identification et distribution des grandes masses d eau dans les mers du labrador et d irminger the main deep water masses present at the time of the css hudson cruises in labrador and irminger seas in june 1990 and october november 1991 have been identified using characteristic temperatures t and salinities s the purpose of this study was to establish the transfer functions between micropaleontological assemblages of top sediments and thermohaline characteristics of water masses the water mass at the top of the labrador sea labrador sea water lsw is formed after intense movements of winter convection in the first 900 m depth of the water column below that depth the lsw parameters reach a double minimum s 34 80 and t 2 9 c only the sediments located on the continental slopes of greenland and labrador between depths of 500 and 1500 m are in contact with the lsw below the lsw the superior fraction of the north east atlantic deep water neadw1 is characterized by a temperature maximum 3 3 c and as such is distinguishable from the inferior fraction neadw2 the latter is ch

seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic blooms this annual population overturning is marked by a 0 7 increase in d 18 o in both species the shell flux of n pachyderma peaks during the spring bloom and in late summer when stratification is close to its minimum and maximum respectively both export periods contribute about equally and account for 95 of the total annual flux shell fluxes of t quinqueloba show only a single broad pulse in summer thus following the seasonal stratification cycle the d 18 oo fn pachyderma reflects temperatures just below the base of the seasonal sml without offset from isotopic equilibrium the d 18 op attern oft quinqueloba shows a nearly identical amplitude and correlates highly with the d 18 oo fn pachyderma therefore t quinqueloba also reflects temperature near the base of the sml but with a positive offset from isotopic equilibrium these offsets contrast with observations elsewhere and suggest a variable offset from equilibrium calcification for both species in the irminger sea the species consistently show a contrast in their flux timings their flux weighted dd 18 o will thus dominantly be determined by seasonal temperature differences at the base of the sml rather than by differences in their depth habitat consequently their sedimentary dd 18 o may be used to infer the seasonal contrast in temperature at the base of the sml citation jonkers l g j a brummer f j c peeters h m van aken and m f de jong 2010 seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic paleoceanography 25 pa2204 doi 10 1029 2009pa001849

ice sheet sources of sea level rise and freshwater discharge during the last deglaciation we review and synthesize the geologic record that constrains the sources of sea level rise and freshwater discharge to the global oceans associated with retreat of ice sheets during the last deglaciation the last glacial maximum 26 19 ka was terminated by a rapid 5 10 m sea level rise at 19 0 19 5 ka sourced largely from northern hemisphere ice sheet retreat in response to high northern latitude insolation forcing sea level rise of 8 20 m from 19 to 14 5 ka can be attributed to continued retreat of the laurentide and eurasian ice sheets with an additional freshwater forcing of uncertain amount delivered by heinrich event 1 the source of the abrupt acceleration in sea level rise at 14 6 ka meltwater pulse 1a 14 15 m includes contributions of 6 5 10 m from northern hemisphere ice sheets of which 2 7 m represents an excess contribution above that derived from ongoing ice sheet retreat widespread retreat of antarctic ice sheets began at 14 0 15 0 ka which together with geophysical modeling of far field sea level records suggests an antarctic contribution to this meltwater pulse as well the cause of the subsequent younger dryas cold event can be attributed to eastward freshwater runoff from the lake agassiz basin to the st lawrence estuary that agrees with existing lake agassiz outlet radiocarbon dates much of the early holocene sea level rise can be explained by laurentide and scandinavian ice sheet retreat with collapse of laurentide ice over hudson bay and drainage of lake agassiz basin runoff at 8 4 8 2 ka to the labrador sea causing the 8 2 ka event

following the last neanderthals mammal tracks in late pleistocene coastal dunes of gibraltar s iberian peninsula abstract the aeolian pleistocene deposits recorded in the rock of gibraltar s iberian peninsula present a significant sedimentary thickness that fills the wide sea caves and covers its steep slopes in catalan bay these deposits register the development of cliff foot and rampant dunes that form a 35 sand ramp 1 km long and up to 300 m in height formed by moderately to well sorted sands slightly carbonated and weakly cemented this morphosedimentary evidence is associated with mis 5 2 sea level fluctuations its internal structure shows lamination sets of 2 3 m in thickness and planar and trough cross bedding in these beds five morphotypes of mammalian footprints have been recognized in vertical cross sections and convex hyporeliefs most of them present a moderate degree of conservation due to the poor cementation of the sands these icnites are related to the activity of terrestrial mammals possibly belonging to homininae proboscidea artiodactila and carnivora the affinity between the footprints and their tracemakers has been established in the basis of their physical parameters the shape of the footprints their comparison with similar footprints and the correlation with the fossil fauna of vertebrates described for the late pleistocene in gibraltar these findings represent the first palaeoichnological record in the aeolian sediments of gibraltar and indirectly corroborate the occupation of the coastal dune landscape by several terrestrial mammals during the late pleistocene in addition they help reconstructing the animal behaviour and interaction with the extensive dune systems that developed at the foot of the rock slopes the age of the tracks has been established within the mis 2 during the probable middle upper palaeolithic transition in the climate refuge of gibraltar

on the use of combined geophysical methods to assess water content and water conductivity of near surface formations abstract we propose to deepen the interpretation of combined geophysical methods georadar seismic and electric to assess physical properties characterizing the near surface porous formations especially the influence of water velocity analysis of multioffset georadar data are used together with seismic methods to estimate lateral and vertical ground water fluctuations this enables us to identify transitions from non saturated to fully saturated porous layers with certainty furthermore the accurate knowledge of seismic velocities helps to estimate the porosity of the ground water formations finally we show how the radar technique may be useful in solving the problem of trade off between bulk resistivity which is deduced from electrical measurements and that of water ionic conductivity and water content these theoretical considerations are illustrated using various measurements conducted at the same test site our interpretation is compared with a few laboratory measurements on water and soil samples this study displays the impact of combined geophysical approaches for providing models of water and ionic transfers down to a depth of several metres

flash flood sediments and ichnofacies of the late pleistocene homeb silts kuiseb river namibia abstract the homeb silt formation consists of eroded remnants of fine grained alluvium that were deposited within the kuiseb river valley in southern namibia during the late pleistocene in holocene times the river deeply incised its valley fill leaving steep walled castles of relict alluvium the homeb silts this study is based on the 25 m thick type exposure of homeb silts at homeb and describes flash flood sediments that were colonised by successive generations of opportunistic arthropods the stacked flood units each comprise a massive tabular siltstone bed overlain by a narrower interval of rapidly alternating sandstone and siltstone with claystone veneers these flood units are interpreted as having accumulated under semi arid climatic conditions by episodic back flooding of the kuiseb river into embayments and tributary mouths soon after deposition as the floodwaters subsided the sediment was colonised by burrowing sediment ingesting organisms mostly arthropods that produced a taenidium ichnofacies after the floodwaters had drained the exposed sediment was colonised by grasses and burrowed by terrestrial arthropods probably ants and termites resulting in an overprint of termitichnus ichnofacies with associated pelletal chambers thirteen horizons of rhizocretions and root tubules occur toward the top of the succession and indicate a gradual reduction in the frequency of flooding these immature calcic palaeosols suggest that the climate in the central namib desert 20 000 years ago was semi arid being wetter and more seasonal than the hyperarid conditions that prevail today

tracks and trackways of myotragus balearicus bate artiodactyla caprinae in pleistocene aeolianites from mallorca balearic islands western mediterranean tracks and trackways of the ruminant goat myotragus balearicus bate 1909 are abundant in the late pleistocene aeolianites of the south coast of mallorca spain the carbonate aeolianites form impressive dunes and related sand ramps that were initiated as echo dunes in front of a 20 40 m high paleocliff of miocene reefal limestone where the dunes built up to the cliff top they covered it as an aeolian ramp the dunes and sand ramps were active during the dry summer months but were passive during the wet winter period the small goat like animals were abundant on the island and for unknown reasons crossed the aeolian accumulations in large numbers this study deals with the tracks formed in the dune deposits all preserved trackways indicate impression into moist sand special features of the tracks include the structure produced by the withdrawal of the foot here called the axis and a disturbance zone of plastic deformation around this on dune crests the disturbance zone surrounds the axis more or less symmetrically however in addition a pressure pad of dislocated slightly rotated sediment bound by curved microfaults is commonly produced posterior to the axis by propulsive pressure of the foot on steep stoss and lee slopes the pressure pad becomes oriented in a down slope position as a result of gravitational slip of the walking animal combination of disturbance of the sediment in this way by manus followed by overprinting of similar disturbance by pes produces highly complicated track structure this structure may be characteristic of artiodactylous mammals in soft sand particularly aeolian deposits the structure is designated as bifidipes aeolis isp nov

evidence from the northeastern atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation a first study from the subtropical western atlantic using 231pa 230th ratios as a kinematic proxy for deep water circulation provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation moc over the last deglaciation however these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary 231pa 230th ratio in terms of circulation vigor can be biased by variations in particle flux and composition we have measured 231pa 230th in a core from the iberian margin in the northeastern atlantic basin and have compared these new results to the data from the western atlantic basin we find that the reduction in the circulation during h1 and yd and the subsequent increases first recognized in the sediment deposited on bermuda rise are also evident in the eastern basin in a totally different sedimentary regime confirming that sedimentary 231pa 230th ratios record basin wide changes in deep water circulation however some differences between the eastern and western records are also recognized providing preliminary evidence to differentiate between renewal rates in the two north atlantic basins and between shallower and deeper overturning our results suggest the possible existence of two sources of glacial north atlantic intermediate deep water gnaiw one in the south labrador sea and another west of rockall plateau both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the laurentide and the fennoscandian ice sheets during the deglaciation these results indicate that additional information on the geometry and strength of the ventilation of the deep atlantic can be obtained by contrasting the evolution of sediment 231pa 230th in different sections of the atlantic ocean

electrical resistivity tomography of vadose water movement cross borehole electrical resistivity tomography ert was used to image the resistivity distribution before and during two infiltration experiments in both cases water was introduced into the vadose zone and the change in resistivity associated with the plume of wetted soil was imaged as a function of time the primary purpose of this work was to study the capabilities and limitations of ert to image underground structure and ground water movement in the vadose zone a secondary goal was to learn specifics of unsaturated flow in a complex geologic setting tomographs of electrical resistivity taken before infiltration image coarser well drained soils sands and gravels as more resistive zones whereas finer grained soils silts and clays which hold more water by capillarity are imaged as more conductive images of changes in resistivity during infiltration show growth of the water infiltration plume with time that is consistent with known geology in the ert images we see the effects of capillary barriers and infer differences between capillary driven flow through fine sediments and gravity driven flow through very permeable sediments images are consistent with numerical flow simulations using hydrological parameter values consistent with soil types inferred from well logs ert can be a useful tool to monitor movement of circuitous moisture fronts in a heterogeneous field setting that would go undetected by borehole measurements

modelling of the groundwater flow and of tracer movement in the porous and fissured media chalk aquifer northern part of paris basin france a groundwater flow model has been developed in order to study the chalk aquifer of paris basin based on most of the geological and hydrological available data the numerical processes are intended to modelling the groundwater flow in the senonian late cretaceous formations and to visualize the tracer movement in groundwater resources in the experimental site of lasalle beauvais northern part paris basin both objectives were achieved as follows i the comprehension of the spatial distribution of the hydraulic conductivity in the chalk aquifer taking into account the characteristics of the hydrogeological system and ii the use of the analytical solution for describing one dimensional to two dimensional solute transport in a unidirectional steady state flow tracer with scale dependent dispersion advection and diffusion mechanisms are taken into account comparison between the breakthrough curves of the analytical and the numerical solutions provided an excellent agreement for various ranges of scale related transport parameters of interest the developed power series solution facilitates fast prediction of the breakthrough curves at each observation point thus the derived new solutions are widely applicable and are very useful for the validation of numerical transport the numerical approach is carried out by mt3dms a modular 3 d multi species transport model for simulation of advection dispersion and chemical reactions of contaminants in groundwater systems and based on total variation diminishing method using the ultimate algorithm the estimation of the infected surface could constitute an approach in water management and allows to prevent the risks of pollution and to manage the groundwater resource from a durable development perspective copyright 2015 john wiley sons ltd

nature of surface electrical conductivity in natural sands sandstones and clays the electrical conductivity of rocks results from conduction through the bulk solution occupying the pores and from surface conduction occurring at the fluid grain interface the nature of the surface electrical conductivity of shaly and clean sands and sandstones is examined surface conduction is characterized by the specific surface conductance which is the sum of three contributions i conduction within the electrical diffuse layer which makes a negligible contribution to the total specific surface conductance ii conduction in the stern layer which is shown to vary significantly with the salinity of the pore fluid at low salinities 10 6 to 10 3 mol 1 1 but becomes independent of salinity at higher salinities iii a mechanism operating directly on the mineral surface independent of salinity and perhaps associated with proton transfer at salinities higher than 10 3 mol 1 1 and at 25 c the specific surface conductance of quartz and clays is equal to 8 9 10 9 s and 2 5 10 9 s respectively equations describing the influence of surface conductivity and microstructure upon the macroscopic electrical conductivity of sands sandstones and shales are also developed

timing of meltwater pulse 1a and climate responses to meltwater injections the temporal relationship between meltwater pulse 1a mwp 1a and the climate history of the last deglaciation remains a subject of debate by combining the greenland ice core project d18o ice core record on the new greenland ice core chronology 2005 timescale with the u th dated barbados coral record we conclusively derive that mwp 1a did not coincide with the sharp bolling warming but instead with the abrupt cooling of the older dryas to evaluate whether there is a relationship between meltwater injections north atlantic deep water nadw formation and climate change we present a high resolution record of nadw flow intensity from eirik drift through the last deglaciation it indicates only a relatively minor 200 year weakening of nadw flow coincident with mwp 1a our compilation of records also indicates that during heinrich event 1 and the younger dryas there were no discernible sea level rises and yet these periods were characterized by intense nadw slowdowns shutdowns clearly deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead our results emphasize that the location of meltwater pulses may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

dinosaur tectonics a structural analysis of theropod undertracks with a reconstruction of theropod walking dynamics abstract a dinosaur trackway in the middle jurassic eolian entrada sandstone of southern utah u s a exposes three undertracks that we have modeled as isolated tectonic regimes showing the development of fold thrust ramp systems induced by the dinosaur s feet the faulted and folded sequence is comparable to crustal scale tectonics associated with plate tectonics and foreland fold thrust belts a structural analysis of the dinosaur tracks shows the timing and direction of the forces exercised on the substrate by the animal s foot during the stride based on the structural analysis we establish a scenario for foot movements and weight distribution in the feet during the end of the weight bearing phase of the stride the weight of the animal was transferred to the front of the digits creating a rotated disk below the foot that was bounded by an extensional fault at the front and a thrust ramp toward the back as the body accelerated the foot was forced backward the rotated disk was forced backward al

characterization of mixing and dilution in heterogeneous aquifers by means of local temporal moments breakthrough curves of a conservative tracer in a heterogeneous two dimensional aquifer are analyzed by means of their temporal moments the average velocity and the longitudinal macrodispersion coefficient of the equivalent one dimensional aquifer obtained through cross sectional averaging of concentration can be defined from the first and second central moments of a breakthrough curve integrated over the outflow boundary of the domain on the basis of an integrated breakthrough curve one cannot distinguish between actual solute dilution which involves concentration reduction and variability of arrival times among parts of the plume at different cross sectional positions analyzing the temporal moments of breakthrough curves at a point within the domain gives additional information about the dilution of the tracer from these local first and second central moments an apparent seepage velocity a and an apparent dispersivity of mixing a can be derived for short travel distances a equals the local scale longitudinal dispersivity it increases with the travel distance but much more slowly than the macrodispersivity at the large distance limit a may eventually reach the level of macrodispersivity lenses of high conductivity where groundwater flow converges are identified as regions of preferential enhanced mixing the spatial distribution of these regions causes a high degree of variability of a within a domain indicating a high degree of uncertainty in the quantification of dilution at early stages in an accompanying paper cirpka and kitanidis this issue the results of conservative tracer transport are utilized for the study of mixing controlled reactive transport

nutrient conditions in the subpolar north atlantic during the last glacial period reconstructed from foraminifera bound nitrogen isotopes 1 surface nitrate concentration is a potentially useful diagnostic in reconstructing the past circulation of high latitude north atlantic waters moreover nutrient consumption in the north atlantic surface impacts the atmospheric concentration of carbon dioxide to reconstruct nutrient conditions in the subpolar north atlantic region during the last ice age a record of foraminifera bound 15n was measured in neogloboquadrina pachyderma sin from core v28 73 south of iceland 57 2 n 20 9 w foraminifera bound 15n is up to 2 lower during the last ice age than during the holocene suggesting as much as 25 less complete nitrate consumption during the former this is consistent with stronger light limitation associated with a deeper summer surface mixed layer perhaps related to the formation of glacial north atlantic intermediate water previously suggested to have occurred near the core site however three single point maxima in 15n in the glacial section and the sharp deglacial 15n rise coincide with heinrich event layers this suggests that increased water column stratification during heinrich events presumably due to surface freshening reduced the nutrient supply from below and led to nearly complete nitrate consumption in the summertime mixed layer the heinrich layers in v28 73 are not accompanied by 18o minima in either n pachyderma sin or globigerinoides bulloides which we tentatively attribute to extreme mixed layer shoaling the reconstructed subpolar north atlantic upper water column changes both glacial interglacial and millennial are inverse to those inferred for the antarctic

using dc resistivity method to characterize the geometry and the salinity of the plioquaternary consolidated coastal aquifer of the mamora plain morocco the direct current resistivity method was applied to the consolidated coastal plioquaternary aquifer of mamora plain located on the atlantic coast of morocco the aim is to determine the depth of the base of the saturated zone in the aquifer and to help in imaging lateral and vertical distribution of groundwater salinity the geoelectric survey showed four geoelectric formations with the following electrical resistivities from top to bottom 20 80 200 2000 200 300 and 5 70 ohm m the latter designates the basement of the aquifer constituted of marls and sandy marls the mean resistivity of 250 ohm m designates the aquifer formation it decreases to less than 25 of its initial values for the soundings near the shore reflecting the oceanic impact on the aquifer formation resistivity the contour map shows that the basement of the saturated zone in the aquifer is deeper in the northwest near the sebou river estuary with values up to 70 m below sea level this results in a larger thickness of the saturated zone of the aquifer leading to a consequent hydraulic potential on the other hand it has been deduced that the extent of marine intrusion inside the continent can be governed by human activities natural properties and substratum geometry of the aquifer as well as by ecological factors an optimal network of electrical soundings has been proposed for the monitoring of saltwater intrusion

ichnology and depositional environment of the middle devonian valentia island tetrapod trackways south west ireland abstract nine tetrapod trackways are described from the middle devonian continental valentia slate formation on the north eastern coast of valentia island in county kerry ireland the trackways occur at three sites dohilla coosadillisk and culoo head the latter two being recorded for the first time morphological and taphonomic analyses of the trackways suggest they were made by populations of similar tetrapods but of varying size body length 0 5 to 1 m width 0 15 to 0 30 m that moved in some cases by terrestrial locomotion and in others possibly by a slow paddling gait while the substrate was submerged by very shallow floodwater sedimentological facies analysis of the trackway bearing sequences has been carried out for the first time and shows that the preserved trackways are associated with the late stages of 1 a principal river channel margin coosadillisk 2 a minor floodplain drainage channel culoo head and 3 a sand rich crevasse splay medial alluvial ridge environment dohilla the valentia island tetrapods inhabited marginal environments of proximal river channels 170 km northwards into the continent from postulated shallow marine habitats as they evolved this capability over a potential 4 5 million year period during the middle devonian

direct dating of the oxygen isotope record of the last deglaciation by 14c accelerator mass spectrometry major trends of quaternary global climate are reflected in the continental ice volume changes which have been reconstructed by oxygen isotope analysis1 2 18o records from deep sea sediments show that the net glacial build up occurs relatively slowly3 but that the end of an ice age occurs quickly in less than 10 000 yr implying a nonlinear response4 5 to simple milankovitch theory6 the latter observation suggests that the cause of the most recent deglaciation was the maximum in summer calorific radiation at the upper latitudes of the northern hemisphere centred around 11 000 yr ago a view supported by early studies7 later work has produced conflicting dates the main source of confusion being problems with obtaining accurate and reliable dates here by using accelerator mass spectrometry we have measured 14c for various species of foraminifera to produce a reliable timescale for the oxygen isotope record our results show that at the end of the last ice age continental ice sheets began to melt more than 4 000 yr before the northern hemisphere maximum of summer calorific radiation

discussion defining the morphological quality of fossil footprints problems and principles of preservation in tetrapod ichnology with examples from the palaeozoic to the present by lorenzo marchetti et al

non tetrapod trace fossils from the middle devonian tetrapod tracksite at zachelmie quarry holy cross mountains poland abstract the middle devonian eifelian dolomites exposed in the zachelmie quarry holy cross mountains southern poland contain the earliest fossil record of tetrapods low diversity but unique assemblages of trace fossils characterize the track bearing interval within the lower complex of the wojciechowice formation the reconstructed environment of the trace fossil rich beds includes ephemeral lakes and or shallow water lagoons separated from an open marine area by sparsely vegetated islands and spits the most abundant non tetrapod trace fossils from these beds are large horizontal to vertical burrows and dish circular to oval shaped shallow depressions the burrows are abundant on the upper surfaces of thick dolomicritic beds especially in some palaeosol levels but they are also associated with tetrapod trackways large semi aquatic or terrestrial animals e g arthropods or vertebrates most likely produced these burrows the circular to oval shaped depressions observed on a large surface and other smaller isolated blocks from the same stratigraphical level are interpreted as fish feeding nesting resting traces piscichnus sanctacrucensis isp nov is proposed as a new ichnospecies of the oval shaped fish trace fossil from the middle devonian of poland a single medium sized undichnia specimen a fish swimming trace is associated with the piscichnus traces the described trace fossils provide new insight into the palaeoecology and taphonomy of the middle devonian tetrapod tracksite from poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the zachelmie quarry

electrical resistance tomography electrical resistance tomography ert is a method that calculates the subsurface distribution of electrical resistivity from a large number of resistance measurements made from electrodes for in situ applications ert uses electrodes on the ground surface or in boreholes it is a relatively new imaging tool in geophysics the basic concept was first described by lytle and dines as a marriage of traditional electrical probing introduced by the schlumberger brothers and the new data inversion methods of tomography development of both the theory and practice of ert was confined mostly to the late 1980s and the 1990s tomographic inversion added important new capabilities as it was more general accurate and rigorous at spatial imaging of geophysical electrical resistance data than earlier pseudosection or curve fitting methods

neogene avian and mammalian tracks from death valley national monument california their context classification and preservation abstract the copper canyon formation consists of over 3000 m of basalt and alluvial fan and lacustrine strata deposited in a small neogene basin lacustrine strata are of two typs fine grained dolomitic carbonates deposited in a playa lake environment and calcitic bioclastic carbonates deposited in a freshwater lake environment bedding surfaces of the playa lake carbonates deposited in shoreline environments commonly contain avian and mammalian footprints tracks of artiodactyls are most abundant those of birds horses carnivores and proboscideans are less common using the binomial avian and mammalian footprint classification scheme of vialov 1966 four different mammalian ichnogenera containing thirteeen ichnospecies as well as six ichnospecies of avian tracks are recognized environmental factors of the ancient copper canyon playa lake which contributed to good footprint preservation included 1 periods of flooding and intense evaporation which resulted in receding shorelines that presented wet fine grained sediment surfaces for impression and subsequent subaerial exposure and 2 periodically high sedimentation rates which insured quick burial of the tracks while vertebrate footprints also occur in sandstones and conglomerates deposited in alluvial fan environments the morphological distinctness of tracks is best preserved in fine grained dolomitic carbonate and siltstone strata deposited in the playa lake environment distinctness of preserved tracks also increases with apparent decrease within a certain range of sediment water content at the time of impression an examination of preserved morphologies has allowed several sediment water content states important to footprint preservation to be deduced changes in sediment water content at the time of impression acted to produce a wide range of track morphologies for each individual trackmaker an examination of track abundance and occurrence within the formation suggests increasing visitation by larger vertebrates to the playa lake as lake water freshened the rare ocurrence of tracks of small mammals and low amount of vertebrate bioturbation within the playa deposits also suggests that the ancient copper canyon playa lake lacked a resident vertebrate population of its own probably receiving only migrating visitors seeking food and water the footprints in the copper canyon formation reflect part of the wide diversity of vertebrates present in southern california during the hemphillian

a comparison of peak and plate electrodes in electrical resistivity tomography application to the chalky groundwater of the beauvais aquifer northern part of the paris basin france electrical resistivity tomography was used in order to explore an experimental site of the lasalle beauvais polytechnic institute france the test was conducted along a profile line of 315 m length using 64 electrodes deployed at an inter electrode spacing of 5 m and the data were recorded using gradient wenner and pole dipole arrays the performance of plate electrodes non conventional flat based is compared with the performance of peak electrodes conventional spike the hydrogeophysical investigation of the chalk aquifer system of beauvais shows that the performance of plate electrodes is satisfactory leading to inversions of small root mean square errors peak and the plate electrodes were tested before and after injection of a salt tracer in the piezometer of the experimental site the study demonstrates the usefulness of plate electrodes efficient less time consuming and the possibility of aquifer characterization by a salt tracer copyright 2010 john wiley sons ltd

reinterpretation of palmate and semi palmate webbed fossil tracks insights from finite element modelling abstract a track from the late cretaceous previously described as being generated by a semi palmate bird was studied with the aid of high resolution laser scanning substrate conditions at the time of track formation were diagnosed fine grained soft waterlogged sediment and used to constrain a finite element track simulator the indentation of a non webbed virtual tridactyl foot in such conditions created a resultant track with features analogous to webbing between digits this webbing was a function of sediment deformation and subsequent failure in 3d specific to rheology variation of substrate conditions and interdigital angle was incrementally stepped apparent webbing impressions were clearly developed only within a limited range of sediment conditions and pedal geometry the implications of this work are that descriptions of webbed tracks should account for the possibility that webbing was indirectly formed through sediment failure and not necessarily the direct impression of a webbed foot additionally dating the earliest occurrence of webbed feet in the fossil record and potentially extending phylogenetic ranges should be treated with caution when based upon evidence from tracks

monitoring an underground steam injection process using electrical resistance tomography we used electrical resistance tomography ert to map the subsurface distribution of a steam flood as a function of time as part of a prototype environmental restoration process performed by the dynamic underground stripping project we evaluated the capability of ert to monitor changes in the soil resistivity during the steam injection process using a dipole dipole measurement technique to measure the bulk electrical resistivity distribution in the soil mass the injected steam caused changes in the soil s resistivity because the steam displaced some of the native pore water increased the pore water and soil temperatures and changed the ionic content of the pore water we could detect the effects of steam invasion by mapping changes in the soil resistivity as a function of space and time the ert tomographs are compared with induction well logs formation temperature logs and lithologic logs these comparisons suggest that the ert tomographs mapped the formation regions invaded by the steam flood the data also suggest that steam invasion was limited in vertical extent to a gravel horizon at depth of approximately 43 m the tomographs show that with time the steam invasion zone extended laterally to all areas monitored by the ert technique

preservation and erosion of theropod tracks in eolian deposits examples from the middle jurassic entrada sandstone utah u s a abstract the middle jurassic entrada sandstone exposed near the town of escalante southern utah consists of large scale cross bedded eolian deposits that are interbedded with horizontally laminated sand sheets and thin sets of eolian cross strata representing periods with a moister climate the flat bedded units contain numerous tracks and trackways from small to large sized theropod dinosaurs these tracks are today exposed in several distinct erosional states allowing detailed studies of track and undertrack formation in eolian deposits tracks that originally were emplaced on sloping surfaces show in their present day erosional state a morphology distinct from those originally emplaced on horizontal surfaces further the range of eroded track morphologies can help identify badly eroded tracks from nonbiogenic structures in similar deposits

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

joint interpretation of hydrological and geophysical data electrical resistivity tomography results from a process hydrological research site in the black forest mountains germany the use of electrical resistivity tomography ert non intrusive geophysical technique was assessed to identify the hydrogeological conditions at a surface water groundwater test site in the southern black forest germany a total of 111 ert transects were measured which adopted electrode spacings from 0 5 to 5 m as well as using either wenner or dipole dipole electrode arrays the resulting two dimensional 2d electrical resistivity distributions are related to the structure and water content of the subsurface the images were interpreted with respect to previous classical hillslope hydrological investigations within the same research basin using both tracer methods and groundwater level observations a raster grid survey provided a quasi 3d resistivity pattern of the floodplain strong structural heterogeneity of the subsurface could be demonstrated and non connectivities between surface and subsurface bodies were mapped through the spatial identification of likely flow pathways and source areas of runoff the deep groundwater within the steeper valley slope seems to be much more connected to runoff generation processes within the valley floodplain than commonly credited in such environmental circumstances further there appears to be no direct link between subsurface water bodies adjacent to the stream channel deep groundwater sources are also able to contribute towards streamflow from exfiltration at the edge of the floodplain as well as through the saturated areas overlying the floodplain itself such exfiltrated water then moves towards the stream as channelized surface flow these findings support previous tracer investigations which showed that groundwater largely dominates the storm hydrograph of the stream but the source areas of this component were unclear without geophysical measurements the work highlighted the importance of using information from previous complementary hydrochemical and hydrometric research campaigns to better interpret the ert measurements on the other hand the ert can provide a better spatial understanding of existing hydrochemical and hydrometric data copyright 2009 john wiley sons ltd

size dependent isotopic composition of planktic foraminifers from chukchi sea vs nw atlantic sediments implications for the holocene paleoceanography of the western arctic abstract in arctic and sub arctic seas shell growth and or secondary calcite overgrowth of neogloboquadrina pachyderma left coiled npl occur along the pycnocline and their 13c and 18o values are size and weight dependent however whereas the npl 18o data from the nw atlantic indicate near equilibrium conditions with ambient waters and a positive relationship between shell weight and 18o content assemblages from box cored sediments of the chukchi sea western arctic are depleted by 2 with respect to equilibrium values with modern conditions and depict a negative relationship between shell weight and its 18o value 0 15 0 03 g on vpdb scale a similar feature is also depicted by the dextral form of n pachyderma npd we associate the reverse shell size or weight vs 18o relationship to the reverse temperature gradient observed along the thermocline between the surface cold and dilute water layer and the underlying near 3 c warmer saline north atlantic water mass the analysis of two late to post glacial sedimentary sequences from the chukchi sea indicates that such a water mass stratification with a reverse thermocline persisted throughout the holocene thus reflecting an early onset of the modern like linkage between the arctic ocean and the north atlantic moreover lower 18o values in both npl and npd together with larger 18o gradients between the different shell sizes at ca 9 7 ka bp suggest 3 c higher temperatures in the upper north atlantic water mass in comparison with the present approximately 1 c at the study site thus likely a higher inflow rate of this water mass during the early holocene

a diverse pleistocene marsupial trackway assemblage from the victorian volcanic plains australia abstract a diverse assemblage of late pleistocene marsupial trackways on a lake bed in south western victoria provides the first information relating to the gaits and morphology of several megafaunal species and represents the most speciose and best preserved megafaunal footprint site in australia the 60 110 ka volcaniclastic lacustrine sedimentary rocks preserve trackways of the diprotodontid diprotodon optatum a macropodid probably protemnodon sp and a large vombatid perhaps ramsayia magna or phascolomys medius and possible prints of the marsupial lion thylacoleo carnifex the footprints were imprinted within a short time period demonstrating the association of the taxa present rather than the time averaged accumulations usually observed in skeletal fossil deposits individual manus and pes prints are distinguishable in some trackways and in many cases some digital pad morphology is also present several parameters traditionally used to differentiate ichnotaxa including trackway gauge and the degree of print in turning relative to the midline are shown to be subject to significant intraspecific variation in marsupials sexual dimorphism in the trackway proportions of diprotodon and its potential for occurrence in all large bodied quadrupedal marsupials is identified here for the first time

application of vertebrate trace fossils to palaeoenvironmental analysis abstract this is a review of the main uses of vertebrate trace fossils ichnofabrics and ichnofacies in the palaeoenvironmental analysis of sedimentary sequences the article accounts for the significant developments produced in the last three decades including the application of the ichnofacies concept to vertebrate trace fossils recognition of footprints in cross sectional view and their distinction from inorganic structures and burrow fills is first discussed the response of different substrates showing contrasting water content and imprinted by different animals or devices is compared in terms of the morphology of the resultant footprint trackways with sand crescents are typical of aeolian cross strata and are absent in associated flat lying to low angle deposits thick packages of highly bioturbated sandy dune and interdune sediments have been interpreted as reflecting periods of increased rainfall neoichnological observations in modern lake basins suggest that distinct zones can be recognized in the margins of fossil ponds and lakes including onshore shoreline and shallow subaqueous zones abundant flamingo like footprints and flamingo nest mounds are good indicators of alkaline and or saline lake waters hippopotamus trails are found closely associated with modern and fossil freshwater wetlands dinosaur and pterosaur swim traces from lacustrine and fluvial deposits can be used to estimate water depth turtle crocodile amphibian hippopotamus and fish swim traces allow one to infer a subaqueous substrate certain modern intertidal fish feeding traces are oriented with the predominant tidal current and can be used as palaeocurrent indicators the preferential orientation of tetrapod trackways in lacustrine and fluvial deposits is analyzed vertebrate trace fossils can help to infer discharge variability in fluvial channels the descriptions of vertebrate ichnofabrics are commonly limited to heavily bioturbated beds due to trampling by vertebrates and to a few examples of ichnofabrics with discrete trace fossils the nature and implications of the recognized vertebrate ichnofacies are still being debated and have a limited utility in palaeoenvironmental analysis the distinction of a potential vertebrate burrow ichnofacies in carbonate bearing palaeosols is proposed to represent well drained soils developed under arid or semiarid climate

imaging and characterisation of subsurface solute transport using electrical resistivity tomography ert and equivalent transport models abstract we assess the usefulness of electrical resistivity tomography ert in imaging and characterising subsurface solute transport in heterogeneous unconfined aquifers a field tracer experiment was conducted at the krauthausen test site germany the spatial and temporal evolution of the injected nabr solute plume was monitored in a 2d ert image plane located downstream of the injection well for 90 days since ert maps changes in bulk electrical conductivity the reconstructed images at selected time intervals are first converted to solute concentration maps by postulating a linear relation the concentration maps are then analysed using an equivalent convection dispersion model cdm which conceptualises the aquifer as a homogeneous medium with a uniform mean flow velocity as demonstrated by associated synthetic model studies ert resolution in terms of recovered equivalent dispersivities is limited due to spatial smoothing inherent to the imaging algorithm since for heterogeneous media local concentrations within the plume deviate from those predicted by the equivalent cdm we also interpret the ert derived pixel breakthrough curves in terms of an equivalent stream tube model stm the stm represents transport in the aquifer by a set of 1d convection dispersion processes allowing the degree of mixing and the heterogeneity of transport within the plume to be quantified we believe that the observed tracer plume is satisfactorily described by the equivalent cdm probably because the tracer plume was small relative to the heterogeneity scale of the aquifer even though application of the stm revealed some deviation from the ideal homogeneous case the equivalent dispersivity in the stm matches the longitudinal dispersivity of the cdm closely consistent with predominantly homogeneous mixing however the stm analysis illustrates how ert results can be used to quantify the variability of parameters relevant to flow and transport in heterogeneous aquifers

mosasaur tooth marks on the ammonite placenticeras from the upper cretaceous of alberta canada mosasaur tooth marks were found in the body chamber and phragmocone of the campanian ammonite placenticeras meeki boehm from the bearpaw formation of the st mary river area near lethbridge they i

characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding a groundwater recharge process of heterogeneous hard rock aquifer in the moole hole experimental watershed south india is being studied to understand the groundwater flow behaviour significant seasonal variations in groundwater level are observed in boreholes located at the outlet area indicating that the recharge process is probably taking place below intermittent streams in order to localize groundwater recharge zones and to optimize implementation of boreholes a geophysical survey was carried out during and after the 2004 monsoon across the outlet zone magnetic resonance soundings mrs have been performed to characterize the aquifer and measure groundwater level depletion the results of mrs are consistent with the observation in boreholes but it suffers from degraded lateral resolution a better resolution of the regolith bedrock interface is achieved using electrical resistivity tomography ert ert results are confirmed by resistivity logging in the boreholes ert surveys have been carried out twice before and during the monsoon across the stream area the major feature of recharge is revealed below the stream with a decrease by 80 of the calculated resistivity the time lapse ert also shows unexpected variations at a depth of 20 m below the slopes that could have been interpreted as a consequence of a deep seasonal water flow however in this area time lapse ert does not match with borehole data numerical modelling shows that in the presence of a shallow water infiltration an inversion artefact may take place thus limiting the reliability of time lapse ert a combination of ert with mrs provides valuable information on structure and aquifer properties respectively giving a clue for a conceptual model of the recharge process infiltration takes place in the conductive fractured fissured part of the bedrock underlying the stream and clayey material present on both sides slows down its lateral dissipation

holocene and eemian sea surface temperature trends as revealed by alkenone and mg ca paleothermometry in this study we review a global set of alkenone and foraminiferal mg ca derived sea surface temperatures sst records from the holocene and compare them with a suite of published eemian sst records based on the same approach for the holocene the alkenone sst records belong to the actualized ghost database kim j h schneider r r 2004 ghost global database for alkenone derived holocene sea surface temperature records available from http www pangaea de projects ghost while the mg ca derived sst database represents a new compilation the actualized ghost database not only confirms the sst changes previously described but also documents the holocene temperature evolution in new oceanic regions such as the northwestern atlantic the eastern equatorial pacific and the southern ocean a comparison of holocene sst records stemming front the two commonly applied paleothermometry methods reveals contrasting sometimes divergent sst evolution particularly at low latitudes where sst records are abundant enough to infer systematic discrepancies at a regional scale opposite sst trends at particular locations could be explained by out of phase trends in seasonal insolation during the holocene this hypothesis assumes that a strong contrast in the ecological responses of coccolithophores and planktonic foraminifera to winter and summer oceanographic conditions is the ultimate reason for seasonal differences in the origin of the temperature signal provided by these organisms as a simple test for this hypothesis eemian sst records are considered because the holocene and eemian time periods experienced comparable changes in orbital configurations but had a higher magnitude in insolation variance during the eemian for several regions sst changes during both interglacials were of a similar sign but with higher magnitudes during the eemian as compared to the holocene this observation suggests that the ecological mechanism shaping sst trends during the holocene was comparable during the penultimate interglacial period although this ecology hypothesis fails to explain all of the available results we argue that any other mechanism would fail to satisfactorily explain the observed sst discrepancies among proxies c 2010 elsevier ltd all rights reserved

large scale dispersion experiments in a sandy aquifer in denmark observed tracer movements and numerical analyses a large scale natural gradient dispersion experiment was carried out in a sandy aquifer in the western part of denmark using tritium and chloride as tracers for both plumes a marked spreading was observed in the longitudinal direction while the spreading in the transverse horizontal and transverse vertical directions was very small the horizontal transport parameters of the advection dispersion equation were investigated by applying an optimization model to observed breakthrough curves of tritium representing depth averaged concentrations no clear trend in dispersion parameters with travel distance for distances between 50 and 200 m could be found suggesting that the asymptotic stage was reached within a short distance from the point of injection a three dimensional numerical model for flow and transport was applied to the aquifer in order to quantify the dispersivity parameters more closely the following best fit dispersivity parameters were identified longitudinal horizontal 0 45 m transverse horizontal 0 001 m and transverse vertical 0 0005 m

estimates of specific yield with the geoelectric resistivity method in glacial aquifers abstract specific yield is the volume of water that drains from a saturated soil due to gravity relative to its total volume methods to determine this hydrogeologic parameter depend on well tests and well sample analyses low cost surface geoelectrical depth sounding after schlumberger is suggested as an alternative method to estimate specific yield this method is based on a determination of the layer resistivities for the saturated and unsaturated zone and on the water resistivity porosity and the degree of saturation are estimated from the electrical resistivity according to archie s law specific yields estimated with the suggested geophysical method agree with estimates after preuss and todd which are based on porosity and median grain size data uncertainties in the relationship between resistivities and porosity and saturation exist due to generalized assumptions on material constants in archie s law for the range of specific yield estimates between 18 and 36 the constants seem to be valid the method after preuss and todd requires a detailed evaluation of porosity and median grain size it produces best results for d 50 values that are larger than 0 3mm these values can vary considerably vertically as well as horizontally in the glacial aquifers derived mainly from fluvial outwash of the receding glaciers in southern new england

north america s largest dinosaur trackway site implications for morrison formation paleoecology little known exposures of the upper jurassic morrison formation from the purgatoire valley of southeastern colorado have yielded the world s largest continuously mapped assemblage of dinosaur trackways body fossils include plant invertebrate and vertebrate remains indicative of predominantly fresh water conditions the tracks occur in a lacustrine sequence characterized by 1 shallow water shales 2 micritic shoreface limestones with ooids intraclasts ripple marks mud cracks and 3 minor quartzose sandstone with salt crystal casts analysis of these sedimentary facies suggests that in southeastern colorado lakes were larger and longer lived than in other morrison paleoenvironments trackway orientations and footprint depth contours pinpoint the location of the paleoshoreline at successive levels in the section detailed mapping of 1 300 footprints in bed 2 has revealed more than 100 trackways which testify to the activity of both quadrupedal and bipedal dinosaurs the respective ratio based on trackway counts is 40 60 the quadrupedal tracks are attributed to sauropods and represent the first ever discovered in north america they also exhibit the first known manus claw impressions and are in need of formal description more than 90 of the bipedal tridactyl prints lack claw impressions and are tentatively therefore referred to the ornithopoda cf gypsichnites possibly a camptosaurus the small proportion with distinct claw impressions may represent allosaurus resulting estimates of species diversity 5 and predator prey ratio 1 30 are in general agreement with the estimates of other authors based on skeletal remains and they suggest that the purgatoire river tracks may accurately reflect the composition of the dinosaur fauna distinctive groupings of parallel non overlapping trackways suggest gregarious behavior among sauropods and tridactylous forms

cross hole resistivity tomography using different electrode configurations this paper investigates the relative merits and effectiveness of cross hole resistivity tomography using different electrode configurations for four popular electrode arrays pole pole pole bipole bipole pole and bipole bipole by examination of two synthetic models a dipping conductive strip and a dislocated fault it is shown that besides the popular pole pole array some specified three and four electrode configurations such as pole bipole am n bipole pole am b and bipole bipole am bn with their multispacing cross hole profiling and scanning surveys are useful for cross hole resistivity tomography these configurations compared with the pole pole array may reduce or eliminate the effect of remote electrodes systematic error and yield satisfactory images with 20 noise contaminated data it is also shown that the configurations which have either both current electrodes or both potential electrodes in the same borehole i e pole bipole a mn bipole pole ab m and bipole bipole ab mn have a singularity problem in data acquisition namely low readings of the potential or potential difference in cross hole surveying so that the data are easily obscured by background noise and yield images inferior to those from other configurations

history and bibliography of the study of fossil vertebrate footprints in the british isles supplement 1973 1983 abstract this paper supplements the history and bibliography of british fossil vertebrate footprints published by sarjeant in 1974 it discusses additional published accounts of these trace fossils issued during the period prior to 1973 and provides a resume of new discoveries and descriptions made during the decade 1973 1983 important among the former are a record of a hitherto unnoticed scottish carboniferous find reports of footprints found by the rev w lister and h c beasley in the triassic rocks of statffordshire a possible record of dinosaur footprints from the lowest cretaceous of wiltshire a more definite instance from the lower cretaceous of surrey and a rather dubious one from ulster new discoveries include a first report of dinosaur footprints from buckinghamshire and accounts of major footprint finds in the triassic sediments of south wales the purbeck formation of dorset and the wealden beds of east sussex and the isle of wight also the first record of dinosaur footprints from the scottish jurassic new information concerning vertebrate footprints from the triassic of shropshire and new conclusions on the taxonomy of the triassic footprints from south wales are presented

short paper fossil vertebrate tracks and indenter mechanics a reconnaissance study is outlined showing how an improved understanding of the formation and character of fossil vertebrate tracks in soft sediments is provided by the application of the mechanical engineer s indenter theory supported by complementary scaled laboratory experiments only the footprint at the bottom of the shaft cut by the animal9s limbs in general offers the best preservation of the shape of the underside of the foot the character of the foot is less well preserved in the deformed bedding beneath the footprint and among laminae deposited in the shaft after the passage of the animal this understanding will help to reduce errors in the use of tracks in taxonomic biostratigraphic palaeoecological behavioural and environmental studies when a limbed vertebrate traverses yielding sediment the limbs deform the substrate into tracks which vary with the nature size and gait of the animal the forcefulness of its limb movements and the sediment properties most previous geological work on tracks and trackways has emphasized their taxonomic biostratigraphical palaeocological and behavioural significance lockley 1986 leonardi 1987 but without an adequate understanding of their environmental implications lockley 1986 and in particular their genesis and preservation as trace fossils the response of an elastic plastic material to an indenter or punch both in terms of theory calladine 1969 hill 1971 johnson et al 1982 and in the light of qualitative laboratory experiments provides a general mechanical model for track formation and a basis for the assessment of track preservation in sediments the indenter represents the animal9s

comment on mixed layer deepening during heinrich events a multi planktonic foraminiferal delta18o approach rashid and boyle reports 19 october 2007 p 439 analyzed oxygen isotopes in planktonic foraminera from marine sediments and concluded that heinrich events massive iceberg discharges into the north atlantic ocean caused upper water masses to deepen we question the robustness of this interpretation and argue that a strongly stratified mixed layer characterized by dense sea ice cover and production of oxygen 18 depleted brines likely prevailed during such events

mechanisms of water storage and flow in the unsaturated zone of the chalk aquifer abstract it is known that the volumes of water draining from some chalk catchments in recessions are significantly greater than can be explained by gravity drainage from fissure porosity the most likely source of this water is slow drainage from the matric porosity above the water table this paper suggests that the location of this storage is in the irregularities on the fissure surfaces studies of resin impregnated blocks of chalk failed to reveal the presence of hydrologically significant microfissures or macropores that could be the source of additional drainage ultrasonic measurements at varying values of effective stress show no indication of changes in the acoustic transmission properties that could be attributed to closure of microfissures drainage and mercury intrusion measurements indicate that there is significant storage on block surfaces the drainage measurements confirm that the storage is of the order of magnitude about 0 3 needed to explain the slow drainage this additional storage explains why the water table is slow to respond after recharge events and why the chalk is resilient to drought the presence of storage in the unsaturated zone implies that the position of the water table may not be an accurate indicator of groundwater resources the concept of filling and draining of irregularities on fissure surfaces also leads to a new model for the generation of fissure flow in the unsaturated zone of the chalk this suggests that fissure flow can be generated at any depth in the profile and in a sequence of uniform vertical permeability is likely to originate near the water table rather than high in the unsaturated zone

shallow karst exploration using mt vlf and dc resistivity methods1 a geophysical test was carried out over a well located and fairly embedded karstic conduit the mt vlf method was selected because of its high resolution and its ability to provide a resistivity parameter sensitive to water and clay this method was used together with dc resistivity methods which allow vertical adjustment of the vlf data and show consistency between the investigation and target depths after correcting the deformations due to the polarization of the primary field the mt vlf data show clearly in the central part of the site that the conduit does not coincide with an anomaly axis but coincides with the boundary between a conductive area and a resistive area 2d modelling confirms that direct detection of the conduit is not feasible and that the conduit is located close to a conductive zone corresponding to a completely clay filled fractured zone this situation was observed on the whole site and the conduit seemed systematically to thread its way between the conductive zones to join the outlet the distribution of the conductive fractured zones and the direction of the hydraulic gradient were two important elements in predicting the location of the conduits a 3d approach would increase the probability of finding the conduits in such a case

dinosaur tracks and possible lungfish aestivation burrows in a shallow coastal lake lowermost cretaceous bornholm denmark abstract the mesozoic succession of the island of bornholm in the baltic sea has hitherto yielded only very few remains after vertebrate life we describe a new find of a well exposed vertebrate trample ground and large densely spaced vertical to inclined burrows from shallow lake deposits belonging to the berriasian skyttegard member of the rabekke formation the succession is terrestrial but a coastal setting is indicated by the great abundance of pyrite concretions and framboidal pyrite organic geochemical and palynological data show that the lake was surrounded by a low diversity gymnospermous vegetation the trampling ground is exposed in a vertical section at the boundary between light grey structureless or trough cross bedded fluvial sand and dark brown organic rich lacustrine mud with densely spaced vertical rootlets wood fragments and large pyrite concretions the tracks are bowl shaped have an irregular flat or slightly conical base are on average 22 cm deep and on average 43 cm wide in the upper part and 23 cm in the lower part but some reach widths up to about 1 m and have a highly irregular shape the underlying sand in some cases shows a faint stratification that is bent downwards adjacent to the mud filled tracks which have near vertical and commonly overhanging margins the morphology of the bowl shaped depressions suggests that they were made by dinosaurs most likely sauropods they were clearly emplaced after deposition of the dark brown mud long vertical to inclined commonly slightly curved j shaped or spiraling cylindrical burrows with a diameter averaging 4 4 cm and lengths up to 45 cm occur densely spaced in the mud they are unbranched have no mud or lag linings the top of the burrows is indistinct or not preserved whereas the base is rounded concave up commonly with a slightly enlarged chamber the length is difficult to estimate precisely because of the missing top and because the burrows cross cut and go in and out of the plane of exposure the burrows have a passive infill of dark mud and at some levels of irregularly alternating laminae of white sand and mud the sand may be of aeolian origin or may represent distal crevasse splays or washovers from adjacent rivers or the nearby sea skeletal remains have not been found in or associated with the burrows which are similar to burrows referred to lungfish or crayfish and they are with hesitation interpreted as representing lungfish aestivation burrows based on the morphological characteristics this is only the second report of dinosaur tracks in denmark and the first in situ find where environmental conditions can be interpreted with some confidence possible lungfish burrows are here reported for the first time from the danish mesozoic the overall rarity of vertebrate remains in the mesozoic succession of bornholm may reflect that the area was a horst island or submerged shoal during much of the jurassic and cretaceous and may not always have had direct land connection with surrounding land areas of the baltic shield or mainland europe

simulated weathering of dinosaur tracks and the implications for their characterization digital models of the tracks of bipedal theropod and ornithopod dinosaurs and the quadrupedal tracks of a sauropod were computationally eroded to investigate the effects of erosion on the shapes sizes and diagnostic details of fossil tracks narrow and or angular details such as claw marks interdigital ridges and internal ridges are removed early in erosion creating the potential for misidentification of eroded theropod tracks as those of ornithopods however with the erosion models presented here all tracks retain their basic shapes as indicated by the relative constancy of their interdigital angles and by the relative constancy of their footlength footwidth ratios surface lengths of tracks did not increase significantly with erosion so that dinosaurian hip height and speed estimates derived from trackways would not be greatly in error if based on eroded surface tracks synthetic undertracks from the surface tracks were also produced using information from published physical models of trac

calcareous nannofloral response to termination ii at 45 n 25 w northeast atlantic abstract termination ii glacial to interglacial transition from oxygen isotope stage 6 to stage 5 is considered to be one of the most rapid and abrupt climatic changes during the late quaternary our high resolution geochemical and nannofloral study of the interval from 140 to 100 ka in the northeast atlantic core t90 9p 45 17 5 n 25 41 3 w shows that termination ii 135 125 ka occurred in two steps of drastic changes interrupted by a short period of stability and followed by at least 25 ka of relatively stable interglacial conditions traditionally referred to as the eemian age substage 5 5 a primary productivity proxy based on coccolith accumulation rate number cm 2 ka 1 shows higher values during the eemian than during glacial stage 6 and interglacial substage 5 4 with the maximum values 70 10 9 coccoliths cm 2 ka 1 at 123 122 ka the coccolith assemblage was dominated by two morphotypes of gephyrocapsa alternating in dominance under different climatic conditions gephyrocapsa muellerae was more abundant in colder periods whereas small gephyrocapsa dominated in the eemian emiliania huxleyi syracosphaera pulchra and florisphaera profunda increased in the eemian whereas coccolithus pelagicus and helicosphaera carteri decreased small gephyrocapsa together with emiliania huxleyi are associated with periods of higher primary productivity the pelagic sedimentary record of termination ii in core t90 9p includes a 5 cm thick layer enriched in ice rafted material a heinrich layer in contrast to termination i where such a heinrich layer h1 is associated with the first meltwater pulse of the deglaciation the record of core t90 9p suggests that the heinrich event of termination ii h11 occurred during the second stage of deglaciation 129 4 127 1 ka it is characterised by accumulation of ice rafted debris and low coccolithophore diversity the coincident apparent drop in coccolith accumulation rate could be explained either by changes in primary productivity due to reduction in salinity and light or by dilution by ice rafted material five models are applied for the deposition of the heinrich layer with changing thickness 3 cm and duration 1000 500 and 250 yr these scenarios result in a lowered constant or even slightly increased primary productivity during this event

use of low cost multistripe laser triangulation mlt scanning technology for three dimensional quantitative paleoichnological and neoichnological studies abstract the purpose of this paper is to test the application of a new low cost 2995 00 us multistripe laser triangulation mlt scanner and three dimensional 3d software for semiquantitative and quantitative analyses of ichnofossils and modern traces the goal of this research is to improve on existing analytical techniques and apply new methods to 3d digital models of ichnofossils and modern traces objectives are to 1 provide researchers with new ways to develop and test hypotheses quantitatively in the fields of paleoichnology neoichnology sedimentology and soil science and 2 discuss uses advantages and limitations of mlt technology related to ichnology we scanned and created digital models of a variety of mostly continental ichnofossils and modern terrestrial traces produced by invertebrates and vertebrates visual methods applied include making uniformly colored specimen surfaces stereo pairs anaglyph stereo images animations and cross sections quantitative methods applied include measuring distances tortuosity indices and angles and producing contour maps of tracks two of the most useful properties measurable from digital models are surface area sa and volume v these are used rarely in ichnology because they are difficult to measure with traditional methods we use sa to calculate area exploited and introduce a method of quantifying surface roughness adapted from research on soil surfaces we measure v of burrows tracks and coprolites as well as introduce a new measure termed volume exploited we hypothesize that different tracemakers make burrows with characteristic v to sa ratios this is partially supported by statistical tests of previously published data we also use v to sa ratios to determine relative compactness a metric adapted from building physics digital models ensure perpetuity of specimens because they preserve 3d data that can be used to make physical copies placed in museums and disseminated easily to researchers and educational institutions of all levels data from digital models can be used to interpret ichnocoenoses bioturbation rates and pedogenic properties and processes in soils and paleosols note that mlt scanning digitizes only surfaces of objects so it is best suited for exogenic traces and casts of endogenic traces

structure of the upper water column in the northwest north atlantic modern versus last glacial maximum conditions 1 during the last glacial maximum the northwestern north atlantic constituted a major conduit for labrador and greenland ice sheet meltwaters vertical density gradients in its upper water masses have been reconstructed by combining information from transfer functions based on dinocysts and from oxygen isotope measurements 18o in planktonic foraminifera transfer functions yield temperature and salinity and thus potential density for the warmest august and coldest february months in the photic zone the 18o values in different size fractions of epipelagic globigerina bulloides and mesopelagic neogloboquadrina pachyderma left coiled npl foraminifera allow us to assess gradients through the pycnocline between surface and intermediate waters based on the calibration of a versus 18o relationship from transfer function reconstructions the size and density of npl shells provide further constraints on these gradients the results show the development of a very strong pycnocline during the lgm with a difference of about 3 summer to 1 5 winter units between surface and underlying waters they indicate conditions unfavorable for vertical convection and support the hypothesis of the spreading of a shallow low salinity buoyant layer over the northern north atlantic this layer depicted a strong e w gradient with maximum seasonal contrast and minimum absolute values westward

mixed layer deepening during heinrich events a multi planktonic foraminiferal δ18o approach proxies from greenland ice cores and north atlantic marine sediment cores document repeated extreme climate swings of a few decades to millennia during the last glacial cycle including periods of intense ice rafting called heinrich events hes we have found similar oxygen isotope variations recorded in mixed layer and thermocline dwelling planktonic foraminifera during hes 0 1 and 4 suggesting that three foraminiferal taxa calcified their shells at similar temperatures in a homogenized upperwater column this implies that the surface mixed layer was deeper during hes similar deepening occurred on the northern margin of the ice rafted debris belt implying that these deep mixed layers during hes were widespread in the region we suggest that an increase in storminess during hes intensified the vertical mixing of meltwater from ice rafting in the upper ocean

vertebrate tracks in pleistocene eolian sand sheet deposits of alaska abstract deformation structures interpreted as vertebrate hoof and foot tracks occur within upper pleistocene eolian sand sheet deposits in the stabilized kantishna sand sea of central alaska and in the nushagak lowland of southwestern alaska exposures of tracks are generally limited to cross sections which reveal concave up deformation structures in which displacement of preexisting strata diminishes downward deposits in both areas contain tracks that are 6 to 16 cm in diameter and are divided by a central ridge reflecting formation by artiodactyl even toed ungulates larger 21 34 cm tracks without a central ridge observed in the nushagak lowland were formed by proboscideans probably woolly mammoth large vertebrate tracks occur within irregularly stratified sand and silty sand that accumulated upon partially vegetated sand sheets and within thin even wind ripple laminae of unvegetated sand sheets the presence of tracks at multiple stratigraphic levels and preservation of roots and rhizocretions within the eolian deposits suggest that vegetated sand sheets may have formed a locally important grazing habitat for large herbivores during at least part of the last glaciation recognition that vertebrate tracks are preserved in eolian sand sheet deposits and in deposits of other environments as well opens a new source of stratigraphic and paleoecological data to aid reconstruction of the vanished ecosystems of beringia

comment and reply on fossil vertebrate footprints in the coconino sandstone permian of northern arizona evidence for underwater origin brand and tang 1991 proposed that certain unusual vertebrate trackways point to subaqueous deposition for at least part of the coconino sandstone they supported their conclusions by demonstrating that western newts produce similar trackway configurations in aquarium experiments while it is encouraging to see vertebrate ichnology play such a prominent role in fundamental questions concerning paleoenvironmental analysis caution must be exercised when using track ways for radical reinterpretation of long standing hypotheses lockley 1991 as reviewed by walker and middleton 1979 several authors suggested a subaqueous origin for the jurassic navajo sandstone traditionally regarded as a classic eolian deposit the presence of tracks fossil wood and root zones was subsequently used to argue convincingly for the original interpretation of an eolian origin stokes 1978 loope 1984 presented similar evidence to argue for an eolian not subaqueous origin for the permian cedar mesa sandstone in eastern utah the interpretations of brand and tang therefore use vertebrate tracks to revive a controversial debate the question becomes can the presence of footprints in a particular facies be used to suggest a subaerial origin while unusual trackway configurations in the same track assemblages are used to argue for subaqueous deposition while brand and tang are to be congratulated for a thoroughexperimental study which presents more coconino track data than have appeared at any time since the inaugural studies of gilmore 1926 1927 several points warrant further comment the majority of trackways in question can be assigned to the ichnogenus laoporus which has usually been attributed to some type of synapsid see baird in spamer 1984 mckeever 1991 moreover such

geoelectrical exploration for groundwater in al maha forest ain jouhra morocco an area of about 30 km2 located in ain jouhra south of rabat morocco was the subject of a geoelectric resistivity investigation the main goal of the investigation was the assessment of the groundwater potential of the uppermost aquifer the aquifer conditions such as depth thickness and boundaries were also investigated the obtained apparent resistivity curves were first analysed qualitatively and classified using simple curve shapes thereafter the data were converted to resistivity and thickness pairs semi quantitatively by means of master curves and then quantitatively by computer modelling using ato and winsev software zohdy 1989 zohdy and bisdrof 1989 lithological control from the available single well with a stratigraphic log aided in the correlation of the resistivity values to different rock units three different ab spacing iso resistivity maps an isopach map of the main groundwater bearing horizon the depth to the aquifer substratum map and five geoelectric cross sections were constructed the interpretation of these soundings indicates the presence of an unconfined to semi confined sandy aquifer with relatively important extent and varying thickness the maximal thickness of the aquifer is recorded in the central part of the investigated area and is thinning southwards to pinch out farther to the south geophysical as well as field data indicate a hydraulic connection between the upper and deeper aquifers indeed the two aquifers are separated from each other by a marly substratum that is indicated throughout the area by the lowest values of the interpreted true resistivity the value of this resistivity varies laterally most likely due to the lateral variation in the shale to sand ratio the altitude of the substratum decreases towards the north and increases southwards regarding the availability of the groundwater in the study area zones with high potential are theoretically expected to occur in the central part where the transversal resistance is greatest however sufficient water supply and high flow rates from wells intended to produce restrictively from the most upper aquifer are not likely to exist this conclusion which seems to be very pessimistic is evidenced from two real field and experimental observations the first is the rapid fall of the level of gharnoug lake despite the ongoing feeding by three wells hence the amount of water level drop cannot be accounted for by the evaporation alone that means that the deeper aquifer is continuously draining the upper aquifer at a high flow rate very low rates are recorded in all the wells that penetrated only the upper aquifer the exception being the well that reached deeper into the lower aquifer the flow rate in this lower aquifer measured 18 litre s 1 copyright 2007 john wiley sons ltd

instabilities in the labrador sea water mass structure during the last climatic cycle in the modern labrador sea the north atlantic deep water components are found below the 2 km deep intermediate labrador sea water lsw mass which is renewed locally through winter convective mixing this water mass structure remained relatively stable since 9 5 14 c ka bp as indicated by isotopic studies of foraminifer assem blages from deep sea cores almost constant differences in 18 o values are observed between major species these av erage 0 5 between the epipelagic species globigerina bulloides and the mesopelagic species neogloboquadrina pachyderma left coiled and 1 between neogloboquadrina pachydermaand the benthic species cibicides wuellerstorfi after correction for cibicides wuellerstorfi specific fractionation these isotopic compositions represent thermohaline conditions in surface waters in the pycnocline with the lsw and in the deep component of the north atlantic deep water respectively a drastically different structure characterized the glacial labrador sea differences in 18 o values of 2 to 2 5 are then observed between globigerina bulloides and benthic species indicative of a strong halocline between the corresponding water masses thus for reduced production of intermediate waters during the same interval neogloboquadrina pachydermashows 13 c and 18 o fluctuations of 1 to 1 5 amplitude in phase with heinrich bond events and higher frequency climate oscillations the 18 o values in neogloboquadrina pachyderma vary between those of globigerina bulloides and of benthic foraminifers suggesting large amplitude bathymetric fluctuations of the halo thermocline above and below the bathymetric range occupied by neogloboquadrina pachyderma minimum 18 o values in neogloboquadrina pachydermamatch intervals of maximum ice rafting deposition such as the late heinrich events thus intervals with a deeper more dilute buoyant surface water layer

interaction between shallow groundwater saline surface water and contaminant discharge at a seasonally and tidally forced estuarine boundary this paper presents findings from a 2 year field investigation of a dissolved hydrocarbon groundwater plume flowing towards a tidally and seasonally forced estuarine river system in perth western australia samples collected from transects of multiport wells along the riverbank and into the river enabled mapping of the fine scale 0 5 m vertical definition of the hydrocarbon plume and its longitudinal extent spear probing beneath the river sediments and water table and transient monitoring of multiport wells electrical conductivity was also carried out to define the zone of mixing between river water and groundwater the hyporheic zone and its variability the results showed that groundwater seepage into the estuarine surface sediments occurred in a zone less than 10 m from the high tide mark and that this distance and the hyporheic transition zone were influenced by tidal fluctuations and infiltration of river water into the sediments the dissolved btexn benzene toluene ethylbenzene the xylene isomers and naphthalene distributions indicated the behaviour of the hydrocarbon plume at the groundwater surface water transition zone to be strongly influenced by edge focussed discharge monitoring programs and risk assessment studies at similar contaminated sites should therefore focus efforts within the intertidal zone where contaminants are likely to impact the surface water and shallow sediment environments