experiencing new perspectives in the application of reflectance spectroscopy in loess research abstract diffuse reflectance spectroscopy drs parameters such as the redness index and hematite goethite ratios are popular in the study of loess paleosol sequences the suggested parameters however have their limitations only some parts of the whole reflectance spectrum are being used and the spectra of some important components may be excluded from the analysis a mathematical statistical method hierarchical cluster analysis was applied to the loess paleosol succession at mala nad hronom slovak republic in order to characterize the entire reflectance spectrum and to classify sediment groups the sedimentary units were classified into seven different cluster groups such as sediments weak and well developed paleosols the distribution of the spectral features in the reflectance spectra was located by using the key wavelength provided by the wilk s lambda analysis the key minerals which play an important role in the classification were determined by characteristic extrema in the second derivative of reflectance spectra of the seven reference minerals hematite goethite muscovite illite montmorillonite kaolinite and calcite mineral groups influence certain wavelengths within the measured range therefore curve sections modified by individual minerals only in a few cases the mentioned mineral groups refer to characteristics of the formation environment and to climate change during the pleistocene

reflectivity modeling of a ground penetrating radar profile of a saturated fluvial formation major horizons in radar reflection profiles may correlate with contacts between stratigraphic units or with structural breaks such as fault surfaces minor reflections may be caused by clutter or in some cases may indicate material properties or structure within stratigraphic units in this study we examine the physical basis for major and minor reflections observed in a shallow unconfined fluvial aquifer near boise idaho u s a we compare a 2d profile from a surface ground penetrating radar reflection transect with the 1d modeled reflection profiles at three wells adjacent to the surface reflection profile the 1d models are based on dielectric constant and electrical conductivity values from borehole logs and vertical radar profile data reflections at the water table capillary fringe at the base of a sand filled channel and at the base of two sand rich lenses in a cobble dominated unit are recognizable in the surfacereflection profile and in all 1d reflectivity models less prominent reflections in stratigraphic units occur in both the surface profile model and the reflectivity model although such minor reflections are not correlated easily general similarities in their presence and location indicate that sometimes the reflections may be useful for recognizing internal facies structure or character

a bayesian approach for inversion of hydraulic tomographic data 1 hydraulic tomography is a promising methodology that shows the potential to map subsurface hydraulic properties at an unprecedented level of detail by interpreting a suite of hydraulic tests in the present work we apply the hydraulic tomography concept to a multiple pulse multiple receiver mpmr cross well configuration which consists of two boreholes subdivided into intervals by packers a short pressure or flow pulse is applied sequentially to all the intervals and for each perturbation the transient heads are recorded at the remaining intervals the resulting tomograms are inverted within the bayesian framework by using the pilot point approach in addition to the values of the hydraulic conductivity at the pilot points we assume that the stochastic parameters of the spatial variability model the structural parameters are unknown using synthetic two dimensional and three dimensional examples we demonstrate the effectiveness of the mpmr configuration and the inversion procedure for characterizing the spatial variability of the hydraulic conductivity with limited or no prior information we observed that increasing the number of source points the locations at which the pulse is alternatively applied provides more details on the spatial variability and that the parameters of the hydrogeological model of spatial variability are inferred with an acceptable although variable level of accuracy in particular the theoretical variance of the log conductivity is estimated with large errors while the estimate of the anisotropic integral scales depends on the distance between the boreholes inversion preserves the overall spatial pattern of hydraulic conductivity although low conductivity values are less connected in the inferred than in the true conductivity fields

quaternary surface processes indicated by the magnetic fabric of undisturbed reworked and fine layered loess in hungary abstract statistical analytical methods were applied to classify the magnetic fabric of samples from different hungarian loess profiles a previous study of the anisotropy of magnetic susceptibility ams of hungarian loess suggested that typical wind blown or undisturbed and redeposited loess were well differentiated by known statistical methods the analyses of new samples require a review of previous results and the terms like typical wind blown reworked and redeposited loess the type of magnetic fabric of fine layered loess is classified by a new mathematical method in ams study of loess hierarchical cluster analysis the following quaternary surface processes were revealed by characteristics of the magnetic fabric of hungarian loess the primary magnetic fabric preserves the possible transport or accumulation direction of dust direction of maximum susceptibility ne sw axis and the structure of the fabric was affected by compaction in the case of loess the deviation of the inclination from vertical indicates the accumulation of dust on a sloping surface the secondary magnetic fabric fabric of the material after reworking or redeposition of loess shows the magnetic fabric characteristics of reworked or redeposited material scattered values of the principal susceptibilities indicate the effect of bioturbation redeposition fine layered loess samples is indicated by the alignment of the direction of maximum and intermediate susceptibilities on a stereographic plot and the degree of alignment possibly indicates the energy of the surface process lower or higher degree of energy connected to different kind of surface process can produce different kind of magnetic fabric the magnetic mineralogy of the pilot samples is determined by isothermal remanent magnetisation irm measurements no differences between loess samples with different sedimentary structure could be shown the dominant phase in the magnetic fabric that determined the magnetic character of samples was magnetite maghemite

identification of groundwater basin shape and boundary using hydraulic tomography abstract shapes and boundary types of a groundwater basin play essential roles in the analysis of groundwater management and contaminant migration hydraulic tomography ht a recently developed new approach for high resolution characterization of aquifers is not only an inverse method but a logical strategy for collecting non redundant hydraulic information in this study ht was applied to synthetic 2 d aquifers to investigate its feasibility to map the irregular shapes and types of the aquifer boundaries we first used the forward model of vsaft2 to simulate hydraulic responses due to ht surveys in the aquifer with irregular geometry and predetermined constant head conditions at some boundaries and no flow conditions at others the simsle simultaneous successive linear estimator inverse model in vsaft2 was then used to interpret the simulated ht data to estimate the spatial distribution of hydraulic properties of the aquifer using a domain with a wrong geometry surrounded by boundaries of a constant head condition the inverse modeling experiment used steady state and transient states data from the ht forward simulations and it used the same monitoring network as in the aquifer with irregular geometry to assess the ability of ht for detecting types and shapes of the boundary as well as heterogeneity in the aquifer results of the experiment show that no flow boundaries which were incorrectly treated as constant head boundaries in inverse models were portrayed as low permeable zones of the aquifer near the boundaries overall the results show that ht could delineate not only the irregular shape of the aquifer in general but also heterogeneity in the aquifer improvements of the estimation with prior information of transmissivity and storage coefficient was also investigated the study shows that using homogeneous initial guess parameters resulted in a slightly better estimate than others moreover this study employs monte carlo simulations to ensure statistically meaningful conclusions

the record of changing hematite and goethite accumulation over the past 22 myr on the chinese loess plateau from magnetic measurements and diffuse reflectance spectroscopy 1 high field isothermal remanence hirm and diffuse reflectance spectroscopy drs wereusedto characterize hematite and goethite in a suite of bulkand particle sized fractioned samples from the chinese loess plateau representing the main changes in magnetic mineralogy over the past 22 myr the record of drs defined hematite largely reflects variations in the pedogenic fraction 8 mm makes the main contribution to goethite concentrations in the bulk samples pedogenic goethite concentrations generally vary inversely with those of hematite the lack of consistent correlations between hirm inferred mineral content and drs measurements casts doubt on the validity of using hirm to characterize the concentrations and relative proportions of hematite and goethite in sediments representing a long time span or a wide grain size distribution the progressive decline in the coercivity of the antiferromagnetic minerals in bulk samples throughout the whole period is mainly an expression of changes in the detrital fraction reflecting changes in the source region possibly involving increased aluminum substitution the good correlation between drs defined hematite and frequency dependent magnetic susceptibility in several chronologically defined subgroups of samples is consistent with the hypothesis that maghemite forms a transitional phase in a weathering sequence from ferrihydrite to hematite the results shed new light on using hirm to characterize hematite and goethite in sediments and on the history of weathering and climate change over the past 22 myr in the dust source regions and on the loess plateau

aquifer heterogeneity characterization with oscillatory pumping sensitivity analysis and imaging potential 1 periodic pumping tests in which a fluid is extracted during half a period then reinjected have been used historically to estimate effective aquifer properties in this work we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation and responses are analyzed through inverse modeling using a steady periodic model formulation we refer to this strategy as multifrequency oscillatory hydraulic imaging oscillating pumping tests have several advantages that have been noted including no net water extraction during testing and robust signal measurement through signal processing through numerical experiments we demonstrate additional distinct advantages that multifrequency stimulations have including 1 drastically reduced computational cost through use of a steady periodic numerical model and 2 full utilization of the aquifer heterogeneity information provided by responses at different frequencies we first perform fully transient numerical modeling for heterogeneous aquifers and show that equivalent results are obtained using a faster steady periodic heterogeneous numerical model of the wave phasor the sensitivities of observed signal response to aquifer heterogeneities are derived using an adjoint state based approach which shows that different frequency stimulations provide complementary information finally we present an example 2 d application in which sinusoidal signals at multiple frequencies are used as a data source and are inverted to obtain estimates of aquifer heterogeneity these analyses show the different heterogeneity information that can be obtained from different stimulation frequencies and that data from several sinusoidal pumping tests can be rapidly inverted using the steady periodic framework

hydraulic partitioning tracer tomography for characterization of dense nonaqueous phase liquid source zones 1 a new technology hydraulic partitioning tracer tomography hptt is proposed to survey spatial distributions of hydraulic properties and dense nonaqueous phase liquids dnapls in the subsurface hptt is nothing more than a set of multiple hydraulic partitioning tracer tests and synthesis of all the tests to map the spatial distributions it involves injection of water at one borehole in a source zone to create a steady state forced gradient flow field then release of conservative partitioning tracers at the same borehole and monitoring heads and tracer breakthroughs at the others the same operation is repeated using different boreholes for the water and the tracer injections to analyze the head and tracer data obtained from the proposed tomographic survey a joint stochastic estimator was developed numerical experiments were then conducted to evaluate the effectiveness of hptt as well as the stochastic estimator results show that prior knowledge of hydraulic heterogeneity is critical for mapping the distribution of dnapls in addition the results suggest that the proposed hptt in conjunction with the stochastic estimator is potentially a viable tool for high resolution characterization of subsurface heterogeneity and contamination

color reflectance of chinese loess and its implications for climate gradient changes during the last two glacial interglacial cycles 1 to examine the relationship between color changes of loess deposits and paleoclimate conditions a north south transect consisting of twelve loess sections were studied color reflectance was measured on loess paleosol samples from the loess transect which accumulated over the last two glacial interglacial cycles the redness value a shows an overall southward increase for both loess and soil units coinciding with the pattern of a southerly increase in pedogenic development and the present north south climatic gradient the redness of loess deposits is linearly correlated with latitude values implying that this parameter is an efficient proxy for the weathering intensity of loess deposits the gradient of weathering intensity is much steeper during interglacials than in glacials by comparison of color records for different time interval

improved predictions of saturated and unsaturated zone drawdowns in a heterogeneous unconfined aquifer via transient hydraulic tomography laboratory sandbox experiments summary interpretation of pumping tests in unconfined aquifers has largely been based on analytical solutions that disregard aquifer heterogeneity in this study we investigate whether the prediction of drawdown responses in a heterogeneous unconfined aquifer and the unsaturated zone above it with a variably saturated groundwater flow model can be improved by including information on hydraulic conductivity k and specific storage s s from transient hydraulic tomography tht we also investigate whether these predictions are affected by the use of unsaturated flow parameters estimated through laboratory hanging column experiments or calibration of in situ drainage curves to investigate these issues we designed and conducted laboratory sandbox experiments to characterize the saturated and unsaturated properties of a heterogeneous unconfined aquifer specifically we conducted pumping tests under fully saturated conditions and interpreted the drawdown responses by treating the medium to be either homogeneous or heterogeneous we then conducted another pumping test and allowed the water table to drop similar to a pumping test in an unconfined aquifer simulations conducted using a variably saturated flow model revealed 1 homogeneous parameters in the saturated and unsaturated zones have a difficult time predicting the responses of the heterogeneous unconfined aquifer 2 heterogeneous saturated hydraulic parameter distributions obtained via tht yielded significantly improved drawdown predictions in the saturated zone of the unconfined aquifer and 3 considering heterogeneity of unsaturated zone parameters produced a minor improvement in predictions in the unsaturated zone but not the saturated zone these results seem to support the finding by mao et al 2011 that spatial variability in the unsaturated zone plays a minor role in the formation of the s shape drawdown time curve observed during pumping in an unconfined aquifer

3 d transient hydraulic tomography in unconfined aquifers with fast drainage response we investigate through numerical experiments the viability of three dimensional transient hydraulic tomography 3dtht for identifying the spatial distribution of groundwater flow parameters primarily hydraulic conductivity k in permeable unconfined aquifers to invert the large amount of transient data collected from 3dtht surveys we utilize an iterative geostatistical inversion strategy in which outer iterations progressively increase the number of data points fitted and inner iterations solve the quasilinear geostatistical formulas of kitanidis in order to base our numerical experiments around realistic scenarios we utilize pumping rates geometries and test lengths similar to those attainable during 3dtht field campaigns performed at the boise hydrogeophysical research site bhrs we also utilize hydrologic parameters that are similar to those observed at the bhrs and in other unconsolidated unconfined fluvial aquifers in addition to estimating k we test the ability of 3dtht to estimate both average storage values specific storage ss and specific yield sy as well as spatial variability in storage coefficients the effects of model conceptualization errors during unconfined 3dtht are investigated including 1 assuming constant storage coefficients during inversion and 2 assuming stationary geostatistical parameter variability overall our findings indicate that estimation of k is slightly degraded if storage parameters must bemore jointly estimated but that this effect is quite small compared with the degradation of estimates due to violation of structural geostatistical assumptions practically we find for our scenarios that assuming constant storage values during inversion does not appear to have a significant effect on k estimates or uncertainty bounds less

morphology and distribution of fossil soils in the permo pennsylvanian wichita and bowie groups north central texas usa implications for western equatorial pangean palaeoclimate during icehouse greenhouse transition analysis of stacked permo pennsylvanian palaeosols from north central texas documents the influence of palaeolandscape position on pedogenesis in aggradational depositional settings palaeosols of the eastern shelf of the midland basin exhibit stratigraphic trends in the distribution of soil horizons structure rooting density clay mineralogy and colour that record long term changes in soil forming conditions driven by both local processes and regional climate palaeosols similar to modern histosols ultisols vertisols inceptisols and entisols all bearing morphological mineralogical and chemical characteristics consistent with a tropical humid climate represent the late pennsylvanian suite of palaeosol orders palaeosols similar to modern alfisols vertisols inceptisols aridisols and entisols preserve characteristics indicative of a drier and seasonal tropical climate throughout the lower permian strata the changes in palaeosol morphology are interpreted as being a result of an overall climatic trend from relatively humid and tropical moist conditions characterized by high rainfall in the late pennsylvanian to progressively drier semi arid to arid tropical climate characterized by seasonal rainfall in early permian time based on known late palaeozoic palaeogeography and current hypotheses for atmospheric circulation over western equatorial pangea the pennsylvanian palaeosols in this study may be recording a climate that is the result of an orographic control over regionalscale atmospheric circulation the trend towards a drier climate interpreted from the permian palaeosols may be recording the breakdown of this preexisting orographic effect and the onset of a monsoonal atmospheric circulation system over this region

validation of hydraulic tomography in an unconfined aquifer a controlled sandbox study in this study we demonstrate the effectiveness of hydraulic tomography ht that considers variably saturated flow processes in mapping the heterogeneity of both the saturated and unsaturated zones in a laboratory unconfined aquifer the successive linear estimator sle developed by mao et al 2013c for interpreting ht in unconfined aquifers is utilized to obtain tomograms of hydraulic conductivity k specific storage ss and the unsaturated zone parameters pore size parameter and saturated water content s for the gardner russo s model the estimated tomograms are first evaluated by visually comparing them with stratigraphy visible in the sandbox results reveal that the ht analysis is able to accurately capture the location and extent of heterogeneity including high and low k layers within the saturated and unsaturated zones as well as reasonable distribution patterns of and s for the gardner russo s model we then validate the estimated tomograms through predictions of drawdown responses of pumping tests not used during the inverse modeling effort the strong agreement between simulated and observed drawdown curves obtained by pressure transducers and tensiometers demonstrates the robust performance of ht that considers variably saturated flow processes in unconfined aquifers and the unsaturated zone above it in addition compared to the case using the homogeneous assumption ht results as expected yield significantly better predictions of drawdowns in both the saturated and unsaturated zones this comparison further substantiates the unbiased and minimal variance of ht analysis with the sle algorithm

different paleoenvironments of late pleistocene age identified in verőce outcrop hungary preliminary results abstract complex geomorphological geological paleopedological and chronometrical investigations were started to reveal the development of the alluvial section and the loess paleosol sequence containing remnants of a late palaeolithic site near ver ce hungary different paleoenvironments were identified in the profiles of the abandoned brickyard influenced by different facies in the margin of fluvial alluvial palaeo danube and proluvial southeast pediment of borzsony mountain area and the environments affected by the climate fluctuation of late pleistocene loess paleosol sequence overlying the base of alluvial materials sediments possibly deposited by palaeo danube were identified in a basal section of the abandoned brickyard the alluvial facies was indicated by sand silt and clay layers in the sediment sequence some parts of the alluvial sediments were covered by loess in the glacial periods intercalated by four paleosol horizons formed during interglacial or interstadial periods the sedimentation of loess and the forming of paleosols were finished by pedimentation processes sheet wash redeposition indicated by the fine layered material at the top of each paleosol horizon another complex fluvial alluvial section was identified at a different part of the brickyard possibly developed synchronous with the loess paleosol sequence during the late pleistocene based on relative and chronometrical dating methods e g archaeological stratigraphy and correlation of the artifacts 14c and luminescence dating the development of the loess paleosol sequence started in marine isotope stage 6 mis6 and the youngest layer dated to mis2

aquifer imaging with pressure waves evaluation of low impact characterization through sandbox experiments understanding the detailed spatial variation of hydraulic properties in the subsurface has been the subject of intensive research over the past three decades a recently developed approach to characterize subsurface properties is hydraulic tomography in which a series of pumping tests are jointly inverted using a heterogeneous numerical model recently cardiff et al 2013 proposed a modified tomography approach named oscillatory hydraulic tomography oht in which periodic pumping signals of different frequencies serve as the aquifer stimulation and pressure responses are recorded at observation locations for tomographic analysis its key advantages over traditional hydraulic tomography are that 1 there is no net injection or extraction of water and 2 the impulse an oscillatory signal of known frequency is easily extracted from noisy data however oht has only been evaluated through numerical experiments to date in this work we evaluate oht performance by attempting to image known heterogeneities in a synthetic aquifer an instrumented laboratory sandbox is filled with material of known hydraulic properties and we measure aquifer responses due to oscillatory pumping stimulations at periods of 2 5 10 and 20 s pressure oscillation time series are processed through fourier transforms and inverted tomographically to obtain estimates of aquifer heterogeneity using a fast steady periodic groundwater flow model we show that oht is able to provide robust estimates of aquifer hydraulic conductivity even in cases where relatively few pumping tests and observation locations are available the use of multiple stimulation frequencies is also shown to improve imaging results

clay minerals and their paleoenvironmental interpretation in the baoji loess section southern loess plateau china abstract clay minerals from the loess paleosol section at baoji in north central china were studied by x ray diffraction major components calculated by comparing major peak heights were estimated as follows illite 55 75 kaolinite 10 25 mixed layer chlorite vermiculite 10 20 chlorite

characterizing subsurface hydraulic heterogeneity of alluvial fan using riverstage fluctuations strategic environmental research and development program serdp er 1365 environmental security and technology certification program estcp er201212 nsf ear from the united state 1014594 jilin university from department of education china global expert award through tianjin normal university from the thousand talents plan of tianjin city from china taiwan typhoon and flood research institute national applied research laboratories natural science foundation of china 51409029

mineralogic and climatic interpretations of the luochuan loess section china based on diffuse reflectance spectrophotometry we examined the top 135 m that is the entire pleistocene of the classic luochuan section on the chinese loess plateau with a diffuse reflectance spectrophotometer from the near ultraviolet through the visible and into the near infrared from the reflectance data we calculated sample brightness which with some caveats is a reasonable proxy for magnetic susceptibility mineralogic changes were identified by factor analyzing the first derivative of the percent reflectance data and examining samples with high factor scores two factors which explain about 96 of the cumulative variance are distinguished by the relative proportion of hematite and goethite the minerals that are responsible for the color changes in the loess sequence both hematite and goethite are present in both loess and paleosol but goethite dominates in loess whereas hematite dominates in paleosol the goethite factor exhibits an inverse correlation with magnetic susceptibility the hematite factor exhibits a weak positive correlation with susceptibility paleoclimatic interpretations are drawn from comparison of susceptibility to the concentration of spectrally identified hematite based on this comparison paleosols in the early pleistocene wucheng formation are characterized by conditions that are drier than today a dry summer monsoon whereas later pleistocene paleosols are characterized by a wet summer monsoon

a field assessment of high resolution aquifer characterization based on hydraulic travel time and hydraulic attenuation tomography 1 in this study the potential of an inversion approach based on hydraulic travel time and hydraulic attenuation tomography was assessed both hydraulic travel time and hydraulic attenuation tomography are based on the transformation of the transient groundwater flow equation into the eikonal equation using an asymptotic approach the eikonal equation allows the calculation of pressure propagation and attenuation along trajectories which is computationally efficient the attenuation and travel time based inversion approaches are naturally complementary hydraulic travel times are determined by the hydraulic diffusivity a combination of hydraulic conductivity and specific storage whereas the attenuation is determined solely by specific storage the potential of our hydraulic tomographical approach was investigated at a well characterized sand and gravel aquifer located in the leine river valley near gottingen germany the database for the hydraulic inversion consists of 392 cross well slug interference tests performed between five wells in which the positions of the sources injection ports and the receivers observation ports isolated with double packer systems were varied between tests the results have shown that the combination of hydraulic travel time and hydraulic attenuation tomography allows the reconstruction of the diffusivity and storage distribution in two and three dimensions with a resolution and accuracy superior to that possible with type curve analysis

changing color of chinese loess geochemical constraint and paleoclimatic significance abstract two loess paleosol sequences on the central chinese loess plateau were investigated to understand spatial and temporal variations in the soil color e g lightness and redness and factors that control those variations color difference between the original samples and pretreated samples suggests that loess lightness is influenced by the pedogenic matter e g iron oxides organic matter and calcium carbonate to varying degrees depending on the concentrations iron oxides and organic matter darken the loess lightness whereas carbonate lightens the loess lightness by contrast the redness is dominantly controlled by the types and concentrations of iron oxides variations in magnetic susceptibility and redness are associated with different magnetic minerals that formed mainly during post depositional processes and therefore both proxies can be employed to reconstruct the history and variability of the east asian summer monsoon since the sensitivity of these two proxies to the summer monsoon variation is different we generate a stacked summer monsoon index by combining these two records and interpret the stacked index as most indicative of precipitation variability the fidelity of this new index is supported by an independent ratio estimated from the first derivative values of the color reflectance spectra our loess based proxies provide a new understanding of the east asian summer monsoon variability as a two phase strengthening of summer monsoon intensity during the penultimate deglaciation

high resolution hematite and goethite records from odp 1143 south china sea co evolution of monsoonal precipitation and el nino over the past 600 000 years abstract precipitation has a larger variability than temperature in tropical monsoon regions thus it is an important climate variable however reconstructions of long term rainfall histories are scarce because of the lack of reliable proxies here we document that iron oxide minerals specifically the ratio of hematite to goethite hm gt is a reasonable precipitation proxy using diffuse reflectance spectrophotometry we measured samples from ocean drilling program odp 1143 drilling site 9 21 72 n 113 17 11 e 2777 m water depth for hematite and goethite whose formation processes are favored by opposing climate conditions in order to determine the content of hematite and goethite we produced a set of calibration samples by removing the iron oxides to generate the natural matrix to which hematite and goethite in known percentages were added from these calibration samples we developed a transfer function for determining hematite and goethite concentration from a sample s spectral reflectance applying this method to odp 1143 sediments top 34 m of a 510 m core with sampling interval of 10 cm we were able to reconstruct a continuous precipitation history for se asia of the past 600 kyr using the hm gt ratio as a proxy of the precipitation variability of asian monsoon the reliability of this hm gt proxy is corroborated by its consistency with the stalagmite 18o data from south china comparing long term hm gt records with the surface temperature gradient of equatorial pacific ocean we found that monsoon precipitation and el nino are correlated for the last 600 kyr the development of el nino like conditions decreased se asia precipitation whereas precipitation increases in response to la nina intensification

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

late quaternary climatic changes revealed by luminescence dating mineral magnetism and diffuse reflectance spectroscopy of river terrace palaeosols a new form of geoproxy data for the southern african interior lyons j r tooth s duller g 2014 late quaternary climatic changes revealed by luminescence dating mineral magnetism and diffuse reflectance spectroscopy of river terrace palaeosols a new form of geoproxy data for the southern african interior quaternary science reviews 95 43 59

should hydraulic tomography data be interpreted using geostatistical inverse modeling a laboratory sandbox investigation the robust performance of hydraulic tomography ht based on geostatistics has been demonstrated through numerous synthetic laboratory and field studies while geostatistical inverse methods offer many advantages one key disadvantage is its highly parameterized nature which renders it computationally intensive for large scale problems another issue is that geostatistics based ht may produce overly smooth images of subsurface heterogeneity when there are few monitoring interval data therefore some may question the utility of the geostatistical inversion approach in certain situations and seek alternative approaches to investigate these issues we simultaneously calibrated different groundwater models with varying subsurface conceptualizations and parameter resolutions using a laboratory sandbox aquifer the compared models included 1 isotropic and anisotropic effective parameter models 2 a heterogeneous model that faithfully represents the geological features and 3 a heterogeneous model based on geostatistical inverse modeling the performance of these models was assessed by quantitatively examining the results from model calibration and validation calibration data consisted of steady state drawdown data from eight pumping tests and validation data consisted of data from 16 separate pumping tests not used in the calibration effort results revealed that the geostatistical inversion approach performed the best among the approaches compared although the geological model that faithfully represented stratigraphy came a close second in addition when the number of pumping tests available for inverse modeling was small the geological modeling approach yielded more robust validation results this suggests that better knowledge of stratigraphy obtained via geophysics or other means may contribute to improved results for ht

geostatistical inverse modeling for the characterization of aquitard heterogeneity using long term multi extensometer data abstract the classical aquitard drainage model compac was used to simulate the deformation of a one dimensional vertically heterogeneous aquitard i e heter compac by coupling heter compac with the quasi linear geostatistical inversion approach the vertical heterogeneities of hydraulic conductivity k v elastic specific storage s ske and inelastic specific storage s skp fields could be characterized with the availability of long term multi extensometer data the methodology was first tested through a group of ten synthetic cases with randomly generated k v s ske and s skp fields results of the synthetic cases revealed that a geostatistical model could characterize the variability of aquitard hydraulic parameter fields and yields improved fits of simulated versus observed zone deformation than a geological model that treats each zone to be homogeneous subsequently the methodology was applied to a research site situated in changzhou city jiangsu province china where long term deformation behaviors of the strata within the aquifer aquitard system have been monitored vertical heterogeneities of k v s ske and s skp fields of the investigated aquitard at the site were characterized using the quasi linear geostatistical approach the correlation length of the three fields that yielded the best quality fit was assessed to be approximately 50 m and the fitting quality was slightly improved in comparison with that produced from calibrating a geological or zonation model through monte carlo analysis of aquitard deformation utilizing the inversed parameters and corresponding uncertainties the investigated aquitard is estimated to have compacted 914 8 42 6 mm before the rise in groundwater levels in adjoining aquifers

non magnetic indicators of pedogenesis related to loess magnetic enhancement and depletion examples from the czech republic and southern siberia abstract we carried out a multiparameter investigation for non magnetic proxies of the intensity of pedogenesis in loess paleosol sections from two different climate settings dolni v stonice central europe and krasnogorskoye southern siberia the work was performed in order to clarify the problem of two opposite scenarios of magnetic susceptibility ms patterns in these two profiles the chinese model with magnetically enhanced paleosols and the siberian alaskan model with magnetically depleted paleosols the age constraints on the krasnogorskoye section were inferred from an independent correlation with the well dated dolni v stonice section based on ms and sediment color cie l and with the ms log from lake baikal the pedologic description of the loess paleosol sections and their correlation was considerably improved by the use of vis spectral proxies cie l reflectance in the red band their weathering intensity can be effectively characterized by diffuse reflectance spectroscopy drs and geochemical cec and rb sr proxies whereas the ms is strongly dependent on the type of soil chernozems vs brown soils the geochemical proxies in particular cec proved to be relatively independent of the soil type these parameters are less affected by region specific conditions than the ms signal the non magnetic proxies indicate relatively dissimilar climatic trends at the two sites during the last glacial interglacial cycle a long distance correlation based solely on the ms signal can be adversely affected by switching between the chinese and the siberian alaskan magnetic modes this having been observed at the krasnogorskoye section in general no single universal proxy of weathering or pedogenesis intensity would be applicable across broad regions or considerable climatic gradients paleoclimatologic interpretations of large regions should always be based on a carefully designed multi proxy approach

characterization of aquifer heterogeneity using transient hydraulic tomography 1 hydraulic tomography is a cost effective technique for characterizing the heterogeneity of hydraulic parameters in the subsurface during hydraulic tomography surveys a large number of hydraulic heads i e aquifer responses are collected from a series of pumping or injection tests in an aquifer these responses are then used to interpret the spatial distribution of hydraulic parameters of the aquifer using inverse modeling in this study we developed an efficient sequential successive linear estimator ssle for interpreting data from transient hydraulic tomography to estimate three dimensional hydraulic conductivity and specific storage fields of aquifers we first explored this estimator for transient hydraulic tomography in a hypothetical one dimensional aquifer results show that during a pumping test transient heads are highly correlated with specific storage at early time but with hydraulic conductivity at late time therefore reliable estimates of both hydraulic conductivity and specific storage must exploit the head data at both early and late times our study also shows that the transient heads are highly correlated over time implying only infrequent head measurements are needed during the estimation applying this sampling strategy to a well posed problem we show that our ssle can produce accurate estimates of both hydraulic conductivity and specific storage fields the benefit of hydraulic tomography for ill posed problems is then demonstrated finally to affirm the robustness of our ssle approach we apply the ssle approach to a hypothetical three dimensional heterogeneous aquifer

a joined rock magnetic and colorimetric perspective on the late pleistocene climate of orlovat loess site northern serbia abstract this study represents the first detailed joined colorimetric and rock magnetic investigation on a loess paleosol sequence in the vojvodina region northern serbia the aim of this paper is to derive new information on the late pleistocene paleoenvironment from a high resolution multi proxy assessment of the iron mineralogical composition at the orlovat loess paleosol sequence the orlovat section is the first site from the banat loess region analyzed for quaternary paleoclimate information and accordingly it is the easternmost loess section in the serbian loess region studied in contrast to other serbian sites the orlovat site is not located in a plateau rock magnetic analysis and the luminescence dating based chronology revealed active slope processes at this site during the late pleistocene this is the most strikingly evidenced by the absence of a middle wurmian mis 3 interstadial pedocomplex present as marker horizon in the serbian plateau loess sites nevertheless important stratigraphic units and distinct pattern of the proxy records can be correlated to other key sites of the vojvodina loess region hence this section provides an opportunity to reconstruct local as well as regional environmental and climatic conditions during the late pleistocene the applied multiproxy approach especially allowed valuable insight in the environmental conditions that prevailed during formation of the last interglacial pedocomplex accordingly in the eemian pronounced summer dryness prevailed during the formation of the eemian soil the dry period was warmer and lasted longer or was characterized by less precipitation as during formation of the modern soil although the soil moisture deficit in the eemian summers was most likely higher the rainfall was more pronounced in the period of from spring to early summer and or autumn as during the holocene these findings support previous observations from the batajnica site a key site of the vojvodina loess region and highlight the eemian as potential past analogue to future climate warming in serbia this study points out the potential of a joined colorimetric or spectrometric analyses and rock magnetic analyses in paleoenvironmental investigations on loess paleosol sequences

holocene proglacial loess in the ranwu valley southeastern tibet and its paleoclimatic implications abstract glaciers and aeolian sediments are widespread on the tibetan plateau although glaciations have played an important role in the formation of loess in many glaciated regions in the northern hemisphere proglacial loess on the tibetan plateau is rarely reported and its origin source and paleoclimatic implications remain unclear we have found a small area of proglacial loess deposits in the ranwu valley southeastern tibet grain size geochemical and geomorphologic evidence as well as observations of local dust storms reveal that the outwash sediments of the laigu glacier 30 km long are the primary source for the local loess we also found that the glacial wind from this glacier is the main transport vector and thus speculate that the onset of the ranwu loess at ca 6 6 ka correlates with the early neoglacial advance of the laigu glacier which generated glacial winds and local dust storms in the closed and deep incised glacial valley this is supported by the basal radiocarbon ages of two ice cores and a synthesis of holocene glacial stadials on the tibetan plateau loess layers and paleoclimatic proxies indicate two drought stages at ca 6 6 6 ka and ca 2 9 ka to the present corresponding to two well documented weakened stages of the indian summer monsoon this study highlights that although local aeolian sediments always cover a small area they also have potential to record some clues of regional climate changes in some alpine regions much more detailed studies should be done to reveal their specific formation mechanisms and paleoclimatic implications

comparison of aquifer characterization approaches through steady state groundwater model validation a controlled laboratory sandbox study 1 groundwater modeling has become a vital component to water supply and contaminant transport investigations an important component of groundwater modeling under steady state conditions is selecting a representative hydraulic conductivity k estimate or set of estimates which defines the k field of the studied region currently there are a number of characterization approaches to obtain k at various scales and in varying degrees of detail but there is a paucity of information in terms of which characterization approach best predicts flow through aquifers or drawdowns caused by some drawdown inducing events the main objective of this paper is to assess k estimates obtained by various approaches by predicting drawdowns from independent cross hole pumping tests and total flow rates through a synthetic heterogeneous aquifer from flow through tests specifically we 1 characterize a synthetic heterogeneous aquifer built in the sandbox through various techniques permeameter analyses of core samples single hole cross hole and flow through testing 2 obtain mean k fields through traditional analysis of test data by treating the medium to be homogeneous 3 obtain heterogeneous k fields through kriging and steady state hydraulic tomography and 4 conduct forward simulations of 16 independent pumping tests and six flow through tests using these homogeneous and heterogeneous k fields and comparing them to actual data results show that the mean k and heterogeneous k fields estimated through kriging of small scale k data core and single hole tests yield biased predictions of drawdowns and flow rates in this synthetic heterogeneous aquifer in contrast the heterogeneous k distribution or k tomogram estimated via steady state hydraulic tomography yields excellent predictions of drawdowns of pumping tests not used in the construction of the tomogram and very good estimates of total flow rates from the flow through tests these results suggest that steady state groundwater model validation is possible in this laboratory sandbox aquifer if the heterogeneous k distribution and forcing functions boundary conditions and source sink terms are characterized sufficiently

hydraulic conductivity imaging from 3 d transient hydraulic tomography at several pumping observation densities 1 3 d hydraulic tomography 3 d ht is a method for aquifer characterization whereby the 3 d spatial distribution of aquifer flow parameters primarily hydraulic conductivity k is estimated by joint inversion of head change data from multiple partially penetrating pumping tests while performance of 3 d ht has been studied extensively in numerical experiments few field studies have demonstrated the real world performance of 3 d ht here we report on a 3 d transient hydraulic tomography 3 d tht field experiment at the boise hydrogeophysical research site which is different from prior approaches in that it represents a baseline analysis of 3 d tht performance using only a single arrangement of a central pumping well and five observation wells with nearly complete pumping and observation coverage at 1 m intervals we jointly analyze all pumping tests using a geostatistical approach based on the quasi linear estimator of kitanidis 1995 we reanalyze the system after progressively removing pumping and or observation intervals significant progressive loss of information about heterogeneity is quantified as reduced variance of the k field overall reduced correlation with slug test k estimates at wells and reduced ability to accurately predict independent pumping tests we verify that imaging accuracy is strongly improved by pumping and observational densities comparable to the aquifer heterogeneity geostatistical correlation lengths discrepancies between k profiles at wells as obtained from ht and slug tests are greatest at the tops and bottoms of wells where ht observation coverage was lacking

stochastic structure constrained image guided inversion of geophysical data abstractinverse modeling of geophysical data involves the recovery of a subsurface structural model and the distribution of petrophysical properties independent information regarding the subsurface structure is usually available with some uncertainty from the expertise of a geologist and possibly accounting for sedimentary and tectonic processes we have used the available structural information to construct a model covariance matrix and to perform a structure constrained inversion of the geophysical data to obtain a geophysical tomogram m we have considered that the geologic models y were built from random variables and were described with a priori probability density function in the bayesian framework we have explored for the a posteriori probability density of the geologic models i e the structure of the guiding image with the markov chain monte carlo method and we inverted at the same time in a deterministic framework the geophysical data the sampling of the geologic models was performed

high resolution hematite goethite records from chinese loess sequences for the last glacial interglacial cycle rapid climatic response of the east asian monsoon to the tropical pacific 1 in order to study the variability of dry versus humid conditions resulting from the east asian monsoon eam we analyzed hematite and goethite from two high resolution chinese loess sections by diffuse reflectance spectroscopy the hematite and goethite concentrations are higher in interglacial paleosols than in glacial loess sediments whereas the hematite goethite hm gt ratios are lower in paleosols than in loess such changes are consistent with higher precipitation and temperature and increased pedogenesis during interglaciation and lower precipitation and temperature and decreased pedogenesis during glaciation the hm gt ratio can be employed as a tool to assess short term variations in humidity and aridity of the eam the hm gt ratios of the last glacial loess displays millennial scale abrupt climate oscillations revealing a pattern of significantly reduced and enhanced summer monsoon moisture our results indicate that the eam responded to tropical pacific climate by millennial scale changes in precipitation during the last glaciation

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

detection of karst conduit patterns via hydraulic tomography a synthetic inverse modeling study abstract karst aquifers are geologic media that consist of enlarged solution conduits the geometry of such conduits is very difficult to delineate and its hydraulic parameters such as hydraulic conductivity k and specific storage ss are difficult to estimate hydraulic tomography ht shown to successfully map the hydraulic heterogeneity of porous and fractured rock aquifers may also be effective in karst aquifers in this study we utilize two synthetic karst aquifers with the branchwork and network conduit patterns bcp and ncp to explore the ability of ht to map conduit patterns and their hydraulic parameters prior to the ht analysis forward models are built to study groundwater flow through synthetic karst aquifers to generate data and to gain insights into flow patterns forward modeling results reveal that 1 flow rates at the outlet of the bcp model is higher than the ncp model even when the same water injection rates are applied at the wells 2 the location of the injection well has a significant impact on the flow rate at the outlet and 3 flow lines mainly follow the conduit pattern these results suggest that the accurate mapping of karst networks is critical next the ht analysis of these data is conducted using a set of six models bcp and ncp to map the heterogeneity of different conduit systems under steady state and transient flow conditions inverse modeling results reveal that the estimated k maps become more reliable as the number of injection tests and the corresponding monitoring data are increased in the ht analysis moreover the results of the bcp model is closer to the original conduit pattern in comparison to the ncp model a comparative study of three inverse models with different number of observation wells and assuming the availability of geological data has shown that a more reliable pattern of the conduits can be mapped by adding geological information even when a small number of observation wells are available overall our results confirm the feasibility of ht in detecting major conduits as well as being able to differentiate between the bcp and ncp network types

on the importance of geological data for three dimensional steady state hydraulic tomography analysis at a highly heterogeneous aquifer aquitard system abstract hydraulic tomography ht has been shown to map subsurface heterogeneity accurately through the joint interpretation of multiple pumping tests previous research has shown that smooth hydraulic conductivity k estimates are obtained beyond where pumping observation data are available using the geostatistical inversion approach when the inversion begins with a homogeneous k and when data densities are not high however geological data are typically available through outcrops and borehole logs to provide geological variability therefore we investigate the usefulness of geological data for ht analysis at a highly heterogeneous field site by 1 comparing calibrated geological models of two different resolutions to two homogeneous and four highly parameterized geostatistical inverse models in terms of both model calibration and validation performances as well as correspondence of estimated k values with permeameter estimated k profiles along boreholes and 2 using geological models as prior information for the geostatistical inversion approach results reveal that the simultaneous calibration of geological models to seven pumping test data yields k values that correctly reflect the general patterns of vertical distributions of permeameter estimated k we also find that the geostatistical inversion approach using a geological model as prior information performs better for both model calibration and validation than using a homogenous k as a prior and more importantly improves the correspondence of k estimates to permeameter test results along wells as well as in preserving geological features where drawdown measurements are lacking overall our results suggest the joint use of both geological and pumping test data for ht analysis when accurate geological data are available

geostatistical inverse modeling of the transmissivity field of a heterogeneous alluvial aquifer under tidal influence summary the record of the head fluctuations of an alluvial aquifer connected to the estuary of a river submitted to tidal influence can be used to reconstruct the transmissivity field of the aquifer a markov chain monte carlo mcmc sampler is used to invert the transmissivity field at a set of pilot points our approach is first successfully benchmarked on a synthetic case study then we present a real case study in which both a semi confined aquifer and a shallow unconfined aquifer are connected to the estuary of the seine river in the western north of france these aquifers experience strong tidal variations up to 8 4 m this test site is equipped with a series of seventeen wells in which the temporal fluctuations of water heads associated with megatidal forcing were recorded during several years in addition to the use of the pilot points method a zoning parameterization with 45 zones is used to determine the vertical leakage coefficient from the semi confined aquifer into the shallow unconfined aquifer the distribution of the vertical leakage coefficient is determined by inverting the hydraulic head at a set of wells localized in the semi confined aquifer we determine jointly the distribution of the hydraulic transmissivity and the vertical leakage from the semi confined into the unconfined aquifer using 72 pilot points the storage coefficient is assumed to be constant over the whole domain its value is determined from three pumping tests that show a consistent value for this parameter log10s 5 and 0 11 as a variance in our approach there are 119 model parameters 72 transmissivity values at the pilot points 45 values of the vertical leakage coefficient and two parameters sill and range for the isotropic variogram the spatial distribution of the hydraulic transmissivity agrees qualitatively with the soil texture variations observed in the semi confined aquifer and core samples analysis

investigating the stratigraphy of an alluvial aquifer using crosswell seismic traveltime tomography in this study we investigate the use of crosswell p wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers our field site was a research wellfield in an unconfined aquifer near boise idaho the aquifer consists of a 20 m thick sequence of alluvial cobble and sand deposits which have been subdivided into five stratigraphic units based on neutron porosity logs grainsize analysis and radar reflection data we collected crosswell and borehole to surface seismic data in wells 17 1 m apart we carefully considered the impact of well deviation data quality control and the choice of inversion parameters our linearized inverse routine had a curved ray forward model and used different grids for forward modeling and inversion an analysis of the model covariance and resolution matrices showed that the velocity models had an uncertainty of 10 m s a vertical resolution of 1 m and a horizontal resolution of 5 m the velocity in the saturated zone varied between 2100 m s and 2700 m s inclusion of the borehole to surface data eliminated the xshaped pattern that is a common artifact in crosswell tomography and the increased angular coverage also improved the accuracy of the model near the top of the tomogram the final velocity model is consistent with previous stratigraphic analyses of the site although the locations of some of the unit boundaries differ by as much as 2 m in places the results of this study demonstrate that seismic tomography can be used to image the sedimentary architecture of unconsolidated alluvial aquifers even when the lithologic contrasts between units are subtle

summer monsoon variations over the last 1 2 ma from the weathering of loess soil sequences in china the loess soil sequence in northern china contains a near continuous record of quaternary paleoclimate magnetic susceptibility and grain size have so far been the only proxies available to address the long term changes of the east asian paleomonsoon extending back to more than one million years in this study the ratio of cbd citrate bicarbonate dithionite extractable free fe2o3 fed a measure of iron liberated by chemical weathering versus the total fe2o3 available fet was measured on samples at 10 cm intervals taken from two loess sections deposited over the last 1 2 ma variations of this index are highly consistent with other pedological indicators but in addition provide a quantitative measurement of the degree of pedogenesis in the loess plateau since chemical weathering in the region mainly depends upon summer precipitation and temperature weathering intensity primarily reflects changes in the east asian summer monsoon the new proxy has been used to document a series of summer monsoon changes of global significance which are not necessarily recorded by magnetic susceptibility

sequential aquifer tests at a well field montalto uffugo scalo italy 1 this paper investigates our ability to characterize an aquifer using a sequential aquifer test in a well field that consists of six wells during the test we pumped water out from the aquifer at one well and monitored the water level changes at the rest of the wells to obtain a set of five well hydrographs by pumping at another of the six wells we obtained another set of five hydrographs this procedure was repeated until each of the six wells was pumped we then analyzed the six sets of hydrographs using the classical drawdown time the drawdown distance and the drawdown distance time methods results of the analysis confirm recent findings that the transmissivity estimates vary significantly at early time and stabilize at late time at late time the estimated values from all hydrographs are similar overall but vary slightly according to the locations of the pumping and observation wells in contrast storage coefficient estimates stabilized rapidly to distinct values associated with the well locations we subsequently used a hydraulic tomography approach to include all hydrographs from the sequential aquifer test to estimate the spatially varying transmissivity and storage coefficient fields the estimated fields appear to be realistic they reflect the geologic setting and the behaviors of the well hydrographs although more definitive confirmation is needed

three dimensional imaging of aquifer and aquitard heterogeneity via transient hydraulic tomography at a highly heterogeneous field site abstract previous studies have shown that geostatistics based transient hydraulic tomography tht is robust for subsurface heterogeneity characterization through the joint inverse modeling of multiple pumping tests however the hydraulic conductivity k and specific storage ss estimates can be smooth or even erroneous for areas where pumping observation densities are low this renders the imaging of interlayer and intralayer heterogeneity of highly contrasting materials including their unit boundaries difficult in this study we further test the performance of tht by utilizing existing and newly collected pumping test data of longer durations that showed drawdown responses in both aquifer and aquitard units at a field site underlain by a highly heterogeneous glaciofluvial deposit the robust performance of the tht is highlighted through the comparison of different degrees of model parameterization including 1 the effective parameter approach 2 the geological zonation approach relying on borehole logs and 3 the geostatistical inversion approach considering different prior information with without geological data results reveal that the simultaneous analysis of eight pumping tests with the geostatistical inverse model yields the best results in terms of model calibration and validation we also find that the joint interpretation of long term drawdown data from aquifer and aquitard units is necessary in mapping their full heterogeneous patterns including intralayer variabilities moreover as geological data are included as prior information in the geostatistics based tht analysis the estimated k values increasingly reflect the vertical distribution patterns of permeameter estimated k in both aquifer and aquitard units finally the comparison of various tht approaches reveals that differences in the estimated k and ss tomograms result in significantly different transient drawdown predictions at observation ports

a travel time based hydraulic tomographic approach 1 hydraulic tomography is a method to identify the three dimensional spatial distribution of hydraulic properties in the subsurface we propose a tomographic approach providing the inversion of travel times of hydraulic or pneumatic tests conducted in a tomographic array the inversion is based on the relation between the peak time of a recorded transient pressure curve and the diffusivity of the investigated system the development of a transformation factor enables the inversion of further travel times besides the peak time of a transient curve as the early travel times of the curve are mainly related to preferential flow features while the inversion based on late travel times are reflecting an integral behavior it can be assumed that the different inversion results reflect the properties of the overall system by comparing the different reconstructions the system interpretation therefore becomes more comprehensive and reliable furthermore the similarity of the proposed hydraulic tomographic approach to seismic travel time tomography allows us to apply the inversion algorithms which are used for seismic tomography we therefore apply the method of staggered grids which enables to refine the grid resulting in a higher nominal resolution to data from a set of interference tests arranged in a tomographic array the tests were conducted in an unsaturated fractured sandstone cylinder in the laboratory the three dimensional reconstructions of the diffusivity distribution are found to be highly reliable and robust in particular the mapped fracture of the sandstone cylinder coincides with our reconstructed diffusivity distribution

the permo jurassic alkaline province of tadhak mali geology geochronology and tectonic significance the tadhak alkaline complexes located along the eastern edge of the west african craton in northeastern mali intrude the 2 ga old basement or the overlying pan african nappes and are covered by cretaceous sediments this magmatic activity was accompanied by doming and rifting northnortheast trending normal faults define two crustal segments exhibiting variously sized 1 km to 17 km intrusive complexes these comprise eroded undersaturated ring complexes with occasional carbonatites in the west and high level phonolitic plugs with shallow intrusive nepheline syenites in the east new rb sr isotopic data indicate 100 ma of within plate magmatic activity in the area without any obvious age progression in addition to the adrar tadhak complex 262 7 ma the following intrusions have been dated tirkine 215 11 ma anezrouf 184 14 ma and tidjerazraze in imanal 161 5 ma a clear break thus exists with the cambrian alkaline granite province of the iforas located on the opposite side of the pan african suture 87sr 86sr initial ratios are similar throughout between 0 7044 and 0 7049 which indicates a bulk earth isotopic composition the conclusion of exclusively mantle origin dupal composition previously demonstrated for the adrar tadhak complex can now be extended to the other complexes this implies repeated tapping of a single mantle source throughout the life of the province the described magmatic and tectonic permo jurassic activity has been triggered by intraplate stresses focussed along the pre existing pan african suture zone together with similar features in europe and africa the permo jurassic tadhak alkaline province heralds the progressive break up of pangaea and the opening of the atlantic ocean

2d joint inversion of geophysical data using petrophysical clustering and facies deformation geologic expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical data sets the merging of such information can result in more realistic solution in the distribution of the model parameters we have evaluated the geophysical inverse problem in terms of gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geologic cross section including the definition of spatial boundaries for the geologic facies the petrophysical relationship problem is formulated as a regression problem upon each facies the inversion of the geophysical data is performed in a bayesian framework we have developed the usefulness of this strategy using a first synthetic case for which we have performed a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface the joint inversion was used to recover the density and resistivity distributions of the subsurface in a second step we considered the possibility that the facies boundaries were deformable and their shapes were inverted as well we used the level set approach to perform such deformation preserving a priori topological properties of the facies throughout the inversion with the help of a priori facies petrophysical relationships and the topological characteristics of each facies we made a posteriori inference about multiple geophysical tomograms based on their corresponding geophysical data misfits we have applied this method to a second synthetic case showing that we can recover the heterogeneities inside the facies the mean values for the petrophysical properties and to some extent the facies boundaries using the 2d joint inversion of gravity and galvanometric resistivity data

steady state hydraulic tomography in a laboratory aquifer with deterministic heterogeneity multi method and multiscale validation of hydraulic conductivity tomograms summary hydraulic tomography potentially is a viable technology that facilitates subsurface imaging of hydraulic heterogeneity to date a comprehensive validation of hydraulic tomography has not been done either at the laboratory or field scales the main objective of this paper is to examine the accuracy of hydraulic conductivity k tomograms obtained from the steady state hydraulic tomography algorithm of yeh t c j liu s 2000 hydraulic tomography development of a new aquifer test method water resources research 36 2095 2105 we first obtain a reference k tomogram through the inversion of synthetic cross hole test data generated through numerical simulations the purpose of reference k tomogram generation is to examine the ability of the algorithm to image the heterogeneity pattern under optimal conditions without experimental errors and with full control of forcing functions initial and boundary conditions as well as source sink terms parallel to the generation of synthetic data we conduct hydraulic tests at multiple scales in a laboratory aquifer with deterministic heterogeneity to generate data that are used to validate k tomograms from hydraulic tomography measurements include multiple k estimates from core slug single hole and cross hole tests as well as several unidirectional flow through experiments conducted on the sandbox under steady state conditions validation of k tomograms involved a multi method and multiscale approach proposed herein which include 1 visual comparisons of k tomograms to the true sand distributions and the reference k tomogram 2 testing the ability of the k tomogram to predict the hydraulic head distribution of an independent cross hole test not used in the computation of the k tomogram 3 comparison of the conditional mean and variance of local k from the k tomograms to the sample mean and variance of results from other measurements 4 comparison of local k values from k tomograms to those from the reference k tomogram and 5 comparison of local k values from k tomograms to those obtained from cores and single hole tests the multi method and multiscale validation approach proposed herein further illustrates the robustness of steady state hydraulic tomography in subsurface heterogeneity delineation

on the importance of geological data for hydraulic tomography analysis laboratory sandbox study abstract this paper investigates the importance of geological data in hydraulic tomography ht through sandbox experiments in particular four groundwater models with homogeneous geological units constructed with borehole data of varying accuracy are jointly calibrated with multiple pumping test data of two different pumping and observation densities the results are compared to those from a geostatistical inverse model model calibration and validation performances are quantitatively assessed using drawdown scatterplots we find that accurate and inaccurate geological models can be well calibrated despite the estimated k values for the poor geological models being quite different from the actual values model validation results reveal that inaccurate geological models yield poor drawdown predictions but using more calibration data improves its predictive capability moreover model comparisons among a highly parameterized geostatistical and layer based geological models show that 1 as the number of pumping tests and monitoring locations are reduced the performance gap between the approaches decreases and 2 a simplified geological model with a fewer number of layers is more reliable than the one based on the wrong description of stratigraphy finally using a geological model as prior information in geostatistical inverse models results in the preservation of geological features especially in areas where drawdown data are not available overall our sandbox results emphasize the importance of incorporating geological data in ht surveys when data from pumping tests is sparse these findings have important implications for field applications of ht where well distances are large

color characteristics of chinese loess and its paleoclimatic significance during the last glacial interglacial cycle abstract the soil color is widely used in paleoclimate and paleoenvironment reconstructions in the chinese loess plateau to better understand the color spatial changes during the glacial interglacial cycle the soil color lightness l characteristic spectra magnetic susceptibilities and mean grain sizes of three loess paleosol sequences were compared results showed that high l and low hematite to goethite ratios hm gt appeared in loess units and low l and high hm gt ratios accompanied paleosol layers indicating glacial interglacial hydrothermal oscillation l in the yulin section was higher than in the chaona and lihuacun sections indicating that different precipitations have great effect on l furthermore hm gt magnetic susceptibility lf and mean grain size are correlated closely with l l and hm gt not only document climatic variations in the glacial interglacial cycle vis a vis loess paleosol sequences but also can identify heinrich cold events and millennial scale dansgaard oeschger d o warm events it suggests that soil color responds sensitively to global climate change driven by ice volumes l and hm gt curves exhibit higher frequencies and larger amplitudes than magnetic susceptibility lf curves indicating that l and hm gt can be regarded as sensitive and reliable proxies for characterizing high resolution climate change during the last glacial interglacial cycle

capturing aquifer heterogeneity comparison of approaches through controlled sandbox experiments 1 groundwater modeling has become a vital component to water supply and contaminant transport investigations these models require representative hydraulic conductivity k and specific storage ss estimates or a set of estimates representing subsurface heterogeneity currently there are a number of approaches for characterizing and modeling k and ss heterogeneity in varying degrees of detail but there is a lack of consensus for an approach that results in the most robust groundwater models with the best predictive ability the main goal of this study is to compare different heterogeneity modeling approaches e g effective parameters geostatistics geological models and hydraulic tomography when input into a forward groundwater model and used to predict 16 independent cross hole pumping tests we first characterize a sandbox aquifer through single and cross hole pumping tests and then use these data to construct forward groundwater models of various complexities both homogeneous and heterogeneous distributions two effective parameter models are constructed 1 by taking the geometric mean of single hole test k and ss estimates and 2 calibrating effective k and ss estimates by simultaneously matching the response at all ports during a cross hole test heterogeneous models consist of spatially variable k and ss fields obtained via 1 kriging single hole data 2 calibrating a geological model and 3 conducting transient hydraulic tomography zhu and yeh 2005 the performance of these parameter fields are then tested through the simulation of 16 independent cross hole pumping tests our results convincingly show that transient hydraulic tomography produces the smallest discrepancy between observed and simulated drawdowns

field study of dispersion in a heterogeneous aquifer 1 overview and site description results are presented for a large scale natural gradient tracer experiment conducted in a heterogeneous alluvial aquifer at a site near columbus mississippi the study was initiated with a 48 hour pulse injection of 10 m3 of groundwater containing bromide and three organic tracers pentaflourobenzoic acid o trifluoromethylbenzoic acid and 2 6 diflourobenzoic acid over a 20 month period seven comprehensive samplings of the tracer plume were performed at approximately 1 to 4 month intervals using an extensive three dimensional sampling well network the dominant feature of the tracer plume that evolved during the study was the highly asymmetric concentration distribution in the longitudinal direction this asymmetry was produced by accelerating groundwater flow along the plume travel path that in turn resulted from an approximate 2 order of magnitude increase in the mean hydraulic conductivity between the near field and far field regions of the site the columbus study is distinct from previous natural gradient experiments because of the extreme heterogeneity of the aquifer the large scale spatial variations in groundwater velocity and the extensive set of hydraulic conductivity measurements for the aquifer

comparative study of transient hydraulic tomography with varying parameterizations and zonations laboratory sandbox investigation the final publication is available at elsevier via http dx doi org 10 1016 j jhydrol 2017 09 045 2017 this manuscript version is made available under the cc by nc nd 4 0 license http creativecommons org licenses by nc nd 4 0

loess soil sequence at toshan northern iran insights into late pleistocene climate change abstract the knowledge of palaeoclimate in iran is still limited however insight into the timing and the dynamics of quaternary climate change in iran might offer valuable information to improve the global palaeoclimate record the loess soil sequence of toshan provides the first high resolution record of late pleistocene climate dynamics in iran and complements the hitherto known sections at neka now deh and agh band to establish a pedostratigraphic record of the north eastern caspian lowland our spectroscopic and grain size analysis are combined to propose i a pedostratigraphical scheme for the sequence at toshan ii describe and estimate the degree of soil development of selected stratigraphical units iii infer palaeoclimatic information and provide iv a correlation with previous loess palaeosol records of n iran as based on pedostratigraphic assumptions the section at toshan hosts a strongly developed reddish brown argillic palaeosol bt as well as eight moderately to weakly developed brownish palaeosol horizons lacking clay illuviation features bw bwk these remnants of fossil soils are separated by finely textured loess and horizons that host characteristics of both loess and mineral subsoils cb cbk giving evidence for syngenetic soil formation the stratigraphical succession of palaeosols loess and syngenetically altered sediments covering the last ca 130 ka gives evidence for recurrent climate changes as well as fluctuations between dominance of soil formation or dust accumulation in relation to changes in moisture regime the formation of bt and bw bwk horizons is related to relatively humid and warm conditions likely corresponding with interglacial and interstadial climate

climatic interpretation of the luochuan and lingtai loess sections china based on changing iron oxide mineralogy and magnetic susceptibility abstract hematite and goethite estimated from diffuse reflectance spectra and magnetic susceptibility ms have been determined from both the luochuan and lingtai loess sections of the loess plateau of central china changing concentrations of these iron oxides and ms were used to determine paleoclimatic change based on a model that relates pedogenic production of hematite and magnetite to precipitation we propose two precipitation phases on the loess plateau during the last 2 6 ma from the wucheng red clay boundary up to paleosol s5 mis 13 precipitation on the loess plateau was moderate probably not frequently exceeding 450 mm yr and highly seasonal from s5 to the present precipitation during interglacial times has gradually increased to the present levels of 600 650 mm yr for the localities examined throughout the pleistocene spanning both glacial and interglacial conditions hematite to goethite ratios display a consistent decrease this decrease suggests that precipitation on the loess plateau has been getting less seasonal and or has been occurring during times when temperature was lower in addition to these long term changes it also appears that iron oxide records from the loess plateau exhibit 400 500 ka cycles from the wucheng red clay boundary to s5 these 400 500 ka cycles may be analogous to similar length cycles recorded in 13 c marine records in the south china sea and may be linked through weathering and silica production as a result of the asian monsoon

iron mineralogical proxies and quaternary climate change in se european loess paleosol sequences abstract the loess paleosol sequences batajnica stari slankamen serbia and mircea voda romania represent key archives for the climate and landscape development of the middle and lower danube basin during the last 700 000 years for deciphering the quaternary climate evolution in these regions the batajnica stari slankamen and mircea voda sites are for the first time studied by a multi proxy approach based on iron mineralogical parameters changes in the iron mineralogical composition are identified and characterized by rock magnetic investigations diffuse reflectance spectroscopy drs and munsell color based proxies the results show that environmental conditions during mid and early middle pleistocene interglacials were more favorable for hematite formation suggesting a more oxidizing pedoclimate as in the more recent interglacials this is also reflected in a gradual increase of the anhysteretic remanent magnetization vs saturation isothermal remanent magnetization arm sirm ratio in the studied profiles changes in this ratio can be linked to a preferential hematitization of coarse grained ferrimagnetica and relates to warmer climate conditions and a more extended estival dry period at the same time rock magnetic parameters indicate a preferential destruction of fine grained magnetic particles in older paleosols resulting from seasonal excess moisture a progressive cooling and decrease of rainfall during the middle and late pleistocene is evidenced not only for interglacial pedocomplexes but also for glacial loess layers this finding is in line with previously published proxy records of silicate weathering and clay formation at these sites and similar trends reported from other sites in the european steppe belt relating iron mineralogical proxies to paleopedological characteristics and proxies of silicate weathering additionally a change in the seasonal pattern of the interglacial temperature and precipitation regime from a mediterranean type to a steppe type climate is revealed highlighting the potential of such a multi proxy approach possible triggers for this paleoenvironmental evolution are discussed as well finally highlighting a quaternary uplift hypothesis which best could explain the inferred trend of cooling aridification and increasing continentality accordingly changes in atmospheric circulation and rain shadow effects induced by small scale uplift of european mountain belts alps carpathians dinaric alps would provide a driving mechanism for the westward extension of the eurasian steppe belt into central and se europe during the quaternary

characteristics and formation mechanism of pedogenic hematite in quaternary chinese loess and paleosols abstract hematite is an important iron oxide mineral in loess paleosol sequences in northwest china samples containing hematite and related minerals in the loess and paleosol units from chinese loess plateau were investigated using powder x ray diffraction xrd scanning electron microscopy sem and high resolution transmission microscopy hrtem the results show that there are at least three genetic types of hematite in quaternary loess paleosol sequences of northern china 1 weathering products of fe bearing silicate minerals such as chlorite and biotite that precipitated as aggregates of hematite nano crystals on mineral surfaces 2 oxidation products of eolian magnetite grains with hematite nano crystals closely associated with magnetite 3 coarse silt sized hematite grains present in the fresh loess hematite with a nanoporous texture indicates that dehydration of iron hydroxide ferrihydrite is the main mechanism for the formation of hematite coating during chemical weathering of fe bearing silicates it is proposed that nano phase hematite is primarily responsible for the red color of the paleosol units paleosol layers are also characterized by higher magnetic susceptibility and increased oxidation of eolian magnetite it is proposed that the major contribution to magnetic susceptibility is from the nano phase magnetite that may be related to microbial activity this research demonstrates that the study of mineral characteristics formation mechanisms and the relationship between hematite other iron oxides and fe bearing silicate minerals helps to understand better the geochemical process in loess both before and after dust deposition in addition our study helps to explain the correlation between magnetic susceptibility and paleoclimate in northern china during the quaternary

estimation of field scale soil hydraulic and dielectric parameters through joint inversion of gpr and hydrological data 1 a method is described for the joint use of time lapse ground penetrating radar gpr travel times and hydrological data to estimate field scale soil hydraulic parameters we build upon previous work to take advantage of a wide range of cross borehole gpr data acquisition configurations and to accommodate uncertainty in the petrophysical function which relates soil porosity and water saturation to the effective dielectric constant we first test the inversion methodology using synthetic examples of water injection in the vadose zone realistic errors in the petrophysical function result in substantial errors in soil hydraulic parameter estimates but such errors are minimized through simultaneous estimation of petrophysical parameters in some cases the use of a simplified gpr simulator causes systematic errors in calculated travel times simultaneous estimation of a single correction parameter sufficiently reduces the impact of these errors we also apply the method to the u s department of energy doe hanford site in washington where time lapse gpr and neutron probe np data sets were collected during an infiltration experiment we find that inclusion of gpr data in the inversion procedure allows for improved predictions of water content compared to predictions made using np data alone these examples demonstrate that the complimentary information contained in geophysical and hydrological data can be successfully extracted in a joint inversion approach moreover since the generation of tomograms is not required the amount of gpr data required for analyses is relatively low and difficulties inherent to tomography methods are alleviated finally the approach provides a means to capture the properties and system state of heterogeneous soil both of which are crucial for assessing and predicting subsurface flow and contaminant transport

clay mineral distribution in surface sediments of the northeastern south china sea and surrounding fluvial drainage basins source and transport clay mineralogy of surface samples throughout the northeastern south china sea scs and surrounding fluvial drainage basins has been investigated to reveal source and transport of detrital fine grained sediments three characteristic end members in clay mineral compositions were observed from three major provenances respectively major kaolinite and moderate illite and chlorite from the pearl river predominant illite and chlorite from taiwan and principal smectite from the luzon arc system the transport of four clay mineral species in the northeastern scs is influenced by various mechanisms smectite derived from the luzon arc system is transported mainly by surface current with significant influence of the kuroshio intrusion illite and chlorite from taiwan are mainly carried by deep water current while kaolinite from the pearl river is affected obviously by the westward guangdong coastal current and longshore current a westerly tongue shaped distribution of high contents of illite and chlorite mainly from taiwan on the eastern shelf may result from the westward guangdong coastal current during the winter the results suggest that clay mineral assemblages in the northeastern scs are mainly controlled by provenance supply and current transport and their downcore records do not bear contemporaneous paleoclimatic features the implication of clay minerals for proxies of the late quaternary east asian monsoon evolution is realized through both the provenance supply and current transport processes c 2010 elsevier b v all rights reserved

permeability and porosity images based on p wave surface seismic data application to a south florida aquifer 1 p wave surface seismic reflection data acquired from a carbonate aquifer in southeastern florida are used to delineate flow units in a proposed aquifer storage and recovery asr horizon the impedance image determined by inversion from p wave reflection data captures most of the boundaries between hydraulic facies the hydraulic facies properties are based on integration of the well logs and the lithology which consists of vuggy carbonate units and sandstones within the proposed asr horizon located in the upper floridan aquifer low permeability zones consist of sandstones and highly permeable zones are carbonates with interconnected vuggy porosity high resolution porosity permeability and impedance images based on cross well reflection and well logs help us evaluate the p wave seismic reflection results we use well logs and cross well seismic data to support whether two dimensional seismic reflection measurements detect important flow units delineated by cross well high resolution seismic data the data analysis demonstrates that major flow units are resolved and imaged with two dimensional seismic reflection techniques although not as clearly as in the high resolution cross well data the results suggest that the surface seismic reflection method integrated with well logs and geology provides the tools to assess water resources in this south florida carbonate aquifer however we recommend conducting a cross well survey in areas where an understanding of the petrophysics is imperative to relating the seismic attributes to rock and fluid properties this can be a critical step for planning purposes when considering a large surface oriented seismic survey

hydrogeological characterization of the south oyster bacterial transport site using geophysical data a multidisciplinary research team has conducted a field scale bacterial transport study within an uncontaminated sandy pleistocene aquifer near oyster virginia the overall goal of the project was to evaluate the importance of heterogeneities in controlling the field scale transport of bacteria that are injected into the ground for remediation purposes geochemical hydrological geological and geophysical data were collected to characterize the site prior to conducting chemical and bacterial injection experiments in this paper we focus on results of a hydrogeological characterization effort using geophysical data collected across a range of spatial scales the geophysical data employed include surface ground penetrating radar radar cross hole tomography seismic cross hole tomography cone penetrometer and borehole electromagnetic flowmeter these data were used to interpret the subregional and local stratigraphy to provide high resolution hydraulic conductivity estimates and to provide information about the log conductivity spatial correlation function the information from geophysical data was used to guide and assist the field operations and to constrain the numerical bacterial transport model although more field work of this nature is necessary to validate the usefulness and cost effectiveness of including geophysical data in the characterization effort qualitative and quantitative comparisons between tomographically obtained flow and transport parameter estimates with hydraulic well bore and bromide breakthrough measurements suggest that geophysical data can provide valuable high resolution information this information traditionally only partially obtainable by performing extensive and intrusive well bore sampling may help to reduce the ambiguity associated with hydrogeological heterogeneity that is often encountered when interpreting field scale bacterial transport data

a field proof of concept of tomographic slug tests in an anisotropic littoral aquifer hydraulic tomography is increasingly recognized as a characterization approach that can image pathways or barriers to flow as well as their connectivity in this study we assess the performance of a transient analysis of tomographic slug test head data in estimating heterogeneity in horizontal hydraulic conductivity kh hydraulic conductivity anisotropy the ratio between vertical and horizontal hydraulic conductivity kv kh and specific storage ss under actual field conditions the tomographic experiment was carried out between two wells in a moderately heterogeneous and highly anisotropic silt and sand littoral aquifer in this field proof of concept the inversion of the two dimensional 2d head dataset was computed with a 2d radial flow algorithm that considers kh kv kh ss and wellbore storage effects this study demonstrated that a transient analysis of tomographic slug tests is able to capture the key features of the littoral environment of the test the vertical profiles of kh and kv are indeed in agreement with those from other field and laboratory tests and ss values exhibit physically plausible profiles furthermore the simulation of independent inter well hydraulic tests slug and pumping tests screened over the entire aquifer using resolved kh kv kh and ss tomograms produce responses very close to field observations this study demonstrates that the effects of fine scale heterogeneity that induces k anisotropy at larger scales can be captured through a transient analysis of tomographic slug tests which are very difficult to quantify otherwise with conventional hydraulic tests thus allowing a better representation of properties controlling flow and transport in aquifer systems