tricyclic terpane maturity parameters response to heating by an igneous intrusion the effects of thermal maturation upon the abundance and composition of the tricyclic terpanes have been investigated within a single sedimentary horizon within the dun caan shale member isle of skye scotland intruded by a 0 9 m thick tertiary dolerite dyke heating by the igneous body caused the concentrations of all 13 h 14 h and 13 h 14 h tricyclic terpanes to increase towards or within the effective oil window recording generation from abundant non hydrocarbon precursors such as kerogen and asphaltene bound components progressive changes in tricyclic terpane composition accompany these concentration changes an increase in the c23 maturity parameter towards the dyke resulted from the relatively greater rate of generation of the isomer combined with the earlier decline in concentration by degradation or isomerisation of the component the tricyclics tricyclics hopanes parameter shows a dramatic increase within the latter part of the oil window due to the greater relative thermal stability of the tricyclic terpanes the quantitative data demonstrate the importance of the processes of generation from non hydrocarbon fractions of the sedimentary organic matter and thermal degradation in the operation of tricyclic terpane maturity parameters

changes in occurrence of cold surges over east asia in association with arctic oscillation 1 it has been newly found that the occurrence of cold surges in east asia is significantly influenced by the arctic oscillation ao in the present study the events of cold surge are objectively determined based on several synoptic criteria and the phase dependency of its occurrences in association with the ao has been revealed during the negative ao phase the frequency of cold surge occurrence is relatively increased than that of neutral and positive ao phases the variation of upper level trough and jet stream over east asia and the siberian high in association of ao are suggested to explain the change of cold surge occurrences

the microbial input in carbonate anhydrite facies of a sabkha palaeoenvironment from guatemala a molecular approach abstract nine representative rock samplesincluding four anhydrites an oil stained dolomite and a laminated mudstone source rock from a sabkha type palaeoenvironment la felicidad 1 well guatemala have been compared in order to tentatively characterize each facies by a geochemical signature each sample has been studied by using basic parameters toc rock eval pyrolysis yields and analyses of alkanes and aromatics by computerized gc ms the following families of compounds have been reviewed n alkanes branched and cyclic alkanes n alkylbenzenes benzohopanes monoaromatic steroids d ring aromatic 8 14 secohopanoids alkylnaphthalenes alkylphenanthrenes alkyldibenzothiophenes and triaromatic steroids despite close geochemical relationships of all the sample a more in depth investigation taking into account molecular patterns and semi quantitative data reveals significant differences among the samples anhydrites may be differentiated from carbonates which illustrates the efficiency of organic geochemistry in environmental palaeoreconstruction even in organiccarbon lean sediments toc 0 04 0 08 in anhydrites in these anoxic marginally mature sediments the strong predominance of triterpanes over steranes tt to st 20 associated with other molecular features leads to the conclusion that the main contribution to the organic matter of all facies is by bacteria several prominent components including novel families iso c23 and iso c27 alkanes tetracyclic terpanes d ring aromatic 8 14 secohopanoids 1 phenylpentadecane undecylnaphathalene and their mono and dimethylated counterparts have been interpreted as derived from halophilic bacteria these conclusions may be extended to all crude oils from the same area which may be considered as true bacterially derived petroleums the la felicidad 1 well data are discussed with reference to other palaeosabkha type sequences from the sw aquitaine basin france in which the bacterial input is less important however in these sabkha sequences 1 phenylpentadecane undecylnaphthalene and related structures have also been identified

biomarker distributions in australian oils predominantly derived from terrigenous source material oils found in many australian sedimentary basins contain a relatively high input of terrigenous organic source material a study of a large number of these oils has permitted a number of biomarker distributions to be determined that appear to be characteristic for oils derived from terrigenous source material these features include the presence of sesquiterpanes absence of tricyclic terpanes relatively high concentrations of a c24 tetracyclic terpane predominance of c29 steranes presence of two unidentified c27 and c30 terpanes and virtual absence of 18 h oleanane the latter observation is significant since it appears that 18 h oleanane appears only in oils of tertiary age derived from terrigenous source material an attempt has also been made to compare the results for the australian oils with published results for oils derived from terrigenous source material in other parts of the world the number of reports in the literature for these oils is fairly limited but it appears that some of the observations for the australian oils can be extended to them this study is an initial attempt to devise a classification scheme that can be used to determine the origin of an oil unambiguously from biomarker parameters in order for this approach to be successful a relatively large number of biomarker parameters need to be assigned as characteristic of a particular type of source material

isentropic analysis of polar cold airmass streams in the northern hemispheric winter abstractan analysis method is proposed for polar cold airmass streams from generation to disappearance it designates a threshold potential temperature t at around the turning point of the extratropical direct etd meridional circulation from downward to equatorward in the mass weighted isentropic zonal mean mim and clarifies the geographical distributions of the cold air mass the negative heat content nhc their horizontal fluxes and their diabatic change rates on the basis of conservation relations of the air mass and thermodynamic energy in the northern hemispheric winter the polar cold air mass below t 280 k has two main streams the east asian stream and the north american stream the former grows over the northern part of the eurasian continent flows eastward turns down southeastward toward east asia via siberia and disappears over the western north pacific ocean the latter grows over the arctic ocean flows toward the eastern coast of north america via hudson bay and disappears ov

application of organic facies studies to sedimentary basin analysis a case study from the yitong graben china abstract an organic facies is defined in this paper as a mappable stratigraphic unit containing organic matter om of a particular genetic type in certain abundance several concepts concerning organic facies are proposed and their significance in basin analysis is discussed in detail a combined sedimentological and organic geochemical investigation has been carried out in the yitong graben and four organic facies and one organic parafacies have been recognized distinct organic basin fill sequences obfs and organic facies association ofa were developed in different sub units of this graben which indicates that the yitong graben had undergone two tectonic subsidence cycles such tectonic subsidence patterns could not have been found out without detailed organic facies analysis confirming that organic facies especially obfs and ofa study is a very useful tool not only for prediction and three dimensional mapping of petroleum source rocks but also for sedimentary basin analysis

the influence of source depositional conditions on the hydrocarbon and nitrogen compounds in petroleum from central montana usa abstract the hydrocarbon and pyrrolic nitrogen compound compositions of 21 crude oils from reservoirs in the heath tyler amsden and swift morrison formations of central montana have been investigated by combined gas chromatography mass spectrometry the biomarker and aromatic hydrocarbon data enabled recognition of three composition types within the heath tyler amsden oils the swift morrison oils displayed different hydrocarbon characteristics and are classified as a separate oil group a number of geochemical parameters e g dibenzothiophene phenanthrene c 20 triaromatic steroid hydrocarbon c 20 c 28 triaromatic steroid hydrocarbons indicate strong variations in petroleum composition from north to south across the region oils from the central montana uplift with high relative c 27 diasteranes c 29 steranes and ts ts tm suggests increasing clay contribution to the source while abundant gammacerane indicates the development of hypersaline conditions with restricted circulation oils from the bull mountain basin represented by the amsden oils show relatively low c 27 diasteranes c 29 steranes and ts ts tm ratios indicating increasing carbonate contribution to the source while the decrease of a gammacerane contribution suggests decreasing salinity levels which may explain the dominance of tricyclic terpane and hence their precursors to the source organic matter while the changes recorded by the biomarker and aromatic hydrocarbon compositions show strong regional variations the nitrogen compounds do not respond so strongly however weak trends coinciding with source carbonate content were apparent in the following ratios 1 8 dimethylcarbazole 1 8 dimethylcarbazole 1 ethylcarbazole and carbazole sum of c 2 carbazoles the second parameter may be responding to variations in salinity since it co varies with the behaviour exhibited by the tricyclic terpanes the source information that can be extracted from biomarkers and aromatic hydrocarbons suggests that primary migration and compositional fractionation during expulsion has exerted little influence on this fraction of petroleum meanwhile primary migration and compositional fractionation during expulsion appear to effect the carbazole and benzocarbazole distributions thereby limiting their application as indicators for source rock facies composition

quaternary reef response to sea level and environmental change in the western atlantic the tropical subtropical western atlantic realm harbours abundant fringing reefs two major barrier reefs belize florida several atolls and large reef fringed carbonate platforms bahamas data from belize and south florida indicate that major barrier reefs were established during the high sea levels of the long and warm marine isotope stage 11 reefs formed during pleistocene sea level highstands whereas erosion non deposition and the formation of subaerial exposure surfaces prevailed during lowstands of sea level florida bahamas exposed reefs and platforms with siliciclastic hinterlands were characterized by deposition of clays and sands on fluvial plains belize elevated terraces and outcrops of reefs of the last interglacial of marine isotope stage 5e are evidence of higher than present sea level and temperature that sustained large reef fringed carbonate platforms and ramps in the florida bahamas region and central america belize mexico including ooid deposition in warm and shallow waters during the highstands of marine isotope stages 5c and 5a at sea levels several metres lower than today fringing reefs developed in parts of the caribbean for example in south florida outlier reefs data from the island of barbados support the contention that the postglacial sea level rise from about 120 m was rapid and punctuated by two meltwater pulses ia and ib which bracket the beginning and end of the younger dryas respectively after reflooding of shelves in the early holocene reefs developed preferentially on highs of the underlying karstified pleistocene limestone surface and on former river channel bars many reefs in the western atlantic region kept pace with holocene sea level rise whereas some were drowned reasons for reef drowning are debated and include sea level rise elevation of antecedent topography and deterioration of environmental conditions such as high nutrient input apart from sea level and antecedent topography factors such as exposure to waves and currents storms and sedimentation have controlled reef development the historical decline of acroporid corals in the caribbean realm has been attributed to cooling following the holocene thermal optimum however historical die offs of reef building corals and other reef organisms suggest that some if not all recent declines were unprecedented during the holocene rising temperatures decreasing carbonate saturation increased frequency of major storms high nutrient concentrations and sedimentation overfishing and disease certainly played a role in decline but systematic studies relating these environmental factors to holocene reef building are only in the early stages

sedimentological evolution of north sound grand cayman a freshwater to marine carbonate succession driven by holocene sea level rise abstract north sound grand cayman contains up to 4 m of sediments that accumulated under the influence of the holocene rise in sea level originally north sound was a dish shaped depression formed by the erosion of the miocene dolostone and pleistocene limestone bedrock at that time a sill along the northern margin isolated the area from the open ocean sedimentation from 5 000 to 3 800 yr b p which took place in a fresh water to brackish water regime resulted in deposition of the composite grain gastropod and bivalve facies as sea level rose above the sill no later than 2 500 yr b p marine waters began to invade north sound and open connections with the caribbean sea were established peats which developed in mangrove swamps were deposited during this transitional phase fully marine sedimentation ongoing for at least the last 2 500 years resulted in the deposition of the halimeda halimeda benthic foraminifera bivalve and bivalve halimeda facies sediment which accumulated at an average of 85 cm 1000 years did not keep pace with sea level which rose at an average of 160 cm 1000 years as a result accommodation space in north sound has progressively increased a sea level curve derived from basal peats and bivalves found in the sediments of north sound is comparable to sea level curves derived for barbados reefs for the last 2 500 years however the north sound curve is 3 m lower than a sea level curve that was derived from peats on barkers peninsula which forms the northwest boundary of north sound this discrepancy attributed to original differences in elevations of the samples highlights some of the problems associated with the construction and interpretation of sea level curves the sedimentary succession in north sound which is similar to that found in the bight of abaco in the bahamas is a record of transient depositional environments that evolved in response to the holocene rise in sea level

geochemical comparison of fluid inclusion and present day oil accumulations in the papuan foreland evidence for previously unrecognised petroleum source rocks abstract petroleum production in papua new guinea is limited to the papuan fold belt present day oil accumulations in fields such as iagifu hedinia and gobe are thought to be mainly derived from clay rich jurassic marine source rocks containing terrestrially derived organic matter that were deposited under oxic conditions in this study other generative source rocks in the papuan foreland are indicated using fluid inclusion fi oil data from three wildcat wells koko 1 bujon 1 and kimu 1 which were drilled on the bosavi arch detailed organic geochemistry of these fi oils and associated free oils or oil stains suggests that none of these were generated from the aforementioned jurassic source rocks instead at least three different generative source rocks are indicated firstly a marine probably late cretaceous or younger source rock deposited under reducing conditions is indicated by the bujon 1 fi oil this source rock had a moderate contribution from higher plant organic matter including oleanane and or lupane the bujon 1 fi oil has similarities with fi oils from the iagifu 7x and p nyang 2x wells in the papuan fold belt secondly an algal dominated lacustrine source rock is indicated by the biodegraded koko 1 rft crude oil the unbiodegraded fi oil from koko 1 and the bujon 1 oil stains from the toro and imburu formations these lacustrine oils have high abundances of tricyclic terpanes pregnane homopregnane and gammacerane contain carotane and have high c26 c25 tricyclic terpane ratios the source of the lacustrine oils is inferred to contain moderate amounts of terrestrial organic matter indicated by a dominance of c29 steranes and abundant aromatic higher plant biomarkers and could be gypsiferous shales embedded in oligocene miocene carbonates or triassic age sediments deposited on igneous basement during early rifting associated with the break up of gondwana the kimu 1 fi oil was generated from a mature marine suboxic source rock but has a different geochemical composition to free oil from a similar interval which was derived from a carbonate rich source rock none of the fi oils correlate well with oil families previously described in papua new guinea accordingly the oils recovered from fis in this part of the papuan basin support the presence of laterally varying source rock compositions and qualities and indicate that there are opportunities to develop new charge models for features across the papuan foreland furthermore koko 1 bujon 1 and kimu 1 fi oils have different geochemical compositions compared to the associated free oils or oil stains indicating that each of these localities has a multi phase charge history further work to lower exploration risk in the papuan foreland should be directed to understanding the distribution maturity and expulsion history of these newly recognised potential source rocks

lower middle jurassic nonmarine source rocks and petroleum systems of the northern qaidam basin northwest china the qaidam basin is a nonmarine petroliferous basin on the northeastern margin of the tibet plateau potential source rocks are reported from tertiary saline lacustrine deposits and jurassic freshwater lacustrine or terrestrial strata the jurassic source rock is similar in terms of depositional system lithology age and organic geochemistry to nonmarine jurassic rocks that are thought to be potentially significant hydrocarbon sources in many basins of central asia including the tarim junggar and other important petroleum producing basins these jurassic source rocks were deposited in freshwater lacustrine systems in intracontinental foreland style basins during the early and middle jurassic these lacustrine strata are associated with coals and coaly mudstones with possible secondary importance as hydrocarbon source rocks oils from the northern qaidam basin can be divided into two groups based on molecular indicators of depositional environment and age diagnostic biomarkers those derived from this jurassic freshwater lacustrine source rock and those derived from a tertiary hypersaline lacustrine source rock the correlation of some qaidam oils to a jurassic source establishes a petroleum system involving these nonmarine jurassic source rocks oils of this petroleum system have been produced from tertiary and mesozoic reservoirs in anticlinal and thrust related traps in northeastern qaidam maturation modeling of the jurassic source rock indicates that these oils were generated and expelled during the miocene pliocene in much of northern qaidam the geological context of the basin suggests that drainage within the basin primarily was vertical probably mainly along faults until evaporite or overpressured shale seals were encountered in the overlying cenozoic section documentation of this petroleum system suggests other exploration targets remain underevaluated in northern and southwestern qaidam furthermore the northern qaidam petroleum system is a useful analog to interpret the role of similar jurassic source rocks in other sparsely documented basins of central asia

energetics and dynamics associated with two typical mobile trough pathways over east asia in boreal winter two dominant types of east asian mobile trough eamt are identified by a novel mobile trough detection algorithm the two major eamts likely pass through to the north and the south of lake baikal in this study both of synoptic and planetary time scales influences on east asia are studied for synoptic scale southern path of mobile trough shows a higher rate of intensification that of northern path southern path has stronger impact on southeast asia temperature fluctuation because of more southern pathway and stronger magnitude of wave train but duration of fluctuation is shorter in southern due to the downstream development for planetary scale the northern path shows a large warm anomaly over southeast asia and a cold anomaly over northeast asia which is associated with the northward shift of the jet stream the southern path shows a cold anomaly over east asia due to a northwesterly anomaly the forcing of high frequency eddy on low frequency eddy is estimated in terms of momentum and energy the reinforcement of high frequency eddy flux on low frequency variation can be observed in northern path but not in southern path the energy difference for two paths is also caused by the variations of barotropic and baroclinic conversion the energy tendency of interaction between two frequency eddies is only responsible for sustention of energy anomaly over southwestern japan

holocene sea level change and coastal landscape evolution in the southern gulf of carpentaria australia a revised holocene sea level history for the southern gulf of carpentaria is presented based on new data from the south wellesley archipelago and age recalibration of previous research results confirm that rising sea levels during the most recent post glacial marine transgression breached the arafura sill ca 11 700 cal yr bp sea levels continued to rise to ca 30 m by 10 000 cal yr bp leading to full marine conditions by 7700 cal yr bp sea level reached present mean sea level pmsl and continued to rise to an elevation of between 1 5 m and 2 m above pmsl sea level remained ca 1 5 between 7000 and 4000 cal yr bp followed by rapid regression to within 0 5 m of pmsl by ca 3500 cal yr bp when placed into a wider regional context results from this study show that coastal landscape evolution in the tropical north of australia was not only dependent on sea level change but also show a direct correlation with holocene climate variability specifically the formation and preservation of beach rock deposits intertidal successions beach and chenier ridge systems hold valuable sea level and holocene climate proxies that can contribute to the growing research into lower latitude holocene sea level and climate histories

new constraints on late holocene eustatic sea level changes from mahe seychelles this study provides new estimates of globally integrated ice sheet melt during the late holocene since 4 ka bp from seychelles in the western indian ocean a tectonically stable far field location where the necessary glacial isostatic adjustment gia correction is small and is relatively insensitive to predictions using different earth viscosity profiles we compare sea level data from seychelles to estimates of eustasy from two gia models ice 5g and eust3 which represent end members in the quantity of global melt during the late holocene we use data from a range of coastal environments including fringing reef present day beaches fossil plateau and mangrove deposits on the largest island of the seychelles archipelago mahe to reconstruct relative sea level changes our data suggest that extensive coastal deposits of carbonate rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests rsl stability during this period mangrove sediments preserved behind these deposits and in river mouths date to c 2 ka and indicate that rsl was between 2 m and present during this interval correcting the reconstructed sea level data using a suite of optimal gia models based on the two ice models mentioned above and a large number c 350 of earth viscosity models gives a result that is consistent with the sedimentological constraints when uncertainties in both model results and data are considered it is possible to rule out eustatic sea levels below c 2 m and more than a few decimetres above present during the past two millennia this uncertainty is dominated by error in the reconstructions rather than the model predictions we note however that our estimates of eustasy are more compatible with the eust3 model compared to the ice 5g model during the late holocene 2 1 ka bp our evidence from seychelles shows that the timing of when eustatic sea level first rose close to present is between the predictions of the two end member gia models presented here 4 ka bp for ice 5g and 1 ka bp for eust3 using all lines of evidence currently available from mahe we suggest that the eustatic contribution during the last 2 ka has been less than 2 m this conclusion is drawn from a tectonically stable far field region that is relatively insensitive to earth and ice model uncertainties and implies that global eustasy has been relatively insensitive to climate fluctuations over the pre industrial part of the last 2 ka

oil source rock correlations limitations and recommendations a rigorous defensible and causal oil source rock correlation definitively ties an individual source rock sample to an individual crude oil using genetically based internally consistent parameter matches such a correlation is a relationship established between the two components which is consistent with all known chemical geochemical and geological information and meets three criteria a the relationship must be causal the oil must arise at least in part from the specified source rock s b chemical data used in the correlation must be comparable the elemental molecular and isotopic data derived from the source rock must be of the same type as that derived from the oil and c all available geological data must be supportive clear geological evidence must exist which allows the proposed source rock to have sourced the oil the three points of this definition are satisfied and the correlation is successful if we solve one analytical and three geological problems natural extraction of crude oil from its source rock i e expulsion differs mechanically and temporally from laboratory extraction leading to a correlation problem referred to as extraction differences and representing the single greatest analytical uncertainty in correlation efforts geologically three aspects confound oil source correlations occurrence of multiple source units and or source units at differing maturity levels lateral and vertical depositional variations in source unit s organic matter and lateral and vertical variation in reservoir unit s organic matter these concerns are overcome by taking five actions for each oil source correlation effort 1 select representative samples using statistically defensible methods 2 establish the inherent compositional variability laterally and temporally due to depositional and maturation processes in each prospective source unit 3 assess the extent of migration induced changes in oil composition including post migration changes such as in reservoir alteration 4 support each correlation with migration histories derived from 4d models 5 iterate correlation results with new data gathered from ongoing exploration efforts these five actions will a allow correlation success to be measured more objectively b establish risking parameters for direct use in basin assessment and c provide baseline criteria for use in assessing the reliability of oil source rock correlations although these approaches will improve conventional oil source rock correlation efforts ultimately they may not be needed if inversion methods become more reliable the ability to invert compositional data for crude oil i e predict the age lithology maturity and other characteristics of a source rock solely through chemical analysis of its expelled oil could eventually result in successful oil source rock correlations in which source rock analysis for oil source rock correlation purposes is less critical

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

oil families and their potential sources in the northeastern timan pechora basin russia oil and rock samples collected throughout the northeastern timan pechora basin identify key oil families and correlate these oil families to stratigraphic units that sourced them based on distinctive molecular characteristics three distinctive hydrocarbon systems have been identified within the northeastern timan pechora basin hydro carbons both oil and gas are found in clastic and carbonate reservoirs from the lower silurian to the triassic three major oil families have been identified based on physical properties gas chromatography liquid chromatography and gas chromatography mass spectrometry family a oils are found in permian silurian reservoirs within the sorokin swell and upper devonian reservoirs within the eastern and western edges of the khoreyver depression this oil family is sourced from an upper devonian bitumen laminated carbonate mudstone informally known as the domanik facies family b oils are found only in upper devonian reservoirs within the central khoreyver depression this oil family is most likely sourced from upper devonian hypersaline marine mudstones with significant bacterial input many of the family b oils were generated at temperatures less than that for peak oil generation family c oils are found in carboniferous lower devonian reservoirs within the northern sorokin swell this family is sourced from marine mudstones that have gloecapsamorpha prisca as well as other marine algae present organic rich lower devonian and silurian shales contain similar molecular characteristics and are potential sources for the family c oils

origin of nama basin bitumen seeps petroleum derived from a permian lacustrine source rock traversing southwestern gondwana abstract biodegraded bitumens associated with quartz and calcite veins in the cambrian fish river subgroup sediments of the nama group of southern namibia have a geochemical signature diagnostic for organic matter that was deposited in a saline lacustrine palaeoenvironment in particular they contain abundant gammacerane carotane and 3 methylhopanes while 24 isopropyl cholestanes and dinosteroids are not detectable sealed tube hydrous pyrolysis of asphaltene and polar fractions yielded saturated hydrocarbons amenable to c isotopic analysis and these analyses show unusually low 13 c values these combined characteristics are also present in immature bitumens from the permian irati formation of brazil and a saline lacustrine facies of the whitehill formation in the karoo basin south africa we conclude that the bitumens originated from whitehill equivalent strata of the kalahari basin deposited in what was an extensive saline lacustrine basin in southwestern gondwana during the early permian in southern africa source rocks of the whitehill formation are generally immature for petroleum generation and it is therefore likely that the nama bitumens were expelled by contact metamorphism during emplacement of karoo dolerite sills and dykes in the jurassic

influence of the madden julian oscillation on wintertime surface air temperature and cold surges in east asia 1 the variations of wintertime surface air temperature sat and the occurrences of cold surges over east asia in association with the madden and julian oscillation mjo are examined the mjo is defined as a combination of the two leading empirical orthogonal function modes of 850 and 200 hpa zonal winds and outgoing longwave radiation in the tropics the spatial pattern and magnitude of sat anomalies over east asia significantly change with respect to mjo phases composite analysis reveals that the mjo sat relationship is mainly affected by strong temperature advection in the lower troposphere in addition occurrences of cold surges are identified using objectively determined synoptic criteria and their relation to the mjo is analyzed most extreme cold surges occur when the mjo convection center is located over the indian ocean and it is suggested that mjo induced circulation anomalies may reinforce the amplification of normal cold surges to extreme cold surges

relationship between the arctic oscillation and cold surges over east asia abstract the present study reveals the changes in the characteristics of cold surges over east asia associated with the arctic oscillation ao based on circulation features cold surges are grouped into two general types wave train and blocking types the blocking type of cold surge tends to occur during negative ao periods that is the ao related polarity of the blocking type however the wave train type is observed during both positive and negative ao periods although the wave train features associated with negative ao are relatively weaker the cold surges during negative ao are stronger than those during positive ao in terms of both amplitude and duration the cold surges during positive ao in which the extent of effect is confined to inland china passes through east asia quickly because of weaker siberian high and aleutian low leading to short duration of these cold surges in contrast the cold surge during negative ao characterized by a well organized anticyclone cyclone couplet with high p

calcareous crusts on exposed pleistocene limestones a case study from grand cayman british west indies abstract calcareous crusts which include laminar up to 6 cm thick and non laminar calcretes have developed on ooid grainstones and skeletal wacke pack grain floatstone in the pleistocene ironshore formation exposed at morgan s harbour tarpon springs and rogers wreck point on grand cayman british west indies non laminar calcretes which consist largely of micrite with variably altered skeletal fragments and lithoclasts derived from the host limestone contain peloids in their basal parts in contrast the laminar calcretes are formed of porous laminae and low porosity laminae calcified roots are common in the porous laminae but rare in the low porosity laminae the 18o values of calcretes from 5 22 to 0 16 have a positive correlation with the 13c values that vary from 10 03 to 6 41 at tarpon springs from 11 57 to 5 43 at morgan s harbour and from 9 89 to 8 68 at rogers wreck point the non laminar calcretes reflect progressive micritization of the bedrock with a basal peloidal zone that passes upward into the micrite zone in contrast laminar calcretes are attributed to accretionary build up dictated by microscale processes that were controlled largely by the interplay of plant roots and their associated microorganisms the positive correlation between the 18o and 13c values from the calcareous crusts indicates that evaporation influenced calcite precipitation the 13c values of the laminar calcretes record a change from vegetation dominated by c3 plants that grew in a cool wet climate to a c3 c4 vegetation that grew in a hotter drier climate the cayman calcretes resemble those found on the pleistocene miami limestone in florida and highlight the possibility that these calcareous crusts may reflect regional climates and may therefore enable regional stratigraphic correlation

geochemical characterisation and genetic origin of oils and condensates in the south viking graben norway abstract geochemical analysis of oil and condensate samples from all major fields and discoveries in the norwegian south viking graben as well as source rock extracts of upper and middle jurassic source horizons was carried out to characterise reservoired hydrocarbons and establish genetic relationships the south viking graben is in a mature phase of exploration and this study aims at unravelling regional trends to improve predictions in exploration and will show the significance of the play models in the area seven hydrocarbon families have been identified based on interpretation of molecular and isotopic characteristics and multivariate analysis of biomarker data these families can be linked to three source horizons three families originate from different facies of the draupne formation and are characterised by pr ph ratios below 2 dominance of c 27 regular steranes over the c 29 homologues and carbon isotopic values for saturate and aromatic fraction lighter than 28 and 27 respectively the upper jurassic heather formation and the middle jurassic vestland group each source one group of hydrocarbons typical for heather sourced hydrocarbons are elevated pr ph ratios between 2 35 and 3 08 low ratios of c 27 c 29 regular steranes and average isotopic values of 28 4 13 c sat and 26 8 13 c aro hydrocarbons from a middle jurassic source are characterised by very heavy isotopic composition highest pr ph ratios of the data set and dominance of c 29 regular steranes over the c 27 homologues among other factors the two remaining families represent mixtures from upper and middle jurassic sources and are mainly encountered in the greater sleipner area the available data in this study allowed characterisation of 84 of the recoverable oil resources which proved that the main source rock in the area is the upper jurassic draupne formation the play concept including a draupne source and tertiary reservoir proves to be most prolific with 239 10 6 s m 3 of recoverable oil equalling 88 of the total characterised oil resources oils in these tertiary reservoirs are however likely to be affected by biodegradation based on the available data the zone of biodegradation in the south viking graben appears to be limited to depths above 2140 m and temperatures below 70 c

mechanisms of petroleum accumulation in the bozhong sub basin bohai bay basin china part 1 origin and occurrence of crude oils the origin of the fourteen major oil fields in the bozhong sub basin bohai bay basin was studied based on the results of rock eval pyrolysis on more than 700 samples and biomarker analysis on 61 source rock samples and 87 oil samples the three possible source rock intervals have different biomarker assemblages and were deposited in different environments the third member of the oligocene dongying formation e3d3 32 8 30 3 ma in age is characterized mainly by high c19 c23 tricyclic terpane 0 75 high c24 tetracyclic terpane c26 tricyclic terpane 2 5 low gammacerane c30 hopane 0 15 and low 4 methyl steranes c29 steranes 0 15 ratios and was deposited in sub oxic to anoxic environments with significant terrigenous organic matter input the first e2s1 35 8 32 8 ma and third e2s3 43 0 38 0 ma members of the eocene shahejie formation have low c19 c23 tricyclic terpane and low c24 tetracyclic terpane c26 tricyclic terpane ratios and were deposited in anoxic environments with minor terrestrial organic matter input but have different abundances of 4 methyl steranes and gammacerane the hydrocarbon generating potential and biomarker associations of these three source rock intervals were controlled by tectonic evolution of the sub basin and climate changes three oil families derived from e2s3 e2s1 and e3d respectively and three types of mixed oils have been identified all large oil fields in the bozhong sub basin display considerable heterogeneities in biomarker compositions and originated from more than one source rock interval which suggests that mixing of oils derived from multiple source rock intervals or multiple generative kitchens and or focusing of oils originated from a large area of a generative kitchen is essential for the formation of large oil fields in the bozhong sub basin e2s3 and e2s1 derived oils experienced relatively long distance lateral migration and accumulated in traps away from the generative kitchen e3d3 derived oils had migrated short distances and accumulated in traps closer to the generative kitchen such a petroleum distribution pattern has important implications for future exploration there is considerable exploration potential for dongying derived oils in the bozhong sub basin and traps close to or within the generative kitchens have better chance to contain oils generated from the dongying formation

heterogeneity of oil composition within a reservoir as a reflection of accumulation history abstract the unaltered petroleums of a small oil field in the f r germany reveal pronounced spatial heterogeneities in bulk and molecular composition over most of the field area the oil in high porosity high permeability sand intervals bears a higher proportion of saturated hydrocarbons and has a higher maturity chemical signature as compared to oils occupying lower porosity lower permeability zones for all sands with less than about 13 porosity a regular relationship was observed between oil composition and porosity permeability with a decrease of the latter petrophysical properties increasingly lower chemical maturities and increasingly different bulk chemical compositions lower proportions of saturated hydrocarbons and higher proportions of nso compounds were recorded maximum contrasts measured for chemical maturities are e g 0 63 versus 0 82 vitrinite reflectance equivalents rc values calculated on the basis of the methylphenanthrene index according to radke and welte 1983 0 31 versus 0 84 for the ratio of triaromatic to mono plus triaromatic steroid hydrocarbons and 0 38 versus 0 47 for the 20s 20s 20r ratio of c29 5 h 14 h 17 h steranes these spatial heterogeneities in the composition of the oils are interpreted to reflect 1 i successive stages of trap filling due to episodes of increasing burial and maturation of the relevant source rocks in combination with 2 ii low rates of in reservoir mixing of these individual oil charges by convection or diffusion recognition of compositional heterogeneities within the oil column of individual fields may not only provide a basis for the reconstruction of reservoir filling history but may also have important implications for improving petroleum production

the application of δ13c toc and c n geochemistry of mangrove sediments to reconstruct holocene paleoenvironments and relative sea levels puerto rico abstract we assessed the use of 13c toc and c n values of bulk sedimentary organic matter om to reconstruct paleoenvironmental and relative sea level change from mangrove environments in puerto rico the modern distribution of 13c toc and c n values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands and was compared to microfossil foraminiferal and thecamoebian assemblages four vertically zoned environments were identified tidal flat 13c 18 6 2 8 toc 10 2 5 7 c n 12 7 3 1 mangrove 13c 26 4 1 0 toc 33 9 13 4 c n 24 3 6 2 brackish transition 13c 28 8 0 7 toc 40 8 11 7 c n 21 7 3 7 and freshwater swamp 13c 28 4 0 4 toc 42 8 4 8 c n 17 0 1 1 these environments had distinct 13c toc and c n values with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone the foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water mhhw likely resulting from washover or transport by storms however the ratio of foraminifera to thecamoebians f t along with 13c toc and c n values refines the distinction between brackish and freshwater environments using linear discriminant analysis we applied the 13c toc c n and f t distributions to a 1 7 m core containing a continuous sequence of rhizophora mangle peat which began accumulating at 1650 1930 ce together microfossils 13c toc and c n values and the core chronology from 137cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery making it unsuitable for relative sea level reconstruction we caution that in the absence of detailed litho bio chemo or chrono stratigraphic analyses as presented here care should be taken in interpreting sea level histories derived from single dates on mangrove peats

mangrove swamp stratigraphy and holocene transgression grand cayman island west indies abstract the island of grand cayman in the western caribbean has an extensive mangrove swamp vegetation numerous cores have been taken in and adjacent to these swamplands and these reveal that the swamps are generally underlain by a transgressive sequence of sediments the basal unit of this sequence consists of a laminated or non laminated crust formed in a subaerial environment locally these crusts are overlain by plastic mud deposited in seasonally flooded environments mangrove peat forms the upper unit of the transgression within most of the swamplands overlying the other units where these are found and reaching thicknesses of more than 4 m the final stage of marine incursion is recorded to the east of north sound where in water depths of 10 200 cm shelly mud occurs overlying mangrove peat in contrast to this to the west of north sound there is a regressive sequence in which shelly marl underlies a localised sea grass peat and mangrove peat this regressive sequence records local progradation of mangroves into marine environments the transgressive sedimentary sequence on grand cayman is similar to transgressive sedimentary sequences described from the florida everglades mangrove complex florida bay and the belize shelf on grand cayman however the stratigraphy is less complex because there are not extensive freshwater peat forming environments or intertidal and supratidal carbonate environments samples of mangrove peat were collected from the peat bedrock interface along a surveyed profile across barkers peninsula on grand cayman radiometric dating of these implies that sea level was approximately 185 cm below the present level at least 2100 years bp comparison of these dates with dates on mangrove peat from elsewhere suggests that submergence on grand cayman has taken place at a similar rate to that in florida

palaeogeography and palaeoenvironments of a tropical coastal wetland and offshore shelf during holocene submergence jamaica abstract from a series of maps representing selected holocene time periods the palaeogeography and palaeoenvironments of the coastal wetland and adjacent offshore shelf at negril western jamaica are described and discussed wetland began to form at about 8250 yr b p and went through a major expansion of surface area between 7250 and 6500 yr b p vegetation influenced by saline water formed during the earlier stages of wetland development but a significant salinity decrease occurred in the late holocene which is attributed to increased freshwater input possibly driven by climatic change discharge from rivers draining through the wetland retarded growth of a sill reef that had become established on a break of slope offshore by 8250 yr b p beach development by c 6500 yr b p and subsequent inland migration controlled lateral expansion of the wetland although its vertical build up has continued in pace with sea level rise

mangrove vegetation changes on holocene terraces of the doce river southeastern brazil article i nfo high resolution sedimentological geochemical and pollen analysis on sediment core from the coastal plain of the doce river southeastern brazil revealed changes in the depositional system and vegetation caused by combined action of oscillations in relative sea level rsl and sedimentary supply during the holocene two main phases were discerned using sedimentary features 13 c 15 n total organic carbon toc total ni trogen n c n and cluster analysis of pollen data temporally synchronized with radiocarbon age dating the data indicates the presence of a lagoon system surrounded by a tidal plain colonized by mangroves and its sedimentary organic matter sourced from c4 plants between 8050 and 7115 cal yr bp however during the mid and late holocene the mangroves shrank and freshwater vegetation expanded c3 plants proba bly due to a marine regression during this phase the development of a lacustrine environment was followed by the colonization of herbs trees and shrubs the continuous sediment infilling into the lake allowed the ex pansion of a herbaceous plain as seen today this geomorphologic and vegetation evolution is in agreement with the mid holocene rsl maximum above present rsl and subsequent fall to the present time

geology compositional heterogeneities and geochemical origin of the yacheng gas field qiongdongnan basin south china sea the yacheng gas field is located in the footwall of the no 1 fault the boundary fault between the yinggehai and qiongdongnan basins the main reservoir is the fan delta sandstones in the lingshui formation the seals are meishan for m ation shales near the no 1 fault and lingshui formation shales away from the no 1 fault all strata are normally pressured in the gas field except for the meishan formation the meishan formation is overpressured near the no 1 fault in the gas field and in the adjacent yinggehai basin away from this fault into the qiongdongnan basin the overpressure diminishes an obvious thermal anomaly occurs below 3600 m in the gas field this anomaly characterized by an abrupt increase in drill stem test and fluid inclusion homogenization temperatures vitrinite reflectance ro and rock eval tmax and by an abnormally low temperature ro tmax gradient diminishes away from the yinggehai basin the gases and condensates have abnormally high aromatic hydrocarbon contents and show obvious heterogeneities away from the no 1 fault the c2 hydrocarbon content and c2 scn increase carbon dioxide content decreases d13c values for methane ethane and carbon dioxide become lighter the heptane and isoheptane values decrease and the relative contents of aromatic hydrocarbons both in c6 c7 light hydrocarbons and in the condensates decrease such heterogeneities reflect the reservoir filling process and origin of the gas field the gas field was charged from both the qiongdongnan and the yinggehai basins hydrocarbons sourced from the qiongdongnan basin have relatively low maturities whereas hydrocarbons from the yinggehai basin have relatively higher maturities and seem to have been in association with hydrothermal fluids the hydro thermal fluids from the yinggehai basin in which methane ethane carbon dioxide and especially aromatic hydrocarbons dissolved under the high temperature and high pressure subsurface conditions migrated along the no 1 fault and caused the abnormally high concentration of aromatic hydrocarbons as well as the thermal anomalies in the gas field especially near the no 1 fault

interannual variation of the east asian cold surge activity abstract the occurrence frequency of the east asian cold surge exhibits an interannual variation in concert with the el nino southern oscillation enso cycle that is the cold surge occurs more less frequently during warm cold enso winters because the cold surge high low dipoles are coupled with the upper level synoptic short waves any mechanism modulating the activity of these waves would affect the cold surge activity the streamfunction budget analysis in the short wave regime indicates that the development of the cold surge short wave train over east asia and the northwest pacific is modulated by the north pacific enso short wave train due to the coupling between the upper level cold surge short wave train and the surface cold surge dipole it is inferred from this streamfunction budget analysis that the interannual variation of the cold surge occurrence frequency is a result of this modulation

hydrocarbon habitat of the offshore bohai basin china the bohai basin is a major continental petroliferous basin located in eastern china of which the offshore part of the basin contains more than one third of the total petroleum resources in the basin although the basin has been explored for nearly 40 years the offshore part of the basin is just reaching a moderately mature stage of exploration and its petroleum geological features are gradually becoming known the subduction of the pacific plate to the eurasia plate resulted in the convective upwelling of the mantle in the bohai area and triggered the development of nne and ne striking extensional faults along the mesozoic structures in the late paleocene causing the formation of the rift basin during the oligocene the depocenters and subsidence centers of the greater bohai basin migrated from west to east and from south to north and finally concentrated in the offshore part of the basin since the oligocene especially during the neogene due to the indentation of the india block to the eurasia plate the right lateral strike slip movement of the tan lu fault was relatively intense in the offshore part of the basin these characteristics led to the differences between the offshore and onshore sectors in sedimentation structural features and petroleum geology during the deposition of the dongying formation the offshore sector became the depocenter and subsidence center of the basin resulting in the deposition of the lower dongying formation mudstone source rocks while these mudstones are immature in the onshore part of the basin in the offshore bohai most major discoveries have been made in the drape anticlines on the rises in the upper tertiary reservoirs while the lower tertiary reservoirs within the half grabens only serve as secondary reservoirs as the neogene depocenter of the basin the offshore part accommodated some fine grained shallow lacustrine clastics of the lower minghuazhen formation serving as important regional seals for the neogene reservoirs a set of shallow faults and a central faulted anticlinal belt in the shallow upper tertiary sequences were formed during the neogene in the offshore sector under the influence of right lateral strike slip faulting of the tan lu fault these shallow faults networked with deep extensional faults serving as hydrocarbon conduits the central faulted anticline belt along the tan lu fault system also provides significant traps

tetrahymanol its widespread occurrence and geochemical significance abstract the occurrence of tetrahymanol gammaceran 3 ol in sediments from various marine depositional environments such as the santa monica basin and palos verdes shelf southern california bight the santa barbara basin off the northern california borderland the atlantic shelf slope and rise and the antarctic region as well as in bacterial algal mats from the santa barbara basin and baja california together with its detection in sediments from the peru upwelling region odp leg 112 and baffin bay odp leg 105 suggests that tetrahymanol occurs ubiquitously in marine samples tetrahymanol is the only known likely biological precursor of gammacerane which is found in many petroleums and shales the common occurrence of tetrahymanol in marine environments implies that primitive organisms similar to tetrahymena or organisms other than tetrahymena other protozoa bacteria are also likely to contain this compound its isomer diplopterol has also been detected in several sediment sections

mangrove sediment carbon stocks along an elevation gradient influence of the late holocene marine regression new caledonia abstract among blue carbon ecosystems mangroves are very efficient in storing carbon in their sediments over decadal to millennial time scales however this ability varies with numerous parameters including climate and sea level variations in new caledonia mangrove ecosystems develop in semi arid conditions with a typical zonation rhizophora spp colonize the seaward side of the intertidal area while avicennia marina develops at higher elevations just below the salt flat within this context we determined both the quantity organic carbon content and carbon stocks and the characteristics carbon over nitrogen ratios c n stable carbon and nitrogen isotopes radiocarbon age of the organic matter stored beneath each mangrove stands carbon stocks were determined down to different limits with depth approximate extension of the root systems one meter depth and the hard substrate within the extension of the root systems the sediment carbon stock was lower than 100 mgc ha 1 regardless of the mangrove species this low value resulted directly from the dry climate that limits mangrove productivity at depth beneath every zone a buried layer enriched in mangrove derived organic matter with c n values around 40 and 13c values around 26 was observed this layer likely resulted from a sea level high stand during the late holocene that allowed a long period of stability of the mangrove slowly accumulating organic matter within the sediment in this buried layer the carbon stock was higher than in the upper sediment and reached up to 665 255 and 300 mgc ha 1 in the salt flat zone the a marina stand and the r spp stand respectively the highest stock determined beneath the salt flat was suggested to be related to a period of sea level stability that lasted 3000 years whereas beneath the other zones which are at lower elevations mangrove colonization was more recent and the sea level was continuously decreasing till recently sea level variations and specifically current sea level rise may strongly influence mangrove development due to their migration along the tidal elevation gradient to maintain the biotic conditions needed for their development

application of biological markers in the assessment of paleoenvironments of chinese non marine sediments abstract in this study we employ molecular organic geochemical data for 22 representative sediment samples from chinese non marine sedimentary basins in an attempt to characterize and assess the non marine depositonal paleoenvironments the samples investigated include oilshale shale mudstone and sodium sulphate rich sediments ranging in age from cretaceous to tertiary it is evidenced by geological and geochemical data that those sediments studied originate from lacustrine environments ranging from freshwater brackish fresh water to hypersaline the aliphatic fractions of the sediment extracts were analyzed by gc and gc ms and relative abundance of compounds and compound classes of normal acyclic and cyclic alkanes were measured from mass chromatograms the results reveal significant differences in the chemical features of the various sample groups which enable them to be characterized and identified in terms of source and or environment related parameters the diagnostic parameters that allow this assessment are the relative abundances of n alkanes acyclic isoprenoid alkanes and 4 methyl steranes hopane sterane ratio gammacerane and homohopane indexes etc in this study data interpretation was also assisted by pattern recognition through principal component analysis the results show that the sample groups of different environmental origin could be unambiguously distinguished on scores plot

coastal morphology and late quaternary history cayman islands west indies abstract instrumental surveys of coastal profiles in the cayman islands western caribbean reveal the presence of a horizontal erosional bench at 1 9 m on grand cayman and a deep horizontal notch at 6 4 m on cayman brac but no raised erosional features on little cayman each island is surrounded by a horizontal constructional raised reef usually below 2 m here dated by u series methods as 124 000 8000 yr old and hence broadly contemporary with other western atlantic raised reefs of similar elevations the different raised erosional features indicate independent vertical tectonic movement of the three islands predating the formation of the raised reef the accordance and horizontality of the raised reef indicates stability of the islands since the last interglacial times an erosional notch at present sea level has formed since the sea reached its present level less than 2100 b p and algal benches on exposed coasts are also in equilibrium with present conditions

sediment accretion and organic carbon burial relative to sea level rise and storm events in two mangrove forests in everglades national park abstract the goal of this investigation was to examine how sediment accretion and organic carbon oc burial rates in mangrove forests respond to climate change specifically will the accretion rates keep pace with sea level rise and what is the source and fate of oc in the system mass accumulation accretion and oc burial rates were determined via 210pb dating i e 100 year time scale on sediment cores collected from two mangrove forest sites within everglades national park florida usa enhanced mass accumulation accretion and oc burial rates were found in an upper layer that corresponded to a well documented storm surge deposit accretion rates were 5 9 and 6 5 mm yr 1 within the storm deposit compared to overall rates of 2 5 and 3 6 mm yr 1 these rates were found to be matching or exceeding average sea level rise reported for key west florida organic carbon burial rates were 260 and 393 g m 2 yr 1 within the storm deposit compared to 151 and 168 g m 2 yr 1 overall burial rates the overall rates are similar to global estimates for oc burial in marine wetlands with tropical storms being a frequent occurrence in this region the resulting storm surge deposits are an important mechanism for maintaining both overall accretion and oc burial rates enhanced oc burial rates within the storm deposit could be due to an increase in productivity created from higher concentrations of phosphorus within storm delivered sediments and or from the deposition of allochthonous oc climate change amplified storms and sea level rise could damage mangrove forests exposing previously buried oc to oxidation and contribute to increasing atmospheric co2 concentrations however the processes described here provide a mechanism whereby oxidation of oc would be limited and the overall oc reservoir maintained within the mangrove forest sediments

coastal and sea level changes during the holocene in bangladesh abstract the aim of the study is to reconstruct the holocene sea level history along a section of the coast of bangladesh detailed litho bio and chronostratigraphic techniques have been applied to unveil the nature of sedimentary sequences in association with the events of the holocene marine transgressions and regressions samples were collected from panigati near khulna the study provides evidence of five periods of marine transgression each followed by a regression during the holocene each minerogenic sediment layer indicates a marine episode and the sediments were deposited under intertidal to estuarine conditions each peat layer is in situ and indicates a regression of the sea it is difficult to separate the regional eustatic components contributing to these relative sea level movements although processes operating locally and regionally are clearly evident a sea level curve together with possible error ranges has been proposed for this part of bangladesh since the early to mid holocene an average relative sea level rise of 1 07 mm yr has been estimated

definition and characterization of petroleum compositional families in williston basin north america using principal component analysis abstract petroleum hydrocarbons in the gasoline range grh and saturate sfh 210 c boiling point fractions carry information that is often obscured by compositional diversity and multiple processes working simultaneously multivariate statistical methods can enhance the analysis and interpretation of compositional data from these fractions especially in conjunction with independent geological information in the present study principal component analysis pca was applied to the grh and sfh data for 171 oil samples from the williston basin these oils were previously classified using polycyclic terpane and sterane biomarker traits our results indicate that only family a oils can be uniquely classified using pca families b c and d oils show grh and sfh characteristic compositions consistent with biomarker defined families but these characteristics are insufficient for independent classification however the pca analyses of the grh and sfh compositional traits proves to be a useful technique in recognizing the effect of mixing of oils derived from different sources

holocene palynology and sea level change in two estuaries in southern irian jaya southern new guinea leads the continental australian plate into convergence to form the new guinea highlands extensive inter tidal deltas are typical of much of this low gradient equatorial coastline in two adjacent estuaries in irian jaya west papua this study uses present elevations of mangrove species zones as a finite indicator of holocene sea levels from pollen diagrams of estuarine cores all cores showed mangroves at levels well below the present tidal range with landward species zones being replaced over time by seaward zones results show tectonic subsidence in the recent period with late holocene relative sea level rise of 0 67 mm year 1

comparison of the synoptic conditions in midlatitudes accompanying cold surges over eastern asia for the months of december 1974 and 1978 part i monthly mean fields and individual events abstract east asian cold surges during two periods of contrasting intensity december 1974 strong and december 1978 weak are studied it is shown that the midlatitude mechanisms initiating cold surges during both months are quite similar in nature synoptic scale short waves passing through the long wave trough position near the east asian coast act to release the cold air southward from the main reservoir over eastern siberia dynamic descent is initiated by these synoptic scale waves entering the northwesterly flow on the western side of the long wave trough anchored on the coast this is the descent center in the local direct circulation in the entrance region of the east asian jet maximum at 200 mb the frequency and intensity of the cold air surges for a given month depend on the large scale circulation pattern the average flow over asia for december 1974 and 1978 presents a contrast with respect to ridging over the midcontinent in december 1978 the flow was characterized by a low zonal inde

radiocarbon dating of mangrove sediments to constrain holocene relative sea level change on zanzibar in the southwest indian ocean mangrove sedimentary deposits are sensitive to changes in sea level and can be used to reconstruct mid to late holocene sea level fluctuations in intermediate and far field locations distant to t

a mechanism for african monsoon breaks mediterranean cold air surges 1 surges of cold air from the mediterranean into northern africa during the boreal summer are documented and their influence on monsoon breaks is analyzed using tropical rainfall measuring mission rainfall estimates and reanalysis products between 1998 and 2006 6 10 cold air surges occurred each summer with low level temperature anomalies ranging from less than 1 k to over 6 k composite analysis indicates that cold air surges over northern africa persist for 2 10 days and travel equatorward at approximately 5 5 m s 1 which is 0 5 1 5 m s 1 faster than the observed climatological low level meridional flow northern african cold surges have characteristics similar to surges observed elsewhere in the world including a hydrostatically induced ridge of surface pressure and an amplified upper tropospheric ridge trough pattern the african cold surge is preceded by the passage of a shortwave trough and an intensification of the upper tropospheric subtropical westerly jet streak over the mediterranean sea these events are associated with increased confluence in the jet entrance region over the central mediterranean an enhanced direct secondary circulation subsidence and low level ageostrophic northerly flow over northeastern africa composite analysis shows that the passage of a cold surge is associated with an enhancement in convective activity over southern algeria western niger northern mali and mauritania 2 to 5 days before the surge reaches the eastern sahel 17 5 n when northeasterly flow channeled between the atlas and ahaggar mountains strengthens and transports relatively moist air from the western mediterranean and eastern north atlantic over the region and increases moisture convergence over western africa north of 20 n over the eastern sahel of sudan and eastern chad the composite results reveal a break in convective activity and decrease in low level convergence when the surge arrives that persists for about 6 days these results offer great promise for improving the short range prediction of rainfall over northern africa

geochemical characteristics of tertiary saline lacustrine oils in the western qaidam basin northwest china abstract based on the systematic analyses of light hydrocarbon saturate aromatic fractions and c isotopes of over 40 oil samples along with related tertiary source rocks collected from the western qaidam basin the geochemical characteristics of the tertiary saline lacustrine oils in this region was investigated the oils are characterized by bimodal n alkane distributions with odd to even c11 c17 and even to odd c18 c28 predominance low pr ph mostly lower than 0 6 high concentration of gammacerane c35 hopane and methylated mttcs reflecting the high salinity and anoxic setting typical of a saline lacustrine depositional environment mango s k1 values in the saline oils are highly variable 0 99 1 63 and could be associated with the facies dependent parameters such as pr ph and gammacerane indexes compared with other tertiary oils the studied tertiary saline oils are marked by enhanced c28 sterane abundance 30 or more of c27 c29 homologues possibly derived from halophilic algae it is noted that the geochemical parameters of the oils in various oilfields exhibit regular spatial changes which are consistent with the depositional phase variations of the source rocks the oils have uncommon heavy c isotopic ratios 24 to 26 and a flat shape of the individual n alkane isotope profile and show isotopic characteristics similar to marine organic matter the appearance of oleanane and high 24 24 27 norcholestane ratios 0 57 0 87 in the saline oils and source rocks confirm a tertiary organic source

oil source correlation in the fulin basin shengli petroleum province east china the fulin basin is located within the giant shengli petroleum province in east china the source rock in the basin is mainly the lower part of the third member es3 of the eocene portion of the shahejie formation it is composed of organic rich dark mudstone and oil shale of lacustrine origin and contains good quality type i ii kerogen these strata reach the oil generative stage at ro 0 4 0 8 the first member es1 of the oligocene portion of the shahejie formation has excellent oil potential in the nearby gunan basin but is immature in the fulin basin and is not an effective source rock the oil and rock samples from both basins can be grouped into three major families based on biomarkers the first family shows low prph 0 3 and notable carotane typical of carbonate evaporite environments this family exists in es1 rocks and the related oils and is early mature 0 2 0 3 and s r s 0 10 0 20 the second family shows high prph 1 a low gammacerane index 0 2 and abundant 4 methyl steranes indicative of freshwater lacustrine conditions like those in es3 this family shows higher maturation 0 30 0 50 and s r s 0 35 0 55 and notable diasteranes the third family is transitional has source and maturity ratios between the above families and occurs in the es3 unit samples from the basin interior based on biomarker similarities between oils and rock extracts all oils in the fulin basin originated from es3 source rocks slight maturation differences indicate that these oils have been derived from different source areas no oil from es1 is found in the fulin basin suggesting es1 source rocks are too immature to generate commercial oil although the nearby gunan basin has much oil generated from es1 source rocks no migrated oil from es1 in this basin reached the kenli faulted zone because of intervening faults which disrupt migration

biological marker compounds as indicators of the depositions history of the maoming oil shale abstract the eocene maoming oil shale from guangdong province occurs as a laterally uniform stratigraphic section typically 20 25 m thick from which the aliphatic hydrocarbon constituents of six representative samples were investigated using gc and c gc ms the sediments evaluated included the basal lignite a vitrinite lens from the overlying claystone and four intervals from the massive oil shale bed as expected the lignite and vitrinite differ markedly from the oil shales the lignite is dominated by bacterial hopanoids and components of higher plant origin including c 29 steroids and triterpenoids such as oleanenes visually the oil shale samples show corroded and degraded phytoclasts spores wispy particles of fluorescent organic material attributable to dinoflagellates and especially in the uppermost sample colonial algal bodies the distributions of biological markers in the oil shales show many features in common notably a dominance of dinoflagellate derived 4 methylsteroids and a significant proportion of higher plant derived n alkanes with marked odd over even carbon number predominance overall they exhibit several features that resemble characteristics of the messel shale the hydrocarbons of the lowest shale horizon suggest that there may have been a gradual transition between deposition of the original peat and the subsequent oil shales the aliphatic hydrocarbons of the uppermost shale are dominated by a number of c 31 and c 33 botryococcane homologues and other unusual branched alkanes possibly derived from green algae all of the samples are immature overall molecular and microscopic examination of the stratigraphic succession of the maoming oil shale suggests a shallow lacustrine environment within which peats were deposited this lake subsequently deepened to support abundant algal populations especially dinoflagellates culminating in a dominance of botryococcoid algae

relative sea level changes during the holocene in bangladesh abstract this paper presents a reconstruction of the holocene paleo environment in the central part of bangladesh in relation to relative sea level changes 200 km north of the present coastline lithofacies characteristics mangal peat diatoms and paleophysiographical evidence were considered to reconstruct the past position and c 14 ages were used to determine the time of formation of the relative sea level during the holocene with standard reference datum the required m s l at the surface of five sections was calculated the relative sea level rsl curve suggests that bangladesh experienced two mid holocene rsl transgressions punctuated by regressions the curve shows an rsl highstand at approximately 7500 cal bp although the height of this highstand could not be determined because the transgressive phase was observed in a bioturbated sand flat facies the curve shows a regression of approximately 6500 cal bp and the rsl was considerably lower perhaps 1 2 m than the present m s l the abundant marine diatoms and mangrove pollens indicate the highest rsl transgression in bangladesh at approximately 6000 cal bp being at least 4 5 to 5 m higher than the modern m s l after this phase the relative sea level started to fall and consequently a freshwater peat developed at approximately 5980 5700 cal bp the abundant mangrove pollens in the salt marsh succession shows the regression at approximately 5500 cal bp when it was 1 2 m higher than the modern sea level the curve indicates that at approximately 5000 cal bp and onwards the rsl started to fall towards its present position and the present shoreline of bangladesh was established at approximately 1500 cal bp and has not noticeably migrated inland since

mid holocene mangrove succession and its response to sea level change in the upper mekong river delta cambodia abstract middle holocene vegetation and mangrove successions are clearly evident in the palynological records of two cores from the upper mekong river delta in cambodia spanning from 9 4 to 6 3 cal ka bp the cores mainly record a transgressive sequence from floodplain freshwater marsh to tidal flat which was overlain by mangrove corresponding to the decelerated sea level rise at 8 3 cal ka bp pioneer mangrove species sonneratia alba and sonneratia caseolaris appeared in the sediments and then was replaced by regressive mangrove succession containing upward increasing abundances of rhizophora apiculata and bruguiera spp high salinity and flooding tolerant community s alba was developed at the western core site psg at 8 2 cal ka bp and the eastern core site pk at 7 5 cal ka bp the time difference of s alba appearance between the two sites might be resulted from the complexity of sedimentary environment where a higher sediment supply was provided to the western floodplain than to the eastern floodplain after 7 5 cal ka bp aggradational stacking of intertidal sediments of which the thickness is larger than the present maximum tidal range may have resulted from continuous sea level rise during 7 5 7 0 cal ka bp

migration of hydrocarbons in the tampen spur area norwegian north sea a reservoir geochemical evaluation abstract this paper describes the application of reservoir geochemical protocols to a study of oil field and regional petroleum compositional variations in the major fields in the tampen spur area the tampen spur high is located in the middle of several oil mature to gas mature source rock kitchens and most of the structures might receive petroleum from several different directions based on the definition of several different petroleum populations within the tampen spur area we define five major petroleum charging systems correlating the petroleum population variations with geological information allows us to derive likely migration fill scenarios for many of the oil fields and requires us to invoke a new upper jurassic carrier system in parts of the area connecting brent group reservoirs across major faults based on this hypothesis two exploration wells were drilled on structures to test this carrier and petroleum was found in one of the structures an understanding of the migration pathways and petroleum drainage efficiency of the basins is of great economic interest because most of the smaller substructures are marginally economic thus it is important to provide an effective risk analysis and ranking of the satellite prospects prior to drilling this study has demonstrated that filling and migration in a geological province are controlled by a series of complex processes and that the filling history of the structures within the tampen spur is more complicated than suggested earlier