duplex style and triangle zone formation insights from physical modeling duplexes are a common feature in thrust belts at many scales their geometries vary significantly from antiformal stacks with significant forethrusting in the cover e g southern pyrennes spain to triangle zones e g foreland canadian rockies to low displacement individually spaced ramp anticlines e g sub andean thrust belt bolivia we present a series of physical experiments demonstrating that the strength of the decollements relative to that of the intervening and overlying rock layers plays a significant role in controlling the duplex style the models comprise brittle layers made of dry quartz sand and decollements made of two types of viscous silicone polymers the strength of the decollements in the models is a function of the shortening rate applied to the model the relative strength of the decollements and surrounding rocks affects the development of active or passive roof duplexes triangle zones it also affects the amount of translation of individual thrust blocks and the spacing of thrust ramps which in turn determine if a duplex evolves into an antiformal stack or into individually spaced ramp anticlines model results indicate that specific associations of structural features form systematically under similar rheological and boundary conditions the presence of relatively strong decollements promotes local underthrusting of the cover individual ramp anticlines internal deformation of thrust sheets low early layer parallel shortening and sequential towards the foreland propagation of structures weak decollements promote forethrusting of the cover antiformal stacks coeval growth of structures and low internal strain with the exception of significant early layer parallel shortening no underthrusting at a regional scale occurred in any model

deep seismic reflection profile in central europe reveals complex pattern of paleozoic and alpine accretion at the east european craton margin 1 the first deep reflection seismic profile was acquired across the teisseyre tornquist zone ttz a major european suture zone southeast of the avalonia baltica collision zone portraying different tectonic deformation styles thick versus thin skinned and phanerozoic crustal accretion episodes over a relatively short distance 240 km the overall crustal structure preserves image of the neoproterozoic passive margin setting but with a significant overprint of the repetitive tectonic convergence cadomian to alpine acting at the baltica margin in contrast to the avalonia baltica collision zone here the polygenetic crustal accretion occurring at the cratonic margin was ultimately shaped by significant strike slip faulting ttz is imaged as a narrow 10 15 km transform zone separating the thinned east european cratonic crust from the malopolska block

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

kinematics and a balanced and restored cross section across the toe of the eastern nankai accretionary prism abstract seismic profiles across the eastern nankai accretionary prism show evidence for diffuse deformation through stratal thickening and uplift of the accreting sediment package thought to reflect the combination of small scale ductile and brittle strains evident within drill cores using a kinematic solution based on changes in stratal thickness and porosities diffuse strains are estimated for a transect across the eastern nankai accretionary prism toe in the vicinity of odp site 808 calculated element displacements are used to reconstruct the undeformed configuration of the prism toe providing a new method for balancing and restoring deformation in accretionary prisms the results of this analysis demonstrate a heterogeneous distribution of strain within the prism toe which appears to correlate with the distribution of brittle deformation structures in drill cores the greatest vertical tectonic thickening and horizontal shortening estimates are obtained within the deepest sediments which also display abundant brittle shears shallower sediments exhibit high volume loss and lower horizontal shortening and in drill cores display very few deformation structures this spatially variable strain distribution may result from inferred high pore pressures near the frontal thrust and decollement inducing a brittle overprint of previous ductile strains

deformation patterns and structural vergence in brittle ductile thrust wedges an additional analogue modelling perspective abstract scaled physical models of brittle ductile thrust wedges investigated the causes leading to the development of the various structural styles observed in fold and thrust belts and accretionary prisms this study focused on some potential controlling factors such as 1 relative strength between the brittle overburden and the viscous decollement layer brittle ductile coupling 2 the effect of very low basal friction and 3 pre shortening rheological stratigraphy including decollement strength type 1 models had a single basal decollement whereas in type 2 models the decollement was embedded in brittle material simulating an upper roof sequence and a lower floor sequence other models investigated the effects produced by an horizon of mechanical weakness at the base of the viscous decollement type 1a and the role of decollement offset type 3 the experiments suggest the occurrence of a genetic relationship between the absolute values of shear stresses and the development of dominating hinterland or foreland verging thrust faults or dually verging thrusts by controlling the orientation of the 1 axis basal friction and decollement offset is found to effectively influence the deformation pattern and structural vergence and could explain the development of dominating backthrusts in cascadian type margins the decoupling of a frontal monocline via the upper decollement type 2 models produced passive roof duplex structures termed composite roof duplex when the frontal monocline coexists with outward fold propagation

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

sequence of deformation at the front of an orogen lublin basin case study poland abstract we provide a detailed description of a late carboniferous fold and thrust belt in the lublin basin based on seismic lines including new high resolution acquisitions and legacy borehole and gravimetric data a series of regional cross sections integrate results of the joint seismic borehole gravimetric interpretation cross section restoration provides estimates of the minimum incremental and total shortening and reveals its along strike variations the lublin basin straddles a leading edge of the variscan orogen and its undeformed foreland therefore it experienced only a minor deformation it preserves a fossilized record of early phases of shortening seismic scale divergent intra formational thrusts and folds in horizontal strata that were later passively rotated by subsequent folds developed above a regional decollement lateral variations of deformation styles from displacement of the entire basin with little internal deformation to dispersion of shortening by numerous contractional structures is attributed to along strike changes in lithology and thickness of the silurian detachment horizon lateral change of detachment strength is quantified using the critical wedge theory our observations deliver a new perspective on factors controlling the localization of incipient structures their differentiation as a function of detachment strength and interplay between folding and thrusting along a leading edge of an organic system

effects of irregular basement structure on the geometry and emplacement of frontal thrusts and duplexes in the quebec appalachians interpretations from well and seismic reflection data abstract irregular basement geometry may affect thrust propagation in foreland fold thrust belts creating a perturbation in structural continuity of hydrocarbon fields here we investigate how the irregular pattern of normal faults along with the presence of uplifts and transverse faults in the grenvillian basement has influenced the geometry and emplacement of frontal thrusts and duplexes in the parautochthonous domain of the southern quebec appalachians during the middle late ordovician taconian orogeny integration of data from surface geology wells and 2d and 3d seismic reflection surveys into a regional scale structural model is used to reconstruct the 3d geometry and emplacement history of one and two horse duplexes in the joly saint flavien gas storage area the normal hinterland to foreland sequence of thrusting in this area is complicated by the differential emplacement of tectonic slices along strike of the orogenic front starting in the sw and developing subsequently to the ne within each structural level the shortening related to duplex emplacement decreases laterally over the distance of 20 km from 49 in the sw joly area to 31 in the ne saint flavien area duplex emplacement resulted from the differential forward propagation deflexion and vertical axis rotation of the roof thrust logan s line which in turn has been induced by the presence of frontal uplift and transverse faults in the basement the structural lithological analysis of tectonic slices and restoration of their initial location allows us to consider the lower slice of the joly duplex as a structural trap comparable to the fractured reservoir in lower ordovician dolomites of the saint flavien duplex

effects of cohesion on the structural and mechanical evolution of fold and thrust belts and contractional wedges discrete element simulations particle based numerical simulations of cohesive contractional wedges can yield important perspectives on the formation and evolution of fold and thrust belts offering particular insights into the mechanical evolution of the systems results of several discrete element method simulations are presented here demonstrating the stress and strain evolution of systems with different initial cohesive strengths particle assemblages consolidated under gravity and bonded to impart cohesion are pushed from the left at a constant velocity above a weak unbonded decollement surface internal thrusting causes horizontal shortening and vertical thickening forming wedge geometries the mean wedge taper is similar for all simulations consistent with their similar residual and basal sliding friction values in all examples presented here both forethrusts and back thrusts occur but forethrusts accommodate most of the shortening fault spacing and offset increase with increasing cohesion significant tectonic volume strain also occurs with the greatest incremental volume strain occurring just outboard of the deformation front this diffuse shortening serves to strengthen the unfaulted domain in front of the deformed wedge preconditioning these materials for brittle dilative failure the reach of this volumetric strain and extent of decollement slip increase with cohesive strength defining the extent of stress transmission stress paths for elements tracked through the simulations demonstrate systematic variations in shear stress in response to episodes of both decollement slip and thrust fault activity providing a direct explanation for stress fluctuations during convergence

thick skin orogen foreland interactions and their controlling factors northern andes of colombia the study draws from reflection seismic in situ stress and low temperature geochronology data on the eastern cordillera llanos foreland basin system of colombia which is an example of the retro wedge of the orogen with an advancing subduction zone the system was obliquely converging during deposition of the lower oligocene lower miocene carbonera to recent guayabo formations recording it by the northeastward depocentre shift in the proximal llanos basin while the southern portion of the foreland did not flex and undergo flexural normal faulting after carbonera deposition the northern portion did the earthquake data indicate that the northern eastern cordillera undergoes strengthening by internal deformation while the southern segment is already strong enough to undergo significant displacements dominantly along its bounding fault systems furthermore the southern segment initiated detachment of the first thick skin blocks from the proximal llanos basin such co existence of different convergence maturity stages along the orogen strike allows unravelling of its development starting with internal deformation and foreland flexure followed by mountain building and large scale boundary fault displacements to the large scale foreland deformation the onset of new foreland accretion seems to be controlled by the resistance of the foreland plate to flexing given that the orogenic engine continues to drive convergence

the structure and evolution of the western mediterranean ridge the mediterranean ridge is a unique accretionary complex consisting of five key elements the frontal slope the upper slope the crest of the ridge the cleft area and the inner plateau the imerse data show that these correspond roughly to the locus of frontal accretion of underplating of a pre messinian wedge of complex faulting and possible strike slip tectonics and of a backstop of hellenic nappes covered by a messinian forearc basin the frontal portion of the complex is a post messinian accretionary wedge composed of messinian evaporites and overlying tightly folded plio quaternary sediments underlain by pre messinian sequences attached to the african plate the basal detachment at the front of the wedge occurs at the base of the evaporites moving further to the northeast the upper slope the basal detachment cuts to deeper levels leading to the development of duplex structures where pre messinian units are subcreted beneath the messinian evaporites just behind the subcreted units the evaporites thin and may be absent on the crest of the ridge this region we interpret as the site of a pre messinian accretionary wedge we suggest that following the deposition of thick evaporites in the messinian the pre messinian accretionary tectonics continued as subsurface accretion subcretion beneath the evaporites although the crest of the ridge is largely devoid of evaporites local deep evaporite basins observed here formed as local closed basins on top of the pre messinian wedge we infer that the messinian sealevel was at about the level of the ridge crest that is 3000 m below present allowing for isostatic adjustment to the removal of the water load this would imply a sealevel drop of at least 2000 m the cleft basins mark the northeast limit of the accretionary complex thick evaporite deposits to the northeast beneath the inner plateau may have been deposited in a messinian forearc basin the evaporites of the inner plateau are underlain by a thin pre messinian sequence and by crystalline basement of the hellenic nappes this basement forms the backstop to the accretionary complex

influence of synkinematic sedimentation in a thrust system with two decollement levels analogue modelling abstract compressive systems in foreland domains are characterised by fold and thrust belts linked to the presence of one or several ductile layers in depth acting as a decollement level the main parameters controlling the structural evolution are the presence of a decollement level the amount and rate of shortening and the amount of synkinematic sedimentation the effect of these parameters has only been studied on a thrust belt scale furthermore only the effect of synkinematic sedimentation on a simple system with one decollement level has been studied at the scale of a single structure the aim of this study was to use analogue modelling to test the effect of shortening rate velocity and the localization of sedimentation on a single system characterised by the presence of two prekinematic decollement levels the main results showed variations in the structural vergence folding geometry symmetric or asymmetric the evolution of the deformation horizontal propagation versus vertical uplift and the decoupling of the lower and upper brittle structures in relation with the main parameters shortening rate and mass transfer the results of the experiments were then compared to natural examples from the sub andean thrust belt

effect of overburden thickness on thrust belt geometry and development laboratory sand models simulating development of thrust belts indicate that 1 distance between the backstop and the first formed thrust is a linear function of initial sand layer thickness 2 spacing between the first two thrusts is most likely a nonlinear function of initial sand layer thickness 3 initial dip of successive ramps decreases progressively toward the foreland because of variations in principal stress directions with depth and or changes of mechanical properties of sand with increasing overburden 4 faults to the hinterland steepen and become less active as hinterland thrust sheets undergo penetrative shear during sand wedge growth and 5 new ramp initiation occurs to the hinterland of the basal detachment tip line these observations can be interpreted both in context of area balance considerations and soil mechanics theory if initial sand layer thicknesses in our models represent syntectonic overburden in natural thrust belts i e distance between the ground surface and the detachment then our results suggest that locations of some thrust belt salients are controlled by along strike variations in stratigraphic thicknesses and that initial thrust spacing decreases progressively to the foreland if the thrust belt involves a foreland tapering basin furthermore our sand model observations suggest that the concept of a fixed rigid backstop in the hinterland of thrust belts may be misleading as a consequence of thickening the hinterland portion of the thrust belt becomes stabilized and effectively becomes the backstop itself

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

broadband calibration of the r v marcus g langseth four string seismic sources 1 the r v marcus g langseth is the first 3 d seismic vessel operated by the u s academic community with up to a four string 36 element source and four 6 km long solid state hydrophone arrays this vessel promises significant new insights into earth science processes the potential impact of anthropogenic sound sources on marine life is an important topic to the marine seismic community to ensure that operations fully comply with existing and future marine mammal permitting requirements a calibration experiment was conducted in the gulf of mexico in 2007 2008 results are presented from deep 1 6 km and shallow 50 m water sites obtained using the full 36 element 6600 cubic inches seismic source this array configuration will require the largest safety radii and the deep and shallow sites provide two contrasting operational environments results show that safety radii and the offset between root mean square and sound exposure level measurements were highly dependent on water depth

late vendian early palaeozoic tectonic evolution of the baltic basin regional tectonic implications from subsidence analysis abstract subsidence analysis was performed on 43 boreholes penetrating the upper vendian lower palaeozoic sedimentary succession of the baltic basin the results were related to lithofacial and structural data to elucidate subsidence mechanisms and the regional tectonic setting of basin development tectonic subsidence patterns are consistent throughout the basin for the time period studied an extensional tectonic subsidence event possibly of two phases is indicated from the late vendian to the beginning of the middle cambrian this event is seen in the southwestern part of the baltic basin peri tornquist zone until the earliest cambrian after which it is also observed in the sw ne trending baltic depression part of the basin basin development during this time is interpreted as recording the latest stages of break up of the precambrian super continent rodinia and ultimately the formation of the tornquist sea the late middle cambrian to middle ordovician tectonic subsidence pattern of the baltic basin is characteristic of post rift thermal subsidence of the newly formed passive continental margin of baltica developed along its southwestern edge a gradual increase in subsidence rate is observed from the middle late ordovician and throughout the silurian particularly for ludlow and pridoli times creating subsidence curves with convex shapes typical of foreland basin development the rate of late silurian tectonic subsidence increases significantly towards the southwest margin of the baltic basin adjacent to the present location of the north german polish caledonides the baltic basin therefore appears to have developed primarily as a flexural foreland basin during silurian oblique collision of baltica and eastern avalonia a foreland setting is supported by the influx of distal turbidites into the basin from southwest sources in the late silurian compressional deformation structures of early devonian lochkovian age are seen in seismic sections in the central part of the baltic basin lithuania these together with a change in subsidence pattern mark the end of the caledonian stage of basin development of the baltic basin

mechanics of the salt range potwar plateau pakistan a fold and thrust belt underlain by evaporites the salt range and potwar plateau are part of the active foreland fold and thrust belt of the himalaya in northern pakistan in this region the distance from the main boundary thrust mbt to the front of the fold and thrust belt is very wide 100 150 km because a thick evaporite sequence forms the zone of decollement recent studies have combined seismic reflection profiles petroleum exploration wells bouguer gravity anomalies and surface geology to construct cross sections in the eastern central and western salt range potwar plateau areas in this study the sections are compared with a model that considers the mechanics of a fold and thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer chapple 1978 davis et al 1983 dahlen et al 1984 dahlen 1984 models which include the effects of evaporites at the base chapple 1978 davis and engelder 1985 suggest that these thrust belts will have 1 narrow 1 cross sectional tapers 2 larger widths than areas not underlain by evaporites 3 symmetrical structures and 4 changes in deformational style at the edge of the evaporite basin the section across the eastern potwar plateau most closely resembles this latter model having 1 a taper of 0 8 0 1 2 a width of 100 150 km 3 thrust faults that verge both to the north and south and 4 structures rotated 30 counterclockwise with respect to the salt range from the observed taper and pore fluid pressures of the eastern potwar plateau estimates of the values for the yield strength of the evaporites o and the coefficient of internal friction of the overlying wedge are calculated as o 1 33 1 50 mpa and 0 95 1 04 which are then applied to the other cross sections in the central and western sections a basement uplift the sargodha high interferes with the front of the fold and thrust belt this feature causes the ramping of the salt range thrust and produces a relatively steep basement slope 2 4 beneath the potwar plateau this dip in the presence of the weak evaporite decollement is sufficient to provide critical taper no topographic slope is necessary and the thrust wedge of the southern potwar plateau is pushed over the decollement without significant internal deformation the northern potwar plateau is strongly folded and faulted yet the topographic slope remains flat although the deformation suggests that evaporites are not present there the observed taper in the northern potwar plateau is best fitted by the model with evaporites at the decollement combining this with published paleomagnetic and geologic constraints a model for the evolution of the northern potwar plateau suggests that the area deformed as a steeply tapered 3 5 5 5 thrust wedge until approximately 2 million years ago when the southward propagating decollement encountered the evaporites between 2 ma and the present the northern potwar plateau has been pushed along the salt decollement without deformation and erosion has reduced its original steep topographic slope to a nearly level surface

mechanism of thin skinned detachment in the amazon fan assessing the importance of fluid overpressure and hydrocarbon generation abstract since about 10 ma a wedge of clastic sediment up to 10 km in thickness has accumulated near the mouth of the amazon river forming the amazon fan thin skinned extensional and contractional structures root into a common basal detachment hundreds of kilometers long extensional faults have formed landward of the prograding delta slope and contractional folds and faults have formed seaward of it by plan view restoration we show that extension and contraction balance we therefore infer that slope instability has provided the driving force for thin skinned deformation on seismic data the detachment appears as a sharp surface within late cretaceous strata however there is no evidence at that level for soft layers such as evaporites or muds abnormal fluid pressure provides a more reasonable mechanism for the detachment at depths of several thousand meters deep wells have encountered fluid overpressures amongst the possible causes of abnormal fluid pressures are compaction and hydrocarbon generation although compaction may have contributed to fluid overpressures encountered in wells we argue that hydrocarbon generation provides the best explanation for detachment in cretaceous rocks which were old and lithified when it occurred in particular the broadly triangular area of detachment coincides with an inferred pod of cenomanian turonian source rock which is interpreted to have been in the gas window during detached deformation we have developed new techniques of sandbox modelling to investigate the geometries of fault patterns produced by fluid flow through porous media for the amazon fan we have been able to reproduce the structural pattern on the assumption that fluid overpressures existed over a broadly triangular area beneath the detachment

echo source discrimination in single pass airborne radar sounding data from the dry valleys antarctica implications for orbital sounding of mars the interpretation of radar sounding data from mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface this can be accomplished through the identification of all radar returns from the surface in order to positively identify subsurface echoes we have developed general techniques for this using airborne radar data from the dry valleys of antarctica these data were collected in a single pass including taylor glacier ice covered lake bonney and an ice free area of taylor valley the pulsed radar 52 5 67 5 mhz was coherently recorded our echo discrimination techniques included a radar simulator using a digital elevation model dem to predict the location and shape of surface echoes in the radar data real and simulated echo strengths were used to calculate a signal to clutter ratio this was complemented by the cross track migration of radar echoes onto the surface these migrated echoes were superimposed on the dem and imagery in order to correlate with surface features using these techniques enabled us to identify a number of echoes in the radar data as arising from the surface and to identify subsurface echoes including a continuous reflector under the main trunk of taylor glacier and multiple reflectors beneath the terminus of taylor glacier surface based radar confirms the thickness of the glacier at three crossing points the results illustrate the importance of using complementary techniques the usefulness of a dem and the limitations of single pass radar sounding data

devonian cretaceous repeated subsidence and uplift along the teisseyre tornquist zone in se poland insight from seismic data interpretation abstract the teisseyre tornquist zone that separates the east european craton from the palaeozoic platform forms one of the most fundamental lithospheric boundaries in europe devonian to cretaceous paleogene evolution of the se segment of this zone was analyzed using high quality seismic reflection data that provided detailed information regarding entire palaeozoic and mesozoic sedimentary cover with particular focus on problems of late carboniferous and late cretaceous paleogene basin inversion and uplift two previously proposed models of development and inversion of the devonian carboniferous lublin basin seem to only partly explain configuration of this sedimentary basin a new model includes late devonian early carboniferous reverse faulting within the cratonic area ne from the kock fault zone possibly first far field effect of the variscan orogeny this was followed by late carboniferous inversion of the lublin basin inversion tectonics was associated with strike slip movements along the ursynow kazimierz fault zone and thrusting along the kock fault zone possibly triggered by deeper strike slip movements late carboniferous inversion related deformations along the ne boundary of the lublin basin were associated with some degree of ductile quasi diapiric deformation facilitated by thick series of silurian shales during mesozoic extension and development of the mid polish trough major fault zones within the lublin basin remained mostly inactive and subsidence centre moved to the sw towards the nowe miasto zawichost fault zone and further to the sw into the present day holy cross mts area late cretaceous paleogene inversion of the mid polish trough and formation of the mid polish swell was associated with reactivation of inherited deeper fault zones and included also some strike slip faulting the study area provides well documented example of the foreland plate within which repeated basin inversion related to compressive transpressive deformations was triggered by active orogenic processes at the plate margin i e variscan or carpathian orogeny and involved important strike slip reactivation of crustal scale inherited fault zones belonging to the teisseyre tornquist zone

fault related folding a review of kinematic models and their application abstract folding that is directly related to fault activity is an important deformation feature that occurs all over the world in mountain belts accretionary wedges fold and thrust belts and intra plate settings in either strike slip compressional or extensional regimes due to their widespread occurrence knowledge about the development of these structures is important to a broad spectrum of geoscience sub disciplines such as structural geology seismology geomorphology petroleum geology and quaternary geology fault related folding has been analyzed intensively over the last 140 years for the sake of this review we divide the folds according to the way the faults and the folds form that is into detachment fault bend and fault propagation folds all fault related folds are caused by changes in fault parameters the simplest method to produce folds is to transport material along faults that have stepped flat ramp flat geometries fault bend fold alternatively the slip can decrease along the length of the fault and depending on whether the fault remains within a detachment layer or steps up through mechanical stratigraphy either a detachment fold or a fault propagation fold is formed respectively detachment folding was first investigated in the early 20th century whereas the full significance of fault propagation folds was recognized quite late in the 1980s seminal work on fault related folding was carried out in the 1930s but quantitative kinematic models have only been available in the last 30 years these models are extremely valuable because they allow a comprehensive understanding of the evolution of fault related folds and lead to more accurate predictions of the sub surface structure from the mid 1990s onwards numerical simulations have been used to identify how fault parameters such as dip and fault bend angle propagation to slip ratio and shape of the trishear zone influence the geometry of the related folding this is directly applicable to the analysis of the shape of anticlines produced however this does not mean that fold geometry is uniquely related to fault geometry on the contrary different kinematic approaches can lead to a similar fold shape

detachment folding in the central and eastern zagros fold belt iran salt mobility multiple detachments and late basement control abstract detachment folding has been studied on the basis of field and subsurface examples from the central and eastern zagros iran we discuss different aspects of detachment folding well illustrated in the studied area in particular we focus on salt mobility multiple decollements and late basement control salt mobility concerns the hormuz basal detachment and the gachsaran upper detachment for the latter it is shown that mobility results not only from folding related diapirism but also from early gravity driven migration from growing anticlines towards intervening synclines concentric folding between two detachment levels is directly observed in the izeh zone central zagros where it is shown that the wave length depends on the distance between the two active decollements and that the fold shape is a function of the level of erosion throughout the zagros detachment folds mainly developed during an initial thin skinned phase of deformation which was followed by the current thick skinned stage this succession is particularly well expressed in the eastern zagros where basement faults cut early detachment folds obliquely