This is the first Common Era mangrove-based relative sea-level (RSL) reconstruction from the east coast of South Africa, a far-field location useful for increasing the global spread of Common Era RSL data. The Mngazana estuary is a permanently open small estuary with the largest Rhizophora mucronata stand in South Africa. Intertidal vegetation at Mngazana is zoned vertically by elevation, with mangrove present between just above Mean Sea Level (MSL) and just below Mean High Water of Spring tides (MHWS). We use the vertical range of modern mangrove vegetation and diatom assemblage analysis to produce RSL estimates. We also developed classical and Bayesian transfer function models but poor fossil diatom preservation prevents us using these models to reconstruct late Holocene RSL. We reconstruct RSL ~0.7 m below present around 1050 CE, rising to present over the last millennium. In contrast to the RSL data from Mngazana, glacial isostatic adjustment (GIA) modelling indicates slightly falling RSL in the last ~1500 years. The lack of evidence for falling RSL in the last millennium at Mngazana suggests that the processes dominating the RSL budget in this region are not currently captured by GIA modelling.
The fringing reef system provides a significant source of sediment, which is crucial for sustaining coastal morphology and protecting the coast from extreme events. Sediment production and redistribution in these systems are governed by both global (ocean warming, sea level rise) and local (hydrodynamics, reef productivity, bathymetry) factors. However, modern carbonate sedimentology and skeletal component variability in fringing reef systems of the northern Indian Ocean remain poorly documented. This study addresses the gap by characterising the modern shallow-marine sediment texture and carbonate assemblage from the south Andaman and Swaraj Dweep. Unconsolidated samples were collected using a Van Veen grab from 30 locations on the south Andaman (Western, Eastern, and Southern sides) and 18 locations on Swaraj Dweep (Southwestern, Northeastern, and Eastern sides) at water depths up to 15 m. The samples were wet-sieved using different mesh sizes (0.5, 0.25, 0.125, and 0.063 mm) and separated into different size fractions. Facies analysis has been done based on the mud proportion in the samples. The samples are predominantly grainstone (86%; 73%), followed by grainstone to packstone (11%; 17%), wackestone to packstone (3% in south Andaman), and mudstone to wackestone (5% in Swaraj Dweep), in south Andaman and Swaraj Dweep, respectively. Fine- to very fine-sand (0.063–0.25 mm) constitutes the bulk of the sediments (55% south Andaman; 52% Swaraj Dweep). This study analyses the two sand-size fractions (0.25–0.5 mm and 0.125–0.25 mm) to investigate the major skeletal carbonate components of these sediments. Coral (52%; 41%), algae (22%; 26%), foraminifera (10%; 21%), and molluscs (9%; 12%) are the dominant components identified for the south Andaman and Swaraj Dweep, respectively. Heterogeneities in sediment size and composition are observed on the different sides of the two studied sites; these patterns are discussed in relation to bidirectional monsoonal pathways, wind fetch, coastal complexity, and reef proximity. Based on these factors, the studied margins are classified into three inferred hydrodynamic exposure classes: high, intermediate, and low. Sheltered, low-exposure margins are generally associated with finer sediments and relatively higher proportions of foraminifera and molluscs, whereas more exposed margins tend to contain coarser sediments and relatively higher proportions of coral and algal material. Overall, this study provides a regional baseline for understanding modern carbonate sediment texture and component distribution in the Andaman fringing reef system, and places these patterns in the context of inferred hydrodynamic exposure to interpret the observed sediment heterogeneity and highlight the need for higher-resolution future studies.
This study examines spatiotemporal variability in surface sediment distribution on a channelized open-coast tidal flat using a spatially extensive, multi-year dataset. The southern Ganghwa tidal flat on the west coast of Korea was surveyed seasonally between 2014 and 2016 and revisited in 2025, enabling assessment of variability across seasonal, interannual, and decadal timescales within a single system. Empirical Orthogonal Function (EOF) analysis was used to identify dominant modes of variability, which were interpreted in conjunction with morphodynamic observations, chlorophyll-a data, and time-series imagery. Three statistically significant modes account for the primary patterns of variability in surface sediment distribution. Among these, interannual variability in wave climate is the dominant control, driving tidal-flat-wide sediment redistribution through wave-induced resuspension and winnowing of fine sediments. Decadal changes, including channel migration, oyster-reef expansion, and relative sea-level rise, exert a secondary influence by modifying hydrodynamic conditions and sediment retention patterns. In contrast, seasonal variability is less strongly expressed in the statistical decomposition, reflecting spatially heterogeneous responses governed by local hydrodynamics and biological stabilization. Surface sediments nevertheless show consistent seasonal tendencies, with winter coarsening driven by elevated wave energy across much of the tidal flat, while localized mud deposition occurs simultaneously in the upper intertidal zone and along channel margins due to biofilm-mediated stabilization and enhanced supply of suspended fine sediment. These results indicate that sediment distribution in channelized open-coast tidal flats reflects the interaction of processes operating across multiple temporal scales, and emphasize the need for process-based facies models that incorporate channel dynamics and biophysical controls.
Fluid mud systems exhibit rapid post-disturbance reorganization, during which vertical density gradients evolve into transient or persistent stratified structures that influence the development of internal sedimentary interfaces. This study investigates how the internal reorganization of density stratification during post-agitation settling influences the formation, evolution, and detectability of lutoclines in two natural sand–mud suspensions with contrasting sedimentary and experimental conditions, based on combined densimetric and acoustic measurements. In both experiments, lutocline-related density gradients developed rapidly, within 1–2 h after agitation, but their subsequent evolution diverged. One suspension remained more heterogeneous, with transient and vertically variable gradients, whereas the other developed a thicker and more vertically coherent fluid mud layer. Iso-density displacement and N2 patterns indicate that the columns did not settle as vertically coherent bodies, but underwent simultaneous upward and downward redistribution during early settling. Acoustic reflectors coincided with density-derived interfaces only in selected profiles, indicating that acoustic detection was unreliable during recently disturbed fluid-mud conditions. Structural coherence reduced detection variability only in the more vertically coherent experiment, but did not consistently reduce mean acoustic-density offset. Even after several hours of settling, stable acoustic positioning did not necessarily imply accurate detection of lutocline depth or fluid-mud thickness. These findings demonstrate that lutoclines in fluid mud are emergent features of internal sedimentary organization, and that their detectability depends on the temporal evolution of density structure. Under transient settling conditions, acoustic detection may misrepresent both the position and thickness of fluid mud layers, reinforcing the need for direct density measurements after mud-layer disturbance.
Long-term Micro-Erosion Meter (MEM) datasets are commonly summarised using average downwearing rates, masking the hierarchical spatial and temporal variability they contain. We analyse a 13-year micro-erosion meter (MEM) monitoring dataset (2011–2024) from the tectonically stable Otway coast, southeastern Australia, using an integrated statistical framework combining robust linear mixed-effects modelling (RLMM), piecewise (broken-stick) mixed-effects analysis, and hierarchical centred autoregressive AR(1) modelling. The integrated modelling framework developed in this study explicitly resolves spatial hierarchy, non-linear temporal structure, and downwearing memory across nested platforms, MEM bolt sites, and point scales. RLMM results demonstrate strong scale dependence in downwearing variability: point-scale observations exhibit high variance and skewness, whereas platform-scale mean downwearing rates are comparatively stable. Relative to classical mixed-effects models, robust estimation substantially reduces residual variance and moderates slope estimates, indicating that extreme MEM values represent temporary spikes in downwearing rates rather than persistent geomorphic trends. Piecewise modelling identifies an early monitoring phase characterised by elevated downwearing rates, followed by a lower long-term downwearing rate, indicating a distinct transition between early and sustained monitoring phases. Hierarchical centred AR(1) modelling shows that downwearing rates are partly influenced by their previous values at the point (φ₁ = 0.325), site (φ₁ = 0.353), and platform (φ₁ = 0.382) scales, indicating that past downwearing conditions continue to influence present-day downwearing. Using the 2011–2024 MEM record, representing the contemporary monitoring period of the long-term Otway dataset, the hierarchical modelling framework reveals scale-dependent mean downwearing rates of 0.264–0.561 mm/yr, highlighting the value of the approach for resolving spatial and temporal structure. Together, these results demonstrate that MEM-derived downwearing rates provide a statistically robust, process-consistent framework for interpreting long-term shore platform evolution.
Marker beds are tools for stratigraphic correlation and may constitute the backbone of basin analysis and chronostratigraphy. They are defined as thin beds with a distinctive character, widely distributed and traceable over large areas, across diverse depositional environments. They may vary systematically in thickness within basins, for example, tephra layers decrease in thickness away from the eruptive source. There are, however, basins with complex morphologies where the intrinsic variability is enhanced by regional or local factors such as tectonics. We explore such variability from a detailed late glacial to recent record in a proximal to distal transect of five sediment cores in the Western Ionian basin. Two significant results arise from this study.First, the well-known Augias marker bed, found extensively in the Ionian abyssal plain since the 1980s, is found in a series of discontinuous depocenters within wedge top basins of the Calabrian accretionary wedge. Furthermore, it is coeval with a turbidite present in shallower settings, even if it is unclear whether these deposits represent the downstream evolution of a single gravity flow or a series of coeval events. Second, sapropel S1 is a cm-thick marker correlatable across the eastern and central Mediterranean. In the study area, sapropel S1 is synchronous with a succession of up to 15 m of finely laminated turbidite-hemipelagite couplets devoid of bioturbation. This exceptionally preserved deposit allows us to trace sediment transport and accumulation related to gravitational instability and possibly times of increased precipitation with unprecedented detail during the early Holocene.
Human modifications to rivers, marshlands, and coastlines can dramatically reorganize sediment sources, leaving distinct lithological and geochemical signatures in the sedimentary record. Kuwait Bay (KB), a semi-enclosed, hypersaline coastal embayment in the northern Arabian Gulf (AG), is particularly sensitive to anthropogenic manipulation due to heightened coastal industrial development and watershed reconstruction of the Tigris and Euphrates Rivers from the mid-20th century to the present day. This study reconstructs the recent stratigraphic evolution of the northeastern margin of KB from two sediment cores collected adjacent to Ras Al-Subiyah in response to upstream and local anthropogenic forcing using a multi-proxy approach that combines downcore X-Ray Fluorescence (XRF), grain-size, lithology-corrected Total Mercury (T-Hg) concentrations, and geochronology by radioisotope 137Cs. Both cores reveal three distinct facies and an overall transition from carbonate-rich muds at depth to siliciclastic sands near the surface. The deposit at depth is characterized by elevated Ca/Ti and Al/Si and low Si/Ti XRF ratios, consistent with a mixture of terrigenous, diagenetic, and marine carbonate deposition under low-energy conditions. A middle transitional facies marks a shift from solely fine-grained carbonate sedimentation to a near equal mix of siliciclastic sands and carbonate mud deposition. XRF ratios reveal a decrease in Ca/Ti and Al/Si and elevated Si/Ti ratios, dated to the mid-1960s to early 1970s, which coincide with a major reduction in the Euphrates River's flow rate, likely reducing fluvial muds to the northern AG and KB. Despite grain size coarsening, T-Hg concentration is elevated in this section, suggesting a localized input unrelated to lithology. The uppermost facies, deposited post-2000, is siliciclastic sand with low Ca/Ti and Al/Si and elevated Si/Ti ratios. Corrected T-Hg remains elevated in this section, suggesting anthropogenic input from the late 1960's to the present day. The transition from the middle to the upper lithofacies is dated to 2000, coinciding with the completion of the Subiya Thermal Power Plant, which shifted local hydrodynamics, increased turbulence, and limited fine-grained accumulation. Our findings suggest that both upstream and local coastal development jointly reorganize sediment provenance and depositional textures in northeastern KB, with T-Hg enrichment not solely controlled by fine-grained sediment accumulation.
Shore platforms along rock coasts have long puzzled geomorphologists regarding their age and formative processes. This study combines cosmogenic nuclide (CN) dating and micro-erosion meter (MEM) measurements to investigate the evolution of microtidal shore platforms on the Otway Coast of Victoria, Australia. CN concentrations across four platforms reveal significantly high values (up to 123,831 atoms g−1) compared to previous studies, indicating formation predating the Holocene. Cross-shore CN distribution shows peak concentrations at the seaward edge, decreasing landward. MEM data collected over 44 years demonstrate active contemporary erosion, with downwearing rates closely related to elevation and tidal inundation frequency. Numerical modelling of both CN concentrations and MEM-calculated downwearing rates suggest platform initiation during at least the Last Interglacial period, with subsequent modification during the Holocene. The results indicate that platform width is morphologically-inherited from past higher sea levels, while the contemporary cross-shore morphology results from Holocene downwearing processes. This study provides evidence for long-term morphological inheritance in shore platform evolution, challenging the notion of purely Holocene formation in resistant lithologies. The findings highlight the complex interplay between inherited landforms and ongoing erosive processes in shaping rock coast geomorphology, contributing to our understanding of coastal landscape evolution over glacial-interglacial timescales.
This study investigates the stratigraphic architecture and evolution of the Blanes canyon head (NW Mediterranean) during the Late Quaternary using high-resolution bathymetry and seismic profiles (TOPAS and Sparker). The canyon forms a morpho-depositional boundary between the sediment-starved La Planassa shelf to the east and the depositional Barcelona shelf to the west. The Messinian Erosion Surface marks the base of the Pliocene succession and controls the accommodation and distribution of Quaternary deposits, which are directly emplaced onto the Miocene substrate due to the limited preservation of Pliocene sediments. Five Quaternary seismic units (A–E) infill the canyon head and are bounded by four unconformities (SB1–SB4) correlated with ∼100 kyr glacioeustatic cycles (MIS 10, 8, 6 and 2). The succession records marked asymmetry between canyon rims driven by inherited structural controls, asymmetric sediment supply and sea-level cyclicity. The western rim is predominantly depositional, comprising stacked progradational, downstepping wedges (Units A–D) formed during forced regression and overlain by Unit E, which records the last lowstand and subsequent transgressive deposits preserving progradational configurations. In contrast, the eastern rim is largely erosional, reflecting the combined influence of limited sediment input, reduced accommodation associated with a structural high, and subaerial exposure during sea level lowstands.Although adjacent to the Tordera River, no direct fluvial connection with the canyon head developed during the Late Quaternary. During lowstands, fluvial sediments were trapped within an inherited structural paleodepression along the western rim, accumulating as regressive infill rather than bypassing to the canyon. Four buried paleochannels record incision and canyon-head retreat during lowstands, followed by progressive infill. Overall, canyon-head evolution reflects structural inheritance modulated by Quaternary sea-level oscillations and sediment supply.
Polymetallic nodules grow through the successive concentric agglomeration of ferromanganese oxides around a nucleus, incorporating critical trace metals such as Co, Cu and Ni. Individual layers alternate through changes in the relative influence of hydrogenetic and diagenetic processes. Linking the internal growth structures with the elemental distribution is essential to reconstruct and compare the heterogeneous formation history of different nodule localities. Here, we integrate three-dimensional high-resolution X-ray computed tomography (μCT) with geochemical mapping to more effectively compare the microtextural and chemical heterogeneity of nodules from the Clarion-Clipperton Zone (CCZ) with nodules from the Cook Islands Exclusive Economic Zone (CI EEZ). CCZ nodules showed an alternation between hydrogenetic and early-diagenetic growth with micro-scale lateral heterogeneity, including a discontinuous diagenetic dendritic layer reflecting local redox conditions. In contrast, CI EEZ nodules generally showed hydrogenetic growth, with the co-precipitation of hydrogenetic Ti at low Mn/Fe ratios (< 0.5). High Mn/Fe ratios (> 5) could be intimately linked with early diagenetic massive and dendritic textures with relatively higher amounts of Ni and Cu. A Mn/Fe ratio < 2.5 was typically noted for hydrogenetic laminae relatively enriched in Co. Mottled textures with intermediate Mn/Fe ratios were considered to be oxic-early diagenetic in origin and transitional between hydrogenetic and diagenetic conditions. This study demonstrates the pronounced influence of local redox conditions on the growth of polymetallic nodules. The novelty of combining high-resolution μCT and geochemical mapping proved to be indispensable to characterize the often overlooked micro-scale textural and chemical heterogeneity of individual layers in polymetallic nodules.
Sediment waves are widespread deep-marine bedforms whose formative processes and lithological characteristics remain incompletely understood. Their origin is commonly attributed to a range of processes including turbidity currents, contour currents, cascading flows, and internal wave activity, but the relative contribution of these mechanisms in mixed systems is still debated. This study investigates sediment waves developed on the distal Bounty Fan (east of New Zealand's South Island), where a ∼ 400 m thick succession of stacked sediment waves is exposed within the northern levee of the Bounty Channel complex.The integration of high-resolution 2D multichannel seismic data with sedimentological and lithological observations from Ocean Drilling Program (ODP) Leg 181 Site 1122 provides a rare opportunity to directly link bedform morphology with internal stratigraphy in a deep-marine system. Importantly, Site 1122 offers a unique and unprecedented continuous core record of more than 400 m of sediment-wave deposits, representing one of the most complete subsurface archives of deep-water sediment waves yet recovered. The sediment waves display wavelengths of ∼1–3 km and heights of ∼30 m, and are expressed in seismic data as laterally continuous, aggradational packages within the levee deposits.Results indicate that the evolution of the Bounty Fan is characterized by distinct phases of development, reflecting changing interactions between turbidity currents, alongslope bottom currents, tectonic forcing, and climatic variability. A major reorganization occurred across the late Pliocene–early Pleistocene boundary, marked by the establishment of a persistent channel–levee system and a shift toward sustained turbidite-dominated sedimentation. A second intensification phase during the mid- to late Pleistocene is associated with increased sediment flux, enhanced levee growth, and more frequent turbidity-current activity, likely linked to tectonic uplift of the Southern Alps and climatic reorganization during the Mid-Pleistocene Transition.Lithological analysis of Site 1122 demonstrates that sediment waves are predominantly composed of stacked turbidite deposits, indicating that their formation is mainly governed by gravity-driven processes rather than contour-current deposition. Although contour currents may exert an influence on the Bounty Fan geomorphology, expressed through levee asymmetry and long-term channel migration, the internal architecture and deposits of the sediment waves reflect repeated overspill of turbidity currents. The vertical facies organization and grain-size trends are consistent with depositional cyclic-step dynamics generated by turbidity flows transitioning between supercritical and subcritical regimes, with thicker and coarser-grained turbidite beds and higher sedimentation rates on stoss sides of sediment waves, and a progressive fining and thinning toward lee sides.This study provides one of the most complete stratigraphic records of deep-water sediment waves to date and offers direct field-scale constraints on their internal architecture. More broadly, it demonstrates that, in this setting, sediment waves are primarily the product of turbidity currents, whereas contour currents likely play a secondary role in shaping the geomorphological asymmetry of the channel–levee system.
Amino acid racemisation (AAR) is a well-established tool in geochronology and palaeothermometry, but previous studies have primarily focused on chronological calibration and kinetic modelling rather than formally evaluating basin-scale spatial autocorrelation. This study applies global and local spatial autocorrelation techniques to evaluate whether AAR indicators exhibit geographic structure across the Caribbean-Atlantic region. Using A/I ratios, isoleucine, and alloisoleucine concentrations measured from 73 georeferenced sediment cores, we computed Moran's I, Geary's C, and Local Indicators of Spatial Association (LISA) to assess spatial dependence. The A/I ratio and isoleucine concentrations show statistically significant positive global autocorrelation, while alloisoleucine shows weaker but statistically significant spatial structuring. LISA results identified significant spatial clusters and outliers for all three AAR indicators, demonstrating that racemisation patterns are not randomly distributed across the basin. These findings indicate that AAR parameters possess basin-scale spatial organisation, providing the first spatially explicit statistical framework for interpreting racemisation patterns in relation to regional environmental and diagenetic processes.
Sediment diagenesis is a key paleoceanographic process for understanding the geological history of the oceans. Submarine plateaus and seamounts host distinctive lithification processes and are sensitive to sea-level and atmospheric changes due to their relatively shallow bathymetry. In this context, the Rio Grande Rise (SW Atlantic Ocean) is well-suited for the investigation of early diagenetic processes on summit carbonates. We analyzed 30 dredged samples collected by the Geological Survey of Brazil in 2011, using optical petrography, scanning electron microscopy, electron probe microanalysis, bulk-rock major elements geochemistry, C and O stable isotopes, and 87Sr/86Sr geochronology. Sample lithologies range from mud- to grain-supported low Mg-calcite carbonates, mainly composed of bioclasts of red algae, foraminifera, bryozoans, echinoderms, and corals, in addition to volcanic sandstone and siltstone, recording the occurrence of an Oligo-Miocene isolated carbonate platform. Diagenetic features included micritization, cementation of fibrous to bladed isopachous low Mg-calcite cementation, euhedral and mosaic calcite, syntaxial overgrowths and recrystallization. δ18O and δ13C values vary between -1.68% to +4.18% and -1.35% to +2.62% (V-PDB), respectively. Volcanic-fluid interaction is indicated by Mg- and Fe-smectite (saponite, nontronite) formation under alkaline conditions, and Fe-Mn oxide cementation since the early Cenozoic. Phosphatization is also a prevalent process that took place during Miocene acidic conditions, promoting cement dissolution and phosphatization under cold, oligotrophic water masses. Our results reveal a complex diagenetic history, which shaped the seafloor of the Rio Grande Rise over the last 25 million years, providing insights into the paleoceanographic changes in the South Atlantic Ocean during the Paleogene-Neogene.
Rubble strips are shore-normal, elongated deposits on coral reef flats, composed of variably sized and shaped mobile coral clasts, which can contribute to the sediment supply on exposed low-lying coral reef islands. As climate change-driven ecological and physical disturbances increasingly impact coral reef systems and associated landforms, understanding the processes and controls governing their morphodynamics is critical. At an exposed intertidal rubble strip in Huvadhu Atoll, we examined: i) the morpho-sedimentological characteristics; ii) short-term (days-weeks) clast mobility using tracer experiments with in situ current and wave measurements; iii) intra-annual morphological changes using repeated UAV photogrammetric surveys; and iv) deposit age and rubble throughput using UTh dating to provide a chronological framework. This deposit is a modern reservoir of coral rubble (less than 250 years in age) which shows a lagoonward increase in clast age. Surface sediments displayed lagoonward surficial sorting with decreasing grain size (D50 = 5–45 mm) and a transition from tabular to branching clasts. Subsurface layers contained substantial sand fractions (>60%) indicating that these landforms are not exclusively coarse-grained. Tracer experiments revealed monthly clast mobility of 40–85% and displacements up to 16.6 m under modal hydrodynamic conditions (offshore Hs = 0.48–2.09 m). Mobility increased with decreasing clast size, from tabular to massive to branching forms, and higher wave-current velocities. Morphological analysis indicated that 15–43% of the rubble strip experienced significant elevation changes bi-weekly to intra-annually, reflecting localised erosion and accretion. Although the net sediment volume of the strip remained stable, sediment was actively redistributed from the algal rim towards the lagoon. Overall, rubble strips are morphodynamically active landforms under moderate forcing conditions, with mobilisation controlled by size and shape attributes, and wave-current velocities.
This study reconstructs millennial- to centennial-scale climate variability in the western Arabian Sea during Dansgaard–Oeschger (DO) events 12–11. It aims to evaluate how abrupt high-latitude climate oscillations influenced the vertical structure of the water column and monsoon-driven circulation in the northwestern Arabian Sea. Sediment from ODP Hole 721A was analyzed using Mg/Ca paleothermometry and stable isotope measurements (δ18O, δ13C) on planktonic (Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina dutertrei) and benthic (Uvigerina peregrina) foraminifera. The proxies were used to reconstruct sea surface temperatures (SST), thermocline variability and intermediate-water structure associated with monsoon dynamics. Results indicate that SST were generally 2.5–5 °C lower than modern values and that the stadial–interstadial transition was accompanied by coherent changes in thermocline and intermediate-water structure. Variations in δ13C and δ18O records further indicate changes in ocean ventilation, carbon cycling, and thermocline structure across stadial–interstadial transition. The data suggest that surface circulation and the thermocline were driven predominantly by local monsoon forcing, whereas intermediate waters responded more strongly to regional circulation changes, including the reorganization of intermediate-water masses. These results support the broader pattern of weaker SW monsoon conditions during DO stadials and relatively stronger SW monsoon during DO interstadials. Overall, the study provides new depth-resolved evidence that abrupt high latitude climatic changes were associated with broad vertical oceanographic reorganization in the Arabian Sea.
The Fujairah Basin, offshore northeastern United Arab Emirates, occupies a tectonically complex position along the northeastern Arabian Plate, close to the transition between the Zagros collision, the Minab–Zendan strike-slip system, and the Makran subduction zone. Although previous studies recognized late basin extension, the timing, geometry, and kinematics of shallow post–Middle Miocene faulting and its relation to present-day seismicity remained poorly constrained. This study integrates 2D seismic lines, 3D seismic cube, three exploration wells, and a high-resolution multibeam bathymetry data to characterize shallow fault architecture, link seafloor ruptures to subsurface structures, and reconstruct the late post-collisional evolution of the basin. The results reveal eight extensional strike-slip duplexes (S1–S8) arranged along NNW–SSE trending sinistral master faults, with lengths increasing northeastward from ∼5–20 km to ∼50 km. In seismic sections, these structures form negative flower geometries, whereas in map view they define rhombic to irregular fault-bounded domains with extensional horses oriented at ∼15–50° to the master faults. Horizontal slices from the 3D seismic data support a sinistral interpretation of the fault system, the map-view arrangement of overlapping master strands, extensional imbricate fans, and associated graben–half-graben arrays. Many shallow subsurface faults extend to the seafloor, where they form curvilinear escarpments, horsts, and grabens that coincide with clusters of shallow microseismicity (<5 km depth), indicating ongoing tectonic activity. Seismic evidence indicates Late Miocene initiation of duplex formation on pre-existing structural highs, followed by Pliocene to Early Quaternary along-strike propagation, overlap, and multiphase reactivation, and culminating in Late Quaternary composite duplexes coeval with eastward tilting and southeastward progradation. These observations indicate that the Fujairah Basin records a post–Middle Miocene transition from compression to transtension, driven by intraplate sinistral shear and extension along the northeastern Arabian margin. The study refines the basin-scale tectonic framework and demonstrates that shallow active deformation in the Fujairah Basin is structurally linked to extensional strike-slip duplex development in a transtensional setting.
Shoreline change assessments are central to coastal management and adaptation planning, yet they commonly rely on a limited number of indicators used as proxies for complex coastal behaviour. Because interpretations of shoreline dynamics and vulnerability depend strongly on measurement methods and observational scales, this study examines how different monitoring approaches influence interpretations of soft coastline shoreline change along the energetic Atlantic coast of southern Ireland. A three-year multi-method monitoring programme (2023–2025) was conducted across five embayed unconsolidated sandy beach systems, integrating long-term aerial imagery and vegetation-line change, Sustainable Coastal Vulnerability Index outputs, repeated seasonal RTK-GNSS cross-shore profiles, high-resolution UAV-derived orthophotos and digital surface models, and targeted post-storm field assessments. Results show that different monitoring methods produce distinct but complementary narratives of shoreline behaviour. Long-term vegetation lines and derived change rates emphasise boundary translation but can mask shorter-term accelerations, regime shifts, or localised erosion hotspots. SCVI classifications provide effective broad-scale screening of exposure and receptors but may misrepresent physical susceptibility where local sediment dynamics or recovery processes are not captured. In contrast, field surveys and UAV-derived topographic datasets reveal spatially variable sediment dynamics, with erosion and accretion occurring simultaneously across different sectors of the same beach systems. These differences highlight the need for monitoring strategies that combine complementary datasets. Based on these findings, an evidence-based tiered monitoring strategy is proposed and distinguishes proxy-based screening, routine cross-shore profile monitoring, and targeted UAV surveys in spatially complex settings, reducing interpretive bias in assessments of shoreline change and coastal vulnerability.
Mixed carbonate-siliciclastic margins such as the Belize Barrier Reef provide sensitive archives of glacio-eustatic variability because reef accretion, erosion, and sediment supply respond directly to sea-level fluctuations. This study investigates the geomorphological imprints of relative sea-level change along more than 100 km of the Belize Barrier Reef margin using high-resolution multibeam bathymetry. The new bathymetric dataset provides deeper insight into reef-margin morphology and identifies constructional and erosional paleo-sea-level indicators. Ridge-crest lineaments and reef-wall notches were used for statistic depth distributions from ten along-strike sectors, which reveal laterally persistent elevation clusters that correspond to distinct paleo-sea-level positions. Ridge-crest lineaments show a dominant concentration near ∼20 m water depth, interpreted as a period of reduced early Holocene sea-level rise, or even possible MIS 5 stillstands, whereas widespread notch horizons at ∼80–85 m and ∼ 100–105 m record prolonged late Pleistocene stillstands preceding and approaching the Last Glacial Maximum. The absence of systematic vertical offsets between sectors indicates negligible neotectonic deformation along the margin. Results demonstrate that reef-margin morphology preferentially preserves intervals of slow or stable sea-level change, while phases of rapid transgression leave limited geomorphic imprint. High-resolution bathymetry thus provides a powerful tool for reconstructing sea-level histories from steep carbonate margins and establishes the Belize Barrier Reef as a key reference archive for late Quaternary sea-level dynamics.
The Neogene Enping Sag is located in the delta front of the paleo-Pearl River Delta, where a series of sand bodies developed along the delta front under the coupling influence of fluvial, wave, and tidal hydrodynamics. Investigating their formation mechanisms not only provides insight on the hydrodynamic processes and paleoclimatic context of delta front depositional environments but also offers guidance for oil and gas exploration and development. Based on integrated analyses of core descriptions, petrographic thin sections, grain-size distributions, XRD analyses, SEM, and high-resolution 3D seismic data, this study identifies the Neogene calcareous interbedded sandstones in the study area as storm-generated coastal sand bars deposited at the front of the paleo-Pearl River Delta. These sand bars occur as multiple sandy ribbons closely wrapping around the delta front. The vertical sedimentary sequence, from bottom to top, consists of nearshore, foreshore, backshore, barrier flat, and mudflat microfacies, collectively recording unstable sedimentary hydrodynamic conditions. Additionally, relatively typical shallow-marine storm-flow depositional sequences are observed below the wave base. Given the generally poor sorting of these storm-generated coastal sand bars, while they can act as high-porosity and moderate-permeability reservoirs under shallow burial conditions, their petrophysical properties degrade significantly under deep burial and intense compactional diagenesis, making them unlikely to develop into high-quality reservoirs. The discovery of these coastal sand bars demonstrates that the paleo-Pearl River Delta was already under the control of an intense East Asian monsoon climate during the Miocene.
The morphodynamics and evolution of embayed beaches are widely recognized as being modulated by the combined effect of inherited geology and hydrodynamic factors. Recent studies have also highlighted the importance of sediment supply, particularly from rivers and streams, in shaping the long-term evolution of these systems. In this work, the morphological response of a low-indented embayed coastal barrier is investigated across multiple temporal scales by combining subsurface barrier architecture and sediment stratigraphy with decadal shoreline and annual topographic profile changes. The results reveal longshore gradients in grain size and berm height linked to wave exposure variations, and contrasting morphological responses alongshore, ranging from progradation in the northern sectors to shoreline retreat and barrier rollover near the main river mouth, with inlet-related processes, foredune progradation, and megacusp-related processes also occurring across the system. The pronounced retreat observed near the river mouth is tentatively linked to changes in the course of the main river and a subsequent reduction in sediment supply, suggesting a shift from a fluvially dominated toward a wave-dominated regime, evolving toward a parabolic embayment form. Available wave records show no significant long-term trends, suggesting that wave climate variability is unlikely to explain the observed alongshore variability. This underscores the role of local sediment sources in controlling embayed barrier configuration, a factor that may become increasingly relevant under ongoing global environmental change, particularly through potential alterations in river discharge regimes.
