compositional variability in oils and formation waters from the ayoluengo and hontomin fields burgos spain implications for assessing biodegradation and reservoir compartmentalization abstract the main scope of this work is the geochemical characterization of 12 crude oils and formation waters of the ayoluengo oilfield basque cantabrian basin nw spain to delineate its reservoir compartmentalization the ayoluengo oil characteristics were also compared with data obtained from crude oil and formation water of the hontomin 2 well located 25 km to the se of ayoluengo the 13 ayoluengo and hontomin oil samples are very similar in composition bulk properties and isotopic signature indicating that these oils are genetically related however the hontomin oil is more mature and it is slightly biodegraded which suggests some differences in the reservoir environments the molecular parameters of both oils confirm a marine origin related to a liassic source rock coincident with the occurrence of lateral facies changes along the sedano sub basin on the other hand the connate waters are analogous and both classified as chloride calcium type given the complex nature of the sedimentology and structures of the reservoir gas chromatographic fingerprints of the analyzed crude oils have been used to detect minor variations in composition that are indicative of reservoir compartmentalization

compositional fractionation of petroleum from reservoir to wellhead in the niobrara shale oil play abstract hydraulic fracturing is routinely used to stimulate unconventional reservoirs in the niobrara shale oil play there are several fracking targets but the actual stimulated rock volume is not well constrained this means that allocating produced oil to specific reservoirs in essence oil reservoir correlation is not straightforward the data presented here support that the chalk units are the principal production zones in the niobrara shale oil play several lines of evidence such as the presence of heavy end n alkanes n c31 consistence in composition of gross fractions the distribution of c27 28 29 diasteranes as well as the pristane to phytane ratio all suggest that oils were produced from the a b chalks particularly from the a chalk during production a selective partitioning of lighter hydrocarbons into the migrating fluids could nevertheless occur in particular as regards the n alkanes domain and their carbon isotopic compositions regarding the latter a depletion of 13c in the produced oil s n alkanes by more than three per mil relative to all of those core extracts was observed this finding suggests that compound specific isotope analysis in both oil reservoir and oil source rock correlations cannot be taken at face value i e by simple matching of values besides that fractionation appears to result in the enrichment of rather aliphatic nitrogen containing compounds in crude oils

can biomass burning produce a globally significant carbon isotope excursion in the sedimentary record negative carbon isotope excursions have been comprehensively studied in the stratigraphic record but the discussion of causal mechanisms has largely overlooked the potential role of biomass burning the carbon isotopic ratios 13 c of vegetation soil organic matter and peat are significantly lower than atmospheric carbon dioxide co2 and thereby provide a source of low 13 c co2 when combusted in this study the potential role of biomass burning to generate negative carbon isotope excursions associated with greenhouse climates is modeled results indicate that major peat combustion sustained for 1000 yr increases atmospheric co2 from 2 5 present atmospheric levels pal to 4 6 pal and yields a pronounced negative 13 c excursion in the atmosphere 2 4 vegetation 2 4 and the surface ocean 1 2 but not for the deep ocean 0 9 release of co2 initiates a short term warming of the atmosphere up to 14 4 c with a duration of 1628 yr which is consistent with the magnitude and length of an observed toarcian excursion event these results indicate that peat combustion is a plausible mechanism for driving negative 13 c excursions in the rock record even during times of elevated pco2

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

geochemical identification of marine and terrigenous condensates a case study from the sichuan basin sw china abstract condensates are extensively produced from the marine lower permian maokou formation and the lower triassic jialingjiang formation the main marine condensate producing strata in southern sichuan basin and also in the terrigenous upper triassic xujiahe formation in the central and southern sichuan basin based on the analyses of light hydrocarbons biomarkers and stable carbon isotopic compositions of marine and terrigenous condensates and the light hydrocarbon composition of natural gases in the jialingjiang fm and xujiahe fm in the sichuan basin the following conclusions are drawn a condensates produced from the carbonate reservoirs of jialingjiang fm and the maokou fm marine condensates belong to a single oil family and the condensates from the terrigenous xujiahe fm terrigenous condensates belong to another family b marine condensates were generated from sapropelic organic matter in the late stage of high maturation and the biomarker composition indicates that they were derived from the lower silurian shale and the lower permian carbonate while the terrigenous condensates were generated from mature humic source rocks c most of the marine condensates and gases encountered in the lower permian maokou fm and lower triassic jialingjiang fm were generated from the same source and a few of the gases in the jialingjiang fm contain admixtures of coal derived gas while terrigenous condensates and gases were generated from the xujiahe fm humic source rocks d effects that could be related to evaporative migration and biodegradation are not evident in the examined condensates

petroleum charge history in the lunnan low uplift tarim basin china evidence from oil bearing fluid inclusions abstract the petroleum charge history in the lunnan low uplift tarim basin china was investigated by comparing the geochemical characteristics of fluid inclusion fi oils from ordovician and triassic reservoirs with crude oils from stratigraphically different reservoirs quantitative grain fluorescence qgf and total scanning fluorescence tsf were used to screen the reservoir samples so as to identify suitable samples for molecular composition of inclusion mci analysis all of the samples contain c 30 n propylcholestanes diagnostic of marine source rocks the ordovician hosted fi oils differ from the triassic hosted fi oils having higher relative abundances of c 19 tricyclic terpane c 24 tetracyclic terpane and rearranged hopanes ts and c 29 ts and higher pr ph ratios while the triassic hosted fi oils have lower pr ph ratios and higher relative abundances of c 23 tricyclic terpane arylisoprenoids 25 norhopanes and c 35 homohopane several of the crude oils are similar to the triassic hosted fi oils based on the geochemical characteristics of the fi and crude oils combined with information on the burial history of the area at least two petroleum charge episodes can be distinguished in the lunnan low uplift an early charge represented by the ordovician hosted fi oils was biodegraded as evidenced by the presence of 25 norhopanes in the triassic hosted fi oils and crude oils but not in the ordovician hosted fi oils ordovician hosted fi oils provide the only evidence for oil generated from cambrian lower ordovician source rocks triassic hosted fi oils and crude oils in the ordovician carboniferous and triassic reservoirs are mixtures of biodegraded oil from an early charge episode and more mature oil from later charge

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

sedimentary organic matter and δ13ckerogen variation on the southern iberian palaeomargin betic cordillera se spain during the latest pliensbachian early toarcian abstract the early toarcian oceanic anoxic event t oae is characterised by major palaeoenvironmental and palaeoceanographical changes ocean anoxia global warming ocean acidification among other and a severe perturbation of the global carbon cycle although widespread oceanic anoxia was a significant control on the occurrence of organic rich facies during the t oae in several locations of the northern tethyan margin the effects of anoxia oceanic productivity and dilution are poorly understood in other worldwide locations such as the southern tethyan and iberian margins in this study we report new geochemical total organic carbon toc total sulphur ts total carbonate content caco3 13c from kerogen isolates 13ckerogen palynofacies and thermal maturation data from the upper pliensbachian lower toarcian successions in la cerradura and fuente vidriera external subbetic domain betic cordillera se spain the obtained results indicate that these successions have low toc contents 0 3 wt with toc reaching up to 0 46 wt around the polymorphum serpentinum ammonite zone boundary in la cerradura 13ckerogen negative carbon isotope excursions cie are observed at the base of the polymorphum zone the pliensbachian toarcian event pl toa and base of the serpentinum zone t oae overall the low maturity kerogen assemblages are dominated by terrestrial om and with a minor marine component small increments in terrestrial om non opaque phytoclasts and palynomorphs are observed just before and during the t oae in the studied area during the early toarcian in the external subbetic domain accumulation and preservation of om was low and with a significant terrestrial contribution similarly to other locations around the southern margins of iberia and tethys the dominance of the opaque phytoclast subgroup the occurrence of classopollis and the relatively more positive 13c of terrestrial kerogen suggest that om was mostly sourced from an area characterised by a semi arid climate i e with pronounced arid periods during most of the polymorphum zone the t oae negative cie is accompanied by an increase in terrestrial om with a slight increase in the non opaque phytoclast subgroup and terrestrial palynomorph subgroup the increase of non opaque phytoclast and terrestrial palynomorphs are in line with the posited enhancements of the hydrological cycle and export of terrestrial om into marine environments during the t oae this study suggests a link between 13c fractionation during photosynthesis in c3 plants and climate during the early toarcian this link suggests coupling of the water and terrestrial carbon cycles before and during the t oae

late triassic charcoal from petrified forest national park arizona usa fossil charcoal has been found in the late triassic chinle formation in petrified forest national park a location that is world famous for its silicified tree trunks the material consists of charcoalified secondary wood and has sufficiently well preserved plant anatomy to show it may be described as araucarian type although it does display some minor differences from the anatomies described for the silicified gymnosperm trunks in the park the presence of the charcoal proves that on occasion natural wildfires most probably ignited by lightning must have occurred in the chinle triassic palaeoenvironments with resulting impacts on the biota of those times it is currently impossible to estimate how often these fires occurred as the incidence of charcoal here and in the whole fossil record apart from the frequency of ancient fires also reflects the preservation and burial conditions of the material there is scant mention of triassic charcoal in the literature a notable absence given the abundance of charcoal that has been recorded in the carboniferous jurassic and cretaceous periods this lack of charcoal may support the theory that atmospheric oxygen levels were lower during the triassic than in the carboniferous

water column euxinia and wildfire evidence during deposition of the upper famennian hangenberg event horizon from the holy cross mountains central poland a palynological study of the uppermost famennian section from kowala quarry holy cross mountains central poland allowed recognition of two miospore zones lv retispora lepidophyta apiculiretusispora verrucosa and ln retispora lepidophyta verrucosisporites nitidus based on palynology and sedimentology the black shale within the upper part of the section is identified as equivalent to the hangenberg black shale which is known globally this black shale contains compounds characteristic of photic zone euxinia including isorenieratane and its derivatives such compounds are absent in the organic poor marls and shales occurring below the ln zone and are present only as traces in the layers just above the black shale indicating fluctuations in the oxygen minimum zone during uppermost famennian sedimentation palynofacies show high amounts of amorphous organic matter and prasinophyte concentrations in the black shale and a subsequent significant decrease of amorphous organic matter concomitant with a rapid increase of terrestrial input mainly miospores with common tetrads in the layers above the black shale this supports the relatively rapid change in the taxonomic composition of phytoplankton caused by fluctuations of the chemocline the whole succession corresponds to one sea level rise and fall the presence of high concentrations of peri condensed polycyclic aromatic hydrocarbons and large amounts of small charcoal particles at the hangenberg event horizon indicate the occurrence of wildfires such observations suggest that atmospheric o2 levels had exceeded the critical threshold of 13 above which wildfires may occur by latest famennian time

three growth in the mesozoic and early tertiary and the reconstruction of palaeoclimates abstract evidence from the distribution and characteristics of fossil wood in the mesozoic and early tertiary indicates that a much warmer global climate prevailed in those times there appears to have been a broad zone of largely non seasonal climate stretching from about 32 n to 32 s palaeolatitudes in addition to this low latitude zone forest growth extended into very high palaeolatitudes where trees cannot grow at the present day a number of theories have been proposed to account for the palaeoclimate responsible for this distribution of forests most notable have been those involving changes in the amount of carbon dioxide in the atmosphere in the positions of the continents or in the obliquity of the earth s axis of rotation evidence from fossil forests indicates that a combination of the effects of an increased quantity of carbon dioxide in the atmosphere and the palaeopositions of the continents in the mesozoic and early tertiary appears at the moment to be the simplest explanation for the climate of those geological times without the need to invoke axial movement

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

wildfires and seasonal aridity recorded in late cretaceous strata from south eastern arizona usa lithostratigraphic and organic chemostratigraphic studies of fluvial lacustrine sediments in the late cretaceous fort crittenden formation in south eastern arizona usa reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level the lower fort crittenden is dominated by marginal wetland to deep water lake deposits whereas the upper fort crittenden is characterized by wetland to deltaic deposits abundance of polycyclic aromatic hydrocarbons pah and reflectance of fusinite substantiate the impact of wildfires within the watershed organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones distinct variations in pah assemblages characterized by the number of aromatic rings indicate that there were variations in the intensities of wildfires assuming no variations in the types of fuel fusinite reflectance values are consistent with combustion temperatures from 470 to 550 c observed in modern wildfires

pentamethylnaphthalenes and related compounds in sedimentary organic matter abstract the isomeric pentamethylnaphthalenes pmns 1 2 3 5 6 pmn 1 2 3 5 7 pmn 1 2 3 6 7 pmn and 1 2 4 6 7 pmn have been synthesised characterised and identified in a number of crude oils and sediments ranging in age from proterozoic to tertiary we suggest that 1 2 3 5 6 pmn forms predominantly from the aromatisation of drimanoid precursors via 1 2 2 5 6 pentamethyltetralin when 1 2 3 5 6 pmn was heated in laboratory experiments the proportions of pmns changed in a manner which reflected the relative stability of the isomers the other pmns in sediments are therefore suggested to arise via acid catalysed isomerisation or transalkylation processes a conveniently measured pentamethylnaphthalene ratio pnr 1 2 4 6 7 pmn 1 2 3 5 6 pmn 1 2 4 6 7 pmn has been defined as a maturity parameter in an indonesian sedimentary sequence the values of pnr changed smoothly with increasing depth with values ranging from 0 1 to 0 4 values in crude oils range from 0 15 to 0 85 suggesting a value of approximately 0 15 for the beginning of the oil window

gas bubbles in fossil amber as possible indicators of the major gas composition of ancient air gases trapped in miocene to upper cretaceous amber were released by gently crushing the amber under vacuum and were analyzed by quadrupole mass spectrometry after discounting the possibility that the major gases n2 o2 and co2 underwent appreciable diffusion and diagenetic exchange with their surroundings or reaction with the amber it has been concluded that in primary bubbles gas released during initial breakage these gases represent mainly original ancient air modified by the aerobic respiration of microorganisms values of n2 co2 o2 for each time period give consistent results despite varying o2 co2 ratios that presumably were due to varying degrees of respiration this allows calculation of original oxygen concentrations which on the basis of these preliminary results appear to have changed from greater than 30 percent o2 during one part of the late cretaceous between 75 and 95 million years ago to 21 percent during the eocene oligocene and for present day samples with possibly lower values during the oligocene early miocene variable o2 levels over time in general confirm theoretical isotope mass balance calculations and suggest that the atmosphere has evolved over phanerozoic time

some aspects of the organic geochemistry of petroleum fluids the most important influences on the compositions of petroleum fluids are in many cases the composition of a petroleum sample may allow the depositional environment of its source rock and its temperature history before and after expulsion to be determined this information assists the search for more petroleum in a region we suggest that this approach should be used more frequently to validate models of petroleum generation and migration in the second part of the paper we discuss the origin and nature of the differences in petroleum composition which are frequently found within individual petroleum reservoirs petroleum accumulations in permeable reservoirs are normally found to be inmechanical equilibrium and verticalchemical equilibrium this is manifested by constant subsurface fluid density at any given depth across the accumulation and increases in subsurface density with depth known as gravitational segregation however even in permeable reservoirs lateral differences in composition inherited from the reservoir filling process are not totally eliminated by mixing processes such as diffusion and convection thus lateral chemical equilibrium is often not achieved and lateral compositional variations are observed in present day oil and gas reservoirs these observations are justified in terms of order of magnitude estimates for the rates at which reservoirwide mixing occurs a case history is presented

a novel sequential extraction system for whole core plug extraction in a solvent flow through cell application to extraction of residual petroleum from an intact pore system in secondary migration studies abstract the rapidly developing field of reservoir geochemistry and studies into secondary migration require new methods and techniques to characterise the composition of organic fluids obtained from reservoir rock samples ideally the composition of residual petroleums should be compared with the mineralogical and petrophysical properties from the same sample this requires a non destructive extraction procedure that keeps the rock in its natural state we have developed a flow through extraction system capable of efficiently extracting core plugs while preserving the pore system of the sample extractions can be performed sequentially to obtain various oil phases present in the pore system i e free or mobile oil can be obtained separately from residual oils adsorbed onto mineral or organic matter surfaces the free and adsorbed residual oils exhibit marked compositional differences due to fractional adsorption effects and maturity variations monitoring the pressures at the inlet and outlet positions of the extraction cell allows the measurement of pressure gradients across the core enabling the calculation of the relative permeability of the sample according to darcy s law application of the sequential flow through extraction method gives a substantial increase in information on the rock sample allowing a better understanding of fluid flow and fluid rock interaction in the subsurface

the climatic significance of late ordovician early silurian black shales the ordovician silurian transition approximate to 455 430ma is characterized by repeated climatic perturbations concomitant with major changes in the global oceanic redox state best exemplified by the periodic deposition of black shales the relationship between the climatic evolution and the oceanic redox cycles however remains largely debated here using an ocean atmosphere general circulation model accounting for ocean biogeochemistry mitgcm we investigate the mechanisms responsible for the burial of organic carbon immediately before during and right after the latest ordovician hirnantian 445 444ma glacial peak our results are compared with recent sedimentological and geochemical data we show that the late katian time slice approximate to 445ma typified by the deposition of black shales at tropical latitudes represents an unperturbed oceanic state with regional organic carbon burial driven by the surface primary productivity during the hirnantian our experiments predict a global oxygenation event in agreement with the disappearance of the black shales in the sedimentary record this suggests that deep water burial of organic matter may not be a tenable triggering factor for the positive carbon excursion reported at that time our simulations indicate that the perturbation of the ocean circulation induced by the release of freshwater in the context of the post hirnantian deglaciation does not sustain over sufficiently long geological periods to cause the rhuddanian approximate to 444ma oceanic anoxic event input of nutrients to the ocean through increased continental weathering and the leaching of newly exposed glaciogenic sediments may instead constitute the dominant control on the spread of anoxia in the early silurian

paleoecology of the fire clay coal bed in a portion of the eastern kentucky coal field vertically continuous increment samples of the fire clay coal bed mid middle pennsylvanian late westphalian b collected from a portion of the central appalachian basin were studied palynologically petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient fire clay paleomire results indicate that four compositional groups can be identified they are 1 a lycospora vitrinite dominant group characterized by high percentages of lycospora and vitrinite macerals and generally low but variable ash yields and sulfur contents 2 a mixed palynoflora high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora 3 a mixed palynoflora moderate low vitrinite group characterized by various admixtures of lycopsid fern and calamite miospores increased percentages of liptinite and inertinite macerals and low ash yields and sulfur contents and 4 a mixed palynoflora high ash yield group characterized by high percentages of small lycopsid fern and occasionally calamite and cordaite miospores high liptinite and inertinite contents high ash yields and moderate to high sulfur contents the fire clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches these two benches upper and lower are highly disparte in occurrence appearance and composition in the study area the lower bench generally is thin 0 5 m laterally discontinuous and mainly composed of dull mainly durain coal lithotypes ash yields typically are high sulfur contents generally are moderate to high compositional group 4 the mixed palynoflora high ash yield group defines all of the increments examined from the lower bench in contrast the upper bench is thick 0 75 m laterally continous and mainly comprised of bright mainly clarain coal lithotypes overall ash yields and sulfur contents for this bench are generally low although vertical variation is apparent all of the compositional groups occur in the upper bench in some columns notably those that are thick and uninterrupted by clastic partings groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers other columns especially those taken in areas of thin 0 5 m fire clay coal are dominated by groups 1 and 4

generation and expulsion of oils from permian coals of the sydney basin australia abstract organic geochemical and petrological assessment of coals coaly shales and fine grained sediments coupled with organic geochemical analyses of oil samples all from permo triassic sections of the southern sydney basin australia have enabled identification of the source for the widely distributed oil shows and oil seeps in this region the permian coals have higher hydrogen indices higher liptinite contents and much higher total organic matter extract yields than the fine grained sediments a variety of source specific parameters obtained from n alkanes regular isoprenoids terpanes steranes and diasteranes indicate that the oil shows and seeps were generated and expelled predominantly from higher plant derived organic matter deposited in oxic environments the source and maturity related biomarkers and aromatic hydrocarbon distributions of the oils are similar to those of the coals the oil coal relationship also is demonstrated by similarities in the carbon isotopic composition of the total oils coal extracts and their individual n alkanes extracts from the permo triassic fine grained sediments on the other hand have organic geochemical signatures indicative of mixed terrestrial and prokaryotic organic matter deposited in suboxic environments which are significantly different from both the oils and coal extracts the molecular signatures indicating the presence of prokaryotic organic matter in some of the coal extracts and oils may be due to thin sections of possibly calcareous lithologies interbedded within the coal measures the genetic relationship between the oils and coals provides new evidence for the generation and expulsion of oils from the permian coals and raises the possibility for commercial oil accumulations in the permian and early triassic sandstones potentially in the deeper offshore part of the sydney basin

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

maturity estimation of phytoclasts in strew mounts by micro raman spectroscopy abstract in order to evaluate the potential for petroleum generation of a sedimentary rock it is important to establish the thermal maturity of its organic matter in rocks with low total organic carbon the kerogen has to be isolated by acid maceration and the traditional maturity assessment via vitrinite reflectance is sometimes hampered by the small amount of vitrinite exposed on polished plugs this study presents an additional route of maturity estimation via raman spectroscopy that is advantageous especially when only a small amount of vitrinite is available previous studies for maturation assessment based on raman spectroscopy were mostly carried out on organic rich rocks prepared as whole rock blocks in this work we developed a maturity assessment based on raman spectra obtained on isolated kerogen dispersed on strew mounts as prepared for palynofacies analysis and spore coloration index rendering additional information without further preparation these strew mounts display a wider area for analysis per gram of isolated kerogen when compared to polished plugs increasing the probability to find phytoclasts in scarce populations the proposed method was developed regarding oil prospection calibrating the raman spectrometer with organic matter from rocks with vitrinite reflectance between 0 3 and 2 1 a set of raman parameters was combined using multilinear regression cross validation of the proposed regression showed that the spectral parameters of translucent phytoclasts resulted in a maturity estimate that correlated well with the vitrinite reflectance

the formation of inertinite rich peats in the mid cretaceous gates formation implications for the interpretation of mid albian history of paleowildfire abstract image analysis and standard point count petrographic data are used to interpret the amount source and variation of inertinite in coal seams of the mid cretaceous gates formation rocky mountain foothills northeastern british columbia inertinite on average is abundant between 40 60 by seam by volume and higher in some zones and within seams fluctuates cyclically the inertinite is interpreted to be almost exclusively fire derived suggesting that fire was a relatively common occurrence in the original peat forming wetlands inertinite enrichment in the gates coals appears to have resulted from preferential destruction of vitrinite precursors by either low temperature decomposition processes or burning rather than by formation of inertinite by a microbial process the position of the gates formation depositional setting east of the rising canadian cordillera is interpreted to have resulted in overall drier conditions in the region and periodic drought in the wetland settings cyclic variation in inertinite vitrinite composition within some of the seams is primarily attributed to climatic variations although variation in subsidence rates could also have been responsible

correlation between hydrogen isotope ratios of lipid biomarkers and sediment maturity abstract we investigated the influence of thermal maturity on the hydrogen isotope ratios of sedimentary hydrocarbons to prove that the isotope ratio of hydrocarbons mirrors paleoclimate signatures d values from n alkanes and acyclic isoprenoids of two sediment sections kupferschiefer ks 258 ma and posidonienschiefer ps 184 ma with different maturation history were investigated both covered thermal maturity from 0 48 to 1 3 rc vitrinite reflectance and reflectance calculated from mpi1 sediment burial up to 4500 m caused thermal maturation of organic matter in the ks horizon from the early zechstein basin of poland whereas contact metamorphic thermal maturation originated in the early toarcian ps posidonienschiefer of the north german vlotho massif the d values of the extracted n alkanes positively correlate with thermal maturity in the ks y 56 mpi1 x 160 vsmow and in the ps y 104 mpi1 x 200 vsmow the d values of isoprenoids i e pristane phytane were even more enriched with increasing maturity y 179 mpi1 x 341 vsmow in the ks y 300 mpi1 x 415 vsmow in ps these results explain why isotope ratios of n alkanes and isoprenoids in mature sediments are generally enriched in d and do not have the expected isotopic difference between n alkanes and isoprenoids of 190 moreover the correlation between sediment maturity parameters and d values suggests that after correction the d values of n alkanes can be used to reconstruct climate and environment in the geological past

petrographical and geochemical characterization of sub bituminous coals from mines in the cesar rancheria basin colombia abstract tertiary coals from the la jagua and calenturitas coal mines in the cesar sub basin colombia were investigated for the first time using organic petrological and organic geochemical methods to assess the thermal maturity and palaeoenvironmental conditions during peat accumulation thirteen seams were sampled from the los cuervos formation at two mines evaluation based on organic petrological analyses and rock eval pyrolysis reveals that the coals are thermally immature and of sub bituminous b to sub bituminous a rank with a predominance of type iii mixed with type ii kerogen 22s 22s 22r homohopane ts ts tm mpi mpr and 1 mp 9 mp ratios are very low this low thermal maturity corresponds to high volatile matter contents petrographically the la jagua and calenturitas coals are dominated by vitrinite with low to high amounts of inertinite and low to moderate amounts of liptinite the detailed petrographic data indicate a predominantly herbaceous plant input and oxidative conditions during deposition mostly with strong tissue destruction further conclusions are deduced from petrographic ratios such as tissue preservation gelification groundwaterac and vegetation indices ash and sulfur contents iso and n alkane distribution and 17 h homohopane ratio in summary the data support a formation in tropical ombrogenic rather wet peats with high bacterial activity

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

geochemical evaluation of aliphatic and aromatic hydrocarbons in palaeogene source rocks from the latrobe group gippsland basin australia abstract twenty seven hydrocarbon source rocks from the proteacidites asperopolus malvacipollis diversus and lygistepollenites balmei biozones palaeogene latrobe group in the gippsland basin were analysed using gas chromatography mass spectrometry based on the molecular geochemistry of the aliphatic and aromatic fractions together with bulk geochemical data including rock eval pyrolysis and total organic carbon contents the thermal maturity palaeoenvironments and organic matter source of these palaeogene samples were systematically evaluated the results provide a useful comparison with those from upper cretaceous source rocks in the gippsland basin jiang and george 2018 2019 similar to the upper cretaceous rocks the aliphatic hydrocarbons in the paleogene samples are mainly comprised of n alkanes isoprenoids terpanes hopanes and steranes the aromatic hydrocarbons are dominated by naphthalene phenanthrene anthracene fluorene dibenzofuran dibenzothiophene and their alkyl homologues other aromatic hydrocarbons detected include land plant derived compounds e g retene methylretenes cadalene simonellite etc and combustion derived compounds e g chrysene pyrene picene benzo b fluoranthene benzo a anthracene etc these 4 to 6 ring polycyclic aromatic hydrocarbons are more abundant in the paleogene samples compared to the upper cretaceous rocks biomarker and aromatic hydrocarbon distributions indicate that the proteacidites asperopolus and malvacipollis diversus samples are immature or are in the early stage of the oil generation window while the lygistepollenites balmei samples correspond to the low maturity to mature stage the samples were all deposited under sub oxic to oxic conditions in fresh water with low salinity possibly in a lacustrine depositional environment the organic matter inputs are from plankton algae and higher land plants but are dominated by organic matter with a terrigenous origin

geochemical characterization of source rocks and oils from northern iraq insights from biomarker and stable carbon isotope investigations abstract the origin of oil in the cretaceous tertiary reservoirs of northern iraq remains controversial consequently a detailed geochemical study including rock eval pyrolysis gas chromatography mass spectrometry and carbon isotope analysis was conducted on 65 source rock core and cuttings samples from the najmah chia gara and balambo formations northern iraq twenty four crude oils were also analyzed to provide new insights into source organic matter depositional environment and correlations between crude oils and their probable source rocks bulk geochemical analysis of candidate source rock samples indicates that the najmah formation has more petroleum potential than the chia gara and balambo formations these three candidate source rocks were deposited in slightly different environments and have different organic matter types as determined by screening analysis and biomarker data the najmah formation contains organic rich toc up to 4 2 wt oil prone type i ii kerogen deposited under anoxic conditions the chia gara and balambo formations contain mixed type ii iii and type iii kerogens oil and gas prone deposited under less reducing conditions with more terrigenous organic matter input unfortunately most of the rock samples contain less than 2 5 wt toc which likely excludes them as source rocks but more deeply buried equivalents may contain more organic matter biomarker and stable carbon isotope compositions suggest that cretaceous and miocene reservoired oils from the northern iraq basins although predominantly derived from marine carbonate organic matter constitute five genetically distinct oil families based on age specific biomarkers the oils were probably derived from three active petroleum systems in northern iraq jurassic jurassic early cretaceous and early to mid cretaceous biomarker maturity parameters indicate that most of the oils were generated in the early oil window similar to the extracts

molecular archaeology export of dead sea asphalt to canaan and egypt in the chalcolithic early bronze age 4th 3rd millennium bc abstract nine archaeological bitumens from excavations in canaan sinai and egypt tel irani ein zik palmahim tel arad jerusalem ein besor site h sheik awad and maadi dated 3900 2200 bc and two natural asphalts of the dead sea area ein gedi floating blocks and nahal heimar have been compared using the following geochemical techniques chloroform extraction and gc and gc ms analyses of c15 alkanes and c15 aromatics isotopic analysis 13c and d on chloroform extracts and asphaltenes and rock eval pyrolysis of the insoluble organic residue all samples are genetically related and are different from other archaeological bitumens from syria and iraq tel irani archaeological bitumen was found to be identical to the floating block asphalts of the dead sea other archaeological bitumens were recognized as having been weathered and biodegraded to various degrees at archaeological sites in the course of the millennia they are regarded as counterparts of floating block asphalts altered by aging this study is the first evidence of the trade and export of raw bitumens from the dead sea area within canaan and to egyptian trading centers on the mainland route to egypt between 3900 and 2200 bc prior to the extensive utilization of bitumen for mummification in ancient egypt

biomarker signatures of sinian bitumens in the moxi gaoshiti bulge of sichuan basin china geological significance for paleo oil reservoirs abstract chen et al precambrian research 296 1 19 2017 presented a biomarker study on solid bitumens and associated source rock extracts from the moxi gaoshiti bulge of the sichuan basin sw china biomarker characteristics revealed that the solid bitumens and related paleo oils belong to the same group and are well correlated to source rocks of the neoproterozoic dengying and lower cambrian qiongzhusi formations the thermal maturity of solid bitumens and their migration direction have been assessed it appears that these interpretations are internally inconsistent and are also inconsistent with much published geochemical data and the biomarker data are over interpreted and flawed

stratigraphic distribution and significance of a 15 million year record of fusain in the upper triassic chinle group southwestern usa abstract we document the occurrence of upper triassic fusain in northern arizona southern utah and northern new mexico in latest carnian to norian age alluvial strata of the monitor butte formation and the sonsela and painted desert members of the petrified forest formation chinle group the fusain identified by standard techniques of macroscopic and microscopic morphology and resistance to chemical oxidation is present at multiple stratigraphic horizons at several locations that are approximately correlative although separated by several hundred km the morphology of this fossil charcoal includes large partially charred silicified to coalified logs completely charred smaller limbs charcoal fragments reworked in fluvial deposits and particulate fusain disseminated in sediments the apparent rarity of fusain in triassic strata previously was cited as evidence for relatively low levels compared to modern of atmospheric oxygen and the consequent infrequent occurrence of wildfire during this time interval however our findings demonstrate a significantly greater abundance of fusain in upper triassic strata than previously acknowledged therefore we suggest that wildfire was not an unusual occurrence during the late triassic this conclusion supports recent experimental studies and geochemical models that indicate atmospheric oxygen levels at or above modern levels during the late triassic

a dynamical interpretation of the tritium maximum in the central equatorial pacific abstract the tropical tritium distribution between 1974 and 1981 is characterized by a maximum along the equator centered between 125 and 145 w it signifies that this region has received the maximum input of high northern latitude water a dynamical interpretation of the maximum shows that it can be explained by the strength of the sverdrup circulation in the central equatorial pacific where there is a strong zonal convergence in the north equatorial countercurrent necc and a strong meridional geostrophic flow towards the equator

lacustrine environmental evolution and implications on source rock deposition in the upper cretaceous paleocene of the south yellow sea basin offshore eastern china abstract lacustrine source rocks are well developed within the upper cretaceous paleocene in the south yellow sea basin sysb in offshore eastern china understanding the deposition of these source rocks could provide critical information for hydrocarbon exploration in the sysb as well as reveal the paleoenvironment across the cretaceous paleogene boundary in eastern china this study investigates the lacustrine environmental evolution during the upper cretaceous taizhou formation k2t to paleocene funing formation e1f within the sysb and its implications on source rock deposition based on core observation combined with organic geochemical indicators multiple maturity parameters vitrinite reflectance tmax and biomarker isomerization ratios reveal that the organic matter om has reached early oil window maturity the om of source rocks is dominated by kerogen type ii iii liptinite and vitrinite anoxic saline brackish deep to semi deep lacustrine environments prevailed during the deposition of k2t2 second member of the k2t e1f2 second member of the e1f and e1f4l lower unit of fourth member of the e1f the deposition of three intervals was influenced by marine incursion as evidenced by geochemical and paleontological results low to moderate toc contents avg 0 78 wt to 1 91 wt which corresponds to low to moderate terrestrial om input are observed through three intervals abundant freshwater together with high terrestrial om flowed into the lacustrine environments during the deposition of e1f4u upper unit of fourth member of the e1f leading to dysoxic oxic and freshwater conditions high terrestrial om input is probably the major controlling factor for relatively high toc contents avg 2 49 in the e1f4u an evolution from balanced fill to overfilled lake type is observed in the upper cretaceous paleocene of sysb consistent with an evolution from semi arid to humid paleoclimate conditions the e1f4u and e1f2 source rocks exhibit fair to good potential whereas poor to fair potential is present in the e1f4l and k2t2 source rocks compared with the paleogene source rocks in onshore eastern china the upper cretaceous paleocene source rocks in the sysb probably hold good potential for generating commercial quantity of oil although further study on hydrocarbon generation kinetics of source rocks and overall basin history are needed

the impact of severe biodegradation on the molecular and stable c h n s isotopic compositions of oils in the alberta basin canada abstract although the effects of biodegradation on the composition and physical properties of crude oil have been well studied effects of in reservoir petroleum biodegradation on molecular and isotopic compositions of crude oils are not yet clearly understood the alberta basin in western canada is one of the world s largest petroleum accumulations and constitutes an ideal example of a natural suite of sequentially biodegraded oils the basin hosts moderately to severely biodegraded petroleum regionally distributed and in single more or less continuous oil columns in this study a series of oil samples from the alberta heavy oil and oil sands provinces with varying degrees of biodegradation were analyzed to assess the impact of progressive biodegradation on the molecular and c h n and s isotopic compositions of oils the results of the molecular characterization of the hydrocarbon fraction of the studied oils show that the oils have suffered biodegradation levels from 2 to 10 toward the alberta saskatchewan border on the peters and moldowan scale of biodegradation abbreviated pm 2 to pm 10 and from tens to hundreds on the manco scale within single reservoirs increasing biodegradation was observed from top to bottom of the oil columns at all sites studied the whole oil stable isotopic compositions of the samples varied in the ranges 13 c 31 2 to 29 0 2 h 147 to 133 15 n 0 3 4 7 and 34 s 0 4 6 4 the maximum differences between values of samples within single oil columns were 13 c 1 4 2 h 7 15 n 1 7 and 34 s 1 0 regional variations in the isotopic compositions of oil samples from different wells averaged values from top to bottom were 1 2 for 13 c 12 for 2 h 4 1 for 15 n and 5 5 for 34 s and hence generally significantly larger variations were seen than variations observed within single oil columns especially for n and s it appears that even severe levels of biodegradation do not cause observable systematic variations in carbon nitrogen or sulfur isotope composition of whole oils this indicates that sulfur and nitrogen isotopic compositions may be used in very degraded oils as indicators for oil charge from different source rock facies

effect of artificial maturation on carbazole distributions as revealed by the hydrous pyrolysis of an organic sulphur rich source rock ghareb formation jordan abstract hydrous pyrolysis experiments were performed on the ghareb formation upper cretaceous jordan a carbonate and organic rich toc 19 6 source rock using a temperature range of 200 to 360 c 72 h the original sediment contains only low amounts of carbazoles maximum 2 2 g g bitumen for 1 methylcarbazole with increasing thermal maturation intense generation begins at temperatures only in excess of 300 c reaching a maximum at 360 c likewise during natural maturation generation occurs at later stages of maturity e g for tithonian source rocks at 0 81 rr and for posidonia shale at 0 88 rr some isomeric changes during hydrous pyrolysis do not resemble those in nature whereas others do the relative abundances of selected c1 and c2 alkylcarbazoles on ternary diagrams reveal differences whereas the benzo a carbazole benzo a carbazole benzo c carbazole ratio is closely similar the latter result supports the contention that maturation plays a key role in controlling carbazole distributions in source rocks however the results for alkylcarbazoles especially the c2 carbazoles are not easy to interpret

precise maturity assessment over a broad dynamic range using polycyclic and heterocyclic aromatic compounds abstract the construction and reliable application of maturation indices is extremely important in deep earth exploration yet predicting levels of maturation on a molecular level especially at overmature stages is still a major challenge here we report robust broad ranging and precise maturity parameters that were developed using a continuous core of thermally overmature lacustrine deposits shahezi fm from the deep songke 2 well sk 2 songliao basin china augmented by shallow cores of lower maturity marine deposits posidonia shale from the hils syncline germany the novel indices presented here are based on the general process of thermally induced cyclization aromatization and aliphatic chain cracking of hundreds to thousands of compounds during maturation the newly developed parameters with an extremely broad dynamic range extending from catagenesis and into metagenesis vitrinite reflectances ro range from 0 9 to 2 2 are based on polycyclic and heterocyclic aromatic compounds measured using fourier transform ion cyclotron resonance mass spectrometry ft icr ms the high coefficient of correlations between the new maturity parameters with ro and tmax demonstrate their utility for assessing precisely the thermal maturity of overmature shales

depositional environment and thermal maturity of the coal bearing longtan shale in southwest guizhou china implications for shale gas resource potential abstract significant knowledge has been assembled on the marine longmaxi shale in the sichuan basin over the past ten years however the distribution of shale gas resources on the periphery of the sichuan basin and in other source rock formations are still not sufficiently understood to improve our understanding on the depositional environment and thermal maturity and their relevance to the source rock quality and shale gas potential of the thick coal bearing longtan shale 36 organic rich shale samples were selected from a single borehole located in the southwestern guizhou province for geochemical and petrographic analysis total organic carbon toc contents are high with 7 7 wt on average reaching partly up to 28 21 wt while carbonate contents are low vitrinite reflectance vrr values and rock eval tmax temperatures range from 1 48 to 1 84 and 482 to 583 c respectively indicating a high thermal maturity which is in accordance with aromatic molecular parameters the remaining present day hydrocarbon generation potential rock eval s2 is rather low due to the high maturity microscopic investigations further show that the organic matter in the rocks is mainly composed of higher land plant particles present as large and poorly rounded vitrinite and inertinite particles indicating a rather short transport distance toc vs total sulfur ts relationships as well as specific hydrocarbon ratios e g pristane phytane and framboidal pyrite size distributions indicate a variable either marine or freshwater environment for the shales in the coal bearing sequence and suggest that original kerogen was either type iii or type ii iii bottom water during deposition was probably oxygen depleted but not anoxic high sedimentation rates can be assumed for the now 700 m thick compacted sequence favorable for the preservation of organic matter overall the present results are in accordance with previous studies of the longtan shale which initially had a high hydrocarbon mainly gas generation potential furthermore the thickness of the formation is much larger in the here studied southwestern part of the guizhou province than in the previously studied northern parts

fossil charcoal as an indicator of palaeoatmospheric oxygen level charcoal results from incomplete combustion of plant material it is produced naturally by wildfire and being relatively tough and unbiodegradable it may be transported and incorporated into a variety of sedimentary environments wildfire requires adequate atmospheric oxygen for the combustion of plant fuel wood leaf litter fossil charcoal from the devonian onwards suggests that the oxygen level in the atmosphere has not fallen below 13 in this interval further the extreme flammability of even wet plant fuel at oxygen levels above 35 makes this the highest figure compatible with the occurrence of terrestrial vegetation

x ray microtomographic imaging of charcoal we assess the potential of x ray microtomography as a tool for the non destructive three dimensional examination of the internal structure of charcoal microtomographic analysis of a series of charcoals produced by the experimental pyrolysis of pine wood at temperatures from 300 and 600 c in nitrogen only and in nitrogen mixed with 2 oxygen indicates that despite substantial shrinkage observed porosity pore size and pore connectivity are all increased by pyrolysis and also by chemical oxidation analysis of a number of altered and unaltered archaeological and geological charcoals has demonstrated the capacity of the technique to identify and map the distribution of authigenic mineral contamination within charcoal fragments the results are of significance to radiocarbon dating in that they provide insights into the mechanisms by which charcoal can be contaminated by extraneous carbon in the natural environment

holocene wildfires related to climate and land use change over the weihe river basin china abstract charcoal particles preserved in the loess palaeosol profiles provide records of wildfires during the holocene total organic carbon magnetic susceptibility and charcoal analysis and osl dating were carried out in the holocene loess palaeosol profiles at two sites in the weihe river basin the analytical results show that natural wildfires occurred frequently during the last glaciation when climate was dominated by northwest continental monsoon and steppe vegetation expanded southerly to the weihe river basin wildfire occurrence decreased during climatic amelioration in the early holocene during the holocene climatic optimum between 8500 b p and 3100 b p natural wildfire occurrence was reduced greatly pedogenic alteration to the accumulated dust was intensified because of the humid warm climate brought on by southeast maritime monsoon localized fire events in connection with human activities of the neolithic occurred in several episodes over the region during the late holocene when climate become drier wildfire occurrence over the upland hills shows a pattern different from that in the guanzhong basin over the upland hills in the north charcoal concentrations show a decreasing trend in the recent loess and topsoil it indicates infrequent biomass burning during the last 3100 years this is attributable to nomadic occupation of the loess hills during the bronze age and the development of a land use pattern of livestock farming in most part of the history over the loess tableland in the guanzhong basin in the south abruptly increased charcoal concentrations in the recent loess and topsoil show very high level of biomass burning this is attributable to the increasingly intensified land reclamation for cereal cultivation from the bronze age this study provides new insights into wildfires over the semi arid and sub humid regions in connection with climate and land use change

petroleum migration faults and overpressure part ii case history the haltenbanken petroleum province offshore norway abstract petroleum inclusion and geochemical data from core extracts were applied to deduce a model for oil migration overpressure development and palaeo leakage of oil from currently dry structures in the haltenbanken vest area the existence of fluorescent oil type inclusions in quartz in the smorbukk asgard 2 field suggest that oil migrated into this structure 70 50 million years before present ma bp this is also the case for the dry structures 6506 12 4 6506 11 3 and 6506 11 1 west of the main smorbukk fault zone black oil inclusions with medium gas oil ratio gor occur in these fields together with condensate type petroleum inclusions this suggests that the dry structures transformed from containing oil to condensate before leakage petroleum extracted from inclusions in these structures and in nearby fields have identical marine type ii kerogen signatures source rocks at the spekk formation level in the current drainage area of smorbukk and these dry structures were immature 70 50 ma bp and the smorbukk sor asgard 3 field did not fill at this early time thus oil must initially have entered into smorbukk from areas to the w sw through the currently pressure sealing smorbukk fault zone which today marks the westward limit of the smorbukk field diagenesis in this fault zone caused the much later overpressure development and petroleum was lost from the 6506 12 4 6506 11 3 and 6506 11 1 structures as overpressure built up regionally petroleum loss from these structures with their often thick seals must have occurred via self propagating open fracture induced mechanisms lack of petroleum in the cretaceous strata above these structures suggests that leakage occurred to even shallower strata this could imply that the cretaceous strata in halten vest were overpressured at the time of leakage in contrast the oil in the cretaceous lysing and lange formation above the jurassic reservoirs in smorbukk and smorbukk sor most likely originated based on geochemistry and gors from the jurassic reservoirs below and not from cretaceous strata this migration event would have been facilitated if it occurred before these sands became overpressured as they are today modelling suggests that the spekk formation became mature in the smorbukk sor region

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

statistical analysis as a tool for assisting geochemical interpretation of the upper triassic yanchang formation ordos basin central china abstract the yanchang formation in the ordos basin is the most important petroleum play not only for conventional oil and gas accumulations but also for newly emerging shale oil and tight gas resources the molecular characterization of the basinwide source rocks predicts three groups of generative petroleum types paraffinic high wax oil mixed base paraffinic naphthenic aromatic low wax oil and gas and condensate supplementary to previous work 68 samples including the crude oils source bitumens and reservoir extracts from the yanchang petroleum play are analyzed the distribution of two terpane classes eight tricyclic terpanes and eight pentacyclic terpanes are determined with subsequent simultaneous rq mode factor analysis for a composite data set of these samples alongside 216 published crude oils worldwide with known facies descriptions thermal maturity has been evaluated as a consistent distribution at first using a combined method of a maturity related biomarker ts ts tm and aromatic parameters methyldibenzothiophene ratios to alleviate the maturity differences effect when discussing geochemical characterization the r mode factor analysis consists of the first two factors that are describing 45 present of the cumulative total variance in the data set and presents a sample grouping pattern in q mode factor analysis which is determined by different contributions of terpane associations i e the tricyclic c21 coupled with pentacyclic c26 c27 c28 and c30 in the same factor space three terpane associations the c26 and c28 terpanes the c21 and c30 terpanes and the c27 pentacyclic terpenes are respectively responsible for discriminating crude oil reservoir extracts and source bitumens in rq mode factor analysis molecular compositions further address more detailed interrelationships among three sample groups that crude oils and reservoir extracts are sharing close genetic relationships both in depositional environment typing and c27 c28 c29 sterane distribution samples from source rocks vary much significantly a mixing process which occurs after oils has been expelled from host source rocks into carrier units during accumulation in addition the migration contamination of c29 sterols when oils are cross through the chang 7 2 unit along migration pathways might also explain this lack of correlation between source rocks and oil reservoir system

evidence of widespread wildfires in coal seams from the middle jurassic of northwest china and its impact on paleoclimate abstract today wildfire is an important disturbance in many continental ecosystems and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions one way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo wildfires a total of 140 jurassic samples including 122 coal samples and 18 rock samples from roof and floor of coal seams were collected from 4 coalfields in northwestern china the samples were analyzed by macropetrography microscopy scanning electron microscopy gas chromatography and gas chromatography mass spectrometry to study the evidences of wildfires and their impact on the paleoclimate high contents of pyrogenic inertinites charcoal natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early middle jurassic in all over northwestern china additionally high molecular weight polycyclic aromatic hydrocarbons were detected in the coal samples these aromatic compounds were formed under high temperature and provide further evidence of wildfires according to a carbon emission model for modern forest fires the total carbon and gas emissions from wildfires in peat swamps of the middle jurassic in northwest china were calculated by the data from 21 575 coal samples of number of 1567 drill core samples the total carbon released from peat swamp forest wildfires was at least 1207 gt corresponding to emissions of co2 co and ch4 of 1926 gt 163 gt and 8 8 gt respectively the huge amount of co2 released by forest fires in the peat swamp systems of the middle jurassic in northwestern china alone was equivalent to 64 20 of the total co2 in the atmosphere at present 3000gt the large amounts of greenhouse gases released by wildfires must have led to long term changes in the atmospheric composition and have caused global warming which could have the reason of affected the paleoclimate

palaeoatmospheres in the phanerozoic except in the recent geological past palaeoatmospheric composition cannot be measured but only inferred from palaeontological or geochemical observations the likely controls on atmospheric composition are reviewed and the role of organisms stressed as monitors recorders motors and moderators of palaeoatmospheric changes whereas there is a good general case for changes in po 2 and pco 2 during phanerozoic time proposals for timing and mechanism in the earlier phanerozoic are speculative at present it seems probable that the late palaeozoic spread of land plants raised o 2 and reduced co 2 levels in the atmosphere the end cretaceous crisis had a transient impact on the atmosphere whose general constancy through geological time is one of the most remarkable features of earth history

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

carbazole distributions in carbonate and clastic source rocks abstract carbazole the benzocarbazoles and their alkyl derivatives have been studied from rock extracts to assess the contribution of facies and maturity in controlling their distribution carbonates from the keg river formation elk point group middle devonian western canada consisting of two different facies reflecting deposition under trangressive and regressive events were used to assess facies influences to study maturation a uniform organo facies of organic rich posidonia shale lower toarcian jurassic northern germany from 0 48 to 1 45 r r was used the organic rich lower keg member deposited under photic zone anoxia contained predominantly c 4 c 5 carbazoles by contrast the upper keg river member deposited under regressive higher salinity environment contains predominantly carbazole itself 1 methylcarbazole and a high abundance of benzo c carbazole relative to benzo a carbazole the distribution of the c 1 to c 3 carbazoles was seen to vary with facies an examination of the carbazole derivatives within the posidonia shale reveals that maturation strongly influences the distribution of carbazole methylcarbazoles 1 8 dimethylcarbazole 1 ethylcarbazole benzo a carbazole and benzo c carbazole quantitative determination of these compounds indicates a maximum yield at 0 88 r r for all derivatives with the exception of carbazole which displays as a maximum at 0 53 r r a systematic variation of compound ratios with maturity to 0 88 r r suggests that selective isomerisation destruction generation of carbazole derivatives may occur in contrast to earlier publications which stress the importance of carbazoles as migration markers in migrated oils the results presented here indicate that facies and maturation do play a significant role in controlling the distribution of carbazole derivatives in source rocks and other sediments

the permian kupferschiefer of southwest poland a geochemical trap for migrating metal bearing solutions abstract the ore grade cu mineralization in southwest poland is associated with the presence of the rote faule zone that overlies the contact of saxothuringian and rhenohercynian zones in these areas the soluble organic matter in the kupferschiefer is altered strongly saturated hydrocarbons and alkylated aromatic compounds are depleted significantly in comparison to non altered shale samples of a similar maturation instead unsubstituted di and tricyclic aromatic hydrocarbons are the dominant components of the extractable bitumen the observed alteration points to late diagenetic oxiadtion reactions caused by upward migrated metalliferous solutions moreover polycyclic aromatic hydrocarbons pah associated with polycyclic aromatic sulphur hydrocarbons pash are abundant in some samples these compounds are considered to originate from the underlying carboniferous strata and were carried upward to the kupferschiefer zone which acted as a geochemical trap

the preservation of fossil biomarkers during meteorite impact events experimental evidence from biomarker rich projectiles and target rocks a devonian siltstone from orkney scotland shows survival of biomarkers in high velocity impact experiments the biomarkers were detected in ejecta fragments from experiments involving normal incidence of steel projectiles at 5 6 km s 1 and in projectile fragments from impact experiments into sand and water at 2 5 km s 1 the associated peak shock pressures were calculated to be in the range of 110 147 gpa for impacts of the steel projectiles into the siltstone target and hydrocode simulations are used to show the variation of peak pressure with depth in the target and throughout the finite volume projectiles thermally sensitive biomarker ratios including ratios of hopanoids and steranes and the methylphenanthrene ratio showed an increase in thermal maturity in the ejecta and especially the projectile fragments measurement of absolute concentrations of selected biomarkers indicates that changes in biomarker ratios reflect synthesis of new material rather than selective destruction their presence in ejecta and projectile fragments suggests that fossil biomarkers may survive hypervelocity impacts and that experiments using biomarker rich rock have high potential for testing survival of organic matter in a range of impact scenarios

the werra cyclotheme upper permian fore sudetic monocline poland insights into fluctuations of the sedimentary environment from organic geochemical studies abstract a study of the extracts of samples recording a transgressive regressive succession of the werra cyclothem zechstein upper permian from the southern margin of the european permian basin the fore sudetic monocline poland provides an insight into major sources of organic matter and diagenetic processes the studied cross section comprises all lithologies representative for the european basin including transgressive sandstones weissliegend and organic rich shales kupferschiefer followed by carbonates as well as regressive anhydrites with intercalations of rock salt due to the variable influence of overlapping diagenetic processes that affected the organic matter i e maturation and late diagenetic oxidation related to base metal mineralisation a reliable comparison of the biomarker results is only possible for the major upper part of the section ca 38 m including carbonates and evaporites but not for the oxidised first 2 3 m from the base of the kupferschiefer the transition from carbonate to evaporate sedimentation is associated with a shift to predominant even c numbered n alkanes increased abundance of carotanes and high homohopane index reflecting enhanced reducing conditions the presence of the c25 regular isoprenoid squalane biphytane and the rapid decrease in the pristane phytane ratio in the evaporites are mainly controlled by the important contribution from both halophilic and methanogenic archaea the occurrence of gammacerane in the anhydrites suggests development of water column stratification at some stages of the sea regression this is associated with appearance of specific aryl isoprenoids with a lycopane carbon skeleton most likely related to botrycoccus braunii race l algae lycopane derivative occurrence suggests that such an algal race could have occurred since permian currently known recent eocene the presence of the abundant freshwater brackish algal biomarkers in evaporititic deposits can be envisaged in the costal part of the zechstein basin with temporary salt wedge estuary water stratification the algae bloomed in the top fertile fresh brackish water layer fed by rivers and the algal biomass was deposited on the sea floor covered with evaporitic brine the stratification periodically broke down during precipitation of the rock salt presumably due to a decrease in riverine water input as revealed by characteristic disappearance of gammacerane and hopane distributions similar to those observed for the carbonate rocks the methylphenanthrenes phenanthrene ratio was used together with methyldibenzothiophenes dibenzothiophene ratio to assess maturity these maturity estimations indicate that the peak of oil window has been reached which is confirmed by other biomarker maturity parameters based on sterane and hopane distributions the maturity stage of oil generation and expulsion was further confirmed by the presence of solid bitumen as cements in the sandstone underlying kupferschiefer and bitumen veins and lenses in the carbonates

organic geochemistry of the lower toarcian posidonia shale in nw europe abstract a suite of core and outcrop samples of the lower toarcian posidonia shale and time equivalent deposits was collected from multiple locations including southern germany swabian alb and franconian alb northern germany the east coast of great britain the netherlands and luxembourg in order to study major differences and similarities with respect to depositional environment and redox potential based on molecular geochemical data all samples are immature or in the early oil window with the highest thermal maturity occurring in the profile from great britain about 0 7 vitrinite reflectance molecular geochemical maturity parameters were used to quantify maturation in detail during shale deposition in the west cleveland basin great britain h 2 s was immediately consumed in the water column by terrigenous input supplying abundant reactive iron to form pyrite these samples are characterized by low dibenzothiophene phenanthrene ratios 95 of 2 and h 2 s in contrast sulfidic euxinic bottom waters possibly with enhanced salinity and stratified water column prevailed due to a more restricted iron supply in luxembourg northern germany and the franconian alb of southern germany a more oxygenated dysoxic bottom water column associated with anoxic sediments i e anoxic dysoxic boundary close to the sediment water interface prevailed in the swabian alb of southern germany despite observed changes within each vertical profile at each site large scale regional trends in depositional conditions can be clearly identified for the early toarcian

geochemistry origin and correlation of crude oils in lower cretaceous sedimentary sequences of the southern mesopotamian basin southern iraq abstract thirty one crude oil samples from lower cretaceous reservoirs in southern iraq were analyzed using bulk property and molecular methods to determine their maturity and biomarker characteristics as well as to obtain information on their respective source rocks all the oils are unaltered non biodegraded have high sulfur content and api gravity is in the range for light to heavy oil 19 40 api they are characterized by low pr ph values even odd predominance and front end biased n alkane distributions based on these parameters the oils were generated and expelled from a marine carbonate source rock bearing type ii s kerogen compositional similarities of hopane and sterane biomarkers with those from potential source rocks allowed identification of the upper jurassic lower cretaceous sulaiy and yamama carbonate succession as the effective source beds a similar composition of normal and isoprenoid hydrocarbons among the oils suggests an origin from a common source rock however biomarker maturity ratios indicate a wide range of maturity this appears to result from the type of burial history of the source rock characterized by a slow passage through the liquid window interval during an extended period of geologic time

charcoalified logs as evidence of hypautochthonous autochthonous wildfire events in a peat forming environment from the permian of southern parana basin brazil abstract evidences of paleowildfires from the upper coal seam s from the faxinal coalfield have been analyzed through petrographic fluorescence and scanning electron microscopy sem specifically at the base 1 and top 2 boundaries of an interlayered tonstein bed and revealed recurrent charcoal deposition in the peat forming environment an unusual accumulation of adjacent large sized 21 8 13 4 cm and larger charred logs occurs throughout the coal seam area 1 6 km 2 beneath the tonstein bed boundary 1 reflecting an extensive wildfire event in hypautochthonous autochthonous conditions the logs display a semifusinite vitrinite semifusinite sandwich like structure sensu jones et al 1993 indicating burning in growth position and reflectance measurements below 1 ro suggest that this was a low temperature fire dryness in the peatland during the fire event was clearly detected by altered fluorescence of spores and algae corroborating previous studies the paleoecological setting can be characterized as a swamp forest based on the presence of pollen clusters and organs observed under fluorescent light and on the identification under sem of the morphogenus agathoxylon hartig as a single wood type reflecting the dominance of arborescent gymnosperms glossopterids in the peatland homogenized cell walls observed under sem ratified the recognition of the material as charcoal the reestablishment of regular conditions of peat deposition following the major fire episode is represented by alternate bands of vitrinite and semifusinite in both boundaries 1 and 2 suggesting an oscillation from dry to wet conditions in the climate pattern and the occurrence of wildfires as common and systemic events fire ignition activity and spread in the peat forming environment resulted from a combination of lightning strikes dryness fuel abundance and high atmospheric oxygen levels

geochemical significance of the aromatic hydrocarbon distribution in the bitumens of the puertollano oil shales spain the bituminous series of the puertollano basin consists of three oil shale beds named pa pb and pc from top to bottom in this work results from the study of the aromatic fractions of the bitumens are presented the gas chromatographic traces are dominated by phenanthrene derivatives associated with variable contributions of arborane fernane derivatives and benzohopanes and overall small amounts of chrysene derivatives and secohopanes the compounds can be considered as part of two sub groups the first one consists of those compounds derived from regular hopanes such as secohopanes benzohopanes fully aromatized hopanes and degradation products of hopanes such as alkylated chrysenes and naphthalenes the second group is composed of arborane fernane derivatives and their degradation products such as alkylated phenanthrenes and tetrahydrophenanthrenes both groups of compounds appear to be indicative of a strong bacterial input to the sedimentary organic matter

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

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

the diversification of paleozoic fire systems and fluctuations in atmospheric oxygen concentration by comparing silurian through end permian 250 million years myr charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long term variations in fire occurrence and fire system diversification are related to fluctuations in late paleozoic atmospheric oxygen concentration charcoal a proxy for fire occurs in the fossil record from the late silurian 420 myr to the present its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13 to 35 the fire window herein we observe that as predicted atmospheric oxygen levels rise from 13 in the late devonian to 30 in the late permian so too fires progressively occur in an increasing diversity of ecosystems sequentially data of note include the occurrence of charcoal in the late silurian early devonian indicating the burning of a diminutive dominantly rhyniophytoid vegetation an apparent paucity of charcoal in the middle to late devonian that coincides with a predicted atmospheric oxygen low and the subsequent diversification of fire systems throughout the remainder of the late paleozoic first fires become widespread during the early mississippian they then become commonplace in mire systems in the middle mississippian in the pennsylvanian they are first recorded in upland settings and finally based on coal petrology become extremely important in many permian mire settings these trends conform well to changes in atmospheric oxygen concentration as predicted by modeling and indicate oxygen levels are a significant control on long term fire occurrence

geochemistry and origin of heavy oils in the south part of zhanhua depression east china abstract the sanhecun sag located in the south of the zhanhua depression has yielded a significant amount of heavy oil in recent years and is becoming a new exploration focus in the jiyang sub basin surprisingly oils in the deep shahejie formation have higher densities and viscosities than those in the shallow guantao formation in this study geochemical and fluid inclusion analyses of oils from different depths were carried out to clarify their source and the cause of the high densities oils in the shahejie formation with high contents of resins and asphaltenes 47 56 are generated from the es4 carbonate source rocks that were deposited in a hypersaline environment with a relatively high terrigenous organic matter contribution maturity parameters and fluid inclusions show that the oils with low saturated hydrocarbon contents and high resin and asphaltene contents were charged to the shahejie formation from 29 ma to 27 ma when the source rocks were in the early oil generation window although subsequent biodegradation further increased oil density the main control on the high densities of oils in the shahejie formation is the nature of the source kerogen oils in the shallow guantao formation can be divided into two groups a group from es3 source rocks in the gunan sag and a second from es3 and es4 source rocks in the bonan sag they were expelled within the oil generation window and charged the reservoirs between 3 ma and the present day oils in the guantao formation have undergone light to heavy biodegradation ranging from pm levels 2 to 5 with the increase of biodegradation level saturated hydrocarbon contents gradually decrease from 50 to 22 while the contents of resins and asphaltenes increase from 28 to 43 biodegradation is the primary cause of oil densification in the guantao formation although oils in the guantao formation suffered more severe biodegradation they still have higher contents of saturated hydrocarbons than those in the shahejie formation source type maturity and biodegradation thus combine in different ways to control the density of heavy oils in the sanhecun sag this study also indicates that low mature oils from es4 carbonate source rocks can charge reservoirs in the southern part of zhanhua depression before late oligocene uplift and low mature oil may be a potential future target in this area

how earth s atmosphere evolved to an oxic state a status report the evolution of the earth s atmosphere is essentially the story of atmospheric oxygen virtually every realm of the earth sciences biology geology geochemistry oceanography and atmospheric science is needed to piece together an understanding of the history of oxygen over the past decade new data from these fields has shown that there were two significant increases in atmospheric o2 levels at around 2 4 2 3 and 0 8 0 6 billion years ago respectively throughout earth history oceanic sulfate concentrations appear to have increased in accord with greater o2 levels while levels of methane a strong greenhouse gas may have inversely mirrored o2 both oxic transitions occurred in eras characterized by bsnowball earthq events and significant disturbances in the carbon cycle perhaps associated with increases in o2 and losses of methane to understand what controlled the oxygenation of the atmosphere it is necessary to determine how o2 is consumed on geologic time scales through reaction with reductants released from the earth s crust and mantle there was apparently a long delay between the appearance of oxygenic photosynthesis and oxygenation of the atmosphere and a plausible explanation is that excess reductants scavenged photosynthetic o2 from the early atmosphere however a quantitative understanding of how and why o2 became abundant on our reducing planet is still lacking thus the study of the early atmosphere remains a frontier field with much to be discovered d 2005 elsevier b v all rights reserved

charcoal taphonomy and significance in geology botany and archaeology abstract charcoal occurs in the natural environment as either a result of wildfire or volcanic processes in addition people may make charcoal either for domestic or industrial use charcoal may be used as a fuel for domestic heating and cooking through a range of industrial uses such as iron smelting more recently the charcoalification process has been used to make biochar that is relatively inert and promotes atmospheric co 2 reduction with such a wide range of uses research has been published in a broad range of journals and often whole areas of study are unfamiliar to other charcoal researchers here we review a range of charcoal studies and their inter relationships we present some of the results of a major international meeting on charcoal brussels september 2008 highlighting the potential of charcoal studies as part of palaeoenvironmental investigations both in a geological and archaeological context

hot on the trail coseismic heating on a localized structure along the muddy mountain fault nevada abstract recent advances in the use of thermal proxies to identify past earthquake slip in exhumed faults have created an extraordinary opportunity to map the geometry of past ruptures in unprecedented detail this approach can reveal along strike differences in the structure and speed of earthquake slip here we present organic thermal maturity data collected along the muddy mountain thrust in nevada to investigate where it was within the fault that earthquake slip occurred and whether this is consistent along strike we observe large changes in thermal maturity which represent temperature rise variations along the fault modeling of thermal maturity measurements yield peak temperatures of 760 1090 c where the principal slip zone psz is narrowest 0 8 mm nearby where the psz is thicker 1 5 mm these temperatures did not exceed 500 c based upon estimates of temperature rise within a submillimeter psz mean frictional work during earthquake slip was 6 3 7 1 mjm 2 these results show that thickness of the active slipping zone can vary at small spatial scales and development of a continuously narrow

modeling atmospheric o2 over phanerozoic time a carbon and sulfur isotope mass balance model has been constructed for calculating the variation of atmospheric o2 over phanerozoic time in order to obtain realistic o2 levels rapid sediment recycling and o2 dependent isotope fractionation have been employed by the modelling the dependence of isotope fractionation on o2 is based for carbon on the results of laboratory photosynthesis experiments and for sulfur on the observed relation between oxidation reduction recycling and s isotope fractionation during early diagenetic pyrite formation the range of fractionations used in the modeling agree with measurements of phanerozoic sediments by others results derived from extensive sensitivity analysis suggest that there was a positive excursion of o2 to levels as high as 35 during the permo carboniferous high o2 at this time agrees with independent modeling based on the abundances of organic matter and pyrite in sediments and with the occurrence of giant insects during this period the cause of the excursion is believed to be the rise of vascular land plants and the consequent increased production of o2 by the burial in sediments of lignin rich organic matter that was resistant to biological decomposition

aromatic biomarkers as indicators of source depositional environment maturity and secondary migration in the oils of cambay basin india abstract aromatic biomarkers have been analysed for source depositional environment maturity and secondary migration in crude oils from different formations of paleocene to eocene age in the ahmedabad mehsana block of north cambay basin and the broach block of south cambay basin north cambay basin oils are characterized by a high abundance of 1 2 5 and 1 2 7 trimethylnaphthalenes tmn and low to medium ratio of dibenzothiophene phenanthrene and low ratio of pristane phytane indicates that these oils have been derived from a source containing predominantly higher plants and that the organic matter was deposited in restricted marine or lacustrine environments in anoxic to suboxic conditions the relative abundance of 1 2 7 tmn suggests that it was derived from the structural degradation of oleanane type triterpenoids present in angiosperms south cambay basin oils are less abundant in 1 2 5 and 1 2 7 tmns and low ratio of dibenzothiophene phenanthrene and high ratio of pristane phytane indicating that the oils were derived from higher plant source organic matter deposited under marine or fluvial deltaic environment in oxic conditions maturity sensitive ratios based on phenanthrene naphthalene dibenzothiophene and their alkyl substituted isomers have been used to calculate the equivalent vitrinite reflectance these parameters indicate a wide range of thermal maturity of the oils ranging from 0 60 to 0 93 vrc methylphenanthrene index and methyldibenzothiophene ratios indicate that the maturity of north and south cambay basin oils are different the north cambay basin oils are less mature than south cambay basin oils pyrrolic nitrogen distribution indicates that the alkylated carbazoles and benzocarbazoles are more abundant in south cambay basin oils as compared to north cambay basin oils these data indicate that north cambay basin oils are less migrated compared to south cambay basin oils this systematic investigation of the aromatic biomarkers in oils of cambay basin has resulted in a new generation migration and entrapment model that has led to the development of new exploration leads

the rise of fire fossil charcoal in late devonian marine shales as an indicator of expanding terrestrial ecosystems fire and atmospheric change fossil charcoal provides direct evidence for fire events that in turn have implications for the evolution of both terrestrial ecosystems and the atmosphere most of the ancient charcoal record is known from terrestrial or nearshore environments and indicates the earliest occurrences of fire in the late silurian however despite the rise in available fuel through the devonian as vascular land plants became larger and trees and forests evolved charcoal occurrences are very sparse until the early mississippian where extensive charcoal suggests well established fire systems we present data from the latest devonian and early mississippian of north america from terrestrial and marine rocks indicating that fire became more widespread and significant at this time this increase may be a function of rising o2 levels and the occurrence of fire itself may have contributed to this rise through positive feedback recent atmospheric modeling suggests an o2 low during the middle devonian around 17 5 with o2 rising steadily through the late devonian and early mississippian to 21 22 that allowed for widespread burning for the first time in devonian mississippian marine black shales fossil charcoal inertinite steadily increases up section suggesting the rise of widespread fire systems there is a concomitant increase in the amount of vitrinite preserved woody and other plant tissues that also suggests increased sources of terrestrial organic matter even as end devonian glaciation was experienced fossil charcoal continued to be a source of organic matter being introduced into the devonian oceans scanning electron and reflectance microscopy of charcoal from late devonian terrestrial sites indicate that the fires were moderately hot typically 500 600 c and burnt mainly surface vegetation dominated by herbaceous zygopterid ferns and lycopsids rather than being produced by forest crown fires the occurrence and relative abundance of fossil charcoal in marine black shales are significant in that these shales may provide a more continuous record of fire than is preserved in terrestrial environments our data support the idea that major fires are not seen in the fossil record until there is both sufficient and connected fuel and a high enough atmospheric o2 content for it to burn