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To investigate the evolution of sediment provenances and transport processes in the central Bay of Bengal (BoB) since the Last Glacial Maximum, we present a comprehensive study on the grain size, clay minerals, rare earth elements, and accelerator mass spectrometry (AMS)14C analyses of the core BoB-24 sediments. Six AMS14C dates were obtained from planktonic foraminiferal Neogloboquedrina dutertrei (N. dutertrei) extracted from the core to reconstruct a reliable age model. The assemblage of clay minerals and the (La/Yb)UCC–δEu relationship indicated that the core contained a mixture of sediments from the Himalayas and Indian Peninsula. These results showed that the Himalayas were the main source of erosional materials during 25–6.5 ka BP, whereas those from the Indian Peninsula increased since the mid-Holocene. Between 25 ka BP and 12 ka BP, the sea level was relatively low, and a large amount of terrigenous detrital material were directly transported from the Himalayas and the Tibet Plateau to the study area by submarine canyons, forming a deposition center on the Bengal Fan. Between 12 ka BP and 6.5 ka BP, the sea level gradually rose and the Indian summer monsoon gradually strengthened, whereas the sedimentation rate and the amount of material transported from the Ganges–Brahmaputra River decreased greatly; the deposition center transferred from the Bengal Fan to the shelf of the BoB. Since 6.5 ka BP, the sea level has risen, reaching its present position. A high sea level and a strengthened East Indian Coastal Current resulted in an increase of material contribution from India, while the deposition center was on the shelf of the BoB. Overall, this study confirmed that both sea level fluctuations and variations of the Indian summer monsoon controlled the evolution of sediment provenances in the central BoB and transfer of the deposition center from the Bengal Fan to the continental shelf. This typical sedimentary pattern observed in the northeastern Indian Ocean improves our general understanding of past land–sea interactions.

The interaction between the Earth's surface and deep geodynamic processes has a great influence on sedimentary patterns and characteristics of sedimentary systems, especially in the continental margin, such as the southern part of the East China Sea Continental Shelf Basin (ECSCSB). However, the exact processes and dynamics are poorly understood. The numerical tool (Badlands) was adopted to simulate the geological evolution of the southern ECSCSB during the Mesozoic transitional regime of the West Pacific continental margin, between 200 and 100 Ma. The numerical model involving four-dimensional (4D) sequence stratigraphy was validated by comparing with the tectono-morphology, sedimentary environments and sediment distribution. According to our findings, the transition was mainly controlled by three structural stages. The first transitional stage of the southern ECSCSB was mainly controlled by lithospheric-scale tectonic evolution. In the second stage, the dynamic topography contributed to slow regional uplift, while the last stage showed mantle-induced dynamic subsidence. The model results on 4D geomorphic characteristics, sediment distribution of basin evolution and deep dynamic topography, provided a quantitative image for geological evolution of the West Pacific continental margin in the Mesozoic.

The Aurora Subglacial Basin (ASB) catchment contains 3-5 m of sea-level equivalent ice volume that drains to the Sabrina Coast, East Antarctica via the Totten Glacier system. Observed thinning and retreat of Totten Glacier indicate regional sensitivity to oceanographic and atmospheric warming. Paleoclimate studies of climatically sensitive catchments are required to understand the evolution of the East Antarctic Ice Sheet (EAIS) and its outlet glacier systems. Recent seismic and sediment studies from the Sabrina Coast document the evolution of the EAIS in the ASB catchment, suggesting that the region has long been sensitive to climatic changes. This study presents new palynological and biomarker data from Sabrina Coast continental shelf sediments. Detailed palynological records were obtained from four short jumbo piston cores (JPC; NBP14-02 JPC-30, -31, -54 and -55), enabling reconstructions of regional vegetation and environments prior to and during Cenozoic EAIS development. The Sabrina Flora is dominated by angiosperms, with Gambierina spp. often exceeding 40% of the assemblage, and diverse Proteaceae, Battenipollis spp., Forcipites spp., Nothofagidites spp., fern, and conifer palynomorphs indicative of an open shrubby ecosystem. Excellent preservation and frequent occurrence of Gambierina spp. clusters suggest that a majority of the Sabrina Flora assemblage is penecontemporaneous with sedimentation; however, some uncertainties remain whether this sedimentation occurred in the Late Cretaceous or the Paleogene. Despite that uncertainty, high abundances of Gambierina spp. and Battenipollis spp., in combination with relatively low (

A number of moderate earthquakes occurred in the South China continental edge or coastal area. Several large earthquakes are sparsely distributed along the seismic belt with the northeast direction between the South China and the continental shelf of the South China Sea. Coulomb stress changes of the 1969 Yangjiang main shock (Ms 6.4) with the following events of the 1986 ML 5.4, the 1987 ML 5.4 and the 2004 ML 5.2 in the Yangbian Bay area are studied. The complex stress patterns of the main shock caused by the dextral Pinggang strike-slip fault imported on the planes of the normal fault, strike-slip fault and thrust fault of three events indicate that the distribution of aftershocks mainly located in the areas of positive stress changes and part of aftershocks fall into the stress shadow area due to the reactivity of the local faults. The 1969 Yangjiang event occurred between the intraplate and the broad plate boundary zone setting when we apply on the empirical relationship between the aftershock durations and the fault-loading rate. The intersection fault model is proposed and could explain the stress changes of the Yangjiang earthquake sequences in South China coastal area. The future hazard assessment requires to take account of the stress increase area along the tip of the main shock source fault and off-fault stress increase area.

To improve the understanding of the relationship between silica source and organic matter accumulation, the origin of silica and its implications for organic matter enrichment in the Upper Ordovician-Lower Silurian (O3w-S1l) black shale in western Hubei Province in the middle Yangtze area, were investigated through geochemical and petrological analyses. The results show that the O3w-S1l black shale is mainly composed of five lithofacies with varying graptolite abundance, total organic carbon (TOC), and silica contents. Biogenic silica and terrigenous siliciclastic input constitute the main silica sources in O3w-S1l black shale and they exhibit an upward inverse variation trend interpreted to be related to sea-level changes. Moreover, with the increase in biogenic silica content or decrease in terrigenous siliciclastic input, TOC values in black shale initially rise and then fall, which is different from originally expected simple linear relationship. We infer that organic matter enrichment and the distribution of silica from different origins are controlled by sea-level changes and variations in terrigenous input in a continental shelf with little hydrothermal influence. An environment with appropriate sea level and terrigenous input should be most favorable for organic matter accumulation, rather than one with excessive high sea level and less terrigenous input.

Site GNL Quintero 1 (GNLQ1), located on the central Chilean coast (32°S), remains the only submerged fini-Pleistocene landscape reported for the southeastern Pacific coast to date. This unique site is characterized by a high frequency and diversity of extinct terrestrial faunal remains supported within a fine-grained sedimentary matrix. Several studies have been performed on the faunal assemblage; however, the sedimentary environment in which the site was formed still remains unclear. In this work, stratigraphic, sedimentological and geochemical analyses conducted on two marine cores are combined with seismic data to determine the depositional conditions affecting the formation of this exceptional shallowly buried submerged landscape. Previous results indicated that site GNLQ1 formed, at least between 28 and 21 ka, in an aquifer-fed freshwater lagoon that developed on a fluvial plain. Here, we show a three-stage sedimentological evolution. In the first stage, a shallow restricted freshwater lagoon formed under relatively arid conditions. Subsequently, the lagoon expanded and deepened under the humid climatic conditions that affected central Chile during the Last Glacial Maximum (LGM). Finally, around 8.5-8 ka, the most recent post-glacial marine transgression (PMT) submerged the site, probably eroding the Late Pleistocene – Early Holocene part of the sequence. Currently, the site lies at ca. 13 m b.s.l. within the shoreface of present-day Quintero Bay, 650 m from the current shoreline. This enhanced understanding of GNLQ1's evolution offers a new perspective on resource availability on the coastal shelf of western South America during the Late Pleistocene, as well as highlighting the unexpected paleontological potential of this area and encouraging future archaeological research of potential prehistoric evidence within these drowned landscapes.

This study aims to identify the influencing factors of the effectiveness in energy investment. For this purpose, 8 different countries with continental shelf in the Eastern Mediterranean region (EMR) are considered. Firstly, 9 different criteria are defined based on the literature review. The significance levels of these factors are determined by considering hesitant interval-valued intuitionistic fuzzy (IVIF) DEMATEL based on 2-tuple linguistic values (2TLV). Therefore, the motivation of this study is to figure out the weights of the criteria for the energy investment projects. Also, the main contributions to the literature are to propose a set of criteria for defining the indicators of the efficiency and to construct a novel decision-making model based on IVIF technique in these projects. The main justifications of this hybrid method can be given as the importance of the distribution, political stability, and technological capacity for the effectiveness in energy investment. Furthermore, hesitant TOPSIS method is used to evaluate these 8 countries regarding the effectiveness in energy investments. It is concluded that Israel and Turkey are the most successful countries in this framework. It is recommended that these countries should have an effective pipeline to transfer the reserves to other countries. Also, these countries in this region should pay attention to political stability. Moreover, countries with energy reserves in the EMR should make the necessary investments to improve their technological infrastructure. Hence, seismic exploration and drilling vessels should be obtained by these countries so that the energy reserves can be located and obtained effectively.

The delivery of potentially reactive iron minerals to the marine environment exerts a major control on ocean and marine sediment biogeochemistry, including the preservation and burial of organic carbon. One aspect of the global iron cycle that has received little attention concerns the phase partitioning of iron in highly chemically-weathered sediments from (sub)tropical mountainous regions, where the sediment is commonly deposited directly onto adjacent continental margins. Here, we report the phase partitioning of particulate iron in surface seafloor sediments deposited from oxic bottom waters along the east coast of China, including the Bohai Sea, Yellow Sea and East China Sea, in addition to the continental shelf region adjacent to the (sub)tropical mountainous island of Hainan in the northern South China Sea. We document highly reactive (FeHR) to total iron (FeT) ratios for the Bohai Sea, Yellow Sea and East China Sea that are typical of global marine sediments deposited under oxic water column conditions. By contrast, FeHR/FeT ratios in Hainan offshore sediments are significantly elevated above normal oxic marine sediments. These Hainan offshore sediments display a strong positive correlation between FeHR/FeT ratios and the chemical index of alteration (CIA) weathering proxy, suggesting that the Fe speciation systematics are controlled by the intensity of chemical weathering. This observation is supported by additional geochemical data and Nd isotope analyses, which suggest a common source lithology for all the studied regions. The Hainan sediments thus document a specific scenario, whereby highly chemically weathered sediments from the mountainous Hainan region bypass the inner shore settings that commonly disproportionately trap Fe (oxyhydr)oxide minerals, depositing high concentrations of FeHR on the adjacent continental margin. Such enrichments likely aid in the preservation of organic carbon in marine sediments, suggesting that organic carbon preservation and burial may be enhanced by elevated FeHR in such settings. We also establish a set of essential criteria for potential recognition of chemical weathering-induced enrichments in FeHR/FeT ratios in ancient marine sediments.

Southwestern Australia has a Mediterranean-type climate, with hot, dry summers and mild, wet winters that support vegetation types ranging from tall closed forest and open woodland, to dense, low heath. At the Last Glacial Maximum, the coast was located as far as 100 km distant of its current location, after which rising post-glacial sea levels radically altered the southwestern coastline, drowning large tracts of the continental shelf, creating islands and rocky cliffs from areas of higher relief, and altering delicately balanced coastal ecosystems. For Aboriginal people living in southwestern Australia these changes would have substantially altered the availability and reliability of important plants and animals, both on the coastal plain and within littoral and estuarine environments, which raises the question of how we define and distinguish the economic strategies employed by people occupying these liminal, transitional landscapes. This paper reviews all available securely dated archaeofaunal records from 31 archaeological sites within the southwestern Australian coastal zone to develop a general economic model of Aboriginal occupation of the region's changing Holocene coastal zones. Faunal records were grouped by bioregion to investigate regional variation in environmental and cultural trends. Archaeological, palaeontological, and palaeoclimatic evidence indicates that people adapted as the coastal plain transformed during the Holocene, altering subsistence strategies and land management practices.

Clay minerals preserved in marine sediments carry important information about sediment transport processes from sources to sinks. To reveal the dynamic transport processes of clay minerals and related controlling factors in the southern South China Sea, spatiotemporal variations of clay mineral assemblages from previous studies (Cores MD05-2893, CG2, SO18287-3, MD01-2393, SO18383-3, and MD97-2150) are integrated to assess their controlling factors over the past 30 ka. Based on the smectite/(illite + chlorite) ratio in six cores, we found that the clay mineral variations on the continental slope off Sunda Shelf (Cores MD05-2893, CG2, and SO18287-3) have been controlled by the sea-level changes during the last glacial sea-level lowstand and by the East Asian monsoon during the Holocene sea-level highstand periods. Meanwhile, the clay mineral variations on the continental slope off the Mekong River (Cores MD01-2393, SO18383-3, and MD97-2150) have been driven by the chemical weathering in the Mekong River basin that associates with the East Asian summer monsoon evolution. Accordingly, we conclude that the glacial-interglacial variation of clay minerals in an integrated picture of the southern South China Sea region since the Last Glacial Maximum has been mainly controlled by sea-level change and East Asian monsoon evolution. However, these controlling factors play independent roles in different parts of the southern South China Sea, which appears more heterogeneous than generally expected.

Most previous Black Sea palynology studies have used pollen-spore assemblages as proxies for climate and landscape changes, and dinocyst assemblages as proxies for surface water salinity. However, there are few data on within-region variations in these assemblages using large sets of surface samples and a full suite of palynomorphs, including terrigenous pollen + spores, freshwater algal spores, and organic remains of marine microplankton, micro- and meiobenthos. Here we fill this knowledge gap, using results from a palynological study of 43 surface samples from water depths of 71–905 mbsl on the Ukrainian Shelf and adjoining continental slope, NW Black Sea. The palynology samples were collected in conjunction with water and sediment chemistry data, grain-size, micropaleontological and meiobenthos data from the EU-FP6 project HERMES “Hotspot Ecosystems Research on the Margins of European Seas”. This dataset uniquely covers shelf and upper slope areas east and west of the Odessa-Sinop Fault Zone (OSFZ) that delimits areas of lower and higher hydrocarbon gas contents, respectively. The new data show that on the wide shelf with a shallow (ca. 80 m) oxycline, pollen assemblages differ from classical models for marine pollen transport. On the Ukrainian Shelf, pollen concentrations are extraordinarily high far offshore and the grains are often pyrite-infilled. These features apparently reflect high pollen preservation potential in low oxygen sediments, probably enhanced by cross-shelf transport of land-derived particulate organic matter. The new data have important consequences for accurate modelling of carbon burial and storage in epicontinental seas, and they provide a baseline for evaluating marine pollen concentrations expected to reflect the early Neolithic farming on the Ukrainian shelf. Furthermore, although large concentrations of dinocysts comprise more than half of the total Non-Pollen Palynomorphs (NPP), the high pollen concentrations skew the P:D index (pollen:dinocyst ratio) commonly used to evaluate changes in paleo-shoreline (proxy sea-level) positions. Despite the discharge of several large rivers to the Ukrainian Shelf, there are negligible traces of freshwater algae in the HERMES samples except at Sta. 15 where Pediastrum is abundant. Overall, palynomorphs of terrestrial origin make up about half (52%) of the acid-resistant organic-walled particles on the outer NW Black Sea Shelf and adjacent slope. The abundances of the major micro- and meiobenthic palynomorph groups show the same trends east and west of the OSFZ as the micropaleontological data reported for the HERMES samples taken at the same sites. The combined microzooplankton and zoobenthos surface assemblage data provide an important new baseline for evaluating historical and past changes in biodiversity and aquatic foodweb structure in the now polluted NW Black Sea. Comparison can also be made with foodweb reconstructions for Permian black shales.

During the past 20,000 years approximately one-quarter of the continental landmass of Australia was inundated by postglacial sea-level rise, submerging archaeological evidence for use of these landscapes. Underwater archaeological sites can offer substantial insights into past lifeways and adaptations to rapidly changing environments, however the vast scale of inundation presents a range of challenges in discovering such sites. Here we present a suite of methods as a model methodology for locating sites in submerged landscapes. Priority areas for survey were based on palaeoenvironmental contexts determined from the onshore archaeological record. Remote sensing was used to identify seabed composition and indicators of palaeolandscapes where high potential for human occupation and site preservation could be identified in Murujuga (or the Dampier Archipelago), northwestern Australia. Target locations were surveyed by scientific divers to test for the presence of archaeological material. Application of this methodology resulted in the discovery of the first two confirmed sub-tidal ancient Aboriginal archaeological sites on Australia's continental shelf. Survey methods are discussed for their combined value to identify different classes of landscapes and archaeological features to support future underwater site prospection.

Major-element geochemistry from two Cores MD05-2899 and MD05-2901 off central Vietnam in the lower continental slope of the western South China Sea is investigated to reconstruct a history of terrigenous sediment variations and East Asian monsoon evolution during the last glacial-interglacial cycle. The results suggest that the Pearl River can play a more important role in contributing terrigenous sediments to the western South China Sea than the Red River in the north, while the Mekong River can transport more terrigenous sediments to the region than the Sunda shelf and the Indonesian islands in the south. The Pearl River provides terrigenous sediments with higher Al2O3, but lower K2O, MgO, and Fe2O3 (Total Fe) than the Mekong River. K2O/Al2O3, MgO/Al2O3, and Fe2O3/Al2O3 ratios are then used as proxies to trace terrigenous sediment variations in the western South China Sea. Higher K2O/Al2O3, MgO/Al2O3, and Fe2O3/Al2O3 ratios indicate strengthened terrigenous sediments input from the southern source and lower the ratios suggest increased terrigenous sediments received from the northern source. These ratios show a glacial-interglacial cycle over the past 130 ka, implying a close relationship with the East Asian monsoon evolution. Northward surface currents forced by strengthened summer monsoon during interglacial periods bring relatively higher amounts of terrigenous sediments from the southern source to the western South China Sea, while relatively higher amounts of terrigenous sediments from the northern source are transported to the western South China Sea by southward surface currents in strengthened winter monsoon during glacial periods. Our study indicates that the terrigenous sediment variations in the western South China Sea are significantly controlled by surface currents under the strong influence of the East Asian monsoon evolution during the last glacial-interglacial cycle.

The Paleo-Tokyo Bay (Kanto Plateau) that persisted during the transgression periods in the Middle-Late Pleistocene is known for its rich marine fauna that accommodated both the warm and cold water taxa brought by the Kuroshio and Oyashio Currents, respectively. However, little is known on the paleoichthyofauna in this area and the processes shaping the marine ichthyofauna of modern southern Kanto. We used fossil fish otoliths and teeth discovered in the Sha’ana Tuffaceous Sand Member belonging to the Chibanian Miyata Formation, exposed at Sha’ana-dai, Miura City, Kanagawa Prefecture, Japan, to reconstruct the paleoichthyofauna and its associated paleoenvironment and explore the content of fish assemblages during this period. The Sha’ana Tuffaceous Sand Member was composed of upper sandy mud and lower muddy sand horizons at the exposure. A total of 1,675 fish remains were collected from this site, of which 1,389 were assigned to 62 distinct taxa (20 orders, 31 families). The taxonomic composition revealed taxa from various environments, including shallow continental shelf, epi- to meso-pelagic settings, and the majority were from a generally temperate climatic zone. Paleoenvironmental analyses suggested that the fish assemblages were from the continental shelf (approximate depth of 100–200 m) in a temperate sea where both warm Kuroshio and cold Oyashio Currents had an influence on the biota. The analysis also showed that two boreal fishes, namely Clupea pallasii and Theragra chalcogramma, once had a wider distribution that extended to the southwestern areas of the Paleo-Tokyo Bay. This study provides a more complete view of the related paleobiogeography of marine fishes during the Chibanian and is essential for reconstructing the evolutionary processes of the rich ichthyofauna in the southern Kanto.

To understand the evolution of the Miocene gravity flow deposits in the Lower Cong—Congo Fan Basin, this paper documents the Miocene sequence stratigraphic framework, the depositional characteristics and the controlling factors of the gravity flow system. Based on the establishment of high-resolution sequence stratigraphic framework, lithofacies characteristics and sedimentary units of the gravity flow deposits in the region are identified by using seismic, well logging and core data comprehensively, and the sedimentary evolution process is revealed and the controlling factors are discussed. The Miocene can be divided into four 3rd-order sequences (SQ1—SQ4). The gravity flow deposits mainly include siliciclastic rock and pelite. The main sedimentary units include slumping deposits, mass transport deposits (MTD), channel fills, levee-overbank deposits, and frontal lobes. In the Early Miocene (SQ1), mainly gull-wing, weakly restricted to unrestricted depositional channel-overbank complexes and lobes were formed. In the early Middle Miocene (SQ2), W-shaped and weakly restricted erosional-depositional channels (multi-phase superposition) were subsequently developed. In the late Middle Miocene (SQ3), primarily U-shaped and restricted erosional channels were developed. In the Late Miocene (SQ4), largely V-shaped and deeply erosional isolated channels were formed in the study area. Climate cooling and continuous fall of the sea level made the study area change from toe of slope-submarine plain to lower continental slope, middle continental slope and finally to upper continental slope, which in turn affected the strength of the gravity flow. The three times of tectonic uplifting and climate cooling in the West African coast provided abundant sediment supply for the development of gravity flow deposits. Multistage activities of salt structures played important roles in redirecting, restricting, blocking and destroying the gravity flow deposits. Clarifying the characteristics, evolution and controlling factors of the Miocene gravity flow deposits in the Lower Congo—Congo Fan Basin can provide reference for deep-water petroleum exploration in this basin.

Dissolved iron (Fe) and manganese (Mn) share common sources and sinks in the global ocean. However, Fe and Mn also have different redox reactivity and speciation that can cause their distributions to become decoupled. The Arctic Ocean provides a unique opportunity to compare Fe and Mn distributions because the wide Arctic continental shelves provide significant margin fluxes of both elements, yet in situ vertical regeneration inputs that can complicate scavenging calculations are negligible under the ice of the Arctic Ocean, making it easier to interpret the fate of lateral gradients. We present here a large-scale case study demonstrating a three-step mechanism for Fe and Mn decoupling in the upper 400 m of the Western Arctic Ocean. Both Fe and Mn are released during diagenesis in porewaters of the Chukchi Shelf, but they become immediately decoupled when Fe is much more rapidly oxidized and re-precipitated than Mn in the oxic Chukchi Shelf water column, leading to Fe hosted primarily in the particulate phase and Mn in the dissolved phase. However, as these shelf fluxes are transported toward the shelf break and subducted into the subsurface halocline water mass, the loss rates of all species change significantly, causing further Fe and Mn decoupling. In the second decoupling step in the shelf break region, the dominant shelf species are removed rapidly via particle scavenging, with smallest soluble Fe (sFe 1000 km offshore with the prevailing current into the low-particle waters of the open Arctic, cFe and dMn appear conserved, while pFe, dFe, and sFe are very slowly removed with variable log-scale distances of transport: pFe ≪ dFe

Turbidity is a key indicator of water quality. It has biotic effects due to low penetration of light into the water such as photosynthesis reduction. The seasonal and interannual variability of turbidity in the Eastern Tropical Pacific coast of Mexico were analyzed using ocean color data. The region has an extended continental shelf, with several river discharges and marked seasonal patterns of wind. Remote sensing data (1998 to 2017) of reflectance, wind, rainfall, and river discharges were analyzed through Hovmoller diagrams and Empirical Orthogonal Functions. The results indicated that wind stress explained 76% of the turbidity variance, while 8% was explained by river discharges and rainfall. In winter, turbidity is intensified by resuspension mechanisms in front of the southern river mouths. In spring, turbidity increases due to phytoplankton particulate concentrations enhanced by coastal upwelling. During summer and autumn, wind stress is weaker and river discharges increase, thus turbidity increases in front of northern river mouths. El Nino-Southern Oscillation generates turbidity anomalies by alteration of rainfall and wind stress. Despite the proximity of the river mouths, the coastal water turbidity is explained by different processes, which need to be assessed in coastal management.

The aim of the current study was to determine the nature of the seasonal variability of the Suspended Particulate Matter (SPM) fluxes from the drainage basin to the estuary in a macrotidal region (Northeastern Brazil), and the estuarine response to a seawater intrusion regarding sediment deposition, which will support the understanding of the global transport of materials at the continent-ocean interface. Thermohaline structure data was acquired using a Conductivity, Temperature, and Depth (CTD) probe with a sampling frequency of 4 Hz. Suspended particulate material was measured by gravimetric measurements applied to exact filtered volume samples. The outflows were measured through the use of an Acoustic Doppler Current Profiler (ADCP) with frequency of 1.5 MHz. The horizontal thermal and saline gradients varied from warmer and less saline waters (2014) to cooler and saline waters (2015). The gradient behavior when linked to volume transport and SPM flows, suggests a minimization of the fluvial flows in 2015, easing the advance of coastal water (CW) towards the inner estuary, leading to an inversion of the baroclinic pressure gradient. The bottom saline front, generated by the entrance of coastal water masses, caused an increase in SPM concentrations due to increased fluid density, resuspension of previously deposited sediment, and erosion of banks. High concentrations of SPM indicate higher volume transport suggesting a hydraulic barrier due to the change/inversion of the baroclinic pressure gradient, resulting in water and material retention. Material deposition was observed during neap tide, while during spring tide the material is resuspended, increasing the concentration, generating cycles of deposition and erosion during the neap-spring tides. The sediment in suspension that reach the estuary, even with low fluvial volume, stay in this environment forming new islands because of deposition. High deposition rates or sediment cycling, if generated by the hydraulic barrier, may indicate that the flows of SPM from the continental drainage to the estuary and adjacent continental shelf are interrupted and the residence time is increased.

20 pages, 15 figures, 3 tables.-- Data availability: Data will be made available on request, A simulation based on a hydro-sedimentary model was conducted for the period between summer 2010 and spring 2012 in the Gulf of Lion (northwestern Mediterranean Sea) to understand the spatial and temporal variability of sediment transport, erosion and deposition on the continental shelf and slope. Datasets of both simulated and observed current, temperature and suspended matter from the shelf and the Cap de Creus Canyon which is the main export route towards the continental slope, were first compared to assess the reliability of the simulation. The simulation shows the massive sediment accumulation near the Rhone River mouth (∼56 % of the inputs), the accretion along the mid-shelf mud belt, and the impact of dense shelf water cascading on sediment resuspension and erosion inside the Cap de Creus Canyon. The two studied autumn–winter periods were strongly contrasted in terms of meteorological conditions and subsequent impacts on the sediment dynamics. During the first period (2010–2011) dominated by marine storms, the shelf sediment underwent strong changes, the Rhone River sediment load accumulated in a relatively small area, stock of littoral sands moved to the inner shelf (20–40 m) while inner shelf fine particles fed the mid-shelf mud belt and the upper Cap de Creus Canyon. During the second period (2011–2012) with very little marine wind and a particularly cold winter, sediment on the shelf underwent little change except for a southwestward growth of the Rhone River prodeltaic deposit. Sediment from the southwestern end of the shelf as well as from the upper Cap de Creus Canyon was flushed toward deeper reaches by dense shelf water cascading. Cascading also had a more moderate impact in the various canyons incising the continental shelf. Our work supports the view of an unbalanced sedimentary system, with a deficit mainly over the inner shelf, whose main driver is probably the strong and fast reduction of particulate matter inputs from the Rhone River (by a factor of 4 in less than one century), This study (including the PhD and Postdoc of G. Mikolajczak) was mainly funded by the AMORAD-project (grant ANR-11-RSNR-0002 of the French program Investissement d’Avenir run by the Agence Nationale de la Recherche). We also benefited from the support of the CHIFRE and DeltaRhone projects of the national EC2CO program. The simulations were performed using HPC resources from CALMIP (Grant P09115) and CINES OCCIGEN (Grant A0040110088). This research was also supported by grant PID2020-114322RB-I00 (FAR-DWO) funded by MCIN/AEI/ 10.13039/501100011033, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Ancient shoreline–shelf depositional systems are influenced by an unusually wide array of geological, biological and hydrodynamic processes, with sediment transport and deposition primarily determined by the interaction of river, wave (including storm) and tidal processes, and changes in relative sea level. Understanding the impact of these processes on shoreline–shelf morphodynamics and stratigraphic preservation remains challenging. Numerical modelling integrated with traditional facies analysis provides an increasingly viable approach, with the potential to quantify, and thereby improve understanding of, the impact of these complex coastal sedimentary processes. An integrated approach is presented here that focuses on palaeotidal modelling to investigate the controls on ancient tides and their influence on sedimentary deposition and preservation – one of the three cornerstones of the ternary process classification scheme of shoreline-shelf systems. Numerical tidal modelling methodology is reviewed and illustrated in three palaeotidal model case studies of different scales and focus. The results are synthesised in the context of shoreline–shelf processes, including a critique and modification of the process-based classification scheme. The emphasis on tidal processes reflects their global importance throughout Earth’s history. Ancient palaeotidal models are able to highlight and quantify the following four controls on tidal processes: (1) the physiography (shape and depth) of oceans (1000s km scale) determines the degree of tidal resonance; (2) the physiography of ocean connections to partly enclosed water bodies (100–1000s km scale) determines the regional-scale flux of tidal energy (inflow versus outflow); (3) the physiography of continental shelves influences shelf tidal resonance potential; and (4) tides in relatively local-scale embayments (typically 1–10s km scale) are influenced by the balance of tidal amplification due to funnelling, shoaling and resonance effects versus frictional damping. In deep time, palaeogeographic and palaeobathymetric uncertainty can be accounted for in palaeotidal models by performing sensitivity analyses to different scenarios, across this range of spatial scales. These tidal process controls are incorporated into an updated predictive decision tree for determining shoreline–shelf process regime in terms of the relative interaction of wave, fluvial and tidal processes. The predictive decision tree considers the effects of basin physiography, shelf width and shoreline morphology on wave, fluvial and tidal processes separately. Uncertainty and ambiguity in applying the widely used three-tier process classification scheme are reduced by using the decision tree in conjunction with a proposed two-tier classification of process regime that is limited to primary and secondary processes. This two-tier classification scheme is illustrated in the three case studies, showing how integration of numerical modelling with facies analysis of the preserved stratigraphic record improves confidence in prediction of tide-influenced shoreline-shelf process regimes. Wider application of this approach will further improve process-based classifications and predictions of modern and ancient shoreline–shelf systems.

The purpose of this study was to characterize the Black Sea canyons associated with contrasting natural environmental conditions from two Black Sea basin regions: the northwestern/northern and the northeastern/eastern zones. The canyon-associated relief, the morphology of the continental shelf and the location of the canyon heads in the two Black Sea areas were analysed and compared. The canyon network reconstruction led to the conclusion that the canyon system pattern is different in the northwestern and northern Black Sea zones compared to the canyon system in the eastern Black Sea zone. Sediments in the deep sea fan areas were supplied in different manners by the canyon systems from the two marine study areas. According to the important different characteristics revealed by this study, the submarine canyons located in the northwestern/northern vs. the northeastern/eastern Black Sea zones appear as two distinct types, namely wide-shelf canyons and narrow-shelf canyons, with specific genetic and morphologic characteristics. The response to sea-level variation reveals an important distinction between the wide-shelf canyons and the narrow-shelf canyons. In highstand conditions, when the shelf is immersed, the wide-shelf canyons become inactive, whereas the narrow-shelf canyons are active in both lowstand and highstand conditions.

Dissolved aluminium (hereafter, dAl) concentrations have been determined on 34 full vertical water column profiles, sampled along the two separate GEOTRACES-India transects (GI-01 and GI-06) to understand the biogeochemical controls on dAl distribution in the northern (the Bay of Bengal, the Andaman Sea and the Arabian Sea), equatorial and subtropical gyre region of the Indian Ocean. Al released due to the partial dissolution of and/or Al desorption from the suspended lithogenic sediments, supplied in a huge amount to the Bay of Bengal (BoB) waters by the Ganga-Brahmaputra (G-B) river system, Indian peninsular rivers and sediment resuspension from the continental shelf and slope, predominantly controls the dAl distribution in the BoB and results in an overall increase in the dAl concentrations throughout the water column towards the northern BoB and the eastern coast of India. Considering the steady-state balance between the dAl input from the lithogenic sediment flux in the upper water column and first-order scavenging removal of dAl, the fractional solubility of Al from the lithogenic sediments in the BoB surface waters is estimated to be in the range of 1.1-4.7 %. Advection of Indonesian Sea surface waters through the Strait of Malacca and dAl input from the partial dissolution of resuspended terrigenous sediments, sourced from the insular shelf of the Nicobar Islands, set major controls on the dAl distribution in the surface and upper thermocline waters of the southern Andaman Sea and the southern BoB region near the Nicobar Islands. Rapid renewal of and vertical mixing in the deeper waters (>1000 m) relative to scavenging removal of dAl results in near-uniform dAl concentrations (∼ 3.7 nM) in the deeper waters at the center of the southern Andaman Sea. In the south-eastern Arabian Sea, the continental outflow of mineral dust and advection of dAl enriched Bay of Bengal surface waters control the dAl distribution in the surface water layer. dAl in the surface waters of the equatorial Indian Ocean, during the late winter sampling period of the GI-06 cruise, is predominantly determined by the mixing between dAl-rich surface waters of the southern BoB and relatively, dAl-depleted surface waters of the southern Arabian Sea under the influence of the Northeast Monsoon Current. The scavenging residence time of dAl in the deep waters of the equatorial Indian Ocean is estimated using a 1-D scavenging-advection-diffusion model and found to be in the range of 92-141 years. Deposition of Australian dust and advection of Indonesian Throughflow Water translates to the dAl enrichment in the upper water column ( 3500 m) advects across the Ninety East Ridge from the Western Australian Basin to bring the dAl-rich waters to the northern end of the Central Indian Ocean Basin.

Beachrock may be considered a reliable indicator of sea level, in addition to a reliable and recognizable source for onshore movement of beachrock clasts by overwash processes associated with extreme events. Key to this is its geomorphology and preservation potential, both of which are poorly understood. Here we examine the processes and deposits associated with beachrock breakdown from Camurupim, NE Brazil and compare its preservation to beachrocks found on continental shelves in South Africa. We study a prominent and continuous 50–60 m-wide beachrock complex that crops out along a 10 km stretch of coastline, and which mostly comprises 1.5 to 2 m-thick trough-crossbedded sandstones. These have generated large joint-bounded blocks that have been transported landwards under extreme energy conditions (based on numerical modelling and comparisons to the contemporary wave climate). Tabular clasts have accumulated as isolated, very coarse boulders on the seaward margin, small clasts in various topographic traps, boulder ridges with large landward- and seaward-dipping clasts on the uppermost part of the outcrop, and subaqueous and subaerial washover fans. Isolated fine meso-boulders emplaced during extreme waves (Hs = ca. 12 m) exhibit fitted textures and pressure-solution contacts, pointing to subsequent rocking and shaking. Smaller clasts in boulder ridges and overwash settings are initially liberated and transported by waves within the annual-decadal frequency spectrum, deposited on the high points of the outcrop. Subsequent movement during less extreme wave action progressively transports the clasts across the surface, where they are often trapped in the fitted fabric on top of the platform. Our breakdown model and overall beachrock preservation scheme is consistent with reported seismic signatures of submerged Holocene beachrock shorelines. Beachrock preservation during transgression is strongly influenced by the original sedimentary facies; thick, trough-crossbedded joint-bound clasts preserve the former shoreline. Clasts from the planar units accumulate as washover fans to landwards of the ridge.

India's National Gas Hydrate Program Expedition 02 (NGHP-02) was conducted to better understand geologic controls on gas hydrate occurrence and morphology, targeting coarse-grained sediments along the lower continental slope offshore eastern India. This study combines seismic, logging-while-drilling data, and a petroleum system approach to provide a regional geologic and lithologic context for: 1) gas hydrate morphology and distribution, and 2) effects of fine-grained sediments (clays and other grains smaller than 63 μm) on gas production in NGHP-02 Area B in the Krishna-Godavari Basin. Area B seismic data show a buried anticline/syncline structure with strong reflectors, R1 and R2, that delineate two of the five lithologic units: Unit I (shallowest), II (R1), III, IV (R2) and V (below the bas of gas hydrate stability). Throughout Area B, gas hydrate morphology depends on its placement within these units. Specifically, core- and grain-scale measurements indicate fines content exerts a primary control on the gas hydrate distribution and morphology. Units I, II and III are generally fine-grained. On the anticline crest, these units host primarily grain-displacing gas hydrate veins linked to pore-occupying gas hydrate in thin, localized, coarser-grained deposits. Diatoms in Unit III increase porosity with depth, reaching ∼70% where it contacts Unit IV, the gas hydrate reservoir associated with reflector R2. The Unit III lithology and porosity allow fluid and dissolved-phase methane to escape Unit IV and form gas hydrate in the fine-grained overburden. Within Unit IV, fine-grained layers are interbedded with coarser-grained gas hydrate reservoir sands, and the fines content even in the sands is high enough to impact hydraulic and mechanical properties during gas production. Fluid motion during gas production can mobilize fines, which can then clog pore throats, limiting production rates. Pore-water freshening during gas hydrate dissociation can increase fines mobilization, particularly given the smectite identified in the fine-grained interbeds.

Atlantic menhaden (Brevoortia tyrannus) is a migratory forage fish whose geographic range extends from the Gulf of Maine to Florida. Despite the ecological and commercial importance of menhaden, few fishery-independent surveys have been conducted to quantify their distributions of abundance and biomass. Active acoustic surveys of menhaden schools were conducted using 38, 120, and 200 kHz scientific echosounders in two regions on the continental shelf south of Long Island, New York during the summer of 2014 and spring, summer, and fall of 2015. Spatial distributions of menhaden schools were considered to be clustered across all surveys where three or more schools were observed. Estimates of school volume were highly variable, ranging from 30 to 48,000 m3. Menhaden aggregations were absent in the spring (April, May, and June) and present in the summer and fall (July, August, and September) surveys. Target strength measurements at 120 kHz during the summer and fall surveys were consistent with predicted values for adult Atlantic menhaden, suggesting that fish size did not change substantially during this time. Peak menhaden abundance was observed during August 2015 (approximately 157,000 fish km−2 with a wet weight biomass density of 35,000 kg km−2). Multifrequency acoustic surveys can provide an efficient and fishery-independent method for quantifying menhaden abundance and distribution in coastal habitats.

The South China Sea (SCS) is classified as an oligotrophic ocean because it has low nutrient and chlorophyll concentrations. We examined the biogeochemical cycle of dissolved manganese (DMn) on the northern slope of the SCS during two cruises (October 2014 and June 2015), and the effect of DMn enrichment on the growth of phytoplankton in field incubation experiments. DMn was measured spectrophotometrically by an on-line pre-concentration and flow injection analysis method. The concentration of DMn varied from 0.6 to 32.4 nM in the Pearl River Estuary, and decreased with distance from the coast. Moreover, DMn concentrations declined significantly (50–90%) as salinity increased between the Pearl River and the SCS. Vertical profiles of DMn reflected a typical scavenge-type distribution, and decreased with depth. Mixing between the Shelf Water and the Western Philippine Sea led to a Mn-rich plume (> 4 nM), which extended from the northern shelf into the slope regions of the SCS. The export of Mn-rich shelf waters was an important source of DMn for SCS, and this lateral input from the continental shelf could exceed atmospheric input. The incubation experiments showed that the addition of Mn stimulated phytoplankton growth. These results suggest that Mn may play an important role in regulating phytoplankton growth in the SCS.

Two surveys using a combination of midwater trawl and acoustics were undertaken in October 2014 and June 2015 to investigate species composition and biomass density of mesopelagic nekton over the continental slope of the South China Sea (CSSCS). In two surveys, diversity and dominant species of nektons (Chondrichthyes, Osteichthyes and Cephalopoda) showed obviously diel and depth–dependent difference. In 2014, in general species richness and diversity of nektons in the 0–100 m at night were greater than that in the 350–650 m during the day and 350–650 m at night. In Jun. 2015, species richness and diversity of nektons in the 350–650 m during the day were much greater than that in the 350–650 m at night and 0–100 m at night. Myctophidae and Diaphus are the most common fishes in the CSSCS mesopelagic zone. Jellyfishes could cause the nautical area scattering coefficient (NASC) to increase, but the effect of jellyfishes on NASC could vary over the light–night cycle and trawl depth. Catch rates of different nektonic categories varied by time of day and depth. Night–time catch rate at trawl depths

Iron (Fe) has been recognized as a key trace element that limits primary production in large oceanic areas. In the oligotrophic South China Sea (SCS), few Fe data have been reported due to the difficulties in collecting trace metal clean seawater samples. Here, we report dissolved Fe (dFe) datasets from the Pearl River estuary and the northern continental slope of the SCS. Samples were collected in October 2014 using our homemade towed-fish and X-Vane sampling system. dFe experienced considerable removal at a salinity

Two new species of Condyloderes are described, C. rohalorum sp. nov. from the deep-sea off California, and Condyloderes flosfimbriatus sp. nov. from the continental shelf in the northern Gulf of Mexico. Additional species are furthermore reported from the two regions, including Condyloderes kurilensis from the Californian deep-sea, one potentially new species from each of the two regions, and the presence of specimens similar to, and potentially conspecific with, the two new species, i.e., Condyloderes cf. C. rohalorum sp. nov. in the Gulf of Mexico, and Condyloderes cf. C. flosfimbriatus sp. nov. from the Californian deep-sea. Examinations of C. rohalorum sp. nov. reveal that the species has two different adult female stages, hence representing the first example of adult female dimorphism known from this genus, and indicating that adult moulting might happen amongst species of Condyloderes.

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 (

Underwater relief and topography may influence currents, waves, temperature, depth and nutrient availability, factors that play important roles on structuring reef communities. The formation of valleys at the continental shelf, for instance, may result in unique geomorphologies that influences environmental factors on a local scale. Therefore, reefs within a valley and on its adjacencies are likely to experience different conditions despite the geographical proximity. An extensive biogenic reef formation at the Brazilian Equatorial shelf occurring within and around a valley was recently described from the geological perspective. Given the relative paucity of biogenic reefs along the Brazilian coast, understanding these biological communities is critical. We assessed benthic and fish communities in these reefs using photoquadrats and visual census, respectively. We studied reefs within the valley, on the West and East of the depression, to evaluate if the stronger tidal currents within the valley and its connection to a submarine canyon would differentially affect benthic and fish communities among these areas. We found higher coral cover and lower macroalgal cover on reefs located within the valley. Fish biomass was similar among areas, but biomass distribution among functional groups was variable. Invertivores and piscivores biomass was greater on reefs within the valley, potentially resulting from higher food availability and nutrient input. This work provides information on biological communities in these outer shelf biogenic reefs around valleys, a novel approach to this formation, showing that environmental factors associated to underwater valleys may structure reef communities even within small spatial scales. This effect may be due to local topography and current condition, to the nutrient-rich currents from the submarine canyon reaching the reefs through the valley and aiding primary productivity, or by a combination of these factors.

In contrast to the benthos whose taxonomic recovery was lagging way behind that of the nekton, highly diverse Smithian conodont and ammonoid faunas were profoundly decimated during the late Smithian, ca. 2 Myr after the Permian-Triassic boundary mass extinction. As body size reduction is a common evolutionary response to heavy environmental stress, we investigate how the size of the P1 elements of different conodont clades responded during the late Smithian crisis based on three sections from the northern Indian Margin. A major and world-wide positive carbon excursion is also a consistent signature of the late Smithian time interval. Where adequate ammonoid biochronological control is lacking (i.e., Kashmir), a new carbonate carbon isotope record provides an independent age proxy for correlations with southern Tibet and the Salt Range. Assuming a positive correlation between the size of P1 elements and body size, we confirm that segminate conodonts underwent a size decrease during the late Smithian. However, segminiplanate conodonts consistently displayed a substantial size increase during the same time interval, thus highlighting clade specific, diverging answers and precluding any simplistic generalization of size responses to the same stress event. Additionally, a moderate but consistent size increase during the early Spathian is documented for both clades, thus obscuring any simple general relation between temperature stress and size among conodonts. Comparison of size time series with the oxygen isotopic composition of conodonts (a proxy for sea-water temperature) suggests that only the size of segminate P1 elements may correlate positively with temperature. Although at a slower pace, the size of segminiplanate P1 elements continued to increase during the early Spathian, when temperature rose again after the late Smithian cooling event. Therefore, temperature alone cannot explain the size variations of segminiplanate conodonts. The late Smithian was also a time of increasing burial of organic matter on continental shelves, but lateral variations of this factor also obscure any relation with the documented size changes. Last but not least, the stratigraphically more comprehensive study in Nammal reveals a segminiplanate gap during the middle Smithian thermal high. The biogeographical expansion of this clade towards the low latitudes during the Griesbachian, the early Smithian, the late Smithian and the early Spathian apparently occurred during the coolest intervals of the Early Triassic, in agreement with their supposed cooler habitat.

This study reports data from the Upper Cambrian Conasauga Group and overlying Copper Ridge Formation of the Central Appalachian region, eastern U.S.A. Geochemical, isotopic and petrographic analysis of core material was carried out to constrain the extent of marine anoxia and to characterize sediment fluxes on the carbonate platform and continental shelf of Laurentia contemporaneous with the Steptoean Positive Carbon Isotope Excursion (SPICE), a Late Cambrian global marine anoxic event. Carbonate rocks (primarily dolostone) record a positive δ13Ccarb excursion starting in the middle Nolichucky Formation, reaching its peak (+4.3‰) at the boundary between the Maynardville and Copper Ridge formations. Strontium isotope ratios in the dolostone units are only slightly offset from the expected Cambrian seawater values, suggesting minimal post-diagenetic disturbance of isotopic and trace element systematics. Selective leaching of carbonate units reveal upward decreasing trends in dissolved redox-sensitive trace metals (e.g., U, Ni, V) indicative of drawdown from regional and global marine anoxia during the peak of the Late Cambrian SPICE event.

Based on experiments, a trawling-induced erosion dynamics was included in a 3D realistic and pre-validated hydro-sedimentary model so as to assess its contribution to the overall regional sediment dynamics in the specific case of the Bay of Biscay continental shelf. The effect of trawling was investigated throughout a 5-year period in terms of horizontal/vertical fluxes and changes in seabed mud content, and compared to the natural variability of sediment fluxes at different spatio-temporal scales. Trawling is shown in the model to significantly contribute to sediment re-suspension, and changes in the seabed at the scale of the shelf. The contribution of trawling to re-suspension is >80% during the high fishing season at many locations on the outer shelf and over the Grande-Vasiere area (a large and intensively trawled muddy zone located in the middle of the shelf). The contribution of trawling is significantly weaker in winter and at annual scale, particularly over zones with (muddy-) sand facies (between 1‰ and 1%), but remains high, and reaches 20% of the annual erosion over muddy areas (e.g. northern part of the Grande-Vasiere). This significant trawling-induced erosion dynamics results in high sediment fluxes which increase natural poleward dynamics from a few percent up to 40%, and contributes to the natural offshore export of sediment on the outer shelf (e.g. +35% of mud fluxes along the 130 m isobath). It is noteworthy that trawling-induced fluxes are larger in winter although the corresponding re-suspension is lower than in summer: this is due to stronger near-bottom flows occurring at this period (largely influenced by energetic wind conditions). In contrast, on the inner shelf, trawling-induced sediment fluxes are rather oriented towards the coast. Finally, simulation results reveal a trawling signature on changes in the seabed. A significant decrease (between 10% and >50%) in mud content is simulated over trawling hotspots, especially over the internal part of the Grande-Vasiere and on mud patches located in front of the Gironde estuary. Conversely, trawling causes or intensifies mud deposition on both sides of these preferentially trawled areas.

The continental shelf around Kodiak Island is incised with numerous submarine canyons, which play an important role in the cross-shelf transport of heat, salt, and nutrients, and the transport of ichthyoplankton of deep-spawning fish from the slope region into the shallow nursery grounds surrounding Kodiak Island. To explore the pathways and variability of flow, and the extent of tidal mixing within the canyons, moorings were placed in the Chiniak, Barnabas, and Amatuli troughs, and off the shelf from Resurrection Bay (Seward Line) and the Kenai Peninsula (Gore Point). In the troughs, intensified flow was evident near the trough walls, and flow was directed by bathymetry with inflow along the upstream (northern) side and outflow along the downstream (southern) side. The presence of mesoscale eddies in the gulf had no unique influence on currents or salinity in the troughs. Tidal mixing was strongest in Chiniak Trough, and this introduced cold, nutrient-rich bottom waters into the upper water column. Intensified bottom flow associated with the Alaskan Coastal Current was evident along the Seward Line and Gore Point, and directed toward the Kennedy-Stevenson Entrances, which are also regions of strong tidal mixing. Observations of tidal mixing were consistent with model results and satellite images showing cooler, phytoplankton-rich water in summer in the nursery grounds that surround Kodiak Island. Patterns of flow within the troughs and in Shelikof Strait were consistent with the springtime advance of ichthyoplankton across the shelf.

The continental shelf morphology offshore of western Sicily suggests that during the Last Glacial Maximum (LGM, 20 ka cal BP), two of the Egadi Islands, Favignana and Levanzo, were connected to Sicily by a wide emerged plain, while Marettimo was only separated from the other islands by a narrow channel. We studied the relative sea-level variation from the LGM until today, focussing on two important time slices: the Mesolithic (9.5–13 ka cal BP) and the Neolithic (6.5–7.5 ka cal BP). In this research, we discuss a sea-level rise model by means of geomorphological, archaeological and geophysical observations and new radiocarbon dating of marine and terrestrial fossil fauna. The results enabled us to provide a detailed palaeogeographical reconstruction of the focal area from the LGM until they became isolated. The evidence that has emerged from this research, in particular the radiometric data, supports the hypothesis that seafaring in the western Mediterranean area may have started between the early Mesolithic and late Epigravettian (between 8.4 and 13.5 ka cal BP), although it probably became a well-established practice only during the Neolithic.

The transport processes and fate of 137Cs in eastern Chinese seas (ECSs) that consists of the Bohai, Yellow, and East China Seas, have not been well established. In this study, we measured the concentrations of 137Cs in the ECSs water and surface sediments during 2013–2014. Combined with a number of published 137Cs inventory data from drainage basins and sediment accumulation rates in the ECSs, the distribution, sources and budgets of 137Cs in the ECSs were investigated. The 137Cs activity in the water column and surface sediments ranged from 0.03 to 1.92 Bq/m3 and from 0.30 to 5.22 Bq/kg, respectively. No 134Cs signal was observed, suggesting that the Fukushima accident had limited impact on the ECSs during the investigation period. Mass balance of 137Cs suggests that at least 7.4 × 1012 Bq/y of 137Cs imported into the ECSs from the Northwestern Pacific that accounts for 0.7% of the 137Cs transported by the Kuroshio Current, and this value is 5.2 times higher than the sum of atmospheric fallout and total riverine input. The apparent half-lives of 137Cs are estimated to be 15.1 y for the ECS and 7.7 y for the YS. The vertical profiles in the continental shelf edge and the Yangtze River Estuary reveal that the upwelling of the Kuroshio Subsurface Water is the main mechanism of 137Cs import into the ECSs. The high level of 137Cs in oceanic water masses and the low level of 137Cs in riverine and coastal waters make 137Cs a good indicator for tracing water mass movement and interaction. In addition, good correlation between 137Cs activity and mean grain size (φ) indicates that 137Cs can serve as an effective tracer to track dispersal pathways of fine sediments in river-dominated marginal seas.

The Bahamas or Lucayan Archipelago located in the western North Atlantic Ocean is highly susceptible to impact of hurricanes considering its location along the major pathways of Atlantic hurricanes and increased storminess in the Atlantic basin. The hydrodynamics of the narrow and steep carbonate continental shelf of Bahamas archipelago provides a stark contrast to the east coast of the United States by means of distinct interaction of shelves with hurricane induced waves, storm tide and currents. The present study implements a coupled ADCIRC-SWAN model to investigate the surge and wave dynamics along the coasts of Bahamas archipelago during Hurricane Joaquin, using multiple reanalyzed wind products. The analysis is focused on the hydrodynamic response of the archipelago considering its varying coastal bathymetry, slope and arching coastlines. Model computed a maximum significant wave height of 15 m, storm surge 1.5 m and coastal currents of 4 m/s during Hurricane Joaquin. Moreover, validation study also shows very good agreement with the buoy observations from the region. Spatio-temporal variability of storm tide and waves along with nonlinear impacts of wave setup and setdown highlights the dominance of waves with moderate influence of storm tides along the coastal zone of the island chain. The study also evaluated interaction of coastal currents with the arching coastlines of the Bahamas. In addition, wave parameters attributed to the sinking of the cargo ship El-Faro during the Hurricane Joaquin have been examined. Significant wave heights exceeding 12.5 m with wave period of 12.5 s and the reversing wave direction during Hurricane Joaquin might have resulted in the capsize of the cargo ship.

Combined seismic images and core data from shallow gas-charged, deep-water sands in the western Bay of Bengal provide a detailed record of channel formation and evolution. The KG-D6 Block, western Bay of Bengal, includes two main Pliocene deep-water channel complex sets, termed the A and B complex sets, currently under gas production by Reliance Industries. These represent sinuous channels developed at the base of the delta slope off of the Godavari River and at the head of a long continental slope into the deep Bay of Bengal. The A complex set includes two main channel complexes, the older A150 and younger A100 channel complexes. The A complex provides an excellent opportunity to explore the geometry, sedimentation, and evolution of a small submarine channel system because of shallow reservoir depth, excellent 3D seismic coverage, availability of cores, and the nearly complete system-wide gas charge of the sandstones. Relict sea-floor topography and the processes of avulsion and splay development figure importantly in the overall evolution of slope channel systems. In the KG-D6 area, a sand-rich avulsion splay derived from an older channel complex became the template upon which the A channel complex set evolved. The component A150 and A100 channel complexes developed along a single sinuous course, with the channel complexes building through coupled channel erosion and coeval levee construction. The Godavari slope channels are not confined by scalloped valley walls and did not migrate laterally during their evolution. Mass transport deposits (MTDs) occur in all parts of the channel-fill section. The A100 channel complex displays a well-developed fining-upward cycle in most sections apparently not reflecting shifts in channel position or meander cuts offs, as inferred for some other deep-water channel systems, but rather through changes in the activity within the channels and through advances and retreats of frontal splays up and down the channel system. The Godavari data demonstrate the importance of avulsion and splay development in the evolution of deep-water sedimentary deposits, even high on passive margin slopes, which has implications for understanding the evolution of sinuous submarine channels and the development and distribution of hydrocarbon reservoir compartments.

Capelin (Mallotus villosus) are an important mid-trophic link within marine food webs, yet there is limited information describing fluctuations in distributions and abundances of capelin in the Alaskan North Pacific. The influence of physical and biological environmental factors on capelin distributions was investigated over continental shelf waters in the central Gulf of Alaska (CGOA). Acoustic, oceanographic, and trawl sampling were conducted in summer and fall of 2011 and 2013 as part of the Gulf of Alaska Integrated Ecosystem Research Program. Continuous acoustic sampling across bathymetric gradients showed capelin distributions on the CGOA shelf were primarily concentrated over submarine banks less than 100 m in depth. Acoustic densities of capelin were higher over banks in summer of both years compared to in deeper troughs (≥ 100 m depth). Length-based distributions indicated that capelin occurring over banks were mostly age-1 fish, while larger age-2 + capelin were more prevalent in troughs. Environmental factors that influenced occurrence and density of capelin in summer 2013 were identified at two spatial resolutions associated with systematic sampling at discrete stations and continuous sampling along transects. At the station resolution (37 km), the probability of capelin occurrence was associated with relatively warmer bottom temperatures and increased chlorophyll concentrations, while capelin density was associated with close proximity to the edges of banks and reduced thermal stratification. At the transect resolution (0.5 km), increases in capelin density were associated with increases in density of a potential competitor (age-0 pollock, Gadus chalcogrammus) over banks and with increases in prey (macrozooplankton) and predator (semi-demersal groundfish) densities in troughs. We infer that in summer, age-1 capelin concentrate over shallow banks on the CGOA shelf in waters that are well-mixed and more productive to feed on abundant copepods, whereas age-2+ capelin primarily occupy deeper waters in troughs where they consume larger euphausiid and amphipod prey. This suggests that distributions of both life stages over the shelf were likely driven by changes in the availability and composition of prey.

This study assesses the genetic structure and gene flow of the salt marsh species Salicornia tegetaria between estuaries and tests three hypotheses: (1) that the relocation of estuaries on a shallow continental shelf during the last glacial maximum created a historical biogeographic barrier, the exact location of which we attempt to pin-point, (2) that there is connectivity and thus gene flow at present between estuaries, and (3) that some estuaries have higher genetic diversity and are therefore of higher conservation priority. DNA samples were collected from 17 estuaries and used to create haplotype networks. Analyses of molecular variance, isolation by distance, selective neutrality and genetic distance between estuaries were also conducted. Eleven ITS ribotypes, one found exclusively between Olifants and Breede Estuaries, and eight rpS16 haplotypes were recovered with a dominant haplotype occurring in most estuaries. The remaining ribotypes and haplotypes from ITS and rpS16 sequences were unique, predominantly on the South and East Coast. A high amount of gene flow and an increase in genetic differentiation from west to east was found. The topography of the continental shelf and diverging ocean currents did provide a historical geographic barrier during the last glacial maximum approximately 18,000 years ago. A high degree of connectivity between estuaries allows for the exchange of genetic material in the direction of the ocean current, but long distance dispersal is also suggested. Repeated habitat fragmentation, most likely due to fluctuating sea levels, contributed to a higher amount of rare haplotypes on the South and East Coast. This study provides baseline information on a salt marsh species for which there is a paucity of data that is widely distributed in an ecosystem that is likely to be heavily impacted by climate change.

As stewardship goals in marine environments expand to encompass ecosystem dynamics, our comprehension of ecological structure must incorporate complex interactions among ecosystem components to define linkages and spatial boundaries for management. For example, the Gulf of Alaska (GOA) is currently considered a single Large Marine Ecosystem (LME), yet the GOA spans a large geographic domain, suggesting that ecosystem linkages may vary depending upon population, community, or process-based assessments. We used six years of larval fish assemblage data (2010–2015), co-collected oceanographic data, satellite-tracked drifters, adult fish trawl surveys, and an individual-based biophysical model to determine the processes that structure larval fish assemblages in the GOA focusing on 1) the local physical environment, 2) seasonality, 3) oceanographically-driven connectivity, and 4) adult fish distributions. Larval assemblages occurred along an eastern to western longitudinal gradient with regionally distinct assemblages in the spring and to a lesser degree in the summer. Assemblage patterns were largely driven by regional spring spawning events and only minimally influenced by temperature, salinity, and bottom depth over the continental shelf. Assemblage analyses and modeled particle trajectories suggest that longitudinal gradients in larval assemblages across the LME are influenced by the prevailing currents that promote connectivity despite variability in species-specific life-history characteristics such as spawning location and pelagic larval duration. Divergences in eastern and western GOA assemblages during the spring, and similarities in the summer, were consistent across most study years, but there were shifts in larval assemblages in the western GOA and not the eastern GOA during 2013 and 2015. Such geographic decoupling of assemblages in recent years highlights the potential for differential regional responses to environmental change across the GOA. Patterns in larval fish assemblages underscore the complex processes that structure pelagic ecosystems and suggest that assemblages diverged along a longitudinal gradient resulting in distinct communities in the eastern and western GOA. We propose that the influence of environmental or climatic variability on regional larval assemblages and life-history traits such as pelagic larval duration and phenology may alter future ecosystem linkages in rapidly changing environments.

In this study a 165–265 m-thick siliciclastic-carbonate (mixed) base-of-slope succession within the Ediacaran Isaac Formation (hereafter termed FIC) in the deep-marine Windermere Supergroup (WSG), southern Canadian Cordillera was analyzed. Excellent outcrop exposure at three study areas (Castle Creek, Hill Section and Milk River), spaced over a distance of 20 km parallel to depositional dip provided the opportunity to observe the stratigraphic and inorganic carbon (δ13Ccarb) isotopic evolution of an ancient mixed, passive margin deep-water system. Based on detailed sedimentological analysis six stratal elements make-up the FIC (channel complexes, levees, siliciclastic-to-carbonate tripartite deposits, scour dominated units, debrites and slides). Within these strata the most voluminous carbonate phase (C1) represents neomorphism of primary aragonite on the slope and during early burial, and thus preserves the primary shallow-marine isotopic signature even after downslope transport. At the base of the FIC δ13Ccarb is negative (−5.2‰) and then progressively increases to 2–3‰ in the middle of the succession, after which it plateaus for about 65 m before declining to a nadir of −6.3‰ at its top. Coincident with these isotopic changes are systematic changes in the architecture and mineralogical composition of the component stratal elements that makeup the FIC, which collectively suggest long-term transgressive followed by regressive conditions that quite possibly are tied to rising and then falling sea-level, and accordingly the state of the continental shelf carbonate factory. Additionally, the upward change in δ13Ccarb closely resembles the trend reported in the upper June beds-Gametrail Formation of the WSG in the northern Canadian Cordillera, but the interpreted association of the latter with the Shuram-Wonoka anomaly (570–551 Ma) makes its correlation with the FIC unlikely. Instead, the FIC excursion potentially correlates with the EN2 excursion in the Doushantuo Formation of South China (and its potential global correlatives), which has been interpreted to be associated with the Gaskiers glaciation (580 Ma). This suggests that the FIC might be a stratigraphic and δ13Ccarb record of conditions that prevailed in the deep sea preceding the Gaskiers, which previously has been unreported from strata of the WSG.

The use of functional trait analysis has been advocated to uncover the global mechanisms behind biodiversity responses to environmental variation, but the application of this approach to the Arctic macrobenthic community is underdeveloped relative to that used for other organism groups. Based on several summer surveys (July to September 2010, 2012, 2014 and 2016) in the Bering Sea, we used biological trait analysis (BTA) to quantify the composition and diversity of macrobenthic biological traits along an environmental gradient ranging from the shallowest portion of the continental shelf to the shelf break and deep basin. Our results show a clear shift in the macrobenthic functional composition through the application of abundance- and biomass-based measurements in six different subregions of the Bering Sea. The macrobenthic community of the south-western shelf and shelf break of the Bering Sea, an area with silty-sand sediment, was mainly composed of taxa characterized by high body flexibility, vermiform, and tube-dweller/burrower modalities or large, semi-motile, deposit feeder and flattened dorsally modalities. However, the community of the north-eastern shelf of the Bering Sea with sandy sediment was mainly characterized by organisms characterized as motile surface crawlers and carnivores/scavengers. Similar to the factors that determine the taxonomic distribution and composition of the macrobenthos, sediment composition and depth were found to be the main factors that affect the distribution of the macrobenthic functional structure in the study area. The species and functional diversity of the macrobenthos show a strong linear relationship, potentially indicating that the community exhibits relatively low functional redundancy and that the benthic ecosystem is vulnerable to species loss or regime shifts.

Coastal mesoscale anticyclonic eddies are regularly generated by the Primorsky Current flowing past the capes in the largest bay of the Japan Sea, the Peter the Great Bay. They were observed in 18 of 21 CTD summer surveys performed from 2001 to 2017. The regional ROMS model is used to study the evolution of the eddy that has been sampled in the oceanographic survey in August 2009. The model is able to reproduce the observed eddy on the days of sampling including its location, size and vertical structure. The Lagrangian maps are computed to investigate and document the generation, deformation and decay of the eddy, to identify the vortex contour and origin of water masses inside it. Such coastal eddies are typical for the summer period in the Bay regulating water exchange between the continental shelf and open sea. They are shown to be generated after intensification of the eastern wind which is sufficiently strong to produce downwelling and increased horizontal density gradients and to generate an anticyclonic vorticity past the capes.

The scope of this study is to investigate the effect of the kinematic rupture process on tsunami propagation and corresponding tsunami hazards in coastal regions. It is significant for the tsunageneric earthquakes of long fault length and subsequent long duration of the fault rupture in the strike direction. Most previous studies on the tsunami hazard assessments of the Manila Trench did not consider the effect of the rupture process of huge plates. The movements of the seabed near the earthquake source are calculated by Okada model. The free surface elevation triggered by the seafloor motion is modeled by the nonlinear shallow water equations. The 2004 Indian Ocean tsunami and the 2011 Japan Tohoku tsunami are used to validate the numerical model by comparing with measurement data. The numerical experiments of the tsunami propagation for the cases of different source rupture velocities in uniform depth and continental shelf are carried out to understand the mechanism of the changes of the tsunami arrival time and the tsunami amplitude due to the kinematic rupture process. Stimulated by the long duration of plate motion of 2004 Indian Ocean tsunami, we propose several typical patterns of the rupture process of the long fault of the Manila Trench and analyze quantitatively on the role of the uncertain rupture process of tectonics source in tsunami propagation in the South China Sea. Our results have highlighted that the slow rupture velocity will remarkable affect the tsunami arrival time and maximum amplitude in the South China Sea, comparing to the instantaneous rupture. It is suggested that the rupture process is essential for assessments of the tsunami hazards generated by submarine mass failure with extreme long earthquake rupture source.

The Leeuwin Current System (LCS) consists of the Leeuwin Current (LC), a surface, poleward current along the west coast of Australia; the Leeuwin Undercurrent (LUC), a subsurface, equatorward current on the continental slope beneath the LC; and zonal flows in the interior ocean that interact with the LC and LUC. To understand the three-dimensional structure of the LCS circulation, we construct a mean flow over twenty years in z coordinates and density coordinates from three-day snapshots of an eddy-resolving ocean general circulation model (OGCM) and carry out a “leak-free” volume budget analysis on the mean flow field in both coordinate systems. The mean flow in z coordinates forms a zonal and a meridional overturning, where a near-surface eastward flow enters the LC, flows poleward and at the same time sinks to the LUC depths, flows equatorward, and finally moves westward out of the LCS, as found in a previous study. On the other hand, the mean flow in density coordinates is mostly isopycnic, except that the upper part of the LC becomes denser as it flows poleward partly owing to sea-surface cooling. The lower part of the LC becomes denser, not because of cooling but because denser water joins the LC from the interior ocean. The LUC becomes lighter as it flows equatorward because its lower part flows westward out of the LCS and its top part is joined by eastward flows from the interior. The mean downwelling in z coordinates is therefore isopycnic and is likely a result of temporal variability.