identifying soft sediment deformation in rocks abstract the correct identification of sedimentary folds and fabrics created during gravity driven deformation of unlithified successions from those tectonic structures formed during regional deformation is essential when interpreting geological histories preserved within the rock record this topic has become increasingly relevant over the past 40 years as improved seismic resolution and coverage have led to the realisation that significant portions of unlithified sediments along the continental margins undergo gravity driven deformation to create mass transport deposits mtd s the late pleistocene lisan formation exposed in the dead sea basin was chosen as a case study because it remains poorly lithified and structures developed within it are unequivocally related to soft sediment deformation ssd created when the succession underwent downslope directed movement this work tests various assertions previously used to deduce if structures were formed in unlithified sediments or during hard rock deformation hrd associated with subsequent tectonism within the lisan formation we describe veins developed along fractures and cleavage forming axial planar to folds that are structures previously assumed to be restricted to hrd in addition truncated folds incorporation of deformed fragile fragments into overlying sediment and cross cutting clastic dykes are all indicative of ssd the key diagnostic feature in establishing ssd is the sedimentary infill of irregular erosive surfaces that truncate underlying structures although compaction and diagenesis have not played a significant role in the case study caution should be exercised when examining structures preserved in the rock record as folds and fabrics originally created by ssd may be considerably enhanced and altered where significant overburden exists

earthquake induced clastic dikes detected by anisotropy of magnetic susceptibility clastic dikes form either by passive deposition of clastic material into preexisting fissures or by fracturing and injection of clastic material during seismic shaking or passive overpressure because of their similar final geometry the origin of clastic dikes is commonly ambiguous we studied the mechanisms of clastic dike formation within the seismically active dead sea basin where hundreds of clastic dikes crosscut soft rock of the late pleistocene lacustrine lisan formation we analyzed the anisotropy of magnetic susceptibility ams of clastic dikes of known origin and defined characteristic ams signatures of depositional or injection filling we discovered that passively filled dikes which contain brownish silt resembling local surface sediments are characterized by an oblate ams ellipsoid and vertical minimum susceptibility axis v3 dikes that contain green clayey sediment connected to a mineralogically identical detrital layer of the lisan formation are characterized by a triaxial ams ellipsoid well grouped subhorizontal and parallel to the dike walls maximum susceptibility axis v1 and subvertical intermediate susceptibility axis v2 field evidence and ams analysis indicate that most of these dikes were emplaced by injection inferred to be due to seismically triggered fluidization this novel application of the ams provides a petrofabric tool for distinguishing passively filled dikes from injection dikes and where appropriate for identifying the latter as seismites

turbulent transport and deposition of the ito pyroclastic flow determinations using anisotropy of magnetic susceptibility the ito pyroclastic flow erupted about 22 000 years ago from aira caldera in southern kyushu japan flow directions were determined by anisotropy of magnetic susceptibility ams which measured the preferential alignment of magnetite microphenocrysts usually 0 25 mm in diameter the microphenocrysts are aligned with the long axis of the clasts during strain and fracture in the vent the grains are then deposited parallel to the flow direction with an imbrication there is no evidence of rolling of clasts or nonflow parallel lineations and thus ams can be used to determine flow directions that occurred immediately before deposition beyond 30 km from the center of the caldera flow directions were predominantly down paleogradient indicating expanded flow and that the depositional system was gravity driven and largely decoupled from the transport system within 30 km measured flow directions are random indicating that sedimentation occurred from a depositional system that was closely coupled to the turbulent transport system individual flow directions at all sites except one varied more than the analytical error demonstrating that a variety of flow directions existed even within a small area of the flow this implies that the depositional system was turbulent

magnetic fabrics and strain in pencil structures of the knobs formation valley and ridge province us appalachians pencil structures which are found in weakly deformed mudrocks reflect the bedding cleavage intersection in weak to moderatelycleaved rocks their presence indicates conditions where bedding and cleavage fabrics are approximately equal in intensity we have determined the anisotropy of magnetic susceptibility ams in pencil structures from a sequence of mudstones of the ordovician knobs formation in the valley and ridge province of the us appalachians magnetic mineralogy was determined by x ray analysis and lowtemperature susceptibility measurements distribution of the magnetic ellipsoid axes is consistent with the incipient tectonic fabric of the pencil mudstones the maximum susceptibility axes parallel the pencils long axes while the minimum axes of susceptibility are normal to the primary sedimentary fabric independent strain quantification permits a correlation between magnetic fabric and tectonic strain an exponential relationship between the ams shape parameter t and tectonic shortening has been found for the interval of 10 25 shortening shortening 17 p exp t this relationship appears to be supported by tectonic strains up to 40 the t parameter t lnf 2 lnl lnl lnf where l lineation is kmax kint and f foliation is kint kmin describes the shape of the magnetic susceptibility ellipsoid which appears more sensitive to strain than past correlation attempts with the magnetic intensity parameter p or p 0 whereas this correlation between strain and ams is only valid within a restricted window of strain 10 40 shortening it establishes the magnitude and directions of tectonic strain in weakly deformed clay rich rocks where strain indicators are otherwise lacking or are poorly developed q 2003 published by elsevier science ltd

magma flow directions of shallow dykes from the east greenland volcanic margin inferred from magnetic fabric studies abstract the role played by plume generated crustal magmatic complexes in the segmentation of volcanic margins is highlighted by a preliminary study of magma flow directions in shallow intrusives from the east greenland volcanic margin we investigate the magmatic texture using anisotropy of magnetic susceptibility for eight dykes of tholeitic affinity belonging to a dyke swarm associated with the tertiary opening of the north atlantic ocean the thickness of the sampled dykes ranges from 3 to 37 m the dykes are of doleritic texture and contain up to 12 of opaque minerals and 35 of plagioclase laths dykes showing a magnetic foliation plane within the dyke plane i e a magnetic fabric usually attributed to magmatic processes represent 40 of the samples from the studied swarm these dykes have a low degree of anisotropy and their ellipsoid of magnetic susceptibility is strongly oblate inverse magnetic fabrics where the maximum principal susceptibility axis lies near the pole to the dyke account for 60 of the data we interpret these inverse fabrics either as alteration minerals with highly prolate ellipsoids of magnetic susceptibility or primary titanomagnetites with oblate ellipsoid of low anisotropy the flow direction is inferred for normal fabric dykes using the mirror imbrication of magnetic lineation analysis of thin sections shows a good agreement between magnetic fabric directions and phenocryst preferred orientations the inferred flow directions are predominantly horizontal throwing a new light on volcanic margin development

numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum 1 a hydrodynamic model incorporating a self consistent treatment of ocean self attraction and loading sal and a physically based parameterization of internal tide it drag is used to assess how accurately barotropic tides can be modeled without benefit of data and to explore tidal energetics in the last glacial maximum lgm m2 solutions computed at high resolution with present day bathymetry agree with estimates of elevations from satellite altimetry within 5 cm rms in the open ocean this accuracy and agreement with atlimetric estimates of energy dissipation are achieved only when sal and it drag are included in the model solutions are sensitive to perturbations to bathymetry and inaccuracies in available global databases probably account for much of the remaining error in modeled elevations the 100 m drop in sea level during the lgm results in significant changes in modeled m2 tides with some amplitudes in the north atlantic increasing by factors of 2 or more dissipation is also significantly changed by the drop in sea level if it drag estimated for the modern ocean is assumed dissipation increases by about 50 globally and almost triples in the deep ocean however it drag depends on ocean stratification which is poorly known for the lgm tests with modified it drag suggest that the tendency to a global increase in dissipation is a robust result but details are sensitive to stratification significant uncertainties about paleotides thus remain even in this comparatively simple case where bathymetry is well constrained

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

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

interpreting magmatic fabric patterns in plutons abstract most plutons have widespread magmatic fabrics the interpretation of which remains controversial we propose a method to constrain likely causes of fabric patterns the application of which indicates the following 1 preserved fabric patterns often form after chamber construction and only rarely provide information about ascent or emplacement 2 fabrics are poor recorders of total strain and are easily reset preserving only the last increment of strain during crystallization 3 in magmatic systems mechanically decoupled from host rocks patterns may result from strain during internally driven flow filter pressing or porous flow in relatively static chambers or by final increments of strain during emplacement 4 with greater emplacement depths fabric patterns increasingly reflect strain caused by regional deformation and 5 given that magmatic fabrics are easily reset and reflect only the last increment of strain of comparatively weak materials they may provide a relatively direct record of paleostress in orogenic belts

injection mechanism of clay rich sediments into dikes during earthquakes 1 clastic dikes may form by simultaneous fracture propagation in rocks and injection of clastic material into the fractures resulting from strong seismic shaking we studied the mechanisms of clastic dike formation within the seismically active dead sea basin where hundreds of clastic dikes cross cut the soft rock of the late pleistocene lacustrine lisan formation we analyzed the anisotropy of magnetic susceptibility ams of dikes with known formation mechanisms and defined the characteristic ams signatures mainly of dikes developed by injection process most of the dikes were emplaced due to fluidization of clay rich sediment and are characterized by triaxial ams ellipsoids the dominant triaxial ams ellipsoids along the dike widths suggest that the fluidization mechanism of clay rich sediment is different from the known liquefaction process of sand the ams analysis supported by field evidence indicates that the injection of clay rich sediment is characterized by two main regimes 1 vertical flow characterized by subvertical v2 axes and subhorizontal v1 and v3 axes the v2 axes may indicate the flow directions during fast flow 2 horizontal slow flow characterized by subvertical v3 axes and subhorizontal v1 and v2 axes a streaked ams pattern mainly composed of v2 and v3 axes represents a turbulent flow that generated local eddies simultaneously with the clastic transport the ams parameters along the dikes and possible grain imbrications along dike walls support organization of grains under high strain rates this application of the ams method provides a petrofabric tool for identifying seismites and inferring their flow kinematics in complex geologic areas

magnetic susceptibility zonation of the melilititic riedheim dyke hegau volcanic field germany evidence for multiple magma pulses the olivine melilitic riedheim dyke complex is related to the tertiary alkaline magmatism within the hegau volcanic field magnetic susceptibility measurements and the mineral composition of oxides together with petrographic observations imply two phases of magma intrusion for the emplacement of this dyke the first intrusion forms the eastern and western margins of the dyke section with high magnetic susceptibility values of up to 75 10 3 si which are related to ferrimagnetic mg al cr bearing titanomagnetites with a magnetite component between 0 59 and 0 75 mol a generally lower magnetic susceptibility of up to 45 10 3 si and a significantly lower and homogeneous magnetite component of the titanomagnetites xmt 0 38 mol are recorded for the second intrusion into the central part of the dyke furthermore a dependence of magnetic susceptibility on the amplitude of the ac field was measured which is more pronounced in the second intrusion hd 25 than in the first one 6 hd 10 confirming the magneto mineralogical data secondary pervasive alteration is more pronounced in the first intrusion phase characterised by a very fine grained and glassy matrix that is more receptive to hydrothermal overprint than the well crystallised matrix of the second intrusion localised thermally induced alteration at the intimately fractured contact between the first and second intrusion phase has oxidised the titanomagnetite of the first intrusion phase but did not significantly effect the second intrusion differences between the dyke sections are also documented by the anisotropy of magnetic susceptibility ams which reflects a magmatic flow fabric with long axis of the ams ellipsoids magnetic lineation parallel to the flow direction and short axis normal to the n s trending dyke boundary the orientation of the magnetic fabric for the individual magma pulses is different with a more moderate plunge of the magnetic lineation within both the western 177 57 and eastern parts 181 50 of the first dyke intrusion compared to a nearly vertical orientation in the second central dyke intrusion 180 78 we suggest that the primary crystallisation history of the two intrusion phases caused the magnetic susceptibility zonation in the riedheim dyke complex

non scaled analogue modelling of ams development during viscous flow a simulation on diapir like structures development of magnetic fabric within a diapirically ascending columnar body was investigated using non scaled analogue model made of plaster of paris containing small amount of fine grained homogeneously mixed magnetite the apparatus for the modelling consists of a manual squeezer with calibrated spring and a perspex container set of weak coloured layers at the bottom of the container was forced to intrude overlying fine grained sand through a hole in a board attached to the squeezer the development of ams fabric is correlated with complex flow pattern indicated by coloured and originally horizontal plaster layers strongly constrictional and vertical fabric in the base and in the lower domain of the diapir resulting from convergent and upwards flows is overprinted by subhorizontal oblate fabrics due to vertical flattening and initial divergent flow in the apical parts the measured ams fabrics are compared with natural examples of magmatic stocks and dykes

sedimentary and structural controls on seismogenic slumping within mass transport deposits from the dead sea basin abstract comparatively little work has been undertaken on how sedimentary environments and facies changes can influence detailed structural development in slump sheets associated with mass transport deposits mtds the nature of downslope deformation at the leading edge of mtds is currently debated in terms of frontally emergent frontally confined and open toed models an opportunity to study and address these issues occurs within the dead sea basin where six individual slump sheets s1 s6 form mtds in the late pleistocene lisan formation all six slumps which are separated from one another by undeformed beds are traced towards the ne for up to 1 km and each shows a change in sedimentary facies from detrital rich in the sw to more aragonite rich in the ne the detrital rich facies is sourced predominantly from the rift margin 1 5 km further sw while the aragonite rich facies represents evaporitic precipitation in the hyper saline lake lisan the stacked system of mtds translates downslope towards the ne and follows a pre determined sequence controlled by the sedimentary facies each individual slump roots downwards into underlying detrital rich layers and displays a greater detrital content towards the sw which is marked by increasing folding while increasing aragonite content towards the ne is associated with more discrete thrusts the mtds thin downslope towards the ne until they pass laterally into undeformed beds at the toe the amount of contraction also reduces downslope from a maximum of 50 to

seismites in the kathmandu basin and seismic hazard in central himalaya soft sediment deformation structures have been analyzed at six sites of the kathmandu valley microgranulometric study reveals that silty levels 60 to 80 silt favor the development of soft sediment deformation structures while sandy levels 60 to 80 sand are passively deformed nonetheless well sorted sand levels more than 80 sand generate over fluid pressure during compaction if located beneath a silty cap leading to fluidization and dike development 3 d geometry of seismites indicates a very strong horizontal shearing during their development using a physical approach based on soil liquefaction during horizontal acceleration we show that the fluidization zone progressively grows down section during the shaking but does not exactly begin at the surface the comparison of bed thickness and strength depth evolution indicates three cases i no soft sediment deformation occurs for thin few centimeters silty beds ii the thickness of soft sediment deformation above sandy beds is controlled by the lithological contrast iii the thickness of soft sediment deformation depends on the shaking intensity for very thick silty beds these 3 cases are evidenced in the kathmandu basin we use the 30 cm thick soft sediment deformation level formed during the 1833 earthquake as a reference the 1833 earthquake rupture zone extended very close to kathmandu inducing there mmi ix x damages a 90 cm thick sediment deformation has therefore to be induced by an event greater than mmi x from a compilation of paleo and historic seismology studies it is found that the great m 8 1 historical earthquakes are not characteristic of the greatest earthquakes of himalaya hence earthquakes greater than m 8 6 occurred kathmandu is located above one of the asperities that laterally limits the extent of mega earthquake ruptures and two successive catastrophic events already affected kathmandu in 1255 located to the west of this asperity and in 1100 to the east

fold and thrust systems in mass transport deposits abstract improvements in seismic reflection data from gravity driven fold and thrust systems developed in offshore mass transport deposits mtds reveal a number of significant features relating to displacement along thrusts however the data are still limited by the resolution of the seismic method and are unable to provide detail of local fold and thrust processes investigation of exceptional gravity driven contractional structures forming part of mtds in lacustrine deposits of the dead sea basin enables us to present the first detailed outcrop analysis of fold and thrust systems cutting unlithified soft sediments we employ a range of established geometric techniques to our case study including dip isogons fault propagation fold charts and displacement distance diagrams previously developed for investigation of thrusts and folds in lithified rocks fault propagation folds in unlithified sediments display tighter interlimb angles compared to models developed for lithified sequences values of stretch which compares the relative thickness of equivalent hangingwall and footwall sequences measured along the fault plane may be as low as only 0 3 which is significantly less than the minimum 0 5 values reported from thrusts cutting lithified rocks and reflects the extreme variation in stratigraphic thickness around thrust related folds we suggest that the simple shear component of deformation in unlithified sediments may modify the forelimb thickness and interlimb angles to a greater extent than in lithified rocks the average spacing of thrust ramps and the thickness of the thrust sequence display an approximate 5 1 ratio across a range of scales in mtds in general thicker hangingwall and footwall sequences occur with larger thrust displacements although displacement patterns on thrusts cutting unlithified yet cohesive sediments are more variable than those in lithified rocks line length restoration of thrust systems in mtds reveals 42 shortening which reduces to 35 in overlying beds a 23 reduction in shortening by folding and thrusting along individual thrusts suggests that heterogeneous lateral compaction may increase by 10 towards the sediment surface thrust systems cutting unlithified sediments display distinct steps in cumulative displacement distance plots representing increased rates of slip along the floor thrust while displacement distance plots along individual thrusts also reveal horizontal steps relating to lithological variation competent units cut by thrust ramps may display the greatest displacement which then progressively reduces both upward and sometimes downward along the ramp this relationship demonstrates that ramps do not necessarily propagate upwards from the underlying flat as in some traditional models but rather initiate by offset of competent horizons in the hangingwall of the detachment critical taper angles in mtds may be an order of magnitude less than in accretionary complexes or lithified rocks overall thrusts cutting unlithified sediments in mtds display more variable displacement and more pronounced displacement gradients toward fault tips compared to thrusts cutting lithified sequences

patterns of magma flow in segmented silicic dikes at summer coon volcano colorado ams and thin section analysis abstract a complex pattern of magma flow is found in two silicic dikes of a radial swarm at summer coon an eroded stratovolcano in southern colorado the two intrusions are broken into multiple segments that suggest vertical dike propagation however anisotropy of magnetic susceptibility ams measurements and thin section observations suggest that magma flow was often subhorizontal and away from the center of the volcano segments that are proximal to the central intrusion are characterized by magma that flowed steeply upward at the proximal segment extremity then laterally along the segment and finally downward at the distal end of the segment magma flow in offset segment tips located far from the volcano center was subhorizontal towards the adjacent segment implying lateral propagation of segment tips towards one another this observation suggests relatively high driving pressure in distal dike segments as supported by dike thickening with radial distance from the center of the volcano the present study indicates that radial dike evolution at stratovolcanoes is dominated by lateral flow of magma and dike segmentation is a poor magma flow indicator a horizontally propagating radial dike has the potential to cause an eruption low on the flank of a composite cone which poses a significant yet largely unrecognized hazard to population centers and infrastructure that may surround the volcano

magnetic and plagioclase linear fabric discrepancy in dykes a new way to define the flow vector using magnetic foliation in basaltic dykes the magnetic lineation k1 maximum magnetic susceptibility axis is generally taken to indicate the flow direction during solidification of the magma this assumption was tested in tertiary basaltic dykes from greenland displaying independent evidence of subhorizontal flow the digital processing of microphotographs from thin sections cut in k1 k2 planes yields the preferred linear orientation of plagioclase which apparently marks the magma flow lineation in up to 60 of cases the angular separation between k1 and the assumed flow direction is greater than 45 this suggests that the uncorroborated use of magnetic lineations in dykes is risky a simple geometrical method is proposed to infer the flow vector from ams in dykes based solely on magnetic foliations

shape fabrics of particles in low concentration suspensions 2d analogue experiments and application to tiling in magma abstract jeffery s equations ascribe a theoretical cyclic nature to the shape fabric of non interacting rigid particles immersed in a viscous fluid undergoing simple shear flow this theoretical behaviour is confirmed at low shear strains 5 first experiment 134 identical particles or 1 second experiment 178 particles with two size classes then become stable at 17 first experiment and at more than 50 second experiment of the population of particles due to the contribution of the tiled particles the shape fabric becomes asymmetrical in its orientation distribution with a maximum lying above the shear plane the latter result provides a new shear sense indicator in addition to the statistical determination of the tiled features the study also suggests that crystalline fabrics in magmas could be acquired at high melt fractions i e early in the crystallization history of the magma

an ams structural and paleomagnetic study of quaternary deformation in eastern sicily abstract an integrated structural anisotropy of magnetic susceptibility ams and paleomagnetic study was carried out on plio pleistocene sedimentary basins in eastern sicily these basins belong to three main tectonic domains the tyrrhenian hinterland domain the catania foredeep domain and the hyblean foreland domain we sampled 329 oriented samples from 25 sites in selected areas from the different tectonic domains the ams is typical for weakly deformed sediments with a magnetic foliation sub parallel to the bedding plane and a well defined magnetic lineation the orientation of the magnetic lineation is strongly controlled by the main tectonic deformation recorded in the basins structural and ams data define a transition from nw se extension in the tyrrhenian hinterland domain to e w compression in the catania foredeep domain to e w extension in the hyblean foreland domain respectively reliable paleomagnetic results have been obtained in 12 out of 25 sampled sites data show that no significant rotations occurred in any of the studied basins at least since the middle pleistocene these results allow us to define an upper limit to the large rotations about vertical axes that have been previously found in the calabria and sicily regions

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

high resolution record of geomagnetic secular variation from late pleistocene lake lisan sediments paleo dead sea we measured geomagnetic secular variation in lake lisan sediments paleo dead sea more than 1500 oriented samples were collected from a 27 3 m section of alternating aragonite and detritus laminae in the dead sea basin ranging in age from 67 to 32 ka the natural remanent magnetization nrm is carried by titanomagnetite in the detrital laminae whereas the aragonite is diamagnetic the nrm is very stable and was acquired several hundred years after deposition the mean direction of 878 horizons is dd 005o id 45o 95d 1o d 22 we observed three modes of directional geomagnetic variation as a function of and by inference time very rapid inter sample changes slow variation in mean direction and inclination shallowing of about 1o m the overall rate of change in direction is 0 57 0 57o year not significantly different from zero for about 83 of the record the rate of change is less than 1o year and comparable to historical values high rates of change are observed more frequently in the lisan than in historical records and peak rates are up to ten times faster a smoothed curve resulting in a maximum rate of change of 0 66o year and a mean 0 10 0 10o year may be a more realistic representation of the field behavior no reverse nrms were observed but geomagnetic field excursions may be present where the vgps deviate by more than 40o from the geographic north at about 52 and 41 ka the latter may represent the laschamp event 1998 elsevier science b v all rights reserved

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

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

asymmetrical to symmetrical magnetic fabric of dikes paleo flow orientations and paleo stresses recorded on feeder bodies from the motru dike swarm romania the fabric in a dike is representative of the magmatic flow considered as newtonian the anisotropy of magnetic susceptibility of the rocks gives a good representation of the shape preferred orientation which in turn is a marker of the magmatic flow generally a symmetrical pattern of the fabric across the dike is in agreement with a flow of magma within a channel the flow direction is then reliable with this imbrication an asymmetrical fabric is dependent on the flow and displacement of the wall we present the case of both symmetrical and asymmetrical dike fabrics recording different emplacements from a pan african calc alkaline dike swarm of basaltic andesitic dacitic rhyolitic composition of the alpine danubian window from south carpathians romania two populations of dikes have been described thick 1 30 m n s trending dikes and thin 1 m e w dikes the first display asymmetrical fabric and record the regional sinistral movement of the walls in contrast the thin dikes are symmetrical and frequently display an arteritic morphology that limits the dike length with no cartographic extension we propose to relate the two types of dikes to the same regional stress field in a continuum of emplacement during a regional brittle event

earthquake induced liquefaction features in a late quaternary fine grained lacustrine succession fucino lake italy implications for microzonation studies abstract the fucino lacustrine basin in central italy is a large flat area mostly devoted to agriculture with urbanization along the perimeter of the ancient lake in 1915 a strong earthquake struck the area mw 7 0 producing large damages and geological effects including surface faulting ground failures and liquefaction a channel excavated in the lacustrine sediments exposed ground failure with dykes of fine grained sediment that we interpret as the result of earthquake induced liquefaction we present the results of a multidisciplinary work aimed at characterizing in detail the geology of the buried stratigraphic succession its susceptibility to liquefaction and the likely source of the fine grained liquefied material the succession down to 20 m deep is formed by fine grained sediments younger than 170 180 kyrs mostly late pleistocene holocene prevailingly silt or silt clay mixtures the geological field analysis indicates that the dykes are filled by prevailing silt liquefied and transported by upward directed flow of short duration as for earthquake induced liquefaction tilting and lateral spreading accompanied the process the overall liquefaction potential derived from the simplified methods is high correlations of x ray powder diffraction mineralogy of samples from drilling cores with those from dykes allowed us to identify the most likely source layer filling dykes corresponding to a silt layer at 7 8 m depths this layer and the dykes lack illite and montmorillonite clay particles these results contribute to improve studies of liquefactions in sediments that differ from typical liquefiable loose sands they have also implications for microzonation studies most samples show grain size curves that do not fit within the field of potentially liquefiable soils suggesting that criteria based on grain size can be poorly significant in seismic microzonation studies of recent late pleistocene holocene lacustrine fine grained successions

magma flow inferred from ams fabrics in a layered mafic sill insizwa south africa the insizwa sill is a 25 km diameter 1000 m thick layered mafic intrusion part of the karoo igneous province in south africa the peridotitic and gabbronoritic rocks are undeformed and mineral fabrics demonstrably result from magma flow a horizontal centimeter scale model layering is visible in numerous outcrops plagioclase crystals are both tabular and elongated their preferred orientation parallel to the layering forms a foliation and a nw se lineation respectively interpreted as the magma flow plane and flow direction throughout the 78 stations of this study 699 specimens magnetic susceptibilities km range from 750 to 10 000 10 6 si the magnetic anisotropy pj ranges from 1 03 to 1 08 magnetic ellipsoids are both prolate and oblate average tjc0 anisotropy of magnetic susceptibility ams fabrics are dominated by multidomain to pseudo single domain magnetite high field magnetic experiments indicate that the paramagnetic contribution from the mafic silicates is less than 50 for low susceptibility rock types the anisotropy results from magnetite grain shape solely as shown by no significant increase in pj with increasing km the magnetic lineation 305j 0 5j is consistent throughout the sill at various scales and coincides with the mineral lineation in average in contrast the magnetic foliation 125j ne 10j is generally perpendicular to the mineral foliation and to the layering several explanations for this odd configuration are discussed the variations of magnetic parameters across the layering and field observations point to a multiple injection the magnetic lineation is consistent with the presence of a single feeder dike situated to the se of the sill d 2002 elsevier science b v all rights reserved

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

zones of inelastic deformation around surface ruptures detected by magnetic fabrics abstract characterizing the inelastic strain field around co seismic faults is a key to understanding earthquake rupture processes we aim to detect zones of inelastic deformation around surface ruptures using anisotropy of magnetic susceptibility ams analyses to characterize the paleo seismic setting we measured 29 normal faults which cut the late pleistocene lacustrine lisan formation and were associated with shallow

evolution of hydrothermal regime along a crustal shear zone tinos island greece 1 structural cathodoluminescence and sims 18o analyses of quartz calcite veins are combined to constrain the evolution in space and time of fluid infiltration in an exhuming detachment shear zone tinos island cyclades greece careful description of vein arrays shows that the plumbing system evolved into an interconnected network just beneath the ductile to brittle transition microtextures of quartz and calcite infilling veins display deformed relics and newly precipitated grains high resolution 18o mapping in relics yields a steady quartz calcite fractionation of 2 at 400 c whereas fractionation increases in neograins from 2 to 5 in 190 m toward the fault or a 150 c temperature fall cooling is associated with a shift of fluid stable isotope signature from 15 to 0 beneath the detachment results are interpreted as advective removal of heat by massive infiltration of surface derived fluids over depths of 10 15 km fluid penetration was promoted by the coalescence of late ductile early brittle veins as the exhuming footwall crossed the ductile brittle transition only small amounts of fluids penetrated the ductile crust beneath the transitional rheology

characterizing seismites with anisotropy of magnetic susceptibility this study was supported by grants from the israeli government under geological survey of israel ds project 40706 and the israel science foundation isf grants 868 17 we are indebted to vladimir lyakhovsky for helpful discussions during the course of this study and to mike jackson bjarne almqvist and jason patton for providing constructive and very helpful reviews

soft sediment deformation structures interpreted as seismites in middle late pleistocene aeolian deposits apulian foreland southern italy abstract soft sediment deformation structures in middle late pleistocene deposits of torre san gennaro brindisi southern italy have been analysed from a morphologic point of view the deformational structures are represented by deformed cross bedding and large injection structures they are restricted to aeolian sediments and the mechanism of deformation is related to liquefaction and or fluidization processes the liquefaction and or fluidization processes have been interpreted as seismic induced after consideration of all other possible trigger agents the discussion about the possible source areas of the palaeoseismic event was carried out through the analysis both of the general magnitude distance relations and the main structural features of the study zone in conclusion we consider the key criteria for trigger mechanism interpretation of soft sediment deformation structures in aeolian deposits and the actual feasibility of using aeolian sediments for the palaeoseismic studies

development of symmetrical and asymmetrical fabrics in sheet like igneous bodies the role of magma flow and wall rock displacements in theoretical and natural cases abstract two orientations of fabrics are recognised in vertical dykes a symmetric orientation associated with magma injected into non deforming wall rocks and an asymmetric orientation usually associated with external non coaxial shearing or magma injected into an active fault the notion of two fabric arrangements stems from two planes of symmetry the dyke symmetry plane dsp and the fabric symmetry plane fsp this paper uses conceptual models to simulate all possible orientations of magma flow indicators that might be produced within a vertical dyke emplaced under coeval internal and external stresses the effect of magmatic buoyancy related stresses are portrayed in terms of magma flow velocities mfv and the external non coaxial tectonic related stresses in terms of wall displacement velocities divided by two wmv 2 the tectonic setting is that of a sinistral transcurrent fault using these assumptions five cases are proposed mfv wdv 2 mfv wdv 2 mfv wdv 2 mfv

the reliability of anisotropy of magnetic susceptibility ams data as flow direction indicators in friable base surge and ignimbrite deposits italian examples abstract the base surge deposits in linosa and procida islands italy show minimum axes k3 of the anisotropy of magnetic susceptibility ams that are mostly parallel to the flow directions inferred from field evidence but sometimes perpendicular to them samples from different heights above the base of an ignimbrite bed vulsini area italy showing a coarse tail reverse grading and a fine grained basal layer have different magnetic fabrics at 10 and 40 cm from the base the declinations of maximum axes k1 of the ams are approximately 90 from the theoretical flow direction whereas at 60 and 75 cm from the base the k1 axes are approximately parallel to the flow direction this bed also shows a decrease upward of the magnetic foliation lineation and degree of anisotropy suggesting that the ams data could be used to obtain information about flow mechanisms the airm data in the case of the ignimbrite bed show that the long shape axes of the ferromagnetic grains are probably aligned with the maximum axes of the ams for this reason the change in the magnetic fabric at different distances from the base is probably due to differences in the flow behaviour rather than the domain state of magnetite grains this study shows that the ams lineations can indicate the flow direction in base surge and ignimbrite deposits but other geological and magnetic information is necessary to assess if these lineations are flow perpendicular or flow parallel

the accuracy of surface elevations in forward global barotropic and baroclinic tide models abstract this paper examines the accuracy of surface elevations in a forward global numerical model of 10 tidal constituents both one layer and two layer simulations are performed as far as the authors are aware the two layer simulations and the simulations in a companion paper deep sea research ii 51 2004 3043 represent the first published global numerical solutions for baroclinic tides self consistent forward solutions for the global tide are achieved with a convergent iteration procedure for the self attraction and loading term energies are too large and elevation accuracies are poor unless substantial abyssal drag is present reasonably accurate tidal elevations can be obtained with a spatially uniform bulk drag c d or horizontal viscosity k h but only if these are inordinately large more plausible schemes concentrate drag over rough topography the topographic drag scheme used here is based on an exact analytical solution for arbitrary small amplitude terrain and supplemented by dimensional analysis to account for drag due to flow splitting and low level turbulence as well as that due to breaking of radiating waves the scheme is augmented by a multiplicative factor tuned to minimize elevation discrepancies with respect to the topex poseidon t p constrained got99 2 model the multiplicative factor may account for undersampled small spatial scales in bathymetric datasets an optimally tuned multi constituent one layer simulation has an rms elevation discrepancy of 9 54 cm with respect to got99 2 in waters deeper than 1000 m and over latitudes covered by t p 66 n to 66 s the surface elevation discrepancy decreases to 8 90 cm 92 percent of the height variance captured in the optimally tuned two layer solution the improvement in accuracy is not due to the direct surface elevation signature of internal tides which is of small amplitude but to a shift in the barotropic tide induced by baroclinicity elevations are also more accurate in the two layer model when pelagic tide gauges are used as the benchmark and when the t p constrained tpxo6 2 model is used as a benchmark in deep waters south of 66 s for antarctic diurnal tides the improvement in forward model elevation accuracy with baroclinicity is substantial the optimal multiplicative factor in the two layer case is nearly the same as in the one layer case against initial expectations that the explicit resolution of low mode conversion would allow less parameterized drag in the optimally tuned two layer m 2 solution local values of the ratio of temporally averaged squared upper layer speed to squared lower layer speed often exceed 10

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

seismically induced soft sediment deformation structures seismites around sumdo in the lower spiti valley tethys himalaya abstract soft sediment deformation structures were observed in 120 m thick fluvio lacustrine sediments exposed in the sumdo area in the lower spiti valley tethys himalaya himachal pradesh india these structures vary in their morphology and pattern and occur at eight stratigraphic levels s1 s8 spaced at irregular intervals the deformation structures include over steepened stratification diapiric flame like intrusions of clayey material or complex type recumbent folding of flame like nature pseudonodules large scale soft sediment folding faulting small scale associated with folding and sand dykes these structures are restricted to single stratigraphic layers separated by undeformed beds and can be correlated over a large distance the deformation of the soft sediments is attributed to the combined effects of fluidization liquefaction and shear stress and can be related to past seismic activity in the area recently on 19 january 1975 a major earthquake kinnaur earthquake of magnitude 6 8 caused extensive damage including ground rupturing in the sumdo kaurik area this earthquake has been related to the activation of the kaurik chango fault the deformed layers seismites reported here lie adjacent to this fault zone and can be related with episodic seismicity along this fault it is evident from this study that the kaurik chango fault has been re activated a number of times and that the area suffered at least nine major earthquakes with a magnitude of more than 6 during late pleistocene holocene time including the 1975 kinnaur earthquake

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

relationship between dip and magma flow in the saint malo dolerite dyke swarm brittany france abstract a low elevation aeromagnetic survey has been recently carried out in northern brittany france revealing magnetic anomalies over both the onshore and offshore areas the shaded aeromagnetic map displays a striped pattern related to a dolerite dyke swarm dated at ca 330 ma the dyke swarm is slightly fanning at its northern and southern ends and is affected by some major n60 sinistral transcurrent faults after sliding the different segments of the dyke swarm along the actually observed offsets about 20 km one can see the dyke swarm as it was originally trending a study of the anisotropy of the magnetic susceptibility ams has also been conducted over 250 specimens uniformly distributed on 13 sites in section the k max plunge of the ams is broadly the same as the dip of the dykes measured on the field on this section the centre of the fanning pattern is superimposed both with the centre of a magma chamber calculated after gravity and magnetic modelling and with the axis of symmetry of the dyke swarm it can also be observed that the k max plunge which is usually vertical above the magma chamber is oblique with respect to the rims of the dykes in the shallow dipping dykes this may be interpreted as a result of the crystallization of an oblique flow also it seems that the magnetic susceptibility increases when the magma flow is steeper beyond a k max inclination of 45 the bulk susceptibility tends to increase in a linear way

explicit tidal forcing in an ocean general circulation model 1 the eight dominant constituents of the semi diurnal and diurnal tides plus accurate phase information have been implemented in a global version of the modular ocean model version 4 developed by the geophysical fluid dynamics laboratory the simulated tidal signal in the southeast asian region has been validated with observations indicating that the amplitudes and phases are reasonably well reproduced by the model tidal currents play an essential role in transport and mixing processes in the indonesian seas and off the australian northwest shelf vertical tidal mixing introduces a distinct signal in the surface mixed layer and upper ocean temperature the results suggest that application of explicit tidal forcing in operational ocean general circulation models ogcms should become feasible in the near term future

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

mechanical modeling and insar measurements of mount sedom uplift dead sea basin implications for effective viscosity of rock salt we present a mechanical model for the growth of an emerging salt diapir in a tectonically active basin the analytical model is applied to and serves to constrain the effective viscosity of rock salt and strain rates during diapirism of the wall shaped mount sedom rock salt diapir dead sea basin the model is based on one dimensional flow of newtonian viscous fluid salt in a vertical channel that has been driven by the load of the overburden and affected by shear along the channel walls because the poiseuille channel flow profile is parabolic and the couette shear flow profile is linear a one dimensional model provides three sets of predicted profiles topography uplift rate and shear strain the present topography of mount sedom represents the shape of the sedom diapir and hence the effective viscosity of rock salt can be constrained by a model that best fits the present topography of the mountain the resulting sedom rock salt viscosity is determined to be between 2 and 3 1018 pa s and the associated strain rate is between 5 and 6 10 13 s 1 geological structures indicate strain rates of 9 10 13 s 1 and 3 10 14 s 1 during the holocene emerging stage and at the plio pleistocene pre emergent stage of the sedom diapir respectively the uplift history of mount sedom predicted by the model and the current topography are compared to interferometric synthetic aperture radar insar measurements of salt uplift the maximum uplift rates of mount sedom are 8 3 and 5 5 mm yr for its northern and southern parts respectively the insar uplift profiles resemble topographic profiles obtained along the same traverses implying that the uplift history during the last 14 000 years is stable steep uplift gradients observed by insar along the western margin of the diapir are higher than predicted by modeling of newtonian viscous flow this could imply that flow of power law viscous fluid may be more suitable than that of newtonian viscous fluid for the sedom rock salt at high strain rates above 8 10 13 s 1

magnetic fabrics of diamagnetic rocks and the strain field associated with the dead sea fault northern israel in order to exploit the potential of ams axes k1 k2 k3 and magnitudes as a tool to estimate the strain field around major faults the ams of calcite bearing diamagnetic rocks that crop out next to the dead sea fault transform dsf were measured the calcite bearing bar kokhba limestone contains magnetic fabrics due mainly to the diamagnetic phase as indicated by the low iron content 130 ppm and strong negative susceptibilities of all the ams principal axes the magnetic fabrics are solely controlled by the alignment of c axes of almost pure calcite crystals and help to assess the strain fields prevailing post deposition and during the tectonic evolution of the dsf based on the ams measurements of 146 diamagnetic samples as well as 65 paramagnetic samples three groups of minimum k3 ams axes are defined 1 wnne plunging axis 2 wnwese axis and 3 weew axis the latter two groups of k3 axes are aligned sub parallel to neogene to pleistocene finite strain axes inferred from meso scale structures i e folds faults and veins next to the dsf this indicates that k3 axes of diamagnetic rocks can be excellent proxies for strain field directions around major faults differences in the degree of anisotropy p 0 up to w2 and in susceptibility difference dk up to w0 2 of the diamagnetic rocks are related to differences in strain magnitudes based on the proximity of the studied outcrops to the fault traces the values of these variables reflect the stored inelastic strain within the calcite matrix due to repeated faulting activity

paleocurrent analysis for the late pleistocene holocene incised valley fill of the yangtze delta china by using anisotropy of magnetic susceptibility data abstract anisotropy of magnetic susceptibility ams analysis has been conducted on samples from borehole core cm 97 from the yangtze river changjiang incised valley fill china to determine the paleocurrent directions to help in reconstructing sedimentary paleoenvironments borehole cm 97 consists of fluvial unit 1 estuarine units 2 6 and deltaic units 7 9 sediments after the last glacial maximum in ascending order the ams results show that the paleocurrent directions for the tide dominated estuarine and deltaic sediments were westerly or northwesterly directed flood tide dominated but give no definite trend for the fluvial sediments comparison between the paleocurrent directions inferred from primary sedimentary structures and in situ ams data shows that they are in good agreement confirming the applicability of ams as a good paleocurrent indicator for sediments deposited in coastal tide dominated environments considering that these sediments were strongly tide influenced and the tidal pattern since 12 kyr bp has not changed significantly we think that the westerly or northwesterly current direction most probably resulted from flood tidal currents and the sedimentary paleoenvironment was a flood tide dominated estuary or delta additionally it has been found that downhole changes of some ams parameters including the mean magnetic susceptibility k the corrected anisotropy degree p j and the magnetic foliation f clearly mark the defined stratigraphic boundaries in the borehole this further extends the validity of ams as a good stratigraphic marker in addition to its long known credibility as a sensible paleocurrent recorder

oceanic tides from geosat altimetry direct tidal analysis of the altimetry from the geosat exact repeat mission s first year is used to derive estimates of the diurnal and semidiurnal oceanic tides the geoid is removed by collinear differences at 34 1 day separation and the orbit error is reduced by subtracting a slowly modulated 1 cycle revolution term a sequence of independent analyses at grid areas of 1 latitude 1 5 longitude using orthotide functions ensures complete definition of the diurnal and semidiurnal species global admittance maps for m2 and s2 within the latitudes 58 n and 59 s compare well with ground truth at 66 open ocean sites maps of differences between geosat and the naval surface weapons center model show important areas of the order of 10 15 cm the integral for the global power input from the moon gives 2 51 tw m2 0 44 tw s2 lower than many previous estimates but in agreement with figures deduced from a recent analysis of satellite orbits

evidence from gabbro of the troodos ophiolite for lateral magma transport along a slow spreading mid ocean ridge the lateral flow of magma and ductile deformation of the lower crust along oceanic spreading axes has been thought to play a significant role in suppressing both mid ocean ridge segmentation and variations in crustal thickness direct investigation of such flow patterns is hampered by the kilometres of water that cover the oceanic crust but such studies can be made on ophiolites fragments of oceanic crust accreted to a continent in the oman ophiolite small scale radial patterns of flow have been mapped along what is thought to be the relict of a fast spreading mid ocean ridge here we present evidence for broad scale along axis flow that has been frozen into the gabbro of the troodos ophiolite in cyprus thought to be representative of a slow spreading ridge axis the gabbro suite of troodos spans nearly 20 km of a segment of a fossil spreading axis near a ridge transform intersection we mapped the pattern of magma flow by analysing the rocks magnetic fabric at 20 sites widely distributed in the gabbro suite and by examining the petrographic fabric at 9 sites we infer an along axis magma flow for much of the gabbro suite which indicates that redistribution of melt occurred towards the segment edge in a large depth range of the oceanic crust our results support the magma plumbing structure that has been inferred indirectly from a seismic tomography experiment on the slow spreading mid atlantic ridge

soft sediment deformation structures interpreted as seismites in lacustrine sediments of the prebetic zone se spain and their potential use as indicators of earthquake magnitudes during the late miocene lacustrine formations of late miocene age in the prebetic area se spain show several types of deformational structures that are interpreted as seismites they are present in both marginal and deep lacustrine facies seismites formed in marginal lake environments comprise sand dikes pillows and intruded and fractured gravels in deep lacustrine facies the seismites are represented by pseudonodules mushroom like silts protruding into laminites mixed layers disturbed varved lamination and loop bedding the measured orientations of these structures are consistent with the orientations of the main faults limiting the basins showing that their origin is clearly related to the tectonic stress field that prevailed in the region during the late miocene the magnitudes of the earthquakes that deformed the sediments have been estimated after published data from both ancient and recent lake deposits accumulated in tectonic active regions elsewhere a rank of earthquake magnitudes with two end members i e the lowest magnitudes recorded by loop bedding in laminites and the highest magnitudes represented by intruded and fractured gravels is proposed