Enhanced Sedimentation Rate Research Articles

Organic carbon oxidation and the associated pyrite formation in deep sediments at the Nankai subduction zone

The preservation of organic carbon (OC) in marine sediments is crucial for Earth's climate by sequestering CO2. While OC is mostly remineralized before it reaches the seafloor, a notable fraction is buried in deep-sea sediments, particularly at subduction zones known for their enhanced sedimentation rates that promote OC burial. The mechanisms behind OC recycling and decomposition within subduction zone sediments are governed by biologically mediated redox reactions involving a range of electron acceptors, which facilitate the sequential oxidation of OC. However, direct evidence regarding such effects on OC in deep sediments remains limited. In this study, we examine the contents of pyrite and trace metals of molybdenum (Mo), vanadium (V), and cesium (Cs) in organic-rich deep sediments from the Nankai subduction zone. We find that the pyrite, sulfate, diagenetic illite, and OC contents covary in Unit V, highlighting the important role of organoclastic sulfate reduction and biotic smectite-to-illite reaction at 60–70 °C in OC oxidation and pyrite formation. The profiles of Mo, V, and Cs also align with these processes in the same interval. Our findings contribute to an in-depth understanding of OC dynamics in subduction zones, emphasizing the complex interactions within deep sediments that may influence the global carbon cycle.

Anisotropy of Magnetic Susceptibility (AMS) Analysis of the Gonjo Basin as an Independent Constraint to Date Tibetan Shortening Pulses

AbstractThe Tibetan Plateau accommodated major upper crustal shortening during Indian Plate oceanic and continental lithosphere subduction. Deciphering whether shortening was continuous or episodic, and how it correlates to major geodynamic changes is challenging. Here we apply anisotropy of magnetic susceptibility (AMS), a sensitive synsedimentary strain indicator, to a ~3 km thick magnetostratigraphically dated sedimentary section (69–41.5 Ma) in eastern Tibet. AMS shows “earliest deformation” fabrics from 69–52 Ma, followed by a sudden change to “pencil structure” fabrics with increasing anisotropy degree at ~52 Ma, dating a sudden increased synsedimentary shortening strain. This change coincides with enhanced sedimentation rates and synsedimentary vertical‐axis rotations of the Gonjo Basin, suggesting a causal link to a marked India‐Asia convergence rate deceleration. We show that AMS analysis provides a strong tool to distinguish between climatic and tectonic causes of sedimentological change and is an asset in identifying discrete tectonic pulses in intensely deformed terrane.

Nitrification of the lowermost stratosphere during the exceptionally cold Arctic winter 2015–2016

Abstract. The Arctic winter 2015–2016 was characterized by exceptionally low stratospheric temperatures, favouring the formation of polar stratospheric clouds (PSCs) from mid-December until the end of February down to low stratospheric altitudes. Observations by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on HALO (High Altitude and LOng range research aircraft) during the PGS (POLSTRACC–GW-LCYCLE II–SALSA) campaign from December 2015 to March 2016 allow the investigation of the influence of denitrification on the lowermost stratosphere (LMS) with a high spatial resolution. Two-dimensional vertical cross sections of nitric acid (HNO3) along the flight track and tracer–tracer correlations derived from the GLORIA observations document detailed pictures of wide-spread nitrification of the Arctic LMS during the course of an entire winter. GLORIA observations show large-scale structures and local fine structures with enhanced absolute HNO3 volume mixing ratios reaching up to 11 ppbv at altitudes of 13 km in January and nitrified filaments persisting until the middle of March. Narrow coherent structures tilted with altitude of enhanced HNO3, observed in mid-January, are interpreted as regions recently nitrified by sublimating HNO3-containing particles. Overall, extensive nitrification of the LMS between 5.0 and 7.0 ppbv at potential temperature levels between 350 and 380 K is estimated. The GLORIA observations are compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulations. The fundamental structures observed by GLORIA are well reproduced, but differences in the fine structures are diagnosed. Further, CLaMS predominantly underestimates the spatial extent of HNO3 maxima derived from the GLORIA observations as well as the overall nitrification of the LMS. Sensitivity simulations with CLaMS including (i) enhanced sedimentation rates in case of ice supersaturation (to resemble ice nucleation on nitric acid trihydrate (NAT)), (ii) a global temperature offset, (iii) modified growth rates (to resemble aspherical particles with larger surfaces) and (iv) temperature fluctuations (to resemble the impact of small-scale mountain waves) slightly improved the agreement with the GLORIA observations of individual flights. However, no parameter could be isolated which resulted in a general improvement for all flights. Still, the sensitivity simulations suggest that details of particle microphysics play a significant role for simulated LMS nitrification in January, while air subsidence, transport and mixing become increasingly important for the simulated HNO3 distributions towards the end of the winter.

Spatial distribution of sedimentation-rate increases in Blanes Canyon caused by technification of bottom trawling fleet

A detailed study of 15 sediment cores from Blanes Canyon and its immediate surroundings (NW Mediterranean Sea) was conducted to compare historic sedimentation rates and evaluate the possible impact of bottom-trawling intensification on the sedimentary regimes over the past 50 years. The canyon axis and flanks, as well as the adjacent open slope, were sampled at water depths ranging from 300 m to 2200 m. Grain size, dry bulk density, and 210Pb concentration profiles were measured to assess possible changes in sedimentation rates over the last century and their temporal and spatial relationship to bottom trawling effort. Sedimentation rates in the upper canyon axis (900–1200 m) had the highest rates of 0.9–2.1 cm·yr−1, quantified since the 1970s. Farther downcanyon, sedimentation rates increased two to five times after the 1970s, from 0.1–0.2 cm·yr−1 to 0.2–0.8 cm·yr−1, which coincides with a rapid growth of the total engine power of the fishing fleet operating in the study area. The enhanced sedimentation rates occur downslope of the main fishing grounds and decrease downcanyon as the distance from trawling grounds increases. These results highlight the ability of bottom trawling to resuspend bottom sediments, leading to net erosion of the canyon rims and flanks. In turn, large volumes of sediment are advected towards the canyon’s interior, ultimately increasing sediment deposition along the canyon axis. Natural sedimentation rates at similar along-canyon distance from shore in the untrawled continental slope (900–1500 m) and in the lower canyon axis (1500–2200 m) are comparable (0.08–0.20 cm·yr−1), suggesting distance from coastal sediment sources as the main control on regional sedimentation in deeper parts of the margin. While submarine canyons have been regarded as preferential cross-margin conduits for sediment dispersal, they can also potentially function as modern depocenters for trawling-induced sedimentation.

The invasion of Caulerpa cylindracea in the Mediterranean: the known, the unknown and the knowable

The spread of the green macroalga Caulerpa cylindracea is one of the most threatening invasions in the Mediterranean Sea. Many correlative and experimental studies have focused on different aspects of C. cylindracea invasion. This paper aims to evaluate the main factors influencing the spread of this alga through an overview of the results from 47 published papers on this topic; a conceptual model synthesizing the main biotic and abiotic factors that influence C. cylindracea spread was proposed. Mechanical destruction of habitats, enhanced sedimentation rate and nutrients loading directly promote the spread of C. cylindracea. Indirect effects due to factors that foster the spread of turf-forming algae at the expense of canopy-forming species and decrease substrate complexity emerged as an important determinant of the success of C. cylindracea. Ultimately, the spread of C. cylindracea appears to be regulated by a complex net of interactions between abiotic and biotic factors. Our conceptual model represents a general tool for the rapid assessment of the factor underpinning the spread of non-native species, a critical step for the control of non-native species that have successfully established viable populations.

Environmental factors affecting the development of the Zoophycos ichnofacies in the Lower Cretaceous Río Mayer Formation (Austral Basin, Patagonia)

The Río Mayer Formation (Berriasian–Albian) is part of the basal infill of the Austral Basin, southwestern Gondwana. In the Los Glaciares National Park (Santa Cruz Province) seven sections were sedimentologically studied in detail. The investigated interval is mainly composed of black mudstones and shales interbedded with marls and fine-grained sandstones. The vertical distribution of these lithologies provided the basis to distinguish three major units (lower, middle and upper). In general, within the Río Mayer Formation, two different developments of the Zoophycos ichnofacies were recognized. First, in the middle unit (Valanginian–Hauterivian), this ichnofacies shows a high degree of bioturbation having a bioturbation index (BI) between 3 and 4; Zoophycos specimens are of large size, the spreiten are nearly 1cm in height and more than 1m in width. This ichnogenus is associated with Chondrites and Bergaueria perata. Environmentally this ichnofacies formed during a transgression, the sedimentation rates were very low and promoted the accumulation of benthic food in the outer shelf. Second, the Zoophycos ichnofacies in the upper unit (Albian) exhibits a less intense degree of bioturbation (BI between 0 and 1) and; Zoophycos is of relatively small size, the spreiten are 0.3cm high and short. Typically are associated Ophiomorpha, Chondrites, Palaeophycus and Teredolites. When this ichnofacies formed, the prodelta margin prograded across the outer shelf and led to enhanced sedimentation rates further offshore resulting in the dilution of the nutrients.

Palaeoenvironment and anthropogenic activity in the southeastern Mediterranean since the mid-Holocene: The case of Tell es-Safi/Gath, Israel

The “younger fill” phenomenon defined by Vita-Finzi, related to sediments that were deposited in many Mediterranean valleys, has been a topic of discussion for several decades. The main challenge regarding this issue is deciphering the origin of the fill: geomorphic processes induced by natural climatic, or by anthropogenic activity. The current research is an attempt to deal with this issue by using a concept in which the environmental records, i.e. climate, hydrology and sedimentology, were examined in conjunction with human history, in the area of the Bronze and Iron Age archaeological site of Tell es-Safi/Gath, in central Israel. The study investigated geomorphic structures of various scales: a single slope, 1st and 2nd order valleys, and larger drainage basins of a few tens to hundreds km2. High-resolution dating of the sediments by OSL and 14C allowed the identification of different sedimentary phases.The sedimentary history of the Tell es-Safi/Gath environs shows that: (a) During the Chalcolithic period and Early Bronze Age (∼4200–3050 BCE), stable conditions prevailed in the small valleys, represented by soil formation; (b) During the Iron Age II and up to the Early Arab period (∼800 BCE–800CE), aggradation took place in the small and the large valleys; (c) During the post-Byzantine/Early Arab periods (after 800 CE), major incision occurred in the large valleys, whereas minor aggradation occurred in the small valleys. Climatic and natural geomorphic processes are the major factors shaping the landscape in the current research area.Anthropogenic activity was expressed at localized sites and for a limited time, in two locations only. One location is the siege trench that surrounds Tell es-Safi/Gath, where sedimentation occurred shortly after the destruction of the site by Hazael, king of Aram Damascus (ca. late 9th century BCE), and in the same locality during the Byzantine period. The other location is the 2nd order valley close to the archaeological site, where enhanced sedimentation rates occurred shortly after site destruction. In addition, these results suggest that the small basin valleys underwent aggradation that continuously recorded the local environmental history, whereas the large drainage basins underwent cut and fill processes related to the regional environmental history in a less continuous record.

A 700‐year record on the effects of climate and human impact on the southern cape coast inferred from lake sediments of eilandvlei, wilderness embayment, south africa

The southern Cape coast, outh frica, is sensitive to climate fluctuations as it is influenced by different atmospheric and oceanic circulation systems. Palaeoecological evidence of Holocene climate variations in this region is presently limited. Here, we present a lake sediment record spanning approximately the last 670 years from ilandvlei, a brackish coastal lake situated mid‐way between Cape Town and Port lizabeth. The results from geochemical and sedimentological analyses point to an increase in minerogenic sediment input from the catchment starting around ad 1400. Changes in the seasonal distribution of rainfall during the Little Ice Age may have altered river discharge and increased erosion rates and fluvial sediment transport in pre‐colonial times. A rising mean lake level, possibly associated with an altered water balance or relative sea‐level rise, may offer an explanation for the deposition of finer sediments. After ad 1450, reduced burial flux of elements associated with autochthonous sediment formation may have resulted from ecological changes in ilandvlei. Enhanced sedimentation rates, increasing carbon, nitrogen, phosphorous and biogenic silica concentrations, as well as high concentrations of proxies for allochthonous sediment input (e.g. aluminium, titanium, zirconium) point to increasing sediment and nutrient flux into ilandvlei from the late nineteenth century onwards. The most likely factor involved in these recent changes is land‐use change and other forms of human impact.

Enhancement in yeast separation and recycling in continuous bio‐ethanol fermentation process in Blenke cascade

AbstractBackgroundContinuous ethanol fermentation productivity strongly depends on yeast concentration. Therefore apparatuses, which can handle high cell concentrations, separation and recycling of adapted yeasts are of high interest.In our work, an enhanced sedimentation rate (ESR) settler for a Blenke cascade system, avoiding large electrical power consumption, was designed. To improve the sedimentation rate, the ESR settler was connected in series with a small conventional gravitational settler. Yeast recycling was executed in two modes, direct and activation modes. Yeast cell samples taken from both cascade and settler were counted and tested for cell viability using methylene blue staining technique and a haemocytometer. The samples were cultured on agar plate with yeast extract peptone dextrose broth and analyzed by HPLC to determine ethanol, residual sugars content and by‐products (of yeast and bacterial origin).ResultsThe results showed that, using ESR settler in series with a small conventional gravitational settler, more than 85% of the yeast cells were sedimented and were recycled by the direct or activation mode. The ethanol productivities were Qp = 19.45 ± 0.13 and Qp = 20.31 ± 0.11 g L−1 h−1 for direct and activation recycle mode, respectively. Continuous fermentation, yeast recycling and sedimentation were contamination‐free processes.ConclusionWith an ESR settler, more adapted yeast can be recycled into the continuous process. High ethanol productivity can be achieved by an activation recycling mode. © 2013 Society of Chemical Industry

Glacial–interglacial productivity and environmental changes in Lake Biwa, Japan: A sediment core study of organic carbon, chlorins and biomarkers

Temporal changes in paleoproductivity of Lake Biwa (Japan) over the past 32 kyr have been studied by analyzing bulk organic carbon and photosynthetic pigments (chlorins) in the BIW95-5 core. Primary productivity was estimated on the assumption of C/N org values of 8 for autochthonous organic matter (OM) and 25 for allochthonous OM and using an equation developed for the marine environment. The estimate indicates that primary productivity ranges from 50 to 90 g C m −2 yr −1 in the Holocene, while it is ∼60 g C m −2 yr −1 on average in the last glacial. Pheophytin a and pheophorbide a are the major chlorins. A downcore profile of chlorin concentration normalized to autochthonous organic carbon (OC) shows a decreasing trend. Chlorin productivity was corrected by removal of the effect of post-burial chlorin degradation. The temporal profile of chlorin productivity thereby obtained resembles that from autochthonous OC. The difference in primary productivity between the Holocene and the glacial for the lake is markedly smaller than that for Lake Baikal situated in the boreal zone. This difference between the two lakes is probably caused by the difference in their climatic conditions, such as temperature and precipitation. Precipitation at Lake Biwa is relatively large during the glacial and the Holocene because of the continuous influence of the East Asian monsoon. Lake Baikal precipitation is generally small as a result of control by the continental (Siberia) climate regime. In addition, a significant difference in productivity between the glacial and the Holocene for Lake Baikal may be essentially controlled by the hydrodynamic systems in the lake. Lake Biwa terrigenous OM input events occurred at least five times over the period 11–32 kyr BP, suggesting enhanced monsoon activity. Molecular examination of the layer with a large input of terrigenous OM during the Younger Dryas indicates that concentrations of terrigenous biomarkers such as n-C 27–C 31 alkanes, lignin phenols, cutin acids, ω-hydroxy acids and C 29 sterols are high, suggesting that soil OM with peat-like material entered the lake as a result of flooding. An enhanced sedimentation rate in the last 3000 years might have been partially caused by agricultural activity around the lake.

Tidal sedimentation in the Tees estuary during the 20th century: radionuclide and magnetic evidence of pollution and sedimentary response

A series of short cores (ca. 0.5 m) were collected from the intertidal zone and reclaimed lowlands of Greatham Creek in the Tees estuary. Magnetic concentration data were combined with radionuclide chronologies based on down-core profiles of unsupported 210Pb activity and 137Cs activity to establish the history of estuarine pollution. The onset of metal pollution is dated to the latter part of the 19th century, peak metal concentrations date from the early 1950s, and the observed decline in metal pollution starts in the early 1980s. Radionuclide chronologies are considered unreliable in the outer part of the estuary where low 210Pb activities cannot be calibrated against 137Cs. In the intertidal zone, 137Cs inventories correlate well with sedimentation rate and can be linked to soil erosion in the catchment rather than the marine delivery of Sellafield radionuclides. In addition, temporal offsets between reliable 210Pb and 137Cs chronologies in the intertidal zone can be attributed to erosion of the upper part of the sedimentary record. Both the intertidal and reclaimed regions exhibit enhanced sedimentation rates for the last 40 years. This is likely to be a response to relative sea-level rise although the impact of engineering works can also be observed in the tidal flats and saltmarshes during the last 25 years in the form of differential erosion and accelerated sedimentation.

Sedimentation on young ocean floor at the Mid-Atlantic Ridge, 29 °N

Measurements of the sediment cover over mid-ocean ridges are potentially useful for tectonic and volcanic problems because sediment thickness variations may reflect variations in seafloor age. In profiler records recently collected with the deeply towed TOBI system, however, we find that sediments on 0–2.5 Ma seafloor do not thicken systematically with distance from the spreading axis as would be expected from increasing seafloor age. Average sedimentation rates calculated from the thicknesses show some tendency to increase with depth as found elsewhere on the Mid-Atlantic Ridge. Many of the deposits drape basement topography and occur on outlying promontories, so sediment is probably deposited from suspension in the bottom nepheloid layer rather than from turbidity currents or other gravity flows. Enhanced sedimentation rates in deeper areas, therefore, occur because of enhanced suspended load within the bottom nepheloid layer or reduced bottom movement which allow particles to settle from suspension. The profiler records reveal a variation in the style of sedimentation from draping and localised ponding on young seafloor, to accumulation in large turbidite ponds farther off-axis, which probably reflects the progressive accumulation in source areas and, due to sedimentation, progressively smoother pathways favourable to turbidity currents.

Enhanced sedimentation rate of bovine erythrocytes at a lowtemperature

Enhanced sedimentation rate of bovine erythrocytes at a lowtemperature

Effect of concentration on enhanced sedimentation rate of erythrocytes in an inclined vessel.

The enhanced rate of sedimentation of erythrocytes in an inclined rectangular vessel was measured under microscopic and macroscopic conditions. The velocity profile, V(x), and the thickness, delta, of the upflow layer generated below the downward-facing wall in the sedimentation vessel were measured under a microscope with polystyrene latex as a tracer particle. Here, x is the distance from the vessel wall. All the data of the velocity profile are represented by a single curve, [Vmax- V(x)]/Vmax = [(delta -x)/delta]2, irrespective of the volume fraction, H, and tilt angle, theta, in the range of 0.05 < H < 0.30 and 10 degrees < theta < 40 degrees, where Vmax is the maximum velocity found at the upflow boundary. The rate of fall of the top surface of the suspension v(H, theta) fits the function, v(H, theta) = v(0, theta)(1-H)exp[-(aH + bH2)], well, irrespective of H and theta. These experimental results are compared with the theory of Acrivos and Herbolzheimer.

Enhanced Erythrocyte Sedimentation Rate and Upflow Layer in Inclined Rectangular Vessel

We have measured the velocity profile within the upflow layer in an inclined rectangular vessel during erythrocyte sedimentation with a microscopic video system and estimated the flow rate of the upflow. A good agreement between experimental data and the theory by Acrivos et al. was obtained. The results show that the Boycott effect or the enhanced sedimentation rate is due to the upflow in an inclined vessel.

Late Pleistocene paleoclimatology of the central equatorial Pacific: A quantitative record of eolian and carbonate deposition

Detailed records of δ 18O, δ 13C, percentage and mass accumulation rate of CaCO 3, and eolian percentage, mass accumulation rate, and grainsize generated for core RC11-210 from the equatorial Pacific reveal the timing of paleoclimatic events over the past 950,000 yr. The CaCO 3 percentage record shows the standard Pacific correlation of high CaCO 3 content with glacial periods, but displays a marked change of character about 490,000 yr ago with older stages showing much less variability. The carbonate mass flux record, however, does not show such a noticeable change. Sedimentation rates vary from about 0.5 to 3.0 cm/1000 yr and, during the past 490,000 yr, sections with enhanced sedimentation rates correspond to periods of high CaCO 3 percentage. Eolian mass accumulation rates, an indication of the aridity of the source region, are usually higher during glacial times. Eolian grainsize, an indication of the intensity of atmospheric circulation, generally fluctuates at a higher frequency than the 100,000-yr glacial cycle. The mid-Brunhes climatic event centered at 300,000 yr ago appears as a 50,000-yr interval of low intensity and reduced variability of atmospheric circulation. Furthermore, the nature of this entire record changes then, with the younger portion indicating less variation in wind intensity than the older part of the record. The late Matuyama increase in amplitude of paleoclimatic signals begins 875,000 yr ago in the eolian record, 25,000 yr before the δ 18O and CaCO 3 percentage amplitude increases about 850,000 yr ago.

Erect Bryozoans Are More Than Baffling: Enhanced Sedimentation Rate by a Living Unilaminate Branched Bryozoan and Possible Implications for Fenestrate Bryozoan Mudmounds

Feeding colonies of the branched cheilostome bryozoan Bugula nertina trap sediment more effectively from sediment-laden water flowing at velocities of a few cmls than do dead colonies, which in turn collect more sediment than bare, smooth substrata. The enhanced sedimentation immediately downstream of live colonies is due apparently to cilia-generated currents. These currents draw water, sediment and organic material, that would otherwise pass by unimpeded, through the colonies and into the stagnant region below and leeward of them. Ancient colonies with organization generally similar to Bugula (such as the Paleozoic fenestrate bryozoans) may also have generated higher sedimentation rates where slightly turbid water passed over them than passive baffling or production offeces or pseudofeces alone would generate. This potentially could have contributed to enigmatic mudmound buildups, such as the Carboniferous Waulsortian mounds, and other muddy facies.

1 傾斜管内の赤血球沈降に伴う血漿の流れ

It has been recognized since Boycott (1920) that erythrocyte sedimentation rate is significantly increased in inclined tubes. To fully understand the enhanced settling process, microscopic observation was made of the motion of erythrocyte-Ringer suspension under gravity settling in two inclined tubes (straight and kinked). Polystyrene particles of approximately 1 μm diameter were put into the suspension to visualize the motion of the fluid (Ringer solution) under microscope-TV camera.A thin layer of cell-free fluid was observed underneath the downward-facing surface of the two tubes, in which strong up-flow was induced. The sedimentation rate and the thickness of the cell-free layer were measured for angles of inclination in the straight tube. Both of them were increased with Increase in tube inclination up to 45 degree. This strongly suggests that the enhanced sedimentation rate may be closely connected with the cell-free layer near the inclined wall. The inclined settling process was discussed from a stand-point of two-phase fluid-dynamics.

The settling of suspensions promoted by rigid buoyant particles

When substantial numbers of buoyant particles are mixed with a sedimenting suspension of heavy particles, the two types of solids undergo rapid lateral segregation from each other. Streams 3–5 mm in diameter containing the less populous species form and flow through a concentrated continuum suspension of the more populous species. This buoyancy driven convection results in greatly enhanced sedimentation rates. A theory is developed on the premise that streams move in plug flow with all resistance to motion confined to a thin lubricating layer at the strean-continuum interface. The model is compared with experimental data and is shown to account correctly for the effect of each system parameter on the observed settling rates.