Abstract The genetic analysis of fold and thrust belts is facilitated by tracking the evolution of their organic endowment (petroleum tectonics). Petroleum tectonic analysis of convergent orogenic systems provides an audit of the processes that control the deformation and kinematics of orogenic belts. The distribution and deformation paths of the organic endowment intervals are key factors in determining the petroleum system evolution of fold and thrust belts. This comparison of orogenic systems illustrates the importance of flexural v. dynamic processes, orogenic wedge taper, mechanical stratigraphy and inherited architecture on the creation, preservation and destruction of petroleum accumulations. The Zagros, Pyrenees, Sevier and Beni Sub-Andean convergent systems share key characteristics of fold and thrust belts, with major differences in scale, degree of incorporation of organic endowment in evolution of the fold and thrust belt and its foreland, and preservation of fold and thrust belt wedge-top deposits. The Zagros is an orogen dominated by flexural processes that is a perfect storm for hydrocarbon generation and preservation. Its multiple stacked sources ensure continuous hydrocarbon generation while stacked detachments foster a low taper and thick wedge-top basins. The Pyrenees is also a flexurally dominated orogen, but the early consumption of its source rocks led to minimal survival of hydrocarbon accumulations during exhumation in a long lasting, high-taper orogenic wedge. The Sevier was initially a flexural orogen that was later dominated by dynamic uplift of the fold and thrust belt and distal foreland subsidence with foreland deformation. The consumption of its pre-orogenic sources during the early low-taper phase indicates a probable robust petroleum system at that time. However, the late high-taper phase exhumed and destroyed much of the early petroleum system. The addition of syntectonic foreland sources to be matured by both local and dynamic subsidence created an additional later set of petroleum systems. Post-orogenic events have left only remnants of world-class petroleum systems. The Beni segment of the Sub-Andean Orogen is a flexural system with probable dynamic overprints. Its most robust petroleum system probably occurred during its early low-taper flexural phase, with dynamic subsidence enhancement. Its late high-taper phase with possible dynamic uplift shuts down and stresses the petroleum systems. Comparison of these orogenic systems illustrates the importance of flexural v. dynamic processes, orogenic wedge taper kinematics, mechanical stratigraphy, distribution of source rocks relative to shortening and inherited architecture on the creation, preservation and destruction of petroleum accumulations in fold and thrust belts.

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 Carbonate platforms affected by salt tectonics form important hydrocarbon reservoirs. In an effort to gain new insights of the impact of diapirism on carbonate systems we have undertaken an integrated structural and sedimentological study of Jurassic carbonate platforms of the Moroccan High-Atlas basin. In this natural laboratory, the scale of outcrop exposure is similar in area to a large offshore seismic data set, and field observations provide high details on the geometries and facies distributions around diapiric structures. The Atlas intracontinental basin initiated during the Triassic, contemporaneously with Atlantic rifting. The Triassic synrift sequence includes thick shales and evaporite deposits accumulated in multiple tectonic sub-basins. A thick (>5000m) Jurassic sequence was deposited during an overall post-rift stage in a west-southwest/east-northeast shallow-marine basin open towards the NeoTethys. Since the Sinemurian, sedimentation was mainly carbonates. However, geodynamic events linked with the evolution of the Atlantic margin produced several phases of clastic influx leading to the development of mixed systems (Toarcian and Bathonian). During the Early Pliensbachian, an extensional tectonic event triggered synsedimentary diapiric movements which locally lasted until the Cretaceous. These movements were responsible for the development of narrow diapiric ridges of large extent (>100km), controlled by normal west-southwest/east-northeast relay faults. These ridges were separating several kilometers-wide elongated mini-basins, which subsidence was induced by salt/shale withdrawal. Regionally, diapiric movements have been discontinuous in time and space, leading to significant thickness variations within the different stratigraphic units. However, diapirism has not had any major influence on the nature and distribution of sedimentary systems at the basin scale. The impact of diapirs remains essentially localized in the immediate vicinity of these structures (km-scale), where they affected both stratigraphic geometries and facies distribution. This impact appears to be very different in oolitic and mixed ramp systems in which subtle differentiation of depositional profiles controlled progressive facies variations, or in bioconstructed carbonate systems in which diapiric movements had a major role on the location and morphology of platform margins and associated “micro-rim-basins.” In return, the geometry of the diapirs has been clearly influenced by the lithology of surrounding rocks.

Abstract We present new crustal and lithospheric thickness maps for Central Eurasia from the combination of elevation and geoid anomaly data and thermal analysis. The results are strongly constrained by numerous previous data based on seismological and seismic experiments, tomographic imaging and integrated geophysical studies. Our results indicate that high topography regions are associated with crustal thickening that is at a maximum below the Zagros, Himalaya, Tien Shan and the Tibetan Plateau. The stiffer continental blocks that remain undeformed within the continental collision areas are characterized by a slightly thickened crust and flat topography. Lithospheric thickness and crustal thickness show different patterns that highlight an important strain partitioning within the lithosphere. The Arabia–Eurasia collision zone is characterized by a thick lithosphere underneath the Zagros belt, whereas a thin to non-existent lithospheric mantle is observed beneath the Iranian and Anatolian plateaus. Conversely, the India–Eurasia collision zone is characterized by a very thick lithosphere below its southern part as a consequence of the underplating of the cold and stiff Indian lithosphere. Our new model presents great improvements compared to previous global models available for the region, and allows us to discuss major aspects related to the lithospheric structure and acting geodynamic processes in Central Eurasia. Supplementary material: Residual geoid anomaly between different order and degree of filtering, our compilation of crustal thickness from publications and our resulting crustal and lithospheric thickness in .txt format are available at: http://www.geolsoc.org.uk/SUP18846

Abstract The Iberian Peninsula, at the western end of the Alpine-Himalayan Belt, displays a complex structure with mountain ranges of diverse structural trends and sedimentary basins between them. The Iberian Peninsula also shows an elevated mean topography, the highest in Europe. In this short paper, we investigate the Alpine evolution of the Iberian Peninsula since Mesozoic times, when Iberia was isolated as an independent plate. This occurred from Albian (formation of the northern plate boundary) to Oligocene times (end of the Pyrenean Orogeny). Iberia was squeezed between Africa and Europe during Tertiary times and all previously established Mesozoic extensional basins were inverted, as were some of the Hercynian structures. The opening of the Valencia Trough, cutting the eastern margin of the Iberian Peninsula, began in Oligocene times. Concomitant crustal and lithospheric stretching during the Neogene along the eastern margin of Iberia produced limited uplifts, some of which are still active. The modern topography of the Iberian Peninsula was developed mainly as the result of three main tectonothermal mechanisms since late Palaeozoic times: variations in crustal densities, and possibly mantle depletion, inherited from the Hercynian Orogeny; crustal and lithospheric thickening during Tertiary compression; and upper mantle thinning during the Neogene-Quaternary.