varves of the dead sea sedimentary record abstract the sedimentary record of the dead sea provides an exceptional high resolution archive of past climate changes in the drought sensitive eastern mediterranean levant a key region for the development of humankind at the boundary of global climate belts moreover it is the only deep hypersaline lake known to have deposited long sequences of finely laminated annually deposited sediments i e varves of varied compositions including aragonite gypsum halite and clastic sediments vast efforts have been made over the years to decipher the environmental information stored in these evaporitic clastic sequences spanning from the pleistocene lake amora to the holocene dead sea a general characterisation of sediment facies has been derived from exposed sediment sections as well as from shallow and deep water sediment cores during high lake stands and episodes of positive water budget mostly during glacial times alternating aragonite and detritus laminae aad facies were accumulated whereas during low lake stands and droughts prevailing during interglacials laminated detritus ld facies and laminated halite lh facies dominate the sequence in this paper we i review the three types of laminated sediments of the dead sea sedimentary record aad ld and lh facies ii discuss their modes of formation deposition and accumulation and their interpretation as varves and iii illustrate how dead sea varves are utilized for palaeoclimate reconstructions and for establishing floating chronologies

cierco pb zn ag vein deposits isotopic and fluid inclusion evidence for formation during the mesozoic extension in the pyrenees of spain the cierco pb zn ag vein deposits located in the central pyrenees of spain crosscut paleozoic metasedimentary rocks and are in close proximity to hercynian granodiorite dikes and plutons galena and sphalerite in the deposits have average delta 34 s values of 4 3 and 0 8 per mil cdt respectively coexisting mineral pairs give an isotopic equilibration temperature range of 89 degrees to 163 degrees c which overlaps with the 112 degrees to 198 degrees c range obtained from primary fluid inclusions coexisting quartz has a delta 18 o value of 19 or 1 per mil vsmow the fluid which deposited these minerals is inferred to have had delta 18 o sub h 2 o and delta 34 s sub h 2 s values of 5 or 1 and 1 or 1 per mil respectively chemical and microthermometric analyses of fluid inclusions in quartz and sphalerite indicate salinities of 3 to 29 wt percent nacl equiv with na super and ca super 2 as the dominant cations in solution the br cl and i cl ratios differ from those characteristic of magmatic waters and pristine seawater but show some similarity to those observed in deep ground waters in crystalline terranes basinal brines and evaporated seawater barite which postdates the sulfides spans isotopic ranges of 13 to 21 per mil 10 to 15 per mil and 0 7109 to 0 7123 for delta 34 s delta 18 o and 87 sr 86 sr respectively the three parameters are correlated providing strong evidence that the barites are products of fluid mixing we propose that the cierco deposits formed along an extensional fault system at the margin of a marine basin during the breakup of pangea at some time between the early triassic and early cretaceous sulfide deposition corresponded to an upwelling of hydrothermal fluid from the paleozoic basement and was limited by the amount of metals carried by the fluid barite deposition corresponded to the waning of upward flow and the collapse of sulfate rich surface waters onto the retreating hydrothermal plume calcite precipitated late in the paragenesis as meteoric or marine waters descended into the fault system possibly during a regression in the overlying basin there are other deposits resembling cierco elsewhere in the iberian peninsula taken as a group they are evidence that hydrothermal circulation systems were widespread during mesozoic extension differences among the deposits can be related to the fact that h 2 s and other solutes had local and variable sources

diagenesis and formation water chemistry of triassic reservoir sandstones from southern tunisia the fluvial triassic reservoir subarkoses and arkoses 2409 5 2519 45 m of the el borma oilfield southern tunisia were subjected to cementation by haematite anatase infiltrated clays kaolinite and k feldspar at shallow burial depths from meteoric waters subsequently basinal brines controlled the diagenetic evolution of the sandstones and resulted initially in the precipitation of quartz overgrowths magnesian siderite minor ferroan magnesite and anhydrite the enrichment of siderite in 12c isotope 13cpdb 14 5 to 9 results from derivation of carbon from the thermal decarboxylation of organic matter during further burial the precipitation of dickite and pervasive transformation of kaolinite into dickite occurred followed by the formation of microcrystalline k feldspar and quartz chlorite and illite prior to the emplacement of oil present day formation waters are na ca cl brines evolved by the evaporation of seawater and water mineral interaction and are in equilibrium with the deep burial 3 1 km minerals these waters are suggested to be derived from the underlying silurian and devonian dolomitic mudstones

sedimentary structures tentatively attributed to seismic events abstract fingerprints of earthquakes in the sedimentary record are as yet difficult to identify this is particularly true for failure phenomena dewatering slumping fault graded and turbidite structures that could have been triggered also by other kinds of energy input other promising candidates are strange biostratinomic features convex down stacking of shells current orientation in wave ripple accumulations as well as certain preservational features found in geosynclinal pelagic limestones but in every case verification of the seismic origin is still needed

the behavior of lithium and its isotopes in oilfield brines evidence from the heletz kokhav field israel twenty four brine samples from the heletz kokhav oilfield israel have been analyzed for chemical composition and li isotope ratios the chemical composition of the brines together with geological evidence suggests derivation from messinian seawater by evaporation that proceeded well into the gypsum stability field but failed to reach the stage of halite crystallization the present salinity of the samples 18 47 g cl l was achieved by dilution of the original evaporitic brine by local fresh waters like brines from other sedimentary basins the li cl ratios in the heletz kokhav samples show a prominent li enrichment five fold to eight fold relative to modern seawater the isotopic ratios of li expressed in the 6 li notation vary from 26 3 to 17 9 all values being significantly higher than that of modern seawater 32 irrespective of their corresponding li concentration 1 0 2 3 mg l the isotopic composition of li and the li cl ratio in the oilfield brines were acquired in two stages a the original evaporated seawater gained isotopically light li during the diagenetic interaction between the interstitial messinian brine and the basin sediments a parent brine with an elevated li cl ratio was formed the brine was later diluted in the oilfields b the 6 li values of the final brines were determined during epigenetic interaction with the heletz kokhav aquifer rocks at the same time the li cl ratio inherited from stage a remained largely unchanged this work represents the first use of lithium isotopic composition to elucidate the origin and evolution of formation waters in sedimentary basins copyright 2002 elsevier science ltd

high resolution stratigraphy reveals repeated earthquake faulting in the masada fault zone dead sea transform abstract a detailed study of the syndepositional masada fault zone mfz provides an example for fundamental characteristics of earthquakes such as long term temporal clustering repeated faulting on the same planes for a limited time of the order of a few thousands of years and the formation of subaqueous breccia layers interpreted as seismites the mfz was studied in outcrops of 70 15 ka lake lisan sediments detailed columnar sections on both sides of well exposed faults show that each individual fault exhibits a cluster up to 4 ky long with 3 5 slip events on the same plane each slip event is associated with the formation of widespread layers exhibiting soft sediment deformation which are interpreted to be seismite layers the uppermost part of the lisan section about 5 m is not faulted hence the last cluster of slip events ended about 25 ky ago the clusters of activity of individual faults coalesce to form larger clusters these are evident in the distribution of seismite layers throughout the entire lisan section which shows earthquake clustering during periods of 10 ky the clusters are separated by relatively quiescent periods of comparable duration

sources of basinal and mississippi valley type mineralizing brines mixing of evaporated seawater and halite dissolution brine abstract origins of basinal brines and mississippi valley type mvt mineralizing fluids have been separately attributed to evaporation of seawater or dissolution of halite although brines originating from the two processes are not mutually exclusive in basins this study shows that the na br cl br diagram cannot distinguish between evaporated seawater and halite dissolution fluid using the na deficit ca excess diagram which was previously proposed to characterize fluid rock interactions of basinal brines it is shown that most basinal brines including wt mineralizing fluids of the viburnum trend deposits were probably initially a mixture of halite dissolution fluid and evaporated seawater using the same diagram we suggest that the mineralizing brines of the gays river mvt deposit were derived from an aquifer of clastics underlying a thick succession of evaporites where halite dissolution fluid and evaporated seawater could have mixed

sea rain lake relation in the last glacial east mediterranean revealed by δ18o δ13c in lake lisan aragonites we investigated the sea rain lake relation during the last glacial holocene in the east med iterranean region by comparing the 18 o and 13 c records of authigenic aragonite deposited in lake lisan the dead sea mediterranean foraminifera and speleothems the lisan formation data display long and short term variations of 18 o representing steady state conditions of the lake e g 5 6 0 5 and 4 5 1 in the upper and lower members of the lisan formation respectively and short term excursions reflecting large floods and droughts the long term steady state 18 o values of the lisan aragonites show similarity to the corresponding time equivalent records of the eastern mediterranean foraminifera and judea mountain speleothems the last glacial deposits are in all of them 2 3 heavier than the holocene ones we interpret this similarity as reflecting the significance of the source effect on the long term behavior of isotopic reservoirs speleothem 18 o is strongly influenced by the marine reservoir that contributes its vapor to rain formation the lake 18 o is dominated by the composition of the inflowing water short term variations in the isotopic composition of rainfall are dominated by the amount effect and the temperature and those of the lake s upper water mass by the lake s water balance 13 c values are more variable than 18 o in the same lisan sequences e g 13 c in the lower member is 1 0 1 7 whereas 18 o is 4 6 0 7 and are 1 to 1 5 higher in the upper member than in the lower and middle members of the lisan formation these variations reflect significant increase in primary productivity of the lake and algal bloom activity it appears that the hypersaline saline lakes were not as dead as the dead sea is and that algal activity had an important impact upon the geochemistry of lake lisan the 18 o data combined with independent geochemical and limnologic information e g level fluctuations indicate that lisan time was characterized by high precipitation high lake stands high atmospheric humidity whereas the holocene dead sea shows the opposite behavior this paleoclimatic reconstruction is consistent with independent evidence for significantly wetter conditions in the east mediterranean region during the last glacial period copyright 2005 elsevier ltd

the geochemical evolution of halite structures in hypersaline lakes the dead sea israel depressions in the floor of the southern basin of the dead sea contain dense 1 26 l 29 g cm 3 brines which formed by evaporation at the lake s surface absorbance of solar radiation heats these brines by about 2 4 c d l as long as the density gradient of the lake prevents overturn as a result bottom halite is dissolved in the warmer brines at about 0 4 g nacl liter c i continuous heating of the brine of these holes and cooling of the overlying liquids at night causes frequent overturns of the brine column followed by mixing and cooling of the nacl rich brine the extra load of halite is precipitated near the holes in the form of halite cones and mushroomlike structures whereas the initial nacl supply to the growing halite structures comes from the floor of the lake the later growth stage is supported by nacl supplied from the upper evaporating brine layer crude mass and heat balances show that the proposed model may well explain the occurrence and distribution of halite islands in the dead sea the model may be applicable to any shallow enough a few meters hypcrsaline lake that is saturated with respect to halite the dead sea is composed of a ca chloridic brine the evolution of which has been proposed by starinsky 1974 the physiography limnology and sedimentological regime of the lake have been studied and described by neev and emery 1967 among many others the dead sea is comprised of two parts a northern basin 300 m deep which forms the bulk of the lake s volume and area and a southern shallow mostly 2 4 m deep basin fig 1 dwindling precipitation since about 1930 klein 1985 and diversion of water from the dead sea drainage system for agricultural needs resulted in the continuous lowering of the lake level at a rate of 50 cm yr l finally toward the end of the 1 960s the two basins became separated since then the brine level in the southern basin is maintained artificially evaporation of the brine results in enrichment of most of its dissolved salts with respect to their concentrations in the northern basin exceptions are na and s042 which are precipitated from

non destructive provenance study of cuneiform tablets using portable x ray fluorescence pxrf abstract portable x ray fluorescence pxrf apparatus of the last generation was tested to determine its potential for routine provenance determination of clay cuneiform tablets which cannot be analyzed by classical intrusive methods a group of tablets from hattusa bogazkoy and from el amarna which were previously provenanced using optical mineralogy om and instrumental neutron activation analysis inaa was analyzed by pxrf and the results were used to establish the grouping according to their elemental concentrations these groups were compared with the previous results retrieved by om and inaa in order to confirm their validity the results corroborate the high potential of the pxrf for non destructive study of well defined closed assemblages of clay derived delicate artifacts such as cuneiform tablets bullae and fine ware pottery consequently a group of previously unexamined tablets from hattusa was analyzed by pxrf and the results are discussed with implications on future research

a late cenozoic regional mesofracture system in southern england and northern france the upper cretaceous and palaeogene rocks of s england and n france are cut by a nw trending system of fractures characterized by swarms of vertical extension joints accompanied by conjugate sets of hybrid and shear joints and normal mesofaults many major photolineaments exhibit the same nw trend as the fractures and are particularly conspicuous in n france where they are coincident with rectilinear drainage channels suggesting a relationship between fracture orientation and physiography in s england this relationship is absent possibly because of the influence of additional fracture systems related to major flexures trending obliquely to the nw se direction these major e w trending flexures and associated fracture systems were formed during the oligocene to early miocene 9helvetic9 phase of deformation and are cross cut obliquely by fractures in the nw trending system the nw trending fractures and lineaments are parallel to neotectonic normal faults in the lower rhine embayment and become less well developed to the west with increasing distance from these major structures the lower rhine faults were reactivated and propagated into the quaternary cover as a consequence of ne sw regional tension generated during the late neogene to recent 9jura9 phase of nw se alpine convergence the nw trending extensional structures in s england and n france are considered to be of about the same age and related to the same stress regime as the neotectonic normal faults of the lower rhine embayment however because fractures of the nw system cutting palaeogene sediments in se england are truncated by the erosion surface beneath the plio pleistocene red crag deposits it is possible that in england fracture initiation did not continue into quaternary times

intrabasin paleoearthquake and quiescence correlation of the late holocene dead sea 1 a comprehensive multisite paleoseismic archive of the late holocene dead sea basin past 2500 years is established by constructing two age depth chronological models of two sedimentary sections exposed at the retreating shores of the modern dead sea two new paleoseismic study sites studied are the ein feshkha nature reserve outcrop located at the northern part of the basin and close to an active underwater transverse fault and the east ze elim gully outcrop at the southern part of the basin age depth regression models are calculated for these sections based on atmospheric radiocarbon ages of short lived organic debris calibrated with a bayesian model the uncertainties on individual model ages are smaller than 100 years the new chronological records are compared to a laminae counting study of the ein gedi core migowski et al 2004 located at the central dead sea basin the ein feshkha outcrop yielded the largest number of seismites in the studied time interval n 52 while lower numbers of seismites are recovered from the ze elim outcrop and ein gedi core n 15 and 36 respectively the seismites show no strong dependence on the limnological sedimentological conditions in the particular sampling sites they coappear in both shallow and deep water environments and in different sedimentary facies during time intervals when the chronologies are comparable it appears that the number of seismites is significantly larger in the northern part of the basin ein gedi and ein feshkha seismic quiescence intervals are apparent at all three sites from 2nd 4th century a d and at 500 150 b c at ze elim and ein gedi several synchronous seismites appear in all sections termed here the intrabasin seismites ibs among them 1927 1293 1202 1212 749 551 419 and 33 a d and 31 and mid 2nd century b c the recurrence time of the ibs from the 2nd century b c to the 14th century a d is 200 years compared with 100 years for all earthquakes on a diagram of epicentral distance versus magnitude historic earthquakes that are correlated with ibs plot in a field of high local intensity the farther and stronger ibs earthquakes require lower local intensities to be recorded this study demonstrates that a painstaking effort is still needed for unraveling the seismic history of the dead sea basin the results also indicate that such a study will likely be highly rewarding

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

barium and radium in the dead sea abstract we have measured ba in dead sea samples collected before and after the 1979 overturn and 226 ra in nine samples collected after the overturn before this overturn ba and the 226 ra data measured by chung and craig 4 show that a distinct two layer structure existed with higher concentrations in the upper layer after the overturn both elements were uniformly distributed in the water column the inventories of ba and ra calculated from these data are the same for the periods before and after the overturn if the inventories were constant during the last meromictic phase then the input rate must be balanced by the removal rate and a mass balance model can be constructed to estimate physical parameters based on known or deduced sources and sinks the sources include inputs from the jordan river springs around the dead sea and submerged springs or seepages etc the sinks include coprecipitation with aragonite gypsum precipitation of barite coprecipitation of ra with barite particulate scavenging and radioactive decay for ra our data include measurements of ba and 226 ra in gypsum aragonite and halite from the dead sea as well as in some of the inflowing rivers and springs the inclusion of particulate scavenging as a sink is a major element of the model we find that without inclusion of a ba scavenging term in the deep water the lake volume at the previous overturn as calculated from the ba data would be unrealistically high in comparison with historical records the inclusion of particulate scavenging for ra in the model reduces the calculated duration of the last meromictic phase significantly our model excludes internal mixing between the upper and lower water masses with this restriction various sets of model parameters were calculated as a function of the ra ba scavenging rate ratio if the ratio is one the calculated age of the last meromictic phase is about a hundred years a substantial increase in the ra input rate is required to balance the removal rate by particulate scavenging as well as decay if the ratio is zero i e no particulate scavenging for ra the age is about 260 years as obtained by stiller and chung 2

basin scale migration of continental rift brines paleohydrologic modeling of the dead sea basin it was suggested that brine of the dead sea rift has originated from a residual product of intensively evaporated seawater that invaded the rift precipitated halite and later interacted through dolomitization with the host rock during subsurface migration detection of this brine in many deep wells located at distances as far as 100 km away from the rift was attributed to long distance migration of the brine the physical feasibility of such migration which probably spanned the past 3 6 m y is quantitatively tested and verified in this study by using paleohydrologic modeling the structural formation of the rift is described by a chronological sequence of geologic cross sections serving as the basis for hydrodynamic calculations which assess the effects of the structure on fluid migration salinity redistribution and heat transport across the sedimentary basin results indicate that two basin scale ground water systems one atop the other but with opposite flow directions coexisted in the dead sea rift valley the first is a topography driven flow of meteoric water from the surrounding highlands toward the rift through relatively shallow aquifers 1 km the second is a density driven migration of the dead sea brine through deep aquifers 4 5 km in the opposite direction the configuration of these flow systems has changed during the structural evolution of the dead sea rift illustrating the interrelationships among basin formation paleohydrology and paleogeochemistry

the evolution of marine evaporitic brines in inland basins the jordan dead sea rift valley marine evaporitic brines frequently display na cl and br concentrations that significantly deviate from seawater evaporation paths yielding markedly conflicting degrees of evaporation calculated for a specific brine here we present 493 new and 33 previously reported analyses of ca chloridic waters of neogene age from the dead sea rift dsr valley to explain such offsets the dsr brines plot along an almost perfect mixing line r2 0 990 on a br cl na cl diagram extending between two end members a and b points a and b are located at na cl 0 804 and br cl 0 00193 and at na cl 0 00773 and br cl 0 0155 respectively within the halite and bischofite stability fields brines a and b originated in a dual mode evaporation basin brine a formed under the classic lagoon scenario mode a with seawater inflow and brine outflow at steady state occasional drops in water level imposed by climatic or tectonic causes resulted in outflow cutoff and in rapid concentration buildup the second mode b initiated upon equilibration of the activity of water in the brine with the overlying relative humidity resulting in composition and salinity approaching that of brine b sustaining it until the next reversal to mode a thick evaporite deposits inhibited infiltration of brines a and b into the subsurface terrain a process that was enabled only when the brine reached the permeable carbonate rock rim and border faults of the basin hence brines that formed during the relatively short shifts from mode a to mode b could not penetrate into the deep subsurface and bittern minerals that were formed during the frequent mode shifts were dissolved and flushed out into the sea upon the next resumption of outflow the proposed model accounts for the deviations of brines from the marine evaporitic evolution curve by brine mixing rather than due to a change in ocean chemistry it also explains the absence of bittern minerals in the thick halite and gypsum anhydrite succession and the compositional gap between the widely different end member hypersaline fluids this model applies directly to the studied dsr brines and evaporites but it may be relevant to other inland evaporitic basins

u series and oxygen isotope chronology of the mid pleistocene lake amora dead sea basin abstract this study establishes for the first time the chronology and limnological history of lake amora dead sea basin israel whose deposits the amora formation comprise one of the longest exposed lacustrine records of the pleistocene time the amora formation consists of sequences of laminated primary aragonite and silty detritus ca sulfate minerals halite and clastic units this sedimentary sequence was uplifted and tilted by the rising sedom salt diapir exposing 320 m of sediments on the eastern flanks of mt sedom the arubotaim cave ac section the chronology of the ac section is based on u disequilibrium dating 230th 234u and 234u 238u ages combined with floating 18 o stratigraphy and paleomagnetic constraints the determination of the 230th 234u ages required significant corrections to account for detrital th and u these corrections were performed on individual samples and on suites of samples from several stratigraphic horizons the most reliable corrected ages were used to construct an age elevation model that was further tuned to the oxygen isotope record of east mediterranean foraminifers based on the long term similarity between the sea and lake oxygen isotope archives the combined u series 18 o age elevation model indicates that the exposed amora sequence was deposited between 740 and 70 ka covering seven glacial interglacial cycles marine isotope stages mis 18 to 5 taking the last glacial lake lisan and the holocene dead sea lacustrine systems as analogs of the depositional limnological environment of lake amora the latter oscillated between wet glacial and more arid interglacial conditions represented by sequences of primary evaporites aragonite and gypsum that require enhanced supply of freshwater to the lakes and clastic sediments respectively the lake evolved from a stage of rapid shifts between high and low stand conditions during 740 to 550 ka to a sabkha like environment that existed at the ac site between 550 and 420 ka this stage was terminated by a dry spell represented by massive halite deposition at 420 ka mis12 11 during mis10 6 the lake fluctuated between lower and higher stands reaching its highest stand conditions at the late glacial mis6 after which a significant lake level decline corresponds to the transition to the last interglacial mis5 low stand lake represented by the uppermost part of the formation 18 o values in the primary aragonite range between 6 0 and 1 3 shifting cyclically between glacial and interglacial intervals the lowest 18 o values are observed during interglacial stages and may reflect short and intense humid episodes that intermittently interrupted the overall arid conditions these humid episodes expressed also by enhanced deposition of travertines and speleothems seem to characterize the negev desert and in contrast to the overall dominance of the atlantic mediterranean system of rain patterns in the dead sea basin some humid episodes during interglacials may be traced to southern sources

hypersaline brine diagenesis and evolution in the dead sea lake lisan system israel abstract water soluble salts were extracted from 57 aragonite and detrital laminae sampled from the pleistocene lake lisan sediments the solutions and solids were analysed for ca mg na k sr cl so 4 and bicarbonate average na cl mg ca sr ca mg cl ca cl sr cl k cl k na and k mg ratios calculated for seven stratigraphie elevations in the lisan column indicate that the dead sea rift sediment brine system has remained practically closed for 70000 years the soluble salts reflect both the hydrologie evolution of the lake as well as diagenetic processes mg ca ratios systematically decrease in younger sediments and this decline is accompanied by a 1 5 4 fold sr enrichment in aragonite solubles relative to salts extracted from detrital laminae the major process responsible for these observations is dolomitization of sr rich aragonite by interstitial brine diagenesis was triggered by slow desiccation of the lake s sediments after the lisan waters started to recede due to a change in climate very sharp chemical gradients which developed in the sediments after deposition have been preserved because further diagenesis was quenched by the advancing dry out h 2 o loss by evaporation induced difrusional migration of na and cl from aragonite laminae into adjacent detrital layers this lowered the na cl ratio in the aragonite and raised it in the detritus relative to the initial dead sea na cl ratio of 0 26 the early lisan brine was similar in its chemical composition and total salinity to that of the present dead sea

sr isotopic composition of siderite for assessing the origin of mineralizing fluids the case study from the jebel awam deposit central morocco abstract the sr isotope ratios were determined for 17 samples of siderite from the polymetallic deposit of jebel awam formed because of a granitic intrusion through metasedimentary palaeozoic rocks about 286 ma in the eastern part of the moroccan meseta the isotopic ratios range from 0 712829 to 0 713960 as siderite contains negligible rb the measured isotopic ratios are the same as its parent fluids in this view the isotopic ratios of the carbonate rule out that the mineralizing solutions were composed of either magmatic fluids as the local granites show a range of initial ratios between 0 706 and 0 709 or seawater whose isotopic ratio about 286 ma was 0 7075 on the contrary the mineralizing fluids were composed of meteoric water circulating mainly through the schists of the palaeozoic basement whose isotopic range was between 0 712 and 0 718 at the time of the ore deposit formation moreover the sr isotope ratios of siderite rule out any possible recrystallization of the carbonate during the alpine orogenesis as a whole this study shows the possibility of using siderite for determining the type of fluids involved in ore deposits provided that the age and the sr isotope ratios of the rocks of the mineralized area are known this may be useful to assess also the provenance of the metals carried by the fluids

high resolution geological record of historic earthquakes in the dead sea basin a 2000 year paleoseismic record of the dead sea area was recovered from a lacustrine sedimentary section the section is being exposed at the ze elim terrace on the shores of the dead sea due to the fast retreat of the lake the section consists of laminated detrital and chemical mainly aragonite sediments that were deposited in the holocene paleo dead sea eight layers in the section show deformed sedimentary structures and are identified as seismites their chronology was determined by radiocarbon dating on organic remains the seismite ages are well correlated with the historically documented earthquakes of 64 and 31 b c and 33 363 1212 1293 1834 and 1927 a d the few historically documented earthquakes that have no correlatives in the ze elim seismite record occurred in times of sedimentary hiatuses at this site e g 749 a d based on modern analogues and the association of similar disturbed layers with syndepositional faults the ze elim terrace seismites indicate m 5 5 earthquakes the average recurrence interval is estimated as 100 300 years and represents slip events on different faults in the dead sea area the ze elim section provides a unique opportunity to correlate two independent and extensive data sets the historical and sedimentary records this study opens the way for better understanding of spatial and temporal distribution of earthquakes along the dead sea transform and elsewhere

40ar 39ar geochronologic constraints on the timing of massive sulfide and vein type pb zn mineralization in the western meseta of morocco the meseta domain of morocco is located on the southern margin of the late paleozoic hercynian orogenic zone 40ar 39ar ages of igneous and hydrothermal minerals biotite and illite were analyzed from a representative massive sulfide deposit at hajar 1 5 mt zn 0 45 mt pb 0 11 mt cu and 900 t ag and a vein type deposit at tighza 1 0 mt pb 0 3 mt zn and 1 000 t ag in the western meseta a weighted mean age of hydrothermal biotite of the hajar deposit is 300 9 2 6 ma 2 uncertainty identical to a hydrothermal illite age of 305 4 4 8 ma these two ages are calculated from about 93 percent of the released 39ar another illite age calculated from 74 percent of the released 39ar 313 4 9 1 ma overlaps with or is slightly older than these concordant ages these 40ar 39ar results indicate that the biotite and illite alteration of the hajar deposit formed almost simultaneously at 304 to 300 ma this age range is younger than the visean age previously assumed on the basis of geologic setting these 40ar 39ar ages are interpreted as the age of hydrothermal activity subsequent to massive sulfide mineralization a magmatic intrusion beneath the deposit may have triggered this hydrothermal activity three 40ar 39ar weighted mean ages and one plateau age from the tighza deposit range from 280 6 to 267 7 ma igneous biotite of the kaolin granite and hydrothermal illite of the ighrem aouss and north veins in the deposit indicate ages of 280 6 5 5 ma 280 6 3 1 ma and 275 5 3 4 ma respectively these three ages are identical within 2 uncertainties the age of the hydrothermal biotite from the mispickel granite 267 7 2 3 ma is slightly younger this younger age may have resulted from two periods of magmatic hydrothermal activity or from resetting of hydrothermal biotite by ar loss regardless these ages indicate that granite intrusion and hydrothermal alteration associated with galena and sphalerite bearing veins occurred mainly at 280 to 275 ma in the tighza deposit the identical ages of the magmatic intrusion and hydrothermal alteration suggest that the vein type pb zn mineralization as well as w mineralization was associated with the magmatic intrusion the influence of the late deformation and metamorphic overprint may be related to the lowest temperature steps of the analytical data the dates obtained from the lowest temperature steps from both the tighza and hajar deposits concentrate between 235 ma and 220 ma this time range is compatible with the geologic constraints on the deformation and these dates are thus attributed to the post visean regional metamorphism

digital topography and bathymetry of the area of the dead sea depression abstract the dead sea depression occupies the central part of that segment of the syrian african rift extending from the mountains of southern lebanon to the arava valley north of the gulf of aqaba on the red sea the lowest continental feature in the world it encloses the dead sea whose surface now lies at about 409 m this shrunken sea consists of a shallow southern basin occupied by evaporation pans and a northern basin 50 km in length by 13 17 km in width with a flat floor some 731 m below msl the depression is asymmetric with the mountains to the east being up to 500 m higher the closed depression has two outlets one at 60 5 m altitude into the mediterranean via the jezreel valley near afula and a second into the red sea at about 200 m altitude in the arava valley a digital terrain model dtm based upon the local 1 50 000 scale topographic maps and modern bathymetric surveys gives elevations to decimeter resolution on a grid with 25 m spacing when visualized as shaded relief or in coloured hypsometric format the dtm graphically shows the overall morphology and its many features these include the local tectonics from the major boundary faults to the associated subsidiary faults and lineaments and their possible relationships with the incised canyons offshore also clearly visible are the volcanic cones on the golan heights the coast paralleling kurkar ridges and the halokinetic disruptions to the deep offshore topography the dtm was used to compute a hypsometric curve for the closed depression from 731 m to 60 m the maximum area and volume of a lake extending to the afula spillway would be 5985 km 2 and 1602 km 3 respectively inflection points were observed at 715 m where the dead sea s flat bottom meets its steep flanks at 385 m where the northern basin meets the flat floor of the southern basin and surrounding plain at 228 with the step up to the basin of the sea of galilee and at mediterranean sea level

the sulfur system in anoxic subsurface brines and its implication in brine evolutionary pathways the ca chloride brines in the dead sea area abstract important elements in the evolutionary history of saline groundwater might be overlooked when they involve both sulfate removal through reduction and input of sulfate via dissolution these two simultaneous and apparently contrasting processes can result in a negligible net effect on the sulfate concentration isotopic composition of sulfur in sulfate and sulfide can be applied to identify the bacterial sulfate reduction bsr though the extent of the process is difficult to quantify saturation with respect to gypsum may suggest that gypsum dissolution also occurs however a more definite identification of these processes and their quantification can be achieved through the use of ammonium concentration in the anoxic brines this approach assumes that the ammonium is derived only from the oxidation of organic matter through bsr and it requires that the c n ratio in the oxidized organic matter be known a minimum estimate for the sulfate reduction can be obtained when the redfield c n ratio 106 16 is assumed several calculation methods are presented to identify the extent of sulfate reduction prior to concomitant with or following gypsum dissolution that are based on combining sulfur isotopic compositions rayleigh distillation equation and calculated gypsum saturation indices the required assumptions are presented and their validation is discussed the subsurface hypersaline ca chloride brines in the vicinity of the dead sea are taken as a case study here sulfur isotope compositions of sulfate and sulfide and high ammonium concentrations indicate bsr occurs in the subsurface the sulfur isotopic composition of the sulfate makes it possible to distinguish between two major groups of brine and their recent evolutionary histories 1 the qedem shalem thermal brines 34 s so4 21 24 which emerge as springs along the shores and are slightly undersaturated with respect to gypsum 2 dsif tappuah brines 34 s so4 30 60 which are found in shallow boreholes and are saturated to oversaturated with respect to gypsum calculations based on their ammonium content suggest that both groups of brine require apparent unreasonably high oversaturations with respect to gypsum prior to the onset of the reduction this implies that the groundwater systems were open with respect to sulfate and that the sulfate reservoir was replenished continuously or intermittently during the bsr the dsif tappuah brines continue to dissolve gypsum during their bsr the dissolving sulfate is derived from relatively isotopically enriched gypsums 34 s so4 20 such as found in the lisan formation these brines approach the steady state isotopic composition 34 s ss dictated by the combination of the 34 s of the dissolving gypsum and the fractionation factor accompanying bsr the sulfur isotopic composition of the qedem shalem brines implies that most of their ammonium content is derived from an earlier phase of bsr and that the last phase of bsr takes place during the brines rapid ascent to the surface prior to this stage they evolved through either 1 dissolution of gypsum with 34 s so4 20 which occurred after the main bsr in the subsurface 2 a previous phase in which the brines were part of a lake and later percolated to the subsurface as such their isotopic composition and ammonium content were determined by the combined effect of freshwater sulfate input to the lake and bsr in the stratified lake

the terminology of structures in thrust belts abstract a review of structures and geometric relationships recognized in thrust belts is presented a thrust is defined as any contractional fault a corollary being that thrusts must cut up section in their transport direction flats are those portions of a thrust surface which were parallel to an arbitrary datum surface at the time of displacement and ramps are those portions of thrusts which cut across datum surfaces ramps are classified on the basis of their orientation relative to the thrust transport direction and whether they are cut offs in the hangingwall or footwall of the thrust lateral variations in the form of staircase trajectories are joined by oblique or lateral ramps which have a component of strike slip movement an array of thrusts which diverge in their transport direction may form by either of two propagation models these are termed piggy back propagation which is foreland directed and overstep propagation which is opposed to the thrust transport direction an array of thrust surfaces is termed an imbricate stack and should these surfaces anastamose upwards a duplex will result the fault bounded blocks are termed horses a duplex is bounded by a higher roof thrust and a lower floor thrust the intersection of any two thrust planes is termed a branch line thrusts can be classified on the basis of their relationship to asymmetric fold limbs which they cut a further classification arises from whether a particular thrust lies in the hangingwall or footwall of another one the movement of thrust sheets over corrugated surfaces or the local development of thrust structures beneath will fold higher thrust sheets these folds are termed culminations and their limbs are termed culmination walls accommodation of this folding may require movement on surfaces within the hangingwall of the active thrust these accommodation surfaces are termed hangingwall detachments and they need not root down into the active thrust this category of detachment includes dip slip hangingwall drop faults which are developed by differential uplift of duplex roofs and out of the syncline thrusts which develop from overtightened fold hinges back thrusts as well as forming as hangingwall detachments may also form due to layer parallel shortening above a sticking thrust or by rotation of the hangingwall above a ramp

earthquake induced barium anomalies in the lisan formation dead sea rift valley israel prominent barium concentration anomalies that appear within earthquake brecciated layers seismites in the late pleistocene lacustrine lisan formation in the dead sea basin dsb are described and discussed here for the first time chemical analyses of samples from vertical profiles through the seismites display asymmetric ba concentration peaks the peaks start a few centimeters above the seismite s base and gradually rise to maxima reaching some 1000 ppm ba before falling off to background values around 100 ppm or abutting against the upper boundary of the breccia layer high resolution sem and electron microprobe analyses disclose that the ba in the anomalies resides within prismatic crystallites mostly 2 m in length composed of a ba sr so4 mineral designated bm henceforth these are lacking altogether in the normal non seismic underlying and overlying sediments the crystallites are much smaller than the adjacent supporting matrix grains of the gradually bedded seismite and show no size sorting relationship with the latter the peaks of the anomalies reflect higher population density rather than larger crystal sizes of the bm crystallites therein mass balance calculations show that the mass of ba2 dissolved in the lake above a unit area of the seismites was mostly several times larger than that found in the seismite the concentration of ba2 in dsb ca chloride brines is mostly lesser than that in the dsb lake ruling out the former as a source of ba to the anomalies we propose that during earthquakes the uppermost bottom sediment layers in the dsb lake were shaken and re suspended into the overlying brine the larger faster settling fragments and grains remained almost intact or were rapidly removed unaffected from the slurry however the finer grains remained in suspension for longer periods allowing nucleation and growth of bm crystallites on their surfaces from the surrounding brine before reaching the bottom the lag of ba trapping behind the breccia accumulation and the asymmetrical peak shapes of the anomalies are accounted for by decreasing dilution of the ba rich finer particles by ba poor coarse grains during seismite accumulation as reflected by the graded bedding of the seismite layers the supply rate of ba2 to the lake by freshwater and brines was more than sufficient to account for the buildup of ba in recurring seismites separated by seismically quiescent intervals as short as 100 yr

soft sediment deformation by kelvin helmholtz instability a case from dead sea earthquakes abstract the standard explanation for soft sediment deformation is associated with overturn of inverted density gradients however in many cases observations do not support this interpretation here we suggest an alternative in which stably stratified layers undergo a shear instability during relative sliding via the kelvin helmholtz instability khi mechanism triggered by earthquake shaking dead sea sediments have long stood out as a classical and photogenic example for recumbent folding of soft sediment these billow like folds are strikingly similar to khi structures and have been convincingly tied to earthquakes our analysis suggests a threshold for ground acceleration increasing with the thickness of the folded layers the maximum thickness of folded layers order of decimeters corresponds to ground accelerations of up to 1 g such an acceleration occurs during large earthquakes recurring in the dead sea

prehistoric earthquake deformations near masada dead sea graben earthquake inducedfluidizations and suspensions of lake sediments associated with syndepositionalfaults formapaleoseismicrecordinthedeadseagraben theassociation offluidized beds with surface faulting supports the recognition of mixed layers as reliable earthquake indicators and provides a tool for the study of very long term 70 kar seismicity along the dead sea transform the faults compose a fault zone that offsets laminated sediments of the late pleistocene lake lisan they exhibit displacements of as much as 2 m layers of massive mixtures of laminated fragments are interpreted as disturbed beds each formed by an earthquake the undisturbed laminated layers between these mixed layers represent the interseismic interval a typical vertical slip of about 0 5 m per event is separated by several hundred years of quiescence the fault zone lies within the dead sea graben 2 km east of masada where archaeology and historical accounts indicate repeated strong earthquake damage the distribution of strikes in the fault zone resembles that of the faults exposed in and around the graben including the seismogenic ones the excellent exposures over hundreds of metres allow an unprecedented temporal and spatial resolution of slip events on faults

ra isotopes and rn in brines and ground waters of the jordan dead sea rift valley enrichment retardation and mixing abstract thirty six springs and wells from the dead sea rift valley were periodically sampled and analyzed the latter included full chemical analyses 222 rn and 226 ra by counting emanometry as well as 228 ra 226 ra and 224 ra 228 ra activity ratios spectrometry sampling stretched over almost 2 yr several hundred rn ra analyses and close to a hundred isotopic ratios were measured most waters in the rift valley have both elevated ra several to 750 dpm l and rn a few hundred to almost 60 000 dpm l content in practically all samples 222 rn activity considerably exceeds that of its parent 226 ra the ra content is the result of all dead sea rift valley waters being mixtures of fresh water with saline brines ra is efficiently extracted from surrounding rocks into the brine end member 228 ra 226 ra ratios are exceptionally low 0 07 to 0 9 mostly less than 0 2 this apparently reflects the u over th enrichment in the source rocks that contribute the ra ra enrichment both 228 ra and 226 ra is locally correlated throughout the rift valley with water salinity this correlation can be used to constrain the age of the brine freshwater mixing process in one of the hydrologic subsystems studied the fuliya block the mixing of the shallow ground water must have occurred in less than 200 to 300 yr ago probably before no more than some 30 yr high radon activities in surface waters along the dead sea rift valley result from the formation of radium enriched linings on the aquifer rock surface the mixing of the radium extracting brines with fresh water leads to continual adsorption of radium as water salinity decreases the unique combination of fast upward flow and continual mixing in the dead sea rift valley accounts for a constant replenishment of radium in the waters this causes a gradual buildup of a radium lining on the aquifer walls until eventually a steady state surface activity is established

holocene earthquakes inferred from a fan delta sequence in the dead sea graben abstract the holocene sequence of the fan delta of nahal darga in israel records deformation associated with earthquakes related to the dead sea transform in general and to the jericho fault in particular the fan delta sequence is well exposed and 20 radiocarbon ages help to date the earthquakes that are inferred from a displacement along faults b liquefaction features associated with 11 separate sandy and silty layers and c slumped allocthonous bodies of sediments located directly above one of the main splays of the jericho fault on average an earthquake larger than m 5 5 has occurred approximately every 600 years this estimate is based on the earthquake record of the complete stratigraphic sequence with erosional hiatuses omitted from the calculations the most recently deformed layer is related to the 1927 jericho m l 6 2 earthquake this layer provides a modern analog for the style of soft sediment deformation associated with earthquakes in the late pleistocene and holocene silty sand beds of the fan delta complexes of the dead sea and its predecessor lake lisan

response of fractured rock subject to fluid injection part i development of a numerical model abstract the selection and development of a numerical model used to investigate the response of fractured rock to injection are described the distinct element method was chosen on the basis of its ability to represent explicitly the fractures and to couple the mechanical deformation to the fluid flow the numerical model was used to simulate fluid injection from a single well into each of four basic model reservoirs the results of these simulations form the basis of the interpretation given in parts ii and iii

the sources and evolution of sulfur in the hypersaline lake lisan paleo dead sea d 34 s values in gypsum are used to evaluate the fate of sulfur in the hypersaline lake lisan the late pleistocene precursor of the dead sea 70 14 ka bp and applied as a paleo limnological tracer the ca chloride lake lisan evolved through meromictic periods characterized by precipitation of authigenic aragonite and holomictic episodes characterized by enhanced gypsum precipitation the lake deposited two major gypsum units the blower gypsum unitq deposited at 56 ka showing d 34 s values of 18 20x and the bupper gypsum unitq deposited at 17 ka displaying significantly higher d 34 s values of 26 28x laminated and disseminated gypsum residing within the aragonite exhibit d 34 s values in the range of 26x to 1x the isotopic composition of the gypsum was dictated by freshwater sulfate input that replenished the upper layer of the lake the mixolimnion bacterial sulfate reduction bsr that occurred under the anoxic conditions of the lower brine the monimolimnion and mixing between these two layers during meromictic periods the sulfate reservoir in the lower brine was replenished by precipitation of gypsum from the upper layer and its subsequent dissolution due to sulfate deficiency induced by bsr activity this process describes a bsulfur pumpq mechanism and its effect on d 34 s in the water can be modeled by a modified rayleigh distillation equation steady state d 34 s values 40x were reached in the lower brine after long meromictic periods following overturn episodes induced by diminishing freshwater input and lake level decline large quantities of d 34 s enriched gypsum precipitated the negative d 34 s values in laminated and disseminated gypsum provide evidence for bsr activity in the lower brine that removed isotopically depleted sulfides from the water column causing significant isotopic enrichment of remaining sulfate following the lake desiccation the sediments were exposed and the latter sulfides oxidized and re crystallized as gypsum d 2005 elsevier b v all rights reserved

evidence from lake lisan of solar influence on decadal to centennial scale climate variability during marine oxygen isotope stage 2 documentation of short term climate variability during the glacial period has been limited by the availability of well dated high resolution archives here we present a paleoclimate reconstruction from varved lacustrine sediments of lake lisan dead sea rift for ca 26 2 17 7 calendar ka the age is based on a floating varve chronology anchored to radiometric dates our reconstruction indicates that small ice rafting events a b c and d as well as heinrich events in the north atlantic are associated with the eastern mediterranean arid intervals study of seasonal sublaminae yields evidence of several additional decadal to century scale arid events that correlate with cooler temperatures at higher latitudes analyses in the frequency domain indicate the presence of periodicities centered at 1500 yr 500 yr 192 yr 139 yr 90 yr and 50 60 yr suggesting a solar forcing on climate

geological characteristics fluid inclusions and h o c s isotopes of the zaopa ag mo prospect in the suizao area hubei province implications for ore genesis abstract the zaopa ag mo prospect is located in the tongbai dabie orogenic belt in central china the orebodies occur as quartz veins and are controlled by secondary faults of the wushan fault zone in the suizao area and hosted by the zhoulou granite we document three hydrothermal stages characterized by albite quartz sulfide veins stage i quartz sulfide stage ii and quartz fluorite assemblages stage iii respectively silver is mainly found in hessite and galena there are three types of fluid inclusions in quartz and fluorite including 1 liquid rich aqueous fluid inclusions l v 2 aqueous carbonic fluid inclusions l v co2 3 pure carbonic fluid inclusions pure co2 laser raman spectroscopic analyses indicate the existence of carbon dioxide in the fluid inclusions the fluid system of the zaopa ag mo prospect is composed of co2 nacl h2o the homogenization temperatures of the three stages are 380 to 495 c 337 to 404 c and 246 to 336 c respectively the salinities of the three stages are 11 1 17 5 wt nacl eq 6 7 12 7 wt nacl eq and 1 6 9 9 wt nacl eq respectively the stage i sulfides molybdenite chalcopyrite pyrite show a 34s value around 0 3 1 to 1 0 indicating a magmatic origin the stage ii sulfides galena sphalerite pyrite also show a 34s value around 0 5 7 to 1 6 again indicating a magmatic origin the c h o isotope data shows that the fluids of the early stage were derived from a magmatic source but the fluids of the late stage mixed with meteoric waters by comparing the characteristics of the mo deposits in china and those from other countries we conclude that the zaopa ag mo prospect is a structurally controlled magmatic hydrothermal vein type deposit

field examples and numerical modelling of oversteps and bends along normal faults in cross section abstract oversteps and bends along cross sections through small scale numerical modelling distinct element analysis has been carried out to simulate the patterns of deformation at oversteps and bends area increase pull apart development and localised stress concentration occur at extensional oversteps and bends stress concentration and a tendency for compaction are typical of contractional oversteps and bends such results are compatible with the structures observed in the field a sensitivity analysis of the modelling has been carried out to investigate the effects of variations in mechanical parameters on deformation although models with weaker properties are more deformable the overall geometry of deformation varies little with variations in mechanical parameters

the geometry of listric normal faults and deformation in their hangingwalls abstract in cross sections containing listric extensional faults area balancing techniques for depth to decollement are usually based on either bed length conservation or displacement conservation listric fault geometry may be constructed from a hangingwall roll over profile using the chevron construction this construction based on conservation of heave necessitates a reduction in fault displacement with decreasing fault dip a modification of this construction utilizing conservation of fault displacement predicts a listric fault that detaches at a shallower depth a new construction based on slip lines uses fault perpendicular displacement segments to generate listric fault shape fault propagation strain may be responsible for anomalous hangingwall geometries and these can be predicted by forward modelling using either a modified chevron construction or a slip line construction

calibration of the 14c time scale to 40 ka by 234u 230th dating of lake lisan sediments last glacial dead sea a new comparison of 14c dates with 234u 230th ages is presented of aragonites from lake lisan the last glacial dead sea between 20 52 cal ka bp the lisan data are coincident with the coral based 14c calendar age calibration through the continuous portion of the curve to 23 5 cal ka bp and with the additional checkpoints at 30 and 40 cal ka bp the agreement with the corals provides evidence for the accuracy of the u th and 14c ages and indicates that lisan aragonites can potentially be used to generate a nearly continuous record of the atmospheric 14c variations through this crucial time interval the lisan data are compared with other records older than 25 cal ka bp from lake suigetsu japan north atlantic foraminifera south african cave deposits and tufa from spain over some age intervals the records show broad agreement over other intervals they diverge all agree that 14c ages were 2 5 0 5 ka younger than calendar ages between 20 32 cal ka bp for ages 32 cal ka bp the lake suigetsu data indicate small differences between 14c ages and calendar ages of less than 1 5 ka the other records broadly agree that 14c ages are too young by 3 1 ka from 32 39 cal ka bp at 40 cal ka bp the foraminifera show equal 14c and calendar ages while the corals lisan aragonites and the spanish tufa indicate a large age difference of 4 5 ka a recent paleomagnetic study of the lisan formation indicates that the high calendar 14c age difference at 40 cal ka bp may be associated with the laschamp paleomagnetic excursion

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

distinct element modeling of structures formed in sedimentary overburden by extensional reactivation of basement normal faults fault and fold patterns in sedimentary rocks have been modeled using a computer code based on the distinct element method dem this numerical method considers the relative motion of disconnected elastic elements governed by newton s laws and frictional sliding criteria forces are transmitted between elements at contact points by changing element size ratios assemblages of elements can simulate different kinematic behavior from localized faulting to distributed flow as an application of the method we investigate folding and faulting patterns that develop in the sedimentary overburden above basement normal faults the number position orientation and sense of slip on faults as well as the fold geometry depend on the basement fault dip and basement rotation the dem model results have practical implications for predicting the evolving characteristics of structural traps and their petroleum potential

genesis of the assif el mal zn pb cu ag vein deposit an extension related mesozoic vein system in the high atlas of morocco structural mineralogical and geochemical evidence the assif el mal zn pb cu ag vein system located in the northern flank of the high atlas of marrakech morocco is hosted in a cambro ordovician volcaniclastic and metasedimentary sequence composed of graywacke siltstone pelite and shale interlayered with minor tuff and mudstone intrusion of synorogenic to postorogenic late hercynian peraluminous granitoids has contact metamorphosed the host rocks giving rise to a metamorphic assemblage of quartz plagioclase biotite muscovite chlorite amphibole chloritoid and garnet the assif el mal zn pb cu ag mineralization forms subvertical veins with ribbon fault breccia cockade comb and crack and seal textures two phase liquid vapor fluid inclusions that were trapped during several stages occur in quartz and sphalerite primary inclusion fluids exhibit t h mean values ranging from 104 c to 198 c final ice melting temperatures range from 8 1 c to 12 8 c corresponding to salinities of 15 wt nacl equiv halogen data suggest that the salinity of the ore fluids was largely due to evaporation of seawater late secondary fluid inclusions have either ca rich saline 26 wt nacl equiv or very dilute 3 5 wt nacl equiv compositions and homogenization temperatures ranging from 75 c to 150 c the 18o and d fluid values suggest an isotopically heterogeneous fluid source involving mixing between connate seawater and black shale derived organic waters low 13cvpdb values ranging from 7 5 to 7 7 indicate a homogeneous carbon source possibly organic matter disseminated in black shale hosting the zn pb cu ag veins the calculated 34sh2s values for reduced sulfur 22 5 to 24 3 are most likely from reduction of so4 2 in trapped seawater sulfate or evaporite in the host rocks reduction of sulfate probably occurred through thermochemical sulfate reduction in which organic matter was oxidized to produce co2 which ultimately led to precipitation of saddle dolomite with isotopically light carbon lead isotope compositions are consistent with fluid rock interaction that leached metals from the immediate cambro ordovician volcaniclastic and metasedimentary sequence or from the underlying paleo neoproterozoic crustal basement geological constraints suggest that the vein system of assif el mal formed during the jurassic opening of the central atlantic ocean

primary carbonates and ca chloride brines as monitors of a paleo hydrological regime in the dead sea basin abstract lakes samra lisan and the dead sea occupied the dead sea basin during the last interglacial 140 75 ka bp last glacial 70 14 ka bp and holocene periods respectively the age of lake lisan and samra was determined by u th dating of primary aragonites comprising parts of the lacustrine sedimentary sequences the lakes have periodically deposited sequences of layered calcitic marls lake samra or laminated primary aragonite lake lisan the deposition of aragonite as the primary carbonate phase reflects the contribution of the incoming freshwater loaded with bi carbonate and high mg ca chloride brine that originated from the subsurface vicinity of the dead sea basin deposition of calcitic marls suggests a minor effect of the brines the ca chloride subsurface brine has been migrating in and out of the wall rocks of the dead sea basin reflecting the regional hydrological conditions during most of the last glacial period and during the late holocene sufficient precipitation above the judea mountains pushed the subsurface ca chloride brines into the lakes causing the deposition of aragonite during the last interglacial period the rain that precipitated above the judea mountains was insufficient to induce brine flow toward lake samra it appears that sporadic floods provided calcium bicarbonate and detritus to produce the samra calcitic marls travertines deposited at the samra lisan boundary indicate the early stage in the resumption of groundwater springs activity that led to the resurgence of ca chloride brine and rise of lake lisan similar variations in the regional rain precipitation and hydrological activity probably characterized the long term geochemical evolution of pleistocene lacustrine water bodies in the dead sea basin enabling the use of the carbonates as paleo hydrological monitors

hierarchic three dimensional structure and slip partitioning in the western dead sea pull apart 1 rifted basins are bounded by marginal belts with fault networks and flexures we analyze the internal structure of such a belt the western margins of the dead sea basin this basin is 150 km long 15 20 km wide with more than 10 km of sediment fill and it is currently subsiding due to slip of the dead sea pull apart the western margin of the dead sea basin is an elongated n s belt with an intricate three dimensional 3 d pattern of zigzag faults flexures and joints the dominant structures are four sets of oblique normal faults arranged in orthorhombic symmetry the faults are steep with prevalent strike directions of nnw and nne large flexures developed along and above these faults forming tilted blocks and localized asymmetric folds two sets of subvertical joints that dominate the area trend nne and nnw subparallel to the strikes of the dominant fault sets the parallel relations between these structures at all scales suggest that they formed during a single tectonic phase three dimensional fault modeling reveals a 3 d strain field with a large vertical shortening a minor horizontal shortening in n s direction belt parallel and a large horizontal e w extension basinward the calculated stress fields associated with the zigzag fault segments are compatible with the observed fault parallel flexures further the calculations predict the formation of local tensile belts above the faults and these tensile belts could explain the penecontemporaneous development of the two joint sets architecture similar to the western margins of the dead sea basin is likely to develop on rifted margins wherever 3 d deformation is required by the rifting kinematics

lake levels and sequence stratigraphy of lake lisan the late pleistocene precursor of the dead sea lake lisan the late pleistocene precursor of the dead sea existed from 70 000 to 15 000 yr b p it evolved through frequent water level fluctuations which reflected the regional hydrological and climatic conditions we determined the water level of the lake for the time interval 55 000 15 000 cal yr b p by mapping offshore nearshore and fan delta sediments by application of sequence stratigraphy methods and by dating with radiocarbon and u series methods during the studied time interval the lake level fluctuated between 340 and 160 m below mean sea level msl between 55 000 and 30 000 cal yr b p the lake evolved through short term fluctuations around 280 290 m below msl punctuated at 48 000 43 000 cal yr b p by a drop event to at least 340 m below msl at 27 000 cal yr b p the lake began to rise sharply reaching its maximum elevation of about 164 m below msl between 26 000 and 23 000 cal yr b p then it began dropping and reached 300 m below msl at 15 000 cal yr b p during the holocene the lake corresponding to the present dead sea stabilized at ca 400 m below msl with minor fluctuations the hypsometric curve of the basin indicates that large changes in lake area are expected at above 403 and 385 m below msl at these elevations the lake level is buffered lake lisan was always higher than 380 m below msl indicating a significantly large water contribution to the basin the long and repetitious periods of stabilization at 280 290 m below msl during lake lisan time indicate hydrological control combined with the existence of a physical sill at this elevation crossing this sill could not have been achieved without a dramatic increase in the total water input to the lake as occurred during the fast and intense lake rise from 280 to 160 m below msl at 27 000 cal yr b p

a 40 000 year unchanging seismic regime in the dead sea rift we studied breccia beds in lacustrine sediments within the active dead sea basin the beds were deformed by m 5 5 earthquakes during the past 60 k y our new analysis considers both the thickness of breccia beds and the lithology of beds directly overlying them in order to identify 11 m 7 earthquakes that originated within the dead sea pull apart between 54 and 16 ka the resulting time series is a unique long record of earthquakes in a well constrained segment of a fault system in which the time interval between consecutive earthquakes increased from hundreds of years to a background recurrence interval of 11 k y since ca 40 ka since this recurrence interval is similar to the m 7 2 recurrence interval in the dead sea basin as extrapolated from present seismicity we suggest that the present seismic regime in the dead sea basin as reflected in its magnitude frequency relation as well as in its deficiency in seismic moment has been stationary for the past 40 k y since the increasing interval between consecutive earthquakes in the studied segment of the dead sea fault is time logarithmic it may be a result of healing of the brittle crust as well as a diminishing strain rate following the first strong earthquake in the sequence

normal fault geometry related to sediment compaction and burial abstract field observations are presented on meso scale normal faults and sandstone dikes which cross cut turbidites in the petroliferous reconcavo basin situated in bahia ne brazil two discrete phases of normal faulting occurred it is argued that the first was probably active during the first 200 m of burial compaction estimates from folded sandstone dikes and the accommodation patterns of shale bedding planes around ball and pillow structures were made first phase fault profiles were initially reasonably straight but refraction on the fault planes increased due to the differing compaction between sandstone and shale the later phase of faulting occurred at a greater depth with steeper fault dips and strong refraction of fault planes at lithological boundaries this greater fault refraction is probably the result of burial and diagenesis which increased the difference in rheological properties between sandstone and shale before faulting occurred thus complex superposed fault geometries may be developed by changing rheological properties and stress conditions during progressive burial it is shown that sandstone dikes were not always intruded vertically injected dikes cannot be used in the same manner that neptunian dikes are conventionally used to estimate tectonic strain if independent evidence of the original orientation of the dike is not available

long term earthquake clustering a 50 000 year paleoseismic record in the dead sea graben the temporal distribution of earthquakes in the dead sea graben is studied through a 50 000 year paleoseismic record recovered in laminated sediments of the late pleistocene lake lisan paleo dead sea the lisan represents more than 10 times the 4000 years of historical earthquake records it is the longest and most complete paleoseismic record along the dead sea transform and possibly the longest continuous record on earth it includes unique exposures of seismite beds earthquake induced structures associated with slip events on syndepositional faults the seismites are layers consisting of mixtures of fragmented and pulverized laminae the places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment water interface during slip events on these faults thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water sediment interface on both sides of the fault scarps modern analogs and the association with surface ruptures suggest that each seismite formed during a m l 5 5 earthquake the 230 th 234 u ages of a columnar section obtained by thermal ionization mass spectrometry give a mean recurrence time of 1600 years of m l 5 5 earthquakes in the dead sea graben the earthquakes cluster in 10 000 year periods separated by quiet periods of similar length this distribution implies that a long term behavior of the dead sea transform should be represented by a mean recurrence of at least 20 000 year record this observation has ramifications for seismic hazard assessment based on shorter records

microfracturing and fluid mixing in granites w sn ore deposition at vaulry nw french massif central abstract the vaulry w sn mineralisation located at the eastern boundary of the blond rare metal leucogranite is contained in a set of subvertical quartz veins locally with muscovite and minor quartz selvages the sequence of deposition was 1 milky quartz predominantly as fracture filling generally affected by subsequent ductile deformation 2 hyaline quartz wolframite cassiterite 3 minor sulphides other sets of quartz veinlets although generally barren are observed in the blond massif fluid migration at the microscopic scale within the granite and in the vicinity of quartz fractures was constrained by studying the geometry of fluid inclusion planes and fluid inclusion chemistry in and outside the mineralised area three major sets of subvertical fluid inclusion planes are recognised a n050 060 e set mostly developed in the veins and in the immediate vicinity a n110 130 e set regionally developed in the granite and a n140 160 e set of local extent as a whole the density of fip decreases from the mineralised zones toward the barren part of the pluton except for the n140 160 e set these are locally abundant around quartz veinlets with similar orientations that form a broad n s band near the blond locality mineralising fluids observed as primary inclusions in cassiterite and in undeformed hyaline quartz are mostly aqueous with moderate salinity and a minor volatile component at variance with many other w sn deposits in the variscan belt ore deposition occurred around 315 c at an estimated depth of 5 5 km under hydrostatic to slightly suprahydrostatic pressures it resulted from fluid mixing in the central part of a large hydrothermal system between two end members i a hot 425 430 c moderately saline fluid that contained a diluted volatile component and although na dominated minor amounts of li and ca the estimated 18o indicates that this fluid was completely equilibrated with the tectono magmatic pile pseudo metamorphic fluid ii a cold 230 c low salinity fluid evolved meteoric water that mixed with and eventually overprinted the early moderately saline fluid responsible for granite muscovitization at 425 430 c later a second hydrothermal system was initiated by the percolation of heated meteoric water with very low salinity the system was by then at least 3 5 km deep and the fluid was heated to 300 c these characteristics are reminiscent of the ca 305 ma episyenitic hydrothermal system known elsewhere in the n limousin

na cl br systematics of mineralizing brines in mississippi valley type deposits new and published analyses of fluid inclusion leachates from mississippi valley type mvt deposits can be divided into two groups on the basis of na br and cl br ratios mvt leachates from the illinois kentucky and cincinnati arch districts and from cubic galena in the viburnum trend have na br and cl br ratios that extend to values significantly above that of seawater which are characteristic of evaporite dissolution brines mvt leachates from polaris and octahedral galena in the viburnum trend have na br and cl br ratios that plot below seawater and along the compositional trend formed by evaporation solubility volume constraints require that brines formed by seawater evaporation had high dissolved metal contents preliminary correlation of leachate compositions allows delineation of two brine provinces in the midcontinent united states 1 an early high br province found only in southeastern missouri and 2 a later low br province of probable permian age that extended from the cincinnati arch to the tri state district these observations along with na cl br data for modern brines from the illinois basin argue against models for single stage midcontinent mvt brine flow based on recharge from late paleozoic arkoma foreland basins to the south

thermodynamic constraints on dead sea evaporation can the dead sea dry up abstract the relation between climatic parameters relative air humidity and the water activity of the dead sea water determines the possible maximum evaporation of the lake using the pitzer thermodynamic approach the activity of the dead sea water during evaporation was calculated and compared to the present relative air humidity above the water long term 1992 1997 quasi continuous meteorological data acquired at sea provide detailed information on the patterns and trends of the relative humidity above the lake present climatic conditions allow the dead sea water to evaporate down to a water activity of 0 50 corresponding to the lowest air humidity measured over the lake this water activity falls in the range of halite precipitation while carnallite precipitation starts somewhat lower a h 2 o 0 49 our dynamic model predicts that for air humidity as low as 50 reflecting present climate conditions the dead sea level may drop to as low as 500 m i e 500 m below mean sea level at that point the lake will have a volume of 88 km 3 and a surface area of 526 km 2 for the sake of comparison at the beginning of 1977 after the southern basin of the dead sea was separated from the northern basin the level of the lake was 402 m its volume was 146 km 3 and its surface area was 815 km 2

reconstructing low levels of lake lisan by correlating fan delta and lacustrine deposits abstract reconstruction of paleo shorelines of lake lisan the late pleistocene precursor of the dead sea is based on sequence stratigraphy of fan delta and lacustrine deposits that are exposed at the perazim valley southwest of the dead sea the shoreline sediments are physically correlated with lacustrine aragonites their ages are determined by u series dating to establish a lake level curve for the time interval between 55 and 35 kyr during most of this period lake lisan was at a relatively low level which fluctuated between 280 and 290 m below sea level m bsl the minimum lake stand 330 m bsl was reached at 47 kyr and lasted for 3 4 kyr this episode is marked by a depositional hiatus in the section and formation of an erosional channel the studied period correlates with the global marine isotope stage 3 the low stand of lake lisan during most of this period indicates relative dry climatic conditions in the region

geochemical identification of fresh water sources in brackish groundwater mixtures the example of lake kinneret sea of galilee israel abstract fresh waters that dilute brines are considered to have a negligible effect on the ion ratios of the resultant mixture we show that the major element composition of the fresh end member can be deduced from the chemical composition of the mixed waters that composition then can be used to differentiate between different neighboring carbonate aquifers which supply the water this is demonstrated for the fuliya and tabgha saline springs located on the northwestern shore of lake kinneret sea of galilee israel at these springs shallow fresh groundwater mixes with brines from deep aquifers seven saline springs and wells located at the fuliya and tabgha blocks were sampled over a year and 32 eastern galilee fresh springs and wells were sampled as representatives of the fresh water end member all samples were analyzed for major and minor ions the saline spring data were used to construct mixing lines followed by their extrapolation to low concentrations in order to derive the ion chloride ratio characterizing the fresh component we constructed ion cl vs cl curves projection of the composition of fresh water on the calculated curve was used to identify a certain fresh water source as a possible end member results indicate that the composition of the water feeding the fuliya springs is different from that at tabgha reflecting interactions with different rocks in each basin the major fresh water end member diluting the fuliya brines is characterized by high mg cl and low sr cl ratios and is consistent with the composition of fresh groundwater in the dolomitic cenomanian and turonian aquifers widely exposed in the fuliya drainage basin the major fresh water end member diluting the tabgha brines on the other hand is characterized by low mg cl and high sr cl ratios and is consistent with the composition of fresh groundwater in the chalky eocene timrat fm and senonian outcrops although the chalky formations in the tabgha drainage basin are exposed over only 20 of the area they contribute most of the solutes to the fresh water end member rain flows over the chalky formations and then infiltrates into the bar kokhba eocene outcrops

strontium and sulphur isotope geochemistry of low temperature barite fluorite veins of the catalonian coastal ranges ne spain a fluid mixing model and age constraints sulphur and strontium isotope analyses from the low temperature barite fluorite veins of the catalonian coastal ranges ne spain reveal the nature and source of the ore forming fluids and constrain the ages of the mineralizations sulphur isotope values in the barite 34s 15 to 20 are similar to those of sulphates in nearly triassic jurassic evaporites 34s 11 to 19 87sr86sr isotopic composition ratios of barites and fluorites are 0 7094 0 7167 the variation of 87sr86sr within individual veins suggests that the sr had two different sources granites rocks in the hercynian basement and seawater or evaporites of triassic early jurassic age vein formation is modelled as a two component mixing process in which the s and sr isotopic composition of the end members change with time the observed difference in mean s and sr isotopic compositions among the veins is interpreted to reflect differences in mineralization age ore deposition occurred between 225 and 195 ma triassic to early jurassic in all cases except the berta mine which may be as young as miocene

from sandstone to carbonate hosted stratabound deposits an isotope study of galena in the upper moulouya district morocco the upper moulouya district displays three main types of lead ores in the hercynian domain 1 aouli vein type deposits hosted in the hercynian basement 2 zeida triassic sandstone hosted and 3 mibladen carbonate hosted stratabound and karstic mineralisations in the mesozoic cover lead and sulfur isotope studies indicate that the aouli vein type and zeida sandstone hosted stratabound mineralisations are formed by a mixing of two fluids one formed by the leaching of the aouli granite massif and the other by leaching of the saharian basement these deposits may correspond to the same triassic metallogenic event focused along fault systems or within permeable sandstone deep fluids were mobilised during the early extensional movements associated with the opening of the atlas rifting basin the mississippi valley type mibladen mineralisation is related to a distinct metallogenic event superimposed on the earlier one and represents a remobilization of earlier concentrations or a more recent leaching of the same sources but with a more pronounced contribution of the local organic matter the upper moulouya area demonstrates the close relationship between vein type and sandstone hosted lead zinc mineralisations and their major differences with mississippi valley type deposits

finite difference modelling of sandbox analogues compaction and detachment free deformation abstract the finite difference method for the modelling of hangingwall deformation above faults is applied to a wider range of problems close agreement has been achieved with the overall geometry of hangingwalls in sandbox analogue models of extensional faulting these results give insights into the dynamics involved and zones of faulting can be indicated using stretch rate and shear rate maps the controlling equations are then presented in a more general form which allows the effects of compaction to be included finally the method is shown to be applicable to vertical and horizontal velocities rather than speed and direction and this has been used to model the crust deforming by brittle failure at the top pure shear at the bottom and with a brittle ductile transition in between this system therefore allows modelling of crustal extension without the use of a detachment

the age and origin of the barite fluorite pbzn veins of the sierra del guadarrama spanish central system spain a radiogenic nd sr and stable isotope study fluorite and barite rich veins sulphides of the sierra del guadarrama spanish central system are usually hosted by hercynian granitoids zoned fluorites from one of these veins have a sm nd age of 145 18 ma this age is similar to the k ar ages obtained in other hydrothermal rocks of the spanish central system 156 152 ma and confirms the existence of an important hydrothermal event during the late jurassic probably related to extensional fracturing accompanying the opening of the north atlantic ocean the 87sr 86sr ratio found in fluorite and barite 0 7154 0 7207 is in most cases lower than that found in the host granitoids 0 7194 and 0 7209 suggesting more than one source of strontium this in turn supports previous models that involve mixing of two fluids during mineralization an ascending hot 300 c and low salinity fluid and a shallow cooler 100 c and more saline brine the ascending fluid probably reacted to a variable extent with the host granitoids and the most likely source for the shallow fluid derived from a marine evaporitic environment with a low 87sr 86sr ratio 0 7069 in the late jurassic the calculated end composition of the fluorites 8 8 to 7 6 as well as the 147sm 144nd variation found in this mineral 0 153 0 405 do not conflict with the mixing model although they can be largely explained by interaction of the ascending fluid with the host granitoids sulphur isotopic compositions of sulphides range between 3 4 and 0 8 and those of barites from 15 5 to 15 8 the near 34s value of the sulphides suggests that their sulphur was derived from the hydrothermal leaching of the granitoids by the ascending fluid the 34s value of barite is consistent with upper jurassic marine sulphate as the source of sulphate in the shallow fluid the absence of equilibrium between reduced and oxidized sulphur species can be easily interpreted as a consequence of the short residence time of the mixed fluid in the open fractures at temperatures between 250 and loo c although no pre cretaceous sediments are found on this part of the iberian hercynian basement the data presented here support the existence of a shallow platform joining central spain with the iberian or the subbetic realm in late jurassic times

the salton sea scientific drilling project in march 1986 a research borehole called the state 2 14 reached a depth of 3 22 km in the salton sea geothermal system of southern california this was part of the salton sea scientific drilling project sssdp the first major i e multimillion dollar research drilling project in the u s continental scientific drilling program the principal goals of the project were to investigate the physical and chemical processes of a high temperature high salinity magmatically driven hydrothermal system the borehole encountered temperatures of up to 355 c and produced metal rich alkali chloride brines containing 25 wt of total dissolved solids the rocks penetrated exhibit metamorphism and ore genesis in action they show a progressive transition from unconsolidated lacustrine and deltaic sediments to hornfelses with lower amphibolite facies mineralogy accompanied by pervasive veins containing iron copper lead and zinc ore minerals the sssdp included an intensive program of rock and fluid sampling flow testing and downhole logging and scientific measurement the purpose of this paper is to introduce this special section of the journal of geophysical research on the sssdp to describe briefly the background of the project and the drilling and testing of the borehole to summarize the initial scientific results and to discuss how the lessons learned are applicable to future scientific drilling projects

holocene climate variability and cultural evolution in the near east from the dead sea sedimentary record abstract a comprehensive record of lake level changes in the dead sea has been reconstructed using multiple well dated sediment cores recovered from the dead sea shore interpreting the lake level changes as monitors of precipitation in the dead sea drainage area and the regional eastern mediterranean palaeoclimate we document the presence of two major wet phases 10 8 6 and 5 6 3 5 cal kyr bp and multiple abrupt arid events during the holocene the arid events in the holocene dead sea appear to coincide with major breaks in the near east cultural evolution at 8 6 8 2 4 2 3 5 cal kyr bp wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions suggesting a parallelism between climate and near east cultural development

effects of layering and anisotropy on fault geometry the geometry and orientation of faults are examined using several field examples of small scale 1 with dihedral angles usually of about 50 as predicted by the coulomb theory of failure in layered rocks the geometry of faults varies with the orientation of layering with respect to the stress field where 1 is approximately normal to layering or anisotropy conjugate faults also develop symmetrically about 1 where rocks have interbedded layers with different mechanical behaviours however faults tend to initiate orthogonal to the more brittle layers i e originate as extension fractures sub parallel to 1 but oblique to the less brittle layers as the fault steps through the layering pull aparts are developed which may reduce the dihedral angle where 1 is oblique c 25 75 to anisotropy one set of faults is developed at a high angle to layering with another at a low angle usually showing a ramp flat geometry large dihedral angles up to 90 may result and 1 does not bisect this angle where 1 is approximately parallel to layering two cases can be recognized where 3 is approximately normal to layering faults with layer parallel flats and contractional ramps develop where 2 is approximately normal to layering conjugate faults develop which are symmetrical about 1 the geometry resembling that in isotropic rocks these observations are in agreement with rock deformation experiments which show the strong effect of anisotropy on fault orientation but the observations incorporate the effects of layering of materials with different deformation characteristics

u th dating of lake lisan late pleistocene dead sea aragonite and implications for glacial east mediterranean climate change u series dating can be an effective means to obtain accurate and precise ages on quaternary carbonates however most samples require a correction for u and th in admixed detritus this complication is often addressed through generation of u th isochrons requiring analyses of several coeval samples in addition presence of water derived hydrogenous th in the carbonate can cause inaccuracies in isochron ages this study reports a high resolution u series chronology of sediments deposited by lake lisan the last glacial precursor of the dead sea the strategy employed combines multiple measurements from a few stratigraphic heights and fewer analyses from many heights in a single described and measured section the resulting chronology is based on ages at 22 heights in a 40 m thick section covering the interval of 70 14 calendar ka bp the effects of admixed detritus are evaluated using trace elements nearly pure aragonite samples indicated by very low abundances of insoluble elements such as nb and zr were found to contain hydrogenous th which causes the uncorrected u 230th age of a modern sample to be 2 5 ka nevertheless accurate ages have been obtained by correcting for the detrital and aqueous interferences the resulting ages are in stratigraphic order and their accuracy is evidenced by consistency of lisan formation u series and 14c ages with the coral based calendar radiocarbon age calibration the u th ages provide a context to unravel the limnological history of lake lisan boundaries between the lower middle and upper stratigraphic units correspond to the mis 4 3 and 3 2 transitions respectively during mis 2 and 4 the lake generally showed a stable two layer configuration and a positive fresh water balance reflected by deposition of laminated aragonite detritus dry intervals during mis 2 and 4 are indicated by thick gypsum layers and an inferred depositional hiatus which are temporally associated with heinrich events h1 at 17 ka and h6 at 65 ka respectively during mis 3 the lake level was unstable with intermittent dry periods indicated by abundant clastic layers and a significant hiatus between 43 49 ka clastic layers are associated with dansgaard oeschger events during mis 3 and indicate lake level declines during abrupt northern hemisphere warmings overall the climate of the eastern mediterranean region shows a strong linkage to the northern hemisphere climate with increasing lake size and stability during cold periods and fluctuations and dessication during warmings and heinrich events

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

recurrence pattern of holocene earthquakes along the dead sea transform revealed by varve counting and radiocarbon dating of lacustrine sediments abstract a high resolution holocene seismic history of the dead sea transform dst is established from laminated sedimentary cores recovered at the shores of the dead sea radiocarbon dating and annual laminae counting yield excellent agreement between disturbed sedimentary structures identified as seismites and the historical earthquake record all recent and historical strong events of the area were identified including the major earthquakes of a d 1927 1837 1212 1033 749 and 31 b c the total of 53 seismites recognized along the entire holocene profile indicate varying recurrence intervals of seismic activity between a few and 1000 years with a conspicuous minimum rate at 2100 31 b c and a noticeable maximum during the past six to eight centuries most of the epicenters of the correlated earthquakes are situated very close to the dead sea within 150 km or up to 400 km north of it along the dst between 1000 b c and a d 1063 and from a d 1600 to recent time the epicenters are all located on the northern segment of the dst whereas prior to 1000 b c and between a d 1000 and 1600 they appear to scatter along several segments of the dst we establish how the local intensity exerts a control on the formation of seismites at historically estimated intensities greater than vii all well documented earthquakes are correlated whereas at intensities smaller than vi none are matching the periods with enhanced earthquake rate along the dst correlate with those along the north anatolian fault as opposed to the intervening east anatolian fault this may indicate some elastic coupling on plate boundary scale that may also underlie escape and extrusion tectonics typical of continental collision

southward migration of rain tracks during the last glacial revealed by salinity gradient in lake lisan dead sea rift abstract the paleosalinity of the late pleistocene lake lisan during its highstand between 27 000 and 15 000 years b p is evaluated from biological data diatoms cyanobacteria fish and ostracods and chemical data sr ca and na ca ratios in authigenic aragonite the data indicate a zone of maximum salinity at the southern part of the lake in the vicinity of the present dead sea basin while most of the freshwater input to lake lisan originated from the jordan river in the north and runoff from the eastern and western parts of the drainage basin our analysis indicates a significant additional contribution from a southern freshwater source at present the contribution of the southern source to the dead sea is minimal hence it appears that in addition to the prevailing rain originating from the mediterranean an additional southern source of rain was more active during the last glacial than today this may be explained by migration of rain tracks whose moisture originated in the atlantic from the mediterranean southwards

gypsum as a monitor of the paleo limnological hydrological conditions in lake lisan and the dead sea the isotopic composition and mass balances of sources and sinks of sulfur are used to constrain the limnological hydrological evolution of the last glacial lake lisan 70 14 ka bp and the holocene dead sea lake lisan deposited large amounts of primary gypsum during discrete episodes of lake level decline this gypsum which appears in massive or laminated forms displays 34s values in the range of 14 28 in addition lake lisan s deposits the lisan formation contain thinly laminated and disseminated gypsum as well as native sulfur which display significantly lower 34s values 26 to 1 and 20 to 10 respectively the calculated bulk isotopic compositions of sulfur in the sources and sinks of lake lisan lacustrine system are similar 34s 10 indicating that freshwater sulfate was the main source of sulfur to the lake the large range in 34s found within the lisan formation 26 to 28 is the result of bacterial sulfate reduction bsr within the anoxic lower water body the monimolimnion and bottom sediments of the lake precipitation of primary gypsum from the ca chloride solution of lake lisan is limited by sulfate concentration which could not exceed 3000 mg l the upper gypsum unit deposited before ca 17 15 ka is the thickest gypsum unit in the section and displays the highest 34s values 25 28 yet our calculations indicate that no more than a third of this unit could have precipitated directly from the water column this implies that during the lake level decline that instigated the precipitation of the upper gypsum unit significant amounts of dissolved sulfate had to reach the lake from external sources we propose a mechanism that operated during cycles of high low stands of the lakes that occupied the dead sea basin during the late pleistocene during high stand intervals i e marine isotopic stages 2 and 4 lake brine underwent bsr and infiltrated the lake s margins and adjacent strata as lake level dropped these brines carrying 34s enriched sulfate were flushed back to the shrinking lake and replenished the water column with sulfate thereby promoting massive gypsum precipitation the holocene dead sea precipitated relatively small amounts of primary gypsum mainly in the form of thin laminae 34s values of these laminae and disseminated gypsum are relatively constant 15 0 7 and are close to present day lake composition this reflects the lower supply of freshwater to the lake and the limited bsr activity during the arid holocene time and possibly during former arid interglacials in the levant

modeling radium distribution in coastal aquifers during sea level changes the dead sea case abstract we present a new approach to studying the behavior of radium isotopes in a coastal aquifer in order to simulate radium isotope distributions in the dynamic flow field of the dead sea aquifer a multi species density dependent flow model sutra ms was used field data show that the activity of 226 ra decreases from 140 to 60 dpm l upon entering the aquifer from the dead sea and then further decreases linearly due to mixing with ra poor fresh water on the other hand an increase is observed in the activity of the shorter lived isotopes up to 52 dpm l 224 ra and 31 dpm l 223 ra which are relatively low in dead sea water up to 2 5 dpm l 224 ra and 0 5 dpm l 223 ra the activities of the short lived radium isotopes also decrease with decreasing salinity which is due to the effect of salinity on the adsorption of radium the relationship between 224 ra and salinity suggests that the adsorption partition coefficient k is linearly related to salinity simulations of the steady state conditions show that the distance where equilibrium activity is attained for each radium isotope is affected by the isotope half life k and the groundwater velocity resulting in a longer distance for the long lived radium isotopes k affects the radium distribution in transient conditions especially that of the long lived radium isotopes the transient conditions in the dead sea system with a 1 m yr lake level drop together with the radium field data constrains k to be relatively low 226 ra cannot be explained by adsorption and it is better explained by removal via coprecipitation probably with barite or celestine