Basin Research - Volume 37, Issue 1, 2025

Submarine channel systems play a crucial role in the delivery of clastic sediments, organic carbon and pollutants across continental margins, and help define the stratigraphic architecture of deep‐sea fans and their associated reservoirs. These systems generate complex lateral migration dynamics and resulting sedimentary architectures, which are often overprinted by a variety of local factors. For example, the debris from channel‐wall collapses may block or restrict channel flow, thereby influencing the kinematics of stacking elements and the sinuosity of channels. Here, we investigate the responses of submarine channels to bank failures, using quantitative approaches from the Niger Delta Fulani Channel. Using 3D seismic data, we introduce a novel approach to interpreting the structural framework of channels, referred to as the structural gradient, which quantifies the relationship between sedimentary architecture and underlying structures. Bank failure mass transport deposits (MTDs) were characterised by downstream changes of cross‐sectional area and the proportion of collapsed material deposited. These parameters were used to correlate the responses of channel width, thickness, aspect ratio and lateral migration, as well as the channel planform parameters (i.e., sinuosity and meander amplitude) to the occurrence of flanking MTDs. Our results demonstrate that bank failures significantly influence channel sinuosity by causing localised swings in channel pathways, impacting the overall channel morphology and stratigraphic evolution. The relationships between all channel parameters depend on the ratios of bank failures, and locations of channel‐wall failures. The combined effects of bank failure confinement and structural growth control channel element stacking patterns, resulting in vertical stacks related to compensational relationships between adjacent channel complexes. Significant confinements by MTD emplacement led to rapid channel infill linked to progressive flow relaxation promoting progressive lateral mobility. Channel migration is limited by MTD accumulation to a maximum width of 1700 m. Channel lateral shift reacts to channel‐wall collapses, resulting in limited lateral mobility at regional scale. We show for the first time how the kinematics of submarine channels evolved in terms of the constraints of channel‐wall collapses and active structural deformation.

Bank failures influence the sedimentary architecture of submarine channel complexes, leading to modifications in the erosion and deposition of sediment‐gravity flows, and driving lateral migrations and vertical aggradations of channel element stacking patterns.

Stratigraphy and its associated grain size preserve a record of the dynamic behaviour of source‐to‐sink systems over time. Sediment supply and available accommodation space primarily control downstream grain‐size fining preserved in stratigraphy. In principle, these grain‐size trends can be inverted to quantify temporal and spatial variation in these driving forces. Here, we illustrate how grain size and stratigraphic thickness can be used to quantify fault growth and interaction using the early‐mid Pleistocene Pirgaki‐Mermoussia (P‐M) fault, Gulf of Corinth, Greece, as a natural laboratory. A 2.5 km long exposed cliff section of the uplifted Kerinitis Gilbert‐type delta, which lies in the hanging wall of the P‐M fault, was selected for study. In the field, we traced out stratigraphic units in the lower part of the Kerintis delta, which are bounded by flooding surfaces, and measured their thickness to reconstruct hanging wall subsidence. We collected down‐system grain‐size data at 31 measurement sites using the Wolman point count method. Our results show the observed grain‐size fining rate increase from 11 to 17 mm.km⁻¹ for the lower delta deposits over a timescale of up to 120 kyr. Using a self‐similarity‐based grain‐size fining model and considering a minimum increase in accommodation generation from 0.6 to 1 mm year⁻¹ over this period, we reconstruct an increase in delta sediment supply from ca. 170 to 460 m³ year⁻¹. The integration of stratigraphic thickness measurements with grain‐size fining trends enables quantitative reconstruction of temporal variations in fault‐driven accommodation space and sediment supply, thereby demonstrating fault slip rate evolution. We show an increase in the P‐M fault slip rate during its early history from 1 to 2 mm year⁻¹, reflecting early interaction of the P‐M fault segments over ca. 120 kyr. Reconstructed catchment‐averaged erosion rates are ca. 20% of the footwall uplift, implying a transient response of the landscape to the P‐M fault growth. These analyses demonstrate how grain‐size data from a well‐constrained geological example can be used to reconstruct landscape dynamics quantitatively in fault‐controlled sedimentary systems with high temporal and spatial resolution.

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.

Seismic profiles and TWTT structural maps highlighting the geometry and spatial distribution of pockmarks associated with listric faults. (a–c) depict some of the pockmarks interpreted in this work. (d–g) 3D visualisation of interpreted pockmarks, which are bounded by black dash polygons and adjacent listric faults. Pockmarks in SE Brazil are either developed along the trace of listric faults, or away from their traces on their hanging‐wall side. The studied pockmarks are evidence for local hydrocarbon escape occurring in the Espírito Santo Basin, SE Brazil, 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.

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.

The eastward increase in cumulative offsets on syn‐flexural normal faults in the Molasse Basin corresponds with the weakening of the European lithosphere in the same direction. As such, syn‐flexural normal faults may contain fingerprints of lithospheric mechanisms that control the flexure of a pro‐foreland basin.

The Central Tibet Watershed Mountains (CTWMs) are located in the hinterland of the Tibetan Plateau, extending over 1000 km from west to east. These mountains currently function as a drainage divide, separating Tibet's rivers into eastward‐ and southward‐flowing systems to the north and the south of the mountains, respectively. The timing of watershed formation remains contentious, which hinders a comprehensive understanding of the geomorphic evolution of the Tibetan Plateau. The Qiangtang basin, where the CTWMs are situated, preserves critical geological records essential for deciphering landscape evolution. The age distributions of new detrital zircon U–Pb data from the Middle and Upper Jurassic sandstones in the northern Qiangtang sub‐basin are consistent with a published data set, with age clusters at 200–300, 500–700, 800–1000, 1800–2000 and 2400–2600 Ma. Qualitative provenance analysis identifies the major source rocks as the Palaeozoic and Upper Triassic strata in the CTWMs, as well as the Triassic turbidites in the Hoh Xil‐Songpan Ganze terrane (HSG), which bound the northern Qiangtang sub‐basin to the south and north, respectively. Minor contributions come from Late Triassic intrusive and volcanic rocks, as well as Jurassic granitoids. The abundant detrital zircon data from the Qiangtang basin offers an opportunity to investigate the formation of the CTWMs through a quantified interpretation of the source‐to‐sink system. The combination of inverse and forward modelling of large detrital data sets facilitates the creation of provenance maps and avoids laborious descriptions of individual age modes. Integrated with sandstone petrographic analysis and paleocurrent data, the provenance of the Jurassic sediments can be quantitatively constrained. The CTWMs within the Qiangtang basin consistently served as significant sources throughout the Jurassic, while younger zircon grains were contributed by local sources, including the Triassic and Jurassic magmatic rocks. The proportion of the HSG source in the north increased throughout the basin in the Middle Jurassic but decreased dramatically in the southern Qiangtang sub‐basin during the Late Jurassic. We interpret that the embryonic stage of the CTWMs, which did not fully prevent sediment transport from the HSG to the southern Qiangtang sub‐basin, persisted from the Early to Middle Jurassic. The formation of a well‐defined watershed occurred in central Tibet in the Late Jurassic, probably triggered by the trench‐parallel mid‐ocean ridge subduction of the Bangong‐Nujing oceanic lithosphere.

The proportions of sediments derived from the Central Tibetan Watershed Mountains changed during the Jurassic. The well‐defined watershed formed in the Late Jurassic.

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.

This study provides novel insights into the intricate stratigraphic architecture, depositional origin and post‐depositional modification of the late Miocene–early Pliocene Utsira Formation at the Sleipner CO2 storage, with a focus on the key factors that govern the migration of the injected CO2.

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.

Sediment delivery to the northern Hikurangi Trough has been driven by transverse gravity flows funnelled through the Māhia Canyon, alongside contributions from the overspill of the axial Hikurangi Channel. Large‐scale sediment waves and scours were formed by flows from the Māhia Canyon during MIS2 in response to substantially higher sediment fluxes.

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.

Sedimentary basins in the distal Cenozoic Andean retroarc yield an important geological archive that provides crucial insights into the tectonic and sedimentary processes associated with the different stages of mountain building. At 33° S, the tectonic and sedimentary processes that have operated during the Neogene and Quaternary periods of Andean orogenesis are well documented, whereas information on the Paleogene period remains fragmentary and partly enigmatic. The Paleogene sedimentation in the distal retroarc at this latitude is represented by the Divisadero Largo Formation, a 70‐m‐thick sedimentary unit that has been extensively studied for its fossil content, leading to the controversial definition of the late Eocene Divisaderan South American Land Mammal Age (SALMA). New zircon U–Pb geochronological data provide a valuable age constraint for Paleogene tectonic and sedimentary processes in the Southern Central Andes. Furthermore, we present the first detailed facies analysis of the Divisadero Largo Formation, combined with a sedimentary provenance study and a seismic subsurface characterisation of this unit. Our results indicate that the age of the Divisadero Largo Formation is Palaeocene to early Eocene (~65–41 Ma). Deposition of this unit occurred in a shallow, lacustrine depositional environment with variable water depths and was characterised by a low accumulation rate of 3 m/Myr. During this time, the sediment source was predominately located in the Andean magmatic arc; however, no conclusive evidence of significant Paleogene deformation exists. These characteristics (age, depositional environment, low accumulation rate and provenance) enable a regional correlation with Paleogene deposits farther south in the Neuquén Basin. In addition, based on U–Pb geochronology and sedimentary features, a 20 Myr hiatus could be defined between the Divisadero Largo Formation and overlying synorogenic deposits, as has been proposed farther south, reflecting the northernmost record of this hiatus. Taken together, these new observations help to refine a tectono‐sedimentary model for the evolution of the Southern Central Andes retroarc basin at 33° S that comprises four stages preceding the well‐documented Miocene contraction phase: (i) Late Jurassic–Early Cretaceous extension; (ii) Late Cretaceous contraction; (iii) Palaeocene–middle Eocene tectonic quiescence; and (iv) a renewed phase of late Eocene–Oligocene extension.

New U/Pb age constraints for the Paleogene Divisadero Largo Formation. First detailed facies analysis of the Divisadero Largo Formation. Paleogene basin correlations in the distal Andean retroarc between 35° and 33° S. Dynamic subsidence in the Paleogene Andean retroarc inferred from sedimentary, provenance and seismic data.