sheets within diapirs results of a centrifuge experiment we carried out a centrifuge experiment to model the diapiric rise of a stratified pdms layer from three perturbations through a non newtonian ductile overburden the experiment carried out at 700 g resulted in three composite diapirs fed by different pdms layers the three resulting diapirs represent two different stages of diapirism one of the diapirs diapir 1 which reached its level of neutral buoyancy and extruded at the surface of the model was tabular in profile and copied by an internal intrusive body the other two diapirs diapirs 2 and 3 were still in the ascending stage when centrifuging was stopped and thus did not extrude at the surface they displayed a typical balloon on string geometry which develops at a high viscosity contrast between a highly viscous overburden and a less viscous buoyant material the internal geometry of these last two diapirs fed by the lower impure pdms however did not copy the shape of their precursors instead they had a finger like shape the finger geometry of the internal part of the diapirs might be the result of the higher viscosity of the impure lower pdms intruding a less viscous clean pdms compared to nature diapir 1 represents a fully developed concentrically expanded pluton or nested diapir while diapirs 2 and 3 resemble composite plutons which host magma batches of dyke like geometry based on the results of our experiment we suggest that truly concentrically expanded plutons develop from the latter

numerical modeling of the effect of composite rheology on internal deformation in down built diapirs a two dimensional finite difference code fdcon is used to estimate the progressive deformation and the effect of a composite rheology i e newtonian combined with non newtonian on finite defor

weakening of rock salt by water during long term creep the rheological properties of rock salt are of fundamental importance in predicting the long term evolution of salt based radioactive waste repositories and strategic storage caverns and in modelling the formation of salt diapirs and associated oil traps1 2 the short term high stress rheology of rock salt is well known from laboratory experiments however extrapolation to appropriately low stresses fails to predict the rapid flow seen in certain natural structures furthermore experiments have failed to reproduce the recrystallized microstructure of naturally deformed salt here we report experiments indicating that the above discrepancies can be explained by taking into account the influence of trace amounts of brine trace brine is always present in natural salt but sometimes escapes during experiments our tests on dry dilated salt show more or less conventional dislocation creep behaviour but brine bearing samples show marked weakening at low strain rates this is associated with dynamic recrystallization and a change of deformation mechanism to solution transfer creep because natural rock salt always contains some brine these results cast substantial doubt on the validity of presently accepted dislocation creep laws for predicting the long term rheological behaviour of salt in nature

light stable isotope systematics of large scale hydrologic regimes in california and nevada surface waters shallow groundwaters and precipitation samples were collected along three traverses which begin at the california coast and are oriented in an east west manner roughly parallel to the atmospheric flow path of meteoric water the hydrogen isotope compositions from short term precipitation records varied as much as 40 at one location and were not representative of the average annual isotopic composition of precipitation the hydrogen isotope ratios of surface waters and shallow groundwaters distinguish segments with isotopic variations that correlate with measured vertical fluxes of meteoric water one coastal segment appears to closely approximate an open system in which precipitation dominates over evapotranspiration most segments are described by rather regular variations in d 3 45 per 100 km which represent different degrees of closure of the hydrologic system caused by variable partitioning of precipitation between runoff and evapotranspiration all partially closed systems imply terrestrial recycling of water a simple model estimates this amount to be about 20 across northern and central california three segments representing the great basin show virtually no geographic variation and appear to represent isotopically closed systems

numerical models of salt diapir formation by down building the role of sedimentation rate viscosity contrast initial amplitude and wavelength formation of salt diapirs has been described to be due to upbuilding i e rayleigh taylor like instability of salt diapirs piercing through a denser sedimentary overburden or syndepositional down building process i e the top of the salt diapir remains at the surface all the time here we systematically analyse this second end member mechanism by numerical modelling four parameters are varied sedimentation rate nu sed salt viscosity eta salt amplitude delta of the initial perturbation of the sedimentation layer and thewavenumber k of this perturbation the shape of the resulting salt diapirs strongly depends on these parameters small diapirs with subvertical side walls are found for small values of nu sed and eta salt or large values of delta whereas taller diapirs with pronounced narrow stems build for larges values of nu sed and eta salt or small values of delta two domains are identified in the four parameter space which separates successful down building models from non successful models by applying a simple channel flow law the domain boundary can be described by the non dimensional law nu sedcrit c 1 1 2 delta 0 rho sed k 2 k 2 c2 where rho sed is the sediment density scaled by the density contrast delta rho between sediment and salt the wavelength is scaled by the salt layer thickness h salt and velocity is scaled by eta salt h salt 2 delta rho g where eta salt is the salt viscosity and g is the gravitational acceleration from the numerical models the constants c 1 and c 2 are determined as 0 0283 and 0 1171 respectively

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

spatial expression of enso drought and summer monsoon in seasonal δ13c of ponderosa pine tree rings in southern arizona and new mexico 1 major climatic impacts from enso and the north american monsoon in the u s southwest provide fortuitous circumstances for exploring the suitability of stable carbon isotope 13c composition of tree rings to represent and reconstruct interannual climate variability we sampled ponderosa pine tree rings at eight sites in seven mountain ranges over a 500 km transect in southern arizona and new mexico we developed 13c chronologies for 1985 1995 by subdividing rings into pre and post monsoon onset segments based on the presence of a false latewood band in each ring induced by the arid period immediately preceding the summer monsoon pooling these segments from multiple trees at each site and analyzing the cellulose component chronologies from two subsets of trees from the same site and separate chronologies from two different sites in the same mountain range indicate strong coherence and signal reproducibility additionally the seasonal 13c patterns showed remarkable coherence across the transect with the spatially disjunct easternmost chronology tending to be most frequently dissimilar the 13c values of ring subdivisions before the false latewood band are generally positively correlated with winter southern oscillation indices soi resulting from the enso teleconnection with southwestern winter early spring precipitation the 13c from these sites correlates with monthly palmer drought severity indices pdsi with the strongest correlations occurring in progressively later months from first formed to last formed subdivisions the post false latewood subdivision 13c was particularly strongly correlated with summer precipitation amount these results confirm the strong influence of moisture on tree ring 13c and support their use in both temporal and spatial modes to infer past climate variability

oxygen and carbon stable isotopes in coast redwood tree rings respond to spring and summer climate signals 1 interannual variability in the oxygen and carbon isotope composition of tree ring cellulose was investigated in coast redwood sequoia sempervirens from three sites in coastal northern california middle and late wood samples from annual tree rings were compared to regional climate indices and gridded ocean atmosphere fields for the years 1952 2003 the strongest climate isotope relationship r 0 72 was found with summer june september daily maximum temperature and middle wood 13 which also responds positively to coastal sea surface temperature and negatively to summer low cloud frequency late wood 18o reflects a balance between 18o enriched summer fog drip and depleted summer rainwater while a combined analysis of late wood 18o and 13c revealed sensitivity to the sign of summer precipitation anomalies empirical orthogonal function analysis of regional summer climate indices and coast redwood stable isotopes identified multivariate isotopic responses to summer fog and drought that correspond to atmospheric circulation anomalies over the ne pacific and nw u s the presence of regional climate signals in coast redwood stable isotope composition consistent with known mechanistic processes and prior studies offers the potential for high resolution paleoclimate reconstructions of the california current system from this long lived tree species

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

the structural evolution of the messinian evaporites in the levantine basin abstract the levantine basin in the south eastern mediterranean sea is a world class site for studying the initial stages of salt tectonics driven by differential sediment load because the messinian evaporites are comparatively young the sediment load varies along the basin margin they are hardly tectonically overprinted and the geometry of the basin and the overburden is well defined in this study we analyse depositional phases of the evaporites and their structural evolution by means of high resolution multi channel seismic data the basinal evaporites have a maximum thickness of about 2 km precipitated during the messinian salinity crisis 5 3 5 9 ma ago the evaporite body is characterized by 5 transparent layers sequenced by four internal reflections we suggest that each of the internal reflection bands indicate a change of evaporite facies possibly interbedded clastic sediments which were deposited during temporal sea level rises all of these internal reflections are differently folded and distorted proving that the deformation was syn depositional thrust angles up to 14 are observed backstripping of the pliocene quaternary reveals that salt tectonic is mainly driven by the sediment load of the nile cone the direction of lateral salt displacement is mainly ssw nne and parallel to the bathymetric trend apparent rollback anticlines off israel result rather from differential subsidence than from lateral salt displacement in the south eastern basin margin the deposition of the isreali slump complex isc is coeval with the onset of salt tectonic faulting suggesting a causal link between slumping processes and salt tectonics the superposition of thin skinned tectonics and thick skinned tectonics becomes apparent in several locations the fold belt off the israeli mediterranean slope mainly results from active strike slip tectonics which becomes evident in faults which reach from the seafloor well below the base of the evaporites owing to the wrenching of the crustal segments which are bounded by deep rooted fault lines like the damietta latakia pelusium and shelf edge hinge line the setting is transpressional south of 32 n where the fault lines bend further towards the west this adds a component of thick skinned transpression to the generally thin skinned compressional regime in the basin above 1 5 km of evaporites a mud volcano is observed with the mud source seemingly within the evaporite layer at the eastern cyprus arc the convergence zone of the african and the anatolian plates deep rooted compression heavily deformed the base of the evaporites whereas at the eratosthenes seamount mainly superficial compression affecting the post messinian sediments and the top of the evaporites is observed

numerical analysis of how sedimentation and redistribution of surficial sediments affects salt diapirism abstract two dimensional finite element models are used to study how sedimentation and redistribution of sediments on the upper surface affects the development of subsurface salt diapirs a rising diapir creates a bulge flanked by topographic lows in a generally accumulating sedimentary pile we find that the rate at which this topography is flattened by erosion and redeposition controls the style of diapirism this is because the redistribution of material from topographic highs to flanking lows is equivalent to changing the effective forces acting on the salt redistributing a potential topography modulates diapiric growth rate the main effects of including surficial sediment redistribution in numerical models of diapirism are 1 1 diapirs grow 10 100 times faster 2 2 diapirs may rise above their level of neutral buoyancy and extrude 3 3 diapirs assume finger or stock like shapes rather than mushroom or balloon on string shapes 4 4 layers in the surrounding sediments remain nearly horizontal and only steepen sharply near the diapir in effect the rate of redistribution of surficial overburden strongly controls the mode of diapirism sediment redistribution referred to as erosion for brevity is modeled using a one dimensional diffusion equation we show the results of two different erosion rates infinitely slow no erosion and extremely fast which redistributes surficial sediments but does not remove them from the system we show that the shapes of model diapirs rising beneath surfaces subjected to rapid erosion simulate salt diapirs in the gulf of mexico columnar diapirs indicate rapid deposition on the shelf and plug like diapirs slow sedimentation on the abyssal plane diapirs rising beneath surfaces with negligible erosion have the mushroom shapes interpreted for salt diapirs in central iran

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

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

tidal dissipation surface heat flow and figure of viscoelastic models of io abstract the distribution of hot spots on io s surface and io s figure constrain models of io s interior voyager observations indicate that most hot spots and volcanic plumes are close to the equator recently however it has been proposed that a large low albedo feature in the south polar region may be the source of 40 of the surface heat flow we calculate spatial distributions of the dissipation rate surface heat flow and the figures of three and four layer maxwell rheology models of io by using the correspondence principle the models are required to satisfy the observed surface heat flow constraint and are consistent with the composition of a dehydrated c2 chondrite they consist of an inviscid fe fes core and viscoelastic silicate mantle and lithosphere layers a comparison of the calculated equilibrium figure with the observed figure of io supports the chosen core radius of 980 km in addition the four layer model has a partially molten asthenosphere a few tens of kilometers thick the preferred three layer model has a mantle shear modulus of 10 10 pa and a viscosity of 2 10 16 pa s consistent with rock properties the tidal dissipation rate for this model is largest along the polar axis integration of the dissipation rate over radius gives a surface heat flow with maxima at the poles and minima near the sub jovian and anti jovian points in contrast the dissipation rate in a molten or partially molten incompressible asthenosphere has maxima near the equator and is close to zero at the poles the asthenosphere dissipation rate is mainly a function of asthenosphere viscosity and thickness the thinner the asthenosphere the smaller is the required viscosity a 50 km thick asthenosphere requires a viscosity of about 10 8 pa s a strong south polar hot spot if it can be confirmed by infrared observation favors dissipation in the mantle but does not exclude dissipation in a partially molten asthenosphere equatorial hot spots and the concentration of prometheus type plumes near the equator favor asthenosphere heating but do not rule out deep mantle dissipation both asthenosphere and deep mantle heating may contribute to io s surface heat flow the properties of magma transport through the lithosphere and the planform of mantle convection might exert a control on the surface expression of heating at greater depth

a history of high temperature io volcanism february 1995 to may 1997 ground based observations of io s infrared thermal emission between february 1995 and may 1997 show several discrete brightenings for which we can constrain locations fluxes and durations several of these were brief high temperature events with temperatures up to at least 1500 k similar to but often smaller than the rare outbursts seen previously loki io s most powerful volcano was relatively active before and probably during galileo s december 1995 io flyby was faint during most of 1996 and began a major long lived brightening between february 20 and march 12 1997 thermal emission was not seen from ra patera site of an active plume in galileo images major outbursts were seen on march 2nd and september 27 1995

numerical modeling on progressive internal deformation in down built diapirs a two dimensional finite difference code fdcon is used to estimate the finite deformationwithin a down builtdiapir the geometry of the down built diapir is fixed by using two rigid rectangular o

large scale topography of io implications for internal structure and heat transfer new stereographic techniques were applied to voyager 1 images to determine the shape and large scale topography of io the best fit triaxial figure has semiaxes of 1830 0 1818 7 and 1815 3 kilometers with random errors of about 200 meters systematic navigation and optical system errors are comparable the resulting figure is consistent with a differentiated satellite in hydrostatic equilibrium the deviation from homogeneity could be explained by the presence of an iron core with a radius of about 800 km most elevations over areas larger than 500 km diameter deviate from the triaxial figure by no more than 1 km we suggest that many of these broad topographic swells and basins may be due to isostatic responses to thermal changes in the lithosphere asthenosphere system in the simplest picture increasing the heat flow converts the basal lithosphere into lower density asthenosphere resulting in isostatic uplift lithospheric thicknesses ranging from 5 to 100 km may result in elevation variations of up to 1 km if the large scale topography is positively correlated with heat flow then the global pattern of basins and swells suggests tidal dissipation in a molten or partially molten asthenosphere rather than in the mantle areas higher than 1 km may consist of low density crustal materials media regio the largest such region is centered near the equator at longitude 70

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

an annually resolved bristlecone pine carbon isotope chronology for the last millennium abstract we present the first near millennium length annually resolved stable isotope record from bristlecone pines pinus longaeva d k bailey the carbon isotope ratios from the cellulose of seven trees from the white mountains of california corrected for anthropogenic changes in atmospheric chemistry are used to reconstruct growing season june through august precipitation back to ad 1085 extremely negative isotope results are strongly correlated with proposed severest el nino events over the last 500 yr and similar values in the first half of the millennium are used to reconstruct a further 13 strong el nino events concentrated in the 12th century and the mid 13th and 14th centuries ring width chronologies from adjacent sites in the white mountains demonstrate a high degree of decadal covariance with the 13c series although there are several periods of notable divergence

origin and deformation of intra salt sulphate layers an example from the dutch zechstein late permian from salt mine galleries and well data it is known that thick rock salt layers can contain anhydrite and carbonate layers with thicknesses on the millimetre to tens of metre scale the relatively thick zechstein 3 anhydrite carbonate layer in the northern netherlands has been studied previously using 3 d seismic data observations from geophysical well logs in this study reveal the presence of thin sulphate layers on the sub seismic scale imbedded in the zechstein 2 z2 salt core samples thin sections seismic data and geochemical measurements were used to determine the mineralogy and origin of one of these z2 sulphate layers bromine analyses show that they mark a freshening event in the z2 salt which can be correlated over large distances in the northern netherlands their core calibrated log signature indicates that the z2 sulphate layers consist either of pure anhydrite or of anhydrite and polyhalite the mineralogy and thickness of the sulphate layers are interpreted to vary between synsedimentary morphologic lows thin anhydrite polyhalite couplets and highs thicker anhydrite layers such a combination of core observations and well log analysis is a powerful tool to detect lateral trends in evaporite mineralogy and to reconstruct the environmental setting of their formation salt internal geometries can further be used to distinguish between different deformation mechanisms in our study area the distribution of sulphate layers within the z2 salt indicates that subjacent salt dissolution was not the dominant process leading to salt related deformation

io evidence for silicate volcanism in 1986 infrared observations of io during the 1986 apparition of jupiter indicate that a large eruptive event occurred on the leading side of io on 7 august 1986 universal time measurements made at 4 8 8 7 and 20 micrometers suggest that the source of the event was about 15 kilometers in radius with a model temperature of 900 kelvin together with previously reported events these measurements indicate that high temperature volcanic activity on the leading side of io may be more frequent than previously thought the inferred temperature is significantly above the boiling point of sulfur in a vacuum 715 kelvin and thus constitutes strong evidence for active silicate volcanism on the surface of io

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

basin geometry and salt diapirs in the flinders ranges south australia insights gained from geologically constrained modelling of potential field data abstract the adelaide basin in australia is a complex of late neoproterozoic to early cambrian rift and sag basins which was inverted during the cambro ordovician delamerian orogeny the deposition of evaporitic sediments during the earliest stage of basin development in the late neoproterozoic willouran age played a major role in the subsequent tectonic evolution of the basin previous studies have shown that early mobilization vertical transport and withdrawal of the evaporites influenced the sedimentation during the late neoproterozoic and early cambrian the evaporites also influenced deformation during the inversion of the basin and the development of the delamerian fold and thrust belt however the control exerted by basement structures in the deposition of the evaporitic beds and the role of these tectonic structures in the later inversion of the basin have been poorly constrained in this work we use a combination of published and original geological observations along with the interpretation of potential field datasets total magnetic intensity and bouguer anomaly data to better constrain the geology of the basin at depth we construct two and a half dimensional forward models of the potential field data along selected profiles across the adelaide basin these models are constrained by the geology at the surface drill hole data and measured petrophysical properties specific gravity and magnetic susceptibility we achieved the best fit between observed and modelled potential fields with a model favouring thick skinned deformation where the diapirs are not randomly distributed but located directly above basement penetrating normal faults furthermore these normal faults were probably active during the sedimentation of the late neoproterozoic and early cambrian sediments and underwent partial or total inversion during the cambro ordovician delamerian orogeny mobilisation and withdrawal of the evaporites was therefore initiated and facilitated by the extension coeval with the opening of the basin and continued during the subsequent delamerian orogeny

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

volcanic eruptions on io heat flow resurfacing and lava composition abstract we model an infrared outburst on io as being due to a large erupting lava flow which increased its area at a rate of 1 5 10 5 m 2 sec 1 and cooled from 1225 to 555 k over the 2 583 hr period of observation the inferred effusion rate of 3 10 5 m 3 sec 1 for this eruption is very high but is not unprecedented on the earth and is similar to the high eruption rates suggested for early lunar volcanism eruptions occur 6 of the time on io these eruptions provide ample resurfacing to explain io s lack of impact craters we suggest that the large total radiometric heat flow 10 14 w and the size and temperature distribution of the thermal anomalies mcewen et al 1992 bull am astron soc 24 935 veeder et al 1994 j geophys res 99 17 095 17 162 can be accounted for by a series of silicate lava flows in various stages of cooling we propose that the whole suite of io s currently observed thermal anomalies was produced by multiple high eruptive rate silicate flows within the past century

the salt dome problem a multilayered approach the dynamical evolution of buoyancy driven geological systems is mainly influenced by two physical parameters density and equivalent viscosity salt structures are an appropriate geological representation of these systems important variations of these parameters are directly related to changes in mass and thus the internal structures themselves and their changes in time become significant parameters in order to decipher these structures in nature by means of experiments it is therefore necessary to extend model calculations on intrusion processes to multilayer systems a two dimensional finite element program has been developed to simulate the rise of individual diapirs through multi layered overburdens exhibiting newtonian viscous rheologies this program includes the following features arbitrarily shaped interfaces between different fluid boundaries layers of finite thickness and subsidence of the model within the model frame as well as time and depth dependent material properties this paper is concerned with single diapirs intruding upbuilt multilayered overburdens the effect of a subsiding salt base due to pure downbuilding and differential loading of gravitationally unstable distributions of mass variable density and viscosity of the overburden with depth control the shape and ascent rates of diapiric bodies the subsidence history of salt structures dominates the development of maximum horizontal pressure gradients with time and thus the ascend histories of diapirs

internal structure of io and the global distribution of its topography abstract the distribution of equatorial long wavelength topography on io consists of alternating basins and swells similar to the pattern expected if tidal heating in a thin asthenosphere controls the elevation of the surface through a conductive lithosphere in isostatic equilibrium the equatorial basin swell pattern is shifted in longitude with respect to theoretical tidal heating patterns however making the correlation between theoretical heat flow and elevation unclear we calculate global topography for multilayer io models with dissipation occurring in a viscous asthenosphere and a solid mantle two models are considered a thermal swell model in which topography and heat flow are positively correlated and a differentiated lithosphere model in which topography and heat flow are negatively correlated both models match the observed pattern of alternating basins and swells along the equator and moderate polar topography if about two thirds of the tidal heating occurs in the asthenosphere and about one third occurs in the underlying solid mantle the mean thicknesses of the model lithospheres are 35 km in the differentiated model and 150 km in the thermal swell model polar topography and the hypsometric distribution of elevations in the differentiated lithosphere model match the observations better than the thermal swell model in a differentiated lithosphere model consistent with the topography the asthenosphere is at least 50 km thick with viscosity about 100 mpa sec and is about 7 more dense than the lithosphere the mantle density exceeds the asthenosphere density by at least 10 the shift of the equatorial basin swell pattern suggests that io s lithosphere has recently undergone a zonal rotation of about 25

the internal geometry of salt structures a first look using 3d seismic data from the zechstein of the netherlands abstract we present a first look at the large scale complexly folded and faulted internal structure of zechstein salt bodies in nw europe using 3d reflection seismic reflection data from two surveys on the groningen high and the cleaver bank high we focus on a relatively brittle folded and boudinaged claystone carbonate anhydrite layer the z3 stringer enclosed in ductile salt a first classification of the structures is presented and compared with observations from salt mines and analogue and numerical models z3 stringers not only are reservoirs for hydrocarbons but can also present a serious drilling problem in some areas results of this study could provide the basis for better prediction of zones of drilling problems more generally the techniques presented here can be used to predict the internal structure of salt bodies to estimate the geometry of economic deposits of all kinds and locate zones suitable for storage caverns structures observed include an extensive network of zones with increased thickness of the stringer these we infer to have formed by early diagenesis karstification gravitational sliding and associated local sedimentation later this template was deformed into large scale folds and boudins during salt tectonics salt flow was rarely plane strain producing complex fold and boudin geometries deformation was further complicated by the stronger zones of increased thickness which led to strongly non cylindrical structures we present some indications that the thicker zones also influence the locations of later suprasalt structures suggesting a feedback between the early internal evolution of this salt giant and later salt tectonics this study opens the possibility to study the internal structure of the zechstein and other salt giants in 3d using this technique exposing a previously poorly known structure which is comparable in size and complexity to the internal parts of some orogens

stable carbon isotopes from tornetrask northern sweden provide a millennial length reconstruction of summer sunshine and its relationship to arctic circulation this paper presents results from the first 1100 years of a long stable carbon isotope chronology currently in development from scots pine pinus sylvestris l trees growing in the tornetrask region of northern sweden the isotope record currently comprises a total of 74 trees with a mean annual replication of 12 thereby enabling it to be compared directly with other tree ring based palaeoclimate reconstructions from this region in developing the reconstruction several key topics in isotope dendroclimatology chronology construction replication co2 adjustment and age trends were addressed the resulting carbon isotope series is calibrated against instrumental data from the closest meteorological station at abisko ad1913 2008 to provide a record of june august sunshine for northern fennoscandia this parameter is closely linked to the direct control of assimilation rate photosynthetically active radiation par and the indirect measures mean july august temperature and percent cloud cover the coupled response of summer sunshine and temperature in this region permits a multiparameter comparison with a local reconstruction of past temperature variability based upon tree growth proxies to explore the stability of this coupling through time several periods are identified where the temperature x ray density and sunshine stable carbon isotope ratio records diverge the most significant and sustained of these occur between c ad1200 1380 and c ad1550 1780 providing evidence for a cool sunny two phase little ice age whilst summer sunshine reconstructed for the 20th century is significantly different from the mean of the last 1100 years p 0 01 so it is the 17th 18th and to a lesser extent the 13th centuries rather than the early medival period that appear anomalous when viewed within the context of the last 1100 years the observed departures between temperature and sunshine are interpreted as indicating a change in large scale circulation associated with a southward migration of the polar front such a change affecting the northern annular mode arctic oscillation would result in more stable anticyclonic conditions cool bright summers over northern fennoscandia thus providing a testable mechanism for the development of a multi phase time transgressive little ice age across europe

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

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

3d seismic study of complex intra salt deformation an example from the upper permian zechstein 3 stringer western dutch offshore mostoftheinformationonsubsurfaceevaporiticstructurescomesfrom3dseismicdata however this data only provide limited information about the internal structure of the evaporites which is known from salt mines and salt diapir outcrops brittle intra salt layers carbonate anhy drite clay ofatleast 10 m thicknessform goodreflectors inevaporites but the structure and dynam ics of such stringers in the salt movement are poorly understood in this study we investigate the intra salt zechstein 3 z3 stringer from 3d seismic data in an area offshore the netherlands observations show complex deformation including boudinage folding and stacking reflections from thin and steep stringer parts are strongly reduced and we present different structural models andtestsofthese wecompareourobservationstostructuralmodelsfromsaltminesandanalogue numerical models of intra salt deformation a smoothed representation of the upper surface of the stringer fragments follows the shape of top salt but smaller scale stringer geometries strongly differ from this and imply boudinage the imaged disharmonic patterns of constrictional folds pro vide evidence for the complexity of the intra salt in agreement with observations in salt mines this may be explained by interaction of the layered salt rheology complex three dimensional salt flow different phases and styles of basement tectonics and movement of the overburden

galileo s first images of jupiter and the galilean satellites the first images of jupiter io europa and ganymede from the galileo spacecraft reveal new information about jupiter s great red spot grs and the surfaces of the galilean satellites features similar to clusters of thunderstorms were found in the grs nearby wave structures suggest that the grs may be a shallow atmospheric feature changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on io patchy emissions were seen while io was in eclipse by jupiter the outer margins of prominent linear markings triple bands on europa are diffuse suggesting that material has been vented from fractures numerous small circular craters indicate localized areas of relatively old surface pervasive brittle deformation of an ice layer appears to have formed grooves on ganymede dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

polydiapirs multiwavelength gravity structures polydiapirs domes in domes result from the evolution of a multiwavelength rayleigh taylor gravitational instability the present work investigates the initiation and development of polydiapirs by means of two dimensional finite difference models of gravitationally unstable triple layered sequences of newtonian fluids the values of viscosities thicknesses and densities were systematically varied for selected examples in triple layered sequences only two types of density stratification are likely to result in multiwavelength instabilities that will eventually develop into polydiapiric structures the limiting factors and evolution of such structures were studied for both these types of density stratifications finite difference calculations on models with physical parameters appropriate to evaporitic sequences and covered by a viscous clastic overburden showed that a very small downward density decrease in the evaporitic source may cause an internal overturn that will compete with the main overturn between source and overburden this may lead to the development of sequential or simultaneous polydiapirs the mature polydiapirs in the models exhibit spines curtain folds pendant repetitions of the source layers inside the large diapirs and anomalous interdiapiric distances all these features are known in natural salt diapirs suggesting that polydiapirs may be far more common in nature than hitherto recognized

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

violent silicate volcanism on io in 1996 we monitored io s volcanic thermal emission from 1 7 to 4 8 m in 1995 96 the data reveal a number of brightenings when io s thermal emission increased several fold we use a model of emission from lava flows to understand observations of two brightenings in 1996 the brightenings were caused by eruptions 3km in extent with eruptive rates of 104 106 m s 1 and with maximum lava temperatures 1400 k these events were probably lava lakes and or fire fountains

magmatic differentiation of io abstract if io has been volcanically active through much of its history it must be highly differentiated we present an initial attempt to quantify the differentiation of the silicate portion of io we suggest that on average each part of io has undergone about 400 episodes of partial melting we employ a widely used thermodynamic model of silicate melts to examine the effect of such repeated differentiation despite many caveats including a grossly oversimplistic model of the differentiation process uncertainties in the initial composition of the mantle and the failure to model more than four episodes of partial melting we are able to make some robust conclusions io should have a roughly 50 km thick low density 2600 2900 kg m 3 alkali rich siliceous crust composed primarily of feldspars and nepheline the crustal magmas should have relatively low melting temperatures

silicate volcanism on io io is currently emitting 1 1 5 w m 2 of tidal energy as a result of its volcanic activity if the lithosphere is more than 20 km thick as appears probable from the surface relief only a fraction of the tidal energy can be dissipated within the lithosphere otherwise it will become thinner the rest of the tidal energy must be dissipated below the lithosphere io is likely to be highly differentiated as a result of the volcanic activity with a low melting temperature fraction such as basalt near the surface and a high melting temperature fraction such as peridotite at depth if solidus temperatures are reached at depths shallower than the thickness of the basalt layer a partial melt zone will separate an all basalt lithosphere above from a peridotite mantle below and part of the tidal energy will be dissipated by viscous deformation within the melt zone most of the energy dissipated below the lithosphere will be transported upward through the lithosphere as silicate magma which is generated in quantities sufficient to resurface the satellite at a rate of a few tenths of a centimeter a year depending on the lithosphere thickness many of the characteristics of the ionian surface have been explained in terms of sulfur volcanism however most of the features observed can be as readily explained by silicate volcanism and silicates are more consistent with the apparent strength of the surface as implied by the relief simulations of basaltic eruptions indicate that the surface temperatures that would result from basaltic eruptions are similar to those measured by the voyager infrared interferometer spectrometer experiment the high rates of emission by the ionian hot spots imply eruption rates that are high compared with typical terrestrial eruptions an eruption rate of 4000 m3 s 1 may be required to explain loki which is currently emitting 1013 w although the near surface materials are mainly silicate they may contain several percent of volatile components rich in s na and k remobilization of these components by the ongoing silicate eruptions causes the plumes provides material to the torus and gives the satellite its characteristic reflectivity

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

subaerial salt extrusions in iran as analogues of ice sheets streams and glaciers abstract ice h20 and salt halite nacl share many physical properties and resemble each other in hand specimens and subaerial gravity driven flows however while most significant bodies of ice accumulate in cold highlands and gravity spread where and soon after they form most significant bodies of salt accumulate in tropical marine basins and have to be buried by 1 km of other rocks before they flow buried salt is driven by differential loading into various categories of piercing structures known as diapirs many diapirs extrude onto the surface as sheets of allochthonous out of place salt thousands of sheets of allochthonous salt have been interpreted in over 35 basins worldwide in the last 25 years mainly in the toes of passive continental margins and in orogenic belts where some are 103 km2 in area most former salt sheets are now submarine or subsurface but several active examples are beautifully exposed in iran these were compared to ice glaciers soon after they were introduced to western science a comparison that has been neglected since here we update this analogy and use modern understanding of flowing ice and salt to examine the similarities and differences that might be mutually beneficial to both fields of study as well as to extraterrestrial scientists the profiles internal structures and fabrics in flowing bodies of ice and salt are sensitive gauges of the histories of their budgets of supply and loss however whereas snow merely compacts where it accumulates salt sheets are fed from below by already deformed salt when salt diapirs first emerge on land they extrude domes that mature to the profiles of viscous fountains that often feed glacier like flows known as namakiers after locally exhausting their deep source layers salt fountains spread to the profiles of viscous droplets normal for ice caps ice typically deforms at 80 usually 90 of its absolute melting temperature while most salt deforms at

experimental modeling of role of gravity and lateral shortening in zagros mountain belt dynamically scaled analogs of the geologic structures of the zagros mountain belt are used to argue that different parts of the zagros mountains of iran record different combinations of the effects of a gravity driven overturn and a southwest northeast lateral shortening superimposed on the zagros overturn partially scaled material models have been used to simulate the zagros geodynamics which involve layer parallel compression of a 6 to 7 km thick phanerozoic carbonate cover containing a pattern of preshortening diapirs the folds in the zagros form rapidly 1 5 mm yr in a 20 to 30 km wide zone reactive some of the preshortening diapirs and generate new synshortening listric diapirs a third set of postshortening diapirs rises from the hormuz decollement behind the fold thrust front model buckle folds superimposed on diapirs or pillows tend to avoid and curve around preshortening diapirs which flatten in the synclines model profiles show that lateral shortening induces residual salt at depth to flow toward and rise through the anticlinal cores as synshortening or postshortening diapirs i suggest that any salt pillows in currently diapir free zones of the zagros fold thrust belt may surface as diapirs through the anticlines in the future in the absence of well data seismic and field observations i have used only three map pattern criteria to recognize the timing of diapirs these are locally obscured by extrusive salt sheets preshortening diapirs are generally small and elongate parallel to fold axes and are restricted to synclines synshortening diapirs are elongate perpendicular to the fold axes and are restricted to anticlines postshortening diapirs can be the same size as synshortening diapirs or larger and can be circular they are more common in the anticlines

formation of dome in dome structures results from experimental studies and comparison with natural examples abstract dome in dome structures are frequent in salt provinces and in high grade rocks of orogens their origin is only poorly understood in the present study we have modelled dome in dome structures which result from constrictional radial in plane shortening of a competent layer embedded in a rising less competent matrix both the layer and the matrix consist of non linear viscous plasticine which display a viscosity contrast of 5 the deforming competent layer is characterized by 1 a striking downward drag along the margins 2 a sample scale first order dome and 3 numerous second order domes and basins straddling the first order dome with increasing layer thickness and strain the amplitude a arc length l and wavelength of the second order domes and basins increase however their growth rate is significantly smaller than that of non rising domes and basins which result from a bidirectional flow this restricted growth of rising domes and basins is attributed to the simultaneous growth of the first order dome and explains why hair pin type folds typical for non rising domes and basins are lacking even at higher finite strain similar dome in dome structures like those produced in the present study have been described from deeper levels of salt and gneiss domes or from foliation triple points of interfering diapirs

a 500 year record of summer near ground solar radiation from tree ring stable carbon isotopes tree ring stable carbon isotope ratios d13c in environments of low moisture stress are likely to be controlled primarily by photosynthetic rate therefore sunshine rather than temperature represents the more direct controlling factor temperature reconstructions based on tree ring d13c results thus rest on the assumption that temperature and sunshine are strongly coupled this assumption is tested using a d13c series from pine trees in nw norway where there are long 100 yr records of both summer temperature and cloud cover it is demonstrated that when summer temperature and d13c diverge summer temperature and cloud cover also diverge and that cloud cover sunshine may provide a stronger and more consistent parameter with which to calibrate tree ring d13c series in this area when a 500 year reconstruction of summer cloudiness is compared with a published reconstruction of summer temperatures in northern sweden based on tree ring maximum densities the two time series are largely parallel with

high temperature silicate volcanism on jupiter s moon io infrared wavelength observations of io by the galileo spacecraft show that at least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on earth today in at least one case the eruption near pillan patera two independent instruments on galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin the most likely explanation is that these lavas are ultramafic magnesium rich silicates and this idea is supported by the tentative identification of magnesium rich orthopyroxene in lava flows associated with these high temperature hot spots

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

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

the shaping of salt diapirs abstract six parameters shape the geometry of passive diapirs associated with stiff overburden rates of salt supply s dissolution d sediment accumulation a erosion er extension e and shortening sh these parameters change in space and time and hence influence the geometry of the structure as it forms a complex six parameter plot representing the evolution history of a salt diapir can be simplified into three separate graphs this study recommends adding to plots of s against a a second of rate of salt supply s this time with extension rate e and a third of rate of sediment accumulation a plotted against extension rate e integrating these three plots on a single diagram results in a complete description of the evolution history of a diapir when it is applied to three dimensional data however if applied to a profile the plot shows only the two dimensional evolution history of the diapir lateral forces extension or compression have a significant role in moulding the geometry of a salt diapir by influencing the space which it occupies by incorporating extension in the moulding plots of salt diapirs this study introduces the rate of sediment accumulation multiplied by extension e a as a significant factor in moulding salt diapirs by using this rate against the rate of salt supply this study redefines the conventionally accepted interpretation of upward narrowing upward widening and columnar diapirs upward narrowing diapirs form when the rate of salt supply is less than the rate of sediment accumulation multiplied by extension upward widening diapirs form when the salt supply is greater than the rate of sediment accumulation multiplied by extension columnar diapirs form when the rate of salt supply is equal to the rate of sediment accumulation multiplied by extension this new relationship explains the absence of columnar and upward widening diapirs in passive margins where thin skinned extension dominates and emphasizes the significance of lateral movement extension and shortening in moulding the geometry of salt diapirs

numerical modelling of the displacement and deformation of embedded rock bodies during salt tectonics a case study from the south oman salt basin large rock inclusions are embedded in many salt bodies and these respond to the move ments of the salt in a variety of ways including displacement folding and fracturing one mode of salt tectonics is downbuilding whereby the top of a developing diapir remains in the same vertical position while the surrounding overburden sediments subside we investigate how the differential displacementofthe top saltsurface causedbydownbuilding inducesductilesaltflowand the associ ated deformation of brittle stringers by an iterative procedure to detect and simulate conditions for the onset of localization of deformation in a finite element model in combination with adaptive remeshing the model set up is constrained by observations from the south oman salt basin where large carbonate bodies encased in salt form substantial hydrocarbon plays the model shows that depending on the displacement of the top salt the stringers can break very soon after the onset of salt tectonics and can deform in different ways if extension along the inclusion dom inates stringersarebrokenbytensilefracturesandboudinageatrelativelyshallowdepth spacingof the boudin bounding faults can be as close as 3 4 times the thickness of the stringer in contrast salt shortening along the inclusion may lead to folding or thrusting of stringers

sinking of anhydrite blocks within a newtonian salt diapir modelling the influence of block aspect ratio and salt stratification summary 2 d finite differences models are used to analyse the strain produced by gravity driven sinking of dense rectangular inclusions through homogeneous and vertically stratified newtonian salt we systematically modelled the descent of dense blocks of different sizes and initial orientations aspect ratios representing the main anhydrite fragments documented within for example the gorleben salt diapir model results demonstrate that size of the blocks is a governing parameter which dictates the amount of strain produced within the block and in the surrounding host salt initial block orientation aspect ratio on the other hand causes fundamental differences in block deformation while the resulting structures produced in the salt are principally the same in all models with homogeneous salt covering shear zones and folding of passive markers in models with vertically stratified salt with different viscosities block descent takes place along complex paths this results from greater strain accommodation by the salt formation with the lowest viscosity and an asymmetrical distribution of initial vertical shear stresses around the block consequently in these models block strain is lower compared with the models with homogeneous salt for the same viscosity as the high viscosity salt and sinking is accompanied by block rotation the latter causes diapir scale disturbance of the pre sinking salt stratigraphy and complex sinking paths of the blocks in particular vertically oriented blocks sink into high viscosity salt and drag with them some low viscosity salt while horizontal blocks sink in the low viscosity salt the resultant sinking velocities vary strongly depending on the sinking path of the block based on model results and observed structural configuration within the gorleben salt diapir we conclude that the internal complexity of a salt diapir governs its post ascent deformation salt structure and its interaction with dense blocks should hence be considered in the assessment of the long term stability of storage sites for hazardous waste

impact of solid second phases on deformation mechanisms of naturally deformed salt rocks kuh e namak dashti iran and rheological stratification of the hormuz salt formation abstract viscosity contrasts displayed in flow structures of a mountain namakier kuh e namak dashti between weak second phase bearing rock salt and strong pure rock salt types are studied for deformation mechanisms using detailed quantitative microstructural study while the solid inclusions rich dirty rock salts contain disaggregated siltstone and dolomite interlayers clean salts reveal microscopic hematite and remnants of abundant fluid inclusions in non recrystallized cores of porphyroclasts although the flow in both the recrystallized dirty and clean salt types is accommodated by combined mechanisms of pressure solution creep ps grain boundary sliding gbs transgranular microcracking and dislocation creep accommodated grain boundary migration gbm their viscosity contrasts observed in the field outcrops are explained by 1 enhanced ductility of dirty salts due to increased diffusion rates along the solid inclusion halite contacts than along halite halite contacts and 2 slow rates of intergranular diffusion due to dissolved iron and inhibited dislocation creep due to hematite inclusions for clean salt types rheological contrasts inferred by microstructural analysis between both salt rock classes apply in general for the dirty salt forming lower hormuz and the clean salt forming the upper hormuz of the hormuz formation and imply strain rate gradients or decoupling along horizons of mobilized salt types of different composition and microstructure

paleomagnetic and inner diapiric structural constraints on the kinematic evolution of a salt wall the bicorb quesa and northern navarres salt wall segments case prebetic zone se iberia abstract paleomagnetism together with an analysis of the internal structure of the bicorb quesa and northern navarres salt wall segments prebetic zone in se iberia were used to constrain their kinematics and driving mechanisms paleomagnetic data from upper triassic red beds of the selected salt related structures and from the miocene rocks belonging to adjacent syn diapiric half grabens reveal 15 30 counter clockwise vertical axis rotations of the salt wall rocks and a 20 clockwise rotation of the jurassic miocene cover block located south of the salt wall this together with the salt wall structure indicates that the origin of the salt wall was linked to the motion of a late miocene thin skinned extensional fault system which detached on the upper triassic evaporites specifically the salt wall formed by the south southwest displacement with a 20 clockwise rotation component of a cover block bounded northwards by the detachment disruptions generated by the motion of pre existent basement faults the upper triassic detachment level was first affected by a counter clockwise vertical axis rotation and during the paleogene earliest miocene building of the iberian chain by tight wnw trending folds and sse directed minor thrusts this study also shows that paleomagnetism together with the analysis of the internal structure can successfully depict the geometry and kinematic evolution of complex salt wall structures