Abstract The Triassic sequence stratigraphic scheme originally proposed by Sharland et al. (2001) for the Arabian Plate based on the identification of maximum flooding surfaces is updated, refined and, where necessary, revised. These changes follow a comprehensive review of data available to Sharland et al. augmented by the analyses of many recent papers, including a full assessment of published biostratigraphic data and other stratigraphic calibration tools. For the first time, sequence boundaries complementary to each maximum flooding surfaces are defined. Type sections, identification criteria, and biostratigraphic calibration are proposed for each sequence boundary and maximum flooding surfaces. We also identify representations of each sequence stratigraphic surface in every country where present across the entire Arabian Plate and discuss possible causative mechanisms that control changes in relative sea level. The combined, but changing, influences of tectonics, climate, and eustasy account for the pronounced cyclicity within the Triassic stratigraphy across the Arabian Plate. A compelling correspondence exists between warming and cooling events identified in other parts of Neo-Tethys and the stratigraphic events identified in this study, thereby suggesting that these events may be of global significance. The petroleum elements present in the Triassic stratigraphy of the Arabian Plate are summarised. Finally, future exploration potential and key risks are highlighted.

Abstract The Triassic–Middle Jurassic (early Mesozoic) stratigraphy of the Arabian Plate is briefly reviewed with reference to updating the relevant portions of the regional sequence stratigraphic model first published in 2001— Arabian Plate Sequence Stratigraphy . Sedimentary cyclicity is evident within early Mesozoic carbonate, evaporitic, and siliciclastic rocks on the Arabian Plate and permits the recognition of plate-wide, third-order sequences, especially constituent maximum flooding surfaces. These sequences can be constrained by biostratigraphy and other age calibration tools where available, with outcrop and well log correlations permitting the sequences to be interpolated between biostratigraphic control points. New data and concepts published since 2001 enable the regional sequence stratigraphic model to be updated; certain surfaces can be recalibrated in terms of age because of better biostratigraphic constraint or new insight into the sedimentary response to sea-level change. This sequence model enables inter-regional correlation that is difficult using lithostratigraphy alone. Eustasy is considered as an important control on sequence development for the early Mesozoic of Arabia, but the interplay of this with tectonics and climate change is also fundamental to the development of the sedimentary cyclicity observed.

ABSTRACT During the Mesozoic Era, episodes of siliciclastic input onto the dominantly carbonate Arabian shelf form important elements of petroleum plays, forming proven and potential reservoirs, source rocks, and seals. This chapter examines the temporal and spatial extent of these siliciclastic episodes. It then compares them against known tectonic, climatic, and eustatic events affecting the Arabian plate that may have been acting independently or coincidently to control siliciclastic input by means of hinterland uplift, influence on denudation and run off, incision, and creation of sediment pathways and accommodation space. Particularly important phases of siliciclastic input occur in (1) the Early Triassic (Olenekian Sudair shale) coincident with major eustatic lowering, an episode of humid climate and rifting on the northern part of the Arabian plate; (2) Late Triassic (late Norian initial Minjur Sandstone) coincident with East Mediterranean rifting, a humid episode and a major eustatic sea-level fall; (3) Middle Jurassic (early Bajocian initial Dhruma Sandstone) coincident with localized uplift and a humid climate and immediately postdating a eustatic sea-level fall in the Aalenian; (4) Early Cretaceous (late Valanginian–Barremian Zubair sandstone) postdating a Valanginian eustatic lowering and coincident with humid climate and uplift in northern and western Arabia; (5) Mid-Cretaceous (latest Aptian–middle Albian Burgan Sandstone) coincident with Arabian shield uplift, humid climate, and a eustatic low. Other episodes of siliciclastic input also occur, although they tend to be more localized. Important seals are formed during the progradation of siliciclastic systems “poisoning” carbonate shelves or during transgression when distal pro-delta siliciclastic systems retreat back across the shelf, capping up-systems tract fluvial or shelfal sandstones, or when they are located above major unconformities, capping carbonate reservoirs. Siliciclastic reservoirs include the well-known and prolific fluvial and paralic sandstones that contribute, for example, to the Burgan field in Kuwait and to the Zubair and Nahr Umr reservoirs of the northern Gulf. Lowstand sands (both lowstand deltas and slope and basin gravity flow deposits) form viable, but underexplored, reservoir targets. Source rocks may be deposited in front of prograding delta systems linked to high nutrient supply and water stratification caused by freshwater overhang, leading to anoxia and preservation of organic matter. A well-known example is the Kazhdumi Formation of the Iranian Zagros. A better understanding of the fundamental controls on siliciclastic input onto the Arabian plate will enable better predictions of these key petroleum play elements and a better understanding of the subsurface risk associated with their occurrence.

Abstract In the period between the Westphalian and the Early Triassic, climatic conditions across Gondwana changed from the Gondwana-wide glaciation in the Late Carboniferous–Early Permian to warm to hot, semi-humid to arid conditions by the Late Permian–Early Triassic. In Afro-Arabia, glaciers advanced to 40° palaeolatitude creating a steep gradient between them and the temperate-humid environment in the vicinity of the equator. Synchronous deglaciation associated with a eustatic rise of sea level in the Early Sakmarian was followed by a flattening of the climate gradient and increased humidity, expressed by blackwater rivers and coal swamps between the South Pole and about 50° palaeolatitude and increasing aridity towards the equator. Brief poleward advances of hot aridity are evident around the Kungurian. Expansion of the hot climate zone to the south took place in the Middle Permian, commencing with a humid to semi-humid phase in the south and semi-arid to arid conditions towards the north. A short pluvial event is locally indicated at the beginning of the Triassic, but warm semi-arid to semi-humid conditions prevailed in the south and hot aridity near the equator. There are variations of that general theme in eastern Gondwana, but the fundamental changes in climate-controlled depositional environments occurred almost synchronously over the whole of Gondwana, including Antarctica. The slight drift of Gondwana towards the equator is therefore an unlikely cause for these changes, as are modifications of ocean–continent geometries or of atmospheric composition. As the main driver was temperature it is suggested that governing control, not only of global temperature but also of the intensity of geotectonic activities, was imposed on the solar system by forces emanating from our galaxy (cosmic ray flux, magnetic intensity, gravitational vectors) and their variation over the course of a galactic year (the time for the solar system to orbit the core of the galaxy).

Abstract Extensive subsurface sampling of the Huqf Supergroup in the Sultanate of Oman has yielded microfossil assemblages of Cryogenian, Ediacaran and Early Cambrian age. Microfossils have been recovered from most stratigraphic units in the Huqf, including Marinoan-equivalent horizons of the Ghadir Manqil Formation (Cryogenian Abu Mahara Group), the Masirah Bay, Shuram and Buah formations of the Ediacaran Nafun Group, and the A3 (latest Ediacaran) and A6 (Early Cambrian) cycles of the Ara Group. Despite the extensive recovery of leiosphaerid acritarchs from the Shuram Formation, there is no indication of the large acanthomorphs typical of other early–middle Ediacaran assemblages. This absence suggests a relatively young (post-extinction) depositional age for the Shuram; however, the signal is complicated by local deep-water conditions and the facies-specific distribution of Proterozoic microfossils. A shallower-water sequence of undivided Nafun Group sediments preserves sphaeromorphic acritarchs in association with filamentous microfossils, fragmentary vendotaenids and possible vaucheriacean algae.

Abstract At the time of the opening of the Tethys Ocean the northern edge of Gondwana was affected by several rifting events. In this study, we used data from deep exploration wells, seismic profiles, and seismic depth maps to reconstruct the pattern of Tethyan rifting in the Levant region and to investigate its effects on the evolution of the Levant crust. The results show a several hundred kilometre wide deformation zone, comprised of graben and horst structures that extend from the inner part of the Levant to the marine basin offshore Israel. The structures are dominated by sets of NE–SW and NNE–SSW oriented normal faults with vertical offsets in the range of 1–8 km. Rifting was associated with a NW–SE direction of extension, approximately perpendicular to the present-day Mediterranean coast. Faulting activity progressed over a period of 120 Ma and took place in three main pulses: Late Palaeozoic (Carboniferous to Permian); Middle to Late Triassic; and Early to Middle Jurassic. The last, and the most intense, tectonic phase post-dates the activity in other rifted margins of northern Gondwana. Rifting was associated with the modification and stretching of the Levant crust. Our results demonstrate an extension discrepancy between the brittle deformation in the upper crust and the amount of total crustal thinning. Seismic reflection data shows that the Levant Basin lacks the characteristics of typical rifted margins, either volcanic or non-volcanic. The evolution of the basin may be explained by depth-dependant stretching, associated with the upwelling of divergent mantle flow and removal of lower crustal layers by decoupling along deep detachment faults.