tectonic evolution of the southern levant margin since mesozoic abstract recognition of syndepositional faults and mechanical analysis of fault slip data are used to reconstruct a high resolution tectonic evolution of israel and to characterize the stress fields associated with the major tectonic deformation events of this area since mesozoic times syndepositional normal faults recognized in mesozoic and paleogene rocks indicate three extensive deformation phases that were active at least during early jurassic campanian and eocene times inversion of fault slip data indicate that a ne sw extension characterizes the two first events whereas orientation of extension during the eocene was n s to nne ssw several scenarios are proposed to explain these newly documented normal faults measured faults also document synchronous strike slip and reverse regimes unambiguous chronological relationships between fault data and bedding attest that a wnw ese to nw se compression is associated with the syrian arc folding event during the late cretaceous times this compression pursued during the development of the dead sea transform plate boundary but its relationship with neogene structures is unclear fault data suggest that folding during the neogene was driven by a regional nnw sse compression a minor ne sw compression was also recognized but no compatible large scale structures were found to date we also show that the post pliocene normal faults developed under a ne sw extension

on the stability of the atlantic meridional overturning circulation during the last deglaciation using a generalized stability indicator l we explore the stability of the atlantic meridional overturning circulation amoc during the last deglaciation based on a paleoclimate simulation from the last glacial maximum as forced by various external climate forcings notably the meltwater forcing the amoc experiences a collapse and a subsequent rapid recovery in the early stage of deglaciation this change of the amoc induces an anomalous freshwater divergence and later convergence across the atlantic and therefore leads to a positive l suggesting a negative basin scale salinity advection feedback and in turn a mono stable deglacial amoc further analyses show that most anomalous freshwater is induced by the amoc via the southern boundary of the atlantic at 34 s where the freshwater transport m ovs is about equally controlled by the upper branch of the amoc and the upper ocean salinity along 34 s from 19 to 17 ka as a result of multiple climate feedbacks associated with the amoc change the upper ocean at 34 s is largely salinified which helps to induce a switch in m ovs from import to export our study has important implications to the deglacial simulations by climate models a decomposition of l shows that the amoc stability is mostly determined by two terms the salinity stratification at 34 s and the change of stratification with the amoc both terms appear positive in model however the former is likely to be distorted towards positive as associated with a common bias existing over the south atlantic in climate models therefore the amoc is potentially biased towards mono stability in most paleoclimate simulations

geometric changes of plate boundaries along part of the northern dead sea transform geochronologic and paleomagnetic evidence the korazim block an elevated pressure ridge along with the faults bounding the sea of galilee and hula pull apart basins are internal structures of the dead sea transform plate boundary k ar dates and paleomagnetic data from basalt flows and sedimentary strata are utilized to determine the stratigraphy and the deformation of the region the integration of the two methods together with structural data yield high resolution age determination of the stratigraphic sequence and provides insight into the timing and style of deformation the korazim block is covered in its southern and central areas by pliocene basalt flows the cover basalt 5 1 3 6 ma and ruman basalt 2 9 2 2 ma formations and in its northern area by basalts yarda basalt 0 9 0 8 ma and sediments 3 0 2 3 and 1 6 0 9 ma of plio pleistocene age the magnetic polarity of a total of 29 lava flows and intercalated sedimentary strata is mixed the mean magnetic declination of the 29 sites shows an anomalous direction which yields 11 4 4 0 counterclockwise rotation with respect to the expected field the mean inclination of 46 0 4 1 does not significantly deviate from the expected field the anomalous declination is interpreted as the consequence of faulting and block rotation accommodating internal deformation this deformation did not begin before late pliocene to early pleistocene probably not before 0 9 ma and may still be active simultaneous right lateral slip of 50 175 m with a small reverse component of 30 90 m along nw trending faults and 11 counterclockwise rotation created internal deformation of the korazim pressure ridge this deformation is the consequence of left lateral slip along the almagor strand of the dead sea transform subparallel to the plate slip vector thus a compression component was formed which presumably led to the internal deformation of the korazim block the recent deformation of the korazim block in relation to the age of adjacent structures and to the age of the dead sea transform permits temporal resolution of geometric changes which must typify transform boundaries such as the dead sea transform internal structures within transforms may change along with the transform internal geometry and become inactive while new structural features may develop

an indicator of the multiple equilibria regime of the atlantic meridional overturning circulation recent model results have suggested that there may be a scalar indicator s monitoring whether the atlantic meridional overturning circulation moc is in a multiple equilibrium regime the quantity s is based on the net freshwater transport by the moc into the atlantic basin it changes sign as soon as the steady atlantic moc enters the multiple equilibrium regime because of an increased freshwater input in the northern north atlantic this paper addresses the issue of why the sign of s is such a good indicator for the multiple equilibrium regime changes in the atlantic freshwater budget over a complete bifurcation diagram and in finite amplitude perturbation experiments are analyzed in a global ocean circulation model the authors show that the net anomalous freshwater transport into or out of the atlantic resulting from the interactions of the velocity perturbations and salinity background field is coupled to the background steady state state freshwater budget and hence to s the sign of s precisely shows whether this net anomalous freshwater transport is stabilizing or destabilizing the moc therefore it can indicate whether the moc is in a single or multiple equilibrium regime

microearthquake activity in the dead sea region summary small earthquakes in the dead sea depression part of the jordan valley dead sea rift were recorded and analysed with 117 identified events of 0 5 ml 4 2 the microseismicity recorded by a local portable network during a period of about 20 months shows a normal rate of seismicity for the region with b values around 0 8 the recorded seismicity is mainly confined to the basin and its boundaries in the southern part of the dead sea basin we found a tendency to clustering which is clearly demonstrated in very similar seismograms of several events recorded at the same station two clusters on the eastern fault are separated by an area with no seismicity for at least 5 yr relative location of events in one of the clusters exhibits a clear north south lineament two active north south left lateral strike slip faults along the east and west boundaries of the southern section of the dead sea basin are distinguished and confirmed by using composite focal mechanism solutions in four out of more than 60 events we found normal faulting where one has a ml 4 1 for 34 events with 1 6 ml 4 2 we found seismic moment estimates m0 of 1 2 1019 m0 2 3 times 1022 dyne cm and brune stress drop estimates s between 0 6 and 92 bars for earthquakes of m0 smaller than about 5 times 1021 dyne cm we found only small variations in corner frequency f0 resulting in decreasing s with decreasing m0 this breakdown of the scaling relation for small earthquakes suggests an fmax slightly lower than 10 hz for the dead sea region the fmax is confirmed by available accelerometer data

the exhaust valve of the north atlantic during glacial periods climate records are marked by large amplitude oscillations believed to be a result of north atlantic na freshwater anomalies which weakened the thermohaline circulation thc and introduced instabilities such oscillations are absent from the present interglacial period with the aid of a semiglobal analytical model it is proposed that the bering strait bs acts like an exhaust valve for the above na freshwater anomalies specifically it is suggested that large instabilities in the thc are only possible during glacial periods because during these periods the bs is closed during interglacial periods when the bs the exhaust valve is open low salinity anomalies are quickly flushed out of the north atlantic by the strong southern ocean winds

the tectonic development of the western margin of the gulf of elat aqaba rift abstract along the western coast of the gulf of elat a 30 km wide shear belt of subparallel faults trending n s to ne sw is developed this shear belt is observed mainly within the precambrian basement terrain sinistral movements on these faults have been recognized based on offsets of magmatic bodies and lithological contacts in rocks of precambrian age the cumulative displacement measured independently at several localities across the belt attains a total of 24 km early neogene volcanism in the form of long dikes trending nw se is known from the eastern desert of egypt of the gulf of suez and along the red sea coast of saudi arabia volcanic bodies of a similar pattern have been identified in eastern sinai these bodies mainly dolerites and basalts intruding mesozoic sediments are parallel to each other and to the gulf of suez they are tens to hundreds of kilometers long and spaced several tens of kilometers apart dating k ar of bodies in sinai saudi arabia and in the eastern desert of egypt suggest an age of 20 22 m y for this extensive volcanism all the dikes are sinistrally displaced by the individual faults of the eastern sinai shear belt the amount of movement recorded using the precambrian markers is identical to movement recorded by offsets of the early neogene dikes this proves that the total 24 km shear of this fault system postdates the 20 22 m y volcanic phase it is assumed that the recorded movements are part of the 105 110 km shear persumed to exist along the gulf of elat which is also younger than 20 22 m y preliminary results suggest that a similar amount of movement is observable along a shear zone developed on the eastern coast of the gulf of elat thus only some 60 km movement are taken up by faults in the gulf itself the evolving model suggests that 1 a the intrusion of very long basaltic dikes in a nw se direction on both sides of the red sea accompanied the initial stage of development of the red sea gulf of suez rift valley 2 b a basic change in the geotectonic regime occurs after the intrusion of this volcanic suite large scale horizontal movements are initiated being recorded as a 105 110 km sinistral movement along the arava jordan rift this movement implies a synchronous opening of the red sea

the stability of the moc as diagnosed from model projections for pre industrial present and future climates the stability of the atlantic meridional overturning circulation moc is investigated for various climate scenario runs using data from the cmip3 archive of coupled atmosphere ocean models apart from atmospheric feedbacks the sign of the salt flux into the atlantic basin that is carried by the moc determines whether the moc is in the single or multiple equilibria regime this salt advection feedback is analyzed by diagnosing the freshwater and salt budgets for the combined atlantic and arctic basins consistent with the finding that almost all coupled climate models recover from hosing experiments it is found that most models feature a negative salt advection feedback in their pre industrial climate freshwater perturbations are damped by this feedback excluding the existence of a stable off state for the moc all models feature enhanced evaporation over the atlantic basin in future climates but for a moderate increase in radiative forcing b1 and 2 co2 scenarios there is a decrease of the fresh water flux carried by the moc into the atlantic the deficit is made up by increased fresh water transport by the gyre circulation in this forcing regime the salt advection feedback becomes less negative for three models from an ensemble of eight it is positive in a 2 co2 climate while two models feature a positive feedback in the pre industrial climate for even warmer climates a1b equilibrium and 4 co2 the salt feedback becomes more negative damping again it is shown that the decrease in northward fresh water transport at 34 s by the moc in b1 equilibrium and 2 co2 is due to a reduction of the inflow of intermediate waters relative to thermocline waters associated with a robust shoaling of the moc in future warmer climates in a1b and 4 co2 climates northward freshwater transport increases again the moc keeps shoaling but both intermediate and thermocline water masses freshen

drainage system reorganization and late quaternary tectonic deformation along the southern dead sea transform the dead sea transform dst accounts for 105 km of left lateral slip between the arabian plate and the sinai subplate since the miocene paleoseismic studies along the arava valley segment of the dst suggest that late quaternary deformation has been primarily concentrated along the axis of the transform valley here we examine late quaternary changes in drainage system characteristics and attribute them to recent tectonic deformation in this region field based geomorphic mapping topographic cross sections and optically stimulated luminescence osl dating of fluvial deposits were used to map and date recent changes in the fluvial characteristics of catchments along the western margin of the southern arava our results reveal coeval migration of channels consistent with tectonically induced surface tilting caused by north south compressional deformation along the western margin of the transform valley osl dating indicates this tilting was initiated in the late pleistocene and continued at least into the mid holocene the late quaternary tectonic deformation along the southern arava segment of the dst is distributed across a wider zone than previously considered and extends out to the margins of the transform valley we associate the inferred wider deformation zone to possible changes in the geometry of motion along the dst

tectono sedimentary evolution of lower to middle miocene half graben basins related to an extensional detachment fault western crete greece crustal extension in the overriding plate at the aegean subduction zone related to the rollback of the subducting african slab in the miocene resulted in a detachment fault separating high pressure low temperature hp lt metamorphic lower from non metamorphic upper tectonic units on crete in western crete detachment faulting at deeper crustal levels was accompanied by structural disintegration of the hangingwall leading to the formation of half graben type sedimentary basins filled by alluvial fan and fan delta deposits the coarse grained clastic sediments in these half grabens are exclusively derived from the non metamorphic units atop the detachment fault being in direct tectonic contact with hp lt metamorphic rocks of the lower tectonic units today the basins must have formed in the period between c 20 and 15 ma prior to the exposure of the hp lt metamorphic rocks at the surface and juxtaposed with the latter during ongoing deformation

instability of the thermohaline circulation with respect to mixed boundary conditions is it really a problem for realistic models abstract this comment discusses two issues raised by a recent study of the stability of the thermohaline circulation tziperman et al a numerical problem is pointed out that may have affected the results of the reported calculations in addition it is argued that the state transition of the model circulation found in the above study is triggered by a convective instability mechanism not the advective mechanism discussed by its authors should this be the case then the conclusion of tziperman et al that the ocean is close to a stability transition point must be questioned

the stability of an evolving atlantic meridional overturning circulation 1 in this study we propose a generalized stability indicator l for a slowly evolving and quasi steady atlantic meridional overturning circulation amoc which represents a feedback related to the amoc and its associated freshwater transport within the atlantic basin as an improvement from previous indicators for the amoc in equilibrium this generalized indicator does not require a divergence free freshwater transport in the atlantic for a collapsed amoc which enables it to correctly monitor the amoc stability through the amoc hysteresis loop in the coupled atmosphere ocean general circulation models from the simulation the indicator l suggests that the amoc is in a stable regime with single equilibrium under the present day and the last glacial maximum lgm climates however under the present day climate a bering strait bs closure will diminish the freshwater outflow from the north atlantic into the arctic as the amoc collapses resulting in a freshwater convergence in the atlantic basin and making the amoc reside in a stable collapsed state i e the amoc exhibits characteristics of multiple equilibria further analysis shows that the bs effect is much reduced under the lgm climate this generalized indicator l has great implications for paleoclimate studies in understanding the abrupt climate change due to the instability of the amoc

active tectonics of the yizre el valley israel using high resolution seismic reflection data abstract we present a series of high resolution seismic reflection lines across the yizre el valley which is the largest active depression in israel off the main trend of the dead sea rift the new seismic reflection data is of excellent quality and shows that the valley is dissected into numerous small blocks separated by active faults the yizre el valley is found to consist of a series of half grabens rather than a single half graben or a symmetrical graben the faults are generally vertical and appear to have a dominant strike slip component but some dip slip is also evident a marked zone of compression near megido is associated with the intersection of the two largest faults in the valley the carmel fault and the gideon fault variable trend of the faults reflects the complexity of the local geology along the boundary between the wide nw se trending farah carmel fault zone and the e w trending basins and ranges in the lower galilee this tectonic complexity is likely to result from a highly variable stress pattern modified by the structures inside it normal faulting in the valley occurred at an early stage of its development as a tectonic depression however strike slip motion on the carmel fault and possibly also on some of the other faults appears to have started together with the onset of normal faulting earthquake hazard in the area appears to be uniform as faults are distributed throughout the yizre el valley

thermohaline circulation hysteresis a model intercomparison we present results from an intercomparison of 11 different climate models of intermediate complexity in which the north atlantic ocean was subjected to slowly varying changes in freshwater input all models show a characteristic hysteresis response of the thermohaline circulation to the freshwater forcing which can be explained by stommel s salt advection feedback the width of the hysteresis curves varies between 0 2 and 0 5 sv in the models major differences are found in the location of present day climate on the hysteresis diagram in seven of the models present day climate for standard parameter choices is found in the bi stable regime in four models this climate is in the mono stable regime the proximity of the present day climate to the stommel bifurcation point beyond which north atlantic deep water formation cannot be sustained varies from less than 0 1 sv to over 0 5 sv

intensification of the atlantic deep circulation by the canadian archipelago throughflow abstract low salinity water export through the canadian archipelago is one of the main components of the freshwater budget in the arctic ocean nevertheless the canadian archipelago is closed in most global ocean models how it is that deep water formation at high latitudes of the northern hemisphere depends on the opening and closing of the canadian archipelago is investigated an ice ocean coupled model whose horizontal resolution is 1 is used without restoring surface salinity to observed data when the canadian archipelago is open the atlantic deep circulation strengthens by 21 this enhancement is caused by intensification of deep water formation in the northern north atlantic ocean surface salinity in these regions is affected by the east greenland current which flows from the fram strait and increases its salinity when the canadian archipelago is opened the low salinity flow through the canadian archipelago affects surface salinity only in the western part of the labrador sea a cyclonic c

stress field fluctuations along the dead sea rift since the middle miocene the dead sea transform dst is the suture between the african and the arabian plates both of which subduct northward under the eurasian plate the collision of these plates with eurasia and their relative motion are the source for their internal deformation especially in the vicinity of the dead sea transform geological observations indicate that two distinct paleostrain regimes operated adjacent to the dead sea rift and in the sinai israel subplate 1 wnw shortening less than 10 and nne extension beginning in the turonian is associated with the development of the syrian arc fold belt and attributed to the syrian arc stress field sas and 2 middle miocene to recent nnw shortening and ene extension associated with the 105 km sinistral displacement along the dead sea transform and the opening of the red sea is attributed to the dead sea stress field dss it was originally suggested that the sas terminated during the middle miocene with initiation of the dss however trend and age analysis of many structures shows that formation of sas compatible structures continued after the middle miocene up to the recent in some middle miocene and younger rocks structures such as faults dikes volcanic lineaments and tectonic stylolites compatible with both stress fields were reported in a few locations structures compatible with both stress fields crosscut each other it is suggested that the movements which resulted in the development of the syrian arc and other sas compatible structures are continuing to the recent and that dss movements are superimposed upon them the overlapping of sas and dss structures adjacent to the dst results from spatial and temporal fluctuations in the overall stress state we propose that such variations could be caused by the superposition of large earthquake stress drops associated with movements along the dst on a steady background plate scale stress regime associated with the sas thus dss compatible structures should form in preseismic activity periods when dst related elastic strain is high on the other hand the sas compatible structures should form during interseismic activity times subsequent to large local stress release along the dst

a diagnostic indicator of the stability of the atlantic meridional overturning circulation in ccsm3 a diagnostic indicator dmov is proposed in this paper to monitor the stability of the atlantic meridional overturning circulation amoc the dmov is a diagnostic for a basinwide salt advection feedback and defined as the difference between the freshwater transport induced by the amoc across the southern border of the atlantic ocean and the overturning liquid freshwater transport from the arctic ocean to the north atlantic as validated in the community climate system model version 3 ccsm3 for an amoc in the conveyor state a positive dmov freshwater convergence in the atlantic basin indicates a monostable amoc and a negative dmov freshwater divergence indicates a bistable amoc based on dmov the authors investigate the amoc stability in the last glacial maximum lgm and analyze the modulation of the amoc stability by an open closed bering strait moreover the authors estimate that the real amoc is likely to be bistable in the present day since some observations suggest a negative dmov freshwater divergence is currently in the atlantic basin however this estimation is very sensitive to the choice of the observational data

prediction of ultrathin lacustrine sandstones by joint investigation of tectonic geomorphology and sedimentary geomorphology using seismic data abstract weak seismic signals from ultrathin 1 7 m sandstones increase uncertainties of thickness estimation imposing a significant challenge for accurate prediction of subtle hydrocarbon reservoirs these types of uncertainties however can be reduced by a combined use of kinematic travel time and dynamic amplitude information extracted from 3d seismic data in this case study in the kuqa depression of the tarim basin china we conducted an investigation of seismic based tectonic geomorphology and then sedimentary geomorphology in four steps 1 reconstruction of basin floor paleogeomorphology using a residual structure map of a closely underlain erosional unconformity 2 study of seismic lithology by seismic modeling and 90 phase adjustment of seismic traces 3 mapping of geomorphologic patterns of depositional systems on stratal slices and 4 combined analysis of tectonic geomorphology and sedimentary geomorphology for a better understanding of depositional history and reservoir distribution results show a good match between valley and lowland systems on the basin floor sandstone thickness trend and lobate sedimentary geomorphologic patterns indicating a widespread yet laterally highly variable ultrathin sandy fan delta system

bering strait throughflow and the thermohaline circulation received 25 august 2005 revised 10 november 2005 accepted 14 november 2005 published 21 december 2005 1 in this study we employ a global coupled climate model to show that the bering strait is important to the variations of the thermohaline circulation three experiments are analyzed a present day control run and two freshwater hosing runs results show that as the thermohaline circulation weakens due to freshwater forcing in the northern north atlantic the bering strait throughflow weakens and even reverses its direction and the export of the arctic freshwater into the northern north atlantic is reduced or the arctic even takes freshwater from the latter thus helping the thermohaline circulation to recover relatively quickly after the end of the freshwater hosing citation hu a and g a meehl 2005 bering strait throughflow and the thermohaline circulation geophys res lett 32 l24610 doi 10 1029 2005gl024424

impact of seawater equation of state on the simulation of atlantic meridional overturning circulation the atlantic meridional overturning circulation amoc plays a central role in the decadal variability of global and regional climate through changing poleward transport of heat however realistic simulation of the amoc i e its strength and spatial structure remains a challenge for ocean general circulation models ogcms and coupled climate models here we investigate how the simulated amoc could be affected by improved accuracy of the seawater equation of state eos with an ogcm two eoss used in this study the unesco eos80 and the stiffened eos derived from the compressibility of sea water and the unesco eos80 compared to the model using the unesco eos80 the model using the stiffened eos yields stronger deep convection in the labrador sea the irminger iceland scotland basin and the greenland iceland norwegian gin seas which leads to an improvement in the simulation of the amoc along 26 5 n the maximum transport is increased from 14 9 to 17 4 sv and the interface between the upper clockwise cell and lower counterclockwise cell is deepened from 2 8 to 3 3 km both matching the observations better taken the labrador sea as an example the processes including both direct and indirect causes that in part responsible for the improved amoc are as follows the use of stiffened eos increases the density throughout the water column and weakens the stability of sea water moreover the enhanced cabbeling and thermobaric effect strengthen the vertical advection intensifying the deep convection and increasing formation of deep water which eventually improves the simulation of the amoc the intensified amoc in turn speeds up the surface return flow transporting more warm and saline water to the high latitudes in the north atlantic which contributes to the densification of surface water similar analyses can be applied to the iceland scotland basin and gin seas thus the enhanced deep convection and formation of deep water in the labrador sea as well as in the iceland scotland basin and gin seas improve the simulated amoc

intraplate deformation by block rotation and mesostructures along the dead sea transform northern israel combined analysis of mega and meso structures yield the strain inferred stress and tectonic history of the margin of the sinai sub plate in northern israel along the dead sea transform three major stress regimes were developed and have affected the region since the middle miocene one is regional and controlled the left lateral shear along the dead sea transform this one has been active since post early miocene is characterized by 1 trending c 345 and deformed the plate margin by horizontal shear and contemporaneous block rotation this style of deformation is similar to simple shear the second one was local and may be subdivided into distinct stress and strain domains it was characterized by 1 trending e w and 3 trending n s which produced a conjugate set of strike slip faults the region underwent n s elongation by horizontal shear and block rotation similar to the pure shear mechanism this stress regime was active in late miocene to early pliocene time the third and youngest stress regime is extentional with 1 vertical and 3 oriented n s this one has been active since post middle pliocene time producing e w normal faults and minor n s elongation the second and third stress regimes show local distribution and developed as a consequence of the bent geometry of the transform vis a vis the plate slip vector finite element and photoelastic models predict the development of local stress fields and elongation of the plate margin parallel and subparallel to the transform plate boundary the strain of the plate margin in northern israel and southern lebanon indicate remarkable elongation parallel to the dead sea transform by a factor of 1 5 2 1 since the miocene this process of intraplate deformation and the consequent strain is unique to the parts of the plate margin which are adjacent to the bent segment of the transform

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

the role of mixed boundary conditions in numerical models of the ocean s climate abstract several simple numerical experiments are conducted using both single and double hemisphere ocean basins under symmetric steady forcing to study de ocean s thermohaline circulation it is shown that a stable steady state obtained under a restoring surface boundary condition on salinity becomes unstable upon a switch to a flux boundary condition the polar halocline catastrope of f bryan occurs it is shown that further integration of this collapsed state ultimately yields a steady stable one cell circulation with the approach being essentially chaotic but with significant energy at decadal period the two hemisphere ocean passes through many stages in which violent overturning occurs o 80 101 m3 a 1 these flushes occurs in both hemispheres and are of one cell structure the time period between them bushes varies from seveal hundred to about one thousand years a single 12 vertical level hemispheric basin spun up from an initial state of rest under mixed boundary conditions restoring boun

multimodel analysis on the response of the amoc under an increase of radiative forcing and its symmetrical reversal the response of the atlantic meridional overturning circulation amoc to an increase of radiative forcing ramp up and a subsequent reversal of radiative forcing ramp down is analyzed for four different global climate models due to changes in ocean temperature and hydrological cycle all models show a weakening of the amoc during the ramp up phase once the external forcing is reversed the results become model dependent for ipsl cm5a lr the amoc continues its weakening trend for most of the ramp down experiment for hadgem2 es the amoc trend reverses once the external forcing also reverses without recovering its initial value for ec earth and mpi esm lr the recovery is anomalously strong yielding an amoc overshoot a robust linear dependency can be established between amoc and density difference between north atlantic na deep water formation region and south atlantic sa in particular amoc evolution is primarily controlled by a meridional salinity contrast between these regions during the warming scenario the subtropical atlantic becomes saltier while the na experiences a net freshening which favours an amoc weakening the different behaviour in the models during the ramp down is dependent on the response of the ocean at the boundaries of na and sa the way in which the positive salinity anomaly stored in the subtropical atlantic during the ramp up is subsequently released elsewhere characterizes the recovery an out of phase response of the salinity transport at 48 circ hbox n and 34 circ hbox s boundaries is able to control the meridional density contrast between na and sa during the transient experiments such a non synchronized response is mainly controlled by changes in gyre salinity transport rather than by changes in overturning transport thus suggesting a small role of the salt advection feedback in the evolution of the amoc

controls of sedimentation in the malawi rift valley central africa abstract the malawi rift is the southermost classic rift valley trough in the cenozoic african rift valley system much of its floor is flooded by lake malawi which is approximately 570 km long 60 km across and up to 500 m deep this rift basin is a potentially useful analogue of many economically important ancient sedimentary troughs rift valley structures are extremely important in controlling both the distribution of sediments in the basin as a whole and also details of sedimentation on a local scale on the basin wide scale an important association between the type of rift boundary structure and amount of rift floor subsidence is recognised this association appears to apply to several section of the african rift system pre rift topography is major control on the position of major rivers and their deltas or turbidite fans along the basin margin the area of pre rift drainage network captured in the course of rift movements is a significant factor in the hydrologic budget of the basin climate is however the dominant control on the hydrologic budget and at present the basin is flooded to overflow level prevailing winds are important in beach ridge and back beach aeolian dune development climatic conditions produce thermal stratification of the lake with an oxic epilimnion down to 250 m depth overlying an anoxic hypolimnion the oxic bottom waters in the shallower parts of the lake appear to promote iron precipitation in the sediments

the mechanisms of the atlantic meridional overturning circulation slowdown induced by arctic sea ice decline abstractwe explore the mechanisms by which arctic sea ice decline affects the atlantic meridional overturning circulation amoc in a suite of numerical experiments perturbing the arctic sea ice ra

fused spectral decomposition seismic attributes and forward seismic modelling to predict sand bodies in meandering fluvial reservoirs abstract understanding the hierarchical architectural elements of fluvial sand bodies is important for planning their development strategy and to enhance oil recovery red green blue rgb blending of multiple seismic attributes and forwarding seismic modelling are commonly used in the analysis of compound sand bodies however rgb blending of multiple seismic attributes can only qualitatively describe the boundaries and thickness of sand bodies the forward seismic modelling techniques previously documented in the literature are not effective when depicting the geometry of and stacking relationships between sand bodies i e reservoir compartmentalisation hence we propose in this work a new workflow that combines fused spectral decomposition seismic attributes sdsas and forwarding seismic modelling to quantitatively predict sand thickness and to characterise stacking relationships between sand bodies first we employ a support vector machine svm algorithm to fuse high middle and low frequency components attributes of seismic data so as to quantitatively predict the thickness of sand bodies second we define the seismic waveform response patterns corresponding to the typical conceptual stacked sand bodies with the constraints of waveform patterns and predicted sand thickness fused sdsas the geometry and stacking relationships of the sand bodies are characterised by forward seismic modelling to illustrate the effectiveness of our proposed workflow we apply it to the neogene minghuazhen formation nm of the qhd 32 6 oil field bohai bay basin china we define five architectural elements of a meandering fluvial reservoir by analysing the hierarchy of sand bodies using our workflow the predicted sand bodies in this workflow were further proven by horizontal drilling and production data

structure and paleostresses in the gilboa region western margins of the central dead sea rift abstract the relationships between tectonic paleostresses and major fault systems are analyzed for the gilboa region the gilboa is a folded block on the western margins of the dead sea transform which has been deformed and uplifted at least since the miocene the tectonic paleostresses in the gilboa were determined by inversion of slip striations along small faults measured in the field and from the trends of basaltic dikes one state of stress dominated the gilboa region since the miocene the principal axes of the calculated stress tensor are 1 at 0 122 2 vertical and 3 at 0 032 this stress fits well with the trends of the syrian arc folds in the gilboa and its is compatible with the observed normal slip along the gilboa fault however this stress is incompatible with the either left lateral slip or normal faulting along the dead sea system possible mechanisms to resolve this incompatibility are discussed

simulated resumption of the north atlantic meridional overturning circulation slow basin wide advection and abrupt local convection abstract the resumption process of the north atlantic meridional overturning circulation moc is investigated in a series of freshwater hosing experiments using a comprehensive coupled climate model four different freshwater perturbations are applied to the north atlantic between 50 n and 70 n leading to a substantial weakening of moc and an expansion of winter sea ice cover over the greenland iceland norwegian gin seas deactivating the freshwater forcing leads to a two phase recovery of the moc the first phase is a slow basin wide advection process whereas the second phase is an abrupt decadal scale transition located in the north atlantic the slow basin wide advection process to an intermediate state of the moc is characterized by a restart of the deep water production in the area of the subpolar gyre and the irminger basin however the ice cover over the gin seas remains whereas the surface density gradually increases in the gin seas on a century time scale the length of this intermediate state depends on the strength of freshwater perturbation which determines the magnitude of the meridional density gradient in the north atlantic the second transition phase is triggered by a model specific density threshold reached in the gin seas when passed the moc abruptly intensifies by 60 within 60 80 years the analysis shows that this abrupt intensification only depends on surface salinity in the gin seas the model results reveal that the simulated sea ice retreat in the gin seas and a rapid increase of the greenland air temperature of the second phase of the resumption of the moc are similar in amplitude to temperature proxies observed during dansgaard oeschger events of the last ice age

response of thermohaline circulation to freshwater forcing under present day and lgm conditions responses of the thermohaline circulation thc to freshwater forcing hosing in the subpolar north atlantic ocean under present day and the last glacial maximum lgm conditions are investigated using the national center for atmospheric research community climate system model versions 2 and 3 three sets of simulations are analyzed with each set including a control run and a freshwater hosing run the first two sets are under present day conditions with an open and closed bering strait the third one is under lgm conditions which has a closed bering strait results show that the thc nearly collapses in all three hosing runs when the freshwater forcing is turned on the full recovery of the thc however is at least a century earlier in the open bering strait run than the closed bering strait and lgm runs this is because the excessive freshwater is diverged almost equally toward north and south from the subpolar north atlantic when the bering strait is open a significant portion of the freshwater flowing northward into the arctic exits into the north pacific via a reversed bering strait throughflow which accelerates the thc recovery when the bering strait is closed this arctic to pacific transport is absent and freshwater can only be removed through the southern end of the north atlantic together with the surface freshwater excess due to precipitation evaporation river runoff and melting ice in the closed bering strait experiments after the hosing the removal of the excessive freshwater takes longer and this slows the recovery of the thc although the background conditions are quite different between the present day closed bering strait run and the lgm run the thc responds to the freshwater forcing added in the north atlantic in a very similar manner

evidence for jericho earthquakes from slumped sediments of the jordan river delta in the dead sea seismic reflection data and historical accounts suggest that a large submarine slump in the dead sea was produced by the most recent large earthquake along the dead sea jordan transform plate boundary the m l 6 25 jericho earthquake of july 11 1927 the correlation supports the use of seismically triggered slump landslide and other sediment failures in lakes to infer the timing of paleoearthquakes furthermore the location of the submarine slump adds to evidence that the 1927 earthquake was caused by rupture on a fault segment beneath the north basin of the dead sea this fault rupture implies that the strain accumulation on the jordan fault north of the dead sea is higher than previously recognized older seismically triggered slumps buried beneath the 1927 slump show that a record of ancient jericho earthquakes can also be found in the sedimentary record the estimated number and age range of these slumps suggest a long average earthquake recurrence time

transient simulation of last deglaciation with a new mechanism for bolling allerod warming we conducted the first synchronously coupled atmosphere ocean general circulation model simulation from the last glacial maximum to the bolling allerod ba warming our model reproduces several major features of the deglacial climate evolution suggesting a good agreement in climate sensitivity between the model and observations in particular our model simulates the abrupt ba warming as a transient response of the atlantic meridional overturning circulation amoc to a sudden termination of freshwater discharge to the north atlantic before the ba in contrast to previous mechanisms that invoke amoc multiple equilibrium and southern hemisphere climate forcing we propose that the ba transition is caused by the superposition of climatic responses to the transient co 2 forcing the amoc recovery from heinrich event 1 and an amoc overshoot

the evolution of barahta rhomb shaped graben mount hermon dead sea transform abstract mount hermon forms part of a ne trending anticlinal structure formed during compression resulting from sinistral movement along the dead sea rift transform at the northern end of the hula valley the dead sea transform branches into five faults one of which the rachaya fault crosses the hermon on its western side with about 1000 m of left lateral displacement the rachaya fault comprises two left stepping segments the southern si on fault and the northern shab a fault as a result of this stepping a rhomb shaped graben was formed two of the bordering faults of the barahta valley are dip slip faults the northern and the western whereas the other two are strike slip faults kinematic calculations reveal that horizontal displacement of about 800 m was transferred from the si on fault to the shab a fault mainly along the eastern diagonal faults the formation of the barahta rhomb shaped graben resulted from a local stress field formed due to the fault configuration and the motion of the arabian block and not due to the regional stress field the structure of the barahta graben can be largely explained by the rotational model rather than by the classic pull apart model it is concluded that stepover of strike slip faults is essential for development of rhomb grabens but the mode of formation is different in each case and depends on the fault configuration and direction of block motion

on the link between the two modes of the ocean thermohaline circulation and the formation of global scale water masses a close link between the formation of global scale water masses such as north atlantic deep water nadw and antarctic intermediate water aaiw and two stable modes of the thermohaline circulation thc is investigated in a coupled model in the upper 2 3 km of the atlantic the thc modes are characterized by meridional overturning circulations of opposite sign with either a dominance of the aaiw cell over the nadw cell off thc mode or vice versa on thc mode a transition between these thc modes is controlled by the relationship between the densities in the source regions of formation of aaiw and nadw water masses this is shown by applying a freshwater perturbation in the region of enhanced aaiw formation in the southern ocean to obtain a hysteresis loop of the nadw circulation transitions between the two modes of the thc occur when the densities in the source regions of aaiw and nadw become comparable to each other

state of stress from focal mechanisms before and after the 1992 landers earthquake sequence the state of stress in the eastern california shear zone ecsz changed significantly because of the occurrence of the 1992 m w 6 1 joshua tree and the m w 7 3 landers earthquakes to quantify this change focal mechanisms from the 1975 galway lake sequence the 1979 homestead valley sequence background seismicity from 1981 to 1991 and the 1992 landers sequence are inverted for the state of stress in all cases the intermediate principal stress axis s2 remained vertical and changes in the state of stress consisted of variations in the trend of maximum and minimum principal stress axes s 1 and s 3 and small variations in the value of the relative stress magnitudes in general the stress state in the ecsz has s 1 trending east of north and 0 43 to 0 65 suggesting that the ecsz is a moderate stress refractor and the style of faulting is transtensional south of the pinto mountain fault in the region of the 1992 joshua tree earthquake the stress state determined from the 1981 to 1991 background seismicity changed on 23 april and again on 28 june 1992 in the central zone s 1 rotated from n14 5 e to n28 5 e on 23 april and back again to n16 5 e on 28 june thus the landers mainshock in effect recharged some of the shear stress in the region of the m w 6 1 joshua tree earthquake comparison of the state of stress before and after 28 june 1992 along the landers mainshock rupture zone showed that the mainshock changed the stress orientation the s1 trend rotated 7 to 20 clockwise and became progressively more fault normal from south to north along the emerson camp rock faults the variation was so prominent that the focal mechanisms of aftershocks could not be fit by a single deviatoric stress tensor the complex distribution of p and t axes suggests that most of the uniform component of the applied shear stress along the northern part of the rupture zone was released in the mainshock the san bernardino mountains region of the m w 6 2 big bear earthquake has a distinctively different state of stress as compared to the landers region with s 1 trending n3 5 w this region did not show any significant change in the state of stress following the 1992 m w 6 2 big bear sequence

north atlantic subsurface temperature response controlled by effective freshwater input in heinrich events abstract the northern north atlantic nna subsurface temperature in response to the slowdown of the atlantic meridional overturning circulation amoc is crucial for ice sheet calving and recovery of the amoc in heinrich events paleoclimate proxies and modeling studies suggest that the nna subsurface exhibits a robust warming during heinrich 1 but with a less clear response during younger dryas yd the mechanism for the potentially different subsurface responses has remained not well understood previous studies show different nna subsurface response depending on hosing at different locations here by examining a suite of water hosing experiments with different hosing regions and intensities we show that regardless of the hosing location nna subsurface temperature response is determined by the effective freshening over the nna deep convective regions through the competition between the warming associated with the suppressed vertical mixing and the cooling associated with the weakened amoc heat transport a weak effective freshening favors advective effect and in turn cooling while a strong effective freshening strengthens the mixing effect and leads to a warming our results suggest that a cooling may occur in the nna subsurface during yd

impact of north atlantic freshwater forcing on the pacific meridional overturning circulation under glacial and interglacial conditions abstractthe pacific meridional overturning circulation pmoc is not well known compared to the atlantic meridional overturning circulation amoc due to its absence today however considering pm

overpressure preventing quartz cementation a reply chemical compaction and the relative importance of the pressure dissolution and illite mica induced dissolution imid models have remained a contentious issue as is the role played by stress in chemical compaction this paper offers further support and evidence as discussed in stricker et al 2016b focusing on the reservoir quality of the triassic skagerrak formation sandstones in the high pressure high temperature hpht central graben north sea the reply discusses alterative reservoir quality interpretations and comments as raised by maast 2016 a series of theoretical and experimental studies as well as field based evidence is presented providing strong support to the important role of stress e g vertical effective stress during chemical compaction the evidence leads to the conclusion that the process of chemical compaction is stress and temperature driven and significantly enhanced by clay minerals playing a catalytic role by increasing the width of diffusion pathway or by modifying the kinetics of the dissolution process

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

interpretive advantages of 90 phase wavelets part 2 seismic applications we examine field seismic data to test the benefits of 90 phase wavelets in thin bed interpretation that are predicted by seismic modeling in part 1 of this paper in an interbedded sandstone shale miocene succession in the gulf of mexico basin a 90 phase shift of nearly zero phase seismic data significantly improves lithologic and stratigraphic interpretation a match between seismic and acoustic impedance ai profiles results in a better tie between seismic amplitude traces and lithology indicative logs better geometric imaging of ai units that does not use dual polarity seismic events results in easier and more accurate reservoir delineation less amplitude distortion and the stratigraphy independent nature of thin bed interference significantly improves stratigraphic resolution and seismic stratigraphic profiling for a ricker like wavelet having small side lobes stratigraphic resolution of 90 phase data is considerably higher than that of zero phase data in this specific case stratigraphic re

dilution of the northern north atlantic ocean in recent decades declining salinities signify that large amounts of fresh water have been added to the northern north atlantic ocean since the mid 1960s we estimate that the nordic seas and subpolar basins were diluted by an extra 19 000 5000 cubic kilometers of freshwater input between 1965 and 1995 fully half of that additional fresh water about 10 000 cubic kilometers infiltrated the system in the late 1960s at an approximate rate of 2000 cubic kilometers per year patterns of freshwater accumulation observed in the nordic seas suggest a century time scale to reach freshening thresholds critical to that portion of the atlantic meridional overturning circulation

geological structure of the eastern side of the lower jordan valley dead sea rift reflection seismic evidence abstract interpretation of recently released seismic reflection lines from the shuna eastern jericho basin combined with re analysis of the lithologic logs of the deep jv 1 and jv 2 boreholes provide new insights into the structure of the sedimentary basin that formed along the dead sea transform fault north of the dead sea in jordan we identified four major seismic boundaries in the reflection profiles the upper two were correlated with borehole stratigraphy these reflection boundaries include the top of the pan african basement r4 the base of the mesozoic r3 the base of the cretaceous r2 and the base of the post eocene section r1 the latter records sedimentation during the dead sea transform tectonic regime the total thickness attained by the older sedimentary units late cretaceous through cambrian is apparently less than 2 km we identified a subsurface structure a faulted monocline with a n s trend sub parallel to the strike of the dead sea transform that is named here al kharrar monocline the al kharrar structural ensemble is buried by syntectonic lacustrine and fluviatile sediments of the jordan valley group the structure formed as part of the dead sea transform deformation overprinting the late cretaceous syrian arc folds continued tectonic deformation is evident from the prominent unconformity at the base of post eocene syntectonic deposits that dip nw w and s away from the structural high along the nw flank of the al kharrar monocline syntectonic sediment thickness is generally less than 0 5 km while along the sw flank it thickens rapidly to nearly 1 km at the southern end of the interpreted seismic lines this rapid southern subsidence probably continues into the north end of the dead sea basin the lake s shoreline being located less than 3 km to the south young bifurcating faults with reverse slip components cutting the eastern part of the al kharrar monocline are attributed to a positive flower structure this pattern suggests strike slip with localized active compression northeast of the dead sea it may result from local transpression between fault strands that appear to be a northward continuation of the eastern boundary fault of the dead sea basin

coseismic stress changes induced by the 1989 loma prieta california earthquake earthquake focal mechanisms from before and after the 1989 loma prieta california earthquake are used to infer the coseismic stress change before the main shock most earthquakes correspond to right lateral slip on planes sub parallel to the san andreas fault and imply a generally n s most compressional stress axis and a vertical intermediate stress axis aftershocks within the main shock rupture zone however display almost every style and orientation of faulting implying an extremely heterogeneous stress field this suggests that the main shock relieved most if not all of the shear stress acting on its fault plane aftershocks that lie on the perimeter of the rupture agree with spatially uniform stress states but only when considered in three groups north south and above the main shock rupture area in each of these areas the stress state may reflect stress transfer by the main shock

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

tectonic analysis of the dead sea rift region since the late cretaceous based on mesostructures we have measured the orientations of small faults slickensides tectonic stylolites vein with secondary mineralization small folds and dikes in israel and sinai these structures are indicators of paleo stress or strain and provide the pattern of tectonic deformation data were collected at 130 stations most with tens of separate measurements most stations showed consistent deformation stations were located on exposures ranging from precambrian crystalline rocks to pleistocene sediments we have defined two tectonic stress fields each relatively uniform in both time and space one stress field with dominating maximum horizontal compression trending w to wnw in the late cretaceous to eocene rocks in the folds and plateaus west of the dead sea rift the second field with dominating horizontal extension trending e to ene in all rocks inside the rift and proximal thereto the first stress field is called the syrian arc stress and the second is called the dead sea stress a change in style of tectonic deformation which corresponds to the two stress fields is manifested also in the major structures in israel the late cretaceous to neogene deformation is characterized by long wavelength folds and monoclines whereas the neogene to recent deformation is characterized by normal and strike slip faults and volcanic activity

structural features of northern tarim basin implications for regional tectonics and petroleum traps the rhombus shaped tarim basin in northwestern china is controlled mainly by two left lateral strike slip systems the northeast trending altun fault zone along its southeastern side and the northeast trending aheqi fault zone along its northwestern side in this paper we discuss the northern tarim basin s structural features which include three main tectonic units the kalpin uplift the kuqa depression and the north tarim uplift along the northern margin of the tarim basin structural mapping in the kalpin uplift shows that a series of imbricated thrust sheets have been overprinted by strike slip faulting the amount of strike slip displacement is estimated to be 148 km by restoration of strike slip structures in the uplift the kuqa depression is a mesozoic cenozoic foredeep depression with well developed flat ramp structures and fault related folds the baicheng basin a quaternary pull apart basin developed at the center of the kuqa depression subsurface structures in the north tarim uplift can be divided into the mesozoic cenozoic and the paleozoic lithotectonic sequences in seismic profiles the paleozoic litho tectonic sequence exhibits the interference of earlier left lateral and later right lateral strike slip structures many normal faults in the mesozoic cenozoic litho tectonic sequence form the negative flower structures in the north tarim uplift these structures commonly directly overlie the positive flower structures in the paleozoic litho tectonic sequence the interference regions of the northwest trending and northeast trending folds in the paleozoic tectonic sequence have been identified to have the best trap structures our structural analysis indicates that the tarim basin is a transpressional foreland basin rejuvenated during the cenozoic

the role of the atlantic freshwater balance in the hysteresis of the meridional overturning circulation we have studied the response of the atlantic meridional overturning circulation to surface freshwater forcing using an ocean gcm coupled to an energy moisture balance atmosphere model the overturning collapses rapidly when a slowly increasing forcing applied to the north atlantic passes a positive threshold and spins up equally quickly when the forcing falls below a negative threshold this well known behaviour is referred to as hysteresis because the thresholds in forcing are different for the transitions in opposite directions however we argue that the behaviour of the atlantic salinity is more fundamental than the forcing hysteresis as a function of freshwater forcing occurs because the states with north atlantic overturning on and off each tend to reinforce their associated salinity distributions and inhibit the transition to the other state during the collapse the atlantic becomes less saline because of the import of 80 sv year of freshwater by ocean transports across 30 s during the spin up this freshwater is exported again we show that qualitatively similar hysteresis behaviour can be produced by perturbing the system without any net freshwater forcing the salinity flip flop is associated with the appearance and disappearance of a shallow reverse overturning circulation south of the equator which is present while the northern overturning is absent and may provide the mechanism for the ocean freshwater influx during collapse

soils as a tool for estimating ages of quaternary fault scarps in a hyperarid environment the southern arava valley the dead sea rift israel abstract on the alluvial fan of nahal shehoret in the extremely arid region of the negev desert israel reg soils developed on stable alluvial surfaces in colluvium along terrace risers and in colluvial units on a complex fault scarp were compared the degree of soil profile development provided an age estimate of the surface that was faulted a maximum age estimate of the scarp or terrace riser and an estimate of the maximum recurrence intervals of faulting events irsl dates of the tectonically displaced alluvial surfaces and colluvial units at the same site enabled us to re evaluate the use of reg soils for relative dating the major faulting event started at 34 8 4 3 ka it displaced a late pleistocene surface of the nahal shehoret alluvial fan dated at 56 10 8 ka renewed fluvial activity and deposition of alluvium on the downfaulted block had almost terminated by 13 6 2 3 ka the scarp was formed during the latest pleistocene and was followed by smaller faulting events which had only minor effects on the fault scarp morphology the similarity of age estimates from irsl dating and the degree of soil development in this environment indicates that soils can be used to date surfaces and colluvial units

relative sensitivity of the atlantic meridional overturning circulation to river discharge into hudson bay and the arctic ocean 1 increases in high latitude river discharge over the 20th century and projected continued increases during the 21st century may have an impact on the atlantic meridional overturning circulation amoc which could feed back to regional and global climate although the general trend in high latitude river discharge is positive there is important geographical spread in the trends while eurasian rivers draining into the arctic ocean show positive trends over the 20th century rivers draining into hudson bay show negative trends since 1964 here the sensitivity of amoc to changes in river discharge into hudson bay and the arctic ocean is studied with an intermediate complexity earth system model it is found that ocean freshening originating from arctic rivers is more effective in slowing down the amoc than freshening originating from hudson bay rivers given the same magnitude of freshening in both regions the lesser impact of hudson bay river discharge on amoc is the result of a buildup of freshwater anomalies in the labrador sea affecting the northward flow of the gulf stream this work highlights that not only the freshening magnitude but the region where this freshening takes place is crucial for the amoc response to altered river discharge climatology

multiple equilibria of the global thermohaline circulation abstract a general circulation model with a highly idealized geometry is used to investigate which fundamentally different equilibria of the global thermohaline circulation may exist the model comprises two identical basins representing the atlantic and pacific oceans which are connected by a circumpolar channel in the south the model circulation is driven in addition to wind forcing by restoring the sea surface temperature to prescribed values and specified freshwater fluxes in the surface salinity budget mixed boundary conditions the boundary conditions are symmetric with respect to the equator and identical for both oceans four fundamentally different stable steady states are found under the same set of boundary conditions two of the equilibria show both oceans in the same state with high altitude deep water formation occuring either in both northern or in both southern oceans respectively two additional equilibria exist in which the thermohaline circulations of the basins differ fundament

seven million years of strike slip and related off fault deformation northeastern marlborough fault system south island new zealand the marlborough fault system mfs south island new zealand is remarkable for the oblique slip nature of its active faulting and can be placed in a framework of pacific australian pac aus plate motions and geodetic strain new zealand illustrates changing degrees of upper plate slip partitioning in an obliquely convergent margin that varies along strike in crustal type and subduction geometry in this paper we focus on the ne part of this transcurrent fault system especially the awatere fault which is the only marlborough fault to offset a major neogene basin strike slip on an ancestral eastern strand of this fault began after 7 4 6 4 ma later vertical axis rotation may have caused it to be abandoned in favor of the currently active strand since 7 ma at least 34 10 km of dextral slip has accrued on the awatere fault 6 km of slip has accrued on two nearby strands and 4 km has accrued on the currently active coastal strand comparison of miocene with late quaternary offsets suggests that rates of strike slip on the fault have been nearly constant or have possibly decelerated we interpret spatial and temporal patterns of strike slip in the mfs to reflect southward migration of transform motion resulting from increased pac aus plate convergence late neogene to present day shortening directions in ne south island are indicative of a partially slip partitioned margin slip partitioning diminishes southward as the underlying subduction interface becomes strongly coupled suggesting a simple mechanical relationship between these processes

multiple equilibria of an asymmetric two basin ocean model abstract an ocean general circulation model is used to examine the role of model geometry and surface buoyancy and wind stress forcing in the asymmetry of the global thermohaline circulation the model domain is a highly idealized atlantic and pacific linked by a circumpolar ocean in the south and the integrations are performed under mixed boundary conditions diagnosed from spinups under various temperature and salinity profiles constructed from the present day climatology the model exhibits a tendency to favor either a conveyor type circulation with sinking in the northern north atlantic and upwelling in the north pacific or a southern sinking state with deep sinking in the antarctic only this bias is not dictated solely by the hydrological cycle nor apparently by the greater northern extension of the atlantic basin but presumably by the overall asymmetry of the geometry equilibria with northern sinking in both basins can appear however when the winds in the southern ocean are reduced or th

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

the atlantic freshwater budget as a diagnostic for the existence of a stable shut down of the meridional overturning circulation 1 which physical processes effectively determine the stability regime of the atlantic meridional overturning circulation moc is not yet fully understood we investigate the role of the oceanic freshwater transport into the basin employing a coupled model of intermediate complexity by modifying the longitudinal variation of surface salinities near the southern border at 33 s the amount of salt flowing out of the atlantic via the brazil current can be regulated in turn this will influence whether the moc exports or imports salt water the latter is associated with a basin scale salinity overturning feedback which can be either positive or negative pulse experiments strongly suggest that its sign determines the existence of a monostable or bistable regime in our model

use of 230th u ages of striated carnotites for dating fault displacements crusts of uranium minerals carnotite and tyuyamunite were found along some fault planes in the northern negev israel field microscope and scanning electron microscope sem examinations of the carnotite showed that they crystallized on previously formed faults and then underwent a later deformation this deformation is evidenced by slickensides and striations that developed on the three scales on the crusts the carnotites were dated by the 230th u method and found to be between 123 and 19 ka indicating that the most recent displacement along the faults occurred during late pleistocene to holocene time hence the u series of deformed carnotite is suggested as a method for dating young displacement along faults

a zonally averaged ocean model for the thermohaline circulation part ii interocean circulation in the pacific atlantic basin system abstract the zonally averaged latitude depth ocean model developed in part i is extended to a two basin system representing the atlantic and pacific steady states are calculated under two different surface boundary conditions to study a possible global thermohaline circulation linking the pacific and the atlantic if the surface temperature and salinity profiles are identical functions of latitude in both the pacific and the atlantic the steady state under restoring boundary conditions consists in spite of the different basin extensions of a two cell structure in each basin upon switching to mixed boundary conditions the state is unstable and a one cell circulation with downwelling at high northern latitudes develops in both basins for a realistic surface salinity profile that is fresher in the pacific the steady state under restoring boundary conditions is completely different it exhibits a global thermohaline circulation with strong interocean man exchange deep water is formed primarily in

high latitude salinity effects and interhemispheric thermohaline circulations a general circulation model for the ocean is used to investigate the interaction between the global scale thermohaline circulation and the salinity distribution it is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing multiple equilibrium solutions are obtained for the same forcing by perturbing the high latitude salinity field in an otherwise equatorially symmetric initial condition the timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation

young faults in the hula pull apart basin central dead sea transform abstract the geometry and nature of structural features inside the hula pull apart basin at the central dead sea transform are presented here two systems of n s left lateral strike slip faults are located on the east and west sides of the hula basin both fault systems are composed of several segments arranged in a right stepping en echelon pattern the northern end of each segment is bent northeastward and usually merges with the next segment elevated regions and small hills appear on the northern side of each bend the strike slip faults are oblique with both vertical and horizontal components the vertical component may be normal or reverse although the hula valley is subjected to general extension the studied structures indicate local compression inside the basin normal faults striking e w comprise the northern border of the hula basin age determination of displaced travertines and basalts along the faults indicates sub recent tectonic activity and suggests migration of normal faulting towards the inner part of the basin the youngest fault displaces travertine dated at 25 300 years

sedimentary facies analysis using sequence stratigraphy and seismic sedimentology in the paleogene pinghu formation xihu depression east china sea shelf basin abstract based on integrated investigation of seismic multi attribute well logs cores and geological data the sedimentary facies and lithofacies analysis are conducted in the paleogene pinghu formation of the xihu depression east china sea the pinghu formation is the main hydrocarbon bearing strata and source rock interval in the xihu depression and represents a second order sequence it can be subdivided into three third order sequences from base to top sq1 sq2 and sq3 from sq1 to sq3 sequences displayed almost similar depositional patterns displaying different characteristics of lithology and facies distribution the fan shaped and lobate proximal tidal delta facies are deposited at the western edges with relatively strong hydrodynamics while the lobate and belt shaped scattered tidal flat facies are deposited at the center of the area with relatively weak hydrodynamics from sq1 to sq3 the distribution of the sand rich tidal delta facies evolves from a large range to a small then larger again are predominantly influenced by the hydrodynamics tectonic and topography this study demonstrates facies analysis using sequence stratigraphy and seismic sedimentology provide useful insight to paleogene oil and gas exploration in east china sea shelf basin and other similar basins and can also be effectively used in areas which lack well or outcrop data

distinctive diamagnetic fabrics in dolostones evolved at fault cores the dead sea transform abstract we resolve the anisotropy of magnetic susceptibility ams axes along fault planes cores and damage zones in rocks that crop out next to the dead sea transform dst plate boundary we measured 261 samples of mainly diamagnetic dolostones that were collected from 15 stations to test the possible effect of the iron content on the ams we analyzed the fe concentrations of the samples in different rock phases dolostones with mean magnetic susceptibility value lower than 4 10 6 si and iron content less than 1000 ppm are suitable for diamagnetic ams based strain analysis the dolostones along fault planes display ams fabrics that significantly deviate from the primary sedimentary fabric the characteristics of these fabrics include well grouped sub horizontal minimum principal ams axes k 3 and sub vertical magnetic foliations commonly defined by maximum and intermediate principal ams axes k 1 and k 2 axes respectively these fabrics are distinctive along fault planes located tens of kilometers apart with strikes ranging between nnw sse and nne ssw and different senses of motion the obtained magnetic foliations k 1 k 2 are sub parallel within 20 to the fault planes based on rock magnetic and geochemical analyses we interpret the ams fabrics as the product of both shape and crystallographic anisotropy of the dolostones preferred shape alignment evolves due to mechanical rotation of subordinate particles and rock fragments at the fault core preferred crystallographic orientation results from elevated frictional heating 300 c during faulting which enhances c axes alignment in the cement supported dolomite breccia due to crystal plastic processes the penetrative deformation within fault zones resulted from the local fault related strain field and does not reflect the regional strain field the analyzed ams fabrics together with fault plane kinematics provide valuable information on faulting characteristics in the uppermost crust

tectonic sedimentology sediment systems deciphering global to local tectonics tectonic sedimentology has broad appeal because it can be applied at many time and length scales such as sedimentary consequences of changing rates of plate creation at mid ocean ridges continent continent collisions plateaux uplift active plate margins extensional rift tectonics and the birth growth and death of individual folds and faults tectonic sedimentology deals with the direct influence of neotectonics on sedimentation and basin development and with the inverse problem of reconstructing the order and development of palaeotectonic structures this review attempts to show how the scope and importance of the subject has developed over the last decade and is divided into five themes i at the largest tectonic scale constraints on mid ocean ridge activity and continent continent collisions come from a precise chemical analyses of fluid inclusions in marine halite deposits dating back to ca 550 ma b sr isotopic ratios of marine phanerozoic calcitic fossils and c chemical composition of archaean and proterozoic banded iron formations ii at regional scales constraints on the timing and extent of continental plateau uplift incision and cratonic tilting are given by a palaeoaltimetry estimates from oxygen isotope depletion in carbonate palaeosols b radiometric dating of palaeowater table speleothems and c preferential river migration iii at basin scales catchment processes are emphasized as key controls on sediment flux from tectonic uplands to sedimentary basins the inadequacy of sediment transport algorithms based on tractive stress and flow power to describe erosion incision and sediment transport during the most formative catchment hydrological events is emphasized iv rates of basin scale fault and fold growth displacement death and basement uplift are provided by application of facies analysis and sequence stratigraphy to accurately dated sediments in sedimentary basins v the effects of changing climate and varying basin base level in modifying tectonic influences on erosion and sedimentation are examined in such cases experimental and numerical modelling using multi variate parameters of subsidence rate sediment supply and sea level change can shed light on the problem future developments will undoubtedly improve such models hopefully establishing full linkage and feedback between sediment water supply and changing climate within an overall tectonic framework that may itself be changing

variability and multiple equilibria of the thermohaline circulation associated with deep water formation abstract in this study the variability of the thermohaline circulation on decadal and centennial time scales that is related to the process of deep water formation is investigated this is done within the context of a simple geostrophic three layer ocean model with a rectangular closed basin when slowly varying the atmospheric forcing the model response shows sudden transitions characterized by local changes in convective activity many different equilibria were found within the thermally driven regime in stommel s sense i e downwelling occurs near the poles next the deep water formation process was analyzed with a one dimensional box model in this box model four different regimes can be identified convective nonconvective periodic and a regime where both convection and no convection are possible with the same mixed boundary conditions these regimes were identified in the circulation of the ocean model a region was traced where convection is possible according to the authors analysis but

holocene seismic and tectonic activity in the dead sea area abstract the dead sea is a large active graben within the dead sea rift which is bounded by two major strike slip faults the jericho and the arava faults we investigated the young tectonic activity along the jericho fault by excavating trenches up to 3 5 m deep across its trace the trenches penetrate through late pleistocene and holocene sediments we found that a zone up to 15 m wide of disturbed sediments exists along the fault these disturbed sediments provide evidence for two periods of intensive activity or more likely for two major earthquakes that occurred during the last 2000 years the earthquakes are evident in small faults vertical throw of a few layers cracks unconformities and wide fissures we further documented evidence for recent sinistral shear along the jericho fault in deformed sediments and damage to an 8th century palace on a subsidiary fault we suggest that the two earthquakes may be correlated with the 31 b c earthquake and the 748 a d earthquake reported by the ancients