run out distance and erosion of debris flows in the nile deep sea fan system evidence from lithofacies and micropalaeontological analyses abstract debrites with different volumes depositional periods and setting are observed in the nile deep sea fan system here we present debrites from four late quaternary environments i within the rosetta submarine channel at 1700 m ii within small basins created by salt tectonics in the eastern province at 1300 m iii on the open slope outside of channels at 2600 m and iv in the distal part of the fan fringe beyond channel terminations at 3050 m water depth the debrites comprise mud clasts in a generally ungraded muddy sand matrix they are relatively thin 20 150 cm in fan fringe in channel and salt tectonic basin settings and somewhat thicker 8 m in the open slope setting benthic foraminiferal assemblages and variation in the planktonic benthic foraminiferal ratios are considered as a useful tool for tentatively evaluating the origin of sediment in these debris flows and estimation of their run out distance similar microfaunal contents of clast matrix combinations document that the debrites in the rosetta channel and salt tectonic basin were locally sourced the debrite from the open slope travelled farther up to 150 km three separate debrites in a fan fringe core were deposited by debris flows that originated over 200 km away in water depths shallower than 1000 m these far travelled debris flows appear to have eroded remarkably little sediment as they travelled for 200 km across low 0 8 1 2 gradient seafloor this lack of erosion is attributed to hydroplaning or increasing pore fluid pressure at the base of debris flows this study confirms that remarkably mobile debris flows can travel long distances to produce thin debrites in the distal fringes of submarine fans

solar forcing of nile discharge and sapropel s1 formation in the early to middle holocene eastern mediterranean we present high resolution records for oxygen isotopes of the planktic foraminifer globigerinoides ruber 18oruber and bulk sediment inorganic geochemistry for holocene age sediments from the southeast mediterranean our 18oruber record appears to be dominated by nile discharge rather than basin scale salinity temperature changes nile discharge was enhanced in the early to middle holocene relative to today the timing of the long term maximum in nile discharge during the early holocene corresponds to the timing of maximum intensity of the indian ocean influenced southwest indian summer monsoon sim this coincidence suggests a major influence of an indian ocean moisture source on nile discharge in the early to middle holocene while presently the atlantic ocean is the main moisture source nile discharge was highly variable on multicentennial time scale during the early to middle holocene being strongly influenced by variable solar activity this solar driven variability is also recorded in contemporaneous sim records however not observed in an atlantic ocean derived west african summer monsoon record from the holocene this supports the hypothesis that the indian ocean moisture source predominantly controlled nile discharge at that time solar driven variability in nile discharge also influenced paleoenvironmental conditions in the eastern mediterranean bulk sediment ba al and v al used as indicators for export productivity and redox conditions respectively varied both in response to solar forcing on multicentennial time scales we suggest that changes in nile discharge on these time scales have been concordant with nutrient inputs to and shallow ventilation of the eastern mediterranean

synchronous basin wide formation and redox controlled preservation of a mediterranean sapropel organic rich sedimentary units called sapropels have formed repeatedly in the eastern mediterranean sea in response to variations of solar radiation sapropel formation is due to a change either in the flux of organic matter to the sea floor from productivity changes or in preservation by bottom water oxygen levels however the relative importance of surface ocean productivity versus deep water preservation for the formation of these organic rich shale beds is still being debated and conflicting interpretations are often invoked1 2 3 4 5 6 7 here we analyse at high resolution the differences in the composition of the most recent sapropel s1 in a suite of cores covering the entire eastern mediterranean basin we demonstrate that during the 4 000 years of sapropel formation surface water salinity was reduced and the deep eastern mediterranean sea below 1 800 m depth was devoid of oxygen this resulted in the preferential basin wide preservation of sapropel s1 with different characteristics above and below 1 800 m depth as a result of different redox conditions we conclude that climate induced stratification of the ocean may therefore contribute to enhanced preservation of organic matter in sapropels and potentially also in black shales

trace element systematics of pyrite from submarine hydrothermal vents abstract submarine hydrothermal sulfide ores occur at mid ocean ridges intra oceanic arcs and in back arc basins associated with host rocks of highly variable composition pyrite is the dominant sulfide mineral in most samples presented within this study and thus the trace element composition of pyrite may reflect the different metal sources and precipitation processes here we report on a systematic study of minor and trace element contents in pyrite from active and inactive submarine hydrothermal vent fields at different plate tectonic settings including the indian and mid atlantic ridges the tonga kermadec intra oceanic arc the lau back arc and the central okinawa trough our results show that the trace element contents of pyrite from different locations vary significantly but for most elements without any systematic correlation to the concentration in the magmatic host rocks only as appears to be depleted in pyrite from ultramafic hosted vent systems that are affected by serpentinization these as depleted pyrites preferentially host au 0 micro or nano particles bismuth is enriched in pyrite from hydrothermal systems that contain a sedimentary component and micro inclusions of sphalerite are either due to fluid sediment interaction or phase separated fluid venting pyrites from individual locations have highly variable concentrations of elements like au co cu se mo ag and sb that are most likely related to fluid evolution and changes in fluid composition sub seafloor hydrothermal fluid seawater mixing influences the distribution of au co cu se and mo in pyrite elements like au ag sb and pb often have a characteristic affinity to as while cd correlates closely with zn a magmatic volatile contribution to the hine hina hydrothermal system may result in the precipitation of cu enriched pyrite our results show that the concentrations of most trace metals in pyrite are a function of the physicochemical parameters of the fluid phase rather than a reflection of the magmatic host rock composition

the timing of mediterranean sapropel deposition relative to insolation sea level and african monsoon changes the mediterranean basin is sensitive to global sea level changes and african monsoon variability on orbital timescales both of these processes are thought to be important to the deposition of organic rich sediment layers or sapropels throughout the eastern mediterranean yet their relative influences remain ambiguous a related issue is that an assumed 3 kyr lag between boreal insolation maxima and sapropel mid points remains to be tested here we present new geochemical and ice volume corrected planktonic foraminiferal stable isotope records for sapropels s1 holocene s3 s4 and s5 marine isotope stage 5 in core lc21 from the southern aegean sea the records have a radiometrically constrained chronology that has already been synchronised with the red sea relative sea level record and this allows detailed examination of the timing of sapropel deposition relative to insolation sea level and african monsoon changes we find that sapropel onset was near synchronous with monsoon run off into the eastern mediterranean but that insolation sapropel monsoon phasings were not systematic through the last glacial cycle these latter phasings instead appear to relate to sea level changes we propose that persistent meltwater discharges into the north atlantic e g at glacial terminations modified the timing of sapropel deposition by delaying the timing of peak african monsoon run off these observations may reconcile apparent model data offsets with respect to the orbital pacing of the african monsoon our observations also imply that the previous assumption of a systematic 3 kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation sapropel phasings finally we surmise that both sea level rise and monsoon run off contributed to surface water buoyancy changes at times of sapropel deposition and their relative influences differed per sapropel case depending on their magnitudes sea level rise was clearly important for sapropel s1 whereas monsoon forcing was more important for sapropels s3 s4 and s5

evidence for a new shallow magma intrusion at la soufriere of guadeloupe lesser antilles insights from long term geochemical monitoring of halogen rich hydrothermal fluids more than three decades of geochemical monitoring of hot springs and fumaroles of la soufriere of guadeloupe allows the construction of a working model of the shallow hydrothermal system this system is delimited by the nested caldera structures inherited from the repeated flank collapse events and the present dome built during the last magmatic eruption 1530 ad and which has been highly fractured by the subsequent phreatic or phreatomagmatic eruptions because it is confined into the low volume highly compartmented and partially sealed upper edifice structure the hydrothermal system is highly reactive to perturbations in the volcanic activity input of deep magmatic fluids the edifice structure sealing and fracturing and meteorology wet tropical regime the current unrest which began with a mild reactivation of fumarolic activity in 1990 increased markedly in 1992 with seismic swarms and an increase of degassing from the summit of the dome in 1997 seismic activity increased further and was accompanied by a sudden high flux hcl rich gas from summit fumaroles we focus on the interpretation of the time series of the chemistry and temperature of fumarolic gases and hot springs as well as the relative behaviours of halogens f cl br and i this extensive geochemical time series shows that the deep magmatic fluids have undergone large changes in composition due to condensation and chemical interaction with shallow groundwater scrubbing it is possible to trace back these processes and the potential contribution of a deep magmatic source using a limited set of geochemical time series t co2 and total s content in fumaroles t and cl in hot springs and the relative fractionations between f cl br and i in both fluids coupling 35 years of geochemical data with meteorological rainfall data and models of ion transport in the hydrothermal aquifers has allowed us to identify a series of magmatic gas pulses into the hydrothermal system since the 1976 1977 crisis the contrasting behaviours of s and cl bearing species in fumarolic gas and in thermal springs suggests that the current activity is the result of a new magma intrusion which was progressively emplaced at shallow depth since 1992 although it might still be evolving the characteristics of this new intrusion indicate that it hasalready reached a magnitude similar to the intrusion that was emplaced during the 1976 1977 eruptive crisis the assessment of potential hazards associated with evolution of the current unrest must consider the implications of recurrent intrusion and further pressurization of the hydrothermal system on the likelihood of renewed phreatic explosive activity moreover the role of hydrothermal pressurization on the basal friction along low strength layers within the upper part of the edifice must be evaluated with regards to partial flank collapse at this stage enhanced monitoring research and data analysis is required to quantify the uncertainties related to future scenarios of renewed eruptive activity and magmatic evolution

sedimentation processes in the eastern mediterranean sea during the late glacial and holocene revealed by end member modelling of the terrigenous fraction in marine sediments we present grain size distributions of the terrigenous fraction of two sediment cores from the southeast levantine sea sl112 and the northern aegean sea sl148 spanning the time interval from the late glacial to the present end member modelling of the grain size distribution allows discriminating between aeolian and fluvial transport of the sediments and helps to infer palaeoenvironmental conditions in the source areas sedimentary and depositional processes during the late glacial and holocene were controlled by climatic variations of both the northern high latitudes and the african climate system the sedimentation at site sl112 off israel is dominated by the suspension load of the river nile and aeolian dust from the sahara variations in grain size reflect the early to mid holocene climate transition from the african humid period to recent arid conditions this climate change was gradual in contrast to the abrupt humidity change documented in western saharan records this implies a successive decrease in nile river sediment supply due to a step wise aridification of the headwaters the grain size data of sl112 show a humidity maximum at 5 kyr bp coincident with a regionally restricted wet phase in the levantine sea the sediments at the north aegean site sl148 consist of riverine particles and low amounts of aeolian dust probably derived from south european sources and with probably minor saharan influence the sedimentation processes are controlled by climate conditions being characterized by enhanced deposition of dust during the cold and dry glacial period and by decreased aeolian influx during the temperate and humid holocene

the bingham canyon porphyry cu mo au deposit iii zoned copper gold ore deposition by magmatic vapor expansion fluid inclusion microthermometry and laser ablation icpms microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry cu au mo ore deposit at bingham canyon utah the bingham canyon orebody is exposed over 1 6 km vertically and has the shape of an inverted cup with distinct metal zoning fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density 0 6 g cm 3 and a salinity of 7 wt percent nacl equiv they have subequal concentrations of na k fe and cu and contain minor co2 the intermediate density fluids were trapped as a single phase mostly at 500 c and 800 bars the au cu rich center near the top of the orebody contains low density vapor inclusions 0 2 g cm 3 coexisting with brine inclusions containing 45 wt percent nacl equiv the vertical transition of different inclusion types indicates phase separation of the single phase input fluid upon volume expansion associated with a pressure drop to 200 100 bars mass balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by 9 1 the vapor contained cu as its dominant cation 1 5 wt and contributed about 95 percent of the total amount of copper transported to the base of the orebody bornite chalcopyrite and native gold were precipitated in a narrow temperature interval from 430 to 350 c into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor dominated fluid system intermediate density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition including similar gold contents as those in the deep center microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral cu rich but au poor ore zone remained denser and the separating brine was less saline 36 wt nacl equiv compared to vapor and brine in the central au cu ore zone this indicates that the peripheral fluids experienced a lower degree of phase separation due to slightly higher fluid pressure at equivalent temperature compared to more strongly expanding fluids in the center of the system the systematic zoning of au cu within the ore shell despite compositionally similar input fluids is interpreted to have resulted from slightly different pressure temperature density evolution paths of magmatic fluids copper was selectively precipitated in the peripheral ore zone in contrast to complete coprecipitation of au and cu in the central upflow zone of the vapor plume the formation of particularly rich cu au ore in the center of the upward expanding fluid plume is consistent with published experimental data showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure due to destabilization of the hydration shell around metal complexes in expanding vapor this interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur bearing complexes as a key chemical control on magmatic hydrothermal metal transport and the deposition of cu and au in porphyry ores our interpretation of selective cu au precipitation as a function of vapor density can explain the more general observation that most gold rich porphyry copper deposits are formed in shallow sub volcanic environments whereas deeper seated porphyry cu mo deposits are generally gold poor

fluid fluid interactions in magmatic hydrothermal ore formation hydrothermal ore deposits have provided some of the first geological evidence for the interaction of multiple fluids in the earth s interior including fluid mixing as well as fluid phase separation physical evidence comes from veins and breccias documenting the impact of fluids in breaking rocks and creating fracture permeability for ore formation as a result of the fluid expansion that is commonly associated with phase separation between melts and multiple fluids chemical evidence of fluid fluid interaction includes the precipitation of minerals in veins as a result of fluid boiling or mixing between chemically contrasting fluids fluid inclusions record interactions of multiple fluids especially in magmatic hydrothermal ore deposits and associated igneous rocks fig 1 in recent years fluid inclusions have contributed to a more quantitative understanding of the role of fluid fluid interactions since new microanalytical techniques allow determination of element concentrations in all types of fluids from low density vapor through aqueous and hypersaline liquids to hydrous salt melts roedder 1984 samson et al 2003 figure 1 geological evidence for fluid phase separation in ore forming magmatic hydrothermal systems a bonanza grade gold 1 wt that was precipitated together with fine grained pyrite in a fluidized breccia resulting from instantaneous boiling and expansion of magmatic fluids ascending from an underlying andesite porphyry intrusion the breccia consists of adularia sericite altered clasts of sedimentary wall rock s and nodules of originally colloidal pyrite with bright specks of gold p g both cemented by roscoelite r vanadium rich muscovite and late calcite c zone vii ore body porgera papua new guinea ronacher et al 2004 b bladed manganocalcite the characteristic habit of calcite precipitated from aqueous epithermal fluids as a result of the ph change following loss of co2 to a separating vapor phase madan bulgaria kostova et al 2004 c growth band in a euhedral quartz

bathymetry of the levant basin interaction of salt tectonics and surficial mass movements abstract a new high resolution bathymetric map of the levant basin between israel and the eratosthenes seamount reveals previously undetected folds faults and channels the map facilitates a regional map view analysis of structures that were previously examined only in cross section the systematic mapping of morpho structural elements in the entire basin is followed by a kinematic interpretation that distinguished between two main processes sculpting the seabed from bottom and top salt tectonics and sediment transport we show that the contractional domain related to salt tectonics is far more complex than previously thought ridges previously interpreted as contractional folds are in fact surficial undulations of the seabed reminiscent of sediment waves moreover other folds previously interpreted as downdip contraction of the westward gliding plio quaternary section are in some parts of the basin caused by updip climbing of this section eastwards as a result of the regional pattern of salt flow away from the nile cone in the context of sediment transport we show that the northern sinai continental slope is covered by a dense net of turbidite channels whereas the levant slope has no channels at all particularly interesting is the levant turbidite channel described and named here for the first time this feature begins at the southeastern corner of the mediterranean at water depths of 1100 m continues along the valley between the sinai and levant slopes and reaches the deepest part of the basin in water depths of 2500 m northeast of the eratosthenes seamount however this prominent feature cannot be explained by the current drainage consisting of two minor rivers that enter the basin at that point and thus most likely reflects periods of wetter climate and or lower sea level when these rivers were more active and possibly connected to the submarine channel system

drifting and standing fields in the geomagnetic field for the past 400 years abstract based on the field model by jackson et al 2000 we reanalyzed the data of historical times and decomposed the geomagnetic field into drifting and standing fields it has been confirmed that the results are consistent with the earlier analyses when the field is expressed in a spherical harmonic series the drifting field is characterized by two remarkable features one is that the drifting field is represented mostly by sectorial harmonics and the other is that the drift velocity does not differ significantly between the harmonics the standing field that remains after subtraction of the drifting field from the main geomagnetic field is stronger than the drifting field the predominance of sectorial terms in the drifting field means that the vertical component for instance of the drifting field is symmetric about the equator on the other hand the standing field is antisymmetric due to this difference the drifting field largely controls the geomagnetic secular variation in the low latitude region whereas the standing field dominates in the middle and higher latitudes

multiproxy late quaternary stratigraphy of the nile deep sea turbidite system towards a chronology of deep sea terrigeneous systems abstract understanding the recent formation of a sedimentary system such as a deep sea turbidite system dsts requires an accurate stratigraphic control on deposits due to the important terrigeneous input which disrupts the sedimentary record dsts is an environment where stratigraphic control is difficult to assess most of the time traditional stratigraphic tools are not accurate enough this has led to a rather limited number of studies concerning stratigraphy in dsts in this study we examine several hemipelagic long piston cores collected from the nile dsts eastern mediterranean in order to understand the recent evolution of the complex sedimentary system in this area the first aim of this study is to show how to obtain a reliable timeframe in dsts indeed we provided a detailed ecostratigraphical scheme based on planktonic foraminiferal distribution oxygen isotope records and lithostratigraphy sapropels and tephra of three cores where the sedimentation is least disturbed we have identified 29 foraminiferal ecozones during the last 250 000 years bp with an approximately 2000 year time resolution the time span of each ecozone was constrained by the oxygen isotope record 14 c ams radiometric data tephrochronology and the sapropel chronology these high resolution ecostratigraphical time subdivisions have been applied in discontinuous mixed hemipelagic turbiditic sequences of a levee record this example shows how to date gravity events formation and time periods of sedimentary accumulations

micropaleontological and taphonomic characteristics of mass transport deposits in the northern gulf of eilat aqaba red sea abstract submarine mass transport deposits mtds are a well known phenomenon in tectonically active regions evidence for such deposits is commonly found in the continental slope sedimentary records as distinct units with coarser grain size compared to the usual and continuous pelagic sedimentation the gulf of eilat aqaba is located between the southernmost end of the dead sea transform and the spreading center of the red sea and is considered as an active tectonic region in this study an innovative approach using symbiont bearing larger benthic foraminifera lbf to identify mtds in the gulf of eilat aqaba gea sedimentary record is presented the abundance size and preservation state of lbf shells were analyzed in two radiocarbon dated sediment cores collected at different deposition environments at water depth of 532 m and 316 m the microfaunal and taphonomic results show that the coarse units are characterized by a generally higher numerical abundance of lbf dominated by operculina ammonoides amphistegina papillosa and amphistegina bicirculata these benthic assemblages are found in deeper depths than their original habitat ranging between 50 and 120 m in accordance with their symbionts light requirements in the coarse units lbf 1 mm appear in high frequency up to 161 specimens per g sediment and poorly preserved shells are also abundant containing up to 247 specimens per g sediment in addition these units also contain high numbers of yellowish and blackish colored lbf shells as opposed to null in the non disturbed units and unlike their natural white color the large shell size indicates that high energy is involved in the displacement of the sediments the poor state of preservation also suggests a turbulent flow during transportation which requires a high energy triggering mechanism the color alteration is probably associated with a diagenetic process related to increasing burial time depth also supported by the stratigraphic older ages of the mtds suggesting a long burial before the sediments were displaced in addition according to the dating of the record some units correlate with historical and pre historical earthquakes reinforcing lbf species as a reliable proxy for mass transport events

western mediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr abstract detailed study of associations of planktonic foraminifera in cores md95 2043 and odp 977 located in the alboran sea mediterranean sea has allowed the identification of 29 new faunal events defined by abrupt changes in the abundances of neogloboquadrina pachyderma right and left coiling turborotalita quinqueloba globorotalia scitula globorotalia inflata globigerina bulloides and globigerinoides ruber white and pink varieties the age model for odp 977 was based on that of md95 2043 cacho et al 1999 paleoceanogr 14 698 705 on the isotopic stratigraphy and on two ams 14c measurements sea surface temperatures ssts were estimated for the last 54 kyr using the modern analog technique mat and were compared with the ssts provided by the uk 37 method the uk 37 record is very similar to the mat annual mean temperature record for the last 8 kyr however for older times alkenone derived temperatures are consistently higher than the annual mat temperatures this offset may be due to an underestimation of the sst provided by the planktonic foraminiferal method for glacial times to an overestimation of the uk 37 record or to changes in the seasonal production of alkenones most of the variability in the fauna is related to the millennial variability of heinrich and dansgaard oeschger d o events during heinrich events hes and most of the other d o stadials g bulloides t quinqueloba and g scitula increased while n pachyderma right coiling g inflata and g ruber decreased by contrast n pachyderma left coiling was only abundant in the hes the main component of the associations n pachyderma right coiling follows a general trend similar to that of sea level and 18o this species reached its highest abundance during the last glacial maximum when sea level was at a lower position the occurrence of a shallower nutricline owing to a shallowing of the interface between atlantic inflowing and mediterranean outflowing waters could have favoured the development of neogloboquadrinids in the vicinity of the strait of gibraltar

thirteen thousand years of southeastern mediterranean climate variability inferred from an integrative planktic foraminiferal based approach over the past 13 ka the hydrology for the southeastern mediterranean was mainly regulated by nile river runoff which in turn was controlled by climate forcing being affected by orbital forcing and the position of the intertropical convergence zone itcz planktic foraminiferal data assemblages stable isotopes and size properties indicate three major periods 1 from 13 0 to 11 5 ka the upper water column was well mixed cold and productive 2 from 11 5 to 6 4 ka hydrology and foraminifers were affected by intensified monsoonal circulation the enhanced size of globigerinoides ruber is interpreted as a response to environmental stress caused by low saline waters 3 after 6 4 ka the southward retreat of the itcz caused a decrease in freshwater discharge and hence a return to ecological equilibrium a drop in foraminifer diversity from 2 9 to 1 1 ka was related to more arid conditions and limited supply of nutrients from the nile river we suggest a link to a negative north atlantic oscillation nao marking the roman humid period in the western mediterranean and in anti phase with the southeastern mediterranean aridity because nile river runoff exerted major control on surface hydrology a connection to indian and pacific climate systems partially controlling precipitation over the nile catchment area is hypothesized from 1 1 to 0 54 ka high foraminifer diversity indicates humid conditions synchronous to the medieval climate anomaly under a positive nao state over the past 0 54 ka encompassing the little ice age another arid period is indicated by a drop in foraminifer diversity

quartz solubility in the two phase region of the nacl h2o system an experimental study with application to the piccard hydrothermal field mid cayman rise

fluid fluid interactions in the earth s lithosphere fluids rich in water carbon and sulfur species and a variety of dissolved salts are a ubiquitous transport medium for heat and matter in the earth s interior fluid transport through the upper mantle and crust controls the origin of magmatism above subduction zones and results in natural risks of explosive volcanism fluids passing through rocks affect the chemical and heat budget of the global oceans and can be utilized as a source of geothermal energy on land fluid transport is a key to the formation and the practical utilization of natural resources from the origin of hydrothermal mineral deposits through the exploitation of gaseous and liquid hydrocarbons as sources of energy and essential raw materials to the subsurface storage of waste materials such as co2 different sources of fluids and variable paths of recycling volatile components from the hydrosphere and atmosphere through the solid interior of the earth lead to a broad range of fluid compositions from aqueous liquids and gases through water rich silicate or salt melts to carbon rich endmember compositions different rock regimes in the crust and mantle generate characteristic ranges of fluid composition which depending on pressure temperature and composition are miscible to greatly variable degrees for example aqueous liquids and vapors are increasingly miscible at elevated pressure and temperature the degree of this miscibility is however greatly influenced by the presence of additional carbonic or salt components a wide range of fluid fluid interactions results from this partial miscibility of crustal fluids vastly different chemical and physical properties of variably miscible fluids combined with fluid flow from one pressure temperature regime to another therefore have major consequences for the chemical and physical evolution of the crust and mantle several recent textbooks e g walther and wood 1986 carrol and holloway 1994 shmulovich et al 1995

the effect of the 2002 glacial flood on dissolved and suspended chemical fluxes in the skafta river iceland abstract this study describes the chemical composition of dissolved degased and suspended fluxes of the 2002 skafta glacial flood which emerged from one of the skafta subglacial lake due to geothermal activity beneath the icelandic vatnajokull glacier the dissolved and suspended fluxes during the flood are compared with those normally observed in the skafta river to determine the effect of such floods on the annual fluxes of material delivered to the coastal waters concentrations of most dissolved elements during the flood were significantly higher than those normally observed in the skafta river in addition dissolved concentrations of nutrients such as sio 2 fe and v increased more than an order of magnitude during the flood these will affect biological processes on a local scale the 34 s composition in the flood water suggests that the dissolved so 4 was derived from the oxidation of h 2 s and the geothermal fluid the total suspended particulate load measured in the skafta river during the 8 day 2002 flood was approximately half of the non flood total annual skafta suspended load as particles carry the bulk of limiting nutrients to the oceans this demonstrates the importance of glacial floods for primary production of coastal waters the composition of the flood water and the skafta subglacial lake together with reaction path modelling suggest that substantial degasing of co 2 and h 2 s occurred at the glacial outlet during the flood this degasing may have released as much as 262 000 and 7 980 tonnes of co 2 and h 2 s respectively to the atmosphere having a considerable impact on the local carbon and sulphur cycles during the flood event

formation of saline brines and salt in the lower crust by hydration reactions in partially retrogressed granulites from the lofoten islands norway anorthosites gneisses and mangeritic rocks from the lofoten islands in northern norway contain cl rich amphibole up to 3 5 wt percent cl and biotite up to 1 5 wt percent cl that developed mostly during regional metamorphism at 600 c and 9 kb by replacement of older anhydrous granulite facies mineral assemblages na k cl halide solid solutions are closely associated spatially with amphiboles that have the highest measured cl contents rocks with cl rich amphiboles and biotites always have minerals that exhibit a wide range in oh cl one sample from a shear zone contains virtually cl free amphibole within a few millimeters of cl rich amphibole coexisting with halide crystals textural evidence indicates that amphibole and biotite evolved from cl poor to cl rich compositions within individual samples oh rich cl poor compositions are always much more abundant than cl rich ones cl rich amphiboles and biotites exclusively occur in rocks that contain relict granulite facies minerals pyroxene and or olivine samples in which no granulite facies minerals remain contain amphiboles and biotites without elevated cl contents in one particular case the restricted development of clrich amphiboles and biotites within a shear zone and the absence of these minerals from undeformed lithologic equivalents outside the shear zone demomstrate that the amphibole and biotite developed by reaction between a preexisting granulite facies mineral assemblage and an aqueous fluid rather than by fluid ansent metamorphism or by magmatic processes we infer from this example that cl rich amphibole nad biotite with the same grani size and texture as in the shear zone developed throughout the lofoten islands by fluid rock reaction mineralfluid equilibria indicate that the aqueous fluid was variable in composition ranging from xh2o h2o h2o cl of 0 99 for equilibrium with the most cl poor amphiboles and biotites to 0 4 0 6 for equilibrium with the most cl rich minerals that coexist with salt the most saline fluids correspond to nacl equivalent concentrations of over 25 mol l the range in oh cl of amphiboles and biotite in individual samples and the restricted occurrence of cl rich minerals in rocks with relict pyroxene and or olivine can be explained by a desiccation model in which small amounts of normal low cl crustal fluid infiltrates rocks with granulite facies minerals and is subsequently enriched in cl by preferential consumption of h2o during the resulting hydration reaction saline fluids developed at the extremes of reaction progress and then produced the cl rich amphibole and biotite compositions coexisting with halide crystals the desiccation model further explains variations in the whole rock concentration of cl in rocks from the lofoten islands the absence of cl rich minerals from completely retrogressed granulites that lack olivine or pyroxene the measured frequency distribution of amphibole and biotite compositions in individual samples and the calculated evolution of fluid composition with reaction progress our results have implications for interpreting measurements of elevated electrical conductivity in the lower crust and for models of granulite genesis that appeal to fluids with low h2o activity amer j science 1998 298 705 757

geomagnetic long term secular variations in italian lower cretaceous shallow water carbonates summary the remanent magnetic properties of an 88 m bore core are unrelated to either the dolomite content or the sedimentological textures and are considered to be carried primarily by biogenetic magnetite that was cemented in during very early diagenesis individual readings represent time intervals of c 720 32 yr and after 40 mt partial demagnetization they provide an almost continuous record of averaged geomagnetic secular variations over a period of some 3 17 myr the magnitude of directional secular variation is twice that of the present day despite being smoothed and the secular variations appear to grade into polarity transitions suggesting no diverence in their mechanisms the rates of change in direction between subjacent levels in the core have a log normal distribution which extends smoothly beyond 90 and has a median value of 13 700 yr the same as for unsmoothed european secular variation during the last 2000 yr the intensity of remanence after 40 mt partial demagnetization appears to provide a reasonable approximation to geomagnetic field intensity this tends to be weaker when the direction is moving faster reflecting averaging but is unrelated to the distance of the vector from the mean direction that is it depends on the rate of change and not on the virtual pole latitude the virtual poles after correction for tectonic rotations about horizontal and vertical axes have latitudes that form a strongly platykurtic fisherian distribution while their longitudes have a circular distribution on which are superimposed two gaussian peaks 180 apart this bore core thus provides detailed information of smoothed geomagnetic secular variation in the lower cretaceous 127 3 ma which shows clear regularities in behaviour some related to changes in the earth s orbital parameters

experimental studies in model fluid systems numerous observations provide strong evidence that fluid fluid coexistence is a widespread phenomenon in many geological processes i oceanic hydrothermal fluids display a wide range in salinity which clearly indicates fluid phase separation of the circulating seawater see foustoukos and seyfried 2007a ii selective enrichment of certain elements and coeval entrapped inclusions of different co existing fluids highlight the role immiscible fluids play in ore formation see heinrich 2007a iii trace element and stable isotope characteristic as well as equilibrium mineral assemblages in contact aureoles prove immiscible fluids to be a ubiquitous feature in most contact metamorphism see heinrich 2007b iv small scale fluid heterogeneity in eclogitic rocks indicate fluid immiscibility to occur in metamorphic rocks up to high or even ultra high pressure see heinrich 2007b unfortunately fluids are principally non quenchable phases and direct quantitative information on fluid properties at p and t is in most cases not available experimental studies are thus central in studying geologic fluids in general and co existing fluids in particular they are still the primary source of quantitative information on physicochemical properties of co existing crustal fluids they allow e g determine i fluid phase relations as function of p t and x ii physical fluid properties like density and viscosity and iii trace element and isotope fractionation between co existing fluids but also between co existing fluids and solids the experimental data can then be used as input in forward modeling approaches the results and or predictions of which may then be tested in natural systems see driesner and geiger 2007 experimental data on co existing fluids in systems of geological relevance already date back to the flrst half of last century e g keevil 1942 since the 1960ies numerous systematic experimental studies on fluid fluid phase relations at crustal p and t conditions were performed e g sourirajan and kennedy

late quaternary central mediterranean biochronology jorissen f j asioli a borsetti a m capotondi l de visser j p hilgen f j rohling e j van der borg k vergnaud grazzini c and zachariasse w j 1993 late quaternary central mediterranean biochronology mar micropaleontol 21 169 189 a high resolution biochronology is presented for the late quaternary of the central mediterranean in the late pleistocene holocene successions three assemblage zones are distinguished on the basis of frequency patterns of planktic foraminifera the age of these zones is determined by accelerator mass spectrometry ams t4c dating the zonal boundaries are dated at 12 700 yr b p the end of termination la and 9600 yr b p the start of termination ib respectively the ams dates show that major changes in the planktic and benthic realms occurred synchronously over wide areas although records of individual species may show important regional differences in the studied areas resedimentation processes revealed by anomalous successions of 14c dates play a far more important role than indicated by the sedimentological and micropaleontological data possibly these processes contribute to the very high accumulation rates in the glacial zone ill although the ams technique has increased the accuracy of lac measurements of older carbonate may still lead to substantial age differences between areas with different sedimentary regimes

the critical point and two phase boundary of seawater 200 500 c abstract the two phase boundary of seawater was determined by isothermal decompression of fully condensed seawater in the range of 200 500 c the pressure at which phase separation occurred for each isotherm was determined by a comparison of the refractive index of fluid removed from the top and bottom of the reaction vessel the critical point was determined to be in the range of 403 406 c 285 302 bar and was located by the inflection in the two phase boundary and by the relative volume of fluid and vapor as a function of temperature the two phase boundary of 3 2 nacl solution was found to coincide exactly with that of seawater over the range tested in the present study the boundary for both is described by a single seventh order polynomial equation the two phase boundary defines the maximum temperature of seawater circulating at depth in the oceanic crust thus the boundary puts a limit of about 390 c for seawater circulating near the seafloor at active ocean ridges 2 5 km water depth and about 465 c at the top of a magma chamber occurring at 2 km below the seafloor

benthic foraminiferal successions across late quaternary mediterranean sapropels abstract benthic foraminiferal records across late quaternary mediterranean sapropels s6 s5 and s1 are reviewed and re considered in the light of recent advances in foraminiferal ecology it is suggested that the main factor controlling the foraminiferal successions that occur immediately before and after sapropel deposition is the amount of time involved in the onset of anoxic conditions and in the re oxygenation of the benthic environment faunas dominated by deep infaunal taxa such as globobulimina and chilostomella reflect a very gradual decrease or increase of bottom water oxygenation post sapropel faunas dominated by small biconvex trochospiral taxa which are inferred to have a much more opportunistic life strategy are typical of a very rapid re oxygenation of the benthic environment after sapropel deposition the time involved in re oxygenation depends upon the mechanism causing sapropel formation the faunal succession found above sapropel s5 suggests a basin with a strong density gradient in the upper part of the water column during sapropel deposition followed by a rapid turnover of the following column and quick re oxygenation of the benthic environment in contrast the faunal succession above sapropel s6 suggests a water column with a more gradual density gradient deeper in the basin a progressive deepening of the halocline and a very slow increase of bottom water oxygenation

climatic variability during the last 90 ka of the southern and northern levantine basin as evident from marine records and speleothems abstract the influence of the northern atlantic and tropical monsoonal systems as recorded by the river nile on the climate variability of the southeastern mediterranean was studied in two cores taken by the r v marion dufresne one core taken se of cyprus representing the northern levantine basin core 9501 980 m water depth and the other located 380 km further south represents the southeastern levantine basin in an area influenced by the river nile plume core 9509 884 m water depth the study was performed at relatively high resolution using several proxies 18o of globigerinoides ruber sediment characteristics and index colour parameters in core sections representing the last 86 ka a low resolution alkenone sea surface temperature record was also measured the time frame in both cores was mostly constrained by wiggle matching with the nearby well dated 18o and 13c record of the soreq cave which is mainly influenced by the eastern mediterranean water vapor the sedimentary record of the southern core is strongly influenced by the river nile contribution throughout the last 86 ka as evidenced by the higher sedimentation rates compared with the northern core 20 cm ka vs 5 cm ka continuously darker sediment colour and higher toc values 0 6 0 9 vs 0 25 wt not including sapropels during sapropels s1 and s3 present in both cores the influence of the river nile became more widespread reaching as far as cyprus yet the influence of the river nile remained stronger in the south as evident by the higher toc values in the southern core throughout the entire 90 ka period and the longer duration of s1 in the southern core an anomalous low 18o interval that is not recorded in western mediterranean occurred between 58 and 49 ka in the levantine basin and is more developed in the northern core this period correlates with d o interstadial 14 and maximum northern hemisphere insolation during the lastglacial cycle suggesting that the warming mainly impacted the northern levant the eastern mediterranean sea and land area was considerably warmer than the western mediterranean throughout the lgm holocene transition and the 18og ruber drop of 4 5 is significantly greater than the 3 shift found for the western mediterranean 18og bulloides both differences reflecting an increased continental effect from the western to eastern mediterranean comparison between the marine and the land 18o records suggests that the origin of rain over the land is composed of mixed signal from the southern and northern levantine basin the study of 18osea land variations demonstrates that various factors have influenced the sea land relationship during the last 90 ka the amount effect has an important influence on rainfall 18o during interglacial periods particularly sapropel periods whereas during glacial periods increased land distances and elevation differences arising from decrease in sea level may have brought about decrease in 18o of rainfall due to rayleigh distillation processes these influences were superimposed on those of sea surface water 18o changes brought about by continental ice melting and the strong effects felt in the southern levantine basin of the high river nile input during periods of enhanced monsoonal activity

deep sea ecosystem variability of the aegean sea during the past 22 kyr as revealed by benthic foraminifera abstract specific responses of the regional deep sea ecosystems to climatic and oceanographic processes during the last 22 kyr are revealed by benthic foraminiferal faunas from two cores in the northern and southern aegean sea under glacial boundary conditions high diversity benthic foraminiferal faunas and elevated benthic foraminiferal numbers indicate enhanced organic matter availability and well ventilated deep water masses in the whole aegean sea the glacial termination is accompanied by significant fluctuations in productivity and deep water ventilation in the northern aegean sea meltwater inflow from mountain glaciers during the bolling allerod warm period resulted in a restriction of local deep water formation as mirrored by a dominance of bolivinids during the deposition of sapropel s1 drops in benthic foraminiferal number and diversity are more significant in the southern aegean sea when compared to the north this suggests the persistence of local deep water formation in the northern aegean sea during s1 deposition in addition faunal fluctuations within s1 at both sites suggest the repeated influence of short term cooling events on the re ventilation and re colonization of aegean deep sea ecosystems during the middle and late holocene benthic foraminiferal faunas document the establishment of oligotrophic and well ventilated conditions in the southern aegean sea the corresponding faunas from the northern aegean sea reflect generally mesotrophic conditions and variable deep water oxygenation during the entire holocene the deep sea ecosystems of this region responded very sensitively to short term changes in humidity and temperature these abrupt climate changes controlled the inflow of nutrients from rivers and the black sea and the formation of local deep water masses

on the timing and nature of the multiple phases of slope instability on eastern rockall bank northeast atlantic one of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments in this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the rockall bank slide complex offshore western ireland is the composite of multiple slope collapse events and if so to differentiate them we conclude that there have been at least three voluminous episodes of slope collapse separated by long periods of slope stability a fourth less voluminous event and possibly a fifth more localized event the oldest event slide a 200 km3 is estimated to be several hundred thousand years old the second event slide b 125 km3 took place at the same location as slide a reactivating the same scar nearly 200 ka ago possibly through retrogression of the scarp slide c 400 km3 took place 22 ka ago and occurred further north from the other slides slide d was a much smaller event that happened 10 ka ago while the most recent event albeit very small scale took place within the last 1 000 years this study highlights the need to thoroughly investigate large slide complexes to evaluate event sequencing as seismic studies may hide multiple small scale events this work also reveals that the same slide scarps can be reactivated and generate slides with different flow behaviors

sedimentary structures and sediment transport across the continental slope of israel from piston core studies the continental terrace of israel consists of nile derived sediments they are classified into three major groups according to their structures 1 irregularly to wavy laminated coarse grained sediments quartz and skeletal debris of the flat outer shelf and upper bend of the slope 10 20 of the bulk which are influenced by currents these sediments are bioturbated to various degrees smectitic silty clays 80 90 form two structural groups 2 laminated turbiditic sediments which accumulate on the slope particularly in the canyons of the northern slope irregular wavy thickly laminated coarse grained sediments of the upper slope and canyon heads merge downslope with parallel thinly laminated fine grained sediments toward the foot of the slope and on the adjacent deep sea floor lamination becomes indistinct and the sediment is visually homogeneous 3 slump generated mud lumps of various size which accumulate on the lower slope and along the transport axes of the canyons these are the most visible evidence for large scale slumping mass movement transportational and depositional processes are far more intensive over the steep northern continental slope of israel and especially in its canyons than over the gentle southern slope very stiff overconsolidated sediments unconformably overlain by the ubiquitous recent silty clayey sediment were cored on steep sections of the middle continental slope and along the canyon walls their preconsolidation stress values suggest that these sections were formerly overlain by more than 40 m of sediment and now are exposed by slumping the downsliding slabs usually disintegrated into small fragments although several huge fragments could be identified along the canyon axes

large scale submarine rotational slumps and growth faults in the eastern mediterranean submarine slumps with areas of 1000 km2 and more disturb the continental margin of israel and nearby areas in them the plio quaternary silty clayey sediments up to 1 5 2 km thick are broken by shore parallel growth faults into 5 10 blocks which are generally rotated and tilted landward the faults flatten downward and become rooted in ridges formed by deformation of the underlying mobile messinian evaporite bearing series deformation is thin skinned and does not visibly extend to deeper levels slumping occurred only where a sufficiently thick overburden accumulated over a sufficiently well developed mobile substrate then gravitational instability developed and led to basinward sliding of the continental margin sediments over the messinian series which acted as a lubricant and a level of decollement the mobility of this series is probably caused by overpressured shale beds that are confined between the impervious evaporites this mechanism explains all the features of the slumps hitherto faults directly related to the slumps of the eastern mediterranean were not identified but since the region is tectonically active it is not possible to exclude the possibility that basinward sliding was triggered either by motion of minor underlying faults or by seismic shaking however it seems that even if this were the case slumping could be triggered only because the continental margin was anyhow gravitationally unstable or close to such a state therefore the gravitational instability was the main factor that controlled the deformation of the pliocene quaternary sediments the slumps of the eastern mediterranean resemble large scale slumps that are known from other passive continental margins in the world

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

did the a d 365 crete earthquake tsunami trigger synchronous giant turbidity currents in the mediterranean sea in the ionian sea one of the most seismically active regions in the mediterranean subduction is commonly associated with uplift of coastal mountains enhanced erosion and seismic activity along the calabrian arc and hellenic arc thus potentially resulting in repetitive mass failures some of the turbidites observed in the deep basins are thick and prominent on seismic records because of the acoustic transparency of their upper structureless mud layer our high resolution study of the most recent of these megabeds the homogenite augias turbidite hat provides key proxies to identify pelagic sediments deposited following the catastrophic causative event radiometric dating in an area 150 000 km2 indicates that the different mediterranean so called homogenite deposits are in fact synchronous and were deposited during a single basin wide event within the time window a d 364 415 unlike interpretations that relate this turbidite to different triggering events including the santorini caldera collapse the turbidite can be traced back to a large tsunami sourced from the a d 365 crete megathrust earthquake correlation of the single event hat over a wide area of the mediterranean from the northern ionian sea to the mediterranean ridge and the anoxic tyro basin south of crete suggests that the a d 365 crete earthquake and tsunami must have produced devastating effects including widespread massive sediment remobilization in the eastern mediterranean sea

fluid immiscibility in metamorphic rocks evidence of fluid immiscibility in metamorphic rocks comes in the best of all worlds from fluid inclusion observations in fact fluid immiscibility should be anticipated over the full range of metamorphic conditions provided that appropriate bulk fluid compositions are present in a review paper entitled metamorphic fluids the evidence from fluid inclusions crawford and hollister 1986 summarized the role of fluid immiscibility in metamorphism was only recognized after serious study of fluid inclusions in metamorphic rocks was underway in the late 1970s and has yet to attract the attention of more than a handful of petrologists studying metamorphic rocks since then tremendous progress has been made a huge amount of fluid inclusion studies have convincingly shown that immiscible fluids can be present in rocks of all bulk compositions and at all p t conditions thermodynamic databases of minerals solid solutions and fluid mixtures along with the development of gibbs free energy minimization programs now allow for detailed prediction of the evolution of phase assemblages and mineral compositions in p t space significant progress has also been made in understanding reaction kinetics diffusional and convective mass transport and the interpretation of fluid rock interaction during metamorphism given the vast fluid inclusion evidence of immiscibility it would appear however that phase petrology and mass transport in any specific rock where fluids are involved are not correctly interpreted if possible or proven immiscibility is not considered relatively few studies directly link mineral reactions with immiscible fluids therefore this review aims at working out the effects of fluid immiscibility on the progress of metamorphic reactions and fluid transport over a wide range of conditions questions arise directly from the fluid inclusion record in metamorphic rocks this chapter however is organized the other way round at first it summarizes phase relations of fluid systems pertinent to

supercritical fluids at subduction zones evidence formation condition and physicochemical properties abstract there is a general consensus that at subduction zones mass transfer from the subducted slab to the overlying mantle wedge is mediated by a hydrous mobile phase however it is under intense debate whether this phase is an aqueous fluid hydrous silicate melt or supercritical fluid with intermediate composition h 2 o concentration in the range of 30 wt 70 wt supercritical fluids with fluid like viscosity and melt like wetting and element carrying capability are an ideal agent for chemical transport at subduction zones after clarifying the phase relations of silicate h 2 o systems and the definition of supercritical fluids this contribution reviews existing evidence for the presence of supercritical fluids at subduction zones mostly from experimental investigation of phase relations of mineral h 2 o and rock h 2 o systems and the atomic structure and physicochemical properties of supercritical fluids h 2 o rich multi phase solid inclusions from continental subduction zones once their bulk water contents can be confirmed may provide a direct record of supercritical fluids experimental results generally indicate that supercritical fluids can derive from the slab at 160 km depth but there is still significant discrepancy between different studies on h 2 o saturated solidus fluid melt critical curve and the second critical end point scep some novel experimental methods are proposed to resolve the controversies over the formation condition of supercritical fluids the special physicochemical properties of supercritical fluids arise fundamentally from their intermediate composition and intermediate degree of polymerization that are distinctive from aqueous fluids or silicate melts probing the structure and properties of supercritical fluids which are required for understanding of their petrological and chemical behavior and geophysical characteristics relies mainly on in situ spectroscopy but first principles molecular dynamics is becoming a potentially powerful alternative approach

comparison of living and dead benthic foraminifera on the portuguese margin understanding the taphonomical processes abstract dead benthic foraminifera 150 m were studied in 23 sediment cores from the portuguese margin at water depths between 20 and 2000 m and located on 4 transects off the douro mondego tagus and sado river mouths and 1 transect in the estremadura for 10 stations the dead faunal vertical distribution 0 8 cm was first investigated in 4 different sediment horizons per core to evaluate the sampling effort necessary to have a representation of the dead fauna deposited under different environmental areas as a result it appears that the faunal vertical distribution is constant except for the deepest environments where fragile taxa were identified in the top layers only dead foraminiferal assemblages in the 4 5 cm layer for all stations were then compared to previously published living foraminiferal assemblages of march 2011 from the same cores to evaluate the taphonomical processes affecting major species this improves the knowledge of the faunal distribution for a better benthic foraminiferal proxy for paleostudies there was a considerable loss of some species in the dead fauna firstly this concerns the fragile organic cemented agglutinated taxa such as reophax spp glomospira charoides or bathysiphon spp secondly some calcitic species such as nonion scaphum cancris auriculus ammonia beccarii or bulimina aculeata that were particularly abundant in the living fauna on the inner shelf under the late winter high river discharge conditions were also far less dominant in the dead fauna lastly other species like cassidulina carinata valvulineria bradyana and bulimina marginata systematically showed higher abundance in the dead fauna at the mid shelf these species related to eutrophic conditions occurring in summer during the upwelling activity were therefore not well represented in the living fauna collected in march transport of allochthonous specimens may also account for higher contribution in the dead community of some species like cibicides lobatulus asterigerinata mamilla or haynesina depressula especially in coastal environments where hydrodynamic processes river flood winter storm coastal drift are more vigorous several species u mediterranea u bifurcata t agglutinans h balthica or b costata however show little or no difference in both abundance and spatial occurrence between the living and dead faunas and provide a stable signal for paleoclimatic investigations

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

size distribution of submarine landslides and its implication to tsunami hazard in puerto rico 1 we have established for the first time a size frequency distribution for carbonate submarine slope failures using detailed bathymetry along the northern edge of the carbonate platform north of puerto rico we show that the cumulative distribution of slope failure volumes follows a power law distribution the power law exponent of this distribution is similar to those for rock falls on land commensurate with their interpreted failure mode the carbonate volume distribution and its associated volume area relationship are significantly different from those for clay rich debris lobes in the storegga slide norway coupling this relationship with tsunami simulations allows an estimate of the maximum tsunami runup and the maximum number of potentially damaging tsunamis from landslides to the north shore of puerto rico

late quaternary nile flows as recorded in the levantine basin the palynological evidence abstract this study aims to trace changes in the river nile flows over the late quaternary and is based on palynomorphs which were embedded in the sea floor of the levantine basin the palynomorphs were extracted from two marine sediment cores which cover the last 86 ka and are located at the two ends of the levantine basin md 9509 at the southern part of the levantine basin and md 9501 at its northern part core md 9509 was taken from the nile cone and is characterized by high sedimentation rates and a good state of palynomorph preservation the assemblages included palynomorphs which were transported via the nile headwaters and therefore enabled the reconstruction of the river nile flows the results demonstrate that the last glacial period 75 16 ka was characterized by a decrease in nile water discharge and an increase in sediment influx while opposite trends were observed prior to the last glacial period as well as during the deglaciation and the holocene based on the study of the spores it is suggested that during the last glacial the main contributors of freshwater and sediment load to the eastern mediterranean sea were the blue nile and the atbara and only during interglacials was there a more significant contribution of the white nile within the northern core md 9501 pollen was preserved only during the formation of sapropels s3 and s1 the comparison of the sapropelic palynological spectra in both core sites clearly indicates that during sapropel deposition climate conditions were more humid in the northern levant reflecting the north south regional mediterranean climatic moisture gradient sapropel formation was a result of the intensification of the monsoonal climate system which was most probably related to the maximum insolation values at 65 n while currently the atlantic is the main influencing climate system in the region one of the most interesting observations in this study is that during heinrich events h2 h6 which originated in the north atlantic and were identified in md 9509 based on minimum arboreal pollen percentages pollen originating from tropical regions was not embedded in the levantine basin these results lend support to the view that episodes of dryness in tropical sub tropical eastern africa were associated not only with low latitude climate controls but also with high latitude glacial stress

climatic forcing of eastern mediterranean deep water formation and benthic ecosystems during the past 22 000 years abstract lateglacial and holocene faunal and stable isotope records from benthic foraminifers in the eastern mediterranean sea ems suggest a high spatiotemporal variability of deep water oxygenation and biogeochemical processes at the sea floor during that time changes in the oxygenation and food availability of the deep sea ecosystems are closely linked to the hydrology of the ems borderlands they reflect orbital and suborbital climate variations of the high northern latitudes and the african monsoon system during the last glacial maximum cool surface waters and high evaporation resulted in maximum convection and oxic deep waters in all sub basins strong wind induced mixing fostered surface water production with seasonal phytodetritus fluxes during the glacial termination and the holocene oxygenation and food availability of deep sea benthic ecosystems were characterized by a pronounced regional differentiation local deep water formation and trophic conditions were particularly variable in the northern aegean sea as a response to changes in riverine runoff and black sea outflow during the interval of sapropel s1 formation in the early holocene average oxygen levels decreased exponentially with increasing water depth suggesting a basin wide shallowing of vertical convection superimposed by local signals in the northernmost aegean sea deep water ventilation persisted during the early period of s1 formation owing to temperature driven local convection and the absence of low salinity black sea outflow at the same time severe temporary anoxia occurred in the eastern levantine basin at water depths as shallow as 900 m this area was likely influenced by enhanced nutrient input of the nile river that resulted in high organic matter fluxes and related high oxygen consumption rates in the water column in the southern aegean and levantine seas we observe a gradual increase in deep water residence times preceding s1 formation by approximately 1 1 5 kyr once oxygen levels fell below a critical threshold the benthic ecosystems collapsed almost synchronously with the onset of s1 deposition the recovery of benthic ecosystems during the terminal phase of s1 formation is controlled by subsequently deeper convection and re ventilation over a period of approximately 1500 years after the re ventilation of the various sub basins had been completed during the middle and late holocene deep water renewal was more or less similar to recent rates during that time deep sea ecosystem variability was driven by short term changes in food quantity and quality as well as in seasonality all of which are linked to millennial scale changes in riverine runoff and associated nutrient input

linked turbidite debrite resulting from recent sahara slide headwall reactivation the northwest african margin has been affected by numerous large scale landslides during the late quaternary this study focuses on a recent collapse of the sahara slide headwall and characterises the resulting flow deposit core and seismic data from the base of the upper headwall reveal the presence of blocky slide debris comprising heavily deformed hemipelagic slope sediments the blocky slide debris spilled over a lower headwall 60 km downslope and formed a thick transparent debris flow unit cores recovered 200 250 km farther downslope contain a surficial turbidite that is interpreted to be linked to the headwall collapse event based on timing and composition one core located approximately 200 km from the headwall scar c13 contains debrite encased in turbidite the debrite comprises sheared and contorted hemipelagic mudstone clasts similar as those seen in the vicinity of the sahara slide headwall and lacks matrix this debrite pinches out laterally within 25 km of c13 whereas the accompanying turbidite can be correlated across 700 km of the northwest african margin the linked turbidite debrite bed is interpreted to have formed through recent failure of the steep sahara slide headwall that either 1 generated both a debris flow and a turbidity current almost simultaneously or 2 generated a debris flow which with entrainment of water and progressive dilution led to formation of an accompanying turbidity current

submarine landslide as the source for the october 11 1918 mona passage tsunami observations and modeling this paper is not subject to u s copyright the definitive version was published in marine geology 254 2008 35 46 doi 10 1016 j margeo 2008 05 001