stanniferous placer development on an evolving landsurface with special reference to placers near st austell cornwall the geomorphic setting of the stanniferous placers of sw england is presented and the history of their development is broadly drawn in particular the relationships between the placers and the major types of primary tin deposit in the region are emphasized the nature and genesis of three placer deposits in the n st austell district are treated in some detail in order to demonstrate the complexity of placer development in the region as a whole stress is placed on an examination of the placer cassiterite morphology to determine the complex genesis of the cornish deposits finally it is emphasized that the initial stages of placer development in the region are due essentially to processes of disintegration with processes of decomposition never playing more than a very minor role

imaging granitic plutons along the iberseis profile abstract the parameters used for the acquisition of the iberseis deep seismic reflection profile in the sw iberian peninsula provide seismic images of the deep crust as well as a high resolution section of the shallow subsurface a very dense array of sources and receivers allowed high resolution tomographic studies in zones of special interest granitic plutons the three dimensional tomographic inversion produced velocity models along a 500 m wide and 1000 m deep strip along the iberseis transect in the areas of la bazana la dehesilla feria and villafranca in these high resolution velocity models sampled by 50 50 50 m cells high velocity anomalies indicate the geology and extension of the granitic plutons at depth this directly correlates with the surface outcrops moreover tomographic models provided valuable information for the geometry and characterization of fractured and fresh domains in a rock volume furthermore a piggy back seismic acquisition experiment using additional seismic instrumentation from the university of paris sud 40 channel dmt provided perpendicular offline recordings of the vibroseis sources this additional recording system was deployed perpendicularly to the main iberseis seismic reflection line and provided additional 3d control

ultrashallow depth imaging of a channel stratigraphy with first arrival traveltime inversion and prestack depth migration a case history from bull creek oklahoma depth imaging in ultrashallow 50 m environments presents twofold challenge 1 coda available for depth migration is very limited and 2 conventional time processing with limited coda generally fails to estimate reliable velocity models for depth migration we studied the combining of first arrival traveltime inversion and prestack depth migration psdm for depth imaging of ultrashallow paleochannel stratigraphy associated with the bull creek drainage system oklahoma restricted by a limited number of geophones 24 we acquired data for inversion and migration through two coincident profiles the first profile for inversion has a wider survey aperture 115 m maximum shot receiver spacing and consequently sparse cmp spacing 2 5 m whereas the second profile for psdm has denser cmp spacing 1 m and consequently a narrower survey aperture 46 m maximum shot receiver spacing we also found that the velocity model from traveltime inversion of the wider aperture data set is more preferable for dep

the spatial distribution and source of arsenic copper tin and zinc within the surface sediments of the fal estuary cornwall uk abstract estuarine sediments commonly form major sinks for contaminants released during industrial activity many industrial processes lead to the release of metals initially in solution which can then be adsorbed on to for example fe hydroxides or clay minerals however in the mining industry there are two major contaminant waste streams 1 metals discharged in solution via mine drainage and 2 particulate grains of the ore forming or related minerals released after ore processing the release of particulate waste can have a major long term impact on environmental geochemistry in this study we have mapped the distribution of arsenic copper tin and zinc within the surficial sediments of the fal estuary cornwall uk an area that drains a historically important polymetallic mining district there are clear spatial variations in the contaminants with the highest levels 2800 p p m as 5000 p p m cu 3000 p p m sn and 6000 p p m zn within restronguet creek on the western side of the estuary mineralogical studies show that small 20 m grains of detrital arsenopyrite chalcopyrite cassiterite and sphalerite are very abundant within the surface sediments most of the sulphide grains are fractured but mineralogically unaltered although some grains show alteration rims caused by oxidation of the sulphides the geochemistry and mineralogy are indicative of sediment supply from the discharge of particulate waste into the estuary during historical mining activity subsequently this particulate waste has been largely physically and biologically reworked within the surface sediments although considerable effort has been made to minimize contaminants released via mine drainage into the estuary the potential flux of contaminants present within the intertidal and subtidal sediments has not been addressed benthic invertebrates living within the area have adapted to be metal tolerant and it is likely that the dominant source of bioavailable metals is a result of alteration of the particulate mine waste present within the intertidal and subtidal sediments

unified imaging of multichannel seismic data combining traveltime inversion and prestack depth migration imaging 2d multichannel land seismic data can be accomplished effectively by a combination of traveltime inversion and prestack depth migration psdm referred to as unified imaging unified imaging begins by inverting the direct arrival times to estimate a velocity model that is used in static corrections and stacking velocity analysis the interval velocity model from stacking velocities is used for psdm the stacked data and the psdm image are interpreted for common horizons and the corresponding wide aperture reflections are identified in the shot gathers using the interval velocity model the stack interpretations are inverted as zero offset reflections to constrain the corresponding interfaces in depth the interval velocity model remains stationary we define a coefficient of congruence j that measures the discrepancy between horizons from the psdm image andtheir counterparts from the zero offset inversion a value of unity for j implies that the interpreted and inverted horizons are consisten

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

3 d stochastic modeling and simulation of fault zones in the albala granitic pluton sw iberian variscan massif a distribution of fracture index fi is obtained from stochastic modeling and simulation to characterize quantitatively the fault system of the mina ratones area in three dimensions 3 d fi is a quantitative estimate of the fracture intensity in discrete domains of the granitic rock massif the resulting 3 d grids expressed as block cells models or contoured isosurfaces of fi show high and low fi zones the correlation of these zones with mapped faults allows two structural domains to be distinguished 1 variably irregular surfaces of high fi and 2 rhomboidal blocks of low fi located inside them high fi domains fi 4 2 m 1 are interpreted as fault zones since there is a good correlation at the surface between the domains and traces of the major fault zones low fi blocks fi 2 5 m 1 correspond to less fractured granite the contact between high and low fi domains is gradual the high and low fi structural domains may correspond with the damage zone fault core and the protolith in the model for fault zone architecture of caine et al 1996 therefore 3 d grids of the fi in granitic areas affected by strike slip brittle tectonics such as mina ratones constitute an image of fault zone architecture

two dimensional geostatistical modeling and prediction of the fracture system in the albala granitic pluton sw iberian massif spain abstract we use a fracture index distribution method of geostatistical modelling and prediction to characterize quantitatively the fracture system in two dimensions 2d in the mina ratones area located in the albala granitic pluton sw iberian massif the fracture index fi is a quantitative estimate of the fracture density in discrete domains to validate the results of geostatistical modeling a detailed structural map of the area was also made on a scale of 1 1000 the resulting grids expressed as pixel maps describe the continuous value of the fi in 2d for the whole mina ratones area based on the modelled distribution of the fi and their correlation with mapped faults we distinguish two structural domains in the studied area elongated bands of fracture zones with high fi values and romboidal blocks located between them with low fi values the separation between both domains is gradual though a threshold value of the fi that separate both structural domains is not clearly defined the fracture zones generally present fi 1 and the individualized blocks fi

flooding the topography wave equation datuming of land data with rugged acquisition topography wave equation datuming overcomes some of the problems that seismic data recorded on rugged surface topography present in routine image processing the main problems are that 1 standard optimized migration and processing algorithms assume data are recorded on a flat surface and that 2 the static correction applied routinely to compensate for topography is inaccurate for waves that do not propagate vertically wave based processes such as stacking dip moveout correction normal moveout correction velocity analysis and migration after static shift can be severely affected by the nonhyperbolic character of the reflections to alleviate these problems i apply wave equation datuming early in the processing flow to upward continue the data to a flat datum above the highest topography this is what i refer to as flooding the topography this approach does not require detailed a priori knowledge of the near surface velocity and it streamlines subsequent processing because the data are regridded onto a regularly sampled datum wave equation datuming unravels the distortions caused by rugged topography and unlike the static shift method it does not adversely effect subsequent wave based processing the image obtained after wave equation datuming exhibits better reflector continuity and more accurately represents the true structural image than the image obtained after static shift

mapping brittle fracture zones in three dimensions high resolution traveltime seismic tomography in a granitic pluton summary fractured and altered zones within a granitic pluton are mapped in three dimensions by means of high resolution seismic traveltime tomography the input traveltimes were picked from offset and azimuth variable vertical seismic profiles ovsp acquired in three boreholes and from seismic shot gathers of four cdp high resolution seismic reflection profiles recorded on the surface for the ovsp data a hydrophone streamer placed in the boreholes recorded the acoustic energy generated a signal with a frequency content between 15 to 150 hz by a vibroseis truck at source points distributed every 30 m in a rectangular grid of 620 m by 150 m the combination of borehole and surface seismic data resulted in an increase in the ray density of the shallow subsurface the tomographic algorithm uses a variable model grid with a finer grid spacing close to the surface were ray density is highest and the velocity variations are strongest therefore the resulting velocity models feature more detail at shallow levels a simple and smooth starting velocity model was derived from p wave velocity logs careful surface geological mapping and borehole geophysical data p and s wave velocity logs and poisson s ratio depth functions provided key constraints for a physically reasonable 3 d interpretation of the tomograms the low velocity anomalies constrained by the tomographic images were interpreted as unconsolidated rock fractures and altered zones which correlate with structures mapped at the surface or velocity anomalies identified in the logs subsequent resolution analysis revealed that the derived velocity model is well constrained to depths of 60 m

characterization of a fractured granitic pluton p and s waves seismic tomography and uncertainty analysis abstract a detailed characterization of the physical properties of a granitic pluton including a three dimensional reconstruction of the fractures network and its surrounding are obtained by high resolution seismic tomography of p and s waves the input p and s wave travel times were picked from three component offset and azimuth variable seismic profile ovsp acquired in a 500 m deep vertical borehole the travel time inversion resulted in two three dimensional p and s wave velocity models and the uncertainty robustness and sensitivity are estimated by performing a monte carlo type analysis and checkerboard test this study provides an indicator of the uniqueness of the determined model the 500 m deep borehole was continuously cored and extensively surveyed by geophysical techniques thus the detailed surface geological mapping fracture index logs borehole televiewer images and p and s wave velocities derived from sonic logs provide solid constraints for the interpretation of the tomographic images the three dimensional tomographic images reveal fracture zones mapped at surface that intersect the borehole at different depths and they can be identified in the core descriptions and in the borehole televiewer images the fractures identified on the cores feature relatively low values for the sonic p and s wave velocities and high values for poisson s ratio for single type lithologies the distribution of poisson s ratio differentiates fractured and altered granite from fresh unfractured domains within the rock poisson s ratios close to 0 3 correlate with fractured volumes consistent with fracture index and sonic logs otherwise poisson s ratio values close to 0 25 are related to unaltered and unfractured rock

prestack layer replacement we present a method of layer replacement based on the kirchhoff integral solution to the scalar wave equation the term layer replacement refers to replacing the overburden velocity with the velocity of the substratum thereby eliminating raypath bendings at the interface between the overburden and the substratum it is the raypath bendings that induce distortions and disruptions on reflections beneath a complex structure when implemented before stack layer replacement provides an opportunity to revise velocity estimates after correcting for the nonhyperbolic moveout on cmp data caused by a complex overburden as a result layer replacement also yields an improved unmigrated stack section imaging can then be completed by time migration after stack we demonstrate the layer replacement technique on field data with irregular water bottom topography

distribution of metals in soils and plants around mineralized zones at cartagena la union mining district se spain a geochemical and mineralogical characterization of three zones namely oxides zones hydrothermal alteration zone and mining wastes zone from a mineralized zone in the upper part of the cartagena la union range was carried out by analysing rocks soils and three plant species piptatherum miliaceum ditrichia viscosa and hirsfeldia incana the transference and bioavailability of some metals especially pb zn as and fe from soils to plants was also checked results show that rocks have a large content of fe and pb which are transferred to surrounding soils also highly enriched in these elements fe ranges from 9 to 35 and pb 1 to 2 9 regarding soil to plant transfer it was shown a differential behaviour for both the three plant species and the soil zones with a higher level of metal accumulation rates for piptatherum miliaceum in the hydrothermal alteration zone values of accumulation rates obtained for pb in piptatherum miliaceum allow considering it a good choice for phytoremediation purposes

high resolution seismic characterization in an urban area subway tunnel construction in barcelona spain traveltime seismic tomography used to aid subway tunnel drilling in barcelona spain provides a detailed characterization of the shallow subsurface including a complex network of faults and dikes we encountered many difficulties while working in this urban setting such as cultural noise and the inability to deploy instruments along much of the tunnel trace because of the street layout furthermore the shallow subsurface is highly heterogeneous because of gas and water lines building foundations and the sewage system obscuring deeper structures we acquired seismic data using a 10 s vibroseis sweep that provided relatively good signal to noise s n ratio first arrival traveltime tomography proved to be a key tool to differentiate rock vol umes characterized by different physical properties in particular the contact between the weathered upper layer and the more competent rock below we interpreted the seismic results using surface geologic observations and borehole cores low seismic velocit

the chemical and physical speciation of trace metals in fine grained overbank flood sediments in the tyne basin north east england deposition of fine sediment contaminated by heavy metals on floodplains in the tyne basin north east england during a major flood in august 1986 provided an unusual opportunity to investigate the chemical and physical speciation of metals in overbank fines selective extractions and heavy liquid analyses were used to assess the chemical forms of sediment associated metal and the relationship between grain size density and metal concentration and to identify sources of metalliferous material generally the highest concentrations of trace metals were found in the 500 250 m size range and in the heavier density fractions 3 3 gml 1 though more than 60 of metals reported to the lightest 3 3 gml 1 density product the principal source of metals appeared to be reworked alluvium contaminated by historic mining activity metal concentrations in flood sediment decrease downstream from former mining areas though at varying rates depending on the physical propeties and chemical phase of individual metals with the exception of cu dominated by lithogenic fraction metals are primarily associated with fe mn oxides pb zn and to a lesser extent with carbonates cd zn organic matter zn cu and an operationally defined exchangeable cd component in the upper and middle parts of the tyne basin physical processes of downstream sediment metal content reduction were found to predominate while in the lower reaches of the tyne sediment metal transport appears to be governed by chemical sorption desorption processes associated with fe mn oxides and organic material finally the results of the study are discussed in a wider context of particulate metal transport in rivers and recommendations are made for refining density based models of metal dispersal

overthrust imaging with tomo datuming a case study through the use of iterative turning ray tomography followed by wave equation datuming or tomo datuming and prestack depth migration we generate accurate prestack images of seismic data in overthrust areas containing both highly variable near surface velocities and rough topography in tomo datuming we downward continue shot records from the topography to a horizontal datum using velocities estimated from tomography turning ray tomography often provides a more accurate near surface velocity model than that from refraction statics the main advantage of tomo datuming over tomo statics tomography plus static corrections or refraction statics is that instead of applying a vertical time shift to the data tomo datuming propagates the recorded wavefield to the new datum we find that tomo datuming better reconstructs diffractions and reflections subsequently providing better images after migration in the datuming process we use a recursive finite difference fd scheme to extrapolate wavefield withou

the magnitude and frequency characteristics of fluvial transport in a devon drainage basin and some geomorphological implications summary magnitude and frequency analysis of fluvial transport based on long and detailed record has been lacking for british rivers continuous monitoring of suspended sediment and solute concentrations for the river creedy devon since october 1972 has provided an opportunity to establish the medium term magnitude and frequency characteristics of river transport in a sizeable 262 km 2 drainge basin results reveal the importance of solute removal substantial variations in the relative magnitude of annual dissolved and suspended sediment yields clear differences in the temporal distribution of sediment and solute removal and contrasts in the magnitude and recurrence of extreme values of dissolved and suspended solids transport consideration of discharge levels most effective for transporting river loads in relation to a natural channel cross section has stressed the importance of events of moderate magnitude and frequency in this drainage system

p wave velocity structure under the changbaishan volcanic region ne china from wide angle reflection and refraction data abstract we present velocity models determined by inverting refracted and reflected arrivals along two active source lines in the changbaishan volcanic region ne china we resolve a prominent low velocity zone lvz in the crust with velocities as low as 5 4 km s away from the lvz the velocity gradients in the crust are relatively smooth with average p wave velocities of about 6 0 6 5 km s the moho is at about 35 km depth thickening to about 40 km under the tianchi volcano and thinning to about 30 km under the lvz the lvz is located about 30 60 km to the north of the summit of the tianchi volcano the most recently active volcano in the region is about 30 75 km in north south extent is at most 35 km in east west extent and is in the depth range of about 10 25 km below the surface we use these results to constrain receiver function inversions and show that the receiver functions in the region are compatible with our findings with these data alone the significance of the lvz in non unique although we do not see any evidence to support the presence of partial melt in the crust and favor the interpretation that the lvz indicates a residual crustal magma chamber

imaging low velocity anomalies with the aid of seismic tomography abstract theoretical considerations snell s law suggest that low velocity fanomalies are undersampled and therefore should be poorly resolved by inversion schemes based on ray tracing methods a synthetic study considering a 40 20 m low velocity anomaly 300 m s placed at the center of a 400 50 m block with gradient background velocity model from 3000 m s at the surface to 4000 m s at the base indicates that the low ray density in ray tracing coverage diagrams of tomographic inversion studies can be used as evidence for the existence of low velocity anomalies combined normal incidence seismic reflection images and the velocity models obtained by tomographic inversions of first arrival travel times form an efficient scheme to resolve low velocity anomalies such as fracture zones furthermore the velocity models derived from tomographic inversions are used in a wave equation datuming algorithm to account for statics caused by a strongly laterally variable shallow surface weathering layer and provide seismic reflection images of fracture zones low velocity anomaly within a granitic pluton

imaging igneous rocks on the north atlantic rifted continental margin summary extruded basalt flows with thicknesses of several kilometres occur ubiquitously along the rifted continental margins of the northern north atlantic their total volume exceeds 1 million km 3 and may reach several million cubic kilometres intruded igneous rock comprising the complementary melt fraction to that extruded at the surface should exist in the lower crust with a volume at least as large as that of the extrusive basalts to image the extrusive and intrusive igneous rocks on the continental margin near the faroe islands in 2002 we shot a 375 km long deep penetration seismic profile across the margin using 85 ocean bottom seismometers for wide angle acquisition and shot a separate reflection profile using a 12 km streamer for optimal imaging by using large airgun sources tuned to produce low frequency energy we were able to constrain the seismic velocity structure of the whole crust we imaged not only layering and structure within the extrusive basalts but also lower crustal intrusions on the continent ocean transition cot combination of good velocity control on the lower crust together with direct imaging of the extrusive basalts enables us to constrain the volumes of extrusive and intrusive igneous rocks produced near the faroe islands to be 340 420 and 560 780 km 3 per kilometre along strike respectively the cot marked both by high velocity intrusions and lower crustal layering is surprisingly narrow with only 50 km separating unstretched continental crust from fully oceanic crust in contrast the extruded basalts flow up to 150 km landward at the paleo surface

heavy metal contamination in the lacustrine sediment of a plateau lake influences of groundwater and anthropogenic pollution in this study heavy metal pollution in sediment cores from the yangzonghai lake a fault controlled highland lake in china was investigated all of the sediment samples were unpolluted or slightly polluted with geoaccumulation indexes igeo of 20 cm all of the heavy metals were controlled by groundwater and the distributions of the concentrations enrichments and pollution indexes were closely associated with springs the surface sediment at a depth of 10 cm however was contaminated by human activities which significantly increased the igeo cf and enrichment factors covering most of the lake all elements exhibit accumulations near the mouth of the yangzong river suggesting that the pollution predominantly came from the river in addition hg cd and as pb also exhibit increased enrichments near the thermal plant and the springs respectively combined with multi statistical analyses it is suggested that hg and cd were mainly polluted by the river and the thermal plant in the surface sediment while as and pb were contributed by the river and groundwater co ni and zn were strongly associated with fe and mainly originated from lithogeochemical processes although their occurrence was affected by the groundwater in the sub surface sediment and the river in the surface sediment this study provided essential information on the heavy metal contamination in both the surface and sub surface sediments of the yangzonghai lake in addition it is suggested that groundwater should be taken into consideration to assess the heavy metal contamination in the sediment of fault controlled plateau lakes

three dimensional p and s wave velocity structure of redoubt volcano alaska the three dimensional p and s wave structure of redoubt volcano alaska and the underlying crust to depths of 7 8 km is determined from 6219 p wave and 4008 s wave first arrival times recorded by a 30 station seismograph network deployed on and around the volcano first arrival times are calculated using a finite difference technique which allows for flexible parameterization of the slowness model and easy inclusion of topography and source receiver geometry the three dimensional p wave velocity structure and hypocenters are determined simultaneously while the three dimensional s wave velocity model is determined using the relocated seismicity and an initial s wave velocity model derived from the p wave velocity model assuming an average vp vs ratio of 1 78 convergence is steady with approximately 73 and 52 reduction in p and s wave arrival time rms respectively after 10 iterations the most prominent feature observed in the three dimensional velocity models derived for both p and s waves is a relative low velocity near vertical pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level this feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit the velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations high velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates no large low velocity body suggestive of a magma chamber is resolved in the upper 7 8 km of the crust

the geology and geomorphology of the beacon cottage farm outlier st agnes cornwall the mid oligocene sediments forming the beacon cottage farm outlier at st agnes cornwall have a stratigraphical and geomorphological importance which is out of all proportion to their modest residual bulk some 300000 m3 during 1986 8 61 holes were sunk into the area surrounding beacon cottage farm many penetrated the palaeozoic floor beneath the outlier collectively these show that the outlier mostly covers rotten granite and killas the sub oligocene unconformity is uneven and varies in altitude by at least 20 m the local bovey formation succession comprises two members basal sand which is often pebbly and sandy silts known commercially as candle clay the whole totalling a maximum of 8 9 m there is indirect evidence either that slopes on the rotted palaeozoic floor locally exceed 45 or that several post mid oligocene faults affect the outlier we conclude that the beacon cottage farm sediments probably represent aeolian colluvially and fluvially redistributed rotten rock residues formed locally during a break in the long period of late palaeogene subtropical weathering and pediplanation the outlier is considered in relation to the geomorphological evolution of the cornubian massif

sediments porewaters and diagenesis in an urban water body salford uk impacts of remediation contaminated sediments deposited within urban water bodies commonly exert a significant negative effect on overlying water quality however our understanding of the processes operating within such anthropogenic sediments is currently poor this paper describes the nature of the sediment and early diagenetic reactions in a highly polluted major urban water body the salford quays of the manchester ship canal that has undergone remediation focused on the water column the style of sedimentation within salford quays has been significantly changed as a result of remediation of the water column pre remediation sediments are composed of a range of natural detrital grains predominantly quartz and clay and anthropogenic detrital material dominated by industrial furnace derived metal rich slag grains post remediation sediments are composed of predominantly autochthonous material including siliceous algal remains and clays at the top of the pre remediation sediments and immediately beneath the post remediation sediments is a layer significantly enriched in furnace derived slag grains input into the basin as a result of site clearance prior to water column remediation these grains contain a high level of metals resulting in a significantly enhanced metal concentration in the sediments at this depth porewater analysis reveals the importance of both bacterial organic matter oxidation reactions and the dissolution of industrial grains upon the mobility of nutrient and chemical species within salford quays minor release of iron and manganese at shallow depths is likely to be taking place as a result of bacterial fe iii and mn iv reduction petrographic analysis reveals that the abundant authigenic mineral within the sediment is manganese rich vivianite and thus fe ii and mn ii released by bacterial reactions may be being taken up through the precipitation of this mineral significant porewater peaks in iron manganese and silicon deeper in the sediment column are most probably the result of dissolution of furnace derived grains in the sediments these species have subsequently diffused into porewater above and below the metal enriched layer this study illustrates that the remediation of water quality in anthropogenic water bodies can significantly impact upon the physical and chemical nature of sedimentation additionally it also highlights how diagenetic processes in sediments derived from anthropogenic grains can be markedly different from those in sediments derived from natural detrital material copyright 2003 john wiley sons ltd

high resolution reflection seismics applied to detection of groundwater resources in glacial deposits sweden a large proportion of sweden s ground water resources is contained in sand gravel glaciofluvial deposits that overlie precambrian crystalline basement and are covered by clay the depth to the sand gravel deposits varies from near surface to about 100 m and their thickness is generally 10 20 m traditionally due to logistics short refraction seismic profiles and penetration tests have been used to localize the sand gravel deposits below the clay and to determine their thickness however when the overlying clay deposits are thick or the glacial deposits show significant 2 d structure refracting waves may not penetrate into the sand gravel deposits or into the crystalline basement reflection seismic methods provide an alternative mapping method and a test profile was acquired over glacial deposits where the structure is well known standard processing shows in general excellent agreement between the seismic image and the structure determined from penetration tests

observed mean sea level changes around the north sea coastline from 1800 to present this paper assesses historic changes in mean sea level around the coastline of the north sea one of the most densely populated coasts in the world typically such analyses have been conducted at a national level and detailed geographically wider analyses have not been undertaken for about 20 years we analyse long records up to 200 years from 30 tide gauge sites which are reasonably uniformly distributed along the coastline and 1 calculate relative sea level trends 2 examine the inter annual and decadal variations 3 estimate regional geocentric sometimes also referred to as absolute sea level rise throughout the 20th century and 4 assess the evidence for regional acceleration of sea level rise relative sea level changes are broadly consistent with known vertical land movement patterns the inter annual and decadal variability is partly coherent across the region but with some differences between the inner north sea and the english channel data sets from various sources are used to provide estimates of the geocentric sea level changes the long term geocentric mean sea level trend for the 1900 to 2011 period is estimated to be 1 5 0 1 mm yr for the entire north sea region the trend is slightly higher for the inner north sea i e 1 6 0 1 mm yr and smaller but not significantly different on the 95 confidence level for the english channel i e 1 2 0 1 mm yr the uncertainties in the estimates of vertical land movement rates are still large and the results from a broad range of approaches for determining these rates are not consistent periods of sea level rise acceleration are detected at different times throughout the last 200 years and are to some extent related to air pressure variations the recent rates of sea level rise i e over the last two to three decades are high compared to the long term average but are comparable to those which have been observed at other times in the late 19th and 20th century

natural change and human impact in a present day fluvial catchment the geul river southern netherlands abstract the geul river has a long history of channel straightening and bank protection but also has several natural meandering parts in addition some formerly fixed or protected stretches of the river have been allowed to meander freely since 1988 therefore it represents an ideal case for evaluating the contribution of human interference to the intrinsic evolution of the river in this paper we compare the response of selected not protected reaches of the present day river to different human modifications the river banks were labelled as stable unstable or erosive as might be expected stretches with a high sinuosity have a high percentage of erosive and unstable bank length while low sinuosity stretches experience hardly any erosion the amount of lateral erosion and sedimentation in natural situations is compared with that in situations with different bank protection and stabilization types erosion rates may locally attain up to 2 m per year detailed grain size analysis of point bar sections enable distinction of successive fining up sequences vertical aggradation rates within the point bars are up to 0 15 m yr 1 the highest rates are found in the youngest point bars collectively the results of this study show that when bank protection is removed the freely meandering river creates its own specific ecosystems and retention capacity increases such a return to natural environmental and ecological conditions is in accordance with the objectives of the european water framework directive

heavy metal contamination in overbank sediments of the geul river east belgium its relation to former pb zn mining activities overbank sediments of the geul river east belgium are highly contaminated by the heavy metals pb zn and cd due to former pb zn mining activities in the drainage basin geochemical variations in vertical overbank sediment profiles sampled 1 km north of the mine tailings of plombieres allow metal fluxes back to the 17th century to be reconstructed the vertical profiles are subdivided into three major units corresponding to different industrial periods based on sedimentological criteria as well as on the distribution of contaminants alluvial sediments with the highest heavy metal concentrations correspond to the major period of mining activity of the 19th century the fact that zn mining at the la calamine open mine started before large scale mining of the pbs zns subsurface exploitations is reflected in the vertical profiles by an increase in zn content before a marked increase in pb and cu the regional extent of contamination in the alluvial deposits was evaluated on the basis of the geochemical analysis of sediments at depths of the 0 20 cm and 80 100 cm most of the upper samples are extremely contaminated significant local variations in heavy metal concentration in the lower samples are interpreted in terms of which overbank sediment horizon has been sampled at a depth of 80 100 cm this indicates that blind sampling of overbank sediments to characterize the degree of contamination in shallow boreholes can give very erratic results

three dimensional seismic refraction tomography a comparison of two methods applied to data from the faeroe basin this paper presents a comparison of two tomographic methods for determining three dimensional 3 d velocity structure from first arrival travel time data the first method is backprojection in which travel time residuals are distributed along their ray paths independently of all other rays the second method is regularized inversion in which a combination of data misfit and model roughness is minimized to provide the smoothest model appropriate for the data errors both methods are nonlinear in that a starting model is required and new ray paths are calculated at each iteration travel times are calculated using an efficient implementation of an existing method for solving the eikonal equation by finite differencing both inverse methods are applied to 3 d ocean bottom seismometer obs data collected in 1993 over the faeroe basin consisting of 53 479 travel times recorded at 29 obss this is one of the most densely spaced large scale 3 d seismic refraction experiments to date different starting models and values for the free parameters of each tomographic method are tested a new form of backprojection that converges more rapidly than similar methods compares favorably with regularized inversion but the latter method provides a simpler model for little additional computational expense when applied to the faeroe basin data bounds on two model features are assessed using regularized inversion with combined smoothness and flatness constraints an inversion of synthetic data corresponding to 100 data recovery from the real experiment shows a marked improvement in lateral resolution at deeper depths and demonstrates the potential of currently feasible 3 d refraction experiments to provide well resolved long wavelength velocity models the similarity of the final models derived from the two tomographic methods suggests that the results from the new form of backprojection can be relied on when limited computational resources rule out regularized inversion

architecture of fault zones determined from outcrop cores 3 d seismic tomography and geostatistical modeling example from the albala granitic pluton sw iberian variscan massif abstract the 3 d seismic tomographic data are used together with field core and well log structural information to determine the detailed 3 d architecture of fault zones in a granitic massif of volume 500 575 168 m at mina ratones area in the albala granitic pluton to facilitate the integration of the different data geostatistical simulation algorithms are applied to interpolate the relatively sparse structural hard control data conditioned to abundant but indirect 3 d soft seismic tomographic data to effectively integrate geologic and tomographic data 3 d migration of the velocity model from the time domain into the depth domain was essential the resulting 3 d model constitutes an image of the fault zone architecture within the granitic massif that honours hard and soft data and provides an evaluation of the spatial variability of structural heterogeneities based on the computation of 3 d experimental variograms of fracture index fault intensity data this probabilistic quantitative 3 d model of spatially heterogeneous fault zones is suitable for subsequent fluid flow simulations the modeled image of the 3 d fault distribution is consistent with the fault architecture in the mina ratones area which basically consists of two families of subvertical structures with nne ssw and ene wsw trends that displaces the surfaces of low angle faults north fault and follows their seismically detected staircase geometry these brittle structures cut two subvertical dykes 27 and 27 dykes with a nne ssw to n s trend the faults present high fi fi 12 adjacent bands of irregular geometry in detail that intersect in space delimiting rhombohedral blocks of relatively less fractured granite fi

high resolution 3d p wave velocity structure beneath tenerife island canary islands spain based on tomographic inversion of active source data 1 we present a high resolution 3 dimensional 3d p wave velocity model for tenerife island canaries covering the top of teide volcano 3 718 m a s l down to around 8 km below sea level b s l the tomographic inversion is based on a large data set of travel times obtained from a 3d active seismic experiment using offshore shots air guns recorded at more than 100 onshore seismic stations the obtained seismic velocity structure is strongly heterogeneous with significant up to 40 lateral variations the main volcanic structure of the las canadas teide pico viejo complex ctpvc is characterized by a high p wave velocity body similar to many other stratovolcanoes the presence of different high p wave velocity regions inside the ctpvc may be related to the geological and volcanological evolution of the system the presence of high p wave velocities at the center of the island is interpreted as evidence for a single central volcanic source for the formation of tenerife furthermore reduced p wave velocities are found in a small confined region in ctpvc and are more likely related to hydrothermal alteration as indicated by the existence of fumaroles than to the presence of a magma chamber beneath the system in the external regions surrounding ctpvc a few lower p wave velocity regions can be interpreted as fractured zones hydrothermal alterations porous materials and thick volcaniclastic deposits

lithogeochemical patterns around pb zn mineralizations in dinantian carbonate rocks of eastern belgium the lithogeochemical distribution patterns of mg sr na zn pb fe mn k corg organic matter and ir insoluble residue in the dinantian limestones and dolomites from the eastern part of belgium have been studied dinant and verviers synclinorium comparison of geochemical data of non mineralized strata revealed higher background values in the strata of the verviers synclinorium where pb zn mineralizations occur in this area a relation may exist with the metallogenetic district herve vesdre theux district proposed by dejonghe 1985b however the higher background values also could relate to the more restricted sedimentation conditions in the verviers synclinorium as opposed to the more open marine conditions in the dinant synclinorium the influence of mineralization on the geochemistry of limestones is limited and unpredictable in dolomites however the effect can be important in these rocks the lithogeochemical distribution of zn pb and mn can be subdivided into three populations i e a regional background a local high background and a halo population the higher trace element concentrations in the halo population is caused by the existence of disseminated sulfide minerals sphalerite galena and pyrite and zn bearing goethite mainly pseudomorphs after pyrite and mn oxides the sulfides relate to the ore emplacement in the local high background only the zn bearing oxides occur their presence and thus the development of the local high background relates to weathering processes

effects of the shallow subsurface on upper crustal seismic reflection images abstract seismic imaging of the upper crust is strongly affected by the interactions of the seismic wavefield with the shallow subsurface in order to better understand these effects we have evaluated the seismic responses of a suite of canonical models of the upper crystalline crust and the near surface region our modelling is restricted to two dimensions but otherwise includes the full seismic wavefield notably the effects of attenuation and topographic variations along the free surface we find that s wave scattering is important in the upper crust and contributes significantly to the vertical component of the seismic reflection response the backscattered wavefield undergoes mode conversions when it interacts with the free surface even moderate topographic variations or velocity variations in the near surface region enhance these mode conversions and cause additional scattering much of the earth s surface is covered by thin layers of unconsolidated material or weathered bedrock with high attenuation and high velocity contrasts at the layer boundaries scattered and mode converted seismic energy gets trapped in these layers and thus interacts repeatedly with the free surface and its topography in analogy to large scale seismic resonance effects of sedimentary valley fills the level and duration of source generated noise depends heavily on the degree of attenuation in the shallow layers low attenuation causes high noise levels and vice versa in contrast the level of source generated noise is less sensitive to near surface layer thicknesses and velocity contrasts

reconstructing historical trends in metal input in heavily disturbed contaminated estuaries studies from bilbao southampton water and sicily estuaries may be important reservoirs for contaminants as they tend to act as sinks for fine contaminant reactive sediments and historically they have acted as centres for industrial and urban development analysis of dated sediment cores from these areas may allow historical trends in heavy metal input to be reconstructed and recent and historical inputs of metal contaminants to be compared undisturbed saltmarsh settings have been used widely in the reconstruction of historical trends in metal input as saltmarshes provide a stable vegetated substrate of dominantly fine sediments and are less prone to erosion and reworking than adjacent mudflat areas in comparison much less research on historical pollution trends has been undertaken at estuarine sites which are prone to severe local disturbance such as intertidal areas which are routinely dredged or where sedimentary processes have been modified by human activities such as shipping salt working port activities land claim etc this paper assesses the usefulness of 210pb and 137cs dating combined with geochemical studies in reconstructing historical trends in heavy metal input and sediment accretion in 3 heavily modified industrialised estuarine areas in europe the bilbao estuary spain southampton water uk and the mulinello estuary sicily of these sites only a salt marsh core from the mulinello estuary provides a high resolution record of recent heavy metal inputs in southampton water only a partial record of changing metal inputs over time is retained due to land claim and possible early diagenetic remobilisation while at bilbao the vertical distribution of heavy metals in intertidal flats is mainly controlled by input on reworked sediment particles and variations in sediment composition where 137cs and 210pb distributions with depth allow a chronology of sediment deposition to be established and early diagenetic remobilisation has been minimal mudflat and saltmarsh cores from even the most heavily disturbed estuarine sites can provide useful information on variations in historical contaminant input when the sediments have been vigorously mixed or reworked large scale compositional variations are present or significant early diagenetic remobilisation has occurred however only general information on the scale of contamination can be obtained

calibrating 3d tomograms of a granitic pluton 1 first arrival time p waves from offset and azimuth variable vertical seismic reflection records are used to tomographically reconstruct the 3d p wave velocity structure around a 500 m deep vertical borehole comparisons with sonic and fracture index logs and core samples indicates that low velocity anomalies in the tomograms correlate with surface mapped fracture zones results also show that low velocity zones intersect the borehole in areas characterized by relatively low values for vp and vs determined from sonic logs these zones are characterized by poisson s ratio close to 0 3 which are indicative of altered or fractured rock and supported by the fracture index and core samples the high velocity anomalies intersect the well in areas characterized by low values of the fracture index and 0 25 or lower this suggests that the relatively high vp velocities are indicative of unfractured rock this study reveals that high resolution tomography produces results consistent with direct observations in a well sampled borehole

the spatial distribution of heavy metal contaminated sediment across terraced floodplains abstract deposits of fine alluvial sediment contaminated by heavy metals derived from mining provide an opportunity to reconstruct the alluvial histories of mineralised catchments field data were collected to identify the spatial distribution of heavy metal contamination in surficial floodplain sediments and establish the relationships between terrace height terrace age and metal concentrations floodplain terrace morphology was mapped and terrace heights were measured for three separate study reaches in the upper sevem basin mid wales concentrations of pb ba and zn were determined in 97 samples taken from fine overbank units capping these terrace surfaces between the three study reaches element concentrations showed wide ranges pb 11 964ppm ba 141 1118 ppm zn 73 1134 ppm they also exhibited significant spatial variation across the floodplain at each study reach e g at llandinam pb 36 964ppm ba 141 1118 ppm and zn 173 1134 ppm peak metal concentrations at morfodion pb 399 ppm ba 474 ppm and welsh pool pb 149 ppm ba 558 ppm were found on terrace surfaces 1 5 2 5m and 2 0 3 0 m above present river level respectively lower concentrations reflect natural background levels of contaminants higher terraces and post mining reworking of spoil heaps and floodplains lower terraces in general the spatial distribution of floodplain contaminants is more significantly correlated with terrace height than with terrace age different flooding mechanisms and styles of channel instability in relation to the timing and mode of sedimentation have resulted in different patterns of floodplain contamination focused deposition particularly in palaeochannels is also an important mechanism for creating strongly contaminated sites within the floodplain environment

combining wave equation imaging with traveltime tomography to form high resolution images from crosshole data traveltime tomography is an appropriate method for estimating seismic velocity structure from arrival times however tomography fails to resolve discontinuities in the velocities wave equation techniques provide images using the full wave field that complement the results of traveltime tomography we use the velocity estimates from tomography as a reference model for a numerical propagation of the time reversed data these backpropagated wave fields are used to provide images of the discontinuities in the velocity field the combined use of traveltime tomography and wave equation imaging is particularly suitable for forming high resolution geologic images from multiple source multiple receiver data acquired in borehole to borehole seismic surveying in the context of crosshole imaging an effective implementation of wave equation imaging is obtained by transforming the data and the algorithms into the frequency domain this transformation allows the use of efficient frequency domain numerical propagat

a 17 yr record of sediment accretion in the salt marshes of maine usa abstract marker horizons of brick dust were established in 1986 in 26 salt marshes along the coast of maine usa in 2003 we measured the sediment accumulation rates for the 17 year period in 11 relocated sites and obtained results varying from 1 4 to 4 2 mm yr the mean accretion rate for all marshes was 2 8 mm yr accretion rates measured from 1986 to 2003 were comparable to those measured at the sites in 1987 and 1990 indicating that marsh accretion rates are similar on annual and decadal time scales inorganic material was found to be the primary constituent of maine salt marsh sediments several marshes show clear evidence of transgression since 1986 in the form of landward moving plant zones or encroachment of mudflat onto salt marsh indications for regressive changes were not observed marsh sediment accumulation rates are generally higher than mean rates of relative sea level rise indicating that most salt marshes are currently keeping pace with sea level rise however if relative sea level rise were to exceed rates of 4 mm yr many salt marshes in maine may not survive

palaeoseismicity of the oquirrh fault utah from shallow seismic tomography the magnitude and frequency of normal fault palaeoearthquakes are usually determined by trenching studies that ascertain the size and number of colluvial wedges along the fault such information can be invaluable in predicting the seismic hazard and potential for a future earthquake in that region digging trenches across normal faults however is environmentally intrusive expensive and limited in the penetration depth to overcome these problems we propose the use of 3 d seismic tomography as a means to identify the shapes and sizes of colluvial wedges along normal faults as an example 2 d and 3 d seismic surveys were conducted across the oquirrh fault utah with the purpose of imaging the normal fault structure to a depth of about 10 m results show that the 3 d tomogram clearly delineates the fault zone and a colluvial wedge both of which correlate extremely well with the geological cross section interpreted from an adjacent trench the thickness of the colluvial wedge image is used in conjunction with a seismic section to compute an estimate of a 6 8 moment magnitude earthquake for the most recent event on this fault which is in close agreement with the 7 0 estimate based on a nearby trenching study these tomographic results demonstrate for the first time that seismic imaging methods can be used in some cases to estimate unambiguously the shapes of colluvial wedges and the sizes of prehistoric earthquakes thus seismic tomography has the possibility of providing cheaper deeper and wider but less resolved images of fault systems than the intrusive excavation of trenches across faults

wave equation velocity replacement of the low velocity layer for overthrust belt data seismic land data are commonly plagued by nonhyperbolic distortions induced by a variable near surface low velocity layer lvl first arrival refraction analysis is conventionally employed to estimate the lvl geometry and velocities then vertical static time shifts are used to replace the lvl velocities with the more uniform faster velocities that characterize the underlying refracting layer this methodology has earned a good reputation as a geophysical data processing tool however velocity replacement with static shifts assumes that no ray bending occurred at the lvl base and that waves propagated vertically through the lvl even though conventional refraction analysis methods which are used to derive lvl models from seismic data are less restrictive these assumptions often are inadequate in thick complex lvl situations where resulting errors may considerably hamper a statics based velocity replacement procedure wave equation datuming may be used to perform lvl velocity replacement when statics are inadequate this method extrapolates the seismic data from the surface to the lvl base with the lvl velocities then it extrapolates the data from the lvl base to an arbitrary datum with the replacement velocity field the marine analog of such a procedure has been well documented in the geophysical literature where the object is to remove distortions caused by an irregular water layer application of wave equation datuming to land data is more difficult because of certain common characteristics of land data irregular shooting large data gaps and crooked line geometry combined with lower signal noise and because the lvl estimation procedure is considerably more difficult we demonstrate wave equation velocity replacement on land data from a western u s overthrust belt the lvl in this region was particularly thick and complicated and ideal for a wave theoretical velocity replacement procedure standard refraction analysis techniques were employed to estimate the lvl then wave equation datuming was used to perform the velocity replacement our derived lvl model was not perfect so some imaging errors were expected because wave equation datuming is highly dependent upon the lvl model nevertheless our results show that wave equation datuming generally allowed better shallow reflector imaging than could be achieved with conventional statics processing

seismic tomography studies of cover thickness and near surface bedrock velocities reflection seismic imaging of the uppermost kilometer of crystalline bedrock is an important component in site surveys for locating potential storage sites for nuclear waste in sweden to obtain high quality images refraction statics are calculated using first break traveltimes these first break picks may also be used to produce tomographic velocity images of the uppermost bedrock in an earlier study we presented a method applicable to data sets where the vast majority of shots are located in the bedrock below the glacial deposits or cover typical for northern latitudes a by product of this method was an estimate of the cover thickness from the receiver static that was introduced to sharpen the image we now present a modified version of this method that is applicable for sources located in or on the cover the general situation for nuclear waste site surveys this modified methodalso solves for 3d velocity structure and static correctionssimultaneously in the inversion process the static correcti

the role of grain dissolution and diagenetic mineral precipitation in the cycling of metals and phosphorus a study of a contaminated urban freshwater sediment this paper describes the detrital mineralogy early diagenetic reactions and authigenic mineral precipitates for freshwater contaminated sediments deposited in an urban water body the salford quays of the manchester ship canal greater manchester uk these sediments contain a mix of natural and anthropogenic detrital grains detrital grains are dominated by quartz and clay grains whilst anthropogenic grains are dominated by metal rich glass grains concentrated at a depth of 12 17 cm in the sediment as a result of historical inputs sediment porewaters contain significant concentrations of fe mn zn and phosphate bacterial fe iii and mn iv reduction are hypothesised to supply fe2 and mn2 to porewaters with phosphate released from fe oxide reduction or organic matter oxidation petrographic observations indicate that the metal rich glass grains are undergoing chemical dissolution during early diagenesis supplying fe and zn to porewaters the most abundant authigenic mineral in the sediments is vivianite fe3 po4 2 8h2o containing a significant level of redlingite with minor framboidal pyrite fes2 electron microprobe analysis shows the vivianite to contain zn cu and pb suggesting that vivianite acts as a long term sink for these metals in this sediment this implies that authigenic vivianite in freshwater sediments may act as a long term sink for metals in a similar manner to sulphides in marine sediments this study highlights that the nature of detrital and diagenetic mineralogy in addition to porewater and sediment chemistry needs to be considered in assessing contaminated sediments

shallow water tides in the northwest european shelf region from topex poseidon altimetry during recent years the accurate measurements from the topex poseidon satellite have improved global ocean tide models considerably however these global ocean tide models are still not accurate enough on the continental shelves for detailed oceanographic studies the need for increasing accuracy in shelf regions calls for inclusion of more than just semidiurnal and diurnal constituents in future global ocean tide models this is because a considerable part of the tidal variability on the shelves is caused by shallow water constituents one example is the m4 constituent which exceeds 50 cm at several locations on the northwest european shelf so far topex poseidon has not been considered for resolving these constituents mainly owing to its coarse ground track resolution reliable empirical estimates of several major shallow water constituents can be obtained from topex poseidon by combining along track and crossover observations estimates of the major shallow water constituents for the northwest european shelf m4 m6 and ms4 are presented in this study and compared with tide gauges and existing hydrodynamic models

2000 years of sediment borne heavy metal storage in the yorkshire ouse basin ne england uk floodplain overbank sediments are often used to evaluate the influence of environmental change on sediment and chemical fluxes within river basins this paper presents the results of an investigation of heavy metal storage in seven floodplain reaches in the yorkshire ouse basin in north east england floodplain heavy metal storage has been greatest since c 1750 and many of the post 1750 sedimentary units exhibit heavy metal values that exceed recommended trigger and guideline values for contaminated land relatively high heavy metal storage occurs from ad 1250 1750 in most of the reaches these patterns are related to 2000 years of pb and zn mining in the yorkshire dales and c 250 300 years of industrial and urbanization activity around leeds and bradford and increased delivery of fine grained sediment during the last millennium possibly owing to factors such as population growth and agricultural expansion during the middle ages and climate change during the little ice age copyright 1999 john wiley sons ltd

anthropocene footprint in the nalon estuarine sediments northern spain abstract four boreholes drilled at depths ranging from 9 to 27 m and retrieved from the nalon estuary asturias northern spain were investigated to assess the impact of the historical human footprint on the sedimentary sequence analytical measurements of grain size geochemical composition major and trace elements and stable pb isotopic ratios were performed two different sections of the sedimentary profile were identified throughout the sedimentary sequence using pb isotopic ratios and then corroborated with grain size characteristics and as hg pb and zn concentrations the upper sediment layer of the boreholes variable depth ranging between 3 and 9 m exhibited an increase in 208pb 206pb ratios and a decrease in 206pb 207pb ratios whereas in the deepest layers these ratios remained unchanged these variations reflected the anthropogenic input of pb into estuarine sediments which can be attributed to mining activities when compared to pb isotopic ratios from coal mined in the region the anthropogenic input can be also noted on the basis of the variability of the trace element concentrations with depth the enrichment factors of as max 7 5 hg max 45 4 pb max 10 3 and zn max 8 6 calculated using local geochemical background values helped distinguish the impact of intense anthropogenic activities which can be attributed to mining exploitation in the nalon river drainage basin despite the closure of several of these mines during the second half of the 20th century geochemical characteristics have revealed the ongoing input of as hg pb and zn into the coastal zone thus the legacy of contamination from these elements mainly from leaching slags and tailing dams is still being recorded in estuarine sediments and requires careful scrutiny on the part of local authorities in terms of its possible effects on the aquatic biota

mineralogical and geochemical signature of mine waste contamination tresillian river fal estuary cornwall uk the mineralized district of sw england was one of the world s greatest mining areas with mining commencing in the bronze age peaking in the 1850s to 1890s but still continuing to the present day consequently it is not surprising that mining has had a major impact on the environmental geochemistry of sw england in this study the mineralogical and geochemical signature of mine waste contamination within the fal estuary at tresillian cornwall has been examined a pulse of mine waste contamination is recognized at approximately 50 cm below present day sediment surface sn as cu pb and zn are all enriched within this contaminated interval with up to 1800 mg kg 1 sn 290 mg kg 1 as 508 mg kg 1 pb 2210 mg kg 1 zn and 1380 mg kg 1 cu within this interval the dominant minerals present include chalcopyrite arsenopyrite pyrite cassiterite fe ti oxides ilmenite and rutile wolframite sphalerite baryte zircon monazite tourmaline and xenotime in addition man made slag products commonly occur the exact timing of the release of mine waste into the estuary is poorly constrained but probably occurred during or immediately following the peak in mining activity in the nearby camborne redruth district which was between 1853 and 1893 the mine waste may have entered the estuary either via the tresillian river and its tributaries or via calenick creek and the truro river and or the carnon river which flows into rostronguet creek