statistical pattern analysis of surficial karst in the pleistocene miami oolite of south florida abstract a robust airborne light detection and ranging digital terrain model lidar dtm and select outcrops are used to examine the extent and characteristics of the surficial karst overprint of the late pleistocene miami oolite in south florida subaerial exposure of the miami oolite barrier bar and shoals to a meteoric diagenetic environment lasting ca 120 kyr from the end of the last interglacial highstand mis 5e until today has resulted in diagenetic alteration including surface and shallow subsurface dissolution producing extensive dolines and a few small stratiform caves analysis of the lidar dtm suggests that 50 of the dolines in the miami oolite have been obscured lost to urbanization though a large number of depressions remain apparent and can be examined for trends and spatial patterns the verified dolines are analyzed for their size and depth their lateral distribution and relation to depositional topography and the separation distance between them statistical pattern analysis shows that the average separation distance and average density of dolines on the strike oriented barrier bar versus dip oriented shoals is statistically inseparable doline distribution on the barrier bar is clustered because of the control exerted on dissolution by the depositional topography of the shoal system whereas patterning of dolines in the more platform ward lower relief shoals is statistically indistinguishable from random the areal extent and depth of dissolution of the dolines are well described by simple mathematical functions and the depth of the dolines increases as a function of their size the separation and density results from the miami oolite are compared to results from other carbonate terrains near surface stratiform caves in the miami oolite occur in sites where the largest and deepest dolines are present and sit at or near the top of the present water table

instruments and methods geophysical imaging of alpine rock glaciers slope instabilities caused by the disappearance of ice within alpine rock glaciers are an issue of increasing concern design of suitable counter measures requires detailed knowledge of the internal structures of rock glaciers which can be obtained using geophysical methods we examine benefits and limitations of diffusive electromagnetics geoelectrics seismics and ground penetrating radar georadar for determining the depth and lateral variability of the active layer the distributions of ice and water the occurrence of shear horizons and the bedrock topography in particular we highlight new developments in data acquisition and data analysis that allow 2 d or even 3 d structures within rock glaciers to be imaged after describing peculiarities associated with acquiring appropriate geophysical datasets across rock glaciers and emphasizing the importance of state of the art tomographic inversion algorithms we demonstrate the applicability of 2 d imaging techniques using two case studies of rock glaciers in the eastern swiss alps we present joint interpretations of geoelectric seismic and georadar data appropriately constrained by information extracted from boreholes a key conclusion of our study is that the different geophysical images are largely complementary with each image resolving a different suite of subsurface features based on our results we propose a general template for the cost effective and reliable geophysical characterization of mountain permafrost

birth death and resurrection the life cycle of suprasubduction zone ophiolites 1 suprasubduction zone ssz ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites this sequence includes the following 1 birth which entails the formation of the ophiolite above a nascent or reconfigured subduction zone this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex 2 youth during which is continued melting of refractory asthenosphere depleted during birth occurs in response to fluid flux from the subducting slab with extensional deformation of the older plutonic suite eruption of refractory lavas and the intrusion of wehrlite pyroxenite 3 maturity with the onset of semistable arc volcanism typically calc alkaline as the subduction zone matures and stabilizes and the intrusion of quartz diorite and eruption of silicic lavas and 4 death which is the sudden demise of active spreading and ophiolite related volcanism which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites 5 resurrection with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction the early stages 1 3 may be diachronous and each stage may overlap in both time and space the existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the ssz tectonic setting

50 ma initiation of hawaiian emperor bend records major change in pacific plate motion the hawaiian emperor bend has played a prominent yet controversial role in deciphering past pacific plate motions and the tempo of plate motion change new ages for volcanoes of the central and southern emperor chain define large changes in volcanic migration rate with little associated change in the chain s trend which suggests that the bend did not form by slowing of the hawaiian hot spot initiation of the bend near kimmei seamount about 50 million years ago ma was coincident with realignment of pacific spreading centers and early magmatism in western pacific arcs consistent with formation of the bend by changed pacific plate motion

mantle plumes and continental tectonics abstract it is now recognised that plumes originate from a thermal boundary layer deep in the mantle a new plume consists of a large head with a diameter of approximately 800 to 1200 km and it is followed by a smaller tail which has a diameter of 100 to 200 km at the top of its ascent the head flattens to form a disk 2000 to 2500 km in diameter that may melt to produce a continental flood basalt or oceanic plateau the tail melts to produce chains of volcanic activity such as the hawaiian emperor chain the ascent of a new plume leads to surface uplift of 500 to 1000 m over a length scale of 2000 km this places the lithosphere under tension but the horizontal forces produced do not result in runaway extension unless the continental lithosphere is already anomalously hot and therefore weak if the lithosphere is cold and strong slow extension leading to a new spreading ridge may postdate plume arrival by 10 to 40 m y the time difference being the time taken to conduct heat from the plume to the overlying lithosphere plume heads may control the timing and position of new ocean ridges but are not the fundamental force that drives plate tectonics the heat from plume tails may weaken the overlying plate and pin the position of spreading the ascent of a mantle plume can also have an important influence on subduction large oceanic plateaus such as the ontong java plateau are more buoyant than normal oceanic crust because they have a thicker basaltic layer and because they are underlain by a 200 km thick layer of hot material from a mantle plume head as a consequence oceanic plateaus are more difficult to subduct than normal oceanic crust this can lead to jamming of plates at subduction zones resulting in a flip in the sense of subduction as appears to have happened in the caribbean region or to obduction of the plateau finally when a plume head is emplaced beneath continental crust heat released from the plume may lead to melting of the overlying crust the granites associated with many greenstone belts and intercontinental magmatic provinces such as the paleozoic lachlan fold belt of eastern australia and the middle proterozoic anorogenic granites of the central and southwestern united states may have formed in this way

ultrahigh pressure minerals and metamorphic terranes the view from china abstract ultrahigh pressure uhp metamorphism refers to mineralogical modifications of continental and oceanic crustal protoliths associated mafic ultramafic rocks initially formed or emplaced in shallow levels of the lithosphere but which subsequently have experienced p t conditions within or above the coesite stability field 2 7 gpa 700 c typical products include eclogite garnet peridotite and uhp varieties of metapelite quartzite marble paragneiss and orthogneiss uhp metamorphic assemblages require relatively cold lithospheric subduction to mantle depths some recrystallization even occurs under forbidden p t conditions characterized by a geotherm of the current explosion of research on continental uhp terranes reflects their significance for mantle dynamics and the tectonics of continental subduction collision exhumation mantle slab interactions and geochemical recycling a further characterization of uhp phases and positive identification of uhp minerals requires new experimental studies coupled with state of the art analyses for example the very rare occurrence of microdiamond inclusions in zircons from dabie sulu uhp rocks may reflect high f o 2 attending recrystallization inasmuch as epidote is rather common rutile needles within garnets from sulu uhp eclogitic rocks may not be the result of exsolution so in such cases the apparent uhp pressure may have been over estimated hadean igneous microdiamond inclusions in jack hills detrital zircons could have originated from mantle xenoliths whereas abundant detrital phanerozoic diamonds containing inclusions of coesite and other eclogitic minerals from new south wales might have been derived from unexposed uhp metamorphic terranes micro mineral intergrowth and nano size minerals may hold important key to deciphering the actual p t paths of subduction and mantle return flow although most exhumed terranes have returned surfaceward relatively rapidly after short time of uhp condition the long duration of storage at great depth and slow exhumation for the largest uhp terranes remain as major problems

geophysical imaging of alpine rock glaciers slope instabilities caused by the disappearance of ice within alpine rock glaciers are an issue of increasing concern design of suitable counter measures requires detailed knowledge of the internal structures of rock glaciers which can be obtained using geophysical methods we examine benefits and limitations of diffusive electromagnetics geoelectrics seismics and ground penetrating radar georadar for determining the depth and lateral variability of the active layer the distributions of ice and water the occurrence of shear horizons and the bedrock topography in particular we highlight new developments in data acquisition and data analysis that allow 2 d or even 3 d structures within rock glaciers to be imaged after describing peculiarities associated with acquiring appropriate geophysical datasets across rock glaciers and emphasizing the importance of state of the art tomographic inversion algorithms we demonstrate the applicability of 2 d imaging techniques using two case studies of rock glaciers in the eastern swiss alps we present joint interpretations of geoelectric seismic and georadar data appropriately constrained by information extracted from boreholes a key conclusion of our study is that the different geophysical images are largely complementary with each image resolving a different suite of subsurface features based on our results we propose a general template for the cost effective and reliable geophysical characterization of mountain permafrost

submarine hot springs and the origin of life the discovery of hydrothermal vents at oceanic ridge crests and the appreciation of their importance in the element balance of the oceans is one of the main recent advances in marine geochemistry1 it is likely that vents were present in the oceans of the primitive earth because the process of hydrothermal circulation probably began early in the earth s history2 here we examine the popular hypothesis3 7 that life arose in these vents this proposal however is based on a number of misunderstandings concerning the organic chemistry involved an example is the suggestion that organic compounds were destroyed on the surface of the early earth by the impact of asteroids and comets but at the same time assuming that organic syntheses can occur in hydrothermal vents7 the high temperatures in the vents would not allow synthesis of organic compounds but would decompose them unless the exposure time at vent temperatures was short8 11 even if the essential organic molecules were available in the hot hydrothermal waters the subsequent steps of polymerization and the conversion of these polymers into the first organisms would not occur as the vent waters were quenched to the colder temperatures of the primitive oceans

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

characterization of the porosity distribution in the upper part of the karst biscayne aquifer using common offset ground penetrating radar everglades national park florida summary the karst biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity and hydraulic conductivity making conceptualization difficult the biscayne aquifer is the primary source of drinking water for millions of people in south florida thus information concerning the distribution of karst features that concentrate the groundwater flow and affect contaminant transport is critical the principal purpose of the study was to investigate the ability of two dimensional ground penetrating radar gpr to rapidly characterize porosity variability in the karst biscayne aquifer in south florida an 800 m long gpr transect of a previously investigated area at the long pine key nature trail in everglades national park collected in fast acquisition common offset mode shows hundreds of diffraction hyperbolae the distribution of diffraction hyperbolae was used to estimate electromagnetic em wave velocity at each diffraction location and to assess both horizontal and vertical changes in velocity within the transect a petrophysical model complex refractive index model or crim was used to estimate total bulk porosity a set of common midpoint surveys at selected locations distributed along the common offset transect also were collected for comparison with the common offsets and were used to constrain one dimensional 1 d distributions of porosity with depth porosity values for the saturated miami limestone ranged between 25 and 41 for common offset gpr surveys and between 23 and 39 for common midpoint gpr surveys laboratory measurements of porosity in five whole core samples from the saturated part of the aquifer in the study area ranged between 7 1 and 41 8 gpr estimates of porosity were found to be valid only under saturated conditions other limitations are related to the vertical resolution of the gpr signal and the volume of the material considered by the measurement methodology overall good correspondence between gpr estimates and the direct porosity values from the whole core samples confirms the ability of gpr common offset surveys to provide rapid characterization of porosity variability in the biscayne aquifer the common offset survey method has several advantages 1 improved time efficiency in comparison to other gpr acquisition modes such as common midpoints and 2 enhanced lateral continuity of porosity estimates particularly when compared to porosity measurements on 1 d samples such as rock cores the results also support the presence of areas of low em wave velocity or high porosity under saturated conditions causing velocity pull down areas and apparent sag features in the reflection record this study shows that gpr can be a useful tool for improving understanding of the petrophysical properties of highly heterogeneous systems such as karst aquifers and thus may assist with the development of more accurate groundwater flow models such as those used for restoration efforts in the everglades

semiautomated georadar data acquisition in three dimensions under favorable conditions georadar techniques can provide vivid images of the shallow subsurface 10 50 m although the significant advantages of 3 d georadar surveying strategies are well documented they generally require much greater expenditures than traditional 2 d approaches we introduce an efficient semiautomated 3 d georadar acquisition and processing scheme that does not jeopardize data quality a standard georadar acquisition unit is integrated with an innovative self tracking laser theodolite with automatic target recognition capabilities georadar and coordinate data are recorded simultaneously as the georadar antennae are transported steadily across a survey area while tracking a target prism mounted between the antennae the theodolite provides real time coordinate information with high accuracy in all directions at 1 m s moderate walking speed the coordinates are determined to better than 0 04 m and at 3 m s they are better than 0 07 m subsequent to acquisition semiautomati

70 m y history 139 69 ma for the caribbean large igneous province it is commonly accepted that large igneous provinces are formed through catastrophic volcanic events occurring over vast areas within a few million years at the initiation of hotspots mantle plumes new 40ar 39ar ages 111 139 ma and geochemical results from the nicoya peninsula costa rica extend the age range of volcanism in the caribbean large igneous province to 70 m y 69 139 ma our results are not consistent with the formation of this vast igneous province through a single plume head at the initiation of a mantle plume such as the galapagos instead we propose that multiple oceanic intraplate igneous structures such as plateaus and hotspot tracks were accumulated through the subduction process the igneous structures could be remnants of the earlier history of the galapagos hotspot making it one of the oldest active hotspots on earth alternatively they could have been derived from several spatially distinct mantle melting events that sampled similar source material e g oceanic lithosphere of similar age

3 d ground penetrating radar applied to fracture imaging in gneiss three dimensional ground penetrating radar georadar techniques suitable for geological engineering applications have been developed and tested initial experiments were conducted on the floor of a quarry in southern switzerland from which ornamental gneissic rock is extracted during a brief two day period constant offset georadar data were recorded over a 650m2 area with a grid cell size of 0 1 m 0 2 m georadar velocities were estimated from the results of expanding spread surveys all georadar data and associated geometry files were recorded automatically in seismic industry formats the experimental georadar data set was processed image enhanced and interpreted using 3 d seismic reflection software operating on a workstation arbitrary vertical sections time slices 3 d images and animated movies in which the observer travels through the entire data volume were constructed from the resultant migrated georadar data semi automatic tracking routines allowed continuous subhorizontal reflectio

extensional collapse and uplift in a polymetamorphic granulite terrain in the archaean and palaeoproterozoic of north china abstract the archaean granulite terrain in the datong huai an area north china comprises a basement complex of felsic and mafic granulite overlain by a sedimentary sequence dominated by metapelite and metapsammite both lithological associations are separated by a tectonic contact and structural textural and stratigraphic data indicate that the terrain was affected by two prominent tectono thermal cycles c a and c b associated with two granulite facies events m1 and m2 which probably occurred 2500 ma and 1800 ma ago respectively of these m1 events were dominant and associated with all major structures in the area in the basement gneiss m1 reached peak metamorphic conditions of 12 14 kbar and 800 900 c during a foliation forming event d 2ba which transposed an earlier s 1ba foliation of unknown age and origin in the allochthonous cover sediments m1 peak conditions of about 8 kbar and 800 c were reached after a prograde thickening event d 1co associated with the formation of a bedding parallel foliation while large amounts of s type granites were emplaced the localised d 2ba and d 1co structures are interpreted as spatially distinct responses at different crustal levels to one metamorphic event juxtaposition of basement and allochthonous cover along a large low angle normal shear zone occurred during d 3 this detachment zone accommodated extension after crustal thickening and allowed unloading of the footwall resulting in a rise of the basement rocks through 4 6 kbar as deduced from syn d 3 decompression textures coeval cooling textures in the allochthonous cover sequence indicate that lateral rather than vertical displacements occurred in the hanging wall of the detachment during c b m2 peak conditions of about 4 6 kbar and 650 700 c were reached coeval with the development of discrete left lateral strike slip zones d 4 that transect both basement and allochthonous cover and accommodated some uplift the deduced c a and c b p t paths have equivalents in many precambrian granulites in general decompressional paths like the one recorded in the basement rocks are linked to processes involving crustal thickening followed by extensional collapse in the datong huai an area it can be shown that low angle detachments may have played an important role in the uplift and cooling history of granulite belts as long ago as the archaean proterozoic boundary

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

comments on deccan flood basalts at the cretaceous tertiary boundary by v courtillot j besse d vandamme r montigny j j jaeger and h cappetta the age of the flood basalts of the deccan area and the length of the interval during which the outpourings took place are not known precisely the authors have tried to date those basalts and estimate how long the volcanic activity lasted on the basis of new paleomagnetic paleontological and geochronological data of the deccan effusives they came to the preliminary conclusion that the volcanic activity may have lasted less than 1 ma and that the majority of the lavas poured out during chron 29r unfortunately the authors were not familiar with our paper on paleomagnetism and radiomettic age determinations of deccan trap lavas 2 in our paper we presented the paleomagnetic data derived from 223 individual lava flows from 16 sections all over the deccan area and gave the k ar age determinations for 13 selected unaltered lava flows we agree that the enormous volume of deccan extrusives poured out in a relatively short interval and that the volcanic activity was probably concerned with the spreading in the central indian ocean in late cretaceous and early tertiary time

3d gpr reveals complex internal structure of pleistocene oolitic sandbar active oolitic sandbars like those in the bahamas figure 1 exhibit complex internal architecture with a multitude of stacked sedimentary structures ooids are round carbonate coated grains that form in tropical climates the internal anatomy of carbonate sandbars is often too complex to be captured in one and two dimensional data outcrops cores and 2d geophysical profiles provide a limited vertical view of the geologic record depositional processes are confined to the momentary subhorizontal boundary surface between sediment and water or air vertical 2d views limit the visibility of features developed on subhorizontal surfaces making interpretation of 3d internal anatomy and reconstruction of related depositional parameters difficult closely spaced 3d data are needed to accurately map sedimentary structures and improve fluid flow modeling used in water and hydrocarbon resource management 3d reflection seismic imaging has successfully been used to delineate oolitic bars in sub surface oil field

hydrogeology of the hawaii scientific drilling project borehole kp 1 2 groundwater geochemistry and regional flow patterns a series of downhole and surface water samples were taken from the i km deep kp 1 borehole located on the eastern flank of the island of hawaii early samples from depths of more than 700 m showed salinities nearly equivalent to seawater but having anomalous cation concentrations that are attributed to ion exchange between formation fluids and residual drilling mud clays later deep samples found only minor variations from seawater cation chemistry that are consistent with low temperature weathering of basalts delta 18 o values are equivalent to seawater values and are consistent with this interpretation carbon 14 activities of dissolved inorganic carbonate indicate a water age ranging from 5890 to 7170 years b p and fluid transport rates of 1 8 to 2 2 m yr fluid samples from perforations at 310 m in the borehole demonstrate that a freshwater aquifer is present at the mauna kea mauna loa interface borehole resistivity logs indicate that it is similar to 200 m thick although it ha s not yet been possible to obtain samples of the freshwater zone without contamination from the deep saline fluids the chloride concentrations of the low salinity zone are estimated using a mixing enthalpy calculation to be less than 100 mg l light stable isotope data indicatemore that the fresh water at 320 m is derived from recharge entering the island at an average elevation of 2000 m inferred c 14 activities of the dissolved bicarbonate in the freshwater zone indicate an average calibrated age of 2200 years b p and an average fluid velocity of at least 14 m yr a regional water flow model is proposed that suggests that the fresh water found at the 320 m depth is derived from rainfall recharge from the middle elevations of mauna kea volcano this rainfall is channeled beneath the mauna loa lavas by the thick soil layer separating the two volcanoes a second shallow fresh to brackish water zone derived from mauna loa recharge is also inferred to exist below the carbonate formation that underlies the shallow basal lens the results of our preliminary study of the groundwater system below the kp 1 drill site demonstrate that intervolcano and interflow aquicludes can have a substantial impact on water circulation and discharge from young island volcanoes less

estimating 3d variation in active layer thickness beneath arctic streams using ground penetrating radar we acquired three dimensional 3d ground penetrating radar gpr data across three stream sites on the north slope ak in august 2005 to investigate the dependence of thaw depth on channel morphology data were migrated with mean velocities derived from multi offset gpr profiles collected across a stream section within each of the 3d survey areas gpr data interpretations from the alluvial lined stream site illustrate greater thaw depths beneath riffle and gravel bar features relative to neighboring pool features the peat lined stream sites indicate the opposite greater thaw depths beneath pools and shallower thaw beneath the connecting runs results provide detailed 3d geometry of active layer thaw depths that can support hydrological studies seeking to quantify transport and biogeochemical processes that occur within the hyporheic zone

integration of sedimentology and ground penetrating radar for high resolution imaging of a carbonate platform ground penetrating radar has not been applied widely to the recognition of ancient carbonate platform geometries this article reports the results of an integrated study performed on an upper jurassic outcrop from the south east paris basin where coral bioherms laterally change into prograding depositional sequences ground penetrating radar profiles illustrate the different bedding planes and major erosional unconformities visible at outcrop a ground penetrating radar profile conducted at the base of the cliff displays a palaeotopographic surface on which the outcropping bioherms settled the excellent penetration depths of the ground penetrating radar 20 m with a monostatic 200 mhz antenna images the carbonate platform geometries ranging between outcrop workscale a few metres and seismic scale several hundreds of metres this study supports recent evidence of icehouse conditions and induced sea level fluctuations controlling the upper jurassic carbonate production

the driving mechanism of plate tectonics relation to age of the lithosphere at trenches sea floor age depth and age trench depth relations suggest that the oceanic lithosphere continues to thicken and subside with age beyond 80 ma if so slab pull fs and ridge push fr forces can be calculated from the age of the sea floor at trenches t and if the shear stress acting on the base of the plate increases with absolute velocity a the approximate force balance equation is dva2 svat32 rt where d s and r are constants related to drag slab pull and ridge push respectively the relation between velocity and age is va2 s vat12 r we have tested this model by linear regression using rate and age data for 15 trenches va mm a 2 9 20 32 vat12 26 250 the strength of this correlation r 0 98 is strong evidence in favor of the validity of this simple model these results suggest that ridge push is just sufficient to overcome drag at the base of the plate and does not contribute significantly to the motions of oceanic plates though the value of r is consistent with the motions of plates not attached to subducted slabs

the driving mechanism of plate tectonics abstract plate velocities reflect the global mantle circulation which carries the heat from the deep part of the earth to the surface three other measurable parameters put strong constraints on the physical processes involved in mantle dynamics the surface topography the geoid and the lateral density heterogeneities mapped throughout the mantle by seismic tomography using these internal loads and the navier stokes equations a first generation of dynamic earth models have been developed in the last five years they have produced satisfactory predictions for the divergence of the surface velocities and for the geoid these predictions are quite sensitive to the assumed radial viscosity variations the best match with observations has therefore helped to discriminate between various possible viscosity structures a new set of models taking the existence of plates into account has been particularly successful in predicting the plate velocities including their vorticity the driving mechanism of plate tectonics is thus put on a firm physical basis and the computed solutions are quantitatively reasonable

drilling the solid earth global geodynamic cycles and earth evolution the physical and chemical evolution of the earth is driven by geodynamic cycles that are global in scale operating over 4 57 ga of earth s history some processes are truly cyclic e g the wilson cycle while others are irreversible e g core formation heat and mass transfer between the lowermost mantle e g core mantle boundary and the surface drives these global geodynamic processes subduction of lithospheric plates transfers cool fractionated material into the lower mantle and leads indirectly to the formation of new oceanic lithosphere while the rise of thermochemical plumes recycles the remnants of these plates back to the surface driven by heat transfer across the core mantle boundary these global geodynamic cycles are responsible for hotspot volcanism the formation of continental crust collisional orogenies continental rifting subduction zone processes arcs accretionary prisms and ore deposits each of these presents opportunities for investigation by continental scientific drilling in addition these cycles affect other processes that are targets of continental scientific drilling the origin and evolution of life and an oxygenated atmosphere the impact of large volcanic eruptions on climate and geological hazards such as earthquakes and volcanic eruptions in this paper we present the scientific rationale for continental scientific drilling to study global geodynamic processes review past successes in this realm that were sponsored in part by icdp and suggest potential new targets for drilling campaigns that focus on solid earth evolution this paper builds on discussions at the 2013 icdp science meeting on the future of continental scientific drilling held in potsdam in november 2013

full resolution 3d radar stratigraphy of complex oolitic sedimentary architecture miami limestone florida u s a abstract at the field scale m s to 100 s m it is often difficult to define the true three dimensional form of depositional units or facies within sediments or sedimentary rocks due to inherent spatial bias in traditional data sources such as outcrops and cores full resolution 3d ground penetrating radar gpr surveying has the potential to overcome this problem southwest of miami paleotopography on the upper pleistocene miami limestone formation indicates the former presence of a large oolitic barrier bar backed by extensive ooid shoals data from three closely spaced cores and two large outcrops on the barrier bar allow initial subdivision of the miami limestone in to a lower mottled oolitic facies and an upper bedded oolitic facies however detailed correlation between the cores and outcrops is problematic due to spatial aliasing a 250 mhz full resolution 3d gpr data set was collected over an area of 45 m 24 m that encompassed the location of the three cores depth of radar wave penetration was around 6 m and both horizontal and vertical resolution was approximately 0 1 m for the 6500 m3 rock volume such that the upper bedded oolitic facies was imaged without spatial aliasing radar surfaces and intervening radar facies define two main radar package types low angle sheet and sigmoidal the low angle sheet radar packages are interpreted as oolitic shoal deposits consisting of tidal bars covered by ebb orientated straight crested sand waves the overlying sigmoidal radar packages record barrier bar formation through alongshore progradation comparable sedimentary successions from both pleistocene and modern deposits in the bahamas suggest that the three evolutionary stages recorded for the miami limestone are typical of many transgressive ooid shoal complexes

ground penetrating radar characterization and porosity evolution of an upper pleistocene oolite capped depositional cycle red bays northwest andros island great bahama bank abstract linkages among surface sediments depositional processes geomorphic forms stratigraphic architecture and pore distribution in bahamian sand bodies and oolite capped depositional successions have been characterized in recent studies an understanding of how these parameters especially porosity are preserved or modified in the eogenetic environment is essential in bridging the gap between modern and ancient analogs two complementary 3d 200 mhz and 400 mhz ground penetrating radar surveys and three shallow cores reveal that the uppermost part of the upper pleistocene marine isotope stage 5e lucayan formation at red bays andros island great bahama bank comprises a single 6 m thick upward shallowing parasequence six radar packages p1 p6 bounded by radar surfaces s1 s6 have been identified in the two 3d radar volumes the stratigraphic succession indicates development of a burrowed backshoal lagoon during early flooding of the bank top followed by deposition of flood tide driven low angle sheet sands and sigmoidal subaqueous dune deposits as the shelf margin sand shoal moved bankward as a function of continued sea level rise constructional accommodation on the front of the prograding subaqueous dune in the northwest part of the survey area and erosional accommodation created by downcutting of a shallow tidal channel into the upper part of the subaqueous dune depositional unit in the northeast part of the study area were filled with peloid and ooid dominated carbonate sands as sea level stabilized the uppermost radar package is a thin 0 15 to 0 55 m partially calichified carbonate sand sheet that mantles the entire survey site and that reflects late highstand and fall of sea level exposure of the studied interval to meteoric vadose diagenesis over the past 100 000 years has resulted in partial stabilization of the largely aragonitic precursor sediment through selective partial dissolution of aragonitic grains mainly ooid cortical layers peloids and mollusk shells accompanied by precipitation of patchily distributed low magnesium calcite cement core data demonstrate a relationship between stratigraphically controlled sedimentological attributes diagenesis and pore distribution three distinctive zones of porosity were present upon deposition a lower zone of relatively high interparticle porosity 21 3 to 33 2 in the medial part of p1 a low porosity zone

deep origin of hotspots the mantle plume model many volcanoes are associated with subduction zones or mid ocean ridges but other areas of unusually high volcanism or hotspots do not have such a direct connection to plate tectonic processes depaolo and manga argue in their perspective that some hotspots are caused by narrow upwelling plumes originating in the lower mantle while others are caused by broad hot upwellings or superswells yet others are not obviously associated with either deep plumes or superswells direct evidence for mantle plumes will require seismic imaging at higher resolution than is currently accessible in a related perspective foulger and natland take the opposing view that hotspot volcanism is a by product of plate tectonics and does not require deep plumes

delineation of macroporous zones in the unsaturated portion of the miami limestone using ground penetrating radar miami dade county florida summary the atlantic coastal ridge in dade county is an ooid shoal formed during the late pleistocene the ridge is composed of the eogenetic karst miami limestone characterized by a heterogeneous distribution of porosity that can manifest as large touching vug macroporous features with sizes in the meters and tens of meters direct evidence for the presence of such large dissolution features is only visible when exposed to the surface which may be problematic in urbanized areas for that reason it is critical to detect any potential precursors for such dissolution features at the subsurface level the purpose of this study was to investigate the ability of ground penetrating radar to detect areas of macroporosity by quantifying changes in electromagnetic wave velocity and relate them to changes in porosity after application of the complex refractive index model crim in order to constrain volumetric water content vwc in the crim an experiment using miami limestone samples was designed to understand 1 the range of typical vwcs and 2 the effect of capillary fringe on water table elevation the results show several areas where increases in em wave travel time associated with contrasts in porosity exceeding 40 cannot be explained by changes in vwcs typically shown in the miami limestone this study may help understand porosity variability in the unsaturated part of the miami limestone and if expanded to larger scales may aid groundwater flow models by better capturing distributions of macroporous areas that may contribute to direct recharge of the biscayne aquifer

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

potential links between ocean plateau volcanism and global ocean anoxia at the cenomanian turonian boundary the cenomanian turonian boundary is marked globally by the extinction of marine invertebrates and an increase in the accumulation and preservation of organic carbon rich sediments black shales the timing of this boundary also coincides with large scale volcanism from at least three large igneous provinces the caribbean and ontong java oceanic plateaus and the madagascar flood basalts in this paper we assess the possibility that hydrothermalism associated with large scale submarine magmatism was responsible for the reduction of dissolved o 2 in the oceans we investigate two potential mechanisms the oxidation of reduced material in hydrothermal effluents and the stimulation of primary productivity in the water column due to the injection of hydrothermal fe into surface waters with the first mechanism we find that a 10 000 km 3 submarine basalt eruption three orders of magnitude larger than recent midocean ridge eruptions could release enough reduced hydrothermal material to consume at least 6 percent of the dissolved o 2 in seawater in a well ventilated ocean such as the present ocean with the second mechanism we calculate that even a small percentage of the hydrothermal fe released from a single large flow could have led to a significant increase in primary productivity in areas where fe was the biolimiting nutrient such as open ocean areas in the pacific the potential impact of both of these o 2 reducing mechanisms at the cenomanian turonian boundary would have been significantly greater if cretaceous oceans were less well ventilated than the present oceans

sediment transport and bedforms in a carbonate tidal inlet lee stocking island exumas bahamas an active oolitic sand wave was monitored for a period of 37 days in order to address the relationship between the direction and strength of tidal currents and the resultant geometry and amount and direction of migration of bedforms in carbonate sands the study area is situated in a tidal channel near lee stocking island exumas bahamas containing an estimated 5 5 to 6 105 m3 of mobile oolitic sand tidal ranges within the inlet are microtidal and the maximum current velocity at the studied site is 0 6 m s 1 at least 300 400 m3 of mostly oolitic sand are formed within or brought into the channel area every year the tidal inlet is subdivided into an ocean orientated segment in which sand waves are shaped by both flood and ebb tides and a platform orientated segment where sand waves are mainly shaped by flood tides the studied sand wave lies on the platformward flood tide dominated segment in a water depth of 3 5 4 5 m during the 37 days of observation the oolitic and bioclastic sand wave migrated 4 m in the direction of the dominant flood current the increments of migration were directly related to the strength of the tide during each tidal cycle bedforms formed depending on the strength of the tidal current tidal range and their location on the sand wave during flood tides a steep lee and a gentle stoss side formed and current ripples and small dunes developed on the crest of the sand wave while the trough developed only ripples the average lee slope of the sand wave is 24 2 and therefore steeper than typical siliciclastic sand waves during ebb tides portions of the crest are eroded creating a convex upward ebb stoss side covered with climbing cuspate and linguoid ripples and composite dunes the area between the ebb lee side and the trough is covered with fan systems sinuous ripples and dunes the migration of all bedforms deviated to a variable degree from the main current direction reflecting complex flow patterns in the tidal inlet small bedforms displayed the largest deviation migrating at an angle of up to 90 and more to the dominant current direction during spring tides

geochemical evidence for an impact origin for a late archean spherule layer transvaal supergroup south africa a late archean layer rich in sand sized spherules of former silicate melt in the monteville formation transvaal supergroup south africa has ir concentrations as high as 6 4 ppb and is clearly enriched in ir relative to associated tuffs carbonates and shales the monteville spherule layer is also enriched in other siderophile elements including the platinum group elements pges the pges in the spherule layer produce a flat meteorite like pattern when they are normalized to chondritic abundances the abundances of ir and other siderophile elements are similar to broadly contemporaneous spherule layers in the hamersley basin of western australia that the mineral compositions textures and sedimentary structures of the spherule layers in the transvaal supergroup and hamersley basin are also very similar suggests that they were all formed by the same processes we think that the best way to explain the high ir concentrations and other characteristics of the monteville spherule layer is that it represents distal impact ejecta there are however significant differences between the monteville spherule layer and early archean spherule layers in the barberton greenstone belt including much higher average and maximum concentrations of ir in the latter the data presented here clearly show that each precambrian spherule layer is unique and needs to be characterized individually as is true for the impact spherule layers of the phanerozoic

integrating surface georadar and crosshole radar tomography a validation experiment in braided stream deposits we have used a combination of surface ground penetrating radar gpr profiling crosshole radar tomography and natural gamma ray logging to characterize a gravelly braided stream deposit in a gravel pit we conducted a survey using 300 mhz surface gpr 250 mhz crosshole radar and densely sampled gamma ray logging at single borehole locations after excavation we validated the geophysical results by comparison with the sedimentological and hydrogeological information obtained from the corresponding outcrop wall we found the visual lithofacies boundaries agreed very well with the images provided by applied geophysical techniques our results illustrate how gpr reflector images are improved using tomographic velocity information in addition the structural interpretation of tomographic velocity fields is guided by the gpr reflector images in combination with natural gamma ray logging results groundwater flow and transport modeling was also performed on different subsurface models the hydrogeological r

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

medieval phases of settlement at benabbio castle apennine mountains italy evidence from ground penetrating radar survey the lack of written sources for many of the medieval castles in the northern apennines italy makes it difficult to completely establish the most ancient historical phases of these settlements the church of san michele belongs to an abandoned fortified settlement of the castle of benabbio in the mountains surrounding lucca thanks to an epigraph still visible on the facade the church foundation is dated back to ad 1218 however several archaeological findings at the settlement seem to suggest stages of encastlement that are older than the church foundation a ground penetrating radar gpr survey has been carried out in the inner part of the church in order to identify the presence of pre ad 1218 buried structures a 0 5 m grid was used to acquire gpr data over the entire pavement of the church using an antenna of 200 mhz of nominal peak frequency a standard sequence of raw data processing was adopted and the interpretation was performed both on vertical radar profiles and time slices the distribution of areas of high back scattered electromagnetic energy shows regular patterns with orthogonal alignments archaeologically compatible with buried stone walls in the western sector of the church the subsurface structures are consistent with the wall remains of a building which due to its size and shape is unlikely to have been used for religious activities this building can be related to an 11the12th century encastlement of the site the other structures detected by gpr prospection can be referred to the construction of the 13th century romanesque church while its renaissance enlargement may have taken place in the late 15th century during this last phase a hypogean room was excavated near the altar and probably used as crypt ossuary the results of this multidisciplinary work have supported some archaeological hypotheses concerning the architectural history of the church dating back to the 11the12th century when the first stone structures of the benabbio castle were erected

pliocene warmth polar amplification and stepped pleistocene cooling recorded in ne arctic russia understanding the evolution of arctic polar climate from the protracted warmth of the middle pliocene into the earliest glacial cycles in the northern hemisphere has been hindered by the lack of co

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

deep root of a continent continent collision belt evidence from the chinese continental scientific drilling ccsd deep borehole in the sulu ultrahigh pressure hp uhp metamorphic terrane china abstract the chinese continental scientific drilling ccsd deep borehole which reached a depth of 5158 m in the sulu ultrahigh pressure uhp metamorphic terrane provides a new window into the deep root of a continent continent collision belt and the tectonic processes by which supracrustal material is recycled into the mantle by subduction and then uplifted to the surface major research themes of the ccsd project were to 1 determine the three dimensional composition structure and geophysical character of the deep root of this orogenic belt 2 investigate the nature and timing of the uhp metamorphism 3 investigate the processes of crust mantle interaction involved in the formation and exhumation of the uhp rocks 4 study the process of fluid circulation and mineralization during subduction and exhumation 5 study the rheological properties of the various rocks during subduction and exhumation 6 develop and refine dynamic models for deep subduction and exhumation of crustal rocks and 7 establish a long term natural laboratory for the study of present day crustal dynamics e g stress strain fluid activity the ccsd has developed precise oriented profiles of the main borehole in terms of lithology geochemistry oxygen isotopes zircon shrimp u pb ages 40ar 39ar ages deformation rheology mineralization physical properties of the rocks petrophysical logs seismic reflections and underground fluids the present paper summarizes the integrated research results of this project especially the new findings concerning the deep root of a continent continent collision

dynamics of orogenic wedges and the uplift of high pressure metamorphic rocks subduction accretion complexes can be approximated as wedge shaped continua with a rigid buttress behind and a subducting litho spheric slab beneath thick wedges undergoing prograde metamorphism have a negligible long term yield strength and are likely to exhibit a complex nonlinear viscous rheology such a wedge will tend to deform internally until it reaches a stable configuration in which the gravitational forces generated by the wedge geometry balance the traction exerted on its underside by the subducting slab accretion of material at the wedge front will lengthen the wedge and cause it to shorten internally to regain the stable geometry this shortening will be expressed as late out of sequence thrusting backthrusting and folding conversely underplating of sediment or crustal slices will thicken the wedge which may need to extend internally to regain stability extension will cause listric normal faults that may merge downward into zones of ductile extension continued underplating at depth and compensating extension above provides a mechanism for bringing high p low t metamorphic rocks to upper levels in the rear of the wedge where they are commonly observed many major tectonic boundaries in convergent orogens such as the coast range thrust in the franciscan complex major nappe contacts in the alps and the contact between the nevado filabride and higher betic nappe complexes in the betic cordillera show abrupt increases in metamorphic grade downward across them this is consistent with their origin or reactivation as uplift related extensional structures

exhumation of high pressure rocks a review of concepts and processes the exhumation of high pressure metamorphic rocks requires either the removal of the overburden that caused the high pressures or the transport of the metamorphic rocks through the overburden exhumation cannot be achieved simply by thrusting or strike slip faulting it may be caused by erosion of shortened and thickened crust but this is unlikely to be the only mechanism for exhuming rocks from depths greater than about 20 km one or more of the following additional mechanisms may be involved 1 corner flow of low viscosity material trapped between the upper and lower plates in a subduction zone can cause upward flow of deeply buried rock and may explain some occurrences of high pressure tectonic blocks in melange this process does not however appear to be adequate to explain the exhumation of regional high pressure terrains 2 buoyancy forces acting directly on metamorphic rock bodies may cause them to rise relative to more dense surroundings this is likely to be the most important mechanism of exhumation of crustal rocks subducted into the mantle but cannot explain the emplacement of coherent tracts of high density metamorphic rock into shallow crustal levels some high pressure blocks emplaced at shallow levels in accretionary terrains may have been entrained in diapiric intrusions of low density mud or serpentinite 3 extension driven by the forces associated with contrasts in surface elevation may explain the exhumation and structural setting of many high pressure terrains extension may occur in the upper part of an accretionary wedge thickened by underplating or it may affect the whole lithosphere in a region of intracontinental convergence if surface elevation has been increased by the removal of a lithospheric root in the second case extension may be accompanied by magmatism and an evolution towards higher temperature during decompression of the metamorphic terrain

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

3d ground penetrating radar imaging of ice complex deposits in northern east siberia abstractice complex deposits are characteristic ice rich formations in northern east siberia and represent an important part in the arctic carbon pool recently these late quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data many of these studies can benefit from a 3d structural model of the subsurface for upscaling their observations or for constraining estimations of inventories such as the local carbon stock we have addressed this problem of structural imaging by 3d ground penetrating radar gpr which in permafrost studies has been primarily used for 2d profiling we have used a 3d kinematic gpr surveying strategy at a field site located in the new siberian archipelago on top of an ice complex after applying a 3d gpr processing sequence we were able to trace two horizons at depths below 20 m taking available borehole and outcrop data into account we have interpreted these two features as interfaces of major lithologic units and der