kinematics of a growth fault raft system on the west african margin using 3 d restoration abstract the ability to quantify the movement history associated with growth structures is crucial in the understanding of fundamental processes such as the growth of folds or faults in 3 d in this paper we present an application of an original approach to restore in 3 d a listric growth fault system resulting from gravity induced extension located on the west african margin our goal is to establish the 3 d structural framework and kinematics of the study area we construct a 3 d geometrical model of the fault system from 3 d seismic data then restore six stratigraphic surfaces and reconstruct the 3 d geometry of the system at six incremental steps of its history the evolution of the growth fault raft system corresponds to the progressive separation of two rafts by regional extension resulting in the development of an intervening basin located between them that evolved in three main stages 1 the rise of an evaporite wall 2 the development of a symmetric basin as the elevation of the diapir is reduced and buried and 3 the development of asymmetric basins related to two systems of listric faults the main fault f1 and the graben located between the rollovers and the lower raft important features of the growth fault raft system could only be observed in 3 d and with increments of deformation restored the rollover anticline associated with the listric fault f1 is composed of two sub units separated by an e w oriented transverse graben indicating that the displacement field was divergent in map view the rollover units are located within the overlap area of two fault systems and displays a mock turtle anticline structure the seaward translation of the lower raft is associated with two successive vertical axis rotations in the opposite sense clockwise then counter clockwise by about 10 this results from the fact that the two main fault systems developed successively fault system f1 formed during the upper albian and the graben during the cenomanian using a new approach of 3 d restoration this study suggests a consistent solution for 1 the processes of deformation of a fault system 2 the faulting kinematics and 3 the incremental steps of deformation

evolution of salt structures during burial of salt sheets on the slope northern gulf of mexico abstract shallow buried allochthonous salt sheets are the dominant type of salt structure along the lower slope of the northern gulf of mexico trailing landward margins of the sheets are buried during continental margin progradation while their leading edges advance basinward under thin cover during burial a series of daughter structures including stocks massifs and remnant structures evolved as the sheet was segmented by extension and differential loading during extension fault bound basins on the upper surface of the sheet initiated the growth of salt rollers some rollers matured into stocks and massifs as sediment accumulated rapidly in circular salt withdrawal basins that were localized over the initial fault bound basins lateral extension is a key mechanism in initiating salt structural evolution however simple vertical subsidence of sediments is the primary displacement mechanism where the salt is completely displaced a salt weld discontinuity identifies its former stratigraphic position a variety of structures in the eastern green canyon area have been identified overlying a neogene salt weld including remnant salt structures mature stocks massifs and sedimentary structures such as turtle structure anticlines

a deep seismic reflection profile across the nova scotia continental margin offshore eastern canada results from two deep seismic reflection lines are presented when combined these lines span the rifted continental margin off nova scotia from crust unaltered by rifting to the ocean basin these data provide crustal and upper mantle reflection geometry to depths of over 50 km and elucidate the rifting process on this margin which occurred during the mesozoic breakup of pangaea the continental crust below the continental shelf and slope becomes progressively thinner toward the ocean continent boundary in the upper crust normal faults accommodated mesozoic extension and these flatten and terminate at 5 6 s two way time in the lower crust and upper mantle mesozoic rifting may be reflected in dipping events which are interpreted to be normal faults all mesozoic extensional faulting could be controlled by the preexisting fabric of the crust which in this region would be related to appalachian compression within the meguma terrane below the continental rise there is some evidence for magmatic un

the enigma of the albian gap spatial variability and the competition between salt expulsion and extension the albian gap is a uniquely large up to 65 km wide and 450 km long enigmatic salt related structure in the santos basin offshore brazil it is located near the basin margin and trends ne i e subparallel to the brazilian coastline the gap is characterized by a near complete absence of albian strata above depleted aptian salt its most remarkable feature is an equivalently large equally enigmatic basinward dipping supra salt rollover that contains a post albian sedimentary succession that is up to 9 km thick owing to its unique geometry size and counter regional aspect the origin and evolution of the albian gap has been the centre of debate for 25 years this debate revolves around two competing models that is did it form as a result of thin skinned i e supra salt extension or progradational loading and salt expulsion the extension driven model states that the albian gap and overlying rollover formed as a result of post albian gravity driven extension accommodated by slip on a large counter regional listric normal fault the cabo frio fault conversely the expulsion driven hypothesis states that the albian gap was established earlier during the albian and that post albian deformation was controlled by differential loading vertical subsidence and basinward salt expulsion in the absence of significant lateral extension this study utilizes a large c 76 000 km2 dense 4 8 km line spacing depth migrated 2d seismic dataset that fully covers and thus permits for the first time a detailed quasi 3d structural analysis of the entire albian gap in this study we focus on 1 the evolution of base salt relief and the original salt thickness variations and 2 the geometry of the post albian rollover and its related faults and salt structures to constrain the kinematics of the albian gap and how this relates to the evolution of the base salt relief we also apply novel structural restoration workflows that incorporate flexural isostasy in addition to a detailed sequential reconstruction of the intra gap rollover sequences our results show that the geometry and kinematics of the albian gap vary along strike and that both post albian extension and expulsion play a significant role in its evolution basinward dipping growth wedges salt rollers and listric normal faults record extension whereas sigmoidal wedges halokinetic sequences and upturned near diapir flaps the latter two associated with large diapirs bounding the downdip edge of the gap record basinward salt expulsion and inflation where the albian gap is relatively wide 50 km these processes alternate and operate at approximately equal proportions our results are consistent with the amount of basinward translation inferred from the analysis of ramp syncline basins located downdip on the sao paulo plateau our results seemingly reconcile one of the longest running debates in salt tectonics as well as having more general implications for understanding the regional kinematics and dynamics of salt related structures in other salt basins in particular the controls on the development of large counter regional faults supplementary material uninterpreted versions of the seismic sections are available at https doi org 10 6084 m9 figshare c 5023088

the impact of analogue material properties on the geometry kinematics and dynamics of convergent sand wedges abstract simulation of geodynamic processes in sandbox experiments requires analogue materials with a deformation behaviour that reproduces the deformation mechanisms of typical crustal rocks we present data on the frictional strength of different sand types employing static and dynamic shear tests the sand types analysed are characterised by an elastic frictional plastic mechanical behaviour with a transient strain hardening and strain softening phase prior to transition to stable sliding this is in conflict with the standard assumption of an ideal cohesionless coulomb material with constant frictional properties the influence of the identified transient material properties on the kinematics growth mechanisms and internal deformation patterns of convergent sand wedges results in characteristic wedge segments which vary depending on material compaction between wedges with well defined segments i e frontal deformation zone frontal imbrication zone and internal accumulation zone with straight slopes and wedges with a continuous convex topographic profile for most materials only the frontal part of the wedge is critical during experimental runs taper and strength of the wedge segments can be shown to be controlled by the frictional properties of active faults wedge segmentation is controlled by a bulk strength increase toward the rear of the wedge due to fault rotation in mechanically less favourable orientations and plastic material hardening the limit between the frontal critical parts of a wedge and internal stable parts is largely controlled by a critical state of stress upon which either renewed failure or fault inactivation occurs on this basis we suggest that critical taper analysis of wedges must be restricted to specific kinematic segments comparison of the experimental results with the nankai accretionary wedge suggests that our interpretation also applies to natural convergent wedges moreover we provide constraints for the selection of adequate granular analogue materials to simulate typical crustal rocks in natural convergent wedges

salt structural styles and kinematic evolution of the jequitinhonha deepwater fold belt central brazil passive margin abstract salt structures in linked extensional contractional systems of passive margin sedimentary basins and deepwater fold belts play an important role in the evolution of rifted continental margins the 100 km wide jequitinhonha basin with its salt detached deepwater fold belt provides insight in the post rift salt deformation processes in deepwater fold belts of the central brazilian continental margin seismic interpretation and kinematic analysis of basin scale 2d sections provide insights into the salt tectonic processes related depositional systems salt basin geometry and kinematic evolution of the deepwater fold belt several salt kinematic domains have been identified the most evident is the long term contractional domain in the distal basin which formed impressive salt cored anticlines salt walls and salt massifs reaching 4 km in thickness the post rift basin evolution was dominated by thin skinned deformation and was initiated by differential loading of early post rift shallow marine carbonates subsequently the system was mainly driven by gravity gliding of the overburden on the aptian salt detachment the depocenters were controlled by early post rift salt mobilization and ranged from asymmetric grabens and rollovers to minibasins with vertically stacked or shifting depocenters and formed the basis of the deepwater fold belt architecture in the jequitinhonha basin the structural styles and kinematic evolution of the deepwater fold belt were strongly controlled by the original salt thickness the distribution of albian campanian depocenters and thickness variations in the overburden sediments early cretaceous short wavelength folds have been overprinted by long wavelength folding owing to increased strength and thickness of the overburden since paleogene times large amplitude salt cored folds developed in the deepwater basin due to contraction of pre existing salt walls and formed margin parallel nnw sse trending narrow structural highs separated by wide depocenters ongoing uplift with reduced sediment accumulation over contractional diapirs or crestal erosion of the deepwater anticlines supported long term strain localization and positive feedback in the active deepwater contractional deformation

raft tectonics the effects of basal slope angle and sedimentation rate on progressive extension abstract in the gulf of guinea the upper cretaceous tertiary sedimentary cover has undergone gravity gliding above an aptian salt layer for various basal slope angles from 0 to 4 gliding started during albian time and evolved up to the present with variable sedimentation rates faulting patterns are seen to vary in particular as a function of the basal slope angle and the syn kinematic sedimentation rates a series of laboratory experiments on small scale models is used to study the effects of the two parameters mentioned above models are composed of two layer slabs with newtonian silicone putty at the base to represent a basal salt decollement and dry sand on top to represent the sedimentary overburden models are allowed to deform under their own weight for various basal slope angles ranging from 0 to 5 with two different syn kinematic sedimentation rates it is shown that the basal slope angle controls the location of faulting in the overburden within a single downslope deformation domain for values smaller than 2 and within two domains lying downslope and upslope for higher values of the width of the deformation domains also varies as a function of overburden faulting always starts with syn kinematic grabens which evolve into symmetric or asymmetric grabens or into tilted blocks bounded by listric normal faults while synthetic listric normal faults characterize the downslope deformation domains both synthetic and antithetic listric normal faults can occur in the upslope deformation domain ductile deformation within the basal decollement layers results from variable combinations of pure shear and simple shear interaction of ductile deformation in the ductile decollement layer with faulting in the overburden locally produces complex and heterogeneous strain patterns notably within salt rollers finally increasing rates of syn kinematic sedimentation are seen to increase the rate of downslope displacement and to enhance and favour the development of listric normal faults

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

a systematic technique for the sequential restoration of salt structures abstract a method is described for the sequential restoration of cross sections in areas of salt tectonics where deformation is confined to the salt and higher layers the subsurface geometry evolves with time through the interaction of various processes sedimentation compaction isostatic adjustment thermal subsidence if present faulting and salt withdrawal diapirism the technique systematically calculates and removes the effects of each of these processes during specified time intervals defined by the interpreted horizons it makes no assumptions about salt kinematics and generally results in the area of the salt layer changing through time the method is described for restoration of extensional terranes but it is also suitable for areas of contractional salt tectonics with only minor modifications after converting an interpreted seismic profile to depth the top layer is stripped off and the underlying section is decompacted according to standard porosity depth functions a deep baseline unaffected by compaction or deformation is used to restore any isostatic compensation or thermal subsidence isostasy is calculated according to the airy model and differential sedimentary loading across a section is shown to be approximately balanced by changes in salt thickness so that the load is evenly distributed after these processes have been reversed the resulting geometry and the seismic data are used to create the sea floor template for structural restoration fault offsets are removed and the layers down to the top salt are restored to this template while the base salt remains fixed the resulting space between the restored top salt and the fixed base salt defines the restored salt geometry in addition the difference between the sea floor template and a fixed sea level provides a measure of the change in water depth ignoring eustatic changes in sea level the technique is applied to an interpreted seismic profile from the eastern green canyon ewing bank area of offshore louisiana the section is characterized by a variety of salt structures including salt rollers a diapiric massif a remnant salt sheet and a salt weld which are shown to have derived from an originally continuous salt sheet which has been modified by sedimentary loading early loading created vertical basin growth that was accommodated primarily by salt withdrawal and associated diapiric rise through the process of downbuilding once the salt weld formed continued sedimentation was accommodated by a lateral increase in basin size caused by down dip extension on listric growth faults

advanced strain and mass transfer analysis in crustal scale oroclinal buckling and detachment folding analogue models abstract the piv particle image velocimetry method became a standard tool for the calculation of displacement fields in physical geodynamic models for understanding the deformation dynamics of geodynamic models in our study we implemented several post processing algorithms on the derived displacement field and calculated the velocity and strain rate components such as the divergence of the velocity field vorticity and shear strain rate in the model of oroclinal buckling we focused on strain analysis of the upper crust and correlated the shear strain rate vorticity and divergence anomalies with visual deformation patterns in the upper crust the divergence of velocity fields in these models correspond to the pop up and pop down belts oriented along the axial trace of the oroclinal bends high shear strain rate domains correlate with horizontal isovolumic shear zones alongside these belts while vorticity shows rotational trend of fold axial traces of the pop up and pop down belts around orocline inflection in another series of models we simulated the development of melt cored crustal scale detachment folds and employed the same set of parameters to investigate the ductile deformation visible in side view of the model domain we developed a method that allows tracing the divergence in subcells locked on target subdomains we tracked and quantified melt flow between the melt source area at the bottom of the model and progressively developing folds this mass transfer analysis revealed polyphase fold evolution where initial fold perturbations quickly amplify as the melt accumulates in the triangular hinge sector below and between the rotating fold limbs while the early amplification leads to decompression driving the melt into the hinge zone area between the limbs the fold lock up stage and continued attenuation of the vertical limbs is associated with melt expulsion from the fold interlimb domain back into the source layer where it can be transferred laterally to the foreland

radial gravitational gliding on passive margins abstract gravitational gliding of uppermost sediments down a passive margin is possible if there is a basal layer of evaporite or other soft material to allow detachment in examples from the gulf of mexico and the brazilian margin gliding has produced three main structural domains an uppermost domain of downdip extension an intermediate domain of rigid gliding and a lowermost domain of downdip contraction domain boundaries are established by changes in slope in this paper we examine three kinds of gravitational gliding depending on the paths followed by material particles in ideal parallel gliding particle paths are parallel straight lines trending downslope this should occur where the margin is perfectly straight in ideal radial gliding particle paths are radii of a circle and the margin is shaped like a circular cone natural margins will not have ideal shapes but divergent gliding will tend to occur off coastal salients convergent gliding off coastal re entrants a simple kinematic model based on ductile behaviour illustrates some essential features of radial gliding changes in radius during divergent gliding produce strike parallel extension during convergent gliding they produce strike parallel contraction vertical strains also differ divergent gliding produces an uppermost domain of strong vertical thinning balanced by extensions in all horizontal directions similarly convergent gliding produces a lowermost domain of strong vertical thickening balanced by contractions in all horizontal directions these deformed states cannot be restored by simple techniques based on section balancing we have done three experiments using analogue materials sand to model the brittle behaviour of sediments silicone putty to model the ductile behaviour of basal layers of evaporite the experiments were properly scaled to account for gravitational forces experiment i reproduced convergent gliding above a basement with a conical upper surface strike parallel contraction was responsible for radial folds on the lower slopes the lowermost domain had a complex fold pattern indicating contraction in all horizontal directions experiment 2 reproduced divergent gliding above a basement with a pyramidal upper surface strike parallel extension produced radial rifts on the upper slopes the uppermost domain had a complex polygonal pattern of normal faults indicating extension in all horizontal directions experiment 3 also reproduced divergent gliding but due to non uniform sediment thickness we have examined the many seismic profiles both downdip and alongstrike available for the brazilian margin alongstrike profiles show structures which we attribute to strike parallel strains around the santos re entrant syn sedimentary growthfolds indicate strike parallel contraction increasing downslope this argues for a mechanism of convergent gliding in contrast around the campos salient normal growth faults and associated salt rollers indicate strike parallel extension decreasing downslope this argues for a mechanism of divergent gliding the pattern of oil fields in the campos area including the giant marlim field seems to be closely controlled by divergent gravitational gliding and associated processes radial gliding should occur on other passive margins as well especially where the coastline is sinuous structures around the western gulf of of mexico seem to indicate convergent gliding at the scale of the entire gulf structures at a smaller scale around the mississippi delta seem to indicate divergent gliding

tectono sedimentary evolution and petroleum systems of the mundau subbasin a new deep water exploration frontier in equatorial brazil the brazilian equatorial margin bem evolved in response to transform motion between brazil and africa in 2012 petrobras drilled the pecem well in the mundau subbasin ceara basin of the bem to record the first deep water oil discovery in the region this work investigates the deep water evolution of the mundau subbasin focusing on its structural and sedimentary evolution and characterizes the petroleum systems in this new exploration frontier for such purposes poststack seismic reflection borehole and geochemical data were used three tectono stratigraphic sequences representing synrift mundau formation transitional paracuru formation and drift strata ubarana formation were divided into seven seismic units different tectonic domains were interpreted proximal distal and romanche fracture zone typical structures of transform margins such as marginal ridges and marginal plateaus were not identified in the mundau subbasin instead the subbasin was predominantly deformed by transtensional movements the mundau and paracuru formations are mature within the oil window whereas the ubarana formation is immature main reservoir intervals consist of approximately 1 m 3 28 ft thick intercalations of sandstone between shales siltstones and marls the seal rocks comprise shales in the ubarana formation whereas the hydrocarbon trap is related to an unconformity and a normal fault this work concludes that the paracuru formation is the main source and reservoir in the deep water mundau subbasin effectively comprising a paracuru paracuru petroleum system the results have significant implications for petroleum exploration in the bem by proposing a developed transitional petroleum system in the distal parts of northeastern brazil

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

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

listric versus planar normal fault geometry an example from the eisenstadt sopron basin e austria in a gravel pit at the eastern margin of the eisenstadt sopron basin a satellite of vienna basin austria neogene sediments are exposed in the hanging wall of a major normal fault the anticlinal structure and associated conjugated secondary normal faults were previously interpreted as a rollover anticline above a listric normal fault the spatial orientation and distribution of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall subsequently in order to assess the 3d distribution and geometry of this fault system a series of parallel ground penetrating radar gpr profiles were recorded behind the outcrop wall both outcrop and gpr data were compiled in a 3d structural model providing the basis for a kinematic reconstruction of the fault plane using balanced cross section techniques however the kinematic reconstruction results in a geologically meaningless normal fault cutting down and up section additionally no evidence for a weak layer serving as ductile detachment horizon i e salt or clay horizon can be identified in stratigraphic profiles instead the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master fault with a maximum displacement in the fault centre decreasing towards the fault tips accordingly the observed deflection of markers in the hanging wall and in a nearby location in the footwall of the normal fault is interpreted as large scale fault drag along a planar fault that records a displacement gradient instead of a rollover anticline related to a listric fault

growth fault rollover systems birth growth and decay growth fault rollover systems are extremely common structures of thin skinned extensional systems resulting from gravity gliding above salt their development is studied using laboratory experiments based on brittle ductile models where the sedimentary cover and synkinematic sediments are simulated using brittle sand and the underlying decollement layer by viscous silicone putty the experiments are compared to natural examples from seismic lines the experimental results are used to present the evolution of growth fault rollover systems these being the result of a finite amplitude instability with three distinct stages birth growth and decay each of these stages is identified with typical structures which can be recognized on seismic sections a discussion is presented on the interactions in time and space between synthetic and antithetic listric faults parallel and transverse to the direction of displacement

allochthonous salt structure and stratigraphy of the north eastern gulf of mexico ii structure the kinematic evolution of allochthonous salt in the north eastern gulf of mexico proceeds in three stages 1 since its middle jurassic deposition the louann salt was loaded by sediments causing episodic basinward movement of salt ultimately leading to large concentrations of salt masses in a slope environment by the end of the lower cretaceous 2 a regime of starved sedimentation during late cretaceous and early oligocene is responsible for the stabilization of these early salt accumulations 3 with renewed rapid accumulation of sediments during the neogene and pliocene extensive allochthonous salt tongues and sheets formed by gravity spreading within the younger sediments of the slope

kar systematics of clay to mica minerals in a multi stage low grade metamorphic evolution the behavior of the ar isotopic system of clay to mica fractions was studied in cambrian greywacke samples along a transect of northwestern morocco these rocks were affected by a progressively increasing metamorphic overprint spanning from diagenetic to epizonal metamorphic conditions k ar isotopic data of 0 2 10 m size fractions recovered from seven samples allowed to recognized three episodes of illite crystallization 1 during an upper ordovician thermal event at 445 ma which is characterized by an illite chlorite mineral paragenesis in the northernmost part of the transect 2 during a carboniferous low grade overprint at 305 ma which is characterized by a similar mineral paragenesis and 3 during a triassic to liassic hydrothermal activity at 205 ma which generated a smectite dominated paragenesis the ages were examined in combining x ray mineralogic and k ar isotopic data in terms of linear arrays in both isochron and harper diagrams to differentiate true isochrons from mixing lines it could also be shown that mixtures of two generations of micaceous minerals can induce different trends in the k ar dates depending whether the first generation of minerals was either or not affected by the event inducing the later generation

quantitative 3d strain analysis in analogue experiments simulating tectonic deformation integration of x ray computed tomography and digital volume correlation techniques abstract the combination of scaled analogue experiments material mechanics x ray computed tomography xrct and digital volume correlation techniques dvc is a powerful new tool not only to examine the 3 dimensional structure and kinematic evolution of complex deformation structures in scaled analogue experiments but also to fully quantify their spatial strain distribution and complete strain history digital image correlation dic is an important advance in quantitative physical modelling and helps to understand non linear deformation processes optical non intrusive dic techniques enable the quantification of localised and distributed deformation in analogue experiments based either on images taken through transparent sidewalls 2d dic or on surface views 3d dic x ray computed tomography xrct analysis permits the non destructive visualisation of the internal structure and kinematic evolution of scaled analogue experiments simulating tectonic evolution of complex geological structures the combination of xrct sectional image data of analogue experiments with 2d dic only allows quantification of 2d displacement and strain components in section direction this completely omits the potential of ct experiments for full 3d strain analysis of complex non cylindrical deformation structures in this study we apply digital volume correlation dvc techniques on xrct scan data of solid analogue experiments to fully quantify the internal displacement and strain in 3 dimensions over time our first results indicate that the application of dvc techniques on xrct volume data can successfully be used to quantify the 3d spatial and temporal strain patterns inside analogue experiments we demonstrate the potential of combining dvc techniques and xrct volume imaging for 3d strain analysis of a contractional experiment simulating the development of a non cylindrical pop up structure furthermore we discuss various options for optimisation of granular materials pattern generation and data acquisition for increased resolution and accuracy of the strain results three dimensional strain analysis of analogue models is of particular interest for geological and seismic interpretations of complex non cylindrical geological structures the volume strain data enable the analysis of the large scale and small scale strain history of geological structures

allochthonous salt structure and stratigraphy of the north eastern gulf of mexico part ii structure abstract the kinematic evolution of allochthonous salt in the north eastern gulf of mexico proceeds in three stages 1 since its middle jurassic deposition the louann salt was loaded by sediments causing episodic basinward movement of salt ultimately leading to large concentrations of salt masses in a slope environment by the end of the lower cretaceous 2 a regime of starved sedimentation during late cretaceous and early oligocene is responsible for the stabilization of these early salt accumulations 3 with renewed rapid accumulation of sediments during the neogene and pliocene extensive allochthonous salt tongues and sheets formed by gravity spreading within the younger sediments of the slope autochthonous salt allochthonous salt and detached allochthonous salt are typical stages of evolution major down to the basin growth faults separate allochthonous salt sheets from their original feeder stocks extension along down to the basin master growth faults is compensated mainly by salt withdrawal and partly by basinward shortening

timing of biogenic gas formation in the eastern qaidam basin nw china abstract quaternary biogenic gas from the qaidam basin nw china is regarded as one of the representative examples of early generation biogenic gas gases formed by microbial activity during sedimentation of source rocks however new age determinations of natural gas and formation waters make this generally accepted assumption questionable gas in the qaidam basin is dominantly methane 99 0 and has 13 c ch 4 values in the range of 68 to 65 reflecting the microbial origin carbon and hydrogen isotope values of methane coupled with carbon isotope values of carbon dioxide and dissolved inorganic carbon dic reflect water derived hydrogen in the methane and a dominant co 2 reduction metabolic pathway for the formation of biogenic methane coproduced formation waters have hydrogen and oxygen isotope values similar to surface water from the golmud and ortmuren rivers t test 0 75 but different from the original formation water t test 1 sequence around 1 35 ma bp this corresponds to a regional uplift erosion and water influx event economic accumulations of biogenic gas were thus most likely generated late in the qaidam basin rather than at the same time as sediment deposition fresh water recharge may be critical to enhancing biogenic methane generation by introducing nutrients and or microbes into the reservoir

model for salt deformation on deep margin of central gulf of mexico basin based on available nonexclusive seismic data a preliminary model has been developed for salt deformation on the deep margin of the central gulf of mexico basin in this model the tertiary clastic wedge prograded to the basinward limit of original jurassic salt by the middle miocene as the salt and overburden thinned basinward lateral flow combined with a strong component of downward force exerted by subsiding voluminous middle miocene loading caused the basinward limit of the louann salt to effectively shear off deposition of the upper miocene and pliocene sediments was confined primarily shoreward of an incipient salt swell but pleistocene sediments were eventually able to breach the barrier deformation of the detached salt produced the features present on the slope today preliminary work indicates that most of the detached salt was propelled basinward and upsection toward the present sigsbee escarpment leaving pinch and swell salt structures behind the various types of residual salt structures have been formed as a result of differences in the history of sedimentary loading different stages of development of pinch and swell structures shown on seismic sections illustrate this model

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

implications of salt sediment interactions on the architecture of the gulf of lions deep water sedimentary systems western mediterranean sea we integrated structural analysis of multichannel seismic data and isopach maps of the quaternary sedimentary cover to evaluate how salt tectonics has influenced the stratigraphic evolution offshore the gulf of lions the interplay between salt tectonics and sedimentation occurs at two scales at local scale listric normal faults create bathymetric relief able to deviate sediment transport axes with implications on depocenters configuration at depocenter scale overburden vertical movements due to salt evacuation or salt diapiric rise create sub basins providing accommodation space for clastic deposition these mechanisms have significant implications on the architecture and the internal organization of turbidite systems offshore the gulf of lions

listric normal faults an illustrated summary movement along listric normal faults is instrumental in formation of several types of structural traps e g rollover anticlines and upthrown fault block closures this type of fault may occur where brittle rocks overlie ductile rocks in an extensional regime the extensional regime may be locally derived within a broader stress regime of another type as evidenced by transtension associated with strike slip movement and arched strata in a compressive setting the flattening of the fault reflects an increase in ductility of the rocks with depth and in some cases deformation of the fault due to compaction or tilting of the upthrown block the dip angle may vary along the strike of the fault in response to changes in throw in cross section a listric fault may consist of relatively short en echelon fault segments this geometry may be particularly characteristic of growth faults sedimentary faults may sole in ductile strata or they may represent the brittle part of a fault flow system fault patterns commonly are characterized by bifurcation some of which may occur near the ends of individual faults comprising a zone although unequivocal recognition of listric normal faults requires unusually extensive outcrop data close subsurface control or high quality seismic data their presence is suggested indirectly by such features as increasing dip either depth toward the controlling fault reverse drag thick progradational sandstone overlying ductile strata and in some cases arcuate fault patterns basins or uplifts listric normal faults form during rifting drifting and evolution of passive continental margins with concomitant basinal development the basement is offset by listric faults as a fundamental element in the development of other types of basins including those which formed during postorogenic extension they also occur as secondary extensional features in an overall compressive stress regime due to plate convergence and during transform or strike slip faulting modified journal abstract

identifying fault segments from 3d fault drag analysis vienna basin austria abstract the segmented growth of the markgrafneusiedl normal fault in the late miocene clastic sediments of the central vienna basin austria was investigated by construction of a detailed three dimensional 3d structural model using high resolution 3d seismic data the fault surface and marker horizons in the hanging wall and the footwall of the markgrafneusiedl fault were mapped and orientation displacement and morphology of the fault surface were quantified individual fault segments were identified by direct mapping of the deflection of the marker horizons close to the fault surface correlating the size of the identified segments with the magnitude of fault drag and displacement distribution showed that fault evolution progressed in several stages the proposed method allows the detection of segments that are not recorded by the magnitude of displacement or fault morphology most importantly detailed mapping of marker deflections in the hanging wall could help to constrain equivalent structures in the footwall which may represent potential hydrocarbon traps

salt flow by aggrading and prograding overburdens the mechanisms responsible for segmentation of salt sheets and their emplacement into higher stratigraphic levels are not separable and act simultaneously three sets of centrifuge models with strongly planar anisotropic anisotropy the ratio between the effective viscosities in pure and simple shear ranging between 4 8 and 16 4 microlaminate overburdens are used to study the effect of aggradation and progradation on segmentation and emplacement of allochthonous salt sheets in the first set of models a tabular buoyant source layer was overlain by tabular anisotropic overburden simulating aggradation during centrifuging the underlying ductile source layer was segmented into individual wall like diapirs by the subsiding blocks formed due to extension and faulting of the overburden the extensional zone in these models started at the spreading edge free face of the model and migrated backwards in the second set of models a tabular buoyant source layer was overlain successively by wedges of anisotropic overburdens simulating progradation during centrifuging the buoyant layer was displaced from the back of the model where loading was higher towards the free face in the front of the model where overburden units were thinner overburden units extended at the back and the middle of the model while contractional structures dominated at the front where asymmetric diapirs formed overhangs that spread basinward to form salt sheets in the third set of models a wedge shaped buoyant source layer was overlain successively by wedges of anisotropic overburden simulating progradation the overburden wedge created a lateral pressure gradient ranging from 144 pa at the back of the model to 80 pa at the front when deformed in the centrifuge in these models as in the second set of models the underlying buoyant mass was displaced basinward by the subsiding thicker overburden units at the back of the model contractional structures dominated the deformation at the leading edge of the wedge comparison of model results suggests that progradation as in the second and third sets of models loads underlying salt differentially displaces it downdip and segments it as it segments at the back the salt flows laterally to areas of lower loading by intruding through the thinner overburden units and forming secondary salt sheets at the front on the other hand aggradation of uniform overburden segments a buoyant sheet into two dimensional salt walls or stocks as in the first set of models