Search

Abstract Deep-sea microorganism research has become a hot topic in life science, owing to its special value in high pressure and low temperature environment. If not kept the in-situ low temperature and high pressure, it will cause the microorganism to lose its activity and lead to a waste of resources. A freeze-sediments valve presents a promising solution to maintain the low temperature and high pressure in situ, improve the success rate of sampling and shorten the sampling time. A series of experiments were conducted to characterize the freeze-sediments valve, including the sampling time without leakage, adaptation to different sediments and the effect of the length, etc. Most important of all, temperature change of sediments is observed in all experiments. Experimental results indicated that the freeze-sediments valve was formed in 5 min without leakage and the freeze-sediments valve could be applied to different sediments without limitations on sediments type and mineral content. Considering the pressure retaining capacity and formation time of freeze-sediments valve, it was found that the freeze-sediments valve with a length of 60–80 mm has good pressure retaining capacity whose value was 41.3–48.4 Mpa and short formation time which was 5 min. Precooling the sampler could be used to shorten the sampling time in the actual environment application. This sampling technique can play a vital role in maintaining in-situ low temperature at −2 to −4 ° Celsius in all the experiments. According to the tests, the sampling technique based on the freeze-sediments valve had the potential to solve the problem of keeping in-situ temperature, low sampling success rate and long sampling time in the future. [ABSTRACT FROM AUTHOR]

The origin of recent mud deposits as well as the coastal turbidity maximum in the French-Belgian-Dutch nearshore area of the southern North Sea is still under debate in the literature. Some models favor the erosion of the Cretaceous chalk cliffs along the English Channel and subsequent NE ward directed transport, other models focus on the erosion of Eocene to earliest Oligocene, and Pleistocene to Holocene clays outcropping on the seafloor off the Belgian coast. In order to validate these hypotheses, the detailed qualitative and quantitative clay mineral composition of these sediments was used as a provenance indicator. By comparing the clay mineral composition of the mud deposits and the associated suspended particulate matter (SPM) with the composition of potential nearby and more remote sources such as the present day marine environment, estuaries and rivers, coastal erosion areas and the geological substratum, the origin of the mud deposits and the SPM could be traced. Results showed that only the clay composition of the Scheldt estuary coincides with those of the mud deposits and the coastal turbidity maximum and that all other potential sources could be excluded. Our data suggest that the clay mineral composition of the mud deposits has a similar composition since at least about 100.000 years, indicating that these deposits originate from a paleo-Scheldt river rather than from the recent river system, as the present-day Scheldt estuary is not source of fine-grained sediments. The present-day SPM in the Belgian-Dutch nearshore area originates mainly from the erosion and resuspension of the existing mud deposits situated in the Belgian nearshore. This study demonstrates the value and suitability of quantitative bulk and clay mineralogy techniques in sediment provenance studies and highlights the importance of incorporating the recent geological history in hydrodynamic studies of sedimentary basins. [ABSTRACT FROM AUTHOR]

The risk assessment code (RAC) is a common method for assessing heavy metal (HM) mobility and their potential health risks, based on HM total concentration and chemical speciation. In this study, both the RAC and the influence of ambient environmental factors were investigated in a river sediment system. Sixty-eight sediment samples were collected from the main river system in Shanghai, China. The total concentration and chemical speciation of Cu, Zn, Ni, Pb, Cd, Cr, As, and Hg were determined in the samples. The influence of sediment environmental factors, such as acid-volatile sulfide (AVS), Fe & Mn, and total organic carbon (TOC), on total metal concentrations and speciation was also investigated. The relationship between the main environmental media and distribution of HMs was discussed using PCA and NMDS. The transfer-transformation behaviors of Pb, Ni, and Cr were mainly controlled by AVS and TOC while Zn, Cu, and Cd were influenced by Fe & Mn and TOC. The relationship between the RAC value of HM and environmental factors revealed that 7% of Cr, 23% of Ni, and 15% of Pb had a high risk of mobility at TOC values below 3.5% and sulfite contents below 10 mmol/kg. In comparison, 29%, 10%, and 10% of Zn, Cu, and Cd, respectively, had a high risk of mobility at TOC < 3.5% and Fe & Mn content > 4 × 10 5 mg/kg. Evidently, the chemical fractions of HM had a strong dependence on the S, Fe, Mn, and organic compounds in the sediment. This study provides a promising pathway for the rapid evaluation of potential risks from HMs in river sediments. [ABSTRACT FROM AUTHOR]

Hybrid event beds (HEBs) are a type of deep-water sediment gravity flow deposit that generally comprise a basal clean sandstone overlain by a variety of muddier and less-permeable sandy facies. They are thought to be emplaced by combinations of turbidity currents, transitional flows and debris flows, all as part of the same transport event. To date, a number of studies have highlighted the common presence of HEBs mainly in the outer and marginal parts of deep-water systems where they replace beds composed dominantly of clean sand up-dip and/or axially over scales of km to 10 s km. In addition to these broad patterns, important yet poorly understood short-length facies changes (over metres to 100 s m) occur, modifying the overall texture and reservoir characteristics at or beneath typical spacing of production wells. The nature and origin of the short length-scale transitions is here addressed in four well-exposed HEB-prone outcrops: the Cretaceous-Paleocene Gottero Sandstone and the Miocene Cilento Flysch, both in Italy, the Carboniferous Mam Tor Sandstone in northern England, and the Carboniferous basal Ross Sandstone Formation, Western Ireland. A series of detailed correlation panels show marked lateral variations in internal bed make-up for most of the hybrid event beds studied. This variability typically involves lateral changes in the proportions of the cleaner basal sandstone and the overlying muddy sandstone division that occur without substantial change in the overall event bed thickness. The variability is inferred to reflect the complex fingering between the up-dip sandstone-dominated part of the event bed and the down-dip linked debrite due to internal erosion (ploughing) of the debrite into the basal clean sand. Where the upper part of the bed is dominated by large mudstone rafts, these may have foundered into liquefied sand and been injected and partly fragmented by the sand intrusions. The variable thickness and continuity of the basal clean sandstones have important implications for reservoir characterisation; significant variability in bed character at interwell scale can be anticipated. Rugose contacts between the intra-bed facies divisions may impact on drainage and sweep efficiency during hydrocarbon production. [ABSTRACT FROM AUTHOR]

The internal structure of one of the common fold structures in the western margin of the South Caspian Basin (SCB) has been characterized in 3D using a depth-migrated seismic cube in offshore Azerbaijan. The fold corresponds to a NNW-SSE anticline with a basinward vergence; i.e., eastwards, because in this direction of the margin the SCB is floored by a probable oceanic crust. The anticline has two culminations cut by mud-diapirs and is bounded by two parallel rim synclines with contrasting sedimentary thickness. This anticline deforms congruently the thick Productive Series (PS; Messinian to Late Pliocene), whereas the most recent sequences (<3.1 Ma; e.g., Akchagyl and Apsheron units) onlap or thin towards the fold crest. We reconstruct the existence of two episodes of folding. During deposition of the uppermost PS sequences (ca. 3.5–3.4 to 3.1 Ma), fold uplift initiated with a significantly lower rate than sedimentation. During this epoch, folding was accompanied by basin tilting and by faulting in a basinward normal fault with a limited right lateral, strike-slip component. Motion along this fault zone promoted the downdip flow of a weak layer formed by fluid- and mud-rich sediments (Maykop Formation), which also migrated along strike to build-up the growing anticline. Henceforth, fold growth accelerated and sedimentary units like the Akchagyl (3.1–1.7 Ma) were deposited preferentially in the subsiding flanks. Seafloor upwarping due to folding conditioned the sediment transport, and large deltas adapted their prograding pattern to the growing anticline crest. This structure resembles a detachment fold with a leading, East-vergent forelimb. Nevertheless, the occurrence of progressive tilting accompanying sedimentation and folding, or the mud inflation of the fold core by deep flow parallel to the anticline axis, make this example in the SCB a special example of this fold type. [ABSTRACT FROM AUTHOR]

Abstract: The Alaknanda and Bhagirathi Rivers originate in the mountainous regions of the Himalayas (Garhwal) and result in high sediment yields causing flood hazards downstream of the Ganga River and high sediment flux to the Bay of Bengal. The rivers are perennial, since runoff in these rivers is controlled by both precipitation and glacial melt. In the present study, three locations in the upper reaches of the Ganga River were monitored for 1yr (daily observations of, more than >1000 samples) for suspended sediment concentrations. In addition, more than one hundred samples were collected from various locations of the Alaknanda and Bhagirathi Rivers at different periods to observe spatial and temporal variations in river suspensions. Further, multi-annual data (up to ∼40yrs) of water flow and sediment concentrations were used for inferring the variations in water flow and sediment loads on longer time scales. In most previous studies of Himalayan Rivers, there has been a general lack of long term water flow and sediment load data. In the present study, we carried out high frequency sampling, considered long term discharge data and based on these information, discussed the temporal and spatial variations in water discharge and sediment loads in the rivers in the Himalayan region. The results show that, >75% of annual sediment loads are transported during the monsoon season (June through September). The annual physical weathering rates in the Alaknanda and Bhagirathi River basins at Devprayag are estimated to be 863tonskm−2 yr−1 (∼3.25mmyr−1) and 907tonskm−2 yr−1 (∼3.42mmyr−1) respectively, which are far in excess of the global average of 156tonskm−2 yr−1 (0.58mmyr−1). [Copyright &y& Elsevier]

Abstract: We present evidence of accumulation of calcareous cyanobacterial “microspheroids” as predominant components of the Cenomanian-Turonian Indidura Formation of northeastern Mexico. The unit at Parras de la Fuente includes a sequence of limestones and marls with well-defined light-dark rhythms at the decimetric to millimetric scale, in which CaCO3 and total organic carbon vary between 43–78% and 0.3–3.6%, respectively. A distinctive feature of the section is the presence of abundant millimeter-scale microlaminae arranged in nearly even-parallel white and dark gray “varve like” dual lamination less than 3mm thick, in which the darker units contain scattered planktonic foraminifera and radiolaria, whereas the lighter microlaminae are dominated by calcitic microspheroids (20–40μm). The white laminae are evidently the result of recurring cycles of calcareous cyanobacterial blooms, possibly associated with fluvial dilution of surface waters. The organic carbon-rich laminated marlstones and laminated biocalcilutites of the Indidura Formation document paleoceanographic conditions favorable to unusual cyanobacterial productivity cycles that were also characterized by strong dysoxic/anoxic bottom conditions. [Copyright &y& Elsevier]

Abstract: A configuration of pebbles on the vertices of a graph is solvable if one can place a pebble on any given root vertex via a sequence of pebbling steps. A function is a pebbling threshold for a sequence of graphs if a randomly chosen configuration of asymptotically more pebbles is almost surely solvable, while one of asymptotically fewer pebbles is almost surely not. In this paper we tighten the gap between the upper and lower bounds for the pebbling threshold for the sequence of paths in the multiset model. We also find the pebbling threshold for the sequence of paths in the binomial model. Finally, we show that the spectrum of pebbling thresholds for graph sequences in the multiset model spans the entire range from to n, answering a question of Czygrinow, Eaton, Hurlbert and Kayll. What the spectrum looks like above n remains unknown. [Copyright &y& Elsevier]

Abstract: The effects of a giant offshore dyke, Saemangeum, have been of special interest on both scientific and environmental aspects. Without any rival worldwide with regard to the ample scale and estuarine setting, the Saemangeum dyke and its vicinity (Saemangeum Area) should be an unprecedented experimental site for monitoring the consequence of the estuarine developments with dykes. In order to unravel geologic changes caused by the Saemangeum dyke, we collected a number of surface sediment samples and bathymetric profiles from a full coverage of the Saemangeum Area, and compared topography and sediment phase on the inter-annual (2002–2006, post-construction) and decadal (1982–2002, between pre- and post-construction) timescales. The dyke construction induced vigorous erosion along the dyke, especially across a few open gaps between dyke segments. These open gaps led to forming deep erosional troughs and the associated channels to the river mouth. At the same time, mild accumulation of sediments occurred on the broad seafloor offshore the erosional zone of dyke sector IV and on shoals between the erosional troughs off dyke sectors I–II. Inside the dyke, tidal flats have become expanded and aggraded with continuously discharged riverine sediments. Sands have been newly introduced into the offshore area of sector IV owing to tidal currents with an orientation forced to be parallel to sector IV (NE–SW), reinforced by high waves during winter. By contrast, the expanded sandy area off sectors I–II resulted from redistribution of pre-existing sands without any new input from offshore. As a whole, the concentrated erosion and sandy-seafloor expansion offshore represent the man-made influences triggered by the Saemangeum dyke. [Copyright &y& Elsevier]

Summary: An approximate analytic solution is given for the first time to previously published equations describing the characteristics of dynamic soil erosion caused by overland flow. The solution describes both the variation in time in total sediment concentration since the commencement of uniform overland flow, and also the dynamic change in the settling velocity characteristics (and size distribution) of eroding sediment. Following calibration for each of the three soils investigated in order to determine unknown but physically-defined model parameters, prediction based on this theory was found to provide good agreement with experimental data. Under steady-state conditions achieved at long time, the solution agrees with the exact solution for transport limiting conditions, and provides a simple expression for sediment concentration in other situations where soil strength affects the sediment concentration ultimately achieved. [Copyright &y& Elsevier]

Abstract: The surface layer of aquatic sediments is a zone characterized by both porosity gradients and intensive mixing. In the standard approach, porosity gradients are ignored when estimating mixing intensity. Here, model formulations with both constant and varying porosity are contrasted to estimate mixing coefficients D b from tracer depth profiles. Complementing the well-known exponential solution of the constant-porosity model, we present a general solution to the variable-porosity model in terms of hypergeometric functions. When using these models in a forward way, the tracer activities predicted by the variable-porosity model are higher than those generated by the constant-porosity model. Similarly, when inverse modelling, D b values estimated by the variable-porosity model are systematically higher than those derived from the constant-porosity model. Still, differences in D b values remain relatively small. When applying both mixing models to excess 210Pb data profiles from slope sediments, a maximal difference of 30% is obtained between D b values, the average deviation being 16%. A systematic exploration of parameter space predicts a maximal underestimation of 60% when deriving D b values from the constant-porosity mixing model. Given the uncertainty imposed by other model assumptions underlying the diffusive mixing model, the influence of porosity gradients on D b values must be classified as rather modest. Hence, the current mixing coefficient database is not biased by the constant porosity approximation. [Copyright &y& Elsevier]

Abstract: Ion microprobe U–Pb dating of detrital zircons from the Chiquitania and San Ignacio groups of Eastern Bolivia show that these rocks were derived mostly from a 1765Ma source and were deposited after 1690Ma. The emplacement of the Lomas Maneches granitoid suit, dated at 1690–1660Ma, accompanied the deposition of these metasediments. These rocks, which collectively define the basement of Eastern Bolivia, were subsequently deformed and metamorphosed during two discrete periods of orogenesis. The oldest of these events, the San Ignacio Orogeny, deformed the terrane through three successive phases of deformation and was accompanied by voluminous syn-tectonic granite intrusion and migmatisation of the 1690Ma sediments and intrusions. U–Pb age data from igneous and metamorphic zircon constrain the San Ignacio Orogeny to between 1340 and 1320Ma, while the orientation of structures suggests deformation was the result of W–NW directed shortening. A 300 million years hiatus, during which the overlying Sunsas Group was deposited, separated the San Ignacio Orogeny from the Sunsas Orogeny. Shortening during Sunsas orogenesis resulted in an intense NW trending structural overprint in the southern and western extremes of the study area. The intensity of deformation decreased toward the northeast such that in the San Ignacio region, Sunsas tectonism resulted in distinct dome and basin fold interference patterns. Late syn- to post-tectonic granites were emplaced in the region of highest Sunsas strain. One of these intrusions, the Taperas granite, yielded an age of ca. 1075Ma. When taken collectively, these new data highlight a number of important points: (1) The deposition of the Chiquitania and San Ignacio groups, and the synchronous emplacement of the Lomas Maneches granitoid suite (1690–1660Ma) have no temporal equivalents in the either the Rondônia and Mato Grosso regions of Brazil to the north or east, or the Proterozoic pre-Andean inliers to the west; (2) the trend of the structures attributed to the San Ignacio Orogeny are oriented at a high-angle to the NW trending pre-Sunsas margin of Amazonia and; (3) the Sunsas Orogeny represents the only geological event with a common age and direction of crustal shortening recorded in both the Amazon Craton and the rocks of Eastern Bolivia. These data are interpreted to suggest that the rocks of Eastern Bolivia represent a geologically distinct microcontinent (the Paragua Craton) that was accreted to the southern margin of Amazon Craton during the Sunsas Orogeny. [Copyright &y& Elsevier]

Abstract: The effects of vegetation barriers and tillage on runoff and soil loss were evaluated in an alley crop system at a research station in central Burkina Faso. On a 2% slope of a sandy loam various local species (grasses, woody species and a succulent) were planted as conservation barriers in order to examine their influence on sediment transport. After each erosive storm, runoff and sediment yield was determined. The dense effective barriers (Andropogon gayanus and dense natural vegetation) slow down flow velocity, build up backwater and promote sedimentation uphill. The through flow in the less effective barriers with woody species and succulents (Ziziphus mauritania and Agave sisalana) was slightly hampered and flow velocity was not reduced enough, resulting in a higher soil transport. Under degraded conditions soil loss diminished 50% with less effective and 70–90% with effective barriers. During the initial cropping phase (light tillage; sowing) erosion was reduced 40–60% with effective barriers and showed an increase of 45% with less effective barriers. In the full tillage (weeding) period erosion decreased by 80–90% for effective and 70% for less effective barriers, aided by the development of the barrier and the crop on the alley. Barriers of natural vegetation and A. gayanus are preferred for diminishing soil loss. Sediment yield could best be predicted by the erosivity index (AI m), second best by runoff amount (mm), closely followed by maximum peak intensity. All these parameters are related to the volume of overland flow needed to transport soil particles. Correlation of soil loss with small rain showers was poor and correlation with big showers was good. Sediment transport with no barrier had the highest correlation, closely followed by less effective barriers. Due to the heterogeneity in development of the effective barrier, correlations were much lower. The bulk of soil loss was only dependent on a few extreme events during the observation period. [Copyright &y& Elsevier]

Abstract: There are certain controls which operate to demarcate the nature and size range of quartz particles in terrestrial detrital sediments. The particles fall into discrete and definable populations, which are separated by ‘Tanner gaps’. Quartz sand nature is determined largely by a eutectic-like reaction, which takes place in the original igneous rock. This reaction delivers a fine mix of quartz and feldspar units, which on weathering deliver quartz sand. The formation of quartz silt is more contentious; it appears that silt production is essentially controlled by the presence in larger quartz particles of ‘Moss defects’, crystalline defects introduced into the quartz structure by earlier events, e.g. the high-low displacive transformation in cooling quartz. There appear to be two modes in airborne quartz particles (which have been called large dust and small dust). The larger mode is the loess mode (around 20–60 μm) and the smaller mode falls into the classification with high-level, long-travel dust (mode around 2–6 μm). The quartz in small dust is around the same size as the clay mineral agglomerate particles (CMA) which form a considerable proportion of high level dust clouds. The CMA particles form from lake deposits; the size is controlled by the openness of the packing in the lake sediments. This can be demonstrated by a simple Monte Carlo model. [Copyright &y& Elsevier]

Abstract: Annually laminated sediments can provide an absolute time scale (by varve counting) and a high-resolution palaeoclimate information (from varve thickness). Both types of information may be directly measured from sediment core surfaces. In this paper, we stress that varve counting and varve thickness measurements derived from fresh core surfaces could not systematically reveal the internal sedimentary structure, even if assisted by high resolution image analysis. We present an example of a homogeneous sediment core for which the varves were only observable after core impregnation and polishing steps. Because the impregnation methods are not yet standardized, the aim of this paper is to give an updated review of the methodology. In this review, we present the major critical points during impregnation steps. In particular, we focus on all of the post-treatment sediment disturbances that can alter the laminated micro-structure and, consequently, varve measurements. Finally, we propose a modified impregnation protocol, especially adapted for tracking varved intervals in long cores. [Copyright &y& Elsevier]

Abstract: Multi-beam bathymetry and backscatter, 3.5 kHz pinger profiles, side-scan sonar and seabed samples have been examined to evaluate along- and down-slope sedimentary processes along the Celtic Margin shelf and upper slope in water depths of 200 to 1500 m. The continental shelf and slope are indented and dissected by major canyon systems. The shelf is characterised by major northeast–southwest trending sand banks that are orthogonal to the shelf edge. Along the shelf edge, several fields of asymmetric sandwaves oriented orthogonal to the canyon axes indicate sediment transport into the canyon heads. Less commonly, sandwaves with weak asymmetry suggest sediment transport onto the shelf. These may be reworked and are partly overprinted by more recent sandwaves. Down-slope sediment transport by turbidity currents is the dominant process through the major canyons. Recent faulting has also played a role in canyon development. Turbidity currents are most likely initiated by faulting, and/or slope failure of the walls that bound the canyon head drainage basins and sediment migration from the shelf. This leads to deep incision of sinuous thalwegs in the upper reaches of canyon floors and downcutting and sediment transport on the mid to lower continental slope. The canyons are V-shaped in the upper reaches and become U-shaped progressively down-slope, suggesting they represent either a transition from erosive to depositional processes or sediment bypass conduits carrying sediment between the shelf and abyssal plain. Over-bank spill from canyons leads to deposition of unconfined turbidite deposits (muds) on the intervening canyon spurs. [Copyright &y& Elsevier]

Abstract: Deposition of Upper Triassic and Lower Jurassic sediments on the Iberian platform system took place in a post-rift intraplate basin which formed part of the western Tethys shelf. Nevertheless, there is evidence for the tensional reactivation of a network of faults with associated magmatic activity. Early Jurassic palaeogeographic reconstructions, based on over 70 sections and 9 oil wells, reveal the presence of a series of highs and lows (depocentres). Two main highs, referred to as the El Maestrazgo High, in the east, and the La Mancha High, in the west, where condensed sections were deposited, were mainly controlled by syndepositional faults. The main depocentres were situated between these two highs areas, in a northwest trending belt in the central, northern and southern areas. Despite partial fault control, development of some Early Jurassic depocentres appears to be mainly controlled by thermal contraction of the lithosphere following Triassic main rifting pulse. The Upper Triassic–Lower Jurassic succession of the Iberian platform system was deposited during four transgressive and regressive cycles of 12 to 6 My duration. The lowermost cycle LJ-1 started in late Norian and lasted until the Sinemurian. The second cycle LJ-2 started in the Sinemurian and ended in the Pliensbachian (Davoei Zone), and can be subdivided into two minor cycles LJ2-1 and LJ2-2. The cycle LJ-3 started with an extensive upper Pliensbachian (Davoei Zone) transgression, whereas the top of its regressive cycle is dated to the Toarcian (Variablilis Zone). Within cycle LJ-3, three cycles can be distinguished. Maximum deepening was reached during the Bifrons Zone and active volcanism took place along the Teruel and Caudiel faults. The transgressive phase of the cycle LJ-4 started in the Thouarsense Zone and extended up to the Insigne Zone; its regressive phase developed during the upper Toarcian (Pseudoradiosa and Aalensis Zones) and part of the Aalenian (Opalinum and Murchisonae Zones). This cycle can be subdivided in two minor cycles, with their transgressive peaks occurring during the Insigne Zone, and the Aalensis Zone respectively. Palaeogeographically this corresponds with the expansion of the marginal carbonate platforms over hemipelagic deposits. The top of the cycle corresponds to a major unconformity with regional emersion during the Aalenian Murchisonae Zone. [Copyright &y& Elsevier]

Global fallout 137Cs was used for dating sediment cores and estimation of recent sedimentation rates (up to 1 cm/y) in the Thane Creek, which lies in the southern part of the Deccan belt of India. The residence time of 210Pb in the Thane Creek water was calculated to be 0.7 years. Further, the concentrations of Pb (up to 70 μg/g) and Hg (up to 10 μg/g) in sediment profiles were measured to assess the anthropogenic input of contaminants due to large-scale industrialization, which has taken place in this area over the last two decades. The depth-wise concentration profile of Hg shows positive evidence of continued fresh input into the Creek. [Copyright &y& Elsevier]