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In this study, the concentration of various elements in marine sediments from Western Marmara Sea Ports has been analyzed and evaluated as well as correlated with similar studies completed earlier in the Western Marmara Sea region by using all the available data. Enrichment factor calculations made according to world average values were also calculated according to Western Marmara background values. In enrichment factor (EF) calculations EF > 3 was found in Cu and Mn calculations in M.Ereğlisi. In M.Ereğlisi, Şarköy and Menekşe the enrichment factor is 1 < EF < 3, and element enrichment is moderate or less in these regions. In the analysis EFZn > 3 in core 1-2, EfAs > 3 in core 10-13, core 14-16, core 18-19, and core 29 also EF > 3 in the enrichment factor analysis for As. In the analysis for Co is EFCo > 3 in core 8-29 samples. Ni enrichment was obtained as EFNi > 3 in core 16-29 samples and EF < 1 and 1 < EF < 3 in all other samples. In enrichment factor calculations using West Marmara Sea background values, it was calculated as EFCu > 3 in core 2 and 12, and EFMn > 3 is for core 1. In other enrichment factor calculations in ports and other locations, all elements were calculated as EF < 1 in some locations and 1 < EF < 3 in some locations. This means that there is little or moderate enrichment according to the latest data. This means that there is little or moderate enrichment in all locations. The reason for the more enrichment of Ni and Mn elements in some locations in the Western Marmara Sea is thought to be anthropogenic. [ABSTRACT FROM AUTHOR]

Continental shelf sediments are places of both rapid organic carbon turnover and accumulation, while at the same time increasingly subjected to human-induced disturbances. Recent research suggests that shelf sediments might have a role to play as a natural climate solution, e.g. by protecting the seafloor against human-induced disturbance. However, we have an incomplete understanding about the centres of organic carbon accumulation and storage on continental shelves. To better constrain the rate of accumulation and the mass of organic carbon that is stored in sediments, we developed and applied a spatial modelling framework that allows to estimate those quantities from sparse observations and predictor variables known or suspected to influence the spatial patterns of these parameters. This paper presents spatial distribution patterns of organic carbon densities and accumulation rates in the North Sea and Skagerrak. We found that organic carbon stocks and accumulation rates are highest in the Norwegian Trough, while large parts of the North Sea are characterised by low stocks and zero net-accumulation. The total stock of organic carbon that is stored in the upper 0.1 m of sediments amounted to 230.5 ± 134.5 Tg, of which approximately 26 % are stored in the Norwegian Trough. Rates of organic carbon accumulation in the Norwegian Trough are on par with those reported from nearby fjords. We provide baseline datasets that could be used in marine management, e.g. for the establishment of carbon protection zones. Additionally, we highlight the complex nature of continental shelves with zones of rapid carbon cycling and accumulation juxtaposed, which will require further detailed and spatially explicit analyses to constrain sedimentary organic carbon stocks and accumulation rates globally. [ABSTRACT FROM AUTHOR]

Over the last few decades, the Barents Sea experienced substantial warming, an expansion of relatively warm Atlantic water and a reduction in sea ice cover. This environmental change forces the entire Barents Sea ecosystem to adapt and restructure and therefore changes in pelagic–benthic coupling, organic matter sedimentation and long-term carbon sequestration are expected. Here we combine new and existing organic and inorganic geochemical surface sediment data from the western Barents Sea and show a clear link between the modern ecosystem structure, sea ice cover and the organic carbon and CaCO3 contents in Barents Sea surface sediments. Furthermore, we discuss the sources of total and reactive iron phases and evaluate the spatial distribution of organic carbon bound to reactive iron. Consistent with a recent global estimate we find that on average 21.0 ± 8.3 per cent of the total organic carbon is associated to reactive iron (fOC-FeR) in Barents Sea surface sediments. The spatial distribution of fOC-FeR, however, seems to be unrelated to sea ice cover, Atlantic water inflow or proximity to land. Future Arctic warming might, therefore, neither increase nor decrease the burial rates of iron-associated organic carbon. However, our results also imply that ongoing sea ice reduction and the associated alteration of vertical carbon fluxes might cause accompanied shifts in the Barents Sea surface sedimentary organic carbon content, which might result in overall reduced carbon sequestration in the future. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'. [ABSTRACT FROM AUTHOR]

The results of studying the content, composition, and distribution of chloroform bitumoids (CBs) in the Holocene sediments of the Barents Sea (cruise 68 of the R/V Akademik Mstislav Keldysh, July–August 2017) are presented. Depending on the sedimentation conditions, CB concentrations varied, on average, as follows (μg of dry weight): Novaya Zemlya archipelago (174) > Svalbard archipelago (131) > Western part (78) > Central part (68) > Franz Josef Land (52). Hydrocarbons were almost half in the CB composition (46% on average, 85% maximum). The distribution of CBs by burial depth has a varying character and depended not only on the grain-size composition of sediments and the content of organic matter, but also on the variability of redox conditions and endogenous flows from a sedimentary stratum. Therefore, the composition markers of alkanes and the IR-Fourier spectra indicated both hydrocarbon sources: sedimentary (Murmansk bank, Franz Josef Land shelf) and point endogenous oil ones (the Svalbard archipelago shelf, the Medvezinskii trench). [ABSTRACT FROM AUTHOR]

We describe a late Miocene to early Pliocene axial drainage system in the East Carpathian foreland, which was an important sediment supplier to the Black Sea and the Dacian Basin. Its existence explains the striking progradation of the northwest Black Sea shelf prior to the onset of sediment supply from the continental-scale Danube River in the late Pliocene to Pleistocene. This axial drainage system evolved due to the diachronous along-strike evolution of the Carpathians and their foreland; continental collision, overfilling, slab breakoff, and subsequent exhumation of the foreland occurred earlier in the West Carpathians than in the East Carpathians. After overfilling of the western foreland, excess sediment was transferred along the basin axis, giving rise to a 300-km-wide by 800-km-long, southeast-prograding river-shelf-slope system with a sediment flux of ~12 × 103 km3/m.y. Such late-stage axial sediment systems often develop in foreland basins, in particular, where orogenesis is diachronous along strike. Substantial lateral sediment transport thus needs to be taken into account, even though evidence of these axial systems is often eroded following slab breakoff and inversion of their foreland basins. [ABSTRACT FROM AUTHOR]

This paper reports the results of investigations in September 2017 on the radioecological state of bottom sediments of the East Siberian Sea during integrated research of the Siberian Arctic seas on cruise 69 of the R/V Akademik Mstislav Keldysh. Evaluation of the results of γ-spectrometric analysis found that the current specific activity of artificial cesium-137 in sediments is two orders of magnitude below the acceptable level and reflects the influence of global fallout from the atmosphere only. Sediments are not contaminated with heavy metals either. Bottom sediments are represented by silts: pelitic, aleuritic–pelitic, and fine aleuritic with a content of pelite (<0.01 mm) fractions of 40–80%. The western and eastern parts of the East Siberian Sea have differences in the distribution and composition of mineral components and element composition due to the influence of the catchments of the Indigirka and Kolyma rivers, respectively. [ABSTRACT FROM AUTHOR]

Abstract—The distribution of Sc, Co, Hf, Cr, Th, and rare-earth elements in samples of surface sediments collected during cruises 67th and 68th of the R/V Akademik Mstislav Keldysh in the Barents Sea and in its bays is analyzed. The results obtained suggest that the predominant part of the bottom sediments of the Barents Sea is composed of thin-grained siliciclastics that was supplied with suspended particulate matter of the North Cape (Atlantic) Current through the erosion of the northwestern Scandinavian coasts and some seafloor areas. Some sediments in the northern part of the sea were formed through the erosion of rocks of the Novaya Zemlya and Franz Josef Land. A certain role in their formation was probably played by material from Svalbard as well as by the Pechora River suspended particulate matter. The established isotopic characteristics (εNd, 207Pb/206Pb and 87Sr/86Sr) of surface sediments suggest that the main contribution to the formation of bottom sediments of the central Barents Sea was made by rocks of the mainland part affected by the North Cape Current. The comparison of the 87Sr/86Sr values ​​in the surface sediments of the central part of the Barents Sea and in the ice-rafted sediments carried by the Transpolar Drift showed their significant difference. This suggests a reatively small contribution of ice-rafted material to the formation of surface sediments of the Barents Sea. [ABSTRACT FROM AUTHOR]

We present a new set of clay mineral and grain-size data for the siliciclastic sediment fraction from International Ocean Discovery Program (IODP) Site U1456 located in the eastern Arabian Sea to reconstruct the variabilities in the continental erosion and weathering intensity in the western Himalaya, elucidate the sediment source-to-sink processes and discuss the potential controls underlying these changes since 3.7 Ma. The clay minerals mainly consist of smectite (0–90%, average 44%) and illite (3–90%, average 44%), with chlorite (1–26%, average 7%) and kaolinite (0–19%, average 5%) as minor components. The compositional variations in the clay minerals at IODP Site U1456 suggest four phases of sediment provenance: the Indus River (phase 1, 3.7–3.2 Ma), the Indus River and Deccan Traps (phase 2, 3.2–2.6 Ma), the Indus River (phase 3, 2.6–1.2 Ma) and the Indus River and Deccan Traps (phase 4, 1.2–0 Ma). These provenance changes since 3.7 Ma can be correlated with variations in the Indian summer monsoon intensity. The siliciclastic sediments in the eastern Arabian Sea were mainly derived from the Indus River when the Indian summer monsoon was generally weak. In contrast, when the Indian summer monsoon intensified, the siliciclastic sediment supply from the Deccan Traps increased. In particular, this study shows that the smectite/(illite+chlorite) ratio is a sensitive tool for reconstructing the history of the variation in the Indian summer monsoon intensity over the continents surrounding the Arabian Sea since 3.7 Ma. [ABSTRACT FROM AUTHOR]

Based on approximately 11,000 km of seismic reflection data collected across the South China Sea oceanic basin, we describe the sedimentary filling characteristics of the basin since its Oligocene opening, as well as connections between this history and contemporaneous regional tectonic events. The seismic lines are spaced ~50 km apart, and the data are tied to International Ocean Discovery Program (IODP) Expedition 349 drilling data. Basin filling occurred in three phases, with basin-wide mean sedimentation rates increasing through time. During the Oligocene to middle Miocene, sediments accumulated primarily in the northern East and Northwest Sub-basins, with a mean basin-wide sedimentation rate of 8 m/m.y. The presence of these deposits over deep basement floor indicates that seafloor spreading initiated in these northern regions. During the late Miocene, deposition occurred primarily in the Northwest Sub-basin and partly in the southern East Sub-basin, with a mean basin-wide sedimentation rate of 30 m/m.y. Basin filling during this time seems to have been linked to slip reversal of the Red River Fault and collision of the North Palawan Block with the Luzon Arc. During the Pliocene and Pleistocene, sediments accumulated rapidly in the northeastern and southern East Sub-basin and the Southwest Sub-basin. The mean basin-wide sedimentation rate was 70 m/m.y. Basin filling during this phase seems to have been associated with the Taiwan and North Palawan collisions, SCS subduction along the Manila Trench, and Tibetan Plateau uplift. Gravity flow deposits predominate throughout the basin fill. [ABSTRACT FROM AUTHOR]

The present study was conducted to assess the pollution status of the coastal sediments of the Bulgarian Black Sea coastal zone using sediment pollution indices. Eleven sites and twenty-two stations from monitoring grid were selected for the collection of samples. The heavy metal concentrations were used to calculate: geoaccumulation index (Igeo); enrichment factor (EF); contamination factor (CF); modified degree of contamination (mCd); pollution loading index (PLI). In addition, ecotoxicological level of trace metals in sediments was also assessed by comparing with the numerical sediment quality guidelines (SQGs). Mean ERM quotient (mERM-Q) and mean PEL (m-PEL-Q) were applied for assessing the potential effects of multiple heavy metal contamination in sediments. The pollution level assessed by indices related to background level of the studied sites ranged from unpolluted to moderate and only in one case considerably polluted due to heavy metals, mainly Pb and Zn. Ecotoxicological risk was assessed as low and moderately low due to the presence of Pb, Cu, Ni. The northern Danube influenced area of the Bulgarian coastal zone was categorized according to the applied indices as slightly polluted with Zn and Pb. The sediments from the "hot spot" points were with higher accumulation of Ni, Cu and Pb. [ABSTRACT FROM AUTHOR]

Two new free-living marine nematode species of the genus Antomicron Cobb, 1920 belonging to the family Leptolaimidae are described from the seabed sediment of Jiaozhou Bay of the Yellow Sea. Antomicron holovachovi sp. nov. is characterised by loop-shaped amphideal fovea; male with five straight tubular and 41 alveolar supplements; short cephalic setae; slightly curved slender spicule with cephalated proximal end and tapered distal end; and rectangular gubernaculum with a short dorsal caudal apophysis. Antomicron chinensis sp. nov. is particularly characterised by loop-shaped amphideal fovea; male with only alveolar supplements, without tubular supplement; slender and slightly inverted S-shaped spicule with cephalated proximal end and tapered distal end; and rectangular gubernaculum with a slender dorsal caudal apophysis. An updated identification key to species of the genus Antomicron is also provided. [ABSTRACT FROM AUTHOR]

A new approach has been applied to studying marine sedimentation using dispersed sedimentary material in sediment traps compared to the surface layer of bottom sediments. Based on long-term studies of a small sea of the Arctic Ocean, it was possible to establish new sedimentary patterns in the conditions of the Subarctic and Arctic zones. The monthly, seasonal, and long-term dynamics of the main components of fluxes of dispersed sedimentary material have been studied. The marine stage of sedimentation of the main components of dispersed sedimentary material over time is discussed; it is shown that the biogenic component of the flux decreases by an order of magnitude when passing from dispersed to concentrated forms. The average values of the vertical fluxes are calculated: the total and those of the contributions of the main biogenic and terrigenous components per 1 m2 of the bottom and over the entire deep sea area of the White Sea. [ABSTRACT FROM AUTHOR]

Summer cyanobacterial blooms represent a threat to the Baltic Sea ecosystem, causing deoxygenation of the bottom water and the spread of the so-called dead zones. The history of the Baltic Sea cyanobacterial blooms is known from in situ and satellite observations since the early 1980s but is still not well understood. By comparing both weekly resolved sediment trap material and a well-dated sediment core from the eastern Gotland Basin with monitoring and satellite cyanobacterial data of the last ca. 35 years, it is shown here that 6- and 7-methylheptadecane lipids (expressed as 6 + 7Me-C 17:0) may be potentially considered semiquantitative biomarkers for diazotrophic cyanobacteria, and more specifically for Nodularia spumigena. Using this organic proxy, it was thus possible to reconstruct the history of cyanobacterial blooms beyond the observational period with a resolution of 2–4 years since 1860. Cyanobacteria were constantly present but in relatively low abundance until 1920, when they started to alternate between periods with high and low abundance. Interestingly, there seems to be no significant increase in cyanobacterial abundance in the 1950s, when eutrophication and deoxygenation of the Baltic Sea increased considerably. While the early increase in cyanobacteria may be related to a small increase in phosphorus loading, decadal to multi-decadal fluctuations are likely related to variability in the Baltic Sea surface temperature and, ultimately, to the Atlantic Multi-decadal Oscillation. A 7000-year 6 + 7Me-C 17:0 record from the Bothnian Sea also suggests a relationship with the mean summer temperature in the Baltic Sea region but at a multi-centennial to multi-millennial timescale. The intensity of the cyanobacterial blooms in the Baltic Sea is thus likely mainly related to natural processes such as temperature variability, at least at a multi-decadal to multi-millennial timescale. [ABSTRACT FROM AUTHOR]

The South China Sea continental margin in the Qiongdongnan Basin (QDNB) area has incrementally prograded since 10.5 Ma generating a margin sediment prism more than 4km‐thick and 150–200 km wide above the well‐dated T40 stratigraphic surface. Core and well log data, as well as clinoform morphology and growth patterns along 28 2D seismic reflection lines, illustrate the evolving architecture and margin morphology; through five main seismic‐stratigraphic surfaces (T40, T30, T27, T20 and T0) frame 15 clinothems in the southwest that reduce over some 200 km to 8 clinoforms in the northeast. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east. Vertical sediment accumulation rate increased significantly across the entire margin after 2.4 Ma, with a marked increase in mud content in the succession. Furthermore, an estimate of sediment flux across successive clinoforms on each of the three selected seismic cross sections indicate an overall decrease in sediment discharge west to east, away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The QDNB Late Cenozoic continental margin growth, with its overall increased sediment flux, responded to the climate‐induced, gradual cooling and falling global sea level during this icehouse period. [ABSTRACT FROM AUTHOR]

Clinoforms are basinward‐dipping and accreting palaeo‐bathymetric profiles that record palaeo‐environmental conditions and processes; thus, clinothems represent natural palaeo‐archives. Here, we document shelf‐edge scale clinoform sets which prograded through the entire width of an epicontinental marine basin (ca. 400 km), eventually encroaching onto the opposite basin flank, where they started to prograde upslope and landward, in defiance of gravity ("upslope‐climbing clinoforms"). The giant westward‐prograding Eridanos muddy shelf‐edge clinothem originated from the Baltic hinterland in the Oligocene and achieved maximum regression in the Early Pleistocene, on the UK Central Graben (CG) and Mid North Sea High (MNSH), after crossing the whole North Sea mesopelagic depocentre and causing near complete basin infill. Here we integrate well and seismic data through the MNSH and CG and examine the Eridanos final heyday and demise, identifying five clinothem complexes (A1, A2, A3, B and C) and six depositional sequence boundaries (SB1 to SB6) in the Miocene‐Recent section. Tectonic and climatic events drove the recent evolution of this system. Early Pleistocene climate cooling, in particular, resulted in a stepwise increase in sediment supply. This climaxed in the earliest Calabrian, following a likely Eburonian eustatic fall (=SB3) when the Eridanos clastic wedge was restructured from a 100–300 m thick compound shelf‐edge and delta system to a "hybrid" shelf‐edge delta at sequence boundary SB3 (ca. 1.75 Ma). In the ca. 40 kyr that followed SB3, a progradation rate peak (>1,000 m/kyr) is associated with clinoforms starting to accrete upslope, onto the east‐dipping slope between CG and MNSH. This "upslope‐climbing clinoform" phase was quickly followed by the maximum regression and final retreat of the Eridanos system in the Early Calabrian (=SB4), likely as the result of climate‐driven changes in the Baltic hinterland and/or delta auto‐retreat. To our knowledge, this contributions represents the first documentation of "upslope‐climbing clinoforms" recorded in the stratigraphic record. [ABSTRACT FROM AUTHOR]

Two nested clinoform set types of different scales and steepness are mapped and analysed from high‐resolution seismic data. Restoration of post‐depositional faulting reveals a persistent pattern of small‐scale, high‐angle clinoforms contained within platform‐scale, low‐angle clinothems, showing a combined overall progradational depositional system. The large clinoforms lack a well‐defined platform edge, and show a gradual increase in dip from topset to foreset. A consistent recurring stratal pattern is evident from the architecture, and is considered a result of interplay between relative sea‐level change and autocyclic switching of sediment delivery focal points that brought sediment to the platform edge. This un‐interrupted succession records how intra‐shelf platforms prograde. Quantitative clinoform analysis may assist in determining the most influential depositional factors. Post‐depositional uplift and erosion requires restoration with re‐burial to maximum burial depth. Backstripping, decompaction and isostatic correction was performed assuming a range of lithologic compositions, as no wells test the lithology. Nearby wells penetrate strata basinward of the clinoforms, proving mudstone content above 50%, which in turn guide restoration values. Typical restored platform heights are 250–300 m, with correspondingly sized platform‐scale clinoform heights. Typical large‐scale clinoform foreset dip values are 1.3°–2.4°. Small‐scale clinothems are typically 100 m thick, with restored foreset dip angles at 4.4° ‐ > 10°. The results suggest that intrashelf platform growth occurs in pulses interrupted by draping of strata over its clinoform profile. The resultant architecture comprises small‐scale clinoforms nested within platform‐scale clinothems. [ABSTRACT FROM AUTHOR]

The Helgoland Mud Area (HMA) in the German Bight, covering an area of approximately 500 km2, is one of a few depocentres for finer sediments in the North Sea. Radiocarbon and 210Pb analyses revealed continuous sedimentation over the last several centuries. Zinc (Zn) and lead (Pb) contents in the sediments show a distinct increase towards the youngest most sediments with the thickness of the heavy metal enriched sediments ranging from 15 to 103 cm. Stratigraphic data indicate that the onset of heavy metal enrichment is diachronous progressing north-westward over the depocentre, paralleled by a decrease in the thickness of the enriched layer. Beginning already during medieval times, the enhanced input of Zn and Pb seemingly is related to silver and zinc mining in the Harz Mountains and the Erzgebirge, well-known mining areas since the Bronze Age. Both regions are directly connected to the HMA by the Elbe and Weser rivers. Zn and Pb enrichment began in the south-eastern HMA and progressed subsequently with an average of 10 m per year north-westward, most likely triggered by variations in river discharge and by the hydrodynamic setting. Quantitative assessments of the Zn and Pb content in the sediments suggest that since the onset of enhanced Zn and Pb deposition, the anthropic Zn and Pb input in the HMA amounts to ~ 12,000 t and ~ 4000 t, respectively. [ABSTRACT FROM AUTHOR]

This study reports on diversity and distribution of planktonic foraminifera (PF) in the Barents Sea Opening (BSO). Populations of PF living in late summer (collected by means of stratified plankton tows) and recently deposited individuals (sampled by interface corer) were compared. High abundances reaching up to 400 ind.m-3 in tow samples and 8000 ind.m-3 in surface sediments were recorded in the centre of the studied area while low abundances were observed in coastal areas, likely due to continental influences. The living and core-top assemblages are mainly composed of the same four species Neogloboquadrina pachyderma, Neogloboquadrina incompta , Turborotalita quinqueloba and Globigerinita uvula. The two species G. uvula and T. quinqueloba dominate the upper water column, whereas surface sediment assemblages display particularly high concentrations of N. pachyderma. The unusual dominance of G. uvula in the water sample assemblages compared to its low proportion in surface sediments might be the signature of (1) a seasonal signal due to summer phytoplankton composition changes at the BSO, linked to the increase in summer temperature at the study site, and/or (2) a signal of a larger timescale and wider geographical reach phenomenon reflecting poleward temperate/subpolar species migration and consecutive foraminiferal assemblage diversification at high latitudes due to global change. Protein concentrations were measured on single specimens and used as a proxy of individual carbon biomass. Specimens of all species show the same trend, a northward decrease in their size-normalized-protein concentration. This suggests that foraminiferal biomass is potentially controlled by different constituents of their organelles (e.g. lipids). The coupling of data from plankton tows, protein measurements and surface sediments allows us to hypothesize that PF dynamics (seasonality and distribution) are decoupled from their metabolism. [ABSTRACT FROM AUTHOR]

The coast of the shallow Azov Sea is characterized by a series of sand spits. Based on the results of drilling conducted on Dolgaya Spit, which separates the water area of Taganrog Bay from the rest of the Sea of Azov, we consider the structure of the upper part of the geological section of these coastal accumulative forms. Core samples obtained during drilling made it possible to determine the change in thickness of Holocene sand-shell deposits and underlying Middle Pleistocene layers. It is shown that the formation of the spit began more than 5 ka ago during the initial stage of the New Black Sea transgression and occurred as a result of sequential attachment of beach bars to it. [ABSTRACT FROM AUTHOR]

The article presents a brief lithological description of modern bottom sediments collected in the Barents Sea during Cruise 67 of the R/V Akademik Mstislav Keldysh at test sites: (1) "Pechora Sea"; (2) "Western slope of the Kanin Shoal"; (3) "Central Barents Sea (Shtokman area)"; (4) "Russkaya Gavan Fjord"; (5) "Medvezhinsky Trough"; (6) area south of Spitsbergen; (7) "Kola Meridian"; (8) "Spitsbergen–Franz Josef Land Archipelago"; (9) "Cambridge Strait." Distribution of Cr, Ni, Cu, Zn, Cd, and Pb in samples of modern bottom sediments (pelitic, aleuritic–pelitic and sandy–aleuritic–pelitic ooze) is compared with background concentrations and contents of these elements in the Post-Archean Australian Shale (PAAS). The data obtained are consistent with the notion that the distribution of heavy metals and other elements in bottom sediments is controlled primarily by the global geochemical background. Relationship of Sc, V, Cr, Ni, Y, Zr, Nb, Mo, Hf, Th, U, and REE concentrations with contents of the fine pelite (<0.001 mm) fraction and organic carbon (Corg) is considered. It was found that most of these elements are characterized by a moderate positive correlation with the fine pelite fraction in samples. Based on the coefficient of their correlation with the Corg content, the above elements can be assigned to three groups with: (1) moderate positive correlation, (2) low positive correlation, and (3) virtual absence of correlation. Distribution of element-indicators of the source rock composition (Sc, Th, Co, Cr, La, and Sm) and REE in modern bottom sediments of the Barents Sea indicates that the majority of them are geochemically mature, and they were sourced from the Kola Peninsula and Spitsbergen (?).Bottom sediments of the Cambridge Strait are represented by geochemically less mature material, which, apparently, entered the sea as a result of erosion of rocks of the Franz Josef Land Archipelago. [ABSTRACT FROM AUTHOR]

Boreholes provided with biostratigraphic data indicate major changes in the Miocene sediment accommodation rates in the northern Campine Block, located in the southern North Sea Basin. Low sediment accommodation rates took place during the early to middle Miocene and abruptly increased into the late Miocene. Two processes likely explain these observations. First, the long‐time (±10 Myr) slow sedimentation of fine sands with a high—in part authigenic—glauconite content (of up to almost 50%) suggests that the southern North Sea area was sediment starved during the early to middle Miocene. Sediment starvation ended with the start of the late Miocene when the area became covered by west‐prograding clinoform sets of coarser sands with mainly reworked glauconite as part of the proto‐Rhine system. The latter sands filled the accommodation space that was left after early to middle Miocene sediment starvation. Second, accelerated subsidence during the late Miocene created additional accommodation space to be filled compared with the early to middle Miocene. A mechanism that explains well the regional accelerated subsidence is lithospheric folding or buckling. The timing and geometry of accelerated rates of subsidence in the southern North Sea area are indeed consistent with deformation that was thought to have been related to lithospheric folding in areas further south (in the direction of the Alps) under NW‐Alpine compression. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of high-quatity deep seabed sediment pressure-main-taining sample dunng the scientiric researches of deep seabed under full sea depth, a mechanical handheld devce with pressure-maintaining function wao designed in accordance with the maneuverabitity of the manned Submarine 0perations. The key components such as pressure-maintaining container and pressure c0mpensati0n device of sediment air-tight sampler under full sea depth were analyzed and calculated. Fnntte element simulation analysis was peff0rmed under full sea-deep pressure environments. The resutts show that the stress and strain of the sampler increase wtth the increase of the applied pressure, the maxirnurn stress and Strain appear at the positions of the end cap and the cylinder seal, and stress and strain are small in the contact position of the square stopper and the pressure-maintaining cylinder end caps with good seating performance. Firrally, the internal pressure tests rand the maitipulator cooperative tests of the full sea-deep Sediment aittight Samplers were carried out. The results of tests verify the feasibility of the pressure-maintaining peforrmance and the of the mairipulator for the full aea-deep Sediment airtight samplers. [ABSTRACT FROM AUTHOR]

Perfluoroalkyl substances (PFAS) and organochlorine pesticides (OCPs) in surface sediments were investigated from the Bering Sea, the Chukchi Sea and adjacent Arctic Ocean in 2010. Total concentrations (dry weight) of Σ 14 PFAS in surface sediments (0.85 ± 0.22 ng g−1) of the Bering Sea were lower than that in the Chukchi Sea and adjacent Arctic Ocean (1.27 ± 0.53 ng g−1). Perfluoro-butanoic acid (PFBS) and perfluoro-octanoic acid (PFOA) were the dominant PFAS in these areas. The concentrations of Σ 15 OCPs in the sediment of the Bering Sea (13.00 ± 6.17 ng g−1) was slightly higher than that in the Chukchi and Arctic Ocean (12.05 ± 2.27 ng g−1). The most abundant OCPs were hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane (DDT) and its metabolites. The composition patterns of HCHs and DDTs indicated that they were mainly derived from the early residues via river runoff. Increasing trends of PFAS, HCHs and DDTs in surface sediments from the Bering Sea to the Arctic Ocean were found, indicating oceanic transport. In summary, the concentrations of OCPs were orders of magnitude greater than the observed PFAS concentrations, and the concentrations of PFAS and OCPs in surface sediments from the Bering Sea to the Chukchi Sea and adjacent Arctic Ocean are at the low to moderate levels by comparing with other coastal and marine sediments worldwide. • PFAS and OCPs were determined in surface sediments of the adjacent Arctic Ocean. • OCPs were orders of magnitude greater than the observed PFAS. • PFOA was the main compound, and the most abundant OCPs were HCHs and DDTs. • Industrial activities may be responsible for high levels of PFAS in the Bering Sea. • An increasing latitudinal trend of OCPs were observed. [ABSTRACT FROM AUTHOR]

Abstract—Lithological–facies zonality of Neo– and Eopleistocene sediments from the Fiji Sea is described for the first time. Processing of corresponding maps and isopachite schemes using A.B. Ronov's volumetric method gave us an opportunity to calculate the quantitative parameters of sedimentation for distinguished types of Pleistocene sediments. Carbonate sediments dominate over other groups of sediments. Carbonate planktonic sediments have been more intensively accumulated in the Neopleistocene than in the Eopleistocene. The highest volcanotectonic activity is typical of Eopleistocene. [ABSTRACT FROM AUTHOR]

With the phasing out of traditional polybrominated diphenyl ethers (PBDEs), significant volumes of alternative brominated flame retardants (aBFRs) are being used and released into the environment compartment, especially in coastal regions. The levels and distribution of PBDEs, aBFRs, and dechlorane plus (DPs) were investigated in the surface sediments of the Yellow Sea (YS) and East China Sea (ECS) to examine the distribution and sources of these hydrophobic contaminants. The level and distribution of pollutants in the sediments of YS and ECS show obvious regional differences. As a major replacement for decabromodiphenyl ether (BDE 209), decabromodiphenyl ethane (DBDPE) was the dominant compound observed in the surface sediments, with a concentration one order of magnitude higher than that of BDE 209. High concentrations were found in the depositional zones of the YS, indicating that these contaminants may originate from land-based pollution sources (likely from the Laizhou Bay manufacturing base) near the Bohai Sea. The pollutants can be carried by the coastal current together with the sediment from the Yellow River, transported through the Bohai Strait and deposited in the mud zone of Northern and Southern YS. Low levels of halogenated flame retardants (HFRs) were found in the estuary of the Yangtze River and ECS, indicating that Yangtze River contributes less HFRs to the region. Riverine discharge, atmospheric deposition, surface runoff, ocean current system, and mud area deposition effects may be significant factors influencing the distributions of HFRs. Image 1 • Halogenated flame retardants were investigated in the sediments of Yellow and East China Seas. • DBDPE was the predominant contaminant and is one order of magnitude higher than BDE 209. • High levels of HFRs were found in the depositional zones of the Yellow Sea. • HFRs from the Bohai Sea was the major source of HFRs in the Yellow Sea. • Yangtze River contributed less HFRs to the sediments of East China Sea. [ABSTRACT FROM AUTHOR]

Summer cyanobacterial blooms represent a threat for the Baltic Sea ecosystem, causing deoxygenation of the bottom water and the spread of the so-called dead zones. The time history of the Baltic Sea cyanobacterial blooms is known from in situ and satellite observations since the early 1980s, but still not well understood. By comparing both weekly-resolved trap sediments and a well-dated sediment core from the Eastern Gotland Basin with monitoring and satellite cyanobacterial data of the last ca. 35 years, it is shown here that 6- and 7-methylheptadecane lipids (expressed as 6+7Me-C17:0) are robust semi-quantitative biomarkers for diazotrophic cyanobacteria, and likely mainly for Nodularia spumigena. Using this organic proxy, it was thus possible to reconstruct the history of cyanobacterial blooms beyond the observational period with a resolution of 2-4 years since 1860. Cyanobacteria were constantly present, but in relatively low abundance until 1920, when they started to alternate between periods with high and low abundance. Interestingly, there seems to be no significant increase in cyanobacterial abundance in the 1950s, when eutrophication and deoxygenation of the Baltic Sea increased considerably. Decadal to multi-decadal fluctuations are likely rather related to variability in the Baltic Sea surface temperature and, ultimately, to the Atlantic Multidecadal Oscillation. A 7000 years long 6+7Me-C17:0 record from the Bothnian Sea also suggests a relationship with the mean summer temperature in the Baltic Sea region, but at a multi-centennial to multi-millennial timescale. The intensity of the cyanobacterial blooms in the Baltic Sea is thus likely mainly related to natural processes such as temperature variability, at least at a multi-decadal to multi-millennial timescale. [ABSTRACT FROM AUTHOR]

In the Bering Sea shelf, annual changes in the sea ice extent are large. In this study, we compare the viable diatom resting stages in sediments during the summer of 2017 when the sea ice retreat was late and 2018 when the sea ice retreat was early. South of St. Lawrence Island, the germinating cell number was 10–100 times greater in 2018 than it was in 2017. The taxonomic composition also showed large annual differences: Fragilariopsis/Fossula spp., which are ice algae species, were abundant in 2017, but Thalassiosira spp. dominated in 2018. Satellite observations confirmed that sea ice diminished before the ice-edge bloom in 2018, but sea ice remained until the ice-edge bloom in 2017. This study shows that the community composition of viable diatom resting stages is largely affected by the timing of the sea ice retreat. [ABSTRACT FROM AUTHOR]

We present new data on the rates of sedimentary denitrification and its component processes (canonical denitrification, anammox and dissimilatory nitrate reduction to ammonium) for intertidal and subtidal sites in the North Sea using nitrogen isotope addition methods. We find overall average denitrification rates of 6.3 (range 0.4–10.6) µmol m−2 h−1, similar to those previously reported for this region and other temperate shelf environments. We find canonical denitrification to be the dominant (>90%) process of the three. At the subtidal sites, most of the denitrification is supported by nitrate generated within the sediments, while at the intertidal site the main source is from the water column. We go on to consider the impact of these rates on nitrogen cycling within the North Sea region and compare the sediment core incubation rate results to estimates derived from modelling approaches. Model rates are somewhat higher than those directly measured and we consider possible reasons for this. • New measurements of denitrification, anammox and DNRA rates in North Sea sediments. • Denitrification is the dominant process and rates measured compare well to other direct measurements. • Model estimates suggest rather higher rates of nitrogen loss compared to direct measurements and some reasons for this difference are considered. [ABSTRACT FROM AUTHOR]

The quantitative characteristics of the bottom sediment color of the Chukchi Sea is presented. The correlation relationships with the contents of grain-size fractions, chemical elements, and biogenic components are analyzed. The diagenetic factor influence is considered. The prospects of the colorimetric index such as saturation S is noted in the matter of lithostratigraphy. [ABSTRACT FROM AUTHOR]

A high-resolution astronomical-tuned magnetostratigraphy was obtained from a continuous 333-m succession recovered at International Ocean Discovery Program (IODP) Hole U1499A in the north margin of the South China Sea (SCS) during joint Legs 367 & 368. A total of 12 magnetic reversals are identified through the Pliocene and Pleistocene. The cycle analysis of natural gamma ray (NGR) data shows an average suite of ca. 33 m and 8 m wavelengths with lesser 1.5-m cycles, which are consistent with the ratios of Milankovitch orbital-climate oscillations caused by long eccentricity (405 kyr), short eccentricity (~100 kyr), and precession (~20 kyr). The astronomical-tuned magnetostratigraphy correlates with nearly all features of the Pliocene-Pleistocene geomagnetic polarity time scale. There was a significant shift to ~100-kyr-dominated cyclicity at ca. 1.3 Ma, which marks the onset of the Mid-Pleistocene Transition, during which the influx of the clay component decreased. A general enrichment in silt-sand influx during the past 0.4 Myr was punctuated by surges in coarser-grained components (lowest NGR) during or at the end of each major global glacial event. Comparison to a high-resolution sediment record spanning the Pliocene-Pleistocene on the southern margin of the SCS (ODP Site 1143) indicates common intervals of changing rates of sediment accumulation. In both regions, there are relatively lower rates of sediment accumulation during the late Zanclean (mid-Pliocene; ca. 4.1 to 3.6 Ma), early Gelasian (ca. 2.5 to 2.0 Ma), early Calabrian (ca. 1.6 to 1.4 Ma) and the earliest Middle Pleistocene (ca. 0.6 Ma). The merger of magnetostratigraphy, cyclostratigraphy and the NGR record to produce a high-resolution profile of bulk sediment accumulation rates and relative clay to sand-silt components is a powerful tool and climate proxy to reconstruct the general history of sediment input into the SCS and its relationships to East Asia monsoon and tectonic evolution. • First astronomical-tuned magnetostratigraphy from South China Sea (SCS) IODP cores • Lower accumulation rates during late Zanclean, early Gelasian and early Calabrian • Mid-Brunhes Event (500 ka) marks the onset of major coarser-grained clastic input. • Astronomical-tuned NGR events correlate to global benthic foraminifer δ18O curve. • Apparent synchronous sediment accumulation trends in northern and southern SCS [ABSTRACT FROM AUTHOR]

In this study, we investigate the role of sedimentary N cycling in the Southern North Sea. We present a budget of ammonification, nitrification and sedimentary NO3- consumption/denitrification in contrasting sediment types of the German Bight (Southern North Sea), including novel net ammonification rates. Dissolved inorganic nitrogen concentration (nitrate, nitrite and ammonium) in the water column showed low levels between 0.2 to 3.2 μmol L-1. We incubated sediment cores with labeled nitrate and ammonium to calculate net and gross N transformation rates. The results show that impermeable sediments are the main site of ammonification (on average 10.2 ± 1.2 mmol m-2 d-1) and that they are an important source for primary producers in the water column, contributing ~ 17 to 61 % of reactive nitrogen in the water column. Ammonification and oxygen penetration depth are the main drivers of sedimentary nitrification. One third of freshly produced nitrate in impermeable sediment and two-thirds in permeable sediment were reduced to N2. The semi-permeable and permeable sediments are responsible for ~ 80 % of the total benthic N2 production rates (~ 890 t N d-1) in the southern North Sea. We conclude that impermeable sediments are important sources of reactive N and that semi-permeable and permeable sediments are the main sinks of reactive N, counteracting eutrophication in the southern North Sea (German Bight). [ABSTRACT FROM AUTHOR]

In this study five sedimentary cores were collected from Gorgan Bay (southeastern part of the Caspian Sea). Concentrations of elements were measured to determine depositional trends and geostatistical assessment of toxic elements was carried out. Al, Fe, K, Mg, Na and S content increased in all 5 cores, from the bottom to near the top layer, with maximum concentrations at 15–45 cm depths. However, for the toxic elements, maximum concentration of As, Cr, Cu, Pb, Zn, Co and Ni varied in different depth of 5-15 cm and 80-120 cm. Enrichment factors (EFs) and pollution load index (PLI) were calculated to assess the enrichment and pollution of heavy elements in the bay sediments. Except for Ca and S, all studied elements showed positive and significant correlations with Fe and Al, which indicate the same source (human or natural). Principal component analysis (PCA) indicated that sediments were influenced by both geologic and anthropogenic impacts. According to the EFs, most toxic elements showed no significant enrichment and no pollution in the core sediments. Based on PLI average value in all cores, the southeast coast of the Caspian Sea (Gorgan Bay) should be classified as not metal polluted, but in recent decades there has been a dramatic increase of toxic elements that needs more attention and also monitoring. [ABSTRACT FROM AUTHOR]

In this study, levels, distributions, and sources of polycyclic aromatic hydrocarbons (18 compounds) and organochlorine pesticides (19 compounds) in surface sediments of 14 stations from Edremit Bay (Aegean Sea) were investigated in April and November 2015. ΣPAH concentrations (0.65–175 ng/g) in Edremit Bay sediments indicated low pollution. ΣPAH levels were decreased in the order of inner (81.1 ± 47.0 ng/g), northern (48.4 ± 15.9 ng/g), and southern (19.0 ± 15.8 ng/g) bays. p,p'-DDE was the only organochlorine pesticide detected in Edremit Bay sediments and found between nd to 1.16 ng/g dw. According to sediment quality guidelines, PAHs and p,p'-DDE levels in Edremit Bay were below the threshold effect level, effect range low, and threshold effect concentration limits and the sediments have no potential ecological risks. Two- to 3-ring PAHs were found at higher levels than 4- to 5-ring PAHs. Molecular PAHs ratios and Principal Component Analysis-Multiple Linear Regression analyses indicated combustion of wood-coal and vehicle emissions might have contributed to PAH levels in the bay. [ABSTRACT FROM AUTHOR]

Bedforms are ubiquitous features in rivers and shallow seas, as mobile sediment is transported by flowing water. The mutual interaction of hydrodynamics and bedform has been widely studied in the laboratory over two‐dimensional bedforms having an angle‐of‐repose (30°) lee side and a relatively simple shape. However, the influence of bedform natural morphology and three‐dimensionality on the flow is still poorly constrained. The present work looks at how a natural three‐dimensional (3‐D) bedform field influences flow properties through high‐resolution numerical modeling. A 3‐D numerical model is set up with Delft3D and verified against lab experiments of idealized 3‐D bedforms. The model is used to simulate water velocities, turbulence, water levels, and bed shear stress above a natural bedform field from the Río Paraná (Argentina). The presence and size of the flow separation zone and turbulent wake depend on the presence and properties of the slip face (defined here as the portion of the lee side with angles >15°) and not on those of the crest. When present, the flow separation and wake lengths are, for the tested settings, respectively, around 5 and 13 times the slip face height. A slip face orientation of 25° or more compared to the flow increases cross‐stream flow and suppresses flow reversal over the slip face. To understand and predict flow and bedform properties, the slip face rather than the crest position should be identified and analyzed. Plain Language Summary: In rivers and at the coast, the water flows fast and moves sand. This often forms underwater dunes, exactly like the movement of sand by wind forms desert dunes. These underwater dunes can be several meters high and are therefore a danger for navigation. They move and can be a risk for offshore structures (like wind farms). Understanding the movement of water above dunes helps to say how dunes will move. In the past, it has often been done over dunes made in the laboratory. In the work presented here, we look at how water is moving above natural dunes, which were measured in the Paraná River in Argentina. For this, we use a numerical model: A computer calculates how the water is moving above the measured dunes. We found that water movement depends on the part of the dunes which is the steepest, called the slip face. It does not depend on the highest point, the crest, as previously thought. Therefore, when studying a dune, the slip face properties should be looked at in order to say how water will move over the dune. Our work will make it easier to say how dunes and water move. Key Points: The slip face is defined as the portion of a bedform lee side with angles steeper than 15°Reverse flow and turbulent wake properties are linked to the characteristics of the slip face more than to bedform heightThe length of the flow separation zone and the turbulent wake are, for the tested settings, 5 and 13 times the height of the slip face [ABSTRACT FROM AUTHOR]

Redox-sensitive elements (uranium, molybdenum and cadmium) and productivity proxies (total organic carbon, calcium carbonate and phosphorous) were analysed to assess the importance of productivity on redox variation for the last ∼18 kyr in a sediment core off Cochin at a water depth of 280 m in the southeastern Arabian Sea. These proxies document a combination of higher productivity and intense suboxic conditions during the last deglaciation (∼18–13 kyr) and late Holocene (5.5 kyr to Present) versus lower productivity and less suboxic conditions between these intervals (∼13–5.5 kyr). The productivity and redox proxies behave similar to one another suggesting that the variations in productivity controlled the redox conditions. This relationship is supported by patterns during the last deglaciation, when a decrease in productivity at ∼16 kyr preceded improved deep water oxygenation by ∼14 kyr. Therefore, productivity changes were responsible for the development of reducing conditions in shallow waters in the southeastern Arabian Sea. [ABSTRACT FROM AUTHOR]

Abstract The combined use of artificial (137Cs, 238,239+240,241Pu, 241Am) and naturally occurring (210Pb/226Ra, 40K) radionuclides as tracers for dating of the Black Sea sediments has allowed to reveal the recent increase in radioactive contamination of this basin with 137Cs after the Chernobyl accident. This is presumably caused by the prolonged input of the man-made radionuclides that showed a rise in the late 1990s – early 2000s, and by a possible post-deposition remobilization of 137Cs from the seabed. Highlights • Three peaks trend was shown for the 137Cs profiles in the Black Sea sediments. • Plutonium data was used as an additional tracer for 137Cs peaks origin verifying. • The upper 137Cs peak indicates the secondary contamination of the basin. • The secondary contamination concept is in good agreement with monitoring data. [ABSTRACT FROM AUTHOR]

Polyhalogenated carbazoles (PHCZs) have recently emerged as a group of halogenated pollutants with broad occurrences and bioaccumulation potential in aquatic systems. However, investigations on their occurrences in coastal waters remain very limited. In the present study we investigated PHCZs in surface sediment collected from 29 sites in Sanmen Bay, East China Sea. The results demonstrated a universal presence of PHCZs in sediment, with concentrations of ∑PHCZs (including all congeners) ranging from 7.7 to 17.5 ng/g dry weight (median: 11.3 ng/g dw). The PHCZ congener composition profile revealed a dominance of 3,6-dichlorocarbazole (36-CCZ) with comparable concentration with that of carbazole. Given that PHCZs are widely distributed in Sanmen Bay sediment and their concentrations rivaled other well-known persistent organic pollutants in the same area, this group of halogenated pollutants merits additional investigations of their potential risks to the studied aquatic system, as well as other important watersheds. [ABSTRACT FROM AUTHOR]

Image 1 [ABSTRACT FROM AUTHOR]

Using inductively coupled plasma mass spectrometry (ICP-MS), the distribution of rare-earth elements (REE) at the surface and Holocene sediments of the Chukchi and East Siberian Seas was studied in two cores of up to 8.5 ka in age. The total REE concentration of the surface sediments of the Chukchi Sea varied from 62 mg kg−1 to 169 mg kg−1. The NASC-normalized REE patterns were relatively similar to each other and are characterized by a slight enrichment in the middle lanthanides. The total REE concentrations in surface sediments from the East Siberian Sea ranged from 123 mg kg−1 to 200 mg kg−1. The normalized patterns showed a strong predominance of light REE, in particular, La and Ce. The main concentrators of REE are the sand and silt fractions of the sediment. The East Siberian Sea is characterized by REE association with elements contained in heavy stable clastic minerals (Zr, Nb, Hf, Th, and Ti). REE in this region are derived from the erosion of the mainland coast and the New Siberian Islands ice complex, as well as from river discharge, primarily from the Lena River, the basin of which comprises ancient crystalline shield and magmatic rocks enriched in light REE. The sediments in the eastern and southern Chukchi Sea have low REE contents, indicating that the terrigenous flux supplying the Chukchi Sea is through the Bering Strait. [ABSTRACT FROM AUTHOR]

• Methane hydrate production was assessed in South China Sea sediments. • Higher hydrate saturation increased the dissociation duration. • Dissociation duration barely affected the return time of sediment temperature. • Double depressurization is employed to increase the production efficiency. Marine methane hydrate is a considerable energy source for use in the near future. With great obstacles to spot production, researchers are focusing on the production characteristics of hydrates in various experimental systems, such as glass beads, clay, silica sand and so on. This study investigated the production behaviors of methane hydrate in the real South China Sea sediments using depressurization method. The hydrate saturations of the remolded hydrate-bearing sediments ranged from 10.10% to 23.76%. The results indicate that an 8% increase of hydrate saturation can prolong the dissociation duration under the same backpressure of 2 MPa by 120 min. In addition, the excess temperature drop caused by the depressurization may induce the unpredictable occurrence of hydrate reformation or icing; therefore, a double depressurization method that depressurizes to 2 MPa (second stage) after 20 min maintenance at 4 MPa (first stage) is employed in order to shorten the temperature drop in the first stage and increase the dissociation rate in the second stage. The results of this study are significant for the spot production of marine hydrates in order to achieve high efficient gas production. [ABSTRACT FROM AUTHOR]