environmental and morphologic controls on wave induced dune response abstract the pacific northwest of the united states exhibits complex spatial patterns of storm induced coastal foredune erosion using oceanographic and morphologic data from three field sites encompassing a range of subaqueous and subaerial coastal profile configurations a relationship is found between morphologic characteristics and dune volume changes during storm events producing high water levels the data suggest that dune erosion increases with increasing backshore beach slope and that under particular oceanographic forcing conditions wave driven processes can grow the lower portion of dunes on low sloping dissipative beaches these observations of environmental and morphologic controls on storm induced dune impacts are further explored using xbeach a state of the art numerical model capable of simulating interactions between hydrodynamics and morphology consistent with the field data model simulations indicate that wave driven dune growth may occur on low sloping beaches in cases where the dynamic still water level still water level plus wave setup is lower than the dune toe however these accretional processes are restricted to events where limited incident wave energy impacts the dune cases with steep backshore beach slopes or dynamic still water levels exceeding the dune toe instead typically result in dune erosion additionally the model simulations suggest that morphologic properties of the shelf nearshore and the dune itself influence storm induced dune volume change therefore morphologic features far from the dune face including shelf geometries shaped in part by the regional historical sediment budget may have important implications on the susceptibility of coastal foredunes systems to storm impacts

from oblique arc continent collision to orthogonal plate subduction in the southeastern central asia orogenic belt during paleozoic evidence from superimposed folds at the northern margin of the north china craton abstract accretionary kinematic history of the central asia orogenic belt caob remains unclear in previous geological studies based on detailed structural analysis of newly identified folds on the northern margin of the north china craton ncc we propose a tectonic model suggesting that paleozoic accretion of the orogenic belt includes two phases of deformation the first phase of deformation is oblique collision of the bainaimiao arc and the ncc which was followed by orthogonal subduction of the paleo asian ocean in the second phase of deformation the change of plate kinematics is supported by two generations of folding namely d1 db and d2 da both d1 db and d2 da folds developed in the bayan obo group bog a meso and neoproterozoic rift sequence deposited on the passive continental margin of the ncc d1 db folds were superimposed by the east west trending d2 da folds the d1 db folds developed as a result of oblique collision of the bainaimiao arc and the ncc the d2 da folds developed in response to the southward orthogonal subduction of the paleo asian ocean plate they formed between latest silurian and early permian coeval with the two accretion events at the northern edge of the ncc our study suggests that multiphase deformation of sedimentary layers on the subducting plates provide important constraints for kinematic evolution of plate tectonics

laboratory investigation of dune erosion using stereo video abstract simple parameterizations of dune erosion are necessary for forecasting erosion potential prior to an oncoming storm dune erosion may be parameterized in terms of the elevation of the total water level composed of surge tide and wave runup above the dune base and period of exposure of the dune to waves in this work we test several versions of this model using observations from a large wave tank experiment designed to model a storm hydrograph and we develop a new method for acquiring the appropriate data with confidence intervals using stereo video techniques the stereo method results in observations of dune morphology at higher spatial and temporal resolutions than traditional survey methods allow resolution of the stereo technique was 0 1 m in the horizontal and 0 04 m in the vertical and errors in stereo observations were on the order of 0 02 to 0 08 m 1 to 2 pixels when compared with surveys a new method was developed to estimate confidence intervals on stereo observations when the unchanging dune top was repeatedly sampled the new confidence intervals encompassed 2 standard deviations of scatter about the mean dune surface 98 of the time observations from the stereo method were used to quantify wave runup and dune erosion we tested a variety of runup statistics based on a gaussian distribution of swash properties and found that the most predictive statistic for dune erosion was the 16 exceedance elevation above the dune base lower than the often used 2 exceedance value we found that the parameterization of runup was sensitive to the definition of beach slope and that the most accurate beach slope for predicting runup was through the region of the beach profile defined by the mean water level plus one standard deviation of swash the dune base retreated along a relatively constant trajectory that was a half of the initial beach slope finally a simple model for dune erosion was tested and found to reproduce 64 of the observed variance in dune erosion rate given known forcing at the dune and 49 of the observed variance in dune erosion rate given parameterized forcing integrating the simple model over time 93 of the observed dune retreat distance was reproduced given offshore forcing

glendonites and methane derived mg calcites in the sea of okhotsk eastern siberia implications of a venting related ikaite glendonite formation mg calcite cemented bioturbation traces glendonite aggregates of idiomorphic bi pyramidal crystals and porous amber colored carbonate concretions were recovered from a methane dominated cold vent area in 380 m water depth at the northern sakhalin slope sea of okhotsk bioturbation traces consist of mg calcite cemented sediment with 13c values between 37 and 46 peedee belemnite pdb which implicate methane as the carbon source glendonite a calcite pseudomorphosis after ikaite caco3 6h2o and amber colored concretions are both composed of varying amounts of calcite and mg calcite with 13c values between 19 and 34 pdb isotope analyses of an ikaite crystal recovered in the vicinity reveals 13c values between 20 and 22 pdb indicating organic matter as the carbon source microscopic investigations of glendonites and amber colored concretions show a porous fabric of a primary calcite phase that is overgrown by a secondary mg calcite cement as ikaite pseudomorphs to porous calcite and as carbon isotope values are the same for the ikaite and the high end member values of glendonite samples the primary calcite phase is suggested to be a former ikaite phase because they share the equal color fabric mineral and isotopic composition with glendonites the amber colored concretions are also suggested to represent calcite that transformed from ikaite a mixture of pseudomorph calcite 13c 20 pdb which originally formed as ikaite from degraded organic matter and mg calcite 13c 43 pdb which crystallized due to the anaerobic oxidation of methane can explain the varying carbon isotope data of the glendonites and the amber colored concretions the growth of ikaite the transformation of ikaite to calcite and the crystallization of mg calcite indicate changing geochemical conditions within a cold vent environment at different times ideal conditions for the ikaite formation are given during the establishment of a cold vent site when upward migrating methane rich fluids enhance the anaerobe decomposition of organic matter which again increases the phosphate and alkalinity concentrations near the sediment surface lower rates of organic matter decomposition during on going venting decrease these high phosphate but also sulphate concentrations and allows other carbonate phases as mg calcite to form this additional carbonate precipitation and the ikaite formation itself lower the high alkalinity and destabilize ikaite which pseudomorphs to porous calcite triggered by the further upward shifting so4 h2s boundary and increasing methane oxidation rates the typical cold vent methane derived carbonate genesis takes place which cements the sediment pore space and induces the secondary mg calcite crystallization within the glendonite fabric taking this scenario into account ikaite formation should be a common process in the beginning of methane dominated vent activity at cold bottom water temperatures glendonite pseudomorphs can be assumed to represent a typical manifestation at fossil and recent cold vents at high latitudes

detachment folding fold amplification and diapirism in thrust wedge experiments 1 the relations between detachment folding fold amplification and salt diapirism in contractional settings have been investigated by means of scaled analogue models the viscosity of the silicone layer simulating salt in nature and the shortening rates were combined in order to reproduce weak type 1 models and strong type 2 models decollements deformation patterns in the roof sequence exhibited two contrasting styles 1 outward propagation of detachment folding along the decollement ofp mode and 2 passive roof duplex prd mode in type 2 models detachment folding propagated away from the most external thrust in the floor sequence while in type 1 models long lived detachment folds almost invariably localized amplified above a floor thrust tip as a result of strain localization a silicone wall intruded occasionally into the crestal graben of detachment folds in type 1 and ofp models best fitting of transition models data points indicates nonlinear relations with regression curves close to the equilateral hyperbola equation for both ofp prd and amplified detachment folds box folds transitions a quantitative comparison of model results with nature has been attempted by plotting salt based fold and thrust belts data points on the scaled transition curves obtained from the modeling such a comparison relates shear stress products and ratios to the conditions favoring the amplification of detachment folds and the potential emplacement of ductile diapirs in their core by reducing the roof sequence strength pore fluid pressure b is inferred to shift the equilibrium of fold and thrust belts toward the field of ofp and diapirism

reinforcement of vegetated and unvegetated dunes by a rocky core a viable alternative for dissipating waves and providing protection abstract coastal dunes can provide protection from flooding during extreme weather events as such consideration should be given to strengthening the protective mechanisms of dunes vegetation has recently been seen as an important factor influencing erosion processes on dunes another means of dune reinforcement is the installation of internal structures within dune systems the purpose of this work is to investigate the potential utility of both vegetation and an internal rocky structure as reinforcing factors on dunes and explain how they differentially dissipate wave energy and influence the morphodynamic response of the dune profile this work consists of a series of experiments on dune profiles with and without an inner rocky structure and with two different distributions of live ipomoea pes caprae plants of the same density under storm conditions the results showed that when vegetation was at forward positions on the dune it decreased run up increased reflected energy and transferred it to low frequency bands and reduced the eroded volume on the exposed dune face when the vegetation was placed on the leeside of the dune it retarded and prevented overwash but not as efficiently as the internal rocky structure did in summary plants are better to dissipate waves and provide protection during the initial swash and collision stages of a storm while a rock structure is better to prevent overwash and dune destruction during the final stages while it is possible to use both means together for maximum protection dune managers should weigh the financial and ecological costs according to each unique project location

prediction of dune erosion due to storms abstract this paper presents results of experimental and mathematical modelling of beach and dune erosion under storm events re analysis of the experimental results on dune erosion in small scale and large scale flumes shows that the dune erosion for extreme conditions is somewhat smaller than that based on earlier analysis results dune erosion caused by wave impact has been modelled by a cross shore profile model crosmor model which is based on a wave by wave modelling approach solving the wave energy equation for each individual wave the model has been applied to the recent deltaflume experiments on dune erosion the three main processes affecting dune erosion have been taken into account the generation of low frequency effects the production of extra turbulence due to wave breaking and wave collision and the sliding of the dune face due to wave impact the calibrated model can very well simulate the observed dune erosion above the storm surge level during storm events in small scale facilities large scale facilities and in the protoype 1953 storm in the netherlands using the same model settings the mathematical model results have been used to develop a new simplified dune erosion rule

observations and modeling of alongshore variability in dune erosion at egmond aan zee the netherlands abstract dunes can erode within a few hours when exposed to high storm surge levels and large waves if the dunes are the primary defense such as in the netherlands this could result in flooding of the hinterland when dunes breach models are often used to analyze how dunes will respond to extreme conditions but they can also be applied to study milder events and with that gain more insight in the processes of dune erosion there is however growing demand for validating existing models under field conditions here we calibrate the xbeach dune erosion model with pre and post storm topography measurements of the dune erosion event in january 2012 at egmond aan zee the netherlands furthermore hydrodynamical data of the intertidal zone along a cross shore transect in the same area collected 3 months prior to the storm event are used to hydrodynamically calibrate and validate xbeach during the january 2012 storm the dune erosion was variable alongshore from the erosion of embryo dunes the forming of a dune scarp to considerable slumping of the entire dune face this caused the erosion volume v to range from 5 to 40 m3 m the calibrated model reproduces the alongshore variability in v with reasonable accuracy additional simulations show that the alongshore variation in v is due to variability on the initial dune topography primarily steepness and that variability in beach and nearshore bathymetry was of secondary importance

evaluation of xbeach performance for the erosion of a laboratory sand dune abstract a new set of laboratory data is used to investigate the bathymetry change of a steep sand dune exposed to waves and high water levels and subsequently compared to the results of numerical simulations using xbeach bichromatic wave boundary conditions are used to simulate a combined short wave and long wave field for two water level elevations corresponding to collision with the dune face and overwashing of the dune crest in the collision regime case episodic slumping due to the undercutting of the dune results in sudden erosional events followed by long periods of wave driven reshaping at the dune toe in the overwash regime case morphological changes are faster and sediment transport rates are higher the xbeach model was used to simulate wave driven erosion of the dune at the two water levels observed in the laboratory the model was not able to precisely recreate the cross shore spatial variability of significant wave height observed in the experiments however near bed wave orbital and mean current velocities were in good agreement with observations following rapid initial adjustment the model results were in agreement with measured dune morphology at successive times xbeach was sensitive to several parameters that control the rate of erosion including the critical avalanching slope under water the threshold water depth and the sediment transport formulation and performed well after careful selection of the best combination of these parameters overall the model predictions were in better agreement with laboratory observations for dune erosion in the overwash regime case than the collision regime case

numerical modelling of erosion and accretion of plane sloping beaches at different scales article i nfo available online 5 february 2011 the paper focuses on the numerical simulation of erosion of plane sloping beaches by irregular wave attack in three wave flumesof differentscales one of the prime objectives of the testswas to provide a consistent data set for the improvement of numerical beach profile models a practical application of this research with waveattack on plane sloping beaches is the erosion of the plane beaches after nourishment three models crosmor unibest tc and delft3d have been used to simulate the flume experimental results focusing on the wave height distribution and the morphological development erosion and deposition along the beach profiles overall the model predictions for wave heights show consistent results generally the computed wave heights hrms and h1 3 are within 10 to 15 of the measured values for all tests under prediction of the largest wave heights close to the shore the three models can simulate the beach erosion of the wave flume tests erosive tests reasonably well using default values of the sand transport parameters the model performance for the accretivetestsislessgoodthanthatfortheerosivetests apractical fieldapplicationofthisresearchistheerosion of nourished beaches asthese beaches generally have rather planebeach slopesimmediately after nourishment various graphs are given to estimate the beach erosion of nourished beaches

characteristics and deformation mechanism of salt related structures in the western kuqa depression tarim basin insights from scaled sandbox modeling abstract three scaled analog sandbox models are constructed to simulate the evolution of thick skinned shortening on broad and narrow salt basins these models simulate the evolution of the cenozoic salt salt related structures in the westernmost kuqa salt bearing depression quele area tarim basin the formation mechanism and the controlling factors of structural deformation in this area are investigated and discussed systematically model results show that the variable depositional width of the salt basin has a major controlling influence on the differential structural deformation in different longitudinal segmentations from east broad to west narrow in the western kuqa depression quele area model results also demonstrate that the early salt structure salt diapir has an important controlling role on the subsequent compressional structural deformation the pre existing thin overburden quele diapir which acts as a stress concentration zone during the subsequent shortening is deformed to the quele salt nappe on the basis of the model results it is suggested that the formation of the long distance quele allochthonous salt sheet is related with the pre existing quele diapir which displaces up paralleling the hanging wall and flows to the surface during the subsequent shortening

beach and dune erosion during storm surges this paper presents the set up and results of an extensive research programme concerning the erosion of coastal dunes during storm surges a large number of two dimensional and three dimensional mobile bed model tests has been carried out to investigate the process of dune erosion the state of art after a series of small scale tests is summarized attention is focussed on large scale tests carried out in the delta flume with random waves up to 2 m significant height sediment concentration and orbital velocity measurements are discussed the large scale tests have confirmed the validity of a modelling technique based on the dimensionless fall velocity parameter h tw the model results are being applied to check the safety of existing coastal dunes as a water retaining structure that has to protect the major part of the netherlands from inundation during storm surges

triassic early liassic extensional systems and their tertiary inversion essaouira basin morocco abstract nne ssw striking late triassic early liassic half grabens of the essaouira basin and the adjacent high atlas are linked by roughly ew striking transfer faults they are overlain by a wide considerably less faulted evaporitic sag basin and extensive basalt flows a pre pliensbachian unconformity truncates the triassic early liassic sequences on the e and ne margin of the basin and is overlain by a mid liassic to cretaceous platform sequence in the cap sim necnafa depression jurassic and early cretaceous salt tectonics caused widespread salt withdrawal structures tertiary nnw to sse compression caused the inversion of ne and nne striking structures and or the formation of salt anticlines the same compression formed ew striking reverse faults and anticlines suggesting the reactivation of late triassic early liassic transfer faults

triassic evaporites and plio quaternary diapirism in western greece wide triassic evaporite outcrops run parallel to the strike of hellenide thrust faults in western greece they crop out along the leading edges of thrust sheets emplaced as part of the foreland migrating fold and thrust belt the evaporites acted as the plane of decollement for thrust sheet emplacement over much of the external hellenides plio quaternary diapirs occur locally within the broad outcrops of triassic evaporite they are the result of local mobilization of evaporite after its emplacement their rise may have been initially triggered by hellenide thrust sheet loading and subsequently accentuated by plio quaternary subsidence geophysical records and onland exposures show that diapiric rise controlled local sedimentation patterns above the sites of earlier hellenide thrusts the subsequent intrusion of diapirs into these cover sediments caused localized extensional structures to develop this is best seen in se zakinthos where strain hardened conjugate faults developed in friable pliocene sandstones early in the intrusion history principal strains calculated from these sets demonstrate patterns of extension sub orthogonal to intrusion margins they are comparable with patterns known from other field and experimental examples but contrast with some recent studies on diapir related strains

polyphase deformation of diapiric areas in models and in the eastern prebetics spain fingerlike bodies of evaporite rocks have been observed in many regions affected by multiple tectonic phases such as the atlas the pyrenees or the zagros mountains where they have been interpreted as fault plane diapiric injections or collapse related salt welds in this article we suggest a new interpretation of these structures as squeezed diapirs based on detailed structural and sedimentological field data of the bicorb quesa diapir eastern prebetics and offer five analog models which simulate the polyphase deformation of the eastern prebetics in this area diapirs formed from the oligocene to langhian during an extensional phase related to the opening of the valencia trough these diapirs were later affected by a serravallian contractional phase which inverted the preexisting grabens and created new folds and thrusts the preexisting diapirs were necked and or squeezed forming secondary welds with a fingerlike geometry that isolated the diapir bulbs from their source layer extrusion of diapiric material was also accelerated during this phase but no new diapirs formed finally the area was again affected by an extensional phase during the tortonian which reactivated the normal faults and created a new set of diapirs the new diapirs formed where the overburden was thinner that is at the toe of the major reactivated faults commonly these faults coincide with the bounding faults of the major grabens formed during the first extensional phase and therefore the new diapirs grow close to the location of the squeezed diapirs the models also show that the faults created during the initial extension prevailed as the main focus for deformation during the polyphase history deformation in the overburden and the viscous layer was mainly accommodated along the major grabens formed during the first extensional stage during shortening the initial major grabens deformed as complex anticlines and during the subsequent extensional phase most deformation occurred by the collapse of these anticlines along preexisting faults fault welds and the flank of the squeezed diapirs the source layer is compartmentalized accumulating and withdrawing material in the same locations the initial grabens and horst as a result the source layer is easily depleted beneath the initial horst forming primary welds

a three dimensional laboratory investigation of beach morphology change during a storm event abstract this study provides laboratory observations of the nearshore hydrodynamics and detailed topographic surveys associated with the morphological response of a beach dune system to oblique waves during a storm event a physical model consisting of a 20 m long sandy steep beach constructed in a wave basin and a wave paddle oriented obliquely to the beach shoreline is used to generate irregular waves at the offshore boundary in the experiment the wave height is varied over time in five segments to simulate the change in the energy from a passing storm and is varied alongshore to initiate an alongshore gradient in waves and wave driven currents to simulate a constant storm surge a high mean water level relative to the dune is used enabling waves to reach the dune toe the results indicate the formation and evolution of a beach scarp the retreat of the scarp initially corresponds to time varying wave energy but becomes controlled by the changing nearshore beach slope over time the alongshore current magnitude is governed by the spatio temporal variability in wave energy and is the main driver of sediment flux the sand that is eroded from the dune initially deposits at the dune toe when nearshore circulation is weak however as the wave energy increases sediment is transported along the beach and is deposited increasing the surf zone width the experimental results indicate that small waves at high water levels relative to the dune can drive the formation of a beach scarp in addition different levels of incident wave energy drive different rates of sediment transport and morphological evolution with high alongshore variability throughout a storm event

testing model parameters for wave induced dune erosion using observations from hurricane sandy models of dune erosion depend on a set of assumptions that dictate the predicted evolution of dunes throughout the duration of a storm lidar observations made before and after hurricane sandy at over 800 profiles with diverse dune elevations widths and volumes are used to quantify specific dune erosion model parameters including the dune face slope which controls dune avalanching and the trajectory of the dune toe which controls dune migration wave impact models of dune erosion assume a vertical dune face and erosion of the dune toe along the foreshore beach slope observations presented here show that these assumptions are not always valid and require additional testing if these models are to be used to predict coastal vulnerability for decision making purposes observed dune face slopes steepened by 43 yet did not become vertical faces and only 50 of the dunes evolved along a trajectory similar to the foreshore beach slope observations also indicate that dune crests were lowered during dune erosion moreover analysis showed a correspondence between dune lowering and narrower beaches smaller dune volumes and or longer wave impact

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

rise closure and reactivation of the bicorb quesa evaporite diapir eastern prebetics spain the bicorb quesa diapir belongs to a complex system of evaporite diapirs located in the se iberian peninsula it was emplaced along the axis of a graben system flanked by two syn diapir growth basins filled by miocene sediments the miocene evolution of the diapir may be divided into three major phases an initial extensional phase during which the graben system formed and the diapir rose a second phase during which regional shortening closed the diapir and a third phase characterized by normal faulting during which diapirism was reactivated cutting the previously formed thrusts and folds this evolutionary trend demonstrates that diapirism was initiated and promoted by regional extension during the two extensional phases the diapir grew by reactive active and passive rise sedimentation during the reactive stage was characterized by strong basin subsidence sharp changes in sediment thicknesses and major coarse grained sediment input during the active stage the coeval basin fill sequence displays progressive angular unconformities gravitational deposits and subtle changes in thickness with the sediments unconformably overlying most of the earlier formed faults finally during the passive stage the sediments synchronous with diapir formation include abundant components from the extruding rocks and show gentler changes in thicknesses a progressive decrease in the input of coarse sediments and the deposition of mudstones and or lacustrine carbonates that clearly extend onto the faulted basin margins

3 d visualization and isochore analysis of extensional diapirs overprinted by compression palinspastic restorations elucidate geologic and hydrocarbon migration histories in salt provinces however salt dissolution and salt flow in and out of the section plane make it difficult to determine the shape of salt bodies before deformation which hampers accurate restorations three dimensional computer visualization of a physical model and analysis of isochores provide clues to the original shape of allochthonous salt bodies that were emplaced during extension and later compressed

style and timing of salt tectonics in the dniepr donets basin ukraine implications for triggering and driving mechanisms of salt movement in sedimentary basins abstract the ukrainian dniepr donets basin ddb is a late palaeozoic intracratonic rift basin with sedimentary thicknesses up to 19 km displaying the effects of salt tectonics during its entire history of formation from late devonian rifting to the tertiary hundreds of concordant and discordant salt structures formed during this time it is demonstrated in this paper that the variety of styles of salt structure formation in the ddb provide important constraints on understanding the triggering and driving mechanisms of salt kinematics in sedimentary basins in general salt movement in the ddb began during the devonian syn rift phase of basin development and exerted controls on the later distribution of salt structures though the geometry of basement faults is not directly responsible for the regular spacing of salt structures post rift salt movements in the ddb occurred episodically episodes of salt movement were triggered by tectonic events specifically two extensional events during the carboniferous an extensional reactivation at the end of carboniferous earliest permian and a compressional event at the end of the cretaceous extensional events that induced salt movement were thick skinned i e basement involved in deformation rather than thin skinned most overburden deformation related to salt movements is ductile regardless of sedimentary bulk lithology and degree of diagenesis while the deformation of sedimentary cover in areas where salt is absent is mainly brittle this implies that the presence of salt changes the predominant mode of deformation of overlying sedimentary rocks episodes of salt movement lasted longer than the periods of active tectonics that initiated them buoyancy erosion and differential loading all played a role in driving halokinesis once tectonic forces had pushed the salt overburden system into disequilibrium among these factors erosion of overburden above growing salt structures acted as a key self renewing force for development of salt diapirs very high sedimentation rates related to high post rift tectonic subsidence rates particularly during the carboniferous were able to bury diapirs and to load salt bodies such that buoyancy erosion and differential loading forces eventually became insufficient to continue driving diapirism until the system was perturbed by an ensuing tectonic event in contrast some salt anticlines and diapirs developed continuously during the entire mesozoic because of much reduced tectonic subsidence rates and sedimentation supply during this time however a lower permian salt series and overhangs of buried diapirs played an important role in preventing overburden piercing and fracturing during the mesozoic and specifically during the late cretaceous salt diapirism phase

two dimensional time dependent hurricane overwash and erosion modeling at santa rosa island abstract a 2dh numerical model which is capable of computing nearshore circulation and morphodynamics including dune erosion breaching and overwash is used to simulate overwash caused by hurricane ivan 2004 on a barrier island the model is forced using parametric wave and surge time series based on field data and large scale numerical model results the model predicted beach face and dune erosion reasonably well as well as the development of washover fans furthermore the model demonstrated considerable quantitative skill upwards of 66 of variance explained maximum bias 0 21 m in hindcasting the post storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied the prediction skill ranged between 0 66 and 0 77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied the sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay the model sensitivity to the sheet flow sediment transport limiter which served as a proxy for unknown factors controlling the resistance to erosion was significantly greater than the sensitivity to the hydraulic forcing parameters if no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response

spatial and temporal evaluation of storm induced erosion modelling based on a two dimensional field case including an artificial unvegetated research dune abstract the objective of this study was to evaluate the temporal and spatial performance of the xbeach model predicting storm surge induced erosion and breaching on the basis of a two dimensional field case within the scope of a physical experiment a large scale artificial unvegetated research dune was built at the german baltic sea coastline and surveyed before during and after a surge event to generate high resolution digital elevation models of the temporal and spatial failure process the measured data was used to set up and calibrate two dimensional xbeach models the numerical results showed that the default settings of the latest xbeach x release led to a very good agreement bss 0 82 between the simulated and measured post storm bed levels in the area of the research dune while a higher agreement was observed on the overwash and inundation dominant eastern side than on the collision dominant western side evaluating the model accuracy during the storm surge using 44 digital elevation models of the seaside slope showed a spatially accurate prediction of the two observed breaches 5 m but also the occurrence of additional breaches with respect to timing and breach width evolution however the results highly deviated from the observation and were found to be very sensitive to changes in grid resolution and to changes of default parameters exchanging the nearshore bathymetry with measurements one and two months prior to the physical experiment where a 49 and 51 lower subaerial beach volume was observed resulted in a significantly overestimated dune erosion 31 and 33 and hence in a lower accuracy of the default model bss 0 69 overall the xbeach model is capable of accurately predicting the evolution of storm induced erosion during a sufficiently long and overwash inundation dominant surge event when current high resolution input data is available

attributes and evolution of an exhumed salt weld la popa basin northeastern mexico an elongate arcuate structure consisting of a fault like displacement surface previously regarded as a reverse fault and parallel synclines within the late cretaceous eocene la popa basin of northeastern mexico are herein reinterpreted as a salt weld and its flanking withdrawal synclines the structure resulted from hanging wall subsidence during evacuation of salt along a formerly diapiric salt wall the la popa weld has an exposed length of 25 km and superficially resembles a growth fault the displacement surface is convex to the southwest and dips south to southwest stratigraphic displacement at the surface is zero at either end and increases to 5 km halfway along the trace of the structure the la popa structure had a two phase history 1 a diapiric phase marked by rise of an elongate salt wall flanked by parallel withdrawal synclines and 2 a subsequent evacuation phase recorded by hanging wall subsidence and stratigraphic welding of footwall and hanging wall as salt evacuated from the former diapir during diapirism thick siliciclastic strata accumulated in the salt withdrawal synclines that formed by downbuilding adjacent to the rising salt wall siliciclastic units thinned toward the salt wall near which they were upturned and developed numerous angular unconformities thick biohermal carbonate lentils accumulated episodically on topographic highs associated with the rising salt wall evacuation of the salt wall caused lateral migration of the hanging wall synclinal hinge and a consequent shift of thickest synkinematic strata toward the developing weld this is the first exposed example of a secondary salt weld described as such in the literature

field experiments of beach scarp erosion during oblique wave stormy conditions normandy france abstract a field based experimental study of beach scarp morphodynamic evolution was conducted on the shoreface of a macrotidal sandy beach subject to storms combined with spring tide events luc sur mer france both video and in situ measurements on an artificial berm are used to understand beach scarp evolution over one tide during stormy conditions image time stacks are used to analyze the swash action on the beach scarp and topographical data of the scarp are recorded with a terrestrial scanner laser to quantify the morphodynamic response of the beach scarp to wave action this work provides a new and unique dataset about beach scarp changes and berm morphology in particular under rising tide and oblique wind wave conditions during one stormy event the berm was completely destroyed however contrasting alongshore changes were measured during the erosive phase with different crest and foot scarp retreats and eroded volumes between the west and the east side of the berm the beach in front of the scarp also shows a contrasting residual evolution indicating an evident longshore sediment transport on the study area as a consequence of incident oblique wave conditions a strong connection between beach evolution and beach scarp changes is clearly identified the scarp erosion increases on the west side of the berm when the beach level is lowered and reduces when the beach surface rises on the east side the beach slope and foreshore elevation as a result of a longshore sediment transport between east and west profiles influence swash activity overall water depth and swash activity became progressively different along the scarp during the experiment swash measurements indicate that the presence of the beach scarp strongly influences the swash motion at high tide the reflection of the uprush on the scarp front induces a collision between the reflected backwash and the following uprush dynamic these collisions reduce and sometimes stop the motion of the following uprush reducing the incoming swash excursion consequently the scarp presence modifies the swash interaction that normally appears on a planar beach surface with a beach scarp the swash energy level is substantially attenuated and its spectrum is characterized by a large band the number of uprush impacts on the scarp front calculated from video images reaches about 25 per 5 min in spite of the swash energy attenuation due to swash swash interactions these impacts provoke the berm destruction in about two hours however the onshore migration of the swash zone induced by the rising tide appears to be important to explain scarp destruction compensating the attenuated swash activity due to backwash uprush interactions

inversion of the broad fourteens basin offshore netherlands a small scale model investigation abstract the southern north sea exhibits spectacular examples of graben inversion which have been extensively documented by oil industry exploration the broad fourteens basin which is located at the southern limit of the southern permian salt basin displays numerous structural patterns of positive inversion which are related to the inversion which are related to the presence and thickness of zechstein salts in the northern part of the broad fourteens basin the zechstein salt is rather thick 500 m allowing decollement of the mesozoic series during both extension and compression salt is missing to the southern part of this graben and both mesozoic series and palaeozoic basement display similar patterns of deformatiqn the mechanical significance of inversion patterns was investigated through laboratory experiments on brittleductile models models were built with sand and silicone putty that represent respectively the frictional behaviour of the mesozoic cover as well as the palaeozoic basement and the viscous behaviour of a decollement layer mainly composed of zechstein salts which is intercalated between them the models were scaled to fit natural configurations observed in the broad fourteens basin all small scale experiments were carried out in two steps 1 graben formation with synkinematic sedimentation and 2 compression at various angles of obliquity to the graben experimental results show that the structures generated by or reactivated during inversion are strongly dependent on a the strength of the decollement layer which is a function of the layer thickness and of the displacement velocity applied at the model boundaries and b the strength of the sedimentary overburden which is a function only of its thickness for a given lithology reactivation of normal faults occurs when the angle between the compression and the direction of the normal faults is smaller than 45 the ductile layer which can be a source for diapirs during extension plays during compression an important ro1e in the thrusting of the graben fill onto the adjacent platforms

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

experimental insights on the geometry and kinematics of fold and thrust belts above weak viscous evaporitic decollement abstract this paper discusses the differences in mechanical properties and kinematics between fold and thrust belts detaching on evaporitic decollements and those detaching on stronger detachments physical experiments are described that model shortening of a thick brittle cover overlying a weak viscous decollement to gain a better understanding of these differences we tested the influence of 1 the decollement layer thickness and 2 the presence of a deformable backstop on the hinterland side and of a decollement pinch out on the foreland side because of the very low shear strength of the viscous decollement folds and thrusts did not propagate according to a piggy back sequence but by centripetal back and forth propagation additional shortening was accommodated by growth of all existing structures fold symmetry and thrust vergence varied between experiments models confined between two rigid vertical endwalls always deformed by symmetric folding and thrusting in models having a deformable backstop and a foreland decollement pinch out forethrusting initially dominated folds were asymmetric and fault blocks rotated in models having a thick decollement layer folds kept growing asymmetrically diapirism also depended on the initial decollement geometry diapirs formed only in models having a deformable backstop and were restricted to the hanging wall of a fault related fold finally the implications of such kinematics on the thermal history are discussed as well as the likelihood of hydrocarbon maturation and preservation

crescent like large scale structures in the external zones of the western gibraltar arc betic rif orogenic wedge the external wedge of the gibraltar arc orogenic system western mediterranean is a natural case of a fold and thrust salient although at the scale of the arc a swing of the structural trend can be observed the presence of closed crescent like structures some of them more than 25 km long and scattered over an area of 3500 km 2 characterize the gibraltar arc external wedge this feature makes it very different from a classical arc shaped fold and thrust belt detailed structural maps of representative crescent like structures are presented synorogenic sediments reveal that they probably formed during a short time interval most probably during a single shortening event the crescent like structures are localized in front of a recess formed by the internal zones that acted as backstop this backstop shape and a viscous substrate essentially triassic evaporites below the fold and thrust external wedge constrain the experimental setting of an analogue model in which we were able to reproduce structures that developed originally with a highly non cylindrical shape during a single straight convergence moreover the tectonic transport directions along the thrusts are broadly comparable in the natural case and the model

the influence of preexisting structure and halokinesis on organic matter preservation and thrust system evolution in the ionian basin northwest greece the opening of the ionian basin and its internal differentiation is attested to by lateral facies and thickness variations of the formations deposited during the pliensbachian and tithonian synrift formations the beginning of the synrift sequence is represented by the siniais limestones pliensbachian and their lateral equivalent the louros limestones the geometric characteristics of the extensional basin depend on both extension related to the latest opening of the tethys ocean and halokinesis of the ionian zone evaporitic substratum the orientation of the extensional regime is deduced from the direction of stratigraphic pinch outs of the synrift formations directions of transport of slump features and direction of movement on synsedimentary faults observed in t e base of these formations in the half grabens the postrift period is marked by an unconformity at the base of the vigla limestones which represents the early berriasian breakup during which sedimentation was synchronous in the entire ionian basin the accumulation of organic matter in the lower and upper posidonia beds of the ionian zone during the toarcian and tithonian is directly related to the geometry of the synrift period of the ionian basin restricted subbasins were formed where the geometry of the basin favored stagnation and consequently the locally euxinic conditions of bottom waters anoxic conditions persisted locally to the postrift period in areas where the upper siliceous zone albian cenomanian of the vigla limestones is well developed these areas probably represent subbasins that were preserved by the continuation of halokinetic movements during the postrift period during the early miocene alpine orogeny collision related compressive stresses on the margin induced the reactivation of preexisting fractures which were responsible for the inversion tectonics that affected the mesozoic basin the geometric characteristics of the inverted basin were dependent on lithology evaporites geometry of the extensional structures and direction of the compressional phase the observed geometries do not always correspond to the classical scheme of inversion tectonics the geological evolution in the ionian basin is an example of inversion tectonics of a basin with an evaporitic substratum the opening of the ionian basin and the inversion tectonics influence both the source rocks and the probable hydrocarbon traps of the ionian zone

lacustrine sedimentation in the diapir controlled miocene bicorb basin eastern spain abstract the miocene bicorb basin is a small elongated basin developed by normal faulting of a thick jurassic cretaceous carbonate succession and subsequent diapirism of upper triassic mudstones and evaporites the basin fill comprises a sequence over 650 m thick formed by two units the lower alluvial unit consists of a complex alternation of conglomerates sandstones mudstones and minor lacustrine limestones the upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished the inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits at the northeast and southwest basin edges alluvial inputs led to the development of delta and fan delta environments where sandstone and conglomerate deposits dominate the latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the nw fault bounded margin pass laterally to breccias the hierarchical arrangement of the upper unit shows five different orders of sequences the first order sequence defines a major vertical trend of lake expansion whereas three second order sequences are linked to major flooding expansion episodes all these sequences are related to the tectonic evolution of the diapir metre scale third and fourth order sequences and fifth order sequences which consist of finely laminated rhythmite deposits probably record climatically forced processes the diapir graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system both factors have also strongly influenced the changes in the gastropod assemblages

sedimentary evidence of the neogene evolution of se spain the neogene sediments of se spain are dominated by gravity flow deposits ranging from millimetre scale dilute turbidites to kilometre scale olistholiths details of the neogene sequences at finestrat alcoy and fontanars provide examples of responses to periodic tectonic events in a variety of background settings the main control on sedimentation in each area was the episodic rise of triassic gypsiferous mudstone diapirs this probably resulted from periodic regional extension and compression due to contraction and spreading of the alboran sea marginal basin

shoreline resilience to individual storms and storm clusters on a meso macrotidal barred beach abstract this study investigates the impact of individual storms and storm clusters on shoreline recovery for the meso to macrotidal barred biscarrosse beach in sw france using 6 years of daily video observations while the study area experienced 60 storms during the 6 year study period only 36 storms were analysed due to gaps in the video data based on the 36 individual storms and 13 storm clusters analysed our results show that clustering impact is cumulatively weak and shoreline retreat is governed by the first storms in clusters while the impact of subsequent events is less pronounced the average post storm beach recovery period at this site is 9 days consistent with observations at other beaches apart from the dominant effect of present storm conditions shoreline dynamics are also significantly affected by previous storm influence while recovery is strongly modulated by tidal range and the bar location our results reveal that not only is the storm energy important but also the frequency of recurrence storms result in greater retreat when time intervals between them are longer which suggests an interaction between short storm events and longer term evolution

large scale dune erosion tests to study the influence of wave periods article i nfo large scale physical model tests were performed to quantify the effects of the wave period on dune erosion attention was focussed on 2d cross shore effects in a situation with sandy dunes and extreme water levels and wave conditions besides profile measurements detailed measurements in time and space of water pressure flow velocities and sediment concentrations were performed in the near near shore area it was concluded that a longer wave period leads to a larger dune erosion volume and to a larger landward retreat of the dune face tests with double peaked wave spectra showed that the influence of the spectral shape on dune erosion was best represented by the tm 1 0 spectral mean wave period better than the peak wave period tp the effect of the wave period on dune erosion was implemented in a dune erosion prediction method that estimates erosion volumes during normative storm conditions for the dutch coast more details of the measurements and additional analyses of physical processes are described in an accompanying paper by van thiel de vries et al van thiel de vries j s m van gent m r a reniers a j h m and walstra d j r submitted for publication analysis of dune erosion processes in large scale flume experiments in this volume of coastal engineering

foredune morphological changes and beach recovery from the extreme 2013 2014 winter at a high energy sandy coast the beach dune response at truc vert sw france is analysed using dgps topographic surveys sampled every 2 4 weeks covering an alongshore distance of 1 5 km combined with wave tide and extreme water level hindcast and beach dune photographs during the 2013 2014 winter which was the most energetic since at least 1948 the beach dune system at truc vert eroded by approximately 180 m3 per beach width divided equally between beach and dune erosion beach and dune erosion was strongly variable alongshore with cuspate type rhythmic dune erosion scarps stripped of vegetation with a cross shore amplitude of 25 m the alongshore variable scarps were coupled with an alongshore variability in elevation of the beach with lower beach levels co located with the megacusp bays the following 10 months showed modest morphological beach and dune changes with for instance destabilisation of the scarped dune by trough blowouts scarp slumping and filling and seasonal beach berm dynamics the most profound morphological and vegetation changes occurred during the subsequent 10 months only 1 5 years after that winter the beach dune system at truc vert almost recovered to its pre winter volume but not to its pre winter foredune profile most of the sand volume recovery occurred during spring summer autumn 2015 when approximately 120 m3 m of sand naturally came back in the system the beach volume recovery rate was relatively steady and uncorrelated with wave conditions with rates twice as large across the megacusp bay profile as across the that of the megacusp horns during that period the widened and risen dry beach provided large fetch length enhancing onshore windblown transport and a rapid rising of the backshore the slumped and filled dune scarp which was providing a high barrier to aeolian transport from the beach to the dune since the 2013 2014 winter reformed as a dune ramp providing efficient conduit for beach dune delivery exchange of sediment by the end of the study this process favoured both natural revegetation into the scarp and incipient foredune formation despite the reinstatement of natural processes between the beach and the dune the dune foot was still located landward by more than 10 m on average with respect to its pre 2013 2014 winter position this study shows that even after the most severe winter over the last 68 years in terms of average wave energy arriving at the coast beach recovery can be a relatively fast process along high energy sandy beaches backed by large dunes in contrast foredune recovery which timing and magnitude can provide a proxy measure for the resilience of the system to climatic variability and change is a much slower process that can take years to decades

numerical analysis of the interaction of irregular waves with two dimensional permeable coastal structures abstract this paper will address the validation and application of a volume of fluid method for coastal structures under the influence of normal incident irregular wave fields several physical processes will be addressed as part of the validation process namely i wave reflection from permeable and impermeable structures ii wave transformation over a small shoal iii wave damping inside of a permeable structure iv the resulting wave induced internal setup and v wave induced forces the numerical model will be validated against a multiple of experimental data sets for two dimensional coastal problems the impact of air relief gaps on the modelled wave induced pressures on a crest wall is analysed for the two dimensional layout of the structure this is analysed to study the importance of the cushion effect from the incompressible air phase subsequent to the validation of the numerical model the internal setup in permeable coastal structures is given separate attention a combination of an analytical prediction of the magnitude of the internal setup and numerical results is used to derive numerically based empirical formulae for the magnitude and the time scale of the internal setup the formulae include the effects of wave height wave period material properties of the coastal structure and the dimensions of the structure the numerical model is based on the openfoam cfd toolbox

analysis of dune erosion processes in large scale flume experiments abstract large scale physical model tests were conducted with different wave periods to examine the physical processes driving dune erosion the model tests have been carried out in a flume 2dv with a sandy dune exposed to extreme surge and wave conditions van gent m r a van thiel de vries j s m coeveld e m de vroeg j h and van de graaff j 2008 large scale dune erosion tests to study the effect of wave periods coastal engineering doi 10 1016 j coastaleng 2008 04 003 detailed measurements in time and space of water pressure flow velocities and sediment concentrations were performed in the near shore area the data revealed that both short and long waves are important to inner surf hydrodynamics depth averaged flows are directed offshore and increase towards the shore line the corresponding mean sediment concentrations rise sharply towards the dune face up to 50 g l near the bed the strong increase in the mean sediment concentration towards the dune face correlates well with the maximum wave surface slope which in turn is coupled to both the pressure gradient and the near bed wave breaking induced turbulence analysis shows that the pressure gradient is only partially coupled to the flow acceleration suggesting that the latter cannot always be used as a proxy for the first weak correlation is obtained with the near bed flows related to the bed shear stress tests with a larger wave period resulted in a larger dune erosion volume during these tests more wave energy combined incident and infragravity waves reached the dune face but more importantly this wave energy is dissipated by fewer waves resulting in more intense wave breakers and steeper wave fronts it is therefore expected that the wave breaking induced near bed turbulence increases resulting in significantly higher o 100 mean sediment concentrations in addition the mean flow velocities are comparable yielding a substantially larger offshore directed sediment transport capacity this increase in offshore directed transport is only partially compensated by a concurrent increase in the wave related onshore transport capacity associated with intrawave processes resulting in a net increase in the dune erosion rate

alpine tectonics and diapiric structures in the pre betic zone of southeast spain abstract the pre betic is the most northerly of the alpine zones forming the betic cordilleras of southern spain it consists of strongly folded and faulted mesozoic and tertiary rocks the oldest of which are ferruginous and gypsiferous triassic mudstones followed by a predominantly carbonate facies of cretaceous palaeogene and miocene age although this sequence is interrupted by a number of minor unconformities the major structures were formed during the middle or late miocene the highly incompetent triassic rocks are the most strongly deformed and form diapiric intrusions discordant to regional structural trends in the younger rocks the latter are essentially of two facies massive competent limestones which are deformed by relatively simple folds of large wavelength and highly incompetent marl limestone interbeds with complex disharmonic folds and crush belts faults include low angle and high angle thrusts gravity slides and wrench faults the regional tectonic strike is ene to ne but the diapiric intrusions mostly follow wnw and n directions these intrusions have pushed the younger rocks aside the result being polyphase structures of several trends less intense post miocene tectonics are mostly associated with continued diapirism and have resulted in the folding and tilting of the late miocene to quaternary elastic sediments

geomorphic and stratigraphic evidence of quaternary diapiric activity enhanced by fluvial incision navarres salt wall and graben system se spain abstract the structural and stratigraphic geological features associated with salt structures have received extensive attention from geologists however there is limited work on the geomorphic and quaternary record of diapiric activity despite its practical implications e g salt and hydrocarbon extraction geostorage activities this work analyses the quaternary geomorphic and stratigraphic evidence of diapiric activity in the navarres salt wall se spain developed along the axis of a neogene graben this salt system is located in a region characterized by a peculiar network of orthogonal grabens that control the configuration and evolution of the drainage network the protruding salt walls are spatially associated with the erosionally unloaded and deeply entrenched graben sections situated close to the regional base level evidence of recent current activity in the navarres salt wall include 1 internally drained areas in a marginal withdrawal basin with long sustained aggradation 2 distorted drainage network defeated and deflected streams wind gaps knickpoints changes in fluvial style which changed from an initial axial longitudinal pattern to a longitudinal marginal distribution at the flanks of the salt wall 3 development of diapiric fault scarps at the edge of the salt wall 4 tilted fluvial terraces dipping away from the salt wall and with localized sediment thickening the available data indicate along strike variability in deformation style and long term vertical deformation rates these range from 0 09 mm yr to significantly higher values 0 2 0 4 mm yr in the section where the salt wall displays a more prominent relief and is affected by deep fluvial entrenchment the regional analysis and the characterization of the navarres salt wall suggest that quaternary diapirism in the region is enhanced by erosional unloading related to fluvial entrenchment which expands from the regional base level through the upstream propagation of an incision wave

applicability of magnetic fabrics in rocks associated with the emplacement of salt structures the bicorb quesa and navarres salt walls prebetics se spain abstract this work assesses the applicability of the analysis of the anisotropy of magnetic susceptibility ams to rocks associated with salt structures magnetic fabrics from 16 sites sampled on upper triassic clays keuper facies interbedded within the salt layers of the bicorb quesa and navarres salt walls prebetic zone se spain are mostly characterized by oblate magnetic ellipsoids with their magnetic foliation parallel to the bedding and magnetic lineation contained in the bedding plane but without a constant relationship with dip direction to evaluate the quality and significance of the low field ams several experiments were carried out to characterize the magnetic mineralogy of representative samples and enable separation of the contributions from paramagnetic and ferromagnetic s l minerals the comparison between the orientation of the observed magnetic lineation and that of the structural elements characterizing the internal geometry of the studied salt structures antiforms minor folds faults and shear zones and flanks indicates that the magnetic fabric is controlled by deformation processes affecting the salt walls during their growth and or evolution samples were also analyzed from sixteen sites from miocene rocks outcropping in several syn diapiric miocene half grabens related to the salt walls studied their magnetic fabric is interpreted to reflect the dominant stretching direction at the syn diapiric half grabens during and or shortly after deposition our results indicate that caution is required in interpreting magnetic lineations related to salt flow mechanics from rocks associated with salt structures

modeling of thrust fronts above ductile and frictional detachments application to structures in the salt range and potwar plateau pakistan series of scaled sandbox models are used to simulate the development of thin skinned simultaneous shortening above adjacent ductile and frictional substrates these models simulate the evolution of the potwar plateau and salt range in pakistan where pale

submarine salt glacier of northern tunisia a case of triassic salt mobility in north african cretaceous passive margin stratigraphical sedimentological and structural data and a bouguer gravity map of medjez el bab meb in northern tunisia are used to illustrate a cretaceous example of salt extrusion on a passive continental margin located just south of the teboursouk thrust front a preferential decollement surface used by the continuous tertiary shortening in this area the meb structure is a simple n40 e box anticline removing the two tertiary foldings eocene and miocene leads to the exposure of the original feature of a simple submarine salt glacier the triassic salt rocks appear as an albian interstratified body between two cretaceous series with stratigraphic normal polarity suggesting a bedding parallel extrusion at the sediment water interface of the triassic salt in cretaceous times the formation of such salt extrusions are associated with extensional faulting probably both in the cover and basement the presence of a slope and basinwards salt flow this scenario is similar to the allochthonous salt described in other salt provinces characterizing passive margins

analog modeling of one way gravitational spreading of hot orogens a case study from the svecofennian orogen fennoscandian shield abstract geodynamic models offer insight into deformation styles of syn and post collisional extensional processes such models often ignore the effect of lateral viscosity contrast between accreted terranes and inherited tectonic boundaries this paper presents a set of crustal scale analog experiments of one way post collisional gravitational spreading testing the effect of crustal heterogeneity by using two mechanically contrasting blocks pre existing cuts with varying dips and three layers with contrasting rheologies two blocks represent strong mature and weak juvenile crustal parts both blocks have three horizontal crustal layers brittle upper weak partially molten middle and dry strong lower layer cuts represent pre existing crustal scale shear zones and tectonic boundaries the experiments indicated that tectonic boundaries may facilitate exhumation and increase extensional strain when the boundaries dip opposite to the flow direction the tectonic boundaries may also split and divide the crust into separate blocks with independent deformation signatures shortening elongation or rotation the tectonic boundaries rotated along vertical axes toward the flow direction the modeling results suggest that in areas with inherited tectonic boundaries and compositional differences the amount of extension is unevenly distributed between the different parts during the widespread unilateral gravitational spreading and that the flow has different effects on the contrasting crustal units in both lateral and vertical directions to validate the modeling the results are compared to geophysical and geological data from the paleoproterozoic svecofennian orogen in the fennoscandian shield the comparison suggests that the orogen underwent 50 extension and was thinned by maximum of 20 via westward gravitational spreading this spreading rotated the crustal scale blocks shear zones and tectonic contacts it also brought exhumed high grade middle crustal blocks into contact with subsided low grade upper crustal blocks we suggest that results of the analog models can be used as proxies in both ancient and modern hot accreted orogens which have undergone post convergence continental mid crustal weakening and have comprised of juxtaposed terranes with varying rheological compositions

aspects of the structural evolution of the lusitanian basin in portugal and the shelf and slope area offshore portugal abstract the study provides a regional seismic interpretation and mapping of the mesozoic and cenozoic succession of the lusitanian basin and the shelf and slope area off portugal the seismic study is compared with previous studies of the lusitanian basin from the late triassic to the cretaceous the study area experienced four rift phases and intermittent periods of tectonic quiescence the triassic rifting was concentrated in the central part of the lusitanian basin and in the southernmost part of the study area both as symmetrical grabens and half grabens the evolution of half grabens was particularly prominent in the south the triassic fault controlled subsidence ceased during the latest late triassic and was succeeded by regional subsidence during the early early jurassic hettangian when deposition of evaporites took place a second rift phase was initiated in the early jurassic most likely during the sinemurian pliensbachian this resulted in minor salt movements along the most prominent faults the second phase was concentrated to the area south of the nazare fault zone and resulted here in the accumulation of a thick sinemurian callovian succession following a major hiatus probably as a result of the opening of the central atlantic resumed deposition occurred during the late jurassic evidence for late jurassic fault controlled subsidence is widespread over the whole basin the pattern of late jurassic subsidence appears to change across the nazare fault zone north of the nazare fault fault controlled subsidence occurred mainly along nnw sse trending faults and to the south of this fault zone a nne ssw fault pattern seems to dominate the oxfordian rift phase is testified in onlapping of the oxfordian succession on salt pillows which formed in association with fault activity the fourth and final rift phase was in the latest late jurassic or earliest early cretaceous the jurassic extensional tectonism resulted in triggering of salt movement and the development of salt structures along fault zones however only salt pillow development can be demonstrated the extensional tectonics ceased during the early cretaceous during most of the cretaceous regional subsidence occurred resulting in the deposition of a uniform lower and upper cretaceous succession marked inversion of former normal faults particularly along ne sw trending faults and development of salt diapirs occurred during the middle miocene probably followed by tectonic pulses during the late miocene to present the inversion was most prominent in the central and southern parts of the study area in between these two areas affected by structural inversion fault controlled subsidence resulted in the formation of the cenozoic lower tagus basin northwest of the nazare fault zone the effect of the compressional tectonic regime quickly dies out and extensional tectonic environment seems to have prevailed the miocene compressional stress was mainly oriented nw se shifting to more n s in the southern part

on the morphological development of embayed beaches abstract the typically curved and stable planform shape of embayed beaches is often observed in the presence of rigid headlands the long term alongshore equilibrium shape is variable and is controlled by headland geometry cellular circulation patterns and wave obliquity at the shoreline we use a process based morphological model to simulate the development of embayed beaches depending on different environmental conditions and geological settings i e topography and geometry the embayment is allowed to develop from an initially straight beach to one which is curved under idealized wave forcing conditions and without external sediment input bay development can be approximated with an exponential function with coefficients representing rate of growth and bay size long term shoreline cutback is both uniform shoreline translation and non uniform shoreline rotation and is parameterized alongshore gradients in flow and transport patterns are related to long term non uniform shoreline cutback rotation of the beach ceases as the bay matures leading to a curved shoreline planform which is a remnant of decaying erosion processes

jurassic tectono sedimentary evolution of the northern lusitanian basin offshore portugal abstract the lusitanian basin is one of a series of rift related basins developed during the rifting that led to the break up of iberia and canada the strong influence of halokinesis on the depositional evolution of its northern sector provides an analogue for the development of other evaporite prone rift basins on atlantic type passive margins in this paper the pre valanginian evolution of the northern lusitanian basin is documented based on regional seismic stratigraphy isochron and time structure maps tied with sonic and stratigraphic data from 10 exploration wells the pre salt structure of the study area is marked by two sets of faults i a n s to ne sw striking set active throughout the jurassic period and ii a nw se striking set active during the late jurassic the latter defines five late jurassic sub basins northeast of a basin margin structure the marinha grande fault the development of half graben basins in the northern lusitanian basin during the jurassic was overprinted by halokinesis over the marinha grande fault and other major marginal basement faults halokinesis climaxed during the oxfordian kimmeridgian rifting with the formation of a 10 km long salt ridge over the marinha grande fault the ridge limited the southward progradation of fluvial deltaic units derived from hanging wall drainage systems and restricted the syn rift sediments to a 15 km long 5 km wide bowl shaped depocentre located 10 km west of the present coastline in order to better characterise the jurassic tectono sedimentary evolution of the northern lusitanian basin the interpreted seismic data is compared with physical models for extensional forced folds above active normal faults and with stratigraphic information from well and outcrop

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

structural segmentation inversion and salt tectonics on a passive margin evolution of the inner kwanza basin angola the kwanza basin angola is divided into the inner and outer kwanza salt basins separated by a chain of synrift basement highs on which aptian 112 122 ma salt is thin or absent north to northwest trending basement structures in the inner kwanza basin have repeatedly been reactivated since neocomian 144 127 ma rifting reactivation formed three northwest striking fold and thrust belts near basement uplifts the thrust belts are bounded by northeast striking rift related transfer fault zones that were apparently reactivated during subsequent shortening three episodes of postrift basement involved shortening are documented in the inner kwanza basin 1 albian early cenomanian 112 96 ma 2 senonian 89 65 ma and 3 oligocene holocene 34 0 ma we relate the albian early cenomanian event to ridge push the senonian event to global plate reorganization and oligocene holocene shortening to uplift of the african superswell structural segmentation of the inner kwanza basin controlled the evolution of salt structures adjacent to basement uplifts diapirs were initiated as buckle folds some anticlines were unroofed by erosion and evolved into passive salt walls elsewhere broad salt walls were triggered by either detached extension or basement block uplift these walls grew until they exhausted their supply of salt thereafter dissolution rates exceeded rates of salt inflow so the walls began to subside withdrawal of salt from the walls produced the elongate sedimentary troughs for which the basin is famous trough fill ranges in age from cenomanian to pliocene and this age varies greatly from trough to trough and along strike within troughs

structural development of the taza guercif basin as a constraint for the middle atlas shear zone tectonic evolution abstract the neogene taza guercif basin in north eastern morocco is located in correspondence of the eastern termination of the rifian arc and is aligned along with the middle atlas shear zone since tortonian the tectonic evolution of the taza guercif basin was tied to repeated advancements of the rifian front and to the transpressive tectonics of the middle atlas shear zone the major structures in this basin consist of thrust related anticlines aligned along with the middle atlas structures and second order normal faults elongated according to the rifian trend the latter are well developed mainly in the north western sector of the basin bab stout area apart from the bab stout area the basin is dominated by compressive and transpressive structures guercif transpressive area the shortening directions responsible for the development of the major and minor compressive structures in the basin vary from nnw to nne but no superposition relationships have been found this change of the paleo stress field orientations is here ascribed to a progressive deformation under the constant push between africa and europe an evolutionary model for the development of these two structural areas in relation to the tectonics of the rif and of the middle atlas is here proposed in this model the sinistral transpressive middle atlas shear zone is regarded as the boundary between the moroccan meseta microplate to the west and the african indenter to the east which is moving faster to the north

wave dune interaction and beach resilience in large scale physical model tests abstract large scale laboratory experiments focusing on the main physical processes driving dune erosion have been performed in a wave flume with a sandy dune exposed to a combination of water levels and wave conditions tomasicchio et al 2011b providing observations of different interaction regimes collapsing overwash and breaching sallenger et al 2003 the large set of data has been considered to obtain measurements of beach dune cross shore profile evolution hydrodynamic properties and suspended sediment concentration results show that erosion develops faster during the first hundred waves there is a clear influence of wave period van gent et al 2008 and water depth on the resilience of the beach dune system and that sediment concentration at a given transect depends on the bar position furthermore the observed data have been adopted to verify the predictive accuracy of two open source process based profile numerical models

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

physical analog centrifuge model investigation of contrasting structural styles in the salt range and potwar plateau northern pakistan abstract we use scaled physical analog centrifuge modeling to investigate along and across strike structural variations in the salt range and potwar plateau of the himalayan foreland fold thrust belt of pakistan the models composed of interlayered plasticine and silicone putty laminae comprise four mechanical units representing the neoproterozoic salt range formation basal detachment cambrian eocene carapace sequence and rawalpindi and siwalik groups neogene molasse on a rigid base representing the indian craton pre cut ramps simulate basement faults with various structural geometries a pre existing north dipping basement normal fault under the model foreland induces a frontal ramp and a prominent fault bend fold culmination simulating the salt range the ramp localizes displacement on a frontal thrust that occurs out of sequence with respect to other foreland folds and thrusts with a frontal basement fault terminating to the east against a right stepping east dipping lateral ramp deformation propagates further south in the east strata to the east of the lateral ramp are telescoped in ene trending detachment folds fault propagation folds and pop up structures above a thick basal detachment salt range formation in contrast to translated but less deformed strata with e w trending salt range structures to the west the models are consistent with salt range potwar plateau structural style contrasts being due to basement fault geometry and variation in detachment thickness

effect of ductile and frictional decollements on style of extension abstract scaled analogue models were used to study the effect of frictional and ductile detachments on thin skinned extension models consisted of two halves one half is the ductile and the other has a frictional detachment extension occurred above two different basal configurations a stretchable rubber sheet and a folded banded sheet intended to produce homogeneous and heterogeneous extension respectively model parameters varied systematically and included the brittle ductile thickness ratio rheologies and bulk strain structures in the two halves are compared in profiles and plan views a series of graben developed above both halves of models extended above a banded sheet although there were differences in style propagation rate and width of the deformation zone between the two halves different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves in contrast in models extended above a stretchable rubber sheet extensional structures such as horst and graben developed only above the ductile detachment model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet however above 20 bulk extension deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction

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

87sr 86sr dating of coralline algal limestones and its implications for the tectono stratigraphic evolution of the eastern prebetic spain abstract the use of 87sr 86sr chronostratigraphy for dating marine carbonates is a powerful method in tectono stratigraphic analysis of fold and thrust belts in this paper we present the results of 87sr 86sr dating of early miocene coralline algal limestones which constrain the age of foreland folding in the eastern prebetic zone of the betic cordilleras spain the first folding phase took place between 23 6 and 19 0 ma associated with erosion and the subsequent deposition of coralline algal limestones deposition of these limestones was terminated by drowning and subsequent folding between 21 5 and 17 2 ma inferred regional variations in the ages of folds in the order of 1 2 m y are thought to reflect the sequential and therefore intrinsically diachronous growth of fold belts the depositional history was primarily controlled by these tectonic movements even though eustasy may have contributed to the drowning of the algal carbonate platforms the unconformities which bound the algal limestones probably formed in direct response to the thrust emplacement of the betic nappe pile and reflect the northward migration of the peripheral bulge and foreland basin