the reconstruction of early and middle miocene climate and vegetation in southern germany as determined from the fossil wood flora abstract early and middle miocene sediments of the north alpine foreland basin nafb in southern germany contain one of the world s richest regional records of silicified wood here we analyze over 1000 identifiable samples belonging to 80 wood anatomical taxa from 61 stratigraphically well dated localities using principally the coexistence approach the samples investigated originate from fluvial sediments representing periods of intensified surface runoff in the nafb and therefore represent and provide information pertaining to the wet end member of the fluctuating climate system the dry end of the climate system is represented in the profiles either by hiatuses or palaeosoils the dataset is split into four xylofloras i the ortenburg xyloflora late ottnangian 17 5 to 17 3 ma originating from a paratropical evergreen carapoxylon xylocarpus forest ii the southern franconian alb xyloflora late karpatian 17 0 to 16 3 ma originating from a subtropical semi deciduous limestone forest iii the upper older series xyloflora early badenian 16 3 to 15 3 ma originating from a subtropical oak laurel forest and iv the upper middle series xyloflora middle badenian 14 3 to 13 8 ma originating from a subtropical dry deciduous forest our investigation documents the following important outcomes 1 the late ottnangian seems to be the warmest period during the investigated time span with a mean annual temperature mat between 22 2 and 24 2 c and a cold month temperature cmt around 16 7 c the late ottnangian is significantly warmer by at least 1 7 c mat and up to 3 4 c cmt than the mid miocene climatic optimum i e mat 17 4 20 5 c and cmt 8 0 13 3 c of the late karpatian to middle badenian 17 to 13 8 my and may correspond to the first climatic optimum 17 7 16 7 ma of the southern oceans pekar s f marchitto t lynch steiglitz j 2002 evidence for water mass changes on the tasmanian slope during the early miocene 19 16 5 ma stable isotope and mg ca records from odp leg 189 site 1168 eos transactions american geophysical union 83 47 fall meet supplement abstract pp11c 06 f 926 927 2 the cooling between both climate optima is documented by the southern franconian alb xyloflora and probably reflects the mi2 build up phase of the antarctic ice sheets 3 from late ottnangian to middle badenian the wet end member of the climate system appears to be humid mean annual precipitation 830 1 350 mm and with relatively even distribution of rainfall throughout the year only the late karpatian is characterized by the occurrence of a distinct dry season probably occurring during the early spring or late autumn 4 we attributed the early to middle badenian vegetation change to an increase in intra basin relief rather than to a different climate

oxygen and carbon isotope signatures in late neogene horse teeth from spain and application as temperature and seasonality proxies abstract here we describe a data set of 249 stable o and c isotope compositions from fossil horse teeth from the upper neogene of central spain and discuss their potential as environmental proxies it has been shown before that horse tooth enamel 18 o is a good proxy for local meteoric water 18 o h2o which in turn bears a distinct relation to temperature during precipitation formation at mid to high latitudes we discuss the reconstructed 18 o h2o values and apply modern 18 o h2o temperature equations for the iberian peninsula to these values results for the early pliocene suggest mean annual temperatures up to 2 3 c higher than today fitting pollen based estimates fairly well temperatures 5 c higher than today are predicted for the early late miocene 11 9 ma these estimations are feasible given the local occurrence of crocodilians and the presence of fruit eating hominids in iberia at that time the estimated amount of cooling since then is similar to the estimated decrease in nw europe based on plants the stable carbon isotope record indicates the virtual absence of c4 plants pointing to an environment consisting of c3 plants under slightly water stressed conditions the long term 13 c trend follows the expected decrease in average global 13 c co2 predicted from planktonic foraminifers within tooth variability is supposed to reflect seasonal change but the amplitude is expected to have been significantly damped by internal time averaging effects related to the mixing with atmospheric o 2 reservoir dynamics enamel maturation and sampling procedure the exact degree of damping is difficult to estimate but theoretical considerations suggest values between 50 and 75 depending on temporal resolution and element used c o reconstructed seasonal temperature ranges for central spain are equal or slightly less than the modern range within tooth 13 c variation is more difficult to explain as it can be attributed to multiple factors such as intra annual changes in 13 c co2 micrometeorology plant response and diet the occurrence of both positive and negative intra tooth 18 o 13 c correlations may be related to orbitally forced variations in seasonality

biostratigraphy and sedimentology of the fluviatile untere serie early and middle miocene in the central part of the north alpine foreland basin implications for palaeoenvironment and climate the early to middle miocene fluviatile untere serie lithostratigraphic unit of the upper freshwater molasse ufm in the north alpine foreland basin nafb crops out in a 40 m long section at untereichen altenstadt central part of the nafb this section yields a unique superposition of two vertebrate assemblages belonging to different biostratigraphic units early part osm c d karpatian and osm e early badenian detailed taxonomic analyses reveal different diversity patterns in the two assemblages nine small mammal and six ectothermic vertebrate taxa occur in the older level ua 540 m while 20 small mammal and 23 ectothermic vertebrate taxa are recorded for the younger level ua 565 m from the latter locality comes a small sized representative of the biostratigraphically significant megacricetodon lappi lineage this evolutionary level has not been documented previously for the eastern part of the nafb bioclimatic analysis combined with lithofacies and architectural element analysis indicates that significant changes in the fluvial sedimentation style surface water runoff and tectonics occurred between the early karpatian and early badenian a meandering fluvial system marly unit is erosively overlain by sandy braided river deposits sandy unit overbank deposits of the marly unit revealed that the older vertebrate fossil assemblage ua 540 m is deposited in an animal burrow that was presumably produced by owls both reptilian and mammalian taxa are indicative of a relatively open environment and dry probably semi arid climate conversely vertebrates from the sandy unit ua 565 m which are accumulated in channel fill deposits suggest closed as well as open habitats with a subtropical humid climate and mean annual rainfall of about 1 000 mm according to the sequence stratigraphic analysis the marly unit is interpreted as a highstand system tract of the tb 2 2 global 3rd order sequence the new results add support to the hypothesis that the erosional unconformity between both sedimentary units spanning the karpatian badenian transition corresponds to the pre riesian hiatus which has been interpreted as part of the styrian tectonic phase and was previously identified only in the eastern and northeastern part of the nafb the biostratigraphic data further indicate that this hiatus lasted longer in the eastern than in the central part of the basin

habitat tracking range dynamics and palaeoclimatic significance of eurasian giant salamanders cryptobranchidae indications for elevated central asian humidity during cenozoic global warm periods article i nfo environmental fluctuations are a driving force in vertebrate evolution but cryptobranchids giant salamanders show little morphologic change since the jurassic here we analyze their fossil distribution in the cenozoic of eurasia and show that morphologic stasis is also maintained by stable environments making giant salamanders an ideal proxy group for environmental and palaeoclimatic studies the climate space of recent and fossil cryptobranchids is best characterized by high humidity with mean annual precipitation values over 900 mm the recorded patchiness of their fossil record can be explained by habitat tracking and or range expansion from higher altitudes into lowland settings during humid periods with increased basinal relief in central asia cryptobranchids are recorded from five intervals four of them are global warm periods paleocene eocene thermal maximum late oligocene warming miocene climate optimum and mio pliocene transition this distribution suggests that during global warmth the asian cold high pressure zone during winter months may be weak or absent thus moist westerly winds penetrate far into the continent the presence of cryptobranchids also indicates that the aridification across the eocene oligocene boundary as reported from mongolia and northwestern china does not occur in the zaysan basin probably due to increased upslope precipitation in the rising altai mountains

determination of trapping pressure and temperature of petroleum inclusions using pvt simulation software a case study of lower ordovician carbonates from the lunnan low uplift tarim basin abstract we report a case study carried out on lower ordovician reservoir carbonates of the lunnan low uplift tarim basin to determine trapping pressures and temperatures of petroleum inclusions from the intersection of isochores of coeval petroleum and aqueous fluid inclusions using pvt sim software there are four types of petroleum inclusions from this sequence their trapping pressures and temperatures are type i 80 105 c 199 230 bar type ii 135 145 c 235 250 bar type iii 155 165 c 344 360 bar and type iv 220 252 c 345 390 bar respectively which are consistently higher than their homogenization temperature and saturation pressures by about 5 15 c and 25 70 bar to confirm the reliability of the pvt simulation approach fluid inclusions were synthesized in calcite under controlled temperature and pressure conditions and studied using the same methods the calculated trapping pressure and temperature of the synthetic petroleum inclusions closely match the actual pressure and temperature applied in the experiment by reference to the burial and geothermal history of the tarim host rocks it was inferred that types i ii and iii petroleum inclusions represent fluids associated with three distinct phases of petroleum emplacement in the lower ordovician strata of this area occurring during late silurian to early devonian cretaceous to early tertiary and late tertiary respectively type iv petroleum inclusions occur only in some fine calcite veins from few samples and are believed to be related to an anomalous thermal event in this area on the basis of the trapping pressures and trapping temperatures of the petroleum inclusions three main phases of the petroleum filling of the lower ordovician reservoirs can be delineated phase i and phase iii petroleum events were related to petroleum migration and accumulation from the lunnan low uplift or nearby area the petroleum of the phase ii petroleum event appears to have originated from middle and upper ordovician source rocks in the northern slope area of the manjiaer depression with a long distance migration

diagenetic history of tight sandstones and gas entrapment in the yulin gas field in the central area of the ordos basin china abstract the ordos basin is a large cratonic basin with an area of 250 000 km2 in central china upper paleozoic coals and shales serve as gas source rocks with peak generation and migration at the end of the early cretaceous recent exploration has verified the huge gas potential in the basin centered gas accumulation system bcgas however the mechanism for the gas accumulation is controversial with an integrated approach of thin section petrography ultra violet fluorescence microscopy fluid inclusion microthermometry raman microspectrometry scanning electron microscopy and x ray diffractometry we identified diagenetic trapping and evaluated the diagenetic history of sandstone reservoirs in the yulin gas field in the central area where structural stratigraphic and or sedimentary lithologic traps have not been found it was revealed that three phases of diagenesis and hydrocarbon charging occurred respectively in the late triassic late jurassic and at the end of the early cretaceous in the first two phases acidic water entered the reservoir and caused dissolution and cementation resulting in porosity increase however further subsidence and diagenesis including compaction and cementation markedly reduced the pore space at the end of the early cretaceous the bulk of the gas migrated into the tight reservoirs and the bcgas trap was formed in the updip portion of this system cementation continued to occur due to low gas saturation and has provided effective seals to retain gas for a longer period of time than water block in the bcgas the mechanism for the gas entrapment was changed from water block by capillary pressure in the bcgas to diagenetic sealing the diagenetic seals in the updip portion of the sand body were formed after gas charging which indicates that there is a large hydrocarbon exploration potential at the basin centered area

miocene burdigalian seawater and air temperatures estimated from the geochemistry of fossil remains from the aquitaine basin france abstract construction work of the highway a65 led the top of the burdigalian molasses de l armagnac formation to outcrop in two close localities near the town of bazas and marimbault situated on the western edge of the aquitaine basin france from this formation a rich fossil assemblage has been recovered and includes both marine and terrestrial fossil remains which offered the opportunity to reconstruct both seawater and terrestrial air temperatures at a regional scale during the burdigalian for this purpose two sets of fossil samples representative of the whole assemblage have been selected for each locality they include teeth and bones of sharks fish rays reptiles and mammals as well as tests of sea urchins and shells of bivalves first we performed rare earth element ree analyses of 53 apatite samples from both localities in order to characterize the diagenetic history of the assemblage we then analysed the oxygen isotope composition of 49 biogenic apatite phosphate samples and 6 biogenic carbonate samples representing both marine and terrestrial organisms using published isotopic fractionation equations both seawater and terrestrial air temperatures were reconstructed calculated seawater temperatures using phosphate and carbonate isotopic thermometers are 23 4 c and 25 1 c respectively for the locality of mendouillet bazas and 24 4 c and 26 1 c respectively for the locality of monbalon miron marimbault calculated terrestrial air temperatures are 18 2 c for the locality of mendouillet and 17 2 c for the locality of monbalon miron these regional temperatures are in good agreement with seawater and terrestrial temperatures calculated for other european localities of contemporaneous periods these results also fit the global climatic context of the mid miocene climatic optimum starting at the end of the burdigalian even though the global climatic conditions were warmer than today during the end of the burdigalian calculated continental and seawater thermal gradient at mid latitude appear to have been comparable to present day ones

petroleum generation and charge history of the northern dongying depression bohai bay basin china insight from integrated fluid inclusion analysis and basin modelling abstract the petroleum generation and charge history of the northern dongying depression bohai bay basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling one and two dimensional basin modelling was performed to unravel the oil generation history of the eocene shahejie formation es3 and es4 source rocks based on the reconstruction of the burial thermal and maturity history calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the es4 source rocks began to generate oil at around 35 ma reached a maturity level of 0 7 ro at 31 30 ma and a peak hydrocarbon generation at 24 23 ma the lower interval of the es3 source rocks began to generate oil at around 33 32 ma and reached a maturity of 0 7 ro at about 27 26 ma oil generation from the lower es3 and upper es4 source rocks occurred in three phases with the first phase from approximately 30 20 ma the second phase from approximately 20 5 ma and the third phase from 5 ma to the present day the first and third phases were the two predominant phases of intense oil generation samples from the es3 and es4 reservoir intervals in 12 wells at depth intervals between 2677 7 m and 4323 0 m were investigated using an integrated fluid inclusion workflow including petrography fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern dongying depression abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography fluorescence spectroscopy and microthermometry data two episodes of oil charge were determined at 24 20 ma and 4 3 ma respectively with the second episode being the predominant period for the oil accumulation in the northern dongying depression the oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence the expelled oil was then charged to the already established traps in the northern dongying depression the proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation migration and accumulation

plant and micromammal based paleoprecipitation proxies comparing results of the coexistence and climate diversity approach abstract both plant and vertebrate communities have been used to reconstruct paleoprecipitation however direct stratigraphic comparisons between the two types of proxies have hardly been performed which is due to the fact that plant and vertebrate fossils usually do not occur together in single geological beds here we focus on a series of 18 sites from the neogene of europe and anatolia that contain both types of fossils and compare paleoprecipitation predictions produced by the coexistence approach plants and the climate diversity approach micromammals most of the sites have overlapping uncertainty intervals for mean annual precipitation as generated by the two methods pointing to a common precipitation related signal in flora and fauna nevertheless a systematic difference appears to characterize drier sites for which micromammal richness based estimates for annual precipitation tend to be lower than plant based coexistence based estimates driest month precipitations are in agreement for drier sites but strongly differ for wetter sites with micromammal richness based estimates being higher overlap is poor for estimates of wettest month precipitation which are higher when based on plant based coexistence possible sources for a bias towards higher annual values in plants are related to the inclusion of local wetland elements in the analysis and or to a lower taxonomic resolution for pollen and spores compared to macroflora micromammal based annual estimates could be biased towards drier values when smaller samples lack rare species that could be preferentially wet adapted several of the higher driest and lower wettest month micromammal based estimates could result from over extrapolation beyond the calibration domain for arboreality as currently existing in the modern western old world on the other hand the use of several se asian reference taxa could add a high precipitation monsoonal component to the plant based predictions in addition wettest month estimates for both plants and micromammals probably suffer from the poor performance of water excess as a limiting factor an attempt to further increase the predictive power of the micromammal based prediction equations was performed by incorporating non linear terms and by using an extended calibration set including selected plant based precipitation estimates for micromammal assemblages without modern analogue in the western old world proxy inter calibration

gratkorn a benchmark locality for the continental sarmatian s str of the central paratethys this paper presents one of the richest and most complete vertebrate faunas of the late middle miocene 12 ma of central europe up to now sixty two vertebrate taxa comprising all major groups fishes amphibians reptiles birds mammals have been recorded based on sedimentological and palaeobiological evidences this fossillagerstatte is assumed to originate from a floodplain paleosol formed on top of a braided river sequence the fauna points to a highly structured somewhat vegetated landscape with a wide array of habitats e g fluvial channels sporadically moist floodplains short lived ponds savannah like open areas and screes it was preserved due to a rapid drowning and the switch to a freshwater lake environment palaeoclimatological data derived from pedogenic features as well as from biota indicate an overall semi arid subtropical climate with distinct seasonality mean annual precipitation 486 252 mm mean annual temperature 15 c this underlines the late middle early late miocene dry spell in central europe from taphonomical point of view the irregularly distributed but roughly associated larger vertebrate remains refer to an in situ accumulation of the bone bed splintered bones gnawing marks as well as rhizoconcretions and root corrosion structures record some pre and post burial modification of the taphocoenose however the findings of pellet remains argue for a very fast burial and thus to a low degree of time averaging for this reason the fossil fauna reflects the original vertebrate community rather well and is a cornerstone for the understanding of late middle miocene terrestrial ecosystems in this region certainly gratkorn will be one of the key faunas for a high resolution continental biostratigraphy and the comprehension of europe s faunal interchanges near the middle late miocene transition

the timing of quartz cementation in mesozoic sandstones from haltenbanken offshore mid norway fluid inclusion evidence the temperature of quartz cementation in mesozoic sandstones from the haltenbanken area offshore mid norway has been evaluated by micro thermometry of primary aqueous fluid inclusions in quartz overgrowths samples were collected from a wide range of burial depths 1 6 to 4 4 km and large area 7500 km 2 there is a systematic increase in homogenization temperatures t h of approximately 75 c between the shallowest and deepest wells when converted to time using burial histories the t h data indicate that cementation was short lived and started roughly synchronously throughout haltenbanken within the last 5 ma it therefore seems that depth and or temperature alone are not enough to bring about quartz cementation some other factor s must also be involved

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

going south latitudinal change in mammalian biodiversity in miocene eurasia for palaeontologists the challenge is to reconstruct biodiversity patterns of the past mammal richness in grids is used to assess the stability of biodiversity hotspots and document changes over time in europe for mammal neogene units 3 to 11 19 5 to 7 6 ma early to late miocene the maps clearly show the patchiness of the fossil record as the miocene was an eventful epoch with severe environmental changes europe slowly became drier and more seasonal both in temperature and precipitation from the early to middle miocene an area of high biodiversity moved from higher to lower latitudes culminating in one of the most remarkable hotspots in the history of mammals the early late miocene vallesian mammal stage faunas from the valles penedes catalonia spain remarkably the surrounding areas did not exhibit similar richness during the subsequent vallesian turnover event 9 7 ma the large and small mammal distribution became more equitable and the hotspots less prominent the richest area was found in the periphery of the humid miocene ecosystem which experienced species influx from the drier south the southward shift was a result of the expansion of the humid area with subsequent closed environments and related mixing of ecosystems coming to a halt in the late miocene when all of europe became equally open

kinetic modelling of petroleum formation and cracking implications from the high pressure high temperature elgin field uk north sea in this paper we use a case study to test the simulation of generation migration and cracking of petroleum fluids by a 2d compositional basin simulator using kinetic models based on chemical classes of compounds the selected area is the high pressure 1100 bar high temperature 190 c elgin field in the north sea this study is mainly focused on kinetic modelling of secondary cracking because in this zone paraffinic condensates with almost 50 c6 alkanes were recently discovered whereas only gas c5 was expected given the high temperature conditions the detailed hydrocarbon composition observed today in the fulmar sands reservoir of the elgin field is compared with the results of several simulations aimed at testing the influence of jurassic source rocks retention properties kinetic parameters and temperature variations on the predicted composition of fluids the influence of pressure was neglected in the modelling on the basis of results published in the literature results show that in this north sea area primary cracking of the kerogen into oil is completed whichever source rock is considered and that secondary cracking of accumulated petroleum compounds in the reservoir is presently in progress under these conditions source rock type and retention during primary and secondary migration have little influence on the present oil composition the occurrence of a monophasic paraffinic fluid in the elgin reservoir despite the high temperature is due to its very recent increase from 160 c to over 180 c in the last million years the fluid composition evolves rapidly and our compositional kinetic scheme accounts correctly for the presence of c6 hydrocarbons in these geological conditions first results using the compositional kinetic scheme of behar et al behar f kressman s rudkiewicz j l vandenbroucke m 1991 experimental simulation in a confined system and kinetic modelling of kerogen and oil cracking organic geochemistry 19 1 3 173 189 for secondary cracking showed a reasonably good fit between calculated and observed detailed fluid composition except for methylated aromatics which are overestimated and methane which is underestimated a recent comparison of kinetic parameters obtained from pyrolysis experiments on model compounds showed that it is not realistic to assume as done previously the same frequency factor for all chemical classes of compounds the higher stability of methylated aromatics relative to saturates observed under laboratory conditions would be extended to geological conditions a second set of simulations using frequency factors and activation energies obtained on these model compounds gave a better fit for methylated aromatics however methane is still strongly underestimated and reasons which could explain this discrepancy are discussed

assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours abstract the thermal maturity of oils extracted from inclusions and the fluorescence colours of oil bearing fluid inclusions have been measured in 36 sandstone samples from australasian oil fields the inclusion oils were analysed using an off line crushing technique followed by gc ms a maturity assessment was made for each inclusion oil using 25 molecular maturity ratios including a newly defined dimethyldibenzothiophene ratio dmdr each inclusion oil was placed in one of 4 maturity brackets approximately equivalent to early mid peak and post oil generation windows the fluorescence colours of oil inclusions were visually discriminated into blue white and yellow plus orange and their proportions estimated using point counting techniques sixteen samples have 85 of oil inclusions with blue fluorescence whilst other samples have more variable fluorescence colours one sample has 100 of oil inclusions with yellow plus orange fluorescence the results show that samples containing mainly blue fluorescing oil inclusions have thermal maturities anywhere within the oil window in particular the molecular geochemical data strongly suggests that oil inclusions with blue fluorescence can have relatively low maturities calculated reflectance

migration history of air breathing fishes reveals neogene atmospheric circulation patterns the migration history of an air breathing fish group channidae snakehead fishes is used for reconstructing neogene eurasian precipitation and atmospheric circulation patterns the study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions and are present regularly if the wettest month exceeds 150 mm precipitation and 20 8c mean temperature the analysis of 515 fossil freshwater fish deposits of the past 50 m y from africa and eurasia shows two continental scale migration events from the snakeheads center of origin in the south himalayan region events that can be related to changes in the northern hemisphere circulation pattern the first migration ca 17 5 ma into western and central eurasia may have been caused by a northward shift of the intertropical convergence zone that brought western eurasia under the influence of trade winds that produced a zonal and meridional precipitation gradient in europe during the second migration between 8 and 4 ma into africa and east asia snakeheads reached their present day distribution this migration could have been related to the intensification of the asian monsoon that brought summer precipitation to their migratory pathways in east africa arabia and east asia

vertebrate microfossils from the upper freshwater molasse in the swiss molasse basin implications for the evolution of the north alpine foreland basin during the miocene climate optimum abstract the older part of the upper freshwater molasse osm in the swiss and south german molasse basin records the extended warm period known as the miocene climate optimum however dating and global correlation of fossils and palaeoclimatic data from osm sediments remains challenging because sections are often incomplete and biostratigraphic data sometimes ambiguous here we present the rare case of a fossiliferous osm section that can be securely dated to the late early miocene and early middle miocene c 16 1 15 7 ma vertebrate microfossils have been recovered from three levels in superposition fish teeth document primary freshwater fishes cyprinidae channidae but otoliths found in the middle level indicate dominance of euryhaline fishes cyprinodontiformes gobiiformes the herpetofaunal assemblages largely consist of taxa that were widely distributed in central europe during the miocene climate optimum and fragments of turtle eggshells assignable to the oofamily testudoolithidae hirsch 1996 the small mammal fauna is dominated by the cricetid megacricetodon bavaricus fahlbusch 1964 the fossil biota implies that the lowermost level late early miocene c 16 1 ma represents a palaeo soil that formed under humid conditions while the levels above it early middle miocene c 15 7 15 8 ma record a warm freshwater pond subject to evaporation middle level and mean annual temperature 17 c in the vicinity of a river with an open hinterland upper level our results together with previous data suggest that the palaeoclimate of the north alpine foreland basin of switzerland and southwest germany was humid during the late early miocene and earliest middle miocene and that the middle miocene onset of seasonality and low mean annual precipitation occurred by c 15 7 15 8 ma we conclude that global climate change and the 100 kyr orbital eccentricity minimum at 15 75 ma may have triggered the decrease in humidity in the north alpine foreland basin

hydrocarbon charging and accumulation history in the niudong buried hill field in the baxian depression eastern china abstract the niudong buried hill field which lies in the baxian depression of the bohai bay basin is the deepest oil gas accumulation in eastern china its precambrian dolomite reservoir occurs at burial depths of 5860 m 6027 m this paper attempts to document the hydrocarbon charging and accumulation history in this field which could greatly enhance the understanding of the mechanisms for the formation of deep hydrocarbon accumulations our previous study of oil trapped in fluid inclusions has demonstrated that the ratio parameters of the fluorescence spectral intensities at 425 nm and 433 nm q 425 433 ratio and at 419 nm and 429 nm q 419 429 ratio can be more effective for revealing hydrocarbon charging history than the previously used fluorescence parameters such as lambda max and red green quotient as well as fluorescence colors the hydrocarbon charging and accumulation history in the niudong buried hill field was studied with an integrated approach involving the application of these two spectral parameters of petroleum inclusion fluorescence as well as utilization of other data including homogenization temperatures of aqueous inclusions coeval with petroleum inclusions and cross cutting relationships of cements and oil veins in pores and fractures the results indicate that the dolomite reservoir in the niudong buried hill field experienced three episodes of hydrocarbon charging in the first two episodes between 38 5ma and 25ma the low mature and mature oils which were derived from source rocks in the sha 4 member of the eocene shahejie formation migrated into the reservoir but part of them leaked out due to normal faulting at the updip margin of the buried hill these early charged oils were preserved mainly in small pores in micritic dolomites by oil wettability and capillary pressure in the neogene the basin subsided as a whole and local faults at the updip margin became inactive and played a sealing role by approximately 13ma the source rocks became highly mature and the generated hydrocarbons then migrated into the reservoir and accumulated therefore the last charging is the most important for hydrocarbon accumulation in the niudong buried hill field

precipitation patterns in the miocene of central europe and the development of continentality abstract understanding climate patterns with their decisive influence on plant distribution and development is crucial to understanding the history of vegetation patterns in europe during the miocene this paper presents the detailed analyses of several precipitation parameters including monthly precipitation of the wettest driest and warmest months for five miocene stages in conjunction with seasonality of temperature those parameters provide a meaningful measure of continentality and can help to document miocene climate changes and patterns and their possible influence on vegetation climate reconstructions provided here are entirely based on palaeobotanical material in total 169 miocene floras were selected including 14 burdigalian 41 langhian 40 serravallian 36 tortonian and 38 messinian localities all floras were analysed using the coexistence approach the analysis of several precipitation parameters the statistical inter correlation of results and the comparison with modern patterns provides a comprehensive account on miocene precipitation miocene climatic changes after the mid miocene climatic optimum mmco are evidenced in our data set by three major factors i e 1 increasing seasonality of temperature 2 changes in the annual distribution of precipitation towards a precipitation peak in summer and 3 a late increase of longitudinal gradients of precipitation parameters evidence of continental climate in eastern europe first appears during the messinian in addition to changes in temperature shifts in the annual distribution of precipitation may have played a major role in post langhian climate changes however the most significant climatic transformations occurred later from the end of miocene through to the present several authors have described patterns of vegetation development in europe that are in good agreement with our finding of the first evidence for continental climate in eastern europe during the messinian our data do not support an onset of opening of vegetation during the tortonian or even earlier as has been described for some parts of eastern and southern europe possibly either non climatic parameters influenced such an early development or our data lack the required resolution and or spatial coverage to fully decipher the influence of continentality on vegetation and to correlate climate and vegetation statistically nevertheless climatic data that quantify continentality can provide a sound basis for explaining the expansion of grassland in eurasia

diagenesis and burial history of great oolite limestone southern england oil is produced from the middle jurassic great oolite limestone in the western wealden basin england additional production was discovered 150 stbopd 42 api in 1986 at the conoco 1 storrington well the storrington discovery is of note because the porosity in reservoir grainstones and packstones is largely primary and averages 19 4 the highest value yet found for the great oolite secondary porosity is of little significance for all wells studied porosity in great oolite grainstones and packstones ranges between 3 and 20 and there is no relation between porosity and lithology locally porosity may be largely occluded by coarse calcite spar which fluid inclusion studies show precipitated in the deep burial environment exploration in the great oolite the efore must seek diagenetic fairways wherein primary porosity has been preserved limestones in the producing interval of the great oolite at 1 storrington contain zoned syntaxial cements are generally high in magnesium content and have stable isotope compositions that indicate the involvement of marine waters relatively heavy dgr18o our interpretation is that the limestones were stabilized early in a mixing zone between freshwater and marine phreatic environments coarse calcite spar in the great oolite contains aqueous and oil inclusions the results of geothermometry studies show that the precipitation of calcite cements occurred at depth near maximum burial and at certain locations was synchronous with oil migration inversion of the basin was a later event the construction of burial history diagrams that incorporate fluid inclusion and maturation data shows that oil migration was during the late cretaceous a distribution pattern for oil inclusions in the great oolite indicates migration was mainly in the western part of the basin and initially into pre late cretaceous traps

depositional diagenetic thermal and maturation histories of cretaceous mishrif formation fateh field dubai rudist reef associated limestones comprising the cretaceous mishrif formation are the major reservoirs in fateh field a giant oil field in offshore dubai in this study mishrif cores from four wells on the western flank of the field were examined to gain insights into the depositional diagenetic thermal and maturation histories of the mishrif formation in this area the wells lowest on the west flank contain relatively deep water lower fore reef facies bounded by two erosional unconformities the upper unconformity marks the laffan mishrif contact and extends over fateh field throughout the region in fateh field the lower intra mishrif unconformity has been identified only on the western flank but is probably present in other locations low on the fateh structure the identification of the lower unconformity indicates two cycles of mishrif sedimentation the cycles are related to deep seated salt movement and epeiric sea level changes fluid inclusion data maturation calculations and burial history modeling indicate that the timing of cementation by blocky calcite spar and oil migration were approximately synchronous and occurred during the oligocene to miocene

a new model for assessing trap integrity and oil preservation risks associated with postrift fault reactivation in the timor sea based on comparisons between structural histories and the distribution of current and paleo oil accumulations it is proposed that the partitioning of postrift strain between faults in relation to trap geometry was critical in determining oil preservation during neogene fault reactivation in the timor sea most of the trap bounding faults in the region have been reactivated however the distribution of postrift displacements is heterogeneous and depends heavily on rift phase fault size location and interaction with nearby faults preferential localization of postrift strain onto larger faults in the population resulted in the partial protection of some fault bound traps with favorable geometries but promoted breaching of others oil columns tend to be preserved where the crest of the trap is bound by a fault segment that has accommodated relatively low postrift displacements less than about 60 m 196 ft during reactivation typically where smaller rift faults are overlapped by larger rift faults complete loss of oil column is generally observed where the crest of the trap is bound by a typically large fault with high postrift displacements greater than about 60 m 196 ft where faults with high postrift displacements are located downdip of the trap crest hydrocarbon columns are preserved down to the depth of the intersection between this fault and the top reservoir horizon a simple trap integrity model based on these observations was found to be largely consistent with a database of 69 drilled traps in the region the mechanisms and models discussed in this study are likely to apply to other petroleum systems where fault reactivation represents a risk to hydrocarbon preservation

miocene precipitation in europe temporal trends and spatial gradients article i nfo it is known from present day climates that both temporal and spatial variations in precipitation can be more pronounced than those in temperature and thus influence ecosystems and human society in more substantial way however very little is known about such variations in the past here we present an analysis of 206 palaeoprecipitation data from two twelve million year long proxy records of precipitation for southwest calatayud teruel basin and central europe western and central paratethys spanning the late early and middle to late miocene 17 8 5 3 ma at a temporal resolution of about 80 kyr and 200 kyr respectively the estimates of precipitation are based on the ecophysiological structure of herpetological assemblages the results show that precipitation variations in both regions have large amplitudes during the miocene with comparable temporal trends at longer time scales with locally 300 mm up to more than 1000 mm more rainfall per year than present the early langhian and the tortonian were relatively wet periods whereas the late langhian and late serravallian were relatively dry with up to 300 to 500 mm less precipitation than present the most humid time intervals were the early and middle tortonian washhouse climate periods overall our data suggest that the latitudinal precipitation gradient in europe from the middle to late miocene were highly variable with a general tendency towards a reduced gradient relative to present day values the gradient decreases during cooling periods and increases during warming periods similar to results from simulations of future climate change interestingly the precipitation gradient was reversed during the second washhouse climate period and the early messinian which may have causes a negative hydrologic balance in the eastern paratethys during the latter time yet our reconstructed gradient curve shows no direct correlation with the global temperature signal from oxygen isotopes which implies a non linear regional response our results further suggest that major fluctuations in the precipitation gradient can be responsible for shifts in ecosystem distribution and particularly for faunal turnover in south western europe

thermal history and tectonic subsidence of the bohai basin northern china a cenozoic rifted and local pull apart basin the bohai basin is a part of the larger bohai bay basin a cenozoic rifted intraplate basin heat flow measurements show that the bohai basin is characterized by present day heat flow varying between 53 and 74 mw m 2 with a mean of 63 mw m 2 however thermal history analyses derived from vitrinite reflectance vr and apatite fission track aft data indicate that tertiary cooling took place following a period of much higher paleo heat flow 70 90 mw m 2 prior to 25 million years to the present furthermore tectonic subsidence analysis reveals that the bohai basin experienced episodic sub rifting processes from the eocene to the end of the oligocene the post rift thermal subsidence was superimposed by intensified subsidence from the late miocene 12 million years in the bozhong depression and from the early quaternary 2 4 million years in the east liao bay indicating a rejuvenation of sedimentation related likely to transpressional structures developed locally on strike slip faults the present results indicate that there is good agreement between the reconstructed thermal history and the timing of the tectonic subsidence stages within the bohai basin the bohai basin is an early cenozoic rifted and local pull apart sub basin of the larger bohai bay basin 2001 elsevier science b v all rights reserved

a fluid inclusion study of cement and vein minerals from the celtic sea basins offshore ireland abstract fluid inclusion petrography and microthermometry have been carried out on jurassic sandstone cements quartz calcite and dolomite and later fracture filling calcite quartz veins from the north celtic sea and the fastnet basins fluid inclusions in the sandstone cements are small 1 8 m monophase liquid only or liquid rich two phase liquid vapour aqueous inclusions all display irregular to elliptical morphologies the two phase aqueous inclusions homogenise to the liquid phase between 60 122 c and have salinities ranging from 7 0 16 0 wt nacl equivalent indicating precipitation of the cements by moderate salinity waters in contrast the veins host both aqueous and petroleum inclusions the aqueous inclusions are liquid rich two phase liquid vapour inclusions 2 30 m long that are typically primary and show irregular and negative crystal shape morphologies their homogenisation temperatures to liquid range from 50 145 c and salinities from 6 20 wt nacl equivalent indicating broadly similar salinities coupled with a wider range of minimum trapping temperatures to those recorded from the cements yellow brown two phase liquid vapour petroleum inclusions are hosted by vein calcite from several wells in the central north celtic sea basin some of these inclusions appear to be primary and all are spatially associated with the aqueous inclusions the two phase liquid vapour petroleum inclusions homogenise mostly to the liquid between 50 130 c petroleum inclusions in the vein calcites indicate that petroleum was transported via fractures at a late stage through the jurassic and cretaceous strata of the celtic sea basins and apparently not through the sandstone matrix

gas accumulation from oil cracking in the eastern tarim basin a case study of the yn2 gas field oil and gas exploration in eastern tarim basin nw china has been successful in recent years with several commercial gas accumulations being discovered in a thermally mature to over mature region the yingnan2 yn2 gas field situated in the yingnan structure of the yingjisu depression produces gases that are relatively enriched in nitrogen and c2 alkanes the 13c1 38 6 to 36 2 and 13c2 values 30 9 to 34 7 of these gases are characteristic of marine sourced gases with relatively high maturity levels the distributions of biomarkers in the associated condensates suggest close affinities with the cambrian lower ordovician source rocks which in the yingjisu sag are currently over mature with 3 4 ro burial and thermal maturity modeling results indicate that paleo temperatures of the cambrian lower ordovician source rocks had increased from 90 to 210 c during the late caledonian orogeny 458 438 ma due to rapid subsidence and sediment loading by the end of ordovician hydrocarbon potential in these source rocks had been largely exhausted the homogenization temperatures of hydrocarbon fluid inclusions identified from the jurassic reservoirs of the yn2 gas field suggest a hydrocarbon emplacement time as recent as about 10 ma when the maturity levels of middle lower jurassic source rocks in the study area were too low 0 7 ro to form a large quantity of oil and gas the presence of abundant diamondoid hydrocarbons in the associated condensates and the relatively heavy isotopic values of the oils indicate that the gases were derived from thermal cracking of early formed oils estimation from the stable carbon isotope ratios of gaseous alkanes suggests that the gases may have been formed at temperatures well above 190 c thus the oil and gas accumulation history in the study area can be reconstructed as follows 1 during the late caledonian orogeny the cambrian lower ordovician marine source rocks had gone through the peak oil wet gas and dry gas generation stages with the generated oil and gas migrating upwards along faults and fractures to form early oil and gas accumulations in the middle upper ordovician and silurian sandstone reservoirs 2 since the late yanshanian orogeny the early oil accumulations have been buried deeper and oil has undergone thermal cracking to form gas 3 during the late himalayan orogeny the seals for the deep reservoirs were breached and the gas and condensates migrated upward and eventually accumulating in the relatively shallow jurassic reservoirs

cenozoic long term terrestrial climatic evolution in germany tracked by δ18o of rodent tooth phosphate even though the cenozoic has been recognized as a period of important climate change long term climatic changes that took place in the continental domain are still questioned for an area southern germany for which other long term palaeoclimatic records exist analysis of oxygen isotope composition of small mammal teeth has been carried out for localities ranging in age from the late eocene c 36 ma to the middle miocene c 10 ma comparison of this long term continental 18o record with the marine record reveals comparable trends the major cenozoic climatic events are thus recognized in the continental oxygen isotope record through comparison with other quantitative palaeoclimatic reconstructions available for the studied area temperatures in southern germany are broadly estimated to have fluctuated between 12 c and 25 c from late eocene to early late miocene according to the different available chronological frameworks either a 2 c considering the classical biostratigraphy or a 6 c considering a revised biostratigraphy decrease in mean air temperature is estimated for the eocene oligocene boundary

evaluating the use of weathering indices for determining mean annual precipitation in the ancient stratigraphic record abstract different quantitative methods have been developed to determine paleo rainfall using paleosols of particular interest are methods that use bulk geochemistry to calculate a weathering index and from that mean annual precipitation twenty three paleosols that formed during a time of significant climate change the paleocene eocene thermal maximum petm were analyzed to evaluate the relative merits of two geochemical proxies that have been developed for estimating paleoprecipitation one depends on the chemical index of alteration without potash cia k and the other uses the calmag weathering index which depends on cao and mgo the paleosols are located in the paleogene fort union and willwood formations in the bighorn basin wy morphologic differences among the paleosols indicate that they formed under varied soil moisture conditions a morphology index was developed from pedogenic features that are sensitive to soil drainage and thus to rainfall to assess that variability quantitative mean annual precipitation map values were calculated for each paleosol using the cia k index and the calmag index which was developed specifically for vertisols those results were compared to the morphology index for 23 paleosols the results indicate that increases and decreases in map calculated from both methods correlate relatively well to changes in the soil morphology index however the results from the calmag weathering index show a stronger correlation the results suggest that the calmag proxy provides a more robust map estimate for vertisols in addition to comparing map estimates to the soil morphology index we compared the map values to paleorainfall estimates determined from paleofloras at the same stratigraphic levels as three of the paleosols that comparison confirms that the calmag method is reliable for reconstructing map from ancient vertisols the results also show that in the bighorn basin vertisols with a b horizon

buried hill play jizhong subbasin bohai bay basin a review and future prospectivity as one of the six subbasins in the lacustrine bohai bay basin the jizhong subbasin is characterized by a dominance of the petroleum reserves located in buried hill traps of paleozoic and proterozoic marine carbonates particularly the latter this paper documents the revitalization of exploration of the buried hill play and discusses other play fairways not previously considered through use of case studies discovery of the largest field renqiu field in 1975 led to the establishment of the buried hill play in this play oil derived from the paleogene lacustrine source rocks charged into and accumulated in the underlying proterozoic marine carbonate reservoirs a number of buried hill fields were discovered within a time span of ca 10 yr in the subbasin with more and more large buried hill structures at depths of less than 5000 m 16 400 ft being drilled the annual reserve addition showed a rapid decline until 2006 the application of new technologies including reprocessing of merged three dimensional seismic data improved logging and testing techniques together with innovative exploration ideas made it possible to revitalize the buried hill play the exploration success lies with the focus change from targeting the conventional shallow to moderately buried hills to the unconventional buried hill pools which include deeply buried hilltop hillslope and intrahill pools case studies of one conventional buried hill field renqiu field and three unconventional buried hill fields chang 3 wengu 3 and niudong 1 fields together with modern geological investigations indicate that there still exists significant exploration potential for the buried hill play in the jizhong subbasin the potential largely lies with the unconventional buried hills the baxian wuqing and baoding depressions are favorable fairways for the deeply buried hill pools represented by the niudong 1 field the wenan slope is the favorable fairway for the intrahill pools represented by the chang 3 and wengu 3 fields

life in the sublittoral zone of long lived lake pannon paleontological analysis of the upper miocene szak formation hungary life and depositional environments in the sublittoral zone of lake pannon a large brackish paratethyan lake from the late miocene were reconstructed from fossils and facies of the szak formation this formation is exposed in several roughly coeval 9 4 8 9 ma outcrops located along strike of the paleo shelf break in northwestern hungary the silty argillaceous marl of the formation was deposited below storm wave base at 20 30 to 80 90 m water depth the abundance of benthic organisms indicates that the bottom water was usually well oxygenated interstitial dysoxia however may have occurred immediately below the sediment water interface as evidenced by occasional preservation of trace fossils such as diplocraterion the fauna comprised endemic mollusks including brackish cockles of the subfamily lymnocardiinae dreissenid mussels congeria and highly adapted uniquely large sized deep water pulmonate snails planorbids and lymnaeids ostracods were dominated by endemic species and in some cases endemic genera of candonids leptocytherids cypridids and loxoconchids fish remnants include a sciaenid otolith and the oldest skeletal occurrence of perca in europe the phytoplankton comprised exclusively endemic coccolithophorids mostly endemic dinoflagellates prevailingly spiniferites and cosmopolitan green algae the late miocene fauna and flora of lake pannon were in many ways similar to the modern caspian biota and in particular cases can be regarded as its precursor

late miocene washhouse climate in europe abstract we present two eight million year long proxy records of precipitation for southwest and central europe covering the middle to late miocene 5 3 13 ma at a temporal resolution of about 60 kyr and 150 kyr respectively the estimates of precipitation are based on the ecophysiological structure of herpetological assemblages amphibians and reptiles from 13 0 ma until about 9 ma both records show a similar trend evolving from a long dry period 13 11 ma into a washhouse climate 10 2 9 8 ma characterized by global warm conditions and several times more precipitation than present the transition from washhouse to a dryer climate between 9 7 and 9 5 ma and the concomitant cooling episode appear to have triggered a severe biotic event known as the vallesian crisis which included the extinction of hominoids in western europe a second washhouse period 9 0 8 5 ma coeval with a global warm episode was unprecedentedly intense in southwest europe but less pronounced in central europe from 8 ma onward a divergence in the two precipitation records is observed with southwest europe staying wetter and central europe becoming dryer than present both precipitation records are combined into a common run off curve as a measure of the relative intensity of the hydrological cycle for moderate latitudes of continental europe the run off curve shows a remarkable positive correlation with atlantic deep water temperatures from ceara rise by lear et al 2003 which are significantly higher up to 3 c during the two washhouse periods and show no other positive excursion of comparable magnitude we discuss potential links and the role of the coeval temporary restriction of the central american seaway on ocean and atmosphere circulation

semianalytical solutions for transport in aquifer and fractured clay matrix system a three dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed a group of semianalytical solutions is derived based on specific initial and boundary conditions as well as various source functions the analytical model solutions are evaluated by numerical laplace inverse transformation and analytical fourier inverse transformation the model solutions can be used to study the fate and transport in a three dimensional spatial domain in which a nonaqueous phase liquid exists as a pool atop a fractured low permeability clay layer the nonaqueous phase liquid gradually dissolves into the groundwater flowing past the pool while simultaneously diffusing into the fractured clay formation below the aquifer mass transfer of the contaminant into the clay formation is demonstrated to be significantly enhanced by the existence of the fractures even though the volume of fractures is relatively small compared to the volume of the clay matrix the model solution is a useful tool in assessing contaminant attenuation processes in a confined aquifer underlain by a fractured clay formation

towards a middle pleistocene terrestrial climate reconstruction based on herpetofaunal assemblages from the iberian peninsula state of the art and perspectives abstract the pattern of the varying climatic conditions in southern europe over the last million years is well known from isotope studies on deep ocean sediment cores and the long pollen records that have been produced for lacustrine and marine sedimentary sequences from greece italy and the iberian margin however although relative glacial and interglacial intensities are well studied there are still few proxies that permit quantitative terrestrial temperature and precipitation reconstruction in this context fauna based climate reconstructions based on evidence preserved in archaeological or palaeontological sites are of great interest even if they only document short windows of that climate variability because a they provide a range of temperature and precipitation estimates that are understandable in comparison with present climate b they may allow the testing of predicted temperature changes under scenarios of future climate change and c quantitative temperature and precipitation estimates for past glacials and interglacials for specific regions latitudes can help to understand their effects on flora fauna and hominids as they are directly associated with those cultural and or biological events moreover such reconstructions can bring further arguments to the discussion about important climatic events like the mid bruhnes event a climatic transition between moderate warmths and greater warmths during interglacials in this paper we review a decade of amphibian and reptile based climate reconstructions carried out for the iberian peninsula using the mutual ecogeographic range method in order to present a regional synthesis from mis 22 to mis 6 discuss the climate pattern in relation to the mid bruhnes event and the thermal amplitude suggested by these estimates and finally to identify the chronological gaps that have still to be investigated

hydrocarbon inclusions in late calcite cements migration indicators in the great oolite group weald basin s england abstract the fluorescence responses of hydrocarbon inclusions in calcite and dolomite cements are used to indicate the timing and longevity of oil migration in great oolite reservoirs of the weald basin of southern england oil migration and late stage calcite cementation were penecontemporaneous processes the gravity of the included hydrocarbons increases towards the basin depocentre through the range of 20 to 40 api reflecting the maturity of the source rocks reservoirs with a spread in the gravity of oil within inclusions were charged throughout source rock maturation those reservoirs with oil inclusions of a single gravity were charged in a discrete event

history of hydrocarbon charge on the atlantic margin evidence from fluid inclusion studies west of shetland fluid inclusions in jurassic reservoir sandstones help us to understand the history of hydrocarbon charge in the west of shetland region the sandstones contain both hydrocarbon and aqueous fluid inclusions hydrocarbons are present in trails of secondary inclusions through detrital grains and as primary inclusions in quartz overgrowths this is direct evidence for at least two episodes of hydrocarbon charge before the present oil entered the rock consistent with indirect evidence from burial history modeling and organic geochemistry fluorescence colors indicate that the two oils are of distinct composition the first oil was degraded reflecting an episode of uplift and exposure to near surface fluids before reburial and migration of a second live oil oils comparable to these two paleocharges were mixed to produce the oils that are encountered in the current reservoir pores showing that they were preserved despite repeated tectonic events at the atlantic margin

calcitization of mg ca carbonate and ca sulphate deposits in a continental tertiary basin calatayud basin ne spain diagenetic carbonates formed through early calcitization of evaporite gypsum anhydrite and or magnesium carbonate dolomite magnesite deposits have been identified throughout the tertiary calatayud basin ne spain the diagenetic carbonates consist in all cases of low magnesian calcite and are related to main sedimentary discontinuities which record episodes of significant subaerial exposure in the basin early calcite replacements predominate in sediments of the intermediate unit in central areas of the basin two types of diagenetic carbonates have been distinguished 1 laminated diagenetic carbonates in which the original structure of sequences formed of laminated magnesite dolomite and primary gypsum is preserved though transformed in calcite 2 brecciated diagenetic carbonates which resulted from extensive dissolution of lenticular gypsum macrocrystals accompanied by dedolomitization processes of dolomite host rock the replacement by calcite resulted from rapid transformation of evaporite deposits either at the contact of these deposits with overlying freshwaters or by percolating freshwater at very shallow burial depth stable isotope carbon and oxygen analyses of the diagenetic carbonates support influence of meteoric derived carbonate rich groundwater for their formation the meteoric isotope signature is supported by its comparison with the stable isotope values determined from diagenetic calcites formed after magnesite in evaporite sequences during the late pleistocene and holocene the diagenetic carbonate bodies formed as a result of a progressive change from highly to moderately concentrated saline lake waters this gradual evolution was related to a climatic shift from dry and hot to cooler and more humid conditions throughout the miocene a trend that has been also recognized in other large tertiary basins of the iberian peninsula in this period

diagenesis and reservoir quality evolution of the eocene sandstones in the northern dongying sag bohai bay basin east china abstract the eocene sandstones in the northern dongying sag bohai bay basin china are reservoirs for large accumulations of hydrocarbons the sandstones are mainly lithic arkoses and feldspathic litharenites texturally and compositionally immature these sandstones have a wide range of porosity 0 4 37 and permeability 0 004 6969 md and show an overall decrease in reservoir quality from 1500 m to 5000 m below sea level the reduction in reservoir quality is a product of several digenetic processes these include compaction precipitation of dolomite and calcite in eodiagenetic stage compaction feldspar dissolution precipitation of quartz cements and clays kaolin and illite and precipitation of ferrocalcite and ankerite in mesodiagenetic stage mineral distribution pattern and isotopic composition suggest carbonate cements in sandstones originate from sources outside the sandstones carbonate cementation together with compaction reduced the sandstones porosity and permeability significantly in a sandstone bed marginal sandstones with distance to sandstone mudstone interface less than one meter always have lower porosity than central sandstones as burial depth exceeds 4000 m marginal sandstones have very low porosities 2 m can be potential effective reservoirs feldspar dissolution and precipitation of clays and quartz cements have little impact on absolute porosity mineral distribution pattern and quantitative data show that leached feldspars are the internal source of authigenic quartz and clays in sandstones and the volume difference between feldspar secondary porosity and related authigenic cements is generally less than 0 25 however although there is little or no net import of matter to the sandstones the pore architecture changes dramatically primary macropores are lost as clays and quartz precipitate while the proportion of microporosity increases occurring mainly between clay crystals the overall result is that permeability is significantly degraded

the application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs abstract fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history temperature pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration cements in petroleum reservoirs contain both oil and aqueous fluid inclusions fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil the lifetime of fluorescence induced by a pulsed laser is related to the api gravity of entrapped oil interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments examples of how fluid inclusions are used to determine the physico chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the wealden basin england the mishrif formation dubai the smackover formation gulf coast u s a and jurassic sandstones offshore norway in the wealden basin temperature data from fluid inclusions are used to determine that oil migration occurred in the cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin the geochemistry of oil inclusions in calcite cements from the mishrif formation dubai are used to determine the type and maturity of entrapped oil temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil in deep smackover reservoirs oil contains h 2 s the origin of the h 2 s is examined by study of fluid inclusions containing h 2 s in jurassic sandstones offshore norway fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid

late miocene climate in the circum alpine realm a quantitative analysis of terrestrial palaeofloras abstract selected mega and microfloras from central and southern europe have been analysed for the time interval tortonian pannonian mn 9 12 with the coexistence approach to obtain quantitative palaeoclimate data the results give a geographically differentiated picture of the late miocene climate in the circum alpine area spatial patterns are presented in maps for mean annual temperature temperature of the coldest month temperature of the warmest month mean annual precipitation and mean annual range of temperature the obtained data show an overall warm humid and homogenous climate with very low latitudinal and longitudinal gradients there is no indication of a mediterranean type of climate palaeogeographic influences on climate patterns are evident the pannonian lake caused mild winters and a lower seasonality of temperature in the pannonian basin

new method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late miocene precipitation gradients in europe existing methods for determining paleoprecipitation are subject to large errors 6350 400 mm or more using mammalian proxies or are restricted to wet climate systems due to their strong facies dependence paleobotanical proxies here we describe a new paleo precipitation tool based on an indexing of ecophysiological groups within herpetological communities in recent communities these indices show a highly significant correlation to annual precipitation r 2 5 0 88 and yield paleoprecipitation estimates with average errors of 6250 280 mm the approach was validated by comparison with published paleopre cipitation estimates from other methods the method expands the application of paleo precipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database this method is applied to two high resolution time intervals from the european neogene the early middle miocene early langhian and the early late miocene early tortonian the results indicate that both periods show significant meridional precipitation gradients in europe these being stronger in the early langhian threefold decrease toward the south than in the early tortonian twofold decrease toward the south this pattern indicates a strengthening of climatic belts during the middle miocene climatic optimum due to southern hemisphere cooling and an increased contribution of arctic low pressure cells to the precipitation from the late miocene onward due to northern hemisphere cooling

genetic features of petroleum systems in rift basins of eastern china abstract most oil bearing basins in eastern china are mesozoic cenozoic continental rifts which have played a habitat for oil and gas in china investigation of the petroleum systems may give a better understanding of the oil and gas habitats in these basins of the essential elements of the petroleum system the source rock is the most important in rift basins however rift tectonic evolution controls all the essential elements and processes necessary for a petroleum system a four stage evolution model is suggested for the controls in the rift basin a rift basin may consist of sub basins depressions and sub depressions and major moderate and minor uplifts a depression or sub depression has its own depocentre mainly occupied by source rock and all kinds of lacustrine sediments and thus has all the essential elements of a petroleum system however only those depressions or sub depressions which are rich in organic matter and deeply buried to generate oil and gas form petroleum systems immature oil another characteristic complicates the petroleum system in the rift basins three types of oil and gas habitats are described as a result of this analysis of the petroleum systems of the 26 largest oil and gas fields discovered in eastern china rift basins uplifts between oil source centres are the most prospective areas for oil and gas accumulations slopes connecting oil source centres and uplifts are the second and the third type is subtle traps in the oil source centre

the evolution of the danube gateway between central and eastern paratethys se europe insight from numerical modelling of the causes and effects of connectivity between basins and its expression in the sedimentary record abstract the pannonian and dacic basins in se europe are presently connected by the danube river across the south carpathians to which they are in a back arc and foreland position respectively part of the paratethys realm during the neogene open water communication between the basins was interrupted by the late miocene uplift of the carpathians different mechanisms have been proposed for the formation of the danube gateway capture of the upstream lake or an upstream river or incision of an antecedent river estimates on its age range from late miocene to quaternary a related issue is the effect of the large mediterranean sea level fall related to the messinian salinity crisis on the paratethys subbasins specifically the isolated pannonian basin in a synthetic numerical modelling study using a pseudo 3d code integrating tectonics surface processes and isostasy we addressed the causes and effects of changes in connectivity between two large sedimentary basins separated by an elevated barrier specifically we aimed to find the expression of connectivity events in the sedimentary record in general and the consequences for the evolution of the pannonian dacic area in particular we studied a range of parameters including the geometry and uplift rate of the barrier downstream sea level change and lithosphere rigidity we found that changes in connectivity are expressed in the sedimentary record through their effect on base level in the upstream basin and supply in the downstream basin the most important factors controlling the response are the elevation difference between the basins and the upstream accommodation space at the time of reconnection the most pronounced effect of reconnection through lake capture is predicted for a large elevation difference and limited upstream accommodation space downstream increase in sediment supply is dependent on the latter rather than the reconnection event itself of the parameters we tested the rigidity of the lithosphere was found to be of major importance by its control on sediment loaded subsidence and generation of accommodation space a downstream sea level change is unlikely to induce capture but may affect the upstream lake level by enhancing incision in a pre existing gateway in the pannonian dacic region the mechanically weak continuously subsiding pannonian lithosphere allowed accommodation of significant volumes of continental sedimentation and as a consequence transfer of excess sediment to the downstream dacic basin was only gradual the messinian sea level fall in the dacic basin could have been recorded in the pannonian basin only if a connection between the basins already existed more detailed modelling of river incision taking into account lateral differences in erodibility in the south carpathians will be required to give better time constraints on the formation of the danube gateway