a numerical study of the mediterranean sea circulation abstract a primitive equation ocean model that makes use of a curvilinear orthogonal grid and a sigma coordinate system was used to simulate the mediterranean sea the model was forced with monthly climatological values of wind stress heat and salinity flux with the help of the curvilinear horizontal grid the larger scales of the entire mediterranean sea are modeled and the topography around the narrow and shallow straits of gibraltar is also reasonably well represented the resulting model inflow and outflow seems to mimic the real mediterranean often in considerable detail levantine intermediate water is formed in the levantine basin and exits through the strait of sicily and the strait of gibraltar deep water formation processes are clearly represented by the model the model results indicate that in the western mediterranean the wind stress is very important in establishing the summer northward shift of the atlantic inflow lateral boundary runoff surface salinity and heat fluxes are necessar

dense water formation in the aegean sea numerical simulations during the eastern mediterranean transient 1 dense water formation processes in the aegean sea eastern mediterranean are studied using a three dimensional numerical ocean model the simulations cover the period 1979 1994 during which major changes that affected the thermohaline circulation of the whole mediterranean sea were recorded sensitivity studies that focus on the role of freshwater budget are presented and the results are evaluated against available hydrological data of the same period the very cold winters of 1987 1992 and 1993 and the extended dry period 1989 1993 that affected the whole eastern mediterranean sea are the main driving mechanisms corresponding to 50 and 32 respectively of the excessive deepwater volume formed in the aegean after 1987 the reduced black sea water outflow during the same dry period was another important forcing mechanism contributing 18 to the total formation while the increased inflow of saline waters from the levantine sea after 1992 was an additional preconditioning factor the locations and mechanisms of water formation processes are identified with combined analysis of data from the march 1987 oceanographic cruise in the aegean sea and the respective model results for that period deep water is found to be formed mainly through open ocean convection in the central and north aegean sea while the contribution of shelf areas is limited intermediate water is also formed through open ocean convection in the southern aegean sea during cold winters as well as in the central and northern aegean during mild winters the total volume of dense water formed during 1979 1994 corresponds to an annual formation rate of 0 24 sv for deep water and 0 34 sv for intermediate water

diagenesis of plio pleistocene sediments of the colorado river delta southern california abstract interbedded mudrocks and fine grained sandstones from three wells in the plio pleistocene colorado river delta in the imperial valley southern california were examined by x ray powder diffraction methods chemical analyses and scanning electron microscopy sem to determine the extent and course of low temperature metamorphic reactions this sequence was compared to tertiary rocks from the u s gulf coast in an effort to explore the kinetics of low temperature reactions in natural systems mineralogical changes observed are 1 the progressive transformation of mixed layer illite smectite to pure illite over the temperature range 70 c to 210 c 2 the apparent appearance of chlorite as a diagenetic mineral at 180 c to 194 c coincident with the onset of r symbol 3 ordering in the illite smectites 3 the loss of kaolinite above approximately 210 c and 4 a progressive decrease in the amount of detrital potassium feldspar over the same temperature interval that brackets the illitization reaction comparison of bulk chemical analyses with analyses of the comparison of tertiary sequences with this plio pleistocene sequence indicates that kinetics significantly influence the appearance of clay mineral assemblages at temperatures below approximately 175 c at temperatures above 175 c temperature rather than time appears to govern the reactions

the thermal history of the bowen basin queensland australia vitrinite reflectance and clay mineralogy of late permian coal measures abstract the thermal history of the bowen basin queensland australia has been investigated using vitrinite reflectance data and clay mineralogy vitrinite reflectance data combined with a study of clay mineral reactions indicates that the maximum temperatures which induced organic maturation of the bowen basin coals and extensive clay mineralisation are not related to deep burial metamorphism during the latest middle triassic earliest late triassic as previously believed the results of the present study indicate that the development of a zone of high heat flow in the latest late triassic had a major control on the thermal history of the bowen basin high palaeogeothermal gradients estimated in the northern bowen basin are interpreted to result from convective heat transfer during a hydrothermal event variable heat distributions due to localised fracture enhanced permeable zones acting as hot reservoirs in the deeper part of the basin may have been responsible for some significant local thermal anomalies in the lower coal measures the estimated palaeogeothermal gradients in the southern bowen basin also indicate high heat flow in the lower sections of the stratigraphy sections in the southern bowen basin however are believed to reflect a rock dominated semi closed system with low water rock ratio where rocks are impervious to circulating fluids and thus heat transfer may have occurred by conduction the correlation between vitrinite reflectance and clay mineralogy shows a delay in illitisation reaction relative to organic maturity for many illite smectite i s mixed layer clays in the northern bowen basin this phenomenon can be explained as a result of insufficient time for the completion of mineral reactions and a variable potassium supply in relatively impermeable rocks the relationship between i s expandability and vitrinite reflectance for the bowen basin data compared to basins with known tectonic regimes suggests a thermal history in a rift setting for the bowen basin the effect of thin igneous intrusions on clay mineral reactions is very limited intensive illitisation due to heating of intrusions can only be observed in narrow zones immediately adjacent to intrusive bodies this further demonstrates that mineral reactions are too slow to record the effect of extremely short heating duration in contrast to organic maturity indicators these differences between mineral and organic parameters aid in the identification of local contact metamorphic effects

a general circulation model for upper ocean simulation abstract a general circulation model gcm of the ocean that emphasizes the simulation of the upper ocean has been developed this emphasis is in keeping with its future intent that of an air sea coupled model the basic model is the primitive equation model of bryan and cox with the additions of optional usage of the mellor yamada level 2 5 turbulence closure scheme and horizontal nonlinear viscosity these modifications are intended to improve the upper ocean simulations particularly sea surface temperature and heat content the horizontal grid spacing is 1 latitude 1 longitude and is global in domain the equatorial region between 10 n and 10 s is further refined in the north south direction to resolution there are 12 vertical levels with six levels in the top 70 m the model incorporates varying bottom topography prior to coupling the ocean model to an atmospheric gcm experiments have been carried out to determine the ocean gcm s performance using atmospheric forcing from observed data

light element distributions n b li in baltic basin bentonites record organic sources abstract distributions of nitrogen boron and lithium were studied in illite smectite from ordovician silurian k bentonites in the baltic basin these trace elements are linked to thermal maturation of organic matter creating fluid signatures that are distinct from those in regionally buried sediments the fluid chemistry is ideally recorded in authigenic illite within the k bentonite because b substitutes in tetrahedral sites of illite li in octahedral sites and n is fixed in the interlayers as nh 4 three nanometric size fractions of illite 10 among these size fractions relate mainly to changes in fluid composition during illite growth bentonite volcanic ash layers mark stratigraphic timelines while illitization of the bentonite k bentonite varies as a function of burial and tectonic temperature gradients in the central baltic basin bentonites were deposited across a carbonate platform near estonia grading to deep basin shales near denmark and poland compositional variations in illite reflect fluids from different sources high n illite 2000 ppm in the southwest basin transitions to high b 250 ppm and high li 100 ppm illite to the northeast these trends follow a thermal gradient decreasing from southwest 200 c to northeast 90 c isotope ratios of b and li show opposing trends in samples across this thermal gradient the bisotopes decrease from southwest to northeast 18 to 4 while li isotopes increase from 5 to 32 the cambrian alum shale a regional hydrocarbon source rock was studied as a potential source of b and li as more than 50 of its b and li was associated with organic matter with increasing thermal maturity illite 11b decreased from 0 to 13 while 7li increased from 20 to 5 these opposing trends are similar to those observed in the k bentonites this suggests that organic sources of n b and li dominate fluids in bentonites from the southwestern baltic basin whereas basement derived fluids dominate in the northeastern baltic basin these trace elements record paleofluid changes during illite crystal growth and can identify pathways of chemically distinct oil and gas related fluids

thermochemical effects on the smectite alteration of gmz bentonite for deep geological repository gaomiaozi gmz bentonite has been recognized as the first choice for using as buffer backfill material in deep geological repository for the disposal of high level nuclear waste in china high salinity and high ph of the pore solutions may cause changes in the mineralogical composition and the swelling capacity of the bentonite results in affecting the long term performance of the engineering barrier system in the present work a series of hydrothermal reactivity experiments were performed using batch reactors at 20 35 and 80 c for evaluating the chemical and mineralogical responses of gmz bentonites the results show that the dissolution of smectite releases si and al under the conditions of 1 m koh at 35 and 80 c and the released si and al may work as a cementing agent in gmz bentonite xrd pattern results show that alteration of the gmz bentonite is expected to be insignificant for reaction with nacl kcl and naoh solutions under low temperatures however it is obviously reacted with koh solutions especially at 80 c during which cementitious material was produced leading to kaolinitization when contacted with koh solutions the basal spacing d001 of the main primary diffraction peaks 001 value of gmz bentonite increases with increasing temperature salinity also can influence the smectite stability and accordingly loss of swelling capacity this conclusion could be explained by the diffusing double layer effects induced by salt solutions and ion exchange

a mixed layer study of the formation of levantine intermediate water a mixed layer model is used to investigate the formation of levantine intermediate water liw over the eastern mediterranean the one dimensional model is initialized with climatological hydrography and integrated over the levantine basin with forcing by climatological surface fluxes realistic and repeated seasonal mixed layer cycles are obtained if the annual surface heat input and water loss are offset by a parameterized horizontal advection the model integrations show that liw is formed during winter in the mixed layer of the northwestern levantine the preferred formation region for liw is found through idealized experiments to be controlled by the preconditioning of the hydrography especially that of the cold cyclonic rhodes gyre rather than by the pattern of the climatological fluxes the annual mean formation rate of liw is estimated to be 1 0 sv using the climatological surface fluxes the magnitude of the annual surface fluxes alters the formation rate and modifies the formation region an additional annual heat flux reduces the formation rate of liw whereas an extra cooling enhances it as well as forming waters denser than liw in the center of the rhodes gyre

correlation of diagenetic data from organic and inorganic studies in the apenninic maghrebian fold and thrust belt a case study from eastern sicily abstract temperature dependent clay mineral assemblages and vitrinite reflectance data have been used to investigate levels of diagenesis from the apenninic maghrebian fold and thrust belt in eastern sicily at the footwall of the peloritani calabride arc data are from units sampled along a regional transect between the nebrodi mountains to the north and mount judica to the south these units developed in very different tectonic settings from those of oceanic to passive continental margin domains deformed during the cenozoic mountain building and related active margin deposits the integration of organic and inorganic thermal indicators allowed us to distinguish among different tectonic settings with thermal maturity generally decreasing from hinterland to foreland as a result of progressively less severe thermal evolution and or tectonic loading during the mountain building specifically the highest vitrinite reflectance vro values ca 0 60 0 75 and percentages of illite layers in illite smectit

active mud volcanoes on the continental slope of the canadian beaufort sea the major geochemical characteristics of red sea brine are summarized for 11 brine filled deeps located along the central graben axis between 19 n and 27 n the major element composition of the different brine pools is mainly controlled by variable mixing situations of halite saturated solution evaporite dissolution with red sea deep water the brine chemistry is also influenced by hydrothermal water rock interaction whereas magmatic and sedimentary rock reactions can be distinguished by boron lithium and magnesium calcium chemistry moreover hydrocarbon chemistry concentrations and 13 c data of brine indicates variable injection of light hydrocarbons from organic source rocks and strong secondary bacterial or thermogenic degradation processes a simple statistical cluster analysis approach was selected to look for similarities in brine chemistry and to classify the various brine pools as the measured chemical brine compositions show remarkably strong concentration variations for some elements the cluster analysis indicates two main classes of brine type i brine chemistry oceanographer and kebrit deeps is controlled by evaporite dissolution and contributions from sediment alteration the type ii brine suakin port sudan erba albatross discovery atlantis ii nereus shaban and conrad deeps is influenced by variable contributions from volcanic magmatic rock alteration the chemical brine classification can be correlated with the sedimentary and tectonic setting of the related depressions type i brine filled deeps are located slightly off axis from the central red sea graben a typical collapse structure formation which has been defined for the kebrit deep by evaluating seismic and geomorphological data probably corresponds to our type i brine type ii brine located in depressions in the northern red sea i e conrad and shaban deeps could be correlated to volcanic intrusion extrusion related deep formation the chemical indications for hydrothermal influence on conrad and shaban deep brine can be related to brines from the multi deeps region in the central red sea where volcanic magmatic fluid rock interaction is most obvious the strongest hydrothermal influence is observed in atlantis ii brine central multi deeps region which is also the hottest red sea brine body in 2011 68 2 c

aegean sea water masses during the early stages of the eastern mediterranean climatic transient 1988 90 abstract the aegean water masses and circulation structure are studied via two large scale surveys performed during the late winters of 1988 and 1990 by the r v yakov gakkel of the former soviet union the analysis of these data sheds light on the mechanisms of water mass formation in the aegean sea that triggered the outflow of cretan deep water cdw from the cretan sea into the abyssal basins of the eastern mediterranean sea the so called eastern mediterranean transient it is found that the central aegean basin is the site of the formation of aegean intermediate water which slides southward and depending on their density renews either the intermediate or the deep water of the cretan sea during the winter of 1988 the cretan sea waters were renewed mainly at intermediate levels while during the winter of 1990 it was mainly the volume of cdw that increased this aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects i during the winter of

friction on subduction megathrust faults beyond the illite muscovite transition abstract previous experimental studies addressing subduction megathrust friction have focused on shallow fault gouges dominated by smectite illite and quartz here we aim to determine the effect of the transition to muscovite rich fault rock at depths beyond the illite dominated region of the seismogenic zone to achieve this rotary friction experiments were performed on simulated muscovite quartz 65 35 gouge at 100 600 c an effective normal stress of 170 mpa pore pressures of 100 and 200 mpa and sliding velocities of 1 100 m s we isolated the effects of muscovite by shearing pure muscovite gouge at 200 600 c under otherwise identical conditions at low shear strains 1 muscovite quartz gouge showed a friction coefficient of 0 4 0 5 while pure muscovite gouge exhibited 0 3 both gouges showed an increase in with and temperature the muscovite quartz gouge was characterised by velocity strengthening or neutral behaviour at 100 350 c velocity weakening at 350 500 c and velocity strengthening at 500 600 c in contrast pure muscovite gouge showed predominantly velocity strengthening or neutral behaviour demonstrating a key role of quartz in producing velocity weakening the velocity weakening regime in the mixed gouge extends that of 250 400 c recently reported for illite quartz gouge up to 500 c taking into account the observed effect of sliding velocity on a b the data for illite quartz and muscovite quartz together help explain the depth extent of seismogenesis on subduction megathrusts interestingly comparison with previous microphysical models suggests that the mechanism causing velocity weakening in phyllosilicate quartz gouges is one of granular flow involving competition between shear induced dilation and compaction through thermally activated quartz deformation

mineral assemblages and low energy sedimentary processes in the flk zinj ds ptk and amk complex palaeolandscape olduvai gorge tanzania the mineralogical composition of the clay stratum level 22 that contains the flk zinj ds ptk amk complex the only example of pene contemporaneous early pleistocene sites occurring on the same palaeolandscape and simultaneously covered by the same ash fall tuff shows significant intra site and inter site differences overall level 22a is related to a more hydrologically closed system with higher salinity and alkalinity than level 22b both levels show fresher water was entering the system from the ds area during deposition textural analysis of the studied samples shows great microporosity and abundant edge to edge and edge to face contacts between crystals these results have major repercussions for the interpretation of the archaeological assemblages in the flk zinj ds ptk amk palaeolandscape first this implies that two distinct archaeological levels formed at different times with different environmental conditions in most of these localities second textural analyses provide evidence that no important sedimentary compaction took place after the deposition of this layer this affects interpretations of palaeolandscape geomorphology third it shows that the sedimentary processes during all the clay sequence occurred in very low energy conditions this reinforces that no significant physical forces disturbed the original configurations of materials contained within these assemblages and reinforces their autochthony behavioural interpretations can thus be more solidly built upon the conception that those sites preserve most of their original in situ properties

mediterranean oceanic response to the interannual variability of a high resolution atmospheric forcing a focus on the aegean sea 1 we investigated the interannual variability of the mediterranean sea thermohaline circulation under present climate conditions using an oceanic model of 1 8 resolution two numerical simulations of 50 year duration were performed in a control simulation the model was forced by a perpetual year forcing inferred from the climatology of the ecmwf fields while in a random simulation the 6 years of the ecmwf fields were randomly applied in this way we were able to test the sensitivity of the thermohaline circulation under an atmospheric interannual variability in particular during the last 10 years of the random simulation a succession of cold winters led to anomalous deep water formation in the aegean sea we focused our analysis on this event this anomalously dense water mostly forms in the central and southern aegean subbasins with a formation rate of about 0 6 sv this led to strong modifications in water mass budgets and circulation with intensified exchanges between these two subbasins the export of those dense waters to the levantine basin remains weak except for a few particular years thus the impact of this event is localized as opposed to the eastern mediterranean transient these results show the possibility for transient events to reoccur in the eastern basin in the forthcoming years

on lunar asymmetries 2 origin and distribution of mare basalts and mascons 1 a novel mechanism is proposed for the emplacement of mare basalts and the formation of mascons that does not involve melting or remelting of the source region the source magmas are the remnants of the primordial lunar magma ocean and are rich in incompatible elements including radioactive isotopes potassium rare earth elements and phosphorus kreep and volatiles exsolution of volatiles as the magmas cooled and crystallized a process called second boiling produced overpressures which drove the dense basalts upward to the surface creating the mascons this process occurred preferentially beneath nearside mare basins where the crust is thinnest and lithostatic pressure is lowest the delay between impact and magmatic extrusion reflects the time needed for the volatile rich magma to cool to its second boiling point radioactive heating buffered the magmas against cooling and solidification allowing for an extended period of magmatism

surface circulation of the eastern mediterranean levantine basin insights from analyzing 14 years of satellite altimetry data 1 the complex multiscale system circulation of the levantine eastern mediterranean em basin is analyzed by applying various spatiotemporal statistical methods on the aviso 14 years 1993 2006 data set of satellite altimetry sea level anomalies the rossby deformation radius at the em is at the order of 10 km which is also the horizontal satellite resolution therefore the geostrophic currents derived from the satellite altimetry measurements represent well the basin and the mesoscale circulations the long term averaged mean dynamic topography mdt is found to capture the different eddy activity regions in the em however these regions are highly turbulent the instantaneous currents in these regions can be different from the mdt derived currents by the same order of magnitude furthermore the turbulence intensity appears to be nonperiodic despite of the seasonal and long term steric periodic variability because these eddies interact with the basin circulation flow they modify it continuously the major exception of this sporadic behavior is the ierapetra eddy southeast of crete it appears to be forced by shear of the summer etesian winds created when the crete mountain ridges block these winds and cause a funneling effect it has a persistent seasonal signature that dominates the variance of the entire levantine basin

on the pressure gradient force over steep topography in sigma coordinate ocean models abstract the error in computing the pressure gradient force near steep topography using terms following coordinates is investigated in an ocean model using the family of vertical differencing schemes proposed by arakawa and suarez the truncation error is estimated by substituting known buoyancy profiles into the finite difference hydrostatic and pressure gradient terms the error due to hydrostatic inconsistency which is not simply a space truncation error is also documented the results show that the pressure gradient error is spread throughout the water column and it is sensitive to the vertical resolution and to the placement of the grid points relative to the vertical structure of the buoyancy field being modeled removing a reference state as suggested for the atmosphere by gary reduces the truncation error associated with the two lowest vertical modes by a factor of 2 to 3 as an example the error in computing the pressure gradient using a standard 10 level primitive equation model appl

diagenetic destruction of reservoir potential in shallow marine sandstones of the broadford beds lower jurassic north west scotland depositional versus burial and thermal history controls on porosity destruction abstract the broadford beds are a shallow marine mixed siliciclastic carbonate unit up to 140 m thick that crops out in the northern inner hebrides adjacent to a major tertiary igneous centre the formation can be divided into three lithological units a lower limestone dominated unit a middle unit of muddy calcareous sandstones and an upper unit of cleaner sandstones the limestones underwent early meteoric diagenesis and early diagenetic processes in the overlying sandstones included the precipitation of berthierine corrensite phosphate and a small amount of mg calcite the most abundant burial cement is ferroan calcite most of which precipitated during mesozoic burial at depths of about 1 km these cements were sourced through the chemical compaction of depositional carbonate within interbedded muddier horizons later calcite cements were precipitated in fractures from meteoric fluids during late jurassic early cretaceous inversion and early tertiary uplift and a final stage of calcite cementation was associated with tertiary hydrothermal activity other burial diagenetic phases include quartz overgrowths and chlorite quartz cementation was initiated before the main phase of calcite cementation but the most significant quartz cementation accompanied the formation of chlorite during tertiary hydrothermal activity overall the most significant factor leading to porosity loss in the broadford beds was the abundance of detrital clays and depositional carbonate in the original sediment this led to extensive calcite cementation that both occuluded primary pores and inhibited the formation of secondary porosity

an extreme cold surge over the greek peninsula summary this paper is devoted to the detailed description of an extreme cold surge that occurred 3 13 march 1987 over greece this event has been rated as the worst snowfall over the last 100 years and duc to its severily and persistence it paralysed the cconornic and communal life of greece for several days emphasis is given to the initiation phase of this event the structural evolution of the cold surge is analysed using both observations and model results model simulations pcrformed with the colorado state university regional atmospheric modelling system provided the necessary data to diagnose the mesoscale structure of the cold outbreak different mechanisms involved in the structural evolution ofthe cold surge are investigated the gustiness of the observed winds and their significant departure from geostrophy are related to the role of an important isallobaric wind the progression of this surge presented characteristics of a density current while near the eastern slopes of the mountain barriers of continental greece cold air damming occurred leading to an accelerated flow parallcl to the mountains heavy snowfall events over greece are often associated with cold air surges prop agating from northern and central europe through the balkans metaxas 1978 livada tselepidaki 1979 prezerakos and angouridakis 1984 these cold surges are accompanied with the passage of a fast moving cold front from the north towards the south very strong winds especially in the gaps between mountains in northern greece and over the aegean sea a sharp temperature decrease over the whole country and a sharp pressure rise the lifetime of these surges is normally from 1 to 3 days extending up to 10 days in exceptional cases their persistence can cause important problems in economic life since the result ing snowfall can prohibit road transportation on the main traffic routes greek forecasters call these cold fronts balkan fronts due to their origin in the frame of this study this terminology will be retained although the classical term cold surge will also be used interchangeably the forecast of the evolution of these fronts as well as the persistence of cold surges over greece is of great importance not only for the impact of snowfall on economic life but also for the safety of navigation in the aegean sea in gale force winds cold surges accompanied by severe weather phenomena have also been reported in the himalayan region nakamura and murakami 1983 over the usa e g bell and bosart 1988 colle and mass 1995 as well as over central america schultz et al 1997 all the aforementioned studies underlined the fact that cold surges are accompanied by strong lower tropospheric northerly winds sharp decreases in temperature and sharp pressure rises in these studies some interesting features accompanying cold surges were also ad dressed mainly cold air damming near mountain barriers as a result of the interaction of the synoptic scale flow with topography bell and bosart 1988 concluded that the component of the pressure gradient force parallel to the mountain was the primary cause for the appearance of an accelerated flow nearly parallel to the mountains colle and mass 1995 demonstrated that pressure ridging east of the mountain barrier caused ageostrophic northerly winds while cold avection of upslope flow led to the damming of cold air schultz et al 1997 showed that the extraordinary equatorial extent of a cold surge was aided by topographic channelling similar to cold air damming

water fluxes through the cretan arc straits eastern mediterranean sea march 1994 to june 1995 abstract five research cruises were undertaken incorporating adcp sections along the cretan arc straits and ctd surveys covering the entire area of the straits and the cretan sea in addition six moorings with 15 current meters were deployed within the straits which monitored flows in the surface 50 m intermediate 250 m and deep 50 m from the bottom layers the adcp cm and ctd datasets enable the derivation of water transports through the cretan arc straits to be assessed flow structure through the cretan arc straits is not the typical flow regime with a surface inflow and deep outflow instead there is a persistent deep outflow of cretan deep water cdw 29 2 with an annual mean of 0 6 sv through the antikithira and kassos straits at depths below 400 m and 500 m respectively cdw outflowing transports are higher 0 8 sv in april june and lower 0 3 sv in october december within the upper water layer 0 400 m the transport and the water exchanges through the straits are controlled by local circulation features which weaken substantially below 200 m the asia minor current amc influences the rhodes and the karpathos straits resulting in a net inflow of water in contrast the mirtoan west cretan cyclone influences the antikithira and kithira straits where there is a net outflow in the kassos strait there is a complex interaction between the east cretan cyclone the ierapetra anticyclone and the westward extension of the rhodes gyre which results in a variable flow regime there is a net inflow in autumn and early winter and a switch to a net outflow in early spring and summer the total inflow and outflow throughout all of the straits ranged from 2 to 3 5 sv with higher values in autumn and early winter and lower in summer the amc carries 2 sv of inflow through the rhodes and karpathos straits and this accounts for 60 80 of the total inflow about 10 15 of the total outflow is of cdw and a further 45 70 occurs through the upper 400 m of the kithira and antikithira straits the kassos strait exhibits a net inflow of 0 7 sv in autumn and early winter with a net outflow of 0 5 sv in early spring and summer

variations in mixed layer illite smectite diagenesis in the rift and post rift sediments of the jeanne d arc basin grand banks offshore newfoundland canada mixed layer illite smectite i s clays were analyzed from 22 deep exploration wells from the jeanne d arc basin on the grand banks offshore newfoundland the host of large commercial hydrocarbon accumulations discovered in the last two and a half decades the fine fraction of the clays 0 1 m consists mainly of mixed layer i s with minor amounts of kaolinite illite and chlorite smectite and or smectite rich i s clays were supplied to the jeanne d arc basin from upper jurassic to tertiary times smectite rich i s clays occur only in shallow samples irrespective of geologic age the proportion of illite in i s mixed layers as well as the degree of ordering increase with depth and temperature indicating that smectite rich i s clays have been progressively illitized in both rift and post rift sediments of the jeanne d arc basin during burial the transition from random to r1 ordered i s occurs between subsurface depths of 1940 and 3720 m and crosses major stratigraphic boundaries the transition fr

recent changes in deep water formation and spreading in the eastern mediterranean sea a review abstract observations of the last decade testify that the characteristics of the deep thermohaline circulation in the eastern mediterranean sea have changed thoroughly the source of the most dense waters of the basin has moved from the adriatic to the aegean sea this new source has proved to be very efficient since the estimated formation rate for the period 1989 95 was more than 1 sv about three times more than the dense water formation rate of the adriatic sea these new waters with hydrological characteristics that are warmer and more saline have replaced almost 20 of the older deep waters of the basin and have uplifted the deep isopycnals by about 500 m this major event can be attributed to important meteorological anomalies in the eastern mediterranean and to changes of circulation patterns the extended dry period of 1988 93 and the exceptionally cold winters of 1987 and 1992 93 created favorable conditions for increased formation of dense water in the aegean furthermore changes in the circulation patterns in the intermediate water range levantine intermediate water liw and cretan intermediate water themselves possibly linked to meteorological anomalies appear to have played an important role in the redistribution of salt as a result of an interruption to exchanges between the ionian and levantine basin the salinities in the latter started to rise high salinity waters were diverted into the aegean malanotte rizzoli p manca b b ribera dacala m theocharis a 1998 the eastern mediterranean in the 80s and in the 90s the big transition emerged from the poem bc observational evidence rapport du commission international de la mer medittanee 35 174 175 and the westward transport of liw was reduced an additional effect of the deep water discharge from the aegean and the resulting uplifting of mid depth waters was to lower salinities in the liw layer this effect is most strongly felt in the ionian sea a 3 d primitive equation numerical model for the eastern mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient these results indicate that the observed changes can be at least partially explained as a response of the eastern mediterranean and more specifically of the aegean to atmospheric forcing variability

the k ar and 40ar 39ar methods revisited for dating fine grained k bearing clay minerals abstract the strengths and weaknesses of the two ar isotopic methods k ar and 40ar 39ar were evaluated on the basis of respective recent applications mainly on low temperature k bearing illite type clay minerals this review includes a presentation of basic analytical and technical aspects for both methods as well as a discussion of varied claims on the two methods and of requests about sample preparation and characterization whenever possible the advantages and weaknesses of each method were compared on coeval results obtained by both methods on the same mineral separates the comparative review examines stratigraphic dating of glauconites indirect dating of low temperature ore deposits dating of burial related illitization and dating of polyphased tectono thermal activity more specifically of fault gouges some pending questions such as the necessary encapsulation due to 39ar recoil and its restoration into step heating patterns are also raised together with the new potential of ar dating of nanometric illite crystals weakness of the k ar method is in its pioneering status that makes many believe that it is no longer accurate because of its traditional analytical aspects and of the k determinations leading to somewhat large uncertainties however precise evaluation of varied applications points to a k ar method having probably larger applicability in sedimentary to diagenetic environments than the 40ar 39ar method the drawbacks become less important if the method is applied to nanometer sized clay minerals in diagenetic to low grade metamorphic environments in this instance the extracted size fractions are generally homogeneous and the relative uncertainty given by the age calculations if mathematically justified can be reduced by duplicate analyses weakness of the 40ar 39ar method is in its basics such as the 39ar recoil the necessary encapsulation the reintegration of the 39ar into the step heating patterns and the meaning of the step heating patterns that are more suggestive of variable 39ar reservoirs created among the clay particles by irradiation than of meaningful geologic ages if the k ar method is the preferred method for dating diagenetic clay processes such as glauconitization illite crystal nucleation and growth or low temperature hydrothermal activities then the 40ar 39ar method has more potential in dating low temperature tectono thermal activities and in detailing mixtures of multi generation illite

unexpected covariant behavior of the aegean and ionian seas in the period 1987 2008 by means of a nondimensional sea surface height index

dense intermediate water outflow from the cretan sea a salinity driven recurrent phenomenon connected to thermohaline circulation changes data collected from different platforms in the cretan sea during the 2000s decade present evidence of gradually increasing salinity in the intermediate and deep intermediate layers after the middle of the decade the observed gradual salt transport toward the deeper layers indicates contributions of dense water masses formed in various aegean sea subbasins the accumulation of these saline and dense water masses in the cretan sea finally led to outflow from both cretan straits with density greater than typical levantine cretan intermediate water but not dense enough to penetrate into the deep layers of the eastern mediterranean we name this outflowing water mass as dense cretan intermediate water dciw a retrospective analysis of in situ data and literature references during the last four decades shows that similar events have occurred in the past in two occasions a in the 1970s and b during the eastern mediterranean transient emt onset 1987 1991 we argue that these salinity driven aegean outflows are mostly attributed to recurrent changes of the eastern mediterranean upper thermohaline circulation that create favorable dense water formation conditions in the aegean sea through salinity preconditioning we identify these phenomena as emt like events and argue that in these cases internal thermohaline mechanisms dominate over atmospheric forcing in dense water production however intense atmospheric forcing over an already salinity preconditioned basin is indispensable for creating massive deep water outflow from the cretan sea such as the emt event

the 1987 aegean dense water formation a streamtube investigation by comparing theoretical model results satellite field and numerical data with contourite distribution abstract we here discuss a detailed investigation of the dense water formation evolution and spreading in the aegean sea during the year 1987 immediately prior to the onset of the eastern mediterranean transient emt we use hydrologic data collected during the lia cruise satellite images for sst sea surface temperature and protheus data a coupled ocean atmosphere numeric model along with theoretical streamtube models these hydrological analyses are related to late quaternary sedimentary drifts in the cyclades plateau and in the myrtoon basin our analysis shows that streamtube dynamics provide a novel model of dense water evolution and spreading in the aegean basin applying this model to dense water masses observed in winter and spring 1987 near samothrace and over the limnos lesbos plateau results in a geostrophic flow of this dense cold water towards the limnos sporades channel in the north aegean sea there it mixes with dense water from the limnos lesbos plateau and finally both move geostrophically towards the cyclades plateau these results indicate that most of the dense water observed near the cyclades formed initially about 3 months earlier at samothrace and limnos shelves during its long pathway it partially mixed with adjacent water masses although our analysis concerns only one year of dense water analyses these results are thought to reflect a more general and recurrent phenomenon in the aegean basin indeed high resolution airgun 10 in seismic reflection data from the cyclades plateau reveal the presence of late quaternary sediment drifts these observations are concordant with results from our theoretical model this suggests a direct link between such a dense water cascading and contourite dynamics the continuation of sediment drifts into the deep basin floor 900 m deep of the myrtoon basin moreover indicates a cascading character of such bottom currents at the flanks of the basin a feature that set further investigations

the role of the north aegean in triggering the recent eastern mediterranean climatic changes drastic changes have occurred in the vertical structure of the deep waters of the eastern mediterranean in the early 1990s as dense water of aegean origin has displaced lighter waters of adriatic origin at the bottom of the deep basins this work suggests that the initiation of this process took place in the north aegean in the winter of 1986 1987 and was intensified by another formation event in 1992 1993 the available observations from the north aegean support such a scenario furthermore we propose that the outflow of black sea waters into the aegean through the dardanelles could act as an insulator of the deeper layer from the atmosphere thus absorbing a large part of the heat and salt exchange despite this fact the existence of the densest bottom water of the mediterranean in the north aegean and the continuation of density increase for a large period of time suggests that it is a region of formation thus that the insulation layer may at times be penetrated we suggest that reduced black sea outflow into the north aegean could facilitate dense water formation during the passage of cold atmospheric fronts in the winter

structural evolution of the sedimentary accretionary wedge of the alpine system in eastern sicily thermal and thermochronological constraints temperature dependent clay mineral assemblages vitrinite reflectance and apatite fission track data have been used to investigate levels of diagenesis and time of exhumation of the double verging sicilide antisicilide accretion ary wedge in eastern sicily the integration of organic and inorganic thermal indicators allowed us to distinguish parts of the accre tionary wedge with different thermal signature and evolution we recognize a warmer core made up of the mount soro and troina units and two colder rims antisicilide and far traveled sicilide units the antisicilide unit was thrust back toward the hinterland and the far traveled sicilide units were gravity driven toward the hyblean plateau in detail the highest percentages of vitrinite reflectance vr o values 0 60 0 96 and percentages of illite layers in illite smectite i s 60 85 are found in the mount soro and troina units apatite fission track data together with the paleotemperature estimates from vitrinite reflectance data and clay mineral based geothermometers indicate that fission tracks were partially to totally annealed during wedge accretion and that the subsequent exhumation occurred mainly in burdigalian times low vr o values 0 35 0 50 and percentages of illite layers in i s 30 60 occur in early thrust top deposits reitano flysch that unconformably overlie the sicilide complex as well as the far traveled sicilide and antisicilide units apatite fission track data for the antisicilide unit confirm low paleo temperature values thus the far traveled sicilide and antisicilide units were probably at higher structural levels in the original accretionary prism and were remobilized since late aquitanian burdigalian times

dating of pliocene colorado river sediments implications for cosmogenic burial dating and the evolution of the lower colorado river we applied cosmogenic 26 al 10 be burial dating to sedimentary deposits of the ancestral colorado river we compared cosmogenic burial ages of sediments to the age of an independently well dated overlying basalt flow at one site and also applied cosmogenic burial dating to sediments with less precise independent age constraints all dated gravels yielded old ages that suggest several episodes of sediment burial over the past 5 3 m y comparison of burial ages to the overlying 4 4 ma basalt yielded good agreement and suggests that under the most favorable conditions cosmogenic burial dating can extend back 4 5 m y in contrast results from other sites with more broadly independent age constraints highlight the complexities inherent in burial dating these complexities arise from unknown and complicated burial histories insufficient shielding postburial production of cosmogenic isotopes by muons and unknown initial 26 al 10 be ratios nevertheless and in spite of the large range of burial ages and large uncertainties we identify samples that provide reasonable burial age constraints on the depositional history of sediment along the lower ancestral colorado river these samples suggest possible sediment deposition and burial at ca 5 3 4 7 and 3 6 ma our calculated basinwide erosion rate for sediment transported by the modern colorado river 187 mm k y 1 is higher than the modern erosion rates inferred from the historic sediment load 80 100 mm k y 1 in contrast basinwide paleo erosion rates calculated from pliocene sediments are all under 40 mm k y 1 the comparatively lower denudation rates calculated for the pliocene sediment samples are surprising given that the sampled time intervals include significant pliocene aggradation and may include much incision of the grand canyon and its tributaries this conflict may arise from extensive storage of sediment along the route of the colorado river slower paleobedrock erosion or the inclusion of sediments that were derived preferentially from higher elevations in the watershed

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

a real time oceanographic nowcast forecast system for the mediterranean sea we describe here a nowcast forecast system for the entire mediterranean sea designed for real time forecasts and closely resembling operational numerical weather prediction systems the core of the system is a high resolution 10 km three dimensional primitive equation based sigma coordinate numerical circulation model assimilating remotely sensed multi channel sea surface temperature and in situ expendable bathythermograph conductivity temperature depth observational data using an optimal interpolational scheme we present results for 1993 and 1994 from this data assimilation model focusing principally on the mesoscale features prevalent in the western and eastern mediterranean sea we show that the model exhibits considerable skill in simulating both the permanent and transient mesoscale features in the mediterranean in particular hitherto less well known and less well studied circulation features in the adriatic and aegean seas are carefully examined and presented particular care is given to discussing the circulation in the entire mediterranean with particular attention to flows through various straits and their variability

modeling the mediterranean sea interannual variability during 1961 2000 focus on the eastern mediterranean transient 1 this work is dedicated to the study of the climate variability of the mediterranean sea in particular the study of the eastern mediterranean transient emt which occurred in the early 1990s simulations of the 1961 2000 period have been carried out with an eddy permitting ocean general circulation model of the mediterranean sea driven by realistic interannual high resolution air sea fluxes using different databases for the river runoff black sea inflow and atlantic thermohaline characteristics at climatological or interannual scales we assess the effects of the non atmospheric hydrological forcings on the simulation of the interannual variations of the mediterranean circulation the evolution of the basin scale heat content is in very good agreement with the observations especially in the surface and intermediate layers while the agreement is lower for the evolution of the salt content convection events in the aegean sea are noticed in the simulations between 1972 and 1976 in the late 1980s and around the emt period the formation rates of cretan deep water cdw are different during these periods allowing or preventing the spreading of cdw into the eastern mediterranean the sequence of the emt events is well reproduced the high winter oceanic surface cooling and net evaporation over the aegean sea in the early 1990s the high amount of dense cdw formed during these winters and then the overflow and the spreading of this cdw in the eastern mediterranean among the preconditioning processes suggested in the literature we find that changes in the levantine surface circulation possibly induced by the presence in the cretan passage of anticyclonic eddies and a lasting period with reduced net precipitation over the eastern mediterranean lead to an increase of the salt content of the aegean sea changes in the black sea freshwater inflow or in the characteristic of the atlantic water entering at the gibraltar strait also modify the thermohaline state of the aegean sea before the emt but as none of these preconditioning factors has a lasting impact on lowering the vertical stratification of the aegean sea we conclude that concerning the emt the major triggering elements are the atmospheric fluxes and winds occurring in winters 1991 1992 and 1992 1993

extreme cooling and dense water formation estimates in open and coastal regions of the adriatic sea during the winter of 2012 generation of dense waters in the adriatic sea during an extreme cooling event in the winter of 2012 including its preconditioning and spreading phases have been investigated using the one way coupled roms and the aladin hr modeling system both climatological and real river fluxes are used in the simulations aside from the convenient dense water formation areas located at the northernmost adriatic shelf we found that a similar amount of dense water with slightly lower density was formed in the eastern and deeper adriatic coastal area which was subjected to extreme heat losses up to 2000 w m2 during peak cooling periods this part of the adriatic has been known for extreme cooling during wintertime bora outbreaks nevertheless no ocean model study has previously reproduced dense water formation in this area the most likely reason for that was an overestimate of river discharges introduced to ocean models from newly available data we estimated that the contribution of eastern adriatic rivers between the neretva river and rijeka bay is more than six times lower than what has been previously documented transport of dense water toward the middle adriatic had a peak value of about 0 6 sv while the speed of initial bottom density current surpassed 40 50 cm s which is several times faster than past events different pathways of the dense water toward the middle and south adriatic depressions have also been documented the contribution of the eastern coastal adriatic area to the overall north adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions indicating that this part of the adriatic is a common place for dense water generation

transient eastern mediterranean deep waters in response to the massive dense water output of the aegean sea in the 1990s abstract we present a detailed account of the changing hydrography and the large scale circulation of the deep waters of the eastern mediterranean emed that resulted from the unique high volume influx of dense waters from the aegean sea during the 1990s and of the changes within the aegean that initiated the event the so called eastern mediterranean transient emt the analysis uses repeated hydrographic and transient tracer surveys of the emed in 1987 1991 1995 1999 and 2001 2002 hydrographic time series in the southern aegean and southern adriatic seas and further scattered data aegean outflow averaged nearly 3 10 6 m 3 s 1 between mid 1992 and late 1994 and was largest during 1993 when south and west of crete aegean influenced deep waters extended upwards to 400 m depth emt related aegean outflow prior to 1992 confined to the region around crete and to 1800 m depth wise amounted to about 3 of the total outflow outflow after 1994 up to 2001 2002 derived from the increasing inventory of the tracer cfc 12 contributed 20 to the total of 2 8 10 14 m 3 densities in the southern aegean sea deep waters rose by 0 2 kg m 3 between 1987 and 1993 and decreased more slowly thereafter the aegean waters delivered via the principal exit pathway in kasos strait east of crete propagated westward along the cretan slope such that in 1995 the highest densities were observed in the hellenic trench west of crete aegean influenced waters also crossed the east mediterranean ridge south of crete and from there expanded eastward into the southeastern levantine sea transfer into the ionian mostly followed the hellenic trench largely up to the trench s northern end at about 37 n from there the waters spread further west while mixing with the resident waters additional transfer occurred through the herodotus trough in the south levantine waters after 1994 consistently showed temperature salinity t s inversions in roughly 1000 1700 m depth with amplitudes decreasing in time the t s distributions in the ionian sea were more diverse one cause being added aegean outflow of relatively lower density through the antikithira strait west of crete spreading of the aegean influenced waters was quite swift such that by early 1995 the entire emed was affected and strong mixing is indicated by near linear t s relationships observed in various places referenced to 2000 and 3000 dbar the highest aegean generated densities observed during the event equaled those generated by adriatic sea outflow in the northern ionian sea prior to the emt a precarious balance between the two dense water source areas is thus indicated a feedback is proposed which helped triggering the change from a dominating adriatic source to the aegean source but at the same time supported the previous long year dominance of the adriatic the emed deep waters will remain transient for decades to come

toward an understanding of deep water renewal in the eastern mediterranean abstract this paper presents a scenario for understanding the unexpectedly large changes of deep waters and thermohaline circulation in the eastern mediterranean during the past decade it is demonstrated as a possible deep water renewal mechanism in the eastern mediterranean in a numerical simulation with a high resolution model which has successfully reproduced the observed 1987 and 1995 regimes as shown by the two meteor cruises a budget study of the model simulation has shown that more than 75 of the salt added to the deep layers of the eastern mediterranean could have come from the top 1000 m by a salinity redistribution process triggered by intensive cooling over the aegean sea a water transformation process analysis is carried out in the model simulation to reveal how colder and fresher dense deep water formed in the aegean is turned into the eastern mediterranean deep water emdw as observed surface heat and freshwater fluxes are diagnosed to show the roles of each component during the trans

temporal evolution of the water mass properties during the eastern mediterranean transient emt in the aegean sea 1 we present time series of temperature and salinity of the aegean sea using the data sets for the period from 1991 to 1996 from 15 oceanographic cruises to depict the temporal variability of the water masses of the aegean sea this period covers an interesting large scale change in the thermohaline circulation in the eastern mediterranean and the aegean sea this change is known as the eastern mediterranean transient emt and was first described during early 1990s our analysis reveals that very dense water formation in the central aegean sea is partially due to the anomalous decrease in winter atmospheric temperature although this alone cannot completely account for the formation of the dense water a synchronous increase in surface salinity accompanied by low temperature values in the winter months is also necessary for the emt event to occur

diagenetic evolution of clay minerals in oil bearing neogene sandstones and associated shales mahakam delta basin kalimantan indonesia the clay fraction of the mahakam delta basin eastern kalimantan indonesia consists of mixed layer illite smectite kaolinite dickite detrital illite and chlorite kaolinite formed early as vermicular particle aggregates and thick dickite booklets formed late in pore spaces the dickite particles probably grew in deeper intervals of the sequence in contact with brines acidified by decarboxylation of organic matter during dissolution of k feldspar and upward migration of potassium in the handil field on the nearshore anticline evolution of the mixed layer illite smectite is characterized by a decrease in expandability with depth in the tunu field located on the next offshore anticline variable amounts of expandable layers suggest a different evolution the conversion process of smectite to illite layers in the mixed layers depends on the lithology of the host rocks transformation in the shales and dissolution precipitation in the sandstones sample location also played a role in the conversion process because the types of illite clays in the two locations differ when they are compared at similar degrees of evolution present day temperatures and paleotemperatures vitrinite reflectance and illitization of the mixed layer illite smectite all suggest that organic matter and clay particles evolved differently in the handil field but similarly in the tunu field integration of the analytical results obtained here and comparison with a two dimensional numerical model suggest that hydrocarbon generation took place in the deeper synclinal zones of the sequence and that oil migrated upward with brines probably inducing most of the illitization in the upper sequence both models emphasize the role of faults in channelizing fluid flow during the final stages of evolution of the basin

open system chemical behavior in deep wilcox group mudstones texas gulf coast usa abstract wilcox group mudstones have been mechanically and geochemically transformed over a temperature range of 20 200 c our research controlled for provenance and age by sampling from five wells parallel to the paleodepositional axis all within the houston delta system across the sampled depths mudstone porosity has been reduced from 25 to

seismic velocity structures in the southern california plate boundary environment from double difference tomography summary we present tomographic images of crustal structures in the southern california plate boundary area with a focus on the san jacinto fault zone sjfz based on double difference inversions of earthquake arrival times absolute arrival times of 247 472 p and 105 448 s wave phase picks for 5493 earthquakes recorded at 139 stations in southern california are used starting with a layered 1 d model and continuing in later iterations with various updated initial models we invert the data for vp and vs in a 270 km long 105 km wide and 35 km deep volume around the sjfz using a spatially variable grid with higher density around the sjfz the examined volume stretches from cajon pass to the northernmost imperial fault zone and includes portions of the southern san andreas fault saf the elsinore fault and the brawley seismic zone in the salton trough because differential traveltimes used in the double difference inversions are most sensitive to near source structures we obtain high resolution around the earthquake sources after 30 iterations we improve the average traveltime misfit by a factor of 16 though ray coverage is limited at shallow depths we obtain detailed images of seismic velocities from 3 to 20 km throughout much of the study area our final velocity results show zones of low velocity and anomalous vp vs ratios associated with various fault strands and sedimentary basins along with clear velocity contrasts across the sjfz and the southern saf the velocity reductions in fault zone regions are generally highest in geometrically complex areas up to 30 50 per cent in the top few kilometres are higher for vs than for vp and follow a flower type pattern with depth in the central section of the sjfz from the san jacinto valley to the trifurcation area the northeast side of the fault has generally higher seismic velocities than the southwest block the obtained contrasts of vp are more persistent and higher up to 20 per cent than the contrasts of vs up to 15 per cent although the differences may stem at least partially from the higher resolution of vp images in the sjfz sections to the northwest and southeast there are patches with reversed velocities contrasts especially in the shallow crust near the san jacinto valley and other basins along the banning fault there is no clear velocity contrast for the southern saf the northeast side has generally lower seismic velocities in the seismogenic zone with patches of contrast reversals in the shallow crust in the brawley seismic zone the northeast side has somewhat lower velocities in the 20 km section near the southern saf and higher velocities farther to the southwest the imaged features have important implications for various aspects of earthquake and crustal dynamics in the region

diagenesis of sandstones at shale contacts and diagenetic heterogeneity frio formation texas diagenetic trends near sandstone shale contacts were studied in 12 cored sequences from four wells between depths of 5200 and 15 700 ft 1585 and 4785 m to evaluate the heterogeneity of diagenetic processes on a local scale and to evaluate the hypothesis that reactive aqueous fluids and components for cements in sandstones were derived from adjacent shales the only evidence suggesting that diagenetic components in sandstones were derived from immediately adjacent shales is an increase in chlorite cement in sandstones toward contacts with shale beds for two of three contacts appropriate for study secondary pores and cements of quartz carbonate and kaolinite do not correlate with proximity to shale beds but have a preference for sandstones that had relatively high ini ial porosities and permeabilities thus the flux of formation water and probably long distance transportation of diagenetic components were more important influences on reservoir quality of sandstones than was the local availability of components multiple regression of 22 independent variables indicates that the best predictors of secondary porosity are kaolinite cement and intergranular porosity sandstone sequences are extremely heterogeneous in the distribution of total thin section porosity secondary porosity and quartz and carbonate cements in addition they have significant variations in the abundance of kaolinite and chlorite cements mass balance calculations for silica and aluminum indicate silica was imported to and aluminum was exported from the sandstones

illite smectite diagenesis in the nanxiang yitong and north china permian carboniferous basins application to petroleum exploration in china the nanxiang basin in henan province and the yitong basin in jilin province located in the eastern part of china are composed mainly of tertiary nonmarine clastic sequences that thicken to more than 4000 5000 m the north china permian carboniferous basin consists of permian carboniferous systems composed of marine and nonmarine coal bearing sequences clay diagenesis in these basins was studied by systematic x ray diffraction analysis the clay mineralogy consists of illite smectite mixed layered illite smectite i s kaolinite and chlorite the major clay reaction is the illitization of smectite with depth and temperature the reactions generally involve discrete smectite stage to smectite plus the randomly interstratified i s r 0 in the reichweite nomenclatur followed by the first rapid change i to the ordered i s of short range stacking r 1 and the second rapid change ii to the metastable stage with the ordered i s of long range stacking r 3 the first rapid change leads to the appearance of i s ordered i s and disappearance of discrete smectite the proportion of smectite layers ps in the i s in the metastable stage remained unchanged 15 20 over a thick burial interval the discrete illite stage finally occurs in highly mature areas potassium feldspar k feldspar in rocks and k ions in present formation waters are available for the i s reactions i s reactions in these areas responded mainly to temperature the i s transition from the randomly interstratified i s r 0 to the ordered i s occurred at 80 95 c and coincided with the onset of the oil window in source rocks and with secondary porosity enhancement of sandstones the transition from the r 1 to r 3 happened around 130 165 c corresponding to the wet gas stage the illite stage corresponds to the dry gas stage of organic materials the duration of burial did not contribute significantly to the reaction integrating the i s reactions with thermal histories hydrological regimes structure sedimentation and sandstone diagenesis of eac basin allows formulation of clay diagenetic models for each specific basin

impact of the spatial distribution of the atmospheric forcing on water mass formation in the mediterranean sea the impact of the atmospheric forcing on the winter ocean convection in the mediterranean sea was studied with a high resolution ocean general circulation model the major areas of focus are the levantine basin the aegean cretan sea the adriatic sea and the gulf of lion two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared the first simulation med16 era40 was forced by air sea fields from era40 which is the ecmwf reanalysis the second simulation med16 ecmwf was forced by the ecmwf analyzed surface fields that have a horizontal resolution twice as high as those of era40 the analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns comparing the companion ocean simulation results with available observations in the adriatic sea and in the gulf of lion shows that med16 ecmwf is more realistic than med16 era40 in the eastern mediterranean although deep water formation occurs in the two experiments the depth reached by the convection is deeper in med16 ecmwf in the gulf of lion deep water formation occurs only in med16 ecmwf this larger sensitivity of the western mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time space resolutions of the forcing on the intense winter convection event in winter 1998 1999 the sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography which can only be reproduced in atmospheric models of sufficient resolution thus well positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter

vertical distribution and temporal trends of 137cs at lemnos and cretan deep basins of the aegean sea greece abstract caesium 137 activity concentrations 137cs were measured between 2003 and 2014 in the water column of lemnos and cretan deep basins of the aegean sea the purpose was to assess water mass dynamics and mixing processes by combining typical oceanographic data with the activity concentrations of 137cs the radiological data combined with dissolved oxygen profiles provided substantially more information than solely temperature and salinity regarding processes such as water mass identification formation and mixing in each basin it was possible to determine stagnant periods where turbulent mixing was dominant as well as periods where replenishment of the deep basins had been taken place at lemnos basin the data profile in 2013 proved evidence of water column ventilation down to 800 m and replenishment of the deep basin by less saline water mass the 137cs information provided evidence for contribution of water from the black sea to the intermediate and deep layers of the south aegean cretan basin the profiles of 2013 and 2014 were characterized by the return of 137cs inventories to pre chernobyl levels

the updip and downdip limits to great subduction earthquakes thermal and structural models of cascadia south alaska sw japan and chile this study examines thermal and structural controls of the updip and downdip rupture limits of great subduction thrust earthquakes data on past great earthquake seismic limits have been compiled for four continental subduction zones cascadia sw japan south alaska and chile these limits have then been compared to the predictions of several models for what constrains great earthquake rupture temperatures on the subduction thrusts have been estimated by finite element numerical models the landward limits of the observed updip aseismic zones correspond to the position where the thrust temperature reaches about 100 c that is depths of about 2 to 10 km for the subduction zones studied this temperature agrees with the dehydration of stable sliding smectite clays to illite chlorite the temperatures in this region are controlled mainly by the thickness of sediment on the incoming crust and by the crustal age and thus heat flow the downdip limits correspond to the depth on the thrust where either 1 the temperature reaches about 350 c which corresponds to thermally activated stable sliding behavior for crustal rocks with a transition to 450 c or 2 about 40 km depth if 350 c is reached at greater depth depths of about 40 km approximately correspond to the intersection of the thrust with the continental forearc moho and this downdip limit may be a consequence of stable sliding serpentinite or talc and other hydrated forearc mantle rocks the primary temperature controls on the downdip region are the age of the subducting oceanic plate and the thrust dip profile secondary control comes from the thickness of incoming sediment the convergence rate and the radioactive heat generation in the overlying forearc the 100 c updip limit occurs near the trench for young subducting plates with a thick sediment section such as cascadia 6 8 ma and up to 80 km landward for older oceanic crust such as south alaska 50 ma the 350 c downdip thermal limit is applicable for young oceanic plates e g cascadia and nankai whereas the forearc mantle limit applies for older plates e g south alaska and chile except near the chile rise for the margins studied that have experienced great earthquakes there is generally good agreement between the postulated thermal and moho limits and the rupture or seismogenic zone as defined by the distribution of aftershocks and by waveform tsunami and dislocation modeling the downdip limit of the interseismic locked zone from dislocation modeling is also in agreement with these limits

distribution of the thermohaline characteristics in the aegean sea related to water mass formation processes 2005 2006 winter surveys 1 aiming at portraying the aegean s water mass structure and identifying dense water formation processes two winter cruises were conducted in 2005 2006 across the plateaus and depressions of the aegean sea the most prominent feature of the water mass distribution in the basin is a distinct x shape of the s characteristics suggesting a complicated coupling of the major aegean sub basins the surface and deep waters are relatively decoupled with diverse origin characteristics while the intermediate layers act as connectors of the main thermohaline cells the central aegean seems to play a key role due to formation processes of water masses with densities equal and or higher than 29 2 kg m3 that take place in the sub basin and disperses in the north aegean on the other hand the south aegean appears greatly influenced by the eastern mediterranean circulation and water mass distribution especially under the eastern mediterranean transient status the transitional mediterranean water monitored in the post emt period and characterized by low temperature at 14 2 c low salinity at 38 92 and low dissolved oxygen at 3 97 ml l with its core around 750 m and above the saline 39 06 cretan deep water altered significantly the south aegean structure the pre emt thermohaline pattern of the central and south aegean deep layers were similar while the bottom density of the central basin was higher than that in the south aegean thus it is possible that the deep waters of the central aegean acted as a dense water reserve supply for the deeper part of the southern basin

the eastern mediterranean sea biogeochemical dynamics in the 1990s a numerical study 1 the coupled physical biogeochemical dynamics of the mediterranean sea have been hindcasted for the decade 1990 2000 with the nucleus for european modeling of the ocean biogeochemical flux model coupled modeling system this work describes and discusses the simulated changes in the eastern mediterranean sea physical and biogeochemical dynamics occurring in the 1990s contemporary to the establishment of the eastern mediterranean transient the physical component of the modeling system reproduces several changes in the eastern mediterranean physical dynamics and thermohaline structure that are consistent with observations pertinent to the transient period the simulated change in the atmospheric forcing during the early 1990s is considered sufficient to develop upwelling favorable conditions that determine an overall upward displacement of the simulated deep eastern mediterranean nutrient pool model results indicate that in the post transient period the displaced nutrients were advected westward along with the reestablishment of the levantine intermediate water pathway and together with the occurrence of strong winter mixing events in the ionian sea they determined an increase of the primary production processes in the euphotic layer along the eastern coast of ionian sea and northern levantine basin the biogeochemical model suggests that such an increase in productivity apparently impacted mostly the microbial branch of the marine trophic web

role of permeability versus temperature in the distribution of the fine 0 2 μm clay fraction in the chipilapa geothermal system el salvador central america abstract detailed x ray diffraction of clay minerals from the less than 0 2 m fraction of altered rocks has been carried out on cuttings and cores from three boreholes ch7 ch9 and ch7b from the geothermal field of chipilapa el salvador central america in most of the low permeable horizons the vertical distribution of i s and c s mixed layers fairly agrees with the general scheme of di smectite to illite and tri smectite to chlorite conversion series with increasing depth max 2600 m and temperature max 220 c the deepest parts of the wells are characterized by chlorite and illite rich illite smectite mixed layers i sr 1 in close agreement with the measured temperature 170 220 c within fracture controlled permeable horizons the distribution of clay minerals strongly disagrees with the classical pattern of di smectite to illite and tri smectite to chlorite conversions observed in low permeable horizons great amounts of smectites and or smectite rich mixed layers occur at temperatures which strongly exceed the current range of smectite stability in natural systems up to 205 c similar discrepancies may also be viewed from chlorite crystallinity in well ch9 and smectite content in smectite rich chlorite smectite mixed layers in well ch7b these high temperature smectites are considered as present or very recent metastable phases representing the first step of kinetically controlled conversion series toward illite and or chlorite such phenomena are restricted to the levels in which the present hydrodynamic conditions promote the crystallization process boiling and mixing of fluids with contrasting temperatures high temperature smectites and smectite rich mixed layers may be of great interest for the understanding of the very recent evolution of geothermal reservoirs they do not only indicate the present horizons of active fluid circulations in geothermal wells smectite coatings at the wall of fractures but they are also potential guides in the determination of the horizons in which permeability has recently decreased

paleogene igneous intrusion and its effect on thermal maturity of organic rich mudstones in the beibuwan basin south china sea abstract the seismic drilling and logging data reveal that a large scale igneous intrusion with a width of 14 km and a maximum thickness of 170 m intruded within the paleogene liushagang formation in the fushan depression beibuwan basin south china sea scs in this study we report the geochemistry and sr nd pb hf isotopic compositions of the igneous rocks and evaluate the thermal effect induced by this large scale igneous intrusion on the host rocks the analyzed igneous samples exhibit strong enrichment in light rare earth elements lree and large ion lithophile elements lile having characteristics similar to intra plate oceanic island basalts oib the sr nd pb hf isotopic data display narrow ranges e g 87sr 86sri 0 7042 0 7044 143nd 144ndi 0 5128 0 5129 206pb 204pbi 18 90 18 94 ehf t 7 56 9 60 geochemical and isotopic compositions suggest a mixed mantle source between depleted mid ocean ridge basalt morb mantle dmm like mantle and enriched mantle type ii emii possibly the hainan mantle plume vitrinite reflectance values major mineralogical changes together with a maturity related biomarker ts ts tm all reveal significant thermal effect induced by the igneous intrusion vitrinite reflectance values of the host rock are up to 2 5 in the intrusion region whereas lower reflectance values 0 62 0 73 occur in the unaffected area of the same strata moreover our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below which should be attributed to the different behavior of hydrothermal fluids these observations suggest that the thermal effect of large scale thick igneous intrusions is much more intense than that of thin igneous intrusions and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process

climatic changes in the aegean sea influence the eastern mediterranean thermohaline circulation 1986 1997 recent changes of water mass characteristics in the south aegean sea have considerably influenced the eastern mediterranean thermohaline circulation a combination of salinity increase 1987 92 and temperature drop 1992 94 caused massive dense water formation and strong outflow towards the deep and bottom parts of the eastern mediterranean this climatic shift the most important since the existence of observations in the basin is a combined effect of extreme meteorological events superimposed on large scale trends it has initiated a series of modifications in the hydrology and dynamics of the entire eastern mediterranean with possible influence on the mediterranean outflow in the north atlantic ocean