sequence stratigraphic architecture of a differentially subsiding bay to fluvial basin the eocene ishikari group ishikari coal field hokkaido japan abstract the eocene ishikari group deposited in a bay to fluvial basin in central hokkaido japan provides important information on fluvial sequence stratigraphy in a differentially subsiding ocean connected setting the ishikari group consists of four million year order depositional sequences isk 1 isk 2 isk 3 and isk 4 composed mainly of meandering braided fluvial systems each depositional sequence contains marine or lacustrine incursion beds which show lake or bay to bay margin tidal facies at maximum flooding surface horizons this indicates that marine or lacustrine incursion into fluvial environments took place when the increase rate of accommodation space due to relative sea level rise exceeded the rate of accumulation fluvial channel stacking density varies in response to stratigraphic position within a depositional sequence namely high channel density in the lower part of the transgressive interval trs lst to tst and the upper part of the regressive interval rgr hst and low channel density in upper trs and lower rgr multistory channels tend to be developed in lower trs whereas single story channels predominate in upper trs and rgr these patterns in the distribution of fluvial channels resulted from changes in accommodation space in response to relative sea level changes sequence boundaries are recognized at fluvial incision surfaces at the base of trs but the development of incised valleys is minor because of the relatively high subsidence rate which obscured the effect of relative sea level fall syndepositional differential subsidence within the paleo ishikari basin resulted in selective development of relatively downstream depositional systems in the more rapidly subsiding area high frequency depositional cycles are also prominently developed in the subsiding area where sedimentation rate was sufficiently high to record high frequency relative sea level cycles or autocycles of deposition

japan sea a pull apart basin abstract recent field work in the hokkaido central belt and marine geology studies along the eastern margin of japan sea in addition to previously published data lead us to propose a new model of opening of the japan sea the synthesis of both on land and offshore structural data gives new constraints about the structural evolution of the system the rhombohedral shape of the japan basin and the particular tectonic behaviour of the margins on both east and west sides can be explained by an early eo oligocene rifting of a pull apart basin accommodated along two large right lateral shear zones east of korea and west of northeast japan and sakhalin it is followed during upper oligocene lower miocene by the main opening of the japan basin as a mega pull apart then a back arc spreading probably related to the subduction process induced the creation of the yamato and tsushima basins at the end of lower miocene and in middle miocene clockwise rotation of southwest japan larger than 20 or major bending of honshu mainland deduced from paleomagnetic studies is unlikely at this time since 1 or 2 my b p to present compression prevails along the eastern margin of the japan sea the generation of marginal basins as pull apart basins along intracontinental strike slip faults is a mechanism which has been proposed by other authors concerning the south china sea the question then is whether the fragmentation of the asiatic continent is an intracontinental deformation related process as proposed here or a subduction related one

sediment resuspension by surface wave action an examination of possible mechanisms abstract detailed spectral and coherence analyses of both nephelometer data and near bottom acoustic concentration profiles support the conclusion of lesht et al 1980 that surfacewave activity is the most important input to the sediment resuspension process the sand sized fraction is suspended primarily by bursts of turbulence which are related to peak values of the envelope of surface waves two mechanisms for the resuspension of fine sediment are considered when the bed is bimodal sand and silt pore water motion induced by wave pressure fluctuations may carry fine particles into the boundary layer where they are suspended motion of the sand matrix as bedload will also expose fine particles to the flow so that they become suspended the combination of these two mechanisms accounts for the observed quasi linear relation between wave orbital velocity and suspended sediment concentration for the long island data the second mechanism is also consistent with observations of near bottom fluid velocity and suspended sediment concentration in norton sound alaska

paleomagnetic evidence for block rotations in central hokkaido south sakhalin northeast asia abstract the eocene to lower miocene strata in the bykov region of south sakhalin island far east russia show a mean paleomagnetic direction of dec 28 7 inc 55 7 95 6 7 and n 22 and a paleomagnetic pole at 66 3 n 245 7 e and a95 8 8 which shows that south sakhalin rotated 25 15 clockwise with respect to northeast asia since the early miocene this pole agrees with that of the eocene to middle miocene sedimentary rocks in central hokkaido japan it suggests that both south sakhalin and central hokkaido have rotated clockwise with respect to northeast asia since the early miocene these clockwise rotations can be interpreted as a vertical axis rotation of the blocks distributed in the north south direction more than 1000 km along the dextral hokkaido sakhalin shear zone considering the development of an en echelon structure of the basins in the shear zone we recognized five blocks each of which had rotated since the early miocene we conclude that this dextral shear is responsible not only for these block rotations but also for the opening of the kuril basin and the japan sea and that the shear motion was caused by oblique convergence between the eurasian and the okhotsk plates since the early miocene

field measurements of the suspended sand concentration profiles and fluxes and of the resuspension coefficient γ0 over a rippled bed measurements of the acoustic backscatter from suspended sand over a rippled bed and of currents were made near the crest of a ridge and runnel beach on the macrotidal north norfolk coast of the united kingdom two 12 min records were taken close to high water in a depth of 1 7 0 2 m visual inspection of the data shows that sand was intermittently suspended to heights of 20 30 cm but that these events were not always correlated with strong wave induced currents the structure of some of the suspension events suggest that they are due to vortex shedding from a rippled bed the observed time averaged concentration profiles were compared with predictions generated using glenn and grant s 1987 combined flow model the nondimensionalised concentrations showed good correspondence in the first 8 to 10 cm above the wave boundary layer supporting the use of a value of 0 74 drawn from atmospheric data for the constant of proportionality between sediment and momentum diffusivity above this height observed values of the proportionality constant tended to approach 1 0 which may have been due to a decrease in sediment settling velocity with height which is consistent with finer sand being suspended higher in the flow or alternatively to nonuniform turbulence in the vicinity of the wave ripples absolute concentrations measured 2 cm above the bed were consistent with values of o 10 4 for the empirical constant 0 in smith and mclean s 1977 pickup function concentrations within the wave boundary layer were observed to decrease much more rapidly than predicted by the model sand transport fluxes were computed for both the cross shore and alongshore components of the flow using a current profile based on the combined flow model of glenn and grant 1987 for the two records vertically integrated fluxes of 1 5 mg s cm width and 0 89 mg s cm width directed towards the shore were calculated for the wave oscillatory component of the transport the mean flow produced shoreward vertically integrated fluxes of 5 1 and 10 5 mg s cm width the uncertainty associated with these estimates is considerable 50 the vertical profile of the total flux wave oscillatory and mean for both records showed a strong shoreward transport close to the bed an offshore transport between 5 and 15 cm above the bed and a further weak onshore flux above this demonstrating the necessity for measurements of the whole concentration profile rather than a few point samples for the calculation of sand transport over a rippled bed in a wave dominated environment

shear fracture patterns and connectivity at geometric complexities along strike slip faults shear fracture patterns and connectivity at geometric complexities such as echelon fault steps and fault bends along strike slip faults are investigated by simulating shear fracture propagation paths using a displacement discontinuity boundary element method together with a maximum distortional strain energy density criterion it is shown that shear fracture patterns and connectivity depend on the specific geometric configurations the applied stress orientations and the coefficient of friction for a given initial configuration of the major faults the subsequent patterns of the associated shear fractures and their linkage can be predicted if the remote state of stress and the coefficient of friction are known the analyses of fault geometries commonly encountered in nature have important implications for evaluating the effect of faults on fluid flow and earthquake hazards associated with the geometric complexities along strike slip faults in the upper crust

vertical profiles of suspended sand concentration and size from multifrequency acoustic backscatter vertical profiles of suspended sand concentration and size are obtained from multifrequency acoustic profiling data collected in 1989 during a nearshore experiment at stanhope lane beach prince edward island the data were acquired with acoustic sounders operating at 1 2 25 and 5 mhz independent estimates of concentration were made using optical backscatter sensors obss the algorithm for inversion of the three frequency backscatter data to particle size and concentration based on the ratios of the different signals was tested in laboratory experiments with an unconfined high reynolds number suspended sediment jet results from the stanhope beach experiment are presented for three different surface wave energy regimes with significant wave orbital velocities ranging from 0 3 to 0 8 m s and peak wave periods of 4 6 s the acoustic estimates of mean concentration are shown to be within 10 on average of those determined with the obs nearest the bottom at 5 to 10 cm height over time scales ranging from 6 5 min to 4 6 s one wave period the acoustic estimates of suspended sediment size near the bottom are within 5 20 of the bottom sediment mean size the statistical variability of the size estimates is high with standard deviations in the estimates ranging between 30 and 50 of the mean the time averaged concentration profiles exhibit an exponential decrease with height above an o 10 cm thick near bottom region of nonexpo nential decrease in contrast the time averaged mean size profiles decrease approximately linearly with height and rather slowly about 25 in 0 5 m

recognition of spatial structures and ensemble averages in the benthic boundary layer simultaneous high frequency spatial and temporal measurements of benthic boundary layer bbl velocity and sediment concentration generate complex data sets in order to investigate the various spatial and temporal structures a pattern recognition method is for the first time adapted and used to investigate different and similar structures patterns of velocity and acoustically measured suspended sediment concentration profiles in the lowest 2 m of the bbl at tiana beach long island this layer is subject to interactions between differently scaled forcing fields which result in structures difficult to predict using existing time average or boundary layer methods under the assumption of no a priori knowledge about either the spatial or temporal structures in the bbl a deterministic mathematical methodology is implemented to recognize spatial structures in the data and classify them in an optimum number of classes the spatial pattern analysis in this paper indicates that 70 of the above mentioned data are represented by only 5 20 of its size spatial patterns different from those predicted from theory or experience are recognized

quantitative evaluation of quaternary crustal deformation around the takayama basin central japan a paleomagnetic and numerical modeling approach abstract neotectonic crustal deformation in central japan is described quantitatively on the basis of paleomagnetic measurements and numerical modeling the welded part of the earliest quaternary nyukawa pyroclastic flow deposit npfd preserves stable remanent magnetization detailed paleo rock magnetic experiments reveal that remanence of the npfd near the takayama basin resides in unimodal titanomagnetite and comprises a component of thermoremanent magnetization trm and three components of thermoviscous remanent magnetization tvrm scatter in the untilted declinations of the syn depositional trm component represents differential rotation about vertical axes related to quaternary activity of three faults enako makigahora and harayama associated with the takayama basin the normal and reversed tvrm components probably acquired by warm water circulation near the active faults during the jaramillo subchron record a complicated rotational sequence since ca 1 ma dislocation modeling successfully simulates the spatial distribution of rotation and the uplift subsidence pattern around the takayama basin assuming strike slip motion on the enako and makigahora faults along the basin margin and vertical displacements on the harayama fault within the basin temporal changes in rotational motions recorded in the tvrms of near fault sites can be modeled by considering transition of active segments of the three faults which is geologically constrained

nitrogen isotope geochemistry of organic matter and minerals during diagenesis and hydrocarbon migration the magnitude of isotopic variations between organic and inorganic nitrogen was examined in samples from three stacked hydrocarbon reservoirs in the fordoche field louisiana gulf coast basin usa measurements were made of 15n in kerogen bitumen oil formation water and fixed nh4 extracted from mudstones nonproductive sandstones and productive sandstones nitrogen isotope fractionation occurs because 14n is released preferentially to 15n from organic molecules during thermal maturation released 14n goes into solution or may be adsorbed by minerals leaving crude oil enriched in 15n diagenetic clay minerals e g illite commonly form in the temperature range of hydrocarbon generation and nh4 may be fixed in clay interlayers with an isotopic ratio similar to that of the migrating fluids results indicate that the influence of organic matter on mineral 15n depends on the timing of authigenic mineral formation relative to fluid migration the average 15n of kerogen 3 2 0 3 and fixed nh4 from mudstones 3 0 1 4 is similar while bitumen increases from 3 5 to 5 1 with depth in deep reservoir sandstones 100 c the 15n of crude oil averages 5 2 0 4 similar to the 15n of bitumen in the proposed source rocks formation waters are 14n enriched with an average 15n of 2 2 2 6 fixed nh4 15n values lie between that of the oil and water the average 15n of fixed nh4 is 3 0 1 2 in productive sandstones and 0 2 2 4 innonproductive sandstones in the shallower reservoir sandstones 90 c fixed nh4 is apparently not influenced by the presently associated fluids productive and nonproductive sandstones have distinctly low average 15n values 1 2 0 8 yet crude oil 11 1 0 3 and water 3 8 0 1 have been 15n enriched by 6 relative to the deeper reservoirs this suggests that the present fluids migrated into the reservoir after authigenic illite had formed fluids become enriched in 15n during migration and the amount of enrichment may be a function of the amount of interaction with argillaceous sediments

evolution history of the hidaka oki offshore hidaka basin in the southern central hokkaido as revealed by seismic interpretation and related tectonic events in an adjacent collision zone abstract off the southern coast of hokkaido the hidaka oki offshore hidaka basin has developed on the western flank of a collision suture under the influence of long standing compressional plate motion and provoked tectonic stresses around the northwestern pacific rim throughout the late cenozoic the basin forming history of the japan arc and kuril arc collision zone is described on the basis of seismic reflection data interpretation we identify two stages of basin formation the older late oligocene miocene faulted en echelon graben pull apart basin and younger plio pleistocene regional downwarping paleoenvironmental changes recorded within the fore arc sediments indicate that the older basin filled up by the late miocene we inferred the volumes of the distinctive basins from the depth conversion of seismic data which suggest episodic uplifts and massive erosion of the hidaka mountains in the middle late miocene and the plio pleistocene estimated sediment supply rates into the basins have a similar level for the both stages cause of an episodic uplift in the older stage is attributed to the delayed opening of the japan sea the eastern eurasian margin underwent n s right lateral faulting at 25 ma as a result of rifting of the kuril back arc basin formation of the japan sea back arc basin since the early miocene ca 20 ma caused eastward motion of the western hokkaido block and transpressive regime along the pre existing n s shear deformation zone

acoustic inversions for measuring boundary layer suspended sediment processes although sound has been applied to the study of sediment transport processes for a number of years it is acknowledged that there are still problems in using the backscattered signal to measure suspended sediment parameters in particular when the attenuation due to the suspension becomes significant the uncertainty associated with the variability in the scattering characteristics of the sediments in suspension can lead to inversion errors which accumulate as the sound propagates through the suspension to study this attenuation propagation problem numerical simulations and laboratory experiments have been used to assess the impact unpredictability in the scattering properties of the suspension has on the acoustically derived suspended sediments parameters the results clearly show the commonly applied iterative implicit inversion can lead to calculated sediment parameters which become increasingly erroneous with range as the sound propagates through the suspension to address this problem an alternative approach to the iterative implicit formulation is investigated using a recently described dual frequency inversion this approach is not subject to the accumulation of errors and has an explicit solution here the dual frequency inversion is assessed and calculated suspended sediment parameters are compared with those obtained from the iterative implicit inversion

measuring suspended sediment concentrations using acoustic backscatter devices abstract in recent years the requirement to develop a technique for measuring suspended sediment concentration profiles with similar temporal and spatial resolution to that of electromagnetic current meter measurements of the flow has led to the development of an acoustic approach acoustic backscatter devices have been constructed and deployed in marine environments and measurements of backscattered signal profiles obtained however the translation from acoustic returns to suspended load has been an empirical procedure resulting in some uncertainty regarding the accuracy and reliability of the conversion process to address this problem a series of laboratory measurements of acoustic backscattering from marine suspensions were conducted using two acoustic backscatter instruments operating at 3 0 and 5 65 mhz a simple semi empirical backscattering theory has been developed to predict the form of the scattered signal and comparisons have been made of the concentrations predicted from the theory against concentration measurements made in laboratory tanks the results show that the main features of the backscattering signal can be explained and accurate concentration estimates can be made from the acoustic returns it is concluded that acoustic backscatter techniques are potentially powerful tools for examining at high resolution the structure of suspended sediment concentration profiles near the seabed

cenozoic basin forming processes along the northeastern margin of eurasia constraints determined from geophysical studies offshore of hokkaido japan abstract the cenozoic evolution of a sedimentary basin on a long lasting deformation zone along the northeastern eurasian margin is investigated using geophysical studies analysis of seismic reflection data with detailed age assignments reveals that an offshore paleogene and early miocene basin around northwestern hokkaido developed as a typical pull apart depression at the right stepping part of n s trending dextral faults numerical modeling estimates the total slip on the paleogene strike slip faults is ca 12 km which matches the actual shape and volume of the basin the total displacement resulted from quite active 1 4 mm year dextral motions along the fault zone during the paleogene and early miocene deformation fields around the fault step also indicate a complicated pattern of vertical axis rotation the emergence of contraction tectonics in the middle miocene is suggested from the foreland type basin configuration observed the temporal variations of sedimentation rate through the cenozoic are estimated utilizing the depth converted seismic record and they confirm an accelerated subsidence implying a forearc foreland transition upon the eurasian margin

metasomatic diamond growth a multi isotope study 13c 15n 33s 34s of sulphide inclusions and their host diamonds from jwaneng botswana abstract the formation of diamond through metasomatic events from volatiles enriched fluids melts brought into pre existing mantle rocks has been suggested from a series of independent studies however the link between these hypothetical volatile rich fluids and deep seated mineral inclusions mostly silicate and sulphides entrapped in diamonds remains unclear yet the relationship between these two species may provide the key to our understanding of diamond crystallization in order to address the relationship between the origin and formation of diamonds and their mineral inclusions we carried out the first coupled stable isotopic study 13 c 15 n and multiple s isotopes as 34 s 33 s 33 s of diamonds containing sulphide inclusions using samples from the jwaneng kimberlite as our model system sulphides extracted from the present collection of 55 diamonds belong to either eclogitic e type 52 diamonds or peridotitic p type 3 diamonds paragenetic suites as attested by their cr and ni content cr 0 18 wt and ni 14 wt for p types sulphur isotopic compositions have been measured in situ by multicollector secondary ion mass spectrometry and reveal that peridotitic sulphide inclusions in diamonds n 4 lie on the terrestrial fractionation line whereas mass independent sulphur isotope fractionations mif are preserved inside eclogitic sulphides inclusions 0 5 33 s n 33 such large mif values extended here to the negative values recorded in archean sediments are thought to be produced through photochemical reactions in the archean atmosphere which implies that sulphides inclusions contain an archean sedimentary sulphur component that was transferred to the earth s mantle in contrast to this isotopic dichotomy between e type and p type sulphides the geochemical characteristics of their host diamonds 13 c 15 n n content n speciation are largely homogeneous throughout the population and differ from silicate bearing diamonds previously studied in the same locality sulphide bearing diamonds appear to define a distinct population which might reflect a different crystallization process characterized by carbon and nitrogen isotopic compositions falling within the range of unfractionated mantle values the lack of a distinct isotopic signature of recycled sedimentary nitrogen and carbon in sulphide bearing diamonds leads us to infer that sulphide bearing jwaneng diamonds were not derived from the same chemical reservoir as their inclusions one possible formation mechanism that is compatible with our observations is diamond crystallization from a mantle derived carbon bearing fluid associated with pre existing sedimentary sulphide minerals this model has important implications for the interpretation of diamond ages obtained from sulphide inclusions using re os systematics here we suggest that the incorporation of a significant amount of mantle related sulphur during a diamond growth event into the original sulphide could lead to a re equilibration of the re os isotope composition in any inclusion and accordingly account for some scatter on re os isochrons

temporal variability of suspended particulate concentrations in the new york bight abstract temporal variability observed in several time series of suspended matter measurements obtained by light scattering and conventional water sampling has been examined to identify significant time scales with respect to synoptic characterization of regional suspended matter distributions in the inner new york bight processes with periods corresponding to surface waves seconds and storms days apparently make the strongest contributions to overall concentration variability and tidal motions appear to have only a weak influence on near bottom suspended load an empirical model is proposed which assumes that concentration variance is linearly related to the mean concentration both increasing in response to such processes as wind wave mixing and boundary layer interactions with the b ttom data obtained during the study support the model this model is used in a numerical experiment which suggests that fair weather variability in processes affecting near bottom concentrations is probably not sufficient to cause serious errors in suspended matter studies in the new york bight

geodynamic implications of paleomagnetic data from tertiary sediments in sakhalin russia nw pacific 1 n s trending right lateral strike slip faults which were active in the tertiary transect sakhalin russia while mesozoic forearc and accretionary rocks testify to an earlier period of subduction several kinematic models have been proposed for the region but the details required to constrain these models such as the timing of the transition from subduction to strike slip tectonics in sakhalin are still unknown even first order tectonic features such as the boundaries of the plates with which sakhalin evolved during the tertiary are poorly known paleomagnetic results from around sakhalin were obtained to constrain the geodynamic evolution of the region comparison of paleomagnetic inclination data with the apparent polar wander paths for the eurasian pacific and north american plates suggests that sakhalin probably evolved with the north american plate although a history including the eurasian plate cannot be ruled out paleomagnetic declination data suggest that significant clockwise vertical axis rotation has occurred in sakhalin since the mid paleocene it is likely that this rotational deformation was accommodated by tertiary activity on right lateral strike slip faults which may be associated with the opening of the japan sea tatar strait and kuril basin these data contradict a published kinematic model for eastern sakhalin where counterclockwise vertical axis rotations were predicted for neogene basins in the east sakhalin mountains agreement is better however with published paleomagnetic data from southern sakhalin where clockwise vertical axis rotations were documented

a potentially new instrument for measuring the in situ concentration of fine sediments in suspension abstract there is at present an instrumentation gap for the accurate measurement of suspended cohesive material over the concentration range between approximately 20 and 200 g l 1 to bridge this gap a laboratory feasibility study on a new process control instrument has been conducted to examine the application of such an instrument for measuring the in situ concentration of fine marine solids in suspension the technique provides a very accurate measurement of fluid bulk density from which the solids concentration can be derived the present study shows the instrument to be capable of accurately measuring the mass of fine sediments in suspension from 3 to beyond 200 g l 1

acoustic detection of seabed gravel movement in turbulent tidal currents abstract the measurement of sediment transport rates in the sea remains one of the most elusive goals for oceanographers sedimentologists and coastal engineers such measurements are required to test and validate sediment transport theories progress in this direction is greatly restricted by the lack of suitable field data and is dependent on progress with new instrumental techniques developments investigated in recent years have included the use of active and passive acoustic devices to detect sediment transport in this letter we describe the measurement of seabed gravel movement using a passive acoustic system for the first time using an underwater tv camera it has been possible to simultaneously observe sediment transport and take acoustic measurements thereby gaining independent assessment of the sensors performance further support has been provided by measurements of the turbulent fluctuations in the nearbed reynolds stresses

three dimensional modeling of pull apart basins implications for the tectonics of the dead sea basin we model the three dimensional 3 d crustal deformation in a deep pull apart basin as a result of relative plate motion along a transform system and compare the results to the tectonics of the dead sea basin the brittle upper crust is modeled by a boundary element technique as an elastic block broken by two en echelon semi infinite vertical faults the deformation is caused by a horizontal displacement that is imposed everywhere at the bottom of the block except in a stress free shear zone in the vicinity of the fault zone the bottom displacement represents the regional relative plate motion results show that the basin deformation depends critically on the width of the shear zone and on the amount of overlap between basin bounding faults as the width of the shear zone increases the depth of the basin decreases the rotation around a vertical axis near the fault tips decreases and the basin shape the distribution of subsidence normalized by the maximum subsidence becomes broader in contrast two dimensional plane stress modeling predicts a basin shape that is independent of the width of the shear zone our models also predict full graben profiles within the overlapped region between bounding faults and half graben shapes elsewhere increasing overlap also decreases uplift near the fault tips and rotation of blocks within the basin we suggest that the observed structure of the dead sea basin can be described by a 3 d model having a large overlap more than 30 km that probably increased as the basin evolved as a result of a stable shear motion that was distributed laterally over 20 to 40 km

broadband acoustic quantification of stratified turbulence high frequency broadband acoustic scattering techniques have enabled the remote high resolution imaging and quantification of highly salt stratified turbulence in an estuary turbulent salinity spectra in the stratified shear layer have been measured acoustically and by in situ turbulence sensors the acoustic frequencies used span 120 600 khz which for the highly stratified and dynamic estuarine environment correspond to wavenumbers in the viscous convective subrange 500 2500 m 1 the acoustically measured spectral levels are in close agreement with spectral levels measured with closely co located micro conductivity probes the acoustically measured spectral shapes allow discrimination between scattering dominated by turbulent salinity microstructure and suspended sediments or swim bladdered fish the two primary sources of scattering observed in the estuary in addition to turbulent salinity microstructure the direct comparison of salinity spectra inferred acoustically and by the in situ turbulence sensors provides a test of both the acoustic scattering model and the quantitative skill of acoustical remote sensing of turbulence dissipation in a strongly sheared and salt stratified estuary

on the remote acoustic detection of suspended sediment at long wavelengths experimental results are presented which indicate a linear relation between the time averaged amplitude of the envelope of the backscattered acoustic pulse at 192 khz and the square root of suspended sediment concentration in the 10 to 103 mg 1 1 range particle sizes ranged from 2 to 140 m the measurements were made in a negatively buoyant mine tailing discharge plume in a submarine channel at depths of 60 to 90 m in rupert inlet british columbia from the theory of acoustic backscatter from a solid elastic sphere in the rayleigh region it is shown that if the pressure amplitude of the backscattered wave is rayleigh distributed then such a linear relation is to be expected expressions for the optimum acoustic frequency for the detection of dilute suspensions at a given range and for the minimum detectable concentration are obtained assuming a thermal noise background the possibility that bubbles contribute to the backscatter is considered and found to be unlikely on the basis of probable bubble lifetimes

carbon and nitrogen isotope disturbances and an end norian late triassic extinction event major perturbations of organic carbon and nitrogen isotope ratios from a norian rhaetian late triassic boundary section in british columbia coincide with an extinction of the dominant deep water invertebrate fauna of the late triassic monotids and most ammonoids the carbon isotope excursion is attributed to the development of widespread oceanic stagnation that favored organic rich shale deposition the coincident nitrogen isotope excursion suggests that progressively more nitrate limited productivity forced a change to nitrogen fixing cyanobacteria populations as ocean stagnation created nutrient starved conditions the biotic crisis and geochemical events of the norian rhaetian boundary predate the latest rhaetian end triassic mass extinction thus the late triassic interval was marked by more than one extinction event

clockwise tectonic rotation of tertiary sedimentary basins in central hokkaido northern japan paleomagnetic data from tertiary sedimentary strata in the yubari and haboro areas of central hokkaido indicate consistently clockwise deflected magnetic declinations the mean declination of middle middle miocene rocks deviates 21 5 from the eurasian reference direction and that of the oligocene to lower middle miocene rocks deviates 30 21 this suggests that these sedimentary basins have rotated 10 30 clockwise about a vertical axis since the middle miocene these clockwise rotations can be explained by a right lateral displacement of a shear zone in central hokkaido this study demonstrates that central hokkaido is not simply a single tectonic unit of northeast japan characterized by counterclockwise rotations from early to middle miocene time

identification of wrench faults using subsurface structural data criteria and pitfalls 1 many structures imaged with reflection seismic can resemble a wrench fault system because of the great structural diversity of strike slip faults and the wide range of contractional and extensional features associated with these faults because of these resemblances numerous faults are misidentified as wrench faults by workers using subsurface structural data credible identification requires combinations of profile and map criteria 1 narrow long straight throughgoing solitary master fault or zone of deformation 2 steep to moderate dip of the master fault at depth 3 offset of the top of basement 4 changes in relative upthrown side separation sense and or fault dip direction at depth or along the strike of the master fault 5 narrow fault slices within the master fault zone that steepen and join at depth negative and positive flower structures 6 different separation sense and orientation of relative upthrown side at these fault slices and 7 coeval en echelon flanking structures the identification should be confirmed with other criteria that refute alternative interpretations the main pitfalls to a reliable identification are not considering alternative structural styles and the misinterpretation of features or patterns that superficially resemble wrench systems the profile geometries of basement involved reverse or normal faults particularly those with structural inversion can resemble the single strand of convergent or divergent wrench faults profile geometries of flower structures can be mimicked by narrow contractional horsts or narrow extensional grabens complexly faulted anticlines or synclines splay faults fault zones intruded by salt or shale and overprinted structures pitfalls in interpreting map relationships are possible when structural patterns combine several tectonic influences are controlled by rock anisotropy or include elements hat are not coeval and if the patterns characteristic of other styles are misinterpreted many erroneous identifications of wrench faults can be eliminated by demonstrating that the investigated fault or feature lacks a straight trace lateral length or throughgoing continuity

shoreface morphodynamics on wave dominated coasts abstract an open ocean shoreface typical of long wave dominated sandy coasts has been examined through a combination of extensive field measurements of wave and current patterns with computations of marine bedload transport and sedimentation sand transport on the upper shoreface is dominantly controlled by waves with only secondary transport by currents sand on the middle and lower shoreface as well as the inner continental shelf is entrained by storm waves and transported by a complex pattern of bottom boundary layer currents storm events have been studied and modeled for the shoreface off tiana beach long island the dominant effect of coastal frontal storms is to cause significant shore parallel bedload transport with important shore normal secondary components these storms tend to result in net offshore transport of sand removed from the beach and surf zone systems the bedload transport during a storm is convergent on the shoreface leading to accretion most accretion occurs on the upper shoreface with lesser deposits covering the middle and lower shoreface as well as the inner continental shelf longer term equilibrium can be maintained by slow return of sand up the shoreface during non storm conditions annual and geologic time scale budgets of shoreface sand transport and sedimentation yield equilibrium net accretion or net deposition the annual balance results from an integration of the event scale bedload transport patterns and morphologic responses these processes and responses have feedback mechanisms which stabilize the system over longer but not geologic time scales geologic time scale balances are controlled by relative sea level changes and relative availability of sediment supply with the event scale shoreface and transporting processes providing the mechanism to produce the changes in long term morphology and sedimentation patterns in the area of study the long term pattern is one of net shoreface erosion and the permanent loss of sand to the shelf floor

distribution of ammonium in minerals of metamorphic and granitic rocks abstract sixty nine analyses are given for nh4 in minerals of metamorphic and granitic rocks mostly from the ryoke belt japan the distribution of nh4 in coexisting minerals is quite systematic suggesting that nh4 is one of the stable geochemical components in high temperature processes biotite has the highest content of nh4 followed by muscovite k feldspar and plagioclase pure quartz is almost free from nh4 calcic plagioclase contains less nh4 than does sodic plagioclase the partition coefficients d pl bi d kf bi and d kf bi are on the average 0 11 0 38 and 0 43 respectively the fractionation of nh4 in these minerals is quite similar to that of rb but much smaller than that of cs distribution of nh4 as well as those of rb and cs appears to be explained by its ionic radius and the shortest cation o distances in alkali positions of minerals

stable isotope o h s c and n systematics of quartz vein systems in the turbidite hosted central and north deborah gold deposits of the bendigo gold field central victoria australia constraints on the origin of ore forming fluids the central and north deborah gold deposits are located in one of 15 mining centers of the bendigo gold field central victoria australia a major world class gold province developed in a turbidite terrane gold mineralization occurs primarily within domes and reverse fault systems in multiply deformed lower ordovician metaturbidites deformation and thrusting occurred between 450 and 420 ma coevally with regional metamorphism at zeolite to greenschist facies in the central and north deborah deposits six stages of quartz veining each with characteristic geometry and mineral paragenesis developed sequentially stages 1 2 and 4 are gold bearing whereas stages 3 5 and 6 are barren gold related quartz veins were deposited at temperatures of 350 25 c based on oxygen isotope geothermometry of silicate phases quartz muscovite and sulfur isotope compositions of coexisting sulfide mineral pairs sphalerite galena this result is consistent with temperatures inferred from fluid inclusions the 18o values of gold bearing vein quartz and coexisting hydrothermal muscovite are uniform within and between the six vein stages ranging from 15 9 to 17 2 per mil and 11 6 to 12 8 per mil respectively the d values of hydrothermal muscovites are also uniform at 68 to 55 per mil ore fluids have calculated 18o values of 8 to 11 per mil and d values of 37 to 17 per mil pyrite of synsedimentary diagenetic origin in slate and sandstone displays sulfur isotope compositions of 23 5 to 8 0 per mil and 0 1 to 11 9 per mil respectively sulfides from gold bearing quartz veins have a range of 7 4 to 8 1 per mil median ca 2 5 the relatively uniform vein pyrites indicate a large uniform sulfur source most likely from desulfidation reactions of sulfide minerals interaction of the ore forming fluid with depleted sulfides at the site of deposition may have shifted the sulfur isotope signatures of source sulfides to more negative values carbon isotope compositions of carbonates range from 5 1 to 9 0 per mil median ca 6 5 nitrogen concentrations and nitrogen isotope compositions of hydrothermal muscovite from quartz veins are 652 to 895 ppm and 2 84 to 4 49 per mil respectively collectively the data define a band in n content vegh rsus 15n coordinate space from higher n and lower 15n in the phanerozoic metasedimenary hosted central and north deborah gold deposits to lower n and higher 15n in predominantly meta igneous hosted neoarchean gold provinces collectively the h o s c and n isotope compositions of ore related hydrothermal minerals indicate that the dilute aqueous carbonic and n bearing ore forming fluids were generated from metamorphic dehydration reactions at deeper crustal levels and were variably influenced by exchange with wall rocks during transport to the site of deposition this genetic model for the central and north deborah gold deposits is consistent with other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes in contrast these data are not consistent with either mantle derived fluids or magmatic fluids nor do they support a deeply circulated meteoric surface water model for vein formation

a comment on the nitrogen record of crust mantle interaction and mantle convection from archean to present by b marty and n dauphas earth planet sci lett 206 2003 397 410

structure of the dead sea pull apart basin from gravity analyses analyses and modeling of gravity data in the dead sea pull apart basin reveal the geometry of the basin and constrain models for its evolution the basin is located within a valley which defines the dead sea transform plate boundary between africa and arabia three hundred kilometers of continuous marine gravity data collected in a lake occupying the northern part of the basin were integrated with land gravity data from israel and jordan to provide coverage to 30 km either side of the basin free air and variable density bouguer anomaly maps a horizontal first derivative map of the bouguer anomaly and gravity models of profiles across and along the basin were used with existing geological and geophysical information to infer the structure of the basin the basin is a long 132 km narrow 7 10 km and deep 10 km full graben which is bounded by subvertical faults along its long sides the bouguer anomaly along the axis of the basin decreases gradually from both the northern and southern ends suggesting that the basin sags toward the center and is not bounded by faults at its narrow ends the surface expression of the basin is wider at its center 16 km and covers the entire width of the transform valley due to the presence of shallower blocks that dip toward the basin these blocks are interpreted to represent the widening of the basin by a passive collapse of the valley floor as the full graben deepened the collapse was probably facilitated by movement along the normal faults that bound the transform valley we present a model in which the geometry of the dead sea basin i e full graben with relative along axis symmetry may be controlled by stretching of the entire brittle and ductile crust along its long axis there is no evidence for the participation of the upper mantle in the deformation of the basin and the moho is not significantly elevated the basin is probably close to being isostatically uncompensated and thermal effects related to stretching are expected to be minimal the amount of crustal stretching calculated from this model is 21 km and the stretching factor is 1 19 if the rate of crustal stretching is similar to the rate of relative plate motion 6 mm yr the basin should be 3 5 m y old in accord with geological evidence

c and n isotopic composition and the infrared absorption spectra of coated diamonds evidence for the regional uniformity of co2h2o rich fluids in lithospheric mantle abstract the 13 c and 15 n values nitrogen abundances and nitrogen aggregation states of coated diamonds from botswana angola sierra leone and siberia have been determined a single cubic micro diamond from the northern territory australia was also analysed the cubic coats of the diamonds and the cubic diamond from australia had a restricted range in isotope composition 13 c 7 2 to 4 1 15 n 8 7 to 1 7 in contrast the cores of the coated diamonds were found to be highly variable 13 c 21 1 to 1 9 and 15 n 2 8 to 12 1 with the majority being positive all of the coats gave the type iaa absorption spectra together with others due to micro inclusions dominated by h 2 o and co 2 whereas the cores contained nitrogen that was more highly aggregated the results suggest that coated diamonds were formed following the influx of co 2 h 2 o rich fluids into diamond bearing lithosphere pre existing diamonds acted as seeds for renewed growth and these are now the cores of the diamonds these cores may be very variable in terms of morphology isotopic composition age nitrogen aggregation state and crystallinity depending on the particular history of the source regions and the conditions of diamond growth it is believed that the influx of volatiles and the growth of the coats was linked to kimberlite magmatism the 13 c and 15 n results for the coats indicate that in terms of c and n isotope composition the source of co 2 h 2 o rich fluids is globally quite homogeneous it is probably located beneath continental lithosphere and in addition may have characteristics similar to the source of the ocean island basalts

coalescence of fractures under shear stresses in experiments a series of uniaxial compression tests were performed on gypsum specimens with preexisting fractures to study the failure mechanism of fractures and rock bridges in fractured rock masses the coalescence mechanism of two parallel and offset fractures was investigated by monitoring the process of fracture initiation and propagation with a video camera the tests showed that two inclined parallel fractures can coalesce by shear failure and or tensile failure under a uniaxial load the coalescence path and mechanism mainly depend on the relative position of the two fractures for instance when the two fractures are coplanar or slightly offset coalescence is generated by shear failure when they are overlapping in the loading direction coalescence is generated by mixed shear and tensile failure two types of preexisting fractures one without initial surface contact and hence frictionless and another with surface contact and friction were used to study the influence of fracture contact conditions on the coalescence path and load it was found that coalescence of fractures with surface contact and friction requires loads as much as 35 higher than that for coalescence of fractures without contact and friction a stress analysis was conducted in this study to explain the different coalescence mechanisms the analytical work indicated that different fracture geometries produce significantly different stress fields in the rock bridge area and hence result in different failure modes

identification of intense intermittent coherent motions under shoaling and breaking waves laboratory measurements of the instantaneous horizontal and vertical turbulent velocities u and w induced by regular waves spilling on a rough impermeable slope were analyzed to elucidate the nature of turbulence generated in the bottom boundary layer and by wave breaking the analyses focused on the instantaneous turbulent events such as the absolute shear stress u w and turbulent kinetic energy k u 2 w 2 2 below trough level inside the surf zone the horizontal and vertical velocity records showed intense intermittent turbulent events that did not occur with the passing of each wave and the instantaneous quantities of and k could not be explained in terms of the phase averaged quantities the intermittent turbulent events extended into the bottom boundary layer inside the surf zone and in this region the infrequent but intense turbulence generated by wave breaking was an order of magnitude larger than the turbulence generated locally at the boundary two techniques were used to analyze the turbulent motions a quadrant analysis technique showed that although the large turbulent motions did not occur with each wave they were phase dependent near trough level and less so near the bottom a conditional sampling technique quantified the intensity and duration of the turbulent motions indicating that coherent events intense events occurred for 10 2 of the record and accounted for approximately 50 20 of the turbulent motion it is likely that the exactitude of these statistics will differ depending on breaker type nevertheless these statistics indicated that large turbulent motions are infrequent but contribute significantly to the turbulence intensity and possibly the suspension of bottom sediments

isotopic variations of the fixed nitrogen in metamorphic rocks the content and isotopic composition of fixed nitrogen nh 4 n in metasedimentary rocks phyllites mica schists and gneisses from prograde metamorphic zones in the erzgebirge saxon ore mountains g d r were measured and show that the nitrogen content decreases and 15n increases with increasing metamorphic grade the geochemical and isotopic behaviour of nitrogen during contact metamorphism was investigated in a mica schist profile through the contact aureole of a granitic pluton the nitrogen concentrations of the wall rocks decrease towards the contact whereas the 15n values become higher various model experiments were carried out in the laboratory to explain the changes observed in the rock samples the nitrogen isotope fractionation factor was determined for the isotopic exchange in the system ammonium sulphate ammonia at 250 c 1 0143 0 0012 and 350 c 1 0128 0 0006 in accordance with the model experiments the conclusion seems warranted that the change in nitrogen content and its isotopic composition in rocks during metamorphic processes depend mainly on the metamorphic temperature

acoustic profiling of suspended sediments in the marine bottom boundary layer an acoustic 3 mhz backscattering profilometer has been developed for study of sediment transport in the bottom boundary layer laboratory experiments indicate reasonable correlations between backscattering intensity and mass concentrations for well sorted fine to coarse quartz sands typical of those found in marine sediments departure of the calibration curves from their expected values is thought to be due to the non spherical shape of the quartz grains field experiments on the inner shelf using the profilometer combined with velocity profiles show individual profiles taken at 1 hz during erosion events are characterized by highly variable concentrations surface wave groups rather than individual waves appear to be correlated with groups of profiles with high concentrations extending 25 100 cm above bottom averaging produces smooth profiles which fit well log normal distributions predicted by steady flow suspended load theories

acoustic imaging of sea bed geometry a high resolution remote tracking sonar hrrts ii abstract a high resolution remote tracking sonar hrrts ii is described which is capable of measuring a 2 d profile of the sea bed over a maximum distance of 5 m under conditions of significant sediment transport the backscattered signal from a pulsed 30 s 5 mhz sonar provides acoustic range measurements of the small scale topography generated by bedforms at any point in time as well as changes in this small scale topography and the average elevation of sections of the sea bed over time bedform height and spacing can be determined accurately although bedform shape is distorted by smoothing of large slope changes as a result of the finite size of the footprint of this narrow beamed 0 74 sonar the system operates on command from a shore based micro computer and topographic resolution of the order of a few millimetres is possible resolution deteriorates as wave energy increases to levels where vibration of the transducer and large concentrations of sediment in the water column result in signal attenuation and a decrease in the signal to noise ratio

neogene strike slip faulting in sakhalin and the japan sea opening we describe structural data from a 2000 km n s dextral strike slip zone extending from northern sakhalin to the southeast corner of the japan sea satellite images field data and focal mechanisms of earthquakes in sakhalin are included in the interpretation since miocene time the deformation in sakhalin has been taken up by n s dextral strike slip faults with a reverse component and associated en echelon folds narrow en echelon neogene basins were formed along strike sup faults and were later folded in a second stage of deformation we propose a model of basin formation along extension al faults delimitating dominos between two major strike slip faults and subsequent counterclockwise rotation of the dominos in a dextral transpressional regime basins becoming progressively oblique to the direction of maximum horizontal compression and undergoing shortening the association of both dextral and compressional focal mechanisms of earthquakes indicates that the same transpressional regime still prevails today in sakhalin we present fault set measurements undertaken in noto peninsula and yatsuo basin at the southern end of the sakhalin east japan sea strike slip zone early and middle miocene formations recorded the same transtensional regime as observed along the west coast of ne honshu during the early and middle miocene the strike slip regime was transpressional to the north in sakhalin and hokkaido and transtensional to the south along the west coast of ne honshu as far as noto peninsula and yatsuo basin dextral motion accommodated the opening of the japan sea as a pull apart basin with the tsushima fault to the west the opening of the japan sea ceased at the end of the middle miocene when transtension started to change to e w compression in the japan arc subduction of the japan sea lithosphere under the japan arc started 1 8 ma ago the evolution of the stress regime from transtensional to compressional in the southern part of the strike slip zone is related to the inception of the subduction of the young philippine sea plate lithosphere under the japan arc during the late miocene subduction related extension is a necessary condition for the opening of the japan sea two possible mechanisms can account for dextral shear in this area 1 counterclockwise rotation of crustal blocks due to the collision of india with asia 2 extrusion of the okhotsk sea block squeezed between the north america and eurasia plates

spatially correlated depth changes in the nearshore zone during autumn storms acoustic reflection measurements of seabed elevation were made at stanhope beach prince edward island during three successive storms in october november 1989 the instruments were located approximately 200 m offshore on the seaward face of a shore parallel bar in a mean water depth of 2 2 m bed elevation measurements were made at 30 min intervals with a range resolution of 1 mm at horizontal spacings between 22 cm and 1 5 m using an array of four acoustic sounders operating at 1 2 25 and 5 mhz it is shown that such an array can be used as 1 an interferometer to determine bedform properties and migration rates 2 a leveling device to determine changes in local bottom slope and 3 an erosion deposition gauge in the interferometric mode time domain autocorrelation and cross correlation analyses of the bottom elevations are used to estimate the wavelengths migration rates and migration directions of sand ripples and megaripples the ripple wavelengths 10 15 cm and heights 3 5 cm are comparable to measurements made by divers ripple migration rates were 1 6 cm h 1 directed offshore in the direction of the mean shore normal near bottom current and increased with increasing mean current speed evidence of megaripple like features 2 5 cm height 1 5 3 m length is found also migrating in the direction of the mean shore normal near bottom drift at speeds of about 20 cm h 1 bedload transport rates in the onshoreoffshore direction are estimated from the bedform migration rates the ripple transport rate was small an order of magnitude smaller than the transport of sediments in suspension by the mean offshore drift in contrast the large scale bedform transport appears to have been comparable to the mean current transport of suspended sediment interestingly it appears that the total bedform transport was comparable to that predicted by watanabe s 1981 net bedload transport formula provided a coefficient appropriate to irregular wave conditions is used during the third and highest energy storm event the measurements indicate transition to flat bed and generalized local erosion at a maximum rate of 8 cm h 1 this erosion event was associated with a general shoreward migration of the bar

three dimensional models of deformation near strike slip faults we use three dimensional elastic models to help guide the kinematic interpretation of crustal deformation associated with strike slip faults deformation of the brittle upper crust in the vicinity of strike slip fault systems is modeled with the assumption that upper crustal deformation is driven by the relative plate motion in the upper mantle the driving motion is represented by displacement that is spectied on the bottom of a 15km thick elastic upper crust everywhere except in a zone of finite width in the vicinity of the faults which we term the shear zone stress free basal boundary conditions are specified within the shear zone the basal driving displacement is either pure strike slip or strike slip with a small oblique component and the geometry of the fault system includes a single fault several parallel faults and overlapping en echelon faults we examine the variations in deformation due to changes in the width of the shear zone and due to changes in the shear strength of the faults in models with weak faults the width of the shear zone has a considerable effect on the surficial extent and amplitude i c1 j l c i rl l b blhi aill i srizcxi ld 3 rr ij i n flail 3il i dilitiiiat df ti ijtluii clicili c i i zor tz a j t s ii acmes strong fault lnnlds havs lnore luc tlixd dxz a ac tip of tne faults and the deformation is partly distributed outside the fault zone the dimensions of large basins along strike slip faults such as the rukwa and dead sea basins and the absence of uplift around pull apart basins fit models with weak faults better than models with strong faults our models also suggest that the length to width ratio of pull apart basins depends on the width of the shear zone and the shear strength of the faults and is not constant as previously suggested we show that pure strike slip motion can produce tectonic features such as elongate half grabens along a single fault rotated blocks at the ends of parallel faults or extension perpendicular to overlapping en echelon faults which can be misinterprete d to indicate a regional component of extension zones of subsidence or uplift can become wider than expected for transform plate boundaries when a minor component of oblique motion is added to a system of parallel strike slip faults

sediment transport in the mouth of the eden estuary abstract observations of water movement and sediment transport were made from a fixed platform at an intertidal location in the mouth of the eden estuary the effects of wave activity on water movement and suspended sediment fluxes were evaluated and an empirical relationship between suspended sediment concentrations and near bed water movement is described the circulation of water in st andrews bay indicates a residual movement onshore near to the bed onshore movement of sediment in the mouth of the estuary is indicated by suspended sediment fluxes and bedload transport determined from bedform migration the relative roles of suspended sediment and bedload transport are discussed morphological changes in the estuary mouth over the three year survey period are relatively small and indicate a stable environment

stratigraphic correlation of upper cretaceous to paleocene forearc basin sediments in northeast japan cyclic sedimentation and basin evolution abstract cretaceous to paleocene sediments are distributed across a 200 km wide and 1400 km long belt in northeast japan to sakhalin twenty six stratigraphic sections including land based and offshore drill holes and surface sections are correlated to delineate the sedimentary history and basin evolution of the yezo forearc basin two second order shallowing upward cycles are recognized in hokkaido but are obscure in north honshu shallow marine to paralic sediments of the first cycle early albian to turonian are represented by the mikasa formation late albian to turonian as the western marginal facies while the eustatic curves e g haq curves reach the highstand maximum at the late cenomanian the campanian to maastrichtian shallow and non marine facies of the second cycle coniacian to maastrichtian are characterized by the hakobuchi group in hokkaido and its correlatives in north honshu this large scale shallowing may have reflected directional changes of the izanagi kula plate motion near the early campanian the uppermost maastrichtian to upper paleocene is possibly absent everywhere in the basin the shallow marine to non marine facies often show several third order depositional sequences with upward coarsening facies successions they may have been controlled by global eustasy even in an active margin setting since the stacking patterns of sequences and the timing of sequence boundaries appear considerably concordant with the oscillation patterns of the haq curves

barrier island evolution middle atlantic shelf u s a part i shoreface dynamics abstract in part i of this paper near bottom fluid velocity and sediment concentration measurements from the shoreface of a middle atlantic barrier long island coast are analyzed to provide insight into the dynamics of erosional shoreface retreat in part ii these data are combined with observations of coastal stratigraphy in order to construct a model for the evolution and behavior of middle atlantic barriers wave motions on the long island shoreface tend to drive sediment onshore calculations of the onshore sediment flux driven by asymmetrical shoaling waves show that for the wave states commonly encountered on the middle atlantic shelf values become strongly positive landward of approximately 10 m water depth upper shoreface but drop to very low values shortly seaward of that isobath on the lower shoreface and inner shelf floor fair weather wave current interaction tends to cause a landward creep of sediment even though the wave orbital component of the near bottom velocity field is nearly symmetrical this movement occurs because the wave approach direction generally lies within 90 of the direction up coast or down coast of the alongshore wind driven current therefore fluid shear stress acting on the sediments tends to be reinforced during the shoreward stroke of the wave orbital motion and partially cancelled during the seaward stroke during major storms the rate of sediment transport increases by at least an order of magnitude and the role of wind driven currents becomes important much more sediment is resuspended by the wave orbital current component because storm waves are more powerful than fair weather swells but the wind driven flow component is also much stronger and is now available for transporting the resuspended sediment storm flows over the shoreface occur in distinct dynamic zones surf zone friction dominated zone transition zone geostrophic zone the zones are defined by dynamical considerations and expand or contract with the intensity of the causative wind stress during peak flow events the characteristic length scales of the friction dominated and geostrophic zones tend to correspond with the morphologic zones of the shoreface and inner shelf the storm intensified wind driven alongshore flows of the lower shoreface are frequently jet like in nature and may be upwelling or downwelling wind driven coastal flows with a strong downwelling component occur during most storms on the long island coast and are particularly important to the coastal sand budget during these events sand is entrained by the storm intensified upper shoreface circulation system of wave driven alongshore currents and rip currents and is fed into the main wind driven coastal current because of the offshore component of bottom flow sand is swept down the lower shoreface and onto the adjacent inner shelf fair weather processes may be unable to return storm deposited sand to the beach from such an offshore position the shoreface transport regime of the long island barrier coast thus consists of long periods of time months during which sand moves slowly toward the beach punctuated by short intense periods hours or days during which sand is transferred from the shoreface to the adjacent inner shelf the long term sense of movement of the shoreface whether retreating the long island case or prograding must depend on the loss or gain of sand by shoreface with respect to the inner shelf the data shows that the coastal sand budget is controlled not only by the upper shoreface cycle withdrawl of sand from the beach prism storage in the breakpoint bar and its subsequent return to the beach but by a cycle of larger spatial and temporal scale in which sand is exchanged between the shoreface as a whole and the adjacent inner shelf

age and speciation of iodine in groundwater and mudstones of the horonobe area hokkaido japan implications for the origin and migration of iodine during basin evolution abstract this paper reports the concentration speciation and isotope ratio 129i 127i of iodine from both groundwater and host rocks in the horonobe area northern hokkaido japan to clarify the origin and migration of iodine in sedimentary rocks cretaceous to quaternary sedimentary rocks deposited nearly horizontally in tenpoku basin and in the horonobe area were uplifted above sea level during active tectonics to form folds and faults in the quaternary samples were collected from the pliocene koetoi and late miocene wakkanai formations fms which include diatomaceous and siliceous mudstones the iodine concentration in groundwater up to 270 mol l is significantly higher than that of seawater with the iodine enrichment factor relative to seawater reaching 800 1500 the iodine concentration in the rocks decreases from the koetoi to wakkanai fms suggesting that iodine was released into the water from the rocks of deeper formations the iodine concentration in the rocks is sufficiently high for forming iodine rich groundwater as found in this area x ray absorption near edge structure xanes analysis shows that iodine exists as organic iodine and iodide i in host rocks whereas it exists mainly as i in groundwater the isotope ratio is nearly constant for iodine in the groundwater at 0 11 0 23 10 12 and it is higher for iodine in rocks at 0 29 1 1 10 12 giving iodine ages of 42 60 ma and 7 38 ma respectively some iodine in groundwater must have originated from paleogene and even late cretaceous fms which are also considered as possible sources of oil and gas in view of the old iodine ages of the groundwater the iodine ages of the rocks are older than the depositional ages implying that the rocks adsorbed some iodine from groundwater which was sourced from greater depths the iodine concentration in groundwater decreases with decreasing chlorine concentration due to mixing of iodine rich connate water and meteoric water a likely scenario is that iodine rich brine formed during the long term basin evolution from the cretaceous to quaternary and that this brine was diluted by mixing with meteoric water during uplifting and denudation of the area

isotope study on organic nitrogen of westphalian anthracites from the western middle field of pennsylvania u s a and from the bramsche massif germany abstract the objective of this study was to examine an aspect of the thermal cycling of organic nitrogen in sediments and metasediments the cycling of organic nitrogen is important because sedimentary organic matter is a shuttle of nitrogen from the atmosphere to the lower crust and thermal decomposition of organic matter is a critical step in the recycling of nitrogen between the different nitrogen pools abundance and isotopic composition of organic nitrogen were determined in the particular case of two low sulfur westphalian anthracites series from pennsylvania and bramsche massif they represent good examples of euramerica coals spanning the whole range of anthractization in single fields gold cell experimental simulation of the denitrogenation process was conducted at moderate pressure to show that both suites make ideal metamorphic profiles without any shift due to change of facies or to hydrothermal disturbance during anthracitization organic nitrogen content decreases rapidly while organic nitrogen isotopic composition does not change with rank increase the preservation of the isotopic signature implies that organic nitrogen isotopes could be used as indicators for the paleoecological and paleodepositional history reconstruction of the basins the striking contrast between the rapid and sharp decrease of nitrogen organic content and the invariance of its isotopic composition during the whole anthracitization suggests that ammonia is an important product of the denitrogenation process

precambrian ammonium biogeochemistry a study of the moine metasediments scotland abstract the content and isotopic composition of ammoniacal nitrogen have been determined in a suite of amphibolite facies metasediments of precambrian age whole rock samples and mica separates from the moine succession proterozoic of scotland were analysed by a combination of capacitance manometry and static vacuum mass spectrometry prior to the analyses the presence of the ammonium ion was confirmed by obtaining infrared ir absorption spectra from the micas principally biotites whole rock ammonium contents are high for amphibolite facies metasediments 140 422 ppm the ammonium ion was not detected in the ir absorption spectra of biotites from one schist however this sample contains neither garnet nor white mica for most of the samples the 15n values are very positive between 12 4 and 16 6 with one sample having a lower value of 8 4 the major variations between samples can be interpreted in terms of original sedimentary features for the ammonium bearing samples muscovites have concentrations between 365 and 633 ppm biotites between 845 and 1739 ppm for individual samples nh4 mu nh4 bi varies between 0 31 and 0 43 a much narrower range than has been reported previously there are no significant or consistent differences in 15n between co existing biotite and white mica nor between the 15n values of the mineral separates and their respective whole rock values the latter suggests minimal selective partitioning of isotopes between micas and plagioclase feldspar the only other potential host for ammonium in the rocks assuming that the ammonium has been derived from organic matter originally present at the time of deposition and by comparison with previous studies it can be inferred that the original 15n value of the moine sediments was somewhere between 5 and 10 similar to recent sediments this suggests that the nitrogen cycle in the proterozoic shelf sea from which the moine sediments were deposited was broadly similar to the present day overall the study underlines how under developed the n system is compared to other stable isotope systems notably c and s and we use the opportunity to highlight some areas that could be developed in the future however one aspect is clear future ammonium studies of metamorphic rocks will need to be performed at high resolution visible scale of heterogeneity with strong mineralogical petrological and field controls

reactivated strike slip faults examples from north cornwall uk abstract several strike slip faults at crackington haven uk show evidence of right lateral movement with tip cracks and dilatational jogs which have been reactivated by left lateral strike slip movement evidence for reactivation includes two slickenside striae on a single fault surface two groups of tip cracks with different orientations and very low displacement gradients or negative left lateral displacements at fault tips evidence for the relative age of the two strike slip movements is 1 the first formed tip cracks associated with right lateral slip are deformed whereas the tip cracks formed during left lateral slip show no deformation 2 some of the tip cracks associated with right lateral movement show left lateral reactivation and 3 left lateral displacement is commonly recorded at the tips of dominantly right lateral faults the orientation of the tip cracks to the main fault is 30 70 clockwise for right lateral slip and 20 40 counter clockwise for left lateral slip the structure formed by this process of strike slip reactivation is termed a tree structure because it is similar to a tree with branches the angular difference between these two groups of tip cracks could be interpreted as due to different stress distribution e g transtensional transpressional near field or far field stress different fracture modes or fractures utilizing pre existing planes of weakness most of the d x profiles have similar patterns which show low or negative displacement at the segment fault tips although the d x profiles are complicated by fault segments and reactivation they provide clear evidence for reactivation profiles that experienced two opposite slip movements show various shapes depending on the amount of displacement and the slip sequence for a larger slip followed by a smaller slip with opposite sense the profile would be expected to record very low or reverse displacement at fault tips due to late stage tip propagation whereas for a smaller slip followed by larger slip with opposite sense the d x profile would be flatter with no reverse displacement at the tips reactivation also decreases the ratio of dmax l since for an original right lateral fault left lateral reactivation will reduce the net displacement dmax along a fault and increase the fault length l finally we compare crackington haven faults with these in the atacama system of northern chile the salar grande fault sgf formed as a left lateral fault with large displacement in its central region later right lateral reactivation is preserved at the fault tips and at the smaller sub parallel cerro chuculay fault these faults resemble those seen at crackington haven

nitrogen and argon signatures in 3 8 to 2 8 ga metasediments clues on the chemical state of the archean ocean and the deep biosphere abstract n and ar elemental and isotopic analyses were conducted on archean metasediments of isukasia west greenland and pilbara craton western australia in order to investigate the n isotopic evolution during the first half of earth s history the selected samples are deep sea sediments and hydrothermal deposits having ages from 3 8 to 2 8 ga and affected by different degrees of metamorphism the release patterns of n and ar obtained by high resolution stepped combustion show the occurrence of at least two trapped components the first is released at 600 c and it is likely contained in fluid inclusions n is released together with primordial 36ar and shows a 15n value of 1 3 1 0 close to that of modern atmospheric n2 15n 0 this component is well preserved in hydrothermal vent silica deposits of north pole pilbara craton and nitrogen may represent ammonium salt dissolved in deep sea hydrothermal fluids the second n component released at temperatures higher than 1000 c is accompanied by radiogenic 40ar and shows a 15n value of 7 4 1 0 in a kerogen rich chert from north pole pilbara craton this n is likely biogenic and negative 15n values may reflect a metabolic isotopic fractionation induced by chemosynthetic bacteria using inorganic nh4 contained in hydrothermal fluids this 15n depleted biogenic component may occur in isukasia banded iron formation 15n 1 7 but further data are needed to confirm such a hypothesis in all other samples metamorphic induced rayleigh distillation has altered the pristine n isotopic signature

vertical suspension profile in the changjiang estuary abstract by using an acoustic suspended sediment monitor assm four patterns of vertical suspension profile have been obtained at spring tide 28 29 may 1994 in the changjiang estuary type i is l shaped at flood tide the vertical gradients in suspended sediment concentration ssc were small

ammonium concentration and nitrogen isotope composition in metasedimentary rocks from different tectonometamorphic units of the european variscan belt the content and isotopic composition of ammonium nh4 were measured by using kjeldahl distillation for 63 samples of predominantly metasedimentary rocks from two different geological settings of the european variscides i e the erzgebirge and the zone of erbendorf vohenstrauss in germany the studied erzgebirge schists represent an early paleozoic passive margin sequence that reappears in different deep subducted metamorphic units this allows an efficient examination of nitrogen loss and isotope fractionation during prograde metamorphism ammonium is found to be progressively depleted accompanied by a shift in 15n from the low grade units 2 kbar 300 c with 638 124 ppm and 15n 2 2 0 6 to the garnet phyllite unit 9 kbar 470 c with 621 190 ppm and 15n 3 5 0 9 the mica schist eclogite unit 12 kbar 550 c with 394 113 ppm and 15n 3 9 0 8 and to the gneiss eclogite unit 12 kbar 730 c with 99 32 ppm and 15n 7 7 2 0 using equilibrium models for rayleigh distillation and batch volatilization suggest that the nitrogen depletion took place by ammonia release only for the mica schists this isotope fractionation can be explained by the loss of molecular nitrogen in comparison with the early paleozoic schists the proterozoic ortho and paragneisses of the erzgebirge gneiss unit 6 8 kbar 650 c contain significantly lower amounts of ammonium 70 ppm and reach relatively low 15n values 2 5 to 3 6 the paragneisses from the zone of erbendorf vohenstrauss zev sampled from the ktb pilot hole represents a separate tectonometamorphic unit that has undergone polyphase metamorphic conditions with the major imprint being amphibolite facies 7 kbar 650 700 c the metagraywackes have nh4 contents of 80 ppm and 15n of approximately 6 gneisses in the vicinity of a late cataclastic shear zone at 2000 m depth are characterized by a shift in nh4 250 ppm and 15n up to 12 which suggest late fluid rock interactions with a nitrogen and 15n enriched fluid

a model of late cenozoic transcurrent motion and deformation in the fore arc of northeast japan constraints from geophysical studies abstract we use recently acquired seismic reflection data and reprocessed sections to interpret the structure of the northern part of the ne japan forearc we identify a nnw sse trending deformation zone bounded by large transcurrent faults trends t1 t4 from west to east on the upper continental slope the lower slope is characterized by a frontal prism and reverse faults bathymetric data reveal several en echelon topographic bulges with nw se elongation aligned parallel to the fault trends the bulges are interpreted as a dextral wrench zone that has developed since the neogene based on structural contours of two late cenozoic seismic horizons clockwise rotation associated the wrenching is indicated by the paleomagnetism of paleogene marine sediments obtained from a drill hole within the faulted zone close to trend t1 a previous seismic refraction study shows remarkable contrast in p wave velocity across trend t2 indicating a considerable rearrangement of crust associated with transcurrent motion along this fault we propose a paleogeographic reconstruction assuming 200 km southward trenchward lateral transportation along trend t2 and its northern extension in our model subduction erosion at the northern japan trench was enhanced by trenchward migration of the fore arc sliver but steadied following rearrangement of the sliver along the transect the calculated variation in subduction erosion is consistent with subduction histories based on existing well data

a comment on the nitrogen record of crust mantle interaction and mantle convection from archean to present by b marty and n dauphas earth planet sci lett 206 2003 397 410 the earth s upper mantle is depleted in 15n isotope with a n15n value around 35x where n15n n nsample n nair31 1000 relative to atmosphere and crust the 15n depleted character rst identi ed from recent i e 6 380 ma diamonds 1 3 see 4 for review was con rmed by studies focusing on volatiles extracted from mid ocean ridge basalts morb vesicles 5 8 archean diamonds as old as 3 2 ga 9 for review see 10 and references therein con rmed the negative n15n values showing that the 15ndepleted character of the earth s upper mantle is a long term feature 11 12 if the nitrogen present within the external reservoirs of the earth i e atmosphere sediments and crust had been simply outgassed from the mantle then one would expect them to display also negative n15n values however the atmosphere sediments and crust have all n15nv 0x in addition the fractionation of nisotopes occurring during basaltic melt degassing at ridges is opposite to what would be required to achieve positive n15n in vesicles 8 13 see below and 1 14 for discussion accordingly there is a so called isotopic imbalance of nitrogen between the mantle and the external reservoirs of the earth fig 1 which cannot be accounted for by outgassing of the earth s mantle only several models have been proposed to account for the nitrogen isotopic imbalance see fig 1 1 a heterogeneous accretion of the earth s volatiles e g 15 2 core mantle isotopic fractionation 7 13 3 hydrodynamic escape and fractionation of the atmospheric nitrogen 6 and 4 the new model presented by marty and dauphas 16 who consider that the nitrogen now present in the diierent mantle reservoirs is dominantly recycled organic nitrogen according to these authors the nitrogen in the upper mantle as sampled by diamonds and morb has a n15n value around 35x because it contains nitrogen of organic origin recycled in the archean which would have had a n15n around 35x the nitro

the benthic boundary layer and sediment transport the major problems facing scientists studying marine boundary layer fluid mechanics in 1979 concerned the specific mechanismic operating in the regions of the top and the bottom of the boundary layer at the top the mechanisms of fluid escapement from the boundary layer and mixing into the ocean interior could only be postulated approximations of diffusivity across the top of the layer were being debated the values of which were more articles of faith than physically validated estimates cf armi 1979 garrett 1979 at the bottom the intermittent generation of stress cf gordon 1975 heathershaw and simpson 1979 was held responsible for the wide variability observed in the drag coefficient and the thickness of the viscous sub layer was claimed to be greater than that traditionally found from laboratory studies caldwell and chriss 1979

comparison of measurements and models of bed stress bedforms and suspended sediments under combined currents and waves abstract this study presents an analysis of data collected in an embayment off a sandy beach protected by shore parallel breakwaters observations were carried out over a forty day period including spring and neap tidal cycles and low and high wave activity measurements were collected on the waves currents bedforms and suspended sediments and these were used to derive estimates of the bed shear stresses ripple dimensions reference concentrations and suspended sediment profiles the aim of the present study was to use the measurements to assess commonly employed empirical formulations applied to sediment modelling in the coastal marine environment assessments are made of four ripple predictors two formulations of reference concentration and power law and exponential suspended sediment shape functions in some cases predicted parameters are well represented during low wave conditions whilst other parameters are better predicted under high wave events the outcome from the work is an evaluation of the predictive capability of the selected empirical formulae at the sandy location and discussions on the comparison between the observations and predictions

a reinterpretation of the crustal n isotope record evidence for a n 15 enriched archean atmosphere a new compilation of n isotope and abundance data for metasedimentary rocks and hyrdothermal micas that proxy for bulk crust show systematic patterns 1 15n values of kerogen in precambrian cherts are more negative relative to siliciclastic counterparts probably due to a mantle hydrothermal component 2 there is a secular trend from average 15n 15 3 1 8 in archean shales through intermediate values in the proterozoic to phanerozoic counterparts where 15n averages 3 5 3 hydrothermal micas in metamorphic hydrothermal systems of palaeozoic and mesozoic age that proxy for crust have 15n within the range of contemporaneous sedimentary rocks 4 hydrothermal micas track the secular trend of 15n for kerogen from 2 7 ga to the phanerozoic 5 within precambrian datasets 15n does not increase with decreasing n content accordingly high 15n values cannot stem either from metamorphism or form rayleigh fractionation 6 previous studies show isotopic shifts during metamorphism are only 1 to 3 up to amphibolite facies values of 10 24 are attributed to a high 15n archean atmosphere a residual signature of ci carbonaceous chondrites where 15n is 30 to 42

multiple growth events during diamond genesis an integrated study of carbon and nitrogen isotopes and nitrogen aggregation state in coated stones the internal structure and growth history of diamonds have been investigated by the study of carbon isotopes and the abundance isotope composition and aggregation state of nitrogen polished plates of zoned diamonds coated stones were laser sectioned for infrared mapping and isotope profiling nine small cubic and three small octahedral diamonds from zaire and two coated stones and five small cubic diamonds specifically from the mbuji mayi area of that country were also investigated the isotope composition and infrared characteristics of the diamonds of cubic habit including coats were found to be indistinguishable with 13c in the range 5 9 to 7 5 and all the nitrogen being present as the paired structure iaa with a 15n of between 3 1 and 8 0 the diamonds of octahedral habit including the cores of the coated stones were more variable 13c varied from 4 9 to 9 8 infrared spectra of the octahedral diamond exhibited either strong iaa characteristics or a combination of iaa and iab platelets were present in most cases 15n values from octahedral diamonds varied from 5 8 to 13 4 the data suggest that the octahedral diamonds represent a variety of growth events separated in time and or space and that the diamonds resided in the lithosphere for a period sufficient for thermal maturation in the case of the coated stones the octahedral diamonds were later involved in an event which added a component from a single relatively homogeneous reservoir cubic habit diamonds were formed at the same time this latter event is believed to be related to the kimberlite eruption comparison of the data with carbon isotope analyses of cubic diamond from other sources suggests that this reservoir could be widespread

40ar 39ar age constraints on the thermal history of the archean abitibi greenstone belt and the pontiac subprovince implications for terrane collision differential uplift and overprinting of gold deposits 40ar 39ar mineral age spectra of granitic and metamorphic rocks in conjunction with existing conventional zircon geochronology indicate that at least two major late archean thermal events affected tectonic blocks of the abitibi southern volcanic zone svz and the juxtaposed pontiac subprovince the earlier thermal activity 2690 2670 ma was accompanied by the intrusion of voluminous syntectonic plutons and caused low pressure greenschist facies metamorphism in the svz and intermediate pressure metamorphism in the pontiac subprovince the second thermal event 2660 2630 ma was coeval with the emplacement of syncollisional s type garnet muscovite granites in the pontiac subprovince and the higher grade lacorne block of the abitibi svz and reset the k ar systems in preexisting rocks magmatic amphibole from the syntectonic round lake batholith 2695 ma u pb zircon age of the abitibi svz has a slightly disturbed ar release spectrum with an upper plateau age of 2669 6 ma signifying that the low gra

nitrogen isotope compositions of metasedimentary rocks in the catalina schist california implications for metamorphic devolatilization history abstract in the catalina schist subduction zone metamorphic complex california metasedimentary rocks show a decrease in n concentration and an increase in 15nair with increasing metamorphic grade lowest grade lawsonite albite rocks contain 632 185 ppm n with 15 n 1 9 0 6 whereas highgrade amphibolite equivalents contain 138 76 ppm n with 15 n 4 3 0 8 loss of n accompanied devolatilization reactions that evolved h2o rich c o h s n fluids through consumption of chlorite and phengitic white mica and production of mineral assemblages containing muscovite biotite garnet and kyanite whole rock n concentrations of up to 200 ppm in veins and pegmatites produced during high p t metamorphism reflect the redistribution of n during devolatilization and partial melting of the metasedimentary rocks bulk fluid rock n isotope fractionations 15n 15nfluid 15nrock of 1 5 1 were calculated with the rayleigh distillation equation taking into account variability in rock composition by comparison of samples with similar k2o concentrations these fractionations are similar to but slightly lower than published calculated fractionations for n2 nh4 exchange at the temperature range of 350 600 c over which most of the devolatilization occurred in the catalina schist approximately 3 4 to 2 25 the n systematics appear to be explained by n2 nh4 exchange and a devolatilization process intermediate in behavior to batch volatilization and rayleigh distillation the observed shifts in n concentration and 15n cannot be explained by nh3 nh4 exchange at these temperatures using the equilibrium models the distillation devolatilization process implicated in this study may govern the behavior of other trace elements partitioned into hydrous fluids during devolatilization e g b cs u similarity of the calculated fluid 15n 1 5 to 5 5 with compositions of natural gases inferred to be derived from metasedimentary sources indicates the possibility of using n as a tracer of large scale volatile transport

acoustic measurements of suspended sand concentration in the c2s2 experiment at stanhope lane prince edward island abstract a 3 mhz acoustic concentration meter acm was deployed with electromagnetic flowmeters in the nearshore region in october 1984 at stanhope lane prince edward island canada as a component of the canadian coastal sediment study the acm measured the backscatter of acoustic energy in a vertical beam pattern within approximately 1 m of the seabed laboratory calibration experiments were conducted to verify a method for converting acoustic backscatter into suspended sand concentration profiles the acm functioned well when there were no air bubbles in the water both the suspended sand concentration profiles and the bottom location were measured with an approximately 1 s time resolution and a 1 cm vertical spatial resolution the suspension of sand is related to the wave and current forcing and is dominated by events of short duration

restoration of the depression structure at the eastern part of central kyushu japan by means of dislocation modeling abstract we have attempted to restore a subsurface structure in the eastern part of central kyushu japan by combining fault motions which were modeled as dislocation planes embedded in an elastic isotropic half space the simulated crustal deformation pattern was compared with the subsurface structures estimated from gravity anomalies and or seismic prospecting the modeling procedure successfully restored all tectonic basins in the area without any need for motive forces for uplift or subsidence the results also suggest that two major tectonic events have occurred in this region those are 1 the formation of half graben caused by north south extension and 2 the formation of the pull apart basin caused by east west compression

nitrogen isotope record of fluid rock interactions in the skiddaw aureole and granite english lake district the skiddaw granite and its contact metamorphic aureole in the english lake district provide an excellent opportunity to test the capability of the n isotope system to trace devolatilization and large scale transfer of crustal fluids in the aureole skiddaw group metasedimentary rocks with relatively uniform lithology and major element compositions show a dramatic decrease in n content toward the granite contact from or 800 ppm at distances 2 5 km from the contact to 1 5 km these rocks have extremely uniform delta 15 n air near 3 7 per mil whereas closer to the contact or 1 km delta 15 n is shifted to higher values up to 8 7 per mil the coupled decreases in n content and increases in delta 15 n are compatible with the removal of n having low delta 15 n in fluids during continuous prograde devolatilization reactions involving the break down of white mica and the stabilization of biotite cordierite and andalusite bearing assemblages in the same metasedimentary rocks the lack of obvious trends in major element concentrations including sio 2 tio 2 sio 2 al 2 o 3 and the ratios of other major oxides to tio 2 and al 2 o 3 with distance from the granitic contact is consistent with minimal change in major element composition during the contact metamorphism ratios of whole rock n b rb and ba concentrations to whole rock k 2 o content are believed to reflect the differing fluid mica partitioning and involving varying relative proportions of white mica and biotite of these trace elements during devolatilization reactions greisenized skiddaw granite from a borehole is enriched in n range of 17 225 ppm for whole rocks and white mica separates relative to the unaltered granite whole rock 30 ppm and has delta 15 n of 1 0 to 4 8 per mil the n concentrations and delta 15 n of the wall rocks and greisenized granites combined with c isotopic data carbonate and carbonaceous matter for the same rocks are consistent with the mobilization of fluids having low delta 15 n and delta 13 c pdb values from the devolatilized aureole into the cooling intrusive body such transport is consistent with the predictions of recent theoretical models of late stage hydrothermal evolution in cooling intrusive systems

u pb zircon geochronology in the southwestern abitibi greenstone belt superior province the abitibi belt is the largest continuous greenstone belt in the superior province of the canadian shield it comprises several composite komatiitic tholeiitic calc alkalic and sedimentary sequences that are folded transected by major faults and intruded by various generations of plutonic rocks precise u pb geochronology has been carried out in the belt for the past decade to solve chronostratigraphic and metallogenetic problems this paper presents new zircon ages and reassesses previously published ones now refined by the addition of abraded and concordant zircon analyses volcanic and subvolcanic units of the timmins area yield the following ages 2727 1 5 ma for a tuff of the upper deloro formation 2703 1 5 ma for a tuff of the upper tisdale formation and 2698 4 ma for the krist fragmental assigned to the top of the tisdale formation the age of a dunite intrusive into the upper deloro formation is revised at 2707 3 ma whereas the aquarius diorite east of timmins yields a poorly define

giant quartz vein systems in accretionary orogenic belts the evidence for a metamorphic fluid origin from δ 15 n and δ 13 c studies abstract nitrogen isotope compositions of hydrothermal micas in giant structurally hosted quartz vein systems place constraints on the origin of the hydrothermal fluids the vein systems are from neoarchean terranes in the superior province of canada and the norseman terrane western australia the four quartz vein systems studied in different terranes formed at metamorphic grades ranging from lower greenschist to lower amphibolite facies coevally with metamorphism of the host terrane nitrogen resides predominantly as nh 4 in hydrothermal mica for lower to upper greenschist facies quartz veins n contents and 15 n values of micas are between 40 and 200 ppm and 15 and 21 respectively whereas in quartz veins formed at the greenschist to amphibolite transition and lower amphibolite facies micas have n contents of 20 70 ppm and 15 n of 11 24 in contrast micas and k feldspars from granitoids in the neoarchean abitibi and red lake greenstone belts are characterized by systematically lower 15 n of 5 to 5 and generally lower n contents of 20 50 ppm comparable to other granitoids carbon and oxygen isotope compositions of hydrothermal ferroan dolomite and calcite show systematic depletions with increasing metamorphic grade the mean values range from 2 2 to 3 7 for 13 c and 13 8 to 12 3 for 18 o in veins formed at lower to upper greenschist facies but from 5 8 to 7 1 for 13 c and 11 4 to 9 8 for 18 o at higher metamorphic grades nitrogen isotope compositions rule out mantle 15 n mean 5 magmatic 15 n 5 to 15 n mean 4 4 2 0 for the quartz veins accordingly the results are consistent with fluids derived from metamorphic dehydration of oceanic crust and sediments within accretionary orogenic belts

on the relationship between bedload and suspended sand transport on the inner shelf long island new york data obtained by a near bottom profiling concentration and velocity system pcv deployed in 10 m water depth at a site 1 km from the long island coastline are used to examine links between bedload and suspended sand concentrations calculations of bedload areal concentration c are based on the empirical results of vincent et al 1981 and use the theoretical formulations of grant and madsen 1978 1979 to describe the interaction between wave and current boundary layers suspended sand concentrations were obtained directly from an acoustic concentration meter acm average suspended sand profiles cz were found to fit closely to a log linear profile cz c1 1 a loge z z1 where c1 is the sand concentration at a height z1 1 cm from the bed and a is empirically determined as 0 22 0 005 a linear correlation is observed between the areal bedload concentration c the volume of bedload per unit area of the bed and the suspended sand concentration 1 cm above the bed c1 with a correlation coefficient of 0 82 significant at the 1 level and supports the hypothesis of einstein 1950 that bedload and suspended load are related through bedload concentration it is also shown that the sedment threshold criterion of komar and miller 1973 when expressed as a ratio here called the komar ratio can be used as a useful predictor for c1 under conditions where the wave orbital currents are much greater than the mean flow these relationships offer the opportunity for the calculation of both bedload and suspended sand transport rates from measurements of the steady current velocity and wave parameters combined with information defining the surficial sediments and local bottom topography