Marine Sediments Research Articles

Analysis of Tidal Cycle Wave Breaking Distribution Characteristics on a Low-Tide Terrace Beach Using Video Imagery Segmentation

Wave breaking is a fundamental process in ocean energy dissipation and plays a crucial role in the exchange between ocean and nearshore sediments. Foam, the primary visible feature of wave breaking areas, serves as a direct indicator of wave breaking processes. Monitoring the distribution of foam via remote sensing can reveal the spatiotemporal patterns of nearshore wave breaking. Existing studies on wave breaking processes primarily focus on individual wave events or short timescales, limiting their effectiveness for nearshore regions where hydrodynamic processes are often represented at tidal cycles. In this study, video imagery from a typical low-tide terrace (LTT) beach was segmented into four categories, including the wave breaking foam, using the DeepLabv3+ architecture, a convolutional neural networks (CNNs)-based model suitable for semantic segmentation in complex visual scenes. After training and testing on a manually labelled dataset, which was divided into training, validation, and testing sets based on different time periods, the overall classification accuracy of the model was 96.4%, with an accuracy of 96.2% for detecting wave breaking foam. Subsequently, a heatmap of the wave breaking foam distribution over a tidal cycle on the LTT beach was generated. During the tidal cycle, the foam distribution density exhibited both alongshore variability, and a pronounced bimodal structure in the cross-shore direction. Analysis of morphodynamical data collected in the field indicated that the bimodal structure is primarily driven by tidal variations. The wave breaking process is a key factor in shaping the profile morphology of LTT beaches. High-frequency video monitoring further showed the wave breaking patterns vary significantly with tidal levels, leading to diverse geomorphological features at various cross-shore locations.

The Paleochrono-1.1 probabilistic model to derive a common age model for several paleoclimatic sites using absolute and relative dating constraints

Abstract. Past climate and environmental changes can be reconstructed using paleoclimate archives such as ice cores, lake and marine sediment cores, speleothems, tree rings, and corals. The dating of these natural archives is crucial for deciphering the temporal sequence of events and rates of change during past climate changes. It is also essential to provide quantified estimates of the absolute and relative errors associated with the inferred chronologies. However, this task is complex since it involves combining different dating approaches at different paleoclimatic sites and often on different types of archives. Here we present Paleochrono-1.1, a new probabilistic model to derive a common and optimized chronology for several paleoclimatic sites with potentially different types of archives. Paleochrono-1.1 is based on the inversion of an archiving model: a varying deposition rate (also named growth rate, sedimentation rate or accumulation rate) and also (for ice cores) a lock-in depth of air (since, in the absence of significant surface melt, the air is trapped in the ice at about 50–120 m below the surface) and a thinning function (since glacier ice undergoes flow). Paleochrono-1.1 integrates several types of chronological information: prior knowledge of the archiving process, independently dated horizons, depth intervals of known duration, undated stratigraphic links between records, and (for ice cores) Δdepth observations (depth differences between events recorded synchronously in the gas and solid phases of a certain core). The optimization is formulated as a least-squares problem, assuming that all probability densities are near-Gaussian and that the model is nearly linear in the vicinity of the best solution. Paleochrono-1.1 is the successor of IceChrono, which produces common and optimized chronologies for ice cores. Paleochrono-1.1 outperforms IceChrono in terms of computational efficiency, ease of use and accuracy. We demonstrate the ability of Paleochrono-1.1 in an experiment involving only the MSL speleothem in Hulu Cave (China), and we compare the resulting age model with the Speleothem Isotope Synthesis and Analysis version 2 (SISALv2) age models. We then demonstrate the multi-archive capabilities of Paleochrono in a new ice-core–speleothem dating experiment, which combines the Antarctic Ice Core Chronology 2023 dating experiment, based on records from five polar ice cores, with data from two speleothems from Hulu Cave, dated using uranium / thorium radiometric techniques. We analyze the performance of Paleochrono-1.1 in terms of computing time and memory usage in various dating experiments. Paleochrono-1.1 is freely available under the open-source MIT License.

Investigating the Element Geochemical Behavior and Provenance of Surface Sediments in the Offshore Area of Sierra Leone, Africa: Insights from Major and Trace Elements

The element geochemical behavior and provenance of marine sediments are of significance to understanding the oceanic material cycle. Here, we tested the grain size and major and trace elements of 35 surface sediments in the offshore area of Sierra Leone, analyzed the content characteristics and controlling factors of the elements, discussed the material source of the sediments, and made a comparative study with the sediments in the offshore area of China. The results show that sandy silt is the main sediment type in the research area, and the average sediment mean grain size (Mz) is 4.15Φ. The content of Ca in the samples is the highest among the major elements (except Si), with an average of 5.1%. The content of Sr is the highest among the trace elements (except Ti, P, and Mn), with an average of 378.2 μg/g. The results of correlation analysis and factor analysis show that there are three main sources of sediments in the research area, namely, terrigenous weathering products, ilmenite-dominated ore, and oceanic biochemical substances. Compared with the sediments in China offshore, the sediments in the study area are more affected by marine biochemistry and have special ore input characteristics.

ANALISIS SENTIMEN PUBLIK TERHADAP KEBIJAKAN EKSPOR SEDIMEN LAUT INDONESIA MELALUI PLATFORM X.COM

Indonesia's marine sediment export policy has become a controversial topic among the public, especially in relation to environmental and socio-economic impacts. This research aims to analyze public sentiment towards Indonesia's marine sediment export policy via the X.com platform (formerly Twitter) using Natural Language Processing (NLP) techniques. Data was taken during the period September to October 2024 using the scraping method using the Twitter API. The dataset consisting of 72 tweets was processed through a data preprocessing step to remove irrelevant elements. Sentiment is analyzed using the BERT (Bidirectional Encoder Representations from Transformers) model, which allows deep detection of sentiment context. The analysis results show that 67% of tweets contain negative sentiment, 25% are neutral, and 8% are positive. This finding shows that the public is worried about the impact of marine sediment export policies.

Holocene onshore/offshore tephra correlation of Mt. Etna, Sicily

The volcanic history of Mt. Etna is mainly known from studies of subaerial deposits and stratigraphy. However, little is known about the offshore deposits, which can provide a more detailed insight into geological and sedimentological processes affecting the flanks of Mt. Etna. During RV Meteor Cruise M178, eight gravity cores were taken offshore across the continental margin east of the volcanic edifice to re-evaluate the volcanic history of pre-historic eruptions and mass wasting events in the area. In total, we investigated 87 marine tephra layers in order to build a marine tephrostratigraphic framework. Based on major element compositions of glass shards, sediment componentry, and petrographic characteristics, 27 layers were identified as primary pyroclastic flow and fall deposits, i.e., directly related to an explosive volcanic eruption. However, most of the remaining tephra layers are interpreted to represent deposits of secondary density currents and are not necessarily related to a volcanic eruption. The marine dataset is complemented by twelve onshore samples taken from major explosive eruptions. Applying geochemical fingerprinting of volcanic glass shard compositions, we correlated eleven marine tephra deposits to seven well-known Mt. Etna eruptions (FV, FF, FG, FL, FS, TV, and M1 eruptions) within the last 12 kyr, which provide valuable time markers in the marine sediment record. Furthermore, we correlated ten marine tephra layers between the marine cores (four individual eruptions) and identified another six primary layers in single cores. In total, we discovered 17 widespread volcanic events in the marine record, including four previously unknown eruptions between 10 and 7.7 ka, which indicate that Mt. Etna was more active than previously thought during this time period.

Early Ediacaran Xueqiong ophiolite in the East Kunlun Orogen, northern Tibetan Plateau: Insights into the early evolution of the Proto-Tethys Ocean

Reshaping the tectonic evolution of the Proto-Tethys Ocean is of paramount significance for comprehending the ocean-continent transitions since the Neoproterozoic. Nevertheless, the intricacies of this evolution, particularly during its early stage, remain a pivotal issue that needs further deciphering. The discovery of early Ediacaran ophiolites within the East Kunlun Orogen offers a crucial clue for exploring this issue. This study presents intergrade field geology, zircon U–Pb geochronology and whole-rock geochemistry on the related rocks from this specific ophiolite identified in the Xueqiong area, easternmost East Kunlun Orogen. Field investigations reveal the currently remaining dismembered Xueqiong ophiolite merely include gabbro, basalt and chert, which are in the form of tectonic blocks within an ophiolitic mélange. Zircon U–Pb dating results show that the gabbro samples from two near rock slices yield consistent weighted mean ages of 597 ± 5 Ma and 601 ± 2 Ma, whereas the basalt sample gives a similar age of 600 ± 6 Ma as well, indicating the magmatic component of the ophiolitic suite was formed at ca. 600 Ma during the early Ediacaran. Geochemical analysis indicates that all the gabbro and basalt share a common parental magma. Patterns of rare earth and trace elements show their properties between the enriched mid-ocean ridge basalt and oceanic island basalt models, along with their characteristic trace element covariances aligning with enriched mid-ocean ridge basalt, suggesting a mantle source similar to the enriched mid-ocean ridge basalt, with interaction with the residual asthenosphere mantle material. Relatively low SiO2, TFe2O3 and MnO2 contents and flat rare earth element patterns of chert, suggesting its lithogenic property and restricted basin setting near the continental margin. These findings collectively indicate that the Xueqiong ophiolite represents remnants of the oceanic lithosphere and overlying deep-sea sediments from the early-stage evolution of the Proto-Tethys Ocean, when the ocean evolution might not have been fully mature and oceanic floor sedimentation capable of receiving terrigenous detritus. This evidence further supports that the Proto-Tethys Ocean in the East Kunlun domain could be traced back at least to the early Ediacaran.

Coupling methane oxidation and N2 fixation under methanogenic conditions in contrasting environments

Microbial methane oxidation under widespread suboxic environment is crucial for understanding methane emission. However, the role of aerobic methanotrophs in mediating methane oxidation and nitrogen fixation is less understood in oxygen-limiting environments. In this study, we identified diazotrophic methanotrophs under oxygen-limited conditions (initial O2 of 6–8 μM) in two contrasting habitats (paddy soil and marine sediment) using DNA-based stable isotope probing combined with amplicon sequencing. Consistently, we documented significant 13CH4 oxidation and 15N2 fixation after 740 days of suboxic isotope labeling. Sequencing analysis revealed the predominance of Methylobacter–affiliated aerobic methanotrophs in the 13C-labeled DNA fractions. These Methylobacter-like OTUs accounted for 97.86 % in paddy soil and 99.49 % in marine sediment of the total pmoA gene sequences; while relative abundances for the nifH gene sequences were 91.59 % in paddy soil and 99.49 % in marine sediment. Taken together, our analyses revealed that Methylobacter is responsible for methane oxidation and nitrogen fixation under oxygen limitation in both habitats, demonstrating convergent emergence of this aerobic methanotroph under oxygen deficiency.

The Jurassic–Cretaceous Transition in the Slovenian Basin (Alpine Atlantic): Further Evidence for Palaeoenvironmental Record in Pelagic Sediments

The Jurassic–Cretaceous Transition in the Slovenian Basin (Alpine Atlantic): Further Evidence for Palaeoenvironmental Record in Pelagic Sediments

River mouths are hotspots for terrestrial organic carbon burial on the Sunda Shelf: Implications for tropical coastal carbon sequestration

Tropical small mountainous rivers (SMRs), characterized by extensive basin weathering, discharge high amounts of sediments and particulate terrestrial organic carbon (OCterr) into the ocean. Burial of OCterr in marine sediments is important for atmospheric CO2 sequestration, yet its rate and efficiency remain not fully understood. Previous studies indicated generally low burial rates and burial efficiencies of OCterr in tropical coastal ocean settings influenced by SMRs but lacked detailed insights into specific processes and quantitative estimates of burial efficiencies. This study investigated δ13C values of bulk OC (δ13COC) and OCterr biomarker proxies (BIT, #ringstetra, ΣIIIa/ΣIIa and %C32 1,15-diol indices) in river surface sediments on the Malay Peninsula and marine surface sediments on the adjacent Sunda Shelf to quantify sedimentary OCterr contents, burial rates, and burial efficiencies along the river-estuary-ocean continuum. The substantial variation in δ13COC and OCterr biomarker proxies between riverbed and shelf sediments revealed a strong decrease in fractional OCterr contribution offshore and alongshore. Using a two-endmember mixing model based on δ13COC, we determined average OCterr contents of 1.40, 0.80, and 0.05 wt% in riverbed, river-mouth, and shelf sediments, respectively. The low OCterr contents in offshore sediments are attributed to physical mechanisms (such as local hydrodynamic regime and clay mineral flocculation) that affect sediment dispersal. This process leads to notably high burial rates of terrigenous sediment (11.5 ± 2.1 kg/m−2(−|-) yr−1) and OCterr (99.2 ± 29.0 g/m−2(−|-) yr−1) at river mouths. In comparison, burial rates of OCterr were significantly lower (0.1–0.5 g/m−2(−|-) yr−1) offshore due to strong degradation of OCterr, resulting in a lower overall OCterr burial efficiency across the study area (18.2 %) compared to the global marginal sea average (21 %). These findings highlight the significance of carbon burial at the mouths of SMRs as CO2 sinks, whereas degradation of OCterr during offshore transport is a potentially large CO2 source in the tropical coastal ocean.

A new approach to high conversion CO2 hydrate sequestration by CO2/water emulsion injection into marine sediments

A new approach to high conversion CO2 hydrate sequestration by CO2/water emulsion injection into marine sediments

Deciphering the CO2 hydrates formation dynamics in brine-saturated oceanic sediments using experimental and machine learning modelling approach

One of the potential strategies for limiting global warming is capturing excess amounts of industry CO2 emissions and sequestrating it inside the oceanic sediments as CO2 hydrates. The seabed consists of sediments with different porosity and sizes, which can significantly impede the kinetics of CO2 hydrates. To address these challenges, in this novel work the CO2 hydrate kinetics and morphologies have been investigated in brine-rich [3.5 wt% NaCl] coarse sediments [porosity = 0.28, Ø =0.5-1.5 mm], granule sediments [porosity = 0.43, Ø =1.5-3 mm] and dual sediments [coarse + granules] inside a high-pressure reactor [3.5 MPa, 1-2 oC] with artificial seabed. According to the key experimental results, the water-to-hydrate conversion [%] was estimated to be 67.24 (± 3.02) % for coarse sediments, 49.58 (± 4.97) % for dual sediments (coarse + granules), and 27.68 (± 5.21) % for granules. In-situ Raman spectroscopy was used to evaluate the real-time solubility of CO2 [0.023 mol/mol], and image processing thresholding was used to identify CO2 hydrate distribution patterns. A mathematical model was proposed as a major contribution to predict CO2 hydrates kinetics in sediments, using 94,203 data points. The model was trained via a supervised machine-learning [ML] algorithm and can predict CO2 hydrate kinetics with an AARD of 7.54-8.47%.

Global Warming – Our Greatest Challenge

The current state of Earth’s climate is the result of a long-lasting, continuous development: it is a snapshot from a film of the Earth’s history that has lasted around 4.5 billion years and is still running. Climate fluctuations are documented by geological findings (marine sediment cores: several million years; ice cores: 800,000 years), by tree rings (10,000 years), historical records (1000 years) and by modern instruments (e.g. thermometers and barometers, 250 years). These data reveal pronounced changes as a characteristic feature of Earth’s climate, which extend over time scales ranging from months to millions of years. In recent decades, climate scientists have analysed many of these data sets and developed dynamic models that have been successfully tested against modern observations and are used to project the future of our climate. Data analysis and climate modelling show that a pronounced impact of human activities on current climate change is apparent.

Reduced magnitude of Early Pleistocene intensification of Northern Hemisphere Glaciation

Increased magnitude and expanding geographic distribution of ice-berg rafted debris in deep ocean sediment cores and increasing amplitude of variability in the benthic oxygen isotope (δ18O) proxy-global ice volume from ∼2.7 Ma marks the intensification of the Northern Hemisphere glaciation (iNHG). However, the location, extent and volume of Northern Hemisphere Ice Sheets (NHISs) is poorly constrained by proximal geologic evidence, and global sea-level records cannot determine individual polar ice sheet contributions alone.Quantitative relationships between sediment transport, water depth and grain size on a wave-graded continental shelf were previously applied to Pliocene shallow-marine sedimentary deposits in Whanganui Basin, New Zealand to provide an independent relative sea level record (PlioSeaNZ; 3.3–2.5 Ma). Here, we extend the duration of the sea-level record from 3.3 to 1.7 Ma (X-PlioSeaNZ) using a well-documented, shallow-marine sedimentary succession, that outcrops in the Rangitikei River Valley of the Whanganui Basin.The resulting glacial-interglacial, relative sea-level fluctuations are up to 45 ± 12.5 m paced by 41 kyr-obliquity frequency during the Early Pleistocene, but also contain modulation of 100 kyr-eccentricity cycle. These maximum sea-level amplitudes are more comparable to the mean of those previously reconstructed from calibrated benthic δ18O (e.g. Miller et al., 2020), and are significantly lower than estimates provided by albeit limited geological evidence proximal to the NHIS (Batchelor et al., 2019). Here we suggest that while NHISs acquired continental extent by 2.6 Ma, their collective volume may be overestimated in benthic δ18O calibrations and area-volume reconstructions, by as much as 50%.We propose that a reduced aspect ratio of ice sheets during iNHG was driven by 41-kyr changes in integrated summer insolation and enhanced by a subglacial regolith feedback reducing resistance to basal sliding. Regardless, the lower ice volume through the iNHG implies a lower ice sheet sensitivity (ice equivalent sea-level per degree Celsius change in temperature) under higher atmospheric CO2 of 4–6 m/°C compared to ∼20 m/°C for the period since the Last Glacial Maximum. This ice sheet sensitivity still has significant implications for society and sea-level will continue to rise under current emissions.

Decoding historical and emerging environmental concerns of C6−36 chlorinated paraffins: Insights from marine sediment cores in the Pearl River Estuary

Chlorinated paraffins (CPs) readily deposit in sediments upon entering estuaries and adjacent seas. Time-series investigations are indispensable for the long-term monitoring of historical releases and identifying CPs of emerging concerns in the marine environment. In this study, short-, medium-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) were investigated using time-of-flight high-resolution mass spectrometry (ToF-HRMS) in sediment cores, dated between the 1920s and the 2010s sampled from Hong Kong waters and Lingdingyang of the Pearl River Estuary (PRE), South China. Levels of SCCPs remained steady since the 1980s, while increasing trends of MCCPs and LCCPs were observed, indicating a market supply shift from SCCPs to MCCPs and LCCPs, potentially influenced by global restrictions. This is the first study to report C18−31 CPs in Chinese marine sediments. C>20 very long-chain CPs (C>20 vLCCPs) subcategorized from LCCPs semi-quantified via ToF-HRMS positively correlated with those of other CP categories, implying their synchronized release in the investigated regions. C>20 vLCCPs, contributing an average of 27% of total CP concentrations in two cores, were found at higher levels than LCCPs (7%). Hence, the risk of C>20 vLCCP contamination should not be ignored. By highlighting the temporal variations in the world’s largest producer and consumer of CPs, the present study augments the database of the continuous deposition of SCCPs and MCCPs in marine sediments in the PRE and highlights the unrecognized risks of LCCP contaminations.

Assessment of heavy metal concentrations, environmental risks and human health implications in marine sediments along the coastal ecosystems of the Republic of Congo.

The aim of this study is to assess the level of heavy metals (HMs) in surface sediments along the coastal estuaries of the Republic of Congo. A variety of approaches were employed, integrating elemental analysis (Atomique Absorption Spectroscopy), environmental, ecological, health risk assessment, and source identification techniques to evaluate the distribution, origin, environmental, ecological and health risks of potentially toxic element (PTE) contamination in sediments. The ascending mean concentration (mg/kg) of Cd (0.4) < Cu (18.6) < Pb (28.8) < Zn (62.1) < Mn (107) < Mg (569.6) complied with the local background, except for Cd and Pb. However, notable variations across sampling points and sites were observed, with a strong relationship between metals and organic matter. The comparing of PTEs with USEPA international standards and sediment toxicity guidelines showed compliance. The assessment of environmental risk parameters, based on the calculation of the geo-accumulation index, concentration factor and pollutant load indices showed low pollution of sediments. The ecological risk assessment, on the other hand, revealed a low level of pollution of biota and a low toxicity risk of ecosystems related to Cd and Pb and then to Cu in some sites. Regarding human health risk assessment, related to the PTEs, the cancerogenic effect indices were calculated for Cd and Pb through ingestion and inhalation pathways, and the non-cancerogenic effect indices were calculated for all HMs through ingestion, inhalation, and cutaneous contact routes, for children and adults, and showed that the results comply with the international standards set by USEPA, ranging from 10-4 to 10-6 and less than 1, respectively, where children were more sensitive and vulnerable than adults to the effects of the PTEs. Ultimately, this study revealed sediment lithology, anthropogenic activities, and mixed origins of HMs, with a large contribution from industrial activities. However, no significant impacts are discernible in the study area. In addition to the importance of this study, it forms part of the region database and could serve as a reference for future monitoring studies, since no data are available in th Congolese coastal environment.

Shewanella youngdeokensis sp. nov. Isolated from Marine Sediment and Sea Water of East Sea in Republic of Korea

The strain DAU334T, which was obtained from samples of sea water and sediments collected from the East Sea in the Republic of Korea, is a rod-shaped, Gram-stain-negative bacterium. It is facultative and positive for the oxidase and catalase enzymes. Based on the analysis of 16S rRNA sequences, it was determined that strain DAU334T had the highest degree of similarity to several strains of Shewanella species, i.e., S. schlegeliana HRKA1T (99%), S. halifaxensis HAE-EB4T (99%), S. pneumatophori SCRC-2738T (99%), S. sairae SM2-1T (99%), and S. marinintestina IK-1T (1419/1440, 99%), respectively. The complete genome sequence consisted of one contig with 4 343 646 bp, and the genome G+C content was 43.12%. The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and average amino acid identity (AAI) between strain DAU334T and its closest relatives were 77.85‒71.10, 82.14‒67.07, and 22.60‒19.70%, respectively. The major fatty acids (>10%) of strain DAU334T were iso-C13:0 and Summed feature 3 (C16:1 w7c and/or C16:1 w6c). The respiratory quinones were ubiquinone 7 (Q7), ubiquinone 8 (Q8), menaquinone 7 (MK-7), menaquinone 8 (MK-8), methylated menaquinone 7 (MMK-7), and an unidentified one. According to the results of polyphasic analyses, the strain DAU334T belongs to a novel species within the genus Shewanella, for which the name Shewanellayoungdeokensis sp. nov. (type strain DAU334T = KCTC 72428T = JCM 35745T = KCCM 43479T) is proposed.

Pyrogenic carbon records of Holocene fire dynamics in the Yellow River Basin: Climate change and human activity forcing

Fire is a crucial component of Earth's ecosystems, with important environmental and socioeconomic implications. In this paper, we analyze black carbon and polycyclic aromatic hydrocarbons in a sediment core (YS-A) from the South Yellow Sea to investigate the driving forces of fire activity in the Yellow River Basin since 7.0 ka BP, when sea level stabilized and the modern pattern of ocean circulation system established. Our results indicate that fire activity gradually increased between 7.0 and 4.0 ka BP, reaching its highest level around 4.0–3.5 ka BP, and weakened between 3.5 and 0.5 ka BP, before rapidly increasing again after 0.5 ka BP. Climate change was found to be the dominant factor influencing fire history, with drier climatic conditions promoting fire activity during 7.0–4.0 ka BP, but suppressing it after 4.0 ka BP. This varied response of fire to climatic conditions is linked to the complex interaction between rainfall, vegetation cover, and fuel availability. Human activity is also shown to exert a complex impact, with some activities, such as deforestation, reducing vegetation cover and limiting fire activity over Late Holocene timescales, while other factors, such as coal burning, increasing high-temperature combustion since 0.5 ka BP. Furthermore, our findings suggest that fire activity has significantly influenced carbon sequestration in marine sediments, leading to an increase in the burial of refractory carbon from approximately 12 % to 18 % between 7.0 and 3.5 ka BP, and a higher proportion of terrestrial organic matter.

Comparison of the Performance of ICP-MS, CV-ICP-OES, and TDA AAS in Determining Mercury in Marine Sediment Samples

Comparison of the Performance of ICP-MS, CV-ICP-OES, and TDA AAS in Determining Mercury in Marine Sediment Samples

Seawater retreated from the Tethyan Himalaya of south Tibet at ca. 49 Ma, not ca. 34 Ma

Timing of seawater retreat from the Tethyan Himalaya is of great importance, as it provides a minimum age control on the initial India-Asia collision. In south Tibet, however, it is still in dispute, with suggested ages ranging from &amp;gt;50 Ma to ca. 34 Ma. Here we present data of (1) larger benthic foraminifera from the topmost Zongpu Formation; (2) planktonic foraminifera; and (3) detrital zircon U-Pb ages from the Youxia and Shenkeza Formations at Guru, Tingri, and Gamba, with a special emphasis on the poorly studied Guru area. At Guru, existence of the Shallow Benthic Zonation (SBZ) 7 Zone index fossils of Alveolina moussoulensis Hottinger and Al. laxa Hottinger constrains the initial deposition of the Youxia Formation at ca. 54 Ma. Coexistence of the youngest planktonic foraminifera Acarinina boudreauxi Fleisher, Ac. coalingensis (Cushman and Hanna), and Ac. bullbrooki (Bolli) from the Youxia and Shenkeza Formations indicates their final deposition at ca. 49 Ma (E 7 Zone, where E stands for Eocene Planktonic foraminiferal Zone). Zircon U-Pb data are generally similar, with the youngest age peak of ca. 68−50 Ma resulting from input of the Gangdese Arc volcanic detritus. The complete lack of &amp;lt;49 Ma data among &amp;gt;1000 accepted ages implies that marine deposition probably ceased at ca. 49 Ma, consistent with the planktonic foraminiferal result. Integrating with previous results, we conclude that seawater retreated from both south Tibet and Zanskar at ca. 49 Ma. The initial collision happened quasi-simultaneously in the western and eastern Tethyan Himalaya, before ca. 49 Ma. Our findings do not support either a younger collisional age or a diachronous collisional process from the west to the east.

Thermodynamic, isothermal, and kinetic analysis of mercury (II) adsorption on marine sediments

This study aims to investigate the potential of marine sediments as effective natural adsorbents for the removal of mercury ions (Hg (II)) from aqueous solutions. Sediment samples with total organic matter ranging from 3.7 % to 8.2 % were collected from five stations, river and sea, with different water salinities (28 to 42 g L−1). To explore the role of sediment′s organic matter in removal efficiency, parts of the collected sediments were subjected to hydrogen peroxide (H2O2) oxidation. The morphology, surface area, and structure of all sediments were investigated. The effects of experimental conditions were studied. The results indicated that 0.5 g of the untreated sediment was capable of quantitatively remove Hg (II) ions up to 100 µg L−1 at the salinity of 35 g L−1 while the H2O2-treated sediments resulted in a 40 % efficiency. Moreover, the adsorption capacity of the untreated sediment was 2.5 times higher than those obtained by H2O2-treated sediments. The pseudo-second-order kinetic model successfully described the adsorption process (R2 ≥0.9992), indicating the rapid adsorption process. The adsorption process was mainly controlled by ion-exchange interactions. These research findings may contribute to the development of new water treatment strategies, highlighting the significance of naturally available materials in addressing environmental challenges.