mushroom diapirs penetrating overburdens with high effective viscosities mushroom diapirs have been attributed to retardation of a rising buoyant source by sinking of denser overburden of similar effective viscosity new physical and numerical models show that mushroom diapirs also form by reactivation of diapirs that have spread and been buried by overburden with higher effective viscosities diapirs were previously thought to become balloon shaped when the viscosity ratio m value exceeds unity however experimental diapirs reactivated after further burial with an m value of 85 were also mushroom shaped having peripheral skirts that enfold their former overburden denser overburden is entrained because the bulb centers rise faster than their peripheries the formation of mushroom bulbs by reactivation differs from some previous models that assume all the overburden to be in place from the start

characterization of magma from inclusions in zircon apatite and biotite work well feldspar less so detrital zircon grains are employed to decipher sediment provenances and crustal evolution and they provide unique evidence of hadean crust mantle differentiation processes we demonstrate that mineral inclusions in zircon provide valuable information on the conditions under which zircon crystallized zircon grains from selected plutonic rocks from dronning maud land antarctica contain inclusions of apatite biotite amphibole and pyroxenes that accurately reflect the chemical compositions of the equivalent phases in the host rock matrix and the compositions of the whole rocks high concentrations of y and low concentrations of sr in apatite inclusions in zircon are diagnostic of evolved felsic granitoid host rocks in contrast the relative abundances and compositions of plagioclase and alkali feldspar inclusions in zircon are decoupled from the composition of the whole rock and they are generally indicative of granitic melts regardless of the bulk rock this is best explained by the late crystallization of zircon relative to the bulk of the feldspars we conclude that inclusions of apatite and mafic phases in zircon constrain the potential source rocks of detrital zircon whereas feldspar inclusions do not

style and timing of salt movement in the persian gulf basin offshore iran insights from halokinetic sequences adjacent to the tonb e bozorg salt diapir abstract the variations in the rate of salt rise is reflected in the sedimentary sequences adjacent to salt diapirs and provides insights into the style of salt movement sedimentation interaction and the timing of halokinetic phases episodic movement of salt diapir is defined by wedge and tabular shaped salt related sedimentary strata halokinetic sequences adjacent to the diapir detailed mapping of depositional strata on 2d seismic sections adjacent to salt diapirs on the tonb e bozorg island persian gulf sw iran reveals the presence of a series of sedimentary sequences related to the halokinetic activity of two salt source layers the hormuz and fars salts respectively the hormuz salt deposited in the uppermost proterozoic mobilized in the lower paleozoic and then continued to move periodically to present and to create the deep salt structures in the tonb e bozorg region the fars salt deposited in the lower miocene and then started rising and created the central salt structure the tonb e bozorg island and several peripheral ring like salt structures around the island our results reveal that both the salt layers within the tonb e bozorg region grew by downbuilding and continued to move periodically by passive and active diapirism to the present salt movement sedimentation interaction during salt diapirism influences petroleum play and therefore is of interest in petroleum geoscience

age budget and dynamics of an active salt extrusion in iran the hormuz salt of kuh e namak iran began rising through its phanerozoic cover in jurassic times and had surfaced by cretaceous times in miocene times the still active zagros folds began to develop and the salt is still extruding to feed a massive topographic dome and two surface flows of salt which have previously been called salt glaciers but are here called namakiers two crude but independent estimates for the rate of salt extrusion and loss are shown to balance the salt budget if the current salt dynamics are assumed to be in steady state first to replace the extrusive salt likely to be lost in solution in the annual rainfall the salt must rise at an average velocity of about 11 cm a second the foliation pattern shows that the extruding and partially dissolved salt column spreads under its own weight the maximum height of the salt dome is consistent with a viscous fluid with a viscosity of 2 6 x 1017 poises extruding from its orifice at a rate of almost 17 cm a k both estimates are consistent in indicating that salt can extrude onto the surface 42 85 times faster than the average long term rate at which salt diapirs rise to the surface the structure fabrics textures and deformation mechanisms of the impure halite all change along the path of the extrusive salt from the dome down the length of both namakiers such changes tend to occur when the flowing salt encounters changes in its boundary conditions and the recognition of buried namakiers is discussed in the light of such observations episodes of salt flow at a rate of 0 5 m per day have been measured along the margin of the n namakier after significant rain showers such brief episodes of rapid flow alternate with long periods when the namakier is dry and stationary the shape of the colour bands cropping out on the n namakier indicate that the flow over the surface of impure salt with a mylonitic texture obeys a power law with n 3 although the reported annual rainfall has the potential of dissolving both namakiers in about 2000 years a superimposed thin marine cover may protect static parts of them for as long as 30 000 to 300 000 years

the mechanical relationship between strike slip faults and salt diapirs in the zagros fold thrust belt analogue models are used to study the mechanical relationship between basement strike slip faults and salt diapirs displacement along a strike slip fault in 1 g models resulted in extension along pre existing jogs and the formation of oblique extensional faults where reactive diapirs were triggered in some models in the centrifuge models prescribed cuts simulating pre existing structures were reactivated during simple shear deformation of the models resulting in formation of pull apart basins which were intruded by diapirs the models show that because of the low ratio of salt to overburden thickness in the zagros 0 15 0 35 it is unlikely that diapirs have formed solely if at all as a result of movement along basement strike slip faults two mechanisms are suggested first pre kinematic thin overburden and continuous movement along a releasing bend in the cover units may have triggered some of the diapirs in the zagros which were later downbuilt to their current geometry by additional sedimentation second movement along the strike slip faults e g the kazerun and mangarak faults induced oblique movement along nw se zagros structures folds or thrusts resulting in the formation of pull apart basins where diapirs were eventually intruded fault plane solution of shallow earthquakes supports the second scenario which is also in agreement with previous interpretations that some of the salt diapirs associated with basement faults are younger than zagros shortening and young southwestwards

concretion morphologies reflecting diagenetic and epigenetic pathways abstract due to complex physicochemical processes concretions develop variable but distinctive morphologies reflecting the state of the sediment in subsequent stages of diagenesis and epigenesis they deserve a study and systematization in their own right at the same time concretional morphologies illustrate the effect of hierarchic self organization which is a basic element also in biological evolution

growth of lithosphere scale fault system in ne tibet numerical modeling constrained by high resolution seismic reflection data abstract the east kunlun fault is an important strike slip shear zone to understand continental deformation in ne tibet the recent high resolution deep seismic reflection profiling across the kunlun fault reveals a thrust fault system and two decollements in the crust along with another thrust fault system which reaches to the depth of upper mantle and cuts off the moho the mechanism of the growth of these shear zones at lithosphere scale which reveals the type of deep deformation is investigated using the finite element method with an elastic plastic constitutive relationship the results show that the thrust fault system in the crust may be explained by the conjugated plastic deformation belts under compression from the indian plate the pre existing fault in the depth may develop to cut the moho toward two new directions rather than along the original direction the vertical and lateral heterogeneity of material frictional property and geometry of the models all affect the feature of the fault growth the growth of the thrust fault system on both sides of the kunlun fault is only located in the crust it means that the kunlun fault does not reach to the moho depth

modeling the influence of sinking anhydrite blocks on salt diapirs targeted for hazardous waste disposal due to the low permeability and high ductility of rock salt many salt diapirs such as those in germany and the netherlands are targeted as long term repositories for disposal of high level radioactive and chemical wastes geophysical and subsurface data show that the gorleben salt diapir which is one of the most extensively investigated diapirs in the world and other salt diapirs of the zechstein formation in germany contain large blocks 80 m thick of high density anhydrite inclusions these blocks which were carried upward by the rising salt are considered to be detached segments of intercalated layers that initially were deposited with the salt results of physical and numerical models presented here show that such detached high density blocks which were entrained and carried upward by the diapir at an earlier stage tend to sink in the late stages of diapiric evolution when the rate of diapiric rise slows down during their descent these high density competent blocks deform by folding and create shear zones at the immediate contact with the less competent salt the descending blocks initiate a secondary internal flow within the salt diapirs they descend and they may deform any repository built within such diapirs which would otherwise be considered as tectonically inactive

the zagros folded belt fars iran constraints from topography and critical wedge modelling summary the late miocene tectonics of the zagros folded belt fars province has for long been related solely to folding of the cover controlled by a ductile decollement between basement and the sedimentary cover however geological constraints topography analysis and seismotectonic studies reveal that basement thrusting may produce locally significant deformation in the cover to determine how the deep seated deformation in the basement may contribute to the overall topography we first examine the filtered large and short wavelengths of the topography we find that the short wavelength component of the topography 20 25 km including the zagros folds is superimposed on the differential uplift at the regional scale in other words the regional base level of folded marker horizons remains parallel to the regional topography of interest modelling reveals that the salt based wedge model alone is not able to reproduce the large wavelength component of the topography of the zagros folded belt this reveals that when a thick relatively to its overburden layer of salt forms the basal decollement it is generally too weak and cannot support the growth of significant topography we then test an alternative thick skinned crustal wedge model involving the crust of the arabian margin which is decoupled above a viscous lower crust this model satisfactorily reproduces the observed topography and is consistent with present day basement thrusting topography analyses and geological constraints we conclude that basement involved thickening and shortening is mechanically required to produce the shape of the zagros folded belt since at least 10 ma finally the involvement of the basement provides mechanical and kinematic constraints that should be accounted for cross sections balancing and further assessing the evolution of zagros at crustal or lithospheric scales

strain pattern within and around denser blocks sinking within newtonian salt structures abstract blocks of dense material such as anhydrite entrained in salt structures have been proposed to sink through their host material here we present the results of numerical models that analyse strain patterns within and around initially horizontal anhydrite blocks viscosity 1021 pa s sinking through newtonian salt with a viscosity of 1017 pa s in addition the influence of the block aspect ratio thickness to width ratio ar is analysed the model results show that the blocks are folded and marginally sheared to approach streamlined shapes the effectiveness of this process is a function of the block ar and influences the sinking velocity of the blocks significantly final sinking velocities are in the range of ca 1 7 3 1 mm a around the block in the salt an array of folds and shear zones develops during block descent the structure of which is principally the same independent of the block ar however the size and development of the structures is a function of the block size monitoring of strain magnitudes demonstrates that the salt is subject to extremely high strains with successively changing stress regimes resulting in closely spaced zones of high adjacent to low strain in comparison to the anhydrite blocks strain magnitudes in the salt are up to one order of magnitude higher

a new conceptual model for the structural evolution of a regional salt detachment on the northeast scotian margin offshore eastern canada in this study we examine using seismic data in conjunction with numerical modeling a regional scale salt detachment and associated synkinematic sediments from the scotian margin offshore eastern canada this part of the scotian margin is characterized by an up to 4 5 km 2 8 mi thick and approximately 175 km 108 mi long synkinematic wedge of jurassic sediments with internal sigmoidal landward dipping reflectors the synkinematic wedge is laterally extensive encompassing an area of approximately 30 000 km2 11 600 mi2 and soles into an interpreted salt detachment the jurassic synkinematic wedge which is interpreted to have formed as an open ended allochthonous salt nappe was loaded by prograding sediments during the jurassic this loading squeezed the salt seaward and caused the overlying sediments to undergo extension and gravity spreading and gliding detaching on the salt sheet the open ended nappe model provides a mechanism for producing a large amount of extension with very little compensating contraction numerical model results indicate that high rates of extension detaching on even a thin salt layer can result in similar sigmoidal landward dipping strata based on the numerical modeling and seismic interpretation results we propose a new conceptual model for the jurassic paleogene structural evolution of the study area this model may also have implications for other passive margin salt basins with regional salt detachments

rheology of rocksalt abstract we review progress in experimental determinations of transient and steady state flow properties and processes of natural rocksalt aggregates focusing primarily on results from avery island louisiana domal salt the steady state flow field established from constant stress and constant strain rate tests at temperatures from 50 to 200 c strain rates from 10 5 to 10 9 s 1 and differential stresses from 20 7 to 2 5 mpa has been separated into two flow regimes each fit by a power law relation at the higher stresses and strain rates this relation is e 1 6 10 4 exp 68 1 rt 10 3 5 3 for which the pre exponential constant is expressed in mpa 5 3 s 1 and the apparent activation energy is in j mol 1 creep rates predicted by equation a do not differ appreciably from those predicted previously the relatively low stress low strain rate data are very well fit by e 8 1 10 5 exp 51 6 rt 10 3 2 4 which is comparable conditions predicts creep rates higher and equivalent viscosities lower than does equation a by two orders of magnitude the change in behavior from a to b is ascribed to a change in rate limiting mechanism from cross slip of screw dislocations to the climb of edge dislocations in this dry material subgrain formation dominates microstructural development during steady state flow of salt and from determinations of average subgrain diameters in crystals from 20 different rocksalt bodies flow stress levels between 0 6 and 1 4 mpa have been estimated these values do not bear directly on arguments concerning the nature of forces initiating salt pillow growth because apparently evidence relating to the early deformational history has been overprinted at that stage fluid assisted grain boundary diffusional processes might dominate dislocation creep leading to a linear stress strain rate mechanical response considering buoyancy forces alone behavior described by equation b rather than a reduces the relief necessary to initiate pillow growth but a 1000 fold amplification is required to produce stress differences near 1 mpa that forces other than buoyancy are important is indicated by the occurrence of these same paleostress levels in bedded salts and in shallow offshore concordant intrusions differential loading generally provides the most plausible initial driving force for the growth of diapiric salt structures

anatomy of mushroom shaped diapirs we produced more than 100 mushroom shaped diapirs in eight centrifuged models under acceleration of 1200 g the modelling results allow natural examples to be recognized mushroom diapirs have an overhanging bulb fringed by one or more skirts which can curl inward to form vortices capable of entraining cover material to various degrees most of the internal folds are downward facing the oldest buoyant unit occurs in the skirt and in the diapiric core younger buoyant units or their immediate cover are infolded in crescentic patterns external mushroom diapirs have skirts that infold cover material with greater maturity the skirts can curl inward to form an external vortex entraining cover in contrast internal mushroom diapirs have skirts confined entirely within the intrusion again with greater maturity these confined skirts may curl inward but they entrain only diapiric material internal mushroom structure results from toroidal circulation confined within the diapir where isoviscosity prevails external mushroom structure results where source and entrained cover have similar effective viscosities entrained inclusions of more permeable country rock threaten the integrity of a mined cavern by creating a plumbing system

deformation and kinematic evolution of the subsurface structures zagros foreland fold and thrust belt northern dezful embayment iran the dezful embayment is located in the foreland part of the zagros fold and thrust belt structural style of folding and thrusting vary in the dezful embayment in this study balanced cross sections and subsurface data including 2d seismic profiles and wells data decoded structural style of the subsurface structures in the northern dezful embayment presence of the multiple decollement horizons is the main controlling factor of the structural style in this area the subsurface anticlines have been formed between two main decollement horizons which include the miocene gachsaran formation as upper decollement and permian dashtak evaporites and lower cretaceous garau shales as the middle decollement horizons geometry of the subsurface anticlines differs much vertically and horizontally growth strata indicate folding is started in middle miocene time in this region anticlines formed as open wide and disharmonic structures active processes in the evolution of anticlines are limb rotation and hinge migration which was resulted in increase of inhomogeneous shortening rate more shortening rate indicates more structural relief in anticlines these anticlines are formed as a detachment folds in initiation and then during their evolution converted to fault propagation fold and fault bend fold final geometric shape of these anticlines depends on the geometry of thrusts propagation that formed in the forelimb

the effect of the salt viscosity on future evolution of the gorleben salt diapir germany abstract the gorleben diapir which has been targeted for radioactive waste disposal contains large blocks of anhydrite numerical models that depict the geometrical configuration of the gorleben diapir are used to understand internal structure of diapir caused by movement of the anhydrite blocks for various salt rheologies it is shown that the rheology of the salt plays a significant role in how and at which rate the anhydrite blocks sink within the diapir the mobility of anhydrite blocks depends on the effective viscosity of salt which has to be lower than threshold value of around 1018 1019 pa s decreasing salt viscosity allows the previously stationary anhydrite blocks to sink if the effective viscosity of salt in post depositional stage of the gorleben diapir falls below this threshold value induced internal flow due to the present anhydrite layer might disturb any repository within the diapir

the influence of viscosity contrast on the strain pattern and magnitude within and around dense blocks sinking through newtonian rock salt abstract dense inclusions in salt cover a wide range of materials and therefore material properties depending on their origin we have modelled the deformation associated with gravity driven sinking of horizontal initially rectangular blocks of dense material through newtonian salt our two dimensional finite differences models analyse the influence and interaction of two parameters 1 the size i e the aspect ratio ar of the block and 2 the viscosity contrast between the salt and the more viscous block over four orders of magnitude the results demonstrate that during gravity driven sinking the blocks are folded and sheared the strain magnitude within the block increases with increasing block ar and decreases with increasing viscosity contrast sinking velocities of the blocks are in the range of 6 mm a 1 and are a function of block and salt deformation that depend on the block mass and ar as well as on the viscosity contrast salt deformation is characterised by the development of an array of characteristic structures that include folds and shear zones as well as a zone characterised by extreme vertical stretching above the block termed entrainment channel strain in the salt is locally more than two orders of magnitude higher than in the block and increases with increasing block ar and viscosity contrast salt deformation is distributed in closely spaced high and low strain zones concentrated in the block vicinity and the entrainment channel

potash in a salt mushroom at hormoz island hormoz strait iran abstract increasing volumes of potash are currently being discovered in a cluster of diapirs of hormoz formerly hormuz salt near bandar abbas iran most of the potash beds studied so far occur in complex recumbent folds in a salt mountain that would be difficult to exploit safely however holocene marine erosion removed any salt mountains from a sub group of near shore zagros diapirs and exposed their deeper structural levels even though these diapirs are still active their potash deposits are likely more tractable to safe exploitation than in a salt mountain as we make clear here for hormoz island geochemical surveys on hormoz island reveal two separate potash anomalies that are valuable pseudo stratigraphic markers integrating field measurements of the attitudes of bedding with lineaments on air photos suggests that hormoz island consists of a mature bell or plume shaped mushroom diapir with potash beds wound around a toroidal axis of rotation near current exposure levels 2d numerical models simulate the salt mushroom on hormoz island and its internal circulation they also suggest that the diapir has a wide overhand above a narrow stem in this gas rich region we use the mushroom diapir model to outline a regional exploration strategy that has the potential of influencing the world potash market thereafter

characterizing halokinesis and timing of salt movement in the abu musa salt diapir persian gulf offshore iran abstract geometric and stratigraphic characteristics of halokinetic sequences adjacent to the salt diapirs highlight the sedimentation response to variation in the rate of salt rise the style of salt movement sedimentation interaction and episodes of salt movement can be reconstructed by mapping these halokinetic sequences adjacent to the diapirs detailed interpretation of 2d seismic profiles adjacent to the abu musa salt diapir within the persian gulf basin offshore iran indicates that this diapir originated from the miocene fars salt which created a central and several ring like peripheral salt structures our results show that the evolution of the salt structures take place in three stages mound dome and post dome associated with sedimentation cycles periodically by passive and active rising to present the pattern of these halokinetic sequences reveals that the fars salt rose since mid miocene coeval sedimentation of the gachsaran formation the main mechanism of driving salt body has been the differential loading caused by down building processes

numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements 1 thin skinned fold and thrust belts related to convergence tectonics develop by scraping off a rock sequence along a weaker basal decollement often formed by water saturated shale layers or low viscosity salt horizons a two dimensional finite element model with a viscoelastoplastic rheology is used to investigate the structural evolution of fold and thrust belts overlying different types of decollements in addition the influence of multiple weak layers in the stratigraphic column is studied model shale decollements are frictional with lower friction angles as the cover sequence model salt layers behave linear viscous due to a lower viscosity as the cover sequence or with a power law rheology single viscous decollement simulations have been compared to an analytical solution concerning faulting versus folding results show that fold and thrust belts with a single frictional basal decollement generate thrust systems ramping from the decollement to the surface spacing between thrust ramps depends on the thickness of the cover sequence the structural evolution of simulations with an additional low frictional layer depends on the strength relationship between the basal and the intersequential decollement tectonic underplating and antiformal stacking occur if the within sequence decollement is weaker in the frontal part of models deformation is restricted to the upper part and imbrication occurs with a wavelength depending on the depth of the intermediate weak layer salt decollement with a viscosity of 10 18 pa s leads to isolated box folds detachment folds multiple salt layers 10 18 pa s result in long wavelength folding our results for both frictional and viscous decollements are in bulk agreement with the mohr coulomb type critical wedge theory citation ruh j b b j p kaus and j p burg 2012 numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements tectonics 31 tc3005 doi 10 1029 2011tc003047

control of folding and faulting on fracturing in the zagros iran the kuh e sarbalesh anticline abstract the kuh e sarbalesh anticline fars region shows a strong and poorly studied curvature in the vicinity of the kazerun transfer zone here we investigated this structure by analyzing the orientation and distribution of fractures in the oligocene early miocene asmari formation a major reservoir rock of the zagros petroleum system and paleo burial conditions far away from the kazerun fault the orientation of fractures is similar to that observed in other folds in the zagros two tensional fracture sets f1 and f2 develop respectively parallel and perpendicular to the fold axis whereas two shear fracture sets dextral f3 and sinistral f4 develop at 30 from f2 closer to the kazerun fault f1 and f2 become less abundant whereas f3 fractures do prevail f3 dextral shear fractures are associated with dextral shear zones sz3 within sz3 sets of tensional fractures f5 occur f4 shear planes are less abundant than f3 sets and are sometimes associated with sinistral shear zones sz4 within sz4 sets of tensional fractures f6 occur the frequency of f3 and sz3 structures increases from south to north suggesting a control by dextral shear along the kazerun fault average fracture spacing is around 20 cm and fracturing saturation values is larger than 0 7 at 20 km distance from the kazerun fault whilst spacing is smaller than 1 cm and saturation is as low as 0 32 typical of well developed fracture systems close to the fault highlighting a strong strain gradient from south to north the orientation of f1 and f2 fracture sets changes from south to north according to the clockwise rotation of the northern part of the fold with respect to the southern part inorganic thermal parameters derived from x ray diffraction analysis of clay minerals indicate that the asmari formation was deformed at burial depths of 3 km assuming a geothermal gradient of 20 c km we suggest that the progressive differential advancement of the thrust front produced the curved shape of the kuh e sarbalesh anticline with associated rotation of the pre early folding f1 and f2 fracture sets observed in the field consistently with a dextral shear associated with the kazerun transfer fault

analogue and numerical modelling of salt supply to a diapiric structure rising above an active basement fault salt diapirs preferably rise above basement faults in extensional basins a series of analogue and numerical models were developed in order to assess the supply of salt from the footwall and hanging wall to a diapir and to study the influence of basin inversion on the diapir development the modelling scenario was based on the klodawa salt structure evolution central poland the experiments show that the ductile material derived from the footwall constitutes the dominant portion of the diapir developed due to model extension and this material occurs both in the footwall and hanging wall parts of the diapir shortening of the analogue models resulted in thinning of the diapir and shifting its stem onto the footwall ductile material become redistributed inside the diapir however footwall material still prevails in the diapir structure results from the numerical models show that the magnitude of the basement fault governs the amount of salt supply to a diapir across the fault and that there is a differential salt supply from the hanging wall and footwall with time

analogue modelling of brittle shear zone propagation across upper crustal morpho rheological heterogeneities abstract crustal shearing of pre tectonic weak bodies e g salt pillows igneous pockets associated with basement strike slip fault systems is common in nature yet the structural pattern arising from the interference between a brittle shear zone and such weak rheological heterogeneities is still not fully explained in the present work different sand box analogue modelling experiments were carried out to better understand not only the shear zone perturbation effect caused by a strictly rheologic viscous weak anomaly but also the one arising from a combined morphological perturbation i e traverse topographic crest obtained results show that the development of different shear zone deformation patterns is in each case essentially determined by the interplay between i ductile wrenching strain accommodation in the viscous weak body and ii coincidence vs mismatch between main brittle viscous rheological boundaries and crest related topographic steps comparison of the experimentally obtained results with complying natural examples is further discussed and essentially focused on the ne atlantic tectono magmatic interference between the gloria transform fault and the tore madeira submarine ridge

rheological and tectonic modeling of salt provinces abstract technological improvements and a more rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden the fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth converted seismic sections scale models are therefore useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps although even unsealed models may help generating ideas the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes previously published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden this paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other intrinsic material properties scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics including those with synkinematic sedimentation

the influence of an embedded viscoelastic plastic layer on kinematics and mass transport pattern within accretionary wedges abstract the major aim of this study was to examine the influence of an embedded viscoelastic plastic layer at different viscosity values on accretionary wedges at subduction zones to quantify the effects of the layer viscosity we analysed the wedge geometry accretion mode thrust systems and mass transport pattern therefore we developed a numerical 2d sandbox model utilising the discrete element method starting with a simple pure mohr coulomb sequence we added an embedded viscoelastic plastic layer within the brittle undeformed sediment package this layer followed burger s rheology which simulates the creep behaviour of natural rocks such as evaporites this layer got thrusted and folded during the subduction process the testing of different bulk viscosity values from 1 1013 to 1 1014 pa s revealed a certain range where an active detachment evolved within the viscoelastic plastic layer that decoupled the over and the underlying brittle strata this mid level detachment caused the evolution of a frontally accreted wedge above it and a long underthrusted and subsequently basally accreted sequence beneath it both sequences were characterised by specific mass transport patterns depending on the used viscosity value with decreasing bulk viscosities thrust systems above this weak mid level detachment became increasingly symmetrical and the particle uplift was reduced as would be expected for a salt controlled forearc in nature simultaneously antiformal stacking was favoured over hinterland dipping in the lower brittle layer and overturning of the uplifted material increased hence we validated that the viscosity of an embedded detachment strongly influences the whole wedge mechanics both the respective lower slope and the upper slope duplex shown by e g the mass transport pattern

modelling fluid flow in clastic eruptions application to the lusi mud eruption abstract clastic eruptions involve the rapid ascension of sedimentary clasts together with fluids gas and or liquid phases that may further deform and brecciate the host rocks these fluids transport the resulting mixture called mud breccia to the surface such eruptions are often associated with geological structures such as mud volcanoes hydrothermal vent complexes and more generally piercement structures they involve various processes acting over a wide range of scales which makes them a complex and challenging multi phase system to model although piercement structures have been widely studied and discussed only a few attempts have been made to model the dynamics of such clastic eruptions the ongoing lusi mud eruption in the east java back arc basin which began in may 2006 is a spectacular large scale clastic eruption the lusi eruptive behaviour has been extensively studied over the past decade and thus represents a unique opportunity to better understand ongoing clastic eruptions and thus fossil clastic systems we use both analytical formulations and numerical models to investigate simple relationships between the mud breccia properties density viscosity gas and clast content and the volumetric flow rate our results show that the conduit radius of such piercement systems cannot exceed a few metres at depth and that clasts if not densely packed will not affect the flow rate when they are smaller than a fifth of the conduit size using published data for the annual gas fluxes at lusi we infer a maximal depth at which exsolution starts this occurs between 1800 m and 3200 m depth for methane and between 750 m and 1000 m for carbon dioxide based on annual gas fluxes we estimate that the conduit radius should be no larger than 1 5 m to match the maximal mud discharge recorded at lusi

holocene marine terraces on two salt diapirs in the persian gulf iran age depositional history and uplift rates slightly inclined holocene marine terraces cover parts of two circular salt diapirs hormoz and namakdan in the persian gulf their relative altitude above present sea level results from a combination of general marine transgression regression affecting the whole area and of local uplift related to salt diapirism differential uplift rate of the studied diapirs in centre to rim profiles was calculated from results based on i radiocarbon ages of skeletal remains of benthic faunas 19 samples which originally grew close to sea level ii original altitude of samples estimated from general sea level oscillation curves for the last 10 kyr and iii present sample altitude measured in the field calculated uplift rates increase from rim to centre on both diapirs in the range from 2 mm yr 1 at the rim to 5 6 mm yr 1 at the interior of hormoz and 1 3 mm yr 1 at the rim to 3 5 mm yr 1 at the interior of namakdan such uplift rate distributions fit into the parabolic profile of newtonian fluid rather than to profiles typical for pseudoplastic fluids the increase in uplift rate with distance from rim to centre of diapirs is gradual as demonstrated also by generally smooth surface of marine terraces no tectonic dissections were found the depositional history on both salt diapirs is similar although they are situated more than 100 km apart marine sedimentation started at about 9 6k cal yr bp on hormoz and at 8 6k cal yr bp on namakdan owing to rapid transgression the sea partially truncated both salt diapirs and rapidly deepened and carbonate mud was deposited on the peripheries of both salt diapirs between 7 and 5k cal yr bp beach deposition replaced carbonate mud soon after 5k cal yr bp the sea retreated from most of the marine terraces on both salt diapirs copyright 2006 john wiley sons ltd

investigating role of the hormuz salt bodies in initiation and evolution of the strike slip faults in the fars zone of the zagros fold and thrust belt insights from seismic data and sandbox modeling the zagros belt has examples of strike slip faults affected by precursor hormuz salt bodies we attempted to examine the role of salt walls in localizing the strike slip faults using field observations seismic profiles and understandings from the sandbox modeling setting and performance of the pre hormuz features in connection to the salt tectonics are major questions the inherited topography below the salt is an important parameter which controlled the structuration of the basin the antecedent troughs provided accommodation for the thick hormuz salt differential loading above the salt helped generation of salt related structures the salt walls caused formation of elongated highs these highs were re shaped in form of strike slip faults during the zagros orogeny the intersection of the salt walls and the zagros induced deformation fronts are location of potential diapirs needless of bending points along the tear faults in contrast the underlying deep seated basement faults are hardly believed to be strike slip

numerical modelling of rise and fall of a dense layer in salt diapirs this thesis uses results of systematic numerical models to argue that externally inactive salt structures which are potential targets for radioactive waste disposal might be internally active due to the presence of dense layers or blocks within a salt layer the three papers that support this thesis use the gorleben salt diapir nw germany which was targeted as a future final repository for high grade radioactive waste as a general guideline the first two papers present systematic studies of the parameters that control the development of a salt diapir and how it entrains a dense anhydrite layer results from these numerical models show that the entrainment of a dense anhydrite layer within a salt diapir depends on four parameters sedimentation rate viscosity of salt perturbation width and the stratigraphic location of the dense layer the combined effect of these four parameters which has a direct impact on the rate of salt supply volume area of the salt that is supplied to the diapir with time shape a diapir and the mode of entrainment salt diapirs down built with sedimentary units of high viscosity can potentially grow with an embedded anhydrite layer and deplete their source layer salt supply ceases however when salt supply decreases dramatically or ceases entirely the entrained anhydrite layer segments start to sink within the diapir in inactive diapirs sinking of the entrained anhydrite layer is inevitable and strongly depends on the rheology of the salt which is in direct contact with the anhydrite layer during the post depositional stage if the effective viscosity of salt falls below the threshold value of around 1018 1019 pa s the mobility of anhydrite blocks might influence any repository within the diapir however the internal deformation of the salt diapir by the descending blocks decreases with increase in effective viscosity of salt the results presented in this thesis suggest that it is highly likely that salt structures where dense and viscous layer blocks are present undergo an internal deformation processes when these dense blocks start sinking within the diapir depending on size and orientation of these blocks deformation pattern is significantly different within the diapir furthermore model results applied to the gorleben diapir show that the rate of descent of the entrained anhydrite blocks differs on different sides of the diapir this suggests that if the anhydrite blocks descent within the gorleben diapir they initiate an asymmetric internal flow within it

viscous dissipation pattern in incompressible newtonian simple shear zones an analytical model an analytical model of shear heating in an inclined simple shear zone with newtonian rheology under a reverse shear sense and an upward resultant pressure gradient is presented neglecting a number of secondary factors the shear heat is expressed as a function of the total slip rates at the boundaries pressure gradient dip and thickness of the shear zone and density viscosity and thermal conductivity of the rock a quartic temperature profile develops with a point of maximum temperature near the bottom part of the shear zone in general the profile is parabolic if pressure gradient vanishes leading to a couette flow the profile attains a bell shape if there is no slip at the boundaries i e a true pouseille flow the present model of shear heating is more applicable in subduction channels and some extruding salt diapirs where the rheology is newtonian viscous and pressure gradient drives extrusion

geomechanical modeling of stresses adjacent to salt bodies part 2 poroelastoplasticity and coupled overpressures we use a fully coupled poroelastoplastic geomechanical model to study how stresses and pore pressures evolve in sediments bounding a spherical salt body drained analyses pore pressures remain hydrostatic demonstrate that sediments yield in response to loading by the salt which leads to a redistribution of stresses and to deformations larger than predicted by poroelastic or solid coulomb plastic models undrained analyses overpressures develop while no dissipation occurs illustrate that salt loading induces pore pressures that extend kilometers away from the salt body we also model the flow and consequent dissipation that occur in the sediments because of this undrained salt loading we show that with time the pressure field dissipates and expands the dissipation process takes millions of years which suggests that pore pressure perturbations caused by salt loading should still be present in mudstones near many salt bodies under drained conditions stress perturbations generate low minimum principal stresses above and below the salt resulting in convergence of pore pressure and minimum principal stress at these locations such conditions are challenging to drill through in undrained systems sharp drops in pore pressure may occur above and below the salt whereas both the pore pressure and the minimum principal stress rise next to the salt in contrast to previous models that do not couple changes in stress to changes in pore pressure the coupled approach presented here has the potential to predict in situ stresses and pore pressures more accurately in a wide variety of geologic settings

potash in salt extruded at sar pohl diapir southern iran abstract recent progress in the search for potassium salts in iran is outlined after reviewing how most potassium ores form by the evaporation of seawater hydrothermal brines we focus on how most ores are deformed within salt diapirs we summarise the history of the 150 or so diapirs of hormoz salt emergent in the zagros mountains of iran and then consider in detail the nature of potash at sar pohl 60 km west of bandar abbas these deposits are unique in that they occur in salt that extruded sub aerially and spread over the surrounding ground surface via gravity driven collapse mapping and drilling of the complex structural geology of sar pohl found the potash beds to be dispersed in distal salt but concentrated in piles of recumbent folds with axes circumferential to the mountain over lows in the vent rim equivalents of the curtain folds surviving in the stems of german diapirs presumably still exist beneath sar pohl and would be safer to mine than the recumbent folds in this soluble mountain however it should be possible to continuously pump water onto the exposed salt and guide the resulting brines through evaporation ponds and then a crystallization plant on the adjacent plains this approach would accelerate natural degradation processes but harvest potash currently draining into the gulf

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 1 geometric and kinematic aspects a new deformation apparatus has been used to model the internal kinematics of salt diapirs composite natural samples consisting of a single layer of anhydrite embedded in halite matrix were constrictionally deformed at temperature t 345 c strain rate 10 7 s 1 maximum viscosity 2 1013 pa s and maximum finite strain ex 122 the anhydrite layer oriented parallel to the major stretching axis x was deformed by fracturing whereas halite behaved viscously at advanced state of constriction ex 90 a strong increase in strain hardening of halite led to a transient tension fracture that healed up and was shortened by folding during the final phase of viscous deformation tiny prismatic anhydrite inclusions disseminated inside the halite matrix were reoriented during constriction resulting in a linear grain shape fabric 3d images of the anhydrite layer based on computer tomography revealed rare kink folds with axes subparallel to x and boudins which result from tension fracture with increasing layer thickness hi the width of boudins wa increases linearly wa 0 3 1 3 hi the normalized width of boudins wd wa hi is almost constant at 1 5 1 0 these geometrical parameters can be used to reveal fracture boudinage under bulk constriction the oblique orientation of most of the boudins with respect to the principal strain axes results from folding of the boudins by a second generation of folds the latter with axes subperpendicular to the layer

a first order model for temperature rise for uniform and differential compression of sediments in basins we deduce algebraic expressions for temperature rise for ideal cases of uniform and spatially varying compression of sediments of single mineralogy according to the results of the present work the temperature rise is related to the coefficient of volume expansion isothermal compressibility dimension bulk density and specific heat of the sediment columns rise of temperature due to compression of sediment is effectively inversely proportional to the volume coefficient of expansion or contraction of sediments compression related temperature rise is expected to augment diagenesis a more realistic model of temperature rise dealing with the rate of compression of sediments that of the pore fluid s and the vacant pore space individually would be required

subsurface profiling of granite pluton using microtremor method southern aravalli gujarat india we report using the microtremor method a subsurface granitic pluton underneath the narukot dome and in its western extension along a wnw profile in proximity of eastern fringe of cambay rift india the dome and its extension is a part of the champaner group of rocks belonging to the mesoproterozoic aravalli supergroup the present finding elucidates development of an asymmetric double plunge along narukot dome microtremor measurements at 32 sites were carried out along the axial trace n95 of the dome fourier amplitude spectral studies were applied to obtain the ratio between the horizontal and vertical components of persisting rayleigh waves as local ambient noise fundamental resonant frequencies with amplitude 1 sigma for each site are considered to distinguish rheological boundary two distinct rheological boundaries are identified based on frequency ranges determined in the terrain 1 0 2219 10 364 hz recorded at 31 stations identified as the champaner metasediment and granite boundary and 2 10 902 27 1119 hz recorded at 22 stations identified as the phyllite and quartzite boundary the proposed equation describing frequency depth relationship between granite and overlaying regolith matches with those already published in the literature the morphology of granite pluton highlights the rootless character of champaner group showing sharp discordance with granitic pluton the findings of manifestation of pluton at a shallower depth imply a steep easterly plunge within the champaner metasediments whereas signature of pluton at a deeper level implies a gentle westerly plunge the present method enables to assess how granite emplacement influences the surface structure

the upward transport of inclusions in newtonian and power law salt diapirs abstract this paper studies the ability of salt diapirs to lift large inclusions of dense rocks rafts dense inclusions will be lifted if salt in the diapir rises faster than the inclusions sink the power law rheologies of six different salts and viscosities estimated for newtonian salt are used to calculate the settling velocity of these inclusions as a function of their radii and densiy as well as the temperature of the salt this is done using the known equation describing the velocity of solid spheres settling in unbounded power law fluid two dimensional numerical models are used to study he effect of the ellipticity of inclusions on their sinking velocity as a function of the power law exponentn the calculations of the settling velocities of inclusions neglect several other factors discussed in the paper a the ambient fluid salt is finite bounded b more than one inclusion translates in the salt c further strain rate softening of salt is caused by its diapiric ascent the results suggest that whereas newtonian salt of 1017 1018 pa s and the power law salt of the vacherie dome would have to rise at unreasonably high speeds in order to lift large inclusions most power law salt diapirs would be capable of lifting inclusions of the sizes observed in the iranian domes up to 3 6 km2 if these rise at geologically reasonable velocities and temperatures

viscosity estimates of salt in the hormuz and namakdan salt diapirs persian gulf the parabolic surface profiles of the hormuz and namakdan salt diapirs in the persian gulf suggest that they have been extruding with newtonian viscous rheologies for the last 10 4 years we derive velocity profiles for these diapirs neglecting gravitational spreading and erosion dissolution while assuming incompressible newtonian rheology of the salt fitting known rates of extrusion at specific points in its elliptical cross section the dynamic viscosity of the salt of the hormuz diapir is found to range between 10 18 and 10 21 pa s approximating its sub circular cross section to a perfect circle the range of viscosity of the salt of the namakdan diapir is obtained as 10 17 10 21 pa s these calculated viscosities fall within the range for naturally flowing salts elsewhere and for other salt diapirs but are broader than those for salts with newtonian rheology deforming at room temperatures the salts of the hormuz and namakdan diapirs are expected to exhibit a broader range of grain size which matches the limited existing data

ultrasonic constraint of the microfracture anisotropy of flysch rocks from the podhale synclinorium poland this paper attempts to show the relationship between joints observed in flysch formations in the field and microfracture fabrics invisible to the naked eye in hand specimens ultrasonic measurements demonstrate that the intensity and orientations of domains memorised by rock specimens are associated with the historical stresses within the rock mass rather than the rock lamination the spatial orientations of these microfractures have been measured and their dynamic elastic properties have been found to correlate with the orientation of macroscopic joint sets measured in the field the elastic properties measured vary because of sedimentary diagenetic processes that occured during the tectonic deformations of these flysch rocks in the podhale synclinorium of poland the structural discontinuities detected by ultrasonic measurements can be perceived as an incipient phase of the macroscopic joints already visible in the field and are attributed to the in situ residual tectonic stresses such historical stresses impart a hidden mechanical anisotropy to the entire flysch sequence the microfractures will develop into macroscopic joints during future relaxation of the exposed rock mass understanding the nature and orientation of the invisible microfracture anisotropy that will become macroscopic in the future is vital for the safe and efficient engineering of any rock mass

a study of erosion rates on salt diapir surfaces in the zagros mountains se iran salt exposures and weathering residuum on several salt diapirs in different geographic climatic settings were studied anhydrite gypsum hematite calcite dolomite quartz and clay minerals are the main constituents of the weathering residuum covering the salt diapirs in various thicknesses erosion rates of residuum as well as of rock salt exposures were measured at selected sites for a period of 5 years by plastic pegs as benchmarks recorded data were standardized to a horizontal surface and to long term mean precipitation for the rock salt exposures the following long term denudation rates were determined of 30 40 mm a 1 for coastal diapirs and up to 120 mm a 1 for mountain salt diapirs long term mean superficial denudation rate measured on weathering residuum of low thickness reached 3 5 mm a 1 on coastal diapirs the total denudation rate estimated for the thin residuum is close to 4 7 mm a 1 based on apparent correlation with the uplift rate on hormoz and namakdan diapirs denudation of rock salt exposures is much faster compared to parts of diapirs covered by weathering residuum the extent of salt exposures is an important factor in the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir salt exposures produce huge amounts of dissolved and clastic load thus affecting the surrounding of the diapir

modeling of grabens extending above evaporites in canyonlands national park utah abstract grabens in canyonlands national park utah began extending above a layer of evaporites when the colorado river cut through the overburden two dimensional finite element models simulate the effects of geometry and rock properties on graben configuration and spacing only those models having a progressively increasing slope or no slope mimicked the natural upslope graben propagation typical rock properties produced the most realistic fault patterns an initial friction angle of 31 a cohesion of 1 mpa and strain weakening comprising cohesion loss and decrease of friction angle to 26 a tensile stress limit narrowed the grabens and reproduced the vertical upper portion of the natural faults the viscous salt resisted overburden spreading and controlled its rate modeled grabens spread at typical rates of 1 2 mm a 1 for a salt viscosity of 1 10 18 pa s and the entire system strained at rates from 6 0 10 14 s 1 to 0 5 10 14 s 1 the faults bounding a graben formed nearly simultaneously at the top surface and propagated downward salt rose beneath the grabens as reactive diapirs overburden adjacent to the canyon flexed as salt was expelled and formed an arching horst and graben a corresponding horst has been found in the field the model results scale to larger dimensions except for the steep upper part of the faults reduced dimensions create vertical or no faults

geology and models of salt extrusion at qum kuh central iran profiles through the summit of a small nearly axisymmetric extrusion of oligocene and miocene salt and simple analogue models of it simulate the profiles of piles of ductile nappes extruded from convergent orogens the salt extrudes from a reactive diapir along a major strike slip fault at about 82 mm a 1 and rises 315 m above the central plateau of iran the salt has the distinctive smooth profile of a viscous fountain in which an asymmetric apron of allochthonous salt gravity spreads over its surroundings from a summit dome curtain folds developed in the source layer extrude from the diapir and are refolded by major recumbent folds with circumferential axes that simulate nappes minor flow folds with circumferential axes refold major folds in the top 10 50 m of surficial salt master joints 100 m long indicate brittle failure of dilated salt by regional stress fields tuned to the dimensions of qum kuh analytical and analogue models of viscous extrusions constrain the dynamic salt budget and a time of extrusion of at least 42 000 years new analogue models suggest that the number amplitude and spacing of major recumbent folds within the extruded salt and ductile nappe piles record the number amount and relative timing of fluctuations in the driving forces

numerical study of tectonic structure evolution in a multi layer evaporite sequence abstract field studies carried out in the klodawa salt structure kss poland reveal that within a carnallite halite kieserite sequence finger like structures developed during an early pre diapiric stage of the kss evolution we used 99 numerical simulations to model finger development and investigate mechanical properties of carnallite halite and kieserite during deformation models used inverse density stratification of a three layer set with varying 1 layer viscosities 2 thicknesses and 3 density difference ratios finger shapes in the models were categorized into single and multiwavelength structures among the single wavelength shapes bulb mushroom thumb and bloated i e without a regular shape structures were distinguished we show two transitions between the single and multiwavelength structures which correspond to the cases of either the lower or upper layer having viscosity more than an order of magnitude larger than the two other layers through comparison of finger shapes developed in the models and in the natural structures we estimate viscosities of 1017 pa s for halite

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

the control of salt supply on entrainment of an anhydrite layer within a salt diapir the influence of four parameters sedimentation rate viscosity of salt stratigraphic location of the anhydrite layer within the salt layer and the perturbation width on salt supply to down built diapirs and its entrainment capacity are studied systematically in numerical models model results show that these four parameters affect salt supply and the evolution history of a salt diapir as such these parameters strongly influence the style and the amount of entrainment of dense inclusions into a diapir in active diapirs i e unburied diapirs salt supply increases with increasing sedimentation rate whereas it decreases with an increase in salt viscosity diapirs initiating from wide perturbation provide more salt supply to feed the diapir presence and initial stratigraphic location of any denser layer e g an anhydrite layer within a salt layer also affects salt supply when lateral forces are negligible salt supply into a diapir depends on these four parameters which directly control the entrainment of any embedded anhydrite layer into the diapir

control of cambrian evaporites on fracturing in fault related anticlines in the zagros fold and thrust belt orientation and distribution of fractures in the oligocene early miocene asmari formation a major reservoir rock of the zagros petroleum system were investigated in two anticlines of the zagros fold and thrust belt the sim and kuh e asmari anticlines developed in the areas of the zagros characterized by the occurrence and absence of cambrian evaporites at the bottom of the stratigraphic pile respectively the aim was to outline major differences in terms of fracture spacing and saturation organic matter maturity and clay minerals based geothermometers suggest that the depth of deformation for the top of the asmari formation in the kuh e asmari anticline was in the range of 1 5 2 7 km assuming a geothermal gradient of 22 5 c km the asmari formation in the sim anticline probably experienced a slightly deeper sedimentary burial maximum 3 km with a geothermal gradient of 20 c km the spacing of fractures is generally 2 3 times larger i e strain accommodated by fracturing is smaller in the sim anticline than in the kuh e asmari anticline this is consistent with regional geological studies analogue and numerical models that suggest that thrust faults geometry and related folds are markedly different in the absence or presence of a weak decollement evaporites the larger spacing in the sim anticline is also consistent with higher temperature predicted for the asmari formation in this area by contrast the orientation of fractures with respect to the fold axes is the same in both anticlines the fracture systems are rather immature in both anticlines the amount and density of fractures in the twofolds are controlled by regional occurrence absence of salt and probably different burial rather than local features fold geometry

surficial deposits on salt diapirs zagros mountains and persian gulf platform iran characterization evolution erosion and the influence on landscape morphology the surfaces of salt diapirs in the zagros mountains are mostly covered by surficial deposits which significantly affect erosion rates salt karst evolution land use and the density of the vegetation cover eleven salt diapirs were selected for the study of surficial deposits in order to cover variability in the geology morphology and climate in a majority of the diapirs in the zagros mountains and persian gulf platform the chemical and mineralogical compositions of 80 selected samples were studied mainly by x ray powder diffraction and x ray fluorescence changes in salinity along selected vertical profiles were studied together with the halite and gypsum distribution the subaerial residuum formed from minerals and rock detritus released from the dissolved rock salt is by far the most abundant material on the diapirs fluvial sediments derived from this type of residuum are the second most common deposits found while submarine residuum and marine sediments have only local importance the mineralogical chemical composition of surficial deposits varies amongst the three end members evaporite minerals gypsum anhydrite and minor halite carbonates dolomite and calcite and silicates oxides mainly quartz phyllosilicates and hematite based on infiltration tests on different types of surficial deposits most of the rainwater will infiltrate while overland flow predominates on rock salt exposures recharge concentration and thick accumulations of fine sediment support relatively rich vegetation cover in some places and even enable local agricultural activity the source material diapir relief climatic conditions and vegetation cover were found to be the main factors affecting the development and erosion of surficial deposits a difference was found in residuum type and landscape morphology between the relatively humid nw part of the studied area and the arid persian gulf coast in the nw the medium and thick residuum seems to be stable under current climatic conditions large sinkholes and blind valleys with sinking streams are common on other diapirs the original thick residuum is undergoing erosion and the new morphology is currently represented by salt exposures and badland like landscapes or by fields of small sinkholes developed in the thin residuum models for evolution of the subaerial residuum and the diapir landscape morphology are described in this paper while the thick residuum with vegetation has very low erosion rates the salt exposures and thin residuum are eroded rapidly during wet periods e g early holocene the diapirs rose and salt glaciers expanded as the influx of salt mass was much faster compared to erosion after the onset of an arid climate c 6 ka bp the rising of the some diapir surfaces decreased or even reversed due to acceleration of erosion thanks to vegetation degradation and changes in the residuum type and thickness

active normal faulting beneath a salt layer an experimental study of deformation patterns in the cover sequence scaled experimental models show that the presence of a viscous layer such as salt facilitates the development of extensional forced folds above active normal faults the geometries of the extensional forced folds and their associated secondary fault patterns depend on the thickness and viscosity of the viscous layer the thickness of the cover sequence the strength and ductility of the cover sequence and the magnitude and rate of displacement on the underlying master normal fault increasing the thickness of the viscous layer and the cohesive strength and ductility of the overburden enhances the decoupling between the deep and shallow deformation alternatively increasing the viscosity of the viscous layer the thickness of the overburden and the magnitude and rate of displacement on the master normal fault reduces the decoupling between the deep and shallow deformation enhanced decoupling facilitates the formation of broad extensional forced folds and the development of detached secondary faults both near and far from the master normal faults the model predicted deformation patterns closely resemble those observed in the gulf of suez the haltenbanken area of offshore norway and the jeanne d arc basin of the grand banks offshore southeastern canada

physical modelling of overburden deformation around salt diapirs abstract salt diapirs produce highly complex deformation patterns in the surrounding overburden which are difficult to image seismically or model numerically to further the understanding of deformation around salt structures we have used physical models with brittle granular overburdens and simulated sedimentation accompanying diapiric rise rigid linear indentors produce a crestal horst above the indentor with two flanking graben large amounts of indentation produce predominantly reverse faults along the margins of the diapir and extensional faults over the crest in contrast hemispherical indentors produced inward dipping concentric reverse faults forefully intruded polymer diapirs produce a narrow crestal graben above the diapir crest downbuilt polymer diapirs produce extensional faults on the flanks of the diapirs which offset the diapir walls no clear secondary rim synclines were developed as polymer is withdrawn evenly from the whole of the polymer layer across the model strong and anisotropic layered overburden were simulated using cohesive clay and mica respectively detachments were formed along mica layers which suppressed faults with large throws cohesive layer deformation began with tensile fractures permitting rotation of fractured rafts around the sides of the diapir these progressively slip off the crest and create large gaps in the stratigraphy

toward 4d modeling of orogenic belts example from the transpressive zagros fold belt abstract latest developments in computer power and computational solutions open new ways to envision complex natural systems advances in high resolution 3d geodynamic modeling in particular allow investigating tectonic processes such as transpression which involve normal and tangential kinematics with respect to the bulk orogenic trends we demonstrate that implementing the 4 dimensions space and time provides and constrains new answers to long lasting discussions as case study we have chosen the zagros simply folded belt in iran which exhibits spatial variations of structural patterns from the homogeneously shortened wide fold belt in the fars to the narrower higher elevated area in the izeh high resolution 4d numerical modeling shows how a low viscosity decollement becoming frictional toward the dezful embayment influences the exposed fold patterns results also emphasize the importance of an oblique backstop to produce en echelon arranged folds where convergence related and backstop controlled folds are mingled in the transpressional orogen