compression behaviour of minerogenic low energy intertidal sediments existing geotechnical approaches that describe volumetric changes in intertidal sediments in response to applied vertical effective stresses are limited by a lack of empirical research into their one dimensional compression behaviour in this paper we address this deficiency by presenting the results of an investigation into the compression behaviour of minerogenic low marsh and tidal flat sediments we have tested samples of these sediment types obtained from greatham creek cowpen marsh tees estuary uk analysis of physical properties and oedometer compression tests demonstrates that contrary to the implicit assumptions of existing models the surface sediments studied are overconsolidated structural variability between samples arises due to sedimentological factors notably variations in organic content we attribute overconsolidation to tidal exposure and falls in groundwater level that permit desiccation and cause capillary suction stresses greater rates of compression with respect to effective stress occur in sediments with higher initial voids ratios and more open unstable initial structures variability in structure decreases with application of higher effective stresses due to the destructuration of the sediments which also creates increased homogeneity of compression behaviour under higher effective stresses we subsequently develop a new conceptual framework to describe compression behaviour in minerogenic intertidal sediments that incorporates overconsolidation we advocate a statistical approach that accounts for structural variability and variations in compression behaviour at effective stresses less than and greater than the yield stress we argue that our conceptual framework is broadly applicable to minerogenic intertidal sediments at different locations and burial depths within holocene stratigraphic sequences providing site specific compression data are collected inter site transfer and application of measured material properties should not be undertaken due to local variations in compression behaviour resulting from varying ecological sedimentological geochemical climatic geomorphic and hydrographic conditions the individual characteristics of different field locations should be carefully considered before the suggested framework is routinely applied

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

effects of firn ventilation on isotopic exchange a new model of isotopic diffusion in the upper few meters of firn tracks the isotopic composition of both the ice matrix and the pore space vapor through time in two dimensions stable isotopes in the vapor phase move through the firn by diffusion along concentration gradients and by advection wind driven ventilation carries atmospheric water vapor into the firn where it mixes with existing pore space vapor unlike previous models our model allows disequilibrium between pore space vapor and the surrounding snow grains we also calculate the isotopic effects of ventilation driven sublimation and condensation in the firn model predictions of isotopic diffusion in firn compare favorably with existing diffusion models model results quantify what other investigators have suggested isotopic change in the upper few meters is more rapid than can be explained by the whillans and grootes 1985 model isotopic equilibration with atmospheric vapor is an important component of post depositional isotopic change and ventilation enhances isotopic exchange by creating regions of relatively rapid sublimation and condensation in the firn

snow isotope diffusion rates measured in a laboratory experiment the diffusion of stable water isotopes in snow was measured in two controlled laboratory experiments two batches of snow of different isotopic composition were stacked alternately with varying layer thicknesses the stack was stored in a freezer room at constant temperature for several months and sampled at regular intervals to analyse the diffusion measured isotope profiles were fitted to a theoretical model with diffusion length as the fit parameter in the first experiment we observed a difference in diffusion rates between layers of different thicknesses which is likely caused by layers of snow not being in proper contact with each other in the second experiment we found very good agreement between measurements and model results the measured diffusivity is compared with theory in which we mainly focus on the temperature dependence of the ice vapour fractionation factors this temperature dependence is slightly different for the different isotopes of water which leads to a difference in diffusion rates we illustrate how our set up can be used to measure the ratio between ice vapour fractionation factors of oxygen 18 and deuterium which determine the relation between the difference in diffusion and the firn temperature

facies analyses and volcanic setting of the giant neves corvo massive sulfide deposit iberian pyrite belt portugal in the iberian pyrite belt volcanic rocks are relatively scarce accounting for approximately only 25 of the geologic record with the remaining 75 consisting of sedimentary units this association is very clear in the host succession to the neves corvo massive sulfide deposit in portugal the neves corvo host succession comprises the products of explosive and effusive rhyolitic eruptions intercalated with mudstone that records a submarine below wave base environment and provides precise biostratigraphic age constraints the first and second volcanic events involved eruptions at local intrabasinal vents the first event generated thick beds of fiamme breccia that are late famennian in age the fiamme were originally pumice clasts produced by explosive eruptions and were subsequently compacted the second event was the late strunian latest famennian effusion of rhyolitic lava that was pervasively quench fragmented the third and final event is younger than the massive sulfide deposits poorly represented in the mine area and minor compared with the two other events the integration of biostratigraphic data with the volcanic facies architecture indicates that the neves corvo ore deposits are similar in age to the late strunian rhyolitic lava although regionally the iberian pyrite belt is essentially a sedimentary succession ore formation at neves corvo can be closely linked to discrete volcanic events that produced a relatively narrow range of volcanic facies

experimental determination of the diffusion rate of deuterated water vapor in ice and application to the stable isotopes smoothing of ice cores abstract the stable isotope records of d and 18o in ice cores show that the isotopic gradients are smoothed out with time by diffusion transport of hydrogen and oxygen atoms through solid ice is slow whereas water vapor diffusion through the interconnected porosity is much faster smoothing occurs preferentially in the upper layers of firn where the density is lowest and is responsible for the gradual alteration of the isotopic stratigraphy results for the diffusion of water vapor in ice are presented they were obtained from laboratory experiments with diffusion couples prepared using artificial snow with different d h values the samples were allowed to diffuse for about one year at a controlled temperature before being cut into thin sections and analyzed with a mass spectrometer the effects of both temperature and density were investigated the measured diffusion coefficients are fully consistent with water vapor diffusion through the ice porosity the computed values are less than the diffusion coefficient of hdo in free air and imply a tortuosity factor in the range 3 2 6 5 depending on the sample density the influence of the grain sizes on the timescale of the isotopic homogenization between the vapor phase and the ice matrix was studied we show that for grain sizes up to 1 mm in diameter solid diffusion within the grains is not a limiting factor and therefore the isotopic equilibrium between the vapor and the solid phases can be considered as immediate the diffusion model developed to compute the diffusion coefficients was further applied to investigate the real case of isotope smoothing in ice cores the smoothing rate is highly dependent on the wavelength of the isotopic signal linked to the accumulation rate and on temperature finally the model was applied to tritium deposition in antarctica from a continuous record of artificial fallout at the south pole 1954 1978 the result shows that in spite of large gradients the initial distribution underwent only limited smoothing that did not exceed 10

spectroscopic analysis of global tide gauge sea level data summary yearly and monthly tide gauge sea level data from around the globe are fitted to numerically generated tidal data to search for the 18 6 yr lunar nodal tide and 14 month pole tide both tides are clearly evident in the results with amplitudes and phases that are consistent with a global equilibrium response global atmospheric pressure data are fitted to global monthly sea level data to study the response of the ocean to pressure fluctuations the global response of sea level to pressure is found to be inverted barometer at periods greater than 2 months a large coherence at 437 days between pressure and sea level data is found for the north sea baltic sea and the gulf of bothnia the results are not entirely conclusive but they tend to support o connor s 1986 suggestion that the apparent enhanced pole tide in these basins may be due to meteorological forcing rather than to a basin scale resonance finally global averages of tide gauge data after correcting for the effects of post glacial rebound on individual station records reveal an increase in sea level over the last 80 yr of between 1 1 and 1 9 mm yr as part of the process of removing the effects of post glacial rebound we fit those effects to the global tide gauge data and obtain very good agreement with results predicted from post glacial rebound models this tends to support the post glacial model results and it suggests that the global tide gauge data are indeed capable of resolving changes in sea level at the mm yr level

experimental determination of snow sublimation rate and stable isotopic exchange snow sublimation is a fundamental process that affects the snow crystal structure and is important for ice core interpretation remote sensing snow hydrology and chemical processes in snow prior studies have shown that sublimation can change the isotopic content of the remaining snow these studies have inferred sublimation rates using field data and were unable to control many of the environmental parameters that determine sublimation rate e g temperature relative humidity snow microstructure we present sublimation rate measurements on snow samples in the laboratory where we have controlled many of these parameters simultaneously we use the same experimental apparatus to determine sublimation rate investigate the isotopic effects of sublimation and study the isotopic exchange between vapor and solid our results suggest that pore spaces in snow are almost always at saturation vapor pressure undersaturation may be possible in large pore spaces or in regions of rapid interstitial airflow we present a revised formulation for determining the mass transfer coefficient for snow as a linear function of reynolds number hm 0 566re 0 075 estimate the fractionation coefficient for sublimating snow and provide evidence for isotopic exchange between vapor and solid

formation of chocolate tablet boudins in a foreland fold and thrust belt a case study from the external variscides almograve portugal abstract chocolate tablet boudins of quartzite are restricted to steep limbs of d 1 folds along the sw coast of portugal the chocolate tablet geometry results from older vertical and younger horizontal quartz veins both sets of veins developed during similar conditions by extension fracture in pre existing necked domains 1 both veins show stretched crystal fibers 2 the boudin aspect ratio is the same in vertical 3 0 1 4 and in horizontal sections 2 9 1 2 3 temperatures obtained from fluid inclusions are similar 200 20 for vertical and 230 22 c for horizontal veins and are compatible with temperatures obtained from illite crystallinity ca 200 ca 250 c given thermal equilibrium between the host rock and the precipitating fluid the chocolate tablet boudins formed close to the metamorphic peak we interpret that the vertical veins developed after the limbs of the d 1 folds had attained their steep attitude and the orientation of the greatest and intermediate principal strain axes had interchanged subsequently the initial strain field was restored and opening of horizontal veins led to the chocolate tablet geometry the direction of the main shortening direction was constant from the initial buckling stage via isoclinal folding and during all boudinage stages

u pb geochronology and petrology of the late paleozoic gil marquez pluton magmatism in the variscan suture zone southern iberia during continental collision and the amalgamation of pangea the origin of plutonic complexes that stitch suture zones developed during collision is not well understood in southern iberia the pulo du lobo suture zone pdlz is intruded by the syn to postcollisional gil marquez pluton gmp thought to be part of the sierra norte batholith u pb la icpms zircon data on various phases of the gmp yield from oldest to youngest 1 a 354 4 7 6 ma unfoliated gabbro 2 a 345 6 2 5 ma foliated intermediate phase 3 a 346 5 5 4 ma unfoliated porphyritic granite 4 a 335 1 2 8 ma unfoliated biotite granite this sequence is consistent with cross cutting relationships observed in the field the range in ages is consistent with interpretations that the gmp is part of the composite ca 350 308 ma snb inherited ages preserved in the gmp intermediate and felsic phases indicate that its magmas traversed through south portuguese zone and pdlz crust during emplacement the ca 345 ma emplacement of the late kinematic foliated intermediate phase constrains the age of late stage strike slip deformation within the pdlz and the lack of a foliation in the older gabbro indicates that is was not proximal to a shear zone neither at the time of emplacement nor during its subsequent history the unfoliated porphyritic granite and unfoliated biotite granite cut the foliation of the intermediate phase indicating emplacement during the waning stages of collision while the ca 335 ma biotite granite intrudes the santa ira flysch thereby providing a tight constraint for the latest stage of deformation in the pdlz

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

development of a foraminifera based transfer function in the basque marshes n spain implications for sea level studies in the bay of biscay abstract in order to reconstruct former sea level we have developed a foraminifera based transfer function using three models based on a modern dataset of 59 samples and 23 species obtained from four basque marshes in northern spain the relationship between observed and foraminifera predicted elevation illustrated the strong performance of the transfer function r 2 jack ranges from 0 74 to 0 81 these results indicated that precise reconstructions of former sea levels are possible error ranges from 0 11 to 0 19 m the transfer function was used to calibrate the foraminiferal assemblages collected from a 50 cm salt marsh core we placed the foraminifera based reconstructions into a temporal framework using 137 cs pb concentrations and 210 pb derived sediment accumulation rates the resulting relative sea level curve is in good agreement with regional tide gauge data both instrumental data and microfossil records suggest a rate of relative sea level rise of approximately 2 mm yr 1 for the 20th century

controlled experiments on the diffusion rate of stable isotopes of water in artificial firn we studied the diffusion rate of stable isotopes of water ice in a controlled laboratory experiment where isotopically different layers of fabricated firn were stacked this experiment was done in order to study the diffusion rate between the isotopically different layers and to compare the measurements with forward calculated diffusion rates of the fabricated firn stack using three different analytical and numerical methods the layers varied in thickness within the stack and the studied period includes variations in firn temperature we sampled the firn stack on five different dates along the 144 day long experiment we obtained a quantitatively good match between the calculated and measured diffusion rates with a root mean square similarity of 67 80 in the depth averaged diffusion rates despite the good average match we found some qualitative discrepancy between our calculations and our measurements the calculated diffusion rates predict 5 faster isotopic decay of thinner layers and 13 slower decay of thicker layers than our measurements show we speculate that grain size and grain fabric may influence the tortuosity of the firn pack and that the current generalization of tortuosity being a function of firn density as the only free parameter is an oversimplification

interseismic strain accumulation and anthropogenic motion in metropolitan los angeles 1 we use global positioning system gps geodesy and synthetic aperture radar sar interferometry to distinguish between interseismic strain accumulation and anthropogenic motion in metropolitan los angeles we establish a relationship between horizontal and vertical seasonal oscillations of the santa ana aquifer use this relationship to infer cumulative horizontal anthropogenic motions from cumulative vertical motions caused by water and oil resource management and estimate horizontal interseismic velocities corrected for anthropogenic effects vertical anthropogenic rates from 1992 to 1999 are slower than 3 mm yr 1 in the santa ana and san gabriel aquifers and faster than 5 mm yr 1 in the chino aquifer and in many oil fields inferred horizontal anthropogenic velocities are faster than 1 mm yr 1 at 18 of 46 gps sites northern metropolitan los angeles is contracting with the 25 km south of the san gabriel mountains shortening at 4 5 1 mm yr 1 95 confidence limits the thrust fault in an elastic edge dislocation model of the observed strain is creeping at 9 2 mm yr 1 beneath and north of a position 6 2 km deep and 8 8 km north of downtown los angeles the model fault is near the los angeles segment of the puente hills thrust but south of the sante fe springs segment of the thrust disagreement between the 6 km locking depth in the model and the 15 km seismogenic depth inferred from earthquakes suggests that the elastic continuum model may be unsatisfactory models with different stiffnesses of sedimentary basin and crystalline basement must be investigated

present day trends of vertical ground motion along the coast lines vertical ground motion vgm rates stand as crucial information either for predicting the impact of the actual sea level rise along low lying coasts or refining geodynamic problems because present day vgm rates have a magnitude smaller than 10 mm yr they remain challenging to quantify and often elusive we focus on the quantification of global scale vgm rates in order to identify global or regional trends we computed vgm rates by combining tide gauges records and local satellite altimetry which yield a new dataset of 634 vgm rates we further compare this database to previous studies that use geodetic techniques and tide gauges records in order to evaluate the consistency of both our results and previous ones the magnitudes differ by less than 5 mm yr and similar subsidence and uplift general tendencies appear even if the asset of our database stands in the greater number of sites the combination of all studies each with different pros and cons yields a hybrid dataset that makes our attempt to extract vgm trends more robust than any other independent study fennoscandia the west coast of north america and the eastern coast of australia are uplifting while the eastern coast of north america the british isles and western europe the eastern mediterranean sea japan and the western coast of australia are subsiding glacial isostatic adjustment gia is expected to provide a major contribution to the present day signal aside from fennoscandia observed vgm often depart from the gia model predictions of peltier 2004 this either results from an underestimate of the model predictions or from the influence of other processes indeed the influence of the geodynamic setting appears in particular along the coasts of western north america or japan where the alternation of transform faults and subduction zones makes it possible to assign contrasted behaviours to the local geodynamic context local mechanisms like anthropogenic processes or sediment compaction also contribute to vgm this remains true for the critical cases of venice the gulf of mexico the ganges delta and the maldives which are particularly exposed to the current sea level rise

ore deposit types and tectonic evolution of the iberian pyrite belt from transtensional basins and magmatism to transpression and inversion tectonics abstract a new interpretation of the structural evolution of the iberian pyrite belt ipb and volcanogenic massive sulfide mineralization vms is presented in this work based on a review of the ore deposit types the analysis of the hosting volcanic sequences and the tectonic evolution the vms deposits of the ipb are hosted by volcanic and siliciclastic rocks four main volcano sedimentary sequences vsc from vsc0 to vsc3 have been assumed the main deposits being located in the vsc0 and at the top of the vsc2 we have defined three main sectors oriented approximately e w and hosting the vms deposits in the northern sector which is mostly located in spain graben basins and local pull aparts are the main structures in this sector two belts can be distinguished the deposits being located at the top of the vsc2 felsic volcanism rio tinto type ipb deposits in the central sector both in spain and portugal half graben basins are the most common structures and the deposits are mostly located in the vsc0 andesitic volcanic sedimentary sequence tharsis type ipb deposits in the southern sector which is only located in portugal a graben basin with a pull apart is again the main structure and the deposits are located in black slates and at the top of a felsic volcanism strunian in age vsc0 the deposits located in graben basin with a pull apart are essentially felsic volcanic hosted with some siliciclastic material mostly black shales by contrast those located in half graben basins are mainly hosted by black shales with minor amounts of andesitic rocks the tectonic evolution shows that as a result of a counterclockwise rotation of the stress axes the formation of the ipb and the associated ore deposits took place during several episodes from transtension with the development of both graben with pull aparts and half graben basins through left lateral e w shearing to transpression at the beginning of the transtensional process several extensional roughly e w trending faults that developed graben and half graben basins were generated and the first volcanic andesite rhyolite rocks vsc0 formed the tharsis type deposits mainly hosted by black slates with some volcanic rocks were formed in the central sector while the neves corvo type deposit hosted by black slates and felsic volcanism formed in the southern one after a period characterized by barren mafic volcanism vsc1 a sinistral shear affected the previous fractures due to the stress axis rotation and felsic crustal volcanism started vsc2 rhyolites and dacites were particularly abundant in two graben basins which developed rollovers in pull apart zones forming the rio tinto type deposits in the northern sector the thermal increase associated with vsc0 and vsc2 gave rise to the development of crustal scale hydrothermal convective cells which generated both types of deposits after a barren vsc3 felsic volcanism subsequently during the variscan transpressional phase the e w extensional faults were reactivated as reverse faults affecting the volcanic sequence vsc0 to vsc3 as well as the interbedded sedimentary rocks mostly black shales as has been recognized at the rio tinto deposit buttressing must have played a significant role in the geometry of inverted structures and the vms ores were intensely recrystallized it should be emphasized that this new regional geological model for the ipb is an approach to provide a better insight into vms deposits and could be a key point for further studies providing a new tool to improve knowledge of the vms mineralizations and exploration guidelines elsewhere in the ipb

diverse slow slip behavior at the hikurangi subduction margin new zealand 1 the installation of a continuous gps cgps network in new zealand since 2002 has enabled the discovery of 15 slow slip events at the hikurangi subduction margin our analysis and interpretation of the cgps data reveal a marked diversity in characteristics of slow slip events sses in the north island with durations varying from 6 days to 1 5 years equivalent moment release between mw 6 3 7 2 and recurrence intervals of repeating sses on the order of 2 years to more than 5 years the duration and magnitude characteristics of hikurangi sses appear to be related to the depth where they occur the deepest longest duration and largest sses occur at the southern hikurangi margin near the downdip limit of deep down to 40 km depth strong interseismic coupling the shallowest shortest duration smallest and most frequent sses occur at the northern and central hikurangi margin near the downdip limit of unusually shallow 10 15 km depth interseismic coupling the direction of slip on the interface in the hikurangi sses is consistent with slip partitioning at the hikurangi subduction margin we also show that moment accumulation rates on the interface for the time periods between sses are 40 higher than for the period of more than a decade averaging through the sses indicating that sses compose a major portion of the overall moment release budget of the hikurangi subduction interface

regional sea level trends in new zealand 1 in terms of sea level data sets able to be used for long term sea level trend analysis the southern hemisphere is a data sparse region of the world new zealand lies in this region presently having four major port data sets used for such trend analysis this paper describes the process followed to compute new sea level trends at another six ports each with very discontinuous tide gauge records in each case the tide gauge has previously only been used for precisely defining an historical local mean sea level msl datum the process used involved a comparison of the old msl datum with a newly defined datum obtained from sea level data covering the last decade a simple linear trend was fitted between the two data points efforts were then made to assess possible bias in the results due to oceanographic factors such as the el nino southern oscillation enso cycle and the interdecadal pacific oscillation ipo this was done by taking the longer time series from the four major ports and assessing the spatially coherent variability in annual sea level using the dominant principal component from an empirical orthogonal function eof analysis the average relative sea level rise calculated from these six newly derived trends was 1 7 0 1 mm yr 1 a result that is completely consistent with the analysis of the long term gauge records most importantly it offers a relatively simple method of improving our knowledge of relative sea level trends in data sparse regions of the world

geochemical discrimination of hydrothermal and igneous zircon in the iberian pyrite belt spain intensely altered felsic volcanic subvolcanic rocks located at vhms footwalls in the aznalcollar mining district iberian pyrite belt spain contain both igneous and hydrothermal zircon grains according to textural evidence in order to discriminate their respective features we present a detailed description showing that these contrasting textural characteristics can be correlated with distinctly different chemical compositions in comparison with igneous zircons emp study shows that hydrothermal zircon grains have lower sio2 and zro2 contents whereas they are enriched in p2o5 al2o3 y2o3 and cao on the other hand la icpms study shows that the ree patterns of hydrothermal zircons strongly differ from those of igneous ones in that a hydrothermal zircons are highly enriched in ree b they display patterns with maximum values for intermediate ree often showing tbn ybn ratios 1 and c hydrothermal zircon grains do not display ce or eu anomalies which are widespread in igneous zircons we conclude that these chemical differences are consistent with zircon xenotime solid solution having reached here values close to a 10 mol which represent the maximum possible degree of xenotime substitution according to the available experimental data the absence of ce and eu anomalies is explained according to the particular characteristics of the hydrothermal environment during intense footwall alteration involving temperatures up to 350 c and destruction of plagioclase or other eu 2 hosting minerals we suggest that discrimination of hydrothermal zircons may open new ways in dating hydrothermal zircons in vhms and other mineralized areas related to intense hydrothermal alteration

effect of accumulation rate on water stable isotopes of near surface snow in inland antarctica 1 postdepositional changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the east antarctic ice divide near dome fuji water stable isotopes major ion concentrations and tritium contents of three 2 4 m deep pits were measured at high resolution 2 cm temporally the snow pits cover the past 50 years with snow accumulation rates in the range of 29 41 kg m 2 a 1 around dome fuji oxygen isotopic profiles in the three pits do not show annual fluctuations but instead exhibit multiyear cycles these multiyear cycles are lower in frequency at dome fuji as compared with the other two sites peaks of water stable isotopes in the multiyear cycles correspond to some ion concentration minima in the pits although such relationships are not observed in coastal regions we propose that the extremely low accumulation environment keeps the snow layer at the near surface which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation sublimation we estimate that oxygen isotopic ratios could be modified by 10 and that the original seasonal cycle could be completely overprinted under the accumulation conditions at dome fuji moreover stake measurements at dome fuji suggest that the large variability in snow accumulation rate is the cause of the multiyear cycles

troposphere mapping functions for gps and very long baseline interferometry from european centre for medium range weather forecasts operational analysis data 1 in the analyses of geodetic very long baseline interferometry vlbi and gps data the analytic form used for mapping of the atmosphere delay from zenith to the line of site is most often a three parameter continued fraction in 1 sin elevation using the 40 years reanalysis era 40 data of the european centre for medium range weather forecasts for the year 2001 the b and c coefficients of the continued fraction form for the hydrostatic mapping functions have been redetermined unlike previous mapping functions based on data from numerical weather models isobaric mapping functions niell 2000 and vienna mapping functions vmf boehm and schuh 2004 the new c coefficients are dependent on the day of the year and unlike the niell mapping functions niell 1996 they are no longer symmetric with respect to the equator apart from the opposite phase for the two hemispheres compared to vmf this causes an effect on the vlbi or gps station heights that is constant and as large as 2 mm at the equator and that varies seasonally between 4 mm and 0 mm at the poles the updated vmf based on these new coefficients and called vmf1 hereinafter yields slightly better baseline length repeatabilities for vlbi data the hydrostatic and wet mapping functions are applied in various combinations with different kinds of a priori zenith delays in the analyses of all vlbi international vlbi service for geodesy and astrometry ivs r1 and ivs r4 24 hour sessions of 2002 and 2003 the investigations concentrate on baseline length repeatabilities as well as on absolute changes of station heights

a new 3d geological model and interpretation of structural evolution of the world class rio tinto vms deposit iberian pyrite belt spain abstract a new 3d geological model and interpretation of structural evolution of the rio tinto world class vms deposit are presented in this work the rio tinto volcanogenic massive sulfide vms deposit is located in the spanish segment of the iberian pyrite belt and is hosted by felsic porphyritic volcanic rocks and tuffs computer generated 3d modeling of the different orebodies and host rocks has been carried out using data from around 3000 drill core logs allowing us to build 93 cross sections and 6 plants both 50 m spacing this has enabled us to recognize the geometry and relationships between the mineralization and the earliest carboniferous transtensional tectonics through the development of an extensional pull apart basin with two sub basins separated by the nw se trending eduardo fault the sub basins cerro colorado and san dionisio were limited by two e w strike slip faults the northern and southern faults and bounded in the east and west by the nw se trending nerva and western faults respectively the generated pull apart basin was first filled by a basaltic magmatism of mantle origin and later following the deposition of the intermediate complex sedimentary unit by rhyodacitic volcanic rocks of crustal origin the evolution of the subsiding basins caused the development of an e w oriented rollover anticline that affected these filling rocks as a result of a counterclockwise rotation of the stress axes the primitive pull apart basin evolved into a basin affected by e w transtensional sinistral shearing its northern and southern limits were favorable areas for increased hydrothermal fluid flow which gave way to the huge concentration of vms mineralization located near the limits the northern and to a lesser degree the southern extensional faults thus become channel areas for feeding and discharging of the vms and stockwork ores the main mineralizing period was related to this stage subsequently during the variscan transpressional phase the e w extensional faults were reactivated as inverse faults affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit fault propagation folds developed above these faults affecting the massive sulfides the transition series and the culm flysch sediments with buttressing playing a significant role in the geometry of tectonically inverted structures the vms mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series and a dextral reactivation of the nw se trending faults also developed finally it should be emphasized that this new 3d geological model is an approach to provide a better insight into the 3d structure of the world class vms rio tinto deposit and could be a key point for further studies providing a new tool to increase knowledge of the vms mineralizations and exploration guidelines elsewhere in the ipb

foraminifera in a new zealand salt marsh and their suitability as sea level indicators abstract vertical distributions of live and dead foraminiferal abundances are investigated in a salt marsh at pounawea in southeastern new zealand for potential use in holocene sea level reconstructions statistical analyses are conducted to determine whether dead foraminiferal abundances can be utilised as a proxy for elevation in southeastern new zealand it is concluded that dead salt marsh foraminifera which can predict elevations to within 5 cm or better are precise sea level proxies holocene sea level reconstructions along the tectonically stable catlins coast based on fossil salt marsh foraminifera can therefore serve as a potential baseline tool to estimate relative vertical tectonic displacement along tectonically active coasts in new zealand

improving the quality of satellite altimetry data over continental shelves 1 satellite altimetry has proven to be a useful tool to study oceanic processes in the deep ocean over continental shelves however the aliasing of unresolved high frequency signals of tidal and wind induced origin is the source of long wavelength errors that corrupt altimetry measurements and limit their use in shallow waters in 2005 ssalto duacs performed a complete reanalysis of altimeter data to accommodate the latest tidal model got2000 and a correction for the aliased high frequency signals using a hydrodynamic model mog2d g this paper examines the quality and the performance of the newly released altimetry data over the northwest european shelf this region is known for complex tides and for frequent storm surges the newly corrected maps of sea level anomalies were compared with a previous altimetry product residual tidal aliasing was analyzed and the impact of mog2d g and got2000 models was assessed altimeter records were compared with tide gauge measurements this research showed a significant reduction in the contamination of data by high frequency aliasing achieved through the use of the aforementioned models however aliased shallow water tidal constituents pose a serious problem and it is obvious that future tidal corrections should feature local tides nonaliased physical sea level variability was also studied focusing on interannual seasonal and intra annual periods from 20 days to 1 year modes the magnitudes and the contributions of each mode to the total variance were estimated it was demonstrated that the newly corrected data can successfully be used to study the variability of sea level over continental shelves

water isotope diffusion rates from the northgrip ice core for the last 16 000 years glaciological and paleoclimatic implications abstract a high resolution 0 05 m water isotopic record o 18 is available from the northgrip ice core in this study we look into the water isotope diffusion history as estimated by the spectral characteristics of the o 18 time series covering the last 16 000 years the diffusion of water vapor in the porous medium of the firn pack attenuates the initial isotopic signal predominantly having an impact on the high frequency components of the power spectrum higher temperatures induce higher rates of smoothing and thus the signal can be used as a firn paleothermometer we use a water isotope diffusion model coupled to a steady state densification model in order to infer the temperature signal from the site assuming the accumulation and strain rate history as estimated using the gicc05 layer counted chronology and a dansgaard johnsen ice flow model the temperature reconstruction accurately captures the timing and magnitude of the bolling allerod and younger dryas transitions a holocene climatic optimum is seen between 7 and 9 ky b2k with an apparent cooling trend thereafter our temperature estimate for the holocene climatic optimum points to a necessary adjustment of the ice thinning function indicating that the ice flow model overestimates past accumulation rates by about 10 at 8 ky b2k this result is supported by recent gas isotopic fractionation studies proposing a similar reduction for glacial conditions finally the record presents a climatic variability over the holocene spanning millennial and centennial scales with a profound cooling occurring at approximately 4000 years b2k the new reconstruction technique is able to provide past temperature estimates by overcoming the issues apparent in the use of the classical o 18 slope method it can at the same time resolve temperature signals at low and high frequencies

nineteenth and twentieth century sea level changes in tasmania and new zealand positive deviations from linear sea level trends represent important climate signals if they are persistent and geographically widespread this paper documents rapid sea level rise reconstructed from sedimentary records obtained from salt marshes in the southwest pacific region tasmania and new zealand a new late holocene relative sea level record from eastern tasmania was dated by ams14c conventional high precision and bomb spike 137cs 210pb stable pb isotopic ratios trace metals pollen and charcoal analyses palaeosea level positions were determined by foraminiferal analyses relative sea level in tasmania was within half a metre of present sea level for much of the last 6000 yr between 1900 and 1950 relative sea level rose at an average rate of 4 2 0 1 mm yr during the latter half of the 20th century the reconstructed rate of relative sea level rise was 0 7 0 6 mm yr our study is consistent with a similar pattern of relative sea level change recently reconstructed for southern new zealand the change in the rate of sea level rise in the sw pacific during the early 20th century was larger than in the north atlantic and could suggest that northern hemisphere land based ice was the most significant melt source for global sea level rise

use of the ela as a practical method of monitoring glacier response to climate in new zealand s southern alps in lieu of direct glacier surface mass balance measurements equilibrium line altitudes elas have been measured over a 28 year period at 50 selected glaciers distributed along the glacierized length of new zealand s southern alps analysis of the data shows that elas are a useful measurement of glacier response to annual climate fluctuations although there is much variability in the degree of response between glaciers in any given year comparisons of individual glacier annual ela with the mean for all annual elas of the southern alps show a large variation of individual glacier response with coefficients of variation r 2 ranging from 0 53 to 0 90 the ela data show detailed but qualitative annual mass balance variations on both regional and individual glacier scales the ela record closely predicts glacier termini responses that follow after appropriate response time delays the recorded variability in climate response for the southern alps suggests no single glacier is truly representative for detailed studies of glacier climate relationships and that a large number of ela measurements may be as good an indicator of climate as a few mass balance measurements given the appropriate mass balance gradient mass balance values may be calculated for any of the monitored glaciers

an updated analysis of long term sea level change in new zealand 1 the original analysis of long term sea level change in new zealand is updated with a new and extended analysis in this new analysis the original hourly sea level data have been re examined to remove obvious errors that were still present new data covering the period 1989 2000 has been added and the sea level record for wellington extended by the inclusion of recently discovered data covering the years 1891 1893 these new results indicate that relative sea levels in new zealand have been rising at an average rate of 1 6 mm yr over the last 100 years a figure that is not only within the error bounds of the original determination but when corrected for glacial isostatic effects has a high level of coherency with other regional and global sea level rise determinations there continues to be no evidence of any acceleration in relative sea levels over the record period

p and sv velocity structure of the south portuguese zone fold and thrust belt sw iberia from traveltime tomography imaging the architecture of the shallow crust of the south portuguese zone fold and thrust belt is essential to extend surface mapped geological information to depth and to help in developing model

the relative utility of foraminifera and diatoms for reconstructing late holocene sea level change in north carolina usa abstract foraminifera and diatoms preserved in salt marsh sediments have been used to produce high resolution records of holocene relative sea level rsl change to determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in north carolina usa regional scale transfer functions were developed using foraminifera diatoms and a combination of both multi proxy from three salt marshes oregon inlet currituck barrier island and pea island we evaluated each approach on the basis of transfer function performance foraminifera diatoms and multi proxy based transfer functions all demonstrated a strong relationship between observed and predicted elevations r 2 jack 0 74 and rmsep 210 pb and 14 c based chronology and we were able to reconcile this with tide gauge records

new zealand 20th century sea level rise resolving the vertical land motion using space geodetic and geological data 1 investigations in long term instrumental tidal records reveal that 20th century sea level along the coast of new zealand is rising at 1 46 0 10 mm yr in agreement with the regional rates from southern australia and tasmania we extend the advanced altimeter gauge approach of combining satellite altimetry and tide gauge data with constraint equations from long term adjacent tide gauge records to assess its performance in open seas and to explore the impact of vertical land motion on the observed relative sea level this approach has again proven to be a robust method with an accuracy of 0 4 mm yr while no clear sea level rise pattern can be inferred once the tide gauge apparent sea level trends are corrected for vertical land motions from gps the advanced altimeter gauge and geological vertical rates are completely consistent and reveal three temporal phases of sea level rise marked by an increase from 1 46 0 10 mm yr to 1 72 0 10 mm yr during the period 1900 1936 followed by a decrease to 1 48 0 10 mm yr during the period 1936 1956 and a substantial increase to 2 60 0 10 mm yr during the period 1956 1975 in contrast the 20th century microfossil proxy records of absolute sea level rise display twice the tide gauge sea level rise rate of 3 17 0 30 mm yr and 3 28 0 45 mm yr respectively once salt marsh records are corrected using gps and geological vertical rates differential autocompaction and transfer functions are possible factors which need further investigation

precipitation regime influence on oxygen triple isotope distributions in antarctic precipitation and ice cores abstract the relative abundance of 17o in meteoric precipitation is usually reported in terms of the 17o excess parameter variations of 17o excess in antarctic precipitation and ice cores have hitherto been attributed to normalised relative humidity changes at the moisture source region or to the influence of a temperature dependent supersaturation controlled kinetic isotope effect during in cloud ice formation below 20 c neither mechanism however satisfactorily explains the large range of 17o excess values reported from measurements a different approach based on the regression characteristics of 10 3 ln 1 17 o versus 10 3 ln 1 18 o is applied here to previously published isotopic data sets the analysis indicates that clear sky precipitation diamond dust which occurs widely in inland antarctica is characterised by an unusual relative abundance of 17o distinct from that associated with cloud derived synoptic snowfall furthermore this distinction appears to be largely preserved in the ice core record the respective mass contributions to snowfall accumulation on both temporal and spatial scales provides the basis of a simple first order explanation for the observed oxygen triple isotope ratio variations in antarctic precipitation surface snow and ice cores using this approach it is shown that precipitation during the last major deglaciation both in western antarctica at the west antarctic ice sheet wais divide and at vostok on the eastern antarctic plateau consisted essentially of diamond dust only despite a large temperature differential and thus different water vapour supersaturation conditions at the two locations in contrast synoptic snowfall events dominate the accumulation record throughout the holocene at both sites

geochemistry of the peramora melange and pulo do lobo schist geochemical investigation and tectonic interpretation of mafic melange in the pangean suture zone southern iberia the peramora melange is part of an accretionary complex between the south portuguese zone a fragment of laurussia and the ossa morena zone para autochthonous gondwana and is an expression of the pangean suture zone in southwestern iberia the suture zone is characterized by fault bounded units of metasedimentary rocks melanges and mafic complexes detailed geologic mapping of the peramora melange reveals a complex pattern of imbricated schists and mafic block in matrix melanges geochemical signatures of the pulo do lobo schist pdl are consistent with derivation from both mafic and continental sources the mafic block in matrix melange displays normal mid ocean ridge basalt nmorb geochemical signature juvenile sm nd isotopic compositions and a range of zircon ages similar to those observed in the pdl suggesting a sedimentary component taken together these data suggest a complex tectonic history characterized by erosion of a nmorb source melange formation and imbrication during underplating occurring during the final stages of continent continent collision

seismic reflection imaging over the south portuguese zone fold and thrust belt sw iberia 1 we reprocessed an 35 km long part of the ibesreis seismic reflection profile which runs over the iberian pyrite belt section of the south portuguese zone sw iberia with the goal to image the upper crust 15 km depth the applied processing sequence enhanced numerous prominent reflections and diffraction patterns within the uppermost 5 s travel time relative to high amplitude source generated noise a complex subsurface characterized by conflicting dips and a survey following winding roads require a crooked line prestack migration scheme for coherent imaging to interpret sources of diffracted energy we additionally employed a diffraction imaging scheme which enhances diffractions at the expense of reflections the final seismic images show south vergent imbricate fold and thrust tectonics documenting the contractive deformation that the south portuguese zone experienced during the variscan orogeny based on surface geological information we correlate a low reflective unit with the shallow upper carboniferous flysch group a highly reflective unit ranging in depth from 2 to 4 km with the middle carboniferous volcano sedimentary complex group which hosts massive sulfide deposits and a moderately reflective unit with the upper devonian phyllite quartzite group below these units another low reflective facies is present which may represent older paleozoic metasediments in addition the seismic and diffraction images reveal bands of high reflectivity and distinct diffraction patterns that were interpreted as extensive layered mafic intrusions these proposed mafic bodies may be related to the same event that triggered a huge hydrothermal activity assumed in early carbonifereous times

snow isotopic content change by sublimation we present results from cold laboratory observations of changes in isotopic d 18 o and dd content by sublimation in snow and ice samples under nearly isothermal conditions the results show large increases in observed d 18 o and dd in snow samples within several centimeters of the surface they contradict the assumption of a non changing isotopic content due to layer by layer transport mechanisms driven by sublimation desublimation processes the data also do not support the idea that isotopic changes of snow and firn are limited by the possibility that the ice matrix incorporates the atmospheric water vapor and that forced water vapor diffusion in the pore space wind pumping is a requirement for isotopic content change the observations show that sublimation from ice samples results in much lower increases in heavy isotope content in the first several millimetres near the sublimating surface over the same time period despite sublimation intensities similar to those of the snow samples the results suggest that continuous phase transitions inside snow recrystallization are the process responsible for the isotopic content change because they are the primary mass exchange mechanism between the snow mass and the surrounding environment modeling the isotopic content of the ice matrix therefore requires inclusion of a two stage process fractionation at the ice matrix surface due to repetitive phase transitions and fractionation due to preferable diffusion of light water isotopes in the pore space for interpretation of the observed natural isotopic profiles in snow the first process can be linked to the time a snow layer undergoes recrystallization while the second process is related to the total ice snow mass gain loss determined by the external environmental conditions

simultaneous long term and short term slow slip events at the hikurangi subduction margin new zealand implications for processes that control slow slip event occurrence duration and migration 1 we document a sequence of simultaneous short term and long term slow slip events sses at the hikurangi subduction zone during the 2010 2011 period the sequence of short term events each 2 3 weeks in duration ruptured much of the shallow plate interface 15 km at central and northern hikurangi over a 6 month period was accompanied by microseismicity and involved patchy irregular migration of sse slip we suggest that the patchy migration of the short term sse is due to large scale 100 3500 km heterogeneities on the plate interface related to seamount subduction and sediment subduction and or underplating this is in contrast to a 2010 2011 long term sse at the central hikurangi margin which evolved steadily over 1 5 years and ruptured much of the plate interface between 20 and 70 km depth we suggest that the occurrence of long term versus short term sses at hikurangi is related to differences in effective normal stresses and relative heterogeneity of the subduction interface the long term sse sequence began 1 year before the short term sequence coulomb stress change models suggest that the long term sse may have triggered initiation of the subsequent short term sse sequence initiation of the short term sequence occurred in a region just updip of or within an interseismically locked portion of the plate interface and may be located within the updip transition from seismic to aseismic behavior alternatively it could be characteristic of a region undergoing partial interseismic coupling this is in contrast to sses observed elsewhere in the world that typically occur within the downdip transition from seismic to aseismic behavior

the kinematics of the plate boundary zone through new zealand a comparison of short and long term deformations summary surveys of shear strain rates derived from repeated triangulation cover about one quarter of the area of the plate boundary zone through new zealand and are well distributed within it using a method developed by haines relating shear strains to the total strain and velocity fields the dilatational and rotational strain rates and the velocities within the deformed zone are derived the plate boundary zone is shown to be two dimensional for the most part in that gradients of the velocity along the length of the zone are small or zero the shear strain rates are not uniform however they reach a maximum along a central axis and decrease gradually to zero toward the sides nor are the two independent components of strain one involving shortening or extension perpendicular and the other shear parallel to the zone equally developed everywhere there is a clear geographic separation with shortening developed over the subduction thrust and shear developed behind in a zone of wrench faulting time variations in the strain field in part of the region above the subduction interface are related to changes in the degree of coupling across the interface a velocity field is computed the relative velocity of the two plates from this data agree very well with that derived from seafloor spreading data these strain and velocity fields derived from geodetic studies give the short term kinematics of the plate boundary zone the long term kinematics of the zone are estimated from 1 uplift and subsidence data which are related to changes in crustal thickness and hence to dilatational strain and 2 variation in the declination of primary magnetization in rocks of known age related to the rotational strain the rate of rotational strain has increased in time from about 2 to 3 myr 1 10 myr ago to about 9 myr 1 today the increase can be understood as a secondary effect of a developing compressional component increasing the coupling between the plates so that more of the motion parallel to the zone is accommodated by distributed shear and less by aseismic slip the rates of strain averaged over the last 1 myr or so and at a scale length of a few tens of kilometres are closely similar in distribution and magnitude to the strain rates derived from short term kinematics while therefore at scale lengths of a few hundred metres or so faulting is very important and the deformation is discontinuous with unstrained blocks faulted with large but uncertain slip against adjacent blocks the deformation at these longer scale lengths is continuous and regular the two consequences of this study are that 1 strain from geodetic data can be directly related to the average long term deformation and therefore can be an important tool in the study of deformation in regions of current tectonic activity and 2 at scale lengths of a few tens of kilometres the deformation of a region can be described as the deformation of a continuum and we can ignore the effects of faulting

relative and absolute sea level rise in western canada and northwestern united states from a combined tide gauge gps analysis 1 empirical studies and climate models suggest large variations of absolute sea level asl changes between oceanic basins such potential variations raise concern on the applicability of global mean asl predictions to specific regions and on estimates of relative sea level rsl hazards we address this issue for the western canada and northwestern united states coastline by estimating the 20th century asl rate using a combination of 34 colocated tide gauge and global positioning system gps stations the tide gauge data are quality controlled and corrected for spatially and temporally correlated sea level transients in order to derive robust rsl trends and standard errors reference frame and other gps specific issues are considered as part of the error budget in absolute gps vertical velocities our combined tide gauge gps analysis aligned to the international terrestrial reference frame 2000 indicates a northeast pacific asl rise of 1 8 0 2 mm a through the 20th century which is similar to accepted rates for the global eustatic mean for the period 1993 2003 we find a regional asl rate of 4 4 0 5 mm a consistent with satellite altimetry on the basis of the intergovernment panel on climate change assessment report 4 mean scenario and our assessment of coastal motions from gps and tide gauge data we derive a map of predicted 21st century rsl rise in western canada and the northwestern united states variations in coastal uplift strongly affect spatial rsl patterns subsidence of southern puget sound may significantly increase rsl rise in the seattle tacoma metropolitan area conversely tectonic uplift along parts of the outer west coast may reduce future rsl rise by up to 50 100

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

reconstruction of the undiffused seasonal oxygen isotope signal in central greenland ice cores the climatologically important seasonal signal in ice core oxygen isotope records is altered by diffusion with time here we use the diffusion model of whillans and grootes 1985 to calculate the effects of isotopic diffusion in nine shallow ice cores recovered over a 150 150 km grid centered on summit greenland two different computational methods give similar results for the back diffused 18o seasonal extrema although back diffusing the ice core 18o records improves the correlations between the individual ice core oxygen isotope and greenland coastal temperature records the correlations remain poor particularly for the low accumulation sites stacking the back diffused isotopic records from several cores results in much higher correlations with a strong winter linkage between west coast stations and central greenland these correlations are also significantly greater than the correlations between the stacked measured diffused isotopic profiles and coastal temperatures our results indicate that the use of ice core isotopic records to identify anomalous seasons requires that diffusion effects be accounted for

isotopic diffusion in polar firn implications for interpretation of seasonal climate parameters in ice core records with emphasis on central greenland if it were possible to properly extract seasonal information from ice core isotopic records paleoclimate researchers could retrieve a wealth of new information concerning the nature of climate changes and the meaning of trends observed in ice core proxy records it is widely recognized however that the diffusional smoothing of the seasonal record makes a proper extraction very difficult in this paper we examine the extent to which seasonal information specifically the amplitude and shape of the seasonal cycle is irrecoverably destroyed by diffusion in the firn first we show that isotopic diffusion firn is reasonably well understood we do this by showing that a slightly modified version of the whillans and grootes 1985 theory makes a tenable a priori prediction of the decay of seasonal isotopic amplitudes with depth at the gisp2 site though a small adjustment to one parameter significantly improves the prediction further we calculate the amplitude decay at various other ice core sites and show that these predictions compare favorably with published data from south pole and locations in southern and central greenland and the antarctic peninsula we then present numerical experiments wherein synthetic ice core records are created diffused sampled reconstituted and compared to the original these show that alter diffusive mixing in the entire fini column seasonal amplitudes can be reconstructed to within about 20 error in central greenland but that all information about sub annual signals is permanently lost there furthermore most of the error in the amplitude reconstructions is due to the unknowable variations in the sub annual signal finally we explore how these results can be applied to other locations and suggest that dye 3 has a high potential for meaningful seasonal reconstructions while siple dome has no potential at all an optimal ice core site for seasonal reconstructions has a high accumulation rate and a low temperature