a comparison of semidiurnal internal tides from different bathymetric locations on the australia north west shelf abstract the vertical structure of the semidiurnal internal tide is calculated from current meter data for three locations of varying bathymetry on the southern part of the australian north west shelf these results are compared to results from a previous study at a fourth location each site is characterized by the ratio c where is the slope of the bathymetry and c 2 f2 n2 2 is the slope of the internal wave characteristics where is the wave frequency f the inertial frequency and n the buoyancy frequency the observations then fall into three categories subcritical c 1 bottom slopes the results at near critical bottom slope c 1 2 show a strong intensification of the near bottom baroclinic currents observations at the super critical slope c 1 9 show a weak bottom intensification and at the subcritical slopes c 0 2 and 0 5 no bottom intensification of currents is observed the observations agree qualita

delineation of shallow resistivity structure in the city of burdur sw turkey by vertical electrical sounding measurements the city of burdur which is built on an alluvium aquifer is located in one of the most seismically active zones in southwestern turkey the soil properties in the study site are characterized by unconsolidated and water saturated sediments including silty clayey and sandy units and shallow groundwater level is the other characteristic of the site thus the city is under soil liquefaction risk during a large earthquake a resistivity survey including 189 vertical electrical sounding ves measurements was carried out in 2000 as part of a multi disciplinary project aiming to investigate settlement properties in burdur city and its vicinity in the present study the ves data acquired by using a schlumberger array were re processed with 1d and 2d inversion techniques to determine liquefaction potential in the study site the results of some 1d interpretations were compared to the data from several wells drilled during the project also the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data 2d least squares inversions were performed along nine ves profiles this provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface the study area is characterized by low resistivity distribution 150 m originating from high fluid content in the subsurface lower resistivity 3 30 m is associated with the quaternary and the tertiary lacustrine sediments while relatively high resistivity 40 150 m is related to the quaternary alluvial cone deposits this study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface based on this we obtained a liquefaction hazard map for the study area the liquefaction potential was classified by considering the resistivity distributions from 2d inversion of the ves profiles the types of the sediments and the extended groundwater level map according to this map the study area was characterized by high liquefaction hazard risk

geoelectrical investigations by means of resistivity methods in karst areas in romania the applicability of resistivity methods to ground water investigations is well recognized as water saturated rock formations have a lower electrical resistivity than dry ones an electrical resistivity survey should result in low resistivity anomalies normally such anomalies are interpreted to indicate areas of potentially significant ground water flows in karst areas however interpretation may not be as straightforward for example large electrically conductive domains can represent water bearing zones whose fluid permeability may be poor alternatively fast flow conduits which may be unsaturated occur as slender objects and not as clear anomalous features in order to deal with such extreme heterogeneities resistivity investigations require some specific adjustments one example is the so called mise a la masse method in romania it was used to trace the cold karst water inflows that detrimentally affected the commercial exploitation of a thermal spring hercules at baile herculane conventional geoelectrical approaches such as using resistivity highs to detect air filled cave passages are proved to be less efficient in the considered karst investigations

abrupt mid holocene onset of centennial scale climate variability on the peru chile margin 1 understanding the natural climate variations in the eastern tropical pacific etp is crucial for predicting the evolution of the el nino southern oscillation enso here we present the first continuous decadal resolution holocene climate record from the peru chile margin near the epicenter of the modern enso system geochemical proxies allow us to reconstruct sea surface temperature phytoplankton productivity and thermocline ventilation variables that are tightly correlated to enso events today despite the observation that the mean state of all three variables did not change over the past 10 000 years our data reveal a dramatic increase in climate variability near 5 ka represented by prolonged periods 50 200 yrs of climate extremes which are absent in the early holocene these centennial scale oscillations do not show typical el nino la nina correlations between proxies we therefore posit that a significant fraction of super enso variance may originate outside the tropics through processes that ventilate the etp subsurface waters

two dimensional joint inversion of radiomagnetotelluric and direct current resistivity data an algorithm for the two dimensional 2d joint inversion of radiomagnetotelluric and direct current resistivity data was developed this algorithm can be used for the 2d inversion of apparent resistivity data sets collected by multi electrode direct current resistivity systems for various classical electrode arrays wenner schlumberger dipole diplole pole dipole and radiomagnetotelluric measurements jointly we use a finite difference technique to solve the helmoltz and poisson equations for radiomagnetotelluric and direct current resistivity methods respectively a regularized inversion with a smoothness constrained stabilizer was employed to invert both data sets the radiomagnetotelluric method is not particularly sensitive when attempting to resolve near surface resistivity blocks because it uses a limited range of frequencies on the other hand the direct current resistivity method can resolve these near surface blocks with relatively greater accuracy initially individual and joint inversions of synthetic radiomagnetotelluric and direct current resistivity data were compared and we demonstrated that the joint inversion result based on this synthetic data simulates the real model more accurately than the inversion results of each individual method the developed 2d joint inversion algorithm was also applied on a field data set observed across an active fault located close to the city of kerpen in germany the location and depth of this fault were successfully determined by the 2d joint inversion of the radiomagnetotelluric and direct current resistivity data this inversion result from the field data further validated the synthetic data inversion results

the significance of the theropod collections of the royal tyrrell museum of palaeontology to our understanding of late cretaceous theropod diversity1 significant specimens of theropod dinosaurs were part of the collections that were transferred to the royal tyrrell museum of palaeontology when it split off from the provincial museum of alberta in 1981 collecting activity of the institution increased dramatically in the period leading up to the opening of the building and displays in 1985 and resulted in the recovery and preparation of many fine theropod skeletons new specimens have been added to the collection every year since the museum opened several mostly small taxa are only represented by isolated bones partial skeletons and or teeth theropod specimens also include footprints coprolites eggs and feathers in amber although theropods are relatively rare in comparison with herbivorous dinosaurs the tyrrell has managed to build one of the finest research collections of late cretaceous forms thirty seven species of theropods in the tyrrell are currently accepted as being valid of which 30 are from the upper cretaceous deposits of alberta

simple data processing of tripotential apparent resistivity measurements as an aid to the interpretation of subsurface structure the advantages of the wenner tripotential method carpenter 1955 for apparent resistivity profiling are described and two new data processing techniques introduced as an aid to the interpretation of apparent resistivity sections pseudo sections these techniques were developed from model data computed using a two dimensional finite difference method oscillatory components present in anomalies on tripotential profiles and related to electrode spacing are shown to be effectively removed by linear filtering that also simplifies their form and aids recognition furthermore it is shown that the ratio of the beta and gamma apparent resistivities is a good indicator of resistivity variation and is particularly sensitive to lateral change model data indicates that over a wide range of conditions enough subsurface information can be obtained by inspection of tripotential resistivity and ratio profiles and from space sections to make possible a useful and sometimes semi quantitative interpretation a rationale for the general interpretation of tripotential data is developed field data are described from an area of weathered granite basement in nigeria a model of the subsurface is developed using parameters derived from the processed observations the observed and calculated apparent resistivity space sections are very similar

genesis of phosphorite crusts off peru abstract authigenic phosphorite crusts from the shelf off peru 9 40 s to 13 30 s consist of a facies with phosphatic coated grains covered by younger phosphatic laminite the crusts are composed of carbonate fluorapatite which probably formed via an amorphous precursor close to the sediment water interface as indicated by low f p2o5 ratios sr and ca isotopes as well as rare earth element patterns agreeing with seawater dominated fluids small negative ce anomalies and u enrichment in the laminite suggest suboxic conditions close to the sediment water interface during its formation increased contents of chalcophilic elements and abundant sulfide minerals in the facies with phosphatic coated grains as well as in the laminite denote sulfate reduction and consequently point to episodical development of anoxic conditions during phosphogenesis the peruvian phosphorites formed episodically over an extended period of time lasting from middle miocene to pleistocene individual phosphatic coated grains show a succession of phosphatic layers with varying contents of organic matter and sulfide rich phosphatic layers coated grains supposedly formed as a result of episodic suspension caused by high turbulence and shifting redox conditions episodic anoxia in the pore water induced pyritization in the outermost carbonate fluorapatite layer phosphatic coated grains were later transported to the place of crust formation where subsequent laminite formation was favored under lower energy conditions a similar succession of phosphatic layers with varying contents of organic matter and sulfide rich layers in the laminite suggests a formation mechanism analogous to that of individual coated grains

oxygen minimum zone expansion in the eastern tropical north pacific during deglaciation concentrations lamination preservation and d 15 n values from cores located between 540 750 m water depth in the gulf of tehuantepec southern mexico these results differ from similar proxies found even 5 n of the site where there is evidence for omz changes related to rapid climate change in the northern hemisphere instead omz expansion in the gulf was contemporaneous with changes in sea ice extent and zonal wind shifts around antarctica pointing to subantarctic mode water and antarctic intermediate water as likely sources of oxygen depleted water these observations reinforce the importance of the southern ocean as a primary modulator of northern hemisphere ocean climate as far as 15 n in the etnp citation hendy i l and t f pedersen 2006 oxygen minimum zone expansion in the eastern tropical north pacific during deglaciation geophys res lett 33 l20602 doi 10 1029 2006gl025975

accumulation and biological mixing of peru margin sediments abstract rates of sediment accumulation and biological particle mixing in eight cores from the peru shelf have been estimated by application of uranium series disequilibrium techniques and radiocarbon dating activities of 210pb 226ra 234th and 238u have been determined in closely spaced intervals in each sediment core biological particle mixing coefficients were determined via a two box advection diffusion steady state mixing model based on the distribution profiles of excess 210pb and in some cases excess 234th activities the sedimentation rates estimated were in the order of a few millimeters yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen minimum zone estimated biological mixing coefficients were in the order of 100 101 cm2 yr 1 for the surface mixed layer and 10 1 100 cm2 yr 1 for the layer below sediment slumping appears to have affected the 210pb distribution of two or three of our cores

orbital motions and coherent structures in the internal tide on a steep shelf off the pacific coast of mexico 1 herein we discuss the results of a study of the structure evolution and break up of an internal tidal wave under conditions of a steep shelf with a slope close to that of the internal wave characteristic measurements were taken in navidad bay on mexico s pacific coast we demonstrate that under the conditions of homogeneous density stratification the internal tidal wave releases its energy and collapses due to resonant excitation in a sequence of third tidal harmonics those harmonics generate multiscale vertical bilateral steps that follow at regular intervals and feature coherent oscillations in the form of vertical jets that cover the entire water column

interpretation of resistivity measurements over 2d structures1 resistivity measurements were carried out in a survey area in the south of germany this area is characterized by complicated subsurface geology schlumberger full arrays and their respective half arrays were recorded simultaneously the results obtained by the one dimensional 1d interpretation of the full array measurements were incorrect because of a resistivity discontinuity this discontinuity under a relatively thick overburden could only be located by the half array soundings its exact location and the resistivity distribution in the subsurface were ascertained by comparing the sounding curves with 2d model curves which are calculated by a finite difference method

numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum 1 a hydrodynamic model incorporating a self consistent treatment of ocean self attraction and loading sal and a physically based parameterization of internal tide it drag is used to assess how accurately barotropic tides can be modeled without benefit of data and to explore tidal energetics in the last glacial maximum lgm m2 solutions computed at high resolution with present day bathymetry agree with estimates of elevations from satellite altimetry within 5 cm rms in the open ocean this accuracy and agreement with atlimetric estimates of energy dissipation are achieved only when sal and it drag are included in the model solutions are sensitive to perturbations to bathymetry and inaccuracies in available global databases probably account for much of the remaining error in modeled elevations the 100 m drop in sea level during the lgm results in significant changes in modeled m2 tides with some amplitudes in the north atlantic increasing by factors of 2 or more dissipation is also significantly changed by the drop in sea level if it drag estimated for the modern ocean is assumed dissipation increases by about 50 globally and almost triples in the deep ocean however it drag depends on ocean stratification which is poorly known for the lgm tests with modified it drag suggest that the tendency to a global increase in dissipation is a robust result but details are sensitive to stratification significant uncertainties about paleotides thus remain even in this comparatively simple case where bathymetry is well constrained

a previously undescribed caenagnathid mandible from the late campanian of alberta and insights into the diet of chirostenotes pergracilis dinosauria oviraptorosauria until recently caenagnathids were a family of oviraptorosaurs represented only by fragmentary material as such caenagnathid biology has never been studied in depth a well preserved mandible provides new information on the anatomy and dietary habits of chirostenotes the mandible is edentulous has a completely fused symphysis with sharp occlusal margins and complex lingual surfaces finite element analysis shows that the lingual ridges are reinforced this suggests that they had a function in food processing these and other features suggest adaptations for an efficient shearing mechanism and the overall morphology is poorly adapted for durophagous behaviour comparisons with three groups with convergently similar mandibles especially dicynodonts indicate caenagnathids were capable of handling an herbivorous diet here an omnivorous diet is proposed for chirostenotes including folivory and small prey

a regional model of the semidiurnal internal tide on the australian north west shelf a fully three dimensional nonlinear primitive equation model is applied to a study of the semidiurnal internal tide on the australian north west shelf a region of strong barotropic and baroclinic tide the model shows a significant internal tide over most of the continental slope region predominantly between 100 and 1000 m depths energy flux is highly variable with regions of onshore flux and regions of offshore flux corresponding to regions of subcritical and supercritical seabed slopes a comparison between the model and detailed observations from one region shows reasonable agreement in vertical displacement currents and depth integrated energy flux the comparison also highlights the difficulty in obtaining appropriate observations to provide a rigorous verification of internal tide models the m2 and s2 internal tides show similar patterns of flow with energy in the s2 internal tide about 25 of that in the m2 constituent estimates of the total baroclinic m2 energy are about 2 2 gw for the north west shelf nearly an order of magnitude larger than suggested by earlier studies this represents about 5 of the dissipation of the m2 barotropic tide in the model domain the seasonal variability in the baroclinic energy flux is about 20 from the mean the baroclinic energy extracted from the tide is expected to make a significant contribution to mixing in the region

peruvian sediments as recorders of an evolving hiatus for the last 22 thousand years highlights review of sediment archives from the peruvian margin since the lgm focus on the evolutionary feature of the hiatus found in archives modern analogue for current dominated environments for paleo reconstructions new results for erosional potential of the non linear internal waves nliws abstract the peruvian continental margin is characterized by the presence of one of the strongest and most distinct oxygen minimum zones omzs in today s oceans therefore it has long been in the focus of oceanographic and geological investigations observations indicate that omzs are expanding in relation with currently changing climate to advance understanding of the temporal evolution of omzs and climate change complete paleoceanographic and palaeoclimatological reconstructions are needed however the development of paleoenvironmental scenarios for the period since the last glacial maximum at this region was hampered by a ubiquitous hiatus and short term interruptions of the stratigraphical record in the present study we combined the stratigraphical information from 31 sediment cores from the peruvian margin located between 3 and 18 s and water depths of 90 to 1300 m within and below today s omz in order to determine the extent of the hiatus and assess the responsible mechanisms a widespread unconformity and related erosional features omission surfaces and phosphorites were observed in sediment cores from the area south of 7 s depicting a prograding feature on the continental slope from south to north during the deglaciation combining recent oceanographic and sedimentological observations it is inferred that tide topography interaction and resulting non linear internal waves nliws shape the slope by erosion carry sediments upslope or downslope and leave widespread phosphoritic lag sediments while the peru chile undercurrent pcuc transports the resuspended sediments southward causing non deposition this exceptional sedimentary regime makes the peruvian margin a modern analogue for such environments overall our compilation of downcore records showed that enhanced bottom currents due to tide topography interaction were progressively evolving and affected a wider area with the onset of the last deglaciation elevated tidal amplitudes and variability of mid depth water masses i e density changes and hydrodynamics in relation with changing climate were potential reasons of this evolving feature of erosion and reworking additionally erosion and non deposition was observed widest and even was encountered on the continental shelf during the early holocene potentially indicating a strong phase of the pcuc mirroring today s el nino like conditions

detecting lateral resistivity inhomogeneities with the schlumberger array a method of detecting lateral resistivity inhomogeneities with a multi electrode cable for the schlumberger array is presented using such a cable system two dipole dipole soundings are gathered in addition to the schlumberger sounding at each point offset differences calculated from the dipole dipole data give qualitative information about lateral resistivity inhomogeneities results from 1d modelling can give quantitative information about the 2d resistivity distribution since the dipole dipole soundings are made to either side of the schlumberger sounding point examples from two different locations in norway are shown at reinoya northern norway a dipping layer confirmed by refraction seismic data was identified in a sedimentary basin with a contamination plume at haslemoen southern norway the method has revealed lateral variations in resistivity in both cases the schlumberger soundings could be fitted with a 1d resistivity model

the organic geochemistry of peru margin surface sediments i a comparison of the c37 alkenone and historical el nino records abstract the alkenone u k 37 paleothermometer has potential as a sedimentary marker for el nino southern oscillation enso events in the peru upwelling regime we assessed this potential by comparing the historical enso record with detailed u k 37 profiles for 210 pb dated cores from the peru margin oxygen minimum zone omz sediments with the greatest potential for holding a sedimentary u k 37 record of el nino events are sediments from the center of the omz sectioned at intervals the yearly sedimentation rate the u k 37 signals of individual el nino events were substantially attenuated in the sediments we examined and periods of frequent enso activity e g 1870 1891 were more readily identified than isolated enso events in periods of less frequent enso activity detailed depth profiles of the c 37 alkenones in a core from 253 m o 2 k 37 values for the five 2 mm sections from 0 1 cm suggests that the u k 37 may be unaffected by the alkenone loss correlation between the c 37 alkenone concentration profiles in two cores from 15 s collected nine years apart are consistent with the use of these compounds for molecular stratigraphy

miocene phosphate rich sediments in salento southern italy abstract the upper middle to lower upper miocene serravallian to tortonian sedimentary succession in salento southern italy includes glauconite and phosphate rich deposits which are associated with pelagic micrite in baia del ciolo and marittima southern salento the succession is composed of shallow water platform carbonates of late oligocene age chattian porto badisco formation which are overlain by a 20 to 30 cm thick level of glauconite rich micrite with abundant reworked particles and fossils of the underlying porto badisco formation this interval is in turn covered by an up to 15 cm thick phosphatic crust livello ad aturia which itself is overlain either by a hemipelagic chalk like carbonate of middle to late miocene age pietra leccese marittima or directly by a micrite of late miocene age messinian novaglie formation baia del ciolo which shallows upwards into a shallow water platform carbonate a large hiatus is present in this succession which likely includes the lower and lower middle miocene in the region of lecce two discrete levels enriched in glauconite and phosphate each associated with a major discontinuity occur within the pietra leccese the strontium isotope ages derived on phosphate nodules and phosphatized and non phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13 5 and 7 5 ma with two clusters at 12 and 10 5 ma the glauconite and phosphate rich sediments resulted from a current dominated regime which was characterized by low overall sedimentation rates erosion and sediment reworking and authigenesis this regime was likely related to a generally westward directed bottom current which was forced to upwell once it arrived at the western border of the eastern mediterranean basin the timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the mediterranean malta gozo southern sicily matese latium abruzzi platform the partial diachrony in phosphogenesis may express the effect of lateral switching in and or focusing of upwelling zones

the first records of elmisaurus saurischia theropoda from north america the discovery of a fused tarsometatarsus in the upper cretaceous campanian strata of dinosaur provincial park shows that elmisaurus previously known only from mongolia also lived in north ameri

resistivity measurements on the sea bottom to map fracture zones in the bedrock underneath sediments1 refraction seismics with the shotpoints and the hydrophone cable on the sea bottom have become the standard geophysical method for investigating rock quality before constructing offshore tunnels in norway in connection with the construction of a sub sea tunnel by the norwegian public roads administration research work was carried out to compare two low velocity zones indicated by refraction seismics with other methods a special resistivity cable for pole dipole measurements on the sea floor with 10 m between the electrodes was constructed a 200 m long profile crossing the two low velocity zones was measured with all combinations of electrode distances the two zones were detected as low resistivity zones a special data processing technique to enhance the anomalies is described resistivity soundings in a seawater environment to detect fracture zones in the bedrock underneath the bottom sediments are discussed it is concluded that severely fractured zones which may cause difficulties for the tunnel construction can be detected both with sea surface and sea floor arrays using long electrode spacings

the western undersea section of the ischia volcanic complex italy tyrrhenian sea inferred by marine geophysical data 1 ischia island represents only the remnant of a once larger volcanic complex to prove this hypothesis about 600 km of new marine geophysical data were analysed results reveal that the western offshore of the island consists of previously unreported e w and ne sw volcanic ridges that follow the regional structural patterns the match between sea borne magnetic anomalies and bathymetric seismic data indicates the presence of a large cooled magmatic system with deeper intrusions along the ne sw direction some of the newly discovered submerged volcanoes are dissected by fault scarps that offset with a strong vertical component recentmost possibly holocene marine and volcanoclastic deposits our data suggest the importance of regional tectonics in particular along the ne sw trend on the patterns of magma uprising and on the recent local deformation in the neapolitan volcanic district

the evolution of tides and tidal dissipation over the past 21 000 years the 120 m sea level drop during the last glacial maximum lgm 18 22 kyr bp had a profound impact on the global tides and lead to an increased tidal dissipation rate especially in the north atlantic here we present new simulations of the evolution of the global tides from the lgm to present for the dominating diurnal and semidiurnal constituents the simulations are undertaken in time slices spanning 500 1000 years due to uncertainties in the location of the grounding line of the antarctic ice sheets during the last glacial simulations are carried out for two different grounding line scenarios our results replicate previously reported enhancements in dissipation and amplitudes of the semidiurnal tide during lgm and subsequent deglaciation and they provide a detailed picture of the large global changes in m2 tidal dynamics occurring over the deglaciation period we show that antarctic ice dynamics and the associated grounding line location have a large influence on global semidiurnal tides whereas the diurnal tides mainly experience regional changes and are not impacted by grounding line shifts in antarctica

tides and tidal torques of the world ocean since the last glacial maximum peltier s 1994 paleobathymetries are used to investigate tides and corresponding balances of torques of the world ocean since the last glacial maximum 21 000 years before present simulations with a numerical tidal model point out that variable ice loads at the earth s surface and rearrangements in the interior led to considerable modifications of the resonance behavior of the oceans associated evident changes of the tidal range were not confined to the vicinity of formerly ice covered areas in contrast to the tidal oscillation system that was subject to almost uniform changes since the beginning of ice retreat the dissipation rate of the m2 tide increased distinctly during the principal melting time from 15 to 8 kyr b p and reached a local extreme eight thousand years ago though surface and volume of the world ocean were already very similar to present conditions postglacial deformations during the following two thousand years caused the decrease of tidal dissipation from the maximum value to the present day level indicating the sensibility of tidal torques and dissipation rates to comparatively small variations of ocean s geometry since the vicinity of the tidal oscillation system to a resonance situation is more decisive with respect to total dissipation than the extension of shelves where most of the tidal dissipation is expected to take place states of extreme dissipation rates do not necessarily coincide with extreme bathymetric conditions

the response of benthic foraminifera to productivity cycles in the eastern equatorial pacific faunal and geochemical constraints on glacial bottom water oxygen levels the stage 2 glacial maximum in eastern equatorial pacific ocean sediments is characterized by a pronounced increase in the organic carbon content which has been attributed either to increased upwelling and higher production along the equatorial divergence during the last glacial period or to enhanced preservation as a consequence of a lower concentration of dissolved o2 in glacial bottom water several lines of evidence are presented based on data from two gravity cores collected from the central panama basin which support the former interpretation first both the abundance and the size of benthic foraminifera of the genus uvigerina increase in stage 2 coincident with the increase in organic carbon concentration most probably because of the greater availability of organic detritus during the glacial period the increase in foraminiferal size and associated greater requirement of oxygen for respiration argues against the probability that oxygen was substantially depleted in the upper centimeter where uvigerina spp are thought to live second the number of meiofaunal faecal pellets increases markedly during the stage 2 maximum indicating a more populous and active infauna which again argues against oxygen depletion third there is no significant decrease in the iodine organic carbon i corg ratio in the stage 2 sediments because iodine is depleted relative to carbon in anoxic basins but enriched in association with organic matter in oxic environments the absence of a depletion in the i corg ratio in stage 2 is evidence that bottom water remained oxygen replete during the last glacial fourth molybdenum is not enriched in sediments deposited in stage 2 the presence of anoxic or dysaerobic bottom water or shallow pore waters during that time would have been recorded by the addition of mo to the sediments via coprecipitation with authigenic iron sulphides the combined faunal and geochemical data are consistent with the notion that panama basin deep waters remained oxygen replete during the last glacial maximum it is concluded that the late stage 2 carbon enrichment in the eastern equatorial pacific more probably reflects higher productivity rather than enhanced preservation

exploration for a cave by magnetic and electrical resistivity surveys ayvacik sinkhole example bozdag izmir western turkey abstractgeophysical survey techniques have been successfully applied to near surface cave detection in karstic terrains we used magnetic and electrical resistivity surveys to delineate the karstic structure of the ayvacik sinkhole which may be considered to be a vertical cave the magnetic total field anomaly map helped reveal the metamorphic and sedimentary units in the study area the total horizontal gradient map which was based on a calculated pseudogravity anomaly successfully identified the contact between the limestone unit and the cave system using these results we positioned and carried out a vertical electrical sounding ves survey with a schlumberger array along a line that consisted of 11 stations the ves data were then processed using a 1d global optimization technique which used a genetic algorithm and a 2d linearized least squares algorithm the results were generally in good agreement with each other and together they pointed out three geologic layers 1 an overburden layer 3

analysis of nonlinear internal waves in the new york bight this paper presents the results on internal wave analysis of the current meter mooring data in the new york bight from the sar internal wave signature experiment sarsex selective sets of current and temperature measurements are analyzed for a parametric study of internal wave characteristics and shear effects on wave parameters are studied based on the limited data from moorings the solitary wave theory has been extended for the wave evolution on a continental shelf by including dissipation and shoaling effects a series of numerical simulations are performed to demonstrate the relative importance of dissipation and shoaling effects from an observed initial wave packet at the upstream mooring the numerical evolution simulation compares reasonably well with the measurements at the distant mooring for the leading two large solitons

a new carnosaur dinosauria theropoda from the lower cretaceous of japan an associated skeleton from the kitadani quarry of the lower cretaceous albian strata in fukui prefecture japan represents a new genus and species of carnosaur dinosauria theropoda the imma

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

two dimensional joint inversions of cross hole resistivity data and resolution analysis of combined arrays in this study a new two dimensional inversion algorithm was developed for the inversion of cross hole direct current resistivity measurements in the last decades various array optimisation methods were suggested for resistivity tomography however researchers have still collected data by using classical electrode arrays in most cross hole applications therefore we investigated the accuracy of both the individual and the joint inversion of the classical cross hole arrays by using both synthetic and field data with the developed algorithm we showed that the joint inversion of bipole bipole pole bipole bipole pole and pole tripole electrode arrays gives inverse solutions that are closer to the real model than the individual inversions of the electrode array datasets for the synthetic data inversion the model resolution matrix of the suggested arrays was used to analyse the inversion results this model resolution analysis also showed the advantage of the joint inversion of bipole bipole pole bipole bipole pole and pole tripole arrays we also used sensitivity sections from each of the arrays and their superpositions to explain why joint inversion gives better resolution than the any individual inversion result

new caenagnathid dinosauria theropoda specimens from the upper cretaceous of north america and asia new specimens of caenagnathid theropods are described from the judith river formation campanian of southern alberta the hell creek formation maastrichtian of south dakota and the bissekty for

growth rates of phosphate nodules from the continental margin off peru modern sea floor phosphorite nodules sampled from off the coast of peru are shown to grow at rates of millimeters per thousand years in spite of the fact that the measured accumulation rates of the underlying sediment are two to four orders of magnitude faster phosphate nodules grow downward into soft sediment and the rates of phosphorus accumulation into nodules are approximately equal to the upward diffusive flux of dissolved phosphate inferred from pore water profiles these results demonstrate that phosphorus in nodules originates from regeneration in sediments rather than as a result of direct precipitation from bottom waters

osteology and relationships of chirostenotes pergracilis saurischia theropoda from the judith river oldman formation of alberta canada a partial skeleton of a small theropod found in the judith river formation of dinosaur provincial park alberta shows that chirostenotes pergracilis is the same animal as macrophalangia canadensi

el nino southern oscillation extrema in the holocene and last glacial maximum 1 the el nino southern oscillation enso is the largest engine of interannual climate variability on the planet yet its past behavior and potential for future change are poorly understood and vigorously contested reconstructions of past enso are indispensable for testing climate models tasked with predicting future enso activity in a warming world but suitable geologic archives are scarce especially for the last glacial period here we reconstruct mean climate and enso variability in the holocene and last glacial maximum lgm from oxygen isotopic ratios 18o of individual foraminifera retrieved from deep sea sediments our results document coordinated adjustments of the tropical pacific enso system between two diametrically opposite states an amplified enso state in the lgm associated with a reduced zonal temperature gradient and a damped enso state in the mid holocene with enhanced gradient orbital precession provided the switch between these states and acted as the dominant external driver of the tropical pacific enso system in the past 25 000 years the linked response of the mean state and variability to orbital forcing provides an integrated framework for testing enso theory and models

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

combined sounding profiling resistivity measurements with the three electrode arrays a combination of dc resistivity sounding and profiling measurements can be used to obtain the maximum information about distribution of resistivities in the earth combined sounding profiling measurements with the amn mnb arrays are considered the resistivity data from such measurements can be presented as a normal sounding curves b combined sounding profiling curves c profiling curves d pseudo sections or as transformations obtained by the so called gradient processing to emphasize the influence of the target objects the examples chosen from numerical modeling and field tests show the efficiency of measurements with three electrode arrays to accurately locate thin conductors and contacts of lithological units of different resistivities an interpreted cross section is compared with the results of other geophysical measurements vlf r dipole em ip showing good correlation

multiscale derivative analysis a new tool to enhance detection of gravity source boundaries at various scales 1 potential fields generally require to be analyzed by different scales owning to sources of different depth and extent fourier or wavelet filtering not always yield an optimal separation of those different source effects often introducing some amount of distortion we propose therefore a new method the multiscale derivative analysis mda based on the enhanced horizontal derivative ehd of the field which does not imply any separation of the effects but simply enhances those related to a given scale such process based on a weighted sum of increasing order derivatives of the field converges quickly toward the actual boundaries of the sources mda applied to gravity data of the of thyrrenian sea italia yields 3 maps of structural lineaments each one characterized by a different scale known partially known or relatively new structures are described in the maps allowing a rapid analysis of all the gravity related structural lineaments of this region

near coastal circulation in the northern humboldt current system from shipboard adcp data the near coastal circulation of the northern humboldt current system is described analyzing 8700 velocity profiles acquired by a shipboard acoustic doppler current profiler sadcp during 21 surveys realized between 2008 and 2012 along the peruvian coast this data set permits observation of i part of the peru coastal current and the peru oceanic current that flow equatorward in near surface layers close to the coast and farther than 150 km from the coast respectively ii the peru chile undercurrent pcuc flowing poleward in subsurface layers along the outer continental shelf and inner slope iii the near surfacing equatorial undercurrent renamed as ecuador peru coastal current that feeds the pcuc and iv a deep equatorward current referred to as the chile peru deep coastal current flowing below the pcuc a focus in the pcuc core layer shows that this current exhibits typical velocities of 5 10 cm s 1 the pcuc deepens with an increasing thickness poleward consistent with the alongshore conservation of potential vorticity the pcuc mass transport increases from 1 8 sv at 5 s to a maximum value of 5 2 sv at 15 s partly explained by the sverdrup balance the pcuc experiences relatively weak seasonal variability and the confluence of eddy like structures and coastal currents strongly complicates the circulation the pcuc intensity is also affected by the southward propagation of coastally trapped waves as revealed by a strong pcuc intensification in march 2010 coincident with the passage of a downwelling coastal wave associated with a weak el nino event

internal solitary waves in the coastal mixing and optics 1996 experiment multimodal structure and resuspension 1 observations of internal solitary waves isws and of their role in sediment resuspension during the coastal mixing and optics 1996 cmo 96 experiment are reported the largest resuspension events observed in the experiment can be related to retarded flow under the wave footprint two distinctly different periods of resuspension events could be distinguished based on the prevailing atmospheric conditions a calm period which we consider characteristic of nominal conditions and an energetic period during which two major storms occurred isws arrived at the mooring site from a variety of sources though a common intermodal dynamics seemed to occur repeatedly both mode 1 and mode 2 isws have been observed the present analysis of the month long portion of the cmo 96 data set constitutes the first reported observations insofar as we are aware of mode 2 waves on the continental shelf both mode 1 and mode 2 isws were found to stimulate resuspension the mode 2 waves seem to be generated locally by resonant or topographic interactions with mode 1 isws internal wave fields of the type described here are expected to exist in a variety of other shallow seas as well

detecting small scale targets by the 2d inversion of two sided three electrode data application to an archaeological survey abstractthe detecting capabilities of some electrical arrays for the estimation of position sizeand depth of small scale targets were examined in view of the results obtained from2d inversions of apparent resistivity data the two sided three electrode apparent resistivity data are obtained by the application of left and right hand pole dipolearrays that also permit the computation of four electrode and dipole dipoleapparent resistivity values without actually measuring them synthetic apparent resistivity data sets of the dipole dipole four electrode and two sided three electrodearrays are calculated for models that simulate buried tombs the results of two dimensional inversions are compared with regard to the resolution in detecting theexact location size and depth of the target showing some advantage for the two sided three electrode array a field application was carried out in the archaeologicalsite known as alaca hoyuk a religious temple area of the hittite period the two dimensional inversion of the two sided three electrode apparent resistivity data hasled to locating a part of the city wall and a buried small room the validity of theinterpretation has been checked against the results of subsequent archaeologicalexcavations introductionthe two dimensional 2d inversion of direct current dc sounding data has become a standard tool for the investiga tion of targets buried at shallow and intermediate depths theapplications include archaeology environmental and hydro geological works mining exploration and engineeringstudies when using the traditional electrode arrays thedata acquisition is usually carried out by expanding electro des along a measurement profile the apparent resistivitydata obtained from all soundings are then used as the input ofa 2d inversion algorithm pelton rijo and swift 1978 andsasaki 1981 first introduced inversion algorithms applied tothe dipole dipole and schlumberger arrays respectively later loke and barker 1996 introduced a fast 2d inversionmethod for the wenner and dipole dipole electrode arrays this algorithm is based on a quasi newton method whichcalculates an approximate value of partial derivatives of theapparent resistivity data with respect to model parameters the finite difference technique is used for the computation ofthe model response one of the remarkable developments in dc methods is theuse of modern measuring systems with multicore cableswhich allows automatic switching between electrodes forpractical field operations the electrodes are located at equallyspaced measurement stations for example morris ronningand lile 1997 described a data acquisition system thatsimultaneously collects schlumberger and two dipole dipoledata however they did not indicate a quantitative inter pretation tool acworth and griffiths 1985 and griffithsand turnbull 1985 described wenner tripotential apparent resistivity measurements to reduce the number of ambiguitiesarising in the qualitative interpretation of apparent resistivitypseudosections the tripotential method produces threeapparent resistivity measurements for each position of acollinear equispaced quadripole of electrodes they used the

early diagenesis of redox sensitive trace metals in the peru upwelling area response to enso related oxygen fluctuations in the water column pore water and solid phase data for redox sensitive metals mn fe v mo and u were collected on a transect across the peru upwelling area 11 s at water depths between 78 and 2025 m and bottom water oxygen concentrations ranging from 0 to 93 m by comparing authigenic mass accumulation rates and diffusive benthic fluxes we evaluate the respective mechanisms of trace metal accumulation retention and remobilization across the oxygen minimum zone omz and with respect to oxygen fluctuations in the water column related to the el nino southern oscillation enso sediments within the permanent omz are characterized by diffusive uptake and authigenic fixation of u v and mo as well as diffusive loss of mn and fe across the benthic boundary some of the dissolved mn and fe in the water column re precipitate at the oxycline and shuttle particle reactive trace metals to the sediment surface at the lower and upper boundary of the omz at the lower boundary pore waters are not sufficiently sulfidic as to enable an efficient authigenic v and mo fixation as a consequence sediments below the omz are preferentially enriched in u which is delivered via both in situ pre cipitation and lateral supply of u rich phosphorites from further upslope trace metal cycling on the peruvian shelf is strongly affected by enso related oxygen fluctuations in bottom water during periods of shelf oxygenation surface sediments receive particulate v and mo with metal oxyhydr oxides that derive from both terrigenous sources and precipitation at the retreating oxycline after the recurrence of anoxic conditions metal oxyhydr oxides are reductively dissolved and the hereby liberated v and mo are authigenically removed this alternation between supply of particle reactive trace metals during oxic periods and fixation during anoxic periods leads to a preferential accumulation of v and mo compared to u on the peruvian shelf the decoupling of v mo and u accumulation is further accentuated by the varying susceptibility to re oxidation of the different authigenic metal phases while authigenic u and v are readily re oxidized and recycled during periods of shelf oxygenation the sequestration of mo by authigenic pyrite is favored by the transient occurrence of oxidizing conditions our findings reveal that redox sensitive trace metals respond in specific manner to short term oxygen fluctuations in the water column the relative enrichment patterns identified might be useful for the reconstruction of past omz extension and large scale redox oscillations in the geological record

deep resistivity structure of the dikili bergama region west anatolia revealed by two dimensional inversion of vertical electrical sounding data within the framework of the national marine geological and geophysical program we re examined deep vertical electrical sounding ves data the data measured in 1968 by the general directorate of mineral research and exploration mta of turkey with the aim of exploring the deep resistivity structure of the dikili bergama region focus on the geothermal potential the geoelectrical resistivity survey was conducted using a schlumberger array with a maximum electrode half spacing of 4 5 km the two dimensional 2d inversion was utilized to interpret the ves data that were collected along 15 to 30 km profiles the 2d resistivity depth cross sections obtained show very low resistivity values near the dikili and kaynarca hot springs the 2d inversion results also indicate the presence of fault zones striking nearly n s and e w and fault bounded graben horst structures that show promising potential for geothermal field resources the 2d gravity model which is in good agreement with the density variation of the region supports the resistivity structure revealed by 2d inversion the lithology information obtained from the borehole near kaynarca also confirms the results of the resistivity interpretation and the density model

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

transuranic nuclides in two coastal marine sediments off peru the fluxes of plutonium isotopes as well as their depth profiles are similar for northern and southern hemispheric varved sediments taken off western american coasts the inventories are in excess of the values predicted for atmospheric fallout in these anoxic sediments there is a general increase in concentration from depths to the near surface these observations are explainable on the bases that anoxic deposits have a substantially higher retentivity of sedimented materials compared to that of their bioturbated oxic counterparts and that there are inputs of resuspended materials previously deposited in the marine environment the 241am distributions are explained by ingrowth from 241pu assuming a substantial input of the parent from the u s thermonuclear tests during the 1950 s and the immobilization of both pu and am in the deposits

the effects of remote internal tides on continental slope internal tide generation abstractinternal tide generation at sloping topography is nominally determined by the local slope geometry density stratification and tidal forcing recent global ocean models have revealed that

influence of marine denitrification on atmospheric n2o variability during the holocene 1 oceanic denitrification centers are thought to be important marine sources for atmospheric n 2 o to consider holocene variability in this source we reconstruct the holocene paleo denitrification history of the peru margin a major marine denitrification center using high resolution sedimentary 15 n data this record along with a contemporaneous one from the western arabian sea altabet et al 2002 shows similarities with the recently available high resolution atmospheric n 2 o record fliickiger et al 2002 while the role of terrestrial processes in the observed n 2 o changes remains uncertain these results suggest that variability in marine denitrification in major upwelling centers such as the peru margin and the arabian sea contributed significantly to atmospheric n 2 o evolution during the holocene

stenonychosaurus inequalis saurischia theropoda from the judith river oldman formation of alberta new findings on metatarsal structure a partial foot of stenonychosaurus from the judith river oldman formation dinosaur provincial park alberta shows features in the metatarsus that have not previously been recognized these include compression of metatarsal ii and exclusion of the proximal half of metatarsal iii from the anterior dorsal surface of the metatarsus exclusion from the anterior surface of metatarsal iii to this extent is unprecedented among theropods and further underscores the distinctiveness of the sauromithoididae

benthic iron and phosphorus fluxes across the peruvian oxygen minimum zone benthic fluxes of dissolved ferrous iron fe2 and phosphate tpo4 were quantified by in situ benthic chamber incubations and pore water profiles along a depth transect 11 s 80 1000 m across the peruvian oxygen minimum zone omz bottom water o2 levels were 2 mol l 1 down to 500 m water depth and increased to 40 mol l 1 at 1000 m fe2 fluxes were highest on the shallow shelf maximum 316 mmol m 2 yr 1 moderate 15 4 mmol m 2 yr 1 between 250 m and 600 m and negligible at deeper stations in the persistent omz core continuous reduction of fe oxyhydroxides results in depletion of sedimentary fe al ratios tpo4 fluxes were high maximum 292 mmol m 2 yr 1 throughout the shelf and the omz core in association with high organic carbon degradation rates ratios between organic carbon degradation and tpo4 flux indicate excess release of p over c when compared to redfield stoichiometry most likely this is caused by preferential p release from organic matter dissolution of fish debris and or p release from microbial mat communities while fe oxyhydroxides can only be inferred as a major p source on the shallow shelf the benthic fluxes presented here are among the highest reported from similar oxygen depleted environments and highlight the importance of sediments underlying anoxic water bodies as nutrient sources to the ocean the shelf is particularly important as the periodic passage of coastal trapped waves and associated bottom water oxygenation events can be expected to induce a transient biogeochemical environment with highly variable release of fe2 and tpo4

a 38 000 year record of floods and debris flows in the ilo region of southern peru and its relation to el nino events and great earthquakes abstract previous work throughout the ilo region of south coastal peru has documented the existence of flood and debris flow deposits produced by two el nino events evidently much more severe than any in recent history these two events have been dated to ca ad 1300 1400 and ad 1607 08 the late pleistocene to holocene record of older sedimentary deposits in this region is dominated by flood and debris flow deposits of similar scale these older deposits have been described and dated from three coastal alluvial fan sites these deposits which are as old as 38 200 years are dominated by massive debris flow deposits several tens of cm thick typically composed of cobble and boulder sized clasts in a matrix of silty sand with characteristics indicating generation by heavy rainfall in an arid environment twenty two radiocarbon dates and a single infrared stimulated luminescence date show that particularly severe el nino events occurred throughout the late pleistocene and two of three divisions of the holocene with significantly different frequencies the period of greatest activity was during the early holocene when at least six such events took place during a period of ca 3600 years beginning near the end of the younger dryas ca 12 000 years ago one of these events produced a debris flow that may have caused abandonment of the paleo indian site at quebrada tacahuay one of the oldest on the andean coast no severe events took place during the middle holocene between ca 8400 and 5300 years ago when a wide variety of other paleoclimate proxy records indicate that the el nino southern oscillation regime was particularly weak since ca 5300 years ago four of these severe events have taken place the late pleistocene sequence is constrained by only two dates which indicate that at least ten severe events took place between ca 38 200 and 12 900 years ago mechanisms probably responsible for generating these large scale deposits include 1 mega ninos that produced anomalously heavy rainfall along most or all of the central andean coast 2 el ninos that occurred shortly after great earthquakes that produced large amounts of sediment or 3 el ninos that produced anomalously heavy local rainfall the existence of these large scale deposits in the ilo region implies a level of hazard much higher than indicated by the historical record alone

evolution of tethyan phosphogenesis along the northern edges of the arabian african shield during the cretaceous eocene as deduced from temporal variations of ca and nd isotopes and rates of p accumulation abstract the evolution of tethyan phosphogenesis during the cretaceous eocene is examined to try to explain fluctuations of phosphogenesis through time and whether or not they reflect long term changes in ocean circulation or in continental weathering twenty seven time stratigraphic phosphate levels in various tethyan sites covering a time span of about 90 myr from the hauterivian to the eocene were analyzed for 44 ca 42 ca and 143 nd 144 nd in their carbonate fluorapatite cfa fraction p and ca accumulation rates and bulk sedimentation rates were quantified throughout the cretaceous eocene negev sequence to examine how changes in 44 ca 42 ca and 143 nd 144 nd are reflected in the intensity of phosphogenesis a clear cut change occurs in e nd t and 44 ca and in the rates of p and ca accumulation and bulk sedimentation through the time analyzed e nd t is much lower in the hauterivian lower cenomanian 12 8 to 10 9 than in the upper cenomanian eocene 7 8 to 5 9 much lower 44 ca values occur in the hauterivian turonian 0 22 to 0 02 than in the coniacian eocene 0 23 to 0 40 p accumulation rates in the negev steeply increase from 2 k yr 1 in the albian coniacian to 1500 mol cm 2 k yr 1 in the campanian whereas a strong decrease is concomitantly recorded in the rates of ca accumulation and bulk sedimentation in addition distinct e nd t values are shown by the phosphorites of the negev 6 7 to 6 4 and egypt 9 1 to 7 6 during the campanian and by those of the negev 7 8 to 6 3 and north africa 10 1 to 8 9 during the maastrichtian eocene the culmination of p accumulation rates in the negev during the campanian occurring with a high in e nd t and 44 ca and a low in sedimentation rates indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area the abrupt e nd t rise after the cenomanian is attributed to increased incursion of pacific radiogenic water masses into the tethys driven by the late cretaceous global sea level rise the connection between north and south atlantic the global post santonian cooling and the progressive widening of the caribbean threshold all acting in combination to significantly intensify the tethyan circumglobal current tcc it also reflects a weakening of the continental nd signal due to a reduction of exposed landmasses caused by increased flooding of continental shelves high 44 ca values at those times also point to a decrease in weathering ca 2 fluxes and expansion of carbonate sedimentation in shelves both enriching seawater with isotopically heavy ca 2 deep ocean circulation intensified by the post santonian cooling of high latitudes increased p inventory in the tethys basin whereas the strengthened tcc and the folded shelf likely resulted in coastal and topographically induced upwelling supplying p rich intermediate waters to southeastern tethys shelves only in the paleocene eocene following major changes in global circulation produced by narrowing of tethys and widening of the atlantic did phosphogenesis shifts its locus of high intensity to the western atlantic tethys and west african atlantic coasts this change in paleocirculation is expressed by distinctly differing e nd t in the middle east and the north and west african phosphorites suggesting different oceanic p sources and current systems for these two major groups of phosphorites our nd isotope results further suggest a weaker tcc during the mid cretaceous becoming more intense in late cretaceous times they also point to the north pacific ocean as major source of deep water formation for the intermediate deep waters in the tethys basin during the late cretaceous

changes in silicate utilisation and upwelling intensity off peru since the last glacial maximum insights from silicon and neodymium isotopes we combine the stable silicon isotope composition 30si of diatoms and the radiogenic neodymium isotope compositions end of past seawater extracted from the authigenic fraction of the sediments mn fe coatings of particles and benthic foraminifers as well as the radiogenic isotope compositions nd sr of the detrital material itself to reconstruct silicic acid utilisation water mass mixing and upwelling intensity from the same marine sediments in the peruvian upwelling region during the past 20 000 years additionally the sedimentary signals were compared to the water column isotope compositions along the peruvian shelf the dissolved end in the water column ranges from 5 7 to 0 6 the corresponding end signatures of the coatings and the benthic foraminifers of the surface sediments range from 4 5 to 1 8 and from 2 5 to 2 2 respectively the detrital end 87sr 86sr signatures range from 6 3 to 0 0 70508 0 71049 all phases show a trend from more radiogenic end values in the north towards less radiogenic values in the south broadly reflecting local weathering inputs and hinterland geology the end signatures of the coatings extracted from sediment core so147 106kl located in the present day centre of coastal upwelling near 12 s have been essentially constant 1 5 throughout the past 20 000 years while the detrital end 87sr 86sr varied between values of 0 7 0 70620 during the last glacial and 4 5 0 70849 during the late holocene reflecting changes in the origin of the sediment and current transport from a more northerly towards a more southerly source and from overall stronger to weaker upwelling the 30si signature of both total biogenic opal 30siopal and of hand picked diatoms 30sidiatom ranged from 0 3 last glacial to 1 4 late holocene confirming large variations in upwelling intensity driving silicic acid utilisation by diatoms our combined bsio2 mar 30siopal and detrital radiogenic isotope results demonstrate that the strongest el nino southern oscillation conditions off peru of the past 20 ka have prevailed during the past 5 ka

internal tide generation by seamounts ridges and islands a numerical investigation is made into the generation of semidiurnal internal tides by tidal flow over steep topographic features in the deep ocean a fully three dimensional free surface nonlinear hydrostatic model the princeton ocean model is used with real stratification representative tidal forcing and gaussian shaped seamounts ridges and islands for the topography the efficiencies of the different topographies in extracting energy from the barotropic tide and in generating an internal tide are considered each topography produces an internal tide characterized by signals propagating away from the feature as beams that follow internal wave characteristic paths the strength of the signals however varies markedly for different topographies this is largely attributed to the way in which the barotropic tide interacts with the three dimensional topography internal wave generation requires a significant vertical displacement of stratified water by the barotropic tide as it flows over topography it is found that for symmetric seamounts and islands the barotropic flow tends to go around the feature producing only a weak internal tide when elongated into a ridge barotropic flow is forced across isobaths generating an energetic internal tide changing the horizontal aspect ratio of the topography from 1 1 a seamount to 3 1 a ridge increases the resulting baroclinic energy flux by nearly an order of magnitude the slope of the topography relative to that of the internal wave characteristics is also shown to be important with strongest generation occurring at regions of critical or supercritical topographic slope

internal tides as a major process in amazon continental shelf fine sediment transport abstract the description of hydrodynamics associated with the extensive reef system on the shelf break adjacent to the amazon river is still a challenge for ocean sciences despite the discharge of more than one billion tons of cohesive sediment per year the outer continental shelf of the world s largest river presents very low concentrations of suspended sediment near the bottom and an absence of modern fine sediment deposits nearly one hundred kilometers before the shelf break the offshore limit of the subaqueous delta consists of a sigmoidal clinoform standing between 40 and 70 m in depth a depositional feature that cannot be explained solely by estuarine like gravitational circulation this paper aims to test the hypothesis that internal tides have a major role in the control of offshore fine sediment transport for that we implement a set of tridimensional non hydrostatic and high resolution up to 2 m vertical and 2 km horizontal delft3d models the experiments showed that even disregarding river plume buoyancy wind drag superficial waves and ocean currents the exclusive interaction between barotropic tidal currents bathymetry and the stratification structure of the ocean is capable of generating asymmetrical current patterns compatible with modern deposition the maximum shelf slope and the relative depth between the outer shelf and the pycnocline represent the main factors influencing the generation and shoreward propagation of internal tides over time spring neap cycles are eventually capable of reverting cross shore subtidal transport tendencies while seasonal variability in ocean stratification modulates the intensity of baroclinic processes

internal bores and breaking internal tides on the oregon continental slope abstractobservations of breaking internal tides on the oregon continental slope during a 40 day deployment of 5 moorings along 43 12 n are presented remotely generated internal tides shoal onto the slope steepen break and form turbulent bores that propagate upslope independently of the internal tide a high resolution snapshot of a single bore is captured from lowered acoustic doppler current profilers ladcp ctd profiles in a 25 h time series at 1200 m the bore is cold salty over 100 m tall and has a turbulent head where instantaneous dissipation rates are enhanced e 10 6 w kg 1 and sediment is resuspended at the two deepest slope moorings 1452 and 1780 m similar borelike phenomena are observed in near bottom high resolution temperature time series mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present w kg 1 and m s 1 and observed internal tides are energetic enough to drive these enhanced dissipation rates globally the authors estimate

comment on a numerical comparison of 2d resistivity imaging with 10 electrode arrays by t dahlin and b zhou ten well known electrode configurations were compared on the basis of 2d inversion results by dahlin and zhou 2004 a similar comparison was made earlier by candansayar and basokur 2001 however in the latter paper the authors proposed joint inversion of the leftand right sided pole dipole arrays called two sided three electrode arrays and concluded that the proposed technique gives a better image of the subsurface than that obtained using four electrode arrays wennerschlumberger and dipole dipole they used synthetic and field data to validate their result it is well known that it is not possible to get the same number of data points for every array for instance the number of data points with a four electrode array such as a wenner configuration cannot be greater than the number with a three electrode array such as the pole dipole configuration for the same number of electrodes in a multi electrode system for example if we have a multi electrode system with 10 electrodes and we scan all possible a and n in the imaging survey the numbers of data points for wenner wenner schlumberger and pole dipole configurations are 12 16 and 36 respectively the number of data points for a wenner configuration cannot be greater than the number of data for the pole dipole configuration and the schlumberger configuration or we can say wenner schlumberger array for a multi electrode system for the same multi electrode system however in the paper by dahlin and zhou 2004 the numbers of data for wenner wenner schlumberger and poledipole configurations are 990 780 and 715 respectively for survey 3 table 1 p 383 it seems that the authors intentionally used a greater number of wenner configuration data points than the other arrays given in their paper and they forced the inversion of wenner configuration data to give better results than the inversion of the other configurations

coastal upwelling and atmospheric co2 changes over the last 400 000 years peru abstract a transfer function relating diatom assemblages in surface sediments and primary production in the photic zone was used to calculate variations in primary production in hole odp leg 112 site 681a over the last 400 kyr primary production off central peru was enhanced during peak glaciations and it decreased during peak interglacials but low and high production periods also occurred in both glacials and interglacials the close resemblance of the primary production curve off peru to the atmospheric co2 vostok record suggests a relationship between the peruvian neritic biological pump and atmospheric pco2

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites