velocity stack processing1 a conventional velocity stack gather consists of constant velocity cmp stacked traces it emphasizes the energy associated with the events that follow hyperbolic traveltime trajectories in the cmp gather amplitudes along a hyperbola on a cmp gather ideally map onto a point on a velocity stack gather because a cmp gather only includes a cable length portion of a hyperbolic traveltime trajectory this mapping is not exact the finite cable length discrete sampling along the offset axis and the closeness of hyperbolic summation paths at near offsets cause smearing of the stacked amplitudes along the velocity axis unless this smearing is removed inverse mapping from velocity space the plane of stacking velocity versus two way zero offset time back to offset space the plane of offset versus two way traveltime does not reproduce the amplitudes in the original cmp gather the gather resulting from the inverse mapping can be considered as the model cmp gather that contains only the hyperbolic events from the actual cmp gather a least squares minimization of the energy contained in the difference between the actual cmp gather and the model cmp gather removes smearing of amplitudes on the velocity stack gather and increases velocity resolution a practical application of this procedure is in separation of multiples from primaries a method is described to obtain proper velocity stack gathers with reduced amplitude smearing the method involves a t 2 stretching in the offset space this stretching maps reflection amplitudes along hyperbolic moveout curves to those along parabolic moveout curves the cmp gather is fourier transformed along the stretched axis each fourier component is then used in the least squares minimization to compute the corresponding fourier component of the proper velocity stack gather finally inverse transforming and undoing the stretching yield the proper velocity stack gather which can then be inverse mapped back to the offset space during this inverse mapping multiples primaries or all of the hyperbolic events can be modelled an application of velocity stack processing to multiple suppression is demonstrated with a field data example

regional distribution of al b ba ca k la mg mn na p rb si sr th u and y in terrestrial moss within a 188 000 km2 area of the central barents region influence of geology seaspray and human activity abstract five hundred and ninety eight samples of terrestrial moss hylocomium splendens and pleurozium schreberi collected from a 188 000 km2 area of the central barents region ne norway n finland nw russia were analysed by icp aes and icp ms analytical results for al b ba ca k la mg mn na p rb si sr th u and y concentrations are reported here graphical methods of data analysis such as geochemical maps cumulative frequency diagrams boxplots and scatterplots are used to interpret the origin of the patterns for these elements none of the elements reported here are emitted in significant amounts from the smelting industry on the kola peninsula despite the conventional view that moss chemistry reflects atmospheric element input the nature of the underlying mineral substrate regolith or bedrock is found to have a considerable influence on moss composition for several elements this influence of the chemistry of the mineral substrate can take place in a variety of ways 1 it can be completely natural reflecting the ability of higher plants to take up elements from deep soil horizons and shed them with litterfall onto the surface 2 it can result from naturally increased soil dust input where vegetation is scarce due to harsh climatic conditions for instance alternatively substrate influence can be enhanced by human activity such as open cast mining creation of technogenic deserts or handling transport and storage of ore and ore products all of which magnify the natural elemental flux from bedrock to ground vegetation seaspray is another natural process affecting moss composition in the area mg na and this is most visible in the norwegian part of the study area presence or absence of some plant species e g lichens seems to influence moss chemistry this is shown by the low concentrations of b or k in moss on the finnish and norwegian side of the fenced border with russia contrasting with high concentrations on the other side intensive reindeer husbandry west of the border has selectively depleted the lichen population

seismic reflection borehole and outcrop geometry of late wisconsin tills at a proposed landfill near toronto ontario the search for new landfill sites in the greater toronto area of southern ontario canada is producing a wealth of data regarding the subsurface stratigraphy and geometry of late wisconsin 25 ka

subsurface deformation mechanisms beneath a flexible pavement using image correlation flexible pavement structures are widely used in road construction especially in circumstances where very high traffic volumes are not expected these structures comprise multiple layers of granula

models of rock varnish formation constrained by high resolution transmission electron microscopy nanometre scale transmission electron microscope imagery of manganiferous rock varnishes from death valley california peru antarctica and hawaii confirms prior infrared mineralogy studies the building blocks of rock varnish are clay minerals that are cemented to the rock by oxyhydroxides of manganese and iron rock varnish is layered on the scale of nanometres with the basic structure defined by the subparallel alignment of detrital clay minerals although only a few examples of bacteria were found possible cell wall encrustations are ubiquitous and aligned with the clay minerals mn fe oxides appear to be mobilized from bacterial casts and then reprecipitate on clay minerals that weather into monolayers these observations have implications for varnish dating and palaeoenvironmental techniques k ar and uranium series dating of rock varnish oxides can only yield minimum ages however this small spatial scale of mobilization would not alter the signal from micron scale microchemical laminations

influence of inheritance and pedogenesis on heavy metal distribution in soils of sicily italy abstract the recognition of the potential health hazards associated with heavy metals has focused attention on the levels and behaviours of these elements both in natural and contaminated environments various soil types developed from different parent materials in sicily italy have been analysed in order to compare heavy metal distribution under different geopedological conditions total metal concentrations metal partitioning and distribution profiles are discussed in relation to the inheritance factor and pedogenic processes parent material composition largely influences the contents of heavy metals in most of the analysed soils mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materials however an exception is represented by the carbonate free alfisols and mollisols which are markedly enriched in heavy metals with respect to the underlying limestones and calcarenites on the basis of chemical and mineralogical results supported by data from sequential extraction sep heavy metal enrichment in these soils is associated with the formation of common to abundant fe mn oxides and clay accumulation for mollisols there is evidence for a major role of organic matter in heavy metal retention in surface horizons in the other pedons pedogenic processes appear to mainly influence the redistribution of heavy metals throughout the soil horizons rather than affecting the total content argillopedoturbation seems to be responsible for a uniform distribution of heavy metals in vertisol profiles on marly clays accumulation of heavy metals in the topsoil of inceptisols on clays with gypsum and entisols on gypsarenites and diatomites is caused partially by adsorption on organic matter and mainly by dissolution of primary gypsum and opal a a pedogenic influence is less evident in young andisols whose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles however a certain redistribution of cu accumulated as metal organic matter complexes is evidenced in the surface horizon by sep

direct observation of heavy metal mineral association from the clark fork river superfund complex implications for metal transport and bioavailability two sets of samples from riverbeds and adjacent floodplains separated by 80 river kilometers were collected from the clark fork river superfund complex montana the largest superfund site in the united states and studied primarily with transmission electron microscopy tem with several supporting techniques to determine heavy metal mineral association seven of the eight samples studied were strongly influenced by material that once resided in mining and smelting dumps and impoundments this material was transported downstream sometime during the last century and a half from the butte anaconda areas the eighth sample was from a deeper floodplain level and dates to premining days the tem observations afford a direct look down to the nanometer level at secondary mineral formation as a result of the breakdown of sulfides and silicates in the acid environment of this massive mine drainage system in the shallow oxic floodplain sediments heavy metals of concern in this system as cu pb and zn are taken up by the formation of sulfates particularly pb in jarosite as well as hydrous metal oxides as cu pb and zn in and on ferrihydrite and a possibly new vernadite like mineral the oxides are long lived in these systems as they were also found in the anoxic riverbeds metals are also taken up by the formation of sulfides in sulfate reducing environments as observed in the formation of nanoclusters of chalcopyrite and sphalerite in all samples clays make up between 5 and 20 of the sediment and carry significant amounts of cu and zn the hydrous oxides secondary sulfides and clays provide several routes for metal transport downstream over long distances besides the potential bioavailability of heavy metals exchanged on and off the hydrous metal oxides and clays nanometer sized sulfides may also be highly reactive in the presence of biologic systems

trace element evidence for the origin of desert varnish by direct aqueous atmospheric deposition abstract smooth rock surfaces in arid environments are often covered with a thin coating of fe mn oxyhydroxides known as desert varnish it is debated whether such varnish is formed a by slow diagenesis of dust particles deposited on rock surfaces b by leaching from the underlying rock substrate or c by direct deposition of dissolved constituents in the atmosphere varnishes collected from smooth rock surfaces in the mojave desert and death valley california are shown here to have highly enriched and fractionated trace element abundances relative to upper continental crust ucc they are highly enriched in co ni pb and the rare earth elements rees in particular they have anomalously high ce la and low y ho ratios these features can only be explained by preferential scavenging of co ni pb and the rees by fe mn oxyhydroxides in an aqueous environment high field strength elements hfses zr hf ta nb th however show only small enrichments despite the fact that these elements should also be strongly scavenged by fe mn oxyhydroxides this suggests that their lack of enrichment is a feature inherited from a solution initially poor in hfses the first two scenarios for varnish formation can be ruled out as follows the high enrichment factors of fe mn and many trace elements cannot be generated by mass loss associated with post depositional diagenesis of dust particles because such a process predicts only a small increase in concentration in addition the highly fractionated abundance patterns of particle reactive element pairs e g ce la and y ho rules out leaching of the rock substrate this is because if leaching were to occur varnishes would grow from the inside to the outside and thus any particle reactive trace element leached from the substrate would be quantitatively sequestered in the fe mn oxyhydroxide layers prohibiting any significant elemental fractionations one remaining possibility is that the fe mn and trace metals in varnish are derived from leaching of dust particles entrained in rain or fog droplets either in the atmosphere or during wet atmospheric deposition the high trace metal enrichment factors require that most of the dust was physically removed before or during varnish formation the remaining aqueous counterpart would be depleted in hfses and th relative to the rees co ni and pb because the former are more insoluble and hence largely retained in the removed dust fraction the high ce la ratios suggest that precipitation of trace metals may have been governed by equilibrium partitioning in an excess of wet atmospheric deposition if varnishes are indeed derived from wet atmospheric deposition they may provide a record of the aqueous component of atmospheric dust inputs to various environments

terminal pleistocene wet event recorded in rock varnish from las vegas valley southern nevada analyses of rock varnish samples from latest pleistocene alluvial fan surfaces in las vegas valley southern nevada reveal replicable lamination patterns that are characterized by low mn orange surface layers and high mn dark basal layers radiocarbon dating from beneath the sampled alluvial fan surfaces suggests that the mn rich basal layers accumulated during a short wet phase 10 11 14c ka when extensive black mats were deposited throughout the region and paleolake records in the great basin also indicate wet conditions during this time period in contrast the mn poor orange surface layers formed under relatively dry conditions in the holocene thus these varnish microlaminations are connected with environmental fluctuations that appear to be related to climate change evidence from las vegas valley together with that from death valley and the mojave desert suggests that the deposition of these mn rich dark basal layers in rock varnish likely corresponded in time to the terminal pleistocene younger dryas aged wet event in the great basin 2000 elsevier science b v all rights reserved

shallow seismic reflection study of a glaciated valley shallow seismic reflection data were recorded along two long 1 6 km intersecting profiles in the glaciated suhre valley of northern switzerland appropriate choice of source and receiver parameters resulted in a high fold 36 48 data set with common midpoints every 1 25 m as for many shallow seismic reflection data sets upper portions of the shot gathers were contaminated with high amplitude source generated noise e g direct refracted guided surface and airwaves spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source generated noise and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi continuous reflection zones the uppermost reflection zone at 20 to 50 ms 15 to 40 m depth originated from a boundary between

results of 2 and 3 d high resolution seismic reflection surveying of surficial sediments to investigate the potential of seismic reflection methods for studying surficial sediments 2 and 3 d high resolution surveys have been conducted across a plot of land adjacent to a landfill in northern switzerland results of the reflection profiling demonstrated that closely spaced common reflection points 2 5 m and high fold 12 data were prerequisites for producing clear images at this site for the 3 d survey an area of 115 160 m was covered with common reflection points every 2 5 2 5 m three dimensional migration of the resultant 18 to 70 fold data proved to be a critical step in correctly locating out of plane reflections and collapsing diffractions that were prominent features in the 2 d profile data within the 3 d data volume a conspicuous reflective zone and a marked decrease in reflection amplitudes at 200 m depth delineates the bedrock surface immediately above this level are continuous reflections from flat lying lacustrine sediments these are in turn overlain by regions of strong reflected energy interpreted as either large erratic blocks anomalous compaction zones or gravel channels lenses

effects of near surface waveguides on shallow high resolution seismic refraction and reflection data waveguides formed between the earth s free surface and sharp subsurface velocity discontinuities such as the watertable may have a significant impact on high resolution seismic refraction and reflection data energy trapped in such waveguides may propagate over long distances with little loss due to geometrical spreading the dispersive nature of the guided waves results in pronounced shingling of the first arrivals this narrows the optimum reflection window between the first arrivals and the ground roll and may lead to mispicking of first breaks and difficulties in identifying and processing shallow reflections

on the role of density and attenuation in three dimensional multiparameter viscoacoustic vti frequency domain fwi an obc case study from the north sea 3 d frequency domain full waveform inversion fwi is applied on north sea wide azimuth ocean bottom cable data at low frequencies 10 hz to jointly update vertical wave speed density and quality factor q in the viscoacoustic vti approximation we assess whether density and q should be viewed as proxy to absorb artefacts resulting from approximate wave physics or are valuable for interpretation in the presence of soft sediments and gas cloud fwi is performed in the frequency domain to account for attenuation easily multiparameter frequency domain fwi is efficiently performed with a few discrete frequencies following a multiscale frequency continuation however grouping a few frequencies during each multiscale step is necessary to mitigate acquisition footprint and match dispersive shallow guided waves q and density absorb a significant part of the acquisition footprint hence cleaning the velocity model from this pollution low q perturbations correlate with low velocity zones associated with soft sediments and gas cloud however the amplitudes of the q perturbations show significant variations when the inversion tuning is modified this dispersion in the q reconstructions is however not passed on the velocity parameter suggesting that cross talks between first order kinematic and second order dynamic parameters are limited the density model shows a good match with a well log at shallow depths moreover the impedance built a posteriori from the fwi velocity and density models shows a well focused image with however local differences with the velocity model near the sea bed where density might have absorbed elastic effects the fwi models are finally assessed against time domain synthetic seismogram modelling performed with the same frequency domain modelling engine used for fwi

three dimensional seismic reflection imaging of a shallow buried paleochannel a suite of reflection seismology investigations of the shallow subsurface was conducted at hill air force base ogden utah at a groundwater contamination site with very large subsurface mechanical heterogeneity the investigations were designed to expand and improve understanding of the subsurface environment developed from well data and previous seismic investigations the goal of the investigations was to image the sides and bottom of a paleochannel eroded in a clay layer 10 15 m below the surface the paleochannel is filled with a mix of sands clays and gravels of different compaction and water saturation the paleochannel acts as a contaminant trap for dense nonaqueous phase liquids dnapls therefore a detailed map of its geometry lateral boundaries and depth is crucial to remediation efforts the results of processing a 3d reflection data set over the channel showed that it is possible to image and delineate the geometry and depth of a very shallow structure seismic results agreed well with

how fast does rock varnish grow rates of rock varnish accumulation have never been systematically documented owing to the difficulty in accurately determining both varnish thickness and age in this study we quantitatively assess varnish accumulation rates through thin sectioning and microscopic examination of rock varnish from radiometrically dated geomorphic features of late quaternary age in the western united states drylands our data indicate that rock varnish grows at rates ranging from 1 to 40 m k y on subaerially exposed rock surfaces and rarely reaches a thickness exceeding 200 m regardless of age our data also indicate that varnish accumulation rates vary greatly from sample to sample at a given site suggesting that varnish thickness does not correlate with the age of the associated geomorphic feature invalidating the potential use of varnish thickness as a relative age indicator in geomorphology and archaeology nevertheless being the slowest known accumulating terrestrial sedimentary deposit rock varnish constitutes a unique long term microscale sedimentary archive of past environmental changes in deserts

microanalytical methods for in situ high resolution analysis of rock varnish at the micrometer to nanometer scale abstract a wide range of analytical techniques were used to investigate rock varnish from different locations negev israel knersvlakte south africa death valley and mojave desert california a 200 nm femtosecond laser ablation inductively coupled plasma mass spectrometer la icp ms an electron probe microanalyzer epma focused ion beam fib slicing and scanning transmission x ray microscopy near edge x ray absorption fine structure spectroscopy stxm nexafs this combination enables comprehensive high spatial resolution analysis of rock varnish femtosecond la icp ms and epma were used for quantitative determination of element concentrations in situ measurements were conducted on thick and thin sections with a resolution of 10 40 m and 2 m respectively the results demonstrate that some elements such as mn co pb ni and cu are highly enriched in varnish relative to the upper continental crust up to a factor of 100 the varnish composition is not influenced by the composition of the underlying rock which is witnessed by plots of mno 2 vs sio 2 contents furthermore the mn free end members fall in the range of average dust compositions the varnishes from the various locations show distinct differences in some elemental ratios in particular mn fe 0 3 25 1 mn ba 4 170 ni co 0 03 1 8 and pb ni 0 4 23 the rare earth element ree patterns vary with la n yb n 3 5 12 and different degrees of ce anomalies ce ce 1 5 5 3 to study the internal structure of the varnish 100 200 nm thick fib slices were prepared and mappings of fe mn n co 3 2 ca c and si at the nm scale performed banded internal structures of mn fe and organic c were observed in the israeli and californian samples however no fe rich layers are present in the south african rock varnish samples furthermore cavities were found that are partly filled by c fe and mn rich material internal structures are different for varnish from different locations which might reflect different types of genesis the results of the combined microanalytical techniques give important detailed insights towards unraveling the genesis of rock varnish

land streamer for shallow seismic data acquisition evaluation of gimbal mounted geophones to increase the speed and efficiency of shallow seismic data recording and thereby decrease acquisition costs the concept of a towed land streamer containing self orienting gimbal mounted geophones is being evaluated our initial experiments at two locations within switzerland demonstrate that good coupling with the ground may be achieved when the gimbal mounted vertical geophones are contained in heavy 1 kg casings and pulled along a very shallow 2 3 cm deep furrow such a furrow may be created by mounting a heavy wheel on the towing vehicle placing the geophones in even heavier casings may provide the necessary good coupling with the ground negating the need for the furrow shot gathers and stacked sections recorded with the gimbal mounted geophones are practically indistinguishable from those recorded with conventional spike geophones the principal advantage of this approach is that significantly fewer field personnel only two or three are required than for conventional shallow seismic surv

dating climatic change in hot deserts using desert varnish on meteorite finds abstract a thin coating of desert varnish occurs on forrest 009 and nurina 004 both equilibrated ordinary chondrite l6 finds from the nullarbor plain australia this finely laminated deposit is chemically and petrographically comparable to the varnish found on terrestrial rocks forrest 009 which has a terrestrial age of 5 9 kyr has a 100 130 m thick coating of desert varnish that has a laterally consistent chemical microstratigraphy comprising a narrow ba and mn poor lower region a thick ba and mn rich central area and a narrow outer zone almost devoid of both cations the interior of the meteorite contains fe oxide and oxyhydroxide veins that have formed by chemical weathering of metals and sulphides as these veins do not cross cut the varnish it must have accreted rapidly relative to the weathering rate of the meteorite the 70 m thick varnish on nurina 004 which has a terrestrial age of 33 4 kyr lacks a consistent chemical microstratigraphy but it is cross cut by fe oxide and oxyhydroxide veins some of which have supplied fe to the varnish this implies that the chemical weathering rate of nurina 004 s interior was slow in comparison to the accretion rate of the varnish the petrography and chemical composition of varnish on forrest 009 indicates that this meteorite may have resided in a relatively humid environment for most of its 5 9 kyr terrestrial history and that the nullarbor recently became more arid this conclusion supports results from an analysis of fe bearing weathering products in the interior of the meteorite by mossbauer spectroscopy which also indicate that forrest 009 experienced an early period of rapid weathering under relatively humid conditions the petrography of varnish on nurina 004 shows that the interior of the meteorite weathered relatively slowly probably because it fell during an arid time which is again in agreement with previous mossbauer spectroscopy results results from both meteorites are in agreement with palaeoclimate data derived from a number of other proxies the implications of this work are that the large number of meteorites that have been collected from several hot deserts of the world may be a powerful source of information on climate change over the last 30 35 kyr

multiple oxygen and sulfur isotopic analyses on water soluble sulfate in bulk atmospheric deposition from the southwestern united states 1 sulfate is a major component of bulk atmospheric deposition including dust aerosol fog and rain we analyzed sulfur and oxygen isotopic compositions of water soluble sulfate from 40 sites where year round dust traps collect bulk atmospheric deposition in the southwestern united states average sulfur and oxygen isotopic compositions 34s and 18o are 5 8 1 4 cdt and 11 2 1 9 smow n 47 respectively samples have an oxygen 17 anomaly 17o with an average value of 1 0 0 6 except for a weak positive correlation between 18o and 17o values r2 0 4 no correlation exists for 18o versus 34s 17o versus 34s or any of the three isotopic compositions versus elevation of the sample site exceptional positive 17o values up to 4 23 are found in samples from sites in the vicinity of large cities or major highways and near zero 17o values are found in samples close to dry lakes comparison of isotopic values of dust trap sulfate and desert varnish sulfate from the region reveals that varnish sulfate has average isotopic values that are 4 8 lower for 18o 2 1 higher for 34s and 0 3 lower for 17o than those of the present day bulk deposition sulfate although other factors could cause the disparity this observation suggests a possibility that varnish sulfate may have recorded a long term atmospheric sulfate deposition during the holocene or pleistocene as well as the differences between sulfur and oxygen isotopic compositions of the preindustrial bulk deposition sulfate and those of the industrial era

factors controlling tungsten concentrations in ground water carson desert nevada an investigation of a childhood leukemia cluster by us centers for disease control and prevention revealed that residents of the carson desert nevada are exposed to high levels of w and this prompted an investigation of w in aquifers used as drinking water sources tungsten concentrations in 100 ground water samples from all aquifers used as drinking water sources in the area ranged from 0 27 to 742 g l ground water in which w concentrations exceed 50 g l principally occurs se of fallon in a geothermal area the principal sources of w in ground water are natural and include erosion of w bearing mineral deposits in the carson river watershed upstream of fallon and possibly upwelling geothermal waters ground water in the fallon area is strongly reducing and reductive dissolution of fe and mn oxyhydroxides may be releasing w however direct evidence that the metal oxides contain w is not available although w and cl concentrations in the carson river a lake and water from many wells appear to be controlled by evaporative concentration evaporation alone cannot explain the elevated w concentrations found in water from some of the wells concentrations of w exceeding 50 g l are exclusively associated with na hco3na hco3 and na cl water types and ph 8 0 in these waters geochemical modeling indicates that w exhibits 10 adsorption tungsten concentrations are strongly and positively correlated with as b f and p indicating either common sources or common processes controlling their concentrations geochemical modeling indicates w concentrations are consistent with ph controlled adsorption of w the geochemical model phreeqc was used to calculate iap values which were compared with published ksp values for primary w minerals fewo4 mnwo4 na2wo4 and mgwo4 were undersaturated and cawo4 and srwo4 were approaching saturation these conclusions are tentative because of uncertainty in the thermodynamic data the similar behavior of as and w observed in this study suggests ground water in areas where elevated as concentrations are present also may contain elevated w concentrations particularly if there is a mineral or geothermal source of w and reducing conditions develop in the aquifer

mineral water interactions in tailings from a tungsten mine mount pleasant new brunswick abstract the pore water geochemistry and mineralogy of tailings derived from a granitic tungsten deposit were characterized by collecting pore water samples at discrete depth intervals throughout the tailings for the analysis of major and minor element concentrations mineralogical samples from the oxidation zone were analyzed by x ray diffraction scanning electron microscopy combined with energy dispersive x ray spectroscopy sem eds electron microprobe emp combined with wavelength dispersive x ray spectroscopy wds and transmission electron microscopy tem the oxidation of sulfide minerals in the near surface tailings leads to a decrease in pore water ph and elevated so 4 as and metal concentrations the unusual mineralogy of this deposit compared with that of commonly studied base metal and gold deposits results in several unique geochemical characteristics the dissolution of fluorite releases f into the pore water the f forms strong complexes with al and enhances the dissolution of aluminosilicate minerals within the oxidation zone as a result high al concentrations up to 151 7 mg l are detected in the near neutral pore water in the oxidation zone the combined dissolution of aluminosilicates and carbonate minerals maintains the ph near 10 in the pore water at depth elevated concentrations of w up to 7 1 mg l are detected in the pore water throughout the tailings likely as a result of the dissolution of wolframite consistent with geochemical model calculations results from sem eds emp wds and tem eds analyses indicate that secondary minerals which occur as orange brown coatings on grains of primary minerals are fe oxyhydroxides examples of these secondary minerals display a fibrous habit at high resolution in the tem one of these minerals which contains substantial amounts of al as and si as impurities was identified by selected area electron diffraction saed analyses to be goethite another mineral contains relatively high amounts of si pb bi and as and saed analyses suggest that the mineral is two line ferrihydrite

seismic reflection imaging of a geothermal aquifer in an urban setting a seismic reflection survey that was conducted in downtown boise idaho to help city planners site a new well for injection of spent geothermal water illustrates some methods to safely and successfully employ a seismic reflection survey in an urban setting the objective of the seismic survey was to estimate the depth and continuity of a basalt and rhyolite volcanic sequence well siting was based on geothermal aquifer depth location of interpreted faults projected thermal impact of injection on existing wells surface pipe extension costs and public land availability seismic acquisition tests and careful processing were used to ensure high quality data while minimizing the potential for damage along city streets a video camera placed in a sewer and a blast vibration monitor were used to confirm that energy from the seismic source a 75 in3 land air gun did not damage nearby buildings street surfaces or buried utilities along the survey lines walkaway seismic tests were also used to compare sign

minimizing field operations in shallow 3 d seismic reflection surveying by appropriately decimating a comprehensive shallow 3 d seismic reflection data set recorded across unconsolidated sediments in northern switzerland we have investigated the potential and limitations of four different source receiver acquisition patterns for the original survey more than 12 000 shots and 18 000 receivers deployed on a 3 3 m grid resulted in common midpoint cmp data with an average fold of 40 across a 322 5 420 0 m area a principal goal of our investigation was to determine an acquisition strategy capable of producing reliable subsurface images in a more efficient and cost effective manner field efforts for the four tested acquisition strategies were approximately 50 50 25 and 20 of the original effort all four data subsets were subjected to a common processing sequence static corrections top mute functions and stacking velocities were estimated individually for each subset because shallow reflections were difficult to discern on shot and cmp gathers generated with the

detailed images of the shallow alpine fault zone new zealand determined from narrow azimuth 3d seismic reflection data previous high resolution seismic reflection investigations of active faults have been based on 2d profiles unfortunately 2d data may be contaminated by out of the plane reflections and diffractions that may be difficult to identify and eliminate although full 3d seismic reflection methods allow out of the plane events to be recognized and provide superior resolution to 2d methods they are only rarely applied in environmental and engineering studies because of high costs a narrow azimuth 3d acquisition and processing strategy is introduced to produce a high resolution seismic reflection volume centered on the alpine fault zone new zealand the shallow 3d images reveal late quaternary deformation structures associated with this major transpressional plate boundary fault the relatively inexpensive narrow azimuth 3d acquisition pattern consisting of inline source and receiver lines was easily implemented in the field to provide 2 by 4 m cmp coverage over an approximately 500 by 200 m area the narrow

geochemical insights into the relationship of rock varnish and adjacent mineral dust fractions abstract rock varnishes are m thin dark manganese mn rich crusts that accrete in the order of few m ka on weathering resistant lithologies although these crusts can form in all climates they are best known in arid to semi arid settings aeolian dust is understood as a major contributor to the distinct trace metal and ree enrichments in rock varnish however the exact proportions of abiotic and biotic formation mechanisms that may explain the oxidation reactions of mn2 to mn4 present as mn oxyhydroxides in the varnish are still a matter of ongoing debate we present here the first systematic study of trace element enrichment processes between the uppermost layer of the varnish sequence and their adjacent 50 m dust fractions across a selection of 41 major and trace elements this approach is used to investigate samples from three fully arid deserts the an nafud in saudi arabia the negev in israel and the mojave in the usa which are compared to the significantly different environment of the semi arid knersvlakte in south africa a new in situ trace element analysis protocol was developed to perform femto and nanosecond sector field la icp ms microanalyses at high spatial resolution which allows us to measure the most recent varnish layers for their comparison with recent dust in agreement with previous studies all varnishes are enriched in mn pb ce co ba zn ni and the rare earth elements ree here we demonstrate that fine 50 m has low trace element mass fractions and enrichment patterns plotting distinctly away from varnish and fine dust based on these geochemical patterns our results indicate a general enrichment mechanism from fine dust to varnish previous studies suggested dust to play an integral role in providing the trace elements that are incorporated into the varnish by ph eh fluctuations in short term rain and fog events we amalgamate and refine previous growth models by providing direct evidence that leaching of about 10 of the mn and other trace elements from clay minerals in rain or fog droplets at ph 5 and subsequent scavenging on varnish surfaces at ph 8 leads integrated over time to the distinct enrichment patterns of the varnish while initial mn oxyhydroxide formation is suggested to follow pathways of metal oxide mediated photo catalysis for the semi arid occurrence in the knersvlakte we present a distinct growth model as both environment varnish and dust composition differ significantly from the arid settings here thick metallic looking varnish occurs mainly on the rim of quartz pebbles lacks microlamination and likely has upscaled growth processes among other aspects we suggest a more complex interplay between photo catalysis nocturnal condensation events on quartz pebbles with subsequent water trapping at the rock soil atmosphere interface due to a salic top soil layer to mainly account for these differences

anthropogenic lead as a tracer of rock varnish growth implications for rates of formation rock varnish is a thin dark coating best known from deserts and is believed to grow extremely slowly varnish samples from near socorro new mexico united states contain as much as 3 7 pbo derived from nearby smelters operating from a d 1870 to 1931 additional varnish measuring as much as 4 m beyond the pb rich layer indicates continued growth from 1931 to 2003 comparison with other varnish confirms that the pb is not an artifact based on pb layer thickness and the period of smelter operation these very young rock varnishes yield growth rates of 28 639 m k y substantially higher than previously documented fastest rates of 40 m k y these rates imply that the average 1 2 m k y rate for older varnish is not the active growth rate rather it is a long term value including periods of nondeposition erosion and active growth therefore models of rock varnish formation should be reevaluated with consideration of much faster maximum growth rates

seismic facies and regional architecture of the oak ridges moraine area southern ontario analysis of over 50 line kilometres of land based shallow seismic reflection profiles has provided a means of investigating the subsurface architecture and stratigraphic relationships of the glac

chronology of rock falls and slides in a desert mountain range case study from the sonoran desert in south central arizona abstract in order to respond to the general paucity of information on the chronology of ubiquitous small rock falls and slides that litter the slopes of desert mountain ranges a case study in the sonoran desert reveals new insight into the desert geomorphology of mountain slopes rock falls and rock slides in the mcdowell mountains that abut metropolitan phoenix usa fall in three chronometric groupings dated by conventional radiocarbon and rock varnish microlamination methods first the oldest events are 74 ka and take the form of stable colluvial boulder fields positive relief features that are tens of meters long and a few meters wide second randomly sampled slides and falls of various sizes and positions wasted during wetter periods of the terminal pleistocene and holocene third an anomalous clustering of slides and falls occurred during the late medieval warm period medieval climatic anomaly when an extreme storm was a possible but unlikely trigger one speculative hypothesis for the cluster of medieval warm period events is that a small to moderate sized earthquake shook heavily shattered bedrock close to failure just enough to cause a spate of rock falls and slides a second speculative hypothesis is that this dry period enhanced physical weathering processes such as dirt cracking however the reasons for the recent clustering of rock falls remain enigmatic while the temporal distribution of slides and falls suggests a minimal hazard potential for homes and roads on the margins of the mcdowell mountains this finding may not necessary match other desert ranges in metropolitan phoenix or mountains with different rock types and structures that abut other arid urban centers

sulfate oxygen 17 anomalies in desert varnishes rock varnishes are ubiquitous in arid regions on earth and are believed to be commonly present on mars here we report high water soluble sulfate and nitrate contents in desert varnishes from the death valley region of southwestern u s a and that sulfate in varnishes possess 17o 18o ratios that do not fall on terrestrial mass dependent fractionation line sulfate from wet and dry atmospheric deposition is probably the source of the 17o anomalies the anomalies are only moderately lower than that of aerosol sulfates collected from the greater los angeles area indicating probably more than half of the sulfate in desert varnish is supplied by atmospheric deposition this finding suggests that earth surface environments are constantly accumulating 17o anomalous sulfate from the atmosphere arid and stable conditions facilitate the preservation of these atmospheric signatures this finding also indicates that different 17o 18o ratios found in different components in the martian meteorites may result from atmospheric chemical processes

spatial temporal and geographic considerations of the problem of rock varnish diagenesis article i nfo the rock varnish literature hosts an abundance of prima facie contradictory empirical data past and perhaps future empirical contradictions however can be resolved by theoretical considerations of different spatial and temporal scales of varnish diagenesis as well as the geomorphic position of different types of varnishes for example twentieth century contamination by lead and other heavy metals has led to claims of accumulation rates in the last century far more rapid than prior published empirical studies a consideration of spatial scales resolves this contradiction nanoscale processes allow migration of lead into varnish deposited well before the twentieth century time of heavy metal pollution evidence of nanometer scale disequilibrium in three samples led to claims that varnish cannot be used in paleoclimatic research these data rest in contrast to replicable patterns in varnish deposition observed by dr tanzhuo liu and others in over ten thousand micro sedimentary basins this contraction can be resolved by understanding that the types of varnishes studied differ and that processes differ substantially between the nanoscale and the micron scale a lack of evidence of mn oxidizers in genetic analyses contrasts with culturing studies and in situ evidence of mn enhancement by bacteria this contradiction has a likely resolution in vastly different temporal scales dna material analyzed may be no older than 200 years but in situ fossilized remains of bacteria may be preserved for thousands of years recording palaeoecological conditions favoring growth of mn enhancing bacteria

shallow 3 d seismic reflection surveying data acquisition and preliminary processing strategies a comprehensive strategy of 3 d seismic reflection data acquisition and processing has been used in a study of glacial sediments deposited within a swiss mountain valley seismic data generated by a downhole shotgun source were recorded with single 30 hz geophones distributed at 3 m 3 m intervals across a 357 m 432 m area for most common midpoint cmp bins traces covering a full range of azimuths and source receiver distances of 2 to 125 m were recorded a common processing scheme was applied to the entire data set and to various subsets designed to simulate data volumes collected with lower density source and receiver patterns comparisons of seismic sections extracted from the processed 3 d subsets demonstrated that high fold 40 and densely spaced cmp bin sizes 3 m 3 m data with relatively large numbers 6 of traces recorded at short 20 m source receiver offsets were essential for obtaining clear images of the shallowest 100 ms reflecting horizons reflections rich in frequenci

design and application of a towed land streamer system for cost effective 2 d and pseudo 3 d shallow seismic data acquisition to reduce the field effort required for 2 d and 3 d shallow seismic surveying we have developed a towed land streamer system it was constructed with self orienting gimbal mounted geophones housed in heavy 1 kg cylindrical casings sturdy seismic cables with reinforced kevlar sheathing robust waterproof connectors and a reinforced rubber sheet that helped prevent cable snagging maintained geophone alignment and provided additional hold down weight for the geophones each cable had takeouts for 12 geophones at 1 m or 2 m intervals by eliminating the need for manual geophone planting and cable laying acquisition of 2 d profiles with this system proved to be 50 100 faster with 30 40 fewer personnel than conventional procedures costs of the land streamer system and total weight to be pulled could be minimized by employing nonuniform receiver configurations short receiver intervals e g 1 m at near offsets were necessary for identifying and mapping shallow 50 m reflections whereas larger re

diversity of rock varnish bacterial communities from black canyon new mexico 1 scientists vigorously debate the degree to which rock varnish is formed through the actions of microorganisms to investigate this enigma we utilized a three pronged approach that combined 1 culture independent molecular methods to characterize bacterial communities associated with varnish that coats the rhyolitic volcanic rocks of black canyon new mexico and rocks with no visible varnish 2 culturing of varnish in media supplemented with reduced forms of manganese and or iron and no or low amounts of carbon to isolate bacteria capable of precipitating iron and or manganese oxides and 3 scanning electron microscopy sem of varnish and nearby rock that lacks macroscopically visible varnish our culture independent studies revealed significant differences between varnish and nonvarnish communities chloroflexi and ktedobacteria dominated one varnish site while the other varnish site was dominated by cyanobacteria the nonvarnish sites were dominated by actinobacteria and to a lesser extent cyanobacteria and were the only samples to contain deinococcus thermus sequences approximately 65 of varnish cultures produced visible manganese precipitates most culture isolates were not closely related to known manganese oxidizers with the exception of bacillus spp sem revealed microbial morphologies and two types of varnish morphologies 1 relatively smooth layers and 2 patches of botryoidal pinnacles which were often associated with increased manganese concentrations bare rock showed evidence of incipient varnish these results have important implications for the detection of life on extraterrestrial planets such as mars where putative varnish coatings have been observed and represent some of the first culture independent characterizations of varnish communities

an in hole shotgun source for engineering seismic surveys we have conducted several source comparisons involving 12 gauge and 8 gauge buffalo guns a 7 3 kg sledgehammer and a 75 kg weight drop the results are strongly site dependent we found that when the near surface consisted of fine grained water saturated sediments the 12 gauge buffalo gun produced up to two orders of magnitude more energy than the conventional hammer across a broad frequency range under such conditions the gun produced the greatest improvement in energy between 200 and 400 hz where it yielded up to ten times more energy than the 75 kg weight drop this indicates that the buffalo gun may be particularly useful as a shallow reflection seismic source however at sites where the near surface materials were coarse grained and the water table was well below the ground surface the advantages of using an in hole shotgun source as opposed to a hammer or weight drop were minimal nevertheless in many areas we believe that the buffalo gun is an excellent source for engineering seismic surv

efficient acquisition processing and interpretation strategy for shallow 3d seismic surveying a case study a new 3d seismic reflection data set has been used to map the shallow subsurface beneath a key region of the swiss rhine valley seismic signals generated by a pipegun were recorded with single 30 hz geophones distributed across a 277 5 357 0 m area the dense distribution of sources and receivers resulted in a binning grid of 2 12 2 12 m and an average fold of 22 to improve the visibility and continuity of reflections a novel processing strategy was designed and applied to the acquired data a combination of regridding and sharing traces in the common midpoint cmp domain resulted in increased s n ratios with only minor loss of resolution this prestack interpolation method yielded composite cmps distributed on a 1 5 1 5 m binning grid and an increased average fold of 44 the composite cmps were subjected to a combined linear and hyperbolic p processing scheme that led to the effective separation of reflections from source generated noise finally 3d depth migration of the stacked data prod

thirty sixth canadian geotechnical colloquium advances in visualization of geotechnical processes through digital image correlation1 digital image correlation dic is an image processing technique that calculates fields of incremental displacement by comparing two digital images and locating numerous small regions in both image

factors controlling as and u in shallow ground water southern carson desert nevada abstract unusually high as and u concentrations 100 g l are widespread in shallow ground water beneath the southern carson desert the high concentrations which locally exceed 1000 g l are of concern from a human health standpoint because the shallow ground water is used for domestic supply possible affects on wildlife are also of concern because the ground water flows into shallow lakes and marshes within wildlife refuges arsenic and u concentrations in ground water of the southern carson desert appear to be affected by evaporative concentration redox reactions and adsorption the relation of these elements with cl suggest that most of the high concentrations can be attributed to evaporative concentration of carson river water the primary source of recharge some ground water contains higher as and u concentrations that cannot be explained by evaporative concentration alone oxidation reduction reactions involving metal oxides and sedimentary organic matter appear to contribute as u inorganic c fe and mn to the ground water arsenic in fe oxide was confirmed by chemical extraction and is consistent with laboratory adsorption studies uranium in both sedimentary organic c and fe oxide coatings has been confirmed by fission tracks and petrographic examination arsenic concentrations in the ground water and chemical extracts of aquifer sediments are broadly consistent with adsorption as a control on some dissolved as concentrations an apparent loss of as from some ground water as evaporative concentration proceeds is consistent with adsorption as a control on as however evidence for adsorption should be viewed with caution because the adsorption model used values for the adsorbent that have not been shown to be valid for the aquifer sediments throughout the southern carson desert hydrologic and geochemical conditions in the carson desert are similar to other areas with high as and u concentrations in ground water including the salton sea basin and southern san joaquin valley of california hydrologic and geochemical conditions that produced some sandstone type u ore deposits including those in the non marine closed basin sediments of the morrison formation near grants new mexico suggest that the carson desert may be a modern analog for those systems

a joint inversion algorithm to process geoelectric and surface wave seismic data part ii applications for the exploration of near surface structures seismic and geoelectric methods are often applied usually these two types of method give independently of each other a sufficiently exact model of the geological structure however sometimes the inversion of the seismic or geoelectric data fails these failures can be avoided by combining various methods in one joint inversion which feads to much better parameter estimations of the model than the independent inversions a suitable seismic method for exploring near surface structures is the use of dispersive surface waves the dispersive characteristics of rayleigh and love surface waves depend strongly on the structural and petrophysical seismic velocities features of the near surface underground geoelectric exploration of the structure underground may be carried out with the well known methods of dc resistivity sounding such as the schlumberger the radial dipole and the two electrode arrays the joint inversion algorithm is tested by means of synthetic data it is demonstrated that the geoelectric joint inversion of schlumberger radial dipole and two electrode sounding data yields more reliable results than the single inversion of a single set of these data the same holds for the seismic joint inversion of love and rayleigh group slowness data the best inversion result is achieved by performing a joint inversion of both geoelectric and surface wave data the effect of noise on the accuracy of the solution for both gaussian and non gaussian sparsely distributed large errors is analysed after a comparison between least square lsq and least absolute deviation lad inversion results the lad joint inversion is found to be an accurate and robust method

a new record of silica rich coating on carbonate substrates in southeast central iran constraints on geochemical signatures abstract there exist few data on the geochemical signatures and occurrence of silica rich coatings developed on siliceous carbonate substrates the rock coatings in the maran e galu area in southeast central iran are composed of four layers a lower thick layer 1 mm of silica a lower thin film of fe mn oxide an upper thick 1 mm silica rich layer and an upper thin film of fe mn oxide energy dispersive x ray spectrometer eds x ray diffraction and bulk coating geochemistry data obtained by xrf and icp ms highlight that the 1 3 mm thick silica rich coatings occur as a silica glaze of opal composition on the siliceous carbonate substrate the coatings were probably formed by the interaction of rainfall water vapor or dew with silicate and carbonate rich detrital atmospheric dust releasing h4sio4with a ph of 5 10 in this semiarid arid desert environment this led to the formation of silica gels as well as minor fe mn oxide gels by evaporation and supersaturation and finally changed to the black brown silica glaze probably at ambient temperatures of 40 c major and minor element signatures are consistent with the known silica glazes displaying enrichment in ba sr p and lrees with little to no eu and ce anomalies and a weak tm anomaly however the very low content of aluminum oxide is well correlated with the known classified silica glaze of genetic type 1 reflecting the absence of detrital clay minerals the low fe and mn contents in bulk coatings 3 6 and 10 magnitudes lower than crustal abundance respectively and lack of biochemical processes in the atmospheric dust highlight the semiarid arid climate setting we thereby conclude that a new variant of silica glaze of 1 3 mm thickness could form on siliceous carbonate substrates under an alkaline ph in semiarid arid regions

seismic reflection and ground penetrating radar imaging of a shallow aquifer in 1995 and 1996 researchers associated with the us air force s phillips and armstrong laboratories took part in an extensive geophysical site characterization of the groundwater remediation field laboratory located at dover air force base dover delaware this field experiment offered an opportunity to compare shallow reflection profiling using seismic compressional sources and low frequency ground penetrating radar to image a shallow unconfined aquifer the main target within the aquifer was the sand clay interface defining the top of the underlying aquitard at 10 to 14 m depth although the water table in a well near the site was 8 m deep cone penetration geotechnical data taken across the field do not reveal a distinct water table instead cone penetration tests show a gradual change in electrical properties that we interpret as a thick zone of partial saturation comparing the seismic and radar data and using the geotechnical data as ground truth we have associated the deepest coherent event in

a workshop examination of shallow seismic reflection surveying in september 1996 the office of basic energy sciences of the u s department of energy doe sponsored a research workshop in berkeley california where approximately 20 participants analyzed the potential and limitations of near surface seismic reflection methods

systematic mn fluctuations in laminated rock varnish developed on coeval early holocene flint artifacts along a climatic transect negev desert israel abstract this study presents an assessment of the potential application of mn content in rock varnish laminae as a paleoclimate indicator to investigate the environmental controls on varnish formation we determined mn composition in rock varnish formed on flint artifacts produced during the earliest holocene from eight coeval prehistoric sites in the negev desert israel these sites lie along a north south annual rainfall transect ranging between 120 and 30 mm yr 1 the varnish is 100 times enriched in mn relative to the content in the desert dust source material chemical profiles across the varnish display 4 6 distinct mn peaks in all sampled sites pointing to systematic fluctuations within the varnish along a wide range of environmental settings the mean mn contents in the various sites range between 10 7 and 15 6 at yet within this range the mn content in the negev varnish does not show a correlation with mean annual rainfall as moisture is needed for mn mobility wetting cycles by dew or light rain which are not adequately represented by the mean annual rainfall amounts but control the number of wetting drying cycles may explain the variance within the results from the arid and hyperarid negev varnish

architectural element analysis applied to glacial deposits internal geometry of a late pleistocene till sheet ontario canada deposits left by continental ice sheets are characterized by sedimentological complexity and stratigraphic heterogeneity but stratigraphic descriptions of such deposits and resulting first generation facies models are still based primarily on one or two dimensional borehole or outcrop data reconstruction of depositional environments hydrogeological investigations of pleistocene glacial deposits and hydrocarbon exploration in pre pleistocene glaciated basin fills require a more detailed understanding of the form and heterogeneity of lithofacies sequences in three dimensions architectural element analysis is used widely by sedimentologists for categorizing internal stratigraphic heterogeneity in sandstones particularly those of fluvial origin this paper demonstrates the first application of architectural element analysis to glacial deposits such as tills outcrop borehole and a broad range of subsurface geophysical data were collected from a thick 60 m till sheet present across an 80 km 2 study area near toronto canada the till sheet is not homogeneous but is composed of three distinct architectural elements and associated lithofacies viz diamict elements interbeds of subglaciofluvial sediments and glaciotectonically deformed zones application of architectural element analysis to these subglacial strata provides insights into the origin of drumlin bedforms and subglacial processes below the laurentide ice sheet and creates a framework for understanding ground water and contaminant movement in underlying aquifers

numerical study of seismic scattering and waveguide excitation in faulted coal seams finite difference p sv simulations of seismic scattering characteristics of faulted coal seam models have been undertaken for near surface p and s wave sources in an attempt to understand the efficiency of body wave to channel wave mode conversion and how it depends on the elastic parameters of the structure the synthetic seismograms clearly show the groups of channel waves generated at the fault one by the downgoing p wave and the other by the downgoing s wave these modes travel horizontally in the seam at velocities less than the s wavespeed of the rock a strong airy phase is generated for the fundamental mode the velocity contrast between the coal and the host rock is a more important parameter than the density contrast in controlling the amplitude of the channel waves the optimal coupling from body wave energy to channel wave energy occurs at a velocity contrast of 1 5 strong guided waves are produced by the incident s sources for source angles of 75 to 90 close to the near side face of the fault as the fault throw increases the amplitude of the channel wave also increases the presence of a lower velocity clay layer within the coal seam sequence affects the waveguiding characteristics the displacement amplitude distribution is shifted more towards the lower wavespeed layer the presence of a washout zone or a brecciated zone surrounding the fault also results in greater forward scattering and channel wave capture by the coal seam

debris flows from small catchments of the ma ha tuak range metropolitan phoenix arizona abstract debris flows debauch from tiny but steep mountain catchments throughout metropolitan phoenix arizona usa urban growth in the past half decade has led to home construction directly underneath hundreds of debris flow channels but debris flows are not recognized as a potential hazard at present one of the first steps in a hazard assessment is to determine occurrence rates the north flank of the ma ha tuak range just 10 km from downtown phoenix was selected to determine the feasibility of using the varnish microlaminations vml method to date every debris flow levee from 127 catchment areas only 152 of the 780 debris flow levees yielded vml ages in a first round of sampling this high failure rate is due to erosion of vml by microcolonial fungi the temporal pattern of preserved debris flow levees indicates anomalously high production of debris flows at about 8 1 ka and about 2 8 ka corresponding to northern hemisphere climatic anomalies because many prior debris flows are obliterated by newer events the minimum overall occurrence rates of 1 3 debris flows per century for the last 60 ka 2 2 flows century for the latest pleistocene and 5 flows century for the last 8 1 ka has little meaning in assessment of a contemporary hazard this is because newer debris flows have obliterated an unknown number of past deposits more meaningful to a hazards analysis is the estimate that 56 flows have occurred in the last 100 years on the north side of the range an estimate that is consistent with direct observations of three small debris flows resulting events from a january 18 22 2010 storm producing 70 mm of precipitation in the ma ha tuak range and a 500 m long debris flow in a northern metropolitan phoenix location that received over 150 mm of precipitation in this same storm these findings support the need for a more extensive hazard assessment of debris flows in metropolitan phoenix

rock varnish in the sonoran desert microbiologically mediated accumulation of manganiferous sediments rock varnish occurs in virtually all environments most commonly in arid and semi arid climates including antarctica rock varnish consists of thin layers of intimately mixed aeolian and chemical sediments often showing botryoidal and more rarely stromatolite like morphologies typical rock varnish samples collected at twin peak mountain park near phoenix arizona consist of abundant quartz with plagioclase illite and a mixed layer fe clay mineral probably corrensite eds sem bse and tem analyses revealed that the typical mn fe minerals occur as minute particles some of these particles and other mineral grains are attached to filaments xrd and electron diffraction showed that the mn fe bearing particles are poorly crystalline the filaments based on morphological criteria are virtually indistinguishable from fungal filaments most filaments are fragments probably broken by scraping during sample collection coccoid and rod shaped forms resembling cyanobacteria and other bacteria respectively are also present unlike definitive minerals these filaments disintegrated in the concentrated energy of the sem electron beam at the instrumental and experimental conditions used in addition no filamentous rod shaped or coccoid forms were observed in samples hydrolysed with 6 n hcl for 24 h at 100 c bacteria and fungi in powdered rock varnish were cultured on four media incubated aerobically in the dark at 25 c the culture media yielded dense growths of spore forming bacteria and filamentous fungi one fungus and two bacillus isolates oxidized and concentrated manganese control experiments revealed that fungi and bacteria are present on and below the surfaces of rock varnish free and hydrolysed peptide protein bound amino acids were identified in the rock varnish amino acids showed virtually no racemization with the exception of d l asp 0 1 relatively high molecular weight humic matter was also separated from the rock varnish high resolution mass spectrometry revealed non hydrocarbon moieties similar to a suwannee river fl humic acid standard micro organisms and their original biochemical compounds do not seem to be preserved for long in the accreting varnish layer the studies showed that the filaments helped to trap mineral particles of rock varnish and that bacteria and fungi abetted mn concentration some structures in the layers of rock varnish resemble stromatolites and present definitions would allow them to be termed as such

definition of subsurface stratigraphy structure and rock properties from 3 d seismic data abstract this paper summarizes how three dimensional 3 d seismic technology is being used primarily in the petroleum industry to define subsurface structure stratigraphy and rock properties a 3 d seismic data volume a provides a more accurate image of the subsurface than can be obtained with 2 d seismic methods b is continuous and so has a much greater spatial sampling than is obtained with 2 d seismic or other subsurface data e g wells and c can be viewed and interpreted interactively from a variety of perspectives thus enhancing the interpreter s ability to generate an accurate description of subsurface features of interest seismic interpretation was once the almost exclusive realm of geophysicists however most 3 d seismic interpretation today is conducted by multidisciplinary teams that integrate geophysical geological petrophysical and engineering data and concepts into the 3 d seismic interpretation these factors plus proper survey design help to increase the chances of success of a 3 d seismic interpretation project although there are cases where the technology is not appropriate or cannot be applied for economic reasons or otherwise the general success of 3 d seismic has led it to become a mainstay of the petroleum industry the approach and technology first developed in that industry have potential applications in other applied and fundamental earth science disciplines including mining environmental geology structural geology and stratigraphy

subglacial emplacement of tills and meltwater deposits at the base of overdeepened bedrock troughs the sedimentary infill of subglacially eroded bedrock troughs in the alps are underexplored archives for the timing extent and character of pleistocene glaciations but may contain excellent records of the quaternary landscape evolution over several glacial interglacial cycles the onset of sedimentation in these bedrock troughs is often reflected by diamicts and gravels directly overlying bedrock in the deepest basin segments subglacial or proglacial depositional environments have been proposed for these coarse grained basal units but their characteristics and origin remain controversial this article presents results from drill cores that recovered a coarse grained basal unit in a major buried bedrock trough system in the lower glatt valley northern switzerland the excellent core recovery allowed a detailed study combining macroscopic microscopic and geochemical methods and gives unprecedented insights into the transition from erosion to deposition in overdeepened bedrock troughs these results show that the basal infill comprises diamicts interpreted as subglacial tills separated by thin sorted interbeds originating from subglacial cavity deposition the stacking may thus represent repeated switching between a coupled and decoupled ice bed interface indicating an ever transforming mosaic of subglacial bed conditions decoupling in response to high basal water pressures is probably promoted by the confined subglacial hydraulic conditions resulting from the bedrock acting as aquitard the narrow reverse sloping outlet and a large catchment area while stratigraphic and lithological evidence suggests that erosion and the onset of basal sedimentation occurred during the same glaciation different scenarios for the relative timing of infilling in relation to formation and glaciation of the bedrock trough are discussed overlying deltaic and glaciolacustrine sediments suggest deposition during subsequent deglaciation of the bedrock trough the basal sediment characteristics are in agreement with previous reports in hydrogeological and seismic exploration and suggest the occurrence of similar basal successions in other subglacially overdeepened basin in the alps and elsewhere

surface and guided wave inversion for near surface modeling in land and shallow marine seismic data in several domains of applied geophysics surface and guided waves are considered as a source of information for characterizing the near surface which in a marine environment includes the seabed by contrast in exploration seismic surveys these waves have traditionally been regarded as coherent noise that should be filtered out as soon as possible the authors consider that surface and guided waves are not noise but a signal that can be lifted from the seismic record and exploited for a variety of well established geophysical solutions surface and guided waves constitute a large part of the recorded energy and with proper acquisition analysis and inversion they can be used to characterize the near surface with surprisingly high resolution in this role they can provide valuable information for tasks such as perturbation correction adjustment for near surface traveltime distortions they can also be used for velocity and geological modeling in this article the authors discuss a workflow for the a

high resolution integrated geophysical investigation at the lancaster gold mine krugersdorp south africa an integrated geophysical approach using seismics and geoelectrical techniques was employed to investigate the architecture of historic narrow reef workings and a proposed open pit mine at lancaster gold mine near krugersdorp south africa the mining activities in the area were mainly carried out within the kimberley reef package in the upper central rand group of the witwatersrand supergroup which hosts several gold bearing conglomerates locally known as reefs the reefs are generally thin 2 m thick and dip between 28 and 32 south the low velocity weathered layer introduces significant static shifts in the reflection seismic data moreover environmental noise from drilling and trucking and the prominent bedrock overburden contact that produces various wave conversions p s conversion caused undesirable noise that contaminates the shot gathers as high amplitude source generated and monochromatic noise the noise was removed from the shot gathers using frequency and velocity filtering techniques the final depth migrated sections are characterised by high resolution images of the subsurface from 10 to 150 m depth which are constrained by the borehole information the reflection seismic data delineate the interfaces between different rock layers and the stopes the refraction and resistivity tomograms on the other hand provide more detailed images of the top 20 50 m of the subsurface and depict the approximate shallow geometry of fluid migration paths mined out areas and bedrock overburden boundaries the integrated results indicate that the study area is characterised by a weathered surface layer with variable low p wave velocity 400 1200 m s and resistivity 150 800 m the deeper layer reveals an increase in resistivity and velocity and it s characterized by discontinuities weak zones cavities or water bearing zones due to the mining activities the combined borehole and geophysical data provide valuable information regarding the physical characteristics of the subsurface and can be helpful for future risk management decisions environmental and engineering studies in the area

3 d seismic imaging of complex structures in glacial deposits a small scale shallow penetration 3 d reflection seismic survey has been carried out over stratified glacial formations to test the method s potential for delineating fine structural details with a reasonable field effort and cost recording was carried out with a 96 channel engineering seismograph blank shotgun shells were used as the energy source field records were obtained with usable reflection energy up to 500 hz exploring approximately a 220 m cubical volume although special processing was required to attenuate strongly dispersed and scattered surface waves a stacked data volume of good quality has been assembled more than 15 reflecting horizons with vertical resolution of about 1 5 m were clearly delineated within the wisconsin sediments results are in good agreement with local outcrops and core information the identified reflectors interbeds within the late wisconsin tills are extremely important these reflectors may provide potential hydraulic channels for the movement of surface c

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

evidence for recent groundwater flow through late wisconsinan till near toronto ontario the northern till is a thick 50 m late winsconsinan diamict unit that occurs throughout south central ontario the till has generally been regarded as massive and uniform with a very low vertical hydraulic conductivity it is similar to many other till units of mid continental north american glaciated terrain in that it is believed to inhibit recharge to underlying aquifers and afford a high degree of protection to these aquifers from surface and near surface sources of contamination standard methods of estimating hydraulic conductivity k for the northern till such as laboratory testing of core samples other studies and rising falling head field piezometer tests this study and other studies characteristically yield values on the order of 10 11 to 10 9 m s typically these values indicate advective traveltimes through the till on the order of hundreds to thousands of years in contrast isotopic evidence 2h 18o and 3h from till pore waters indicates the presence of modern post 1952 wate

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

3 d high resolution reflection seismic imaging of unconsolidated glacial and glaciolacustrine sediments processing and interpretation shallow 3 d seismic reflection techniques have been used to map glacial deposits in a swiss mountain valley a dense distribution of source and receiver positions resulted in a small subsurface sampling of 1 5 m 1 5 m and a high fold of 40 common processing operations that included pseudotrue amplitude scaling deconvolution and band pass filtering successfully enhanced shallow reflections relative to source generated noise careful top muting helped avoid erroneous stacking of direct and guided waves azimuth dependent velocity analyses proved to be unnecessary three dimensional 3 d migration of the stacked data yielded the final high resolution images of the shallow subsurface 15 170 m because most reflections and diffractions were migrated to their correct subsurface locations confident interpretations of 3 d structures were possible time slices and cross sections along arbitrary directions proved to be powerful analysis tools even small scale features 20 m wide such as subglacial cha

guided waves in near surface seismic surveys much of the earth s surface is covered by a thin blanket of unconsolidated sediments or weathered bedrock boundaries within or at the base of this surficial layer e g watertable bedrock surface transition to unweathered rock are commonly associated with a strong seismic contrast layers contained between the surface and shallowest boundaries may be efficient waveguides and as such associated with significant source generated seismic noise whereas rayleigh waves groundroll can be described in terms of normal modes we demonstrate that the faster shingled guided waves can be explained in terms of leaking modes due to the relatively high poisson s ratios in the shallow subsurface guided waves are composed dominantly of multiply reflected p waves we compare our results with those obtained using a conventional acoustic waveguide approximation and discuss methods for extracting information from guided waves for geotechnical and environmental applications

shallow seismic surveying of an alpine rock glacier to map the internal structure and lower boundary of an alpine rock glacier we recorded three shallow seismic profiles and drilled four 70 m deep holes through to the underlying bedrock although analysis of the seismic data using standard reflection processing schemes did not yield conclusive results because of the dominantly low frequency returned signals and the presence of strong source generated noise tomographic inversions of first arrival times were successful in mapping several critical subsurface features a thin low velocity layer of loose boulders air voids and snow was found to extend across the entire surveyed area below this layer two distinct velocity regimes superimposed on a general increase in velocity with depth were identified a broad regime of high velocities was interpreted to contain boulders with numerous ice filled voids whereas an adjacent regime of relatively low velocities was explained in terms of boulders with air and water filled voids this latter region of degrad

shallow 3d seismic reflection imaging of fracture zones in crystalline rock a limited 3d seismic reflection data set was used to map fracture zones in crystalline rock for a nuclear waste disposal site study seismic reflection data simultaneously recorded along two roughly perpendicular profiles 1850 and 1060 m long and with a 400 x 400 m receiver array centered at the intersection of the lines sampled a 680 x 960 m 2 area in three dimensions high levels of source generated noise required a processing sequence involving surface consistent deconvolution which effectively increased the strength of reflected signals and a linear tau p filtering scheme to suppress any remaining direct sv wave energy a flexible binning scheme significantly balanced and increased the cmp fold but the offset and azimuth distributions remain irregular a wide azimuth range and offsets 800 m are only found at the edges of the site three dimensional dip moveout and 3d poststack migration were necessary to image events with conflicting dips up to about 40 degrees despite the irregular acquisition geometry and the high level of source generated noise we obtained images rich in structural detail seven continuous to semicontinuous reflection events were traced through the final data volume to a maximum depth of around 750 m previous 2d seismic reflection studies and borehole data indicate that fracture zones are the most likely cause of the reflections

manganese rich rock coatings from iceland manganese rich rock coatings are widespread in iceland especially in fractures in basalt lavas three common types of coating are described a thick subsurface coating is found on whaleback forms on high plateaux the most common type is thinner and occurs in hydrothermal clay filled fracture systems which are especially well developed in tholeiite lavas a third type occurs in younger rocks and is associated with tephra rich loessic sediment which fills open fractures and vesicles there are differences in the chemistry morphology and mineralogy of these coatings which are interpreted as being due to the different microenvironments in which they form the fracture microenvironment is regarded as being of much more importance to coating thickness and chemistry than simple age and in this respect the hydrothermal clays seem to favour rapid manganese concentration on the other hand there are variations in coating type both laterally and vertically through the lava succession which are related to regional distribution of hydrothermal alteration and rock type the regional patterns are the result of iceland s lateral drift and as a result there is an incidental connection between coating type and rock age there is some evidence to suggest that the manganese coatings may be both forming and being degraded rapidly in the present environment

manganese accumulation in rock varnish on a desert piedmont mojave desert california and application to evaluating varnish development abstract rock varnish coatings tend to become thicker darker and more continuous over time leading to the use of changes in overall varnish color and the percentage of clast surfaces covered by varnish as relative age indicators manganese is the most characteristic element of subaerial rock varnishes and the progressive development of varnish coats can be quantified by measuring the amount of mn accumulated on a given area of rock surface manganese oxides were dissolved off varnished clasts collected from alluvial surfaces on the soda mountains piedmont in the mojave desert california and the amount of mn was measured using inductively coupled plasma emission spectroscopy on the distal piedmont maximum varnish development increases from a mid to late holocene surface typically containing up to 0 15 mg cm2 of accumulated mn to an early to mid holocene surface with up to 0 21 mg cm2 however varnish is less developed on a nearby late pleistocene surface suggesting extensive abrasion of clasts on the pleistocene desert pavements or disturbance of the clasts varnish is better developed on the proximal piedmont typically containing up to 0 30 mg cm2 of mn although varnish from a pleistocene surface is again no better developed than from a nearby early to mid holocene surface these data demonstrate that rock varnish can show significant spatial variation in degree of development on geomorphic surfaces of similar age and imply that collecting varnish as old as a geomorphic surface may be difficult on surfaces as young as late pleistocene

direct major and trace element analyses of rock varnish by high resolution laser ablation inductively coupled plasma mass spectrometry la icpms laser ablation inductively coupled plasma mass spectrometry la icpms was used to determine major and trace element concentrations in rock varnish samples from the lahontan range near fallon nv and from a remote wilderness area near the san juan river in southeastern utah the data indicate that rapid la icpms analyses provide ample analytical resolution for semi quantitative compositional determinations of both trace and major elements in the varnish despite the presence of a rock substrate component in most analyses the overall major element contents of rock varnish from the two localities are grossly similar to rock varnish from other locations analyzed by solution icpms electron microprobe and energy dispersive scanning electron microscopy sem differences between microprobe and la icpms analyses may stem from different sampling scales and different degrees of substrate involvement it was possible to detect significant variations in trace element contents in the rock varnish samples the lahontan range is situated within a belt of w mineralization and varnish from that locality contained significantly higher w and mo contents than varnish from localities outside the w belt lead tl bi cd and as contents of varnish coated pebbles from near the san juan river in southeastern utah varied by an order of magnitude as a function of the position of the sampling site on the pebble elevated heavy element contents on the skyward facing varnish surfaces indicate that heavy elements may be preferentially scavenged at the locations most likely to receive direct inputs of atmospherically deposited airborne particulates the source of metal rich airborne particulates in this case is probably any one of several large coal fired power plants in the four corners region proximal to the san juan study area these patterns indicate that rock varnish chemistry is influenced by atmospherically derived fluxes of both dissolved and particulate constituents and that rock varnish can be used as a passive environmental indicator for a wide variety of elements in much the same manner as moss and lichens

bearing capacity of plane strain footings on layered soils a study has been carried out of the bearing capacity of sand layers overlying clay soils for the case where the thickness of the sand layer is comparable to the width of a rigid foundation placed on the soil surface a review of previous work is given and a discussion is presented of the dimensionless groups that govern the behaviour of this type of foundation a parametric study is carried out using both finite element and finite difference methods this study is based on the use of soil parameters obtained from an assessment of the range of values that might be expected to be appropriate for full scale structures the results of the parametric study are used to illustrate the mechanics of the system and also to develop charts that may be used directly in design in particular the results illustrate that the shear strength of the clay has an important influence on the mechanisms of load spread within the fill resume lion a roaliso une otude sur la capacito portante de couches de sable reposant sur des sols argileux pour le cas oo liopaisseur de la couche de sable est comparable la largeur diune fondation rigide posoe sur la surface du sol lion prosente une revue des travaux antorieurs et une discussion sur les groupes sans dimension qui rogissent le comportement de ce type de fondation une otude paramotrique est roalisoe en utilisant les mothodes tant des oloments finis que des difforences finies cette otude est fondoe sur liutilisation des paramtres de sols obtenus en partant de liovaluation de la plage des valeurs que lion pourrait siattendre trouver dans des structures pleine ochelle les rosultats de liotude paramotrique ont oto utilisos pour illustrer le mocanisme du systme et aussi pour dovelopper des abaques qui peuvent tre utilisoes directement dans la conception en particulier les rosultats illustrent que la rosistance au cisaillement de liargile a une influence importante sur les mocanismes de ropartition de la charge liintorieur du remblai mots clos capacito portante sols multicouches analyse numorique traduit par la rodaction

marine guided waves subbottom property estimation and filtering using physical modeling data abstractmarine guided waves are strongly dispersive and commonly observed in seismic surveys worldwide in areas of shallow water with a hard seafloor they are energetic and can obscure deeper reflection signals we have conducted several ultrasonic physical modeling experiments to observe marine guided waves the guided wave dispersion curves from these surveys fit theoretical calculations very well we next developed a new method to extract the subbottom s wave velocity and density from water column guided waves using least squares inversion we have also developed a dispersion curve filter in the velocity frequency domain to attenuate the guided waves we then applied these techniques to the physical modeling data which have different water depths and different subbottom materials the extracted results s wave velocity density and water depth match the actual values well the dispersion domain filter clarifies reflections by attenuating the guided waves which benefits further processing and int