le bassin de tizi n test haut atlas maroc exemple d evolution d un segment oblique au rift de l atlantique central au trias detailed mapping completed by a microtectonic study of the tizi n test triassic basin located along the tizi n test fault zone in the moroccan high atlas has allowed us to improve the knowledge on the geometry of the structures and the activity of faults during the triassic extensional events related to the rifting of the central atlantic the latter are reflected by the development of a rift at present inverted and deformed by the collision of africa and europe comprising kilometric scale grabens and half grabens bounded by major faults trending ene wsw with a dip towards the nnw and a dip slip syndepositional motion inverse analysis of fault slickenside populations shows a heterogeneous triassic state of stress however in the most significant measurement sites the maximum horizontal stress 1 is vertical while the minimum stress 3 is horizontal with a nw se trend the strike slip component appears to be very small during the triassic a noticeable fact because of the obliquity of the basin w

release fault a variety of cross fault in linked extensional fault systems in the sergipe alagoas basin ne brazil abstract two types of cross faults are herein recognized transfer faults and the newly termed release faults transfer faults form where cross faults connect distinct normal faults and horizontal displacements predominate over vertical ones in contrast release faults form where cross faults associated with individual normal faults die out within the hangingwall before connecting to other normal faults and have predominantly vertical displacements release faults are geometrically required to accommodate variable displacements along the strike of a normal fault thus they form to release the bending stresses in the hangingwall and do not cut normal fault planes nor detachment surfaces at depth release faults have maximum throws adjacent to normal faults and may be nearly perpendicular or obliquely oriented to the strike of the latter such geometry appears not to depend upon pre existing weaknesses but such variable orientation to normal faults is an inherent property of release faults release faults commonly appear as simple normal faults in seismic sections without implying extension along the strike of rift and basins three dimensional strain deformation occurs in the hangingwall only between the terminations of an individual normal fault but regionally release faulting is associated with plane strain deformation in linked extensional fault systems

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

release faults associated structures and their control on petroleum trends in the reconcavo rift northeast brazil release faults are rift cross faults which develop to accommodate the variable displacements of the hanging wall block along the strike of normal faults release faults are nearly perpendicular or obliquely oriented to the strike of the normal fault they are related to they have maximum throws adjacent to the parent normal fault and die out in the hanging wall away from it they form to release the bending stresses in the hanging wall and do not reflect the orientation of the regional stress field in a basin commonly they show normal oblique displacements and are preferentially located along the strike ramps release faults may also act at the scale of an entire basin reaching displacements of thousands of meters joints shale and salt diapirs may develop in association with release faults because all these structures represent domains of stress release they may work as conduits for oil migration and oil traps in extensional basins this is the case of the reconcavo basin in northeastern brazil a cretaceous failed rift connected to the eastern brazilian continental margin basins in the reconcavo basin two large scale release faults with displacements in the order of 3 km developed in the hanging wall of the rift border faults and control the location of the main oil fields

fault scarps and deformation rates in lazio abruzzo central italy comparison between geological fault slip rate and gps data abstract we compare new and literature data concerning the integrated deformation rate since 18 ka for the central apennines with deformation rate data derived from a 6 year gps campaign we constructed topographic profiles across the majority of the active faults in the area we derived deformation rate data from displaced post glacial sediments and slopes associated with the last major glacial retreat that occurred in the region about 18 kyr ago paleoseismic investigations in this region clearly show that offset of these features is the cumulative effect of repeated surface faulting earthquakes with magnitudes in the range 5 5 ms 7 0 a cumulative throw rate diagram incorporating both our values and the values extracted from the literature i e previously published trenching studies scarp profiles and offset terraces is presented providing a regional picture of the spatial deformation rate distribution in the central apennines during the latest pleistocene and holocene by converting cumulative throw rates into heave rates we calculate maximum extension rates of ca 2 mm year at the location of the same transect where 6 2 mm year has been measured with gps over 6 years this discrepancy between geodetic and geological fault slip rate data implies that we have to be cautious whenever we use gps data for seismic hazard assessment purposes or when attempting to reconstruct the tectonic processes in an area because geodetic data may be unrepresentative of the longer term deformation rates on the other hand this discrepancy may provide insights into the mechanics of the seismic cycle we discuss various scenarios that may explain the mis match between long term and short term measurements

normal fault development during two phases of non coaxial extension an experimental study we use scaled experimental analog models to study the effect of a pre existing fault fabric on fault development during extension in our models a homogeneous layer of wet clay undergoes two noncoaxial phases of extension whose directions differ by up to 45 the normal faults that develop during the first phase create a pronounced fault fabric that influences normal fault development during the second phase in all models the pre existing faults are reactivated during the second phase of extension their sense of slip depends on the angle between the first and second phase extension directions specifically the component of dip slip relative to strike slip decreases as the angle between the first and second phase extension directions increases new normal faults also form during the second phase of extension in all models the number of new fault segments increases as the angle between the first and second phase extension directions increases the orientations of the new normal fault segments are both orthogonal and oblique to the second phase extension direction indicating that both the secondphase extension direction and the pre existing fault fabric control the orientation of new fault segments some of the new normal faults cut and offset the pre existing faults whereas others terminate against them producing complex fault patterns and interactions the modeling results explain fault interactions observed in the jeanne d arc rift basin of offshore newfoundland canada and the reactivation of abyssal hill normal faults at outer highs near subduction zones

transverse versus longitudinal extension in the foredeep peripheral bulge system role of cretaceous structural inheritances during early miocene extensional faulting in inner central apennines belt this study reports on the rocca di cave extensional fault system which is located in the prenestini mountains central italy of the apennines fold and thrust belt and presently represents the oldest exposure of early orogenic foreland fault system of the apennines this fault system was oriented perpendicular to the strike of the foredeep peripheral bulge system indicating that the onset of convergence was marked by a foredeep parallel extension instead of the commonly observed foredeep perpendicular stretching associated with lithosphere flexuring the studied fault system is formed by a 10 km long and 2 km wide e w elongated area that includes two mutually orthogonal sets of faults oriented about e w and n s respectively e w and mainly n s striking faults developed during a preorogenic santonian to campanian in age e w oriented extension kinematics which caused first uplift and erosion and then drowning of the cretaceous carbonate platform and the onset of a pelagic environment both fault sets were later reactivated in the early miocene when the area was forming part of the foreland region ahead of the eastward migrating apennines fold and thrust belt and was undergoing local n s oriented i e foredeep parallel stretching this extensional stage implied the sedimentation of hundreds of meters of synkinematic strata in the northern block of the rocca di cave fault system coevally with episodes of subaerial erosion in areas of the southern block further extensional and right lateral reactivation of inherited faults occurred in the late miocene during the progressive incorporation of the area into the apennines belt

slope sediment yield in arid lowland continuous permafrost environments canadian arctic archipelago abstract surface wash erosion was measured at runoff plots on low to moderate slopes in clayey and sandy silts underlain by continuous permafrost on the fosheim peninsula ellesmere island due to snow redistribution in winter total precipitation on the plots varied from 34 to 150 mm with corresponding surface runoff values of 0 to 102 mm where runoff occurred at least 80 of it was derived from snowmelt suspended sediment removal was plot data precipitation vegetation and surface grain size from the fosheim peninsula and banks island were used to develop a statistical model of suspended sediment removal by surface wash on undisturbed slopes for any given grain size the model predicts a rise in erosion from zero precipitation because of an absence of runoff to a peak at about 50 mm a decline as precipitation increases to 300 mm and a further increase in erosion beyond this inflection point this non linear response is due to the complex interaction of moisture primarily snow and vegetation cover erosion at any given precipitation value varies through three orders of magnitude depending on surface grain size the maximum erosion predicted is 1 kg m 2 a 1 for a runoff plot with 1100 mm of precipitation a corresponding vegetation cover of 77 and a median surface grain size of 7

tectonic evolution of the sergipano fold belt ne brazil during the brasiliano orogeny abstract the sergipano fold belt sfb represents the southern segment of a brasiliano age 600 ma continental collision zone which extends over ne brazil and continues into central africa as the north equatorial fold belt major sinistral transcurrent fault shear zones and thrusts separate domains with individual lithological tectonometamorphic and magmatic characteristics the principal steeply dipping strike slip zones trend east west to wnw ese lithological correlations across the shears have not proved possible which suggests that displacements were probably large but as yet are unquantified major folding and thrusting affected all the domains folds have a southerly vergence with nw se to wnw ese trends consistent with a ne sw to nne ssw shortening direction although small differences in shortening trends exist between individual domains the southernmost allochthonous domain of carbonate to clastic shelf slope sediments was subject to a single phase of folding and thrusting onto the sao francisco craton accompanied by greenschist facies metamorphism north of this domain lies the macurure domain which is separated from the southernmost allochthonous domain by the major sao miguel do aleixo transpressive shear zone polyphase deformation amphibolite facies metamorphism and massive granitic intrusion characterize this domain north of the macurure domain lie the migmatites and granites of the poco redondo domain which represent a deeper crustal level they are separated from the macurure domain by the belo monte shear a late tectonic leucogranite in the poco redondo domain yields a 600 ma rb sr isochron finally the poco redondo domain was overthrust from the north by the caninde gabbroic complex associated with carbonates pelites and amphibolites metamorphosed to greenschist and upper amphibolite facies this has previously been interpreted as an ophiolite sequence although the relative movements or absolute ages of the domains are unknown their distinct geological differences suggest that they are separate crustal blocks which underwent large lateral movement during the brasiliano collision

scaling properties of normal fault populations in the western corinth graben greece implications for fault growth in large strain settings abstract a variety of one dimensional and two dimensional map techniques of fractal analysis have been employed to investigate the scaling properties of the dominant wnw trending normal fault population of the western corinth graben in central greece to assess possible constraints on fault geometry during fault growth the data have been compiled separately from the northern and southern domains of the graben which have experienced differing amounts of finite strain based on power law distributions of the fault throw the applied extension is estimated at 30 and 22 for the northern and southern domains respectively however the fault spacing and fault length populations in both domains obey similar power law relationships these conclusions are also supported by maximum throw vs trace length data which demonstrate that the faults in the northern domain have systematically higher values for the slip to length ratios than those in the southern domain it is proposed that the corinth graben has reached fracture saturation that is the fault spacing stops evolving and displacement increases rather than faults lengthening to accommodate the increasing extension this growth process consistent with throw distributions along individual faults may be explained either in terms of a stress feedback mechanism or by the mechanical interaction between the wnw trending normal faults with a set of nne trending transverse faults

mesozoic rifting in the basque cantabrian basin spain inherited faults transversal structures and stress perturbation terra nova 24 70 76 2012 abstract in the basque cantabrian basin northern iberian margin inherited wnw ese striking faults were reactivated during the mesozoic extensional stage associated with the opening of the bay of biscay syn rift structures in the area include different sets apparently indicating multiple extensional stages in particular abundant ne sw striking extensional elements have been interpreted in the past as having developed during a late rifting left lateral transtensional stage however the development of these structures also fits well with an analytical model of ridge perpendicular extension along strike stretching imposed by displacement variations along inherited faults locally produced an additional stress field oriented obliquely to the regional one this caused rotation of the local minimum stress and development of anomalously oriented transversal structures a single extensional stage is thus inferred during mesozoic rifting with a stretching direction oriented approximately perpendicular to the trend of the bay of biscay oceanic ridge

extensional fault control on the sedimentation patterns in a continental rift basin el castellar formation galve sub basin spain in the galve sub basin the sedimentary record of the upper hauterivian lower barremian el castellar formation is divided into two stages by a marlstone interval with gypsum stage 1 shows a great variety of subenvironments and facies alluvial palustrine and lacustrine whereas in stage 2 an extensive shallow carbonate lake developed sedimentation was controlled by a system of south dipping ene wsw listric normal faults laterally bounded by nnw sse steeper transfer faults faults controlled sedimentation from a basin scale basin margins and main characteristics and evolution of sediments to a regional and a local scale thickness and facies distribution of the synrift series as well as the location and evolution of lakes and minor alluvial fans the changes between stages 1 and 2 are related to the passing from an independent movement of faults to the movement of all the extensional faults as a whole at a sole detachment level the interval with gypsum was caused by underground water flow changes associated with the interrelation and connection of the faults in the transition period these changes have been correlated with the transition from the rift initial stage to the rift climax stage which took place in the hauterivian barremian transition

basement fabric controls rift nucleation and postrift basin inversion in the continental margin of ne brazil abstract in passive continental margins the brittle reactivation of shear zones and their role in the deformation and deposition of sedimentary basins are still a matter of debate in this research we investigated the role of the brittle reactivation of precambrian shear zones in the nucleation of rift and postrift faults in the onshore portion of the sergipe alagoas and pernambuco basins in northeastern brazil we combine and interpret a dataset of aeromagnetic and topographic data associated with reflection seismic and borehole data to analyze the evolution of a portion of the atlantic continental margin of brazil our results indicate that in the crystalline basement the magnetic lineaments are correlated with ductile structures as shear zones and the continuity of these lineaments in the sergipe alagoas and pernambuco basins is interpreted as the shear zones below the sedimentary cover of these basins we document the following phases of the brittle reactivation of basement shear zones 1 the opening of the south atlantic ocean in the early cretaceous under an extensional stress regime and 2 tectonic inversion induced by the mid atlantic ridge push and the andean cordillera rise in the neogene quaternary under a predominantly strike slip stress regime during the rift phase the brittle reactivation of the shear zones controlled the locations and architectures of the rifts these structures acted as zones of weakness and were reactivated as normal faults the brittle reactivation of shear zones was still active during the postrift phase and was responsible for the development of compressional structures the reverse faulting and related folding pattern indicate tectonic inversion in the late cretaceous cenozoic the structures formed during the postrift phase under a strike slip regime are consistent with the present day stress field indicating that tectonic inversion is an active phase of the brazilian margin

lithospheric structure of tibet and western north america mechanisms of uplift and a comparative study we seek to determine the mantle lid thickness of the lithosphere and to constrain the mechanisms that are responsible for the cenozoic uplift of the tibetan plateau located behind the himalaya collision zone and the western united states located behind the san andreas transform convergent plate boundary selected first p arrivals of international seismological centre isc data at distances less than 22 are analyzed by the two station method to constrain the upper mantle structure of the basin and range br colorado plateau cp great plains gp and tibetan plateau tp the data are presented as plots of apparent velocity versus distance to the second station we show that these observations of apparent velocities versus distance as well as those that concern the attenuation of sn provide estimates of the mantle lid thicknesses we obtain the following mantle lid thicknesses br 20 40 km cp 35 50 km gp 150 195 km and tp 135 180 km sn is not observed for paths beneath the br and cp while sn efficiently propagates beneath the gp sn is also observed beneath most of tibet except in the north central part of the tp a possible interpretation of our observations is that indian continental lithosphere underthrusts only about the southern 2 3 of tibet

pleistocene cryostructures and landslide at petit bost southwestern france 45 n abstract remnants of a pleistocene landslide have been observed during field investigations of quaternary alluvial formations of the isle river at petit bost southwestern france the main features of the landslide induced deformation give a good indication of its size and depth the surface of rupture is located in a 0 5 m thick very plastic mottled clay at the top of an alluvial gravel the clay is overlain by 1 7 m thick loamy colluvial deposits with a polygonal net of bleached wedges that testify to past permafrost conditions the mechanical parameters used in stability calculations for the case of an infinite planar sliding surface that fits well the geomorphological data are given by triaxial tests stability calculation indicates that the slope is very stable at present and that rupture can only have occurred in fully unconsolidated and undrained conditions this likely happened during permafrost degradation and subsequent thawing of ice rich soil layers oedometric tests indicate post sliding over consolidation of the clay with regards to the debate on permafrost distribution in france during the pleistocene this study gives support to a wide extent of permafrost at least to the latitude 45 n southward during the coldest periods it also points out that frost induced slope instability may have played a major but still underestimated role in many french regions north to this latitude

quaternary fault control on the coastal sedimentation and morphology of the sao francisco coastal plain brazil abstract the role of neotectonic faulting in shaping topography and controlling sediment deposition has been increasingly documented along the stable continental margin of south america but the level of the present day tectonic stability of this margin is still a matter of debate this paper presents an investigation of the effects of quaternary fault reactivation on the sao francisco coastal plain sfcp this feature is a 56 km long progradational coastal plain located in the sergipe alagoas basin along the continental margin of brazil the sfcp is bounded on the west by a system of normal faults striking n s to ne sw the horst that bounds this plain is capped by the miocene barreiras formation and quaternary debris flow and fluvial deposits whereas the graben is filled with braided stream deposits and sandy beach ridge sediments the faulting contributed to the generation of accommodation space for the deposition of coastal sediments on the plain these processes started with the reactivation of cretaceous faults during the miocene during the quaternary fault reactivation and associated soft sediment deformation occurred between 82 and 8 3 ka with minor pulses between 1700 and 60 cal yr bp several faults along this margin are tectonically active and may represent the onshore continuation of gravitational collapses that have been documented offshore along the continental shelf and slope

structural geology and 4d evolution of a half graben new digital outcrop modelling techniques applied to the nukhul half graben suez rift egypt abstract lidar based digital outcrop mapping in conjunction with a new surface modelling approach specifically designed to deal with outcrop datasets is used to examine the evolution of a half graben scale normal fault array in the suez rift syn rift deposition in the nukhul half graben was controlled by the graben bounding nukhul fault the fault can be divided into four segments based on the strike of the fault the morphology of hangingwall strata and the variation in throw along strike the segments of the fault became geometrically linked within the first 2 5 m y of rifting as evidenced by the presence of early syn rift abu zenima formation strata at the segment linkage points fault perpendicular folds in the hangingwall related to along strike variations in throw associated with precursor fault segments persist for a further 1 8 m y after linkage of the segments suggesting that the fault remains kinematically segmented we suggest this occurs because of sudden changes in fault strike at the segment linkage points that inhibit earthquake rupture propagation or because displacement is geometrically inhibited at fault linkage points where the orientation of the intersection line of the segments is significantly different from the orientation of the slip vector on the fault system length throw plots and throw contour patterns for minor faults show that some faults initiated in pre rift strata whereas late east striking faults initiated in the syn rift basin fill the late initiating faults are spatially associated with the east striking baba markha fault which was active throughout the rift history but developed as a transfer fault between major block bounding fault systems around 6 7 ma after rift initiation

deep seismic reflection evidence for continental underthrusting beneath southern tibet the himalaya and adjacent tibetan plateau constituting earth s largest region of elevated topography and anomalously thick crust formed as a consequence of cenozoic collision between india and asia itself considered the archetypal continent continent collision1 3 here we report the first results from an attempt to image the structure of the crust beneath this region using deep seismic reflection profiling our 100 km long profile acquired in the tethyan himalaya shows a mid crustal reflection that prob ably marks the active thrust fault along which the indian plate is underthrusting southern tibet upper crustal reflections with geo metries suggestive of large scale structural imbrication of the upper crust and moho reflections from the base of the double normal thickness crust underlying the region these results lend substantial support to the view that crustal thickening beneath southernmost tibet was accomplished by wholesale underthrusting of indian continental crust beneath the structurally imbricated upper crust comprising the tethyan himalaya

gravity field over northern eurasia and variations in the strength of the upper mantle the correlation of long wavelength gravity anomalies in northern eurasia with seismic velocity anomalies in the upper mantle reverses in sign between western and eastern eurasia the difference between western and eastern eurasia can be explained by the presence of a low viscosity zone in the uppermost mantle beneath eastern eurasia that is absent to the west the location of the lateral change in viscosity corresponds with the geologic boundary between the older shields and platforms of the baltics russia and siberia and the younger geologically active mountain belts of eastern asia this relation provides evidence that differences in the strength of the upper mantle control the locus of intracontinental deformation

the holocene paleoearthquakes on the 1915 avezzano earthquake faults central italy implications for active tectonics in the central apennines abstract extensive paleoseismological research was conducted in the fucino plain central italy in order to better understand the seismogenic characteristics of the fault responsible for the 1915 avezzano earthquake ms 7 0 and improve the general knowledge regarding active tectonics in the central apennines evidence for late pleistocene holocene surface faulting events was obtained through the study of thirteen sites across four different fault branches the paleoseismological analysis outlined the occurrence of ten surface faulting events in the past 33 000 years seven of which occurred during the holocene radiocarbon thermoluminescence and archaeological dating permitted the definition of an event chronology and the estimation of a recurrence interval for surface faulting events ranging between 1400 and 2600 years on the basis of the observed offsets it was possible to calculate vertical slip rates for the individual fault branches ranging between 0 24 mm yr 1 and 0 5 mm yr 1 and an extension rate across the fucino plain ranging between 0 6 and 1 mm yr 1 the chronology of surface faulting events appears linearly distributed in time and the observed recurrence times are similar to those inferred by other paleoseismological studies along different active apennine faults the general consequence of the large time span between strong earthquakes is that even a 2000 year long historical record such as the italian earthquake catalogue does not cover the entire seismic cycle of all the active apennine faults a comparison of the extension rate across the fucino plain with that across the entire central apennines as inferred from the sum of seismic moments of earthquakes which occurred in the interval 1000 1992 shows a seismicity deficit in the period indicated this confirms that a number of seismogenic faults were not active during the past 1000 years

early tertiary sinistral transpression and fault reactivation in the western voring basin norwegian sea implications for hydrocarbon exploration and pre breakup deformation in ocean margin basins the nyk high is an approximately northeast trending late cretaceous to early tertiary structural high situated in the western voring basin offshore norway it is defined by a thick sequence of upper cretaceous to lower tertiary sediments that dip toward the southeast and are cut by normal faults with throws up to 1500 m 4921 ft across fault sediment thickness variations and stratigraphic onlap relationships show that these faults were active during campanian to early paleocene extension prior to the separation of norway from greenland ca 55 ma sediments preserved in the hanging walls of these rift related normal faults are deformed by two populations of folds one set is oriented clockwise of the fault strike the other is oriented parallel to the fault strike stratigraphic relationships show that both sets of folds formed subsequent to rifting during the latest paleocene to the earliest eocene we interpret these folds as having developed during minor sinistral transpression which was partitioned between the northeast southwest sinistral strike slip reactivation of the normal faults and the northwest southeast coaxial shortening folding within the fault hanging walls the nyk high is oriented counterclockwise to the inferred line of the continental breakup we speculate that transpression was driven by north northwest forces arising from the differential topography along the incipient plate boundary and the presence of hot buoyant material beneath this elevated axial region such deformation will not necessarily impact significantly on source rock maturity or the distribution of reservoir sands but can give rise to unusual structural trap geometries it is also likely to increase the connectivity of trap bounding faults

fault growth mechanisms and scaling properties in foreland basin system the case study of monte alpi southern apennines italy abstract the present work focuses on the comprehension of the growth mechanisms and dimensional properties of the pre pliocene monte alpi fault network by mean of integrated field and laboratory analyses after this multidisciplinary approach detailed throw profiles are computed for each fault belonging to the monte alpi network subsequently the dimensional properties of the individual faults are calculated data obtained from this work are discussed in terms of fault growth mechanisms and timing of deformation and reported in a conceptual tectonic evolution model of the messinian foreland basin system data suggest that originally isolated fault segments developed during the earliest stages of foreland basin formation by re activation of a pre existing early cretaceous fault set and formation of an orthogonal one these two fault sets formed a scale independent network differently the same fault sets were also active during its subsequent development forming a scale dependent fault network characterized by t and y shaped fault intersections this deformation controlled the half graben depocenters evolution filled by up to ca 600 meters of terrigenous deposits during the late messinian time

the passa tres lode gold deposit parana state brazil an example of structurally controlled mineralisation formed during magmatic hydrothermal transition and hosted within granite abstract the passa tres granite is a nne ssw elongated shape intrusion located in the parana state southern brazil this intrusion was emplaced within metapelites of the mesoproterozoic votuverava group which are part of the n040 e trending lancinha shear zone gold mineralisation within the passa tres granite is held by meter scale quartz veins forming orebodies with variable massive banded sheared and or brecciated internal textures structural data indicate the existence of two orthogonal directions of structures n s and e w dipping 60 75 w and 45 70 s respectively mineralised veins contain in addition to the quartz of the gangue and in chronological order fluorite pyrite chalcopyrite gold aikinite molybdenite muscovite carbonate and baryte gold occurs as native grains within fractures that affect pyrite commonly associated with chalcopyrite and aikinite quartz veins are sometimes bordered by aplitic dykes additionally some of the veins exhibit a thin margin of k feldspar minerals that could represent the early stage of vein formation these observations the presence of unidirectional solidification textures ust along with abundant expression of pegmatite rich pockets within granite that crops out close to the surface allow the reconstruction of the granite architecture in terms of late magmatic evolution magmatic hydrothermal transition and position of the cupola n s and e w systems are interpreted to be contemporaneous and conjugate normal displacements are predominant and main mineralised veins are essentially located within extensional pull apart structures the structural model suggests that the normal faults were initiated along former low angle planes associated with aplite and or early quartz veins that subsequently controlled the opening of the pull apart structures that represent the economic orebodies zircon from the granite and muscovite grains from mineralised veins were dated by u pb and ar ar methods respectively zircons from the main facies medium grained gem and microgranite gef provided undistinguishable ages which were pooled to give an age of 611 9 3 6 ma a less abundant leucocratic facies white granite geb yielded a significantly younger age of 592 8 7 1 ma muscovites from quartz veins gave ar ar ages of 612 9 2 to 608 8 2 ma transitional vein with a k feldspar border 611 7 2 to 608 8 2 ma mineralised veins and 608 4 2 ma barren quartz vein thus the passa tres granite and its gold mineralisation appear to represent a unique example of an intrusion related gold system in which the mineralisation concentrates in the core of the magmatic intrusion in the form of meter scale veins strongly controlled by tectonics

the growth of non colinear normal fault systems what can we learn from 3d seismic reflection data abstract many rift zones exhibit a range of fault orientations rather than simple colinear faults that strike orthogonal to the inferred least principal stress the formation of non colinear fault sets has implications for assessing rift zone kinematics as well as determining palaeo stress state in extensional basins using 3d seismic reflection data we deduce the likely mechanisms responsible for the formation of a population of non colinear faults in the maloy slope area of the northern north sea three basement displacing fault populations exist on the maloy slope i large 1 km throw n s striking faults ii smaller

structural controls on jurassic gold mineralization and cretaceous tertiary exhumation in the foreland of the southern patagonian andes new constraints from la paloma area deseado massif argentina abstract fluid rock interaction occurring within high permeability conduits represented by fault fracture meshes is well known to control the development of hydrothermal ore deposits in this study we document the fundamental role of four sets of precursor joints reactivated as dilational faults displaying variable normal dip slip and strike slip components of motion in the formation of epithermal au ag deposits of economic interest paleostress analysis unravels how all the resulting four sets of hybrid extension shear fractures are kinematically compatible with an extensional stress field characterized by multiple permutations between the 3 and the 2 axes such permutations are interpreted to be associated with dominantly normal fault reactivation of suitably oriented early joint sets as a result of continued regional extension and by orthogonal stretching produced by differential downthrow of the hanging wall blocks of laterally terminating jurassic normal faults later fault reactivation appears to be associated with far field propagation of andean stresses marked by superposed strike slip and reverse fault slip components recording roughly e w horizontal compression this late fault reactivation could be related with a late early cretaceous shortening event known to have affected the studied sector of the deseado massif the subsequent tectonic evolution of the study area occurred within the general framework of a slow cretaceous to tertiary exhumation recorded by apatite fission track cooling ages our new thermochronometric results recording steady state cooling at a rate of c 1 c ma during the last 90 ma shed new light onto the post jurassic geodynamic evolution of the foreland of the southern patagonian andes

underlying structural control of small scale faults and fractures in west candor chasma mars 1 orientations of small scale faults and fractures within the interior layered deposits of west candor chasma were measured to investigate what information about the geologic history of valles marineris they can contribute deformational features were separated into six categories based on morphology and their orientations were analyzed the elevations at which the deformational features formed are recorded as a proxy for stratigraphic level deformational features occur over a continuous range of elevations and display regionally consistent preferred orientations indicating their formation was controlled by a regional stress regime the two most abundant preferred orientations of 35 and 110 are approximately parallel to the chasma walls and the inferred underlying normal faults the alignment of three populations of small faults at 140 consistent with the morphology of release faults indicates a large scale fault underlying the southeastern border of ceti mensa the preferred orientations imply these small scale deformational features formed from a continuation of the same imposed stresses responsible for the formation of valles marineris indicating these stresses existed past the formation of the interior layered deposits the origins of a fourth preferred orientation of 70 is less clear but suggests the study area has undergone at least two periods of deformation

growth folds above propagating normal faults abstract growth folds above the upper tips of normal faults are ubiquitous in extensional settings especially during the early phases of extension and in salt rich basins as slip accumulates on the underlying normal fault the geometry and size of the fold changes these changes reflect the dip throw displacement and propagation rate of the underlying normal fault as well as the thickness and rheology of the overlying cover these changes also have a marked impact on the architecture and distribution of synkinematic sediments as well as the styles of secondary deformation accommodating strain within the growing fold here we analyse a large dataset of natural and physically and numerically modelled growth folds to i characterise their diagnostic features ii investigate the controls on their geometry size and differences and iii describe how they grow with increasing extensional strain we demonstrate that larger fault throws and a thicker and weaker cover are associated with larger growth folds in contrast small fault throws as well as thin and strong brittle cover are associated with smaller growth folds we show that the geometry and size of growth folds vary through time the width and thus the wavelength of the fold is established relatively early during fold growth whereas fold amplitude increases gradually with increasing fault throw fold width and amplitude become increasingly similar during fold evolution until the fold is breached by the underlying normal fault we also derive a number of preliminary empirical relationships between readily observable structural and stratigraphic parameters in our dataset that may help estimate the geometry and size of poorly exposed i e in the field or imaged i e in the subsurface growth folds in addition we discuss how fault growth models i e constant length vs propagating may impact the three dimensional evolution of growth folds finally our work shows that growth folds are likely more common than previously thought for example although they are well documented in areas characterised by weak ductile cover strata and low strain rates our dataset illustrates that growth folds may also occur in brittle relatively strong rocks and in regions with high strain rates however the underlying controls on fold occurrence remain elusive

basement involved reactivation in foreland fold and thrust belts the alpine carpathian junction austria the late eocene early miocene alpine carpathian fold and thrust belt ftb lies in the transition between the eastern alps and the western carpathians se of the bohemian crystalline massif our study shows the involvement of crystalline basement from the former european jurassic continental margin in two distinct events a first extensional event coeval with eggerian karpatian c 28 16 ma thin skinned thrusting reactivated the rift basement fault array and resulted from the large degree of lower plate bending promoted by high lateral gradients of lithospheric strength and slab pull forces slab break off during the final stages of collision around karpatian times c 17 16 ma promoted large wavelength uplift and an excessive topographic load this load was reduced by broadening the orogenic wedge through the reactivation of the lower plate deep detachment beneath and ahead of the thin skinned thrust front with the accompanying positive inversion of the basement fault array and ultimately by the collapse of the hinterland summits enhanced by transtensional faulting although this work specifically deals with the involvement of the basement in the alpine carpathian junction the main conclusions are of general interest to the understanding of orogenic systems

complex geometry and kinematics of subsidiary faults within a carbonate hosted relay ramp abstract minor fault geometry and kinematics within relay ramps is strongly related to the stress field perturbations that can be produced when two major fault segments overlap and interact here we integrate classical fieldwork and interpretation of a virtual outcrop to investigate the geometry and kinematics of subsidiary faults within a relay ramp along the tre monti normal fault in the central apennines although the tre monti fault strikes parallel to the regional extension ne sw it shows predominant dip slip kinematics suggesting a nw se oriented extension acting at sub regional scale 1 10 km conversely the slickenlines collected on the front segment of the relay ramp highlight right lateral kinematics the subsidiary faults in the relay ramp show a complex geometry variable attitudes and slickenlines describe multiple kinematics left lateral dip slip right lateral independently of their orientation our fault slip analysis indicates that a local stress field retrieved from the kinematic inversion of the slickenlines collected on the front segment and likely promoted by the interaction between the overlapping fault segments that bound the relay zone can explain most of the geometry and kinematics of the subsidiary faults further complexity is added by the temporal interaction with both the regional and sub regional stress fields

tectonics and sedimentation in a paleo mesoproterozoic rift sag basin espinhaco basin southeastern brazil abstract sedimentologic paleogeographic stratigraphic structural and tectonic studies in a paleo mesoproterozoic metasedimentary succession espinhaco megasequence southeastern brazil indicates deposition in a rift sag basin four basin evolution stages are recognized prerift rift transitional and flexural the four stages can be represented by six unconformity bounded tectonosequences the unconformities are recognized in the field and mappable even on a regional scale the prerift and rift stages of the espinhaco basin were filled by products of continental depositional systems the prerift stage probably represents the first product of the rifting process before the development of the half grabens that characterize the rift stage during the rift stage mechanical subsidence due to lithospheric stretching was predominant and led to episodic rising of the depositional base level as a result the basin fill is characterized by coarsening upward intervals paleocurrent patterns indicate that block tilting and half graben subsidence uplift controlled sediment dispersion the first marine incursion within the espinhaco basin marks the change in the subsidence regime of the basin the evolution of the transitional and flexural stages was probably controlled by thermal subsidence due to thermal contraction of the lithosphere during cooling the transitional stage was characterized by relatively low subsidence rates higher subsidence rates and a consequent sea level rise characterize the flexural stage of the espinhaco basin in which three second order transgressive progradational sequences can be recognized

facies and microfacies of slope deposits abstract this paper reviews the facies and microfacies of the main types of slope deposits lamination and sorting when preserved are good evidence for overland flow features due to deformation folds boudins coatings and tails due to the rotation of clasts are associated with the early stages of deformation in earth slides other mass movements such as debris flows rock avalanches earth flows and to a certain extent dry grain flows may be characterised by similar microscopic facies typically a poorly sorted porphyric material porosity gives evidence for both liquefaction debris flows and frost induced mass movement solifluction however this criterion is thought to be irrelevant for fossil deposits owing to the rapidity and scale of post depositional changes wetting and drying freezing and thawing bioturbation at present only a detailed analysis of both the macro and micromorphological characteristics of the deposits allows an accurate identification of past slope dynamics

an analysis of the stability of thawing slopes ellesmere island nunavut canada active layer detachment slides are locally common on fosheim peninsula ellesmere island where permafrost is continuous the active layer is 0 5 0 75 m thick and summer temperatures are unusually

preserved extensional structures in an inverted cretaceous rift basin northwestern argentina outcrop examples and implications for fault reactivation 1 during the cretaceous eocene interval a system of intracontinental rift basins the salta group rift evolved in northwestern argentina individual segments of the rift later suffered different degrees of inversion during cenozoic shortening the tres cruces subbasin on the west side of the eastern cordillera was strongly deformed being now part of a thick skinned thrust belt with a predominantly n s structural trend on its eastern border tilting due to folding and thrusting and subsequent erosion have produced exceptional outcrops of preserved east trending extensional structures including half grabens rollover anticlines and extensional fault propagation folds farther west the synrift succession is only intermittently exposed although the interference of north and east trending structures as well as peculiar dome shaped anticlines with spur like extensions suggest that north and east trending cretaceous faults were reactivated particularly near their intersections compilation of published data and analysis of our new data focused on the salta rift indicates three main factors favoring the contractional reactivation of normal faults dip angles lower than approximately 60 especially for faults striking roughly normal to contraction strikes no closer to the contraction direction than approximately 30 and low downdip fault curvatures occasional dip slip reactivation of east trending faults does not match the present and long term andean stress regimes and presents an unresolved problem

static stress interactions in extensional earthquake sequences an example from the south lunggar rift tibet 1 an extensional earthquake sequence occurred in 2004 8 across a graben in the south lunggar rift on the tibetan plateau we use insar data to determine the location fault geometry and slip distribution of these earthquakes and to test whether the sequence is compatible with static stress triggering the mw 6 2 and 6 3 earthquakes in 2004 and 2005 both ruptured west dipping faults on the east side of a graben in 2008 a mw 6 7 earthquake ruptured a pair of east dipping fault segments on the other side of the graben offset from the earlier ruptures we compute first order dislocation models of stress change and demonstrate that the order and spatial configuration of this sequence of events is compatible with triggering by static stress transfer a continuation of the sequence would be most likely to occur on the northern extension of the 2008 rupture although variable slip rate along the rift may mean that the sequence has run its course the insar data for the 2008 earthquake also reveal slip on a fault that cuts the graben at a highly oblique angle we suggest that this is a release fault accommodating differential throw in the hanging wall and associate the deformation with a mw 6 0 aftershock activity on such a release fault has not been directly imaged before the zhongba sequence is one of several examples of recent clustered normal fault earthquakes on the plateau and may be an example of phase locking of similar faults

morphology and geotechnique of active layer detachment failures in discontinuous and continuous permafrost northern canada abstract fifty active layer detachment failures triggered after forest fire in the discontinuous permafrost zone central mackenzie valley 65 n are compared to several hundred others caused by summer meteorological triggers in continuous permafrost fosheim peninsula ellesmere island 80 n most failures fall into compact or elongated morphological categories the compact type occur next to stream channels and have little internal disturbance of the displaced block whereas the elongated types can develop on any part of the slope and exhibit greater internal deformation frequency distributions of length to width and length to depth ratios are similar at all sites positive pore pressures expected theoretically were measured in the field at the base of the thawing layer effective stress analysis could predict the instability of slopes in both areas providing cohesion across the thaw plane was set to zero and or residual strength parameters were employed the location of the shear planes or zones in relation to the permafrost table and the degree of post failure secondary movements including headwall recession and thermokarst development within the failure track differed between the localities reflecting dissimilarity in the environmental triggers and in the degree of ground thermal disturbance

detachment faulting and the evolution of passive continental margins major detachment faults play a key role in the lithospheric extension process in the basin and range province and may also be important in other continental extension terranes such detachment faulting leads to an inherent asymmetry of extensional structure and of uplift subsidence patterns detachment models developed for the formation of metamorphic core complexes can also be applied to the formation of passive continental margins we therefore suggest the existence of upper plate and lower plate passive margins these give rise to a complementary asymmetry of opposing margins after continental breakup transfer faults offset marginal features and allow margins to switch from upper plate to lower plate characteristics along strike

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

environmental assessment from the sedimentary record of high latitude fiords the sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution the scale of millennia and high resolution decadal to less than daily unlike the lacustrine record which has been used very successfully in these studies the sedimentary processes and thus the sedimentary deposits of fiords differ 1 in the role of salt water in inhibiting mixing and promoting flocculation and through the role of sea ice 2 in the exchange of mass and energy with the much larger ocean beyond and 3 in the role of benthic biota in the sedimentary environment the work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes as well as glacial periglacial and geomorphic history and that they are important proxies for long term climate and hydrology recommendations for advancing this work include long term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment integration of results from fiords in opposite polar latitudes and among proxies especially from lacustrine and ice core records will produce valuable insights assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type

quantifying exposure of linear infrastructures to earthquake triggered transverse landslides in permafrost thawing slopes seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains in addition rapid ice melting in low permeability fine grained soils can lead to excess pore water p

the geometry kinematics and rates of deformation within an en echelon normal fault segment boundary central italy abstract the geometry kinematics and rates of deformation have been investigated within an en echelon fault segment boundary between two left stepping major normal faults in the central apennines italy examination of faulted post glacial sediments and geomorphic features attributed to glacial retreat 18 ka reveals that the two major faults dominate the recent slip with rates that are 5 10 times greater than the other faults at the centres of the major faults slip is parallel to the regional extension direction ne sw defined by focal mechanisms and borehole breakouts slip vector azimuths defined by striations on faults in the stepover zone indicate ne sw extension on nw se faults sub parallel to the regional extension direction together with significant and contemporaneous nw se extension along the strike of the apennines on ese wnw and ene wsw faults thus distributed three dimensional strain occurs in the stepover between the two major bounding faults extension rates summed across the stepover are 0 68 mm y parallel to the regional extension compared to 2 mm y at the centre of one of the major faults extension rates along strike of the fault zone are 0 14 mm y within the stepover and zero at the centres of the two major bounding faults the above information is used to discuss how extension is partitioned between different structures during the growth and linkage of normal faults

mapping the descent of indian and eurasian plates beneath the tibetan plateau from gravity anomalies the collision of india with asia has produced a complicated continental continental plate boundary involving folding and faulting of variable trends and styles within and along the margins of the tibetan plateau numerous lines of evidence including the development of two scales of folding in tibet suggest that the lowermost crust is behaving in a ductile fashion this weak lower crust might then decouple the fundamental plate tectonic motions in the uppermost mantle from the complex pattern of surface faulting in this study we use bouguer gravity anomalies to map out the geometry of indian and eurasian plate interactions in the mantle beneath the plateau based on both the inferred geometry of the moho and lateral variations in lithospheric strength determined from mechanical modeling in our preferred model the lithosphere beneath tibet consists of two distinct units 1 the underthrust to the north indian plate which sutures with the eurasian plate in the upper mantle below the yarlung zangpo suture or the gangdese igneous belt 200 400 km north of the main boundary thrust and 2 the underthrust to the south eurasian plate a subducting slab of indian upper mantle extends about 200 km into the asthenosphere north from the mantle suture and exerts a bending moment of about 3 5 1017 n on the indian plate thus the mantle lithosphere appears to be behaving in the simple fashion of converging oceanic plates while the more buoyant continental crust deforms under high gravitational potential in a complex pattern controlled by its lateral and vertical strength heterogeneity

wide and narrow margins of the brazilian south atlantic two contrasting end members of passive continental margins here referred to as wide and narrow margins are present in the south atlantic although some margin segments are intermediate between these two styles narrow margins are characterized by a large bounding fault 4 km throw near the shelf edge a sharp transition zone 10 20 km wide from normal thickness to substantially thinned continental crust or oceanic crust where the total width of extended continental crust is usually less than 100 km wide continental margins are characterized by a broad continental shelf and a wide zone 50 600 km of thinned crust with an even distribution of faults wide margins usually have a more gentle continental shelf and slope narrow narrow wide wide and wide narrow conjugate margin pairs exist in the south atlantic and are suggested to be controlled mainly by the opening kinematics and the thermal structure of the lithosphere during rifting basement structure and strain rate appear to have exerted little control on the style of margin extension although basement architecture appears to control the trend of the initial rifts the positions of fracture zones which separate narrow and wide segments and the rate of lateral rift propagation

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

relict mountain slope deposits of northern portugal facies sedimentogenesis and environmental implications this paper deals with the formation processes and the palaeoenvironmental significance of relict slope deposits located on the uppermost part of the north portugal mountains for this purpose seven key sites representative of the different lithofacies have been selected and analysed in detail the data show that three main dynamic processes are responsible for the emplacement of regional fossil slope deposits runoff debris flows and dry grain flows the ubiquity of these processes and the lack of frost related features or landforms do not support the existence of severe pleistocene climates in this part of the lberian peninsula as postulated by previous work pedological data gathered at one of the study sites show that a subalpine environment was probably present at 700 800 m altitude between 29 and 14 kyr using data from the pyrenees mountains a 6 5 to 12 c depression in mean annual temperature has been tentatively postulated for this pleniglacial period copyright 2003 john wiley sons ltd

fault growth and linkage implications for tectonosedimentary evolution in the chezhen basin of bohai bay eastern china the chezhen basin has highly representative structural features of the jiyang depression bohai bay area the structural geometry and the boundary fault linkage exert a strong influence on basin development and depositional environment based on structural analysis at least six early fault segments are identified in the northern boundary of the chezhen basin these fault segments are important in controlling stratal architecture and distribution the antecedent structures controlled subbasin initiation and development the cenozoic rift initiated in the early eocene with the development of six isolated fault segments associated with deposition of the es4 member during the deposition of the lower es3 member these six fault segments quickly linked and formed the present architecture frame fault linkage has not resulted in a redistribution of displacement with the expansion of the chezhen basin the depocenters of the upper strata were kept in nearly the same sites until the early miocene then the activity of the chengnan fault ceased fault linkage is a significant event in basin evolution and its process may be very rapid however the fault linkage exerted considerable control on sedimentation and evolution of the basin this study demonstrates that it is necessary to integrate structural and stratigraphic data to reconstruct the temporal and spatial evolution of normal fault zones

late quaternary glacial history of lake hazen basin and eastern hazen plateau northern ellesmere island nunavut canada the glacial history of the broad interior of northeastern ellesmere island is first documented here studies of glacial geomorphology and marine and lacustrine sedimentology indicate that the regio

comparison of surface slip and focal mechanism slip data along normal faults an example from the eastern gulf of corinth greece abstract focal mechanism and surface slip data are used to investigate whether kinematics are similar at depth and at the surface along an active normal fault in the gulf of corinth greece we present a new database of slip data from the lateral termination of the south alkyonides fault segment safs and the en echelon stepover between it and an adjacent fault and use published data on surface slip and focal mechanism data pertaining to slip at depth during the 1981 alkyonides earthquake sequence the focal mechanisms exhibit similar fault plane orientations and kinematics to those measured at the surface within the stepover both data sets show that contemporaneous c n s and c e w extension is being accommodated by c e w and c n s oriented normal faults and the overall deformation is distributed oblate vertical flattening the deviation of the surface slip direction from 350 increases with distance from the centre of the safs the deviation of the focal mechanism t axes from 350 fit well with the surface data implying that the coseismic slip on the safs at depths of 7 10 km exhibits a similar kinematic pattern as that observed at the surface our results imply that it is critical to know the along strike position of data on a fault if either focal mechanisms or surface slip are to be used to infer regional strain and stress trajectories

linked fault families in basin formation abstract recent models of faulting tectonics in basins and passive margins have emphasized the linked nature of faults in a way that is analogous to that developed for thrust regimes a linked fault system requires three components ramps flats and sidewalls or transfers basins that are the result of other processes are not considered in this contribution and the examples used are drawn from the midland valley and northumberland basins of the u k where existing mapping by the british geological survey as well as field work undertaken by the author indicate that such models are appropriate this paper summarizes the geometric features and constraints of such models and emphasizes the role of each of the three critical components of a linked system for large deformations that result in the formation of major extensional and strike slip basins the principal geometries can be understood by reference to regionally and locally balanced fault models that involve detachment ramp and sidewall or transfer elements tip strains and both lateral and vertical accommodation zones are included in the general model but these probably account for less than 10 of the total upper crustal strain the basic analysis of a linked basin system requires the transfer of displacement on and between the fault and shear zone components the geometry of the stratigraphic units is used to deduce the active linkage on the fault system in oblique slip systems and where the dominant extensional ramp is connected to oblique transfer and detachment systems lateral and sidewall sub basins and intra basin uplifts occur as part of continuing slip on the fault system these control facies distribution and depocentre evolution the existence of a basin forming linked system frequently controls later deformation of basins and margins and an appreciation of basin growth faults and stratigraphic geometry is essential in the interpretation of inverted basins and orogenic belts involving supracrustal formations

longitudinal evolution of the suez rift structure egypt abstract a three dimensional study of the structure of the suez rift has been carried out using field and subsurface data in an attempt to determine the role of transverse faults and the longitudinal evolution of the rift as in most intracontinental rifts the structure of the gulf of suez area is governed by normal faults and tilted blocks whose crests constitute the main target of exploratory wells the fault pattern consists of two major sets of trends 1 1 longitudinal faults parallel to the rift axis and created in an extensional regime where 3 was trending ene wsw and 2 2 transverse faults with a n s to nne ssw dominant trend the transverse faults are inherited passive discontinuities while most of the longitudinal faults were created during neogene times in a purely extensional regime both sets were simultaneously active producing a zigzag pattern and rhombic shaped blocks the transverse faults can show horizontal strike slip components and act as relays between major normal faults although the suez rift appears as a simple narrow elongated trough dominated by two almost symmetrical shoulders its internal structure is asymmetrical cross profiles show that all the major blocks are tilted in the same direction however the tilt direction changes twice along the rift to the north and to the south of the rift the blocks are tilted eastward while in the central part they are tilted westward to the north the change of dip is accompan ed by a graben type twist zone without transverse faulting at least in the neogene series to the south the change of dip is accompanied by a more complex structure involving both a major transverse fault and a horst type twist zone in this latter case the transverse fault does not cut through the entire rift balanced cross sections established from subsurface data show that the tilt angle and the amount of extension increase from north to south while the width of the blocks decreases indicating a pole of opening close to the northern end of the gulf minimum values for the amount of opening range from 5 km in the north to about 20 km in the south

constraining mountain front tectonic activity in extensional setting from geomorphology and quaternary stratigraphy a case study from the matese ridge southern apennines abstract rugged peaks large intermontane basins and frequent seismicity all characterize the active extensional tectonic setting of the southern apennines the matese ridge typifies the active tectonic setting of the southern apennines with steep carbonate mountain fronts and large depositional centres moderate to high magnitude earthquakes have affected the northern western and eastern sectors of the matese ridge in historical times however the seismogenic potential of the extensional fault system bounding the southern matese mountain front has not been fully assessed to date to unravel the active tectonic setting of the southern matese mountain front we have carried out a comprehensive geomorphological and tectonic geomorphology investigation of the mountain front and its piedmont and have constrained results through chronological i e tephrostratigraphical and 40ar 39ar and structural data our study highlights that in the last 600 ka activity along e w trending normal faults has identified a locus of higher slip rate tectonic activity in the central part of the analysed mountain front these active e w striking normal faults are inherited reactivated structures which have interacted with newly formed nw se striking normal faults during ne sw extension active on the regional scale causing fault bending and local extension to be oriented n s consequently lower slip rates have been recorded along the nw se striking normal faults at the north western and south eastern tips of the southern matese front the long term displacement rate of the fault system at the boundary of the central part of the southern matese front is consistent with mean values of displacement of faults that in the southern apennines show evidence of activity during the late quaternary despite strong historical seismicity clustering primarily around the study area our data highlight that it cannot be ruled out that moderate to high magnitude seismicity could affect the southern matese mountain front our case study represents an example of the possible modes of formation and evolution of mountain front basin systems in extensional setting and shows how the combination of different data sets allows unravelling the interaction between tectonic erosional and sedimentary processes which lead to landscape evolution of active mountain belts

calcite twinning strains from syn faulting calcite gouge small offset strike slip normal and thrust faults we have evaluated the stress strain behavior of calcite precipitated and mechanically twinned in small offset strike slip normal and thrust faults of a variety of ages and from a variety of tectonic settings n 3001 twin measurements 63 strain analyses from 18 field sites five strike slip faults with syn faulting horizontally striated calcite rake 0 were studied and we report the orientations of the contemporaneous stress strain field associated with each fault intrusion of the marathon large igneous province mafic dikes 2 1 ga in archean crust minnesota usa post keweenaw rift 1 1 ga faulting island lake fault central ontario canada subduction associated with metamorphic core complex formation cretaceous china subduction cretaceous to miocene italy and continental extension recently active furnace creek fault death valley california usa seven normal faults with synfaulting dip slip striated calcite were studied and are from the following tectonic settings a normal fault slip surface in an ordovician piedmont fold appalachian s paleo subduction associated with cretaceous metamorphic core complex formation china 3 sites the paleo extensional atlantic margin 55 ma ireland 1 site with a u pb calcite age continental extension 1 active site mojave desert a transcurrent margin jamaica 1 active fault site and subduction 2 active faults along the eur african margin in italy with calcite u th disequilibria ages and crete respectively six thrust fault examples are all from convergent orogenic settings the basal thrust of the penokean 1850 ma fold and thrust belt the penokean orogen foreland in mesabi range banded iron formation folds an offset breccia body in the permian gondwanide belt ellsworth mountains antarctica the frontal thrust of the gondwanide cape belt south africa the paleocene frontal prospect thrust sevier belt wyoming and an alpine foreland back thrust lulworth cove u k for each strike slip fault system the twinning shortening strain is horizontal and at an angle of 0 60 to the respective fault plane dextral or sinistral although in the majority of cases the shortening axis is parallel to fault strike 13 of 23 results in each normal fault example dip slip kinematic striations dominate the faulted surface yet the orientation of the maximum principal compressive stress 1 and shortening strain axis e1 are not 45 to the fault plane as predicted but are sub horizontal and either strike parallel 25 of 35 results or strike normal 10 of 35 results thrust faults preserve shortening strain axes parallel to the dip slip kinematic direction within the fault plane plane strain and not at 45 to the principal plane 5 of 5 results none of the fault stress strain field results reported here support the andersonian or mohr coulomb criteria for stress strain relations predicted along faults

climate and material controls on periglacial soil processes toward improving periglacial climate indicators one of the distinguished efforts of a l washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators this paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies with a focus on solifluction and thermal contraction cracking and associated landforms structures landforms resulting from solifluction reflect both the depth subjected to freeze thaw and the thickness of frost susceptible soils the thickness of a solifluction structure can be used to infer the dominant freeze thaw regime and minimum seasonal frost depth ice wedge pseudomorphs have limited potential as a climate indicator because 1 they mainly reflect extreme winter temperatures 2 their thermal thresholds depend on the host material and 3 they need to be distinguished from frost wedges of other origin produced under different thermal and or material conditions monitoring studies of currently active ice wedges suggest that ice wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed however to improve the resolution of periglacial paleoclimate indicators

fault growth and interactions in a multiphase rift fault network horda platform norwegian north sea abstract physical models predict that multiphase rifts that experience a change in extension direction between stretching phases will typically develop non colinear normal fault sets furthermore multiphase rifts will display a greater frequency and range of styles of fault interactions than single phase rifts although these physical models have yielded useful information on the evolution of fault networks in map view the true 3d geometry of the faults and associated interactions are poorly understood here we use an integrated 3d seismic reflection and borehole dataset to examine a range of fault interactions that occur in a natural multiphase fault network in the northern horda platform northern north sea in particular we aim to i determine the range of styles of fault interaction that occur between non colinear faults ii examine the typical geometries and throw patterns associated with each of these different styles and iii highlight the differences between single phase and multiphase rift fault networks our study focuses on a ca 350 km 2 region around the 60 km long n s striking tusse fault a normal fault system that was active in the permian triassic and again in the late jurassic to early cretaceous the tusse fault is one of a series of large 1500 m throw n s striking faults forming part of the northern horda platform fault network which includes numerous smaller 2 10 km long lower throw nd stage nw se striking faults grew interacted and linked with the n s striking tusse fault documenting a range of interaction styles including mechanical and kinematic isolation abutment retardation and reactivated relays our results demonstrate that i isolated and abutting interactions are the most common fault interaction styles in the northern horda platform ii pre existing faults can act as sites of nucleation for 2 nd stage faults or may form mechanical barriers to propagation iii the throw distribution on reactivated 1 st stage faults will be modified in a predictable manner if they are intersected or influenced by 2 nd stage faults iv sites of fault linkage and relay breaching associated with the first phase of extension can act as preferential nucleation sites for 2 nd stage faults and v the development of fault intersections is a dynamic process involving the gradual transition from one style to another

form and internal structure of active layer detachment slides fosheim peninsula ellesmere island northwest territories canada three recent shallow landslides over permafrost are described slides occur in low to medium plasticity clays containing some bands of silts and fine sands slope failure results from rapid thaw at the base of the active layer of soil that is ice rich due to antecedent two sided freezing displaced slide blocks retain their integrity because of hardening of the active layer by cryodesiccation and summer evaporation blocks move over a soft basal shear zone a few millimetres to several centimetres thick compression in the toe zone of slides is low at sites where runout is possible but in other locations causes emergent shears and complex folding failure histories are varied and range from simple unitary slides to complex sequential failures in which active layer segments are mobilized progressively higher up the slope this study demonstrates the importance of active layer thermal and hydrological regimes in addition to material properties in determining the mode of slope failure

3d structure and evolution of an extensional fault network of the eastern dampier sub basin north west shelf of australia abstract insights of spatial and temporal development of fault network in 3d is crucial for understanding the process evolution of complex fault network and for evaluating the regional and local stresses control on structure development we demonstrate a fault network on the eastern dampier sub basin north west shelf of australia which consists of 1 a ene trending fault array that has a through going segment at depth and a series of left stepping fault splays at upper levels and 2 a network of ene and nne trending intersecting faults decoupled from the basement structures this research shows that the segmented ene trending fault array developed through three extensional phases in the late paleozoic in the early jurassic and in the late middle jurassic fault analysis shows that the summed displacement of the segmented en echelon faults behaves as a single fault and that the basement fault controlled the fault array in the upper section through vertical linkages a typical coherent fault system the nne and ene trending intersecting faults formed simultaneously in the late middle jurassic as such they might have controlled by 3d strain field released from the rosemary and mermaid fault systems bounding the fault network this implies that fault geometry derived from 3d seismic interpretation need to be treated with caution as the alignment of fault sets may not directly relate to regional far field stress but in some cases significantly modified by local stresses induced by reactivated larger faults this study provides an analogue for the interpretation of other rift systems where structures were controlled by competing forces of regional and local stresses and where reactivated and newly formed structures coexist in polyphase of extensions

fluid flow evolution in the albanide fold thrust belt insights from hydrogen and oxygen isotope ratios of fluid inclusions tectonic forces generated during thrust emplacement along active margins may drive complex fluid flow patterns in fold thrust belts and foreland basins isotope data 2h and 18o of fluid inclusions hosted in calcite vein cements are used to reconstruct regional fluid migration pathways in the albanide fold thrust system the calcite veins used in this study developed in a sequence of naturally fractured cretaceous eocene carbonate rocks as a result of episodic throughput of fluids from the early stages of burial onward the acquired fluid inclusion isotope data demonstrate that fluids circulating in the carbonates were derived from an underlying reservoir that consisted of a mixture of meteoric water and evolved marine fluids probably derived from deep seated evaporites the meteoric fluids infiltrated in the hinterland before being driven outward into the foreland basin and ascended as soon as fracturing induced a sufficient increase in permeability structural and petrographic observations provide time constraints for the various phases of fracture infilling and reveal an increasing dominance of meteoric water in the system through time as migration pathways shortened and marine formation fluids were progressively flushed out similar fluid flow evolutions have previously been recorded in various fold thrust belt settings elsewhere in the world