meteoric diagenesis of plio pleistocene limestones at enewetak atoll abstract petrographic lithologic mineralogic and minor elemental data from plio pleistocene carbonates at enewetak atoll indicate that these sediments have been calcitized in the near surface meteoric diagenetic environment shallow 100 m mostly pleistocene sediments remain aragonite rich with a few discrete meter scale calcite rich intervals developed either at pleistocene soil zones or in thin 5 m paleophreatic lenses deeper 100 to 180 m mostly pliocene sediments are characterized by pervasive calcitization of aragonite extensive dissolution with well developed moldic porosity and the occurrence of isopachous bladed and pore filling equant calcite cements pervasively calcitized pliocene limestones exhibit a narrow range in 18o value 1 0 53 a wide range in 13c value 1 1 63 and low mean sr 0 02 wt and mg 0 25 wt contents these data are most consistent with diagenetic alteration of plio pleistocene carbonates by meteoric phreatic calcitization although in some intervals calcitization in the mixed meteoric marine environment may have also occurred petrographic data document the superposition of subaerial exposure surfaces a d paleophreatic lenses in the subsurface of enewetak sr isotope data and stratigraphic forward modeling are consistent with the multiphase meteoric phreatic calcitization of pliocene limestones in response to subaerial exposure shortly after sediment deposition and during pleistocene sea level lowstands quantitative water rock interaction modeling of whole rock chemical trends suggests that calcitization occurred in an open diagenetic system at water rock w r volume ratios of 103 to 105 proxy indicators of climate e g retention of aragonite at depth and the development of caliche at subaerial exposure surfaces are consistent with an arid to semi arid plio pleistocene climate moreover a limited supply of meteoric waters in the vadose environment despite vertically and temporally extensive paleovadose environments is consistent with limited calcitization of the pleistocene sequence alternatively previous estimates of the rates of vadose calcitization may be too high to be applicable at enewetak stratigraphic shortening of the plio pleistocene sequence in response to carbonate dissolution during atoll emergence is not consistent with available data

the end permian mass extinction a rapid volcanic co2 and ch4 climatic catastrophe abstract the end of the permian was a time of crisis that culminated in the earth s greatest mass extinction there is much speculation as to the cause for this catastrophe here we provide a full suite of high resolution and coeval geochemical results trace and rare earth elements carbon oxygen strontium and clumped isotopes reflecting ambient seawater chemistry and water quality parameters leading up to the end permian crisis preserved brachiopod low mg calcite based seawater chemistry supplemented by data from various localities documents a sequence of interrelated primary events such as coeval flows of siberian trap continental flood basalts and emission of carbon dioxide leading to warm and extreme greenhouse conditions with sea surface temperatures sst of 36 c for the late permian although anoxia has been advanced as a cause for the mass extinction most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling but not a general cause instead we suggest that renewed and increased end permian siberian trap volcanic activity about 2000 years prior to the extinction event released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering eventually these rapidly discharged greenhouse gas emissions less than 1000 years before the event ushered in a global hothouse period leading to extreme tropical ssts of 39 c and higher based on these sea surface temperatures atmospheric co 2 concentrations were about 1400 ppmv and 3000 ppmv for the late and end permian respectively leading up to the mass extinction there was a brief interruption of the global warming trend when sst dropped concurrent with a slight but significant recovery in biodiversity in the western tethys it is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the permian after aerosol deposition global warming resumed and the biotic decline proceeded and was accompanied by suboxia in places of the surface ocean which culminated in the greatest mass extinction in earth history

the carbon isotope shift at the permian triassic boundary in the southern alps is gradual carbon isotope ratios in marine carbonate rocks have been shown to shift at some of the time boundaries associated with extinction events for example cretaceous tertiary1 and ordovician silurian2 the permian triassic boundary the greatest extinction event of the phanerozoic3 is also marked by a large 13c depletion4 5 new carbon isotope results from sections in the southern alps show that this depletion did not actually represent a single event but was a complex change that spanned perhaps a million years during the late permian and early triassic these results suggest that the permian triassic p tr extinction may have been in part gradual and in part stepwise 6 7 but was not in any case a single catastrophic event

stable isotope and trace element stratigraphy across the permian triassic transition a redefinition of the boundary in the velebit mountain croatia article i nfo stable isotopes of carbonates 13 ccarb 18 ocarb organic matter 13 corg 15 norg and major trace and rare earth element ree compositions of marine carbonate rocks of late permian to early triassic age were used to establish the position of the permian triassic boundary ptb at two continuous sections in the velebit mountain croatia the chosen sections rizvanusa and brezimenjaca are composed of two lithostratigraphic units the upper permian transitional dolomite and the overlying sandy dolomite the contact between these units characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains was previously considered as the chronostratigraphic ptb the sandy dolomite is characterized by high content of non carbonate material up to 30 wt insoluble residue originated from erosion of the uplifted hinterland a relatively rich assemblage of permian fossils including geinitzina globivalvulina hemigordius b ioclasts of gastropods ostracods and brachiopods was found for the first time in sandy dolomite 5 m above the lithologic boundary in the rizvanusa section a rather abrupt negative 13 ccarb excursion in both sections appears in rocks showing no recognizable facies change within the sandy dolomite 2 at rizvanus aa nd 1 2 at brezimenjaca 11 m and 0 2 m above the lithologic contact respectively this level within the lower part of the sandy dolomite is proposed as the chemostratigraphic ptb in the rizvanus as ection the 13 corg values decline gradually from 25 in the upper permian to 29 in the lower triassic the first negative 13 corg

diagenetic origin of carbon and oxygen isotope compositions of permian triassic boundary strata bulk carbonate 13 c and 18 o compositions of profiles across permian triassic p t boundary sections in china italy austria and iran show wide varieties of trends the 13 c depletions occur in all sections and range from 2 to 8 pdb in magnitude these excursions take place over intervals ranging from less than 0 1 to more than 40 m the 18 o values may increase or decrease toward the p t boundary but decrease sharply by 2 9 pdb at or above the boundary cross plots of 13 c and 18 o values from all sections show positive covariance wide differences in magnitudes trends and position of the excursions relative to the boundary as well as the covariance patterns suggest that p t boundary 18 o and 13 c values are partially or entirely diagenetic in origin formed in association with exposure surfaces this interpretation implies that p t boundary sections studied till date were subaerially exposed before during and after the mass extinction resulting in the removal of strata containing key information about the extinction mechanism this inference is consistent with the paleontological studies that have shown the presence of gaps at the boundary and further supported by the sharp lithologic changes observed at virtually all p t boundary sections subaerial exposures are documented by detailed sedimentologic and isotopic studies from central tethyan sections in abadeh and shah reza in iran proposed p t boundary extinction models are based on isotopic values that are diagenetic in origin and stratigraphic sections that are incomplete leading to extinction mechanisms with little physical supporting evidence

carbonatization of oceanic crust by the seafloor hydrothermal activity and its significance as a co2 sink in the early archean abstract early archean 3 46 ga hydrothermally altered basaltic rocks exposed near marble bar eastern pilbara craton have been studied in order to reveal geological and geochemical natures of seafloor hydrothermal carbonatization and to estimate the co2 flux sunk into the altered oceanic crust by the carbonatization the basaltic rocks are divided into basalt and dolerite and the basalt is further subdivided into type i having original igneous rock textures and type ii lacking these textures due to strong hydrothermal alteration primary clinopyroxene phenocrysts are preserved in some part of the dolerite samples and the alteration mineral assemblage of dolerite chlorite epidote albite quartz actinolite indicates that the alteration condition was typical greenschist facies in other samples all primary minerals were completely replaced by secondary minerals and the alteration mineral assemblage of the type i and type ii basalts chlorite k mica quartz carbonate minerals albite is characterized by the presence of k mica and carbonate minerals and the absence of ca al silicate minerals such as epidote and actinolite suggesting the alteration condition of high co2 fugacity the difference of the alteration mineral assemblages between basalt and dolerite is probably attributed to the difference of water rock ratio that in turn depends on their porosity carbonate minerals in the carbonatized basalt include calcite ankerite and siderite but calcite is quite dominant the 13c values of the carbonate minerals are 0 3 1 2 and mostly within the range of marine carbonate indicating that the carbonate minerals were formed by seafloor hydrothermal alteration and that carbonate carbon in the altered basalt was derived from seawater whole rock chemical composition of the basaltic rocks is essentially similar to that of modern mid ocean ridge basalt morb except for highly mobile elements such as k2o rb sr and ba compared to the least altered dolerite all altered basalt samples are enriched in k2o rb and ba and are depleted in na2o reflecting the presence of k mica replacing primary plagioclase in addition noticeable co2 enrichment is recognized in the basalt due to the ubiquitous presence of carbonate minerals but there was essentially neither gain nor loss of cao this suggests that the co2 in the hydrothermal fluid seawater was trapped by using ca originally contained in the basalt the cao co2 ratios of the basalt are generally the same as that of pure calcite indicating that ca in the basalt was almost completely converted to calcite during the carbonatization although mg and fe were mainly redistributed into noncarbonate minerals such as chlorite the carbon flux into the early archean oceanic crust by the seafloor hydrothermal carbonatization is estimated to be 3 8 1013 mol yr based on the average carbon content of altered oceanic crust of 1 4 10 3 mol g the alteration depth of 500 m and the spreading rate of 1 8 1011 cm2 yr this flux is equivalent to or greater than the present day total carbon flux it is most likely that the seafloor hydrothermal carbonatization played an important role as a sink of atmospheric and oceanic co2 in the early archean

late guadalupian to lopingian permian carbon and strontium isotopic chemostratigraphy in the abadeh section central iran abstract the abadeh section well exposed in the hambast valley in central iran has long been one of the most extensively studied sections because of its continuous carbonate dominated strata from lower permian to lower triassic however biostratigraphy and correlation with the equivalent sequences in other regions remain controversial in this paper both carbon isotope excursion 13 c carb and strontium isotope ratio 87 sr 86 sr based on bulk carbonate samples have been measured to serve as chemostratigraphical proxies to estimate the three different chronostratigraphical boundaries in the lopingian at the abadeh section including the permian triassic event pteb the guadalupian lopingian glb and the wuchiapingian changhsingian boundaries wcb these three boundaries are important for understanding the marine biological evolution around this critical interval based on the 13 c excursions the rising trend of 87 sr 86 sr and the value around 0 7073 and the occurrence of microbialite beds the permian triassic event boundary bed 25 at the meishan section is suggested at 0 5 m below the base of the main microbialite bed the glb is suggested at 46 5 m based on the position of the minor 13 c carb negative depletion coupled with the values between 0 7069 and 0 7070 of 87 sr 86 sr and its beginning point of the rising trend which is above the lowest value 0 7068 of 87 sr 86 sr ratio in the paleozoic the relationship between section thickness and their high resolution depositional age projecting age is interpolated for the whole lopingian using locally weighted regression scatter plot smoother lowess of strontium isotopic ratio based on the negative 13 c excursion and the value 0 7072 of 87 sr 86 sr ratio the wcb is estimated at 1 m above the lithologic boundary between unit 6 and unit 7 much lower than the boundary defined by previous conodont biostratigraphy but similar to other index fossils this boundary is projected as ca 254 6 ma in 87 sr 86 sr age projecting model and is close to zircon u pb dating age from south china

isotopic chemostratigraphy of the microbialite bearing permian triassic boundary section in the zagros mountains iran carbon isotopic chemostratigraphy and a sr isotope datum provide age constraints to the uppermost permian lowermost triassic section in central zagros mountains iran the 77 m thick carbonate dominated section contains two microbialite beds that consist of abiotic carbonate crystals and possible calcimicrobes the textures resemble those reported from the lowermost triassic elsewhere which were likely developed under unusual environmental and ecological conditions after the end permian extinction our results show that the lower section up to the lower microbialite bed has high 13 c values of 3 to 4 which are typical values for the latest permian from 3 m above the base of the lower microbialite the values abruptly decreases to 0 3 in the upper section the 13 c curve records another negative excursion and gradual increase to 2 0 the curve coincides with the global trend from other permian triassic boundary sections and places the chemostratigraphic boundary within the lower microbialite the 13 c negative excursion postdates geochemical and or ecological changes that triggered the microbialite development if the trigger was increased alkalinity by a vast carbon flux the source carbon should not have significantly light value of 13 c

carbon isotope stratigraphy across the permian triassic boundary a review abstract the palaeozoic mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon isotope excursion at the permian triassic p t boundary well known from a plethora of marine and continental sediments potential causes for this negative 13 c trend and their links to the latest permian mass extinction have been intensively debated in the literature in order to draw conclusions regarding causation a general 13 c curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background the most important features of the p t carbon isotope trend are the following the 4 7 13 c decline lasting 500 000 years is gradual and began in the changhsingian at the stratigraphic level of the c bachmanni zone the decreasing trend is interrupted by a short term positive event that starts at about the latest permian low latitude marine main extinction event horizon eh indicating that the extinction itself cannot have caused the negative carbon isotope excursion after this short term positive excursion the 13 c decline continues to a first minimum at about the p t boundary a subsequent slight increase is followed by a second occasionally two peaked minimum in the lower and middle i isarcica zone the negative carbon isotope excursion was most likely a consequence of a combination of different causes that may include 1 direct and indirect effects of the siberian trap and contemporaneous volcanism and 2 anoxic deep waters occasionally reaching very shallow sea levels a sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon isotope trend is questionable at least for the time span a little below the eh and somewhat above the p t boundary

stable isotopes of carbon and sulphur as indicators of environmental change past and present stable isotopes of carbon 12 c and 13 c and sulphur 32 s and 34 s are fractionated during some of the transformations between reservoirs in the global carbon and sulphur cycles the main processes controlling the isotopic composition of earth surface reservoirs are for carbon photosynthesis respiration and equilibration between oceanic dissolved inorganic carbon and atmospheric co 2 and for sulphur bacterial sulphate reduction and sulphide reoxidation thus the different reservoirs of carbon and sulphur in the global cycles attain characteristic isotopic compositions that can be used as a fingerprint for different carbon and sulphur sources and to track changes in the balance of carbon and sulphur stored in different reservoirs these isotopic signals can be used both to examine contemporary anthropogenic impacts on the cycling of carbon and sulphur and where isotopic compositions are faithfully preserved in ancient sediments to examine historical changes in global geochemical cycles through geological time a number of case studies are discussed to illustrate how isotopic techniques represent one of the most powerful and important tools available in the study of both the causes and affects of ancient and modern global environmental change

the source process of the 2001 july 26 skyros island greece earthquake summary the spatial and temporal distribution of slip during the 2001 july 26 skyros greece earthquake moment magnitude m 6 5 is investigated using broadband data recorded at regional distances the applied method involves estimation of the source time functions of the examined event through an empirical green s function approach and inversion of their shapes to estimate kinematic source parameters our test inversions to statistically identify the fault plane together with the distribution of aftershocks clearly indicate sinistral strike slip faulting in view of the fact that the skyros epicentre lies near the western termination of the dextral strike slip north anatolian fault naf into the aegean sea this sinistral strike slip motion for the first time instrumentally identified has great tectonic significance the best values searched through the inversion are 0 7 s for the rise time and 2 4 km s 1 for the rupture velocity most of the slip appears to be concentrated in a relatively small area around the hypocentre while a smaller slip patch was found at relatively large depth 18 24 km at least two of the large aftershocks following the main event also occurred at the deeper part of the fault smaller amounts of slip are distributed in a wider area with dimensions similar to those inferred from the aftershock distribution studies and the empirical relations applicable to greece

source parameters for small events associated with the 1986 north palm springs california earthquake determined using empirical green functions using small events as empirical green functions which include path site and instrument effects on the p waveforms source parameters were estimated for 25 ml 3 4 to 4 4 events associated with the 1986 north palm springs earthquake the static stress drops ranged from 3 to 80 bars for moments of 0 7 to 11 1021 dyne cm there was a spatial pattern to the stress drops of the aftershocks which showed increasing values along the fault plane toward the northwest compared to relatively low values near the hypocenter of the mainshock the highest values were outside the main area of slip and are believed to reflect a loaded area of the fault that still has an higher level of stress which was not released during the main shock the relatively high stress drop of a preshock in 1983 located close to the hypocenter of the main shock is also interpreted as evidence that stress drops of magnitude 3 and 4 events can be used as indicators of the stress level in a particular area

isotope excursions and palaeotemperature estimates from the permian triassic boundary in the southern alps italy abstract the end permian mass extinction event coincides with a dramatic negative shift in both the 13c and the 18o isotope record at or near the extinction horizon from multiple marine and terrestrial sections round the globe this study has identified the isotope excursions in a shallow water carbonate dominated section at val brutta in the southern alps high resolution bulk rock sampling revealed that there is an average 13ccarb negative shift of 4 and a 18ocarb shift of 6 this is similar to the isotope record at other nearby localities this section like many others shows a degree of recrystallisation which hampers absolute palaeotemperature calculations however some brachiopod fossils including specimens of comelicania and janiceps found within the beds that contain the bulk rock anomaly appear to be remarkably well preserved and still retain their internal structure and the primary isotopic variation across the shell as such they have been successfully analysed and the data used to produce a palaeotemperature estimate at the time of the isotope anomaly of between 26 and 29 c for latest permian

seismic remote sensing for the earthquake source process and near source strong shaking a case study of the october 16 1999 hector mine earthquake a new methodology to automatically determine the earthquake source process and near source strong ground motions using regional and local distance data was used to study the october 16 1999 hector mine earthquake mw7 1 broadband displacement data were inverted for the seismic moment tensor and to resolve the fault plane ambiguity independent of aftershock location and surface faulting information the identified nnw striking fault plane was used to invert for the distribution of fault slip over a planar surface the slip model was used to predict near fault peak ground velocity which was found to agree well with the trinet shakemap and also with near fault observations that were not available at the time of the initial analysis our method if automated is capable of providing near source strong ground motion information within 30 minutes of the earthquake origin time even in cases where there are few near fault recording instruments

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

empirical green s function study of the january 17 1994 northridge california earthquake the january 17 1994 northridge main shock was analyzed using an empirical green s function approach to estimate the spatial and temporal distribution of fault slip far field source time functions obtained from seismograms recorded by the berkeley digital seismic network bdsn and terrascope stations reveal the distributed nature of the source and the presence of a second large subevent the location of the fault beneath the san fernando valley as well as the updip directivity of the rupture contributed to the locally heavy damage due to this earthquake

intrabasin variability of the carbon isotope record across the permian triassic transition sverdrup basin arctic canada abstract a major late paleozoic depocentre the sverdrup basin canadian high arctic has been largely left out of the latest permian extinction debate as early workers presumed middle to late permian strata were absent basin scale sequence stratigraphic and chemostratigraphic correlations indicate late permian strata are only missing on the basin margins where they were removed by sub triassic erosion whereas continuous deposition is recorded in the basin centre the varying degree of sub triassic erosion has significant impact on the carbon isotope record across the latest permian extinction event where both the apparent rate and magnitude of carbon isotope shift vary as a function of basin position the intrabasin variability in apparent 13corg shift across the event is equivalent to that observed globally in contrast to the abrupt isotope shifts recorded on the basin margin similar to many records reported globally the basin centre section shows a systematic shift associated with the latest permian extinction the earth likely underwent a prolonged period of increasing environmental stress leading up to the event

u pb ages of detrital zircons from the permo triassic series of the iberian ranges a record of variable provenance during rift propagation abstractthe provenance of the permo triassic series of the talayuelas anticline iberian ranges have been studied using u pb geochronology laser ablation inductively coupled plasma mass spectrometry of detrital zircons these intracontinental siliciclastic series were formed by extensive sandy braided fluvial systems associated with ephemeral lake deposits and aeolian sediments with paleocurrents suggesting constant nw se transport directions upper permian reddish sandstones from the upper alcotas formation lopingian contain a dominant variscan zircon population 290 360 ma which indicates source areas located in the axial zone of the variscan belt in the core of the ibero armorican arc however in the lower triassic sandstones of the canizar formation olenekian the variscan zircon population is almost completely replaced by cadomian zircons 520 750 ma with important avalonian 390 520 ma mesoproterozoic 900 1750 ma eburnian 1 78 2 35 ga and post eburnian and archaean 2 4 ga zi

carbon isotopic shift and its cause at the wuchiapingian changhsingian boundary in the upper permian at the zhaojiaba section south china evidences from multiple geochemical proxies abstract the late permian environmental change connecting the guadalupian lopingian g l middle upper permian boundary mass extinction and the permain triassic p tr boundary mass extinction has attracted more and more attentions a significant negative shift for carbon isotope had been found at the wuchiapingian changhsingian w c boundary in the upper permian recently however the cause s of this negative excursion is still unknown to resolve this problem we analyzed the bulk organic carbon isotope total organic carbon toc content pyritic sulfur spy content major element concentrations and molecular organic biomarkers in the wujiaping and dalong formations in the upper permian from the zhaojiaba section in western hubei province south china our results show that 1 there was a significant negative excursion in organic carbon isotopes at the w c boundary and again a negative excursion at the top of changhsingian stage 2 the significant negative excursion at the w c boundary was probably a global signal and mainly caused by the low primary productivity and 3 the negative carbon isotope excursion at the top of changhsingian was probably caused by the siberian traps eruptions a decline in oceanic primary productivity at the w c boundary probably represents a disturbance of the marine food web leading to a vulnerable ecosystem prior to the p tr boundary mass extinction

the unusual sedimentary rock record of the early triassic a case study from the southwestern united states abstract sedimentary systems as well as the earth s biota changed dramatically following the end permian mass extinction this global sedimentological transformation is reflected in the widespread occurrence of flat pebble conglomerates subtidal wrinkle structures microbialites and carbonate seafloor fans in various lower triassic sections as a case study a facies analysis of the lower triassic virgin limestone member of the moenkopi formation and the middle and upper members of the union wash formation southwestern united states was conducted and all unusual facies were documented within a palaeoenvironmental framework the occurrence of the flat pebble conglomerates and wrinkle structures is significant because these reflect a long term reduction in vertical bioturbation in the case of the subtidal microbialites and carbonate seafloor fans their formation is linked to an increase in alkalinity the presence of these facies in the uppermost lower triassic strata of the southwestern united states indicates that reduced levels of infaunal bioturbation as well as and perhaps a consequence of unusual ocean chemistry extended for 5 6 million years after the end permian mass extinction suggesting that depositional environments as well as the biota were significantly affected by the extinction event

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

evidence for recurrent early triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations abstract carbon cycle disturbance associated with mass extinction at the end of the permian period continued through the early triassic an interval of approximately 5 million years coincidence of carbon cycle stabilization with accelerated middle triassic biotic recovery suggests a link between carbon cycling and biodiversity but the cause of early triassic carbon isotope excursions remains poorly understood previous modeling studies have focused exclusively on the initial negative excursion in 13c across the permian triassic boundary and have not addressed the cycles of positive and negative excursions observed through the early triassic this study uses a simple carbon cycle box model to investigate potential causes underlying the series of early triassic carbon isotope excursions and to assess possible relationships between isotope excursions and coeval patterns of carbonate deposition according to the model introduction of carbon with the isotope composition of volcanic co2 produces small negative carbon isotope excursions followed by larger and more protracted positive excursions positive excursions result because increased pco2 causes warming enhancing marine anoxia and associated regeneration of phosphate and thus allowing greater productivity in addition carbonate weathering is more sensitive than organic carbon weathering to changes in atmospheric pco2 and climate causing an increase in the overall 13c composition of weathered carbon therefore the full early triassic record of negative and positive carbon isotope excursions can only be accounted for within the model by several pulses of carbon release characterized by varying mixtures of organic and mantle isotope compositions thermal metamorphism of coal and carbonate rocks in the crust of the siberian craton during eruption of the siberian traps flood basalts provides the most plausible mechanism for such a carbon release scenario if multiple episodes of co2 release account for early triassic carbon cycle instability regardless of their precise trigger then cessation of co2 release is likely to explain acceleration of biotic recovery early in the middle triassic

discerning primary versus diagenetic signals in carbonate carbon and oxygen isotope records an example from the permian triassic boundary of iran abstract sedimentary successions across the permian triassic boundary ptb are marked by a prominent negative carbon isotope excursion this excursion found in both fossil e g brachiopod and bulk carbonate at many sites around the world is generally considered to be related to a global carbon cycle perturbation oxygen isotopes also show a negative excursion across the ptb but because 18o is more prone to diagenetic overprint especially in bulk carbonate these data are often not used in palaeoenvironmental analyses in the present study bulk rock and brachiopod 13c and 18o as well as conodont 18o were analyzed in ptb successions at kuh e ali bashi and zal nw iran in order to evaluate diagenetic overprints on primary marine isotopic signals the results show that the use of paired c o isotopes and mn sr concentrations is not sufficient to identify diagenetic alteration in bulk materials because 13c 18o covariation can be due to environmental factors rather than diagenesis and sr ca and mn ca ratios can vary as a function of bulk rock lithology comparison of 13c profiles shows that all bulk carbonate is altered to some degree although the general bulk rock trend mimics that of the brachiopod data with a systematic offset of 1 2 0 4 this suggests that the first order 13c trend in bulk carbonate is generally robust but that the significance of small scale carbon isotope fluctuations is uncertain especially when such fluctuations are linked to lithologic variation the ptb interval which is marked by a low carbonate boundary clay in the study sections may be especially prone to diagenetic alteration e g via late stage dolomitization comparison of oxygen isotope profiles for bulk rock and well preserved fossils both brachiopods and conodonts shows that the former are offset by 2 1 0 4 diagenetic modeling suggests that these offsets were the product mainly of early diagenesis at burial temperatures of 50 80 c and water rock ratios of

a geological based reservoir zonation scheme in a sequence stratigraphic framework a case study from the permo triassic gas reservoirs offshore iran abstract reservoir zonation can lead to an insight about the lateral and vertical distribution of reservoir and non reservoir zones from bore hole to regional scales based on available data sets scale of study and purposes there are various reservoir zonation schemes but correlatability is crucial in any reservoir zonation procedure in this study it is attempted to create a reservoir zonation scheme based on geological attributes in the permo triassic successions of the eastern persian gulf area which can be used to inter field regional investigation and correlation then the applicability of two routinely used reservoir zonation procedures including hydraulic flow units hfu and flow units based on a stratigraphic modified lorenz plot was examined the petrophysical based hfus were not correlatable between the studied wells and fields the larger scale flow units were correlatable at the field and to some extent inter field scales but the identified geological reservoir zones grzs were correlatable at both intra and inter field scales in a sequence stratigraphic framework grzs were defined based on sharp changes in depositional facies diagenetic features or both and also any meaningful accompaniment in diagenetic features and pore types which show similar sequence stratigraphic positions this indicates a close relationship between the depositional sequences and post depositional diagenetic processes and therefore grzs are linked to a sequence stratigraphic framework the grz concept may be applicable to reservoir characterization of the permo triassic successions in the persian gulf and adjacent areas however this concept can only be applied if the combined depo diagenetic processes and the resulting reservoir quality are controlled by sequence stratigraphic position without pervasive and non facies related late diagenetic overprints

biological processes controlling the development of modern peat forming ecosystems abstract although no precise modern analogue exists for the peat forming ecosystems mires of tertiary times it is argued that the principles underlying peat formation are essentially unchanged in the sense that a peat forming ecosystem has an incomplete decomposition process normally because of waterlogging leaving a residue of organic material in its overall energy flow budget the study of modem mires is therefore of relevance to tertiary coal geologists the classification of modern mires is best achieved by reference to their hydrological characteristics particularly the source of water entering the system flow fed rheotrophic mires are often relatively rich in nutrients and clastic while rainfed ombrotrophic mires are poor the transition from one hydrological state to the other can occur during mire development and involves a physical elevation of the mire surface by the growth of peat such mires have a two layered diplotelmic structure in which the surface layer acrotelm is periodically aerobic has a loose structure and a high hydraulic conductivity while the lower layer catotelm is compacted anaerobic and has a low hydraulic conductivity the hydrological outcome is that precipitation landing upon a raised ombrotrophic mire drains from the elevated mire surface laterally through the acrotelm the water retention of the mire and its elevated water table is dependent on the poor water conductivity of the catotelm the transition to the ombrotrophic condition is accompanied by higher rates of peat accumulation and increasing mire acidity it begins with isolated colonization of hummock forming plants that later converge into an extended cupola this ecological transition may be a consequence of external changes such as climatic alteration increased precipitation evaporation ratio or autogenic internal successional developments basin subsidence however or eustatic sea level rise in the case of coastal systems can operate in the reverse direction and prevent the permanent establishment of an ombrotrophic system the ombrotrophic mire is ultimately limited in the depth of its peat development by microbial respiration within the catotelm as the catotelm extends with peat accumulation the total respiratory activity of the profile will equilibrate with primary productivity and peat formation slows down to an eventual standstill on the assumption that peatland hydrology operated in a similar way in former times the deep peats and eventually coals of tertiary times can best be explained therefore in terms of stacks of sequential mires rather than single continuously forming ecosystems

a study of the 2 december 2002 m5 5 vartholomio western peloponnese greece earthquake and of its largest aftershocks broadband data from the greek national seismological network are used to study the moderate size m5 5 earthquake which occurred on 2 december 2002 near the town of vartholomio in western peloponnese greece time domain moment tensor inversion applied to retrieve the focal mechanism of the mainshock and of three of the larger aftershocks of the sequence revealed almost pure strike slip faulting along nw se or ne sw trending nodal planes the relative source time functions for the mainshock obtained from an empirical green s function analysis do not reveal any clear directivity to any of the stations a careful observer might suggest directivity towards nw if any optimum values are 0 4 s for the rise time and 2 7 km s for the rupture velocity the spatial and temporal distribution of fault slip showed that the major part of the resolved slip occurred beneath the mainshock s epicenter 20 km underneath the western coast of peloponnese this probably accounts for the considerable damage observed to the nearby towns the resolution between the two nodal planes does not permit an identification of the fault plane however the statistics on the slip distribution model the preliminary analysis of aftershock locations and macroseismic data favour the nw se trending plane as the fault plane which is connected with sinistral strikeslip motions these are the first implications for sinistral strike slip motions in this area and more data are needed in the future to get more reliable resolution of the motions d 2004 elsevier b v all rights reserved

comment on permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology by e heydari j hassanzadeh w j wade and a m ghazi palaeogeography palaeoclimatology palaeoecology 193 405 424 2003 a

permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology the uppermost permian strata of the abadeh section in iran consist of 56 m of skeletal limestone abadehian that grades upward into 18 m of grey bioturbated lime mudstone djulfian which in turn grades upward to 18 m of red nodular wackestone dorashamian containing an abundant pelagic fauna the overlying lowermost triassic includes two enigmatic layers at its base immediately above the boundary is a 1 m thick layer of inorganically precipitated synsedimentary carbonate cement the cement is composed of 10 20 cm long crystals oriented either perpendicular to the bedding or as dome shaped features resembling botryoids about 0 5 m of wackestone overlies the cement layer the second layer is a 1 5 m thick grainstone overlying the cement horizon and consists of recrystallised spherical grains ooids or peloids the remainder of unit a is composed of 100 m of grey bioturbated to nodular lime mudstone the lithofacies succession of the uppermost permian is interpreted to represent deposition under increasing water depth related to rising of relative sea level which led to drowning of the carbonate platform to below storm wave base sedimentologic characteristics lithology wide distribution and slow sedimentation rates indicate that strata immediately below the permian triassic p t boundary dorashamian interval were deposited in deep oxygenated waters the enigmatic lowermost triassic synsedimentary carbonate cement and grainstone layers are interpreted to have been deposited in shallow waters indicating a rapid and major drop in relative sea level at the end of permian time in this area followed by a relative sea level rise during the earliest triassic precipitation of synsedimentary cement immediately above the p t boundary in iran and elsewhere south china suggests a global change in ocean chemistry one possible explanation is that dissolved calcium and bicarbonate concentrations in seawater increased sufficiently to promote spontaneous carbonate precipitation a rare event in the phanerozoic but common during precambrian time alternatively a massive heating event could have resulted in co2 degassing and decreases in oceanic carbonate solubility both leading to inorganic synsedimentary carbonate precipitation inorganic precipitation of synsedimentary carbonate cement may indicate that biochemical production of carbonate was halted due to the p t boundary events our study indicates that shallow and moderately deep waters during the latest permian were well oxygenated in the open ocean setting of the central tethys sea in iran therefore p t mass extinction scenarios that invoke upon widespread marine anoxia should be viewed with caution

carbon isotope excursions and microfacies changes in marine permian triassic boundary sections in hungary abstract several permian triassic boundary sections occur in various structural units within hungary these sections represent different facies zones of the western palaeotethys margin the gardony core in the ne part of the transdanubian range typically represents the inner ramp while the balvany section in the bukk mountains of northern hungary represents an outer ramp setting the two sections have different patterns for their 13 c values the balvany section shows a continuous change towards more negative 13 c values starting at the first biotic decline followed by a sharp quasi symmetric negative peak at the second decline the appearance of the 13 c peak has no relationship to the lithology and occurs within a shale with low overall carbonate content indicating that the peak is not related to diagenesis or other secondary influences instead the shift and the peak reflect primary processes related to changes in environmental conditions the continuous shift in 13 c values is most probably related to a decrease in bioproductivity whereas the sharp peak can be attributed to an addition of c strongly depleted in 13 c to the ocean atmosphere system the most plausible model is a massive release of methane hydrate the quasi symmetric pattern suggests a rapid warming cooling cycle or physical unroofing of sediments through slope failure and releasing methane hydrate the gardony 1 core shows a continuous negative 13 c shift starting below the p t boundary however the detailed analyses revealed a sharp 13 c peak in the boundary interval just below the major biotic decline although its magnitude doesn t reach that observed in the balvany section based on careful textural examination and high resolution stable isotope microanalyses we suggest that the suppression of the 13 c peak that is common in the oolitic boundary sections is due to combined effects of condensed sedimentation sediment reworking and erosion as well as perhaps diagenesis

comment on permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology by e heydari j hassanzadeh w j wade and a m ghazi palaeogeography palaeoclimatology palaeoecology 193 405 424 2003 b

sponge microbial build ups from the lowermost triassic chanakhchi section in southern armenia microfacies and stable carbon isotopes abstract the end permian mass extinction was the most severe biotic crisis in earth s history in its direct aftermath microbial communities colonized some of the space left vacant after the severe decline of skeletal metazoans the permian triassic boundary microbialites were peculiarly abundant on low latitude shallow marine carbonate shelves of central tethyan continents armenia features particularly well preserved and diverse basal triassic sponge microbial build ups btsmbs which were not studied in detail to date here the chanakhchi section in southern armenia is described petrographically and by means of stable isotope analyses the armenian btsmbs formed in a distally open marine setting on a pelagic carbonate ramp in the course of two phases of microbial growth during the induan lower triassic the btsmbs are represented by predominantly thrombolitic but also dendrolitic and digitate stromatolite biostromes and mounds that vary in height between 5 cm to 12 m the digitate stromatolites are associated with calcium carbonate crystal fans ccfs microfacies analyses revealed that the btsmbs exhibit a number of different growth forms and internal fabrics the formation of ccfs was apparently not devoid of biological influence and took place above the sediment surface the abundance of sponges in the btsmbs reveals that ecologically complex metazoan microbial reefs have been present already early after the end permian mass extinction however the formation of biostromes and mounds did not depend on sponges or other metazoans btsmbs that formed during the second microbial growth phase revealed similar 13c values like the surrounding sediment in contrast the 13cmicrobialite and 13csediment values from the btsmbs and ccfs of the first growth phase show a difference of up to 2 3 suggesting a significant influence of photoautotrophy during microbially induced carbonate precipitation

carbon sulfur oxygen and strontium isotope records organic geochemistry and biostratigraphy across the permian triassic boundary in abadeh iran pelagic deposits at abadeh represent a complete biostratigraphic record across the permian triassic boundary ptb the presumed water depth during deposition of these sediments was between 60 and 90 m similar to other permian triassic boundary sections the succession at abadeh is characterised by a negative carbon isotope shift of approximately 4 the values start to decrease in the lower c changxingensis c deflecta s l zone reach 0 12 v pdb in the uppermost permian just below the ptb remain low to the early i isarcica zone 0 32 and increase subsequently in the upper i isarcica zone for the time interval of the ptb negative carbon isotope excursion between the c iranica and the i isarcica zones no correlation exists between the 13ccarb and the 18ocarb the above observations argue against the conclusion of heydari et al 2001 that the carbon isotope event at the p t transition is an alteration artefact and not a global signal the decrease in 13ccarb is accompanied by a 5 and potentially up to 10 increase in 34ssss together these features are thought to reflect a complex global event notably the development of widespread anoxic oceans with anoxic bottom layers rising onto the shelves for the carbon isotope drop other factors such as the collapse of ocean primary productivity may also have played a role the 87sr 86sr ratios of dzhulfian seawater show only a minor increase from 0 70705 to 0 70710 reaching 0 70720 in the dorashamian the increase becomes steeper in the early triassic reaching 0 70754 in the n dieneri zone the rise of the strontium isotope values is thought to be related to enhanced continental weathering under humid climatic conditions in the uppermost permian c meishanensis h praeparvus zone and the lack of a dense land vegetation in the early triassic prior to the spathian upper olenekian

massive volcanism at the permian triassic boundary and its impact on the isotopic composition of the ocean and atmosphere abstract bulk carbonate and conodonts from three permian triassic p t boundary sections at guryul ravine kashmir abadeh central iran and pufels bula bulla italy were investigated for 13 c and 18 o carbon isotope data highlight environmental changes across the p t boundary and show the following features 1 a gradual decrease of 4 to more than 7 starting in the late permian changhsingian c bachmanni zone with two superimposed transient positive excursions in the c meishanensis h praeparvus and the m ultima s mostleri zones 2 two 13 c minima the first at the p t boundary and a higher occasionally double minimum in the lower i isarcica zone it is unlikely that the short lived phenomena such as a breakdown in biological productivity due to catastrophic mass extinction a sudden release of oceanic methane hydrates or meteorite impact s could have been the main control on the latest permian carbon isotope curve because of its prolonged 0 5 ma duration gradual decrease and the existence of a 1 positive shift at the main extinction horizon the p t boundary 13 c trend matches in time and magnitude the eruption of the siberian traps and other contemporaneous volcanism suggesting that volcanogenic effects such as outgassed co 2 from volcanism and even more thermal metamorphism of organic rich sediments as the likely cause of the negative trend

the 24 may 2009 mw5 2 earthquake sequence near lake doirani fyrom greek borders focal mechanisms and slip model using empirical source time functions inversion abstract on 24 may 2009 gmt 16 17 a moderate size mw5 2 earthquake sequence burst north of lake doirani along the greek fyrom borders and ruptured a n282 e striking normal fault of 6 km in length dipping at an angle of 60 to the north the focal mechanisms for 25 of the stronger events obtained through time domain moment tensor inversion reveal the prevalence of normal faulting along wnw ese striking planes sometimes dip slip motions are combined with a considerable strike slip component broad band waveforms from the hellenic unified seismological network husn and neighbouring networks were used to invert source time functions stfs and calculate the slip model for the strongest event gmt 16 17 stfs were obtained through an empirical green s function approach no directivity could be clearly identified for this moderate magnitude event slip was released in a single patch of dimensions 6 km 8 km maximum slip is estimated at 15 cm while average slip on the ruptured area area of subfaults of non zero slip was 3 cm one characteristic of the slip model was the large rise time for a moderate size event which was estimated to be 1 0 s implying a slow slip rate function brune s static stress drop is calculated 5 bars it must be noted that the north dipping plane is identified as the fault plane slip vector trending n332 e based on the model variance of the stfs inversion

petrophysical record of the late silurian shallow water carbonate facies across the lau event prague synform czech republic and dynamic time warping alignment of the magnetic susceptibility logs

reply to the comments on permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology by e heydari j hassanzadeh w j wade and a m ghazi palaeogeography palaeoclimatology palaeoecology 193 405 424 2003 reply

late early triassic microbial reefs of the western united states a description and model for their deposition in the aftermath of the end permian mass extinction abstract research in the western united states to reinvestigate and characterize the previously reported stromatolites of the latest early triassic spathian virgin limestone member of the moenkopi formation has shown that these microbial build ups formed patch reef mounds detailed field analysis of these reef mounds and the surrounding beds has established that they attained 1 2 m of topographic relief above the seafloor a petrographic study of these microbial mounds illustrates that they consisted of microbial fabrics as well as voids with early marine cements and formed in the absence of in situ metazoans these reef mounds formed during the aftermath of the end permian mass extinction that spanned the early triassic due to the devastation of marine metazoans at this extinction the early triassic has often been deemed a reef gap because no metazoan reefs are found at this time whereas colonial metazoan reefs are globally absent from lower triassic strata microbial build ups similar to these described from the western united states have been found in south china armenia southern turkey and greenland a regional early permian to late early triassic unconformity exists in the study region however analysis of these microbial reefs within a global context suggests that conditions favouring microbial reef development must have existed as long as 4 8 m y after the end permian mass extinction a depositional model of these microbial mounds indicates that flooding of the shelf with anoxic and or co2 rich deep waters may have fostered their occurrence

catastrophic environmental transition at the permian triassic neo tethyan margin of gondwanaland geochemical isotopic and sedimentological evidence in the spiti valley india abstract interpreting global consequences of the permian triassic p tr extinction requires examination across paleogeographic realms of pangaea the spiti valley in india remnant of the peri gondwanan shelf preserved trails of this environmental catastrophe in the neo tethys ocean we document new sedimentological observations and high resolution trace element concentrations and carbon oxygen lead isotope data across the p tr boundary in spiti framboidal pyrites fossils and laminated lithology of the late permian shales indicate deeper anoxic depositional environment while 13 c org excursions of 2 4 and 3 1 in atargu and guling outcrops respectively identify the p tr transition across a clayey partly gypsiferous ferruginous layer sedimentological similarities of this layer to other neo tethyan sections from transcaucasia and iran indicate subaqueous oxidation of shallow marine sediments on a regional scale light rare earth element enriched late permian shales with conspicuous ce eu anomalies reflect their source from the adjacent panjal trap basalts ca 289 ma of kashmir continental crustal nb ta and zr hf anomalies appear at the p tr boundary sediments and prevail through the overlying early triassic carbonates original pb isotope ratios along with an increasing pb abundance closer to the p tr boundary distinguish the volcanic source of the late permian shales from the continental crustal siliciclastic signature of the early triassic carbonates our 13 c org trace element and pb isotope record from spiti indicate catastrophic changes in sediment sources and facies with effects on carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing also observed elsewhere along northern gondwanaland simultaneous eruption of siberian volcanics and bolide impacts in parana basin of brazil and elsewhere implicating impact triggered volcanism left catastrophic regional global imprints on sea level climate marine anoxia and tectonic stability that connected the p tr crisis across terrestrial and marine realms worlwide

anoxia as a cause of the permian triassic mass extinction facies evidence from northern italy and the western united states facies faunal and geochemical evidence from the permian triassic boundary sediments of the dolomites and idaho indicates a major anoxic event in the earliest triassic in both regions the basal beds consist of finely laminated micrites with common syngenetic pyrite the only fauna consists of occasional bedding plane assemblages of lingula or clacaria a typical lower dysaerobic assemblage this is a level where previous studies have shown a major negative carbon isotope excursion and a cerium anomaly in the dolomites the pyritic micrite directly overlies strata containing a diverse and typically permian marine fauna of algae foraminifers including fusulinids and articulate brachiopods implying an abrupt extinction in contradiction to many previous views sequence stratigraphic analysis of the dolomite boundary sediments reveals a minor sequence boundary in the late permian followed by extremely rapid transgression leading to the development of the relatively deep water pyritic micrite a maximum flooding surface at the permo triassic boundary a further pulsed deepening in the lower griesbachian recorded in both the dolomites and idaho lead to the widespread establishment of dysaerobic facies it is clear that most of the extinctions occurred at the erathem boundary although the subsequent failure of the marine benthos to fill the empty ecospace in the ensuing griesbachian may have been due to the widespread development of dysaerobic conditions

uranium depletion across permian triassic boundary in persian gulf and its implications for paleooceanic conditions abstract high resolution uranium analyses as well as oxygen carbon and strontium isotopes data through permian triassic boundary ptb in the marine sections of three offshore wells in persian gulf are illustrated in this paper a decreasing trend in u content from upper permian strata toward the ptb is recorded in all wells such a trend could not be adequately explained by the facies changes diagenetic events salinity variations dolomitization or total organic carbon toc content of the samples distinct and negative uranium anomalies coincide with the onset of the carbon isotope shifts which might indicate influx of anoxic waters the th u ratios below the ptb in the studied sections are mainly less than 2 reinforcing this possibility reducing conditions associated with the anoxia would have gradually increased the rate of u fixation on the deep sea floor resulting in low u concentration in the shallow water carbonates a negative 18o shift of about 4 could be seen at the ptb in all studied wells such excursion indicates a meteoric diagenesis below the boundary also abnormally higher 87sr 86sr ratios below the ptb indicate significant input of radiogenic 87sr during subaerial exposures at the end of permian this palaeoexposure surface is also reflected in depleted oxygen isotope values of this interval biostratigraphic studies also show that some important guide forms of late permian are absent in studied wells that could be due to several factors including non sedimentation subaerial exposure and erosion thus a near surface meteoric realm or emergent surface could be considered for the ptb in studied wells

the combined inversion of seismic and geodetic data for the source process of the 16 october 1999 mw 7 1 hector mine california earthquake we investigate the source process of the m w 7 1 hector mine earthquake by inverting broadband regional and local seismic displacement waveforms com bined with global positioning system gps and synthetic aperture radar interfer ometry insar geodetic measurements we find that the three data sets individually produce remarkably similar slip distributions over a multisegment fault a simulta neous inversion of the three data sets is presented and the sensitivity of the combined inversion to the weighting of the three independent data sets is examined the results indicate that the overall length of the fault that slipped is 42 km with a peak slip of 5 50 m and total scalar seismic moment of 6 8 10 19 n m the majority of slip is located on the western branch of the lavic lake fault to the northwest of the hypo center although the overall rupture is bilateral with appreciable slip on the bullion fault to the southeast some slip is located on an eastern branch of the lavic lake fault an apparent bifurcation which is also evident from aftershock locations the average slip and stress drops are 2 70 1 62 1 60 m and 78 36 and 55 bars for the western lavic lake the eastern lavic lake and bullion faults respectively the results also indicate that the overall rupture process is relatively slow which is char acterized by a several second delay before the onset of significant slip a 1 8 km sec rupture velocity of the primary asperity and long spatially variable dislocation rise times

petrography and geochemistry of the permian triassic boundary interval yangou section south china implications for early griesbachian seawater δ 13 c dic gradient with depth abstract the carbon isotopic composition 13 c carb recorded in shelf carbonates has been widely used as a proxy for the isotopic composition 13 c dic of surface ocean water to establish paleocean chemistry and circulation patterns however 13 c carb values do not necessarily preserve the 13 c dic due to post depositional diagenetic alteration in order to examine the early griesbachian surface to deep 13 c dic gradient with depth the diagenetic features of the permian triassic boundary interval beds 18 to 35 from yangou section located in the yangtze carbonate platform interior south china are delineated to compare with those of the slope gssp meishan section the petrographic and geochemical observations show that the early griesbachian carbonates in the yangou section underwent pervasive dolomitization in its early diagenetic history three types of early replacement dolomites and one type of dolomite cement are present the dolomite crystals display internal zonation with high ca calcian dolomite hcd core being encased successively by calcite and an outermost fe rich hcd cortex the initial dolomitization took place in anoxic seawater and underwent subsequent diagenetic system involved with meteoric water the two most negative 13 c values in claystones of beds 21 3 and 35 are probably related to meteoric diagenesis above and or below the meteorically influenced beds the dolomite and calcite have uniformly positive 13 c values the primary carbon isotopic compositions are probably preserved in the early griesbachian carbonate from the platform yangou section which could probably be related to the poor formation of the outermost fe rich hcd cortex compared to the slope carbonate from the meishan section the platform carbonate from the yangou section has lower primary 13 c carb values it is estimated that the 13 c dic gradient with depth between yangou and meishan is less than the previously suggested the results highlight the need for evaluation of local 13 c carb as record of 13 c dic in paleoseawater and carry important implications for understanding the permian triassic carbonate successions throughout the world

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

erosional truncation of uppermost permian shallow marine carbonates and implications for permian triassic boundary events on shallow marine carbonate buildups in south china turkey and japan uppermost permian skeletal limestones are truncated by an erosional surface that exhibits as much as 10 cm of topography including overhanging relief sedimentary facies microfabrics carbon isotopes and cements together suggest that erosion occurred in a submarine setting moreover biostratigraphic data from south china demonstrate that the surface postdates the uppermost permian sequence boundary at the global stratotype section and truncates strata within the youngest known permian conodont zone the occurrences of similar truncation surfaces at the mass extinction horizon on carbonate platforms across the global tropics each overlain by microbial buildups and their association with a large negative excursion in 13 c further suggest a causal link between erosion of shallow marine carbonates and mass extinction previously proposed to account for marine extinctions the hypothesis of rapid carbon release from sedimentary reservoirs or the deep ocean can also explain the petrographic observations rapid unbuffered carbon release would cause submarine carbonate dissolution accounting for erosion of uppermost permian skeletal carbonates and would be followed by a pulse of high carbonate saturation explaining the precipitation of microbial limestones containing upwardgrowing carbonate crystal fans models for other carbon release events suggest that at least 5 10 18 g of carbon released in 100 k y would be required of previously hypothesized permian triassic boundary scenarios thermogenic methane production from heating of coals during siberian traps emplacement best accounts for petrographic characteristics and depositional environment of the truncation surface and overlying microbial limestone as well as an associated carbon isotope excursion and physiologically selective extinction in the marine realm

strike slip motions in the gulf of sigacik western turkey properties of the 17 october 2005 earthquake seismic sequence abstract the october 2005 series of earthquakes that occurred in the gulf of sigacik western turkey reveal the operation of pure strike slip faults as evidenced from the 49 focal mechanisms we determined in a region dominated by n s extension and bounded by well documented graben structures the sequence is characterized by the occurrence of three moderate size events 17 october 2005 05 45 utc mw 5 4 17 october 2005 09 46 utc mw 5 8 and 20 october 2005 21 40 utc mw 5 8 with an eastward propagation and close spatial separation

rupture processes of large deep focus earthquakes from inversion of moment rate functions we determine the source time histories of five recent 1994 1996 large deep focus earthquakes using a method that inverts for fault slip from far field moment rate functions the moment rate functions are obtained through the deconvolution of multiple body wave phases using broadband records from global seismic network gsn and geoscope stations tests of this method on synthetic data indicate that it is successful in determining the low frequency rupture characteristics of deep earthquakes under a variety of complicating conditions we find that source parameters such as average rupture velocity and stress drop are highly variable among the events studied and that some unusual characteristics exhibited by the june 9 1994 great bolivian earthquake are also found for other events comparison of the slip distributions with background seismicity and aftershock locations indicates that most of the moment release for large deep focus earthquakes is probably occurring within the active slab interior this provides further evidence that temperature controlled mechanisms such as transformational faulting play a large role in deep earthquake faulting most of the events studied also show a tendency for horizontal rupture propagation suggesting that isobaric processes may be an important factor in controlling progression of the rupture large gaps in the slip distributions point to possible occurrence on multiple fault planes

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

mantle plume the invisible serial killer application to the permian triassic boundary mass extinction the earth experienced a severe mass extinction at the permian triassic boundary ptb about 252 million years ago this biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the precambrian time the eruption of the largest continental flood basalt the siberian traps overlapped this mass killing many hypotheses have been proposed but no definitive conclusion currently exits here we present characteristics of three sections from iran and china and propose that an active mantle plume initiated a series of processes which led to the mass mortality and produced major sedimentological mineralogical and geochemical changes observed in the transition from the paleozoic to the mesozoic the injection of mantle plume related igneous dike swarms into the continental margin facilitated the release of massive amounts of ch 4 primarily from the dissociation of marine gas hydrates and secondarily from the maturation of organic rich sediments and fracturing of hydrocarbon reservoirs the bulk of the ch 4 was aerobically oxidized in the water column producing dissolved co 2 with low 13 c values this co 2 saturated seawater became acidic to the point of dissolution of shelf carbonates promoting precipitation of siliciclastic rich strata in the transition from the permian to the triassic methane derived co 2 also lowered carbon isotopic composition of seawater leading to the observed decline in 13 c composition of organic and inorganic marine carbon at the ptb gas charged oceans released large volumes of co 2 and ch 4 into the atmosphere which created a severe global warming the end permian inferno causing the release of additional ch 4 from the dissociation of polar gas hydrates these events lowered 13 c compositions of terrestrial carbon simultaneously feeder dikes from the mantle plume formed the siberian traps flood basalt marine mass extinction was the result of a change in seawater composition due to the injection and oxidation of ch 4 in the water column causing low ph high concentrations of co 2 ca 2 and hco 3 and low co 3 2 values combined with a hot seawater temperature these changes made calcification of marine organisms difficult and produced major physiological crisis including reduced metabolic rates high sensitivity to environmental stress and hampered growth and reproduction terrestrial mass extinction can be attributed to severe global warming and soil acidification produced by increased atmospheric co 2 acid rain that was generated by so 2 derived from the siberian trap eruption and loss of habitat cessation of the plume activity during early triassic stopped the release of ch 4 into the ocean and terminated continental flood basalt eruption ending the environment of death on land and in sea the cut off of co 2 production in the ocean instantly increased carbonate saturation of seawater resulting in extensive seafloor cementation it also resulted in the deposition of marine carbonates by microbial activities in the hostile post extinction environment from the trigger to recovery the perturbation which included the end permian mass mortality could have lasted for at least 2 myr several major mass extinctions of the phanerozoic are temporally accompanied by flood basalt eruptions so far these two events have been interpreted in a cause and effect relation flood basalt eruption causes mass extinction this study proposes that flood basalts and their time correlative biological crises are themselves the consequence of a complex perturbation caused by mantle plume activities if so major disturbances in the near surface of the earth are ultimately controlled by changes in the mantle the physical sedimentological observations presented here combined with previous paleontological evidence cast doubt on other interpretations which use geochemical variables numerical modeling biomarkers and ce anomaly to suggest that late permian ocean was anoxic all the way to the photic zone

broadband analysis of the 21 september 1993 klamath falls earthquake sequence the source characteristics of the klamath falls earthquake sequence were estimated from broadband seismograms recorded by the berkeley digital seismic network bdsn terrascope and western united states iris stations solutions were obtained for events ranging in size from mw 3 8 to mw 6 0 an empirical green s function inverse approach was used to estimate kinematic source parameters of the two mw 6 0 mainshocks both events were found to have ruptured northwest on adjacent segments of the lake of the woods system of normal faults the two main shocks abut where there is a pronounced 10 to 20 clockwise rotation of strike which may have initially acted as a barrier to a through going mw 6 2 event

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

uranium depletion across the permian triassic boundary in middle east carbonates signature of oceanic anoxia we present a geochemical profile through a 445 m 1459 9 ft section of shallow water carbonate platform strata in the upper part of the khuff formation the permian triassic boundary ptb is recognized in this section based on the immediately preceding negative shift in bulk rock carbonate carbon isotope composition equivalent to the end permian extinction horizon combined with biostratigraphic control from nearby wells these strata show an abrupt and long lasting decrease in bulk rock uranium u content coincident with the carbon isotope shift because of low siliciclastic content and the consequently low potassium and thorium of these carbonates the decrease in u is clearly reflected in the total gamma ray gr profile recorded by wire line logging published log curves show similar distinctive gr profiles throughout a large area of the middle east indicating that u depletion across the ptb is a regional characteristic this feature cannot be explained as diagenetic and is not related to the organic matter content of the host sediments but it is suggested to reflect the global depletion of u in earliest triassic seawater caused by the abrupt onset of deep ocean anoxia and the resulting increase in u precipitation in oxygen poor sediments this explanation carries the implication that similar u depletion should be characteristic of lowermost triassic carbonates from shallow water oxygenated settings worldwide analogous signatures of u depletion should also have developed in shallow water carbonates deposited contemporaneously with episodes of deep ocean anoxia during other periods of geological time these predictions can be tested by high accuracy u profiling of other well characterized carbonate successions potentially yielding a new approach for tracking the degree of oceanic circulation throughout earth s history

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

sea level events in the south pacific linked with the messinian salinity crisis cores drilled through the carbonate cap of niue a mid oceanic carbonate platform in the south pacific contain an unusually well resolved stratigraphic section of the latest miocene at 35 to 140 m depth below sea level intensely leached and chalky intervals associated with pronounced 18 o and 13 c depletions mark the position of dissolution unconformities representing eight episodes of eustatic falls that outstripped the local rate of subsidence we demonstrate on the basis of sr isotope chronostratigraphy that these eustatic changes are correlative with the messinian salinity crisis events in the mediterranean sea level changes of about 10 m amplitude commenced at 6 14 ma and culminated in a large sea level fall that reached at least 30 m at 5 26 ma corresponding to the miocene pliocene boundary evaluation of the sea level history reported here and the contemporaneous mediterranean events supports the model of coupling between tectonic and eustatic factors that caused the onset and demise of the salinity crisis the available evidence suggests that during messinian time glacio eustatic falls and rises are likely to have modulated the connection between the atlantic and the mediterranean and influenced the evaporite deposition and may have contributed significantly to the final phase of isolation and desiccation of the mediterranean and its subsequent refilling during the zan clean deluge

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

deev jahi model of the permian triassic boundary mass extinction a case for gas hydrates as the main cause of biological crisis on earth the smoking gun revealing the secrets of the end permian mass mortality is a unique 1 2 m thick layer consisting of 5 20 cm long crystals of calcite that occurs precisely at the permian triassic boundary ptb in iran armenia turkey and china this layer is interpreted as synsedimentary abiotic seafloor cement indicative of precipitation from a highly carbonate supersaturated seawater its 13 c composition 13 c 0 pdb is 4 to 5 pdb lower than the typical upper permian values 4 to 5 pdb suggesting the involvement of massive amounts of gas hydrate ch 4 13 c 60 pdb the temporal coincidence of the cement layer with the ptb suggests that the process that promoted seafloor cementation was also responsible for the biological crisis a cementation model is developed based on accumulation dissociation cycle of gas hydrates which also explains the mass extinction at the ptb the upper permian accumulation period of gas hydrates ended abruptly adjacent to the ptb and the dissociation event began releasing 3 2 to 4 7 10 18 g ch 4 into the ocean oxidation of ch 4 in the water column created a seawater that was charged with co 2 an oceanic acid bath and had lower than normal o 2 content but not anoxic this oceanic acid bath first dissolved suspended fine grained carbonate particles and small calcareous organisms followed by extensive dissolution of platform carbonates raising ca 2 and hco 3 concentrations of seawater when the release of ch 4 declined the acid bath ocean became a soda ocean precipitating massive amount of seafloor cements observed globally at the ptb the study suggests that prior to cement precipitation the ptb ocean was charged with co 2 warm had low oxygen high ca 2 and high hco 3 concentrations these conditions collectively created stressful conditions causing the marine mass mortality the leakage of ch 4 to the atmosphere produced a super hot climate resulting in the biological devastation on land the proposed kill mechanism is developed on the basis of the physical clue the cement layer left behind by the killing process the change in ocean chemistry the accumulation dissociation cycles of gas hydrates also explain the 13 c pattern of marine carbonates and the periodicity of mass extinction events during the phanerozoic accumulation periods were long 5 to 20 my providing favorable conditions for ecosystem development pardeess phase the dissociation events were short and catastrophic 10 to 500 ky causing low oxygenation super hot climate and biological devastation doozakh phase it appears that most mass extinctions of the phanerozoic have been related to the internal working of the earth system during the phanerozoic methane has played the role of the deev jahi a female demon in persian mythology whose task is to attack the earth every so often to kill life on land and in sea

increased terrigenous influx but no drowning palaeoenvironmental evolution of the tunisian carbonate platform margin during the late aptian during the aptian some carbonate platforms of the sub tropical realm for example on the northern tethys margin or in the gulf of mexico were affected repeatedly by severe perturbations in the carbonate production factory and drowning preferentially during global warming events such as the early aptian oceanic anoxic event 1a and a prominent mid late aptian warming interval these platform growth crises have been explained mainly by strongly increased coastal runoff for example siliciclastics and nutrients in combination with pronounced eustatic sea level rises in the last few years increasing evidence suggests that carbonate platforms of lower latitudes were generally less or even not affected by environmental perturbations during these events this raises the question as to the responsible factors that promoted platform growth or decline in different latitudinal areas in this study upper aptian middle gargasian to uppermost clansayesian inner tropical carbonate ramp deposits of the serdj formation at djebel serdj north central tunisia are studied in detail with regard to microfacies lithology biostratigraphy and chemostratigraphy these data allow reconstruction of the palaeoenvironmental evolution of the tunisian carbonate platform margin and investigation of its response to the prominent mid late aptian warming interval the unusually expanded 600 m thick serdj formation consists of limestones marlstones and siltstones suggesting deposition within mid ramp to inner ramp palaeoenvironments deposits of the mid late aptian are represented by quartz rich platform carbonates and siltstones probably resulting from increased coastal runoff on the tunisian shelf as a response to global warming and accelerated water cycling the siliciclastic input was accompanied by elevated nutrient levels as indicated by a partial decline in the abundance of oligotrophic biota and mass occurrences of orbitolines and green algae carbonate platform drowning during the mid late aptian as reported from the sub tropical realm has not been identified a comparison with other tropical river influenced platforms suggests that none of them drowned during the mid late aptian one important reason might be widespread arid to semi arid climatic conditions within lower latitudes during that time promoting platform growth due to comparably low nutrient runoff

northwestern turkey earthquakes and the crustal structure inferred from surface waves observed in western greece records of several earthquakes occurring in turkey in 1999 obtained at broadband seismic stations in western greece have been used to study the dispersion of surface waves mainly love waves the observed group velocity dispersion curves have been inverted into horizontally layered models of the earth s crust by a modified method of the single parameter variation as compared with a previous model for the territory of greece the dispersion data require significantly lower velocities in the uppermost crust and smaller crustal thickness in particular the resulting model displays s wave velocities between 1 3 and 2 4 km sec in the upper 2 km and a crustal thickness of about 33 km manuscript received 31 july 2000

sr isotopic variation in shallow water carbonate sequences stratigraphic chronostratigraphic and eustatic implications of the record at enewetak atoll sr isotope data from two boreholes within the lagoon at enewetak atoll have been used to evaluate the use of such data to correlate date and monitor sea level change in shallow water carbonate sequences correlative stratigraphic intervals of relatively invariant 87sr separated by abrupt transitions to lower 87sr with increasing depth are recognized in both boreholes conversion of 87sr values to age via calibration with the seawater 87sr trend with age indicates that correlative and synchronous deposition of atoll sediments occurred at 0 4 1 2 and 2 1 ma in contrast a 5 m y hiatus is recognized in one borehole but not the other sr isotope stratigraphy sis is a powerful stratigraphic and chronostratigraphic tool in shallow water carbonate sequences only when significant secular variation of 87sr occurs and retention of depositional 87sr values is demonstrated the latter is best demonstrated when 87sr data are integrated with 18o 13c sr content data and petrographic observations several diagenetically altered intervals have greater 87sr values low 13c values and low sr ca ratios relative to adjacent intervals a combination that is consistent with open system meteoric diagenesis calcite cements from these intervals have early pleistocene 1 2 ma 87sr values despite their occurrence well within the late pliocene 2 1 ma sequence thus local sedimentological and diagenetic processes have produced intralagoon variability in the sis of the two boreholes complicating subsurface stratigraphic correlations the occurrence of anomalously young calcite cement relative to adjacent limestone is a direct response of the interaction of sea level change and meteoric phreatic diagenesis whereby overlying metastable carbonates with greater 87sr values are dissolved during periods of atoll emergence and sea level lowstand liberating sr and soil gas co2 to the pore fluid which is then incorporated into downflow meteoric phreatic diagenetic calcite the stratigraphic relation between the sites of carbonate dissolution and diagenetic calcite precipitation suggest an early pleistocene 1 2 ma sea level fall of between 34 and 64 m moreover the stratigraphic position and inferred age of paleophreatic lens calcite when backtracked for subsidence suggest that early pleistocene 1 2 ma sea level was 72 81 m range of 60 100 m below present sea level the enewetak record of early pleistocene sea level lowstand elevation agrees reasonably well with proxy sea level records inferred from sequence stratigraphy and deep sea foraminiferal 18o data however the enewetak record of the amplitude of early pleistocene sea level change is more consistent with the deep sea foraminiferal 18o proxy than the sequence stratigraphy proxy

diagenetic overprint on negative δ13c excursions across the permian triassic boundary a case study from meishan section china the meishan section d from china is the global stratotype section and point gssp of the permian triassic boundary ptb the succession has been divided into 115 beds with the ptb being placed in the middle of bed 27 in this section and the laterally equivalent section a the diagenetic features of beds 24 to 62 are examined in this study to determine if the negative shift in 13ccarb across the permian triassic boundary is diagenetic in origin or not bed 24 is formed of skeletal packstones whereas beds 25 to 62 are formed of claystones or argillaceous dolomitic limestones the dolomite crystals are typically 30 m long subhedral to euhedral and held in a very fine groundmass formed of calcite and clay minerals the cathodoluminescent features and backscattered images show that the dolomite crystals are zoned with a non luminescent low calcium calcian dolomite lcd core being encased successively by an irregular dull orange calcite zone a euhedral bright orange high calcium calcian dolomite hcd cortex and an outermost ferroan hcd zone available evidence indicates that the zoned dolomite crystals formed episodically the dolomite crystals following their initial syndepositional formation with euhedral lcd cores and hcd cortices were subsequently modified by calcitization mediated by meteoric water and overgrowth of fe rich hcd during burial the limestones in bed 24 display 13c values ranging from 1 72 to 2 92 18o values from 7 74 to 4 84 in beds 25 to 62 the bulk samples have 13c values from 0 76 to 1 28 and 18o values from 8 58 to 3 99 there is a positive correlation between these isotopic compositions and dolomite content it is estimated that the first formed dolomite and the precursor limestones have 13c value of 2 19 and 18o value of 1 14 the dramatic negative 13c excursions of calcite in beds 26 and 28 are related to meteoric diagenesis whereas the negative 13c excursions of bulk samples in the dolomite bearing beds are ascribed to the diagenetic modifications that post dated the initial formation of dolomite the results show that the 13c signals recorded in the gssp that spans the ptb are a mixture of original and diagenetic signals for the dolomite bearing bulk samples diagenesis contributes 1 7 to the negative shift in the 13c hence diagenetic alteration needs to be considered before using 13ccarb to estimate the dissolved inorganic carbon in the ancient oceans and to calculate the global carbon cycle

permian triassic extinction pattern revealed by foraminifers and geochemical records in the central persian gulf southern iran abstract permian triassic boundary ptb foraminifers are studied from the upper part of the dalan formation and the base of the kangan formation in four wells a b e f on and near the qatar arc persian gulf iran isotope studies including 13c and 18o values from wells b and e and 87sr 86sr ratios in wells b e and f have also been carried out to possibly provide a high resolution extinction pattern of foraminifers in the ptb interval the latter has been thoroughly investigated in iran turkey south china vietnam slovenia carnic alps and bukk mountains kashmir greenland and serbia the distribution of the last appearance of foraminiferal genera from the ptb interval in all of the wells is very similar featuring a stepwise extinction from 3 to 2 m before the boundary and compares to that observed in some of the sections from elsewhere i e south china vietnam slovenia and serbia the 13c value in wells b and e shows a negative shift at the base of a thrombolite unit immediately after the considered ptb and another negative shift at about 11 m below it in well e the thrombolite unit is assumed as earliest triassic but questionable with no supportive conodonts the 18o isotope values in wells b and e demonstrate the same negative upward trend due to dysoxic or anoxic conditions in the end permian oceans the uniform reduction without any sharp incline in the 18o profile suggests concurrent global warming the highest 87sr 86sr ratio fluctuations in wells b e and f coincide with the appearance of thrombolites changes in the profiles of carbon oxygen and strontium isotopes close to the ptb in wells b e and f seem to correspond to lithofacies variations from limestone to dolostone and a reduction in foraminiferal diversity these changes substantiate a clear perturbation in the marine environmental and global geochemistry elements through the ptb interval the 13c 18o and 87sr 86sr values obtained from the studied wells are comparable to those in other ptb stratigraphic sections in the paleo tethyan region

biomagnetostratigraphy of the vikinghogda formation svalbard arctic norway and the geomagnetic polarity timescale for the lower triassic a bio magnetostratigraphy for the lower triassic is constructed using the ammonoid biostratigraphy from arctic boreal successions combined thermal and alternating field demagnetisation determines the triassic magnetic field polarity in 86 of specimens with 36 showing linear trajectory line fits and the remainder great circle trends towards the characteristic magnetisation mean pole directions for the deltadalen 50 159 dp dm 3 9 5 1 lusitaniadalen 56 163 dp dm 4 4 5 4 and vendomdalen 57 143 dp dm 4 4 5 4 members fall close to the european lower triassic apparent polar wander path mean directions for two of these member means pass the reversal test the remanence is predominantly carried by magnetite the polarity stratigraphy when integrated with the ammonoid and meager conodont data is similar to that determined from successions in the sverdrup basin canada the permian triassic boundary post dates a pronounced palynofloral turnover and pre dates a short duration reverse magnetozone lt1n 1r in the correlated shangsi section in s china lt1n 1r occurs after the fad of h parvus but in the arctic is within the otoceras boreale zone the late griesbachian to early smithian is mostly reverse polarity with three normal polarity intervals overlain by mid and late smithian normal polarity the spathian contains four reverse polarity intervals the oldest one within the early spathian with the remainder in the late spathian transition into the anisian is within the uppermost reverse magnetozone a feature documented in other sections of this age the polarity pattern is correlated to other marine sections indicating the robustness of the bio magnetostratigraphic composite and its utility in calibrating lower triassic time

neotectonic and seismological data concerning major active faults and the stress regimes of northern greece northern greece is an intracontinental region behind the hellenic subduction zone with widespread seismic activity ranging from low to high with strong destructive earthquakes of mg6 0 in historical to recent times geological and seismological data indicate that recent seismic activity is mainly localized along large inherited fault zones which have transected northern greece since oligocene miocene times the main active fault zones in thrace and eastern and central macedonia strike approximately east west with lengths of 40 120 km fault segments strike wnw ese to ene wsw and range from 10 to 30 km in length in western macedonia the main active fault zones strike ne sw to ene wsw with lengths of 40 60 km and consist of 10 30 km segments the region s strong earthquakes are usually associated with reactivation of these fault segments and are estimated at m 5 6 6 5 focal mechanisms and fault slip data from the fault zones indicate a change in the trend of extension axes from nne ssw in eastern macedonia thrace to nnw sse in western macedonia thus neotectonic and seismological data suggest that variations in fault patterns as determined from the large inherited fault zones transecting northern greece are the major factor governing this change in the trend of maximum extension this interpretation is consistent with the long lived arcuate shape of the hellenic subduction zone of these the best known are the 1978 thessaloniki earthquake of m 6 5 papazachos et al 1979 and the 1995 kozani grevena earthquake pavlides et al 1995 mountrakis et al 1996c 1998 papazachos et al 1998a with the latter occurring in the low seismicity western macedonia region the rupture zones in northern greece need a thorough re examination in the light of recent advances in our understanding of active faulting and the new data provided by the aristotle university seismological network our aim is to identify the large active fault zones in northern greece from their geometric kinematic and seismotectonic features to define controlling stresses and to elucidate the continuity or extent of these zones the main aim is to better understand the active deformation of these areas and to determine whether fault deformation in northern greece is concentrated into relatively narrow bands or zones as one of the major issues in continental mechanics is how fault slips in the upper crust reflect more distributed flow in the lower lithosphere e g mckenzie jackson 1983 molnar gipson 1994 bourne et al 1998 information about active faulting and driving stresses in such areas is very useful brittle deformation within intracontinental regions is usually associated with distributed faulting and seismic activity however within such broad deforming regions some parts although transected by large faults are characterized by relatively less intense seismic activity and slip rates northern greece lies in the inner part of the continental collision region of nw greece and albania close to the intensely north south aegean extended sea this deformation is driven by the hellenic subduction zone and the westward extrusion of anatolia fig 1a in the older greek seismic code some large areas of macedonia e g western macedonia are classified as almost aseismic and other adjacent ones e g central macedonia as highly seismic recent instrumental data obtained from the regional seismological network of the aristotle university of thessaloniki after its installation in 1980 have confirmed the existence of significant seismicity in northern greece fig 1b particularly along narrow rupture zones papazachos et al 2001 furthermore large earthquakes have been reported in historical times papazachos papazachou 2003 and several strong and destructive ones have been recorded instrumentally during the last century 650 d mountrakis et al fig 1 a schematic map showing the position of northern greece in the broader eastern mediterranean geotectonic regime modified from papazachos papazachou 2003 b spatial distribution of instrumentally recorded earthquakes 1911 2004 with magnitudes mg3 0 for the broader study area ctf cephalonia transform fault rtf rhodes transform fault ptf paphos transform fault geology and seismotectonics of northern

the 14 february 2008 earthquake m6 7 sequence offshore south peloponnese greece source models of the three strongest events abstract we investigate the rupture process of the strongest events of the 14 february 2008 sequence which ruptured 30 km of the western hellenic trench three were the strongest events of the sequence the first one m 6 7 occurred on 14 february 2008 at a depth of 30 km on a low angle 10 thrust fault followed within 2 h by an m 6 1 aftershock at a depth of 33 km also on a low angle thrust fault and the third one on 20 feb 2008 of m 6 0 which is characterized as a strike slip event at shallower depth 10 km we used the m 6 1 aftershock as empirical green s function egf to invert for the slip distribution of the strongest m 6 7 event of the sequence we were able to identify the low angle plane strike 288 dip 10 and rake 73 as the fault plane the slip model is dominated by two distinct slip patches which extend towards sse from the hypocenter thus implying rupture directivity toward the island of crete a result which is further supported by our teleseismic waveform inversion results maximum slip is estimated at 270 cm while average slip on the ruptured area area of subfaults of non zero slip was 70 cm most of the slip 95 of total is confined in an area of 34 22 km 2 we attribute the occurrence of the shallow strike slip event just above the interplate thrusting at depth to slip partitioning due to the deflection of slip vectors from the expected plate convergence vector

slip distribution of the 7 september 1999 athens earthquake inferred from an empirical green s function study the source process during the 7 september 1999 athens greece earth quake is investigated using broadband seismograms recorded at regional distances source time functions are estimated through an empirical green s function approach and their shapes are inverted to reveal the spatial and temporal distribution of fault slip the resulting slip distribution pattern implies that about 50 of the total slip occurred at a depth greater than the hypocentral depth indicating downward rupture propagation whereas 25 of the total slip was concentrated at a shallower patch forward calculations of the displacement field at the surface show that the shallower slip patch is possibly responsible for the asymmetry observed in the displacement field and it may have contributed significantly to the distribution of damage