-margin settings often involves diapirism. Diapirs may predate the onset of shortening, such that they exert a pronounced influence on how contractional strain is accommodated, or they may be triggered by the shortening. Analog models have been used to help understand the interaction and evolution of detachment folds, thrust faults, and diapirs, but few surface or subsurface datasets provide adequate three-dimensional images to test and refine the experimental results. Here we use 3D depth-migrated seismic data from the Sureste Basin, offshore SE Mexico, to map two structures, one dominated by salt-cored anticlines and one characterized by thrust faults. Associated diapirs include both pre- and syncontractional stocks and walls. We show that although analog models in the literature nicely reproduce some of the seismic geometries, there are also apparent mismatches. Whereas models often generate decapitated diapirs and thrust-fault salients centered on the diapirs, such features are absent in the study area. Moreover, in contrast to model thrust faults that dip 20-45°, faults in the study area are steeper, ranging from 50 to 75°. We bring in observations from other salt basins to discuss these discrepancies, possible explanations, and suggestions for improving the applicability of models to nature.