challenges in reservoir characterization geohorizons from a summary of the state of the art and current trends within reservoir characterization practice and research this paper suggests and discusses new avenues and focal points for the future despite today s high activity level and the many recent apparent advances within reservoir characterization practice and technology the province average recovery factors have not increased significantly production forecasts are still notoriously in error and the mainstream day to day geoscience reservoir engineering approach to modeling mapping gridding visualizing and forecasting the behavior of reservoirs in a typical oil company has not changed noticeably during the last five years even if the large and easy reservoirs have been found and developed in many basins evidence suggests that researchers are not outsmarting nature to give up more of its oil now than she did before even recently predicted production profiles turn out to be surprisingly erroneous so what can be done what are the major challenges in reservoir characterization research which are the areas with the greatest potential payoff suggestions for future research activities are scattered throughout this paper but it is believed than in order to outsmart nature you have to know her hence detailed reservoir tomography by some known e g seismic or as yet undiscovered technology whichmore yields images of all faults the correct structure map and geological architectural flow unit and barrier details down to 1 m resolution is on top of the reservoir characterization research wish list less

lead isotope study of zn pb ore deposits associated with the basque cantabrian basin and paleozoic basement northern spain a total of forty three galena samples from syngenetic and epigenetic pb zn mineralizations emplaced in the lower cretaceous basque cantabrian basin and paleozoic basement of the cinco villas massif in the western pyrenees have been analyzed for pb isotopic composition galena from sedex mineralizations hosted in carboniferous clastic rocks in the cinco villas massif display an homogeneous lead isotopic signature 206pb 2044pb 18 43 207pb 204pb 15 66 208pb 204pb 38 69 suggesting a single lead reservoir these values are slightly more radiogenic than lead from other european hercynian deposits possibly reflecting the influence of a more evolved upper crustal source underlying paleozoic sediments are proposed as lead source for the cinco villas massif ores analyses from twenty six galena samples from the four strata bound ore districts hosted in mesozoic rocks reveal the existence of two populations regarding their lead isotopic composition galena from the western santander districts e g reocin is characterized by more radiogenic isotope values 206pb 204pb 18 74 207pb 204pb 15 67 208pb 204pb 38 73 than those from the central and eastern districts troya legorreta central and western vizcaya 206pb 204pb 18 59 207pb 204pb 15 66 208pb 204pb 38 73 in all districts the most likely source for these mineralizations was the thick sequence of lower cretaceous clastic sediments the existence of two separate lead isotopic populations could be the result of regional difference in the composition of the basement rocks and the clastic sediments derived of it or different evolution histories in both sub basins isotopic ratios indicate an increase in crustal influence as the age of the ores decreases

mid latitude mesoscale variability neither homogeneous quasi geostrophic turbulence nor the effect of eddies on the interior ocean circulation remains the major focus of mesoscale research as was the case for much of the preceding 20 years following identification of the phenomena concentration on basin wide geographical exploration of eddy properties was rather well established by 1978 over the last few years a promising zero order description and rationalization of the mesoscale field has become available that is eddy energy is largest near strong flows intensification not only in western boundary currents but along their mid latitude open ocean extension roughly as indicated by gyre scale numerical models where eddies develop as a result of instability processes in the mid latitude jet and recirculation regimes and then propagate into the ocean interior our point of view is that mesoscale eddies drive recirculations but do not play a crucial role in the dynamics of the mean flow in the ocean interior in the north atlantic for example the idea is that the downstream increase in transport of the gulf stream is eddy driven but not the flow through the florida straits in addition the fluctuating response to forcing by variable winds may now be widely perceived as forming the horizontally homogeneous background signal in subtropical gyres the time dependent field associated with thermohaline flows at abyssal depths also has a special character

statistical analyses of eddies in the western mediterranean sea based on synthetic aperture radar imagery abstract we analysed 7188 sentinel 1a synthetic aperture radar sar images acquired in a 3 year period between october 2014 and september 2017 in the western mediterranean sea and found imprints of about 14 300 oceanic eddies with diameters ranging from 0 4 km to 160 1 km those eddies manifest on the sar imagery either through the accumulation of surfactants or through wave current interaction and considering the favourable wind speed ranges for both mechanisms we performed statistical analyses to gain insight into the eddies spatio temporal distribution their typical sizes and shapes and into the predominant mechanisms that are responsible for their formation the vast majority of the detected eddies is elliptical with a tendency for only large mesoscale eddies towards a circular shape we found no general influence of the wind on the eddies orientation although mesoscale eddies tend to orient into the main current direction in each subregion submesoscale eddies do not show such tendency submesoscale eddies in the western mediterranean sea are predominantly cyclonic 90 and with increasing eddy diameter there is a transition from cyclonic to anticyclonic sense of rotation in general we found highest densities of submesoscale eddies in autumn when the biological activity is still high and when mean regional winds are already strong but variable in addition instabilities of thermal fronts during summer and autumn and instabilities of the main and secondary currents influence the formation of submesoscale eddies some of our results confirm those previously obtained for other regions

on the intrinsic shape of oceanic eddies derived from satellite altimetry abstract the fundamental issue of mean eddy shape at the sea surface has been simplified as axially symmetric for a long time this assumption is worth of a reexamination following significant advances in precise tracking of individual eddies thanks to the recent availability of merged altimeter data with a grid resolution of 1 4 1 4 and a time interval of one day based on an orientationally aligned average of the effective boundaries of nearly 2 6 million individual eddies available to date a characteristic shape of a standard eddy has been derived which is found to be a very good approximation to a mathematical ellipsoid with a semimajor axis of a 87 0 km and a semiminor axis of b 54 0 km the oval nature of oceanic eddies appears to be universal in a climatological sense but the best fit ellipse varies with space and time statistically the eddy ellipse has two preferred angles for its major axis a primary angle of 104 284 nearly north south and a secondary angle of 171 351 nearly east west the intrinsic geometric asymmetry in eddy shape and orientation is believed to be one of the fundamental reasons behind the previously observed geophysical anisotropy in eddy properties future integrated analysis in an eddy centric coordinate system with an ellipse geometry may open a new window into nonlinear mesoscale oceanography in terms of eddy kinetics and eddy dynamics

plankton distribution within a young cyclonic eddy off south western madagascar abstract mesoscale eddies are major features in ocean dynamics that significantly influence ocean production depending on their polarity life stage location and time of formation eddies in the south west indian ocean have been the focus of many studies especially in the mozambique channel where southward moving cyclonic and anticyclonic eddies feed into the agulhas current however eddies formed south of madagascar that move westwards towards the coast of south africa have been much less studied despite their significant contribution to the agulhas current this study aims to understand how the plankton communities i e pico nano phyto microzoo and mesozooplankton are distributed in a cyclonic eddy generated off southern madagascar we also investigate a possible link between the madagascar shelf and the eddy temperature salinity fluorescence and plankton abundance were measured at 25 stations spaced at 18 5 km intervals across a young 1 month old cyclonic eddy and at three locations on the madagascar shelf in july 2013 a patch of enhanced chlorophyll a concentration was found at four stations in the eddy homogeneously distributed vertically in the upper mixed layer and characterised by a higher proportion of diatoms compared to the other stations abundances of picoplankton nanoplankton ciliates and dinoflagellates were very similar within and outside the eddy zooplankton followed a contrasting pattern with higher biomass at four stations just to the west of this high diatom patch the mesozooplankton composition at these four stations revealed greater species similarities with the madagascar shelf than with the other stations suggesting a link between the shelf and the western side of the eddy the periphery of the eddy seems to have been primarily influenced by a strong geostrophic current propagating from the southern shelf of madagascar which then wrapped itself around the eddy this filament may be the source of the high zooplankton biomass in the eddy periphery which would account for the similarities in zooplankton community composition between the eddy periphery and the shelf

regional variations in the influence of mesoscale eddies on near surface chlorophyll eddies can influence biogeochemical cycles through a variety of mechanisms including the excitation of vertical velocities and the horizontal advection of nutrients and ecosystems both around the eddy periphery by rotational currents and by the trapping of fluid and subsequent transport by the eddy in this study we present an analysis of the influence of mesoscale ocean eddies on near surface chlorophyll chl estimated from satellite measurements of ocean color the influences of horizontal advection trapping and upwelling downwelling on chl are analyzed in an eddy centric frame of reference by collocating satellite observations to eddy interiors as defined by their sea surface height signatures the influence of mesoscale eddies on chl varies regionally in most boundary current regions cyclonic eddies exhibit positive chl anomalies and anticyclonic eddies contain negative chl anomalies in the interior of the south indian ocean however the opposite occurs the various mechanisms by which eddies can influence phytoplankton communities are summarized and regions where the observed chl response to eddies is consistent with one or more of the mechanisms are discussed this study does not attempt to link the observed regional variability definitively to any particular mechanism but provides a global overview of how eddies influence chl anomalies

lead isotope behaviour in a polyphased pb zn ore deposit les malines cevennes france les malines mine cevennes france provides an example of pb zn ore bodies that underwent a polyphased evolution on the pb pb diagram experimental points of the les malines ore types always plot in the central part of the field defined for the cevennes metallogenic province this homogeneity the similarities with the pb isotopic compositions of the surrounding rocks and the comparison with pb isotopes evolution of whole rocks and minerals of the neighbouring continental lands which emerged during triassic and liassic times rule out the participation of extraneous pb during the successive concentration stages and agree with an initial metal stock transformed and mobilized in a pb closed system hercynian k feldspars are the main source of the pb preconcentrated during triassic times most of the cevennes pb zn ore bodies could derive from this triassic metal stock nevertheless local pb isotopic anomalies suggest hydrothermal sources for some pb zn ore bodies located along the cevennes fault

the ocean mesoscale regime of the reduced gravity quasigeostrophic model abstracta statistical equilibrium geostrophic turbulence regime of the stochastically forced one layer reduced gravity quasigeostrophic model is identified in which the numerical solutions are

coherent mesoscale eddies in the north atlantic subtropical gyre 3 d structure and transport with application to the salinity maximum the mean vertical structure and transport properties of mesoscale eddies are investigated in the north atlantic subtropical gyre by combining historical records of argo temperature salinity profiles and satellite sea level anomaly data in the framework of the eddy tracking technique the study area is characterized by a low eddy kinetic energy and sea surface salinity maximum although eddies have a relatively weak signal at surface amplitudes around 3 7 cm the eddy composites reveal a clear deep signal that penetrates down to at least 1200 m depth the analysis also reveals that the vertical structure of the eddy composites is strongly affected by the background stratification the horizontal patterns of temperature salinity anomalies can be reconstructed by a linear combination of a monopole related to the elevation depression of the isopycnals in the eddy core and a dipole associated with the horizontal advection of the background gradient by the eddy rotation a common feature of all the eddy composites reconstructed is the phase coherence between the eddy temperature salinity and velocity anomalies in the upper 300 m layer resulting in the transient eddy transports of heat and salt as an application a box model of the near surface layer is used to estimate the role of mesoscale eddies in maintaining a quasi steady state distribution of salinity in the north atlantic subtropical salinity maximum the results show that mesoscale eddies are able to provide between 4 and 21 of the salt flux out of the area required to compensate for the local excess of evaporation over precipitation

characteristics of surface signatures of mediterranean water eddies in this work we obtain new results on the manifestation of meddies or of other deep eddies at the sea surface further developing the results by bashmachnikov and carton 2012 the quasi geostrophic equations are used to describe a near axisymmetric vortex in the upper ocean forced at its lower boundary by the isopycnal elevation of a moving meddy the solution thus obtained provides a better approximation of the characteristics of meddy surface signals the results show that in subtropics large meddies with dynamic radius rm 30 km are always seen at the sea surface with aviso altimetry that medium size meddies with rm 20 km may be seen at the sea surface only if they are sufficiently shallow and strong while small meddies with rm 10 km generally cannot be detected with the present accuracy of altimetry data the intensity of meddy surface signals decreases to the south with the decrease of the f n ratio the seasonal variation in intensity of the surface signal for northern meddies 45 n is on the order of 2 3 cm but for subtropical meddies 35 n it can be on the order of 5 10 cm the radii of meddy surface signals range from 1 to 2 times the radii of the corresponding meddies for most of the observed subtropical meddies the upper limit should be used numerical experiments show that surface signals of meddies translated with drift are efficiently dispersed by the radiation of rossby waves at the same time for meddies translated by a background current the surface signal does not show strong dissipation

a mesoscale eddy pair southwest of taiwan and its influence on deep circulation 1 a pair of mesoscale eddies namely an anticyclonic eddy ae and a cyclonic eddy ce generated southwest of taiwan was investigated using long term moored observations augmented with satellite and reanalysis data ae ce increased the upper ocean current to 100 cm s 50 cm s and generated temperature anomaly t up to 7 5 c 3 0 c the vertical structure of ae presented a phase difference between t and velocity with the core of t located south of the zero velocity line this phase difference induced a 28 5 12 0 tw 1 tw 1012 w westward eddy heat transport southwest of taiwan ae also presented strong nonlinearity in the upper ocean and yielded an annual mean volume transport of 0 86 0 15 sv energy analysis showed that both baroclinic and barotropic instabilities were important for the generation and growth of the eddy pair and contribution from wind work was relative small in the deep sea ae ce intensified the deep currents and generated large positive negative t the deep and surface currents flowed in opposite directions during the eddy events which is consistent with the interpretation that the eddy pair is dominated by the first baroclinic mode the observed deep penetrating eddy pair could greatly influence the deep circulation of the northeastern south china sea

australia s southern margin a product of oblique extension abstract recently developed detachment models of continental margin formation interpret the southern margin of australia to have formed when the lower plate australian margin was pulled out from beneath the upper plate antarctic margin data now available and summarised in this paper point very strongly to a generally nw se direction of initial continental extension for the southern margin in contrast to the widely held picture of simple n s rifting the evidence for this extension direction comes from the analysis of deep seismic data acquired by the bureau of mineral resources in 1986 in the central great australian bight gab the gravity field of the gab seismic and magnetic basement structures in the eyre sub basin polda trough ceduna depocentre and duntroon basin and from the analysis of the magnetic seafloor spreading anomalies produced during the slow first phase of drifting between australia and antarctica further it is now believed that the formation of the southern margin of australia can be described in terms of three phases of continental extension el to e3 and two phases of drifting d1 and d2 in summary these phases were as follows 1 e1 approximately 300 km of late jurassic or older to early cretaceous nw se oriented extension in the gab with strike slip motion in the nascent otway basin and along the tasmanian margin 2 e2 120 km of early cretaceous nne ssw oriented extension which formed the basins of southeastern australia otway bass gippsland and which probably produced a structural overprinting in the gab basin 3 e3 d1 minor continental extension and the first 500 km of slow drift between australia and antarctica on an azimuth of 165 wrenching on the tasmanian margin 4 d2 2600 km of fast drifting between australia and antarctica on a n s azimuth

storm tracks in the southern hemisphere subtropical oceans ocean storm tracks have previously been associated with the midlatitude western boundary currents wbcs and the antarctic circumpolar current acc here we identify and examine large scale baroclinically unstable waves occurring within waveguides associated with potential density gradients in the subtropical regions of the southern hemisphere sh oceans where the trade winds and westerlies meet and at depths associated with mode water formation in contrast to the northern hemisphere subtropics the sh pathways are more extensive allowing large scale coherent disturbances to communicate information westward from the midlatitudes to the subtropics south pacific ocean and from the subtropics to the tropics indian ocean particular consideration is given to the subtropical south pacific ocean as this is a region where resonant interactions between large scale rossby waves and significant topographic features have been reported to occur using an ocean general circulation model and a simple potential energy transfer diagnostic we identify the relevant nonlinearly modified structures comparing their propagation characteristics to planetary rossby waves calculated using a shallow water model although at first appearance baroclinic disturbances resemble planetary rossby waves we show they are inherently nonlinear multiscale and are amplified where topography occurs the location of the disturbances coincides with regions of high variability in sea surface height observed in satellite altimetry and their speeds closely match the large scale coherent westward propagating structures described in the observational literature our study provides evidence that in addition to the midlatitude wbcs and the acc significant ocean storm tracks are also manifest in the sh subtropics

three dimensional baroclinic eddies in the ocean evolution propagation overall structures and angular models abstractthe evolution and dynamics of an initially gaussian baroclinic vortex embedded in a resting stratification environment are investigated with a three dimensional primitive equation model th

vertical structure of mesoscale eddies in the eastern south pacific ocean a composite analysis from altimetry and argo profiling floats 1 the mean vertical structure of mesoscale eddies in the peru chile current system is investigated by combining the historical records of argo float profiles and satellite altimetry data a composite average of 420 526 profiles acquired by argo floats that surfaced into cyclonic anticyclonic mesoscale eddies allowed constructing the mean three dimensional eddy structure of the eastern south pacific ocean key differences in their thermohaline vertical structure were revealed the core of cyclonic eddies ces is centered at 150 m depth within the 25 2 26 0 kg m 3 potential density layer corresponding to the thermocline in contrast the core of the anticyclonic eddies aes is located below the thermocline at 400 m depth impacting the 26 0 26 8 kg m 3 density layer this difference was attributed to the mechanisms involved in the eddy formation while intrathermocline ces would be formed by instabilities of the surface equatorward coastal currents the subthermocline aes are likely to be shed by the subsurface poleward peru chile undercurrent in the eddy core maximum temperature and salinity anomalies are of 1 c and 0 1 with positive negative values for aes ces this study also provides new insight into the potential impact of mesoscale eddies for the cross shore transport of heat and salt in the eastern south pacific considering only the fraction of the water column associated with the fluid trapped within the eddies each ce and ae has a typical volume anomaly flux of 0 1 sv and yields to a heat and salt transport anomaly of 1 3 1011 w and 3 8 103 kg s 1 respectively

impacts of mesoscale activity on the water masses and circulation in the coral sea the climatological vision of the circulation within the coral sea is today well established with the westward circulation of two main jets the north caledonian jet ncj and the north vanuatu jet nvj as a consequence of the separation of the south equatorial current sec on the islands of new caledonia vanuatu and fiji each jet has its own dynamic and transports different water masses across the coral sea the influence of mesoscale activity on mean flow and on water mass exchanges is not yet fully explored in this region of intense activity our study relies on the analysis of in situ satellite and numerical data indeed we first use in situ data from the bifurcation cruise and from an argo float jointly with satellite derived velocities to study the eddy influence on the coral sea dynamics we identify an anticyclonic eddy as participating in the transport of nvj like water masses into the theoretical pathway of ncj waters this transfer from the nvj to the ncj is confirmed over the long term by a lagrangian analysis in particular this numerical analysis shows that anticyclonic eddies can contribute up to 70 90 of the overall eddy transfer between those seemingly independent jets finally transports calculated using s adcp measurements 0 500 m show an eddy induced sensitivity that can reach up to 15 sv i e the order of the transport of the jets

the influence of nonlinear mesoscale eddies on near surface oceanic chlorophyll oceanic rossby waves have been widely invoked as a mechanism for large scale variability of chlorophyll chl observed from satellites high resolution satellite altimeter measurements have recently revealed that sea surface height ssh features previously interpreted as linear rossby waves are nonlinear mesoscale coherent structures referred to here as eddies we analyze 10 years of measurements of these ssh fields and concurrent satellite measurements of upper ocean chl to show that these eddies exert a strong influence on the chl field thus requiring reassessment of the mechanism for the observed covariability of ssh and chl on time scales longer than 2 to 3 weeks the dominant mechanism is shown to be eddy induced horizontal advection of chl by the rotational velocities of the eddies

southern ocean eddy phenomenology mesoscale eddies are ubiquitous features in the southern ocean yet their phenomenology is not well quantified to tackle this task we use satellite observations of sea level anomalies and sea surface temperature sst as well as in situ temperature and salinity measurements from profiling floats over the period 1997 2010 we identified over a million mesoscale eddy instances and were able to track about 105 of them over 1 month or more the antarctic circumpolar current acc the boundary current systems and the regions where they interact are hot spots of eddy presence representing also the birth places and graveyards of most eddies these hot spots contrast strongly to areas shallower than about 2000 m where mesoscale eddies are essentially absent likely due to topographical steering anticyclones tend to dominate the southern subtropical gyres and cyclones the northern flank of the acc major causes of regional polarity dominance are larger formation numbers and lifespans with a contribution of differential propagation pathways of long lived eddies areas of dominance of one polarity are generally congruent with the same polarity being longer lived bigger of larger amplitude and more intense eddies extend down to at least 2000 m in the acc eddies show near surface temperature and salinity maxima whereas eddies in the subtropical areas generally have deeper anomaly maxima presumably inherited from their origin in the boundary currents the temperature and salinity signatures of the average eddy suggest that their tracer anomalies are a result of both trapping in the eddy core and stirring

tracer transport in cold core rings pinched off from the kuroshio extension in an eddy resolving ocean general circulation model 1 using an eddy resolving ocean general circulation model we examine the cold core rings pinched off from the kuroshio extension ke focusing on their tracer transport the origin of the tracers in the rings and how they are trapped are directly investigated by releasing two passive tracers corresponding to the ke water and the water in the mixed water region mwr to the north of the ke the cold core rings carry the tracer in the mwr wrapped by the ke water from the surface to the bottom at the pinch off in and above the upper thermocline 26 4 these tracers are trapped in the ring and move along the ring until the rings rejoin the kuroshio even in the lower thermocline 26 4 27 2 a substantial part of the tracers moves along the ring while gradual leakage occurs vorticity balance in the rings is consistent with the passive tracer experiment indicating that water in the upper thermocline moves along the rings while the synchronous movement in and below the lower thermocline is severely contaminated by baroclinic rossby waves these direct estimations are compared with the indirect diagnoses using pv the ratio of drift velocity of ring to its tangential velocity nonlinear parameter and the largest closed contour of stream function in the comoving frame of the ring these indirect diagnoses are consistent with the direct estimation in the upper thermocline but are not good indicators below the lower thermocline the cause of their insufficient performance is discussed

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

quantifying eulerian eddy leakiness in an idealized model an idealized eddy resolving ocean basin closely resembling the north pacific ocean is simulated using mitgcm we identify rotationally coherent lagrangian vortices rclvs and sea surface height ssh eddies based on the lagrangian and eulerian framework respectively general statistical results show that rclvs have a much smaller coherent core than ssh eddies with the ratio of radius is about 0 5 rclvs are often enclosed by ssh anomaly contours but ssh eddy identification method fails to detect more than half of rclvs based on their locations two types of eddies are classified into three categories overlapping rclvs and ssh eddies nonoverlapping ssh eddies and nonoverlapping rclvs using lagrangian particles we examine the processes of leakage and intrusion around ssh eddies for overlapping ssh eddies over the lifetime the material coherent core only accounts for about 25 and about 50 of initial water leak from eddy interior the remaining 25 of water can still remain inside the boundary but only in the form of filaments outside the coherent core for nonoverlapping ssh eddies more water leakage about 60 occurs at a faster rate guided by the number and radius of ssh eddies fixed circles and moving circles are randomly selected to diagnose the material flux around these circles we find that the leakage and intrusion trends of moving circles are quite similar to that of nonoverlapping ssh eddies suggesting that the material coherence properties of nonoverlapping ssh eddies are not significantly different from random pieces of ocean with the same size

lead isotopic composition of hercynian granitic k feldspars constrains continental genesis lead isotope compositions have been determined in many k feldspars from granitic rocks emplaced during the variscan hercynian orogeny sensu lato around 300 myr in various parts of europe and the eastern us the ratios show a regular geographical pattern with contours arched around southern france and parallel to the atlantic coast of the us this distribution parallels predriftpalaeogeographical zones during the palaeozoic the lead isotope pattern of variscan granitic rocks is similar to that of some orogenic volcanic suites but is better explained by crustal melting than by an hercynian mantle crust material mixing the continental crust from these areas must be older than 3 000 myr large scale fluid circulation in the crust during orogenic processes apparently explains the observed geographical patterns of lead isotopes

pairwise surface drifter separation in the western pacific sector of the southern ocean the southern ocean plays a critical role in global climate yet the mixing properties of the circulation in this part of the ocean remain poorly understood here dispersion in the vicinity of the southern antarctic circumpolar current front one of the branches of the antarctic circumpolar current is studied using 10 pairs of surface drifters deployed systematically across the frontal jet and its flanks drifter pairs were deployed with an initial separation of 13 m and report their position every hour the separation of the pairs over 7 months in terms of their finite scale lyapunov exponents fsle dispersion and diffusivity is characterized and related to expected behavior from quasi geostrophic qg and surface quasi geostrophic sqg theories the fsle analysis reveals two submesoscale regimes with sqg like behavior at scales below 3 2 km and mixed qg sqg behavior at scales between 3 2 and 73 km the dispersion analysis however suggests qg like behavior for the smallest scales both dispersion and diffusivity appear isotropic for scales up to 500 km finally there is no clear indication of a cross jet variation of drifter dispersion

plumbotectonic evolution of the ossa morena zone iberian peninsula tracing the influence of mantle crust interaction in ore forming processes the ossa morena zone in the variscan belt of the iberian peninsula is characterized by a complex geotec tonic evolution it hosts a neoproterozoic paleozoic sequence that records the existence of two orogenic events cadomian and variscan separated by rift and stable platform stages middle cambrian to late devonian volcanogenic and sediment hosted massive sulfides skarns magmatic ni cu deposits synmetamorphic and intragranitic and perigranitic veins and replacement bodies are related to different magmatic hydrothermal systems ranging in age from 650 ma to about 250 ma the lead isotope signatures from 26 different mineral deposits show variable ratios of 206pb 204pb 17 49 18 44 207pb 204pb 15 47 15 67 and 208pb 204pb 37 37 38 78 that have low average values 9 7 but high values 38 3 as a whole the lead isotope data define an irregular cluster that plots around the stacey and kramers 1975 growth curve but clearly marks the existence of two main ore forming events during cadomian and variscan times the most radiogenic samples are from some minor zn pb stratiform sedimentary exhalative mineralization they are interpreted as having a dominantly crustal derivation 10 1 in which most of the lead was leached from a pre cadomian continental basement with a long crustal history this basement has strong geochemical affinities with the oldest rocks of the iberian terrane however most of the ore samples investigated plot below the stacey and kramers 1975 reference curve indicating polyphase but variable mixing of lead from upper crustal and mantle lead reservoirs at the terrane scale clear mixing lines between the two end member reser voirs are evident only in the oldest volcanic rock and sedimentary rock hosted massive sulfide deposits related to the cadomian late neoproterozoic early cambrian magmatic arc in the other deposit types lead isotopes have more restricted values the crustal lead is interpreted as having been derived from ancient crust 2 1 2 5 ga and the derived shales montemolin formation that predated the cadomian orogeny the mantle derived lead may have been derived from three different sources neoproterozoic tholeiitic orthoamphibolite syn cadomian calc alkaline andesite or calc alkaline metaluminous plutonic rocks intruded during the variscan orogeny the first two sources probably controlled the lead isotope signatures of the cadomian massive sulfide deposits and the variscan synmetamorphic veins the input of primitive lead is especially significant during variscan times 350 300 ma and is interpreted as having been related to the existence of a large primitive reservoir that controlled the variscan magmatic metallogenic and hydrothermal evolution of the ossa morena zone this primitive lead is recognized in most of the magmatic hydrothermal deposits including the typically crust derived w and pb bearing perigranitic hydrothermal systems likewise associated plutonic rocks have more primitive lead isotope signatures than their counterparts in other iberian terranes the lead isotope evolution of the region is consistent with recent geophysical data that suggest that a deep large mafic sill was intruded below the ossa morena zone during variscan times this sill was a likely key factor in the different pb isotope evolution of the ossa morena zone compared with the nearby iberian terranes and the entire western mediterranean province which are char acterized by lengthy crustal histories with very little input of primitive lead the extensive mantle crust inter action probably explains the wide variety and the unusual metallogenic features of the ossa morena zone

vertical structure of eddies and rossby waves and their effect on the atlantic meridional overturning circulation at 26 5 n the meridional overturning circulation moc at inline image in the atlantic has a standard deviation of 4 9 sv and contains large fluctuations at subannual periods the geostrophic component of the moc is believed to be influenced on subannual time scales by eddies and rossby waves to quantify this effect the vertical structure and surface characteristics of westward propagating signals are studied using altimetric data and full depth mooring measurements from the rapid array at inline image westward propagating features are observed in the western north atlantic in both data sets and have periods of 80 250 days in the first baroclinic mode these features are still observed by the rapid moorings 20 km offshore of the western boundary the western boundary also exhibits deep variability characterized by enhanced energy in higher baroclinic modes the effect of eddies and rossby waves on the geostrophic transport is quantified by representing their vertical structure with the first baroclinic mode in total 42 of the variance of the transbasin thermocline transport inferred from geostrophic calculations at inline image can be attributed to first mode variability which is associated with eddies and rossby waves at periods of 80 250 days the standard deviation of the transbasin thermocline transport due to eddies and rossby waves is estimated to be 2 6 sv

structural control and geological significance of the zn pb ores formed in the benasque pass area central pyrenees during the post late ordovician extensional event of the gondwana margin abstract the benasque pass area central pyrenees is located in the eastern part of the variscan lys caillaouas massif where cambro ordovician rocks of the hesperian massif crop out in the area several zn pb deposits are located in variscan structures lead isotopes indicate a late ordovician early devonian model age for the deposits in the region an unconformity between pre late ordovician and late ordovician rocks has been defined by several authors and has been identified in the study area the first structures observed in the benasque pass area consist of a pre variscan cleavage which only affects the pre late ordovician rocks in the study area the main structures correspond to two variscan generations i e w trending north verging folds which are associated with the main foliation s 1 d 1 ii e w trending upright folds and associated small south directed thrusts d 2 d 2 structures are the ones hosting the zinc lead ore in the benasque pass area d 1 and d 2 variscan structures have developed under low grade metamorphic conditions some faults observed in the north and the south of the study area may have alpine movement in the benasque pass area the strongly silicified and brecciated zinc lead ore is mainly developed in the d 1 short limb of the mina peak syncline within which s 1 foliation is intensely folded and cross thrust by d 2 structures taking into account their model age all these zinc lead deposits seem to be stratiform stratabound or filling open spaces in origin and related to the pre variscan extension described for the central pyrenees however the zinc lead ore is hosted in strongly silicified and brecciated variscan structures the 34 s isotopic composition of sulfides indicates that the metamorphism and deformation did not completely obliterate the original isotopic composition suggesting that sulfur in the benasque pass has mainly come from the reduction of marine sulfate extracted from the rocks of the metasedimentary sequence in the benasque pass area the lead isotope ratios are homogeneous and have a pre variscan model age which is also the age of the host rocks in the case of the benasque pass the deposits occurred in variscan structures making it impossible to recognize their original pre variscan characteristics indicated by lead isotopes model age the correlation between the pb isotope data for deposits from the benasque pass and aran valley also located in the central pyrenees and those for other deposits from the southern european gondwana is evident and the isotopic data set closely fits the two stage pb evolution model for sardinia terrane the coherence of the pb isotope trends in all the deposits suggests that pb was extracted at various times from sources with similar time averaged u pb th pb and th u values through a process of leaching of the basement rocks by large volumes of hydrothermal fluids in the case of the pyrenees central and eastern the lead and other metals present in the deposit were extracted by hydrothermal fluids from the upper crust rocks during the post late ordovician extensional event of the gondwana margin

40 ma of hydrothermal w mineralization during the variscan orogenic evolution of the french massif central revealed by u pb dating of wolframite we present u pb thermal ionization mass spectrometer tims ages of wolframite from several granite related hydrothermal w sn deposits in the french massif central fmc located in the internal zone of the variscan belt the studied wolframite samples are characterized by variable u and pb contents typically 10 ppm and show significant variations in their radiogenic pb isotopic compositions the obtained u pb ages define three distinct geochronological groups related to three contrasting geodynamic settings i visean to namurian mineralization 333 327 ma coeval with syn orogenic compression and emplacement of large peraluminous leucogranites ca 335 325 ma ii namurian to westphalian mineralization 317 315 ma synchronous with the onset of late orogenic extension and emplacement of syn tectonic granites ca 315 310 ma and iii stephanian to permian mineralization 298 274 ma formed during post orogenic extension contemporaneous with the permian volcanism in the entire variscan belt the youngest ages 276 274 ma likely reflect the reopening of the u pb isotopic system after wolframite crystallization and may correspond to late hydrothermal alteration e g ferberitization our results demonstrate that w sn mineralization in the fmc formed during at least three distinct hydrothermal events in different tectono metamorphic settings over a time range of 40 ma

picoplankton and nanoplankton composition on and around a seamount affected by an eddy dipole south of madagascar abstract picoplankton and nanoplankton community abundances were sampled on and around a seamount located on the madagascar ridge in november 2016 prochlorococcus synechococcus picoeukaryote and nanoplankton community abundances both on the seamount and in the immediate vicinity approximately 100 km surrounding it were analysed using flow cytometry the original aim of the study was to estimate whether or not the seamount had an effect on the picoplankton and nanoplankton community distribution however coupled altimetry and in situ ship data indicated that a dipole eddy was also sampled during this time which had a substantial effect on the results results reveal that picoeukaryotes contributed the most to carbon biomass within the anticyclone showing higher abundances in the stations situated within the southern slopes of the seamount which also fell within the anticyclone the southern slope of the seamount contained higher synechococcus prochlorococcus and picoeukaryote abundances whereas nanoplankton dominated in the cyclonic eddy species composition and abundance was significantly different on versus off the seamount driven by nanoplankton biomass these results indicate significantly high abundance above the slopes of the seamount driven by picoeukaryotes which seem to be amplified by the dipole presence the resulting variability in microbial abundance both on the southern slopes of the seamount as well as within the dipole has far reaching implications with regard to larger organism proliferation and carbon export during such events in this region

scales of lateral petrophysical heterogeneity in dolomite lithofacies as determined from outcrop analogs implications for 3 d reservoir modeling petrophysical data from dolomite outcrops of the mississippian madison formation at sheep canyon wyoming exhibit three scales of lateral variability in single rock fabric units these include a near random component nugget effect a short range structure and a long range cyclic trend hole effect the nugget effect is high and accounts for 31 39 and 48 50 of the variance in porosity and permeability respectively short range lateral variability is reflected by correlation lengths of 6 5 16 ft 2 5 5 m laterally long range periodicities are equivalent to approximately 10 of the petrophysical variance and have wavelengths of 31 and 140 ft 9 5 and 42 6 m for porosity and permeability 55 ft 16 8 m for log10 permeability respectively cross sectional and plan view petrophysical models and streamline simulations explore the effects of these scales of heterogeneity on fluid flow although short range variability accounts for most of the petrophysical heterogeneity the longer range trends can significantly affect fluid flow behavior results indicate that breakthrough time and sweep efficiency vary depending on the magnitude of the lateral long range petrophysical variability that exists in a dolomite reservoir as the component of the long range periodicity hole effect increases from approximately 0 to 25 of the total petrophysical variability a corresponding increase in breakthrough time and sweep efficiency occurs however as the magnitude of the lateral long range petrophysical variability increases beyond 25 of the total petrophysical variability e g from 25 to 50 a corresponding reduction in breakthrough time occurs because the spatial continuity of permeability is greater results indicate that heterogeneity caused by lateral petrophysical cyclicity should be incorporated into dolomite reservoir models for hole effect magnitudes that are greater than 10 of the petrophysical variance to properly characterize and model these scales of variability in a petroleum reservoir outcrop analogs are essential to provide accurate quantitative descriptions of lateral variability in dolomite rock fabrics

composite rock types as part of a workflow for the integration of mm to cm scale lithological heterogeneity in static reservoir models abstract lithological heterogeneity in the form of sedimentary structures such as cross and planar and as interfaces between massive beddings is known to impact fluid flow and fluid rock reactions in the subsurface such heterogeneity exists at mm to cm scale and is typically not accounted for in conventional geological models due to technical restrictions posed by the wireline log resolution and the inefficiency of reservoir modelling softwares to handle such fine scale information hence multiphase flow and reactive transport simulations based on conventional models fail to appropriately account for the impact of sedimentary heterogeneity we present a new workflow which allows building reservoir models where such fine scale lithological heterogeneity can be integrated thereby overcoming the limitations associated with log resolution and modelling softwares first the rock types are coupled as composites in a systematic manner at a discretization level that can be handled by the modelling softwares the mm scale rock properties quantified from core samples are accounted for in the composite rock type characterization lithotype logs of the composites are derived by modifying the color coded depth record based on a combination of different wireline logs the lithotype logs form the basis for property population in the reservoir models the coupling of core and wireline data allows to account for the mm to cm scale heterogeneity in coarsely discretised reservoir models the application of the new workflow is demonstrated for the development of a 2 d reservoir model at the co2crc s otway research site with a vertical resolution of 5 cm while incorporating sedimentary heterogeneity at 5 mm scale the composite rock type method would allow for the impact of fine scale heterogeneity to be directly accounted for in static reservoir models

cross spectral analysis of the sst 10 m wind speed coupling resolved by satellite products and climate model simulations this study aims to determine the spatial temporal scales where the sst forcing of the near surface winds takes places and its relationship with the action of coherent ocean eddies here cross spectral statistics are used to examine the relationship between satellite based sst and 10 m wind speed w fields at scales between 10 2 10 4 km and 10 1 10 3 days it is shown that the transition from negative sst w correlations at large scales to positive at oceanic mesoscales occurs at wavelengths coinciding with the atmospheric first baroclinic rossby radius of deformation and that the dispersion of positively correlated signals resembles tropical instability waves near the equator and rossby waves in the extratropics transfer functions are used to estimate the sst driven w response in physical space w c a signal that explains 5 40 of the mesoscale w variance in the equatorial cold tongues and 2 15 at extratropical sst fronts the signature of ocean eddies is clearly visible in w c accounting for 20 60 of its variability in eddy rich regions to provide further insight on the role of ocean eddies in the sst driven coupling the analysis is repeated for two climate model ccsm simulations using ocean grid resolutions of 1 circ eddy parameterized lr and 0 1 circ eddy resolving hr the lack of resolved eddies in lr leads to a significantly underestimated mesoscale w variance relative to hr conversely the w c variability in hr can exceed the satellite estimates by a factor of two at extratropical sst fronts and underestimate it by a factor of almost six near the equator reflecting shortcomings of the ccsm to be addressed in its future developments

structure and surface properties of eddies in the southeast pacific ocean 1 a number of studies have posited that coastally generated eddies could cool the southeast pacific ocean sep by advecting cool upwelled waters offshore we examine this mechanism by characterizing the upper ocean properties of mesoscale eddies in the sep with a variety of observations and by estimating the surface layer eddy heat flux divergence with satellite data cyclonic and anticyclonic eddies observed during two cruises featured deep positive salinity anomalies along the 26 5 kg m 3isopycnal indicating that the eddies had likely trapped and transported coastal waters offshore the cyclonic eddies observed during the cruises were characterized by shoaling isopycnals in the upper 200 m and cool near surface temperature anomalies whereas the upper ocean structure of anticyclonic eddies was more variable using a variety of large scale observations including argo float profiles drifter records and satellite sea surface temperature fields we show that relative to mean conditions cyclonic eddies are associated with cooler surface temperatures and that anticyclonic eddies are associated with warmer surface temperatures within each data set the mean eddy surface temperature anomalies are small and of approximately equal magnitude but opposite sign eddy statistics drawn from satellite altimetry data reveal that cyclonic and anticyclonic eddies occur with similar frequency and have similar average radii in the sep a satellite based estimate of the surface layer eddy heat flux divergence while large in coastal regions is small when averaged over the sep suggesting that eddies do not substantially contribute to cooling the surface layer of the sep

average lead isotope growth curves for shale hosted zinc lead deposits canadian cordillera average lead isotope growth curves for shale hosted zinc lead deposits have been constructed empirically for a large but well defined tectonic segment of the canadian cordillera the model defined is applicable to the dating of galena lead from shale hosted deposits in the selwyn basin and in the ogilvie richardson wernecke and mackenzie mountains in the eastern fold belt and in much of the omineca crystalline belt this area of the cordillera generally had a coherent geochemical evolution lead for deposits was extracted from sediments which had been deposited along the western margin of the north american craton and which were derived largely from upper crustal crystalline rocks that formed the western part of the canadian shield the average shale growth curves involve three stages of evolution the third most recent stage of the three stage model starts at 1 89 m y and evolves to 0 m y with mu of 12 16 and omega of 49 09 the first two stages follow the two stage model of stacey and kramers 1975 the model allows precise model age estimates with an error generally less than 0 05 m y to be made for deposits of known age this is particularly useful in property evaluation during exploration because in many cases the certainty of a syngenetic or epigenetic origin can control future philosophy about exploration and or evolution of a deposit or an area model ages in concert with stratigraphic information commonly indicate the likelihood of epigenetic or syngenetic origins

re evaluation of lead isotopic data southern massif central france three independent pb isotope homogenizing processes operating on large volumes of rock material during limited intervals in the phanerozoic have been used to define a unique evolutionary curve for rock and ore lead isotopic compositions of the southern massif central france the model is begin gathered text x text t 18 641 text text 9 text 56 e text l1 t 1 text hfill text y text t 15 678 text text 0 text 06934 e text l2 t 1 text hfill text z text t 38 701 text text 30 text 8 e text l3 t 1 text hfill end gathered where xt yt and zt are the calculated isotopic ratios 206pb 204pb 207pb 204pb and 208pb 204pb respectively at time t years ago and l1 l2 and l3 are the decay constants of 238u 235u and 232th respectively the model gives the following ages for averages of the three sets of data used in its generation age of mineralization for carbonate hosted lead zinc ore of les malines ca 150 ma emplacement of the saint guiral liron granite ca 290 ma and an estimated average age of a group of cambrian syngenetic deposits ca 520 ma these ages are in close agreement with ages determined by independent methods

the pretty hill formation as a natural analogue for co2 storage an investigation of mineralogical and isotopic changes associated with sandstones exposed to low intermediate and high co2 concentrations over geological time abstract the pretty hill formation of the otway basin australia has been studied as a natural analogue for geological storage of anthropogenic co2 in order to examine the effects that co2 concentration and reservoir heterogeneity have on co2 related reactions new petrographic data are presented which validate the use of hylogger as a tool to investigate high resolution vertical changes in reservoir mineralogy the integrated data set confirms earlier interpretations showing that chlorite has been altered to kaolinite and siderite ankerite in reservoir facies exposed to moderate and high co2 concentrations while chlorite remains the dominant clay mineral in all parts of the formation where co2 content is low differences have been observed in the degree of co2 related reaction relative to co2 concentration and reservoir heterogeneity where co2 content is very high c 98 mol and associated with high water saturations both chlorite and detrital feldspars have undergone complete reaction in the reservoir facies resulting in quartzose sandstones with a kaolinite matrix and with siderite as the dominant carbonate precipitate conversely where co2 content is moderate c 29 57 mol and within the gas leg of the reservoir chlorite has undergone significant reaction but much of the original feldspar is preserved suggesting relatively minor reaction carbonate cements from the moderate co2 gas leg comprise calcite siderite and ankerite occurring as cemented zones associated with rock heterogeneities and the present day gas water contact heterogeneities within the gas leg are likely to have associated pore fluid contacts whereby relatively high water saturations will be present in the fine grained baffles and seals the most advanced feldspar reaction occurs locally at the contact between baffles and reservoir rock while reactions have been significantly impeded in the finer grained units due to their low permeabilities stable isotope data presented for carbonate cements analysed from wells with low and moderate co2 levels show no clear distinction relatively early formed calcite has 13c values that require an organic carbon source suggesting precipitation unrelated to the reservoir co2 in the otway basin in contrast diagenetically late calcite and siderite samples display two distinct 13c groups dependent on carbonate type where the calculated fluid carbon isotope compositions are similar to documented magmatic co2 reservoired in the nearby caroline field this suggests that magma derived co2 may have been more prevalent through the pretty hill formation than previously thought although the co2 has not been contained over the long term in the low co2 sites it may have caused the local dissolution of carbonate and laumontite cement and also contributed a source of carbon for late stage calcite cements these studies illustrate the importance of understanding both the reservoir composition and vertical heterogeneity of potential storage systems fluid mineral reactions are likely to be advanced within stacked reservoir facies and impeded within siltstone layers while the distribution of carbonate cement may increase the reservoir heterogeneity by the formation of cemented siltstone sandstone layers thereby creating impermeable barriers or baffles to co2

time dependent linear theory for the generation of poleward undercurrents on eastern boundaries abstracta time dependent inviscid linear theory for the generation of poleward undercurrent flow under upwelling conditions along midlatitude ocean eastern boundaries is proposed the theory relies on a conceptual separation of time scales between the rapid coastal trapped wave response to upwelling winds and the subsequent slow interior quasigeostrophic evolution solutions are obtained under idealized conditions in which the coastal boundary and the continental slope topography are uniform alongshore and the time dependent wind stress forcing is applied over a limited meridional range uniform cross shore and directed alongshore a time dependent coastal boundary condition on the slow time scale interior flow consisting of the low frequency geostrophically balanced sea surface height disturbance over the outer shelf is obtained from consideration of the fast time scale coastal trapped response a quasigeostrophic potential vorticity equation is then solved to determine the interior response t

westward motion of mesoscale eddies abstract since the pioneering work of nof the determination of the westward drift of mesoscale eddies under the planetary beta effect has been a recurrent theme in mesoscale oceanography and several different formulae have been proposed in the literature here recpatiulation is sought and within the confines of a single layer model a generalized formula is derived although it is similar to nof s the present formula is established from a modified definition and with fewer assumptions it also recaptiulates all other formulae for the one layer model and applies to a wide variety of situations including cases when the vortex develops a wake of rossby waves or undergoes axismmetrization following the derivation of the formula a physical interpretation clarifies the migration mechanism which can be divided between a self induced propulsion and a reaction from the displaced ambient fluid numerical simulations with primitive and geostrophic equations validate the formula for a variety of length sc

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

some aspects of vortex structure related to tropical cyclone motion abstract some effect of tropical cyclone structure on the vortex motion are examined in a nondivergent barotropic numerical model with no basic current as suggested earlier by demaria the initial maximum wind speed has little effect on the track vortex translation associated with the beta effect depends sensitively on the strength of the flow between 300 and 1000 km from the center if the flow in this annulus is made more cyclonic the track will turn cyclonically and move more toward the west in the northern hemisphere the dynamics of this beta drift is studied via a decomposition into symmetric and asymmetric circulations the symmetric flow experiences a slight weakening of the maximum wind speed and an anticyclonic circulation is induced beyond 600 km the asymmetric circulation is dominated by an azimuthal wavenumber one circulation with an anticyclonic gyre east of the center a cyclonic gyre to the west and a nearly uniform broad scale ventilation flow between the gyres the vortex translati

a small scale oceanic eddy off the coast of west africa studied by multi sensor satellite and surface drifter data a small scale oceanic eddy which was generated in autumn 2011 at the headland of cap vert off the coast of senegal west africa and then propagated westward into the open north atlantic ocean is studied by multi sensor satellite and surface drifter data the eddy was generated after a sudden increase of the trade winds causing an enhanced southward flow and upwelling at the coast of senegal after this wind burst event an extremely nonlinear cyclonic eddy with a radius of about 10 to 20 km evolved downstream of cap vert with rossby number larger than one our analysis suggests that the eddy was generated by flow separation at the headland of cap vert the eddy was tracked on its way into the open north atlantic ocean from satellites over 31 days via its sea surface temperature and chlorophyll a chl signature and by a satellite tracked surface drifter the satellite images show that this small scale eddy transported nutrients from the upwelling region westward into the oligotrophic north atlantic thus giving rise to enhanced chl concentration there maximum chl concentration was encountered few days after vortex generation which is consistent with a delayed plankton growth following nutrient supply into the euphotic zone within the eddy furthermore the eddy was imaged by the synthetic aperture radar sar onboard the envisat satellite it is shown that the radar signatures of cold eddies result from damping of short surface waves by biogenic surface films which arise from surface active material secreted by the biota in the cold eddy as well as by the change of the stability of the air sea interface highlights processes during the onset of coastal upwelling off west africa multi sensor remote sensing and in situ observations highly nonlinear small scale eddy generation at cap vert nrcs reduction in parts of the eddy due to biogenic surface films

a revised identification of the oldest sea floor spreading anomalies between australia and antarctica we propose that magnetic anomalies south of australia and along the conjugate margin of antarctica that were originally identified as anomalies 19 to 22 may be anomalies 20 to 34 the original anomaly identification has two troublesome aspects 1 it does not account for an extra anomaly between anomalies 20 and 21 and 2 it provides no explanation for the rough topography comprising the diamantina zone with our revised identification there is no extra anomaly and the diamantina zone is attributed to a period of very slow spreading 4 5mm yr half rate between 90 and 43 m y the ages bounding the interval of slow spreading 90 and 43 m y correspond to times of global plate reorganizations our revised identification opens up the possibility that part of the magnetic quiet zone south of australia formed during the cretaceous long normal polarity interval breakup of australia and antarctica probably occurred sometime between 110 and 90 m y b p the breakup unconformity identified by falvey in the otway basin may correspond to a eustastic sea level change

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

observed evolution of a california undercurrent eddy abstracta california undercurrent eddy cuddy was repeatedly surveyed using multiple seagliders for over three months found and tracked off of the washington vancouver island coasts this cuddy t

the evolution and propagation of quasigeostrophic ocean eddies abstractthe long term evolution of initially gaussian eddies is studied in a reduced gravity shallow water model using both linear and nonlinear quasigeostrophic theory in an attempt to understand westward propagating mesoscale eddies observed and tracked by satellite altimetry by examining both isolated eddies and a large basin seeded with eddies with statistical characteristics consistent with those of observed eddies it is shown that long term eddy coherence and the zonal wavenumber frequency power spectral density are best matched by the nonlinear model individual characteristics of the eddies including amplitude decay horizontal length scale decay and zonal and meridional propagation speed of a previously unrecognized quasi stable state are examined the results show that the meridional deflections from purely westward flow poleward for cyclones and equatorward for anticyclones are consistent with satellite observations examination of the fluid transport properties of the eddies shows that an

intraseasonal to seasonal variability of the intermediate waters along the kuroshio path east of taiwan the variability of the intermediate water iw east of luzon and taiwan is investigated using data acquired from moored instrumented lines and shipboard hydrographic and current velocity surveys the iw is defined as the water mass with a local salinity minimum along the kuroshio path an empirical formula is developed to estimate the iw salinity minimum east of taiwan using temperature measurements around 580 m depth properties of the iw east of taiwan vary greatly as a result of variable contributions from three water masses including the high salinity south china sea intermediate water scsiw the low salinity north pacific intermediate water npiw and the intermediate salinity kuroshio intermediate water kiw our analysis concludes that npiw is predominantly found east of taiwan and the northward transport of kiw from northeast of luzon to east of taiwan is not a steady process concurrent mooring measurements at these two locations enable us to correlate the variations of the layer thickness of the kuroshio near its origin klto northeast of luzon to the nature of the iw east of taiwan when the kuroshio is deep i e large klto kiw is transported northward across the luzon strait where its salinity increases presumably due to turbulence mixing with scsiw this modified kiw is then transported to the east of taiwan when the kuroshio is shallow i e small klto the kiw transport east of luzon is nil or southward east of taiwan npiw feeds in below the kuroshio and is transported northward beyond the i lan ridge

a linear stochastic field model of midlatitude mesoscale variability abstracta semiempirical model of midlatitude sea surface height ssh variability is formulated and tested against two decades of weekly global fields of merged altimeter data the model is constrained to match approximately the observed ssh wavenumber power spectrum but it predicts the spatiotemporal ssh field structure as a propagating damped linear response to a stochastic forcing field an objective coherent eddy identification and tracking procedure is applied to the model and altimeter ssh fields with a focus on eddies with lifetimes l 16 weeks the model eddy dataset reproduces the basic global mean characteristics of the altimeter eddy dataset including the structure of mean amplitude and scale life cycles the number distributions versus lifetime and the distributions of all eddy length scale realizations the model underpredicts the numbers of eddy realizations with large amplitudes and large scales overpredicts the growth of mean amplitude and scale with lifetime and modestly overpre

metallogenic provinces and the remobilization process studied by lead isotopes lead zinc ore deposits from the southern massif central france the two main problems of ore genesis are the origin of metals and the process es of emplacement lead isotopes have proven to be a powerful tool for studying these questions we have studied pb zn mineralizations from montagne noire and cevennes southern massif central france by means of lead isotopes this study shows the existence of two populations of ore deposits defined by 17 76 206 pb 204 pb 17 94 and 18 25 206 pb 204 pb 18 63 a general model of lead evolution in these deposits is proposed after evolving in the earth s mantle until approximately 3 b y ago the lead became incorporated into a segment of continental crust then the less radiogenic population of ore deposits was emplaced contemporaneously with the formation of cambrian carbonate host rocks the second population is related to the emplacement of hercynian granitoids or in more general terms to fluid circulations associated with the hercynian orogeny it can also be shown that some of the deposits are remobilized from preexisting ore deposits

a tale of two eddies the biophysical characteristics of two contrasting cyclonic eddies in the east australian current system mesoscale cyclonic eddies are known to be highly productive less well known are the dynamics and productivity of smaller cyclonic eddies known as frontal eddies that form on the landward side of western boundary currents in this study we investigate the physical and biogeochemical properties of two contrasting cyclonic eddies in the east australian current eac the first murphy a mesoscale cyclonic eddy that formed at 28 s with a diameter of 160 km and high surface chlorophyll a concentrations which lived 47 days the second freddy a smaller frontal eddy 35 km diameter that formed from a shelf water billow 7 days prior to sampling at 31 5 s and was advected off the shelf along the eac front from 200m to 4000m of water both eddies were at least 1000m deep with a similar steric height anomaly we introduce and employ the method of closest approach using shipboard adcp velocities to estimate the eddy centers which reveals significant tilting through the water column we estimate rotation rates of 4 10 days and 1 9 days and rossby numbers 0 25 0 1 and 0 6 0 1 from the surface to 600m for murphy and freddy respectively high resolution altimetry measurements from the saral altika satellite provide estimates of the ageostrophic component of rotation our results show that the frontal eddy is significantly more ageostrophic energetic and productive than the mesoscale cyclone despite its small size and short life 4 weeks we suggest that frontal eddies have potential to contribute significantly to the net productivity of the tasman sea region this article is protected by copyright all rights reserved

rock physics diagnostics of depositional texture diagenetic alterations and reservoir heterogeneity in high porosity siliciclastic sediments and rocks a review of selected models and suggested work flows rock physics has evolved to become a key tool of reservoir geophysics and an integral part of quantitative seismic interpretation rock physics models adapted to site specific deposition and compaction help extrapolate rock properties away from existing wells and by so doing facilitate early exploration and appraisal many rock physics models are available each having benefits and limitations during early exploration or in frontier areas direct use of empirical site specific models may not help because such models have been created for areas with possibly different geologic settings at the same time more advanced physics based models can be too uncertain because of poor constraints on the input parameters without well or laboratory data to adjust these parameters a hybrid modeling approach has been applied to siliciclastic unconsolidated to moderately consolidated sediments specifically in sandstones a physical contact theory such as the hertz mindlin model combined with theoretical elastic bounds such as the hashin shtrikman bounds mimics the elastic signatures of porosity reduction associated with depositional sorting and diagenesis including mechanical and chemical compaction for soft shales the seismic properties are quantified as a function of pore shape and occurrence of cracklike porosity with low aspect ratios a work flow for upscaling interbedded sands and shales using backus averaging follows the hybrid modeling of individual homogenous sand and shale layers different models can be included in site specific rock physics templates and used for quantitative interpretation of lithology porosity and pore fluids from well log and seismic data

multi stage fluid incursion in the palaeozoic basement hosted saint salvy ore deposit nw montagne noire southern france abstract the saint salvy vein hosted zn ge deposit occurs in an e w fault system which flanks the southern margin of the late variscan sidobre granite and cross cuts cambrian black shales of the palaeozoic basement comprehensive mineralogical and geochemical studies of vein samples have revealed four mineralizing events m1 m4 related to late and post variscan tectonic events a further late stage event may be related to weathering m1 skarn deposits and m2 patchily mineralized quartz veinlets are associated with granite emplacement quartz contains low salinity h2o co2 nacl dominated fluids 6wt nacl equiv of relatively high temperature 300 580 c trapped under moderate to high pressure estimated m1 fluid d and calculated fluid 18o plot within the metamorphic water field there appears to be no involvement of magmatic fluids by contrast m3 barren quartz and m4 zinciferous economic mineralization stages have h2o co2 nacl cacl2 fluid inclusions with high salinities 23 25 wt nacl equiv and low temperatures 80 140 c which were trapped under low pressure conditions the high salinity and nacl cacl2 content of both m3 and m4 indicates that their parent fluids leached evaporitic salts m3 fluids are meteoric water dominated falling close to the meteoric water line d and 18o averaging 64 and 8 respectively m4 fluids have highly distinctive d averaging 101 and calculated fluid 18o varying from 1 2to 7 1 the unusually low d composition of m4 suggests the involvement of organic fluids in which h is derived directly or indirectly from organic matter the relatively high 18o of m4 fluids indicates that considerable isotopic exchange with sedimentary material took place displacing the 18o from the meteoric water line the data imply interaction of meteoric waters with evaporite and hydrocarbon bearing sedimentary sequences most probably the adjacent aquitain basin the main economic mineralization m4 stage took place during a tensional event probably coincident with the lias dogger transition calculated 34sh2s of m4 sulphide 5 4to 8 2 is almost identical to 34s of local cambrian sulphides 4 7to 9 4 suggesting a genetic link abundant siderite associated with m4 sphalerite has 13c ranging from 2 6to 4 4 indicating that carbon was sourced from sedimentary carbonate mobilized by or equilibrated with the hydrothermal fluid late stage sulphides exhibit extraordinary and highly distinctive 34s sphalerite has extremely low 34s 42 5to 50 5 whereas pyrite has an extraordinary large range from 33 2 to 74 3 closed system sulphate reduction is held to be responsible for the extremely high 34s whereas more open system reduction produces the very low values the coincidence of isotopically low 13c 7 6to 11 9 for co genetic calcite suggests the involvement of organic matter in the reduction process

modulation of kuroshio transport by mesoscale eddies at the luzon strait entrance measurements of kuroshio current velocity at the entrance to luzon strait along 18 75 n were made with an array of six moorings during june 2012 to june 2013 strong positive relative vorticity of the order of the planetary vorticity f was observed on the western flank of the kuroshio in the upper 150 m on the eastern flank the negative vorticity observed was about an order of magnitude smaller than f kuroshio transport near its origin is computed from direct measurements for the first time kuroshio transport has an annual mean of 15 sv with a standard deviation of 3 sv it is modulated strongly by impinging westward propagating eddies which are identified by an improved eddy detection method and tracked back to the interior ocean eight kuroshio transport anomalies 5 sv are identified seven are explained by the westward propagating eddies cyclonic anticyclonic eddies decrease increase the zonal sea level anomaly sla slope and reduce enhance kuroshio transport large transport anomalies of 10 sv within o 10 days are associated with the pairs of cyclonic and anticyclonic eddies the observed kuroshio transport was strongly correlated with the sla slope correlation 0 9 analysis of sla slope data at the entrance to luzon strait over the period 1992 2013 reveals a seasonal cycle with a positive anomaly i e an enhanced kuroshio transport in winter and spring and a negative anomaly in summer and fall eddy induced vorticity near the kuroshio has a similar seasonal cycle suggesting that seasonal variation of the kuroshio transport near its origin is modulated by the seasonal variation of the impinging mesoscale eddies

a mechanism for the latitudinal dependence of peak spectrum sea surface height variability previous studies have shown that the power spectrum of satellite observed sea surface height ssh variability peaks at a certain frequency or a wave number band at a given latitude lin et al 2008 attributed this latitudinal dependence to the critical frequency of the first baroclinic mode rossby waves in the tropical and subtropical oceans their study was based on the linear rossby wave theory and focused on ssh variability in the tropical and subtropical oceans since the altimetry data do not adequately resolve lengths of baroclinic rossby waves at and near the critical frequency in high latitudes in this study we expand their analysis to high latitude oceanic basins and to include nonlinear eddy effects by using a linear wave model and a high resolution model output from the ogcm for the earth simulator ofes it is found that the linear wave mechanism by and large remains valid in the tropical and subtropical oceans in higher latitudes as well as in some regions in the western tropical and subtropical oceans other mechanisms like nonlinear eddy play more important role in determining the ssh variability

the prevalence of oceanic surface modes satellite observations have revolutionized oceanography capturing diverse phenomena over much of the globe however it remains to understand how surface fields like sea surface height reflect the motion occurring at depth the vertical structure of ocean eddies is often expressed in terms of baroclinic modes which are basis functions derived assuming a flat ocean bottom bathymetry alters the modes though weakening the bottom velocities using analytical solutions we demonstrate that with realistic bathymetry and or bottom friction the bottom velocities are nearly zero the resulting surface modes should be ubiquitous in the ocean this would explain the dominant mode of variability obtained from globally distributed current meter data and is consistent with energy spectra derived from sea surface height data the results yield a simple way to infer subsurface velocities from satellite data and suggest that ocean analyses should be made in terms of surface modes and topographic waves

a database approach for constraining stochastic simulations of the sedimentary heterogeneity of fluvial reservoirs quantitative databases storing analog data describing the geometry of sedimentologic features are commonly used to derive input for geostatistical simulations of reservoir sedimentary architecture however geometrical information alone is inadequate for the detailed characterization of sedimentary heterogeneity a relational database storing fluvial architecture data has been developed and populated with literature and field derived data from modern rivers and ancient successions the database scheme characterizes fluvial architecture at three different scales of observation recording style of internal organization geometries and spatial relationships of genetic units classifying data sets according to controlling factors e g climate type and context descriptive characteristics e g river pattern the database can therefore be filtered on both architectural features and boundary conditions to yield outputs tailored on the system being modeled to generate input to object and pixel based stochastic simulations of reservoir architecture when modeling heterogeneity with stochastic simulations the choice of input parameters quantifying spatial variation is problematic because of the paucity of primary data and the partial characterization of supposed analogs this database driven approach permits the definition of various constraints referring to either genetic units e g architectural elements or material units i e contiguous volumes of sediment characterized by the same value of a given categorical or discretized variable e g same lithofacies type clay and silt content and others which permit the realistic description of fluvial architecture heterogeneity applications of this database approach include the computation of relative dimensional parameters and the generation of auto and cross variograms and transition probability matrices which are necessary to effectively model spatial complexity

palaeomagnetic dating of widespread remagnetization on the southeastern border of the french massif central and implications for fluid flow and mississippi valley type mineralization summary palaeomagnetic dating techniques have been applied to determine the age of fluid migration that produced the mississippi valley type mvt pb zn ba f deposits in the cevennes region of southern france 15 sampling sites in two gently deformed areas around the largentiere and croix de pallieres mines on the cevennes border were selected for palaeomagnetic study they yielded a very well defined direction of remagnetization corresponding to an early middle eocene age this remagnetization cannot be related to the formation of magnetite as a result of the transformation of smectite to illite because the latter has been well dated as a mesozoic event the magnetic overprint in this area is related to a chemical phenomenon during fluid migration the age of remagnetization corresponds to a major uplift in the pyrenees mountains located to the south of the cevennes this implies that fluid migration occurred from the south to the north as a result of hydraulic head established in the pyrenees orogenic belt during orogenesis and suggests that the mvt deposits in the cevennes region formed from a gravity driven fluid system as described by garven freeze 1984a b

evidence for wind driven current fluctuations in the western north atlantic two subsurface current meter moorings were deployed for 20 months along 70 w in a low energy portion of the western north atlantic the resulting data were compared with estimates of the wind stress curl in an attempt to seek a relationship between currents below the mixed layer and meteorological forcing at subinertial frequencies currents and temperature tend to be significantly coherent with the curl and are most coherent with the curl at remote locations usually more than 500 km away from the mooring and generally to the east coherences generally decrease with increasing frequency the current response is surface intensified a linear stratified model for stochastically wind forced rossby waves in a flat bottomed ocean is presented as an attempt to rationalize the results the effort was not entirely successful so that it appears that a more realistic model perhaps including bottom topography and mean currents will be needed to rationalize these observations fully

lead isotope models for the genesis of carbonate hosted zn pb shale hosted ba zn pb and silver rich deposits in the northern canadian cordillera isotope analyses of galena from syngenetic barite zinc lead and epigenetic zn pb and ag rich deposits from the northern canadian cordillera are subdivided into four distinct fields and lines on 207 pb 204 pb and 208 pb 204 pb vs 206 pb 204 pb plots these lines used in conjunction with constraints imposed by stratigraphy by k ar isotopic dates and by minor element analyses in sphalerite define three metallogenic events dating about 0 52 0 37 and 0 09 b y which are summarized as follows 1 old carbonate hosted zn pb deposits formed in the lower cambrian about 0 52 b y ago define closely a maximum source age of 1 9 b y this is the first lead isotopic indication of hudsonian basement in the northern canadian cordillera spatial association of these deposits to unconformities and generation of lead in an upper crustal but generally uranium poor environment supports a karstic model for their origin 2 shale hosted ba zn pb mineralization from upper devonian to lower mississippian about 0 37 b y old rocks is indistinguishable in lead isotope composition from the majority of post lower ordovician to devonian young carbonate hosted zinc lead deposits these deposits formed near 0 37 b y ago from brines dewatered from the selwyn shale basin where solutions were guided by faults either within the basin e g shale hosted ba zn pb deposits formed along grabens near hinge lines close to the margin of the basin or peripheral to and away from the basin e g carbonate hosted zn pb deposits lead for these deposits evolved in an upper crustal uranium rich carbonaceous shale basin environment from which lead relatively rich in radiogenic component was extracted 8 although most ag rich deposits occur as veins not directly associated with plutons some veins occur within or are directly associated with cretaceous plutons indicating a general age of mineralization of 0 09 b y an apparent hudsonian source is indicated some highly radiogenic leads characteristic of the silver deposits were probably formed by preferential leaching of lead from uranium rich minerals

the effect of bottom pressure decoupling on the speed of extratropical baroclinic rossby waves abstract in layered models of the ocean the assumption of a deep resting layer is often made motivated by the surface intensification of many phenomena the propagation speed of first mode baroclinic rossby waves in such models is always faster than in models with all the layers active the assumption of a deep resting layer is not crucial for the phase speed enhancement since the same result holds if the bottom pressure fluctuations are uncorrelated from the overlying wave dynamics in this paper the authors explore the relevance of this behavior to recent observational estimates of too fast waves by chelton and schlax the available evidence supporting this scenario is reviewed and a method that extends the idea to a continuously stratified fluid is developed it is established that the resulting amplification factor is at leading order captured by the formula where cfast is the enhanced phase speed cstandard the standard phase speed 1 z is the standard first mode for the velocity and pressur

assessment and geological characterisation of the co2crc otway project co2 storage demonstration site from prefeasibility to injection abstract the co2crc otway project located in south eastern australia has demonstrated geological storage of co 2 in a depleted natural gas field prior to injection a comprehensive site characterisation study established that the site should meet the requirements of safe and effective storage in contrast to the conventional methods applied to characterising oil and gas reservoirs for production purposes co 2 storage site assessments place greater emphasis on injectivity capacity and long term containment the site location was assessed in the context of accessibility for monitoring activities and impact on local communities and natural resources additional well log data and cores were acquired from the gas field in conjunction with the drilling of the crc 1 injector well in order to reduce the uncertainty surrounding the geological heterogeneity of the reservoir capacity of the seal to retain co 2 fault seal geomechanics and regional hydrodynamics specialised core analysis revealed that small scale sedimentary features related to depositional environment impact reservoir quality co 2 trapping and plume migration behaviour based on these effects a depositional model was established to better understand storage potential away from well control finally a nearby gas storage facility provided a valuable analogue for the project and added confidence that the co2crc otway project site would be suitable to inject store and contain co 2 within the technological and economical limits of the project following the injection period long term monitoring of the reservoir as well as the overlying aquifers soil groundwater and the atmosphere above the site have confirmed the storage concept is effective and that the co 2 is safely contained as a result the site characterisation methodology serves as an example for others contemplating co 2 storage into depleted gas fields

quantifying and interpreting striations in a subtropical gyre a spectral perspective abstractthe amplitude origin and direction of striations in the subtropical gyre are investigated using simulated and analytical multidimensional spectra striations defined as banded structures in the low frequency motions account for a noticeable percentage of zonal velocity variability in the east north pacific enp 25 42 n 150 130 w and central north pacific cnp 10 22 n 132 e 162 w regions in an eddying global ocean model thus they likely are nonnegligible in mixing and transport processes striations in the enp region are nonzonal and are embedded in the nonzonal gyre flow whereas striations in the cnp region are more zonal as are the mean gyre flows an idealized 1 5 layer model shows the gyre flow partially determines their directions which qualitatively resemble those in the global eddying model in the linear limit structures are quasi stationary frequency 0 linear rossby waves and the gyre flow influences the direction by influencing the nature of the zero rossby wave f

divergent pathways of cyclonic and anti cyclonic ocean eddies satellite altimetry is used to study the propagation pathways of warm and cold ocean eddies in different ocean basins we consider eddies that have a life span longer than 3 months and we present three regional studies in the southeast indian the southeast atlantic and the northeast pacific oceans the case studies show that simple theories for vortex propagation on a plane work in regions where energetic eddies propagate though a weak background flow under these conditions anticyclonic cyclonic eddies propagate westward and equatorward poleward this divergence in the eddy pathways implies a net equatorward eddy heat flux and has implications for the meridional transport of freshwater carbon nutrients etc

a multidimensional spectral description of ocean variability abstractan updated empirical analytical model for the frequency and wavenumber distribution of balanced motion in the ocean is presented the spectrum model spans periods longer than the inertial but shorter than a decade and wavelengths between 100 and 10 000 km assuming geostrophic dynamics a spectrum model for the streamfunction is constructed to be consistent with a range of observations including sea surface height from satellite altimetry velocity from moored and shipboard instruments and temperature from moorings first order characteristics of the observed spectra including amplitude and spectral moments vary slowly geographically the spectrum model is horizontally anisotropic accommodating observations that zonal wavenumber frequency spectra are dominated by a nondispersive line qualitative and quantitative agreement is found with one dimensional frequency and wavenumber spectra and observed vertical profiles of variance illustrative application is made of the model spectrum to obse