Basin Research最新文献

Three-dimensional seismic imaging combined with offshore well data analyses is used to interpret inverted faults underlying a thick Layered Evaporite Sequence in the Southern North Sea. By observing changes in evaporite volume above and away from an inversion structure, we infer that reactivation of thick-skinned normal faults induced multi-layered, trans-structural flow in the overlying evaporites. This flow acted to decouple deformation and prevent stress transmission from below to above the salt. The induced salt flow is layer-dependent, occurring mainly within the halite lithologies of the Layered Evaporite Sequence between a folded anhydrite stringer. This stringer folding predates inversion, which later induced stringer fold amplification and deflection nearer to the top of the evaporite sequence. These findings provide insights into the complexities of stratified evaporite rheologies and the timing of basin deformation, with wider implications for contractional salt tectonics wherever thick- and thin-skinned deformation may be coeval.

For nearly three decades, Equinor's Sleipner Carbon Capture and Storage project has demonstrated how the application of geological principles, modelling techniques and analysis of repeated time-lapse (4D) seismic data has helped to characterise the CO₂ plume migration within the late Miocene–early Pliocene Utsira Formation. However, the influence of stratigraphic complexity on fluid migration has been rather poorly understood. This has resulted in a significant degree of uncertainty in the geological characterisation of the storage formation, including the distribution of mudstone-rich elements, which may serve as baffles and barriers for migration of fluid, and elements that allow for their bypass. Our study, utilising high-quality 3D seismic data integrated with wireline-logs, time-lapse seismic and regional contextual information, has shown that the Utsira Formation in the South Viking Graben represents a confined, channelized submarine fan system characterised by a complex stratigraphic architecture. The study has highlighted that the intricate interplay between fan lobes, channel erosion, channel infill and draping of lobes, lobe-complexes and channel incision surfaces by mud-rich layers, provides a first-order control on CO₂ storage compartments and exerts a substantial influence on vertical and lateral fluid flow pathways. The latter is well expressed by the morphology of several mapped CO₂-filled layers. Both generally discontinuous channel-base mud-rich drapes and more continuous lobe-complex and fan mudstone drapes have been locally compromised by processes linked to channel erosion and sand injection, in some cases combined with faulting and fracturing. This complex stratigraphic pattern has probably been exacerbated by post-depositional deformation that triggered fluid and sediment expulsion from the Utsira Formation and the underlying early-Miocene Skade Formation. These factors allowed for increased vertical connectivity between originally disconnected sandstone bodies and fluid migration from deeper to shallower layers, prior to injection of CO₂, thus serving as preferred pathways post-injection.

Subduction trenches receive sediment from sediment gravity flows sourced from transverse pathways and trench parallel axial transport pathways. Understanding the interplay between axial and transverse sediment transport in shaping stratigraphic architectures is hindered by the episodic nature of sedimentary gravity flows and limited datasets, yet such insights are crucial for reconstructing sedimentary flow pathways and interpreting sedimentary records. We investigate sediment routing pathways to the northern Hikurangi Trough of New Zealand using a combination of multibeam, 2D and 3D seismic reflection and International Ocean Discovery Program core data from Site U1520. Site U1520's location downstream of axial and transverse conduits of sediment delivery makes it an excellent location to observe how these processes interact in deep marine settings. We characterise regional basin floor geomorphology and sub-surface architecture of the upper ~110 m siliciclastic sequence of the Hikurangi Trough deposited over the past ~42 ka (Seismic Unit 1; SU1). Sediment delivery to the trough is fed by sediment gravity flows sourced from both the shelf-incising transverse Māhia Canyon to the south-west and the axial Hikurangi Channel to the south. Flows sourced from these systems have a strong influence on the geomorphology of the region and are responsible for forming large-scale bathymetric features such as erosional scours and sediment waves. Sedimentary features identified within SU1 indicate that sediment transport via the transverse Māhia Canyon was more significant than that of the axial Hikurangi Channel throughout the last 42 ka, particularly during the last glacial period when sea levels were lower, and sedimentation rates were extremely high (up to ~20 m/kyr). This study emphasises the need for a nuanced consideration of transverse and axial systems and how they may influence sediment records and the geomorphic characteristics of trench systems.

Downstream changes of fluvial styles and related grain size triggered by localised tectonically-induced changes in riverbed gradient are still poorly understood, especially in terms of their impact on the accumulation of alluvial successions. In this study, we analyse the morpho-sedimentary response of rivers crossing multiple fault-controlled subsiding areas, by using field data from the age-constrained, fluvial deposits of the Pleistocene Dandiero Basin (Eritrea) to create scaled, controlled laboratory experiments performed at the Eurotank Stratigraphic Analogue Modelling Facility (Utrecht University, NL). With this experimental series, we quantified the impacts of degradational/aggradational fluvial dynamics showing that stream bed degradation occurs upstream of subsiding depocenters following the localised increase in river slope. Following a tectonic-induced decrease in river slope, aggradation occurs downstream of the fault zones, and marked in-channel aggradation promotes the branching of major river trunks into minor channels and the development of unchannelised tabular bodies. Experiments also show that highly subsiding areas promote the accumulation of fine-grained deposits, but their accumulation zones shift downstream following localised bed aggradation. We show that where multiple subsiding areas occur along a river, localised depocenters separated by degradational areas occur, causing general starvation in the downstream subsiding reaches, where lacustrine deposition became common. These findings suggest that the role of active faults could have been significantly overlooked when studying how changes in allogenic forcings impact alluvial strata. The results obtained in this study offer a solid basis for creating a predictive model for facies distribution in river dynamics, providing insights into detecting neotectonic signatures in active rivers and identifying tectonic imprints on ancient fluvial successions.

Flexure in pro-foreland basins results from the interplay between (sub)surface loading, foreland plate strength, inherited crustal architecture, and the degree of plate coupling. It is expected that lateral variations in these controlling mechanisms will result in along-strike variations in the flexural profile of the foreland basin. This will directly influence the position and width of the forebulge, thereby altering the associated extensional stress field in space and time around which syn-flexural normal faults accommodate deformation. As such, spatiotemporal variations in the growth of the syn-flexural normal faults in foreland basins may provide valuable information regarding the evolution of an orogen-foreland basin system. However, the relation between syn-flexural normal fault growth and the mechanisms controlling foreland basin flexure remains underexplored. Here, we quantify lateral and vertical throw distributions for growth strata of syn-flexural normal faults in the German Molasse Basin. This allowed us to develop a 4D fault growth model. Our results indicate that the flexure in the German Molasse was associated with both the nucleation of new faults and selective reactivation of pre-flexural faults, with the latter depending on fault burial depth at the onset of flexure. Furthermore, our results suggest that localisation of the extensional strain and deformation at the top of the European plate during flexure controlled the nucleation site of the syn-flexural normal faults in the German Molasse. Additionally, the spatiotemporal variation in the onset of syn-flexural normal fault activity suggests a northward migration rate of 7.8 mm/year of the orogen-foreland basin system. This is consistent with previous estimates based on other independent methods. Lastly, a west-to-east increase in cumulative syn-flexural offsets down-dip the normal faults in the German Molasse Basin may have been controlled by orogen-parallel lithospheric strength variations in the downgoing European plate.

Buried pockmarks are features associated with fluid seepage through ancient seafloors. In this work, high-quality 3D seismic reflection and well data are used to investigate the geometry, distribution and significance of listric faults and associated pockmarks in a salt minibasin from offshore Espírito Santo, SE Brazil. The results show that six out of ten pockmarks interpreted in the study area have crescent, elliptical, or elongated shapes. They occur along the trace of listric faults and on their immediate hanging-wall blocks, with pockmarks' long axes being nearly parallel to the strike of the faults. The pockmarks are approximately 1300–6200 m long, 600–4000 m wide, 30–139 m deep, and buried 50 to 500 m below the modern seafloor. They can be divided into fault-strike (type I) and fault hanging-wall (type II) pockmarks based on their spatial relationships. Type I represents pockmarks developed along the trace of listric faults, which acted as fluid conduits. Type II pockmarks were developed away from fault traces on their hanging-wall blocks. Their occurrence near listric faults was controlled by multiple factors, including the relative depth, length, area, and maximum displacement of listric faults. In addition, listric faults below horizon H4—an Upper Paleogene unconformity—do not show pockmarks around them. Listric faults with greater length, area, and maximum displacements were more likely to form pockmarks. In conclusion, the studied pockmarks are evidence for local hydrocarbon escape occurring in the Espírito Santo Basin since the Miocene. The results presented here can be applied to other regions around the world prone to geohazards and where carbon and hydrogen storage solutions are being proposed.

Orogenic wedges juxtapose tectonic units that originated far from each other, and tracing these back to their origin is often difficult. We have studied two contrasting serpentinite–sediment associations of the Alpine-Apennine orogenic wedge of eastern Elba Island with the help of a detrital zircon study of the sediments and a geochemical comparison of the relic phases of their associated serpentinites. We demonstrate that these very likely originated in different branches of the Ligurian Ocean and in contrasting tectonic settings, one during opening of Alpine Tethys and the other during Apenninic contraction-exhumation. First, the Early Cretaceous Palombini shales are associated with abyssal ocean floor serpentinite–ophicalcites of a Ligurian ophiolite (LO) that originated in the western branch of the Ligurian Ocean during ultraslow spreading. They have an Adria/African zircon provenance, indicating proximity to Adria rather than Corsica-Europe and the associated serpentinites are highly depleted and relatively little deformed. The second sediment–serpentinite association has a tectonised serpentinite band in contact with highly deformed, Miocene blueschist facies metasediments. Detrital zircons of these metasediments (Acquadolce (AD) and Pseudomacigno) record major Eocene–Oligocene U–Pb zircon age peaks, with an igneous provenance in the western and central Alps respectively. An age peak at ca. 38 Ma links the Pseudomacigno sediments to calc-alkaline volcanic rocks of the central Adamello massif, whilst an Oligocene age peak at ca. 32 Ma indicates western Alpine sources for the AD Unit. The associated massive, highly tectonised AD serpentinite represents most likely a mantle sliver of subcontinental lithospheric mantle, which together with Oligocene blueschist facies rocks underwent synorogenic Apenninic tectonic extrusion during W-directed subduction–rollback of the eastern branch of the Ligurian Ocean.