internal structure of aeolian dunes in abu dhabi determined using ground penetrating radar a ground penetrating radar survey of aeolian dunes in the al liwa area of abu dhabi reveals a variety of dipping reflectors which are interpreted as primary sedimentary structures the interpretation of the radar profiles has been confirmed by bulldozing trenches through the study area and comparing logged sections in the trenches with the radar profiles nnw sse orientated radar profiles approximately parallel to the prevailing wind direction show two sets of dipping reflectors which are interpreted as sets of cross stratification and second and third order bounding surfaces radar profiles orientated wsw ene across the prevailing wind direction are dominated by concave up reflectors which are interpreted as trough shaped scours and sets of trough cross stratification produced by oblique progradation of barchanoid dunes nested troughs with small sets of trough cross stratification within larger troughs may be due to reactivation following wind reversal or the superposition of small dunes on larger dunes and the fill of large dune troughs by smaller dunes convex upwards reflectors are interpreted as linear spurs on the convex portions of sinuous dunes or erosional remnants between troughs overall there is a tendency for the larger second order bounding surfaces to dip downwind which confirms brookfield s ideas of the relative migration paths of dunes and draa

imaging the structure and reconstructing the development of a barchan dune using ground penetrating radar abstract the formation mechanism and development processes of aeolian landforms are significant research topics of aeolian environment the analysis of the sedimentary structure and stratigraphic sequence of sand dunes is the key content of this study ground penetrating radar gpr has been widely used in investigations of aeolian landforms to help detect underground sediment structures early studies using gpr to investigate dune sands were aimed at studying sedimentary structures and establishing the cause of gpr reflections but seldom displayed the complete dune structures in this study gpr techniques were used to reveal sedimentary structures and reconstruct the development process of a barchan sand dune in the mu us sandy land from the perspective of three dimensional space through reasonable arrangement of gpr survey lines in grids based on the analysis of 41 gpr profiles this study identified five major dune radar facies and three radar surfaces the results showed the following 1 the dune structures were mainly sets of low to high angle crossbedding with and low angle superposition surfaces which could be divided into modern and old deposition 2 the modern deposition was dominated by trough cross bedding distributed in the centre of the barchan dune and the old deposition was dominated by tabular cross bedding and lateral accretion bedding in dune wings the leeward slope form was a significant factor impacting the formation of the dune structure 3 the sedimentary structure showed the barchan dune experienced two major episodes in the early stage parabolic dunes migrated over fixed sand dunes and were subsequently covered by the upwind barchan dune due to the impacts of wind erosion the oldest age preserved in modern and old deposition can be approximately 1997 and 1970s respectively the sedimentary structures imaged by gpr can reveal these geomorphologic processes which can help better understand the formation mechanisms and development processes of sand dunes

radar reflections from sedimentary structures in the vadose zone ground penetrating radar gpr is a suitable technique for imaging sedimentary structures in the vadose zone because small texture related capillary pressure variations lead to changes in water content and electromagnetic properties to study exactly how gpr reflections are generated by sedimentary structures gpr profiles of an aeolian sedimentary succession are combined with measurements of textural electromagnetic and water retention characteristics from a trench time domain reflectometry indicates that small variations in texture in the high angle dune sediment are associated with changes in water content synthetic modelling shows that these changes cause clear gpr reflections in an experimental approach to estimate the radar response of structures below the wave resolution i e features smaller than 4 variations in grain size distribution and porosity in a thin section were used to reconstruct water retention curves and impedance models of the thinly layered sediment synthetic radar records calculated from the impedance models show that reflections from the studied subcentimetre scale structures are composites of interfering signals although these low amplitude interfering signals will commonly be overprinted by more prominent reflections they may cause reflection patterns that change with frequency and do not represent primary bedding

annual layers revealed by gpr in the subsurface of a prograding coastal barrier southwest washington u s a abstract the southwest washington coastline has experienced extremely high rates of progradation during the late holocene subsurface stratigraphy preserved because of progradation and interpreted using ground penetrating radar gpr has previously been used successfully to document coastal response to prehistoric storm and earthquake events new gpr data collected at ocean shores washington suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought gpr records for this location at 200 mhz reveal a series of gently sloping seaward dipping reflections with slopes similar to the modern beach and spacings on the order of 20 45 cm field evidence and model results suggest that thin 1 10 cm possibly magnetite rich heavy mineral lags or low porosity layers left by winter storms and separated by thick 20 40 cm summer progradational sequences are responsible for generating the gpr reflections these results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using gpr such records of annual coastal behavior where available will be invaluable in understanding past coastal response to climatic and tectonic forcing

a study of the geoelectrical properties of peatlands and their influence on ground penetrating radar surveying1 geophysical surveys and chemical analyses on cores were carried out in three ontario peatlands from which we have gained a better understanding of the peat properties that control the geophysical responses the electrical conductivity depends linearly on the concentration of total dissolved solids in the peat pore waters and the pore waters in turn bear the ionic signatures of the underlying mineral sediments the ionic concentration and thus the electrical conductivity increase linearly from the surface to basement the average bulk electrical conductivity of peatlands at ellice marsh near stratford and at wally creek area forest drainage project near cochrane are of the order of 25 ms m the mer bleue peatland near ottawa has extremely high electrical conductivity reaching levels of up to 380 ms m near the base of the peat the mer bleue peatland water has correspondingly high values of total dissolved solids which originate from the underlying champlain sea glaciomarine clays the dielectric permittivity in peats is largely controlled by the bulk water content ground penetrating radar can detect changes in water content greater than 3 occurring within a depth interval less than 15 cm the principal peatland interfaces detected are the near surface aerobic to anaerobic transition and the peat to mineral basement contact the potential for the successful detection of the basement contact using the radar can be predicted using the radar instrument specifications estimates of the peatland depth and either the bulk peat or the peat pore water electrical conductivities predicted depths of penetration of up to 10 m for ellice marsh and wally creek exceed the observed depths of 1 to 2 m at mer bleue on the other hand we observe that as predicted a 100 mhz signal will penetrate to the base of a 2 m thick peat but a 200 mhz signal will not

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

the potential of lacquer peel soil profiles for palaeo geochemical analysis using xrf analysis this paper discusses the suitability of hand held xrf analysis to extract palaeo geochemical information from lacquer peel soil sections that have been taken to document pedological information at geological and archaeological sites this not only allows the study of sections from archaeological and geological sites that have since disappeared but can also answer new archaeological questions on the nature of activities undertaken at such sites seven lacquer peels from different time periods and different geogenetic backdrops have been studied with hand held xrf niton xl3t goldd detector five of these lacquer peels were studied to assess possible interference from mounting materials glues textiles and framing boards used four of these lacquer peels were studied for their palaeo geochemical information these lacquer peels were taken from prehistoric agricultural plots and settlement sites ranging in age from the neolithic to the iron age values for si k al fe ti sr zr and rb reflect lithogenetic and pedological processes the contents of s ca and p were used as a proxy for anthropogenic influence the lacquer peels provided consistent and reliable geochemical readings with the hand held xrf observed correspondence between pedological predictions archaeological hypotheses and the measured results testifies to the suitability of hand held xrf for palaeo geochemical characterization interference from the primarily organic fixing and mounting agents used was absent consequently hand held xrf analysis allows extraction of palaeo geochemical information from lacquer peel soil sections which opens up a new potential data set for reconstructing past pollution and to geochemically re assess geological and archaeological sites from existent lacquer peels adding a geochemical dimension to lacquer peels of pedological archaeological and geological sites

structure and development of shell cheniers in essex southeast england investigated using high frequency ground penetrating radar abstract the stratigraphy and internal structure of contemporary shell cheniers on the southern essex coast england were investigated using a high frequency 900 mhz ground penetrating radar gpr system the cheniers lie on the seaward edge of laterally eroding saltmarshes at the junction with the tidal flats four main types of chenier are recognised each with a characteristic morphology and dynamic status migrated radar reflection profiles obtained from each of the chenier types achieved a sub decimetre vertical resolution ground truthing data demonstrate that the radar profiles accurately delineate the subsurface stratigraphy and sedimentary structure of the cheniers interpretation of the radar stratigraphy derived from the radar reflection profiles allows various deposits to be identified these have resulted from overwashing overtopping sedimentation across the whole of a seaward dipping beachface or berm ridge welding onto the upper beachface each chenier is characterised by a different spatial arrangement of these four basic depositional units the results from the gpr surveys support the hypothesis that each of the chenier types represents a distinct phase in the development of these contemporary coastal landforms however a simple model involving a linear progression through chenier types 1 4 with time appears inappropriate instead two main evolutionary pathways are proposed with the sequence of development being principally controlled by the nature of the cheniers longer term sediment budgets

pool patterning in a northern peatland geophysical evidence for the role of postglacial landforms a hydrogeophysical study conducted in a 2200 ha peatland in central maine shows evidence that a laterally continuous esker deposit extends below the peat soil following the direction of glacier retreat and coinciding with the presence of a pool system ground penetrating radar gpr electrical resistivity er imaging and terrain conductivity measurements were constrained with limited hydrological measurements direct sampling of inorganic sediments and radiocarbon dating of peat soils to develop a conceptual model for pool formation that could explain the unique pool patterning observed in other northern peatlands gpr profiles revealed three dimensional images of two esker crests below the easternmost edge of the pool area gpr data was supported by er imaging and terrain conductivity data and allowed for facies differentiation to infer processes related to esker formation during the glacier front retreat hydrologic data showed preferential flow of groundwater towards the esker suggesting that pools may persist as a result of enhanced peat decomposition and carbon loss due to oxygenation and or upward supply of alternative electron acceptors from the mineral soil along narrow permeable inorganic esker crests variations in pool depths and radiocarbon dating of peat samples from the pool bottom support a model whereby pools originate at a focus centered along the two esker crests and subsequently spread laterally outwards

soil moisture content estimation using ground penetrating radar reflection data abstract ground penetrating radar gpr reflection travel time data were used to estimate changes in soil water content under a range of soil saturation conditions throughout the growing season at a california winery data were collected during three data acquisition campaigns over an 80 by 180 m area using 100 mhz surface gpr antennas gpr reflections were associated with a thin low permeability clay layer located 0 8 1 3 m below the ground surface that was identified from borehole information and mapped across the study area field infiltration tests and neutron probe logs suggest that the thin clay layer inhibited vertical water flow and was coincident with high volumetric water content vwc values the gpr reflection two way travel time and the depth of the reflector at the borehole locations were used to calculate an average dielectric constant for soils above the reflector a site specific relationship between the dielectric constant and vwc was then used to estimate the depth averaged vwc of the soils above the reflector compared to average vwc measurements from calibrated neutron probe logs over the same depth interval the average vwc estimates obtained from gpr reflections had an rms error of 0 018 m3 m 3 these results suggested that the two way travel time to a gpr reflection associated with a geological surface could be used under natural conditions to obtain estimates of average water content when borehole control is available and the reflection strength is sufficient the gpr reflection method therefore has potential for monitoring soil water content over large areas and under variable hydrological conditions

continuous and simultaneous measurement of reflector depth and average soil water content with multichannel ground penetrating radar ground penetrating radar is a fast noninvasive technique that can monitor subsurface structure and water content distribution to interpret traveltime information from single common offset measurements additional assumptions such as constant permittivity usually are required we present a fast ground penetrating radar measurement technique using a multiple transmitter and receiver setup to measure simultaneously the reflector depth and average soil water content it can be considered a moving minicommon midpoint measurement for a simple analysis we use a straightforward evaluation procedure that includes two traveltimes to the same reflector obtained from different antenna separations for a more accurate approach an inverse evaluation procedure is added using traveltimes obtained from all antenna separations at one position and its neighboring measurement locations the evaluation of a synthetic data set with a lateral variability in reflector depth and an experimental example with a large variability in soil water content are introduced to demonstrate the applicability for field scale measurements the crucial point for this application is the access to absolute traveltimes which are difficult to determine accurately from common offset measurements

high resolution water content estimation from surface based ground penetrating radar reflection data by impedance inversion 1 mapping hydrological parameter distributions in high resolution is essential to understand and simulate groundwater flow and contaminant transport of particular interest is surface based ground penetrating radar gpr reflection imaging in electrically resistive sediments because of the expected close link between the subsurface water content and the dielectric permittivity which controls gpr wave velocity and reflectivity conventional tools like common midpoint cmp velocity analysis provide physical parameter models of limited resolution only we present a novel reflection amplitude inversion workflow for surface based gpr data capable of resolving the subsurface dielectric permittivity and related water content distribution with markedly improved resolution our scheme is an adaptation of a seismic reflection impedance inversion scheme to surface based gpr data key is relative amplitude preserving data preconditioning including gpr deconvolution which results in traces with the source wavelet distortions and propagation effects largely removed the subsequent inversion for the underlying dielectric permittivity and water content structure is constrained by in situ dielectric permittivity data obtained by direct push logging after demonstrating the potential of our novel scheme on a realistic synthetic data set we apply it to two 2 d 100 mhz gpr profiles acquired over a shallow sedimentary aquifer resulting in water content images of the shallow 3 7 m depth saturated zone having decimeter resolution

a quantitative three dimensional depositional model of gravelly braided rivers a quantitative three dimensional depositional model of gravelly braided rivers has been developed based largely on the deposits of the sagavanirktok river in northern alaska these deposits were described using cores wireline logs trenches and ground penetrating radar profiles the origin of the deposits was inferred from observations of 1 channel and bar formation and migration and channel filling interpreted from aerial photographs 2 water flow during floods and 3 the topography and texture of the river bed at low flow stage this depositional model quantitatively represents the geometry of the different scales of strataset the spatial relationships among them and their sediment texture distribution porosity and permeability in the model are related to sediment texture the geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type e g ripples dunes bedload sheets bars associated with deposition of the strataset in particular the length to thickness ratio of stratasets is similar to the wavelength to height ratio of associated bedforms furthermore the wavelength and height of bedforms such as dunes and bars are related to channel depth and width therefore the thickness of a particular scale of strataset i e medium scale cross sets and large scale sets of inclined strata will vary with river dimensions these relationships between the dimensions of stratasets bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits the depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs

the use and application of gpr in sandy fluvial environments methodological considerations ground penetrating radar gpr is a popular technique for imaging and interpreting sedimentary architecture however current literature shows a wide range in the quality of information provided on the gpr methodology and processing technique it is therefore difficult to judge the validity of the gpr interpretations and this produces inherent difficulties for comparison between surveys this paper describes the key steps required to collect process and interpret gpr surveys in sandy fluvial sediments gpr data from the south saskatchewan river canada are used to illustrate each stage of data collection and processing particular attention is given to the appropriate set up conditions for the gpr software and hardware the selection of data processing techniques and velocity analysis methods for the interpretation of gpr reflectors are also investigated using ground truth control provided by a cut face exposure this paper presents recommendations for a systematic and rigorous methodology for the collection processing and interpretation of gpr data in sandy fluvial environments the paper suggests that all data collection parameters and processing steps should be recorded or tabulated in any gpr publication to facilitate comparisons between surveys

neotectonics and late holocene paleoseismic evidence in the plio quaternary daroca half graben iberian chain ne spain implications for fault source characterization this work has been supported by project cgl2017 85045 p ministerio de economia industria y competitividad gobierno de espana

imaging rainfall drainage within the miami oolitic limestone using high resolution time lapse ground penetrating radar 1 the vadose zone of the miami limestone is capable of draining several centimeters of rainfall within a fraction of an hour once the water enters the ground little is known about the flow paths in the oolitic rock a new rotary laser positioned ground penetrating radar gpr system enables centimeter precise and rapid acquisition of time lapse surveys in the field two dimensional 2 d gpr time lapse surveying at a 3 min interval before during and after rainfall shows how buried sand filled dissolution sinks efficiently drain the bulk of the rainwater hourly repeated 3 d imaging of a dissolution sink in response to surface infiltration shows how the wetting front propagates at a rate of 0 6 1 2 m h traversing the 5 m thick vadose zone within hours at the same time some of the water migrates laterally into the host rock guided by stratigraphic unit boundaries average lateral propagation measured over a 28 hour period was of the order of 0 1 m h on a seasonal time frame redistribution involves the entire rock volume comparing 3 d surveys acquired after wet summer and dry winter conditions shows good gpr event correspondence but also time shifts up to 20 ns caused by the change of overall water content within the vadose zone high precision time lapse gpr imaging can therefore be used to noninvasively characterize natural drainage inside the vadose zone ranging from transient loading to seasonal variation

simulation of ground penetrating radar waves in a 2 d soil model we have developed a pseudospectral forward modeling algorithm for ground penetrating radar gpr based on an explicit solution of the 2 d lossy electromagnetic wave equation complex soil structures can be accommodated with heterogeneous spatial distributions of both wave velocity and electrical conductivity this algorithm uses a gaussian line source with uniform directivity and there are conductive buffer regions surrounding the soil model to approximate absorbing boundary conditions three soil models are used to illustrate different aspects of radar wave propagation the first model is lossless with homogeneous layers imbedded in a homogeneous background medium the second model has the same lossless layers in a lossy background medium and the third model is lossless and uses a nonsaturated water flow simulation to create a complex spatial velocity distribution two separate simulations with different source frequencies are presented for each soil model results indicate that higher frequency gpr will produce a sharper wavelet and can map soil layering structures with high resolution in a conductive soil however higher frequencies attenuate more rapidly and the radar may not detect deeper layers

sedimentary architecture of a spit end salisbury beach massachusetts the imprints of sea level rise and inlet dynamics abstract in the vicinity of tidal inlets the facies architecture of barrier islands is largely controlled by inlet channel shifting and the transfer of sand between the ebb tidal delta and the adjacent shore including processes of inlet sediment bypas sing merrimack river inlet is situated in a mixed energy setting and is characterized by episodic shifting of the ebb channel prior to being stabilized in 1881 here we delineate the internal structure and evolution of the updrift barrier spit terminus by integrating data obtained from ground penetrating radar transects and sediment cores to document the effects of inlet associated sedimentation processes our results document complex radar and sedimentological facies which define two distinctive associations of facies the inlet distal and proximal within the core of the present barrier these facies are associated with three phases of barrier terminus evolution i barrier retrogradation characterized by the preservation of washover and backbarrier marsh facies deposited during sea level rise ii downdrift barrier progradation characterized by channel fill and swash platform deposits overlain by foreshore deposits generated by long shore currents and swash bars migrating to the foreshore from the swash platform and iii foreshore seaward progradation characterized by cross beds this study illustrates the highly complex nature of inlet associated spit ends of barriers likewise our results shed light on the mechanisms of spit elongation and recurving in a setting where the estuary opening is narrowing

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

hierarchical dynamic stratigraphy in various quaternary gravel deposits rhine glacier area sw germany implications for hydrostratigraphy the approach of dynamic stratigraphy aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales this approach was used to investigate quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties facies analysis within 62 gravel pits laboratory permeability measurements of field samples and geophysical surveys 3 d georadar 2 d seismic reflection led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units 1 particles and pores micro scale that reflect depositional and diagenetic fluid dynamics as well as source material behaviour e g grain size roundness lithological composition this was found to be important for the hydrogeochemistry of groundwater in gravel aquifers e g higher sorption capacity of carbon rich limestone particles for organic pollutants 2 strata meso scale contain the recognition of sorting fabric texture and stratinomic features which can give an indication of transport and depositional dynamics five major lithofacies groups for example were distinguished within fluvial gravel bed deposits their variable hydraulic properties led to their subdivision into 12 hydrofacies types they form the smallest mappable hydrostratigraphic units which may result in either preferred pathways for fluid flow or flow barriers 3 depositional elements macro scale enable reconstruction of sedimentary geomorphic elements and their dynamics within a depositional system e g gravel bed braided river systems are dominated by gravel sheet gravel dunes and scour pool depositional elements hydrostratigraphically the architecture of depositional elements influences the hydraulic connectivity and local permeability structure distribution within an aquifer body five types of depositional elements in fluvial gravel bed deposits were distinguished and their geometries dimensions quantified 4 facies bodies mega scale composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics e g a coarse grained prograding delta system hydrostratigraphically facies bodies represent major compartments of an aquifer six major types of meltwater controlled facies bodies were identified in the study area 5 genetic sequences mega scale reflect the shifts of depositional environments caused by allocyclic changes e g glacial advance recorded by a coarsening upward sequence or autocyclic changes of landscape shaping events these sequences may form separate hydrostratigraphic units or aquifer storeys 6 basin fill giga scale comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long term glacier dynamics or short term flood events the regional distribution of permeable gravel units and for example less permeable diamicts builds the larger scale hydrostratigraphy

large scale structure of calamus river deposits nebraska usa revealed using ground penetrating radar the large scale i e bar scale structure of channel deposits of the braided low sinuosity calamus river nebraska is described using ground penetrating radar gpr profiles combined with vibracores basal erosion surfaces are generally overlain by medium scale trough cross stratified sets 3 25 cm thick very coarse to medium sands that are associated with relatively high amplitude discontinuous gpr reflectors overlying deposits are bioturbated small scale cross stratified sets 3 cm thick and vegetation rich fine to very fine sands that are associated with low amplitude discontinuous reflectors near surface peat and turf have no associated gpr reflectors in along stream profiles through braid and point bars most gpr reflectors dip downstream at up to 2 relative to the basal erosion surface but some reflectors in the upstream parts of bars are parallel to the basal erosion surface or dip upstream in cross stream profiles through bars gpr reflectors are either approximately parallel to bar surfaces or have low angle inclinations up to 6 towards cut banks of adjacent curved channels basal erosion surfaces become deeper towards cut banks of curved channels these structures can be explained by lateral and downstream growth of bars combined with vertical accretion convex upwards forms up to 0 5 m high several metres across and tens of metres long represent episodic accretion of unit bars scroll bars and bar heads stratal patterns in channel fills record a complicated history of erosion and deposition during filling including migration of relatively small bars a revised facies model for this type of sandy braided river has been constructed based on this new information on large scale bedding structure

mapping the architecture of glaciofluvial sediments with three dimensional georadar three dimensional 3 d ground penetrating radar georadar mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units to investigate the potential of this high resolution technique and at the same time study the architecture of quaternary glaciofluvial deposits georadar data have been collected on a dense grid established across a sequence of braided river gravels and sands in northeastern switzerland results of this survey are striking 3 d images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of approx 15 m clearly defined are the dominant flow direction of the ancient braided river system the boundaries between different sedimentary facies and the level of the ground water table trough fill sediments and subhorizontal channel deposits observed on 7 m high quarry walls can be followed confidently in the subsurface the orientation shape and size of the troughs and the strike and dip of the cross bedding are all well resolved

variations in free phase gases in peat landforms determined by ground penetrating radar 1 the spatial variability of biogenic gas produced by methanogenic archaea is difficult to assess within saturated peat soils and is often poorly quantified this study uses ground penetrating radar to noninvasively estimate the vertical distribution of biogenic free phase gas fpg in two distinct peat landform types in the glacial lake agassiz peatland minnesota a near crest bog and a midslope lawn i e both as defined by surface vegetation communities ground penetrating radar velocities retrieved from common midpoint surveys were modeled using the complex refractive index model to estimate free phase gas volumes along one dimensional vertical profiles near crest bog landforms are characterized by vertical variability in gas content with accumulations along the peat column up to 24 by volume of fpg localized within the deep peat e g 2 4 m depth midslope lawn sites show lower total volumes up to 12 free phase gas and less variability that result in a more even free phase gas distribution throughout the vertical profile high resolution data also suggests the presence of thinner layers 1 m containing up to 40 free phase gas at a near crest site our results suggest that spatial distribution of free phase gas along the peat column may vary in the glacial lake agassiz peatlands depending on peat landform statistical analysis supports vertical variability of ground penetrating radar velocity data with a 95 confidence limit our results could potentially be upscaled using surface vegetation communities to estimate landscape scale gas storage potential in peat landforms

application of ground penetrating radar methods in soil studies a review abstract applications of ground penetrating radar gpr in soil surveys promise cost and time benefits together with the possibility of repeating surveys at the same locations due to the method s non destructiveness to the ground surface after its successful application to earth sciences surveying of the deep subsurface gpr was used in soil surveys however its application in soil surveys has been difficult this paper aims to provide an overview of the application of gpr in soil surveys this paper focuses on methods to estimate the soil water content by various approaches such as determining the electromagnetic signal velocity in a soil by analyses of reflections ground wave or guided wave approaches and the full waveform inversion method to characterize soil and peat stratigraphy with an emphasis on organic horizons and to detect tree roots gprs have been relatively successfully applied in a wide spectrum of surveys but under favourable conditions more complex techniques using numerical modelling that have emerged in recent years might have the potential to be more successful

effects of sand supply on the morphodynamics and stratigraphy of active parabolic dunes bigstick sand hills southwestern saskatchewangeological survey of canada contribution 20060654 sand supply is a major controlling factor on parabolic dune form and stratigraphy in inland settings in this study aerial photographs ground penetrating radar gpr and stratigraphic analysis d

the application of gpr and eri in combination with exposure logging and retrodeformation analysis to characterize sinkholes and reconstruct their impact on fluvial sedimentation this work illustrates the practicality of investigating sinkholes integrating data gathered by ground penetrating radar gpr electrical resistivity imaging eri and trenching or direct logging of the subsidence affected sediments in combination with retrodeformation analysis this mutidisciplinary approach has been tested in a large paleosinkhole developed during the deposition of a quaternary terrace on salt bearing evaporites the subsidence structure exposed in an artificial excavation is located next to puilatos a village that was abandoned in the 1970s due to severe subsidence damage detailed logging of the exposure revealed that the subsidence structure corresponds to an asymmetric sagging and collapse paleosinkhole with no clear evidence of recent activity the sedimentological and structural relationships together with the retrodeformation analysis indicate that synsedimentary subsidence controlled channel location the development of a palustrine environment and local changes in the channel pattern gpr profiles were acquired using an array of systems with different antenna frequencies including some recently developed shielded antennas with improved vertical resolution and penetration depth although radargrams imaged the faulted sagging structure and provided valuable data on fault throw they did not satisfactorily image the complex architecture of the fluvial deposit eri showed lower resolution but higher penetration depth when compared to gpr roughly capturing the subsidence structure and yielding information on the thickness of the high resistivity alluvium and the nature of the underlying low resistivity karstic residue developed on top of the halite bearing evaporitic bedrock data comparison allows the assessment of the advantages and limitations of these complementary techniques highly useful for site specific sinkhole risk management this article is protected by copyright all rights reserved

identifying causes of ground penetrating radar reflections using time domain reflectometry and sedimentological analyses ground penetrating radar gpr is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves however little is known about the exact cause of gpr reflections because few studies have coupled wave theory to petrophysical data in this study a 100 and 200 mhz gpr survey was conducted on aeolian deposits in a quarry time domain reflectometry tdr was used to obtain detailed information on the product of relative permittivity er and relative magnetic permeability lr which mainly controls the gpr contrast parameter in the subsurface combining tdr data and lacquer peels from the quarry wall allowed the identification of various relationships between sediment characteristics and erlr synthetic radar traces constructed using the tdr logs and sedimentological data from the lacquer peels were compared with the actual gpr sections numerous peaks in erlr which are superimposed on a baseline value of 4 for dry sand are caused by potential gpr reflectors these increases in erlr coincide with the presence of either organic material having a higher water content and relative permittivity than the surrounding sediment or iron oxide bands enhancing relative magnetic permeability and causing water to stagnate on top of them sedimentary structures as reflected in textural change only result in possible gpr reflections when the volumetric water content exceeds 0ae055 the synthetic radar traces provide an improved insight into the behaviour of radar waves and show that gpr results may be ambiguous because of multiples and interference

discriminating between onlap and lithologic interfingering in seismic models of outcrops seismic models of outcrops have shown that near the limits of resolution the seismic reflection tool records rapid facies changes as false lap outs we examined one such outcrop the triassic platform flank of picco di vallandro durrenstein in northern italy to develop criteria for recognizing false lap out patterns using measured sections photo mosaics of the continuous outcrop and petrophysical measurements on samples two contrasting impedance models were constructed one model supported by field observation shows interfingering between basin marls and slope carbonates the second model shows onlap of basin marls against slope carbonates but with similar overall geometries to the first model vertical incidence seismic models were produced at frequencies between 50 and 150 hz and with displays of seismic amplitude as well as two seismic attributes instantaneous phase and reflection strength at 50 hz the two lithologic models are seismically indistinguishable both showing onlap of basin units onto the slope at 90 hz displays of instantaneous phase begin to reveal the stratigraphic interfingering whereas seismic amplitude displays require frequencies of 150 hz to do so reflection strength accurately portrays the distribution of the two major facies in the entire range of examined frequencies but does not show sufficient detail to reveal interfingering vs onlap the same trends were visible with finite difference modeling of the full waveform here the differences between interfingering and onlap become visible at 150 hz in the phase model where seismic amplitude displays at this frequency are still ambiguous the phase model however fails to differentiate between slope dip and the basin sediment wedge whereas this wedge is clearly mapped by the reflection strength a combination of instantaneous phase and reflection strength provides a decisive advantage over conventional amplitude displays in recognizing rapid facies changes in seismic reflection data

seismic models of a shelf margin depositional sequence upper san andres formation last chance canyon new mexico abstract the seismic resolution of stratal geometries and facies distributions observed in san andres formation permian outcrops in last chance canyon guadalupe mountains new mexico is studied by seismic modeling of a published detailed stratigraphic cross section the outcrops in last chance canyon are composed of two fourth order depositional sequences an aggrading carbonate bank upper san andres 3 usa3 followed by a strongly progradational offlapping mixed carbonate siliciclastic succession upper san andres 4 usa4 each sequence comprises a number of subsidiary high frequency sequences fifth order two alternative impedance models were used model a in which all facies transitions are reflecting boundaries and model b in which only time significant surfaces act as reflectors and lateral facies transitions are represented by horizontal velocity gradients the vertical incidence modeling technique was used to compute perfectly migrated time and depth sections with different frequencies using a low frequency wavelet 25 hz the sequence boundary separating the two fourth order cycles usa3 and usa4 is poorly imaged instead one is tempted to incorrectly interpret an onlap pattern generated by a high frequency cycle within usa4 as this major sequence boundary in addition the 25 hz runs show toplap and downlap lap out patterns in an overly oblique fashion obscuring true asymptotic stratal relationships both at 35 hz and 50 hz profiles based on model b image the genetic structure of both usa3 and usa4 relatively well at 50 hz model a incorrectly shows a transition from a ramp to a rimmed margin within usa4 the 35 hz models are qualitatively compared with a published exxon production research co seismic line located approximately 50 km along depositional str ke to the northeast model a shows an unexpected good match with the exxon seismic line whereas model b comes much closer to the depositional anatomy observed in outcrop our results show that the resolution of stratal geometries and facies distributions in last chance canyon is strongly related to carbonate sandstone alternations and the way impedance contrasts at carbonate sandstone transitions are represented

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

morpho stratigraphic characterization of a tufa mound complex in the spanish pyrenees using ground penetrating radar and trenching implications for studies in mars abstract the isona tufa mound complex itmc associated with artesian springs of the areny montsec aquifer spanish pyrenees is a potential analog for water constructed landforms on mars we used ground penetrating radar gpr trenching sedimentological description of exposures and radiocarbon and u series dating methods for the geological characterization of the itmc preliminary geomorphological mapping combined with sedimentological analyses permitted the recognition of the different facies and their spatial distribution gpr surveys conducted next to an outcrop and a trench provided electromagnetic wave velocity in tufas 0 09 and 0 11 m ns 1 and determined the correspondence of the radar signatures with facies types this was used to reconstruct the tufas internal structure and the depositional stages for two different contexts 1 an upper unit representing the morpho stratigraphic record of paleosprings tufa 1 composed of relict tufa mounds older than 350 ka bp and 2 a lower unit tufa 3 associated with groundwater aquifer outlets basturs lakes the gpr data allowed depicting the signatures for the vent pool rimstone palustrine dam cascade and slope facies a relationship was inferred between the age of the tufas and the radar signature in terms of relative amplitude and signal attenuation older dry tufas with advanced diagenesis and karstification are characterized by well defined gpr reflectors and lower attenuation than younger tufas associated with aquifer discharge and shallower water tables u series and radiocarbon ages obtained from the basturs lakes tufas indicate that these have been active since 106 ka bp during both cold and mild marine isotopic stages mis we hypothesize that tufas related to the deep seated areny montsec confined karst aquifer were insensitive to climate variations landforms reminiscent of the itmc have been detected during the last decade on mars since gpr will be part of the exomars rover of the european space agency esa mission projected for 2018 we anticipate that our results may be able to constrain the interpretation of landforms possibly related to water on mars

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

the geochemical evolution of syncollisional magmatism and the implications for significant magmatic hydrothermal lead zinc mineralization gangdese tibet abstract in addition to well known subduction processes the collision of two continents also generates abundant ore deposits as in the case of the tibetan plateau which is the youngest and most spectacular collisional belt on earth during the building history of the gangdese magmatic belt several magmatic flare up events developed however significant magmatic hydrothermal lead zinc mineralization dominantly accompanied the magmatism during the syncollisional period 65 41 ma based on integrated geochemical and isotopic data we provide insights into the genesis and evolution of syncollisional magmas and their implications for significant magmatic hydrothermal lead zinc mineralization the sr nd isotopic compositions of most syncollisional igneous rocks 87sr 86sr 0 7034 0 7123 end t 9 0 to 1 8 indicate a mixing origin between mantle derived basaltic magmas and ancient crustal melts and fractional crystallization is a fundamental mechanism by which syncollisional magmas evolve towards intermediate to silicic compositions most lead zinc mineralization related plutons are high silica 76 14 wt sio2 on average high oxygen fugacity average fmq 2 5 granites with highly evolved chemical signatures average eun eun 0 33 high rb sr average 3 9 and they represent the final products from primary magmas due to the contribution of ancient crustal melts to the genesis of mineralization related parent magmas the spatial distribution of pb zn deposits within the northern gangdese magmatic belt is controlled by the lithospheric architecture in compressional environments magmas have low evacuation efficiency and long magma chamber lifespan which is favorable for basaltic parents evolved to high silica granites through sufficient fractional crystallization this scenario contributes to our understanding of the significant magmatic hydrothermal lead zinc mineralization that occurred in the syncollisional period

the tectonic and volcanic history of rhea as inferred from studies of scarps ridges troughs and other lineaments abstract analyses of landforms on rhea are used to define 13 types of geomorphic features interpreted to be of tectonic and volcano tectonic origin all types except one seem to be extensional in origin they occurred after the formation of population i craters and are contemporaneous with a major resurfacing event the troughs grabens grooves pit chains scarps and other lineaments vare pure extensional features while the ridges are volcanic features formed in an extensional stress field this global surface extension was followed by an era of global compression which produced megaridges and megascarps these compressional features are not numerous enough to fit the theoretical stresses predicted by the typical thermal models of rhea all the extensional landforms appear to form a global grid pattern this planetary wide grid is similar in direction to the theoretical pattern of a tidally distorted planet that suggests either an orbital variation very early in the history of rhea or the existence of an unknown process which has oriented the stress field during the extensional period

upper pleistocene to holocene peatland evolution in southern brazilian highlands as depicted by radar stratigraphy sedimentology and palynology paleoenvironmental interpretation of proxy data derived from peatlands is largely based upon an evolutionary model for ombrotrophic bogs in which peat accumulates in still environments reports on proxies obtained from minerotrophic fens where hydrologic inputs are variable are less common in this study a highland peatland in southern brazil is presented through ground penetrating radar gpr and sedimentological palynological and geochronologic data the radar stratigraphic interpretation suggests a relatively complex history of erosion and deposition at the site since the beginning of marine isotope stage 3 mis 3 interstadial period in spite of this radar stratigraphic and palynologic interpretations converge electromagnetic reflections tend to group in clusters that show lateral coherence and correlate with different sediment types while pollen grains abound and are well preserved as a result the study of minerotrophic fens provides a source of proxies suggesting that ombrotrophic bogs are not the only reliable source of data in wetlands for palynological analysis

comparison of laser grain size analysis with pipette and sieve analysis a solution for the underestimation of the clay fraction classically the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method based on the stokes sedimentation rates for the fine fractions results from the two methods are compared with results from laser diffraction size analysis which is based on the forward scattering of monochromatic coherent light from a point of view of laboratory efficiency the laser sizing technique is far superior accuracy and reproducibility are shown by measurements on certified materials it appears that laser grain size measurements of certified materials correspond very well with the certificated measurements tests were also done on a set of randomly selected sediments of fluvial aeolian and lacustrine origin except for the 2 m clay fraction there is a coarsening of the mean diameter of one to two size classes 0 25 caused by the non sphericity of the particles the platy form of the clay particles induces considerable differences eight size classes between pipette and laser measurements the 2 m grain size defined by the pipette method corresponds with a grain size of 8 m defined by the laser particle sizer for the studied sediments using a higher grain size level for the clay fraction when laser analysis is applied enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique

ground penetrating radar evaluation of the internal structure of fluvial tufa deposits devanos anavieja system ne spain an approach to different scales of heterogeneity

internal structure of a trough blowout determined from migrated ground penetrating radar profiles ground penetrating radar gpr was used to investigate the relationship between the geomorphological development of a large aeolian trough blowout and the stratigraphy and internal sedimentary structure of its associated deposits although analogous many of the data processing techniques routinely applied in seismic reflection are very rarely applied in gpr studies in this study a simple migration program was used that significantly enhanced the quality of gpr images from a large trough blowout at raven meols on the sefton coast northwest england these improvements aided subsequent data interpretation which was achieved through application of the principles of radar stratigraphy gpr shows the pre blowout dunes to have a complex internal structure that suggests they were formed in the presence of at least a partial vegetation cover subsequent to stabilization of these dunes a thin soil developed this dune soil forms an important radar sequence boundary and delineates a complex topography beneath the depositional lobe of the blowout the internal structure of the depositional lobe of the blowout does not conform to a model of simple radial foreset deposition as derived from contemporary process studies reported in the literature instead the pattern of deposition has been extensively modified by the antecedent dune topography and by varying spatial and temporal exposure to important sand transporting winds that is partly controlled by interactions between the regional wind pattern and local dune morphology trough blowout deposits in coastal aeolian sedimentary sequences are likely to be recognized by the presence of laterally continuous packets of relatively high angle cross strata which often display a spatially variable radial dip pattern that is only very poorly or partially developed in addition a soil or other surface representing a significant hiatus in dune deposition is likely to underlie the blowout deposits the topography of which will show a clear relationship to the dip and orientation of the overlying cross strata

late quaternary landscape development at the margin of the pomeranian phase mis 2 near lake wygonin northern poland abstract in central europe late quaternary landscapes experienced multiple phases of geomorphologic activity in this study we used a combined geomorphological pedological sedimentological and palynological approach to characterize landscape development after the last glacial maximum lgm near lake wygonin in northern poland the pedostratigraphical findings from soil pits and drillings were extrapolated using ground penetrating radar gpr and electric resistivity tomography ert during the pomeranian phase glacial and fluvioglacial processes dominated the landscape near lake wygonin at the end of the glacial period periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains at approximately 15 290 14 800 cal yr bp a small pond formed in a kettle hole profile bwi 2 the lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time the increase of juniperus and rock rose helianthemum in the pollen diagram is a prominent marker of the younger dryas at the end of the younger dryas a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments no geomorphologic activity since the beginning of the holocene is documented in the terrestrial and wetland archives the anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains secale cereale and translocated soil sediments dated to 1560 1410 cal yr bp proving agricultural use of the immediate vicinity with the onset of land use gully incision and the accumulation of colluvial fans reshaped the landscape locally since 540 460 cal yr bp further gully incision in the steep forest tracks has been associated with the intensification of forestry outside of the gully catchments the weakly podzolized rubic brunic arenosols show no features of holocene soil erosion

three dimensional ground penetrating radar imaging of sedimentary structures fractures and archaeological features at submeter resolution contemporary geoscientific shallow subsurface assessment chiefly relies on outcrops drilling excavations and sometimes geophysics often the information gathered is insufficient to accurately characterize the archaeological and or geologic record and ongoing shallow subsurface processes that affect a variety of economic and environmental aspects of our society the extra effort of acquiring very dense ground penetrating radar gpr survey grids and three dimensional 3d data processing transforms uncorrelatable and uninterpretable gpr signals into clear images of complex shallow subsurface anatomy with an unprecedented resolution here we present two examples of noninvasive 3d shallow subsurface imaging example 1 images decimeter to meter scale sedimentary structures in a pleistocene oolite shoal barrier bar setting example 2 images the fracture network in a triassic limestone quarry denser than quarter wavelength grid acquisition in combination with 3d migration processing focuses scattered energy and removes out of plane reflections in addition to conventional vertical cross sections horizontal depth slices and data volume animations reveal previously unseen diagnostic patterns of past human activities laterally changing depositional processes and fracture networks including near vertical joints with millimeter apertures

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

gpr based detection of pleistocene periglacial slope deposits at a shallow depth test site abstract pleistocene periglacial slope deposits ppsd almost completely cover the mountainous regions of germany and are the parent material for soil formation it is therefore necessary to map their thickness and spatial distribution the mapping of periglacial slope deposits can be performed more quickly than conventional probing by drilling or soil profile analysis if ground penetrating radar gpr is used because the use of gpr to map soils or soil depth depends to a large degree on the suitability of soil properties the performance of gpr in mapping layered substrates was evaluated at a test site with varying water content and substrate properties we focus on the efficiency of gpr in mapping loess rich layers above layers with a high stone content within a depth range of 1 m different materials such as loess metabasalt and slates including heavily weathered slates saprolite were studied the test site was equipped with several time domain reflectometry tdr probes to monitor soil water content changes for the period of one year systematic investigations of the reflection patterns were performed with 100 200 400 500 and 900 mhz antennae with respect to the quality of measurement dielectric coefficient and soil water content of different material combinations it became clear that the 400 mhz antenna is most suitable for creating images of loess and stone layers at the depth range of 1 m and under natural climatic conditions the results prove that the most important effect the substrates at the test site have on gpr is produced by the differences in water content of bordering layers making the soil water capacity of the materials a decisive parameter for evaluating gpr performance the water content dependent dielectric permittivities show higher values for saprolite heavily weathered slate compared to loess by a factor of 1 3 to 2 with water content increasing from 15 to 40 vol respectively in doing so we discovered the dielectric permittivity of loess to be 1 2 to 1 5 times higher than that of unweathered slate at the same water content we were able to locate horizontal layer boundaries at the test site starting at a minimum of 0 5 vol water content difference and a reflection coefficient r 0 02 between the layers the results obtained at the test site show the ability of gpr to detect layering in ppsd at different water contents and help to predict the performance of gpr measurements in mapping of ppsd

how did the ad 1755 tsunami impact on sand barriers across the southern coast of portugal idl pest oe cte la0019 2013 plani2c ed481b 2014 132 0 post doc eu fp7 research project risc kit ga 2013 603458 e fct investigator program ref if 01047 2014

ground penetrating radar as a tool to detect rock heterogeneities channels cemented layers and fractures in the luxembourg sandstone formation grand duchy of luxembourg a combined study of radar profiles and thin section analysis supported by modelling of synthetic radar traces reveals that ground penetrating radar gpr reflections generated in diagenetically altered sandstones cannot always be interpreted unequivocally this is illustrated in the luxembourg sandstone formation which has been altered diagenetically by selective carbonate cementation and fracturing cemented lenses and concretions developed along the bedding planes especially at places with high primary carbonate content cementation resulted in the alternation of cemented carbonate rich sandy layers thickness 30 50 cm and variable length and uncemented carbonate poor sandstone layers the ability of gpr to detect the geometry of these lenses and vertical fractures with centimetre apertures has been tested at several antenna frequencies 100 200 250 and 500 mhz relative dielectric permittivity calculations were carried out to assess variations of this electric property within the cemented and uncemented layers as a function of porosity calcite and water content in the pores two dimensional full waveform modelling was also carried out to study the effect of conductivity in the sandstones and the effect of interlayer clay seams at the penetration depth of the radar 7 m with 250 mhz cemented lenses and concretions could only be detected with gpr when the porosity contrast was sufficiently high which is not always the case this conclusion is supported by the modelling the data also proved the ability of radar to detect large open vertical fractures along which sandstones are weathered the study has implications for investigations which will use gpr to detect three dimensional distribution of diagenetic pore filling precipitates as well as secondary porosity development along fractures

cyclical evolution of a modern transgressive sand barrier in northwestern spain elucidated by gpr and aerial photos abstract the internal structure of a modern baymouth barrier is analyzed in detail including its historical evolution and the factors controlling it historical evolution was reconstructed using available aerial photographs from 1956 to 2003 detailed geophysical data were acquired using ground penetrating radar gpr and analyzed along with airphotos to reconstruct the recent evolution of a barrier located in northwestern spain the gpr data reveal the internal architecture of the barrier which consists of two main radar facies 1 washover deposits associated with landward barrier migration and vertical aggradation and 2 beach deposits associated with seaward barrier progradation the reconstruction of the stratigraphic sequence indicates the occurrence of two erosive periods followed by an accretionary period the erosion along the barrier is outlined by the presence of three well defined bounding surfaces the stratigraphic record of the subsequent recovery phase depends on the impact level of the erosive phase which is controlled by the presence of ephemeral inlets along the barrier this alternating behavior implies a discontinuous shoreline trajectory in spite of a net landward migration this trend is consistent with regional sea level rise albeit being intensified locally by the interplay of sediment starvation and storm regime landward barrier retreat occurs by overwash and inlet breaching which permits barrier preservation of volume due to a continuous constructive destructive cycle the results acquired from this example expand our understanding of the internal structure and evolutionary trends of transgressive sand barriers

aquifer architecture analysis using ground penetrating radar triassic and quaternary examples s germany applying the concept of analogue studies long used in reservoir characterization outcrop analogues in two aquifer units of southern germany have been investigated upper triassic keuper alluvial sandstones stubensandstein and quaternary glaciofluvial gravels architectural element analysis of the outcrops is combined with ground penetrating radar profiles derived a few meters behind the outcrop walls such calibration is used to better understand the three dimensional sedimentary architecture many sedimentary units at the same time represent hydraulic flow units and are characterized by specific radar signatures this approach leads to promising results not only in unconsolidated aquifers but also in fully consolidated sedimentary rocks our studies will lead to a database with which more realistic predictions of the hydraulic behaviour of sedimentary aquifers systems needed for numerical hydrogeological simulations will be possible

geostatistical analysis of ground penetrating radar data a means of describing spatial variation in the subsurface we have investigated the use of ground penetrating radar gfr as a means of characterizing the heterogeneity of the subsurface radar data were collected at several sites in southwestern british columbia underlain by glaciodeltaic sediments a cliff face study was conducted in which geostatistical analysis of a digitized photograph of the face and the radar image of the face showed excellent agreement in the maximum correlation direction and the correlation length determined from these two data sets other two dimensional 2 d sections of radar data were divided into sedimentary architectural elements on the basis of the distinct radar appearance of these sedimentary units examples of four sedimentary units were used to obtain semivariograms from the radar data and resulted in maximum correlation lengths between 0 5 and 4 8 m a 3 d radar survey collected over a package of gravel and sand foresets was analyzed to determine the paleoflow direction a correlation length of 4 m was found in that direction

ground penetrating radar monitoring of a controlled dnapl release 200 mhz radar a controlled release of tetrachloroethylene was performed in a saturated natural sandy aquifer to evaluate the effectiveness of various geophysical techniques for detecting and monitoring dense nonaqueous phase liquids dnapls in the subsurface tetrachloroethylene typical of most dnapls has a low relative dielectric permittivity 2 3 which contrasts with the high relative permittivity 80 of the pore water it displaces making it a potential target for detection by ground penetrating radar gpr gpr data were acquired using 200 mhz antennas radar sections collected at different times over the same spatial location clearly show the changes induced by the movement of dnapl in the subsurface temporal changes can be examined through the evolution of a radar data trace collected at a single spatial location normal moveout analysis of common midpoint cmp data demonstrates induced changes in electromagnetic em wave velocities of up to 30 percent caused by the presence of dnapl the distribution o

pseudo unconformities in seismic models of large outcrops traditionally seismic modeling has concentrated on one dimensional borehole modeling and two dimensional forward modeling of basic structural stratigraphic schemes which are directly compared with real seismic data two dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines examples include the dolomites north italy the vercors se france and the high atlas morocco the seismic models are generally constructed using the following procedure a construction of a detailed lithologic model based on direct outcrop observations b division of the lithologic model into lithostratigraphic units c assignment of petrophysical properties to these lithostratigraphic units d ray tracing to compute time or depth sections of reflectivity e convolution of the reflectivity sections with source wavelets of different frequencies the lithologic detail modeled in the case studies led to some striking results particularly the discovery of pseudo unconformities pseudo unconformities are unconformities in seismics but correspond to rapid changes of dip and facies in outcrop none of the outcrop geometries studied were correctly portrayed seismically at 25 hz peak frequency however in some instances the true relationship would gradually emerge at peak frequencies of 50 100 hz the examples given in this study demonstrate that detailed outcrop derived seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less ideal conditions and what pitfalls may befall the interpreter of real seismic data

estimation of porosity and water saturation in dual porosity pyroclastic deposits from joint analysis of compression shear and electromagnetic velocities in situ measurements of porosity and water saturation of pyroclastic deposits have the potential to improve interpretations of geology and hydrology in volcanic regions and provide more accurate estimates of dense rock equivalent for volcanic eruptions however rock property models must consider the dual porosity structure of pyroclastic deposits i e vesicles within pumices and intergranular pores vesicularity intergranular porosity and water saturation all affect the density elasticity and dielectric properties of pyroclastic materials which control seismic and electromagnetic velocities the data from active seismic and ground penetrating radar techniques may improve porosity and water saturation estimation if the responses of seismic and electromagnetic waves to porosity and water saturation variations are complementary in pyroclastic rocks we develop a dual porosity petrophysical model to calculate seismic and electromagnetic velocities of pumice with known intergranular porosity vesicul

a ground penetrating radar survey of a delta front reservoir analog in the wall creek member frontier formation wyoming ground penetrating radar gpr measurements in conjunction with outcrop sedimentology were carried out at murphy creek reservoir in the upper cretaceous turonian wall creek member of the frontier formation in wyoming the objectives were to apply gpr to map geometrical details of a top truncated lowstand delta front and to estimate the volumes of the prograding bar deposits of the delta lobe eleven gpr profiles totaling about 4400 m 14 435 ft were acquired using 50 mhz antennas on a coarsely spaced two dimensional grid of lines lying parallel and perpendicular to the average depositional dip ground penetrating radar reflections were detected from within the outcrop to a depth of about 10 15 m 33 49 ft four southerly dipping major surfaces identified in the gpr data are correlated with the boundaries of progradational delta front facies stacked as distal mouth bar deposits in the outcrop the major boundaries correspond to lithological changes between relatively clean sandstones that are interpreted to have been deposited during floods with high sediment supply alternating with bioturbated sandstones and mudstones deposited during interflood periods with correspondingly low sedimentation rates these two lithological units which also correspond to the two main gpr facies repeat at least three times with no change in dominant average sand grain size subsequent erosion by transgressive ravinement caused the significantly truncated lowstand delta long after the sandstones were deposited the bar assemblage volume at successive stages of growth is estimated using measurements from the outcrop and the gpr data the migrating bars have an estimated average half length of 650 m 2132 ft a lower bound on the average volume of the bar is 3 9 106 m3 1 37 108 ft3 as the volume of the bars increases the bar deposits appear to have a landward as well as a basinward component of accretion

karst and early fracture networks in carbonates turks and caicos islands british west indies abstract historically studies of quaternary carbonates have not adequately addressed the influence of early fracture networks on diagenesis because of this lack of detail understanding and predicting fracture related diagenetic heterogeneities and preferential fluid flow pathways in ancient carbonate successions is particularly challenging the pleistocene oolitic grainstones of the caicos platform provide an excellent opportunity to evaluate the relative importance of fractures on early diagenetic alteration styles and are a suitable analog for subsurface carbonate reservoirs detailed analyses of fractures e g orientation aperture spacing fill material from caicos outcrops combined with high resolution three dimensional ground penetrating radar 3d gpr assisted in exploring the causality and distribution of fractures and relationship to karst four models were evaluated to explain the observed distribution of dolines 1 gravitational fractured margin controlled 2 tectonic fracture controlled 3 antecedent topography controlled and 4 a hybrid model based on observations of numerous fractures n 306 on the western caicos platform early fractures are abundant and dominantly margin parallel these fracture networks are well established in limestones prior to mineralogical stabilization thereby indicating that diagenetic heterogeneities evolve very early in carbonate diagenesis the spatial distribution of dolines on providenciales is likely the result of a complex interplay between the antecedent topography margin parallel fracture systems and meteoric fluids resultant diagenetic alteration is far more complicated than simple unconfined meteoric lenses associated with topographic highs any attempts to model early diagenesis in carbonates should not dismiss the role of fractures as diagenetic facilitators and diagenetic anisotropy templates

bar top hollows a new element in the architecture of sandy braided rivers abstract discrete hollows in the bar tops of the south saskatchewan river are described that form a newly recognized morphological element of sandy braided rivers these bar top hollows which are up to 1 7 m deep and may extend for 10 30 m down and across flow have a circular to ovoid planform and are shown through use of ground penetrating radar to be filled by a series of distinct often angle of repose foresets the hollows form by both erosion and bar top deposition and may be generated by bar tail accretion cross bar channel cutoff and subsequent fill or lateral accretion at the bar head bar top hollows occur in the upper part of the bar depositional sequence and may thus prove useful indicators for braid bar reconstruction in ancient sediments and should not be confused with channel scour

radar facies of paraglacial barrier systems coastal new england usa analysis of a large data base of ground penetrating radar gpr profiles from both natural and developed paraglacial barriers along the coast of new england has allowed identification of eight reflection configurations that characterize this type of mid to high latitude coastal environment bedrock anchor points yield primarily hyperbolic configurations whereas glacial anchor points and sediment source areas are characterized by chaotic parallel and tangential oblique configurations beaches and dunes produce predominantly sigmoidal oblique hummocky reflection free and bounding surface configurations back barrier sediments may yield basin fill configurations but generally include abundant signal attenuating units the gpr data calibrated with information from cores were collected across swash aligned and drift aligned barriers in a variety of wave and tidal energy settings application of a 120 mhz antenna as used in this study enables portrayal of a range of sedimentary units from individual bedforms on single records to entire barrier elements using large numbers of intersecting gpr sections at maximum vertical resolutions that vary between 0 2 m and 0 7 m the most important drawback of gpr in the coastal environment is attenuation of the electromagnetic em signal by layers of salt marsh peat or by brackish or salty groundwater primarily along barrier edges this disadvantage is offset by many benefits data can be collected at rates of several km per day making gpr an excellent reconnaissance tool a core that is used in the calibration of gpr data can be matched with great accuracy to its position on the complementary gpr record allowing detailed correlation between lithostratigraphy and reflection configuration