crustal concealing of small scale core field secular variation summary the earth s magnetic field is mainly produced within the earth s liquid and electrically conducting core as a result of a process known as the geodynamo many other sources also contribute to the magnetic signal accessible to observation at the earth s surface partly obscuring the main core magnetic field signal thanks to a series of very successful satellites and to advances in magnetic field modelling techniques considerable progress has however been made in the recent years toward better identifying the signal of each of these sources in particular temporal changes in the field of internal origin happen to be detectable now in spherical harmonic degrees up to perhaps 16 all of these changes are usually attributed to changes in the core field itself the secular variation on the ground that the lithospheric magnetization cannot produce such signals it has however been pointed out on empirical grounds that temporal changes in the field of internal origin produced by the induced part of the lithospheric magnetization could dominate the core field signal beyond degree 22 this short note revisits this issue by taking advantage of our improved knowledge of the small scale field changes and of the likely sources of the lithospheric field we rely on a simple extrapolation of the observed spatial spectrum of the field changes beyond degree 16 and use a forward approach based on a recent geological model of lithospheric magnetization this leads us to confirm that the main cause of the observed changes in the field of internal origin up to some critical degree n c is indeed likely to be the secular variation of the core field but that the signal produced by the time varying lithospheric field is bound to dominate and conceal the time varying core signal beyond that critical degree in very much the same way the permanent component of the lithospheric field dominates and conceals the permanent component of the core field beyond degree 14 all uncertainties taken into account we estimate n c to lie between 22 and 24 we however also note that in practice the main limitation to the observation of the core field small scale secular variation is not so much its concealing by the field of lithospheric origin but its fast changing nature and small magnitude this leads us to conclude that whereas cumulative small scale lithospheric field changes might be detected some day detection of core field secular variation beyond degree 18 is likely to remain a severe challenge for some time

paleoclimate and location of the border between mediterranean climate region and the saharo arabian desert as revealed by speleothems from the northern negev desert israel speleothem bearing karstic caves of the northern negev desert southern israel provides an ideal site for reconstructing the paleoclimate and paleo location of the border between mediterranean climate region and the saharo arabian desert major periods of speleothem deposition representing humid periods were determined by high resolution 230 th u dating and corresponding studies of stableisotopecompositionwereusedtoidentifythesourceofrainfallduringhumidperiodsandthevegetationtype majorhumidintervals

the chronostratigraphy of a quaternary sequence at the distal part of the nile littoral cell haifa bay israel the current detailed chronostratigraphic framework of the last 1 ma of an eastern mediterranean sequence haifa bay israel aims to examine the relative roles of sea level changes climate and tectonics seven continuous marine cores up to 120 m long were recovered from shallow water depths the cores were dated by optically stimulated luminescence 14 c magnetostratigraphy 230 th 234 u 26 al 10 be occurrence of index fossils and correlated to the global sea level curve and marine isotope stages mis the sedimentary sequence accumulated during the last ca 1 0 ma consists of 21 transgression regression units with hiatuses between them five marine terrestrial cycles which occur in the lower part of the sequence are attributed to the jaramillo subchron and the brunhes matuyama boundary and correspond to mis 29 21 the top 50 m includes three sedimentary cycles deposited in the last ca 400 ka the regressive phases during this interval correspond to glacial mis 8 6 and 2 while the transgressions correspond to interglacial mis 11 7 5 and 1 thus for the first time this study documents the longest quaternary succession dated so far in a key area of the levant sensitive to global history of sea level changes and glacial interglacial fluctuations copyright 2012 john wiley sons ltd

global vector and scalar magsat magnetic anomaly maps empirical and analytical techniques for modeling ionospheric fields in magsat data have been developed that facilitate ionospheric field removal from uncorrected anomalies to obtain better estimates of regional lithospheric anomalies this task has been accomplished for equatorial x z and b component and polar z and b component measurements the techniques for modeling ionospheric fields have been integrated into a processing sequence that incorporates some of the important data processing techniques developed during the last decade data processing techniques include retention of common signal in a correlation analysis of adjacent passes analysis of field differences between dawn and dusk data at points where their orbits cross and retention of common signal in a covariant spherical harmonic analysis procedure results suggest that implementation of the above processing scheme leads to the mapping of the most robust magnetic anomalies of the lithosphere vector components as well as scalar

scalar magnetic anomaly maps of earth derived from pogo and magsat data a new pogo scalar magnetic anomaly map at 400 km altitude is presented which consists of spherical harmonics of degree 15 60 on the basis of the common features of this map with two new magsat anomaly maps dawn and dusk two scalar magnetic anomaly maps of the earth are presented using two selection criteria with different levels of stringency these selection criteria suppress the noncrustal components of the original maps by different amounts the more stringent selection criteria seek to eliminate as much contamination as possible at the expense of suppressing some anomaly signal this map is represented by spherical harmonics of degree 15 60 the less stringent selection criteria seek to retain as much crustal signal as possible at the expense of also retaining some contaminating fields this map is represented by spherical harmonics of degree 15 65 the resulting two maps are highly correlated with degree correlation coefficients greater than 0 8

australian desert dune fields initiated with pliocene pleistocene global climatic shift development of continental aridity has been linked to late cenozoic global cooling but the evidence is indirect based on terrestrial loess deposits and eolian silt in marine sediments whereas direct dating of the inception of arid landforms has been frustrated by a lack of suitable methods here we report the first age determination of a major arid zone dune field based on cosmogenic 10 be and 26 al measurements of drill cores from dunes in the simpson desert central australia results show that the dune field began to form ca 1 ma whereas dating using quartz optically stimulated luminescence indicates episodic dune building during late quaternary ice ages less intense desertification began earlier the previous cosmogenic exposure dating showed that neighboring stony deserts began to form at the onset of quaternary ice ages 2 4 ma aridity deepened and the dune field formed when ice age cycles increased their amplitude and switched their periods from 40 k y to 100 k y ca 1 ma

222ra and 226ra in geothermal waters of bayindir izmir turkey the radioactivity levels 222rn and 226ra and physico chemical properties of geothermal waters from two spas of bayindir are investigated radon and radium measurements were made with collector chamber method the radon concentrations range from 3 0 to 13 3 bq l whereas the radium varies from 0 35 to 1 71 bq l it has been observed that radon levels increase in winter and decrease in summer the 222rn 226ra ratio was found to range from 4 91 to 30 53 physico chemical properties of water samples were also analysed water samples have considerably stable total dissolved solids values slight acidity low electrical conductivity and temperature 42 48 c

geomagnetic repeat station crustal biases and vectorial anomaly maps for germany summary geomagnetic repeat station data of germany from 1964 to present have been studied to determine their accuracy and crustal biases like the data from geomagnetic observatories repeat station data contain contributions from the regional and local crustal field but their spatial density is by far not high enough to resolve such anomalies knowing this crustal bias therefore is important in using repeat station data to map or model the main field to confirm the results obtained by using a global geomagnetic field model we constructed regional lithospheric field models using additional information from satellite and aeromagnetic data the compatibility of the different data types is good and we present vectorial anomaly maps for germany with a spatial resolution of approximately 37 km which could be useful for future geological interpretation of magnetic anomalies the anomalies contributing to the repeat station bias however can be of smaller scale and their amplitudes range up to absolute values of 177 nt in the north x 106 nt in the east y and 176 nt in the vertical z component average uncertainty estimates in the order of 5 8a nd 5n t inx y and z respectively are obtained from comparisons to a global model the estimates however vary a lot between stations and components the uncertainties should mostly result from measurement errors insufficient elimination of external field contributions or relocations of stations which had been regarded as insignificant there might also be a small contribution from insufficient description of secular variation in the global model used

using motionally induced electric signals to indirectly measure ocean velocity instrumental and theoretical developments abstract the motion of conductive sea water through the earth s magnetic field generates electromagnetic em fields through a process called motional induction direct measurements of oceanic electric fields can be easily converted to water velocities by application of a first order theory this technique has been shown to obtain high quality velocities through instrumental advances and an accumulation of experience during the past decades em instruments have unique operational considerations and observe for instance vertically averaged horizontal velocity from stationary sensors or vertical profiles of horizontal velocity from expendable probes or autonomous profiling floats the first order theory describes the dominant electromagnetic response in which vertically averaged and vertically varying horizontal velocities are proportional to electric fields and electric currents respectively after discussions of the first order theory and deployment practices operational capabilities are shown through recently published projects that describe stream coordinate velocity structure of the antarctic circumpolar current quickly evolving overflow events in the denmark strait and time development of momentum input into the ocean from a hurricane a detailed analysis of the gulf stream at its separation point from the continental slope serves as a case study for interpreting em measurements including the incorporation of geophysical knowledge of the sediment in addition the first order approximation is tested by the many features at this location that contradict the approximation s underlying assumptions sharp horizontal velocity gradients steep topography and thick and inhomogeneous sediments numerical modeling of this location shows that the first order assumption is accurate to a few percent a few cm s 1 in almost all cases the errors in depth varying velocity are 1 are substantiated by the direct observations and can be corrected by iterative methods though errors in the depth uniform velocity are 1 1 or less in almost all regions of the ocean an error similar to the instrumental accuracy of em instruments

chronology of upper quaternary offshore successions from the southeastern mediterranean sea israel pleistocene and holocene transgressions advancing over the shelf that was exposed during glacial maxima drowned any continental and shallow marine sediments deposited during low sea level stands to complement records from sequences exposed on land core material from the shallow continental shelf is needed to reconstruct climatic and sea level fluctuations two cores drilled offshore ashqelon off the southern mediterranean coast of israel in a water depth of 10 and 25 m were analyzed sedimentary facies and faunal analyses indicate that most of the sediments were deposited in nearshore environments with only short intervals of continental episodes luminescence dating of alkali feldspar and quartz as well as 14 c ages of mollusks date the cores to marine oxygen isotopic stages 6 1 between b140 and 5 ka comparison between the dating methods shows that most alkali feldspar ages agree with independent sea level and sedimentological constraints while quartz ages are overestimated r 2003 elsevier science ltd all rights reserved

new insights on intraplate volcanism in french polynesia from wavelet analysis of grace champ and sea surface data in this paper we discuss the origin of superswell volcanism on the basis of representation and analysis of recent gravity and magnetic satellite data with wavelets in spherical geometry we computed a refined gravity field in the south central pacific based on the grace satellite ggm02s global gravity field and the kms02 altimetric grid and a magnetic anomaly field based on champ data the magnetic anomalies are marked by the magnetic lineation of the seafloor spreading and by a strong anomaly in the tuamotu region which we interpret as evidence for crustal thickening we interpret our gravity field through a continuous wavelet analysis that allows to get a first idea of the internal density distribution we also compute the continuous wavelet analysis of the bathymetric contribution to discriminate between deep and superficial sources according to the gravity signature of the different chains as revealed by our analysis various processes are at the origin of the volcanism in french polynesia as evidence we show a large scale anomaly over the society islands that we interpret as the gravity signature of a deeply anchored mantle plume the gravity signature of the cook austral chain indicates a complex origin which may involve deep processes finally we discuss the particular location of the marquesas chain as suggesting that the origin of the volcanism may interfere with secondary convection rolls or may be controlled by lithospheric weakness due to the regional stress field or else related to the presence of the nearby tuamotu plateau

sand residence times of one million years in the namib sand sea from cosmogenic nuclides the namib sand sea is one of the world s oldest and largest sand deserts1 yet little is known about the source of the sand in this or other large deserts2 in particular it is unclear whether the sand is derived from local sediment or comes from remote sources the relatively uniform appearance of dune sands and low compositional variability within dune fields3 make it difficult to address this question here we combine cosmogenic nuclide measurements and geochronological techniques to assess the provenance and migration history of sand grains in the namib sand sea we use u pb geochronology of detrital zircons to show that the primary source of sand is the orange river at the southern edge of the namib desert our burial ages obtained from measurements of the cosmogenic nuclides 10be 26al and 21ne suggest that the residence time of sand within the sand sea is at least one million years we therefore conclude that despite large climatic changes in the namib region associated with quaternary glacial interglacial cycles4 5 the area currently occupied by the namib sand sea has never been entirely devoid of sand during the past million years

improved magnetic anomalies of the antarctic lithosphere from satellite and near surface data summary the antarctic magnetic anomaly map compiled marine and airborne surveys collected south of 60 s through 1999 and used magsat data to help fill in the regional gaps between the surveys orsted and champ satellite magnetic observations with greatly improved measurement accuracies and temporal and spatial coverage of the antarctic have now supplanted the magsat data we combined the new satellite observations with the near surface survey data for an improved magnetic anomaly map of the antarctic lithosphere specifically we separated the crustal from the core and external field components in the satellite data using crustal thickness variations estimated from the terrain and the satellite derived free air gravity observations regional gaps in the near surface surveys were then filled with predictions from crustal magnetization models that jointly satisfied the near surface and satellite crustal anomalies comparisons in some of the regional gaps that also considered newly acquired aeromagnetic data demonstrated the enhanced anomaly estimation capabilities of the predictions over those from conventional minimum curvature and spherical harmonic geomagnetic field models we also noted that the growing number of regional and world magnetic survey compilations involve coverage gaps where these procedures can contribute effective near surface crustal anomaly estimates

longshore sand transport estimates along the mediterranean coast of israel in the holocene abstract the nile littoral cell one of the world s longest runs 650 km along the southeastern mediterranean from abu quir bay near alexandria egypt to haifa bay on the northern israeli coast haifa bay constitutes the northernmost final depositional sink of nile derived quartz sand transported from the nile delta by longshore currents generated by approaching breaking waves the northward net sand transport along the mediterranean coast of israel results from larger waves approaching from west south west and south west compared to their counterparts from west north west and north west this study utilizes an extensive new database gathered from sediment drill cores marine geophysical maps and field observations to measure the volume of sand deposited in haifa bay and the adjacent zevulun plain during the holocene it then compares this volume to recent data including measurements of sand accumulation along haifa port s main breakwater constructed in the southern entrance of the bay as well as longshore sand transport estimates along the northern carmel coast research findings estimate the annual average quantity of sand transported to haifa bay throughout the period at 80 000 90 000 m3 the findings further conclude that this amount has not changed appreciably over the past 75 years evaluating calculated values over the long term it is suggested that the characteristics of longshore sand transport along the coast of israel have not changed significantly during the past 7900 8500 years it is obvious that this conjecture should be treated with reservations

cm5 a pre swarm comprehensive geomagnetic field model derived from over 12 yr of champ orsted sac c and observatory data a comprehensive magnetic field model named cm5 has been derived from champ rsted and sac c satellite and observatory hourly means data from 2000 august to 2013 january using the swarm level 2 comprehensive inversion ci algorithm swarm is a recently launched constellation of three satellites to map the earth s magnetic field the ci technique includes several interesting features such as the bias mitigation scheme known as selective infinite variance weighting sivw a new treatment for attitude error in satellite vector measurements and the inclusion of 3 d conductivity for ionospheric induction sivw has allowed for a much improved lithospheric field recovery over cm4 by exploiting champ along track difference data yielding resolution levels up to spherical harmonic degree 107 and has allowed for the successful extraction of the oceanic m2 tidal magnetic field from quiet nightside data the 3 d induction now captures anomalous solar quiet features in coastal observatory daily records cm5 provides a satisfactory continuous description of the major magnetic fields in the near earth region over this time span and its lithospheric ionospheric and oceanic m2 tidal constituents may be used as validation tools for future swarm level 2 products coming from the ci algorithm and other dedicated product algorithms

error distribution in regional inversion of potential field data summary an increasing number of regional inversions of gravity and magnetic field data have recently been computed some based on satellite and ground data some on satellite data only in each case it is important to quantify the errors resulting from the confined data region or the satellite parameters in this study we investigate the error distribution of regional inversions for scalar gravity and vector geomagnetic data from satellite data only we include the effects of satellite altitude size of the data region signal to noise ratio and spherical harmonic degree of an a priori global field model we evaluate our results on the basis of a regional inversion of the earth s magnetic field

compatibility of high altitude aeromagnetic and satellite altitude magnetic anomalies over canada results from equivalent source distributions derived jointly from high altitude average 4 km aeromagnetic and magsat derived average 400 km magnetic anomalies over canada indicate that long wavelength components 500 2500 km in these fields are extremely compatible with one another with a correlation coefficient of 0 95 the jointly estimated anomaly field at the earth s surface can be used as a long wavelength adjustment surface for regional near surface magnetic anomaly compilations and in assessing the performance of other downward continuation techniques because near surface anomalies are not available over all regions of the world we compare the jointly estimated anomaly field to the results of two different downward continuation techniques the evaluation of anomalies at the earth s surface from spherical harmonic coefficients derived from satellite altitude data and the use of downward continuation methods based on harmonic splines numerical and visual comparisons of these downward conti

local time stacking of geomagnetic solar daily variations 1 regular geomagnetic solar daily variations the sq signal is used in electromagnetic induction studies to investigate the electrical conductivity structure of earth s upper mantle traditionally sq induction studies employ observatory magnetic data from a few quiet days in which the overprint on the regular sq ionospheric current vortices from various irregular disturbances is minimal active days are typically discarded a procedure which results in a gappy time series that is difficult to analyze furthermore the quiet day selection is largely arbitrary since daily geomagnetic activity levels range continuously from very quiet to very active this fact precludes the establishment of rigorous quiet active thresholds the average local time variation on active days resembles typical quiet day variations except for a multiplicative scaling factor a multiyear stack of yearlong geomagnetic time series aligned with respect to local time incorporates regular active days while greatly attenuating the effects of irregular geomagnetic disturbances external and internal current systems that rise and fall in step with the sun s transit across the sky above an observatory contribute coherently to the local time stack all other current systems are incoherent and tend to stack out an exact 1 year long stack preserves the seasonal variation the resulting stacked time series contains no gaps is dominated by regular solar daily variations and can be used for improved sq induction studies and comprehensive geomagnetic field modeling hourly geomagnetic values from niemegk boulder mbour and meanook observatories between 1970 and 2002 along with the ap index are used in this study

the downward continuation of magsat crustal anomaly field over southeast asia a general method for the local downward continuation at ground level of geopotentials measured by low orbiting satellites at different altitudes is proposed such a continuation is the inverse solution of the external dirichlet problem the stability of the solution with respect to the altitude and the distribution of data points is discussed principal component analysis is shown to perform well and leads to a stable solution the method proposed has the advantage of being directly applicable to measured data points which are not evenly spaced and at different altitude as an illustration it is applied to magsat data over southeast asia two independent maps of the vertical component of the anomaly field at a constant altitude near ground level are derived for dawn descending orbits and dusk ascending orbits data separately the two maps reveal similar anomalies and confirm the correlation of the magsat derived anomaly field with the mosaic structure of the continental crust in southeast asia stable continental blocks are associated with positive anomalies and intervening collision belts correspond to well defined negative anomalies a very prominent low is observed above the himalaya and extends over the tibet plateau confirming an anomalous crustal and thermal structure of the plateau

first scalar magnetic anomaly map from champ satellite data indicates weak lithospheric field 1 satellite magnetic anomaly maps derived by different techniques from magsat pogo data vary by more than a factor of 2 in the deduced strength of the lithospheric magnetic field here we present a first anomaly map from new champ scalar magnetic field data after subtracting a recent orsted main and external field model we remove remaining unmodeled large scale external contributions from 120 track segments by subtracting a best fitting uniform field in order to preserve n s trending features the data are not filtered along track direct integration of the spherically gridded data yields the final degree 14 65 spherical harmonic expansion of the total intensity anomaly at the mean satellite altitude of 438 km apart from enhanced long wavelength features and a smoother general appearance our initial map is strikingly similar to one of the lower strength magsat pogo maps

late pleistocene holocene marsh episodes along the carmel coast israel abstract late pleistocene holocene sequences in the southern carmel coastal plain of israel were obtained from two cores 12 and 16 m deep at the western and eastern longitudinal troughs separated by a north south kurkar sandstone ridge the core sequences unconformably overlie the kurkar and were analyzed using x ray radiography grain size analysis organic matter and water content the sequences include a brown sandy clay units indicating terrestrial conditions of aeolian sand and dust deposition and pedogenesis dated between 20 200 19 650 and 9540 9130 cal yr bp western trough and to 14 000 13 000 and 7680 7510 cal yr bp eastern trough they are related to gradual warming and wetter climate when the coastline was far to the west b overlying dark silty clay sediments indicating fresh to brackish shallow water marsh with organic and fossil rich hydromorphic mineral soil which prevailed at the western trough until 9010 8640 cal yr bp 900 yr and dried while the coastline was 1 km to the west the marsh deposits were exposed for 3600 yr and populated by pre pottery neolithic and chalcolithic settlements before they were covered by marine aeolian sand at 5100 yr the kabara marshes at the eastern trough are asynchronous with the western marshes and prevailed from 7680 to 7510 cal yr bp until the present the genesis of these marshes may be related to the transition to a drier climate resulting in an increasing frequency of large floods as indicated by the high sedimentation rate as well as to sea level rise and its effect on groundwater level

source of arsenic based on geological and hydrogeochemical properties of geothermal systems in western turkey abstract turkey is an area of complex geology with active tectonics and high geothermal potential especially the western part of turkey is a region of abundant geothermal activity faults accommodating the deep circulation of hydrothermal fluids of meteoric origin are the primary means by which of geothermal systems are controlled in this region many of the thermal activities are related to the improved dilation on the e w strikes of the graben faults this situation serves as a suitable environment for the presence of high levels of arsenic in geothermal water resources the highest concentrations of naturally occurring aqueous arsenic as are found in certain types of geothermal waters generally those related to major graben faults in this regard high arsenic concentrations in geothermal resources have been detected in western turkey including but not limited to biga peninsulla gediz graben kucuk and buyuk menderes graben with values ranging from 1 to 1419 ppb in geothermal fluids the thermal waters have surface temperatures of up to 100 c and reservoir temperatures range from 150 to 248 c in the menderes graben from 120 to 287 c in the gediz graben and from 153 to 174 c in biga peninsula hydrogeochemically the menderes graben and gediz graben thermal waters are of the na hco 3 ca hco 3 and na so 4 types whereas some geothermal fluids such as those of tuzla and kestanbol in the biga peninsula cesme and urla are of the na cl type

resolution of direction of oceanic magnetic lineations by the sixth generation lithospheric magnetic field model from champ satellite magnetic measurements the champ satellite continues to provide highly accurate magnetic field measurements from decreasing orbital altitudes 350 km at solar minimum conditions using the latest 4 years 2004 2007 of readings from the champ fluxgate magnetometer including an improved scalar data product we have estimated the lithospheric magnetic field to spherical harmonic degree 120 corresponding to 333 km wavelength resolution the data were found to be sensitive to crustal field variations up to degree 150 down to 266 km wavelength but a clean separation of the lithospheric signal from ionospheric and magnetospheric noise sources was achieved only to degree 120 this new mf6 model is the first satellite based magnetic model to resolve the direction of oceanic magnetic lineations revealing the age structure of oceanic crust

simple models for the beattie magnetic anomaly in south africa abstract the origin of the approximately 1000 km long beattie magnetic anomaly bma in south africa remains unclear and contentious key issues include the width depth and magnetization of its source in this study we use uniformly magnetized spheres prisms and cylinders to provide the simplest possible models which predict the 1 km altitude aeromagnetic measurements along a profile across the bma the source parameters are adjusted by forward modeling in case of a sphere an inversion technique is applied to refine the parameters our results suggest that two similarly magnetized and adjacent sources with a vertical offset can explain the observed magnetic anomaly the best fitting model corresponds to two highly magnetized 5 a m 1 sheet like prisms extending from 9 to 12 km depth and from 13 to 18 km depth respectively and with a total width reaching 80 km other less preferred models show thicker and deeper magnetized volumes associated magnetizations seem to be mostly induced although a weak remanent component is required to improve the fit we also compare our results with the interpretation of independent magnetotelluric and seismic experiments along the same profile it suggests that the geological sources for the bma are mostly located in the middle crust and may be displaced by a shear zone or a fault contrary to previous models suggesting a serpentinized sliver of paleo oceanic crust within the natal namaqua mobile belt we propose that granulite facies mid crustal rocks within this belt may cause the bma

reconstructing the history of sediment deposition in caves a case study from wonderwerk cave south africa we applied cosmogenic isotope burial dating magnetostratigraphy and grain size distribution analysis to elucidate the history of the sedimentary sequence composed of fine quartz sands and silts of wonderwerk cave located on the southern edge of the kalahari desert south africa the source for the quartz sand is the kalahari sand dunes presently located 100 km to the north of the cave field observations and grain size analysis suggest a sediment transport scenario that includes eolian transport of kalahari sand abraded to a size of 70 100 m to the kuruman hills temporary storage on the hill slopes and valleys surrounding wonderwerk cave and later transport and deposition inside the cave our results suggest simple burial ages for sediments from both the front and back of the cave that range between 2 63 0 17 ma and 1 56 0 10 ma following initial exposure of 310 620 k y however 26 al 10 be ratios of 3 98 0 24 and 4 08 0 22 measured in a sand sample collected from the surface outside the cave may imply an initial burial signal equivalent to 0 78 0 15 ma thus reducing the possible age range of the buried samples to between 1 85 0 23 and 0 78 0 18 ma the paleomagnetic results for the front of the cave gave a polarity sequence of n r n n where n indicates normal polarity and r indicates reverse polarity this sequence can be correlated with both the older and younger cosmogenic burial age ranges the correlation suggests that in the cave front cosmogenic burial ages and the acquisition of stable remanent magnetization were not significantly affected by chemical and physical processes and that postburial production of cosmogenic isotopes was insignificant in contrast at the back of the cave the paleomagnetic polarity sequence of r n cannot be correlated with the cosmogenic burial ages since the temporal gap between the initial penetration of the sediment into the cave and the final acquisition of a stable remanent magnetization may have been long 10 5 yr and the single polarity transition can be correlated to any reverse normal transition that occurred during the quaternary this highlights the need for caution when cosmogenic burial ages and paleomagnetic sequences are compared the buried sediments in wonderwerk cave show similar grain size distributions to the fine sand sediment presently exposed at the surface in the vicinity of the cave furthermore calculated preburial 10 be concentrations for the buried sediment are similar to those measured in sediment outside the cave these similarities suggest that the environmental conditions and rates of geomorphic processes that persisted during sand deposition in wonderwerk cave during the late pliocene and early pleistocene may have been similar to those currently experienced in the southern kalahari the kuruman hills and the western ghaap plain these conditions favor the transport of fine grained quartz sand to the vicinity of the cave

quaternary stratigraphy and paleogeography of the galilee coastal plain israel the quaternary deposits in the galilee coastal plain comprise alternating calcareous sandstone red loam dark clay and uncemented sand the calcareous sandstone in the lower part of the sequence represents a pliocene to early pleistocene marine transgression and is covered unconformably by the late quaternary sequence the base of this sequence has an estimated age of 500 000 yr it is covered unconformably by marine calcareous sandstone in the west which represents the global high sea level stand of isotope stage 7 1 and is known as one of the tyrrhenian events in the mediterranean area the overlying members represent the low sea level stand of stage 6 the first a red paleosol indicating a relatively wet phase and the second an eolianite unit representing a drier phase the eolianite forms longitudinal subparallel ridges that formed contemporaneously the overlying marine sandstone which contains one of the diagnostic fossils of the tyrrhenian events the gastropodstrombus buboniuslmk accumulated during the global high stand of stage 5 5 the last glacial period left no sedimentary record the holocene is represented by a marine clay unit that is covered by sand the present study establishes a complete and detailed chronostratigraphic sequence for an eastern mediterranean beach which contains the gastropods buboniuslmk s buboniuson the galilee coast is attributed to stage 5 5 and therefore establishes an east west mediterranean correlation which can be used for linking mediterranean events to paleo sea levels and global climate changes

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

slow rates of rock surface erosion and sediment production across the namib desert and escarpment southern africa slow erosion has characterized the namib desert the namibian escarpment and the adjacent namibian highlands over the pleistocene paired analyses n 66 of in situ produced 10be and 26al in quartz bearing samples of bedrock primarily from inselbergs of sediment from dry river and stream channels and of clasts from desert surfaces reveal large inventories of these cosmogenic nuclides indicating significant landscape stability over at least the past million years bedrock samples n 47 collected in three transects from the coast across the escarpment and into the highlands show no spatial pattern in elevation normalized nuclide abundance despite a difference in mean annual precipitation map between sample sites at the coast map 400 mm yr 1 average model erosion rates inland of the escarpment 3 2 1 5 n 9 are indistinguishable from average rates seaward of the escarpment 3 6 1 9 n 38 indicating that rock on the pedimented coastal plain is eroding at the same rate as rock in the highlands sediment samples n 3 from small streams suggest that the landscape as a whole is eroding more rapidly than the bedrock outcrops and that a basin in the steep escarpment zone is eroding several times faster 16 m my 1 than either a basin in the highlands 5 m my 1 or a basin in the coastal plain 8 m my 1 data from large rivers n 4 constrain erosion rates averaged over 105 yrs and 104 to 105 km2 between 3 and 9 m my 1 small quartz clasts n 12 collected from four desert surfaces record extraordinarily long variable and in some cases complex exposure histories simple 10be model ages are as high as 1 8 my some minimum total histories considering both 10be and 26al and including both burial and exposure exceed 2 7 my as a group the namibian cosmogenic data do not support the model of significant and on going escarpment retreat the similarity of erosion rates calculated from 10be analysis of fluvial sediments and longer term 107 yr average mass removal rates estimated by others using fission track analysis of rock suggests that namibian erosion rates have reached a steady state and are changing little over time at outcrop scales the concordance of 10be and 26al in most bedrock samples suggests that the model of steady uniform bedrock erosion is valid there is no indication of intermittent burial shedding of thick rock slabs or stripping of previous cover at an intermediate scale a transect of bedrock samples north of gobabeb demonstrates that the northern boundary of the massive namib sand sea has been steady and unshifting similarly low cosmogenically estimated erosion rates across west and central namibia suggest that the landscape is in geomorphic steady state its overall appearance changing only slowly through time

new global vector magnetic anomaly maps derived from magsat data new global maps of the vector magnetic anomaly field of earth are derived from magsat data improvement on earlier published vector and scalar maps is achieved with the following procedure 1 the noise level of vector measurements associated with the discontinuities of the in flight sensor attitude determination is reduced by selecting the data 2 a monthly model of the main field is computed to account for secular variation using only quiet day data 3 the time dependence of the ring current effect is taken into account using hourly values of the dst index based on ground obseivations 4 sectorial indices based on ground observations are introduced to select profiles corresponding to low magnetic activity these indices provide a better discrimination of quiet data than the global kp index usually used for that purpose 5 a time and longitude dependent dynamic model of the equatorial electrojet is derived and used to correct magnetic measurements at low latitudes anomaly maps of x and z components are obtained using selected measurements within the reduced altitude range 350 425 km these maps are compared with earlier magsat anomaly maps and their respective resolutions are discussed these maps evidence large anomalies of lithospheric origin within the oceanic domain in particular the z map displays a characteristic pattern of long wavelength anomalies in these areas it is first shown that some of these anomalies particularly in the north atlantic and indian oceans may be correlated with the age of the lithosphere then a significant similarity between magnetic and geoid anomalies above ocean basins is evidenced this suggests that long wavelength oceanic magnetic anomalies may also be attributed to variations of the thickness of the magnetized layer associated with ocean floor topography

earth s lithospheric magnetic field determined to spherical harmonic degree 90 from champ satellite measurements summary the champ magnetic field mission is providing highly reliable measurements from which the global lithospheric magnetic field can be determined in unprecedented resolution and accuracy using almost 5 yr of data we derive our fourth generation lithospheric field model termed mf4 which is expanded to spherical harmonic degree and order 90 after subtracting from the full magnetic field observations predicted fields from an internal field model up to degree 15 an external field model up to degree two and the predicted magnetic field signatures for the eight dominant ocean tidal constituents we fit and remove remaining external fields and polar electrojet signatures in a track by track scheme from a subset of least disturbed tracks we estimate the mf4 model by least squares damping ill determined coefficients by regularization the resulting mf4 model provides a good representation of the lithospheric field down to an altitude of about 50 km at lower latitudes with reduced accuracy in the polar regions crustal features come out significantly sharper than in previous models in particular bands of magnetic anomalies along subduction zones become visible by satellite for the first time

an improved geomagnetic data selection algorithm for global geomagnetic field modelling a spherical harmonic degrees 60 global internal field model is described called bgs g l 0706 this model includes a degree 15 core and piecewise linear secular variation model and is derived from quiet time orsted and champ satellite data sampled between 2001 0 and 2005 0 for the satellite data selection a wide range of geomagnetic index and other data selection filters have been used to best isolate suitably quiet magnetospheric and ionospheric conditions only a relatively simple degree one spherical harmonic external field model is then required it is found that a new vector magnetic disturbance index vmd the existing longitude sector a indices the auroral zone index ie and the polar cap index pc are better than kp and dst at rejecting rapidly varying external field signals at low middle auroral and polar latitudes the model quality is further enhanced by filling spatial and temporal gaps in the quiet data selection with a second selection containing slightly more disturbed data it is shown that vmd provides a better parametrization than dst of the large scale rapidly changing external field the lithospheric field model between degrees 16 and 50 is robust and displays good coherence with other recently published models for this epoch bgs g l 0706 also shows crustal anomalies consistent with other studies although agreement is poorer in the southern polar cap intermodel coherency reduces above about degree 40 most likely due to incompletely filtered signals from polar ionospheric currents and auroral field aligned currents the absence of the pc index for the southern hemisphere for 2003 onwards is a particular concern

an isochron method for cosmogenic nuclide dating of buried soils and sediments we describe an improved method for dating buried paleosols using measurements of the cosmic ray produced radionuclides 10be and 26al in quartz grains and apply it to a sequence of intercalated tills and paleosols in central missouri usa that record plio pleistocene advances of the laurentide ice sheet a buried paleosol implies a period of surface exposure and nuclide accumulation followed by burial and a halt to nuclide production if the paleosol is formed in a sedimentary unit such as till this unit may also have been emplaced with unknown 26al and 10be concentrations inherited from past surface exposure if the inherited nuclide concentrations are the same at all depths in the soil as is true for well mixed sediments such as till then the 26al and 10be concentrations at different depths in the paleosol will show a linear relationship the slope of this line depends on the duration of burial of the paleosol but not on the inherited nuclide concentrations or on the sample depths thus one can date strata overlying buried paleosols by measuring 26al and 10be at multiple depths in the paleosol and calculating the burial age of the paleosol from the resulting isochron we focus on applying this approach to till paleosol sequences but the basic idea of forming an 26al 10be burial isochron with a set of samples that share the same burial age but differ in other aspects of their exposure history applies to other stratigraphic settings as well the method yields ages for four tills in missouri that are stratigraphically consistent agree with paleomagnetic age constraints and show that ice advanced into missouri near 1 25 ma near 0 8 ma and twice between ca 0 4 and 0 2 ma

geomagnetic field anomalies over the lombok island region an attempt to understand the local tectonic changes during the last years several investigations on the earthquakes and related tectonic structures along the java trench have been conducted in this study we focus on the lombok island west nusa tenggara indonesia which lies between the centres of the highest intensity of contiguous negative positive geomagnetic anomalies in this region the geological and tectonic structures however are not known in detail for this island whereas a better knowledge of these conditions could lead to better estimate the potential earthquake risks and thus a possible improvement of the existing early warning system we have performed a ground based geomagnetic survey at 56 stations in the lombok island during october november 2006 for a detailed mapping and interpretation of geomagnetic anomalies related to the geological and tectonic characteristics the 2d and 3d magnetic maps show a general geomagnetic anomaly pattern in the lombok island which consists of repeated contiguous negative positive anomalies two forward models have been proposed for a profile connecting a strongest apparent dipolar structure the first model assumes a uniformly magnetized sphere as the source of the anomaly and could be interpreted as a specific local structure composed by a quite large magnetic body the second model considers several rocks with different susceptibilities and magnetizations and could be interpreted as a discontinuity in the geological structures this model agrees with the local geological surface conditions and the known large scale regional tectonic structure therefore it is used to interpret our results in terms of tectonic characteristics which suggests the potential existence of a new tectonic element e g a local normal fault in this region

response of the nile and its catchment to millennial scale climatic change since the lgm from sr isotopes and major elements of east mediterranean sediments abstract changes in 87 sr 86 sr and major element geochemistry from two sediment cores 9509 and 9501 in the eastern mediterranean em were used to resolve changes in sediment provenance and hence determine climate changes in the nile catchment and eastern sahara desert over the past 25 ka the sediment was described by a three end member system comprising blue nile bn 87 sr 86 sr 0 7506 sr 210 ppm white nile wn 87 sr 86 sr 0 7094 sr 72 5 ppm and saharan dust sd 87 sr 86 sr 0 7183 sr 99 ppm the sedimentary record of these cores represents the suspended load carried down the nile river and discharged into the s e levantine basin and thus records palaeoclimatically controlled changes in erosion and transport in the catchment during arid periods 0 5 ka bp and prior to 11 ka bp fluxes of bn sediment at 9509 6 g cm 2 yr 10 12 g cm 2 yr respectively were greater than during the peak of the african humid period ahp from 5 to 11 ka bp 2 yr this latter period witnessed the deposition of the youngest organic rich sediment termed sapropel s 1 in the em basin by contrast the flux of wn increased during the ahp from 5 g cm 2 yr at 13 ka bp to 15 g cm 2 yr in the ethiopian highlands bn catchment increases in the amount and duration of the monsoon during the ahp caused more vegetation to grow resulting in less soil erosion in the wn catchment increased rainfall caused more catchment erosion and higher sediment flux through the sudd marshes the sedimentation rate in core 9509 increased during the ahp because of the greater importance of the wn sediment flux relative to the bn sediment flux saharan dust flux also decreased during the ahp reaching a minimum at 6 ka bp core 9509 due to greening of the sahara desert at the onset of s 1 the changes in nile flow as determined by 87 sr 86 sr and climatic changes in the em basin determined by 18 o of planktonic foraminifera were simultaneous confirming that such isotopic tracers cannot be used directly to determine the cause of the circulation changes in the em at this time the increase in the proportion of bn sediment at 9509 with a somewhat higher grain size during the h 1 period 15 17 ka bp was caused by erosion and redistribution of sediment from the nile delta and or the israeli coast as sea level rose

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

luminescence chronology of upper pleistocene and holocene aeolianites from netanya south sharon coastal plain israel abstract the coastal cliff at netanya south in the sharon coastal plain of israel was investigated with luminescence dating methods twenty four samples were taken from the exposed aeolianites and intercalated paleosols the 24 irsl and 24 tl age estimates suggest that the lower 45 m of the section were deposited in oxygen isotope stage 3 the uppermost 7 m of the section are of holocene age and clearly separated by a hiatus of 20 30 ka from the lower part

what triggered the early to mid pleistocene tectonic transition across the entire eastern mediterranean abstract subduction plays a fundamental role in plate tectonics and when interrupted it may trigger a series of geodynamic and sedimentary responses synchronous structural modifications recorded across the entire eastern mediterranean region are dated to a relatively short period early to mid pleistocene these deformations are documented within plates e g arabian sinai and african plates along plate boundaries e g dead sea and north anatolian faults and cyprus arc and in the mediterranean basin during the same period the northward subduction of the sinai plate was interrupted when the eratosthenes seamount cyprus arc collision initiated subduction collision processes of the eastern mediterranean serve as a unique modern analogue for similar settings worldwide understanding their association with accompanying neo tectonic processes is therefore predominantly important by fostering a detailed and comprehensive approach this research provides a coherent tectonic picture for the eastern mediterranean early to mid pleistocene tectonic transition in order to explore its triggering mechanisms since the neogene convergence across the eastern mediterranean was accompanied by eurasian indentation by arabia northward motion westwards anatolia escape and southwards aegean propagation this semi counterclockwise plate motion was temporarily interrupted by the incipient seamount arc collision which is suggested here as a trigger of the early to mid pleistocene tectonic transition

can electromagnetic disturbances related to the recent great earthquakes be detected by satellite magnetometers abstract on december 26 2004 the world s fourth largest earthquake since 1900 and the largest since the 1964 prince william sound alaska earthquake occurred off the west coast of northern sumatra with a magnitude of 9 3 on march 28 2005 another event of magnitude 8 7 took place in the same region the december 26 2004 earthquake has prompted scientists to investigate possible electromagnetic signatures of this event using ground magnetic observations iyemori et al iyemori t et al 2005 geomagnetic pulsations caused by the sumatra earthquake on december 26 2004 geophys res lett 32 l20807 doi 10 1029 2005gl024083 have suggested that a 3 6 min long geomagnetic pulsation observed shortly after this event was generated by the earthquake they have speculated that a 30 s magnetic pulsation was also caused by the earthquake here for the first time champ satellite magnetic and electron density data are examined to find out if electromagnetic signatures which are possibly related to these recent megathrust earthquakes are observed in satellite magnetic data we have shown that some specific features are observed after the two earthquakes with periods of about 16 and 30 s our results favor an external source origin for the 30 s pulsation moreover after more than 1 h champ magnetic data indicate the existence of a feature characterized by the same parameters duration amplitude and frequency content which could be associated with each earthquake respectively further investigations are required in order to answer the question of whether these signals can be associated with earthquakes and to assign their possible usefulness with respect to earthquake development

electromagnetic induction in the oceans and the anomalous behaviour of coastal c responses for periods up to 20 days 1 electromagnetic transfer functions at coastal sites are known to be strongly distorted by the conductivity of the seawater this ocean effect is generally considered to be small for periods greater than a few days we revise this statement by detailed and systematic model studies in the period range from 1 to 64 days with subsequent comparison of the modelled and observed electromagnetic responses the conductivity model consists of a radial symmetric 1 d section that is overlaid by a thin spherical surface shell the conductance of which is compiled using the noaa etopo topography bathymetry and map of sediment thicknesses the simulations were performed for spatial resolutions of the surface shell of 5 5 2 2 and 1 1 respectively and for two continental and oceanic underlying 1 d conductivity models the inducing source is described by the spherical harmonic p10 in dipole coordinates comparisons are made for the coastal geomagnetic observatories apia hermanus kakioka kanoya and simosato where an anomalous behaviour of the local response has been previously detected from the comparison of observed and modelled responses we conclude that peculiarities in the observed coastal responses in the period range from 1 to 20 days can be explained to a large amount by induction in the oceans we show that correction for the ocean effect results in responses that are much better interpretable by 1 d conductivity models compared to the uncorrected responses

chronostratigraphy of aeolianites from the sharon coastal plain of israel abstract the sharon coastal plain in israel is composed mainly of sand dune fields and aeolianite ridges three major sand accumulation periods are documented in the terrestrial record along the cliffs of the sharon coastal plain between 65 to 50 ka from 7 to 5 ka and from 5 to 0 2 ka these seem to correlate with the periods of sapropel formation in the mediterranean sea and so with periods of strongly increased african monsoon activity the accumulation of the stratigraphically oldest aeolianite kurkar unit 5 appears to correlate with sapropel s2 formed about 55 ka bp the uppermost aeolianite calcareous sandstone unit 2 seems to correlate with sapropel s1 formed at about 7 8 4 0 ka bp major soil formations occurred between 35 and 25 ka resulting in a rhodoxeralf soil grumusolic dark brown soil and between 15 and 12 ka resulting in a rhodoxeralf hamra soil at least seven weak weathering horizons regosol type soils are intercalated in the aeolianite of unit v and two regosols are present in the holocene aeolian sand of unit i

modeling the lithospheric magnetic field over france by means of revised spherical cap harmonic analysis r scha 1 we have recently proposed the revised spherical cap harmonic analysis r scha modeling technique the new mathematical functions represent faithfully the spatial variations of potential fields in a restricted area in this paper we tackle the inverse problem and outline the efficiency of the new basis functions with respect to real magnetic data processing simultaneously repeat stations observatory aeromagnetic and champ satellite data provides our first vector lithospheric field model over france which extends from surface to 500 km of altitude the magnetic field is represented with a minimum horizontal spatial representation of 40 km at the mean earth radius the magnetic lithospheric map consistency is confirmed with a comparison to known geological features the model variation with altitude also suggests that the major french magnetic anomaly the paris basin anomaly is produced by a deep rooted geological structure these results demonstrate the superiority of regional modeling over global modeling for delineating small scale details in the lithospheric field in view of forthcoming satellite missions like swarm the revised spherical cap harmonic analysis method will help to accurately represent the lithospheric field for more detailed geological interpretations

fifth generation lithospheric magnetic field model from champ satellite measurements 1 six years of low orbit champ satellite magnetic measurements have provided an exceptionally high quality data resource for lithospheric magnetic field modeling and interpretation here we describe the fifth generation satellite only magnetic field model mf5 the model extends to spherical harmonic degree 100 as a result of careful data selection extensive corrections filtering and line leveling the model has low noise levels even if evaluated at the earth s surface the model is particularly suited for inferring large scale structure and composition of the lithosphere it is also meant to serve as the long wavelength part of continental and global scale marine and aeromagnetic anomaly maps

the origin and disappearance of the late pleistocene early holocene short lived coastal wetlands along the carmel coast israel abstract the formation of short lived backswamps along the carmel coast of israel coincides with the rapid global sea level rise during the late pleistocene early holocene transition the current study shows that the wetland phenomena originated around 10 000 yr ago and dried up shortly before the local pre pottery neolithic humans settled on the wetland dark clay sediments 9430 cal yr bp palaeontological and stable isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the carmel coastal plain the water body contained typical brackish calcareous fauna with variable numerical abundance and low species richness of ostracods and foraminifera the 18o and 13c of the ostracod cyprideis torosa show close similarity to the present pleistocene coastal aquifer isotopic values this study therefore concludes that the wetlands were shallow water bodies fed by groundwater with no evidence of sea water mixing it seems that they developed as the result of high groundwater levels transportation of sediments landward and deposition of sand bars at the paleo river mouths it is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr

satellite observations of magnetic fields due to ocean tidal flow the ocean is an electrically conducting fluid that generates secondary magnetic fields as it flows through earth s main magnetic field extracting ocean flow signals from remote observations has become possible with the current generation of satellites measuring earth s magnetic field here we consider the magnetic fields generated by the ocean lunar semidiurnal m2 tide and demonstrate that magnetic fields of oceanic origin can be clearly identified in satellite observations

magnetic anomaly map of the world merging satellite airborne marine and ground based magnetic data sets abstract we report here a simple but practical method to combine systematically the magnetic surveys of disparate specifications from marine ground aeromagnetic and satellite platforms that aims to be helpful in the framework of the world digital magnetic anomaly map project because the satellite coverage and data quality is more uniform than near surface surveys it is adopted as the base map for wavelengths larger than 400 km and up to spherical harmonic degree inclusive of 16 2500 km after checking that satellite models and large aeromagnetic wavelengths are not consistent we filter out wavelengths longer than 400 km in aeromagnetic compilations existing regional grids and when available individual surveys are merged to give a more uniform spatial variation of the magnetic anomalies the effects of merging the grids are examined by plotting profiles and difference maps of the overlapping regions a preliminary global map is obtained after combining the magnetic anomaly map with the downward continued champ satellite derived magnetic anomaly map forthcoming availability of new datasets as well as improvements in the procedure will help to produce increasingly reliable maps

aeolian beach ridges and their significance for climate and sea level concept and insight from the levant coast east mediterranean abstract relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results most studies link the aeolian coastal deposits to regressive phases some to high sea level stands and a few to intermediate relative sea level positions we interpret the apparent contradictions as indicating the lack of an over arching concept and the inconsistent usage of sea level related terms in this paper we present an integrated morpho sedimentological concept for a microtidal mid latitudinal coast and review existing data from the levant east mediterranean coast to evaluate the concept and to eliminate nomenclatural confusion a coastal depositional environment in a semi arid environment consists of shallow marine aeolian and alluvial facies which together form an aeolian beach ridge complex as a package of strata which respond simultaneously to sea level change a transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit under regression the complex represents the falling stage and the associated downdip surface marks the lowstand on the levant coast we find chronologically well constrained offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between 200 ka and 10 ka the complexes represent the falling stage systems tract fsst of a short lived 5th order depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge three of these fssts and their up dip and down dip super bounding surface together form the 4th order 100 ka sequence of the last interglacial glacial cycle the absence of transgressive highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex the falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold on the levant coast sand delivery to the backshore continued during relative sea level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues the significance of the dune soil succession for climate is limited because the dunes are governed by relative sea level change the vegetation response to changes in precipitation is non linear and the dune dynamics are characterised by low resilience and hysteresis

a global lithospheric magnetic field model with reduced noise level in the polar regions 1 due to persistent ionospheric current systems at high latitudes satellite magnetic measurements have high noise levels in the polar regions consequently small scale lithospheric features are much more difficult to resolve there than at lower latitudes using linear combinations of spherical harmonics sh we define localized functions which are band limited to a given maximum degree thus a model s sh resolution can be varied over the globe we produce a lithospheric field model from champ satellite data which resolves features to sh degree 90 at low latitudes but only to sh degree 60 in the polar regions the new model can be downward continued from satellite altitude to the earth s surface without generating spurious high latitude anomalies citation lesur v and s maus 2006 a global lithospheric magnetic field model with reduced noise level in the polar regions geophys res lett 33 l13304

magnetism at depth a view from an ancient continental subduction and collision zone recent sophisticated global data compilations and magnetic surveys have been used to investigate the nature of magnetization in the lower crust and upper mantle two approaches to constraining magnetizations are developed providing minimum 0 01 si and maximum 0 04 si susceptibility estimates given some assumed thickness 15 km here these values are higher than are found in many continental rocks are there rocks deeper in the crust or upper mantle that are more magnetic than expected or are the model assumptions incomplete what is the magnetic behavior of deep crustal and upper mantle rocks when slightly cooler than the curie or neel temperatures of their magnetic minerals after being exhumed from locations of high grade metamorphism at greater depth different sets of equilibrium metamorphic minerals can be considered that would form under different conditions results on 1501 samples from the western gneiss region wgr norway mainly from mafic and ultramafic bodies subducted to depths of 60 200 km and temperatures of 750 up to 950 c at the very highest pressures show that rocks did not fully equilibrate to the dominant metamorphic facies conditions there is a large variation in petrophysical properties oxide minerals and mineral assemblages in wgr samples though they cannot explain the broad high amplitude deep seated anomalies measured in this region the presence of magnetite and exsolved titanohematite and hemo ilmenite in samples shows those magnetic phases are preserved even at eclogite facies conditions in part because complete eclogite facies equilibrium was rarely achieved

spherical prism magnetic effects by gauss legendre quadrature integration summary regional spherical coordinate observations of the earth s crustal magnetic field components are becoming increasingly available from shipborne airborne and satellite surveys in assessing the geological significance of these data theoretical anomalous magnetic fields from geologic models in spherical coordinates need to be evaluated this study explicitly develops the elegant gauss legendre quadrature formulation for numerically modelling the complete magnetic effects i e potential vector and tensor gradient fields of the spherical prism we also use these results to demonstrate the magnetic effects for the crustal prism and to investigate the crustal magnetic effects at satellite altitudes for a large region of the middle east centred on iran

constant cosmogenic nuclide concentrations in sand supplied from the nile river over the past 2 5 m y quartz sand in the eastern mediterranean coastal plain is supplied through an extended transport system which includes the nile river east mediterranean longshore currents and inland eolian transport while the concentrations of cosmogenic nuclides 26 al and 10 be and their ratio in modern sand deposited along the coast of the eastern mediterranean reflect the combined effect of exposure and burial during transport the concentrations of these nuclides in buried sands are the result of decay of this initial dosing samples of modern exposed sand n 3 collected from the coastal plain of israel yield an average 26 al 10 be ratio of 4 8 0 2 significantly lower than the expected ratio of 6 8 for exposed quartz grains at the surface a similar ratio of 4 5 0 3 was measured in a late pleistocene sand sample indicating similar exposure burial histories during transport in spite of the difference in climatic conditions the results imply a steady preburial cosmogenic nuclide ratio related to the nile river9s ability through storage and recycling to buffer the effects of climatic and tectonic perturbations on cosmogenic nuclide concentrations in the transported quartz all ancient and buried sand samples n 11 fall on a decay path that originates from the concentrations and ratio of 26 al and 10 be in modern sand suggesting steady preburial concentrations of cosmogenic nuclides in quartz sand over the past 2 5 m y

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

third generation of the potsdam magnetic model of the earth pomme the potsdam magnetic model of the earth pomme is a geomagnetic field model providing an estimate of the earth s core crustal magnetospheric and induced magnetic fields the internal field is represented to spherical harmonic sh degree 90 while the secular variation and acceleration are given to sh degree 16 static and time varying magnetospheric fields are parameterized in geocentric solar magnetospheric gsm and solar magnetic sm coordinates and include disturbance storm time dst index and interplanetary magnetic field imf by dependent contributions the model was estimated from five years of champ satellite magnetic data all measurements were corrected for ocean tidal induction and night side ionospheric f region currents the model is validated using an independent model from a combined data set of orsted and sac c satellite measurements for the core field to sh degree 13 the root mean square rms vector difference between the two models at the center of the model period is smaller than 4 nt at the earth s surface the rms uncertainty increases to about 100 nt for the predicted field in 2010 as inferred from the difference between the two models

geomagnetic excursions reflect an aborted polarity state abstract geomagnetic excursions represent short episodes of a few thousand years at most during which the field considerably exceeds its normal range of variability during a polarity state paleomagnetic records have now been obtained with extremely high temporal resolution which have improved our knowledge of these short events we have compiled the most detailed records of excursions that had occurred during the brunhes and matuyama chrons we show that virtual geomagnetic poles vgps of at least one record of each event are able to reach the opposite polarity in the next step we have computed different simulations of excursions during which the dipole progressively vanishes before growing back without reversing this scenario produces very few reversed directions which are only visible at some latitudes we infer that it is impossible to reach the ratio of reversed to intermediate vgps present in the paleomagnetic records if the excursions were not associated with a short period of reversed dipole field therefore excursions should be regarded as two successive reversals bracketing an aborted polarity interval we propose that the same underlying mechanisms prevail in both situations excursions or reversals and that below a certain strength the field reaches an unstable position which preludes either the achievement of a reversal or its return to the former polarity

the deep structure of the carmel fault zone northern israel from gravity field analysis the carmel yizre el jordan fault system is a major structural feature in the geology of israel there is a great difference in topographical features structural style seismic activity crustal structure and other geological characteristics to the north and south of this fault system we examine the gravity field of the region around the fault system by combining the techniques of upward continuation and horizontal gradient analysis the results suggest the existence of a system of deep seated n s trending faults that are probably related to the continental breakup of the region in the triassic jurassic the present complex deformation of the area is the result of interaction between the older faults system and the younger stresses resulting from the formation of the dead sea rift