quaternary deformation and uplift of coral reef terraces produced by oblique subduction and underthrusting of the bahama platform below the northern hispaniola forearc abstract active tectonics linked to the rise of the hispaniola forearc explain the morphological characteristics spatial distribution and u th geochronological ages of the uplifted coral reef terraces of the la isabela formation in both the eastern cordillera septentrional and the samana peninsula of northeastern dominican republic depositional coral reef terraces of mis 5e tii 7e tiii and 9 tiv stages occur respectively at maximum heights of about 25 m 80 m and 120 m above the current sea level the development of heterogeneous brittle deformation structures in the coral limestone at all scales document active tectonics and include small faults shear fractures extensional joints and calcite veins their geometric and kinematic characteristics as well as the stress tensors calculated from fault slip and fracture orientation data are all compatible with ene to ne trending regional shortening and indicate that a left lateral transpressive regime is deforming the forearc during the quaternary along the northern hispaniola coastline the tectonic uplift mimics the distribution of the bathymetric features on the subducting bahamas platform outboard the hispaniola puerto rico trench the highest calculated uplift rates in the eastern cordillera septentrional and samana peninsula correspond to the collision zone of the silver spur and navidad bank 0 4 m ka respectively uplift rates decrease towards the west 0 2 m ka where the oblique collision of carbonate ridges and related forearc deformation would not have been recorded since at least the early pleistocene oblique subduction and underthrusting of the bahamas platform followed by basal erosion at the subduction channel explain the observed time transgressive pattern of uplift and subsidence in the northern hispaniola forearc and the change from accretionary to erosive processes in the convergent margin

mechanical significance of structural patterns identified by remote sensing studies a multiscale analysis of tectonic structures in crimea abstract based on remote sensing analyses of two panchromatic spot scenes that cover the western and eastern parts of crimea completed with the study of landsat thematic mapper scenes and local aerial photographs we determined the geometry of major structures folds and fractures the strikes of large fractures are quite homogeneous in the studied area three important sets are common n10 ne sw and nw se two strikes are particularly developed in the western part of crimea n25 and n105 along important faults we recognised the sense of motion which often corresponds to the latest or to the major stages of movement we also determined stress tensors by inversion of microtectonic data sets collected in the field combining remote sensing analysis with mechanical studies provides new views on the structural evolution of crimea we thus characterised major tectonic events responsible for most of the deformation in eastern crimea the structural patterns fit well with two major tectonic events 1 the latest one is a plio quaternary faulting event normal slip along n10 faults and strike slip motion along n10 and nw se faults corresponding to a transtensional regime with 3 trending e w 2 large fractures nw se and ne sw sets and fold and thrust development reveal a transpressional regime with 1 trending nne ssw during the berriasian in western crimea we characterised a more complex pattern of four major tectonic events 1 the plio quaternary tectonic phase induced left lateral displacement along nw se faults and normal slip along wsw ene faults and this deformation is in agreement with the strike slip regime that we reconstructed with 3 trending nne ssw 2 as for eastern crimea the berriasian phase was well expressed with folds thrusts and strike slip faults under a transpressional regime with 1 trending n s to nnw sse the two other events well identified in western crimea are 3 a n s directed extension that developed large n105 faults and 4 a nw se directed extension involving ne sw normal faults that we relate to the development of peripheral troughs in the oligocene western crimea suffered a more complicated structural evolution than eastern crimea from eastern to western crimea we also noticed the systematic deviation in the trends of the principal stress axes of the recent stress field and in the berriasian stress field as well these differences may be related to the presence of a major crustal discontinuity the transverse alushta simferopol fault

impacts of age dependent tree sensitivity and dating approaches on dendrogeomorphic time series of landslides different approaches and thresholds have been utilized in the past to date landslides with growth ring series of disturbed trees past work was mostly based on conifer species because of their well defined ring boundaries and the easy identification of compression wood after stem tilting more recently work has been expanded to include broad leaved trees which are thought to produce less and less evident reactions after landsliding this contribution reviews recent progress made in dendrogeomorphic landslide analysis and introduces a new approach in which landslides are dated via ring eccentricity formed after tilting we compare results of this new and the more conventional approaches in addition the paper also addresses tree sensitivity to landslide disturbance as a function of tree age and trunk diameter using 119 common beech fagus sylvatica l and 39 crimean pine pinus nigra ssp pallasiana trees growing on two landslide bodies the landslide events reconstructed with the classical approach reaction wood also appear as events in the eccentricity analysis but the inclusion of eccentricity clearly allowed for more 162 landslides to be detected in the tree ring series with respect to tree sensitivity conifers and broad leaved trees show the strongest reactions to landslides at ages comprised between 40 and 60 years with a second phase of increased sensitivity in p nigra at ages of ca 120 130 years these phases of highest sensitivities correspond with trunk diameters at breast height of 6 8 and 18 22 cm respectively p nigra this study thus calls for the inclusion of eccentricity analyses in future landslide reconstructions as well as for the selection of trees belonging to different age and diameter classes to allow for a well balanced and more complete reconstruction of past events

paleostress and statistical analysis using quartz veins from mineralized and non mineralized zones application for exploration targeting abstract quartz vein orientations thickness and spacing data are analyzed from 10 transects each of mineralized and non mineralized zones of gadag region which is a gold bearing terrain within the dharwar craton southern india paleostress analysis reveals that the veins emplaced when fluid pressure pf varied from pf 2 intermediate principle stress to pf 2 to pf

an offshore onland transect across the north eastern black sea basin crimean margin evidence of paleocene to pliocene two stage compression abstract the tectonic evolution of the black sea bs is a subject of debate there are several unsolved questions 1 the timing and the spatial progression of the bs basin opening and 2 the timing of cenozoic shortening along the northern margin of the eastern bs basin the timing of the main compressional deformations related to the inversion of the greater caucasus gc basin is assumed to be oligo miocene however late cretaceous early paleocene shortening linked to the final closure of the northern branch of the neotethys is also suggested the crimean mountains cm to the north of the eastern bs is one of the key areas to investigate in order to fix the tectonic evolution of the bs to precise the timing of the cenozoic shortening of the eastern bs we focus on an integrated onshore offshore transect from the eastern cm to the sorokin trough north of eastern bs we use newly collected stratigraphic and structural data from the eastern cm and a new interpretation of multichannel seismic lines we define 1 the offshore seismic stratigraphy and constrain the relative chronology of deformations 2 the age of seismic units by correlation of the seismic data with the subbotina 403 well log and 3 we construct an on to off shore transect of eastern cm northern eastern bs region our results evidence a polyphased cenozoic compression in the northern part of the eastern bs 1 paleocene earliest eocene and 2 oligocene miocene maikopian normal faults appear to be related to a formation of the foreland basin instead of evidencing the eastern bs cretaceous rifting finally this study allows precising the shortening phases within eastern cm and eastern bs since the early paleocene linking them to the neotethys closure and the gc tectonic evolution

dyke intrusion into a pre existing joint network the aiguablava lamprophyre dyke swarm catalan coastal ranges abstract a structural analysis has been performed in the upper permian lamprophyric dyke swarm of aiguablava costa brava ne iberia emplacement of sub vertical dykes is related to the presence of a widespread joint network mostly developed during the cooling and decompression of the late variscan leucogranitic host rocks the joint pattern consists on multiple sub vertical joint sets among which two orthogonal sets at n23 and n113 are predominant a sub horizontal set is also prominent the sub vertical dykes have a mean n100 n125 trend which corresponds to the trend of one of the main joint sets however dyke segmentation is noticeable at the dm to cm scale and this is inferred to be related to dyke propagation and emplacement along the variably oriented pre existing joints a mean robust sub horizontal nne ssw net dilation direction was measured from matching dyke jogs markers in the host rock and analysis of maximum dyke thicknesses and this is in line with the minimum principal stress axis 3 derived from a three dimensional paleostress analysis from dyke orientations the inferred maximum principal stress axis 1 is sub vertical indicating that dykes intruded under conditions of tectonic extension furthermore a mohr construction allowed calculation of the stress ratio 0 29 close to a prolate stress ellipsoid and a driving pressure ratio r 0 27 which corresponds to a magmatic pressure almost equal to the intermediate principal stress axis 2 it is inferred that many of the pre existing joint sets were exploited by the magma the wnw ese joint set normal to 3 being the most favorable for dyke emplacement the present study highlights the structural control of a pre existing fracture network on emplacement of the aiguablava lamprophyres in the upper crust during late permian nne ssw brittle extension

clustering of fracture orientations using a mixed bingham distribution and its application to paleostress analysis from dike or vein orientations abstract the clustering and classification of fracture orientations are important in rock mechanics and in brittle tectonics the latter of which includes the paleostress analysis of extension fractures hosting dikes or mineral veins here we present an unsupervised clustering method for the orientations of extension fractures using mixed bingham distributions the method not only detects the elliptical clusters and girdles made by the poles to such planar features but also determines the appropriate number of those groups by means of bayesian information criterion bic without a priori information the method was tested with artificial data sets and successfully detected the assumed groups when the clusters had little overlaps however clusters with the common maximum concentration orientation and large aspect ratios were distinguished provided that their minimum concentration orientations were separated by a large angle our method separated two stress states from natural data from a miocene dike swarm in sw japan the method also evaluated the probabilities of the stresses to form each of the dike

age and geodynamic evolution of the black sea basin tectonic evidences of rifting in crimea the timing and direction of opening of the black sea basin are debated however parts of its margins were inverted during cenozoic and can be studied onshore the crimean mountains are located in the middle of the northern margin of the basin and at the onshore prolongation of the mid black sea high we present the first detailed mapping of large striated normal faults in crimea these faults define graben structures that trend parallel to the continental margin kinematic analysis of the faults combined with new biostratigraphic data show that the syn rift sequence is valanginian to late albian in age it consists of siliciclastic deposits with limestone olistoliths in contrast the post rift late cretaceous carbonaceous sequence of crimea is devoid of normal faults or olistoliths it unconformably overlies the graben structures the onset ages and the trends of extension are quite similar in the northern crimea and the southern turkey inverted margins of the basin the early cretaceous extension directions are normal to the mid black sea high and the black sea margins we conclude that rifting of black sea basin occurred from the valanginian to the late albian 39 ma and drifting during the late cretaceous based on the directions of rifting on the lack of evidence of strike slip motions near the mid black sea high and on published paleomagnetic data we propose that the black sea opened with rotations accommodated by transform faults at its western and eastern margins as a response to asymmetric slab rollbacks of the neo tethys plate the inversion of the crimean margin results from two successive shortening events early eocene ne sw compression eocene to present se nw compression their timing support the idea that compressional stresses generated by continental collisions in turkey were transmitted through the strong black sea lithosphere up to crimea

fission track lengths in the apatite annealing zone and the interpretation of mixed ages abstract measurements of confined fission tracks in apatites from deep boreholes show that their mean length is reduced and the length distribution becomes progressively broader through the fission track annealing zone at subsurface temperatures of around 100 c and above the length distribution characteristically becomes very broad without a pronounced peak the lengths of the longest tracks remain essentially constant at all stages of natural annealing observed in the boreholes this pattern is similar to that found in laboratory annealing of spontaneous fission tracks in apatite from an outcrop sample of the same formation these observations show that confined track lengths can be used as important indicators of the type of thermal history that a sample has experienced in the temperature zone of increasing track stability the length distributions reported here provide a basis for interpretation of fission track ages that might otherwise be ambiguous an apatite age which results from a uniform slow cooling history will have a broad negatively skewed length distribution while a bimodal distribution provides clear evidence of a two stage history involving partial annealing by a discrete thermal event the apparent fission track age associated with a bimodal length distribution will be a mixed age intermediate between the original age and that of the later event

geological storage of carbon dioxide carbon dioxide co2 is the main compound identified as affecting the stability of the earth s climate a significant reduction in the volume of greenhouse gas emissions to the atmosphere is a key mechanism for mitigating climate change geological storage of co2 or the injection and long term stabilization of large volumes of co2 in the subsurface in saline aquifers in existing hydrocarbon reservoirs or in unmineable coal seams is one of the more technologically advanced options available a number of studies have been carried out and are reported here they are aimed at understanding the safety physical and chemical behaviour and long term fate of co2 when stored in geological formations until efficient alternative energy options can be developed geological storage of co2 the subject of this volume provides a mechanism to reduce carbon emissions significantly whilst continuing to meet the global demand for energy

thermal effects of linked lithospheric and upper crustal scale processes insights from numerical modeling of the cenozoic central catalan coastal ranges ne spain processes influencing the thermal state of the continental crust such as heat upwelling related to rifting and isotherm reorganization due to mass redistribution by erosion deposition and fault tectonic transport operate at different scales and their effects overlap in this paper we use lithospheric as well as crustal scale numerical modeling tools in order to quantify the contributions of these various factors to the geothermal field establishing their relative relevance we apply the models to address the thermal evolution of the catalan coastal ranges ne spain during the cenozoic a period that is characterized by a change in tectonic style from pyrenean compression to extension related to the western mediterranean rifting results of the lithospheric scale thermal model for extensional basins show an increase in the geothermal surface gradient of about 11 c km in the catalan coastal ranges during the neogene related to extensional thinning of the lithosphere in the valencia trough western mediterranean predictions of the upper crustal scale thermal model incorporating fault motions and surface mass redistribution erosion and sedimentation point to little changes in the isotherms due to fault block movements in the paleogene and neogene in contrast erosion appears to have a significant effect on the then nal history of basement rocks sited in the shallowest crust comparison of the integrated lithospheric and upper crustal scale modeling results with apatite fission track and apatite u th he thermochronology data reveals larger amounts of neogene to present cooling than predicted by the models on the basis of this unresolvable mismatch we suggest that similar to present forced fluid convection along fault planes played an important role in the evolution of the geothermal field during the neogene stage of rifting copyright 2007 by the american geophysical union

parametric and non parametric statistical approaches to the determination of paleostress from dilatant fractures application to an early miocene dike swarm in central japan abstract several methods have been proposed for determining paleostress states from orientations of dilatant fractures such as dikes and veins recently a stochastic inversion method was invented to objectively estimate the principal stress axes and the stress ratio whether a fracture is dilated or not is controlled by the balance of the fluid pressure and the normal stress acting on it the magnitude of normal stress depends on the fracture orientation which causes anisotropic orientation distribution of dilatant fractures the inversion method assumes that the orientation distribution of fractures can be approximated by a bingham distribution an exponential probability distribution on the unit sphere of which symmetric axes are interpreted as the principal stress axes however it is unknown if the exponential type of distribution function is suitable or not here we examine the distribution functions and propose two improved methods one method uses the shifted power law function as the shape of probability distribution which is more flexible than the bingham distribution and is applicable to various shapes of orientation distributions furthermore an index of the driving fluid pressure can be estimated with a confidence interval the other is a non parametric distribution free method which can avoid the a priori assumption on the shape of distribution function without significantly losing accuracy or precision the new methods were applied to an early miocene dike swarm formed during the back arc opening of the japan sea a normal faulting stress regime with the minimum principal stress axis trending roughly perpendicular to the arc was obtained from the dikes a moderately high stress ratio and a high fluid pressure were also estimated

thermochronology of lower cretaceous source rocks in the idaho wyoming thrust belt lower cretaceous organic rich source rocks that are thermally mature to postmature crop out on the absaroka darby and prospect plates in linear belts that run parallel to the trace of the thrusts in the idaho wyoming portion of the idaho wyoming utah thrust belt although the common assumption is that burial by thrust plates and the synorogenic sediments derived from them have been responsible for thermal maturation of the organic rich strata commercial amounts of hydrocarbons have not been found in structural traps in this portion of the thrust belt in a companion paper burtner and nigrini demonstrated that gravity driven fluid flow in the idaho wyoming portion of the thrust belt was responsible for moving large amounts of heat from the depths of the early cretaceous foreland basin eastward toward the stable platform in this paper we demonstrate through the application of organic maturation indicators and a new refinement of the apatite fission track technique that this process heated lower cretaceous organic rich source rocks to temperatures sufficient to generate hydrocarbons hydrocarbon generation and migration occurred prior to the development of the thrusts that are often assumed to have played a major role in the generation and entrapment of hydrocarbons in this portion of the thrust belt

analysis of co2 leakage through low permeability faults from natural reservoirs in the colorado plateau east central utah the numerous co 2 reservoirs in the colorado plateau region of the united states are natural analogues for potential geologic co 2 sequestration repositories to better understand the risk of leakage from reservoirs used for long term underground co 2 storage we examine evidence for co 2 migration along two normal faults from a reservoir in east central utah co 2 charged springs geysers and a hydrocarbon seep are localised along these faults these include natural springs that have been active for long periods of time and springs that were induced by recent drilling the co 2 charged spring waters have deposited travertine mounds and carbonate veins the faults cut siltstones shales and sandstones and the fault rocks are fine grained clay rich gouge generally thought to be barriers to fluid flow the geologic and geochemical data are consistent with these faults being conduits for co 2 to the surface consequently the injection of co 2 into faulted geologic reservoirs including faults with clay gouge must be carefully designed and monitored to avoid slow seepage or fast rupture to the biosphere

the low frequency gas shadow on seismic sections about six years ago greg partyka and his colleagues at amoco research showed how an old technique the fourier transform could be used effectively for seismic interpretation and visualization this idea has come to be known as spectral decomposition in recent years many spectral decomposition techniques have been developed and utilized for stratigraphic analysis and direct hydrocarbon detection with the refined spectral decomposition techniques now available the low frequency shadow beneath gas reservoirs is another old idea that has renewed importance and interest in the exploration community almost a decade ago dan ebrom studied a variety of possible mechanisms for the low frequency shadow and why it might be associated with hydrocarbons he presented his analysis at the 1996 seg summer research workshop

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

interaction of faults and perturbation of slip influence of anisotropic stress states in the presence of fault friction and comparison between wallace bott and 3d distinct element models abstract two decades after their birth the validity of fault slip inversion methods is still strongly debated these methods are based upon a very simplified mechanical background the wallace bott hypothesis following previous studies the 3d distinct element method 3dec software is used to explore the effect of varying stress anisotropy i e the shape ratio on slip perturbation along pairs of faults two end member configurations are modelled in taking into account fault friction and internal deformation of faulted blocks the first model deals with a relatively simple case where two nonintersecting conjugate normal faults are reactivated in an oblique normal stress regime the second one simulates an extreme situation where two perpendicular intersecting faults are submitted to oblique extension the average direction of fault slip predicted by 3dec models is compared to the corresponding slip predicted by the simplified wallace bott model for the two simulated cases it is shown that results from 3dec and wallace bott models are mutually consistent and argue for the validity of fault slip data inversion methods consistency remains even if slip is significantly deviated near the intersection line of faults these deviations depend on the degree of anisotropy of applied stresses in presence of fault friction furthermore modelling results suggest that for intersecting faults with convergent slip directions consideration of fault friction in the models leads to reduction of slip perturbation in other words modelling results lead to the nonintuitive conclusion that the validity of the simplified wallace bott model is strengthened when 3dec model s complexity i e the number of parameters incorporated increases

paleostress and fluid pressure regimes inferred from the orientations of hishikari low sulfidation epithermal gold veins in southern japan abstract the orientation distribution of dilational fractures is affected by the state of stress around the fractures and by the pressure of the fluid that opened the fractures thus the distribution can be inverted to determine not only the stress but also the pressure condition at the time of vein formation however epithermal ore veins that we observe today are the results of a great number of intermittent upwelling of overpressured fluids with different pressures here we define driving pressure index dpi as the representative non dimensionalized fluid pressure for the fluids we collected the orientations of 1000 ore veins in the hishikari gold mine which were deposited at around 1 ma in southern kyushu japan it was found that the majority of the veins were deposited under an extensional stress with a nw se trending 3 axis and a northeasterly inclined 1 axis with relatively high stress ratio the representative driving pressure ratio was 0 2 data sets obtained at different depths in the mine indicated a positive correlation of representative driving pressure ratios with the depths the correlation suggests repeated formation and break of pressure seals during the mineralization our compilation of the pliocene quaternary stress regimes in southern kyushu including the result of the present study suggests that epithermal gold mineralization was associated with distributed extensional deformations in southern kyushu and strain localization into an intra arc rift seems to have terminated the mineralization

fluid overpressure and stress drop in fault zones using the average aspect length maximum thickness ratios of 379 mineral filled extension mode i veins from an active fault zone the fluid overpressure during their development with reference to the minimum compressive principal stress 3 is estimated at 20 mpa emplacement of such veins increases 3 and can generate a temporary stress barrier to the propagation of subsequent hydrofractures on meeting a subhorizontal stress barrier vertically propagating hydrofractures may change into water sills where the fluid pressure is at or above lithostatic in this model stress barriers and thus water sills can form at any depth in and in any type of fault zones for such a high fluid pressure the product of the coefficient of sliding friction and the normal stress in the modified griffith criterion becomes essentially zero and the driving stress associated with faulting equal to twice the in situ tensile strength of the host rock for typical in situ tensile strengths of 2 3 mpa the driving stresses for slip on overpressured fault planes is 4 6 mpa these results are in good agreement with the commonly measured average static stress drops of 3 6 mpa during earthquakes

plate tectonic evolution of the southern margin of eurasia in the mesozoic and cenozoic abstract thirteen time interval maps were constructed which depict the triassic to neogene plate tectonic configuration paleogeography and general lithofacies of the southern margin of eurasia the aim of this paper is to provide an outline of the geodynamic evolution and position of the major tectonic elements of the area within a global framework the hercynian orogeny was completed by the collision of gondwana and laurussia whereas the tethys ocean formed the embayment between the eurasian and gondwanian branches of pangea during late triassic early jurassic times several microplates were sutured to the eurasian margin closing the paleotethys ocean a jurassic cretaceous north dipping subduction boundary was developed along this new continental margin south of the pontides transcaucasus and iranian plates the subduction zone trench pulling effect caused rifting creating the back arc basin of the greater caucasus proto south caspian sea which achieved its maximum width during the late cretaceous in the western tethys separation of eurasia from gondwana resulted in the formation of the ligurian penninic pieniny magura ocean alpine tethys as an extension of middle atlantic system and a part of the pangean breakup tectonic system during late jurassic early cretaceous times the outer carpathian rift developed the opening of the western black sea occurred by rifting and drifting of the western central pontides away from the moesian and scythian platforms of eurasia during the early cretaceous cenomanian the latest cretaceous paleogene was the time of the closure of the ligurian pieniny ocean adria alcapa terranes continued their northward movement during eocene early miocene times their oblique collision with the north european plate led to the development of the accretionary wedge of the outer carpathians and its foreland basin the formation of the west carpathian thrusts was completed by the miocene the thrust front was still propagating eastwards in the eastern carpathians during the late cretaceous the lesser caucasus sanandaj sirjan and makran plates were sutured to the iranian afghanistan plates in the caucasus caspian sea area a north dipping subduction zone jumped during paleogene to the scythian turan platform the shatski terrane moved northward closing the greater caucasus basin and opening the eastern black sea the south caspian underwent reorganization during oligocene neogene times the southwestern part of the south caspian basin was reopened while the northwestern part was gradually reduced in size the collision of india and the lut plate with eurasia caused the deformation of central asia and created a system of nw se wrench faults the remnants of jurassic cretaceous back arc systems oceanic and attenuated crust as well as tertiary oceanic and attenuated crust were locked between adjacent continental plates and orogenic systems

the conversion tectonics from spreading to subduction paleostress analysis of dike swarms during the subduction initiation in the oman ophiolite

full paleostress tensor reconstruction using quartz veins of panasqueira mine central portugal part i paleopressure determination abstract paleostress tensor restoration methods are traditionally limited to reconstructing geometrical parameters and are unable to resolve stress magnitudes based on previous studies we further developed a methodology to restore full paleostress tensors we concentrated on inversion of mode i fractures and acquired data in panasqueira mine portugal where optimal exposures of mineralized quartz veins can be found to carry out full paleostress restoration we needed to determine 1 pore paleo pressure and 2 vein attitudes the present contribution focuses specifically on the determination of pore pressure to these aims we conducted an extensive fluid inclusion study to derive fluid isochores from the quartz of the studied veins to constrain p t conditions we combined these isochores with crystallisation temperatures derived from geochemical analyses of coeval arsenopyrite we also applied the sphalerite geobarometer and considered two other independent pressure indicators our results point to pore pressures of 300 mpa and formation depths of 10 km such formation depths are in good agreement with the regional geological evolution the obtained pore pressure will be merged with vein inversion results in order to achieve full paleostress tensor restoration in a forthcoming companion paper

3 d mohr circle analysis of vein opening indarama lode gold deposit zimbabwe implications for exploration the indarama lode gold deposit is hosted by vertically dipping basalt in the late archaean midlands greenstone belt of zimbabwe major deformation events at 2 68 and 2 58 ga established a complex array of fractures a limited range of orientations of this fracture network opened towards the end of the younger deformation event creating a lode pattern where 92 of mineralised veins dip at less than 50 mainly to the e and w and most strike directions are represented a clustered distribution of poles to the quartz carbonate veins indicates a constrictional stress field at the time of vein opening where 1 and 2 were near horizontal directed nnw sse and ene wsw respectively and 3 was near vertical 3 d mohr circle analysis demonstrates that 2 was approximately 67 of 1 the stress ratio and that the driving pressure ratio r was approximately 0 4 reflecting the role of fluid pressure mean stress and the maximum shear stress in controlling conditions of fracture opening

stochastic modeling for the stress inversion of vein orientations paleostress analysis of pliocene epithermal veins in southwestern kyushu japan plio pleistocene epithermal quartz veins in southern kyushu japan include gold deposits the coherent trend of the ore veins suggests tectonic control for their formation however the stress regime during the formation has been controversial to solve this problem we improved existing methods for inferring paleostresses from vein orientations it was assumed that veins making a cluster were formed intermittently from thermal fluids with various pressures the present method determines stress ratio and stress axes with 95 confidence regions the method was applied to mid pliocene quartz veins cropping out at hashima southwestern kyushu we obtained a normal faulting regime of stress with the trend of sigma3 at 167 10 and the stress ratio at 0 20 0 13 0 09 the low stress ratio and the lack of slickenlines and slickenfibers on vein walls suggest that the host rock was subject to a small differential stress i e a weak tectonic stress when the veins were formed

tree ring analysis in the reconstruction of slope instabilities associated with earthquakes and precipitation the crimean mountains ukraine the crimean mountains in ukraine constitute a seismically active region that is abundant in various types of mass movement the limestone escarpments that rise above the black sea coast in the vicinity of the town of yalta are particularly subject to considerable rockfall landslide and debris flow processes that often endanger infrastructure and human life one of these very active slopes is the area of the ancient taraktash rockslide characterised by active block type movements lateral spreading toppling and incipient sliding rockfalls ongoing sliding activities and debris flows the aims of this study were i to employ tree ring analysis to reconstruct a record of slope instabilities mainly block type movements rockfalls landslides and debris flows within the taraktash slope deformation over a period of more than two centuries and ii to establish the degree of correlation between periods of enhanced slope activity and both historical earthquakes and climatic data the temporal frequency of significant slope processes was addressed through a tree ring analysis that took 738 increment cores from 255 crimean pine trees pinus nigra ssp pallasiana the tree ring record reveals periods of increased activity of block type movements rockfalls and landslides during the major earthquakes in 1790 1875 1927 and 1986 although the slope processes studied are predominantly driven by seismic activity their intensity and duration are also dependent on climatic factors this is especially true for landslides and debris flows which occurred mainly in years characterised by high precipitation totals

relationships between faults extension fractures and veins and stress faults are commonly related to extension fractures defined here as including extension veins extension fracturing is integral to fault initiation and propagation and extension fractures also form after fault slip in these situations fault planes contain the intermediate principal stress 2 and slip is perpendicular to the line of intersection between the fault and the extension fractures however for reactivated faults multiple fault sets and faults formed according to the healy theory 2 is not necessarily within the fault plane a theoretical analysis shows that the trace of an extension fracture on a fault can make angles from 0 to 90 with the maximum resolved shear stress the angle depends on the fault orientation relative to the principal stresses and the ratio between the stresses extension fractures only intersect faults perpendicular to the maximum resolved shear stress on faults containing the maximum or intermediate principal stresses or when their magnitudes are equal 1 2 field observations show that extension fractures can intersect faults along lines at oblique angles to slip directions as predicted by the theory such angles may be indicators of fault reactivation multiple sets of faults or healy theory faulting

new approach for the quantification of paleostress magnitudes application to the soultz vein system rhine graben france abstract quartz veins often appear in pre existing cracks and are the witnesses of paleofluid flows a new method of paleostress magnitude quantification is proposed in this paper based on the knowledge of i the geometrical distribution of vein poles ii empirical considerations of rupture criteria and iii the fluid pressure stress axis orientations deduced from the geometrical distribution of the vein poles define angular relations allowing the reduced stress tensor and the ratio characterization p f values quantified with fluid inclusion studies and intrinsic curves drawn with empirical relations depending on the rheologic properties of the pre fractured rock are combined to graphically fit the final mohr circle the resulting absolute stress magnitudes take into account the fluid pressure influence application of this method on the quartz vein system of soultz sous forets rhine graben france gives realistic magnitudes of the oligocene extension and are similar to those found in previous study with other methods

contact analyses and permeability measurements of polished fracture surfaces in sambagawa metapelitic schists and ryoke mylonites from the median tectonic line japan 1 fractures play a vital role in fluid flow through rocks and highly fractured zones can be the most permeable part of a fault zone however the evaluation of the hydraulic properties of natural fractured rocks at great depths is not easy because of the complexity of fracture geometry and the scaling problem from laboratory to nature as a first step toward the estimation of flow rate through fractured zones at depth this paper examines the issue of permeability estimation in the case of flow between polished surfaces of known topography or roughness via an integrated study of permeability measurements at effective pressures up to 180 mpa surface roughness measurements and contact analyses using the hertzian theory of surface asperities of fractures as a function of stress apertures between two polished surfaces in specimens of sambagawa pelitic schist and ryoke mylonite were estimated from permeability measurements assuming the cubic law the aperture of contacting surfaces has also been calculated from contact analyses of representative asperities despite some imperfections in the agreement between these two approaches the overall features of progressive reduction in aperture upon an increase in effective pressure were successfully predicted deviations between the two approaches are probably due to complex deformation of multiple contacting asperities or limitations of our contact analysis method

variability of apatite fission track annealing kinetics ii crystallographic orientation effects a method is presented that permits the length of any horizontal confined fission track inclined at a specified angle to the crystallographic c axis in apatite to be converted to an equivalent track length parallel to the crystallographic c axis the model is based on the results of annealing experiments for six selected apatites five calcian fluorapatites and durango apatite representing a subset of the 15 total apatite specimens studied an iterative process of calculation is required to project fission track lengths onto the c axis and computer source code implementing the solution to this problem is presented this method of projecting apatite fission track lengths onto the crystallographic c axis is shown to remove effectively fission track length variation within single fission track populations due to anisotropic track length reduction for all 15 apatites studied in addition a model is developed that offers predictions that closely reproduce published experimental data concerning the relationship between fission track density etched fission tracks per unit area of apatite surface and the arithmetic mean fission track length finally it is shown that natural fission track populations exhibit fission track length anisotropy similar to that of fission track populations created and annealed in the laboratory this observation implies that the same process by which apatite fission tracks anneal in the laboratory is responsible for annealing of apatite fission tracks in the geological environment

modification of fracture porosity by multiphase vein mineralization in an oligocene nontropical carbonate reservoir taranaki basin new zealand the nontropical oligocene carbonate rich tikorangi formation is an important oil producer in the taranaki basin new zealand hydrocarbons are hosted and produced from mineralized natural fracture systems petrographic trace element stable isotope 18o and 13c and fluid inclusion data have enabled a complex sequence of eight paragenetic events to be determined the tikorangi formation host rock was cemented by low mg calcite event 1 during burial diagenesis from temperatures of 27c corresponding to 0 5 km burial and continued until 37c 1 km burial depth producing tight pressure dissolved fabrics with essentially no porosity and permeability the host rock was partially dolomitized 5 50 event 2 by ca and fe rich dolomite rhombohedra at burial depths and temperatures of 1 0 1 5 km and 35 50c without secondary porosity development subsequent brittle fracturing formed by neogene compression event 3 is constrained to a period following lithification and dolomitization but before precipitation of first generation vein calcite event 4 this initial ferroan low mg vein calcite formed after a period of burial from fe rich meteorically modified fluids at temperatures of about 50 60c and 1 4 1 9 km burial depth baroque dolomite formed event 5 following a period of mg enriched basinal fluid input precursory to hydrocarbon emplacement per se the dolomite formed mainly as a primary cement but also as a calcite replacement at temperatures following further burial to 2 2 5 km and temperatures of 65 80c formation of celestite and quartzine phases event 6 coincided with or marginally postdated dolomite at similar depths and temperatures to event 6 and formed as both replacements and cements second generation ferroan vein calcite formed event 7 at cooler temperatures 53 65c perhaps resulting from the introduction of cooler meteoric fluids from upsection the presence of petroleum fluid inclusions in the second generation calcite suggests precursory hydrocarbon bearing fluids have migrated along with aqueous fluids from about 10 ma with hydrocarbon emplacement event 8 occurring in the last 6 m y following a period of rapid late miocene burial an improved understanding of the paragenesis of the tikorangi formation may assist in hydrocarbon production from its reservoirs

impact of fluid pressure on failure mode in shear zones numerical simulation of en echelon tensile fracturing and transition to shear abstract en echelon veins are a set of tensile fractures that develop during the initiation of shear zones under certain conditions but factors that control fracture patterns remain unclear in this study we performed numerical simulations using the two dimensional distinct element method to understand the influence of effective normal stress on the development of fractures during shear deformation at low effective normal stress 10 mpa dilation takes place at an angle of 40 45 to the shear boundary and en echelon arrays of tensile fractures develop in contrast at high effective normal stress 150 mpa en echelon veins are not developed but a distinct shear plane forms a transient behavior characterizes intermediate effective normal stress 50 mpa early tensile cracks are generated and then propagate to form larger brittle faults in this case the larger strain energy released in the later stage is due to the greater shear strength under crustal conditions effective normal stress varies due to the change in fluid pressure our results suggest that en echelon veins are indicators of high fluid pressure close to lithostatic conditions i e effective normal stress close to zero and that a transition of the failure mode from tensile to shear could occur in response to a dynamic change of fluid pressure during fracturing

jurassic arc volcanism on crimea ukraine implications for the paleo subduction zone configuration of the black sea region article i nfo the early cretaceous and younger opening of the black sea has obliterated much of the older record of tethyan subduction below southeastern europe the earlier mesozoic evolution was dominated by opening and closure of tethyan oceans between gondwana and laurasia with their consumption at least in part accommodated along the southern eurasian margin crimea ukraine a peninsula in the northern black sea represents the northernmost region of southeastern europe that exposes a record of a pre cretaceous tethyan active margin to shed new light on the paleosubduction zone configuration of the southeastern european margin in the jurassic we report 40

single fractures under normal stress the relation between fracture specific stiffness and fluid flow abstract fracture specific stiffness and fluid flow through a single fracture under normal stress are implicitly related through the geometry of the void space and contact area that comprise the fracture data from thirteen different rock samples each containing a single fracture show that relationships between fracture specific stiffness and fluid flow through a fracture fall into two general classes of behavior fractures either fall on a loosely defined universal curve relating fluid flow to fracture specific stiffness or else the flow is weakly dependent on fracture specific stiffness the second relationship shows that flow decreases slowly with increasing fracture specific stiffness the first relationship shows that flow decreases rapidly for increases in fracture specific stiffness to understand this behavior computer simulations on simulated single fractures were performed to calculate fluid flow fracture displacement and fracture specific stiffness as a function of normal stress simulated fractures with spatially correlated and uncorrelated aperture distributions were studied fractures with spatially uncorrelated aperture distributions tend to exhibit a weak dependence of fluid flow on fracture specific stiffness because these fractures tend to have multiple connected paths across the sample which can support flow with uniformly distributed contact area thus an increment in stress will increase the stiffness of the fracture without greatly reducing the amount of fluid flow on the other hand fractures with spatially correlated aperture distributions tend to belong to the universal relationship because correlated fractures tend to have only one or two dominant flow paths and the contact area is limited to a few regions resulting in a compliant fracture thus an increment in stress on a spatially correlated fracture will result in an increase in stiffness and rapid decrease in fluid flow these spatial correlations in fracture void geometry can be differentiated in the laboratory based on the observed fracture specific stiffness fluid flow relationship for a single fracture under normal loading

hydraulic connection and fluid overpressure in upper crustal rocks evidence from the geometry and spatial distribution of veins at botrona quarry southern tuscany italy abstract veins are the geologic record of fluids that filled fractures at depth in the crust in southern tuscany italy well exposed oligocene early miocene sandstones hosting vein systems provide insight into the role of pore fluid and the stress state at the time of vein formation the stress ratio 2 3 1 3 and driving stress ratio r p f 3 1 3 were determined by analysing the distribution length and aperture of fractures and veins and the magnitude of fluid overpressure the derived fluid overpressure for the whole vein system ranges from 30 mpa to 64 mpa with an average of 43 mpa these values indicate that veins formed under supra hydrostatic pressure conditions despite their spatial contiguity two different vein arrays show very different stress and driving pressure ratios one vein system is characterised by 0 62 and r 0 60 the other by 0 54 and r 0 78 the described vein systems are an example of a close spatial association of two non hydraulically connected vein systems representing fluids focused through the upper crust

morpho tectonic evolution of the crimean mountains ukraine as constrained by apatite fission track data introductionthe crimean mountains cm formthe westernmost prolongation of thecaucasus crimean thrust and foldbelt fig 1 muratov et al 1984 nikishin et al 1998 2001 saintotet al 1999 saintot and angelier 2002 despite the fact that the regionis one of the best explored territoriesin the former soviet union e g muratov 1960 kazantsev 1982 muratov et al 1984 slavin 1989 saintot et al 1999 nikishin et al 2001 mileev et al 2006 the scarcityof geochronological data limits geo dynamic reconstructions and does notallow veri cation of often contradic tory evolutionary scenarios see e g gintov and borisenko 1999 mileevet al 2006 this paper presents the rst ther mochronological data from the cm aimed at improving the existing mod els of exhumation uplift and land scape evolution e g muratov 1960 lysenko 1972 1976 saintot et al 1999 nikishin et al 2001 mileevet al 2006 this work also constrainsthe genesis and chronology of elevatedkarsti ed palaeosurfaces which occurmore extensively in the cm than inother european alpides understand ing the chronology and preservationof the palaeosurfaces in the cm andtheir relationship to post orogenicdeposits has important implicationsfor the survival of old inherited land forms in the mobile mountain belts ingeneral geological and geomorphologicalsettingthe cm are considered to be theremnantsofananticlinoriumstructure destroyed during the formation of theblack sea basin in short the tectonicevolution of the cm comprises i triassic earlycretaceous i e cimme rian compressional phases whenanticlinorium and s to se vergentthrust and fold structures formed mileev et al 1996 yudin 1999 golonka 2004 ii severalextensionalphasesduringthelateberriasian lateeocene associated with platform sed imentation kazantsev 1982 slavin 1989 and iii apost eocenecompres sive stage related to the collision of thearabian plate with eurasia leading tothe subduction of the east black seabasin under the russian platform andexhumation and uplift of individualblocks of the anticlinorium frombeneath the platform deposits saintotet al 1999 nikishin et al 2001 mileev et al 2006 according to mileev et al 1992 the accretional wedge of the cmformed in two main stages during theearly middle jurassic and late juras sic early cretaceous berriasian thelate cimmerian late jurassic berriasian compressional phase isbelieved to be the most importantphase for the genesis of the anticlino rium and the s to se vergent nappes mileev et al 1996 2006 saintotet al 1999 as pointed out by priva lov 2001 during the late cimmerianphase the regional stress eld was notpurely compressional but transpres sional inducing clockwise rotation ofthe cm in the late berriasian subsi dence commenced and late cimmerianstructures were unconformably over lain by platform sediments mainlysandstones conglomerates and lime stones continuous platform depositsare preserved along the northernmargin of the cm kazantsev 1982 with thickness varying from 0 3 to8 km field observations in the north ern slope of the cm revealed localizedthrusting of upper jurassic limestoneonto lower cretaceous platformdeposits kazantsev 1982 yudin 1999 sedimentation in platformregimes terminates in the late eocenein response to the uplift induced bythe east black sea basin indentation which was in turn caused by thearabia eurasia collision nikishinet al 2001 oligocene neogene sed imentation represented e g by theabstract

a mohr circle construction for the opening of a pre existing fracture abstract the opening of a fracture is dependent on the fluid pressure and the local stress regime around the fracture for a fracture to open the fluid pressure must exceed the normal stress acting on the fracture the mohr circle provides a useful tool allowing the visualization of these relationships this construction determines the range of fracture orientations that are able to open as well as determining the opening direction of these fractures this is then used to produce ratios of the magma pressure and the principal stresses for some dykes from the lizard ophiolite u k

fracture permeability created by perturbed stress fields around active faults in a fractured basement reservoir several researchers have suggested that perturbed stress fields associated with active faults significantly affect flow properties in the subsurface to examine this insight quantitatively we combine an elastic dislocation model of active faults and a stress compliant function for fracture apertures to evaluate flow properties in a fractured basement reservoir in the yufutsu field japan the most productive well in the reservoir shows about 90 of rotation of the axes of horizontal stresses along the well trajectory whereas the directions of horizontal stresses at nonproductive wells are commonly oriented consistently with those of the regional stresses additionally results of step rate hydraulic injection tests at the nonproductive well indicate that fracture apertures fluctuate significantly in response to the magnitude of stresses normal to the fracture surfaces these observations support the important effect of perturbed stress fields on flow properties the observed stress orientation profiles are correlated to those from a geomechanical model nonproductive wells were drilled in the area where the regional stress state prevails and the most productive well penetrates the area near the tips of active faults where the stress concentration leads to enhancements in fracture permeability by opening or shearing the modeled perturbed stress fields combined with a stress compliant function for opening of fracture apertures can explain the observed difference of well performances to the first order the model demonstrates that areas near the tips of active faults have high potentials for hydrocarbon production in fractured basement reservoirs

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

evidence of early cretaceous remagnetization in the crimean peninsula a palaeomagnetic study from mesozoic rocks in the crimean and western pontides conjugate margins of the western black sea

the exhumation of the western greater caucasus a thermochronometric study this study provides 39 new thermochronometric analyses from the western part of the greater caucasus a region in which existing data are extremely limited and of questionable quality the new results are consistent with field studies that identify triassic to middle jurassic cimmerian and oligo miocene alpine orogenic erosional events an inverse relationship between the fission track and depositional ages of oligo miocene sedimentary samples also implies some degree of eocene erosion of the greater caucasus and intermediate sediment storage cooling ages and field relationships within the core of the range west of mt elbrus require 5 km of permo triassic exhumation and restrict the overall amount of cenozoic exhumation to 2 5 km current exhumation rates are typically low and do not support a plio pleistocene increase in climate driven denudation high 1 km ma 1 rates of exhumation are restricted to the southern flank of the range in northwest georgia despite a general lack of significant seismicity within the study region this exhumation peak is close to the largest instrumentally recorded earthquake in the caucasus ms 7 0 this may suggest that exhumation is associated with the decoupling of the sedimentary succession from its crystalline basement in the southern part of the range and the inversion of the largely jurassic fill of the greater caucasus basin rates of exhumation are compatible with this being driven by active shortening further sampling and analysis are required to provide a higher resolution low temperature thermochronology of alpine exhumation to isolate the drivers for palaeogene dziruli massif cooling and uplift and to constrain better the extent of the current localized phase of rapid exhumation

burial and exhumation of corsica france in the light of fission track data 1 the mesozoic and cenozoic exhumation and cooling history of corsica is reconstructed by fission track ft data on basement and sedimentary rocks apatite ages are 105 16 ma zircon ages are 160 145 ma the jurassic and cretaceous ages show that parts of the variscan basement escaped alpine influence the basement was thermally affected by rifting prior to jurassic opening of the ligurian piedmont ocean then it cooled to near surface temperatures in paleocene eocene times subduction buried parts of the basement and overlying flysch to greater depth in the oligocene both collapse of the nappe stack and rifting prior to opening of the ligurian provencal basin affected the apatite ft system of the basement in different partly overlapping areas causing a complex age pattern the study shows that thorough analysis of ft data and thermal modeling allow to assign age populations to distinct cooling processes even when several thermotectonic events contributed to generate an intricate age pattern

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

slab rollback suggested by latest miocene to pliocene forearc stress and migration of volcanic front in southern kyushu northern ryukyu arc abstract the northern ryukyu arc has active backarc rift neutral stress forearc and active accretionary prism the okinawa trough has been shaped by the episodic rifting in the backarc paleostresses were inferred in this study from mesoscale faults in neogene forearc sediments called the miyazaki group southeast kyushu in the northern ryukyu arc the forearc stress changed from compressional to extensional from the latest miocene through early pliocene time the stress history is concordant with the transition in tectonic regime from folding to rifting in the backarc the transition in the stress state occurred simultaneously also with trenchward movement of the volcanic front these phenomena suggest that the subducting slab under southern kyushu became steeper in the early pliocene extensional tectonics ceased sometime in the late pliocene or early to mid pleistocene concordant with the counterclockwise change of subducting direction of the philippine sea plate

tree age control on reconstructed debris flow frequencies examples from a regional dendrogeomorphic reconstruction in the crimean mountains the crimean mountains ukraine are renowned for the highest occurrence of debris flows along the northern coast of the black sea but information on their origin frequency and triggers is widely lacking this study reconstructs a regional time series of debris flows in eight catchments located on the slopes above yalta dendrogeomorphic analyses were performed on 1122 increment cores selected from 566 black pines pinus nigra ssp pallasiana with clear signs of external damage induced by past debris flow activity the trees sampled were divided into old and young trees the sample contains 361 young trees with post 1930 innermost rings and 205 old trees with pre 1930 germination dates the two groups of trees were analyzed separately to identify possible age effects in the reconstructed debris flow series and to assess the ability of p nigra to record geomorphic disturbances over time we date a total of 215 debris flows back to ad 1701 and observe a mean decadal frequency of 6 9 events with a peak in activity during the 1940s 20 events the young trees record an increase in debris flow activity over the last 70 years whereas the frequency of events remained fairly constant in the old trees for the same period by contrast the formation of reaction wood became increasingly scarce with increasing tree age whereas the occurrence of abrupt growth suppression increased copyright 2014 john wiley sons ltd

3 d mohr circle construction using vein orientation data from gadag southern india implications to recognize fluid pressure fluctuation abstract in this paper orientations of quartz veins from the archaean age lode gold bearing region of gadag southern india are used to determine the relative stress and fluid pressure p f conditions by constructing 3 d mohr circle anisotropy of magnetic susceptibility ams analysis of the host massive metabasalt reveals that the magnetic foliation is nw se striking which is related to early ne sw compression d1 d2 deformation that affected the region the quartz veins have a wide range of orientations with nw se striking veins steep northeasterly dips being the most prominent vein emplacement is inferred to have taken place under nw se compression that is known to have caused late deformation d3 in the region it is argued that the nw se fabric defined the pre existing anisotropy and channelized fluid flow during d3 the permeability was initially low which resulted in high p f 2 3 d mohr circle analysis indicates that the driving pressure ratio r was 0 94 a condition that favoured fracturing and reactivation of fabric elements foliations and fractures having a wide range of orientations this led to an increase in permeability and fluid flowed burped into the fractures resulting vein emplacement and sealing of fractures led to a reduction of p f 2 it is argued that at this low p f nw se oriented structures continued to remain susceptible to reactivation and vein emplacement while fractures of all other orientations were inactive and remained sealed as a consequence the study area has a cluster of nw se oriented veins r is calculated to be 0 07 from 3 d mohr circle analysis at low p f when fractures with nw se orientation only were susceptible to dilation however it is envisaged that any emplacement of veins in these fractures would have sealed them thus reducing the permeability and initiating the next cycle of rise in p f 2 thus it is concluded that the quartz veins in the gadag region are a consequence of an interplay between conditions that fluctuated from p f 2 to p f 2

scaling the 3 d mohr circle and quantification of paleostress during fluid pressure fluctuation application to understand gold mineralization in quartz veins of gadag southern india abstract in this study orientations of 157 quartz veins occurring in metabasalts of the gadag region dharwar craton southern india are used to plot the 3 d mohr stress circle which provides information about relative stress fluid pressure pf conditions as well as stress state during pf fluctuation to scale the 3 d mohr circle vein orientation data are integrated with a available estimates from fluid inclusions of highest recorded pf 390 mpa and lowest recorded pf 50 mpa and b intrinsic rupture criterion that empirically quantify rock properties based on the scaled 3 d mohr circle the absolute magnitudes of the three principal stresses are quantified for high and low pf of 157 veins investigated here 14 veins are identified as having favourable orientation for dilation at high as well as low pf these 14 veins have a mean strike of 150 which is similar to the orientation of the gold bearing quartz lodes reported in the region the effective normal stress n n pf prevalent during dilation of fracture fabric anisotropy with 150 strike is calculated to be 11 5 mpa at high pf and 1 0 mpa at low pf thus it is interpreted that in the gadag region a change in n of 10 5 mpa prevailed during pf fluctuation and associated separation of gold from the fluid

dikes emplaced into fractured basement timna igneous complex israel dikes are usually envisioned as arrays of parallel segments dilated perpendicular to the direction of the least compressive stress we describe here four dikes of highly irregular shape intruded in the fractured basement in the timna igneous complex southern israel the dikes include a doleritic dike 2 3 km long and 1 6 m to 32 m thick and three andesitic dikes up to 1 5 km long and 8 m thick the dikes each display significant variations of dip up to 60 strike up to 160 and thickness the thickness variations correlate better with the segment attitude than with the position along the dikes we show that the irregular shapes of the timna dikes are the result of emplacement into fractured host rock under different paleostress states and driving pressures three dilation styles that differ by the geometry of the initial cracks are analyzed an array of randomly oriented cracks style a a single linear crack style b and an array of interconnected nonparallel cracks style c the analysis of style a provides the stress state during dike emplacement including the orientations of the three principal stresses 1 2 3 the stress ratio 2 3 1 3 and the normalized driving pressure r pm 3 1 3 the stress ratio indicates the shape of the stress ellipsoid and it ranges from 0 for 2 3 prolate ellipsoid to 1 for 1 2 oblate ellipsoid the normalized driving pressure r indicates the relative magnitude of the internal magma pressure pm with respect to the tectonic stresses and it ranges from r 0 for pm 3 to r 1 for pm 1 we found that for three dikes in timna 0 25 indicating small differences between the two horizontal principal stresses and for one dike 0 9 indicating a large difference between the two horizontal principal stresses the normalized driving pressure r is about 0 08 in two horizontally propagating dikes and about 0 25 in two vertically propagating dikes style b predicts an elliptical thickness profile along the dike due to dilation of a linear crack this prediction agrees with the profile of one of the dikes the predicted thicknesses due to dilation of the interconnected array of cracks style c are in good agreement with the thickness variations of the doleritic dike and in fair agreement with two of the andesitic dikes deviations from the ideal geometry suggest separate stages of propagation and dilation in some of the dike segments

the history of vein formation determined by 40ar 39ar dating of adularia in the hosen 1 vein at the hishikari epithermal gold deposit japan the hosen 1 vein has a symmetrical banded structure within the hishikari epithermal gold deposit in japan the vein can be divided into four macroscopic bands we used 40ar 39ar dating of adularia by incremental step heating to determine the duration of mineralization in the individual bands of the vein and the history of vein formation plateau ages were obtained from all adularia samples and no significant excess 40ar is recognized from inverse isochrons the derived age spectra suggest that thermal overprinting of the epithermal system did not affect the plateau ages although early bands must have been reheated by the thermal pulses associated with later bands the 40ar 39ar ages of adularia indicate that vein formation occurred episodically in distinct periods separated by intervals of about 30 000 to 110 000 yr the hosen 1 vein grew in at least six increments at the 20 m level and at least four increments at the 62 5 m level the total duration of mineralization from the margin to the center of the hosen 1 vein was about 260 000 yr during which time the temperature of the hydrothermal fluid decreased from 190 to 210 c to less than 170 c

volcano load control on dyke propagation and vent distribution insights from analogue modeling 1 the spatial distribution of eruptive vents around volcanoes can be complex and evolve as a volcano grows observations of vent distribution at contrasting volcanoes from scoria cones to large shields show that peripheral eruptive vents concentrate close to the volcano base we use analogue experiments to explore the control of volcano load on magma ascent and on vent location results show that the local loading stress field favors eruption of rising magma away from the volcano summit if a central conduit is not established or is blocked two sets of scaled experiments are developed with contrasting rheological properties to analyze similarities and differences in simulated magma rise below a volcano 1 golden syrup magma analogue is injected into a sand plaster mixed layer crust analogue under a cone 2 water or air magma analogues is injected into gelatin under a sand cone rising dykes approaching the cone stress field are stopped by the load compressive stress with continued intrusion dyke overpressure builds up dykes extend laterally until their tips are able to rise vertically again and to erupt in the flank or at the base of the volcano lateral offset of the extrusion point relative to the edifice summit depends on substratum thickness volcano slope and dyke overpressure the 3d geometry of golden syrup intrusions varies with experimental parameters from cylindrical conduits to dyke and sill complexes experimental results are compared with illustrative field cases and with previously published numerical models this comparison enables applications and limitations of the analogue models to be highlighted and allows us to propose a conceptual model for the evolution of vent distribution with volcano growth

coastal cliffs rock slope failures and late quaternary transgressions of the black sea along southern crimea abstract rock slope failures represent a significant hazard along global coastlines but their chronology remains poorly documented here we focus on the geomorphology and chronology of giant rockslides affecting the crimean mountains along the black sea coast geomorphic evidence suggests that high 100 m limestone cliffs flanking the southern slopes of the crimean mountains are scarps of rockslides nested within larger deep seated gravitational slope deformations dsgsds such pervasive slope failures originated due to lateral spreading of intensively faulted late jurassic carbonate blocks moving atop weak plastic late triassic flysch and tuff layers by introducing a dating strategy relying on the combination of the uranium thorium dating u th of exposed calcareous speleothems covering the landslide scarps with the 36cl exposure dating of rock walls we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces for the three representative large scale rockslides between the towns of foros and yalta the initiation of the dsgsds as evidenced by the widening of crevices and the onset of speleothem accumulation was 300 ka bp but the recent cliff morphology along the coast is the result of late pleistocene holocene failures spanning 20 0 5 ka bp the exposures of rockslide scarps occurred mostly at 20 15 8 5 4 and 2 0 5 ka which substantially coincide with the last major black sea transgressions and or more humid holocene intervals our study suggests that before ultimate fast and or catastrophic slope failures the relaxation of rock massifs correlative with karstification cracks opening and incipient sliding lasted on the order of 104 105 years rapid late glacial holocene transgressions of the black sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides simultaneously affecting the majority of the sw coast of the crimean peninsula

a new energy density calculation method for reservoir delineation using seismic low frequency signal abstract in comparison to high frequency signals low frequency seismic signals suffer less from scattering and intrinsic attenuation during wave propagation penetrate deeper strata and thus can provide more energy information related to the hydrocarbon reservoirs based on the asymptotic representation for the frequency dependent reflections in the fluid saturated pore elastic media we first derive a novel equation of the reservoir energy density and present an efficient workflow to calculate the reservoir energy density using low frequency seismic data then within a low frequency range from 1 to 30 hz we construct an objective function to determine the optimal frequency using the energy densities calculated from the post stack seismic traces close to the wells next we can calculate the reservoir energy density using the instantaneous spectra of optimal frequency at the low frequency end of the seismic spectrum tests on examples for synthetic and field data demonstrate that the proposed reservoir energy density can produce high quality images for the fluid saturated reservoirs and it produces less background artefacts caused by elastic layers this method provides a new way to detect the location of hydrocarbon reservoirs and characterize their spatial distribution