uncertainties in the relative positions of the australia antarctica lord howe and pacific plates since the late cretaceous we determined parameters that describe finite rotations and their uncertainty regions for relative plate motion at the spreading centers between the pacific and antarctica plates between australia and antarctica and between the lord howe rise and australia we combined these to yield a range of possible finite rotations describing the relative positions of the pacific australia antarctica and lord howe plates since the late cretaceous if the pacific australia plate boundary has had its present trend since anomaly 18 time reconstructions show 330 110 km of motion of the pacific plate relative to the lord howe rise since anomaly 5 time 9 8 m y 420 110 km since anomaly 6 time 19 5 m y 770 330 km since anomaly 13 time 35 6 m y and 820 260 km since anomaly 18 time 43 0 m y we examined two cases for times prior to anomaly 18 assuming a late cretaceous age of australia antarctica separation if a plate boundary existed between the lord howe rise and pacific plates since the late cretaceous with no plate boundary in antarctica reconstructions with the lord howe rise fixed predict 610 200 km of westward motion of the pacific plate between the times of anomalies 31 and 22 followed by 260 100 km of northward motion between the times of anomalies 22 and 18 if the lord howe rise was fixed to the pacific plate until the eocene but a plate boundary existed between east and west antarctica reconstructions show very little motion across this boundary between the times of anomalies 31 and 22 followed by convergence between the times of anomalies 22 and 18 this second case also brings 70 80 m y paleomagnetic poles from the pacific and east antarctica plates into better agreement than the first case but large uncertainties in the reconstructions do not allow the first case to be conclusively eliminated

a reappraisal of the 1894 atalanti earthquake surface ruptures central greece this article presents the results of new field and aerial photo surveys of the atalanti fault and of the mesoseismal area of the 20 and 27 april 1894 earth quakes coupled with a reanalysis of contemporary reports and previous investiga tions these are used to gain a better understanding of the faults responsible for these events and their seismic behavior the first shock was smaller and probably located inshore or offshore the malessina peninsula no resolving field evidence has been found to locate the seismogenic structure responsible for this shock on the basis of the limited information available we suggest the malessina escarpment a 12 km long ene trending nw dipping fault as a possible structure responsible for this event on the other hand the second and largest shock is definitely related to the atalanti fault sensu stricto a main wnw trending n dipping active fault extending between the platirema valley a few km nw of the town of atalanti and larymna the total length of the rupture recognized in the field is about 32 km but it can be extended further se up to 40 km no evidence for a longer rupture extending some other 20 km to the nw between the karagiozis river and ag kostantinos is found the complex geometry of the fault with bends and step overs appears to be controlled by preexisting transverse structures minimum coseismic vertical throws measured in the field after more than a century elapsed from the earthquake are 30 80 cm thus consistent with contemporary reports indicating 1 m average slip rates are not well constrained the available estimates fall in the range 0 1 0 5 mm yr confirming the smaller amount of crustal extension taking place in this area with respect to other nearby regions such as the corinth gulf no new data are available to define the average recurrence interval typical of the atalanti fault however a reconsideration of the existing information induced us to rule out the possibility that the famous 426 b c earthquake occurred on the atalanti fault on the basis of the extent and size of the rupture recognized in the field a m 6 8 is estimated for the second and largest shock

evolution of faulting and plate boundary deformation in the southern taranaki basin new zealand abstract faulting and folding in the southern taranaki basin constrain the evolution of the new zealand plate boundary since 80 ma sedimentary rocks up to 8 km thick record multiple phases of deformation which have been examined using 2d and 3d seismic reflection data resulting in fault displacement time curves and basin wide isopach maps with temporal resolutions of 5 10 myr and 1 4 myr pre and post 23 ma respectively three main phases of tectonic activity have been recognised late cretaceous and palaeocene extension 80 55 ma mainly oligocene and younger contraction and plio pleistocene 3 7 0 ma extension most of the largest faults e g cape egmont fault accrued displacement during the late cretaceous and were reactivated one or more times during subsequent episodes of deformation the oldest phase of extension occurred during gondwana break up and was ubiquitous throughout the basin contraction along the eastern boundary of the basin associated with the onset of hikurangi margin subduction commenced as early as late eocene the zone of contraction widened and migrated westward during the miocene with reverse faults and folds in westernmost parts of the basin formed in the late miocene 7 5 ma initiation and episodic widening of this zone of contraction may have been partly triggered by changes in the rate of plate convergence contraction is now mainly confined to the northern south island and has been succeeded to the north by plio pleistocene extension the present day transition zone between extension in the north and contraction in the south is defined by a wnw trending line across the basin the extension contraction transition migrated southward during the late miocene and pliocene consistent with steepening of the subducting plate and associated southward movement of the southern termination of the hikurangi subduction system

kaikoura canyon new zealand active conduit from near shore sediment zones to trench axis channel kaikoura canyon is one of a few major active conduits between a near shore sediment transport system and a deep ocean channel it is the sink for mobile zones of gravel sand and mud that migrate northwards off northeastern south island new zealand it is presently the primary source for the 1500 km long hikurangi channel which supplies overbank turbidites to a filled trench an ocean plateau basin and a distal fan drift swath data seismic profiles side scan sonographs aerial photographs cores grab samples and current meter data are used to define the shape and texture of the canyon and adjacent shelf in order to better understand how coastal processes and canyon interact to supply sediment to the deep ocean kaikoura canyon is 60 km long up to 1200 m deep and generally u shaped in profile its head is within 500 m of the shore and within 200 m of rocky projections from the shore platform in a mountain backed bay without large rivers the canyon head incises the 18 m depth contour and boulders pebble gravel and megarippled coarse sand reach the canyon rim fine sand migrating northward along the shelf under the influence of waves and currents is trapped in a southward projecting canyon head gully which incises the thickest part of the holocene sediment prism it is estimated that about 1 5 106 m3 of sediment falls into the canyon head each year tensional fractures around the canyon rim suggest that sediments in the canyon head gully are unstable gravel turbidites with post last glacial age shells are at or near the seabed in the lower canyon but are blanketed by many thin silt and sand possibly storm generated turbidites in the upper canyon the top gravel contains a twig that is about 170 years old suggesting that the last major collapse in the canyon head coincides with many onshore rockfalls triggered by rupture of a major strike slip plate boundary fault in about 1833 an underlying gravel is about 300 years old and may again coincide with fault rupture most of the large earthquake triggered failures may ignite to form self perpetuating autosuspension flows that feed a 1500 km long deep sea turbidite channel

tectonic rotations about vertical axes during the last 4 ma in part of the new zealand plate boundary zone the declinations of the primary magnetization of sedimentary rocks in the northern part of the new zealand plate boundary zone after thermal or alternating field cleaning have been used to determine tectonic rotations about vertical axes of rigid crustal blocks the pattern of rotations during the last 4 ma combined with structural style and continuity defines seven structural domains each ca 100 100 200 km across which contain crustal blocks up to 100 km across and 20 km thick large crustal blocks tens of km across in two of these domains have rotated clockwise more than 20 relative to one of the margins of the plate boundary zone in the last 4 ma their behaviour appears to be controlled by the nature of the plate boundaries such as the presence of an underlying subducted slab and the strength of the crust at the back of the overlying crustal wedge small crustal blocks 10 km across may have rotated clockwise through angles greater than 20 during the last 4 ma floating on an underlying zone of more distributed deformation the tectonic rotations of the large crustal blocks and the nature of the deformation at their boundaries combined with an interpolation of the relative plate positions can be used to reconstruct the plate boundary zone at ca 4 ma

three dimensional numerical experiments of strain partitioning at oblique plate boundaries implications for contrasting tectonic styles in the southern coast ranges california and central south island new zealand a three dimensional numerical model is used to investigate the nature and distribution of crustal scale deformation and strain partitioning across obliquely convergent transpressive plate boundaries a uniform elastic plastic crustal layer obeying murrell s extension to three dimensions of the griffith failure criterion was deformed under basal kinematic boundary conditions that correspond to the oblique convergence between two mantle lithospheres one of which detaches and subducts beneath the other the results show deformation concentrated in relatively narrow shear zones the character planar versus curved and dip of these shear zones or crustal scale faults depend on the relative amount of convergence versus transcurrent motion imposed across the plate boundary in models dominated by transcurrent boundary conditions two separate sets of coexisting structures develop 1 a pair of planar relatively shallow dipping thrust zones arranged in a v structure that accommodate convergent motion and 2 a set of curved near vertical strike slip zones arranged in a flower structure that accommodates the transcurrent motion in models dominated by convergence both contractional and transcurrent deformations are accommodated by oblique slip across a single pair of structures that have the same geometry as the thrust shear zones there is a gradational behavior between these end member partitioned and nonpartitioned modes for intermediate boundary conditions in all cases the dip of the shear zones predicted by the numerical model is in good agreement with the dip of ideal faults predicted by mohr s incipient faulting hypothesis the two basic modes are interpreted to underlie the contrasting tectonic styles of the southern coast ranges california and central south island new zealand factors other than obliquity of convergence which play a role in strain partitioning are discussed

ground subsidence quaternary faults and vulnerability of utilities and transportation networks in thessaly greece ground fissures and subsidence have caused extensive damage in structures and the utility networks roads railroad line larisa nato airport telecommunication network in the plain of thessaly central greece in the last 20 years the fact that these fissures are parallel to quaternary faults controlling the structural evolution of the thessaly basin marked by intense recent seismic activity led some scientists to regard them as manifestation of tectonic creep even premonitory phenomena of major future seismic events a careful study of the geometric characteristics and of the kinematics of these ground fissures however revealed that they only reflect shear failure of the ground due to compaction of loose sediments following significant decline of the groundwater level due to over pumping i e a geotechnical and not a tectonic process furthermore theoretical considerations and modeling predict surface fissuring along zones of anomalous basement normal fault controlled topography this explains the correlation between ground fissures and active quaternary normal faults

a model for tectonic rotations about a vertical axis abstract the rotation of a rigid ellipsoidal inclusion within a highly viscous fluid orientated so that two of the principal axes remain horizontal is used as a model for the rotation of crustal inclusions in wide zones of continental deformation this model is also applicable to other geological problems involving the rotation of inclusions in a matrix the pattern of behaviour in such a model is shown to be complex in general the rotation rate of the inclusion is a function of all components of the velocity field of the deforming medium and the horizontal aspect ratio of the inclusion however for a given velocity field this aspect ratio must exceed a critical value before the inclusion can rotate continuously inclusions with lower aspect ratios will rotate for a certain range of orientations in an opposite direction to the sense of shear in the deforming zone the possibility of the inclusion changing shape during rotation adds to the complexity of behaviour

petroleum source in the tazhong uplift tarim basin new insights from geochemical and fluid inclusion data abstract a total of 108 drill stem test dst crude oil samples and 10 reservoir fluid inclusion samples were investigated geochemically to identify the characteristics and origin of the crude oil in the tazhong uplift tarim basin nw china results show that the majority of oils share typical biomarker characteristics from the middle upper ordovician o2 3 source rock and related crude oil features these features include a distinct v shape in the relative abundance of c27 c28 and c29 regular steranes and low abundances of dinosterane 24 norcholestanes triaromatic dinosteroids and gammacerane only a few oils display typical biomarker features indicating a cambrian lower ordovician o1 genetic affinity such as linear or anti l shape c27 c28 and c29 regular sterane distributions and relatively high concentrations of dinosterane 24 norcholestanes triaromatic dinosteroids and gammacerane it appears that most of the oils studied were derived from the o2 3 intervals as suggested by previous studies however the 13c values of individual n alkanes indicate that most of the crude oils in the tazhong uplift represent a mixture of two end member oils an o1 derived oil such as from well td2 or tz62 s and an o2 3 derived oil such as from well ym2 the data suggest that most of the oils in the uplift have a mixed origin and do not originated from the middle upper ordovician strata alone this conclusion is supported by data on the molecular composition of petroleum inclusions this new oil mixing model is critical for reconstructing the hydrocarbon formation and accumulation history for the region and may have important implications for further petroleum exploration in the tarim basin

geodetic constraints to the kinematics of the kapareli fault reactivated during the 1981 gulf of corinth earthquakes abstract comparison of historical and of post seismic triangulation data is used to model vertical crustal movements in the vicinity of the kapareli fault or the alkynonides earthquakes north fault one of the two antithetic normal faults which reactivated during the 1981 gulf of corinth ms 6 7 earthquakes this fault is characterized by a much smaller geomorphological signature than the south or perachora fault of the same seismic sequence analysis of geodetic data on the basis of polynomial filtering and elastic dislocation modelling as well as analysis of structural and coastal change data permits us to conclude that the upper bound in the uncertainty level of most of the available elevation changes is 20 30 cm usually lower than the corresponding dislocation signal in addition the available geodetic data have a systematic pattern and are consistent with structural data for this reason they permit more precise constraints on the geometry and the role of the kapareli fault or the alkyonides earthquakes north fault its total length is estimated about 17 km about 50 longer than its surface trace about 30 40 cm subsidence of its hanging wall as well as at least 15 cm maximum uplift of its footwall is also inferred this new evidence suggests that although in the long term the kapareli fault may represent a rather secondary antithetic fault to the alkyonides earthquakes south perachora fault during the 1981 earthquakes it probably had a more important structural role

geodetically determined strain across the southern end of the tonga kermadec hikurangi subduction zone summary a method of simultaneous reduction is presented for determining strain rates from multiple triangulation surveys where common triangulation stations have been used but the angles of the old survey have not necessarily been reobserved this method is applied to triangulation in the northern south island at the southern end of the tonga kermadec hikurangi subduction zone from a profile of shear strain across the indian pacific plate boundary the displacement of the indian plate relative to the pacific is calculated to be 54 9 mm yr at an azimuth of 84 f lo in remarkable agreement with the motion predicted by global plate tectonic models most of this motion occurs within a 15okm wide zone bounded on the east by the hikurangi trough within this zone the motion is partitioned near the hikurangi trough no slip is occurring at the upper surface of the subducting pacific plate the subduction thrust and motion is predominantly thrusting normal to the trough axis to the west is a region of predominantly dextral strike slip faulting this pattern is consistent with fitch s model of oblique subduction to the south of the profile a change is observed in the azimuth of the faulting along a line which marks the southern extent of the subduction slab indicating the end of the partitioned motion

gas genetic type and origin of hydrogen sulfide in the zhongba gas field of the western sichuan basin china abstract natural gases and associated condensate oils from the zhongba gas field in the western sichuan basin china were investigated for gas genetic types and origin of h 2 s by integrating gaseous and light hydrocarbon geochemistry formation water compositions s isotopes 34 s and geological data there are two types of natural gas accumulations in the studied area gases from the third member of the middle triassic leikoupo formation t 2 l 3 are reservoired in a marine carbonate sequence and are characterized by high gas dryness high h 2 s and co 2 contents slightly heavy c isotopic values of ch 4 and widely variable c isotopic values of wet gases they are highly mature thermogenic gases mainly derived from the permian type ii kerogens mixed with a small proportion of the triassic coal type gases gases from the second member of the upper triassic xujiahe formation t 3 x 2 are reservoired in continental sandstones and characterized by low gas dryness free of h 2 s slightly light c isotopic values of ch 4 and heavy and less variable c isotopic values of wet gases they are coal type gases derived from coal in the triassic xujiahe formation the h 2 s from the leikoupo formation is most likely formed by thermochemical so 4 reduction tsr even though other possibilities cannot be fully ruled out the proposed tsr origin of h 2 s is supported by geochemical compositions and geological interpretations the reservoir in the leikoupo formation is dolomite dominated carbonate that contains gypsum and anhydrite petroleum compounds dissolved in water react with aqueous so 4 species which are derived from the dissolution of anhydrite burial history analysis reveals that from the temperature at which tsr occurred it was in the late jurassic to early cretaceous and tsr ceased due to uplift and cooling thereafter tsr alteration is incomplete and mainly occurs in wet gas components as indicated by near constant ch 4 13 c values wide range variations of ethane propane and butane 13 c values and moderately high gas dryness the 34 s values in so 4 elemental s and h 2 s fall within the fractionation scope of tsr derived h 2 s high organo s compound concentrations together with the occurrence of 2 thiaadamantanes in the t 2 l reservoir provide supplementary evidence for tsr related alteration

a well preserved 250 million year old oil accumulation in the tarim basin western china implications for hydrocarbon exploration in old and deep basins abstract a giant oilfield ym 2 with an estimated reserve of close to one billion bbl was recently discovered in an ordovician carbonate reservoir at a burial depth of 5800 6200 m in the northern tarim basin western china biomarker and isotope geochemistry of the hydrocarbons indicate that the oil was derived from ordovician marine source rocks at early to peak oil generation authigenic illite k ar dating fluid inclusion analysis fluid inclusion pvtx and thermal history modeling indicate that the accumulation is of primary in origin and the original charge occurred in the permian during the late hercynian orogenic stage approximately 290 250 million years ago the physiochemical compositions of the hydrocarbons and formation water remained largely unchanged since the initial accumulation the excellent preservation of such an old accumulation at such a great depth is due to continuous burial of the ym 2 structure since the triassic a thick effective seal and a relatively low geothermal gradient with a current reservoir temperature of 127 130 c this finding suggests that under suitable conditions old petroleum accumulations can be well preserved and some old and deep basins may be prospective frontiers for future exploration

origin of diamondoid and sulphur compounds in the tazhong ordovician condensate tarim basin china implications for hydrocarbon exploration in deep buried strata abstract in this paper we analyse the ordovician condensate in the tazhong area of the tarim basin nw china using a new high resolution comprehensive two dimensional gas chromatography with time of flight mass spectrometry gc gc tofms results show that 4778 compounds at a signal to noise ratio of more than 100 were detected reflecting the advantage of this method in the analysis of condensate abundant adamantane series compounds and some diamantane series compounds as well as a series of sulphur containing compounds including the benzothiophene series and the dibenzothiophene series were detected for the first time in the study area combined with the results of a study on oil and gas sources and migration accumulation we address the origin of these compounds it is implied that the diamondoids were not formed in situ due to oil cracking in reservoir approximately 5500 m deep at temperature around 139 c whereas the cracking of oil to gas may have occurred in the deeper buried cambrian dolomite reservoir at a reservoir temperature of 180 220 c 8500 11 000 m depth the oil cracked gas secondary cracking product might have migrated to and accumulated in the shallower buried ordovician reservoir accompanied by abundant diamondoids the formation of sulphur containing compounds may be related to thermochemical sulphate reduction tsr which similar to the oil cracking took place in the deeper buried cambrian reservoir under high temperature tsr so 4 2 in the formation water is reduced to h 2 s and organic sulphur compounds leading to the enrichment of sulphur in crude oils e g benzothiophene and dibenzothiophene series as such it is implied that the tazhong area could potentially be explored for deep buried oil cracked gas

active deformation in the bolivian andes south america a method is described for determining the horizontal field of velocity and velocity gradients in the bolivian andes in the vicinity of the bolivian orocline using the following data 1 space geodetic measurements of crustal motions 2 the style distribution and rate of late miocene quaternary folding and faulting and 3 paleomagnetic measurements of rigid body rotations about a vertical axis these data were analyzed in a network of 26 triangles which spanned the bolivian andes by solving the velocity gradient compatibility equations between adjacent triangles subject to the input data constraints this yielded 120 140 linear equations to constrain 108 unknowns making the problem moderately overdetermined a series of experiments were carried out with different combinations of the input data to determine the best fit in the least squares sense field of quaternary horizontal velocities and velocity gradients the azimuths of velocity vectors in the high andes are subparallel to both the relative plate convergence vector and the symmetry axis of the bolivian orocline with magnitudes relative to stable south america in the range 7 17 mm yr 1 accommodating up to 30 of the relative plate convergence however the azimuths of velocities along the range front are nearly orthogonal to the range with a component of distributed range parallel dextral or sinistral shear within the eastern cordillera and altiplano the horizontal velocity field requires bending about a vertical axis of both limbs of the bolivian orocline the field of horizontal dilatation assuming homogeneous deformation of the entire crustal thickness requires vertical velocities of material points up to 2 5 mm yr in the sub andean zone decreasing to 0 1 mm yr farther east in the eastern cordillera and altiplano the direction of maximum gradients of buoyancy stress determined from the field of gradients of appropriate combinations of velocity gradients using a thin sheet model of viscous flow are broadly parallel to the direction of maximum topographic gradients in the eastern cordillera providing support for the idea that the bulk behaviour of the bolivian lithosphere is fluid like a comparison of these gradients with buoyancy stress gradients calculated from crustal thickness contrasts suggest that the bulk lithospheric viscosity is in the range 0 5 1 0 1022 pa s gradients of velocity gradients along the eastern margin of the bolivian andes can be interpreted in terms of marked gradients of viscosity with viscosity increasing toward the brazilan shield in the cratonic core of south america buoyancy stresses calculated from crustal thickness contrasts calibrated with the crustal thicknesses at the changeovers from thrust to strike slip or normal faulting suggest that the average lithosphericscale deviatoric stresses are in the range 7 15 mpa

continental extension of the pacific plate at the southern termination of the hikurangi subduction zone the north mernoo fault zone offshore new zealand a complex transition from subduction at the hikurangi margin to transpressive continental collision across the southern alps occurs in the ne south island region of new zealand offshore the southern limit of oceanic subduction is constrained by the chatham rise a submerged continental plateau on the pacific plate which is presumably too buoyant for normal subduction in the nw corner of the rise is the north mernoo fault zone nmfz a 100 by 300 km region of basement involved active normal faulting of late miocene circa 8 6 ma to recent age the nmfz evolved contemporaneously with the rotation and development of the adjacent plate boundary zone growth faulting is characteristic within the sedimentary cover which is generally less than 2 km thick but the distribution of faulting has varied temporally the amount of mid pliocene recent extension is estimated to be not more than a few percent the nmfz consists of an array of overlapping south dipping normal faults which are typically 2 5 km apart and which trend roughly e w at a high angle to the plate boundary zone late quaternary surface traces are widely distributed on the mid to upper continental slope but many surface scarps are poorly preserved due to extensive erosion of the seafloor the western end of the fault zone crosses submarine canyons at the southern end of the hikurangi trough and almost abuts two fold and thrust fault systems on the ne south island continental margin although few data constrain the kinematics of extension a single mw 6 1 earth quake at the western end of the nmfz suggests planar rotating faults with a component of left lateral oblique slip two possible models of regional extension are considered 1 lateral buckling of the upper crust in which faulted slivers of crust are peeled off as the chatham rise slides past the transpressive marlborough fault system toward the southern alps and 2 flexure of the edge of continental pacific plate as the chatham rise is bent downward into the southern end of the hikurangi subduction zone improved seismological data and deep crustal seismic reflection profiles may help to constrain the kinematics of deformation

multiple stage migration and accumulation of permian lacustrine mixed oils in the central junggar basin nw china abstract the permian lacustrine petroleum system in the central junggar basin northwest china has recently obtained exploration success these accumulations are characterized by mixed oils and multiple stage migration and accumulation this process however has not been well constrained limiting the understanding of the general laws of hydrocarbon migration and accumulation and making it difficult to define exploration strategies here we reconstruct this process mainly based on oil bearing fluid inclusion analyses including petrography homogenization temperature and sequential extraction inclusion petrography shows that petroleum inclusions dominantly display yellow fluorescence while intergranular free oils mostly display strong blue green fluorescence this implies that the reservoirs seem to have experienced at least two stages of hydrocarbon charge from different sources and or maturities the sources maturities are determined through reservoir sequential extraction analyses the free oils are mixed and sourced from the lower permian fengcheng formation p1f and the middle permian lower wuerhe formation p2w while the inclusion oils are also mixed and derived mainly from the p1f source both oils are characterized by moderate maturity homogenization temperature measurements of oil bearing fluid inclusions combined with reconstruction of reservoir burial and thermal history not only further verify multiple hydrocarbon charging events but also characterize the timing which indicates a three stage petroleum charging model during the first stage of the late triassic carboniferous reservoirs were charged by p1f sourced oils which were dysmigrated or remigrated to jurassic reservoirs during the second stage i e the early cretaceous in contrast the third stage from the late cretaceous represents another hydrocarbon charge event that is the primary oil accumulation sourced from the p2w rocks according to this model both primary and secondary oil accumulations contribute to the current region s exploration success and provide future exploration targets

the collision tectonics of the southern greek neotethys continental collision in the aegean area has produced a collage of micro continental blocks which were accreted to the active margin of eurasia in early tertiary times studies undertaken in the argolis peninsula of southern greece located at the southern end of the pelagonian continental terrane confirm that this block was rifted from gondwana in mid triassic times by mid jurassic times at the latest actively spreading oceanic basins had opened in both the pindos and vardar zones on either side of this block identification of late cretaceous oceanic basalts within an accretionary complex in the eastern argolis peninsula extends the history of the neotethys beyond late jurassic ophiolite emplacement previously believed to be the result of continental collision the cretaceous ocean basins were relict jurassic features as no rifting event is known which can account for their formation following ophiolite obduction after a phase of late cretaceous oceanic spreading in the eastern vardar oceanic basin early tertiary collision occurred as a result of northeast dipping subduction along the eastern margins of both pindos and vardar branches of the neotethys two distinct nappe emplacement vectors are identified in the argolis peninsula after accounting for neotectonic rotations these are interpreted to reflect sw directed orthogonal collision in the west and nw directed emplacement in the east resulting from tranpressional collision along the southern end of the pelagonian block

large tectonic rotations in a wide zone of neogene distributed dextral shear northeastern south island new zealand abstract the new zealand plate boundary zone in the northern part of south island new zealand comprises a series of active dextral strike slip faults referred to as the marlborough fault zone mfz which link oblique continental convergence farther south along the alpine fault to subduction of the pacific plate along the hikurangi margin new paleomagnetic data are presented which together with previous studies suggest coherent neogene clockwise rotation up to 130 about a vertical axis of crustal blocks in the mfz starting at 20 ma there is a striking correlation between the amount of observed rotation and the trend of mesozoic basement structures creating this part of the new zealand orocline in a zone of distributed dextral shear about 100 km wide which has persisted for about 20 ma in the southern part of the mfz crustal blocks appear to be on a scale of 1 10 km with boundaries that are subparallel to the basement strike this way deformation is accommodated by a combination of fault slip and rotation in a zone of more pervasive dextral shear resulting in coherent bending of the basement structure in the central part of the mfz this rotation appears to be that of elongate crustal blocks 50 km 10 km in size rotating 80 clockwise at an average rotation rate 4 ma in detail the rotation rate has decreased towards the present from 6 ma at 20 ma to

validation of tectonic reconstructions by crustal volume balance new zealand through the cenozoic we describe a procedure that allows us to quantitatively test hypotheses about the tectonic evolution of a region including areas for which there is little or no geologic record and apply it to the pacific australian plate boundary in the new zealand region since 65 ma the derived models are a first attempt to quantify the effects of the development of the modern plate boundary on four major components of the tectonic evolution of new zealand i e sedimentation paleogeography growth of crustal root and nonrigid deformation the technique balances total rock volume through time using estimates of these factors although the solutions are non unique the uncertainties in each factor can be estimated and used to define the models the plate reconstructions we present are minor modifications of earlier work developed to test whether those proposed reconstructions are self consistent and consistent with present day crustal structure and sediment distribution they are digital and geographically referenced and they have the advantage that new data can be readily incorporated and new concepts tested against several criteria the model of the evolution of new zealand9s crustal root is new and incorporates a previously unpublished compilation the models show that rock redistribution is accounted for by erosion and sedimentation during the period 65 25 ma the pacific australian plate boundary began propagating through new zealand ca 45 ma in these models development of the boundary has no effect on nonrigid deformation until ca 25 ma that time marked the start of a significant increase in land area and of the nonrigid deformation of a large region in the center of the new zealand continent since ca 20 ma 575 000 km 3 of sediments were deposited in basins around new zealand and a crustal root with a volume of 2 200 000 km 3 is interpreted to have developed beneath the landmass a large area in the center of late cretaceous and tertiary reconstructions of the new zealand region inferred from outcrop well and seismic reflection data deformed eroded and was eventually amalgamated within the continental crust of new zealand a redistribution of 3 080 000 km 3 of rock at 0 porosity

subsidence and evolution of the thessaloniki plain greece based on historical leveling and gps data comparison of historical leveling and of recent gps data reveal that the wider thessaloniki plain north greece a 2500 years old delta has subsided in the last 50 years up to 3 5 m these results are consistent with independent estimates of subsidence in the suburbs of thessaloniki and testify to a plain wide effect rather localized increased subsidence resulting from hydrocompaction due to intense pumping is superimposed on the plain wide subsidence the latter seems to mimic the long term tendency of landscape change as the correlation between recent surface deformation and deformation derived from boreholes reveals furthermore differential subsidence seems to control the flow of rivers and the overall morphology of the delta the significance and necessity of geoid corrections in the comparison of historical and gps data is also indicated

abrupt strike slip fault to subduction transition the alpine fault puysegur trench connection new zealand swath bathymetry and other geophysical data collected over the fiordland margin southwest of new zealand are used to investigate the mechanism of transform subduction transition between the alpine fault and the puysegur trench two segments of the pacific australian plate boundary in this region the cenozoic southeast tasman basin which obliquely underthrusts fiordland at the puysegur trench is separated from the cretaceous tasman basin by the resolution ridge system a major lithospheric discontinuity of the downgoing plate interpretation of seafloor morphology shows that the alpine fault extends offshore along the fiordland coast and splits into west and east branches the west branch cuts obliquely across the margin and connects sharply to the puysegur subduction front at the northeastern tip of the resolution ridge system earthquake and seismic reflection data indicate that the west branch is genetically controlled by downgoing plate structures associated with the resolution ridge system hence the west branch is interpreted as the surface trace of the plate boundary segment extending between the alpine fault and the puysegur trench we conclude that the development of the strike slip segment of the plate boundary and its sharp transition to the puysegur subduction are controlled by inherited structures of the australian plate furthermore according to geophysical data presented here a tearing of the downgoing plate can be interpreted beneath the west branch a review of geophysical data along the region of the alpine fault hikurangi trough northeast new zealand shows a progressive transform subduction transition that is accommodated by motion partitioning between the subduction interface and strike slip faults this transition is accounted for by an interplate coupling that progressively increases toward the alpine fault in relation with a gradual thickening of the downgoing crust the comparison between the fiordland and the hikurangi strike slip subduction transitions show that presence of inherited downgoing plate crustal faults properly oriented with respect to the plate motion facilitates a sharp strike slip subduction transition

recent vertical movements across the atalandi fault zone central greece repeated leveling data collected over a 14 km long traverse crossing the atalandi fault that last broke in 1894 revealed small amplitude motions for the interval 1969 1984 these motions are significant against random errors and are probably free of systematic errors in addition no local or superficial ground effect may account for the observed elevation changes which correlate with the tectonic pattern in the area as they show a relative downward motion of the hanging wall of a normal fault this motion is similar to the co seismic slip geomorphological observations and observations of submerged archaeological sites on the other hand corroborate long term motions which are unlikely to be explained as cumulative co seismic slip and are possibly similar to the short term motions leveling data reveal

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

focal mechanisms of large earthquakes in the south island of new zealand implications for the accommodation of pacific australia plate motion b the plate motion model nuvel 1 predicts oblique convergence between the pacific and australian plates in the south island of new zealand we used p and sh body waveform analysis to constrain the focal mechanisms of the 15 largest earthquakes ms 5 8 that have occurred in this region since 1964 in order to see how the plate motion is accommodated at the southern end of the alpine fault convergence is achieved by oblique slip movement along a concentrated zone of deformation in the southern offshore region one event may be related to thrusting of the australian plate beneath the pacific plate and another strike slip event probably demonstrates movement on an active strike slip fault system parallel to but offset from the southern limit of the alpine fault this geometry provides a possible mechanism for the rapid uplift of the fiordland region deformation in the northern south island is more distributed in the south west marlborough region partitioning occurs between strike slip faulting in the se and reverse faulting farther nw in the buller region we suggest that the partitioning developed as a consequence of an increasing component of shortening that was accommodated by slip on reactivated pre existing normal faults in the buller region shortening in the buller region may have deflected the ne end of the alpine fault towards the nw forming the prominent bend the marlborough fault system with its youngest and most active faults to the se probably developed in an attempt to maintain a through going strike slip structure as each of the strike slip faults was transported towards the north west partitioning of the opposite polarity with reverse faulting se of the strike slip faulting occurs in north east marlborough the boundary between the two different styles of partitioning in ne and sw marlborough appears to coincide with a change in the nature of the downgoing slab and a change in strike of faults of the marlborough fault system a normal faulting earthquake on the northern edge of the chatham rise probably results from a complex interaction of the buoyant continental crust in that region with the subduction zone and the overlying marlborough fault system

tectonic rotation about the termination of a major strike slip fault marlborough fault system new zealand the marlborough fault system comprises a series of major right lateral strike slip faults that link the alpine fault to the hikurangi subduction zone in the pacific australia plate boundary zone in new zealand all of the major active faults of the marlborough fault system have continuous traces except for the clarence fault which terminates abruptly near the ward syncline paleomagnetic data from upper miocene and lower pliocene sedimentary rocks between the marlborough faults indicate a consistent post early pliocene regional clockwise rotation of about 20 an additional rotation of about 10 is evident at many localities near the termination of the clarence fault it is proposed that the additional rotation relative to the rest of the region is caused by a velocity gradient that likely exists between the active awatere fault and the termination of the clarence fault the existence of such a velocity gradient is consistent with inferences from geodetic strain data which suggest that one third of the displacement in the marlborough fault system occurs between the awatere and clarence faults the kinematics of rotation can be modelled by treating the area as a rigid block that pivots about the termination of the clarence fault the block rotation model satisfies field constraints on the styles of deformation observed at the boundaries of the block and is consistent with available paleomagnetic and geodetic data

block rotation and deformation by strike slip faults 2 the properties of a type of macroscopic discontinuous deformation study of the general features of deformation by systems of subparallel strike slip faults shows that the governing constraints are kinematic the fault blocks must remain in contact with each other and the deformed area must fit with its surroundings as a result fault blocks that move laterally without significant internal deformation also rotate about vertical axes relative to boundaries of the fault domain by an amount that is quantitatively related to fault slip spacing and orientation areas where left and right lateral faults move simultaneously are usually divided into domains that contain faults of one kind only deformation of such multidomain areas is nonhomogeneous but the differences between domains can compensate for each other so that the regional deformation is quite simple strike slip faulting combined with block rotation is an efficient mechanism of deformation because modest offsets and rotations change the linear dimensions of faulted areas by several tens of percents which may often greatly exceed the results of other types of coeval deformation paleomagnetic data can provide an independent measure of block rotations and should be used to supplement structural data block rotation changes the initial angles between right and left lateral faults and also their orientation relative to the stress field the faults probably tend to rotate away from the axis of maximum compression rotated faults continue to move because they are weak surfaces since the deformation depends on geometric factors such as fault orientation and domain geometry it is not simply related to the stress field these properties including rotation of material units characterize discontinuous deformation in general

25 norhopanes formation during biodegradation of petroleum in the subsurface abstract quantitative data from petroleum systems in china liaohe basin and canada athabasca tar sands support the theory that 25 norhopanes are produced during biodegradation of petroleum in the subsurface within a single oil column both case histories showed increasing severity of degradation indicated by destruction of hopanes and production of 25 norhopanes downward to the oil water contact in the athabasca samples between the peters k e moldowan j m 1993 the biomarker guide interpreting molecular fossils in petroleum and ancient sediments prentice hall englewood cliffs new jersey p 363 scale of biodegradation levels 5 9 concentrations of c 28 20s triaromatic steroids and other biodegradation resistant compounds increased by 35 reflecting a concentration effect as a consequence of removal of more degradable compounds over the same interval the concentrations of c 28 17 25 norhopane and c 29 17 25 norhopane increased by an order of magnitude thus requiring that the balance be met by their net production during degradation a detailed molecular investigation of the athabasca bitumen revealed that c 30 17 hopane degrades faster than c 29 17 hopane whilst the rate of formation of both c 29 17 25 norhopane and c 28 17 25 norhopane are similar complicating a straightforward interpretation of demethylation of hopanes to form 25 norhopanes hopane degradation in the athabasca tar sand may also occur without the production of 25 norhopanes the results show that even within a single petroleum accumulation a number of mechanisms control changes in the abundance and composition of hopanes and 25 norhopanes

coastal wetlands as recorders of earthquake subsidence in the aegean a case study of the 1894 gulf of atalantiearthquakes central greece abstract earthquakes may have a major impact on the morphology and evolution of coasts in tectonically active areas in the area of the gulf of atalanti central greece a damaging earthquake sequence in 1894 is reported to have caused nearshore slumping tsunami induced flooding and decimetre to metre scale coastal subsidence the earthquakes caused major changes to coastal configuration in particular the separation of the gaiduronisi peninsula from the mainland detailed stratigraphical microfossil and radiometric 210pb and 137cs analyses of coastal wetlands around the gulf of atalanti show that these environments preserve evidence of sudden lasting subsidence contemporaneous with the 1894 events with foraminiferal assemblages at a site on the mainland opposite the island indicating an abrupt change from supratidal soil to intertidal marine conditions the elevation change indicated by this terrestrial to marine transition is 30 80 cm the coastal stratigraphy in the atalanti area however lacks laterally extensive sharp soil mud contacts or tsunami deposits of the type used in identifying past earthquake subsidence events at plate boundary settings despite the major earthquake induced changes in coastal configuration the stratigraphical signature of the 1894 earthquakes is relatively subtle and is consequently difficult to distinguish from other rapid coastal changes e g storm events or barrier breaching without high resolution dating control and reference to documentary records for this reason coastal wetland stratigraphies are only likely to be useful in identifying pre historical or poorly documented earthquakes in the aegean at sites where metre scale coseismic elevation changes and or major tsunami inundation have occurred in addition the resolution of the biostratigraphic data reported here is insufficient to distinguish between the contrasting fault rupture models for the 1894 events the coastal elevation changes recorded in these wetlands however are best accounted for by a slip of 1 m on a multi segment fault

extensional compressional tectonics associated with the aegean arc comparison with the andean cordillera of south peru north bolivia extensional compressional tectonics are analysed along the convergent boundaries of the aegean arc and of the andean cordillera of south peru and north bolivia this paper deals only with deformations of miocene pliocene and pleistocene ages the prevailing regime in the aegean basin is extensional yet two compressional tectonic phases of u miocene l pliocene and of l pleistocene age have been recorded they are also known in many places all around the mediterranean thus forces that induce compressional tectonics in the aegean seem to have their origin outside the region they seem to be linked with changes in the conditions of convergence change in rate between the arabo african and eurasian plates beneath the andean cordillera of south peru north bolivia the subduction zone plunges at an angle of 25 30 as it does under the aegean arc there as in the aegean sea tectonics are predominantly extensional and several short lived compressional phases break up this extensional regime the latter may also be induced by changes of the conditions of convergence here between the nazca and south american plates beneath central peru north of the nazca ridge the subduction zone plunges at a small angle about 10 there neotectonic deformations are different in the recent they are essentially compressional or expressed by strike slip faulting geological data from the aegean and andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries

the use of engineering seismological models to interpret archaeoseismological findings in tolbiacum germany a case study archaeological excavations carried out from 2001 to 2003 at the vicus tolbiacum site located in the present day city of zulpich germany unearthed heavily damaged and destroyed late roman fortification works damage includes 0 17 m wide tensile cracks in a 3 1 m wide wall tilted walls and fortification towers horizontal displacement of wall sections of 0 95 m and rotation of wall fragments engineering seismological models are used to test the hypothesis that the observed building damage is of seismogenic nature the site is located at the western edge of the lower rhine embayment lre in the northern part of the rhine rift valley more than 20 damaging earthquakes occurred in the area over the past 300 years several paleoseismic events with magnitudes of at least 6 4 occurred during the holocene site specific strong motion seismograms are modeled for assumed large earthquakes at active faults in the lre using stochastic methods and calibrated q models and duration models nonlinear site amplification is calculated based on an s velocity model from refraction seismic experiments and downhole measurements finite element simulation of the dynamic behavior of a fortification tower shows a natural period of the soil building system of about 3 0 sec horizontal and vertical displacements at the top of the 8 m tall tower reached 0 12 m and 0 06 m respectively for the simulated event no indications of man made activity exist that could explain the damage running water can also be excluded as a threat to the buildings due to the orographic situation and slow acting gravitational causes can be excluded due to the damage structure the destruction and damage is regarded as most probably seismogenic and site intensity is assessed at ix on the european macroseismic scale ems98 grunthal 1998 this result marks the first time an intensity above viii is described for a tectonic earthquake in germany preliminary dating results from three carbon 14 14c accelerator mass spectometry ams samples lead to the second half of the fourth century a d

interpretation of source rock depositional environment and age from seep oil east coast of new zealand biomarker fingerprints of crude oil samples from four onshore east coast basin oil seeps were analyzed to assess source rock characteristics including type of organic matter input redox conditions sedimentary facies and age results show that samples generally form two groups correlating with geographic location a northern and a southern group source rocks associated with all seep samples are interpreted to be marine however results suggest northern samples had more terrigenous organic matter input to their source rock s while southern samples had more marine input results suggest northern sample source rock s had more oxic depositional environments whereas southern sample source rock had more reducing environments a shale source rock sedimentary facies was indicated for all samples these observations suggest that southern samples may be derived from slightly higher quality source rocks higher hi deposited in more reducing conditions although source rocks in both regions are oil prone biomarker age parameters suggest that the northern oil samples are from a younger cenozoic source rock whereas the southern oil samples are from an older cretaceous source rock source rock characteristics depositional environment and age point to the presence of two different source rocks we postulate that northern oils samples from younger source rock with more terrigenous organic matter input represent the upper paleocene waipawa formation whereas southern oil samples from older source rock with more marine organic matter input represent the upper cretaceous to paleocene whangai formation

seismicity structure and tectonics of the wellington region new zealand summary the wellington region lies on the border between the pacific and australian plates the former being subducted the plate interface lies at shallow depth under the region 10 60 km so that detailed and long term monitoring of the seismicity of the zone where large thrust earthquakes are expected to occur is possible hypocentres for events recorded by a 12 station seismic network for the period 1978 1982 7231 events have been refined by the use of a threedimensional velocity model derived from a simultaneous inversion of arrival time data from 129 local events for both hypocentres and velocity the hypocentres show that the subducting pacific plate is defined by a nw dipping zone of relatively intense activity the plate interface as given by the upper envelope of this activity is offset vertically by 7 km on average along a nw se line through cook strait parallel to the direction of absolute motion of the pacific plate rather than to the direction of convergence the strike of the interface at deeper levels also changes across this line this distortion may partly reflect effects of the transition to continent continent type convergence further south within the subducting pacific plate the seismic activity defines two parallel zones separated by about 20 km the lower zone being much less active and perhaps merging with the upper zone at a depth of 80 90 km composite focal mechanisms of events in the upper zone imply predominantly down dip tension with a compression axis perpendicular to the plate interface the mechanism in the lower zone also implies down dip tension but the compression axis has rotated to be horizontal and along strike indicating a component of lateral shearing within the plate these two types of mechanism correlate well with those found previously for events at depths of 150 km or more thus it seems that the large negative buoyancy of the subducted lithosphere dominates the internal stress field throughout the length of the seismically active region the lithosphere acting as a stress guide there is no evidence for a significant number of events with mechanisms indicating thrusting along the plate interface the seismic velocity in the region corresponding to the upper seismic band is close to that typical for oceanic crust which here is probably considerably thicker than normal there is no evidence for a substantial increase in velocity down

timing of cretaceous extension and miocene compression in northeast south island new zealand constraints from rb sr and fission track dating of an igneous pluton the tapuaenuku plutonic complex is a large alkaline intrusion that was emplaced into upper jurassic lower cretaceous torlesse greywacke argillite near the axis of the inland kaikoura range northern south island new zealand concordant rb sr k ar and titanite zircon fission track cooling ages of circa 105 to 93 ma record a phase of igneous activity that was related to a period of mid cretaceous extension in south island new zealand the updoming and uplift which accompanied the extension and igneous activity are also reflected by the uplift of the marine split rock formation above sea level where it was eroded on this was deposited a terrestrial sequence followed by shallow marine deposits which may represent the onset of a long period of transgressive marine sedimentation the result of slow thermal subsidence after magmatism and rifting from late cretaceous to oligocene this burial of the pluton is identified not only from the sedimentary relationships of the local stratigraphy but also by the apatite fission track ages which record later exhumation during this time new zealand remained passively part of the pacific plate in the early miocene at circa 22 ma the intrusion cooled through the partial annealing zone of apatite approximately 120 60 c exhumation was the result of early miocene thrusting and shortening in marlborough and inception of the present day transpressive plate boundary between the indo australian and pacific plates through new zealand further evidence for this period of uplift and accompanying denudation is seen through the large quantities of coarse grained clastic sediments which were deposited in marlborough at this time the uplift rate required to raise the top of pluton to its present altitude 2885 m based on a constant rate from 22 ma until the present day is approximately 0 2 mm yr 1 however estimates of present day uplift rates of 10 mm yr 1 from summit heights and raised marine benches suggest that two periods of late cenozoic uplift must have occurred with a long period of quiescence between a conclusion supported by a major mid miocene unconformity below quaternary sediments in marlborough

palaeoseismic studies in greece a review abstract there are numerous reports of ancient human constructions i offset and destroyed by seismic surface faulting or ii with small displacements along horizontal discontinuities testifying to high acceleration effects or iii containing destruction layers below which skeletons of people killed and buried by fallen debris have been found in these cases destructions can safely be assigned to earthquakes that can be dated with stylistic archaeological techniques in coastal areas on the other hand identification of exposed species of the sublittoral zone that have escaped erosion in the mid littoral or supralittoral zones testify to quick probably co seismic uplifts which can be dated with conventional or ams radiometric techniques the amplitude of these uplifts is up to 9 m in the hellenic arc and more than 1 m in the aegean back arc basin finally two cases of seismic faulting deduced from auger core study of the holocene stratigraphy are reported identification of such palaeoseismic effects has important implications for estimation of recurrence intervals and maximum magnitude of seismic shocks in study areas

holocene emergence in euboea island greece abstract detailed mapping along the northwestern coastline of euboea has provided new evidence of colonization by lithophaga lithophaga l reaching about 3 8 m above the present biological msl such marine biological marks together with morphological notches correspond to the occurrence of two sequences of holocene vertical displacements higher than those reported by previous studies on the central part of the southern coast and along the northern coast of the island a well developed emerged notch is found at 1 7 0 1 m above present mean sea level whereas the uppermost part of the lithophagid holes suggest a former emerged shoreline at least at 3 8 0 1 m radiocarbon ams dating of lithophaga shells found in their burrows showed that the lower uplifted shoreline corresponds to a tectonic event probably coseismic apparently dated at 2200 a bp while the higher shoreline corresponds to an older relative sea level transgression possibly of tectonic origin apparently dated about 5570 a bp the apparent radiocarbon age of lithophagid shells can be about 350 to 400 years older than the uplift event that exposed them due to incorporation of host rock carbon nevertheless the two new paleoshorelines provide evidence that repeated uplift movements greater than those reported by previous authors occurred during the late holocene uplifting the western part of the island

origin of the neogene shallow gas accumulations in the jiyang superdepression bohai bay basin natural gas resources occur extensively along the east coast of china with a number of large and medium sized gas fields being discovered in recent years gas reservoirs include neogene paleogene and the underlying mesozoic and paleozoic basement of the total proven natural gas reserves in the jiyang superdepression bohai bay basin almost 89 7 is present in the shallow neogene gas pools in traps formed on top of the paleotopographic highs and along the margin of the secondary depressions these gases are closely associated with heavy oils occurring as gas caps or associated gases within the heavy oil pools or in separate gas pools above or updip from the heavy oil pools the gases contain over 95 methane and small quantities of c 2 alkanes nitrogen and carbon dioxide the stable carbon isotopes of methane in these gases are up to 10 more positive than those of the thermogenic gases in the deep paleogene reservoirs with propane more enriched in 13 c than butane this study demonstrated that the majority of the petroleum source rocks in the jiyang superdepression tend to be oil prone and are currently within or shallower than the conventional oil window 0 45 1 0 ro the chemical and carbon isotopic compositions of the gases together with the moderate to severe biodegradation of the associated heavy oils in the shallow neogene strata clearly suggest that the formation of the shallow natural gases in the jiyang superdepression result from the anaerobic degradation of accumulated oils in reservoir

geodetic constraints on the fault pattern of the 1978 thessaloniki northern greece earthquake ms 6 4 summary repeated measurement of a 110 km long high precision spirit levelling traverse indicates that between 1958 and 1978 about 25 cm of subsidence occurred along a distance of 30 km in the mygdonian quaternary graben near thessaloniki northern greece observed displacements are significant against random and systematic errors and most are unrelated to near surface effects and can be assigned to the 1978 thessaloniki destructive earthquakes the available data do not permit a formal inversion but an elastic dislocation analysis indicates that the main shock of the seismic sequence ms 6 4 was probably associated with a ne dipping wnw trending blind normal fault marking the southwestern margin of the mygdonian graben in agreement with seismological and structural data there also exists evidence for incipient faulting in the central southern part of the mygdonian graben

geodetically controlled taphrogenesis in back arc environments three examples from central and northern greece abstract repeated leveling data collected in the vicinity of three tectonic grabens in the hellenic back arc area reveal a tendency to continuation of taphrogenesis processes that started in the quaternary or earlier these processes are associated with earthquakes of short or long recurrence intervals corinthiakos tens of years atalandi hundreds of years although in most cases the geodetic displacement signal is small i suggest that it reflects real motions because first the measurement specifications are very strict and second geologic and other data confirm geodetically derived displacements

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

formation mechanisms of secondary hydrocarbon pools in the triassic reservoirs in the northern tarim basin abstract the northern tarim basin tabei is a rich composite hydrocarbon accumulation region with multi layers of oil and gas reservoirs in the ordovician carboniferous and triassic strata in the triassic the tabei region was dominated by non marine sedimentation that developed deltaic sandstone reservoirs with favourable petrophysical properties for hydrocarbon accumulations hydrocarbons in the triassic hydrocarbon pools are dominated by oil and condensate gas analysis of the hydrocarbons in combination with well testing and drilling data reveals that oils in the triassic hydrocarbon pools are commonly biodegraded and originated mainly from the middle upper ordovician source rocks the predominant dry gases in the reservoirs are cracked from oils derived from the cambrian source rocks the origin of hydrocarbons in the triassic pools is similar to those in the underlying reservoirs fluid inclusions and k ar dating confirm that the hydrocarbons were accumulated during the himalayan orogenic movement because the middle upper ordovician source rocks already experienced peak hydrocarbon generation in the late hercynian orogeny late permian the triassic hydrocarbon pools are from secondary adjustment of earlier oil and gas pools from the underlying ordovician and carboniferous reservoirs due to the rapid subsidence of the kuqa foreland basin to the north of the tabei region since the beginning of the himalayan orogenic movement the triassic reservoir strata was changed from south dipping to north dipping resulting in the formation of plunging anticlines and hydrocarbon migration toward the south at the same time fault reactivation occurred in the area causing the hydrocarbons from the deeper reservoirs to migrate into the triassic structural traps through faults and unconformities and thus formed the widespread secondary hydrocarbon pools the structure inversion during the triassic and the formation of nose structures since the himalayan orogeny 250 290 ma permian controlled the secondary accumulation in the triassic reservoirs the reformation process of the hydrocarbon pools continued until the late himalayan orogeny when the gas was charged and developed condensate pools in the eastern area

geochemistry of palaeozoic marine petroleum from the tarim basin nw china part 1 oil family classification abstract a series of palaeozoic marine oils ranging from condensates to very heavy oils from the cratonic region of the tarim basin nw china have been examined to delineate oil families crude oils from the mesozoic foreland kuqa depression were also analyzed for comparison the genetic family was assessed using bulk hydrocarbon isotopic composition alkylation pattern of polycyclic aromatic hydrocarbons pahs and biomarker distributions detailed oil oil correlation suggests two distinct families occur in the cratonic region despite the diversity of the reservoir rocks and some variability in oil physical properties the tabei and tazhong oils are classified in general into a single family with a possible indication for secondary subdivision these oils are characterized by low pristane phytane pr ph ratio high dibenzothiophene phenanthrene dbt p ratio light bulk isotopic composition high degree of pah alkylation high proportion of c23 and c24 tricyclic terpanes and low abundance of c24 tetracyclic terpane and triaromatic dinosteroids this family is inferred to have a middle upper ordovician source rock the tadong family distinctly different from the tabei and tazhong families is characterized by relatively high pr ph ratio low dbt p ratio slightly heavier bulk isotopic compositions and low degree of pah alkylation it also has a unique biomarker signature with a high proportion of triaromatic dinosteroids possibly indicating cambrian lower ordovician source rocks the oils from the kuqa depression are easily distinguished from the other two families due to their terrigenous origin the major characteristics of the kuqa oils are high pr ph ratio very low dbt p ratio heavy bulk isotopic composition low pah alkylation degree high proportion of c20 and c21 tricyclic terpanes and c24 tetracylic terpane and abundance of triaromatic dinosteranes and 4 methyl 24 ethyltriaromatic cholestanes these characteristics are consistent with terrestrial organic source rocks deposited under sub oxic conditions

geochemistry mineralogy and petrology of a new find of ultramafic lamprophyres from bulljah pool nabberu basin yilgarn craton western australia abstract four variously pipe or sill like carboniferous 305 ma bodies have been located near the ne edge of the archaean yilgarn craton the rocks comprise ba ti bearing tetraferriphlogopite tetraferriannite low al ti diopside calcite perovskite and groundmass titanomagnetite chromite up to 41 3 cr2o3 with minor apatite mg mn ilmenite rare earth phosphate k ba feldspar up to 17 bao baryte and an unidentified ba zr silicate the last three reflect very high whole rock ba up to 5 652 ppm aegirine rich pyroxenes occur in fenitic alteration assemblages together with high si al and low mg ca whole rock geochemistry these features are diagnostic of ultramafic lamprophyres damkjernites and aillikites although the rocks also show some affinities with classical kimberlites mineral concentrates from loam samples yield an array of minerals of mantle origin including garnets dawson and stephens groups g1 3 5 9 and 10 chromian diopsides up to 6 2 cr2o3 magnesiochromites up to 20 mgo 70 cr2o3 and four compositional groups of ilmenites low mn picroilmenites mn rich mg poor and two moderate mn mg compositions actual spinel lherzolite nodules are common in one body and the presence of spinel and or garnet lherzolites can be inferred in the others from the concentrates the bulljah bodies are therefore of deep mantle origin as confirmed by the recovery of a single microdiamond they thus extend the field of potentially if not necessarily economically diamondiferous rocks beyond kimberlites and lamproites when added to other recent lamprophyre finds the bulljah discoveries suggest that the yilgarn craton could like many other ancient cratons be ringed and or dotted by a diverse array of alkaline and lamprophyric rocks of varying ages which remain to be discovered

fault parameters of the 1980 mw 6 5 volos central greece earthquake from inversion of repeated leveling data the 1980 volos almyros seismic sequence the last of an unusual clustering of earthquakes with surface magnitude 6 0 7 0 which hit thessaly central greece between 1930 and 1980 is among the least studied recent earthquakes in greece repeated measurement of three first order spirit leveling traverses crossing the meizoseismal area of the seismic sequence indicates that between 1970 1971 and 1988 1989 a subsidence of about 35 cm is observed at the almyros neogene quaternary graben the observed displacements are significant against random and systematic errors and can be assigned to the 1980 earthquake sequence inversion of leveling data using an elastic dislocation model constrained by structural and seis mological data indicates that the mainshock mw 6 5 and the largest aftershock mw 6 1 were probably associated with reactivation of two subparallel homothetic nor mal faults marking the northern margin of the almyros neogene quaternary graben

bending within the axial tectonic belt of new zealand in the last 9 myr from paleomagnetic data abstract tongaporutuan stage late miocene 11 6 myr sedimentary rocks at two localities within the axial tectonic belt of new zealand have a direction of magnetisation in which the declination is 020 11 and 030 8 d 95 the directions of magnetisation in rocks of similar age outside the belt have a declination like that of the earth s present axial dipole 360 the clockwise deviation of the declination is inferred to indicate bending of the rocks within the zone of deformation between the pacific and indian plates due to the oblique convergence of these plates

a seismic crustal section across the east cape convergent margin new zealand abstract crustal seismic reflection measurements were made along a 250 km profile across the pacific australian plate boundary north of new zealand data were recorded to 16 s two way time and have defined a major sedimentary basin corresponding to the southern end of the raukumara basin a fore arc basin reaching a depth of about 13 km this basin contains a lower generally conformable sequence of sediments and an upper sequence dominated by several major uncomformities the eastern part of this basin is cut by several recently active eastward dipping high angle thrust faults which are interpreted to be caused by the recent convergence at the adjacent pacific australian plate boundary the eastern margin of the basin is marked by a sharp change in character on the seismic data we interpret this feature as a terrane boundary coinciding with a major transcurrent fault which has juxtaposed a detached fragment of an island arc fore arc with a thin 15 km crust to the east against a passive margin sedimentary sequence to the west the southern raukumara basin is floored by cretaceous age oceanic crust fragments of which were obducted onto the north island about 22 ma ago the area has had a complex history a schematic model for the evolution of this margin during the past 22 ma is developed suggesting that the raukaumara basin has developed as a combination of fore arc basin processes and oblique crustal extension

the last 25 ma of rotational deformation in part of the new zealand plate boundary zone abstract the marlborough fault system is a zone of dextral transpression in continental crust and marks the southern end of the hikurangi subduction system between the obliquely convergent australian and pacific plates detailed mapping over an area of 100 km2 has revealed a complex history of deformation during the last 25 ma the development of a thrust belt in the miocene referred to as d1 deformation was synchronous with the deposition of a thick submarine fan complex the beginning of d1 deformation may mark the initiation of the subduction zone in this part of the plate boundary zone subsequently in the plio pleistocene the region formed a zone of dextral shear marked by major strike slip faults and zones of distributed deformation referred to as d2 deformation crustal blocks less than 5 km across may have rotated ca 60 clockwise about vertical axes relative to the pacific plate in the last 4 ma the pattern of deformation during the last 10 ka to 100 years is consistent with the long term d2 deformation and suggests that large crustal blocks resting on the subducted pacific plate have rotated clockwise about vertical axes relative to the pacific plate accommodated by dextral shear further to the sw in the marlborough fault system the overall effect of the deformation has been the rotation of the edge of the southern part of the hikurangi margin from a w to nw trend in the early miocene to a ne trend today

kinematics and deformation of central and southwestern greece from historical triangulation data and implications for the active tectonics of the aegean abstract changes in the coordinates of 38 stations 32 of which were common to three historical triangulation surveys 1889 1905 1927 1930 and 1950 1970 in central greece were computed based on conventional adjustment techniques and the assumption of a nearly fixed baseline length some of the calculated coordinate changes are significant against the a posteriori network adjustment errors and are likely to indicate tectonic motions consistent with those deduced from geological and geophysical data and other geodetic studies comparison of the first survey network with gps data more explicitly the historical geodetic data confirm the rotational character of the deformation in the area but they show that the strain pattern is likely to have changed after 1930 between 1890 and 1930 strain was changing smoothly as if no strain discontinuities existed while the peloponnesus was under contraction from the northeast probably reflecting accommodation of strain from the arc significant left lateral shear in the gulf of corinth and n s extension in the whole of the study area were observed only after 1930 estimates of strain are consistent with those deduced from comparison of historical triangulation and gps data corrected for the scale error that exists in the terrestrial geodetic data in greece and estimates of strain from seismological data the change in the kinematic pattern after 1930 seems to be confirmed by changes in the shear strain computed directly from changes in observed angles between stations and from changes in the seismicity rates such changes although not unusual in the geological record are not easy to explain but may reflect elastic rebound effects in area with an extremely complicated tectonic fabric or hysteresis in the accommodation of e w compression from the arc by n s stretching

reconstructions of the new zealand region for the neogene abstract the major structural elements of the present day plate boundary zone through new zealand are a subduction zone under the northern half of the country linked by a wide transform zone to the southward extension of the plate boundary through fiordland and the macquarie ridge using finite rotations of the pacific australian plate pair a sequence of reconstructions of the relative positions of the plates is presented reconstructions of the plate boundary zone based on paleomagnetic data involve essentially the same structural elements as today but with large clockwise changes in their trend with time

the relationship between strain rates crustal thickening palaeomagnetism finite strain and fault movements within a deforming zone the deformation of continental lithosphere generally does not occur on a single fault but is distributed over a zone up to a few hundred kilometers wide if the deformation rate is constant throughout the zone and if the velocity is continuous everywhere and does not change with time the deformation gradient tensor can be obtained analytically this tensor directly determines the amount of crustal thickening and is related in a complicated manner to the finite strain tensor the declination of remnant magnetization measured within the zone can also be rotated by the deformation because palaeomagnetic measurements are generally made on rigid blocks which have not been deformed there is no simple relationship between such rotations and the finite strain expressions for all these quantities are obtained in terms of the velocity gradients which are taken to be constant the history of western north america is used to illustrate the relationship between the present deformation by strike slip and thrust motions the rotations of the remnant magnetization vectors and the shape of accreted terranes at the surface distributed deformation is taken up by motion on faults which separate the zone into blocks the displacement rate on the faults their strike and the finite rotations of the blocks are all controlled by the velocity gradients analytic expressions relating these quantities are obtained a deforming zone containing normal faults which crosses central greece takes up both strike slip and extension and illustrates the relationship between the structures within and the motion across the zone a similar but more complicated zone in northeastern iran involves both strike slip and shortening

geochemistry and charge history of oils from the yuqi area of tarim basin nw china abstract the geochemistry origin and charge history of oils from the yuqi area of tarim basin have been investigated through gc gc ms and fluid inclusion microthermometry analysis the yuqi oils accumulated mainly in three intervals 1 in the lower middle ordovician yingshan formation o 1 2 y carbonate reservoirs 2 in the overlying upper triassic halahatang formation t 3 h and 3 in the lower cretaceous yageliemu formation k 1 y sandstones oils from different reservoirs have distinct physical properties varying from extra heavy o 1 2 y heavy t 3 h to light oils t 3 h and k 1 y however their geochemical compositions show a high degree of similarity which indicates that they derive from the same source rock abundant tricyclic terpanes gammacerane dibenzothiophene and c 21 c 22 steranes together with a low level of diasteranes indicate an anoxic marine source rock for oils in the yuqi area oil oil correlation shows that yuqi oils derive from the same source bed as tahe oils the co occurrence of intact n alkanes and 25 norhopanes in all the samples supports the proposition that there is a mixture of an early filled severely biodegraded oil and a late filled fresh oil in this study charge history is examined on the basis of integration of fluid inclusion homogenization temperature data with 1d burial thermal history models two episodes of oil charging are identified in the o 1 2 y reservoir well yqx1 1 at around 436 420 ma middle late silurian and 10 3 ma miocene to pliocene respectively for the samples from the t 3 h and k 1 y intervals only one episode of oil charge is indicated by the homogenization temperatures of coexisting aqueous inclusions with an inferred timing around 10 3 ma the t 3 h heavy oil reservoir is assumed to be a secondary hydrocarbon pool which accumulated by re migration and re distribution of hydrocarbons from o 1 2 y hydrocarbon pools the few early biodegraded oils in the k 1 y light oils were probably picked up along the migration pathway during the late fresh oil charging

complex crustal deformation of the 2016 kaikoura new zealand earthquake revealed by alos 2complex crustal deformation of the 2016 kaikoura new zealand earthquake revealed by alos 2

up dip partitioning of displacement components on the oblique slip clarence fault new zealand abstract active strike slip faults in new zealand occur within an obliquely convergent plate boundary zone although the traces of these faults commonly delineate the base of mountain ranges they do not always accommodate significant shortening at the free surface along the active trace of clarence fault in northeastern south island new zealand displaced landforms and slickenside striations indicate predominantly horizontal displacements at the ground surface and a right lateral slip rate of ca 3 5 5 mm year during the holocene the inland kaikoura mountain range occupies the hanging wall of the fault and rises steeply from the active trace to altitudes of ca 3 km the geomorphology of the range indicates active uplift and mountain building which is interpreted to result in part from a vertical component of fault slip at depth these data are consistent with the fault accommodating oblique slip at depth aligned parallel to the plate motion vector and compatible with regional geodetic data and earthquake focal mechanisms oblique slip on the clarence fault at depth is partitioned at the free surface into 1 right lateral displacement on the fault and 2 hanging wall uplift produced by distributed displacement on small scale faults parallel to the main fault decoupling of slip components reflects an up dip transfer of fault throw to an off fault zone of distributed uplift such zones are common in the hanging walls of thrusts and reverse faults and support the idea that the dip of the oblique slip clarence fault steepens towards the free surface

seven million years of strike slip and related off fault deformation northeastern marlborough fault system south island new zealand the marlborough fault system mfs south island new zealand is remarkable for the oblique slip nature of its active faulting and can be placed in a framework of pacific australian pac aus plate motions and geodetic strain new zealand illustrates changing degrees of upper plate slip partitioning in an obliquely convergent margin that varies along strike in crustal type and subduction geometry in this paper we focus on the ne part of this transcurrent fault system especially the awatere fault which is the only marlborough fault to offset a major neogene basin strike slip on an ancestral eastern strand of this fault began after 7 4 6 4 ma later vertical axis rotation may have caused it to be abandoned in favor of the currently active strand since 7 ma at least 34 10 km of dextral slip has accrued on the awatere fault 6 km of slip has accrued on two nearby strands and 4 km has accrued on the currently active coastal strand comparison of miocene with late quaternary offsets suggests that rates of strike slip on the fault have been nearly constant or have possibly decelerated we interpret spatial and temporal patterns of strike slip in the mfs to reflect southward migration of transform motion resulting from increased pac aus plate convergence late neogene to present day shortening directions in ne south island are indicative of a partially slip partitioned margin slip partitioning diminishes southward as the underlying subduction interface becomes strongly coupled suggesting a simple mechanical relationship between these processes

ontong java plateau and late neogene changes in pacific plate motion aided by a new geometrical technique called hot spotting we recently proposed a new model for the absolute motion of the pacific plate this model called wk97 assumed the hawaiian hotspot is under loihi and that there was a change in plate motion at 3 6 ma the model located the louisville hotspot close to the hollister ridge a shallow volcanic ridge associated with a geoid high seismicity and recent volcanism most of the tectonic implications of wk97 however were not addressed furthermore although several recent studies suggest that the geochemistry of hollister lavas may indicate a mixture between louisville melt material and pacific antarctic ridge mid ocean ridge basalt these studies strongly disagree with wk97 and consider it seriously flawed here we discuss numerous tectonic predictions of wk97 and present a large amount of observational evidence in support of it we find that a late neogene collision between the ontong java plateau and the northern margin of the australia plate appears to have altered the motion of the pacific plate as inferred from hotspot volcanism by forcing it to rotate counter clockwise this rotation about a low latitude pole appears to have induced right lateral shear stress along the entire pacific plate divergent boundary which resulted in the formation of extensional transform faults microplates and propagating ridges this change in motion also appears to have triggered concomitant circum pacific tectonism including trench migration and back arc rifting the wk97 suggests that long lived plume fed volcanism on the pacific plate appears very limited perhaps only to five to six hotspots hawaii louisville cobb caroline and perhaps marquesas and bowie the geometry of these chains are consistent with our model despite some evidence for volcanic age progressions most other pacific neogene hotspots are most likely crack spots i e sites of extensional volcanism at preexisting zones of weakness reactivated by plate stresses indeed several volcanic ridges such as hollister ridge near the louisville hotspot appear to have formed in response to stresses following the change in absolute plate motion wk97 also obviates the need for simultaneous different directions of mantle flow in the south central pacific transpression at the san andreas and alpine strike slip faults and aleutian arc explosivity since 6 ma also appear to be consequences of the changes in pacific plate motion furthermore both the wk97 model and observed relative plate motions suggest that adjoining plates have changed their absolute motions as well and that large changes in absolute plate motion do not necessarily imply large changes in relative plate motion our findings support slab pull as the dominant plate tectonic driving force highlight the rheological difference between strong oceanic lithosphere and weak continental crust and suggest that wk97 presently provides a unifying albeit preliminary framework for relating both intraplate and circum pacific tectonism and volcanism in the late neogene

the neotectonics of the aegean an alternative view minor reverse faults in widely dispersed neogene outcrops in the central aegean have led several people to suggest that the regional extension which started in the lower pliocene or earlier was interrupted by short periods of compression the durations of these postulated compressional episodes are short compared to the time scale on which convective forces acting on the base of the lithosphere can change thus possible mechanisms for driving such motions are limited in this paper we offer alternative explanations for these observations and in particular show that these apparently compressional episodes are probably not regional in extent and may not be truly compressional in origin in some places they are more likely to be a consequence of the considerable rotation that is found in extensional terranes the plio quaternary paleogeography of the central aegean is satisfactorily explained by uplift in the footwall blocks of normal faults and does not require regional compression studies of the faulting associated with recent large earthquakes suggest that the sort of microtectonic analysis which is typically carried out on small faults in surficial sediments is more likely to reflect the internal deformation of blocks bounded by major fault structures than be a reliable indicator of regional stress patterns

the last million years of deformation in part of the new zealand plate boundary zone abstract tectonic deformation of pleistocene sediments is occurring within the plate boundary zone in the north island of new zealand folds associated with an active fault are forming mainly by flexural slip and contain comformable and unconformable relations which show that the folding started ca 1 0 ma simple geometric models of fold growth indicate that the fold structure has shortened at an average rate of 0 76 0 1 mm a 1 across 4 5 km though with an increase in the last 100 ka of about 1 8 times the average rate which is entirely compatible with the rate of shortening observed in the last 50 years from retriangulation studies areas for 15 km to the southeast of the fold structures show significantly lower horizontal shortening rates the strain rates across the plate boundary zone vary both with position and time with a negative correlation between the uplift pattern and the inferred geological shortening rates this can be explained by the presence of large semi rigid blocks within the plate boundary zone which are back tilting and overriding weaker more rapidly deforming areas the available evidence suggests that a large proportion of the deformation is occurring seismically

iodine 129 chronological study of brines from an ordovician paleokarst reservoir in the lunnan oilfield tarim basin abstract previous studies have shown that brines in an ordovician paleokarst reservoir of the lunnan oilfield in the tarim basin china are the product of mixing of paleo evaporated seawater in the east with paleometeoric waters in the west in order to put time constraints on the brine and related hydrocarbons in this field 10 brine samples were collected for which the iodine concentrations and 129 i i ratios were measured and discussed the iodine concentration 3 70 31 2 mg l and the 129 i i ratio 189 897 10 15 show that the iodine in the paleoseawater and meteoric water mw had different origins and 129 i characteristics the paleoseawater has a high iodine content 31 mg l indicating that iodine was introduced into the reservoir along with thermally generated hydrocarbons possibly in the cretaceous from the caohu sag in the eastern area based on consideration of all possible origins of iodine and 129 i in the brines it is suggested that the meteoric water maintained its initial iodine content 0 01 mg l and 129 i i ratio 1500 10 15 whereas the iodine enriched paloseawater ipsw exhibited a secular 129 i equilibrium n sq 39 atom l as a result of fissiogenic 129 i input in the reservoir over a long period of time the model of brine evolution developed on that basis confirmed that meteoric water entered the reservoir in the miocene at about 10 ma and partially mixed with the iodine enriched paleoseawater the movement of meteoric water was facilitated by faults created during the himalayan orogeny then became more dense after dissolving paleogene halite and infiltrated into the reservoir at high pressure the iodine and 129 i concentration in the brine contains information about the path and history of the fluid in the reservoir this may be useful in oil exploration since the movement of water was to some extent related to hydrocarbon migration

the nature and origins of decametre scale porosity in ordovician carbonate rocks halahatang oilfield tarim basin china at 7 km depths in the tarim basin hydrocarbon reservoirs in ordovician rocks of the yijianfang formation contain large cavities c 10 m or more vugs fractures and porous fault rocks although some yijianfang formation outcrops contain shallow formed near surface palaeokarst features cores from the halahatang oilfield lack penetrative palaeokarst evidence outcrop palaeokarst cavities and opening mode fractures are mostly mineral filled but some show evidence of secondary dissolution and fault rocks are locally highly c 30 porous cores contain textural evidence of repeated formation of dissolution cavities and subsequent filling by cement calcite isotopic analyses indicate depths between c 220 and 2000 m correlation of core and image logs shows abundant cement filled vugs associated with decametre scale fractured zones with open cavities that host hydrocarbons a sm nd isochron age of 400 37 ma for fracture filling fluorite indicates that cavities in core formed and were partially cemented prior to the carboniferous predating permian oil emplacement repeated creation and filling of vugs timing constraints and the association of vugs with large cavities suggest dissolution related to fractures and faults in the current high strain rate regime corroborated by velocity gradient tensor analysis of global positioning system gps data rapid horizontal extension could promote connection of porous and or solution enlarged fault rock fractures and cavities supplementary material stable isotopic analyses and the velocity gradient tensor and principal direction and magnitude calculation are available at https doi org 10 6084 m9 figshare c 4946046 thematic collection this article is part of the the geology of fractured reservoirs collection available at https www lyellcollection org cc the geology of fractured reservoirs

origin of deep strata gas of tazhong in tarim basin china abstract tazhong is located in the interior of the taklamakan desert in the tarim basin deep carbonates are targeted exploration areas with abundant gas and the largest ordovician gas condensate field has been discovered the hydrocarbon is mainly distributed in the reef shoal complex of the upper ordovician lianglitage formation and in the interbedded weathered reservoirs of the lower middle ordovician yingshan formation despite the deep burial depth of the reservoirs and strong heterogeneity the reservoir bodies are large multiple layered and enrichment in hydrocarbons indicates a great exploration potential the ordovician gas condensate reservoir in the tazhong consists mainly of methane with a gas dryness coefficient of 0 91 0 98 the ordovician gas in the tazhong belongs to secondary oil cracking gas the comprehensive analysis of natural gas composition stable carbon isotopes and adamantane content showed that the natural gas was from paleo reservoir cracking at depth basin geothermal history burial history fluid inclusion data and geological analysis show that the gas accumulation occurred 5 ma ago the sulfur isotope of sulfides the presence of 2 thia adamantane and existence of light co 2 carbon isotopes indicate that the h 2 s was formed via tsr the natural gas accumulated through migration along faults

the kinematics of the plate boundary zone through new zealand a comparison of short and long term deformations summary surveys of shear strain rates derived from repeated triangulation cover about one quarter of the area of the plate boundary zone through new zealand and are well distributed within it using a method developed by haines relating shear strains to the total strain and velocity fields the dilatational and rotational strain rates and the velocities within the deformed zone are derived the plate boundary zone is shown to be two dimensional for the most part in that gradients of the velocity along the length of the zone are small or zero the shear strain rates are not uniform however they reach a maximum along a central axis and decrease gradually to zero toward the sides nor are the two independent components of strain one involving shortening or extension perpendicular and the other shear parallel to the zone equally developed everywhere there is a clear geographic separation with shortening developed over the subduction thrust and shear developed behind in a zone of wrench faulting time variations in the strain field in part of the region above the subduction interface are related to changes in the degree of coupling across the interface a velocity field is computed the relative velocity of the two plates from this data agree very well with that derived from seafloor spreading data these strain and velocity fields derived from geodetic studies give the short term kinematics of the plate boundary zone the long term kinematics of the zone are estimated from 1 uplift and subsidence data which are related to changes in crustal thickness and hence to dilatational strain and 2 variation in the declination of primary magnetization in rocks of known age related to the rotational strain the rate of rotational strain has increased in time from about 2 to 3 myr 1 10 myr ago to about 9 myr 1 today the increase can be understood as a secondary effect of a developing compressional component increasing the coupling between the plates so that more of the motion parallel to the zone is accommodated by distributed shear and less by aseismic slip the rates of strain averaged over the last 1 myr or so and at a scale length of a few tens of kilometres are closely similar in distribution and magnitude to the strain rates derived from short term kinematics while therefore at scale lengths of a few hundred metres or so faulting is very important and the deformation is discontinuous with unstrained blocks faulted with large but uncertain slip against adjacent blocks the deformation at these longer scale lengths is continuous and regular the two consequences of this study are that 1 strain from geodetic data can be directly related to the average long term deformation and therefore can be an important tool in the study of deformation in regions of current tectonic activity and 2 at scale lengths of a few tens of kilometres the deformation of a region can be described as the deformation of a continuum and we can ignore the effects of faulting

crustal deformation of the marlborough fault zone in the south island of new zealand geodetic constraints over the interval 1982 1994 crustal deformation across the marlborough fault zone in the south island of new zealand has been investigated by resurveying with the global positioning system gps a triangulation and trilateration network across part of the zone the principal strain rates which mostly have errors between 5 and 10 vary systematically across the region the principal axis of horizontal contraction gradually swings from se nw southeast of the hope fault to almost east west in the west the component of velocity parallel to the strike of the faults can account for 95 of the relative motion between the australian and pacific plates this component exhibits little variation west of the alpine wairau fault and shows an almost linear variation from the wairau fault to the east coast the horizontal strain rate northwest of the wairau fault is a small east west uniaxial contraction 0 1 ppm yr 1 if it is assumed that the crustal blocks bounded by the major faults are primarily driven by basal shear tractions with stresses on the faults being relatively insignificant then the slip rates expected on the faults may be derived from the observed velocity variations across the fault zone these predicted slip rates are in good agreement with geologically observed slip rates the larger slip rates on the hope fault are related to the observation that the strain field extends southeast of the fault over a distance large compared with the spacing between the faults the agreement between predicted and geological slip rates lends support to the idea that the observed pattern of deformation reflects that in the lower lithosphere

utility of goi qgf and qgf e for interpreting reservoir geohistory and oil remigration in the hudson oilfield tarim basin northwest china abstract the physical mechanisms responsible for hydrocarbon migration in carrier beds are well understood however secondary migration is one of poorly understood facets in petroleum system the carboniferous donghe sandstone reservoir in the tarim basin s hudson oilfield is an example of a secondary or unsteady reservoir that is oil in this reservoir is in the process of remigration making it a suitable geologic system for studying hydrocarbon remigration in carrier beds experimental methods including grains containing oil inclusions goi quantitative grain fluorescence qgf and quantitative grain fluorescence on extract qgf e together with the results from drilling logging and testing data were used to characterize the nature of oil remigration in the donghe sandstone the results show that 1 significant differences exist between paleo and current oil reservoirs in the donghe sandstone which implies that oil has remigrated a significant distance following primary accumulation 2 due to tectonic inversion oil remigration is slowly driven by buoyancy force but the oil has not entered into the trap entirely because of the weak driving force oil scarcely enters into the interlayers where the resistance is relatively large 3 the oil remigration pathway located in the upper part of the donghe sandstone is planar in nature and oil moving along this pathway is primarily distributed in those areas of the sandstone having suitable properties residual oil is also present in the paleo oil reservoirs which results in their abnormal qgf e a better understanding of the characteristics of oil remigration in the donghe sandstone in the hudson oilfield can contribute to more effective oil exploration and development in the study area

slip distribution of the lake tennyson earthquake new zealand as inferred from static stress changes and off fault aftershocks the fault plane of an earthquake can be estimated in many different ways one is to examine the distribution of a well located aftershock sequence to see if a fault plane is evident here we present a new method where we take an earthquake aftershock sequence with distinguishable off fault clusters and vary the slip distribution to achieve a good correlation between regions of increased coulomb failure stress cfs and aftershock occurrence we find with the lake tennyson earthquake that simply taking an area outlined by aftershocks to estimate a fault plane may not be valid if we do this patterns of increased cfs have negative correlation with off fault aftershock occurrence however if we restrict slip to only deeper regions and over a smaller area then the correlation between regions of increased cfs and aftershock off fault occurrence is good

a microgravimetric network in east central greece an area of potential seismic hazard summary the eastern mediterranean is a region of complex tectonic processes and associated horizontal and vertical displacements a high precision gravity network has been established in the atalanti area of central greece to monitor temporal gravity changes on an annual or more frequent basis a total of 68 sites have been measured in 1981 and 1982 with a maximum single instrument standard deviation of 0 08 gravity units after a least squares network adjustment analysis of the gravity differences between the two measuring epochs exhibits no change of gravity over the network with a precision of 0 1 1 gravity units it is proposed that the gravity values given form a stable base for continued observations which will enable the authors to resurvey the region in the event of precursory foreshocks observation of the atlantic network will continue on an annual basis preserving the same observation sequence for reasons of symmetry

unfolding the wadati benioff zone in the kermadec new zealand region abstract as the deep seismic zones are associated with subducted oceanic crust it is important to establish the extent and continuity of each of these zones using consistent earthquake locations then the former oceanic crust can be restored to the surface of the earth by unfolding the seismic zone about the trench this unfolded crust should be used in plate reconstructions this process has been carried out for the deep seismic zone in the kermadec new zealand region where the deep seismic zone is defined by a careful selection of i s c hypocenters and the former oceanic crust is established by unfolding plate reconstructions using two sets of rotation poles show that the deepest parts of the observed seismic zone along its length were not subducted at the same time further the currently observable zone is not directly associated with earlier volcanism in northwest new zealand between 6 and 20 ma ago

the role of strike slip fault systems at plate boundaries a new analysis shows that most 59 plate boundaries have a relative velocity vector that is markedly oblique greater than 22 to the boundary normal a significant proportion 14 have vectors that are nearly 22 parallel to the boundary accommodation of the oblique motion usually involves strike slip faulting but the kinematic role of these faults differs at divergent and convergent boundaries four main types of plate boundary related strike slip faults are distinguished ridge transforms boundary transforms trench linked strike slip faults and indent linked strike slip faults discrimination of the four types should be possible in ancient orogenic belts but is complicated by the common reactivation of the strike slip zones in other roles plate boundary related strike slip faults form major lineaments at the present day ridge transforms have a low preservation potential in continents boundary transforms and indent linked faults often re use old lineaments but trench linked strike slip faulting is an effective method of forming new lineaments in continental crust strike slip faulting in general is less commonly recognized in ancient orogenic belts than its abundance in present plate boundary orogens requires this under recognition results both from poor understanding of strike slip kinematics and from deeper prejudices about the way in which orogenic belts form

field examples of strike slip fault terminations in mongolia and their tectonic significance deformation at the ends of large intracontinental strike slip faults that do not simply link other major structures often involves rotations about a vertical axis we use earthquake slip vectors surface rupture in earthquakes and geomorphology to examine the ends of three major strike slip faults in mongolia in these places a simple pattern is seen consisting of a thrust fault on one side with a displacement that decreases away from the strike slip fault consistent with local rotational deformation strike slip faults that terminate in this way allow the style of faulting to change spatially within a deforming area for example from dominantly strike slip to dominantly dip slip while still accommodating the overall deformation required by larger scale regional motions such a change in fault style should also be accompanied by a change in the rotation rate about a vertical axis which may be detected paleomagnetically the kind of strike slip fault termination described here may have consequences for how large strike slip fxaults evolve and grow and for the variation in displacement along their length

active tectonics of the andes nearly 90 mm a 1 of relative plate convergence is absorbed in the andean plate boundary zone the pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved along any traverse across the plate boundary zone the sum of relative velocities between points must equal the relative plate motion we have developed a kinematic synthesis of displacement and strain partitioning in the andes from 47 s to 5 n relevant for the last 5 ma based upon 1 relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080 2 moment tensor solutions for over 120 crustal earthquakes since 1960 3 structural studies of deformed plio pleistocene rocks 4 topographic geomorphic studies 5 palaeomagnetic data and 6 geodetic data we recognize four neotectonic zones with subzones and boundary transfer zones that are partitioned in different ways these zones are not coincident with the classic zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form the long term segmentation and finite evolution of the andes may not occur in constantly defined segments in space and time in segment 1 47 39 s the slip vector is partitioned into roughly orthogonal benioff zone slip with large magnitude large slip surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50 and dextral slip in the curved liquine ofqui fault system giving 5 10 of anticlockwise fore arc rotation in segment 2 39 20 s the slip vector is partitioned into benioff zone slip roughly parallel with the slip vector andean crustal shortening and a very small component of dextral slip including that on the atacama fault system between 39 and 34 s a cross strike dextral transfer which deflects the chile trench and the volcanic arc absorbs the shortening contrast between segments 1 and 2 in segment 3 20 6 s the slip vector is partitioned into roughly orthogonal benioff zone slip crustal shortening sinistral trench parallel faulting and northeast southwest extension compatibility between segments 2 and 3 is maintained by the sinistral east southeast trending cochabamba shear zone and north trending dextral faults in segment 4 6 s to 5 n the slip vector is partitioned into roughly orthogonal benioff zone slip and dextral strike slip faulting in the fore arc and volcanic chain

late cenozoic uplift of the eastern cordillera bolivian andes abstract this paper analyses late cenozoic uplift in the bolivian andes using the morphology of well preserved regional paleosurfaces in the eastern cordillera that define three axially draining braided river catchments that formed between 12 and 9 ma rock uplift since the formation of the paleodrainage systems which has been quantified using four different methods is 1705 695 m with a mean erosion of 230 90 m as a consequence of entrenchment of the drainage systems the lack of faulting or tilting in the regions immediately farther west strongly suggest that rock uplift of the paleodrainage systems also extends to the western margin of the eastern cordillera balanced structural cross sections require crustal deformation at depth beneath the eastern cordillera in order to accommodate underthrusting of the brazilian shield beneath the thin skinned fold and thrust belt on the eastern margin of the bolivian andes in this case the observed uplift of the eastern cordillera is easily explained by sliding up a ramp in the major decollement dipping in the range 4 16 w as a consequence of the observed 60 110 km of shortening farther east in the subandean zone contemporaneous uplift of the western margin of the eastern cordillera is easily explained in terms of crustal thickening as a result of ductile squeezing in the lower crust accommodating at depth the subandean shortening it remains unclear how this uplift relates to that of the regions farther west in the altiplano and volcanic arc except that uplift in the eastern cordillera coincides with a phase of intense shortening in the northern altiplano commencing at 9 5 ma and continuing to 2 7 ma and possibly younger