Coarse Sediment Research Articles

Sedimentology and sequence stratigraphy of the Early Cretaceous Centenario Formation (upper member) in the north-eastern border of the Neuquén Basin, Argentina

The Centenario Formation is a unit known in literature by the content of oil reservoirs in the Productive Trend Río Colorado (PTRC) situated in the north-eastern border of the Neuquén Basin. The formation is composed of a lower and upper member, the latter being the object of this study. The analysis of five wells distributed in a cross section of 10 km length, allowed the analysis of 150 m of cored succession that cover almost all the stratigraphic extent of the upper member. Facies analysis allowed defining ten of them (A–J), recording storm, tidal, and fluvial processes, as well as trace-fossils mainly of the Cruziana and Cruziana-Skolithos ichnofacies and microbialites distributed in different parts of the succession. Nine Facies Associations (I–IX) were defined and them account for marine, marginal-marine and fluvial environments. The marine record documents deposits from the offshore to shoreface that form part of a first and thickest stratigraphic sequence (Sequence I) dominated by a starved transgression (TST), followed by a shallow and wave-dominated delta system (HST) evidencing multiple directions of progradation, and showing quartz dominated composition derived from old sedimentary units. An erosive sequence boundary denotes the beginning of a new depositional cycle (Sequence II). It starts with estuarine facies (TST) containing the coarsest deposits in the entire succession (conglomerates) that are probably correlatable with incised valleys and fluvial deposits documented in outcrops and subsurface. A remarkable change to a lithic composition with abundant volcaniclastic fragments evidences a supply from younger units than the underlying sequence; additionally, tidal action is amplified by a non-lineal coast. A marine interval records the end of the transgression (MFZ), and later a coarsening upward arrangement (HST) product of bay head deltas grading laterally into mud flats. The uppermost part of the unit records the change in the coast line with the advance of fluvial deposits denoting the new sedimentary change with the reorganization of the depositional system (Sequence III). It starts with unconfined fluvial deposits (LST) that present the peculiarity of bimodal grain-size deposits and well-sorting as a result of reworking of previous eolian deposits. The abundant kaolinite contrasts with the underlying sequence and indicates meteoric water input. The fluvial deposits, oil reservoirs, are sealed by marginal marine deposits on top (TST). The succession is incomplete by erosion of the intra-Senonian unconformity, but the stacked sequences exhibit a similar staking trend as in the outcropping Agua de la Mula Member of the Agrio Formation. The last one is a good surface analog unit for comparing sedimentary processes, sequence stratigraphy and ichnology. Taking into account previous studies and outcrops and subsurface correlations, this study restricts the upper member of the Centenario Formation time-equivalent to the Agua de la Mula Member of the Agrio Formation; a post-earliest Barremian age is disregarded. The integration of all available information confirms that conglomerates recorded in subsurface, and also outcrops are the result of incised valleys related to sea level drops. In this sense the Chachauén volcano outcrops are probably the exposed records of the Centenario Formation, rather than the Agrio Formation. Finally, this study confirms a complex sedimentary evolution of the north-eastern basin border, with tectonic controls and a variable coastal line that allows explaining short distance facies changes. This study demonstrates the usefulness of ichnological approaches with sedimentology, particularly in intervals completely oil-impregnated where sedimentary features are frequently difficult to analyze for paleoenvironmental interpretations.

Modelling of sediment supply from torrent catchments in the Western Alps using the sediment contributing area (SCA) approach

AbstractThe production of coarse sediment in mountain landscapes depends mainly on the type and activity of geomorphic processes and topographic and natural conditions (e.g. vegetation cover) of these catchments. The supply of sediment from these slopes to mountain streams and its subsequent transport lead to sediment connectivity, which describes the integrated coupled state of these systems. Studies from the Northern Calcareous Alps show that the size of the sediment contributing area (SCA), a subset of the drainage area that effectively delivers sediment to the channel network, can be used as a predictor of sediment delivery to mountain streams. The SCA concept is delineated on a digital elevation model (DEM) using a set of rules related to the steepness and length of slopes directly adjacent to the channel network, the gradient of the latter and the vegetation cover. The present study investigates the applicability of this concept to the Western Alps to identify geomorphologically active areas and to estimate mean annual sediment yield (SY) in mainly debris‐flow‐prone catchments. We use a statistical approach that shows a parameter optimisation and a linear regression of SY on SCA extent. We use a dataset of ~25 years of assessed coarse sediment accumulation in 35 sediment retention basins. In the investigated catchments, sediment transport is governed by several factors, mainly by the extent of vegetation‐free areas with a minimum slope of 23° that is coupled to the channel network with a very low gradient of the latter. With our improved framework, we can show that the SCA approach can be applied to catchments that are widely distributed, in a large spatial scale (hectare area) and very heterogeneous in their properties. In general, the investigated catchments show high connectivity, resulting in significant correlations between long‐term average yield and the size of the SCA.

Erosion, deposition and contamination by high‐magnitude subaqueous debris flows and turbidity currents: Insights from the failure of a tailings dam near Quesnel Lake, British Columbia

AbstractThe 4 August 2014 failure of Mount Polley mine tailings dam in central British Columbia, Canada, is the worst environmental disaster in British Columbia history. Around 25 million m3 of water, tailings solids and dam construction materials travelled as a slurry flow down nearby Hazeltine Creek. About 18.6 million m3 of tailings and displaced coarse sediment entered into the narrow, deep, fjord‐like Quesnel Lake. Multibeam echosounding, sub‐bottom profiling, sediment cores and theoretical models are used to examine erosion and deposition on the Hazeltine Creek fan‐delta and the bed of Quesnel Lake by subaqueous sediment density flows generated from the slurry. Strong to very strong subaqueous debris flows eroded two deep subaqueous channels on the fan‐delta in a period of less than 12 h. A model for subaerial debris‐flow erosion overestimates submerged delta‐front erosion rates in the channels because of evolution of the subaqueous debris flows and incomplete liquefaction of the eroding bed. The debris flows deposited a localized debrite with a hummocky surface composed of fine tailings and coarse displaced fan‐delta and fluvial sediment. A flat, featureless, surface composed of fine‐grained sediment adjacent to the debrite is interpreted as debrite/turbidite resulting from debris flows proximally and turbidity currents distally. Copper concentrations in cores are highly elevated compared to background concentrations in pre‐event native lacustrine sediment. Deposits from subaqueous sediment flows generated by earthquakes and glacial lake outburst floods are generally thinner than those in Quesnel Lake caused by the tailings dam failure.

Analysis of Application of Sediment Trap in Rivers as An Effort Reservoir Sedimentation Control

Reservoir sedimentation can be overcome by reducing the amount of sediment that enters the reservoir, by building check dam. The check dam has more deposited coarse sediment load than fine sediment load. Fine sediment that escapes the check dam will flow further and eventually enter the reservoir pond. Therefore it is necessary to build a building that can capture fine sediments. Construction is planned as a system of sediment trap in irrigation channels. The purpose of this study is to analyze the possibility of applying the sediment trap in the river to deposit sediments that escape the check dam. The analysis begins with the selection of the location of the sediment trap, then calculate the dimensions of the sediment trap and the amount of sediment that has settled. Based on the analysis of the selected dimensions with several combinations of gradation of sediment grains, sediment deposition that occurs ranges from 42 - 68%. So it can be concluded making the sediment trap in the river can be done. However, for the application of these sediment traps further research is needed regarding the dimensions of sediment traps that are most optimal for sediment deposition.

Residence and movement patterns of the marbled flounder Pseudopleuronectes yokohamae around a spawning ground in southern Suo Nada, Seto Inland Sea, Japan

The residence and movement patterns of the marbled flounder Pseudopleuronectes yokohamae were investigated around a spawning ground located off the coast of Nagasaki point, southern Suo Nada, Seto Inland Sea, Japan. Twenty marbled flounder (9 females and 11 males) tagged with ultrasonic transmitters were released on November 29, 2017, before the peak spawning season (peak spawning season: mid–late December), and their distributions were recorded by 15 acoustic receivers until January 21, 2018. Eighteen fish roamed around in the study site or disappeared from the study site but appeared again. The 18 fish then emigrated from the study site by mid-December. The remaining two (1 female and 1 male) of the 20 tagged fish resided until mid-January and continuously roamed around areas of silt–clay to very coarse sand bottom sediments both day and night during the peak spawning season. Movement patterns of marbled flounder may be related to spawning site selection or reproductive behaviors. The fish that emigrated may have roamed around the study site or surrounding areas in order to judge whether to spawn there, but most of them may not have in the study site. In contrast, the remaining two fish may have reproduced within the study site.

Effects of large wood (LW) blockage on bedload connectivity in the presence of a hydraulic structure

Large wood (LW) commonly forms log jams, influencing bed composition and biota via complex flow-sediment-wood interactions. A LW blockage, often induced by river-crossing infrastructure, can strongly alter channel hydraulics and sediment transport patterns, thus inducing a ‘forced’ channel morphology. For studying the deposition of bedload gravel fractions in the presence of a rigid LW jam, a novel experimental setup is presented. Using a mobile bed stream table, the effects of a channel-spanning blockage (a ‘dam jam’), resting at a bridge pier, on sediment transport and scour dynamics are examined. Changes in channel morphology were measured using Structure from Motion (SfM) photogrammetry and manually obtained bedload measurements. For the experiment without LW accumulation in place, natural bedload transport was observed over the entire channel length - about 20% of fed colour gravel was recovered from the sediment trap at the outlet, while a total bedload interruption occurred in presence of the LW accumulation, resulting in trapping all fed gravel material upstream of the obstructed cross-section. The volumetric deviation between SfM and manual measurements was less than 0,4%. The porosity characteristics of the LW accumulation were analysed using volumetric meshing techniques. With our experiments, we demonstrated that a relatively high log jam porosity has significant impact on channel morphology. By interrupting the hydraulic energy gradient, the movement of coarse sediment transport is damped, forcing deposition and initiating the development of a sediment wedge upstream of the infrastructure. Our quantitative results provide new insights into how LW can force channel morphology (particularly sediment storage) through the alteration of channel hydraulics. We further elaborate on how novel laboratory-based SfM techniques can be used to enhance the current understanding of complex flow-sediment-wood interaction processes at engineered in-stream structures.

You cannot conserve a species that has not been found: The case of the marine sponge Axinella polypoides in Liguria, Italy

Abstract Detailed knowledge about the distribution of species in need of protection is required for the management of Marine Protected Areas, a major tool to reduce marine biodiversity loss. Such knowledge is deficient for most marine invertebrates. Axinella polypoides is a marine sponge included on the list of protected species by the Barcelona Convention (1976) and the Bern Convention (1987). This large and erect species has an important ecological role in habitat forming and benthic–pelagic coupling. Bathymetrical, geographical and ecological data over the last 60 years were collated from publications and reports, together with new surveys to assess the distribution and protection status in Liguria of A. polypoides. It identified a more widespread distribution than previously thought, which points at a general need for dedicated investigations on the occurrence of species that require protection. Bathymetrical distribution was trimodal, with peaks corresponding to different geomorphological settings: coastal cliff bases (around 38 m depth), inner shelf shoals (52 m) and rocks amidst coarse sediment on the outer shelf (79 m). Density was significantly greater at the shallowest depths. The species was mostly found in the coralligenous biocoenosis, in association with other characteristic species or forming a monospecific facies. On (sub)vertical cliffs, A. polypoides often exhibited an unusual cane shape, rather than the typical bushy morphology, thus causing confusion with the congeneric A. cannabina, a more southern species. Records of the latter in the Ligurian Sea therefore need confirmation. Only a minority (22.6%) of A. polypoides records were in Marine Protected Areas, the remainder being located in areas with no current environmental protection plans in place. While the occurrence of this species in MPAs remained stable over the decades, the only quantitative historical data available indicated that populations in non‐protected areas were declining owing to anthropogenic impacts (fishing and anchoring).

Distribution and possible sources of polycyclic aromatic hydrocarbons (PAHs) and metals in marine surface sediments off northern Mozambique

Liquid natural gas (LNG) exploration has started off the coast of northern Mozambique, in the Rovuma Basin, East Africa. In advance of gas production, we collected in 2018 over 100 samples of surface sediments from 40 locations in the pristine and exploration areas at water depths of 5–2000 m. We have determined the levels of hydrocarbons (total hydrocarbon contents (THC) and 49 individual PAHs), heavy metals, arsenic, grain size and total organic carbon. While sediment composition varied strongly from coarse sediment to high mud contents (<63 μm), background levels of hydrocarbons and metals were found in most samples. We found anthropogenic contamination at one site in Pemba harbor. We observed no petroleum-related contamination, including the Palma area with numerous exploration wells. Elevated concentrations of barium and THC at some locations in this area are attributed to drilling activities but are not considered to be of environmental concern.

Impact of check dam series on coarse sediment connectivity

Check dams are frequently built in mountain streams as sequences of stair-like grade-control structures to stabilise longitudinal profiles and decrease bedload transport rates. However, their effect on sediment connectivity is still not properly understood owing to missing field data about particle mobility through check-dam sequences. In this study, we tracked tagged particles in a reach intensively managed by torrent control works (i.e., a straightened channel stabilised by a sequence of consolidation check dams and bank reinforcements) and in an untreated pool-riffle reach with similar catchment-scale characteristics. Data on water level and particle mobility were collected over two years and five resurveys. In addition, we measured the grain-size characteristics of armour and subarmour bed layers to assess potential armouring processes in relation to the presence of the check dams. The tracking of tagged particles showed clear differences in the longitudinal and channel-unit patterns of particle retention between the studied reaches after two bankfull events. The presence of the torrent control works accelerated the downstream transport of the tagged particles despite lower calculated unit stream powers in comparison with those in the unmanaged reach. We observed a close-to-normal longitudinal distribution of the tagged particles and longer travel distances in the managed reach. In contrast, the pool-riffle reach indicated high retention of recovered particles in fresh bar deposits and a left-skewed distribution of the final travel distances. In addition, the managed reach with check dams indicated strong bed armouring processes that likely made the vertical exchange of particles between sedimentary layers difficult. In contrast to the general perception of check dams as decelerators of downstream sediment fluxes, our field experiment demonstrated a specific case when sequences of consolidation check dams in small and relatively low-gradient managed channels can act as boosters of longitudinal sediment connectivity.

Experiments on restoring alluvial cover using gravel augmentation in a variable width channel with irregular meanders

In partially-alluvial channels, an understanding of cover formation over a non-alluvial substrate is necessary for effective river management or restoration. Urban rivers, for example, are often sediment starved such that the underlying substrate may be exposed. Few experiments have investigated cover development in meandering channels, particularly where width and meander geometry are irregular as is often the case for partially alluvial channels. The purpose of this work is to support the development of sediment augmentation strategies to mitigate channel degradation and restore alluvial cover. The experiments also provide new insight into the impact of sediment supply rates on alluvial cover dynamics in variable-width channels. Under constant flow discharge and a continuous supply of sediment, sediment disperses downstream of the feed location and cover develops in a fragmented fashion. Cover initiation occurs downstream of bend apexes and develops as a series of discrete fixed bars whose morphology differs as a function of bend geometry and channel width. Cover expands and bars merge with time under steady sediment supply and discharge, eventually thickening to an equilibrium state in which sediment supply and output are approximately balanced. Higher sediment supply rates result in more extensive and thicker cover at equilibrium, including cover expanding into the cross-overs between the main bars. Coarse and fine fractions of the sediment supply are preferentially retained in the cover sediment because of fine particle deposition on bar tops and burial of initial coarse deposits. Models of areal cover with feed rate and cover thickness are proposed and compared with other studies. More experimentation is needed, but augmentation of alluvial gravel cover is a feasible approach to maintaining a sediment balance in partially-alluvial channels and for developing mobile alluvial cover in engineered channels.

Demersal fish communities in KwaZulu-Natal, South Africa, indicate partial congruence with proposed conservation biozones

The KwaZulu-Natal shelf, on the east coast of South Africa, is inhabited by diverse communities of demersal fishes; however, previous studies deeper than 30 m have largely investigated these with extractive techniques. Using baited remote underwater videos (BRUVs), this study quantified how depth and substrate type correlated with the composition of demersal fish communities between 35 and 100 m, and assessed whether the communities displayed congruence with three benthic biozones, which were modelled using abiotic surrogates for purposes of conservation planning: Biozone 1 (warm; coarse sediment dominant; low seafloor oxygen, phosphate and organic carbon concentrations), Biozone 2 (flat; coarse sediment dominant; high seafloor oxygen and low phosphate and organic carbon concentrations) and Biozone 3 (shallow; warm; fine sediment dominant; low seafloor oxygen and higher organic carbon concentrations). A total of 118 fish taxa were recorded from 200 BRUV deployments conducted on different substrate types. All diversity indices differed significantly among substrate types, whereas depth correlated significantly with only the number of fish species per site and Margalef’s diversity index. Multivariate analyses determined that substrate type and depth explained significant amounts of the variation in fish communities. A significant difference was also detected between the fish communities of Biozones 1 and 3, with Biozone 3 being the most distinct of the three biozones investigated. Overall congruence between fish communities and their associated biozones ranged between 41% and 45%. This suggests that, at a broad spatial scale, the demersal fish communities could be adequately represented by Biozone 3 and a second biozone comprising Biozones 1 and 2 combined.

Valorisation of Auriferous Indices: Case of the Siribaya Deposit, Western Mali

The purpose of this paper is to understand the valorization of gold showings in the Seribaya deposit, western Mali. Samples taken from Air Core (AC) boreholes were subjected respectively to the magnetic susceptibility test and the X-ray fluorescence analysis. These results lead to the development of a simple methodology, based on signatures/indicators geochemical to identify lithology or to locate mineralization. We note that, compared to other chemical elements, Arsenic remains the most correlated with gold in the study area. Since this correlation remains weak (r = 0.16), it shows that Arsenic does not always accompany gold. There would be a generation of Arsenic related to mineralization, and other generations that would not be. The observation of the strip logs led to the identification of the lithologies (focusing on the immobile elements, Ti, V, Cr, Y, Zr) and the establishment of the alteration profile. Highly altered levels (Saprolite ± Saprock) are characterized by the disappearance of most mobile elements. A medium to strong correlation between gold mineralization and magnetic susceptibility measurements has been observed, in some places, and at depths. These mineralized intervals typically consist of quartz veins, suggesting that they have structural control over the mineralization. Gold mineralization is believed to be related to quartz veins. In addition, gold would be in paragenesis with a generation of Arsenic hosted in coarse sediments.

Innovative method for installing soil moisture probes in a large‐scale undisturbed gravel lysimeter

AbstractAquifers of coarse gravel are an important source for drinking water; however, coarse sediments are also particularly susceptible to the rapid and long‐range transport of pollutants through the vadose zone. Therefore, understanding the flow and solute transport in unsaturated gravel material is of utmost importance for the protection of drinking water resources. Experimental investigations of flow and transport processes are dependent on suitable sensor technology, but it is a considerable challenge to install soil moisture sensors in gravelly material. In this note, we developed a novel method to install soil moisture sensors with minimal disturbance in a large lysimeter with undisturbed gravelly sedimentary material, based on drilling access cavities in frozen material. We investigated whether it is possible to obtain reliable soil moisture measurements and found that the probes measured the flow dynamics pattern well but could not quantify realistic absolute water content values.

Transport characteristics of non-uniform suspended sediment in the Jingjiang Reach after the Three Gorges Project operation

三峡工程运用后，坝下游荆江段来沙量大幅度减小，处于严重的不平衡输沙状态，次饱和水流冲刷河床使悬沙量沿程恢复.基于实测水沙资料，分析了三峡工程运用后荆江段非均匀悬沙恢复特点.提出了恢复效率的概念用以表征悬移质沿程恢复的程度，并根据实测水沙资料计算了荆江段1994-2017年非均匀悬沙的恢复效率.结果表明：三峡工程运用前，荆江段各粒径组悬沙恢复效率绝对值均接近0，故该时期内各粒径组泥沙冲淤幅度不大；三峡工程运用后，各粒径组悬沙恢复效率绝对值均明显增大，且粗沙（d>0.125 mm）恢复效率绝对值远大于细沙（d<0.125 mm），故粗沙恢复程度更高.这主要是由于荆江段床沙组成中粗沙部分含量大，而细沙含量小.最后建立了三峡水库蓄水后非均匀悬沙恢复效率与来水来沙条件（来沙系数）的关系，结果表明：各粒径组悬移质恢复效率均与来沙系数呈正相关关系，全沙、细沙和中沙的决定系数（R²）分别为0.89、0.67和0.69，相关性较高，故荆江段各粒径组悬移质泥沙恢复效率较大程度上受到来水来沙条件的影响.;The amount of suspended sediment entering the Jingjiang Reach of the middle Yangtze River has been greatly reduced owing to the operation of the Three Gorges Project (TGP), which caused the sediment transport of the reach at a severe non-equilibrium state, and the suspended sediment concentration recovered during the channel scour process. Therefore, the characteristics of non-equilibrium transport of non-uniform suspended sediment were analyzed based on the measured flow and sediment data. In addition, the recovery efficiency was proposed to represent the recovery speed for suspended sediment load, and the corresponding values were calculated annually from 1994 to 2017 based on the measured data of the Jingjiang Reach. Calculated results show that the suspended sediment recovery efficiency of all particle-size groups was very close to zero before the TGP operation, which means that the channel deformation was small during this period. However, the recovery efficiency of each particle-size group increased greatly after the operation of TGP, and the recovery efficiency of coarse sediment (d>0.125 mm) was much higher than that of fine sediment (d<0.125 mm). This is mainly because the content of coarse sediment in bed-material of Jingjiang Reach is large, while the content of fine sediment is relatively small. Finally, empirical relationship was developed between the recovery efficiency and incoming flow-sediment regime, which shows that the recovery efficiency of each group was negatively related to incoming sediment coefficient, with the correlation coefficient for the total, fine and coarse sediment being 0.89, 0.67 and 0.69, respectively. Therefore, it can be concluded that the recovery efficiency of suspended sediment was significantly affected by the incoming flow and sediment conditions.

Dropstones in the Mar del Plata Canyon Area (SW Atlantic): Evidence for Provenance, Transport, Distribution, and Oceanographic Implications

AbstractA variety of gravel‐ to cobble‐sized rocks, recovered from the Mar del Plata (MdP) Canyon area (Western South Atlantic at 38°S) and interpreted as ice‐rafted debris, represent the first evidence that large icebergs have floated in the Falkland (Malvinas) Current from the southern polar high latitudes far northward. Detailed petrographic analyses identified the Antarctic Peninsula, sub‐Antarctic islands in the Scotia Sea, and Tierra del Fuego as plausible source areas. The drift process could have started as early as at the beginning of the last deglaciation, according to an age obtained from a cold‐water coral fragment associated with one of the dropstones. At the end of the Last Glacial Maximum, large icebergs have been supplied to the Antarctic Circumpolar Current, captured by those ocean current branches that circumvent the Falkland (Malvinas) Islands and entered the Argentine Margin. When the iceberg fleets approached the Brazil‐Falkland (Malvinas) Confluence Zone with its steep latitudinal temperature gradient, the icebergs got oceanographically trapped and melted off rapidly. The sediment load sinking down to the seafloor formed a dropstone blanket particularly where the MdP Canyon had incised into the continental slope. Here, mass‐flow processes, induced by local slope instability, and along‐slope sediment resorting, due to the erosional effects of strong and persistent contouritic bottom currents, favored local enrichment in dropstones in the form of a loose, coarse sediment drape inside morphological depressions. The bottom current velocity would be locally strong enough to rework this sediment, leaving coarse rafted debris as a lag deposit.

Ecological management technology for coarse sediment area in the Yellow River Basin

Across wide range of research survey of the Pisha stone area landform, erosion and vegetation characteristics, on the basis of conducting the Pisha stone under different conditions of underlying surface erosion characteristics of the test, at the same time the wide range of investigation, access, summarizes the local government and the management experience and management pattern of the masses, summarizes the research of Yulin Pisha stone areas covered sand erosion governance approach and the prevention and control technology.

Review of the syn-rift to early post-rift depositional systems of the Cretaceous Mauléon rift: sedimentary record of continental crust hyperextension and mantle denudation (Western Pyrenees)

The Mauléon Basin, in the northwestern Pyrenean Belt, is related to Early Cretaceous rifting and mantle denudation. Here we review the evolution of depositional systems in the Mauléon Rift Basin during Albian and Cenomanian time. This review includes the lithostratigraphy, regional distribution, boundaries, age and facies sedimentology of the basin’s syn-rift formations and their members. We construct paleogeographic maps to elucidate (1) the 3D distribution of sedimentary facies and depositional systems during the Albian and Cenomanian from the Iberian proximal margin to the hyperextended domain and (2) the link between major extensional structures and sedimentation during rifting and mantle denudation. The Mauléon Rift was supplied during most of the Albian by sediments from the Iberian proximal margin. The southern margin had a steep and abrupt topographic boundary related to a northward crustal rollover along the south-dipping Saint-Palais detachment. This feature controlled the deposition of coarse-grained turbidites at the base of the margin that abruptly gave way to low-density turbidites, then deep-basin deposits in the hyperextended domain. During uppermost Albian to Early Cenomanian time, mantle denudation occurred in the eastern Mauléon Basin and the vergence of the detachment systems reversed. Minor debris-flow deposits formed at the foot of fault scarps associated with the newly formed north-dipping detachments. Elsewhere, sediment from deltaic systems to the west in the Saint-Jean-de-Luz area deposited low-density turbidites in the hyperextended domain. During the post-rift stage, the flux of coarse sediment from the detachment footwall gradually declined as deformation waned, and low-density turbidites expanded onto the hyperextended domain from the European Upper Cretaceous carbonate platform. These paleogeographic reconstructions, in addition to offering a synthetic view of the evolution of sedimentary environments during rifting, offer new insight into the post-rifting exhumation of the lower crust and mantle.

Restoring Dynamic Fluvial Processes in Urban Rivers: Learning from the Aire and Isar Rivers

In process-based restoration, the objective is not to create a complex river form directly; instead, interventions are intended to “prompt” the natural processes to restore such forms. The improvements in ecological conditions are actually made over time by flowing water during floods (using the stream’s energy), and by the growth of riparian vegetation (using incoming solar energy). On the Aire River in Geneva, ecological function was restored to a formerly canalized river by providing the river with an <i>espace de liberté</i>. A grid of channels cut into the valley bottom allowed the river to freely flood, erode its bed and banks, and deposit bars, creating complex surfaces on which riparian vegetation established to support the food web of the riverine ecosystem. The diamond-shaped bits of land left between these channels (“lozenges”) gradually erode and evolve as the river migrates, creating complex channel forms. The Isar River in Munich restoration involved adding coarse sediment load, creating erodible bed and banks in place of formerly rigid boundaries, expanding process space for river migration, erosion, and deposition, and increased human access to the river over 8 km. Since restoration, natural transport of sediment has resulted in deposition of gravel bars, whose forms evolve during floods, supporting diverse habitats. The Isar and Aire Rivers provide compelling examples of processbased restoration meeting 4 criteria for process-based restoration: space, energy, materials, and time. They demonstrate the possibilities of urban river restoration to achieve both ecological and social goals through restoration of fluvial process.

Penurunan Kadar BOD dan COD Limbah Cair Dengan Sistem Coarse Screen, Sedimentasi, Biofilter Anaerob-Aerob

Waste from abattoir activities has high organic matter content. One wastewater alternative that suitable for abattoirs is used to utilize a combination of the anaerobic biofilter and aerobic biofilter. Which including a coarse screen, sedimentation, anaerobic biofilter, and aerobic biofilter. It made the treatment system can reduce levels of BOD snd COD waste batters. This study aims to determine the difference between the residence time variations of aerobic biofilter in reducing the BOD and COD levels of wastewater from abattoirs. The research is experimental. Using one group pretest-posttest design. Data analysis used the analysis of variance = 0,05.The analysis result of BOD and COD content wast decreased after treatment at each residence time, with 6 hours of residence time in an aerobics biofilter was reduced 70 percent BOD levels and 66,2 percent COD. 24 hours residence time had the ability to reduced 80 percent BOD content and 7 percent of COD content.Based on a one way analysis of variance results that there is a significant difference from all residence time because of Pvelue (0,00

A Survey of Sediment Fineness and Moisture Content in the Soyang Lake Floodplain Using GPS Data

Abstract Soyang Lake is the largest lake in Republic of Korea, bordering Chuncheon, Yanggu, and Inje in Gangwon Province. It is widely used as an environmental resource for hydropower, flood control, and water supply. Therefore, we conducted a survey of the floodplain of Soyang Lake to analyze the sediments in the area. We used global positioning system (GPS) data and aerial photography to monitor sediment deposits in the Soyang Lake floodplain. Data from three GPS units were compared to determine the accuracy of sampling location measurement. Sediment samples were collected at three sites: two in the eastern region of the floodplain and one in the western region. A total of eight samples were collected: Three samples were collected at 10 cm intervals to a depth of 30 cm from each site of the eastern sampling point, and two samples were collected at depths of 10 and 30 cm at the western sampling point. Samples were collected and analyzed for vertical and horizontal trends in particle size and moisture content. The sizes of the sediment samples ranged from coarse to very coarse sediments with a negative slope, which indicate eastward movement from the breach. The probability of a breach was indicated by the high water content at the eastern side of the floodplain, with the eastern sites showing a higher probability than the western sites. The results of this study indicate that analyses of grain fineness, moisture content, sediment deposits, and sediment removal rates can be used to understand and predict the direction of breach movement and sediment distribution in Soyang Lake.