Marine Sedimentary Environments Research Articles

The origin, historical variations, and distribution of heavy metals in the Qiongzhou Strait and nearby marine areas

We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas. The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula, whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait. The maximum Cd, Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments, whereas the concentrations of Cr and Cu slightly exceed the standards. Correlations exist between the concentrations of Cu, Pb, Zn, Cr and Cd, and the concentrations of these metals are positively correlated with the mean particle size (φ value), indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments. An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels, thereby indicating that, in terms of heavy metals, the marine sedimentary environment in this region is only mildly impacted. Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff. The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago, which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.

Sedimentary environment evolution in a marine hangingwall dipslope setting. El Qaa Fault Block, Suez Rift, Egypt

AbstractSedimentation in hangingwall dipslope settings is still a relatively underexplored topic in rift basin studies. A better understanding of the evolution of marine sedimentary environments in this kind of settings has to address the variations occurring both along the strike and down the dipslope. Previous work was mainly built on the analysis of subsurface data, relying on the visualization of coarse resolution (10s of m) seismic sections and sparsely located borehole logs (km apart). This study focuses on the sedimentology and stratal arrangement of excellent quality Miocene marine early syn‐rift and rift climax successions continuously exposed for more than 20 km along the strike of the hangingwall dipslope in the El Qaa Fault Block, Suez Rift, Egypt. The integration of traditional sedimentary field techniques and terrestrial LIDAR scanning allowed for a detailed analysis of dip and dip direction for the different depositional units. Three different phases of tilting were identified for the hangingwall dipslope, which controlled the overall evolution of the marine sedimentary environment in the area. The tilt of the hangingwall not only determined variations in facies, thickness and grain‐size of the deposits down the dipslope but also along its strike. The studied exposures of the El Qaa Fault Block dipslope constitute a unique outcrop analogue for marine sedimentation in hangingwall dipslopes.

Kinetics and thermodynamics of dissolved petroleum hydrocarbons in sediment under sophorolipid application and their effects on oil behaviour end-results in marine environment

The behaviour end-result of dissolved petroleum hydrocarbons (DPHs) is known to interact with sediments in marine environments.

The carbon and oxygen isotopic compositions and their evolution of the Xixiangchi Group carbonate rocks in Sichuan Basin and their geological implications

Carbon and oxygen isotope analysis of Xixiangchi Group shows that the bottom boundary of the Upper Cambrian is defined for the first time. The Xixiangchi Group formed in a high salinity on shore marine sedimentary environment with a warm to dry climate and underwent a slow regression after a rapid transgression in the early and middle stages, In the late stage it entered a rapid regression after a slow transgression.

Definition of new trace-metal proxies for the controls on organic matter enrichment in marine sediments based on Mn, Co, Mo and Cd concentrations

Trace metal enrichments in sedimentary deposits are of prime interest because they are governed by processes that also control the production and preservation of organic matter. Consequently, trace metals have been used in reconstructions of the (palaeo)depositional environment of organic-rich deposits, but most of these studies have primarily focused on hydrographically restricted basins and the response of trace metals to changing redox conditions whereas the role of trace metals in the nutrient cycle and primary productivity in upwelling settings remains relatively unexplored.In this study we present a comprehensive database of published trace metal concentration data in modern organic-rich deposits from a variety of marine settings. Scrutiny of the compiled dataset has resulted in the development of novel trace metal based proxies that allow the distinction between two marine end-member depositional settings that are associated with enhanced organic carbon burial: open marine settings on the continental margin associated with upwelling (e.g. Namibian Margin) and hydrographically restricted marginal marine basins (e.g. Black Sea).It is shown that high Cd/Mo values are typical for sediments from continental margin upwelling settings whereas Co and Mn concentrations (expressed as Co∗Mn values) are high in samples from hydrographically restricted marine basins. The Cd/Mo ratios are thought to track the relative importance of productivity versus preservation with high values in productivity driven systems attributed to the transfer of Cd to the sediments from re-mineralised plankton biomass. Co∗Mn values, on the other hand, are believed to reflect the supply and reactive behaviour of Co and Mn and can be used to assess circulation patterns in the water column and the relative contribution of deep versus surface/river water influx to the basin. It is demonstrated that the combined use of the Cd/Mo and Co∗Mn proxies provides a highly effective way to distinguish modern/recent marine sedimentary environments, which holds promise for its use in palaeo-environmental reconstructions.

Using sediment geochemistry to infer temporal variation of methane flux at a cold seep in the South China Sea

Release of methane from the seafloor throughout the world's oceans and the biogeochemical processes involved may have significant effects on the marine sedimentary environment. Identification of such methane release events in marine sediment records can hence provide a window into the magnitude of ancient seeps. Here, we report on analysis of the geochemical composition of samples in a 12.3 m long sediment core (DH-5) collected from a seep site in the South China Sea (SCS). Our aim has been to investigate whether the evidence for the presence of methane release event within sediments is discernible from solid-phase sediment geochemistry. We show that sedimentary total sulfur (TS), δ34S values of chromium reducible sulfur (δ34SCRS) along with total organic carbon (TOC) and total inorganic carbon (TIC) content can be used to infer the presence of methane release events in cold seep settings. At least three methane release events were identified in the studied core (Unit I at 400–550 cm, Unit II at 740–820 cm, and Unit III at 1000–1150 cm). According to the characteristic of redox-sensitive elements (eg., Mo, U and Mn), we suggest that methane flux has been changed from relatively high (Unit I) to low (Unit II and III) rates. This inference is supported by the coupled occurrence of 34S-enriched sulfides in Unit II and III. AMS 14C dates from planktonic foraminifera in Unit I suggest that high methane flux event occurred at ∼15.4–24.8 kyr BP, which probably resulted in locally-focused aerobic methane oxidation. Overall, our results suggest that TS, TOC, TIC and δ34SCRS have potential for identifying present and fossil methane release events in marine sediments.

Recent sedimentary record of storms and floods within the estuarine-inner shelf region of the East China Sea

Although extreme weather events make a strong impact in shallow marine sedimentary environments, there is still a paucity of past records for the Holocene period. Estuarine-inner shelf mud regions deposited from rivers that transport a large amount of suspended sediment represent an important archive of the Holocene. Two cores (S5-2 and JC07) retrieved from the estuarine-inner shelf regions of the East China Sea provided an opportunity to use sensitive grain size and 210Pb dating to reconstruct a history of extreme weather events in the Yangtze River basin. Here, we show that the average sedimentation rates of the two cores, S5-2 (1930–2013) and JC07 (1910–2013), were estimated to be 3.11 and 1.56 cm/yr, respectively. The results indicated that sediment supply played an important role in sedimentation of the estuarine-inner shelf mud region of the East China Sea. Sand content strongly increased in the late 1980s, a result of downstream riverbed erosion of the Yangtze River and submerged deltas. The grain size versus the standard deviation method was used to identify grain-size intervals with the highest variability along a sedimentary sequence. The Yangtze estuary mud area coarse population correlated well with historical literature on Yangtze River floods since AD 1930. Extreme storm events corresponded well with historical literature on the Zhe-Min mud region of the East China Sea. The spectral analyses of the sample core coastal population demonstrated that flood and storm events were consistent with a ~3–8 a periodic change of El Niño Southern Oscillation (ENSO), suggesting that the flood events usually follow ENSO years in the Yangtze River. Consequently, sediment records preserved in the two cores demonstrated different sedimentary responses to Yangtze River floods and storms, which is important to recover centennial scale flood events, to infer extreme precipitation, and to understand climate change in the estuarine-inner shelf of the East China Sea. Nevertheless, more efforts are still needed to simulate paleo-flood and predict future flood events in the context of global warming.

Enrichment of Fusobacteria in Sea Surface Oil Slicks from the Deepwater Horizon Oil Spill.

The Deepwater Horizon (DWH) oil spill led to rapid microbial community shifts in the Gulf of Mexico, including the formation of unprecedented quantities of marine oil snow (MOS) and of a massive subsurface oil plume. The major taxa that bloomed in sea surface oil slicks during the spill included Cycloclasticus, and to a lesser extent Halomonas, Alteromonas, and Pseudoalteromonas—organisms that grow and degrade oil hydrocarbons aerobically. Here, we show that sea surface oil slicks at DWH contained obligate and facultative anaerobic taxa, including members of the obligate anaerobic phylum Fusobacteria that are commonly found in marine sediment environments. Pyrosequencing analysis revealed that Fusobacteria were strongly selected for when sea surface oil slicks were allowed to develop anaerobically. These organisms have been found in oil-contaminated sediments in the Gulf of Mexico, in deep marine oil reservoirs, and other oil-contaminated sites, suggesting they have putative hydrocarbon-degrading qualities. The occurrence and strong selection for Fusobacteria in a lab-based incubation of a sea surface oil slick sample collected during the spill suggests that these organisms may have become enriched in anaerobic zones of suspended particulates, such as MOS. Whilst the formation and rapid sinking of MOS is recognised as an important mechanism by which a proportion of the Macondo oil had been transported to the sea floor, its role in potentially transporting microorganisms, including oil-degraders, from the upper reaches of the water column to the seafloor should be considered. The presence of Fusobacteria on the sea surface—a highly oxygenated environment—is intriguing, and may be explained by the vertical upsurge of oil that provided a carrier to transport these organisms from anaerobic/micro-aerophilic zones in the oil plume or seabed to the upper reaches of the water column. We also propose that the formation of rapidly-sinking MOS may have re-transported these, and other microbial taxa, to the sediment in the Gulf of Mexico.

Study on the marine sedimentary environment evolution of the southern Laizhou Bay under the impact of port projects

The southern Laizhou Bay is mainly composed of silt-sandy coasts with diverse landforms, and its marine hydrodynamic environment is sensitive to human activities. Marine hydrodynamic and sedimentary environments of the study area have changed under the influence of large-scale port projects in recent years. In this paper, the evolution of hydrodynamic environment, deposition rate, and geochemical characteristics were studied based on sediment grain size, element analysis and 210Pb dating of two cores, in order to analyze the influence of Weifang Port on marine environmental evolution, and provide theoretical and practical basis for protecting marine environment in developing marine resources reasonably. Results showed that sediments of the two cores were relatively coarser and mainly composed of silty sand. Sediments above 230 cm in core WF1 and 218 cm in core WF2 were deposited since 1855 when the Yellow River appeared to deposit its sediments within the modern active delta, and the average deposition rate was between 0.3 and 0.5 cm a−1. Implement of Weifang Port projects in 1997 and 2007 created great influence on the sedimentary environment evolution in the surrounding waters, and the deposition rate was significantly increased. The average annual deposition rates were 5.1 cm and 3.5 cm in WF1 and WF2 respectively between 1997 and 2007. Content of heavy metals in sediments showed no obvious change in the vertical, indicating that the heavy metals were less affected by human activity and there was no significant accumulation of such metals in the study area.

Sorption kinetics of TNT and RDX in anaerobic freshwater and marine sediments: Batch studies.

Examination of the partitioning of explosives onto sediment in marine environments is critical to predict the toxicological impacts of worldwide explosive-contaminated sites adjacent to estuaries, wetlands, and the coastal ocean. Marine sediments have been identified as sites of enhanced munitions removal, yet most studies addressing these interactions focus on soils and freshwater sediments. The present study measured the kinetics of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) sorption onto 2 marine sediments of varying grain sizes (silt vs sand) and organic carbon (OC) content. Abiotic sediment sorption tests were performed at 23 °C, 15 °C, and 4 °C by spiking TNT and RDX solutions directly into anaerobic sediment slurries. Marine sediments showed significantly higher compound uptake rates (0.30-0.80 h(-1) ) than freshwater silt (0.0046-0.0065 h(-1) ) for both compounds, probably because of lower compound solubilities and a higher pH in marine systems. Equilibrium partition constants are on the same order of magnitude for marine silt (1.1-2.0 L kg(-1) sediment) and freshwater silt (1.4-3.1 L kg(-1) sediment) but lower for marine sand (0.72-0.92 L kg(-1) sediment). Total organic carbon content in marine sediments varied linearly with equilibrium partition constants for TNT and was moderately linear for RDX. Uptake rates and equilibrium constants of explosives are inversely correlated to temperature regardless of sediment type because of kinetic barriers associated with low temperatures.

Challenges to Geosteering and Completion Optimization of Horizontal Wells in the Cotton Valley Formation, East Texas

Summary Cotton Valley tight gas sands in the East Texas basin of North America consist of very-fine-grained, well-sorted quartz arenites and subarkoses that are overprinted by significant diagenetic processes. Stratigraphic variations in rock type control gas production. Hydraulic fracturing delivers economic gas production. We drilled horizontal wells more than 4,000 ft long consisting of more than 12 hydraulic-fracturing stages. The good gas-producing rock-type reservoirs are usually less than 14-ft thick and exhibit strong diagenetic overprint. Low gas prices challenge the use of sophisticated geosteering logs. By use of a very-basic gamma ray (GR) log and very-limited offset-pilot-well data, chasing such thin and variable sand bodies over a distance of 4,000 ft in a marginal marine sedimentary environment is daunting. Apart from this, horizontal wells that target thin layers present unique challenges to completion optimization. We acquired quad-combo log data, including azimuthal-density image data, by use of a logging-while-drilling (LWD) tool. We performed extensive log modeling by combining the horizontal well logs with logs from the two offset vertical wells, and achieved consistent interpretation. Log modeling has helped the post-drill well diagnosis in geosteering, completion design, and production performance. It has also supported formation evaluation. This study will highlight an integrated-study work flow in tight gas sands by use of openhole and cased-hole data. It will demonstrate the geosteering challenges, explain the log-modeling process, and display the formation-evaluation results. Geomechanical study, together with hydraulic-fracturing data and production-log data, will be used to confirm that good gas-producing rock types are easier to fracture, and they contribute better to production.

Insight into the genome sequence of a sediment-adapted marine bacterium Neptunomonas antarctica S3-22T from Antarctica

Neptunomonas antarctica S3-22T was isolated from marine sediment of the Nella Fjord, Antarctica. Here we report the draft genome sequence of N. antarctica, which comprises 4,568,828bp with a mean G+C content of 45.7%. We found numerous genes related to resistance, motility and chemotaxis, nitrogen metabolism, aromatic compound metabolism and stress response. These metabolic features and related genes revealed genetic basis for the adaptation to the marine sediment environment in Antarctica. The genome sequence of N. antarctica S3-22T may also provide further insights into the ecological role of the genus Neptunomonas.

The Research of the Mineralogical and Element Geochemical Characteristics of Bauxite in Yunfeng, Qingzhen, in Central Guizhou Province, China

The mineralogical and geochemical characteristics of the Yunfeng bauxite in Qingzhen were investigated through the handle specimen observation, thin section analysis, XRD、SEM and Element geochemistry. The mineral analyses reveal that diaspore, kaolinite and chlorite are the major minerals in the bauxite with small amounts of boehmite and pyrite. Geochemical investigations reveal that the main components in the bauxite are Al2O3, SiO2 and TFe2O3, the minorcomponents are TiO2, MgO and P2O5. In the process of weathering, some trace elements, such as Zr, Cr, Nb and Hf, are enriched. Zr vs Hf and Nb vs Ta display higher positive correlation. Trace elements show that Loushanguan Formation is the main source of material for the bauxite formation and there may be exist other precursor rock provide few material for the bauxite formation. Ore deposit formed in a O-poor,reducing Marine sedimentary environment.

Power limits for microbial life.

To better understand the origin, evolution, and extent of life, we seek to determine the minimum flux of energy needed for organisms to remain viable. Despite the difficulties associated with direct measurement of the power limits for life, it is possible to use existing data and models to constrain the minimum flux of energy required to sustain microorganisms. Here, a we apply a bioenergetic model to a well characterized marine sedimentary environment in order to quantify the amount of power organisms use in an ultralow-energy setting. In particular, we show a direct link between power consumption in this environment and the amount of biomass (cells cm-3) found in it. The power supply resulting from the aerobic degradation of particular organic carbon (POC) at IODP Site U1370 in the South Pacific Gyre is between ∼10-12 and 10-16 W cm-3. The rates of POC degradation are calculated using a continuum model while Gibbs energies have been computed using geochemical data describing the sediment as a function of depth. Although laboratory-determined values of maintenance power do a poor job of representing the amount of biomass in U1370 sediments, the number of cells per cm-3 can be well-captured using a maintenance power, 190 zW cell-1, two orders of magnitude lower than the lowest value reported in the literature. In addition, we have combined cell counts and calculated power supplies to determine that, on average, the microorganisms at Site U1370 require 50–3500 zW cell-1, with most values under ∼300 zW cell-1. Furthermore, we carried out an analysis of the absolute minimum power requirement for a single cell to remain viable to be on the order of 1 zW cell-1.

Methylation index as means of quantification of the compliance of sedimentary mercury to be methylated.

Methylmercury (MeHg) is the most bioavailable and toxic mercury species in the marine environment. MeHg concentration levels, methylation rates leading to MeHg formation, and methylation index (MI) are all used to assess the compliance of mercury to be methylated in the marine sedimentary environment. This paper reports on the works conducted on the MI upgrade. This paper proposes a new formula for calculating MI. Apart from labile mercury(II) and organic matter, it includes redox potential and abundance of sulfur-reducing bacteria (SRB), both essential factors for MeHg generation. The obtained MI is validated against actual sedimentary MeHg concentrations proving the potential usefulness of MI as a factor characterizing status of sedimentary environment regarding possible occurrence of MeHg. Moreover, values of the methylation index in particular regions show that MI values correspond well to environmental conditions in those areas. The values calculated correlate well with MeHg concentrations; however, the correlation coefficients vary between different regions. This has been attributed to the lack of empirical coefficients. Thus, MI could be used as a characteristic of the sedimentary environment indicating the potential presence of MeHg. It could also be used in methylation rate modeling, provided that empirical constants are applied to improve model performance.

Catabolic rates, population sizes and doubling/replacement times of microorganisms in natural settings

Directly assessing the impact of subsurface microbial activity on global element cycles is complicated by the inaccessibility of most deep biospheres and the difficulty of growing representative cultivars in the laboratory. In order to constrain the rates of biogeochemical processes in such settings, a quantitative relationship between rates of microbial catalysis, energy supply and demand and population size has been developed that complements the limited biogeochemical data describing subsurface environments. Within this formulation, rates of biomass change are determined as a function of the proportion of catabolic power that is converted into anabolism—either new microorganisms or the replacement of existing cell components—and the amount of energy that is required to synthesize biomass. Catabolic power is related to biomass through an energy-based yield coefficient that takes into account the constraints that different environments impose on biomolecule synthesis; this method is compared to other approaches for determining yield coefficients. Furthermore, so-called microbial maintenance energies that have been reported in the literature, which span many orders of magnitude, are reviewed. The equations developed in this study are used to demonstrate the interrelatedness of catabolic reaction rates, Gibbs energy of reaction, maintenance energy, biomass yield coefficients, microbial population sizes and doubling/replacement times. The number of microorganisms that can be supported by particular combinations of energy supply and demand is illustrated as a function of the catabolic rates in marine environments. Replacement/doubling times for various population sizes are shown as well. Finally, cell count and geochemical data describing two marine sedimentary environments in the South Pacific Gyre and the Peru Margin are used to constrain in situ metabolic and catabolic rates. The formulations developed in this study can be used to better define the limits and extent of life because they are valid for any metabolism under any set of conditions.

Ichnology of shallow marine clastic facies in the Belait Formation, Brunei Darussalam

Trace fossil assemblages from a variety of outcropping tidal and shoreface facies in the Belait Formation of Brunei Darussalam were characterized to determine their value in distinguishing shallow marine sedimentary environments on a low energy margin. Most trace fossil assemblages in tide-dominated environments have a proximal Cruziana ichnofacies, although higher energy tidal channels have a distal Skolithos ichnofacies. Tidal sand flats tend to have more diverse and abundant traces than tidal channels. Trace fossils are more abundant in tidal mud flat facies than in tidal channels and sand flats, and whilst mud flat assemblages are more diverse than tidal channel assemblages, they are less diverse than sand flat assemblages. Generally, these assemblages are similar to those in equivalent depositional environments in higher tidal range settings. W ave-dominated environments also have Cruziana assemblages, except for the upper shoreface that has a distal Skolithos assemblage. Lower shoreface assemblages are more abundant and diverse than upper shoreface assemblages and belong to the proximal Cruziana ichnofacies. Trace fossils are more abundant and diverse in offshore transition facies than in either the upper or lower shoreface and belong to the distal Cruziana ichnofacies; assemblages in interbedded storm sands often include a minor component of the Skolithos ichnofacies. These assemblages are comparable to those from wave-dominated deposits from higher energy settings, except for the upper shoreface environment which contains a lower energy assemblage than in equivalent facies elsewhere. T race fossils tend to be less diverse, less abundant and individual traces generally are smaller in tide-dominated depositional environments when compared to wave-dominated depositional environments. Also, Ophiomorpha form complex burrow systems in wave-dominated environments in contrast to simple burrows in tide-dominated environments.

Multiple sulfur isotope signatures of sulfite and thiosulfate reduction by the model dissimilatory sulfate-reducer, Desulfovibrio alaskensis str. G20.

Dissimilatory sulfate reduction serves as a key metabolic carbon remineralization process in anoxic marine environments. Sulfate reducing microorganisms can impart a wide range in mass-dependent sulfur isotopic fractionation. As such, the presence and relative activity of these organisms is identifiable from geological materials. By extension, sulfur isotope records are used to infer the redox balance of marine sedimentary environments, and the oxidation state of Earth's oceans and atmosphere. However, recent work suggests that our understanding of microbial sulfate reduction (MSRs) may be missing complexity associated with the presence and role of key chemical intermediates in the reductive process. This study provides a test of proposed metabolic models of sulfate reduction by growing an axenic culture of the well-studied MSRs, Desulfovibrio alaskensis strain G20, under electron donor limited conditions on the terminal electron acceptors sulfate, sulfite or thiosulfate, and tracking the multiple S isotopic consequences of each condition set. The dissimilatory reduction of thiosulfate and sulfite produce unique minor isotope effects, as compared to the reduction of sulfate. Further, these experiments reveal a complex biochemistry associated with sulfite reduction. That is, under high sulfite concentrations, sulfur is shuttled to an intermediate pool of thiosulfate. Site-specific isotope fractionation (within thiosulfate) is very large (34ε ~ 30‰) while terminal product sulfide carries only a small fractionation from the initial sulfite (34ε < 10‰): a signature similar in magnitude to sulfate and thiosulfate reduction. Together these findings show that microbial sulfate reduction (MSR) is highly sensitive to the concentration of environmentally important sulfur-cycle intermediates (sulfite and thiosulfate), especially when thiosulfate and the large site-specific isotope effects are involved.

Investigation of piezoelectric bimorph bender transducers to generate and receive shear waves

This paper further demonstrates the ability of piezoceramic bimorph bender elements to preferentially generate and receive near-surface shear waves for in situ sediment characterization measurements, in terrestrial as well as marine clay soils. The bimorph elements are housed in probe transducers that can manually be inserted into the sediment and are based on the work of Shirley [J. Acoust. Soc. Am. 63(5), 1643–1645 (1978)] and of Richardson et al. [Geo.—Marine Letts. 196–203 (1997)]. The transducers can discretely generate and receive horizontally polarized shear waves, within their bimorph directivity patterns. The use of multiple probes allows one to measure the shear wave velocity and attenuation parameters in the sediment of interest. Measured shear wave data on a hard clay terrestrial soil, as well as on soft marine sediments, are presented. These parameters along with density and compressional wave velocity define the elastic moduli (Poisson’s ratio, shear modulus, and bulk modulus) of the sediment, which are of interest in various areas of geophysics, underwater acoustics, and geotechnical engineering. Discussion will focus on use of the probes in both terrestrial and marine sediment environments. [Work supported by ARL:UT Austin.]

Biomineralization mediated by anaerobic methane-consuming cell consortia.

Anaerobic methanotrophic archaea (ANME) play a significant role in global carbon cycles. These organisms consume more than 90% of ocean-derived methane and influence the landscape of the seafloor by stimulating the formation of carbonates. ANME frequently form cell consortia with sulfate-reducing bacteria (SRB) of the family Deltaproteobacteria. We investigated the mechanistic link between ANME and the natural consortium by examining anaerobic oxidation of methane (AOM) metabolism and the deposition of biogenetic minerals through high-resolution imaging analysis. All of the cell consortia found in a sample of marine sediment were encrusted by a thick siliceous envelope consisting of laminated and cementing substances, whereas carbonate minerals were not found attached to cells. Beside SRB cells, other bacteria (such as Betaproteobacteria) were found to link with the consortia by adhering to the siliceous crusts. Given the properties of siliceous minerals, we hypothesize that ANME cell consortia can interact with other microorganisms and their substrates via their siliceous envelope, and this mechanism of silicon accumulation may serve in clay mineral formation in marine sedimentary environments. A mechanism for biomineralization mediated by AOM consortia was suggested based on the above observations.