the eastern jura relations between thin skinned and basement tectonics local and regional the thesis area of hans cloos in the eastern jura straddles the boundary between the paleogene structures of the tabular jura a part of the southeastern end of the rhine graben and the neogene folds and thrusts of the folded jura a recent reflection seismic survey in the area adjacent to the east provides new information on the subsurface structure and the relation between three superposed tectonic events the main boundary fault zones of a deep and complexly faulted late paleozoic trough trending ene were reactivated in the early tertiary faulted flexures and small folds rooted in the basement and paleozoic with an amplitude of usually 100 to 300 m were produced rather than the normal faults typical for the extensional fields of the rhine bresse graben system in the west and the bavarian molasse basin in the east this suggests their being part of a transform zone between these extensional fields during jura decollement in the neogene these inherited deeply rooted sub decollement structures remained passive their small size is kinematically incompatible with the intense subsequent thrusting and folding of the thin mesozoic tertiary skin however thrust ramps were apparently nucleated at the respective southern foot of these paleogene flexures and folds the best defined and simplest of these composite structures is the mandach structure within the tabular jura a south facing flexure of about 300 m relief developed in the paleogene by reactivation of the northern border fault zone of the paleozoic trough in the neogene a north vergent decollement thrust which is connected with the regional jura decollement in the middle triassic evaporites was initiated at its site

rollback orogeny model for the evolution of the swiss alps the construction of the european alps and the himalayas has been related to the convergence and subsequent collision of two continental plates nearly all models of orogeny build on this concept and all of them relate the stacking of nappes and the build up of topography to compressional forces at work in response to the collision between two continental plates for the central european alps however these models fail to explain the first order observations of a mountain belt which particularly includes the striking isostatic imbalance between the low surface topography and the thick crust beneath the alps here we review and synthesize data on the geologic architecture of the central alps the chronology and pattern of crustal deformation and information about the deep crustal structure derived from seismic tomography furthermore we discuss the intrinsic and explicit assumptions in the kinematic models of alpine evolution in the context of plate tectonic considerations we combine these views with progress in understanding that has been gained through subduction and collision isostatic mass and force balancing and with information that has been collected on the modern seismic regime we conclude that a rollback orogeny model for the european plate offers the most suitable concept to explain the ensemble of surface and deep lithosphere observations in this model gravity forces drive the evolution of the orogen and the construction of surface topography is accomplished without the requirement of a hard collision between two continents

continental scale salt tectonics on mars and the origin of valles marineris and associated outflow channels a synthesis of deformation patterns within and around the thaumasia plateau mars points to a new interpretation for regional deformation and the origin of valles marineris and associated outflow channels the morphology of the thaumasia plateau is typical of thin skinned deformation akin to a mega slide in which extensional deformation in syria planum and noctis labyrinthus connects via lateral zones of transtension and strike slip claritas fossae and valles marineris to a broad zone of compressional uplift and shortening defined by truncated craters and thrust faults along the coprates rise and thaumasia highlands however the low regional slope 1 results in gravitational body forces that are too small to deform the basaltic lava flows conventionally thought to compose the flanks of the tharsis volcanic province instead we conclude that geothermal heating and topographic loading of extensive buried deposits of salts and or mixtures of salts ice and basaltic debris would allow for weak detachments and large scale gravity spreading we propose that the generally linear chasmata of valles marineris reflect extension collapse and excavation along fractures radial to tharsis either forming or reactivated as part of one lateral margin of the thaumasia gravity spreading system the other dextral lateral margin is a massive splay of extensional faults forming the claritas fossae which resembles a trailing extensional imbricate fan the compressional mountain belt defined by the coprates rise and thaumasia highlands forms the toe of the mega slide topographic observations and previous structural analyses reveal evidence for a failed volcanic plume below syria planum that could have provided further thermal energy and topographic potential for initiating regional deformation either intrusively through inflation or extrusively through lava flow and or ash fall emplacement higher heat flow during noachian time or geothermal heating due to burial by tharsis derived volcanic rocks would have contributed to flow of salt deposits as well as formation of groundwater from melting ice and dewatering of hydrous salts we further propose that connection of overpressured groundwater from aquifers near the base of the detachment through the cryosphere to the martian surface created the outflow channels of echus coprates and juventae chasmata at relatively uniform source elevations along the northern margin of the mega slide where regional groundwater flow would have been directed toward the surface our hypothesis provides a unifying framework to explain perplexing relationships between the rise of the tharsis volcanic province deformation of the thaumasia plateau and the formation of valles marineris and associated outflow channels

deformation in the jura mountains france first results from semi permanent gps measurements new gps estimates of relative motion across the jura mountain belt with respect to the eurasian plate indicate less than 1 mm yr of convergence considerably less than previous estimates velocity uncertainties have been evaluated by several methods and range from 0 2 to 0 5 mm yr for the semi permanent stations the major statistically significant strain feature inferred by the jura gps measurements is along arc extension compatible with tectonic studies that the detected deformation is small in magnitude highlights two important issues previous estimates are over stated and that the approach of using semi permanent gps installations is capable of detecting small tectonic signals using the upper bound as the rate of convergence we estimate that this would generate an earthquake of magnitude 5 5 5 every 15 to 75 yr

deep electrical resistivity tomography for the prospection of low to medium enthalpy geothermal resources summary the growth of the geothermal industry sector requires innovative methods to reduce explo ration costs whilst minimizing uncertainty during subsurface exploration until now geoelec trical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow reaching prospecting methods commonly used in hydro geophysical studies we present a recent technology for geoelectrical prospection and show how geoelectrical methods may allow the investigation of medium enthalpy geothermal resources until about 1 km depth the use of the new acquisition system which is made of a distributed set of independent electrical potential recorders enabled us to tackle logistics and noise data issues typical of urbanized areas we acquired a 4 5 km long 2 d geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a 700 m geothermal exploration well geo 01 satigny in the greater geneva basin western switzerland to show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs the processed resistivity model is consistent with the interpretation of the active seismic data and density variations computed from the inversion of the residual bouguer anomaly the combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing mesozoic geological units up to palaeogene neogene units that can be used for medium enthalpy geothermal exploitation our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth this new cost efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources

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

24 norcholestanes as age sensitive molecular fossils biomarkers molecular fossils are organic compounds in holocene to precambrian sedimentary deposits that can be related to specific chemical compounds produced in the biosphere we demonstrate here that 24 norcholestane biomarkers i e c26 steranes saturated hydrocarbons having a steroid skeleton can be useful to constrain the age and paleolatitude of geologic samples the biological precursors of 24 norcholestanes remain unclear but samples from more than 100 basins provide evidence that 24 norcholestanes may be derived directly or indirectly from diatoms ratios of 24 norcholestanes to 27 norcholestanes show an initial increase above background in jurassic oils but they increase dramatically in cretaceous oils coincident with diatom evolution the highest ratios are found in oils and rock extracts from oligocene or younger marine siliceous source rocks in which the sources were deposited at paleolatitudes 30 n

seismic wave attenuation from borehole and surface records in the top 2 5km beneath the city of basel switzerland summary we investigate attenuation q 1 of sediments of 2 5 3 5 km thickness underneath the city of basel switzerland we use recordings of 195 induced events that were obtained during and after the stimulation of a reservoir for a deep heat mining project in 2006 and 2007 the data set is ideally suited to estimate q as all events are confined to a small source volume and were recorded by a dense surface network as well as six borehole sensors at various depths the deepest borehole sensor is positioned at a depth of 2 7 km inside the crystalline basement at a mean hypocentral distance of 1 8 km this allows us to measure q for frequencies between 10 and 130 hz we apply two different methods to estimate q first we use a standard spectral ratio technique to obtain q and as a second measure we estimate q in the time domain by convolving signals recorded by the deepest sensor with a q operator and then comparing the convolved signals to recordings at the shallower stations both methods deliver comparable values for q we also observe similar attenuation for p and s waves qp qs as expected q increases with depth but with values around 30 50 it is low even for the consolidated permian and mesozoic sediments between 500 and 2700 m

balanced sections and the propagation of decollement a jura perspective 1 the propagation of thrusting is an important problem in tectonics that is usually approached by forward kinematical modeling of balanced sections although modeling techniques are similar in most foreland fold thrust belts it turns out that in the jura there are modeling problems that require modifications of widely used techniques in particular attention is called to the role of model constraints that complement the set of observational constraints in order to fully define the model in the eastern jura such model constraints may be inferred from the regional geology which shows a peculiar noncoaxial relation between thrusts and subsequent folds this relation implies changes in the direction of translation and the mode of deformation in the course of the propagation of decollement these changes are conjectured to be the result of a change in partial decoupling between the thin skinned fold thrust system nappe and the obliquely subducted foreland as a particularly instructive case in point a cross section through the weissenstein range is discussed a two step forward kinematical model is proposed that uses both local observational constraints as well as model constraints inferred from regional data as a first step a fault bend fold is generated in the hanging wall of a thrust of 1500 m shortening as a second step this structure is transferred by flexural slip into the actual fold observed at the surface this requires an additional 1600 m of shortening and leads to folding of the original thrust thereafter the footwall is deformed so as to respect the constraint that this deformation must fit into the space defined by the folded thrust as the upper boundary and the decollement surface as the lower boundary and that in addition should be confined to the area immediately below the fold in modeling the footwall deformation a mix of balancing methods is used fault propagation folds for the competent intervals of the stratigraphic column and area balancing for the incompetent ones further propagation of decollement into the foreland is made possible by the folding process which is dominated by a sort of kinking and which is the main contribution to structural elevation and hence to producing a sort of critical taper of the moving thin skinned wedge

critical taper analysis reveals lithological control of variations in detachment strength an analysis of the alpine basal detachment swiss alps although evidence for weak detachments underlying foreland thrust belts exists very little is known about the lateral variations in effective strength as well as the geological nature of such variations using critical taper analysis we show that a detailed and systematic measurement of surface slope of the central european alps reveals variations in strength parameter f along the detachment based on the argument that the alps are close to the critical state we show that the basal detachment is very weak near the deformation front but strengthens toward the hinterland very low f effective coefficient of friction plus normalized cohesion values of 0 54 but may also require additional mechanisms of dynamic weakening

decollement tectonics in the jura forelandfold and thrust belt abstract interpretation of more than 1500 km of industry seismic reflection lines from theswiss and french jura mountains and the western swiss molasse basin demonstrates that themesozoic and cenozoic cover of the jura fold and thrust belt has been deformed over a veryweak basal decollement and displaced for many kilometers toward the nw and that thebasement is not involved a depth to the basement map derived from depth conversion of theseismic lines shows a rather smooth flat basement dipping 1 3 to the s se the low amplitudebroad folds of the molasse basin and the external plateau jura are controlled by evaporitepillows or anticlines of middle triassic age the high amplitude folds of the haute chaine jura however are related to nw or se vergent thrusts with at least kilometric dipslip displacementthat has doubled the entire jurassic sequence the plateau jura evaporite related folds located in the foreland are interpreted as early stage buckle folds with further deformation afault ramp nucleates and develops into thrust related folds as observed in the haute chaine thus within the fold and thrust belt deformation increases toward the hinterland in the molassebasin however low amplitude folds represent an early deformation stage which could notdevelop further owing to the load of the overlying thick tertiary clastic wedge

strain displacement and rotation associated with the formation of curvature in fold belts the example of the jura arc abstract a new simplified genetic classification scheme for arcuate fold thrust belts is proposed based on total strain patterns and displacement vector fields we distinguish three extreme end member models 1 oroclines pure bending of an initially straight belt 2 piedmont glacier with divergent transport directions and 3 primary arcs a simple geometric model set up for the simulation of strain patterns in primary arcs with uniform transport direction demonstrates that divergent strain trajectories and rotations of passive marker lines do not require any divergence in displacement directions these often quoted arguments are insufficient for the identification of oroclinal bending or piedmont glacier type of arc formation only three dimensional restorations of an arc provide the critical information about displacement directions in their absence arc parallel stretches and rotations in comparison with total strains provide the most useful criteria for the distinction of arc formation modes as an example the jura fold thrust belt of the external alps is discussed a large set of strain data includes total shortening estimates based on balanced cross sections local strain axes orientations from the inversion of fault populations homberg c 1996 unpublished phd thesis universite de paris vi france tectonic stylolites and micro strains from twinning in sparry calcite strain trajectories maximum shortening direction computed from these data define a strongly divergent fan with a 90 opening a complete displacement vector field for the entire jura has been determined from balanced cross sections augmented with three dimensional block mosaic restorations philippe y 1995 unpublished phd thesis universite de chambery france displacement vectors diverge by about 40 markedly less than strain trajectories the non parallelism between strain trajectories and transport directions indicates that considerable wrenching deformation did occur in both limbs of the jura arc paleomagnetically determined clockwise rotations of 0 13 from ten sites kempf o et al terra nova 10 6 10 behind the right hand half of the jura arc and two sites with a combined 23 anticlockwise rotation behind the left hand half of the arc are and additional argument in favor of such a wrenching deformation we conclude that the jura arc formed as a primary arc with a minor component of piedmont glacier type divergence in transport directions

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

tectonics of the central swiss molasse basin post miocene transition to incipient thick skinned tectonics in this paper we investigate the tectonics of the central swiss molasse basin smb situated between the central european alps and the jura fold and thrust belt based on re interpreted 2d reflection seismic data and geological 3d modeling we present new insights into the structural configuration and evolution of the central smb during the thin skinned main deformation phase of the jura fold and thrust belt 12 4 ma the central smb was riding passively above a major detachment horizon within triassic evaporites which roots beneath the external crystalline massifs of the central alps in the smb low amplitude detachment folds and detachment rooted wsw ene striking thrust and reverse faults are related to this event younger major nne ssw and nnw sse trending strike slip fault zones cross the basin over a length of several kilometers affecting the cenozoic and mesozoic cover units and extending into the pre mesozoic crystalline basement in cases the fault zones apparently reactivate inherited permo carboniferous trough pct bounding paleozoic normal faults seismic data further reveals mild inversion of wsw ene striking pcts these structures clearly cut the basement cover contact thus postdating the main deformation phase of the jura fold and thrust belt present day earthquake focal mechanisms and epicenter distribution show strike slip faulting and basement seated seismicity respectively thus corroborating our observations from seismic interpretation our data suggests a change from late miocene thin skinned to pliocene to present day incipient thick skinned tectonics this major change reflects the establishment of a mid crustal detachment and may be related to changes in slab dynamics of the subducting european lithosphere

identification and significance of 3β ethyl steranes in sediments and petroleum abstract 3 ethyl steranes 5a c occur in ancient sediments and petroleum particularly those of paleozoic and proterozoic age this newly recognised modification to the sterane ring system has no known direct counterpart in the steroid metabolism of extant organisms when they are present in a sample the pattern of side chain substitution and some aspects of the isomer distributions of co occurring 3 ethyl steranes 5a c 3 methyl steranes 3a c 2 methyl steranes 2a c and desmethyl steranes 1a c are similar this suggests that these ring a alkylated steranes are not synthesised de novo by their source organism s but arise via microbial modifications to sedimentary sterenes during the early stages of diagenesis

critical taper model of fold and thrust belts and accretionary wedges the fold and thrust belts and submarine accretionary wedges that lie along compressive plate boundaries are one of the best understood deformational features of the earth s upper crust although there is considerable natural variation among the many fold and thrust belts and accretionary wedges that have been recognized and explored several features appear to be universal in cross section fold and thrust belts and accretionary wedges occupy a wedge shaped deformed region overlying a basal detachment or decollement fault the rocks or sediments beneath this fault show very little deformation the decollement fault characteristically dips toward the interior of the mountain belt or in the case of a submarine wedge toward the island arc the topography in contrast slopes toward the toe or deformation front of the wedge deformation within the wedge is generally dominated by imbricate thrust faults verging toward the toe and related fault bend folding two north american fold and thrust belts that exhibit these features are shown in figure 1 neither of these two examples is tectonically active today the southern canadian fold and thrust belt was active during the late jurassic and cretaceous 150 100 ma whereas the southern appa lachians were deformed during the late carboniferous to permian alle ghenian orogeny 300 250 ma figure 2 shows two examples that are currently active the taiwan fold and thrust belt produced by the sub duction of the eurasian plate beneath the philippine sea plate suppe 1981 1987 and the barbados accretionary wedge produced by the sub

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 2 oil source correlation and secondary migration mechanisms abstract the chemical compositions of crude oils from over 20 oilfields in the zhanhua depression bohai bay basin were studied in order to understand their genetic relationships thermal maturity and biodegradation ranking molecular geochemical parameters indicate the presence of three possible oil families in reservoirs ranging from paleozoic basement to neogene a number of biomarker features support deposition of the source rocks for these oils under a wide range of depositional environments the majority of the oils discovered in the depression belong to the fl family and display characteristics consistent with a dominantly freshwater to slightly brackish water lacustrine source rock in the es 3 member of the shahejie formation the somewhat geographically restricted sl family oils are apparently linked to saline lacustrine carbonate evaporite source rocks distributed mostly in the upper es 4 member of the shahejie formation from the bonan gubei sag areas the thermally less mature bl family oils occur mostly within the es 1 es 2 or dongying formation reservoirs near the central sag areas and show close affinities to the interbedded or intercalating es 1 calcareous mudstones and oil shales deposited in a slightly saline to dominantly brackish water lacustrine setting the sl and fl family oils are generally mature whereas most of the bl family oils usually show low maturity oil source correlation demonstrates strong genetic relationships between the mature es 4 and es 3 source rocks of the eocene oligocene shahejie formation in the sag areas and the oils accumulated in the shallow neogene petroleum plays the geochemical data provide strong support for two sharply contrasting hydrocarbon migration scenarios 1 short distance lateral migration is dominant in the central sag areas and 2 the fault fracture mesh facilitated vertical migration and coupled with the regional porous guantao formation sand sheets makes the structural stratigraphic and lithological features over basement high blocks the focal points for petroleum accumulation therefore further exploration in this highly mature petroleum province should focus on heavy oils in the shallow neogene strata and light oils in the tight sandstones of the deep sag areas

tertiary sequence of deformation in a thin skinned thick skinned collision belt the zagros folded belt fars iran 1 we describe how thin skinned thick skinned deformation in the zagros folded belt interacted in time and space homogeneous fold wavelengths 15 8 5 3 km tectono sedimentary evidence for simultaneous fold growth in the past 5 5 2 5 ma drainage network organization and homogeneous peak differential stresses 40 15 mpa together point to buckling as the dominant process responsible for cover folding basin analysis reveals that basement inversion occurred 20 ma ago as the arabia eurasian plate convergence reduced and accumulation of neogene siliciclastics in foreland basin started by 10 ma ongoing contraction occurred by underplating of arabian crustal units beneath the iranian plate this process represents 75 of the total shortening it is not before 5 ma that the zagros foreland was incorporated into the southward propagating basement thrust wedge folds rejuvenated by 3 2 ma because of uplift driven by basement shortening and erosion since then folds grew at 0 3 0 6 mm yr and forced the rivers to flow axially a total shortening of 65 78 km 16 19 is estimated across the zagros this corresponds to shortening rates of 6 5 8 km ma consistent with current geodetic surveys we point out that although thin skinned deformation in the sedimentary cover may be important basement involved shortening should not be neglected as it requires far less shortening moreover for such foreland folded belts involving basement shortening underplating may be an efficient process accommodating a significant part of the plate convergence

petroleum migration and accumulation in the bozhong sub basin bohai bay basin china significance of preferential petroleum migration pathways ppmp for the formation of large oilfields in lacustrine fault basins abstract this paper discusses migration styles and primary controls of petroleum migration pathways in heterogeneous carrier beds in bozhong sub basin bohai bay basin modeling of secondary petroleum migration pathways has been conducted using a simple three dimensional model which assumes that the positions of petroleum migration pathways are controlled by the morphology of the sealing surfaces the modeling results have accurately predicted the petroleum occurrences and have been supported by petroleum geochemical studies most commercial petroleum accumulations are on the predicted preferential petroleum migration pathways ppmp formed by focusing of numerous small petroleum streams close to the kitchens and most large fields petroleum reserves greater than 1 10 8 ton have more than one preferential petroleum migration pathway to convey petroleum to the traps the focusing of petroleum originated from a large area of the generative kitchens into restricted channels is essential for the formation of large oilfields the strong porosity and permeability heterogeneities of the carrier beds and the relatively high prediction accuracy by a model that does not take into consideration of the effect of heterogeneity suggest that the positions of petroleum migration pathways in heterogeneous carrier beds in the lacustrine fault basins are determined primarily by the morphology of the sealing surfaces at regional scales

thermal mechanical modeling of salt based mountain belts with pre existing basement faults application to the zagros fold and thrust belt southwest iran 1 two dimensional thermal mechanical models of thick skinned salt based fold and thrust belts such as the zagros sw iran are used to address 1 the degree of deformation and decoupling between cover and basement rocks due to the presence of a weak salt detachment 2 the reactivation potential of pre existing basement normal faults due to brittle or ductile behavior of the lower crust as related to cold or hot geothermal gradients and 3 variations in deformation style and strain distribution the geometry and kinematics of the orogenic wedge and the activity of pre existing basement faults are strongly influenced by the geothermal gradient defined by the moho temperature mt and basement rheology we infer that the mt plays a major role in how the lower and upper crust transfer deformation toward the foreland in relatively hot geotherm models mt 600 c at 36 km depth the lowermost basement deforms in a ductile fashion while the uppermost basement underlying the sedimentary cover deforms by folding thrusting and displacements along pre existing basement faults in these models cover units above the salt detachment occur within a less deformed wide plateau in the hinterland in relatively cold geotherm models mt 400 c at 36 km depth deformation is mainly restricted to basement imbricate thrusts that form within the orogenic hinterland detachment folding thrusting and gravity gliding occur within cover sediments above uplifted basement blocks gravity gliding contributes to a larger amount of shortening in the cover compared to the basement

numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements 1 thin skinned fold and thrust belts related to convergence tectonics develop by scraping off a rock sequence along a weaker basal decollement often formed by water saturated shale layers or low viscosity salt horizons a two dimensional finite element model with a viscoelastoplastic rheology is used to investigate the structural evolution of fold and thrust belts overlying different types of decollements in addition the influence of multiple weak layers in the stratigraphic column is studied model shale decollements are frictional with lower friction angles as the cover sequence model salt layers behave linear viscous due to a lower viscosity as the cover sequence or with a power law rheology single viscous decollement simulations have been compared to an analytical solution concerning faulting versus folding results show that fold and thrust belts with a single frictional basal decollement generate thrust systems ramping from the decollement to the surface spacing between thrust ramps depends on the thickness of the cover sequence the structural evolution of simulations with an additional low frictional layer depends on the strength relationship between the basal and the intersequential decollement tectonic underplating and antiformal stacking occur if the within sequence decollement is weaker in the frontal part of models deformation is restricted to the upper part and imbrication occurs with a wavelength depending on the depth of the intermediate weak layer salt decollement with a viscosity of 10 18 pa s leads to isolated box folds detachment folds multiple salt layers 10 18 pa s result in long wavelength folding our results for both frictional and viscous decollements are in bulk agreement with the mohr coulomb type critical wedge theory citation ruh j b b j p kaus and j p burg 2012 numerical investigation of deformation mechanics in fold and thrust belts influence of rheology of single and multiple decollements tectonics 31 tc3005 doi 10 1029 2011tc003047

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

3d effects of strain vs velocity weakening on deformation patterns in accretionary wedges abstract shear zones are weaker than surrounding rocks whether weakening depends on accumulated strain or strain rate is debated we used a three dimensional numerical code with a visco plastic brittle rheology to investigate the influence of strain and strain rate weakening often referred to as velocity weakening on the evolution of thin skinned fold and thrust belts two model setups are used i a uniform setup to recognize the effects of each weakening mode on the structural evolution and dynamics of fold and thrust belts and ii a dual setup with two adjacent domains of decollement strength to investigate the structural response of laterally varying systems strain weakening and velocity weakening lead to remarkably different structural patterns in particular strain weakening favours out of sequence shear zones whilst some amount of finite plastic strain has to be achieved before the structural development initiates weakening in contrast velocity weakening starts with the onset of high strain rate bands and does not favour out of sequence deformation we also tested separately the influences of shortening velocity cover sequence thickness and weakening style and amount on the structural evolution of the dual systems the shortening velocity has a minor effect in strain weakened models velocity weakening and a thinner cover sequence enhance the occurrence of strike slip shear zones we conclude that the weakening mode strongly influences the fault patterns and the dynamics of thrust wedges inversely natural fault patterns are keys to discriminate weakening processes

superimposed folding and oblique structures in the palaeomargin derived units of the central betics sw spain the subbetic units consist of a deformed wedge of sedimentary rocks deriving from the south iberian palaeomargin in the westernmost segment of the alpine mediterranean orogenic belt in the central betics shortening produced folding thrusting and nappe stacking the structural trend is ne sw to ene wsw and the internal structure of the thrust sheets which shows no preferred vergence is strongly controlled by the rheology of the decollement level a viscous layer of triassic evaporites and of the overlying carbonate rock sequence the relationships of piggyback basin miocene sediments with the main structures show that the latter developed during the aquitanian burdigalian transition superimposed folding is described for the first time in the study area the origin of the interference cannot be determined at present but may be related to initially oblique structures refolded during progressive deformation a revision of previously published palaeomagnetic data in the light of the data presented in this paper in conjunction with a model of the structural evolution of the subbetic units of the western betics permits us to establish milestones of the tectonic evolution of the external zones in the northern branch of the gibraltar arc

application of 24 norcholestanes for constraining source age of petroleum abstract two c26 sterane ratios the 24 nordiacholestane ratio ndr and the 24 norcholestane ratio ncr are useful for assessing petroleum source age values for these parameters generally increase in the cretaceous when diatoms were rapidly radiating and further in the oligo miocene due to widespread high latitude deposition of diatomaceous sediments sources with shale lithologies tend to exhibit the highest ratios while carbonate and terrigenous rich lithologies generally show lower ratios on the north slope of alaska elevated ratios are observed for cretaceous hrz oils and mixed oils containing cretaceous input compared to older triassic and jurassic derived oils tertiary sourced oils from romania and bulgaria have much higher ratios relative to jurassic sourced oils in the black sea region oleanane was observed in comparable levels in some black sea tertiary and jurassic oils and source rocks ndr and ncr coupled with other age diagnostic indicators such as oleanane and dinosterane provide powerful tools for differentiating age of source and organic facies for oils from the black sea and sub andean basins of peru and ecuador respectively oils derived from sources deposited in low tropical latitudes tend to have little diatom input and as a consequence do not display high values regardless of age

interactions between tectonics erosion and sedimentation during the recent evolution of the alpine orogen analogue modeling insights 1 on the basis of a section across the northwestern alpine wedge and foreland basin analogue modeling is used to investigate the impact of surface processes on the orogenic evolution the basis model takes into account both structural and lithological heritages of the wedge during shortening erosion and sedimentation are performed to maintain a critical wedge frontal accretion leads to the development of a foreland thrust belt underplating leads to the formation of an antiformal nappe stack in the internal zones important volumes of analogue materials are eroded out of the geological record which in the case of the alps suggests that the original lengths and volumes may be underestimated the foreland basin evolves differently depending on the amounts of erosion sedimentation its evolution and internal structuring is governed by the wedge mechanics thought to be the main controlling mechanism in the development of the molasse basin in a feedback interaction with surface processes

extended 3β alkyl steranes and 3 alkyl triaromatic steroids in crude oils and rock extracts abstract in oils and precambrian to miocene age source rocks from varying depositional environments we have conclusively identified several novel 3 alkyl sterane and triaromatic steroid series including 1 3 n pentyl steranes 2 3 isopentyl steranes 3 3 n hexyl steranes 4 3 n heptyl steranes 5 3 4 dimethyl steranes 6 3 butyl 4 methyl steranes 7 triaromatic 3 n pentyl steroids and 8 triaromatic 3 isopentyl steroids we have also tentatively identified additional homologs with 3 alkyl substituents as large as c11 the relative abundances of these compounds vary substantially between samples as indicated by 1 the ratio of 3 n pentyl steranes to 3 isopentyl steranes and 2 the ratio of 3 n pentyl triaromatic steroids to 3 isopentyl triaromatic steroids these data suggest possible utility for these parameters as tools for oil source rock correlations and reconstruction of depositional environments although no 3 alkyl steroid natural products are currently known several lines of evidence suggest that 3 alkyl steroids result from bacterial side chain additions to diagenetic 2 sterenes

chemostratigraphic reconstruction of biofacies molecular evidence linking cyst forming dinoflagellates with pre triassic ancestors new data from numerous detailed mass spectrometric studies have detected triaromatic dinosteroids in precambrian to cenozoic rock samples triaromatic dinosteroids are organic geochemicals derived from dinosterols compounds known in modern organisms to be the nearly exclusive widely occurring products of dinoflagellates we observed the ubiquitous occurrence of these dinosteroids in 49 late triassic through cretaceous marine source rocks and the absence of them in 13 permian carboniferous source rocks synergistic with the dinoflagellate cyst record however finding dinosteroids in lower paleozoic and precambrian strata presents challenging results for molecular paleontologists evolutionary biologists palynologists and especially for those concerned with the food web at various times of biological crisis other than the few species known as parasites and symbionts many other dinoflagellate species are important as primary producers the presence of precambrian to devonian triaromatic dinosteroids gives chemostratigraphic evidence of dinoflagellates or other organisms with similar chemosynthetic capabilities in rocks significantly older than the oldest undisputed dinoflagellate fossils dinoflagellate cysts from the middle triassic 240 ma and older than the putative silurian 420 ma dinocyst arpylorus antiquus calandra sargent from tunisia this systematic chemostratigraphic approach can shed light not only on lineages of dinoflagellates and their precursors but potentially on many other lineages especially bacteria algae plants and possibly some metazoans

viscous overthrusting versus folding 2 d quantitative modeling and its application to the helvetic and jura fold and thrust belts abstract this paper presents two dimensional 2 d numerical simulations of the shortening of a stiff viscous layer with a pre existing weak zone that is embedded in a weaker viscous matrix the model bottom remains straight during shortening and represents a detachment surface four deformation styles are observed that depend on the ratio of the layer and matrix viscosities l m the thickness ratio of the bottom matrix and the overlying stiff layer hm hl and the power law stress exponent of the matrix nm the numerical results are used to quantify the conditions for which each deformation style occurs 1 pure shear dominated deformation occurs for l m 50 and hm hl 50 and hm hl 1 and 4 folding and overthrusting occur for a power law viscous matrix and 0 5

interaction of folding and thrusting during fold and thrust belt evolution insights from numerical simulations and application to the swiss jura and the canadian foothills abstract we use two dimensional numerical simulations to investigate the interaction of folding buckling and thrusting localized shearing during the structural evolution of fold and thrust belts ftb we model layer parallel shortening of mechanically strong layers resting above a weaker layer referred to as detachment we consider a viscoplastic rheology with linear viscosity and frictional plastic drucker prager yield criterion the detachment thickness is larger in one model half and only this geometrical thickness perturbation triggers folding and thrusting in the simulations we conduct a systematic analysis to quantify the impact of model parameters such as magnitude of the thickness perturbation or detachment rheology frictional or viscous on the ftb evolution the magnitude of the perturbation determines whether or not folding is favoured over thrusting and hence controls the progressive interaction of folding and thrusting during ftb evolution the asymmetry of modelled anticlines is proportional to the relative height of the initial perturbation we also adapt the model configuration to specific mechanical stratigraphies of two regions in natural ftb namely the haute chaine of the jura mountains switzerland and the foothills of alberta canada the modelled fold and thrust geometries agree with different types of observed anticlinal structures such as symmetric detachments folds and asymmetric thrust folds our results suggest that an initial stage of low amplitude buckling likely occurred prior to the main folding and thrusting phase we argue that folding and thrusting are equally important and interacting processes during the structural evolution of many natural ftb

the central european graben system rifting imitated by clay modelling abstract central europe is traversed by an active graben belt between the north sea and the mediterranean along with a lateral rift rift offset between some segments along these offsets connecting the individual segments specific patterns have been observed which may be physiographically compared with transform faults a series of clay experiments were carried out to understand rhinegraben type graben formation especially the transform like features were modelled to learn more about the kinematics of transform faulting in the continental domain it has been attempted to approach natural structural and lithological boundary conditions of graben formation by varying the experimental conditions in such a manner that experimental and in situ conditions resemble in an optimal way the experiments are related to the paleogene extensional stage of the evolution of the rift system and do not consider the pliocene to recent kinematics of shear rifting

evolution of the molasse basin germany switzerland abstract in the molasse basin 500 1000 m thick mesozoic sediments overlie the variscan basement and locally permo carboniferous grabens containing a largely unknown thickness of clastic sediments the vindelician basement high extended southwestward from the bohemian massif and separated the southern part of the german basin from the tethys shelf triassic early and middle jurassic sediments progressively transgressed over this high which became fully inundated during the late jurassic following a temporary regression sedimentation resumed in the early cretaceous and after another hiatus in the late aptian to campanian during the latest cretaceous to earliest tertiary the area of southern germany became uplifted resulting in a progressive northwestward truncation of cretaceous strata and the late jurassic carbonates at the same time the bohemian massif became upthrusted along northwest striking wrench faults similar faults controlled the upthrusting of the landshut neuoetting high over which some 1 000 m of mesozoic sediments were eroded these wrench and thrust tectonics are part of an extensive compressional deformation in central europe that is supposed to be caused by the latest cretaceous earliest tertiary collision of the adriatic african and european plates during the alpine orogeny the area subsided again during the late eocene and developed into the molasse basin proper in which oligocene to miocene elastics reach a thickness of some 5 000 m near the alpine thrust front subduction and flexuring of the foreland caused numerous essentially basin parallel synthetic and antithetic normal faults the latter form the primary traps for oil and gas accumulations in the molasse basin

structural styles and decoupling in stratigraphic sequences with double decollements during thin skinned contractional tectonics insights from numerical modelling abstract six series of particle based numerical experiments were performed to simulate thin skinned contractional tectonics in stratigraphic sequences with double decollements during horizontal shortening the models were assigned with varying rock competence depth and thickness of the upper decollement which resulted in significantly different styles of deformation and decoupling characteristics above and below the upper decollement the models composed of the least competent material produced distributed sinusoidal detachment folds with many shallow structures profoundly decoupled from the deep seated folds the models composed of a more competent material are dominated by faulted box folds with minor disharmonic folds developed in their limbs in contrast the results of models composed of the most competent material are characterised by localised piggyback thrusts fault bend folds and pop up structures with tensile fractures developed in fold hinges depth of the upper decollements also plays an important role in controlling structural decoupling i e the shallower the upper decollements the higher the degree of decoupling becomes thicker upper decollements can provide sufficient mobile materials to fill fold cores and contribute to the formation of secondary disharmonic folds helping enhance structural decoupling our modelling results are comparable to the structural features exhibited in the dezful embayment of the zagros fold and thrust belt with the miocene gachsaran formation acting as the shallow upper decollement and the fars with the triassic dashtak formation as its intermediate decollement this study demonstrates that rock competence depth and thickness of the upper decollements can jointly affect the structural styles and decoupling our modelling results are instructive for structural interpretation of deep zones in fold and thrust belts that exhibit distinct structural decoupling features

paleozoic oil source rock correlations in the tarim basin nw china we studied a suite of 40 oils and extracts of purported source rocks from the tarim basin in nw china the main group of oils comes from tazhong and tabei wells which sample the largest known petroleum accumulations in the basin these oils can be statistically correlated with extracts of ordovician rocks based upon high relative concentrations of 24 isopropylcholestanes and low relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes in contrast extracts from cambrian rocks have low relative concentrations of 24 isopropylcholestanes with high relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes although some tarim basin cambrian rocks yield high total organic carbon contents we see little evidence in the analyzed oil samples to suggest that they came from cambrian source rocks

structural characteristics of the transitional zone from internal to external parts of the zagros orogen iran abstract mapping and detail field investigations integrated with geophysical data in bakhtyari area across the transitional zone of the zagros orogen shows a number of sw verging thrust sheets kinematic analysis of these sheets using deformed structures at the basal thrust zone as well as geophysical data from basement top allow us to recognize internal and external thrust sheets the former show duplex thrust system with ductile brittle deformation conditions while the latter have imbricate fan thrust system with brittle deformation condition only the internal thrust sheets along which the basement is also involved converge downward to form a crustal scale ductile thrust referred here as the root zone to the zagros orogen this root zone proposed as a suture to the zagros orogen and the boundary between the afro arabian plate and the eurasia plate the time for initiation of thrusting based on the late miocene age of syn tectonic bakhtyari conglomerate is compatible with the time of continent continent collision between the afro arabian plate and the eurasia plate determined by the plate reconstructions

extensional neotectonics around the bend of the western central alps an overview the western alps active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive compressive tectonics along its borders we examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics numerical modeling gps morphotectonics fieldwork and brittle deformation analysis extension appears to be the dominant process in the present day tectonic activity in the western alps affecting its internal areas all along the arc shortening in contrast is limited to small areas located along at the outer borders of the chain strike slip is observed throughout the alpine realm and in the foreland the stress orientation pattern is radial for 3 in the inner extensional zones and for 1 in the outer transcurrent tranpressional ones extensional areas can be correlated with the parts of the belt with the thickest crust quantification of seismic strain in tectonically homogeneous areas shows that only 10 20 of the geodesy documented deformation can be explained by the alpine seismicity we propose that alpine active tectonics are ruled by isostasy buoyancy forces rather than the ongoing shortening along the alpine europe adria collision zone this interpretation is corroborated by numerical modeling the neogene extensional structures in the alps formed under increasingly brittle conditions a synthesis of paleostress tensors for the internal parts of the west alpine arc documents major orogen parallel extension with a continuous change in 3 directions from ene wsw in the simplon area to n s in the vanoise area and to nnw sse in the briancon area minor orogen perpendicular extension increases from n to s this second signal correlates with the present day geodynamics as revealed by focal plane mechanisms analysis the orogen parallel extension could be related to the opening of the ligurian sea during the early middle miocene and to compression rotation of the adriatic indenter inducing lateral extrusion

thrust development in the eastern jura mountains related to pre existing extensional structures abstract from tunnel and map data three detailed balanced cross sections of the mesozoic cover of the jura fold and thrust belt in the hauenstein area eastern jura mountains switzerland were constructed viable models of the kinematic evolution of the structures document different stages of thrust development most thrust propagate first from the basal decollement in the middle triassic evaporites to the opalinus shales in some cases they continue for a short distance layer parallel and then break through to the surface in other cases they get stuck in the opalinus shales with further shortening either a delamination occurs where the incompetent layers were wedged under the overlying competent limestones the thrust breaks through the limb of the anticline at a higher level otherwise the thrust steepens and breaks through the hinge of the fold the resulting kinematically viable sections confirm that the miocene thrusts nucleate at inhomogeneities of the sub decollement relief these are possibly related to the borders of an underlying palaeozoic trough system reactivated as faulted flexures during the eocene to early miocene

dinosteranes 4 23 24 trimethylsteranes and other biological markers in dinoglagellate rich marine sediments of rhaetian age abstract alkane biological marker distributions and concentrations have been determined in 18 samples from a section of rhaetian age from the bristol trough and a quantitative micropalaeontological analysis carried out taking into account previous geological investigations of the sequence three end member depositional settings have been recognised from changes in total organic carbon content the biological markers and the micropalaeontological composition these depositional environments are attributed as follows the first which occurs in the lower part of the section corresponds to deposition in a supratidal sabkha type setting with the major organic input being of allochthonous origin the second also in the lower part of the section indicates the occurrence of periods of marine incursion with enhanced salinity resulting from evaporation in the upper part of the section marginal marine conditions are apparent with higher organic carbon biological marker and amorphous organic matter contents at the top suggesting the establishment of more stable conditions of oxygen depletion some sediments in the sequence are notable for containing an abundance of cysts of rhaetogonyaulax rhaetica one of the oldest marine dinoflagellates comparison of microfossil abundances with hydrocarbon abundances extends the circumstantial evidence for the dinophyceae being the major biological source of dinosteranes 4 23 24 trimethylcholestanes and some other 4 methyl steranes in marine sediments the presence of dinosteranes and their 24 ethyl counterparts extends the stratigraphic range of occurrence of such components back to the rhaetian c 31 methyl steranes in the sediments from the second depositional setting are tentatively assigned a 4 22 23 24 tetramethyl sterane skeleton and a dinoflagellate origin

control of folding by gravity and matrix thickness implications for large scale folding 1 we show that folding of a non newtonian layer resting on a homogeneous newtonian matrix with finite thickness under influence of gravity can occur by three modes 1 matrix controlled folding dependent on the effective viscosity contrast between layer and matrix 2 gravity controlled folding dependent on the argand number the ratio of the stress caused by gravity to the stress caused by shortening and 3 detachment folding dependent on the ratio of matrix thickness to layer thickness we construct a phase diagram that defines the transitions between each of the three folding modes our priority is transparency of the analytical derivations e g thin plate versus thick plate approximations which permits complete classification of the folding modes involving a minimum number of dimensionless parameters accuracy and sensitivity of the analytical results to model assumptions are investigated in particular depth dependence of matrix rheology is only important for folding over a narrow range of material parameters in contrast strong depth dependence of the viscosity of the folding layer limits applicability of ductile rheology and leads to a viscoelastic transition our theory is applied to estimate the effective thickness of the folded central asian upper crust using the ratio of topographic wavelength to moho depth phase diagrams based on geometrical parameters show that gravity does not significantly control folding in the jura and the zagros mountains but does control folding in central asia applicability conditions of viscous and thin sheet models for large scale lithospheric deformation derived in terms of the argand number have implications for the plate like style of planetary tectonics

high temperatures in the late cretaceous arctic ocean to understand the climate dynamics of the warm equable greenhouse world of the late cretaceous period it is important to determine polar palaeotemperatures the early palaeoceanographic history of the arctic ocean has however remained largely unknown because the sea floor and underlying deposits are usually inaccessible beneath a cover of floating ice a shallow piston core taken from a drifting ice island in 1970 fortuitously retrieved unconsolidated upper cretaceous organic rich sediment from alpha ridge a submarine elevated feature of probable oceanic origin a lack of carbonate in the sediments from this core has prevented the use of traditional oxygen isotope palaeothermometry here we determine arctic palaeotemperatures from these upper cretaceous deposits using tex86 a new palaeothermometer that is based on the composition of membrane lipids derived from a ubiquitous component of marine plankton crenarchaeota from these analyses we infer an average sea surface temperature of approximately 15 degrees c for the arctic ocean about 70 million years ago this calibration point implies an equator to pole gradient in sea surface temperatures of approximately 15 degrees c during this interval and by extrapolation we suggest that polar waters were generally warmer than 20 degrees c during the middle cretaceous approximately 90 million years ago

formation of an active thrust triangle zone associated with structural inversion in a subduction setting eastern new zealand 1 we analyze a thrust triangle zone which underlies the continental shelf of hawke bay eastern new zealand within the hikurangi subduction margin this triangle zone differs from many other examples in that it is active 90 km from the leading edge of the overriding plate and formed due to polyphase deformation involving opposed dipping thrust duplex and backthrust with the later structure forming in response to inversion of an extensional graben the component structures of the zone mainly developed sequentially rather than synchronously high quality marine seismic reflection lines tied to well and seabed samples reveal the three dimensional structure of the zone together with its 25 myr evolution and late quaternary activity the triangle zone occurs in the lateral overlap between a stack of nw dipping blind thrusts and a principal backthrust the kidnappers fault the nw dipping thrusts initiated in the early middle miocene during the early stages of subduction with subsequent thrust duplex formation producing major uplift and erosion in the late miocene early pliocene the active backthrust formed during the late miocene to early pliocene as a thin skinned listric extensional fault confined to the cover sequence structural inversion of the extensional fault commenced in the early middle pliocene produced the backthrust and marks the formation of the thrust triangle zone the thrust duplex and backthrust accrued strain following inversion however the later structure accommodated most of the surface deformation in the quaternary section balancing of the triangle zone together with a detailed analysis of reverse displacements along the backthrust reveal spatial and temporal variations of strain accumulation on the two principal components of the zone although the formation of the triangle zone is strongly influenced by regional tectonics of the subduction system these variations may also in part reflect local fault interaction for example high quaternary displacement rates on the backthrust accounts for 70 of the displacement loss that occurs on the southern segments of the overlapping lachlan fault understanding the tectonic evolution of such complex polyphase thrust triangle zones requires the preservation of growth strata that record sequential deformation history in the absence of such data synchroneity of opposed dipping thrusts in triangle zones cannot be assumed

the gondwana connections of northern patagonia a multidisciplinary study u pb sensitive high resolution ion microprobe geochronology hf and o isotopes in zircon sr and nd isotopes in whole rocks as well as major and trace element geochemistry has been carried out on granitoid samples from the area west of valcheta north patagonian massif argentina these confirm the cambrian age of the tardugno granodiorite 528 4 ma and the late permian age of granites in the central part of the yaminue complex 250 ma together with petrological and structural information for the area we consider a previously suggested idea that the cambrian and ordovician granites of northeastern patagonia represent continuation of the pampean and famatinian orogenic belts of the sierras pampeanas respectively our interpretation does not support the hypothesis that patagonia was accreted in late palaeozoic times as a far travelled terrane originating in the central transantarctic mountains and the arguments for and against this idea are reviewed a parautochthonous origin is preferred with no major ocean closure between the north patagonian massif and the sierra de la ventana fold belt supplementary material u pb shrimp analytical data geochemical analyses and sample global positioning system locations are available at www geolsoc org uk sup18722

secular and environmental constraints on the occurrence of dinosterane in sediments abstract the distribution patterns of sedimentary a ring methylated steranes have changed markedly over geological time although dinosterane and its isomer 24 ethyl 4 methylcholestane have been tentatively identified in three proterozoic rock units they are either not detectable or occur in low abundance relative to 3 methyl steranes throughout most of the palaeozoic between permian and middle triassic times 260 220 ma ago 4 methyl sterane abundances in marine sediments increased markedly the presence of dinosterane in some middle triassic marine sediments is contemporaneous with the appearance of fossil cysts of uncontested dinoflagellate affinity 4 methyl steranes including dinosterane or their precursor sterenes and sterols then show a continuous presence often in high abundance in marine sediments from the late triassic through to the present day assemblages of 4 methyl steranes and their precursors but with dinosterane absent or in low relative abundance are often the predominant steroids in lacustrine sediments in the cainozoic dinosterane appears to arise predominantly from marine dinoflagellates and as a consequence is a useful biological marker for mesozoic and cainozoic marine organic matter the isomer 24 ethyl 4 methylcholestane is likely to have multiple origins although its very high abundance in tertiary lacustrine sediments and oils compared to older materials suggests that dinoflagellates could also be the source in these cases

the distribution of molecular fossils derived from dinoflagellates in paleogene lacustrine sediments bohai bay basin china steroids with unconventional side chains in ancient sediments and petroleum have been increasingly used as age diagnostic markers triaromatic dinosteroids and dinosteranes occur widely throughout the eocene oligocene shahejie formation in the southeastern bohai bay basin china consistent with its abundant fossil dinoflagellate assemblages in addition 24 norcholestane biomarkers which commonly appear in marine oils have been found in this lacustrine formation although a firm link has not been established between 24 norcholestane and specific modern taxa both diatoms and dinoflagellates are shown to be likely sources of 24 norcholestanes although the shahejie strata lack intact diatom frustules they do exhibit a good relationship between 24 norcholestane other molecular fossils of dinoflagellates and dinocysts dinoflagellates are important precursor taxa of 24 norcholestanes and the various species identified in eocene oligocene lacustrine shales and mudstones of the shahejie formation are all potential sources of the 24 norcholestanes

seismic reflection evidence for thick skinned tectonics in the northern jura newly released seismic reflection data from the northern jura mountains and southern rhine graben provide the first high quality subsurface images from this area these throw light on the details of the fault patterns in the area and show that the ferrette and le glaserberg jura structures are largely the result of thrust faulting however the faults differ in their nature from those usually assumed in jura tectonics they are not low angle thrusts converging on a decollement zone in triassic evaporites they appear instead to be high angle faults that cross the entire sedimentary section indicating that thick skinned tectonics prevailed in this part of the jura embryonic jura folds can be seen on the images from the nearby mulhouse horst folds that are not supported by thickened triassic evaporites the existence of recent earthquake activity taken together with the prevalence of thick skinned tectonics suggests that occasional large earthquakes cannot be ruled out in this area

a biomarker study of immature crude oils from the shengli oilfield people s republic of china abstract a suite of crude oils from the shengli oilfield in northwestern china was subjected to detailed chemical analysis crude oils in this suite believed to be derived from source rocks deposited under fresh brackish and saline environments have chemical compositions and biological marker compounds indicative of immature source rocks in this respect the crude oils are unusual apparently having been formed and expelled from source rocks that have been subjected only to mild thermal stress prior to the main zone of petroleum generation

deformation of brittle ductile thrust wedges in experiments and nature 1 even though the rheology of thrust wedges is mostly frictional a basal ductile decollement is often involved by comparison with purely frictional wedges such brittle ductile wedges generally display anomalous structures such as backward vergence widely spaced thrust units and nonfrontward sequences of thrust development laboratory experiments are used here to study the deformation of brittle ductile thrust wedges results are compared with natural systems in the jura mountains and the northern pakistan salt range and potwar plateau two series of three models are used to illustrate the effects of varying the basal wedge angle and shortening rate v these two parameters directly control variations in relative strength between brittle and ductile layers bd coupling wedges with strong bd coupling low and high v give almost regular frontward sequences with closely spaced thrust units and as such are not significantly different from purely frictional wedges weak bd coupling high and low v gives dominantly backward thrusting sequences intermediate bd coupling produces frontward backward oscillating sequences the spacing of thrust units increases as coupling decreases back thrusts develop in parts of a wedge where bd coupling is weak regardless of the thrust sequence wedges with weak bd coupling need large amounts of bulk shortening more than 30 to attain a state of equilibrium at which stable sliding along the base occurs on this basis we argue that a state of equilibrium has not yet been attained in at least some parts of the jura mountains and eastern salt range and potwar plateau thrust systems

3d cartographic modeling of the alpine arc we built a 3d cartography of the alpine arc a highly non cylindrical mountain belt using the 3d geomodeller of the brgm french geological survey the model allows to handle the large scale 3d structure of seventeen major crustal units of the belt from the lower crust to the sedimentary cover nappes and two main discontinuities the insubric line and the crustal penninic front it provides a unique document to better understand their structural relationships and to produce new sections the study area comprises the western alpine arc from the jura to the northwest up to the bergell granite intrusion and the lepontine dome to the east and is limited to the south by the ligurian basin the model is limited vertically 10 km above sea level at the top and the moho interface at the bottom we discarded the structural relationships between the alps sensus stricto and the surrounding geodynamic systems such as the rhine graben or the connection with the apennines the 3d model is based on the global integration of various data such as the dem of the alps the moho isobaths the simplified geological and tectonic maps of the belt the crustal cross sections ecors crop and nfp 20 and complementary cross sections specifically built to precise local complexities the database has first been integrated in a gis project to prepare their implementation in the geomodeller by homogenizing the different spatial referencing systems the global model is finally interpolated from all these data using the potential field method the final document is a new tri dimensional cartography that would be used as input for further alpine studies

the exhumation history of the european alps inferred from linear inversion of thermochronometric data thermochronometric data collected across the alps over the last three decades allows for investigation of the evolution of this orogen which is subject to changes in climate and geodynamics exhumation rates are inferred from the thermochronometric ages using a statistical inversion method based on the fact that the distance a sample traveled since closure is equal to the integral of the exhumation rate from the present day to the age of the sample exhumation rates are assumed to be spatially correlated but are free to vary through time this results in the quantification of exhumation rates across the alps since 32 ma along with assessments of the quality of these inferences we find that exhumation rates are initially fast in the internal arc of the western alps at rates up to 0 8 km myr at 30 ma decreasing at 20 ma to 0 3 km myr to remain slow to the present at the same time around 20 ma rates across the external crystalline massifs of western alps increase to 0 6 km myr we also find that the onset of high exhumation rates in the tauern window and the lepontine dome occurs at around 20 ma a time characterized by major reorganizations in the alpine chain a general increase in exhumation rates at around 5 ma over the entire alps is not confirmed instead we find that the western alps exhibit a 2 to 3 fold increase in exhumation rate over the last 2 ma during a recent event not seen further east in spite of very similar topographic characteristics we attribute this strong signal to detachment of the european slab in the western alps combined with efficient glacial erosion

structure and evolution of a rocksalt mudrock tectonite the haselgebirge in the northern calcareous alps the northern calcareous alps are part of the eastern alps in austria and germany the mesozoic units of this fold and thrust belt were detached thrusted and stacked along the evaporitic haselgebirge formation exposed in salt mines rocksalt and mudrock form a two component tectonite the rock type haselgebirge consists of 10 70 wt halite with silt to gravel or block sized components within a halite matrix and the kerngebirge with 70 wt halite all rock types studied are fault rocks by use of a temperature independent subgrain size piezometer the paleo differential stress of halite was calculated at ca 2 5 mpa in altaussee and ca 4 5 mpa in berchtesgaden including data from a grain size piezometer temperatures were estimated at ca 150 20 c and 110 10 c this implies very high strain rates which are about 10 10 10 9 s 1 during the tectonic movement the halite deformed recrystallized and crystallized as veins in mudrock fractures we interpret high overpressure of the pore fluid to have significantly contributed to fracturing of the mudrock

norcholestane in miocene onnagawa siliceous sediments japan abstract a significant amount of 24 norcholestane with 20r 5 h 14 h 17 h stereochemistry is often found in marine siliceous sediments of the middle miocene onnagawa formation japan some onnagawa siliceous sediments are abnormally abundant in 24 norcholestane the primary production in the northeastern japan sea during the middle miocene was markedly increased due to the invasion of nutrient rich cold seawater from the north accompanied by the tectonic opening of the japan sea 24 norcholestane in high relative abundance is derived mainly from the marine diatoms which were enhanced during this event the drastic ecological change caused by rapid tectonic opening of the japan sea and global climatic deterioration during middle miocene time is suggested to be influential in the formation of 24 norcholestane rich onnagawa siliceous sediments

triangle zones geometry kinematics mechanics and the need for appreciation of uncertainties abstract triangle zones are important structures found in foreland fold and thrust belts all over the world and are commonly associated with tectonic wedging however tectonic wedging and consequently the formation of passive hinterland verging roof thrusts requires particular mechanic conditions such as pre fractured rocks syntectonic sedimentation or a specific stratigraphic layering with variable mechanically weak and rigid formations in this contribution models of triangle zones and hypotheses regarding their formation are reviewed our results show that the term triangle zone is often used in a contradictory sense and interpretations are affected by large uncertainties passive roof thrusts are not necessarily required in all cases and suggested models of triangle zones even if they are geometrically and kinematically viable are hampered by their mechanical implications with respect to a large number of published triangle zones and associated kinematic as well as mechanic models we present a new definition and classification scheme which is discussed and applied to natural examples worldwide we show that natural examples of triangle zones can be separated into two types 1 detachment dominated and 2 ramp dominated triangle zones both types imply particular mechanic conditions of involved detachments and regional dynamics regarding the large uncertainties associated with triangle zone interpretation we suggest to only use the term triangle zone in a very stringent manner and only if irrefutable evidences for stratigraphic repetitions within a duplex are given the results should then be validated with additional kinematic and mechanic considerations geometric and kinematic uncertainties as well as implications of the proposed model explaining observed triangular structures should be reflected in the nomenclature used

linking the northern alps with their foreland the latest exhumation history resolved by low temperature thermochronology the evolution of the central alpine deformation front subalpine molasse and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the alps its latest exhumation history is poorly understood due to the lack of late miocene to pliocene sediments we constrain the late miocene to pliocene history of this transitional zone with apatite fission track and u th he data we used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data two investigated sections across tectonic slices show that the subalpine molasse was tectonically active after the onset of folding of the jura mountains this is much younger than hitherto assumed thrusting occurred at 10 8 6 5 ma and potentially thereafter this is contemporaneous with reported exhumation of the external crystalline massifs in the central alps the jura mountains and the subalpine molasse used the same detachments as the external crystalline massifs and are therefore kinematically coupled estimates on the amount of shortening and thrust displacement corroborate this idea we argue that the tectonic signal is related to active shortening during the late stage of orogenesis

structural evolution of orogenic wedges interplay between erosion and weak decollements orogenic wedges commonly display an inner wedge where crystalline units have been exhumed and an outer wedge formed by imbricated sedimentary units detached from the basement analog experiments have shown that similar structures can emerge naturally in the presence of weak decollements due to the interplay between erosion and deformation in this study we further investigate this hypothesis using two dimensional visco elasto plastic numerical models our experiments assume a basal and an intermediate decollement within the wedge experiments with a frictional strength of the basal decollement lower or equal to that of the intermediate decollement show a structural evolution of fold and thrust belts dominated by out of sequence thrusting conversely when the intermediate decollement is weaker than the basal decollement distinct outer and inner wedges are formed this process leads to episodic migration of midcrustal ramps tectonic underplating and antiformal stacking facilitated by erosion comparison between our models and the himalayan wedge suggests a low effective friction 0 10 which is probably due to dynamic weakening during large m8 himalayan earthquakes the deeper decollement along which the lower plate thrusts beneath the high himalaya must be a thermally activated ductile shear zone with an apparent friction of 0 18 fold and thrust belts worldwide exhibit various architectures in which different decollement levels might be activated thus our study provides a framework to help assess under which conditions a variety of structures observed in orogenic systems can arise

constraining seismic parameters with a controlled source audio magnetotelluric method csamt summary precise seismic two way traveltime twt determinations are often limited by the knowledge of the overburden thickness and its seismic velocity values between 500 and 1800 m s 1 are conceivable according to the water content the csamt method has been successfully applied to determine the thickness of the quaternary fluvio glacial deposits and tertiary molasse interbedded marls and siltstones overlying mesozoic carbonates along a 3 km profile through a syncline in the swiss jura fold and thrust belt the homoclinal structure within the syncline is well constrained by a petroleum exploration vibroseis profile which indicates a sse dipping mesozoic series and a similarly oriented increasing thickness of molasse and quaternary the csamt places tight constraints on the apparent resistivities of the three formations quaternary 300 1000 m molasse 5 15 m mesozoic 100 1000 m furthermore modelling of the csamt sounding data provides absolute thicknesses for both the quaternary 80 20 m and the molasse 10 210 m layers revealing a true dip of the top mesozoic substratum of 7 to the sse the seismic velocities of the quaternary weathering layer and the molasse can thus be determined at 800 and 2100 m s 1 respectively

development of contrasting folding styles in the western yangtze block south china insights from numerical modeling abstract two contrasting folding styles are well developed along both sides of the qiyueshan fault south china the western part is characterized by chevron anticlines and box synclines in the eastern sichuan domain while the eastern part features typical chevron synclines and box anticlines in the western hunan hubei domain these contrasting structures are important in better understanding the intracontinental orogeny around the eastern sichuan basin in this study we conducted a series of 2 d numerical simulations using the finite difference method the model results indicate that the key parameters include stratigraphic competence number and distribution of intermediate weak layers and thickness of basal weak layer among them the thickness of basal weak layer plays the most important role in shaping the two distinct structural styles in the models with thin basal weak layer 8 km a series of coherent chevron synclines are developed and mainly form decollement folds these characteristics are similar to the structural styles revealed by seismic profiles in the western hunan hubei domain this weak layer may represent the accumulation of mechanically weak rocks e g slate schist and phyllite in neoproterozoic lengjiaxi and tieshajie groups in the western hunan hubei domain which is also consistent with the geophysical observations e g weak seismic reflection high electrical conductivity and bouguer gravity low anomaly both the differential thickness of basal weak layer along the flat ramp flat decollement and the overlying multiple intermediate weak layers contribute to the formation of the contrasting folding styles around the eastern sichuan basin

unprecedented occurrence of novel c26 c28 21 norcholestanes and related triaromatic series in evaporitic lacustrine sediments a novel series of c26 c28 21 norcholestanes and their triaromatic analogs have been tentatively identified as major components in eogene evaporitic sediments in jinxian sag of the bohai bay basin northern china these compounds may be viewed as representatives of a new class of molecules whose biological or diagenetic origin remains to be determined their unprecedented high abundance in the evaporitic lacustrine sediments and related oils show important source and or depositional environment controls in addition to thermal maturity

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 1 source rock characterization and quantitative assessment abstract in the prolific zhanhua depression of the bohai bay basin eastern china over 76 of the proven petroleum reserves occur in the neogene guantao and minhuazhen formations detailed geological and geochemical mapping of the phanerozoic strata in this area reveals that oil shales and dark mudstones in the es4 es3 and es1 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in several discrete sag areas bounded by extensive basement related fault networks in contrast source rocks along the paleo topographic highs are currently immature with respect to the generation of conventional oils this study examined the key molecular characteristics for the common isoprenoid hopanoid and steroid biomarkers in relation to source facies variations in lacustrine sediments the hydrocarbon source potential and expulsion efficiency for each of the source rock units were evaluated which integrated the source rock characteristics with regional thermal subsidence and sediment burial an important observation made during this study is the striking contrast between the source potential and proven oil reserves within each stratigraphic section illustrating how significant the migration of hydrocarbon fluids derived from deep mature source kitchens through over 2000 m of fine grained formations must have been to form several giant oil accumulations in the shallow strata these results support the concept of the neogene fault fracture mesh petroleum plays proposed by zhang et al 2004 marine petroleum geology 21 651 668 and the vital role that the faults and fracture systems have in controlling hydrocarbon migration conduits and accumulation habitat in this rift basin

present day deformations of the jura arc inferred by gps surveying and earthquake focal mechanisms this study presents a compilation of more than 40 years of seismotectonic data including 54 computed focal mechanisms combined with 15 years of gps data coming from a dense network of 35 permanent gps stations within the jura arc and its vicinity these data are compared to previous available geomorphological geophysical and structural studies in order to discuss the 3d distribution of the deformation within the jura arc gps data show coherent schemes in terms of velocities and allowed to discriminate between two provinces ne of the belt and in its front foreland they also constrain a low but significant overall strain tensor with a nnw sse shortening of 2 16 nanostrain year associated with an ene wsw extension of 0 44 nanostrain year the seismotectonic approach is based on a data set of 2 400 events and 54 focal mechanisms inversions of the focal mechanisms both globally and in homogeneous sectors highlight a general strike slip deformation regime with sigma1 oriented nw se and sigma3 oriented ne sw we discriminate two different sectors in terms of basement cover un coupling 1 potentially decoupled deformation between the basement and the sedimentary cover in the ne part and 2 coupled deformation in the sedimentary cover and its basement in the jura foreland

results of a walk above vertical seismic profiling survey acquired at the thonex 01 geothermal well switzerland to delineate fractured carbonate formations for geothermal development abstract this paper deals with the design acquisition and processing of vertical seismic profiling data collected in 2016 at the directional thonex 01 geothermal well drilled in 1993 in the geneva canton switzerland the aim of the study was to obtain additional information from existing abandoned well for downhole geophysical characterization of potential geothermal reservoirs in the geneva area the main results obtained by this study allowed an improved subsurface image by multi offset acquisitions near and around the deviated well specifically we were able to 1 improve the velocity model of the geneva basin which at present is only constrained by one unique deep exploration well located at the south west of the basin far away from the study area 2 image the transition between the tertiary molasse siliciclastic sediments and the mesozoic carbonates 3 define an acquisition strategy for future vertical seismic profiling surveys in support of the geothermal exploration campaigns in the area this study has demonstrated the value of vertical seismic profiling method for the refinement of the subsurface geology at local scale and its usefulness to assist the planning of second well associated with geothermal doublets

mechanical validation of balanced cross sections the case of the mont terri anticline at the jura front nw switzerland abstract close to north west front of the jura thrust belt in switzerland the mont terri anticline is located at a disruption of the muschelkalk decollement due to a former normal fault numerous geological data are available thanks to a motorway tunnel cross cutting the fold and an underground laboratory original field data two geological maps a borehole and a highway tunnel constrain the inner structure the anticline is characterized by an overturned frontal limb a steep back limb and a ramp cross cutting older normal faults three geological cross sections and three 2d kinematic models are proposed as various combinations of fault bend folding fault propagation folding and detachment folding the main motivation of this study is to illustrate how geometrical constructions can be constrained by the kinematic approach of limit analysis which determines the optimal deformation including faults that verifies mechanical equilibrium and the coulomb criterion matching some of the important kinematic steps assumed in each three interpretations to the optimal deformation leads us to define the compatible ranges of values of the frictional parameters these ranges allow us to assess the likeliness of the important kinematic steps of each kinematic model the present analysis provides a quantitative link between the assumed evolution of the internal structure and the concomitant evolutions of the topography and of the frictional parameters

present day and future tectonic underplating in the western swiss alps reconciliation of basement wrench faulting and decollement folding of the jura and molasse basin in the alpine foreland abstract the western alps form a geodynamically active mountain belt showing the typical features of an evolving orogenic wedge with its pro wedge geometry to the nnw and its retro wedge structures to the sse renewed tectonic underplating of european continental crust occurred after the orogenic wedge underwent major dynamic disequilibrium following the break off of the southward subducting slab of the european passive margin the most important of these basement imbricates are the mont blanc aiguilles rouges and gastern aar crystalline massifs also forming the alps highest mountains the upper plate present day orogenic wedge of the western alps includes the molasse basin and the jura fold and thrust belt both decoupled from the basement over a basal decollement surface the overall geometry of this wedge appears to be strongly unstable according to simple wedge models in its attempt to regain stability out of sequence thrusts form in the existing basement nappes but also new basement nappes should develop beneath the southern portion of the molasse basin new out of sequence thrusts in the cover trigger higher than average uplift rates concentrated around the newly forming structures and are accompanied by a concentration of earthquakes tectonic underplating is further corroborated by neotectonics and the tectonic structures observed in the prealpes molasse basin and jura similarly uplift rates and earthquakes along the southern edge of the jura mountains seem to witness the development of a new incipient basement nappe at depth partial inversion of former permo carboniferous grabens in the basement a possible spatial coincidence of areas with strong earthquake activity and zones with uplift rates above surrounding values suggest a common mechanism for their origin in the western swiss alpine foreland combined with information from basement geometry and wedge dynamics it is proposed that the common mechanism is the development of basement imbricates by tectonic underplating the proposed model for ongoing and possible future tectonic underplating beneath an active alpine orogenic wedge also allows to reconcile the models of basement wrench faulting in the molasse basin and jura with the distant push theory where the molasse basin and jura develop over a basal decollement horizon

the last erosional stage of the molasse basin and the alps we present a synoptic overview of the miocene present development of the northern alpine foreland basin molasse basin with special attention to the pattern of surface erosion and sediment discharge in the alps erosion of the molasse basin started at the same time that the rivers originating in the central alps were deflected toward the bresse graben which formed part of the european cenozoic rift system this change in the drainage direction decreased the distance to the marine base level by approximately 1 000 km which in turn decreased the average topographic elevation in the molasse basin by at least 200 m isostatic adjustment to erosional unloading required ca 1 000 m of erosion to account for this inferred topographic lowering a further inference is that the resulting increase in the sediment discharge at the miocene pliocene boundary reflects the recycling of molasse units we consider that erosion of the molasse basin occurred in response to a shift in the drainage direction rather than because of a change in paleoclimate climate left an imprint on the alpine landscape but presumably not before the beginning of glaciation at the pliocene pleistocene boundary similar to the northern alpine foreland we do not see a strong climatic fingerprint on the pattern or rates of exhumation of the external massifs in particular the initiation and acceleration of imbrication and antiformal stacking of the foreland crust can be considered solely as a response to the convergence of adria and europe irrespective of erosion rates however the recycling of the molasse deposits since 5 ma and the associated reduction of the loads in the foreland could have activated basement thrusts beneath the molasse basin in order to restore a critical wedge in conclusion we see the need for a more careful consideration of both tectonic and climatic forcing on the development of the alps and the adjacent molasse basin

extremely high sea surface temperatures at low latitudes during the middle cretaceous as revealed by archaeal membrane lipids the middle cretaceous 125 88 ma greenhouse world was characterized by high atmospheric co 2 levels the general absence of polar ice caps and much higher global temperatures than at present both 1 8 o based and model based temperature reconstructions indicate extremely high sea surface temperatures ssts at high latitudes however there are a number of uncertainties with sst reconstructions based on 1 8 o isotope data of foraminifera due to diagenetic overprinting effects and tenuous assumptions with respect to the 1 8 o value of cretaceous seawater the paleoecology of middle cretaceous marine organisms and seawater ph here we applied a novel sst proxy i e text tetraether index of 86 carbon atoms based on the membrane lipids of marine crenarchaeota derived from middle cretaceous sedimentary rocks deposited at low latitudes the text proxy indicates that tropical ssts in the proto north atlantic were at 32 36 c during the early albian and late cenomanian early turonian this finding agrees with sst estimates based on 1 8 o paleothermometry of well preserved foraminifera as well as global circulation model calculations the text proxy indicates cooler ssts 27 32 c for the equatorial pacific during the early aptian which is in agreement with sst estimates based on 1 8 o paleothermometry

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

relating orogen width to shortening erosion and exhumation during alpine collision we investigate along strike width changes of the thickened accreted lower plate talp in the central and in the eastern alps we set the width of the talp in relation to the inferred amount of collisional shortening and exhumation along six orogen scale cross sections taking the present day along strike gradients in the amount of collisional shortening to represent the temporal evolution of the collisional wedge it may be concluded that the cross sectional area of the talp diminishes during ongoing shortening indicating that the erosional flux outpaced the accretionary flux higher amounts of collisional shortening systematically coincide with smaller widths of the talp and dramatic increases of the reconstructed eroded rock column higher amounts of shortening also coincide with larger amplitudes of orogen scale upright folds with higher exhumation and with higher exhumation rates hence erosion did play a major role in reducing by 30 km the vertical crustal thickness in order to accommodate and allow shortening by folding long term climate differences cannot explain alternating changes of width by a factor of almost 2 along straight segments of the orogen on length scales less than 200 km as observed from the western central alps to the easternmost eastern alps sedimentary or paleontological evidences supporting such paleo climatic differences are lacking suggesting that erosional processes did not directly control the width of the orogen

duplex structures and imbricate thrust systems geometry structural position and hydrocarbon potential duplexes and imbricate thrust systems form some of the most complex hydrocarbon traps in overthrust belts the geometry of a duplex is controlled by the ramp angle thgr and height hr the final spacing between adjacent thrusts a prime and the relative displacements on them d1 d2 for constant thgr and hr three different classes are recognized 1 independent ramp anticlines and hinterland sloping duplexes 2 true duplexes and 3 overlapping ramp anticlines imbricate thrust systems consist of several thrust faults each of which loses displacement upsection and eventually dies out by progressively transferring its displacement to a fold at its tip or by distributing it among several splays hybrid duplexes are ormed from systems of fault propagation folds that are subsequently carried over ramps so they have a more complex geometry and a greater structural relief these different types of thrust systems occur as outcrops and prospect scale structures and they define the regional structural styles of most fold and thrust belts second and third order duplexes and imbricate thrust systems occur in specific structural positions such as footwalls hanging walls and frontal zones of major thrust ramps and in cores of major anticlines several types of duplexes and imbricate thrust systems form important hydrocarbon traps examples include the system of independent anticlines of the turner valley and highwood oil and gas fields the hinterland sloping duplex consisting of the chestnut ridge sandy ridge system of the ben hur oil field the partly overlapping anticlines of the waterton and savanna creek gas fields and the completely overlapping anticlines of the rose hill oil field

a model of displacement and strain for arc shaped mountain belts applied to the jura arc abstract a plan view geometric model for simple parallel differential displacements is presented as an analogue for models of arcuate mountain belt formation we use the model to predict strain patterns produced by parallel displacement in front of a rigid versus deformable indenter a rigid indenter is simulated by an irregular quadrilateral displaced a constant amount along its hinterland boundary a deformable indenter is simulated by an irregular quadrilateral displaced along a hinterland boundary that is allowed to rotate some simple test cases show that the deformable indenter model leads to a pattern of strain very similar to that encountered in arcuate mountain belts short axes orientations are most deviated from the transport direction along the lateral edges of the model with minimum displacement and shortening and vary across the central domain mirroring strain features with variable orientations from mountain belts such as fold trends and minor deformation features such as horizontal stylolite peaks the rigid indenter model also generates short axes deviated from the transport direction but showing far less variation displacement strain relationships from the jura mountains switzerland and france are quantified based upon a simplified version of the finite displacement field for the jura fold thrust belt of philippe y 1995 rampes laterales et zones de transfer dans le chaines plissees unpublished phd thesis universite de savoie we find that the model short axis orientation pattern is very similar over at least the eastern and central jura to the stylolite patterns from the region whilst the long axes closely match the fold axes trends the model suggests that the jura mountains could have formed as a result of a progressive deformation with uniform transport in a general northwest direction