High-resolution 3D Seismic Data Research Articles

Seismic geomorphology and evolution of Mid-Late Miocene deepwater channels offshore Taranaki Basin, New Zealand

Deepwater channels play a significant role in deep marine environments by transporting sediments to deep marine environments, but they are also hydrocarbon reservoirs. In contrast, traditional seismic interpretation techniques have provided insights into these features; intricate channel-fill heterogeneities present challenges in revealing small features or associated elements. This study integrates high-resolution 3D seismic data, relative time geologic models (RGT), spectral decomposition, and geobody to identify the Middle-late Miocene submarine channels, their evolution, and their associated deposition elements. The geomorphologic and stratigraphic analysis results have revealed four depositional elements in the study area. These include (1) channel complexes, (2) distributary channels, (3) frontal splay channel complexes, and (4) crevasse splays. However, the channels lack constructional levee development outside the channel banks, which is linked to the limited sediment supply to deep areas. The identified channels are characterized by a narrow to wide width (0.37 km to 1.92 km), a low to high degree of sinuosity, medium incision depths, and lateral migration. The channel fill geometries are highly variable, displaying horizontal to sub-horizontal, lateral accretion, divergent, and inclined reflection packages. Most channels originate as large and wide channels from the northeast and prograde southwest direction of the Taranaki coastline, and they have evolved differently at different development stages. The channel fills exhibit a variable basal amplitude reflection, ranging from medium to high, indicating the presence of sand-prone and mixed facies, such as sand and mudstone. The spectral decomposition maps show variable color intensity, which implies different facies associations within the channels. The channel evolution is likely to be controlled by the interplay of sediment discharge, faults, sea level changes, variable gravity flow strength, and the type of materials supplied from the shelf edge.

Investigating relationships between shoreline process regime, shelf-margin architecture, and deep-water sand delivery: Insights from the early post-rift Hammerhead shelf margin (Bight Basin, southern Australia)

Shelf margins represent a crucial area along source-to-sink systems where sediments are partitioned from the shelf to slope and basin-floor areas. Reconstructing the evolution of these depositional systems is key for interpreting the interplay between past accommodation and sediment supply, and sediment dispersal mechanisms into deep water. In the Bight Basin, on the southern margin of Australia, the Hammerhead shelf margin prograded during the Late Cretaceous following break-up between Australia and Antarctica. This understudied interval offers important insights into source-to-sink processes in a post-rift, greenhouse, high sediment supply setting. A dynamic stratigraphic approach using high-resolution 3D seismic data across the Hammerhead shelf margin has been used to quantitatively characterise 28 clinothems developed over ∼ 1.9 Myrs each with an average duration of ∼ 67,000 years. By applying a shallow-marine process-based classification to shorelines, alongside quantitative analysis of the architecture of their coeval deep-water deposits downdip, statistical relationships and clear links between shallow-marine processes, stratigraphic architecture, and deep-water sand delivery are revealed. A statistically significant relationship between fluvial dominated shorelines, high slope gradients, and mass-transport deposit development is demonstrated, as is a requirement for fluvial influence at the shoreline for the initiation of long run-out turbidite systems. These long run-out turbidite systems are interpreted to have been formed by repeated density flows which lead to greater sediment transfer efficiency and increased sediment supply. This research has direct application to improve prediction of reservoir locations within the Bight Basin for resource exploration and/or carbon sequestration and may also be applied to improve deep-water sediment predictability in other basins worldwide developed in similar tectonic and climatic settings.

Ponding and compartmentalization of a giant Paleogene slope fan by mass transport complexes, offshore Newfoundland, Canada

The Ephesus fan is a giant channel-lobe complex that extends across 460 km2 in the lower structured slope of the West Orphan Basin, offshore Newfoundland, Canada. Based on biostratigraphic dating of offset wells, the fan was likely deposited during the Oligocene. High resolution 3D seismic data reveal that the fan overlies a succession of mass transport deposits that initially created a flatter topographic surface, with later slumping events building elongated ridges. Subsequent high density turbidity currents coursed into the area through a single feeder channel, depositing as lobes onto the flatter area via a network of distributary channels. The lobes were circumferentially ponded and internally compartmentalized by the slump ridges, and the ponding forced the fan to assume its unique, 46 km-wide shape. Distributary channels were initially directed to the south side of the fan, due to the higher relief of the mass transport deposits to the north. After the infill of the accommodation space to the south, subsequent sediment input levelled the remaining rugose topography, and some distributary channels were able to avulse north. Throughout deposition of the fan, distributary channels also continued down-dip from the lobe complex, indicating some sediment bypass continuing down the lower slope. Overlying laminated mudrock displays pervasive polygonal faulting, signaling dewatering processes and the end of deposition by muddy submarine landslides and high density turbidity currents.

Architecture and depositional processes of a submarine channel during the late Miocene in the Yinggehai basin, northwestern South China Sea

Submarine channels are the most extensive sediment transport systems on Earth. They transport sediment over hundreds of kilometers and form sediment deposits in the deep-sea, which can act as hydrocarbon reservoirs. During the Late Miocene, a sinuous submarine channel with sediment processes was discovered in the Yinggehai Basin, northwestern South China Sea. However, process interpretations of the factors that influence the stacking patterns, distribution, and morphology of these sinuous channel deposits in this region are not well understood. Based on the interpretation of high-resolution 3D seismic data and exploration well data, and insights from flow dynamics, we analyzed the factors influencing channel morphology, the architecture of the channel, and its associated geomorphic evolution. The channel can be divided into three sections (Sections Ⅰ, Ⅱ, and Ⅲ) in terms of its planform, and into two seismic units (Unit 1 and Unit 2) in terms of its vertical structure. The sinuous submarine channel originated from a combination of inherent structural features from secondary faults and strong erosion from turbidity currents, which occurred due to a sharp decline in sea level during the Late Miocene. Changes in the channel's orientation led to erosion and channel-margin failures, causing an increase in channel width and a decrease in margin gradient. The distribution and stacking patterns of the deposits are greatly influenced by the provenance, sea level changes, and the morphology of the channel. In Sections Ⅰ and Ⅲ, a river-like secondary flow with a limited lateral density gradient leads to vertical deposits. In Section Ⅱ, changes in the channel's orientation altered its morphology and induced topographic forcing, producing a strong river-like secondary flow. This flow consistently caused sediment to accumulate on the inner bank and erode on the outer bank, leading to lateral stacking of deposits in Unit 2. During the filling of Unit 2, diapiric activity uplifted the strata, resulting in thinner deposition in Section Ⅲ, while deposition thickness increased in Section Ⅱ with sufficient provenance. Unit 1 of Section Ⅲ displays desirable properties for a hydrocarbon reservoir, including thick sandstone with good sorting and roundness. This study provides valuable insights into the diverse architectures of spatially and temporally linked submarine channels, and establishes a correlation between the evolutionary process of the channel and the stacking patterns of its constituent elements.

Accurate Delimitation of Mine Goaves Using Multi-Attribute Comprehensive Identification and Data Fusion Technologies in 3D Seismic Exploration

Existing goaves (e.g., shafts and roadways) in mines represent important hidden dangers during the production of underlying coal seams. In this view, the accurate identification, analysis, and delimitation of the scope of goaves have become important in the 3D seismic exploration of mines. In particular, an accurate identification of the boundary swing position of goaves for 3D seismic data volumes within a certain depth interval is key and difficult at the same time. Here, a wide-band and wide-azimuth observation system was used to obtain high-resolution 3D seismic data. The complex structure of a mine was analyzed, and a seismic double processing system was applied to verify the fine processing effect of a goaf and improve the resolution of the 3D seismic data. Based on the seismic attribute identification characteristics of the goaf structure, we decided to adopt multi-attribute comprehensive identification and data fusion technologies to accurately determine the position of the goaf and of its boundary. Combining this information with the mine roadway engineering layout, we verified the accurateness and correctness of the goaf boundary location. Our study provides a good example of the accurate identification of the 3D seismic data of a roadway goaf.

Coupling relationship and genetic mechanisms of shelf-edge delta and deep-water fan source-to-sink: A case study in Paleogene Zhuhai Formation in south subsag of Baiyun Sag, Pearl River Mouth Basin, China

The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration. Based on the newly acquired high-resolution 3D seismic, logging and core data of Pearl River Mouth Basin (PRMB), this paper dissected the shelf-edge delta to deep-water fan (SEDDF) depositional system in the Oligocene Zhuhai Formation of Paleogene in south subsag of Baiyun Sag, and revealed the complex coupling relationship from the continental shelf edge to deep-water fan sedimentation and its genetic mechanisms. The results show that during the deposition of the fourth to first members of the Zhuhai Formation, the scale of the SEDDF depositional system in the study area showed a pattern of first increasing and then decreasing, with deep-water fan developed in the third to first members and the largest plane distribution scale developed in the late stage of the second member. Based on the development of SEDDF depositional system along the source direction, three types of coupling relationships are divided, namely, deltas that are linked downdip to fans, deltas that lack downdip fans and fans that lack updip coeval deltas, with different depositional characteristics and genetic mechanisms. (1) Deltas that are linked downdip to fans: with the development of shelf-edge deltas in the shelf area and deep-water fans in the downdip slope area, and the strong source supply and relative sea level decline are the two key factors which control the development of this type of source-to-sink (S2S). The development of channels on the continental shelf edge is conducive to the formation of this type of S2S system even with weak source supply and high sea level. (2) Deltas that lack downdip fans: with the development of shelf edge deltas in shelf area, while deep water fans are not developed in the downdip slope area. The lack of “sources” and “channels”, and fluid transformation are the three main reasons for the formation of this type of S2S system. (3) Fans that lack updip coeval deltas: with the development of deep-water fans in continental slope area and the absence of updip coeval shelf edge deltas, which is jointly controlled by the coupling of fluid transformation at the shelf edge and the “channels” in the continental slope area.

Tectonic influence on the evolutionary dynamics of deep-water channel systems along the active accretionary prism margin in the Rakhine Basin, Myanmar: A high-resolution 3d seismic analysis

This study reveals the morphological transformations of a deep-water channel system within the Rakhine Basin in the northeastern Bay of Bengal through a comprehensive analysis of high-resolution 3D seismic data integrated with drilling logs. Employing the “source-channel-sink” paradigm, this investigation examined the impact of various factors, including tectonic transformations, sediment influx, slope dynamics, climatic changes, and relative sea-level fluctuations, on the evolutionary trajectory of these channel systems. Applying precise time-slicing techniques integrating root-mean-square amplitude attributes, coherent amplitude attributes, and horizontal amplitudes on seismic profiles, this investigation recognized three distinct stages in the evolution of channel-levee complexes (CLCs): the Middle Miocene erosional deep-water channel-levee complex (CLC-1), the Pliocene erosional-depositional deep-water channel-levee complex (CLC-2), and the Pleistocene depositional deep-water channel-levee complex (CLC-3). Comparative analysis revealed that the CLC-3 exhibits unique characteristics, including shallower channel depth (D), wider channel width (WC), extensive U-shaped cross-sectional area (S), broader natural levee width (WL) and height (H), and the highest tortuosity coefficient (LC/LS) when contrasted with the other two CLCs. Furthermore, this study substantiated how tectonic processes, primarily the collision between the Indo-Eurasian plates, resulting in the Himalayan and Indo-Burma Range orogenies, have shaped the region's geological and climatic framework, thereby influencing monsoon circulation and precipitation patterns, which in turn augmented detrital material influx into the basin. Moreover, this tectonic collision has led to gradual changes in the slope gradient of the Rakhine Basin and its deep-water areas, impacting internal flow velocities and channel curvature, thus governing deep-water channel systems' development and spatial distribution. Also, episodic sea level fluctuations were identified as significant contributors to sediment transport from shelves to deep-water regions and sediment deposit reworking. Overall, this study underscores the role of tectonic changes after the Eocene in driving the evolutionary dynamics of the deep-water channel system within the Rakhine Basin, Myanmar.

Influence of sedimentary processes and fault tectonics on the evolution of submarine canyons in the East Andaman Basin: Insights from high-resolution seismic data analysis

The Andaman Sea Basin, a well-known back-arc spreading centre and a mature petroliferous basin, presents a unique and complex scenario for understanding the interplay of sedimentary processes and fault tectonics on seafloor geomorphology evolution, particularly in the eastern shelf region. This study, using high-resolution 3D seismic data and published exploratory well-seismic interpretation results, aims to establish a comprehensive stratigraphic framework for the Tanintharyi region, spanning the Lower Miocene, Middle Miocene, Upper Miocene, Pliocene, and Quaternary. A submarine canyon system was identified and investigated along the Tanintharyi continental slope within the East Andaman Basin, comprising thirteen slope-confined canyons arranged predominantly in an east-west vertical slope orientation. By analysing seismic reflection features, five distinct seismic facies have been identified, including basal lag (BL), slump and debris-flow deposits (SDFDs), canyon confined sheets (CCSs), laterally inclined packages (LIPs), and channel-levees (CLs). The evolution of this canyon system, a vital focus of this study, can be categorised into three phases based on the morphology and sedimentary structures observed: canyon initiation, canyon extension, and erosion-sedimentation. The findings of this study highlight the critical controlling role of faults in canyon evolution, with the intensity of fault activity displaying a negative correlation with canyon size, indicating the direct impact of faults on geomorphological changes. In addition, the geomorphological changes induced by fault activity have resulted in changes in sediment supply, dispersal, and sedimentation rates, thus significantly impacting the spatial distribution and dimensions of slope-confined canyons within the East Andaman Basin, with far-reaching implications.

The complex interaction between channel–levee systems and mass transport complexes in the Pliocene–Quaternary Rakhine Basin, offshore Myanmar

Channel–levee systems (CLSs) and mass transport complexes (MTCs) are prevalent in deep-water basins, yet their interplay remains enigmatic. This study uses high-resolution 3D seismic data to investigate the architecture of CLSs and MTCs, aiming to explore how CLSs influence the distribution of MTCs in the Rakhine Basin, Bay of Bengal. Two models are built to illustrate the interaction between CLSs and MTCs. In the first model, large-scale aggradational CLSs created unfilled relief in their overbank environments, which acted as spatially confined topography for subsequent mass-wasting deposits. In this model, the interaction between large-scale CLSs and confined MTCs controls the distribution of confined MTCs. In the second model, laterally migrating CLSs do not create such prominent topographic relief in their overbank environments. This characteristic renders them inconsequential in influencing the distribution of subsequent mass-wasting processes. Consequently, spatially extensive MTCs develop within unconfined settings. This configuration gives rise to lithological traps, which might be common and represent potential drilling targets on continental margins. This study could contribute to a better understanding of the interplay between CLSs and MTCs and have some enlightenment on looking to provide some insight into the search for lithological traps in the Rakhine Basin.

Variability of frontally emergent and confined mass-transport complexes in the Qiongdongnan basin, northern South China sea: New perspectives from 2D and 3D seismic data

The frontal emplacement of the submarine and sublacustrine mass-transport complexes (MTCs) are subdivided into the frontally emergent and confined types. However, it remains unclear what factors control the variability of the frontal emplacement of submarine MTCs. High-resolution 2D and 3D seismic data are utilized to investigate the variability of four MTCs_1–4. The results show that (1) Four MTCs_1–4 herein in the lower slope are subdivided into frontally emergent MTCs_1 and 2 and frontally confined MTCs_3 and 4 (2) The magnitude (e.g., length, width, area and volume); of (frontally) emergent MTCs_1 and 2 is larger than that of confined MTCs_3 and 4; (3) Their flow directions and sources are variable; (4) Height drop (HD) and depth of the basal shear surface (DB) of emergent and confined MTCs_1–4 are greatly variable. Their HDs and DBs as controlling factors present/determine their gravitational potential energy, and HD/DB ratio controls their emplacement type (frontal emergence or confinement). High gravitational potential energy (mainly determined by high HD) of the sliding mass enables landslides to ramp out on the coeval seafloor, resulting in the creation of the gentle and/or moderate fontal ramps. Low potential energy (mainly presented by large DB) of the sliding mass prevents landslides from overrunning the undeformed downslope strata, forming the steep frontal ramps. Scales of sedimentation accumulation rate, slope gradient and earthquakes as possible triggering factors affect variability of MTCs_1–4. The sources of emergent MTCs_1 and 2 are from the continental margin slope. Confined MTC_3 comes from the upper slope of the northern flank of the Xisha uplift and confined MTC_4 derives from a point source (local lower slope). The variability of their gravitational potential energy, mainly depending on variable HDs and DBs, predominantly determines the emplacement variability of submarine MTCs and eventually affects their variable evolutions. This study provides new perspectives and enriches the repository of frontally confined and emergent (submarine) MTCs.

Research on fault-controlled hydrocarbon accumulation in rifted lacustrine basins based on structural geological modeling: a case study of the Banqiao area in Bohai Bay Basin, China

The Banqiao area in the Bohai Bay Basin has experienced three stages of extensional deformation, leading to the formation of numerous fault-bound traps. Faults, acting as boundary conditions for these traps, play a crucial role in hydrocarbon accumulation. In this study, we conducted a 3D structural modeling of the area using high-resolution 3D seismic data and established a fault-reservoir database based on previous research. Our findings reveal four levels of faults in the Banqiao area: basin-controlling faults, boundary faults, derivative master faults, and secondary adjusting faults. The structural units can be categorized into subsag areas, slope areas, stress tran-sition zones, bifurcation and main incised fault zones, and southern block areas. The segmented growth of the main boundary faults controls the evolution of the subsags, with the subsidence center gradually shifting eastward from Rift Phase I to Rift Phase II, aligning with the distribution of source rocks. Fault-bound traps in the Banqiao area include single faults, intersecting faults, and side faults. Faults primarily act as barriers to lateral hydrocarbon migration during the process of hydrocarbon accumulation, while also providing pathways to a lesser extent. By integrating the fault-reservoir database with the fault system classification, we identified four types of fault-controlled hydro-carbon accumulation models: like-dipping fault barrier model, oppositely-dipping fault barrier model, intersecting fault barrier model, and reactivation-controlled secondary hydrocarbon ac-cumulation model. This structural geological model effectively demonstrates the spatial configura-tion of faults and their role in hydrocarbon accumulation in the Banqiao area. The fault control mechanisms presented in the model can also be applied to other blocks in the Bohai Bay Basin, laying a foundation for future petroleum exploration in continental rifted basins and facilitating the ap-plication of big data algorithms in various geoscientific research fields.

Gravity tectonics controls on reservoir-scale sandbodies: Insights from 3D seismic geomorphology of the canyons buried in the upper slope of the Eastern Niger delta basin

High-resolution 3D seismic data analysis was integrated with a calibrated well and biostratigraphy data to present the first overview of a buried Pleistocene canyon system on the upper slope of the eastern Niger Delta, the Galabor Canyon. Attribute maps of specific horizons allow documenting the changing morphologies and infill lithologies of two main branches of the canyon through two stages of activity separated by a reference horizon dated at 0.99 Ma based on well calibration. At the upper slope, growth faults dissect the canyon heads, the catchment of which encroaches a network of valleys incised on the outer shelf. The canyon fill is composed of muddy channels and mass-transport deposits, largely derived from the collapse of canyon walls and sand-rich bodies forming a tract sourced by shelf-edge deltas at the outlet of the incised valleys. High-density turbiditic processes likely control the distribution of sand bodies along the canyon, ranging from tributary fans on the upper slope to 6 km-wide meander belts on the middle slope. The sandy deposits accumulate in minibasins formed along the canyon path, downstream of the subsiding hanging wall of the growth faults and upstream of shale ridges that damp the flow in the canyon. These results show that canyons can be major targets for sand reservoir exploration on the upper slope of large muddy deltas.

The infill of tunnel valleys in the central North Sea: Implications for sedimentary processes, geohazards, and ice-sheet dynamics

Tunnel valleys are widespread in formerly glaciated regions such as the North Sea and record sediment transport beneath ice sheets undergoing deglaciation. However, their complex infill architecture often makes their implications for ice-sheet processes difficult to unravel. Here, we use high resolution 3D (HR3D) seismic-reflection data, improved-resolution conventional 3D seismic-reflection data, and geotechnical information from industry-acquired boreholes to image the infill architecture of buried Quaternary tunnel valleys in the North Sea in unprecedented detail. Ten cross-cutting generations of tunnel valleys are mapped beneath the seafloor of the North Sea where only seven were visible previously. Each generation of tunnel valleys potentially reflects a different glaciation, although our evidence may imply that it is possible to rapidly erode and infill multiple generations of tunnel valleys within a single glacial cycle. The infill of the oldest tunnel valley generations reflects sedimentation during relatively gradual ice-sheet retreat, with occasional episodes of overriding by re-advancing grounded ice. Tunnel valleys formed in more recent glaciations are characterised by more variable sedimentation patterns that reflect dynamic fluctuations of the ice margin, including readvances and stagnation, during valley filling and ice retreat. Numerous subglacial landforms are also imaged within the tunnel valleys; these sometimes contain shallow gas accumulations that represent geohazards for seafloor infrastructure installations. In addition, we document examples where salt diapirism has caused fluids to migrate upwards from depth through faults and into the near-surface tunnel valleys. In instances where this occurs, the relatively porous and often highly continuous subglacial landforms present within their infill may allow these fluids to spread laterally for kilometres or even escape from the seafloor; it is therefore important to consider tunnel valleys when monitoring possible CO2 leakage from carbon capture and storage efforts.

Three-dimensional seismic evidence for depositional undulations nucleated around pre-existing relief, South China Sea

Sediment undulations are widely distributed along continental shelf and slope worldwide. The driving mechanisms of undulations are crucial for assessing the long-term stability of continental slope, which, however, remain poorly understood. We used high-resolution 3D seismic data to investigate the internal architecture and origin of a field of seafloor and subsurface undulations along the slope of South China Sea (SCS). The undulations have narrow troughs and broad ridges. The reflection geometries in the troughs between undulations tend to be continuous and not offset by faults. These troughs terminate at different subsurface depths, commonly ranging from 50 to 400 ms in two-way travel time (TWTT) below the seafloor, often at locations related to subsurface geological structures, such as buried faults and steps within mass transport deposits (MTDs). These subsurface terminations therefore suggest that the undulations are probably depositional features not linked to creep-related basal detachment. The troughs between undulations display an absence of growth features, while the undulations increase in amplitude from base to top (characteristics that are also incompatible with gravitational deformation). Erosional and depositional features are commonly found in the undulations; thus, we interpret the narrow troughs between undulations to represent the areas where sediment-laden bottom currents undergo passage from supercritical to subcritical conditions. These troughs nucleated mostly from fault scarps and seafloor steps induced by past slope failures. Previous alternative interpretations report that these features originate from subsurface creep; alternatively, the present interpretation as sediment transport structures has significant implications for seafloor management and engineering projects.

The Impact of Pre-Existing Faults on Fault Geometry during Multiphase Rifts: The Jiyang Depression, Eastern China

The combination of multi-phase extension and pre-existing fault reactivation results in a complex fault pattern within hydrocarbon-bearing basins, affecting hydrocarbon exploration at different stages. We used high-resolution 3D seismic data and well data to reveal the impact of multi-phase extension and pre-existing fault reactivation on Cenozoic fault pattern changes over time in the Jiyang Depression of eastern China. The results show that during the Paleocene, a portion of NW-striking pre-existing faults reactivated under NS extension and controlled the basin structure (type 1). Other parts of the NW-striking pre-existing faults stopped activity and served as weak surfaces, and a series of NNE-striking faults were distributed in an en-echelon pattern along the NW direction at shallow depths (type 2). In areas unaffected by pre-existing faults, NE-striking faults formed perpendicular to regional stresses. During the Eocene, the regional stresses shifted clockwise to near-NS extension, and many EW-striking faults developed within the basin. The NE-striking faults and the EW-striking faults were hard-linked, forming the ENE-striking curved faults that controlled the structure in the basin (type 3). The NNE-striking faults were distinctly strike-slip at this time, with the ENE-striking faults forming a horsetail pattern at their tails. Many ENE-striking faults perpendicular to the extension direction were formed in areas where the basement was more stable and pre-existing faults were not developed (type 4). There were also developing NS-striking faults that were small in scale and appeared in positions overlapping different main faults (type 5). Additionally, different fault patterns can guide different phases of hydrocarbon exploration. Type 1, type 2, and type 3 faults are particularly suitable for early-stage exploration. In contrast, type 4 and type 5 faults are more appropriate for mature exploration areas, where they may reveal smaller hydrocarbon reservoirs.

Post-rift magma plumbing system in the northern Great South Basin, New Zealand

Late Cretaceous magmatism has been widely documented in the Great South Basin (GSB) of New Zealand, which is mainly relevant to the Gondwana break-up (105–83 Ma) and the separation of Zealandia from Australia and Antarctica (83–66 Ma). However, the magma plumbing system in the GSB is still poorly understood. In this study, we used a high-resolution 3D seismic reflection data to investigate the igneous intrusions that developed in the northern part of GSB. These igneous intrusions occurred from ∼75 Ma to ∼58 Ma that corresponded to the spreading of the Tasman Sea and the Southern Ocean. Most of the igneous intrusions developed above listric faults which formed during rifting stage. Moreover, dykes are also observed between the listric faults and igneous intrusions. Listric faults, dykes and sills formed the magma plumbing system of GSB. This study explored the possible origin of post-rift magmatism in the GSB, and addressed the post-rift magma plumbing system in detail, which greatly promoted the understanding of GSB’ evolution, resource exploration and marine geological hazard assessment.

Multiple sediment source infill in a low-accommodation basin: implications for the late Paleozoic sediment routing system in the southeastern Ordos Basin

AbstractLate Paleozoic strata in the southeastern Ordos Basin comprise targeted reservoirs for tight gas exploration. As a typical intracratonic basin, the Ordos Basin is characterized by low-accommodation space and a complex sediment infilling process, which attracts much attention. During the early Permian, the southeast area was fed by sediments from multiple sediment sources, which makes it difficult to identify the pinch-out of the sand bodies and reconstruct the sediment routing system. In this study, we reconstruct the paleo-topography of the late Paleozoic setting using high-resolution 2D and 3D seismic data. Thus, we identify two types of topography: the eastern block is presented as a semiclosed depression, and the western block is observed as a flat platform. Based on detrital zircon U–Pb data and heavy mineral assemblages, we reconstruct the provenance area and show that early Permian sediments originate from the northern margin of the Ordos Basin and from the northern Qinling orogenic belt in the south. By integrating the trace element contents, carbon and oxygen isotope data and sedimentary structure from core samples, we can observe the paleoenvironment and the corresponding facies associations in these blocks. The eastern block was infilled by a prograding delta; the western block was infilled by a tide-dominated delta or a wavy-dominated delta. By using stratigraphic forward modelling, we find that most sediments in the semiclosed setting are progradational and intensely interacted. In contrast, the sediments in the western block present an open setting, infilled and gently interacted. The fine-grained deposits were not easily preserved due to tidal or wave reworking processes in the shallow-water marine setting, and they were transported into deep-water areas. Furthermore, to explore the dominant factors in a pattern of fluvial–deltaic sand bodies formed in the low-accommodation basin, we rebuild the sediment routing system parameters and plot them on a bubble chart. According to the fitness between the depositional volume and the above parameters, we determine the key factors in the routing systems that formed. The results show that the sediment supply has a high relevance to the depositional volume in a semiclosed setting, such as the eastern block, while the terrain height may drive sedimentation in an open marine setting, such as the western block. We demonstrate that two different infill patterns and different sand-body stacking patterns with multiple sediment sources in a low-accommodation basin may serve as a model for similar settings.

Sand-rich Pleistocene deep-water channels and their implications for gas hydrate accumulation: Evidence from the Qiongdongnan Basin, northern South China Sea

Deep-water turbidite channels are conduits for transporting terrigenous clastic sediments into the ocean, and channel deposits can also act as high-quality hydrocarbon reservoirs. In this study, based on high-resolution 3D seismic data and logging-while-drilling data, four Pleistocene turbidite channels are identified and characterized in the deep-water area. These deep-water channels are sinuous with V- or U-shaped on the seismic profiles, and their evolutionary history can be divided into Unit 1 (Erosion-dominated stage), Unit 2 (Erosion-Deposition stage), Unit 3 (Erosion-Deposition stage), and Unit 3 (MTDs-dominated stage). The internal fillings of these channels are almost basal lags with high-amplitude reflections at the bottom, pelagic sediments with low-amplitude reflections, and mass transport deposits with translucent/transparent seismic facies. Since sand-rich sediments dominate the deep-water channel-levee systems in Unit 3 in the study area, they could act as shallow gas reservoirs and facilitate the accumulation of gas hydrates. By analyzing the source-to-sink systems around the basin, the source of the sediments within the deep-water channels is discussed, which are mainly from the Truong Son Belt. Floods, sea level fluctuations, and earthquakes are the most likely triggering mechanisms of turbidity currents in the Qiongdongnan Basin. This study provides new insights into the Quaternary deep-water sedimentary process, gas hydrate exploration, and source-to-sink systems in the northwestern South China Sea.

Sedimentary deformation relating to episodic seepage in the last 1.2 million years: a multi-scale seismic study from the Vestnesa Ridge, eastern Fram Strait

Seafloor hydrocarbon seepage is a natural fluid release process that occurs worldwide on continental shelves, slopes, and in deep oceanic basins. The Vestnesa sedimentary ridge in the eastern Fram Strait hosts a deep-water gas hydrate system that became charged with hydrocarbons ∼2.7 Ma and has experienced episodic seepage along the entire ridge until a few thousand years ago, when seepage activity apparently ceased in the west but persisted in the east. Although it has been documented that faults and fractures play a key role in feeding the seeps with thermogenic gases, the mechanisms controlling seepage periodicity remain poorly understood. Here we integrate high-resolution P-cable 3D seismic and Chirp data to investigate the spatial and temporal evolution of high-resolution fractures and fluid flow features in the west of the Vestnesa Ridge. We characterize sediment deformation using a fracture density seismic attribute workflow revealing two highly deformed stratigraphic intervals and associated small-scale pockmarks (<20 m diameter). Chronostratigraphic constraints from the region show that these two highly deformed intervals are influenced by at least three major climatic and oceanic events during the last 1.2 million years: the Mid-Pleistocene Transition (∼1.25–0.7 Ma), the penultimate deglaciation (∼130 ka) and the last deglaciation (Heinrich Stadial 1: ∼16 ka). These periods of deformation appear associated with seismic anomalies potentially correlated with buried methane-derived authigenic carbonate and have been sensitive to shifts in the boundary of the free gas-gas hydrate interface. Our results show shifts (up to ∼30 m) in the depth of the base of the gas hydrate stability zone (GHSZ) associated with major changes in ocean bottom water temperatures. This ocean-driven effect on the base of the GHSZ since the Last Glacial Maximum coincides with the already highly deformed Mid-Pleistocene Transition sedimentary interval and likely enhanced deformation and gas leakage along the ridge. Our results have implications for understanding how glacial cycles impact fracture formation and associated seepage activity.

Machine learning elucidates the anatomy of buried carbonate reef from seismic reflection data

A carbonate build-up or reef is a thick carbonate deposit consisting of mainly skeletal remains of organisms that can be large enough to develop a favourable topography. Delineation of such geologic features provides important input in understanding the basin's evolution and petroleum prospects. Here, we introduce a new attribute called the Reef Cube (RC) meta-attribute that has been computed by fusing several other seismic attributes that are characteristics of the reef through a supervised machine-learning algorithm. The neural learning resulted in a minimum nRMS error of 0.28 and 0.30 and a misclassification percentage of 1.13% and 1.06% for the train and test data sets. The Reef Cube meta-attribute has efficiently captured the anatomy of carbonate reef buried at ∼450 m below the seafloor from high-resolution 3D seismic data in the NW shelf of Australia. The novel approach not only picks up the subsurface architecture of the carbonate reef accurately but also accelerates the process of interpretation with a much-reduced intervention of human analysts. This can be efficiently suited for delimiting any subsurface geologic feature from a large volume of surface seismic data.