transition from a singly vergent to doubly vergent wedge in a young orogen the greater caucasus the greater caucasus mountains due to their youth 5 ma provide an opportunity for insight into the early stages of orogen development during continent continent collision however their recent tectonic evolution and first order architecture remain unclear here we investigate the evolution of the orogen by integrating new observations of the fluvial geomorphology and neotectonics of the range with prior work on seismicity geodetic strain bedrock geology and foreland basin structure we find that the range contains four zones along strike that differ in structural architecture topography and first order tectonic history in particular two south directed singly vergent zones at the western and eastern tips of the orogen are separated by both a central doubly vergent zone that is dominated by north directed deformation and an eastern doubly vergent zone in which south directed thrusting dominates we hypothesize that the along strike changes in vergence and locus of deformation reflects different stages in the development of a doubly vergent orogen with the tips of the range preserving an early singly vergent form and the center recording a more advanced orogen the differences between the two doubly vergent zones seem to be driven by the initial stages of collision between the structurally thickened crust of the greater and lesser caucasus orogens which initiated at 5 ma

role of decollement material with different rheological properties in the structure of the aljibe thrust imbricate flysch trough gibraltar arc an analogue modelling approach abstract the miocene aljibe thrust imbricate flysch trough in the external zone of the gibraltar arc shows large changes in structural style towards the foreland rheological variation of the decollement rocks triassic evaporitic rocks and mesozoic limestones appears to be the main factor controlling the contrasts in structural style that characterise adjacent wedge domains in order to test this hypothesis we carried out analogue experiments involving three dimensional variations of decollement material a plate of viscous material was placed in the central part of the models at the base of the sand multilayers different geometries of the viscous plate were used experimental results show a strong link between the rheological properties of the decollement material and the structure of the overlying thrust wedge these results compare well with the internal geometry and vergence distribution in the aljibe thrust imbricate indeed the tectonic style of the wedge can be explained as a consequence of variations of rock type along the basal decollement

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

cenozoic evolution of neotethys and implications for the causes of plate motions africa north america eurasia plate circuit rotations combined with red sea rotations and new estimates of crustal shortening in iran define the cenozoic history of the neotethyan ocean between arabia and eurasia the new constraints indicate that arabia eurasia convergence has been fairly constant at 2 to 3 cm yr since 56 ma with slowing of africa eurasia motion to 1 cm yr near 25 ma coeval with the opening of the red sea ocean closure occurred no later than 10 ma and could have occurred prior to this time only if a large amount of continental lithosphere was subducted suggesting that slowing of africa significantly predated the arabia eurasia collision these kinematics imply that africa s disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern eurasia slowed its motion the slow steady rate of northward subduction since 56 ma contrasts with strongly variable rates of magma production in the urumieh dokhtar arc implying magma production rate in continental arcs is not linked to subduction rate

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

structural development and stress evolution of an arcuate fold and thrust system southwestern greater caucasus republic of georgia abstract the southern front of the greater caucasus is quite rectilinear in plan view with the exception of part of the rioni basin where marine and continental deposits of cretaceous neogene age were locally folded and uplifted this resulted in the formation of an arcuate fold and thrust system that extends 45 km into the foreland although previous studies suggested that this system has developed only since miocene times our new detailed and systematic field measurements of brittle and ductile structures show a very complex history consisting in four main phases of brittle deformation and folding dated from eocene to quaternary times we collected microtectonic data at 248 faults and calculated the related paleostress tensors the first two phases which we document here predated folding and were characterised by dominant transcurrent faulting and subordinate reverse motions the greatest principal stress 1 was perpendicular and later parallel to the mountain belt afterwards nw se e w and ne sw trending south vergent asymmetrical folds started to form in the western sector of the study area folds are sinuous in plan view whereas to the east they show a left stepping en echelon geometry another two brittle deformation phases took place after the folding due to the activity of a set of right lateral strike slip faults that strike nw se and ne sw respectively as well as by left lateral strike slip faults mostly striking nw se ne sw and nne ssw these two additional phases were produced by a ne sw to n s trending 1 the arcuate belt is marked by along strike variations in the tectonic regime and deformation geometry plus belt parallel stretching based on our field data integrated with published analogue models we suggest a possible explanation for the rioni structure in terms of the oblique asymmetric indentation of an upper crustal blocks moving to the ssw

landslides triggered by earthquakes and their relations with faults and mountain slope geometry an example from ecuador abstract a large number of landslides occurred during two seismic events respectively 6 9 and 6 1 msw on 5 march 1987 in the ecuadorian andes these landslides have been mapped digitized and coregistered with topography at 1 50 000 scale geometry of coseismic and holocene faulting has been assessed integrating field and geophysical data landslide distribution and holocene tectonic features have been compared with earthquake foci geological deposits slope area inclination and orientation and vegetation cover the macro seismic field deduced by landslide distribution is ellipse shaped with the major axis striking nne and coinciding with the trend of the coseismic and holocene faults landslide distribution also shows a correlation with respect to the dip direction of these faults and the orientation of mountain slopes slopes parallel to the coseismic fault planes sloping towards wnw are almost unaffected by landsliding while this increases on the slopes at high angle to the fault plane and lying along its strike if these results could be confirmed in other areas a method of reconstruction of geometry of seismogenetic faults from topographic effects appears feasible

western versus eastern black sea tectonic evolution pre rift lithospheric controls on basin formation abstract we demonstrate the key role of pre rift rheology on the kinematics of basin formation in the western and eastern black sea basins constraints on modelling results are provided by a large data set based on more than 50 000 km of multichannel seismics offshore and onshore wells regional gravity and magnetic surveys refraction seismics and field studies the model supports the presence of important differences in the thickness and in the thermal state of the lithosphere which rifted to form the western middle barremian and the eastern middle paleocene black sea subbasins a 200 km and a 80 km thick pre rift lithosphere appear to have driven the deformation in the western and in the eastern black sea respectively differences in the geometry and in the mechanical properties of the pre rift lithosphere have a strong control on the depth of necking and thus on the basin morphology the model sheds light on palaeotectonic and palaeogeographic reconstructions duration of rifting events location of subsiding areas and erosional surfaces the western and the eastern parts of the black sea appear to be two distinct basins characterised by different evolutionary paths determined by different pre rift conditions

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

latest pleistocene holocene tectonics of the ecuadorian andes abstract a structural study was carried out in the most tectonically active areas of the ecuadorian andes including part of the interandean valley the cordillera real and the subandean zone since the pleistocene the region has undergone complex wrench tectonics which are still active apparently two different stress states have coexisted within different parts of the andean range during the latest pleistocene and holocene 1 1 the external part of the chain including the cordillera real and the westernmost part of the subandean zone has been subject to a east northeast west southwest direction of greatest principal stress associated motions are partitioned between right lateral oblique thrusting and pure right lateral strike slip faulting along north south to north northeast trending structures as a whole these define a right lateral transpressive shear zone 2 2 in the interandean valley which lies above a major tertiary suture zone deformations are consistent with a north south direction of greatest horizontal principal stress associated with recent development of a left lateral transtensional shear zone in the first zone fault displacements are at least an order of magnitude larger than in the second zone the present tectonics of the area is explained by a kinematic model in which the wedge shaped cordillera real crustal block bounded to the east by a right lateral shear zone and to the west by a left lateral shear zone is being uplifted and extruded northward with respect to the cordillera occidental and to the stable south american foreland this motion is the result of oblique convergence between the nazca and south american plates

topography as a major factor in the development of arcuate thrust belts insights from sandbox experiments abstract we have used sandbox experiments to investigate and to illustrate the effects of topography upon the development of arcuate thrust belts in experiments where a sand pack shortened and thickened in front of an advancing rectilinear piston the geometry of the developing thrust wedge was highly sensitive to variations in surface topography in the absence of erosion and sedimentation the surface slope tended to become uniform as predicted by the theory of critical taper under these conditions the wedge propagated by sequential accretion of new thrust slices in contrast where erosion or sedimentation caused the topographic profile to become irregular thrusts developed out of sequence for example erosion throughout a hinterland caused underlying thrusts to remain active and inhibited the development of new thrusts in the foreland where initial topography was irregular in plan view accreting thrusts tended to be arcuate they were convex towards the foreland around an initially high area concave towards the foreland around an initially low area initial plateaux tended to behave rigidly while arcuate thrust slices accreted to them thrust motions were radial with respect to each plateau within transfer zones to each side fault blocks rotated about vertical axes and thrust motions were oblique slip at late stages of deformation the surface slope of the thrust wedge tended towards a uniform value initial mountains of conical shape representing volcanoes also escaped deformation except at depth where they detached arcuate thrust slices accreted to front and back where a developing thrust wedge was subject to local incision accreting thrust slices dipped towards surrounding areas of high topography forming vs across valleys arcuate structural patterns are to be found around the three highest plateaux on earth tibet pamirs and altiplano and around the tromen volcanic ridge in the neuquen basin of northern patagonia we infer that these areas behaved in quasi rigid fashion protected as they were by their high topography

the caucasus an actual example of the initial stages of continental collision abstract a field study of the neotectonics of the georgian caucasus is combined with geophysical geodetic and geological information in order to obtain a mechanical model of actual deformation the analysis of satellite photos together with topographical and geological maps shows that the great caucasus is bisected by a nne trending sinistral strike slip fault zone the western great caucasus is thrusted to the south over the rioni basin while on the other hand its northern flank is a monocline that descends gently into the russian platform active volcanism is present from elbruz to kazbeg the eastern great caucasus is limited by thrusts to the north and to the south and intermediate structures are disposed in a fan like shape no recent volcanism is observed the eastern limit of the chain is a nnw trending dextral strike slip fault zone seismicity from a local network illustrates the activity of the thrusts and gives evidence for the strike slip faults microtectonic data confirm the recent activity and the sinistral character of the borjomi kazbeg strike slip fault the strike slip faults bordering the eastern caucasus may be seen as the limits of a plastic wedge in front of the arabian plate at an early stage of continental collision

cenozoic recent tectonics and uplift in the greater caucasus a perspective from azerbaijan the greater caucasus is europe s highest mountain belt and results from the inversion of the greater caucasus back arc type basin due to the collision of arabia and eurasia the orogenic processes that led to the present mountain chain started in the early cenozoic accelerated during the plio pleistocene and are still active as shown from present gps studies and earthquake distribution the greater caucasus is a doubly verging fold and thrust belt with a pro and a retro wedge actively propagating into the foreland sedimentary basin of the kura to the south and the terek to the north respectively based on tectonic geomorphology active and abandoned thrust fronts the mountain range can be subdivided into several zones with different uplift amounts and rates with very heterogeneous strain partitioning the central part of the mountain range defined by the main caucasus thrust to the south and backthrusts to the north forms a triangular shape zone showing the highest uplift and fastest rates and is due to thrusting over a steep tectonic ramp system at depth the meridional orogenic in front of the greater caucasus in azerbaijan lies at the foothills of the lesser caucasus to the south of the kura foreland basin

kinematics of an arcuate fold thrust belt the southern eastern carpathians romania abstract flysch and molasse nappes of the eastern carpathians strike mainly n s and were folded and imbricated since the late early cretaceous boundaries of stratigraphic and structural units and calculated fold trend axes from the southern part of the eastern carpathians indicate a curvature of the orogen by 80 kinematic data from fault slip analysis of all nappe systems exposed in the arc document an overall nw se contraction nappes of the external moldavides nappe complex underwent deformation since the late cretaceous peaking in the miocene and exhibit fanning subhorizontal contraction axes from e w in the n striking part of the eastern carpathians through wnw ese and nw se in the northern part of the arc to nnw sse in its southwestern part geometric relations between faults and folds indicate that this fan pattern reflects an extended interval and was contemporaneous to nappe stacking and subsequent continental collision statistical analysis reveals correlation between orientation of the fanning kinematic axes and the structural trend where fanning of subhorizontal contraction axes is systematically smaller than change of strike of fold thrust structures orogen parallel extension in the tarcau nappe of the moldavides nappe complex is estimated to be 20 this low value of orogen parallel extension indicates a primary arc in contrast to bending of a previously straight fold thrust belt low orogen parallel extension and the observed pattern of structural and kinematic axes can be simulated in sand wedge indentation models where the indenter moves oblique to its margins in these models thrust traces and fold axes are curved around the arc but are parallel to the margins of the indenter away from the corner area the movement directions of the thrust faults in the models are deflected from normal to fault strike towards the movement direction of the indenter leading to fanning contraction directions similar to those observed in the eastern carpathian arc thus the main controlling factors on arc formation were the plate margin geometry i e the shape of the upper plate and the movement direction of the upper plate relative to the orientation of its margins the influence of the geometry of the continental margin in the lower plate was mainly by imposing constraints on the movement direction of the upper plate

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

kinematics of the alpine arc and the motion history of adria the alps have been interpreted traditionally in terms of north or northwest directed convergence between africa and europe1 with adria the continental underpinnings of the adriatic sea and northern italy acting as a promontory of the african continent2 this has been supported by recent analyses of africa europe relative plate motions3 5 which indicate dominantly north south directed convergence during the tertiary phase of intracontinental shortening we show here however that kinematic indicators from alpine tectonites are difficult to reconcile with this motion history figs 1 and 2 and are explained best by roughly west northwest directed adria europe motion since about 70 million years ago combined with an arc normal pattern of motion driven by local body forces this implies that adria has moved independently of both africa and europe since at least the late cretaceous

sedimentary basin tectonics from the black sea and caucasus to the arabian platform introduction the palaeozoic to recent evolution of the tethys system gave way to the largest mountain chain of the world extending from the atlantic to pacific oceans the alpine himalayan mountain chain which is still developing as a result of collision and northwards con vergence of continental blocks including apulia in the west the afro arabian plate in the middle and the indian plate in the east this special publication addresses the main problems of the middle part of this system incorporating the balkans black sea and greater caucasus in the north and the afro arabian plate in the south since the early mesozoic a number of small to large scale oceanic basins opened and closed as the intervening continental fragments drifted northwards and diachro nously collided with and accreted to the southern margin of the eurasian plate despite the remark able consequences of this in terms of subduction obduction and orogenic processes little is known about the timing and palaeogeographic evolution of the region this includes the amounts of short ening and interplay between synconvergent extension and compression development of magmatic arc and arc related basins and the timing and mechanism of their deformation the chapters pre sented in this special publication present new information that help to fill some of the gaps of the puzzle

tectonic and gravity induced deformation along the active talas fergana fault tien shan kyrgyzstan abstract this paper shows by field palaeoseismological data the holocene activity of the central segment of the intracontinental talas fergana fault tff and the relevance of possible future seismic shaking on slope stability around a large water reservoir the fault striking nw se is marked by a continuous series of scarps deflected streams and water divides and prehistoric earthquakes that offset substrate and holocene deposits fault movements are characterised by right lateral strike slip kinematics with a subordinate component of uplift of the ne block structural geological and geomorphological field data indicate that shallow and deep landslides are aligned along the tff and some of them are active where the tff runs close to the reservoir the fault trace is obscured by a series of landslides affecting rock and soil materials and ranging in size from small slope instabilities to deep seated gravity induced slope deformations dgsds the largest of these which does not show clear evidence of present day activity involves a volume of about 1 km3 and is associated with smaller but active landslides in its lower part with volumes in the order of 2 5 104 m3 to 1 106 m3 based on the spatial and temporal relations between landslides and faults we argue that at least some of these slope failures may have a coseismic character stability analyses by means of limit equilibrium methods lems and stress strain analysis by finite difference numerical modelling fdm were carried out to evaluate different hazard scenarios linked to these slope instabilities the results indicate concern for the different threats posed ranging from the possible disruption of the m 41 highway the main transportation route in central asia to the possible collapse of huge rock masses into the reservoir possibly generating a tsunami

tectonic paleostress fields and structural evolution of the nw caucasus fold and thrust belt from late cretaceous to quaternary abstract the nw caucasus fold and thrust belt essentially corresponds to the inverted western flysch zone of the great caucasus mountains a deep basin that developed from late jurassic to eocene times between the scythian plate to the north and the transcaucasian terranes to the south the shatsky ridge sw of the nw caucasus zone the flysch basin was strongly affected by compression in late eocene times when the characteristic wnw trending folds and thrusts of the nw caucasus belt developed some authors regard the main compressive deformation as miocene in age by means of remote sensing analysis we elucidate the geometry of major structures in the belt wnw trending south vergent thrusts and folds and major vertical and transverse nne ssw to ne sw deep fault zones the later structures are interpreted as ancient faults that were active during the development of the flysch basin paleostress investigations reveal seven main tectonic episodes in the evolution of the nw caucasus since late cretaceous combining structural interpretation remote sensing analysis and paleostress field reconstruction we propose a model for the structural evolution of the belt during the late cretaceous paleocene the western caucasus zone was under transtensional regime with an e w to ne sw trending 3 that generated oblique normal movements along nne ssw transverse faults and wnw ese margins of the flysch basin this tectonism could correspond to rifting related to the formation of the eastern black sea basin at the paleocene eocene boundary a transpressional event with an e w to nw se trending 1 developed and the nne ssw to ne sw trending faults could have been inverted this event could correspond to an attenuation in the eastern black sea basin formation or to the incipient accretion of the transcaucasian terranes during the eocene another e w to nw se oblique extension transtensional event affected the flysch basin that could be related to a known rifting phase in the eastern black sea basin strong nne ssw to ne sw compression characterises late eocene tectonism the fold and thrust belt developed at this time as a result of the direct collision of the shatsky ridge with the scythian plate a ne sw extension followed the late eocene event related to basin development around the newly formed fold belt a wnw ese oblique contraction affected the belt during the early miocene as the result of arabian plate convergence with the caucasian system the latest inferred event is a compressional regime with nnw sse trending 1 that is affecting the nw caucasus belt from sarmatian times until the present under this oblique compression the belt has deformed as in a dextral shear zone and the thrust surfaces have acquired lenticular shapes this study highlights the occurrence of oblique movements in the nw caucasus area prior to and after the dominant late eocene compression from the late cretaceous until the eocene the structural development of the nw caucasus was closely related to the evolution of the eastern black sea basin from the late eocene until quaternary times it was rather related to the arabia eurasia plate convergence

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

influence of inherited taper on structural variability and conglomerate distribution cordilleran fold and thrust belt western united states north south changes in thickness of the prethrust stratigraphy of the north american cordillera within the united states controlled kinematic development of the late mesozoic sevier fold and thrust belt variation in stratigraphic thickness determined the initial slope o of the basal decollement beneath the thrust wedge as predicted by critical wedge theory segments of the sevier thrust belt with initially thick precambrian and paleozoic stratigraphic sections are structurally simple and are composed of few thrust sheets segments with thin prethrust stratigraphy and comparably low values of o are intensely imbricated the difference in structural style resulted because wedge segments with higher values of o required less internal deformation to build and maintain the critical taper required for thrust wedge advance transverse structural zones across which kinematic style differed formed at the terminations of thrust belt segments and controlled the locations of long lived antecedent drainage systems that transported gravel to the foreland therefore along strike changes in prethrust stratigraphic thickness resulted in an observed disjunct distribution of conglomerate in synorogenic deposits of the thrust wedge and foreland basin

oligocene uplift of the western greater caucasus an effect of initial arabia eurasia collision the greater caucasus is europe s largest mountain belt significant uncertainties remain over the evolution of the range largely due to a lack of primary field data this work demonstrates that depositional systems within the oligocene early miocene maykop series on either side of the western greater caucasus wgc display a similar provenance and divergent palaeocurrents away from the range constraining a minimum age for the subaerial uplift of the range as early early oligocene an eocene oligocene hiatus basal oligocene olistostromes and a marked increase in nannofossil reworking also point to initial deformation in the earliest oligocene the initial uplift of the wgc occurred during the final assembly of the tethysides to its south uplift commenced after the late eocene final suturing of northern neotethys and during the initial collision of arabia with the southern accreted margin of eurasia this suggests that compressional deformation was rapidly transferred across the collision zone from the indenting arabian plate to its northern margin

recent tectonic stress evolution in the lesser caucasus and adjacent regions the stress indicators describing the recent provided by active tectonics framework and palaeo stress provided by micro fault kinematics and volcanic cluster patterns show the scale and temporal changes in stress states since the beginning of arabian eurasian collision the recent stress derived from the active fault kinematics in the lesser caucasus and adjacent area corresponds to a strike slip regime with both transtension and transpression characteristics the kinematics of active structures of various scale are conditioned by tectonic stress field with general north south compression and east west extension the distribution of neogene to quaternary volcanic cluster geometries and micro fault kinematic data evidence the time and orientation variability of the stress field since the beginning of the arabian eurasian collision in addition to the general north south compression orientation two other nw se and ne sw secondary orientations are observed the first one was dominant between the palaeogene and the late early miocene and the second one has prevailed between the late miocene and the quaternary since the continental collision of arabia with eurasia the tectonic stress regime in the lesser caucasus and adjacent area changed from compression thrusting and reverse faulting to transtension transpression strike slip faulting with various vertical components

active tectonics in the lesser caucasus coexistence of compressive and extensional structures detailed spot image analysis which completed field data and a microseismicity study was done on the central caucasian mountain belt georgia armenia and eastern turkey north of the front of the arabian collision in order to clarify the relationships between compression extension and volcanism in fact this region is characterized by relatively complex active tectonics associating both n s compressive e w thrusts and folds and e w extensional n s normal faults and dikes structures accompanied by considerable neogene to quaternary volcanism and ne sw left lateral and nw se right lateral strike slip faults these different structures are all intricately imbricated and can be observed at different scales the general layout implies an important variation in the stress state for instance this passes from a n s compression in the spitak earthquake fault zone to an e w extension at the aboul samsar volcanic axis these results agree well with the n s convergence between arabia and eurasia and the e w lateral expulsion of the anatolian and iranian blocks a detailed cartographic network of active structures was drawn and their kinematic relationships were specified in places recent offsets on strike slip faults were estimated at about 500 to 1000 m suitable sites for future determination of fault velocity displacements were also selected this study shows that some strike slip faults behave partly like faults which transform the e w extension of the n s striking normal faults into a n s compression along the e w thrusts one of the characteristics of this region is the continuous important volcanic activity at least from the jurassic until now this persistence evidences a lithospheric thinning which remained in spite of the recent arabian eurasian collision because of the e w extension linked to the opposite lateral expulsion of the anatolian and iranian blocks this geodynamic evolution can explain the juxtaposition and superimposition of volcanic structures and thrusts in a general compressive context

the chronological record of the woolly mammoth mammuthus primigenius in japan and its temporary replacement by palaeoloxodon naumanni during mis 3 in hokkaido northern japan abstract the chronological record of the woolly mammoth mammuthus primigenius in japan is reevaluated on the basis of new and previously published radiocarbon dates obtained from 9 of the 11 known specimens the dates range from 45 110 480 to 16 320 90 years bp however the exact provenance of the youngest specimen from yubari is unknown excluding this specimen woolly mammoths appear to have been present in japan from around 45 ka to 20 ka although perhaps not continuously remains of naumann s elephant palaeoloxodon naumanni from yubetsu eastern hokkaido gave a radiocarbon date of 30 520 220 years bp since this species was adapted to temperate forests and previous pollen analysis indicated there was a slight climate amelioration from about 34 ka to 26 ka correlated with mis 3 it is probable that p naumanni temporarily displaced m primigenius during this period in hokkaido

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

controls on the geometry of fold thrust belt salients salients convex to the foreland curves in the map traces of orogens typically involve fold thrust belts formed along the foreland margin of orogens an examination of the map view shape degree of asymmetry dimensions and structural trend line patterns i e the variation in fold trend and fault strike along the length of the belt of 20 fold thrust belt salients worldwide illustrates relationships between salient geometry and the geologic setting in which the salient formed in order to understand these relationships we used simple sandbox models to simulate the formation of three of the several types of salients specifically we examined indenter controlled salients the geometry of which reflects interaction of a fold thrust belt with a hinterland indenter basin controlled salients the geometry of which reflects lateral variations in the thickness of predeformational basin fill and detachment controlled salients the geometry of which reflects lateral variations in the strength of a detachment surface our models demonstrate that thrusts in these three types of salients initiate with a curved shape and that rocks within thrust sheets on the limbs of salients can undergo a vertical axis rotation in response to simple shear without requiring major rotation of the fault trace furthermore trend line patterns distinguish basin controlled from indenter controlled salients specifically structural trend lines in basin controlled salients converge at the end points of the curve while in indenter controlled salients they diverge at the end points of the curve the asymmetry of a salient correlates with the asymmetry of the predeformational basin and or of the indenter and with the convergence direction thus our results explain geometric characteristics of individual salients and address controversies concerning paleomagnetic data in salients they also may help prioritize petroleum exploration targets in salients foreland basin oil fields concentrate at the apex of basin controlled salients because the geologic factors that generate the salient also contribute to localizing oil fields

insights from the talysh of azerbaijan into the paleogene evolution of the south caspian region the age and mode of formation of the south caspian basin are disputed an 10 km thick predominantly middle eocene clastic and volcanic succession is exposed in the talysh mountains of azerbaijan at its western margin here high k alkali basalts pass laterally to the east and southeast into volcanogenic sandstone dominated turbidity current and debris flow deposits these southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western south caspian basin new ar ar ages cluster around 39 ma with an upper 1400 m thick volcanic interval being deposited in 2 2 0 2 m y we interpret that this rapid deposition and magmatism records a major back arc extensional transtensional event in the talysh north of the north dipping neotethyan subduction zone this event is recognized across much of southwest asia and may indicate a period of significant basin formation within the adjacent south caspian basin a transition into upper eocene lower oligocene strata dominated by fine grained turbidity current and hemipelagic sediments with slope instability features is interpreted to mark the end of rifting and volcanism in the talysh and the start of the arabia eurasia collision overlying oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the talysh region

late cenozoic deformation of the kura fold thrust belt southern greater caucasus although the geometry and kinematics of the first order structures accommodating arabia eurasia convergence are relatively well known in turkey and iran major shortening structures remain poorly understood within the central portion of the collision zone in eastern anatolia and the caucasus new remotely sensed neotectonic mapping synthesis of regional geologic and stratigraphic data and balanced cross sections suggest that the kura fold thrust belt has accommodated the majority of arabia eurasia convergence since the early pliocene between the longitudes of 45 e and 49 e this belt lies southeast of the n80 w striking greater caucasus mountains and forms an eastward narrowing band of elevated topography that roughly parallels the range front for 400 km along strike the belt is separated from the greater caucasus to the north by the 10 to 25 km wide alazani basin and comprises a series of predominantly south verging folds deforming eocene quaternary flysch and molasse to document structural geometries within the kura fold thrust belt we have used the real time interactive mapping system rims software to analyze advanced spaceborne thermal emission and reflection radiometer aster visible to near infrared vnir and digital elevation model dem data this neotectonic mapping indicates an along strike eastward decrease in both structural complexity and the degree to which deformed geomorphic surfaces are dissected existing geologic maps indicate a corresponding eastward decrease in the depth of exposure by integrating the structural geometries determined in our analysis of remote sensing data with existing geologic data we have constructed two balanced cross sections which suggest these systematic along strike variations result from a west to east decrease in total shortening within the kura fold thrust belt we interpret this variable shortening to stem from eastward propagation of the kura fold thrust belt comparison of our preliminary total shortening estimates with those predicted by current plate motions suggest that the kura fold thrust belt has accommodated 30 40 25 km of total arabia eurasia convergence since 5 ma and thus forms a first order structural system within the central portion of the collision zone