run up of internal waves on a gentle slope in a two layered system this paper describes the dissipative phase of internal wave run up on uniform slopes of 0 030 and 0 054 rad as observed in a series of laboratory experiments the waves were generated continuously at the interface of two miscible layers of differing density as each wave in the perodic train propagated onto the slope it steepened and developed into a solitary like wave before finally overturning surrounding fluid was engulfed into the wave as it overturned and the resulting gravitational instability produced considerable turbulence and mixing the broken wave took the form of a discrete bolus of dense fluid which propagated for some distance up the slope bulk parameters which characterize the nature of the bolus were defined and the dependence of these on the incident wave parameters and their behaviour during the run up phase were examined

on the formation and propagation of nonlinear internal boluses across a shelf break high resolution two and three dimensional numerical simulations are performed of first mode internal gravity waves interacting with a shelf break in a linearly stratified fluid the interaction of nonlinear incident waves with the shelf break results in the formation of upslope surging vortex cores of dense fluid referred to here as internal boluses that propagate onto the shelf this paper primarily focuses on understanding the dynamics of the interaction process with particular emphasis on the formation structure and propagation of internal boluses onshelf a possible mechanism is identified for the excitation of vortex cores that are lifted over the shelf break from where from the simplest viewpoint they essentially propagate as gravity currents into a linearly stratified ambient fluid

a facies model for internalites internal wave deposits on a gently sloping carbonate ramp upper jurassic ricla ne spain abstract internal waves are waves that propagate along the pycnocline the interface between two density stratified fluids even though internal waves are ubiquitous in oceans and lakes their impact in the sedimentary record has remained largely unrecognized internal waves can remobilize the sediment from the depth at which the internal waves break onto the sea floor in shelf or ramp settings internal wave deposits internalites have to be distinguished from tempestites while in slope and deeper settings internalites require distinction from turbidites the upper kimmeridgian carbonate ramp succession cropping out near ricla ne spain provides some key evidence to differentiate the depositional processes induced by breaking internal waves from those related to surface storm waves sandy oolitic grainstone eventites previously interpreted as tempestites contain evidence of reworking by turbulent events related to breaking internal waves underlying rationale are 1 they occur in distal mid ramp position detached from the coeval shallow water successions 2 they do not have the characteristic coarsening and thickening upward trend of storm deposits 3 they gradually thin out to disappear both up dip and down dip interbedded with mid ramp lime mudstones and 4 they show little or no erosion towards the shallower areas a facies model for internalites produced by two sediment populations sand and mud on a gently sloping carbonate ramp is proposed the individual internalites occurring at ricla include several architectural elements sequentially organized in dip direction which can be related to the flows associated with breaking internal waves erosion in the breaker zone swash run up and tractive backwash flow individual internalites stack with down and up slope shingling configuration in dm thick packages thought to reflect the up slope and down slope migration of the breaker zone in turn related to depth variations of the palaeo pycnocline packages occur in dm to m thick clusters suggested to reflect changes in sediment supply and or variations in water stratification affecting the energy of internal waves

poincare wave induced mixing in a large lake a 10 000 km2 hypoxic dead zone forms during most years in the central basin of lake erie to investigate the processes driving the hypoxia we conducted a 2 yr field campaign where the mixing in the lake interior during the stratification period was examined using current meters and temperature loggers data as well as 600 temperature microstructure profiles from which turbulent mixing was computed near inertial poincare waves drive shear instability generating 1 m amplitude and 10 m wavelength high frequency internal waves with 1 mdensity overturns that lead to an increase in turbulent dissipation by one order of magnitude the instabilities are associated with enhanced vertical shear at the crests and troughs of the poincare waves and may be correlated with the local gradient richardson number poincare wave induced mixing should be an important factor when the burger number 0 25 the strong diapycnal mixing induced by the poincare wave activity will also significantly modify the energy flux paths for example we estimate that in lake erie 0 85 of the wind energy is transferred to the lake interior below the surface layer of this 40 is dissipated in the interior metalimnion and 60 is dissipated at the bottom boundary in smaller lakes 0 42 of wind energy is transferred to the deeper water with 90 dissipated in the boundary and 10 in the interior metalimnion 2012 by the association for the sciences of limnology and oceanography inc

comparative stable isotope geochemistry of ni cu zn and fe in chondrites and iron meteorites high precision ni isotopic variations are reported for the metal phase of equilibrated and unequilibrated ordinary chondrites carbonaceous chondrites iron meteorites mesosiderites and pallasites we also report new zn and cu isotopic data for some of these samples and combine them with literature fe cu and zn isotope data to constrain the fractionation history of metals during nebular vapor solid and planetary metal sulfide silicate phase changes the observed variations of the 62ni 58ni 61ni 58ni and 60ni 58ni ratios vary linearly with mass difference and define isotope fractionation lines in common with terrestrial samples this implies that ni was derived from a single homogeneous reservoir while no 60ni anomaly is detected within the analytical uncertainties ni isotopic fractionation up to 0 45 per mass difference unit is observed the isotope compositions of ni and zn in chondrites are positively correlated we suggest that in ordinary chondrites exchange between solid phases in particular metal and silicates and vapor followed by mineral sorting during accretion are the main processes controlling these isotopic variations the positive correlation between ni and zn isotope compositions contrasts with a negative correlation between ni and zn and cu isotope compositions which when taken together do not favor a simple kinetic interpretation the observed transition element similarities between different groups of chondrites and iron meteorites are consistent with the genetic relationships inferred from oxygen isotopes iiia pallasites and iva l chondrites copper is an exception which we suggest may be related to separate processing of sulfides either in the vapor or during core formation

peak metamorphic temperatures in type 6 ordinary chondrites an evaluation of pyroxene and plagioclase geothermometry quantifying the peak temperatures achieved during metamorphism is critical for understanding the thermal histories of ordinary chondrite parent bodies various geothermometers have been used to estimate equilibration temperatures for chondrites of the highest metamorphic grade type 6 but results are inconsistent and span hundreds of degrees because different geothermometers and calibration models were used with different meteorites it is unclear whether variations in peak temperatures represent actual ranges of metamorphic conditions within type 6 chondrites or differences in model calibrations we addressed this problem by performing twopyroxene geothermometry using quilf95 on the same type 6 chondrites for which peak temperatures were estimated using the plagioclase geothermometer nakamuta and motomura 1999 we also calculated temperatures for published pyroxene analyses from other type 6 h l and ll chondrites to determine the most representative peak metamorphic temperatures for ordinary chondrites pyroxenes record a narrow overlapping range of temperatures in h6 865 926 c l6 812 934 c and ll6 874 945 c chondrites plagioclase temperature estimates are 96 179 c lower than pyroxenes in the same type 6 meteorites plagioclase estimates may not reflect peak metamorphic temperatures because chondrule glass probably recrystallized to plagioclase prior to reaching the metamorphic peak the average temperature for h l and ll chondrites 900 c which agrees with previously published oxygen isotope geothermometry is at least 50 c lower than the peak temperatures used in current asteroid thermal evolution models this difference may require minor adjustments to thermal model calculations

on the breaking of internal solitary waves at a ridge an experimental laboratory study has been carried out to investigate the propagation of an internal solitary wave of depression and its distortion by a bottom ridge in a two layer stratified fluid system wave profiles density fields and velocity fields have been measured at three reference locations namely upstream downstream and over the ridge experiments have been performed with wave amplitudes in the range 0 2 1 9 times the depth of the upper layer and a ratio between the lower and the upper layer in the range 3 0 8 5 the ridge slope was varied from 0 1 to 0 33 and the maximum ridge height was two thirds of the thicker fluid layer over the ridge the flow has been classified into i cases when the bottom ridge has little influence on the propagation and spatial structure of the internal solitary wave ii cases where the internal solitary wave is significantly distorted by the blocking effect of the ridge though no wave breaking occurs and iii cases for which the internal solitary wave is broken as it encounters and passes over the bottom ridge a detailed description of the processes leading to wave breaking is given breaking has been found to take place when the fluid velocity in the lower layer exceeds 0 7 of a local nonlinear wave speed defined at the top of the ridge the breaking condition is also expressed in terms of the amplitude of the incident wave the layer thickness ratio and the relative height of the ridge the wave breaking can be determined from the input parameters of the experiment the transmitted waves have been found to always consist of a leading pulse solitary wave followed by a dispersive wavetrain the solitary wave amplitude is significantly reduced only when breaking takes place at the ridge internal waves of mode two are generated in cases with strong breaking

origin of the rudstone floatstone beds in the upper jurassic arab d reservoir khurais complex saudi arabia abstract detailed description and analysis of cores from more than 50 wells through the kimmeridgian arab d reservoir arab d member and upper part of the jubaila formation in khurais abu jifan and mazalij oil fields are used to establish a consistent depositional model that represent a shift in the conceptual understanding of the upper jurassic carbonates of saudi arabia the jubaila fm and arab d mb conform to a shallowing upward carbonate evaporite succession in which three main carbonate facies belts occur capped by anhydrite the lower facies belt corresponds to the jubaila formation and consists of a series of eventites triggered by breaking internal waves interbedded peloidal wackestones represents the background sedimentation where neritic lime mud was churned by pellet producing benthonic fauna eventites consist of a lower intraclastic rudstone floatstone interval a middle grainstone packstone interval and an upper barren mudstone interval the middle facies belt is made of microbial coral stromatoporoid buildups the upper facies belt consists of the following shallow water lithofacies with cladocoropsis green algae foraminifers peloids and oolitic grainstones and oolitic cryptomicrobial mudstone to grainstone the stacking patterns of the internalites internal wave deposits in the jubaila fm suggests alternating periods with different internal waves activity namely different strength and bathymetric position of the pycnocline and intermittent production and accumulation of the neritic lime mud this interpretation represents a change to previous interpretations turbidites and tempestites and has important implications in both the perceptions of depositional processes in play and the criteria behind stacking lithofacies into parasequences and sequences

weathering of meteorites from oman correlation of chemical and mineralogical weathering proxies with 14c terrestrial ages and the influence of soil chemistry fifty four fragments of ordinary chondrites from 50 finds representing all searched areas in central oman and all weathering stages were selected to compare the physical chemical and mineralogical effect of terrestrial weathering with 14c terrestrial ages 14c ages range from 2 0 to 49 kyr with a median value of 17 9 kyr the peak of the age range which is between 10 20 kyr falls in an arid climate period a comparison of the chemical composition of omani chondrites with literature data for unweathered h and l chondrites demonstrates a strong enrichment in sr and ba and depletion in s during weathering water contents in h chondrites increase with terrestrial age whereas l chondrites show a rapid initial increase followed by nearly constant water content correlating sr ba and h2o with age indicates two absorption trends i an initial alteration within the first 20 kyr dominated by h2o uptake mainly reflecting fe ni metal alteration and ii a second baand sr dominated stage correlated with slower and less systematic weathering of troilite that starts after h2o reaches 2 wt sulfur released from troilite partly combines with ba and sr to form sulfate minerals other parameters correlated with 14c age are degree of weathering color of powdered meteorites and the ni fe ratio chemical analyses of 145 soils show a high degree of homogeneity over the entire interior oman desert indicating large scale mixing by wind soil samples collected from beneath meteorite finds typically are enriched in ni and co confirming mobilization from the meteorites high cr and ni concentrations in reference soil samples which decrease from ne to sw are due to detrital material from ultramafic rocks of the oman mountains

three dimensional simulation of high frequency nonlinear internal wave dynamics in cayuga lake three dimensional 3d hydrostatic and nonhydrostatic versions of the mitgcm were applied to simulate the dynamics of the internal wave field basin scale seiches nonlinear surges and high frequency nonlinear internal waves nliws in cayuga lake ny the simulations were performed using up to 226 million computational cells with several horizontal grid resolutions varying from 450 450 m to 22 22 m vertical grid spacing was not varied and ranged from 0 5 m to 2 95 m the 22 22 m nonhydrostatic grid reproduced qualitatively the formation propagation and shoaling of observed nliws using 10 grid points along the wavelength and a grid lepticity of o 1 this ensured respectively that the waves were not aliased and physical dispersion predominated over numerical dispersion using a sensitivity analysis we generalize that correctly simulating nliws in real domains using second order discretization requires grid resolutions that are an order of magnitude smaller than the wavelength and amplitude with 2 consistent with published work on idealized domains local gyre like circulation was simulated near mid basin headlands and transverse shoaling of nliw packets on lateral boundaries was associated with topographic reflection and refraction in agreement with published field observations from estuaries which show nliw propagation in long narrow quasi 2d systems e g finger lakes lochs fjords estuaries and straits is fundamentally 3d these results therefore help fill the gap in understanding and correctly modelling the multiscale 3d dynamics of nliws in complex natural systems this article is protected by copyright all rights reserved

experimental investigation of sediment resuspension beneath internal solitary waves of depression internal solitary waves isws of depression are common features of coastal environments and believed to resuspend sediments where they shoal in this study the sediment resupension process associated with isws propagating over a flat bed was investigated in the laboratory the first ever profile measurements of the three dimensional instantaneous velocity field beneath the isws revealed that resuspension occurs during burst like vertical velocity events which lift sediments into the water column in the adverse pressure gradient region beneath the trailing part of the wave resuspension was not observed when the wave induced viscous bed stress was maximal directly beneath the isw trough prediction of wave induced resuspension was therefore unsuccessful using a traditional viscous bed stress based shields diagram a parameterization for isw induced resuspension is proposed as a function of the maximum instantaneous vertical velocity in the bursts wmax here we have replaced the viscous bed stress with isw 2wmax2 where isw is the instantaneous resuspending bed stress and 2 is the near bed fluid density from these results it is possible for field oceanographers to predict the occurrence of isw induced resuspension from the bulk wave and stratifications characteristics in a two layer stratification further research is required to extend the parameterization to larger reynolds numbers at field scale

response of the benthic nepheloid layer to near inertial internal waves in southern lake michigan 1 time series measurements of water transparency water temperature and current velocity were made at a station located in 58 m of water in southern lake michigan during the summer of 1995 currents generated by near inertial internal waves are correlated with variations in the thickness and in the vertical distribution of suspended sediment in the benthic nepheloid layer although a direct causal link between internal wave action and changes in the nepheloid layer could not be established the data suggest that local resuspension by shoaling internal waves maintains the layer during the stratified period the origin and maintenance of the benthic nepheloid layer is most likely the result of local resuspension due to a combination of internal wave action and longer term processes

large eddy simulation of sediment transport currents over ripples a large eddy simulation has been performed to study the detailed sediment dynamics that occur in channel flow over ripples the code solves the navier stokes equations and an advection diffusion equation for the sediment and has been verified to produce quantitatively accurate hydrodynamic results for the flow domains used in this study the main features of interest in this flow are seen because of the high resolution of the grid especially near the ripple boundary this yields a detailed bottom shear stress distribution properly identified coherent structures and resolved sharp gradients in the sediment concentration globally the sediment is carried up into the flow from locations where the shear stress is high on the upslopes of ripple crests and is advected downstream by the current and upward by the vertical velocity component regions of positive vertical velocity are associated with gortler vortices which represent a significant sediment transport mechanism in this flow

multiple parent bodies of ordinary chondrites abstract thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder like form taking into account the effect of consolidation state on thermal conductivity the very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long lived radioactive elements in chondritic abundances are the only source of heat the maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs the thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal near the surface however where the material is unconsolidated and the thermal conductivity is much lower the thermal gradient is quite large this result contradicts the conventional onion shell model of chondrite parent bodies but because the internal temperature is almost constant through the whole body it supports a multiple parent bodies model according to which each petrologic type of chondrite comes from a different parent body

seasonal variation of solitary wave properties in lake constance 1 the properties of internal solitary waves isws depend on the stratification of the water body in most climatic regions the stratification in lakes and oceans varies during the year and hence the properties of the isws can also be expected to change over the seasons on the basis of a long term temperature time series recorded over 6 years this paper investigates seasonal changes in the characteristic properties of isws in lake uberlingen a subbasin of lake constance a large number of isws with amplitudes ranging from 3 m to 30 m were identified more than 15 of the leading isws of a wave train were associated with density inversions often indicating shear instabilities or trapped cores for all waves the propagation depth and the value of a nonlinearity index nlp providing the degree of nonlinearity were determined propagation depth being the rest height of the isotherm undergoing maximum displacement and nlp the ratio between wave amplitude and propagation depth the index nlp was found to be a good parameter for predicting the occurrence of inversions the statistical analysis of the wave properties derived from the observations revealed that the degree of nonlinearity of the isws changes with season complementary to the statistical analysis the seasonally averaged isw properties were compared with wave prototypes obtained numerically from the dubreil jacotin long djl and the stratified korteweg devries kdv models the simulations indicate that the typical stratification and its seasonal variation are responsible for the degree and the seasonality of nonlinearity of the isws

interference pattern of the sound field in the presence of an internal kelvin wave in a stratified lake internal kelvin waves ikws initiated by rotation of the earth are one of the main hydrodynamic phenomena in large stratified lakes where baroclinic rossby radius of deformation is smaller than the horizontal scale of the lake ikws can be identified using the spectra of internal waves where in the presence of ikws the inertial frequency is at maximum ikws play a rather important role in the lake s dynamics for different processes both in the water layer and sediment especially at the periphery of lake due to influence of internal waves on the sound propagation acoustical methods can be used for estimation of behaviour of ikws in this paper the spatiotemporal variability of the mid frequency 1 khz sound field in the presence of ikws in a deep stratified lake kinneret is studied using numerical simulations based on normal mode theory due to the specific character of perturbation of the water layer ikws can cause specific variations of interference pattern in particular a significant shift of the sound interference pattern both in spatial and frequency domain these shifts can be easily measured and used for reconstruction of ikw parameters

stable calcium isotopic composition of meteorites and rocky planets abstract new measurements of mass dependent calcium isotope effects in meteorites lunar and terrestrial samples show that earth moon mars and differentiated asteroids e g 4 vesta and the angrite and aubrite parent bodies are indistinguishable from primitive ordinary chondritic meteorites at our current analytical resolution 0 07 sd for the 44 ca 40 ca ratio in contrast enstatite chondritic meteorites are slightly enriched in heavier calcium isotopes ca 0 5 and primitive carbonaceous chondritic meteorites are depleted in heavier calcium isotopes ca 0 5 the calcium isotope effects cannot be easily ascribed to evaporation or intraplanetary differentiation processes the isotopic variations probably survive from the earliest stages of nebular condensation and indicate that condensation occurred under non equilibrium undercooled nebular gas conditions some of this early high temperature calcium isotope heterogeneity is recorded by refractory inclusions niederer and papanastassiou 1984 and survived in planetesimals but virtually none of it survived through terrestrial planet accretion the new calcium isotope data suggest that ordinary chondrites are representative of the bulk of the refractory materials that formed the terrestrial planets enstatite and carbonaceous chondrites are not the enrichment of light calcium isotopes in bulk carbonaceous chondrites implies that their compositions are not fully representative of the solar nebula condensable fraction

the origin of volatile element depletion in early solar system material clues from zn isotopes in chondrules abstract volatile lithophile elements are depleted in the different planetary materials to various degrees but the origin of these depletions is still debated stable isotopes of moderately volatile elements such as zn can be used to understand the origin of volatile element depletions samples with significant volatile element depletions including the moon and terrestrial tektites display heavy zn isotope compositions i e enrichment of 66zn vs 64zn consistent with kinetic zn isotope fractionation during evaporation however luck et al 2005 found a negative correlation between 66 zn and 1 zn between ci cm co and cv chondrites opposite to what would be expected if evaporation caused the zn abundance variations among chondrite groups we have analyzed the zn isotope composition of multiple samples of the major carbonaceous chondrite classes ci 1 cm 4 cv 2 co 4 cb 2 ch 2 ck 4 and ck cr 1 the bulk chondrites define a negative correlation in a plot of 66 zn vs 1 zn confirming earlier results that zn abundance variations among carbonaceous chondrites cannot be explained by evaporation exceptions are cb and ch chondrites which display zn systematics consistent with a collisional formation mechanism that created enrichment in heavy zn isotopes relative to the trend defined by ci ck we further report zn isotope analyses of chondrite components including chondrules from allende cv3 and mokoia cv3 as well as an aliquot of allende matrix all chondrules are enriched in light zn isotopes 500 ppm on 66zn 64zn relative to the bulk contrary to what would be expected if zn were depleted during evaporation on the other hand the matrix has a complementary heavy isotope composition we report sequential leaching experiments in un equilibrated ordinary chondrites which show sulfides are isotopically heavy compared to silicates and the bulk meteorite by ca 0 65 per mil on 66zn 64zn we suggest isotopically heavy sulfides were removed from either chondrules or their precursors thereby producing the light zn isotope enrichments in chondrules

sr stable isotope composition of earth the moon mars vesta and meteorites abstract high precision stable sr isotopic variations 88 sr 86 sr are reported in a variety of terrestrial samples martian and lunar meteorites hed undifferentiated primitive meteorites chondrules and refractory inclusions almost all the whole rock samples are isotopically indistinguishable at a 50 parts per million ppm level the exceptions are cv and co chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material five separated chondrules and one refractory inclusion from allende are isotopically light with 88 86 sr fractionations up to 1 73 whereas the matrix is enriched in the heavy isotopes 88 86 sr 0 66 the depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in sr however in that case more than 60 of the original material would be unaccounted we propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy sr from neutral sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix we conclude that cv and co chondrites are not the primary building blocks for earth and mars

internal hydraulic jumps in a long narrow lake high resolution three dimensional numerical modeling and field observations were used to describe the nonlinear response of cayuga lake to surface wind forcing the degeneration of the basin scale internal wave field was characterized according to the composite froude number g2 wedderburn number wn and lake number ln which are measures of hydraulic control and bulk and integral wind disturbance force to the baroclinic restoring force respectively the typical cayuga lake response was a nonlinear surge when 1 1 in a lake the occurrence of the hydraulic jump was correctly predicted using scaling parameters it was also shown that topographically induced internal hydraulic jumps form when the nonlinear surges interact with a sill contraction topographic feature in contrast to published literature the observed high frequency nonlinear internal waves were preferentially associated with internal jumps as opposed to steepened internal surges computed vertical diffusivities showed mixing was enhanced by two orders of magnitude within both the surges and hydraulic jumps as they propagated through the basin and interacted with topography our results can be generalized to other lakes and fjords with similar long narrow geometry and topographically separate side basins

progressive aqueous alteration of cm carbonaceous chondrites abstract cm chondrites are aqueously altered rocks that contain 9 wt h 2 o i e indigenous water bound in phyllosilicates also present are clumps of serpentine tochilinite intergrowths previously called poorly characterized phases or pcp pentlandite and ni bearing pyrrhotite we studied 11 cm chondrites that span the known range from least altered to most altered we used various petrologic properties many previously identified that provide information regarding the degree of aqueous alteration there are no known unaltered or slightly altered cm chondrites e g rocks containing numerous chondrules with primary igneous glass some cm properties result from processes associated with early and intermediate stages of the alteration sequence i e hydration of matrix alteration of chondrule glass and production of large pcp clumps other petrologic properties reflect processes active throughout the alteration sequence these include oxidation of metallic fe ni alteration of chondrule phenocrysts changes in pcp composition reflecting an increase in the phyllosilicate sulfide ratio and changes in carbonate mineralogy reflecting the development of dolomite and complex carbonates at the expense of ca carbonate on the basis of these parameters we propose a numerical alteration sequence for cm chondrites because there are no known cm samples that display only incipient alteration the least altered sample was arbitrarily assigned to subtype 2 6 the most altered cm chondrites currently classified cm1 are assigned to subtype 2 0 these highly altered rocks have essentially no mafic silicates they contain chondrule pseudomorphs composed mainly of phyllosilicate however their bulk compositions are cm like and they are closer in texture to other c2 chondrites than to ci1 chondrites which lack chondrule pseudomorphs using several diagnostic criteria we assigned petrologic subtypes 0 1 to every cm chondrite in our study que 97990 cm2 6 murchison cm2 5 kivesvaara cm2 5 murray cm2 4 2 5 y 791198 cm2 4 que 99355 cm2 3 nogoya cm2 2 cold bokkeveld cm2 2 que 93005 cm2 1 lap 02277 cm2 0 met 01070 cm2 0 the proposed cm numerical alteration sequence improves upon the existing scheme of browning et al 1996 in that it does not require a complicated algorithm applied to electron microprobe data to determine the average matrix phyllosilicate composition the new sequence is more comprehensive and employs petrologic subtypes that are easier to use and remember than mineralogic alteration index values new neutron activation analyses of que 97990 que 93005 met 01070 murchison and crescent together with literature data confirm the compositional uniformity of the cm group different degrees of alteration among cm chondrites do not lead to resolvable bulk compositional differences this suggests that the textural differences among individual cm chondrites reflect progressive alteration of similar hypothetical cm3 0 starting materials in different regions of the same parent body with minimal aqueous transport of materials over appreciable e g meters distances

sediment resuspension in the wakes of hurricanes edouard and hortense a unique set of physical and optical observations of sediment resuspension was obtained during the passage of two hurricanes edouard and hortense the eyes of these hurricanes passed within approximately 110 and 350 km respectively of our study site on the continental shelf 100 km south of cape cod massachusetts within a two week period in the fall of 1996 sediments were resuspended to more than 30 m above the ocean bottom during both hurricanes the sediment resuspension processes associated with the two hurricanes are shown to differ primarily because of the separation distances between the eyes of the hurricanes and the observational site e g local versus remote forcing observed particle size distributions were shifted toward smaller scales during hurricane edouard because of flocculate disaggregation caused by high levels of localized shear and turbulence

cs rb ba systematics in phengite and amphibole an assessment of fluid mobility at 2 0 gpa in eclogites from trescolmen central alps eclogites from trescolmen that contain abundant hydrous minerals phengite amphibole paragonite zoisite talc apatite show petrographic evidence for fluid infiltration under conditions of 2 0 to 1 8 gpa 650 c large ion lithophile elements lile e g cs rb ba and sr were analysed by in situ techniques in all eclogite mineral phases in order to characterize the behaviour of fluid mobile elements at high pressure in situ analysis of carefully chosen metamorphic assemblages circumvents the problem of partial late stage alteration which can severely influence the calculated element budgets of whole rock samples phengite is the dominant host for cs rb and ba in both eclogite and adjacent garnet mica schist samples and incorporates 90 of the budgets of these elements in whole rocks lile contents of phengites in phengite rich rocks are likely to record the cs rb and ba rb ratios of their host rock protoliths the lile patterns of eclogite are consistent with protoliths derived from basalt that underwent seafloor alteration whereas those of mica schist are almost identical to average upper continental crust in contrast lile patterns of eclogite samples that lack phengite but do contain amphibole are unlike any plausible protolith but are identical to those of amphibole in phengite bearing samples this observation points to homogenization of the lile in different lithologies which we correlate with petrographic evidence for fluid infiltration because phengite in garnet mica schist has a strong capacity to buffer the fluid with respect to cs rb and ba homogenization of amphiboles is best explained by fluid infiltration from the surrounding metapelites into eclogite bodies implying at least metre scale fluid mobility the amphibole homogenization can be most easily modelled by a pervasive open system fluid flux through the eclogites possibly facilitated by ductile deformation during the early stages of uplift simple calculations give minimum fluid rock ratios of 0 001 to 0 004 demonstration of the mobility of very small volumes of fluid through eclogite is an important prerequisite of many subduction zone models that try to explain across arc variations in trace element geochemistry the low fluid rock ratios from this study are not in contrast with oxygen isotope heterogeneities reported from other eclogite localities fluid mobile elements such as cs rb and ba are more sensitive indicators of small volume fluid rock interaction and are therefore potentially valuable for understanding fluid infiltration processes in systems where oxygen isotope shifts are not large enough to be detectable

internal waves vs surface storm waves a review on the origin of hummocky cross stratification hummocky cross stratification hcs is considered a diagnos tic structure of surface storm activity at the shoreface offshore transition however the origin of hcs is still debated laboratory experiments have not yet reproduced it and direct observations on the continental shelves do not exist most hydrodynamic interpretations invoke pure oscilla tory flows unidirectional dominated combined flows and oscillatory dominated flows but they all share the assump tion of hcs to reflect the combined action of surface storm waves and related currents within this context of uncertain ties internal waves gravity waves propagating along the pycnocline provide an alternative mechanism to explain the origin of hcs internal waves breaking on the shelf create episodic high turbulence events and induce upslope and downslope currents as well as oscillatory flows at the depth where the pycnocline intersects the sea floor in this scenario both the oscillatory and the unidirectional components needed for hcs to form are not necessarily linked to surface storm waves but can occur at various depth as far and near there is a pycnocline where internal waves can form

sediment suspension with rippled bed experiments on the suspension of sediment were performed in flume with and without sediment layer on the bottom for movable bed runs three dimensional sand ripples were found to affect seriously the features of suspended sediment the horseshoe vortices and the resulting bursts in the lee of the ripples entrain intermittently a large amount of sediment into the outer layer of flow details of the suspension process were studied using a sand ripple model made of plaster the result revealed that the vertical component of turbulent eddies is responsible for the suspension of sediment and the statistical distribution of the component was found to be the gaussian law the statistical distribution of the concentration fluctuation was observed to be highly skewed and the reason was determined to be the fact that the concentration increases with the power of eight against the vertical fluid velocity the period of the intermittent ejection of sediment agreed reasonably with those reported for natural geophysical flows thus the suspension of sediment in flows with rippled beds was proved to be significantly correlated with bursting phenomenon behind sand ripples

internal solitons on the pycnocline generation propagation and shoaling and breaking over a slope in part 1 a study is made of the internal solitary wave on the pycnocline of a continuously stratified fluid a korteweg de vries kdv equation for the interfacial displacement is developed following benney s method for long nonlinear waves experiments were conducted in a long wave tank with the pycnocline at several different depths below the free surface while keeping the total depth approximately constant a step like pool of light water trapped behind a sliding gate served as the initial disturbance condition the number of solitons generated was verified to satisfy the prediction of inverse scattering theory the fully developed soliton was found to satisfy the kdv theory for all ratios of upper layer thickness to total depth in part 2 of this study we investigate experimentally the evolution and breaking of an internal solitary wave as it shoals on a sloping bottom connecting the deeper region where the waves were generated to a shallower shelf region it is found through quantitative measurements that the onset of wave breaking was governed by shear instability which was initiated when the local gradient richardson number became less than the internal solitary wave of depression was found to steepen at the back of the wave before breaking in contrast with waves of elevation two slopes were used with ratios 1 16 and 1 9 and the fluid was a boussinesq fluid with weak stratification using brine solutions

mean flow and turbulence structure over fixed two dimensional dunes implications for sediment transport and bedform stability detailed measurements of flow velocity and its turbulent fluctuation were obtained over fixed two dimensional dunes in a laboratory channel laser doppler anemometry was used to measure the downstream and vertical components of velocity at more than 1800 points over one dune wavelength the density of the sampling grid allowed construction of a unique set of contour maps for all mean flow and turbulence parameters which are assessed using higher moment measures and quadrant analysis these flow field maps illustrate that 1 the time averaged downstream and vertical velocities agree well with previous studies of quasi equilibrium flow over fixed and mobile bedforms and show a remarkable symmetry from crest to crest 2 the maximum root mean square rms of the downstream velocity values occur at and just downstream of flow reattachment and within the flow separation cell 3 the maximum vertical rms values occur within and above the zone of flow separation along the shear layer and this zone advects and diffuses downstream extending almost to the next crest 4 positive downstream skewness values occur within the separation cell whereas positive vertical skewness values are restricted to the shear layer 5 the highest reynolds stresses are located within the zone of flow separation and along the shear layer 6 high magnitude high frequency quadrant 2 events ejections are concentrated along the shear layer kelvin helmholtz instabilities and dominate the contribution to the local reynolds stress and 7 high magnitude high frequency quadrant 4 events occur bounding the separation zone near reattachment and close to the dune crest and are significant contributors to the local reynolds stress at each location these data demonstrate that the turbulence structure associated with dunes is controlled intrinsically by the formation magnitude and downstream extent of the flow separation zone and resultant shear layer furthermore the origin of dune related macroturbulence lies in the dynamics of the shear layer rather than classical turbulent boundary layer bursting the fluid dynamic distinction between dunes and ripples is reasoned to be linked to the velocity differential across the shear layer and hence the magnitude of the kelvin helmholtz instabilities which are both greater for dunes than ripples these instabilities control the local flow and turbulence structure and dictate the modes of sediment entrainment and their transport rates

carbonate ramp evolution during the late oligocene chattian salento peninsula southern italy abstract oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs detailed studies on the facies organization platform type and internal architecture are scarce within this context the chattian carbonate units cropping out in salento southern italy allow detailed study of the distribution of skeletal components and facies architecture the lower chattian castro limestone previously considered as a fringing reef is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo escarpment in the substrate epiphytic biota and sediment dweller organisms thriving in seagrass meadows dominated production in the shallow water euphotic zone seawards large rotalid foraminifers dominated a detritic mesophotic zone near the edge of the escarpment also in the mesophotic zone luxurious growth of corals built discrete mounds with no evidences of wave resistant growth fabrics basinward 25 to 30 dipping clinobeds abut against the escarpment where coral rudstone floatstone textures resulted from downfall of corals and sediments the upper chattian porto badisco calcarenite represents a homoclinal ramp dominated by packstone textures in the euphotic inner ramp autochthonous biota suggests the occurrence of extensive seagrass meadows basinward large rotalid packstone and small coral mounds developed in mesophotic conditions and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone comminuted skeletal debris depleted of light dependent organisms typifies deposition in the dysphotic aphotic zone in both examples the middle ramp meso oligophotic zones was the most prolific in terms of carbonate production whereas shallow water seagrass related production euphotic was much less important corals built mounds also in the mesophotic zone but never reached sea level hydrodynamic conditions in the meso oligophotic zone are better explained by breaking of internal waves and their induced up and down slope currents instead of the surface storm waves

observations of second baroclinic mode internal solitary waves on the continental slope of the northern south china sea 1 a temperature and current velocity mooring located on the upper continental slope of the northern south china sea recorded a number of second baroclinic mode mode 2 internal solitary waves isws these types of waves are seldom observed in nature the mode 2 isws typically showed upward downward displacement of isotherms in the upper lower water column and three layers of eastward westward and eastward current from the uppermost to bottommost portions of a wave in summer westward propagating mode 2 isws were observed only occasionally these waves generally appeared after mode 1 isws a feature that may relate to the diurnal tide with a period of approximately 24 hours the displacement of isotherms induced by mode 2 isws was 20 14 m at 75 m and 22 15 m at 240 m and the characteristic time scale was approximately 8 0 4 3 min in winter mode 2 isws were more active but mode 1 isws were rarely observed isotherm displacement by mode 2 isws in winter was 30 18 m at 75 m and 26 16 m at 240 m and the average characteristic time scale was 6 9 4 6 min the mode 2 isws thus had larger amplitudes and smaller time scales in winter than they did in summer the observed vertical temperature profile also showed notable seasonal change the thermocline was shallow in summer and deep in winter in winter vertical temperature profiles indicated that the main thermocline was located near middepth over the upper continental slope near the 350 m isobath mode 1 isws were more active in summer than in winter reflecting the larger ursell numbers for mode 1 isws in summer among mode 2 isws in summer 90 appeared after mode 1 isws these results suggest that mode 2 isws could be related to mode 1 isws in contrast mode 2 isws were more active in winter than in summer with larger mode 2 ursell numbers also found in winter among winter mode 2 isws 72 appeared without mode 1 isws mode 2 isws in winter could be related to the main thermocline being located near middepth these seasonal variations of mode 2 isws were correlated with the seasonal change of local stratification further study on the different generating mechanisms of mode 2 isws in summer and winter is needed

high temperature strontium stable isotope behaviour in the early solar system and planetary bodies abstract this study presents comprehensive strontium stable isotope 88sr 86sr data measured by multiple collector inductively coupled plasma mass spectrometry mc icp ms for a suite of carbonaceous chondrites differentiated meteorites lunar martian and terrestrial samples carbonaceous chondrites comprise a mixture of refractory inclusions and chondrules that have light 88sr values between 0 35 to 0 05 and matrix material that possesses a heavy 88sr composition of 0 65 confirming the results of earlier studies consequently bulk carbonaceous chondrites are relatively heterogeneous in composition ranging from 0 12 to 0 35 most likely reflecting clast matrix variability the light 88sr compositions of the refractory inclusions are consistent with mass dependent fractionation of other refractory elements ca and eu and are most likely produced by non equilibrium fractionation undercooling in the nebula gas during condensation of hibonite from the solar nebula simon and depaolo 2010 stable calcium isotopic composition of meteorites and rocky planets earth planet sci lett 289 457 466 carbonaceous chondrites angrites and martian meteorites have indistinguishable compositions at the level of analytical uncertainty of this study however statistical analysis indicates that melts derived from the earth s mantle have heavier 88sr values than bulk carbonaceous chondrites and martian meteorites but compositions indistinguishable from eucrites 88sr 0 26 0 12 moreover terrestrial basalts and andesites have restricted 88sr values 0 30 0 07 suggesting that mantle melting delivers rather homogenous melts to the earth s surface with respect to 88sr in contrast glasses from evolved terrestrial rocks and lunar basalts extend to very light 88sr values 0 20 the sr stable isotope composition covaries with europium anomaly eu eu as an index of plagioclase fractionation and 88sr can be successfully modelled by the heavy isotopes of sr being preferentially partitioned into plagioclase with a fractionation factor of 1 0007 for 88sr 86sr our results demonstrate that sr stable isotopes may be significantly fractionated at high temperatures and their measurement can provide insights into planetary evolution and magmatic processes

sediment resuspension and mixing by resonantly generated internal solitary waves the observation of internal solitary waves isws propagating upstream along a strongly stratified bottom layer on the california shelf is reported an increased concentration of particulates in the water column accompanies the passage of these isw packets the estimated local richardson number in the bottom vicinity is around 1 4 and a vertical coefficient of eddy diffusivity of order 1022 m2 s21 is associated with the upstream propagating leading isw the leading isw gave rise to reversed flow in an 8 m layer above the bottom it is argued that the upstream propagating isws were generated by resonant flow over bottom topography internal waves generated in this way seem to be frequent in the record of a month long experiment model results suggest that the isws can carry up to 73 of such generated long wave energy the ocean conditions at the site are similar to those of other coastal sites which suggests that the phenomenon described here may be common

alteration processes in the cv chondrite parent body based on analysis of nwa 2086 meteorite analysis of the nwa 2086 cv3 chondrite showed a matrix chondrule ratio of 52 similar to bali mokoia and grosanaja nearly twice as many chondrule fragments as intact ones demonstrate that an early fragmentation phase occurred prior to final accretion after this event no substantial mechanical change or redeposition is evident rims with double layered structures were identified around some chondrules which in at least one case is attributed to an accretionary origin the rim s outer parts with a diffuse appearance were formed by in situ chemical alteration during this later process mg content decreased fe content increased and olivine composition was homogenized producing a rim composition close to that of the matrix this alteration occasionally happened along fractures and at confined locations and was probably produced by fluid interactions iron oxides are the best candidate for a small grain sized alteration product however technical limitations in the available equipment did not allow exact phase identification these results suggest that nwa 2086 came from a location possible more deeply buried in the cv parent body than mokoia or bali and suffered less impact effects although there is no evidence of sustained thermal alteration this meteorite may represent a sample of the cv parent asteroid interior and provide a useful basis for comparison with other cv meteorites in the future

the degeneration of large scale interfacial gravity waves in lakes mechanisms for the degeneration of large scale interfacial gravity waves are identified for lakes in which the effects of the earth s rotation can be neglected by assuming a simple two layer model and comparing the timescales over which each of these degeneration mechanisms act regimes are defined in which particular processes are expected to dominate the boundaries of these regimes are expressed in terms of two lengthscale ratios the ratio of the amplitude of the initial wave to the depth of the thermocline and the ratio of the depth of the thermocline to the overall depth of the lake comparison of the predictions of this timescale analysis with the results from both laboratory experiments and field observations confirms its applicability the results suggest that for small to medium sized lakes subject to a relatively uniform windstress an important mechanism for the degeneration of large scale internal waves is the generation of solitons by nonlinear steepening since solitons are likely to break at the sloping boundaries leading to localized turbulent mixing and enhanced dissipation the transfer of energy from an initial basin scale seiche to shorter solitons has important implications for the lake ecology

shoaling internal solitary waves 1 the evolution and breaking of internal solitary waves in a shallow upper layer as they approach a constant bottom slope is examined through laboratory experiments the waves are launched in a two layer fluid through the standard lock release method in most experiments the wave amplitude is significantly larger than the depth of the shallow upper layer so that they are not well described by korteweg de vries theory the dynamics of the shoaling waves are characterized by the iribarren number ir which measures the ratio of the topographic slope to the square root of the characteristic wave slope this is used to classify breaking regimes as collapsing plunging surging and nonbreaking for increasing values of ir for breaking waves the maximum interface descent hi is predicted to depend upon the topographic slope s and the incident wave s amplitude and width asw and lsw respectively as hi 4saswlsw this prediction is corroborated by our experiments likewise we apply simple heuristics to estimate the speed of interface descent and we characterize the speed and range of the consequent upslope flow of the lower layer after breaking has occurred

determination of molybdenum isotope fractionation by double spike multicollector inductively coupled plasma mass spectrometry 1 molybdenum isotopic compositions are precisely determined by mc icp ms measurements using a mo double spike the double spike is added prior to chemical purification so that laboratory and instrumental mass fractionations are separated from natural mass dependent fractionation fractionation is determined on four mo mass ratios providing an internal consistency check the external standard reproducibility is at 0 06 per mil on the 98mo 95mo ratio 2 standard deviation using a normal microconcentric nebuliser with a cyclonic spray chamber the minimum quantity of mo is 1 g for high precision results a hydrothermal molybdenite shows fractionation of 0 3 per mil on the 98mo 95mo ratio relative to our standard johnson matthey 1000 g ml 0 3 icp standard solution lot 602332b fine grained sediments show fractionation of 0 1 and 0 3 per mil on the 98mo 95mo ratio the observed mo isotope fractionation is small but resolvable with the presented high resolution technique

flow separation and resuspension beneath shoaling nonlinear internal waves 1 laboratory observations are presented showing the structure and dynamics of the turbulent bottom boundary layer beneath nonlinear internal waves nliws of depression shoaling upon sloping topography the adverse pressure gradient beneath the shoaling waves causes the rear face to steepen flow separation to occur and wave induced near bottom vortices to suspend bed material the resuspension is directly attributed to the near bed viscous stress and to near bed patches of elevated positive reynolds stress generated by the vortical structures these results are consistent with published field observations of resuspension events beneath shoaling nliws elevated near bed viscous stresses are found throughout the domain at locations that are not correlated to the resuspension events near bed viscous stress is thus required for incipient sediment motion but is not necessarily a precursor for resuspension resuspension is dependent on the vertical velocity field associated with positive reynolds stress and is also found to occur where the mean wave averaged vertical velocity is directed away from the bed the results are interpreted by analogy to the eddy stress and turbulent bursting resuspension models developed for turbulent channel flows

the double spike toolbox the double spike technique is a well established method for correcting for instrumental mass fractionation in mass spectrometry the precision of the technique is controlled by the choices of double spike composition and the proportions in which the double spike and sample are mixed to make these choices easier we provide software the double spike toolbox for calculating optimal double spikes which are chosen purely on the basis of minimising error propagation in addition we provide cocktail lists of optimal double spikes for all 33 elements that have 4 or more naturally occurring isotopes using some sensible default parameters as examples we discuss the application of the software to fe pb and ca isotopes

role of internal waves in the generation of nepheloid layers on the northwestern alboran slope implications for continental margin shaping 1 the role of internal waves in the sediment dynamics of the northwestern alboran continental slope was investigated in a selected area around the guadiaro submarine canyon nepheloid layer distribution was identified using closely spaced ctd transmissometer profiles collected during two hydrographic surveys a well defined pattern of suspended sediment distribution consisting of surface intermediate and near bottom nepheloid layers was found intermediate and bottom nepheloid layers were always observed within the canyon and on the adjacent continental slope spanning mainly from 200 to 500 m depth in addition a current meter with a turbidimeter was deployed in the lower section of the guadiaro canyon at 600 m depth 25 meters above the seafloor time series analysis indicated that the currents temperature and turbidity within the canyon fluctuate mainly at semidiurnal tidal frequencies suggesting the presence of semidiurnal internal tides affecting the near bottom suspended sediment concentration along the canyon axis high resolution bathymetry from the study area was used to evaluate the internal wave reflection conditions at semidiurnal tidal frequency for the entire continental slope region critical slope conditions were reached on the upper continental slope and along the canyon axis coinciding with the region in which nepheloid layers were observed this region also coincides with a zone of erosion on the upper continental slope of the study area previously identified by hernandez molina 1993 these results indicate that the generation of intermediate and bottom nepheloid layers as well as the erosion and shaping of the northwestern alboran continental slope may result from the interaction of internal waves and the seafloor morphology

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

correlated alteration effects in cm carbonaceous chondrites three parameters are proposed to determine the relative extent of alteration in cm chondrites the mineralogic alteration index monitors the relative progress of coupled substitutions in the progressive alteration of cronstedtite to mg serpentine and increases with increasing alteration to calculate values of this index an algorithm has been developed to estimate the average matrix phyllosilicate composition in individual cm chondrites the second parameter is the volume percent of isolated matrix silicates which decreases with progressive alteration due to mineral hydration finally the volume percent of chondrule alteration monitors the extent of chondrule phyllosilicate production and increases as alteration proceeds these parameters define the first cm alteration scale that relies on multiple indicators of progressive alteration the following relative order of increasing alteration is established by this model murchison bells pollen murray mighei nogoya cold bokkeveld the relative degree of aqueous processing cochabamba and boriskino experienced is less precisely constrained although both fall near the middle of this sequence a comparison between the mineralogic alteration index and literature values for the whole rock chemistry of cm chondrites reveals several correlations a positive nearly linear correlation between bulk h content and progressive cm alteration suggests an approximately constant production rate of new phyllosilicates relative to the mineralogical transition from cronstedtite to mg serpentine the abundance of trapped planetary 36ar decreases systematically in progressively altered cm chondrites suggesting the wholesale destruction of primary noble gas carrier phase s by aqueous reactions because low temperature fluid rock reactions are generally associated with large isotopic mass fractionation factors we also compared our model predictions with 18o values for bulk cm samples although some of these data are poorly resolved the order of increasing 18o values approximates the order of increasing alteration predicted by our model parameters multiple correlations between diverse alteration parameters strongly suggest that a different cm chondrites experienced similar kinds of processes and conditions and b cm materials experienced in situ alteration on the cm parent body or bodies

frequency spectra and intermittency of the turbulent suspension process in a sand bed river previous research suggests that the turbulence driven suspension process in sand bed channels is dominated by intermittent energetic eddies with length scales of the order of channel depth because of the scarcity of data on the turbulent suspension process in alluvial channels the possible variability in suspension intermittency and turbulent frequency content due to contrasts in flow depth velocity or bedforms remains unclear however the present study analyses eddy correlation suspension signals from seven deployments in varied flow conditions around a sandy meander bend deployment depths at near bankfull flow stages varied from 2 to 5 5 m velocities at 0 75 1 m height from 0 6 to 0 9 m s 1 and local mean suspended sand concentrations ranged from 30 to 150 mg l 1 in the intermittence and spectral content of sand suspension between the various deployments are analysed and results are compared with previously published findings study data suggest that the dominant eddy sizes involved in sediment mixing across the sensor level are consistently of the order of 1 5 times flow depth and lie within the energy bearing turbulent range when sand suspension is analysed in the time domain in the various deployments energetic burst like suspension events occupying only 1 5 of the record duration account for 20 90 of the suspension work the degree of intermittence in the suspension process was observed to increase in deeper flows where mixing events contributing extreme vertical sediment fluxes appear to be relatively more frequent

europium isotopic variations in allende cais and the nature of mass dependent fractionation in the solar nebula we measured the 153eu 151eu ratio by mc icp ms for a terrestrial basalt two terrestrial soils and four meteorites whole rocks and or chondrules of bjurbo le forest city murchison and allende and found no isotopic variations by contrast two cai separates from two different pieces of allende show a 153eu deficit of up to one per mil such a shortage in the heavy isotopes which had also been identified in allende cais for sr patchett p j 1980b sr isotopic fractionation in allende chondrules a reflection of solar nebular processes earth planet sci lett 50 181 188 cannot reflect evaporative fractionation the lack of sm isotope fractionation in the same samples further makes fractionation by purely kinetic processes an unlikely cause of the anomalous eu isotopic composition an alternative interpretation is condensation from a vapor already significantly depleted in eu but in such a scenario the fate of the missing material is unclear we therefore prefer yet another interpretation based on the low ionization potential of eu and sr in which electromagnetic separation of the ionized gas preferentially depletes the nebular gas in heavy isotopes

internal solitary waves control offshore extension of mud depocenters on the nw iberian shelf abstract hydrodynamic conditions and near bottom sediment transport on the nw iberian shelf associated with a 5 day storm in september 2014 were monitored during the post storm relaxation period active bottom sediment transport by internal solitary waves isws on a mid shelf mud depocenter located in between 110 and 130 m water depth wd was observed to explore the potential of internal waves in sediment transport and its link to development of mid shelf mud depocenters we apply a weakly nonlinear model based on the variable coefficient gardner equation to estimate the flow fields and bottom shear stress induced by shoaling of mode 1 long internal solitary waves shoreward propagation of the isws in three representative periods pre intra and post storm is simulated respectively transformation of the internal wave from a single sech2 shape characterized by negative polarity and small amplitude to a dispersive trailing wave packet with varying amplitude and inverse polarity are satisfactorily reproduced model results indicate enhancement of the maximum orbital velocity of the isws during and after the storm on the outer shelf 130 220 m wd including the seaward margin of the mud depocenter bottom shear stress consequently becomes strong enough 0 1 pa to winnow unconsolidated sediment and constrains the offshore extension of the depocenter the enhanced bottom orbital velocity and the asymmetry in the excursion direction of mode 1 long isws in the post storm period prove to be efficient in transporting fine grained sediment across shelf our results suggest that mid shelf mud depocenters are not necessarily areas under permanently calm conditions where fine grained sediment can settle straightforwardly they could also result from convergent sediment transport from both onshore and offshore directions and sediment may go through numerous cycles of resuspension transport deposition before its ultimate lasting burial

facies heterogeneity at interwell scale in a carbonate ramp upper jurassic ne spain abstract the well exposed upper kimmeridgian carbonate ramp near arroyo cerezo iberian basin eastern spain provides an excellent analog to stratigraphically equivalent subsurface reservoirs such as the carbonate ramps of the arab d of the middle east and the smackover of the gulf of mexico critical questions regarding interwell scale heterogeneity and correlation motifs for low angle ramp systems can be addressed using continuous exposures that encompass a full range of inner to outer ramp facies outcrops in this area provide a complete exposure of the ramp succession in depositional dip direction at arroyo cerezo a 40 m thick and 1 3 km long dip oriented continuous outcrop has been studied lithofacies and bounding surfaces have been mapped on a continuous photomosaic to build a detailed 2d cross section complemented by five stratigraphic sections 300 m apart and petrographic analysis the reconstructed section shows the facies transition from relative proximal to distal carbonate ramp settings carbonate facies associations are grouped according to the dominant carbonate types buildup dominated systems and coated grain dominated systems detailed mapping of facies and bounding surfaces documents distinct ramp depositional units with downdip facies changes occurring within the 1 3 km length of the outcrop the arroyo cerezo outcrop indicates that the ramp facies continuity when based on a 5 10 km distance well log correlation is mostly apparent use of detailed spatial and temporal analysis of high quality outcrop analogs promotes more realistic models for understanding the interwell meter scale heterogeneity and the scale of these depositional heterogeneities although being below resolution of subsurface tools governs in fact along with diagenetic modifications the fluid flows within a reservoir the scale of these stratigraphic heterogeneities needs to be considered in order to optimize and enhance hydrocarbon production and last recovery

chemical alteration and ree mobilization in meteorites from hot and cold deserts the effects of terrestrial weathering on ree mobilization are evaluated for a variety of uncommon meteorites found in antarctica and in hot deserts the meteorites analyzed include 7 non cumulate eucrites 10 shergottites 3 nakhlites 2 lunar meteorites 4 angrites 10 acapulcoites 1 winonaite and 1 brachinite in situ concentration measurements of lanthanides and selected other minor and trace elements were made on individual grains by secondary ion mass spectrometry sims in antarctic meteorites oxidation converts ce 3 to ce 4 which is less soluble than the trivalent ree resulting in ce anomalies the mineral most affected is low ca pyroxene however not all grains of a given mineral are and distinct analyses of a single grain can even yield ree patterns with and without ce anomalies the effect is most pronounced for antarctic eucrites in which ce anomalies are observed not only in individual minerals but also in whole rock samples although ce anomalies are observed in meteorites from hot deserts as well the most characteristic signs of chemical alteration in this environment are a lree enrichment with a typical crustal signature as well as sr ba and u contaminations these can modify the whole rock ree patterns and disturb the isotope systematics used to date these objects the lree contamination is highly heterogeneous affecting some grains and not others of a given mineral mainly olivine and low ca pyroxene the two minerals with the lowest ree concentrations the major conduit for ree movement is through shock induced cracks and defects and the highest levels of contamination are found in altered material filling such veins and cracks meteorites that experienced low shock levels and those that are highly recrystallized are the least altered copyright 2003 elsevier ltd

high frequency internal waves in large stratified lakes observations are presented from lake biwa and lake kinneret showing the ubiquitous and often periodic nature of high frequency internal waves in large stratified lakes in both lakes high frequency wave events were observed within two distinct categories 1 vertical mode 1 solitary waves near a steepened kelvin wave front and vertical mode 2 solitary waves at the head of an intrusive thermocline jet were found to have wavelengths 64 670 m and 13 65 m respectively and were observed to excite a spectral energy peak near 10 23 hz 2 sinusoidal vertical mode 1 waves on the crests of kelvin waves vertically coherent in both phase and frequency and bordering the thermocline jets in the high shear region trailing the vertical mode 2 solitary waves vertically incoherent in both phase and frequency were found to have wavelengths between 28 37 and 9 35 m respectively and excited a spectral energy peak just below the local maximum buoyancy frequency near 10 22 hz the waves in wave event categories 1 and 2 were reasonably described by nonlinear wave and linear stability models respectively analysis of the energetics of these waves suggests that the waves associated with shear instability will dissipate their energy rapidly within the lake interior and are thus responsible for patchy turbulent events that have been observed within the metalimnion conversely the finite amplitude solitary waves which each contain as much as 1 of the basinscale kelvin wave energy will propagate to the lake perimeter where they can shoal thus contributing to the maintenance of the benthic boundary layer

the age of the inner core abstract the energy conservation law when applied to the earth s core and integrated between the onset of the crystallization of the inner core and the present time gives an equation for the age of the inner core in this equation all the terms can be expressed theoretically and given values and uncertainties of all relevant physical parameters the age of the inner core can be obtained as a function of the heat flux at the core mantle boundary and the concentrations in radioactive elements it is found that in absence of radioactive elements in the core the age of the inner core cannot exceed 2 5 ga and is most likely around 1 ga in addition to have an inner core as old as the earth concentrations in radioactive elements needed in the core are too high to be acceptable on geochemical grounds

observations of highly nonlinear internal solitons over the continental shelf surface disturbances caused by strong near surface internal waves are widely seen in coastal regions as bands of slick and rough water propagating shoreward these surface slicks are typically manifestations of optical and radar backscatter properties above internal solitons and have strong surface current pulses associated with them during a recent experiment studying coastal internal waves extremely strong solitary internal wave packets were observed over a three week period on a very shallow and strongly stratified pycnocline off northern oregon during periods of strongest tidal forcing solitons were consistently observed on the leading edge of a semidiurnal internal tide bore with pycnocline displacements up to 25m downward from a 7m initial depth in the first few solitons the extreme nonlinearity of these internal waves is believed to be unique in ocean observations this note characterizes these highly nonlinear solitary internal waves siw and presents a second order kdv model which reproduces the form of the displacements and the small change in soliton width with amplitude predicted by this model

numerical investigation of solitary internal wave induced global instability in shallow water benthic boundary layers abstract the time dependent boundary layer induced by a weakly nonlinear solitary internal wave in shallow water is examined through direct numerical simulation waves of depression and elevation are both considered the mean density field corresponds to that typical of the coastal ocean and lakes where the lower fraction of the water column is subject to the stabilizing effect of a diffuse stratification sufficient resolution of the inviscid dynamics of the boundary layer is ensured through use of a legendre spectral multidomain discretization scheme in the vertical direction at higher reynolds numbers where the simulations become underresolved because of restrictions in available computational resources spectral accuracy and numerical stability at the scales of physical interest are preserved through use of a penalty scheme in the vertical and explicit spectral filtering thus a highly accurate description of the qualitative dynamics of the wave induced global instability is possible and finesca

breaking of internal kelvin waves shoaling on a slope in stratified flow breaking of internal waves over slopes induces resuspension of bottom sediments and transport of mass when internal waves shoal and break flow dynamics and mass transport diff

iron isotope fractionation in the earth s lower mantle the two main iron bearing silicate phases in the mantle ferroperovskite and ferropericlase are expected to partition iron isotopes differently theoretical calculations suggest that the spin state of iron strongly influences the iron isotopic composition of ferropericlase whereas the iron isotopic composition of ferroperovskite is almost independent of spin state

internal wave detection using the moderate resolution imaging spectroradiometer modis 1 the moderate resolution imaging spectroradiometer modis with its combined attributes of fine spatial resolution large swath area and near daily global coverage has for the first time allowed sunglint the near specular reflectance pattern of sunlight off the ocean surface to be used to analyze and survey high frequency nonlinear internal solitary wave occurrences on a near global scale the sunglint area within the modis swath is large enough to cover an entire basin and it s spatial resolution is fine enough to identify internal wave signatures whose wavelength is greater than a few hundred meters this paper describes the use of modis for high frequency nonlinear internal wave detection presents the results of a survey that detected 3581 internal wave occurrences in modis imagery over the period between august 2002 through may 2004 and discusses ways modis imagery can be used to improve the study of internal waves

near bed solibores over the continental slope in the faeroe shetland channel abstract on two occasions within a 12 day measurement period in the faeroe shetland channel strongly nonlinear wave trains were observed at the sea bed propagating up the continental slope in water depths 450 m the events were separated by a period of 4 days and whilst resembling in appearance a density current running up a slope are termed solibores displaying the properties of both turbulent internal bores and nonlinear internal solitary waves isw each solibore displays a steep leading edge followed by a train of nonlinear waves with amplitudes of o 10 m and periods of 5 20 min wave induced particle velocities are consistent with isw whilst a zone of strong horizontal convergence at the leading edge of the solibores causes the formation of a rotor with flow in the opposite sense to a forward overturning surface wave in both cases upward vertical velocities 10 cm s 1 are immediately followed by a return downward flow of equal magnitude a ctd and microstructure transect conducted during the passage of the first solibore illustrates its behaviour as an up slope intrusion of cold dense water with concurrent rates of turbulent dissipation e of o 10 7 w kg 1 and resulting in short term maximum vertical diffusivities kz of o 10 1 m2 s 1 in the long term however kz 140 days which again indicate intermittency in periods of enhanced sediment flux the solibores are consistent with the results of numerical and laboratory experiments on hydraulic jumps resulting from shoaling isw the influence of the slope is proposed to be the reason for their slightly different forms and effects on sediment transport thus the first solibore propagating directly up the slope is proposed to result from an overturning hydraulic jump caused by kinematic instabilities and which subsequently forms a horizontal density intrusion the second solibore represents a dispersive wave train due its oblique direction of propagation which reduces the effective bottom slope allowing dispersion to balance nonlinear effects and prohibiting overturning

vortex shedding and sediment resuspension associated with the interaction of an internal solitary wave and the bottom boundary layer 1 in this note we present results on the interaction of fully nonlinear internal solitary waves with the oceanic bottom boundary layer we show that for fully nonlinear solitary waves it is the interaction of the wave induced velocity field with the upstream boundary layer vorticity that leads to a vortex shedding instability beneath the wave the vortex shedding provides an efficient mechanism for transporting sediment out of the bottom boundary layer bottom boundary stress profiles suggest that the vortex shedding can lead to the resuspension of sediment in contrast to past studies we find that neither a separation bubble or a wave with a recirculating region are required for vortex shedding to occur

coherence scales of wave induced suspended sand concentration fluctuations multifreqiiency acoustic backscatter measurements made in the nearshore zone are analyzed to determine the correlation structure of the instantaneous suspended sediment concentration field at horizontal separations of 20 cm large amplitude backscatter fluctuations representing suspended sediment concentrations more than a factor of 10 greater than the mean and with vertical coherence scales many times greater than the logarithmic wave boundary layer thickness are shown to be spatially correlated at horizontal separations less than the wave orbital amplitude over successive wave cycles the time lag between the appearance of fluctuations in different acoustic beams is inversely proportional to the fluid velocity showing that the fluctuations in backscatter amplitude contain real information on fluctuations in suspended sediment concentration advected with the fluid it is found that the instantaneous suspended sediment field in shore normal cross section is punctuated by spatially discrete clouds extending well above the logarithmic wave boundary layer the fluctuations appear to be present even in the absence of small scale ripples it is suggested that the sediment clouds may be due to vortex shedding from megaripples other bed forms of intermediate scale or coherent structures in combined wave current flows

burst resuspension of seabed material at the foot of the continental slope in the rockall channel to better understand the relationship between near bottom hydrodynamics and sediment resuspension in the transition zone between the continental slope and the abyssal plain an array of three moorings equipped with near bottom sediment traps and current meters was deployed in a triangular configuration of at the foot of the south east slope of the rockall channel north atlantic in addition a fast sampling adcp was moored in the centre of the triangle microscopic observations combined with grain size analysis revealed that the material intercepted by the traps was mainly composed of loose phytodetritus and aggregates organic carbon and 13corg analyses further indicate that this material is relatively fresh and hence probably only transported over short distances the total mass flux measured by the traps suggests input from either laterally advected or resuspended material during the deployment period the measured flux was variable in time and space with a strong increase at the deepest site at the very foot of the slope the measured flux did not correlate significantly with daily averaged current speed suggesting that processes other than those related to elevated bed shear stress are involved in the resuspension mechanism rapid changes in the hydrodynamics probably related to internal motions are evidenced by abrupt bursts in the current velocity and in the near bottom turbidity their occurrence at slack tidal waters appears to be at the origin of the resuspension observed at the foot of the slope of the rockall channel high resolution current velocity measurements suggest that resuspension is dominated by energetic highly localised and short term resuspension events despite the abyssal depths part of these events resemble in many ways the solibores which have been previously observed to enhance sediment transport at much shallower depths over the continental slope while others rather appear to be associated to gravity waves

ree and hf distribution among mineral phases in the cv ck clan a way to explain present day hf isotopic variations in chondrites chondrites are among the most primitive objects in the solar system and constitute the main building blocks of telluric planets among the radiochronometers currently used for dating geological events sm nd and lu hf are both composed of refractory lithophile element they are thought to behave similarly as the parent elements sm and lu are generally less incompatible than the daughter elements nd and hf during geological processes as such their respective average isotopic compositions for the solar system should be well defined by the average of chondrites called chondritic uniform reservoir chur however while the sm nd isotopic system shows an actual spread of less than 4 in the average chondritic record the lu hf system shows a larger variation range of 28 bouvier a vervoort j d and patchett p j 2008 the lu hf and sm nd isotopic composition of chur constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets earth planet sci lett 273 48 57 to better understand the contrast between sm nd and lu hf systems the ree and hf distribution among mineral phases during metamorphism of karoonda ck and vigarano type cv carbonaceous chondrites has been examined mineral modes were determined from elemental mapping on a set of five ck chondrites from types 3 6 and one cv3 chondrite trace element patterns are obtained for the first time in all the chondrite forming minerals of a given class ck chondrites as well as one cv3 sample this study reveals that ree are distributed among both phosphates and silicates only 30 50 of sm and nd are stored in phosphates at least in chondrites types 3 5 as such they are not mobilized during early stages of metamorphism the remaining fraction of sm and nd is distributed among the same mineral phases these elements are therefore not decoupled during metamorphism of the whole rock total of lu the fraction held in phosphate decreases significantly as the degree of metamorphism increases 30 for types 3 and 4 less than 5 in type 6 in contrast to lu hf is mainly hosted by silicates with little contribution from phosphates throughout the ck metamorphic sequence a significant part of sm and nd are stored in phosphates in types 3 5 and these elements behave similarly during ck chondrite metamorphism that explains the robustness of the sm nd ratios in chondrites through metamorphism and the slight discrepancies observed in the present day isotopic nd values in chondrites on the contrary lu and hf are borne by several different minerals and consequently they are redistributed during metamorphism induced recrystallization the lu hf ratios are therefore significantly disturbed during chondrites metamorphism leading to the high discrepancies observed in present day hf isotopic values in chondrites

sediment resuspension mechanisms and their contributions to high turbidity events in a large lake high resolution field data collected during april to october of 2008 2009 were analyzed to investigate the quantitative contribution of sediment resuspension to high turbidity events in central lake erie resuspension events were distinguished within high turbidity events according to turbidity fluorescence and acoustic backscatter timeseries as well as satellite images we observed 16 high turbidity events causing a total duration of 20 d out of 344 d with elevated nearbed turbidity 10 ntu of these events 64 were correlated with algal biomass with the remaining 18 5 and 4 being attributed to sediment resuspension by surface waves storm generated currents and enhanced nearbed turbulence induced by high frequency internal waves respectively this is the first time that resuspension by enhanced nearbed turbulence from high frequency linear internal wave degeneration has been observed in a large lake resuspension was parameterized as a function of the instantaneous critical bottom velocity bottom shear stress and the shields parameter from the in situ measurements we suggest an extended shields diagram for silty bed material that can be used to predict resuspension in other aquatic systems with similar sediment composition 20 cohesive sediment

the degeneration of internal waves in lakes with sloping topography in a laboratory study we quantified the temporal energy flux associated with the degeneration of basin scale internal waves in closed basins the system is two layer stratified and subjected to a single forcing event creating available potential energy at time zero a downscale energy transfer was observed from the wind forced basin scale motions to the turbulent motions where energy was lost due to high frequency internal wave breaking along sloping topography under moderate forcing conditions steepening of nonlinear basin scale wave components was found to produce a high frequency solitary wave packet that contained as much as 20 of the available potential energy introduced by the initial condition the characteristic lengthscale of a particular solitary wave was less than the characteristic slope length leading to wave breaking along the sloping boundary the ratio of the steepening timescale required for the evolution of the solitary waves to the travel time until the waves shoaled controlled their development and degeneration within the domain the energy loss along the slope the mixing efficiency and the breaker type were modeled using appropriate forms of an internal iribarren number defined as the ratio of the boundary slope to the wave slope amplitude wavelength this parameter allows generalization to the oceanographic context analysis of field data shows the portion of the internal wave spectrum for lakes between motions at the basin and buoyancy scales to be composed of progressive waves both weakly nonlinear waves sinusoidal profile with frequencies near 10 24 hz and strongly nonlinear waves hyperbolic secant squared profile with frequencies near 10 23 hz the results suggest that a periodically forced system may sustain a quasi steady flux of 20 of the potential energy introduced by the surface wind stress to the benthic boundary layer at the depth of the pycnocline

footprints of obliquely incident internal solitary waves and internal tides near the shelf break in the northern south china sea a mooring system and two sites of bottom currents were deployed over the slope and near the shelf break on the propagating paths of internal solitary waves isws west off dongsha atoll in the northern south china sea data indicated that energetic isws obliquely shoaled onto the shelf west off dongsha atoll in an approximately 290 degrees direction causing strong reversing currents some exceeding 80 cm s near the bottom two types of sandwaves and short scour channels are discernible on the seafloor near the shelf break which have reasonable correlations with the obliquely incident isws and internal tides type 1 sandwaves featured by isws at the depths of 130 150 m have flat crests interacting with the isobaths at an angle of nearly 45 degrees which slightly incline and migrate upslope type 2 sandwaves are associated with internal tides which have crests parallel to the isobaths and distinctly incline and migrate downslope short channels are parallel to the depth contours and truncate the strata which could be formed and maintained by along slope currents that are probably produced by the obliquely isws on a large gradient gamma 0 8 degrees the isws can move coarse grains or suspend fine grains but do not change the long term trend of sediment transport on the seabed with larger gradients gamma c 1 which is dominated by internal tides these features are likely widespread near the shelf break in the northern south china sea and other seas but are limited on mild slopes where isws do not break

the neodymium stable isotope composition of the silicate earth and chondrites abstract the non chondritic neodymium nd 142nd 144nd ratio of the silicate earth potentially provides a key constraint on the accretion and early evolution of the earth yet it is debated whether this offset is due to the earth being formed from material enriched in s process nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation collisional erosion or a some combination of these processes neodymium stable isotopes are potentially sensitive to early sulfide segregation into earth s core a process that cannot be resolved using their radiogenic counterparts this study presents the first comprehensive nd stable isotope data for chondritic meteorites and terrestrial rocks stable nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry all three of the major classes of chondritic meteorites carbonaceous enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of 146 144nd 0 025 0 025 2 s d n 39 enstatite chondrites yield the most uniform stable isotope composition 146 144nd 26 ppm with considerably more variability observed within ordinary 146 144nd 72 ppm and carbonaceous meteorites 146 144nd 143 ppm terrestrial weathering nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on 146 144nd in chondrites the small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium aluminium rich inclusions the terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition morb glasses and residual mantle lithologies all of these terrestrial rocks possess a broadly similar nd isotope composition giving an average composition for the bulk silicate earth of 146 144nd 0 022 0 034 n 30 in the samples here magmatic differentiation appears to only have an effect on stable nd in highly evolved magmas with heavier 146 144nd values observed in samples with 70 wt sio2 the average stable nd isotope composition of chondrites and the bulk silicate earth are indistinguishable at the 95 confidence level however mantle samples do possess variable stable nd isotope compositions 146 144nd 75 ppm with an average 146 144 nd value of 0 008 if these heavier values represent the true composition of pristine mantle then it is not possible to completely rule out some role for core formation in accounting for some of the offset between the mantle and chondrites overall these results indicate that the mismatch of 142nd between the earth and chondrites is best explained by a higher proportion of s process nd in the earth rather than partitioning into sulfide or s rich metal in the core

measurements of the viscous tangential stress in the airflow above wind waves 1 the stress and drag at the surface of the ocean are crucial parameters for both short term forecasting and the modeling of long term global climate trends however the partition between viscous turbulent and wave stresses and in particular the effects of airflow separation are not well understood we present direct measurements of the velocity in the airflow above wind generated waves we observe intermittent separation of the viscous sublayer past the crest of the wind waves leading to dramatic along wave variability in the surface viscous tangential stress these results hold for wind speeds that would normally be considered low to moderate these viscous stress measurements in the airflow above the wavy surface and within the separated region are to the best of the authors knowledge the first of this kind

reply to shanmugam g comment on internal waves an underexplored source of turbulence events in the sedimentary record by pomar et al earth science reviews 111 2012 56 81 earth science reviews 2012