Does the syn- versus post-rift thickness ratio have an impact on the inversion-related structural style?

Abstract

Abstract. Many extensional basins worldwide are modified by subsequent compressional episodes, which lead to inverted structures. The structures associated with the reactivation of pre-existing faults are critically important in the formation of suitable subsurface traps for hydrocarbons. Major concerns regarding inverted structures are the trap integrity and fault seal. In general, the preferred structures have simple four-way closures due to the minor forced folding of the post-rift cover, as opposed to (reverse) fault-related structures, which have a higher risk of breaching. Such reverse-fault-bounded structures have been generally observed in basins with a thick syn-rift fill and a relatively thin post-rift sequence at the time of inversion (Mode I). In contrast, gentle/open forced folds have been described in basins with thicker post-rift sequences than the syn-rift basin fill (Mode II). Five physical sandbox models, coupled with particle image velocimetry (PIV) analysis, have been performed to address the influence of the syn- versus post-rift thickness ratio on the inversion-related structural style of the post-rift cover. The main control on the development of Mode I or Mode II inversion structures within the post-rift sequence appears to be different due to the amount of compressional displacement accommodated by the inherited listric fault and the thickness of the post-rift cover. These observations do have a direct impact on the understanding of the geo-energy systems associated with inverted structures and are broadly comparable with natural data examples from Aotearoa/New Zealand, Israel, Romania, and the Republic of Türkiye.