This interdisciplinary session explores the causes and consequences of processes shaping submarine landforms and seafloor evolution. Topics include erosional and depositional dynamics, marine bioconstructions, gravitational driven and current-induced sediment transport, submarine landslides, active deformation, volcanic activity, faulting and folding, and emphasis is given to subseafloor fluid migration and venting at the seafloor. Contributions may address marine or lacustrine environments across all physiographic regions, including coastal zones, marginal seas, continental shelves and slopes, oceanic plateaus, abyssal hills, mid-ocean ridges and accretionary wedges. We welcome studies that integrate diverse approaches, such as satellite-derived and hydroacoustic seabed characterizations, visual and ROV-based observations, seismic imaging and sedimentary, geochemical, and/or geological sampling. Such interdisciplinary studies provide exciting opportunities to advance quantitative geomorphology, extend it offshore, and deepen our understanding of the processes shaping submarine landscapes.
Orals: Thu, 7 May, 16:15–18:00 | Room -2.20
Submarine mass-wasting processes significantly shape continental margins and represent major geohazards, such as tsunamis and damage to offshore infrastructure. Despite being a classic example of a passive margin, the Indian continental margin remains relatively understudied in terms of submarine mass-wasting processes compared to other global margins. This margin contains several petroliferous basins, with the Krishna-Godavari Basin being a key area for deep-water hydrocarbon exploration along the Eastern Indian Margin.
Recent high-resolution multibeam bathymetric data from the Krishna Basin have revealed, for the first time, the presence of a giant submarine slide. The headscarp lies about 10 km offshore, near the mouth of the Krishna River, which delivers a large sediment load to the margin. Morphometric analysis reveals a slide scar with a perimeter of approximately 60 km and a surface area of about 1,600 sq. km, making it one of the largest documented submarine slides along the Indian continental margin. The associated mass transport deposits (MTDs) extend over an area of ~5000 sq. km, reaching up to 160 km seaward from the scar, indicating a large-scale sediment remobilisation event.
The morphology of the slide scar and the widespread distribution of the MTDs suggest the occurrence of multiple landslide events following an initial megaslide. An integrated analysis of marine geophysical data and geological context indicates that several factors likely contributed to slope instability. These include the presence of gas hydrates, high sediment influx in the upper slope region from the Krishna River, regional fault systems, and neotectonic activities - all of which appear to be primary contributors to the megaslide. Additionally, recent studies propose that intense cyclonic activity in the Bay of Bengal may also act as a trigger for recurrent submarine slides, highlighting the complex interplay of geological and climatic influences in this region.
How to cite: Cheriya Moothoor, B., Rajan, A., and Palayil, J. K.: The Krishna Slide: A newly discovered massive submarine slide off the Eastern Indian Margin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-250, https://doi.org/10.5194/egusphere-egu26-250, 2026.
Deltaic sedimentation plays a crucial role in shaping submarine geomorphology. During the deposition of the Neogene Hanjiang Formation, the Enping Sag was situated at the front of the ancient Pearl River delta. Influenced by the interplay of fluvial, wave, and tidal hydrodynamics, it developed a complex submarine geomorphological pattern. Investigating the genesis and distribution of sand bodies at the Neogene delta front in this area is essential for understanding the spatial arrangement of various sedimentary bodies and their geomorphological effects. Based on a high-frequency sequence stratigraphic framework, this study integrates core, thin-section, well-log, and seismic data. Utilizing seismic sedimentology, thin-layer seismic inversion, and 3D geological modeling, combined with fifth-order relative sea-level curves, we systematically characterize the three-dimensional distribution of sedimentary microfacies within sub-layers of the Hanjiang Formation and their impact on submarine geomorphology. Results indicate that sedimentation during this period was predominantly controlled by fluvial-wave interactions, forming delta-front deposits comprising five microfacies. Subaqueous distributary channels, trending approximately north–south, consist mainly of medium-grained sandstone with muddy intraclasts and scour-fill structures, forming a distinct submarine channel system. Channel-adjacent deposits (e.g., crevasse splays and natural levees) form belt-like gentle slopes or levee microtopography along channel margins, characterized by poor sorting. Wave influence promoted the development of shore-parallel coastal sand bars and extensive inter-bar sheet sands. Coastal bars are composed of medium- to fine-grained sand, exhibit segmented grain-size curves and bioturbation, and form elongated uplifted geomorphological units. Sheet sands are dominated by silty fine sand containing bioclasts, forming broad, flat submarine plains. Relative sea-level fluctuations significantly influenced submarine geomorphological evolution: during lowstands, subaqueous distributary channels and adjacent sands dominated, producing an incised and aggradational channel–levee landscape; during highstands, coastal bars and sheet sands were widespread, shaping a shore-parallel bar–sheet sand geomorphology.
How to cite: Bai, Y., Wang, G., and Yin, Z.: Impact of Delta-Front Sedimentation on Submarine Geomorphology: A Case Study of the Neogene Hanjiang Formation, Northern Enping Sag, South China Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1516, https://doi.org/10.5194/egusphere-egu26-1516, 2026.
Turbidity currents are one of the largest sediment-moving processes across our planet, connecting terrestrial sources to deep sea sinks. They play an important part in the transport and burial of organic material, transport contaminants such as microplastics and can reach velocities of multiple meters per second, at which point they form a hazard to submarine infrastructure. In lacustrine environments, they influence water quality by delivering nutrients and oxygen along the water column. Understanding what triggers the formation of turbidity currents is therefore key. Recently, some works have shed a light on the role of transient storage of sediment in the triggering of turbidity currents in oceans. In this model, the near-shore sea bed is preconditioned by the delivery of fresh sediment, either by river inflow or alongshore transport, until it is remobilized by wave action, slope failure or otherwise, and a turbidity current forms. However, the role of transient sediment storage in lakes has received little attention. In this contribution, its potential to precondition the bed for turbidity current generation in the Rhône River-fed lacustrine channel in Lake Geneva will be investigated.
A combination of repeat event-wise gridded boat-towed Acoustic Doppler Current Profiler (ADCP) measurements, years-long infrared timelapse camera imagery and months-long moored ADCP measurements were used to study the occurrence of turbidity currents and coinciding changes in the bed depth near the Rhône River mouth at Lake Geneva.
The boat-towed ADCP measurements revealed an aggradation over three months and a subsequent degradation over two weeks of up to 11 m near the river mouth. The structure of the bed changes pointed out that they were caused by a progradation and transgression of the delta lip. Timelapse images of the Rhône River plume showed an abrupt plume retreat symptomatic of a sudden slope failure, rather than a gradual erosion of the bed. In fjord systems, such failures have been proven to cause strong turbidity current events. Indeed, in this work timelapse images of a similar abrupt plume retreat were linked to a strong turbidity current event in the Lake Geneva lacustrine channel, establishing a link between transient storage of sediment followed by slope failures, and strong turbidity current generation in lakes.
How to cite: Thorez, S., Lemmin, U., Barry, D. A., and Blanckaert, K.: Field observations of a delta-lip failure generating a turbidity current in a lake, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5211, https://doi.org/10.5194/egusphere-egu26-5211, 2026.
The submerged landforms that presently form part of the continental shelf of northern Spain, constituted the coastal environment during the late Pleistocene, when sea levels were significantly lower. These landscapes likely included large floodplains, various river mouths and estuarine conditions that are largely absent from modern coastal settings. These landforms are crucial for reconstructing topographic features and resource availability during the Pleistocene, prior to the inundation of the Atlantic margin during the sea level increments of the Holocene.
The research presented is an ongoing Marie Skłodowska-Curie Actions (MSCA) project that aims to explore the modern continental shelf and delineate areas of high potential for human territorial evidences. It employs the geophysical and sedimentary analysis of data from a series of exploration projects that were conducted along the continental shelf to investigate the palaeoenvironment, namely the PaleoSUB Project (2017-2020). Initial sea bed surveys were carried out using sonar equipment to produce digital elevation models (DEMs) and seismic datasets to serve as the foundations for the reconstruction of this submerged landscape. Moreover, the bathymetric surveys are complemented with data extracted from vibro-core samples, collected from off-shore contexts within the bathymetric survey zone. The data includes sedimentological analysis, malacofauna species and isotopic analysis, and x-ray florescent (XRF) geochemical assessments of the submarine deposits. Radiocarbon and Optically Stimulated Luminescence (OSL) dating were also conducted to place the datasets within a chronological framework.
The integration and interpretation of these results allow for clearer temporal identification of palaeoshorelines and seasonal environmental variations derived from the aforementioned multiple proxy indicators. Collectively, these approaches aim to reconstruct the most accurate localised environmental scenarios along the continental shelf of northern Spain, contributing to an improved understanding of human territorial expansion through geomorphological and morphometric analyses, modelling techniques, and prehistoric contextualisation within an underwater landscape. This interdisciplinary approach is the first of its kind in the region, combining the physical properties with the theoretical knowledge of human practices.
How to cite: Mifsud, J.: Lost Pleistocene Territories: Exploration of Submerged Geomorphological Palaeo-Landforms along Northern Spain., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10463, https://doi.org/10.5194/egusphere-egu26-10463, 2026.
Halimeda (calcareous green algae) bioherms are among the largest accumulations of biogenic sediment within the Great Barrier Reef Marine Park, covering more than 6000 km2 of the continental shelf and exceeding the area of adjacent coral reefs at equivalent latitudes1. Previous studies have documented their circular to reticulate shapes, the internal structure and thickness, underscoring their uncertain genesis and major contribution to the global Holocene neritic carbonate factory2,3. However, a detailed understanding of the formation and development of these uniquely shaped bioherms has been limited by the lack of high-resolution bathymetric maps, surface sediment samples, and densely spaced core material that target geomorphological variability.
This study presents new data from the RV Investigator voyage IN2022_V07 “Halimeda bioherms: Origins, function and fate in the northern Great Barrier Reef (HALO)”. The first sub-metre resolution (50 cm) multibeam bathymetry data and sub-bottom profiles reveal spectacular bioherm shapes and patterns not previously visible on 30 m models. Geomorphometric analysis of the 50 cm DEMs using ESRI ArcGISPro 3.3 quantified the surface characteristics and produced the first benthic terrain classification based on pattern recognition rather than differential geometry to define benthic features (Geomorphon Landforms tool).
Sixty-nine surface grab samples were collected using Boxcorer and Smith-McIntyre grab from three sites between 15° and 13° S. These samples were analysed for grain size, total carbonate and composition to characterise sedimentary variation across modern bioherms. Results highlight variability among different benthic structures, implying distinct and dynamic environmental settings.
In addition, forty-two densely spaced vibrocores (up to 6 m long) were recovered and scanned with high-resolution CT. Split cores were logged for facies and scanned with multi-sensor core logger (magnetic susceptibility, spectrophotometer, X-ray fluorescence). Subsamples at regular intervals (10cm) have been processed for grain size, total CaCO3% and microfossil analysis. Radiocarbon dates indicate the cores range from 12 ka to present. Initial observations revealed a range of morphotypes, including Halimeda floatstone-rudstone and Foraminiferal wackestone-packstone facies and layers of dense coral, mollusc, rhodolith and lithified clumps. This new dataset significantly advances our understanding of Halimeda bioherm morphology, development, and regional influences, providing new insights into their formation processes and ecological significance.
References:
1. McNeil, M. A., Webster, J. M., Beaman, R. J., and Graham, T. L., 2016, New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia: Coral Reefs, v. 35, no. 4, p. 1343-1355. doi: 10.1007/s00338-016-1492-2
2. McNeil, M., Nothdurft, L. D., Dyriw, N. J., Webster, J. M., and Beaman, R. J., 2021, Morphotype differentiation in the Great Barrier Reef Halimeda bioherm carbonate factory: Internal architecture and surface geomorphometrics: The Depositional Record, v. 7, p. 176– 199. doi: https://doi.org/10.1002/dep2.122
3. McNeil, M., Nothdurft, L. D., Hua, Q., Webster, J. M., and Moss, P., 2022, Evolution of the inter-reef Halimeda carbonate factory in response to Holocene sea-level and environmental change in the Great Barrier Reef: Quaternary Science Reviews, v. 277. doi: 10.1016/j.quascirev.2021.107347
How to cite: Szilagyi, Z., Nothdurft, L., Duce, S., Webster, J., McNeil, M., Braga, J.-C., Graham, T., Byrne, M., Behrens, B. C., Yokoyama, Y., Beaman, R., Paumard, V., Shragge, J., Nau, A., Berry, C., Kim, C., Goh, S., Reeves, J., Picton, L., and Bostock, H.: Surface morphology and internal architecture of Holocene Halimeda bioherms in the northern Great Barrier Reef, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14867, https://doi.org/10.5194/egusphere-egu26-14867, 2026.
Large erosional products such as scalloped scars, mass transport complexes and rockfalls are common features found on the steep slopes of isolated carbonate platforms. Factors and processes controlling these instabilities and their interactions are a subject of ongoing discussion. Here we are presenting novel multibeam data and seafloor imagery from the slopes of Rennell Island and the Indispensable Reefs, Solomon Islands.
Rennell Island and the Indispensable Reefs are located in the western Pacific Ocean, around 200 km south of the main Soloman Islands archipelago on top of the Louisiade Plateau. The plateau is separated by the San Cristóbal Trench from the Solomon Block, an elongate microplate underlying the main Solomon Islands and bounded by a dual subduction zone between the Australia and Pacific plates. While the Indispensable Reefs consist of three atolls reaching the modern sea surface, Rennel Island is an uplifted, dolomitized reef complex surrounded by modern coral reefs. These data were collected during several cruises, May to August 2025 onboard RV Hydra, and showcases spectacular slope morphologies and erosional features.
Seafloor imagery reveals calcareous algae (e.g., Halimeda, coralline algae) as major carbonate producer from the photic down to the mesophotic zone on the slopes of both Rennell Island and the Indispensable Reefs. The southwestern slope of Rennel Island is characterized by several scalloped scars along the upper slope ranging in width from 2.5 to 17.6 km. In combination with large reef blocks (> 6 km long) located on the lower slope, these scars document multiple historic catastrophic slope failures. In addition, the presence of numerous gullies, each hosting downslope wandering sandwaves, suggest regular export of skeletal carbonate sands. The three atolls of the Indispensable Reefs are separated from each other by two E/NE–W/SW striking channels ranging in width from 3.4 to 4.3 km. Reef blocks located in the central part of both channels indicate rockfalls derived from the adjacent atoll flanks. The southwestern slopes of all three atolls are characterized by several scalloped scars ranging in width from 4.6 to 10 km and dozens of u-shaped gullies, each 10s of meters wide. A prominent, 15 km long canyon deeply incises the central atoll. Its head has a width of 7.2 km and is sourced from several gullies connected via incised channels to the shallow water lagoon. Combined with a higher number of channels cutting through the western reef rim compared to the eastern rim, this canyon represents a main off-platform export path. However, the frequent presence of gullies along the northeastern mid-slope, followed towards the slope-foot by downslope wandering sandwaves, indicate an additional sediment export system.
The large number of prominent head scarps on the southwestern slopes suggests that the leeward sides of both platforms tend to be more easily destabilised, which might be caused by the tectonic regime. Platform-top morphologies indicate a strong influence of the North Vanuatu Jet on the westward-driven sediment transport, while the presence of gullies and sandwaves on the eastern slope of the Indispensable Reefs suggest a more complex sediment dynamics.
How to cite: Petrovic, A., Gafeira, J., O'Callaghan, J., Myers, L., Bond, T., von Krusenstiern, K., and Stewart, H.: Erosional processes on the slopes of Rennell Island and the Indispensable Reefs (Solomon Islands, Western Pacific), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19223, https://doi.org/10.5194/egusphere-egu26-19223, 2026.
Submarine channels in the Levant Basin, eastern Mediterranean Sea, are prominent morphological features that provide key insights into sedimentary processes and basin evolution. These northward trending channels were formed by turbidity currents and play an important role in shaping the basin morphology and stratigraphy. The most prominent channel is the >200 km-long Levant Channel (LC), originating from the northern Sinai Peninsula margins. Yet, its present activity and the recurrence interval of turbidity-current events remain poorly constrained.
In this study we aim to address these knowledge gaps by sampling a series of downcore records along LC, combining stratigraphic and micropaleontological analyses with radiocarbon-based geochronological constraints. Piston and box cores were collected from two sites along the LC thalweg: a southern site located ~60 km offshore Tel Aviv at ~1300 m water depth, and a northern site ~45 km farther down-channel at ~1500 m water depth. Piston cores reach lengths of up to ~6.5 m, while box cores recover shorter sequences (≤0.5 m), complementing the stratigraphic record and providing high-resolution coverage of surface sediment.
Sediment in both cores are predominantly non-laminated and clastic, yielding last-glacial radiocarbon ages, with the lowermost sections exceeding the radiocarbon dating limit (>45 ka BP). Sediment in reverse stratigraphic order (i.e. a downcore decrease in sediment age) is observed in the southern core. Age reversals, together with the clastic, non-laminated facies indicate mixed sediment deposition, most likely associated with repeated turbidity-current events. Above this interval, a finely laminated sediment dated to ~9 ka BP corresponding with Sapropel S1, is observed, reflecting undisturbed hemipelagic sedimentation.
Foraminiferal assemblages independently support the radiocarbon-based age model and provide additional evidence on sediment mixing. The warm-water planktonic species Globigerinoides ruber (pink), characteristic of warm interglacial conditions, is restricted to Sapropel S1 and younger sediments, whereas the cold-water species Globorotalia scitula, typical of glacial conditions, occurs exclusively below S1. Coexistence of these species in the upper glacial interval of the northern core indicates sediment mixing. Shelf-derived benthic foraminifera (e.g., Ammonia tepida, A. parkinsoniana, Cribroelphidium vadescens and Planorbulina mediterranensis) are abundant throughout both Holocene and glacial sediments in the southern core but are largely absent from the northern core, suggesting sustained delivery of shallow-shelf material at least to the southern LC site.
In summary, the Levant Channel was active during the last glacial period, with shelf-sourced turbidites, but became largely inactive during the Holocene, with hemipelagic sedimentation prevailing. This shift reflects the impact of eustatic sea-level rise and related continental shelf widening on submarine mass transport across continental margins. Similarly, previous regional studies on submarine landslides and turbidite activity within submarine canyons along the eastern Mediterranean continental margin revealed intense mass wasting activity in the last glacial period that declined through the deglaciation and the transition to the Holocene.
How to cite: Katz, O., Sivan, L., Hyams-Kaphzan, O., Kanari, M., and Torfstein, A.: Last Deglacial to early Holocene changes in activity of the Levant Submarine Channel, Eastern Mediterranean Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19299, https://doi.org/10.5194/egusphere-egu26-19299, 2026.
Seamounts number in the hundreds of thousands across all ocean basins and constitute a fundamental component of the ocean floor. They provide constraints on intraplate magmatism, mantle melting processes, lithospheric stress and flexure, and the evolution of oceanic plates. At the same time, seamounts are hotspots of biodiversity, and their morphology modifies ocean circulation and mixing, further influencing benthic ecosystems. Addressing these aspects requires high-resolution bathymetric mapping, yet most seamounts inferred from satellite-derived gravity data have never been directly surveyed.
The German marine research community contributes to systematic seafloor mapping during transits of the large German research vessels through the underway research-data project coordinated within the German Marine Research Alliance (DAM). While this approach steadily improves coverage and contributes to international efforts such as Seabed 2030, the scale of the remaining mapping gap of about 75% motivates complementary strategies that increase scientific return without substantially increasing ship time. Within the SEAMAP project, we pursue a collaborative approach in which research vessel transits are actively planned to intersect previously uncharted seamounts, with minimal impact on cruise logistics and primary scientific objectives. The goal is to link underway data acquisition to active research questions in geodynamics and ocean sciences.
We present initial results from SEAMAP. Modified transits have so far been planned for five research cruises, resulting in new multibeam bathymetric coverage of approximately 80 previously unmapped seamounts across a range of tectonic settings and plate ages. The acquired data are being integrated into studies addressing intraplate volcanic construction, machine-learning-based bathymetry prediction and validation, and flow–topography interactions, including enhanced mixing and turbulence in seamount wakes. In parallel, SEAMAP supports rapid data availability by integrating new bathymetric products into the harmonized data streams for German research vessels established by DAM. These results illustrate how targeted seamount mapping during transit legs can efficiently improve seafloor coverage while supporting interdisciplinary ocean science on the role of seamounts within the Earth system.
How to cite: Ruepke, L., Wiemer, G., Wölfl, A.-C., Damaske, D., Brix, S., dos Santos Ferreira, C., Devey, C., Dorschel-Herr, B., and Schwarzkopf, F.: SEAMAP: targeted underway bathymetry for mapping uncharted seamounts and assessing their role in the ocean system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20325, https://doi.org/10.5194/egusphere-egu26-20325, 2026.
Bottom trawling represents the largest anthropogenic source of physical disturbance to seafloor morphology, sediment texture and composition, and benthic habitats. Past studies have shown that the morphological traces left by bottom trawling in the Baltic Sea remain stable for a year to more than a decade depending on area. The persistence of trawling-induced morphology is particularly relevant with the currently declining fishing pressure. The steeply declining trawling intensity provides the opportunity to establish baseline maps of trawling impacts and investigate how a trawled seafloor re-naturalizes after trawling has stopped. Here, we train a convolutional neural network to map trawl marks in bathymetric grids of 1 m resolution largely provided by the German Federal Maritime Agency for Kiel Bay, Fehmarn Belt, Mecklenburg Bay and Arkona Basin in the Western Baltic Sea. The model operates directly on bathymetric grids and is robust to artifacts, allowing monitoring of trawl marks with low effort. The calculated trawl mark density is a measure of the cumulative morphological impact of trawling in the different areas. For the Fehmarn Belt marine protected area, where bottom trawling was excluded in 2025, differential bathymetric data show no substantial seafloor recovery after one year, and new trawl marks are observed. Small areas of low trawling activity around seafloor obstacles such as pockmarks, boulders and wrecks allow the direct comparison of a pristine (Holocene-like) seafloor with an adjacent heavily trawled seafloor. Here, seafloor roughness decreases with increasing trawling intensity, potentially related to sediment resuspension and flattening by ground ropes that are not directly image by acoustic surveys. Untrawled seafloor locally elevates slightly above the surrounding trawled seafloor, potentially caused by long-term erosive effects of sediment reworking by bottom trawling. Initial results suggest a relationship of near-subseafloor free methane fronts to areas of intense trawling, suggesting that trawling can also effect the flux of climate relevant trace-gases into the water column. We further analyze vertical profiles of benthic microbial communities at stations with different trawling intensity.
How to cite: Feldens, P., Schulze, I., Seidel, E., Geersen, J., Piontek, J., and Schönke, M.: The spatial extent of trawl marks in the German Baltic Sea basins and their relation to the composition of the subsurface. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13394, https://doi.org/10.5194/egusphere-egu26-13394, 2026.
The subsequent refilling of the Mediterranean Sea following the Messinian Salinity Crisis (~5.33 Ma) represents one of the most extreme flood events in Earth history.
The magnitude of the sea level drawdown during the Messinian Salinity Crisis is heavily debated since its discovery in the 70s. Previous studies utilized a diverse range of methods and proxies to quantify the drawdown. Estimates vary significantly, spanning from less than 500 metres to more than 2 km. This variability largely reflects the method-dependent nature of the reconstructions: flexural–isostatic models typically yield lower drawdowns (hundreds of metres), geomorphic canyon analyses suggest intermediate to large values (~500–1500 m), while evaporite mass-balance and isotopic approaches imply the highest drawdowns, consistent with kilometre-scale or greater drops in the Eastern Mediterranean.
New marine seismic reflection data reveal a prominent, amphitheatre-shaped, erosional scarp at the base of the Noto Canyon, whose morphology and dimensions are consistent with its interpretation as the terminal spillway of the Zanclean Flood. The feature represents the largest fossil waterfall identified to date. The morphology of the canyon and the geometry of its scarp, including its amphitheatre shape, relief, and lateral extent, are the products of the extraordinary hydraulic energy unleashed during the catastrophic Atlantic inflow.
The geological setting is challenging, featuring steep canyon flanks, out-of-plane reflections, and complex sedimentary layering. Notwithstanding, the geomorphology that has been preserved enables an estimation to be made of a sea-level drawdown of approximately 2200 m in the Eastern Mediterranean. Numerical hydrological and landscape-evolution models reproduce similarly large drawdowns, but emphasise temporal and local variability rather than a single static lowstand, suggesting that much of the published spread reflects methodological sensitivity, rather than fundamentally incompatible sea-level scenarios.
These findings demonstrate the substantial influence of gateway geomorphology in constraining past sea-level changes, and provide a more accurate understanding of both the magnitude and erosional impact of the Zanclean Flood and the associated ~2200 m sea-level drawdown in the Eastern Mediterranean, with broader implications for Mediterranean palaeogeography and hydrodynamics during extreme paleo-flood events.
How to cite: Haimerl, B., Hübscher, C., Micallef, A., and Camerlenghi, A.: Noto Canyon, Sicily: Terminal Spillway of the Zanclean Flood and Earth’s Largest Fossil Waterfall Indicating a ~2200 m Sea-Level Drawdown, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6914, https://doi.org/10.5194/egusphere-egu26-6914, 2026.
Posters on site: Thu, 7 May, 08:30–10:15 | Hall X3
Accurate hydrographic surveying in coastal environments requires not only high-resolution multibeam echosounder (MBES) measurements but also structured and reproducible data processing workflows that enable validation of applied corrections. This study presents a stepwise methodology for MBES data processing and quality assessment, focusing on the evaluation of successive correction stages and their impact on bathymetric products. The workflow is implemented using the open-source software GLOBE and demonstrated on MBES data acquired in the Argolic Gulf (Greece), provided by the Hellenic Navy Hydrographic Service (HNHS).
The Argolic Gulf is a semi-enclosed coastal basin with variable bathymetry, making it a suitable test case for assessing the influence of navigation, sound velocity, and tidal corrections. The dataset originates from a nearshore hydrographic survey conducted with a hull-mounted SeaBat 7125 multibeam echosounder system. Data delivered by the HNHS included raw multibeam soundings, associated navigation data, sound velocity profiles, and official tide information required for standard hydrographic post-processing. Processing of sound velocity profiles was carried out using DORIS, an open-source software package.
The proposed workflow consists of a sequence of correction steps, including navigation correction, sound velocity adjustment, tidal referencing, geometric transformations, and targeted filtering of outliers. Each step is evaluated independently through the generation of intermediate Digital Terrain Models (DTMs), enabling direct comparison of bathymetric surfaces before and after each correction. Stepwise validation is based on systematic map comparison. Intermediate DTMs generated in GLOBE, are imported into the open-source GIS environment QGIS, where thematic depth maps, bathymetric difference surfaces, and representative depth profiles along characteristic transects are produced. This combined map- and profile-based evaluation supports supervision and validation of applied corrections, facilitating the identification of systematic artefacts such as sound velocity–related curvature patterns, navigation-induced shifts, and localized swath-edge noise.
The stepwise comparison of intermediate bathymetric surfaces enables systematic validation and supervision of MBES corrections, demonstrating that individual correction effects can be assessed independently and that the reliability of the final bathymetric product can be evaluated prior to acceptance. The proposed workflow supports reproducible hydrographic surveying and contributes to improved reliability and interpretability of MBES-derived bathymetric surfaces in coastal and nearshore environments.
How to cite: Boursoukis, I. and Anastasiou, D.: Stepwise Validation of Multibeam Echosounder Data Processing Using an Open-Source Processing Workflow: A Case Study in the Argolic Gulf (Greece), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11449, https://doi.org/10.5194/egusphere-egu26-11449, 2026.
This study is part of the KOMSO project that focusses on standardised measurement methods for the long term carbon storage potentials in the Baltic Sea while the contemporaneous methane release of the seafloor works as an antagonistic player. We want to understand how pockmarks are formed and how stable these structures are. Another open question is whether vessel traffic affects the shape and degassing amount of the structures.
The Baltic Sea was formed during the last Weichselian glaciation and underwent a multi-phase development. It was finally flooded during the Littorina transgression, while the basins and bays of the southern Baltic Sea contain thick glacial and post-glacial sediments. In particular, the Littorina and late Holocene deposits contain sediments rich in organic matter. Depending on the varying depth of the sulphate-methane transition zone in the different basins, which is partly modified through submarine groundwater discharge, methane is produced below this zone. This results in the accumulation of free gas within the sediments. The migration of the shallow biogenic gas forms gas fronts and leakage zones in the form of pockmarks at the seafloor.
In a first step, we mapped the pockmarks in the various basins using a bathymetric grid with a general resolution of up to 10 m, in smaller areas also up to 1 m. We catalogued the mapped pockmarks according to the following criteria: (i) their location (near the coast or in the central basin, and water depth), (ii) their lateral and vertical dimensions (diameter and depth), and (iii) their form (elongate or round, single structure or clustered, depression/negative or upbending/positive). Additional parametric sediment echo sounder (SES) profiles (vertical 2D sections) allow further conclusions to be drawn, such as the stratigraphic affiliation of the gas escaping from the pockmarks and the depth of the underlying gas front.
Adjacent to some existing pockmarks, the seafloor forms upward bulges above gas chimneys that may indicate the build-up of methane overpressure in the shallow subsurface. Whether these doming structures develop into new pockmarks needs to be evaluated with future differential bathymetric surveys. During the course of the projects, we will repeat SES profiles in order to determine any possible temporal or seasonal variation in the size of the pockmarks.
How to cite: Seidel, E., Feldens, P., Geersen, J., and Böttner, C.: Pockmarks in the southern Baltic Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18126, https://doi.org/10.5194/egusphere-egu26-18126, 2026.
Hadal trenches at subduction margins represent hotspots where episodic tectonic events can reorganize sedimentation and biogeochemical processing. In particular, earthquake-triggered depositional pulses may redistribute and rapidly bury matter including nitrogen. Despite this potential importance, nitrogen burial in the deepest trench environments is still poorly constrained, and how earthquakes modulate nitrogen inputs, internal cycling, and delivery toward subduction remains unclear. Here, we measured elemental and isotopic geochemical parameters from high-resolution long sediment cores drilled at the Japan Trench during IODP Expedition 386. By integrating high-resolution event stratigraphy with robust chronological constraints, we quantified nitrogen inputs, transformations, and burial under two contrasting depositional regimes: background sedimentation and earthquake-triggered event deposition. We find that earthquake event layers deliver nitrogen-bearing material and are associated with substantially enhanced nitrogen burial relative to background intervals. Estimated nitrogen burial fluxes rise from ~24 to ~300 Tg N yr-1 and the event-driven flux exceeds published deep-sea mean burial estimates by ~1.5×102. In addition, earthquake-triggered event deposition markedly increases the relative proportion of bioavailable nitrogen in trench sediments, from 82.6% in background intervals to 91.4%. Collectively, these changes in the bioavailable nitrogen supply may diversify nitrogen transformation pathways, manifesting as a more complex nitrogen-cycling signal in hadal trench sediments. We propose a "seismic nitrogen pump" in which earthquakes transiently accelerate nitrogen cycling through organic matter activation and mass transport, enhancing sedimentary retention and potentially reshaping the subducting nitrogen reservoir. Our findings challenge the view of trenches as static nitrogen repositories, identifying tectonic forcing as a key driver of subduction-zone biogeochemistry and underscoring the need to incorporate episodic perturbations into global nitrogen budgets and deep carbon–nitrogen coupling frameworks.
How to cite: Li, S., Bao, R., Lin, X., Liu, M., Strasser, M., and Chu, M.: Earthquake regulation of nitrogen dynamics in subduction zone , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4426, https://doi.org/10.5194/egusphere-egu26-4426, 2026.
Understanding methane seepage dynamics in Arctic cold seep systems is crucial for knowing the implications of their impact on the Arctic Ocean habitats. The Barents Sea, characterized by active sub-seafloor fluid flow, serves as an ideal setting for investigating the environmental factors that interact with seepage dynamics in Arctic cold seep habitats. This study presents a multidisciplinary investigation of cold seeps explored during the AKMA3 expedition (May 2023) along the Vestbakken shelf and slope (SW Barents Sea). The research combines (i) detailed visual analyses of seafloor imagery acquired by the Aurora Remotely Operated Vehicle (ROV), (ii) sedimentological and biogeochemical analyses on three ROV-collected push cores and blade corers, and (iii) a preliminary assessment of living benthic foraminiferal communities. ROV video annotation allowed the identification and classification of multiple distinct microhabitats and cold seep indicators along the explored seafloor based on seafloor characteristics. A clear relationship between sediment type and the distribution of chemosynthetic communities on the seafloor is evident in ROV track analysis. Sedimentological and geochemical data provided quantitative evidence of seep-related processes and enabled a refined characterization of the substrate associated with each microhabitat type. Geochemical profiles revealed fine-scale lateral variability in sediment composition and porewater chemistry, reflecting the heterogeneous and dynamic nature of seepage in the area. The analysis of living foraminiferal assemblages revealed systematic differences between shelf and slope sites, indicating biological responses to seep-driven environmental gradients and variations in the depth of the sulfate–methane transition zone (SMTZ). Together, these multidisciplinary observations provide new insight into the significance of seafloor composition in controlling seepage dynamics near the sediment-water interface and, ultimately, shaping these habitats in the high Arctic.
How to cite: Hemmateenejad, F., Caneva, A., Redaelli, C., Fallati, L., Barrenechea Angeles, I., Argentino, C., Panieri, G., and Savini, A.: Characterizing Arctic cold seep habitats from shelf to slope (a case study in the Vestbakken province), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-747, https://doi.org/10.5194/egusphere-egu26-747, 2026.
Iceberg scours are created by drifting icebergs that plough into the seafloor with their keels. These prominent geomorphic features are widespread in the Arctic and provide critical insights into past ice-sheet dynamics and ocean circulation. At local scales, iceberg scours influence benthic ecosystems, pose risks to offshore seafloor infrastructure, and can trigger submarine landslides. Here, we report on multibeam echosounder and subbottom profiler data from the 2025 AOC cruise on R/V Dana that document iceberg scours from the newly discovered Dana IV seamout (71°40’N, 15°W) in more than 975 m of water depth. Semi-automated mapping of 212 iceberg scours shows that they are predominantly oriented in northeast-southwest direction. Iceberg scours occur in two clusters around 810 m and 860 m water depth and are typically ~20 m deep, 330 m wide, and >2 km long. The longest iceberg scour is more than 10 km long and more than 60 m deep, crossing the entire seamount. Some iceberg scours trend parallel indicating multi-keeled or tabular icebergs. One iceberg scour terminates in a landslide scar, documenting that icebergs can be geohazards hundreds of kilometers away from their source. Sediment core data from the top of the seamount indicate that the timing of scouring is older than the Last Glacial Maximum. Given the large water depths in which we find iceberg scours and evidence for multi-keeled icebergs, we attribute them to giant or tabular paleo-icebergs that were more than 1 km thick. The absence of parallel lineations speak against a grounded iceshelf this far south in the North Atlantic. We conclude that these scours are formed by individual icebergs that probably came from an ice sheet calving front at the Northeast Greenland shelf edge or migrated from the Arctic Ocean southward through the Fram Strait during past glacial maxima.
How to cite: Böttner, C., Ramsgaard Stoltenberg, M., O’Brien, A., S. Hansen, O., Detlef, H., Gjelstrup, C., Seidenkrantz, M.-S., Stedmon, C., and Pearce, C.: Iceberg scours at almost 1 km water depths on the newly discovered Dana IV Seamount, Greenland Sea, North Atlantic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16869, https://doi.org/10.5194/egusphere-egu26-16869, 2026.
The seabed in the western Gulf of Oman, offshore of Fujairah, UAE remains poorly characterised and mapped. Earlier regional studies were too coarse to resolve the origin and evolution of Holocene seafloor geomorphic and tectonic features. Here, we integrate high-resolution multibeam bathymetry and derivative terrain attributes (slope and bathymetric position index), multibeam backscatter, and seafloor grab samples to map seabed morphology and constrain sediment distribution. The surveyed area reveals a wide array of geomorphic elements, including paleoshoreline terraces, paleoreefs, sandwaves, sand ridges, sandbanks, circular and eroded pockmarks, contourite sandwaves, submarine landslides, and fault traces to name a few. These observations enable the reconstruction of Quaternary seafloor evolution, highlighting the coupled influence of tectonics, eustatic sea-level change, and deep marine currents on the seabed development. The refined mapping also resolves several previously misidentified features from earlier basin-scale interpretations. This improved understanding provides a robust geologic framework for offshore geohazard assessment and supports evidence-based planning for marine infrastructure in the eastern UAE Offshore.
How to cite: Aldhanhani, O., Ali, M., Alsuwaidi, A., and Abdelmaksoud, A.: Seafloor Morphology and Evolution of Eastern UAE’s Offshore, Gulf of Oman, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17122, https://doi.org/10.5194/egusphere-egu26-17122, 2026.
This study presents a multidisciplinary geological and environmental characterization of the submerged offshore area of Taranto (Apulia, southern Italy), developed within the framework of the Italian National Cartographic Project (CARG), coordinated by ISPRA. The investigated area includes Mar Piccolo, Mar Grande, and the northern Ionian Sea, forming a complex coastal–marine system characterized by strong environmental heterogeneity, high marine biodiversity, and intense anthropogenic pressure.
The study area comprises three marine basins with different geomorphological and hydrodynamic settings: the shallow and semi-enclosed Mar Piccolo, the circular Mar Grande basin and the open northern Ionian Sea, reaching depths of up to 1,500 m. This variability exerts a strong control on sedimentary processes, habitat distribution, and the spatial imprint of human activities on the seafloor.
The research integrates high-resolution geophysical and acoustic datasets acquired through Multibeam Echosounder (MBES), Side-Scan Sonar (SSS) and Sub-Bottom Profiler (SBP) surveys. Seabed morphology and habitat mapping are primarily based on Side-Scan Sonar data acquired using a dual-frequency system (100–500 kHz). The data were processed into georeferenced acoustic mosaics with a spatial resolution of 0,50 m and analyzed within a GIS environment for detailed seabed classification and interpretation.
Acoustic backscatter analysis allowed the identification and mapping of benthic habitats, including seagrass meadows and bioconstructions, through correlation with substrate type, bathymetry, and light penetration. The high spatial resolution of the SSS mosaics also enabled the recognition of seabed features related to anthropogenic activities, such as dredging marks and infrastructure-related modifications, whose distribution was mapped at an areal scale due to their density and spatial extent.
Stratigraphic interpretation is based on the identification of key seismic unconformities and depositional sequences within a sequence-stratigraphic framework spanning from the Last Glacial Maximum to the present. In the Mar Piccolo basin, this framework is constrained by borehole data, radiocarbon dating, and sedimentary facies analysis. Correlation with the shelf domain is locally hindered by the disturbances related to the anthropic activities, while the correlation with the slope domain is is made more complex by the presence of substrate outcrops and chaotic seismic bodies, interpreted as submarine landslides related to sea-level fall stages.
The resulting integrated geodatabase gives its contribution to the first comprehensive geological map project of the Italian seabed and provides a robust framework for reconstructing sedimentary dynamics, sea-level fluctuations, and cumulative anthropogenic impacts. These results support sustainable coastal management, marine ecosystem conservation, and ecological transition strategies in line with current Blue Economy and environmental policy objectives.
How to cite: D'Abbicco, V., De Giosa, F., de Luca, A., Fracchiolla, T., Gianolio, G., Lisco, S., Mastronuzzi, G., and Moretti, M.: Submarine geomorphology and late Quaternary evolution of the Taranto offshore (southern Italy) under natural and anthropogenic controls., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12660, https://doi.org/10.5194/egusphere-egu26-12660, 2026.
The lake region of the Massif Sud of New Caledonia, designated as a Ramsar site in 2014, represents the largest freshwater reservoir on the island and hosts fossil remnants of an ancient detrital system, the Fluvio-Lacustrine Formation (FLF). This formation is mainly composed of sediments eroded from the surrounding lateritic massifs and displays a high degree of internal structural complexity. Recent studies conducted at ISEA (University of New Caledonia) have shown that certain sedimentary levels are particularly enriched in metallic elements, raising questions about potential recurrent transfers between these sediments and present-day fluvial systems. To investigate the system as a whole using a “source-to-sink” approach, we carried out the POPCORN campaign (Post-obduction tectono-sedimentary characterization of the Cornes Sud platform of New Caledonia: What influence of ultrabasic massifs?), scheduled from 2 to 22 April 2026. The campaign aims to acquire very high-resolution (VHR) Sparker seismic profiles and multibeam bathymetry across the Cornes Sud platform, extending offshore from the FLF, combined with Kullenberg coring to provide geological and chronostratigraphic calibration of the geophysical data. The Cornes Sud platform, located between Grande Terre and Île des Pins, has received very limited investigation compared to the southwestern lagoon (Le Roy and Cabioch, 2004; Le Roy and Jorry, 2013; Le Roy et al., 2008, 2019) and the eastern margin (Chardon et al., 2008; Le Roy et al., 2022a, 2022b; Kerouédan et al., 2024a, 2024b). The western and eastern lagoons display contrasting morphologies associated with opposite vertical movements since the New Caledonian obduction (Lagabrielle et al., 2005 ; Tournadour et al., 2021). The Cornes Sud platform lies in direct continuation of the Massif Sud and forms the southern link between these two lagoons. It is characterized by several channelized systems (5-Miles, Prony, and Port Boisé), all affected by the Havannah Fault. The acquisition of Sparker seismic profiles and multibeam bathymetry, combined with sediment sampling, will allow identification and characterization of the tectono-sedimentary architecture of this poorly explored area and reconstruction of sedimentary and associated metallic element transfer pathways from continental fluvio-lacustrine systems (Fluvio-Lacustrine Formation, FLF) to carbonate platform deposits. This campaign forms part of a strategic research effort aimed at improving geological and environmental knowledge of a largely unexplored coastal zone. It is integrated within a broader research program focused on the FLF conducted by the same scientific team (TelluS-SYSTER PONCES and METALFLAP projects) and represents a key component of the land–sea continuum. The diversity of methodologies employed, together with the multidisciplinary nature of the research team, will enable reconstruction of the post-obduction evolution of the Massif Sud of New Caledonia based on sedimentary records, from the onshore Fluvio-Lacustrine Formation to the offshore Cornes Sud platform. Preliminary results from the POPCORN campaign will be presented here, focusing on seafloor morphology, sedimentary architecture, and styles of tectonic deformation within the study area. Particular emphasis is placed on identifying offshore expressions of the Fluvio-Lacustrine Formation previously studied on land.
How to cite: Gaullier, V., Pattier, F., Parmentier, J.-B., Champilou, N., Schmitt, F., Mathian, M., Zanella, A., and Gunkel-Grillon, P.: Post-obduction tectono-sedimentary architecture of the Cornes Sud platform (New Caledonia): New insights from the POPCORN geophysical cruise (April 2026), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13908, https://doi.org/10.5194/egusphere-egu26-13908, 2026.
Offshore infrastructures are essential for energy production, telecommunication, and transportation sectors. High-frequency offshore acoustic backscatter is widely used as a proxy for seabed and soil classification. When properly interpreted, it can significantly reduce exploration costs by optimizing survey design, guiding targeted sampling strategies, and improving the detection and interpretation of natural seafloor features. In the context of offshore wind farms, acoustic backscatter data are particularly valuable for early-stage site screening, preliminary economic assessment, and the identification of potential geohazards prior to detailed geotechnical investigations. Although hydroacoustic surveys can cover large areas efficiently, their ability to estimate geotechnical properties is still limited. Hence, this study aims to investigate the relationship between high-frequency acoustic backscatter and geotechnical parameters of marine sediments. The dedicated research cruise RHYSMA was conducted in the Bay of Morlaix to acquire both hydroacoustic and geotechnical data on 8th of May 2025 during ten days. Eleven sites were selected to represent a wide range of sediment types with average water depth varying approximately 3m to 50m, ranging from muddy sediments to boulders, and exposed rock. Such diversity provides a natural laboratory to investigate the interaction between acoustic signals and sediment properties. Acoustic measurements were performed using SIMRAD EK80 single beam echosounders with frequencies ranging from 90 kHz to 440 kHz, with incidence angles varying from 0° to 70°. In total 10 cores were obtained; 840 kg of sediments and 9 hours of seafloor videos were recovered. Hydroacoustic data was calibrated and fitted using the Generic Seafloor Acoustic Backscatter (GSAB) model to estimate the seabed angular response and to assess the influence of angle and frequency on different sediment types. Typical backscatter ranges from -15 dB up to -4 dB in the exposed rock. Geotechnical results show particle sizes ranges from 4 microns up to 8 cm boulders, while dry densities range from 1 to 1.6 g/cc and specific gravity spans from 2.64 to 2.96 and fine content for sediment ranges from 1% percent to 56%. Preliminary results indicate an emerging relationship between acoustic backscatter and sediment porosity particularly for high frequency response at near-normal incidence angles (~0°). Overall, this study improves the understanding of acoustic backscatter behavior across contrasting sediment types and highlights the complexity of seabed acoustic responses.
How to cite: Manikanta, V., Terzariol, M., Fezzani, R., Ehrhold, A., Cattaneo, A., Simplet, L., and Klingelhoefer, F.: Towards a Relationship Between Acoustic Backscatter and Soil Geotechnical Properties: insights from Bay of Morlaix, France, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21389, https://doi.org/10.5194/egusphere-egu26-21389, 2026.
The breaching of the Weald–Artois Ridge, which once connected the UK to mainland Europe, represents one of the most significant events shaping the paleolandscape of the Belgian, UK, and French sectors of the Southern North Sea from the Middle Pleistocene onwards. The timing and mechanism of its breaching, which led to the formation of the Dover Strait, remain the subject of ongoing debate. This event marks the onset of regular inundation of the Belgian Continental Shelf (BCS) during sea-level highstands, alternating with exposure during sea-level lowstands. In this region, erosion is dominant, resulting in the frequent exposure of Paleogene-Neogene strata. Nevertheless, a discontinuous cover of Pleistocene and Holocene sediments persists. Together with erosional features, this sedimentary record offers valuable evidence of the region’s complex history.
In recent years, new and higher resolution 2D seismic and acoustic datasets have been acquired for both scientific and commercial purposes in the more offshore sections of the BCS, an area where data availability was previously limited. This study integrates these datasets to develop a more comprehensive understanding of the discontinuous Pleistocene deposits. In a first step, the erosional boundary between Paleogene– Neogene strata and overlying Quaternary deposits was mapped and gridded in unprecedented detail. The resulting surface not only refines the position and morphology of previously described escarpments and valleys but also reveals new escarpments and a series of elongated linear and curved scours of uncertain origin. As these scours are possibly related to either tidal, fluvial, glacial or ice berg scouring, understanding the origin and sequence of these features is essential for reconstructing Quaternary palaeolandscapes and may provide further insights in the breaching of the Weald-Artois Ridge.
Finally, this study aims to identify, sample and describe the various Pleistocene units in the area. Supplementary analyses, such as pollen and microfossil studies, as well as radiocarbon and optically stimulated luminescence (OSL) dating will ultimately enable the development of a comprehensive and updated reconstruction of the palaeolandscape evolution of the outer BCS and adjacent regions.
How to cite: Dekoninck, W., De Batist, M., Missiaen, T., Plets, R., and Mestdagh, T.: Enigmatic buried scours provide new clues for the Middle to Late Pleistocene paleolandscape reconstruction of the outer Belgian Continental Shelf, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16800, https://doi.org/10.5194/egusphere-egu26-16800, 2026.
Offshore drilling operations in continental and ultra-deep waters are mandatory to guarantee energy security and perform CCUS activities to reduce the environmental impact of O&G Industry.
However, offshore environments are related to high levels of risk that must be taken into consideration during operation planning. This is mainly because of shallow and buried geohazards that could potentially occur and affect asset integrity and operations, with time and economic losses, damage to equipment and in extreme cases environmental issues and human losses.
ENI has developed a workflow in accordance with IOGP standards for offshore drilling operations to identify and characterize natural hazards on and below the seafloor and eventually provide solutions to meet the project requirements for different departments (e.g. Exploration, Engineering, Drilling and Completion). This goal is achieved through continuous analyses and integration with bathymetric, seismic, geotechnical, satellite data and well-logs.
The workflow investigates two different domains, seafloor and sub-seafloor, both at regional and local scale.
The seafloor domain is examined through the computation of morphometric attributes to detect and characterize obstacles like boulders and depressions along the seabottom, perform heterogeneity analyses and identify preferential flow-paths. A flow analysis is further developed internally to estimate the energy of debris flows against the assets in terms of velocity and excess density.
The sub-seafloor domain is investigated by means of seismic interpretation and seismic attribute computation from available data to identify and characterize buried faults and landslides, hard-grounds and seismic anomalies possibly related to oil or gas spikes. Direct Hydrocarbon Indicators are further evaluated to classify the seismic anomalies in terms of negligible, low, moderate or high gas risk.
Open-source SAR images are then interpreted to detect natural oil seeps in the environment and link them to geological objects like salt diapirs, faults and fracture networks.
This allows a better understanding of the migration paths of natural oil and gas to the surface mitigating also the possible environmental impact.
Field data like CPTUs and core-logs are interpreted to detect buried landslides or local hard grounds and estimate geotechnical parameters of the shallow soil cover up to 30 m. These results are further implemented to perform a slope stability analysis and risk zonation close to the facilities.
In conclusion, cross-sections, detailed slope analyses and statistics are performed to detect geohazards close to the well location and along the pipeline route.
If available, well-to-well correlations are investigated by means of well-logs to identify different soil units.
All these results are collected into a final report comprehensive of geomorphological, bathymetric and slope maps. The report contains also a top-hole prognosis indicating all the geohazards crossed by the asset to support offshore operations.
Geohazard studies are continuously updated from the exploration to the development phases of the project to obtain a complete and functional knowledge of the area of interest as new data are available.
This integrated approach has been effectively applied to different scenarios, significantly reducing the uncertainties and allowing the quick detection and management of geohazards to mitigate the risks of offshore activities.
How to cite: Borsari, F., Fornari, M., and Luigi, M.: Integrated Geohazard Risk Assessment for Offshore Operations Combining Multiple Data Sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7538, https://doi.org/10.5194/egusphere-egu26-7538, 2026.
Shelf-to-basin sediment transport plays a key role in the evolution of continental margins and the carbon cycle. Yet, the mechanisms linking oceanographic forcing to sediment resuspension and redistribution remain poorly quantified. Intermediate nepheloid layers (INLs) are widely recognized as substantial sediment conveyors in this context, but their formation mechanisms, morphologic imprint, and spatio-temporal evolution remain elusive in direct observations and process-based interpretation.
Here, we present multidomain observations from the Eastern Levant Basin (ELB) that document the internal-wave-induced origin and seasonal recurrence of INLs. We integrate ultra-high-resolution (decimeter-scale) multichannel Seismic Oceanography (SO), high-resolution bathymetry, in situ conductivity-temperature-depth (CTD) profiles, oceanographic reanalysis products from the Copernicus Marine Service, and spaceborne Synthetic Aperture Radar (SAR) imagery, to link water-column stratification, internal wave activity, sediment resuspension, sediment transport, and their morphologic outcomes. These data sets span multiple years and capture the same processes during comparable seasonal stratification regimes, allowing assessment of process persistence rather than isolated events.
Our results show that during periods of strong seasonal column stratification (i.e., Brunt-Vaisälä frequencies in the order of N ≈ 0.01 s⁻¹), shoaling internal waves promote sediment resuspension from the shelf edge and basinward transport. Seismic profiles reveal laterally continuous, gently inclined low-amplitude reflection packages with thicknesses of up to 10 meters that detach from the seabed and are interpreted as INLs flowing up to 10 km from the continental slope. This is confirmed by in-situ CTD measurements showing aligned water-column turbidity peaks up to 10 kilometers offshore the area of resuspension. Calculated internal wave (IW) beam angles relative to local slope show a clear correlation between transmissive (subcritical) zones, seafloor erosion, and locations of sediment detachment, while reflective (supercritical) areas show the appearance of sediment-wave patterns interpreted as upslope-migrating steps. Our results are consistent across different years and geophysical datasets. Co-located SAR imagery independently confirms the presence and orientation of internal wave packets during these periods.
Together, these observations provide robust field-based evidence that internal wave-driven sediment mobilization is a seasonally recurrent process, governed by water-column stratification and seafloor criticality. These observations link sediment transport, oceanographic dynamics, and slope geomorphology in an increasingly stratified, warming ocean.
How to cite: Gadol, O., Makovsky, Y., Bialik, O., and Azevedo, L.: Multidomain observations of internal wave-induced shelf-to-basin sediment transport in the Eastern Levant Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20423, https://doi.org/10.5194/egusphere-egu26-20423, 2026.
Solid mineral resources form the essential material foundation for the sustainable development of human society. The international seabed hosts vast and potentially valuable mineral deposits, among which deep-sea polymetallic nodules represent a key marine resource. Focusing on a specific area in the Western Pacific, this study aims to identify and classify small-scale polymetallic nodules in the deep-sea environment. We employ super-resolution reconstruction methods to enhance the resolution of deep-sea hydroacoustic images. Subsequently, a super-pixel segmentation approach is applied to construct a sample enhancement model for deep-sea objects, enabling in-depth extraction of multi-dimensional heterogeneous features from seabed targets and facilitating the effective development of training samples. Constrained by geological seabed samples, an accurate recognition model for seabed polymetallic nodules is established, achieving intelligent mineral classification based on multi-source data such as bathymetry and backscatter. Ultimately, by leveraging the generalization capability of the model, the recognition and classification of untrained samples can be accomplished, thereby promoting the application of the proposed algorithm in large-scale deep-sea mineral exploration.
How to cite: Wang, M., Wu, Z., Kong, L., Liu, Y., Zhao, D., Chen, J., Hu, H., and Meng, X.: Accurate Recognition of Deep-Sea Small-Size Polymetallic Nodules Based on Multi-source Data and Deep Learning Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9687, https://doi.org/10.5194/egusphere-egu26-9687, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 3
EGU26-17175 | ECS | Posters virtual | VPS26
Physical geomorphometry: From a concept to practical applicationsTue, 05 May, 14:33–14:36 (CEST) vPoster spot 3
Physical geomorphometry is young way that describe land surface morphology through gravitational energy and mass and energy movement. Unlike statistical and general geomorphometric approaches, physical geomorphometry bridging land surface characteristics and fundamental physical processes allows to interpret geomorphological primitives from genetic point of view. In this study we incorporated latest achievements of physical geomorphometry concept to demonstrate a transition from theoretical aspects to practical applications of the concept.
In the research we applied a set of physical geomorphometric (PG) indices that describes landform development from different points of view. Moreover, we used a modified algorithm of physically based elementary land-surface segmentation algorithm that integrates dynamic least-squares DEM generalization with object-based image analysis. The method is evaluated across contrasting environments, including glacial and karst landscapes, and is further extended to marine settings for seabed landform classification. Key contribution is the application of PG signature concept that unify the set of PG indices and therefore quantitatively describes landforms based on the balance and magnitude of geomorphic energies.
Our results demonstrate that the approach allows us to obtain genetically interpretable landforms both in terrestrial and submarine landscapes. Physical geomorphometric signature is highly effective in landform groups comparison and detection of each group’s potential affinity to development i.e. their disequilibrium. It also helped us to define transitional forms of landforms that are usually overlooked by general geomorphological methods.
Overall, the work highlights robustness and applicability of the concept of physical geomorphometry in various application in geosciences and beyond, that was partially demonstrated in the research.
How to cite: Popov, A. and Minár, J.: Physical geomorphometry: From a concept to practical applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17175, https://doi.org/10.5194/egusphere-egu26-17175, 2026.
EGU26-724 | ECS | Posters virtual | VPS26
Stratigraphic Controls on Gas Migration and Pockmark Formation at the foreset of a Prograding Clinoform System west of North Island, New ZealandTue, 05 May, 15:03–15:06 (CEST) vPoster spot 3
Methane stored in shallow marine sediments significantly affects seafloor stability, and influence ocean-atmosphere interactions. Since methane is a potent greenhouse gas, its release influences regional biogeochemical cycles and benthic ecosystems. Along continental margins, favourable conditions promote biogenic methanogenesis and gas hydrate formation. Understanding how methane migrates beneath the base of hydrate stability is therefore essential, particularly because hydrate dissociation near the feather edge of continental slope releases methane to the seabed. Pockmarks form when gas escapes from shallow overpressure zones. Overpressure may develop through hydrate dissociation or through the accumulation of free gas below low-permeability layers. Once pressure exceeds the sealing capacity of the overlying sediments, gas can migrate upward and eventually vent at the seabed.
In the offshore Taranaki Basin, west of New Zealand’s North Island, high-resolution 3D seismic data reveal ~300 pockmarks between 300-700 m water depth. Beneath many of these pockmarks, the seismic data show tiers of near-vertically stacked shallow-gas bright spots, indicating focused migration pathways in the shallow subsurface across the foresets of a prograding clinoform system.
The theoretical stability limit for pure methane hydrates locally aligns with the shallowest bright anomalies. However, most anomalies lie within the free-gas zone landward of the methane-hydrate outcrop and beneath large parts of the pockmark field. Over the past ~16 kyr, bottom-water temperatures along the slope have warmed by ~2.25 °C, shifting the hydrate-stability feather edge downslope by ~1.7 km. This warming-driven retreat can account for only ~20% of the observed pockmarks. While the presence of gas hydrates can deflect gas updip, there is no clear seismic evidence for a bottom-simulating reflection. Instead, gas appears to ascend upslope through a range of stratigraphic heterogeneities, such as cyclic steps that climb obliquely, scour rims, channel cuts, and levee deposits, which collectively provide localized pathways for migration.
In gently dipping (2-3°) slope, free gas beneath the hydrate stability zone would preferentially migrate updip along permeable strata toward the shelf edge. However, 3D seismic data show bright spots concentrated within scour rims, channel levees, and the crests of cyclic steps that act as effective traps updip of the upper limit of hydrate stability at the clinoform foresets. Gas is accumulated within levee deposits of vertically aggrading and laterally shifting channel-levee systems, where repeated cut-and-fill cycles build stacked fining-upward units. The climbing geometry of cyclic steps redirects gas vertically upslope along their crests, enhancing upward migration, while fine-grained scour infill inhibit lateral migration.3D visualization shows that such traps form multiple tiers of shallow-gas pockets linked by focused gas-flow. Together, these relationships demonstrate that fluid migration is strongly controlled by sedimentary architecture shaped by turbidity current-controlled depositional processes at the foresets of the prograding clinoforms. The clustering of numerous pockmarks above these vertically stacked gas zones strongly indicates that stratigraphic focusing, rather than along-slope migration at the base of the hydrate stability zone, controls gas ascent.
How to cite: Bhattacharya, I. and Sarkar, S.: Stratigraphic Controls on Gas Migration and Pockmark Formation at the foreset of a Prograding Clinoform System west of North Island, New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-724, https://doi.org/10.5194/egusphere-egu26-724, 2026.
