the meandering gulf stream as seen by the geosat altimeter surface transport position and velocity variance from 73 to 46 w the surface geostrophic velocity field for the gulf stream region was analyzed for the position structure and surface transport of the gulf stream for 2 5 years of the geosat altimeter exact repeat mission synthetic data using a gaussian velocity profile were generated and fit to the sea surface residual heights to create a synthetic mean sea surface height field and profiles of absolute geostrophic currents most of cross track velocity variance was due to the meandering of the gulf stream rather than to rings or complicated velocity profiles which suggested that the simple model parameters are an efficient description of the gulf stream fluctuations an analysis of the model parameters and the actual geostrophic velocity profiles revealed two different flow regimes for the gulf stream connected by a narrow transition region coincident with the new england seamount chain the upstream region was characterized by relatively straight gulf stream paths long eulerian time scales and eastward propagating meanders the downstream region had more large meanders no consistent propagation direction and shorter eulerian time scales a 25 reduction in surface transport occurred in the transition region with a corresponding reduction in current speed and no change in gulf stream width a significant anomaly in surface transport near 69 w suggested the existence of small scale recirculation gyres there the highest variance empirical orthogonal functions of position and surface transport were significantly correlated with larger surface transports leading more northerly positions by a month

millennial scale changes in sea surface temperature and ocean circulation in the northeast pacific 10 60 kyr bp 1 a new centennial scale mg ca temperature record from the california margin odp site 1017e reveals large millennial scale oscillations between 10 to 60 kyr this record indicates that sea surface temperature on the california margin warmed rapidly on the deglacial by 7 4 0 8 c and was preceded by a pre bolling temperature oscillation of 2 6 1 2 c millennial scale events of the last glacial episode were marked by sea surface temperature oscillations of between 3 and 7 c on the california margin and interstadials were associated with an increase in surface water salinity the data are consistent with evidence for a glacial southward shift in the polar jet stream and concomitant strengthening of the relatively cold fresh california current during stadial events the data also support previous hypotheses suggesting a tight coupling between the north atlantic and northeast pacific response to climate instability of the last glacial episode

mean flow and variability in the kuroshio extension from geosat altimetry data using altimeter data from the geosat exact repeat mission erm we investigated the mean flow and temporal and spatial variations of the kuroshio extension in the region of 140 180 e and 30 40 n mean surface height profiles were estimated along individual tracks by assuming the velocity profile of the kuroshio extension to be gaussian shaped and by successively fitting this synthetic current s height profile to the residual height data using the mean profiles from ascending and descending tracks we derived the mean surface height field by an inverse method and obtained the absolute surface height fields for the first 2 5 years of the geosat erm both the mean and the instantaneous height fields thus derived compared well with the available hydrographic data and the sst patterns from the noaa satellites the mean surface height difference across the kuroshio extension attains its maximum around 146 e between the two quasi stationary meanders and its decrease thereafter is mainly due to large scale recirculations on the southern side of the kuroshio extension the ratio of the eddy kinetic energy over the mean kinetic energy has a nearly constant value of 1 5 2 0 along the kuroshio extension path propagation of mesoscale fluctuations in the height fields is generally westward except for the upstream region of the kuroshio extension effects of deep mean flow and baroclinic shear are found to be important in explaining the observed propagation speeds in the upstream region of 141 e and 154 e annual variations in the surface height difference across the kuroshio extension h have a september maximum with an average amplitude of 0 2m for large scale interannual fluctuations anomalies in h are found to be significantly correlated with those of the current axis positions a larger surface height difference corresponds to a more northerly position of the kuroshio extension the interannual changes in h are possibly related to the 86 87 enso event in the low latitude pacific ocean

most diamonds were created equal abstract diamonds crystallize deep in the mantle 150 km leaving their carbon sources and the mechanism of their crystallization debatable they can form from elemental carbon by oxidation of reduced species e g methane or reduction of oxidized ones e g carbonate bearing minerals or melts in response to decreasing carbon solubility in melts or fluids or due to changes in ph the mechanism of formation is clear for fibrous diamonds that grew from the carbonate bearing fluids trapped in their microinclusions however these diamonds look different and based on their lower level of nitrogen aggregation are much younger than most monocrystalline mc diamonds in the first systematic search for microinclusions in mc diamonds we examined twinned crystals macles assuming that during their growth microinclusions were trapped along the twinning plane visible mineral inclusions 10 m and nitrogen aggregation levels in these clear macles are similar to other mc diamonds we found 32 microinclusions along the twinning planes in eight out of 30 diamonds eight inclusions are orthopyroxene four contain 50 k2o probably as k2 mg ca co3 2 but the major element compositions of the remaining 20 are similar to those of carbonate bearing high density fluids hdfs found in fibrous diamonds we conclude that the source of carbon for these macles and for most diamonds is carbonate bearing hdfs similar to those found here and in fibrous diamonds combined with the old ages of mc diamonds up to 3 5 ga our new findings suggest that carbonates have been introduced into the reduced lithospheric mantle since the archaean and that the mechanism of diamond formation is the same for most diamonds

response of diatom and silicoflagellate assemblages in the central gulf of california to regional climate change during the past 55 kyrs abstract high resolution studies of diatoms and silicoflagellates of the past 55 kyrs in cores md02 2517 2515 from the central gulf of california goc reveal profound changes in goc surface waters roperia tesselata a diatom proxy for late winter early spring upwelling and dictyocha stapedia a subtropical silicoflagellate indicative of goc sea surface temperatures ssts 24 c are common during the holocene but rare during marine isotope stage mis 2 and most of mis 3 a relationship that likely reflects a more northerly position of the north pacific high nph during the holocene in contrast during most of mis 2 27 15 ka the persistent presence of distephanus speculum a silicoflagellate associated with ssts during mis 3 55 27 ka increased dominance of azpeitia nodulifera diatom implies that stratified tropical waters were present year round whereas silicoflagellate assemblages suggest that stratified tropical conditions alternated with more productive upwelling conditions on millennial timescales reduced biosiliceous productivity during heinrich events likely reflected a reduction in both surface water nutrient levels and in the strength of northwest winds due to a weakened and more southerly nph conversely enhanced biosiliceous productivity during mis 3 interstadials was probably linked to heightened nutrient levels and a strengthened nph abrupt relative abundance increases of the silicoflagellate dictyocha aculeata approximate the termination of mis3 heinrich events and may signal times when nutrient rich deep waters associated with the resumption of enhanced atlantic meridional overturning circulation penetrated into the central gulf

a kalman filter analysis of sea level height in the tropical pacific abstract the kalman filter is implemented and tested for a simple model of sea level anomalies in the tropical pacific using tide gauge data from six selected island stations to update the model the kalman filter requires detailed statistical assumptions about the errors in the model and the data in this study it is assumed that the model errors are dominated by the errors in the wind stress analysis the error model is a simple covariance function with parameters fit from the observed differences between the tide gauge data and the model output the fitted parameters are consistent with independent estimates of the errors in the wind stress analysis the calibrated error model is used in a kalman filtering scheme to generate monthly sea level height anomaly maps for the tropical pacific the filtered maps i e those which result from data assimilation exhibit fine structure that is absent from the unfiltered model output even in regions removed from the data insertion points error estimates an

crust derived potassic fluid in metamorphic microdiamond abstract a highly potassic coh fluid with dissolved phosphate chloride and sulfate sulfide was identified as nanometer size inclusions in metamorphic microdiamonds of kokchetav dolomite marble and garnet quartz pyroxene rock using an analytical electron microscope aem coupled with an energy dispersive x ray edx spectrometer this provides a direct piece of evidence for the formation of metamorphic microdiamonds from such a fluid although this crust derived potassic fluid and the associated solid precipitates are in some respects similar to the fluid inclusions in fibrous cloudy mantle diamonds distinct chemical differences exist this potassic coh fluid in addition has the potential to trigger high to ultrahigh k magmatic and k metasomatic processes in mantle

mantle fluid evolution a tale of one diamond abstract microinclusions analyzed in a coated diamond from the diavik mine in canada comprise peridotitic minerals and fluids the fluids span a wide compositional range between a carbonatitic melt and brine the diamond is concentrically zoned the brine microinclusions reside in an inner growth zone and their endmember composition is k19na25ca5mg8fe3ba2si4cl32 mol the carbonatitic melt is found in an outer layer and its endmember composition is k11na21ca11mg26fe7ba2si10al3p2cl5 the transition in inclusion chemistry is accompanied by a change in the carbon isotopic composition of the diamond from 8 5 in the inner zone to 12 1 in the outer zone we suggest that this transition reflects mixing between already evolved brine and a freshly introduced carbonatitic melt of different isotopic composition the compositional range found in diamond on dvk 294 is the widest ever recorded in a single diamond it closes the gap between brine found in cloudy octahedral diamonds from south africa and carbonatitic melt analyzed in cubic diamonds from zaire and botswana thus all microinclusions analyzed to date fall along two arrays connecting the carbonatitic melt composition to either a hydrous silicic endmember or to a brine endmember this connection suggests that many diamonds are formed from fluids derived form a mantle source not significantly influenced by local heterogeneities

the causation and sensitivity of the northern winter planetary waves abstract we have made high resolution calculations of the wintertime stationary atmospheric response to planetary scale topographic and thermal forcings a numerical model has been used that solves the spherical primitive equations linearized about observed zonal wind and temperature fields the model s lid is placed high enough so that spurious reflections do not affect the results considerable attention has been paid to numerical accuracy the model s response to realistic forcing is in general agreement with observational analysis of van loon et al we find that in middle latitudes the response to topographic forcing strongly dominates the response to thermal forcing in the midlatitude troposphere the topographic response is insensitive to changes in the zonal wind the interannual variability of the tropospheric waves is due more to the heating response the 500 mb amplitude of the interannual variability due to the sum of both forcings is as indicated by our model and as measured at the himalaya

evidence for changes in the north atlantic deep water linked to meltwater surges during the heinrich events abstract deep sea sediment records from north atlantic cores 40 n 55 n provide evidence of several massive iceberg discharges known as heinrich events during the last glacial period high resolution benthic 18 o and 13 c records from north atlantic sediment cores were used to monitor the impact of heinrich events on thermohaline circulation and to estimate the sensitivity of deep oceanic circulation to changes in freshwater input to the north atlantic surface waters our data indicate that major rearrangements of deep water masses were directly associated with these massive iceberg discharges to trace in detail the deep water conditions in the north atlantic benthic 13 c values in several cores were used to generate time slices before during and after heinrich event 4 dated at 35 ka bp although north atlantic deep water continued to form during the oxygen isotope stage 3 at 37 ka bp deep circulation was characterized by an increased incursion of deep waters of southern origin which reduced the 13 c composition of north atlantic deep waters particularly in the eastern atlantic basin north atlantic deep water production was reduced during heinrich layer 4 hl4 at 35 ka bp synchronously with the changes in the surface water hydrology deep convection processes may have occurred in areas not affected by the salinity decrease soon after hl4 33 ka bp the 13 c distribution was similar to that before the event similarly a rapid return to initial 13 c values was observed at the end of the most clearly defined heinrich events hl5 hl4 and hl1 comparison between deep circulation patterns corresponding to hl4 the last glacial maximum and heinrich event 1 indicates that each of these periods was characterized by a different circulation state associated with changes in convection sites

global statistical space time scales of oceanic variability estimated from the topex poseidon altimeter data four years of the topex poseidon altimeter data are used to produce estimates of statistical space time scales of ocean variabilities for the sea surface height a three dimensional space time correlation function with an anisotropic directional dependence is assumed the function has gaussian distributions in radial directions in the space time coordinates and ellipsoidal contour surfaces the function can reveal the space time scales and propagations of the variabilities and statistical errors in the altimeter data we evaluated the space time scales using the best fit correlation function to the altimeter data the scales show geographical differences this means that dominant variabilities depend on regions we show an optimum interpolation oi method as an example of the application of the fitted correlation function the oi is applied to the altimeter data in the space time domain to make grid point data with higher accuracy than those obtained from a usual spatial two dimensional oi 2 d oi the values of the correlation function are used for the correlation coefficients of the first guess error in the oi a propagation diagram obtained from the space time oi 3 d oi shows clear propagations of planetary disturbances with larger amplitude the grid point values from the 3 d oi show better correspondences with sea levels from tide gauges than those from the 2 d oi the advantage is due to the data of the different cycles being additionally adopted and the correlation function reflecting propagation of the ocean variabilities

nanometer size p k rich silica glass former melt inclusions in microdiamond from the gneisses of kokchetav and erzgebirge massifs diversified characteristics of the formation media of metamorphic microdiamond in uhp rocks due to host rock buffering abstract nanometer size p k rich silica glass former melt inclusions were identified within metamorphic microdiamonds from garnets of ultrahigh pressure uhp gneisses of the kokchetav and the erzgebirge massifs by analytical electron microscopy aem the chemical characteristics of these inclusions within microdiamonds are surprisingly similar among various gneissic rocks from both kokchetav and erzgebirge but are significantly different from the si poor ultrapotassic fluid inclusions within microdiamonds from garnets of the kokchetav uhp marble these contrasting findings not only provide constraints on the characteristics compositions of the formation media of metamorphic microdiamonds but also imply that the formation media must have been buffered by the hosting rocks resulting in the observed diversities as reported here in addition depending on the rock types and thus on the nature of the formation media from which metamorphic microdiamonds were formed the respective characteristic morphologies of the microdiamonds differ the p k rich silica melt tends to form octahedral or cubo octahedral microdiamonds within garnet in gneissic rocks whereas the si poor ultrapotassic fluid tends to form spheroids cuboid microdiamonds with rugged surfaces within garnet in marble consequently the buffered media in hosting rocks played a decisive role in determining the different morphologies and growth rates mechanisms of metamorphic microdiamonds in general

millennial climate oscillations in ne pacific surface waters over the last 82 kyr new evidence from alkenones 1 a climate instability in the last glacial corresponding to dansgaard oeschger d o events has been already recognized in the california margin in northeast pacific detailed sea surface temperature sst changes in this region however have not been so far well elucidated here we report estimates of alkenone derived ssts with the do time scale from odp hole 1017e off point conception over the last 80 kyr our results show that alkenone ssts clearly record d o and heinrich events we also found that alkenone ssts during 82 58 ka and 18 15 ka were considerably higher and those in 15 12 ka were lower than those derived from 18o of planktonic foraminifera these results appear to reflect fluctuations of water masses

low energy phase boundary pairs and preferred crystallographic orientations of olivines in nanometer sized ultrapotassic fluid inclusions of aykhal diamond abstract the healed internal conjugated cleavages at the core of aykhal octahedral diamond sample ah2 were decorated with 111 dia facetted ultrapotassic fluid melt inclusion pockets containing nanosized graphite phlogopite and olivine fo92 inclusions these olivines are either rounded in pockets with ample fluid or facetted by the 111 dia mold in the pockets with a fluid film transmission electron microscopy revealed two distinct crystallographic characteristics of olivine inclusions 1 pronounced crystallographic texture of olivines grouped in specific diamond domain and 2 frequent parallelism or sub parallelism of specific low energy faces of the two phases mainly 010 ol 120 ol 001 ol and 111 dia 110 dia 100 dia in the order of decreasing preference forming prominent 010 ol 111 dia 010 ol 110 dia 001 ol 110 dia 120 ol 111 dia and 120 ol 110 dia low energy phase boundaries with thin liquid film of 1 2 nm in between these findings not only testify to the extremely low adhesion energies of olivine diamond boundary pairs but also imply that in the presence of a fluid phase the interfacial energetics and the energetically favored crystallographic orientations of olivine inclusions in diamond can be controlled simply by the settlement attachment of low energy facets of olivine crystals precipitating from the parental fluid upon the low energy 111 dia or 110 dia surfaces of diamond such interfacial energetics control and the resultant low energy boundary pairs are characteristically distinct from the common topotaxy or epitaxy between oxide silicate mineral pairs but are in a sense like the van der waals heteroepitaxy in artificial systems

exploration of the eddy field in the midlatitude north pacific abstract fourteen moorings were deployed across the midlatitude north pacific 165 e to 152 w for approximately 2 years during 1983 85 ten mooring sites had previously been occupied at similar latitudes 30 40 n nominal for roughly two years 1980 82 along 152 e taken together these observations form the basis for the first systematic basinwide zonal exploration of the eddy field based on moored instrument techniques in the midlatitude north pacific along the kuroshio extension system and north pacific drift eddy kinetic energy ke at abyssal depths decays sharply moving east from 152 e and has decreased by a factor of 4 by 165 e there is a plateau in abyssal ke of about 10 cm2 s 2 across the emperor seamounts from 165 to 175 e abyssal ke drops to roughly 5 cm2 s 2 at 175 w and 1 cm2 s 2 at 152 w for a total decay of a factor of about 50 across the midlatitude north pacific upper level ke decreases by a total of roughly two orders of magnitude approximately 103 to 101 from 152 e to 152 w

sea level variabilities in the gulf stream between cape hatteras and 50 w a geosat study sea level residuals relative to a 2 year mean sea level in the gulf stream downstream of cape hatteras between 80 w and 50 w longitude are studied using geosat altimetry between november 1986 and december 1988 spectral slopes computed at four nominal locations along the gulf stream 72 w 65 w 60 w and 55 w range between 1 5 and 0 9 significantly less steep than the 2 5 spectral slope found at bermuda because of increased short wavelength energy the spectra tend to become more white going eastward but this trend is not statistically significant energy at the annual cycle decreases eastward from around 40 of the total variance at 72 w to 20 of the total variance at 55 w maximum residual geostrophic sea surface velocities associated with the annual cycle were of the order of 70 cm s comparison between the gulf stream path from sea level residual maps and the north wall edge observed from noaa infrared ir imagery shows an rms difference of 49 km between 75 w and 60 w longitude but not all sea level maps show a clearly defined gulf stream using the ir estimates for gulf stream position sea level residuals were modeled as the meandering of a sea level front shaped as 0 5 m tanh x x0 50 km sin with the angle between the geosat track and the gulf stream edge and x0 is based on the observed ir north wall positions this showed that the annual signal in terms of the location and phase of its maxima is dominated by the meandering of the gulf stream

seasonal axis migration of the upstream kuroshio extension associated with standing oscillations the topex poseidon altimeter data from october 1992 to october 1998 are analyzed to investigate the seasonal cycle of the sea surface height ssh in the upstream region of the kuroshio extension after removing steric height changes caused by surface buoyancy fluxes two maxima of the seasonal ssh amplitude are found around the crest and trough of the quasi stationary meanders as standing waves accompanied with nodes of amplitude minima seasonal variations are identified in the subsurface temperature at 400 m depth similar to those of ssh in amplitude and phase associated with the standing waves the current follows a straight path in fall and then changes to a meandering path in spring from a composite map of the seasonal kuroshio extension axes nodes of minimum displacement are found one node is located over the izu ridge while the others are located in the areas where meridional acceleration is large the seasonal axis migration of the upstream kuroshio extension is regulated by these nodes

the fall dump a new perspective on the role of a shade flora in the annual cycle of diatom production and export flux investigations of diatom fluxes recorded in laminated sediments using scanning electron microscope techniques together with evidence from sediment trap studies have contributed to a reappraisal of the annual cycle of diatom production and export flux we propose that where there is a strong seasonal thermocline and nutricline a number of diatoms hitherto regarded as typical sparse summer flora characteristic of oligotrophic waters are able to generate substantial production at depth these species including rhizosolenia spp stephanopyxis palmeriana thalassiothrix spp and some coscinodiscus spp may represent a shade flora that have adapted to grow in low light conditions and or to regulate their buoyancy to move between a deep nutrient source and the euphotic zone although rates of growth and primary production are substantially lower than species characteristic of spring bloom or upwelling conditions the total primary production integrated over the several month period of summer stratification may be as significant as the spring bloom or greater the term fall or autumn bloom as a counterpart of the spring bloom is therefore a misnomer whereas the spring bloom involves a rapid burst of reproduction and sedimentation the fall dump is the sedimentation of a long lived episode of production lasting the duration of the seasonal thermocline and triggered by the fall winter mixing that breaks down stratification the fall dump may produce as much or in some cases more export production than the spring bloom the results of this study suggest that a reorientation of thinking on diatom ecology and palaeoecology may be required

a tem study of the oriented orthopyroxene and forsterite inclusions in garnet from otroy garnet peridotite wgr norway new insights on crystallographic characteristics and growth energetics of exsolved pyroxene in relict majoritic garnet regularly oriented orthopyroxene opx and forsterite fo inclusions occur as opx rutile rt or fo rt inclusion domains in garnet grt from otroy peridotite electron diffraction characterization shows that forsterite inclusions do not have any specific crystallographic orientation relationships cor with the garnet host in contrast orthopyroxene inclusions have two sets of cor that is cor i grt opx and 110 grt 100 opx 13 off and cor ii grt opx and 110 grt 100 opx 14 off in four garnet grains analysed both variants of orthopyroxene have a blade like habit with one pair of broad crystal faces parallel sub parallel to 110 grt plane and the long axis of the crystal opx for cor i and opx for cor ii along grt direction whereas the lack of specific cor between forsterite and garnet along with the presence of abundant infiltrating trails veinlets decorated by fo rt at garnet edges provide compelling evidence for the formation of forsterite inclusions in garnet through the sequential cleaving infiltrating precipitating healing process at low temperatures the origin of the epitaxial orthopyroxene inclusions in garnet is not so obvious in this connection the reported cor the crystal habit and the crystal growth energetics of the exsolved orthopyroxene in relict majoritic garnet were reviewed clarified the exsolved ortho pyroxene in a relict majoritic garnet follows cor iii 112 grt 100 opx and grt opx based on the detailed trace analysis on published sem images these exsolved orthopyroxene inclusions are shown to have the crystal habit with one pair of broad crystal faces parallel to 112 grt 100 opx and the long crystal axis along grt opx such a crystal habit can be rationalized by the differences in oxygen sub lattices of both structures and represents the energetically favoured crystal shape of orthopyroxene inclusions in garnet formed by solid state exsolution mechanism considering the very different cor crystal habit as well as crystal growth direction the orthopyroxene inclusions in garnet of the present sample most likely had been formed by mechanism s other than solid state exsolution regardless of their regularly oriented appearance in garnet and the cor specification between orthopyroxene and garnet in fact the crystallographic characteristics of orthopyroxene and the similar chemical compositions of garnet at opx rt inclusion domains fo rt inclusion domains trails and garnet rim suggest that the orthopyroxene inclusions in the garnet are most likely formed by similar cleaving infiltration process as forsterite inclusions though probably at an earlier stage of metamorphism this work demonstrates that the oriented inclusions in host minerals with or without specific cor can arise from mechanism s other than solid state exsolution caution is thus needed in the interpretation of such cor so that an erroneous identification of exhumation from uhp depths would not be made

stationary and traveling mesoscale perturbations in the kuroshio extension current abstract several hundred xbt observations in the western north pacific were collected each month over a 2 year period 1976 78 they have been assembled into a monthly map sequence of thermocline temperature in the kuroshio extension current having 100 km spatial resolution the overall time men of the maps exhibits mesoscale 200 600 km perturbations which correlate with several major bathymetric features especially the shatsky rise time variability about the mean decreases significantly cast of the shatsky rise in addition time variable mesoscale disturbances propagate zonally westward at 3 8 cm s 1 attempts to explain the observed propagation phase velocity through simple analytic baroclinic rossby wave theory lead to the implication that there exists in the region an eastward deep mean flow of 3 or 4 cm s 1 direct current measurements of long duration are required to help resolve and explain these observations

characterization and validation of the heat storage variability from topex poseidon at four oceanographic sites oceanic heat storage and heat storage rate are correlated to the sea surface height anomaly signals from the topex poseidon altimeter data from 1992 to 1998 the height anomaly data are decomposed through two dimensional finite impulse response filtering the signal components are the basin scale seasonal westward propagating rossby waves eastward propagating kelvin waves and mesoscale eddies and a small scale residual the sum of these filtered components does not depart significantly from the original signal correlations and rms differences are calculated to compare heat storage estimates on the basis of altimeter and in situ data at four sites tropical atmosphere ocean array hawaii ocean time series program california cooperative oceanic fisheries investigations and hydrostation s the heat storage anomaly differences range from 52 to 64 x 10 7 j m 2 and the correlations range from 0 67 to 0 88 the heat storage rate rms differences range from 97 to 228 w m 2 and the correlations range from 0 66 to 0 82 the fraction of the variance associated with rossby waves varies from 13 in the equatorial pacific to 62 in the tropical north pacific conversely in the same regions the nonpropagating signal goes from 74 to 13

a near field sea level record of east antarctic ice sheet instability from 32 to 27 myr 1 fossil facies and isotope analyses of an early high paleolatitude 55 s section suggests a highly unstable east antarctic ice sheet from 32 to 27 myr the waxing and waning of this ice sheet from 140 to 40 of its present volume caused sea level changes of 25 m ranging from 30 to 50 m related to periodic glacial 100 000 to 200 000 years and shorter interglacial events the near field gippsland sea level gsl curve shares many similarities to the far field new jersey sea level njsl estimates however there are possible resolution errors due to biochronology taphonomy and paleodepth estimates and the relative lack of lowstand deposits in njsl that prevent detailed correlations with gsl nevertheless the lateral variations in sea level between the gsl section and njsl record that suggest ocean siphoning and antisiphoning may have propagated synchronous yet variable sea levels

high resolution paleoceanography of the guaymas basin gulf of california during the past 15 000 years abstract deep sea drilling project site 480 27 54 10 n 111 39 34 w 655 m water depth contains a high resolution record of paleoceanographic change of the past 15 000 years for the guaymas basin a region of very high diatom productivity within the central gulf of california analyses of diatoms and silicoflagellates were completed on samples spaced every 40 50 yr whereas icp aes geochemical analyses were completed on alternate samples sample spacing 80 100 yr the bolling allerod interval 14 6 12 9 ka note ka refers to 1000 calendar years bp throughout this report is characterized by an increase in biogenic silica and a decline in calcium carbonate relative to surrounding intervals suggesting conditions somewhat similar to those of today the younger dryas event 12 9 11 6 ka is marked by a major drop in biogenic silica and an increase in calcium carbonate increasing relative percentage contributions of azpeitia nodulifera and dictyocha perlaevis a tropical diatom and silicoflagellate respectively and reduced numbers of the silicoflagellate octactis pulchra are supportive of reduced upwelling of nutrient rich waters between 10 6 and 10 0 ka calcium carbonate and a nodulifera abruptly decline at dsdp 480 while roperia tesselata a diatom indicative of winter upwelling in the modern day gulf increases sharply in numbers a nearly coincident increase in the silicoflagellate dictyocha stapedia suggests that waters above dsdp 480 were more similar to the cooler and slightly more saline waters of the northern gulf during much of the early and middle parts of the holocene 10 to 3 2 ka at about 6 2 ka a stepwise increase in biogenic silica and the reappearance of the tropical diatom a nodulifera marks a major change in oceanographic conditions in the gulf a winter shift to more northwesterly winds may have occurred at this time along with the onset of periodic northward excursions el nino driven of the north equatorial countercurrent during the summer beginning between 2 8 and 2 4 ka the amplitude of biogenic silica and wt fe al and ti proxies of terrigenous input increase possibly reflecting intensification of enso cycles and the establishment of modern oceanographic conditions in the gulf increased numbers of o pulchra after 2 8 ka suggest enhanced spring upwelling

horizontal eddy fluxes of momentum and kinetic energy in the near surface of the kuroshio extension abstract sequential monthly mean temperature fields in the mid latitude western north pacific 30 45 n 140 180 e constructed from transpac xbt expendable bathythermograph data over a two year period are employed to analyze the interaction between mesoscale variability and the mean flow of the kuroshio extension an empirical temperature dynamic height regression and the geostrophic approximation lead to the computation of mean and eddy horizontal velocity components over the region from which horizontal eddy processes in both the mean momentum and the mean kinetic energy balances of the kuroshio extension are estimated the kuroshio extension generally loses mean kinetic energy as it travels from the coast of japan from 140 to 180 e with much larger eddy kinetic energy west of the shatsky rise 160 e than east of there concentrating upon zonally averaged quantities in both subregions east and west of the shatsky rise horizontal eddy momentum fluxes due to transient mesoscale variability i e

estimates of the geostrophic stream function in the western north pacific from xbt surveys the upper ocean temperature and dynamic height fields are correlated in the western north pacific ocean this relationship can be used to map a relative geostrophic stream function of the kuroshio extension using temperature data from expendable bathythermograph xbt surveys we have examined the ability of the north pacific ship of opportunity xbt program known as transpac to carry out this procedure estimates of 600 1200 dbar geostrophic shear were generated from the xbt data utilizing objective mapping techniques these estimates were compared with measured currents at 600 m relative to 1200 m along 152 e from 27 n to 42 n the estimated and measured relative currents are positively correlated with an rms error of 6 cm s over a measured dynamic range of 30 cm s however the xbt estimated shears consistently underestimate the measured values by a factor of 2 to 3 the underestimate of the amplitude is the result of both undersampling and mapping produres that eliminate high wavenumber contributions of the dynamic height variability these factors appear to be responsible for previous differences in amplitude between directly measured and transpac xbt estimated values of relative eddy kinetic energy and reynolds stress the transpac xbt survey can only monitor qualitatively the dynamic topography of the kuroshio extension meanders and rings the variability outside of the extension with a temperature range of 3 c cannot be resolved because of inaccuracies in the temperature dynamic height relationship to monitor the kuroshio extension variability in the future it is recommended that transpac xbt resources in the western north pacific concentrate on obtaining a denser sample of the field during the fall and winter seasons because of incomplete ship track coverage in spring and summer

modeling of radial microcracks at corners of inclusions in garnet using fracture mechanics radial microcracks around inclusions in garnet are important indicators of ultrahigh pressure metamorphism and have been used to interpret changes in pressure as a function of temperature during decompression of metamorphic terrains we investigate the growth of microcracks from inclusion corners using a two dimensional fracture mechanics based boundary element method code and propose that microcracks emanating from inclusions are primarily controlled by inclusion shape and size and do not require high confining lithostatic pressure or significant decompression to initiate results suggest that inclusions 100 m diameter develop microcracks during modest decompression the magnitude of decompression required to initiate microcracks decreases with increased degree of faceting and increased inclusion size the potential for crack growth at each corner depends on the corner sharpness and the overall shape of the inclusion we integrate model results with petrographic observations to understand mechanisms and conditions of garnet microcracking during regional metamorphism

evidence for barotropic wave radiation from the gulf stream abstract highly energetic velocity fluctuations associated with topographic rossby waves are frequently observed over the continental slope and rise off the united states and canadian east coast it has been suggested that the energy source for these waves could be eastward propagating gulf stream meanders which can couple to the westward propagating rossby waves if the meander shape is time dependent in this study a historical archive of all available current meter data from the western north atlantic has been examined for evidence of energy radiation from the gulf stream via barotropic topographic rossby waves maps of abyssal eddy kinetic energy eke and reynolds stress were constructed for four frequency bands including motions with periods between 256 and 7 8 days to examine distributions of these quantities over the largest possible geographical area maximum eddy kinetic energy is observed along the mean axis of the gulf stream at low frequencies 50 250 days but this maximum shifts north a

energetics of the kuroshio extension at 35 n 152 e abstract a simplistic interpretation of eddy heat fluxes from a two year current meter mooring deployment in the kuroshio extension leads to the conclusion that the eddy field is denying at 152 e contradicting observations from the surface to 300 m that indicate the region to be one of steady or growing eddy energy thus a simplified version of the method used by hall to construct the velocity field of the current from the moored data has been used to examine the baroclinic and barotropic energy conversions in the cyclonic and anticyclonic portions of the current for both geographic and stream coordinates although the error bars are large in stream coordinates significant conversions of mean to eddy potential energy occur on the anticyclonic side of the current at both 350 and 625 dbar with smaller average conversions of eddy to mean energy over the cold portion barotropic conversions in this coordinate system are small but qualitatively the calculated reynolds stresses agree with previous obser

bimodality of the kuroshio abstract a barotropic ocean model is used to study the bimodal behavior of the kuroshio to the south of japan by considering the combined effects of the beta plane the kyushu coastal perturbation the izu ridge and the sw ne tilted coastline the two frequently observed meander patterns have been numerically verified as the two quasi steady solutions contained n the model the small meander state is identified as an upstream disturbance largely forced by the izu ridge its width decreases as the strength of the current increases the large meander state is forced by the presence of both the kyushu wedge and the izu ridge topography for small volume transports the large meander state behaves like the small meander state in that the meander width decreases as the current speed increases for large volume transports it behaves like a lee rossby wave in that the width of the meander increases as the current speed increases the birth of the large meander state occurs as a consequence of the ocean spin do

diamond and its olivine inclusions a strange relation revealed by ab initio simulations abstract the study of diamond and its solid inclusions is of paramount importance to acquire direct information on the deepest regions of the earth however although diamond is one of the most studied materials in geology the diamond inclusion relationships are not yet understood do they form simultaneously syngenesis or are inclusions pre existing objects on which diamond nucleated protogenesis here we report for the first time adhesion energies between diamond d and forsterite fo to provide a crucial contribution to the syngenesis protogenesis debate the following interfaces were investigated at quantum mechanical level i 001 d 001 fo ii 001 d 021 fo and iii 111 d 001 fo our data along with the ones recently obtained on the 110 d 101 fo interface revealed an unexpected thermodynamic behaviour all interfaces showing almost equal and low adhesion energies accordingly diamond and olivine have an extremely low chemical affinity and cannot develop preferential orientations even during an eventual epitaxial growth combining these results with those of our previous work concerning the morphology constraints of diamond on its inclusions we can state that the two main arguments used so far in favour of diamond inclusions syngenesis cannot be longer considered valid at least for olivine

three dimensional cathodoluminescence imaging and electron backscatter diffraction tools for studying the genetic nature of diamond inclusions as a step towards resolving the genesis of inclusions in diamonds a new technique is presented this technique combines cathodoluminescence cl and electron backscatter diffraction ebsd using a focused ion beam scanning electron microscope fib sem instrument with the aim of determining in detail the three dimensional diamond zonation adjacent to a diamond inclusion ebsd reveals that mineral inclusions in a single diamond have similar crystallographic orientations to the host within 0 4 the chromite inclusions record a systematic change in mg and cr from core to the rim of the diamond that corresponds with a 80 c decrease of their formation temperature as established by zinc thermometry a chromite inclusion positioned adjacent to a boundary between two major diamond growth zones is multi faceted with preferred octahedral and cubic faces the chromite is surrounded by a volume of non luminescent diamond cl halo that partially obscures any diamond growth structures the cl halo has apparent crystallographic morphology with symmetrically oriented pointed features the cl halo is enriched in 200 ppm cr and 80 ppm fe and is interpreted to have a secondary origin as it overprints a major primary diamond growth structure the diamond zonation adjacent to the chromite is complex and records both syngenetic and protogenetic features based on current inclusion entrapment models in this specific case a syngenetic origin is favoured with the complex form of the inclusion and growth layers indicating changes of growth rates at the diamond chromite interface combined ebsd and 3d cl imaging appears an extremely useful tool in resolving the ongoing discussion about the timing of inclusion growth and the significance of diamond inclusion studies

paleoceanographic history of the guaymas basin gulf of california during the past 15 000 years based on diatoms silicoflagellates and biogenic sediments high resolution records of calcium carbonate biogenic opal diatoms and silicoflagellates from western guaymas basin gravity core ggc55 and piston core jpc56 and eastern guaymas basin dsdp site 480 reveal a complex paleoceanographic history of the central gulf of california during the past 15 000 years prior to 6 2 ka the eastern and western guaymas basin proxy records were remarkably similar after conditions similar to those of today during the bolling allerod the younger dryas yd saw a major drop in diatom production coincident with increased calcium carbonate and tropical microfossils suggestive of el nino like conditions biosiliceous productivity began increasing during the latter part of the yd but it was only during the earliest holocene 11 6 to 11 0 ka that conditions similar to those of the bolling allerod returned to the central gulf between around 11 0 and 6 2 ka tropical diatoms and silicoflagellates were virtually absent from the central gulf as relatively cooler and fresher surface waters resembling those of the modern northern gulf were present in the central gulf beginning at about 6 2 ka tropical diatoms and silicoflagellates began increasing in the central gulf and coccoliths returned to western gulf sediments the onset of modern day monsoon conditions in the american southwest required the presence of warm ssts in the northern gulf which probably did not occur until after about 5 4 ka when tropical diatoms and silicoflagellates became relatively common in the central gulf modern east west contrasts which arise from late winter early spring coastal upwelling on the mainland side and lower diatom productivity on the western side of the gulf commenced between 6 2 and 5 4 ka possibly due to a shift in the direction of late winter early spring winds more towards the southeast or down the axis of the gulf this proposed wind shift might have ultimately been due to a late holocene strengthening of enso like conditions in the eastern equatorial pacific published by elsevier b v

nitrogen isotopic variations in the gulf of california since the last deglaciation response to global climate change high resolution records of the nitrogen isotopic composition of organic matter 15norg opal content and opal accumulation rates from the central gulf of california reveal large and abrupt variations during deglaciation and gradual holocene changes coincident with climatic changes recorded in the north atlantic homogenous sediments with relatively low 15norg values and low opal content were deposited at the end of the last glacial period during the younger dryas event and during the middle to late holocene in contrast laminated sediments deposited in the two deglacial stages are characterized by very high 15norg values 14 and opal accumulation rates 29 41 mg cm 2 yr 1 abrupt shifts in 15norg were driven by widespread changes in the extent of suboxic subsurface waters supporting denitrification and were amplified in the central gulf record due to variations in upwelling vertical mixing and or the latitudinal position of the intertropical convergence zone

gulf stream surface transport and statistics at 69 w from the geosat altimeter geosat altimeter height measurements for the gulf stream for three subtracks from the exact repeat mission were processed to remove the geoid and mean gulf stream height a gaussian model for the gulf stream velocity profile was used to predict the form of the residual height profiles seen by geosat and the mean height profile using estimates of the width and position derived from the height residuals estimates of the maximum surface velocity and the surface transport were obtained by a least squares fit of the synthetic height profiles to the data location statistics from the geosat data were in good agreement with values obtained from infrared images of the gulf stream maximum surface velocities were typically between 1 2 and 2 0 m s 1 the time series showed that surface transport is correlated primarily with the magnitude of the surface velocities although an anomalously large increase in surface transport in the winter of 1987 1988 was caused by an increase in the width of the gulf stream an analysis of the average annual signal in transport showed maximum values in the late fall and minimum transport in the late spring maximum minimum surface transport generally occurred when the gulf stream was north south of its mean position

two year moored instrument results along 152 e results from a 2 year nominal deployment of a moored array along 152 e from 28 n to 41 n are presented with emphasis on similarities and differences between settings approximately year to year ten moorings and 38 instruments were involved from the fall of 1980 to 1982 current temperature meters spanned the water column from 500 to 4000 m depths with occasional instruments in the vicinity of 300 m and near the bottom 6000 m upper level features located in the center of the array near 35 36 n were generally stable relative to the axis of the kuroshio extension varying from deployment to deployment with meanders in this flow regime some properties of the abyssal 4000 m currents were comparatively more variable with these changes not connected to meandering of the kuroshio extension in an obvious way the vertical structure and frequency distributions of eddy kinetic energy were similar in shape and to some extent in amplitude from deployment to deployment especially relative to meanders of the kuroshio extension but translated in the opposite direction

low frequency variability in regions of the kuroshio extension and the gulf stream using sea surface height data collected by the topex poseidon altimeter we studied the low frequency variability in the kuroshio extension and gulf stream the most significant signals are the basin wide background seasonal cycle and low frequency wave activity generated over major bottom bathymetry and subsequent westward propagation in both regions the spatial structures of the seasonal cycle in the two regions are quite different in the kuroshio extension the seasonal cycle has a northeast southwest orientation and lies closer to the western boundary whereas it has an east west orientation and lies more offshore in the gulf stream the close relationship between the low frequency wave activity and major bottom bathymetry features is discussed through both empirical orthogonal functional eof analysis and calculation of eddy kinetic energy and reynolds stress the spatial structures of these eddy statistics are fundamentally different from those of high frequency mesoscale variability they are not in the proximity of maximum time mean flow but rather they lie mostly to the west of major bottom bathymetry the close association of the clusters of local maximum eddy properties with major bottom topographic features in both regions wave generation over the major bottom topographic features and subsequent westward propagation and difference of the eddy statistics from that associated with high frequency mesoscale variability all suggest that unlike in the case with high frequency mesoscale variability generation in which internal dynamics of the background mean flow such as nonlinear instability plays a fundamental role external forcing through bottom topography must play a fundamental role in generating the low frequency wave activity

zonal velocity structure and transport in the kuroshio extension abstract the meridional structure of the zonal flow in the kuroshio extension is investigated using a combination of data from hydrographic sections and moored current meter arrays we emphasize 165 e between 30 and 42 n where high quality and very stable current measurements at 150 and 4000 m extend over a two year period from october 1983 to october 1985 hydrographic ctd o2 sections were occupied during the initial deployment and a second time when the array of six moorings was reset in 1984 the deep currents were extremely reproducible from one year to the next and revealed a pattern of weak eastward flow at 4000 m under the axis of the kuroshio with strong westward flow on either flank when combined with the hydrographic data the total transport of the eastward flowing kuroshio extension was estimated to be 57 0 3 7 sv sv 106 m3 s 1 essentially the same as when referenced to the broom 57 0 2 0 sv south of 34 n the velocities were westward at all levels with a net transport of 8

first evidence of hydrous silicic fluid films around solid inclusions in gem quality diamonds abstract diamonds form from fluids or melts circulating at depth in the earth s mantle analysis of these fluids is possible if they remain entrapped in the diamond during its growth but this is rarely observed in gem quality stones we provide the first evidence that typical mineral inclusions in gem quality diamonds from the siberian and kaapvaal cratons are surrounded by a thin film of hydrous silicic fluid of maximum thickness 1 5 m the fluid contains si 2 o oh 6 si oh 4 and molecular h 2 o and was identified using confocal micro raman spectroscopy and synchrotron based x ray tomographic microscopy as the solid mineral inclusions have both peridotitic and eclogitic affinities and occur in two cratonic regions our results demonstrate the strong connection between water rich fluids and the growth of gem quality lithospheric diamonds the presence of the fluid films should be taken into account for a proper evaluation of h 2 o contents in the mantle based on h 2 o contents in solid inclusions and for a robust assessment of diamond formation pressures based on the residual pressures of the inclusions

an error covariance model for sea surface topography and velocity derived from topex poseidon altimetry in order to facilitate the use of satellite altimeter derived sea surface topography and velocity in oceanographic models a methodology is presented for deriving the total error covariance and its geographic distribution from topex poseidon measurements the model is formulated using a parametric model fit to the altimeter range observations the topography and velocity are modeled with spherical harmonic expansions whose coefficients are found through optimal adjustment to the altimeter range residuals using bayesian statistics all other parameters including the orbit geoid surface models and range corrections are provided as unadjusted parameters the maximum likelihood estimates and errors are derived from the probability density function of the altimeter range residuals conditioned with a priori information estimates of model errors for the unadjusted parameters are obtained from the topex poseidon postlaunch verification results and the error covariances for the orbit and the geoid except for the ocean tides the error in the ocean tides is modeled first as the difference between two global tide models and second as the correction to the present tide model the correction derived from topex poseidon data a formal error covariance propagation scheme is used to derive the total error our global total error estimate for the topex poseidon topography relative to the geoid for one 10 day period is found to be 11 cm rms when the error in the geoid is removed thereby providing an estimate of the time dependent error the uncertainty in the topography is 3 5 cm rms this level of accuracy is consistent with direct comparisons of topex poseidon altimeter heights with tide gauge measurements at 28 stations in addition the error correlation length scales are derived globally in both east west and north south directions which should prove useful for data assimilation the largest error correlation length scales are found in the tropics errors in the velocity field are smallest in midlatitude regions they are less than 2 cm s over most of the southern ocean for both variables the largest errors are caused by uncertainty in the geoid more accurate representations of the geoid await a dedicated geopotential satellite mission substantial improvements in the accuracy of ocean tide models are expected in the very near future from research with topex poseidon data consequently estimates of the time dependent sea surface topography from topex poseidon could achieve a total uncertainty of less than 3 cm rms this level of accuracy from a spaceborne sensor represents a remarkable engineering achievement and a major contribution to ocean science

zonal jets over topography on a beta plane with applications to the kuroshio extension over the shatsky rise abstract the response of an initially zonal barotropic or baroclinic jet to an isolated seamount or a meridional ridge is investigated here using a three dimensional primitive equation model with a free surface an eastward jet with an axial speed u and a half width ly over a plane is supercritical if the froude rossby number u l2y is greater than about 0 25 and subcritical otherwise a westward jet with a negative u and hence a negative u l2y is always supercritical following this definition proposed by armi an obstacle renders barotropic zonal jets subcritical or less supercritical especially to the west of the obstacle for an initially supercritical eastward jet a significant obstacle projects its influence upstream through a migrating hydraulic jump broadening and weakening the incoming jet for subcritical and westward jets the westward influence is achieved by the propagation of long rossby waves in the barotropic regime the westward influence increases with u l2y and the height

new insight into polycrystalline diamond genesis from modern nanoanalytical techniques abstract technical developments in analytical methods that reach nanometer spatial resolution have enabled the interrogation of smaller submicron sized inclusions in diamond that had previously been elusive this has inspired and enabled studies of non classical diamond species from different geological settings resulting in a strongly faceted and dynamic picture of diamond formation this article reviews the leap of knowledge achieved by employing state of the art analytical methods with high spatial resolution to polycrystalline diamonds from different settings i e from kimberlite from crustal ultra high pressure metamorphic terranes and alluvial carbonados while crustal metamorphic diamonds are generally formed under oxidizing conditions polycrystalline diamond from the earth s mantle and carbonado have inclusion suites reflecting variable and sometimes extreme redox conditions diamond fluid compositions however fall in the same compositional field for worldwide diamond fluids regardless of their geodynamic environment on the basis of thermodynamic equilibrium data for c h o fluids in the mantle we argue that submicron inclusions in diamonds are products of local remobilization connected to fluid fluxed partial melting and redox freezing thus evidence from these inclusions complements information from classical work on larger inclusions and allows a unique direct insight into the medium in which diamond formed

interannual variability in the heat content of the kuroshio extension associated with the 1982 enso event abstract interannual variability in vertically averaged temperature over the upper 400 m of ocean i e upper ocean heat content in the vicinity of the kuroshio extension experienced significant changes during the 1982 enso year as compared to the preceding three years interannual variability was dominated by a mesoscale anomaly pattern whose variance increased by 40 on average in early 1982 over what it had been the previous three years this was accompanied by a general anomalous cooling south of the kuroshio extension and an anomalous warming north of the current associated with a decrease in the intensity of the kuroshio extension east of 150 e this activity occurred at the same time that the tropical and equatorial western north pacific was experiencing a rapid reduction in upper ocean heat content mesoscale anomalies of vertically averaged temperature in the kuroshio extension during the 1982 enso year were comparable in magnitude i e 3 c with maximum anomalous vertically averaged tem

estimating the surface transport of meandering oceanic jet streams from satellite altimetry surface transport estimates for the gulf stream and kuroshio extension abstract a method has been developed to detect the location width maximum velocity and suffice transport of a meandering oceanic jet stream from satellite altimetry ale method is based on a nonlinear least squares scheme in which gaussian shaped velocity profiles are fitted to explain the observed current variability in the meandering region the method has been applied to 25 geosat tracks in the kuroshio extension and gulf stream for the first you of the geosat exact repeat mission a reasonably smooth circulation pattern has emerged for the surface transport for both currents at opposed to the widely varying direct transport estimates after leaving the coast both currents have surface strength of the order of 90 103 m2 a 1 equivalent to a 90 cm height jump i e the sea surface height difference across the jet they continue to gain strength downstream until a maximum of the order of 130 10 3 m2 a 1 is reached near 150 e for the kuroshio and 63 w for the gulf stream the gulf stream the

syngenetic inclusions of yimengite in diamond from sese kimberlite zimbabwe evidence for metasomatic conditions of growth syngenetic inclusions of yimengite k cr ti mg fe al 12o19 a potassium member of the magnetoplumbite mineral group have been recorded in an octahedral macrodiamond from the sese kimberlite 50 km south of masvingo zimbabwe one yimengite inclusion carries lamellae of chromite suggesting peridotitic diamond paragenesis the diamond and inclusions were studied in situ in a plate polished parallel to 011 cathodoluminescence cl imaging has shown blue colour and octahedral zonation of the diamond lack of cracks and the location of five yimengites in different growth zones nitrogen n contents at ppm in the diamond determined by fourier transform infrared spectroscopy ftir steadily decrease from 576 core to 146 rim n aggregation 1ab is correspondingly 40 in the core and 30 in the rim hydrogen h content is high in the core moderate in the intermediate and very high in the rim zones four yimengites were dated using the laser 40ar 39ar method three inclusions yielded total gas ages that agree with or are younger than or within error of the sese kimberlite eruption age 538 11 ma but may be compromised by gas loss one inclusion with the highest tapped interface gas yield gave a total gas age of 892 21 ma that is a likely minimum yimengite age time t c constraints from n aggregation systematics give a range of possible ages from kimberlite eruption date back to archean and do not resolve the variable results of the 40ar 39ar dating compared with the published chemistry of yimengite from kimberlites inclusions from the sese diamond contain higher al mg and sr and have lower concentration of fe3 the chondrite normalised ree pattern of the yimengite shows enrichment in lree and depletion in hree but lree hree fractionations are lower than for lindsleyite mathiasite series mantle titanates and rather similar to the ree concentrations in kimberlite and lamproite rocks it is suggested that sese yimengite formed in the lithospheric mantle from metasomatism of chrome spinel by a fluid rich in ti k ba and lree

response of the north american monsoon to regional changes in ocean surface temperature 1 the north american monsoon nam an onshore wind shift occurring between july and september has evolved in character during the holocene largely due to changes in northern hemisphere insolation published paleoproxy and modeling studies suggest that prior to 8000 cal years bp the nam affected a broader region than today extending westward into the mojave desert of california holocene proxy sst records from the gulf of california goc and the adjacent pacific provide constraints for this changing nam climatology prior to 8000 cal years bp lower goc ssts would not have fueled northward surges of tropical moisture up the goc which presently contribute most of the monsoon precipitation to the western nam region during the early holocene the north pacific high was further north and ssts in the california current off baja california were warmer allowing monsoonal moisture flow from the subtropical pacific to take a more direct northwesterly trajectory into an expanded area of the southwestern u s west of 114 w a new upwelling record off southwest baja california reveals that enhanced upwelling in the california current beginning at 7500 cal year bp may have triggered a change in nam climatology focusing the geographic expression of nam in the southwest usa into its modern core region east of 114 w in arizona and new mexico holocene proxy precipitation records from the southwestern u s and northwestern mexico including lakes vegetation pollen and caves are reviewed and found to be largely supportive of this hypothesis of changing holocene nam climatology

large scale rossby wave in the mid latitude south pacific from altimetry data we present observations of large scale rossby wave propagation in the mid latitude south pacific 25 s from analyzing 4 years of topex poseidon altimetry data using wavelet transform we separate phase propagation from amplitude modulation the dominant rossby wave has a wavelength of about 40 with a period close to 2 years phase speed 6 4 cm s its amplitude modulates both interannually and intraannually in addition we also found a shorter scale rossby wave with a wavelength of about 16 and a period close to 9 months

long baroclinic rossby waves detected by topex poseidon residual sea surface height anomaly fields are obtained over the north atlantic basin from topex poseidon altimeter data evidence of westward propagating anomalies characterized as first mode baroclinic rossby waves is presented the phase speeds are obtained from the analysis of the autocorrelation matrices of the residual surface height anomaly in three dimensions on a 5 5 grid periods are calculated by least squares fitting a sinusoidal function to the time series at each grid point zonal and meridional wavelengths are obtained from the phase speed and period and are least squares fit to the data as a consistency check zonally averaged westward phase speeds vary between 1 and 27 km d between 50 and 5 n increasing southward phase speeds are directed to the southwest north of approximately 25 n and to the northwest south of this latitude the sea surface height signal is divided into two spectral bands the first with periods between 280 and 450 days and the second with periods between 120 and 280 days for the first band the average of the periods taken over the whole basin is 370 days in the second band a signal of period between 6 and 7 months is evident also throughout the basin the zonally averaged zonal wavelengths associated with the first band are in the range of 400 4600 km between 50 and 5 n and for the second band are in the range 270 2500 km between 45 and 5 n longer wavelengths are found close to the southern boundaries shorter wavelengths are found in the northern portion of the basin comparison with results from numerical models suggests that the baroclinic waves observed at midlatitudes are generated at the eastern boundary by fluctuations of the wind stress curl waves observed south of 20 n support the hypothesis of direct wind forcing

a comparison of surface eddy kinetic energy and reynolds stresses in the gulf stream and the kuroshio current systems from merged topex poseidon and ers 1 2 altimetric data analyses of surface eddy kinetic energy eke inferred from 5 years of merged topex poseidon and ers 1 2 altimetric data are presented in the gulf stream gs and the kuroshio ks current systems focusing on anisotropy and eke seasonal interannual and long term variations as well as reynolds stresses for both gs and ks a descriptive analysis of the eke field shows that it is anisotropic along the path of the currents and assesses the close relationship between the spatial distribution of eke high levels and bottom topography a striking ocean feature is found in the gs shaped as a zonal double blade structure in the eke field centered at 37 n 71 5 w that likely corresponds to a regular and permanent lateral displacement of the mean path of the current at this geographical location maps of eke seasonal means for years 1993 1996 and 1997 provide a detailed description of the surface variability meanders pinched off eddies etc and show strong interannual variations in the ks eke monthly mean changes in the ks reveal a well marked seasonal cycle during the first 3 years 1993 1995 with eke peaking in july august this is followed by a constant increase of its level from the beginning of year 1996 till the beginning of 1997 during this increase the zonal velocity variance u 2 is up to 30 higher than its meridional counterpart suggesting a zonal acceleration of the eastward flow eke seasonal changes are also found in the ks current 30 35 n 130 140 e and also show a regular annual cycle during the first 3 years which precedes by 2 months the eke seasonal cycle in the ks extension maximum in may june the maximum in eke in both regions precedes by 2 months the maximum surface transport found by qiu et al 1991 and zlotnicki 1991 occurring in july and late september respectively no such annual cycle is found in the gs region during the first 3 years year 1996 is anomalous in both current systems with mean eke level that increases by more than 20 compared to the other years also eke monthly mean changes in the ks reveal a well marked positive tendency in the eastern part of the current of more than 300 cm2 s 2 yr 1 and a negative tendency both in its eastern part and in the ks current this feature is absent from the gs at last eddy mean flow interaction is presented both the spatial averaging of turbulent quantities and the relative contribution of the different terms of the horizontal momentum fluxes are discussed a tentative explanation is given for the anomalously large u 2 at the end of 1996 in the ks extension

wind influence on the mesoscale activity along the gulf stream and the north atlantic currents two independent data sets are used to diagnose the wind effect on the mesoscale activity in the north atlantic ocean the oceanic surface variability is described with topex poseidon sea surface height measurements from october 1992 to september 1997 spatial extensions and temporal variations of high mesoscale activity are compared with the zonal and meridional components of the ers 1 wind stress the ekman pumping and the zonal sverdrupian velocity regions with high mesoscale surface variability seem to be correlated to regions with eastward sverdrupian velocities when the sverdrupian velocity is eastward and increases with time the mesoscale activity is intensified indicating a growth of instability rates theoretical and numerical results based on the interplay of barotropic eastward sverdrup flows and westward propagation of long rossby waves suggest that the wind controls western regions where baroclinic instability is favored interactions between the eddy field and the mean circulation are therefore analyzed to try to extract the instability mechanism responsible for the growth of the mesoscale activity along the gulf stream and the north atlantic current our results seem to suggest that the seasonal changes of mesoscale activity associated with eastward currents are linked to seasonal changes of the eastward sverdrupian velocity

tio2nanoparticle trails in garnet implications of inclusion pressure induced microcracks and spontaneous metamorphic reaction healing during exhumation a new mechanism of cleaving healing of garnet in metamorphic rocks during exhumation is reported almandine garnet with submicron multiple phase inclusions characteristic of the grail reaction garnet rutile kyanite ilmenite low quartz was found by analytical electron microscopy to have non epitaxial rutile nanoparticles distributed along internal 110 microcrack trails at the acute corner of submicron multiple phase inclusions defined by the intersecting 110 and 011 mould surfaces such garnet microcracks were formed during lithostatic decompression due to a relatively high compressibility of quartz in the inclusion pockets and stress concentration at the acute corner spontaneous healing with accompanied formation of non epitaxial rutile nanoparticles was activated predominantly via the grail reaction due to high surface tension at the tip of microcracks and to a lesser extent decreasing lithostatic pressure or increasing inclusion pressure upon exhumation this new mechanism of microcracking and healing involves stress build up fracture propagation mineral reaction transport of elements to the reaction site and lowering of reaction boundaries by capillarity effect all under the influence of thermodynamic and kinetic factors at the submicron scale thus tio2 nanoparticle trails in garnet provide additional information on the p t path and may shed light on exhumation rates mechanisms and metamorphic reactions processes careful scrutiny of host minerals on the submicron scale is required to tell whether there are other metamorphic reaction facilitated healing processes being overlooked by inappropriate techniques or being obliterated by the predominant healing processes of fluid infiltration and resorption zoning

distribution of silicoflagellates in plankton and core top samples from the gulf of california plankton and surface sediment samples from the gulf of california were examined to determine the present geographic distribution of silicoflagellate species in this area variations in the species composition of the silicoflagellate assemblage were found to be related to water mass distributions eight species were identified in these samples octactis pulchra is associated with high levels of primary productivity in the surface waters and is found in greatest abundance in the central gulf of california dictyocha messanensis dominates the silicoflagellate assemblage in stations outside the gulf of california and increases in relative abundance with decreasing amounts of octactis pulchra dictyocha calida dictyocha sp a and dictyocha sp b are associated with equatorial waters and have the highest relative abundance near the mouth of the gulf dictyocha epiodon and distephanus speculum are associated with cold california current water and dictyocha epiodon is present in minor abundance in gulf samples dictyocha sp 2 has a patchy distribution with low relative abundance

crystallographic orientations of olivine inclusions in diamonds abstract in this work we report for the first time the crystallographic orientations of olivine inclusions trapped in diamonds from the kaapvaal craton south africa determined by single crystal x ray diffraction and analyze them together with all available data in the literature the overall data set indicates no preferred orientation of the olivine inclusions with respect to their diamond hosts however diamonds containing multiple olivine inclusions sometimes show clusters of olivines with the same orientation in the same diamond host we conclude that such clusters can only be interpreted as the remnants of single olivine crystals pre dating the growth of the host diamonds

millennial variability and long term changes of the diatom production in the eastern equatorial pacific during the last glacial cycle 1 the modern eastern equatorial pacific eep is a major natural source for atmospheric carbon dioxide and is thought to be connected to high latitude ocean dynamics by oceanic teleconnections on glacial interglacial timescales a wealth of sedimentary records aiming at reconstructing last quaternary changes in primary productivity and nutrient utilization have been devoted to understanding those linkages between the eep and other distant oceanic areas most of these records are however clustered in the pelagic eep cold tongue with comparatively little attention devoted to coastal areas here we present downcore measurements of the composition and concentration of the diatom assemblage together with opal biogenic silica concentration at site md02 2529 recovered in the coastal panama basin piston core md02 2529 collected in an area affected by a multitude of processes provides evidence for strong variations in diatom production at the millennial timescale during the last glacial cycle the maxima in total diatom concentration occurred during the early marine isotopic stage mis 4 as well as during the mis 4 3 transition and mis 3 rapid changes in diatom concentrations during the mis 3 mimics bond cycles as independently recorded by the sea surface salinity estimation derived from planktonic foraminifera from the same core such patterns indicate a clear linkage between diatom production in the coastal eep and rapid climate changes in the high latitude north atlantic in parallel the long term succession of the diatom community from coastal diatoms predominantly thriving during mis 5 and 4 toward pelagic diatoms dominant during mis 3 and 2 points to a long term change in the surface hydrology during heinrich events diatoms strongly reduced their production probably because of enhanced stratification in the upper water column after the last glacial maximum diatom production and valve preservation strongly decreased in response to the advection of nutrient depleted h2sio4 warmer water masses our high resolution record highlights how regional climatic processes can modulate rapid changes in siliceous primary production as triggered by wind induced local upwelling indicating that millennial climatic variability can overtake other prominent hydrological processes such as those related to silicic acid leakage

dynamics of mineral crystallization from precipitated slab derived fluid phase first in situ synchrotron x ray measurements precipitation of daughter minerals we performed for the first time a single crystal x ray diffraction experiment by synchrotron radiation at diamond light source in combination with electron probe microanalyses this measurement allowed the unique identification of each mineral phase and reciprocal orientations we demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals such information is discussed in relation to the physico chemical aspects of nucleation and growth shedding light on the mode of mineral crystallization from a fluid phase trapped at supercritical conditions

development of the california current during the past 12 000 yr based on diatoms and silicoflagellates detailed diatom and silicoflagellates records in three cores from the offshore region of southern oregon to central california reveal the evolution of the northern part of the california current during the past 12 000 yr the early holocene prior to 9 ka was characterizedbyrelativelywarmseasurfacetemperatures sst owingtoenhancednortherlyflowofthesubtropicalwaterscomparable tothemoderndavidsoncurrent progressivestrengtheningof thenorthpacifichighleadtointensificationofthesouthwardflowofthe california current at 8 ka resulting in increased coastal upwelling and relatively cooler sst which persisted until 5 ka reduced southward flow of the california current between 4 8 ka and 3 6 ka may have been responsible for a period of decreased upwelling modern seasonal oceanographic cycles as evidenced by increased spring early summer coastal upwelling and warming of early fall sst evolved between 3 5 and 3 2 ka widespread occurrence of paleoceanographic and paleoclimatic change between 3 5 3 0 ka along the eastern margins of the north pacific was likely a response to increasing enso variability in the tropical pacific published by elsevier b v

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

eddy variability in the kuroshio extension as revealed by geosat altimetry energy propagation away from the jet reynolds stress and seasonal cycle abstract altimetric sea level data around the kuroshio extension collected during the first year of the geosat exact repeat mission erm starting in november 1986 have been analyzed for energy propagation away from the jet the reynolds stress pattern and the seasonal cycle of the eddy field space time diagrams and wavenumber frequency spectra are employed to discern the dominant direction of phase propagation revealing westward and inward phase propagation towards the jet i e energy propagation away from the jet which is consistent with the notion that the widespread eddy variability from the jet is the result of transient rossby wave response to forcing provided by growing pulsating and decaying meanders of the jet it can be shown that any theory based on the linear instability cannot normally account for the energy propagation because any linear instability that is wavelike away from the jet is by necessity not the fastest growing linear instability rather a nonlinear instability mec

evidence for an additional heinrich event between h5 and h6 in the labrador sea 1 an additional heinrich ice rafting event is identified between heinrich events 5 and 6 in eight cores from the labrador sea and the northwest atlantic ocean it is characterized by sediment rich in detrital carbonate 40 caco3 with high concentration of floating dropstones high coarse fraction 150 m content and has a sharp contact with the underlying but grades into the overlying hemipelagic sediment it also shows lighter 18onpl values indicating freshening due to iceberg rafting and or meltwater discharge this event is correlated with dansgaard oeschger event 14 and interpreted as an additional heinrich event h5a the thickness of h5a in the labrador sea reaches up to 220 cm this additional heinrich event has also been reported in cores ps2644 and so82 5 from the northern north atlantic with the recognition of h5a the temporal spacing between heinrich events 1 to 6 becomes more uniform 7 ka

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

co existing fluid and silicate inclusions in mantle diamond we document the compositions of co existing silicate macro inclusions and fluid micro inclusions in the fibrous coats of eight coated diamonds from the panda kimberlite canada the mineral inclusions in the diamond coats come from either the peridotite suite cr pyrope orthopyroxene olivine and cr diopside or the eclogite suite omphacite therefore fibrous diamonds grow in the same paragenetic environments as octahedral diamonds the inclusions document a more fertile source composition lower mg and higher cao than for equivalent phases in octahedral diamonds from panda and worldwide however moderate to high cr2o3 contents in garnet and clinopyroxene inclusions suggest that this apparent fertility is due to a secondary process geothermometry of the silicate inclusions yields low equilibration temperatures of 930 to 1010 c the co existing fluid micro inclusions are dominated by h2o carbonate and kcl fluid inclusions in both the peridotitic and eclogitic samples fall along linear arrays between fe ca mg carbonate and kcl inclusions in the one eclogitic sample also contain quartz we suggest that the diamonds have trapped both metasomatised minerals and the metasomatic fluid and so provide a snap shot of a metasomatic event in the mantle

diatoms in the gulf of california seasonal flux patterns and the sediment record for the last 15 000 years flux and taxonomic composition of the diatom assemblage was determined for biweekly sediment traps in the central gulf of california over a 2 year period fluxes and relative abundance of taxa are not significantly different in traps from the eastern side of the guaymas basin and the western side of the carmen basin indicating that patterns of diatom production are uniform across the central gulf at all seasons of the year the annual maximum in diatom flux occurred during the winter season of both years either as a sustained event over many weeks 1990 or as a series of short blooms 1991 1992 of the most abundant taxa only hyalochaete chaetoceros species showed a clear seasonal cycle with a flux maximum in the spring of both years factor analysis defines five assemblages representing 1 summer and fall conditions of surface stratification and nutrient limitation 2 winter bloom triggered by onset of strong northwesterly winds 3 late spring to summer production probably related to sporadic events during periods of weak southeasterly winds 4 spring 1991 inferred to reflect the distal edge of a coastal upwelling phase 5 lateral advection of resuspended sediments from the continental shelf possibly resulting from trapped coastal waves during summer hurricanes and from storms during the 1991 1992 el nino southern oscillation enso the diatom data support the inference that subtropical pacific water penetrates deeper into the gulf during enso events in order to compare the sediment trap record to a sediment core a second factor analysis was done using only the taxa which are preserved in the sediment and omitting the most abundant taxa which showed little downcore variation this produces five factors representing 1 summer fall low production 2 early winter bloom 3 late winter spring upwelling 4 enso conditions and 5 a late spring summer assemblage of uncertain significance variation of species characterisic of each factor was examined in piston core atlantis ii 125 8 56jpc taken from the oxygen minimum zone in guaymas basin correlation to nearby deep sea drilling project hole 480 indicates that the core penetrates to about 15 ka with laminated sediments in the holocene 0 10 ka and late deglacial 11 13 ka and massive nonlaminated sediments around younger dryas time 10 11 ka and before 13 ka downcore variations in the diatom assemblage do not correspond directly to presence of laminations implying that the processes controlling bottom water oxygen content are not determined by conditions of surface water production presence of calcareous nannofossils downcore correlates inversely with two diatom assemblages enso and winter bloom indicators and not with occurrence of laminations suggesting that occurrence of calcareous nannofossils in the sediment is at least partly a function of surface water production prior to 12 ka production was lower than at present during all seasons implying weaker winds throughout the year subtropical waters extended to the midgulf as they do today during enso events between 11 and 12 ka conditions were similar to those of the present with relatively high winter and spring production resulting from northwesterly winds enso events were still common although less so than during the preceding period younger dryas time was one of transition with intermediate conditions a slackening of winter spring northwesterly winds and reduction of total annual production and increased occurrence of enso conditions in the early to middle holocene winter northwesterlies increased to a maximum resulting in very high production but apparently did not persist into spring subtropical waters mostly disappeared from the gulf in the late holocene northwesterly winds have supported high production during both winter and spring seasons

the pressure path of solid inclusions in minerals the retention of coesite inclusions during uplift abstract an inclusion model allows calculation of the stresses in and around minerals included in other minerals during changes in pressure and temperature the equations are applied to illustrate cooling and uplift histories of quarzo feldspathic rocks from 500 c and various pressures to ambient conditions even in the absence of pore fluid pressure microfractures may open at external pressures of 200 400 mpa and temperatures of 200 400 c due to differential volume changes of the constituent minerals coesite included in garnet cannot have formed during progressive metamorphism from quartz at lithostatic pressures below the coesite stability field because of differential volume changes coesite inclusions are captured by their host minerals at ultra high pressures and they persist to lower pressures because of the large volume increase occurring at the coesite to quartz transition the pi t path followed by the sio2 inclusion traces the boundary between the stability fields of coesite and quartz until radial fractures develop in the host at low external pressure

bathymetric influences upon the character of north pacific fronts 1976 1980 thermal fronts in the north pacific from june 1976 to may 1980 have been mapped at the 300 m level by using temperature data obtained in the region 30 45 n 160 e 160w in the transpac xbt volunteer observing ship program the origins of the paths of the major frontal bands in the study region i e the kuroshio extension the subarctic fronts and the subtropical front appear to be related to the principal bathymetric features of the western mid latitude north pacific i e the shatsky rise the emperor seamount chain and the hess rise in the long term mean the kuroshio extension front at 35 n was observed to have bifurcated at the shatsky rise near 160 e into two bands one band continued northeast along the shatsky rise to 42 n to become the north subarctic front the other band continued zonally eastward where it encountered the emperor seamounts near 36 n 170 e and trifurcated into bands which tracked through passages between the seamounts near 37 n 34 n and 32 n respectively downstream the most northern of these three bands became the south subarctic front near 39 n the middle band continued as the kuroshio extension front at 35 n and the most southern band became the subtropical front near 32 n the middle band tracked north of the hess rise while the most southern band tracked south of the hess rise a near meridional frontal band linked the north and south subarctic fronts in the emperor seamount region near 170 e in the annual mean and individual seasonal mean maps the essential character of topographic influence of the long term mean was observed however the individual frontal bands varied seasonally about the long term mean by 2 of latitude also all four major frontal bands were not always observed and intermittent linkages and additional filaments also occurred

silicic acid biogeochemistry in the gulf of california insights from sedimentary si isotopes reflects transient iron limitation our new d 30 si record from the guaymas basin shows dramatic variations at millennial timescales low d 30 si values synchronous with heinrich events are interpreted as resulting from the decline in si oh 4 utilization at times of decreased upwelling strength while nearly complete si oh 4 utilization was observed at times of invigorated upwelling and increased opal burial during the holocene the bolling allerod and the last glacial period we attribute the complete utilization of si oh 4 to the occurrence of transient fe limitation at these times our study highlights the importance of fe limitation on si and c cycling in coastal upwelling regions and suggests that upwelling dynamics in combination with fe availability have the potential to modulate marine si distribution and opal burial even at short timescales citation pichevin l r s ganeshram b c reynolds f prahl t f pedersen r thunell and e l mcclymont 2012 silicic acid biogeochemistry in the gulf of california insights from sedimentary si isotopes paleoceanography 27 pa2201

the paleoclimatic response of the southern californian margin to the rapid climate change of the last 60 ka a regional overview abstract high resolution planktonic foraminiferal census and stable isotope data from a core transect odp site 1017 893 and 1014 demonstrate remarkable similarities along the southern california margin during the last glacial 60 10 ka bp modern analog technique and 18 o derived sea surface temperatures sst demonstrate sst shifts were regionally expressed supporting the hypothesis that the relative strength of local surface ocean currents affected the advection of subpolar and subtropical water into the region divergent alkenone sst records suggest the flux of planktonic organisms shifted seasonally during the last glacial in response to changing environmental conditions when considered as seasonal sst reconstructions summer oligotrophic surface ocean conditions appear to have a muted response to orbital and millennial scale climate change compared to the surface ocean during high nutrient winter conditions

origin of rutile needles in star garnet and implications for interpretation of inclusion textures in ultrahigh pressure metamorphic rocks the asterism effect of star garnet has been attributed to the oriented distribution of needle like rutile inclusions rutile needles occur in garnet from a wide range of metamorphic settings and rock bulk compositions and their origin has been ascribed to different mechanisms such as exsolution and used to interpret petrological and tectonic processes results from an optical and transmission electron microscopy of idaho star garnet indicate a co precipitation origin it was found that rutile needles are predominantly oriented along the rt grt and rt grt directions following multiple crystallographic orientation relationships cors i e cor 1 2 2 3 4 and 5 in 6 ray star garnet and are oriented solely along the rt grt directions following exclusively cor 2 in 4 ray star garnet the sole presence of cor 2 grt needles in the common 4 ray star garnet in contrast to the presence of both grt and grt needles with multiple cors in the rare 6 ray star garnet suggests that the cor 2 grt needle probably is the energetically most favoured variant as is also supported by the coincidence site lattice considerations the unique crystallography controlled microstructures of 4 ray star garnet including the cloudy domains behind the 111 grt or 100 grt fronts with abundant inclusions of rutile needle rutile compound needle and multiple phase inclusion as well as the clear domains behind the 110 grt fronts with only a few above inclusions concentrated exclusively within the linear grt oriented continuous tube like domains further suggest that the cor 2 grt needles in 4 ray star garnet most likely have a growth in origin co precipitating with garnet at its growth fronts close to thermodynamic equilibrium conditions the 6 ray star garnet on the other hand most likely formed under far from equilibrium conditions thereby yielding a maximum of 99 crystallographic variants of rutile needles with multiple cors in a single crystal in the light of these findings along with the common occurrences of the sole cor in many inclusion host systems owing to the requirement to minimize the energy barrier in an exsolution process the presence of both rt grt and rt grt needles with multiple cors in garnet of sulu eclogite and erzegebirge quartzofeldspathic rock would therefore cast doubt on the assertion of an exsolution origin of rutile needles in garnet from these ultrahigh pressure rocks