Basin Research最新文献

In the Palaeocene North Sea, pulses in turbidite fan deposition and shelfal progradation have been correlated with episodes of regional uplift caused by a precursor of the Icelandic Plume. In the East Shetland Platform, the specific impacts of dynamic uplift on the regional palaeogeographic evolution are less understood. Using new, high-resolution 3D seismic data from an underexplored proximal area, we investigate the palaeogeography of the East Shetland Platform in terms of the extent and timing of erosion versus deposition, focusing on how these can be used to reconstruct changes in relative sea-level along strike. Using a combination of well data, clinoform-based seismic stratigraphy and seismic attribute analysis of >60,000 km² of 3D data, we have obtained palaeogeographic maps of multiple Palaeocene to Early Eocene units, with high temporal resolution for the Late Palaeocene–Early Eocene Moray Group. This includes six unconformity-bounded units marked by prograding clinoforms of the Dornoch Formation, which are covered by backstepping sequences of the Beauly Member (Balder Formation). Temporal and spatial changes in the distribution of downdip depocentres and updip unconformities indicate strong lateral variability in patterns of shelf accommodation/erosion and local sediment supply. This results from a complex interplay among laterally uneven relative sea-level fall, inherited topography, time-varied sediment entry point distribution and along-shore sediment transport regimes. Unconformities and palaeogeographic maps suggest a first-order control on erosion and sediment distribution promoted by the transiently and differentially uplifted topography of Shetland, which is characterized by an anomalous erosive history in the Bressay High, in the centre of our study area, where the Lower Dornoch Formation has been eroded and marked fluvial incision is observed. Ultimately, results indicate shorter-wavelength and shorter-period variations in uplift than what is typically assumed for dynamic topography, perhaps as a result of additional modulation by lithospheric structures or influence of previous rift-related faults.

Overpressure-driven hydrofracturing pervasively occurs in sedimentary basins worldwide. Hydrofracture zones can vertically penetrate several kilometres of rocks and are dominant pathways for basin-scale fluid migration and energy circulations. Although hydrofracture zones have been extensively described and analysed in the literature, the mechanisms on how hydrofracture zones form and evolve are still poorly understood. In this study, we explore the formation and evolution of a hydrofracture zone in the northern South China Sea, using numerical models constrained by borehole and seismic data. We show that the radius of hydrofracture zone decreases with the strata permeability. The growth of hydrofracture zone is mainly controlled by rock density ($��\rho �$), pressure at the origin of hydrofracture zone (p_b), Poisson's ratio (v), and the radius of the hydrofracture zone at its origin (r). Moreover, as the hydrofracture zone grows, a transition layer forms between the overpressured hydrofracture zone and the overlying hydrostatic pressure zone. The thickness of this transition layer is controlled by strata permeability, strata thickness, overpressure, and pressure gradient within the hydrofracture zone. This study quantitatively explores the development and evolution of overpressure-driven hydrofractures for the first time, and has wide applications in geohazard assessment, hydrocarbon exploration, carbon circulation, and climatic change.

During the Early Cretaceous, massive evaporite accumulations formed in the opening South Atlantic. However, the depositional model of these salts is still poorly constrained at the scale of the West African margin. The present study focuses along the proximal domain of the south Gabon-Congo-Cabinda margin and is based on (i) log interpretations of 246 wells crossing undeformed to weakly deformed evaporite intervals and (ii) a structural characterization of the basement. The evaporites show 11 regional evaporite depositional cycles (CI–CXI) bounded by meter-thick shale beds. The cycles display alternating meter-scale carnallite-halite beds that can be correlated over several hundred kilometres, and CVI, CVII, CVIIIa and CX culminate in localized tachyhydrite accumulations. Cross section correlations and isopach maps help to understand the palaeogeographical evolution of each cycle and depositional environments that evolved from relatively deep at the base of cycles, to very shallow at their top. CI formed a mosaic of halite-prone depocenters deposited in pre-salt topographic relief. CII and CIII were deposited uniformly over a flattened basin in a highly extended brine pond. From CIV to CVIIIa, the stratigraphic architecture of the salts was shaped by freshwater inflow sourced from the north and possible basement movements. This setting, together with an increased confinement of the proximal domain from the distal one with basin drawdown, favoured the development of depocenters with perennial subaqueous conditions and extreme salinities, in which more than 70 m of tachyhydrite accumulation could locally be preserved. From CVIIIb to CXI, the basin returned to a flat depositional setting without well-developed depocenters and with increasing subsidence westwards. Marine influx increased starting from CX, allowing the deposition of sulphate beds. The salt section is capped by anhydrite deposits interbedded with clastic and dolomite, before the final marine invasion of the basin. For the first time, this study provides a large-scale depositional tectonostratigraphic setting of the Aptian salts in the proximal domain of the West African margin. The results are of interest for K-Mg salts exploration resources in the Aptian and pave the way for further investigation of the salt depositional environment in the distal domain of the margin.

The shelf-margin deltas are the primary ‘sources’ of interest in siliceous submarine fan source-to-sink systems. However, less has yet to be discovered about the roles and effects of the shallow water platform situated on continental slopes. Using the Miocene sediments of the Ledong-Lingshui Sag in the western part of the Qiongdongnan Basin (QDNB), this paper studies the YC35 coarse-grained submarine fan that developed in the Meishan Formation (Fm.). The material sources, depositional characteristics, and developmental mechanisms of this fan were investigated. The restored palaeogeomorphology, based on high-resolution 3D seismic data, shows that a shallow water platform exists. According to geochemical palaeoenvironmental data, the shallow water platform was ideal for forming carbonate deposits in the Meishan Fm., owing to the warm and humid palaeoclimate and the shifting trend in palaeowater depth. Based on the combined source tracing of heavy minerals, coherence slices, and seismic profiles, the shallow water platform and the Ningyuan River source on Hainan Island contributed to the YC35 coarse-grained submarine fan. Compared to submarine fans formed during different periods, coarse-grained fan stands out due to its distinct sedimentary structure, rock composition, and microlithological characteristics. Aside from not following the usual Bowmar sequence, there is an excess of gravel and no clear bedding or lamination. A large number of rock fragments, mostly granite and sedimentary rock (carbonatite), make up the rock composition. According to these results, the shallow water platform significantly affects submarine fan material composition. In addition, the attribute slice based on the root mean square reveals that shallow water platforms moderate peripheral deposition. We attribute the development and proximal supply of the shallow water platform to diapirism and forced regression. Our research provides novel insights and comprehension into the investigation of submarine fan sedimentary systems.

Sand transport and its deposition in deep marine basins are controlled by diverse climatic, tectonic, physiographic and oceanographic processes. Disentangling the impact of each of these drivers on the sedimentary record is a fundamental challenge in the study of source to sink systems. In this study, we investigate seismic and borehole data by combining statistical and spectral analyses to identify the factors controlling sand deposition in the deep Levant Basin (Eastern Mediterranean) during the Pliocene–Quaternary (PQ). We interpret the sand content in boreholes from gamma ray (GR) logs and identify two major trends in sand/shale ratios. On a million-year scale, we demonstrate that since the Early Pliocene (5.3 Ma), sand content gradually increased until it formed a ca. 100 m thick and widespread sheet of sand at the top of the section. On a shorter time scale, we identify oscillations in sand content depicting significant power of periodic components at the 350–450 ky, 90–150 ky and 10s ky bands. The long-term increase in sand content reaching the deep Levant Basin is interpreted as a result of the Nile Delta propagation, which had continuously shortened the distance between the edge of the Nile delta that is the source of sand, and the deep Levant Basin. The superimposed short-term oscillations are interpreted as Milanković cycles, reflecting hydroclimatic oscillations of water and sediment discharge into the Eastern Mediterranean Sea by the Nile River. This demonstrates the hydroclimatic control on sand deposition in the deep Levant Basin. Our observations are consistent with the development of a submarine channel system along with the accretion of the Nile delta, which may have served as a pathway for sand delivery via high-energy turbidity currents that reached the Levant Basin.

Crustal-scale high-displacement (>10 km) normal faults are not captured in existing tectono-sedimentary models of rift basins. We used 2D and 3D seismic reflection and well data to perform a structural and source-to-sink analysis of the southern part of the Klakk Fault Complex and the western part of the Vingleia Fault Complex, Mid-Norwegian rifted margin. The north–south trending Klakk Fault Complex has a zig-zag to sinuous plan-view geometry, forming a series of structural recesses and salients along strike. In cross-section, the fault complex has a listric to convex-up or low-angle planar geometry with displacements above 20 km. This fault complex exhumed basement highs, the Frøya High and Sklinna Ridge, in its footwall and created a series of supradetachment basins, for example, the Rås Basin, in its hanging wall. In contrast, the northeast-southwest trending Vingleia Fault Complex has a zig-zag geometry in plan view and planar to listric geometry in cross-section and displacement of up to 5 km. This fault has the Frøya High in its footwall and the southern Halten Terrace in its hanging wall. Restoration of selected structural cross-sections shows a prominent fault-parallel ridge, up to 15 km east of the Klakk Fault Complex interpreted as a palaeodrainage divide. This divide separates steep drainages developed along the west-dipping footwall scarp to the Klakk Fault Complex, from broader, gentler east-dipping drainages up to ca. 10 km long developed on a back-tilted dip slopes along the eastern side of the Frøya High and Sklinna Ridge. Progressive headward erosion of active flank catchments was enhanced around topographically elevated structural salients to the point of capturing previous dip-slope-directed drainages during the earliest Cretaceous. A network of submarine canyons develop down-dip of the drainage catchments along the Klakk Fault Complex scarp, whose geometries and length are controlled by their location with respect to the structural salients or recesses, and the presence of fault terraces. The middle Jurassic-earliest Cretaceous synrift deposits form two seismic sequences that are filled with five distinctive seismic facies that record the evolution from a linked normal fault during rift climax to a high-displacement stage. During the high displacement stage, exhumed local continental core complexes formed structural salients, separated along strike by structural recesses at the heads of supradetachment basins. Key elements of the high-displacement fault stage include (i) the development of structural salients at sites of rift climax displacement maxima, (ii) development of supradetachment basins in rift climax displacement minima and (iii) migration of major depocentres away from the centre of rift climax fault segments. We synthesise these observations into a generic tectono-sedimentary model for high-displacement faults.

The Yinggehai Basin is situated at the junction of Indochina and the northern South China Sea (SCS). The origin of the Yinggehai Basin is generally believed to be controlled by the rotation of the Indochina block along the Red River shear zone (RRSZ), which was formed by the collision of India with Asia during the Oligocene. However, the Eocene structural mechanisms of this basin remain debatable. Some studies suggest that the Eocene reactivation of the palaeo-suture zone (which serves as a precursor to the RRSZ) has influenced the region. In contrast, others propose that the NNW–SSE extension of the northern SCS caused by the subduction of the palaeo-SCS towards Borneo in the Eocene has played a significant role. To address these controversies, our study takes into account these two crucial factors using physical analogue modelling. The experimental results, including slow sinistral strike-slip along the palaeo-suture zone and the adjacent NNW–SSE extension, successfully explain the observed fault pattern during the Eocene period. It is noteworthy that the former primarily controlled the Eocene structure in the northern region of the Yinggehai Basin, whereas the latter played a pivotal role in shaping the ENE–WSW Eocene structures on the eastern slope of the basin. The westward propagating faults of the Qiongdongnan basin are cut off by the Yinggehai Basin structures at later large-scale rotation stage. The experiment indicates that the basin evolution exhibits diachronous characteristics, with subsidence in the south occurring later than in the north. Our modelling results provide valuable insights into the key controlling factors that shaped the evolution of the basin during each stage. Furthermore, our findings offer evidence of the interaction between two significant tectonic processes: Indochina extrusion and the opening of the SCS.

The shelf-slope margin is a geomorphic zone with a change in gradient between subaqueous shelves and slopes, which extends towards the submarine basin-floor. It is important because it partitions distinct sedimentary and biogenic processes between the shallow and deep-water realms. The initiation of a shelf-slope profile from pre-existing conditions, and the evolution of shelf margins in space and time has been the focus of numerous studies, particularly from seismic data sets on passive margins, although markedly less-so from active tectonic settings. This study documents the initiation and evolution of a shelf-slope margin in the well-studied Eocene Aínsa Basin (Spanish Pyrenees) through the segmentation of a mixed carbonate-siliciclastic ramp via contractional tectonics and differential subsidence. The basinward propagation of a series of thrusts through the ramp allowed the maintenance of shallow-water, predominantly carbonate sedimentation on their uplifted hanging wall anticlines. Conversely, the deepened foot wall synclines became muddy slope environments, and their axes became the main loci of siliciclastic turbidity current bypass and deposition. The deflection of turbidity currents around uplifted areas towards the synclinal lows allowed for the continuation of carbonate production at the bathymetric highs, which kept pace with subsidence. The interface between shallow- and deep-water sedimentation (i.e. the shelf-slope margin) was an erosional and composite submarine scarp surface generated by several phases of large-scale mass wasting of the aggrading shelf carbonates, and healing by onlap of slope turbidites against the scarp. Continued thrust propagation and basin deepening led to the progressive headward degradation of the surfaces, resulting in an apparent retrogradation of the shelf-slope margin and onlapping slope deposits. This model for the tectonically controlled conversion of a submarine ramp into a shelf-slope profile contrasts with conventional models that consider shelf-slope margins to be inherently progradational after initiation. This study also challenges the notion that large-scale degradational surfaces and thick successions of submarine landslides are inherently diagnostic of canyons and their fill.

Bedforms associated with turbidite systems are commonly observed on seafloor. Previous studies have analysed bedform morphological and sedimentary features to determine their formation mechanisms and flow dynamics. However, the seafloor topography and ocean circulation have comprehensively influenced both down- and along-slope turbidity flow processes, complicating the spatial distribution of the related bedforms. Three-dimensional seismic data (3D) were used to depict the morphological and sedimentary features of the bedforms around the canyon mouth on the slope of the Rovuma Basin (offshore Mozambique), to reveal the spatial distribution and related flow processes of the bedforms. The results show that the spatial morphological and sedimentary features of the submarine bedforms at canyon mouths are controlled by the combined action of down- and along-slope factors. The along-slope bottom currents influence the deposition distribution of the turbidity current at the canyon mouth. However, slope breaks control bedform morphological and sedimentary features during downslope turbidity currents. Coarse-grained material of turbidity current flows along the axial zone of the canyon mouth, forming a linear series of crescent-shaped net-erosional cyclic steps characterized by short steep stoss sides and long gentle lee sides. The fine-grained material of the turbidity currents is deflected towards the northern flank of the axial zone by the bottom currents and deposited as undulating net-depositional cyclic steps at upper reach of the northern flank, showing long gentle stoss sides and short steep sides. Slope breaks enhance the erosion on cyclic steps by altering the velocity of turbidity current, forming net-erosional cyclic steps with the manifestation of both short and steep stoss and lee sides at lower reaches of northern flank. The turbidity current in the axial zone formed lateral flow diversions caused by the obstruction of the cyclic steps. The flow diversions converge with the downslope flowing unconfined turbidity current at the northern flank and constitute a confluence characterized by continuous variation of flow properties, forming the cyclic steps featuring irregular morphology.

The Miocene sequence in the Roer Valley Rift System consists of alternating open-to-shallow marine, coastal and fluvio-deltaic deposits. In this study, well logs, bio-chronostratigraphy and seismostratigraphy are used to characterize major units and their bounding unconformities and to infer sediment dispersal patterns. Three major unconformities occur in the sequence: the early, middle and late Miocene unconformities (EMU, MMU and LMU). The EMU formed due to tectonic motions related to the Savian phase. After formation of the EMU, a broad depocentre developed in the south-eastern part of the Roer Valley Graben (RVG). Sediment accumulation increased during this period and peaked in the middle Langhian, after which it diminished again to a low level during the late Serravallian. The decrease in sediment accumulation coincided with a period of tectonic subsidence along the major bounding fault zones (i.e. the Peel Boundary Fault System, the Feldbiss Fault System and the Veldhoven Fault System). The resulting transgression caused sediment starvation in the central RVG. Subsequently, global sea-level fall during the early Tortonian caused large-scale erosion, and formation of incised valleys on the highs adjacent to the RVG (Peel Block and Campine Block), as well as the south-eastern RVG, forming the MMU. However, sedimentation continued during this period in the central part of the RVG where no erosional hiatus developed. From the Tortonian onwards, accumulation rates increased again. The depocentre shifted towards the north-west and clinoforms developed in the RVG. During the latest Miocene, the depocentre was concentrated along the south-western margin of the RVG. Meanwhile, the depositional environment of the entire RVRS gradually shallowed as the LMU was formed.