possible role of superheated magma in the formation of orbicular granitoids orbicular structures in granitoid rocks generally occur in minor intrusions inside or at the edges of larger granitoid plutons some orbs are associated with comb layering at or near pluton margins the orbs typically consist of cores enclaves of various rock types around which are concentric shells of rhythmically precipitated felsic and mafic layers dominated by radial and tangential arrangements of elongate crystals the orbs therefore contrast strongly with the enclosing granitoid rock which has a typical granitoid microstructure with randomly distributed crystals orbicular shells and comb layering have similar features and both require the absence of nuclei in the magma which permits a significant degree of undercooling and forces crystallization to occur only on solid objects superheating is an effective way of destroying nuclei as has been shown experimentally and so orbicular granitoids may have crystallized from formerly superheated magma effective superheating could be caused by engulfment of hydrous felsic or intermediate magma by hot mafic magma or more probably by injection of water into a felsic or intermediate magma the rarity of orbicular granitoids implies that superheating situations are also rare most magmas carrying sufficient nuclei to permit normal crystallization

sediment dynamics of an artificially deepened mesotidal coastal lagoon an environmental magnetic investigation of tauranga harbour new zealand abstract tauranga harbour new zealand s largest barrier enclosed coastal lagoon comprises two sub basins with separate catchments inlets and tidal channel systems this study sets out to assess and investigate the sediment dispersal system of tauranga harbour using standard environmental magnetic and sedimentological methods compilations of rock magnetic and grain size data of surficial sediments collected from inflowing rivers various estuarine environments estuaries tidal flats and tidal channels and the adjacent nearshore mirror the net and differential sediment fluxes into and through the two sub basins of this lagoon for all studied depositional environments the magnetogranulometric ratios sirm and arm are positively correlated with magnetic mineral content sirm arm in the sense that larger magnetic particles are associated with higher magnetic enrichment grain size analyses show that magnetic enrichment during particle transport and deposition can result from grain size as well as from grain density fractionation the periodically changing accumulation erosion conditions provide for a selective retention of specific grain sizes and an enhancement of the heavier magnetic mineral particles magnetic crystal size and clastic grain size correlate poorly over the whole study area but group within similar depositional environments coarser magnetic and clastic grain sizes and higher magnetite enrichment in the southern sub basin can be reconciled with episodic flood runoff of the wairoa river and a much larger artificially deepened southern tidal inlet which likely enables higher tidal current velocities our approach of combining magnetic and clastic grain size could be successfully implemented to establish a conceptual model of sediment dynamics and gravitational sorting within tauranga harbour

detecting and characterizing mesoscale and submesoscale structures of mediterranean water from joint seismic and hydrographic measurements in the gulf of cadiz 1 marine seismic and hydrographic data from the go cruise in the gulf of cadiz acquired in april 2007 are analyzed to determine the physical nature and geometric characteristics of acoustic reflectors in the water column seismic data show strong reflectors near the surface above mediterranean water mw undercurrents above a meddy and within a submesoscale mw structure these reflectors are associated with thermohaline layering wavelet analysis of seismic and hydrographic data both in terms of reflectivity shows strong signals with 12 48 m vertical wavelength scales hydrological data with its high vertical resolution capture weaker signals with shorter wavelengths at the edge of a meddy lateral intrusions of fresher water are revealed by reflectors with 25 75 m thickness analyses of marine seismic data allow detection of submesoscale eddies that hydrographic sections identify only occasionally

quantification of tidal asymmetry and its nonstationary variations tidal wave deformation and tidal asymmetry widely occur in tidal estuaries and lagoons tidal asymmetry has been intensively studied because of its controlling role on residual sediment transport and large scale morphological evolution there are several methods available to characterize tidal asymmetry prompting the need for an overview of their applicability and shortcomings in this work we provide a brief review and evaluation of two methods namely the harmonic method and the statistical method the latter comprises several statistical measures that estimate the probability density function and various forms of skewness we find that both the harmonic and statistical methods are effective and have complementary advantages the harmonic method is applicable to predominantly semidiurnal or diurnal regimes while the statistical methods can be used in mixed tidal regimes assisted by harmonic data a modified skewness measure can isolate the contribution of different tidal interactions on net tidal asymmetry and also reveal its subtidal variations the application of the skewness measure to nonstationary river tides reveals stronger tidal asymmetry during spring tides than neap tides and the nonlinear effects of river discharges on tidal asymmetry in the upper and lower regions of long estuaries

orbicular oxides in carbonatitic kimberlites a renewed interest in mineral spheres that exhibit oscillatory layering is assured with the spectacular discovery of hematite beads in meridiani planum mars the martian blueberries are variously interpreted as sedimentary concretions impact spherules or accretionary lapilli we draw attention to a possible alternative that the spheres of oxides are of igneous origin in carbonate rich upper mantle systems two spherical oxide assemblages from cabonatitic kimberlites in the central namibia formerly south west africa volcanic field show similarities and contrasts to orbicular structures in carbonatites from uganda south africa germany finland and russia structures have rapakivi appearances that bear upon the controversial issue of a relation between kimberlites and carbonatites the first example is from a carbonatitic kimberlite adjacent to the mukorob kimberlite sesu stricto oblate spheroidal nuggets 2 1 5 0 5 cm have olivine now serpentine calcite cores with concentrically layered bands of ilmenite calcite and pedestals of ilmenite ilm 55 geik 40 hem 5 with intergranular calcite the spheres are matrix supported in massive ferroan calcite serpentine with minor apatite f 1 5 wt and barite the matrix contains xenocrystic mg al chromite 55 wt cr 2 o 3 mantled by ilmenite ilm 51 geik 43 hem 6 but the dominant groundmass oxide mineral is mg al ti mat magnetite the second example is from the carbonatite facies of the hatzium kimberlite and is also in a dike mat magnetite pellets 2 3 cm have alternating wide 1 mm and thin 0 25 mm bands of magnetite nucleated on a complex mixture of calcite feo 0 1 wt and serpentine 4 wt feo 0 5 1 wt al 2 o 3 the matrix assemblage of serpentine calcite mat magnetite has mineral compositions similar to the spheroids but is distinguished by abundant ba phlogopite and lesser apatite f 2 wt phlogopite is strongly zoned in patches and bands is kink banded and contains inclusions of mat magnetite calcite the assemblage is typical of phoscorites also known as camaforites in other carbonatites but the ilmenite spheroids appear to be restricted to mukorob our interpretation is that both types result from the nucleation of immiscible liquids a high density and high viscosity ore carbonate silicate component in a low viscosity phosphoric carbonatite melt on olivine or olivine magnetite assisted by frothing and slow degassing on decompression and dike intrusion

tidal distortions and flood dominance at five small tidal inlets in southern maine maximum and mean flood current velocities exceeded ebb current velocities by an average of more than 20 cm s 1 at five small inlets along the southern coast of maine distortion of the tidal wave as it interacts with these shallow inlets such that the rising tide duration averages 3 22 h less than the falling tide duration may be the cause of flood current dominance at these inlets tide records from three locations at ogunquit inlet located along the southern coast of maine show that the 29 day average tide duration asymmetry increases from a rising tide that is 0 07 h longer than the falling tide for the offshore record to a rising tide that is 2 15 and 5 15 h shorter than the falling tide for the inlet throat and bay records respectively previous field studies and numerical models of tidal asymmetry have not examined tidal distortion in very shallow inlets where the channels shoal to depths shallower than the forcing tide amplitude at the inlets investigated in this paper channels are shallower than the ocean tide amplitude by an average of 30 cm a model is presented that explains how the shallow inlet bathymetry truncates the ocean tide and produces an inlet tide characterized by an extended falling tide and a shortened rising tide duration the dominance of flood tidal currents at these inlets produces net landward sediment transport

crystallization of orbicular rocks exemplified by the slattemossa occurrence southeastern sweden the orbicular rock at slattemossa southeastern sweden has a quartz monzodioritic composition the cores of the orbicules crystallized directly from the orbicule forming magma cores made up of xenoliths have not been observed outside the core follow first an inner mafic a felsic and then an outer mafic shell the orbicules occur in a matrix which is similar to the core they grew simultaneously and show an almost perfect parallelism in evolution after initial normal crystallization of the magma superheating probably triggered by a sudden addition of volatiles destroyed earlier formed nuclei and also affected the already crystallized part of the rock cooling caused heterogeneous nucleation and rapid crystallization which formed the inner mafic shell this is enriched in mafic minerals especially biotite compared to the core at the same time the grain size becomes significantly smaller depletion in malic components possibly intensified by a sudden change in physical conditions destabilized biotite and amphibole crystallization causing oversaturation in plagioclase components forming a felsic shell having a sharp boundary with the mafic shell plagioclase is extremely altered mafic minerals were then stabilized probably due to depletion of plagioclase components and an outer mafic shell formed with the return to homogeneous nucleation matrix formation concluded the crystallization orbicules might have moved in the magma causing some squeezing of magma surrounding the orbicules but major movements involved the settling of the whole package of orbicules and matrix in the surrounding non orbicular magma less

the benfontein kimberlite sills magmatic reactions and high intrusion temperatures the kimberlite sills at benfontein south africa were intruded as xenolith poor phenocryst rich carbonated peridotite magmas the dominant pre intrusion phenocryst phases are olivine fo sub 86 92 mg ilmenite ss 13 0 18 0 wt percent mgo 0 5 3 0 wt percent cr 2 o 3 mg al chromite and ree perovskite post intrusion magmatic reaction mantling has encapsulated all pre existing groundmass oxides in mg al titanomagnetite the benfontein sills appear to have been emplaced at much higher temperatures than are probably typical for most other kimberlites in a high heat flow environment comparable to that recorded by the lesotho geotherm under open system vapor composition conditions an adiabatic diapiric upwelling of peridotitic magma may be capable of producing the high temperatures that apparently prevailed during the intrusion the temperature of reaction for coupled fe based and c based fo 2 buffers in the upper mantle for example emog mh hematite mol percent isopleths increases with decreasing pressure and at near surface pressures approximates the temperature of intrusion for the phase compositions observed at benfontein modified journal abstract

pedogenic hematitic concretions from the triassic new haven arkose connecticut implications for understanding martian diagenetic processes abstract the triassic new haven arkose locally contains mm scaled pedogenic hematitic concretions within red arkosic sandy mudstones that provide insights into concretion forming processes on earth and mars concretions represent 8 of the sediment by mass 7 by volume are irregularly distributed and have a near normal size distribution with a mean diameter of 1 53 mm and graphic standard deviation of 0 64 mm x ray diffraction xrd and attenuated total reflectance atr spectroscopy indicate that the concretions are composed of ambient sediments quartz montmorillonite and feldspar and a minor phosphatic phase that is also implied by geochemistry however the concretions preferentially exclude coarser grain sizes and are cemented by hematite and goethite optical observations and synchrotron x ray fluorescence xrf chemical mapping indicate that concretions are massive to weakly zoned with respect to hematitic cements compared to the surrounding sediments concretion rare earth elements ree are elevated in total abundances exhibit light rare earth element lree enrichment and possess negative ce anomalies th u ratios are lower due to elevated u mass balance calculations indicate that 20 of the concretions are composed of iron oxides and that 30 mm3 of ambient sediment is required to provide the hematitic cement in a single 1 5 mm diameter concretion element mobility during concretion formation was tested assuming different immobile elements al ti zr assuming zr immobility provides intermediate results and indicates the following gains in concretions pb 572 fe 322 mn 142 ree 438 116 v 138 u 124 ni 84 and nb 58 other elements show either gains or losses of less than 50 ce anomalies low th u and elevated v and u abundances point to a significant redox influence on element distributions in the concretions high iron content crude internal concentric banding and redox controls suggest that the concretions are formed in seasonally variable but generally moist soil conditions with annual precipitation 130 cm trace element enrichment patterns are broadly consistent with derivation from downward percolating weathering fluids although the new haven arkose pedogenic concretions have significant differences and were clearly formed by different mechanisms than hematitic spherules discovered on mars they nevertheless exhibit a number of textural e g sphericity size distributions and geochemical e g ni enrichments similarities that support models suggesting that the martian spherules are formed as sedimentary concretions

tidal truncation and barotropic convergence in a channel network tidally driven from opposing entrances residual circulation patterns in a channel network that is tidally driven from entrances on opposite sides are controlled by the temporal phasing and spatial asymmetry of the two forcing tides the napa sonoma marsh complex in san francisco bay ca is such a system a sill on the west entrance to the system prevents a complete tidal range at spring tides that results in tidal truncation of water levels tidal truncation does not occur on the east side but asymmetries develop due to friction and off channel wetland storage the east and west asymmetric tides meet in the middle to produce a barotropic convergence zone that controls the transport of water and sediment during spring tides tidally averaged water surface elevations are higher on the truncated west side this creates tidally averaged fluxes of water and sediment to the east during neap tides the water levels are not truncated and the propagation speed of the tides controls residual circulation creating a tidally averaged flux in the opposite direction

sediment dynamic processes of the yuehu inlet system shandong peninsula china in order to investigate the sediment dynamic behavior of the yuehu a small inlet system characterized by abundant sediment supply and rapid sediment infilling measurements and sampling were undertaken to obtain data sets of tidal water levels current velocities suspended sediment concentrations grain size parameters deposition rates and organic carbon contents sediment budget and the time velocity asymmetry patterns of the inlet system were analyzed the results show that the deposition rates are relatively high within the tidal basin the total sediment flux cannot be balanced by the input from the open sea the aerosol and biological production rather the material from land which has been intensified by agricultural activities over the past several decades represents a major component for the balance thus the denudation rate must be reduced to protect the yuehu as a natural reserve furthermore it is found from the present study that the yuehu inlet system exhibits all of the four time velocity asymmetry patterns with varied frequencies of occurrence compared with the two asymmetry patterns identified for larger inlet systems such phenomena are partly due to the adjustment of entrance channel geometry this behavior may be representative of the small tidal inlets at their late stage of morphological evolution and therefore may be utilized to prolong the lifespan of small inlet systems c 2003 elsevier ltd all rights reserved

hematite spherules at meridiani results from mi mini tes and pancam 1 we report on observations of hematite bearing spherules at meridiani planum made using the microscopic imager mi mini thermal emission spectrometer mini tes and panoramic camera pancam instruments on the mars exploration rover opportunity spherules were observed on soil surfaces and in outcrop rocks both on undisturbed surfaces and in abraded surfaces ground using the rock abrasion tool rat spherule size and shape change little along the 850 m eastward traverse from eagle crater to endurance crater but spherules decrease and then slightly increase in size along the 6 km traverse from endurance south to victoria crater local populations range from submillimeters to several millimeters in diameter an additional small diameter 100 m size population is possible an increase in irregular shapes is found near victoria crater this combined with the size decrease south of endurance suggests either a changing depositional environment or variation in the duration and timing of diagenetic events the dominant smaller size population observed early in the mission in aeolian areas and ripple crests is observed as the primary size population in abraded outcrop farther south this suggests that successively younger beds are exposed at the surface along the southward traverse stratigraphically higher units removed by erosion could be recorded by the present surface lag deposit coordinated systematic observations are used to determine optical and infrared hematite indices of the surface soils in pancam and mini tes in spite of the systematic variation seen in mi both pancam and mini tes indices are highly variable based on the local surface and neither show systematic trends south of endurance the lack of a 390 cm 1 feature in mini tes spectra suggests concentric or radial interior structure within the spherules at scales too fine for mi to observe mini tes does not detect any silicate component in the spherules a bound water component in soils or in exchange with the atmosphere is observed these spherules have been previously interpreted as concretions formed within what were once water saturated diagenetically altered dirty evaporate sandstone sediments our observations support this interpretation however no single terrestrial analog provides a model that can account for all attributes of the spherules on mars

modelling tidal energetics of the columbia river estuary abstract the columbia river estuary is shallow and has a mixed diurnal and semidiurnal tide strong riverflow broad tidal flats and variable channel cross section it is weakly non linear with respect to tidal forcing as measured by a ratio of tidal amplitude to depth these features common to many shallow estuaries were incorporated into a one dimensional harmonic transport model the harmonic method utilizes the fact that nearly all of the energy in the system is in a few fundamental tidal frequencies the first overtides thereof and the mean flow this allows the representation of the flow as a series of harmonic components whose spatial variability is determined by the model the model provides a qualitative explantation for and accurate quantitative predictions of along channel variations in tidal properties in terms of the momentum balance near the mouth of the estuary the boundary shear stress the pressure gradient and the acceleration terms are all important in the force balance and the tide behaves like a damped oscillator far upriver the pressure gradient is primarily balanced by friction at the bed and tidal wave propagation can be described as a diffusion process changes in the channel width in mid estuary cause partial reflection of the tidal wave and a maximum in tidal range this partial reflection decreases the tidal energy flux in the upstream direction the distribution of the time averaged energy fluxes was also determined from the model the analysis shows that there are two regions of high energy dissipation energy is supplied near the mouth of the estuary by the divergence of the landward flux of tidal potential energy and far upriver by the divergence of the seaward flux of fluvial potential energy these two regions of high dissipation are separated by a region of low dissipation the energy flux divergence minimum this spatial division of the estuary is mirrored in the system biology and geology it is likely that the energy flux divergence minimum is a common feature of shallow estuaries with strong riverflow

shoreline recovery on wave dominated sandy coastlines the role of sandbar morphodynamics and nearshore wave parameters abstract this study quantifies and characterises the temporal variability of shoreline recovery on a high energy sandy coastline using a 10 year dataset of daily shoreline and sandbar positions from a coastal imaging station at narrabeen collaroy beach australia following a total of 82 individual storm events rates of the cross shore return of the shoreline to its pre storm position were analysed observed rates during shoreline recovery were characterised by an overall mean of 0 2 m day temporal variability in rates was most evident at shorter timescales of 1 2 weeks and included rates most frequently between 0 and 0 3 m day less frequent more rapid rates of up to 2 m day and also minor landward movements this temporal variability was significantly correlated with nearshore forcing parameters describing the ratio of wave height to wave period the cross shore proximity and attachment of the sandbar to the shoreline and the rate of cross shore sandbar migration these findings are summarised in a new conceptual model that characterises temporal phases and rates of shoreline recovery corresponding to stages of onshore sandbar migration following a storm from fully detached storm deposited sandbar morphology through to complete sandbar welding with the shoreline more gradual shoreline recovery rates are observed with fully detached and semi attached sandbar conditions in contrast more rapid rates of shoreline recovery occur when sandbars are closer and attached to the shoreline observed to be on average 3 4 times greater than for detached sandbars in conditions with attached and semi attached sandbars shoreline recovery rates are negatively correlated to the forcing of nearshore wave steepness and dimensionless fall velocity and coupled with concurrent rates of onshore sandbar migration the findings provide insight into key parameters influencing shoreline recovery following storms

the daily scale entrance dynamics of intermittently open closed estuaries intermittently open closed estuaries ioce are a dynamic form of estuary characterised by periodic entrance closure to the ocean entrance closure is a function of the relative balance between on and offshore sediment transport with closures occurring during periods of low fluvial discharge whereby the estuary ebb tidal prism is reduced although the broad scale processes of entrance closure are becoming better understood there remains limited knowledge on channel morphodynamics during an individual closure event in this study the entrance dynamics of three ioce on the coast of victoria australia were monitored over a daily timescale following both artificial and natural openings the influence of changing marine and fluvial conditions on the relative sedimentation rate within the entrance channel was examined ioce in victoria showed two distinct modes of entrance closure a lateral accretion whereby the estuary gradually closes by longshore drift driven spit growth during low river flows and b vertical accretion where the channel rapidly aggrades under high 2 m near normal waves during storms when fluvial discharge and wave heights simultaneously increase large swells will not always close the mouth due to an increase in the ebb tidal prism the estuary water depth and the maximum channel dimensions following opening were not proportional to the opening duration with this being a function of the wave and fluvial conditions occurring following lagoon drainage based on the findings of this work implementing a successful artificial entrance opening is dependent on reduced onshore sedimentation rates which occur when wave energy is low 2 m hs relative to river flow copyright

in situ u pb and nd hf sr isotopic investigations of zirconolite and calzirtite abstract although the calcium and titanium bearing zirconsilicates zirconolite and calzirtite are common minerals in carbonatites little is known regarding their trace element or isotopic characteristics available data indicate that they can have significant contents of u pb nb ta zr hf rare earth elements rees minor sr and low rb sr and lu hf ratios their compositions indicate that they have potential for u pb age determination together with nd hf and possibly sr isotopic analyses in this study zirconolite and calzirtite from carbonatites occurring at phalaborwa south africa prairie lake canada afrikanda and kovdor kola russia guli siberia russia and jacupiranga brazil were selected for an isotopic analysis by in situ techniques ion microprobe analyses using a cameca 1280 ion microprobe show that reliable pb pb ages can be obtained from these minerals as they have extremely high u concentrations coupled with negligible common pb although these minerals have low rb sr ratios their low sr concentrations in most cases render in situ sr isotopic analyses difficult in contrast their high sm nd and hf concentrations with generally low lu hf ratios permit precise in situ isotopic analysis of nd and hf

paragenetic trends of oxide minerals in carbonate rich kimberlites with new analyses from the benfontein sill south africa the relationship among kimberlites carbonate rich bodies associated with them and the carbonatites associated with alkalis rock complexes are reviewed particular attention is paid to the parageneses of oxide minerals in six carbonate kimberlites peuyuk tunraq wesselton liqhobong de beers and benfontein new analyses of spinel limonite and perovskite from the lower benfontein sill are consistent with previous reports and can be divided into 1 early macrocrysts and cores of grains and 2 late rims and groundmass grains the evolution of a carbonate rich residuum with progressive crystallization appears to be typical of carbonate rich kimberlite magmas and is texturally related to the two stages of oxide precipitation in these carbonate kimberlites thus early mg ilmenite and cr rich spinel are separated by reaction textures and carbonate from later mg al titanomagnetite perovskite and accessory utile and apatite the spinels span a large range in composition from mg al chromite to mg al titanomagnetite with an intermediate gap this simplified paragenetic scheme and in particular the spinel trend is repeated in the five other carbonate kimberlites reviewed it may be representative of the hypabyssal kimberlites in general and others where fluidization processes did not completely disrupt the crystallization sequence

ocean internal wave spectra inferred from seismic reflection transects 1 internal waves affect many important dynamical processes in the ocean but in situ observations of internal waves are infrequent and spatially sparse here we show that remote sensing of internal waves by marine seismic reflection methods can provide quantitative information on internal wave energy and its spatial variability at high lateral resolution and full ocean depth over large volumes of the ocean seismic images of the norwegian sea water column show reflections that capture snapshots of finestructure displacements due to internal waves horizontal wave number spectra derived from digitized reflection horizons in the open ocean compare favorably to the garrett munk tow spectrum of oceanic internal wave displacements spectra within 10 km laterally and 200 m vertically of the continental slope show enhanced energy likely associated with internal wave sloping boundary interactions

rapakivi texture an indication of the crystallization of hydrosilicates ii rapakivi granites have puzzled all who have seriously studied them typical rapakivi texture is a mixture of variously mantled non mantled or partly mantled concentrically zoned plastically distorted fragmented reaggregated large and small ovoids commonly they are potash feldspar often mantled by and having a variable content of plagioclase some display remarkable sphericity in form composition zoning sequence and crystallization pattern each ovoid reflects an individual development up to five concentric internal plagioclase rims have been observed and some ovoids may be isolated in autoliths and wall rocks anomalies and contradictions arise from any assumption of genesis from a cooling melt the recorded objective data imply that the magma from which rapakivi textures develop had similar diffusive and rheological properties to those of a partly dewatered macromolecular paste or a mixture of gelatinous hydrosilicates as indicated by deep oil wells this system is found at somewhat elevated temperatures at considerable depths within accumulated sediments in addition to the very specific diffusive and rheological properties of such partly dewatered sediments the system has as its major components normal solvated macromolecules of mixed clays silica gels and hydrous ferromagnesian minerals which are characterised by distinctive particle sizes and geometric shapes platelets spheres and rods respectively thixotropic liquefaction and intrusion of such concentrated gelatinous magma or sediment paste introduces relative movement between the component macromolecules whereby they can reduce surface energy by interaction to assume a close packed condition and aggregate during laminar flow into macro accretions comprised essentially of their respective particle shapes syneresis of these precursor accretions desorbs ions including the small montmorillonite particles behaving as a colloidal electrolyte these diffuse from the illitic cores to form a montmorillonite rich rim which it is suggested crystallizes together with the illitic cores to form mantled or polymantled feldspar ovoids crystallization of the rapakivi massif is associated with strong temperature rise stemming from exothermic crystallization of the close packed metastable colloids this follows the development of the characteristic texture the rounded and rimmed precursor accretions are formed during earlier lower temperature episodes of thixotropic liquefaction which are isothermal the fluidity is an earlier event there is high temperature dependent on the rate of water loss but no molten stage forty six typical features of rapakivi texture are described and illustrated each of which is directly attributable to specific interactions in an alternately dynamic and static colloidal system individual correlation between each observed distinctive feature of the rapakivi texture and the well documented physico chemical process is complete for sediment derived granites therefore the rapakivi texture can confidently be assumed to be an indication of the crystallization of their sedimentary hydrosilicate precursors

seismic reflection imaging of water mass boundaries in the norwegian sea 1 results from the first joint temperature and seismic reflection study of the ocean demonstrate that water mass boundaries can be acoustically mapped multichannel seismic profiles collected in the norwegian sea show reflections between the norwegian atlantic current and norwegian sea deep water the images were corroborated with a dense array of expendable bathythermographs and expendable conductivity temperature depth profiles delineating sharp temperature gradients over vertical distances of 5 15 m at depths over which reflections occur fine structure from both thermohaline intrusions and internal wave strains is imaged low amplitude acoustic reflections correspond to temperature changes as small as 0 03 c implying that seismic reflection methods can image even weak fine structure

hematite spherules in basaltic tephra altered under aqueous acid sulfate conditions on mauna kea volcano hawaii possible clues for the occurrence of hematite rich spherules in the burns formation at meridiani planum mars abstract iron rich spherules 90 fe2o3 from electron microprobe analyses 10 100 m in diameter are found within sulfate rich rocks formed by aqueous acid sulfate alteration of basaltic tephra on mauna kea volcano hawaii although some spherules are nearly pure fe most have two concentric compositional zones with the core having a higher fe al ratio than the rim oxide totals less than 100 93 99 suggest structural h2o and or oh 1 the transmission mossbauer spectrum of a spherule rich separate is dominated by a hematite fe2o3 sextet whose peaks are skewed toward zero velocity skewing is consistent with al3 for fe3 substitution and structural h2o and or oh 1 the grey color of the spherules implies specular hematite whole rock powder x ray diffraction spectra are dominated by peaks from smectite and the hydroxy sulfate mineral natroalunite as alteration products and plagioclase feldspar that was present in the precursor basaltic tephra whether spherule formation proceeded directly from basaltic material in one event dissolution of basaltic material and precipitation of hematite spherules or whether spherule formation required more than one event formation of fe bearing sulfate rock and subsequent hydrolysis to hematite is not currently constrained by analogy a formation pathway for the hematite spherules in sulfate rich outcrops at meridiani planum on mars the burns formation is aqueous alteration of basaltic precursor material under acid sulfate conditions although hydrothermal conditions are present on mauna kea such conditions may not be required for spherule formation on mars if the time interval for hydrolysis at lower temperatures is sufficiently long

observations and numerical modelling of the mediterranean outflow splitting and eddy generation during the canigo project the generation of dipolar eddies in the mediterranean water mw layers off south portugal was recorded by subsurface floats from february to november 1998 the role of the bottom topography on the spreading of the mw in the gulf of cadiz and on the generation of these mw eddies was studied in the framework of the medtop project some of the hydrological and velocity observations collected during medtop in 2001 and 2002 also revealed the association of anticyclones meddies and cyclones in the region just south of the portimao canyon the evolution of these structures is studied with subsurface floats deployed in the vortices the splitting of the mw plume in the gulf of cadiz and the generation mechanisms of the mw vortices in the region from portimao canyon to the estremadura promontory are investigated using a bottom following numerical primitive equations model in a regional ocean configuration incorporating the realistic topography of the iberian continental slope the model reproduces the mw division into different cores in the gulf of cadiz as well as the generation of baroclinic dipoles downstream of portimao canyon the role of the bottom topography in the eddy generation process is discussed

primary and secondary niobium mineral deposits associated with carbonatites abstract this work reviews the character and origin of primary and supergene economic deposits of niobium associated with carbonatites the brazilian supergene deposits account for about 92 of the total worldwide production of nb with the primary st honore carbonatite and other sources accounting for only for 7 and 1 respectively the emphasis of the review is upon the styles of nb mineralization and the geological factors which lead to economic concentrations of nb bearing minerals primary economic deposits of nb are associated principally with carbonatites found in diverse types of plutonic alkaline rock complexes primary magmas are principally those of the melilitite nephelinite and aillikite clans although many primary niobium deposits are associated with carbonatites ijolites and syenites in the same alkaline complexes can also contain significant nb mineralization in the form of niobian titanite and diverse nb zr silicates marianoite wohlerite these potential sources of nb have not as yet been explored or exploited primary nb deposits can be regarded as large tonnage low grade typically

processes controlling morphodynamics of artificially breached barriers abstract naturally and artificially breached tidal inlets can promote fast morphological changes along the adjacent detrital barriers as they evolve in response to the contemporaneous wave regime inlet migration results in downdrift barrier erosion while updrift sand accumulation and concomitant barrier extension are commonly observed this study addresses the performance of placement of a sandfill designed to create an artificial dune along the updrift tip of a sand barrier aiming to constrain inlet migration stabilize its location and reduce sand transfers from the ocean into the lagoon induced by storm overtopping of the barrier herein we investigate the patterns of inlet drifting and processes regulating the progressive loss of efficiency of this soft engineering solution we show that besides updrift inlet migration which occurs with temporary reversal of the prevailing direction of drift currents meandering of the ebb channels that envelop the flood delta is quite effective in triggering or enhancing erosion of the updrift barrier tip in periods when the inlet main channel is migrating in the opposite direction this additional erosional process which acts along the back barrier facade is responsible for the increase of the erosion rate of the artificial dune and regardless of the direction of wave induced drift direction of the inlet this finding discloses the relevance of taking into account not only the oceanic processes waves but also processes operating on the lagoonal side of the barriers in future engineering operations designed for tidal inlet management

imaging meddy finestructure using multichannel seismic reflection data 1 this work illustrates the great potential of multichannel seismic reflection data to extract information from the finestructure of meddies with exceptional lateral resolution 10 15 m we present seismic images of three meddies acquired in the gulf of cadiz sw iberian peninsula which consist of concentric reflectors forming oval shapes that sharply contrast with the background oceanic structure the seismic images reveal the presence of different regions within the meddies that are consistent with those observed in historical temperature t and salinity s data the core region characterized by smooth t and s variations is weakly reflective the double diffusive upper and lower boundaries and the lateral interleaving outer edges characterized by stronger t and s contrasts display strong reflectivity bands these new observations clearly show differences between layers developed at the upper and lower boundaries that can contribute to the knowledge of mixing processes and layering formation in oceans

genesis of the graphite orbicules in the huangyangshan graphite deposit xinjiang china evidence from geochemical isotopic and fluid inclusion data abstract the huangyangshan graphite deposit in the east junggar orogen china contains intriguing graphite orbicules this contribution is designed to present reasonably comprehensive assessment of their origin in this deposit the intrusive orebodies are mechanically juxtaposed against contacts with granitic wall rocks the orbicules are typically concentrically zoned in texture with a notable binary configuration involving a central core and an outer shell the orbicule cores possess mineralogical and compositional variations that are more or less similar to those of the granitic wall rocks the orbicule shells are composed of various ferromagnesian minerals clinopyroxene hornblende in stark contrast to the matrix where hornblende sanidine and albite have higher mg ab and an values respectively the replacement of silicates by graphite and sulfides pyrrhotite chalcopyrite pyrite is common the graphite throughout the matrix and orbicules features a patchy distribution of major elements c and dispersed elements cr ni co s cu zn as pb etc the carbon isotopic compositions of the orbicular ore are 20 9 to 20 5 analogous to those of the surrounding strata i e 25 6 to 19 3 the sulfur isotopic compositions of sulfides in the orbicular ore are 4 8 to 2 6 which differ from those of the surrounding strata i e 16 0 23 0 fluid inclusions principally comprise the volatile component ch4 and solid daughter minerals graphite chalcopyrite with tm 450 c vapor liquid two phase fluid inclusions formed under conditions of th 143 6 367 5 c p 3 194 bar and fo2 52 76 to 31 15 the hydrogen and oxygen isotopic values of the orbicular ore are d 110 3 to 107 0 and 18owater 10 1 11 7 zircons from the orbicular ore have 206pb 238u ages of 304 359 ma with a weighted average of 319 0 6 4 ma overlapping the geochronological age of the granitic host rocks 305 1 321 4 ma the orbicular ore has sio2 concentrations ranging from 53 30 to 72 61 wt falling within the compositional fields of granite quartz monzonite granodiorite diorite and monzodiorite in the tas classification diagram the sr nd and hf isotopic data from the orbicular ore indicate mixing between materials derived from the depleted mantle and materials derived from the crust with a dominant mantle contribution the petrographic geochemical isotopic and fluid inclusion characteristics indicate that the processes of incorporation of h2o and wall rock fragments liquid immiscibility and exsolution of a late magmatic fluid were responsible for orbicule formation in the huangyangshan deposit the following genetic model is proposed 1 in the late carboniferous a new orbicular magma containing organic matter derived ch4 and deep mantle so2 emplaced within the huangyangshan pluton contemporaneously crystal fragments and h2o were incorporated into the orbicular magma from the granitic host rocks 2 h2o saturation was reached in the orbicular magma and fostered segregation of a hydrous ferromagnesian melt orbicules with a silicic residual melt matrix 3 at approximately 630 c 2000 bar and 18 lgfo2 graphite and sulfides formed en masse through deuteric alteration 3ch4 2so2 2 fe2 7 si4o11 2 oh 2 hornblende 3c graphite 2fes pyrrhotite 8sio2 quartz 2 fe3si4o10 oh 2 fe3 oh 6 chlorite following the expulsion of a late magmatic fluid from the ferromagnesian melt

sea level fluctuations in the fleet an english tidal lagoon abstract tidal elevation data are presented for places along the length of the fleet which is a tidal lagoon behind chesil beach on the south coast of england harmonic analysis of the data is not able to represent the observations adequately particularly at the inner end of the lagoon however careful inspection of the data shows that the tidal regime is capable of being understood in terms of the non linear propagation of long waves in very shallow water distortion of the tidal wave by unequal progression speeds of high and low water and the set up of mean level by frictional effects are shown to be the important physical mechanisms controlling the observed water level fluctuations a one dimensional numerical model which incorporates these processes is able to reproduce the observations satisfactorily whilst the model predicts strong effects of wind stress the meteorological influences in the observed data appear to be largely due to external surges in the english channel which propagate into the lagoon through its entrance

new insights into embayed beach rotation the importance of wave exposure and cross shore processes although embayed beach rotation has been viewed and modeled as an alongshore sediment transport process acting on a uniform beach profile recent research suggests a more complex response whereby alongshore variability in cross shore sediment fluxes may be more significant this study utilizes 5 years of fully three dimensional beach surveys at narrabeen collaroy beach se australia to quantify the control of alongshore nonuniform wave exposure and cross shore processes on embayed beach rotation empirical orthogonal function analysis of the alongshore variability in subaerial beach volume width and berm slope confirms that the dominant mode of subaerial beach variability is an onshore offshore sediment exchange that is strongly controlled r 0 8 by the alongshore gradient in breaker wave height and coincides with a uniform flattening steepening of the berm slope a secondary rotation like signal is observed in both the subaerial beach volume width data and significantly the berm slope this inverse flattening steepening of the berm slope between beach extremities is most likely a proxy for differing cross shore processes within the surf zone between the exposed and sheltered ends of the embayment particularly with regards to dissipation of storm wave energy by offshore sandbars and beach recovery following storms analysis of the corresponding wave data reveals two distinct time scales of wave forcing characteristic of short term erosion and longer term recovery processes a new conceptual model is presented of three differing modes of embayed beach rotation with the newly identified beach rotation mode controlled by offshore sandbars considered of particular importance at embayments where headland sheltering of oblique waves is pronounced

physical chemical and sedimentological aspects of the mediterranean outflow off iberia a multidisciplinary study of the mediterranean outflow in the region west of the strait of gibraltar and off the southern and southwestern coasts of the iberian peninsula was developed in the frame of the canary islands azores gibraltar observations project two high resolution ctd surveys which included water sampling for chemical nutrients and dissolved oxygen and sedimentological analyses took place in september 1997 summer cruise and january 1998 winter cruise in the study region the correspondence between the high salinity mediterranean water mw layer and the low nutrient content and relatively high abundance of particles was a general result further details of the thermohaline analysis and of the geostrophic computations especially for the layer of mw are compared with the results obtained for the chemical properties and the sedimentological characteristics

controls of local geology and cross shore longshore processes on embayed beach shoreline variability 10 shoreline variability along the 3 6 km long narrabeen beach embayment in se australia is 11 investigated over a 5 year period we apply the one line shoreline change model lx shore 12 which couples longshore and cross shore processes and can handle complex shoreline 13 planforms non erodible emerged headlands and submerged rocky features the model 14 skilfully reproduces the three dominant modes of shoreline variability which are by 15 decreasing order of variance cross shore migration rotation and a third mode possibly 16 related to breathing model results confirm previous observations that longshore processes 17 primarily contribute to the rotation and third modes on the timescales of months to seasons 18 while cross shore processes control the shoreline migration on shorter timescales from hours 19 storms to months additional simulations simplifying progressively the bathymetry show 20 how the inherent geology strongly modulates the spatial modes of shoreline variability the 21 offshore central rocky outcrop is found to limit the rotation in contrast the submerged rocky 22 platforms that extend from the headlands enhance the shoreline rotation mode and increase 23 alongshore variability of the cross shore migration mode owing to increased alongshore 24 variability in wave exposure offshore wave transformation across large scale submerged 25 rocky features and headland shape are therefore critical to contemporary shoreline dynamics 26 2

petrology and geochemistry of the orbicular granitoid of sierra de velasco nw argentina and implications for the origin of orbicular rocks the velasco orbicular granitoid is a small 65 15 m irregularly shaped body that crops out within the huaco granite central sierra de velasco nw argentina it consists of ellipsoid shaped orbicules of 3 to 15 cm length immersed in an aplitic to pegmatitic matrix the orbicules are formed by a core made up of a k feldspar megacryst partially to totally replaced by plagioclase an inner shell of radial and equant plagioclase crystals a layer of tangentially oriented biotite laths and an outer shell of plumose plagioclase crystals containing diffuse rings of tangentially oriented biotite the orbicular granitoid formed in situ in a pocket of evolved and volatile rich melt segregated from the surrounding partially crystallized huaco granite possibly via a filter pressing mechanism the segregated melt entrained relatively few k feldspar megacrysts into the pocket leaving behind a concentration of megacrysts around the pocket high water concentration caused effective superheating of the melt and destruction of nuclei with only the large megacrysts surviving as solids sudden water pressure loss and exsolution of the volatile phase perhaps related to a volcanic eruption or fracturing of the surrounding granite caused rapid undercooling of the melt the orbicules grew in the undercooled melt by heterogeneous nucleation on the megacrysts which acted as nucleation seeds and crystallization of reversely zoned radial plagioclase and sporadic crystallization of tangential biotite rings according to fluctuations in its saturation orbicular growth gave way to crystallization of the equiaxial inter orbicular matrix in two stages when sufficient polymerization of the melt was attained the time scale of formation of the orbicular granitoid was fast possibly a matter of a few weeks or months

groundmass oxide minerals in the koidu kimberlite dikes sierra leone west africa petrology and oxide mineral chemistry are presented on 5 kimberlite dikes that are classified into three groups 1 one dike is highly carbonated and highly oxidized mh and is characterised by chlorite mn titanomagnetite rutile hematite after chlorite maghemite after titanomagnetite with ilmenite and perovskite being absent 2 three dikes are typified by atoll textured spinels phlogopite euhedral mn picroilmenite of intermediate oxidation state wm fmq with coexisting deuterically serpentinized olivine ni fe alloys and magnetite 3 the remaining dike records an early crystallization event under very low wm redox conditions that precipitated anionic deficient spinels and a mg ti cr wustite type phase followed by late stage more oxidizing fmq mnpicroilmenite spinels are complexly zoned and crystallization trends among the dikes are diverse underscoring the fact that no single compositional trend or evolutionary sequence is typical of kimberlites ilmenites are euhedral and criteria for groundmass crystallization are established extraordinarily high mno max 17 wt contents and high geikielite 62 mole concentrations expand the ilmenite field typically assigned to that of kimberlites zirconium nb and cr are present in concentrations of 0 5 3 wt as oxides in ilmenite these highly incompatible elements along with mn are concentrated in late stage melt fractions the high pyrophanite contents which are more typical of silicic alkali suites are accompanied by phlogopite in the koidu dikes objective evaluations of kimberlite carbonatite relations as outlined in the literature cannot be made based on the oxide mineral group much of the compositional data for oxides in kimberlites are on mantle derived xenolith suites and are not from oxides derived from the crystallization of kimberlitic melts assessments of the fo2 s of kimberlites have considerable potential in evaluating diamond survival through redox reactions manganese rich nb zr cr ilmenites are typical of many kimberlites and should be considered in the suite of index minerals employed in prospecting

tidal velocity asymmetries and bedload transport in shallow embayments abstract tidal circulation can cause a net transport of sediment when the tidal velocity is asymmetric about a zero mean flood or ebb dominant and the sediment transport rate is related nonlinearly to velocity the relationship between tidal elevation and velocity is elucidated here to permit determination from tide gauge data and sediment transport relations whether tidal asymmetry needs to be considered as a mechanism for net sediment transport in the embayment of interest a relationship between elevation and velocity in a shallow water nonlinear system is derived through the continuity equation and shown to be significantly different than the linear relation finite difference numerical solutions of the one dimensional shallow water nonlinear equations are compared to the continuity relation and are in agreement especially toward the landward end of the channel tide gauge data collected at the landward end of the embayment are most useful for predicting velocity asymmetries throughout a major portion of the embayment channel the ratio of flood to ebb bedload transport and its relation to an asymmetric tidal elevation has been determined for both the linear relation between elevation and velocity and the nonlinear relation results show that the ratio of flood to ebb bedload transport as calculated from the nonlinear relation between elevation and velocity is similar to the flood to ebb ratio calculated from the linear relation because of offsetting effects

flow asymmetry associated with astronomical tides implications for the residual transport of sediment 1 tidal current asymmetry is usually associated to nonlinear tidal interactions in shallow water generating compound tides and overtides the present paper demonstrates that tidal asymmetry is not only caused by nonlinear tidal interaction but is also generated by astronomical tides in absence of shallow water effects in particular the k1 o1 and m2 constituents give an asymmetrical periodic flow pattern with the largest peak velocities persistently in the same direction a theoretical explanation for this phenomenon is presented and an inventory is made of other subordinate constituents that may contribute to repetitive asymmetric flow patterns tidal current asymmetry may induce residual transport of sediment analytical expressions are derived which quantify the residual transport of sediment due to the k1 o1 and m2 tides as a function of the phases and amplitudes of these constituents and the time lag between variation in suspended sediment transport and flow velocity the residual transport induced by the k1 o1 and m2 tides is compared to the residual transport due to the asymmetry associated with the m2 and m4 tides the former mechanism is particularly relevant in diurnal or mixed mainly diurnal tidal regimes where the k1 and o1 tides are dominant

eddy generation in the mediterranean undercurrent abstract in the framework of the european union mast iii project canary islands gibraltar azores observations 24 rafos floats were deployed in the mediterranean water mw undercurrent off south portugal between september 1997 and september 1998 a preliminary analysis of this lagrangian approach complemented with xbt and current meter data show some of the major aspects of the flow associated with the undercurrent as well as associated eddy activity floats that stayed in the undercurrent featured a downstream deceleration and a steering by bottom topography three meddy formations at cape st vincent could be isolated from the float data the dynamical coupling of meddies and cyclones was observed for a considerable period of time the generation of two dipolar structures in the portimao canyon region also was observed with the float data a major bathymetric relief gorringe bank was not only an important constraint to the eddy trajectories and of the flow at the mw levels but also a site for meddy formation

seismic reflection imaging of shallow oceanographic structures 1 multichannel seismic mcs reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure however the shallowest layers of the water column z 150 m have remained unexplored by this technique until recently in order to explore the feasibility of shallow seismic oceanography so we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m the influence of the acquisition parameters was quantified seismic data processing dedicated to so was also investigated conventional seismic acquisition systems were found to be ill suited to the imaging of shallow oceanographic structures because of a high antenna filter effect induced by large offsets and seismic trace lengths and sources that typically cannot provide both a high level of emission and fine vertical resolution we considered a test case the imagery of the seasonal thermocline on the western brittany continental shelf new oceanographic data acquired in this area allowed simulation of the seismic acquisition sea trials of a specifically designed system were performed during the aspex survey conducted in early summer 2012 the seismic device featured i four seismic streamers each consisting of six traces of 1 80 m ii a 1000 j sig sparker source providing a 400 hz signal with a level of emission of 205 db re 1 pa 1 m this survey captured the 15 m thick 30 m deep seasonal thermocline in unprecedented detail showing images of vertical displacements most probably induced by internal waves

morphodynamics of intermittently open closed coastal lagoon entrances new insights and a conceptual model abstract ocean entrances to coastal lakes and lagoons are a complex sensitive and important part of the coastal environment they provide estuarine water exchange between inland waterways and the open ocean and are increasingly the focus of intense urban and industrial development coastal lagoons that are only intermittently connected to the ocean are particularly sensitive during periods of closure water quality issues are exacerbated along with the increased risk of flooding mechanical clearance was undertaken in 2006 at the ocean entrance to narrabeen lagoon sydney australia historically this site has intermittently opened and closed both naturally and mechanically with the ingress of marine sand into the entrance restricting water exchange between the estuary and the ocean this instantaneous reset of the system provided a unique opportunity to monitor and quantify generic inlet sedimentation processes and mechanisms an intensive data collection campaign was undertaken for one entire year following the clearance this dataset includes current and water level measurements calculation of the alongshore sediment supply and regular highly detailed morphological surveys of the infilling lagoon entrance system this contribution utilises this unique dataset to quantify the sediment ingress volumes rates and pathways within the accreting flood tide delta of the lagoon entrance it was found that ingress of sand into the system proceeds via a rapid landward infilling process as opposed to backfilling toward the ocean with the evolution of the flood tide delta occurring in distinct phases the location of the divergence point of the flood tidal current the amount of available accommodation space within the entrance system and the influence of storm events were found to be key factors in the evolving morphodynamics of this intermittently open closed coastal lagoon

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

mid depth internal wave energy off the iberian peninsula estimated from seismic reflection data energy levels of internal waves are estimated from seismic reflection data three legacy seismic sections from 1993 and 1997 obtained off the iberian peninsula have been analyzed for acoustic reflections within the water column the reflections are aligned continuously for up to several kilometers over large parts of the sections and in the depth interval from 200 to 2000 m depth variations of these reflections are thought to be caused by the background internal wave field from the variations we derive horizontal wave number spectra of normalized internal wave displacement the general slope of the power density spectra is remarkably consistent for all sections and agrees well with model spectra for internal waves significant differences within the sections can be found when sufficiently large subsections are averaged the spatial variation of the energy level indicates increasing internal wave activity with shallower water depths as well as near a subsurface eddy

thermohaline fine structure in an oceanographic front from seismic reflection profiling we present acoustic images of oceanic thermohaline structure created from marine seismic reflection profiles across the major oceanographic front between the labrador current and the north atlantic current the images show that distinct water masses can be mapped and their internal structure imaged using low frequency acoustic reflections from sound speed contrasts at interfaces across which temperature changes the warm cold front is characterized by east dipping reflections generated by thermohaline intrusions in the uppermost 1000 meters of the ocean our results imply that marine seismic reflection techniques can provide excellent spatial resolution of important oceanic phenomena including thermohaline intrusions internal waves and eddies

intermittently closed open lakes and lagoons their global distribution and boundary conditions abstract intermittently closed open lakes and lagoons icolls are a particularly dynamic form of estuary characterised by periodic entrance closure to the ocean closure occurs when a subaerial sand berm stabilises across the entrance channel during times of low fluvial discharge icolls are of global importance as they provide valuable ecological habitats for many species and are associated with a wide range of management issues due to their cycle of entrance closure and opening icolls are found to be more widespread globally than previously described with 1477 of these estuaries being identified in this study this constitutes an estimated 3 of the world s estuaries and 15 of all estuaries along microtidal coastlines icolls are concentrated along microtidal to low mesotidal coastlines in the mid latitudes and predominantly on coasts with temperate climates this distribution is related to greater wave heights as driven by high intensity winds and a longer fetch distance the highest proportion of icolls are present in australia 21 all global icolls south africa 16 and mexico 16 in australia a comparison with fluvial input found that it is less important than marine processes in determining icoll formation and that icolls are associated with a relative tidal range of

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

estimating movement of reflectors in the water column using seismic oceanography the observation of spatial and temporal dynamics of the ocean is fundamental to understand global and regional aspects of water mixing physical oceanography has traditionally observed ocean structures with in situ measurements often limited in temporal and or spatial resolution in exploration seismology a set of techniques has been developed over the last decades to image and characterize the physical properties of sub seafloor structures by inversion methods at high horizontal resolution the two different fields have made contact in seismic oceanography where the well developed methods of marine reflection seismology have been applied to the dynamic ocean however one aspect so far ignored in seismic oceanography is the dynamical temporally varying nature of water structures here we show that it is possible to estimate temporal variations of reflectors in water structures as an inversion parameter the new dynamic property reflector movement velocity gives an additional parameter to characterize ocean water dynamics

hydro morphological modelling of small wave dominated estuaries small intermittently open or closed estuaries are characteristic of the coasts of south africa australia california mexico and many other areas of the world however modelling attention has tended to focus on big estuaries that drain large catchments and serve a wide diversity of interests e g agriculture urban settlement recreation commercial fishing in this study the development of a simple parametric system dynamics model to simulate the opening and closure of the mouths of small wave dominated estuaries is reported in the model the estuary is conceived as a basin with a specific water volume to water level relationship connected to the sea by a channel of fixed width but variable sill height changes in the form of the basin are not treated in the model while the dynamics of the mouth channel are central to the model the magnitude and direction of the flow through the mouth determines whether erosion or deposition of sediment occurs in the mouth channel influencing the sill height the model is implemented on the great brak estuary in south africa and simulations reveal that the raised low water levels in the estuary during spring tide relative to neap tide are occasioned by the constriction of the tidal flow through the shallow mouth freshwater inflows to the estuary are shown to be significant in determining the behaviour of the inlet mouth a factor often ignored in studies on tidal inlets further it is the balance between freshwater inflows and wave events that determines the opening or closure of the mouth of a particular estuary

petrogenesis of orbicular ijolites from the prairie lake complex marathon ontario textural evidence from rare processes of carbonatitic magmatism abstract a unique occurrence of orbicular ijolite is hosted in a matrix of contemporaneous holocrystalline ijolite at the 1 1 ga prairie lake carbonatite complex marathon ontario canada and is the only known occurrence of this textural type in a rock of ijolitic composition this mineralogical and petrological study of this orbicular ijolite highlights many of the differences from other rare occurrences of orbicular rocks described from carbonatites granites diorites and lamprophyres the orbicules occur along distinct densely packed bands in equigranular nepheline rich ijolite and range up to 6 cm in diameter macroscopically the orbicules show variability in the mineralogy of their cores detailed imaging of the cores shows evidence of quench textures radial outward zoning is common near the cores with concentric banding occurring toward the margins of the orbicules the mineralogy of the orbicules consists of nepheline diopside calcite apatite andradite melanite garnet titanite fe rich phlogopite titaniferous magnetite perovskite with secondary natrolite calcite and cancrinite the mineralogy of the host ijolite is similar to that of the orbicules mineral compositions from the orbicular ijolite and the host ijolite are similar within the orbicules anhedral minerals are found occurring in a matrix of garnet throughout the distinct concentric bands the textures within the concentric bands of the orbicules are best described as annealing recrystallization textures the rims of the orbicules form interlocking crystals with the host ijolite resulting in near indistinguishable boundaries the orbicules are interpreted to represent interaction of a partially crystallized quenched ijolitic melt which was in contact with a second pulse of consanguineous ijolite magma immersion in the latter resulted in sub solidus diffusion and annealing recrystallization orbicular textures were produced from previously formed quenched ijolite which was recrystallized producing the monominerallic concentric layers sequentially from the margins toward the center of the orbicule this proposed model for the formation of orbicular ijolite from prairie lake highlights the complexities of these rock types and supports previous models of magma mixing during the later stages of carbonatite emplacement and crystallization

kimberlite lamproite ultramafic lamprophyre and carbonatite relationships on the dharwar craton india an example from the khaderpet pipe a diamondiferous ultramafic with associated carbonatite intrusion abstract are kimberlites lamproites ultramafic lamprophyres and carbonatites genetically associated or not there are strong opinions for and against any relationship the 20 ha khaderpet pipe discovered by rio tinto exploration is an unusual diamondiferous carbonatite kimberlite clan rock kcr association in the anumpalle cluster of the wajrakarur kimberlite field in the dharwar craton of peninsular indian the khaderpet pipe has a discrete sovite phase intrusive into kcr breccia not noticed elsewhere in the wajrakarur kimberlite field petrographically the kcr is a clast supported lithic breccia and crystal lithic tuff with occasional pelletal lapilli clasts show a weak horizontal imbrication the overall appearance of the tuffs and breccias is suggestive of terminal blocked vent accumulations that formed by under pressure with spallation of country rock causing an abundance of granitoid debris the sovite phase has up to 95 calcite occasionally showing flow textured polycrystalline laths set in a minor saponite matrix there are mineralogical gradations from an olivine rich ultramafic to a calcite dominant rock resembling pure carbonatite rare ree mineral phases in the carbonatite include allanite and other ree rich unidentified mineral phases xenocrystic high pressure phases in both ultramafic and carbonatite include mantle derived diamonds lherzolitic eclogitic and subcalcic pyrope ti poor andradite chrome diopside picrochromite and picroilmenite extensive metasomatism in the form of reddening of country rock feldspars by hematite introduction of green chlorite and saponitic alteration of breccia clasts and the ultramafic phase is common the chemistry of the khaderpet ultramafic component suggests that the kcr is transitional between kimberlite and ultramafic lamprophyres like certain other pipes in the wajrakarur kimberlite field with strong enrichment in lree cao and co2 however low mgo 13 and high cao 10 values are more typical of ultramafic lamprophyres such as alnoite or aillikite the significant carbonate content and the presence of accessory ti andradite would lead to the kcr being classified as an ultramafic lamprophyre under the iugs classification the khaderpet carbonatite component shows extreme enrichment in ree approaching that of world average carbonatite given the chemical and petrological characteristics of a carbonatite along with the associated and widespread aureole of metasomatism this phase is considered to be a late stage fractionation product of the khaderpet diamond bearing ultramafic magma

the geomorphology and evolution of intermittently open and closed estuaries in large embayments in victoria australia abstract intermittently open and closed estuaries ioce are common landforms on open ocean microtidal coasts they are often viewed as evolutionary end members of open estuaries where all the accommodation space has been infilled by sediment while ioce are typically recognised to form in wave dominated microtidal environments they can also form within embayments where the relative balance between waves and tides is highly spatially and temporally variable this study examines the geomorphology and infill of two such embayed ioce in victoria southern australia in order to assess how these systems compare to their open ocean counterparts in order to gain an understanding of the boundary conditions of such landforms it is found that ioce s can occur in embayments where there is sufficient energy to form a beach berm the infill of these systems broadly follows the transgressive stillstand pathways of open coast systems but the facies are modulated by the size of the catchment and open ocean wave exposure these boundary conditions also affect the evolution of the coastal plain in which the embayed ioce may form and in turn the estuary planform the entrance dynamics of these estuaries are highly variable and it appears that they may switch between permanently open or closed states in relation to modification of boundary conditions such as roughness it is inferred that the relative tidal range rtr of the marine environment at the estuary mouth is an important determination of entrance condition with the observed systems being close to the maximum rtr value on the open coast at which these landforms can exist

experimental study of barium partitioning between phlogopite and silicate liquid at upper mantle pressure and temperature barium partition coefficients for phlogopite crystallized from a natural lamproite at 10 30 kbar and 900 1150 c show a three fold decrease in partition coefficient d with increasing pressure from 10 to 30 kbar e g from 0 75 to 0 23 and 35 50 increase in d with increasing temperature from 1000 to 1100 c at 10 and 15 kbar e g from 0 51 to 0 75 the variation with temperature is contrary to most recorded variations of d and is attributed to a compositional control in the phlogopite d correlates with substitution of titanium in the phlogopite thus as the titanium content increases with increasing temperature the barium content and hence d increases application of partitioning data for barium in models for lamproite genesis suggests that phlogopite of metasomatic origin and possibly some barium rich accessory phases are present in the source rocks for lamproite and phlogopite plays a major role in the generation of lamproitic magma

shoreline change mapping using crowd sourced smartphone images abstract shoreline change information is critical for effective management of the coastal zone this study presents a low cost method for mapping shoreline change that harnesses smartphone images collected by the community and uploaded to social media platforms a smartphone camera cradle installed overlooking a coastal region is used to constrain the crowd sourced camera extrinsic parameters and accompanying signage instructs participants on how to share their image to social media using a site specific hashtag identifier surveyed ground control points solve for the focal length of the smartphone lens and more accurately resolve the camera extrinsic parameters shoreline position is subsequently mapped on georectified images using an edge detection technique based on the red and blue colour channels a validation of the method was conducted at two sandy beaches in se australia and resulted in strong community participation 400 images submitted over 7 months by 198 individual contributors concurrent shoreline surveys using rtk gnss indicated that shoreline accuracy using this crowd sourced approach is comparable to that of established coastal imaging systems with cross shore shoreline accuracy best for these two elevated validation sites camera elevation 17 3 m 27 1 m above msl in the camera nearfield rmsd 1 4 m and rmsd ranging between 2 6 and 3 9 m over coastal stretches spanning up to 1 km minimal differences in shoreline accuracy were observed between low resolution images characteristic of those uploaded to social media and higher resolution images sourced from the smartphone the successful application of this low cost approach combined with the proliferation of smartphones and social media usage open up new possibilities for crowd sourced shoreline change mapping at suitable coastal locations worldwide

flood and ebb dominance in estuaries in korea abstract ebb dominance which is mainly observed at the youngsan river estuary yre and flood dominance at the keum river estuary kre are conspicuous features in the southwestern coastal zones of korea in considering the sources of this asymmetry which include not only bottom friction irregular bathymetry and tidal flats other issues also need to be considered since dominance occurs extensively in coastal regions near the yre ebb and the kre flood this study concludes that the rotational directions of m 2 tidal ellipses at the eastern side of the yellow sea can produce the differences between maximum currents in flood and ebb and thus flood ebb dominance in southwestern korea is closely related to the tidal characteristics of the yellow sea an analysis of kelvin and poincare waves in the yellow sea also indicates that flood ebb dominance is caused by the southward propagation of an m 4 tide while an m 2 tide propagates northward which is another characteristic feature of the yellow sea this reinforces the above conclusion flood ebb dominance which is generated by these mechanisms at the outer sea becomes more pronounced landward with an increase in the amplitude of m 4 tides however the mechanisms involved in the growth of an m 4 tidal constituent at the kre and at the yre are very different while flood dominance at the kre is mainly due to energy dissipation by friction ebb dominance at the yre is largely caused by the vast tidal flats in addition shallow water tides propagating from the outer sea also serve to reinforce flood dominance at the kre as well as ebb dominance at the yre

a fluid dynamic appraisal of a model for the origin of comb layering and orbicular structure the destructive power of intruding magmas is sometimes overstated as a consequence of the belief that high drag force is automatically the result of high viscosity or because a magma contains phenocrysts or xenoliths which cause abrasion however consideration of the principles of fluid dynamics indicates that the opposite may generally be the case abrasion by particles suspended in a viscous magma is negligible and the drag forces associated with viscous flow are not necessarily large inasmuch as high viscosity acts to limit flow rate these contentions are demonstrated analytically for the aqueous suspension model of the formation of orbicules and comb layering proposed by moore and lockwood for which the effects of an aqueous fluid and magma may be compared as a result of this analysis a magmatic origin for comb layering and orbicle growth is preferred a conclusion compatible with other interpretations of comb layering

a study of non linear tidal propagation in shallow inlet estuarine systems part i observations the offshore tide becomes strongly distorted as it propagates into shallow estuarine systems observations of sea surface elevation and horizontal currents over periods ranging from three days to one year at nine stations within nauset inlet estuary document the non linear interaction of the off shore equilibrium tidal constituents despite strong frictional attenuation within the estuary the overtides and compound tides of m2 s2 and n2 in particular reach significant amplitude resulting in strong tidal distortion high frequency forced constituents in sea surface are phase locked consistently leading the forcing tides by 60 70 resulting in a persistent distortion where falling tide is longer than rising tide forced constituents in currents are more nearly in phase with equilibrium constituents producing flood currents which are shorter but more intense than ebb currents a compound fortnightly tide msf modulates the mean water level such that lowest tides occur during neap phase instead of spring phase this fortnightly tide can be contaminated by storm surge changing the phase characteristics of this constituent implications of the overtides compound tides and lower frequency tides on near bed suspended and dissolved material transport are profound

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

evidence from opportunity s microscopic imager for water on meridiani planum the microscopic imager on the opportunity rover analyzed textures of soils and rocks at meridiani planum at a scale of 31 micrometers per pixel the uppermost millimeter of some soils is weakly cemented whereas other soils show little evidence of cohesion rock outcrops are laminated on a millimeter scale image mosaics of cross stratification suggest that some sediments were deposited by flowing water vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis microscopic images support the hypothesis that hematite rich spherules observed in outcrops and soils also formed diagenetically as concretions

the k1 tide on the continental shelf from nova scotia to cape hatteras abstract a description is given of the k1 tide over the northeast continental shelf off north america from nova scotia to cape hatteras analyzed pressure data obtained from w brown and j irish university of new hampshire have been used to draw up the k1 cotidal map and existing current data have been analyzed to give the associated velocity map offshore there is a sweep of the tide from north to south in general agreement with what is known of the oceanic k1 tide in the north atlantic on the shelf there is a trapping of phase lines to the coast creating in particular a virtual amphidrome south of cape cod maximum amplitudes of around 15 cm are found in the gulf of maine lowest around 7 cm south of cape cod the k1 currents are generally barotropic and current ellipses are aligned with the local topography maximum currents of about 10 cm s 1 are found south of cape cod a simple model for the k1 pressure field is developed using the free and forced inviscid barotropic waves on a two dimensi

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins