salinity stratification of the mediterranean sea during the messinian crisis a first model analysis abstract in the late miocene a thick and complex sequence of evaporites was deposited in the mediterranean sea during an interruption of normal marine sedimentation known as the messinian salinity crisis because the related deposits are mostly hidden from scrutiny in the deep basin correlation between onshore and offshore sediments is difficult hampering the development of a comprehensive stratigraphic model since the various facies correspond to different salinities of the basin waters it would help to have physics based understanding of the spatial distribution of salt concentration here we focus on modelling salinity as a function of depth i e on the stratification of the water column a box model is set up that includes a simple representation of a haline overturning circulation and of mixing it is forced by atlantic exchange and evaporative loss and is used to systematically explore the degree of stratification that results under a wide range of combinations of parameter values the model demonstrates counterintuitive behaviour close to the saturation of halite for parameter values that may well be realistic for the messinian we show that a significantly stratified mediterranean water column can be established in this case atlantic connectivity is limited but may be closer to modern magnitudes than previously thought in addition a slowing of mediterranean overturning and a larger deep water formation region both in comparison to the present day are required under these conditions we would expect a longer duration of halite deposition than currently considered in the msc stratigraphic consensus model

simple climatic indices for the tropical atlantic ocean and some applications two indices related to the sea surface temperature sst variability in the tropical atlantic are proposed one index describes the sst averaged over the whole basin 30 n to 20 s 60 w to 15 e and the other illustrates a meridional dipole between the northern and southern hemispheres the computational method for obtaining these indices is intentionally kept simple the objective being to reproduce the signature of the main results previously provided from more complicated statistical analyses monthly time series for both indices are produced from 1964 up to the present time the whole basin index exhibits principally a sustained warming which has intensified since about 1975 and it has a significant periodicity close to that of the quasi biennial oscillation the dipole index exhibits a decadal scale variation and its building up seems to be related to other worldwide climatic changes as for instance el nino southern oscillation extreme episodes rainfall variabilities over the brazilian nordeste and african sahel

intra salt deformation implications for the evolution of the messinian evaporites in the levant basin eastern mediterranean abstract we present new evidence of deformation features supporting a multiple deformation phase mechanism of the messinian evaporites through the interpretation of pre stack depth migration psdm seismic data including all intra salt base of salt bs and top of salt ts reflectors the mechanism presented here involves a syn depositional deformation event caused by a nw basin tilting during the last stage of the messinian salinity crisis msc this was followed by post depositional differential sediment loading through radial spreading of the nile cone after the msc inside the evaporite sequence the upper intra salt units may reside in a brittle domain with predominant thrust faults while the lower units in a ductile deformation domain with folds instead a nw flowing channel system is for the first time observed on the ts horizon suggesting a northwestward basin depocenter during the ts formation the observed nnw nne flow of the water bottom wb channels indicates the direction of the current basin depocenter which suggests a dramatic clockwise shift during post messinian a model of the messinian evaporite evolution in the levant basin during the msc has been established the model is based on our observations and the detailed intra salt interpretation and is divided into four stages a the horizontal deposition of all the intra salt units excluding the uppermost unit b the deposition of the uppermost unit and basin nw tilting occurred coevally or sequentially c the ts erosion and the development of nw trending ts channels and d the deposition of post messinian sediments over the evaporite sequence

the equatorial undercurrent in the central atlantic and its relation to tropical atlantic variability seasonal to interannual variations of the equatorial undercurrent euc in the central atlantic at 23 w are studied using shipboard observation taken during the period 1999 2011 as well as moored velocity time series covering the period may 2005 june 2011 the seasonal variations are dominated by an annual harmonic of the euc transport and the euc core depth both at maximum during september and a semiannual harmonic of the euc core velocity maximum during april and september substantial interannual variability during the period of moored observation included anomalous cold warm equatorial atlantic cold tongue events during 2005 2008 the easterly winds in the western equatorial atlantic during boreal spring that represent the preconditioning of cold warm events were strong weak during 2005 2008 and associated with strong weak boreal summer euc transport the anomalous year 2009 was instead associated with weak preconditioning and smallest euc transport on record from january to july but during august coldest sst anomalies in the eastern equatorial atlantic were observed the interannual variations of the euc are discussed with respect to recently described variability of the tropical atlantic ocean

regional isostatic response to messinian salinity crisis events abstract the salinity crisis of the mediterranean during messinian time was one of the most dramatic episodes of oceanic change of the past 20 or so million years resulting in the deposition of kilometer thick evaporitic sequences a large and rapid drawdown of the mediterranean water level caused erosion and deposition of non marine sediments in a large lago mare basin both the surface loading by the lower messinian evaporites and the removal of the water load resulted in isostatic flexural rebound that significantly affected river canyons and topographic slopes we use flexure models to quantitatively predict possible signatures of these events and verify these expectations at well studied margins the highly irregular shape of the reconstructed basin calls for a three dimensional model near basin margins plate bending effects are most pronounced which is why flexure is particularly important for a relatively narrow basin like the mediterranean we focus on one specific sea level scenario for the messinian salinity crisis where most of the evaporite load was deposited during a sea level highstand followed by a rapid desiccation evaporite loading at current sea level is expected to cause subsidence of the deep basins by hundreds of meters and simultaneous uplift of continental parts of the margins differential uplift may lead to significant slope angle changes and thus gravity flows the relative scarcity of lower evaporite sequences along the margins may be a result of these phenomena normal faulting of lower evaporite and older sediments and rocks is expected on the margins desiccation enhances erosion of the freshly exposed continental shelf and slope subsidence and riverbed sedimentation occurs on the continental margins and significant uplift towards the basin center reverse faulting is predicted at the margins finally regional isostatic uplift following zanclean flooding is predicted to destabilize margin slope deposits and to cause marginal uplift river down cutting and normal faulting

distribution of uranium and thorium in core samples from the underground research laboratory lease area southeastern manitoba canada abstract petrographic examination of core samples from seven boreholes in the underground research laboratory lease area of the lac du bonnet batholith revealed that the granitic core can be divided into four sample groups 1 grey granite 2 pink granite 3 deep red granite and 4 cream coloured clay rich granite the order of these four groups represents an evolutionary sequence that can be related to the alteration of the grey granite u and th concentrations were determined for the four groups of granitic core samples the u concentration in the four groups of core samples showed a distinct variation whereas the th concentration showed little variation the distribution pattern of u in the four sample groups can be related to its mobility and concentration under various stages of rock alteration while the uniform distribution of th is interpreted to be due to its limited mobility

alteration of uraninite from the nopal i deposit pen a blanca district chihuahua mexico compared to degradation of spent nuclear fuel in the proposed u s high level nuclear waste repository at yucca mountain nevada abstract at the nopal i uranium deposit primary uraninite nominally uo 2 x has altered almost completely to a suite of secondary uranyl minerals the deposit is located in a basin and range horst composed of welded silicic tuff uranium mineralization presently occurs in a chemically oxidizing and hydrologically unsaturated zone of the structural block these characteristics are similar to those of the proposed u s high level nuclear waste hlw repository at yucca mountain nevada petrographic analyses indicate that residual nopal i uraninite is fine grained 5 10 m and has a low trace element content average about 3 wt these characteristics compare well with spent nuclear fuel the oxidation and formation of secondary minerals from the uraninite have occurred in an environment dominated by components common in host rocks of the nopal i system e g si ca k na and h 2 o and also common to yucca mountain in contrast secondary phases in most other uranium deposits form from elements largely absent from spent fuel and from the yucca mountain environment e g pb p and v the oxidation of nopal i uraninite and the sequence of alteration products their intergrowths and morphologies are remarkably similar to those observed in reported corrosion experiments using spent fuel and unirradiated uo 2 under conditions intended to approximate those anticipated for the proposed yucca mountain repository the end products of these reported laboratory experiments and the natural alteration of nopal i uraninite are dominated by uranophane nominally ca uo 2 2 si 2 o 7 6h 2 o with lesser amounts of soddyite nominally uo 2 2 sio 4 2h 2 o and other uranyl minerals these similarities in reaction product occurrence developed despite the differences in time and physical chemical environment between yucca mountain approximate laboratory experiments and yucca mountain approximate uraninite alteration at nopal i suggesting that the results may reasonably represent phases likely to form during long term alteration of spent fuel in a yucca mountain repository from this analogy it may be concluded that the likely compositional ranges of dominant spent fuel alteration phases in the yucca mountain environment may be relatively limited and may be insensitive to small variations in system conditions

investigation of the north brazil current retroflection and north equatorial countercurrent variability 1 eight years of topex poseidon altimeter derived sea height anomaly and climatological hydrographic data are used to investigate the temporal and spatial variability of the north brazil current nbc retroflection and the north equatorial countercurrent necc the nbc retroflection exhibits a mean position of 6 6 n 2 0 with a strong annual signal and year to year variability the annual cycle of its location follows the meridional migration of the itcz and the strength of the wind stress curl over the equatorial atlantic a marked shift in the annual mean location of the nbc retroflection is observed in 1998 1999 that appears to be linked to an increase in wind stress curl during this period the mean latitude of the necc is estimated to be 6 0 n 1 3 with a semiannual cycle showing maximum northerly locations in february and august the baroclinic transport of the necc varies predominantly on an annual cycle with maximum transport of 12 sv occurring in november

discovery of vast fluvial deposits provides evidence for drawdown during the late miocene messinian salinity crisis the late miocene messinian salinity crisis msc was a significant oceanographic event that caused widespread evaporitic accumulation throughout the mediterranean basin although multiple hypotheses exist regarding the origin of evaporitic and post evaporitic deposits researchers remain divided on the magnitude of base level fall and on whether these accumulations record deep water or non marine conditions here we introduce a previously unknown upper messinian fluvial deposit comparable in size to the late miocene nile river fluvial valley fill and show that near complete desiccation of the eastern mediterranean was responsible for its development the basin wide accumulation which is located offshore cyprus syria lebanon and israel lies directly atop deep basin evaporites and related erosional surfaces and is one of the largest known riverine deposits associated with the terminal msc from marked onshore incision and basinward thinning trends the source of the accumulation is presumed to be a formerly unidentified drainage basin in southern turkey and western syria the deposit extends 500 km into the western levant basin where its depositional sink is marked by six well developed backstepping lobes based on the deposit s seismic stratigraphy and morphology which provide clear evidence of subaerial exposure we question current hypotheses proposing a deepwater origin for late messinian accumulations we also draw specific attention to the development of extensive circum mediterranean nonmarine conditions prior to zanclean marine transgression and to the previously overlooked role of fluvial systems in diluting hypersaline lakes in evaporitic basins

isopycnal and diapycnal circulation of the upper equatorial atlantic ocean in 1983 1984 isopycnal circulation and diapycnal processes in the equatorial atlantic ocean are investigated using eight cruises from november 1982 to july 1984 an eastward decrease of the transport of the equatorial undercurrent is observed averaging 18 2 106 m3 s 1 at 35 w to 10 2 106 m3 s 1 at 4 w there is also a meridional convergence at the undercurrent level and a larger meridional divergence in the surface layer of 15 106 m3 s 1 between 35 w and 4 w in the eastern equatorial atlantic the undercurrent core density as well as the salinity above the undercurrent experience a large seasonal cycle during the season where the eastern atlantic thermocline is closest to the surface and surface waters are coldest the current peaks in denser waters and subsurface salinity maximum are weaker an analysis of the salinity on isopycnal surfaces indicates that there is significant diapycnal mixing in the upper thermocline in the eastern atlantic the upper thermocline vertical heat diffusivity coefficient scaled over 1 of latitude varies between 3 cm2 s 1 during the upwelling season and nearly 0 early in the year this seasonal mixing is an important element of undercurrent dynamics the turbulent heat flux at the base of the surface layer averages 50 w m 2 between 1 5 n and 1 5 s the surface layer heat budget implies an average oceanic gain of 60 w m 2 between 1 5 n and 1 5 s which could result from exchanges with the atmosphere the heat flux and fresh water seasonal cycles needed to close the budgets are not realistic however the eastern equatorial atlantic thermocline seasonal upwelling is associated with a large inflow into the surface layer over the two years this flow averaging 11 12 106 m3 s 1 originates from the upper thermocline and diapycnal transports near the core of the undercurrent or below are found to be small below the core of the undercurrent we also find that mixing is not intense for instance at 26 5 in the upper part of the thermostad vertical heat diffusivity is only 0 6 cm2 s 1 assuming that mixing takes place over 1 of latitude the uncertainties on these budgets are however large and assumptions on the dynamics that were used could not be checked

evidence for deep water deposition of abyssal mediterranean evaporites during the messinian salinity crisis scientific drilling of the abyssal evaporites beneath the deepest parts of the mediterranean basin gave rise to the idea that the mediterranean sea completely evaporated at the end of the messinian herein we show using new organic geochemical data that those evaporites were deposited beneath a deep water saline basin not in a subaerial saltpan as originally proposed abundant fossil organic lipids were extracted from evaporites in mediterranean deep sea drilling project cores the archaeal lipid distribution and new analyses using the ace salinity proxy and tex86 temperature proxy indicate that surface waters at the time of evaporite deposition had normal marine salinity ranging from 26 to 34 practical salinity units and temperatures of 25 28 c these conditions require a deep water setting with a mixed layer with normal marine salinity and an underlying brine layer at gypsum and halite saturation after correction for isostatic rebound our results indicate maximum drawdown of 2000 m and 2900 m relative to modern sea level in the western and eastern mediterranean basins respectively our results are consistent with previously proposed scenarios for sea level drawdown based on both subaerial and submarine incision and backfilling of the rhone and nile rivers which require messinian sea level drops of 1300 m and 200 m respectively this study provides new evidence for an old debate and also demonstrates the importance of further scientific drilling and sampling of deeper part of the abyssal messinian units

refining the mediterranean messinian gap with high precision u pb zircon geochronology central and northern italy astronomically tuned cyclic sedimentary successions provide unprecedented insight into the temporal evolution of depositional systems and major geologic events however placing astronomically calibrated records into an absolute time frame with confidence requires independent and precise geochronologic constraints astronomical tuning of the precessionally modulated sedimentary cycles of the mediterranean basin deposited during the messinian salinity crisis 5 96 5 33 ma has indicated an 90 k y messinian gap corresponding to the evaporative drawdown of the mediterranean following the closure of the mediterranean atlantic gateway in the messinian deposits a volcanic ash dated by 40 ar 39 ar geochronology was used to anchor the sedimentary cycles to the insolation curve however the uncertainty of the 40 ar 39 ar date introduces a potential two cycle 40 k y uncertainty in the tuning using high precision chemical abrasion thermal ionization mass spectrometry ca tims u pb geochronology on single zircon grains from two messinian ash layers in italy we obtained dates of 5 5320 0 0046 ma and 5 5320 0 0074 ma with sub precessional resolution combined with our astronomical tuning of the messinian lower evaporites the results refine the duration of the messinian gap to at most 28 or 58 9 6 k y which correlates with either the tg12 glacial interval alone or both tg12 and tg14 glacial intervals supporting the hypothesis of a glacio eustatic contribution in fully isolating the mediterranean from the atlantic ocean our new u pb dates also allow us to infer a precessionally modulated cyclicity for the post evaporitic deposits and hence enable us to tune those successions to the insolation curve

upper equatorial atlantic variability during 2002 and 2005 associated with equatorial kelvin waves on the basis of moored 35 degrees w 0 degrees and 23 degrees w 0 degrees and satellite observations we contrast the upper equatorial atlantic variability during 2002 with those during 2005 inspection of the interannual boreal summer cold tongue variability revealed a warm cold event in 2002 2005 with relaxed intensified winds in the west and the equatorial undercurrent euc embedded in a shallower deeper thermocline at 23 degrees w during both years 2002 and 2005 equatorial kelvin waves are present in moored observations as 20 degrees c isotherm depth anomalies and dynamic height anomalies basin wide sea surface height anomalies are used to derive an equatorial kelvin wave mode the time evolution of this mode represents the basis for a regression analysis to investigate related oceanic variability compared to the exceptionally strong wave activity in 2002 equatorial kelvin waves were generally weaker during 2005 the main effect of equatorial kelvin waves on zonal velocity anomalies at 23 degrees w 0 degrees is evident well below the euc core their direct influence on cold tongue sea surface temperature is small but they are found to affect the equatorial thermocline slope prior to the cold tongue onset in 2002 2005 the presence of equatorial kelvin waves is associated with a flattened steeper thermocline slope that is crucial for the shallowing deepening of the euc core at 23 degrees w and that might precondition the development of the warm cold event

structural framework and deformation history of the western cyprus arc abstract an extensive grid of high resolution multichannel seismic reflection profiles complemented with wider spaced deep penetrating industry seismic profiles revealed that the pre messinian miocene structural architecture of the antalya basin and its southwestern extension into the florence rise is characterized by a very prominent broadly northwest southeast striking and largely southwest verging fold thrust belt with occasional northeast verging backthrusts during the messinian a number of prominent thrusts remained active however numerous thrusts which were active during the pre messinian miocene became inactive during the uppermost messinian quaternary the stain was partitioned into five broadly northwest southeast trending morphotectonic domains each delineated by a distinctive seafloor morphology a a domain across the inner and western antalya basin is dominated by extensional faults b a domain immediately south of the extensional faults is characterized by contractional structures c a halokinetic zone in southwestern antalya basin north of the foothills of the anaxagoras mountain is characterized by numerous positive flower structures beneath a corrugated seafloor d a domain characterized by fluid escape structures immediately southeast of the halokinetic zone and e a domain across the crestal portion of the florence rise is dominated by prominent inversion structures detailed mapping documented that several of these tectonic domains can be readily correlated with previously mapped tectonic elements in the eastern mediterranean as well as structures mapped across the adjacent landmass the change from ubiquitous pre messinian miocene contraction to partitioned strain of the latest messinian quaternary is likely related to the collision of the eratosthenes with cyprus and the resultant jostling of the tectonic blocks

the structural evolution of the messinian evaporites in the levantine basin abstract the levantine basin in the south eastern mediterranean sea is a world class site for studying the initial stages of salt tectonics driven by differential sediment load because the messinian evaporites are comparatively young the sediment load varies along the basin margin they are hardly tectonically overprinted and the geometry of the basin and the overburden is well defined in this study we analyse depositional phases of the evaporites and their structural evolution by means of high resolution multi channel seismic data the basinal evaporites have a maximum thickness of about 2 km precipitated during the messinian salinity crisis 5 3 5 9 ma ago the evaporite body is characterized by 5 transparent layers sequenced by four internal reflections we suggest that each of the internal reflection bands indicate a change of evaporite facies possibly interbedded clastic sediments which were deposited during temporal sea level rises all of these internal reflections are differently folded and distorted proving that the deformation was syn depositional thrust angles up to 14 are observed backstripping of the pliocene quaternary reveals that salt tectonic is mainly driven by the sediment load of the nile cone the direction of lateral salt displacement is mainly ssw nne and parallel to the bathymetric trend apparent rollback anticlines off israel result rather from differential subsidence than from lateral salt displacement in the south eastern basin margin the deposition of the isreali slump complex isc is coeval with the onset of salt tectonic faulting suggesting a causal link between slumping processes and salt tectonics the superposition of thin skinned tectonics and thick skinned tectonics becomes apparent in several locations the fold belt off the israeli mediterranean slope mainly results from active strike slip tectonics which becomes evident in faults which reach from the seafloor well below the base of the evaporites owing to the wrenching of the crustal segments which are bounded by deep rooted fault lines like the damietta latakia pelusium and shelf edge hinge line the setting is transpressional south of 32 n where the fault lines bend further towards the west this adds a component of thick skinned transpression to the generally thin skinned compressional regime in the basin above 1 5 km of evaporites a mud volcano is observed with the mud source seemingly within the evaporite layer at the eastern cyprus arc the convergence zone of the african and the anatolian plates deep rooted compression heavily deformed the base of the evaporites whereas at the eratosthenes seamount mainly superficial compression affecting the post messinian sediments and the top of the evaporites is observed

decoding the mediterranean salinity crisis this historical narrative traces the steps to unravel over a span of 40 years an extraordinary event in which 5 of the dissolved salt of the oceans of the world was extracted in a fraction of a million years to form a deposit more than 1 million km 3 in volume a buried abyssal salt layer was identified with reflection profiling and sampled during the deep sea drilling project leg 13 the dolomite gypsum anhydrite and halite in the drill cores paint a surprising picture of a mediterranean desert lying more than 3 km below the atlantic ocean with brine pools that shrank and expanded by the evaporative power of the sun the desert drowned suddenly when the gibraltar barrier gave way the explanation of deep basin shallow water desiccation and the notion of a catastrophic zanclean flood had a mixed reception however the hypothesis became broadly accepted following subsequent drilling expeditions nevertheless as experts examined the evaporate facies and sequences of equivalent age in the terrestrial outcrops weaknesses appeared in the concept of repeated flooding and drying to account for the magnitude of the deposits the rosetta stone used to decipher conflicting interpretations turns out not to be the deposits but the erosion surfaces that enclose them these surfaces and their detritus formed in response to the drop in base level during evaporative drawdown extend to the basin floor evaporative drawdown began halfway through the salinity crisis when influx from the atlantic no longer kept up with evaporation prior to that time a million years passed as a sea of brine concentrated towards halite precipitation during the later part of this interval more than 14 cyclic beds of gypsum accumulated along shallow margins modulated by orbital forcing the thick salt on the deep seabed precipitated in just the next few cycles when drawdown commenced and the brine volume shrank upon closure of the atlantic spillway the remnants of the briny sea transformed into salt pans and endorheic lakes fed from watersheds of eurasia and africa the revised model of evaporative concentration now has shallow margin shallow water and deep basin deep water precursors to desiccation

high and low temperature alteration of uranium and thorium minerals um ara granites south eastern desert egypt abstract the um ara area in the south eastern desert of egypt contains a number of uranium occurrences related to granitic rocks u rich thorite thorite and zircon are the main primary uranium and thorium bearing minerals found in mineralized zones of the um ara alkali feldspar granites uranophane is the most common secondary uranium mineral u rich thorite contains blebs of galena has rims of uranophane and contains inclusions of zr rich thorite electron probe microanalysis epma provides an indication of a range of solid solution between thorite and zircon in which intermediate phases such as th rich zircon and zr rich thorite were formed these phases have higher sum of all cations per formula 2 05 to 2 06 apfu for 4 oxygen atoms than that of ideal thorite and zircon this is attributed to the presence of substantial amount of interstitial cations such as ca u and al in these phases some zircon grains are stoichiometric in composition other altered grains display lower sio 2 and zro 2 contents enrichment of th and u in altered zircon preferentially involves coupled substitution ca 2 th u 4 2zr 4 2si 4 implying that significant u and th may enter the zr and si position in zircon negative correlation of zr vs hf and al may indicate that hf and al have been introduced to the zircon during later fluid alteration rather than during the primary magmatic event a two stage metallogenetic model is proposed for the alteration processes and origin of u and th bearing minerals in the um ara alkali feldspar granite 1 the first stage was dominated by hydrothermal alteration and accompanied by albitization k feldspathization desilicification chloritization hematitization silicification argillization fluoritization and corrosion of primary u bearing minerals solid solution between thorite and zircon occurred during this stage the second stage occurred at the near surface profile where circulating meteoric water played an important role in mobilizing the early formed primary u bearing minerals uranium was likely transported as a calcium uranyl carbonate complexes when these complexes lost their stabilities by precipitation of calcite they decomposed in the presence of silica to form uranophane

high resolution strontium isotope stratigraphy of the messinian deep mediterranean basins implications for marginal to central basins correlation new 87sr 86sr data from dsdp odp messinian cores from deep mediterranean basins suggest that the usually envisaged correlation of offshore upper evaporites with onshore upper gypsum deposits of sicily cyprus and crete recording the stage 3 5 53 5 33 ma of the messinian salinity crisis may be not entirely correct high resolution stratigraphic calibration of sr isotope data indicates that only a very thin unit commonly 50 m in the uppermost part of the seismic upper evaporites is characterized by the typically lower values for sr isotopes with respect to the global ocean which characterize stage 3 onshore successions lago mare event these deposits mainly consist of interbedded clastic or cumulate gypsum and marls halite recovered from cores in the upper evaporites unit is actually characterized by sr isotope values consistent with stage 2 deposits of onshore successions according to these results the messinian trilogy of the western mediterranean basin could be as a whole correlated with the halite unit of the eastern basin suggesting that different hydrologic conditions characterized the two deep areas during the peak of the salinity crisis

timing and intensity of groundwater movement during egyptian sahara pluvial periods by u series analysis of secondary u in ores and carbonates abstract wet climatic episodes are known to have prevailed in the egyptian sahara several times during the late quaternary most recently during the holocene 8000 yr ago earlier wet episodes have been recognized as having occurred during the past 300 000 yr and have been dated by u series methods in speleothems and in lake travertines we show here that the times of enhanced groundwater movement can also be determined by 230 th 234 u dating of secondary u in ores of uranium iron and phosphate we also present evidence that such acceleration of groundwater movements is indicated by relatively low 234 u 238 u activity ratios in the secondary uranium our new data show that pluvial periods in egypt occurred during marine oxygen isotope stages 4 5 6 and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23 000 yr precession cycle of the milankovich curve modulated by the 100 000 yr eccentricity cycle

internal seismic stratigraphy of the messinian evaporites across the northern sector of the eastern mediterranean sea abstract a dense grid of high resolutions multichannel seismic reflection profiles from the northern basins of the eastern mediterranean rhodes finike antalya cilicia adana and latakia basin allow documenting a messinian evaporite succession of variable thickness bounded at its base and top by two strong seismic reflectors named respectively bs bes or the n reflector and ts tes or the m reflector messinian evaporite succession is thickest in the deep antalya basin 2000 2400 ms twt but is notably thinner in across the rhodes and finike basins in the west and the adana cilicia latakia basins in the east five acoustically distinctive messinian subunits are identified in the antalya basin 2e 2a three of these subunits 2e 2c 2a are acoustically stratified with strong laterally continuous reflections while two 2d 2b are acoustically transparent with few coherent reflections interval velocities and the internal acoustic character of subunits are used in conjunction with correlations with borehole data to suggest the lithological composition of the subunits subunit 2e is possibly composed of detrital sediment and resedimented primary lower gypsum associated with the intensive subaerial erosion immediately after the onset of the messinian drawdown correlations with the dsdp sites 375 and 376 suggest that the acoustically transparent subunits 2d and 2b are likely composed of massive halite with interbeds of anhydrite magnesium and potassium salts and minor siliciclastics subunit 2c is probably composed of interbedded siliciclastic and evaporites and or trapped fluids subunit 2a probably corresponds to the gypsum horizons interbedded with carbonates and siliciclastics comparison between the messinian subunits in the eastern and western mediterranean shows remarkable acoustic similarities in both regions there is a stratified lower subunit 2e sequentially overlain by a thick transparent subunit 2d thin stratified subunit 2c and thick transparent subunit 2b which are all capped by a mainly stratified subunit 2a these similarities strongly suggest similarities in the sedimentary evolution of basins in the eastern and western mediterranean

isotope geochemistry of the miocene and quaternary carbonate rocks in rabigh area red sea coast saudi arabia abstract the rabigh area a coastal region north of jeddah city saudi arabia contains raised quaternary coral reefal terraces and reworked coral fragments mixed with sand and gravel this area has a thin exposure lower miocene shallow marine carbonate rocks that laterally pass into evaporites the miocene carbonate and evaporite rocks conformably overly the lower miocene siliciclastic sequence are in turn capped by the harrat basaltic boulders the miocene carbonates are made up of dolomitic packstone wackestone and mudstone whereas the overlying quaternary reefal terraces are composed of coral boundstone and grainstones the quaternary reefal terraces of rabigh area have been dated using the uranium series dating method to obtain precise dates for these corals the calculated ages 128 212 and 235 ka indicate that deposition took place during high sea level stands associated with interglacial times during oxygen isotope stages ois 5 and 7 the youngest age 128 ka clearly corresponds to stage 5e of the last interglacial period the obtained ages correlate well with those of the emerged reefs on the sudanese and egyptian coasts at the western side of the red sea the broad distribution of wet climate pluvial deposits on the continents and high sea level stands indicate a wide geographical range of the interglacial events of the oxygen isotope stages ois 5 and 7 the oxygen and carbon isotopic composition of the miocene and quaternary carbonate rocks in rabigh area show a broad range of 13c and 18o the quaternary carbonate rocks have significantly higher 13c than the miocene ones but low 13c values of the miocene samples likely indicate a high contribution of carbon from organic sources at the time of deposition linear trends are evident in both groups of samples supporting the likelihood of secondary alteration

equatorial currents transport changes for extreme warm and cold events in the atlantic ocean 1 in this work the equatorial atlantic ocean circulation dynamics for warm and cold composite events are analyzed warm and cold typical years were composited from the respective five warmest and the five coldest years of the available record equatorial currents velocity and transport are calculated during a typical warm event the circulation decreases in the upper ocean while during the typical cold event there is intensification the strengthening weakening of the circulation during cold warm events increases decreases the stress between the equatorial undercurrent euc and the south equatorial current sec associated with an increase decrease in entrainment of cold waters into the surface and their westward transport the euc showed striking differences between both composited events for the cold warm event the euc shows a greater reduced transport and core velocity and a deeper shallower structure

time scales of upper ocean temperature variability inferred from the pirata data 1997 2000 1 time series from the pirata 10 minute measurements are investigated in order to study the upper ocean thermal field time scales of variability using the serial covariance power spectra method and wavelet analysis this is one of the few studies that analyze in time and space the pirata buoy data in the region analysis of the depth of the 20 c isotherm show distinct patterns for the northwestern atlantic at 8n 38w and the southeastern atlantic at 10s 10w in the west warm surface waters are accompanied by a shallower thermocline while in the east warm surface waters are associated with its deepening consistent with houghton 1991 at higher frequencies the dominant signals in sea surface temperature are the diurnal and semi diurnal cycles spectral analysis of the depth of the 20 c isotherm show a predominance of the semi diurnal period in the eastern atlantic there are two additional dominant bands in the spectra 10 14 days 25 27 days and for the depth of the 20 c isotherm there is also a lower frequency band at 20 40 days associated with tropical instability waves at the equator the first band can be associated with atmospherically forced motions and the lower frequency band with barotropic instability waves

main processes of the atlantic cold tongue interannual variability the interannual variability of the atlantic cold tongue act is studied by means of a mixed layer heat budget analysis a method to classify extreme cold and warm act events is proposed and applied to ten various analysis and reanalysis products this classification allows 5 cold and 5 warm act events to be selected over the period 1982 2007 cold warm act events are defined by the presence of negative positive sea surface temperature sst anomalies at the center of the equatorial atlantic in late boreal spring preceded by negative positive zonal wind stress anomalies in the western equatorial atlantic an ocean general circulation model capable of reconstructing the interannual variability of the act correctly is used to demonstrate that cold act events develop rapidly from may to june mainly due to intense cooling by vertical mixing and horizontal advection the simulated cooling at the center of the basin is the result of the combined effects of non local and local processes the non local process is an upwelling associated with an eastward propagating kelvin wave which makes the mixed layer more shallow and preconditions the upper layers to be cooled by an intense heat loss at the base of the mixed layer which is amplified by a stronger local injection of energy from the atmosphere the early cooling by vertical mixing in march is also shown to be a good predictor of june cooling in july horizontal advection starts to warm the mixed layer abnormally and damps sst anomalies the advection anomalies which result from changes in the horizontal temperature gradient are associated in some cases with the propagation of rossby waves along the equator during warm act events processes are reversed generating positive sst anomalies a downwelling kelvin wave triggers stratification anomalies and mixed layer depth anomalies amplified by a weaker injection of energy from the atmosphere in may june in july warm act events are abnormally cooled due to negative horizontal advection anomalies resulting from processes similar to those that occur during cold act events this additional cooling process extends the period of cooling of the act reducing sst anomalies

intense salt deformation in the levant basin in the middle of the messinian salinity crisis abstract while numerous studies have shown that salt related deformation in the levant basin began in the late pliocene or early pleistocene here we show that the first salt related deformation event occurred 3 4 myr earlier in the middle of the messinian salinity crisis considering that the entire crisis lasted only about 650 kyr and that halite deposition in the deep basin may have lasted only 50 kyr this deformation event must have been very short at some point after deposition of nearly half of the evaporitic sequence the upper 200 m thick clastic rich layer glided downdip and formed a series of steep contractional ridges on the deep basin floor however unlike the recent salt motion which is derived from northwestward tilting of the levant continental margin towards the cyprus arc and by basinward progradation of the nile derived overburden the short intra messinian deformation event is enigmatic it predates the nile derived overburden and its direction does not match northwestward tilting we postulate that it may reflect the uplift of the carmel block northeast of the study area and possibly the entire north levant coast in a wider view intra messinian deformation is a circum mediterranean phenomenon possibly reflecting reorganization of the africa eurasia boundary

seasonal variations of halite saturation in the dead sea hypersaline lakes and seas were common in the past precipitating thick evaporitic salt deposits the only modern analogue for the paleo limnology of deep salt saturated aquatic environments exists in the dead sea in this study we present new insights from the dead sea on the role of seasonal thermohaline stratification and water balance on the seasonal and depth variations of the degree of saturation of halite salt and the rate of halite growth along the water column we developed methodologies to accurately determine the empirical degree of halite saturation of the lake based on high accuracy densitometry and to quantify halite growth rate along the water column during summer the epilimnion is undersaturated and halite is dissolved whereas during winter the entire water column is supersaturated and crystallizes halite this result is not trivial because the variations in the water balance suggest the opposite summer is associated with higher loss of water by evaporation from the lake compared to the winter hence the thermal effect overcomes the hydrological balance effect and thus governs the seasonal saturation cycle the hypolimnion is supersaturated with respect to halite and crystallizes throughout the year with higher super saturation and higher crystallization rates during winter during summer simultaneous opposing environments coexist an under saturated epilimnion that dissolves halite and a supersaturated hypolimnion that crystallizes halite which results in focusing of halite deposits in the deep hypolimnetic parts of the evaporitic basins and thinning the shallow epilimnetic deposits this article is protected by copyright all rights reserved

u series age and origin of two secondary uranium deposits central eastern desert egypt at two sites in the central eastern desert of egypt secondary uranium minerals are found at the surfaces of tabular fractured rock bodies which host primary uranium mineralization at depth at el atshan the host rock is a 28 m thick bostonite sill cutting siltstones and at el erediya the host rock is a 20 cm jasperoid vein cutting granite whereas the primary mineralization at depth is pre tertiary we obtain u series ages for the secondary mineralization at both sites of 80 000 to 140 000 yr we interpret this episode of uranium mobilization to have resulted from ground water saturation during humid oxygen isotope climatic stage 5 at both sites adsorbed uranium in the host rock immediately below the secondary ores is shown to have been the result of subsequent mobilization during the last 60 000 yr

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

velocity and temperature observations during the seasonal response of the equatorial atlantic experiment at 0 28 w continuous 2 7 year time series of upper ocean currents and temperature at 0 28 w collected during the seasonal response of the equatorial atlantic experiment are presented the thermocline underwent distinctive annual cycles in response to forcing by the surface wind stress and the core of the equatorial undercurrent tracked the thermocline while the vertical position of the thermocline and the undercurrent appear to be simply related the transport of the undercurrent did not show a replicating annual cycle and the speed at the undercurrent core remained relatively constant near surface flow when averaged over the 2 7 years was not statistically different from zero and a westward flowing south equatorial current was rarely established despite strong easterly wind stress in all 3 years cross equatorial flow was also zero in the mean at this location

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

the demise of a salt giant driven by uplift and thermal dissolution abstract the development of giant salt basins and eventual cessation of rapid salt deposition is founded on a delicate balance of salinity and heat fluxes within the water body governed by tectonic climatic and eustatic change the onset of salt deposition in such basins is widely accepted to be initiated by basin restriction however the processes that lead to the termination of salt deposition are comparatively unclear here we use an array of 2d and 3d seismic surveys to reveal that the truncation surface at the top of a thick salt sequence in the eastern mediterranean is far more extensive than previously thought we show that uplift of the salt driven by deformation and thermal dissolution initiated the demise of the salt giant even prior to the final dilution and emplacement of brackish lago mare and fluvial deposits progressive uplift of the salt through the thermocline and into the under saturated epilimnion led to dissolution we argue that dissolved salt was recycled and re precipitation from the hypolimnion in the deepest sections of the basin contemporaneous with dissolution of halite from the shallower epilimnion these findings explain how rapid basinwide salt deposition was brought to an end in the eastern mediterranean and present a novel process for sculpting the final architecture of a salt giant

lago mare episodes around the messinian zanclean boundary in the deep southwestern mediterranean abstract we present a high resolution analysis of planktonic foraminifers calcareous nannofossils ostracods dinoflagellate cysts and pollen grains in four sequences from dsdp odp holes in the southwestern mediterranean alboran and balearic basins 976b 977a 978a and 134b encompassing the previously defined messinian zanclean boundary the study focuses on 1 the marine reflooding which closed the messinian salinity crisis prior to the zanclean gssp 2 the nature of the lago mare in the deep basins indicated by paratethyan dinoflagellate cysts which appears to comprise several paratethyan influxes without climatic control and 3 the depositional context of the youngest messinian evaporites which accumulated in a marine environment relatively close to the palaeoshoreline isolation of the aegean basin during the paroxysmic second step of the crisis is considered to have stored paratethyan waters which may then have poured into the mediterranean central basins after deposition of the evaporitic sequence

how dry was the mediterranean during the messinian salinity crisis the messinian salinity crisis msc 5 97 5 33 ma is an enigmatic episode of paleoceanographic change when kilometers thick evaporite units were deposited in the mediterranean basin it is generally accepted that during the msc interval there was a dry climate in the mediterranean region it is difficult to assess how dry the climate was during the msc because a modern analogue in size and duration is absent here we reconstruct hydrological changes in the mediterranean basin during the three main msc stages using excellently preserved biomarkers we used the hydrogen isotopic composition of the long chain n alkanes dn alkanes to reconstruct the hydrological changes on the land adjacent to the mediterranean sea additionally the d of long chain alkenones dalkenones is used to observe changes in the mediterranean sea water source the dn alkanes recorded during the deposition of primary lower gypsum stage 1 in monte tondo indicate a d of the precipitation comparable to the present day mediterranean implying a similar hydrologic regime indicated by experiments modelling the miocene pliocene transition elevated dalkenones values from halite unit stage 2 of the realmonte mine are associated with kainite and giant polygons consistent with presumably high evaporative conditions during halite deposition the dn alkanes recorded during the deposition of upper gypsum stage 3 in eraclea minoa indicate a dprecipitation typical for much drier settings similar to the red sea region the relative contribution of the different alkenones from eraclea minoa is similar to the one observed in present day marine settings suggesting that during stage 3 connections to the open ocean were likely maintained however the dalkenones records during deposition of the evaporites in eraclea minoa are similar to those synchronously registered in the black sea implying that a similar hydrologic regime characterized by extended drought covered large areas of southeastern europe based on the dalkenones similarity and the paratethys type of lago mare fauna in the mediterranean we speculate that the surface water during stage 3 was at times derived from the black sea

genesis of secondary uranium minerals associated with jasperoid veins el erediya area eastern desert egypt uranium mineralization in the el erediya area egyptian eastern desert has been affected by both high temperature and low temperature fluids mineralization is structurally controlled and is associated with jasperoid veins that are hosted by a granitic pluton this granite exhibits extensive alteration including silicification argillization sericitization chloritization carbonatization and hematization the primary uranium mineral is pitchblende whereas uranpyrochlore uranophane kasolite and an unidentified hydrated uranium niobate mineral are the most abundant secondary uranium minerals uranpyrochlore and the unidentified hydrated uranium niobate mineral are interpreted as alteration products of petscheckite the chemical formula of the uranpyrochlore based upon the electron probe micro analyzer epma is a left text u 1 07 text ca 0 28 text pb 0 03 text na 0 21 text mg 0 02 right sigma 1 6 b left text nb 0 57 text si 0 62 text zr 0 35 text p 0 20 text fe 0 17 text al 0 06 text ti 0 03 right sigma 2 it is characterized by a relatively high zr content average zro2 6 6 wt the average composition of the unidentified hydrated uranium niobate mineral is text u left text u 1 89 text ca 0 49 text pb 0 13 text na 0 06 text mg 0 02 right sigma 2 59 text nb left text nb 1 31 text fe 0 34 text si 0 14 text p 0 10 text ti 0 05 text zr 0 03 text al 0 03 right sigma 2 0 where u and nb represent the dominant cations in the u and nb site respectively uranophane is the dominant u6 silicate phase in oxidized zones of the jasperoid veins kasolite is less abundant than uranophane and contains major u pb and si but only minor ca fe p and zr a two stage metallogenetic model is proposed for the alteration processes and uranium mineralization at el erediya the primary uranium minerals were formed during the first stage of the hydrothermal activity that formed jasperoid veins in el eradiya granite 130 160 ma this stage is related to the late jurassic early cretaceous phase of the final pan african tectono thermal event in egypt after initial formation of el erediya jasperoid veins a late stage of hydrothermal alteration includes argillization dissolution of iron bearing sulfide minerals formation of iron oxy hydroxides and corrosion of primary uranium minerals resulting in enrichment of u ca pb zr and si during this stage petscheckite was altered to uranpyrochlore and oxy petscheckite uranium was likely transported as uranyl carbonate and uranyl fluoride complexes with change of temperature and ph these complexes became unstable and combined with silica calcium and lead to form uranophane and kasolite finally at a later stage of low temperature supergene alteration oxy petscheckite was altered to an unidentified hydrated uranium niobate mineral by removal of fe

the uplift history of the arabian plateau as inferred from geomorphologic analysis of its northwestern edge abstract the arabian plateau ap is an oligocene sub horizontal regional planation surface extending throughout the western half of the arabian peninsula its present elevation of about 1 km required a prominent uplift since the late eocene in order to reconstruct the uplift history we documented abundant abrasive and fluvial terraces that were left along and across the raised judea mountains jm which comprised the nw edge of the ap using the ages of those terraces and the differences in height between them we found that the jm was uplifted in three major phases a few hundred meters during the late eocene early oligocene 500 m during the early miocene early middle miocene and 350 m during the late pliocene the two earliest uplift phases predate the formation of the dead sea transform dst which today separates the jm from the ap meaning that these two phases affected the continuous rigid lithosphere extending southeastwards to the ap interiors moreover restoration of the paleogeography predating the lateral offset along the dst eliminates the main height differences across it and suggests that the dst does not play a major role in the vertical position of its bordering plates but rather forms a relatively narrow deformation strip within the ap those two early phases of uplift can be corroborated by previous thermochronology studies which exhibit similar ages around the red sea but may reflect the uplift age of the entire region the present sub horizontal morphology of the ap is in contrast to the presumed original northeastward drainage and may suggest a subsequent long wave moderate tilting to the sw three possible mechanisms were suggested for the uplift of the ap a long wavelength flexure of the arabian plate during early stages of the uplift and lithospheric thinning or dynamic topography during later stages of the uplift

chronology with a pinch of salt integrated stratigraphy of messinian evaporites in the deep eastern mediterranean reveals long lasting halite deposition during atlantic connectivity abstract the messinian salinity crisis msc 5 97 5 33 ma is considered an extreme environmental event driven by changes in climate and tectonics which affected global ocean salinity and shaped the biogeochemical composition of the mediterranean sea yet after more than 50 years of research msc stratigraphy remains controversial recent studies agree that the transition from the underlying pre evaporite sediments to thick halite deposits is conformal in the deep eastern mediterranean basin however the age of the base and the duration of halite deposition are still unclear also disputed is the nature of the intermediate and upper msc units which are characterized as periods of increased clastic deposition into the eastern mediterranean based on marginal outcrops and seismic data we provide a multidisciplinary study of sedimentary geochemical and geophysical data from industrial offshore wells in the levant basin which recovered a sedimentary record of deep basin mediterranean evaporites deposited during the msc in combination with previous observations of the msc throughout the mediterranean basin our results promote the need for a new chronological model remarkably the one kilometer thick lower part of the evaporitic unit is composed of essentially pure halite except for a thin transitional anhydrite layer at its base the halite is undisturbed and homogeneous lacking diverse features apparent in more proximal sections indicating a deep sea depositional environment we find that distinct meters thick non evaporitic intervals interbedded with the halite previously thought to be clastic layers are diatomites while xrd analysis confirms an increase in clastic components in these sediments they are composed primarily of well preserved marine and freshwater planktonic diatoms the occurrence of marine planktonic diatoms in these intervals indicates the input of atlantic waters into the mediterranean basin during the deposition of the massive halite unit seismic stratigraphy and well log cyclostratigraphy further support deep basin halite deposition which started about 300 kyr earlier than widely assumed 5 97 ma we propose that halite deposition in the deep mediterranean took place during stage 1 of the msc rather than being limited to the short 50 kyr msc acme when sea level was presumably at its lowest thus brine formation salt precipitation and faunal extinction occurred at least in part in a deep non desiccated basin with a restricted yet open mediterranean atlantic connection that allowed inflow of oceanic water we observe an increase in heavy minerals and reworked fauna within the clastic evaporitic interbedded evaporites of the basinal msc section and argue that these settings correspond in the deep basins with a significant sea level drawdown during stage 2 of the msc as observed in the marginal sections this correlation is corroborated by astrochronology and chemostratigraphic markers such as the distribution of n alkanes and biomarker based thermal maturity indices the levant deposits indicate that high sea level and partial connectivity with global oceans promoted the deposition of deep basin deep water halite while sea level drawdown promoted deposition of reworked and transported material from the margins into deep mediterranean basins this study modifies the current understanding of the mechanisms governing salt deposition throughout the msc with implications for other evaporitic events in the geologic record

determining uraniferous host rocks and minerals as a source of dissolved uranium in granite aquifers near the central ogcheon metamorphic belt korea korea has suffered from high u concentrations in some groundwater especially in daejeon near the central ogcheon metamorphic belt however clear explanation has not been yet reported for the uranium sources in groundwater this study is focused on identifying the potential uraniferous host rocks and finding the exact u minerals serving as uranium sources in groundwater near daejeon korea for this work we performed an in situ gamma ray spectrometer survey and a laboratory microscopic study with electron micro probe analysis the measurements for radioactive element content did not show any prominent k and th anomaly spots but they did result in several observations of considerable u anomalies in pegmatite and hydrothermally altered granite in which uraninite coffinite and uranophane were found by electron micro probe analysis the occurrences of u minerals are the first such discovery except in the low grade u deposits of the ogcheon metamorphic belt in korea all observed u minerals were intimately associated with hydrothermal alteration the remarkably low th u ratios in the studied uraniferous rocks also suggest that the u enrichment was genetically related to a post magmatic hydrothermal process however many of the uraniferous parts were controlled by a reducing environment and occurred near the border between graphite rich mica schist and jurassic leucocratic granite the findings on these uraniferous rocks can be used in elucidating the source of highly enriched u groundwater in granite aquifers as well as in understanding the occurrence of igneous u minerals which has not been previously reported in korea

distribution of rare earth elements and oxyhydroxide phases within a weathered felsic igneous profile in hong kong abstract variation in type and abundance of oxyhydroxide phases and the fractionation of rare earth elements ree within a weathered felsic pyroclastic profile in hong kong were investigated in order to assess the key factors and micro environmental conditions controlling their distribution during weathering at rock and mineral scales three types of oxyhydroxide phases fe mn and ce rich were recognized based on their most abundant elements the fe rich types appeared in all samples at different stages of weathering the mn rich types however were limited to samples at advanced stages of weathering while the ce rich types were found solely in samples from oxyhydroxide rich zones fractionation of ree likely started at the early stages of weathering but became evident only at the advanced stages characteristics of ree patterns especially the direction negative or positive and extent of ce anomalies correlated very well with the appearance and abundance of mn oxyhydroxides and were attributed to the co existence of distinct micro environmental conditions within the profile these conditions resulted from two major competing processes leaching and fixation and oxidation precipitation and reduction dissolution which operated simultaneously within the profile at any given stage of weathering

genesis of kasolite associated with aplite pegmatite at jabal sayid hijaz region kingdom of saudi arabia abstract in this study we report kasolite pb uo 2 sio 4 h 2 o for the first time as a main uranyl mineral in the mineralized aplite pegmatite of jabal sayid hijaz region it commonly forms clusters of yellow acicular crystals in the voids and fractures the mineral chemistry and mineralogical characteristics of kasolite were investigated using different techniques calcium iron and phosphorus are detected in kasolite in addition to its major constituents uranium lead and silicon lead does not exist as a radiogenic product and not even as a substitute for uranium in the mineral structure alternatively galena mineralization could be considered as a source for lead the fluoride and carbonate complexes played a significant role in the formation of kasolite high temperature hydrothermal solutions reacted with pre existing uranium bearing metamictized accessory minerals such as pyrochlore u rich thorite and zircon to form uranous fluoride complexes these complexes are predominant in reducing environment and at ph 4 when the fluids approached the surface passing through fracture system the oxygen fugacity f o 2 and the ph increased because of the loss of volatile components at these conditions uranous fluorides would convert to uranyl fluoride complexes uo 2 f 3 further decrease in temperature was associated with the decay of the activity of fluorine ion by the dilution of hydrothermal solutions and precipitation of fluorite at this condition uranyl carbonate complexes are favoured these complexes were combined later with silica and lead to form kasolite

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

the buried afiq canyon eastern mediterranean israel a case study of a tertiary submarine canyon exposed in late messinian times abstract the afiq submarine canyon was one of a series of canyons initially incised in a drowned shelf edge and slope of the eastern mediterranean margins in early oligocene times p19 zone during most of the early miocene submarine erosion or non deposition prevailed this was followed by deposition of pelagic marls and debris flows in early middle miocene n8 times large scale sliding in late middle miocene times n14 resulted in the collapse of the slope the removal of most of the middle miocene sequence and the formation of a box shaped scar back cutting incision ultimately resulted in the incision of the shelf in late miocene times a sea level fall ranging between 50 and 800 m below the canyon s rim resulted in the deposition of the messinian lower evaporites mavqiim formation within the canyon a subsequent rise of a similar extent led to the deposition of the upper evaporites be eri gypsum which are found on the canyon s southern shoulder the final messinian sea level drop below the canyon s floor resulted in a subaerial environment in the canyon the erosion of the upper evaporites and the subsequent deposition of fluvial and brackish sediments afiq formation the latter correspond to the lago mare sediments known throughout the mediterranean the rapidly rising sea level during the pliocene along with the high rate of nilotic clastic sedimentation resulted in the final burial of the afiq canyon and a pronounced seaward progradation 20 30 km of the shelf edge

interannual north equatorial countercurrent variability and its relation to tropical atlantic climate modes 1 a synthesis product of the surface geostrophic circulation is used to quantify the interannual variability of the wind driven north equatorial countercurrent necc the first mode of a complex empirical orthogonal function ceof decomposition of zonal geostrophic velocity in the necc region reveals pronounced latitudinal displacements in addition to variations in current strength while north south migrations of the necc are mainly captured by the real pattern the imaginary pattern accounts for variations in its strength associated with these spatial patterns is prevailing propagation toward the northwest that is most pronounced northward of the mean necc position 6 n there is evidence that the zonal propagation characteristics are consistent with long rossby waves forced in the northeastern tropical atlantic the relationship between interannual necc variations and the tropical atlantic climate modes is investigated through regression and composite analyses sea surface temperature and wind stress patterns resembling the meridional and zonal modes are found for the ceof regression composite analysis further shows consistent patterns for warm phases of the meridional mode and cold phases of the zonal mode the response of the necc to a positive meridional and negative zonal mode event may be viewed as a northward shift of its core and a current strengthening respectively these results support a link between the two dominant tropical atlantic climate modes and show that the relation between interannual necc variability and the meridional and zonal modes can primarily be regarded as a response to changes in the wind field

giant polygons in the realmonte mine agrigento sicily evidence for the desiccation of a messinian halite basin abstract the messinian realmonte salt deposit consists of a 400 600 m thick halite succession that can be divided into four main lith ologic units base to top a cumulates of plates settled out from a stratified water column b plate cumulates in a shallowing upward sequence containing six kainite layers near the top of the unit c cu mulates of skeletal hoppers with chevron overgrowths precipitated from a nonstratified water body and d skeletal halite and anhydrite spectacular vertical fissures cut through the upper part of unit b at its boundary with salt unit c these fissures are spaced at intervals of up to 5 m apart extend down to a depth of 6 m and are filled by red mud the salt beds affected by the fissures are commonly upturned buckled and are truncated and onlapped by the succeeding flat lying halite beds of unit c additionally the upturned layers are cut by vertical dissolution pipes that extend down to as much as a depth of 4 m below the fissured surface to explain the observed superimposed structures we propose two mechanisms both induced by the desiccation of the evaporite basin 1 when the salt surface was exposed the halite layers were buck led broke into polygonal crusts and formed tepee structures the buckling was caused by a net volume increase due to thermal expan sion and what is more important precipitation of new halite induced by evaporative pumping of brines moving up from the groundwater table the buckled salt layers were then affected by meteoric dissolu tion which created vertical pipes 2 the tepee structures and the associated zone of dissolution pipes are further crosscut by a new network of large polygons these new polygonal sets are outlined by deep fissures in which red silt collected blown by the wind or carried by episodes of surface flooding this type of deep contraction crack is known to be produced by volumetric changes induced by annual temperature fluctuations the documentation of contraction polygons and other exposure fea tures represents the first report of desiccation events during the de position of the sicilian salt no geological data are yet available to settle the questions if the salt of sicily is correlatable with the halite present beneath the floor of the mediterranean and if the desiccation of the realmonte salt basin could have been induced by a local tectonic causes uplift of the basin floor by thrust activity b simple evaporitic drawdown c basinwide drop of the mediterranean sea level or d complex interaction among these factors

age refinement of the messinian salinity crisis onset in the mediterranean we propose a revised age calibration of the messinian salinity crisis onset in the mediterranean at 5 971 ma based on the recognition of an extra gypsum cycle in the transitional interval of the perales section sorbas basin spain and the revision of the magnetostratigraphy of the monticino section vena del gesso basin italy this age re calibration allows to state more accurately that i the interval encompassing the msc onset is continuous thus ruling out any erosional feature or stratigraphic hiatus related to a major sea level fall affecting the mediterranean ii the first gypsum was deposited during the summer insolation peak at 5 969 ma associated with an eccentricity minimum and roughly coincident with glacial stage tg32 iii the msc onset was preconditioned by the tectonically driven reduction of the hydrological exchanges with the atlantic ocean and finally triggered by glacial conditions in the northern hemisphere and by arid conditions in northern africa

temperature seasonality control on modern halite layers in the dead sea in situ observations layered halite sequences are found in deep basins throughout the geological record however analogs for such sequences are commonly studied in shallow environments here we studied active precipitation of halite layers from the only modern analog for deep halite precipitating basins the hypersaline dead sea in situ observations in the dead sea link seasonal thermohaline stratification halite saturation and the characteristics of the actively forming halite layers the spatiotemporal evolution of halite precipitation in the dead sea was characterized by means of monthly observations of 1 lake thermohaline stratification temperature salinity and density 2 degree of halite saturation and 3 textural evolution of the active halite deposits we present the observed relationships between the textural characteristics of layered halite deposits i e grain size consolidation and roughness and the degree of saturation which in turn reflects the limnology and hydroclimatology the lake floor is divided into two principal environments a deep hypolimnetic lake floor and a shallow epilimnetic lake floor in the deeper hypolimnetic lake floor halite continuously precipitates with seasonal variations 1 during summer consolidated coarse halite crystals form rough surfaces under slight supersaturation 2 during winter unconsolidated fine halite crystals form smooth lake floor deposits under high supersaturation these observations support interpretations of the seasonal alternation of halite crystallization mechanisms the shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations and by intensive summer dissolution of part of the previous year s halite deposit which results in thin sequences with annual unconformities this emphasizes the control of temperature seasonality on the characteristics of the precipitated halite layers in addition precipitation of halite on the hypolimnetic floor at the expense of the dissolution of the epilimnetic floor results in lateral focusing and thickening of halite deposits in the deeper part of the basin and thinning of the deposits in shallow marginal basins

genetically related mo bi ag and u f mineralization in a type granite gabal gattar eastern desert egypt abstract molybdenum bismuth silver and uranium fluorine mineralization in the gabal gattar area are genetically related both are hosted in fractionated and hydrothermally altered a type granite while mo bi ag ore is hosted in ns striking quartz veins the u f mineralization forms batches and micro veinlets controlled by nne to nw trending structures u was incorporated in late magmatic hypogene minerals e g zircon and xenotime and in u th minerals closely associated with fluorite molybdenite native bismuth galena chalcopyrite sphalerite aikinite pbcubis 3 berryite s 16 cu ag 6 bi 7 pb 3 and native silver were identified in the quartz veins fluid inclusions occur in fluorite type 1 associated with u minerals and in quartz type 2 from mo bearing veins type 1 and 2 inclusions homogenize at temperatures between 220 c and 106 c their salinity ranges from 1 3 to 10 wt nacleq respectively f rich fluids accumulated at the last stage of granite crystallization extracted ore metals and deposited them in a shallow hydrothermal system mo bi and ag precipitated earlier from saline fluids due to cooling fluid mixing and wallrock sulfidation u f minerals precipitated from low salinity fluids after high input of meteoric water

tropical pacific decadal variability and the subtropical tropical cells abstract the decadal scale variability in the tropical pacific has been analyzed herein by means of observations and numerical model simulations the two leading modes of the sea surface temperature sst variability in the central western pacific are a decadal mode with a period of about 10 yr and the enso mode with a dominant period of about 4 yr the sst anomaly pattern of the decadal mode is enso like the decadal mode however explains most variance in the western equatorial pacific and off the equator a simulation with an ocean general circulation model ogcm forced by reanalysis data is used to explore the origin of the decadal mode it is found that the variability of the shallow subtropical tropical overturning cells is an important factor in driving the decadal mode this is supported by results from a multicentury integration with a coupled ocean atmosphere general circulation model cgcm that realistically simulates tropical pacific decadal variability finally the sensitivity of the shal

paratethyan ostracods in the spanish lago mare more evidence for interbasinal exchange at high mediterranean sea level abstract a gigantic cascade of atlantic waters filling the deep desiccated mediterranean basin at the beginning of the pliocene has commonly been envisaged to end the messinian salinity crisis msc the mediterranean lowstand during its final lago mare phase however has long been subject to major controversy and has recently been seriously questioned again here we present high resolution ostracod distribution patterns of the msc successions in the black sea basin zheleznyi rog section russia and the mediterranean cuevas del almanzora section spain to study the origin and migration history of the lago mare ostracods we conclude that two major phases of faunal migration have taken place in the messinian the first phase corresponds to the maeotian pontian boundary interval 6 1 6 0 ma of the paratethys where mainly pannonian species suddenly invaded the black sea region the second migration event corresponds to the lago mare phase of the mediterranean when first 5 55 5 47 ma some opportunistic taxa species of cyprideis and loxoconcha genera and then 5 40 5 33 ma a more diverse assemblage of paratethyan species occupied the entire mediterranean region the spanish ostracod assemblages show a high percentage of paratethyan pontian ostracods in agreement with previously studied italian lago mare sections the similar palaeoenvironmental changes that developed roughly synchronously in the western and central mediterranean marginal basins provide more evidence for intrabasinal exchange at high water level during the final stage of the lago mare phase this indicates that the mediterranean in the latest messinian was full of water comparable to the present caspian sea and that the zanclean deluge if happened only surged some tens up to few hundred metres into the mediterranean

new imaging of the salinity crisis dual messinian lowstand megasequences recorded in the deep basin of both the eastern and western mediterranean through several examples we show that following sea level fall and marginal erosion during the messinian salinity crisis msc clastic inputs into the eastern and western mediterranean sea are not distributed evenly in space and time but are mainly limited to the lower section of the messinian salinity crisis depositional megasequence significant similarities around the basin allow us to propose a mediterranean messinian salinity crisis depositional episode that can be divided into two seismic megasequences the messinian lower megasequence mlm and the messinian upper megasequence mum their distinctive seismic facies correspond to systems tracts deposited during three main stages that represent a complete sea level cycle 1 a falling stage systems tract including mass transport deposits and forced regressive clinoforms deposited in in the early part of the falling stage and related to the increasing rate of relative sea level fall this stage is characterized by a marked shift in the depocenter towards the deep basins 2 an early lowstand characterized by massive clastic inputs from major messinian rivers the rhone nile and antalya gulf rivers or smaller river systems offshore south lebanon these clastics were deposited in an oversaturated basin as evidenced by the interfingering chaotic and transparent seismic facies of the messinian lower megasequence mlm 3 a late lowstand starting with rapid deposition of massive halite with no detrital inputs into the deep basin the upper part of the evaporites clearly onlaps the messinian erosional surface at the margins and is evidence for a transition between a late lowstand stage and an early transgressive stage these deposits belong to the messinian upper megasequence mum we interpret the transition between the two megasequences as the peak of the salinity crisis the end of the relative sea level fall and the maximum dispersal of sands into the deep mediterranean basins

microscale controls on the fate of contaminant uranium in the vadose zone hanford site washington abstract an alkaline brine containing uranyl uo22 leaked to the thick unsaturated zone at the hanford site we examined samples from this zone at microscopic scale to determine the mode of uranium occurrence microprecipitates of uranyl uo22 silicate within lithic clast microfractures and constructed a conceptual model for its emplacement which we tested using a model of reactive diffusion at that scale the study was driven by the need to understand the heterogeneous distribution of uranium and the chemical processes that controlled it x ray and electron microprobe imaging showed that the uranium was associated with a minority of clasts specifically granitic clasts occupying less than four percent of the sediment volume xanes analysis at micron resolution showed the uranium to be hexavalent the uranium was precipitated in microfractures as radiating clusters of uranyl silicates and sorbed uranium was not observed on other surfaces compositional determinations of the 1 3 m precipitates were difficult but indicated a uranyl silicate these observations suggested that uranyl was removed from pore waters by diffusion and precipitation in microfractures where dissolved silica within the granite equilibrated solution would cause supersaturation with respect to sodium boltwoodite this hypothesis was tested using a reactive diffusion model operating at microscale conditions favoring precipitation were simulated to be transient and driven by the compositional contrast between pore and fracture space pore space conditions including alkaline ph were eventually imposed on the microfracture environment however conditions favoring precipitation were prolonged within the microfracture by reaction at the silicate mineral surface to buffer ph in a solubility limiting acidic state and to replenish dissolved silica during this time uranyl was additionally removed to the fracture space by diffusion from pore space uranyl is effectively immobilized within the microfracture environment within the presently unsaturated vadose zone

variability of the atlantic off equatorial eastward currents during 1993 2010 using a synthetic method 1 we have developed validated and applied a synthetic method to monitor the off equatorial eastward currents in the central tropical atlantic this method combines high density expendable bathythermograph xbt temperature data along the ax08 transect with altimetric sea level anomalies slas to estimate dynamic height fields from which the mean properties of the north equatorial countercurrent necc the north equatorial undercurrent neuc and the south equatorial undercurrent seuc and their variability can be estimated on seasonal to interannual timescales on seasonal to interannual timescales the synthetic method is well suited for reconstructions of the necc variability reproduces the variability of the neuc with considerable skill and less efficiently describes variations of the seuc which is located in a region of low sla variability a positive correlation is found between interannual variations of the necc transport and two indices based on an interhemispheric sea surface temperature sst gradient and southeasterly wind stress in the central tropical atlantic the neuc is correlated on interannual timescales with ssts and meridional wind stress in the gulf of guinea and zonal equatorial wind stress this study shows that both altimetry and xbt data can be effectively combined for near real time inference of the dynamic and thermodynamic properties of the tropical atlantic current system

lithology and characteristics of the messinian evaporite sequence of the deep levant basin eastern mediterranean abstract as the lithological composition of the messinian salt sequence of the levant basin is still controversial and unconstrained we reveal for the first time the lithology of the entire evaporite sequence from deep basin depth migrated seismic and borehole data the data presented here shows that the seismic transparent layers are composed of pure and uniform halite while the reflective layers are bundles of thin clay layers interbedded in the halite background the thin clay layers inside the deep basin evaporites have a cumulative thickness of 25 40 m high amplitude fan structures are observed on the deepest internal reflector which may suggest clay transportation among all the internal reflectors the upper units are more deformed while the deeper units are more coherent and flat two sets of folds faults are shown on the shallower intra units folds with nne ssw trending axes and thrust faults strike nw se on a regional scale the top salt reflector is generally horizontal while the other internal reflectors dip toward the nw the shallowest intra unit is the only one that has a wedge shape thickening to the nw while the other intra units generally have uniform thicknesses

slow variability in the equatorial west central pacific in relation to enso abstract six years of upper ocean velocity temperature and surface wind data collected in the west central pacific at 0 170 w reveal a slow ocean dynamical mode associated with the el nino southern oscillation enso latent and sensible heat flux calculations using the basin wide tropical atmosphere ocean tao array data show a coincident slow ocean atmosphere thermodynamical mode beginning with the la nina conditions in 1988 through the peak el nino conditions in 1992 the equatorial undercurrent euc speed decreased along with the surface zonal wind stress and the zonal pressure gradient simultaneous with these were increasing trends in the richardson number above the euc core and in sea surface temperature sst after peak warming was achieved the variations in all of these quantities reversed in a movement toward their previous la nina conditions as this evolved within the ocean the sensible and latent heat fluxes increased with large values emanating eastward from the western pacific the

unusual conditions in the tropical atlantic ocean in 1984 au cours de la 1ere moitie de 1984 les conditions oceaniques et atmospheriques dans l atlantique tropical ont ete a bien des egards similaires a celles dans le pacifique au cours de l el nino l ocean superieur a ete inhabituellement chaud dans sa partie orientale les pluies ont ete abondantes sur des regions normalement arides au sud de l equateur et l upwelling cotier a ete contrarie dans une region sud ouest africain ou il constitue un phenomene saisonnier le changement de tsm sst qui apparait lorsque d inhabituels courants portant a l est au sud de l equateur transportent de l eau chaude de surface vers l afrique contribue au changement des conditions atmospheriques ces dernieres en retour contribuent au changement de la circulation oceanique et de la tsm