the cold climate origin of inertinite rich gondwana coals abstract in the inertinite rich permian coals of australian there occurs a close association between inertodetrinite and alginite of a kind which has been generally overlooked in the past the association is believed to be a consequence of the environment of deposition and especially the climate which is inferred to have been one of wet cool summers and freezing winters the inertodetrinite formed by drying out of a gelified homogenised precursor the algae lived at the periodically desiccated surface of the accumulating peat much of the evidence for these conclusions has come from the combined use of light microscopy and transmission electron microscopy

botryococcus a planktonic green alga the source of petroleum through the ages transmission electron microscopical studies of oil shales and petroleum source rocks abstract the hydrocarbon secreting alga botryococcus has been identified in organic remains of sediments ranging from precambrian to recent and is believed to have been a major source material for petroleum generation throughout the geological time in some petroleum source rocks of lower palaeozoic and precambrian age identification of the alga is only possible by electron microscopy transmission electron microscopy tem has been used in the present study to identify microstructures of the algal remains in a range of oil shales and petroleum source rocks it has been established that botryococcus is the predominant alga in the kukersite oil shale of estonia similarly the alga has been shown to be a major contributor to petroleum source rocks in cambrian and precambrian sedimentary basins in australia tem has been applied to observations of botryococcus in torbanites and to products from simulated maturation experiments on torbanite a comparison with algal remains from cambrian and precambrian sediments ranging from undermature to overmature enabled the distinction of organic matter in various stages of oil generation maturation thermal effects on alginite have been established by reflectance and fluorescence and compared with experimental results

ketones in a proterozoic dolerite sill abstract a dolerite sample from the middle proterozoic mcarthur basin in northern australia has solid bitumen on fracture surfaces and liquid hydrocarbon fluid inclusions in secondary calcite mineralization the extract of this sample is rich in polar compounds and contains an unusual and novel series of saturated ketone isomers including homologous series of n alkan 2 ones and n alkan 3 ones together with a complicated series of branched mid chain ketones these ketone isomers were identified by the monitoring of diagnostic mass chromatograms including those due to rearrangement ions n alkanes are only three to four times more abundant than the ketones the n alkan 2 ones have a similar distribution to the n alkanes and may have been formed by the pyrolysis and oxidation of carboxylic acids followed by decarboxylation of the resultant keto acids the n alkan 3 ones and the mid chain isomers have a distribution which is biased towards the low molecular weight isomers probably due to the pyrolysis of a different kerogen moiety perhaps alkyl chains cross linked by ether groups ketones are known to occur when oil shales are pyrolysed and in hydrothermal oil so by analogy the natural pyrolysis of kerogen in the fine grained sediments by the dolerite sill resulted in the generation of liquid products predominantly n alkanes and ketones which were preserved as hydrocarbon bearing fluid inclusions and as solid bitumen in a fracture

thermal evolution of the ore hosting isa superbasin central and northern lawn hill platform hydrocarbon migration pathways and organic mineral matter associations were used to identify brine pathways in paleoproterozic to early mesoproterozoic rocks from the lawn hill platform mount isa several types of organic matter are identified and their thermal imprints are used to reconstruct the thermal history of the northern to central parts of the isa superbasin three major thermal hydrothermal episodes are recognized from the organic maturation studies isotherm plots on a 175 km long structural sedimentological north south section of the isa superbasin highlight specific fault systems that acted as hot fluid conduits during the geologic history of the basin some of these systems indicate continuing activity into the south nicholson basin supported by the presence of low reflectance type b bitumen this bitumen has not been overprinted by later hydrothermal episodes and therefore represents the latest thermal event along the north south profile a general southward increase in temperature is evident the lowest temperatures are recorded in proximity to the basin margin on the southern flank of the murphy inlier thermal processes and their sequence of events in the basin are recorded by organic maturation subsequent hydrocarbon generation its migration and destruction coincident with transport and precipitation of minerals as some timing and trapping mechanisms for minerals may have analogues with hydrocarbon entrapment relative timing of processes leading to organic maturation hydrocarbon generation and migration are utilized in this study to enhance understanding of ore grade mineralization in the proterozoic successions of the mount isa basin multiple hydrocarbon generation events are recognized these events record the transient passage of potential metal bearing fluids rather than background conductive heat flow from the basement such hydrothermal fluids are responsible for inverse maturation profiles in the vicinity of the termite range fault and extreme maturation reflectance values up to 6 percent ro at the grevillea prospect at century intermediate ro values of 2 percent document the passage of fluids of less than 200 degrees c interaction between these hydrothermal fluids and organic matter resulted in the creation of transient microporosity that was subsequently filled with sulfide minerals principally sphalerite porous sphalerite texture of previous workers pervasive destruction of organic matter in the host sediments at century records high water rock ratios during this mineralizing event previous models for century mineralization interpreted an in situ gas and oil accumulation at the time of mineralization this study shows that initial maturation of organic matter at century coincided with the influx of hydrothermal fluids responsible for mineralization there is no evidence for the existence of an earlier hydrocarbon accumulation in this study samples were only collected from organic matter rich intervals mainly shales and siltstones interbedded sandstones were not sampled therefore it is not possible to determine which siliciclastic lithologic units transmitted the hydrothermal fluids however elevated reflectance values consistently occur adjacent to faults both supersequence boundaries surfaces of major lithologic contrast suggesting that these features controlled fluid migration carbonate lithologic units sampled in this study are primarily from the loretta supersequence walford dolomite these rocks preserve the residue of a primary migrated hydrocarbon overprinted by a hydrothermal fluid event responsible for destruction of the oil and the formation of mesophase textures characteristic of mississippi valley type deposits

post oil solid bitumen network in the woodford shale usa a potential primary migration pathway abstract an important if not predominant component of porosity in many gas shales has been identified in organic matter an organic network in shales has been described in the literature as organic matter generalized term kerogen primary or bitumen secondary recognition of the type and origin of an organic network in shales has relevance in establishing the origin and timing of porosity and fracture development the pervasive nature of the organic network adopting the shape of pores in type ii kerogen rich woodford shale suggests it is the residue of primary oil migration we use the term post oil solid bitumen to distinguish this bitumen occurrence from pre oil solid bitumen defined as a precursor of oil three forms of this post oil solid bitumen network are recognized in reflected white light at 500 magnification and confirmed in backscattered scanning electron microscope images at 2500 magnification namely speckled 1 2 m wispy 2 5 m and connected 5 m the post oil solid bitumen network demonstrates the prior occurrence of oil generation and migration within this hydrocarbon source rock provides porosity for hydrocarbon storage sites and forms hydrocarbon migration pathways

lower palaeozoic and precambrian petroleum source rocks and the coalification path of alginite organic rich samples derived from a middle cambrian formation in the georgina basin and from the middle proterozoic of the mcarthur basin in northern and central australia yielded alginite ranging from immature oil shale material to overmature residue a maturation scale has been developed based on the thermal evolution of alginite as determined from reflectance and fluorescence the coalification path of alginite is marked by jumps in contrast to the linear path of wood derived vitrinite six zones have been recognised ranging from undermature zone i through the mature zones ii iii followed by a stable stage of no change zone iv to the overmature zones v and vi the onset of oil generation in alginite as evident from the present study is at 0 3 ro alg and is expressed in a change of fluorescence from yellow to brown and a coalification jump from 0 3 to 0 6 ro of alg in many boreholes zone iii can be distinguished between 0 6 and 0 8 ro of alg where subsequent oil generation occurs zones ii and iii represent the oil window a zone of little or no change designated zone iv at 0 91 0 ro of alginite follows zones ii iii a marked coalification jump characterises zone v where a pronounced change in reflectance occurs to 1 0 ro alg signifying peak gas generation the border of oil preservation lies at the transition of zone v and vi at 1 6 ro alg in zone vi gas generation only occurs comparison of reflectance results with experimental and geochemical pyrolysis data supports high activation energies for hydrocarbon generation from alginite and therefore a later onset of oil generation than other liptinite macerals i e cutinite exinite resinite as well as a narrow oil window transmission electron microscopy tem confirms that alginite does not go through a distinct intermediate stage but that the percentage of unreacted organic matter decreases as maturation proceeds a clear distinction can be made in tem between immature alginite alginite after oil generation and alginite residue following gas generation alginite beyond 1 6 ro acquires very high densities and the appearance of inertinite in tem bitumens pyrobitumens make a pronounced contribution to the organic matter throughout the basins and have been shown to effect pyrolysis results by suppressing tmax the bitumens pyrobitumens have been divided into four groups based on their reflectance and morphology which in turn appears to be an expression of their genetic history their significance is in aiding the understanding of the basins thermal history and the timing of oil and gas generation

the application of electron microscopy and microanalysis in conjunction with organic petrology to further the understanding of organic mineral association examples from mount isa and mcarthur basins australia organic petrology supported by electron microscopical and micro analytical techniques was applied to organic matter in proterozoic sediments to better understand hydrothermal processes responsible for ore grade mineralisation it was shown that organic maturation was not only closely linked to the geological history of the sediments but also highlighted heat transfer by convection as differentiated from conduction solely through sediment burial and step wise subsidence water rock ratios effect organic maturation in hydrothermal systems and erratic reflectance profiles are indicators of convective heat transfer identification and characterisation of organic materials in terms of source rock and migrated hydrocarbons was shown to be a powerful tool in reconstructing the thermal history of sediments identifying hydrothermal episodes fluid pathways and heat source in the northern australian proterozoic basins higher reflectance of organic matter towards the central parts of the mount isa basin and some of the most northerly parts point to proximity to higher heat flow at times in contrast to relatively low temperatures prevailing in the western parts of the basin next to the murphy inlier a close correlation shown between peak organic reflectance values and super sequence boundaries farther highlighted the valuable information to be gained from organic petrology by allowing the separation of processes responsible for metal dissolution and transportation from those inducing precipitation c 2001 elsevier science b v all rights reserved

thermal history and source rock characterization of a paleozoic section in the awbari trough murzuq basin sw libya abstract in some areas of the murzuq basin sw libya the lower silurian member comprises highly radioactive shales hot shale which are regarded as the most significant factor controlling petroleum generation in the basin in this context it was the goal of our project to study the distribution and maturity of the hot shale in the framework of basin evolution organic geochemical organic petrological and basin modelling methods were used to obtain a more thorough understanding four wells from the northern and central part of the awbari trough have been selected for this study the hot shale contains mainly type ii kerogen with high toc values ranging from 3 to 23 which is considered as an indication for excellent source rock potential a good petroleum potential is further supported by hydrogen indices varying between 220 and 380 mg hc g toc numerical 1d basin modelling was performed for four wells in order to assess the thermal maturity of the tanezzuft hot shale and its evolution through time mean random equivalent vitrinite reflectance results using vitrinite like particles for lower silurian hot shale pyrolysis t max values and fluorescence colours indicate that the hot shale is immature to early mature in the southern part and clearly more mature in the northern part of the basin other potential source rocks from silurian tanezzuft middle upper devonian awaynat wanin and lower carboniferous marar formations were analysed thermal history modelling indicates that the present day geothermal gradients and heat flows vary at different locations but that paleotemperature evolution is mostly related to deepest burial peak temperatures were reached either in the late carboniferous before hercynian uplift occurred or in the jurassic cretaceous the latter scenario being more probable because much oil has been preserved

global ocean meridional overturning abstract a decade mean global ocean circulation is estimated using inverse techniques incorporating air sea fluxes of heat and freshwater recent hydrographic sections and direct current measurements this information is used to determine mass heat freshwater and other chemical transports and to constrain boundary currents and dense overflows the 18 boxes defined by these sections are divided into 45 isopycnal neutral density layers diapycnal transfers within the boxes are allowed representing advective fluxes and mixing processes air sea fluxes at the surface produce transfers between outcropping layers the model obtains a global overturning circulation consistent with the various observations revealing two global scale meridional circulation cells an upper cell with sinking in the arctic and subarctic regions and upwelling in the southern ocean and a lower cell with sinking around the antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges

overturning circulation driven by breaking internal waves in the deep ocean a global estimate of the water mass transformation by internal wave driven mixing in the deep ocean is presented the estimate is based on the energy conversion from tidal and geostrophic motions into internal waves combined with a turbulent mixing parameterization we show that internal wave driven mixing in the deep ocean can sustain 20 30 sv of water mass transformation one third or more of this transformation is attributed to lee waves generated by geostrophic motions flowing over rough topography primarily in the southern ocean while these results are uncertain due to many assumptions poorly constrained parameters and data noise that enter in the calculation the result that lee wave driven mixing plays an important role in the abyssal ocean circulation is likely robust the implication is that lee wave driven mixing should be represented in ocean and climate models but currently it is not citation nikurashin m and r ferrari 2013 overturning circulation driven by breaking internal waves in the deep ocean geophys res lett 40 doi 10 1002 grl 50542

hydrous pyrolysis maturation of vitrinite like and humic vitrinite macerals implications for thermal maturity analysis abstract the evaluation of thermal maturity of lower paleozoic sedimentary rocks is somewhat complex mainly because of the absence of humic vitrinite maceral material various sedimentary basins of this age contain a syndepositional vitrinite like maceral that resembles vitrinite but has a lower reflectance samples of shales from outcrops and boreholes from the ponta grossa formation middle devonian or older in the parana basin were studied for maturation assessment hydrous pyrolysis assays were conducted for 27 combinations of time and temperature to compare the reflectances of the vitrinite like maceral and humic vitrinite in response to increasing temperature and time this data confirmed that the maturation pathway of the vitrinite like maceral is lower than that of humic vitrinite the spore coloration index for the outcrop samples was also evaluated for natural series studies the combination of the natural and artificial series led to the development of two stage linear regression equations that estimate the equivalent vitrinite reflectance values from measured vitrinite like maceral reflectances to validate the proposed equations reported measurements of vitrinite like maceral reflectances from sedimentary basins in china north america and europe were selected from the literature for comparison the validations showed that the values obtained from the proposed equations correlated well with other maturity parameters

petroleum generation simulation over six years of hydrocarbon formation from torbanite and brown coal in a subsiding basin abstract dry samples of torbanite and soft brown coal from which mineral matter and material soluble in chloroform have been removed have been artificially matured in an attempt to simulate conditions in a subsiding sedimentary basin with a constant geothermal gradient sealed tubes were increased in temperature by 1 c per week beginning at 100 c a tube containing each source material was opened and analysed at yearly intervals for six years olefins and carbon monoxide were not significant products at any stage at less than 300 c torbanite generated a paraffinic crude oil in 35 yield while the brown coal gave a wet co2 rich natural gas in most respects these experiments which are possibly as slow as can be realistically planned within a human time scale appear to have duplicated geochemical hydrocarbon generation

petroleum geology and geochemistry of middle proterozoic mcarthur basin northern australia ii assessment of source rock potential five potential source rocks have been discovered in the middle proterozoic of the mcarthur basin the lacustrine barney creek formation mcarthur group and the marine velkerri formation roper group compare favorably in thickness and potential with demonstrated petroleum source rocks in the phanerozoic the former contains up to 7 total organic carbon toc and kerogen types i and ii toc values in the latter range up to 6 5 and the kerogen is type ii petrographic examination shows the organic matter is mostly lamalginite which on maturation yields nonfluorescent lamalginite and bitumen extractable hydrocarbon yields from mature samples indicate that good to excellent source rocks are present and there is ample evidence of migration having occurred tmax values derived from rock eval analysis may be used to define maturation levels in much the same way as in phanerozoic sediments at low maturation levels the reflectivities of lamalginite and bitumen are lower than vitrinite reflectance values calculated from methylphenanthrene indices but converge in the mature zone this convergence reflects both the inherent lower reflectivity of hydrogen rich macerals and the source control on methylphenanthrene indices at low maturity maturation levels in mcarthur group sediments vary from marginally mature to overmature with abrupt changes over short distances associated with faults hydrocarbon generation occurred prior to the deposition of the younger proterozoic sediments of the roper group in contrast the source rocks in the roper group re marginally mature to mature throughout the study area and are overmature only where they are affected by igneous intrusions considerations of burial history suggest that hydrocarbon generation may have occurred during deposition of the roper group although an early paleozoic timing cannot be excluded

comments on some permian conodont faunas reported from southeast asia and adjacent areas and their global correlation abstract some important conodont faunas reported from southeast asia excluding south china and japan are re evaluated on the basis of the improved taxonomy and resulting newly established provincialism these faunas are representative of either the equatorial warm water province ewwp or the peri gondwana cool water province gcwp except that the fauna from jilin north china represents the north cool water province ncwp the gcwp is marked by vjalovognathus and or merrillina in the cisuralian vjalovognathus merrillina and mesogondolella in the guadalupian and vjalovognathus and mesogondolella sheni or merrillina in the lopingian the ewwp is characterized by the absence of gondolelloides and vjalovognathus in the early and middle cisuralian abundance of sweetognathus and pseudosweetognathus in the kungurian late cisuralian dominance of jinogondolella and sweetognathus in the guadalupian and dominance of clarkina and iranognathus in the lopingian mixed faunas are recognized in regions on the border between the ewwp and gcwp including western timor during the artinskian southeast pamirs during the kungurian and the salt range during the guadalupian and lopingian

petrology of liquefaction residues from the breckinridge cannel western kentucky abstract solid residues from the liquefaction at four temperatures of the breckinridge coal bed an alginite rich coal from western kentucky provide examples of the changes to be expected in the relatively rare alginite rich zones of humic coals vitrinite reacts at low temperatures and in the 385 c 15 min residue its product appears to be vitroplast which is a matrix between relatively unreacted bituminite alginite particles both alginite and bituminite show signs of softening by 427 c 15 min both macerals still fluoresce at 427 c 15 min by 435 c 15 min the residues are dominated by a granular residue most likely derived from bituminite with some alginite contribution possible an anisotropic semi coke possibly derived from the repolymerization of tars and oils was observed at all temperatures framboidal anisotropic sulfides pyrrhotite distinctly different from any sulfide observed in the raw coal are well developed in the higher temperature residues

an overview of pre devonian petroleum systems unique characteristics and elevated risks abstract the radiation of land plants at the onset of the devonian resulted in a change in the character of available biomass which in turn introduced changes to the nature of petroleum systems this study examines the nature of pre devonian petroleum systems prior to this significant evolutionary event conventional hydrocarbon resources have been associated with pre devonian petroleum systems across the globe including the neoproterozoic infracambrian huqf supergroup of the oman basin the riphean vendian sequences of east siberia the cambrian of the murzuq basin the ordovician of the tarim basin and the silurian qusaiba of saudi arabia although individual accumulations can be quite significant e g hassi messaoud has ultimate recoverable reserves of 10 billion barrels the relative importance of pre devonian derived oils is thought to be limited compared to the global conventional resource base with growing interest in unconventional resources the relative importance of these systems is expected to increase as resource plays such as the ordovician utica shale of the appalachian basin the cambrian of china and possibly the silurian of central and eastern europe develop the advanced ages of these systems result in some unique properties and amplify risks that exist in younger petroleum systems differences in the nature of the biomass contributing to pre devonian source rocks may give rise to oils that display unique geochemical characteristics for example there are some precambrian oils where c 29 steranes dominate even though land plants were absent there are also ordovician source rocks dominated by gloeocapsamorpha prisca a primitive prokaryote which yield oils containing limited amounts of c 20 components and nearly lack pristane and phytane the potential for unconventional reservoirs in pre devonian systems may also be highly dependent upon the age of the system as biological evolution influences the availability and nature of biogenic silica an important factor controlling brittleness and fracability literature has shown that biogenic silica from different sources displays varying degrees of resistance to diagenesis which allows the formation of a silica network and influences brittleness for example radiolaria present during the cambrian are more resistant to diagenesis than diatoms which did not evolve until the jurassic risks associated with preservation of hydrocarbons are also amplified in pre devonian petroleum systems many such systems have been exposed to significant thermal stresses resulting in the cracking of oil and wet gas others have had complex tectonic histories potentially resulting in the breaching of seals or changes in pvt conditions that can result in gas loss gas loss may also occur through diffusion from these older reservoirs as a result of long residence times

global abyssal mixing inferred from lowered adcp shear and ctd strain profiles abstract internal wave wave interaction theories and observations support a parameterization for the turbulent dissipation rate e and eddy diffusivity k that depends on internal wave shear vz2 and strain z2 variances its latest incarnation is applied to about 3500 lowered adcp ctd profiles from the indian pacific north atlantic and southern oceans inferred diffusivities k are functions of latitude and depth ranging from 0 03 10 4 m2 s 1 within 2 of the equator to 0 4 0 5 10 4 m2 s 1 at 50 70 diffusivities k also increase with depth in tropical and subtropical waters diffusivities below 4500 m depth exhibit a peak of 0 7 10 4 m2 s 1 between 20 and 30 latitudes where semidiurnal parametric subharmonic instability is expected to be active turbulence is highly heterogeneous though the bulk of the vertically integrated dissipation e is contributed from the main pycnocline hotspots in e show some correlation with small scale bottom roughness and near bottom flow at sites where st

abyssal upwelling and downwelling driven by near boundary mixing abstracta buoyancy and volume budget analysis of bottom intensified mixing in the abyssal ocean reveals simple expressions for the strong upwelling in very thin continental boundary layers and the interior near boundary downwelling in the stratified ocean interior for a given amount of antarctic bottom water that is upwelled through neutral density surfaces in the abyssal ocean between 2000 and 5000 m up to 5 times this volume flux is upwelled in narrow turbulent sloping bottom boundary layers while up to 4 times the net upward volume transport of bottom water flows downward across isopycnals in the near boundary stratified ocean interior these ratios are a direct result of a buoyancy budget with respect to buoyancy surfaces and these ratios are calculated from knowledge of the stratification in the abyss along with the assumed e folding height that characterizes the decrease of the magnitude of the turbulent diapycnal buoyancy flux away from the seafloor these strong diapycnal upward and downwa

microbial remains in some earliest earth rocks comparison with a potential modern analogue abstract carbonaceous matter cm from ca 3 5 ga hydrothermal black cherts of the pilbara craton of western australia and the barberton greenstone belt of south africa yielded transmission electron microscopy tem images that are suggestive of microbial remains and possible remnants of microbial cell walls these are compared to a potential modern analogue the hyperthermophilic methanocaldococcus jannaschii derived from an active seafloor hydrothermal environment and cultured under similar conditions a striking resemblance to the early archaean forms was evident in wall structure and thermal degradation mode cell disintegration of the cultures occurred at 100 c marking the limits of life complete disintegration deformation and shrinkage occurred at 132 c a multidisciplinary approach to the characterisation of the cm was undertaken using organic petrology tem coupled with electron dispersive spectral analysis eds high resolution tem hrtem to determine molecular ordering and elemental and carbon isotope geochemistry reflectance measurements of the cm to determine thermal stress yielded a range of values corresponding to several populations and pointing to different sources and processes the 13c values of dresser formation cm 36 5 to 32 1 are negatively correlated with toc 0 13 0 75 and positively correlated with c n ratio 134 569 which is interpreted to reflect the relative abundance of high ro oxidised recycled cm and preferential loss of 12c and n during thermal maturation tem observations inferred carbon isotopic heterogeneity and isotope fractionations of 27 to 32 are consistent with the activity of chemosynthetic microbes in a seafloor hydrothermal system where rapid silicification at relatively low temperature preserved the cm

buoyancy forcing by turbulence above rough topography in the abyssal brazil basin abstract observations of turbulent dissipation above rough bathymetry in the abyssal brazil basin are presented relative to regions with smooth bathymetry dissipation is markedly enhanced above rough topography of the mid atlantic ridge with levels above bathymetric slopes exceeding levels observed over crests and canyon floors furthermore mixing levels in rough areas are modulated by the spring neap tidal cycle internal waves generated by barotropic tidal flow over topography are the likely mechanism for supplying the energy needed to support the observed turbulent dissipation a model of the spatial and temporal patterns in the turbulent dissipation rate is used to constrain the diapycnal advection in an inverse calculation for the circulation in an area of rough bathymetry this inverse model uses both beta spiral and integrated forms of the advective budgets for heat mass and vorticity and contains sufficient information to resolve the full three dimensional flow the inverse model solution re

the late triassic callide coal measures queensland australia coal petrology and depositional environment abstract the late triassic carnian rhaetian callide coal measures are preserved in a partly fault bounded basin remnant in east central queensland australia the sequence comprises up to 150 m of interbedded clastic sedimentary rocks and at least four major coal seams including one coal body up to 23 m thick the sequence was deposited initially in high gradient alluvial fan systems which gave way through time to sandy low sinuosity rivers the restricted intermontane and entirely alluvial nature of sediment accumulation is here considered to have influence the petrographic characteristics of callide coals and their external geometry the main coal seam from the callide measures shows variation in the predominance of some macerals indicating successions of environmental changes the application of transmission electron microscopy tem to the study of the callide coal has enabled a better understanding of the nature and origin of some of the less understood macerals such as micrinite and vitrinite b two forms of vitrinite have been observed each with a distinct reflectance range the wood sourced vitrinite a displays an average reflectance of 0 56 implying a higher rank than the 0 49 ro total vitrinite reflectance recorded in previous publications vitrinite b and a together represent the most commonly occurring macerals in the callide coal samples of the present study the lower reflecting vitrinite b which forms bands often several hundred m in thickness in tem shows sub micron electron transparent laminae of lipid rich material alternating with a more conventional vitrinite material the vitrinite b is interpreted to represent accumulations of leaves the callide coal has entered the oil window and oil has been generated from some exinite cutinite and resinite as evident from change in fluorescence and the presence of exsudatinite in cell cavities and cleats vitrinite b is seen under the microscope to also be generating oil micrinite the origin of which has been much debated occurs in selected horizons only as lenticular bodies suggesting cell filling or filling of spaces between laminations in vitrinite b tem shows micrinite to consist predominantly of sub micron pyrite and possibly other mineral particles adsorbed on humic acids

microbial remains and other carbonaceous forms from the 3 24 ga sulphur springs black smoker deposit western australia well preserved carbonaceous materials including filamentous microbial remains have been isolated from an archaean sedimentary package overlying the sulphur springs volcanic hosted massive sulphide vhms deposit in the pilbara of western australia one of the oldest best preserved vhms deposits on earth the isotopically light carbonaceous material 13 c values of 26 8 to 34 0 v pdb occurs as finely striated lenticular to banded organic matter om within fine grained epiclastic sediments and silicified materials that overlie the deposit the predominant banded lenticular carbonaceous material occurs parallel to original sedimentary bedding planes and is distinctly visible in light microscopy transmission electron microscopy tem reveals this om as bundles of filamentous and tubular structure closely resembling both modern day and more ancient microbial forms documented from sea floor hydrothermal environments total organic carbon toc has a range of 1 0 to 2 3 while the thermal maturity of the filamentous microbial bundles indicated by reflectance ro points to maximum temperatures since deposition ca 3 24 ga of around 90 100 c a factor that has enabled the preservation of their morphology these results and the intimate association of sulphides with the om are suggestive of a well developed archaean sediment hosted microbial community situated within a basinal environment associated with an active centre of seafloor hydrothermal activity 2007 elsevier b v all rights reserved

investigation of thermal maturity of lower palaeozoic hydrocarbon source rocks by means of vitrinite like maceral reflectance a tarim basin case study evaluation of the maturity of chinese lower palaeozoic sediments has not been satisfactorily accomplished because of the absence of vitrinite and the relatively high level of maturity of the organic matter in the tarim basin one of the largest petroliferous basins in china important lower palaeozoic marine sediments contain a widely distributed type of maceral resembling vitrinite especially characterised by syndepositional occurrence elongate shape homogenous texture and weak anisotropy the term vitrinite like maceral is used to describe the maceral in this paper because of insufficient evidence for its origin thirty five lower palaeozoic source rocks mainly from five boreholes in the tarim basin have been investigated by organic petrologic methods and a positive correlation between the vitrinite like maceral reflectance and sample depth has been recognized this correlation is better than that between bitumen reflectance and depth artificial maturation data show that the maturation pathway of vitrinite like macerals is quite different from that of vitrinite there is a distinct step in the development of reflectance of vitrinite like macerals with increasing maturation by combining the reflectance data from naturally and artificially matured samples the relationship between vitrinite like maceral reflectance and vitrinite reflectance can be divided into three stages which are well represented by three linear regression equations the equations provide a convenient method to evaluate the maturity of lower palaeozoic sediments by allowing an equivalent vitrinite reflectance to be derived from the measured vitrinite like maceral reflectance

sulfur distribution and isotopic composition in peats from the okefenokee swamp georgia and the everglades florida abstract peat cores from three aquatic environments freshwater brackish and marine have been analyzed for organic pyritic and sulfatic sulfur contents and isotope ratios peat collected from each environment has a unique combination of sulfur content distribution and isotope ratio freshwater peat from the okefenokee swamp contains the least sulfur 0 26 to 0 48 primarily organic sulfur and is vertically uniform in sulfur content and isotope ratio the organic sulfur isotope ratio of the okefenokee pear 12 3 to 12 8 per mil is similar to that of sulfate in associated surface waters cores from presently brackish and marine peats from the florida everglades have high organic pyritic and sulfatic sulfur contents with vertical variability in sulfur content and isotope ration the isotope ratio of organic sulfur in the brackish and marine peat is lighter than that of sulfate associated with their respective peat forming environments organic sulfur in the marine peat is isotopically lighter than in the brackish peat freshwater peats subsequently overlain by sediment associated with brackish to marine waters may have a sulfur content distribution and isotopic ratio indistinguishable from peats derived under brackish or marine conditions the primary source of sulfur in peats is dissolved sulfate associated with the peat forming system the sulfate concentration of the waters in which a peat forms is of major importance in determining the isotopic composition of the sulfur form found in peat the content distribution and isotopic ratio of low and high sulfur peats are similar to those reported for coals indicating that the fundamental sulfur geochemistry of coals may have been established during the peat forming stage of coalification the organic sulfur content and isotope ratio of a coal may be useful in estimating the relative sulfate ion concentration of the waters present during the peat forming stage of coalification where transgressive sequences are not involved the sulfate ion concentration of paleowaters could be used to interpret the paleoenvironment during the peat forming stage of coalification and thus information about the organic sulfur content and isotope ratio of coals may prove useful in helping to assess coal quality in advance of mining

mechanism of formation and chemical structure of coorongite i role of the resistant biopolymer and of the hydrocarbons of botryococcus braunii ultrastructure of coorongite and its relationship with torbanite abstract coorongite was collected on the shores of the darwin river reservoir australia where a profuse growth of botryococcus braunii b race occurs the products generated on pyrolysis 400 c of the coorongite hydrocarbons ketones and fatty acids were compared to those from the resistant biopolymer prb b of b braunii b race this biopolymer is located in the outer cell walls which build up the matrix of the colonies the spectroscopic features ftir solid state 13c nmr of coorongite and of prb b were also compared both on unheated materials and on pyrolysis residues these observations indicated that the non labile and predominant fraction of coorongite c 75 of the bitumen free sample is composed of selectively preserved prb b this material only undergoes minor alteration in spite of highly oxic conditions during coorongite formation highly unsaturated isoprenoid hydrocarbons botryococcenes are also major constituents of b braunii b race yet they are completely degraded during coorongite formation as a result of early diagenesis under subaerial conditions however prolonged laboratory exposure of b braunii to the atmosphere production of botryococcus rubber resulted in the partial transformation of botryococcenes in a highly resistant abiotic polymer with a chemical structure that is clearly different of that of prb b but the formation of this polymer was not fast enough to compete with botryococcene degradation under the natural conditions of coorongite formation the physical structure of coorongite uv fluorescence microscopy tem is consistent with an extensive bacterial reworking elimination of cell content coalescence of the outer walls containing the selectively preserved prb b partial fusion of colonies the presence of concentric lamellae corresponding to outer wall limits should allow one to distinguish coorongite samples derived from botryococcus accumulations from those originating from bacterial reworking of other organisms while torbanite and some coorongites derive from a common algal source they clearly show distinct structures as a result of markedly different conditions of early diagenesis of the botryococcus biomass accordingly torbanite with its well separated fossil colonies retaining most of their initial organization cannot be derived from coorongite burial of coorongite and elimination of most of the labile fraction during subsequent diagenesis would yield kerogens with a chemical composition and an oil potential similar to those of torbanite however such kerogens would be characterized by a markedly different chiefly amorphous structure

an isopycnal view of near boundary mixing and associated flows abstract the effectiveness of mixing near a sloping boundary is reduced not just by the ratio of the stratification there to that in the interior but by the square of this ratio this result has previously been derived and interpreted by invoking the upgradient vertical buoyancy flux associated with secondary circulation as this opposes the downgradient vertical diffusive flux here it is shown that the result may be derived very simply by considering the diffusive flux across an isopycnal rather than a horizontal surface the reduction in the buoyancy flux comes from the increased isopycnal spacing and the reduced distance to the boundary derivation of the secondary circulation in the isopycnal diapycnal framework is more subtle however as it involves allowing for the curvilinear nature of the coordinates