maturation and bulk chemical properties of a suite of solid hydrocarbons abstract in this paper we present strong correlations of solid hydrocarbon reflectance shro to vitrinite reflectance vro and bulk chemical properties aromaticity tmax h c etc these correlations suggest that like kerogen in coals and sedimentary rocks solid hydrocarbons vary systematically during maturation as a consequence shro is especially useful as a maturity indicator in rocks lacking vitrinite such as pre devonian rocks and many organic rich marine rocks unlike other organic maturationv indicators the utility of solid hydrocarbons is not limited by botanical evolution but rather the generative potential of the petroleum system solid hydrocarbons also known as solid bitumen asphalt dead oil migrabitumen and pyrobitumen are genetically defined as solid phase accumulations of predominantly hydrocarbons produced by petroleum generation in source rocks they may occur over a range of concentrations in outcrop and well samples in all components of petroleum systems although accumulations of solid hydrocarbons from exhumed reservoirs are well reported the extent and utility of disseminated solid hydrocarbons in shales is less understood solid hydrocarbons are found in organic rich to very lean mature rocks as a residual product of generation disseminated solid hydrocarbons exhibit three optical forms anisotropic coked granular and relatively uniform homogenous only the homogenous solid hydrocarbons are recommended for correlation purposes with other thermal indicators

solid bitumen reflectance and rock eval tmax as maturation indices an example from the nordegg member western canada sedimentary basin abstract marine organic rich rock units commonly contain little for vitrinite reflectance v r 0 measurement the most commoly used method of assessing thermal maturity this is true of the lower jurassic nordegg member a type i ii sulphur rich source rock from the western canada sedimentary basin this study examines the advantages and pitfalls associated with the use of rock eval t max and solid bitumen reflectance b r 0 to determined maturity in the nordegg vitrinite reflectance data from cretaceous coals and known coalification gradients in the study area are used to extrapolate v r 0 values for the nordegg t max increases non linearly with respect to both b r 0 and extrapolated v r 0 values a sharp increase in the reflectaance of both solid bitumen and vitrinite occurs between t max 440 450 c and is coincident with a pronounced decrease in hydrogen index values and the loss of solid bitumen and telalginite fluorescence over the same narrow t max interval this t max range is interpreted as the main zone of hydrocarbon generation in the nordegg and corresponds to extrapolated v r 0 values of 0 55 0 85 the moderate to high sulphur contents in the kerogen played a significant role in determining the boundaries of the nordegg oil window a linear relationship between b r 0 and extrapolated v r 0 as proposed elsewhere is not true for the nordegg b r 0 increases with respect to extrapolated v r 0 according to jacob s 1985 formula v r 0 0 618 b r 0 0 40 up to v r 0 0 72 b r 0 0 52 beyond this point b r 0 increases sharply relative to extrapolated v r 0 according to the relatioship v r 0 0 277 b r 0 0 57 r 2 0 91 the break in the b r 0 v r 0 curve at 0 72 v r 0 is thought to signifiy the peak of hydrocarbon generation and represents a previously unrecognized coalification jump in the solid bitumen analogous to the first coalification jump of liptinites

oolitic sandbody depositional models and geometries mississippian of southwest britain implications for petroleum exploration in carbonate ramp settings abstract a 1000 m thick early mississippian carbonate supersequence the carboniferous limestone of southwest britain consists of three third order depositional sequences these comprise parasequences in various configurations and the whole forms a carbonate ramp stack within this framework five major oolitic carbonate sandbodies developed a castell coch limestone b stowe oolite c brofiscin oolite d gully oolite and e high tor limestone the depositional regime was storm and wave dominated throughout and the major sandbodies represent a range of progradational carbonate beaches barriers and detached subtidal shoals analysis of the three dimensional shapes and distribution of these five examples shows that they evolved to produce three major carbonate sandbody geometries a strings b sheets and c wedges these geometries are characterised using the five field examples and offered as a template which may assist in the exploration and reservoir modelling of petroleum rich high energy ramp systems progradation for up to 40 km of barrier islands stowe oolite and beach ridge plains gully oolite formation generated strings and thick sheets individually up to 10 20 m thick thin shoreface retreat carbonate packstone grainstone sheets up to 5 m thick high tor limestone developed during transgressions as veneers across flooding surfaces these are comparable with sheet sands developed in siliciclastic shelf depositional systems progradation for up to 30 km and vertical aggradation of shoreline detached oolite shoals castell coch limestone brofiscin oolite generated basinwards expanding or thinning wedges up to 30 m thick tectonically controlled stacking of strandplain sheets produced a composite carbonate sandbody up to 80 m thick gully oolite the intrinsic sedimentary and extrinsic eustacy tectonism climate factors which controlled these sandbody geometries are addressed establishing the positions of the sandbodies accurately within depositional sequences allows them to be located within inferred seismic sequence geometries and provides one possible solution to the difficult problem of predicting carbonate facies distribution in subtle stratigraphic plays in this ramp system the most homogeneous sandbodies up to 30 m grainstones with greatest reservoir facies potential are represented by shoal belt wedges potential grainstone reservoir facies in the prograding shorelines are limited to the upper parts of individual shoreface sequences max 10 m grainstones for shoreline carbonate sandbodies the greatest reservoir and stratigraphic trapping potential exists in the earliest ramp parasequences where enveloping offshore sediments are siliciclastic mudstones in later stages potential seals are likely to be less reliable low porosity outer ramp carbonates

organic geochemistry of lower cretaceous sediments from northwestern pacific guyots odp leg 143 organic geochemical data of lower cretaceous shallow water sediments from two sites 865 and 866 drilled during odp leg 143 are presented the organic matter is mainly terrestrial at the bottom of the sedimentary column at site 865 whereas algal and or bacterial organic matter is dominant at site 866 this is the first evidence of shallow water deposition of organic matter during the early cretaceous in the northwestern pacific the lower aptian organic carbon rich layers from the shallow water sediments of site 866 are geochemically similar to coeval mid water sediments of site 463

the role of solid bitumen in the development of porosity in shale oil reservoir rocks of the upper cretaceous in colombia abstract the la luna formation turonian santonian age has been traditionally considered as one of the main hydrocarbon source rocks in the middle magdalena valley basin mmv in colombia at present this formation is also considered as an organic matter rich reservoir of shale oil type unconventional petroleum system of interest due to its significant resources of recoverable oil given the interest in this formation and the need to increase the knowledge of its physico chemical characteristics a series of petrographic geochemical toc content and rock eval pyrolysis and textural analyses picnometry and mercury intrusion porosimetry mip were carried out to investigate two of its members galembo and salada that were sampled from a core well perforated at the center of the basin the organic fraction of both members galembo and salada is made up mainly of a kerogen of type ii typical of a marine paleoenvironment solid bitumen and hydrocarbons the content in organic matter of terrestrial origin is very scarce to null these rocks have a degree of maturity that corresponds to the oil window and their high hydrogen content in combination with a relatively high carbon content makes them excellent source rocks the uneven distribution of the various types of organic matter along the galembo and salada members particularly of the solid bitumen that is concentrated at the lower levels of both members has resulted in large variations in porosity pore size distribution and modal pore throat characteristics even with small variations centimetric in depth the sedimentary levels in which kerogen is the predominant type of organic matter have a pore size distribution in the range of mesopores and macropores of small size whereas the solid bitumen rich levels show a predominance of pores of small pore size with a modal pore throat diameter below 10 nm the preliminary adsorption data obtained for all these samples to be published in a study that will follow this indicate that they contain some micropores which is significant in the case of levels with a high content in solid bitumen

storm generated depositional types and associated trace fossils in lower carboniferous shallow marine carbonates of three cliffs bay and ogmore by sea south wales abstract four distinct storm generated or induced depositional types have been recorded in lower carboniferous shallow marine limestones of ogmore by sea and three cliffs bay south wales type a deposits have whole and oriented horn coral lag deposits and graded limestones with large regular zoophycos they are interpreted as storm generated turbidite deposits in an area below storm wave base type b deposits are characterized by graded limestones and short wavelength hummocky cross bedding with rhizocorallium and small arcuate zoophycos small planolites like burrows and were probably formed by storm currents at depths just above storm wave base type c deposits consist of crinoidal lag deposits and long wavelength hummocky cross bedding with escape burrows and were probably deposited just below fair weather wave base type d deposits contain skeletal sandstone lag deposits and large scale low angle cross bedding generally without bioturbation apart from borings indicating a shore face or beach environment the depositional types belong to the courceyan limestone zaphrentis zone and arundian limestone caninia zone it appears that the pattern of trace fossils and bioturbation as well as sedimentary structure and texture change characteristically with changing wave effect depth in this area

comparative studies of organic matter petrography of the late palaeozoic black shales from southwestern poland abstract there are at least two sapropelic units associated with late palaeozoic black shales in central europe the older unit of late carboniferous age is the lower part of the anthracosia shales in the intrasudetic basin and the younger one is the well known zechstein kupferschiefer in both the foresudetic monocline and the northsudetic basin the first unit is of lacustrine origin while the second one represents deposition in a shallow marine depositional environment both units contain high amounts of organic matter thus being typical black shales the organic matter dispersed in these shales was studied petrographically in general the vitrinite reflectance of the shales studied indicates variable but moderate organic matter maturity 0 68 1 25 equivalent to the oil window detailed microscopic studies of the organic material dispersed in the lower unit of the anthracosia shales showed that liptinite especially alginite is the most abundant component secondary altered organic matter i e solid hydrocarbons rarely occurs organic components together with mineral matter constitute a lacustrine sapropelic association a humic terrestrial association and an intermediary association the character and predominance of alginite and lacustrine sapropelic association are indicative of an open lacustrine depositional environment in general this organic composition is typical of type i kerogen microscopic analysis of the kupferschiefer revealed a mixture of liptinite vitrinite and inertinite macerals and other organic components such as amorphous sapropelic mass asm and solid bitumens the most common organic components are liptinite macerals bituminite and alginite predominate and are diagnostic macerals of this unit the amount of bituminite locally exceeds 85 vol other liptinite macerals such as sporinite and liptodetrinite are present in significantly lower amounts one exception being asm which may be present in higher amounts humic constituents vitrinite and inertinite are rare present in small amounts in the kupferschiefer beds the organic matter composition points to type ii kerogen for this unit

paleoenvironmental characterization of a jurassic sequence on the bombarral sub basin lusitanian basin portugal insights from palynofacies and organic geochemistry abstract a middle upper jurassic sedimentary succession has been cut by the ramalhal 1 borehole in the bombarral sub basin lusitanian basin portugal the succession comprises the brenha montejunto abadia and lourinha formations which are composed of limestones marls sandstones and clays the main objective of this study was to characterize the organic matter using palynofacies and geochemical analyses to determine the depositional paleoenvironments and the hydrocarbon generation potential the total organic carbon content is generally less than 1 wt but reaches 4 1 wt in one sample due to the presence of perhydrous coal the rock eval pyrolysis results reveal lower values hi usually nether to 100 mghc gtoc showing that the studied samples have type iii kerogen and a low potential for oil generation the t max values varies between 319 and 443 c and biomarker data obtained for these samples indicate a maturation ranging between immature and eventually mature the palynofacies data indicate predominance of the phytoclast group 80 with different degradation degrees and a modest contribution of palynomorph group especially sporomorphs and the amorphous organic matter aom group solid bitumen was observed in some samples from the montejunto and brenha formations determining the relative percentages of the kerogen groups allowed for the identification of seven intervals that established variations in the depositional environment

carbonate platforms of passive extensional continental margins types characteristics and evolution abstract carbonate platforms of extensional margins may be grouped into several major categories homoclinal ramps have gentle slopes into deep water may have skeletal or ooid pellet sand shoal complexes that grade without break in slope into deep ramp nodular limestone and then into pelagic hemipelagic basin facies they generally lack significant slump and sediment gravity flow deposits in the deeper water facies distally steepened ramps differ from the above in having a marked increase in slope at the seaward edge of the deep ramp and abundant slumps slope breccias and turbidites however clasts of shallow platform margin facies are generally absent from breccias rimmed shelves have linear trends of shelf edge lime sands and reefs a marked increase in slope into deep water and foreslope and slope sands breccias with clasts of platform margin rocks and turbidites grading seaward into basin hemipelagic pelagic muds they may be divided into accretionary bypass and erosional margins isolated platforms are broad flat topped shallow platforms surrounded by deeper water few hundred meters to 4 km deep many are bypass margins but accretionary and erosional margins also occur finally incipiently to completely drowned or open platforms may develop by rapid submergence of ramps shelves or isolated platforms shallow platform margin facies are shifted landward and the earlier shallow water platform is covered with transgressive lags and deeper water blankets of hemipelagic or pelagic facies or open marine whole fossil wackestone the carbonate prisms commonly develop above a basal clastic phase ramps develop early and evolve into rimmed shelves however with drowning rimmed shelves may evolve up into ramps rimmed shelves may also develop into ramps where miogeoclinal faces prograde into filling marginal basins carbonate miogeocline deposition terminates when the shelf becomes a prograding clastic shelf or where it becomes part of a collisional orogen the various platform types may be recognized from continental margin sequences ranging from proterozoic to holocene in age

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

onset of late palaeozoic glacio eustasy and the evolving climates of low latitude areas a synthesis of current understanding studies of depth sensitive carbonate successions in the uk indicate that regular orbitally forced glacio eustatic sea level oscillations which characterized the late palaeozoic started abruptly around 330 ma early asbian the gondwanan ice sheet was highly sensitive to orbitally forced variations in solar insolation and the resultant sea level oscillations had an approximate 100 ka periodicity studies of fossil soils and palaeokarst from low latitude settings suggest that pre asbian climates were relatively stable with infrequent changes however climatic changes became increasingly frequent in the asbian and brigantian with regular fluctuations of a sub 100 ka periodicity occurring during glacial lowstand intervals

the genesis of coal from the viewpoint of coal petrology abstract the genesis of the microscopic constituents of coal macerals and of maceral associations microlithotypes representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats peat microscopy especially promoted the understanding of humification and biological gelification both of which are decisive for the genesis of huminites vitrinites in brown coals and hard coals respectively microbial activity during peatification has been documented by chemists microbiologists and petrologists and recently by electron microscopical observations in coals this activity leads to the incorporation of lipid substances into the humic matter and later influences the chemical physical and technological properties of vitrinites geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal in this process the hydrogel brown coal is transformed to the bitumogel bituminous coal coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration the formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the coalification jumps of the macerals especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite bitumen and micrinite dead carbon bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals bituminite fluorinite and exsudatinite and suggests a higher proportion of algal material in coals than was thought earlier the genesis of various types of inertinite macerals will probably become an increasingly important subject of research especially with regard to rank inertinites that seem to attain their high inertinitic reflectance initially during coalification besides the origin of macerals the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu the peat forming vegetation palaeoclimate water and nutrient supply acidity marine and calcareous influence and fire with examples from euramerican carboniferous coals gondwana coals and tertiary brown coals vegetation water and oxygen supply eh conditions are most important for the generation of coal facies vegetation has been reconstructed with the help of palaeobotany including palynology cuticular analysis and wood anatomy in brown coals and with the study of petrified permineralized peats preserved in coal balls the microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative however the results of palynological and cuticular analyses should be evaluated with caution considering the varying resistance of palynomorphs and cuticles and in the case of palynomorphs their possible extrapaludal origin microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies especially in brown coals the much disputed origin of brown coal lithotypes is considered in detail for hard coals there seems to be agreement that coal layers rich in vitrites and liptinite poor clarite were deposited in wet forest swamps that microlayered liptinite rich clarites are sub aquatic humic muds and that inertinite rich durites represent oxidized peats the origin of liptinite rich durites is controversial either subaquatic muds or oxidized peats the latter perhaps from raised bogs a recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous oligotrophic conditions although raised bogs with a dense arborescent vegetation are known from borneo it seems not probable that most seams which were deposited in foredeeps or steadily sinking graben zones are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams but as in modern peats striking changes of coal facies are commonly caused by hydrological events e g inundations as a consequences of crevasses or of fires that burned the peat the origin of the inertinite rich gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub arctic peats is recommended coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite as well as by hydrogen rich vitrinites with a relatively low reflectance and high fluorescence all due to a strong bacterial activity in peats of low acidity proposals for further research are made in the conclusions

three dimensional kinematic and microphysical evolution of florida cumulonimbus part i spatial distribution of updrafts downdrafts and precipitation abstract this paper is the first in a three part study that examines the kinematic and microphysical evolution of florida cumulonimbus and focuses on the convective to stratiform transition of the storm this first paper lays the groundwork for the subsequent papers by defining the problem under study delineating the setting for the storm and describing the spatial distribution of updrafts downdrafts and precipitation high resolution radar data of a typical line of storms associated with the florida sea breeze is the centerpiece of this study the high resolution data reveal details of the internal structure of the squall line that were beyond the resolution of previous squall line studies radar reflectivity filled in between cells at upper levels as the storm evolved reflectivity values were only weakly associated with updraft and downdraft magnitude the updrafts and downdrafts in the storm tended to be irregular in their three dimensional shape and less than 5 km in horizontal extent at any giv

origin of contrasting features and preservation pathways in kerogens from the kashpir oil shales upper jurassic russian platform abstract a kerogen termed abs base from the gorodische section russian platform was studied using a combination of microscopic spectroscopic and pyrolytic methods in order to determine its chemical structure source organisms and formation pathway s this kerogen was mainly formed via degradation recondensation of phytoplanktonic material selective preservation and natural sulphurisation pathways only played a minor role whereas a substantial contribution of ether linked lipids was noticed revealing large oxygen cross linking such observations allowed us to put forward for the first time to the best of our knowledge a substantial role for the oxidative reticulation pathway in the formation of a kerogen comparision with a previously studied sample from the same outcrop revealed contrasting features which reflect differences in preservation pathways triggered by different depositional conditions

solid bitumen occurrences in the arruda sub basin lusitanian basin portugal petrographic features abstract the middle jurassic to cretaceous sedimentary record in the lusitanian basin portugal reveals the presence of disseminated solid bitumen the present work is focused on the petrographic characteristics of solid bitumen identified in the freixial 1 and benfeito 1 boreholes arruda sub basin lusitanian basin that display different thermal maturities microscopy techniques reflected and transmitted white light incident blue light and sem and organic geochemistry analyses total organic carbon total sulfur and insoluble residue were used to study these samples from the results obtained by optical microscopy fluorescence and reflectance it was possible to distinguish three types of solid bitumen they were labeled as solid bitumen a present in all the samples solid bitumen b and solid bitumen c these ones observed in some of them they correspond to allochthonous migrated bitumens in blue incident light some bitumen do not show fluorescence while others reveal fluorescence that range from yellow solid bitumen b to dark brown solid bitumen a all bitumens are optically isotropic bitumen reflectance varies between 0 70 and 2 60 r r and the vitrinite reflectance ranges from 1 11 to 1 48 r r based on the r r values the solid bitumen identified in these samples are classified as impsonite epi and cata or pyrobitumen no relation can be established with confidence for the reflectance of bitumens with the reflectance of vitrinite

extratropical transition of tropical cyclones over the western north pacific part i evolution of structural characteristics during the transition process abstract the development of extratropical cyclone structural characteristics that resulted from the extratropical transition of typhoon ty david 1997 and ty opal 1997 over the western north pacific is examined david moved poleward ahead of a midlatitude trough that was moving eastward as the dominant midlatitude circulation feature over the western north pacific during the transition david coupled with the midlatitude trough which led to the evolution of an intense cyclone that became the primary circulation over the north pacific although opal also moved poleward ahead of a midlatitude trough the principal midlatitude feature over the western north pacific was a preexisting stationary cyclone over the kamchatka peninsula during transition opal weakened and became a secondary cyclone to the preexisting primary north pacific cyclone the structural characteristics of the evolving extratropical cyclone with respect to each case are examined in the context of the interaction between a vortex an

the paradox of drowned reefs and carbonate platforms shallow water carbonate platforms and reefs are drowned when tectonic subsidence or rising sea level outpaces carbonate accumulation and benthonic carbonate production ceases drowned platforms are common in the geologic record but they present a paradox if one considers rates of processes involved during the early holocene when sea level rose at rates of 6 000 to 10 000 m yr mm 1 000 yr most reefs and platforms were outpaced by the rising sea during the late holocene with sea level rising 500 to 3 000 m yr in the atlantic caribbean area reefs and platforms started to recover built to sea level and prograded seaward 1 000 m yr is thus a conservative estimate of the average growth potential of modern reefs and platforms independently accumulation rates of prograding platforms in the geologic record suggest growth potential in excess of several hundred microns per year the growth potential of 1 000 m yr exceeds any relative rise of sea level caused by long term processes in the geologic record newly formed ocean crust subsides at a maximum of 250 m yr basin subsidence averages 10 to 100 m yr and sea level rises due to increased sea floor spreading amount to less than 10 m yr rapid pulses of relative rise of sea level or reduction of benthic growth by deterioration of the environment remain the only plausible explanations of drowning the geologic record shows examples of both of these processes global mass extinctions of reefs and platforms occurred in the middle cretaceous eustatic rise due to submarine volcanism or desiccation of a small ocean basin and the late devonian global crisis of ocean environment extraterrestrial cause drowning controlled by regional tectonics prevailed in the jurassic and early cretaceous of the tethyan realm and the drowning of mesozoic platforms in the western north atlantic seems to have been dictated by plate tectonic drift to higher latitudes

variations of organo mineral microfacies of posidonia shale from the lower saxony basin and the west netherlands basin application to paleoenvironmental reconstruction abstract high resolution organic petrological analysis has been carried out on core samples of the posidonia shale from four wells two located in northwestern germany lower saxony basin and two in the western netherlands west netherlands basin the organo mineral microfacies defined by maceral composition and associated mineral matter show a wide range of variations related to the proportions of individual liptinite macerals of marine origin and of terrestrial macerals macerals of vitrinite inertinite groups and sporinite variations in organo mineral microfacies in which the organic components are sensitive to paleoenvironmental changes are considered as a potential indicator of changes in depositional conditions sedimentation of organic matter is controlled by several factors the most important in the marine environment being primary biomass productivity and influx of transported terrestrial organic matter biological degradation related to bacterial activity and the oxygen content of the bottom water the level of degradation in organic rich sediments is mainly related to oxygen availability which in turn influences the diversity of algae and the quality and quantity of the preserved organic matter these two factors can be directly linked to maceral preservation and the organo mineral microfacies in order to evaluate the relationships between different types of organic matter and paleoenvironmental conditions two indices the oxidation index and the degradation index have been proposed these indices illustrate the transition from highly degraded to well preserved macerals provide information on the types of organic matter and permit recognition of precursors for degraded amorphous organic matter aom use of these indices not only enables determination of the organo mineral microfacies but also sheds light on the aom precursors in the posidonia shale information derived from the indices can also be used to reconstruct the paleoenvironments

equatorial aridity and climatic oscillations during the early carboniferous southern britain evidence from palaeosols palaeokarsts and styles of meteoric diagenesis shows that the early carboniferous climate of southern britain was dominantly seasonally semi arid this semi aridity occurred while the region was in an equatorial palaeolatitudinal position the cause of the seasonal aridity was possibly the deflection of easterly winds into a major low pressure zone set up over gondwana during the southern hemisphere summer

sedimentation during carbonate ramp to slope evolution in a tectonically active area bowland basin dinantian northern england the bowland basin northern england contains a series of carbonates and terrigenous mudstones deposited during the ivorian to early brigantian two regional depositional environments are indicated by facies and facies associations wackestone packstone and calcarenite facies indicate deposition in a carbonate ramp environment while lime mudstone wackestone calcarenite and limestone breccia conglomerate facies often extensively slumped represent a carbonate slope environment stratigraphic relations suggest that the depositional environment evolved from a ramp into a slope through the dinantian two main sediment sources are indicated by the sequence an extra basinal terrigenous mud source and a supply of carbonate from the margins of the basin deposition from suspension and from sediment gravity flows in situ production and remobilization of sediment during sedimentary sliding were important processes operating within the basin periods of enhanced tectonic activity in the late chadian to early arundian and late asbian to early brigantian are indicated by basin wide horizons of sedimentary slide and mass flow deposits both intervals were marked by a decline in carbonate production resulting from inundation and uplift emergence the first of these intervals separates deposition on a seafloor with gentle topography carbonate ramp from a situation where major lateral thickness and facies variations were present and deposition took place in a carbonate slope environment the second interval marks the end of major carbonate deposition within the bowland basin and the onset of regional terrigenous sedimentation

mesoscale and convective scale characteristics of mature hurricanes part i general observations by research aircraft abstract the analysis of instrumented aircraft data from four recent mature hurricanes reveals common mesoscale and convective scale features the structure and organization of the convection precipitation and wind flow are studied by combining the airborne observations using basic instrumentation with quantitative radar measurements three predominant precipitation features seen are 1 the eyewall 2 a stratiform rain region adjacent to and outside the eyewall and 3 rainbands that contain both convective and stratiform regions the eyewall is so named because it surrounds the rain free eye but several additional features distinguish it from other convective bands in the hurricane in particular the updraft tangential wind maximum and highest rainfall have preferred locations relative to each other with the updraft being radially inward from the rain and wind maxima the 10 dbz radar reflectivity contour indicative of the inner edge slopes substantially outward with height and there is evide

application of confocal laser scanning microscopy clsm to autofluorescent organic and mineral matter in peat coals and siliciclastic sedimentary rocks a qualitative approach abstract organic matter occurring in the form of macerals and natural solid bitumens in peats coals and siliciclastic sediments of various stratigraphic ages and locations was studied by means of conventional incident light microscopy and clsm classical optical microscopic investigations are restricted by conventional 2 d imaging and are often hindered by the associated out of focus blur effects the qualitative application of clsm overcomes these limitations permitting to reveal precisely 3 d morphology and detailed microstructure of autofluorescent organic matter the in depth examinations along z axis in xy xz or yz scanning modes at increments of 250 nm are capable to reconstruct 3 d internal configuration and arrangement occurring in autofluorescent macerals the non invasive and non destructive laser raster technique is applied to characterize in situ autofluorescent organic particles at micron to sub micron scale resolution in polished whole rock pellets in this study we demonstrate that clsm is suitable to i detect fine scale microstructure of autofluorescent organic matter iii reconstruct 3 d morphology at cellular and tissue level iii analyze maceral composition in terms of its relicts and fragments beyond the classical optical assignment limits iv detect and examine inorganic components enclosed in the embedding mineral bituminous groundmass and v differentiate mineral constituents from the remaining organic matter clsm as an optical microscopic technique was applied to generate high resolution 2 d and 3 d images projections as well as 3 d reconstructions of autofluorescent objects excited with aid of laser induced light operating at variable visible wavelengths clsm is applicable to support microscopic studies of thermally immature and mature organic matter within the oil and early gas windows enclosed either within siliciclastic and carbonate sediments or in peat and low to medium rank coals the application of this technique will be of great interest to a wide range of geology related disciplines such as petroleum geology biostratigraphy marine geology peat petrography and archeology

origin and modification of cambrian dolomites red heart dolomite and arthur creek formation georgina basin central australia the early to middle cambrian red heart dolomite and lower arthur creek formation of the southern portion of the georgina basin australia is an entirely dolomitized succession of shallow water evaporitic mudflat and deeper water subtidal lithologies three types of dolomite have been identified and are interpreted as 1 syndepositional dolomite 2 regional replacement dolomite and 3 void filling dolomite cement syndepositional dolomite derived from saline pore fluids developed in a sabkha environment is a minor dolomite type with very fine crystal mosaics and has a mottled non zoned cathodoluminescence the widespread regional replacement dolomite ranges from fine to medium crystalline forming mainly planar s and non planar a crystal mosaics and displays blotchy mottled non zoned cathodoluminescence void filling dolomite commonly forms planar s to planar e medium to very coarse crystal mosaics rare non planar c very coarsely crystalline saddle dolomite also exists void filling dolomite has a successively zoned cathodoluminescence pattern from non to brightly to dully luminescent geochemically the syndepositional dolomite has 18o pdb values ranging between 5 3 and 8 6 o regional replacement dolomites exhibit a wide range of 18o values from 3 3 to 10 9 o whereas void filling dolomite has 18o values ranging from 10 8 to 14 3 o all three dolomite types have similar 13c pdb values in the range between 1 7 and 1 7 o three initial dolomitization episodes are interpreted 1 a sabkha stage forming the syndepositional dolomite and dolomitizing the evaporitic mudflat lithologies 2 a brine reflux stage replacing the subtidal lithologies and 3 a burial stage forming the void filling dolomite type final dolomite stabilization occurred during burial at elevated temperatures in the presence of basinal fluids resulting in progressive recrystallization and stabilization of the earlier formed syndepositional and replacement dolomites both textural and geochemical evolution should be taken into account when studying the origin of dolomites based on their present geochemical composition sulphates are represented by very fine crystalline syndepositional anhydrite in association with the syndepositional dolomite and coarse to very coarse anhydrite cement evaportic mudflat sabkha and burial environments are inferred for the origin of the former and the latter anhydrite types respectively evaporite dissolution breccias indicative of the former presence of evaporites are common throughout the succession

environmental gradients in carbonate sediments and rocks detected by correspondence analysis examples from the recent of norway and the dinantian of southwest england continuous sedimentary gradients are only crudely expressed by standard facies and microfacies methods which are more appropriate to situations where changes occur in relatively discrete steps in carbonate sediments and rocks continuous gradients are often represented by the arrangement of component grain types in a relay that is a systematic shifting of the relative importance of the components subdivision of such relays into micro facies can only be arbitrary correspondence analysis is shown to be useful for detecting isolating and describing relays particular use is made of the arch effect in which samples and components from data sets with a strong unidimensional structure a relay plot in the form of an arch in the plane of the first two factor axes a relay index indicating the position of samples in the relay can be extracted from the analysis and plotted on maps and stratigraphic logs to reveal details of the sedimentary gradient in areal and or stratigraphic context examples are given from i recent shallow marine carbonate sediments from northern norway illustrating a relatively simple depositional setting where surface sediments are viewed in plan and ii lower carboniferous carbonates of southwest england representing a more complex regional study of a particular stratigraphic interval viewed in cross section in both examples the relays can be related to identifiable environmental gradients

the relationship between storm motion vertical wind shear and convective asymmetries in tropical cyclones abstract the influence of the direction of storm motion on the azimuthal distribution of electrified convection in 35 atlantic basin tropical cyclones from 1985 to 1999 was examined using data from the national lightning detection network in the inner 100 km flashes most often occurred in the front half of storms with a preference for the right front quadrant in the outer rainbands r 100 300 km flashes occurred predominantly to the right of motion although the maximum remained in the right front quadrant the results are shown to be consistent with previous studies of asymmetries in rainfall radar reflectivity and vertical motion with respect to tropical cyclone motion the motion effect has been attributed to the influence of asymmetric friction in the tropical cyclone boundary layer the authors previously found a strong signature in the azimuthal distribution of lightning with respect to vertical wind shear because both effects show clearly vertical wind shear and storm motion must themse

the mesozoic cenozoic organic facies in the lower tagus sub basin lusitanian basin portugal palynofacies and organic geochemistry approaches abstract studies of the mesozoic and cenozoic sequence crossed by the barreiro 4 borehole provide an improved understanding of the organic matter deposited in the lower tagus sub basin lusitanian basin portugal and the implications for the potential source rock and depositional environment this study focused on 43 samples middle jurassic to neogene that were subjected to palynofacies and organic geochemistry analyses total organic carbon rock eval pyrolysis and molecular biomarker analysis the palynofacies data indicate that the sequence contains mainly phytoclasts non opaque phytoclasts however the middle jurassic samples are dominated by amorphous organic matter aom continental and or marine palynomorphs are present in all the samples the cretaceous samples are characterized by small amounts of kerogen that have high contents of solid bitumen the total organic carbon toc content is generally less than 1 wt the rock eval s1 and s2 parameters vary from 0 01 to 3 50 mghc g rock and 0 15 to 34 03 mghc g rock respectively with the highest values corresponding to the cretaceous samples the hydrogen index hi and oxygen index oi values range from 35 to 552 mghc g toc and 4 to 180 mghc g toc respectively the tmax values range from 416 to 437 c the biomarker analysis showed that n alkanes with 15 30 carbon atoms are present and usually have a unimodal distribution with a predominance of low to medium molecular weight compounds the cpi values range between 0 63 and 3 65 and the pristane phytane ratios vary between 0 48 and 1 64 indicating alternation of oxic anoxic conditions along the sequence the distribution of terpanes shows small amounts of tricyclic and tetracyclic terpanes in most of the samples except for some cretaceous samples and a predominance of pentacyclic terpanes the amount of 17 h 22 29 30 trisnorhopane tm usually exceeds the amount of 18 h 22 29 30 trinorneohopane ts the 20s 20s 20r and ratios of the c29 steranes generally have values below the range of equilibrium indicating an immature stage of the om

generation and migration of oil in the maturin subbasin eastern venezuelan basin abstract regional geochemical evaluation of the possible cretaceous and tertiary source rocks and oil oil and oil source rock correlation studies have identified the calcareous shales and limestones of the upper cretaceous querecual and san antonio formations of the guayuta group with amorphous marine type ii organic matter as the source rocks for oil in the maturin subbasin the deposition of the source rocks took place on a passive continental margin whilst the generation and migration of oil occurred in a foreland basin during miocene recent times the oils found in the northern part of the subbasin in different reservoirs cretaceous eocene oligocene miocene and pliocene formations are of mature marine type with or without bacterial alteration geochemical data indicate that some of these oils were mixed with the highly altered residue of a previously accumulated oil based on maturity and migration modelling it appears that the oils essentially migrated from active upper miocene recent kitchens in the cretaceous source rocks below the main thrusts the highly altered residue was formed during the upper miocene by the biodegradation of oil migrating during the middle and upper miocene large areas of mature to overmature cretaceous source rocks now exposed in the interior mountain front were in active oil kitchens during the lower and middle miocene before being involved in thrusting around 12 myr bp long distance 150 300 km southward lateral migration of oils during the middle miocene gave rise to the altered moderately mature marine oils in the shallow miocene stratigraphic reservoirs of cerro negro orinoco oil belt in the southern fringe of the subbasin

satellite derived rain rates in vertically sheared tropical cyclones 1 when tropical cyclones interact with environmental vertical wind shear they often take on an asymmetric structure prior observational and modeling studies have identified a preference for rainfall enhancement in the directions that are down shear and also to the left of the shear vector in the northern hemisphere this study composites hundreds of snapshots of the rain fields for atlantic tropical cyclones between 1988 2004 taken from satellite borne passive microwave radiometer estimates quadrant mean rain rates are fairly symmetrical in weakly sheared hurricanes for cases with shear greater than 10 m s 1 the favored downshear and left of shear quadrants have a factor of two greater rain rates in the inner core than the non favored quadrants beyond 100 km from the center this asymmetry increases to a factor of four or more the magnitude of the asymmetry is greater for tropical storms although the mean rain rates are less

using an object based approach to quantify the spatial structure of reflectivity regions in hurricane isabel 2003 part i comparisons between radar observations and model simulations abstractwhen a hurricane undergoes extratropical transition et its rainbands evolve from a circular and compact shape to a more elongated fragmented and dispersed configuration with an exposed circulation center this study calculates five metrics to measure these spatial changes in reflectivity regions as hurricane isabel 2003 underwent et a mosaic of observations from the weather surveillance radar 1988 doppler wsr 88d network is compared to reflectivity simulated by the advanced research weather research and forecasting wrf arw model six simulations are performed by varying the cumulus and microphysics parameterizations to produce a range of reflectivity configurations a bias correction is applied to model simulated reflectivity prior to the calculation of spatial metrics because lower reflectivity values are generally underrepresented while higher values are generally overrepresented however the simulation with kain fritsch cumulus and morrison two moment microphysics overpredicts ref

sensitivity of simulated tropical cyclone structure and intensity to horizontal resolution abstract the weather research and forecasting wrf model is used to test the sensitivity of simulations of hurricane ivan 2004 to changes in horizontal grid spacing for grid lengths from 8 to 1 km as resolution is increased minimum central pressure decreases significantly by 30 hpa from 8 to 1 km grid spacing although this increase in intensity is not uniform across similar reductions in grid spacing even when pressure fields are interpolated to a common grid this implies that the additional strengthening of the simulated tropical cyclone tc at higher resolution is not attributable to sampling but is due to changes in the representation of physical processes important to tc intensity the most apparent changes in simulated tc structure with resolution occur near a grid length of 4 km at 4 km grid spacing and below polygonal eyewall segments appear suggestive of breaking vortex rossby waves with sub 4 km grid lengths localized intense updraft cores within the eyewall are numerous and bo

secondary porosity creation of enhanced porosities in the subsurface from the dissolution of carbonate cements as a result of cooling formation waters abstract theoretical calculations indicate that the cooling of pore waters initially in equilibrium with a carbonate mineral can result in the water becoming undersaturated with respect to that mineral if the formation water has an initial ph below 6 9 then cooling will result in a water with a considerable potential to leach calcite the temperature of formation waters may be forced to decrease where faults act as major vertical migration pathways for waters escaping from a compacting basin where faults cease to act as permeable pathways the escaping formation water may be forced through an aquifer in a partly carbonate cemented aquifer the cooled formation waters are capable of dissolving the carbonate minerals and creating porosities that are higher than would otherwise be expected on the basis of burial depth

facies and petrophysical signature of the tournaisian visean lower carboniferous sea level cycle in carbonate ramp to basinal settings of the wales brabant massif british isles we studied the relationships between stratigraphic distribution of outcrop spectral gamma ray magnetic susceptibility and carbonate facies stacking patterns across the regionally significant transgressive regressive cycle at the tournaisian visean boundary tn v early carboniferous in southern great britain and ireland south wales north staffordshire and dublin basin the tn v boundary coincides with a prominent climatic pulse connected with the late paleozoic glaciation of gondwana the aim was to correlate the gamma ray and magnetic susceptibility log patterns in carbonate ramp and basin settings and discuss the global regional nature and magnitude of this transgressive regressive cycle a robust ramp to basin correlation was produced based on the log patterns facies stacking patterns and foraminifer biostratigraphy the concentrations of k and th the clay gamma ray values and partly magnetic susceptibility are dependent on facies and show systematic changes along the inferred bathymetric profile from inner ramp to outer ramp and basin a model of carbonate productivity driven dilution of fine grained siliciclastics in caco3 as the major control on the petrophysical patterns is discussed the cleaning up and cleaning down petrophysical trends are related to down dip and up dip shifts of the carbonate factory with changing relative sea level in middle to outer ramp and basin settings this generates petrophysical trends just opposite to paleozoic carbonate shelves where peaks in magnetic susceptibility are known to be associated with peak regressions a distinct late tournaisian to early visean regressive to transgressive cycle with a prominent sequence boundary located close to the tn v stage boundary can be seen in the sections glacioeustatic origin of the sequence boundary is inferred from its correlation with tn v boundary sections from europe carbon isotope data from south china and the glacial deposits in the southern hemisphere mentioned by previous authors

black shale formation in the late paleocene early eocene arctic ocean and paleoenvironmental conditions new results from a detailed organic petrological study abstract the study of particulate organic matter om in arctic ocean sediments from the late cretaceous to the eocene iodp expedition 302 has revealed detailed information about the aquatic marine om fluxes biological sources preservation and export of terrestrial material here we present detailed data from maceral analysis vitrinite reflectance measurements and organic geochemistry during the campanian paleocene fluxes of land derived om are indicated by reworked and oxidized macerals vitrinite inertinite and terrigenous liptinite cutinite sporinite in the early eocene drastic environmental changes are indicated by peaks in aquatic om up to 40 45 lamalginite telalginite liptodetrinite dinoflagellate cysts and amorphous om up to 50 bituminite these events of increased aquatic om flux similar to conditions favoring black shale deposition correlate with the global 13c events paleocene eocene thermal maximum petm and elmo event freshwater discharge and proximity of the source area are documented by freshwater algae material pediastrum botryococcus and immature land plant material corphuminite textinite we consider that erosion of coal bearing sediments during transgression time lead to humic acids release as a source for bituminite deposited in the early eocene black shales

effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries deduced from trmm abstract vertical wind shear and storm motion are two of the most important factors contributing to rainfall asymmetries in tropical cyclones tcs global tc rainfall structure in terms of azimuthal distribution and asymmetries relative to storm motion has been previously described using the tropical rainfall measuring mission microwave imager rainfall estimates the mean tc rainfall distribution and the wavenumber 1 asymmetry vary with storm intensity and geographical location among the six oceanic basins this study uses a similar approach to investigate the relationship between the structure of tc rainfall and the environmental flow by computing the rainfall asymmetry relative to the vertical wind shear the environmental vertical wind shear is defined as the difference between the mean wind vectors of the 200 and 850 hpa levels over an outer region extending from the radius of 200 800 km around the storm center the wavenumber 1 maximum rainfall asymmetry is downshear left right in the northern

sequence sequence stratigraphy sea level changes and depositional systems in the cambro ordovician of the north china carbonate platform abstract the cambro ordovician strata in north china were deposited over a very extensive craton extending some 1500 km east west and 1000 km north south the dominantly shallow water carbonate succession reaches up to 2000 m in thickness and two megasequences transgressive regressive cycles can be distinguished lower cambrian through lower ordovician strata and middle through upper ordovician strata separated by a major palaeokarst the first megasequence consists of nine sequences which are generally 50 150 m in thickness the lower cambrian sediments consist of phosphorites and phosphatic sandstones deposited during the flooding of the craton carbonates mudrocks and evaporites were deposited in the early cambrian under an arid climate laying the foundation for the subsequent long period of shallow water carbonate deposition which lasted some 70 m y the middle and lower upper cambrian sequences consist predominantly of mudrocks and storm deposits tempestites in the lower part and oolitic grainstones and tidal flat lime mudstones in the upper part these represent outer mid and mid inner ramp depositional systems respectively of the transgressive and highstand systems tracts these sequences have strong similarities with the grand cycles in the cambro ordovician successions of north america in the upper cambrian there is a distinctive unit of glauconitic purple red mudstone several metres thick which is interpreted as the deposits of the maximum flooding of the first megasequence in the upper cambrian there was a phase of tilting of the north china carbonate platform to the north and storm deposits especially intraclastic conglomerates and hummocky cross stratified grainstones packstones were very common at this time also common in upper middle and lower upper cambrian strata are stromatolitic thrombolitic bioherms several metres in diameter the upper upper cambrian through lower ordovician strata are dominantly fine grained limestones and dolomites deposited in shallow subtidal and inter to supra tidal environments on a low energy epeiric sea platform this part of the succession is the regressive part of the first megasequence so that overall the platform shows an evolution from platform initiation to platform foundation to a ramp depositional system and then an extensive epeiric platform on a small scale the succession is composed of metre scale shallowing upward cycles parasequences arranged into cycle sets of 10 30 m thick the middle upper ordovician megasequence consists mostly of shallow water carbonates with several thick evaporite units minor palaeokarsts and palaeosoils separate the sequences which are composed of metre scale cycles regional uplift affected the north china platform in the ordovician and sedimentation did not resume until the carboniferous there is a good correlation of the two transgressive regressive megasequences described here with the global 2nd order relative sea level curve for the cambro ordovician

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

late dinantian palaeokarst of england and wales implications for exposure surface development palaeokarst is an important feature of late dinantian exposure surfaces soil filled depressions are widely developed these are comparable to modern day solution dolines and were probably interspersed by areas of relatively bare limestone pavement the palaeokarst primarily exhibits a smooth mamillated to potholed surface form consistent with its formation beneath a soil cover areas between the depressions have been extensively stylolitised and would likely have originally been characterized by small scale fretted and sculpted karren forms typical of subaerial karstification palaeokarst pits making up the depressions are thought to have been initiated through stem flow drainage from trees rain water intercepted by the crown of the tree was concentrated at specific sites on the emergent surface and dissolution beneath the trunk produced cylindrical pits that propagated vertically downwards trees responsible for concentrating drainage may also have enhanced the acidic nature of the rain water through leaching of organic acids from foliar and woody tissues downward propagation of the pits was limited to the uppermost 1 2 m and enlargement primarily occurred through lateral amalgamation of adjacent pits once initiated continued development of the depressions would have been self perpetuating the preferential accumulation of volcanic ash and organic matter enhancing water retention and encouraging further vegetation growth in contrast intervening areas would have been characterized by slow vertical denudation only karstification likely took of the order of a few hundred years in the case of potholed palaeokarstic surfaces formed solely by stem flow drainage to a few tens of thousands of years where the palaeokarst is more mature

reflectance measurements of zooclasts and solid bitumen in lower paleozoic shales southern scandinavia correlation to vitrinite reflectance abstract reflectance measurements have been carried out on zooclasts graptolites chitinozoans and vase shaped microfossils and other organic particles vitrinite like particles porous granular vitrinite like particles and solid bitumen in middle cambrian to upper silurian shales from central and southern sweden and the danish island of bornholm baltic sea the most abundant organic components in all the shales are fragments of graptolites and vitrinite like particles the reflectance distribution of these two types of components is largely identical and it is suggested that the vitrinite like particles are fragments of graptolites without any recognizable morphology reflectance measurements of graptolites and vitrinite like particles yield well defined reflectance populations in samples with average r graptolite and average r vitrinite like of 0 75 r o the reflectance distributions are bimodal because of increasing bireflectance and the average reflectance value of the well defined lower reflecting population is arbitrarily used as maturity indicator our results suggest that with increasing thermal maturity the reflectance of graptolites increases faster than the predicted vitrinite reflectance the relationship between graptolite reflectance and equivalent vitrinite reflectance can be expressed by the equation vr eqv 0 73 r graptolite vitrinite like low 0 16 the gas generation window which normally is considered to begin at a vitrinite reflectance of 1 3 r o in post lower paleozoic rocks containing vitrinite starts accordingly at 1 56 r o graptolite reflectance porous granular vitrinite like particles occur in minor amounts and they may represent graptolite fragments with a non smooth surface they generally yield slightly higher reflectance than non granular vitrinite like particles and graptolite fragments the middle cambrian to furongian upper cambrian shales may contain sparse fragments of vase shaped microfossils vsm that seem to follow the maturation trend of chitinozoans in the present sample set the reflectance of chitinozoans and vsm is comparable to that of graptolites at the same level of maturity reflectance measurements of solid bitumen are a poor maturity indicator probably because bitumen can have various origins and morphologies and it may not be indigenous to the host rock

the effect of a river delta and coastal roughness variation on a landfalling tropical cyclone 1 numerical simulations on an f plane are performed using the weather research forecasting wrf model to study how the presence of a river delta and variations in coastal roughness might affect the motion and the structure of a tropical cyclone tc near landfall in each delta experiment an idealized triangular shaped delta pointing to the west with length 150 km and a river mouth size of 100 km is inserted along the coastline the surface roughness and the moisture availability of the delta vary among the delta experiments and the surface properties are uniform in the rest of the land area in another set of experiments where there is no delta the roughness of a whole land area has different values along the north south oriented coast results suggest that the tc in the control experiment ctrl with no delta or roughness variation along the coast is weaker than all the delta cases during a certain period before landfall moisture supply from the delta appears to have an effect on sustaining the approaching tc despite the relatively small scale of the delta tracks of the tcs in the roughness variation experiments deviate from that of the ctrl the roughness variation along the coast apparently affects the convergence patterns higher roughness induces stronger convergence and hence increases the vertical advection term in the potential vorticity tendency distribution over the rougher area hence a tc tends to move toward a region with higher roughness

solid bitumen as a determinant of reservoir quality in an unconventional tight gas siltstone play abstract in this study of the triassic montney tight gas siltstone play in the western canadian sedimentary basin petrophysical measurements of drill core samples porosity pore throat size water saturation and grain size are integrated with rock eval toc data organic petrography observations and sem imaging to show that reservoir quality in the gas window is strongly influenced by the pervasive presence of pore occluding solid bitumen and pyrobitumen at higher thermal maturity the solid bitumen formed as a pore filling liquid oil phase that was diagenetically and thermally degraded with further burial and increase in temperature the proportion of solid bitumen filling the intergranular paleopore network can be expressed as bitumen saturation and this attribute is found to be the dominant control on pore throat size and absolute permeability the samples with low bitumen saturation and large pore throat radius 0 01 m have water saturations that generally increase as pore throat size diminishes a relationship consistent with capillary theory for conventional water wet conditions the samples with high bitumen saturation and small pore throat radius

solid bitumen in calcite veins from the natih formation in the oman mountains multiple phases of petroleum migration in a changing stress field abstract solid bitumen in calcite veins in natih limestone on the southern flank of the jebel akhdar anticline provide evidence for at least two previously unrecognized petroleum migration events in the oman mountains we present field observation of bituminous calcite veins combined with microscopy using highly polished thin sections this allows imaging of solid bitumen in reflected light and study of its microstructural context in transmitted light straight and en echelon black impregnated bedding normal natih a calcite veins strike 110 they formed as one of the earliest structures in an extensional stress regime at the end of cretaceous turonian santonian either by flexure of the arabian plate wasia aruma break or by subsidence during subduction the veins always contain planar arrays of small during the first migration event microfracturing during obduction of the semail ophiolite and emplacement of the hawasina thrust sheets in santonian campanian times formed pathways for oil into the veins mosaic type solid bitumen formed during further vein growth it has a higher solid bitumen reflectance br r 3 40 3 76 combined with a high optical anisotropy compared to the underlaying thermally overmature natih b source rock br r 3 10 3 14 the higher reflectance of mosaic type solid bitumen is interpreted to result from deformation and does not reflect maximum burial temperatures which are inferred to have been about 225 c the second migration event is indicated by low reflective homogeneous type solid bitumen with palaeotemperatures br r 0 86 0 92 about 145 c lower than maximum burial it occurs along pressure solution seams which cross cut the veins showing that this is the latest event in the paragenetic sequence interpreted to have formed after lateral intraformational oil migration from the active natih oil kitchen located approximately 40 km sw of the study area during doming and uplift of the oman mountains in oligocene to pliocene times

algal bloom episodes and the formation of bituminite and micrinite in hydrocarbon source rocks evidence from the devonian and mississippian northern williston basin canada organic petrology incident light microscopy of middle devonian inter reef laminates and devonian mississippian epicontinental black shales williston basin canada indicates that algal bloom episodes and consequential bacterial activity played a significant role in the accumulation of amorphous bituminite iii rich organic microfacies corpohuminite like algal akinete cells produced by filamentous algae during algal bloom periods are persistent maceral inclusions within the potential hydrocarbon source rock intervals these cells ro mean range 0 24 0 90 are regarded as positive indicators of stressful palaeoenvironmental conditions unicellular tasmanites and leiosphaeridia marine alginite and variably degraded alginite remnants ghosts within the amorphous kerogen may be products of cell lysis photo oxidation and microbial alteration these processes are characteristic of algal bloom periods minute ca 1 m spheroidal and coccoidal bacteria like macerals are dispersed throughout the bituminite iii network attesting to the importance of microbial activity within the water column and sediment during and after organic matter accumulation dispersed granules laminations and replacement textures of micrinite like macerals within bituminite iii are interpreted as remnants of microbial alteration rather than a residual product of thermal maturation and hydrocarbon generation

microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in toarcian source rocks of different maturities abstract this study is part of a comprehensive research program on the generation and migration of petroleum from the organic rich posidonia shale lower toarcian jurassic of the hils syncline northern germany four cores of the complete posidonia shale with varying amounts of underlying pliensbachian and overlying aalenian mudstones provided the sample base depending upon their distance from a presumed subjacent heat source the vlotho massif the cores display progressive levels of increasing thermal maturation with r 0 values 0 48 0 68 0 88 and 1 45 which span the limits of the oil generation window primary stratigraphic lithologic and petrographic attributes of the four sections are all very similar each includes a lower marlstone member about 5 m thick overlain by 11 31 m of calcareous clay shale clay minerals calcite pyrite kerogen and quartz are the principal constituents thus there is no evidence that depositional conditions of the posidonia shale varied significantly over the sampled area the omnipresence of framboidal pyrite clearly formed from the activity of sulphate reducing bacteria at or near the depositional interface is strong evidence that uniform reducing anoxic conditions were persistent at all localities this conclusion supports the assumption that initially each section was identical in overall properties and that significant differences observed in geochemistry organic macerals and other properties are directly related to the variable levels of thermal maturation kerogen from the least mature section r o 0 48 is type ii and composed of alginite a alginite b liptodetrinite bituminite and some terrestrial sporinite vitrinite and inertinite macerals with increasing maturation the alginite macerals exhibit a progressive change in morphology and fluorescence properties alginite of the least mature section displays a strong green fluorescence at 0 68 r o alginite macerals exhibit yellow orange fluorescence and are structurally well preserved although geochemical data indicate generation and loss of large amounts of oil at 0 88 r o hydrocarbon generation is almost complete and few primary alginites remain they have been transformed into secondary liptinites designated as metaalginite which have similar fluorescence colours at the highest maturation level 1 45 r o metaalginites are only weakly fluorescent with a shift toward red colours calcite and or bitumen filled bedding plane micro and macrofractures occur exclusively in the organic rich posidonia shale at maturity levels of 0 68 r o and above such features are totally absent in the immature posidonia section and in the adjacent organic poor mudstones this observation indicates that the fractures developed in direct response to overpressuring i e pore pressure exceeding lithologic load related to oil and gas generation in the source rock the fractures undoubtedly provided important expulsion conduits for generated products

changes in optical properties of liptinite macerals from early mature to post mature stage in posidonia shale lower toarcian nw germany abstract detailed organo petrological analysis was carried out on core samples of posidonia shale lower toarcian from two wells which are located in northwestern germany lower saxony basin organic matter in one well is early mature vrr 0 5 whereas organic matter in the other is post mature vrr 3 5 results of organo petrological analyses demonstrate that telalginite tasmanales alginite in early mature oil shales appears brown to dark brown in reflected white light whereas in fluorescence mode it shows a yellow color of high intensity in contrast in post mature oil shales relics of former telalginite named postmature telalginite for the purposes of the maceral analysis occur in three forms of replacement of former telalginite bodies whose shape and size are preserved one form consists of a chain of carbonate crystals or of a completely recrystallized calcareous mass both are associated with homogeneous and heterogeneous migrabitumen the second form is completely composed of epigenetic pyrite the third form of postmature telalginite is rare and consists of impsonite in mature posidonia shale lamalginite is relative frequent and has been encountered in three forms discrete 10 m and layered in post mature posidonia shale all these forms are no longer recognizable part of the micrinite dispersed in the mineral groundmass may have been derived from lamalginite in oil shales of early mature stage bituminite i is characterized by a very low reflectance and a brownish fluorescence color it often includes yellow fluorescent liptodetrinite and has indistinct lense shape on the contrary in post mature oil shales on the basis of morphology it appears as light gray lenses which consist of massive micrinite bituminite ii in early mature oil shales occurs as thick elongated homogeneous lenses and streaks associated with tiny carbonate crystals and with yellow brownish fluorescence often with greenish fluorescent oil expulsions in post mature oil shales postmature bituminite ii consists of a network of micrinite between tiny carbonate crystals apart from these common bituminites minor contents of other bituminites have been recorded sporinite in early mature oil shales has a very low reflectance and an orange brown fluorescence of moderate intensity in post mature oil shales sporinite shows reddish orange internal reflections and is filled with pyrite crystals or with weak fluorescing minerals which emphasize the sporinite form this study demonstrates that the use of the terms postmature telalginite postmature bituminite and postmature sporinite in the macerals analysis of post mature oil shales is highly profitable particularly in understanding the transformation processes which are the result of the formation of secondary products secondary macerals and epigenetic minerals in the primary liptinite macerals

some optical characteristics of solid bitumen in visual kerogen preparations solid bitumen probably derived from liquid hydrocarbon can be identified in visual kerogen strewn slides or palynology slides this kind of material may have been previously identified as amorphous or structured kerogen organic matter in most petroleum source rocks is too dispersed to be studied in situ therefore it is isolated from the mineral matrix and concentrated to make strewn slides for optical study both insoluble and soluble bitumen may be observed in visual kerogen slides when no solvent extraction is used during sample preparation examination of a series of samples prepared both as thin sections and visual kerogen strewn slides led to the observation of solid bitumen in the strewn slides when an organic petrographer sees solid bitumen particles in visual kerogen slides they may be classified as either woody herbaceous coaly or most often amorphous kerogen types thompson and dembicki 1986 describe four kinds of amorphous kerogens optically and relate them to source rock hydrocarbon generating potential a fifth kind of amorphous kerogen is documented in this paper this material appears through the microscope as thin smooth brown flakes in transmitted light with a white to grey color in reflected light some of the particles appear to have the structure of the space between mineral grains where they form at this time it is not possible to identify the exact mode of origin of this material such as thermal alteration of oil gas deasphalting of oils or water washing and biodegradation of oils however the homogenous flowed appearance implies a liquid hydrocarbon origin therefore it is suggested that this kind of kerogen be called solid bitumen the petrographic documentation of solid bitumen in visual kerogen strewn slides can be very meaningful to organic geochemists and geologists because it may indicate that liquid hydrocarbons have been generated in or migrated through the rock interval of interest further study is needed to optically characterize the various stages of maturation of solid bitumen in visual kerogen preparations

solid bitumen bituminite and thermal maturity of the upper jurassic lower cretaceous chia gara formation kirkuk oil field zagros fold belt kurdistan iraq abstract the upper jurassic lower cretaceous chia gara formation a proven marine source rock characterised by predominance of amorphous organic matter aom is known from few outcrops in ne iraq and a number of exploration wells in the zagros fold belt this study presents comprehensive organic petrographic and mineralogical investigations of the dispersed organic matter and rock forming minerals of the tithonian berriasian chia gara formation intersected by the kirkuk well k 109 drilled in the giant kirkuk oil field ne iraq the organic petrographic analyses including incident light microscopy and confocal laser scanning microscopy clsm were applied to carbonate source rocks with low to moderate organic carbon contents our data demonstrate the predominance of bituminite and solid bitumen among the examined dispersed organic matter followed by oil exudates and oil globule inclusions as well as the presence of minor contributions of alginite i e tasmanites and leiospheridia liptodetrinite and vitrinite based on optical characteristics and clsm spectral fluorescence measurements examinations of bituminite point towards the presence of bituminite type iii the bituminite type iii encloses dark orange fluorescent amorphous components suggesting a genetic relationship either with liptodetrinite and or with solid bitumen the qualitative assessment of solid bitumen reveals several dissimilar forms identified in the analysed samples the photometric and spectral fluorescence measurements point to distinct reflectance values ranging between 0 19 and 0 43 sbrr and lambda max values extending from 515 nm to 590 nm respectively the corresponding results of the solid bitumen exhibit 1 a lack of a relationship with depth and 2 suggest its poor property as a reliable maturity indicator for the examined samples the presence of oil exudates oil globule inclusions and their association with solid bitumen suggests a genetic relation with the examined residues of liquid hydrocarbon phase the performed thermal maturities assessments of dispersed organic matter point towards early mature to peak mature oil window with vitrinite reflectance values ranging between 0 52 vrr at 2801 m to 0 83 vrr at 3089 m depth mineralogical analyses revealed the predominance of calcite over dolomite in the examined limestone to marl lithofacies e g clear rimmed dolomite with localised intensive dolomitisation in the phyllosilicate rich matrix predominance of calcite and siderite is observed followed by zinc blende and pyrite the composition of organic matter in the examined chia gara formation with predominance of bituminite and solid bitumen makes the major marine source rock of iraq s cretaceous petroleum systems distinctive in terms of hydrocarbon generation and migration at an oil window stage as it provides suitable explanations for its generally low hydrogen index hi with only minor terrestrial input in addition the results presented herein can be helpful for future evaluation of thermal maturities and characterisation of optical appearances of dispersed organic matter in carbonates by incident light microscopy and especially by clsm during hydrocarbon prospecting

hurricane vortex dynamics during atlantic extratropical transition abstract simulations of six atlantic hurricanes are diagnosed to understand the behavior of realistic vortices in varying environments during the process of extratropical transition et the simulations were performed in real time using the advanced research weather research and forecasting wrf model arw using a moving storm centered nest of either 4 or 1 33 km grid spacing the six simulations ranging from 45 to 96 h in length provide realistic evolution of asymmetric precipitation structures implying control by the synoptic scale primarily through the vertical wind shear the authors find that as expected the magnitude of the vortex tilt increases with increasing shear but it is not until the shear approaches 20 m s 1 that the total vortex circulation decreases furthermore the total vertical mass flux is proportional to the shear for shears less than about 20 25 m s 1 and therefore maximizes not in the tropical phase but rather during et this has important implications for predictin

late chadian early arundian high resolution biostratigraphy in the ogmore by sea section south wales mendip shelf and the mid avonian unconformity the study of the foraminiferal fauna in the ogmore section in south wales produced a detailed late chadian early arundian biostratigraphy and sequence stratigraphy with a higher resolution than in the arundian stratotype in hobbyhorse bay the earliest visean late chadian pedogenic horizon close to the gully oolite and caswell bay mudstone boundary mfz9 corresponds to the mid avonian unconformity the entry of primitive archaediscids of mfz10 within the caswell bay mudstone is followed by more advanced archaediscids of mfz11 at the base of the high tor limestone the mid avonian unconformity at the chadian arundian boundary is not confined to the london brabant massif but is also present in central europe the east european platform the urals west siberia and probably also in kuzbass and north america the global extent of the the mid avonian unconformity suggests that it is a consequence of early to mid visean glacioeustacy

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

ramp sedimentation in the dinantian limestones of the shannon trough co limerick ireland abstract during the late chadian and arundian lower carboniferous an extensive carbonate ramp limerick ramp developed over county limerick southwest ireland dipping northwestwards three distinct facies can be recognised corresponding to position on this ramp inner mid and outer ramp the inner ramp facies of oolitic and crinoidal grainstones herbertstown limestone formation in east limerick formed a major shoal behind which peritidal limestones were deposited the mid ramp facies of muddy bioclastic limestones and shales cooperhill facies in north limerick formed between fairweather and storm wave bases the outer ramp basinal facies of mudstones and thin graded resedimented limestones rathkeale beds in west limerick developed below storm wave base when fine terrigenous input was high later in the arundian there was progradation of the nearshore oolitic and crinoidal grainstones over the mid ramp facies by the holkerian the deep water basinal facies in west limerick was buried beneath mid ramp facies durnish limestone the initiation of the limerick ramp is closely related to the formation of the shannon trough in the late courceyan accelerated subsidence in the shannon area during deposition of waulsortian facies marked the onset of a sag phase following a quiescent period in early chadian subsidence was renewed in the late chadian and arundian when major facies changes occurred on the ramp comparison of the shannon trough with the dublin basin shows that in the latter tectonic events in the chadian and arundian particularly syn sedimentary faulting created a sharp division between platform and basinal sedimentation such tectonic influence is not recognised in the shannon trough here differential subsidence and eustatic sea level changes led to more permanent ramp existence modified only by westwards progradation

facies sequences on a carbonate ramp the carboniferous limestone of south wales during early carboniferous times a major sea level rise led to the development of an extensive carbonate ramp over what is now south wales differential subsidence and sea level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho tectonic settings inner mid and outer ramp the inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence the sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments the peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing up cycles the sequence contains many subaerial breaks and tectonic uplift resulted in base level changes and fluvial incision the mid ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base sedimentation periodically exceeded sea level rise and subsidence and regressive progradational oolitic sand bodies developed the thickest of which are stacked units with up to four individual sand bodies storm processes were of major importance in this setting the outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major waulsortian reef mounds also developed none of the shallowing phases seen in the other ramp zones can be detected in this sequence subsidence and eustatic sea level rise seem to have been the major controls on deposition but the recognition of eustatic sea level falls is difficult the detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record

organic petrographic investigations of the kupferschiefer in northern germany abstract results of an organic petrographic study of the kupferschiefer zechstein upper permian in northern germany are presented because vitrinite occurs only sporadically in this black shale the random reflectance r r of a relatively high reflecting vitrinite like variety of bituminite was measured as a maturity parameter and the problems connected with this procedure were investigated the main organic component is bituminite generally with an abundance of more than 90 sporomorphs and algae are relatively scarce inertinite is usually a trace component and vitrinite is present only in some samples taken close to the coast of the zechstein sea migrabitumen also occurs in small amounts in a few samples the range of the bituminite reflectance values is often considerable and depends on rank anisotropy particle size porosity and shearing interpretation of the reflectance values is made difficult by differences of up to 0 4 r r between layers within the kupferschiefer hydrothermal alteration may also be present the difference between the reflectance of the light and normal varieties of bituminite disappears between 0 9 and 1 2 r r bituminite behaves in a way very similarly to vitrinite during coalification their reflectance is identical between 2 and 4 r r below 2 r r the reflectance of bituminite is lower than that of vitrinite linear regression curves valid up to 4 r r were calculated for r max versus r r and for r r versus r max taking certain limitations into consideration bituminite reflectance may be used as a coalification parameter

aspects of generation and migration of hydrocarbons from coal bearing strata of the hitra formation haltenbanken area offshore norway abstract the haltenbanken area situated 150 200 km offshore mid norway is a proven gas condensate and oil producing province with continuing exploration potential in this structurally and stratigraphically complex area with multiple source rock possibilities we have examined the upper triassic lower jurassic hitra formation to determine its possible contribution to the hydrocarbon pools in the area the 400 m thick hitra formation consists of interbedded shales siltstones sandstones and coal seams in this study conventional cores of the hitra formation from depths varying from 2 4 and 4 6 km have been examined with the objective to obtain a better understanding of hydrocarbon generation migration and expulsion processes in these coals as function of variation in facies and maturity in addition to basic geochemical measurements toc rock eval and gc analysis of c15 saturated hydrocarbons microscopic studies normal and uv reflected light were carried out to determine the abundance and initial distribution of hydrogen rich macerals including fluorescent mobile phases such as exsudatinities geochemical and microscopal evidence was obtained suggesting that some of the interbedded sandstones show indications of impregnation by migrated hydrocarbons some bitumen filled micro fractures were observed extending from the coals towards the adjacent sands a preliminary interpretation of these data is that these fractures represent conduits carrying hydrocarbons from the coal seams towards the sandstones the role of the kerogen type variations on the amount of hydrocarbons generated and the mechanism and efficiency of hydrocarbon expulsion from the coals is discussed

late carboniferous tectonic subsidence in south wales implications for variscan basin evolution and tectonic history in sw britain detailed stratigraphic data have been used to backstrip seven sections from the carboniferous south wales coal basin resulting tectonic subsidence curves for the interval 319 305 ma namurian westphalian d are convex up indicating increasing subsidence rate with time with rates between 130 and 250 m ma 1 suggesting a foreland basin setting forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north northeasterly direction across sw england between 319 and 305 ma could have generated the backstripped subsidence patterns sensitivity tests show that while many of the forward model parameters are poorly constrained and the model results non unique backstripped subsidence patterns allow reasonable constraint on the different model cases so that model predictions can be treated as one possibility in a limited range the predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of sw england these results suggest that subsidence in other late carboniferous uk basins may also have been influenced by flexure due to a propagating orogenic load

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

the effect of organic matter type and organic carbon content on rock eval hydrogen index in oil shales and source rocks abstract the amount of gas prone kerogen woody fungal and inert and the organic carbon content toc are the two predominant factors affecting the hydrogen index hi in the 226 samples of lacustrine and marine oil shales and source rocks studied hi decreases as a function of the amount of gas prone kerogen and increases as a function of toc in addition the type of amorphous kerogen influences the hydrogen index and this can be roughly estimated from the fluorescence intensity of the amorphous kerogen nearly eighty percent of the variation in hi in these samples can be accounted for by the percentage of gas prone kerogen the toc content and the fluorescence of the amorphous kerogen in a multiple regression analysis hydrogen index increases as a function of toc up to about 10 toc the relationship can be approximated by a quadratic equation and then levels off a possible explanation for this is that the capability of a rock to generate and expel hydrocarbons during pyrolysis increases with toc when the retention capacity of the rock matrix is saturated at about 10 toc further increases in toc have no effect on hi it is also possible that the quality i e oil proneness of the amorphous kerogen is poorer in low toc samples than in high toc samples the samples came from the following oil shales and source rocks rundle queensland eocene miocene mae sot northwestern thailand eocene pliocene river river northwestern colorado eocene toolebuc western queensland late albian the posidonienschiefer southwestern germany toarcian an argentinian lacustrine deposit eocene miocene the kimmeridgian sections from four north sea wells blocks 21 30 and 210 monterey shale california miocene and sections from six wells from the alaskan tertiary north slope north aleutian shelf navarin basin norton sound most samples appear to be thermally immature t a i less than 1 8 ro less than 0 6 so they should be considered only potential source rocks the lacustrine oil shales have a higher conversion ratio yeild toc or s1 s2 toc than do the marine oil shales in samples with only amorphous and algal kerogen these in turn have a higher conversion ratio than the marine source rocks these differences are roughly reflected in the fluorescence intensity of the amorphous kerogen free hydrocarbons are higher in the marine source rocks than in the marine oil shales and are lowest in the lacustrine oil shales

geochemical and petrographic characterization of late jurassic early cretaceous chia gara formation in northern iraq palaeoenvironment and oil generation potential the marine late jurassic to early cretaceous chia gara formation is well exposed in northern iraq it is built of organic rich limestones and calcareous shales the organic rich sediments have been investigated to determine the type and origin of the organic matter as well as their petroleum generation potential kerogen microscopy shows that these sediments are characterized by large amounts of predominantly amorphous organic matter with a total organic carbon content of 7 42 the large amounts of organic matter are mainly due to good preservation under anoxic conditions as evidenced by numerous pyritized fragments and biomarkers that are diagnostic for the depositional environment the investigated biomarkers are characterized by a dominance of low to medium molecular weight compounds a low pr ph ratio 1 0 a composition of c27 c29 regular steranes and the presence of tricyclic terpanes indicating a strong decay of marine organic matter preserved under reducing conditions a small amount of terrigenous organic matter is according to the n alkane distribution also present the chia gara sediments thus have a high oil but a low gas generation potential due to the high content of hydrogen rich type ii and mixed type ii iii kerogens with a minor contribution of type iii kerogen

the impact of horizontal grid spacing on the microphysical and kinematic structures of strong tropical cyclones simulated with the wrf arw model abstract using the advanced weather research and forecasting numerical model the impact of horizontal grid spacing on the microphysical and kinematic structure of a numerically simulated tropical cyclone tc and their relationship to storm intensity was investigated with a set of five numerical simulations using input data for the case of hurricane rita 2005 the horizontal grid spacing of the parent domain was systematically changed such that the horizontal grid spacing of the inner nest varied from 1 to 5 km by an increment of 1 km this while keeping geographical dimensions of the domains identical within this small range of horizontal grid spacing the morphology of the simulated storms and the evolution of the kinematic and microphysics field showed noteworthy differences as grid spacing increased the model produced a wider more tilted eyewall a larger radius of maximum winds and higher amplitude low wavenumber eyewall asymmetries the coarser resolution simulations also produced larger v

maturity studies and source rock potential in the southern sverdrup basin arctic canada abstract the purpose of the study is to better understand the relationship between organic matter optical properties and the presence of potentially large oil and gas accumulations in arctic canada the type and thermal maturity of the dispersed organic matter of the mesozoic formations in the southern sverdrup basin melville island have been studied using organic petrology and rock eval pyrolysis all types of organic matter are present in the strata of mesozoic age hydrogen rich liptinite is dominated by alginite botryococcus and tasmanites dinoflagellate cysts and amorphous fluorescing matrix sporinite cutinite resinite and liptodetrinite made up the lesser hydrogen rich exinite vitrinite reflectance in cretaceous sediments ranges from 0 36 to 0 65 ro in jurassic sediments it ranges from 0 40 to 1 0 ro and in the triassic from 0 45 to 1 30 ro showing an overall increase with depth of burial cretaceous sediments of the deer bay formation are thermally immature and contain organic matter of terrestrial origin the upper jurassic shales of the ringnes formation contain predominantly organic matter of liptinitic and exinitic origin with a considerable vitrinitic input at optimum maturation levels potential source beds of this formation would have a good hydrocarbon generating potential the hydrocarbon potential however would be limited to the generation of gases due to the leanness of the source rocks parts of the lower jurassic jameson bay formation are organic rich and contain a mixed exinitic vitrinitic organic matter botryococcus colonial algae but visible organic matter is dominated by high plant remains mainly spores the schei point group shales and siltstones contain organic matter of almost purely marine origin whereas the predominantly higher plant derived organic matter found in the deer bay jameson bay and partly in the ringnes formations have higher toc among the schei point group samples the cape richards and eden bay members of the hoyle bay formation are richer in toc 2 0 than the murray harbour formation cape caledonia member this may reflect differences in the level of maturity or in the depositional environment more anoxic conditions for the former regional variations in the level of thermal maturity of mesozoic sediments in sverdrup basin appear to be a function of burial depth the mesozoic formations thicken towards the basin centre nne direction reflecting the general pattern of increasing thermal maturity north of sabine peninsula however the regional thermal maturation pattern of the mesozoic is not solely a reflection of the present day geothermal gradient which indicates that anomalous zones of high geothermal gradient may have existed in the past at least since when the mesozoic sediments attained maximum burial depth the contour pattern of the regional variation of maturity at the base of numerous triassic formations is similar to that of the structural contours of the sverdrup basin indicating that present day maturation levels are largely controlled by basin subsidence

palynofacies and source rock potential of jurassic sequences on the arruda sub basin lusitanian basin portugal abstract the study of the organic matter present in sedimentary rocks is fundamental for the characterization of the potential source rocks as well as to define the depositional paleoenvironments parameters of organic petrology and organic geochemistry and their variations along sedimentary successions are essential tools to achieve these goals two borehole successions freixial 1 and benfeito 1 from arruda sub basin lusitanian basin that comprise siliciclastic carbonate deposits of jurassic age have been studied in order to characterize the organic matter and its vertical variability as well as its hydrocarbon potential palynofacies and geochemical data indicate both marine including zooclasts and terrestrial organic matter where the phytoclasts predominated despite an important contribution of the amorphous organic matter aom different types of solid bitumen were observed most of the analyzed samples have total organic carbon content toc lower than 1 wt and hydrogen index hi values lower than 100 mghc g toc revealing types iii and iv kerogen however one set of samples exhibit toc values higher than 1 wt and higher hi values depicting a type ii kerogen the biomarker data showed a dominance of n alkanes with 15 30 carbon atoms having a unimodal distribution pristane phytane ratio varies between 0 04 and 1 84 indicating an alternation of oxic anoxic conditions along the sequences typical terpane distributions are characterized by the presence of tricyclic and tetracyclic terpanes as well as pentacyclic terpanes rare in carbonated samples from freixial 1 borehole the amount of 17 h 22 29 30 trisnorhopane tm usually exceeds the amount of 18 h 22 29 30 trinorneohopane ts the values of the ratio 22s 22s 22r epimers of c32 homohopanes revealed that most samples reached equilibrium values the 20s 20s 20r and isomerization ratios in c29 sterane calculated for the studied samples range between 0 19 0 61 and 0 20 0 70 respectively with several samples reaching the equilibrium values the vitrinite reflectance values are higher than 0 5 indicating that the organic matter reached the oil generation window according to the data obtained in this study the abadia montejunto cabacos and brenha formations can be considered potential source rocks of hydrocarbons gas and or oil in this section of the lusitanian basin