Integrated 3D forward stratigraphic and petroleum system modeling of the Levant Basin,Eastern Mediterranean

The Eastern Mediterranean Levant Basin is a proven hydrocarbon province with recent major gas discoveries. To date, no exploration wells targeted its northern part, in particular the Lebanese offshore. The present study assesses the tectono‐stratigraphic evolution and related petroleum systems of the northern Levant Basin via an integrated approach that combines stratigraphic forward modeling and petroleum systems/basin modeling based on the previous published work. Stratigraphic modeling results provide a best‐fit realisation of the basin‐scale sedimentary filling, from the post‐rift Upper Jurassic until the Pliocene. Simulation results suggest dominant eastern marginal and Arabian Plate sources for Cenozoic siliciclastic sediments and a significant contribution from the southern Nilotic source mostly from Lower Oligocene to Lower Miocene. Basin modeling results suggest the presence of a working thermogenic petroleum system with mature source rocks localised in the deeper offshore. The generated hydrocarbons migrated through the deep basin within Jurassic and Cretaceous permeable layers towards the Latakia Ridge in the north and the Levant margin and offshore topographic highs. Furthermore, the basin model indicates a possibly significant influence of salt deposition during Messinian salinity crisis on formation fluids. Ultimately, the proposed integrated workflow provides a powerful tool for the assessment of petroleum systems in underexplored areas.     

Subsidence and exhumation of the Mesozoic Qiangtang Basin: Implications for the growth of the Tibetan plateau

The subsidence and exhumation histories of the Qiangtang Basin and their contributions to the early evolution of the Tibetan plateau are vigorously debated. This paper reconstructs the subsidence history of the Mesozoic Qiangtang Basin with 11 selected composite stratigraphic sections and constrains the first stage of cooling using apatite fission track data. Facies analysis, biostratigraphy, palaeo‐environment interpretation and palaeo‐water depth estimation are integrated to create 11 composite sections through the basin. Backstripped subsidence calculations combined with previous work on sediment provenance and timing of deformation show that the evolution of the Mesozoic Qiangtang Basin can be divided into two stages. From Late Triassic to Early Jurassic times, the North Qiangtang was a retro‐foreland basin. In contrast, the South Qiangtang was a collisional pro‐foreland basin. During Middle Jurassic‐Early Cretaceous times, the North Qiangtang is interpreted as a hinterland basin between the Jinsha orogen and the Central Uplift; the South Qiangtang was controlled by subduction of Meso‐Tethyan Ocean lithosphere and associated dynamic topography combined with loading from the Central Uplift. Detrital apatite fission track ages from Mesozoic sandstones concentrate in late Early to Late Cretaceous (120.9–84.1 Ma) and Paleocene–Eocene (65.4–40.1 Ma). Thermal history modelling results record Early Cretaceous rapid cooling; the termination of subsidence and onset of exhumation of the Mesozoic Qiangtang Basin suggest that the accumulation of crustal thickening in central Tibet probably initiated during Late Jurassic–Early Cretaceous times (150–130 Ma), involving underthrusting of both the Lhasa and Songpan–Ganze terranes beneath the Qiangtang terrane or the collision of Amdo terrane.     

Rifting and pre‐rift lithosphere variability in the Orphan Basin,Newfoundland margin,Eastern Canada

The Orphan Basin, lying along the Newfoundland rifted continental margin, formed in Mesozoic time during the opening of the North Atlantic Ocean and the breakup of Iberia/Eurasia from North America. To investigate the evolution of the Orphan Basin and the factors that governed its formation, we (i) analysed the stratigraphic and crustal architecture documented by seismic data (courtesy of TGS), (ii) quantified the tectonic and thermal subsidence along a constructed geological transect, and (iii) used forward numerical modelling to understand the state of the pre‐rift lithosphere and the distribution of deformation during rifting. Our study shows that the pre‐rift lithosphere was 200‐km thick and rheologically strong (150‐km‐thick elastic plate) prior to rifting. It also indicates that extension in the Orphan Basin occurred in three distinct phases during the Jurassic, the Early Cretaceous and the Late Cretaceous. Each rifting phase is characterized by a specific crustal and subcrustal thinning configuration. Crustal deformation initiated in the eastern part of the basin during the Jurassic and migrated to the west during the Cretaceous. It was coupled with a subcrustal thinning which was reduced underneath the eastern domain and very intense in the western domains of the basin. The spatial and temporal distribution of thinning and the evolution of the lithosphere rheology through time controlled the tectonic, stratigraphic and crustal architecture that we observe today in the Orphan Basin.     

The extension of the Vøring margin (NE Atlantic) in case of different degrees of magmatic underplating

The nature of the Lower Crustal Body (LCB) underneath the western part of the Vøring margin (NE Atlantic) is studied with three scenarios of its extension history: (a) The LCB is Caledonian crust. (b) Half the LCB is Caledonian crust and the other half is emplaced as magmatic underplating in Late Palaeocene. (c) The entire LCB is emplaced as magmatic underplating. The extension of the margin transect is obtained with a procedure that accounts for the extension and thinning of the sedimentary basins. This procedure has been extended to include magmatic underplating. The lithosphere is modelled with deposition of sediments and four rift phases since the Early Devonian until today. The forward modelling is mass conservative and the present‐day thicknesses of the formations, crust, LCB and magmatic underplate are reproduced. The state of the lithosphere and the sedimentary basins are shown and compared at the beginning and at the end of the rift phases. It is concluded that the scenario with the LCB as only underplating requires an unrealistic amount of extension. A scenario where underplating accounts for maximum half the LCB is more likely. Two different interpretations for the Moho underneath the Utgard High are tested: one with a shallow base‐crust and another with a deeper and flatter base‐crust. Tectonic modelling of the two versions favours the latter interpretation. The modelling shows that the Late Jurassic rift phase was much more prominent than the Late Cretaceous and Palaeocene rift phase for all cases of underplating. A strong Late Jurassic rift phase is consistent with the accumulation space needed for the thick Cretaceous formations. There are no observations of magmatism from the Late Jurassic, although this rift phase is stronger than the Cretaceous and Palaeocene rift phase.     

Post‐breakup burial and exhumation of the southern margin of Africa

Despite many years of study, the processes involved in the development of the continental margin of southern Africa and the distinctive topography of the hinterland remain poorly understood. Previous thermochronological studies carried out within a monotonic cooling framework have failed to take into account constraints provided by Mesozoic sedimentary basins along the southern margin. We report apatite fission track analysis and vitrinite reflectance data in outcrop samples from the Late Jurassic to Early Cretaceous sedimentary fill of the Oudtshoorn, Gamtoos and Algoa Basins (Uitenhage Group), as well as isolated sedimentary remnants further west, plus underlying Paleozoic rocks (Cape Supergroup) and Permian‐Triassic sandstones from the Karoo Supergroup around the Great Escarpment. Results define a series of major regional cooling episodes. Latest Triassic to Early Jurassic cooling which began between 205 and 180 Ma is seen dominantly in basement flanks to the Algoa and Gamtoos Basins. This episode may have affected a wider region but in most places any effects have been overprinted by later events. The effects of Early Cretaceous (beginning between 145 and 130 Ma) and Early to mid‐Cretaceous (120–100 Ma) cooling are both delimited by major structures, while Late Cretaceous (85–75 Ma) cooling appears to have affected the whole region. These cooling events are all interpreted as dominantly reflecting exhumation. Higher Late Cretaceous paleotemperatures in samples from the core of the Swartberg Range, coupled with evidence for localised Cenozoic cooling, are interpreted as representing Cenozoic differential exhumation of the mountain range. Late Cretaceous paleotemperatures between 60°C and 90°C in outcropping Uitenhage Group sediments from the Oudtshoorn, Gamtoos and Algoa Basins require burial by between 1.2 and 2.2 km prior to Late Cretaceous exhumation. Because these sediments lie in depositional contact with underlying Paleozoic rocks in many places, relatively uniform Late Cretaceous paleotemperatures across most of the region, in samples of both basin fill and underlying basement, suggest the whole region may have been buried prior to Late Cretaceous exhumation. Cenozoic cooling (beginning between 30 and 20 Ma) is focussed mainly in mountainous regions and is interpreted as representing denudation which produced the modern‐day relief. Features such as the Great Escarpment are not related to continental break up, as is often supposed, but are much younger (post‐30 Ma). This history of post‐breakup burial and subsequent episodic exhumation is very different from conventional ideas of passive margin evolution, and requires a radical re‐think of models for development of continental margins.     

Subsidence analyses from the Betic Cordillera, southeast Spain

Fifty‐four Mesozoic–Cenozoic stratigraphic sections from the Betic Cordillera of southeast Spain have been analysed in order to estimate the timing and amount of lithospheric stretching that occurred at the western end of the Tethyan Ocean since the Hercynian Orogeny. The standard backstripping technique has been used in order to calculate the water‐loaded subsidence of basement for each section. Water‐loaded subsidence curves were then inverted in order to determine the variation of lithospheric strain rate as a function of time, which yields estimates of timing, magnitude and intensity of stretching. Rifting commenced during the Late Permian/Early Triassic times and continued intermittently throughout the Mesozoic in response to the opening of the Tethyan Ocean to the east and the opening of the Atlantic Ocean to the west. Two major events in the Permo‐Triassic/Early Jurassic and the Late Jurassic/Early Cretaceous can be clearly identified. Stretching factors are generally small (1.1–1.25) probably because the Betic Cordillera was located at the westernmost end of the Tethys. Peak strain rates of ～10^?15 s^?1 were obtained for Mesozoic rift events and these values are in broad agreement with those obtained throughout the Tethyan Realm. We have also analysed the Neogene extensional event, which played an important role in forming the existing Mediterranean Sea. A combination of well‐log information and calibrated seismic reflection data was modelled. Peak strain rates in these younger basins are almost one order of magnitude faster than those estimated for the Mesozoic basins. These higher values appear to be typical of back‐arc extensional basins elsewhere. To the west and north of the Betic Cordillera, the Guadalquivir foreland basin developed as extension took place further east. Backstripped sections from this basin clearly record the northward migration of foreland basin subsidence through time.     

Cooling of the Sverdrup Basin during Tertiary basin inversion: implications for hydrocarbon exploration

ABSTRACT The regional thermal history of the north‐eastern Sverdrup Basin, Canadian Arctic Archipelago, has been assessed using apatite fission‐track thermochronology and vitrinite reflectance data. Fission‐track data for 27 samples from six wells through the Mesozoic section on Axel Heiberg and Ellesmere Islands reveal significant Palaeocene cooling associated with basin inversion during the Eurekan Orogeny. Fission‐track data for 29 outcrop samples, ranging in stratigraphic age from Cambrian to Tertiary, also reveal significant Palaeocene cooling. Vitrinite reflectance data from carbonaceous shales and coal seams in well and outcrop samples are consistent with these conclusions. The degree of Palaeocene cooling observed is greatest for well and outcrop samples in the cores of anticlines or the hanging walls of thrust faults, such as the Fosheim anticline, and faults, such as the Lake Hazen fault system, and the East Cape and Vesle Fiord thrust faults. Palaeocene cooling is largely attributed to the denudation of structures during the Eurekan Orogeny. At one locality on north‐western Ellesmere Island, which is on the northern flank of the Sverdrup Basin, the underlying Franklinian basement rocks yield Early Cretaceous fission track ages with relatively long mean track lengths. This indicates that this part of the basin was uplifted at this time and that subsequent sedimentation and subsidence in the Cretaceous and early Tertiary were modest. This locality thus appears to be on the rift shoulder, which developed along the flank of the Amerasia Basin in the Lower Cretaceous. At a locality on western Axel Heiberg Island, which is downflank from the rift shoulder, the Upper Jurassic Awingak sandstone has a Late Cretaceous fission track age. This is best explained by heating above the total annealing temperature for fission‐tracks in apatite by extensive Lower Cretaceous intrusions and subsequent heat dissipation and cooling in the Late Cretaceous followed by further substantial cooling due to Tertiary denudation. These results indicate that maximum burial temperatures occurred in the presently exposed Mesozoic section prior to basin inversion during the Eurekan Orogeny. It can therefore be inferred that peak hydrocarbon generation and primary migration predated the formation of structural traps during the Tertiary at shallow depths within the northern Sverdrup Basin.     

Intraplate subsidence and basin filling adjacent to an oceanic arc–continent collision: a case from the southern Caribbean‐South America plate margin

The upper Campanian–Lower Eocene synorogenic sedimentary wedge of the Ranchería Basin was deposited in an intraplate basin resting on a tilted continental crustal block that was deformed by collision and subsequent subduction of the Caribbean Plate. Upper Cretaceous–Lower Eocene strata rest unconformably upon Jurassic igneous rocks of the Santa Marta Massif, with no major thrust faults separating the Santa Marta Massif from the Ranchería Basin. The upper Campanian–Lower Eocene succession includes, from base to top: foraminifera‐rich calcareous mudstone, mixed carbonate–siliciclastic strata and mudstone, coal and immature fluvial sandstone beds. Diachronous collision and eastward tilting of the plate margin (Santa Marta Massif and Central Cordillera) favoured the generation of accommodation space in a continuous intraplate basin (Ranchería, Cesar and western Maracaibo) during the Maastrichtian to Late Palaeocene. Terrigenous detritus from the distal colliding margin filled the western segments of the continuous intraplate basin (Ranchería and Cesar Basins); in the Late Paleocene, continental depositional systems migrated eastwards as far as the western Maracaibo Basin. In Early Eocene time, reactivation of former extensional structures fragmented the intraplate basin into the Ranchería‐Cesar Basins to the west, and the western Maracaibo Basin and Palmar High to the East. This scenario of continent–oceanic arc collision, crustal‐scale tilting, intraplate basin generation and fault reactivation may apply for Upper Cretaceous–Palaeogene syntectonic basins in western Colombia and Ecuador, and should be considered in other settings where arc–continent collision is followed by subduction.     

Southwest Barents Sea rift basin evolution: comparing results from backstripping and time‐forward modelling

We present tectonic models of progressive basin formation in the south‐west Barents Sea derived as part of the PETROBAR project (Petroleum‐related studies of the Barents Sea region). The basin architecture developed as a multi‐stage rift preceding the creation of the sheared/transtensional margin conjugate to NE Greenland. N‐ to NNE‐striking basins, with sediment thicknesses in places exceeding 15 km, are separated by basement highs. We use two basin analysis approaches, BMT? backstripping and TecMod?time‐forward modelling, to determine stretching factors through time along the profile PETROBAR‐07. This 550 km‐long profile derived from wide‐angle reflection/refraction seismic data acquired in 2007, coincident with deep multichannel seismic reflection data. Detailed stratigraphic analysis of the reflection profile, in concert with a dense grid of 2D profiles tied to wells, provides timing and water depth constraint for the models. Velocity analysis of the wide‐angle data provides constraint on the cumulative crustal stretching. The north‐west trending cross‐section extends from continental craton, at the Varanger Peninsula, to within 16 km of the interpreted continent–ocean boundary. Rifting along the profile was episodic, with four distinct phases of basin formation during the Carboniferous, the Late Permian–Triassic, the Late Jurassic–Early Cretaceous and the Late Cretaceous–Eocene. Collectively, the basins exhibit a general trend of younging, narrowing, and deepening oceanward, suggesting a gradual focusing of rifting prior to final breakup. Cumulative stretching factors derived from BMT and TecMod correlate well with observed crustal thinning, and the two models provide uncertainty bounds for stretching factors for the separate rift phases. In contrast to orthogonally rifted margins, stretching is relatively minor immediately prior to transform breakup, with greater stretching occurring during earlier rift phases.     

How do pre‐existing normal faults influence rift geometry? A comparison of adjacent basins with contrasting underlying structure on the Lofoten Margin,Norway

Recent studies of natural, multiphase rifts suggest that the presence of pre‐existing faults may strongly influence fault growth during later rift phases. These findings compare well with predictions from recent scaled analogue experiments that simulate multiphase, non‐coaxial extension. However, in natural rifts we only get to see the final result of multiphase rifting. We therefore do not get the chance to compare the effects of the same rift phase with and without pre‐existing structural heterogeneity, as we may in the controlled environment of a laboratory experiment. Here, we present a case study from the Lofoten Margin that provides a unique opportunity to compare normal fault growth with and without pre‐existing structural heterogeneity. Using seismic reflection and wellbore data, we demonstrate that the Ribban Basin formed during Late Jurassic to Early Cretaceous rifting. We also show that the rift fault network of the Ribban Basin lacks a pre‐existing (Permian‐Triassic) structural grain that underlies the neighbouring North Træna Basin that also formed during the Late Jurassic to Early Cretaceous. Being able to compare adjacent basins with similar histories but contrasting underlying structure allows us to study how pre‐existing normal faults influence rift geometry. We demonstrate that in Lofoten, the absence of pre‐existing normal faults produced collinear fault zones. Conversely, where pre‐existing faults are present, normal fault zones develop strong “zigzag” plan‐view geometries.     

Subsurface evidence for late Mesozoic extension in western Mongolia: tectonic and petroleum systems implications

New seismic reflection profiles from the Tugrug basin in the Gobi‐Altai region of western Mongolia demonstrate the existence of preserved Mesozoic extensional basins by imaging listric normal faults, extensional growth strata, and partially inverted grabens. A core hole from this region recovered ca. 1600 continuous meters of Upper Jurassic – Lower Cretaceous (Kimmeridgian–Berriasian) strata overlying Late Triassic volcanic basement. The cored succession is dominated by lacustrine and marginal lacustrine deposits ranging from stratified lacustrine, to subaqueous fan and delta, to subaerial alluvial‐fluvial environments. Multiple unconformities are encountered, and these represent distinct phases in basin evolution including syn‐extensional deposition and basin inversion. Prospective petroleum source and reservoir intervals occur, and both fluid inclusions and oil staining in the core provide evidence of hydrocarbon migration. Ties to correlative outcrop sections underscore that, in general, this basin appears to share a similar tectono‐stratigraphic evolution with petroliferous rift basins in eastern Mongolia and China. Nevertheless, some interesting contrasts to these other basins are noted, including distinct sandstone provenance, less overburden, and younger (Neogene) inversion structures. The Tugrug basin occupies an important but perplexing paleogeographic position between late Mesozoic contractile and extensional provinces. Its formation may record a rapid temporal shift from orogenic crustal thickening to extensional collapse in the Late Jurassic, and/or an accommodation zone with a Mesozoic strike‐slip component.     

The formation of a failed continental breakup basin: The Cenozoic development of the Faroe‐Shetland Basin

Ultra‐large rift basins, which may represent palaeo‐propagating rift tips ahead of continental rupture, provide an opportunity to study the processes that cause continental lithosphere thinning and rupture at an intermediate stage. One such rift basin is the Faroe‐Shetland Basin (FSB) on the north‐east Atlantic margin. To determine the mode and timing of thinning of the FSB, we have quantified apparent upper crustal β‐factors (stretching factors) from fault heaves and apparent whole‐lithosphere β‐factors by flexural backstripping and decompaction. These observations are compared with models of rift basin formation to determine the mode and timing of thinning of the FSB. We find that the Late Jurassic to Late Palaeocene (pre‐Atlantic) history of the FSB can be explained by a Jurassic to Cretaceous depth‐uniform lithosphere thinning event with a β‐factor of ~1.3 followed by a Late Palaeocene transient regional uplift of 450–550 m. However, post‐Palaeocene subsidence in the FSB of more than 1.9 km indicates that a Palaeocene rift with a β‐factor of more than 1.4 occurred, but there is only minor Palaeocene or post‐Palaeocene faulting (upper crustal β‐factors of less than 1.1). The subsidence is too localized within the FSB to be caused by a regional mantle anomaly. To resolve the β‐factor discrepancy, we propose that the lithospheric mantle and lower crust experienced a greater degree of thinning than the upper crust. Syn‐breakup volcanism within the FSB suggests that depth‐dependent thinning was synchronous with continental breakup at the adjacent Faroes and Møre margins. We suggest that depth‐dependent continental lithospheric thinning can result from small‐scale convection that thins the lithosphere along multiple offset axes prior to continental rupture, leaving a failed breakup basin once seafloor spreading begins. This study provides insight into the structure and formation of a generic global class of ultra‐large rift basins formed by failed continental breakup.     

Salt thickness and composition influence rift structural style,northern North Sea,offshore Norway

“Salt” giants are typically halite‐dominated, although they invariably contain other evaporite (e.g. anhydrite, bittern salts) and non‐evaporite (e.g. carbonate, clastic) rocks. Rheological differences between these rocks mean they impact or respond to rift‐related, upper crustal deformation in different ways. Our understanding of basin‐scale lithology variations in ancient salt giants, what controls this and how this impacts later rift‐related deformation, is poor, principally due to a lack of subsurface datasets of sufficiently regional extent. Here we use 2D seismic reflection and borehole data from offshore Norway to map compositional variations within the Zechstein Supergroup (ZSG) (Lopingian), relating this to the structural styles developed during Middle Jurassic‐to‐Early Cretaceous rifting. Based on the proportion of halite, we identify and map four intrasalt depositional zones (sensu Clark et al., Journal of the Geological Society, 1998, 155, 663) offshore Norway. We show that, at the basin margins, the ZSG is carbonate‐dominated, whereas towards the basin centre, it becomes increasingly halite‐dominated, a trend observed in the UK sector of the North Sea Basin and in other ancient salt giants. However, we also document abrupt, large magnitude compositional and thickness variations adjacent to large, intra‐basin normal faults; for example, thin, carbonate‐dominated successions occur on fault‐bounded footwall highs, whereas thick, halite‐dominated successions occur only a few kilometres away in adjacent depocentres. It is presently unclear if this variability reflects variations in syn‐depositional relief related to flooding of an underfilled presalt (Early Permian) rift or syn‐depositional (Lopingian) rift‐related faulting. Irrespective of the underlying controls, variations in salt composition and thickness influenced the Middle Jurassic‐to‐Early Cretaceous rift structural style, with diapirism characterising hangingwall basins where autochthonous salt was thick and halite‐rich and salt‐detached normal faulting occurring on the basin margins and on intra‐basin structural highs where the salt was too thin and/or halite‐poor to undergo diapirism. This variability is currently not captured by existing tectono‐stratigraphic models largely based on observations from salt‐free rifts and, we argue, mapping of suprasalt structural styles may provide insights into salt composition and thickness in areas where boreholes are lacking or seismic imaging is poor.     

环北极沉积盆地结构与构造演化特征——来自环北极地质长剖面的证据

通过对北极地区不同盆地结构的系统研究与对比分析,绘制了环北极沉积盆地群长剖面,剖面全长约13 000 km,涉及季曼-伯朝拉盆地等15个盆地和微陆。由于整个剖面尺度巨大,在若干缺乏详细资料的地区采用将邻近地区的其他剖面平移到本剖面中,或由其两侧的剖面地层和构造形式推测。剖面涉及的盆地多属叠合性质,涵盖克拉通盆地、裂谷盆地、前陆盆地、被动大陆边缘盆地等多种盆地类型;各区域沉积厚度差异显著,最厚的东巴伦支海等盆地沉积了自古生界至新生界的地层,沉积厚度可达近15 km ,而沉积最薄处的拉普捷夫海等盆地则只发育了从中生界上白垩统至新生界的沉积,厚度不超过4 km。以北大西洋—北冰洋洋中脊为界,北极地区分属欧亚板块和北美板块,很多盆地为大陆的一部分或大陆向北冰洋的延伸部分（大陆架）。各盆地的发育主要受波罗的板块、西伯利亚板块与劳伦古陆显生宙以来的构造演化控制;加里东运动、埃尔斯米尔运动、海西运动（乌拉尔运动）及大西洋洋脊自南向北的扩张对环北极盆地均有显著影响,具体表现为造成盆地类型的改变、改变盆地沉降速率等。     

Structural evolution and the partitioning of deformation during basin growth and inversion: A case study from the Mizen Basin Celtic Sea,offshore Ireland

The Celtic Sea basins lie on the continental shelf between Ireland and northwest France and consist of a series of ENE–WSW trending elongate basins that extend from St George’s Channel Basin in the east to the Fastnet Basin in the west. The basins, which contain Triassic to Neogene stratigraphic sequences, evolved through a complex geological history that includes multiple Mesozoic rift stages and later Cenozoic inversion. The Mizen Basin represents the NW termination of the Celtic Sea basins and consists of two NE–SW-trending half-grabens developed as a result of the reactivation of Palaeozoic (Caledonian, Lower Carboniferous and Variscan) faults. The faults bounding the Mizen Basin were active as normal faults from Early Triassic to Late Cretaceous times. Most of the fault displacement took place during Berriasian to Hauterivian (Early Cretaceous) times, with a NW–SE direction of extension. A later phase of Aptian to Cenomanian (Early to Late Cretaceous) N–S-oriented extension gave rise to E–W-striking minor normal faults and reactivation of the pre-existing basin bounding faults that propagated upwards as left-stepping arrays of segmented normal faults. In common with most of the Celtic Sea basins, the Mizen Basin experienced a period of major erosion, attributed to tectonic uplift, during the Paleocene. Approximately N–S Alpine regional compression-causing basin inversion is dated as Middle Eocene to Miocene by a well-preserved syn-inversion stratigraphy. Reverse reactivation of the basin bounding faults was broadly synchronous with the formation of a set of near-orthogonal NW–SE dextral strike-slip faults so that compression was partitioned onto two fault sets, the geometrical configuration of which is partly inherited from Palaeozoic basement structure. The segmented character of the fault forming the southern boundary of the Mizen Basin was preserved during Alpine inversion so that Cenozoic reverse displacement distribution on syn-inversion horizons mirrors the earlier extensional displacements. Segmentation of normal faults therefore controls the geometry and location of inversion structures, including inversion anticlines and the back rotation of earlier relay ramps.     

Upper Triassic – Jurassic sequence stratigraphy and its structural controls in the western Ordos Basin, China

Upper Triassic, Lower–Middle Jurassic and Upper Jurassic strata in the western Ordos Basin of North China are interpreted as three unconformity-bounded basin phases, BP-4, BP-5 and BP-6, respectively. The three basin phases were deposited in three kinds of predominantly continental basin: (1) a Late Triassic composite basin with a south-western foreland subbasin and a north-western rift subbasin, (2) an Early–Middle Jurassic sag basin and (3) a Late Jurassic foreland molasse wedge. Within the Late Triassic composite basin BP-4 includes three sequences, S4-1, S4-2 and S4-3. In the south-western foreland subbasin, the three sequences are the depositional response to three episodes of thrust load subsidence, and are mainly composed of alluvial fan, steep-sloped lacustrine delta and fluvial systems in front of a thrust fault-bounded basin flank. In the north-western rift subbasin, the three sequences are the depositional response to three episodes of rift subsidence, and consist of alluvial fan – braid plain and fan delta systems basinward of a normal fault-bounded basin margin. In the sag basin BP-5 includes four sequences, S5-1, S5-2, S5-3 and S5-4, which reflect four episodes of intracratonic sagging events and mainly consist of fluvial, gentle-gradient lacustrine delta and lacustrine systems sourced from peripheral uplifted flanks. BP-6, deposited in the foreland-type basin, includes one sequence, S6-1, which is the depositional response to thrust load subsidence and is composed of alluvial fan systems. The formation and development of these three kinds of basins was controlled by Late Triassic and Jurassic multi-episode tectonism of basin-bounding orogenic belts, which were mainly driven by collision of the North China and South China blocks and subduction of the western Pacific plate.     

The synrift phase of the early Domeyko Basin (Triassic,northern Chile): Sedimentary,volcanic, and tectonic interplay in the evolution of an ancient subduction‐related rift basin

The geodynamic setting along the SW Gondwana margin during its early breakup (Triassic) remains poorly understood. Recent models calling for an uninterrupted subduction since Late Palaeozoic only slightly consider the geotectonic significance of coeval basins. The Domeyko Basin initiated as a rift basin during the Triassic being filled by sedimentary and volcanic deposits. Stratigraphic, sedimentological, and geochronological analyses are presented in order to determine the tectonostratigraphic evolution of this basin and to propose a tectonic model suitable for other SW Gondwana‐margin rift basins. The Domeyko Basin recorded two synrift stages. The Synrift I (~240–225 Ma) initiated the Sierra Exploradora sub‐basin, whereas the Synrift II (~217–200 Ma) reactivated this sub‐basin and originated small depocentres grouped in the Sierra de Varas sub‐basin. During the rift evolution, the sedimentary systems developed were largely controlled by the interplay between tectonics and volcanism through the accommodation/sediment supply ratio (A/S). High‐volcaniclastic depocentres record a net dominance of the syn‐eruptive period lacking rift‐climax sequences, whereas low‐volcaniclastic depocentres of the Sierra de Varas sub‐basin developed a complete rift cycle during the Synrift II stage. The architecture of the Domeyko Basin suggests a transtensional kinematic where N‐S master faults interacted with ~NW‐SE basement structures producing highly asymmetric releasing bends. We suggest that the early Domeyko Basin was a continental subduction‐related rift basin likely developed under an oblique convergence in a back‐arc setting. Subduction would have acted as a primary driving mechanism for the extension along the Gondwanan margin, unlike inland rift basins. Slab‐induced dynamic can strongly influence the tectonostratigraphic evolution of subduction‐related rift basins through controls in the localization and style of magmatism and faulting, settling the interplay between tectonics, volcanism, and sedimentation during the rifting.     

Thermotectonic evolution of the Ukrainian Donbas Foldbelt revisited: new constraints from zircon and apatite fission track data

The Donbas Foldbelt (DF) is the compressionally deformed segment of a large Late Palaeozoic rift cross‐cutting the southern part of the East European Craton and is traditionally described as a classic example of an inverted intracratonic rift basin. Proposed formational models are often controversial and numerous issues are still a matter of speculation, primarily due to the lack of absolute time constraints and insufficient knowledge of the thermal evolution. We investigate the low‐temperature thermal history of the DF by means of zircon fission track and apatite fission track (AFT) thermochronology applied to Upper Carboniferous sediments. In all samples, the AFT chronometer was reset shortly after deposition in the Early Permian (～275 Ma). Samples contained kinetically variable apatites that are sensitive to different temperatures and using statistic‐based component analysis incorporating annealing characteristics of individual grains assessed by D_par , we identified several distinct age populations, ranging from the Late Permian (～265 Ma) to the Late Cretaceous (～70 Ma). We could thus constrain the thermal history of the DF during a ～200 Myr long period following the thermal maximum. We found that earliest cooling of Permian and Permo‐Triassic age is recorded on the basin margins whereas the central parts were residing in or slowly cooling through the apatite partial annealing zone during Jurassic and most of Cretaceous times, and then finally cooled to near‐surface conditions latest around the Cretaceous/Palaeogene boundary. Our data show that Permian erosion was less significant and Mesozoic erosion more significant than generally assumed. Inversion and pop‐up of the DF occurred in the Cretaceous and not in the Permian as previously thought. This is indicated by overall Cretaceous AFT ages in the central parts of the basin.     

Tectonic evolution of sedimentary basins of northern Somalia

Regional seismic reflection profiles tied to lithological and biostratigraphic data from deep exploration wells have been used to determine the structure and evolution of the poorly known basins of northern Somalia. We recognize six major tectonostratigraphic sequences in the seismic profiles: Middle‐Late Jurassic syn‐rift sequences (Adigrat and Bihen Group), ?Cenomanian‐Campanian syn‐rift sequences (Gumburo Group), Campanian‐Maastrichtian syn‐rift sequences (Jesomma Sandstones), Palaeocene post‐rift sequences (Auradu Limestones), Early‐Middle Eocene post‐rift sequences (Taleh Formation) and Oligocene‐Miocene (Daban Group) syn‐rift sequences. Backstripping of well data provides new constraints on the age of rifting, the amount of crustal and mantle extension, and the development of the northern Somalia rifted basins. The tectonic subsidence and uplift history at the wells can be explained by a uniform extension model with three episodes of rifting punctuated by periods of relative tectonic quiescence and thermal subsidence. The first event initiated in the Late Jurassic (~156 Ma) and lasted for ~10 Myr and had a NW‐SE trend. We interpret the rift as a late stage event associated with the break‐up of Gondwana and the separation of Africa and Madagascar. The second event initiated in the Late Cretaceous (~80 Ma) and lasted for ~20–40 Myr. This event probably correlates with a rapid increase in spreading rate on the ridges separating the African and Indian and African and Antarctica plates and a contemporaneous slowing down of Africa's plate motion. The backstripped tectonic subsidence data can be explained by a multi‐rift extensional model with stretching factor, β, of 1.09–1.14 and 1.05–1.28 for the first and second rifting events, respectively. The model, fails, however, to completely explain the slow subsidence and uplift history of the margin during Early Cretaceous to Late Cretaceous. We attribute this slow subsidence to the combined effect of a sea‐level fall and regional uplift, which caused a major unconformity in northern Somalia. The third and most recent event occurred in the Oligocene (~32 Ma) and lasted for ~10 Myr. This rift developed along the Gulf of Aden and reactivated the Guban, Nogal and Daroor basins, and is related to the opening of the Gulf of Aden. As a result of these events the crust and upper mantle were thinned by up to a factor of two in some basins. In addition, several distinct petroleum systems developed. The principal exploration play is for Mesozoic petroleum systems with the syn‐rift Oligocene‐Miocene as a subordinate objective owing to low maturity and seal problems. The main seals for the different plays are various shales, some of which are also source rocks, but the Early Eocene evaporites of the Taleh formations can also perform a sealing role for Palaeogene or older generated hydrocarbons migrating vertically.