high resolution 40ar 39ar dating of the oldest oceanic basement basalts in the western pacific basin 1 we report new 40ar 39ar ages for the oldest pacific oceanic floor at ocean drilling program site 801c in the pigafetta basin and site 1149d close to the izu bonin subduction zone in the nadezhda basin these ages were determined by applying high resolution incremental heating experiments including 15 30 heating steps to better resolve the primary argon signal from interfering alteration signatures in these low potassium ocean crust basalts combined with previous results from pringle 1992 for site 801b and 801c we arrive at a multistage history for the formation of the pigafetta ocean crust the oldest part of the pacific plate was formed at the spreading ridges at 167 4 1 4 3 4 ma n 2 2 internal absolute error offering an important calibration point on the geological reversal timescale grts since it represents the old end of the mesozoic magnetic anomalies this mid ocean ridge basalt sequence however is overlain by more tholeiites and alkali basalts that were formed 7 3 1 5 myr later around 160 1 0 6 ma n 7 2 internal error the older age group is confirmed independently by radiolarian ages ranging from late bajocian to middle bathonian 167 173 ma bartolini and larson 2001 and by profound differences in the structural characteristics of this basement section pockalny and larson 2003 thin layers comprising hydrothermal deposits separate these sequences which in addition to the difference in isotopic age show distinct major and trace element compositions this indicates that key volcanic and hydrothermal activity took place 400 600 km away from the spreading ridges on the basis of a jurassic 66 km myr half spreading rate in the pacific it remains unclear if these processes were active continuously after the initial formation of the pacific oceanic crust but all our observations seem to point to an episodic history site 1149d gives another important calibration point on the grts of 127 0 1 5 3 6 ma n 1 2 internal absolute error for anomaly m12 that is slightly younger when compared to current timescale compilations 134 2 2 1 ma gradstein et al 1995 this might suggest that the dated basalt from site 1149d does not represent the age of the ocean crust formed at its ridge axis it may also be part of the early cretaceous intraplate events that have produced dolerite sills in the pacific crust at sites 800 and 802 around 114 126 ma

downhole magnetic measurements of odp hole 801c implications for pacific oceanic crust and magnetic field behavior in the middle jurassic 1 downhole horizontal and vertical magnetic field measurements within the 474 m thick jurassic crustal section drilled at odp hole 801c in the western pacific show anomalies that are in phase indicating that this site formed in the southern hemisphere and moved across the paleoequator to its present location at 18 6 n the inclination computed from the horizontal and vertical anomaly logging data varies significantly downhole and can be explained by progressive rotation of the lava sequence as it is buried during accretion this is compatible with the observed dips in the formation micro scanner fms data which show up to 42 of rotation toward the fossil spreading axis we restore the magnetic inclination to prerotated values and obtain an estimated pretilt inclination of 39 9 6 6 corresponding to a paleolatitude of 22 7 5 s the magnetic logging data document six polarity units within the drilled volcanic extrusive crust the upper 132 m thick logged section of lavas contains four polarity units which apparently formed 7 myr after the formation of the underlying basement the lower 212 m logged section of the hole is reversely magnetized with an intervening normal polarity zone more than one reversal downhole would indicate a rapid reversal rate given the time it takes to form the extrusive section of oceanic crust 45 000 years at a fast spreading rate of 66 km myr previous results from a contemporaneous section in spain suggest rapid reversals throughout the late bajocian early bathonian stage 170 165 ma nevertheless the complicated formation history prevents quantification of the geomagnetic reversal rate for the 801c crustal section

jurassic magnetostratigraphy 2 middle late oxfordian of aguilon iberian cordillera northern spain abstract a reproducible magnetic polarity pattern has been obtained from four overlapping stratigraphic sequences of ammonite rich gray pelagic limestones spanning part of the middle and late oxfordian g transversarium toe bimammatum ammonite zones progressive thermal demagnetization removed a present field overprint fold tests both between and within outcrops are positive the mean direction of magnetization is 322 45 95 6 which implies a paleolatitude of 26 n frequent changes of polarity were observed the magnetostratigraphic sequence contains the ammonite zones subzones and horizons of the tethyan faunal realm using the reference horizons provided by this detailed ammonite zonation the polarity zones can be readily correlated among all sections the composite polarity pattern is predominantly of reversed polarity punctuated by a number of relatively shorter duration normal polarity intervals in order to compare this sequence to that of the marine magnetic anomalies we have revised the age estimates for the pre m25 marine magnetic normaly pattern according to the most recent time scale based on those ages the sedimentary record at aguilon suggests a much greater frequency of polarity changes than does either model derived from the two sets of marine magnetic anomalies of this time this sedimentary record probably is a truer approximation of the actual geomagnetic polarity history because of the continuity of sedimentation in these sections and the inherent ambiguities involved in determining a polarity pattern from the very low amplitudes that everywhere characterize this part of the marine record

origin of the pacific jurassic quiet zone understanding the marine magnetic anomaly record is critical for constructing realistic geodynamo models of global geomagnetic field polarity reversal mechanisms and long term geomagnetic field behavior one of the least understood portions of the marine magnetic anomaly record is also the oldest part of the record the jurassic quiet zone jqz where anomalies become weak and difficult to correlate the reason for the existence of the jqz is unclear it has been suggested that the jqz is a true polarity superchron similar to the cretaceous normal superchron continental magnetostratigraphic studies have suggested that the jqz is a period of rapid polarity reversal of low field intensity or both we show results of a deep tow survey of pacific jurassic crust that confirms the existence of magnetic anomalies within the jqz we tie ocean drilling program hole 801c 167 4 ma into the record and show that seafloor spreading magnetic anomalies are present around the hole and extend to 170 ma crust we find a rise in reversal rate with increasing age with reversal rates over 10 rev m y at 160 ma and at 167 ma anomaly amplitudes decrease in the record from 155 ma until 162 ma where low amplitude anomalies are difficult to correlate prior to 167 ma anomalies regain amplitude and remain strong until the end of our record at 170 ma the jqz thus appears to be a combination of low amplitude magnetic anomalies combined with rapid field fluctuations which could be due to either intensity or polarity changes

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

hydrochemistry of aquifers in the southern dead sea area southern jordan the demand for water resources in the area south of the dead sea due to continued development especially at the arab potash company apc works necessitates that water quality in the area be monitored and evaluated based on the local geology and hydrogeology the objective of this paper is to provide information on the past and present status of the main aquifers under exploitation or planned for future development two main aquifers are discussed the safi water field presently being operated and the dhiraa water field which is being developed the aquifer developed in the safi water field is shallow and fed by the hasa fault system which drains a significant portion of the karak mountains this aquifer seems to be well replenished within the core where no obvious long term degradation in water quality can be identified however in the low recharge areas within the distal portions of the alluvial fan there has been a degradation in water quality with time the degradation is caused by the dissolution of the lisan marl which is present at the outskirts of the fan system based on hydrochemistry of water in the wells the dhiraa field is a deep 800 950 m aquifer drilled specifically for the extraction of brackish water present in the kurnub aquifer available data indicate that there are at least three distinct water types within this field these water types are variable in quality and there may be potential for mixing of these waters thus affecting the quality of the freshest waters presently available tritium and oxygen isotope analysis indicate that the water is old and possibly nonrenewable

advanced insights into magmatism and volcanism of the mozambique ridge and mozambique basin in the view of new potential field data summary a new plate tectonic model is presented which describes the emplacement of the mozambique ridge off southeast africa as the result of long lasting volcanic activity 140 122 ma during the initial opening between africa and antarctica thus an oceanic origin for the mozambique ridge is proposed this model is based on a new and systematic high resolution magnetic anomaly data set acquired across the mozambique ridge and throughout the mozambique basin data from the mozambique basin allow the identification of mesozoic magnetic anomalies from m0r to m26 124 61 155 3 ma with previously unmatched accuracy small scale fracture zones are recognized by offsets of magnetic anomalies in the westernmost part of the basin additionally a bend in the major fracture zones f and e between m17r and m18n 142 84 144 04 ma and a recognized sinusoidal change in spreading direction with an amplitude of about 15 indicate that the basin experienced several small scale changes in spreading direction through time a maximum change in spreading direction to almost 0 at around m11n 135 69 ma is followed by a short lived increase in spreading half rate from 23 5 km ma 1 to about 27 5 km ma 1 in the time frame from m10r to m9n 134 30 132 83 ma we propose that this is related to the initial opening of the south atlantic ocean represented by the onset of seafloor spreading between the falkland plateau and africa in the conjugate georgia and natal basins across the mozambique ridge high amplitude magnetic anomalies at major structural boundaries suggest that the different plateaus of the ridge were formed at different times a simple 2 d gravity and magnetic model for the ridge supports the hypothesis of multiple volcanic episodes which formed the ridge though long lasting volcanic activity between about 140 and 122 ma together with new and verified rotation parameters from the mozambique basin and its conjugate the riiser larsen sea antarctica a series of plate tectonic reconstructions are presented which demonstrate when and how the different parts of the ridge evolved through time

recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system southwest of north china plain many cities around the world are developed at alluvial fans with economic and industrial development and increase in population quality and quantity of groundwater are often damaged by over exploitation in these areas in order to realistically assess these groundwater resources and their sustainability it is vital to understand the recharge sources and hydrogeochemical evolution of groundwater in alluvial fans in march 2006 groundwater and surface water were sampled for major element analysis and stable isotope oxygen 18 and deuterium compositions in xinxiang which is located at a complex alluvial fan system composed of a mountainous area taihang mt alluvial fan and yellow river alluvial fan in the taihang mountainous area the groundwater was recharged by precipitation and was characterized by ca hco3 type water with depleted 18o and d mean value of 8 8 18o along the flow path from the mountainous area to taihang mt alluvial fan the groundwater became geochemically complex ca na mg hco3 cl so4 type and heavier 18o and d were observed around 8 18o before the surface water with mean 18o of 8 7 recharged to groundwater it underwent isotopic enrichment in taihang mt alluvial fan chemical mixture and ion exchange are expected to be responsible for the chemical evolution of groundwater in yellow river alluvial fan transferred water from the yellow river is the main source of the groundwater in the yellow river alluvial fan in the south of the study area and stable isotopic compositions of the groundwater mean value of 8 8 18o were similar to those of transferred water 8 9 increasing from the southern boundary of the study area to the distal end of the fan the groundwater underwent chemical evolution from ca hco3 na hco3 to na so4 a conceptual model integrating stiff diagrams is used to describe the spatial variation of recharge sources chemical evolution and groundwater flow paths in the complex alluvial fan aquifer system

geology and hydrochemistry of the deep sandstone aquifers of jordan the deep sandstone aquifer complex of jordan consists of hundreds of meters of paleozoic to lower cretaceous sandstones that extend from the saudi arabian border in the south up to northern jordan in the south this aquifer is known as the disi aquifer and is near the surface well understood and heavily exploited toward the north thick accumulations of later mesozoic and cenozoic sedimentary sequences cover the complex the depth of the aquifer in this area makes it less viable as a water resource thus little is known about its origin movement and chemical evolution a number of exploration and production wells have penetrated this aquifer throughout central and northern jordan the data from these wells can help to draw a reasonable understanding about this aquifer and its water most of the aquifer is under artesian pressure and the piezometric head data point to a general flow north with drainage of the aquifer into the dead sea rift basin stable isotopes show that the water differs from modern meteoric water in the region and thus is possibly late pleistocene in age the water is slightly brackish and according to jordanian standards it can be used for drinking under certain conditions geochemical modeling shows that here is no evidence that the salinity is primarily the result of prolonged water rock interactions but more likely the result of mixing with possibly trapped connate water throughout the complex

cretaceous anomalous subsidence and its response to dynamic topography in the songliao basin northeast china to understand the formation mechanisms and evolution of the songliao basin we applied backstripping and strain rate inversion methods to 20 wells and reinterpret two seismic sections in the songliao basin the obtained data were used to reconstruct the tectonic subsidence history and further assess the potential subsidence mechanisms of this area the predicted post rift subsidence based on the uniform stretching model that followed earlier lithospheric thinning events was much lower than the subsidence provided by backstripping the anomalous subsidence during the post rift stage was between 200 m and 800 m in the songliao basin and the depocenter of anomalous subsidence moved eastward between ca 110 and 80 ma before returning to the west between ca 80 and 65 ma regional variations in the subsidence rates suggest a possible deficit in the negative buoyancy mantle loading that is induced by the sinking slab beneath the songliao basin in addition the anomalous post rift subsidence was primarily driven by downward drag pressure from the subducting western izanagi slab and asthenospheric mantle flow beneath the songliao basin the basement rifting in the songliao basin during the early cretaceous and the normal faulting that occurred during the post rift stage resulted in a secondary contribution to the anomalous post rift subsidence unlike the songliao basin several early cretaceous rift basins south of the yanshan belt were only filled during the syn rift subsidence and the anomalous post rift uplift of the yanshan belt was driven by deep mantle flow

high resolution magnetic signature of active hydrothermal systems in the back arc spreading region of the southern mariana trough high resolution vector magnetic measurements were performed on five hydrothermal vent fields of the back arc spreading region of the southern mariana trough using shinkai 6500 a deep sea manned submersible a new 3 d forward scheme was applied that exploits the surrounding bathymetry and varying altitudes of the submersible to estimate absolute crustal magnetization the results revealed that magnetic anomaly derived absolute magnetizations show a reasonable correlation with natural remanent magnetizations of rock samples collected from the seafloor of the same region the distribution of magnetic anomaly derived absolute magnetization suggests that all five andesite hosted hydrothermal fields are associated with a lack of magnetization as is generally observed at basalt hosted hydrothermal sites furthermore both the pika and urashima sites were found to have their own distinct low magnetization zones which could not be distinguished in magnetic anomaly data collected at higher altitudes by autonomous underwater vehicle due to their limited extension the spatial extent of the resulting low magnetization is approximately 10 times wider at off axis sites than at on axis sites possibly reflecting larger accumulations of nonmagnetic sulfides stockwork zones and or alteration zones at the off axis sites

climatological signals of the paleogroundwater in jordan abstract isotopic data on paleowaters from various groundwater basins in jordan have been compiled in order to document the various types in terms of age and 18 o d relationships the data indicate that the various types of water can be correlated with the various climatic pluvial phases which have affected the area since the beginning of the wurm period thus the oldest waters 30 ka have d values d d 8 18 o which range from 0 5 to 9 middle to late wurm waters from 8 6 to 17 middle holocene from 13 to 18 and modern precipitation from 21 to 30 moreover the slopes of the regression lines which describe the various suites of data have been decreasing from 9 3 for the oldest waters 8 1 for middle to late wurm waters 6 4 for middle holocene water and 6 2 for modern precipitation the trends of the groundwater isotopic contents with time suggest that although pluvials are part of the climatic cycles in the region there seems to be a significant change in the climatic conditions at the source of the moisture from one pluvial period to the next this change suggests lower relative humidity over the water masses i e the mediterranean sea through time moreover the slopes of the regression lines suggest increasing re evaporation before recharge through time also suggesting lower relative humidity in the areas of precipitation the data suggest that the timing of recharge of waters in the area can be roughly estimated based on the oxygen and deuterium isotopic signature

pre cretaceous tectonic evolution of the pacific plate and extension of the geomagnetic polarity reversal time scale with implications for the origin of the jurassic quiet zone abstract linear magnetic anomalies resulting from seafloor spreading were mapped in the vicinity of the magnetic bight in the western pacific ocean new aeromagnetic data allowed the magnetic bight to be more accurately mapped from m21 to m28 and enabled the identification of low amplitude magnetic lineations in the jurassic quiet zone these lineations were formed by magnetic field reversals prior to m29 a revised jurassic geomagnetic polarity reversal time scale was constructed with nineteen reversals older than m29 numbered m30 m38 these reversals extend the record of geomagnetic polarity back in time by approximately 8 ma and are important constraints on the origin of the quiet zone in particular they imply that the jurassic was not a period of constant normal polarity an explanation offered by some authors further they cast doubt on a model of systematically decreasing geomagnetic field strength with increasing age during this period the early history of the northern pacific plate and pacific farallon izanagi p f i triple junction was traced by mapped magnetic isochrons the pacific plate seems to have evolved from a small plate that formed near the phoenix farallon izanagi triple junction about 180 188 m y ago at approximately 17 n 160 e in present coordinates until m21 time the evolution of the northern pacific plate was relatively simple and the p f i triple junction migrated north northwest with respect to the pacific

geomagnetic polarity reversal model of deep tow profiles from the pacific jurassic quiet zone the jurassic magnetic quiet zone jqz contains magnetic lineations but their low amplitudes make correlation and interpretation difficult part of the problem is the separation of source and sensor for old deep ocean crust we increased anomaly amplitudes by collecting magnetic data along two deep tow profiles over western pacific jqz lineations a magnetic polarity reversal timescale was constructed by matching deep tow anomalies with a simple rectangular block magnetization model for oceanic crust the polarity sequence covers 11 m y 156 167 5 ma and contains 88 pre m29 polarity chrons extending to chron m41 a limitation of this model is its poor representation of the oldest anomalies upward continued to sea level on deep tow profiles these anomalies have both long and short wavelength components but only the latter are easily modeled on a datum close to the source an alternative polarity model was constructed to match the anomalies upward continued to sea level this model retains only 44 of the deep tow model polarity chrons because of short wavelength attenuation by upward continuation because of the inferred periods and magnetization contrasts we think many of the short wavelength anomalies represent paleofield intensity fluctuations in contrast polarity reversals have been documented by prior magnetostratigraphic work for the younger part of the timescale covered by our model thus our data may show a transition from a geomagnetic field behavior dominated by intensity fluctuations to one dominated by reversals

the interaction of two major old water bodies and its implication for the exploitation of groundwater in the multiple aquifer system of the central and northern negev israel abstract in the beer sheva region of the negev desert the only significant fresh groundwater is contained within the judea group carbonate aquifer it is found that this aquifer holds two distinctly different old water bodies one such groundwater body has evolved in equilibrium with the carbonate aquifer rocks after being recharged during the holocene in the hebron mountains north of the study area at present modern recharge as denoted by the tritium and radiocarbon contents is very minor a subtle piston effect generated by contemporary replenishment is discussed in representative hydrographs in beer sheva wells another groundwater body identified in the judea group aquifer derives from the underlying kurnub group aquifer the regional artesian kurnub group aquifer nubian sandstone contains an older and brackish groundwater body which has been recharged in sinai during pleistocene pluvials faulting in the beer sheva region facilitated hydrologic contact between the two aquifers exploitation of the judea group has released confining pressures and resulted in the intrusion of kurnub group water into the overlying judea group carbonate aquifer this process is most significant in those wells drilled close to major faults where salinity increases with pumping the intruding water originating from the kurnub group sandstone aquifer has not yet equilibrated chemically with the carbonate host the low ph and high temperatures that have been encountered indicate continuing and very recent intrusion in the beer sheva area in the absence of direct significant modern recharge as determined from tritium and 14 c values all waters should be considered as paleowaters that are being mined a complete revision of the hydrologic concept by which the multiple aquifer system can be exploited is required to take into account the fact that the fresh judea group groundwater is actually an old holocene water body intruded by brackish and older pleistocene water along fault zones

jurassic magnetostratigraphy 3 bathonian bajocian of carcabuey sierra harana and campillo de arenas subbetic cordillera southern spain abstract four sections in majocian bathonian middle jurassic pelagic limestone with standard ammonite zonation have yielded magnetic polarity sequences magnetic directions in these red to white limestones were obtained by thermal demagnetization and were stable from about 300 c to in excess of 450 c the polarity patterns indicate that the majority of the bajocian and bathonian is characterized by quite frequent reversals of the magnetic field lengthy periods of constant polarity particularly constant normal polarity were not observed the average frequency of reversals is about 6 per ammonite zone which roughly may be interpreted as a frequency of a reversal every 260 000 years a rate comparable to that of the miocene pliocene paleolatitudes of these sites 25 28 are about 10 south of their present positions variable clockwise block rotations within the subbectic region have rotated these sites relative to stable iberia

oxfordian magnetostratigraphy of poland and its correlation to sub mediterranean ammonite zones and marine magnetic anomalies abstract a nearly continuous magnetostratigraphic polarity pattern was compiled from several ammonite zoned carbonate successions of southern poland and from a composite magnetostratigraphy from the iberian range of spain the array of sections spans the middle two thirds of the oxfordian within the sub mediterranean province cordatum through bifurcatus ammonite zones the average paleopole calculated from eight of these polish sections is at 78 5 n 184 9 e p 2 6 m 3 5 the sub mediterranean polarity pattern is consistent with an independent polarity pattern derived from the boreal realm sections of the british isles and improves the inter correlation between these faunal realms cycle stratigraphy published for these ammonite subzones from southern france enabled temporal scaling of the polarity pattern thereby facilitating correlation to marine magnetic anomalies m28 through m33 as modeled from deep tow magnetometer surveys in the western pacific the bases of the middle and upper oxfordian substages as defined in the sub mediterranean zonation in poland correspond approximately to chrons m33 and m29 of that pacific m sequence model

structural evolution of preexisting oceanic crust through intraplate igneous activities in the marcus wake seamount chain multichannel seismic reflection studies and seismic refraction surveys with ocean bottom seismographs in the marcus wake seamount chain in the northwestern pacific ocean reveal p wave velocity structures of hot spot origin seamounts and adjacent oceanic crust inside the seamounts are central high velocity 6 5 km s structures extending nearly to the top that may indicate intrusive cores thick sediment layers up to 4 km with p wave velocities of 4 5 km s have accumulated on seafloor that predates seamount formation downward crustal thickening of up to 2 km was documented beneath a large seamount cluster but thickening was not confirmed below a small seamount cluster volume ratios of an intrusive core to a seamount body are 15 20 indicating that most of the supplied magma was consumed in forming the thick sedimentary and volcaniclastic layer constituting the seamount flanks underplating and downward crustal thickening may tend to occur when second or later intrusive cores are formed in a seamount p wave velocities in the lowest crust and in the uppermost mantle below the seamount chain are 0 1 0 2 km s higher and 0 3 0 5 km s lower respectively than velocities below oceanic crust we explain this difference as a result of sill like intrusion of magma into the lower crust and uppermost mantle reflected waves observed at offsets 200 km are from mantle reflectors at depths of 30 45 km and 55 70 km the shallower reflectors may indicate structures formed by intraplate igneous activities and the deeper reflectors may correspond to the lithosphere asthenosphere boundary

magnetostratigraphy of the middle upper jurassic sedimentary sequences at yanshiping qiangtang basin china a series of important geological events occurred in the tibetan plateau area during the jurassic such as the collision of the lhasa and qiangtang terranes the closure of the meso tethyan ocean the opening of the neo tethyan ocean and the cessation of the mega monsoon the similar to 3000 m thick jurassic sedimentary sequence in the qiangtang basin on the central tibetan plateau which is called the yanshiping ysp group recorded these geological events however the chronology of the sequence is surprisingly poorly constrained here we perform a detailed palaeomagnetic analysis on the similar to 1060 m thick middle and upper portions of the ysp group the xiali and suowa formations in the ysp section of the eastern qiangtang basin three bivalve zones at stratigraphic intervals of similar to 40 140 640 800 and 940 1040 m are identified which yield a bathonian callovian age for the lower xiali fm a callovian oxfordian age for the lower suowa fm and an oxfordian kimmeridgian age for the upper suowa fm a total of 544 oriented palaeomagnetic samples were collected from the section by combining thermal and alternating field demagnetizations clear characteristic remanent magnetization chrm directions are isolated for most of the samples the robust chrm directions pass fold and reversals tests which support the primary nature of the chrms and yield a palaeopole at 76 8a degrees n 297 2a degrees e dp 2 2a degrees dm 3 7a degrees a total of 27 normal and 26 reversed polarity zones were successfully recorded in the section combined with fossil age constraints results suggest that the section is plausibly composed of a callovian early kimmeridgian age sedimentary sequence

saline groundwater in israel its bearing on the water crisis in the country abstract one of the major causes for the deterioration of water quality bearing heavily on the water crisis in israel is the ongoing contamination of its water resources by saline water bodies the present paper reviews the geochemical processes forming saline water lists and explains certain chemical and isotopic parameters which enable understanding these processes and describes the saline groundwater bodies and various salinization phenomena occurring in the country s various aquifers deterioration of groundwater in israel is caused by numerous natural processes such as encroachment of sea water migration of connate highly pressurized brines penetrating into fresh groundwater by subsurface dissolution of soluble salts originating in surrounding country rocks and by water rock interaction in addition to sea water two saline water bodies were identified as the main factors causing salinization of fresh groundwater a ca chloride brines encountered in the jordan dead sea rift valley in various parts of the negev and of the coastal plain and b na chloride saline water identified in the subsurface of the negev and in the southern part of the coastal plain intensive exploitation of groundwater in israel has disturbed the natural equilibrium which prevailed between fresh and saline water the newly established groundwater flow regimes have facilitated the migration of saline water bodies their participation in the active hydrological cycle and the progressive contamination of fresh groundwater these processes which were not anticipated by planners and water resources managers emphasize that large scale groundwater exploitation was undertaken without giving sufficient consideration to the occurrence and subsurface migration of saline water and brines

a new look at the chemical and hydrological evolution of the dead sea abstract hydrological models of the dead sea ds indicate that subrecent equilibrium conditions have been maintained by input and evaporation of about 1600 106 m3 yr of surface waters recent diversions of the headwaters have led to a drop of about 0 95 m yr suggesting that waters stored in adjacent aquifers are being drained at a rate of about 200 106 m3 yr chemical modeling of the ds indicates that the chemical evolution of the waters can be explained by a simple mixture and evaporation model this model requires the input of 50 106 m3 yr of hot spring waters similar to those emanating at zohar and evaporation factors of about 50 this model suggests that the ds salts have accumulated over the past 5000 years this indicates that the initiation of the present ds was triggered by the onset of the mid holocene pluvial stage as well as by draining of the freshwater lakes present upstream from the lake review of the data of the springs responsible for the chemical nature of the ds suggests that these waters are of meteoric continental origin and that it is likely that these waters have experienced deep circulation in the rift system before discharging at the surface due to convective forces operating in the rift

geological and seismological field observations in the epicentral region of the 27 september 2003 mw 7 2 gorny altay earthquake russia abstract the m w 7 2 altay chuya earthquake of 27 september 2003 that occurred in gorny altay southern siberia russia is the first event of this magnitude to occur in the region in historical time the 60 km long surface ruptures of the right lateral event follow a preexisting but previously unmapped northwest southeast fault trace along the northern slope of the north chuya range additional secondary coseismic ruptures were also observed on adjacent faults the earthquake triggered landslides rock falls and liquefaction as well as destruction of houses and other construction in the kurai and chuya basins the 2003 event induced several thousand aftershocks during the years after the mainshock that formed a cloud of epicenters aligned with the main coseismic rupture trace the local earthquake tomography of the event source shows the correspondence between the fault trace at the surface and a long narrow low velocity zone penetrating vertically into the crust down to a depth of 15 17 km if the three dimensional 3d geometry of the aftershock cloud approximates the ruptured fault plane at first order then the fault is mainly vertical or slightly southwest dipping confirming the right lateral reverse kinematics of the fault compatible with northeast southwest shortening accommodated by a combination of right lateral and thrust faults together with the average surface displacement observed in the field u 1 2 m the surface of the fault plane determined by the aftershocks distribution 80 17 km gives a magnitude m w 7 2 in good agreement with the harvard determination natural exposures produced by the 2003 surface faulting together with previous paleoseismic observations across the primary and secondary earthquake induced features have revealed the occurrence of several strong events magnitudes about 7 8 during the last 5000 yr the characteristics of the altay event suggest that the gorny altay region similar to mongolia and gobi is characterized by large infrequent m 7 8 earthquakes along faults moving at rates of a few mm yr or less

resolving sedimentological uncertainties using magnetostratigraphic correlation an example from the middle jurassic of burgundy france abstract magnetostratigraphic analysis was undertaken on a core 85 m long core from the shallow water carbonate platform of bathonian to late callovian age in burgundy france to establish high resolution magnetic correlations in a succession devoid of good stratigraphic markers and with diachronous lithofacies magnetic extracts reveal that the magnetic minerals carrying the characteristic remanence are mainly detrital titanomagnetites and fine grained biogenic magnetite of probable bacterial origin comparison of magnetic properties with lithologic data from wireline logs indicates that large grains are predominant in marly deposits whereas fine grained minerals are common mainly in pure limestones we have established a polarity sequence for the core that is independent of lithology and in ludes 17 polarity zones with the help of faunal zonation based on brachiopods and ammonites the polarity sequence was compared with the magnetostratigraphy established previously in four other sections from the same area the magnetostratigraphic correlation corroborates that platform flooding occurred during the early callovian an age in agreement with biostratigraphic interpretation constraining the age of successive onlaps a characteristic reverse polarity interval within the ammonite calloviense subzone is present in all the cores confirming the utility of magnetostratigraphy for stratigraphic correlation studies throughout the paris basin and burgundy