path and variability of the agulhas return current the combined analysis of hydrographic kinematic and dynamic data collected during the 1997 1999 kapex cape of good hope experiments reveals a quasi stationary meandering pattern of the agulhas retroflection current east and upstream of the southwest indian ridge the current meanders between 38 s and 40 s in a spatially and temporally continuous fashion and has a core width of approximately full size image 1 k with an associated transport of full size image 1 k in the upper full size image 1 k peak surface velocities decrease from full size image 1 k near the agulhas retroflection to full size image 1 k around 32 e meander troughs northward extremes are found predominantly near 26 8 e 32 6 e and 38 9 e while crests southward extremes are located with high probability near 29 7 e 35 5 e and 42 9 e resulting in a typical wavelength of full size image 1 k cold eddies are shed along the northern boundary of the current from meander troughs into the recirculation regime between the agulhas current proper and the agulhas return current strongest cyclonic eddies are preferably shed in austral autumn the cyclonic eddies so formed propagate westward at an average phase speed of full size image 1 k with however a variability of at least the same magnitude subsequently the cyclones are absorbed by the next meander trough located upstream and to the west of the shedding trough

modulation of sst interannual variability in the agulhas leakage region associated with enso abstractthe agulhas leakage transports warm and saline water from the indian ocean into the south atlantic ocean forming part of the upper returning arm of the meridional overturning circulation which can influence climate ocean atmosphere interactions and the strength of agulhas leakage control sea surface temperature sst in the agulhas leakage corridor which may in turn affect regional climate variability in a high resolution run of the community climate system model version 3 5 ccsm3 5 it is found that the interannual variability of agulhas leakage sst is linked to el nino southern oscillation enso anomalous wind stress curl over the south indian ocean associated with enso excites westward propagating oceanic rossby waves that initiate southwestward propagating anomalies along the coast of africa it takes approximately 2 years for this signal to reach the southern tip of south africa and enter the south atlantic where it accounts for 20 30 of the interannual ssh variability in the agu

volumetric flattening an interpretation tool volumetric flattening is a novel method for automatically flattening 3d seismic cubes that converts seismic volumes to volumes of horizon slices with little or no effort an interpreter can scan over the resulting horizon slices to see channels and other geologic features as they were laid down furthermore the flattening transformation captures the shapes of all horizons in the cube this transformation leads naturally to numerous interpretation applications ranging from isopach analysis to stratigraphic attributes this algorithm is currently able to reconstruct across nearly vertical faults and incorporate hard constraints such as manual picks and well ties in summary this data driven method exploits the computer s ability to honor all of the data in all three dimensions to remap the data to a more geologically intuitive format

seismostratigraphic inversion appraisal ambiguity and uncertainty geologic process models predict the geometry of geologic strata and their petrophysical properties based on mathematical models of geological processes that affect the formation and evolution of geologic strata such processes include erosion sediment transport and deposition the resulting forward model is typically nonlinear given observations and a misfit measure one may attempt inversion of these models to estimate process parameters that yield compatible predictions for seismostratigraphic inversion seismic data are used as observations we tested such an algorithm in a prograding delta environment to examine the effect of using different seismic attributes as observations and thus different choices of misfit measures the first measure based on the degree of parallelism between seismic reflectors and modeled geologic strata demonstrated a trade off between geologic time and the sediment influx rate used to parameterize the model a second misfit measure used unwrapped seismic instantaneous phase as a crude proxy to relative geologic time which regularized the model parameters then last we combined the two measures to take advantage of their individual characteristics for most of these inversion experiments we obtained results that capture the geometry of the geologic strata as observed on the seismic data with the exception of the depositional time rate trade off where the same strata can be obtained in a shorter geologic interval when rates are increased we found the inversion to be surprisingly stable with a unique cluster of acceptable parameters despite the nonlinearity of the geologic forward model

the behavior of trace elements during schwertmannite precipitation and subsequent transformation into goethite and jarosite schwertmannite is a ubiquitous mineral formed from acid rock drainage ard and plays a major role in controlling the water chemistry of many acid streams the formation of schwertmannite was investigated in the acid discharge of the monte romero abandoned mine iberian pyrite belt sw spain schwertmannite precipitated from supersaturated solutions mainly owing to the oxidation of fe ii to fe iii and transformed with time into goethite and jarosite in a few hours schwertmannite precipitation removed more than half of the arsenic load from solution whereas the concentration of divalent trace metals zn cu pb cd ni and co remained almost unchanged in the laboratory natural schwertmannite was kept in contact with its coexisting acid water in a flask with a solid liquid mass ratio of 1 5 for 353 days during this time the ph of the solution dropped from 3 07 to 1 74 and the concentrations of sulfate and fe increased during the first 164 days schwertmannite transformed into goethite plus h3o jarosite but subsequently goethite was the only mineral to form some of the trace elements such as al cu pb and as were depleted in solution during the first stage as schwertmannite transformed into goethite plus h3o jarosite on the contrary the transformation of schwertmannite to goethite with no jarosite during the second stage released al cu and as to the solution despite the variation in their concentrations in solution approximately 80 of the total al and cu inventories and more than 99 as and pb remained in the solid phase throughout the entire aging process

geochemical evolution of groundwater in the carbonate aquifers of sierra de segura betic cordillera southern spain summary sierra de segura betic cordillera with a total area of over 3000 km 2 is the source of the two principal rivers in southern spain the guadalquivir and the segura due to the orographic effect of these mountains precipitations are considerably more abundant than in nearby lowland areas where the climate is semi arid sierra de segura is constituted of mesozoic and cenozoic sedimentary rocks among which there are thick limestone dolomitic formations which have given rise to extensive outcrops of permeable materials in geomorphological terms there is a large plateau intensively karstified that constitutes the main recharge area discharge takes place via a large number of springs of which the 50 most important add up to a mean spring flow of about 13 500 l s the active geochemical processes in aquifers of sierra de segura with their corresponding time sequence are dissolution of co 2 dissolution of calcite incongruent dissolution of dolomite dedolomitization exsolution of co 2 and precipitation of calcite more evolved water has higher temperature magnesium content and mg ca ratio therefore these parameters can be utilised as indicators of the degree of hydrochemical evolution in addition a good correlation between water temperature and magnesium concentration or mg ca ratio indicates that an increase in temperature accelerates the kinetics of the dissolution of dolomite finally the distribution of the temperatures in the vadose zone determined by atmospheric thermal gradient implies an apparent stratification of the predominant hydrochemical processes and of the groundwater physical and chemical characteristics

acid mine drainage at cerro rico de potosi i unabated high strength discharges reflect a five century legacy of mining intensive mining and processing of ag sn pb and zn ores have occurred in various locations within and around the city of potosi bolivia since 1545 surface and subsurface waters stream sediments and soils are contaminated with various ecotoxic metals in the headwaters of the economically vital yet highly impacted upper rio pilcomayo watershed previous studies have documented downstream trace metal contamination however not addressed specific sources the amd discharges identified in this study help link downstream pollution to primary origins the majority of amd would be considered high strength due to metal concentrations and acidity orders of magnitude greater than typical amd discharges from both operating and abandoned portals as well as tailings related deposits displayed a high degree of heterogeneity with total metal concentrations ranging from 0 11 to 7480 0 022 to 889 0 0006 to 65 3 0 001 to 310 0 12 to 72 100 0 3 to 402 0 012 to 34 8 and 0 24 to 19 600 mg l of al as cd cu fe mn pb and zn respectively net acidity and ph ranged from 10 to 246 000 mg l as caco3 equivalent and 0 90 6 94 standard units respectively data were gathered during two sampling events centered around the most extreme periods of the dry and wet seasons of one water year loadings to local streams were marginally greater for most metals in the wet season if observed loadings are historically representative cerro rico amd has contributed thousands of tonnes of ecotoxic metals to the upper rio pilcomayo over the last five centuries metal and hydrogen ion concentrations in the majority of amd sampled were several orders of magnitude above discharge limits set by the bolivian government yet no action has historically or contemporarily been taken

least squares horizons with local slopes and multigrid correlations most seismic horizon extraction methods are based on seismic local reflection slopes that locally follow seismic structural features however these methods often fail to correctly track horizons across discontinuities such faults and noise because the local slopes can only correctly follow laterally continuous reflections in addition seismic amplitude or phase information is not used in these methods to compute horizons that follow consistent phase e g peaks or troughs to solve these problems we propose a novel method to compute horizons that globally fit both local slopes and multi grid correlations of seismic traces in this method we first estimate local reflection slopes by using structure tensors and compute laterally multi grid slopes by using dynamic time warping to correlate seismic traces within multiple laterally coarse grids these coarse grid slopes can correctly correlate reflections that may be significantly dislocated by faults or other discontinuous structures we then compute a

domain transform a tool for imaging and interpreting geomorphology and stratigraphy in seismic volumes the presence of complex structure on seismic data often makes it difficult to recognize and interpret depositional systems in the volume a number of techniques under the broad topic of chronostratigraphy have been developed in recent years to address this problem and enable more complete imaging and interpretation of seismic geomorphology and stratigraphy a domain transform dt is an interpretation guided process designed to remove some or all structural deformation from a seismic volume it improves the imaging of paleo depositional systems by creating a volume that consists of approximations of paleo depositional surfaces such volumes are ideal for imaging analysis and interpretation of seismic geomorphology and stratigraphy

acid mine drainage at cerro rico de potosi ii severe degradation of the upper rio pilcomayo watershed ag pb sn and zn ores have been intensively mined and processed at cerro rico de potosi bolivia since 1545 acid mine drainage amd and mineral processing plant effluent are prime sources of water contamination in the headwaters of the upper rio pilcomayo watershed streams receiving amd drainage from the slopes of cerro rico and surrounding landscapes were sampled during the dry july august 2006 and wet march 2007 seasons of one water year in stream waters contained total metal concentrations of up to 16 mg l as 4 9 mg l cd 0 97 mg l co 1 100 mg l fe 110 mg l mn 4 1 mg l pb and 1 500 mg l zn with ph ranging from 2 8 to 9 5 amd impacted streams contained elevated concentrations of the same major ecotoxic constituents present in amd discharges at concentrations orders of magnitude greater than in those streams unimpacted by amd many of the amd impacted water bodies are more degraded than class d of the bolivian receiving water body criteria rendering them unfit for domestic or agricultural use natural attenuation is insufficient to render waters safe for use however some of these waters are currently being utilized for irrigation and livestock watering the data indicate that historic and current mining activities have transformed these key natural resources into potential human and environmental health hazards

new tools for seismic stratigraphic interpretation stratal convergence and instantaneous isochron attribute cubes derived from volumetric flattening of experimental strata interpreting seismic data requires inferences to be made from the geometry character and spatial association of seismic reflections seismic attributes that highlight such associations are essential for understanding basin fill histories in this article we describe two novel attributes obtained from an automatic full volume flattening algorithm and apply them to a synthetic seismic volume of experimental strata the stratal convergence attribute colors reflections according to their degree of convergence which is commonly high in areas where strata thin because of erosion or nondeposition the instantaneous isochron attribute measures thickness between reflections and is therefore generally proportional to sediment accumulation rate these attributes distinguish bounding surfaces and depocenter migration in well constrained experimental strata by showing the diagnostic value of each attribute our study motivates field based applications of full volume flattening and attribute co rendering for seismic stratigraphic interpretation

characteristics energetics and origins of agulhas current meanders and their limited influence on ring shedding abstractthe agulhas current intermittently undergoes dramatic offshore excursions from its mean path because of the downstream passage of mesoscale solitary meanders or natal pulses new observations and analyses are presented of the variability of the current and its meanders using mooring observations from the agulhas current time series experiment act near 34 s using a new rotary eof method mesoscale meanders and smaller scale meanders are differentiated and each captured in a single mode of variance during mesoscale meanders an onshore cyclonic circulation and an offshore anticyclonic circulation act together to displace the jet offshore leading to sudden and strong positive conversion of kinetic energy from the mean flow to the meander via nonlinear interactions smaller meanders are principally represented by a single cyclonic circulation spanning the entire jet that acts to displace the jet without extracting kinetic energy from the mean flow synthesizing in situ observations with altimeter

horizon volumes with interpreted constraints abstracthorizons are geologically significant surfaces that can be extracted from seismic images color coding of horizons based on amplitude or other attributes can help reveal ancient sedimentary environments and structural features extracted horizons are also used for building structure models and stratigraphic interpretations we propose two methods for constructing seismic horizons aligned with reflectors in a 3d seismic image the first method generates horizons one at a time the second method generates an entire volume of horizons at once by first computing a relative geologic time volume from seismic normal vectors rather than gradually building a horizon by extending one or more seed points to a surface along seismic reflectors both of our methods generate whole horizons at once by solving partial differential equations derived from seismic normal vectors the most significant new aspect of both methods is the ability to specify perhaps interactively during interpretation a small number of

building 3d subsurface models conforming to seismic structural and stratigraphic features abstractsubsurface modeling from seismic and borehole data is important for reservoir prediction geophysical exploration and production a reasonable model should honor borehole rock properties and conform to seismic structural and stratigraphic features such a subsurface model can be difficult to build in cases complicated by faults and unconformities automatic and semiautomatic methods have been proposed to build subsurface models from seismic and borehole data however seismic structural and stratigraphic features and borehole measurements are not fully used in most methods i have developed a workflow to fully use seismic and borehole data to build subsurface models that honor borehole measurements and conform to seismic horizons faults unconformities and stratigraphic features such as channels in this workflow i first automatically remove the faulting and folding in seismic and borehole data and map them into an unfaulted and flattened space in which seismic reflectors and borehole measure

geotime a 3d automatic tool for chronostratigraphic seismic interpretation and filtering chronostratigraphic seismic interpretation provides insight into basinal evolution because it maps the internal stratigraphic architecture this method has been widely used for well placement optimization and reservoir model building after many years of research at total a software tool called geotime has been developed for automatic chronostratigraphic analysis of seismic data particularly in complex geologic settings this tool first creates automatically from the seismic a 3d isogeologic time volume which highlights all stratigraphic surfaces then a 3d wheeler diagram volume is obtained by segmenting the seismic volume into different depositional or nondepositional packages this diagram provides better understanding of the spatial distribution of deposition through geologic time finally this tool can be used to automatically or semi automatically track chronostratigraphic surfaces

3 d seismic attributes using a semblance based coherency algorithm seismic coherency is a measure of lateral changes in the seismic response caused by variation in structure stratigraphy lithology porosity and the presence of hydrocarbons unlike shaded relief maps that allow 3 d visualization of faults and channels from horizon picks seismic coherency operates on the seismic data itself and is therefore unencumbered by interpreter or automatic picker biases we present a more robust multitrace semblance based coherency algorithm that allows us to analyze data of lesser quality than our original three trace cross correlation based algorithm this second generation semblance based coherency algorithm provides improved vertical resolution over our original zero mean crosscorrelation algorithm resulting in reduced mixing of overlying or underlying stratigraphic features in general we analyze stratigraphic features using as narrow a temporal analysis window as possible typically determined by the highest usable frequency in the input seismic data in the limit one may confidently apply our new semblance based algorithm to a one sample thick seismic volume extracted along a conventionally picked stratigraphic horizon corresponding to a peak or trough whose amplitudes lie sufficiently above the ambient seismic noise in contrast near vertical structural features such as faults are better enhanced when using a longer temporal analysis window corresponding to the lowest usable frequency in the input data the calculation of reflector dip azimuth throughout the data volume allows us to generalize the calculation of conventional complex trace attributes including envelope phase frequency and bandwidth to the calculation of complex reflector attributes generated by slant stacking the input data along the reflector dip within the coherency analysis window these more robust complex reflector attribute cubes can be combined with coherency and dip azimuth cubes using conventional geostatistical clustering and segmentation algorithms to provide an integrated multiattribute analysis

impact of agulhas leakage on the atlantic overturning circulation in the ccsm4 abstractthe impact of agulhas leakage variability on the strength of the atlantic meridional overturning circulation amoc in the community climate system model version 4 ccsm4 is investigated in this model an advective connection exists that transports salinity anomalies from the agulhas region into the north atlantic on decadal 30 40 yr time scales however there is no identifiable impact of agulhas leakage on the strength of the amoc suggesting that the salinity variations are too weak to significantly modify the stratification in the north atlantic it is argued that this study is inconclusive with respect to an impact of agulhas leakage on the amoc salinity biases leave the south atlantic and indian oceans too homogeneous in particular erasing the observed salinity front in the agulhas retroflection region consequently salinity variability in the southeastern south atlantic is found to be much weaker than observed

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

hydrogeochemical characteristics of streams with and without acid mine drainage impacts a paired catchment study in karst geology sw china summary a paired catchment study was used to assess hydrochemical characteristics of streams in amd acid mine drainage impacted and non amd impacted catchments in a karstic region sw china the catchments shared similar geology slope aspect area and climate but different land use since one encompassed mining activities as a result hydrogeochemical characteristics of the amd impacted water were dominantly controlled by oxidation of pyrite while that of non amd impacted were influenced by water rock reactions it is also coincident with the source of 34 s so4 in both waters upstream unit ion fluxes of the amd impacted catchment for ca mg h fe and so 4 were 17 g m 2 yr 2 g m 2 yr 0 0002 g m 2 yr 17 g m 2 yr and 136 g m 2 yr respectively while unit ion fluxes of the non amd impacted catchment were much lower than that of the amd impacted catchment along the flow fluxes of h ca mg fe and so 4 decreased in the amd impacted water but increased in the non amd impacted water the observation was coincident with variations of ion concentrations in both waters along the flow supported by phreeqc modeling of minerals such as goethite jarosite ss melanterite scorodite calcite and dolomite it suggests that the transport of constituents of interest except for ca and mg is dramatically different in these catchments results provide important information on karst system response to amd together with the baseline data to understand the degree and type of impairment

stratal slicing benefits and challenges in the petroleum industry seismic interpretation meth odology varies according to a subject s scale in basinal to field scale hundreds of meters the goal is to map gross stratigraphic and structural features that are associated with petroleum systems including stratigraphy and depositional history hydrocarbon generation migration and entrapment seismic stratigraphy and sequence stratigraphy are common tools for this purpose at the reservoir scale meters to tens of meters the goal becomes characterizing distribution and physical properties related to volumetrics and production in a reservoir system in this task details are crucial seismic lithology and inversion seismic geomorphology and sedimentology and attribute analysis are some of the tools developed for this purpose

stable sulfur and oxygen isotopes as geochemical tracers of sulfate in karst waters abstract karst water resources which are extremely sensitive to mining activities are critical for the support of human societies and ecological systems in many regions worldwide in order to determine the sources and fate of dissolved sulfate in low ph karst waters hydrochemical variations of karst waters with and without acid mine drainage amd impacts were investigated along with stable isotope dynamics as expected hydrochemical characteristics and isotopic compositions of the amd and amd downstream water adw were dramatically different from that of the non amd impacted water naw the sources of sulfur isotopes in sulfate were predominantly pyrite oxidation for the amd and adw and atmospheric deposition for the naw based on the general isotope balance model the relative proportions of sulfate oxygen derived from water and air were calculated the mean proportion of sulfate oxygen derived from water in adw was roughly double that of amd this suggests that the sulfate associated with amd is predominantly influenced by aerobic pyrite oxidation while that of adw is likely affected by the dissolution of pyrite under anaerobic conditions in reservoir sediment this observation was coincident with the noted variations of hydrochemical characteristics and was supported by principal component analysis these results provide a better understanding of how stable isotopes of sulfate and water can be used to track mining contamination in karst aquifers which could benefit remediation planning for these distinctive systems

an introduction to this special section chronostratigraphy in 1977 we saw the publication of aapg memoir 26 seismic stratigraphy applications to hydrocarbon exploration in this book peter vail and his colleagues in a series of papers introduced the industry to the concepts of seismic sequences the construction of chronostratigraphic charts and how the seismic data could be used to estimate the global rise and fall of sea level in this work they also showed how the shape of the reflections and their lapping relationships could be used to predict depositional environment which could be used to predict sediment type and facies

the wheeler diagram flattening theory and time abstract wheeler diagrams are excellent tools to represent time stratigraphy these diagrams are produced by considering interpreted surfaces as snapshots of geologic times linked with transit cycles of the base level the base level defined in the nineteenth century can be regarded as an ultimate time reference for stratigraphic units the application of the base level concept to deep marine settings is a more recent development even though the same definition applies to all depositional environments flat timelines are also known as flattening theories can produce similar looking diagrams and have an edge that they operate in 3d however flattening of a dataset can be achieved with various techniques which are reviewed and the optimum algorithm which has a future application for hydrocarbon and research communities is improved to honor geological constraints such as faults and horizons a secondary aspect of the wheeler diagrams is the dual nature of geological timelines the diagrams are originally plotted on a relative geological time scale and no formal technique has yet been recommended for time calibration in this paper a nomogram approach is proposed to calibrate the timelines the representation of unconformities that are parallel to bedding planes is another important idea presented in this paper

the impact of tailings dam spills and clean up operations on sediment and water quality in river systems the rios agrio guadiamar aznalcollar spain the aznalcollar tailings dam at boliden apirsa s aznalcollar los frailes ag cu pb zn mine 45 km west of seville spain was breached on 25 april 1998 flooding approximately 4600 hectares of land along the rios agrio and guadiamar with approximately 5 5 million m3 of acidic water and 1 3 106 m3 of heavy metal bearing tailings most of the deposited tailings and approximately 4 7 106 m3 of contaminated soils were removed to the aznalcollar open pit during clean up work undertaken immediately after the spill until january 1999 detailed geomorphological and geochemical surveys of the post clean up channel floodplain and valley floor and sediment and water sampling were carried out in january and may 1999 at 6 reaches representative of the types of river channel and floodplain environments in the rio guadiamar catchment affected by the spill the collected data show that the clean up operations removed enough spill deposited sediment to achieve pre spill metal ag as cd cu pb sb tl zn concentrations in surface sediment these concentrations however are still elevated above pre mining concentrations and emphasise that mining continues to contaminate the agrio guadiamar river system dilution by relatively uncontaminated sediment appears to reduce metal concentrations downstream but increases in metal and as concentrations occur downstream presumably as a result of factors such as sewage and agriculture river water samples collected in may 1999 have significantly greater dissolved concentrations of metals and as than those from january 1999 probably due to greater sulphide oxidation from residual tailings with concomitant release of metals in the warmer early summer months these concentrations are reduced downstream probably by a combination of dilution and removal of metals by mineral precipitation single chemical extractions de ionised water cacl2 0 01 mol l 1 ch3coonh4 1 m ch3coona 1 m and ammonium oxalate 0 2 m on alluvial samples from reaches 1 and 6 the tailings pre spill alluvium and marl have shown that the order of sediment borne contaminant mobility is generally zn cd cu pb as pb and as are relatively immobile except possibly under reducing conditions much of the highly contaminated sediment remaining in the floodplain and channel still contains a large proportion of tailings related sulphide minerals which are potentially reactive and may continue to release contaminants to the agrio guadiamar river system our work emphasises the need for pre mining geomorphological and geochemical data and an assessment of potential contributions of contaminants to river systems from other non mining sources

stratal slice the next generation vail and his colleagues 1977a b laid a foundation for seismic chronostratigraphy by analyzing the relative rise of sea level indicated by coastal onlap these workers invented a novel way of converting a stratigraphic cross section in the depth or traveltime domain to a chronostratigraphic chart in the wheeler domain figure 1a and figure 1b with the widespread use of seismic data in the industry such conversion can now be achieved conveniently with the proper software at the basinal regional or prospect scale figure 1c and figure 1d

agulhas eddies a synoptic view using geosat erm data abstract warm core rings formed in the agulhas retroflection transfer water from the indian ocean to the south atlantic in an attempt to measure the strength of this exchange a combination of satellite altimeter and hydrographic data are used to examine agulhas eddy paths and decay rates in the south atlantic because the surface dynamic height of a warm core eddy is higher than surrounding waters the rings are visible in satellite altimeter measurements over 20 agulhas eddies have been tracked from maps of anomalous sea surface height ssh derived from the geosat exact repeat mission erm dataset the correlation r2 of dynamic height referenced to 2000 dbar and anomaly ssh for one coincidentally sampled area is 97 within an agulhas eddy dropping to a fraction of that outside of it indicating that the ssh anomaly signal is a reliable measure for strong features like agulhas eddies the sizes and distribution of the agulhas eddies in the erm record compare favorably with those in recent hydrogr

storm track response to ocean fronts in a global high resolution climate model synoptic atmospheric eddies are affected by lower tropospheric air temperature gradients and by turbulent heat fluxes from the surface in this study we examine how ocean fronts affect these quantities and hence the storm tracks we focus on two midlatitude regions where ocean fronts lie close to the storm tracks the north west atlantic and the southern ocean an atmospheric climate model of reasonably high resolution 50 km is applied in a climate length 60 year simulation in order to obtain stable statistics simulations with frontal structure in the sea surface temperature sst in one of the regions are compared against simulations with globally smoothed sst we show that in both regions the ocean fronts have a strong influence on the transient eddy heat and moisture fluxes not just in the boundary layer but also in the free troposphere local differences in these quantities between the simulations reach 20 40 of the maximum values in the simulation with smoothed sst averaged over the entire region of the storm track over the ocean the corresponding differences are 10 20 the effect on the transient eddy meridional wind variance is strong in the boundary layer but relatively weak above that the potential mechanisms by which the ocean fronts influence the storm tracks are discussed and our results are compared against previous studies with regional models aquaplanet models and coarse resolution coupled models

geochemical distribution and removal of as fe mn and al in a surface water system affected by acid mine drainage at a coalfield in southwestern china the chemical characteristics formation and natural attenuation of pollutants in the coal acid mine drainage amd at xingren coalfield southwest china are discussed in this paper based on the results of a geochemical investigation as well as geological and hydrogeological background information the chemical composition of the amd is controlled by the dissolution of sulfide minerals in the coal seam the initial composition of the groundwater and the water rock interaction the amd is characterized by high sulfate concentrations high levels of dissolved metals fe al mn etc and low ph values ca2 and so42 are the dominant cation and anion in the amd respectively while ca2 and hco3 are present at significant levels in background water and surface water after the drainage leaves the mine site the ph and alkalinity increase asymptotically with the distance along the flow path while concentrations of sulfate ferrous iron aluminum and manganese are typically controlled by the deposition of secondary minerals low concentrations of as and other pollutants in the surface waters of the xingren coalfield could be due to relatively low quantities being released from coal seams to adsorption and coprecipitation on secondary minerals in stream sediments and to dilution by unpolluted surface recharge although as is not the most serious water quality problem in the xingren region at present it is still a potential environmental problem

relative geologic time age volumes relating every seismic sample to a geologically reasonable horizon the age volume described in this paper can significantly increase the amount of useful geologic information extracted from a seismic data volume this paper has three goals the first is to introduce and describe the relative geologic time volume referred to herein as either an rgt volume or an age volume every seismic sample in an age volume contains an estimate of the relative geologic time for that sample which automatically relates every sample to a geologic horizon the second goal is to discuss some of the applications and advantages of using a rgt volume to store and access seismic interpretation for example it can be used to sculpt a seismic volume along a desired horizon or view depositional changes as a function of geologic time the third goal is to describe two methods for generating such a volume the first employing standard interpretation techniques and the second relying on unwrapping instantaneous phase unwrapping the instantaneous phase is a new holistic approach to interpreting seismic data that can produce a very detailed seismic interpretation the goal of building and using an rgt volume is to extract significantly more geologic information from the seismic data than is available from conventional methods the rgt volume is both a way of storing and retrieving seismic horizons to generate such a volume each seismic sample needs to be assigned an estimate of relative geologic time which in essence connects it to a geologically reasonable horizon in normal sections these relative geologic time values will increase with depth or traveltime high gradients in the rgt volume could be indicative of faults unconformities fluid contacts or interpretation errors while a constant value surface in a rgt volume is a seismic horizon figure 1 contains a portion of the seismic data used to illustrate the

pattern and velocity of propagation of the global ocean eddy variability 1 satellite altimeter data are used to study the characteristics of the horizontal propagation of eddy variability of the global oceans decade long time series of sea surface height is analyzed for finding the maximum cross correlation with neighboring time series within a window of space and time lags the space and time lags corresponding to the maximum correlation allow an estimate of the propagation velocity of the eddy variability that dominates the variance of sea surface height anomalies the method cannot distinguish the various forms of eddy variability isolated eddies and fronts the meandering of ocean currents or planetary waves however the results provide at a given location of the global oceans a uniquely determined propagation velocity that represents a time averaged description of the tendency of the movement of the local eddy variability the propagation velocity is highly inhomogeneous in space outside the equatorial zone the zonal propagation is intrinsically westward modified by ocean currents which could reverse the zonal propagation to eastward in regions like the gulf stream and the antarctic circumpolar current at midlatitudes and high latitudes the propagation pattern is highly affected by the path of ocean currents and the shape of bottom topography at tropical latitudes the meridional propagation is convergent toward the equator in the western basins and divergent away from the equator in the eastern basins comparison with the simulations of an eddy permitting ocean general circulation model shows overall agreement especially in the latitudinal variation of the zonal propagation velocity the result suggests that the model has captured the essence of the dynamics governing the propagation of ocean eddy variability

migration of cu zn cd and as in epikarst water affected by acid mine drainage at a coalfield basin xingren southwest china epikarst water which is one of the most important water resources in karst mountain areas is extremely sensitive to mining activities acid mine drainage amd with high levels of heavy metals can degrade the water quality a typical coalfield basin was chosen to research the migration process of heavy metals it was found that the chemical compositions of the stream water in the research field were controlled by the dissolution of carbonate rocks or and the weathering and oxidation of pyrite in the mining area excluding a few sites in the mining area as v was dominant species of arsenic in the form of h2aso4 or haso4 2 in the research field based on the mass balance concept it was found that fluxes of as zn cu and cd in water from the mining area site 17 affected by amd were 18 871 281 and 12 kg year 1 respectively also concentrations of cd zn as and cu in the stream water decreased along the flow because these ions deposited from the water to the stream bed as the redistribution processes in environment