characterization of karst hazards from the perspective of the doline triangle using gpr examples from central ebro basin spain ground penetrating radar gpr is a widespread technique to locate and characterise karst hazards cavities and paleocollapses in this paper we show that the internal structure of sediments obtained from gpr surveys can also be used as an indicator of active karst processes a classification of karst hazard problems by means of gpr in the gpr doline triangle is proposed with three end members cavities evidences of subsidence and paleocollapses these end members show particular signatures in the gpr profiles the field examples shown in this paper indicate that gpr survey is a geophysical technique that offers a very high resolution and provides structural and sedimentological information of the subsoil the use of grid maps elaborated from gpr data is an efficient way to determine anomalous sectors lateral changes of electromagnetic properties different reflectivity and qualitative penetration depth variations or velocity wave propagation changes their relationships with the structural features obtained from gpr profiles on lap geometries zones with depressed reflectors folded reflectors or laterally abrupt structural limits can be used as indicators of karstic processes

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

contourite erosive features caused by the mediterranean outflow water in the gulf of cadiz quaternary tectonic and oceanographic implications abstract contourite depositional systems have been the focus of much recent research but still relatively little is known about contourite erosive features and their associated processes based on multibeam bathymetry side scan imagery and different resolution seismic records a detailed description and classification of the major erosive submarine valley features of the contourite depositional system of the gulf of cadiz middle slope is presented for the first time four types of erosive features have been differentiated including contourite moats contourite channels marginal valleys and large isolated furrows and interpreted in terms of their tectonic and oceanographic implications during the quaternary the study of the distribution and characteristics of erosive features is essential to better understand the present and past interaction of the mediterranean outflow water mow with the middle slope seafloor and allows us to propose a new and more precise scheme for the mow circulation patterns this scheme includes a main along slope circulation responsible for the excavation of the contourite moat and channels and a secondary down slope circulation responsible for the erosion of marginal valleys and isolated furrows three evolutionary stages have been observed in the development of the erosive system during the quaternary that can be related to changes in the distribution and splitting of the mow as a consequence of the segmentation of the ne sw diapiric ridges by neotectonic effects 1 early pleistocene to mid pleistocene linear diapiric ridges 2 mid pleistocene to late pleistocene diapiric reactivation and 3 late pleistocene to holocene main recent phase of diapiric ridges segmentation and rotation this study provides important regional clues for establishing the evolution of the erosive features in relation with neotectonic effects and represents a good example of the potential of erosive features as evidences for the reconstruction of the paleoceanography and recent tectonic changes

dating of sirius group tillites in the antarctic dry valleys with cosmogenic3he and21ne we measured in situ produced cosmogenic3he and21ne in boulder and bedrock surface samples in and near sirius group tillites from two localities in southern victoria land antarctica pyroxene quantitatively retains cosmogenic3he for millions of years the deposit at mt fleming has a minimum exposure age of 6 5 ma while 6 ma is a probable minimum age for the table mountain tillite these lower limits not taking into account erosion of the sampled surfaces are based on the samples with the highest concentrations of cosmogenic noble gases and currently accepted production rates since the plagioclase bearing mt fleming samples almost certainly lost part of their cosmogenic ne the minimum exposure age at this location is presumably even 50 higher than the stated value the concentrations of cosmogenic ne in our samples constrain uplift rates of the transantarctic mountains to 170 m ma these data contradict the hypothesis of a collapse of the east antarctic ice sheet in the pliocene coupled with high uplift rates and support the model of a stable ice sheet since the middle miocene

small scale variability of the cross shelf flow over the outer shelf of the ross sea 1 the importance of cross shelf transport across the ross sea on local and remote processes has been well documented in the ross sea mid water intrusions of circumpolar deep water cdw are modified by shelf water near the shelf break to form modified circumpolar deep water mcdw in 2010 2011 we deployed multi platform technologies focused on this mcdw intrusion in the vicinity of mawson and pennell banks to better understand its role in ecosystem processes across the shelf the high resolution time and space sampling provided by an underwater glider a short term mooring and a ship based survey highlight the scales over which these critical cross shelf transport processes occur mcdw cores were observed as small scale well defined features over the western slopes of pennell and mawson banks the mean transport along pennell bank was estimated to be about 0 24 sv but was highly variable in time hours to days the observations suggest that the core of mcdw is transported by a predominately barotropic flow that follows topography around the banks toward the south until the slope of the bank flattens and the warmer water moves up and over the bank this pathway is shown to link the source mcdw with an area of high productivity over the shallows of pennell bank

semiautomated geologic mapping using self organizing maps and airborne geophysics in the brazilian amazon abstracta self organizing map som approach has been used to provide an integrated spatial analysis and classification of airborne geophysical data collected over the brazilian amazon magnetic and gamma ray spectrometric data were used to extract geophysical signatures related to the spatial distribution of rock types and to produce a geologic map over the prospective anapu tuere region particular emphasis was given to discriminating and identifying rock types and the processes related to gold mineralization which are known to occur in the anapu tuere region som was able to identify and map distinctive geophysical signatures related to the various geologic units identified on the published geologic map furthermore som was able to identify and enhance very subtle signatures derived jointly from the magnetic and gamma ray spectrometric data that could be related to geologic processes present in the area these results demonstrate the effectiveness of using som as a tool for geophysical data analysis

cosmogenic 3he and 21ne dating of biotite and hornblende stable cosmogenic isotopes such as 3he and 21 ne are useful for dating of diverse lithologies quantifying erosion rates and ages of ancient surfaces and sediments and for assessing complex burial histories although many minerals are potentially suitable targets for 3he and 21 ne dating complex production systematics require calibration of each mineral isotope pair we present new results from a drill core in a high elevation ignimbrite surface which demonstrates that cosmogenic 3he and 21 ne can be readily measured in biotite and hornblende 21 ne production rates in hornblende and biotite are similar and are higher than that in quartz due to production from light elements such as mg and al we measure 21 ne hbl 21 ne qtz 1 35 0 03 and 21 ne bio 21 ne qtz 1 3 0 02 which yield production rates of 25 6 3 0 and 24 7 2 9 at g 1 yr 1 relative to a 21 ne qtz production rate of 19 0 1 8 at g 1 yr 1 we show that nucleogenic 21 ne concentrations produced via the reaction 18 o n 21 ne are manageably small in this setting and we present a new approach to deconvolve nucleogenic 21 ne by comparison to nucleogenic 22 ne produced from the reaction 19 f n 22 ne in f rich phases such as biotite our results show that hornblende is a suitable target phase for cosmogenic 3he dating but that 3he is lost from biotite at earth surface temperatures comparison of 3he concentrations in hornblende with previously measured mineral phases such as apatite and zircon provides unambiguous evidence for 3he production via the reaction 6li n 3h 3he due to the atypically high li content in the hornblende 160 ppm we estimate that li produced 3he represents 40 of total 3he production in our samples and must be considered on a sample specific basis if 3he dating in hornblende is to be widely implemented

delineation of sinkhole boundary using dutch cone soundings abstract the foundation design for expanding a cogeneration power plant in central florida renowned for its sinkhole prone geology provided a challenge for geotechnical engineers because of limited available land the expanded power plant was built on an adjacent 5 acre tract where a 50 ft diameter by 5 ft deep depression had been identified dutch cone soundings a relatively underutilized method were used to characterize the site and reduce uncertainty for this application dutch cone soundings provided higher quality data at a lower cost than the more common standard penetration test spt method to investigate the subsurface conditions of the 5 acre tract ground penetrating radar gpr and four exploratory spt borings were conducted the spt borings confirmed that the depression was caused by an ancient sinkhole because of a relatively high groundwater table and a layer of very dense organic hardpan near the surface the penetration depth of gpr was limited to 5 10 ft below ground surface and thus could not define the sinkhole s boundary to delineate the sinkhole s boundary 38 dutch cone soundings were made to 20 160 ft deep conducted in three phases around the depression the phase 1 soundings were spaced at 100 to 200 ft intervals around the depression to estimate the influence zone the results of phase 1 soundings were used to place phase 2 and 3 soundings at ca 50 and 20 ft intervals respectively to define the boundary of the ancient sinkhole using the results of the dutch cone soundings the area around the sinkhole was delineated into the following zones sinkhole collapsing zone where strata 2 and 3 were not encountered zone under sinkhole influence where stratum 1 was not encountered zone beyond sinkhole influence where strata 1 2 and 3 were encountered because the sinkhole influence zone was ca 200 ft in diameter heavy facilities were constructed at least 50 ft from the zone completed in 1993 the expansion has not had foundation settlement problems since that time

shear wave velocity to evaluate in situ state of cohesionless soils shear wave velocity vs measurements were carried out in a triaxial testing program on three different cohesionless soils the vs was measured using bender elements during consolidation and at ultimate steady state after consolidation the soil samples were loaded in shear under constant strain rate triaxial compression either drained or undrained to determine their ultimate steady or critical state uss at large strains the vs measurements were used to develop relationships between the void ratio e mean normal effective stress p and vs the shear loading results were expressed within the framework of critical state soil mechanics the results of the vs and uss information were combined with the state parameter concept to develop an equation to use field measured vs to estimate the in situ consolidation state within a soil thus the contractive dilative boundary with respect to vertical effective stress for large strain loading can be determined from in situ measurements of vs these can then b

prediction of the location of future rupture surfaces of a slowly moving loess landslide by electrical resistivity tomography a slowly moving loess landslide along the river danube in south hungary was studied using electrical resistivity tomography our aim was to determine the fracture system of the study site due to the homogeneous composition of the loess it seems to be the only possibility to get information about the landslide and its further evolution the applicability of the electrical resistivity tomography technique for such a supposedly dense fracture system was studied by numerical modelling and the results have been verified in the field the dip of the fractures could not always been observed and they could not be explored deeply however it was possible to map their surface projection to get the desired information about the structure of the landslide fracture zones could have been especially well localized enabling the prediction of the positions of future rupture surfaces and thus the delineation of the endangered zone although the area outside of the already subsided one is not endangered yet the area which has already started to move is going to break into two parts of the about 5 m wide blocks at the front of the landslide may fall or slide down anytime a large area was assumed to move as one unit most of our predictions have been verified by the mass movements that occurred about one and half years after the measurements the electrical resistivity tomography method proved to be a good tool to characterize the fracture system of such a landslide area enabling the prediction of future rupture surfaces and also delineation of the endangered area its use is therefore highly recommended to monitor landslides to provide early risk warnings to avoid damage to constructions or endangering human life

sorption and diffusion of helium in garnet implications for volatile tracing and dating abstract we present data on he sorption in garnet obtained by loading garnet samples with he at 250 10 bar in the temperature range 800 990 c for this temperature range we find a three fold decrease in he sorption from 2 1 10 5 800 c to 0 72 10 5 cm 3 stpg 1 bar 1 990 c we use the sorption data of partially saturated samples to obtain the activation energy e a 660 120 190 kj mol and frequency factor d 0 10 15 6 8 5 2 cm 2 s for he diffusion in garnet the results of our study suggest that garnet is probably one of the most retentive silicate minerals for he which is in agreement with its very low ion porosity the high retentivity results in a high closure temperature t c for the u th he system for cooling rates as low as 0 1 1 c ma t c lies between 590 and 630 c accordingly u th he dating of garnet may provide information about the medium to high temperature cooling path of a rock at the lower end of the temperature range of currently used isotopic systems in garnet in addition the high retentivity for he makes garnet a potentially useful mineral in the field of exposure age dating currently it is the only known common silicate mineral occurring in upper crustal rocks which probably retains cosmogenic noble gases under all climatic conditions for geochemical studies using noble gases as tracers for geofluids garnet is a perfect container if temperatures never exceed 600 c that is all originally trapped noble gases are quantitatively retained

cosmogenic neon in recent lavas from the western united states the absolute cosmogenic production of 21ne 21nec and 3he 3hec in olivine fo81 is measured for the well dated tabernacle hill flow values scaled to sea level and high latitude 60 are 45 atoms g yr for 21nec and 109 atoms g yr for 3hec for the past 17 800 years production rates for 21nec are about 50 higher than the theoretical values given by lal 1991 a ratio of 21nec 3hec of 0 41 0 05 is measured in olivines that have a range of 25 in cosmogenic exposure there is no evidence of 3hec loss in samples older than 100 000 years volcanic plagioclase is shown to be a suitable mineral for cosmogenic 21nec dating of surfaces 21nec in co existing plagioclase and olivine phenocrysts have a constant ratio of 0 42 04 in samples with more than 106 atoms of 21nec using all of the 21nec data and the 3hec as a cosmic ray flux monitor production of 21nec in ab36 plagioclase is calculated at 16 8 1 7 atoms g yr for the past 17 800 years the production of 21nec from 23na is estimated at 160 50 atoms g yr at 60 and sea level or equivalent to that on 24mg

cosmogenic 3he in terrestrial rocks the summit lavas of maui we have identified terrestrial cosmic rayproduced 3he in three lava flows on the crest of haleakala volcano on maui 3 km above sea level and 0 5 million years old although these lavas like all oceanic basalts contain primordial 3he from the mantle the cosmogenic component 3hec can be identified unambiguously because it is extractable only by high temperature vacuum fusion in contrast a large fraction of the mantle helium resides in fluid inclusions and can be extracted by vacuum crushing leaving a residual component with 3he 4he ratios as high as 75 those in the atmosphere which can be liberated by melting the crushed grains cosmogenic 3he is present in both olivines and clinopyroxenes at 0 8 1 2 10 12 ml stp g and constitutes 75 5 of the total 3he present the observed 3hec levels require a cosmic ray exposure age of only some 64 000 years much less than the actual age of the lavas if there is no erosion using a model that includes effects of uplift or submergence as well as erosion we calculate an apparent erosion rate of the order of 8 5 m 106 years for the western rim of the summit crater as an example of the application of measurements of cosmogenic rare gases to terrestrial geological problems

angle dependent reflectivity by means of prestack migration most present day seismic migration schemes determine only the zero offset reflection coefficient for each grid point depth point in the subsurface in matrix notation the zero offset reflection coefficient is found on the diagonal of a reflectivity matrix operator that transforms the illuminating source wave field into a reflected wave field however angle dependent reflectivity information is contained in the full reflectivity matrix our objective is to obtain angle dependent reflection coefficients from seismic data by means of prestack migration multisource multioffset after downward extrapolation of source and reflected wave fields to one depth level the rows of the reflectivity matrix representing angle dependent reflectivity information for each grid point at that depth level are recovered by deconvolving the reflected wave fields with the related source wave fields this process is carried out in the space frequency domain in order to preserve the angle dependent reflectivity in the im

bottom currents and their influence on the sedimentation pattern in the el arraiche mud volcano province southern gulf of cadiz abstract the completion of iodp expedition 339 within the cadiz contourite depositional system along the southern iberian margin which was created and maintained by the mediterranean outflow water has brought increased amounts of attention to this natural contourite laboratory in contrast a lot less attention is given to the southern gulf of cadiz despite the ubiquitous presence of tectonic ridges small contourite deposits mud volcanoes and cold water coral mounds the el arraiche mud volcano province eamvp is located in the southern gulf of cadiz and is characterized by an extensional regime creating two tectonic ridges named renard and vernadsky also nine mud volcanoes and numerous cold water coral mounds are present in this area the northward flowing bottom currents are deflected by the topographic obstacles and flow in a westward direction at the foot of the nw se oriented renard ridge calculations indicate that this bottom current is capable of turning around the tip of the renard ridge and continues its path along its northern edge the locations of the contourite deposits at the foot of the renard ridge are controlled by the steepness of the ridge slopes of more than 12 are associated to contourite deposits while less steep ones merely show hemipelagic deposits the moats around the mud volcanoes originate due to a combination of subsidence and the action of bottom currents as the seismic data show separated mounded drift deposits perpendicular to the moats as well as subsidence rims some mud volcanoes have a less incised northern and a deeper southern moat which indicates eastward flowing bottom currents this orientation is consistent with the shoreward component of the internal tides which flow vigorously in this area with peaks of speed over 30 cm s the integration of geophysical and hydrographic datasets in the eamvp sheds new light on the dynamic nature of the interaction of bottom currents and topographic features

integrating s wave seismic reflection data and cone penetration test data using a multiangle multiscale approach a cone penetration test cpt is the most common geotechnical testing method used to estimate in situ the strength properties of soil although cpt provides valuable information this information is restricted to the location of the measurement we propose a new concept to integrate shallow s wave reflection seismic data with cpt data in order to obtain laterally continuous subsoil information in this vein a valid quantitative means to relate seismic reflections to cpt data is a primary requirement the approach proposed here is based on the characterization of the scaling behavior of the local fine scale s wave velocity information extracted from the seismic reflection data and the same behavior of the cpt cone resistance the local velocity contrast information is extracted by linearized zoeppritz inversion of the amplitude preserved prestack reflection data we have formulated a multiscale analysis approach employing the continuous wavelet transform in order to quantitatively characterize the nature

cosmogenic 3he and 21ne production rates calibrated against 10be in minerals from the coso volcanic field this study calibrates the production rate of cosmogenic 3 he in pyroxene olivine garnet zircon and apatite as well as 21 ne in quartz and pyroxene against the known production rate of 10 be in quartz the devil s kitchen rhyolite from the coso volcanic field in southeastern california elev 1300 m was chosen for this study due to its young age 610 ka and diverse mineral assemblage based on 10 be our two rhyolite samples have apparent exposure ages of 49 and 93 ka indicating substantial erosion after eruption combining data from the two samples we estimate sea level high latitude 3 he spallation production rates of 145 11 141 16 and 144 30 at g 1 a 1 2 for pyroxene olivine and spessartine garnet respectively for zircon and apatite we estimate apparent 3he spallation production rates of 114 8 and 149 28 at g 1 a 1 2 respectively the rates for zircon and apatite are reported as apparent production rates because we do not explicitly address the redistribution of spallation produced 3 he from adjacent minerals these estimates quantitatively account for production of 3 he from both cosmogenic and radiogenic neutron reactions on 6 li within the analyzed phases and also implanted from nuclear reactions in neighboring minerals the high u th and li content of this rhyolite provides a particularly rigorous test of this correction we estimate 21 ne production rates of 17 7 1 6 and 34 1 3 2 at g 1 a 1 2 in quartz and pyroxene fe mg 0 7 by mass respectively although high u and th contents create the potential for significant production of nucleogenic 21 ne this component is small due to the young eruption age of the rhyolite

uncertainties in the mean ocean dynamic topography before the launch of the gravity field and steady state ocean circulation explorer goce 1 in anticipation of the future observations of the gravity mission gravity field and steady state ocean circulation explorer goce the present day accuracy of mean dynamic topography mdt is estimated from both observations and models a comparison of five observational estimates illustrates that rms differences in mdt vary from 4 2 to 10 5 cm after low pass filtering the fields with a hamming window with wavenumber n 120 corresponding to an effective resolution of 167 km rms differences in observational mdt reduce to 2 4 8 3 cm for n 15 1334 km differences in data sources geoid model in situ data are mostly visible in the small scale oceanic features while differences in processing filtering inverse modeling techniques are reflected at larger scales a comparison of seven different numerical ocean models demonstrates that model estimates differ mostly in western boundary currents and in the antarctic circumpolar current rms differences between modeled and observed mdt are at best 8 8 cm for n 120 and reduce to 6 4 cm for n 15 for models with data assimilation a minimal rms difference of 6 6 cm n 120 to 3 4 cm n 15 is obtained with respect to the observational mdts the reduction of differences between mdts with increasing filtering scales is smaller than expected while it is expected that goce will improve mdt estimates at small spatial scales improvement of mean sea surface estimates from satellite altimetry may be needed to improve mdt estimates at larger scales

abyssal erosion and scarp retreat deep tow observations of the blake escarpment and blake spur abstract deep tow surveys conducted at two sites at the base of the blake spur and blake escarpment serve to delineate the contact between mesozoic platform carbonates of the blake plateau and adjacent abyssal strata the continental margin in the surveyed areas consists of steep limestone cliffs and headlands with over 2 km of relief this extreme topography distorts the hydrographic structure of the water column and intensifies abyssal current flow in the surveyed areas significant lateral scarp retreat is indicated by the presence of broad nearly horizontal benches of mesozoic limestone presently exposed at the base of the blake spur and escarpment in 4 5 5 km water depth and by angular apparently truncated limestone ledges that crop out on the cliff face at the blake spur the contact between mesozoic platformal limestones and basinal tertiary strata does not occur directly at the foot of the cliff but is exposed on the abyssal plain within a 50 m deep erosional moat here strong 2 knots south flowing bottom currents occur within 100 m of the sea floor the coincidence of this vigorous current flowing within the moat near the base of the escarpment and the eroded character of the sea floor suggests that currents are an important mechanism in sculpting this abyssal headland and contributing to lateral scarp retreat similar erosional processes are indicated along the blake escarpment near 29 03 n where the relatively straight cliff face is interrupted by occasional steep walled box canyons on the headland between the canyons the mesozoic outcrop projects into the blake bahama basin for several kilometers as a broad arcuate gently sloping bench these outcropping benches of mesozoic strata at the base of the escarpment are analogous to larger scale buried benches observed in the subsurface that were formed by pre miocene erosion neogene and quaternary scarp retreat is suggested by the location of the contact between mesozoic rocks and younger strata seaward of the steeper cliff face and is probably the result of current induced erosion focused erosion may be facilitated by the presence of a thin 50 m filament of corrosive antarctic bottom water aabw that flows vigorously along the base of the cliff at both sites the recessed position of the canyons shelters them from the main flow of this abyssal current but the steepness and morphology of the canyon walls suggest that additional unidentified erosional processes are focused at the canyon heads

the cosmic ray produced he 21ne ratio in ultramafic rocks although production of noble gases in meteorites are well studied since many years e g bogard and cressy 1973 the first analysis of cosmic ray produced helium in terrestrial rocks were performed only in 1986 by kurz and by craig and poreda later marti and craig 1987 reported cosmic ray produced neon in summit lavas from maui more data on cosmogenic helium and neon were reported by staudacher and allegre 1991 on ultramafic nodules from asia the absolute production rate of cosmic ray produced helium has been determined by kurz 1986 1987 in olivine rich basalts from hawaii with known k ar or 14c ages the resulting hec production rate is 3 72 10 18cm stp g a this allows cosmogenic he to be used to determine cosmic ray exposure ages of surface samples for neon no such absolute production rate has yet been determined in order to develop a complementary dating method using cosmogenic 21ne staudacher and allegre 1991 measured the cosmogenic he 21ne ratio in ultramafic nodules their value was 1 4 which is significantly smaller than the value of 3 5 obtained in this work here we discuss the cosmogenic he 21ne ratio in view of new noble gas data on olivine separates of oceanites from reunion island and on ultramafic nodules from mongolia

statistical analysis of airborne gamma ray data for geologic mapping purposes crixas itapaci area goias brazil q mode factor analysis k means clustering and g mode clustering were used on digitized gamma ray spectrometer data from an aerial survey of the crixas itapaci area goias brazil the data points including seven variables eu eth k total count u th u k and th k were digitized for a 2 km square grid for the northwest corner of the area the data were gridded at 1 km the q mode classification method supplied results that do not show a good correspondence with the known geology the k means clustering procedure barely identified the main lithologic features of the area the g mode technique produced results that correlate well with the known geology and identified the greenstone belts present in the area by discriminating their ultramafic and mafic components from adjacent felsic rocks statistical analysis of aerial gamma ray spectrometer data can be very helpful in mapping geologic units in poorly known areas it can also be used for mineral exploration purposes if mineralization is known to be associated with lithologies that can be identified by the techniques used in this study

bathymetric influences on antarctic ice shelf melt rates ocean bathymetry exerts a strong control on ice sheet ocean interactions within antarctic ice shelf cavities where it can limit the access of warm dense water at depth to the underside of floatin

the liquefaction of sands a collapse surface approach recent large scale slides occurring during the hydraulic placement of an artificial island berm in the beaufort sea resulted from the liquefaction of the berm sand subsequent laboratory tests and

calibration chamber tests of a cone penetrometer in sand the results of a series of tests using a cone penetrometer in sand in a large calibration chamber are reported sand at three different densities and a range of stress states was studied the principal finding from the tests is that cone resistance in sand depends primarily on the horizontal stress and the angle of friction but is relatively unaffected by the vertical stress a relationship between qc h and tc is proposed and compared with previous work in calibration chambers l article presente les resultats d une serie d essais effectues avec un penetrometre a cone dans du sable dans une chambre d etalonnage le sable a ete etudie avec trois densites differentes dans un intervalle d etats de contrainte les essais ont demontre surtout que la resistance au cone dans le sable depend d abord de la contrainte horizontale et de l angle de friction mais reste relativement peu influencee par la contrainte verticale on propose une relation entre qc h et tc et on la compare avec des recherches anteri

a study on the subsoil of the tower of pisa based on results from standard and high quality samples in this paper an updated geotechnical characterization of the soils underlying the leaning tower of pisa is presented based on results from a recent experimental investigation as well as on resul

factor analysis of engineering geophysical sounding data for water saturation estimation in shallow formations abstractthe engineering geophysical sounding method has been applied for in situ investigation of unconsolidated near surface formations since the 1990s in this study we offer an alternative to geophysical inversion methods for data processing factor analysis is applied to engineering geophysical sounding and cone penetration test data to extract information on water saturation of the shallow region a linear correlation is indicated between water saturation and one of the new variables derived by factor analysis we used a general formula for estimating water saturation and applied it on data measured in 12 shallow boreholes situated over a nuclear waste disposal site we extended the statistical procedure to estimate the spatial distribution of water air saturation between the boreholes we compared the statistical results to inversion estimations the study showed that factor analysis gives a quick and reliable solution for the assessment of hydrogeological conditions in shallow prospecting sites

a microelectromechanical system digital 3c array seismic cone penetrometer a digital 3c array seismic cone penetrometer has been developed for multidisciplinary geophysical and geotechnical applications seven digital triaxial microelectromechanical system accelerometers are installed at 0 25 m intervals to make a 1 5 m long downhole seismic array the accelerometers have a flat response up to 2 khz the seismic array is attached to a class 1 digital seismic cone which measures cone tip resistance sleeve friction pore pressure and inclination the downhole 3c array can be used together with impulsive seismic sources and or high frequency vibrators that are suitable for high resolution shallow applications results from two field experiments showed that a good data quality including a constant source function within an array and a dense depth sampling allowed robust estimation of seismic velocity profiles in the shallow subsoil using horizontal and vertical seismic sources downhole 9c seismic array data can be easily acquired the quality of the shear wave data is much superior when the surface seismic source is a controlled high frequency vibrator in stead of a traditional sledge hammer a remarkable correlation in depth in a fine scale between low strain seismic shear wave velocity and high strain cone tip resistance could be observed the array measurements of the full elastic wavefield and the broad spectral bandwidth are useful in investigating frequency dependent seismic wave propagation in the porous near surface soil layers which is informative of the in situ fluid flow properties stable estimates of dispersive seismic velocity and attenuation can be obtained

using in situ produced cosmogenic isotopes to estimate rates of landscape evolution a review from the geomorphic perspective the application of in situ produced cosmogenic isotopes to problems in geomorphology has increased rapidly over the past decade at least 57 papers and numerous abstracts have been published since the mid 1980s when the first mass spectrometric measurements of terrestrially produced cosmogenic isotopes were made taken at face value these studies provide quantitative information about rates of landscape evolution and landform age however the significance of calculated erosion rates and exposure ages depends strongly on the models used to interpret isotopic data the validity of assumptions inherent to these models and the geologic surroundings in which the samples were collected this paper attempts to place cosmogenic isotope studies in a geomorphic context by reviewing fundamentals of the method and evaluating the validity of assumptions under which these data have been interpreted at present the establishment of high precision cosmogenically based glacial and alluvial chronologies is stymied by the evolution of geomorphic surfaces the erosion of rock from sampled boulders the potential for isotope inheritance from previous exposure and the uncertainty of isotopic measurements uncertainties in isotope production rates and the observed variability of exposure ages on individual geomorphic surfaces limit the confidence with which cosmogenic ages can be correlated reliably with those obtained by other techniques estimation of erosion rates at single points on the landscape gives useful small scale information extrapolation of these rates over longer time and larger spatial scales is less sure and most likely biased toward lower erosion rates by die inadvertent selection of resistant sample sites however because erosion rates are so poorly constrained at present even estimates to within a factor of 2 may be of significant value to geomorphologists and tectonicists

test of national uranium resource evaluation gamma ray spectral data in petroleum reconnaissance advances in interpretation techniques have made possible effective use of aerial high sensitivity gamma ray spectral data to explore for petroleum in selected environments these data were collected by the u s department of energy during the national uranium resource evaluation nure program throughout the conterminous u s and most of alaska between 1974 and 1981 the tests reported here were limited to portions of the following 1 degree by 2 degree national topographic map series ntms quadrangles the west half of the palestine quadrangle the east half of the san angelo quadrangle and the southeast quarter of the big spring quadrangle all of which are in texas the radiometric uranium and potassium data were normalized for surface lithology including soil differences as well as for variations in counting geometry and hydrologic conditions using a new technique based on thorium measurements and geochemical relationships between thorium and potassium and between thorium and the uranium series

identification and quantitative analysis of sinkhole contributing factors in florida s karst abstract sinkholes are one of the major geohazards in karst areas causing loss of life and significant economic loss as well sinkhole forming mechanism varies depending on the geological environment and florida s sinkholes are formed through the process of interaction between groundwater flow and cover soils the significance of this paper is 1 to identify key sinkhole contributing factors and 2 to quantify the impact of those factors on sinkhole formation particularly this study accounted for geomechanical factors that contribute to sinkhole raveling due to erosion and mechanical stability of overburden soils identification of key sinkhole contributing factors will allow developing a probabilistic sinkhole prediction model the study area was focused on east central florida where cover collapse sinkholes often occur uniform distribution transformation was employed for the quantitative analysis on each factor and then case studies with specific examples are then presented to validate the results of the quantitative analysis in conclusion the identified key factors are hydraulic head difference soil permeability thicknesses of aquifer systems and proximity to karst features e g existing sinkhole the critical permeability kcrit showing a rapid increase of sinkhole occurrence is about 20 cm h thickness and characteristics of cover soils seem a controlling factor of sinkhole types and the overburden thickness around 40 to 45 m tends to form the collapse type a multivariate regression analysis indicates that the thickness of the surficial aquifer system is the most significant factor and then the head difference and the proximity to karst features follow in order

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

cosmic ray produced neon and helium in the summit lavas of maui a 3he component attributed to cosmic ray induced spallation reactions 3hec in silicate minerals has recently been identified in lava flows on the summit of haleakala volcano on maui1 3 this3hec is observed in the helium extracted by fusion of olivine and pyroxene phenocrysts after first removing almost all of the mantle derived helium by vacuum crushing a procedure which releases the volatiles trapped in fluid inclusions within the phenocrysts cosmic ray produced 3he was found in the high altitude 3 000 m summit lavas which are 500 000 years old but was not observed in sub surface samples which were overlain by younger basalts2 or in a 200 yr old lava flow at sea level on maui1 2 we report here the identification of cosmic ray produced 21nec in addition to 3hec in gases extracted by fusion of olivines and clinopyroxenes after vacuum crushing the observed 3he 21ne c ratios and the ratio of 21nec in olivine to that in clinopyroxene are consistent with an in situ origin of 3hec and 21nec by cosmic ray spallation reactions this component could be important for interpreting helium isotopic data in terrestrial reservoirs geophysical applications could include determinations of erosion rates and exposure histories of terrestrial rocks

topographic control of basin and channel flows the role of bottom pressure torques and friction the topographical control of western boundary currents within a basin and zonal jets in a channel is investigated in terms of the potential vorticity pv and barotropic vorticity bv the curl of the depth integrated velocity budgets using isopycnic adiabatic wind driven experiments along the western boundary the wind driven transport is returned across latitude lines by the bottom pressure torque while friction is only important in altering the pv within an isopycnic layer and in allowing a closed circulation these contrasting balances constrain the geometry of the flow through integral relationships for the bv and pv for both homogenous and stratified basins with sloping sidewalls the northward subtropical jet separates from the western wall and has opposing frictional torques on either side of the jet which cancel in a zonal integral for bv but alter the pv within a layer streamline in a channel with partial topographic barriers the bottom pressure torque is again important in returning wind driven flows along western boundaries and in transferring bv from neighboring wind driven gyres into a zonal jet the depth integrated flow steered by topography controls where the bottom friction alters the pv which can lead to different pv states being attained for separate subbasins along a channel

ages of the second caldera of piton de la fournaise volcano reunion determined by cosmic ray produced3he and21ne abstract cosmic ray produced 3 he and 21 ne in olivine separates from the plaine des rempart close to the second caldera of piton de la fournaise reunion indicate identical exposure ages of 62 000 yrs this age is only slightly less than the formation age of the basalt which is 65 000 2000 yrs and represents the final stage of eruption phase 2 the lower part of the wall of the second caldera just above the plaine des sables shows a cosmic ray exposure age of 23 800 2000 yrs this is probably the age for the collapse of the second caldera and represents the first direct dating of a fault in addition this age agrees with the range of 41 000 19 000 yrs given by k ar ages of different lava flows further six rocks that represent the final filling of the second caldera show low exposure ages of between 3300 and 5100 yrs these ages date the final stage of eruption phase 3 at 3400 1000 yrs and set an upper limit on the formation of the third caldera the enclos fouque this work shows that 21 ne and 3 he exposure age dating are powerful techniques for determining young ages in mafic samples and for obtaining ages for geological phenomena such as faulting because neon has three isotopes cosmogenic initial and morb type neon can be effectively resolved and combined use of 21 ne c and 3 he c represents a significant improvement in exposure age dating

multivariate statistical analysis of geophysical data in nevada regional magnetic gravity and gamma ray data in nevada were analyzed using a multivariate statistical method the algorithms used are part of the public domain geographical resource analysis support system grass twenty seven statistical groups clusters were found to be the optimum number that best represents the geophysical data the resulting map of the distribution of these groups shows linear features which define a geophysical trend not previously recognized this trend is clearly related to the northern nevada rift and extends from near the northern border of nevada to the southern part of the state with a northwest southeast trend to about 37 n latitude where a change of direction occurs to a northeast southwest trend although not spatially coincident the roberts mountains thrust the golconda thrust and the 0 706 contour of the 87sr 86sr ratio exhibit similar trends over part of their lengths the significance of this geophysical trend is uncertain one possible interpretation is that it

high he 4he ratio in xenoliths from takashima evidence for plume type volcanism in southwestern japan cenozoic basalts distributed along the southwestern japan arc system have geochemical features different from typical island arc basalts suggesting that the volcanism might have been triggered by a mantle plume to identify the source materials in these volcanics noble gas isotopic compositions of olivines separated from dunite xenoliths in alkaline basalts from takashima northwestern kyushu were measured most samples contain morb type helium however some samples showed he 4he ratios significantly higher than the morb value from 9 4 up to 16 6 times the atmospheric ratio of 1 4 10 6 this finding strongly supports the contribution of a mantle plume to the volcanism of this region

most frequent value based factor analysis of direct push logging data an improved iteratively re weighted factor analysis procedure is presented to interpret engineering geophysical sounding logs in shallow unsaturated sediments we simultaneously process cone resistance electric resistivity and nuclear data acquired by direct push tools to give robust estimates of factor variables and water content in unconsolidated heterogeneous formations the statistical procedure is based on the iterative re weighting of the deviations between the measured and calculated data using the most frequent value method famous for its robustness and high statistical efficiency the iterative approach improves the result of factor analysis for not normally distributed data and extremely noisy measurements by detecting a strong regression relation between one of the extracted factors and the fractional volume of water we establish an independent method for water content estimation along the penetration hole we verify the estimated values of water volume by using a highly overdetermined quality checked interval inversion procedure the multidimensional extension of the statistical method allows the estimation of water content distribution along both the vertical and horizontal coordinates numerical tests using engineering geophysical sounding data measured in a hungarian loessy sandy formation demonstrate the feasibility of the most frequent value based factor analysis which can be efficiently used for a more reliable hydrogeophysical characterization of the unsaturated zone this article is protected by copyright all rights reserved

adjoint sensitivity of an ocean general circulation model to bottom topography abstract bottom topography or more generally the geometry of the ocean basins is an important ingredient in numerical ocean modeling with the help of an adjoint model it is shown that scalar diagnostics or objective functions in a coarse resolution model such as the transport through drake passage the strength of the atlantic ocean meridional overturning circulation the deacon cell and the meridional heat transport across 32 s are sensitive to bottom topography as much as they are to surface boundary conditions for example adjoint topography sensitivities of the transport through drake passage are large in choke point areas such as the crozet kerguelen plateau and south of new zealand the atlantic meridional overturning circulation is sensitive to topography in the western boundary region of the north atlantic ocean and along the scotland iceland ridge many sensitivities are connected to steep topography and can be interpreted in terms of bottom form stress that is the product of bottom pre

cosmogenic neon and helium at reunion measurement of erosion rate abstract we report analyses of both helium and neon for olivine separates from a drill core at an altitude of 2330 m in oceanite at piton de la fournaise volcano we show for the first time that cosmogenic 21 ne like cosmogenic 3 he decreases exponentially with core depth we obtain an attenuation length of 165 6 g cm 2 1 for cosmogenic 21 ne identical to the value found previously for cosmogenic 3 he alone 1 for each depth in the core the measured amount of cosmogenic 21 ne is about 13 lower than predicted based on the high precision k ar age of 65 200 2000 yrs 1 2 and this result is attributed to erosion assuming a constant erosion rate we derive a value of 3 5 1 7 mm yr 1 from the 21 ne data the same order of magnitude as the value obtained from cosmogenic 3 he at haleakala 1 3 this work highlights the important potential of both cosmogenic helium and neon for measuring in situ exposure ages and erosion rates

hindcast gis and susceptibility modelling to assist oil spill clean up and mitigation on the southern coast of cyprus eastern mediterranean this study uses new oil spill models bathymetric meteorological oceanographic geomorphological and geological data to assess the impact of distinct oil spill scenarios on the southern coast of cyprus eastern mediterranean this approach results from the urgent need to predict oil spill dispersion after new oil terminals and depots were built at vasilikos southern coast of cyprus the terminals have been able to receive tankers with 500 000 deadweight tonnes from november 2014 the new geomorphological and geological data in this work show the shoreline of cyprus to be of high susceptibility due to a the presence of a narrow continental shelf capable of trapping large quantities of hydrocarbons b the existence of uplifted wave cut platforms coastal lagoons and pools forming natural traps for oil and c the presence of important tourist and natura 2000 sites under particular weather and oceanographic conditions oil spills offshore larnaca bay will quickly spread and reach the shoreline 46 h after the initial accident significantly the models in this paper show a reduction from 84 to 19 in the volume of oil trapped on the coast if dispersants are applied with the latter 19 being potentially kept at bay using booms and mechanical removal techniques based on these results we suggest the early use of dispersants booms and mechanical removal procedures to prevent the spreading of oil spilt in the broad area of larnaca bay

use of piezocone to predict maximum stiffness of venetian soils a comprehensive geotechnical in situ and laboratory investigation into the soils forming the upper quaternary basin of the venetian lagoon has been carried out in addition to standard tests measurements of shear wave velocity were performed using crosshole seismic piezocone bender element system and resonant column tests despite the incompatible strain levels of the seismic and piezocone tests it is shown that piezocone tip resistance and excess pore pressure can be used for a preliminary estimate of the small strain shear modulus gmax for the venetian soils foreword flooding of the well known historic city of venice due to high tides is increasing in frequency as a consequence of both the natural and anthropic subsidence in the venice area and the eustatic sea level rise to prevent this construction of a mobile gate system located at the three lagoon inlets was pro posed at the end of the 1980s for the design of the gate foundations geotechnical inves tigations were carried out at the inlets and particularly in a limited area at the malamocco inlet herein called the ma lamocco test site mts several types of in situ tests in cluding crosshole tests cht and seismic piezocone tests scpt were performed on contiguous verticals ministero dei lavori pubblici 1994 the geotechnical laboratory inves tigation also included bender element bet and resonant col umn tests rct on high quality undisturbed samples obtained using a large diameter 220 mm sampler field and laboratory test results are considered here with the aim of relating g

the role of heating winds and topography on sea level changes in the north atlantic seasonal and interannual to decadal variations of large scale altimetric sea surface height ssh owing to surface heating and wind forcing in the presence of topography are investigated using simplified models the dominant forcing mechanisms are time scale dependent on the seasonal time scale locally forced thermosteric height explains most of the ssh variance north of 18 n first mode linear long baroclinic rossby waves forced by changes in the winds and eastern boundary conditions explain most of the variance between 10 n and 15 n and are also important east of greenland on interannual to decadal time scales local thermosteric height remains important at several locations in the middle and high latitudes a topographic sverdrup response explains interannual to decadal ssh between 53 n and 63 n east of greenland farther south the linear rossby wave model explains ssh variations on interannual to decadal time scales between 30 n and 50 n from mid basin to the eastern boundary propagation of the eastern boundary condition into the interior dominates the interannual to decadal ssh signals south of 30 n the effect from nao related heat flux on ssh is small but forcing the topographic sverdrup models with nao regressed winds gives slightly better agreement with the observed ssh in the subpolar gyre on interannual to decadal time scales than using the full winds

influence of topography on the large scale ocean circulation abstract the influence of the bottom topography on the large scale ocean circulation is discussed and illustrated with a simple model based on the ideal fluid thermocline equations the requirement that fluid remains in linear vorticity balance while conserving its density leads to a coupled problem but one that can be reduced to a single characteristic equation under an assumption of uniform potential vorticity on density surfaces the characteristics are intermediate between the f h contours found in a homogeneous ocean and the f contours found in an ocean with a motionless abyss the extent to which topography influences the circulation in upper layers is quantified and is shown to depend on both the strength of the bottom currents and on the vertical profile of stratification in a realistic limit in which the abyssal waters are sluggish and weakly stratified the circulation in surface layers is relatively indifferent to the topography beneath the direction in which a current deflects around a top

integrated data analysis for mineral exploration a case study of clustering satellite imagery airborne gamma ray and regional geochemical data suites abstractpartitioning cluster algorithms have proven to be powerful tools for data driven integration of large geoscientific databases we used fuzzy gustafson kessel cluster analysis to integrate landsat imagery airborne radiometric and regional geochemical data to aid in the interpretation of a multimethod database the survey area extends over 3700 km2 and is located in the northern cape province south africa we carefully selected five variables for cluster analysis to avoid the clustering results being dominated by spatially high correlated data sets that were present in our database unlike other more popular cluster algorithms such as k means or fuzzy c means the gustafson kessel algorithm requires no preclustering data processing such as scaling or adjustment of histographic data distributions the outcome of cluster analysis was a classified map that delineates prominent near to surface structures to add value to the classified map we compared the detected structures to mapped geology an

a preliminary sinkhole raveling chart abstract sinkholes are a major geohazard in karst areas where soluble carbonate bedrock exists downward seepage resulting from the groundwater recharge continuously erode cover soils into cavities within the underlying bedrock resulting in raveling of cover soils identifying these raveled soils or zones is critial in preventing and mitigating the sinkhole collapse in this study a proof of concept was performed to demonstrate the concept of a sinkhole raveling chart that can quantify the severity levels of raveling the raveling chart is constructed based on cone penetration test cpt data collected through multiple sinkhole active sites in central florida a preliminary analysis e g data preparation grouping and zoning was carried out to construct the prototype sinkhole raveling chart this prototype raveling chart as a function of tip resistance qc and sleeve friction fs could delineate not only the raveled and non raveled zones but also the areas that correspond to different levels of raveling severity