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

regional flow perturbation folding within an exhumation channel a case study from the cycladic blueschists abstract kilometre scale cylindrical folds and associated parasitic folds that trend at small angles to the transport lineation are analysed along a 100 km long transport normal segment of the cycladic blueschists in an attempt to reconstruct the 3d structural architecture within an exhumation channel reversals in the polarity of both fold vergence and the hinge lineation obliquity occur in a flow normal direction defining transport parallel culmination and depression surfaces that root downwards onto an underlying detachment fold patterns generated around culmination and depression surfaces support models of flow perturbation folding where folds initiate at small angles or sub parallel to transport in response to wrench dominated differential shearing successive culmination and depression surfaces are separated from one another by along strike distances of 20 km although atypical fold geometries developed in the flanks of major culmination and depressions follow their own patterns revealing that smaller perturbations occur within the larger scheme major culminations are interpreted to reflect regions of surging flow marked by increased velocity during exhumation whilst the opposite is true for depressions this behaviour implies that on a regional scale differential shear varies laterally in an irregular sinusoidal manner defining areas of relative high and relative low displacement within the exhumation channel

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

distinguishing tectonically and gravity driven synsedimentary deformation structures along the apulian platform margin gargano promontory southern italy abstract the assessment of deformation types within the slope of a carbonate platform can be complicated by the possible interaction of rooted tectonically induced and superficial gravity driven structures an ideal case study to document and distinguish tectonically and gravity driven structures is provided by the cretaceous slope to basin carbonates exposed in the gargano promontory southern italy these carbonates formed adjacent to the apulian platform margin which was oriented approximately ne sw to nw se along the southern and northern edges of the promontory respectively slump related folds are characterised by axial planes typically oriented either sub parallel or at small angles to the strike of the inferred paleoslope in fact the strike of folds is roughly ne sw in the southern portion of the study area whereas it is nw se in the northern part correspondingly gravity driven normal and reverse faults strike sub parallel and at acute angles to the adjacent apulian paleoslope cretaceous tectonic faults in the slope to basin carbonates form two principal sets striking nw se and wnw ese the former set is made up of normal faults and the latter one includes mainly oblique slip normal faults neither normal nor oblique slip normal faults show any relationship with the geometry of the paleoslope the results obtained from this study may help the interpretation of subsurface data in those geological contexts in which the interplay of gravitational and tectonic processes is responsible for deformation

nature of thrust zones in deep water sand shale sequences outcrop examples from the champsaur sandstones of se france compressional structures are commonly found in deep water turbidite successions that contain important hydrocarbon reservoirs here we present a field study of deformation in the champsaur sandstones of the french alps to illustrate the geometry of natural thrust zones in weakly lithified turbidites the evolution of these zones results from a combination of faulting and folding a general model for thrust zone evolution is developed where even though there is a tendency to produce localised through going slip surfaces folding can occur at various stages segments of dismembered fold limbs carried up thrust ramps potentially increase the fault zone permeability and fluid communication through the stratigraphic pile the propensity for folding is increased by the presence of thin bedded sand shale successions while imaging these detailed architectures may lie beyond the reach of seismic methods in the sub surface it may be possible to predict the nature of thrust zones from knowledge of the sand shale stratigraphy and vice versa

interpreting soft sediment deformation and mass transport deposits as seismites in the dead sea depocenter we have studied the history of earthquakes over the past 70 kyr by analyzing disturbed sedimentary layers around the margins of the dead sea however we know little about disturbances in the basin depocenter where water depth is 300 m and accessible only by drilling in this study we compare disturbances from the dead sea depocenter with the contemporaneous earthquake record 56 30 ka that was recovered on the western margin of the lake this comparison allows us to discern the characteristics of disturbance in the different subaqueous environments and identify the source and sedimentary process of mass transport deposits our observations indicate that i the long disturbance sequences in the dead sea depocenter are composed of in situ deformation slump and chaotic deposits ii earthquake triggered kelvin helmholtz instability is a plausible mechanism for the in situ deformation in the lake center iii the slump is slope area sourced iv the unit of chaotic deposits is lakeshore sourced and v earthquake triggered slope instability is a viable mechanism for the slump and chaotic deposits we further suggest that long sequences of disturbance in seismically active lake depocenters can be used to infer earthquake clusters

shear instability in a highly stratified estuary abstract shear instability is found to be the principal mechanism of vertical exchange within the pycnocline of a salt wedge estuary a field program involving high resolution velocity and density measurements as well as high frequency acoustic imagery allowed direct comparison of instantaneous richardson number distributions to the occurrence of shear instability the theoretical stability threshold of 0 25 is consistent with the measurements based on estimates of gradients that contain the mean as well as fluctuations due to internal waves an effective stability threshold based on mean gradients is found to be approximately one third reflecting a significant contribution of internal wave shear the integral effect of the mixing process is to homogenize the gradients of velocity and density producing linear profiles of these quantities across the pycnocline a turbulent prandtl number of unity is suggested by the vertical distributions of velocity and density during periods of active vertical mixin

physical and numerical modeling of the entrainment by a high concentration mud suspension abstractthis paper presents the results of a physical and numerical model study on the entrainment by a high concentration cohesive sediment suspension this turbulent near bed suspension is referred to as a concentrated benthic suspension cbs in the current configuration the cbs entrains low concentrated overlying water the results of the physical and numerical experiments are in line with the results of similar experiments published in literature in which in contrast the upper turbulent layer entrains water and sediment from the lower layer the entrainment rate for these experiments is almost inversely proportional to the bulk richardson number e ri n with n 1 indicating a profound effect of the side wall of the experimental facility we anticipate that the conditions studied in this paper are characteristic for the behavior of many high concentration systems such as the mouth of the amazon river and in the loire estuary and ems river a sequence of entrainment during high flow velocit

particle trapping in estuarine tidal flows particle trapping in estuarine turbidity maxima etm is caused primarily by convergent mean and or tidal fluxes of sediment the result is an approximately bell shaped along channel distribution of vertically integrated tidal cycle mean suspended sediment concentration observations from the columbia river estuary suggest that 1 strong two layer or internal along channel residual and overtide flows are generated by time varying stratification and 2 correlations between the near bed velocity and the suspended sediment fields at these frequencies are important in landward transport of sediment a new spatially and temporally integrated form of the sediment conservation equation has been derived to analyze this trapping process time changes in tidally averaged sediment concentration between two estuarine cross sections can be shown to be related to the divergence of the seaward river flow transport the divergence of velocity shear sediment stratification correlations for the mean flow and each tidal constituent and net erosion or deposition at the bed vertically integrated variables other than seaward river transport are absent from this integrated balance analysis of sediment fluxes using this balance supports the idea that internal residual and overtide circulations are primarily responsible for the landward sediment transport on the seaward side of etm found near the upstream limits of salinity intrusion the balance also shows that attempts to represent fluxes causing trapping of sediment in an etm as a product of a time mean vertically integrated along channel gradient and a diffusivity inevitably lead to the appearance of countergradient transport and thus a negative diffusivity on the seaward side of the etm this result occurs because the trapping process is inherently nonlinear and at least two dimensional and because a one dimensional representation is physically unrealistic

geotechnical properties of evaporite soils of the dead sea area the dead sea basin is the lowest point on earth and is tectonically subsiding during the holocene period the climate became much drier with increasing evaporation whereby initially lacustrine sediments were deposited from the non marine brines giving a multi layered stratigraphy of lime carbonate and halite sediments the lime carbonate sediments are comprised of laminated clay to silt sized clastic sediments calcite and authigenic aragonite and gypsum the halite commonly appears as rock salt chemical industries based on harvesting the salts from the dead sea have developed on both the israeli and the jordanian sides of the basin the lime carbonate soils are used for dike construction and these soils together with significant salt layers are encountered in the foundations of structures dikes and tailings dams requiring definition of their geotechnical properties use of standard soil mechanics definitions and testing approaches for the lime carbonates have been found inapplicable particularly in view of their exceptionally high saline content and it has been necessary to develop new concepts the rock salt is encountered at shallow depths with unit weights considerably lower than those usually discussed in the literature and with correspondingly different mechanical properties the geotechnical properties of these soils and approaches used to define them are discussed in the paper

turbulence and internal waves at the equator part ii details of a single event abstract in the low richardson number shear flow above the pacific equatorial undercurrent a single vertical microstructure profile intersected the overturning crest of a packet of high horizontal wavenumber waves the observed dissipation rates within the overturning wave were so high that if they were representative of the volume averaged rate the total wave energy would have been dissipated within a single buoyancy period the chaotic structure and temperature fluctuations with horizontal scales less than 2 m of the two wave crests and troughs west of the overturning wave crest suggest that recent mixing had occurred there wave crests and troughs east of the overturning wave crest showed little or no sign of turbulent mixing similar high horizontal wavenumber waves believed to be shear instability waves have been observed in low richardson number regions of the midlatitude seasonal thermocline although the equatorial waves have a horizontal wavelength appropriate for shear instability waves t

shoreline change patterns in sandy coasts a case study in sw spain abstract coastal changes on sandy shorelines are continuous and occur at diverse spatial and temporal scales gaining knowledge on beach change processes increases our capability to manage risks especially shoreline erosion affecting the increasing population living in coastal areas processes and factors involved in medium and short term beach changes depend on the morphological and dynamic characteristics of the coast in this work the decadal behaviour of 58 sandy beaches along the 150 km long south atlantic coast of spain between the guadalquivir river mouth and the strait of gibraltar is analysed in order to investigate the relationships between shoreline change patterns and the diverse morphological and dynamic factors controlling beach evolution in the area for this purpose georectified aerial photographs spanning the period 1956 2008 were compared in a gis environment to calculate rates of shoreline change short term evolution of beach profiles was also analysed in selected areas of interest results show that the study area exhibits a great variety of shoreline evolution trends with erosion prevailing in the northern and central sectors and stability or even accretion in the southern sector in general sediment availability is the main factor determining coastal erodibility in the area largely conditioned by the reduction in fluvial sediment supply caused by river basin regulation nearshore bathymetry also has a great significance as it controls wave refraction diffraction patterns and wave energy concentration on certain zones human interventions on the coast also represent a major influence on beach erodibility in the study area severe detrimental effects are caused at certain points by shore normal engineering structures blocking longshore drift additionally extensive urban development in backbeach environments has a significant influence on the sediment budget at certain areas on the basis of these results a morphological and evolutionary classification of sandy beaches is proposed taking into account the way beach morphology influences erosion accretion processes rectilinear beaches and enclosed beaches typically show dynamic equilibrium or even accretion trends whereas reef supported beaches tend to be dominated by erosion headland bay beaches show complex evolution patterns greatly influenced by local conditions such as specific shoaling processes or local winds this classification is useful not only in forecasting general shoreline behaviour in the near future but also in selecting the most appropriate type of intervention when managing retreating coasts

morphological changes and human impact in the entella river floodplain northern italy from the 17th century abstract in this article the morphological changes undergone by the entella river northern italy over the last four centuries has been investigated the historical analysis has allowed reconstruction of fluvial evolution and shoreline dynamics and demonstrated their relationship to human disturbance over a very long period compared to most previous studies in italy and europe a set of 12 historical and current maps and aerial photos ranging from the 17th century to the present were entered into a geographic information system gis in order to calculate four morphological parameters i e channel length width sinuosity and centreline shifting and the distance of the shoreline modification of the entella river over the 360 years period 1656 2016 include i a reduction in channel length by 128 m 3 ii a mean narrowing of 56 m 46 iii a decrease in total sinuosity from 1 10 to 1 05 with a variation in river pattern from sinuous to straight iv a total shifting of the centreline of 30 m this evolutionary trend is consistent with most of the previous studies on italian and european rivers conversely the total channel shortening and the recent phase of substantial morphological stability with a slight increase in channel width and length seems to be in contrast with the results of other studies we correlated the channel planform changes and the regression of the shoreline at least until the latter 20th century to the reduction in sediment supply produced by the morphological modifications due to human intervention at the beginning of the 19th century and later from the 1950s to the end of the 20th century channelization channel diversion land use changes and coastal defences accounted for this supply change to the entella river and its floodplain furthermore our findings reveal that human disturbance has contributed to increased flood risk in the plain through the progressive reduction in width of the riverbed and the increasing urbanization along its riverbanks at the same time channelization seems to have a negative effect not only on the morphological evolution of the river but also in terms of prevention and flood risk reduction within the floodplain

the onset of the dead sea transform based on calcite age strain analyses the onset and evolution of the dead sea transform are re evaluated based on new in situ u pb dating and strain analyses of mechanically twinned calcites direct dating of 30 syn faulting calcites from 10 different inactive fault strands of the transform indicates that the oceanic to continental plate boundary initiated between 20 8 and 18 5 ma within an 10 km wide distributed deformation zone in southern israel ages from the northern dead sea transform 17 1 12 7 ma suggest northward propagation and the establishment of a well developed 500 km long plate bounding fault in 3 m y the dominant horizontal shortening direction recorded in the dated twinned calcites marks the onset of left lateral motion along the evolving plate boundary the observed changes in the strain field within individual fault strands cannot be simply explained by local weakening effects along strands of the dead sea transform or by gradual changes in the euler pole through time

interpreting fold and fault geometries from within the lateral to oblique parts of slumps a case study from the anglo brabant deformation belt belgium abstract using a rigorous comparison of as many slump fold based and slump related fault based methods as possible also small complex data sets can be used to deduce a reliable slump transport direction and sense this is exemplified using late early ordovician to middle ordovician slump features of the anglo brabant deformation belt the suggested procedure involves a an analysis of fold data by means of 1 the mean axis method 2 the separation arc method 3 the axial planar intersection method 4 the fold hinge azimuth and interlimb angle method 5 the fold axial surface strike and interlimb angle method and 6 the axial surface dip and dip direction method b an analysis of slump related fault data by means of 1 the mean fault orientation method 2 the fault separation method 3 the fault intersection method and 4 the best fit girdle to fault poles method and finally c a rigorous comparison of the results of the different methods several possible diagnostic criteria are put forward for distinguishing slump deformation features trending at low angles to transport direction oblique to lateral parts of slump sheets or internal lobes or tongues and slump deformation features trending at high angles to transport direction frontal to central parts of slump sheets these criteria include the relationship between fold interlimb angle and axial surface dip the plunge of the fanning axis of the reverse slump related faults and the plunge of the intersection of the reverse and normal slump related faults such criteria greatly facilitate the interpretation of the often confusing results of many classical methods moreover the plunge azimuth of the intersection of the normal and reverse slump related faults and the mismatch between slump transport direction inferred from fold based and fault based methods may both be diagnostic for dextrally deformed or sinistrally deformed slump sheet parts

stability and instability on maya lowlands tropical hillslope soils abstract substantial lake core and other evidence shows accelerated soil erosion occurred in the maya lowlands of central america over ancient maya history from 3000 to 1000 years ago but we have little evidence of the wider network of the sources and sinks of that eroded sediment cascade this study begins to solve the mystery of missing soil with new research and a synthesis of existing studies of tropical forest soils along slopes in nw belize the research aim is to understand soil formation long term human impacts on slopes and slope stability over time and explore ecological implications we studied soils on seven slopes in tropical forest areas that have experienced intensive ancient human impacts and those with little ancient impacts all of our soil catenas except for one deforested from old growth two years before contain evidence for about 1000 years of stable tropical forest cover since maya abandonment we characterized the physical chemical and taxonomic characteristics of soils at crest shoulder backslopes footslopes and depression locations analyzing typical soil parameters chemical elements and carbon isotopes 13 c in dated and undated sequences four footslopes or depressions in areas of high ancient occupation preserved evidence of buried clay textured soils covered by coarser sediment dating from the maya classic period three footslopes from areas with scant evidence of ancient occupation had little discernable deposition these findings add to a growing corpus of soil toposequences with similar facies changes in footslopes and depressions that date to the maya period using major elemental concentrations across a range of catenas we derived a measure ca mg al fe mn of the relative contributions of autochthonous and allochthonous materials and the relative age of soil catenas we found very low ratios in clearly older buried soils in footslopes and depressions and on slopes that had not undergone ancient maya erosion we found high ca mg al fe mn values on slopes with several lines of evidence that suggest relative youth soils possibly formed since maya abandonment carbon isotopes 13 c also provide some evidence of past vegetation change on slopes we found strong evidence for maize or other alien c 4 species in an ancient terrace soil and additional evidence in buried footslopes but only evidence for c 3 species like tropical trees on the backslopes and other crest shoulders the fact that steep slopes preserved no evidence of c 4 species inputs may mean that the ancient maya maintained forests here alternatively ancient maya land uses eroded slopes with the 13 c signatures detected today being the result of more recent soil development under forest over the last millennium additional evidence that these soils are recent in age includes elevated ca mg al fe mn values skeletal soil profiles and low soil magnetic susceptibility besides the evidence for truncating backslopes and aggrading footslopes the ancient maya built agricultural terraces that accumulated soils and altered drainage all these ancient maya slope alterations would have influenced modern tree distributions because many tree species in the modern forest show strong preferences for different soil types and topographic situations that the ancient maya changed

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

salt tectonics in pull apart basins with application to the dead sea basin the dead sea basin displays a broad range of salt related structures that developed in a sinistral strike slip tectonic environment en echelon salt ridges large salt diapirs transverse oblique normal faults salt walls and rollovers laboratory experiments are used to investigate the mechanics of salt tectonics in pull apart systems the results show that in an elongated pull apart basin the basin fill although decoupled from the underlying basement by a salt layer remains frictionally coupled to the boundary the basin fill therefore undergoes a strike slip shear couple that simultaneously generates en echelon fold trains and oblique normal faults trending mutually perpendicular according to the orientation of basin boundaries sedimentary cover deformation can be dominantly contractional or extensional at the extremities of pull apart basins forming either folds and thrusts or normal faults respectively these guidelines applied to the analysis of the dead sea basin show that the various salt related structures form a coherent set in the frame of a sinistral strike slip shearing deformation of the sedimentary basin fill

the structure of the dead sea basin abstract the dead sea basin is located along the left lateral transform boundary between the arabian and sinai plates its structure and history are known from surface geology drilling seismic reflection and other geophysical data the basin comprises a large pull apart almost 150 km long and mostly 8 10 km wide which is flanked by a few kilometres wide zones of normal faulting the basin formed at about 15 ma or earlier close to the beginning of the transform motion and it reached about half its present length before the end of the miocene a strong negative gravity anomaly records a thick sediment basin fill 5 km under half its length reaching a maximum of 10 km the fill includes a few km of salt ca 6 4 ma which forms several diapirs at any one time large parts of the basin subsided simultaneously but the site of fastest subsidence seems to have shifted northward sedimentation rates reached at least hundreds of metres per million years or more in the miocene and 1 km myr in later periods the basin structure is dominated by longitudinal faults intrabasinal faults which delimit the pull apart and which are the extensions of the major strike slip faults north and south of the basin and normal faults which extend along the basin margins the latter faults express a small component of extension across the basin whereas the pull apart resulted from the much larger lateral motion along the basin in addition transverse faults divide the pull apart into several segments with somewhat different histories the pull apart grew by becoming longer parallel to the transform motion at shallow levels this was probably achieved by normal slip on transverse listric faults while the fill between them was little deformed the crust under the basin was stretched and thinned during basin lengthening which caused its subsidence basin formation was accompanied by uplifting of its flanks by 1 km sparse igneous activity occurred along the basin and its flanks its presence suggests a thermal anomaly in the lower lithosphere beneath the basin and adjacent parts of the transform

fluidization of mud in estuaries the south alligator river located in the northern territory australia is a macrotidal estuary with suspended sediment concentration values reaching 10 g 1 1 in september 1986 in the dry season the estuary was well mixed in temperature and salinity while the vertical gradients in suspended sediment concentration were small at flood tides for most of the ebb tide duration a lutocline separated a clear upper layer from an extremely turbid bottom layer both layers being of comparable thickness the tidal evolution of the suspended sediment concentration is consistent with that computed by a numerical model based on the equation of conservation of mass of suspended sediment in this model sediment is entrained from the bottom and mixed vertically upward by eddy diffusion but through a richardson number dependence sediment induced buoyancy effects inhibit vertical mixing the final depth of the turbid layer can be readily estimated analytically as a result of a balance between the rate of kinetic energy input and the buoyancy flux determined by the particle fall velocity the presence of a lutocline helps form mud banks on the inner side of a meander

soft sediment deformation within seismogenic slumps of the dead sea basin abstract the late pleistocene lisan formation preserved next to the dead sea provides exceptional 3 d exposures of folds and faults generated during soft sediment slumping and deformation it is possible to generate a range of four different scenarios associated with overprinting in a single slump event the progressive evolution of slump systems may be broadly categorised into initiation translation cessation relaxation and compaction phases thrust packages typically define piggyback sequences during slump translation with back steepening of imbricate faults leading to collapse of folds back up the regional palaeoslope detailed evaluation of slumped horizons may also permit structures to be traced across apparently separate and distinct slumped units the recognition that slumps may be reworked by younger seismically triggered events suggests that in some cases the seismic recurrence interval may be shorter than previously anticipated

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

mixing by shear instability at high reynolds number 1 shear instability is the dominant mechanism for converting fluid motion to mixing in the stratified ocean and atmosphere the transition to turbulence has been well characterized in laboratory settings and numerical simulations at moderate reynolds number it involves rolling up i e overturning of the density structure within the cores of the instabilities in contrast measurements in an energetic estuarine shear zone reveal that the mixing induced by shear instability at high reynolds number does not primarily occur by overturning in the cores rather it results from secondary shear instabilities within the zones of intensified shear separating the cores this regime is not likely to be observed in the relatively low reynolds number flows of the laboratory or in direct numerical simulations but it is likely a common occurrence in the ocean and atmosphere

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

the distribution geometry and kinematic significance of caledonian buckle folds in the western moine nappe northwestern scotland within internal regions of orogenic belts systems of ductile thrusts and folds may form which are geometrically and kinematically analogous to those observed in foreland thrust belts the moine nappe of sutherland northwestern scotland developed during wnw directed caledonian displacements under amphibolite facies conditions broad zones of mylonite associated with the ductile ben hope and moine thrusts both contain numerous small scale folds which can be attributed to transient flow perturbations it is possible to isolate and differentiate generations of such folds basedon their association with particular major thrust zones and or their geometry in regions of lower strain between these thrusts there are a series ofkilometre scale buckle folds the axial traces of which define arcuate trends those with hinges orthogonal to transport are northwestvergent whilst those plunging subparallel to the mineral lineation display variable vergence the spatial distribution of these geometries suggests a causal relationship with displacements on specific underlying thrusts we propose that they reflect larger kilometre scale and possibly longer lived flow perturbations the transport parallel folds are persistent features that often centre on earlier structural culminations and are thought to reflect components of differential shear the most prominent set of regional buckle folds root downwards into the ductile moine thrust and openly refold the structurally overlying ben hope thrust and its associated buckle folds thus supporting a foreland propagating sequence of ductile displacements

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

the engines of gravity driven movement on passive margins quantifying the relative contribution of spreading vs gravity sliding mechanisms movement of gravity driven systems on passive margins is fuelled by the loss of gravitational potential energy two end member modes gravity spreading and gravity gliding are defined by whether the potential energy loss is due to deformation and movement towards the base of the system spreading or by movement parallel to the base of the system gliding most natural systems consist of a mixture of the two processes hitherto use of these concepts has been limited or equivocal due to lack of a quantitative measure in some cases characterisation of gliding vs spreading systems based on secondary attributes has resulted in controversy because there is a lack of consensus as to which of these are truly diagnostic this paper presents a new simple quantitative method based on vector analysis providing a numerical measure of the relative contribution of spreading vs gliding the method is applied to synthetic examples where deformation can be tracked and to natural examples where a valid palinspastic reconstruction is available the results confirm that most natural examples exhibit mixed mode behaviour and that some have been mischaracterized much of the angola margin is dominated by spreading the method can also provide an estimate of the absolute amount of gravitational potential energy released in the movement and the energy contribution made by gliding vs spreading determining the dominant process has implications for predicting the development of seafloor topography and stratal architecture

secondary detachments within carbonates of the saraburi group triassic khao khwang fold and thrust belt thailand abstract permian limestones of the saraburi group in central thailand deformed during the triassic indosinian orogeny exhibit detachments formed in response to the following variations in lithology thin shale beds within a limestone sequence massive limestone overlaying well bedded limestone massive limestone overlying interbedded limestones and shales within well bedded limestones thin shales interbedded with limestones overlying limestones where shales are present the decoupling of layers is similar to examples previously described in the literature from outcrop and analogue models however more unusually detachments are also present within limestone units while detachment folds are typically developed above a basal weak unit usually salt or shale in the study area is an example developed entirely within well bedded limestones instead of flow of the weak unit into the core of the fold room problems in the core of the fold are accommodated by pressure solution parallel to bedding thrusts small fault propagation folds and intense folding variations in structural style are largely influenced by the spacing intensity of bedding limestone clay content and the efficiency of pressure solution during deformation and the presence absence and thickness of interbedded shales a ductile detachment zone is developed between well bedded limestones and overlying massive limestones the detachment zone separates highly folded sequence dominated by steep dips from a weakly folded sequence dominated by gentle dips pressure solution processes and variability in pressure solution intensity related to clay content play a very strong role in accommodating the difference in deformation styles across the detachment

structural styles in the deep water fold and thrust belts of the niger delta the deep water niger delta includes two large fold and thrust belts products of contraction caused by gravity driven extension on the shelf that exhibit complex styles of thrusting these contractional structures formed above multiple detachment levels in the overpressured shales of the akata formation using the patterns of growth sedimentation fold shapes fault plane seismic reflections and combined conventional and shear fault bend folding theories we describe and model the structural styles and kinematics of the fault related folds and imbricate thrust systems that compose these belts individual fault related folds involving both forethrusts and backthrusts are characterized by long planar backlimbs that dip less than the associated fault ramps with upward shallowing of dips in growth strata above the backlimbs suggesting components of progressive limb rotation forelimbs are short compared to backlimbs but growth strata show more consistent dips that suggest a component of folding by kink band migration thus we employ a combination of classic and shear fault bend fold theories to describe these structures including the influence of a weak basal detachment zone in the overpressured shales we expand upon these theories to model the kinematics of imbricate thrust systems which display a complex history of thrusting related to spatial and temporal variations in deposition across the delta regional patterns of folded growth strata are used to define break forward break backward and coeval thrusting involving single and multiple detachment levels we define two main types of imbricate thrust systems type i system with a single basal detachment level and type ii imbricate system with multiple basal detachment levels which cause massive structural thickening of the akata formation and refolding of shallow thrust sheets through the sequential restoration of two regional cross sections across these systems we resolve the structural styles the timing and sequences of thrusting as well as the regional amounts of shortening all of which have important implications for hydrocarbon maturation and charge in the deep water niger delta

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

using laterally compatible cross sections to infer fault growth and linkage models in foreland thrust belts abstract we investigate changes in shortening displacement and fold geometry to understand the detailed along strike structural variation within fold thrust belts and infer thrust growth and linkage mechanisms field observations from the vercors in se france are used to characterise deformation style in the region parallel cross sections are constructed analysed and used to create shortening and thrust displacement profiles from the northern to southern vercors sections show changes in structural style and shortening accommodation from thrust dominated in the north to fold dominated in the south the total shortening distance in the vercors does not change significantly along strike 3400 4650 m however displacements along individual thrust zones do vary significantly and displacement profiles show a range in displacement gradients 16 107 m km despite relatively simple shortening patterns in the vercors sections show a more complex 3d internal structure of the fold thrust belt thrust displacements and geometries suggest both large scale thrust zones and small scale thrusts are soft linked transferring displacement along strike through transfer zones short soft linked thrust segments indicate an intermediate stage of thrust growth and linkage well documented for normal fault systems which form prior to the formation of thrust branches and hard linked displacement transfer

medium and short term channel planform changes on the rivers tay and tummel scotland abstract channel planform change was analysed using a variety of data sources for the medium term 25 years and

morphological changes of the floodplain reach of the taro river northern italy in the last two centuries summary the quantitative analysis of the planform changes of the unconfined reach of the taro river in the italian northern apennines has allowed the channel evolution in the last 200 years to be outlined nine sets of maps and orthophotos ranging from 1828 to 2011 have been used to evaluate the medium term changes in channel morphology along the entire time interval as well as the short term changes in the most recent decade starting from the digitized channel limits and bars a number of shell scripts based on gis commands has been used for fast and automatic calculation of the main morphological parameters channel length width braiding sinuosity centerline shifting and for the drawing of graphs showing in detail their continuous variations along the entire study reach the analysis of the differences in parameters on subsequent dates has revealed that at least until the end of the 20th century continuous reduction in channel width up to a total of 75 and braiding 43 as well as continuous increase in channel length 13 and sinuosity 29 took place this is in agreement with most of the previous studies on other rivers both in italy and abroad in contrast with the results of other studies the most recent evolutionary trend of the taro river shows substantial morphological stability with possible slight narrowing the identification of the variations along the channel facilitated by the analysis of the parameter curves and supported by the historical documentation reveals that these variations can be substantially attributed to human activities in particular the continuous narrowing is largely due to the recurrent subtraction of riverbed areas to be used for agricultural and industrial purposes as well as to the construction of 10 bridges with the relevant bank protections the intense mining between 1950s and 1980s seems to have caused a sharp incision and partial narrowing only the morphological changes due to the reduction in the flow regime which seem to emerge from the sporadic and discontinuous hydrological data are expected to be negligible and in any case are immaterial when compared with the remarkable changes due to human activities

the structural evolution of sheath folds a case study from cap de creus abstract it has long been recognised that within zones of intense non coaxial deformation fold hinges may rotate progressively towards the transport direction ultimately resulting in highly curvilinear sheath folds however there is a surprising lack of detailed and systematic field analysis of such evolving sheath folds this case study therefore focuses on the sequential development of cm scale curvilinear folds in the greenschist facies el llimac shear zone cap de creus spain this simple shear dominated dextral shear zone displays superb three dimensional exposures of sheath folds defined by mylonitic quartz bands within phyllonite increasing amounts of fold hinge curvature are marked by hinge segments rotating into sub parallelism with the mineral lineation lm whilst the acute angle between the axial planar hinge girdle and foliation also displays a sequential reduction although lm bisects the noses of sheath folds it is also clearly folded and wrapped around the sheath hinges lm typically preserves a larger angle with the fold hinge on the lower limb l compared to the upper u limb l u suggesting that lm failed to achieve a steady orientation on the lower limb adjacent sheath fold hinges forming fold pairs may display the same sense of hinge arcing to define synthetic curvature or alternatively opposing directions of antithetic curvature such patterns reflect original buckle fold geometries coupled with the direction of shearing the ratio of long short fold limbs decreases with increasing hinge curvilinearity indicating sheath folds developed via stretching of the short limb rather than migrating or rolling hinge models this study unequivocally demonstrates that both hinges of fold pairs become curvilinear with sheaths closing in the transport direction recording greater hinge line curvilinearity compared to adjacent return hinges this may provide a useful guide to bulk shear sense

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

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

upslope verging back thrusts developed during downslope directed slumping of mass transport deposits acknowledgements sm acknowledges the israel science foundation isf grant no 1436 14 and the ministry of national infrastructures energy and water resources grant 214 17 027 rw was supported by the israel science foundation isf grant no 1245 11

strains and folds within thrust sheets an analysis of the heilam sheet northwest scotland abstract the changes of shape and orientation of fossil worm burrows have been used to carry out a detailed strain analysis of the heilam thrust sheet in the moine thrust zone northwest scotland the strains have been factorised into components of layer parallel shear 1 layer normal shear 2 and layer parallel shortening or elongation variations in the 1 shear are largely lithologically controlled some strain is due to flexural processes as the thrusts and overlying beds change dip over thrust ramps or are tightened by later deformation while there may also be a component of drag which increases towards the overlying thrust this predating the shear due to flexure a contoured map of the values suggests that major folds within the thrust sheet developed as a result of stick or drag on the floor thrust prior to ramp climb this led to differential movement in the transport direction causing layer parallel shortening accompanied or followed by buckling of the layers a map showing layer normal shear strains 2 suggests that the heilam sheet forms a major surge zone the central part having moved further wnw than the northern and southern parts this has led to components of lateral shear along parts of the sheet especially in the north producing curvature of the imbricate faults

unconformities related to the jurassic cretaceous synrift post rift transition of the northern north sea in the jurassic cretaceous north sea basin the synrift sequence is separated from the post rift sequence by the base cretaceous or late cimmerian unconformity the unconformity covers almost the entire basin has a distinct character in seismic reflection data and wireline logs and hence is easily identified and correlated making it the most important marker horizon in the area the unconformity displays great local complexity in many localities and great variability on a regional scale from one locality to another thus the unconformity is classified as a nonconformity a disconformity and an angular unconformity we suggest that these variations basically reflect different structural position within the basin so that the short wavelength variation is dominated by local structural development e g the rotational history of a fault block whereas the long wavelength variation reflects basin scale tectonic thermal and isostatic processes the merging of this unconformity with younger erosional surfaces its complex configuration and polychronous character makes the general term base cretaceous unconformity inadequate thus the term northern north sea unconformity complex is used here

complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones abstract many of the complex strain patterns seen in shear zones and thrust zones such as variable fabric orientations refolded folds and fabrics together with folds with hinges almost parallel to the main transport direction can be explained in terms of differential movement within the shear zones these strains are developed at the frontal and lateral tips of the zones as they propagate examples are taken from the moine thrust zone of scotland which show variations in strains particularly at the lateral tips the form of differential movement described here may lead to complex strain paths and non plane strain ellipsoids and the spatial variations in finite strain may be used to delineate zones of extensional and compressional flow and differential movement in the shear zones or thrusts

distinguishing coeval patterns of contraction and collapse around flow lobes in mass transport deposits abstract gravity driven mass transport deposits mtds form by the downslope directed movement of sediment associated with slope failure simple models suggest that extension forms at the upslope head area contraction is focussed in the downslope toe of the slump while differential shear associated with strike slip is restricted to the lateral margins of the slump although the head and toe are considered to be dominated by layer parallel shear lps differential layer normal shear lns may be generated around the lateral margins of slumps and potentially also within mtds where flow has been separated into different lobes despite this realisation that lns must form there has been little work into the geometries and spatial relationships of resulting structures using the late pleistocene lisan formation exposed around the dead sea basin as our case study we examine detailed

quantitative analysis of seismogenic shear induced turbulence in lake sediments spectacular deformations observed in lake sediments in an earthquake prone region lisan formation pre dead sea lake appear in phases of laminar moderate folds billow like asymmetric folds coherent vortices and turbulent chaotic structures power spectral analysis of the deformation indicates that the geometry robustly obeys a power law of 1 89 similar to the measured value of kelvin helmholtz kh turbulence in other environments numerical simulations are performed using properties of the layer materials based on measurements of the modern dead sea sediments which are a reasonable analogue of lake lisan the simulations show that for a given induced shear the smaller the thickness of the layers the greater is the turbulent deformation this is due to the fact that although the effective viscosity increases the reynolds number decreases the bulk richardson number becomes smaller with decrease in the layer thickness the latter represents the ratio between the gravitational potential energy of the stably stratified sediments and the shear energy generated by the earthquake therefore for thin layers the shear energy density is larger and the kh instability mechanism becomes more efficient the peak ground acceleration pga is related to the seismogenic shear established during the earthquake hence a link is made between the observed thickness and geometry of a deformed layer with its causative earthquake9s pga

distinguishing thrust sequences in gravity driven fold and thrust belts abstract piggyback or foreland propagating thrust sequences where younger thrusts develop in the footwalls of existing thrusts are generally assumed to be the typical order of thrust development in most orogenic settings however overstep or break back sequences where later thrusts develop above and in the hangingwalls of earlier thrusts may potentially form during cessation of movement in gravity driven mass transport deposits mtds in this study we provide a detailed outcrop based analysis of such an overstep thrust sequence developed in an mtd in the southern dead sea basin evidence that may be used to discriminate overstep thrusting from piggyback thrust sequences within the gravity driven fold and thrust belt includes upright folds and forethrusts that are cut by younger overlying thrusts backthrusts form ideal markers that are also clearly offset and cut by overlying younger forethrusts portions of the basal detachment to the thrust system are folded and locally imbricated in footwall synclines below forethrust ramps and these geometries also support an overstep sequence however new short cut basal detachments develop below these synclines indicating that movement continued on the basal detachment rather than it being abandoned as in classic overstep sequences further evidence for synchronous thrusting where movement on more than one thrust occurs at the same time is provided by displacement patterns on sequences of thrust ramp imbricates that systematically increases downslope towards the toe of the mtd older thrusts that initiate downslope in the broadly overstep sequence continue to move and therefore accrue greater displacements during synchronous thrusting our study provides a template to help distinguish different thrust sequences in both orogenic settings and gravity driven surficial systems with displacement patterns potentially being imaged in seismic sections across offshore mtds

stratification effects by cohesive and noncohesive sediment this study focuses on stratification effects induced by the interaction between suspensions of fine grained cohesive and noncohesive sediment and the turbulent flow in estuarine and coastal environments a concise literature review reveals that this interaction may cause an appreciable modification of the vertical profiles of velocity vertical eddy viscosity diffusivity and reynolds stresses this interaction is further studied with a one dimensional vertical 1dv numerical model which includes the standard k turbulence model with buoyancy destruction terms application of this model to the experimental results by coleman 1981 shows that the measured changes in the velocity profile can be explained entirely by sediment induced buoyancy effects it is argued that capacity for cohesive sediment is cc e a fluid mud layer is formed upon the deposition of the cohesive sediment flocs contrary to the case with noncohesive sediment where the depositing grains immediately form a rigid bed thus a two layer fluid system develops causing significant damping of the vertical mixing processes decreasing the carrying capacity further this positive feed back results in a catastrophic collapse of the turbulence field and the concentration profile a scaling law for this saturation behavior is derived from classical stratified flow theory this law is sustained with a series of numerical experiments with the 1dv model it also predicts the suspended sediment concentrations observed in the yellow river to the right order of magnitude it is concluded that sediment induced buoyancy yields appreciable stratification effects at already moderate suspended sediment concentrations in the case of cohesive sediment these stratification effects can result in a catastrophic collapse of the turbulent flow field and the vertical profile of suspended sediment concentration

earthquake deformations in the lisan deposits and seismotectonic implications summary earthquake deformations and induced sedimentary structures preserved in quaternary sediments include faults folds fissures slumps sand boils and other effects of liquefaction such deformations and structures are well preserved in the lisan deposits of the dead sea of most importance are the fold type deformations known as decollement structures which are present all along the eastern side of the lisan and seem to decrease gradually westwards to disappear in the middle of the lisan these may indicate that palaeoearthquakes originating along the araba fault have triggered such structures due to shaking of elastoplastic unconsolidated sediments over gentle slopes dipping to the west preliminary results from studies on decollement structures preserved in a section representing some 1733 years of continuous deposition in the uppermost pleistocene in the vicinity of wadi araba indicate that 1 seismic activity has fluctuated with time average recurrence period is about 340 20yr for earthquakes with magnitudes greater than or equal to 6 5 earthquakes with magnitude greater than 7 seem to have occurred along the araba fault 2 deduced earthquake magnitudes conform to the frequency magnitude relationship log n 5 24 0 68m 3 the deduced seismic slip rate along the araba fault seems to be not less than 0 64 0 04 cm yr 1

structural evolution of the orange basin gravity driven system offshore namibia the orange basin records the development of the late jurassic to present day volcanic rifted passive margin of namibia regional extension is recorded by a late jurassic to lower cretaceous syn rift megasequence which is separated from a cretaceous to present day post rift megasequence by the late hauterivian ca 130 ma break up unconformity the late cretaceous post rift evolution of the basin is characterized by episodic gravitational collapse of the margin gravitational collapse is recorded as a series of shale detached gravity slide systems consisting of an up dip extensional domain that is linked to a down dip zone of contraction domain along a thin basal detachment of turonian age the extensional domain is characterized by basinward dipping listric faults that sole into the basal detachment the contractional domain consists of landward dipping listric faults and strongly asymmetric basinward verging thrust related folds growth stratal patterns suggest that the gravitational collapse of the margin was short lived spanning from the coniacian ca 90 ma to the santonian ca 83 ma structural restorations of the main gravity driven system show a lack of balance between up dip extension 24 km and down dip shortening 16 km gravity sliding in the namibian margin is interpreted to have occurred as a series of episodic short lived gravity sliding between the cenomanian ca 100 ma and the campanian ca 80 ma gravity sliding and spreading are interpreted to be the result of episodic cratonic uplift combined with differential thermal subsidence sliding may have also been favoured by the presence of an efficient detachment layer in turonian source rocks

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

observation and analysis of shear instability in the fraser river estuary 1 we investigate the occurrence of shear instability in the fraser river estuary instabilities observed with an echo sounder are compared with a linear stability analysis based on observed velocity and density profiles we find that each set of observed instabilities coincides with an unstable mode predicted by the taylor goldstein equation each of these instabilities occurs in a region where the gradient richardson number is less than the critical value of 1 4 both the taylor goldstein predictions and the echo soundings indicate the instabilities are concentrated either above or below the density interface this one sidedness is in contrast to the archetypal kelvin helmholtz instability although the dominant source of mixing in the estuary appears to be caused by shear instability when the tide produces strong near bed velocities small scale overturning due to boundary layer turbulence is apparent throughout the depth

seismic induced slump in early pleistocene deltaic deposits of the baza basin se spain abstract early pleistocene lacustrine deposits of the baza basin in se spain show a 2 m thick sheet with deformation structures intercalated within horizontal strata along a 180 m exposure we recognise an alternation of compressional thrusts and extensional normal faults and tensional joints structures these structures are interpreted as a planar slump analysis of the different structures together with the sedimentary facies indicates that this slump moved towards the north in a subaqueous deltaic environment 2 5 m deep with a paleoslope of

assessment of channel changes due to long term bedload supply decrease roubion river france this paper presents the observations made in the watershed of the upper roubion river which drains a submediterranean mountainous environment and in two of its main tributaries the soubrion and bine creeks our aim was to analyze contemporary morphological and sedimentary changes in response to a progressive decrease in bedload supply this decrease is linked to an increase of forest cover in the watershed during the 20th century following rural depopulation and to a correlated decrease in peak flows several variables were systematically measured width slope bed level change sediment size along 23 km of river whereas dendrochronological data floodplain cross sections and estimated recurrence intervals of sediment entrainment based on critical shear stress calculations were also produced for specific sites to complete our analysis evidence of three major phenomena was obtained on both the roubion and its tributaries i bed degradation ii development of stable pavement in incised reaches and iii channel narrowing associated with the development of alluvial forest on recently abandoned portions of the pre existing active channel forest development began in the 1950s these three phenomena show positively covariant relationships that lead us to propose a descriptive model of mountain fluvial system adjustments to progressive decrease of bedload

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

anthropogenic influence on recent evolution of shorelines between the conero mt and the tronto r mouth southern marche central italy abstract a study of the shoreline evolution during the last two centuries along the southern portion of the marche region between the promontory of the conero mountain and the tronto river mouth has been carried out on the basis of historical data and taking into account the effects of both natural events and anthropogenic interventions the research started with searching acquiring georeferencing and digitizing all the available maps surveyed from 1835 to the present the above data set has been used to implement a vector geodatabase containing the successive position and shape of shorelines with particular attention to the neighboring river mouths since transitional and beach deposits have been almost completely eroded during the last decades the adoption of traditional techniques of geomorphologic and sedimentological analyses has not been possible the results of the above analyses have been correlated with the main natural events and human interventions occurring during the considered time span the results of this comparison highlights that the evolution of river mouths and neighboring beaches mostly depends on deforestation carried out in their hydrographic basins in the study area the progradation of river mouths continued after the end of the little ice age ended around 1850 namely it has been observed that the retreat coincided with the start of reforestation and agricultural development in the 20 s of the last century during the following decades further interventions such as construction of dams and check dams extraction of sediments from thalwegs fillings modifications of stream paths abandonment of agricultural practices etc contributed to a severe reduction of river solid load with subsequent retreat of both river mouths and beaches thus making it necessary to protect them with artifacts

anthropogenic effects on shoreface and shoreline changes input from a multi method analysis agadir bay morocco abstract in many situations the links between shoreline fluctuations and larger scale coastal change embracing the shoreface are not always well understood in particular meso scale years to decades sand exchanges between the shoreface and the shoreline considered as important on many wave dominated coasts are rather poorly understood and difficult to identify coastal systems where sediment transport is perturbed by engineering interventions on the shoreline and shoreface commonly provide fine examples liable to throw light on these links this is especially so where shoreface bathymetric datasets which are generally lacking are collected over time enabling more or less fine resolution of the meso scale coastal sediment budget agadir bay and the city of agadir together form one of the two most important economic development poles on the atlantic coast of morocco using a combined methodological approach based on wave current modelling bathymetric chart differencing determination of shoreline fluctuations and beach topographic surveying we highlight the close links between variations in the bed of the inner shoreface and the bay shoreline involving both cross shore and longshore sand transport pathways sediment budget variations and new sediment cell patterns we show that the significant changes that have affected the bay shoreline and shoreface since 1978 clearly reflect anthropogenic impacts notably blocking of alongshore sand transport by agadir harbour completed in 1988 and the foundations of which lie well beyond the depth of wave closure construction of the harbour has led to the creation of a rapidly accreting beach against an original portion of rocky shoreline updrift and to a net sand loss exceeding 145 000 m 3 year between 1978 and 2012 over 8 5 km 2 of the bay shoreface downdrift shoreline retreat has been further exacerbated by sand extraction from aeolian dunes and by flattening of these dunes to make space for tourist infrastructure digital elevation models of part of the bay beach between 2012 and 2014 confirm this on going sand loss these changes have involved the establishment of two divergent longshore bay sediment cells instead of the original single unidirectional cell a prospective view of these changes suggests that perturbation of longshore drift and the on going bay sediment budget deficit will eventual directly pose threats to the harbour access and to coastal tourism on which the economic growth of agadir has been built

structure and dynamics of fluid muds on the amazon continental shelf thick layers of fluid mud occur in strong tidal flows over the inner portion of the amazon continental shelf in regions of strong salinity fronts associated with the plume discharged from the amazon river detailed shipboard profile measurements obtained in this region during a multidisciplinary amazon shelf sediment study amasseds provide an unprecedented opportunity to examine the structure and dynamics of fluid muds under natural conditions the analysis focuses on flows in which the motion is fully turbulent and suspended sediment dominates the stratification under these conditions a comparison of measurements and one dimensional model calculations indicates that vertical transport is controlled by suppression of turbulent mixing at gradient richardson numbers near 1 4 this constraint produces a distinctive vertical structure and leads to an upper bound on the total amount of suspended sediment that may be carried in a turbulent suspension by a tidal flow

the nature of roof thrusts in the moine thrust belt nw scotland implications for the structural evolution of thrust belts buried thrust systems commonly analysed in terms of duplex structures are often interpreted as forming in a particular sequence this model considers that only one thrust is active at a time and the resulting structural geometry is well ordered however a reappraisal of structural geometries from the moine thrust belt in nw scotland has shown that many apparent duplex structures are more complex although the upper roof thrust of some duplexes may be folded and bulged by underlying imbricate slices in accordance with simple duplex models the footwall to these roof thrusts cut up and down stratigraphic section in conflict with the simple duplex models examples include the glencoul thrust with its underlying imbricate system and the foinaven duplex simultaneous slip on an array of imbricate thrusts can bulge duplex roofs relationships classically used to infer piggy back sequences of thrust propagation however activity on more hinterland ward imbricate thrusts can cause the roof onto which they branch to truncate more foreland ward structures in this fashion the duplex roof can cut up and down stratigraphic section mimicking an extensional fault by varying thrust activity in three dimensions within an imbricate system local parts of roof thrusts can generate domains of overstep behaviour that have only local significance existing interpretations of overstep relationships in the moine thrust belt as representing late orogenic low angle extensional faults may need revision the new interpretations of deformation activity where displacements in thrust arrays happen synchronously rather than sequentially are consistent with emergent thrust and fold belts with analogue experiments and with mechanical models of orogenic wedges

the three dimensional shape and localisation of deformation within multilayer sheath folds abstract sheath folds are widely believed to develop by the passive geometric amplification of folds in which layering has no mechanical influence during non coaxial deformation where layering becomes rheologically significant then active sheath folds may form in which the inner nose of the sheath decouples along detachments and undergoes a translation relative to the outer folded layers that surround and envelope the nose we present a systematic 3 d analysis of multiple folded layer geometries in a serially sectioned natural sheath fold weak layers which are reactivated as detachments define different shaped sheath folds relative to other layers with the sense of cut off along detachments reversing across the axial surface as the inner fold nose has protruded into the surrounding sheath envelope detachment layers are more tightly folded meaning that such active sheath folds are non similar shapes the obliquely oriented bifurcating en echelon nature of the fold hinges developed in adjacent layers suggest that pre cursor folds formed with pronounced 3 d obliquity relative to the subsequent shear plane mineral lineations folded around sheath closures display asymmetric star burst patterns consistent with recrystallisation during active folding and hinge rotation we show that the eye fold shapes exposed in any 2 d y z slice can be used to predict the geometry of marker horizons back along the x axis in the third dimension this self similarity may be of value when tracing stratiform mineralised horizons in large scale sheath folds

are slump folds reliable indicators of downslope flow in recent mass transport deposits abstract despite the widespread use of slump folds as indicators of palaeoslope orientation there is a lack of detailed analysis of variations in fold geometries and orientations down the length of individual slump profiles within mass transport deposits mtds to address this gap in knowledge we have systematically recorded more than 500 structural measurements of fold hinges and axial planes along a 25 m section through a mesoscopic slump profile our case study is performed in wet unconsolidated late holocene sediments which are only recently exposed due to falling water levels in the dead sea in this situation the modern slope is exposed and directly visible slumping having occurred in the past few centuries fold hinges define broad arcs at high angles to flow in the downslope toe of the slump and progressively swing to become sub parallel to flow in the upslope region greatest amounts of shortening 35 are recorded at the toe suggesting that the swing in trends of fold hinges and axial planes is a consequence of differential layer normal shear rather than downslope strain gradients significant variations of 90 occur in the orientation and vergence of slump folds on either side of a 10 m wide gully which cuts the slump sheet in some instances folds have nucleated around longer 10 cm wooden sticks that were incorporated into the slump whereas shorter wooden fragments align parallel to the flow direction the differences in orientations of wooden sticks and wooden fragments are consistent with differential layer normal shear on each side of a flow cell evaporite concretions grew within the sediments during slumping and influenced the geometry and kinematics of slump folds suggesting that slope failure may have been a slow creep event generated by slope instability rather than a result of catastrophic failure associated with large earthquakes our work illustrates the problems associated with using partial datasets where classical structural analysis of transects

seismically induced slump on an extremely gentle slope 1 of the pleistocene tecopa paleolake california a superbly exposed 5 km 2 slump is developed in middle pleistocene lacustrine deposits of the tecopa basin california united states a subhorizontal detachment

coseismic horizontal slip revealed by sheared clastic dikes in the dead sea basin despite the hazard caused by near surface destructive horizontal displacements during earthquakes field evidence for coseismic slip along horizontal discontinuities is exceptionally rare mainly due to the lack of adequate exposure and markers however within the seismically active dead sea basin the late pleistocene lisan formation contains vertical clastic dikes that are sheared laterally at maximum depths of 15 m and thereby provide unique profiles of such horizontal displacement in order to investigate how coseismic horizontal shearing is distributed near the surface we document an 1 m thick brittle shear zone consisting of up to 11 slip surfaces that can be traced for tens of meters in the lisan formation displacements along individual slip surfaces are up to 0 6 m and the total displacement across the shear zone is up to 2 0 m displacement profiles and gradients indicate that the brittle shear zone formed by simple shear and deformation was associated with slip partitioning and transfer between primary and secondary slip surfaces evidence for concurrent displacement along slip surfaces during a single event indicates that the brittle shear zone was formed during a coseismic event subsequent to 30 ka we consider the mechanical effect of seismic wave related transient stress which when added to the initial static effective stress may result in concurrent horizontal shear failure along detrital rich layers in the lisan formation the exceptional quality of exposures and markers enables us to document for the first time the details of near surface horizontal shearing and indicates that displacement along horizontal bedding planes is a viable mechanism to absorb coseismic deformation in well bedded near surface strata

fluvial dynamics in the castel di sangro plain morphological changes and human impact from 1875 to 1992 abstract in recent years morphology and hydrogeology of the castel di sangro plain have undergone significant man made changes the plain is located in a very complex geological area where the latium abruzzi carbonate platform the morrone rotella pizzone carbonate platform and the molise nappe meet hydrology hydrogeology morphology and neotectonics of the area are conditioned by interlocking and overlapping of such palaeogeographic units some of them can be clearly recognised in the upper and middle sangro area after outlining the geological structural and geomorphological features of the area the authors discuss the morphological changes which occurred in the sangro river pattern and its alluvial plain from 1875 to 1992 as a result of construction of major hydraulic structures dams river bed cementation urbanisation of flood plain and spring areas wells elements inferred from comparison of maps and aerial photographs were also considered the study provides a concise description of objective observations on both natural and man induced fluvial processes and groundwater flows

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

channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years article i nfo the timing and extent of the morphological changes that occurred in the last 200 years in a large gravel bed river the piave river eastern italian alps that was heavily impacted by human activities training structures hydropower schemes and gravel mining have been analyzed by historical maps aerial photos repeated topographic measurements and geomorphological surveys results show that the channel underwent a strong narrowing during the twentieth century but with a faster pace during the 1970s 1990s and with an associated shift from a dominant braided pattern to a wandering morphology bed incision up to 2 m mostly from gravel mining has been documented for this period large areas of the former active channel were colonized by riparian forests both as islands and as marginal woodlands the ceasing of gravel extraction in the late 1990s seems to have determined a reversal in the evolutionary trend with evidence of vegetation erosion channel widening even though a significant aggradation phase is not present we conclude that alteration of sediment regime has played a major role on the long term channel evolution however only relevant flood events rin10 15 years appear to determine substantial island erosion and therefore the proportion of island vs channel area fluctuates depending on flood history

velocities and driving pressures of clay rich sediments injected into clastic dykes during earthquakes summary we studied the velocities and driving pressures associated with clastic dyke formation in the ami az plain where hundreds of clastic dykes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin flow of clastic material into fractures and opening of the fractures are two mechanisms that occur during earthquake induced clastic dyke emplacement two analytic models were established based on field observations and experimental viscosity tests to estimate the velocities and driving pressures that were associated with dyke emplacement a a channel flow for upward injection of a clay water mixture and b a profile of fracture dilation based on the elastic theory analysis the two models predict that pressures between 1 and 10 mpa are generated in the source layer and dykes in the last stage of the injection process in addition the channel flow model predicts that the injection velocity reaches metres to tens of metres per second and the emplacement time of the clastic dykes is on a scale of seconds it is suggested that the high pressure values represent the static stress drop during earthquake events or represent dynamic stresses resulting from the seismic waves which passed through the soft lacustrine rocks in both cases the predicted high pressure values indicate that the clastic dyke was emplaced in close proximity of an active segment of the dead sea fault during the late pleistocene holocene

tsunami and seiche triggered deformation within offshore sediments abstract most studies of tsunami and seiche related deposits have focussed on coastal and near coastal zones which are most readily accessible with few investigations of deeper water settings and the potential soft sediment deformation effects of such waves the late pleistocene lisan formation outcropping to the west of the dead sea contains superb examples of sedimentary slump folds formed in water depths of

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

structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf abstract detailed observations of the structure within internal solitary waves propagating shoreward over oregon s continental shelf reveal the evolving nature of interfaces as they become unstable and break creating turbulent flow a persistent feature is high acoustic backscatter beginning in the vicinity of the wave trough and continuing through its trailing edge and wake this is demonstrated to be due to enhanced density microstructure increased small scale strain ahead of the wave trough compresses select density interfaces thereby locally increasing stratification this is followed by a sequence of overturning high density microstructure and turbulence at the interface which is coincident with the high acoustic backscatter the richardson number estimated from observations is larger than 1 4 indicating that the interface is stable however density profiles reveal these preturbulent interfaces to be o 10 cm thick much thinner than can be resolved with shipboard velocity measurements by as

deepwater fold and thrust belt classification tectonics structure and hydrocarbon prospectivity a review abstract deepwater fold and thrust belts dwftbs are classified into near field stress driven type 1 systems confined to the sedimentary section and type 2 systems deformed by either far field stresses alone or mixed near and far field stresses dwftbs can occur at all stages of the wilson cycle up to early stage continent continent collision type 1 systems have either weak shale or salt detachments they occur predominantly on passive margins but can also be found in convergent related areas such as the mediterranean and n borneo examples include the niger and nile deltas the west coast of africa and the gulf of mexico type 2 systems are subdivided on a tectonic setting basis into continent convergence zones and active margin dwftbs continent convergence zones cover dwftbs developed during continent arc or continent continent collision and those in a deepwater intracontinental setting e g w sulawesi makassar straits active margins include accretionary prisms and transform margins the greatest variability in dwftb structural style occurs between salt and shale detachments and not between tectonic settings changes in fold amplitude and wavelength appear to be more related to thickness of the sedimentary section than to dwftb type in comparison with shale salt detachment dwftbs display a lower critical wedge taper more detachment folds long and episodic duration of deformation and more variation in vergence structures unique to salt include canopies and nappes accretionary prisms also standout from other dwftbs due to their relatively long continuous duration rapid offshore propagation of the thrust front and large amount of shortening in terms of petroleum systems many similar issues affect all dwftbs these include the oceanward decrease in heat flow offshore increase in age of mature source rock and causes of trap failure e g leaky oblique and frontal thrust faults breach of top seal by fluid pipes one major difference between type 1 and type 2 systems is reservoir rock high quality continent derived quartz rich sandstones are generally prevalent in type 1 systems more diagenetically reactive minerals derived from igneous and ophiolitic sources are commonly present in type 2 systems or many are simply poor in well developed turbidite sandstone units however some type 2 systems particularly those adjacent to active orogenic belts are partially sourced by high quality continent derived sandstones e g nw borneo s caspian sea columbus basin in some cases very high rates of deposition in accretionary prisms adjacent to orogenic belts coupled with uplift due to collision results in accretionary prism related fold belts that pass laterally from sub aerial to deepwater conditions e g s caspian sea indo burma ranges the six major hydrocarbon producing regions of dwftbs worldwide gulf of mexico niger delta nw borneo brazil west africa s caspian sea stand out as differing from most other dwftbs in certain fundamental ways particularly the very large volume of sediment deposited in the basins and or the great thickness and extent of salt or overpressured shale sdetachments

bed parallel slip identifying missing displacement in mass transport deposits abstract bed parallel slip bps where neighbouring beds slide past one another along bedding planes is notoriously difficult to identify without reference to pre existing features such as steep faults or dykes that act as markers to record bps offset while bps is intuitively thought to operate during downslope sliding of mass transport deposits mtds in sedimentary basins there is a conspicuous lack of supporting outcrop or seismic data to corroborate this and bps displacement may therefore have remained unaccounted for this study addresses this gap in knowledge by investigating late pleistocene mtds developed around the dead sea basin and provides the first detailed analysis of bps that pervades a gravity driven setting in particular we examine the role of bps that crosscuts earlier normal and reverse faults that act as markers to allow metre scale patterns of horizontal displacement to be identified in mtds the studied bps always forms with a consistent top to the east sense of offset that corresponds with gravity driven downslope movement towards the depo centre of the basin bps frequently develops adjacent to competent detrital rich beds and forms discrete glide planes with little or no visible deformation in sediments on either margin although detachment folds are occasionally developed above the slip plane and confirm directions of easterly movement early downslope dipping normal faults that are cut by later bps planes results in older over younger stratigraphic relationships across the bps surface together with sawtooth patterns where multiple bps planes have developed conversely early upslope dipping normal faults that are cut by bps create younger over older stratigraphic relationships combined with missing section and staircase patterns where multiple bps planes exist as bps in sub horizontal sequences does not have a vertical component of displacement it may be examined in terms of horizontal heave bps increases heave in upslope dipping normal faults whereas it reduces heave in downslope dipping normal faults and may even become negative where sections are repeated across sawtooth profiles in addition bps increases heave in upslope dipping reverse thrust faults and reduces heave across downslope dipping backthrusts although individual bps planes may have limited displacement the net consequence of multiple planes of bps that form in the shallow subsurface is to distort patterns and estimates of extension and contraction across fault zones in mtds

sediment transport and bed morphology at river channel confluences river channel confluences form important morphological elements of every river system being points at which rapid changes in flow sediment discharge and hydraulic geometry must be accommodated this article presents results of a quantitative investigation of sediment transport at channel confluences accomplished through both scaled laboratory flume simulation and complementary monitoring of a natural channel confluence bed morphology at channel confluences is characterized by three distinct elements avalanche faces at the mouth of each confluent channel a deep central scour and a bar within the separation zone formed at the downstream junction corner these elements are controlled predominantly by the confluence angle and the ratio of discharges between the tributary and mainstream channels as confluence angle and discharge ratio increase the sediment contributions from the confluent channels are progressively segregated in their paths through the junction with sediment being transported around rather than through the centre of the confluence this segregation of sediment loads is accompanied by the retreat of the main channel avalanche face from the confluence an increase in the scour depth a change in the orientation of the scour and an increase in the size of the separation zone bar field measurements closely replicate the flume simulation a model of sediment transport and bed morphology links these features to the fluid dynamics of these sites an understanding of confluence dynamics is important not only in considerations of channel morphology and design criteria but must form the basis for the interpretation of confluence sediments in the ancient record

recent geomorphological changes of the middle and lower calore river campania southern italy the geomorphological changes experienced by the middle and lower calore river southern italy between 1957 and 1998 were investigated data derived from field surveys and interpretation of topographic maps and aerial photos were introduced into a geographic information system gis and processed the results showed that the calore river underwent a mean narrowing of 66 with a peak of 86 the channel length increased by approximately 75 m and the sinuosity from 1 311 to 1 314 the extension of fluvial bars reduced by more than 83 while their number increased from 151 to 381 field evidence of riverbed lowering such as river terraces formed in the considered time span and exhumation of foundations of bridges and flood walls were also constantly detected due to these channel adjustments the calore river morphology changed from transitional to single thread these results were coherent with those reported in the pre existing literature about channel adjustments experienced by many rivers during the twentieth century they all were explainable with a reduction of the bedload transport this latter in turn is completely in accordance with the environmental changes that affected the calore river system in the considered period i e damming and or channelization of the main tributaries reduction of liquid discharge due to water withdrawals and sediment mining from the riverbed

varve counting reveals high resolution radiocarbon reservoir age variations in palaeolake lisan the laminated lacustrine sediments deposited in the last glacial lake lisan represent annual deposits of primary aragonite and silty detritus that reflect the annual supply of bicarbonate bearing freshwater to the lake a varve counting curve was constructed for the time interval of ca 17 4 22 cal ka bp based on aragonite u th and atmospheric radiocarbon ages of organic debris recovered from the studied section radiocarbon in the primary evaporitic aragonite comprises both atmospheric and old carbon reflecting the reservoir age the aragonite reservoir ages were determined by comparing the aragonite radiocarbon dates to the varve counting curve and are found to lie in the range 1900 600 a and display a continuous decline this opens the possibility for high annual resolution monitoring of the reservoir age similar in quality to tree ring counting during the upper part of marine isotope stage mis 2 our work also demonstrates that a uniform reservoir age correction is inappropriate when determining the chronology of short term climate events in lacustrine environments copyright 2009 john wiley sons ltd

sources and transport routes of fine detritus material to the late quaternary dead sea basin abstract the sources and routes of transport of fine detritus material fdm to the lakes filling the late quaternary dead sea basin were studied by petrographic mineralogical grain size chemical and sr nd isotope analyses on sediments of the late quaternary lacustrine formations including river flood material dust and loess from the lake watershed the lacustrine formations comprise two sedimentary facies one that consists of alternating laminae of primary aragonite and silty detritus material aad facies and another that consists mainly of laminated detritus particles and generally lacks aragonite ld facies the aad facies characterizes the glacial intervals e g mis2 and 4 when lake levels were high while the ld facies characterizes interglacials e g mis1 5 and warmer glacial intervals e g mis3 when lake levels were low the detritus of both aad and ld facies show similar mineralogy mainly quartz and calcite grains with minor feldspars and clays but distinct grain sizes 8 10 m and 50 60 m respectively and distinct 87 sr 86 sr and end 0 711 0 712 and 7 to 8 versus 0 709 0 710 and 5 respectively the aad and ld fdm comprise desert dust of mixed granitic basaltic composition that was blown from the sahara desert and from the nile delta to the northern negev desert e g the loess deposits and the judean mountains bordering the dead sea basin mainly during glacial intervals along with enhanced mediterranean rain fronts the aad fdm reflects an enhanced transport of saharan granitic dust to the vicinity of the lake mainly during glacials the ld fdm was recycled from the loess surface cover of the negev desert mainly during interglacials and warm glacial intervals