Abstract The Elan Bank microcontinent was separated from East India during the Early Cretaceous break-up. The crustal architecture and rifting geometry of East India and the Elan Bank margins document that the early break-up between India and Antarctica was initiated in the eastern portions of the Cauvery and Krishna–Godavari rift zones, and in the southern portion of Elan Bank. However, the westwards break-up propagation along the Krishna–Godavari Rift Zone continued even after the break-up in the overstepping portion of the Cauvery Rift Zone. Eventually, the western propagating end of the Krishna–Godavari Rift Zone became hard-linked with the failed western portion of the Cauvery Rift Zone by the dextral Coromandel transfer fault zone. Consequently, the break-up location between India and Antarctica shifted from its initial to its final location along the northern portion of the Elan Bank formed by the western Krishna–Godavari Rift Zone. The competition between the two rift zones to capture continental break-up and asymmetric ridge propagation resulted in a ridge jump and the Elan Bank microcontinent release.

Abstract Coupled thermal-kinematic finite-element modeling done in 3D is used to study spatial and temporal distribution patterns of the lower crustal viscosity at transform margins during their continent-ocean transform development and passive margin stages. Modelled scenarios combine different pre-rift thermal regimes and lower crustal rheologies. The outcome indicates that substantial parts of the lower crust have the potential to flow at geologically appreciable strain rates. This discovery can lead to our better understanding of lateral variations in uplift/subsidence, upper and lower crustal thicknesses, and Moho depth. Modeled low viscosity zones having effective viscosities below 1018 Pa s make up ductility distributions, which vary spatially and temporally during the entire margin evolution. Thermal history-related ductility patterns can be divided into three categories, including: (1) reduced lower crustal viscosities controlled by continental rifting and break-up in extensional and pull-apart terrains near transforms; (2) reduced lower crustal viscosities along the transform caused be the migrating ridge and oceanic crust; and (3) the background reduced viscosity resulting from the equilibrium temperature field. Superposition of these ductility patterns and the complex interaction of the underlying perturbations of the temperature field result in differences in the potential for lower crustal flow both in space and time. Our modeling results provide templates for the understanding of lower crustal flow at transform margins in general. They await follow-up studies focused on comparing their results with data on thermal regime, maturation history, and uplift/subsidence patterns.

Abstract The main objective of this book is to provide a global overview of divergent margins based on geological and geophysical interpretation of sedimentary basins along the South, Central and North Atlantic conjugate margins, from plate tectonics and crustal scales to a more detailed description of stratigraphical and structural elements that are responsible for petroleum plays. These themes are complemented by geodynamic concepts based on physical and numerical models, and by comparisons with present-day embryonic margins, which are succinctly discussed in some papers. Supplementary material: Three plate animations of the Atlantic Ocean are available at www.geolsoc.org.uk/SUP18620 .

Abstract The West Carpathian thrustbelt advanced northeastwards over the European Platform. Its thrust sheets comprise sediments of the Early Cretaceous rifts that evolved on a passive margin of the European Platform, the Late Cretaceous–Paleocene basins formed by rift inversion, and the Eocene-Oligocene flexural basin. Geochemical analyses established a clear link between pooled oils in the foreland and the Oligocene Menilite Formation inside the thrustbelt. In order to understand the driving forces for this oil migration scenario, finite-element models of fault-propagation and fold-bend folds are used to study the mean stress distribution in the thrust sheets and the foreland. Mean stress has a profound control on the pore fluid pressure through the relationship affected by sediment porosity, and sediment skeleton and fluid compressibilities. Modelling results suggest that only fault-propagation folds are capable of generating foreland-directed mean stress gradients as they are characterized by a large foreland area of decreased mean stress, by coupled increased/decreased mean stress areas on advancing/receding sides of the ramp tip, and an overall mean stress decrease inside the thrust sheet in the direction towards the foreland. This interpretation is in accordance with the dominant fold-and-thrust style in the Western Carpathians inferred from balanced cross-section restoration. It shows that frontal fault-propagation folding was active during the late Oligocene–Early Miocene, providing an effective tectonic driving force for hydrocarbon migration from source rocks inside the thrustbelt towards reservoirs in the foreland.

Abstract The Oligocene–Sarmatian paleostress data and the data on the timing of the main Carpathian– Pannonian fault systems show that tectonic events can be characterized in eight periods. Oligocene was characterized by strike-slip-controlled stretching of the eastern Alpine domain, which continued during the Egerian. Egerian was the onset time for the first strike-slip faults inside the ALCAPA (Eastern Alps–Carpathians–Pannonian Basin) microplate. The eastward Alpine movements slowed down in Ottnangian, whereas the ALCAPA strike-slip system became denser. Karpatian was the time of northeastward movements of ALCAPA along a couple of bounding strike-slip fault systems, which were most effective during early Badenian. The northwestern strike-slip boundary of ALCAPA progressively became inactive in the eastward direction during middle Badenian. The ALCAPA started to experience the eastward expansion of the normal faulting from its western end during the same time. The eastward motion of the ALCAPA microplate further slowed down during the late Badenian, and a separate motion of the Tisza–Dacia microplate initiated. ALCAPA stopped in Sarmatian and accommodated a separate eastward motion of Tisza–Dacia by west–east extension. The data on fault timing and kinematics indicate that the subduction rollback in the remnant Carpathian Flysch Basin was the most important driving mechanism of the Carpathian– Panonian development, which controlled the northeasterly distance traveled by the ALCAPA microplate and its internal deformation. The terminal collision, oceanic slab break-off, Eastern Alpine lateral extrusion, and the topography and rheology of the orogenic foreland were less important driving mechanisms.

Abstract Interpretation of magnetic, gravity, seismic, and geological data shows that the curvilinear Late Paleozoic orogen affected the location of Central Atlantic syn-rift faults. While northeast-southwest striking thrust faults were perpendicular to extension, prominent curvatures, such as the Pennsylvania salient, introduced structural complexities. East-northeast/west-southwest striking, dextral, transpressional strike-slip faults of this salient became reactivated during Carnian-Toarcian rifting. They formed sinistral, transtensional strike-slip “rails” that prevented the Georges Bank–Tarfaya Central Atlantic segment from orthogonal rifting, causing formation of a pull-apart basin system. Central Atlantic segments to the south and north underwent almost orthogonal rifting. “Rails” lost their function after the continental breakup, except for minor younger reactivations. They were not kinematically linked to younger oceanic fracture zones. Atlantic segments initiated by normal rifting differ from the segment initiated by the Georges Bank–Tarfaya strike-slip fault zone. They contain Upper Triassic-Lower Jurassic evaporites having salt-detached gravity glides, while the connecting transfer segment does not. Their structural grain is relatively simple, divided mostly by northeast-southwest striking normal faults. Northwest-southeast striking oceanic fracture zones kinematically link with continental faults in a few places, controlling the sediment transport pathways across the uplifted continental margin. The connecting Georges Bank–Tarfaya Central Atlantic segment, initiated as a sinistral transfer-zone, has a complex structural grain, characterized by numerous small depocenters and culminations. Their boundaries are formed by east-northeast/west-southwest striking, sinistral, strike-slip, north-northeast/south-southwest, striking normal and west-northwest/east-southeast striking, dextral, strike-slip faults. Sediment transport pathways have complex trajectories, weaving through local depocenters.