Abstract The study focuses on Equatorial Atlantic margins, and draws from seismic, well, gravimetric and magnetic data combined with thermo-mechanical numerical modelling. Our data and numerical modelling indicates that early drift along strike-slip-originated margins is frequently characterized by up to 10°–20° spreading vector adjustments. In combination with the warm, thinned crust of the continental margin, these adjustments control localized transpression. Our observations indicate that early-drift margin slopes are too steep to hold sedimentary cover, which results in their inability to develop a moderately steep slope undergoing cycles of gravitational instability resulting in cyclic gravity gliding. These slopes either never develop such conditions or gain them at later development stages. Our modelling suggests that the continental margin undergoing strike-slip-controlled break-up experiences warming due to thinning along pull-apart basin systems. Pull-apart basins eventually develop sea-floor spreading ridges. Margins bounded by strike-slip faults located among pull-apart basins with these ridges first undergo cooling. However, spreading ridges leaving the break-up trace along its strike eventually pass by these cooling margins, warming them again before the final cooling proceeds. As a result, the structural highs surrounded by several source rock kitchens witness a sequential expulsion onset in different kitchens along the trajectory of spreading ridges. Supplementary material: Discussion of the methods used, chronostratigraphic results and strike-slip margin characteristics are available at http://www.geolsoc.org.uk/SUP18518

Abstract The paper focuses on the Romanche transform margin on the African side of the Equatorial Atlantic, and draws from thermomechanical numerical modelling and subsequent GIS-based thermal history grid processing. Our modelling indicates that the early post-break-up thermal history of the transform margin is controlled by the cooling patterns of the adjacent pull-apart terrains, the pre-rift heat-flow regime, laterally passing seafloor spreading centres, and cooling of the newly accreted oceanic crust in two corridors located in front of and behind the spreading centres. The pre-rift thermal regime controls the background heat flow on top of which the thermal transients develop. If it is cold, the transient anomalies are very distinct on this background. If it is warm, the transient anomalies tend to blend in with background heat flow much better. The most prominent anomalies are related to thinning in the pull-apart terrains located between transforms. They are up to three times wider than anomalies related to the laterally passing spreading centre, the anomaly of which becomes no wider than 20–25 km. Together with oceanic crust accreted in corridors in front of and behind the passing centre, its heat transfer into the transform margin tends to slow down the cooling of the syn-break-up anomalies developed in the pull-apart terrains by rifting.

Abstract The study focuses on the role of wrenching-involved continental break-up in microcontinent release, drawing from a review of examples. It indicates that the main groups of release mechanisms in this setting are associated with ‘competing wrench faults’, ‘competing horsetail structure elements’, ‘competing rift zones’ and ‘multiple consecutive tectonic events’ controlled by different stress regimes capable of release. Competing-wrench-fault-related blocks are small, up to a maximum 220 km in length. They are more-or-less parallel to oceanic transforms. The competing horsetail-structure-element-related blocks are larger (up to 610 km in length) and are located at an acute angle to the transform. Competing-rift-zone-related blocks are large (up to 815 km) and are either parallel or perpendicular to the transform. The multiple-consecutive-tectonic-event-related blocks have variable size and are generally very elongate, ranging up to 1100 km in length. The role of strike-slip faults in release of continental blocks resides in: linking the extensional zones, where the blocks are already isolated, by their propagation through the remaining continental bridges and subsequent displacement; facilitating rapid crustal thinning across a narrow zone of strike-slip-dominated faults; and slicing the margin into potentially detachable fault blocks.

Abstract A tectono-stratigraphic analysis of a broadband 3D seismic survey over the outer slope of Côte d'Ivoire margin, west Africa, revealed that Cenomanian and younger strata seal well-developed rift fault blocks up to 15 km across. Growth strata indicate that these were formed during rifting that culminated in seafloor spreading in the late Albian, challenging existing plate reconstructions for the opening of the equatorial Atlantic ocean. A previously unrecognized system of volcanic edifices linked at depth to a network of sill complexes has also been identified. These are aligned along a NE–SW trend, concordant with kilometre-wide ridges, interpreted as folds formed by steep, crustal faults with an oblique-slip component. These trends are similar to those of fracture zones in the region and indicate that the Côte d'Ivoire was a transform margin in the late Albian. These results highlight the potential of offshore Côte d'Ivoire for deep-water rift plays with large traps formed by extensional fault blocks together with prospective Albian reservoirs ponded in their hanging walls. In addition, the volcanoes and ridges generated seabed relief along the newly created transform margin, forming confined basins for potential deposition of Turonian and younger turbidites and the generation of stratigraphic traps.