baltic sea ice sar segmentation and classification using modified pulse coupled neural networks a method for segmentation and classification of baltic sea ice synthetic aperture radar sar images based on pulse coupled neural networks pcnns is presented also automated training which is based on decomposing the total pixel value distribution into a mixture of class distributions is presented and discussed the algorithms have been trained and tested using logarithmic scale radarsat 1 scansar wide mode images over the baltic sea ice before the decomposition into mixture of class distributions an incidence angle correction specifically designed for these baltic sea ice sar images is applied because the data distributions in the uniform areas of these images are very close to gaussian distributions the data are decomposed into a mixture of gaussian distributions using the expectation maximazation algorithm only uniform image areas are used in the decomposition phase the mixture of distributions is compared to the distributions of the baltic sea ice classes based on earlier scatterometer measurements and visual video interpretations of the sea ice classes the parameter values for the pcnn segmentation are defined based on this mixture of distributions the pcnn segmentation results are also compared to the operational sea ice information of digitized ice charts and to visual interpretation of the sea ice class

modelling the effect of time dependent river dune evolution on bed roughness and stage this paper presents an approach to incorporate time dependent dune evolution in the determination of bed roughness coefficients applied in hydraulic models dune roughness is calculated by using the process based dune evolution model of paarlberg et al 2009 and the empirical dune roughness predictor of van rijn 1984 the approach is illustrated by applying it to a river of simple geometry in the 1 d hydraulic model sobek for two different flood wave shapes calculated dune heights clearly show a dependency on rate of change in discharge with time dunes grow to larger heights for a flood wave with a smaller rate of change bed roughness coefficients computed using the new approach can be up to 10 higher than roughness coefficients based on calibration with the largest differences at low flows as a result of this larger bed roughness computed water depths can be up to 15 larger at low flow the new approach helps to reduce uncertainties in bed roughness coefficients of flow models especially for river systems with strong variations in discharge with time

mapping of different sea ice regimes using images from sentinel 1 and alos synthetic aperture radar airborne c and l band synthetic aperture radar sar images were acquired for three test sites over different sea ice regimes around svalbard in march 2007 complemented by optical imagery environmental data and ice observations one objective was to use the high resolution low noise radar data for investigations on the technical performance of european space agency s sentinel 1 mission for sea ice mapping the other to assess the potential gain of additional use of l band sar data currently available from advanced land observing satellite alos the airborne sar images were employed to simulate data products resembling the interferometric wide swath mode iwsm of sentinel 1 and alos palsar fine resolution mode frm in order to quantify the information loss due to the higher noise level and coarser spatial resolution at the iwsm noise level zones of deformation level ice and new ice can be well separated at like polarization at cross polarization the noise level is too high for a robust automated classification including thin ice but deformed and level ice can be discriminated palsar frm is on average better suited to distinguish deformed and level ice over all ice regimes it was worse for separating new from thicker level ice at two test sites for the third test site with very few patches of new ice the palsar frm showed larger intensity contrasts between new and level ice than sentinel 1 iwsm the spatial resolution provided by the iwsm and frm is sufficient to identify most ice features and types without ambiguities typical characteristics of the imaged ice regimes are described

geodynamic control on carbonate diagenesis petrographic and isotopic investigation of the upper jurassic formations of the paris basin france abstract the oxfordian and kimmeridgian carbonates of the eastern edge of the paris basin display poor reservoir properties stable isotope investigation of these non recrystallized cements through both microdrilling sampling and in situ sims secondary ion mass spectrometry analysis shows that they originated from slightly buffered meteoric fluids 3 smow to 8 smow flowing through the malm carbonate aquifers of the eastern edge of the paris basin after a review of the post upper jurassic history of the paris basin it appears that meteoric water supplies leading to such cementations were associated with the evolution of the basin s geodynamic setting and notably with the lcu late cimmerian unconformity major event which corresponds to the uplift of the london brabant massif denudation of the oxfordian and kimmeridgian carbonates on the southern flank of the london brabant massif to the north of the study area then lead to lateral recharging of the associated aquifers with meteoric fluids this scenario is similar to the one proposed to explain cementations of the jurassic carbonates in the wessex weald basins which emphasizes the main role played by the cretaceous unconformities over carbonate diagenesis at the scale of the northwestern tethys margin

classification of sea ice types in envisat synthetic aperture radar images in this paper sea ice in the central arctic has been classified in synthetic aperture radar sar images from envisat using a neural network nn based algorithm and a bayesian algorithm since different sea ice types can have similar backscattering coefficients at c band hh polarization it is necessary to use textural features in addition to the backscattering coefficients the analysis revealed that the most informative texture features for the classification of multiyear ice myi deformed first year ice fyi dfyi and level fyi lfyi and open water nilas are correlation inertia cluster prominence energy homogeneity and entropy as well as third and fourth central statistical moments of image brightness the optimal topology of the nn trained for envisat wide swath sar sea ice classification consists of nine neurons in input layer six neurons in hidden layer and three neurons in output layer the classification results for a series of 20 sar images acquired in the central part of the arctic ocean during winter months were compared to expert analysis of the images and ice charts the results of the nn classification show that the average correspondences with the expert analysis amount to 85 83 and 80 for lfyi dfyi and myi respectively the bayesian pixel based method can provide a higher resolution in the classified image and therefore better capability to identify leads compared to the nn method both methods may be effectively used in the central arctic where myi is predominant

the origin and timing of multiphase cementation in carbonates impact of regional scale geodynamic events on the middle jurassic limestones diagenesis paris basin france the middle jurassic carbonates of the eastern part of the paris basin display surprisingly low values of porosity and permeability 15 and k 0 5 md the main objective of this study is to determine the causes and timing of the cementation that altered the petrophysical properties of these carbonates thereby destroying their potential as oil reservoirs a fate that did not befall their equivalents in deeper central parts of the paris basin using petrographic and geochemical analyses stable o and c isotopes sr isotopes major elements we identify six calcitic spar stages two dolomite stages and several episodes of fracturing and stylolitization ordered in paragenetic sequence cement quantification shows the predominance of two blocky calcite cement stages 75 of total cementation o and sr isotopes from these calcite cements suggest that the parent fluids resulted either from a mixing of trapped jurassic seawater and meteoric water or from buffered meteoric waters in the geological history of the paris basin major meteoric water inputs were possible during the early cretaceous when the middle jurassic carbonates cropped out at its northern and eastern borders lateral meteoric recharge may have occurred as a result of two separate uplift events late cimmerian unconformity and late aptian unconformity and the related exposures of carbonates to the north of the study area this palaeohydrological circulation brought about a significant reduction of porosity from 40 to 10 through calcite cement precipitation the early cretaceous events are of great importance in the diagenetic evolution of the sedimentary basins bordering the london brabant massif across all of northwestern europe a subsequent dolomite and calcite cementation stage accounts for about 5 of the total cement volumes this late cementation may have been caused by hydrothermal fluids ascending along permeable fractures during the late oligocene extension episode

the onset of the dead sea transform based on calcite age strain analyses the onset and evolution of the dead sea transform are re evaluated based on new in situ u pb dating and strain analyses of mechanically twinned calcites direct dating of 30 syn faulting calcites from 10 different inactive fault strands of the transform indicates that the oceanic to continental plate boundary initiated between 20 8 and 18 5 ma within an 10 km wide distributed deformation zone in southern israel ages from the northern dead sea transform 17 1 12 7 ma suggest northward propagation and the establishment of a well developed 500 km long plate bounding fault in 3 m y the dominant horizontal shortening direction recorded in the dated twinned calcites marks the onset of left lateral motion along the evolving plate boundary the observed changes in the strain field within individual fault strands cannot be simply explained by local weakening effects along strands of the dead sea transform or by gradual changes in the euler pole through time

evolution of porewater composition through time in limestone aquifers salinity and d h of fluid inclusion water in authigenic minerals jurassic of the eastern paris basin france past water circulations can significantly reduce the porosity and permeability of marine limestones this is particularly the case in the middle bathonian bajocian to upper oxfordian jurassic limestones from the eastern border of the paris basin the knowledge of the timing the temperature and composition of paleowaters is essential to model the hydrological evolution in this area where the callovian oxfordian claystones are studied for the storage of nuclear wastes in this way fluid inclusions hosted in low temperature 60 c authigenic calcite quartz and celestite crystals were analyzed by raman spectroscopy and mass spectrometry to determine the chlorinity and d h ratios chlorinity measurements mmol cl per liter of water in fluid inclusions trapped in authigenic crystals during the late jurassic early cretaceous period revealed unexpected high values up to 3800 mmol l 1 indicating that brines were involved in some of the diagenetic crystallization processes by contrast fluid inclusions in calcite cements of cenozoic age within the oxfordian limestones have low cl concentration less than 150 mmol l 1 thus showing that a dilution event caused by water infiltrations during the cretaceous uplift of this part of the basin has flushed out the original saline porewater by coupling d of fluid inclusion with 18o of calcite crystals we estimate that calcite precipitation occurred at temperatures between 25 and 53 c the hydrogen isotope composition of calcite forming water is different between the middle jurassic d ranging from 20 to 35 8 v smow and the overlying oxfordian limestone d from 59 5 to 44 8 v smow present day groundwaters are also of distinct composition on both sides of the oxfordian claystones indicating that limestone aquifers underwent independent hydrologic evolutions since the early diagenetic jurassic cementation

reconstruction of low temperature 100 c burial in sedimentary basins a comparison of geothermometer in the intracontinental paris basin abstract the thermal evolution of sediments in the shallowest part of sedimentary basins is challenging to investigate as most of the geothermometers are at their application limits this is typically the case of the callovian oxfordian claystones at the eastern border of the paris basin a recent 2000 m deep well penetrated the entire jurassic and triassic sedimentary series and permitted coring of sediments never reached by previous drilling in this part of the basin thanks to the use of several independent geothermometers apatite fission track thermochronology fluid inclusion microthermometry clay mineralogy and sedimentary organic matter evolution the burial history of the mesozoic series has been reconstructed modeled and calibrated using kinetic algorithms relevant to the various paleothermometers used in addition to these conventional methods an innovative approach was developed using the temperature dependence of the magnetic mineral assemblage within clay rich sediments mageval thermal modeling indicates that the callovian oxfordian and the lower triassic experienced maximum burial temperatures of 50 5 c and 90 10 c respectively i e about 25 c higher than present day this temperature offset implies the erosion of several hundred meters of sediments which depending on the thermal flux and conductivity considered most likely constituted upper cretaceous chalk deposits falling sea level resulted in the exposure and subsequent dismantling of the chalk cover at the beginning of cenozoic times the eastern border of the basin was then subjected to slow erosion and discrete tectonic deformation

a calcite reference material for la icp ms u pb geochronology u pb dating of calcite is an emerging but rapidly growing field of application in geochronology with great potential to inform problems in landscape basin and mountain belt evolution through age determination of diagenetic cements vein mineralisation and geological formations difficult to date otherwise in this brief we present isotope dilution u pb isotope measurements on a sample of calcite wc 1 that has been and will continue to be used as a reference material for in situ u pb laser ablation inductively coupled plasma mass spectrometry la icp ms dating and which is suitable to be distributed to the geochronological community we present in situ measurements using la icp ms to demonstrate the suitability of wc 1 for use as a u pb dating reference material in spite of it not being isotopically homogeneous the wc 1 calcite sample is 254 4 6 4 ma old and comprised of 85 to 98 radiogenic lead it presents a suitable reference material that can facilitate dating of calcite ranging in age from precambrian to late neogene age

morphology and flow fields of three dimensional dunes rio parana argentina results from simultaneous multibeam echo sounding and acoustic doppler current profiling 1 most past studies of river dune dynamics have concentrated on two dimensional 2 d bed forms with constant heights and straight crest lines transverse to the flow and their associated turbulent flow structure this morphological simplification imposes inherent limitations on the interpretation and understanding of dune form and flow dynamics in natural channels where dune form is predominantly three dimensional for example studies over 2 d forms neglect the significant influence that lateral flows and secondary circulation may have on the flow structure and thus dune morphology this paper details a field study of a swath of 3 d dunes in the rio parana argentina a large 0 35 km wide 1 2 km long area of dunes was surveyed using a multibeam echo sounder mbes that provided high resolution 3 d detail of the river bed simultaneous with the mbes survey 3 d flow information was obtained with an acoustic doppler current profiler adcp revealing a complicated pattern of dune morphology and associated flow structure within the swath dune three dimensionality appears intimately connected to the morphology of the upstream dune with changes in crest line curvature and crest line bifurcations junctions significantly influencing the downstream dune form dunes with lobe or saddle shaped crest lines were found to have larger more structured regions of vertical velocity with smaller separation zones than more 2 d straight crested dunes these results represent the first integrated study of 3 d dune form and mean flow structure from the field and show several similarities to recent laboratory models of flow over 3 d dunes

variability in bedform morphology and kinematics with transport stage bedform geometry is widely recognized to be a function of transport stage bedform aspect ratio height length increases with transport stage reaches a maximum then decreases as bedforms washout to a plane bed bedform migration rates are also linked to bedform geometry in so far as smaller bedforms in coarser sediment tend to migrate faster than larger bedforms in finer sediment however how bedform morphology height length and shape and kinematics translation and deformation change with transport stage and suspension have not been examined a series of experiments is presented where initial flow depth and grain size were held constant and the transport stage was varied to produce bedload dominated mixed load dominated and suspended load dominated conditions the results show that the commonly observed pattern in bedform aspect ratio occurs because bedform height increases then decreases with transport stage against a continuously increasing bedform length bedform size variability increased with transport stage leading to less uniform bedform fields at higher transport stage total translation related and deformation related sediment fluxes all increased with transport stage however the relative contribution to the total flux changed at the bedload dominated stage translation related and deformation related flux contributed equally to the total flux as the transport stage increased the fraction of the total load contributed by translation increased and the fraction contributed by deformation declined because the bedforms got bigger and moved faster at the suspended load dominated transport stage the deformation flux increased and the translation flux decreased as a fraction of the total load approaching one and zero respectively as bedforms washed out to a plane bed

evidence for an early cretaceous mineralizing event above the basement sediment unconformity in the intracratonic paris basin paragenetic sequence and sm nd dating of the world class pierre perthuis stratabound fluorite deposit world class stratabound fluorite deposits are spatially associated with the basement sediment unconformity of the intracratonic paris basin and the morvan massif in burgundy france the reserves are estimated to be about 5 5 mt of fluorite within six fluorite deposits in this study we aim to determine the age of the major fluorite mineralization event of the pierre perthuis deposit 1 4 mt fluorite by a combined study of the paragenetic mineral sequence and sm nd dating on fluorite crystals fluorite occurs as isolated cubes or filling geodes in a triassic silicified dolomitic formation three fluorite stages associated with sphalerite pyrite galena barite and quartz have been distinguished using optical cathodoluminescence and scanning electron microscopes seven crystals of the geodic fluorite stage were analyzed for their rare earth element ree contents and their 147sm 144nd and 143nd 144nd isotopic compositions the normalized ree distribution displays homogeneous bell shaped patterns for all the geodic fluorite samples with a mid ree enrichment over the light ree and heavy ree the 147sm 144nd varies from 0 3108 to 0 5504 and the 143nd 144nd from 0 512313 to 0 512518 a six point sm nd isochron defines an age of 130 15 ma initial 143nd 144nd 0 512054 mswd 0 21 this sm nd isochron provides the first age for the stratabound fluorite sediment hosted deposit related to an unconformity in the paris basin and highlights a major early cretaceous fluid circulation event mainly above the basement sediment unconformity during a flexural deformation of the paris basin which relates to the rifting of the bay of biscay and the formation of the ligurian sea in the western europe domain

flow structure and resistance over subaquaeous high and low angle dunes a prominent control on the flow over subaqueous dunes is the slope of the downstream leeside while previous work has focused on steep 30 asymmetric dunes with permanent flow separation little is known about dunes with lower lee slope angles for which flow separation is absent or intermittent here we present a laboratory investigation where we systematically varied the dune lee slope holding other geometric parameters and flow hydraulics constant to explore effects on the turbulent flow field and flow resistance three sets of fixed dunes lee slopes of 10 20 and 30 were separately installed in a 15 m long and 1 m wide flume and subjected to 0 20 m deep flow measurements consisted of high frequency vertical profiles collected with a laser doppler velocimeter we show that the temporal and spatial occurrence of flow separation decreases with dune lee slope velocity gradients in the dune leeside depict a free shear layer downstream of the 30 dunes and a weaker shear layer closer to the bed for the 20 and 10 dunes the decrease in velocity gradients leads to lower magnitude of turbulence production for gentle lee slopes aperiodic strong ejection events dominate the shear layer but decrease in strength and frequency for low angle dunes flow resistance of dunes decreases with lee slope the transition being nonlinear over the 10 20 and 30 dunes shear stress is 8 33 and 90 greater than a flat bed respectively our results demonstrate that dune lee slope plays an important but often ignored role in flow resistance

the influence of kinetics on the oxygen isotope composition of calcium carbonate paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution and calcium carbonate although oxygen isotope separation is expected on theoretical grounds the temperature dependence remains uncertain because other factors such as slow exchange of isotopes between dissolved co2 species and water can obscure the temperature signal this is problematic for crystal growth experiments on laboratory timescales and for interpreting the oxygen isotope composition of crystals formed in natural settings we present results from experiments in which inorganic calcite is precipitated in the presence of 0 25 m dissolved bovine carbonic anhydrase ca the presence of dissolved ca accelerates oxygen isotope equilibration between the dissolved carbon species co2 h2co3 hco3 co32 and water thereby eliminating this source of isotopic disequilibrium during calcite growth the experimental results allow us to isolate for the first time kinetic oxygen isotope effects occurring at the calcite water interface we present a framework of ion by ion growth of calcite that reconciles our new measurements with measurements of natural cave calcites that are the best candidate for having precipitated under near equilibrium conditions our findings suggest that isotopic equilibrium between calcite and water is unlikely to have been established in laboratory experiments or in many natural settings the use of ca in carbonate precipitation experiments offers new opportunities to refine oxygen isotope based geothermometers and to interrogate environmental variables other than temperature that influence calcite growth rates

effect of sediment transport boundary conditions on the numerical modeling of bed morphodynamics abstractexperimental sediment transport and river morphologic studies in laboratory flumes can use two sediment supply methods an imposed feed at the upstream end or a recirculation of sediment f

sand dunes in steady flow at low froude numbers dune height evolution and flow resistance the development of sand dunes in an erodible bed exposed to flowing water is considered using a numerical flow model the bed is initially given a small perturbation which is followed in the time domain examples are given where a sinusoidal perturbation reaches the fully developed steady equilibrium shape the flow modeling is based on a k turbulence closure the sediment transport is assumed to be bed load only with an avalanche like movement on the steep dune front the model is also found capable of predicting the growth in wavelength if the initially prescribed wavelength is sufficiently short results of the dune development are presented for different initial wavelengths it is demonstrated that an equilibrium shape is developed for a range of wavelength depth ratios as long as this ratio is sufficiently small

numerical modeling of subaqueous sand dune morphodynamics the morphodynamic evolution of subaqueous sand dunes is investigated using a 2 d reynolds averaged navier stokes numerical model a laboratory experiment where dunes are generated under stationary unidirectional flow conditions is used as a reference case the model reproduces the evolution of the erodible bed until a state of equilibrium is reached in particular the simulation exhibits the different stages of the bed evolution e g the incipient ripple generation the nonlinear bed form growing phase and the dune field equilibrium phase the results show good agreement in terms of dune geometrical dimensions and time to equilibrium after the emergence of the first ripple field the bed growth is driven by cascading merging sequences between bed forms of different heights a sequence extracted from the simulation shows how the downstream bed form is first eroded before merging with the upstream bed form superimposed bed forms emerge on the dune stoss sides during the simulation an analysis of the results shows that they emerge downstream of a slight deflection on the dune profile the deflection arises due to a modification of the sediment flux gradient consecutive to a reduction in the turbulence relaxation length while the upstream bed form height decreases as they migrate superimposed bed forms grow on the dune stoss side and eventually provoke the degeneration of the dune crest cascading merging sequences and superimposed bed forms dynamics both influence the dune field evolution and size and therefore play a fundamental role in the dune field self organization process

past hot fluid flows in limestones detected by δ47 u pb and not recorded by other geothermometers geothermometers are commonly used to reconstruct the diagenetic and thermal history of rocks however characterizing the timing origin and temperature of paleofluid flow remains challenging because it must be assessed indirectly through the analysis of microscopic cements that precipitate and fill intergranular spaces during fluid circulation here we measure both the clumped isotope 47 temperature and in situ u pb age of individual diagenetic calcite cements within a sedimentary section of the paris basin france whose thermal history has been previously inferred to be 70 c have been measured for calcite cements containing single phase aqueous fluid inclusions challenging the commonly accepted assertion that the absence of nucleation of a vapor phase indicates crystallization at low temperature 70 c we suggest that the kinetics of mineralization events prevented the recording of short lived hot fluid flows by other

late devensian and holocene relative sea level change in north wales uk deglacial sea level index points defining relative sea level rsl change are critical for testing glacial isostatic adjustment gia model output only a few observations are available from north wales and until recently these provided a poor fit to gia model output for the british irish ice sheet we present results of an integrated offshore geophysical seismic reflection coring drilling rig sedimentological micropalaeontological foraminifera biostratigraphical palynology and geochronological ams 14c investigation into a sequence of multiple peat organic sediment horizons interbedded within a thick estuarine marine sequence of minerogenic clay silts to silty sands from the ne menai strait north wales ten new sea level index points and nine new limiting dates from the devensian late glacial and early holocene are integrated with twelve pre existing holocene sea level index points and one limiting point from north wales to generate a regional rsl record this record is similar to the most recent gia predictions for north wales rsl change supporting either greater ice load and later deglaciation than in the gia predictions generated before 2004 or a modified eustatic function there is no evidence for a mid holocene highstand tidally corrected rsl data indicate initial breaching of the menai strait between 8 8 and 8 4 ka bp to form a tidal causeway with final submergence between 5 8 and 4 6 ka bp final breaching converted the ne menai strait from a flood dominated estuary into a high energy ebb tidal delta with extensive tidal scouring of pre existing late glacial and holocene sequences the study confirms the value of utilising offshore drilling coring technology to recover sea level records which relate to intervals when rates of both eustatic and isostatic change were at their greatest and therefore of most value for constraining gia models copyright 2011 john wiley sons ltd

carbonate clumped isotope bond reordering and geospeedometry carbonate clumped isotope thermometry is based on the preference of 13c and 18o to form bonds with each other at elevated temperatures such bond ordering is susceptible to resetting by diffusion of c and o through the solid mineral lattice this type of bond reordering has the potential to obscure primary paleoclimate information but could also provide a basis for reconstructing shallow crustal temperatures and cooling rates we determined arrhenius parameters for solid state reordering of c o bonds in two different calcites through a series of laboratory heating experiments we find that the calcites have different susceptibilities to solid state reordering reaction progress follows a first order rate law in both calcites but only after an initial period of non first order reaction that we suggest relates to annealing of nonequilibrium defects when the calcites are first heated to experimental temperature we show that the apparent equilibrium temperature equations or closure temperature equations for carbonate clumped isotope reordering are analogous dodson s equations for first order loss of daughter isotopes for each calcite the sensitivity of apparent equilibrium temperature to cooling rate is sufficiently high for inference of cooling rates within a factor of 5 or better for cooling rates ranging from tens of degrees per day to a few degrees per million years however because the calcites have different susceptibilities to reordering each calcite defines its own cooling rate apparent equilibrium temperature relationship the cooling rates of carrara marble inferred from carbonate clumped isotope geospeedometry are 10 6 10 3 degrees per annum and are in broad agreement with rates inferred from thermochronometric methods cooling rates for 13c depleted calcites from the late neoproterozoic doushantou cap carbonates in south china are on the order of 102 104 degrees per annum consistent with rapid cooling following formation of these calcites by a short lived hydrothermal event bristow et al 2011 nature v 474 p 68 71 most of the uncertainty in these estimates relates to uncertainty in arrhenius parameters for different calcites thus while the carbonate clumped isotope geospeedometer shows promise for recording cooling rates in settings and lithologies where other geospeedometers may not be applicable the uncertainty in cooling rate will be large without independent knowledge of the reordering kinetics of each study material thus the full potential of the method will only be realized if reordering kinetics can be accurately determined for each study material or predicted on the basis of mineral composition texture or other observable parameters

impact of basin burial and exhumation on jurassic carbonates diagenesis on both sides of a thick clay barrier paris basin ne france several diagenetic models have been proposed for middle and upper jurassic carbonates of the eastern paris basin the paragenetic sequences are compared in both aquifers to propose a diagenetic model for the middle and late jurassic deposits as a whole petrographic optical and cathodoluminescence microscopy structural fracture orientations and geochemical 18o 13c ree studies were conducted to characterize diagenetic cements with a focus on blocky calcite cements and their connection with fracturation events four generations of blocky calcite cal1 cal4 are identified cal1 and cal2 are widespread in the dominantly grain supported facies of the middle jurassic limestones about 90 of the cementation whereas they are limited in the oxfordian because grain supported facies are restricted to certain stratigraphic levels cal1 and cal2 blocky spars precipitated during burial in a reducing environment from mixed marine meteoric waters and or buffered meteoric waters the meteoric waters probably entered aquifers during the late cimmerian jurassic cretaceous boundary and late aptian early cretaceous unconformities the amount of cal2 cement is thought to be linked to the intensity of burial pressure dissolution which in turn was partly controlled by the clay content of the host rocks cal3 and cal4 are associated with telogenetic fracturing phases the succession of cal3 and cal4 calcite relates to the transition towards oxidizing conditions during an opening of the system to meteoric waters at higher water rock ratios these meteoric fluids circulated along pyrenean oligocene and alpine fractures and generated both dissolution and subsequent cementation in oxfordian vugs in mud supported facies and in poorly stylolitized grainstones however these cements filled only the residual porosity in middle jurassic limestones in addition to fluorine inputs fracturation also permitted inputs of sulphur possibly due to weathering of triassic or purbeckian evaporites or h2s input during paleogene times

modeling river dune evolution using a parameterization of flow separation this paper presents an idealized morphodynamic model to predict river dune evolution the flow field is solved in a vertical plane assuming hydrostatic pressure conditions the sediment transport is computed using a meyer peter muller type of equation including gravitational bed slope effects and a critical bed shear stress to avoid the necessity of modeling the complex flow inside the flow separation zone we follow an approach similar to one used earlier to simulate the dynamics of wind blown desert dunes in case of flow separation the separation streamline acts as an artificial bed and sediment avalanches down the leeside distributing evenly on the leeside at the angle of repose model results show that bed slope effects play a crucial role in the determination of the fastest growing wavelength from a linear analysis flow separation is shown to be crucial to take into account if the dune lee exceeds a certain threshold slope if flow separation is not included dune shapes are incorrectly predicted and the dune height saturates at an early stage of bed form evolution yielding an underprediction of dune height and time to equilibrium the local bed slope at the dune crest plays a critical role for obtaining an equilibrium dune height the simulation model is able to predict the main characteristics of dune evolution such as dune asymmetry dune growth and saturation at a certain dune height dune dimensions migration rates and times to equilibrium compare reasonably well to various data sets

incidence angle dependence of hh polarized c and l band wintertime backscatter over arctic sea ice synthetic aperture radar sar incidence angle has a significant effect on the microwave backscatter from sea ice this paper investigates the incidence angle dependence of c and l band hh polarized microwave backscatter coefficient over arctic first year sea ice fyi and multiyear sea ice myi in winter advanced land observation satellite phased array type l band sar l band and radarsat 2 c band images are used to derive ice type specific incidence angle dependencies calculated using linear regression models for l band mean ice type specific incidence angle dependencies for fyi and myi are 0 21 and 0 30 db 1 respectively and for c band they are 0 22 and 0 16 db 1 respectively to validate our results we calculated root mean square deviation rmsd by comparing the ice type specific dependence from 2010 with individual dependencies from 2009 based on ice types and frequencies the rmsd is found to be smaller than the standard deviation of ice type specific dependencies for both frequencies the rmsd values for the l band incidence angle dependencies are 0 03 and 0 04 db 1 for fyi and myi respectively for c band the rmsd values for the fyi and myi dependencies are 0 03 and 0 01 db 1 respectively subsequently we demonstrate that after applying incidence angle normalization the variability of c and l band sar backscatter reduces and separability of ice types increase substantially

shape and dimensions of stationary dunes in rivers the shape and dimensions length height of sand dunes in rivers are calculated by use of the measured bed shear stress distribution downstream a rearward facing step the transport of sediment is split up into bed load and suspended load which makes it possible to explain the transition to plane bed the model can predict flow resistance curves in alluvial streams

a major late jurassic fluid event at the basin basement unconformity in western france 40ar 39ar and k ar dating fluid chemistry and related geodynamic context the malm lower cretaceous period is often considered to represent a period of time markedly devoid of crustal deformations and of heat and mass transfers in western france although numerous evidences of such transfers are reported in varied basins from western iberia to western africa migrating evaporitic derived brines and seawater interacted with both the sedimentary cover and the basement in the poitou high located at the boundary between aquitaine and paris basins occurring after sedimentation this activity induced significant alterations of the sediments by dolomitization and silicification and the basement by adularization and locally by concentration of f ba pb zn assemblages that are typical of carbonate hosted metal deposits thus metals were leached from metamorphic granitic basement already weathered and peneplaned during triassic time and were redeposited by brines during this main fluid event the main objective of this study was to decipher the timing of this major fluid heat mass transfer on the basis of 40ar 39ar and k ar dating of epigenetic minerals having similar paragenetic and geochemical signatures over an extended area from the atlantic ocean coast to the french massif central a late jurassic fluid stage 146 156 ma significantly younger than what is generally reported in western europe was obtained this fluid event occurred within a segment of a continental margin that was located away from main rift zones and far more than 500 km from major deformation areas such as the main rift or orogenic zones all over western europe these results yield a new concept based on wide wavelength relationships between fluid movements and geodynamic events affecting both the sedimentary basins and their basements

sensitivity of c band synthetic aperture radar polarimetric parameters to snow thickness over landfast smooth first year sea ice abstract c band linear and polarimetric parameters derived from synthesis and decomposition of radarsat 2 sar data are analyzed and evaluated with respect to snow covers of variable thickness on smooth first year sea ice sfyi the study is conducted for two selected temperature conditions 1 cold 7 9 c and 2 warm 0 4 c first the polarimetric sar response from the snow cover at cold conditions is analyzed with an objective to investigate the sensitivity of linear and polarimetric backscatter to snow thickness second the changes in these sensitivities are examined as a function of change in surface air temperature from 7 9 c to 0 4 c through the changes manifested in snow geophysical properties the dependence of linear and polarimetric backscatter response on radar incidence angle for different snow thicknesses is also evaluated our results demonstrate strong to weak relationships between the polarimetric parameters and snow thickness under cold conditions but virtually no relationship under warm conditions the strength of this sensitivity varies with parameter type radar incidence angle and snow geophysical properties under the cold conditions fourteen polarimetric parameters demonstrate a positive relationship and nine demonstrate a negative relationship with snow thickness this parameter sensitivity to snow thickness indicates an increase in volume or mixed scattering component with increase in snow thickness the cause of this is primarily an increased microwave interaction with a greater number of dry snow grains and or more interaction with increased brine volumes in the brine wetted snow and upper sea ice layer a comparison of polarimetric signatures at warm conditions to that at cold conditions shows both an increase and a decrease in response for all snow thicknesses for thin or medium snow cover every time a polarimetric parameter response increases or decreases as a consequence of an increase in temperature there is always an opposite response in the same polarimetric parameter for thick snow cover this is primarily due to the masking effect of moist snow likely caused by reduced penetration depth resulting in dominant surface scattering from the air moist snow interface and or the dry snow brine wetted snow interface as opposed to the snow ice interface normal probability density functions pdfs employed to determine the snow thickness separation capability of polarimetric parameters show near overlapping signatures of all snow classes under warm conditions suggesting that snow thickness estimation using snow thermodynamics at warm conditions is not possible

the fluid dynamics of river dunes a review and some future research directions 1 dunes are present in nearly all fluvial channels and are vital in predicting flow resistance sediment transport and deposition within many rivers progress in understanding the fluid dynamics associated with alluvial dunes has been significant in the last 15 years and has witnessed huge advances in field laboratory and numerical investigations progress has been made in detailing the principal features of mean and turbulent flow over asymmetric dunes that possess flow separation in their leesides and how these forms affect both downstream boundary layer structure and stress partitioning over the dune additionally the links between sediment transport over dunes and instantaneous coherent flow structures are being increasingly understood with the feedback of dune three dimensionality upon flow and sediment dynamics over these bed forms beginning to be recognized as vital such research now provides an outstanding background for beginning to address areas of greater complexity that will enable a fuller understanding of these important natural features this review paper summarizes the principal features of mean and turbulent flow over alluvial sand dunes five areas are then highlighted and discussed as a possible focus for future research 1 the influence of dune leeside angle upon flow processes in the dune wake and downstream flow field 2 the influence of three dimensionality in dune shape upon the generation of turbulence and distribution of bed shear stress 3 flow field modification resulting from bed form superimposition and amalgamation 4 the scale and topology of dune related turbulence and its interactions with sediment transport and the flow surface and 5 the influence of suspended sediment on the dune flow field and dune morphology

case study bed resistance of rhine river during 1998 flood detailed field measurements during the 1998 flood of the rhine river in the netherlands show that both manning in and darcy weisbach friction factor if increase with discharge the changes in bedform roughness height and friction factors are attributed to the increased dune height during floods there is a near peak hysteresis in the dune height measurements at a given discharge dunes are significantly larger after than before the peak discharge the trend is most apparent for the bovenrijn with weaker variations for the waal the methods of engelund and vanoni hwang provide similar estimates of form drag when combined with van rijn s method to estimate grain resistance both methods tend to overpredict the measured bed friction factor after the peak discharge these methods perform best when field bedform measurements are available to estimate form drag the composite effect of primary and secondary dunes should be considered in the analysis of resistance to flow

u pb dating of geodic calcite new insights on western europe major tectonic events and associated diagenetic fluids this study presents the first application of the u pb dating method to highly pb depleted diagenetic geodic calcites of the jurassic formations of the paris basin that leads to a reappraisal of the palaeohydrological history of this region composite u pb ages from multiple geodes combined with 18 o analyses reveal two main phases of diagenetic fluid circulations linked with major regional tectonic events dogger formations recorded a first diagenetic fluid episode at 147 8 3 8 ma i e at the very beginning of the emersion of the basin during the tithonian period and 30 ma earlier than previously assumed 18 o results confirmed that most of the calcitic cement phases that closed the porosity of these formations precipitated at the beginning of the cretaceous period oxfordian formations recorded another major meteoric fluid circulation at 33 5 2 8 ma related to the initial stage of the european cenozoic rift system ecris consequently the porosity of the mesozoic formations of the studied area may have been closed sooner than previously thought before the main ecris rifting phase of oligocene age this study shows that u pb dating of secondary geodic calcite offers a new powerful way for reconstructing the coupled palaeohydrological and diagenetic history of sedimentary basins supplementary material pb pb diagrams 238 u and 235 u series isochron diagrams and effect of blank correction on u and pb isotopic compositions and on ages calculation are available at https doi org 10 6084 m9 figshare c 3886885

the dynamical balance of flow in the menai strait abstract observations of sea surface slope and along channel current from two experiments are used to explore the dynamical balance in the tidally energetic menai strait a regression analysis is used to deduce a new value for the sea bed frictional drag coefficient which achieves a close balance of the forces involved the regression results are consistent between the two experiments and highly significant over 90 of the variance is explained and indicate that the friction coefficient for the menai strait is significantly larger than that usually employed for shelf sea flows but consistent with values of the chezy coefficient for open channel flow the tidal cycle of along channel flow is highly distorted as a result of shallow water frictional effects and there is a net transport of water to the south west of the order of 25 30 million tonnes per tidal cycle the non linear advective acceleration term in the dynamical balance is shown to be small

residual flow bedforms and sediment transport in a tidal channel modelled with variable bed roughness abstract the frictional influence of the seabed on the tidal flow in shelf seas and estuaries is usually modelled via a prescribed spatially temporally invariant drag coefficient in practice the seabed exhibits considerable variability particularly spatially that should in principle be included in simulations local variations in the seabed roughness k s alter the flow strength and hence local sediment transport rates the effect of using a spatially temporally varying k s is assessed here with reference to a tidal channel menai strait n wales in which the variability of the bedforms has been monitored using multi beam surveying the channel not only exhibits strong tidal flow but also a residual induced flow that is used here as diagnostic to assess various bed roughness formulations tested in a telemac model tidal simulations have been carried out with both constant and temporally spatially variable k s and the predicted residual flow is shown to be sensitive to these representations for a mean spring neap sn cycle with variable k s the average residual flow is calculated to be 525 m 3 s 1 consistent with observations this residual flow can be recovered using imposed constant values of k s in the range 0 15 m to 0 3 m the results suggest that the overall effective roughness of the seabed is less than half of the maximum local roughness due to the dunes in mid channel but more than the spatially averaged k s value in the channel as a whole by about 50 simulations carried out with an m 2 alone tide using variable k s produce a somewhat smaller by 7 residual flow of 491 m 3 s 1 the use of an equivalent m 2 tide of amplitude enhanced by 7 3 reconciles these estimates the main contribution to k s is made by dunes which are modelled using van rijn s 2007 formulation subject to an additional history effect the modelled k s is found to equal approximately the observed height of the dunes along mid channel transects rather than half the height as expected this is attributed to the non equilibrium nature of the bedforms in the reversing tidal flow which exhibited shorter wavelength and more symmetrical profiles than dunes in steady flow

on the formation of tide produced seiches and double high waters in coastal seas we describe a mechanism by which the tide forcing a coastal water body produces an oscillation at the natural period of the water body a seiche around the time of high water the seiche appears as a distortion in the tidal curve which can under certain conditions produce a double high water the formation of the seiche is explored with a numerical simulation of a sea strait forced by the tide at its open ends a seiche of wavelength equal to twice the length of the strait is formed when the mean depth of the strait is similar to the tidal range the rapid reduction of friction as high water is approached appears to be an important part of the formation process observations of water level in the centre of a shallow sea strait in north wales confirm that there is a residual oscillation around high water with the form of a damped seiche the crest of the seiche occurs just before and the trough just after the maximum in the fitted tidal curve the seiche slows the fall of the tide after high water and on one occasion at neap tides the fall is reversed and a double high water is formed it is possible that this mechanism hitherto unidentified contributes to the formation of double high waters in other shallow coastal locations

modeling of spatial lag in bed load transport processes and its effect on dune morphology in the present study two bed load transport models are introduced in an existing idealized dune model these allow for the modeling of the spatial lag between the sediment transport rate and bed shear stress along dune surfaces this lag is an important factor in determining transitions between bedform regimes results of the original dune model using an equilibrium transport formula are compared with 1 a new model version that directly models spatial lag with a relaxation equation and 2 a new model version including pick up and deposition processes both bed load models use mean particle step length as an important parameter which is varied to assess which value is appropriate for the dune regime laboratory experiments are simulated with the model this shows that the results are best with the pick up and deposition model version combined with a step length of 25 times the particle diameter it is furthermore shown that in principle the model is also able to wash out fully grown dunes by increasing the step length parameter see more at http ascelibrary org doi 10 1061 28asce 29hy 1943 7900 0001254 sthash to4wr5cu dpuf

basin scale thermal and fluid flow histories revealed by carbonate clumped isotopes δ47 middle jurassic carbonates of the paris basin depocentre the reconstruction of past diagenetic conditions in sedimentary basins is often under constrained this results from both the analytical challenge of performing the required analyses on the minute sample amounts available from diagenetic mineral phases and the lack of tracers for some of the diagenetic parameters the carbonate clumped isotopes thermometry 47 opens new perspectives for unravelling the temperatures of diagenetic phases together with the source of their parent fluids two parameters that are otherwise impossible to constrain in the absence of exploitable fluid inclusions here is reported the study of a large number of sedimentary and diagenetic carbonate phases from middle jurassic reservoirs of the paris basin depocentre by combining detailed petrographic observations with a large number of 47 data n 45 on a well documented paragenetic sequence including calcite and dolomite burial cements the data reveal carbonate crystallization at temperatures between 29 c and 98 c from fluids with 18owater values between 7 and 2 in response to the progressive burial and uplift of the paris basin throughout 165 myr of basin evolution coupled to the time temperature evolution previously estimated from thermal maturity modelling these temperatures allow determining the timing of four successive cementation episodes the overall dataset indicates a history of complex water mixing with a significant contribution of hypersaline waters from the triassic aquifers migrated upward along faults during the cretaceous subsidence of the basin subsequent large scale infiltrations of meteoric waters induced a dilution of these pre existing brines in response to the paris basin uplift in the tertiary overall the data presented here allow proposing an integrated approach to characterize the cementation events affecting the studied carbonate reservoir units based on temperature oxygen isotope composition and salinity of the parent fluids as well as on petrographic grounds this article is protected by copyright all rights reserved

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

unified view of sediment transport by currents and waves i initiation of motion bed roughness and bed load transport attention is given to the properties of sediment beds over the full range of conditions silts to gravel in particular the effect of fine silt on the bed composition and on initiation of motion critical conditions is discussed high quality bed load transport data sets are identified and analyzed showing that the bed load transport in the sand range is related to velocity to power 2 5 the bed load transport is not much affected by particle size the prediction of bed roughness is addressed and the prediction of bed load transport in steady river flow is extended to coastal flow applying an intrawave approach simplified bed load transport formulas are presented which can be used to obtain a quick estimate of bed load transport in river and coastal flows it is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions the proposed model is fully predictive in the sense that only the basic hydrodynamic parameters dep

dynamics of the terra nova bay polynya the potential of multi sensor satellite observations research on processes leading to formation maintenance and disappearance of polynyas in the polar regions benefits significantly from the use of different types of remote sensing data the sentinels of the european space agency esa together with other satellite missions provide a variety of data from different parts of the electromagnetic spectrum at different spatial scales and with different temporal resolutions in a case study we demonstrate the advantage of merging data from different spaceborne instruments for analysing ice conditions and ice dynamics in and around the frequently occurring terra nova bay polynya tnbp in the ross sea in the antarctic starting with a list of polynya parameters that are typically retrieved from satellite images we assess the usefulness of different sensor types on regional scales several 100 km passive microwave radiometers provide a view on the mutual influence of the three ross sea polynyas on sea ice drift and deformation patterns optical sensors with meter scale resolution on the other hand allow very localized analyses of different polynya zones the combination of different ranges of the electromagnetic spectrum is essential for recognition and classification of ice types and structures radar images together with data from thermal infrared sensors operated at tens to hundreds of meters resolution improve the separation of the outlet zone of the polynya from the adjacent pack ice the direct comparison of radar and passive microwave images reveals the visibility of deformed ice zone in the latter a sequence of radar images was employed to retrieve ice drift around the tnb which allows analysing the temporal changes of the polynya area and the extension and structure of the outlet zone as well as ice movements and deformation that are influenced by the katabatic winds

mapping sea ice types from sentinel 1 considering the surface type dependent effect of incidence angle automated classification of sea ice types in synthetic aperture radar sar imagery is complicated by the class dependent decrease of backscatter intensity with incidence angle ia in the log domain this decrease is approximately linear over the typical range of space borne sar instruments a global correction does not consider that different surface types show different rates of decrease in backscatter intensity here we introduce a supervised classification algorithm that directly incorporates the surface type dependent effect of ia we replace the constant mean vector of a gaussian probability density function in a bayesian classifier with a linearly variable mean during training the classifier first retrieves the slope and intercept of the linear function describing the mean value and then calculates the covariance matrix as the mean squared deviation relative to this function the ia dependence is no longer treated as an image property but as a class property based on training and validation data selected from overlapping sar and optical images we evaluate the proposed method in several case studies and compare to other classification algorithms for which a global ia correction is applied during pre processing our results show that the inclusion of the per class ia sensitivity can significantly improve the performance of the classifier

improving paleohydrological and diagenetic reconstructions in calcite veins and breccia of a sedimentary basin by combining δ47 temperature δ18owater and u pb age abstract in sedimentary basins the precise temperature and timing at which relatively shallow

coupling δ47 and fluid inclusion thermometry on carbonate cements to precisely reconstruct the temperature salinity and δ18o of paleo groundwater in sedimentary basins abstract diagenetic minerals may provide information about the burial history of geological units and can have practical applications for instance for reconstructing the geochemical and thermal histories of sedimentary basins clumped isotope or 47 thermometry on carbonates opens a new avenue for interpreting carbonate formation temperature and thermal history of rocks yet most of current knowledge on 47 systematics has been acquired via theoretical or experimental studies with only limited validation by the rock record at geological conditions timescales here we investigate calcitic and dolomitic cements representative of three genetically different cementation phases from a well documented mineral paragenesis of a carbonate unit middle jurassic paris basin france we compare 47 with fluid inclusions microthermometry fim data that were independently obtained from the same calcite and dolomite crystal specimens the range of homogenization temperatures th found for cal1 cal2 and dol1 fluid inclusions fit remarkably well i e within 47 measurements t 47 for a temperature range between 60 and 100 c and salinities between 0 and 15 wt nacl eq this provides a consistent rock based validation of the experimentally determined 47 calibration with formation temperature for both calcite and dolomite mineralogy such findings also confirm the applicability of 47 thermometry in low temperature diagenetic environments i e below circa 100 c which provides higher precision than fim measurements i e typical uncertainties of 6 c with three 47 measurements though significantly less time consuming importantly this study underlines how the coupling of both techniques can help to evaluate the degree of preservation of the original temperature information captured by either fluid inclusions or 47 compositions and interpret each proxy as confidently accurately as possible moreover because both fim and 47 measurements can provide independent constraints on the geochemistry of diagenetic paleofluids via their salinity and 18 o composition this study also highlights the benefits of coupling both techniques to further unravel the nature of paleofuids finally we propose a practical guideline as a basis for future applications of combined fim and 47 thermometry

the response of subaqueous dunes to floods in sand and gravel bed reaches of the dutch rhine the branches of the river rhine in the netherlands characterized by a sand gravel bed in the upstream part and a sand bed in the downstream part of the river system show migrating dunes especially during floods in the last 20 years these dunes have been studied extensively high resolution echo sounding measurements of these dunes made with single and multibeam equipment were analysed for three different sections of the rhine river system during several floods this analysis was done to quantify the growth decay and migration rates of the dunes during floods in addition the migrating dunes were used to calculate bedload transport rates with dune tracking the results of dune growth and decay and migration rate are shown to be very different for the various sections during the various floods and these differences are related to differences in grain size of the bed and to differences in the distribution of discharge over the main channel and the floodplain the relations are used to show that the growth and migration rate of dunes and the calculated bedload transport rates during the rising stage of a flood wave can be predicted from the mobility of the bed material with simple power relations