Abstract: Rollover is the folding of the hanging-wall sedimentary record in response to slip on listric normal faults, and is a common feature of sediment-rich, gravity-driven tectonic provinces. Rollovers have been extensively studied by means of geometrical reconstruction, and numerical and analogue modelling. However, the detailed interaction between the kinematics of bounding listric normal faults and their hanging-wall deformation is not yet fully understood. In this study, we use 3D seismic-reflection data from the Forcados-Yokri area, western Niger Delta, Nigeria, to study the lateral linkage and landwards backstepping history of an array of listric normal faults, particularly focusing on their influence on the development and evolution of hanging-wall rollovers. Five individual, partly overlapping rollover structures have been studied with respect to their relative initiation and decay time, their spatial distribution, and their relationship to the tectonic history of their respective bounding faults. We demonstrate that the studied rollovers are highly dependent on the development of their bounding faults in terms of initiation time, lateral linkage, internal structural development and decay. Fault–rollover interaction is dynamic and changes through time depending on the temporal evolution of listric faults. Four genetic types of fault–rollover interaction were identified in this study: (1) the rotation of a rollover–crestal-collapse system, controlled by a changing lateral bounding-fault orientation during fault growth; (2) a stepwise shift of rollover–crestal-collapse systems associated with rollover abandonment, controlled by the initiation of a new fault in the footwall of an older structure; (3) a gradual shift of successive rollovers controlled by branching main faults; and (4) a general landwards and upwards migration of crestal-collapse faults within a rollover above stationary listric main faults.

Abstract This study focuses on a regional comparison of interpretations from selected 2D seismic transects between large salt and salt-free basins offshore southern Brazil (Espirito Santo basin, Campos basin, Santos basin, and Pelotas basin) and southwest Africa (Kwanza basin, Benguela basin, Namibe basin, and Walvis basin). Based on tectonostratigraphic analysis of megasequences and first-pass geometric reconstructions of synrift settings, including sedimentary decompaction and isostatic correction, it provides a comprehensive basin-to-basin documentation of the key geological parameters controlling asymmetries in basin evolution. The diversity in the tectonic and stratigraphic architecture of the conjugate margin basins reflects variations in the interplay of a number of controlling factors, of which the most important are: (A) the structural configuration of each margin segment at the time of break up; (B) the postbreakup subsidence/uplift history of the respective margin segment; (C) variations in the type, quantity, and distribution of margin sediment (including salt); (D) the evolution of the large salt basins during sag to postsag stages; and (E) sea-level changes.

Abstract Large rock inclusions are embedded in many salt bodies and these respond to the movements of the salt in a variety of ways including displacement, folding and fracturing. One mode of salt tectonics is downbuilding, whereby the top of a developing diapir remains in the same vertical position while the surrounding overburden sediments subside. We investigate how the differential displacement of the top salt surface caused by downbuilding induces ductile salt flow and the associated deformation of brittle stringers by an iterative procedure to detect and simulate conditions for the onset of localization of deformation in a finite element model, in combination with adaptive remeshing. The model set-up is constrained by observations from the South Oman Salt Basin, where large carbonate bodies encased in salt form substantial hydrocarbon plays. The model shows that, depending on the displacement of the top salt, the stringers can break very soon after the onset of salt tectonics and can deform in different ways. If extension along the inclusion dominates, stringers are broken by tensile fractures and boudinage at relatively shallow depth. Spacing of the boudin–bounding faults can be as close as 3–4 times the thickness of the stringer. In contrast, salt shortening along the inclusion may lead to folding or thrusting of stringers.

Abstract We use an integrated approach of seismic interpretation, sedimentary and structural analysis, and reconstruction to obtain a better understanding of the basin evolution and salt tectonic mechanisms in the classic Northwest German salt basin. Our data consist of pre stack depth migrated 2D lines and 3D seismic volumes, non-depth migrated seismic data, and well data. The study area, located at the southwest margin of the Central European Basin, underwent a heterogeneous evolution and a complex salt tectonic history. We propose that a gravity-gliding system in the Early to Middle Triassic caused rafting, initial salt movement, mini-basin growth at the basin margin, and salt pillow growth in the center of the basin. A second phase of salt movement was initiated by the formation of a basement graben at the beginning of middle Keuper time, triggering reactive diapirism, breakthrough, and extrusion of the salt. Subsequent downbuilding continued up to the Jurassic producing sedimentary wedges, salt flanges, and salt re-sedimentation. We suggest that the latest (reactivation) phase of salt rise by diapir shortening is due to Late Cretaceous to early Tertiary basin inversion. In comparison to the passive margin of the Gulf of Mexico basin, which is characterized by lateral progradation, the intra-continental Central European basin shows a polyphase salt tectonic evolution that occurred under different stress regimes and sedimentary environments.