geomorphic relations among glacial lake algonquin and the munising and grand marais moraines in eastern upper michigan usa abstract data obtained from ground penetrating radar gpr optically stimulated luminescence osl dating and geostatistical reconstructions of lake algonquin water planes indicate that high standing outwash aprons flanking the munising moraine s southern margin in eastern upper michigan terminate as large coalescing gilbert type ice contact deltas graded to the main level of lake algonquin nearly 30 km of gpr imagery provides clear evidence of topset and foreset beds diagnostic of deltaic deposition landform assemblages suggest that the deltas likely evolved from subaqueous grounding line fans formed along a retreating ice margin characterized by widespread stagnation in time these deltas aggraded to the main lake algonquin level as the ice margin stabilized an osl date of 12 5 1 1 ka on a nearby beach ridge associated with the main algonquin shoreline is consistent with this interpretation these new data coupled with the presence of nested fans at the downstream end of meltwater channels incised into the delta indicate that lake algonquin was falling as delta deposition waned eventually reaching a level concordant with the lower orillia level before final abandonment large regionally extensive heads of outwash marking the crest of the munising moraine are graded to the upper margins of these deltas and by inference must also correlate with main lake algonquin and the associated two rivers deglaciation ca 13 12 5 ka the deltas in turn are conspicuously crosscut by outwash aprons that are graded to levels much lower than any recognized upper group lake algonquin shoreline because these aforementioned heads of outwash part of drexler and others grand marais moraine correlate with the marquette moraine farther west they likely date to the marquette advance ca 11 5 ka thus landforms related to two rivers and to marquette glaciations appear to comingle across the study area in the absence of extensive exposures and datable materials our work highlights the fact that crosscutting relationships and distinct differences in base level can provide an important first step for untangling the complicated landform relationships in this part of michigan

the utility of conductivity surveying and resistivity sounding in evaluating sand and gravel deposits and mapping drift sequences in northeast scotland abstract two types of ground geophysical survey using portable equipment capable of one man operation have been used with the aim of elucidating the thickness and extent of sources of potentially workable sand and gravel in northeast scotland vertical resistivity soundings have provided point data that allow extrapolation of the drift succession between exposures boreholes and trial pits lateral profiling of ground conductivity using a non contacting electromagnetic conductivity meter has proved to be of little use as an aid to conventional geological mapping in determining the position and extent of surface spreads of sand and gravel resistivity sounding using offset wenner apparatus in particular represents a rapid low cost method applicable by industry to the preliminary investigation of the thickness of sand and gravel at proposed extraction sites especially in areas where modern geological maps are not available or where ground disturbance has to be minimised

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

resolving scales of aquifer heterogeneity using ground penetrating radar and borehole geophysical logging accurate and reliable characterization of aquifer heterogeneity remains one of the foremost problems in hydrogeology in this study ground penetrating radar gpr and borehole geophysical logging are used to investigate scales of heterogeneity present locally 500 m laterally within an outwash deposit comprised of inter bedded and cross bedded sands and gravels of glaciofluvial origin at a small scale 15 m laterally gamma log data in adjacent boreholes show evidence of fining upward sequences occasional coarsening upward sequences and abrupt changes in grain sizes which appear to be laterally continuous at scales of 10 m at the site scale 500 m laterally gpr profiles show a strong reflection interpreted as the water table reflectors in the unsaturated zone are more clearly defined than those beneath the water table due to signal attenuation within the saturated sediments undulating to discontinuous reflectors at scales of 10 15 m are interpreted to result from interbedded and cross bedded sands and gravels a few laterally continuous horizontal to sub horizontal reflectors which extend at least up to 360 m are interpreted as unconformities based on evidence of gravel bars truncation of underlying units as well as scour and fill features in a nearby gravel pit exposure overall the integration of these two geophysical methods provided evidence of unit correlation at the two scales of investigation

an east west sst anomaly pattern in the midlatitude north atlantic ocean associated with winter precipitation variability over eastern china 1 winter precipitation tends to vary consistently over most regions of eastern china the present study reveals that the variation in winter precipitation over eastern china is positively correlated to an east west sea surface temperature sst anomaly pattern in the midlatitudes and high latitudes of the north atlantic ocean when the sst is higher lower in the eastern north atlantic ocean and lower higher in the western north atlantic ocean winter precipitation over eastern china tends to be above below normal the east west sst anomaly pattern in the north atlantic modifies the atmospheric circulation over the atlantic ocean and europe and the anomalous circulation extends to downstream east asia through the propagation of rossby waves and exerts influence on winter precipitation over eastern china the formation of the east west sst anomaly pattern in the north atlantic may be associated with anomalies in the north atlantic thermohaline circulation and in surface winds over the north atlantic ocean

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

sedimentology and ground penetrating radar characteristics of a pleistocene sandur deposit abstract the kronhede sandur forms part of a ca 1500 km2 late pleistocene outwash system located in western jylland denmark a sedimentological study was carried out in the proximal part of the sandur the sediments were deposited during progradation of the glacier as shown by a general coarsening upward lithology terminating with a jokulhlaup episode characterized by large compound dune migration and slack water draping mapping of a more than 200 m long well exposed pitwall and ground penetrating radar measurements in a 50 200 m grid along the pitwall made it possible to outline the three dimensional geometry of the jokulhlaup deposit forming the top part of the succession the paper describes the sedimentology of the sandur deposits and the application of the ground penetrating radar technique to sedimentary architecture studies

ground penetrating radar surveys used in archaeological investigations during 1982 and 1983 two ground penetrating radar surveys were carried out in conjunction with archaeological investigations in canada the first survey was a detailed high resolution radar survey at the site of a sixteenth century basque whaling station on the labrador coast designed to locate the graves of the basques the second was a rapid low resolution reconnaissance survey as part of a prehistory impact assessment program at the site of the new national museum of man in hull quebec both surveys were experimental and were designed to see whether ground penetrating radar would be useful for identifying and locating anomalies of archeological significance radar was successful in detecting archeological anomalies several meters in size at both locations and the high resolution survey was moderately successful in identifying basque graves ongoing work involves comparing radar results with the archaeological investigations to increase the understanding of how radar can be applied to archaeology a

late holocene syngenetic ice wedge polygons development bylot island canadian arctic archipelago the initial configuration of the syngenetic ice wedge polygons that developed in the outwash plain of glacier c 79 after 6000 bp was modified by the accumulation of wind blown and organic sediments that began after 3670 110 bp the late holocene sedimentation led to an increase in the thermal contraction coefficient of the soil and the formation of third and fourth order contraction cracks partially explaining the current configuration of the polygonal network the upturning of the sedimentary strata bordering the ice wedges was associated with the summer thermal expansion and resulting internal creep of the soil the mean annual soil displacement coefficient was in the order of 2 5 2 7 10 5 c at the thousand year scale the late holocene sedimentary strata under the centre of the polygons were undisturbed which will make it possible to use this sedimentary record in further studies to attempt paleoenvironmental reconstructions from cores

combined ert and gpr methods for investigating two stepped lateritic weathering systems abstract electrical resistivity tomography ert and ground penetrating radar gpr surveys have been carried out in eastern senegal for investigating two stepped lateritic systems developed upon crystalline basement rocks the geo electrical pseudo sections derived from ert data provide a broad view of the lateritic weathering mantle which is characterised by a decrease in resistivity with increasing depth high resistivities characterise hardened ferruginous materials in particular the ferricrete while the lower resistivities are related to the clayey horizons such as the saprolite gpr provides high resolution and continuous subsurface data on the hardened ferruginous horizons the underlying clay horizons however drastically restricted the investigation depth an anomalous area showing an obvious disruption of the reflections was detected in one of the radar records suggesting contrasting iron and clay contents of superimposed lateritic weathering materials with differentiated porosity rate and kaolinite amount both ert and gpr allow quite similar investigation depths of the hardened ferruginous surface horizons observations from trial boreholes located near the profiles contribute to better interpretation of the ert and gpr results the thickness of the weathering horizons depicted from ert and gpr data roughly corresponds to that measured in the boreholes the two geophysical methods are affected in different ways by lateritic terrains but ert and gpr surveys combined with borehole observation help to reduce ambiguous geological interpretations ert and gpr images show the variability of the lateritic weathering facies identified in the boreholes of each landsurface middle and high glacis depending on different erosion and weathering ferruginisation processes that have shaped these landsurfaces and allowed the development of more or less mature underlying lateritic weathering profiles

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

discussion of the utility of conductivity surveying and resistivity sounding in evaluating sand and gravel deposits and mapping drift sequences in northeast scotland by c a auton

an application of ground penetrating radar to peat stratigraphy of ellice swamp southwestern ontario ground penetrating radar gpr has been applied to the mapping of stratigraphy and peat thickness of a large bog in southwestern ontario the gpr survey was undertaken in conjunction with a conventional coring survey and measurement of peat physical properties the results indicate that gpr responds to peat moisture content and bulk density which vary with stratigraphic changes in particular the acrotelm catotelm boundary and the basal clay are gpr reflectors the presence of gyttja above the clay is indicated by complex basal reflections ground penetrating radar is a viable alternative to an intensive coring survey for evaluating peat depth and extent

early palaeocene palaeoclimatic inferences from fossil floras of the western interior usa abstract twenty one early palaeocene floral assemblages were collected from a variety of alluvial depositional environments from sites in the williston powder river and raton basins of the western interior of the usa leaf fossils were assigned to morphotypes and their physiognomy was quantified for palaeoclimatic analysis two methods were used climate leaf analysis multi variate program clamp and leaf margin analysis lma temperature estimates and trends derived from clamp and lma indicate that early palaeocene palaeotemperatures decreased from the latest cretaceous particularly in northern areas of north america climatic zones shifted southwards from their latest cretaceous positions resulting in a steepened north south temperature gradient and decreased equability in the early palaeocene sub tropical conditions prevailed as far north as the raton basin with the 20 c mean annual temperature isotherm megathermal mesothermal boundary located at approximately 45 n palaeolatitude the 13 c mean annual temperature isotherm mesothermal microthermal boundary was located at approximately 55 n palaeolatitude to the south of the williston basin clamp estimates indicate that precipitation increased significantly in all areas sampled directly after the k t boundary event especially in the southern rockies precipitation levels decreased somewhat after this initial peak but remained high throughout the early palaeocene evidence from this and other studies suggests that seasonality increased from the latest cretaceous into the palaeocene and was most pronounced in central and northerly areas of the north american continent

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

long term bed load transport rate based on aerial photo and ground penetrating radar surveys of fan delta growth coast mountains british columbia sequential aerial photography sonar bathymetry ground penetrating radar gpr and sediment sampling and analysis provide the basis for calculating the volumetric and mass rate of progradation of the delta of fitzsimmons creek a steep high energy debris flow dominated channel draining about 100 km2 of the southern coast mountains of british columbia fitzsimmons creek is typical of small mountain rivers in the region gpr imaging is used to define the pre depositional morphology of the receiving basin a technique that improves the accuracy of the volumetric survey the 52 year record 1947 1999 of progradation yielded an average annual volumetric transport rate of 1 00 0 16 104 m3 year 1 for bed load corresponding to a mass transport rate of 1 60 0 28 104 mg year 1 bed load yields are consistent with those obtained in hydrogeomorphically similar basins in the region and elsewhere decade based annual rates which vary from 0 64 0 11 104 to 2 85 0 38 104 mg year 1 provide poor estimates of the 52 year average indeed the 52 year record may also not be long enough to fully integrate the significant fluctuations in the sediment efflux from fitzsimmons creek the methodology proposed in this paper can be transferred to other comparable mountain environments worldwide

a numerical three dimensional conditioned unconditioned stochastic facies type model applied to a remediation well system in this study a three dimensional stochastic facies based aquifer model was developed the model can be used to numerically simulate flow and solute transport in heterogeneous groundwater aquifers the stochastic generation process can be conditioned by using available facies information in one vertical plane or two orthogonal vertical ones in this study the information was obtained from a facies interpretation of a vertical georadar profile in a natural gravel formation in switzerland in the domain outside the known profile unconditioned lenses and layers were generated at random according to statistical information on coherent sedimentary structures based on observations in adjacent gravel pits jussel et al 1994a the method was applied to a single extraction well designed to capture an initially block shaped contaminant plume a total of 80 conditioned and unconditioned synthetic aquifers was generated the flow and transport simulations were performed using a finite element flow model and a random walk transport model the results are presented as the ensemble of integral solute mass recovery curves of single realizations one would expect conditioning to reduce the bandwidth of the recovery curves representing the uncertainty but the results show that the bandwidth even increased this effect was attributed to a discrepancy in the mean volumetric fraction of the different facies types in the conditioned and the unconditioned cases moreover a simulation using a homogeneous model with constant equivalent flow and transport parameters overestimated the remediation efficiency the influence of a linear reversible equilibrium sorption on the remediation well efficiency was taken into account by an uncorrelated random field of the retardation factor based on values from the literature however the impact of the variability in hydraulic conductivity clearly exceeded the effect of the variability in the retardation factor

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

investigation of large scale washover of a small barrier system on the southeast australian coast using ground penetrating radar abstract prehistoric depositional signatures for large scale washover involving marine inundation events such as storms and tsunami have been the subject of considerable research over the last 15 years much of this research has focused on the identification of sandsheets in back barrier environments as depositional records for extreme washover events all these deposits must have a sediment source and by their nature the most likely source of sediment for washover into back barrier environments is the barrier itself this study identifies an erosional signature for large scale washover from a small coastal barrier on the southeast australian coast a distinct lens of marine sand up to 90 cm thick confined vertically by peat is found in the upper fill of a closed freshwater back barrier lagoon sequence this sand lens is attributed to a large scale washover event during the last 800 years and was possibly deposited by a tsunami the hypothesis for this study was that any event that breached the dune system must have caused considerable geomorphic change to the dunes and hence may have left an erosional signature ground penetrating radar transects of the system show an erosional contact between a series of truncated pre event dunes and several small overlying post event dunes this study outlines a relatively simple non invasive method for the identification of an erosional signature for prehistoric large scale washovers caused by storm surge exceptionally large waves or tsunami

nass river on the move radar facies analysis of glaciofluvial sedimentation and its response to sea level change in northwestern british columbia the nass valley of northwestern british columbia is a glacial fiord containing extensive glaciomarine and glaciofluvial sediments two parallel braidplains separated by a bedrock ridge were deposited within the fiord mapping of these deposits led to the hypothesis that the braidplains must have terminated at deltas however a lack of surface exposures meant that ground penetrating radar was needed to investigate these deposits radar facies analysis aided in the identification of braidplain braid delta and glaciomarine depositional environments as well as underlying bedrock several deltas graded to different sea levels were discovered allowing inferences to be made about the relationship of falling sea level to sediment architecture the upper section of the western braidplain is graded to a sea level of 185 m above sea level asl indicating that the proto nass river flowed on the western side of the bedrock ridge when the sea was at that level however the river moved to the east side of the ridge as sea level fell depositing the extensive aiyansh braidplain braid delta which is graded to a 152 m sea level stand several other deltas also formed at this sea level stand avulsion occurred and the river flowed on the west side of the ridge again when sea level fell to 134 m asl the river remained in this position throughout late glacial time and eventually evolved into the modern nass river the coarse grained deposits are indicative of forced regression with both stepped top attached and detached stratal architecture present

gpr derived architecture of a lahar generated fan at cotopaxi volcano ecuador the internal geometry of volcaniclastic fans produced by aggradation during lahar events is difficult to examine in modern settings because of the frequent lack of three dimensional exposures this makes it challenging to i reconstruct the spatial and temporal evolution of such fans and ii interpret observed facies stratigraphy in the context of lahar flow dynamics from proximal to distal fan reaches this research therefore presents the results of a ground penetrating radar gpr survey of the rumipamba fan at the mouth of the burrohuaycu quebrada on the southwestern flank of cotopaxi volcano a survey grid consisting of 50 individual gpr profiles representing a total length of 19 4 km was constructed covering most of the 4 km2 large fan surface all gpr profiles were collected using a pulseekko 100 with a 400 v transmitter fan sediments consist of sandy and gravelly lahar deposits alternating with volcanic fallout including ash and pumice lapilli at times reworked by fluvial processes deposits could be ground truthed to a depth of 3 m whereas gpr penetration depth reaches 15 m data interpretation was based on classification into 15 distinct radar facies characterized by the nature of their bounding surfaces and or internal features cross referenced where possible with shallow exposures three main facies were identified parallel irregular and clinoform erosional contacts were distinguished from aggradational ones vertical channel fill and lateral accretion flow parallel versus flow transverse and proximal distal variations in deposit architecture were featured the results of this study confirm the existence of two major channel systems in the northern and southern extremities of the fan and the more recent formation of a smaller central fan channel system deposit architecture is complex and facies chronologies illustrate that lahars have affected the entire survey area

using ground penetrating radar to detect layers in a sandy field soil abstract pollutant transport in sandy soils can be very complex due to the presence of coarse sand lenses water flows laterally over the coarse material and subsequently breakthrough occurs in concentrated pathways called fingers this funneled flow process is a form of preferential flow reducing solute travel time and degradation of organic chemicals in this paper we test ground penetrating radar gpr as a tool for detecting layers in the soil several gpr transects were established on a fine sandy loam soil throughout the growing season and subsequent fall period to find the best time to reveal layer structures the effect of the spatially varying moisture content on the radar velocity was determined from actual measurements with soil samples and by using the common mid point cmp technique the optimal time to find coarse layers with gpr in this soil was at the end of the fall season when the soil was wetted and evaporation had decreased the depth of layers as indicated by gpr was highly sensitive to the soil moisture content and could be in error by as much as 0 4 m on a depth scale of 1 5 to 2 m if an average propagation velocity was used a satisfactory depth prediction of textural interfaces was obtained non destructively by collecting data in both reflection and cmp mode

3 d architecture and sequence stratigraphic evolution of a forced regressive top truncated mixed influenced delta cretaceous wall creek sandstone wyoming u s a abstract ground penetrating radar gpr is used to delineate the 3 d facies architectural elements and examine the evolution of a top truncated forced regressive mixed influenced delta front in the cretaceous wall creek member of the frontier formation wyoming the gpr data provide a bridge between outcrop facies architecture and recently published high resolution 2 d seismic studies of quaternary delta systems the gpr data were integrated with outcrops photomosaics cores and gps data two orthogonal grids of 2 d gpr profiles provide information on the 3 d facies architecture and stratigraphy of the deltaic deposits three main gpr architectural elements are identified within the delta front 1 mouth bars are characterized by seaward dipping reflections foreset beds in dip view and mounded bidirectionally downlapping reflections in strike view 2 shallow delta slope channels show truncation and onlap and also show low angle landward northwest dipping reflections the mouth bars are locally interrupted by 3 sub horizontal radar reflections that are interpreted as tidally modulated bars within the mouth bar radar facies both top preserved proximal and top truncated distal examples are observed top preserved proximal bars show evidence of mounded bar crests and landward accretion as is observed in the upstream end of mouth bars on the modern atchafalaya delta in the gulf of mexico distal bar deposits primarily comprise the top truncated seaward dipping foresets the gpr interpretation shows two laterally overlapping delta lobes interpreted to represent autocyclic delta switching the older lower lobe forms a fan shaped delta lobe composed of top truncated coalesced mouth bars the second phase of bars is largely top preserved building over the older bars the presence of thicker bedsets and upstream accretion suggests that the younger lobe was quickly abandoned as seen in the overlying transgressive ravinement although marine erosion during transgression was less effective on these later stage bar deposits ravinement increased landward a comparison of the architectural elements at a more regional scale in two separate wall creek delta lobes murphy creek and raptor ridge 30 km apart indicates that the bar complexes were deposited on the delta fronts as accretionary forced regressive deposits during a relative sea level fall the older river dominated deltaic deposits at the murphy creek site prograded southeastward 124 whereas the younger and more tidally influenced raptor ridge bar deposits expanded southward 171 before final abandonment and regional transgression the most distal lowstand lobe sediments within the offlapping parasequence at raptor ridge are more completely preserved and also show the greatest tidal influence compared to the more severely top truncated murphy creek which is in an otherwise more landward location this challenges the notion that tidal facies are predominantly associated with transgressive or highstand systems tracts greater preservation of deltaic facies in forced regressive and lowstand deltas as shown here has also been documented in quaternary shelf edge deltas such as the lagniappe in the gulf of mexico and the mahakham in kalimantan

late quaternary stratigraphy and sea level history of the northern delaware bay margin southern new jersey usa a ground penetrating radar analysis of composite quaternary coastal terraces abstract ground penetrating radar gpr and lithologic data reveal six pleistocene sea level highstand sequences forming two composite terraces along the northern margin of delaware bay in southern new jersey usa the upper terrace 18 to 9 m msl is underlain by four estuarine marine sequences of middle pleistocene age while the lower terrace 6 m msl contains 2 middle to late pleistocene sequences separating the 2 terraces is a variably sloping escarpment cedarville created by erosion during at least 2 high sea level events intensive radar imaging and boring of these 6 unconformity bounded units allows for their interpretation in a sequence stratigraphic context identifying transgressive highstand and regressive phases higher than present sea levels of 14 12 6 and 16 m during the middle pleistocene and 5 m during the middle and or late pleistocene are indicated by these sedimentary sequences suggesting relative stability of this section of the atlantic coastal plain during the past 500 ka gpr analysis of coastal drainage modification reveals a contrasting lowstand sequence of incised paleovalleys supporting the interpretation that these bay margin deposits contain one of the most complete sections of late quaternary highstand stratigraphy in the mid atlantic region for appendix see http www elsevier nl locate quascirev

ground penetrating radar survey of a prehistoric site in southern italy abstract in this paper we present and discuss the results of a ground penetrating radar gpr study carried out in an area of southern italy where a karst cave with prehistoric remains was found the aim of the study involved the imaging of the subsurface stratigraphy both inside and outside the cave in order to assist archaeologists in an excavation programme the survey grid comprised 18 intersecting gpr profiles problems associated with the use of the gpr within a cave environment are highlighted and the data processing sequence designed to extract useful geo archaeological signatures is described interpretation of the radar sections was controlled by the excavation of two trenches inside and outside the cave allowing detailed outlining the complex stratigraphy and the reconstruction of palaeolithic and neolithic subsurface horizons

high resolution subsurface gpr imaging and sedimentology of coastal ponds maine u s a implications for holocene back barrier evolution ground penetrating radar gpr transects and sediment cores have been used to examine the basement morphology stratig raphy and environmental history of maritime ponds along the pen insular coast of maine silver lake lily pond and north pond are shallow 3 m water bodies bordered by steep bedrock ridges in the north east and west and sandy barriers to the south the bedrock basins of the ponds are formed in metasedimentary rocks surrounded by resistant pegmatitic intrusions a dense network of gpr traverses obtained over the ice covered silver lake reveals a series of prominent wavy parallel and basin fill reflector geometries terminating against the bedrock or grading into the barrier sediments and interpreted as organic lake bottom facies the transparent units represent sand rich horizons mostly eolian in origin convex up structures found both on the surface and within the basin fill sequence are interpreted as pre served parts of coastal dunes the present study indicates that fresh water conditions prevailed since at least 4 6 ka with an initial sedi mentation rate of 1 7 mm yr the position of this unit below the con temporary sea level suggests presence of a welded barrier by that time radar profiles taken along the shores of lily pond a small water body behind the sand dune barrier indicate a significantly larger areal extent of the pond in the past a succession of organic deposits over lying a pleistocene glaciomarine unit indicates progressive inundation of the paleo lagoon by rising sea level saltwater peat seaward of lily pond was buried by washover sands about 1 2 ka and a narrow pond existed here prior to dredging and artificial infilling of its eastern part in the 1950s 60s the organic and eolian units are absent in the north pond where sedimentary fill consists of glaciomarine clay overlain by marine sands a proposed three stage model of pond evolution along an embayed coastline consists of 1 organic accumulation in an up land depression during lower sea level 2 predominantly washover or tidal deposition in a lagoon stage 2a or blocked coastal pond stage 2b during initial transgression and 3 mainly eolian and organic de position behind a prograded or aggraded barrier future accelerated rise in relative sea level and inadequate sediment supply will cause many back barrier ponds to reenter stage 2 of the proposed model

interpretation of drill core and georadar data of coarse gravel deposits abstract pollution in the shallow subsurface has led to an increasing need of understanding how to quantitatively characterize both the heterogeneity of gravel aquifers and the influence of heterogeneity on groundwater flow and solute transport models play an important role in decision making processes especially in the context of better characterizing and in forecasting the behavior of a given geological system the objective of the present paper is the derivation of a gradual lithofacies based interpretation of outcrop drill core and ground penetrating radar gpr or georadar data of different quality the presented method allows a probability estimation of drill core layer descriptions and radarfacies types representing defined sedimentary structure types the method includes a determination of initial structure type probabilities for grain size categories and combinations thereof described in drill core layer descriptions as well as a subsequent differentiation of these structure type probabilities in an iterative process considering additional information like main constituent quantity fraction and sorting of single grain size categories color chemical precipitation layer thickness and adjacent layer the radarfacies types are calibrated with drill cores located in the vicinity of georadar sections the calibration process consists of the assignment of the calculated structure type probabilities from the drill core layer descriptions to the corresponding radarfacies types considering the proportion in thickness between drill core layers and georadar structures the structure type probabilities can be given for points along boreholes and a grid with arbitrary mesh size along georadar sections the method is applied to field examples from the rhine wiese aquifer near basel in switzerland the resulting structure type probabilities can be used for conditioning stochastic simulations of geological models however the conditioned stochastic simulation of the rhine wiese aquifer is the topic of another paper the results show the importance of a detailed sedimentological analysis of outcrops and drill cores as well as its significance on the distinction of sedimentary structure types

imaging the subsurface stratigraphy in the ubehebe hydrovolcanic field death valley california using ground penetrating radar abstract ground penetrating radar gpr surveys were carried out to collect subsurface images of the basaltic base surge deposits in the ubehebe hydrovolcanic field death valley national park california antennae with frequencies of 50 100 and 200 mhz were used this technique allowed the collection of useful geologic data for example the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated different radar responses were also obtained from base surge deposits and underlying sedimentary rocks which enable their recognition where no outcrops are available furthermore gpr data confirmed the presence of small eroded craters which are partially filled by alluvium in this case an unconformity between the overlying horizontally bedded alluvium and the underlying bowl shaped base surge deposits can be recognized within the crater and the thickness of the alluvium estimated common mid point cmp surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0 095 0 1 m ns

ground penetrating radar for environmental applications abstract ground penetrating radar gpr is a near surface geophysical technique that can provide high resolution images of the dielectric properties of the top few tens of meters of the earth in applications in contaminant hydrology radar data can be used to detect the presence of liquid organic contaminants many of which have dielectric properties distinctly different from those of the other solid and fluid components in the subsurface the resolution approximately meter scale of the radar imaging method is such that it can also be used in the development of hydrogeologic models of the subsurface required to predict the fate and transport of contaminants gpr images are interpreted to obtain models of the large scale architecture of the subsurface and to assist in estimating hydrogeologic properties such as water content porosity and permeability its noninvasive capabilities make gpr an attractive alternative to the traditional methods used for subsurface characterization

ground penetrating radar 2 d and 3 d subsurface imaging of a coastal barrier spit long beach wa usa abstract the ability to effectively interpret and reconstruct geomorphic environments has been significantly aided by the subsurface imaging capabilities of ground penetrating radar gpr the gpr method which is based on the propagation and reflection of pulsed high frequency electromagnetic energy provides high resolution cm to m scale and shallow subsurface 0 60 m near continuous profiles of many coarser grained deposits sediments of low electrical conductivity this paper presents 2 d and 3 d gpr results from an experiment on a regressive modern barrier spit at willapa bay wa usa the medium grained sand spit is 38 km long up to 2 3 5 km wide and is influenced by a 3 7 m tidal range spring as well as high energy longshore transport and high wave energy depositional processes the spit has a freshwater aquifer recharged by rainfall the gpr acquisition system used for the test was a portable digital pulseekko system with antennae frequency ranging from 25 to 200 mhz and transmitter voltages ranging from 400 to 1000 v step sizes and antennae separation varied depending on the test requirements in addition 100 mhz antennae were used for conducting antennae orientation tests and collecting a detailed grid of data 50 50 m sampled every meter the 2 d digital profiles were processed and plotted using pulseekko software the 3 d datasets after initial processing were entered into a landmark workstation that allowed for unique 3 d perspectives of the subsurface to provide depth near surface velocity measurements were calculated from common midpoint cmp surveys results from the present study demonstrate higher resolution from the 200 mhz antennae for the top 5 6 m whereas the 25 and 50 mhz antennae show deeper penetration to 10 m for the study site 100 mhz antennae provided acceptable resolution continuity of reflections and penetration the dip profiles show a shingle like accretionary depositional pattern whereas strike profiles show a horizontal and subhorizontal nearly continuous reflection pattern results from the gpr experiment reveal upper shoreface reflections with dip towards the ocean at about 1 2 the loss of signal from below a depth of 6 8 m indicates a lithofacies change because of the storm wave base the parallel broadside and perpendicular broadside antennae orientation tests show detailed stratigraphy continuity and depth of penetration the cross polarization test exhibits reduced continuity of reflections and less depth of penetration but dipping reflections are apparent the grid pattern data provided a detailed view of 3 d geometry of individual reflections high quality data were obtained processed and directly exported into a landmark workstation for interpretation the resulting interpretations of the upper shoreface beds from the test cube 50 50 m total 2600 traces are shown as vertical sections slices horizontal sections time slices contour maps 3 d representations of individual beds and an isopach map the 3 d depositional framework allows a more detailed interpretation than widely spaced 2 d profiles

very high resolution seismics as a tool for sequence stratigraphy applied to outcrop scale examples from eastern tyrrhenian margin holocene pleistocene deposits three eastern tyrrhenian continental margin areas with very different depositional and tectonic settings were analyzed using single channel very high resolution reflection seismics coupled with sea floor sampling fourth and fifth order depositional sequences derived from quaternary glacio eustatic processes are now buried at shallow depths within the continental shelf the sequences have been reconstructed in detail with great lateral continuity the tectonic setting did not influence the development of high order sequences which are probably synchronous at a global scale within these sequences it has been possible to recognize all the systems tracts hypothesized by sequence stratigraphy models confirming that this method does not depend upon time or scale the geom try of depositional sequences is strongly dependent on sedimentation rate i e on the distance from sources local factors such as transport pattern variations caused by sea level changes paleotopography of the transgressed surface characteristics of feeding hydrographic nets and interactions with bioconstructions must be considered because they play an important role in the geometrical development of depositional sequences in high order depositional sequences lowstand systems tracts are volumetrically predominant highstand and transgressive systems tracts seem to be linked to point sources because they have a three dimensional 3 d geometry on the contrary lowstand systems tracts are related to linear sources parallel to the shelf break they cause the progradation of the whole margin so that they form the margin structure almost entirely