rock composition dolomite stoichiometry and rock water reactions in dolomitic carbonate rocks dolomitic carbonate rock units from a variety of phanerozoic localities and depositional environments throughout north america were evaluated with respect to their dolomite content and dolomite composition by x ray diffraction analysis dolomite compositions range from 48 to 57 mole caco 3 with well defined modes at 51 nearly stoichiometric dolomite and 55 distinctly calcian dolomite caco 3 values of percentage of dolomite also exhibit a pronounced albeit less well defined bimodal distribution with modes at 97 dolostones and 20 dolomitic limestones dolomite similar distributions characterize most other published data on phanerozoic dolomitic carbonates these data suggest that two separate processes may lead to two distinct populations of sedimentary dolomite 1 dolomitic limestones originate in diagenetically closed systems during magnesian calcite dissolution calcite and dolomite precipitation reactions and 2 dolostones originate in diagenetically open systems during th

mesozoic volcanism in the middle east geochemical isotopic and petrogenetic evolution of extension related alkali basalts from central lebanon mesozoic picritic and alkali basalts from central lebanon represent a significant part of an extension related upper jurassic to upper cretaceous discontinuous volcanic belt which occurs throughout the middle east volcanism was associated with an episode of intraplate extension that followed a period of continental break up where mesozoic micro continental blocks separated from gondwana as the neotethys ocean opened in jurassic times this volcanic episode produced mafic lava flows ranging in thickness from 5 to 20 m along with some minor pyroclastic flows these flows are stratigraphically intercalated with thick carbonate platform deposits the basalts are made up of about 15 20 olivine fo 78 91 30 35 clinopyroxene salite 40 50 plagioclase an 56 71 and opaque fe ti oxides 5 geochemically the rocks exhibit a relatively wide range of sio 2 40 4 to 50 5 wt and mgo 5 1 to 15 5 wt contents are relatively enriched in tio 2 1 7 to 3 7 wt and vary in composition from alkali picrite and basanite to alkali basalt the mg numbers range from 0 56 to 0 70 with an average of 0 63 the rocks are enriched in incompatible trace elements such as zr 86 247 ppm nb 16 66 ppm and y 19 30 ppm such compositions are typical of those of himu oib and plume related magmas the ree patterns are fractionated la yb n 11 lree enriched and are generally parallel to subparallel elemental ratios such as k p 1 1 4 7 la ta 11 13 la nb 0 57 0 70 nb y 0 68 1 55 and th nb 0 20 0 36 suggest that crustal contamination was minor or absent this may be related to a rapid ascent of the magma in agreement with the nature mafic oceanic like and the small thickness about 12 km of the mesozoic crust of the eastern mediterranean region the 143 nd 144 nd isotopic compositions of the lavas range from 0 512826 to 0 512886 and 87 sr 86 sr from 0 702971 to 0 703669 suggesting a himu like mantle source trace element compositions indicate a melt segregation depth of 100 110 km well within the garnet lherzolite stability field the geochemical characteristics of the rocks are typical of within plate alkali basalts and suggest that the magmas were derived from a fertile possibly plume related enriched mantle source petrogenetic modelling indicates that the magmas were produced by very small degrees of batch partial melting f 1 5 of a primitive garnet bearing mantle source garnet lherzolite

dolomitization a critical view of some current views the principal models in vogue today for dolomitization are the mixing zone and the sabkha models despite the wide acceptance of these models there has been little critical assessment of their validity such an assessment is the objective of the present paper a close look at the dorag mixing zone model badiozamani 1973 reveals several serious weaknesses 1 the range of freshwater seawater mixtures that meet the dorag requirement for dolomitization shrinks to a small window if the geologically more realistic disordered dolomite is used in the calculations instead of the ordered dolomite on which the model is based 2 in none of the known modern coastal mixing zones in limestone or lime sediments has replacement by dolomite been observed 3 in a number of dolomites interpreted to be of mixing zone origin dolomite has precipitated without dissolution of the calcite substrate evidence that negates the fundamental premise of the dorag model in addition to these weaknesses isotope and trace element data used to identify mixed water dolomite are inadmissible because 1 isotopic fractionation factors for dolomites remain unresolved 2 isotope values uncorrected for temperature for a host of dolomites interpreted to be of different origins overlap 3 nonisomorphous trace elements such as na in dolomite cannot on theoretical grounds be relied on to identify dolomitizing fluids similar overall objections can be brought against folk and land9s 1975 schizohaline version of mixing zone dolomitization in summary mixing zone models have such weak underpinnings that they should be questioned as viable explanations for massive dolomitization contemporaneous dolomite formation in modern sabkhas is well documented but the important question of whether the mechanism of dolomite formation is replacement or direct precipitation remains to be resolved in the well studied sabkha at abu dhabi brine chemistry changes have been used as evidence of a replacement origin for the dolomite but it is shown here that this evidence is far from unequivocal an alternative origin of direct precipitation of dolomite is offered an origin in keeping with dolomite precipitation known from other modern sabkhas and saline lakes and in line with our laboratory experience with dolomite synthesis moreover it is suggested here that in general contemporaneous dolomite will form at low temperatures only by direct precipitation a mechanism that requires special conditions of highly super saturated waters of high mg ca ratio and elevated co 3 hco 3 concentrations this may explain why modern dolomite is mainly restricted to evaporitic environments a bias not shared by ancient dolomites in contrast replacement dolomite appears to require at low temperatures long reaction times or 10 4 yr a requirement that is mainly to be met in large regional groundwater flow systems both marine and nonmarine a third dolomitization model considered here is that of baker and kastner 1981 based on the experimental finding that sulfate ions inhibit or retard dolomitization a number of modern sedimentary dolomites are not in accord with this model in that they are forming from brines with large sulfate concentrations 2 to 70 times that of seawater thus the baker kastner model should be held in abeyance until these serious contradictions are resolved the current emphasis on mixing zone and sabkha dolomitization has diverted attention from other promising avenues of approach to the dolomite problem four of these avenues each of which deemphasizes the special water approach are briefly addressed and are as follows 1 influence of temperature and time 2 mass transfer processes 3 burial diagenesis of epigenetic dolomites 4 fluid inclusion studies at elevated temperatures the dolomite problem essentially disappears ordered dolomite can be made in the laboratory in days at 100 degrees c what is more at temperatures above 60 degrees c ca rich waters become dolomitizing fluids which makes most natural subsurface waters capable of dolomitization at low temperatures time may be the key element so that seawater will become a major dolomitizing fluid only where stable circulation systems such as kohout convention can drive seawater through carbonate platforms for many thousands to millions of years this paper has tried to show that currently favored models of dolomitization carry serious uncertainties enough to warn us to look more critically at the validity of these models and also it is hoped enough to spur new efforts to find new solutions to the problems of dolomitization

the role of corsica in initiating nocturnal offshore convection in the region of corsica located in the western mediterranean sea the mean daily lightning activity as an indicator for deep convection in late summer and autumn shows a distinct maximum in mid afternoon and a secondary maximum at night during the night most of the lightning activity is located offshore and near the island s coastline currently there are no observational data which could be used to explain this nocturnal offshore convection but understanding its formation mechanism is important for accurately forecasting the regional weather in this article we explore two possible mechanisms initiating nocturnal offshore convection i convergence with subsequent lifting due to the interaction between drainage winds and the synoptic flow over the sea and ii dynamically induced lee side convergence due to the island barrier effect to this end we perform numerical simulations with the consortium for small scale modeling cosmo model at a convection permitting horizontal grid spacing of 2 8 km for two cases with different synoptic conditions and low level wind directions the simulation results show that the island s drainage flow can either favour or hinder the development of deep convection furthermore convective initiation is very sensitive to terrain elevation and model initialisation time and small changes of these parameters can determine whether deep convection can be successfully simulated

permian early mesozoic tectonism and continental margin formation in israel and its implications for the history of the eastern mediterranean summary the early mesozoic tectonic reorganization of the tethys region also affected the levant area here two processes were superimposed a the pattern of long wavelength vertical motions of the arabo nubian platform changed in the late permian when israel and nearby areas began to subside b rifting occurred in this subsiding area probably in several phases late anisian and ladinian carnian norian and liassic differential movements reached 2 3 km and magmatism occurred in the liassic and perhaps also in the triassic the tectonism was strongly felt up to 50 km landward of the present coast the crust was thinned and modified under the present continental margin and in the main rifts passive margin conditions were established in late liassic times over the previously faulted area later in the jurassic a carbonate shelf was constructed along this subsiding margin its basinward edge was 1 1 5 km high which shows that the adjacent se mediterranean was already a deep sea hence this basin and its passive margin are considered to have been shaped by the early mesozoic rifting which is recognized in israel the rifting process probably signifies oblique separation of the tauride block from the levant part of gondwana

multiple step recrystallization within massive ancient dolomite units an example from the dinantian of belgium south of the caledonian brabant wales massif a more than 200 m thick tournaisian to lower visean replacive dolomite unit can be followed for several hundred kilometres from the boulonnais france to aachen germany field observations of features such as karst cavities occurring at the top of the lower visean dolomite which are filled by lower visean crinoidal limestone indicate that dolomitization and karstification took place during the early visean this early development of the dolomite is in agreement with the presence of stylolites cutting the dolomite fabric the minor element composition of the majority of the dolomites remains almost uniform throughout the entire studied area values for fe mn na and sr are normally in the range 700 4700 ppm 15 400 ppm 80 300 ppm and 50 200 ppm respectively the 13c values range 0 72 to 5 31 o mainly reflect the carbon isotopic composition of the precursor limestones the 18o values in contrast are highly variable ranging from 19 15 to 0 85 o this rather large range of 18o values is explained by multiple step re equilibration recrystallization during progressive burial and subsequent uplift of the dolomites these processes are also responsible for the high 87sr 86sr values of the dolomites which range from about 0 7088 to 0 7098 they are distinctly more radiogenic than lower visean marine carbonates 0 7076 0 7078 correlation however of 18o values or 87sr 86sr ratios with dolomite and or cathodoluminescenec cl textures has not been very successful this suggests that recrystallization may remain unrecognized if only petrographic techniques are used nevertheless certain cl textures can be related to specific interactions with the ambient recrystallizing fluids

thermally forced convection over a mountainous tropical island abstractobservations from the dominica experiment domex and cloud resolving numerical simulations are used to study a thermally forced convection event over the caribbean island of dominica on 18 april 2011 a clear diurnal cycle of island thermal forcing and cumulus convection was observed with cumuli initiating over the southwestern flank of the ridge and deepening as they drifted eastward apart from errors in cloud fraction and notably precipitation the simulations verified well against the observations provided horizontal grid spacings of 500 m or less were used the simulated flows developed an island scale solenoidal circulation with an organized and intense updraft over the ridge that focused convective initiation sensitivity tests investigated the impacts of topographic forcing subcloud winds and cloud radiative feedbacks on the island scale horizontal inflow and cloud vertical mass flux these experiments confirmed that thermal forcing drove the island convection and that the inflow an

petroleum prospects of lebanon some remarks from sedimentological and diagenetic studies of jurassic carbonates abstract only seven exploration wells have been drilled in lebanon to date failing to encounter oil or gas in commercial quantities and to penetrate into unexposed pre jurassic reservoirs this paper shows that the sedimentological and diagenetic characteristics of the major lebanese jurassic carbonate rock unit the kesrouane formation thickness 1000 m negate jurassic hydrocarbon prospectivity in northern mount lebanon the jurassic platform in this region was subjected to a first emergence and invasion by meteoric waters in the late jurassic causing a pervasive cementation a second phase of uplift and meteoric flushing occurred in the cenozoic thus only the areas located far from the jurassic and post cretaceous phreatic realms e g offshore tripoli nw lebanon may have been less affected by meteoric diagenesis and still provide promising prospects a 1993 seismic survey offshore tripoli confirmed the presence of late triassic evaporites in northern lebanon this also adds confidence to the results of the nahr ibrahim electrical survey which earlier suggested the presence of these evaporites in the subsurface of central lebanon the pre jurassic sequence hence is sealed and protected from the meteoric invasion observed in the overlying jurassic rocks accordingly the qartaba horst structure central northern lebanon would be equally if not more attractive for a pre jurassic play

chemostratigraphy of the jurassic system applications limitations and implications for palaeoceanography current chemostratigraphical studies of the jurassic system primarily involve the use of one sedimentary component marine organic carbon one divalent transition metal substituted in carbonate manganese and two isotopic tracers strontium isotope ratios 87 sr 86 sr and carbon isotope ratios 13 c carb and 13 c org in carbonate and in organic matter other parameters such as mg ca and sr ca ratios in calcite oxygen isotope ratios 18 o in carbonate sulphur isotope ratios 34 s in carbonate hosted sulphate nitrogen isotope ratios 15 n org in organic matter osmium isotope ratios 187 os 188 os in black shales and neodymium isotope ratios 143 nd 144 nd in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors stratigraphical patterns in total organic carbon toc can be of either local or regional significance depending on the lateral extent of the former nutrient rich and productive water mass divalent manganese follows a similar pattern being concentrated most probably as a very early diagenetic phase only in oxygen depleted waters that typically underlie zones of elevated organic productivity shifts in mg ca and sr ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes strontium isotope ratios from pristine skeletal calcite provide a global signal 13 c values from carbonates with minimal diagenetic overprint potentially do the same although small spatial differences in palaeo water mass composition may have been locally significant oxygen isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful because they reflect palaeotemperature the evaporation precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase nitrogen isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis neodymium isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems preliminary data on sulphur isotope ratios in carbonates and osmium isotope ratios in organic rich shales both potentially offering global correlation indicate that these tracers may be valuable although the records at present are not sufficiently well established to allow high resolution regional correlation in all cases biostratigraphically well dated reference sections against which the relevant geochemical data have been calibrated are required in the first instance to date studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern boreal and southern tethyan europe carbon isotope stratigraphy has been undertaken primarily but not exclusively on bulk pelagic sediments from the alpine mediterranean or tethyan domain and strontium isotope stratigraphy has been undertaken largely on calcitic skeletal material belemnites and oysters from northern and southern europe in many sections including those containing ammonites multi parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means strontium isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record

sensitivity of deep convection to terrain forcing over mediterranean islands the influence of mountainous islands on the initiation of deep convection is investigated using the consortium for small scale modeling cosmo model a case study and sensitivity analysis is performed for 26 august 2009 when moist convection occurred over both corsica and sardinia islands in the western mediterranean sea sensitivity runs with systematically modified topography are explored to evaluate the relative importance of the land sea contrast and the terrain height for convection initiation whereas no island precipitation is simulated when the islands are completely removed all simulations that represent these land surfaces develop convective precipitation although convection initiates progressively earlier in the day over taller islands the precipitation rates and accumulations do not show a fixed relationship with terrain height this is due to the competing effects of different physical processes firstly whereas the forcing for low level ascent increases over taller islands the boundary layer moisture supply decreases which diminishes the conditional instability and precipitable water secondly whereas taller islands enhance the inland propagation speeds of sea breeze fronts they also block these fronts mechanically and prevent them from reaching the island interior as a result the island precipitation is rather insensitive to island terrain height except for one particular case in which the island precipitation increases considerably due to an optimal superposition of the sea breeze and upslope flow comparing the two islands convective precipitation develops earlier over corsica due to its increased terrain height and reduced convective inhibition however precipitation amounts are substantially larger over sardinia where a stronger land sea contrast gives rise to a more intense and organized line of sea breeze convergence these results demonstrate the complexity of interactions between sea breezes and orography and reinforce that an adequate representation of detailed topographic features is necessary to account for thermally induced wind systems that initiate deep convection

geochemical behaviour of ni cr cu zn and pb in an andosol cambisol climosequence on basaltic rocks in the french massif central abstract the objective of this study is to identify parameters influencing trace elements te vertical distributions in an andosol andic cambisol climosequence in order to understand processes involved in the current distribution of trace elements from basaltic rocks to associated soils six pedons developed on tertiary massive basaltic formations located at similar position in the hill slopes submitted to the same wet mountainous climate but under various microclimatic conditions altitude and annual rainfall were considered the six studied soils are andic and rich in organo metallic complexes two different and quantitative methods were used to compare the geochemical distributions of major and trace elements both being calculated with ti as invariant element isovolumetric mass balance and enrichment factors anthropogenic pedogenetic microclimatic inherited factors were discriminated anthropogenic influences are pointed out for k in two pedons and for pb in all studied sites distributions of other te are affected by discontinuities between underlying rocks and soil horizons zinc and cu distributions are controlled by organic matter whereas cr and ni distributions are influenced by pedogenetic processes results emphasize the relative trace element immobilization in andic soils under temperate climate

dolomitization by penesaline sea water in early jurassic peritidal platform carbonates gibraltar western mediterranean peritidal carbonates of the lower jurassic liassic gibraltar limestone formation which form the main mass of the rock of gibraltar are replaced by fine and medium crystalline dolomites replacement occurs as massive bedded or laminated dolomites in the lower 100 m of an 460 m thick platform succession the fine crystalline dolomite has d 18 o values either similar to or slightly higher than those expected from early jurassic marine dolomite and d 13 c values together with 87 sr 86 sr ratios that overlap with sea water values for that time indicating that the dolomitizing fluid was early jurassic sea water absence of massive evaporitic minerals and or evaporite solution collapse breccias in these carbonate rocks indicates that the salinity of sea water during dolomitization was below that of gypsum precipitation the occurrence of peritidal facies a restricted microbiota and rare gypsum pseudomorphs are also consistent with penesaline conditions salinity 72 199 the medium crystalline dolomite has some d 18 o and d 13 c values and 87 sr 86 sr ratios similar to those of early jurassic marine dolomites which indicates that ambient sea water was again a likely dolomitizing fluid however the spread of d 18 o d 13 ca nd 87 sr 86 sr values indicates that dolomitization occurred at slightly increased temperatures as a result of shallow 500 m burial or that dolomitization was multistage these data support the hypothesis that penesaline sea water can produce massive dolomitization in thick peritidal carbonates in the absence of evaporite precipitation taking earlier models into consideration it appears that replacement dolomites can be produced by sea water or modified sea water with a wide range of salinities normal penesaline to hypersaline provided that there is a driving mechanism for fluid migration the gibraltar dolomites confirm other reports of significant early jurassic dolomitization in the western tethys carbonate platforms

the paradox of drowned reefs and carbonate platforms shallow water carbonate platforms and reefs are drowned when tectonic subsidence or rising sea level outpaces carbonate accumulation and benthonic carbonate production ceases drowned platforms are common in the geologic record but they present a paradox if one considers rates of processes involved during the early holocene when sea level rose at rates of 6 000 to 10 000 m yr mm 1 000 yr most reefs and platforms were outpaced by the rising sea during the late holocene with sea level rising 500 to 3 000 m yr in the atlantic caribbean area reefs and platforms started to recover built to sea level and prograded seaward 1 000 m yr is thus a conservative estimate of the average growth potential of modern reefs and platforms independently accumulation rates of prograding platforms in the geologic record suggest growth potential in excess of several hundred microns per year the growth potential of 1 000 m yr exceeds any relative rise of sea level caused by long term processes in the geologic record newly formed ocean crust subsides at a maximum of 250 m yr basin subsidence averages 10 to 100 m yr and sea level rises due to increased sea floor spreading amount to less than 10 m yr rapid pulses of relative rise of sea level or reduction of benthic growth by deterioration of the environment remain the only plausible explanations of drowning the geologic record shows examples of both of these processes global mass extinctions of reefs and platforms occurred in the middle cretaceous eustatic rise due to submarine volcanism or desiccation of a small ocean basin and the late devonian global crisis of ocean environment extraterrestrial cause drowning controlled by regional tectonics prevailed in the jurassic and early cretaceous of the tethyan realm and the drowning of mesozoic platforms in the western north atlantic seems to have been dictated by plate tectonic drift to higher latitudes

on the effects of islands geometry and size on inducing sea breeze circulation abstract model scaling of the characteristics of the sea breeze circulation involved with circular and slab elongated symmetric midlatitude islands was performed larger horizontal and vertical velocities were indicated over the small circular islands as compared to those over corresponding elongated islands the circulation characteristics of both types of islands become similar when the half width of the island is about the same as the distance of inland penetration of the sea breeze in a nonisland case evaluation of the results through a wale analysis is presented

cloud trails past the lesser antilles abstractobservations and cloud resolving simulations of elongated cloud plumes or cloud trails past the lesser antilles islands in the caribbean sea are presented analysis of one year of visible satellite images reveals that each island forms cloud trails on 30 40 of days typically in the afternoon in response to diurnal island heating on around 10 of days the cloud bands are very well organized with lengths of and durations of min radiosonde analysis suggests that the well organized events are favored by moderate to strong trade winds 6 10 m s 1 and stronger trade inversions the simulated cloud trails which are consistent with observations in their morphology and diurnal cycle are organized by quasi linear bands of thermally forced convergence within the heated island wake they are sensitive to overland surface fluxes inversion strength and height terrain height and trade wind speed while surface fluxes control the strength of the wake thermal circulations the inversion controls pr

petrologic and geochemical constraints on the origin of subsurface dolomite enewetak atoll an example of dolomitization by normal seawater dolomite is present 1 250 1 400 m below sea level in eocene strata of enewetak atoll petrographically the deep enewetak dolomite postdates brittle compaction of rigid grains in the host eocene strata the 87 sr 86 sr ratio of these dolomites 0 70865 0 70901 indicates that they formed at one or more times between the middle miocene and the present since the top of the lower miocene is more than 900 m above the deep dolomitic interval the dolomite must have formed at a minimum burial depth of 900 m stable oxygen isotope determinations suggest dolomite precipitation from cold marine water lower miocene and eocene carbonate strata on the atoll are apparently in open communication with cold modern ocean water suggesting that those same strata were in open communication with ocean water during dolomitization at a depth of about 1 000 m modern pacific ocean water becomes undersaturated with respect to calcite but is still supersaturated with respect to dolomite therefore it is proposed that the deep enewetak dolomite precipitated from cold deep ocean water undersaturated with respect to calcite at a burial depth of more than 900 m

golden grove dolomite barbados origin from modified seawater abstract the largest dolomite occurrence on barbados part of a roadcut at golden grove is about 40 m long and 0 5 2 5 m thick dolomite at golden grove constitutes about 10 40 vol of the host limestone an algalforaminiferal facies of late pleistocene age with local patches consisting of up to 100 vol dolomite almost all dolomite is a replacement of matrix and predominantly mg calcite skeletal grains an average of less than 0 1 vol of the rock is fibrous to bladed radial and radiaxial dolomite cements with calcite banding the partially dolomitized algal foraminiferal facies is unconformably overlain by scleractinian coral reef limestones replacive dolomitization appears to have been very localized at the stratigraphic level of golden grove the petrographic data suggest that replacive dolomitization took place after deposition of the algal foraminiferal facies and prior to deposition of the overlying coral reef facies 18o 1 1 to 4 4 pdb values of the replacive dolomites suggest seawater with variable temperature and or slight degrees of evaporation as the principal agent of dolomitization in addition variable and highly negative 13c values of the replacive dolomites 23 5 to 8 913c the main source of this 13c depleted carbonate probably was oxidized methane with a possible but very minor contribution of carbonate derived from bacterial gsulfate reduction methane may have been supplied by bacterial methanogenesis relatively close to the site of dolomitization or by upward seepage of thermogenic methane derived from underlying tertiary hydrocarbon reservoir s it is possible albeit speculative that the localized availability of methane via fractures and or its localized oxidation somehow induced dolomitization at golden grove furthermore the 13c 18o and 87sr 86sr ratios 0 70913 0 70919 of replacive dolomites of golden grove calcites 13c 14 0 to 3 9 pdb 18o 5 0 to 2 2 pdb and of groundwaters from the present coastal mixing zone and inland carbonate aquifers 87sr 86sr 0 70911 0 70924 13c 123 to 5 9 pdb 18o 5 0 to 2 smow effectively role out that replacive dolomitization at golden grove was caused in a typical coastal freshwater seawater mixing zone or that dolomitization was influenced by meteoric waters to any significant degree the small amounts of banded dolomite cements however may have formed in a typical coastal mixing zone

tectono stratigraphic evolution of the western margin of the levant basin offshore cyprus abstract stratigraphic interpretation of twenty four 2d seismic reflection profiles coupled with available well data from the ocean drilling program odp offshore cyprus enabled identification of the main unconformities and the seismic packages in the western part of the levant basin and their correlation with major geodynamic events the basic concepts of seismic stratigraphy were applied to improve our understanding of the tectonostratigraphy and the sedimentary architecture of eratosthenes isolated carbonate platform this platform is composed of dominant retrograding and aggrading mesozoic carbonate build ups and its evolution partly resembles that of the egyptian margin deep water mixed carbonates and siliciclastics probably prevailed in the basin during the early cretaceous during the late cretaceous these platforms were drowned following the convergence of the two plates both the eratosthenes seamount esm area and the levant basin progressively became part of a foreland basin along the cyprus arc different units in the eratosthenes carbonate platforms ecps and the transition to the deep levant basin are detailed here for the first time we present a 3d conceptual model for the evolution of the western margin of the levant basin we discuss the effect of the miocene collision between the cyprus arc and eratosthenes to understand the presence of upper miocene mass transport complexes mtcs in the deep basin and the tilting of the top of the adjacent ecps we briefly examine the deformation mechanisms of the messinian salt near the paleo shelves of the ecps

dolomitization of the capitan formation forereef facies permian west texas and new mexico seepage reflux revisited interpretation of seepage reflux dolomitization is commonly restricted to intervals containing evaporites even though several workers have modelled reflux of mesosaline brines this study looked at the partially dolomitized forereef facies of the capitan formation to test the extent of reflux dolomitization and evaluate the possible role of the near backreef mesosaline carbonate lagoon as an alternative source of dolomitizing fluids the capitan formation forereef facies ranges from 10 to 90 dolomite most of the dolomite is fabric preserving and formed during early burial after marine cementation before and or during evaporite cementation and before stylolitization within the forereef facies dolomite follows depositional units with debris flow and grain flow deposits the most dolomitized and turbidity current deposits the least the amount of dolomite increases with stratigraphic age and decreases downslope within the reef facies dolomite is restricted to haloes around fractures and primary cavities except where the reef facies lacks marine cements and in contrast is completely dolomitized this dolomite distribution supports dolomitization by sinking fluids oxygen isotopic values for fabric preserving dolomite 1 8 o 0 9 1 0 n 101 support dolomitization by sea water to isotopically enriched sea water these values are closer to the near backreef dolomite 1 8 o 2 1 0 7 n 48 than the hypersaline backreef dolomite 1 8 o 3 6 0 9 n 11 therefore the fabric preserving dolomite is consistent with dolomitization during seepage reflux of mainly mesosaline brines derived from the near backreef carbonate lagoon the occurrence of mesosaline brine reflux in the capitan formation has important implications for dolomitization in forereef facies and elsewhere first any area with a restricted carbonate lagoon may be dolomitized by refluxing brines even if there are no evaporite facies present secondly such brines may travel significant distances vertically provided permeable pathways such as fractures are present therefore the absence of immediately overlying evaporite or restricted facies is not sufficient cause to eliminate reflux dolomitization from consideration

what controls the transition from shallow to deep convection abstract in this study a 2d cloud system resolving model csrm is used to assess the control mechanism for the transition from shallow to deep convection in the diurnal cycle over land by comparing with a 3d csrm under conditions taken from the large scale biosphere atmosphere field study in the amazon the authors show that the 2d csrm reproduces the main features evident in previous 3d simulations reasonably well to extract the essence of the transition from shallow to deep convection the observed case is idealized to isolate two control parameters the free troposphere stability and the relative humidity the emergence of a distinct transition between shallow and deep convection shows that the convective transition is an intrinsic property of the system a transition time is defined to evaluate the key mechanism of the transition the authors show that the transition coincides with the time when the lapse rate of the virtual potential temperature of the clouds becomes larger than that of the env

tectono stratigraphic evolution of the northern levant basin offshore lebanon abstract seismic interpretation constrained by a detailed assessment of the levant paleogeography allowed subdividing the sedimentary infill of the northern levant basin offshore lebanon in eight major seismic packages fifteen seismic facies have been identified with distinctive characteristics the levant basin architecture is pre determined by a late paleozoic early mesozoic rift that led to the formation of a passive margin dominant aggrading carbonate platforms are observed along the levant margin and deepwater mixed settings i e carbonates and siliciclastics are suggested to prevail in the basin the collision of afro arabia with eurasia led to the development of a flexural basin in the northernmost offshore lebanon since the late cretaceous a southward migration of this flexural depocenter in the miocene is hindered by the change in the stress field along the latakia ridge and by the westward escape of the anatolian plate in late miocene and pliocene times interplay between major geodynamic events as well as sea level fluctuations in the mesozoic and cenozoic induced important marginal uplifts and emersion sediments sourced from the erosion of nubian siliciclastic material and from the exposed granitic red sea rift shoulders and arabian shield were driven into the levant basin the sediment sources diversity the mechanisms of sediment transport through varied pathways i e the levant margin canyons the latakia region and the nile delta deep sea cone are expected to strongly impact the reservoir characteristics and prospectivity of the northern levant basin

flow and mixing in new mexico mountain cumuli abstract convection and cloud formation over mountains during weak winds and strong insolation were studied using an instrumented aircraft previous studies in cloudless situations had shown the existence of convergence over the mountain range at low levels and divergence aloft the present observations indicate that cumulus clouds and even thunderstorms in their early stages do not significantly affect the strength of the low level convergence furthermore net divergence was found around clouds up to at least 6 km msl this favors the vertical mixing model of a cumulus cloud over the lateral entrainment model in one case the convergent low level heat island circulation over the mountain was observed to change to an almost non divergent asymmetric circulation as a thunderstorm over the mountain reached maturity

initiation of convective storms at radar observed boundary layer convergence lines abstract the origin of 653 convective storms occurring over a 5000 km2 area immediately east of the colorado rocky mountains from 18 may to 15 august 1984 was examined seventy nine percent of the 418 storms that initiated within the study area occurred in close proximity to radar observed boundary layer convergence lines this percentage increased to 95 when only the more intense storms 60 dbze were considered colliding convergence lines initiated new storms or intensified existing storms in 71 of the cases a new storm took a median time of 24 min to grow to 30 dbz following line collision the convergence lines ranged in length between ten and several hundred kilometers both radar and mesonet stations indicated that the primary convergence was concentrated in a zone 0 5 to 5 km in width these lines were characterized on doppler radar as thin lines of enhanced reflectivity between 0 and 20 dbze and as a line of strong radial or azimuthal gradient in doppler velocity these lines were observed ev

why precipitation is mostly concentrated over islands in the maritime continent abstract high resolution observations and regional climate model simulations reveal that precipitation over the maritime continent is mostly concentrated over islands analysis of the diurnal cycles of precipitation and winds indicates that this is predominantly caused by sea breeze convergence over islands reinforced by mountain valley winds and further amplified by the cumulus merger processes comparison of a regional climate model control simulation to a flat island run and an all ocean run demonstrates that the underrepresentation of islands and terrain in the maritime continent weakens the atmospheric disturbance associated with the diurnal cycle and hence underestimates precipitation the implication of these regional modeling results is that systematic errors in coarse resolution global circulation models probably result from insufficient representation of land sea breezes associated with the complex topography in the maritime continent it is found that precipitation in the maritime continent

stable isotope evidence for the origin of diagenetic carbonate minerals from the lower jurassic inmar formation southern israel the oxygen isotope compositions of diagenetic carbonate minerals from the lower jurassic inmar formation southern israel have been used to identify porewater types during diagenesis changes in porewater composition can be related to major geological events within southern israel in particular saline brines played an important role in late pliocene pleistocene dolomitization of these rocks diagenetic carbonates included early siderite 18osmow 24 4 to 26 5 13cpdb 1 1 to 0 8 late dolomite ferroan dolomite and ankerite 18osmow 18 4 to 25 8 13cpdb 2 1 to 0 2 and calcite 18osmow 21 3 to 32 6 13cpdb 4 2 to 3 2 the petrographic and isotopic results suggest that siderite formed early in the diagenetic history at shallow depths the dolomitic phases formed at greater depths late in diagenesis crystallization of secondary calcite spans early to late diagenesis consistent with its large range in isotopic values a strong negative correlation exists between burial depth temperature and the oxygen isotopic compositions of the dolomitic cements in addition the 18o values of the dolomitic phases in the northern negev and judea mountains are in isotopic equilibrium with present formation waters this behaviour suggests that formation of secondary dolomite post dates the tectonic activity responsible for the present relief of southern israel upper miocene to pliocene and that the dolomite crystallized from present formation waters such is not the case in the central negev in that locality present formation waters have much lower salinities and 18o values indicating invasion of freshwater and are out of isotopic equilibrium with secondary dolomite recharge of the inmar formation by meteoric water in the central negev occurred in the pleistocene and halted formation of dolomite

a numerical study of three catastrophic precipitating events over southern france ii mesoscale triggering and stationarity factors in the western mediterranean basin large amounts of precipitation can accumulate in less than a day when a mesoscale convective system mcs stays over the same area for several hours heavy precipitating events hpes in this region especially southern france are not only characterized by significant precipitation rates typically more than 200 mm in less than 24 or 48 hours but also by quasi stationary behaviour the aim of this present study is to use realistic simulations of past events to analyze and better understand the physical mechanisms which lead to the stationarity of hpes over southern france using a high resolution 2 5 km non hydrostatic mesoscale atmospheric model we focused on three hpes 13 14 october 1995 the cevennes case 12 13 november 1999 the aude case and 8 9 september 2002 the gard case the experimental design for simulating realistic structures and evolutions of the hpes with the meso nh model has been presented in a companion paper in that study the evolution of the synoptic patterns in which the hpes occurred were analysed in this paper the importance of mesoscale ingredients such as the moist and conditionally unstable low level jet llj is examined in terms of their ability to focus the deep convection over the same area for several hours the cevennes case is typical of a so called cevenole event in france for which orographic forcing is the primary mechanism which acts to continuously generate convective cells upwind of the massif central the unusual location of the gard event is explained by a cold pool induced by the evaporation of precipitation which acts as a relief like feature to force the conditionally unstable and moist llj to rise this constitutes a quasi stationary forcing as the cold pool is blocked in the rhone valley for the third case diabatic cooling and the massif central act to enhance the precipitation but have almost no impact on the location of the anchoring point of the precipitating system

powder x ray diffraction analysis of homogeneous and heterogeneous sedimentary dolostones abstract the ca molar ca ca mg 100 in sedimentary dolomite which ranges from 48 ca to 62 5 ca can be determined by atomic absorption spectrometry electron microprobe analysis or powder x ray diffraction analysis the latter procedure which relies on the fact that the position of the d104 reflection depends linearly on the ca content offers an easy and relatively inexpensive method of determining ca in dolomite to date such analyses have assumed that the dolostone is homogeneous with respect to the ca content of its constituent dolomite crystals herein the xrd technique is extended to compositionally heterogeneous dolostones a considerable amount of important information can be derived from x ray diffractograms of dolostones if they are analyzed with peak fitting techniques pf xrd specifically this technique allows 1 determination of the ca with an accuracy of 0 5 ca 2 identification of heterogeneous dolostone samples formed of more than one population of dolomite crystals as defined by their ca content and 3 derivation of the proportion of each population of dolomite crystals with an accuracy of 10 the pf xrd technique is a powerful analytical tool that provides valuable information on the major element composition of low fe dolomite compared to other techniques the pf xrd technique is accurate rapid relatively inexpensive and easy to use

a review of the tectonics of the northern middle east region the structure of the northern part of the arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region the palmyra and sinjar zones share a common history of development involving two stages of rifting one in the triassic jurassic and the other during late cretaceous to early tertiary times deformation of the palmyra zone during the mio pliocene is attributed to north south compression on the eastern block of the dead sea transcurrent system which occurred after continental collision in the north in southeast turkey the asymmetry of the palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow triassic evaporites an important nw se cross plate shear zone has been identified which can be traced for 600 km and which controls the course of the river euphrates over long distances in syria and iraq transcurrent motion along this zone resulted in the formation of narrow grabens during the late cretaceous which were compressed during the mio pliocene to a large extent present day structures in the region result from compressional reactivation of old lineaments within the arabian plate by the transcurrent motion of the dead sea fault zone and subsequent continental collision

evolution of the vertical thermodynamic profile during the transition from shallow to deep convection during cupido 2006 abstract the evolution of the vertical thermodynamic profile associated with two cases of deep orographic convection were studied with data from an instrumented aircraft mobile surface based radiosondes and stereo photogrammetric analyses the data were collected during a field experiment i e the cumulus photogrammetric in situ and doppler observations cupido experiment in 2006 performed over the santa catalina mountains in southern arizona in both cases the vertical thermodynamic profile was modified in a way that supported subsequent deep convection in one case a midtropospheric stable layer was eroded through low level warming and cooling at the cloud top level that was likely due to an adiabatic adjustment of the profile through the action of gravity waves in the second case dry air aloft was moistened through the action of the shallow convection thus preventing the erosion of the convective turrets through entrainment of dry air these cases illustrate mechanisms for convective conditi

some outstanding issues in the geology of lebanon and their importance in the tectonic evolution of the levantine region abstract the concept of pervasive and disruptive late neogene quaternary strike slip tectonics in lebanon has made establishing a satisfactory pre neogene palaeogeographic and palaeotectonic history for the area difficult research has allowed clarification of three fundamental issues that permit the setting of lebanon against its adjacent regions to be more firmly assigned the first issue is the identification of the significance of the 100 km long nne ssw trending monocline of the western lebanon flexure this feature is interpreted as a modified and rejuvenated early mesozoic hinge line that is presumed to be the northern continuation of the carmel sinai hinge line to the south the second issue is the correlation of the mount lebanon bekaa and anti lebanon complex with the adjacent intracontinental palmyride fold belt of syria through recognition in each of common divisions in structural style between a higher northern zone dominated by broadly spaced box folds and a lower southern zone with more numerous closely spaced and more internally complex folds the third issue involves the identification of major two stage late cretaceous to palaeogene syrian arc tectonism within lebanon resolution of these issues suggests a tectonic model for the region whereby the levantine region formed in two main phases the first of these was the multiphase late palaeozoic early mesozoic rifting of the area which imposed a fundamental extensional fabric over much of the region the second tectonic phase was the subsequent inversion of these extensional structures in the two stage syrian arc deformation of senonian and late palaeogene age which gave rise to the main lebanon structures it is this syrian arc tectonism rather than the late cenozoic strike slip that was probably the main structuring agent which affected the lebanon area the transpression from the braided dead sea fault motion although locally complex is an essentially neotectonic overprint on an already existing fabric offset of syrian arc structures in lebanon suggests that the total sinistral motion of the yammouneh fault segment of the dead sea fault is around 47 km

chromium and copper in micromorphological features and clay fractions of volcanic soils with andic properties abstract in volcanic soils of the solofrana valley south western italy contamination by cr and cu occurs as a consequence of agricultural practices and surface deposition of polluted river sediments by periodic floods in this study the metal distribution in micromorphological features and clay fractions 1 both cr and cu are present in the subsurface infillings with concentrations of 273 and 243 mg kg 1 in deeper horizons the fragments of stratified fine textured alluvial deposits incorporated in the soil matrix contain low concentrations of both metals 13 63 mg kg 1 for cr and 18 24 mg kg 1 for cu suggesting that cr and cu migration in colloidal or ionic form is restricted to a limited distance the contribution of the clay fraction

late pleistocene mixing zone dolomitization southeastern barbados west indies field geochemical and petrographic data for late pleistocene dolomites from southeastern barbados suggest that the dolomite precipitated in the zone of mixing between a coastal meteoric phreatic lens and normal marine waters the dolomite is localized in packstones and wackestones from the algalamphistegina fore reef calcarenite facies stable isotopic evidence suggests that meteoric water dominated the diagenetic fluids responsible for dolomitization carbon isotopes in pure dolomite phases average about 15 0 pdb this light carbon is attributed to the influence of soil gas co2 and precludes substantial mixing with seawater a narrow range of oxygen isotopic compositions coupled with a wide range of carbon compositions attest to the meteoric diagenetic overprint dolomitization likely occurred with as little as a five per cent admixture of seawater strontium compositions of the dolomites indicate probable replacement dolomitization of original unstable mineralogy the dolomite is characterized by low sodium values low concentrations of divalent manganese and iron suggest oxidizing conditions at the time of dolomitization a sequence of petrographic features suggests a progression of diagenetic fluids from more marine to more meteoric early marine diagenesis was followed by replacement dolomitization of skeletal grains and matrix limpid euhedral dolomite cements precipitated in primary intra and interparticle porosity subsequent to replacement dolomitization as waters became progressively less saline dolomite cements alternated with thin bands of syntaxial calcite cement the final diagenetic phase precipitated was a blocky calcite spar cement representing diagenesis in a fresh water lens this sequence of diagenetic features arose as the result of a single fall in eustatic sea level following deposition a stratigraphic eustatic diagenetic model constrains both the timing and rate of dolomitization in southeastern barbados dolomitization initiated as sea level began to fall immediately following the oxygen isotope stage 7 3 high stand some 216 000 yr bp due to the rapidity of late pleistocene glacio eustasy dolomitization locally complete is constrained to have occurred within about 5000 yr

hydrothermal dolomite a product of poor definition and imagination abstract the latest dolomite bandwagon is the hydrothermal dolomite model in its present form this bandwagon is doomed or at least very much overstated for at least two reasons 1 there are several definitions of hydrothermal and hardly any author specifies which one s he is using 2 very few of the dolomites hitherto called hydrothermal have been demonstrated to be hydrothermal according to any definition except the worst as presently applied the term hydrothermal dolomite is confusing and or meaningless we suggest to use white s geol soc amer bull 68 1957 1637 time honored definition of hydrothermal as aqueous solutions that are warm or hot relative to its surrounding environment with no genetic implications regarding the fluid source hence a dolomite should be called hydrothermal only if it can be demonstrated to have formed at a higher than ambient temperature regardless of fluid source or drive furthermore this definition does not carry a lower or upper temperature limit even a dolomite formed at 40 c could be hydrothermal by extension dolomites formed at temperatures lower than ambient are not hydrothermal even if they formed at a rather high temperature for example groundwater may penetrate a rock sequence through a highly permeable pathway such that it is heated to 150 c at a depth where the surrounding rock has a temperature of 250 c we suggest to call dolomite formed from this water hydrofrigid dolomite formed in or near thermal equilibrium with the surrounding rocks may be called geothermal furthermore not all saddle dolomite formation requires advection fluid flow to transport mg saddle dolomite can be formed in at least three ways i e from advection local redistribution of older dolomite during stylolitization and as a by product of thermochemical sulfate reduction in a closed or semi closed system only the first and the last of these three possibilities have a chance of being hydrothermal almost all dolomites and dolostones in the western canada sedimentary basin have recently been re interpreted as hydrothermal applying the rationale outlined above reveals however that this basin contains very little hydrothermal dolomite rather most dolomites in this basin and almost all dolostones south of the peace river arch are geothermal and or the proof of a hydrothermal origin has not been made this has important implications beyond the various case studies at hand as attempts to tie dolomitization to orogenic events become moot at least in the southern part of the basin

tropical island convection in the absence of significant topography part ii nowcasting storm evolution abstract this paper examines influences on the short range prediction of organized convection under conditions of strong diurnal forcing the analyses are based on data provided by the maritime continent thunderstorm experiment which was conducted in 1995 over the tiwi islands 11 s 50 100 km north of the australian continent organized convection over the tiwi islands is often dubbed hector by residents and researchers alike the authors purpose is to utilize results from these analyses to improve convective storm nowcast systems and their associated forecast and warning products the environmental near surface wind direction is shown to be singularly influential in statistically predicting the location of convection and its time of occurrence over the tiwi islands this finding is robust despite the fact that mean wind speeds were merely 1 4 m s 1 the island boundary layer water vapor mixing ratio derived from a morning sounding and inland surface stations is shown to be correlated with measu

mountain volume control on deep convective rain amount during episodes of weak synoptic forcing abstractthermally driven upslope flows in mountainous areas provide favorable conditions for diurnal deep moist convection especially during episodes of weak synoptic forcing the present study inv

reflux stratabound dolostone and hydrothermal volcanism associated dolostone a two stage dolomitization model jurassic lebanon the kesrouane formation which is characterized by pervasive dolomitization has a stratigraphic thickness that exceeds 1000 m it is part of a broad carbonate platform deposited in the levant region and represents 60 of the lebanese jurassic rocks two genetically distinct dolostones are recognized within this unit 1 fine to medium crystalline non planar grey dolostone and 2 coarse crystalline planar beige dolostone the former is stratabound and of early jurassic age 87 sr 86 sr 0ae707455 this dolostone locally exhibits pseudomorphs of evaporite nodules pointing towards seepage reflux dolomitization by hypersaline to marine related fluids exposures of the coarse crystalline dolostone are associated with regional pre cretaceous faults along which late jurassic volcanics also occur sedimentological and diagenetic considerations coupled with microthermometry support a hydrothermal origin for this dolostone with th values of primary inclusions between 50 and 80 c the related dolomitizing fluids are mesosaline 3ae5 12ae0 eq wt nacl and are believed to result from the mixing of evaporative brines and sea water dolomitization is thus believed to have occurred in two stages whereby fluids invaded the host rocks first by seepage reflux explaining the resulting early jurassic stratabound dolostone and later through fracture flow along the faults associated with the late jurassic volcanism explaining the coarse crystalline hydrothemal dolostone

a numerical study of the convection triggering and propagation associated with sea breeze circulation over hainan island based on high resolution numerical simulations the effects of sea breeze circulation sbc on associated convective initiation and propagation over hainan island are investigated the results show that the blocking of synoptic wind on the windward side of the mountains inhibits the occurrence of windward side valley breeze and sea breeze in the context of low mountains weak synoptic wind not only favors the combination of the sbc with the valley breeze circulation on the leeward side of the mountains but also makes the convergence zone between the synoptic wind and the leeward side combined circulation stay near the tops of the mountains leading to the accumulation of large quantities of water vapor taking place over the mountaintops the combined effect of enhanced water vapor and high temperatures over the mountaintops can result in the generation of much larger convective available potential energy cape than the surrounding areas the coupling of the large cape with the considerable converging ascending motion and abundant water vapor near the tops of the mountains promotes the occurrence of a strong convection band cb over the mountaintops during the cb propagation under the steering of synoptic wind the flow across the cb continuously and strongly opposes the sbc front and the fronts of the kelvin helmholtz billows behind resulting in successive and strong lifting motion as well as large quantities of water vapor and high cape near these fronts these lead to an apparent downstream wave like propagation of the cb

halloysite characteristics and formation in the northern golan heights the mineralogy of alteration products of late pleistocene basaltic scoriae and that of a paleosol from the northern golan heights was examined these products had relatively high specific surface areas ssas and cation exchange capacities cecs that were attributed to kaolinite smectite mixed layers 10a halloysite traces of smectite and illite the latter is attributed to aeolian deposition using specific surface area data from 18 to 59 clay were calculated to have formed in the weathered scoria the 10a halloysite was particularly well preserved in the paleosol the absence of significant amounts of short rage ordered minerals allophane ferrihydrite is attributed to the long dry summers and to the relatively old age of the parent materials sem observations of weathered rock and of mildly dispersed clay revealed two types of clay particles a hexagonal or prism like idiomorphic suggesting kaolinite and b rounded composite of a diameter approx 0 5 um appearing to be made up of spherical segments joined together by one or more flat faces hrtem of the 10a particles in the paleosol showed elongated ellipsoids tapered at one end and with internal layering or spiraling and spheroids with spiraling layering with a diameter 130 150 nm less common are sheet like crinkly films sio2 al2o3 molar ratios vary between 1 9 and 3 0 the particles have high fe up to 5 5 and ti up to 3 1 contents ti contents were higher in the peripheral parts of the spheroidal and in the crinkly sheet like particles sem observations suggest that while spheroidal and ellipsoidal 10a halloysite formed by solid phase transformation of volcanic glass the crinkly sheet like particles formed by precipitation on vesicle walls morphological features also suggest transformation of halloysite particles into kaolinite the absence of significant amounts of 10a halloysite in the modern soils indicates their xeric moisture regime

depositional sequences in shallow carbonate dominated sedimentary systems concepts for a high resolution analysis abstract oxfordian and berriasian sections representing shallow water carbonate dominated sedimentary systems have been studied in the swiss and french jura in spain and in normandy they all display a hierarchical stacking of depositional sequences facies evolution and stacking pattern allow to define elementary small scale medium scale and large scale sequences some depositional sequences display well marked sequence boundaries others are limited by transgressive or maximum flooding surfaces the hierarchical organisation of such sequence stratigraphic elements implies that sea level fluctuations were an important factor in their formation and that these fluctuations had different frequencies the superposition of high frequency sea level changes on a long term sea level trend leads to repetition of diagnostic surfaces defining sequence boundary and maximum flooding zones wherein the corresponding high frequency surfaces are well developed chronostratigraphic tie points permit us to estimate the duration of large scale sequences this time control and the observed hierarchical stacking suggest that the high frequency sea level changes were controlled by climatic cycles in the milankovitch frequency band the variability of stacking pattern and facies evolution between sections illustrates the complexity of the studied environments furthermore because of the minimal accommodation space available in these shallow water settings much of the geologic time is not recorded nevertheless detailed analysis of the depositional sequences allows the interpretation of the evolution of the sedimentary system with a high time resolution thus there is a potential to monitor sedimentological ecological and diagenetic processes on a time scale of 20 to 100 ka

characterization of heavy metals in contaminated volcanic soils of the solofrana river valley southern italy a number of volcanic agricultural soils from the solofrana river valley southwestern italy irrigated for a long time with contaminated river water or subjected to overflowing were collected and examined for fundamental soil parameters and total content and distribution of fe cr cu mn ni pb and zn micromorphological properties the effect of main soil characteristics on the distribution of heavy metals in the various forms and metal uptake or effects on vegetables were also investigated chromium and cu were the only metal contaminants occurring in soils in broad ranges of concentrations cr 62 335 and cu 70 565 mg kg 1 and in the surface horizons always above the regulatory levels cr 150 cu 120 mg kg 1 as established by the italian ministry of the environment for soils of public private and residential areas chromium and cu but also ni pb and zn were concentrated in silt 20 2 am and clay 50 mn was uniformly distributed among all the extracted fractions for all metals the soluble and exchangeable forms made a small contribution to the total significant amounts of cr and cu were recovered in the acid ammonium oxalate extraction suggesting association of metals with shortrange order aluminosilicates and organo mineral complexes the amounts of metals extracted by oxalate were found to be approximately equal to two thirds of the sequentially removed non residual amounts the results of dtpa extraction confirmed the low bioavailability of heavy metals in soil the metal concentration in dwarf beans and lettuces growing on one contaminated soil did not exceed the maximum concentration recommended by the european union however the enzyme activities in the bean roots indicated the induction of anti oxidative defense mechanisms due to metallic stress optical microscopy om showed occurrence of clay and silt coatings along elongated pores in the surface and subsurface soil horizons suggesting a risk of metal rich sediment transfer along the soil pore network during water movement d 2003 elsevier science b v all rights reserved

climatology of heavy precipitation over corsica in the period 1985 2015 the island of corsica in the western mediterranean is frequently struck by devastating heavy precipitation events hpes which endanger property and lives alike in the framework of the hymex hydrological cycle in the mediterranean experiment project multiple hpes from 2012 were observed and studied and to provide context a climatology for hpes based on 31 years 1985 2015 of surface observations was derived based on 173 events hpes 100 mm d 1 strike the island around 5 6 times a year and show a distinct seasonal cycle they occur predominantly during autumn with more than half of the hpes occurring from september to december and almost 20 in october the most active month the eastern half of the island is most affected by hpes composite fields for all events show a cyclone over the western mediterranean west of corsica and warm and moist low level air upstream of the orography predominantly over the tyrrhenian sea southeast of the island the events are classified using their synoptic and mesoscale environment obtained from era interim data using equivalent orthogonal functions eofs and a principal component pc analysis together with the k means clustering algorithm three clusters of events are identified each has a different seasonal cycle dominant wind direction and precipitation distribution warm southeasterly events occur predominantly in autumn produce the most extreme events and affect the coasts and slopes of eastern corsica alike cool southeasterly events occur predominantly in winter and affect mostly the slopes along the east side of the orography southwesterly events are more often associated with large scale atlantic cyclones and occur throughout almost the entire year and with the highest precipitation over the mountains

an organogenic origin for widespread dolomite in the cambrian eilean dubh formation northwestern scotland abstract dolomite precipitation from seawater is normally inhibited by the presence of sulfate the low activity of the carbonate ion and the high enthalpy of hydration of the magnesium ion however in modern microbial sediments anoxic degradation of cyanobacterial material by sulfate reducing bacteria can significantly alter ambient water chemistry sulfate is removed and enzymatic breakdown of proteins releases ammonia thereby increasing ph and carbonate alkalinity to levels necessary for dolomite formation magnesium may be supplied from complexed ion pairs in solution and from the breakdown of cyanobacterial sheaths and mucilage in the ancient past where benthic microbial communities dominated the depositional environment it is postulated that large scale shallow subsurface modif cation of ambient waters by sulfate reducing bacteria created conditions favorable to widespread dolomite formation early diagenetic cherts from the cambrian eilean dubh formation of northwestern scotland preserve successive stages of the taphonomic history of cyanobacterial biofabrics in sediments of a continuously aggrading shelf depth related sequential degradation of cyanobacterial mat is accompanied by the appearance and increase in abundance of authigenic dolomite culminating in a crystalline dolomitic fabric with only residual organic clots silicified oolitic grainstone fabrics preserve various ooid morphologies these form a diagenetically modified sequence in which progressive degradation of component microbial material together with leaching of the ooid shell is accompanied by the appearance and increase in abundance of intragranular authigenic dolomite total dissolution of ooids re ulted in the release of a package of crystals as sediment similar sequences are observed in peloids and intraclasts ensuing dolomitic rock fabrics bear no clue to their origin except where grains are preserved in early silicified windows these relationships can be explained by biochemical modification of porewaters during organic diagenesis and provide evidence for widespread authigenic dolomite formation in the shelf sediments this organic degradational model may serve as a basis for understanding the origin of thick platformal dolostone sequences of the proterozoic

emplacement of giant mud volcanoes in the south caspian basin 3d seismic reflection imaging of their root zones exceptional quality 3d data for the largest mud volcano yet described provide the first detailed imaging of the plumbing architecture that connects a major volcanic edifice to its source layer at depth the volcano is in the south caspian basin and consists of an extruded submarine mud bicone 10 km wide and 1 4 km thick overlying an oval caldera 1 2 1 6 km in width and 0 5 km in depth the caldera narrows downwards into a zone of collapsed country rock forming a downward tapering cone 1 km in height the vertex of which is located close to the top of the mud source layer the imaged structural elements lead to an evolutionary model a narrow steep fluidization pipe fed the oldest pioneer cone we propose that numerous additional fluidization pipes injected the country rock forming a densely intruded cylindrical zone similar to gryphon swarms observed at outcrop onshore wall rock erosion and compaction of the intruded zone led to collapse of the downward tapering cone that linked upwards into ring faults that define the caldera margins later mud flowage focused on the conical sheared margins volumetric contraction of the extruded volcanic cone led to an unusual concentric system of minor outward facing normal faults this model has many similarities to syntheses of igneous maar diatreme caldera systems for which it may be analogous

cloud resolving simulations of deep convection over a heated mountain abstract cloud resolving numerical simulations of airflow over a diurnally heated mountain ridge are conducted to explore the mechanisms and sensitivities of convective initiation under high pressure conditions the simulations are based on a well observed convection event from the convective and orographically induced precipitation study cops during summer 2007 where an isolated afternoon thunderstorm developed over the black forest mountains of central europe but they are idealized to facilitate understanding and reduce computational expense in the conditionally unstable but strongly inhibited flow under consideration sharp horizontal convergence over the mountain acts to locally weaken the inhibition and moisten the dry midtroposphere through shallow cumulus detrainment the onset of deep convection occurs not through the deep ascent of a single updraft but rather through a rapid succession of thermals that are vented through the mountain convergence zone into the deepening cloud mass emerging t

crustal configuration in the northern levant basin based on seismic interpretation and numerical modeling abstract the interpretation of five 2d pstm seismic reflection sections 14 s twt covering the northern levant basin revealed a total of 10 horizons among which one is interpreted as an interface that may represent the moho the interpretation of seismic packages and their bounding surfaces as well as the seismic facies analysis were constrained by published 2d seismic interpretations of the northern lebanese offshore a total of nine seismic packages are identified in the basin with ages varying from the mid jurassic to the quaternary the filling of the basin is made up of thick cenozoic and mesozoic strata deposited above rifted triassic early jurassic interval the sediments are deposited in deep water mixed settings resulting from high stand systems various types of carbonate platforms and low stand systems siliciclastic and carbonate deep water turbidite complexes carbonate and siliciclastic systems are sealed by 1 1 5 km of evaporites and underlie plio quaternary hemipelagic and pelagic sediments intercalated by turbiditic sheets the time horizons were converted into depth using two methods the first one is based on stacking velocities and the second one on velocities resulting from refraction data 2d crustal modeling was achieved by integrating free air gravity anomaly geoid heights and topography data on the five interpreted pstm seismic lines the models representing five sections across the northern levant basin show a progressively attenuated crystalline crust in an ew direction away from the basin s eastern margin the crystalline crust is best interpreted as a strongly thinned continental crust under the levant basin represented by two distinct components an upper and a lower continental crust the moho appears to be situated between 20 and 23 km in the central and southern lebanese offshore estimated surface heatflow in the basin is around 40 mw m2 which is lower than reported values for the onshore and the margin these differences in heatflow values between the offshore the margin and the onshore have an important impact on hydrocarbon maturation and assessment of potential petroleum systems

on the interaction between sea breeze and summer mistral at the exit of the rhone valley the three dimensional structure and dynamics of the combination of the sea breeze and the mistral at the rhone valley exit in southeastern france have been investigated experimentally and numerically on 22 june 2001 the mistral refers to a severe northerly wind that develops along the rhone valley the exit of this valley is located near the mediterranean sea where sea breeze circulation often develops the sea breeze and the mistral coexist this day because of the weakness of this mistral event the event was documented in the framework of the experience sur site pour contraindre les modeles de pollution atmospherique et de transport d emissions escompte field experiment several important data sources are used airborne doppler lidar uhf wind profilers radiosoundings and surface stations as well as nonhydrostatic mesoscale simulations this paper examines the various mechanisms that drive the time and spatial variability of the mistral and the sea breeze in various regions of the rhone valley in the morning the sea breeze penetrates inland near the western side of the rhone valley then moves back because of the reinforcement of the mistral flow caused by the deepening of the leeward surface low due to convection at noon at midday the sea breeze penetrates inland in the middle of the rhone valley only in contrast to pure sea breeze episodes when the sea breeze can extend inland over a horizontal range of more than 150 km the presence of the mistral prevents the sea breeze from penetrating more than 40 km onshore in the late afternoon the sea breeze reaches the eastern side of the rhone valley but over a smaller horizontal range because of higher local topography and because the mistral is more intense in this part of the rhone valley the situations of sea breeze mistral interactions can have a severe impact on regional air quality indeed the southerly sea breeze which advects toward the countryside the pollutants emitted from the large coastal city of marseille france and its industrialized suburbs cannot penetrate far inland because of the mistral blowing in the opposite direction this leads to the stagnation of the pollutants near the area of emission that is also the most densely inhabited area of the region over one million inhabitants

field geometry petrography and geochemistry of a dolomitization front late jurassic central lebanon this contribution describes the field geometry petrography and geochemistry of a well exposed dolomitization front in upper jurassic carbonates and attempts to highlight the sedimentological structural and relative sea level controls on multiphase dolomitization and related diagenetic events the data presented reflect the superposition of various diagenetic phases which have resulted in a single dolostone body whose dimensions are well defined in the field local microbial intraclastic dolomites of late tithonian age accumulated in a hypersaline lagoon during relative sea level fall these pre date beige hydrothermal dolostones 51 to 55 mol caco3 18o 9 3 to 4 0 v pdb 13c 1 5 to 2 1 v pdb 87sr 86sr 0 70742 matrix porosity 6 klinkenberg permeability 0 5 md whose dolomitizing fluid circulated along faults and invaded the nearby facies first the burrows were dolomitized then the bulk rocks resulting in the investigated tongue shaped dolomite body upon late jurassic early cretaceous uplift near surface water percolated through and altered the underlying beige dolostones this event was followed by a ferroan dolomite cement phase which occurred during further burial this contribution featuring a well defined geometric pattern of a dolomitization front with a large petrographic and geochemical data set may also serve as a case study illustrating the complexity of superimposed diagenetic processes which have to be taken into account in modelling exercises of multiphase hydrothermal dolomitization

tectonics and magmatism associated with mesozoic passive continental margin development in the middle east early triassic cretaceous rifting and magmatism occurred along the western edge of the arabian peninsula from egypt in the south to syria in the north associated with the development of the neotethyan passive continental margin which is preserved in the present day eastern mediterranean a change in the direction and rate of extension during the early cretaceous had a profound effect upon the developing continental margin and controlled the pattern of rifting magmatism and sedimentation extensive late jurassic early cretaceous volcanism occurred throughout the region and is clearly rift related major and trace element including rare earth element and sr nd isotopic compositions suggest derivation of the most primitive mafic magmas from an enriched mantle source with minimal evidence of crustal contamination the magmas appear to have ascended rapidly to the surface through large scale faults isopach maps have been constructed for a series of time intervals during the mesozoic using well data from egypt israel iraq jordan lebanon and syria these reveal the distribution and orientation of the main depocentres the main tectonic feature from the late triassic until the late jurassic was a basin which extended northeastwards from northern israel to the palmyrides in central syria by the early cretaceous however deposition switched to a n s oriented basin in central and northern israel and lebanon the distribution of late jurassic early cretaceous magmatism coincides with this new basin and indicates the location of the major extensional fault zones

what is the mechanism for the modification of convective cloud distributions by land surface induced flows abstract the aim of this study is to determine the mechanism that modulates the initiation of convection within convergence zones caused by land surface induced mesoscale flows an idealized modeling approach linked quantitatively to observations of vegetation breezes over tropical benin was used a large eddy model was used with a prescribed land surface describing heterogeneities between crop and forest over which vegetation breezes have been observed the total surface fluxes were constant but the bowen ratio varied with vegetation type the heterogeneous land surface created temperature differences consistent with observations which in turn forced mesoscale winds and convection at the convergence zones over the crop boundaries at these convergence zones optimum conditions for the initiation of convection were found in the afternoon the equivalent potential temperature was higher in the convergence zones than over anywhere else in the domain due to reduced entrainment and the mesoscale convergence

initiation of deep convection at marginal instability in an ensemble of mesoscale models a case study from cops the present study investigates the initiation of precipitating deep convection in an ensemble of convection resolving mesoscale models results of eight different model runs from five non hydrostatic models are compared for a case of the convective and orographically induced precipitation study cops an isolated convective cell initiated east of the black forest crest in southwest germany although convective available potential energy was only moderate and convective inhibition was high measurements revealed that due to the absence of synoptic forcing convection was initiated by local processes related to the orography in particular the lifting by low level convergence in the planetary boundary layer is assumed to be the dominant process on that day the models used different configurations as well as different initial and boundary conditions by comparing the different model performance with each other and with measurements the processes which need to be well represented to initiate convection at the right place and time are discussed besides an accurate specification of the thermodynamic and kinematic fields the results highlight the role of boundary layer convergence features for quantitative precipitation forecasts in mountainous terrain

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

new distribution coefficient for the incorporation of strontium into dolomite and its implications for the formation of ancient dolomites late tertiary dolomites form the bahamas exhibit a strong inverse correlation between sr and mol mgco sub 3 it is proposed that this relation is a result of a distribution coefficient dependent on the concentration of ca in dolomite because these dolomites precipitated from water with a sr sup 2 ca sup 2 ratio similar to that of seawater a distribution coefficient d sub sr sup dolomite of 0 0118 is calculated for sr in stoichiometric dolomite this coefficient increases by about 0 0039 for every additional mol caco sub 3 in nonstoichiometric dolomite these data have three important implication first the new d sub sr sup dolomite is substantially lower than previously suggested second a relation has been established among the sr sup 2 ca sup 2 ratio of dolomite forming waters the major element composition of dolomites and the sr content of dolomites allowing the determination of the sr sup 2 ca sup 2 ratio of fluids involved in the formation of ancient dolomites third some published data sets on dolomites show a similar relation between sr content and major element composition suggesting that these dolomites may also have formed from seawater other data sets deviate from the correlation defined by little bahama bank dolomites indicating either dolomitization in fluids other than seawater or changes ofmore the sr sup 2 ca sup 2 ratio of seawater through time less

constrains on the origin and history of the eastern mediterranean basin abstract the basin formed along the northern passive margin of gondwanaland as a relict of the mesozoic neotethys in early mesozoic time though direct information from the basin itself is meagre the geology of its passive margins and the regional framework of the tethys evolution constrain the formation and history of the basin the eastern mediterranean and its passive margins are interpreted to have formed as a result of several faulting and continental breakup phases from early permian to middle jurassic times before pangaea s complete disintegration this led to the detachment of the eratosthenes and tauride blocks from the margins of the levant and herodotus basins respectively the latter merged in the northeast with the cyprus basin that extended along arabia s northern margin the main rifting probably occurred in the triassic leading to seafloor spreading in the herodotus and cyprus basins while along the levant margin important rifting also occurred in the jurassic during the initial rifting stages extension perpendicular to the levant margin was important but subsequently the tauride block drifted mainly northward the existence of the passive margins and slopes of the eastern mediterranean is documented at least from the end of the middle jurassic until then the basin was probably narrow 200 300 km but during the main phase of the africa laurasia separation it grew to twice its present width or more this scenario depends critically on the interpretation that the tauride block was originally located next to northeastern africa on the western side of the eratosthenes block plate convergence and consumption of the northern portion of the basin have taken place since mid cretaceous times but the active convergent boundary on its northern side formed only in the neogene by modification of earlier structures some intra plate deformation also took place especially in the neogene but it hardly changed the original configuration of the remaining portion of the basin