impact ejecta layer from the mid devonian possible connection to global mass extinctions we have found evidence for a bolide impacting earth in the mid devonian 380 million years ago including high concentrations of shocked quartz ni cr as v and co anomalies a large negative carbon isotope shift 9 per mil and microspherules and microcrysts at jebel mech irdane in the anti atlas desert near rissani morocco this impact is important because it is coincident with a major global extinction event kacak otomari event suggesting a possible cause and effect relation between the impact and the extinction the result may represent the extinction of as many as 40 of all living marine animal genera

a major circulation anomaly in the western bering sea the alaskan stream ceased to flow northward into the western bering sea starting in summer 1990 this unexpected lack of inflow caused by a southward shift in the path of the alaskan stream persisted through at least fall 1991 if the anomalous flow continues substantial changes in the physical environment will occur possibly leading to impacts on the rich fisheries stocks in the region

variations of okhotsk sea oxygen minimum zone comparison of foraminiferal and sedimentological records for latest mis 12 11c and latest mis 2 1 abstract benthic foraminiferal assemblage compositions foraminiferal and sedimentological proxies were analyzed in core md01 2415 from the northern slope of the okhotsk sea to compare variations of productivity and oxygen minimum zone omz intensity during the latest marine isotope stage mis 12 11c and latest mis 2 1 the benthic assemblages reveal close similarity between the two climatic cycles the absence of benthic assemblages during the latest mis 12 and the presence of the low productivity angulogerina angulosa assemblage during the latest mis 2 suggest the disappearance of the omz this regime was related to almost perennial ice cover with periods of active ice rafting during the latest mis 12 while it was attributed to prolonged seasonal ice cover low surface productivity and enhanced formation of well oxygenated water masses in the okhotsk sea during the latest mis 2 in deglacial times the omz gradually intensified as evidenced by the high productivity uvigerina akitaensis assemblage during the early termination t tv and early ti and the low oxygen tolerant bolivina spissa assemblage during the late tv and late ti the orbitally forced similar rises of the global sea level during tv and ti caused a large offshore supply of organic matter synchronously nutrients from the melting sea ice and shelf erosion promoted high surface mainly carbonate productivity as a result a high and sustained flux of particulate degraded and refractory organic matter enhanced oxygen consumption in bottom waters and sediments leading to the similar gradual omz intensifications the b spissa assemblage also points to expansion of oxygen depleted water mass from the north pacific into the okhotsk sea fostering the omz intensifications the phytodetritus related islandiella norcrossi assemblage indicates weakening of the omz during full interglacial times of mis 11c and mis 1 after stabilization of the global sea level nutrients were mainly delivered by regional upwelling and fluvial discharge favoring increased biogenic opal and carbonate production in the surface water similar to the present in this way moderate to high although less than deglacial and pulsed flux of predominantly particulate organic matter caused the weakening of the oxygen consumption and omz notably during mis 11c the benthic assemblage with the dominance of the taxa with dissolution resistant tests such as miliammina herzensteini karreriella baccata and martinottiella communis reflects carbonate dissolution events in sediments these events might have been resulted from an interruption of the local surface carbonate production and inflow of more carbonate corrosive water masses from the north pacific driven by a drawdown of the global ocean carbonate saturation

petrography and reservoir physics ii relating thin section porosity to capillary pressure the association between pore types and throat size porosity in reservoir rocks is configured into a few types of pores whose size and shape are controlled by depositional fabric and postdepositional processes the size shape and abundance of each pore type can be objectively determined from thin section using image analysis and pattern recognition procedures each pore type tends to be associated with a limited range of throat sizes the association between pore type and throat size can be determined using regression procedures linking pore type data obtained from thin section with capillary pressure data to do so a set of samples is required wherein the association between pore type and throat size is fixed but where pore type proportions vary between samples this condition is met by a sample suite representing res rvoir facies from a single core or in many cases from a single field the relationship between pore type and throat size is an effective means to relate reservoirs in terms of the efficiency of the porous microstructure to multiphase flow parameters derived from the relationship can be used to construct accurate physical models that subdivide physical response in terms of the contributions of each pore type

hydrogen index as reflecting intensity of sulphidic diagenesis in non bioturbated shaly sediments abstract based on 13 published porewater h 2 s and sulphate profiles the amount of h 2 s escaping from non bioturbated shales varies between some few to 45 of the amount of bacterially generated h 2 s this finding permits calculation of the original organic carbon toc or content of immature nonbioturbated shales using toc and sulphur content data in two immature non bioturbated sequences from hungary toarcian and oligocene the first order correlation between hi and toc toc or was found to be stronger than that between hi and toc indicating that sulphate reduction was the leading process both in decrease in toc content and degradation of kerogen source potential

the shedding of an anticyclonic eddy from the alaskan stream as observed by the geosat altimeter the evolution of a meander into an anticyclonic eddy which separates from the alaskan stream in the vicinity of the central aleutian islands is observed in two years of sea surface height anomalies computed from geosat exact repeat mission altimeter data the trajectory of the center of mass is estimated using a modified perpendicular bisector method eddy separation is inferred to occur where the trajectory makes a distinct turn to the southwest the observed region of meander growth and eddy separation agrees with that predicted by theory the evolution of meander eddy height and radius is estimated from least squares fits of the data to an axially symmetric gaussian profile the heights and radii are used to calculate the strength vorticity and energetics of the meander eddy ekman dynamics are assumed to govern the eddy decay spin down times based on vorticity are much longer than those based on energetics this is consistent with an eddy s ability to maintain its integrity as it decays representative height diameter and velocity scales of the eddy are characteristic of rings spawned by other current systems assuming a ring structure for this eddy the estimated ring volume represents a 21 transport anomaly referenced to the mean annual transport into the bering sea

eddy shedding from a boundary current around a cape over a sloping bottom abstract the authors discuss laboratory experiments that elucidate the mechanism of formation and westward drift of anticyclonic baroclinic vortices from a buoyant surface current flowing along a lateral boundary and around a cape experiments were carried out with a sloping bottom in order to simulate the topographic effect they showed how a vortex can be generated from the current where it separates and reattaches to the cape and that under some conditions the eddy is able to detach from the cape and drift westward following isobaths two important timescales regulate the flow the time tf that the current takes to generate a vortex and the time td that the vortex takes to drift westward for a distance equal to its radius when these two timescales are either of the same order of magnitude or tf td the vortex was able to form at the cape but it did not detach and drift westward the influence of the depth of the lower layer h0 on the flo

pyritization processes and greigite formation in the advancing sulfidization front in the upper pleistocene sediments of the black sea pyritization in late pleistocene sediments of the black sea is driven by sulfide formed during anaerobic methane oxidation a sulfidization front is formed by the opposing gradients of sulfide and dissolved iron the sulfidization processes are controlled by the diffusion flux of sulfide from above and by the solid reactive iron content two processes of diffusion limited pyrite formation were identified the first process includes pyrite precipitation with the accumulation of iron sulfide precursors with the average chemical composition of fesn n 1 10 1 29 including greigite elemental sulfur and polysulfides formed from h2s by a reductive dissolution of fe iii containing minerals serve as intermediates to convert iron sulfides into pyrite in the second process a direct pyrite precipitation occurs through prolonged exposure of iron containing minerals to dissolved sulfide methane driven sulfate reduction at depth causes a progressive formation of pyrite with a 34s of up to 15 0 the s isotopic composition of fes2 evolves due to contributions of different sulfur pools formed at different times steady state model calculations for the advancement of the sulfidization front showed that the process started at the pleistocene holocene transition between 6360 and 11 600 yr bp our study highlights the importance of anaerobic methane oxidation in generating and maintaining s enriched layers in marine sediments and has paleoenvironmental implications

multi fractal distribution analysis for pore structure characterization of tight sandstone a case study of the upper paleozoic tight formations in the longdong district ordos basin abstract with proven gas potential the gas charging and accumulation mechanisms for the upper paleozoic tight gas reservoir in the longdong district of the ordos basin remain controversial pore structure is the most direct and critical factor that affects gas charging and accumulation in the reservoir however the pore structure characterization of tight sandstone is far more difficult than that for conventional reservoir rocks due to significant heterogeneity the present work aims to introduce a new quantitative method for pore structure characterization that integrates multi fractal distribution analysis an effective and profitable method for quantitative heterogeneity analysis and high pressure mercury intrusion porosimetry hpmip twenty one samples from targeted tight formations with different gas bearing status were obtained for analysis the results show that the best formations for gas charging and accumulation in the upper paleozoic tight sandstone formations in the longdong district are the formations with more large pores more homogeneous small pores and well developed micro fractures the existence of micro fractures is the key factor that affects gas charging and accumulation tight sandstone samples were categorized into three types in accordance with the hpmip curve configuration due to the high heterogeneity of pore structures analyses based solely on hpmip curve configuration has its shortcomings which can be compensated by multi fractal distribution analysis the multi fractal distribution of target tight formations could be interpreted as two linear segments representing large pores and small pores the separating points of the two segments vary from 0 1 m to 0 5 m in different samples due to different pore structures large pores are not ideal fractals in gas bearing formations due to the existence of micro fractures whereas they are fractals in dry formations where micro fractures are not developed small pores are all ideal fractals with the highest heterogeneity in type samples and the lowest heterogeneity in type samples a conclusion was made in this work if the slope of segment one in the multi fractal distribution of mercury saturation shg versus capillary pressure pc is larger than 1 this measure could be accepted as an empirical indicator for the existence of micro fractures

quantitative characterization of carbonate pore systems by digital image analysis a new method of digital image analysis can quantify pore parameters over more than three orders of magnitude from a submicron to a millimeter scale this porosity characterization does not require knowledge of lithology age burial depth or diagenesis of the sample the method is based on digital analyses of images from thin sections at variable magnifications taken under an optical microscope om and under an environmental scanning electron microscope esem the results help explain variations in permeability for carbonate samples with a variety of complex pore structures the analyses however can be done on any thin sections of other rock types the om images provide macroporosity information whereas the esem images yield information on microporosity the boundary between macroporosity and microporosity is defined at a pore area of 500 m2 which translates to a pore length of approximately 20 m which is roughly the thickness of a thin section and thus the resolution of the om the digitized thin section images are binarized into a macropore and a matrix phase om or a micropore and a solid phase esem a standard digital image analysis program is used to detect all individual pores and to measure pore area and pore perimeter based on these analyses one can calculate for each sample the amount of macroporosity the amount of microporosity within the matrix intrinsic microporosity the shapes of the macropores perimeter over area and the pore size distribution comparison of total porosity determined from plugs indicates that macroporosity and microporosity values based on this methodology match the plug data confirming the validity of the method the combination of macroporosity and microporosity data yields pore size distribution and pore shape information that can explain the distribution of physical properties in particular permeability in parameter sensitivity analyses using neural networks permeability appears to be mainly controlled by the macropore shape in high permeability samples and by the amount of intrinsic microporosity in the low permeability samples

multi year meanders and eddies in the alaskan stream as observed by topex poseidon altimeter the birth life and decay of long lived anticyclonic eddies or meanders in the alaskan stream are observed from topex poseidon t p satellite their surface height anomalies approach 72 cm average diameter is about 160km and they live for 1 to 3 years propagating along the stream with mean speed of 2 5 km d 1 of the six observed the last three were formed after the first t p observations in september 1992 of these two evolved from eddies near alaskan panhandle in winter drifting across the northern gulf of alaska before entering the alaskan stream while another formed in the stream west of shelikof strait

effect of maturation on the indigenous δd signatures of individual hydrocarbons in sediments and crude oils from the perth basin western australia abstract we measured the stable hydrogen isotopic composition d of selected aliphatic hydrocarbons in nine sediments of various maturity and two crude oils all from the northern perth basin on shore western australia the sediments and crude oils are from the lower triassic hovea member sapropelic interval of the kockatea shale the n alkanes pristane and phytane from two immature sediments have d values that represent the expected isotopic compositions of their precursors phytane is enriched in deuterium d relative to pristane in all sediment extracts and crude oils this is attributed to either different sources or to different isotopic effects during their derivation from phytol with increasing maturity pristane and phytane become enriched in d while the n alkanes generally remain at a constant isotopic composition a more rapid enrichment of d in isoprenoids relative to n alkanes with increasing maturity suggests that hydrogen isotopic exchange is occurring via a carbocation mechanism the phytane diastereomer ratio for each of the sediments correlates linearly with the progressive enrichment of d in phytane and therefore maturity suggesting that significant hydrogen exchange occurs at the chiral carbons of phytane the d values of pristane and phytane from the crude oils are similar or more positive relative to the d values of the n alkanes the average d values of pristane and phytane for the sediments correlate well with equivalent vitrinite reflectance values as does the conventional biomarker maturity parameter t s t m indicating that d values may be useful for establishing maturity over a wider range than conventional biomarker parameters the results provide further evidence that care must be taken not to over interpret d values of sedimentary hydrocarbons in samples of high thermal maturity

anaerobic methane oxidation and a deep h2s sink generate isotopically heavy sulfides in black sea sediments the main terminal processes of organic matter mineralization in anoxic black sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2 4 m and methanogenesis below the sulfate zone the modern marine deposits comprise a ca 1 m deep layer of coccolith ooze and underlying sapropel below which sea water ions penetrate deep down into the limnic pleistocene deposits from 9000 years bp sulfate reduction rates have a subsurface maximum at the so42 ch4 transition where h2s reaches maximum concentration because of an excess of reactive iron in the deep limnic deposits most of the methane derived h2s is drawn downward to a sulfidization front where it reacts with fe iii and with fe2 diffusing up from below the h2s fe2 transition is marked by a black band of amorphous iron sulfide above which distinct horizons of greigite and pyrite formation occur the pore water gradients respond dynamically to environmental changes in the black sea with relatively short time constants of ca 500 yr for so42 and 10 yr for h2s whereas the fes in the black band has taken ca 3000 yr to accumulate the dual diffusion interfaces of so42 ch4 and h2s fe2 cause the trapping of isotopically heavy iron sulfide with 34s 15 to 33 at the sulfidization front a diffusion model for sulfur isotopes shows that the so42 diffusing downward into the so42 ch4 transition has an isotopic composition of 19 close to the 23 of h2s diffusing upward these isotopic compositions are however very different from the porewater so42 43 and h2s 15 at the same depth the model explains how methane driven sulfate reduction combined with a deep h2s sink leads to isotopically heavy pyrite in a sediment open to diffusion these results have general implications for the marine sulfur cycle and for the interpretation of sulfur isotopic data in modern sediments and in sedimentary rocks throughout earth s history

reconstruction of palaeohydrological conditions in a lagoon during the 2nd zechstein cycle through simultaneous use of δd values of individual n alkanes and δ 18 o and δ 13 c values of carbonates for the first time 18o and 13c values from carbonates and d values of individual n alkanes were used to reconstruct palaeohydrological conditions in a lagoon at the southern margin of the central european zechstein basin cezb a 12 m core covering the complete ca2 interval and adjacent anhydrites a1 and a2 was analyzed for 18o and 13c values of dolomitized carbonates and d values of individual n alkanes 18ocarb values 2 to 5 vs vpdb were strongly influenced by evaporation and temporal freshwater input into the lagoon the 13ccarb values 1 to 4 vs vpdb were controlled mainly by changes in primary production both isotopic ratios show an inverse relationship throughout most of the core contradicting diagenetic alteration since 13ccarb values are not altered significantly during dolomitization assuming a temperature range of 35 40 c in the lagoon 18ocarb values of 2 5 to 8 vs vsmow for the lagoonal water can be reconstructed the lagoon may have desiccated twice during the ca2 interval as indicated by very high 18ocarb and low 13ccarb values coinciding with increasing amount of anhydrite in the analyzed sample these events seem to reflect not just local but a regional intra ca2 cyclicity measured d values of the short chain n alkanes namely n c16 and n c18 which are widely used as indicators for photosynthetic bacterial and algal input reflect the isotopic composition of the lagoonal water assuming constant fractionation during incorporation of hydrogen into lipids of 160 an average d value of 70 vs vsmow can be reconstructed for the lagoonal water accounting for very arid conditions the long chain n alkanes n c27 n c28 n c29 and n c30 thought to be derived from the leaf waxes of terrestrial higher plants were shown to be depleted in d relative to the short chain alkanes therefore indicating a different hydrogen source terrestrial plants in arid areas mainly use water supplied by precipitation by using a smaller fractionation of 120 due to evaporation processes in the leaves reconstructed values vary between 74 and 9 vs vsmow these values are not indicating extremely arid conditions implying that the long chain n alkanes were transported trough wind and or rivers into the lagoon at the zechstein sea coast dwater values reconstructed using the n c16 alkane and 18o water values independently reconstructed on the same sample using the temperature dependant fractionation for dolomites are good agreement and suggest high amounts of evaporation affecting the coastal lagoon altogether our results indicate that hydrogen isotopic ratios of n alkanes give information on their origin and are a useful proxy for palaeoclimatic reconstruction

a double thermostad warm core ring of the gulf stream abstractan unusual double thermostad warm core ring of the gulf stream was discovered in the slope sea south of georges bank during the r v endeavor cruise 578 in may 2016 the ring s stratificat

the identification of crocetane in australian crude oils abstract the c 20 irregular isoprenoid crocetane 2 6 11 15 tetramethylhexadecane has been unambiguously identified in a series of western australian crude oils from the canning ordovician devonian and perth lower triassic basins pmi 2 6 10 15 19 pentamethylicosane was found to co occur with crocetane in the same samples in addition a newly observed series of c 22 c 24 irregular isoprenoids possessing the same carbon skeleton have also been tentatively identified in each of these crude oils on the basis of gc retention times and mass spectral characteristics this may indicate a source for crocetane in the canning and perth basin crude oils from the diagenesis of pmi the stable carbon isotopic composition for combined crocetane phytane in these samples suggests crocetane is not unusually depleted in 13 c compared with all previous reports this is the first reported occurrence of biomarkers attributable to methanogenic archaea in crude oils

heterogeneity of intergranular intraparticle and organic pores in longmaxi shale in sichuan basin south china evidence from sem digital images and fractal and multifractal geometries abstract previous studies have determined many types of pores in shale such as organic pores inorganic pores and microfractures in this study pores are classified as intergranular intraparticle and organic pores based on the location of their occurrence the heterogeneities of the three pore types and their effects on the occurrence of shale gas which is of utmost practical importance for shale gas exploration and development are discussed in this study the three types of pores are quantitatively characterized using fractal and multifractal methods the mean fractal dimension and mean width of the multifractal spectrum of these pores are found to be different i e 1 5985 and 1 665 for intraparticle pores 1 5869 and 1 475 for intergranular pores and 1 6 and 1 3725 for organic pores intraparticle pores have the highest heterogeneity intergranular pores have intermediate heterogeneity and organic pores have the lowest heterogeneity sem images show that organic pores have good connectivity homogeneous distribution and small range of aperture change but have the lowest heterogeneity even where pores are abundant thus they provide the largest shale gas occurrence space in contrast intergranular pores are less abundant have lower connectivity and have higher heterogeneity than organic pores thereby providing a relatively smaller shale gas occurrence space finally intraparticle pores are the least abundant and possess the poorest connectivity largest range of aperture change and highest heterogeneity of the three pore types thereby providing the smallest shale gas occurrence space we conclude that organic pores are crucial to the occurrence of shale gas and can provide a new index for the evaluation of shale gas exploration and development

on the structure paths and fluxes associated with agulhas rings in january 1993 two agulhas rings were sampled in the eastern south atlantic during the world ocean circulation experiment one time hydrographic section a11 the first of these ring 1 was sampled at 36 s 4 e in the subtropical frontal zone and was smaller and less energetic than other more typical agulhas rings owing partly to its interactions with the north subtropical front the other ring 2 was sampled at 33 s 10 e in the subtropics this ring was average in size and reasonably representative of the rings observed in the southeast atlantic during the early 1990s the path of the rings is found to be dominated by advection in the mean flow rather than self induced velocities of eddies under the effect we observe significant differences in reduced gravity and available heat and salt anomalies in the rings from these we infer temporal variability in the stratification of rings upon their formation at the agulhas retroflection this temporal variability in the structure of rings will affect the fluxes associated with them data collected within ring 2 show that neglecting consideration of the water beneath the 10 c isotherm underestimates the volume flux by half and the potential temperature and salinity flux by in excess of one third and one half respectively using a base of the 3 5 c isotherm and including the high salinity intermediate water from the indian ocean is found to be more appropriate with these conditions six agulhas rings per year entering the subtropical south atlantic would equate to a volume flux of 9 sv and an absolute potential temperature and salinity flux of 84 sv c and 322 sv psu 1 sv psu 106 kg s 1 the significant flux of intermediate water from the indian ocean may be as important in the return path of the thermohaline circulation as the intermediate water that enters the south atlantic through drake passage further the water associated with agulhas rings and cooler than 10 c potentially contributes a larger volume flux to the warm water return path than the corresponding surface and upper thermocline water

water column anoxia enhanced productivity and concomitant changes in δ13c and δ34s across the frasnian famennian boundary kowala holy cross mountains poland the investigation of the trace element and organic geochemistry of the frasnian famennian boundary section at kowala holy cross mountains poland shows that the lower water column was oxygen deficient during late frasnian and early famennian times the abundance and carbon isotopic composition of diaryl isoprenoids biomarkers indicative for green sulfur bacteria prove that euxinic waters reached into the photic zone at least episodically total organic carbon toc contents show two maxima that are time equivalent to the kellwasser horizons deposited in shallower water settings enhanced toc concentrations are explained by a higher primary productivity presumably as a consequence of an enhanced nutrient supply from the continent the increase in the abundance of hopanes and bituminite suggests that the bacterial contribution to toc increased at the frasnian famennian transition the sulfur isotopic composition of pyritic and organically bound sulfur shows a 27 excursion across the boundary the observation that the 34s values of organic bound sulfur closely resemble that of pyrite sulfur indicates a common sulfur source likely early diagenetic sulfide a change in the 13c of total dissolved inorganic carbon as a consequence of an enhanced burial of 12c enriched organic carbon is indicated by a 3 excursion measured for toc as well as for individual n alkanes and isoprenoids the burial of large amounts of organic carbon is expected to result in a decrease in pco2 and should affect the photosynthetic carbon isotope fractionation ep the fact that we observe no change in ep can be explained by the circumstance that ep was most probably at maximum values as a consequence of high atmospheric and oceanic dissolved co2 concentrations during the devonian

chemostratigraphy of the posidonia black shale sw germany i influence of sea level variation on organic facies evolution abstract during the toarcian widespread deposition of organic rich mudrocks black shales occurred across europe linked to a 3rd order sea level rise we provide a high resolution multi proxy chemostratigraphic study of the dotternhausen sections in sw germany embedded in a stratigraphic and palecological framework chemostratigraphy and paleoenvironmental reconstruction is based on rock eval and elemental analysis of bulk organic matter and biomarker analysis of aliphatic hydrocarbon fractions aliphatic biomarker ratios applied to reconstruct the facies development include pristane phytane and pristane phytane n c 17 n c 18 ratios carbon preference index c 27 c 29 sterane and hopane sterane distribution results show that sea level change exerted the major control on the composition of primary produced organic matter and on its redox controlled preservation changes in primary production and in the ratio of terrestrially versus marine derived organic matter take place drastically at the onset of black shale deposition the relative proportion of terrestrial versus marine biomass accumulation is independently assessed by highly correlative bulk organic matter properties hi values and biomarker ratios cpi the terrestrially derived end member yields hi values of 50 100 mg hc toc and cpi values of 1 4 2 0 whereas the marine end member has hi values of 600 700 mg hc toc and cpi values of 0 95 1 05 correspondingly the shift in plant versus bacteria derived biomass is discriminated by hi values and hopane sterane ratios data were grouped according to their position in the lowstand lst lower and upper transgressive tst highstand systems tract hst and maximum flooding surface mfz of the sequence stratigraphic framework occurrence of organic matter with a significant bacterial contribution is restricted to the lst and lowermost tst and shows hopane sterane ratios of 0 25 0 5 marine phytoplanktonic matter dominates the upper tst hst and mfz with organic matter giving hopane sterane ratios between 0 5 and 1 7 samples from the hst yield hi values between 450 and 500 mg hc toc which is consistently lower by 150 mg hc toc when compared to the tst the lower quality of the organic matter deposited in the hst is due to its longer settling times through a thicker oxygenated water column a strong correlation with relative sea level stand and the c 27 c 29 sterane ratio is observed lst exhibits c 27 c 29 sterane ratios of 0 7 during transgression values increase to 1 0 reaching a maximum at 1 4 during sea level highstand thus reflecting decreasing terrigenous input and shifts in near shore versus open marine algal communities episodic fluctuation of anoxia is discussed on the basis of a monsoonal climate model which infers significant surface run off during summer monsoon providing high nutrient supply and associated high primary productivity in combination with a density stratified water column excellent preservation conditions for organic matter were established dry winter conditions with inversion of the surface water flow regime led to seasonal export of bottom waters and episodic establishment of dysoxic conditions variations in the extent of annual flushing of sub basins on the toarcian shelf controlled long term organic matter accumulation rate paleoclimate variability and its connection with sea level stand is thus of paramount importance for different modes of organic matter accumulation and redox system stability

2d multifractal analysis and porosity scaling estimation in lower cretaceous carbonates abstractthe study of scaling porosity in carbonate rocks has great importance because 1 porosity measurements are usually made at scales that are different from the one of interest and 2 carbonate formations contain most of the hydrocarbon reservoirs and aquifers in the world despite these facts scaling porosity in heterogeneous media such as carbonate rocks is still an open problem the heterogeneity of carbonate rocks mainly resides in their complex texture we have extended previous studies on carbonate multifractal behavior in pore space morphology at different scales and we have developed a new equation based in fractal geometry that could be used to scale the porosity in our methodology we 1 perform a multifractal analysis in thin section images of a set of complex carbonate rocks from the lower cretaceous 2 review the effect of magnification in scanning electronic microscope and thin section images 3 deduce a new scaling equation for porosity and finally 4 evaluate this equati

rapid thermohaline transition in the pacific western subarctic and oyashio fresh core eddies seven years of conductivity temperature depth data enable direct computations of volume transport and a description of the temporal changes of water properties in the western subarctic pacific the cooling of the western subarctic surface layer is shown through the observation of the thermohaline transition which occured in the western subarctic during 1990 1997 its main consequences were changes of the oyashio path and restratification of the western subarctic water the example presented here uses data obtained during the canada russia international north pacific ocean climate study as well as the russian project subarctic to show that a warming and ventilation of the midlayers of the western subarctic 200 1000 dbar occurred because of the influx of warm subtropical waters to the oyashio and sea of okhotsk and to the weak coastal oyashio before the transition this influx appears to have reversed in the early 1990s now subarctic intermediate waters displace the remnants of subtropical waters that penetrated to the sea of okhotsk through the soya strait and create strong stratification in the oyashio area this transition appears to have begun during the reinforcement in the coastal oyashio

an integrated biomarker isotopic and palaeoenvironmental study through the late permian event at lusitaniadalen spitsbergen abstract the largest extinction of the phanerozoic occurred near the permian triassic p tr boundary some 252 ma ago several scenarios and drivers have been proposed for this event here we report for the first time an integrated study comprising sedimentological data biomarker distributions abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes 34spyrite 13ccarb 13corg for a late permian section from lusitaniadalen spitsbergen norway sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the late permian strong evidence for waxing and waning of photic zone euxinia throughout the late permian is provided by chlorobiaceae derived biomarkers including 13c data and 34spyrite implying multiple phases of h2s outgassing and potentially several pulses of extinction a rapid decrease in abundance of various land plant biomarkers prior to the marine collapse event indicates a dramatic decline of land plants during the late permian and or increasing distance from palaeoshoreline as a consequence of sea level rise changes in d of selected biomarkers also suggest a change in source of organic matter om or sea level rise we also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse compound specific isotope analyses csia of algal and land plant derived biomarkers as well as 13c of carbonate and bulk om provide strong evidence for synchronous changes in 13c of marine and atmospheric co2 attributed to a 13c depleted source the source could be associated with isotopically depleted methane released from the melting of gas clathrates and or from respired om due to collapse of the marine ecosystem

possible algal origin of long chain odd n alkanes in immature sediments as revealed by distributions and carbon isotope ratios a pliocene oil shale pula hungary a c3 plant triticum aestivum and a c4 plant zea mays were compared using isotopic composition of bulk organic matter along with distributions and individual carbon isotope ratios of n alkanes from organic extracts the microalga botryococcus braunii a race was thus shown to be the main source of the predominant 27 29 and 31 n alkanes of pula sediment therefore the dominance of odd carbon numbered n alkanes in the range c25 35 in extracts from immature sediments shall not be systematically assigned to higher plant contribution but algal input is also possible in fact the long chain n alkanes with an odd predominance previously observed in extracts of various immature sediments are likely to be derived at least partially from algae

pore structure and fractal characteristics of ordovician majiagou carbonate reservoirs in ordos basin china fractal analysis was performed on carbonate core plug samples from the ordovician majiagou carbonate reservoirs in the ordos basin using mercury intrusion capillary pressure micp nuclear magnetic resonance nmr and the x ray computed tomography ct measurements to improve our understanding of the pore structure characteristics the relationships between pore structure parameters and the fractal dimensions were investigated the pore systems are dominated by secondary intercrystalline pores and enlarged dissolution pores as well as microfractures the fractal curves from micp analysis break into two segments at the swanson s parameter the small pore throat systems can be described by the fractal theory whereas pores connected by relatively large throats greater than the pore throat radius at the pittman s hyperbola s apex are not cylindrical in shape cannot be described by a capillary tube model and tend to have apparent fractal dimensions larger than 3 0 the fact that the entirety of the capillary curve cannot be fit by a single fractal dimension implies that there are multiple pore systems present with different fractal dimensions the ct analysis shows that the pores are dispersed in the three dimensional spaces mainly with elliptical shapes the nmr measurements are sensitive to pore body size and micp probes pore throat dimensions the latter being complementary to the pore body size distribution none of the ct micp and nmr techniques provide right or wrong answers to the pore throat systems but they probe different aspects of the pore systems this study assumes the pore shapes to be spherical in general and then the fractal dimension is calculated from the nmr transverse relaxation time t2 spectrum the fractal dimensions of all the samples are calculated and the accuracy of the fractal model is verified by the high regression coefficients almost all the pore systems can be described by fractal theory and the fractal dimensions are strongly correlated with the t2 values separating the immovable fluid and the free fluid microfractures may bias t2 toward larger values making it hard to derive fractal dimensions from nmr measurements the coexistence of small pores pore radius 50 m results in a heterogeneous pore distribution and a high fractal dimension reservoir quality increases with the complexity degree of the microscopic pore structure conversely samples that are dominated by small pore systems tend to have a lower fractal dimension and a less complex pore structure

satellite and hydrographic observations of the bering sea green belt abstract green belt is the aptly named region of high productivity occurring principally along and above the shelf slope boundary in the bering sea topex altimeter measurements of sea surface topography seawifs imagery of chlorophyll a concentration and shipboard measurements of salinity and fluorescence are used to describe the surface structure of the green belt and its relationship to the bering slope current eddy field during the 2000 2001 and 2002 spring blooms during spring 2000 high surface chlorophyll a concentrations 10 mg m 3 were observed within a 200 km wide band adjacent to and seaward of the shelf break in the northwest bering sea this high concentration chlorophyll band was associated with an anticyclonic eddy group that propagated along isobaths above the continental slope and entrained chlorophyll from the shelf slope front during spring 2001 anticyclonic eddies in the northwest bering sea had propagated off slope prior to the onset of the spring bloom and were too far from the shelf slope front to entrain frontal chlorophyll during the bloom a second chlorophyll front associated with the leading edge of the off slope eddies was observed between these two fronts was a region of relatively low chlorophyll a concentration 1 mg m 3 the eddy field during the 2002 spring bloom was observed to propagate northwestward adjacent to the shelf break and entrain chlorophyll from the shelf slope region in a manner similar to what was observed during the 2000 spring bloom these observations suggest that eddies are important if not the principal agents that cause variability in the distribution of chlorophyll during the spring bloom in the central bering sea

area perimeter relation for rain and cloud areas following mandelbrot9s theory of fractals the area perimeter relation is used to investigate the geometry of satellite and radar determined cloud and rain areas between 1 and 1 2 x 106square kilometers the data are well fit by a formula in which the perimeter is given approximately by the square root of the area raised to the power d see equation in the pdf where d is interpreted as the fractal dimension of the perimeter it is concluded that rain and cloud perimeters are fractals they have no characteristic horizontal length scale between 1 and 1000 kilometers

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

variability of the kuroshio extension jet recirculation gyre and mesoscale eddies on decadal time scales abstract twelve years of sea surface height ssh data from multiple satellite altimeters are used to investigate the low frequency changes and the interconnections of the kuroshio extension ke jet its southern recirculation gyre and their mesoscale eddy field the dominant signal is characterized by the steady weakening of the ke jet recirculation gyre from 1993 to 1996 followed by a gradual strengthening after 1997 during the weakening period of 1993 96 the ke path migrated southward in general and this path migration reversed in direction during the strengthening period of the ke jet and recirculation gyre after 1997 by hindcasting the ssh signals using linear vorticity dynamics it was found that weakening strengthening in the ke jet and recirculation gyre is consistent with westward propagation of negative positive ssh anomalies generating in the eastern north pacific and strengthening during their westward propagation when the ke jet and recirculation gyre were in a weak mode during 19

pore structure and fractal analysis of lower carboniferous carbonate reservoirs in the marsel area chu sarysu basin abstract evaluation of carbonate heterogeneity closely related to pore geometry and connectivity is important in oil and gas field production and reservoir prediction to profoundly understand the heterogeneity of lower carboniferous carbonate reservoirs in the marsel area including visean c1v and serpukhovian c1sr the pore structure and fractal characteristics are investigated using routine petrophysical measurements x ray diffraction xrd cast thin section analysis scanning electron microscopy sem and mercury injection capillary pressure micp tests the origin of potentially prolific reservoir the relationships between fractal dimension and reservoir physical properties mineral composition and pore structure are also discussed xrd results reveal that the mineral compositions are highly heterogeneous in c1v and c1sr routine petrophysical experiments indicate that c1v and c1sr are generally tight however some high porosity permeability zones exist in c1sr which is described as a potentially prolific reservoir the cast thin section and sem analyses identify three main pore types in the potentially prolific reservoir interparticle dissolution pores intercrystalline dissolution pores and moldic pores the micp data reflect that the pore throat radii in the prolific reservoir range from 0 29 to 4 6 m whereas those in tight section are typically

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

sterane biomarkers as indicators of palaeozoic algal evolution and extinction events abstract algae are among the oldest organisms known to inhabit the earth s biosphere with a record dating back some 2 7 ga only few marine algae produce hard parts that can be preserved over geologic time and consequently their fossil record is incomplete molecular fossils or biomarkers add complementary information to the fossil palynomorph record steroids are important constituents of eukaryotic cell membranes and are preserved in sediments as steranes c28 and c29 steranes are indicators for the presence of green and c27 steranes for the presence of red algae respectively the relative abundance of steranes allows the investigation of the fossil record for palaeozoic algal diversification and evolution in this study 500 palaeozoic rock samples representing a broad facies variety from the upper ordovician to the p t boundary were investigated for sterane compositions in addition three profiles covering the hirnantian the f f and the hangenberg event were analyzed for possible shifts in the sterane distribution associated with extinction events a sharp increase of the c28 c29 sterane ratio from 0 70 at the devonian carboniferous boundary implies a fundamental change in the green algae assemblage from more primitive mainly c29 sterane producing algae to modern c28 sterane producing algae for all investigated extinction events a pronounced but short lived rise in the c28 sterane content occurs that is attributed to an episodic increase in prasinophytes the gradual radiation of algae may have been triggered by frequent mass extinctions in the upper devonian culminating with the massive decline of acritarchs at the d c boundary the coeval rise in the c28 c29 sterane ratio indicates the presence of an non encysting algal group and coincides with the global augmentation of numerous filamentous codiacea siphonales and the rise of euspondyle and metaspondyle dasycladales

modification of a kenai eddy along the alaskan stream 1 a kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and argo float observations this eddy formed in december 2006 south of the kenai peninsula and propagated southwestward along the alaskan stream the eddy held horizontally uniform warm core water in january 2007 in late winter 2007 this core water was cooled from the top and a subsurface temperature maximum was formed around 26 5 two years later in summer 2009 warm and low dissolved oxygen low do water characterized by a temperature maximum around 26 5 was observed again in the eddy core and was likely the remnant of original core water at the same time cold and high do water intrusions occurred in the eddy core suggesting that strong modification of core water was ongoing after summer 2009 the core water was fully changed through interaction with another eddy

remotely propagating salinity anomaly varies the source of north pacific ventilation abstract the dense shelf water dsw produced in the sea of okhotsk causes the deepest ventilation in the north pacific and plays a key role in overturning to the depth of intermediate layers salinity determines the density of dsw in cold seas such as this however the variability of dsw salinity has yet to be quantified and its causes remain unknown because of the paucity of available observation data here we describe the variability of dsw salinity in the period from 1950 to 2005 through the analysis of a newly compiled hydrographic dataset expanded with russian measurements in the sea of okhotsk and the bering sea dsw salinity exhibits a decreasing trend of 0 0024 0 0015 y 1 over 1950 2005 in addition to decadal scale variability with a typical magnitude of 0 1 we have found that dsw variability is controlled largely by surface salinity anomalies that propagate along pathways associated with ocean currents from the bering sea to the sea of okhotsk these salt pathways can be traced farther upstream to the alaskan stream and western subarctic gyre we suggest that this is a possible pathway which consists of a previously undefined upper branch of the north pacific overturning cell along this pathway the effects of the nodal tide that has an 18 6 year period may also propagate from the kuril straits and the aleutian passes our results indicate that long term atmospheric variations and enhanced hydrological cycles over the north pacific which are associated with global climate changes are conducted to the intermediate layer through surface salt pathways and subsequent dsw ventilation and lead to variability in material circulation and biogeochemical cycles

significance of polycyclic aromatic hydrocarbons pahs in permian triassic boundary sections abstract in this study the abundances of several polycyclic aromatic hydrocarbons pahs table 1 i xxi have been measured throughout three permian triassic p tr sections from meishan south china kap stosch area east greenland and peace river basin western canada dibenzothiophene i and dibenzofuran ii were found to decrease in abundance just before or shortly after the p tr transition in all three sections while perylene iii was observed to increase in abundance at the onset of the main extinction horizon bed 25 in meishan perylene has been attributed to a wood degrading fungal source and therefore it seems possible these phenomena are related to the demise of land plants further distinct patterns of various combustion derived pahs occurring in each section imply that forest fire events occurred within the late permian and early triassic in the meishan section high amounts of combustion derived pahs pyrene iv fluoranthene v benzo a anthracene vi benzofluoranthenes sum i e vii benzo a pyrene viii benzo e pyrene ix and coronene x occur within bed 25 also containing ash attributed to the fallout from massive volcanic eruptions in siberia and or china

large scale variability in the midlatitude subtropical and subpolar north pacific ocean observations and causes abstract altimetric data from the 8 yr topex poseidon t p mission oct 1992 jul 2000 are used to investigate large scale circulation changes in the three current systems of the midlatitude north pacific ocean the north pacific current npc the alaska gyre and the western subarctic gyre wsg to facilitate the understanding of the observed changes a two layer ocean model was adopted that includes first mode baroclinic rossby wave dynamics and barotropic sverdrup dynamics the npc intensified steadily over the t p period from 1992 to 1998 much of this intensification is due to the persistent sea surface height ssh drop on the northern side of the npc a similar ssh trend is also found in the interior of the alaska gyre both of these ssh changes are shown to be the result of surface wind stress curl forcing accumulated along the baroclinic rossby wave characteristics initiated from the eastern boundary in addition to the interior ssh signals the intensity of the alaska gyre is shown to depend

origin of petroleum in the neoproterozoic cambrian south oman salt basin abstract the south oman salt basin sosb is host to the world s oldest known commercial deposits most of the south oman oils have been proven to be associated with the source rocks of the neoproterozoic to cambrian huqf supergroup but the assignment of oils to specific huqf intervals or facies has been hampered by the geochemical similarity of the organic matter across the entire huqf sequence possibly as a consequence of limited change in the local palaeoenvironment and biota over the time of its deposition this study was conducted to establish improved correlations between organic rich rock units and reservoir fluids in the sosb through detailed molecular and isotopic analysis of the huqf supergroup with special emphasis directed towards understanding the ara carbonate stringer play unusual biomarkers tentatively identified as a norsteranes show distinctive patterns among carbonate stringer oils and rocks different from those observed in nafun sediments and ara rocks from the athel basin these putative a norsteranes form the basis for new oil source correlations in the sosb and provide for the first time geochemical evidence of a self charging mechanism for the carbonate stringer play the paucity of markers specific to the nafun group shuram buah and masirah bay formations confounds attempts to quantify their respective contributions to huqf oil accumulations nafun inputs can only be determined on the basis of subtle differences between nafun and ara biomarker ratios the most useful geochemical characteristics delineating nafun group organic matter from ara group intra salt source rocks included low relative abundance of mid chain monomethyl alkanes x compounds low relative abundance of gammacerane 28 30 dinorhopane 25 28 30 trinorhopane and 2 methylhopanes low c 22 t c 21 t and high c 23 t c 24 t cheilanthanes ratio values based on these parameters molecular evidence for major contributions of liquid hydrocarbons from nafun group sediments shuram buah and masirah bay formations is lacking our results suggest that the majority of sosb hydrocarbon accumulations originate from within the ara group either from the carbonate stringers or from the package of sediments that comprises the thuleilat athel silicilyte and u shale formations subtle aspects of the composition of some carbonate stringer and post salt huqf oils could suggest some degree of sourcing from the nafun rocks but stronger evidence is needed to confirm this

molecular proxies as indicators of freshwater incursion driven salinity stratification salinity related stratification in marine environments is one of the main drivers for the development of persistent anoxia and euxinia it therefore plays a vital role in the sedimentary preservation of organic matter and has also been associated with oceanic anoxic events during several mass extinctions in earth s history here we present a novel molecular proxy using relative abundances of methyltrimethyltridecylchromans mttcs as indicators of riverine freshwater incursions into middle to late devonian paleoreefs exposed to conditions of prevailing anoxia photic zone euxinia and water column stratification this paper aims at re instigating a discussion about the origin of these compounds to potentially broaden their utilization as paleoproxies adding freshwater stratification to the general salinity reconstructions the co variation of mttc abundance profiles and 13c values with other biomarker parameters in the sediments studied here indicate a link of mttcs to terrigenous input pointing towards a previously suggested early diagenetic formation of these compounds from phytol with higher plant derived alkylphenols

cold core anticyclonic eddies south of the bussol strait in the northwestern subarctic pacific abstract summer hydrographic surveys from 1993 to 1997 in the area south of the kuril islands in the northwestern subarctic pacific showed the existence of anticyclonic eddies south of the bussol strait at almost the same location but with variable sizes and intensities depending on the year every eddy had a cold low salinity and low potential vorticity core suggesting a strong influence from the okhotsk sea water two formation processes and annual variations were found with satellite data analyses one is the case where eddies are locally formed south of the bussol strait and intensified from summer to fall with the supply of okhotsk sea water as observed in 1993 in the other case kuroshio warm core rings that had translated northeastward are arrested near the bussol strait and amplified with the supply of okhotsk sea water as seen from summer to autumn in 1995 in winter eddies tend to move northeastward with decay the 1992 eddy moved northeastward then northward in winter and was eventually

different response of δd values of n alkanes isoprenoids and kerogen during thermal maturation abstract this study investigates the extent of post depositional alteration of d values of n alkyl lipids isoprenoids and kerogen isolated from a continuous 450 m core that covers the transition from thermally immature to early mature sediments in the lacustrine kissenda formation lower cretaceous gabon basin large variations in d values up to 40 for n c 17 and up to 30 for n c 29 alkanes as well as up to 10 for kerogen in closely spaced samples are evident throughout the core and remain preserved even at the bottom of the section d values of individual n alkanes show a slight overall d enrichment with depth and a general trend of increasing d values with increasing n alkane chain length characterizes all samples particularly in those below 600 m depth hydrogen isotopic compositions of kerogen samples overlap with those of n alkanes throughout the section d values of pristane and phytane are more negative than those of n c 17 alkane by as much as 120 at shallow depths but increase dramatically and approach d values of n c 17 alkane in the samples closest to the oil window integration of analytical and computational results indicates that 1 n alkanes and isoprenoids have the potential to preserve the original biological signal before the onset of oil generation 2 isomeric and structural rearrangements taking place at the beginning stages of oil generation do not influence significantly the d values of n alkanes and kerogen however these processes have a major effect on the isotopic composition of isoprenoids causing isotopic d enrichment up to 90

fractal and multifractal analysis of carbonate pore scale digital images of petroleum reservoirs the petrophysical evaluation of the reservoir capacity is of great importance in predicting the reserves and productivity of petroleum fields which may directly affect petroleum exploration in the past such kind of evaluation was mainly based on the experimental measurements of the petrophysical porosity and permeability of reservoir rock samples assessing quantitatively the microstructures of carbonates including irregularities of pore shapes and frequency distributions of pore sizes is becoming one of the most challenging efforts in pore scale analysis based on the digital analyses of the two dimensional images from thin sections taken under the environmental scanning electron microscope esem at various magnification scales the current paper tries to quantify the pore spaces of carbonate samples by fractal and multifractal methods which have been demonstrated to be effective the study area is located in the western hubei and eastern sichuan china as many as 25 carbonate samples from various members in five formations of the permian triassic periods and 132 esem images were chosen in this study all individual pores had been recognized and their areas and perimeters had been calculated as well the box counting fractal dimensions and four major multifractal parameters associated with the multifractal spectra are used the results show that the values of the petrophysical porosity and permeability are closely related to the box counting dimensions and the multifractal parameters which demonstrates that the textural arrangements of the pores control the porosity and permeability to a certain extent there is also a link between the reservoiring capabilities of different formations and the fractal and multifractal parameters the reservoiring capability assessment result is in agreement with the field research analysis

the shedding of mesoscale anticyclonic eddies from the alaskan stream and westward transport of warm water abstract the south flowing waters of the kamchatka and oyashio currents and west flowing waters of the alaskan stream are key components of the western sub arctic pacific circulation we use ctd data argo buoys woce surface drifters and satellite derived sea level observations to investigate the structure and interannual changes in this system that arise from interactions among anticyclonic eddies and the mean flow variability in the temperature of the upstream oyashio and kamchatka currents is evident by warming in mesothermal layer in 1994 2005 compared to 1990 1991 a major fraction of the water in these currents is derived directly from the alaskan stream the stream also sheds large anticyclonic aleutian eddies averaging approximately 300 km in diameter with a volume transport significant in comparison with that of the kamchatka current itself these eddies enclose pools of relatively warm and saline water whose temperature is typically 4 c warmer and salinity is 0 4 greater than that of cold core kamchatka eddies in the same density range aleutian eddies drift at approximately 1 2 km d 1 and retain their distinctive warm and salty characteristics for at least 2 years selected westward pathways during 1990 2004 are identified if the shorter northern route is followed aleutian eddies remain close to the stream and persist sufficiently long to carry warm and saline water directly to the kamchatka current this was observed during 1994 1997 with substantial warming of the waters in the kamchatka current and upstream oyashio if the eddies take a more southern route they detach from the stream but can still contribute significant quantities of warm and saline water to the upstream oyashio as in 2004 2005 however the eddies following this southern route may dissipate before reaching the western boundary current region

pore structure evaluation of tight reservoirs in the mixed siliciclastic carbonate sediments using fractal analysis of nmr experiments and logs abstract the study on mixed depositional reservoirs is widely attended in recent years however the mixed depositional reservoirs are generally characterized by complex pore structure which is caused by strong heterogeneity complex mineral compositions and varying pore sizes presenting a major challenge to describe the difference in pore structure between different samples to address this challenge the pore structure of mixed depositional reservoirs was evaluated by the fractal dimensions and the influences of various mineral compositions on pore structure were analyzed the fractal dimensions derived from nmr measurements or nmr logging data can be divided into two segments at t 2cutoff values representing different fractal values and characteristics of pore structure for the e 3 2 formation in yingxi field the fractal dimension of movable fluid pores ranges from 2 628 to 2 917 average 2 765 whereas the bound fluid pore systems are not following the fractal theory meanwhile the fractal dimensions show a negative relationship with movable fluid porosity and permeability the effects of various mineral compositions on fractal laws of the pore networks are different fractal dimension increases with the increases of clay mineral contents and the decrease of dolomite content while the effect of calcite content on fractal laws of the pore system is uncertain and quartz from different genetic type represents different effect on fractal dimensions this study is contributed for petroleum exploitation in mixed depositional reservoirs and shows that the fractal dimension can comprehensively indicate the complexity of the pore structure in mixed depositional reservoirs

significance of δdkerogen δ13ckerogen and δ34spyrite from several permian triassic p tr sections for the first time we report d of kerogen dkerogen for three permian triassic p tr sequences hovea 3 perth basin western australia jameson land east greenland and lusitaniadalen spitsbergen we have compared dkerogen with 13c of kerogen 13ckerogen and 34s of total reduced inorganic sulfur tris essentially pyrite 34spyrite of all the sections and for one sample set with 13c of carbonate 13ccarbonate to establish i similarities between the sections and ii evaluate whether these signals are local and or global stable isotope shifts occur for all three sample sets either at the p tr transition western australia or coinciding with the marine ecosystem collapse spitsbergen and east greenland dkerogen reflects organic matter om kerogen type and is not sensitive to the low level of thermal maturation reliable palaeoenvironmental information in terms of the use of d can therefore only be obtained for the p tr transition from hydrogen compound specific isotope analyses csia of biomarkers nabbefeld et al 2010b the negative shifts in 13ccarbonate primary and 13ckerogen are attributed to the release of 13c depleted carbon into the atmosphere whereas the isotopic excursions in 34spyrite relate to palaeoredox changes however the global coincidence in timing of the shifts in dkerogen 34spyrite and 13ckerogen suggests a relation between the sulfur carbon and hydrogen cycles the negative shifts in 13ccarbonate primary are in general attributed to the release of 13c depleted source of carbon into the oceans and atmosphere whereas 13ckerogen can reflect the latter in certain cases but can also be superimposed by varying sources of om kerogen type isotopic excursions in 34spyrite relate to global changes in the palaeoredox conditions that affect sulfur cycling in the ancient seas

characteristics of mesoscale eddies in the kuroshio oyashio extension region detected from the distribution of the sea surface height anomaly abstract this study investigates the distribution of the sea surface height anomaly ssha with the aim of quantifying the characteristics of mesoscale eddies in the kuroshio oyashio extension region koer where intense mesoscale eddies are commonly observed during hydrographic surveys dense distributions of both anticyclonic eddies aes and cyclonic eddies ces are detected for the first time in koer with sufficient temporal and spatial coverage using the okubo weiss parameter without smoothing their contribution to the total ssha variance is estimated to be about 50 the zones of highest amplitudes are located north and south of the axis of the kuroshio extension ke for aes and ces which represent warm core and cold core rings respectively the areas extend poleward along the japan and kuril kamchatka trenches especially for aes eddies of both polarities and with moderate amplitudes are also recognized along the subarctic front saf eddies in areas north and south of the ke generally pro

recent variability in the pacific western subarctic boundary currents and sea of okhotsk abstract the objective of this research is to describe physical processes which are the cause of the recent variability of the pacific western subarctic waters rapid thermohaline changes have occurred within the oyashio and kamchatka current during the last decade this variability has included a warming of the kamchatka current warm intermediate layer but a cooling and freshening of the upper layer in the oyashio and sea of okhotsk the example presented here uses data obtained during the canada russia inpoc and woce projects as well as the new russian studies with high resolution station grid the possible physical mechanism that generated the upper layer freshening during the thermohaline transition is examined major components of the fresh water budget of the okhotsk sea are considered in order to describe the dramatic changes in salinity which have recently occurred in the pacific subarctic significant changes in precipitation and other fresh water inputs are demonstrated it is suggested that upper layer of the oyashio and kamchatka current became cooler and fresher because of the export of cold fresher waters from the bering and okhotsk seas these waters from the marginal seas have cooled the bottom of the halocline reducing evaporation and acting as a feedback that has kept the upper layer of the western subarctic boundary currents fresh it is also shown that the outflow of the cold sea of okhotsk water has changed its path during this recent thermohaline transition

chlorobiaceae in palaeozoic seas revealed by biological markers isotopes and geology biomarker hydrocarbons in oils and sediments have considerable potential for assessing the nature of biological processes in the past but only a few can be uniquely related to particular organisms reef hosted oils in the silurian of the michigan basin canada and the devonian of western canada have high abundances of 1 alkyl 2 3 6 trimethylbenzenes their precise structures suggest that they are diagenetic products of aromatic carotenoids of the green sulphur bacteria individual components are enriched in 13c by 7 8 relative to the saturated hydrocarbons of the same oil an isotopic anomaly of this magnitude and direction correlates with a component of photosynthetic carbon assimilation by the reductive tricarboxylic acid cycle these results together with data on palaeoenvironments provide compelling evidence for the existence in ancient restricted seas of microbial communities containing chlorobiaceae organisms with distinctive biochemistry which leave morphologically identifiable remains

fractals in petrology abstract a fractal power law distribution is the only statistical distribution applicable to a scale invariant process one of the major problems in petrology is the distribution of trace elements in the earth s crust extreme values of this distribution result in ore deposits there is accumulating observational evidence that tonnage grade statistics of ore deposits are often fractal power law rayleigh distillation and chromatographic models can explain power law fractal distributions for the extreme values of trace element concentrations an alternative fractal approach to problems in petrology is to use self affine fractals the standard approach is to take a fourier transform of a continuous signal an example would be the concentration of a mineral along a linear track if the fourier coefficients scale as a power law of the wavelength the distribution is a self affine fractal many well logs give this result multifractal analyses can also be applied to problems in petrology

paleoenvironmental implications of novel c30 steranes in precambrian to cenozoic age petroleum and bitumen petroleums and bitumens from early proterozoic 1800 ma to miocene 15 ma age marine strata contain 24 isopropylcholestanes a novel group of c30 steroids the abundance of these compounds relative to 24 n propylcholestanes varies with source rock age late proterozoic vendian and early cambrian oils and or bitumens from siberia the urals oman australia and india have a high ratio of 24 isopropylcholestanes to 24 n propylcholestanes 1 while younger and older samples have a lower ratio 0 4 temporal changes in this parameter may reflect the relative abundance of certain porifera sponges and certain marine algae through time geochemical indicators such as this which can constrain the source rock age of a migrated oil are useful in source rock identification during petroleum exploration

satellite and hydrographic observations of eddy induced shelf slope exchange in the northwestern gulf of alaska 1 satellite and hydrographic observations of oceanographic conditions in the northwestern gulf of alaska indicate that anticyclonic eddies propagating adjacent to the continental shelf alter the structure of the shelf break front and in doing so influence the shelf slope exchange of biota and water mass properties eddies typically form in the northern gulf of alaska during fall and winter and propagate southwestward within an 200 km wide corridor along and above the continental slope eddy activity within this corridor diminishes in the downstream direction the trajectories of faster propagating 4 km day eddies tend to lie closer to the shelf break than do the trajectories of slower propagating 1 5 km day eddies the interaction between azimuthal eddy currents and the shelf break frontal jet 1 establishes an upwelling zone associated with the leading flank of the eddy that strengthens cross slope gradients 2 weakens cross slope gradients and promotes shelf slope exchange where the eddy is adjacent to the shelf and 3 reestablishes a weak upwelling zone associated with the trailing flank of the eddy

polycyclic aromatic hydrocarbons of pyrolytic origin in ancient sediments evidence for jurassic vegetation fires abstract polycyclic aromatic hydrocarbon pah distributions in an upper jurassic succession from offshore korea bay basin were consistent with a pyrolytic source being dominated by non alkylated species levels of these pahs were significantly higher in samples containing abundant fusinite macerals which are believed by some to be the product combustion the data were consistent with a pah origin from periodic conflagration throughout the upper jurassic of vegetation adjacent to a tectonically formed lake distribution of pahs exhibited some differences from those of combustion origin in recent and some ancient sediments and were characterized by the dominance of the highly peri condensed compounds benzo e pyrene benzo g h i perylene and coronene this characteristics reflects either preferential formation or preferential preservation under the prevailing sedimentary conditons of the highly peri condensed structures

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

anticyclonic eddies in the alaskan stream abstract anticyclonic eddies propagating southwestward in the alaskan stream as were investigated through analysis of altimetry data from satellite observations during 1992 2006 and hydrographic data from profiling float observations during 2001 06 fifteen long lived eddies were identified and categorized based on their area of first appearance three eddies were present at the beginning of the satellite observations another three formed in the eastern gulf of alaska off sitka alaska and four were first detected at the head of the gulf of alaska near yakutat alaska the other five eddies formed along the as between 157 and 169 w and were named as eddies while the eddies that formed in the gulf of alaska mainly decayed before exiting the gulf of alaska the as eddies mostly crossed the 180 meridian and reached the western subarctic gyre four of five as eddies formed under negative or weakly positive wind stress curls which possibly caused as separation from the coast comparison of eddy propag

changes of palaeoenvironmental conditions recorded in late devonian reef systems from the canning basin western australia a biomarker and stable isotope approach abstract although the late devonian extinctions were amongst the largest mass extinction events in the phanerozoic the causes nature and timing of these events remain poorly restrained in addition to the most pronounced biodiversity loss at the frasnian famennian f f boundary and the end famennian there were also less extensively studied extinction pulses in the middle to late givetian and the frasnian here we used a combination of palynological elemental molecular and stable isotope analyses to investigate a sedimentary record of reef systems from this time period in the canning basin western australia the acquired data generally showed distinct variations between sediments from i the time around the givetian frasnian g f boundary and ii later in the frasnian and indicated a distinct interval of biotic stress particularly for reef builders in the older sediments alterations of pristane phytane ratios gammacerane indices chlorobi biomarkers dkerogen and chroman ratios describe the change from a restricted marine palaeoenvironment with an anoxic euxinic hypolimnion towards a presumably open marine setting with a vertically mixed oxic to suboxic water column simultaneous excursions in 13c profiles of carbonates organic matter om and hydrocarbons in the older sediments reflect the stratification induced enhancement of om recycling by sulfate reducing bacteria alterations in sterane distributions and elevated abundances of methyltrimethyltridecylchromans mttcs and perylene indicate an increased terrigenous nutrient input via riverine influx which would have promoted stratification phytoplankton blooms and the development of lower water column anoxia the detected palaeoenvironmental conditions around the g f boundary may reflect a local or global extinction event our data furthermore suggest a contribution of the higher plant expansion and photic zone euxinia to the late devonian extinctions consistent with previous hypotheses furthermore this work might contribute to the understanding of variations in devonian reef margin and platform top architecture relevant for petroleum exploration and development in the global devonian hydrocarbon resources

petrography and reservoir physics i objective classification of reservoir porosity porosity observed in thin section can be objectively classified using a combination of digital acquisition procedures and pattern recognition algorithms pore types are derived from the frequency distributions of sizes and shapes of patches of porosity exposed in thin section each pore type is represented by a characteristic distribution of sizes and shapes found in thin section most sandstone reservoirs contain fewer than six pore types much of the intersample variability in reservoir physics is associated with changes in pore type abundance the advantages of this approach to porosity classification are 1 the criteria for classification are objectively defined 2 classification procedure is rapid accurate and precise 3 pore types are understood easily in ter s of conventional genetic classification schemes and 4 pore type data are related strongly to petrophysical properties

the influence of an alaskan stream eddy on flow through amchitka pass flow into the bering sea through amchitka pass in the central aleutian islands is shown to respond to the presence of a large meander eddy in the alaskan stream south of the pass maximum flow into the aleutian basin of the bering sea occurs when the eddy center lies nearest to the axis of amchitka pass a conceptual model of low frequency circulation variability within the bering sea based upon results of empirical orthogonal function analyses of sea surface height anomalies measured by the geosat radar altimeter is presented

oxic facies and the late devonian mass extinction canning basin australia the close association of anoxic or dysoxic sedimentary rocks and the major late devonian frasnian famennian mass extinction has focused considerable attention on anoxia as the major cause or as a major factor in a multicausal scenario the record of the late devonian biotic crisis in the well known reef complexes of northwestern australia canning basin in contrast to many localities elsewhere does not display sedimentological evidence of anoxia through the frasnian famennian boundary interval analysis of continuous drill core through this interval has yielded three positive 13 c isotopic excursions only one of which coincides with total organic carbon toc maxima in our data multi element geochemical proxies suggest that toc maxima preceding positive shifts in 13 c most likely resulted from higher productivity caused by nutrient influx from continental weathering given the close association between toc maxima and regional relative sea level falls our interpretation supports the view that anoxia was not a fundamental driver of mass extinction and stresses the importance of integrated data sets and understanding regional controls on environmental changes and or stresses

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

pore throat structure and fractal characteristics of tight sandstones in yanchang formation ordos basin abstract pore throat structure is a key factor that influences the storage and fluid flow capacity of tight sandstone reservoirs by performing petro physical characteristic tests scanning electron microscopy and casting thin sections the main pore types of tight sandstone reservoir samples collected from the upper triassic yanchang formation in the baibao area of the southwest ordos basin in china were identified to be dissolved pores intergranular pores intercrystalline pores and micro cracks meanwhile the size of the pore throat was widely distributed whereas its shape varied given the advantages and disadvantages of various technical methods high pressure mercury injection hpmi and nuclear magnetic resonance nmr technology were used to study the distribution characteristics of a full size pore throat all 10 samples showed bimodal and unimodal distribution characteristics and their distribution characteristics were consistent with the results of the petro physical characteristics high pressure mercury injection and movable fluid saturation tests the throat distribution characteristics of the reservoir were studied by applying constant rate mercury injection crmi and the throat radius ranged from 0 43 m to 9 76 m with an average of 3 34 m the fractal features of the pore throat and throat were quantitatively characterized by crmi the fractal curves of the pore throat showed self similarities and the fractal dimension d ranged between 2 6297 and 2 9529 with an average of 2 7865 the fractal curves of the throats were broken down into two segments and the fractal dimensions corresponded to two ranges namely the small dt1 and large throats dt2 fractal dimensions the average of fractal dimension dt1 was 2 9170 and the average of fractal dimension dt2 was higher than that of dt1 with an average of 2 9828 thereby indicating the complex structure and strong heterogeneity of the former the fractal dimensions d dt1 and dt2 were negatively correlated with permeability movable fluid saturation average throat radius clay mineral content and laumontite content positively correlated with quartz content and showed poor correlation with feldspar compared with dt2 the fractal dimension dt1 had a higher correlation with pore throat parameters and mineral content given the higher self similarity of small throats their distribution is considered highly homogeneous