crustal structure due to collisional and escape tectonics in the eastern alps region based on profiles alp01 and alp02 from the alp 2002 seismic experiment 1 alp01 and alp02 are the longest profiles recorded during alp 2002 a large international seismic refraction and wide angle reflection experiment undertaken in the eastern alps in 2002 alp01 crosses the alpine orogen from north to south thus providing a cross section mainly affected by the collision between europe and the adriatic microplate alp02 extends from the eastern alps to the pannonian basin supplying evidence on the relation between alpine crustal structure and tectonic escape to the pannonian basin during this experiment 363 single channel recorders were deployed along these profiles with an average spacing of 3 2 km recordings from 20 inline shots were used in this study two dimensional forward modeling using interactive ray tracing techniques produced detailed p wave velocity models that contain many features of tectonic significance along alp01 the european moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the eastern to the southern alps the adriatic moho continues further south at a significantly shallower depth moho topography and a prominent south dipping mantle reflector in the alpine area support the idea of southward subduction of the european lithosphere below the adriatic microplate the most prominent tectonic feature on the alp02 profile is a vertical step of the moho at the transition between the alpine and pannonian domains suggesting the existence of a separate pannonian plate fragment the development of the pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the alpine collision area to the pannonian basin

bryozoan faunas in the middle miocene of hungary biodiversity and biogeography a study of the badenian middle miocene marine deposits of hungary yielded a rich bryozoan fauna of 238 species comprising 59 cyclostomes 176 cheilostomes and 3 ctenostomes six palaeobiogeographic groups have been identified among this fauna on the basis of the present day and fossil distribution of the species similarities within the central paratethys and between the central paratethys the mediterranean and the atlantic have then been calculated using jaccard s index the results indicate strong affinities between the central paratethyan basins of hungary austria poland and romania the higher number of species and the lower level of endemism observed in hungary is explained by the vicinity of this basin to the entrance of the water seaway connecting the mediterranean to the paratethys a decrease in taxonomic diversity between the early and the late badenian is also observed accompanied by the absence of most tropical taxa from the late badenian this points towards a less optimal climate and a more pronounced isolation of the badenian sea from the oceanic waters the major result of the comparative study between central paratethyan and mediterranean bryozoan faunas is the presence of numerous common species the number of endemic paratethyan species is however relatively high indicating that the bryozoan faunas of both seas evolved in a relative isolation the exchange of faunas between the mediterranean and the paratethys was probably regulated by an anti estuarine circulation permitting an easier incursion of mediterranean species into the paratethys but hindering the paratethyan endemics from entering the mediterranean the stronger affinity between hungarian and mediterranean faunas also shows that this basin was closer to the entrance of the water seaway connecting the two areas and thus the mediterranean species entered more easily the similarity index between central paratethys and atlantic faunas is much lower than with the mediterranean this indicates that the palaeobiogeographic domain formed by the mediterranean and the paratethys was relatively homogeneous during the middle miocene and that the relationships with the atlantic were weaker exchange of benthic organisms between the central paratethys and the indo pacific during the middle miocene is considered here as extremely improbable

the messinian problem in the pannonian basin eastern hungary insights from stratigraphic simulations abstract earlier studies revealed a prominent unconformity in the messinian stratigraphic record of the lacustrine pannonian basin but it was unclear what factors were responsible for the formation of this unconformity and thus its origin remained controversial the problem was further complicated by the fact that stratal patterns in the messinian varied significantly along the paleo margins of the lake our study introduces quantitative stratigraphic simulations to analyze the role of subsidence sediment supply and lake level changes in the formation of the unconformity and the various architectural patterns that evolved in response to the messinian events the results suggest that a relative lake level fall occurred in the messinian accompanied and followed by tectonic inversion in several parts of the basin since the rate of tectonic subsidence and or uplift varied in space and time the size of the relative lake level fall varied significantly across the basin while various stratal architectural patterns formed in the same time interval the age of the unconformity was estimated based on seismic correlations with paleomagnetic chronozones to be between 5 6 ma which was refined by stratigraphic simulations galeacysta etrusca cysts were found in the unconformity which confirmed its late messinian age the surface is called the intra messinian unconformity imu in this paper seismic interpretations and simulations of stratal architecture led to the formulation of a basin fill model and identification of four stratigraphic architectural patterns related to messinian events including a major lake level fall and coeval and subsequent uplift events in certain parts of the basin

the importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs abstract the effect of shale composition and fabric upon pore structure and ch 4 sorption is investigated for potential shale gas reservoirs in the western canadian sedimentary basin wcsb devonian mississippian d m and jurassic shales have complex heterogeneous pore volume distributions as identified by low pressure co 2 and n 2 sorption and high pressure hg porosimetry thermally mature d m shales 1 6 2 5 vro have dubinin radushkevich d r co 2 micropore volumes ranging between 0 3 and 1 2 cc 100 g and n 2 bet surface areas of 5 31 m 2 g jurassic shales which are invariably of lower thermal maturity ranging from 0 9 to 1 3 vro than d m shales have smaller d r co 2 micropore volumes and n 2 bet surface areas typically in the range of 0 23 0 63 cc 100 g co 2 and 1 9 m 2 g n 2 high pressure ch 4 isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon toc content methane sorption in d m shales increases with increasing toc and micropore volume indicating that microporosity associated with the organic fraction is a primary control upon ch 4 sorption sorption capacities for jurassic shales however can be in part unrelated to micropore volume the large sorbed gas capacities of organic rich jurassic shales independent of surface area imply a portion of ch 4 is stored by solution in matrix bituminite solute ch 4 is not an important contributor to gas storage in d m shales structural transformation of d m organic matter has occurred during thermal diagenesis creating and or opening up microporosity onto which gas can sorb as such d m shales sorb more ch 4 per weight percent wt toc than jurassic shales inorganic material influences modal pore size total porosity and sorption characteristics of shales clay minerals are capable of sorbing gas to their internal structure the amount of which is dependent on clay type illite and montmorillonite have co 2 micropore volumes of 0 78 and 0 79 cc 100 g n 2 bet surface areas of 25 and 30 m 2 g and sorb 2 9 and 2 1 cc g of ch 4 respectively dry basis a reflection of microporosity between irregular surfaces of clay platelets and possibly related to the size of the clay crystals themselves mercury porosimetry analyses show that total porosities are larger in clay rich shales compared to silica rich shales due to open porosity associated with the aluminosilicate fraction clay rich sediments low si al ratios have unimodal pore size distributions

palaeontological evidence of communication between the central paratethys and the mediterranean in the late badenian early serravalian abstract in the middle miocene the area of present day eastern slovenia was situated at the eastern mouth of the slovenian corridor a hypothetical seaway connecting the central paratethys and the mediterranean the exact location and time of closure of a seaway between the two neighbouring marine realms are still a matter of debate we studied badenian late langhian and early serravallian calcareous nannoplankton assemblages from eastern slovenia for their palaeogeographical significance by comparing them to contemporaneous central paratethyan and mediterranean assemblages and the assemblages described in selected odp and iodp reports assemblage composition and the sequence of biostratigraphic events observed in slovenia were very similar to that in several mediterranean sites comparison with the world ocean suggests that this similarity reflects communication between the mediterranean and paratethyan populations rather than a universal trend of nannoplankton evolution late badenian assemblages from different localities within the central paratethys exhibit considerable variation with respect to the presence of discoasters considered as typical of the mediterranean and the presence of rhabdosphaera poculi and hayella challengeri considered as typical of the eastern paratethys our results suggest the mixing of mediterranean and eastern paratethyan influences throughout the entire central paratethys during the late badenian the observed variability explains how opposing views on the status of the marine connection between the central paratethys and the mediterranean in the late badenian can arise from palaeontological studies of fossil assemblages considering only a single site or a small area the gastropod species pereiraea gervaisi migrated from the mediterranean to the central paratethys where it is only known from the immediate proximity of the hypothesised slovenian corridor this supports the thesis that the communication between the two seas took place via the slovenian corridor and not some other marine connection like the hypothetical axios vardar trench

ophiolitic detritus in cretaceous clastic formations of the dinarides nw croatia evidence from cr spinel chemistry cr spinel is a common heavy mineral in the sandstones of cretaceous synorogenic sedimentary formations of the nw dinarides croatia the rocks occur in isolated exposures in the uplifted basement units of medvednica ivanscica umberak and samobor mountains near zagreb in this area evidence of the early alpine evolution of the dinarides is obscured due to strong dismemberment of pre tertiary tectonostratigraphic units resulting from an intense tectonic history as well as due to the widespread sedimentary cover of the pannonian basin electron microprobe analyses of detrital cr spinels from the ostrc formation reveal that in the early cretaceous the ophiolitic source area was predominantly composed of harzburgite peridotites and associated cumulate rocks which developed in a supra subduction zone setting the supply of cr spinels with the same chemical signature remained dominant until the end of the cretaceous suggesting that exposed remnants of the same ophiolite belt persisted through the cretaceous and or that recycling was significant similarities with data reported from the northern calcareous alps and the transdanubian central range imply that a rather extensive harzburgitic ophiolite belt probably extended along the adriatic margin during the early cretaceous a slight trend of increasing variation in the cr is observed from the early to the latest cretaceous suggesting that the source areas became more heterogeneous with the ongoing cretaceous tectonic evolution differences in cr spinel compositions in two contemporaneous latest cretaceous formations are well in line with existing data on heavy mineral proportions which together identify contrasting hinterland geology for these formations and strongly suggest the coeval existence of two separate basins

remobilization of deep basin brine during exhumation of the illizi basin algeria abstract understanding the processes that drive fluid flow in sedimentary basins has important implications for models of metallic ore and petroleum migration and accumulation in the subsurface potential drive mechanisms include gravity driven flow compaction driven flow and density driven convection in this study we demonstrate that the brine hosted in ordovician sandstone in the illizi basin in algeria is genetically linked to triassic liassic evaporites deposited 400 km to the north in the berkine basin this observation confirms that long distance lateral brine migration has occurred within the basin in the past we assess the hydrogeologic record preserved in aqueous fluid inclusions within the ordovician sandstone document a marked increase in formation water salinity during cooling and exhumation and evaluate the drive mechanisms for late stage remobilization of deep brines within the basin it is hypothesized that the release of overpressure during exhumation of the illizi basin may have been a critical contributor to updip fluid flux this model could be applicable to other exhumed basins worldwide

geochemical constraints on the origin and volume of gas in the new albany shale devonian mississippian eastern illinois basin this study involved analyses of kerogen petrography gas desorption geochemistry microporosity and mesoporosity of the new albany shale devonian mississippian in the eastern part of the illinois basin specifically detailed core analysis from two locations one in owen county indiana and one in pike county indiana has been conducted the gas content in the locations studied was primarily dependent on total organic carbon content and the micropore volume of the shales gas origin was assessed using stable isotope geochemistry measured and modeled vitrinite reflectance values were compared depth of burial and formation water salinity dictated different dominant origins of the gas in place in the two locations studied in detail the shallower owen county location 415 433 m 1362 1421 ft deep contained significant additions of microbial methane whereas the pike county location 832 860 m 2730 2822 ft deep was characterized exclusively by thermogenic gas despite differences in the gas origin the total gas in both locations was similar reaching up to 2 1 cm3 g 66 scf ton lower thermogenic gas content in the shallower location lower maturity and higher loss of gas related to uplift and leakage via relaxed fractures was compensated for by the additional generation of microbial methane which was stimulated by an influx of glacial melt water inducing brine dilution and microbial inoculation the characteristics of the shale of the maquoketa group ordovician in the pike county location are briefly discussed to provide a comparison to the new albany shale

geological deformations in the pannonian basin during the neotectonic phase new insights from the latest regional mapping in hungary abstract the present paper introduces the new 1 500 000 scale map of young geological deformations in hungary including all important deformation structures faults and folds related to the neotectonic evolutionary phase the new map is based on the interpretation of nearly 2900 2d seismic profiles and 70 3d seismic volumes as well as on the critical evaluation of the results of published neotectonic studies an important novelty of the map is that not only the near surface manifestations of the neotectonic faulting but also their roots in the underlying pre pannonian substratum are displayed allowing correlation between various reactivated fault segments of longer fault zones and aiding the better understanding of the regional structural context the new map provides a significantly more accurate definition actual position extension and geometry of the neotectonic structures and provide more details compared to previous regional studies the prevailing e ne w sw striking neotectonic fault pattern clearly reflects the control of identically oriented pre pannonian fault systems during the neotectonic deformations markedly different orientations in the neotectonic structures indicate important differences in the overall orientation of the underlying fault systems these observations demonstrate that neotectonic activity is predominantly due to the reactivation of pre existing predominantly synrift structures all over the pannonian basin as also indicated by previous studies despite experiencing the largest middle to late miocene extension and the formation of the deepest depocenters in the whole pannonian basin se hungary practically lacks any observable neotectonic activity which is a striking but still poorly understood feature detailed 3d seismic analysis of fault segment geometries indicates a consistent regional pattern sinistral shear along e ne w sw oriented and dextral shear along w nw e se oriented fault zones respectively these observations together with the e w trending contractional transpressional structures folds reverse faults imbricates occurring in western and southern hungary indicate a dominantly strike slip stress regime with a laterally slightly rotating from n s to nne ssw maximum horizontal stress axis 1 during the neotectonic phase lateral displacement along major root zones amounts to a maximum of 2 3 km during the neotectonic phase

magnetic fabric of late miocene clay rich sediments from the southern pannonian basin the magnetic fabric of late miocene sediments from the southern pannonian basin was studied on oriented samples collected from 19 geographically distributed localities all of them are characterized by near horizontal magnetic foliation plane after tilt correction indicating weak deformation well developed lineations were observed for 16 localities which are interpreted as due to compressional transpressional deformation except from three localities where the fabric must have been formed in an extensional setting comparison between the orientation of the map scale folds and faults and magnetic lineation directions shows that magnetic lineation is either related to nne ssw directed compression leading to the formation of folds or it can be connected to nw se or nne ssw trending dextral faults

river gradient anomalies reveal recent tectonic movements when assuming an exponential gradient decrease along a river course abstract high resolution digital models combined with gis or other terrain modelling software allow many new possibilities in geoscience in this paper we develop describe and test a novel method the gla method to detect active tectonic uplift or subsidence along river courses it is a modification of hack s sl index method in order to overcome the disadvantages of the latter the core assumption of the gla method is that over geological time river profiles quickly adjust to follow an exponential decrease in elevation along the river course any large deviation can be attributed to active tectonic movement or to disturbances in erosion sedimentation processes caused by an anthropogenic structure e g artificial dam during the testing phase the locations of identified deviations were compared to the locations of faults identified on a 1 100 000 geological map results show that higher magnitude deviations are found within a maximum radius of 200 m from the fault and the majority of detected deviations within a maximum radius of 600 m from faults or thrusts however these results are not the best that could be obtained because the geological map that was used and the only one available for the area is not of the appropriate scale and was therefore not precise enough comparison of deviation magnitudes against psinsar measurements of vertical displacements in the vicinity revealed that in spite of the very few suitable points available a good correlation between both independent methods was obtained r 2 0 68 for the e research area and r 2 0 69 for the w research area the gla method was applied to the three test sites where previous studies have shown active tectonic movements it shows that deviations occur at the intersections between active faults and river courses as well as also correctly detected active uplift attributed to the increased sedimentation rate above an artificial hydropower dam and an increased erosion rate below the method gives promising results and it is acknowledged that the gla method needs to be tested in other locations around the world

the dinaric fault system large scale structure rates of slip and plio pleistocene evolution of the transpressive northeastern boundary of the adria microplate located at the northeastern corner of the adria microplate the alps dinarides junction represents a key region for understanding how the adria microplate interacts with stable europe however little is known on how the present day deformation imposed by the rotation of the adria microplate is absorbed across the dinarides using morphotectonic analysis based on satellite and aerial images accurate topographical maps and digital elevation models combined with field investigations we mapped in detail the three main active faults of the northern dinarides geomorphic and geological cumulative displacements ranging from a few meters to several kilometers have been identified on those faults and dated for the most recent ones using 36 cl exposure dating those results yielded a total right lateral motion of 3 8 0 7 mm yr oriented n317 comparing our results with the motion expected from adria rotation models suggests that the northern dinarides absorbs most of the predicted adria eurasia motion thus representing the eastern boundary of the microplate however a significant e w component is lacking suggesting that part of the stress imposed by the microplate rotation is transferred farther to the east finally bounds placed on the plio pleistocene kinematics confirm that faulting onset occurred during the early pliocene and evidence a significant kinematic change at the early middle pleistocene boundary

neogene quaternary structures in the border zone between alps dinarides and pannonian basin hrvatsko zagorje and karlovac basins croatia analysis of neogene quaternary structures from seismic lines surface measurements and geological mapping is presented from the border zone between the alps dinarides and pannonian basin first early miocene extension was possibly characterised by ene directed extension it was partly synchronous with nw se shortening second middle miocene extension was possibly characterised by nw se to wnw ese directed extension again this event was followed by a new generation of thrusts related to end sarmatian shortening the last late miocene e w to wnw ese directed extension was followed by a final shortening that created major map scale folds basement pop ups and inverted former basins geometry onlap and thickness patterns of the youngest syn tectonic basin fill indicate that this last n s to nw se directed shortening started in late pontian and continued up to the present time when taking into account the wider surrounding area it seems that the structures related to this latest shortening are arranged in often perpendicular directions centred at the eastern end of the periadriatic lineament to explain this fan like pattern of synchronous shortenings a kinematic model is proposed combining counter clockwise rotation with north or northwestward shift of the dinaridic block with respect to the more stable alpine buttress

experimental investigation of changes in methane adsorption of bitumen free woodford shale with thermal maturation induced by hydrous pyrolysis this study quantifies the effects of organic matter om thermal maturity on methane ch4 sorption on the basis of five samples that were artificially matured through hydrous pyrolysis achieved by heating samples of immature woodford shale under five different time temperature conditions ch4 sorption isotherms at 35 degrees c 50 degrees c and 65 degrees c and pressures up to 14 mpa on dry solvent extracted samples of the artificially matured woodford shale were measured the results showed that ch4 sorption capacity normalized to toc varied with thermal maturity following1 the trend maximum oil 367 degrees c oil cracking 400 degrees c maximum bitumen early oil 333 degrees c early bitumen 300 degrees c immature stage 130 degrees c the langmuir constants for the samples at maximum oil and oil cracking stages are larger than the values for the bitumen forming stages the total pore volume determined by n 2 physisorption at 77 k increases with increased maturation mesopores 2 50 nm in width were created during the thermal conversion of organic matter and a dramatic increase in porosity appeared when maximum bitumen and maximum oil generation stages were reached a linear relationship between thermal maturity and brunauer emmett teller bet surface area suggests that the observed increase in ch4 sorption capacity may be the result of mesopores produced during om conversion no obvious difference is observed in pore size distribution and pore volume for samples with pores 2 0 nm with the increase of thermal maturity based on co2 physisorption at 273 k the isosteric heat of adsorption and the standard entropy for artificially matured samples ranged from 17 9 kj mol 1 to 21 9 kj mol 1 and from 85 4 j mol 1 k 1 to 101 8 j mol 1 k 1 respectively these values are similar to the values of immature woodford kerogen concentrate previously observed but are larger than naturally matured organic rich shales high temperature hydrous pyrolysis might have induced lewis acid sites on both organic and mineral surfaces resulting to some extent in chemical interactions between the adsorption site and the methane c h bonds the formation of abundant mesopores 2 50 nm within organic matter during organic matter thermal maturation makes a great contribution to the increase in both bet surface area and pore volume and a significant increase in 2 6 nm pores occurs at maximum oil generation and oil cracking to gas ultimately controlling the methane adsorption capacity therefore consideration of pore size effects and thermal maturity is very important for gas in place gip prediction in organic rich shales c 2014 elsevier ltd all rights reserved

dynamics and energetics of bubble growth in magmas analytical formulation and numerical modeling we have developed a model of diffusive and decompressive growth of a bubble in a finite region of melt which accounts for the energetics of volatile degassing and melt deformation as well as the interactions between magmatic system parameters such as viscosity volatile concentration and diffusivity on the basis of our formulation we constructed a numerical model of bubble growth in volcanic systems we conducted a parametric study in which a saturated magma is instantaneously decompressed to one bar and the sensitivity of the system to variations in various parameters is examined variations of each of seven parameters over practical ranges of magmatic conditions can change bubble growth rates by 2 4 orders of magnitude our numerical formulation allows determination of the relative importance of each parameter controlling bubble growth for a given or evolving set of magmatic conditions an analysis of the modeling results reveals that the commonly invoked parabolic law for bubble growth dynamics r t1 2 is not applicable to magma degassing at low pressures or high water oversaturation but that a logarithmic relationship r log t is more appropriate during active bubble growth under certain conditions a second aspect of our study involved a constant decompression bubble growth model in which an initially saturated magma was subjected to a constant rate of decompression model results for degassing of initially water saturated rhyolitic magma with a constant decompression rate show that oversaturation at the vent depends on the initial depth of magma ascent on the basis of decompression history explosive eruptions of silicic magmas are expected for magmas rising from chambers deeper than 2 km for ascent rates 1 5 m s 1

remigration and leakage from continuous shale reservoirs insights from the sichuan basin and its periphery china shale gas in the sichuan basin and its periphery potentially plays an important role in the world shale gas industry an understanding of remigration and leakage from continuous shale reservoirs is very important for shale gas exploration especially in the sichuan basin and its periphery the shale gas accumulation models that relate to remigration and leakage were developed within the wufeng and longmaxi black shales in the jiaoshiba and the youyang blocks first a tectono sedimentary history of the wufeng and longmaxi black shales in the sichuan basin and its periphery was developed based on the published literature the history exhibits a continuous distribution of high quality wufeng and longmaxi black shale which is the foundation of the shale gas formation second the shale gas remigration accumulation model in the anticlines was clarified by using data collected from the shale gas fields in jiaoshiba block the shale gas model for the jiaoshiba block was developed on the basis of a continuous shale reservoir distribution differentiated structural deformation and a gas self sealed system third the shale gas fault failure leakage model in the fault blocks and the erosion model in the residual areas were revealed based on the shale reservoir and shale gas content heterogeneity in the youyang block these two models were validated by available data including 13 two dimensional seismic lines and 2 shale gas exploration vertical wells in the youyang block shale gas areas with high gas resource and gas production rates in the anticlines were defined by the remigration accumulation model the fault failure leakage model was used to find shale gas with limited commercial potential whereas commercial shale gas was largely lacking according to the erosion residual model the study on remigration and leakage from continuous shale reservoirs in the sichuan basin and its periphery can be used to better understand and improve the exploration efforts based on resource preservation

stratigraphic correlation and structural position of lower cretaceous flysch type deposits in the eastern southern alps nw slovenia lower cretaceous syn orogenic sediments derived from the obducted ophiolites of the meliata maliac vardar neotethys ocean are typically found in the dinarides and the austroalpine units correlative flysch type deposits linking both regions through the southern alps had been reported from the bohinj area nw slovenia but their stratigraphic and structural framework remained poorly known our research focused on stratigraphic and structural field studies in a 50 km2 area between lake bled and lake bohinj in the julian alps the mixed carbonate siliciclastic sediments informally named the studor formation range in age from the valanginian possibly late berriasian to the aptian they occur on top of two different stratigraphic successions which we assign to two separate nappes the first succession consists of deep water middle triassic to lower cretaceous deposits of the bled basin and belongs to the pokljuka nappe which is the uppermost nappe of the julian nappe stack the second succession consists of upper triassic to lower jurassic platform carbonates and a thin jurassic cretaceous deep water sequence this succession was deposited in the marginal area of the julian carbonate platform julian high and now belongs to the underlying krn nappe the original dinaric thrust contacts between the pokljuka and krn nappes are obliterated by younger deformations the present day boundaries between these two nappes are steep ne sw and younger nw se trending faults the post nappe deformation sequence characterizing the alps dinarides transition zone has been recognized 1 oligocene early miocene nw se contraction 2 early middle miocene extension and 3 late miocene to recent inversion and transpression

delayed disequilibrium degassing in rhyolite magma decompression experiments and implications for explosive volcanism recent numerical models and analog shock tube experiments show that disequilibrium degassing during magma ascent may lead to violent vesiculation very near the surface in this study a series of decompression experiments using crystal free rhyolite melt were conducted to examine the development of large supersaturations due to delayed homogenous spontaneous bubble nucleation melts were saturated at 900 c and 200 mpa with either 5 2 wt dissolved h2o or with 4 2 wt h2o and 640 ppm co2 and isothermally decompressed at linear rates of either 0 003 0 025 or 8 5 mpa s to final pressures between 25 and 175 mpa additional isobaric saturation experiments 900 c 200 25 mpa using pure h2o or mixed h2o co2 fluids establish reference equilibrium solubility curves values homogenous nucleation is triggered in both h2o only and h2o co2 experiments once the supersaturation pressure pss reaches 120 150 mpa and the melt contains two times its equilibrium water contents bubble number density and nucleation rate depend on the supersaturation pressure with values on the order of 102 cm3 and 1 cm3 s for pss 120 mpa 106 cm3 and 103 105 cm3 s for pss 130 150 mpa and 107 cm3 and 106 cm3 s for pss 160 175 mpa nucleation rates are consistent with classical nucleation theory and infer an activation energy for nucleation of 1 5 10 18 j nucleus a critical bubble radius of 2 10 9 m and an effective surface tension for rhyolite at 5 2 wt h2o and 900 c of 0 10 0 11 n m the long nucleation delay limits the time available for subsequent diffusion such that disequilibrium dissolved h2o and co2 contents persist to the end of our runs the disequilibrium degassing paths inferred from our experiments contrast markedly with the equilibrium or quasi equilibrium paths found in other studies where bubble nucleation occurs heterogenously on crystals or other discontinuities in the melt at low pss homogenous and heterogenous nucleation rates are comparable however as are bubble number densities so that at a given decompression rate it appears that nucleation mechanism rather than nucleation rate determines degassing efficiency by fixing the pressure depth at which vesiculation commences and hence the time available for equilibration prior to eruption although real systems are probably never truly crystal free our results show that rhyolitic magmas containing up to 104 crystals cm3 and perhaps as high as 106 crystals cm3 are controlled by homogenous rather than heterogenous nucleation during ascent

an outline of neotectonic structures and morphotectonics of the western and central pannonian basin abstract neotectonic deformation in the western and central part of the pannonian basin was investigated by means of surface and subsurface structural analyses and geomorphologic observations the applied methodology includes the study of outcrops industrial seismic profiles digital elevation models topographic maps and borehole data observations suggest that most of the neotectonic structures in the pannonian basin are related to the inverse reactivation of earlier faults formed mainly during the miocene syn and post rift phases typical structures are folds blind reverse faults and transpressional strike slip faults although normal or oblique normal faults are also present these structures significantly controlled the evolution of landforms and the drainage pattern by inducing surface upwarping and river deflections our analyses do not support the postulated tectonic origin of some landforms particularly that of the radial valley system in the western pannonian basin the most important neotectonic strike slip faults are trending to east northeast and have dextral to sinistral kinematics in the south western and central eastern part of the studied area respectively the suggested along strike change of kinematics within the same shear zones is in agreement with the fan shaped recent stress trajectories and with the present day motion of crustal blocks derived from gps data

tertiary to recent oblique convergence and wrenching of the central dinarides constraints from a palaeostress study the late eocene to neogene tectonic evolution of the dinarides is characterised by shortening and orogen parallel wrenching superposed on the late cretaceous and eocene double vergent orogenic system the central dinarides exposes nw trending tectonic units which were transported towards the adria apulian microcontinent during late cretaceous palaeogene times these units were also affected by subsequent processes of late palaeogene to neogene shortening neogene extension and subsidence of intramontane sedimentary basins and pliocene quaternary surface uplift and denudation the intramontane basins likely relate to formation of the pannonian basin major dextral se trending strike slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen parallel wrenching of the whole central dinarides during the neogene indentation of the apulian microplate into the alps and back arc type extension in the pannonian basin these fault systems have been evaluated with the standard palaeostress techniques we report four palaeostress tensor groups which are tentatively ordered in a succession from oldest to youngest 1 palaeostress tensor group 1 d1 of likely late eocene age indicates e w shortening accommodated by reverse and strike slip faults 2 palaeostress tensor group 2 d2 comprises n nw trending dextral and w wsw trending sinistral strike slip faults as well as wnw striking reverse faults these indicate ne sw contraction and subordinate nw se extension related to oligocene to early miocene shortening of the dinaric orogenic wedge 3 palaeostress tensor group 3a d3a comprises mainly nw trending normal faults which indicate early middle miocene ne sw extension related to syn rift extension in the pannonian basin the subsequent palaeostress tensor group 3b d3b includes ne trending se dipping normal faults indicating nw se extension which is likely related to further extension in the pannonian basin 4 palaeostress tensor group 4 d4 i s characterised by mainly nw trending dextral and ne trending sinistral strike slip faults together with some e trending reverse faults they indicate roughly n s shortening and dextral wrenching during late miocene to quaternary this is partly consistent with the present day kinematics with motion of the adriatic microplate constrained by gps data and earthquake focal mechanisms the north north westward motion and counterclockwise rotation of the adriatic microplate significantly contribute the shortening and present day wrenching in the central dinarides d 2005 elsevier b v all rights reserved

postcollisional cooling history of the eastern and southern alps and its linkage to adria indentation indentation of rigid blocks into rheologically weak orogens is generally associated with spatiotemporally variable vertical and lateral block extrusion the european eastern and southern alps are a prime example of microplate indentation where most of the deformation was accommodated north of the crustal indenter within the tauern window however outside of this window only the broad late stage exhumation pattern of the indented units as well as of the indenter itself is known in this study we refine the exhumational pattern with new u th sm he and fission track thermochronology data on apatite from the karawanken mountains adjacent to the eastern periadriatic fault and from the central eastern southern alps apatite u th sm he ages from the karawanken mountains range between 12 and 5 ma and indicate an episode of fault related exhumation leading to the formation of a positive flower structure and an associated peripheral foreland basin in the southern alps apatite u th sm he and fission track data combined with previous data also indicate a pulse of mainly late miocene exhumation which was maximized along thrust systems with highly differential amounts of displacement along individual structures our data contribute to mounting evidence for widespread late miocene tectonic activity which followed a phase of major exhumation during strain localization in the tauern window we attribute this exhumational phase and more distributed deformation during adriatic indentation to a major change in boundary conditions operating on the orogen likely due to a shift from a decoupled to a coupled system possibly enhanced by a shift in convergence direction

landscape response to recent tectonic deformation in the sw pannonian basin evidence from dem based morphometric analysis of the bilogora mt area ne croatia abstract bilogora mt area is a transpressional structure located in the ne of croatia linked with the tectonic evolution of the drava depression the structure formed during pliocene and quaternary from the inversion of nw striking drava depression boundary fault which originated as a normal fault and was reactivated as a dextral strike slip fault during pliocene and quaternary time bilogora mt area underwent more than 400 m of differential uplift while still ongoing tectonic deformation is documented by historical and instrumental seismicity 3 5 m l 5 6 in this geomorphic study the recent deformation in the bilogora mt area although obscured by landscape evolution variables was assessed using dem based landscape morphometry and a set of morphometric indexes local relief and slope angle variability distributions were combined with morphometric indexes computed at the scale of the drainage basin we analyzed hypsometric curves with the hypsometric integral hi basin asymmetry af and parameters of longitudinal stream profiles c f c max l l and k sn analyzed morphometric parameters were combined into a cumulative index of relative tectonic activity rta this index summarizes drainage basin response to the possible recent tectonic activity results suggest that most of the tectonic activity is probably located along the ne front of the bilogora mt area in its nw and central part this activity could be likely related to recent tectonic activity along the kalnik mt fault zone and drava depression boundary fault zones respectively a subordinate area characterized by recent tectonic activity could be suggested within the southernmost part of the study area quaternary activity in this area is probably related to ne striking faults in vicinity of the town daruvar that continue towards the northeast into the study area though methodology presented here represents a good identification tool of possible ongoing deformation this study will be followed by detailed fieldwork and paleoseismological investigations at the identified locations

homogeneous bubble nucleation in rhyolitic magmas an experimental study of the effect of h2o and co2 1 rapid decompression experiments were performed to study homogeneous bubble nucleation in a crystal free rhyolitic liquid at 800 c bubble nucleation was produced by lowering the pressure at 1 10 mpa s 1 from an initial value between 200 and 295 mpa to a final value below the volatile saturation pressure psat six volatile compositions with 4 1 7 7 wt h2o and 10 1200 ppm co2 were investigated for each composition we determined the critical pressure phon below which homogeneous nucleation can proceed the samples quenched below phon showed a nucleated core with a large number of uniformly spaced bubbles with decreasing pressure bubble number densities increased from 1015 m 3 the degree of supersaturation required for homogeneous nucleation phon psat phon increased with decreasing h2o content or increasing co2 content huge values of phon 135 to 310 mpa were measured in the h2o poor compositions 4 1 4 6 wt h2o 50 1100 ppm co2 much lower values from 60 to 160 mpa were obtained in the h2o rich compositions 7 0 7 7 wt h2o 10 630 ppm co2 the high phon in liquids with 4 5 wt h2o should result in the buildup of large degrees of supersaturation during magma ascent a very late nucleation event and a rapid explosive vesiculation by contrast rhyolitic liquids with much larger water contents have higher saturation pressures and much lower phon bubble nucleation may therefore occur at depth in the volcanic conduit favoring a subsequent near equilibrium degassing

magneto biostratigraphy and paleoenvironments of the miocene freshwater sediments of the sarajevo zenica basin abstract the sarajevo zenica basin of bosnia herzegovina was part of the dinaride lake system a large network of miocene long lived freshwater basins in southeastern europe the basin contains a thick sedimentary succession of carbonates coals and mixed siliciclastic deposits that reflects the paleoclimatic and tectonic evolution of the region in this study we present novel integrated magneto bio stratigraphic and sedimentological data and reconstruct the paleoenvironmental evolution of the sarajevo zenica basin during its two main evolutionary phases thrusting and extension the basal oligo miocene freshwater paleoenvironments are characterized by alternating palustrine shallow lacustrine and distal fluvial phases the base level fluctuations are largely controlled by syn sedimentary pulses of tectonic loading during the final phase of thrusting in the internal dinarides the majority of this succession is considered early miocene in age which contrasts with previous oligocene age estimates the subsequent extensional phase initiated not later than 18 4 ma this coarsening upward sequence of lacustrine carbonates silts sands and conglomerates is correlated between 17 2 and 15 ma c5cr c5br by means of integrated bio magnetostratigraphy during this upper extensional phase subsidence and sediment influx was generally controlled by activity along the basin bounding normal fault overruling smaller scale climatic influences we conclude that the existence of the long lived sarajevo lake is coeval with other dinaric and southern pannonian lakes and overlaps in time with the miocene climatic optimum sedimentation in the sarajevo zenica basin terminated at 15 14 ma which concurs with both the end of the climatic optimum as well as the cessation of extension in the dinarides these results will help to better quantify the paleoclimatic changes in the dinaride lake system as well as the regional tectono sedimentary events such as potential migrations of deformation across the dinarides

mechanics of basin inversion finite element modelling of the pannonian basin system abstract this finite element modelling study addresses the contraction of rheologically layered and laterally heterogeneous lithosphere representative for the pannonian basin and its surroundings the time interval and strain rate adopted in the experiments reflect the pliocene quaternary inversion of the basin several sets of fully coupled elastoviscoplastic thermo mechanical plane strain 2d models explore the evolution of buckling and stress strain changes across the lithosphere the viscous rheology of the asthenosphere allows for a detailed simulation of isostatic rebound during deformation the numerical models predict the successive development of surface undulations caused by crustal and or lithosphere folding at three different characteristic wavelengths among these the longest wavelength folds occur systematically at the rim of the basin as marginal bulges while the short wavelength folds overprint the earlier folds and are observed at a later stage during compression the thermo mechanical evolution of the lithosphere in response to progressive horizontal contraction is described in terms of a characteristic delay of the changes in the stress regime and a reduction of elastic strain in the strong crustal layers the models predict a change in stress state along the flanks of the basin caused by the development of weak basin lithosphere in their vicinity comparing the modelling results with tectonic features of the pannonian basin has resulted in the identification of three different stages in the pliocene quaternary basin inversion of the pannonian carpathian system

sedimentology and stratigraphy of the neogene rift type north croatian basin pannonian basin system croatia a review abstract development of the rift type north croatian basin located in the south western neogene pannonian basin system and belonging to the central paratethys realm was controlled by tectonics climate volcanic activity and eustatic fluctuations the extrabasinal controls produced a succession of depositional environments from terrestrial to marine and back to terrestrial and the deposits form a large scale transgressive regressive cycle basin evolution is subdivided into the syn rift phase which lasted from the early miocene ottnangian until the middle miocene middle badenian and in the post rift phase from the middle miocene late badenian to the quaternary these complex controls on deposition generated the opening and closing of connections to the open sea that occasionally resulted in the formation of unfossiliferous continental deposits or generated the radiation of endemic species such that it has been necessary to use regional neogene stages for stratigraphic analysis of the central paratethys history earlier stratigraphic studies of the north croatian basin that had been primarily based on biostratigraphy and superposition were improved by recent results yielded from radiometric dating and integrated biostratigraphy they have been focused mainly on the early middle miocene and the miocene pliocene boundaries that separate intervals of the specific depositional evolution of the basin most important depositional and palaeogeographic differences concern a relatively long period of development of the early continental phase that lasted from the ottnangian to the early badenian in contrast to parts of the pannonian basin system characterized by marine deposition in the early badenian the ncb was characterized by long lived fresh water lacustrine deposition the fresh water lake slavonia that developed from the middle pliocene to the early pleistocene indicates an independent phase of evolution of the south pannonian basin system so the cernikian regional stage was introduced for the lacustrine succession those stratigraphic and palaeogeographic differences additionally support the complexity of the pannonian basin system within the central paratethys realm supporting heterogeneous depositional development of continental rift type basins

paleogene early miocene igneous rocks and geodynamics of the alpine carpathian pannonian dinaric region an integrated approach a review of paleogene early miocene igneous rocks of the alpine carpathianpannonian dinaric region is presented in this paper we attempt to reveal the geodynamic link between paleogene early miocene igneous rocks of the mid hungarian zone and those of the alps and dinarides our summary suggests that paleogene early miocene igneous rocks of all these areas were formed along a single subduction related magmatic arc the study also highlights orthopyroxene rich websterite mantle xenoliths from west hungary and east serbia that were formed in the vicinity of a subducted slab we discuss the location and polarity of all potential subduction zones of the area that may account for the igneous rocks and orthopyroxene rich mantle rocks however results of seismic tomography on subducted slabs beneath the studied area combined with geological data demonstrate that igneous rocks and mantle rocks cannot be explained by the same subduction process we propose that the paleogene early miocene arc was mainly generated by the budva pindos subduction zone subordinately by penninic subduction whereas mantle rocks were possibly formed in the vicinity of the older vardar subduction zone continental blocks possibly moved together with their mantle lithosphere the present diverging shape of the proposed arc has been achieved by considerable shear and rotations of those lithospheric blocks

lateral extrusion in the eastern alps revisited refining the model by thermochronological sedimentary and seismic data 1 this study comprises a reassessment of the classical model of lateral extrusion in the eastern alps by using recently published geochronological data sedimentary ages from intramontane basins ages and distribution of magmatic rocks and information from seismic profiles extrusion related faulting continuously propagated from the western toward the central eastern part of the eastern alps during oligocene to middle miocene times this is confined by oblique convergence between the adriatic and european plates during middle miocene times extrusion became not only lateral in terms of parallel to the trend of the eastern alps but was characterized by a displacement vector at a high angle to the strike of the orogen this resulted in the exhumation of the schladming and pohorje blocks that were exhumed within extensional bridges at the northern and southern terminations of the pols lavanttal fault system respectively from middle miocene to recent times extrusion was controlled by overall extension between the dinaric and carpathian subduction zones the influence of north directed compression triggered by the northward moving adriatic plate diminished and the influence of the retreating carpathian subduction zone increased this gave rise to miocene volcanism that is exclusively found east of the dinaric subduction zone we therefore consider that lateral extrusion in the eastern alps can be subdivided into distinct tectonic phases with less pronounced eastward extension related displacement between late oligocene and middle miocene times as soon as the eastern alps passed the dinaric subduction zone the entire domain became highly extensive

geomorphological significance of the palaeodrainage network on a karst plateau the una korana plateau dinaric karst croatia abstract karst plateaus often have a complex geological and geomorphological history it is widely accepted that their development requires a long period of karst denudation this study reconstructs the palaeodrainage network of a karst plateau analyses its properties and establishes its geomorphological significance the main purpose of this research was to deepen our understanding of a key stage in the evolution of karst plateaus the transition from a fluvial land surface to one dominated by karst surface processes the study was conducted on a large part of the una korana plateau the largest plateau in the dinaric karst the majority of the plateau is made of carbonate rocks of triassic jurassic and cretaceous age that set the conditions for the development of the karst we have reconstructed the palaeodrainage network based on 1 25 000 topographic maps with 10 m contours the transition of the surface drainage network to the underground karst drainage network is still in progress so depending on the degree of karstification the drainage network was divided into three categories active dry and relict it was found that 90 5 of the pre existing drainage network has undergone some degree of karstification the active surface drainage network gradually shifted to a dry network then to a relict network the surface drainage network is gradually replaced by a dense network of dolines today the flat and karstified inter fluvial area is drained underground towards the main watercourses and these drain the entire region over the surface towards the pannonian basin this is the largest known karst palaeodrainage network in the dinaric karst that has been reconstructed in this way

modelling recent deformation of the pannonian lithosphere lithospheric folding and tectonic topography article i nfo we investigated the role of lithospheric folding in the quaternary inversion of the pannonian basin by a series of analogue models to this aim build up of stresses due to intraplate compression in the hot and weak pannonian lithosphere changes in the style of deformation and related surface processes were modelled the primary response of the lithosphere to compression appears to be deformation in the form of large scale folding as a consequence of the folding differential crustal motions occur affecting present day surface morphology and landscape processes the analogue experiments examined folding mechanisms of the hot pannonian lithosphere characterised by extremely low strengths except for a thin layer of brittle upper crust modelling results confirmed the existence of a large wavelength 350 400 km component of deformation accounting for large scale vertical crustal motions the amplitude of folding is sufficient to generate the amount of observed uplift and subsidence our analogue models supported by the results of stress analyses suggest that despite the low rate of convergence between the adriatic microplate adria push and the european plate the weak pannonian lithosphere has been an efficient transmitter of compression during the basin inversion crustal thickness variations are of key importance in governing regional deformation pattern and influence the timing and extent of the basin inversion effects of alternating strong and weak units in the brittle crust were also examined by means of two series of conceptual models in which the order of thin and thick crustal blocks was opposite strain localisation in the brittle crust was strongly controlled by the moderate initial thickness variations the concept gives a plausible explanation for the presence of anomalous rates of uplift and subsidence and multi wavelength folding inside the basin models taking into account horizontal movements due to lateral extrusion were constructed with an oblique face of the indenter this kinematic boundary condition resulted in a complex internal structure of the folded layers the presented analogue experiments together with previous numerical modelling studies demonstrate the link between large scale lithospheric folding and topography evolution in the pannonian basin system

modes of orogen parallel stretching and extensional exhumation in response to microplate indentation and roll back subduction tauern window eastern alps the tauern window exposes a paleogene nappe stack consisting of highly metamorphosed oceanic alpine tethys and continental distal european margin thrust sheets in the eastern part of this window this nappe stack eastern tauern subdome etd is bounded by a neogene system of shear the katschberg shear zone system kszs that accommodated orogen parallel stretching orogen normal shortening and exhumation with respect to the structurally overlying austroalpine units adriatic margin the kszs comprises a 5 km thick belt of retrograde mylonite the central segment of which is a southeast dipping low angle extensional shear zone with a brittle overprint katschberg normal fault knf at the northern and southern ends of this central segment the kszs loses its brittle overprint and swings around both corners of the etd to become subvertical dextral and sinistral strike slip faults the latter represent stretching faults whose displacements decrease westward to near zero the kinematic continuity of top east to top southeast ductile shearing along the central low angle extensional part of the kszs with strike slip shearing along its steep ends combined with maximum tectonic omission of nappes of the etd in the footwall of the knf indicates that north south shortening orogen parallel stretching and normal faulting were coeval stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the kszs to have begun at 23 21 ma leading to rapid cooling between 21 and 16 ma this exhumation involved a combination of tectonic unroofing by extensional shearing upright folding and erosional denudation the contribution of tectonic unroofing is greatest along the central segment of the kszs and decreases westward to the central part of the tauern window the kszs formed in response to the indentation of wedge shaped blocks of semi rigid austroalpine basement located in front of the south alpine indenter that was part of the adriatic microplate northward motion of this indenter along the sinistral giudicarie belt offsets the periadriatic fault and triggered rapid exhumation of orogenic crust within the entire tauern window exhumation involved strike slip and normal faulting that accommodated about 100 km of orogen parallel extension and was contemporaneous with about 30 km of orogen perpendicular north south shortening of the etd extension of the pannonian basin related to roll back subduction in the carpathians began at 20 ma but did not affect the eastern alps before about 17 ma the effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the tauern window area therefore we propose that roll back subduction temporarily enhanced rather than triggered exhumation and orogen parallel motion in the eastern alps lateral extrusion and orogen parallel extension in the eastern alps have continued from 12 to 10 ma to the present and are driven by northward push of adria

seismicity and earthquake focal mechanisms in north western croatia article i nfo the seismicity of nw croatia seismically the most vulnerable part of the country is presented based on historical records and reanalysed and relocated earthquakes occurring after 1908 the improved picture of the distribution of seismicity shows consistent grouping of foci in space mostly within eight epicentral areas the database of fault plane solutions has been considerably enlarged and now lists 22 earthquakes the earthquake mechanisms consistently reveal the subhorizontal to moderately dipping p axis predominantly n s directed in the central part of studied area to nw se and ne sw directed in the western and eastern parts respectively they indicate the prevalence of compressional tectonics with reverse faulting in the central part versus strike slip motions in the western and eastern sectors these data are in agreement with stress calculations and kinematics of quaternary structures obtained by geological studies the completeness of the catalogue estimated by comparing the cumulative activity rate for a large number of subcatalogues to the reference contemporary rate exhibits large spatial heterogeneity taking this into account we have computed and mapped the parameters of the frequency magnitude recurrence relation the b value and the activity rate

homogeneous bubble nucleation in rhyolitic melt experiments and nonclassical theory 1 the transfer of volatiles from the earth s interior to the atmosphere occurs through degassing of magma the dynamics of which assert a significant control on volcanic eruptions the first and most critical step in degassing is the nucleation of gas bubbles which requires that a sufficient number of volatile molecules cluster together to overcome the free energy associated with the formation of a new interface between nucleus and surrounding melt this free energy is a function of surface tension typically assumed to equate to the macroscopically measurable value surface tension estimates inferred from bubble nucleation experiments in silicate melts are however lower than direct macroscopic measurements making it difficult to accurately predict magma ascent and decompression rates from measured bubble number densities in pyroclasts we provide a potential resolution to this problem through an integrated study of bubble nucleation experiments and modeling thereof based on nonclassical nucleation theory we find that surface tension between critical bubble nuclei and the surrounding melt depends on the degree of supersaturation and is lower than the macroscopically measured value this is consistent with the view that far from equilibrium the interface between a nucleus and surrounding metastable bulk phase is diffuse instead of sharp as a consequence the increase in nucleation rate with supersaturation is significantly larger at high supersaturations than predicted by classical nucleation theory

simple kinetic models of petroleum formation part ii oil gas cracking kinetic schemes describing oil gas cracking are a required component of models which predict the masses compositions and phases of petroleum expelled from source rocks an additional application is in predicting the temperature zone over which reservoired oil deposits will be degraded to gas this simple first order kinetic model calibrated on closed system laboratory pyrolysis of 16 different source rock samples describes the bulk conversion of oil c6 molecular range to gas c1 5 molecular range cracking rates vary markedly between samples depending on the saturate to aromatic ratio of the generated oil the initial hydrogen index hl0 of the sample taken as an indirect measure of the saturate to aromatic ratio of the oil it generates correlates strongly with optimized rate constants for oil cracking in individual samples thus cracking rates are predictable using a simple routinely performed geochemical screening measurement source rocks with high hl0 tend to generate saturate rich oils with a high mean activation energy and a tight distribution of bond energies which crack relatively slowly over a high but relatively narrow temperature range source rocks with low hl0 generate aromatic rich oils with a low mean activation energy and a broad distribution of bond energies which crack relatively rapidly over a lower but relatively wide temperature range this is an important contributing factor in the observed gas proneness of type iii source rocks with low hl0 the projected cracking window defined limits at 10 90 of initial oil degraded reference heating rate 2 c ma 1 varies from 155 to 205 c in very high quality source rocks hl0 600 mg g c 1 to 115 205 c in very poor quality source rocks hl0 50 mg g c 1 an order of magnitude increase decrease in heating rate elevates depresses these temperature windows by ca 15 c the extrapolations to the geological subsurface are subject to a confidence limit no better than 7 c extrapolation to the reservoir environment requires caution because kerogen an important potential catalyst and hydrogen donor allowing 100 cracking efficiency in the source rock is absent furthermore fractionation during expulsion causes saturate enrichment of expelled ultimately reservoired oils thus in reservoir cracking should be at least as slow as cracking in good quality source rocks and coke or pyrobitumen formation is needed to conserve the hydrogen balance a case history based on deep petroleum pools of the uk central north sea confirms these projections demonstrating no positive evidence of significant in reservoir cracking at temperatures as least as high as 174 c and perhaps even 195 c previous studies have overestimated the importance of in reservoir cracking future studies aiming to predict petroleum composition in traps should concentrate on understanding the charge composition expelled from the kitchen

the evolution of pore scale fluid saturation in low permeability sandstone reservoirs in many tight gas basins of the western united states distinguishing between productive and non productive low permeability sandstones and predicting relative amounts of gas and water production is difficult comparison of gas shows calculated water saturations and saturation height profiles between gas productive and non productive sandstones of equal reservoir quality all appear similar capillary pressure derived height functions are difficult to apply and classic rock typing procedures lack the predictive capability that is common to more traditional reservoirs basin reconstructions suggest the timing of petroleum charge and migration preceded maximum burial and uplift this initial charge was likely a primary drainage displacement with reservoir porosity greater by a factor of 2 3 relative to values found today and permeability greater by 1 3 orders of magnitude these reservoir systems became low permeability following initial charge reflecting continued diagenesis throughout burial subsequent uplift and erosion with burial decreasing pore volume caused water saturations and gas columns to increase during uplift and erosion gas columns adjusted to changing structural configuration in some cases this led to gas accumulations being leaked and spilled in other cases structural readjustment resulted in capillary imbibition and in some cases secondary or higher order drainage and imbibition within trapped accumulations gas expansion upon uplift further increased gas columns in cases where gas columns were spilled or within migration pathways imbibition led to residual or near residual water saturations conventional formation evaluation is fundamentally rooted in concepts associated with primary drainage displacement tight gas reservoirs that have experienced late uplift following an earlier phase of charge are unlikely to be characterized by primary drainage and are much more likely to be characterized by imbibition or secondary or higher order drainage and possibly imbibition the hysteresis between primary drainage and imbibition or secondary or higher order drainage and imbibition in tight gas reservoirs is significant and unlike many more traditional reservoirs does not tend to converge on a narrow range of values estimates of water saturation are scalar values and do not contain information that allows the saturation history and displacement direction to be deciphered recognition that reservoirs are unlikely to be in primary drainage equilibrium is a fundamental paradigm shift that impacts petroleum evaluation at all scales ranging from basin potential to completion decisions within a given well although this paper is written from the perspective of tight gas petroleum systems the principles are equally applicable to low permeability oil reservoirs

characterizing the shale gas resource potential of devonian mississippian strata in the western canada sedimentary basin application of an integrated formation evaluation devonian mississippian strata in the northwestern region of the western canada sedimentary basin wcsb were investigated for shale gas potential in the subsurface thermally mature strata of the besa river horn river muskwa and fort simpson formations attain thicknesses of more than 1 km 0 6 mi encompassing an area of approximately 125 000 km2 48 300 mi2 and represent an enormous potential gas resource total gas capacity estimates range between 60 and 600 bcf section of particular exploration interest are shales and mudrocks of the horn river formation including the laterally equivalent lower besa river mudrocks muskwa formation and upper besa river formation which yield total organic carbon toc contents of up to 5 7 wt fort simpson shales seldom have toc contents above 1 wt horn river and muskwa formations have excellent shale gas potential in a region between longitudes 122w and 123w and latitudes 59n and 60n national topographic system nts 94o08 to 94o15 in this area which covers an areal extent of 6250 km2 2404 mi2 average toc contents are higher 3 wt as determined by wire line log calibrations and have a stratal thickness of more than 200 m 656 ft gas capacities are estimated to be between 100 and 240 bcf section and possibly greater than 400 tcf gas in place a substantial percentage of the gas capacity is free gas caused by high reservoir temperatures and pressures muskwa shales have adsorbed gas capacities ranging between 0 3 and 0 5 cm3 g 9 6 16 scf t at reservoir temperatures of 60 80c 140 176f whereas besa river mudrocks and shales have low adsorbed gas capacities of less than 0 01 cm3 g 0 32 scf t liard basin region because reservoir temperatures exceed 130c 266f potential free gas capacities range from 1 2 to 9 5 cm3 g 38 4 to 304 scf t when total pore volumes 0 4 6 9 are saturated with gas the mineralogy has a major influence on total gas capacity carbonate rich samples indicative of adjacent carbonate platform and embayment successions commonly have lower organic carbon content and porosity and corresponding lower gas capacity 1 toc and 1 porosity seaward of the carbonate slave point edge muskwa and lower besa river mudrocks can be both silica and toc rich up to 92 quartz and 5 wt toc and most favorable for shale gas reservoir exploration because of possible fracture enhancement of the brittle organic and siliceous rich facies however an inverse relation between silica and porosity in some regions implies that zones with the best propensity for fracture completion may not provide optimal gas capacity and a balance between favorable reservoir characteristics needs to be sought

influence of tectonic exhumation on porosity of wufeng longmaxi shale in the fuling gas field of the eastern sichuan basin china thermal cracking of organic matter om can enhance gas shale porosity however thermally matured shales are generally characterized by low porosity with high om content in tectonic exhumation settings the wufeng longmaxi shale in the fuling gas field china was investigated via bulk analysis and scanning electron microscopy to reveal the influence of tectonic exhumation on the porosity of om rich shale thermal maturity and organic and mineralogical compositions are regionally homogeneous in the fuling gas field shale porosity is positively correlated with total organic carbon toc and clay mineral content in the gentle and open anticlines respectively the om hosted pores were preserved with spherical morphologies because of overpressure associated overburden stress unloading in the gentle anticlines whereas om hosted pores in the open anticlines are characterized by high aspect ratios and are regularly aligned perpendicular to lateral compression stress a simple simulation confirmed that tectonic folding and compaction during exhumation caused the loss of porosity in the inner arcs of the open anticlines only pressure shadows formed by assemblages of clay mineral platelets and mechanically competent grains inhibited tectonic compaction of some om hosted pores in the open anticlines tectonic compaction of porosity generally increased the mean value of water saturation in the open anticlines the extremely high water saturation 60 in the high toc interval 2 wt was generally associated with natural fractures suggesting the occurrence of gas leakage

tertiary deformation history from seismic section study and fault analysis in a former european tethyan margin the mecsek villany area sw hungary abstract outcrop scale structural data and seismic section interpretation are combined to unveil a very complicated tertiary deformation history of a once tethyan margin the mecsek villany area of hungary this combination of data helped to reconstruct the possible activity of individual fault zones at least four ene wsw striking zones the northern imbricates the south mecsek zone the gorcsony mariakemend ridge and the villany mountains were confirmed as regional long lived transpressive zones with very complicated internal deformation frequently with oppositely dipping thrust faults tertiary structural history began with a roughly n s directed shortening in the south mecsek zone it was followed by a ne sw directed transpression activating practically all important wrench zones together with perpendicular transfer faults basins were created along some of these deformation zones but were also affected by major tilts due to inversion after a relatively quiescent period in the middle miocene the late sarmatian inversion followed shortly after this event was relayed by a ne sw directed extension transtension an important inversion period characterised by nw se compression occurred in late pannonian messinian when all the former wrench zones were reactivated as right lateral shear this event is responsible for the present topography of the region

understanding of hc migration in sedimentary basins present state of knowledge abstract great advances were made during the decade of 1975 1985 in the understanding of hc migration by establishing that the main mechanisms were polyphasic flow whatever its stage and that migration in solution in water and or by molecular diffusion was insignificant except for methane ethane and benzene research is now focusing on points which still have not been satisfactorily answered such as 1 1 behaviour of source rocks during hc expulsion the main driving force for fluid expulsion has been recognized to be excess fluid pressure within the source rock with respect to its surrounding environment of permeable beds the pressure build up is due mainly to accommodation by the fluids of part of the mechanical stresses which are exerted on the rock mainly sedimentary load but also stresses developed by tectonics to thermal expansion of water and to hc formation from kerogen in response to increasing temperatures however it is not clear whether or not petroleum expulsion proceeds preferentially along oil wet networks kerogen or oil wet mineral surfaces nor it is not clear whether or not microfracturing provoked by an internal fluid pressure higher than allowed by the mechanical strength of source rocks is necessary for hc expulsion 2 2 modifications of the compositions of hc phases e g oil versus gas or the distribution of biomarkers during migration and losses of hydrocarbons along the migration pathways although careful observations of natural sample series and also experimentation have been done no clear picture has emerged for the moment however compositional effects seem to be due more to changes in thermodynamic conditions along migration pathways which provoke inter alia hydrocarbon phase separation retrograde condensation than to differential retention by mineral surfaces it is likely that while careful observations on a large variety of source rock samples are needed to more clearly understand source rocks functioning progress in understanding hc migration will come increasingly from modeling and experimentation models which mathematically simulate natural processes are necessary to help the human mind in handling such complex phenomena and therefore are of precious help to focus research on the most important points they replace migration in its geological and historical dimensions with numerical or conceptual tools while observation only describes the present state models are also the tools by which knowledge on migration can be applied to exploration problems however quantitative applications of models require numerous and precise geological data that are difficult to gather at early stages of exploration in the field of experimentation it will be easier to design crucial experiments now that hc migration mechanisms are better understood thanks to experimentation it should also be possible to validate models however so as to reach such aims substantial progress has to be made in the technology of experimental systems

tertiary paleomagnetic results and structural analysis from the transdanubian range hungary rotational disintegration of the alcapa unit abstract we carried out an integrated paleomagnetic and structural study in the transdanubian range western and central hungary as a result the tertiary tectonic history of this area can be characterized by three events of counterclockwise ccw rotation and four or five phases of brittle deformation the change of the orientation of stress axes between phases is mainly apparent and reflects the rotation of the faults predating a particular rotation event the first two rotation events r1 and r2 were probably governed by the rollback mechanism of the subducting european plate we suggest that these rotations were taking place from 18 17 and 16 14 5 ma respectively i e simultaneously with the rotations of the north hungarian paleogene basin and the main part of the western carpathians however the angle of both rotations was less in the transdanubian range due to increasing distance from the subduction front the differential rotation was accommodated by extensional faulting by formation of a graben system on the other hand the youngest rotation event r3 seems to be connected to the renewed rotation of the adriatic plate around 5 ma our combined data set strongly supports earlier conclusions namely that the different subunits of the eastern alpine western carpathian northern pannonian unit alcapa did not form a rigid unit although they moved in similar manner

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

the tectonic evolution of a critical segment of the dinarides alps connection kinematic and geochronological inferences from the medvednica mountains ne croatia the transition zone between the alps and dinarides is a key area to investigate kinematic interactions of neighboring orogens with different subduction polarities a study combining field kinematic and sedimentary data microstructural observations thermochronological data rb sr and fission track and regional structures in the area of medvednica mountains has revealed a complex polyphase tectonic evolution we document two novel stages of extensional exhumation the first stage of extension took place along a late cretaceous detachment following the late early cretaceous nappe stacking burial and greenschist facies metamorphism two other shortening events that occurred during the latest cretaceous oligocene were followed by a second event of extensional exhumation characterized by asymmetric top ne extension during the miocene top nw thrusting took place subsequently during the pliocene inversion of the pannonian basin the cretaceous nappe burial late cretaceous extension and the oligocene earliest miocene contraction are events driven by the alps evolution in contrast the latest cretaceous eocene deformation reflects phases of dinaridic contraction furthermore the miocene extension and subsequent inversion display kinematics similar with observations elsewhere in the dinarides and eastern alps all these processes demonstrate that the medvednica mountains were affected by alpine phases of deformations to a much higher degree than previously thought similarly with what has been observed in other areas of contractional polarity changes such as the mediterranean black sea or new guinea systems the respective tectonic events are triggered by rheological weak zones which are critical for localizing the deformation created by both orogens

paleogeographic evolution of the southern pannonian basin 40ar 39ar age constraints on the miocene continental series of northern croatia the pannonian basin originating during the early miocene is a large extensional basin incorporated between alpine carpathian and dinaride fold thrust belts back arc extensional tectonics triggered deposition of up to 500 m thick continental fluvio lacustrine deposits distributed in numerous sub basins of the southern pannonian basin extensive andesitic and dacitic volcanism accompanied the syn rift deposition and caused a number of pyroclastic intercalations here we analyze two volcanic ash layers located at the base and top of the continental series the lowermost ash from mt kalnik yielded an 40ar 39ar age of 18 07 0 07 ma this indicates that the marine continental transition in the slovenia zagorje basin coinciding with the onset of rifting tectonics in the southern pannonian basin occurs roughly at the eggenburgian ottnangian boundary of the regional paratethys time scale this age proves the synchronicity of initial rifting in the southern pannonian basin with the beginning of sedimentation in the dinaride lake system beside geodynamic evolution the two regions also share a biotic evolutionary history both belong to the same ecoregion which we designate here as the illyrian bioprovince the youngest volcanic ash level is sampled at the glina and karlovac sub depressions and both sites yield the same 40ar 39ar age of 15 91 0 06 and 16 03 0 06 ma respectively this indicates that lacustrine sedimentation in the southern pannonian basin continued at least until the earliest badenian the present results provide not only important bench marks on duration of initial synrift in the pannonian basin system but also deliver substantial backbone data for paleogeographic reconstructions in central and southeastern europe around the early middle miocene transition

mesozoic plate tectonic reconstruction of the carpathian region abstract palaeomagnetic palaeobiogeographic and structural comparisons of different parts of the alpine carpathian region suggest that four terranes comprise this area the alcapa tisza dacia and adria terranes these terranes are composed of different mesozoic continental and oceanic fragments that were each assembled during a complex late jurassic cretaceous palaeogene history palaeomagnetic and tectonic data suggest that the carpathians are built up by two major oroclinal bends the alcapa bend has the meliata oceanic unit correlated with the dinaric vardar ophiolite in its core it is composed of the western carpathians eastern alps and southern alcapa units transdanubian range bukk this terrane finds its continuation in the high karst margin of the dinarides further elements of the alcapa terrane are thought to be derived from collided microcontinents czorsztyn in the n and a carbonate unit tisza in the se the tisza dacia bend has the vardar oceanic unit in its core it is composed of the bihor and getic microcontinents this terrane finds its continuation in the serbo macedonian massif of the balkans the bihor getic microcontinent originally laid east of the western carpathians and filled the present carpathian embayment in the late palaeozoic early mesozoic the vardar ocean occupied an intermediate position between the western carpathian austroalpine transdanubian high karst margin and the bihor getic serbo macedonian microcontinent the vardar and pindos oceans were opened in the heart of the mediterranean adriatic microcontinent in the late permian middle triassic vardar subducted by the end of jurassic causing the bihor getic serbo macedonian microcontinent to collide with the internal dinaric western carpathian margin an external penninic vahic ocean tract began opening in the early jurassic separating the austroalpine western carpathian microcontinent and its fauna from the european shelf further east the severin ceahlau magura also began opening in the early jurassic but final separation of the bihor getic ribbon and its fauna from the european shelf did not take place until the late middle jurassic the alcapa and the tisza dacia were bending during the albian maastrichtian the two oroclinal bends were finally opposed and pushed into the gates of the carpathian embayment during the palaeogene and neogene at that time the main n s shortening in distant alpine and hellenic sectors was linked by a broader right lateral shear zone along the former vardar suture

primary migration by oil generation microfracturing in low permeability source rocks application to the austin chalk texas fracturing of low permeability source rocks is induced by pore pressure changes caused by the conversion of organic matter to less dense fluids oil and gas these fractures increase the permeability and provide pathways for hydrocarbon migration an equation for the pressure change is derived using four major assumptions 1 the permeability of the source rock is negligibly small 0 01 d 10 20 m2 so that the pore pressure buildup by the conversion is much faster than its dissipation by pore fluid flow 2 the stress state is isotropic so that horizontal and vertical stresses are equal the source rock fails when the pore pressure equals the overburden pressure 3 the properties of the rock organic matter and fluids remain constant during oil generation this assumption is valid when the change in depth i e pressure and temperature is small 4 only two reaction rates are required for the conversions a low temperature reaction rate for the kerogen oil conversion e approx 24 kcal mol a approx 1014 m y and a high temperature reaction rate for oil gas conversion e approx 52 kcal mol a approx 5 5 1026 m y the equations for generation rate and pressure change are applied to the austin source rock by adjusting the several variables to fit geochemical data core saturations and observed levels of oil and gas production this application demonstrates that the equations are easily applied in calculating depths of primary migration for low permeability source rocks

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

regional velocity depth anomalies north sea chalk a record of overpressure and neogene uplift and erosion a normal velocity depth trend for the upper cretaceous danian chalk group is determined by identifying interval velocity data that represent maximum burial in areas unaffected by overpressuring these data are derived from 845 wells throughout the north sea basin data from pelagic carbonate deposits on a stable plateau constrain the trend for shallow depths positive velocity anomalies relative to the trend are mapped along the western and eastern margins of the north sea basin and reflect regional neogene uplift and erosion of up to 1 km along the present day limit of the chalk a hiatus at the base of the quaternary increases in magnitude away from the basin center where a complete cenozoic succession is found this hiatus is consistent in size with the missing section estimated from chalk velocities when allowance is made for the quaternary reburial of the chalk negative velocity anomalies in the central and southern parts of the basin outline an area within which overpressures in the chalk exceed 10 mpa equivalent to a burial anomaly greater than 1 km relative to the normal trend the chalk pressure system is primarily dependent on overburden properties because retention of overpressure generated by the load of the upper overburden depends on the thickness and sealing quality of the lower overburden therefore the chalk is considered to represent a regional aquitard and the hydrodynamic model of long distance migration within the chalk is rejected the neogene uplift and erosion of the margins of the north sea basin and the rapid late cenozoic subsidence of its center fit into a pattern of late cenozoic vertical movements around the north atlantic

mississippian barnett shale fort worth basin north central texas gas shale play with multi trillion cubic foot potential the mississippian barnett shale serves as source seal and reservoir to a world class unconventional natural gas accumulation in the fort worth basin of north central texas the formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce at present production is mainly confined to a limited portion of the northern basin where the barnett shale is relatively thick 300 ft 92 m organic rich presentday total organic carbon 3 0 thermally mature vitrinite reflectance 1 1 and enclosed by dense limestone units able to contain induced fractures the most actively drilled area is newark east field currently the largest gas field in texas newark east is 400 mi 2 1036 km 2 in extent with more than 2340 producing wells and about 2 7 tcf of booked gas reserves cumulative gas production from barnett shale wells through 2003 was about 0 8 tcf wells in newark east field typically produce from depths of 7500 ft 2285 m at rates ranging from 0 5 to more than 4 mmcf day estimated ultimate recoveries per well range from 0 75 to as high as 7 0 bcf efforts to extend the current barnett play beyond the field limits have encountered several challenges including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth patterns of oil and gas occurrence in the barnett in conjunction with maturation and burial history data indicate a complex multiphased thermal evolution with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas

apparent polar wander path for adria extended by new jurassic paleomagnetic results from its stable core tectonic implications abstract as a continuation of a systematic paleomagnetic research in the northern part of stable adria which provided a well defined apparent polar wander apw path for the cretaceous eocene we present new paleomagnetic results for the jurassic these new data were obtained from 15 geographically distributed localities from the trento platform eastern southern alps using standard paleomagnetic approach the lower jurassic shallow water carbonates are not considered for tectonic interpretation due to inconsistent inclinations the middle and upper jurassic rosso ammonitico provided excellent kinematic constraints with the new jurassic results an apw is now defined for adria for the 167 40 ma interval it is well constrained for timing of important changes like the speed and the sense of rotations this apw suggests that the cw rotation and southward shift changed to the opposite at 155 1 5 3 ma signifying a dramatic change in the life of the neo tethys from opening to closing the latter is manifested in fast ccw rotation and northward movement of adria up to 102 9 2 4 ma and moderate displacements in the same manner in post 103 ma times combined data sets from stable istria and the foreland of the southern alps point to an approximately 15 cw rotation with respect to africa at the end of the cretaceous and an about 25 in the ccw sense after the eocene

palaeomagnetic evidence for tertiary counterclockwise rotation of adria abstract with the aim of obtaining tertiary palaeomagnetic directions for the adriatic foreland of the dinaric nappe system we carried out a palaeomagnetic study on platform carbonates from stable istria from the northwestern and the central dalmatia segment of imbricated adria despite the weak to very weak natural remanences of these rocks we obtained tectonically useful palaeomagnetic directions for 25 sites from 20 localities all exhibit westerly declinations both before and after tilt correction concerning the age of the magnetizations we conclude that five subhorizontal and magnetite bearing eocene localities from stable istria are likely to carry primary remanence whereas three tilted and hematite bearing ones were remagnetized in the northwestern segment of imbricated adria the cluster of the mean directions improved after tectonic correction indicating pre tilting magnetization in contrast maastrichtian eocene platform carbonates from central dalmatian were remagnetized in connection with the late eocene oligocene deformation or miocene hydrocarbon migration based on the appropriate site locality means we calculate mean palaeomagnetic directions for the above three areas and suggest an alternative interpretation of the data of kissel et al j geophys res 100 1995 14999 for the flysch of central dalmatia the four area mean direction define a regional palaeomagnetic direction of dec 336 inc 52 k 107 95 9 from these data we conclude that stable istria in close coordination with imbricated adria must have rotated by 30 counterclockwise in the tertiary relative to africa and stable europe we suggest that the latest miocene early pliocene counterclockwise rotations observed in northwestern croatia and northeastern slovenia were driven by that of the adriatic foreland i e the rotation of the latter took place between 6 and 4 ma

the effect of magma flow on nucleation of gas bubbles in a volcanic conduit abstract we solve the dynamics of magma ascent and the kinetics of bubble nucleation and growth simultaneously which allow us to predict bubble sizes and number densities under ascent conditions as magma rises toward the surface the pressure decreases and eventually becomes less than the solubility pressure when the degree of supersaturation becomes great enough bubbles nucleate nucleation will stop as the concentration of volatiles in the melt decreases due to growth of existing bubbles and hence the degree of supersaturation decreases we show that a second nucleation event may occur just below the fragmentation level near that level the degree of supersaturation continuously increases as the magma is rapidly decompressed as a result nucleation will not stop until fragmentation occurs this second nucleation event should be taken into account when interpreting bubble size distribution measurements made on natural pumices the bubbles of the second nucleation event have high internal gas pressures up to 2 mpa greater than the liquid pressure suggesting that the second nucleation event may enhance fragmentation of magma we apply the model to the calculation protocol defined at the volcanic eruption mechanism modeling workshop durham 2002 we found that as a result of disequilibrium degassing fragmentation occurs higher in the conduit than under equilibrium degassing

surface tension of hydrous silicate melts constraints on the impact of melt composition abstract the first step in magma degassing is the nucleation of gas bubbles the ability of magma to nucleate bubbles is moderated by its surface tension which is thought to vary with melt composition temperature and h2o content numerous experimental studies of bubble nucleation in silicate melts have quantified surface tension but those experiments have been run at different temperatures and used melts with different dissolved h2o contents the influence of bulk melt composition may thus be masked in this study we decompress hydrous silicate melts that range from phono tephrite to high silica rhyolite to investigate conditions needed to trigger homogeneous bubble nucleation importantly dissolved water contents are very similar amongst the melts and all were decompressed at 1150 1200 c isolating the influence of melt composition on bubble nucleation despite the 25 wt range in sio2 content both the total pressure drop and the degree of supersaturation needed to trigger bubble nucleation vary a little because supersaturation varies little for all melts falls to fall within a relatively narrow range of 0 065 to 0 080 n m 1 in addition for an even wider range of anhydrous melts is nearly constant although five times higher it thus appears that the bulk composition of silicate melt has little impact on it is also known that the variation in with temperature is minor and thus most differences between measured values probably result from differences in h2o content

in the wake of a counterclockwise rotating adriatic microplate neogene paleomagnetic results from northern croatia in northern croatia the neogene sediments cover complicated basement rocks which consist of alpine and dinaridic elements in the zagorje area and variscan alpine formations of the tisia tisza megatectonic unit in the slavonian mountains mts the neogene sediments were deposited in two separate basins before the karpatian but sedimentation became uniform from the karpatian onwards 17 5 ma of the 24 localities that we have studied so far paleomagnetically from northern croatia 16 localities are of karpatian or younger age while the rest are pre karpatian

preservation of lateral pressure disequilibrium during the uplift of shale reservoirs a pressure gradient increase from normal pressure in oil zones to overpressure in dry gas zones indicates a lateral disequilibrium of pore pressure in many shale reservoirs in this work conditions for the preservation of the lateral pressure disequilibrium during uplift and erosion are investigated numerical simulations were conducted by coupling pressure volume temperature pvt and fluid dynamic calculations results show that temperature decrease and pore volume expansion during erosion tends to increase the pressure gradient in the gas or condensate zone and tends to decrease the pressure gradient in the black oil zone therefore the pvt effect tends to enhance lateral pressure disequilibrium during erosion low permeability is crucial for the preservation of the lateral pressure disequilibrium the persistence of disequilibrium over geological time tens of millions of years requires extremely small vertical permeability sub picodarcy range and horizontal permeability 10 nd or even lower the horizontal permeability is 10 100 times smaller than laboratory measurements on shale plugs indicating a discontinuity of laminations and fractures within a shale formation

first post ir irsl dating results of quaternary deposits from bilogora ne croatia implications for the pleistocene relative uplift and incision rates in the area abstract bilogora is a hilly terrain in the sw pannonian basin along the sw margin of the drava depression in croatia it is genetically linked to the tectonic evolution of the drava depression during the neogene and quaternary and the associated palaeo drava river system the quaternary sedimentary succession is represented by four aggradational drava river terraces composed of thick series of gravel intercalated by sand silt and clays stratigraphically the oldest terraces exposed in the investigated area are unconformably overlain by pleistocene loess and loess like deposits in order to establish a chronological framework of the quaternary deposits luminescence dating was applied on loess and loess like sediments as well as sand intercalated within the terrace gravel deposits the dating was performed on feldspar coarse grains from the sand and on the polymineral fine grained material from loess using the pirir 290 protocol the luminescence signals of the sand are in saturation and therefore very likely point to a middle pleistocene age of the river terrace whereas the covering loess can be correlated to the last glacial the obtained pirir 290 dating results indicate the timing of the abandonment of the investigated river terrace whereas the relation of the relative displacement values of the investigated river terrace to the obtained age could imply the relative uplift rates of the area according to the relative displacement values sampling heights above the present drava river level and the obtained pirir 290 ages of 359 ka and 450 ka the calculated relative uplift rates were 0 56 mm a for mucna reka and 0 43 mm a for cabuna for the same sampling locations the calculated relative incision rates of the drava river were of 0 09 and 0 22 mm a the results of relative uplift rates show a higher value concentrated in the nw part of bilogora being associated with multiple mapped neotectonic active faults in the drava depression boundary fault zone and kalnik mt fault zone on the other hand the low incision rates that probably accommodate a portion of the tectonic uplift of bilogora point to lower erosion of the paleo drava river moreover the drava river is dominated by the aggradation of alluvial deposits during the quaternary we believe that the computed incision rates represent only one relative portion of the drava process whereas the tectonics sediment transportation and accumulation were dominant processes in the study area and can be correlated with the climate oscillations during the pleistocene and holocene

application of stacking and inversion techniques to three dimensional wide angle reflection and refraction seismic data of the eastern alps summary we present new methods for the interpretation of 3 d seismic wide angle reflection and refraction data with application to data acquired during the experiments celebration 2000 and alp 2002 in the area of the eastern alps and their transition to the surrounding tectonic provinces bohemian massif carpathians pannonian domain dinarides data was acquired on a net of arbitrarily oriented seismic lines by simultaneous recording on all lines of seismic waves from the shots which allows 2 d and 3 d interpretations much 80 of the data set consists of crossline traces low signal to noise s n ratio in the area of the young orogens decreases the quality of travel time picks in these seismically heterogeneous areas it is difficult to assign clearly defined arrivals to the seismic phases in particular on crossline record sections in order to enhance the s n ratio signal detection and stacking techniques have been applied to enhance the pg pn and pmp phases further inversion methods have been developed for the interpretation of war r data based on automated 1 d inversion pg and the application of the delay time concept pn the results include a 3 d velocity model of the crust based on pg waves time and depth maps of the moho and a pn velocity map the models based on stacked data are robust and provide a larger coverage than models based on travel time picks from single fold unstacked traces but have relatively low resolution especially near the surface they were used as the basis for constructing models with improved resolution by the inversion of picks from single fold data the results correlate well with geological structures and show new prominent features in the eastern alps area and their surrounds the velocity distribution in the crust has strong lateral variations and the moho in the investigation area appears to be fragmented into three parts

mechanisms of shale gas storage implications for shale gas exploration in china this article reviews the mechanisms of shale gas storage and discusses the major risks or uncertainties for shale gas exploration in china at a given temperature and pressure the gas sorption capacities of organic rich shales are primarily controlled by the organic matter richness but may be significantly influenced by the type and maturity of the organic matter mineral composition especially clay content moisture content pore volume and structure resulting in different ratios of gas sorption capacity gsc to total organic carbon content for different shales in laboratory experiments the gsc of organic rich shales increases with increasing pressure and decreases with increasing temperature under geologic conditions assuming hydrostatic pressure gradient and constant thermal gradient the gsc increases initially with depth due to the predominating effect of pressure passes through a maximum and then decreases because of the influence of increasing temperature at greater depth this pattern of variation is quite similar to that observed for coals and is of great significance for understanding the changes in gsc of organic rich shales over geologic time as a function of burial history at an elevated temperature and pressure and with the presence of moisture the gas sorption capacities of organic rich shales are quite low as a result adsorption alone cannot protect sufficient gas for high maturity organic rich shales to be commercial gas reservoirs two models are proposed to predict the variation of gsc and total gas content over geologic time as a function of burial history high contents of free gas in organic rich shales can be preserved in relatively closed systems loss of free gas during postgeneration uplift and erosion may result in undersaturation the total gas contents lower than the sorption capacity and is the major risk for gas exploration in marine organic rich shales in china

cenozoic exhumation of the southern british isles rocks that crop out across southern britain were exhumed from depths of as much as 2 5 km during cenozoic time this has been widely attributed to paleocene regional uplift resulting from igneous underplating related to the iceland mantle plume our compilation of paleothermal and compaction data reveals spatial and temporal patterns of exhumation showing little correspondence with the postulated influence of underplating instead being dominated by kilometer scale variations across cenozoic compressional structures which in several basins are demonstrably of neogene age we propose that crustal compression due to plate boundary forces transmitted into the plate interior was the major cause of cenozoic uplift in southern britain witnessing a high strength crust in western europe

overpressure generation and evolution in lower paleozoic gas shales of the jiaoshiba region china implications for shale gas accumulation abstract overpressured shale gas plays have been found in the lower paleozoic marine shales of jiaoshiba region in the sichuan basin china the black shales from the upper ordovician wufeng group o3w and the lower part of lower silurian longmaxi group s1l are the producing reservoirs overpressure is widespread in the o3w s1l shales with the pressure coefficient up to 1 74 fluid inclusion microthermometric and raman spectroscopic techniques pvt and basin modeling are used to investigate overpressure generation and evolution in the o3w s1l shales the results show that thermocatalytic dry gas generation is the main genetic mechanism for overpressure development in the o3w s1l shales with specific characteristics as follows 1 the maximum burial depth of overpressured shales is more than 6200 m without anomalously low density and high primary porosity according to wireline log and core data 2 the over mature o3w s1l shales with the mean toc values ranging from 3 36 wt to 4 48 wt and the vitrinite reflectance values of 2 7 2 9 ro determined by kerogen ftir fourier transform infrared spectroscopy characteristics has excellent potential to produce dry gas 3 overpressured reservoirs are characterized by high gas saturations and the pressure coefficients positively correlate with gas saturation 4 the abnormally high pressures recorded in the fluid inclusions are coincident with high homogenization temperatures which is supportive of overpressure occurring during dry gas generation and provides convincing in situ evidence for gas generation overpressuring the calculated pore fluid pressures for methane inclusions within the maximum buried o3w s1l shales are approximately 90 3 139 4 mpa suggesting that gas generation produced a maximum pressure gradient of 23 1 mpa km which is equivalent to the lithostatic magnitudes the overpressure evolution in the o3w s1l shales is noticed to have evolved through four stages a rapidly increasing overpressure caused by thermocatalytic gas generation 145 85 ma a rapid pressure release 85 61ma overpressure preservation 61 20 ma and a relatively slow pressure release 20 ma present during post generation evolution 85 ma present of the o3w s1l shales both the overpressure and pressure coefficients decreased with time due to the intensive tectonic uplifts and denudation and approximately 19 0 28 5 of the initial total gas content was continuously released until the present day overpressure state the study of overpressure evolution in the o3w s1l shales provides basic information for the further study of the conversion between adsorbed gas and free gas and the method and technique used in this study to stress the overpressure generation and evolution may be generally applied to other overpressured or normally pressured shale gas systems

on the formation and evolution of the pannonian basin constraints derived from the structure of the junction area between the carpathians and dinarides 1 the large number and distribution of rollback systems in mediterranean orogens infer the possibility of interacting extensional back arc deformation driven by different slabs the formation of the pannonian back arc basin is generally related to the rapid miocene rollback of a slab attached to the european continent a key area of the entire system that is neglected by kinematic studies is the connection between the south carpathians and dinarides in order to derive an evolutionary model we interpreted regional seismic lines traversing the entire serbian part of the pannonian basin the observed deformation is dominantly expressed by the formation of miocene extensional detachments and half grabens the extensional geometries and associated synkinematic sedimentation that migrated in time and space allow the definition of a continuous and essentially asymmetric early to late miocene extensional evolution this evolution was followed by the formation of few uplifted areas during the subsequent latest miocene quaternary inversion the present day extensional geometry changing the strike across the basin is an effect of the clockwise rotation of the south carpathians and apuseni mountains in respect to the dinarides our study infers that the carpathian rollback is not the only mechanism responsible for the formation of the pannonian basin an additional middle miocene rollback of a dinaridic slab is required to explain the observed structures furthermore the study provides constraints for the pre neogene orogenic evolution of this junction zone including the affinity of major crustal blocks obducted ophiolitic sequences and the sava suture zone

equivalent linear site response analysis on the site of the historical trakoscan castle croatia using hvsr method this paper presents a major extension of seismic vulnerability research project on the site of trakoscan castle based on the initial horizontal to vertical spectral ratio hvsr results from stanko et al 2016 the estimated hvsr site frequencies and hv amplification at trakoscan castle can only be used as an indication of the initial soil site frequency and amplification so called natural soil model corresponding to the subsoil profile without the influence of an earthquake the equivalent linear eql site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration pgarock that corresponds to return periods of 95 0 08 g 475 0 18 g and 1000 years 0 31 g the aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect which is the result of an alluvial basin and topographic influences the main objective of this research is the formation of local microseismic zones based on an eql analysis surface spectral acceleration and amplification maps at the predominant frequency based on the hvsr frequency response of the core structure of trakoscan castle and the tower itself fundamental and higher frequency modes maps of surface spectral acceleration and soil amplification at different frequencies 3 5 and 10 hz are developed for different input pgarock levels 0 08 0 18 and 0 31 g to evaluate seismic response of the castle observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop shortening of predominant frequencies lengthening of the period particularly in the alluvial basin has been observed with higher input pgarock in the eql analysis this effect is not manifested in the trakoscan hill and predominant frequencies match hvsr frequencies the use of certain geophysical survey methods at historical sites is a big problem because terrain features e g steep hills mountains ridges slopes cliffs create lack of space and make it impossible to carry out geophysical investigation microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity also computational modelling can greatly improve the results the eql site response analysis on the site of trakoscan castle has confirmed and improved the results of seismic response and vulnerability based on hvsr method

characterization of pore pressure fracture pressure shear failure and its implications for drilling wellbore stability and completion design a case study from the takouazet field illizi basin algeria abstract this work presents the assessment of overburden stress pore pressure and fracture pressure distribution in the paleozoic stratigraphic units in the takouazet field eastern illizi basin algeria we studied a vertical exploration well where significant hydrocarbon discoveries have been established in devonian and ordovician sandstone reservoirs overburden stress interpreted from density log has an average 1 07 psi ft 24204 04 pa m gradient pore pressure derived from sonic log reveals that hydrostatic conditions prevail in devonian and ordovician units whereas abnormal pore pressure with a maximum 0 66 psi ft 14929 60 pa m gradient was recorded against the marine silurian shale fracture pressure was modeled using effective stress ratio models as well as a poisson s ratio based approach rock property based fracture pressure estimate is more sensitive to lithological variations and hence this estimate was used for determining safe drilling mud window and casing placements the estimated pore pressure and fracture pressure were calibrated with direct downhole formation pressure measurements and leakoff test lot measurements respectively shear failure using mohr coulomb rock failure criterion detected the minimum allowable mud pressure to avoid wellbore instability issues and the result was validated with caliper log observations it indicated that solid production from the reservoir is very likely during initial production from the reservoir and a solid control mechanism has been suggested also widening of breakouts and deteriorating wellbore interpreted from time lapse formation imaging logs strongly suggest against open hole completion based on interpreted pressure gradients and image log analyses optimum drilling mud and casing design and completion policies were recommended for safe and successful operational planning

principles of geochemical prospect appraisal our current understanding of the geochemical processes responsible for the creation of commercial accumulations of oil and gas can be reduced to simple rules and equations to allow the petroleum geologist to use geochemistry to estimate before drilling the likely volumes and compositions of oil and gas delivered to the trap in most sedimentary basins oil is expelled from source rocks between 120 and 150 c whereas most gas and gas condensate are released between 150 and 230 c when the initial potential of source rocks exceeds 10kg mt oil expulsion efficiencies are between 60 and 90 expelled oil and gas migrate as petroleum rich phases driven by fluid potential gradients most flow is laterally updip in beds with effective horizontal permeabilities greater than 1 md in lower permeability rocks the petroleum fluids move vertically up or down along the path of least resistance i e the most permeable or thinnest beds separating them from a high permeability lateral carrier bed the residual saturations of petroleum left behind along the migration pathway are of the order of a few percent of the porosity geochemical analysis of source rocks helps determine the yields and compositions of petroleum fluids expelled in the catchment area of a prospect these fluid masses are converted to volumes from knowledge of the phase relations and densities of petroleum fluids evaluation of the total volume of rock through which the petroleum potentially can migrate and the mean porosity of the rocks that constitute the migration pathway allow migration losses to be assessed these losses constrain both the range of migration of petroleum fluids away from the mature source rock and the volumes of petroleum remaining for entrapment in the prospect

tectonic units of the alpine collision zone between eastern alps and western turkey abstract we present a map that correlates tectonic units between alps and western turkey accompanied by a text providing access to literature data explaining the concepts used for defining the mapped tectonic units and first order paleogeographic inferences along strike similarities and differences of the alpine eastern mediterranean orogenic system are discussed the map allows 1 for superimposing additional information such as e g post tectonic sedimentary basins manifestations of magmatic activity onto a coherent tectonic framework and 2 for outlining the major features of the alpine eastern mediterranean orogen dinarides hellenides anatolides and taurides are orogens of opposite subduction polarity and direction of major transport with respect to alps and carpathians and polarity switches across the mid hungarian fault zone the dinarides hellenides taurides and apennines consist of nappes detached from the greater adriatic continental margin during cretaceous and cenozoic orogeny internal units form composite nappes that passively carry ophiolites obducted in the latest jurassic earliest cretaceous or during the late cretaceous on top of the greater adriatic margin successions the ophiolites on top of composite nappes do not represent oceanic sutures zones but root in the suture zones of neotethys that formed after obduction suturing between greater adria and the northern and eastern neotethys margin occupied by the tisza and dacia mega units and the pontides occurred in the latest cretaceous along the sava izmir ankara erzincan suture zones the rhodopian orogen is interpreted as a deep crustal nappe stack formed in tandem with the carpatho balkanides fold thrust belt now exposed in a giant core complex exhumed in late eocene to miocene times from below the carpatho balkan orogen and the circum rhodope unit its tectonic position is similar to that of the sakarya unit of the pontides we infer that the rhodope nappe stack formed due to north directed thrusting both rhodopes and pontides are suspected to preserve the westernmost relics of the suture zone of paleotethys

magma fragmentation in eruptions a process known as fragmentation is how erupting magma from a volcano breaks up into fine particles and ash and it determines the type of eruption gentle or violent that occurs theoretical and laboratory studies show that treating magma as a brittle material can explain its behaviour at the point of fragmentation when it is transformed from a foam into a gassy spray

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

the link between tectonics and sedimentation in asymmetric extensional basins inferences from the study of the sarajevo zenica basin abstract the coupled tectonic and depositional history of extensional basins is usually described in terms of stratigraphic sequences linked with the activity of normal faults this depositional kinematic interplay is less understood in basins bounded by major extensional detachments or normal fault systems associated with significant exhumation of footwalls of particular interest is the link between tectonics and sedimentation during the migration of normal faulting in time and space across the basin one area where such coupled depositional kinematic history can be optimally studied is the late oligocene miocene sarajevo zenica basin located in the dinarides mountains of bosnia and herzegovina this intra montane basin recorded oligocene pliocene sedimentation in an endemic and isolated lake environment we use field kinematic and sedimentological mapping in outcrops correlated with existing local and regional studies to derive a high resolution evolutionary model of the basin the novel results demonstrate a close correlation between moments of normal faulting and high order sedimentological cycles while the overall extensional basin was filled by a largely uni directional sediment supply from the neighbouring mountain chain the migration in time and space of listric ne dipping normal faults was associated with a gradual shift of the sedimentological environment transgressive regressive cycles reflect sequential displacements on normal faults and their footwall exhumation defining a new sedimentological model for such basins this early middle miocene extension affected the central part of the dinarides and was associated with the larger opening of the neighbouring pannonian basin the extension was preceded and followed by two phases of contraction the oligocene early miocene thrusting took place during the final stages of the dinarides collision while the post middle miocene contraction is correlated with the regional indentation of the adriatic continental unit this latter phase inverted the extensional basin by reactivating the inherited basal listric detachment

seismic response and vulnerability of historical trakoscan castle croatia using hvsr method the trakoscan castle was built on the rocky peak of the hill in the thirteenth century castle structure has weakened with time wars inappropriate protection and earthquakes on 16 march 1982 the tower castle and part of second floor were damaged by an earthquake ml 4 5 with an epicenter 20 km distance from mt ivancica afterwards it was completely reconstructed today the cultural heritage of the trakoscan castle is protected as a historical entity by the republic of croatia the horizontal to vertical spectral ratio hvsr method was applied for the purpose of local seismic response protection from earthquake structural seismic vulnerability of weak points and structural restoration of the trakoscan castle related to the 1982 earthquake microtremor measurements in free field and in the tower castle the free field hvsr results soil fundamental frequencies amplification factors shear wave velocity distribution estimated bedrock depth and directional effects on ground motion are compared to the local geology propagation path and topographic effects to the estimated local seismic response the dynamic behavior of the tower castle is demonstrated along different axes by the comparison of the directional hvsr analysis to the horizontal components ns v and ew v and the amplitude spectra ns ew and ud the modal frequency response identifies weak points of the tower castle structure based on the hvsr analysis the damage at trakoscan site related to the 1982 earthquake occurred due to the local geology and topographic effects seismic energy directed through the alluvial basin and trapped into the hill and the improper way of the tower castle construction in the past and the reconstruction after the earthquake

constraining burial history and petroleum charge in exhumed basins new insights from the illizi basin algeria intracratonic sag basins commonly have relatively simple tectonic histories however later tectonic activity involving exhumation can make reconstructing the burial history a challenging task this is important because the relative timing of hydrocarbon generation and trap formation can be a key factor in risk assessment if trap formation postdates peak hydrocarbon generation exploration plays are typically downgraded mechanisms for charge in such exhumed basins are critical factors for understanding exploration risk this study uses data collected from an ordovician gas condensate field in the illizi basin of algeria to document the charging of a trap formed or modified during exhumation of the basin following maximum burial integrated analysis of sonic compaction data thermal history indicators and stratigraphic well data was used to constrain the burial and thermal history of the region hydrocarbon generation in the lower silurian source rock is interpreted to have occurred during the carboniferous prior to hercynian exhumation and during the late cretaceous early eocene maximum burial prior to eocene exhumation structural reconstructions indicate that the field was initially located on the southern flank of a long lived intrabasinal paleozoic paleohigh the large low relief structural closure that defines the present day accumulation formed as a result of northward tilting of the illizi basin during eocene uplift of the hoggar massif the study demonstrates that the timing of trap formation at the ordovician field postdates the main local hydrocarbon generation events within the basin suggesting that alternative hydrocarbon charge mechanisms are required this study indicates considerable potential to charge updip traps on the flanks of exhumed petroliferous basins via redistribution of the preexisting hydrocarbons within the basin

generation accumulation and resource potential of biogenic gas biogenic gas is generated at low temperatures by decomposition of organic matter by anaerobic microorganisms more than 20 of the world s discovered gas reserves are of biogenic origin a higher percentage of gases of predominantly biogenic origin will be discovered in the future biogenic gas is an important target for exploration because it occurs in geologically predictable circumstances and in areally widespread large quantities at shallow depths in rapidly accumulating marine sediments a succession of microbial ecosystems leads to the generation of biogenic gas after oxygen is consumed by aerobic respiration sulfate reduction becomes the dominant form of respiration methane generation and accumulation become dominant only after sulfate in sediment pore water is depleted the most important mechanism of methane generation in marine sediments is the reduction of co2 by hydrogen electrons produced by the anaerobic oxidation of organic matter co2 is the product of either metabolic decarboxylation or chemical decarboxylation at slightly higher temperatures the factors that control the level of methane production after sediment burial are anoxic environment sulfate deficient environment low temperatu e availability of organic matter and sufficient space the timing of these factors is such that most biogenic gas is generated prior to burial depths of 1 000 m in marine sediments most of the biogenic gas formed can be retained in solution in the interstitial pore waters because of higher methane solubility at the higher hydrostatic pressures due to the weight of the overlying water column under certain conditions of high pressures and or low temperatures biogenic methane combines with water to form gas hydrates biogenic gas usually can be distinguished from thermogenic gas by chemical and isotopic analyses the hydrocarbon fraction of biogenic gas consists predominantly of methane the presence of as much as 2 of heavier hydrocarbons can be attributed to admixture of minor thermogenic gas due to low temperature degradation of organic matter the amounts of hydrocarbon components other than methane generally are proportional to temperature age and organic matter content of the sediments biogenic methane is enriched in the light isotope 12c dgr13c1 lighter than 55 ppt owing to kinetic isotope fractionation by methanogens the variations in isotopic composition of biogenic methane are controlled primarily by dgr13c of the original co2 substrate which reflects the net isotopic effect of both addition and removal of co2 the methane isotopic composition also can be affected by mixing of isotopically heavier thermogenic gas the possible complicating factors require that geologic chemical and isotopic evidence be considered in attempts to interpret the origin of gas accumulations accumulations of biogenic gas have been discovered in canada germany italy japan trinidad the united states and ussr in cretaceous and younger rocks at less than 3 350 m of burial and in marine and nonmarine rocks other gas accumulations of biogenic origin have undoubtedly been discovered however data that permit their recognition are not available

variability of orogenic magmatism during mediterranean style continental collisions a numerical modelling approach abstract the relationship between magma generation and the tectonic evolution of orogens during subduction and subsequent collision requires self consistent numerical modelling approaches predicting volumes and compositions of the produced magmatic rocks here we use a 2d magmatic thermomechanical numerical modelling procedure to analyse rapid subduction of a narrow ocean followed by mediterranean style collision which is characterized by the gradual accretion of lower plate material and slab migration towards the orogenic foreland our results suggest that magmatism has a large scale geodynamic effect by focusing deformation throughout the entire subduction and collision process the rheological structure and compositional layering of the crust impose a key control on the distribution of magmatic rocks within the orogen compared to previous simplified homogeneous crustal models a compositionally layered crust causes an increase in felsic material influx during continental collision and results in shallower magmatic sources that migrate with time towards the foreland changes in the deformation style may be locally driven by magma emplacement rather than by slab movement our modelling also demonstrates that the migration pattern of the deformation front and the magmatic arc relative to the location of the suture zone may be driven by lower crustal indentation in the overriding plate during early stages of collision the modelling predicts a gradual change in magma source composition with time from typical calc alkaline to ones associated with relamination and eduction during subduction collision and slab detachment this transition explains the compositional changes of magma their temporal and spatial migration as well as the observed link with deformation in the dinarides orogen of central europe selected as a case study

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

tectonic evolution of the northwestern internal dinarides as constrained by structures and rotation of medvednica mountains north croatia this paper attempts to explain the tectonic history and the possible reasons for the change of trend of the northwestern part of internal dinarides in a transitional area between the southern eastern alps central dinarides and tisia north of zagreb structural and palaeomagnetic data collected in pre neogene rocks at medvednica mts combined with palaeomagnetic data available form neogene rocks in the surrounding area point to the following conclusions 1 the reason for dramatic deflection in structural trend of the internal dinarides in the area north of zagreb is a 130o clockwise rotation and eastward escape of a tectonic block comprising medvednica mts and the surrounding inselbergs bounded to the north by the easternmost tip of the periadratic lineament in medvednica mts the main period of tectonic escape and associated clockwise rotation occurred in late palaeogene possibly in oligocene earliest miocene 2 when rotated into the original position the trend of observed pre neogene structures of medvednica mt becomes parallel to the major structural trend of the central dinarides in view of their original orientation these structures are interpreted in the following way a the first d1 deformational event is attributed to the aptian albian nappe stacking in the central northern dinarides that was accommodated by a top to the north directed shearing and northward propagation of already obducted ophiolites of the central dinaridic ophiolite zone this nappe stacking which resulted in a weak regional metamorphism in tectonic units underlying the ophiolites was orogen parallel or at a very acute angle to known structural and possibly palaeogeographic trends this implies a major left lateral shear component along the former adriatic margin and obducted dinaridic ophiolite zone b this was followed by early albian orogen perpendicular shortening d2 that was accommodated by folding and top to the west thrusting this deformation resulted in gradual cooling of the metamorphic stack and also in uplift and erosion of the higher structural units c d3 deformational event was driven by renewed e w shortening that took place after the paleocene most probably during the middle eocene oligocene i e synchronous with the main dinaridic tectonic phase of the external dinarides this shortening was probably triggered by collision and thrusting of tisia over the northern segment of the internal dinarides d this was finally followed by d4 pervasive right lateral n s shearing that is tentatively interpreted as being related to the right lateral shearing of the sava zone during the eocene oligocene e following the main period of tectonic escape and induced clockwise rotation in late palaeogene possibly in oligocene earliest miocene the medvednica mts and the surrounding area were affected by repeated extensions and inversions since the early miocene to recent times palaeomagnetic data suggest that in the early miocene but probably before the karpatian this area was part of a regional block that shifted northwards and rotated in counter clockwise sense a second episode of counter clockwise rotation occurred at the present latitude in post pontian times since ca 5 ma driven by the counter clockwise rotating adriatic plate

exhumation charge the last gasp of a petroleum source rock and implications for unconventional shale resources petroleum oil and gas forms from the bacterial or thermal breakdown of kerogen during progressive burial in sedimentary basins during times of petroleum generation kerogens in organic rich source rocks expel petroleum to form a fluid phase in the pore system capable of migrating under hydrodynamic and buoyancy forces to ultimately escape to the surface or accumulate within petroleum traps in the subsurface the relative timing of petroleum charge and trap formation is a vital component in the accumulation of petroleum deposits exhumed basins have been historically viewed as higher risk targets for conventional petroleum exploration because of inter alia the switch off of petroleum generation in the source rock at the commencement of cooling during exhumation however even at the switch off point the source rock may retain a significant volume of petroleum sorbed in kerogen and within its pore system herein we demonstrate that if the source rock is exhumed to shallower depths after peak burial pore pressure reduction and the associated volumetric expansion of the petroleum particularly of the gaseous phase in the pore system will result in the discharge of additional petroleum into the adjacent carrier bed or reservoir formations because most onshore sedimentary basins are characterized by major exhumation events at some point in their history this represents an additional and underappreciated mechanism for a late stage petroleum charge in exhumed sedimentary basins the modeling also indicates that both the initial pre exhumation total gas storage capacity and the exhumation gas charge are likely to be volumetrically more significant for gas bearing source rocks that have been exposed to higher initial pressures and lower thermal gradients the concepts presented here also have implications for petroleum resources retained within unconventional shale reservoirs because high graded shale plays may be associated with systems where the magnitude or rate of relative overpressure dissipation has limited exhumation charge from the unconventional to conventional reservoirs within the basin

characteristics and controlling factors of lacustrine tight oil reservoirs of the triassic yanchang formation chang 7 in the ordos basin china abstract tight sandstone oil reservoirs have received increasing attention in petroleum exploration and exploitation previous research concerning tight oil reservoirs has predominantly focused on marine basins however in china tight oil reservoirs are mostly distributed in lacustrine basins taking the tight oil sandstones of the yanchang formation chang 7 oil reservoir interval the chang 7 for short in the ordos basin as an example five factors are identified that control their formation and occurrence firstly three episodes of oil charging took place during the early cretaceous which were 142 139 ma 128 122 ma and 114 106 ma respectively continuous generation and episodic expulsion led to multiple episodes of oil accumulation secondly widely distributed source rocks toc 1 0 provide hydrocarbons to the chang 7 the distribution of tight oil was controlled by the outer boundary of the source rock distribution while the transition areas between generation expulsion centers were the accumulation and enrichment zones in the chang 7 thirdly with the favorable conditions for retained hydrocarbons massive continuous tight reservoir beds average porosity 7 6 and average permeability 0 15 md developed in the chang 7 capable of forming large scale successive tight oil reservoirs fourthly different source reservoir assemblages have different expulsion patterns and amounts which led to different charging degrees and sizes of tight oil accumulations type iii source reservoir interbeds will be the most favorable target for exploration and exploitation in the chang 7 ordos basin finally under the driving mechanism of non buoyancy migration and accumulation pressure differences between source and reservoir rocks pdbsr serve as the primary expulsion and migration force for crude oil during the main accumulation periods in the chang 7