excess total organic carbon in the intermediate water of the south china sea and its export to the north pacific national basic research program of china ministry of science and technology 2009cb421200 national science foundation of china nsfc 40821063 90711005 40490264

constraints on hydraulic parameters and implications for groundwater flux across the upland estuary interface abstract analyses of independent laboratory and field scale measurements from two sites on sapelo island georgia reveal heterogeneity in hydraulic parameters across the upland estuary interface regardless of the method used short duration pumping tests amplitude attenuation of tidal pumping data sediment grain size distributions and falling head permeameter tests we obtain hydraulic conductivity of 10 4 m s 1 for the fine grained well sorted clean sands that make up the upland areas proximal to the upland estuary boundary the tidal pumping analyses and permeameter tests suggest that hydraulic conductivities decrease by more than two orders of magnitude a result consistent with the presence of a clogging layer such a clogging layer may arise due to a variety of physical chemical or biological processes the extent and orientation of the layers of reduced hydraulic conductivity near the upland estuary boundary influence the nature of the aquifer s response to tidal forcing where the lower conductivity layer forms a relatively flat creek bank tidal pumping produces a primarily mechanical response in the adjacent aquifer where the creek bank is nearly vertical there is a more direct hydraulic connection between the tidal creek and the adjacent aquifer the clogging layer likely contributes to the development of complicated flow pathways across the upland estuary boundary effective flow paths calculated from tidal pumping data terminate within the marsh beyond the boundary of the upland aquifer suggesting a diffuse regime of groundwater discharge in the marsh we postulate that in many settings submarsh flow may be as important as seepage faces for groundwater discharge into the marsh estuary complex

tracing the nd isotope evolution of north pacific intermediate and deep waters through the last deglaciation from south china sea sediments abstract the intermediate and deep waters of the pacific ocean play a crucial role for regulating global climate changes on the millennium timescale however due to poor preservation of carbonate sediments in the deep pacific little attention has been received to better understand deep ocean circulation and its relationship with abrupt climate events here we present the first authigenic nd isotope e nd record extracted from fe mn oxyhydroxides of the south china sea scs sediments so17940 2 1727 m water depth in order to investigate changes of intermediate and deep water circulations in the pacific ocean since the last glacial maximum lgm in general the seawater e nd record extracted from the scs sediments paralleled the existing nd isotopes of fish teeth debris from the eastern north pacific core during the last deglaciation demonstrating that our authigenic e nd can faithfully record the seawater e nd evolution in the deep pacific ocean at the onset of the deglacial period our data exhibit a clear negative shift in e nd towards a gradually increased component of antarctica intermediate water aaiw and reached a maximal influx during the mid heinrich stadial 1 hs1 16 kyr bp between the hs1 and younger dryas deep water circulation gradually shifted back to the modern condition during the bolling allerod warm interval a pronounced negative e nd excursion had occurred during the pre boreal pb suggesting a rapid reorganization of deep water ventilation in the pacific ocean and was predominated by aaiw this is most likely due to poor ventilation in the western north pacific associated with an intensified summer monsoon during the pb early holocene warm period after the pb period the seawater e nd values were once again dominated by pacific deep water at the study site

evolution of the north pacific subtropical gyre during the past 190 kyr through the interaction of the kuroshio current with the surface and intermediate waters the north pacific subtropical gyre npsg has two important functions i e one in ocean heat transfer and another as a driving force for circulation of the surface and intermediate waters on the basin scale in the present study we describe records of the vertical thermal structures and distributions of water masses in the upper ocean of the subtropical northwest nw pacific for the past 190 kyr using two sediment cores collected from the kuroshio current area in the east china sea and the npsg area during the two glacial periods the kuroshio current was weakened owing to changes in ocean atmosphere circulation and eustasy the differences in the mg ca derived temperatures between surface and thermocline waters show the changes of depth and temperature warming of thermocline during glacial periods conversely the planktonic foraminiferal assemblages demonstrate that the indicator of the intermediate water from the central area of the npsg increased synchronously with thermocline warming during marine isotope stage mis 6 these results suggest that warm intermediate water strongly affected the changes in the water column structure of the subtropical nw pacific during mis 6 however during mis 2 cold water had precedence over intermediate water probably owing to the southward shift of the subtropical front associated with the reduced transport of the kuroshio current thus the npsg has evolved differently during the two glacial periods mis 2 and mis 6 through interactions between the kuroshio current surface water and intermediate water

palaeomagnetism and the age of the cracow volcanic rocks s poland summary permian rhyodacites melaphyres and tuffs from the cracow area south poland were sampled for the palaeomagnetic and isotope studies single grain u pb dating of most zircon grains separated from the rhyodacites gave mean age of magma emplacement of 294 2 2 1 ma some zircons however displayed younger ages 268 7 3 4 ma probably related to the metasomatic alterations of these rocks two permian components of magnetizations related to these processes were isolated and together with previously defined late carboniferous permian palaeomagnetic poles from south poland were used for construction of the regional apparent polar wander path apwp the early permian segment of this apwp shows a certain departure from the coeval part of the fennoscandian apwp due to anticlockwise rotations of studied rocks most probably caused by mid permian sinistral tectonic movements along reactivated prominent variscan faults of central europe this sense of tectonic mobility does not support the hypothesis about transformation from pangea b to pangea a along an intra pangea dextral megashear during the permian older than previously assumed ages of the post variscan igneous rocks of central europe reduce overlap of gondwana s and laurussia s parts of the early permian pangea a

new early permian paleomagnetic results from the brive basin french massif central and their implications for late variscan tectonics in order to assess the structural evolution of the brive basin and the paleozoic activity of surrounding major faults in the french massif central we carried out a paleomagnetic study on early permian rocks from this basin positive fold tests and solely reversed polarities indicate that the characteristic remanent magnetization is likely to be primary early permian tilt corrected site mean declinations vary from 207 167 indicating that the brive basin experienced internal vertical axis rotations on the contrary late permian paleomagnetic site means exhibit a circular fisherian distribution showing no relative rotations detailed analyses of permian paleomagnetic data from five contemporaneous basins of the french massif central reveal that these basins share the same equatorial paleolatitude with stable europe throughout the permian however in early permian three of the five basins experienced differential rotations the saint affrique basin not only suffered internal deformation during the early permian but the basin as a whole underwent a full scale counterclockwise vertical axis block rotation with respect to stable europe as a consequence paleomagnetic data from similar late orogenic basins have to be thus carefully considered for establishment of apparent polar wander paths

late permian palaeomagnetic results from the brive basin massif central france abstract a palaeomagnetic study has been carried out in the brive basin in order to understand the continental deformation of the french massif central since the permian fifteen sites of permian age red sandstones have been sampled in the brive basin which is situated in the west of the sillon houiller fault france laboratory analyses have revealed well behaved and only reversed magnetic polarity for the higher temperature component the effects of positive folding test and kiaman reversal chron indicate that the magnetic remanent is probably primary the so called autunian and saxo thuringian stages show very close palaeomagnetic directions with an angular difference of 1 2 6 9 they likely correspond to the same geological period i e late permian and allow us to calculate one palaeomagnetic pole for this basin 48 8 n 162 5 e n 15 and a95 2 6 comparing this result with previous palaeomagnetic studies from other permian basins in the south massif central and stable europe we may conclude that 1 the brive basin has been part of stable europe since at least the late permian and no younger palaeomagnetically detectable movement of this basin has be found with respect to stable europe 2 no significant movement along the sillon houiller fault has been detected since the permian the relative latitudinal movement of the permian basins of the massif central i e brive saint affrique and lodeve is negligible no significant rotation for each of these basins with respect to stable europe has been observed except for the st affrique basin this later basin experienced a counter clockwise rotation of 7 with respect to stable europe which represents probably a local phenomenon

implications of cabbeling on the formation and transformation mechanism of north pacific intermediate water 1 the world ocean atlas 1994 is used to study the formation and transformation of north pacific intermediate water npiw paying attention to the broad subarctic tropical frontal zone satfz four neutral density surfaces n 26 5 26 9 27 2 and 27 4 are mapped to span the npiw layer with the n 26 9 surface identified with the salinity minimum of npiw various dianeutral motion processes cabbeling thermobaricity vertical turbulent mixing and double diffusion and water mass property conversion are quantified cabbeling appears to be the most important spatially dianeutral transport is strongest in the satfz within the satfz subdomain 36 n 44 n 142 e 140 w with assumed epineutral and dianeutral diffusivities of k 103 m2 s 1 and d 10 5 m2 s 1 cabbeling contributes to a maximum dianeutral downwelling transport of 0 9 sv on the n 26 5 neutral density surface the upper boundary of npiw and 0 7 sv on the n 26 9 surface at the npiw core in meridional sections cabbeling shows epineutral extension from the satfz towards the subtropical gyre most apparent along the n 26 9 surface dianeutral transport is found to be sensitive to the epineutral diffusivity k on the upper two surfaces n 26 5 and 26 9 where the transport is dominated by cabbeling with only half an order of magnitude increase in diffusivity k 103 5m2 s 1 the total npiw about 3 sv can be accomplished by cabbeling alone these results suggest that cabbeling plays a crucial role in the npiw transformation since cabbeling describes physically the dianeutral downwelling resulted from epineutral mixing strong cabbeling in the satfz implies that npiw sources are first transformed by cabbeling from the upper to the lower neutral density surfaces and subsequently npiw is carried by epineutral advection and gyre circulation into the subtropical interior thus cabbeling is revealed as the principle mechanism responsible for transforming subpolar source waters into subtropical npiw water via the satfz

guadalupian middle permian paleobiogeography of the neotethys ocean abstract a matrix of presence absence data of guadalupian middle permian brachiopod genera from sicily tunisia oman turkey north iran central afghanistan karakoram salt range and south thailand has been analyzed by multivariate methods cluster analysis principal coordinate analysis minimum spanning trees and parsimony analysis of endemicity the application of these different and independent paleobiogeographical methods has led to the individuation of three bioprovinces the cathaysian sicily and tunisia cimmerian oman turkey north iran salt range south thailand and transhimalayan karakoram and central afghanistan provinces these provinces have been placed on a paleogeographical reconstruction based on paleomagnetic data which we used to decipher the principal factors that governed brachiopod distribution in the neotethys ocean during the guadalupian as a conclusion the pattern of biotic provinces at this time resulted from the complex interplay between latitudinal thermal gradient oceanic paleocurrents and the continental drift of the cimmerian terranes across zonal climate belts

advective flow through the upper continental shelf driven by storms buoyancy and submarine groundwater discharge data from monitoring wells on the carolina usa continental shelf require a reevaluation of pore water exchange across the seafloor temperature salinity and 226ra data from 3 offshore wells require rapid and frequent pore water exchange to depths of several meters through sands and other permeable sediments the exchange is driven by tidal pumping storms buoyancy and submarine groundwater discharge tidal pumping causes semidiurnal temperature cycles in one well that can only be explained by rapid fluid flow the effect of large storms is evident in sudden temperature changes 2 4 m below the seabed in two wells these changes require considerable pore water exchange sudden cooling of the ocean may cause pore waters to become buoyant with respect to the ocean and trigger pore water convection to several meters depth as observed in one well the wells also display frequent large factor of ten changes in 226ra activity this requires a substantial input of 226ra enriched fluids to replace 226ra that is lost during exchange events these data support a fourth flow process which is groundwater seeping from the underlying limestone the pore spaces in the overlying sand provide a temporary reservoir for these fluids we conclude that pore water residence times in 2 4 m thick sands on this continental margin are on the order of a few months or less

tidal dynamics of the water table in beaches tidal motions of the water table height inside a sloping beach are investigated via field measurements and theoretical considerations only the movements forced by the tide are considered so a beach with negligible wave activity was chosen for the field measurements the data show that even in the absence of precipitation the time averaged inland water table stands considerably above the mean sea level also the water table at a fixed point inside the beach is far from sinusoidal even though its variation is forced by an essentially sinusoidal tide this latter effect is due to the boundary condition along the sloping beach face which acts as a highly nonlinear filter the observed behavior of the water table is explained in terms of perturbation extensions to the classical deep aquifer solution one extension deals with the nonlinearity in the interior the other with the boundary condition at the sloping beach face

changes in pacific ocean circulation following the miocene onset of permanent antarctic ice cover we integrate micropaleontological and geochemical records benthic stable isotopes neodymium isotopes benthic foraminiferal abundances and xrf scanner derived elemental data from well dated pacific ocean successions 15 12 7 ma to monitor circulation changes during the middle miocene transition into a colder climate mode with permanent antarctic ice cover together with previously published records our results show improvement in deep water ventilation and strengthening of the meridional overturning circulation following major ice expansion at 13 9 ma neodymium isotope data reveal however that the provenance of intermediate and deep water masses did not change markedly between 15 and 12 7 ma we attribute the increased 13c gradient between pacific deep and intermediate water masses between 13 6 and 12 7 ma to more vigorous entrainment of pacific central water into the wind driven ocean circulation due to enhanced production of intermediate and deep waters in the southern ocean prominent 100 kyr ventilation cycles after 13 9 ma reveal that the deep pacific remained poorly ventilated during warmer intervals at high eccentricity whereas colder periods low eccentricity were characterized by a more vigorous meridional overturning circulation with enhanced carbonate preservation the long term 13c decline in pacific intermediate and deep water sites between 13 5 and 12 7 ma reflects a global trend probably related to a re adjustment response of the global carbon cycle following the last 400 kyr carbon maximum cm6 of the monterey excursion

tectonics and plate tectonics model for the variscan belt of europe abstract a plate tectonics model is presented to explain the tectonometamorphic characteristics of the european variscides after the closing of two oceanic domains by two sided subduction 500 420 ma and obduction 420 380 ma collision of the european and african continental plates occurred we propose that the subsequent complex intracontinental deformation 380 290 ma is the result of a double subduction of the continental lithosphere accompanied by crust mantle decollement this mechanism explains the progressive crustal thickening and migration of the deformation through time from the sutures toward the external parts of the variscan belt accounting for this model and for the relationships between the european variscides and the other paleozoic peri atlantic belts caledonides appalachian mauritanides and morocco we infer the relative positions of africa america and europe between the silurian and the permian

filling sequence in late paleozoic continental basins a chimera of climate change a new light shed given by the graissessac lodeve basin se france abstract the characteristics of sedimentary deposits in continental basins especially those controlled by extension are often used to infer global climatic changes we question the relevance of such an approach because the stratigraphic pattern of those basins are mostly similar whatever their latitudes paleolatitudes i e their general climatic conditions namely the transition from 1 an ancestral drainage network to 2 deep lake with a dominance of black and grey shale deposits 3 shallow oxic lake with a dominance of red pelites deposits and to eventually 4 a new drainage network such transitions observed in late palaeozoic continental basins throughout laurasia and gondwana are generally interpreted as evidence of global change from a wet climate to an arid climate from the sedimentological and structural analysis of a late palaeozoic basin the graissessac lodeve basin in the south of the variscan french massif central we proposed a new tectono stratigraphic sequence of this basin from the late carboniferous to the early trias we estimate the paleo area from 295 450 km 2 to 880 1150 km 2 of the basin and we deduce a subsidence curve from the late carboniferous to the late permian from 600 200 m my to 100 10 m my we conclude that the graissessac lodeve basin stratigraphic pattern corresponds to a classical continental rift sequence controlled by tectonics in order to assess a possible control of the stratigraphic sequence by the climate we have reconstructed the paleo depth of the lake with 1 the morphometric analysis of the wave ripples and 2 with an estimation of the lacustrine slope considering the tectonic origin of the lake we find that the maximum lacustrine depth has evolved from a range of 80 300 m during the late carboniferous to 40 45 m during the late permian from our estimates of the different configurations of the basin we show that the volume of the water in the lake has remained nearly constant between 10 and 30 km 3 from the late carboniferous 300 my to the late permian 250 my eventually we conclude that the sedimentological indicators of shallowing and episodic drying observed from the late carboniferous to late permian in this basin and probably in all the pangea basins of the same type are the consequence of the basin enlargement by tectonics and its sedimentary filling rather than climatic change

tidally driven groundwater flow and solute exchange in a marsh numerical simulations 1 tidal fluctuations drive groundwater flow in salt marsh sediments this flow could cause significant chemical exchange across the sediment water interface and could affect marsh ecology numerical models of a generalized tidal creek and marsh were constructed to calculate flow patterns and solute exchange between the marsh and creek the governing equation for saturated unsaturated flow was modified to account for tide related changes in total stress groundwater flow occurred primarily in the creek bank even when the marsh platform was inundated at high tide for marsh sediments with a hydraulic conductivity of 10 4 m s 1 groundwater ages in simulations lasting 60 days were on the order of days near the creek bank and increased to 50 60 days with distance into the marsh the volume of water that discharged between high and low tide was 0 22 0 31 m3 per meter length of channel which for a creek drainage density of 0 012 m 1 corresponds to 10 14 l m 2 d 1 sediment permeability and capillarity were important controls on flow and groundwater age in the marsh sediment compressibility affected groundwater age for compressible sediments representative of mud but not for sediments with lower compressibilities representative of sand simulations were relatively insensitive to dispersivity a comparison of simulation results with other estimates of groundwater exchange from the north inlet south carolina suggest that tides could drive observed exchange there only if the pleistocene sands underlying muddy marsh sediments outcrop within the tidal range

ventilation of north pacific intermediate waters the role of the alaskan gyre hydrographic data tritium data and potential vorticity calculations suggest that although north pacific intermediate water is formed in the northwest the alaskan gyre might be an additional ventilation site the proposed ventilation is quantified by a vertical column tritium inventory which indicates an excess of 0 08 kg of tritium in the alaskan gyre an evaluation of the energy stored in the water column and of wind and buoyancy forcing shows that during winter conditions enough energy can be pumped into the system to force 26 80 to outcrop in the alaskan gyre model results suggest that relatively limited outcrops in time and space tens of days and several hundred kilometers in diameter can account for the excess tritium

paleomagnetic data from late paleozoic dykes of sardinia evidence for block rotations and implications for the intra pangea megashear system paleomagnetic studies of dyke swarms from the variscan belt of europe can be used to reconstruct internal postorogenic rotations within the fold belt here we present paleomagnetic data from 13 late variscan dykes from sardinia ranging in age from 298 5 to 270 10 ma the dykes can be grouped on the basis of their different directions in strike in a northern a central eastern and a south eastern province paleomagnetic component directions have been obtained using thermal and alternating field demagnetization techniques which give reproducible results the paleomagnetic mean directions differ significantly between northern sardinia and south eastern and central eastern sardinia the latter two regions yielding statistically similar paleomagnetic mean directions these results indicate that sardinia fragmented into two arguably three crustal blocks after emplacement of the dykes which experienced differential relative rotations as is also indicated by the differences in overall strike directions the determination of timing sense and magnitude of these rotations has major implications for the reconstruction of the geodynamic evolution of the region in post carboniferous times we argue that the observed block rotations occurred during the permian as the result of post variscan intra pangea mobility possibly related to the transformation of an early permian pangea b to a late permian pangea a

distribution and modification of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract a multiship ctd survey was conducted in the kuroshio oyash interfrontal zone in the area of 30 41 n 140 e 180 from may to june 1992 to examine the distribution modification process and formation site of north pacific intermediate water npiw low salinity oyashio water and high salinity kuroshio water merge along the kuroshio extension just off the east coast of japan and together flow eastward eastward geostrophic transport and salinity across the kuroshio strong current indicate that the mixture of the kuroshio and oyashia waters along the kuroshio extension can produce new npiw transport estimate suggests that the new npiw bifurcates into the interfrontal zone and into the recirculation of the subtropical gyre a salinity minimum structure can he also created due to the isopycnal mixing along the kuroshio extension between the oyashio and kuroshio waters which have different salinity and vertical velocity structures the low salinity oyashio water seen along the oyashio branches and t

comparison of four numerical models for simulating seepage from salt marsh sediments a boundary integral equation method biem model and three differently formulated finite element method fem models were implemented to explore the spatial and temporal patterns in marsh pore water seepage that each generated the biem model is based on the laplace equation coupled to a dynamic free surface condition that assumes that as the water table changes the aquifer instantaneously loses or gains an amount of water equal to the change in head times the specific yield the fem models all implement a simplified richards equation that allows gradual desaturation or resaturation and thus flow in both the saturated and unsaturated zones of the aquifer two of the fem models are based on the governing equation for the usgs model sutra and thus take into account fluid and aquifer compressibility one of these was modified to take into account the effect of tidal loading on the total stress which is assumed to be constant in the derivation of the original version of sutra the third fem model assumes that neither the fluid or aquifer matrix is compressible so that changes in storage are due solely to changes in saturation the unmodified sutra model generated instantaneous boundary fluxes that were up to two orders of magnitude greater and spatially more uniform than those of the other models the fem model without compressibility generated spatial and temporal patterns of the boundary fluxes very similar to those produced by the biem model the sutra model with the tidal stress modification gave fluxes similar in magnitude to the biem and no compressibility models but with distinctly different distributions in space and time these results indicate that accurate simulation of seepage from marsh soils is highly sensitive to aquifer compressibility and to proper formulation of the effect of tidal loading on the total stress in the aquifer they also suggest that accurate simulation may require total stress correction not only for tidal loading but for changes in the water table as well finally to aid the development of methods for the measurement of compressibility we present a schematic pore scale model to illustrate the factors that may govern the compressibility of marsh soils

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

transport of north pacific intermediate water across japanese woce sections 1 under the auspices of the world ocean circulation experiment woce hydrographic program japan carried out a total of four sections in the north pacific p2 at 30 n p13 at 165 e p9 at 137 e and p8 at 130 e these japanese and several other woce sections are used to estimate the transport of north pacific intermediate water npiw in the subtropical gyre previous studies speculate about 3 sv 1 sv 106 m3 s 1 of npiw transport originating mainly in okhotsk sea entering the subtropical gyre southward via the mixed water region in the east of japan the total subpolar input is 3 2 sv when another source of npiw in the gulf of alaska estimated at 0 2 sv in this study is added this transport from the japanese woce sections a mean of 2 8 0 2 sv compares well with several other sections a mean of 2 5 0 2 sv from a total of five meridional and two zonal sections a mean transport of 2 7 0 2 sv is found in the defining npiw layer between n 26 5 and 27 4 neutral density surfaces the transport shows a steady southward and westward increase about 3 sv transport is found mainly in the southern south of 25 n and western west of the dateline sections closer to the subarctic tropical frontal zone and in the eastern subtropical gyre npiw transport is less than 2 sv this implies that a lower subpolar input of about 2 sv is sufficient for subtropical ventilation recirculation entrainment with the upper and lower waters and epineutral and dianeutral mixing likely add about 1 sv to the npiw transport to interpret the transport distribution a simple water mass mixing scheme is applied which includes two formation sources okhotsk intermediate water oiw and gulf of alaska intermediate water gaiw in the subpolar regions and a transformed aged npiw anpiw in the northwestern subtropical gyre southeast of japan the anpiw mixing fraction increases southward and westward while oiw and gaiw fractions decrease this suggests that after npiw source water parcels enter the subtropical gyre they largely recirculate within the wind driven gyre and thus become aged therefore one usually sees very low oxygen and cfc values in the npiw layer in the subtropical gyre

using the radium quartet for evaluating groundwater input and water exchange in salt marshes the fluxes of 226ra half life 1600 years and 228ra half life 5 7 years from the north inlet salt marsh to the sea are much larger than can be supported by decay of their th parents in the surface marsh sediments these fluxes are sustained almost entirely by groundwater flow through the marsh an average groundwater flow of approximately 10 cm3 cm 2 day 1 is indicated if the groundwater activities we have measured are representative the fluxes of 223ra half life 11 4 day and 224ra half life 3 6 day are factors of 22 and ten more than those expected from the flux of 226ra groundwater also sustains most of the flux of the short lived isotopes the measured ra activity ratio pattern in the marsh creeks matches the groundwater signature but is distinct from the pattern of the parent thorium isotopes in the sediment we present a model to explain the anomalous distribution pattern of these isotopes despite their large throughput the inventories of desorbable 226ra and 228ra in the top 15 cm sediment layer are very low nevertheless the activities of 226ra and 228ra in the porewaters are large indicating a low distribution coefficient 10 for radium and a short retention time 10 days in the surface sediment layer we surmise that groundwater flow may be a significant source of radium isotopes in the waters of shallow estuaries and coastal margins this source must be recognized while considering mass balance of any tracer be it radium nutrients other metals or 18o

nd isotopic composition in the central north pacific three vertical profiles of seawater concentration and isotopic composition of nd were determined for the western to central north pacific ocean in the subarctic oceanic region at depths greater than 500 m one vertical profile of nd isotopic composition was indistinguishable from most previously reported profiles from here the data indicate a rather homogeneous nd isotopic composition in the subarctic oceanic region at middle to deep depths 500 m two stations in the subtropical oceanic region exhibited similar nd isotopic composition profiles to those previously reported the maxima end values at depths of 800 1000 m end 3 4 to 2 7 which correspond to the north pacific intermediate water npiw are found at both subtropical stations this implies a ubiquitous distribution of npiw showing a radiogenic end value in the north pacific the subsurface minimum at a depth of 200 m which indicates the penetration of the north pacific tropical water nptw with an unradiogenic nd isotopic signal was observed at one station in the western pacific this station had much lower end than the central station at depths around 5000 m suggesting the greater prominence of antarctic bottom water aabw in the western subtropical pacific than in the central to eastern subtropical pacific results of a model calculation assuming boundary exchange indicate that the hawaiian islands play an important role in supplying radiogenic nd to the central pacific similar to some continental margins we show that nd isotopic composition is a versatile tracer for ocean circulation and the geochemical cycle of nd in the north pacific further studies on the distribution of nd isotopic composition in the pacific ocean including the southern pacific will better elucidate the circulation and geochemical cycle of nd in the pacific

groundwater lens dynamics of atoll islands a variable density groundwater model is used to analyze the effects of various controls on the size of the freshwater lens the structure of the transition zone and the propagation of tidal fluctuations in a two layer atoll island groundwater system modeling results indicate that mixing of fresh water and saltwater occurs primarily as a result of oscillating vertical flow due to tidal fluctuations and depends to a lesser extent on transverse dispersion along the dominantly horizontal recharge discharge path of flow the controls on the amount of mixing are 1 the accumulated vertical distance which increases with tidal range and is restricted by vertical permeabilities and 2 vertical longitudinal dispersion comparison of cross sectional simulations of atoll islands using nontidal and tidal models shows that the nontidal model must use artificially high values of transverse dispersivity to compensate for the lack of tidally driven vertical mixing processes although the tidal model has high computational requirements it can be used to calibrate vertical permeabilities and is best suited for problems dealing with groundwater resource evaluations hydrologic events and hydrologic processes the limitations of the nontidal model are that it cannot be used for calibration of vertical permeabilities and will not realistically simulate those cases in which transition zones are thick or recharge low

deep oxygen penetration drives nitrification in intertidal beach sands we discovered a hotspot of elevated nitrate concentration median 431 m in shallow beach pore water that extended across the entire length of two barrier islands in the southeastern united states of america we investigated this feature by surveying groundwater geochemistry measuring fluctuations in in situ dissolved oxygen do concentrations modeling groundwater flow and quantifying nitrification rates nitrification of groundwater ammonium was the only possible nitrate source with a measured potential rate of 0 84 mol m 2 h 1 however the observed nitrate concentrations were far in excess of the predicted maximum achievable by aerobic nitrification assuming a 2 1 ratio of o n and around 200 m do in air saturated seawater groundwater do concentrations within the hotspot 65 cm depth were consistently 20 50 m the nitrate hotspot was located at the top of the water table beneath dry undersaturated sand that allowed the penetration of air and the dissolution of excess oxygen into the pore fluids the total dissolved nitrogen concentration of the hotspot was higher than anywhere else on the island indicating nitrogen accumulation within the hotspot most likely via ammonium adsorption vertical dispersion was the dominant pathway for nitrate loss from the hotspot this nitrate was consumed in underlying anoxic sand coupling microbial pathways of nitrogen oxidation and reduction and removing bioavailable nitrogen from the beach ecosystem

assessing oxygen depletion in the northeastern pacific ocean during the last deglaciation using i ca ratios from multiple benthic foraminiferal species paleo redox proxies are crucial for reconstructing past bottom water oxygen concentration changes brought about by ocean circulation and marine productivity shifts in response to climate forcing carbonate i ca ratios of multiple benthic foraminifera species from odp hole 1017e a core drilled within the californian oxygen minimum zone omz on the continental slope are employed to re examine the transition from the well oxygenated last glacial into poorly oxygenated modern conditions the redox and export productivity history of this site is constrained by numerous proxies used to assess sensitivity of i ca ratios of benthic foraminifera to changes in bottom and pore water o2 concentrations reconstructed iodate io3 availability from the i ca ratio of epifaunal cibicidoides sp shallow infaunal uvigerina peregrina and deep infaunal bolivina spissa foraminifera the reconstructed io3 availability profile is used to determine the contribution of bottom water o2 relative to oxidant demand on pore water o2 concentrations these results suggest that high export productivity on the california margin drove pore low water o2 concentrations during the bolling in contrast low bottom water o2 concentrations at 950 m water depth only contributed to reduced sediments during the allerod increased contribution of modified north pacific intermediate water to the california current system ventilated the california omz during the late glacial and the younger dryas such that water overlying the site was oxygenated these results highlight the promising potential of this new proxy for understanding the relative influence of bottom water o2 concentration and pore water oxidant demand on omzs

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

expansion of the southern california oxygen minimum zone during the early to mid holocene due to reduced ventilation of the northeast pacific abstract oceanic deoxygenation observed since the 1950s has drawn increasing concern as dissolved oxygen do regulates marine biodiversity and biogeochemical cycles yet the do time series from direct instrumental measurements is insufficiently long several decades to constrain the centennial to millennial variability here we present redox sensitive metal re u and mo records from santa barbara basin sbb california to reconstruct subsurface do through the holocene significantly higher authigenic metal fluxes and coherent benthic foraminifera faunal responses along a published depth transect reveal vertical expansion and intensification of the southern california oxygen minimum zone omz prior to 6 ka comparison with post industrial trace metal records suggests low oxygen conditions were more extreme during early to mid holocene mh highlighting the magnitude of omz variability in the absence of anthropogenic influences inconsistencies between authigenic metal fluxes and local oxygen control indicate a remote weakening of the north pacific intermediate water npiw formation prior to the mh reduced ventilation of the mid depth north pacific is supported by state of the art earth system model simulations with realistic mh 6 ka forcing highlighting the importance of brine rejection during sea ice formation in changing the buoyancy of npiw and its basin wide influences on north pacific omz evidence from holocene marine lake records and model simulations further suggests a southward intertropical convergence zone itcz migration and a consequent deepening of the aleutian low al towards late holocene which favors more sea ice brine rejection thus mid depth ventilation in the north pacific was closely associated with atmospheric circulation during the holocene

the origin of the north pacific intermediate water possible source regions of the north pacific intermediate water npiw were investigated with synoptic conductivity temperature depth surveys in the okhotsk sea kuril basin a pycnostad referred to as the okhotsk sea mode water osmw was found in the density range of 26 6 27 the pycnostad is not seen in the western subarctic gyre wsag thus it is an indicative water peculiar to the okhotsk sea the maximum thickness is at 26 7 26 9 centered at 26 8 which coincides with the npiw density range in the north pacific subtropical gyre in the oyashio area east of the southern kuril islands and hokkaido waters that have intermediate temperature salinity and potential vorticity between the osmw and the wsag water were distributed suggesting a following transport route of the npiw source water the thick thus low q q is potential vorticity and low salinity water mass outflowing from the okhotsk sea mixes with the relatively warm saline and high q wsag water to form the oyashio water a coastal part of the oyashio water flows southwestward along the east coast of the southern kuril islands and hokkaido retaining the pycnostad q minimum a large part of the low q oyashio water flows further southward and merges with the kuroshio extension and then flows eastward forming new npiw in this process a salinity minimum develops and the q minimum disappears because of the mixing with a saline kuroshio water old npiw without a pycnostad in the npiw density range these results suggest that the origin of npiw is the water mass in the okhotsk sea osmw and the density of the water mass primarily determines the npiw density centered at around 26 8

a proposed biogeography of the deep ocean floor abstract while there are many generalized schemes representing the biogeographic distribution of life in the deep sea reviewed here a comprehensive analysis has not been undertaken since vinogradova 1979 vinogradova 1997 for the abyssal and belyaev 1989 for the hadal the purpose of this paper is to propose global biogeographic provinces for the lower bathyal and abyssal benthos 800 m depths in order to aid high seas management efforts biological samples from these depths are sparse so delineation of biogeographic provinces was initially hypothesized using oceanographic proxies and examined with documented locations of select benthic marine species these biogeographic provinces were first developed in 2009 via an expert consultation workshop to delineate biogeographic provinces in offshore regions the global open ocean and deep sea goods classification we have refined the goods deep sea classification by incorporating additional high resolution hydrographic and organic matter flux data for the seafloor water mass characteristics temperature and salinity and particulate organic flux to the seafloor were the strongest determinants in the final delineation of provincial boundaries this process resulted in the delineation of 14 lower bathyal and 14 abyssal provinces the bathyal and abyssal classifications presented here should be used with other management tools and analyses e g predictive habitat modeling seamount classifications etc to help determine where marine protected areas should be placed and to minimize the negative impacts of commercial activities in the high seas

paleomagnetic evidence for rotation during stephano permian extension in southern massif central france we present results of a preliminary paleomagnetic study devised as a test of a tectonic model proposed by van den driessche and brun 1 to interpret the main structural features of the montagne noire south massif central france this model suggests that crustal extension during stephanian to permian times is responsible for a major fiat lying detachment the inferred geometrical relationships between fault azimuth and extension direction is befieved to induce a counter clockwise rotation of the paleozoic cover during its northward motion in order to test this model we have sampled autunian lower permian grey and red sandstone beds within two basins opened during the extension the lod ve and the st affrique basins the paleomagnetic study of six sites three in each basin using thermal demagnetization procedures reveals the presence of 3 magnetization components a first one a which is unblocked below 400 o c is interpreted as a recent overprint due to weathering of the sandstones the b component is unblocked between 400 o and 575 o c this b component is assumed to be primary although the gentle dip of the beds does not allow a fold test it fits the lower permian field direction in the lod ve basin in situ d m 194 i m 6 o k 50 tilt corrected d m 194 i m 10 o k 53 in contrast it shows a systematic difference in declination in the st affrique basin in situ d m 173 i m 2 5 o k 101 tilt corrected d m 172 lm 6 o k 37 this is interpreted as a post autunian counter clockwise rotation of at least 20 o of the st affrique basin thus supporting one of the main implications of the tectonic model finally red sediments from two sites of the lod ve basin yield a third component c with unblocking temperatures up to 670 c and carried by hematite its direction is also consistent with the permian field direction showing that hematite crystallisation occurred early in the diagenesis history of the sediments

syn extension rotations in the permian st affrique basin massif central france paleomagnetic constraints abstract we present the results of a paleomagnetic study of the permian sedimentary basin of st affrique southern massif central france this study was devised to test for tectonic rotations in the montagne noire area during the stephano permian extension in the hecynian chain and to complete a preliminary study 1 in which we suggested an counterclockwise rotation of st affrique basin with respect to the neighbouring lodeve basin this rotation was attributed to the domino like rotation of the basement of st affrique i e the paleozoic monts de lacaune imbricate units as expected from the tectonic interpretation of the montagne noire area made by van den driessche and brun 2 3 however the rotation of the basin during permian should induce declination differences between the basal and the upper part of the stratigraphic sequence we therefore conducted vertical sampling of the basin throughout the permian sequence two sites of stephanian age gave no results but twelve sites from the lower to the upper permian have been sampled in the st affrique basin and did provide results paleomagnetic analysis using thermal procedures confirms our previous analysis and allowed us to demonstrate three magnetization components the low temperature a component is unblocked by 300 c and conforms to the present day dipole field direction an intermediate temperature component b has also been isolated with unblocking temperatures of 300 to 550 600 c and this component was possibly carried by magnetite between 600 and 680 c a third component c may be suspected at some sites but it has not been isolated with confidence at a site showing a tilted block geometry produced by syn sedimentary normal faulting site p7 it is shown that the b component is an early magnetization acquired during faulting of the succession and we are therefore able to give it a stratigraphic age the mean directions of the b component which are computed at the stratigraphic stage level show the following counterclockwise deviations from the reference magnetic field direction for stable europe 21 4 5 for the upper autunian 10 7 for the saxonian 10 9 for the lower thuringian and 4 6 and 3 5 4 5 for two successive stages of middle upper thuringian age we thus consider that 1 the comparison of the lowest units of st affrique and lodeve basins 1 and 2 the evolution in paleomagnetic declination during the permian within the st affrique basin itself provide evidence in space and time of a rotation of the basin during its formation we attribute this rotation to the domino like rotation of its basement the monts de lacaune imbricate units during the stephano permian extension in the hercynian chain 2 3

strain removal applied to paleomagnetic directions in an orogenic belt the permian red slates of the alpes maritimes france abstract detailed investigations of relationships between strain and directions of characteristic remanent magnetization chrm have been conducted on the permian red series of the alpes maritimes france the analysis of the results obtained by structural and paleomagnetic studies on 14 sites leads to the following observations in most sites the mean direction of the strain shortening axis is close to the expected permian paleomagnetic direction in this case we observe a large scatter of the chrm directions within each site which is interpreted as an increase of an initial dispersion due to strain moreover this dispersion more or less increases with strain intensity in other cases where the angle between the shortening axis and the paleomagnetic direction is high the whole population is deflected towards the cleavage xy plane these observations lead us to assume a material line like behaviour of the chrm vectors and consequently an attempt has been made to recalculate these directions by strain removal these calculations give positive results at two levels 1 a statistically significant improvement in the clustering of the within site distributions and 2 after tilt correction using unstrained bedding planes a significant improvement in the clustering of the between site distribution the formation mean direction after strain removal is in good agreement with known permian results for stable europe

ordovician palaeogeography with new palaeomagnetic data from the montagne noire southern france a joint palaeomagnetic and ar 40 ar 39 study has been performed on two olistolithic blocks from the cabrieres wildflysch in the montagne noire region of the massif central in france there andesitic volcanic and volcaniclastic rocks of llanvirn early caradoc age ca 470 458 ma occur despite extensive secondary alteration destruction of the dominant magnetic mineral phase and ar 40 ar 39 whole rock experiments that demonstrate that the volcanic rocks suffered significant argon loss a positive fold test and the presence of dual polarities suggest that a primary ordovician magnetisation has mostly survived this is one of the few documented cases where the argon system was substantially reset whilst a subordinate set of small relatively unaltered magnetite grains probably hosted in silicates still carry the original in this case ordovician remanence the new data show that the montagne noire region was located at high southerly latitudes 68degrees 19 15 during the mid ordovician this latitude represents the location for nw gondwana of which the massif central was a part palaeomagnetic data from all the central european massifs and terranes demonstrate a close link to the gondwana margin during the lower and middle ordovician

hawaiian imprint on dissolved nd and ra isotopes and rare earth elements in the central north pacific local survey and seasonal variability abstract dissolved neodymium isotopes 143nd 144nd expressed as end and rare earth elements rees have the potential to trace the provenance of lithogenic material as well as water masses the central north pacific is poorly investigated with respect to its nd isotope signature and ree cycling and little is known about the contributions of volcanic islands such as hawaii relative to dust input from asian deserts to the surface water ree budgets here we present dissolved nd isotope and ree data along with long lived radium isotope activities from hawaii ocean time series station aloha and coastal waters from oahu sampled for a geotraces process study in february 2011 the data are supplemented with seasonal samples from aloha our results show a clear influence of the hawaiian islands on the coastal ocean and surface waters at aloha during february expressed by higher surface water ra activities radiogenic surface end end 1 4 to 1 0 and elevated eu anomalies eu eu 1 3 seasonal cycles of asian dust deposition most likely contribute to the seasonal end variability of surface waters at aloha as suggested by more negative end and the lack of eu anomalies in summer neodymium isotopes in the intermediate and deep water column at aloha trace typical north pacific water masses such as north pacific intermediate water and north pacific deep water we suggest that a radiogenic end excursion in 1000 2000 m water depth observed in various north pacific profiles is controlled by advection of a modified upper circumpolar deep water or north equatorial pacific intermediate water we further present an updated average end signature of 3 5 0 5 for north pacific deep water and show that ree patterns of deep waters at aloha are dominantly controlled by vertical processes

changes in intermediate water conditions in the northern south china sea using globorotalia inflata over the last 20 ka intermediate circulation is one of the crucial controls of thermohaline changes in seawater due to the lack of data for some of the more significant indicators there has been little research into past intermediate waters in the south china sea scs in particular little is known of the thermohaline properties of intermediate water here we present paired mg ca and 18o data for the planktonic foraminifera globorotalia inflata from core ghe27l in the northern scs these data provide records of temperature and residual 18oseawater 18oresidual being used as a proxy for salinity to tentatively investigate changes in the intermediate water of the scs over the last 20 ka our results show that g inflata in the scs grew principally within the 200 450 m water depth interval thermohaline changes recorded by g inflata indicate warm and relatively freshening water during the last glacial maximum lgm 20 17 7 ka bp changing to warm and saline waters between 17 7 and 13 6 ka bp in general waters during the 13 6 8 3 ka bp period were characterized by high temperatures and salinity with obvious millennial scale fluctuations after which during the holocene they became cold and fresh we suggest that the temperature and salinity of the intermediate water of the scs recorded by g inflata in core ghe27l were possibly associated with a switch in intermediate water masses during the lgm the intermediate water in the northern scs was mainly impacted by north pacific intermediate water npiw but that subsequently the influence of antarctic intermediate water strengthened during the last deglaciation and pre boreal period 17 7 8 3 ka bp after this period npiw was the principal control of the intermediate water of the scs again

a magnetotectonic study of the hercynian montagne noire france a paleomagnetic study of eleven sites of devonian limestones sampled along the flanks and hinge of a polyphase hercynian recumbent fold in the montagne noire reveals well defined directions of characteristic remanent magnetization chrm the directions have good within site precision but a large between site scatter which fails to be reduced by a classical tilt correction this is readily understood if widespread remagnetization occurred between the two major hercynian phases of folding a and b which are known to have shaped the montagne noire this remagnetization appears to be an instance of a continent wide chemical event that wiped out much of the magnetic memory of devonian and lower carboniferous rocks in laurasia baltica and northern gondwana possibly due to groundwater circulation following the major hercynian tectonic phases comparison of observed and predicted hercynian magnetic directions allows one to determine through a fairly simple geometric construction the tectonic elements of the later phase b it is found that different rotations affected the flanks and hinge zone of the folds generated by phase a thus demonstrating how a pre existing structure can control the development of deformation in a later tectonic phase the effects of the non cylindrical phase b can next be removed to reveal the broad tectonic features of phase a deformations the reversed kiaman polarity of the chrm allows a determination of the age of phase b which is found to be about 300 310 ma and of the age of the remagnetization itself at about 310 320 ma the search for the age of remagnetization included paleomagnetic measurements at two lower permian sites from the nearby lodeve basin these provide new data for the permian pole of europe and point out the limitations of some earlier studies due to insufficient magnetic cleaning finally the principal shortening directions of the two phases can be determined from the magnetic data and are found to have rotated counterclockwise by 30 between phase a and phase b this feature already observed in the collision of india against eurasia may be related to the progressive suturing of former subduction zones during the hercynian collision of gondwana against laurasia this study demonstrates the potential of remagnetizations for the solution of rather complex tectonic problems we propose the term magnetotectonics for this rapidly expanding field of studies in which the methods of paleomagnetism and structural analysis are closely associated

tidally driven multiscale pore water flow in a creek marsh system intertidal wetlands are complex hydrological systems characterized by strong dynamic interactions between coastal surface water and groundwater driven particularly by tides we simulated such interactions with a focus on three dimensional variably saturated pore water flow in a creek marsh system that bordered a tidally dominated main channel simulated intra tidal groundwater dynamics exhibited significant flow asymmetry with non zero mean flow velocities over the tidal period the tidally averaged flow led to pore water circulation with three dimensionality linked strongly to the marsh topography over a range of spatial scales near the creek bank around the creek meander and over long marsh sections inclined towards the main channel particle tracking revealed that time scales associated with these circulations differed by orders of magnitude under the simulated conditions the creek served as the main outlet of the pore water circulation paths especially those linked with infiltration into the upper marsh surface areas away from the main channel local net efflux influenced by the creek channel curvature varied along the creek but produced a total discharge largely proportional to the creek length water infiltrating the soil in the lower marsh surface areas away from the creek tended to discharge directly to the main channel however the total discharge to the main channel was much less than that into the creek this study highlights the hydrological complexity of intertidal marshes and the need for further research on interactions among marsh morphology hydrology and ecology which underpin the functionalities of these wetland systems

elevated foraminifera bound nitrogen isotopic composition during the last ice age in the south china sea and its global and regional implications 1 we report a new foraminifera bound d 15 n fb d 15 n record from the south china sea scs extending back to 42 ka this record shows a 1 2 glacial to interglacial d 15 n decrease with a deglacial d 15 n maximum similar to that observed in many bulk sedimentary d 15 n records and in a caribbean fb d 15 n record the glacial to interglacial d 15 n decrease is smaller than in the caribbean record indicating that at least half of the caribbean d 15 n decrease into the holocene was regional not global supporting the interpretation of a holocene increase in atlantic nitrogen fixation at the same time the glacial to interglacial d 15 n decrease observed in the scs may also be explained as a regional signal of increasing nitrogen fixation into the holocene other aspects of the scs record suggest an effect of physical circulation on fb d 15 n fb d 15 n starts to increase toward its deglacial maximum before the last ice age ends and it continues to decrease through the later holocene in contrast to the more pure glacial deglacial interglacial steps in the caribbean record these changes have parallels in other pacific d 15 n records precessionally driven east asian monsoon records and the slow holocene warming of scs surface waters in addition the scs record exhibits two one point high d 15 n spikes in multiple foraminiferal species that coincide with apparent hydrographic events thinning or weakening of the thermocline in the late glacial and early holocene as well as during the noted events may have yielded a higher d 15 n for thermocline nitrate and thus a higher fb d 15 n

deglacial subarctic pacific surface water hydrography and nutrient dynamics and links to north atlantic climate variability and atmospheric co2 the glacial to holocene evolution of subarctic pacific surface water stratification and silicic acid si dynamics is investigated based on new combined diatom oxygen 18odiat and silicon 30sidiat isotope records along with new biogenic opal subsurface foraminiferal 18o alkenone based sea surface temperature sea ice diatom and core logging data from the ne pacific our results suggest that 18odiat values are primarily influenced by changes in freshwater discharge from the cordilleran ice sheet cis while corresponding 30sidiat are primarily influenced by changes in si supply to surface waters our data indicate enhanced glacial to mid heinrich stadial 1 hs1 ne pacific surface water stratification generally limiting the si supply to surface waters however we suggest that an increase in si supply during early hs1 when surface waters were still stratified is linked to increased north pacific intermediate water formation the coincidence between fresh surface waters during hs1 and enhanced ice rafted debris sedimentation in the north atlantic indicates a close link between cis and laurentide ice sheet dynamics and a dominant atmospheric control on cis deglaciation the bolling allerod b a is characterized by destratification in the subarctic pacific and an increased supply of saline si rich waters to surface waters this change toward increased convection occurred prior to the bolling warming and is likely triggered by a switch to sea ice free conditions during late hs1 our results furthermore indicate a decreased efficiency of the biological pump during late hs1 and the b a possibly also the younger dryas suggesting that the subarctic pacific has then been a source region of atmospheric co2

remanence rotation due to rock strain during folding and the stepwise application of the fold test numerical modeling was conducted to determine the effects of simple models of folding strain on prefolding fisherian distributions of magnetization i found that the constant volume simple shear associated with flexural slip flexural flow folding can rotate a prefolding magnetization to have a maximum precision parameter k value at partial unfolding and thus appear to be synfolding in age if the magnetization is treated as a passive line marker this behavior only occurs for steep initial magnetizations the initial homogeneity of the fisherian precision parameters from each limb is degraded by this type of deformation and may be used to detect a strain modified remanence if the magnetization is carried by rigid mechanically active ellipsoidal or spherical particles a maximum k value at partial unfolding will occur for any initial inclination with the special case that rigid spheres will be rotated to cause a maximum k value at 50 unfolding for any initial inclination homogeneity of limb precisions is not affected in this case a discontinuous model of strain during folding in which pressure solution removes material at an axial planar spaced cleavage and causes limb dips steeper than bedding dips could also produce a maximum k value at partial unfolding strain and remanence studies of flexural slip folding in the allentown formation dolomite and the bloomsburg formation red sandstones and mudstones suggest that 1 the rigid grain model may be a more realistic model of magnetic particle behavior during shear strain and 2 about one quarter to one third of the theoretically predicted simple shear strain occurs in these rocks this amount of strain cannot explain the synfolding behavior observed in the allentown formation but could explain the maximum k values at 80 90 unfolding seen in the bloomsburg formation and perhaps other appalachian clastic rocks

remagnetizations and postfolding oroclinal rotations in the cantabrian asturian arc northern spain devonian carbonates in the cantabrian arc reveal characteristic magnetizations with coherent shallow upward inclinations the magnetizations appear to be carried by magnetite within site directions are very well grouped but site mean declinations range from easterly to south southwesterly in in situ as well as tilt corrected coordinates as has also been observed in previous studies of other formations in the arc the widely varying declinations of all studies roughly correlate with the overall structural trends of the arc and suggest that the sites underwent rotations in a process that involved folding about vertical axes and tightening of arc upon tilt correction the inclinations of our study on the other hand become scattered and it is concluded that the magnetizations were acquired after late carboniferous folding about horizontal axes the oroclinal rotations therefore also must have occurred after the late carboniferous folding phase the previous paleomagnetic results had been interpreted mostly as primary magnetizations residing in hematite however inclination only fold tilt tests applied to these results suggest that many if not all of the directions were acquired during the earlier stages of the late carboniferous folding thus all paleomagnetic results from the cantabrian arc appear to be remagnetizations but the ages of the remagnetizations vary from pre to synfolding for the mostly hematitic formations to postfolding for the devonian carbonates the reversed polarity inclinations of the hematite bearing formations have mean values ranging from 25 to 5 whereas the carbonates have a mean inclination of 8 on the basis of inclinations predicted for the area from results from stable europe the pyrenees and the iberian meseta the ages of these remagnetizations can be inferred to range from about 320 ma to 260 ma because all the remagnetizations reveal rotated declination patterns the oroclinal rotations occurred well after the main phase of hercynian deformation 320 280 ma while the timing of the rotations is unconstrained at the younger end they must have occurred during or after the permian best estimate is less than 260 ma which is much later than anticipated from other geological considerations

a modeling study of the dynamics of pore water seepage from intertidal marsh sediments a numerical boundary integral equation model has been used to simulate tidally driven transient variations in pore water seepage from salt marsh sediments into tidal channels and its subsequent recharge by tidal inundation in general the results show that the maximum seepage discharge occurs at or near the intersection of the creek bank and the channel water surface over a tidal cycle typically two thirds of the total seepage discharge occurs through the creek bank with only about a third discharging from the channel bottom of the creek bank discharge up to a third occurs through the seepage face that develops above the tide line at tidal stages below mean tide these results indicate that placement of seepage meters only on the channel bottom will not give samples or measures representative of the total seepage of the total recharge only about 5 occurs through the upper part of the creek bank with the remainder infiltrating vertically through the marsh platform during early stages of tidal submergence for the platform recharge about 80 occurs within 3 m of the creek bank thus most of the water that seeps out of marsh sediments is derived from sediments that lie within several meters of the creek bank and accordingly has had a relatively short residence one to two years in the marsh compared to the distal portion of the marsh this relatively rapid flushing may enhance the productivity of spartina alterniflora in the creek bank environment and control the differential generation of radium quartet isotopes

effects of unstable flow on solute transport in the marsh soil and exchange with coastal water recent studies of marsh hydraulics have focused on tide induced pore water circulation as the main drive for solute transport in the marsh soil and exchange with coastal water our study revealed another important mechanism provided by unstable fingering flow which largely modified solute transport paths in the marsh interior downward penetration of salt fingers forced ambient pore water and solute plumes to move upward and exit the marsh soil through marsh platform at relatively high concentrations up to two orders of magnitude higher than exit solute concentrations at the tidal creek bed the mixing of solute with ambient pore water in the marsh interior was intensified greatly by fingering flow a critical distance to the creek was determined based on a field scale model simulation to distinguish tidal circulation dominated and fingering flow dominated solute transport zones the new transport mechanism has implications for understanding the fate of solutes in particularly salt marshes of low creek densities

iron sources and dissolved particulate interactions in the seawater of the western equatorial pacific iron isotope perspectives this work presents iron isotope data in the western equatorial pacific marine aerosols and top core margin sediments display a slightly heavy fe isotopic composition 56 fe of 0 33 0 11 2sd and 0 14 0 07 respectively samples reflecting the influence of papua new guinea runoff sepik river and rabaul volcano water are characterized by crustal values in seawater fe is mainly supplied in the particulate form and is found with a 56 fe between a0 49 and 0 34 0 07 the particulate fe seems to be brought mainly by runoff and transported across continental shelves and slopes aerosols are suspected to enrich the surface vitiaz strait waters while hydrothermal activity likely enriched new ireland waters dissolved fe isotopic ratios are found between a0 03 and 0 53 0 07 they are almost systematically heavier than the corresponding particulate fe and the difference between the signature of both phases is similar for most samples with 56 fe dfe pfe 0 27 0 25 2sd this is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases the dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved fe this process seems to be locally significantly more intense than fe reductive dissolution documented along reducing margins it may therefore constitute a very significant iron source to the ocean thereby influencing the actual estimation of the iron residence time and sinks the underlying processes could also apply to other elements

limits on conservative behavior of nd isotopes in seawater assessed from analysis of fish teeth from pacific core tops abstract neodymium nd isotopes have become an accepted water mass tracer for paleoceanographic reconstructions however high rates of radiogenic nd input from volcanic islands arcs in the western equatorial pacific wep and the subarctic north pacific sanp can significantly alter the isotopic composition of ambient seawaters leading to questions about the conservative nature of nd isotopes in the pacific here we present the first comprehensive study of nd isotopes preserved in core top fossil fish teeth debris from 31 sites in the pacific to define the vertical and horizontal distributions of seawater nd isotopes and to test the reliability of nd isotopes as a water mass tracer in the pacific we found that nd isotopic values of northward flowing lower circumpolar deep water lcdw are significantly modified in the western central equatorial pacific and the sanp as a result of local radiogenic inputs from young circum pacific island arcs consequently modified lcdw with 5 end is created in the central equatorial pacific while recirculated north pacific deep water npdw acquires a radiogenic nd isotope value 2 end in the sanp nd isotopic ratios of fish teeth debris in the central north pacific plotted against salinity or phosphate concentration from the overlying bottom water produce a mixing envelope between modified lcdw and npdw indicating that these nd isotopic values represent the southern and northern sourced end member values for the central north pacific and that mixing of these water masses defines vertical profiles of nd isotopes in this region in the eastern equatorial pacific eep three water masses modified lcdw npdwsanp and npdwwestern pacific combine to produce nd isotopic values that reflect this conservative mixture therefore nd isotopes behave as a conservative water mass tracer in the central north pacific and the eep but high rates of lithogenic inputs from young circum pacific island arcs compromise the conservative behavior of nd isotopes in the wep and sanp

the drift history of iran from the ordovician to the triassic new late ordovician and triassic palaeomagnetic data from iran are presented these data in conjunction with data from the literature provide insights on the drift history of iran as part of cimmeria during the ordovician triassic a robust agreement of palaeomagnetic poles of iran and west gondwana is observed for the late ordovician earliest carboniferous indicat ing that iran was part of gondwana during that time data for the late permian early early tri assic indicate that iran resided on subequatorial palaeolatitudes clearly disengaged from the parental gondwanan margin in the southern hemisphere since the late early triassic iran has been located in the northern hemisphere close to the eurasian margin this northward drift brought iran to cover much of the palaeotethys in approximately 35 ma at an average plate speed ofc 7 8 cm year 21 and was in part coeval to the transformation of pangaea from an irvin gian b to a wegenerian a type configuration

subtidal advective water flux as a potentially important nutrient input to southeastern u s a saltmarsh estuaries an initial study was conducted to assess the importance of the advective movement of interstitial water from subtidal creek sediments in enriching the overlying creek water of the estuary the process of advection was measured in two creeks of a south carolina estuarine saltmarsh and results indicated that significant amounts of inorganic nutrients nh4 and po4 3 were added to the overlying creek water by this process the nutrient concentrations in the advected water were as much as an order of magnitude higher than in the overlying water column a comparison of runoff from the marsh surface during low tide to advection from subtidal creek bottoms indicated the importance of the latter in contributing nh4 and po4 3 to the estuarine water column data indicated however that runoff from the marsh surface appeared to be a greater source of no3 no2 to the tidal creek waters mean n 5 sites advective flux across one of the creeks was 3 1 mg nh4 n m 2 tide 1 0 02 mg no3 no2 n m 2 tide 1 and 0 31 mg po4 3 p m 2 tide 1 which was 6 times and 2 5 times higher for nh4 and po4 3 respectively than surface runoff a process known to export nutrients to tidal creek water from the nearby vegetated marsh when normalized over the areal extent of subtidal creek bottom in the estuary subtidal advection is estimated to contribute approximately 3 times as much nh4 and 1 3 times as much po4 3 to the estuarine water column than low tide runoff from the vegetated marsh surface

roles of the okhotsk sea and gulf of alaska in forming the north pacific intermediate water recently obtained world ocean circulation experiment woce sections and pre woce hydrography are used to study the water mass structure and formation and transformation of north pacific intermediate water npiw five neutral density surfaces are selected and mapped encompassing npiw from 400 to 900 m in the subtropical latitudes with a distance of 100 m between a pair of surfaces npiw is defined as a subtropical gyre salinity minimum which is well followed by a neutral density surface n 26 9 formation and transformation of npiw is examined by the mapped turner angle on neutral density surfaces apparent diffusive double diffusion is found in the alaskan gyre on n 26 5 neutral surface in the northwest subpolar gyre and the okhotsk sea on n 26 9 neutral surface and mainly in the okhotsk sea on the two deep neutral surfaces n 27 2 and n 27 4 these diffusive regions indicate transformation sources for npiw along with additional information of potential vorticity and stream function it is found that there are two different npiw formation sources one in the gulf of alaska characterized by high potential vorticity and the other in the okhotsk sea characterized by low potential vorticity the former lies shallower at n 26 2 26 5 but its effect deepens to npiw core density level at n 26 8 on the basis of potential vorticity distribution the latter includes the influence of the northwest subpolar gyre and extends much deeper to n 27 4 we call them gulf of alaska intermediate water gaiw and okhotsk intermediate water oiw respectively gaiw contributes to npiw in the eastern part of the subtropical gyre east of date line whilst oiw dominates in the west and entire lower part of npiw seasonal flow stream function mapped on neutral surfaces shows that the contribution of gaiw to npiw occurs mainly in the wintertime because in winter a significant northward shift of zero wind stress curl makes the gulf of alaska an additional source for npiw

role of stratigraphy in governing pore water seepage from salt marsh sediments 1 numerical modeling experiments have been used to study the effects of marsh stratigraphy on the seepage of pore water into tidal channels if the mud sand contact lies at the elevation of the channel bottom and the hydraulic conductivity of the basal sand is at least an order of magnitude greater than the overlying mud the locus of maximum seepage shifts from the tide line as in a purely mud marsh to the toe of the creek bank the ratio of creek bank seepage to bottom seepage also shifts from greater than to less than one furthermore as the ratio of the hydraulic conductivities of sand to mud increases the ratio of the total seepage from the sand mud marsh to that from a pure mud marsh increases in a nonlinear fashion reaching an asymptotic limit of about 20 at a conductivity ratio of about 1000 if the mud sand boundary is progressively lowered so that mud also lies beneath the channel the seepage dynamics gradually revert toward those of a purely mud marsh the ecological implications of these results for regularly flooded low marshes are discussed

frontal densification and displacement a scenario of north pacific intermediate water formation abstract the formation of north pacific intermediate water npiw requires a densification of 0 2 0 3 through interior transformation processes evidence of this density anomaly is discovered on neutral density surfaces in the subarctic tropical frontal zone satfz showing an eastward tongue of positive density anomaly coincident with a cabbeling maximum tongue the northward displacement of the satfz with depth east of dateline enables the transformed dense water from overlying thermocline to sink into the northeast subtropical npiw domain the further southward and southwestward spreading across the subtropical gyre yields the observed distribution of npiw

new insights into hydrological exchange between the south china sea and the western pacific ocean based on the nd isotopic composition of seawater abstract rare earth element ree concentrations and nd isotopic compositions end of 16 seawater profiles collected in the northern south china sea scs and the philippine sea were investigated 1 to establish the distribution of the nd isotopic composition of water masses along the tropical western pacific and the scs until now underexplored 2 to constrain hydrological exchanges between the scs and the philippine sea through the luzon strait and 3 to test in the context of the semi closed marginal sea scs the possible impact of the process of exchange of nd between scs water masses and unradiogenic sediments from its north western margin end values for mid and deep water masses of the philippine sea and the scs range from 2 3 to 4 4 and generally increase slightly as water depth increases in the philippine sea end values for the north pacific intermediate water npiw reach 2 7 0 4 at mid depths 500 to 1400 m below 1800 m the pacific deep water pdw is characterised by less radiogenic nd 4 1 0 5 indicating the intrusion of southern sourced water for most of the stations in the northern scs water masses below 1500 m pdw display homogenous end values 4 1 identical to those of the pdw in the philippine sea end values for the south china sea intermediate water scsiw 500 1500 m vary from 3 0 to 3 9 as a result of the vertical mixing of the npiw with the pdw in the scs seawater end values for the scs display local modification 5 3 to 7 0 in areas where water passes above sediment drift deposit systems this implies locally confined boundary exchange with unradiogenic sediments around 11 insufficient to alter the nd isotopic composition of the pdw in the northern scs in addition end values analysed for the first time in nepheloid layers collected along the north western margin of the scs do not exhibit any significant modification of the seawater end which remains into a narrow range between 3 7 and 4 3 similar to that of the pdw a compilation of end from the sea surface water of the scs indicates lower end values in the western and the central scs 3 3 to 9 5 induced by sediments riverine input which are characterised by unradiogenic end around 11 finally as significant variations are observed in seawater end at mid depth between the scs and the philippine sea end values could be used in the future to track intermediate water mass exchange in the luzon strait a process which at present remains poorly understood

thrust related diapiric and extensional doming in a frontal orogenic wedge example of the montagne noire southern french hercynian belt abstract the montagne noire which is situated at the toe of the orogenic wedge of the french massif central south european variscides appears to be a well suited area for studying the origin and evolution of middle to upper crustal domes adjacent to foreland basins the data reported in the present paper show that the montagne noire dome is a particular type of basement involved frontal culmination in an orogenic wedge and foreland basin system this frontal culmination is characterized by a syn contractional ht decompression recorded by clockwise ptt paths and widespread strata overturning in thrust and fold structures which controlled the sedimentation in the adjacent foreland basin these unusual characteristics are interpreted to be a result of the succession of thrusting diapirism and extensional collapse antiformal stacking of syn metamorphic thrust sheets controlled the first stages of the foreland basin development diapirism was essentially responsible for the ht decompression and widespread strata overturning extensional doming was a result of late to post metamorphic collapse acting on the pre existing high amplitude dome diapirism and associated isothermal decompression metamorphism which constitute the essential difference between the montagne noire and ordinary frontal ridges in orogenic wedges were probably enhanced by a local partial melting of the upper to middle crust it is suggested that the occurrence of these phenomena in front of an orogenic wedge was related to local over thickening due to the superposition of an upper crustal antiformal stack on top of a lower crustal ramp anticline

the pathway and circulation of north pacific intermediate water 1 it has been speculated that the subtropical north pacific intermediate water npiw was formed by a shortcut of okhotsk sea source into the western subtropical gyre because this is the geographically shortest distance and based on incomplete data this mechanism is contradictory to the distribution of seawater properties and dynamically is inconsistent with a basin wide distribution of npiw and associated gyre circulation a lengthy transpacific pathway has been identified for the transformed npiw source waters that first enter the eastern subtropical gyre which is robust in a water mass age distribution using an updated hydrography and a water mass mixing scheme combining property distribution with flow streamfunction the present study establishes a dynamically self consistent gyre circulation of npiw and its pathway from the subpolar formation regions source to the indonesian throughflow sink

a paleomagnetic study of permian and triassic rocks from the toulon cuers basin se france evidence for intra pangea block rotations in the permian 1 the identification of a massive shear zone separating gondwana from laurasia during late palaeozoic times is one of the prerequisites for the controversial pangea b to a transition here we present new paleomagnetic data from permian and triassic sediments and volcanic rocks from the toulon cuers basin se france likely to be situated within this intra pangea shear zone a total of 150 samples from 14 sites were collected in the field 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690 c after removal of an initial viscous magnetic component from room temperature up to 200 c a second component of reverse polarity oriented to the south and up was identified in almost all samples of permian age the triassic samples behave similarly with the notable difference that here two polarities of magnetization are present positive field tests suggest the primary character of this characteristic magnetization the latitudes of the resulting early to mid permian paleopoles agree well with the corresponding segment of the apparent polar wander path apwp for europe whereas the longitudes are strung out along a small circle segment indicating relative rotations between the sampled regions and stable europe the triassic poles instead plot close to the triassic segment of the european apwp and provide an upper time limit for the observed rotations these results suggest a wrench faulting event associated with intra pangea crustal instability and transformation during the permian

nonhomogeneous seawater sr isotopic composition in the coastal oceans a novel tool for tracing water masses and submarine groundwater discharge here we present high precision 2 3 ppm 87sr 86sr measurements in coastal waters together with salinity to evaluate water mass mixing and the influence of submarine groundwater discharge sgd in coastal waters and marginal seas nonhomogeneous sr isotopic variations in water columns were documented in the southern okinawa trough sot south china sea and kao ping canyon kpc where seawater 87sr 86sr varied up to 70 ppm seawater sr isotopic composition changes only slightly in the upper 200 m of the sot but was detectable and highly correlated with salinity indicating a mixing between radiogenic north pacific tropical water high 87sr 86sr and high salinity at 100 150 m and a less radiogenic component with low 87sr 86sr and low salinity at 200 m vertical profiles of seawater 87sr 86sr along the kpc show significant variations suggesting dynamic mixing affected by continental inputs i e river runoff and sgd in this region these results highlight the potential use of seawater sr isotopes as a powerful tracer for determining mixing ratios and the dynamic mixing of oceanic water masses especially in coastal and marginal seas

palaeomagnetic studies in the permian basin of largentiere and implications for the late variscan rotations in the french massif central summary detailed geological observations and palaeomagnetic analyses were carried out in the largentiere stephano autunian basin and on the stephanian deposits of the ales coalfield both located at the southeastern margin of the french massif central because of unfavourable rock types the ales stephanian deposits did not yield any results the palaeomagnetic pole 164 9 e 45 4 n k 89 a 95 4 1 deduced from a study of the autunian sediments of the largentiere basin agrees very well with the reference pole for stable europe the lodeve largentiere area that is the southeastern border of the massif central has been stable since early permian time with respect to stable europe whereas the western part the saint avrique rodez basin and probably the brive basin has been rotated counterclockwise