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Despite several decades of study, details of the relationship between sea level and other factors controlling carbonate sedimentation require clarification. To address this issue, ODP Leg 166 drilled a slope to basin transect adjacent to the Great Bahama Bank to document Neogene and Quaternary sea level changes, and to precisely date the major unconformities within the slope and basinal succession. Here we describe the complex connection between the cyclicities evident in a range of sediment physical property parameters at Leg 166 sites and their relationship to sea level fluctuations, diagenesis, and the morphology of the adjacent carbonate bank margin. The characteristics of fifth-order petrophysical cycles in Miocene slope sediments of the Great Bahama Bank are fundamentally different from those in overlying late Pliocene and Pleistocene slope sediments. These intervals are separated by an early Pliocene sequence with characteristics that are transitional between the overlying and underlying sequences. We interpret the more symmetric character of the Miocene cycles as reflecting cyclic sedimentation controlled by the interaction between sea level fluctuations and the ‘ramp’ morphology of the adjacent platform, and the markedly asymmetric late Pliocene and Pleistocene cycles as representing the interaction between sea level and a ‘rimmed’ platform morphology. In the case of the Miocene cycles, diagenetic overprints cause values for petrophysical properties controlled by porosity to be inverted compared to cycles in essentially unaltered late Pliocene and Pleistocene sediments. A detailed understanding of the relationship between petrophysical cycles, diagenesis, sea level fluctuations, and platform margin morphology offers the potential to provide a proxy for inferring the controls on carbonate sedimentation in situations where the nature of the carbonate platform margin is unknown (e.g., where regional seismic data is poor or absent) and/or where sea level effects cannot be reliably determined by other means. These petrophysical proxies should be of greatest benefit where downhole logging data is used as the primary basis for sediment characterization. [Copyright &y& Elsevier]

Submarine sediment flows is one of the main means for transporting sediment to the deep sea, often traveling long-distance and transporting significant volumes of sediment for tens or even hundreds of kilometers. Its strong destructive force often causes serious damage to submarine utilities on its course of movement. The sediment concentration of the sediment flow determines its density difference with the ambient seawater, and this density difference determines the flow ability of the sediment flow, and thus affects the final deposition locations of the transported sediment. In this paper, sediment flows of different sediment concentration with various silt and clay weight ratios (referred to as silt/clay ratio) are studied using flume tests. Our test results indicate that there is a critical sediment concentration at which sediment flows travel the fastest for a specific sediment composition. The critical sediment concentrations and their corresponding maximum velocities for each of the four silt/clay ratios are obtained. The results further indicate that the clay content is linearly negatively correlated with the critical sediment concentration. As the sediment concentration increases, the flow behaviors of sediment flows transform from the flow state to the collapsed state, and the fluid properties of the two turbid suspensions with changing flow behaviors are both Bingham fluids. Additionally, this paper also provides a microscopic explanation of the above-mentioned results by analyzing the arrangement of particles within the sediment flow. • The concept of critical sediment concentration is proposed, under which the turbidity current have the fastest flow velocity. • Sediment component of turbidity current influenced critical sediment concentration. • Model of particle arrangement was constructed to explain the fastest velocity. [ABSTRACT FROM AUTHOR]

Tropical storm Pabuk (4th January 2019) struck southern Thailand, causing damage to the low-lying coastal area. The combination of waves, storm surge, and high tide resulted overwash and inundation of regions on the West coast of the Gulf of Thailand (GOT) side. After the event, we conducted a field survey from January 7–10 and 15–20, 2019 to investigate the effect of storm surges and the degree of damage from the site under the eye of storm affected area up to the north 500 km from the landfall sites. This paper investigates how variations in coastal geomorphological features respond to the storm surge generated by tropical storm Pabuk at a regional scale. Coastal damage was observed along the beach from the presence of the scour, beach scarp, knocked down trees, and destroyed buildings and infrastructure. The most damaged area was at Nakhon Si Thammarat (NST), where the tropical storm made landfall with maximum wind speeds of almost 100 km/h and a storm surge height of 5 m. At NST site, the washover deposits extended as far as 80 m from the coastline with a maximum inundation of 330 m. From this study, two types of washover deposits including perched fan and washover terrace were identified. The thickest washover sediment, 60 cm thick, was discovered in a relatively low-lying area adjacent to a small estuary. Mud rip-up clasts, planar stratification, cross stratification, foreset bedding, scouring at base, and sharp and erosional contact are characteristics of sedimentary structures found in storm sediments. Bedform surfaces, such as current ripples with indicated storm surge direction, were well-preserved at several sites. We suggest that the local geomorphological controlling factors, especially coastal elevation have played important roles in the difference of coastal geomorphological responses as well as the type of washover deposits. • The inundation distance has been significantly influenced by both the total water level and the height of the coast. • The microtidal coast may contribute to storm surge with more consequences and destruction than mesotidal coasts. • Local morphology strongly affects washover sediment thickness more than distance from landfall. • The washover terrace typically results in a thick layer of washover deposit, whereas the perched fan does not. [ABSTRACT FROM AUTHOR]

Abstract Sediment particles derived from the continents have compositional variability that allows them to be used as tracers from their sources. Because of the patchwork of geological terrains that make up the continents, radiogenic isotope daughters of long-half-life parents provide a powerful tool for understanding the origins and dispersal patterns of sediments. Weathering processes that prevail in different climatic zones further imprint the geochemical signature of sources. Fine-grained sediments, clays and silts, can travel long distances in winds and ocean currents, and changes in their composition through time may allow understanding changes in their transporting media and climate significance. This paper presents new K/Ar age values of fine sediments in the Atlantic Ocean basin. The paper also presents a brief overview of the important factors of sediment delivery to the Atlantic Ocean, and reviews the new K/Ar data within the context of published clay mineralogy and 87Sr/86Sr from the same samples. Additionally, the paper presents previously published K/Ar and 87Sr/86Sr and ε Nd from Atlantic Ocean sediments, and uses the map distributions as a way to qualitatively compare the compositional trends of the four tracers as many of the data are from different samples. Although the information for all of these provenance tracers is incomplete and it would be fruitful to fill in many different aspects, this compilation of previously published K/Ar, 87Sr/86Sr and ε Nd data compared with the new data demonstrates that the distribution of K/Ar ages is broadly consistent with the other compositional information and with the geology of the surrounding continents. K/Ar provenance ages offer a simple and reliable tracer of sediment sources that is complementary to other methods. Highlights • K/Ar age values of terrigenous sediments provide useful natural tracers. • The sample preparations and measurements are rapid and simple. • Mapped distribution of K/Ar ages follows expected pattern from geology of surrounding continents. • The pattern of K/Ar ages complements those from clay mineralogy 87Sr/86Sr and ε Nd. [ABSTRACT FROM AUTHOR]

Slope instability is one of the most effective processes shaping the sea floor of continental margins. The end-products of slope instability, mass-transport deposits (MTDs), have been documented in the literature using diverse approaches. This paper tests a new methodology, applied to a region offshore Espírito Santo (SE Brazil), for the evaluation of MTDs' occurrence on continental slopes. A MTD inventory was, in a first stage, made for a cropped region of SE Brazil using a high resolution three-dimensional (3D) seismic volume. This MTD inventory consists of four MTDs that were mapped and exported into a Geographic Information Systems (GIS) database. MTD favourability scores were computed in a second stage using algorithms based on statistical/probabilistic analyses (Information Value Method), over unique terrain conditions, in a raster basis. Terrain attributes derived from the Digital Terrain Model (DTM) were used as proxies to several driving factors of MTDs, and as predictors in the models. As a result, three models are discussed independently in this paper according to the different datasets used to interpret MTDs (Models 1, 2 and 3). The results were prepared by sorting all pixels according their favourability value, in descending order, and the robustness and accuracy of the MTD favourability models were evaluated by success-rate curves. The curves aided the quantitative interpretation of the models expressing their goodness of fit to the interpreted MTDs. This work is important because the outputs resulting from the methodology confirm that this new method can be applied to submarine slopes. From the three models, Model 3 obtained the highest goodness of fit (0.862). Based on our results, a sensitivity analysis was undertaken and key predisposing factors were identified. This new methodology has the potential to become a very important and valid approach for the recognition of submarine slopes prone to failure on continental margins around the world. [ABSTRACT FROM AUTHOR]

Barrier island response and recovery to storms, and island transgression with relative sea level rise, can be influenced by the framework geology. The influence of framework geology on barrier island geomorphology has previously been examined in areas where the framework is rhythmic alongshore or consists of an isolated paleo-channel or headland. The purpose of this paper is to examine the influence of framework geology on beach and dune geomorphology at Padre Island National Seashore (PAIS), Texas, USA, where the framework geology is variable alongshore. Alongshore beach and dune morphometrics and offshore bathymetric profiles were extracted from a combined topography and bathymetry digital elevation model (DEM) using an automated approach along the ~100 km study area, and an electromagnetic induction (EMI) survey was used to map the subsurface framework geology. Wavelet decomposition, Global Wavelet (GW), and bicoherence analyses were used to test for spatial relationships between and within the extracted alongshore metrics. GW trendlines demonstrate that beach and dune morphometrics are structurally controlled. Hotspots in wavelet coherence plots between framework geology and alongshore island morphometrics indicate that the paleo-channels dissecting the island influence beach and dune morphology, with large dunes found in the area directly landward of the paleochannels. Bicoherence analysis of alongshore beach and dune morphometrics indicates that low-frequency oscillations due to framework geology interact with higher-frequency oscillations, with greater small-scale variability in the dune line directly landward of the paleo-channels. These results suggest that the paleo-channels of PAIS non-linearly influence beach and dune morphology, which in turn alters the response of the island to storms and sea level rise. It is argued that an understanding of the framework geology is key to predicting island response to sea level rise and framework geology needs to be included in barrier island models. This paper demonstrates that an irregular framework geology influences small-scale coastal processes, and creates interactions across scales that influence beach and dune morphology and affects barrier island response to storms and sea level rise. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate the position of the Holocene transgression on the coast of the Valencia Gulf. To achieve this goal, a sedimentological and micropaleontological analysis of samples of fossil benthic foraminifera in cores from six boreholes drilled in three different wetlands (Almenara marsh, Moro marsh and Valencia lagoon) was carried out. In order to assess the extent of sea level change, at least three factors must be taken into account: 1) eustatic rise (global scale) 2) neotectonics (regional scale) and 3) the sedimentary factor (local and regional scale). Regarding the first factor, some authors have noted that the Holocene transgression reached +1 m above the current sea level in this area. As for the second factor, while the Valencia lagoon is located on a subsiding coast the northernmost marshes are located on a tectonically stable coast. Finally, sedimentation rates are highly variable depending on the area; whereas in the Valencia lagoon the shoreline generally shifts seawards (progradation) in the northernmost areas the coast is currently undergoing retrogradation, although the anthropic factor clearly interferes with this pattern. One of the main conclusions is that in the Valencian coast the Holocene maximum relative sea level did not exceed the present-day one, except in the case of the subsiding area of the Valencia lagoon. The calculation of sedimentation rates, the relative sea-level curve and the evolution of the water column in the different wetlands seem to corroborate it. Radiocarbon and AAR analyses allowed us to date the maximum extent of the Holocene transgression on the Valencian coast at around 5500 cal yr BP in all cases. Despite the different subsidence the three studied wetlands reflected the predominant marine influence until 5500–5200 BP, which was later followed by a growing fluvial or continental incidence, when glacioeustatic adjustments defined the patterns of coastal progradation. [Display omitted] • Location of the MIS 1 coastline position in three West Mediterranean wetlands. • The global Holocene eustatic rise invaded the three wetlands at least 5300 years BP. • Subsidence rate determined different MIS 1 relative sea-level rise in the wetlands. • Tectonic stability in the northern wetlands involved slower relative sea-level rise. [ABSTRACT FROM AUTHOR]

A fast, reliable, through water and non-intrusive bed-profile measurement technique that is economical and easy to use in a wide range of laboratory experiments involving sediment transport is proposed. A consumer-grade 3-D range sensing technology which by its low cost, easy operation and relatively good accuracy is becoming an attractive alternative to expensive 3-D laser scanners. The Microsoft XBOX 360 kinect sensor 2.0 is a low-cost and highly popular depth camera, which can be used to scan 3D surface terrain of dynamic objects and has the potential to scan terrain below and above water. Through the software matching of kinect 2.0, a data storage and analysis system are formed, which makes it has the ability to obtain underwater terrain data. In addition, the correction model of water refraction error is established, which can eliminate the measurement error caused by water refraction. Up to four different water conditions, kinect 2.0 is tested. Finally, the influences of water depth, suspend load volume concentration and moving flow velocity on the measurement accuracy of kinect 2.0 are explored, and the compensation methods of measurement error caused by the above factors are given. The results of this paper can provide reference for underwater topographic survey. • A new method for obtaining underwater terrain was obtained. • The measurement accuracy of the method is discussed. • A two-dimensional profile of dam body and a three-dimensional dam surface was obtained with kinect 2.0. [ABSTRACT FROM AUTHOR]

Current ichnofacies models for shelf environments are largely based on analysis of ancient sedimentary deposits and have rarely been applied to studies of modern siliciclastic shelves. Siliciclastic shelf margins are key components of source rocks and unconventional shale plays that can be used as modern analogs to ancient systems. This paper examines the sedimentology and ichnology of shelf margin cores of the Mississippi River Delta containing strata formed during the 2004 (Ivan) and 2005 (Katrina and Rita) hurricane events in the Gulf of Mexico, together with those from the Kikori-Fly-Purari rivers in the Gulf of Papua, New Guinea and the Tūranganui-a-Kiwa/Poverty Bay shelf deposits of the Waipaoa River basin, offshore New Zealand. The cores provide examples of modern-day traces created by marine organisms on muddy shelves and are used to evaluate ichnological models that have been applied to determine sedimentation rates and depositional processes in ancient settings. In total, six facies were recognised based on lithology and ichnological characteristics: (1) laminated very fine sand, produced by waxing and waning currents, displaying scarce to moderate bioturbation; (2) laminated silty mud, formed by waxing and waning currents, exhibiting scarce, very low to moderate bioturbation; (3) normally graded sand and silt, created by suspension settling following a wave-enhanced sediment-gravity flow (WESGF), which reveals low to moderate bioturbation; (4) fluid mudflow/suspension settling deposits, characterised by structureless mud with low to high bioturbation; (5) biogenically mottled silty mud deposited by suspension settling which show high bioturbation intensity; and, (6) storm-generated facies of laminated sand formed by rapid sediment accumulation on the shelf. The different study areas show remarkably similar traces with variable intensity, diversity, abundance and distribution. The Mississippi River Delta cores are typified by Helminthopsis , Chondrites , Schaubcylindrichnus, Skolithos , Siphonichnus , navichnia, fugichnia and abundant bivalve shells. The deposits from the Gulf of Papua consist of Phycosiphon , Chondrites, Schaubcylindrichnus, Skolithos , Helminthopsis, Arenicolites, worm-like traces and abundant bivalve shell fragments. In addition to the traces and bivalves, Tūranganui-a-Kiwa/Poverty Bay shelf includes Asterosoma , Thalassinoides and gastropods. These traces are consistent with the newly defined Phycosiphon Ichnofacies (MacEachern and Bann, 2020), which characterise muddy prodelta settings. This research demonstrates that the neoichnology of modern shelf sediments match models developed from studies of ancient systems, and provides a robust tool for analysing and interpreting ancient shelf strata. • Four processes were interpreted to have formed the sediment facies in three continental shelves. • Facies from three different shelf margins display similar biogenic features with varying diversity and bioturbation. • Traces recognised to belong to recently proposed Phycosiphon Ichnofacies were recognised. • Link between sedimentation rate, bioturbation, facies and events processes is shown usingrectangular diagram. [ABSTRACT FROM AUTHOR]

Sediments occurring in clastic depositional coastal and marine environments share similar sedimentary characteristics despite their different provenances. Identifying the deposits' origin found at a specific site may be essential, but also a challenging task. This paper discusses a fast methodology to recognise the primary source of sediments using end-member modelling, applied specifically to particle shape distributions instead of the classical approach of using grain-size distributions only. Artificial mixtures of coastal cliff and nourished sediments from Sylt Island (North Sea) were measured with a dynamic image analyser. Roundness, sphericity, convexity, and aspect ratio shape descriptors were analysed using the EMMAgeo R-based algorithm to compare mixtures to original sediments. Roundness distribution appeared to be a useful shape descriptor for distinguishing nourished sediments and their content in mixed samples. This method may be applied for future sediment pathway analyses, e.g., for tracking nourishment materials. [Display omitted] • End-member analysis was applied to shape descriptors distributions. • Roundness is equally useful in end-member modelling as grain-size distributions. • Shape descriptors may be useful in recognition of sediment origin. • Discrimination between nourished sediments and nearby deposits is possible. [ABSTRACT FROM AUTHOR]

RITMARE is the Italian contribution to a sea research program promoted by the European Commission aiming to create an integrated maritime policy. In this context a geodatabase about tsunami events recorded along the Italian coasts, as reported in recent scientific papers, has been realized. Each scientific paper occurring in the geodatabase is linked to its area of interest by means of a Geographical Information System (GIS). The geodatabase is available on the RITMARE website (www.ritmare.it) through a map server. [ABSTRACT FROM AUTHOR]

Ocean satellites provide accurate and precise data across various scales, making them a vital tool for investigating the association between global change and ocean processes. However, low-quality data creates unavoidable gaps in satellite data, diminishing its usefulness and continuity. These deficiencies can be resolved by implementing machine learning techniques as valuable tools. This paper details a new satellite data prediction tool titled "SatelliteFixer". The SatelliteFixer model, utilizing a custom-built random forest structure, can generate dependable data with enhanced temporal-spatial continuity. This model has demonstrated feasibility with diverse satellite data sources and light bands, and outperforms the basic machine learning approach. The juxtaposition of model data with in-situ cruise sampling results allows for widespread analysis of the movement and dispersion of suspended sediment. The above entails the inversion of long-term events and the observation of short-term events, which enables accurate seasonal analysis using continuous data without the influence of uneven data volume distribution and outliers, and is also the first-time satellite data has tracked the entire process of pulsed artificial flooding. SatelliteFixer provides a fresh outlook for detailing the varying trends on consecutive timescales and successional spaces among ocean processes. • A data-driven model for ocean satellite missing data prediction is established based on a specially designed machine learning structure. • The feasibility and availability of model result are demonstrated with MODIS Aqua and GOCI visible light data. • As an example of application, SatelliteFixer data are used with in-situ cruise data to analyze the transportation and distribution of suspended sediment. • SatelliteFixer data enables the accurate seasonal analysis and the first tracking of the entire process on pulsed artificial flooding. [ABSTRACT FROM AUTHOR]

The São Francisco delta in eastern Brazil is considered a classical example of a wave-dominated delta constructed in a glacial isostatic adjustment (GIA) far-field region. Although this delta is widely mentioned in the international literature, few details about its sedimentary architecture have been published. In this paper, we use a new dataset consisting of 15 boreholes and 26 radiocarbon datings to discuss the 3D architecture of the delta and the role played by GIA far-field effects in delta construction. The delta plain consists of a 10–12 m thick littoral sand sheet that progrades over a muddy subaqueous clinoform, forming a compound clinoform. Delta construction began between 8.4 and 7.2 ka BP and included a stage of normal regression that lasted until 5.7 ka BP, followed by a stage of forced regression. The transition between these two stages is marked by the highest position of the sand–mud transition in the boreholes. This forced regression is due to a 3–4-m drop in relative sea level since the mid-Holocene, which is characteristic of GIA far-field regions. Additionally, as a consequence of this drop in relative sea level, there is a progressive increase in the altitude of the beach-ridge deposits continentward, which combined with the development of extensive dune fields in the later stages of delta construction, contributes to the increased resilience of the delta to ongoing sea-level rise. The 3D architecture of the delta was strongly influenced by antecedent topography. The delta was built on a bathymetric depression on the shelf that almost entirely traps the sediment load of the São Francisco River. The uneven relief inside this bathymetric depression ultimately controlled lateral variations in the total thickness of the delta edifice. • Two-stage delta construction in GIA far-field regions: normal and forced regression. • Drop in sea level since mid-Holocene in GIA far-field regions increases delta resilience to ongoing sea-level rise. • Antecedent topography strongly controlled the delta 3D architecture. • 3D architecture of the São Francisco wave-dominated delta is presented for the first time. [ABSTRACT FROM AUTHOR]

The Tianxiu vent field (TVF) is the first active ultramafic-associated hydrothermal field to be discovered at the termination of a detachment fault on the slow-spreading Carlsberg Ridge. Most hydrothermal chimneys in the TVF are developed on the basaltic apron. This paper presents mineralogical, petrological, and geochemical data for altered basalts in and surrounding the TVF. The basalt samples can be classified into seafloor-weathered and hydrothermally altered (i.e., slightly saponite-altered, highly saponite-altered, and silicified) types. At the periphery of the TVF, the basalts have experienced seafloor weathering, which has resulted in slight mineralogical and geochemical changes. In the TVF, most basalts have interacted with diffuse low-temperature hydrothermal fluids, leading to variable degrees of saponite alteration. As the distance from the vents decreases, basaltic glass, olivine, and pyroxene are progressively replaced by saponite; Zn, Cu, Co, and U are enriched; and Ca and Mn are depleted. Magnesium, Fe, and Li have been lost due to olivine replacement by saponite, and have been gained due to pyroxene replacement by saponite. In the fluid flow conduits, the basalts have interacted with focused medium- to high-temperature fluids, which has led to the replacement of saponite by opal; depletion in Mg, Fe, Li, and rare earth elements; and enrichment in Zn, Cu, Co, and U. We propose a new hydrothermal alteration model for basalts in an ultramafic-associated vent field. Based on a comparison with mafic-hosted vent fields along mid-ocean ridges, we propose that: (1) the permeable host rocks promote lateral fluid flow, widespread mixing with cold seawater, and pervasive low-temperature hydrothermal alteration; and (2) H 2 S-poor reducing fluids reduce the solubility of U and inhibit the precipitation of Fe, leading to high Cu/Fe and Zn/Fe ratios, and high U concentrations. The hydrothermal alteration model for the TVF is applicable to similar vent fields and can guide exploration for seafloor massive sulfide deposits along slow-spreading ridges. Schematic diagram depicting the hydrothermal circulation and alteration in the Tianxiu vent field. The location of profile B-B′ (azimuth: ∼160°) is shown in Fig. 1b. The basalts in the shallow part of the TVF are generally affected by low-temperature diffuse flow, leading to saponite-alteration. The basalts within the fluid channels are affected by high-temperature fluids, leading to silicification. As alteration intensity increase, Zn, Cu, Co and U continue to be enriched in the basalts, while Ca and Mn continue to be depleted. 49 V-MDD08 and 49 V-MDD09 indicate the locations of the boreholes. E1 and A2 indicate the locations of the inactive and active smoker clusters. [Display omitted] • Hydrothermal altered basalts were drilled from an ultramafic-associated vent field on termination of a detachment fault. • Permeable strata lead to a large hydrothermal alteration zone with variety of saponite-alteration and silicification. • As alteration intensity increase, Zn, Cu, Co and U continue to be enriched, while Ca and Mn continue to be depleted. • A new hydrothermal alteration model of basalt in ultramafic-associated vent field was proposed. [ABSTRACT FROM AUTHOR]

Geological evidence of megathrust earthquakes along the Mexican Pacific coast relies predominantly on tsunami deposits. Records of coseismic relative sea-level changes are scarce even though such evidence can complement and constrain tsunami records, providing information to reconstruct past earthquake rupture dimensions to improve the earthquake hazard assessment of the region. This paper provides the first diatom-based quantitative reconstruction of coastal subsidence along the Mexican subduction zone through the analysis of coastal wetland sediments. We use the stratigraphic signature of the 1995 Colima-Jalisco earthquake (M w 8.0) as this earthquake is instrumentally well-constrained, allowing us to evaluate our findings and establish approaches to investigate earlier earthquakes. Deposits beneath the wetland Estero Potrero Grande reveal a stratigraphic sequence, < 28 cm beneath the wetland surface, that resembles a signature of rapid submergence. This sequence consists of a horizontal bed of silt with highly humified organic matter abruptly overlain by a horizontal bed of grey silt. The abrupt stratigraphic contact between the two units extends across >1 km of the wetland. Using 14C ages and 137Cs chronohorizons to build an age-depth model, we estimate the age range (1985–2003 CE) and mean age (1995 CE) of this abrupt stratigraphic contact, coincident with the year of the earthquake. Three elemental log-ratios (S/Zn, Br/Zn and Ca/Zn) indicate an abrupt increase of salinity across the stratigraphic contact, which we interpret as marsh submergence recording coseismic coastal subsidence, reflected as relative sea-level rise. Fossil diatom assemblages confirm this trend, and through quantitative approaches we estimate its magnitude (−0.06 ± 0.08 m and − 0.11 ± 0.23 m), which is comparable with coastal subsidence measured by geodetic instruments. Our records reveal a millimetric spike of sand, which we interpret as a signature of the tsunami that accompanied this great earthquake. These findings demonstrate that coastal wetland sediments from the Mexican Pacific coast can record tectonic induced relative sea-level changes. This approach can allow us to better understand the long-term spatial and temporal behavior of this subduction zone. • Deposits beneath the costal wetland Estero Potrero Grande record coastal subsidence produced by the 1995 Colima-Jalisco earthquake (M w 8.0). • The lithological expression of this event, an organic silt- silt couplet, was mapped for over 1 km across the wetland. • Elemental log-ratios and diatom assemblages are the proxies that reveal the abrupt increase of salinity conditions above the stratigraphic contact. • Through a diatom-based quantitative approach we estimate the magnitude of coastal subsidence and relative sea level changes before, during and after this earthquake. • Sediment gran size analyses reveal the occurrence of a high-energy event, interpreted as the signature of the tsunami produced by this earthquake. [ABSTRACT FROM AUTHOR]

The approach and results of our 2019 paper (Brooke et al., 2019) have been criticised by Dougherty (2022). We examined the sensitivity of a tropical, coarse sand strandplain to changes in relative sea level as expressed through beach-ridge morphology and the elevation of beach berms preserved in the succession of cyclone-generated beach ridges at Cowley Beach, Queensland, Australia. Rather than presenting a new sea-level curve for this region as suggested by Dougherty, our 2019 study of the Cowley Beach strandplain revealed that when compared with the modelled Holocene relative sea-level record and sea-level indicator data for north-eastern Queensland, the strandplain morphology and stratigraphy provide a first-order representation of sea-level position. Importantly, Dougherty (2022) has overlooked the processes involved in the formation of beach ridges at this site and the spatial coverage of our analysis of the strandplain morphology. Both these factors are fundamental to the approach and conclusions of our 2019 paper. We reiterate here that the Cowley Beach strandplain morphology and succession of beach-berm deposits have elevation patterns that match well the broad trend in the regional relative sea-level model for the past 7 ka. We highlight those key beach-ridge formative processes and data limitations neglected in the Dougherty Comment. Finally, we note the challenges and opportunities for further research into the sedimentary records preserved in this distinctive type of tropical strandplain. • First-order changes of sea level can be detected in the Cowley Beach strandplain. • The coarse sandy ridges comprise a berm capped by cyclone-generated surge deposits. • Processes forming these ridges are in marked contrast to temperate strandplains. • There is negligible aeolian deposition contributing to these low-relief ridges. • Uncertainties in ridge elevation, age and GPR data limit sea-level reconstruction. [ABSTRACT FROM AUTHOR]

This paper integrates sedimentary, tectonic and volcanic geological processes inside a model of volcano-tectonic activity in oceanic intraplate domains related to rifted continental margins. The study case, the eastern Canary Basin (NE Atlantic), is one of the few places in the world where giant MDTs and Quaternary volcanic and hydrothermal edifices take place in intraplate domains. In this paper, we analyse how two structural systems (WNW-ESE and NNE-SSW) matching with the oceanic fabric control the location of volcanic systems, seafloor tectonic reliefs and subsequently the distribution of main sedimentary systems. Linear turbidite channels, debris flow lobes and the lateral continuity of structural and volcanic reliefs follow a WNW-ESE trend matching the tracks of the oceanic fracture zones. Furthermore, escarpments, anticline axes and volcanic ridges follow a NNE-SSW trend matching normal faults delimiting blocks of oceanic basement. The morpho-structural analysis of all the above geomorphological features shows evidence of a volcanic and tectonic activity from the middle–upper Miocene to the Lower–Middle Pleistocene spread over the whole of the eastern Canary Basin that reached the western Canary Islands. This reactivation changes the paradigm in the seamount province of Canary Islands reported inactive since Cretaceous. A tecto-sedimentary model is proposed for this period of time that can be applied in other intraplate domains of the world. A tectonic uplift in the study area with a thermal anomaly triggered volcanic and hydrothermal activity and the subsequent flank collapse and emplacement of mass transport deposits on the Western Canary Slope. Furthermore, this uplift reactivated the normal basement faults, both trending WNW-ESE and NNE-SSW, generating folds and faults that control the location of turbidite channels, escarpments, mass transport deposits and volcanic edifices. • Tecto-sedimentary model for intraplate oceanic settings: eastern Canary Basin. • Quaternary tectonics controls the sedimentary dynamic in the eastern Canary Basin. • Volcanic and tectonic reactivation since the Miocene until Quaternary. • Turbidite channels, MTD and volcanic cones are controlled by oceanic fracture zones. • Structural reliefs are controlled by deep faults delimiting oceanic basement blocks. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel method to reconstruct sea-level change in coastal freshwater back-barrier marshes. Freshwater environments have long been considered to be unsuitable for the reconstruction of Holocene sea-level changes as they provide limiting, rather than precise, sea-level index points. We recorded the stratigraphy of a small beach and back-barrier coastal Phragmites (reed) marsh at Hallsands, south Devon, southwest England, using hand-drilled cores and ground-penetrating radar, and collected five new sea-level index points from the base of a Holocene peat sequence to refine the regional Holocene relative sea-level curve. We demonstrate that the samples, despite their freshwater origin, yield accurate sea-level index points as determined from the quantifiable relationship between tide levels and groundwater. By means of water-table monitoring and groundwater modelling we show that the primary controls on the water table in the marsh are: (1) stratigraphy; (2) peat permeability; and (3) recharge rates in the back-barrier marsh. The five index points document relative sea-level positions between 7200 and 2400calyr BP. Three points are in good agreement with previously collected regional data from intertidal deposits and two points usefully fill gaps in the existing reconstruction. An amended Holocene relative sea-level curve for south Devon, based on 30 data points, is presented. We conclude that the combined approach of data collection and modelling used in this paper can be applied to similar coastal settings around the world and allows the collection of sea-level index points from locations not previously thought suitable for this purpose. [Copyright &y& Elsevier]

Abstract: Deep-water potential estuarine and marine benthic habitat types were defined from a variety of new and interpreted data sets in central San Francisco Bay and offshore Golden Gate area including multibeam echosounder (MBES), side-scan sonar and bottom grab samples. Potential estuarine benthic habitats identified for the first time range from hard bedrock outcrops on island and mainland flanks and some Bay floor regions, to soft, very dynamic bedforms consisting of sediment waves and ripples. Soft sediment ranges from mud and sand to bimodal (two or more grain sizes) sediment of gravel, pebbles, and cobbles. In addition, considerable anthropogenic features (i.e., pipelines, bridge abutments, dredged channels, dump sites) were distinguished. Of the 52 potential benthic habitat types mapped (compressed to 14 types for this paper), 24 were of unconsolidated sediment with five of these comprised of dynamic bedforms or sediment waves and dunes, five of mixed (soft over hard) substrate type, six of hard substrate or rock outcrop, 13 of anthropogenically disturbed areas and four hard anthropogenic features. Rock outcrops and rubble are considered the primary habitat type for rockfish (Sebastes spp.), lingcod (Ophiodon elongatus) and in shallow water for herring (Clupea pallasii) spawning. Dynamic bedforms such as sand waves are considered potential foraging habitat for juvenile lingcod, may be sub-tidal habitat for the Pacific sand lance (Ammodytes hexapterus) forage fish, and possibly resting habitat for migratory fishes such as sturgeon (Acipenser medirostris). The potential marine benthic habitats identified in San Francisco Bay are not unlike those found in other estuaries around the world and this study should contribute significant information that will be of interest to scientists, managers and fishers investigating and utilizing bay and estuarine resources. As described in the many papers of this special issue, the understanding of the interrelationship of geology and ecology is critical to the identification of essential habitats and the sustainability of a healthy ecosystem. [Copyright &y& Elsevier]

Abstract: This paper presents a comprehensive study of wave refraction, wave and wind driven sediment transport, foredune development and Holocene barrier evolution over a variety of time scales at Moçambique Beach, Santa Catarina State, Southern Brazil. The motivation for this study was to examine the relationships between estimated wave driven sediment transport, medium and long term aeolian transport, foredune development, and Holocene barrier volumes and morphology. An analysis of 2years of wave rider data for the region shows two well defined peaks of frequencies: one of swell waves from the south with a period of 12s, and another peak of sea waves from east-northeast with a period of 7s. Longshore sediment transport rates were calculated using high resolution hindcast wave data for the South Atlantic Ocean, which was calibrated by the measured buoy data. The dominant southerly waves drive a longshore gradient in wave energy from south to north, and nearshore/surf zone sediment transport increases from south to north. Beach grain size is fine in both the south and north, and medium in the center. The combination of grain size and wave energy variations creates a marked alongshore variation in surf zone beach types ranging from low energy dissipative in the south, moderate energy intermediate in the central area to moderate to high energy dissipative in the north. Estimates of aeolian sediment transport, volumetric changes in foredune deposition and total Holocene dunefield volumes were also calculated. Results indicate that the morphological behavior of the foredune profiles reflects the gradients of longshore sediment transport and the exposure to wind energy and aeolian sediment delivery, with a maximum of sediment volume and transport towards, and in the central part and northern end of the barrier. Holocene (0–7000years) barrier volumes vary along the embayment, mimicking the trends in both calculated wave and wind driven sediment transport. The Short and Hesp (1982) model was more suitable in predicting the long term (Holocene) barrier evolution than the size and volume of the foredune. The combination of wide beach, high energy dissipation, maximum sediment supply, and high exposure to strong onshore winds is found in the northern end of the embayment where Holocene subaerial barrier volumes are at a maximum. Overall, this study proves that foredune development is closely related to wind exposure, wave energy and gradients of longshore sediment transport, and that dunefield development reflects the increase downdrift in potential sediment supply from the southern to the northern end of the beach, and the change alongshore from low energy dissipative, through intermediate, to high energy dissipative beach-surf zone environments. This paper significantly extends previous models of beach and dune interactions in that it (i) actually determines wave driven sediment transport for various sections of a long embayment, (ii) relates those transport patterns to surf zone/beach morphodynamic types and variations in alongshore sediment patterns, and (iii) correlates foredune volumes and Holocene barrier volumes (which reflect proxy Holocene onshore transport rates) with wave driven sediment transport rates. [Copyright &y& Elsevier]

Abstract: In the present paper, we report a new powerful technique of studying bar morphology using multi-sensor and multi-temporal satellite images with examples from the inaccessible field sites of the Han Estuary in Korea. The technique utilizes the ability of multi-spectral optical sensors for classifying the types of land cover, and the ability of synthetic aperture radar (SAR) for acquiring radar imagery during day and night, irrespective of cloud cover. Combining the data acquired by both types of sensors at different times, the bar morphology of the Han Estuary is analyzed in this study. The Han Estuary is situated on the North Limit Line (NNL) dividing North and South Korea, and considered to have retained its rich ecological value. However, because of the limited access to the estuary, little information is available on the morphology of the Han Estuary, and the technique based on satellite remote sensing described in this paper is the most suitable and only approach to obtaining information on such inaccessible areas. In the present paper, the bar morphology of the Han Estuary from the years 2000 to 2009 is investigated using multi-temporal spaceborne optical sensors including those on board of SPOT-5, LANDSAT-7, QuickBird, KOMPSAT-2, and OrbView-3, and also C-band synthetic aperture radar (SAR) on board of RADARSAT-1 and ENVISAT with limited field survey data. Sixteen sets of optical data and twelve sets of SAR data were used to study the spatial and temporal variations of bar morphology and the effects of tide and precipitation. The results show that there was some variation in shape and size of bars depending on the location. The tidal effect is large on the bars closer to the open Yellow Sea, and the effect of precipitation was observed on the bars located in the mouths of rivers. Based on the changes of the bar–water boundary, a topographical map was produced, showing the relative height of bars. Using the technique of satellite remote sensing, this paper has shown, for the first time, the long-term bar morphological characteristics of the restricted Han Estuary on the NLL, and the authors anticipate that the results together with the relative height map of bars will constitute the basis of future morphological and ecological studies in this important estuary. [Copyright &y& Elsevier]

Submarine fans are the largest sediment accumulations on Earth and are key to study the sediment-transfer zone between terrestrial source area and deep-sea depositional sink. They provide information of past climate, tectonics, carbon global inventory, and can be prolific hosts for oil/gas resources. In this paper, we present, for the first time, an analysis of the entire Magdalena Submarine Fan (MSF), from the shelf break to the distal domain, based on ~224,000 km2 of multibeam bathymetry, as well as backscatter, subbottom profiler and regional/local seismic reflection data recently acquired in southwestern Caribbean Sea. The aim is to describe in detail the MSF morphology and depositional architecture, propose a fan segmentation landform assemblage, and determine its extent within the deep basin. Three fan segments are identified: upper, middle and lower fans. The upper fan extends from the coastline to a depth of ~3000 m. Its eastern sector is characterized by a canyon system off the present-day mouth of the Magdalena River, through which most of the sediments are transported downslope to be deposited in intra-slope basins bounded by structural highs of the South Caribbean Deformed Belt. The western upper fan is characterized by distinct channel-levee complexes that are partially removed by mass transport complexes that originated near the continental shelf edge. The upper to middle fan transition is marked by a decrease in regional gradient from 1° to about 0.3° and local relief, a change from large, irregular sediment waves to more regular waves that slowly decrease in amplitude downslope, and the appearance of erosional megascours. The middle fan bedform assemblage evidences the presence of a channel-lobe transition zone in this sector of the MSF, separating well-defined, upper fan channels from lower fan depositional lobes. The middle to lower fan transition occurs between ~3800 and ~3950 m and is defined by a further decrease in gradient and by a change from sediment waves to planar parallel-bedded reflectors on subbottom profiles. The lower fan extends to a maximum depth of ~4250 m and is characterized by an almost flat seabed (slope of 0.05°), interrupted by a few isolated bathymetric highs and low-relief channels (<5 m deep). The entire area of the lower fan is interpreted as an area of turbidity current deposition, with relatively sandy sediments in the south and west giving way to muddier sediments in the northeast, which could correspond to distal fan lobes. The identification of four regional seismic facies related to MSF sedimentation allowed us to constrain the fan extent in the southwestern sector of the Caribbean. Distally, within the Colombia Basin the fan terminates against areas of elevated seafloor (Kogi-Coyaima and Quimbaya seamounts, Aruzi and Ticuna hills, and Beata Ridge), which have acted as barriers to sedimentation. Nevertheless, it was determined that the MSF extends beyond the Colombia Basin and locally reaches the Lower Nicaraguan Rise. In this new scenario, we established that the MSF is much more extensive than previously recognized, with an area of ~237,000 km2, which puts it among the World's largest submarine fans. • The morpho-structure of the entire Magdalena Submarine Fan (MSF) is presented • Upper, middle and lower fan segments are proposed from diverse landform assemblages • Channel-levee complexes partially removed by extensive MTCs defines the upper fan • Middle fan, with sediment waves and megascours, is defined as sediment bypass area • Evidence of turbidity current sedimentation, with probable lobes, in the lower fan [ABSTRACT FROM AUTHOR]

Sandy beaches are highly dynamic due to the transport of sediment by waves and currents. While beach erosion is mainly driven by cross-shore currents, beach recovery is driven by the onshore-directed transport of sediment by incoming short waves. This latter process is complex and often inaccurately predicted by morphodynamic models. This is partly because of the omission of the effects of bed form-induced and surface-generated turbulence on sediment pick-up in these models. In this paper, the phase relationship between the oscillatory flow, turbulence and suspended sediment concentration was investigated based on field measurements obtained beneath shoaling waves, spilling breakers and surf bores. Wave-averaged and intra-wave variability in turbulence and suspended sediment concentration were analysed on a wave-by-wave basis, where individual waves were extracted and then grouped according to relative wave height. Beneath shoaling waves, small but steep wave ripples were shown to affect the phasing of suspended sediment concentration and to cause an offshore-directed short-wave suspended sediment flux. Beneath spilling breakers and surf bores, sediment was mainly stirred under the wave crest and the short-wave suspended sediment flux was onshore-directed. Based on the analysed data, several mechanisms were suggested to cause sediment stirring: friction between the wave orbital motion and the seabed, penetration of surface-generated turbulence towards the seabed, increased bed shear stress at the wave front due to acceleration skewness, and during conditions with strong undertow, wave-current interactions. [ABSTRACT FROM AUTHOR]

The Fairway Basin is an intracratonic deep-water basin inherited from cretaceous rifting, perched between the Lord Howe Rise and the New Caledonia Basin in the Southwest Pacific. Its originality lies in its atypical present-day physiography and its carbonate-dominated sedimentary setting since the Miocene. Although very limited well controls are available, its overall structure, seismic stratigraphy and architecture are relatively well known. However, little is known on the detailed sedimentary processes controlling its recent infill. Its remote location from any major clastic sediment sources provides a great setting to study deep-water carbonate sedimentary processes. In this paper, we propose a detailed analysis of surface morphologies based on existing multibeam and subbottom echosounding data together with an analysis of the Neogene to Quaternary basin-fill based on seismic reflection data. This allows us to discuss active sedimentary processes, notably gravity flow processes which are thought to be active since the Middle Miocene. These processes are evidenced by both surface and subsurface features, such as submarine canyons, channels and lobes, composite scarps and mass transport deposits (MTDs). In the northern part of the basin, a 400 km-long axial turbidite system is developed close to the Lansdowne Bank, a partly drowned isolated carbonate platform, where present-day sediment remobilisation seems to be essentially sourced from intra-slope instabilities. These reworked sediments extend over an area of 16,000 km2. Along with this axial turbidite system, seismic data show two main mass transport complexes (covering an area of ca 20% of the basin's surface) originating from the slopes of the basin. The potential triggering mechanisms of MTDs of the northern complex might be directly attributed to overloading and high slope values of the Lansdowne Bank area (>1.5°). For the southern complex, surface slope values are lower (<1.4°), and the role of fluid migration and escape is discussed. The Fairway Basin indeed shows strong evidences for fluid generation (e.g. polygonal faulting, pockmarks, presence of a widespread Opal-A/Opal-CT diagenesis-related bottom simulating reflectors) and fluid overpressures. • A basin isolated from terrestrial sediment sources during Neogene • Mainly neogene sedimentary processes occurred in unconsolidated unit (Ooze). • Gravity process (turbidites, MTDs) are the dominant sedimentary process. • Slope values, fluids and lithological/diagenetic boundaries could control MTD dynamics. • Distribution of main sedimentary process is constrained by a structural inheritance. [ABSTRACT FROM AUTHOR]

In their paper, Bellwald et al. (2019) present a frequency curve of mass movements from a total of 22 fjords and 6 lakes in west and mid-Norway. However, the time-series analysis that is used to create this frequency curve is somewhat flawed, as mass-transport deposits (MTDs) receive a weight that is positively correlated to their age uncertainty, instead of an equal weight. Here, I propose an alternative frequency curve in which the weight of each MTD is equal, independent of its age uncertainty. I conclude that this error in the frequency curve does not significantly impact the interpretations made by the authors, but that similar errors may lead to wrong interpretations when such a frequency curve would be used in a quantitative manner. [ABSTRACT FROM AUTHOR]

Abstract This paper documents the analysis of a coastal boulder deposit that was recently identified along the northern Adriatic coast (Premantura Promontory, Istria, Croatia). Accumulations of large boulders have not previously been reported in the northern Adriatic, which can be viewed as a semi-enclosed basin. A multidisciplinary approach was used to investigate the site including geological and geomorphological surveys, together with the use of an Unmanned Aerial Vehicle (UAV), digital photogrammetric analysis, hydrodynamic modelling and 14C AMS datings. Measurements of boulder position, elevation, size, shape and density were fed into hydrodynamic equations that are used to estimate the minimum storm and tsunami wave height required to enable the accumulation of boulders. Biogenic marine carbonate encrustations observed on 14 boulders suggest the infra- and sublittoral zones as source areas, while for most of the boulders a subaerial origin is hypothesised. The boulder deposit occurs on a flat promontory where the topography, together with the stratified limestone bedding planes and dense joint pattern constitute the predisposing factors for boulder size and detachment. Comparisons between satellite images taken between 2008 and 2017, pictures collected from Internet and a 2012 snorkel survey of the Istrian coast made it possible to highlight the emplacement of a boulder with an estimated weight of 7.65 t during late 2013 or early 2014. The study examines the mechanisms that may be responsible for the detachment and transport of these large limestone rock fragments from the emergent part of the coast and from the sea bed towards inland areas. The results suggest the occurrence of very recent extreme weather conditions as well as multiple historical storm events and exclude a tsunami origin of the boulders. Highlights • A multidisciplinary study of a coastal boulders deposit in the northern Adriatic Sea is presented • Geomorphological surveys, hydrodynamic modelling, Radiocarbon datings and climatic analysis were performed • The emplacement of a 7tons boulder during a strong sirocco storm occurred in 2014 was reconstructed • Multiple historical and recent storm events are hypothesised as origin of the studied boulders [ABSTRACT FROM AUTHOR]

Abstract An integrated analysis of multibeam bathymetry and single- and multichannel seismic records were used to image the morpho-stratigraphy of the Alentejo Margin (Southwest Portuguese Continental Margin). The complex interaction of several alongslope and downslope processes in the area leads to the formation of various bottom current driven depositional and erosive features (moat) as well as gravity-driven features (gullies and landslides) in the Alentejo Margin. These processes feed each other contributing for the active sedimentary pattern on the area. Sines Contourite Drift (SCD) is a ~2311 km2 sedimentary feature with a perimeter of 303.9 km, 98 km length and 35 km width. Landslides occur either on steep and on gentle slopes between ~200 and 3200 mwd (meters water depth) in the study area, which has a total extent of ~85 km × 82 km. Scar concentration is higher in the middle- and lower-slope, whereas the thickest debris deposits are found in the slope basin area - Lebre Basin (LB). Translational landslides, with planar failure planes parallel to the slope surface are the main landslide typology verified in the study area. Several triggering and pre-conditioning factors, resulting from the interaction of alongslope and downslope processes, contribute for varied landslides scar concentration. Steep-slope and high sedimentation rates favour sediments under-consolidation, promoting excess pore water pressure and weak layers formation. In this paper, we show that the interaction of bottom currents with pre-existing tectonic structures promotes the complex interaction of both alongslope and downslope processes thus promoting an active and diversified geomorphological evolution and generalised slope instability. Highlights • Complex morphology from interaction of along- and downslope sedimentary processes • Sines contourite drift results from interplay of MOW and pre-existing structure • High contouritic deposition over irregular structure creates cluster of landslides. • Interplay of MOW, tectonic uplift and seismicity creates multi scale landslides. • Wide slide scars on gentle slopes and contiguous, narrow scars on steep slopes [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the response of a mixed sand and gravel (MSG) barrier coastline to storms and sudden relative sea-level change using the numerical model XBeach-G. The barrier beaches of southern Hawke's Bay, New Zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 Hawke's Bay earthquake. Historic (1931) and contemporary (2017) morphodynamics of one tectonically uplifted (+1.5 m) and one subsided (−0.78 m) barrier were modelled under energetic waves (H s 1–6 m). XBeach-G was designed to simulate pure gravel beach morphodynamics, but despite this, the model demonstrated high quantitative skill when calibrated for the MSG coast. Results reveal the storm impact regimes of each profile and potential linkages to decadal-scale barrier development observed in historical beach profile data. Storm-swash processes at the uplifted profile indicate long-term barrier stability due to a lack of change at the barrier crest, and ridge building observed in model simulations provides a potential formative mechanism for decadal-scale beach progradation. At the subsided barrier, modelled historic crest build-up (up to 0.3 m) and narrowing (over 5 m) indicate an overtopping mode of response to sudden relative sea-level rise. Simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time. Simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions, but further work is needed to distinguish the relative importance of historical sudden sea-level rise versus deficits in sediment supply to this shoreline. Highlights • XBeach-G used to simulate storm, sea-level response of mixed sand/gravel barriers • Results analysed from sites exposed to earthquake-driven relative sea-level change • Chronic barrier narrowing potentially linked to sudden relative sea-level rise • Barrier with subsidence history may now be exposed to catastrophic breakdown. [ABSTRACT FROM AUTHOR]

Abstract Dense shelf waters have been recognised as a key factor in transporting sediment and organic matter across continental slopes; however, the effect of their circulation on continental shelves is still overlooked. The Adriatic Sea is one of the areas in the Mediterranean where dense shelf water forms and flows as a bottom-hugging gravity current along the continental margin. A fraction of this dense water passes beyond the shelf break and flows downslope through cascading, while a large (lighter and faster) portion remains on the shelf, with a principal vein flowing between 80 and 120 m water depth. This paper presents the 3D shape, internal architecture and sediment facies of a variety of large-scale sedimentary features detected on the continental shelf and at the shelf edge, between 50 and 300 m water depth. These features include giant comet marks, large flute-shaped scours, muddy sediment waves, very large dunes with superimposed bedforms, active and relict sand ridges and shelf edge contourites. Both erosional and depositional features show an overall internal geometry and orientation consistent with water masses flowing southward, and are located where flows become accelerated by topographic constraints and deviated by the curvature of the shelf edge. In this study, the morphology and seismic stratigraphic structure of large-scale bedforms are investigated in an effort to place constraints on bedform evolution and preservation, especially as predictive tools for sand resource management, and to bring new evidence of the interaction between unidirectional hydrodynamic processes and seafloor dynamics on the shelf. Highlights • An extensive geophysical and coring survey revealed large-scale bedforms on the southern microtidal Adriatic shelf. • Bedforms formed in marine conditions, their age of deposition was inferred through radiocarbon dating and seismostratigraphy. • Sedimentary features, erosional and depositional, have orientations compatible with unidirectional flows. • Bottom currents, including shelf dense waters, are accelerated by bathymetric highs and shelf edge curvature. • Bedforms are palimpsest or relict depending on their location in respect to the unidirectional flow. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the complex interplay between allocyclic, autocyclic and antecedent controls on the development of the proximal portions of a wave-dominated, gravel-rich submerged delta. The inner shelf of the Orange River delta of southern Namibia is investigated using seismic stratigraphic methods and vibracore data, in conjunction with onshore electromagnetic data. The aim is to define and interpret the major seismic stratigraphic units and to examine the controls on the stratigraphic evolution of the area. The stratigraphy comprises a crystalline bedrock and sedimentary rock basement, the contact of which exhibits a break-in-slope in the palaeo-bathymetry surface. The basement is truncated by a subaerial unconformity which includes two palaeo channels incised into a bedrock palaeo-promontory offshore of the modern Orange River Mouth. The incision of these channels is attributed to episodic periods of river rejuvenation linked to tectono-eustatic events of the late Cretaceous and end Neogene, during which sea level dropped below the shelf break. The ensuing smaller glacio-eustatic sea-level oscillations of the Quaternary led to the formation of bypass valleys which did not incise the existing channels and allowed remnants of original (old), course channel fill to remain in the lower sequences of the valley fill. North and offshore of the bedrock palaeo-promontory, the basement is overlain by a widespread, thick (up to 3 m) gravel lag associated with repeated ravinement events that represent multiple cycles of subaerial and wave ravinement erosion including those of the last post-glacial transgression. This gravel lag represents the proximal portion of the world's largest diamond placer deposit. Gravel spit, barrier and linear beach facies occur between −70 and −55 msl and are interpreted to have developed under high rates of coarse sediment supply during a stillstand preceding MWP-1B. A constructional phase of delta progradation followed, interposed with backstepping which we consider representative of the final shoreline trajectory from MWP-1B through 1D. The overlying thick (up to at least ~70 m), fine-sandy to muddy clinoform unit is the proximal portion of the modern delta of the Orange River which has prograded during the Holocene and episodically accumulates fine sediments during flood events in modern times. Gravel deposits are winnowed by cyclical erosion processes in combination with the oceanographic regime to strongly partition the grain sizes of the shelf stratigraphy. Gravel deposits (e.g. lags and barrier beaches etc.) are preserved by inheritance of the sediment stock and by later sheltering from wave energy due to antecedent topography. Where gravel beaches and deltas formed, their preservation in the stratigraphy is enhanced due to existing low-gradient palaeo-slope and punctuated rises in sea level which overstepped the shelf geomorphology. Highlights • Examine controls on nearshore stratigraphy of Orange River's wave-dominated delta • Stratigraphy fractionated into gravel and mud • Related to sediment supply, multiple erosion cycles and energetic wave regime • Show evidence for meltwater pulses and wave sheltering from antecedent topography [ABSTRACT FROM AUTHOR]