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Storm-dominated shelf sedimentation marginal to a delta: an example from the Devonian of southwestern Virginia and eastern West VirginiaRandall, A. Henry January 1984 (has links)
The Chemung Formation in the south-central Appalachians constitutes part of the thick Devonian - lower Mississippian Acadian clastic wedge. Sediment in the Chemung was derived from a progressively-uplifted source area to the east and accumulated in the proximal environments of an epeiric sea. Sandstones within the dominantly muddy formation are found in a variety of sequence types characterized by hummocky cross stratification. Individual beds usually have sharp erosive bases and gradational tops. A hydrodynamic interpretation of hummocky sequences suggests that they are the result of extremely large but infrequent storm events and are surrounded by fair-weather deposits of mud rock. The Chemung shelf is envisaged as a very low-gradient (<0.5 ft./mile) clastic ramp extending hundreds of miles toward the craton interior. Transport of sand from the nearshore onto the shelf over distances up to 200 miles was facilitated by storm generated gradient currents. Coarsening/thickening- upward sequences of storm beds represent progradational shelf sand lobes. Three facies associations represent environments of deposition and record changing styles of storm sedimentation on the shelf. The distal inner shelf environment is characterized by discrete hummocky sandstone sequences deposited by only the largest of storms. The proximal inner shelf environment is a much higher energy environment in which periodic storms and fair-weather waves shoal on the low gradient sea floor producing thicker and amalgamated storm sequences. A low-energy shoreline environment is situated landward of the proximal inner shelf and contains only minor storm and fair-weather deposits. The widespread occurrence of hummocky sequences within the Chemung illustrates the importance storm processes can have in the transportation and deposition of sediment in shallow-marine settings. / Master of Science
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An analysis of channel bank erosion and development of a catchment sediment budget modelJanes, Victoria Jennifer Julie January 2013 (has links)
Increased sediment loads within river catchments have well-documented detrimental effects on water quality and catchment management plans are required to address reduction and mitigation of these problems. In order to do this it is essential that tools are available that deliver reliable sediment generation data at appropriate temporal and spatial scales. Currently, most sediment generation models do not include bank erosion individually as a sediment source. Therefore, to enable improved accuracy in predictions of future sediment pressures under environmental change, explicit modelling of the rates of sediment production by the bank erosion is required to provide a more complete representation of the catchment sediment budget. In this study, an existing prototype national bank erosion index has been refined. Using Geographical Information Systems (GIS) digitised overlays, channel migration rates were calculated for several UK catchments. Relationships between the rate of channel bank erosion and factors controlling the rates of channel migration were investigated, including channel sinuosity, slope, upstream catchment area, and restriction of migration due to valley width. Significant correlations between bank erosion and sinuosity, upstream area and channel confinement were observed. The non-linear influence of channel planform geometry (curvature and sinuosity) on migration rates was further investigated using an existing meander migration model. A new bank erosion model was developed to incorporate the influence of both channel confinement and sinuosity. As the model incorporates the key physical controls on bank erosion, hence it is expected that it will have wide applicability in catchment- to national-scale bank erosion assessment. A computationally efficient catchment routing model was developed. Data output from a newly developed catchment overland sediment and runoff estimation model (ADAS APT) was used as input to the routing model. The newly developed bank erosion model and an existing floodplain sedimentation model were incorporated within the routing methodology to provide a catchment sediment budget model. The model was applied to the Exe catchment, Devon, UK and validated against observational data. Model estimations of annual sediment generation through bank erosion, sediment deposition on floodplains, and sediment load at the catchment outlet were within the range of observed values. The catchment sediment budget model developed in this thesis provides a more comprehensive representation of catchment sediment processes than existing alternative methodologies.
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A study of radionuclides, lead and lead isotope ratios in Scottish sea loch sedimentsShimmield, Tracy Marjory January 1993 (has links)
This research involved the study of sediment cores from Loch Etive, Loch Long, Loch Goil and Loch Fyne with the aims of investigating the geochemistry of natural, and manmade radionuclides and heavy metals within the sea loch environment. The main aims of the research were to determine accumulation rates and the extent of mixing within these sediments and to assess the fluxes, sources and temporal variations in input of pollutant heavy metals to these environments. In recent years it has been suggested that Pb is mobile in sea loch sediments which questions the validity of applying ²¹⁰Pb dating in this environment. This has important implications with respect to interpreting sediment cores to assess temporal trends of pollutant inputs and investigating the rates of physical and biogeochemical processes that are taking place in the coastal environment. Hence, one of the aims of this research was to determine whether Pb was mobile in these sediments. The ²⁰⁶Pb/²⁰⁷Pb isotope ratio can potentially be used to determine the extent of pollutant Pb input from leaded petrol to the environment and a further objective of the work was to investigate the isotopic signature of pollutant Pb in the sediment. Concentration of ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁸U, ¹³⁷Cs, ¹³⁴Cs and ²⁴¹Am in the sediments were analysed using gamm a spectroscopy and the heavy metals, Pb, Zn and Cu were determined using X-ray Fluorescence. Stable Pb isotope ratios were determined using Inductively coupled plasma Mass spectrometry. The results obtained indicated that Pb is not subject to diagenetic mobility in these sediments and that ²¹⁰Pb profiles can be used to determine sedimentation rates for most of the sediment cores. lt was not possible to determine accumulation rates for the two cores from Loch Fyne by ²¹⁰Pb dating, and in this case the sedimentation rate was assessed by correlating the maximum concentration of ¹³⁷Cs in the sediments with the maximum ¹³⁷Cs discharge from Sellafield, BNFL's reprocessing plant located on the Cumbrian coast. The flux of ²¹⁰Pb to the lochs varied significantly suggesting that there has been sediment focusing of fine and/or organic rich material to the deeper sites, resulting in an enhanced flux of ²¹⁰Pb to these sediments. Sellafield waste radionuclides also provided useful chronologies by relating sediment maximum concentrations to maxima in the discharges. ¹³⁷Cs was observed to be subject to diffusive movement, invalidating the use of its total depth of penetration as a chronological indicator. The temporal trends of pollutant metal input agreed well with known historical trends and the Pb isotope profiles indicated that the onset of deposition from pollutant Pb from petrol occurred in the late 1920's. The maximum input of Pb from petrol peaked in the early 1980's and since then there has been a decrease in this input. The two sea lochs which were closest to the industrial centre of Glasgow exhibited a large anthropogenic pollutant input, confirming that these sediments have been highly perturbed by human activities, either directly as a result of sludge dumping or due to changes in land use (eg. road construction, deforestation, etc.) in the catchment. All the sea lochs reflected a change in the supply of material to the sediments over the last eighty years, indicating that increased anthropogenic activity has had an effect on these environments.
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Sediment transport dynamics in South African estuariesBeck, Julia S. 12 1900 (has links)
Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2005. / Estuaries are complex water bodies and differ considerably from fluvial river systems. In estuaries the
flow reverses regularly due to the tidal currents and flow depths depend primarily on the tides and not
the flow. An estuary has two sources of sediment: the river during floods and the ocean that supplies
marine sediment through littoral drift which is transported by tidal currents into the estuary.
Oversimplified models cannot be used to investigate the hydrodynamics and geomorphology of an
estuary due to its complexity.
Sedimentation of South African estuaries has created several environmental and social problems.
Sediment transport imbalances have been caused by changes in the river catchments such as increased
sediment yields and flood peak attenuation due to dam construction. Historically floods used to flush
estuaries to maintain the long-term sediment balance in the river-estuary system, but with reduced
flood peaks, sediment transport capacities at the estuaries are reduced and flushing efficiency
decreased, resulting in marine transport dominating in many estuaries.
Two-dimensional (horizontal, 2DH) numerical models have been found to be appropriate tools for
studying hydro- and sediment dynamics in SA estuaries. The modelling shows that the sediment
balance in the estuary relies on a delicate balance between dominant flood and ebb flows. Although
the models performed very well, there are still additional processes to include such as time varying
roughness changes and cohesive sediments. For long-term and long reach simulations, onedimensional
(or quasi-two-dimensional) models will also be required in future.
Mathematical modeling can be used to simulate the flushing of sediments during floods, but attempts
should be made to calibrate these models when adequate field data become available in the future. The
modelling has shown that floods play a very important part in estuarine sediment transport processes.
Physical modelling was undertaken of the breaching of an estuary mouth. The main aim was to
illustrate the merits of breaching at higher water levels as well as to investigate the changes in the
mouth during breaching. The data obtained from the experiments were used to calibrate and verify a
mathematical model. Mathematical modelling of the breaching process at the Klein River estuary
confirms what has been observed during numerous breachings in the field, i.e. that breaching at higher
water levels and towards the southeast side is more effective.
Sediment transport by both waves and currents was investigated. It was found that with increasing
wave and stream power, sediment transport rates would increase if both waves and currents travelled
in the same direction. In contrast, it seems that with the current direction opposing that of the waves,
Hydraulics of Estuarine Sediment Transport Dynamics in South Africa
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greater wave heights resulted in lower sediment transport rates. A new sediment transport equation,
based on stream power, wave power, as well as sediment size was calibrated and verified, and
compared to the well-known Bijker formula.
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Coupled fully three-dimensional mathematical modelling of sediment deposition and erosion in reservoirsSawadogo, Ousmane 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The investigation of reservoir sedimentation has become an important and valuable research topic in
engineering practice. Sediment deposition in reservoirs can affect
ood levels, drainage for agriculture
land, pumpstation and hydropower operation and navigation.
An extensive review of the technical literature pertaining to suspended sediment transports as well as
deposited sediment
ushing from reservoirs has shown that most studies on sediment are still based on
empirical formulas and experimental work, despite the availability of sophisticated computers. This is
because sediment transport and particularly sediment deposition and erosion are complex processes, that
involve the interaction of many physical factors which are not easily modelled numerically. In addition,
most of the existing three-dimensional numerical models are not coupled hydrodynamic and sediment
transport models. They first simulate the velocity field and water depth and then the concentration
and bed change are calculated. Furthermore, they are not fully three-dimensional models for using
layer-averaged approaches in conjunction with Saint-Venant equations.
The key objective of the present research was to develop a coupled fully three-dimensional (3D) numerical
model based on Navier-Stokes equations which includes both the sediment transport component and
hydrodynamic parameters. In this regard, a physical model was set up in a laboratory
ume in order
to investigate the bottom outlet sediment
ushing under pressure in a controlled environment. The
proposed coupled fully 3D numerical model was used to simulate the experimental tests. Results from
these simulations were in good agreement with the measurements. The geometric features of the
scour hole (temporal and spatial hole development) upstream of the bottom outlet were reasonably
well predicted compared to the experimental data. Furthermore, the velocity field upstream of the
bottom outlet was in good agreement with measurements. The proposed numerical model can be
considered reliable provided that the model is correctly set up to reflect the condition of a particular
case study. Finally, the coupled fully 3D numerical model for turbulent suspended sediment transport in
reservoirs was validated against a range of typical reservoir sediment transport and deposition laboratory
flume cases. The proposed suspended sediment transport model successfully predicted both sediment
deposition and entrainment processes and therefore, it can be used for turbulent suspended sediment
transport assessments in reservoirs. / AFRIKAANSE OPSOMMING: Die ondersoek van damtoeslikking het 'n belangrike navorsing onderwerp in ingenieurswese praktyk
geword. Sedimentdeponering in damme kan vloed vlakke, dreinering van landbo grond sowel as pompstasie
en hidrokrag werking en navigasie benvloed.
'n Omvattende ontleding van die tegniese literatuur met betrekking tot gesuspendeerde sedimentvervoer
asook die spoel van gedeponeerde sediment uit reservoirs het getoon dat die meeste studies oor sediment
steeds op empiriese formules en eksperimentele werk gebaseer is, ten spyte van die beskikbaarheid van
gesofistikeerde rekenaars. Dit is omdat sedimentvervoer en veral sedimentafsetting en -erosie komplekse
prosesse is, wat die interaksie van baie fisiese faktore behels en nie moeiteloos numeries gemodelleer kan
word nie. Daarbenewens, in die meeste van die bestaande drie -dimensionele numeriese modelle is die
hidrodinamika en sedimentvervoer modelle nie gekoppel nie. Die numeriese modelle simuleer eerstens die
snelheid veld en waterdiepte en dan word die sedimentkonsentrasie en bedverandering bereken. Verder
is die bestaande modelle nie ten volle driedimensioneel nie, en gebruik laag-gemiddelde benadering in
samewerking met Saint- Venant vergelykings.
Die hoofdoelwit van die huidige navorsing was om 'n gekoppelde volle drie -dimensionele (3D) numeriese
model gebaseer op Navier -Stokes-vergelykings wat beide die sediment vervoer komponent en hidrodinamiese
parameters insluit, te ontwikkel. In hierdie verband is 'n fisiese model opgestel in 'n laboratorium
kanaal om die bodem uitlaat spoel van sediment onder druk in 'n beheerde omgewing te ondersoek.
Die voorgestelde gekoppelde 3D numeriese model is gebruik om die eksperimentele toetse na te boots.
Resultate van hierdie simulasies het goed ooreengestem met die metings. Die geometriese eienskappe
van die erosie gat (tyd en ruimtelike gatontwikkeling) stroomop van die bodemuitlaat was redelik goed
voorspel vergeleke met die eksperimentele data. Verder is die snelheid veld stroomop van die bodem
uitlaat ook goed voorspel. Die voorgestelde numeriese model kan beskou word as betroubaar met die
wete dat die model korrek opgestel is om die toestand van 'n bepaalde gevallestudie te weerspiel. Ten
slotte, is n gekoppelde 3D numeriese model vir turbulente gesuspendeerde sediment vervoer in reservoirs
ontwikkel en getoets teen 'n reeks laboratorium kanaal eksperimente. Die voorgestelde gesuspendeerde
sediment vervoer model voorspel suksesvol beide die sediment afsetting- en erosieprosesse en daarom
kan dit gebruik word vir die simulasie van turbulente gesuspendeerde sediment vervoer in damme.
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Pennsylvanian framework of sedimentation in ArizonaHavenor, Kay Charles, 1931- January 1958 (has links)
No description available.
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Sedimentation studies in the vicinity of Willcox Playa, Cochise County, ArizonaPine, Gordon Leroy, 1938- January 1963 (has links)
No description available.
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Συνθήκες ιζηματογένεσης και παλαιογεωγραφική εξέλιξη των ιζημάτων της τομής Φανερωμένη σε σχέση με άλλες τομές της περιοχής στη λεκάνη της Σητείας στην ΚρήτηΠετράκος, Γιώργος 01 April 2014 (has links)
Η παρούσα διπλωματική διατριβή με τίτλο << Συνθήκες ιζηματογένεσης και παλαιογεωγραφική εξέλιξη των ιζημάτων της τομής «Φανερωμένη» σε σχέση με άλλες τομές της περιοχής στη λεκάνη της Σητείας στην Κρήτη >>, εκπονήθηκε στα πλαίσια του Προπτυχιακού Προγράμματος Σπουδών του τμήματος Γεωλογίας της σχολής Θετικών Επιστημών του Πανεπιστημίου Πατρών.
Στόχος της εργασίας αυτής ήταν η ιζηματολογική και γεωχημική ανάλυση της τομής «Φανερωμένη» της νήσου Κρήτης με σκοπό να μελετηθούν όσο το δυνατό καλύτερα τα αποθετικά τους περιβάλλοντα, οι συνθήκες σχηματισμού τους, η γεωδυναμική εξέλιξη της περιοχής καθώς και ο εντοπισμός και η αξιολόγηση πιθανών μητρικών πετρωμάτων υδρογονανθράκων. / This thesis is entitled "Treaties sedimentary and palaeogeographic evolution of the sediment section "Phaneromene" compared with other sections of the basin area of Sitia in Crete >> , produced as part of the curriculum of the Geology Department of the Faculty of Sciences University of Patras.
The aim of this work was the sedimentological and geochemical analysis of the intersection " Phaneromene " the island of Crete in order to study the best possible way the depositional environments , the conditions of their formation , the geodynamic evolution of the region and the identification and evaluation of potential parent rocks for hydrocarbons .
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Some aspects of the sedimentology of the superficial deposits of the Eden estuary, FifeEastwood, Keith Melvyn January 1977 (has links)
Little attention has previously boon given to the sediments of the Eden estuary, Fife, Scotland. This research was performed in order to identify, delineate and account for the observed sedimentary facies in the superficial sediments of the intertidal zone.
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Sedimentation in the New River Estuary, SouthlandThoms, Martin Charles January 1981 (has links)
The New River Estuary is a large mesotidal estuary connected to Foveaux Strait by way of an inlet, and has two principle rivers (the Oreti and the Waihopai) flowing into it. The purposes of this study have been to describe the sediment distribution within the estuary; investigate the sediment source-sink relationships.; to calculate whether on a net basis sediment is being deposited in or eroded from the New River Estuary, and to investigate some of the influences on the sediment dynamics of this estuary. Textural analysis of the sediment indicated that there are three sedimentary environments within the estuary, and each is distinguishable due to the relative mix of fine sand. It was shown that Foveaux Strait is a dominant source of medium-fine sand. The Oreti River and the channels of the main estuary body are also important sources of these sediments. Medium-fine sand is transferred into the estuary and very fine sand is transferred out of the estuary and onto the continental shelf. Aerial photographs indicated that estuarine morphology was stable over a 31 year period (from 1947 to 1978). However a network of scour rods indicated that the intertidal sediment surface was spatially and temporally dynamic. It was calculated that on a net basis sediment was deposited in the estuary over a five month period. An important influence on the sedimentation of the New River Estuary has been the reduction of the tidal com partment by 25%, due to the reclamation of 12.2 km2.
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