Sediment accumulation and budget in the continental margins provides abundant information of source-sink processes from the land to the sea, including weathering, human activities and sedimentary ...environment. Here we show the distribution of mud areas, modern sedimentation rates and sediment budget in the Bohai Sea, Yellow Sea and East China Sea. Using grain size data of >18,000 surface sediment samples and 210Pb data from 413 sites, we identify five areas with sediments mainly composed of fine-grained fractions (mean grain size >6 φ) and find a relatively high sedimentation rates of >1.5mm/yr in the mud areas. Near the Yellow and Yangtze River deltas sedimentation reaches >95.0mm/yr. Approximately 1185.4×106tons of fine-grained sediment accumulate annually in the mud areas of the east China seas. Atmospheric deposition contributes <2% (18.37×106 tons/yr), while the riverine sediment inputs account for >75% (917×106tons/yr). The remainder comes from all other sources including coastal erosion and resuspension of bottom sediments. In addition, ~45% of the fluvial sediment supply deposits on the subaerial delta, ~40–50% is trapped on the subaqueous delta and shelf, and the remainder <5% escapes the shelf edge. The results will be a strong foundation for understanding of the transport, deposit and preservation of sediment and other relevant material (e.g. carbon and nutrient etc.) of terrestrial materials in the sea.
•Distribution of modern sedimentation rates in the Bohai Sea, Yellow Sea and East China Sea were illustrated.•Five mud deposit areas with sediments mainly composed of fine-grained fractions were identified.•The sediment budget and mass balance within a source-sink perspective was constructed.
This study investigated the distribution and characteristics of microplastics in surface sediments of the Gulf of Thailand (GoT), and discussed the correlation between sediment grain size and ...microplastic content. The results indicate the abundance of microplastics is 150.4 ± 86.2 pieces/kg dry weight, representing a medium microplastic pollution level compared to other sea areas. Small microplastics (0.5–1 mm) take up >70% of total microplastic numbers. Fibrous microplastics are the dominant component of microplastics. According to micro-Fourier transform infrared spectroscopy, rayon (37%) and polyester (PES: 16%) are the most typical polymer types found in sediments. The results imply that secondary microplastics are the dominant pollutant, while fibrous microplastics are mainly from municipal sewage discharge. We also find that inconspicuous correlation between grain size and microplastics, which is caused by the multi-sources and different flow field. This study deepens our understanding of the environmental risks posed by microplastics to marine ecosystems in the GoT.
•Gulf of Thailand has medium plastic pollution level compared to surrounding areas.•Small microplastics (0.5–1 mm) dominate the microplastic share.•Fibrous microplastics are the dominant component in sediments.•Rayon and polyester are most common polymers found in sediments.
This study focuses on sedimentary research at the subaqueous Changjiang (Yangtze River) delta, based on five high-resolution seismic profiles and seven borehole cores with accurate AMS 14C datings. ...Three distinct seismic units were identified from the seismic profiles according to seismic reflection characteristics, and five sedimentary facies were recognized from borehole cores. These facies constituted a fining upward sedimentary sequence in relation to postglacial sea-level transgression. Three sequence surfaces (sequence boundary (SB), transgressive surface (TS), and maximum flooding surface (MFS)) demarcate the boundaries between early transgressive system tract (E-TST), late transgressive system tract (L-TST), early highstand system tract (E-HST) and late highstand system tract (L-HST), which constitute the sixth order sequence. These system tracts were developed coevally with postglacial sea-level rise. E-TST (~19–12kaBP) corresponds to an incised-valley infilling in the early stages of postglacial transgression whereas L-TST (~12–7.5kaBP) was formed during the last stage of postglacial transgression. The progradational structure of L-TST reflected in seismic profiles is possibly related to the intensification of the East Asian summer monsoon. E-HST (~7.5–2kaBP) was deposited in response to the highstand after maximum postglacial transgression was reached, while L-HST (~2kaBP–present) was initiated by accelerated progradation of the Changjiang delta.
•Sedimentary facies in relation to postglacial sea level change were revealed.•A facies mode of the tidally dominated paleo-Changjiang estuary was proposed.•A sixth order sequence had been recognized in the subaqueous Changjiang delta.
The study of critical geological processes of sediments from source to sink in the East China Sea (ECS) is of great significance for further understanding the surface processes, material cycling, and ...sedimentary evolution in the East Asian continental margin. Based on the high-resolution clay mineralogy and REEs in fine-grained sediments of Core CSHC-15, this study has analyzed the periodic transition mechanism of sinks in fine-grained sediments in the ECS from a source-to-sink perspective. The clay mineral provenances of Core CSHC-15 exhibited distinct periodic abrupt shifts between the Changjiang and Taiwan island over the past 200 kyr, indicating the periodic transitions of sinks in fine-grained sediments between the inner shelf of the ECS and the Okinawa Trough. When the sea level rose or fell to a critical depth (around −25 m or −50 m), the changes in the accommodation space of the continental shelf and the shelf fronts were the direct factors leading to the periodic transitions of sinks in fine-grained sediments in the ECS. The intense eccentricity cycles (100-kyr) of the clay mineral parameters of Core CSHC-15 reflected the impacts of the East Asian Winter Monsoon (EAWM). This study confirms that long-term (eccentricity and longer cycles) climate signals of the source areas can be extracted from the clastic sedimentary records of the ECS. The new finding highlights the periodic transition mechanism of sedimentary sinks in the ECS that will promote the progress of sedimentary geology since the Late Quaternary.
•We report high-resolution clay mineralogy and REEs in fine-grained sediments of Core CSHC-15.•The provenances exhibited periodic abrupt shifts between Changjiang and Taiwan over the past 200 kyr.•Frequent abrupt shifts in provenances indicate the periodic transitions of sinks.•The changes in accommodation space and shelf fronts are the direct factors leading to the periodic transitions of sinks.
Sediment accumulation in continental margins during the Quaternary Period was substantially influenced by both sea-level fluctuations and climate changes. However, the response of sediment ...accumulation to these changes on an orbital timescale, remains poorly understood, for two main reasons: the scarcity of sedimentary records with a high-resolution chronology, and the difficulty in distinguishing the role of sea-level from regional climate signals. Here we present the results of sediment color reflectance (c*), grain size and total organic carbon (TOC) content of core BH08 (212.4 m in length, spanning the last ~1 Myr) recovered from the Bohai Sea, China. The chronology of core BH08 on the orbital timescale is constrained by both magnetostratigraphy and astronomical tuning. Sedimentary facies analysis suggests that the sedimentary sequence is dominated by the alternation of a deltaic system and floodplain deposition. Principal components analysis of the grain-size data reveals two principal components (PCs), including PC1, reflecting the 31–500 μm fraction, and PC2, reflecting the 18–66 μm fraction. Comparison of sample scores on PC1, PC2 and c* with the alternation of sedimentary environments reveals that PC1 and c* reflect cycles of deltaic and floodplain deposition at ~100-kyr and ~40-kyr periodicities, while PC2 exhibits a ~20-kyr periodicity, in addition to the ~100-kyr and ~40-kyr cycles. We infer that PC1 and c* are mainly sea-level dependent, whereas PC2 is controlled by the combination of changes in monsoon climate and sea level. We suggest that Milankovitch-scale monsoon climate fluctuations controlled the sediments supply to the Bohai Sea during the last ~1 Myr, while the redistribution of sediments by marine processes (e.g., tidal currents) has partially obscured the monsoonal signal in the grain-size proxy (e.g., PC1) which instead is sensitive to sea-level change. Our results provide an example of the influence of climate and sea-level on sediment accumulation in a shallow continental margin setting influenced by monsoonal climate in an icehouse world.
•A 1-Myr record of orbitally-forced continental margin deposits is presented.•Principal components analysis of grain size reveals sea-level and climate signals.•Sedimentation in the Bohai Sea is influenced by sea level and monsoonal climate.•Monsoon signal could be obscured by marine process (e.g., tidal currents).
Sedimentary architecture dominated by transgression–regression cycles in the shallow Bohai shelf region contains information about global sea-level, climate and local tectonics. However, previous ...studies of transgression–regression cycles in this region at orbital timescales that extend back to the early Pleistocene are sparse, mainly because of the shortage of well-dated long cores. Although transgression–regression sedimentary cycles in the region have been interpreted in terms of local tectonics, sea-level, and climate change, the detailed structure of marine transgressions and their significance for Quaternary global sea-level variations remains to be examined. In this study, we present an integrated sedimentological, geochemical and paleontological study of a 212.4 m (∼1 Ma) core (BH08) recovered from the Bohai Sea, China, for which an astronomically-based age model is available. Correspondence between marine-terrestrial sedimentary cycles and global sea-level fluctuations suggests that stacking of marine and terrestrial sediments was driven mainly by glacio-eustatic sea-level fluctuations in a context in which tectonic subsidence was largely balanced by sediment supply over the last ∼1 Ma. We report a dominant 100-kyr cycle beginning at ∼650 ka, which reflects the worldwide influence of the mid-Pleistocene transition (MPT) in sea-level records. We find that neritic deposits after the MPT were relatively thicker than before the MPT, which indicates an important control of the MPT on sedimentary architecture through lengthening of the duration of sea-level highstands.
•Marine and terrestrial deposition alternated in the Bohai Sea over the last ∼1 Ma.•Sea-level changes governed the sedimentary architecture in the Bohai Sea.•The MPT influenced the deposition through modulating sea-level changes.
The East Siberian Arctic Shelf (ESAS) is a crucial area for sea ice formation and exportation in the Arctic Ocean. Precise sedimentary identification in the ESAS is vital to trace sea ice transport. ...However, tracking sea ice transport is challenging due to the complexity of the sediment sources and transport processes in the ESAS. In this study, we investigated Sr, Nd, and Pb isotopes in residual fractions of recent surface sediments in the ESAS to explore the distribution, sources, and transport pathways of terrigenous materials and track regional sea ice transport. Our results show that approximately 20–30% of the Western Laptev Sea (WLS) sediments were derived from Siberian flood basalt, characterized by a high εNd (ca. -9.0) and a high 87Sr/86Sr ratio (ca. 0.715). Furthermore, most sediments of the Eastern Laptev Sea–Western East Siberian Sea (ELS–WESS) were derived from ancient clastic and metamorphic rocks, with the lowest εNd values (ca. -12.3), highest 87Sr/86Sr ratios (ca. 0.717), and highest 207Pb/206Pb ratios (ca. 0.836). Additionally, sediments in the Eastern East Siberian Sea–Western Chukchi Sea (EESS–WCS) had the highest εNd values (ca. -7.6), lowest 87Sr/86Sr ratios (ca. 0.712), and relatively high 207Pb/206Pb ratios (ca. 0.830) due to the influence of Okhotsk–Chukotka volcanic belt (OCVB) weathering products, which contributed approximately 10–20% of the local sediments. Eastern Chukchi Sea (ECS) sediments showed relatively low εNd values (ca. -9.2), low 87Sr/86Sr ratios (ca. 0.712), and the lowest 207Pb/206Pb ratios (ca. 0.810), which probably influenced by coast erosion inputs from Alaska and Yukon River material transported via Pacific Sea Water. Based on the sediment provenance with Nd isotope, sea ice formed in the WLS and ELS–WESS is predominantly transported by the Trans-Polar Drift (TPD) to the Eurasian Basin and Fram Strait. This study provides insights for further understanding and tracking sea ice transport processes from the ESAS to the Arctic Ocean.
•Western Laptev Sea sediments are derived from Siberian flood basalt and old crust.•Eastern East Siberian Sea sediments are influenced by Okhotsk–Chukotka volcanic belt.•Eastern Laptev Sea and Western East Siberian Sea are the primary sources of sea ice sediment in the Eurasian Basin.•The combination of SrNd isotopes and smectite can improve the sediment source identification in the Arctic.
The long-term evolution of deep-sea turbidity current activity is closely related to climate and sea level changes; however, the impact of abrupt climate change (e.g. millennial-scale events in high ...northern latitudes) is poorly known. In this paper, deep-sea turbidite records in the western part of the lower Bengal Fan were identified since the Last Glacial Maximum (LGM) to investigate the effects of abrupt climate change on the development of the Earth's largest deep-sea fan. Our records show a termination of turbidite activity in the western lower fan at 16.6 ka–15.4 ka almost contemporaneous with Heinrich 1 event (a cooling stadial in high northern latitudes). The trigger of this termination in turbidite activity may have been a sharp decrease in erosion rates during a time of relatively stable sea level and rapid source-sink processes. The subsequent episodes of the Bolling/Allerod warm interstadial and Younger Dryas cold stadial and the rapid sea level rise event that followed possibly induced adjustment of turbidity current activities in the Bengal Fan, as indicated by other published records. In summary, we show that close links exist between abrupt climate changes in the high-latitude Northern Hemisphere and deep-sea turbidity current activity in the low-latitude South Asia.
•Deep-sea turbidite records in the Bengal Fan since LGM were recovered.•Termination of turbidite in the western lower fan was triggered by HS1 event.•Links between high latitudes climate and low latitudes sedimentation were revealed.
Delta are vital habitats for people and biotic communities. Many of the world's large river deltas are shrinking because of relative sea level rise and intensifying human interventions in the basin. ...Among these, the Yellow River Delta (hereafter YRD) has been enormously impacted by frequent channel avulsions and a Water-Sediment Regulation Scheme (WSRS) through upstream reservoirs since 2002. However, it remains undisclosed how the YRD responses to these human interventions. Here, modern sedimentation and inter-annual to multi-decadal timescales evolution of the YRD were studied using a dataset including 10 sediment cores collected in the subaqueous delta during the 2014 WSRS, satellite images, hydrographic and bathymetric data from 1976 to 2014. Our results show that the sedimentation of the delta can be divided into three stages: 1976–1995, 1996–2001, and 2002–2014. The area of subaerial delta generally increased from 3884 km2 to 4441 km2 during the whole 1976–2014 period except for a net land loss during 1996–2000. >70% of the delta coastline became artificial after 2000. Bathymetric data reveals that the subaqueous delta was seriously eroded after 1996 due to a shortage of sediment supply, with an estimated 2.3 × 108 t/yr and 1.1 × 108 t/yr of sediment respectively transported to the delta's adjacent sea during 1996–2001 and 2002–2014. The deltaic sediment became coarser due to the impact of the WSRS. Radionuclide 7Be uncovers a rapid sediment accumulation of ∼12 cm at the active delta front during the 2014 WSRS. The evolution of the YRD has become complex under the influence of natural and anthropogenic factors. The YRD thus provides an exemplar shift from natural to human-dominated delta. These results are important for the delta management decision making.
•Impacts of natural and artificial forces on the subaqueous delta was uncovered by sediment cores.•Channel shifts and dam regulation play vital roles in the sedimentation of the subaqueous delta.•Evolution of both the subaerial and subaqueous delta was delineated using multiple data sets.•The delta has shifted from a natural system to a human-dominated one.
Microplastics have been found everywhere and caused most significant pollution on earth, especially to the marine environment. However, microplastic pollution of marine environment is rarely studied ...based on the watershed-estuary-offshore system. In this study, a technical analysis framework of source-sink process of microplastics has been proposed based on watershed-estuary-offshore system. The impacts of human activities and hydrologic conditions on the microplastic distribution patterns in the sediments of Laizhou Bay were investigated. It is found that the river input from watershed to estuary is the main pathway for the microplastics in coastal areas to enter the sea. Population clusters, such as cities, towns and rural areas are increasingly important microplastic emission hotspots in the Laizhou Bay. Social and economic activities, productions and lifestyles in the watershed area have significant impacts on the distribution of microplastics, and the urbanization intensifies the process. A microplastic unit source-concentration response matrix model is established to simulate the transport of microplastics in the Laizhou Bay, which further confirm that river inputs are an important source of microplastics in the watershed-estuary-offshore system. It can also be concluded that the concentration of microplastics in river sediment is mainly affected by the natural conditions of the upstream watershed, the scale of human activities and the level of urbanization.
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•Microplastics are transported from watershed to river, and eventually to the estuary.•Population clusters are increasingly microplastic emission hotspots in coastal area.•Natural status and human activities affect microplastic in river sediment.•Transport of microplastics is studied by unit source-concentration response matrix.
