Search

Wuxu ore district is an important lead-zinc-antimony polymetallic ore field within the Danchi metallogenic belt of South China. Although previous geochemical studies have indicated that the deposit type is medium to low-temperature magmatic-hydrothermal, the existing metallogenic models remain controversial due to the thick covering layer and lack of exposure of granitic bodies. To address this issue, this study utilised four CSAMT parallel profiles across the Wuxu anticline to perform two-dimensional inversion, yielding high-resolution subsurface resistivity models. By comparing the resistivity anomalies along the regional strike shown by the profiles and integrating geochemical and ore deposit structural analyses, a detailed geological interpretation was conducted. A significant high-resistivity body beneath the core region of the Wuxu anticline is interpreted to be the Yanshanian period granitic intrusion. There are westward- and eastward-dipping high-conductivity belts existing within the western and eastern wings and appear to sandwich the inferred high-resistivity code of the Wuxu anticline, respectively. They may represent the deep faults extending underground and are the result of decoupling of lithological interface within the anticline and thereby rock fracturing. The high-conductivity feature may be the result of filling with high-conductivity saline fluids, and possible hydrothermal alteration. The regional compression stress during the Caledonian period and the early Yanshanian period promoted the formation of the anticline and rock fracturing of both wings of the anticline. After that, the regional extension background of the late Yanshanian period made the fault zones reactivated, becoming the site and channels for magmatic intrusion, upward transporting of hydrothermal fluid and alteration, causing lead-zinc-antimony polymetallic ore formation. The exposed ore deposits above may also corroborate this view point. In summary, our resistivity model visually depicts the spatial distribution of the granitic intrusion controlling ore formation and major structures such as anticlines, fault zones, and hydrothermal alteration zones in the 3-D space, providing new geophysical constraints for solving the controversy over the metallogenic model for Wuxu ore district. [ABSTRACT FROM AUTHOR]

The deep Lower Jurassic Ahe Formation (J1a) in the Dibei–Tuzi area of the Kuqa Depression has not been extensively explored because of the complex distribution of fractures. A study was conducted to investigate the relationship between the natural fracture distribution and structural style. The J1a fractures in this area were mainly high‐angle shear fractures. A backward thrust structure (BTS) is favorable for gas migration and accumulation, probably because natural fractures are more developed in the middle and upper parts of a thick competent layer. The opposing thrust structure (OTS) was strongly compressed, and the natural fractures in the middle and lower parts of the thick competent layer around the fault were more intense. The vertical fracture distribution in the thick competent layers of an imbricate‐thrust structure (ITS) differs from that of BTS and OTS. The intensity of the fractures in the ITS anticline is similar to that in the BTS. Fracture density in monoclinic strata in a ITS is controlled by faulting. Overall, the structural style controls the configuration of faults and anticlines, and the stress on the competent layers, which significantly affects deep gas reservoir fractures. The enrichment of deep tight sandstone gas is likely controlled by two closely spaced faults and a fault‐related anticline. [ABSTRACT FROM AUTHOR]

The impacts of the growth and linkage of fault segments on sedimentation in a lacustrine rift basin, the Weixinan Depression, the Beibuwan Basin, in the northern South China Sea, which has been demonstrated to have huge petroleum potential, are elucidated on the basis of well-constrained 3D seismic data. Two main fault systems, the No. 1 boundary fault system and the No. 2 fault system, were developed in the Weixinan Depression. The evolution of the lower basement is based on the No. 1 fault system, which controls the distribution of depocenters (ranging from 450–800 m) within the lower structural layer. It includes the five fault segments isolated at the initial stage, the interaction and propagation stage, the linkage stage, and the decline stage. The No. 2 fault system governs the deposition of the upper structural layer with a series of discrete depocenters in the hangingwall. Initially, it comprises several right-order echelon branching faults. Each branch fault rapidly reached the existing length and maintained a constant length while establishing soft links with each other in the subsequent displacement accrual. The development of topographic slopes, transition zones, transverse anticlines, and related fault troughs and gullies related to the activity of the No. 1 boundary fault system is the main controlling factor that induces the differential development of the western, middle, and eastern sections of steep slope fans. The differential subsidence effect along the No. 2 fault system is responsible for the multiple 'rising-stable' stage changes in the relative lake level during the development of axial delta deposits. This study will help elucidate the different controls of extensional fault systems on associated sedimentation, as well as rift basin development in the South China Sea and similar areas throughout the world. [ABSTRACT FROM AUTHOR]

The Malay Basin is a mature hydrocarbon province currently being re‐assessed for CO2 storage. Selecting an appropriate storage site requires a comprehensive understanding of the structural and stratigraphic history of the basin. However, previous studies have been limited to observations from either regional 2D seismic lines or individual 3D seismic volumes. In this study, we access and utilise a basin‐wide (ca. 36,000 km2) 3D seismic and well database to describe the structural and stratigraphic features of the basin, particularly those within the uppermost ca. 4 km (Oligocene to Recent) and gain new insights into the basin's evolution. E–W transtensional rift basins first developed due to sinistral shear across an NW‐SE strike‐slip zone. The NW‐SE basin morphology seen today was generated during the late Oligocene–early Miocene, during which time dextral motion across marginal hinge zones created en‐echelon antithetic, extensional faults and pull‐apart basins, especially well preserved along the western margin of the basin. Collisional forces to the southeast during the early to middle Miocene resulted in the shallowing of the basin, intermittent connection to the South China Sea and a cyclic depositional pattern. Around 8 Ma (late Miocene), a significant uplift of the basin resulted in a major unconformity with up to 4.2 km of erosion and exhumation in the southeast. In the centre and northwest of the basin, the inversion of deeper E–W rifts resulted in the folding of Miocene sequences and the formation of large anticlines parallel to the rift‐bounding faults. The Pliocene to Pleistocene history is more tectonically quiescent, but some extensional faulting continued to affect the northwest part of the basin. Larger glacio‐eustatic sea‐level fluctuations during this time resulted in major changes in sedimentation and erosion on the Sunda Shelf, including the formation of a middle‐Pliocene unconformity. These structural events have created a variety of hydrocarbon traps across the basin of different ages, including transpressional anticlines, rollover anticlines and tilted fault blocks. Each of these has discrete and distinct trap elements with important implications for their CO2 storage potential. [ABSTRACT FROM AUTHOR]

The ca. 2.96 Ga Dominion Group (DG) preserves the first subaerial volcano-sedimentary succession on the Kaapvaal Craton. Based on field and core observations, this study provides revised stratigraphic logs and geological maps from the area around Ottosdal that refine the understanding of the stratigraphic and tectonic evolution of these ancient rocks. Fluvial sandstone and conglomerate of the Rhenosterspruit Formation (RsF) were deposited on granite basement, followed by andesitic to basaltic volcanic rocks of the Rhenosterhoek Formation (RhF). These amygdaloidal andesitic to basaltic lava units show fragmentation around lava flows that may represent an indication of prevalent subaerial environment. However, local hyaloclastite and pillow lava units indicate periodic aqueous conditions. The Syferfontein Formation (SF) has the most extensive exposures in the Ottosdal area and represents the youngest volcanic unit of the DG. The porphyritic and spherulitic volcanic rocks tell a story of subaerial volcanism interspersed with periods of lacustrine deposition of sandstone and shale. The Witwatersrand Supergroup (WSG) overlies the DG along an angular unconformity. Folding affected the succession of the DG, WSG and the Ventersdorp Supergroup (Rietgat Formation). This event is reflected in small-scale folds and mullion structures in the central part of the study area and by larger scale north-north-west-south-southeast-striking anticlines and synclines. Folding was accompanied by northwest-southeast-striking thrust faulting, either during or shortly after the formation of the Ventersdorp Supergroup. In the study area, post-Ventersdorp deformation is restricted to east-northeast-west-southwest-striking faults. [ABSTRACT FROM AUTHOR]

A transfer zone in rift basins preserves important information on regional tectonic evolution and plays significant roles in hydrocarbon accumulation. Based on the systematic analysis of 3D seismic data and hydrocarbon accumulation conditions, the geometry, kinematics, and reservoir control of a large synthetic overlapping transfer zone in the south of the Wenchang A subsag in the Zhujiang (Pearl) River Mouth basin were investigated. Results indicate that the development and evolution of the transfer zone was controlled by the interaction between pre-existing faults and regional stress transformation. The intense rifting of the main faults of the transfer zone controlled the development of source rocks and fault-controlled slope break paleogeomorphology. The strike-slip overprint since the Oligocene is conducive to the formation of a large-scale fault-anticline trap, and the secondary faults in the transfer zone contribute to the hydrocarbon transportation. The conjugate intersection area of the NE- and NW-trending faults offers more opportunity for hydrocarbon migration and accumulation. [ABSTRACT FROM AUTHOR]

The geological structure affects the occurrence of coalbed methane (CBM), and identifying its structural characteristic boundaries is significant for CBM development. Based on the 3# coal seam top elevation observation data of the South Shizhuang CBM district in Qinshui Basin, this study comprehensively used trend surface analysis, curvature analysis and multi-element overlay analysis to study the geological structure characteristics of this area and identify its geological structure boundaries. First of all, through the analysis of the fitting degree test and significance test, it was proved that the fourth-order trend surface can be better used to identify the geological structure characteristics in this area. On this basis, the geological structural units of the study area were identified on a regional scale, and the study area was divided into the northwest depression zone, the middle fold area and the eastern slope zone. Then, by using the contour curvature analysis method, the fold geological structure boundaries were identified on a local scale, and combined with the coal seam roof elevation model for optimization and adjustment, 73 fold structural boundaries were finally identified, including 37 anticlines and 36 synclines. The results showed that: (1) The fold structures of the 3# coal seam in the South Shizhuang CBM district are primarily wide and gentle secondary folds, with symmetrical wings and a roughly NNE trend. (2) The northwest depression zone is dominated by syncline structure. (3) In the middle fold zone, anticlines and synclines are evenly distributed. (4) The eastern slope zone is dominated by anticline structure and has small terrain fluctuations, making it a favourable area for CBM development. The identification results can provide a reference for the exploration, planning and development site selection of CBM resources in the study area. [ABSTRACT FROM AUTHOR]

The West Kunlun foreland is dominated by segmented fold-and-thrust belts with significant potential for hydrocarbon exploration, while the extent of exploration in this area has been relatively limited. In this paper, by conducting complex structural interpretation, the geometric and kinematic characteristics, as well as the variations in the segmented fold-and-thrust belts within this region are revealed. The West Kunlun foreland fold-andthrust belts are divided into three structural segments, which exhibit distinct structural styles. The Pusha-Kedong segment in the east is characterized by large-scale northward propagation, with high-angle basement-involved faults in the root belt and thin-skinned thrusts in the front belt. Additionally, three-row anticlines developed in the middle to the upper structural layers. The Kashi-Yecheng segment, located in the middle, is characterized by strike-slip faults and basement-involved structural wedges transitioning to detachment structures. Within this segment, the Sugaite structure in the mountain front is a wedge structure composed of basement-involved faults and an upper back-thrust fault. Meanwhile, the Yingjisha structure in the thrust front consists of a fold in the lower part and a backthrust system above it. The lower fold is controlled by the Cambrian detachment thrust, which terminates upward in the Paleogene, while the back-thrust faults truncate upper structural layers and terminate downwards in the Miocene strata. The Wupoer segment in the northwest is controlled by the Main Pamir Thrust and the Front Pamir Thrust, which are low angular forward thrust faults with an arc distribution. A piggyback basin has developed in the root belt and upper structural layer since the Pliocene. Based on the deformation characteristics and the accumulation of oil-gas reservoirs discovered so far, two types of oil and gas-rich thrust belts with different hydrocarbon exploration fields in the West Kunlun foreland are described. [ABSTRACT FROM AUTHOR]

We explore CO2 injection into a layered permeable rock consisting of high permeability reservoir layers, separated by low permeability mudstone, and taking the shape of an anticline within a laterally extensive aquifer. We first show how the storage capacity of the formation depends on the capillary entry pressure of the inter-layer mudstone, so that CO2 cannot flow from one layer into the next. We then consider a formation composed of two layers, overlain by a cap rock. For injection into the lowest layer, we show that the injection rate, capillary entry pressure and buoyancy driven flux through the mudstone determine whether the lower or upper layer fills to the spill point first. We also show that at the end of the injection phase, CO2 may continue to flow from the lower to the upper layer. This implies that injection should be stopped once the injected volume matches the static capacity of the formation in order to prevent spilling after injection. We present a series of analogue experiments of a two layered system that illustrate some of the principles described by the model, and assess the implications of the results for field scale systems [ABSTRACT FROM AUTHOR]

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin (also referred to as the ECSSB). However, the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial. Under the guidance of sedimentology and stratigraphy, this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description, well logging, and seismic data analysis. This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta, estuary, and gravity flow deposits in the central anticline zone of the Xihu Depression. The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt, which cannot be explained by previous study results, such as southern transgression or fluvial deltas and even lacustrine deposition. Moreover, the tidal channels, tidal sand flats, and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs. The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression. [ABSTRACT FROM AUTHOR]

The gravity data of Gebel El-Maghara area and its surrounding region in northern Sinai Peninsula, Egypt have been subjected to high precision edge detection filters in order to evaluate the structural and tectonic settings of the study area. Various traditional and modern edge detection filters were tested on synthetic gravity data and then the most successful filters in detection the boundaries of the causative bodies have been used to accomplish the study's objectives. By examining the power spectrum of the gravity data, three gravity maps were generated using low-pass, band-pass and high-pass filters, respectively, representing deep, intermediate and shallow gravity anomalies. The STDR filter and its total horizontal derivative were applied to these gravity maps to image the causative structural features (faults and contacts) and construct structural maps at these different depths. The findings demonstrate that the major trend of faults and contacts at deep depths predominantly aligns along the WNW–ESE direction, while at shallow depths, the main orientation is observed along the NE–SW direction. It is worth noting that the trend of structures at shallow depths demonstrates a good agreement with the structural trends derived from both surface structural map and Landsat images. This trend disparity supports the hypothesis that the formation of the anticlines in the study area is linked to thin-skinned tectonic processes associated with the Syrian Arc system. [ABSTRACT FROM AUTHOR]

This study establishes the structure of the Tisserfine basin, located in the eastern Moroccan High Atlas, through an integrated interpretation of geophysical data. Several types of data were integrated in this work: a gravity map, 243 vertical electrical soundings (VES), a seismic reflection profile; logs of 10 boreholes, geological maps, and field structural measurements. The gravity map shows a succession of lows and highs-oriented WSW-ENE, paralleling the regional structures (synclines and anticlines). Gravity lows are correlated with Triassic evaporites (mostly clays) that were uplifted into high elevation areas (anticlines). Gravity highs correspond to the accumulation of limestones, sandstones, and marls in synclines. A multiscale analysis of gravimetric lineaments shows the main faults bordering the anticlines and synclines. The seismic reflection profile indicates that the Tisserfine syncline is affected by several faults; the Mesozoic formations in the axis of the syncline exceed a depth of 3000 m, and that the anticlines (corresponding to topographic highs) present very high dips (69–87°). The results of 2D resistivity models are in good agreement with geological data and reveal several faults. The models exhibit a conductive layer (marls, 800 m-thick), with intercalations of highly resistive levels inferred to be sandstones. The basement is characterized by very high resistivity values, matching limestones or dolostones. The hydrogeological units consist of two unconfined and three confined aquifers. The piezometric outline shows that the groundwater flows converge towards the Tisserfine wadi with a direction flow to the east. The presence of water throughout the year in several places at the Tisserfine and Zouzfana wadis (e.g. Dfilia (Aghlal) springs) represents the drainage of an unconfined aquifer. [ABSTRACT FROM AUTHOR]

Fars sub-basin is located in the Zagros fold-thrust belt and includes a large number of hydrocarbon reserves, especially gas. The existence of numerous basement faults and strike-slip in this region along with the uplift and depocenter of basement blocks has been considered effective factors in controlling sedimentary basins before, after, and synchronous with sedimentation. In this study, the role of the Razak fault basin in the external Fars area as an effective factor in controlling the sedimentary basin was evaluated. For this purpose, by providing isopach maps and 3D modeling from the basin floor at synsedimentary formations, the activity of the Razak fault along with its role in increasing or decreasing the hydrocarbon potential of the region and adjacent anticlines, was investigated. The results show that the inactivity of this fault at the sedimentation time of the Dalan, Gadvan, Darian, and Kazhdumi formations, while at the deposition time, the formations of Kangan, Dashtak, Hith, Fahlian, Laffan, Ilam, and Pabadeh remained active and controlled the sedimentation in the basin. Also, the uplift and depocenter of the basement blocks occurred to the Razak fault's performance, caused an increase in the hydrocarbon potential of the Dehram Group in the anticlines of Marz, Varavi, Tabnak, Dehnow, Khalfani, Chiru, and Madar. While the northeastern part of the study area and the anticlines of Bonashkatu, Pishvar, Bavush, Gavbast, and Gezzeh are less important. In addition, Khami and Bangestan reservoirs are also without hydrocarbon potential due to the Razak fault's performance. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi National Journal of Earth Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The question of uplift in the Sarawak Foreland is addressed in a multi-disciplinary approach, namely by assigning surface vitrinite reflectance measurements to depth, and by vitrinite reflectance-to-depth conversion using functions from two previous studies. Additional erosion and uplift data were obtained by comparing eroded anticlinal crests with adjacent synclines and their preserved sediments. The combined data pool suggests two types of uplift (I) a regional uplift in the Neogene affecting the entire coastal area, and (II) a tectonically focused uplift. The amount of the latter uplift and erosion is directly linked to rise of anticlinal structures during the Upper Pliocene, with a total uplift ranging from 700 to 4,000 m in areas along prominent regional faults. Within a very short time window major sedimentation, folding, trap formation and trap destruction took place both as a consequence of folding and erosion. Only anticlines in the offshore and the proximal onshore appear to have survived without major crestal erosion. Since the end of the Pleistocene, a rise of foreland sections by some 132 m is recognized. The rapid Pliocene burial and the erosion that consequently removed the overburden thereafter may have negatively affected the petroleum system and hydrocarbon accumulation within the Miri area, which was left largely intact only in the Siwa-Seria anticlinal trend. All anticlines were targeted by petroleum exploration. However, only the Siwa-Seria trend has proved to be economically successful. This has highlighted the significance of overburden in relation to depth of burial and the thermal effect needed to mature the source rocks capable to generate hydrocarbons. [ABSTRACT FROM AUTHOR]

In microseismic monitoring, the reconstruction of a reliable velocity model is essential for precise seismic source localization and subsurface imaging. However, traditional methods for microseismic velocity inversion face challenges in terms of precision and computational efficiency. In this paper, we use deep learning (DL) algorithms to achieve precise and efficient real-time microseismic velocity modeling, which holds significant importance for ensuring engineering safety and preventing geological disasters in microseismic monitoring. Given that this task was approached as a non-linear regression problem, we adopted and modified the Attention U-Net network for inversion. Depending on the degree of coupling among microseismic events, we trained the network using both single-event and multi-event simulation records as feature datasets. This approach can achieve velocity modeling when dealing with inseparable microseismic records. Numerical tests demonstrate that the Attention U-Net can automatically uncover latent features and patterns between microseismic records and velocity models. It performs effectively in real time and achieves high precision in velocity modeling for Tilted Transverse Isotropy (TTI) velocity structures such as anticlines, synclines, and anomalous velocity models. Furthermore, it can provide reliable initial models for traditional methods. [ABSTRACT FROM AUTHOR]

In our research we studied thirty minor folds in Qaiwan and Goizhah anticlines, 22 km northeast of Sulaimani District, Northeastern Iraq. They are located within the Zagros Imbricate Zone between the Zagros High Folds Zone and Zagros Suture Zone. The study area is occupied by the alternative of competent and incompetent layers of Cretaceous formations which facilitates the formation of minor folds at the limbs and hinge zone of the major fold. This work aims to find the relationship between these minor folds and major folds and how these minor folds assist in understanding the regional structure, and tectonic history and finding tectonic episodes that responded to the development of the anticlines. Pi (π) diagrams were constructed to find the characteristics of the folds. Fleuty's (1964) and Ramsey's (1967) classifications were used to classify the tightness, fold types, and fold style. Two paleostress directions were revealed from congruous and incongruous minor folds in the direction (NE‒SW) and (NW‒SE), respectively. The sub-congruous minor folds attributed to the oblique collision and anticlockwise rotation of the Arabian plate with respect to the Eurasian plate. Back-thrusting paleostress was detected from the opposite break-thrust fold of the forelimb of the minor folds. The homogeneous flattening during continuous folding processes changes the geometry of the folds from classes 1B and 1C to classes 2 and 3. The proportion of incompetent to competent layers changed the shape of the hinge zone from rounded to angular. As the incompetence increased the hinge zone become more rounded. The intensity of folding and structural origin of the folds as fault propagation folds maybe flipped the vergency of some minor folds in the southwestern limbs of the major fold from northeast to southwest. [ABSTRACT FROM AUTHOR]

Copyright of Advanced Applied Geology is the property of Shahid Chamran University of Ahvaz and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mud volcanoes are fed largely by fracture systems, but fracture systems are common in fold-and-thrust belts (FTBs), and not all of them extrude mud volcanoes. One popular hypothesis is that mud volcanoes extrude up normal faults and fractures in the crests of thrust-related anticlines. Using a high-resolution depth-migrated seismic cube in the northwestern Gulf of Mexico, we demonstrate the occurrence of buried mud volcanoes (shale sheets) that appear to have been fed by fluids moving up the thrust faults themselves. Mobile shales in this deepwater FTB detach a mostly welded allochthonous salt sheet. The main phase of shortening was during the Miocene, accompanying the sedimentation. Shortening generated multiple detachment levels, stacked duplexes, thrusts, and folds affecting the Oligocene mobile shales. Above these detachments, syn-sedimentary shortening initially generated detachment folds that progressively evolved into upward-propagating listric thrusts and fault-propagation anticlines. Shale sheets formed near the central thrust domains, associated with higher fault dips and larger fault displacements. We argue that their feeder systems were probably thrust-related shear zones that widened upward and comprised networks of anastomosing fractures. Finally, we propose that the position of mud volcanoes with respect to the underlying thrust systems depends on the path of least resistance to the surface. Although overpressured muds may vertically reach the surface via extensional fractures in the crests of thrust-related anticlines, we have shown to the contrary that when thrusts are emergent in a deepwater FTB, fluids continue up the inclined thrusts and adjacent fractures, forming mud volcanoes at the thrust tips. [ABSTRACT FROM AUTHOR]

The balancing technique, called 2D kinematic forward modelling, is a powerful tool to understand the kinematic evolution of fold-and-thrust belts. This study presents a new 2D kinematic forward model for the westernmost Internal Jura fold-and-thrust belt (FTB), situated immediately adjacent to the Geneva Basin. The technique used not only provides a new valid balanced cross-section but also offers new insights regarding the kinematic evolution of the Western Internal Jura FTB. Our model proposes a pure thin-skinned style dominated by forward stepping deformation accompanied by minor back-stepping thrust sequences. A first deformation step is attributed to the thrusting of the Crêt de la Neige Anticline, followed by the Crêt Chalam Thrust and its imbrications. This is followed by thrusting along the Tacon and the Bienne thrusts. Imbricate fault-bend folding explains the steep southern limb of the Crêt de la Neige and the Bellecombe anticlines. 2D kinematic forward modelling yields a total amount of shortening by 23.6 km for the Western Internal Jura FTB. In addition to the primary décollement located at the base of the Keuper Group evaporites, three other décollements are found within the marly layers of the Aalenian "faciès de transition" units, the Oxfordian "Couches d'Effingen-Geissberg" members and the Berriasian Goldberg formation. The multiple thrust horizon approach is supported by new precise seismic interpretations. Our model provides a valid alternative to previous models that either propose local thickening of the Triassic evaporites or inversion of normal faults in the basement. This fully explains the elevated position of the Mesozoic cover in the Jura FTB. [ABSTRACT FROM AUTHOR]

Reflector-normal angles and reflector-curvature parameters are the principal geometric attributes used in seismic interpretation for characterizing the orientations and shapes, respectively, of geological reflecting surfaces. Commonly, the input data set for their computation consists of fine 3-D grids of scalar fields representing either the seismic-driven reflectivities (e.g. amplitudes of 3-D seismic migrated volumes) or model-driven reflectivities, computed, for example, from the derived elastic impedance parameters. Conventionally, the computation of curvature parameters at each gridpoint is based on analysing the local change in the inline/crossline dips, considering the potential existence of a local quadratic reflecting surface in the vicinity of that point. This assumption breaks down for subsurface points in the vicinity of either complex reflecting surfaces (e.g. brittle/rough/tilted synclines/anticlines, ridges/troughs and saddles) and/or sharp, discontinuous geological features (e.g. fault edges/tips, pinch-outs, fracture systems, channels and small geobodies), where the values of the computed curvature become extremely high. However, while these high values can indicate the existence of non-reflecting objects, they do not deliver their specific geometric characteristics. In this study, we present a novel method that better characterizes the shapes of these complex geological features by extending the assumption of local surfaces (2-D surfaces in 3-D space) into local hypersurfaces (3-D hypersurfaces in 4-D space), with their corresponding (three rather than two) principal (and effective) curvature parameters. We demonstrate the advantages of our method by comparing the conventional dip-based surface curvature parameters with the hypersurface curvature parameters, using a synthetic model/image with different types and shapes of geological features and a seismic image of real data containing a complex fault and hidden buried channels. [ABSTRACT FROM AUTHOR]

This work uses sandbox analog models to analyze the formation and subsequent inversion of a decoupled extensional system comprised of two segmented half-grabens separated by a diffuse accommodation zone with thick early syn-rift salt. The segmented half-grabens strike perpendicular to the direction of extension and subsequent shortening. Rifting first created a basement topography that was infilled by model salt, followed by a second phase of extension and sedimentation, followed afterwards by inversion. During the second phase of extension, syn-rift syncline minibasins developed above the basement extensional system and extended beyond the confines of the fault blocks. Sedimentary downbuilding and extension initiated the migration of model salt to the basement highs, forming salt anticlines, reactive diapirs, and salt walls perpendicular to the direction of extension, except for along the intervening accommodation zone where a slightly oblique salt anticline developed. Inversion resulted in decoupled cover and basement thrust systems. Thrusts in the cover system nucleated along squeezed salt structures and along primary welds. New primary welds developed where the cover sequence touched down on basement thrust tips due to uplift, salt extrusion, and syn-contractional downbuilding caused by the loading of syn-contractional sedimentation. Model geometries reveal the control imposed by the basement configuration and distribution of salt in the development of a thrust front from the inversion of a salt-bearing extensional system. In 3D, the interaction of salt migrating from adjacent syn-rift basins can modify the expected salt structure geometry, which may in turn influence the location and style of thrust in the cover sequence upon inversion. Results are compared to the Northern Lusitanian Basin, offshore Portugal, and the Isábena area of the South-Central Pyrenees, Spain. [ABSTRACT FROM AUTHOR]

Deformation on shale‐rich continental margins is commonly associated with thin‐skinned extension above mobile shales. Normal faulting and shale mobilization are widespread on such margins, being associated with and controlled by progradation and gravitational failure of deltaic sedimentary wedges. However, due to uncertainties in seismically imaging mobile shales, our understanding of problems like how base mobile‐shale controls deformation, and the shape, size, and distribution of shale structures remains poorly understood. Here, we use 3D seismic reflection data from the platform region of the Tarakan Basin, offshore eastern Indonesia to investigate the temporal and spatial evolution of thin‐skinned deformation of the Neogene sedimentary section. Our detailed seismic interpretation reveals up to 74 km long, concave‐ and convex‐into‐the‐basin normal faults, dipping both basinward (eastwards) and locally landward (westwards), which detach downwards on a basal mobile shale (Early‐Middle Miocene). The base of the mobile‐shale unit dips gently (<17°) seaward, although older (Eocene‐Early Miocene), rift‐related normal faults originate local structural highs deforming the base of mobile shales. Our isochore (thickness map) analysis shows that supra‐shale normal faulting commenced in the Middle Miocene and was accompanied by the formation of hanging‐wall rollover folds and associated crestal grabens, with the subsequent along‐ and across strike migration of the deformation related to the nucleation, lateral linkage and reactivation of individual fault systems. Updip growth normal faulting was also accompanied by the downslope flow of mobile shale, accompanied by parallel and perpendicular variations of the differential loading in the delta system, and local contraction and mobile‐shale upbuilding, resulting in the growth of large, margin‐parallel shale anticlines further downdip. The growth faults and anticlines are locally overlain by up to 5 km tall mud pipes and volcanoes. We suggest that variations in the rate of sedimentary loading, mobile‐shale flow, fault growth and gravitational failure of the delta system above a seaward‐dipping, but locally rugose base mobile‐shale surface, controlled Neogene deformation in the Tarakan Basin. We also demonstrate how variations in the trend and dip of the base mobile‐shale surface influence the position, timing of formation and evolution of supra‐shale normal faults and their associated depocentres along shale‐rich, deltaic margins. [ABSTRACT FROM AUTHOR]

South West Abu-Sennan (SWS) area near the southern periphery of the Abu-Gharadig petroliferous basin in the Egyptian Northern Western Desert is an important hydrocarbon field characterized by being a multi-reservoir with a complex structural architecture. Therefore, in this study, we illustrated the regional structural role that facilitated having Jurassic mature source rocks (Masajid and Khatatba formations) through surgical seismic interpretation and observed the controlling petroleum system of the study area using a set of 20 seismic lines and 4 wells data. The study resulted in having the SWS oil field controlled by a strike-slip movement that occurred during the Upper Cretaceous time accompanying the African Plate movement against the Eurasian Plate superimposing an ENE–WSW strike-slip fault zone in the region and a strong pattern of NW–SEoriented faults due to numerous phases of extension. The associated structures include horsts, normal fault propagation folds, and strike-slip-related anticlines. The strike-slip tectonics played a major role in forming entrapment for the Jurassic expelled hydrocarbons. The seismic horizons flattening exercise performed on AR/G member and Khoman Formation demonstrated that the main reason for not having hydrocarbon accumulations in the Jurassic levels in the study area is that the trap configuration was ready to accumulate hydrocarbon but after the hydrocarbon generation and migration time. The study concluded that the hydrocarbons migrated along the faults which cut deeply to the source rocks and entrapped in the possible cretaceous reservoirs during the late cretaceous time. The conducted workflow in this study can be utilized to better explore and develop cretaceous reservoirs in the study and neighbouring areas. [ABSTRACT FROM AUTHOR]

Fluid inclusion microthermometry of synkinematic veins is used to estimate the maximum syntectonic load that was deposited on the wedge top in the central Appalachians (northeastern United States) during the Alleghanian orogeny. The restored loads indicate two major depocenters during the Alleghanian orogeny: one above Broadtop synclinorium, with as much as 7 km of Pennsylvanian– Permian load probably sourced by the erosion of rocks uplifted by the growing Blue Ridge massif and emplacement of the North Mountain thrust sheet; the other above the Anthracite belt, with as much as 16 km of syntectonic load likely sourced by the erosion of rocks uplifted by the growing Reading Prong massif. The loads were generally <3 km in the intervening Juniata culmination. In areas of high load, the structural architecture of the basin is that of widely spaced thrusts (~17–22 km) with large leading- edge anticlines in the Cambrian–Ordovician lithotectonic unit, while in areas of low load, thrusts are more closely spaced (~15 km) and deformed into an imbricate stack. The relationship between observed syntectonic loads, thrust spacing, and structural style reflect modeled relationships. [ABSTRACT FROM AUTHOR]

Fault‐related folds are present in most tectonic settings and can serve as structural traps for hydrocarbons. These structures have therefore been widely studied by both structural and petroleum geologists using a range of techniques. Approaches include field‐ and seismic‐based methods, and numerical and analogue modelling. Geomechanical models attempt to examine the mechanical and geometric features of folds. This study investigates the effects of variations in a range of parameters, including detachment and ramp geometry, friction coefficient and internal friction angle, on the geometry and development of detachment folds and fault‐bend folds. For this purpose, we ran seven series of numerical, 3D elastic‐plastic finite element models using ABAQUS software (26 model runs in all). Each model set‐up consisted of five layers whose mechanical properties were based on those of stratigraphic units in the Zagros fold‐and‐thrust belt, SW Iran. The models were labelled series A to F and series H. Models in series A investigated the impact of concave, convex, wavy and oblique detachment surfaces on the development of detachment folds; those in series D examined the role of ramp dip and of listric, oblique and wavy ramps on the development of fault‐bend folds. Models in series B and E, and series C and F, examined the effects of variations in the friction coefficient and of the internal friction angle, respectively, on the development of these two classes of folds. Finally, hybrid models in series H were provided to evaluate the results. Major results were as follows. Firstly, the geometry of modelled detachment and fault‐bend folds was found to be influenced by the geometry of the associated ramps and detachment faults. Thus the crests of anticlines and the trough lines of synclines were located at points of maximum curvature and at inflexion points on a wavy detachment fault or wavy ramp, respectively. Second, two important additional factors controlling fold style were identified: the friction coefficient, and the presence of along‐strike geometric variations in the ramp or the detachment fault. Layers with low friction coefficients and high internal friction angles formed detachment folds with thick hinges and thin limbs; conversely, layers with high friction coefficients and low internal friction angles created detachment folds with thick limbs and thin hinges. Application of the results to modelling of the Ahwaz anticline in the Dezful Embayment, SW Iran, was successful, and in general the modelled structure was consistent with that observed in the field. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeast Petroleum University is the property of Journal of Northeast Petroleum University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work uses sandbox analogue models to analyze the formation and subsequent inversion of a decoupled extensional system comprised of two segmented half-grabens with thick early syn-rift salt. The segmented half grabens strike perpendicular to the direction of extension and subsequent shortening. Rifting created first a basement topography that was infilled by model salt, followed by a second phase of extension and sedimentation, followed afterwards by inversion. During the second phase of extension, syn-rift syncline minibasins developed above the basement extensional system and extended beyond the confines of the fault blocks. Sedimentary downbuilding and extension initiated the migration of model salt to the basement highs, forming salt anticlines, reactive diapirs, and salt walls perpendicular to the direction of extension, except for along the transfer zone where a slightly oblique salt anticline developed. Inversion resulted in decoupled cover and basement thrust systems. Thrusts in the cover system nucleated along squeezed salt structures and along primary welds. New primary welds developed where the cover sequence touched down on basement thrust tips due to uplift, salt extrusion, and syncontractional downbuilding caused by loading of syn-contractional sedimentation. Model geometries reveal the control imposed by the basement configuration and distribution of salt in the development of a thrust front from the inversion of a saltbearing extensional system. In 3D, the interaction of salt migrating from adjacent syn-rift basins can modify the expected salt structure geometry, which may in turn influence the location and style of thrust in the cover sequence upon inversion. Results are compared to the northern Lusitanian Basin, offshore Portugal and the Isàbena area of the South-Central Pyrenees, Spain. [ABSTRACT FROM AUTHOR]

This work uses sandbox analogue models to analyze the formation and subsequent inversion of a decoupled extensional system comprised of two segmented half-grabens with thick early syn-rift salt. The segmented half grabens strike perpendicular to the direction of extension and subsequent shortening. Rifting created first a basement topography that was infilled by model salt, followed by a second phase of extension and sedimentation, followed afterwards by inversion. During the second phase of extension, syn-rift syncline minibasins developed above the basement extensional system and extended beyond the confines of the fault blocks. Sedimentary downbuilding and extension initiated the migration of model salt to the basement highs, forming salt anticlines, reactive diapirs, and salt walls perpendicular to the direction of extension, except for along the transfer zone where a slightly oblique salt anticline developed. Inversion resulted in decoupled cover and basement thrust systems. Thrusts in the cover system nucleated along squeezed salt structures and along primary welds. New primary welds developed where the cover sequence touched down on basement thrust tips due to uplift, salt extrusion, and syn-contractional downbuilding caused by loading of syn-contractional sedimentation. Model geometries reveal the control imposed by the basement configuration and distribution of salt in the development of a thrust front from the inversion of a salt-bearing extensional system. In 3D, the interaction of salt migrating from adjacent syn-rift basins can modify the expected salt structure geometry, which may in turn influence the location and style of thrust in the cover sequence upon inversion. Results are compared to the northern Lusitanian Basin, offshore Portugal and the Isàbena area of the South-Central Pyrenees, Spain. [ABSTRACT FROM AUTHOR]

Many works in the last decades underline the role of evaporites, not just as a conditioning factor but as the engine for subsidence and eventually basin inversion. The western Mediterranean alpine ranges are being investigated in this regard because of the presence of discontinuous units of Permian to Triassic evaporites, deposited in the western Tethys basins. This work presents a thorough analysis of two particular structures (Cañada Vellida and Miravete anticlines) in the intraplate Maestrazgo basin (eastern Iberian Chain, Spain) in which evidence to support their reinterpretation as salt‐driven structures have been recently reported. Our analysis includes (i) a comprehensive stratigraphic and structural study of the folds along their entire trace, (ii) the compilation of thickness and distribution of evaporite–bearing and supraevaporite units, paying special attention to changes in the thickness of units in relation to anticlines, and (iii) the study of fault patterns, sometimes in relation to the mechanical stratigraphy. All three aspects are also documented and discussed on a regional scale. The new data and interpretations reported here reinforce the extensional origin of the Late Jurassic–Early Cretaceous basins, and the role of regional extensional tectonics as the responsible for the development of first‐order syn‐sedimentary normal fault zones driving the formation and evolution of sub‐basins. These basins were subsequently inverted and deformed, including the formation of complex, box‐geometry anticlines that, in their turn, controlled deposition in Cenozoic basins. The review of the arguments that support the alternative of salt tectonics for the origin of such anticlines has allowed us to delve into the sedimentary and tectonic evolution of the inverted extensional basins and to propose a specific model for the development of these faulted anticlines. The role of salt levels and other interlayered detachments in the structuring of sedimentary basins and their inversion is also pondered. The observations in the eastern Iberian Chain reported here have implications to assess ongoing reinterpretations in terms of salt tectonics in other alpine basins and ranges of the western Mediterranean. [ABSTRACT FROM AUTHOR]

Erosional scars, slumps, slides and debrites (mass‐transport deposits) on submarine slopes form relief that influences turbidity current behaviour. However, the interaction of mass‐transport deposit emplacement kinematics (i.e. rapid emplacement versus creep), the morphology of the evolving seafloor topography and subsequent flow types is complicated. This study describes two outcrop examples of deep‐water, predominantly turbiditic, deposits overlying mass‐transport deposits, from the Eocene slope succession of the Aínsa Basin (Spanish Pyrenees). In both examples, the mass‐transport deposit substrate continued to creep contemporaneously with turbidity current deposition and bypass. In the first case study, structures in the mass‐transport deposits are extensional and oriented parallel to flow. In the second, structures are compressional and oriented perpendicular to flow. Mudstones dominate the slope succession, but deposits overlying mass‐transport deposits form sandstone‐prone accumulations. Lateral confinement by flow‐parallel extensional faults enhanced channel‐formation. Channel incision occurred close to the exhumed fault plane on the hangingwall. Incision ceased as the fault gradually locked‐up, and channels avulsed to the hangingwall of a newly active normal fault, while the abandoned channel was filled by a thinning and fining‐upward succession. Barriers formed where the long axes of compressional anticlines developed in mass‐transport deposits formed perpendicular to flow. Here, turbidites filled the bathymetric lows in the axes of synclines. Continued tightening of synclinal depocentres led to repeated stoss side trapping and upslope accretion of coarse‐grained sediment accumulation. This generated thickening and coarsening‐up, followed by thinning and fining‐upward successions, tracking the decreasing, then increasing flow bypass associated with topographic expression on the mass‐transport deposit. This study shows how post‐emplacement creep, and orientation of topographic features on mass‐transport deposits, influence the routing and deposition of contemporaneous turbidity currents, and illustrates examples of facies successions that could be misinterpreted as the product of other autogenic submarine slope processes, such as lateral migration of sinuous channels, or compensational lobe stacking. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of History / Habaršy Tarihi Seriâsy is the property of Al-Farabi Kazakh National University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present study investigated the Sahab area's highly radioactive anomalous zone, utilizing a GRS-500 differential gamma-ray spectrometer to measure gamma-ray activity in the field. Solid-state nuclear track detectors were used to determine uranium concentrations. Our data revealed that gamma-ray activity ranged between 100 and 2500 counts per second, whereas uranium concentrations ranged between 88 ± 9.7 and 355.6 ± 37.4 ppm. The highest uranium concentrations and gamma-ray activity were identified along fault traces and synclines, whereas the lowest levels were detected close to anticlines. As a result, this recommended approach may be utilized to discover concealed structures (faults and folds). Furthermore, higher gamma-ray and uranium concentrations were associated with the Al-Hisa Phosphorite Formation. The correlation coefficient between gamma-ray activity and uranium content was 0.92. The association between gamma-ray activity and lithology revealed that the Al-Hisa Phosphorite Formation had the highest gamma-ray activity levels, which reached 2500 counts per second. The gamma-ray activity was between 200 and 600 counts per second in the Muwaqqar Chalk Marl Formation, 200 to 800 counts per second in the Wadi As Sir Limestone Formation and 100–400 counts per second in the Superficial Deposits and Um Rijam Chert. [ABSTRACT FROM AUTHOR]

The study area is located in southern Iraq in Mesopotamia hydrocarbon province. It’s part of supergiant liner anticline that extends from south to north, South Rumaila, North Rumaila, West Qurna-1, and West Qurna-2. The major fold oriented north-northwest and extends approximately 120Km. All available data was integrated and used in this study to support a better image of the subsurface of the Sa'adi structure. The Sa'adi reservoir in the study area is considered as a secondary reservoir. Therefore, a three-dimensional seismic survey, and seven VSPs, in addition, to well tops that drive from a set of well logs are used in this study. The three-dimensional seismic interpretation and subsurface structure maps of both Tops of Sa'adi and Tanuma formations were performed by Halliburton software (OpenWorks, DecisionSpace Geoscience, and Seismic Analysis). The structure maps of Lower Sa'adi_I and Lower Sa'adi_II have been created based on well tops. A set of well logs (Quad combo) were used to identify the well tops in more than four hundred wells that penetrated the Sa'adi reservoir and distributed over the study area using Geolog software. The structure maps of Lower Sa'adi_I and Lower Sa'adi_II in addition to the cross-sections were set up by Petrel 2018 (Schlumberger software). The study gives highly accurate structure maps of top of Upper Sa'adi, top of Lower Sa'adi_I, top of Lower Sa'adi_II, and top of Tanuma formations. The Sa'adi structure in study area is classified as asymmetrical, non-cylindrical, horizontal, antiform, brachy, gentle anticline. [ABSTRACT FROM AUTHOR]

The Dezful Embayment, in the southwest of the Zagros orogenic belt, contains anticlines that have different geometries in vertical and horizontal sections. One of these anticlines is the NW–SE trending Bibi-Hakimeh anticline, with a length of 71 km and a width of 5 to 8 km. In this research, using the interpretation of six reflection seismic sections, well data and surface outcrops we have investigated the percentage of shortening and changes in the structural geometry of the Bibi-Hakimeh anticline in the Dezful Embayment (southwest of Iran). The interpreted seismic lines show the presence of the forethrust and backthrust in the forelimb and backlimb of this anticline. In the Bibi-Hakimeh anticline, a relatively large thickness of the Gachsaran Formation is observed at limbs, and a small thickness is observed in the hinge zone of the anticline. The movement of this Formation from the top of the anticline towards the limbs has caused to be the lowest thickness of the Gachsaran Formation in the hinge zone of the anticline. Asymmetric and disharmonic geometry of the Bibi-Hakimeh anticline is due to the forethrusts and backthrusts and the presence of the Gachsaran Formation as detachment level. The lowest percentage of shortening is related to the SE part of this anticline is ~10.44% and the highest percentage of shortening is related to its middle part is ~12.41%. [ABSTRACT FROM AUTHOR]

The crustal shortening of the Andean forearc in northern Chile was accommodated by a combination of both thin- and thick-sinned structural styles. However, fold-related inversion of normal faults appears to be the most important structures in the area. To understand the upper crustal shortening mechanisms that acted during the tectonic uplift of this region, an original structural investigation was carried out, integrated with outcrop and regional-scale observations, balanced cross-sections, and pre-shortening restorations of structures exposed along the Paipote fold-and-thrust belt. On this basis, we presented the first balanced cross-section of this region extending for nearly 27 km is presented. The structural styles consisted of east-directed asymmetrical folds involving Paleozoic to Cenozoic strata. The folds were kinematically related to inverted normal faults and thrust ramps that penetrated downward into the basement. The inverted structures resulted from the reverse reactivation of preexisting Upper Paleozoic to Jurassic west-dipping, basement-rooted normal faults that accommodated the tectonic extension that preceeding the Andean orogenesis. The reverse-reactivation of these extensional structures controlled the development of east-verging anticlines, along which the Mesozoic syn-rift strata were elevated above their regional elevation. Other folds exhibit the typical geometry of fold-related thrust ramps (fault–bend folds and fault–propagation folds). These are proposed to result from the development of low-angle thrusts propagating across precursor normal faults with shortcut trajectories, that detach along Jurassic shales, thus forming complex thin-skinned structures in shallow structural levels. The latter is responsible for accommodating a major crustal shortening (nearly 5 km). The east-directed tectonic transport direction was influenced by the original attitude of precursor extensional faults. • Thick-skinned fold-and-thrust belts. • Tectonic of the western Central Andes. • Basin inversion. • Fold-related thrusts. • Paipote Fold-and-Thrust Belt. [ABSTRACT FROM AUTHOR]

Thrust folds have developed significantly in the meso-Cenozoic rock units of the Errachidia-Boudnib basin. The study areas correspond to the north part of the Pre-African Trough, which is located between the Anti-Atlas and the Atlas systems. It is characterized by faulted anticlines that are indicative of a foreland orogenic context. The Atlas system's structural evolution underwent several stages, starting with a Triassic extensional event followed by a period of fault reactivation during the Atlas compression. This research focuses on examining the thrust and detachment folds associated with both reverse and strike-slip components. For this purpose, we performed detailed geological mapping and interpretation of folding and fault slip data. As a result of shortening, field observations reveal that the study area exhibited well-developed thrusting geometry. Preexisting blind faults and multiple decollement levels within favorable formations such as Cenomanian evaporitic marls, Cenomanian-Turonian marls rich in organic matter, and Senonian argillites influence the folding patterns, which are not uniform. The findings demonstrate two key points. First, the most significant folds have formed along major blind thrusts. Subsequently, between these major faults, detachment folds were developed within the Jurassic-Cretaceous strata. Currently, due to erosion, certain thrusts have become visible, including the Ta'bbast thrust fault, Ait Atman (from the first stage), and the Timazguit fault zone (from the second stage). The South Atlas fault largely remains a blind fault. Additionally, the study emphasizes the presence of strike-slip components and en-echelon folding, indicating a transpressional regime during the uplift of the Atlas system. • Significant Thrust Fold Development. • Evolutionary Stages of Atlas System. • Influence of Preexisting Faults on Folding Patterns. • Key Findings on Fold Formation and Fault Visibility. [ABSTRACT FROM AUTHOR]

Gravity-driven sliding of sediments down subaqueous slopes results in mass transport deposits (MTDs) recognised both in outcrop studies and from offshore margins where they may extend for 100's km. While seismic sections may reveal the large-scale geometry of such features, they fail to capture some of the structural and stratigraphic detail necessary for a fuller understanding of the processes involved. Using the late Pleistocene Lisan Formation sediments exposed around the Dead Sea Basin as our case study, we show that interplay between bed-parallel translational slides and associated normal faults may result in stratigraphic repetition through a process we term 'slide stacking'. This mechanism, where retrogressive slope failure results in slides cutting across earlier normal faults, produces repeated sequences with older over younger stratigraphic relationships more usually attributed to compressional (thrust) deformation. Slide stacking results in a ∼25% attenuation of the upper sequence above the basal shear surface (BSS), which is itself associated with liquefaction and fluidised sediment. The displaced stratigraphy above the BSS is also marked by sedimentary rafts that are broken into blocks by normal faults and become increasingly separated from one another during downslope translation. The hangingwalls of synthetic listric faults form roll-overs that are progressively tightened towards the underlying BSS to create overturned anticlines that apparently verge upslope. The paradoxical situation therefore arises of contractional geometries, such as older over younger stratigraphic repetition across slides, and upslope-verging recumbent anticlines with locally overturned limbs being created during downslope-directed gravity-driven extension. The downslope margin of the slide stack displays earlier normal faults that created scarps where much of the sedimentary buttress, that would otherwise support the toe of the slide, was removed. Consequently, this leads to predominantly superficial and unrestrained downslope slipping, resulting in very localised contractional geometries that do not balance the overall extension, as in classical gravity-failure models. Localised deformation of the sedimentary sequence that unconformably overlies the slide stack indicates that downslope translation continued after the initial rapid slope failure, suggesting that the entire MTD remained inherently unstable. Slide stacking operates at km scales with stratigraphic repetition governed by the throw of earlier normal faults and the amount of downslope translation. [Display omitted] • We introduce a new mechanism of slide-stacking that results in repetition of stratigraphic sequences in extensional settings marked by gravity-driven slides and MTDs. • Repetition of beds during slide stacking creates 'contractional-style' structures linked to extension. • Slide Stacking is marked by bed-parallel slides cutting earlier normal faults resulting in repeated sequences, older over younger stratigraphic relationships, and attenuated beds. • Slide Stacking is akin to 'terracotta tiles slipping over one another down a pitched roof' with translated 'tiles' of sediment infilling space evacuated along earlier normal faults. • The recognition of slide stacking on seismics may be confused with repeated thrust slices that would also form downslope of headwall scarps. [ABSTRACT FROM AUTHOR]

Syn-tectonic deposition of sediments (growth strata) preserves a direct record of mountain building-erosion and basin deformation. When and how these sediments incorporated into forward propagating fold-and-thrust (FTB) belts can shed light on the above processes. Despite many years of research, there is still ongoing debate about the timing and mechanisms of the southern Qaidam fold-and-thrust belt in the northeastern Tibetan Plateau. Here, we provide insight into the deformation of the Qaidam Basin and the broader tectonic processes of the northeastern Tibetan Plateau through detailed analysis of the Dafengshan (DFS), Jiandingshan (JDS) and Heiliangzi (HLZ) anticlines along the southern Qaidam FTB. Identification of the growth strata by Area-Depth analysis and age determination indicate that deformation of the DFS anticline initiated in the mid-Miocene (∼15 Ma), and has successively experienced lateral growth (∼15–8.0 Ma) and uplift (∼8.0 Ma-present). This timeline of deformation coincides with periods of mountain building in the northeastern Tibetan Plateau and might be related to the removal of mantle beneath northern Tibet. The synchronization of growth strata with an increase in sedimentation and exhumation rates reveals the reactivation of the tectonic belt around the basin in the mid-Miocene, creating the current basin-range landform; since ∼8 Ma, compression has expanded rapidly into the interior of the Qaidam Basin, leading to incorporation of basin deposits into the FTB. Geomorphological analyses coupled with 3-D fold modeling demonstrate that the JDS and HLZ-fold train with S-shaped configuration is a coherent fold system developed by lateral growth and linkage of two different fold segments in the context of the N–S directional compression of the plateau. Considering the prevalent S-shaped constructions within the basin and the current seismicity, we propose that the dominant structures in the southwestern Qaidam Basin are a series of thrust faults and folds controlled by the compression component of the East Kunlun Fault, with a limited influence from the Altyn Tagh Fault. [ABSTRACT FROM AUTHOR]

Quantification of drainage basins and their networks on fold limbs can lead to a better understanding of spatial relationship between active tectonics and drainage variations. This study aims to evaluate the effect of vertical fold growth on the morphometry of drainage basins and their related networks formed in the Asmari Anticline in the Zagros Fold-Thrust belt. This belt is one of the youngest continental collision zones hosting one of the largest petroleum provinces in the world so that giant oil fields are found in its anticlines. We selected the Asmari Anticline due to the variability of drainage basins and stream networks across the fold's forelimb and backlimb. The basin area (Ba), topographic slope (TS), hypsometric integral (HI), basin shape (Bs), drainage basin orientation (DBO), crescentness index (CI), sinuosity of the main drainage (Smd), spacing ratio (R), and fault density (FD) for 68 drainage basins were calculated. Also, the morphometric characteristics of drainage networks including drainage density (Dd), drainage density of 1st-order streams (Dd1), and drainage frequency (Fs) were analyzed for each limb. Results show that southwestern limb (forelimb) is characterized by high topographic and dip slope, large and relatively circular basins, with high values of CI, Smd and DBO, implying pronounced lateral and headward erosion. Conversely, the smaller and elongated basins, with higher values of hypsometric integral and spacing ratio in the northeastern limb, show lower erosion of backlimb. Higher Dd, Dd1, and Fs values in the southwestern limb (9.54, 6.39, and 39.92 respectively) than the northeastern limb (8.96, 5.69, and 28.33 respectively), suggest higher rates of forelimb erosion, especially where dendritic drainage pattern is developed. This study implies that the fold's divide migration towards NE during fold growth has played a role in the variations of the morphometric parameters in the southwestern and northeastern limbs of the Asmari Anticline. Also, faults and fractures have important effects on the mentioned morphometric parameters. Higher density of faults dominantly with NW-SE trend in the SW limb, especially where trellis drainage pattern is developed, has also facilitated the lateral erosion of the steeply dipping forelimb, resulting in the enlargement of basins with higher values of Ba, CI, DBO, S (spacing of adjacent basins outlets), and Smd. • Morphometric parameters in the forelimb and backlimb of the Asmari Anticline in Zagros were analyzed. • Forelimb is characterized by lateral and headward erosion, and larger, fairly circular, and crescent-shaped basins. • Migration of fold divide and fault orientation control the variation in the morphometry of drainage system in limbs. [ABSTRACT FROM AUTHOR]

Affected by Tianshan uplift, the southern Junggar Basin has experienced multi-stage tectonic movements and formed many large-scale anticlines with zonal distribution. The key to hydrocarbon exploration is to accurately implement anticline traps. This paper is guided by the fault-related folds theory to tectonically interpret several seismic profiles in the southern Junggar Basin and then summarize the anticline types and their hydrocarbon accumulation characteristics. This paper showed that the southern Junggar Basin has a tectonic assemblage pattern of "multi-detachment layers and multi-phase superposition". According to the superimposed shape of the anticlines, they could be divided into overthrust anticlines, compound anticlines and multiple superimposed anticlines, and the horizontal and vertical positions of the different types of anticlines are different. The hydrocarbon accumulating characteristics of the different types of anticlines are shown to be different. The highs of the overthrust anticlines and compound anticlines are stable, and the degree of exploration is relatively high. Although the degree of exploration of multiple overlapping anticlines is low, multiple layers can be exploited simultaneously in the process of oil development, with great hydrocarbon potential. The characteristics of hydrocarbon accumulation in the southern Junggar Basin are discussed in order to provide guidance for efficient hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petroleum Research & Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Petroleum Research & Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two-way wave depth migration (TWDM) can achieve a wider imaging angle in media with significant lateral velocity changes and better imaging results for complex structures with high dip angles than in conventional one-way wave depth migration. Conventional one-way wave migration uses a boundary condition to approximately solve the second-order wave equation, leading to limited propagating angles and inaccurate imaging results, especially for complicated structures. Theoretically, a full-wave equation is of second order and requires two boundary conditions to solve it. The dual-sensor acquisition system can provide sufficient boundary conditions; however, it is challenging to acquire ideal, cost-effective, and factual seismic data, particularly in 3D seismic exploration. Overcoming these shortcomings, we propose a solution that uses conventional surface data to accurately estimate the wavefield at the second layer as another boundary condition. Based on the eigen-decomposition theory, a one-way propagator to suit arbitrary variant velocity on the surface is introduced.The conventional Fourier finite-difference (FFD) and generalised screen propagator (GSP) are utilised to perform the proposed TWDM schemes. The impulse responses proved that the proposed scheme using FFD and GSP operators had no limitation on the propagation angle. The single-shot migrated results in the flat model confirmed that the proposed schemes could achieve better amplitude-preserving performance than the conventional one-way schemes. The dip model showed that the proposed scheme was consistent with the characteristics of one-way wave propagators in imaging steep dippings. Imaging results of the Marmousi model further confirmed that the proposed scheme could obtain more accurate imaging sections for complex structures, especially for steep flanks and deep-seated anticlines. The application of actual dual-sensor seismic data demonstrated that the proposed scheme could achieve a higher imaging quality than the dual-sensor method. [ABSTRACT FROM AUTHOR]

In the Central Iberian Zone, the Cadomian orogenic collapse is represented by chaotic megabreccias, olistostromes and mélange deposits reflecting a drastic change from slope-related deposits, fed by denudation of the Cadomian arc, to offshore-dominant settings episodically punctuated by phosphogenetic processes. In the Ibor and Alcudia anticlines, the pre-rift unconformity is marked by paraconformable to angular discordant contacts separating variable tilted strata of the Ediacaran Lower Alcudian – Domo Extremeño Supergroup and the upper Ediacaran – lower Terreneuvian Ibor Group from the overlying Terreneuvian San Lorenzo and Fuentepizarra formations. The sedimentation of the San Lorenzo Formation reflects two palaeogeographic scenarios: (i) a low-angle stable basement recording shoaling-upward siliciclastic cycles, and (ii) perturbations of basement fault scarps feeding slope-related conglomeratic channels, with NE-directed palaeocurrents, and sourced from topographic palaeohighs controlled by the movement along synsedimentary normal fault systems, such as the so-called El Guijo Fault. The intra-Fortunian age of the pre-rift unconformity is constrained by the ichno- and microfossil content of the succession, and is bracketed between the first occurrence of Treptichnus pedum in the Arrocampo Formation (Ibor Group) and of Anabarella plana in the Fuentepizarra Formation. [ABSTRACT FROM AUTHOR]