seismic reflection profiles across the southern dead sea basin abstract the main structural and stratigraphic elements that form the southern dead sea basin sdsb which is part of the dead sea transform fault system have been broadly delineated with various degrees of certainty by a number of researchers the recent exchange of seismic data between israel and jordan enable us to fill in some of the dashed lines and eliminate some of the question marks that appear on the previously published geological cross sections two east west seismic time sections one from each side of the international border that dissect the basin have been selected composed and interpreted a remarkable correlation of the three major sedimentary sequences that form the basin fill miocene clastics pliocene salt and pleistocene holocene clastics and evaporites has been established between the lines and hence across the entire width of the sdsb the miocene and pliocene series are cut off in the east by the ghor safi fault that is the equivalent of the western sedom fault thus indicating that all three major structural steps known to exist in the west 1 rim block 2 intermediate block and 3 deep block occurs also in the east and that the sdsb is indeed a full graben the ghor safi fault is the northern extension of the major arava strike slip fault the very thin miocene if at all and lack of pliocene salt in the eastern intermediate block unlike the western one suggests that the ghor safi fault was initiated earlier then the sedom fault salt is present over the entire width of the basin but does not exceed the 900 m that were penetrated by the sedom deep 1 borehole the salt is conformable with the overlying thick pleistocene and except for the sedom diapir no halokinesis phenomena have been recognized to be associated with both units

evolution of the mount woods inlier northern gawler craton southern australia an integrated structural and aeromagnetic analysis structural mapping integrated with interpretation and forward modelling of aeromagnetic data form complimentary and powerful tools for regional structural analysis because both techniques focus on architecture and overprinting relationships this approach is used to constrain the geometry and evolution of the sparsely exposed mount woods inlier in the northern gawler craton the mount woods inlier records a history of poly phase deformation high temperature metamorphism and syn and post orogenic magmatism between ca 1736 and 1584 ma the earliest deformation involved isoclinal folding and the development of bedding parallel and axial planar gneissic foliation s1 this was accompanied by high temperature upper amphibolite to granulite facies metamorphism at ca 1736 ma during subsequent north south shortening d2 open to isoclinal south southeast oriented f2 folds developed as the palaeoproterozoic successions of the inlier were thrust over the archaean nuclei of the gawler craton the syn d2 engenina adamellite was emplaced at ca 1692 ma the post d2 history involved shear zone development and localised folding exhumation of metamorphic rocks and deposition of clastic sediments prior to the emplacement of the ca 1584 ma granite balta suite the mount woods inlier is interpreted as the northern continuation of the kimban orogen

nature of the continent ocean transition on the non volcanic rifted margin of the central great australian bight a region of 50 120km width defines the continent ocean transition cot in the central great australian bight it is characterized by a thin apron of post break up sediments overlying complexly deformed sediments and intruded crust bounded landward by a basement ridge complex and oceanward by rough oceanic basement recently acquired deep reflection and refraction seismic data have significantly enhanced understanding of the cot and basement ridge modelled gravity and magnetic data and features interpreted from seismic data are consistent with aspects of extensional and break up models proposed for the west iberia margin many of the features and relationships observed beneath the outer margin of the central great australian bight can be explained by extension within a lithosphere scale pure shear environment involving four layers brittle upper crust and upper mantle and ductile lower crust and lower lithospheric mantle the cot is interpreted to be underlain by extended continental lithosphere thus the continentocean boundary is unequivocally defined between oceanic crust and the cot and appears to be associated with sea floor spreading magnetic anomaly 33 indicating that break up and sea floor spreading did not commence until c 83 ma early carnpanian time later than the currently accepted 95ma age the major part of the basement ridge complex is probably a combination of serpentinized peridotites and mafic intrusions or extrusions derived by mantle upwelling and limited partial melting the magmatic products of this process probably cooled during chron 34 producing a distinctive magnetic anomaly but one that does not relate to break up and sea floor spreading

geophysical testing of balanced cross sections of fold thrust belts with potential field data an example from the fleurieu arc of the delamerian orogen south australia abstract the delamerian south australia and ross antarctica orogens once formed a continuous chain along the paleo pacific margin of gondwana correlations between the two are based on many characteristics including style of shortening and deformation constraining structural features in one of these orogens impacts on interpretations of tectonic processes for the other balanced cross sections have provided crucial information on the internal architecture of the delamerian orogen south australia and form a key piece of evidence in some widely circulated models for the deformational style these sections have not been constrained by geophysical investigations which can provide significant information about the subsurface geometry we present magnetic forward models for two balanced cross sections of the fleurieu arc in the delamerian orogen the forward models require a larger volume of magnetic basement at shallower depths than predicted by balanced sections requiring a revision of currently proposed shortening mechanisms the shortening mechanism inferred from the models requires less imbrication of upper crustal units and more folding above thrusts that involve both basement and cover sequences this style of shortening compares favorably with published observations from the ross orogen in antarctica

physical modeling of sedimentation adjacent to diapirs and comparison with late precambrian oratunga breccia body in central flinders ranges south australia the interaction of sedimentation with the change in shape of a developing diapir is modeled in a series of simple sandbox experiments this model replicates the pillow diapir and postdiapir stages of salt movement modeling produced rim synclines crestal unconformities and turtle structure anticlines all features known to be associated with diapirs by changing experimental parameters such as diapir shape sedimentation was simulated around various diapiric situations one experiment closely matches the sediment distribution around the oratunga diapir one of the controversial breccia bodies in the late precambrian cambrian adelaide geosyncline exposed in the flinders ranges of south australia rim synclines unconformities and bedding attitude around oratunga resemble those described around salt domes in addition the distribution size orientation and lithology of breccia within the oratunga diapir resemble breccia associated with active salt diapirs in iran these data suggest the breccia was emplaced as a salt diapir

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

extensional salt tectonics in a contractional orogen a newly identified tectonic event in the spanish pyrenees a new coniacian early santonian extensional salt tectonics event has been identified in the cotiella thrust sheet of the central spanish pyrenees we present a new interpretation of the cotiella thrust system and describe exceptional outcrop examples of postrift gravity driven extensional growth faults the thrust sheet contains three kilometer scale extensional faults with as much as 5 5 km of coniacian lower santonian growth strata in their hanging walls these postrift listric growth faults detached on the prerift triassic evaporites on the uplifted and eroded southern flanks of early cretaceous rift basins early alpine late santonian maastrichtian contractional deformation reactivated and reversed the displacement on both the early cretaceous rift faults and some of the postrift salt detachment faults hanging walls of the listric growth faults deformed into major antiforms but the original extensional geometries are well preserved continued alpine shortening incorporated these reactivated extensional fault systems into the thin skinned thrust sheets of the southern pyrenees these postrift extensional structures account for significant thickness variations in the postrift succession and for along strike changes in the styles of the thrust structures the late cretaceous extensional salt tectonics is interpreted to result from gravity induced northward sliding on the early cretaceous rift margin toward the axis of the rift basin the listric growth faults are similar to those found on the gulf of mexico margin in the southern north sea and the south atlantic margins

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

3d structural model of the polish basin abstract a 3d structural modelling of the permian mesozoic polish basin was performed in order to understand its structural and sedimentary evolution which led to basin maturation permian cretaceous and its tectonic inversion late cretaceous paleogene the model is built on the present day structure of the basin and comprises 13 horizons within the permian to quaternary rocks the analysis is based on 3d depth views and thickness maps the results image the basin scale symmetry the perennial localization of the nw se oriented basin axis the salt movements due to tectonics and or burial and the transverse segmentation of the polish basin from these observations we deduce that salt structures are correlated to the main faults and tectonic events from the model analysis we interpret the stress conditions the timing and the geometry of the tectonic inversion of the polish basin into a nw se oriented central horst mid polish swell bordered by two lateral troughs emphasis is placed on the zechstein salt considering its movements during the mesozoic sedimentation and its decoupling effect during the tectonic inversion moreover we point to the structural control of the paleozoic basement and the crustal architecture teisseyre tornquist zone on the geometry of the polish basin and the mid polish swell

structure and origin of the fleurieu and nackara arcs in the adelaide fold thrust belt south australia salient and recess development in the delamerian orogen abstract the regional map pattern of structural trends in the early paleozoic adelaide fold thrust belt of south australia resembles an upright letter s in general structures in the fold thrust belt verge toward the gawler craton to the west so the northern curve nackara arc of the s is a salient whereas the southern curve fleurieu arc is a recess the map view axial trace of the nackara arc coincides with the thickest portion of the adelaidean late proterozoic basin and the map view axial trace of the fleurieu arc coincides with the intersection between the adelaidean and kanmantoo cambrian basins our structural analysis of the adelaide fold thrust belt demonstrates that the cross sectional structural geometry of the nackara arc contrasts markedly with that of the fleurieu arc in the nackara arc the belt consists of open detachment folds that probably formed above an evaporite hosted decollement whereas in the fleurieu arc the belt consists of an imbricate fan of basement involved thrusts further the foreland edge of the nackara arc coincides with a blind ramp whose strike parallels fold axes of the arc whereas the foreland edge of the fleurieu arc coincides with emergent thrusts that cut obliquely across earlier formed folds of the arc in the transition region between the two arcs the fold thrust belt consists of an intensely sheared basal duplex overlain by open folds structural contrasts between the nackara and fleurieu arcs indicate that the two curves did not form in the same way we present a model for development of these curves based on a comparison of their structural features to those of curves in other fold thrust belts and based on previous studies of curve formation using sandbox analogs we suggest that curvature of the nackara arc reflects the control of basin stratigraphy on the width of a fold thrust belt while curvature of the fleurieu arc reflects oroclinal bending of the fold thrust belt when it impinged on the southeastern corner of the gawler craton our model explains the structural contrast between the two arcs and illustrates correlations between fold thrust belt curve formation and pre deformational basin geometry

sedimentary thickness variations and deformation intensity during basin inversion in the flinders ranges south australia abstract the central and northern parts of the adelaide fold belt in the flinders ranges south australia consist of a sequence of neo proterozoic cambrian sediments overlying a meso proterozoic basement complex both of which were mildly deformed in an intracratonic setting during the 500 ma delamerian orogeny the fold belt lies within a prominent heat flow anomaly average heat flows of 90 mwm 2 reflecting extraordinary enrichments in heat producing elements in the meso proterozoic basement suggesting that anomalous thermal regimes may have been significant in localising delamerian deformation however spatial variations in deformation intensity correlate more closely with variations in the thickness of the sedimentary sequence than with observed variations in heat flow suggesting that the thickness of the sedimentary blanket plays a crucial role in localising delamerian deformation during basin inversion we use simple numerical models of lithospheric strength to investigate the potential role of sedimentary thickness variations on the distribution and style of deformation focussing on the impact of a variable thickness sediment pile deposited above a radioactive basement we show that for thermal parameters appropriate to the flinders ranges moho temperatures may vary by 25 30 c for every additional kilometre of sediment for a brace goetze lithospheric rheology controlled by a combination of temperature dependent creep processes and frictional sliding the observed variations in thickness of the sedimentary pile are sufficient to cause dramatic reductions in the vertically integrated strength of the lithosphere by many orders of magnitude thereby providing a plausible explanation for observed correlation between sediment thickness and deformation intensity during basin inversion

paleomagnetic and petrologic study of the age origin and significance of early and late paleozoic events in the long mountain granite wichita mountains oklahoma the cambrian long mountain granite exposed in the western wichita mountains oklahoma is red granophyric alkali feldspar granite the red granite abruptly transitions into a green granite in the subsurface both red and green granites have similar geochemical signatures anisotropy of magnetic susceptibility analysis shows that the green granite retains a primary magnetic fabric that is consistent with the sill like emplacement of the wichita granite group demagnetization of green granite specimens yields a characteristic remanent magnetization chrm residing in magnetite with east declinations and moderate down inclinations the paleopole 9 0 n 314 6 e is interpreted as a primary cambrian thermal remanent magnetization or an early magnetization related to deuteric hydrothermal alteration the paleopole position is consistent with some other poles for cambrian igneous rocks in southern oklahoma but is to the southwest of the cambrian part of the apparent polar wander path the red granite contains abundant secondary hematite that occurs in fractures as grain boundary coatings and along cleavage and exsolution planes in alkali feldspars the iron in the hematite appears to be sourced from the oxidation of primary magnetite and ilmenite and the breakdown of silicate ferromagnesian minerals the red granite has about two orders of magnitude lower magnetic susceptibility and natural remanent intensity than the green granite the magnetic fabric is interpreted as an alteration fabric the chrm of red granite has southeast declinations and shallow inclinations and is interpreted as a chemical remanent magnetization crm residing in hematite the paleopole 44 9 s 304 9 e falls near the 290 300 ma segment of the north american apparent polar wander path which is consistent with inferred timing of exposure of the long mountain granite the crm is interpreted to have been acquired during alteration by low temperature weathering fluids near the surface during the late paleozoic the results from the red granite are not consistent with alteration caused by widespread paleoclimatic conditions in the late permian and they are interpreted as related to local tectonic and or weathering events

modes of active intraplate deformation flinders ranges australia 1 the flinders ranges form one of the most seismically active zones within the australian continent with seismogenic strain rates over the last 30 years of 10 16 s 1 active deformation in the region reflects late neogene increases in stress levels in the indo australian plate as a response to increased plate boundary forcing from collision zones with the neighboring asian and pacific plates geological and geophysical observations suggest two modes of active deformation in operation in the flinders ranges over the last several million years 1 low amplitude 200 500 m long wavelength 200 km lithospheric flexure and 2 active reverse faulting along the range front with fault slip rates of up to 50 m myr 1 numerical models are developed to explore the contribution of each of these deformation modes to the observed geophysical signals an elastic mode of deformation is suggested by a distinctive long wavelength positive correlation between gravity and topography in which the flinders ranges are bordered by anomalous topographic and gravity lows now occupied by playa lake systems centered some 50 km outboard of range bounding faults numerical models show that flexural instabilities localized by vertical loads arising from older tectonic structuring produce a first order match with observed topography and gravity numerical models are also used to illustrate how the localized failure evident in the contemporary seismicity and quaternary faulting record within the flinders ranges reflects thermal weakening associated with extraordinary concentrations of heat producing elements in the crust as reflected in modern day heat flows of 90 mw m 2

implications of passive salt diapir kinematics for reservoir segmentation by radial and concentric faults abstract reservoirs associated with salt diapirs that are circular or elliptical in plan view can be segmented by radial faults concentric faults both or neither explanations for this variation are offered based on integration of fault kinematics published studies and seismic examples strata around diapirs can be divided into three structural domains with characteristic fault styles 1 roof zone between the present day depositional surface and crest of a buried inactive diapir this zone is characterised by doming radial faults and occasionally conic graben doming is usually caused by differential compaction and increases with depth 2 a steeply dipping sheath of strata surrounds the diapir out to a distance of less than one diapir radius recording near surface diapir growth in poorly lithified sediments these contain early gravity slumps and late concentric extensional faults regional layer bound polygonal fault systems form radial faults within approximately one diapir radius the only significant radial faulting mechanism below the roof zone 3 diapir root zone of strata whose structural architecture records the diapirs initiating mechanism typically rim synclines or graben that detach on the salt source layer concentric faults at radial distances of a kilometre or more have been found only in root zone rim synclines and sheared sheath strata these models and observations can assist seismic interpretation and structural model building in areas of poor geophysical imaging for instance below overhanging salt

cause and evolution of intraplate orogeny in australia abstractintraplate orogeny remains an enigmatic process in terms of plate tectonics regional continental stress elds agree well with stress orientations predicted by the main forces driv ing and resisting plate motion however regional continental stress elds fail to explain major localized compressive plate deformation in continental interiors far away from plate bound aries global or plate wide intraplate stress models typically assume a laterally homogeneous plate rheology and are con ned to modeling the present without addressing the antiquity of the current stress eld an understanding of intraplate stress and deformation requires the linking of spatial variations in continental rheology with time dependent plate geometry and driving forces here we demonstrate how the complex interplay between juxtaposed weak and strong geological provinces and changes in far eld plate boundary forces has caused intra plate orogenesis and tectonic reactivation in southeastern australia during the tertiary our ndings are contrary to the opinion that continental interiors are insensitive to compression at plate margins and help to explain the mechanisms causing intraplate orogenesis keywords

effective sub zechstein salt imaging using low frequency seismics results of the grundy 2003 experiment across the variscan front in the polish basin abstract the extent of the variscan deformation front is one of the key problems of the regional geology of the central european permian basin system particularly in its polish part conventional reflection seismics usually fails to produce a satisfactory image of the pre permian strata due to the shielding effect of zechstein upper permian evaporites thus we used a novel seismic acquisition technique to study the base of the permian complex and its variscan basement in the grundy 2003 experiment we combined wide angle reflection refraction measurements with the near vertical reflection seismics by the use of the constant geophone array with dense 100 m receiver spacing occupying 50 km long profile 3d design of the experiment covering 50 10 km area helped in eliminating the effect of out of plane propagations and local inhomogeneities an effective integration of traveltime tomography cdp reflection processing and prestack depth migration of wide angle reflections applied to our data allowed us to present the model in which we deduced the contact zone of the variscan overthrust structure variscan front with its molasse filled foredeep the latter might be a gas generation zone which is of a great importance for hydrocarbons prospecting in this area

quick look techniques for evaluating two dimensional cross sections in detached contractional settings for more than 30 yr geologists and geophysicists have used balancing techniques to constrain their cross sectional interpretations in detached contractional settings the quality of the resulting interpretations commonly directly correlates to the quality of the data the balancing and interpretational experience of the interpreter and the time allotted for the interpretation we demystify the balancing process and present quick look techniques for quickly and effectively detecting and preventing common cross section balancing errors in detached contractional settings common balancing problems are highlighted through close scrutiny of hanging wall and footwall ramps and flats such analysis helps identify inconsistencies in the numbers of ramps and flats in the strata and stratal thicknesses in corresponding ramps and in displacement along the fault these techniques possess the additional advantages of being useful at any stage of the interpretational process for time or depth sections and being easily comprehensible by students geologists geophysicists and managers alike the quick look techniques however are not an all encompassing panacea they do not guarantee a unique and or correct cross sectional interpretation instead they serve to focus the interpreter s attention on potentially problematic areas in the cross section that might require explanation and or reinterpretation

northeastern brazilian margin regional tectonic evolution based on integrated analysis of seismic reflection and potential field data and modelling abstract integration of regional seismic reflection and potential field data along the northeastern brazilian margin complemented by crustal scale gravity modelling is used to reveal and illustrate onshore offshore crustal structure correlation the character of the continent ocean boundary and the relationship of crustal structure to regional variation of potential field anomalies the study reveals distinct along margin structural and magmatic changes that are spatially related to a number of conjugate brazil west africa transfer systems governing the margin segmentation and evolution several conceptual tectonic models are invoked to explain the structural evolution of the different margin segments in a conjugate margin context furthermore the constructed transects the observed and modelled moho relief and the potential field anomalies indicate that the reconcavo tucano and jatoba rift system may reflect a polyphase deformation rifting mode associated with a complex time dependent thermal structure of the lithosphere the constructed transects and available seismic reflection profiles indicate that the northern part of the study area lacks major breakup related magmatic activity suggesting a rifted non volcanic margin affinity in contrast the southern part of the study area is characterized by abrupt crustal thinning and evidence for breakup magmatic activity suggesting that this region evolved partially with a rifted volcanic margin affinity and character