Deposition Cycles Research Articles

Sedimentary sequence and evolutionary characteristics of the rift system of Neoproterozoic Nanhua System and Doushantuo Formation: A case study from the northeastern margin of Sichuan Basin

Neoproterozoic strata are widely developed in the Upper Yangtze region of South China, among which the Sinian Dengying Formation has been discovered with numerous large gas fields in the Sichuan Basin, and hence they have become an essential domain for natural gas exploration and development. The early‐to‐middle Neoproterozoic Nanhua System and Doushantuo Formation are characterized by rifting deposits in the northeastern margin of Sichuan Basin, but their depositional succession and sequence architectures are still unclear, which has largely restricted our understanding of the resource potential of these strata. In this paper, based on the outcrops of the Neoproterozoic Nanhua System and Doushantuo Formation in the northeastern margin of Sichuan Basin, we describe the stratigraphic distribution and sedimentary evolutionary characteristics, and establish the regional stratigraphic framework, sedimentary cycle and evolutionary sequence of the Nanhua System and Doushantuo Formation. The results show that the lithology of the Nanhua System and Doushantuo Formation is primarily composed of conglomerate, conglomeratic sandstone, medium‐fine sandstone, siltstone, mudstone, shale and tillite; a variety of sedimentary facies including alluvial fan, river, delta, coastal shore, shelf, basin and tillite were developed; five third‐order sequences could be identified, representing multiple cycles of marine transgression and regression. The climate during the deposition of the Nanhua System and Doushantuo Formation underwent from a warm and humid pre‐glacial period through cold and arid multiple glacial periods to a warm and humid interglacial period, which consequently formed a sedimentary sequence of alluvial fan and fluvial delta to tillite during the early period, shelf basin to tillite during the middle period and slope basin to delta facies during the late period. In terms of a plan view, the depositional pattern is composed of alluvial fans and deltas at the proximal part of the rift, deep‐water shelf to slope at the middle part of the rift and slope to basin facies at the central part of the rift. Finally, we propose that large‐scale distribution of high‐quality source rocks developed in the interglacial Datangpo and Doushantuo formations, while fluvial‐deltaic reservoirs occurred in the Gucheng, Nantuo and Doushantuo formations, thus showing favourable resource potential and exploration prospects within the Sichuan Basin.

Efficient formaldehyde sensor based on PtPd nanoparticles-loaded nafion-modified electrodes

The noble metal-based electrochemical sensor design for efficient and stable formaldehyde(FA) detection is important ongoing research. In this paper, PtPd/Nafion/GCE is prepared by electrochemical cyclic voltammetry deposition method based on electrodepositing nanostructured platinum (Pt)-palladium (Pd) nanoparticles in Nafion film-coated glassy carbon electrode (GCE). The influence of deposition parameters and chemical composition (atomic ratio of Pt and Pd) on the electrochemical behaviour of PtPd/Nafion/GCE has been investigated. PtPd/Nafion/GCE displays a remarked electrocatalytic activity for the oxidation of FA and exhibits a linear relationship in the range of 10–5000 μM, with a detection limit of 3.3 μM in 0.1 M H2SO4 solution. It is proved that the detection performance of PtPd/Nafion/GCE electrode is valuable for further application with low detection limit, wide linear range, favourable selectivity and high response.

Microbial drivers of DMSO reduction and DMS-dependent methanogenesis in saltmarsh sediments

Saltmarshes are highly productive environments, exhibiting high abundances of organosulfur compounds. Dimethylsulfoniopropionate (DMSP) is produced in large quantities by algae, plants, and bacteria and is a potential precursor for dimethylsulfoxide (DMSO) and dimethylsulfide (DMS). DMSO serves as electron acceptor for anaerobic respiration leading to DMS formation, which is either emitted or can be degraded by methylotrophic prokaryotes. Major products of these reactions are trace gases with positive (CO2, CH4) or negative (DMS) radiative forcing with contrasting effects on the global climate. Here, we investigated organic sulfur cycling in saltmarsh sediments and followed DMSO reduction in anoxic batch experiments. Compared to previous measurements from marine waters, DMSO concentrations in the saltmarsh sediments were up to ~300 fold higher. In batch experiments, DMSO was reduced to DMS and subsequently consumed with concomitant CH4 production. Changes in prokaryotic communities and DMSO reductase gene counts indicated a dominance of organisms containing the Dms-type DMSO reductases (e.g., Desulfobulbales, Enterobacterales). In contrast, when sulfate reduction was inhibited by molybdate, Tor-type DMSO reductases (e.g., Rhodobacterales) increased. Vibrionales increased in relative abundance in both treatments, and metagenome assembled genomes (MAGs) affiliated to Vibrio had all genes encoding the subunits of DMSO reductases. Molar conversion ratios of <1.3 CH4 per added DMSO were accompanied by a predominance of the methylotrophic methanogens Methanosarcinales. Enrichment of mtsDH genes, encoding for DMS methyl transferases in metagenomes of batch incubations indicate their role in DMS-dependent methanogenesis. MAGs affiliated to Methanolobus carried the complete set of genes encoding for the enzymes in methylotrophic methanogenesis.

WO3/Bi2WO6 photoanode enhancement for photoelectrocatalytic water oxidation; scan rate effect optimization in the cyclic voltammetry deposition method

The photoelectrocatalytic approach is a very efficient technology for eliminating microorganisms and organic contaminants. The development of photoanode is widely recognized as a crucial approach to enhancing the efficiency of photoelectrocatalytic cells. The key goal of this methodology is to enhance the efficacy of photoelectrocatalytic oxidation by optimizing composited photoanode fabrication. This research development focuses mainly on fabricating composite WO3/Bi2WO6 semiconductor thin films with high water oxidation efficiency and favorable photoelectrocatalytic E. coli degradation applications. Cyclic voltammetry was utilized to create WO3/Bi2WO6 thin coatings on conducting glass while optimizing the photoelectrocatalytic activity via the scan rate parameter. The characteristics of the developed electrode, including charge transfer resistance, optical properties, morphology, crystal structure, chemical composition, and oxidation numbers, were investigated to improve photoelectrocatalytic activity. It was observed that the scanning rate significantly influenced the characteristics of the WO3/Bi2WO6 electrode and the photoelectrocatalytic activity on water oxidation. It was discovered that the WO3/Bi2WO6 electrode prepared with a scan rate of 25 mV/s exhibited the greatest photoelectrocatalytic water oxidation as well as distinguishing characteristics from other conditions. The decision to utilize decreased scanning rates has been determined to optimize the reaction kinetics and improve the film-forming properties of WO3/Bi2WO6. Significantly, the developed electrode can also be used to eliminate 87.5% of E.coli in 15 minutes via a photoelectrocatalytic catalytic mechanism. The photoanode composed of WO3/Bi2WO6 has promising capabilities in removing microorganisms and organic pollutants, making it a viable candidate for future advancements in wastewater management applications.

Highly Porous Polymer Beads Coated with Nanometer-Thick Metal Oxide Films for Photocatalytic Oxidation of Bisphenol A.

Highly porous metal oxide-polymer nanocomposites are attracting considerable interest due to their unique structural and functional features. A porous polymer matrix brings properties such as high porosity and permeability, while the metal oxide phase adds functionality. For the metal oxide phase to perform its function, it must be fully accessible, and this is possible only at the pore surface, but functioning surfaces require controlled engineering, which remains a challenge. Here, highly porous nanocomposite beads based on thin metal oxide nanocoatings and polymerized high internal phase emulsions (polyHIPEs) are demonstrated. By leveraging the unique properties of polyHIPEs, i.e., a three-dimensional (3D) interconnected network of macropores, and high-precision of the atomic-layer-deposition technique (ALD), we were able to homogeneously coat the entire surface of the pores in polyHIPE beads with TiO2-, ZnO-, and Al2O3-based nanocoatings. Parameters such as nanocoating thickness, growth per cycle (GPC), and metal oxide (MO) composition were systematically controlled by varying the number of deposition cycles and dosing time under specific process conditions. The combination of polyHIPE structure and ALD technique proved advantageous, as MO-nanocoatings with thicknesses between 11 ± 3 and 40 ± 9 nm for TiO2 or 31 ± 6 and 74 ± 28 nm for ZnO and Al2O3, respectively, were successfully fabricated. It has been shown that the number of ALD cycles affects both the thickness and crystallinity of the MO nanocoatings. Finally, the potential of ALD-derived TiO2-polyHIPE beads in photocatalytic oxidation of an aqueous bisphenol A (BPA) solution was demonstrated. The beads exhibited about five times higher activity than nanocomposite beads prepared by the conventional (Pickering) method. Such ALD-derived polyHIPE nanocomposites could find wide application in nanotechnology, sensor development, or catalysis.

Microbial interaction patterns and nitrogen cycling regularities in lake sediments under different trophic conditions

Exploring how nitrogen (N) cycling microbes interact in eutrophic lake sediments and how biogenic elements influence the nitrogen cycle is crucial for understanding biogeochemical cycles and nitrogen accumulation mechanisms. In this study, sediment samples were collected from various areas of Taihu Lake with different trophic conditions in all four seasons from 2015 to 2017. Using high-throughput sequencing and molecular ecological network analysis, we investigated the microbial interaction patterns and the role of nitrogen cycling in sediments from lakes with different trophic conditions. The results showed distinct structures of sediment microbial networks between lake areas with different trophic conditions. In the more eutrophic region, network indices indicate higher transfer efficiency of energy, material, and information, more significant competition, and weaker niche differentiation of the microbial community. The sedimentary environment in the moderately eutrophic area exhibited greater potential for denitrification, nitrification, and anammox compared to the mesotrophic area, but the inhibition between N functional microbes and limitations in N removal processes were also more likely to occur. The topological structure of the networks showed that the carbon (C), sulfur (S), and iron (Fe) cycles had a strong influence on the nitrogen cycle in both lake areas. In the moderately eutrophic lake area, C- and S-cycling functional bacteria facilitated a closed cycle of the coupled N fixation–nitrification–DNRA (dissimilatory nitrate reduction to ammonium) process and reduced N removal. In the mesotrophic lake area, C- and S-cycling functional bacteria promoted both N fixation and mineralization, and Fe-cycling functional bacteria coupled with denitrifiers enhanced the nitrogen removal process of products from nitrogen fixation and mineralization. This study improved the understanding of the nitrogen cycling mechanism in lake sediments under different trophic conditions.

Bedrock Geologic Database of the Vincennes 30- x 60-Minute Quadrangle, Indiana

Located in the eastern Illinois Basin, the Vincennes 1:100,000-scale quadrangle comprises portions of Daviess, Knox, Sullivan, and Greene Counties in Indiana. It is situated in the rolling topography of the Wabash Lowland and dominated by Pennsylvanian-age coal-bearing strata. Pennsylvanian siliciclastics in the Vincennes quadrangle host economically significant coal seams. The most widespread coal beds occur in the Carbondale Group, but the Raccoon Creek Group hosts superior coal quality (low sulfur, low ash) in Indiana. Both surface and underground mining of these coals have been extensive, with expansive impacts on the landscape and subsequent reclamation. Bedrock outcrop is largely obscured by multiple cycles of glacial sediments, and extensive fluvial activity of the Wabash River has formed deep channels (paleo and active) filled with outwash and alluvium. The geological map of Gray and others (1970) is the fundamental compilation of previous geological knowledge from this area. Additional geological information for the Vincennes quadrangle comes from previous 1:24k-scale mapping through the STATEMAP program. Specifically, Fraser and others (1998) conducted bedrock mapping in the 7.5-minute Wheatland and Washington quadrangles, and Fraser and Zlotin (1997) did some mapping in the 7.5-minute Montgomery quadrangle. Conolly and others (1996) performed a coal availability study in the 7.5-minute Wheatland quadrangle. However, the most information for the 1:100k Vincennes quadrangle and, more broadly, the western corridor, comes from the Indiana-scale coal seam mapping conducted between 2011 and 2017 based on the Indiana Coal Stratigraphic Database (NCRDS) and Indiana Coal Quality Database (ICQD), and geophysical logs from petroleum wells archived in the Petroleum Database Management System (PDMS). These data were previously presented in Esri-based Indiana Coal Atlas StoryMaps for the entire western corridor (Drobniak and others, 2017a, 2017b, 2017c, 2017d). This geologic map was funded in part through the STATEMAP Program supported by the U.S. Geological Survey under Cooperative Agreement No. G21AC10646. The Bedrock Geologic Database of the Vincennes 30- x 60- Minute Quadrangle is a composite geodata set that conforms to "GeMS (Geologic Map Schema)--a standard format for the digital publication of geologic maps," available at http://ngmdb.usgs.gov/Info/standards/GeMS/. Metadata records associated with each element within the geodata set contain more detailed descriptions of their purposes, constituent entities, and attributes. An OPEN shapefile version of the data set is also available. It consists of shapefiles, DBF files, and delimited text files and retains all information in the native geodatabase, but some programming will likely be necessary to assemble these components into usable formats.

Paleo-Depositional Systems in the Krishna Godavari Basin, East Coast of India

Krishna-Godavari (K-G) basin is a continental passive marginperi-cratonic basin. It is located along the east coast of India. The basin got initiated through rift/syn-rift tectonics between Permo-Triassic to early Cretaceous periods. It consists of the deltaic plains of the Krishna and Godavari Rivers and the inter-deltaic regions. The areal extent of on land part is about 15,000 sq. km whereas the offshore area covers about 215000 sq. km up to 1,000 m isobath. The basin contains about 5 km thick sediments with several cycles of deposition, ranging in age from late Carboniferous to Pleistocene. The major geomorphologic units of the K-G basin are upland plains, coastal plains, Recent flood plain, and delta plain. Exploration for hydrocarbons in this basin was started in 1958 conducting geological mapping. Geophysical surveys using gravity and magnetic methods were started in 1964, and the seismic surveys were carried out from 1972 in the basin to identify the favourable sites of hydrocarbon accumulation. During the last four decades, 647 deep wells were drilled in different parts of the basin for exploration of oil and gas and their production activities of which 465 well are on landwhich include 85 development wells. More than 225 prospects were drilled out of which 83 are hydrocarbon bearing. &#x0D; Cretaceous sediments having a thickness of about 6 km are known in the peri-cratonic K-G basin. Archaean basement consisting of khondalites, charnockites and some sedimentary rocks occur towards north and west of the basin. Lower Gondwana rocks overlie the basement and are exposed in a limited areas adjoining the Godavari Graben. There are several horsts and grabens in the basin. Many growth faults are also known here. The Pranhita Godavari Graben is a linear intra-cratonic rift that is in the south-central part of Peninsular India. The stratigraphic column of the basin includes older Talchir Formation of Permo-Carboniferous overlain by Barakar formations which in turn underlie the Chintalapudi sandstone of Permian age. The tectonic history of the K-G basin comprises of the Rift Stage, Syn-rift Stage, Drift Stage, and Late Drift Stage. A Petroleum System can be summarized as an independent stratigraphic compartment within which three primary requisites for hydrocarbon accumulation viz., the source, reservoir, and cap rocks occur. The basin has good hydrocarbon potential, and expletory efforts to locate oil and gas pools through seismic-stratigraphic analysis may enhance the discovery rate.

Rutile to tourmaline index – a tool for the recognition of the hydrodynamics of the depositional environment; a case study from the Campanian Szozdy Delta System, SE Poland

The newly discovered mid-Campanian Szozdy Delta System (Roztocze Hills, SE Poland) located in the southern part of the Polish Cretaceous Basin, at the northern edge of the Łysogóry-Dobrogea Land, has revealed interesting features concerning the relationship between the abundance of rutile and tourmaline. A distinct inverse relationship between rutile and tourmaline can be readily recognised in the succeeding units of the tripartite cyclothems (calcareous mudstone, calcareous sandstone, and calcareous gaize) representing the submarine part of the Szozdy Delta System. In the Szozdy section, both minerals are of similar shape (highly rounded), durability, and size; they are, however, characterised by markedly different densities. Therefore, it might be expected that these two mineral phases will be strongly dependent, both vertically and spatially, on the local energy of the sedimentary environment hydrodynamic power that existed during the deposition of the succeeding units of the cyclothems. The lighter tourmaline was likely transported further to the more quiescent prodelta environment, rendering the prodelta facies overrepresented in this mineral, whereas the heavier rutile was deposited closer to the river discharge. Such relative change in the abundance of these two mineral phases, emphasised by a standardised Z-score statistics, is referred here to as rutile to tourmaline index (RuTidx). Accordingly, as the RuTidx increases, the hydrodynamic power in the sedimentary environment increases as well. Since these two mineral phases are comparatively immune to alteration during the sedimentary cycle, the RuTidx is considered here to be an independent tool in recognising the hydrodynamics of the depositional environments of any age.

Sequence stratigraphy in extraterrestrial settings: The Jezero crater, Mars

The analysis of high-resolution images provided by the Perseverance rover indicates the presence of a Gilbert-type deltaic complex in the western part of the Jezero crater, which includes fluvial topsets, as well as subaqueous clinoforms. While previously considered to be genetically related, the topsets and the foresets are separated by subaerial unconformities and belong to different sedimentation cycles (depositional sequences) and systems tracts. Based on the stratal stacking patterns observed at Kodiak butte, the clinoforms belong to falling-stage systems tracts, as indicated by the downstepping trajectory of the clinoform rollovers, the occasional preservation of offlap, and the sharp-based nature of the clinoforms. In contrast, the topsets are part of the lowstand systems tracts of the overlying depositional sequences, and are separated from the underlying foresets by truncation surfaces (i.e., subaerial unconformities).The possible environments for the deposition of clinoforms in the Jezero crater range from lacustrine to marine. In the latter case, a connection between the Jezero Basin and a northern ocean can be inferred, allowing for the possibility of tidal processes influencing the patterns of deposition within the deltaic complex. This may explain the rhythmites observed in the deltaic foresets, although other explanations for the cyclic changes in lithology and energy conditions, such as seasonal variations in fluvial discharge and sediment load, are also possible. The location of the Jezero crater in the shoreline area of the Isidis Basin, which is a bay of the northern ocean, may have created a configuration of interconnected embayments able to amplify the otherwise small tidal range expected from the two moons of the planet. Clarification of the paleogeography at the time of deltaic progradation (c. 3.6–3.8 Ga) has major implications for the strategy of exploration for early life forms on Mars. The acquisition of rock samples from the Jezero Basin and the northern ocean are essential to gain further insight into the early land-ocean interaction and possible co-evolution of life and environments on Mars.

Depositional evolution of Eocene deep-lake mudrock lithofacies driven by astronomical forcing in the Dongying Depression, China

With the deepening of shale oil and gas exploration and development, researchers are more eager to understand the depositional evolutionary pattern of mudrock lithofacies, and the astronomical cycle is an important mechanism driving the depositional evolution of mudrock. In this paper, stratigraphy is divided based on astronomical cycle, and a stratigraphic sequence is established by using long eccentricity and precession cycles to dissect well sections with cores in the connecting well profiles. The relationship between the type of lithofacies development in response to the long eccentricity cycle is found. The lake basin mainly developed mudstone-dominated facies during high-value periods of long eccentricity, while sandstone facies developed in the slope zone and marl facies developed in the deep-lake zone during low-value periods. The relationship between lithofacies subcycles and amplitude variations in precession within the long eccentricity cycles has been determined. Sandstone or marl developed during periods of maximum precession, while mudstone developed during periods of minimum precession. The model of climate and depositional cycles controlled by long eccentricity and precession has been summarized. First, during periods of low long eccentricity, the amplitude of precession is small. This leads to cold and arid climates with reduced rainfall, resulting in less terrestrial input to the basin and a period of contraction. During periods of high long eccentricity, the climate is hot. This leads to hot and humid climates with increased rainfall, resulting in stronger terrestrial input to the lake basin and a period of expansion. Second, the amplitude variations in precession also affect the strength of terrestrial input. During periods of maximum precession, the received solar radiation is low, resulting in a dry and cold climate with reduced rainfall, weakening the terrestrial input to the basin. During periods of minimum precession, the received solar radiation increases, resulting in a hot and humid climate with increased rainfall, strengthening the terrestrial input to the basin. This study systematically investigates the depositional model and factors controlling the mudrock layers in the research area. The research results can contribute to the prediction of “sweet spots” for shale oil and gas and provide references for similar sedimentary basins.

The influence of tide-brought nutrients on microbial carbon metabolic profiles of mangrove sediments

Mangrove ecosystems in the intertidal zone are continually affected by tidal inundation, but the impact of tidal-driven nutrient inputs upon bacterial communities and carbon metabolic features in mangrove surface sediments remains underexplored, and the differences in such impacts across backgrounds are not known. Here, two mangrove habitats with contrasting nutrient backgrounds in Shenzhen Bay and Daya Bay in Shenzhen City, China, respectively, were studied to investigate the effects of varying tidal nutrient inputs (especially dissolved inorganic nitrogen and PO43−-P) on bacterial community composition and functioning in sediment via field sampling, 16S rDNA amplicon sequencing, and the quantitative potential of microbial element cycling. Results showed that tidal input increased Shenzhen Bay mangrove's eutrophication level whereas it maintained the Daya Bay mangrove's relatively oligotrophic status. Dissolved inorganic nitrogen and PO43−-P levels in Shenzhen Bay were respectively 12.6–39.6 and 7.3–29.1 times higher than those in Daya Bay (p < 0.05). In terms of microbial features, Desulfobacteraceae was the dominant family in Shenzhen Bay, while the Anaerolineaceae family dominated in Daya Bay. Co-occurrence network analysis revealed more interconnected and complex microbial networks in Shenzhen Bay. The quantitative gene-chip analysis uncovered more carbon-related functional genes (including carbon degradation and fixation) enriched in Shenzhen Bay's sediment microbial communities than Daya Bay's. Partial least squares path modeling indicated that tidal behavior directly affected mangrove sediments' physicochemical characteristics, with cascading effects shaping microbial diversity and C-cycling function. Altogether, these findings demonstrate that how tides influence the microbial carbon cycle in mangrove sediments is co-correlated with the concentration of nutrient inputs and background status of sediment. This work offers an insightful lens for better understanding bacterial community structure and carbon metabolic features in mangrove sediments under their tidal influences. It provides a theoretical basis to better evaluate and protect mangroves in the context of global change.

Modelled broad-scale shifts on seafloor ecosystem functioning due to microplastic impacts on bioturbation

Bioturbating species play an essential role in regulating nutrient cycling in marine sediments, but their interaction with microplastics (MP) remains poorly understood. Here we investigated the linkage between MP and ecosystem functioning using experimental observations of luminophore distribution in the sediment to parametrize bioturbation coefficients (Db). this information as fed into a simplified transport-reaction model, allowing us to upscale our experimental results. We found that the composition of bioturbators modulated shifts in the ecosystem functioning under microplastic stress. Maldanid worms (Macroclymenella stewartensis), functionally deep burrowing and upward-conveyor belt feeders, became less active. The Db of M. stewartensis reduced by 25% with the addition of 0.002 g MP cm−2 at surface sediment, causing accumulation of organic matter in the oxic sediment zone and stimulating aerobic respiration by 18%. In contract, the tellinid bivalve Macomona liliana, functionally a surface -deposit feeder that excretes at depth, maintained particle mixing behaviour in MP-contaminated systems. This study provides a mechanistic insight into the impacts of MP and indicates that the functional role of bioturbating species should be involved in assessing the global impact of MP. The model allowed us to understand the broad-scale impact of MP on seafloor habitat.

The control of turbidite deposition on pyrite sulfur isotopic composition in sediments on the continental slope of the South China Sea

Sulfate reduction is a commonly reported process in a variety of continental margin settings that affects the carbon (C), sulfur (S), and iron (Fe) marine sedimentary cycles. However, sulfate reduction in unstable environment (turbidite deposition) is easily ignored, which results in a lack of understanding of the C, S, and Fe biogeochemical cycle. Therefore, to elucidate the role of turbidite sedimentation in the global C, S, and Fe biogeochemical cycle, total organic carbon (TOC), total sulfur (TS), iron speciation, pyrite contents, and sulfur isotopic composition in sediments (CL94) on the South China Sea continental slope were analyzed, along with sediment grain sizes, calcium carbonate (CaCO3) content, and K/Al and Ti/Al ratios. Based on petrographic characteristics, grain size parameters, and element geochemistry (K/Al and Ti/Al ratio), it was concluded that the mid-section (322–350 cm) of Site CL94 is a turbidite layer. Compared with normal sedimentary environment, δ34SCRS (−39.7 ‰ on average) exhibits a high value in turbidite layer, which could be related to the high deposition rate and relatively closed environment caused by the turbidity current deposition. Furthermore, in situ deposition is virtually entirely unaffected by external influences, and this is the primary source of sulfide and reactive iron in the relatively closed environment. Thus, pyrite concentration in the turbidity layer fluctuates in conjunction with variations in sulfide and active iron. Moreover, the identification and data extraction of methane seeps were further complicated by the fact that the TS/TOC ratio and δ34SCRS features induced by the turbidity current were extremely similar to those of sediments around methane seeps. The examination of pyrite sulfur isotopic composition and TS/TOC ratios for detecting methane seepage requires further investigation.

Seasonal variation regulate the endogenous phosphorus release in sediments of Shijiuhu Lake via water-level fluctuation

Freshwater lakes undergo substantial alterations of the phosphorus (P) cycle in the water-sediment ecosystem due to thermal change. The impact process of seasonal fluctuation on P cycling in sediments has been scarcely investigated. P forms in sediments from a freshwater lake in China were analyzed using sequential extraction technique. The vertical distribution of soluble reactive P (SRP), Fe2+, and S2− in the interstitial water was measured using diffusion gradient technique (DGT). Fick's Law and DIFS model were used to obtain the diffusion fluxes of SRP and the kinetic parameters in the water-sediment system. The results showed that total P (TP) concentrations in the solid sediments varied from 207.5, 266.6 and 130.3 mg/kg to 614.7, 1053.1, and 687.6 mg/kg in winter, spring, and summer, respectively. The concentrations of individual P forms in spring were higher than those in other seasons, with Fe-bound P (Fe–P) concentration being the highest across all seasons. Notably, significant variations of SRP concentrations were found in the interstitial water between sedimentary depths of approximately 2 cm and 6 cm, particularly in the summer. Furthermore, higher diffusion fluxes of SRP through the interface were found in summer. A stable anaerobic environment failed to develop in spring with high water level, preventing the desorption of solid Fe–P and diffusion of Fe2+ into the water due to the afflux and deposition of P-containing particulate into deeper sediment layers along with organic material. Under extreme high-temperature in summer, decreased rainfall and rising temperatures boosted the activity of aquatic organisms in the water, thereby reducing P fixation by sediments and leading to P release. This process increased the risk of P excess and potential eutrophication in the water. Generally, clarifying the resupplying processes of endogenous P in sediment systems experiencing seasonal variations is critical for eutrophication management of lakes.

BILOZERSKA SERIES OF THE UKRAINIAN SHIELD: PROBLEMS OF STRATIGRAPHY AND CORRELATION

The article discusses the problematic issues of the geological structure of the Bilozersky synclinorium of the Ukrainian Shield, its stratigraphic structure, formation composition and absolute age of the rock associations that compose it. The interrelationships of interregional correlation of the Bilozerska and Kryvyi Rih series of the Ukrainian Shield are considered. Significant adjustments to the current stratigraphic scheme of the Bilozerska series are proposed. The necessity of abolishing the upper metasedimentary stratum (Pereverzevska Suite) and returning to the traditional twoshell structure of the Bilozerska series, which consists of a sub-iron-bearing essentially terrigenous and iron-bearing terrigenous-chemogenic ferruginous-siliceous suite, is noted. The author’s interpretation of the folded structure of the central zone of the Bilozerska structure is proposed, which allows to explain all the complexities of its stratigraphy in a consistent manner, to reconcile the stratigraphic position of the Teplivska Association of the Bilozersky synclinorium with the position of the Talc Horizon of the Kryvyi Rih series, and to show a complete correspondence in the general sequence of stratons between the sediments of the Bilozerska and Kryvyi Rih series. The complete lithologic, stratigraphic, and formational correlation of the Bilozerska series with the section of the Kryvyi Rih series within the Skelyuvatsko- Saksagan sedimentary cycle is shown by a set of features. It is recommended to unite the Kryvyi Rih and Bilozerska series into a single supra-regional and superserial taxon – the Kryvyi Rih-Bilozersky complex.

Chemical Alteration of Riverine Particles in Seawater and Marine Sediments: Effects on Seawater Composition and Atmospheric CO2

Numerous studies have shown that riverine particles react with seawater. Reactions include dissolution of reactive silicate minerals (e.g., feldspars) and formation of authigenic clays and carbonates. Previous studies have either focused on mineral dissolution (marine silicate weathering) or authigenic phase formation (reverse weathering). A comprehensive study that assesses all processes affecting the marine alteration of riverine particle has -to our knowledge- not yet been conducted. Our contribution aims to fill this gap. We first quantify cation exchange between seawater and riverine particles that occurs when particles enter the marine realm and show that significant global cation fluxes are induced by this process (-1.3 Tmol Na yr-1, -0.2 Tmol K yr-1, -0.4 Tmol Mg yr-1, +1.2 Tmol Ca yr-1) where the positive sign indicates cation release into seawater while the negative sign denotes uptake on particles. We then use thermodynamic and kinetic modeling to investigate how much of the suspended particle load dissolves in contact with seawater and estimate corresponding global release rates for dissolved cations and silica assuming congruent dissolution (+0.06 Tmol Na yr-1, +0.15 Tmol Ca yr-1, +2.8 Tmol Si yr-1). Subsequently, we investigate rates of mineral dissolution and authigenic clay and carbonate formation in marine sediments applying reactive transport modeling, porewater data and mass balance calculations. Our best estimates for net fluxes across the sediment/water interface (dissolution–mineral formation) result as +1.5 Tmol Na yr-1, -2.5 Tmol K yr-1, -2.0 Tmol Mg yr-1, +2.5 Tmol Ca yr-1, and +1.9 Tmol Si yr-1 where most of the Na and Ca release is induced by plagioclase dissolution, K is taken up in authigenic clays and Mg is removed from solution by authigenic clay and carbonate formation. We conclude that the alkalinity of seawater is not significantly affected by marine silicate alteration since cation release fluxes (Na, Ca) are as high as cation uptake fluxes (K, Mg) on equivalent basis. Moreover, marine silicate weathering and reverse weathering are closely coupled since Al required for clay formation is mostly provided by feldspar dissolution while Al removal in authigenic clay promotes and maintains feldspar dissolution in marine sediments. Authigenic carbonate formation in anoxic subsurface sediments sequesters significant amounts of carbon (2.5 Tmol C yr-1) according to our estimates where most of the Ca and alkalinity required for carbonate formation are provided by the dissolution of Ca-bearing silicate minerals. This hidden sedimentary cycle provides a sink for dissolved inorganic carbon that may drive a slow draw-down of atmospheric CO2 on geological timescales. Marine silicate alteration has an even stronger effect on the geochemical evolution of seawater by generating large fluxes of dissolved K, Mg, Ca and Si.

The environmental transformation mechanism of the coal- and oil shale-bearing interval in the Eocene Dalianhe Formation, Yilan Basin, Northeast China

Assemblages of multiple organic matter (OM)-related sedimentary energy systems are common in the Eocene nonmarine basins of Northeast China. During the Middle Eocene Climatic Optimum, oil shale developed in large quantities in the Yilan Basin. Numerous scientific papers have concentrated on the sedimentary cycle and industrial quality of the coal- and oil shale-bearing intervals, whereas few studies have studied the genetic environmental transformation mechanism of the coal and oil shale deposits. The Dalianhe Formation cover thick oil shale member and coal unit, which is a natural archive for studying the environmental evolution of lake swamp systems. In the present paper, the thermal maturity of organic matter (OM), oil shale industrial quality, coal rank, source of OM and paleoenvironmental conditions associated with OM accumulation in the Yilan Basin are investigated through bulk geochemical analyses, organic maceral analyses and biomarker composition analyses. The coal in the Yilan Basin is classified as subbituminous coal with high total organic carbon (TOC) values, high oil yields, low ash yields, and type II OM. The quality of the low-maturity oil shale in the Coal-Bearing Member is better than that in the Oil Shale Member. The oil shale in the Yilan Basin has type I-II OM and relatively high oil yields, which corresponds to the considerable content of liptinite with a predominantly alginite composition. Based on the higher Pr/Ph values, coal was deposited under oxic–dysoxic conditions, and the OM in the coal mainly originated from terrestrial plants, whereas the oil shale accumulated in a dysoxic environment with lower Pr/Ph values, and featured mixed OM sources, including terrestrial plants and low aquatic organisms. Affected by lake level fluctuations and wide peat swamping, the thickest and highest-quality coal and oil shale developed in swamps under a dysoxic–oxic water column in freshwater environments. Subsequently, the lake basin expanded rapidly, and the sedimentary environment changed to a dysoxic–oxic semideep–deep lake, in which extremely thick mudstone and a large amount of inferior oil shale with low oil yields accumulated under the influence of gravity flows. The basin continued to rapidly subside, the water column became anoxic–dysoxic, and the deposition of mudstone, siltstone and fine sandstone predominated.

Freshwater mussels promote functional redundancy in sediment microbial communities under different nutrient regimes

Abstract Animals are a critical component of biogeochemical cycles. While animal mediated fluxes of nutrients and energy have received considerable attention, the impacts of these fluxes on microbial community structure and function are comparatively understudied. Here, we investigated if freshwater mussel influences on biogeochemical cycling in stream sediment are accompanied by changes in sediment microbial community composition and ecoenzymatic activity, and if these relationships change under different nutrient regimes. We predicted that mussel effects on ecosystem function are reflected by modified sediment microbial communities. We hypothesized that if changes in either sediment ecoenzymatic function or microbial community composition are driven by mussel‐derived nutrient amendments, we should see muted changes in microbial community assemblages or function when a given nutrient is abundant. However, if microbial communities and function are influenced by other mussel functions, then we should see uniform changes regardless of nutrient availability. We transplanted freshwater mussels and natural river sediment to flow‐through mesocosms and monitored changes in microbial community composition over 1 week. Our results indicate that mussels always changed sediment microbial community composition, but the way communities changed was dependent on ambient nutrient concentrations. On the final day we measured the activity of ecoenzymes known to correlate to microbial function and nutrient availability. Mussels homogenized the stoichiometric ratios of ecoenzyme activities, indicating a consistent function of sediment microbes associated with freshwater mussels. Our results suggest that mussels may promote functional redundancy in sediment microbial communities and highlight the importance of animals in controlling biogeochemical transformations under changing nutrient conditions. Read the free Plain Language Summary for this article on the Journal blog.

Interkingdom network analyses reveal microalgae and protostomes as keystone taxa involved in nutrient cycling in large freshwater lake sediment.

Few studies have explored the role of interkingdom interactions between bacteria and microeukaryotes in nutrient cycling in lake ecosystems. We conducted sediment sampling from 40 locations covering Hongze Lake and analyzed their chemical properties. Intra- and interkingdom networks were constructed using 16S and 18S rRNA gene amplicon sequencing. Microeukaryotic intranetworks were more complex in spring than in autumn, while no clear variation in the complexity of bacterial intranetworks was found between autumn and spring. Larger and more complex bacterial-microeukaryotic bipartite networks emerged in spring than in autumn, correlated with lower carbon, nitrogen, and phosphorus levels in spring, likely resulting in intense microbial competition. Bacteria and microeukaryotes played different topological roles in interkingdom networks, with microeukaryotes contributing to the networks' greater complexity. Seven keystone modules were identified in spring and autumn nutrient cycling. Importantly, keystone taxa in these modules belonged to photoautotrophic microalgae or predatory protostomes, indicating that these organisms are key drivers in lake sediment nutrient cycling. Our results suggested that nutrient content variation in autumn and spring changes interkingdom networks' topological structure between bacteria and microeukaryotes. Microalgae and protostomes are essential in freshwater lake nutrient cycling and may be targeted to modulate nutrient cycling in large freshwater ecosystems.