Fluvial Sedimentology Research Papers - Academia.edu (original) (raw)

Diamond-bearing gravels of the Lichtenburg-Ventersdorp area of the North West Province are associated with north-south orientated sinuous 'runs' that occur almost entirely on a flat erosional surface of the Malmani dolomites (Transvaal... more

Diamond-bearing gravels of the Lichtenburg-Ventersdorp area of the North West Province are associated with north-south orientated sinuous 'runs' that occur almost entirely on a flat erosional surface of the Malmani dolomites (Transvaal Supergroup) at some 1,500 m elevation. East to west, this dolomite plain measures 150 km, and north-south it is on average 40 km wide. This unconformity, which first developed before the Pretoria Group sedimentation over a period of at least 80 Myr, is marked by siliceous breccias (palaeo-karst infill) and conglomerates (reworked breccias). It was exhumed in pre-Karoo and post-Gondwana times. Glacial pavements and remnants of thin Lower Karoo sediments are also found on this polyphase surface. The gravels that make up these 'runs' and sinkholes directly or indirectly linked to these runs, are coarse-grained, very poorly-sorted, and are best described as diamictites. The 'runs' are narrow, elongated, generally positive ridges that meander across the dolomite surface and are up to 30 km long and between 80 to 300 m wide. They have always been regarded as post-Cretaceous drainage features linked to southward-flowing river systems. Diamonds were discovered in these 'runs' and they have produced some 12 million carats. However, no Cainozoic fossils or artefacts have ever been found in almost 90 years of mining. From new field evidence, geomorphological studies, age dating from inclusions in diamond and zircon and clay analyses, it is proposed that these coarse-grained runs represent proximal palaeo-eskers of the last deglaciation of the Dwyka continental ice sheet, that are preserved on this ancient 'palimpsest' surface. The age of the deposit is constrained by two populations of agate within the diamictites that are linked to two separate volcanic units of the Pretoria Group. In addition, the youngest crustal zircon ages from the gravels are 1 Ba, but mantle zircons from Lichtenburg suggest that these have been derived from Cambrian age kimberlites. Analysis of inclusions in diamond support a Neoproterozoic to Cambrian source for the diamonds, so the absence of diamonds from Mesozoic kimberlites and Cainozoic fossils within the gravels support the conclusion that the runs are of Karoo age.

Sediment transport is a prevalent vital process in uvial and coastal environments, and \incipient motion" is an issue inseparably bound to this topic. This study utilizes a novel hybrid method based on Group Method of Data Handling (GMDH)... more

Sediment transport is a prevalent vital process in uvial and coastal environments, and \incipient motion" is an issue inseparably bound to this topic. This study utilizes a novel hybrid method based on Group Method of Data Handling (GMDH) and Genetic Algorithm (GA) to design GMDH structural (GMDH-GA). Also, Singular Value Decomposition (SVD) was utilized to compute the linear coeecient vectors. In order to predict the densimetric Froude number (Fr), the ratio of median diameter of particle size to hydraulic radius (d=R) and the ratio of sediment deposit thickness to hydraulic radius (t s =R) are utilized as eeective parameters. Using three diierent sources of experimental data and GMDH-GA model, a new equation is proposed to predict incipient motion. The performance of development equation is compared using GMDH-GA and traditional equations. The results indicate that the presented equation is more accurate (RMSE = 0:18 and MAP E = 6:48%) than traditional methods. Also, a sensitivity analysis is presented to study the performance of each input combination in predicting incipient motion.

Many techniques are available to actively manage reservoir sedimentation, and an equally important suite of adaptive strategies are available for managing the impacts of sedimentation without manipulating the sediment. Successful... more

Many techniques are available to actively manage reservoir sedimentation, and an equally important suite of adaptive strategies are available for managing the impacts of sedimentation without manipulating the sediment. Successful reservoir management to combat the effects of sedimentation may employ a combination of active plus adaptive strategies. This paper describes both active and adaptive strategies to manage reservoir sedimentation, and may be useful as a checklist of options to consider in addressing a sedimentation problem. Widespread application of both active and adaptive strategies will be required to successfully address the growing sedimentation problem worldwide.

Fluvial geomorphology affects river character, behaviour, evolution, trajectory of change and recovery potential, and as such affects biophysical interactions within a catchment. Water bodies in South Africa, in common with many other... more

Fluvial geomorphology affects river character, behaviour, evolution, trajectory of change and recovery potential, and as such affects biophysical interactions within a catchment. Water bodies in South Africa, in common with many other water-stressed parts of the world, are generally under threat due to increasing natural and anthropogenic influences including aridity, siltation and pollution, as well as climate and environmental change. This study reports on a case study to characterise the geomorphology of different river systems in South Africa, with the aim of better understanding their properties, controls, and implications for biophysical interactions including water quality, biodiversity (aquatic and riparian), and human activity within the catchment. The approach adopted is based on the River Styles® framework (RSF), a geomorphology-based approach developed for rivers in New Zealand and Australia, but applied here for the first time to South Africa. Based on analysis of remote sensing imagery, SRTM-2 digital topographic data and field observations on sites through the entire river system, six geomorphic elements were identified along the Sabie River, northeast South Africa (gorge, bedrock-forced meander, low-moderate sinuosity planform controlled sand bed, meandering sand bed, low sinuosity fine grained sand bed, and floodouts), using the RSF classification scheme and based on the RSF procedural tree of Brierley and Fryirs (2005). Previous geomorphological studies along the Sabie River have shown that different reaches respond differently to episodic floods; we use these data to link river geomorphological character (as defined by the RSF) to the hydrodynamic conditions and processes giving rise to such character. This RSF approach can be used to develop a new management approach for river systems that considers their functional biophysical behaviour within individual reaches, rather than considering them as homogeneous and uniform systems.

In certain cases, the rivers draining mountain ranges create unusually large fan-shaped bodies of sediment that are referred to as fluvial megafans. We combine information from satellite imagery, monthly discharge and precipitation... more

In certain cases, the rivers draining mountain ranges create unusually large fan-shaped bodies of sediment that are referred to as fluvial megafans. We combine information from satellite imagery, monthly discharge and precipitation records, digital elevation models, and other sources to show that the formation of fluvial megafans requires particular climatic conditions. Specifically, modern fluvial megafans in actively aggrading basins are produced by rivers that undergo moderate to extreme seasonal fluctuations in discharge that result from highly seasonal precipitation patterns. The global distribution of modern megafans is primarily restricted to 15–35 latitude in the Northern and Southern Hemispheres , corresponding to climatic belts that fringe the tropical climatic zone. No relationship exists between megafan occurrence and drainage-basin relief or area. The tendency of rivers with large fluctuations in discharge to construct megafans is related to the instability of channels subject to such conditions. Because of the correlation between seasonal precipitation and megafan occurrence, the recognition of fluvial megafan deposits in ancient stratigraphic successions may provide critical information for paleoclimate reconstructions.

Reservoir characterization and structural mapping using integration of well logs and 3-D seismic data was carried out to determine the prolificacy of OVU field, onshore Niger delta. The distribution of reservoir physical parameters... more

Reservoir characterization and structural mapping using integration of well logs and 3-D seismic data was carried out to determine the prolificacy of OVU field, onshore Niger delta. The distribution of reservoir physical parameters (porosity, permeability etc.) and availability of traps that favour hydrocarbon accumulation in the field were evaluated. Four hydrocarbon bearing reservoirs were delineated out of several identified sands in the field out of which three horizons were mapped. Two major growth faults, an antithetic fault and five synthetic faults were delineated. Structural closures were identified as rollover anticlines with the trapping mechanism delineated as a Fault assisted anticlinal structure. The computed range of values for gross thickness, volume of shale, net to gross, water saturation, hydrocarbon saturation, total porosity and absolute permeability with respect to each reservoir are: 18-125m, 9-17%, 83-92%, 18-28%, 62-82%, 21-23%, and 736-3965mD respectively. Hydrocarbon reserves calculations reveals a total reserve of 30.9 billion stock tank barrels of oil. With the very good to excellent calculated values of petrophysical parameters and high hydrocarbon reserve together with the suitable trapping mechanisms makes the study field prolific. Few wells exist in the southwestern corner of the field where a closure is identified in this study. The area should therefore be subjected to further evaluation with a view to increasing the number of wells there.

Sequence stratigraphic models for thick fluvial successions continue to evolve to account for controlling factors other than base-level fluctuation. For instance, many models place a sequence boundary at the base of amalgamated... more

Sequence stratigraphic models for thick fluvial successions continue to evolve to account for controlling factors other than base-level fluctuation. For instance, many models place a sequence boundary at the base of amalgamated channel-belt deposits that cap coarsening-upward accumulations, relating this surface to a drop in base level. However, this surface often demonstrates scouring that is no deeper than the thickness of a single channel-fill and may show interbedding between facies above and below, suggesting the surface might, instead, be associated with lateral channel-belt migration. Additionally, these successions commonly develop significantly inland of likely influence by marine shoreline fluctuations and may not respond to eustatic base-level controls, particularly when factoring lag time for effects to propagate upstream. Furthermore, these deposits are typically found in settings of relatively continuous subsidence accompanied by high sedimentation rates, such as foreland basins, in which accommodation is produced proximal to the source, trapping much of the sediment before it reaches a position where it can be impacted by eustatic base-level controls. Deposits that accumulate during early phases of foreland development do not have a connection to the marine realm, yet demonstrate similar patterns to those that do. Other models suggest accommodation is produced by tectonically-induced subsidence, with filling in response to either a slowing of space production or to simple progradation, as coarser proximal deposits accumulate over finer distal deposits. Other factors include variability in discharge relative to sediment supply and distributive vs. contributive channel patterns. With each addition comes new terminology that, in the end, still ties successions to “sequence boundaries,” which, by definition, are “unconformities and their correlative conformities.” Part of the complexity may arise from applying concepts where they don’t fit. One model might work for passive margins, another for foreland basins, and another for rift basins, yet there will always be exceptions, even between one foreland basin and another or within the same basin. Sequence stratigraphy is an effective tool for analyzing sedimentary basins, but we might be handicapping ourselves by forcing it into situations for which it was not designed. It might be more effective to apply simpler, less restrictive terminology to describe and interpret thick fluvial successions.

The petrographic and geochemical composition of the Dharla River sediments has been examined to infer their sediment type, degree of weathering, provenance, and tectonic settings. Petrographically the sediments are characterized by the... more

The petrographic and geochemical composition of the Dharla River sediments has been examined to infer their sediment type, degree of weathering, provenance, and tectonic settings. Petrographically the sediments are characterized by the high quartz content (64.97 to 74.24 wt%), followed by feldspar (7.04 to 15.20 wt%), mica (5.38 to 19.92 wt%), lithic fragment (3.46 to 8.14 wt%), and heavy minerals (1.98 to 6.94 wt%). Geochemical composition shows marked enrichment of SiO 2 (mean ~ 74.16%) and a strong negative correlation with the other major oxides because of quartz dilution. The Chemical index of alteration (CIA, 45.52 to 63.51); Plagioclase index of alteration (PIA, 43.13 to 66.55); W index (20.15 to 32.86) and Rb/Sr ratios (0.35 to 0.98) suggest low to moderate intensity of chemical weathering in the source area. Geochemical classifications of the studied samples show mostly litharenitic immature type of sediments also reflects high index of compositional variability (ICV, 0.96 to 1.72). The ternary diagrams of Al 2 O 3-(CaO + Na 2 O)-K 2 O (or A-CN-K) and of mafic rocks, felsic rocks and degree of weathering of the source rocks (or MFW) and several immobile trace element ratios (e.g. light rare earth element/heavy rare earth element or LREE

The Terani Member represents the syn-rift, Early Cretaceous sequence exposed in the Cauvery Basin. These are the first sediments associated with the initiation and subsequent break-up of eastern Gondwanaland and the separation of India... more

The Terani Member represents the syn-rift, Early Cretaceous sequence exposed in the Cauvery Basin.
These are the first sediments associated with the initiation and subsequent break-up of eastern Gondwanaland
and the separation of India from Antarctica. This article presents extensive field studies to obtain and interpret
sedimentological and ichnological evidence from these syn-rift deposits, and understand facies changes,
environment of deposition and evolution of the basin from the syn-rift to the passive margin phase. The ichnotaxa
found include Thalassinoides isp.,Ophiomorpha isp., insect burrows resembling Skolithos serratus, Planolites
isp., Palaeophycus tubularis, and Chondrites isp. Six lithofacies have been identified, viz. 1. Claystones, 2.
Claystone-sandstone alternations, 3. Feebly cross-laminated, bioturbated sandstones, 4. Planar cross-stratified
clayey sandstones, 5. Lensoid massive sandstones, 6. Conglomerate to very coarse-grained sandstones. Three
distinct depositional environments are interpreted from the association of these facies, viz. upper delta plain
deposits/ fluvial channel-flood-plain, estuarine/lower delta plain deposits and sub-marine deposits. Based on
these associations deposition in the Ariyalur-Pondicherry sub-basin is interpreted to have evolved from an initial
fluvial environment to a transitional marine (paralic) environment from the early rift stage to the late rift stage.
The transition from the syn-rift to the passive margin phase is marked by a hiatus in the depositional record
representing the break-up unconformity.

Lo studio sistematico e diacronico di documenti e cartografie inedite d’archivio è necessario per catalogare gli antichi opifici idraulici, attivi fino al secolo scorso sul territorio, come mulini per la macinatura dei cereali, gualchiere... more

Lo studio sistematico e diacronico di documenti e cartografie inedite d’archivio è necessario per catalogare gli antichi opifici idraulici, attivi fino al secolo scorso sul territorio, come mulini per la macinatura dei cereali, gualchiere per follare i panni di lana, segherie e frantoi ad acqua. Tutte queste strutture si differenziano per la tecnologia dei meccanismi in due categorie: mulini a ruota orizzontale e mulini a ruota verticale. In Basilicata erano presenti entrambe le tecnologie, accomunate dallo stesso sistema di conduzione dell’acqua, una condotta forzata detta torre, o "arubah". I documenti d’archivio hanno permesso di analizzare le caratteristiche costruttive di oltre 800 strutture idrauliche e le principali attività di manutenzione necessarie per il funzionamento costante degli opifici idraulici, di cui ad oggi resta come testimonianza materiale la diffusa presenza di ruderi, accertata anche da rilievi diretti sul campo. Lo studio ha permesso di individuare le caratteristiche del territorio e dei corsi d’acqua maggiormente favorevoli per il posizionamento di un mulino ed ha messo in evidenza le principali cause del danneggiamento delle strutture, dovuto oltre che all’abbandono, anche all’ubicazione dei mulini sul territorio in relazione alle dinamiche fluviali

The Late Cretaceous Bottom Conglomerate Formation from Khasi Group occurs as isolated and coalescent cones. Development of three discrete lithofacies namely clast supported and matrix supported boulder conglomerate, interstratified pebbly... more

The Late Cretaceous Bottom Conglomerate Formation from Khasi Group occurs as isolated and coalescent cones. Development of three discrete lithofacies namely clast supported and matrix supported boulder conglomerate, interstratified pebbly conglomerate and granule conglomerate, and large scale tabular cross bedded pebbly conglomerate within the Bottom Conglomerate Formation represents the debris flow, mudflow and water-flow deposits of alluvial fan respectively. Proximity of this alluvial fan to Dawki fault indicates that this fault and its associated faults provided the basin depression, geomorphic contrast together with the climate favoring the debris flow process to build an alluvial fan. Thin section studies of the matrix of these conglomerates revealed quartzose wacke nature, indicating mineralogical maturity and textural immaturity of these sediments. The thin section studies also suggest prevalence of humid climate during deposition. The high proportion of zircon, and transparent heavy mineral assemblage of augite, rutile, monazite, sillimanite, spinel, sphene, dumortierite, and anatase, suggests that the sediments under study are derived from mixed provenance such as Proterozoic Supracrustal High Grade Granulite Metasediments, Gneissic Complex, Late Proterozoic Porphyritic Granitoids, Shillong Group, Khasi Metabasics with some inputs from the Sylhet Trap Basalts and their associated intrusives. Geochemical studies of these sediments support the mixed provenance for these sediments, and indicate humid climate during their deposition, thereby supporting the thin section and heavy mineral studies.

The objectives of the study were to: determine bathymetry of the reservoir; understand seasonal hydrological regimes of the reservoir; determine factors influencing reservoir bathymetry and, examine the implications of the reservoir's... more

The objectives of the study were to: determine bathymetry of the reservoir; understand seasonal hydrological regimes of the reservoir; determine factors influencing reservoir bathymetry and, examine the implications of the reservoir's bathymetry on livestock water demand and policy decision making. The determined reservoir bathymetries and capacities at low, medium and full levels confirmed drastic changes in water volumes and eventually, a threat to water security for livestock. This unsteady equilibrium in reservoir's bathymetry and water volumes was mainly due to high mean annual siltation rates (>5,000 tyr-1). Using 3D spatial analysts tools in ArcGIS 10.3 and spreadsheet Microsoft Excel to analyze the data based on the study, hypsometric curves showed strong non-linear relationships among water depth and water surface; water depths and water volume, as well as water surface area and water volume. Generally, through inter-seasonal comparisons of reservoir's bathymetries and water volumes between 2015 and 2017, this study illustrates the significance of bathymetric study of small reservoirs as a plinth to provide policy context and guidelines on water resource management for livestock, as a missing component in general studies of bathymetry, which are usually predominated by understanding the physical processes, but with little or no emphasis on their meaning towards addressing societal needs. Hence, a community engaged strategy to addressing upstream sediment-generating activities would help in stabilizing the bathymetry of the reservoir and eventually enhance water security for livestock. Contribution/Originality: This study is one of very few studies which have investigated implications of bathymetric surveying on sustainable water resource management for livestock. The study documents how bathymetric surveying can be used to understand seasonal hydrological regimes and storage capacity loss of small reservoirs so as to prepare for water security.

Geophysical, sedimentological, palynological, absolute-age dating and archeological techniques were used to study the deposits of the Early Medieval fluvial channel in the area of the Great Moravia Empire agglomeration Pohansko near... more

Geophysical, sedimentological, palynological, absolute-age dating and archeological techniques were used to study the deposits of the Early Medieval fluvial channel in the area of the Great Moravia Empire agglomeration Pohansko near Břeclav. Artificial profile situated on the base of ERT profiles and the archeological results led to opening of the fluvial channel. Newly documented fluvial channel erosively cut the complex of flood loams. Gravel lag covers the bottom of the channel and grade upwards into sandy channel infill with fining upward trend. Fluvial sandy dunes forming the most characteristic architectural element of the infill are represented mostly by trough cross-stratified medium-grained sands. These sands were penetrated by the piece of oak wood. Both the OSL dating of the sandy deposits and the dating of the oak wood (14C and dendrochronology) point to the 9th century AD when the Great Moravia Empire was on its peak expansion. Active fluvial channel was probably used as a part of the fortification system and a possible wood bridge existed here in the front of the proposed Western Gate of the Pohansko agglomeration. Palynological studies reveal some fragmentation of the landscape and agricultural activities in the close surroundings. Deposits of the studied fluvial channel were covered by the beds of the younger flood loams.

This chapter describes the internal megascopic features of a sediment. These are termed sedimentary structures, and are distinguished from the microscopic structural features of a sediment. Sedimentary structures are divided into primary... more

This chapter describes the internal megascopic features of a sediment. These are termed sedimentary structures, and are distinguished from the microscopic structural features of a sediment. Sedimentary structures are divided into primary and secondary classes. Primary structures are those generated in a sediment during or shortly after deposition, whereas secondary sedimentary structures are those that form sometime after sedimentation. The chapter discusses various examples of both primary and secondary structures. Primary sedimentary structures are divisible into inorganic structures, and organic structures. The observation, interpretation, and classification of inorganic sedimentary structures are considered. The chapter describes two basic approaches to observe sedimentary structures. The first approach is to pretend the outcrop is a borehole and to measure a detailed sedimentological log. This records a vertical section of limited lateral extent. The second method is to create a two-dimensional survey of all, or a major part, of the outcrop.

The purpose of this field trip is to allow participants to examine the stratigraphy, sedimentology, and palaeontology of the Shoalhaven Group and the Illawarra Coal Measures of the southern Sydney Basin exposed along the south coast of... more

The purpose of this field trip is to allow participants to examine the stratigraphy, sedimentology, and palaeontology of the Shoalhaven Group and the Illawarra Coal Measures of the southern Sydney Basin exposed along the south coast of New South Wales from Batemans Bay north to Wollongong (Figs 2 and 3). A number of key localities have been selected for inspection and are described and discussed in this guide, along with a brief description on the regional geological setting and geologicaJ history of the southern Sydney Basin.

A segment of the Upper Rhine River presenting both anastomosed and braided was investigated. This area gives us the opportunity to study settlement dynamics during two key periods of the Holocene. The Roman Period characterised by a first... more

A segment of the Upper Rhine River presenting both anastomosed and braided was investigated. This area gives us the opportunity to study settlement dynamics during two key periods of the Holocene. The Roman Period characterised by a first major anthropogenic impact on the environment and poorly documented climatic changes. The Little Ice Age, when human settlement and climate may be well documented with high reliability.
A wide methodological approach has been completed to combine results from geomorphology, stratigraphy, geophysics, G.I.S., palynology, dendrochronology and archaeology. This dataset shows:
1/ documentary flood frequency variations of the Rhine River during the last 800 years. These chronological variations show some dissimilarity with other French rivers reconstructed documentary flood series. That attests a primary control of catchment’s characteristics and regime type on long term hydrological dynamics.
2/ changes in the Rhine River and floodplain dynamics during Little Ice Age before major anthropogenic river management of 19th century. Planform changes, riverine forest, land use evolution, and anthropological settlement processes are described and quantified. These results allow the identification of major stratigraphic agent factors role responsible of these changes.
3/ the alluvial landscape character where the Oedenburg site settled, together with the evolution of the riverine forest influenced by the Rhine River hydrodynamics.
4/ settlement dynamics during Antiquity. Four major settlement phases have been evidenced by spatial distribution analysis of roman coins found by pedestrian prospecting during the last twenty years. Settlement dynamics may have been influenced by either historical or environmental impacts.
5/ variations in alluvial dynamics of the Rhine River during Antiquity such as high water table or flooding events.

According to ancient literary tradition, Utica is considered to be one of the first three Phoenician foundations in the Western Mediterranean, supposedly founded in 1101 BC by Levantines from Tyre. In the Phoenician and Roman periods it... more

According to ancient literary tradition, Utica is considered to be one of the first three Phoenician foundations in the Western Mediterranean, supposedly founded in 1101 BC by Levantines from Tyre. In the Phoenician and Roman periods it was an important merchant coastal town, on a promontory facing the sea. Over the centuries Utica lost its access to the sea, and its ports silted up as a consequence of the activity of the wadi Medjerda, which flowed to the south of the city. Despite over a century of investigation by archaeologists and associated researchers, the location of the city’s harbour structures from the Phoenician and Roman periods remains unknown, buried under sediments resulting from the progradation of the Medjerda. Based on the study of sedimentary cores, the research presented here highlights the existence of a long maritime façade to the north of the Utica promontory in Phoenician and Roman times. A deep-water marine environment is attested in the former bay from the 6th mill. BC and the depth of the water column along the northern façade was still 2 m around the 4th – 3rd c. BC. Another core to the east of the Kalaat El Andalous promontory showed the possibility that this sector was a sheltered harbour during the Phoenician and Roman periods. This paper illustrates the contribution of geoarchaeology to address this archaeological problem and to understand the relations of this important port city with the sea.

Increased anthropogenic activities, especially within the river corridor, have progressively disrupted natural flow regimes and segmented channel–floodplain connectivity. Consequent alterations in flow dynamics have caused geomorphic and... more

Increased anthropogenic activities, especially within the river corridor, have progressively disrupted natural flow regimes and segmented channel–floodplain connectivity. Consequent alterations in flow dynamics have caused geomorphic and hydrological changes in channel morphology and behaviour, decreasing their natural replenishment capacity, thereby causing their degradation. The simultaneous disconnection of the channel from its natural floodplain due to intensive cultivation and surface paving has also reduced possible floodwater outlets or seepage zones, which would have otherwise functioned as storm runoff storage buffers that reduced the flood peak downstream. Such occurrences of flow disruption, especially in low-relief topographic regions buffeted by high intensity monsoonal storms, accentuate flood-like situations, since natural channel capacities to transport excess storm-water are diminished, with this further enhancing ongoing or inducing riverbank erosion. Such events have accounted for much loss of life, livelihood and property worldwide and to mitigate their intensity, river restoration techniques have been promoted. These place greater emphasis on ecological management measures that attempt to restore and rehabilitate the geomorphic and hydrological functionality of the stream to a prior, more pristine state to achieve channel stability and regulate flows. Thus, frameworks based on river corridor management, riparian buffer creation and the River Styles Framework instituted guidelines, aided by geospatial analysis techniques, have yielded significant management strategies for such flood-and erosion-affected degraded channel corridors. This paper presents a recent review of such ecological techniques of flood and channel management, especially in monsoonal environments, while highlighting the issues concerning their implementation in developing nations.

Multidisciplinary analysis on high-resolution undisturbed core material gives new insight in the development of the Late-Pleistocene Rhine-Meuse system (southern North Sea Basin, the Netherlands). Over 120 quartz OSL-dates allowed... more

Multidisciplinary analysis on high-resolution undisturbed core material gives new insight in the development of the Late-Pleistocene Rhine-Meuse system (southern North Sea Basin, the Netherlands). Over 120 quartz OSL-dates allowed constructing a detailed geochronological framework and makes the Rhine-Meuse record by far the best dated Late-Pleistocene fluvial record in the world. The Late-Pleistocene Rhine-Meuse sedimentary sequence starts with fine-grained sediments from the last interglacial and early glacial period (130-80kyr BP). These sediments are overlain by a massive sequence of coarse grained sediments that were deposited between 80-15 kyr BP. The sequence is mapped as twelve sedimentary units based on regionally traceable bounding surfaces and sediment characteristics. Strong climatic and sea-level controls are evident as variations in sedimentary characteristics (grainsize, lithology, geometries) and architecture (erosion-deposition history, reworking, preservation) while part of the system architecture is related to forebulge upwarping and collapse, caused by glaciations in Scandinavia and Britain. Results from 3D landscape evolution modelling indicate a strong non-lineair relation between sediment source areas (Germany) and the depositional record (Netherlands) and explains grain-size and incision/aggradation trends. The model shows that particularly the timing of delayed responses needs to be taken into account to explain the type and timing of sediment-delivery to the study area.

The study is bounded in the mentioned interfluves areas between Teesta, Lish, Ghish rivers in Jalpaiguri district, West Bengal. Here it is tried to show the geomorphic characteristics of this area and how anthropogenic and physical... more

The study is bounded in the mentioned interfluves areas between Teesta, Lish, Ghish rivers in Jalpaiguri district, West Bengal. Here it is tried to show the geomorphic characteristics of this area and how anthropogenic and physical factors influence the planforms of these rivers and their interfluves. And the changes in planforms, interfluves with time. Several literatures have been endured to study this area of interest and to frame the work planning of pre-field, field and post field. Few databases and methodologies are selected, like- Satellite images (Landsat-8of 2017 and Landsat -2 of 1977), Cartosat DEM, Google Earth images, field data, rainfall data. Field photographs are taken at Sevoke of Tista river, Kalagaity area for river Lish and Uttarphulbari, Gompadara for Ghish river. It would help a lot give a clear vision of that area and to make out the present conditions of these rivers and its surrounding. Sediment samples are collected along the river bank and GPS points are marked on that particular places of sediment collection. Raw data are processed with the help of QGIS, Arc GIS, Global Mapper, Geomatica softwares. In every case of landuse and landcover features, like- river, riverine deposits, agricultural plot, build-up area are increased in percentage but beside these forest lands, deforested lands are also decreased. Several projects and river dams this situation. Before and after construction of Gajoldoba barrage, a huge changes (rivers’ planform and interfluves) in a 40 years gap is shown here. This work is done in Geomatica. Required topographic profiles are generated for measurement of terraces of these rivers in this study area. Hill, lower hill, dissected fan surface, flood plain, active channel, ridgeline, rivers, streams, river bars (vegetated, unvegetated), fan like deposits, landslide traces, steep bank face, swamp, dams and weirs, canal, settlement, roads, railways are identified and mapped. And the temporal oscillation of rivers’ channels are observed. Landslides and high amount of rainfall (St- Bagrokothe) and river dams majorly insist the high deposition of sediments in these channels and oscillation of rivers. This study can be improved more by studying the frequency of landslide, flood, earthquake and channel depositional pattern to understand whether these channel bars are climatically induced or tectonically induced.

Los sedimentos de la cuenca del Usumacinta son compuestos de arcilla, limo, barro y grava, esenciales por albergar una vida secreta y participar en la dinámica de este ecosistema fluvial. Los lugareños los llaman “arena”, “guijarros” o... more

Los sedimentos de la cuenca del Usumacinta son compuestos de arcilla, limo, barro y grava, esenciales por albergar una vida secreta y participar en la dinámica de este ecosistema fluvial. Los lugareños los llaman “arena”, “guijarros” o “piedras”, y han fungido como recursos desde tiempos inmemoriales para la producción de cerámica, la mejora del suelo o como material de construcción. Las sociedades se han expandido y alimentado gracias a ellos, pero con el crecimiento urbano y la transformación de los ecosistemas, hemos alterado sus dinámicas de generación, transporte y acumulación; ni más ni menos que todo aquello que resulta fundamental para la vida de un territorio conformado por una cuenca y un río compartido por Tabasco, Chiapas y el altiplano guatemalteco.
Con esta publicación buscamos explicar en doce preguntas la naturaleza e importancia de los sedimentos del Usumacinta: ¿para qué se utilizan actualmente?, ¿qué usos han tenido a lo largo del tiempo?, ¿cómo pueden aprovecharse? ¿están contaminados? Nuestras respuestas buscan contribuir a la construcción de una relación sostenible entre el Usumacinta y los seres humanos que viven en sus riberas. Con este ejemplo bien podría abordarse la misma problemática respecto a cualquier otra cuenca.
Esta publicación se realizó en el marco de una estrecha colaboración científica con la participación de investigadores mexicanos y franceses que, iniciada en 2018, concluye en 2022: el proyecto VAL-USES
“Desde el aprovechamiento tradicional hacia la valorización integral de los sedimentos en la cuenca del río Usumacinta”, un proyecto interdisciplinario aprobado y financiado por la Agencia Nacional de Investigación en Francia y el Consejo Nacional de Ciencia y Tecnología en México.

It is quite impossible to travel far in India without observing the remarkable ferruginous crust to which F. Buchanan in 1807 gave the name of laterite. In Indian peninsula it is a post-Cretaceous stratigraphic succession with polycyclic... more

It is quite impossible to travel far in India without observing the remarkable ferruginous crust to which F. Buchanan in 1807 gave the name of laterite. In Indian peninsula it is a post-Cretaceous stratigraphic succession with polycyclic nature of evolution which marks the unconformity with Recent Quaternary Alluvium. There are perennial problems and research gaps in the investigation of laterites in India as well as West Bengal – (1) defining, indentifying and classifying lateritic materials, (2) mode of formation of laterite and its other horizons, (3) determining the ages of laterites, (4) reliability of laterites as palaeoclimatic indicators, (5) identifying topographic requirements and pedo-geomorphic processes for laterite formation and (6) reconstructions of former lateritized landscapes. The formation of north – south lateritc cover (i.e. Rarh Bengal) on the Rajmahal Traps, Archaean granite – gneiss, Gondwana sedimentary, Paleogene gravels and Old Deltaic Alluvium is analyzed here to resolve the aforesaid problems and to depict the variable characteristics of laterites with special reference to its tectono – climatic evolution in northwest marginal part of the Bengal Basin. This paper reveals that the low-level secondary laterites (probably Pliocene – Early Pleistocene age) of Rarh Bengal are composed of heterogeneous iron – aluminum rich gravelly materials which were derived from the high-level primary laterites (probably Eocene – Miocene age) of Plateau since Paleogene Period by the peninsular river system, following the underlying structure of the Bengal Basin. Alongside the roles of drifting of Indian Plate, establishment of monsoon climate, neo-tectonic uplifts and re-lateritisation of ferruginous shelf deposits are determined here to unearth the palaeogenesis of primary and secondary laterites in West Bengal.

Statistical analyses reveal information of the hydrodynamics and environments of deposition of sedimentary rocks. The sediments of the outcrop sections from Uwakande 1, Obubra southeastern Nigeria were studied for their textural... more

Statistical analyses reveal information of the hydrodynamics and environments of deposition of sedimentary rocks. The sediments of the outcrop sections from Uwakande 1, Obubra southeastern Nigeria were studied for their textural variations. Grain size analysis, and pebble morphogenesis
carried out shows that the sediments are coarse to very coarse in size, poorly sorted, and very positively skewed. This in conjunction with the various bivariate plots employed, aid in discriminating between beach and river depositional environments. Pebble morphometric analysis of the conglomerates showed that the mean values of the various morphometric parameters range as follows: flatness ratio (S/L = 0.397 to 0.514), elongation ratio (I/L = 0.657 to 0.784), maximum projection sphericity (ΨP = 0.605 to 0.899), Oblate-Prolate index (ŌP = -1.738 to 1.594), coefficient of flatness (39.70 to 51.37), and roundness (-0.367 to 0.722). This study is significant in providing evidence of fluvial conditions during the deposition of the Eze-Aku Formation in the Turonian, and
reveals the type of transporting medium; the mode of sediment deposition; as well as the environment into which the sediments encountered in the study area were deposited.

O presente apontamento faz parte de um conjunto de textos geocientíficos acerca das províncias de Benguela e Namibe, num total de 150, recolhidos, analisados e catalogados conforme a Classificação Decimal Universal (BN, 2005) e citados de... more

Unsustainable land uses may result in poor watershed management, increased soil erosion, poorly-planned urban development, increased runoff, and sewage pollution, creating an environmental stress gradient across coastal coral reefs. This... more

Unsustainable land uses may result in poor watershed management, increased soil erosion, poorly-planned urban development, increased runoff, and sewage pollution, creating an environmental stress gradient across coastal coral reefs. This study was aimed at: 1) Evaluating water quality within and outside the Canal Luis Peña Natural Reserve (CLPNR), Culebra Island, Puerto Rico; 2) Determining if there was any significant environmental stress gradient associated to land-based non-point source pollution; and 3) Characterizing shallow-water coral reef communities across the gradient. Strong gradient impacts associated 293 to sediment-laden and nutrient-loaded runoff pulses, in combination with non-point raw sewage pulses, and sediment bedload, impacted coastal coral reefs. Water quality showed significant spatio-temporal fluctuations (p<0.0001), largely responding to heavy rainfall and subsequent runoff pulses. Benthic community structure showed significant spatial variation along the environmental stress gradient (p=0.0002). Macroalgae, dead coral surfaces, algal turf, and low coral species richness, species diversity index (H'c), and evenness (J'c) dominated benthic assemblages across reefs frequently impacted by runoff pulses and sediment bedload. The combination of fecal coliform and enterococci concentrations were correlated with variation in benthic community structure (Rho=0.668; p=0.0020). The combined variation in salinity, dissolved oxygen and enterococci concentrations explained 75% of the observed spatial variation in benthic assemblages (R 2 =0.7461; p=0.0400). Local human stressors affected coral reefs within no-take CLPNR and risk analyses suggest it may offset its ecological benefits. There is a need to design and implement integrated coastal-watershed management strategies to address multiple land use activities, including erosion-control best management practices, watershed reforestation, and sewage pollution control.

The 265m thick outcrop shows a deltaic depositional sedimentary system. It shows one major shallowing upward cycle that include 8 facies within 6 smaller shallowing upward cycles. These facies are shale at the lower part of the sequence,... more

The 265m thick outcrop shows a deltaic depositional sedimentary system. It shows one major shallowing upward cycle that include 8 facies within 6 smaller shallowing upward cycles. These facies are shale at the lower part of the sequence, medium to coarse sandstone at the upper part of the sequence, however; it shows soft sediment deformation and cross bedded interbedded sandstone -shale in the middle part of the sequence. Also, in the middle part sandstones increase in thickness and amount upward. The six shallowing upward cycles has been delaminated based on the presence of mud cracks, Hummock cross bedding, mud clasts, Skolithos and upward dominance of thick medium to coarse sandstones as signs of shallowing upward within this generally shaly-sand sequence.
This deltaic sequence has been divided into three parts. The prodelta, lower delta front and upper delta front. The prodelta includes the shale facies and the well bedded yellow fine Sand-Shale facies as distal and proximal facies respectively. The lower delta front includes the Soft sediment deformation yellow fine Sand-Shale facies and the Hummocky cross-bedded yellow fine Sand-Shale facies as distal lower delta front, moreover; both the Soft Sediment Deformation- Cross bedded f-m Sand-Shale facies and the Skolithos f-m Sand-Shale facies interpreted as the proximal part of the lower delta front . The upper delta front is made up of both the Sahley yellow f-m Sandstone facies and the White m-c Sandstone as upper delta front.

The Geomorphology, as interdisciplinary and multi-scale knowledge body, demonstrates that such approaches are possible and even desirable in Science. Thus, I present this work which has the general aim of testing the possibility of... more

The Geomorphology, as interdisciplinary and multi-scale knowledge body, demonstrates that such approaches are possible and even desirable in Science. Thus, I present this work which has the general aim of testing the possibility of multi-scalar and interdisciplinary analysis for the landform evolution phenomena having as verification locus the Ribeirão Mata Porcos watershed. Located in the mid-southeastern region of the Moeda Syncline, this watershed is inserted in western flank of the Quadrilátero Ferrífero, Minas Gerais state, Brazil. The specific aims of this work are to (i) understand the events responsible for the morphogenesis of main valleys, headwaters, and on the Ribeirão Mata Porcos watershed; (ii) characterize the pedological coverage of headwaters; and (iii) characterize the fluvial depositional levels in the rivers of higher hierarquical order. Consequently, morphometric analysis, field and laboratory procedures were performed. At the watershed scale, a more aggressive denudation, the occurrence of knickpoints as well as tectonic tilting affecting the drainage reorganization were noted. At the headwaters scale, pedological coverage with distinct evolution patterns were found. These patterns demonstrated the action of a geochemical weathering front which has been propagated from downstream to upstream, possibly related to both fluvial incision and chemical downwearing at the lower hillslopes segments. At the main valleys scale, six depositional records were recorded. Two of them are Holocenic floodplains. Another one, which has characteristics of a cut-in-bedrock terrace, was generated during the Lower Pleistocene. Two originally-fluvial deposits were elaborated between the Middle and Lower Pleistocene. The latters, initially cut-in-bedrock terraces were disturbed by hillslope processes. The multi-scalar approach of all these data demonstrated the existence of a transient geomorphological state defined by the Quaternary river capture of Rio das Velhas and by the searching of a new equilibrium profile in the Ribeirão Mata Porcos watershed, as well as in its tributaries and headwaters. Finally, I conclude that if the investigation had been carried out in only one of those elements (i.e., headwaters or main valleys), the connections would not have been found. So, the performed approach was an essential procedure for a better understanding of Quaternary geomorphological changes in the Ribeirão Mata Porcos watershed and it is, therefore, potentially applicable to other study areas.

Stratigraphic exposures, fluvial archives and borehole data have been allowed to reconstruct the alluvial history of Late Pleistocene to Late Holocene and climate changes in the monsoonal wet – dry region of lower Damodar Basin (West... more

Stratigraphic exposures, fluvial archives and borehole data have been allowed to reconstruct the alluvial history of Late Pleistocene to Late Holocene and climate changes in the monsoonal wet – dry region of lower Damodar Basin (West Bengal, India). The facies architectures and climate proxies suggest that five to six climate changes occurred in between ~ 14 ka and 6 ka. Supporting evidence from the floodplain of Damodar River demonstrates that the successive phases of aggradation and incision were linked to the south-west monsoonal variability of Late Quaternary period. The onset of semi-arid climate was associated with caliches, pond and backswamp deposits of wanning low energy floods. The relatively warm-humid climate was associated with sandy bedforms, valley fills, slack water deposits and ferruginous nodules. This paper presents a synthesis of the available palaeoclimatic records from the lower Ganga Basin and the rivers of western and central India for the palaeoenvironmental significance of Late Quaternary deposits and discusses the influence of palaeoclimatic controls on the fluvial architectures and archives that developed below the floodplain of Damodar River. We have taken some representative studies from the region to reveal the spatial variability in fluvial successions in response to climate changes during this period.

Clay is one of the most important minerals having both geological and industrial significance. Clay lenses in the Dupi Tila Formation of the Bengal Basin have been investigated to characterize and determine their origin in terms of... more

Clay is one of the most important minerals having both geological and industrial significance. Clay lenses in the Dupi Tila Formation of the Bengal Basin have been investigated to characterize and determine their origin in terms of geological environment. Clay samples have been collected from the fresh cropped surface from the areas of Dupigaon (Jaintiapur Clay), Birisiri (Bijoypur Clay), and Bandarban (Bandarban Clay) in Bangladesh. Characterizations of the clay deposits have been carried out by field investigation, scanning electron microscope (SEM), Xray diffraction (XRD), laser particle size analysis techniques, and X-ray fluorescence (XRF). Field investigation shows that clays are white, yellowish to variegated in color with a thickness of 15 cm to about 4 m, and moderately soft. The X-ray diffraction analysis reveals that kaolinite is the predominant clay mineral in all samples with minor amounts of quartz and feldspar. SEM analysis indicates that abundant tiny disc and irregular shape of kaolinite crystals are mixed with sparse gathers of K-feldspar and detrital quartz grains. The presence of silt in all the clay samples has been verified by the gran size ranges from laser particle size analysis. The grittiness is the result of the deposition of silt considering the highest percentage in Bandarban and Bijoypur and lowers in Jaintiapur. The XRF analysis shows that SiO 2 (68e75%) is the most abundant among major oxides, Al 2 O 3 and Fe 2 O 3 come next, along with the lower percentage of MnO, MgO, CaO, Na 2 O, K 2 O, TiO 2 , P 2 O 5 , and SO 3. The average concentration of different trace elements has been ranging from 3 to 430 ppm. Several geochemical indices suggest that the sediments might be derived from the Shillong plateau and the Himalayas in the north and the Naga-Lushai-China Hill-Arakan Yoma mobile belt in the northeast, which are highly weathered sedimentary terrains. Provenance studies and elemental ratio supports the evidence of the felsic origin of the studied sample. The Chemical Index of Alteration (CIA) value of 93% indicates the occurrence of significant weathering in different sediment recycling phases. From the results of the aforementioned analyses, it is clear that clay lenses in the Dupi Tila Formation are in-situ in origin and parent materials are detrital rather than authigenic nature confirmed by the presence of detrital quartz and reviewing the depositional environment, which gives us the insights of the geological condition of that time as well as the possible mode of sediment transportation.

Three freely meandering rivers in the Amazon basin were analyzed for statistical scaling properties and oxbow lake size-frequency distributions. The rivers are the Purus (central Amazon, planform data), Juruá (central Amazon, planform... more

Three freely meandering rivers in the Amazon basin were analyzed for statistical scaling properties and oxbow lake size-frequency distributions. The rivers are the Purus (central Amazon, planform data), Juruá (central Amazon, planform and oxbow lake data), and Madre de Dios (Peruvian Amazon, oxbow lake data). Long reaches were found to be power- law scaling over more than two orders of mag- nitude. These river planforms are self-affine fractals. Oxbow lake data suggest that the lakes are sampled from a skewed hyperbolic (Pareto) size-frequency distribution.
To examine the long-term behavior of freely meandering rivers, a deterministic continuum model of meandering rivers has been used for extensive simulations of free meandering mo- tion. The simulation outcomes are consistent with a dynamical state of self-organized criticality, which has the following characteristic behavior: (1) stationary mean sinuosity of the final state; (2) robustness, in the sense that the same final state is reached from any initial conditions; and (3) formation of a spatiotemporal fractal structure.
Sensitivity tests showed that this behavior is not affected by valley confinement down to a valley width of 50 w (river width), and by chute cutoffs of mature meanders up to 3 w long, but the average sinuosity value reached in the final state is sensitive to valley width less than 100 w, and chutes longer than 1.5 w.
Comparison with empirical data confirmed the validity of the simulations as models of river meandering. All tests found data and simulation results to be in close agreement.

Field studies suggest that a cohesive floodplain is a necessary condition for meandering in contrast to braided rivers. However, it is only partly understood how the balance between floodplain construction by overbank deposition and... more

Field studies suggest that a cohesive floodplain is a necessary condition for meandering in contrast to braided rivers. However, it is only partly understood how the balance between floodplain construction by overbank deposition and removal by bank erosion and chutes leads to meandering. This is needed because only then a dynamic equilibrium exists and channels maintain meandering with low width-depth ratios. Our objective is to understand how different styles of floodplain formation such as overbank deposition and lateral accretion cause narrower channels and prevent chute cutoffs that lead to meandering. In this study we present two experiments with a self-forming channel in identical conditions, but to one we added cohesive silt at the upstream boundary. The effect of cohesive silt on bank stability was tested in auxiliary bank erosion experiments and showed that an increase in silt reduced erosion rates by a factor of 2. The experiment without silt developed to a braided river by continuous and extensive shifting of multiple channels. In contrast, in the meandering river silt deposits increased bank stability of the cohesive floodplain and resulted in a reduction of chute cutoffs and increased sinuosity by continuous lateral migration of a single channel. Overbank flow led to deposition of the silt and two styles of cohesive floodplain were observed; first, overbank vertical-accretion of silt, e.g. levee, overbank sedimentation or splays; and second, lateral point bar accretion with silt on the scrolls and in the swales. The first style led to a reduction in bank erosion, while the second style reduced excavation of chutes. We conclude that sedimentation of fine cohesive material on the floodplain by discharge exceeding bankfull is a necessary condition for meandering.

Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of... more

Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.

The geomorphic, tectonic and seismic aspects of the Ganga plain have been studied by several workers in the recent decades. However, the northern part of this tectonically active plain has been the prime focus in most of the studies. The... more

The geomorphic, tectonic and seismic aspects of the Ganga plain have been studied by several workers in the recent decades. However, the northern part of this tectonically active plain has been the prime focus in most of the studies. The region to the south of the Ganga River requires necessary attention, especially, regarding the seismic activities. The region lying immediately south of the Outer Himalayas (i.e. the Ganga plain) responds to the stress regime of the Himalayan Frontal Thrust Zone by movement along the existing basement faults (extending from the Indian Peninsula) and creating new surface faults within the sediment cover as well. As a result, several earthquakes have been recorded along these basement faults, such as the great earthquakes of 1934 and 1988 associated with the East Patna Fault. Large zones of ground failure and liquefaction in north Bihar (close to the Himalayan front), have been recorded associated with these earthquakes. The present study reports the soft sediment deformation structures from the south Bihar associated with the prehistoric earthquakes near the East Patna Fault for the first time. The seismites have been observed in the riverine sand bed of the Dardha River close to the East Patna Fault. Several types of liquefaction-induced deformation structures such as pillar and pocket structure, thixotropic wedge, liquefaction cusps and other water escape structures have been identified. The location of the observed seismites within the deformed zone of the East Patna Fault clearly indicates their formation due to activities along this fault. However, the distance of the liquefaction site from the recorded epicenters suggests its dissociation with the recorded earthquakes so far and hence possibly relates to any prehistoric seismic event. The occurrence of the earthquakes of a magnitude capable of forming liquefaction structure in the southern Ganga plain indicates the transfer of stress regime far from the Himalayan front into the peninsular region through these basement faults. Northward extension of the East Patna Fault coincides with the region of the Himalayan front, which corresponds to a less slip potential. Therefore, an association of frequent earthquakes in this region indicates strain release along the East Patna Fault.

رودخانه حاجی عرب یک رودخانه فصلی در جنوب استان قزوین است. این مطالعه جهت بررسی رسوبات این رودخانه و تعیین رخسارههای رسوبی آن صورت گرفته است. از چهار گمانه و با بیشینه عمق ۳.9متری تعداد 75نمونه از اطراف تپه باستانی قرهتپه برداشت شده... more

رودخانه حاجی عرب یک رودخانه فصلی در جنوب استان قزوین است. این مطالعه جهت بررسی رسوبات
این رودخانه و تعیین رخسارههای رسوبی آن صورت گرفته است. از چهار گمانه و با بیشینه عمق ۳.9متری
تعداد 75نمونه از اطراف تپه باستانی قرهتپه برداشت شده است. دانه بندی رسوبات به روشهای الک
خشک، الک تر و الک شیکر لیزری انجام شده است. بررسی رسوبات این رودخانه به شناسایی سه دسته
رخساره رسوبی منجر شد که عبارتند از: رخسارههای گلی ( ، )Fl ,Fm ,Frماسهای ()Sm ,Sp ,Sl ,Sh
و گراولی ( ،)Gh ,Gcm ,Gms ,Gci ,Gmg ,Gmmکه در قسمتهای مختلف محیط رودخانهای ته-
نشست کردهاند. براساس رخسارههای شناسایی شده، عناصر ساختاری خارج کانال ( ،)FFماسه با اشکال
لایهای ( ،)SBبار گراولی و اشکال لایهای ( ،)GBجریان گراویتهای ( )SGو کانال ( )CHدر این حوضه
رسوبی شکل گرفتهاند. مدلهای رسوبی این رودخانه شامل رودخانههای مآندری با بار ریزدانه، مآندری با
بار ماسهای، بریدهبریده با بسترگراولی و بریدهبریده گراولی کمعمق میباش

Point bars formed by meandering river systems are an important class of sedimentary deposit and are of significant economic interest as hydrocarbon reservoirs. Standard point-bar models of how the internal sedimentol-ogy varies are based... more

Point bars formed by meandering river systems are an important class of sedimentary deposit and are of significant economic interest as hydrocarbon reservoirs. Standard point-bar models of how the internal sedimentol-ogy varies are based on the structure of small-scale systems with little information about the largest complexes and how these might differ. Here a very large point bar (>25 m thick and 7-13 km across) on the Mississippi River (USA) was examined. The lithology and grain-size characteristics at different parts of the point bar were determined by using a combination of coring and electrical conductivity logging. The data confirm that there is a general fining up-section along most parts of the point bar, with a well-defined transition from massive medium-grained sands below about 9 to 11 m depth up into interbedded silts and fine–medium sand sediment (inclined heterolithic strata). There is also a poorly defined increase in sorting quality at the transition level. Massive medium sands are especially common in the region of the channel bend apex and regions upstream of that point. Downstream of the meander apex, there is much less evidence for fining up-section. Finer sediment accumulated more readily after the establishment of a compound bar in the later stages of construction , at the terminal apex and in the bar tail. This work implies that the best reservoir sands are likely to be located in the centre of the point bar, deposited in a simple bar system. Reservoir quality decreases towards the bar edge. The early-stage channel plug is largely composed of coarsen-ing-upward cycles of silt to clay and is dominated by clay and clayey silt material with poor reservoir characteristics.

This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage / MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six... more

This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage / MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a 3D geological model. The incised-valley fill consists of a ca. 50 m thick and 10-20 km wide sand-dominated succession and includes a well-developed sequence dating from the Eemian interglacial (Last Interglacial).
The lower part of the valley fill contains coarse-grained fluvio-glacial and fluvial Rhine sediments that were deposited under Late Saalian (MIS 6) cold-climatic periglacial conditions and during the transition into the warm Eemian interglacial (MIS 5e-d). This unit is overlain by fine-grained fresh-water flood-basin deposits, which are transgressed by a fine-grained estuarine unit that formed during marine high-stand. This ca. 10 m thick sequence reflects gradual drowning of the Eemian interglacial fluvial Rhine system and transformation into an estuary due to relative sea-level rise. The chronological data suggests a delay in timing of regional Eemian interglacial transgression and sea-level high-stand of several thousand years, when compared to eustatic sea-level. As a result of this glacio-isostatic controlled delay, formation of the interglacial lower delta took only place for a relative short period of time and delta progradation was limited. During the cooler Weichselian Early Glacial period (MIS 5d-a) deposition of deltaic sediments continued and extensive westward progradation of the Rhine delta occurred.
Major parts of the Eemian and Weichselian Early Glacial deposits were eroded and buried as a result of sea-level lowering and climate cooling during the early Middle Weichselian (MIS 4-3). Near complete sedimentary preservation occurred along the margins of the incised valley allowing the detailed reconstruction presented here.

This paper contributes to the study of the paleogeographic evolution of the lower Guadalquivir during the Late Holocene. From a geoarchaeological approache, the historical landscapes of the floodplains of Santiponce (Italica), Seville... more

This paper contributes to the study of the paleogeographic evolution of the lower Guadalquivir during the Late Holocene. From a geoarchaeological approache, the historical landscapes of the floodplains of Santiponce (Italica), Seville (Hispalis) and Coria del Río (Caura) are reinterpreted.