Abstract The Sivas Basin in central-eastern Anatolia is a north-verging salt-bearing fold-and-thrust belt including synorogenic salt tectonics. It formed between the northern leading edge of the Taurides platform and the Kırşehir block since Late Cretaceous time. We have constructed five regional cross-sections supported by field data and 2D seismic to constrain the structure of the basin and its evolution. The area is divided into three tectonic domains from south to north: (1) a Maastrichtian to Eocene north-verging fold-and-thrust belt, which terminates by a regional Eocene evaporitic level; (2) an Oligo-Miocene salt domain which contains two generations of minibasins separated by a salt canopy, forming a salt-and-thrust belt; and (3) a late Miocene to present day foreland basin. The cross-sections show the along-strike variations and the increasing shortening in the fold-and-thrust belt from west ( c. 15 km) to east ( c. 25 km). The thick salt allows for the intracutaneous propagation of the fold-and-thrust belt below a domain of salt withdrawal minibasins, decoupled as the initial salt thickness increases. In that case, the salt domain is thrusted both frontward and backward. Efficient exhumation followed by erosion of the fold-and-thrust resulted in synorogenic salt tectonics in the foreland and thus increased the mechanical resistance between them.

ABSTRACT The Papua New Guinea fold and thrust belt petroleum system is studied along a 200-km (124-mi)-long transect. The kinematic scenario includes the Jurassic rifting and passive margin, the erosion during the Upper Cretaceous related to the Coral Sea rifting and Pliocene–Pleistocene shortening, with an early growth of the Hedinia Anticline limiting lateral migration of oil in the adjacent Darai Plateau. Data from seven wells and two fields were used to calibrate section boundary conditions and properties. Apart from the high-pressure trend in the Kutubu/Moran structures, all data are well reproduced, and the modeled section appears quantitatively predictive. The modeling demonstrates three major pathways for water: (1) topographically driven flow from the onset of mountain building; (2) deep updip basinal flux, flowing along the tilted reservoirs; and (3) across fault escape from connected reservoir bodies. Type II or mixed type II/III is used to model the Triassic and Jurassic source rock. Maturation starts in the Middle Cretaceous and increases strongly during the late tectonic burial, with three main accumulations: (1) the deep part of the Mubi zone, with vertical migration along faults; (2) the Hedinia and Kutubu anticlines charged during Orubadi and Era deposition; and (3) the Darai Plateau.

ABSTRACT Deep seismic profiles, recorded in the foothills of the Northern Emirates, image the thrust-belt architecture and document the wide underthrusting of Mesozoic sedimentary units in the footwall of the Hawasina–Sumeini allochthon in the Dibba Zone, beneath the Semail Ophiolite. Integrated structural and geophysical modeling helped to constrain the structural architecture of two regional transects crossing the foreland and adjacent foothills. 2-D forward kinematic and thermal modeling was performed with Thrustpack® along the transects, whereas CERES2D® complete petroleum system modeling was subsequently performed along the northern transect. One hundred twenty kilometers (75 mi) of convergence occurred from the Santonian to the end of Early Miocene, of which about 80 km (50 mi) correspond to the obduction of the Semail Ophiolite and Sumeini–Hawasina units over the Arabian margin, whereas the remaining approximately 40 km (25 mi) were accommodated by the fold-and-thrust structures of the Oman belt. Paleogene source rocks of the foredeep only reached the beginning of the oil window. In contrast, Mesozoic source rocks of the underthrusted foreland are overmature or in the gas window in the foothills, but still preserve hydrocarbon (HC) potential further west in the foreland. Frozen kitchens may still be preserved in the hinterland, due to the high thermal conductivity of its former ophiolitic cover.

Abstract Four-dimensional analogue X-ray tomography imagery is used to investigate the role played by pre-existing salt structures during compressive deformation. Initially linear salt structures evolve towards more axisymmetric diapirs. Depending on the diapir geometry and on its thickness relative to the sedimentary column thickness, the diapirs are either (1) shortened and localize sharp overturned folds for vertical pipe-like diapirs or else (2) act as preferentially oriented ramps, the diapir being incorporated in the fold for pillow-like diapirs. The ridges have a strong effect on the lateral extent and orientation of folds: they disconnect the folds formed on either side of the salt wall. Compressional relays between ridges allow for a folded connection between both sides. The Zagros Mountains in southern Iran offer a large variety of comparable structures, associated with the Hormuz salt level which acts as the regional décollement. Most of the salt structures have been active from the Early Palaeozoic until the present day. The first-order critical taper is controlled by the distribution of Hormuz décollement level and by its thickness. At a smaller scale, the fold geometry and size are locally controlled by the pre-existing salt structures, which are the main source of heterogeneity in the deformation.

Abstract One-dimensional and two-dimensional basin modeling has been performed along a regional transect crossing the Córdoba Platform allochthons and the autochthonous Veracruz Basin in order to infer the burial and kinematic evolution and to determine timing of hydrocarbon migration and charge in this famous Mexican petroleum province. Vitrinite reflectance, Rock-Eval data, and bottom-hole temperatures have been used to calibrate the heat flow and thermal evolution of the Veracruz Basin, where no erosion occurred. The Córdoba Platform and Veracruz Basin in Eastern Mexico comprise the southern most extent of the Laramide foreland fold-and-thrust belt,which developed along the eastern border of the North American Cordillera from Late Cretaceous to Eocene. Unlike in the Canadian Rockies, where pre-orogenic strata are relatively isopachous, this segment of the North American craton has been strongly affected by the Jurassic rifting and opening of the Gulf of Mexico. Substantial thickness and facies changes between horsts and grabens control the lateral and vertical distribution of Mesozoic source rocks and hydrocarbon reservoirs. In the east, thick Paleogene and Neogene sequences in the Cordilleran foreland provide a continuous sedimentary record in the Veracruz Basin. In the west, however, the Middle Cretaceous carbonates of the Córdoba Platform generally constitute the main outcropping horizon in the adjacent thrust belt, making it difficult to reconstruct its burial evolution from the Laramide orogeny onward. Cemented veins were sampled in reservoir intervals of the thrust belt. Petrography, stable isotope analyses, and fluid inclusion studies (microthermetry, Synchroton Fourier Transform Infra-Red analyses) on these samples revealed the diagenetic history of the reservoirs. Where diagenetic phases could be constrained in time and with respect to the tectonic evolution, fluid inclusion temperatures provide an additional paleothermometer in areas where major erosion occurred. Pressure-temperature modeling of simultaneously entrapped aqueous and oil-bearing inclusions indicates more than 4.5 km of erosion of Late Cretaceous-Paleocene sequences in the thrust belt, which can be accommodated in palinspastic sections only by restoring a hypothetical foredeep basin. This implies that the current east-dipping attitude of the basement beneath the Córdoba Platform developed after Laramide deformation, accounting for a major change in paleofluid dynamics. Fluid flow and basin modeling of the Veracruz section has been performed using CERES2D to infer the paleofluid dynamic associated with the petroleum system evolution. Following the initial phase of geometric model building and calibration against the thermal and burial history inferred, the modeling accounted for the past migration pathways for both water and oil and gas fluids. Unlike in most other foreland fold-and-thrust belts, hydrocarbons generated in Jurassic source rocks from the Veracruz foreland are currently migrating westward toward the thrust belt, accounting for a post-Laramide charge of the frontal duplexes of the Cordilleran thrust belt.

The mechanisms of magma crust accretion at large igneous provinces (LIPs) are questioned using arguments based on the north Atlantic case. Published and new data on the calculated flow vectors within dike swarms feeding the early traps and subsequent seaward-dipping reflector lavas suggest that most of the mafic magmas forming the north Atlantic LIP transited through a small number of igneous centers. The magma was injected centrifugally in dike swarms at some distance away from individual igneous centers along the trend of the maximum horizontal stress acting in the crust, feeding lava piles via dikes intersecting the ground surface. This mechanism is similar to that observed in present-day Iceland and, more generally, in mafic volcano-tectonic systems. The absence of generalized vertical magma transit in a LIP has major geodynamic consequences. We cannot link the surface extent of LIP magmas to the dimensions of the mantle melting zone as proposed in former plume head models. The distribution of LIP magmas at the surface is primarily controlled by the regional stress field acting within the upper crust, but is also affected by magma viscosity. The igneous centers feeding LIPs most likely represent the crustal expression of small-scale convective cells of the buoyant mantle naturally located beneath the mechanical lithosphere.

Abstract The process of faulting within a crustal-scale rift basin, subjected to transpression, is simulated in a series of small-scale experiments using sand and silicone layers. The structural scenario involved three stages: (1) extension; (2) sedimentation; (3) coeval shortening and strike-slip motion. A sandpack, placed above a basal silicone layer, was submitted to extension and produced a system of horst and grabens. Following the extension phase, the resulting surface topography was covered with silicone material, thus introducing a potential décollement between the pre- and post-rift sediments. These latter strata were made of sand. After sedimentation, deformation by transpression was applied using the same amount of shortening and an increasing strike-slip displacement in the different experiments. The strain partitioning increased with the amount of horizontal shear, and strike-slip faults developed at the more advanced stages of transpression. Two phases of faulting were observed before the horst and graben faults could be reactivated. The first phase was characterized by conjugate reverse faults, striking parallel to the rift-bounding faults, compatible with a stress regime in compression. A second phase of faulting was recognized at the end of transpression, leading to the generation of Riedel R-type strike-slip faults. The stress regimes responsible for the kinematics of fault generation and reactivation were interpreted using the Coulomb failure criterion and assumed a friction angle of 30° for the undisturbed sand. The reactivation of the steep normal faults in the horst and graben occurred only after a large strike-slip displacement. The general sequence of fault generation and reactivation suggested a temporal change in the stress regime. This change was caused by the permutation of the minimum and the intermediate principal stress axes and also by a progressive rotation, in the horizontal plane, of the axis of the maximum compressive stress. The spatial variation of the stress regime was also strongly controlled by the geometry of the interbedded silicone layer. A regular and undeformed post-rift silicone layer introduced a more efficient mechanical decoupling between the post-rift cover and the stretched basin. In summary, when a pre-existing graben was present, there was a succession of two distinct ‘tectonic phases’, whereas without a rift, the resulting fault kinematics reflected a single stress state and one tectonic phase.