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A petroleum trap is “the place where oil and gas are barred from further movement” (Levorsen, 1967). The highest point of the trap is called the crest, or culmination. The lowest point at which hydrocarbons may be contained in the trap is called the spill point, this lies on a horizontal contour, the spill plane. The vertical distance from the crest to a spill plane is the closure of the trap. A trap may contain oil, gas, or both. The oil:water contact is the deepest level of producible oil. Some oil fields have a layer of heavy oil, termed a tar mat, at the oil:water contact. Tar mats impede the flow of water into a reservoir when petroleum is produced. Fluid contacts in a trap are generally planar, but some are tilted. The cause of the tilting can be either hydrodynamic flow, production, or a change in facies. A change in grain size across a reservoir causes a tilted contact. Seals are impermeable rock. Shales are the commonest seal, but evaporate the most effective. Traps may be classified as structural, diapiric, stratigraphic, hydrodynamic, or combination. Structural traps consist of anticlinal, compactional, and fault and fault-related. Diapiric traps include salt domes and mud diapirs. Stratigraphic traps include those related to unconformities, channels, barrier bars, pinchouts, reefs, and diagenetic. In hydrodynamic traps, downdip movement of water is essential to prevent the upward movement of oil and gas. Many oil and gas fields around the world are not due solely to structure or stratigraphy or hydrodynamic flow, but to a combination of two or more of these forces. Such fields are termed combination traps. Timing of trap development relative to petroleum migration is important. If traps predate migration, they will probably be productive.

The Qilian orogen consists of the North Qilian belt, the Central Qilian block and the South Qilian belt and is regarded as part of the northern margin of the Proto-Tethys Ocean. The tectonic mechanism responsible for the early Paleozoic magma generation in the Qilian orogen is crucial to understanding the ocean-continent configurations and the closure of the Proto-Tethys Ocean. This paper compiles the early Paleozoic mafic and granitic intrusions in the South Qilian belt and the Central Qilian block, to constrain the subduction and accretion of the South Qilian ocean. The early Paleozoic mafic intrusions in the Central Qilian block indicate that the influence of slab-derived fluids dominates their petrogenesis, while the mafic intrusions in the South Qilian belt were mostly affected by involvement of significant sediment-derived melts in their formation. They are supportive of a melange model, in which melting of melange diapirs originating at the slab-mantle interface generates fluid-metasomatised magma source in the deep mantle under the Central Qilian block and sediment-derived melts-metasomatised magma source under the Hualong block in the South Qilian belt, consistent with northward subduction of the South Qilian ocean. It is proposed that northward intra-oceanic subduction of the South Qilian Ocean occurred at 530-470 Ma in front of the Hualong block and continued at 470-446 Ma but was then accompanied by the development of a mature volcanic arc. Continuous subduction resulted in accretion of the Hualong block northwards onto the Central Qilian block, and this collision started at ca. 446 Ma and lasted to ca. 420 Ma. The final closure of the South Qilian ocean was marked by the onset of continental collision between the Qaidam-Quanji block and the amalgamated Hualong-Central Qilian block at ca. 440 Ma, and also the cause of the A-type granitoids after final collision occurred at ca. 420 Ma.

We present a new seismic reflection dataset and use it to characterize fossil mud volcanoes in the southwestern Songliao graben basin in northeastern China. The results reveal a link between mud volcanism and slab rollback along the eastern Asian margin. This study focuses on the upper 3 km of the Lujiapu sub-basin, which lies in the southwestern Songliao basin. The base of the sequence consists of Lower Cretaceous siliciclastic deposits that are penetrated by mud volcano fluidization pipes. These deposits are overlain by Upper Cretaceous strata that have been deformed by the mud volcanoes. The sequence is capped by undeformed Neogene–Quaternary sediments. These observations constrain the timing of mud volcanism to the Santonian–Campanian (~87–72 Ma). During Late Cretaceous diapirism, normal faulting at the tops of the mud volcanoes formed horsts and grabens. Surface anticlines and inversion structures near the mud volcano source layer indicate that basin inversion occurred during deposition of the Sifangtai and Mingshui formations (Campanian). Similar structures are also identified in the central Songliao basin. Thus, we propose that slab flattening to deepening during paleo-Pacific Plate subduction led to basin inversion. This process triggered the migration of high-pressure fluids and brecciated plastic rocks along pre-existing normal faults, which in turn produced the mud volcano system.

Gravity-driven failure is common on continental margins with salt or overpressured shale and is driven by a combination of margin tilt and depositional loading. Failure is characterized by proximal extension and distal contraction detached on the weak layer. In this chapter, I first summarize the drives, mechanics, and processes of gravity-driven failure, as well as the role of the distribution of the detachment layer(s). I then use worldwide examples to illustrate typical structural styles in the absence of diapirism. Finally, I discuss the initiation and evolution of salt diapirs, modern concepts on the nature of mobile shale bodies, and the role of allochthonous salt in partitioning the deformation.

Syntectonic deposits of the Mesopotamian flexural basin have been dated in the Lurestan and Fars salients in the Zagros foldbelt since the early 2000's but not in the Dezful embayment where most of the Zagros foreland oil is trapped. We use 237 samples collected for magnetostratigraphy to date shallow marine to fluvial-alluvial pre-growth and growth strata deposits along a >2700 m section in the NE flank of the Jarik anticline in north Dezful embayment. The Jarik anticline grew by a combination of compression and coeval diapirism like other structures in north Dezful embayment. The correlation of the local magnetostratigraphy with the Geomagnetic Polarity Time Scale indicates ages of 14.1 Ma and ~13.6 Ma for the bases of the Mishan and Aghajari formations. The bases of Lahbari Mb. and Bakhtyari Fm. are ~9.0 Ma and ~7.0 Ma. The onset of growth strata in the NE flank of the Jarik anticline is ~12.8 Ma with a duration of 5.8 Myr for this anticline. This study presents for the first time the age of syntectonic deposition and folding in the Dezful embayment that is essential to determine burial and generation of hydrocarbons in this oil-rich province. © 2019 Elsevier Ltd, This research has been partially funded by projects Alpimed (PIE-CSIC-201530E082) and Subtetis (PIE-CSIC-201830E039).

New versions of the universal Jd-Di exchange clinopyroxene barometer for peridotites, pyroxenites and eclogites, and also garnet barometer for eclogites and peridotites were developed. They were checked using large experimental data sets for eclogitic (∼530) and peridotitic systems (>650). The precision of the universal Cpx barometer for peridotites based on Jd-Di exchange is close to Cr-Tschermakite method produced by Nimis and Taylor (2000). Cpx barometer was transformed by the substitution of major multiplier for KD by the equations dependent from Al-Na-Fe. Obtained equation in combination with the thermometer of Nimis and Taylor (2000) allow to reconstruct position of the magma feeder systems of the alkali basaltic magma within the mantle diapirs in modern platforms like in Vitim plateau and other Southern Siberia localities and several localities worldwide showing good agreement of pressure ranges for black and green suites. These equations allow construct PTX diagrams for the kimberlite localities in Siberia and worldwide calculating simultaneously the PT parameters for different groups of mantle rocks. They give very good results for the concentrates from kimberlite lamproites and placers with mantle minerals. They are useful for PT estimates for diamond inclusions. The positions of eclogite groups in mantle sections are similar to those determined with new Gar–Cpx barometer produced by C. Beyer et al. (2015). The Fe rich eclogites commonly trace the boundary between the lower upper parts of subcontinental lithospheric mantle (SCLM) at 3–4 GPa marking pyroxenite eclogites layer. Ca-rich eclogites and especially grospydites in SCLM beneath Precambrian kimberlites occurs near pyroxenite layer but in younger mantle sections they became common in the lower parts. The diamondiferous Mg Cr-less group eclogites referring to the ancient island arc complexes are also common in the middle part of mantle sections and near 5–6 GPa. Commonly eclogites in lower apart of mantle sections are remelted and trace the high temperature convective branch. The Mg- and Fe-rich pyroxenites also show the extending in pressure trends which suggest the anatexic melting under the influence of volatiles or under the interaction with plums.

Available online xxxx Editor: T.A. Mather Keywords: Oman ophiolite dunitic mantle-crust transition zone syn-magmatic faulting melt-rock reactions high temperature hydrothermalism melt hybridization On Earth, most of the critical processes happen at the frontiers between envelopes and especially at the Moho between the mantle and the crust. Beneath oceanic spreading centers, the dunitic transition zone (DTZ) appears as a major interface between the upwelling and partially molten peridotitic mantle and the accreting gabbroic lower crust. Better constraints on the processes taking part in the DTZ allows improved understanding of the interactions between silicate melts and hydrated fluids, which act competitively to generate the petrological Moho. Here we combine mineral and whole rock major and trace element data with a structural approach along three cross-sections up to 300 m thick above the fossil Maqsad mantle diapir (Oman ophiolite) in order to understand the vertical organization of the DTZ with depth. Our results highlight that most of the faults or fractures cross-cutting the DTZ were ridge-related and active at an early, high temperature magmatic stage. Chemical variations along the cross-sections define trends with a characteristic vertical scale of few tens of meters. There is a clear correlation between the chemical variation pattern and the distribution of fault zones, not only for fluid-mobile elements but also for immobile elements such as REE and HFSE. Faults, despite displaying very limited displacements, enhanced both melt migration and extraction up to the crust and deep hydrothermal fluids introduction down to the Moho level. We propose that these faults are a vector for upwelling melt modification by hybridization, with hydrothermal fluids and/or silicic hydrous melts, and crystallization. Infiltration of these melts or fluids in the country rock governs part of the gradational evolutions recorded in composition of both the olivine matrix and interstitial phases away from faults. Finally, these faults likely control the thermal structure of the mantle-crust transition as evidenced by the spatial distribution of the crystallization products from percolating melts, organizing the transition zone into pure dunites to impregnated dunites horizons. In this context, the DTZ appears as a reactive interface that developed by the combination of three primary processes: tectonics, magmatism and deep, high temperature hydrothermal circulations. Accordingly, these features fundamentally contribute to the variable petrological and geochemical organization of the DTZ and possibly of the lower crust below oceanic spreading centers, and may be a clue to interpret part the heterogeneity observed in MORB signatures worldwide.

A submarine channel network, named Abalama Channel System (ACS), has been recognised in the subsurface of the Niger Delta continental slope. It overlies a mass-transport complex (MTC) and consists of six channel segments, delimited by five avulsion points and one confluence point. High-resolution 3D seismic data are used to investigate the development of the ACS and to describe the interaction between the channels and the underlying MTC. The MTC mainly consists of highly disaggregated materials (MTC matrixes) and in plan-view has a very complex fingered geometry, characterised by the presence of erosional remnants (remnant blocks). The different character of the MTC matrixes compared to that of the remnant blocks likely resulted in a bathymetry characterised by negative and positive relief, which provided the initial confinement for the channels of the ACS. In areas where the MTC-induced confinement was weak or decreased abruptly, channels tended to develop higher sinuosity, increasing channels instability and ultimately causing avulsions. Three ideal categories of submarine channel avulsions are observed. Type 1 is characterised by parent and avulsion channel having similar size and maturity; Type 2 is characterised by a large, high-maturity parent channel and a small, low-maturity avulsion channel; Type 3 emphasizes the larger scale and higher maturity of the avulsion channel compared to the parent channel. In the distal part of the study area, topography related to mud diapirs provided lateral confinement that captured flows avulsed at different times resulting in a channel confluence phenomenon. Submarine channel network evolution recorded by avulsion and confluence points represents an important research theme in deep-water sedimentology, as it controls the final distribution of sediments and the extension of sands in the whole deep-water depositional system; hence this study can be used to guide hydrocarbon exploration in analogue systems.

The Fars geological province is located in the southern part of the Zagros belt, which extends from the Kazerun fault zone to the Strait of Hormuz and is marked mostly by emergent Hormuz salt plugs and east–west structural trends. The sedimentary succession in the Zagros is 10–14 km thick resting on the metamorphic basement. Main detachment horizons in the Fars geological province are Hormuz salt, with the basal detachment horizon and evaporites of the Dashtak formation as the intermediate detachment layer. The structure of the Fars geological province is a result of the interaction of the Zagros orogeny and Hormuz salt diapirism. The geometrical characteristics of the folded structures change dramatically across the north–south trending Fars High. In the central Fars area, variations in the mechanical stratigraphy inherited from basement geometry are the main reason behind this difference in structural style. The folding style in the Fars geological province also is significantly affected by the interaction of the Hormuz salt diapirism and tectonics associated with the Zagros orogeny. The preexisting diapirs of the Hormuz salt controlled the spatial distribution, shape, size, and orientation of folds.

Detailed observations on Venus tessera terrain reveal the presence of tectonic structures, characterized by a subcircular trough, limiting an internal area with the average elevation of the surrounding terrain. We named this new type of tectonic structures Circular Troughs. Here we show the results of a morphometric study and a structural analysis based on data from 609 structures obtained through a global survey on Venus. Circular Troughs have an average outer radius of 12 ± 4.4 km, an average inner radius of 9 ± 3.9 km and an average trough width of 3 ± 1.2 km. A comparison with other tectonovolcanic structures on Venus shows that they are smaller and their size-distribution is more bounded. Although Circular Troughs show morphological similarities with some corona types, their size distribution is significantly smaller than coronae indicating a shallower geodynamic formation process. A shape preferred orientation analysis shows that Circular Troughs in Western Ovda are elongated parallel to long-wavelength tessera folds indicating that they are at least partially deformed by them, thus Circular Trough formation predates or it is contemporary with folding. A detailed structural analysis suggests that they were generated by small scale diapirism exclusively developed in tessera terrain. Several hypotheses could explain this small scale diapirism inside tessera terrain including volcanically driven compositional diapirism, small scale thermal diapirism or compositional cold diapirism, considering that the probable dessication of an ancient ocean would have generated evaporitic deposits in the past later buried by younger geological units., This research has been funded by Spanish Ministry of Science Grant PGC2018-095340-B-I00.

Mega-pockmarks, which can reach a few kilometers in width and a few hundred meters in depth, and associated fluid escape features in the Northern Zhongjiannan Basin, South China Sea, have received much attention in the recent years, due to their large variety of morphologies and sizes. In this work, an integrated interpretation of detailed multibeam bathymetry, conventional multi-channel seismic reflection and seismic oceanography sections covering the northern Zhongjiannan Basin, South China Sea, are used to image the seafloor morphology, the subsurface geology and the water column, in order to better understand the geological and oceanographic controls on the formation and evolution of the widespread fluid escape features in this region. Regional uplift and volcanism took place in this area near the Palaeogene–Neogene boundary and, during the Neogene–Quaternary post-rift thermal subsidence period, differential subsidence and diapirism deformed the overlying kilometer-scale successions. Mainly after the Miocene, focused flow of fluids originated at depth occurred along gas pipes, polygonal faults, tapered reflectors and faults into the shallow sediments, resulting in intense fluid blowouts and complex fluid escape structures on the seafloor. Our results show that elongated pockmarks, pockmark gullies and gullies in the northern slope are generally controlled by underlying buried channels and gullies. However, pockmark gullies and gullies in the southern slope are controlled by gravity sliding/slumping, along with crescent pockmarks developing parallel to water depth contours. To varying degrees, intense fluid escape activities associated with mud diapirism and gas escape in the study area resulted in mud extrusion and the formation of mud volcanoes, complex seabed morphologies and irregular pockmarks. Mega-pockmarks, collapse structures and blind valleys have formed at the apexes of tectonic uplifts related to volcanism and above basement highs, which suggests that these processes played a role in creating pathways for fluid escape. Bottom currents associated with the South China Sea Western Boundary Current, imaged here for the first time with the seismic oceanographic method, mainly flow to the south, and erode the seafloor, making pockmark walls and slopes of gullies and channels in the north steeper than those in the south. Some fluid escape structures, such as the mega-pockmarks and pockmark gullies, are buried by sediment transported by the bottom currents. Turbidity currents flowing downslope along the long pockmark gullies also erode the seafloor and make the NW slopes of the mud volcanoes less steep than those in the SE. Eddies imaged by the seismic sections may also play a role in transporting sediment to the deep sea in this area. Some of the reported fluid escape structures are still active, as indicated by the fluid pathways that reach the seafloor and plumes in the water column imaged by the seismic sections.

In this paper we address the problem of the distinction between diapiric, salt-driven and compressional structures, using the outstanding example of the Central High Atlas (Morocco). A remagnetized component carried by magnetite has been isolated in 32 new paleomagnetic sites. It is characterized by: maximum unblocking temperatures around 450 °C, syn-folding behavior and normal polarity. These 33 mean paleomagnetic directions were analyzed together with other 68 from published works around the study area to construct a robust paleomagnetic dataset along a cross-section perpendicular to the main structures. The remagnetization direction (n: 100, Dec: 332.2°, Inc: 34.5°, η: 6.2°, ξ: 2.0°, A/n: 6.427°) and the paleo-dip of beds (the attitude of the beds at the remagnetization occurrence) were calculated through small circle methods. The remagnetization can be dated as ca. 100 Ma. Because of its occurrence between the extensional and compressional periods, this remagnetization offers the possibility of restore the basin to its pre-inversion geometry. Comparison between present-day and pre-inversion structure allows discriminating three different evolutionary patterns: (i) thrusted and welded salt-walls mainly structured during the extensional stage (Ikkou ridge) with steep limbs close to the salt-wall core. (ii) Jurassic salt-walls with weaker deformation, restricted to the areas adjacent to the structure (Tadaghmamt and Timedouine); in this case, Cenozoic compression is limited to welding of the salt-walls and buttressing of the sedimentary sequences against faults. (iii) salt-rollers gently initiated during the Jurassic (Toumliline diapir), thrusted during the Cenozoic compression. Results show the importance of salt tectonics both during extension and compression, as well as the control of the compressional features by the inherited extensional structures. The performed restorations prove that paleomagnetism is a useful, independent tool to obtain palinspastic restorations and to separate, and quantify, the imprint generated during the basinal stage from the inversional features., MINECO (Spanish Ministry of Economy and Competitiveness) cofinanced by the ERDF (European Union) (research projects CGL2012-38481 and CGL2016-77560)

Felsic and mafic magmas in continental crustal settings are derived by melting of the lower crust and mantle, respectively. This occurs in subduction zone, collisional, extensional and intraplate settings. This chapter reviews the linked processes of magma segregation, ascent and emplacement in the deep to mid-crust, with an emphasis on felsic magmas and continental crustal settings. We follow felsic magmas from their segregation and extraction from deep crustal anatectic zones, to their focusing into either bulk or channelled ascent pathways, to their emplacement in large tabular magma reservoirs in the mid-crust. We argue that crustal-scale magma plumbing systems are self-organised from the bottom-up, whereby the efficiency and rate of melt segregation and the mechanism of magma focusing in source regions determine the mode of magma ascent and eventual length and time scales of pluton location and growth in the mid-crust.

Methane can be released from the vast marine hydrate reservoirs that surround continents into oceans and perhaps the atmosphere. But how these pathways work within the global carbon cycle now and during a warmer world is only partially understood. Here we use 3-D seismic data to identify what we interpret to be a gas venting system that bypasses the hydrate stability zone (HSZ) offshore of Mauritania. This venting is manifested by the presence of the acoustic wipe-out (AWO) across a densely faulted succession above a salt diapir and a set of morphological features including a substantial, ∼260 m wide and ∼32 m deep, pockmark at the seabed. The base of the HSZ is marked by a bottom simulating reflector (BSR) which deflects upwards above the diapir, rather than mimicking the seabed. We use a numerical modelling to show that this deflection is caused by the underlying salt diapir. It creates a trapping geometry for gas sealed by hydrate-clogged sediment. After entering the HSZ, some methane accumulated as hydrate in the levees of a buried canyon. Venting in this locality probably reduces the flux of gas to the landward limit of feather edge of hydrate, reducing the volume of gas that would be susceptible for release during a warmer world.

The Asturian Basin is one of several basins developed in the North Iberian Margin during the opening of the Bay of Biscay. The infill of the basin ranges from the Upper Paleozoic to the present, holding a thick Mesozoic sedimentary sequence with Keuper evaporites at the base and up to 4000 m of Jurassic and Cretaceous deep marine sediments. The structural architecture of the offshore Asturian basin is strongly related to salt tectonics. We present new interpretations showing minibasin-scale halokinetic features, diapir geometry, and presalt structures that illustrate the relationship between diapirism and regional tectonic events. Two salt tectonic domains are identified based on the style of salt deformation: a Western Salt Domain, dominated by vertical salt walls, and an Eastern Salt Domain toward the deeper part of the basin, with fewer diapirs and more salt-detached thrust faults. Additionally, this domain shows more prominent salt sheets with greater lateral extent. We propose a halokinetic structural evolution that is representative for the interpreted salt-related structures: (1) Early Permian to Triassic stretching was followed by Keuper evaporite deposition; (2) Upper Jurassic to Lower Cretaceous rifting triggered reactive to passive diapirism over the footwalls of presalt normal faults; and (3) Paleogene shortening caused existing diapirs to be rejuvenated and squeezed, developing salt sheets before getting buried by the Miocene posttectonic sediments.

The continental edge of the Western Iberian Margin is marked by two contrasting basins, the mostly onshore Lusitanian Basin and the mostly deepwater Peniche Basin. These two rift basins were originated during the opening of the North Atlantic Ocean and have similar characteristics and are geographically separated by an elongated basement high that strikes quasiparallel to the Portuguese coastline. The basins evolved during the Mesozoic as part of the Iberia Peninsula. The petroleum geology history of the relatively unexplored Lusitanian Basin is reconstructed in this chapter through the detailed stratigraphic mapping of outcrop and legacy exploratory drilling. The lesser-known Peniche Basin, to the west of the bounding basement high, is part of the deepwater continental margin of Iberia; knowledge of this basin is derived from seismic stratigraphic comparisons with Lusitanian Basin. The Lusitanian Basin developed over a Paleozoic basement terrane amalgamated during the Variscan orogeny. Triassic rift siliciclastic infill was followed by thick Norian to Hettangian salt-rich clays deposited in continental and coastal evaporitic sabkhas, named the Dagorda Formation. Carbonate deposition was installed during the Early and Middle Jurassic with marine sediments of epicontinental ramp and platform environments. The late Jurassic characterizes a new rifting episode with realignment of the old basement structuring and erosion of the basin rift shoulders. The Early Cretaceous sedimentation was marked by the break-up of the North Atlantic whereas the late Cretaceous marks the tectonic inversion of the basin and its continued deformation. Salt pillows deforming the Late Triassic Dagorda unit date back from Early to Mid-Jurassic, whereas Late Jurassic tectonics and basin inversion are contemporaneous with the rise of salt diapirs and the massive salt walls of the Lusitanian Basin. Salt rise occurred preferentially through Hercynian basement faults continuing unabated throughout the Cenozoic. The late Cretaceous piercing of some diapirs and intense deformation along the bodies of the buried and piercing salt domes are related to the Alpine compressive events. These deformations continued until recent times along the bodies of buried piercing salt diapirs and salt canopies related to the Alpine contraction. Petroleum exploration is active in both basins with acreage award commitments that include state-of-the-art seismic survey imagery to be followed by exploratory drilling. Salt structuring shaped the basins' architecture, providing the basis for structural closures or stratigraphic terminations, which are paramount to all of the deepwater hydrocarbon prospects that involve the presalt Triassic red-beds play, the lower Jurassic salt diapir play and the postsalt upper Jurassic and Cretaceous turbidites play.

The Ionian fold-and-thrust belt (FTB) is formed by a piggyback sequence of W-directed thrusts that were emplaced over the Apulian Platform during the late Oligocene to the latest Miocene. From bottom to top, the Cika, Kurveleshi, and Berati belts constitute the three main thrust sheets of the Ionian FTB. All of them contain a rather similar thick sequence (~ 2–3 km) of basinal, pelagic carbonates of latest Triassic to Eocene age. The Late Triassic evaporite sequence (in Keuper facies) acts as a regional decoupling level for thrusting during the Alpine contraction. The structure of three major structures of Triassic evaporites has been studied in detail in central and southern Albania. They document different styles of salt tectonics in the precursor Ionian basin and different initial conditions for the structural style during the subsequent Alpine contraction. The Dumre diapir is interpreted as a thick salt plug, which has been squeezed and displaced toward the west, promoting a marked change in the geometry of the overlying thrust that passes from a frontal to a lateral hanging-wall ramp. In southern Albania, a variation of the Triassic salt structures was reconstructed toward the W and SW, possibly representing a downslope evolution from salt pillows (Delvina and Picari-Kardhiq) to massive salt walls (Butrinti-Xarra). The geometry of the Ionian FTB, also incorporating the role played by different Triassic salt structures, constitutes a refined scenario for hydrocarbon exploration in central and southern Albania.

The Permian-Cretaceous Polish Basin belonged to the system of epicontinental depositional basins of Western and central Europe and was filled with several kilometers of siliciclastics, carbonates, and also thick Zechstein (Upper Permian) evaporites. The Polish Basin was inverted in Late Cretaceous-Paleocene times. Presence of the Zechstein evaporites gave rise to formation of various salt and salt-related structures. These are either peripheral structures such as salt rollers, thin-skinned half grabens, and low-relief salt pillows located within flanks of the Polish Basin, or complex salt diapirs and high-relief salt pillows located within its axial part. Late Cretaceous inversion caused significant compressional reactivation of salt diapirs. Their inversion-related growth strongly influenced Late Cretaceous depositional systems characterized by localized unconformities and thickness reductions. The main petroleum system is related to hydrocarbon accumulations within the Carboniferous and Rotliegend reservoirs sourced by the Carboniferous shales. The secondary Zechstein Main Dolomite petroleum system contains source and reservoir rocks, and the regional seal.

The principal objective of this paper is to summarize the large data set gathered in the last few years on the Early-Middle Jurassic diapiric evolution in the well-exposed Central High Atlas in Morocco. Field data on both structural geology and sedimentology of halokinetic sequences, significant remote sensing mapping using good quality satellite images, thermal modeling and subsidence analysis, balanced and restored cross sections, and analog modeling allowed us to construct an integrated tectono-sedimentary interpretation of a salt-related rift basin. Three characteristic regions are summarized here to show the tectonic and diapiric evolution of the study region: Tazoult, Azourki, and Imilchil. Salt ridges (Tazoult, Jbel Azourki, and Tassent salt walls) above blind basement faults developed a polygonal array bounding thick synclines (minibasins) with different orientations. The Imilchil minibasins show diachronous age of their infill, which is a typical characteristic of diapiric regions. The Tazoult and Jbel Azourki salt walls developed an allochthonous salt body starting during the Late Pliensbachian-Aalenian time. Although only Lower and Middle Jurassic halokinetic sedimentary sequences are preserved in most of the Central High Atlas, younger synclines (minibasins) along the northern boundary of the Atlas (Demnate region) show development of Late Jurassic and Early Cretaceous minibasins. At the larger scale, the diachronous evolution of the extension and diapirism along the Atlas Basin suggests that diapirism and salt withdrawal play an important role during the development of the High Atlas in Morocco, Saharan Atlas in Algeria, and Tunisian Atlas in a similar way as it is fabulously imaged across the onshore and offshore Atlantic Moroccan basins., This study is a contribution of the Group of Dynamic of the Lithosphere (GDL-ICTJA-CSIC) as part of a collaborative research project funded by Statoil Research Centre, Bergen (Norway). The Spanish Ministry of Education and Science provided additional funding (MEC) through the projects Intramural Especial (CSIC 201330E030) and MITE (CGL 2014-59516).

The southern Norwegian Barents Sea and the Northeast Greenland shelf are conjugate margins that formed a contiguous salt basin during the Pennsylvanian to Early Permian. Modern seismic data and cross-section restoration are used to evaluate three aspects of the salt tectonics: the relationship between evaporite deposition and rifting; the nature of the Gipsdalen Group layered evaporite sequence (LES); and the origin and evolution of salt-related deformation. The evaporites were originally thicker in basins and thin or absent on structural highs, but the relationship between rifting and salt deposition varied. To the east, the salt filled broad, mostly unfaulted sag basins and was thus primarily postrift. In the Nordkapp and Danmarkshavn basins, it was thicker in prominent half-graben but also present on the rift shoulders, suggesting that the salt was syn- to early postrift. In the Tromso basin, the salt appears confined to the basin center and thus was probably synrift. The Gipsdalen Group is an LES comprising halite, anhydrite, carbonates, and siliciclastics. On rift shoulders, evaporites were deposited in between carbonate build-ups. In basins, several halite-dominated intervals were separated by relatively competent strata that became completely disrupted in diapirs. The triggers and evolution of salt-related deformation varied widely. The Tromso and Danmarkshavn basins were characterized by thick-skinned extension, with drape folds, reactive diapirs related to presalt faults, and thin-skinned salt rollers. In Greenland, minor gravity-driven deformation generated salt-cored anticlines. In the Nordkapp basin, Lower Triassic progradation led to pillow formation over presalt faults, with passive diapirism facilitated by erosional thinning of the roofs. Erosional breakthrough also occurred at the Tiddlybanken diapir, but the initial pillow was formed by Triassic contraction. Finally, Cenozoic shortening generated several salt-cored domes over inverted basins.

Integrating seismic, well information, and geological surface data, a tectonic overview of the role played by the Triassic in the structural evolution of the Southern Pyrenees is presented. Several interpreted seismic lines and regional cross sections based on surface and subsurface data illustrate how Triassic evaporites and shales of the Muschelkalk and Keuper facies acted as the main detachment levels in the southward translation of the main thrust sheets. 2D seismic data tied to well-log data, together with regional cross sections, reveal that several tectonic contacts, classically described as lateral ramps, are bounded by large normal faults, often inverted during the Alpine compression. These normal faults are rooted into the Triassic evaporitic section and represent salt withdrawal surfaces that define salt rollers. Most of the diapirs and halokinetic structures in the Southern Pyrenees are located along the frontal foothills, referred to as Sierras Marginales, and in the core of the larger structures of the main South Pyrenean Units like the Boltana, Olson, and Mediano anticlines. Diapirs from this frontal zone are detached and unroofed, suggesting southward thrust transport after emplacement. Additionally to salt-related structures, evidence of passive margin salt-related structures can also be found in the Nogueras Zone and neighboring units, represented by diapirs or salt rollers as observed in present-day passive margins of salt provinces.

The special geological bodies in this chapter refers to the geological bodies that have adverse effects for the stability of ocean engineering foundations, they belong to the potential hazard geology factors, their existence makes the engineering site condition become more complicated, and under the action of an external force they may cause foundation instability or drastic changes. This chapter analyzes and discusses the formation conditions, distribution characteristics, and induced engineering hazards of the representative special geological bodies, namely mud diapirs, mud volcanoes, coral reefs, and ancient river channels.

An overview of the structural evolution of the Basque-Cantabrian Basin (BCB) based on surface geological data, exploration wells and 2D seismic is summarized in four geological N-S cross sections. Most of the folds and thrusts of the BCB are reflected in these cross sections, including some notable structures of the basin, which were originated due to Late Jurassic-Early Cretaceous salt tectonics. The main salt-related structures and their influence in the Late Jurassic-Early Cretaceous sedimentation in the basin are highlighted. The structure of the eastern and western zones of the basin evolved differentially as a result of contrasting initial rift geometries. The difficulty of any structural reconstruction of the BCB using a uniform orientation of the main shortening direction uniquely is discussed. The Tertiary compression has produced an important shortening in both the Mesozoic cover and the basement, where a strike-slip (transpressive) tectonic model is proposed to accommodate the deformation of the sedimentary cover. Salt tectonics is also demonstrated to have played an important role in some of the petroleum system processes in the BCB, controlling the hydrocarbon trap generation, as well as the geochemical evolution and maturation of the source rocks.

A variety of distinct salt tectonic features are present in northern and central Tunisia. In the Tunisian Tell and Atlas, the allochthonous nature of the Upper Triassic (Carnian to Norian) salt has been confirmed in several exploration wells, and also supported by reflection seismic evidence. The structural context of these domains is basically that of a NE-SW trending system of inverted early Mesozoic rift basins, where subsequent, multiple late Mesozoic to Cenozoic compressional episodes were responsible for the formation of a SE-vergent thrust-fold belt. This part of Tunisia remains an exploration challenge despite the clear evidence for the presence of a petroleum system. In central Tunisia, in the Kairouan segment of the onshore Pelagian basin, the interpretation of 2D seismic reflection data and exploration wells shows that the Middle to Upper Triassic evaporites formed numerous large diapiric salt walls. These regional-scale salt walls show important along-strike variations, alternating between reactive and active diapir segments. Due to several periods of regional extension, halokinesis began as soon as the early Jurassic and continues until the present. The deformation of individual salt diapirs and diapiric salt walls reflects distinct tectonic phases in the evolution of the basin. The interpreted styles of salt tectonics in the Kairouan region offer a better understanding of the timing and geometry of the salt-related hydrocarbon traps in central Tunisia.

In northwestern Europe, the upper Permian Zechstein evaporites are a highly efficient seal for Carboniferous gas trapped in clastic Rotliegend reservoirs. The Zechstein evaporite succession and postsalt sediments experienced complex deformation during several tectonic phases in the German and Dutch part of the Southern Permian Basin, including extension and compression or transpression. However, controlled by late Permian topography, the number and thickness of the individual evaporite cycles vary, mainly correlating with the basin, slope, and platform settings of the Zechstein Sea. The main trigger mechanisms for early salt movement comprise extension and rafting of Lower Triassic sediments, syn-depositional fault activity within the subsalt, subsequent differential loading of postsalt sediments, and intrasalt heterogeneities. This latter caused thin-skinned salt tectonics with passive diapirism, which seeded the number of the salt highs observed today. Later reactivation, cessation, or formation of new salt highs was triggered by the massive change from extensional to compressional tectonics that began in Cretaceous times. Regional fault patterns were reactivated or newly formed during these tectonic phases, and they are often marked by elongated salt walls. A large drop in tectonic stresses since the onset of the Cenozoic caused a rather tabular draping of thick clastics and marks the cessation of major salt movements across the greater part of the Dutch and German Zechstein Basin. Since then, most of the Zechstein salt has been considered to be at rest.

The salt basins of Morocco and Mauritania were developed on the NW African margin of the Central Atlantic. The age of the salt in Morocco is Upper Triassic to Liassic, as Central Atlantic Magmatic Province basalts can be found within it. The age of the Mauritanian salt is poorly constrained but it is considered analogous to that of the salt found in Morocco. The salt in both basins deposited during the synrift, or more specifically, the syn-stretching stage of continental rifting between the African and North American plates. It therefore has a patchy, discontinuous original distribution in fault-controlled extensional troughs. The map-view distribution of the large variety of allochthonous salt tectonic features is interpreted to broadly reflect the pattern of the underlying extensional troughs. Whereas the much larger Moroccan salt basin has 200 + km wide segments extending even onshore, the smaller offshore Mauritanian salt basin has only an average 50 km width in a dip direction. Assuming a system of individual troughs in the proximal part of the syn-stretching margin, the present-day distribution of the salt diapirs, tongues and sheets may correspond to only a few extensional depocenters in Mauritania. As most of the allochthonous salt features are detached from their feeders, the average thickness of the original prekinematic salt is estimated to average no more than a few hundred meters over the entire area of the salt basin. A major difference between the Moroccan and Mauritanian salt basins is the role the salt plays in providing regional decollement levels for thrust-fold belt segments during the Cenozoic inversion of the margin associated with the Atlas mountain building. With the Cenozoic inversion more prominent in Morocco, the resulting overall pattern of salt tectonics is more complex in Morocco than in Mauritania.

Most of the methods currently used for pore pressure prediction in sedimentary basins assume one-dimensional compaction based on relationships between vertical effective stress and porosity. These methods may be inaccurate in complex tectonic regimes where stress tensors are variable. Modelling approaches for compaction adopted within the geotechnical field account for both the full three-dimensional stress tensor and the stress history. In this paper a coupled geomechanical-fluid flow model is used, along with an advanced version of the Cam-Clay constitutive model, to investigate stress, pore pressure and porosity in a Gulf of Mexico style mini-basin bounded by salt subjected to lateral deformation. The modelled structure consists of two depocentres separated by a salt diapir. 20% of horizontal shortening synchronous to basin sedimentation is imposed. An additional model accounting solely for the overpressure generated due to 1D disequilibrium compaction is also defined. The predicted deformation regime in the two depocentres of the mini-basin is one of tectonic lateral compression, in which the horizontal effective stress is higher than the vertical effective stress. In contrast, sediments above the central salt diapir show lateral extension and tectonic vertical compaction due to the rise of the diapir. Compared to the 1D model, the horizontal shortening in the mini-basin increases the predicted present-day overpressure by 50%, from 20 MPa to 30 MPa. The porosities predicted by the mini-basin models are used to perform 1D, porosity-based pore pressure predictions. The 1D method underestimated overpressure by up to 6 MPa at 3400 m depth (26% of the total overpressure) in the well located at the basin depocentre and up to 3 MPa at 1900 m depth (34% of the total overpressure) in the well located above the salt diapir. The results show how 2D/3D methods are required to accurately predict overpressure in regions in which tectonic stresses are important.

The Sarvestan plain is bounded by highly elevated anticlines associated with thrusts or transpressional faults and hosts the NNW–SSE Sarvestan transfer zone. Surface and subsurface geological data, and 22 seismic lines allowed us to reconstruct the 3D geometry of the area. Mixed layer illite–smectite and 1D burial and thermal modelling were used to constrain the complex geological evolution of the Sarvestan plain where inherited structures strongly controlled the geometry of syn- to post-collisional contractional structures. Paleozoic–Mesozoic rifting related extension generated E–W and NNW–SSE normal fault systems. Such faults were associated with changes in the thickness of the sedimentary cover. Lateral facies changes were later induced by the Cretaceous obduction of ophiolites, cropping out some tens of km north of the study area. During the Miocene the footwall and the hanging wall of the Sarvestan Fault had different thermal evolution. This is tentatively explained by flow of Cambrian salt from the plain area towards the hanging wall of the Sarvestan Fault, associated with salt diapirism during Lower–Middle Miocene time. Salt tectonics is invoked also to explain, at least in part, the development of the overturned anticline in the hanging wall of the Sarvestan Fault. An early phase of contractional deformation occurred in the Middle Miocene (since 15 My, i.e., after the deposition of the Agha Jari Fm) generating the E–W oriented folds buried below the plain, likely inverting inherited normal faults. The erosion of these structures was followed by the deposition of the Bakhtiari Fm conglomerates in Middle–Late Miocene times. A later phase of contractional tectonics generated the thrust faults and the anticlines bounding the Sarvestan plain some 6–5 My ago. The Sarvestan dextral transpressional fault, that likely acted as a strongly oblique ramp of the Maharlu thrust, mainly structured in this period, although its activity may have continued until present.

Detailed morphological analyses of a Pleistocene-Holocene submarine channel system in terms of its hierarchical framework, were carried out using a 3D seismic volume from offshore Espirito Santo, SE Brazil. The channel morphology shows marked variations, with five segments (Segments a to e) being identified along its full length. For example, the cross-sectional area of the channel decreases by a factor of 70 from Segment a to Segment c, and is then followed by a nearly four-fold increase from Segment c to Segment d. The significant changes in channel morphology relate to temporal and spatial variations in flow volume within the channel. In the same channel system, the valley reveals three distinct segments (Segments A to C), with similar aspect ratios but marked variations in morphology along the valley distance. Valley morphological changes are chiefly affected by erosional processes. Segment B is characterised by the largest valley-base width, valley width, and cross-sectional area compared to the other two segments. Valley enlargement in Segment B results from relatively high degrees of lateral channel migration and associated cut bank erosion, leading to the widening of the valley, especially the valley base. In Segment C, the valley is characterised by inner bank erosion in the form of shallow-seated mass failures, which only enlarged the upper part of the valley wall. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. salt diapirs, tributaries, overbank collapse) in the development of channel systems. Hence, the morphological analyses developed in this work provide an effective tool for studying channels and valleys on continental slopes around the world.

Details of fluid flow mechanisms are presented. Porosity and permeability considerations are introduced including the data requirements for quantitative estimations. The link between methane seepage and fluid flow characteristics is explained and details of evidence from seismic data analysis are given together with amplitude versus offset (AVO) modeling. The uncertainty analysis of the single bottom-simulating reflector (BSR) and double BSR (DBSR) is discussed in detail with real data examples from offshore USA and India. The hydrocarbon seepage-to-leakage mechanism is explained with seismic anisotropic modeling of real parameters and correlated with field data examples. The cold seep plumbing system, which includes structural elements such as source of the fluid, hydrocarbon venting structures, pockmarks, mud diapirs, seismic chimneys, and pipes, is discussed. The plumbing mechanism is explained with reference to structural fluid flow characteristics, including faults and fractures, and sedimentary fluid flow characteristics, including a discussion on mud volcanoes and sand injection. The complexity of the plumbing mechanism with its changing conduit system and associated geological structures is presented.

Evaporite successions may undergo significant lithostratigraphic changes laterally and vertically in tectonically-active basins. The Las Minas Gypsum, a lacustrine unit of Late Tortonian age and up to 160. m thick in the Las Minas-Camarillas basin (SE Spain), consists of a number of shallowing-upward cycles. Each cycle is made up of a lower interval with marl and carbonate, and an upper interval with gypsum. In the upper interval, the base displays carbonate-gypsum laminites (couplets, yearly microcycles) showing a large variability of textures and fabrics; gypsum textures are cumulates and bottom-grown crystals. Laminites are overlain by selenitic gypsum. The carbonate is a primary dolomite induced by sulphate-reducing bacterial activity. Native sulphur was formed in early diagenesis and during exhumation was partly transformed into late diagenetic gypsum. The isotopic compositions of gypsum suggest that the sulphate mainly derived from chemical recycling of Triassic evaporites; however, marine sulphate was probably supplied by episodic marine incursions. A perennial saline lake characterized by irregular bottom topography and depositional settings with variable subsidence ratios is interpreted. In addition to climate, saline diapirism, Neogene volcanism, synsedimentary faulting and seismicity influenced the evaporitic deposition. Las Minas-Camarillas basin is an example of how in tectonically active zones different factors interplay to produce significant variability of the evaporitic sedimentation and cyclicity. © 2014 Elsevier B.V., This study was supported by projects CGL2005-05337 and CGL2009-11096 of the Spanish Government and 2009-SGR1451 of the Catalan Government, and a Ramón y Cajal programme (L. Gibert) of the Spanish Government. One of the authors (J.P. Calvo) is included in the Research Group UCM-910607 (Universidad Complutense Madrid).

Halite is the most soluble common mineral. Salt karst is concerned with extremely soluble and erodible rock-salt geomorphology, which demonstrates a dynamic end member to karst processes. Salt outcrops are rare, due to the high solubility, and common total dissolution underground, but subsurface salt is common, and commonly associated with environmental problems. These are associated with salt hazards, generally due to anthropogenic modification of hydrological systems, causing aggressive water to attack salt rock. Most salt outcrops appear under desert conditions, where the salt mass escapes total dissolution. In such outcrops, runoff produces well-developed karst terrains, with features including karren, sinkholes, and vadose caves. Existing salt relief is probably not older than Pliocene, but the known well-developed salt karst systems are of Quaternary age. Up to now, accessible caves that have been radiocarbon dated are of Holocene age, indicating rapid formation of new caves and destruction of old ones. The largest cave is the 6.7-km-long Malham Cave, Mt. Sedom (Israel). Such caves are dendritic vadose caves with shafts and canyons, whose downstream part joins smoothly the base level or ends within the salt body.

The Gulf of Cadiz, NE Atlantic, represents an area of extensive formation of methane-derived authigenic carbonates (MDAC), indicative of fluid seepage. These MDAC, that reach extraordinary length and thickness, were geophysically mapped and sampled and the recovered carbonate-cemented material has δ13C values as low as − 56.2‰ VPDB, indicating methane as the major carbon source. The MDAC form two main lithologic groups, one mainly comprising dolomite and the second dominated by aragonite. The dolomite-dominated samples were found along fault-controlled diapiric ridges, on some mud volcanoes and mud diapirs, all on the pathway of the Mediterranean Outflow Water, and along fault scarps. Aragonite pavements were found associated with mud volcanoes and along fault scarps, but are otherwise not restricted to the pathways of the Mediterranean Outflow Water. Based on the results from this study, we propose that the two lithologic groups reflect different geochemical formation environments associated with a formation model based on their morphology, mineralogy and geochemistry. The aragonite-dominated samples represent precipitation of authigenic carbonates at the sediment–seawater interface or close to it, in a high alkalinity environment resulting from anaerobic oxidation of methane-rich fluids venting into sulphate-bearing porewaters. In contrast, the dolomite-dominated samples result from cementation along fluid conduits inside the sedimentary column with a somewhat restricted seawater ventilation. The dolomite chimneys form in places presently swept by the strong flow of the Mediterranean undercurrent so that the unconsolidated sediments are eroded and the chimneys are exposed at the seafloor. The widespread and large abundance of MDAC is a direct evidence of extensive methane seepage episodes in the Gulf of Cadiz. The coincidence of the different lithologic types in close spatial and temporal association indicates a persistence of seepage episodes in some structures over large periods of time, Centro de Estudos do Ambiente e do Mar, Universidade de Aveiro, Portugal, Department of Geosciences, University of Aveiro, Portugal, UNESCO Center for Marine Geosciences, Moscow State University, Russia, Geological Institute, Eidgenössische Technische Hochschule Zürich, Suiza, MARUM-Center for Marine Environmental Sciences, University of Bremen, Alemania, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, España, Instituto Geológico y Minero de España, España

Publisher Summary The Gulf of Cadiz is located in the SW Iberian Peninsula and can be considered as the structural front of the Betic-Rifian Arc, located at the westernmost tectonic belt of the Alpine–Mediterranean convergence zone between the African and Eurasian plates. This front is an olistostrome, comprising a large volume of shale and salt diapirism. A variety of seep-related geomorphic features has been described in this region, such as mud volcanoes, carbonate mounds, pockmarks, brine pools, and gas-related sediments. These structures contain precipitates in the form of slabs, pavements, and chimneys, generated by aggregation of carbonate cement resulting from microbial oxidation of gas emissions. These increase the complexity of the soft bottoms where they are formed, promoting a mixture of hard- and soft-bottom fauna. On stable hard substrates, corals, gorgonians, and sponges increase this complexity even more, resulting in a higher number of species than in adjacent soft bottoms. In adjacent soft bottoms, fisheries for different demersal and benthic species occur, although no detailed information is available on their impact upon mud volcano communities. Mud volcanoes, pockmarks, and other fluid escape structures are common along the Iberian margin of the Gulf of Cadiz. They are interpreted as indicators of gas-rich, overpressured sediments occurring at different depths. Geomorphic features related to fluid flow and availability of hard bottoms (e.g., chimneys, slabs) is influenced by the erosion patterns that affect each volcano. Therefore, different habitat types occur in association with different volcanoes.

This contribution examines the nature of carbonate platforms within marine rifts. It is presented through description and discussion of two relatively well studied carbonate dominated rifts: the surface outcrops of the Cenozoic of the Gulf of Suez – Red Sea – Gulf of Aden and the subsurface of the Cretaceous of the South Atlantic. Carbonate platforms are commonest in the late syn-rift and rift to drift phase of extensional basin evolution and mainly occur on fault-block highs, over salt diapirs or on delta-tops. These different types of carbonate platform can be studied in detail from the Cenozoic outcrops and shallow subsurface from the Middle East and facies and sequence stratigraphic models erected. Such models can be used as an aid to interpret the subsurface Cretaceous examples from the South Atlantic. During the later stages in the evolution of extensional basins (drift phase), these localised platforms develop into thick and extensive, subsiding margin platforms.

Submitted by Patrícia Correia (patriciacorreia@ua.pt) on 2019-02-22T15:19:59Z No. of bitstreams: 1 Margreth et al. - 2011 - Growth and demise of cold-water coral ecosystems o.pdf: 1671035 bytes, checksum: d91e02c8655200c4c2edab1ea6e3cd9d (MD5) Approved for entry into archive by Patrícia Correia (patriciacorreia@ua.pt) on 2019-02-22T15:20:14Z (GMT) No. of bitstreams: 1 Margreth et al. - 2011 - Growth and demise of cold-water coral ecosystems o.pdf: 1671035 bytes, checksum: d91e02c8655200c4c2edab1ea6e3cd9d (MD5) Made available in DSpace on 2019-02-22T15:20:14Z (GMT). No. of bitstreams: 1 Margreth et al. - 2011 - Growth and demise of cold-water coral ecosystems o.pdf: 1671035 bytes, checksum: d91e02c8655200c4c2edab1ea6e3cd9d (MD5) Previous issue date: 2011 This study is funded by the Swiss National Science Foundation Projects 200021-111694 and 200020-117928, with additional support from the Commission for Oceanography and Limnology of the Swiss Academy of Sciences. Cruise TTR 17-Leg 1 (SAGAS-08 Cruise) was funded by the Spanish Projects CTM 2005-08071-C03-01 and CGL200613327-C04-04 (R&D National Plan of the Ministry of Science and Innovation, Spain) and by UNESCO. LMP participation was supported by SAGAS project and the ESF EuroCORE-EuroMARGINS project MVSEIS (O1-LEC-EMA24F/PDCTM72003/DIV/40018). AR was financially supported by the Deutsche Forschungsgemeinschaft projects TRISTAN and Paläo-TRISTAN (Du 129/37-2 and Du 129/37-3), which he gratefully acknowledged. The authors are deeply indebted to the Training Through Research Program (TTR). Thanks to the captain and crew of the R/V Professor Logacev (Moscow), thanks to Prof M. Ivanov (Moscow) and his students for support and collaboration during the cruise. C.F. Lopez Rodriguez is thanked for sampling core TTR17-MS419G at the core repository of University of Granada. L. Haxhiaj (IFM-GEOMAR) is thanked for his support with stable isotope measurements. P. Grootes and M. Hüls from the Leibniz-Laboratory for Radiometric Dating and Stable Isotope Research at Kiel University are greatly acknowledged for performing AMS 14C dating. We thank three anonymous reviewers for their constructive feedback on the manuscript. published

10 pages, 7 figures, Our analysis of geoacoustic data from the Middle American margin provides an insight into the formation and evolution mechanisms of mound structures observed on the continental slope offshore Costa Rica. Based on high-resolution deep-towed sidescan sonar and sub-bottom profiler (SBP) data six different mound and fluid seepage structures at the Hongo mound field are characterized in detail. The Hongo mound field is located on the lower continental slope offshore Nicoya peninsula in the prolongation of the subducting Nicoya fracture zone. The mounds have oval to circular shapes with diameters of 500-1600 m and relief heights of 60-100 m. High backscatter anomalies near the mound summits indicate carbonate precipitation and focused fluid seepage activity within the last 10 ka. The data do not show evidence for mud extrusions and the structures were probably formed by a combination of carbonate precipitation and mud diapirism. Based on seismic stratigraphy analysis, mud diapirism is at least active since 42.5-57 ka and average vertical growth rates vary between 6-24 cm/ka. However, if diapirism represents the dominant mound evolution mechanism, mound heights of 80 m point to much older mound ages of 330-1330 ka. © 2009 Elsevier B.V. All rights reserved, Funding for the cruise and subsequent work has been provided by the German Ministry of Education and Research (BMBF) and the German Research Foundation (DFG). This publication is contribution 179 of the Sonderforschungsbereich 574 “Volatiles and fluids in subduction zones” at Kiel University

In 2001, a high-resolution seismic survey was conducted for the detailed study of the distribution, both spatially and vertically, of gas hydrate and free gas accumulations west of Svalbard, as part of the HYDRATECH and INGGAS projects. High-resolution single-channel seismic reflection and the 4-component ocean-bottom seismometer (OBS) data illustrate the widespread nature of gas hydrates and free gas accumulations north of the Knipovich Ridge off Western Svalbard, by the presence of a nearly-continuous polarity-reversed bottom-simulating reflection (BSR) on down-slope seismic profiles. In the absence of a distinct and/or a continuous BSR, it is the sudden change in reflection amplitude and frequency content that marks the base of the hydrate zone. The BSR coincides with the top of the free gas zone. Compressional wave velocity analyses and modelling reveal increased velocities above the BSR attributed to a gradual increase of partial hydrate saturation (6–10% of pore volume). A sharp drop in compressional-wave velocity across the BSR is due to free gas accumulation. The sub-bottom depth of the BSR closely matches the calculated stability limit for methane hydrates. To the east of the Knipovich Ridge, mud diapirism is observed in a deeper basin (∼2250 m water depths). The domes rise from an extensive chaotic source zone buried under a 200–400 ms thick sediment drape, and are more pronounced in the south. At some places, there is evidence of stratigraphically-controlled shallow gas accumulations (bright spots) and short cross-cutting BSR-like features that might point towards the presence of hydrate and/or free gas. The diapiric movement is believed to be a recent and still ongoing process of mass mobilisation. In both the cases, the nearby and tectonically-active slow-spreading, Knipovich Ridge is assumed to play an important role in the generation of elevated heat and methane fluxes as well as faulting and subsequent fluid migration. As a result, shallow subsurface hydrates (

25 pages, 9 figures, 9 tables., During the BASACALB-TTR9 cruise of the R/V Professor Logachev (1999), two mud volcanoes (called Marrakech and Granada) were discovered in the southern sector of the mud diapir province in the West Alboran Basin (WAB). This paper presents icropaleontological and geophysical data on these mud volcanoes from gravity core samples, sidescan sonar (OKEAN) images and high-resolution seismic lines. Mud breccia recovered from the Granada mud volcano is matrix-supported with well-consolidated clasts of limestone, marlstone, claystone, siltstone, sandstone and mudstone, whereas mud breccia from the Marrakech mud volcano contains unconsolidated clasts. The mud breccia matrix contains abundant Miocene calcareous nannofossils (CN), together with Pliocene^Pleistocene species and reworked late Cretaceous and Paleocene^Eocene species. CN dating indicates that clasts in the mud breccia derive from late Cretaceous, Paleocene, Eocene, and probable Miocene sediments. These data suggest that the mud diapirs and mud volcanoes in the WAB can be derived from the olistostromes of Unit VI, the basal stratigraphic sequence in the Alboran Sea basin. Unit VIconsists of lower Miocene sediments that incorporated late Cretaceous and Paleocene^Eocene materials and basement-derived rock fragments. The mud volcanic deposits are covered by a thin drape of pelagic marls, suggesting that these two volcanoes are currently inactive. Structures determined on highresolution seismic profiles across mud volcanoes and surrounding diapirs correspond to the late-stage, Pliocene-to- Quaternary diapir development. This stage is thought to have developed during a compressional tectonic setting that produced folding and wrench tectonics throughout the basin. Mud ascent at that time resulted in active diapirism and mud volcanoes on the seafloor., We are grateful to M.K. Ivanov, of the TTR program, for his all-encompassing help. Moreover, we wish to express our gratitude to the BASACALB TTR9 scienti¢c party. We thank referees J.A. Flores, E. De Kaenel, A. Kopf and N. Kenyon for their thoughtful comments and detailed criticism, which helped to clarify the manuscript. We also thank C. Laurin for her careful and detailed linguistic revision. Funding for the BASACALB Cruise and this work was provided by Project REN2001-3868-C03 (MCYT, Spain).

We present an approach to three-dimensional numerical solutions of gravity advection (Rayleigh‐Taylor) and thermal convection (Rayleigh‐Benard) problems. The inverse problem of gravity advection is solved numerically by replacing positive timesteps with negative ones. The inverse problem of thermal convection is ill-posed problem, and we suggest a variational approach to solve the problem. We test the numerical methodology on restoration models of diapirs and a thermal plume. The numerical approach can be used to reconstruct evolutions of salt and mud diapirs, mantle plumes and lithospheric slabs.

Publisher Summary For the South Caspian basin, the findings of Buryakovsky et al. can be summarized as follows. (1) Regionally developed abnormally high-formation pressures were encountered onshore of Azerbaijan and offshore of the South Caspian basin. (2) Paleogene to Neogene shales and argillaceous rocks, widespread in the geologic section of Azerbaijan and the South Caspian basin, consist of montmorillonite (smectites), hydromica (illite) and mixed-layered minerals. (3) The incomplete compaction of such argillaceous rocks, even at depths down to 6.5 km, is explained by the comparatively young age, a high-sedimentation rate (up to 1 km per one million years), their great thickness, and incomplete squeezingout of pore water. (4) The montmorillonite content of the Baku Archipelago shales is constant down to depths of 6.5 km, because the formation of secondary montmorillonite from hydromicas predominates over the transformation of primary montmorillonite. (5) A formula was proposed for the limiting depth at which montmorillonite can occur for any specific thermobaric conditions and, particularly, when the actual pore pressure differs from the normal hydrostatic one. (6) The sealing properties of argillaceous rocks at depths greater than 6.5 km probably persist, because of the presence of large amounts of montmorillonite. If accompanied by (1) good reservoir rock properties, (2) abnormally high pore pressures in shales and sandstones, and (3) relatively low-formation temperatures (which allow hydrocarbons to persist), the writers suggest that the South Caspian basin may contain commercial oil and gas accumulations at depths of 9 km, and deeper. (7) Development of abnormally high pore pressures may lead to lateral rock-density variation and, under certain geologic conditions, to folding, clay diapirism, mud volcanism, and earthquakes.

The chapter uses conclusions of previous chapters, and briefly describes characteristics of the oil and gas bearing formations in the South Caspian basin. The main oil and gas bearing formation in the Eastern Azerbaijan and the offshore areas of Apsheron and Baku archipelagoes is in the middle Pliocene productive series, based on the characteristic mineral composition of both light and heavy minerals. The productive series is separated into two divisions, lower and upper, and into several suites according to lithology. Core data, paleontological studies, and log response suggest that sediments of the productive series were deposited in a shallow-water, fluvial-deltaic environment. The productive series is again divided into seven sedimentary sequences according to the transgression and regression cycles during the basin development. Reservoir-rock properties of the productive series, which are very good, vary both within the section and over the area. Paleogene to Neogene argillaceous rocks, which are widespread in the geologic section of the Azerbaijan and the South Caspian basin, make up to 50 to 95% of the section and play a key role in establishing lithologic, mineralogical, geochemical, and thermobaric characteristics of the basin. Undercompaction of argillaceous rocks, even at depths down to 6.5 km, is explained by the comparatively young age, a high sedimentation rate, their great thickness, and incomplete squeezing-out of pore water. Development of abnormally high-pore pressures may lead to the lateral variation of rock density, and under certain geologic conditions to folding, clay diapirism, mud volcanism, and earthquakes.

A large number of serpentinite seamounts in the western pacific Izu-Ogasawara-Mariana forearcs indicate the serpentinite diapirism under the tensional stress field in the forearc regions. The presence of blueschist-facies rocks in the serpentinite seamounts provides evidence that the serpentinites generated from the hanging-wall peridotites have penetrated the high-pressure metamorphic region at depth in the accretionary prism. The high-pressure metamoprhic terranes in the circum-Pacific regions, the Franciscan Complex, California, and the Kamuikotan metamorphic belt, Japan, are accompanied with serpentinite melange with tectonic blocks of deeper high-grade metamorphic rocks, whereas the Sanbagawa metamorphic belt, Japan, does not contain any serpentinite melange. It is highly probable that the former were formed under tensional stress regime, and the latter under compressional one.

A review of the tectonic control and sedimentary patterns of the late Neogene piggyback basins of the Barbados Ridge Complex is proposed, mainly based on the analysis of seismic reflection profiles and sidescan sonar images. The geometrical relationships between the thrust faults and the syntectonic deposits show that the frontal piggyback basins are controlled by active thrusting. Deformations, with distinct scales, control their evolution: (1) a rapid tilting, strictly localized at the back limb of anticlines, and attributed to migration of active axial surfaces during fault-bend fold propagation; (2) a complex activation of the major thrust system, at a scale of a few kilometers: blind thrusts corresponding to frontal propagation develop seaward whereas motion along thrusts occurs backward. At about 50 km back of the deformation front, abundant muddy material raises up through pre-existing faults and disturbs arcward piggyback basins. The superimposition of the diapiric structures upon deformations linked to tectonic accretion (development of backthrusts and reactivating of forward verging thrusts) and inherited oceanic basement ridges leads to the individualized development of sub-basins bounded by steep topographic features. Most of the sediments of the South Barbados piggyback basins originate from the South American continent and are massively transported to the abyssal plain through canyons. Their course is driven by the main regional structures and their morphology reflects the tectonic activity of the features where they run. Oceanic ridges, by damming and collecting turbidite material control the thickness of sediments added to the complex and then the depth of the decollement and size and filling of the piggyback basins. Tectonics, by generating routes along the faults and excess fluid pressures control the main location and importance of mud diapirs and authigenic deposits. These stiff carbonate crusts preferentially develop on diapiric domes or on the back limb of anticlines up to the edge of supra-prism basins. Clayey diapiric material may be found within the basins where they form important mud flows as well as sliding masses. Tectonic and diapiric structures control gravity reworking processes, whereas structural relieves locally disturb bottom currents and hence control some erosion processes. The development of the piggyback basins of the BRC is closely linked to the evolution of a thrust wedge. The formation of frontal basins is mainly controlled by a forward-verging thrust system that forms a brittle wedge, whereas the development of the arcward basins is mainly controlled by subcretion of deep muds that induces mud diapirism, ductile deformation in the lowermost part of the wedge, a regional gentle slope, and the occurrence of both backward and forward verging thrusts. The evolution of the piggyback basins of the BRC also reflects the north to south changes in width and thickness of the wedge which are mainly related to variations of the increase of the sediment supply. Piggyback basins then evolve from minor depressions filled with very poor sediments in the north to about 10 km long overfilled basins in the south of the complex where abundant sedimentation occurs.

The Miocene Bicorb Basin is a small elongated basin developed by normal faulting of a thick Jurassic–Cretaceous carbonate succession and subsequent diapirism of Upper Triassic mudstones and evaporites. The basin fill comprises a sequence over 650 m thick formed by two units. The lower, alluvial unit consists of a complex alternation of conglomerates, sandstones, mudstones, and minor lacustrine limestones. The upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished. The inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits. At the northeast and southwest basin edges, alluvial inputs led to the development of delta and fan-delta environments where sandstone and conglomerate deposits dominate. The latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the NW fault-bounded margin pass laterally to breccias. The hierarchical arrangement of the upper unit shows five different orders of sequences. The first-order sequence defines a major vertical trend of lake expansion whereas three second-order sequences are linked to major flooding-expansion episodes. All these sequences are related to the tectonic evolution of the diapir. Metre-scale, third- and fourth-order sequences and fifth-order sequences, which consist of finely laminated rhythmite deposits probably record climatically forced processes. The diapir–graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system. Both factors have also strongly influenced the changes in the gastropod assemblages. Elsevier Science B.V. All rights reserved

A structural model encompassing the southern North Sea basin west of the Central Graben has been developed. This model consists of a rift system affecting the post-salt section around the basin margin and a large area of detached compressional buckle folds within the basin. This pattern is initially a response to gravity sliding of the post-salt section on the salt within the basin during the late Triassic to late Jurassic. A close relationship between the location and trend of the peripheral graben system and basement structures in the pre-salt is noted. Pre-Jurassic extension across the peripheral graben systems was balanced by the sum of fault heaves at the pre-salt (Rotliegend) level and shortening across salt-cored buckle folds in the post-salt section. Salt pillows and swells passively infilled the cores of these gravity-induced buckle folds. Cretaceous and Tertiary inversion involved basin tilt and renewed movement on basin-bounding basement faults; notably, reverse movements did not propagate from basement structures up into the peripheral graben systems. The post-salt sedimentary section experienced gravity spreading in response to inversion-related uplift, resulting in syn-inversion extensional faulting in the Sole Pit High, where the Mesozoic section was thickest. This extension, combined with a loss of fault heave in the pre-salt section, was balanced by amplification of salt-cored buckle folds in the centre of the basin. In the context of the model described here, salt pillows represent passive infill of thin-skinned, compressional buckle folds which later amplified during thick-skinned basement shortening. Crestal collapse of such folds occurs via normal faulting, accompanied by reactive diapirism. Such reactive diapirs establish conduits through which salt may leak, leading to pillow deflation and ultimately conduit preservation as a salt wall (flanked by rim synclines in areas where the buckle folds were emergent). The salt structures described here are related to cover folds and faults, which in turn reflect episodes of basin extension, tilting and inversion. Hence individual salt structures can be said to be only remotely connected with regional, intraplate stresses.

Publisher Summary This chapter explores the problem of magma-transport structures and diking at oceanic ridges by presenting a structural study of dike orientations in the peridotite section of the Oman ophiolite. Dike orientation was systematically measured in the vicinity of mantle diapirs exposed in the Oman ophiolite. Collectively, diking reflects a continuous history of melt injection, from the early gabbro and pyroxenite dikes emplaced in a concurrently melting peridotite to the dominantly gabbro dikes emplaced in peridotites at subsolidus temperatures and to the microgabbro and diabase dikes emplaced in peridotites that have cooled below 500°C. The diabase dikes—emplaced when the ridge was cooling—have excellent preferred orientations that are mainly parallel to the sheeted-dike trend. A group of dikes is oriented parallel to the sheeted-dike complex and ascribed to a relatively regionally organized lithospheric stress field. Another group is composed of flat-lying sills and moderately inclined dikes controlled by the locally organized asthenospheric stress field created by the diapir flow divergence just below the ridge. Melt is injected in either the sills or the dikes. This feature suggests a relatively rapid shift in the orientation of the local stress field, which is attributed to the effects of a large-volume and relatively violent melt surge from the rising diapir into the newly accreting crust. Because orientations in the high-temperature dikes are, at present, so poorly clustered, more work is required before conclusions on this interesting class of intrusions may be drawn.

Publisher Summary This chapter describes the sequence and duration of magmatic events accompanying the development of a mantle plume using calculations of decompression melting in axisymmetric thermal diapirs and axisymmetric thermal plumes. These calculations are motivated by growing evidence in support of a mantle plume origin for many continental flood basalt provinces as well as some oceanic plateaus. The calculations establish the temporal relationships between near-surface magmatic activities associated with mantle plumes and heat transport into the hot thermal boundary layer feeding the plume. There are three stages in the magmatism of a mantle plume. The first stage occurs as the plume approaches the lithosphere from below, and it is characterized by rapid uplift and rapid melt generation but relatively little crust production. The second stage occurs as the plume's head spreads out beneath the lithosphere, and it is marked by rapid subsidence and rapid crust production. The last stage corresponds to the contraction of the plume and the melt zone toward a steady state, and it is marked by slow subsidence and greatly diminished crustal production. Basal heat flow increases during plume formation, thereby supporting the suggestion that deep mantle plumes thermally couple the core to the mantle.

Various shapes of moving salt were simulated in response to gravity contrast and tectonic movement, and the deformations and fractures of the surrounding sediments examined. The varying parameters in the model include the burial depth of the salt base, the overhang depth of the salt cap, the salt body's size, the salt speed, and the sediment depositional rate, as well as variation of the surrounding rock properties with depth, such as Lame constants, shearing strength and internal friction. Mohr's criterion for failure was applied, allowing an indication of where fractures occur and their orientations. Including the thermal effects, salt yields features favorable to hydrocarbon accumulation as shown by the simulations: (1) fractures occurring near the vertical salt body and below the mushroom salt cap provide a continuous pathway for hydrocarbon migration due to the enhancement of permeability; (2) the overhanging salt cap sheet provides a potential seal for the accumulations; (3) the thermal effect of salt enhances the maturity of the source rocks; and (4) the observed faulting around the salt are accounted for by primary and secondary fractures, as exhibited through the simulations. In this study of Barents Sea, Norway, we find that the salt probably started to rise during the Early-Mid Triassic and Jurassic when the sediment cover was 1700-2400 m. Depositional faulting was associated with salt diapir motion. The modelling also indicates that at least 1000 m of the salt cap was eroded, based on the dip angles of sedimentary strata against the salt stock.