classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

effects of nonplastic fines on static liquefaction of sands des essais triaxiaux en compression non draines ont ete effectues sur des echantillons reconstitues de sable du nevada et d ottawa avec variation systematique de la teneur en fines particules inferieures a 0 074 mm afin d evaluer l effet de la fraction fine sur le potentiel de liquefaction statique lors d un chargement monotonique les fines etaient non plastiques les resultats indiquent clairement que la presence de fines peut augmenter considerablement le potentiel de liquefaction statique des quatre sables propres etudies lorsqu on utilise la technique du montage a sec avec un entonnoir les fines semblent creer dans le sol une structure particulaire tres compressible ce qui accroit ainsi le potentiel de liquefaction alors meme que la densite augmente accroitre la teneur en fines d un sable propre peut aboutir a l augmentation du potentiel de liquefaction jusqu a un seuil maximum pour lequel les fines dominent le comportement non draine du sol a ce point la le potentiel de liquefaction tend a devenir constant vis a vis de l indice de densite on a trouve que la liquefaction statique complete pouvait intervenir a un indice de densite superieur a 60 pour des teneurs en fines elevees

the western desert versus nile delta a comparative molecular biomarker study abstract the western desert and the nile delta are prolific petroleum producing basins the correlation and matching between their petroleum systems have been briefly studied overall geochemical and biological marker analyses of twelve crude oil and condensate samples taken from seven oil gasfields located in the nile delta and the western desert basins of egypt were effective in identifying and geographically defining two major oil families related by age and source rock depositional environment these samples were classified respectively as late cretaceous tertiary and jurassic early cretaceous the source rocks giving rise to the late cretaceous tertiary oils are associated with abundant terrestrial organic matter the source rocks giving rise to jurassic early cretaceous oil are presumably generated from a mixed terrestrial marine source meanwhile the western desert oil samples show prominent c 30 steranes elevated c 27 monoaromatic steroids and a distinct homohopane distribution suggesting this oil type is derived from a more marine influenced source rock than terrigenous sourced oil in the nile delta the most crucial geochemical fingerprinting biomarkers that have been used to differentiate between nile delta and the western desert oil are oleananes highly branched isoprenoids hbi sterane isomerization 24 norcholestanes aromatic steroid hydrocarbons and c 30 24 n propylcholestanes

aspherical structure of the core mantle boundary from pkp travel times maps of aspherical structure in the vicinity of the core mantle boundary have been constructed from a tomographic analysis of p df and p ab travel times in the distance range 150 180 these maps reveal long wavelength features not previously detected by mantle tomography the peak to peak amplitude of these features is on the order of 1 s in vertical travel time too large to be explained by conventional thermal boundary layer models or dynamically supported topography on the core mantle boundary we hypothesize the existence of one or more chemical boundary layers whose large scale accumulations on the surface of the core may in some ways be analogous to continents at the earth s surface

global anisotropy in the upper mantle inferred from the regionalization of phase velocities a data set of 2600 paths for rayleigh waves and 2170 paths for love waves was selected in order to resolve azimuthal anisotropy of surface waves in the period range 70 250 s the epicenters were chosen so that the paths provide uniform spatial and azimuthal coverage of earth a synthetic seismogram is computed for each path and compared to the observed seismogram in order to infer the phase velocity along each path to process such a large data set a new tomographic technique is designed a good correlation is found with surface tectonics in the whole period range for love waves and at shorter periods for rayleigh waves the directions of maximum velocities are also well correlated with plate tectonics motions for the 2 azimuthal term of rayleigh waves when the power spectrum of heterogeneities is computed it is found that for love waves the even orders are usually larger than the odd orders for rayleigh waves the degrees 2 and 6 dominate only at long periods suggesting a deep origin for these components

earthquake history of the sumatran fault indonesia since 1892 derived from relocation of large earthquakes abstract we map the fault planes of m 7 0 earthquakes along the sumatran fault in sumatra western indonesia for the period since 1892 to obtain precise hypocenter locations of large earthquakes and identify fault planes of m 7 0 earthquakes we relocated 27 m 6 0 earthquakes from 1921 to 2012 using the modified joint hypocenter determination method we found that six m 7 0 events appear to have occurred on segments of the sumatran fault as follows kumering for the 1933 m s 7 5 event the northwestern and southeastern parts of tripa for the 1935 m s 7 0 and 1936 m s 7 2 events respectively the southeastern half of sunda for the april 1943 m s 7 1 event ketaun for the first m s 7 3 event of the june 1943 doublet and suliti and sumani for the second m s 7 6 event of the june 1943 doublet we also identified the faults of four m 7 0 earthquakes between 1892 and 1920 by using information on crustal deformation and damage distributions from the results of earthquake locations between 1892 and 2012 and the corresponding fault lengths of m 7 0 earthquakes we have interpreted the large m 7 0 earthquake history of the sumatran fault for the past 120 years possible seismic gaps for m 7 0 earthquakes along the sumatran fault are the northern half of the sunda segment and the semangko dikit sianok barumun toru renun aceh and seulimeum segments

convection under a lid of finite conductivity in wide aspect ratio models effect of continents on the wavelength of mantle flow 1 mantle convection in the earth and mars are dominated by large scale flow and this can be due at least in part to the effect of thermally insulating continent like heterogeneities indeed the presence of a finitely conducting lid on top of a convective isoviscous fluid at infinite prandtl number induces the formation of a zone of hot upwelling centered beneath the lid and a large horizontal cellular circulation on each side of the lid in a previous paper this lateral cellular circulation was limited in size by the dimensions of the model we now use very large aspect ratio models in order for this circulation to be unhampered the large scale circulation consists of the constructive superposition of hot and cold plumes attracted to and expelled from respectively the conductive lid the width of the cellular circulation increases with the rayleigh number of the fluid and we propose a scaling law to explain this expansion scaling laws for the velocity of the plumes and heat transfer by this large scale circulation are also developed although the model used is much simpler than actual planetary mantles the driving mechanism for the large scale circulation must operate in a similar fashion important implications in terms of heat transfer can therefore be predicted

lateral heterogeneity and azimuthal anisotropy of the upper mantle love and rayleigh waves 100 250 s the lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring rayleigh and love wave phase velocities in the period range 100 250 s spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1 m 10 slow regions are evident at the east pacific rise northeast africa tibet tasman sea southwestern north america and triple junctions in the northern atlantic and indian oceans fast regions occur in australia western pacific and the southern atlantic these features are also found by a completely different analysis based on the backus gilbert method the backus gilbert method also shows that the obtained phase velocities are averaged values within an area of about 2000 km radius and the errors are about 1 of the phase velocity in the zeroth order spherically symmetric earth inversion for azimuthal dependence shows that for low angular order the fast phase velocity directions seem to correlate well with the plate motion vectors however resolution analysis by the backus gilbert method shows that the current data do not have enough resolution for everywhere on the globe only a few regions currently have adequate azimuthal coverage thus confirmation of the above correlation requires a more complete data set

the backus gilbert approach to the three dimensional structure in the upper mantle i lateral variation of surface wave phase velocity with its error and resolution summary the backus gilbert method is applied to obtain the phase velocity variations on a sphere from the measured phase velocity narrow peak kernels with radii of about 2000 km are obtained for almost everywhere on the sphere the phase velocity results are thus interpreted as an average within such regions the most trouble comes from the antipodal peak in the resolution kernel this is evaluated as contamination and is incorporated in the error estimation the total error which is a root mean square of contamination from the antipodal peak and statistical error estimated from the data covariance matrix is about 1 per cent of the phase velocity in the average earth model which is the preliminary reference earth model prem however there is about a factor of 2 variation of errors on the sphere maximum variations of phase velocity are about 3 4 per cent of the phase velocity in the average earth model and thus there still remain anomalies which exceed estimated errors the estimated errors correspond to one standard deviation under the assumptions of uncorrelated gaussian distribution for high confidence interval they show that statistically significant anomalies are scarce for the current data set generally love wave phase velocity maps show more resolved features than rayleigh wave maps and we can see in high confidence maps fast velocities in old oceans and old continents and slow velocities in tectonically active regions like the east pacific rise and various back arc regions

source rock characteristics and hydrocarbon generation modelling of upper cretaceous mukalla formation in the jiza qamar basin eastern yemen abstract the upper cretaceous mukalla coals and other organic rich sediments which are widely exposed in the jiza qamar basin and believed to be a major source rocks were analysed using organic geochemistry and petrology the total organic carbon toc contents of the mukalla source rocks range from 0 72 to 79 90 with an average toc value of 21 50 the coals and coaly shale sediments are relatively higher in organic richness consistent with source rocks generative potential the samples analysed have vitrinite reflectance in the range of 0 84 1 10 ro and pyrolysis t max in the range of 432 454 c indicate that the mukalla source rocks contain mature to late mature organic matter good oil generating potential is anticipated from the coals and coaly shale sediments with high hydrogen indices 250 449 mg hc g toc this is supported by their significant amounts of oil liptinite macerals are present in these coals and coaly shale sediments and py gc s 2 pyrograms with n alkane alkene doublets extending beyond nc 30 the shales are dominated by type iii kerogen hi one dimensional basin modelling was performed to analysis the hydrocarbon generation and expulsion history of the mukalla source rocks in the jiza qamar basin based on the reconstruction of the burial thermal maturity histories in order to improve our understanding of the of hydrocarbon generation potential of the mukalla source rocks calibration of the model with measured vitrinite reflectance ro and borehole temperature data indicates that the present day heat flow in the jiza qamar basin varies from 45 0 mw m 2 to 70 0 mw m 2 and the paleo heat flow increased from 80 ma to 25 ma reached a peak heat flow values of approximately 70 0 mw m 2 at 25 ma and then decreased exponentially from 25 ma to present day the peak paleo heat flow is explained by the gulf of aden and red sea tertiary rifting during oligocene middle miocene which has a considerable influence on the thermal maturity of the mukalla source rocks the source rocks of the mukalla formation are presently in a stage of oil and condensate generation with maturity from 0 50 to 1 10 ro oil generation 0 5 ro in the mukalla source rocks began from about 61 ma to 54 ma and the peak hydrocarbon generation 1 0 ro occurred approximately from 25 ma to 20 ma the modelled hydrocarbon expulsion evolution suggested that the timing of hydrocarbon expulsion from the mukalla source rocks began from 15 ma to present day

long wavelength s wave velocity structure throughout the mantle summary long wavelength s wave velocity anomalies are obtained for the entire mantle by inverting 6ooo long period 40 100s sh body waves and lo00 long period 100 500 s love waves in the shallow mantle the patterns of fast and slow velocity anomalies correlate well with age and tectonics in the depth range of 400 1000 km we find two antipodal fast velocity anomalies one in the western pacific and the other in south america they form a fairly strong i 2 anomaly moreover the 1 2 anomaly is the largest spherical harmonic component throughout the entire mantle except for in the layer of 1000 1300 km depth a fast velocity anomaly near the caribbean previously reported by several other investigators is found between the depths of 1000 and 1300km with diminishing amplitudes it can be traced to canada and the aleutians and may be related to old subducted slabs in the same depth interval similar size anomalies can be found in the middle of the pacific and in the indian ocean these could be checked by more detailed studies to judge the reliability of this study heterogeneity power has a peak at the surface and a secondary peak at the bottom of the mantle d consistent with the existence of chemical and or thermal boundary layers at the base of the mantle we also find a fast velocity anomaly which surrounds the pacific ocean this feature has been found by other researchers previously but its interpretation is difficult due to the trade off between velocity anomaly and core mantle boundary deformation

the effect of hot spots on the oceanic age depth relation hot spots located both midplate and on midocean ridges can bias the empirical age depth relation ocean floor bathymetry for seafloor greater than 80 m y b p in age has been previously used to determine if the oceanic lithosphere behaves as a cooling half space or as a cooling plate however large areas of the ocean basins do not fit a simple age depth relation anomalously shallow swells approximately 1000 km wide and 1 km high surround hot spots such as iceland the azores and the cape verde islands by sorting seafloor depth data by distance to the nearest hot spot track we show that the along isochron variation in depth in the north atlantic correlates with distance from a hot spot track due to the absence in the north atlantic of seafloor both old and far from hot spots we compare depth versus age at constant distance and do not observe flattening of the age depth relation in any distance range the age depth relation depth meters 2700 295 t m y 1 2 derived for seafloor 1200 to 1800 km from a hot spot track represents our best estimate of the age depth relation appropriate to seafloor unaffected by a hot spot track in the north atlantic the previously inferred flattening of the age depth relation appears to be caused by the inclusion of hot spot swells this implies that hot spots may be the primary means of heat transfer from the deeper mantle to the base of the lithosphere

petrographic composition and depositional environments of cretaceous coals and coal measures in the middle benue trough of nigeria abstract cretaceous coals and coal measure sequences in the area around the obi lafia part of the middle benue trough of nigeria were studied petrographically the turonian santonian awgu formation and the maastrichtian lafia formation constitute the sedimentary successions in both outcrop and borehole profiles of this area maceral analyses of 32 coal samples from this area allow subdivision of the coal beds into three different coal facies the vitrinite fusinite coal facies the trimaceritic coal facies and the shaly coal facies in the vitrinite fusinite coal facies vitrinite constitutes on average 67 3 liptinite 4 2 inertinite 17 1 and mineral matter 11 4 the trimaceritic coal facies has 42 3 vitrinite 22 4 liptinite 23 8 inertinite and 11 5 mineral matter in the shaly coal facies vitrinite constitutes 29 9 liptinite inertinite and mineral matter are 13 8 22 0 and 34 3 respectively correlation of the distribution of microfossils in the interseam sediments with the tissue preservation gelification groundwater and vegetation indices of the coal facies indicates that the vitrinite fusinite coal facies was deposited in wet forest swamp subenvironments along and within lagoons the trimaceritic facies was deposited in limno telmatic clastic marsh subenvironments in lower delta plains the shaly coal facies shows characteristics of various subenvironments but generally tends to be more marine than the other two facies

the empirical age depth relation and depth anomalies in the pacific ocean basin this paper presents a new age depth relation and a comprehensive depth anomaly map for the pacific ocean age depth and sediment thickness were averaged for each 1 1 area bathymetry was corrected for isostatic effects due to sediment and water load and for the variation of sound velocity in water seafloor existing at extreme distance from hot spot tracks is found to be anomalously deep hot spots were treated as thermal anomalies and data within 800 km of them were eliminated from further analysis an age depth equation was determined by fitting a least squares line to the remaining data the resulting depth versus age distribution confirms the linear dependence of depth on age up to 80 ma all older seafloor is within 800 km of hot spots or hot spot tracks and is shallower than predicted this flattening of the age depth distribution requires that a separate function be fit to data older than 80 ma as a result data representing the deepest seafloor older than 80 ma were selected for curve fitting and the age depth distribution was approximated by an exponential function it is impossible to distinguish between the infinite half space and cooling plate models of the lithopshere using the age depth data from the pacific ocean a depth anomaly map prepared by comparing observed depth with the depth predicted by the new age depth formula shows several newly recognized features including swells over the louisville ridge in the south pacific and in the gulf of alaska seamounts

depth and age in the north pacific the concept of the oceanic lithosphere as a cooling thermal boundary layer on top of a viscous upper mantle accounts for the increase in depth with age of the ocean floor analyses of the exact nature of this relation provide constraints on the rheology and structure of this layer in past studies problems with uncertainties of age and in sediment thickness have limited the value of this relation on older ocean floor in this study we evaluate different tectonic histories for the quiet zones and construct a revised isochron chart for the north pacific we check and modify the current sediment thickness charts using new deep sea drilling data and revised ideas concerning reflectors in the southwestern north pacific averaging the synbaps digital data base into half by half degree elements and correcting for sediment load we plot basement depth versus age for the entire north pacific because of the skewness in the data associated with seamounts we present the data as contours about the mode and find that two thirds of the observations lie within 300 m of this value on crust between 0 and 80 ma the ocean floor subsides with the square root of age on ocean floor older than 100 ma the depths in general flatten with age with areally correlateable swells and valleys the hawaiian and line island swells correlate positively and the mariana basin valley negatively with geoid height the flattening in the depths indicates that the thermal boundary layer has reached equilibrium conditions under older ocean floor further the correlation of the swells and valleys with geoid height presents evidence for organized convection in the upper mantle beneath older lithosphere in the north pacific

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

organic geochemical characteristics and depositional environments of the jurassic coals in the eastern taurus of southern turkey abstract in this study organic matter content type and maturity as well as some petrographic and physical characteristics of the jurassic coals exposed in the eastern taurus were investigated and their depositional environments were interpreted the total organic carbon toc contents of coals in the feke akkaya kozan gedikli and kozan kizilinc areas are 24 54 66 78 and 49 15 respectively the feke akkaya and kozan kizilinc coals have low hydrogen index hi values while the kozan gedikli coals show moderate hi values all coal samples display very low oxygen index oi values the kozan gedikli coals contain type ii organic matter om the feke akkaya coals contain a mixture of type ii and type iii om and the kozan kizilinc coals are composed of type iii om sterane distribution was calculated as c27 c29 c28 from the m z 217 mass chromatogram for all coal samples tmax values for the feke akkaya kozan gedikli and kozan kizilinc coals are 439 412 and 427 c vitrinite reflectance values ro for the feke akkaya and kozan kizilinc coal samples were measured as 0 65 and 0 51 and these values reveal that the feke akkaya and kozan kizilinc coals are at subbituminous a or high volatile c bituminous coal stage on the basis of biomarker maturity parameters these coals have a low maturity the pristane phytane pr ph ratios for the feke akkaya kozan gedikli and kozan kizilinc coals are 1 53 1 13 and 1 25 respectively in addition all coals show a homohopane distribution which is dominated by low carbon numbers and c35 homohopane index is very low for all coal samples all these features may indicate that these coals were deposited in a suboxic environment the high sterane hopane ratios with high concentrations of steranes low pr ph ratios and c25 c26 tricyclic ratios 1 may indicate that these coals formed in a swamp environment were temporarily influenced by marine conditions

geochemical characterisation of early cretaceous lacustrine sediments of bima formation yola sub basin northern benue trough ne nigeria organic matter input preservation paleoenvironment and palaeoclimatic conditions the bima formation is the oldest lithogenetic unit occupying the base of the cretaceous successions in the yola sub basin of the northern benue trough it is differentiated into lower b1 middle b2 and upper b3 bima members integrated organic and inorganic geochemical studies were applied on the lacustrine sediments of the bima formation with the aim of reconstructing the palaeodepositional environment and organic matter input in response to climate and tectonism the analysed sediments were deposited in a freshwater lacustrine environment with a low salinity stratified water column and suboxic to relatively anoxic conditions as indicated by the bulk geochemical parameters the biomarkers provide evidence for a contribution of aquatic algae and microorganisms with a significant amount of terrigenous organic matter input the preservation of the organic matter is possibly attributed to the stratified water column with low salinity and suboxic to relatively anoxic conditions based on the geochemistry of major and trace elements the sediments were deposited during semi arid climatic conditions within passive continental margin setting this agrees with the tectonic events in the west and central african rift system wcars during the early cretaceous period

aspherical earth structure from fundamental spheroidal mode data free oscillation data reveal heterogeneity in the earth s mantle whose geographical pattern is dominated by spherical harmonics of angular degree two and correlates well with the hydrostatically referenced geoid the heterogeneity can be modelled as localized in the transition zone 420 670 km depth and may be related to a large scale component of mantle convection

organic facies and maturation of jurassic cretaceous rocks and possible oil source rock correlation based on pyrolysis of asphaltenes scotian basin canada abstract this paper establishes source rock characterization and oil oil and oil source rock correlations of selected organic rich shale source rocks and selected light oils and condensates from jurassic and cretaceous formations of the scotian basin multiple source rocks of kerogen types iia oil prone iia iib oil and condensate prone iib condensate and gas prone iii gas prone and iv nonsource are identified in various stratigraphic horizons vitrinite reflectance and t inmax data indicate variable maturation histories in different parts of the basin which are related to differences in lithology related heat conductivity and the presence of older sediments closer to areas of rifting multiple linear regression and cluster analyses of aromatic hydrocarbon ratios reveal two oil families some kerogen type iib rock extracts match many of the light oil and condensates in terms of the aromatic hydrocarbon distributions a second family of oils could not be correlated with any of the analyzed source rock extracts pyrolysis gas chromatography of asphaltenes from the cohasset a 52 and sable island 3h 58 wells are significantly different in n alkane aromatics and phenol content the asphaltene pyrolyzates of samples from venture b 52 and s desbarres o 76 have a high aromatic content low content of n alkanes and high phenol values s desbarres which is typical of a terrestial source they correlate well with one another and also with sable island light oil the n triumph g 43 whole rock and extract asphaltene pyrolyzates are dominated by normal hydrocarbons with aromatic phenolic and thiophenic compounds in low concentrations suggesting an algal source algal type organic matter may have made a contribution to the cohasset petroleum as its asphaltene pyrolyzate is also dominated by normal hydrocarbons

organic geochemical characteristics and depositional setting of paleogene oil shale mudstone and sandstone from onshore penyu basin chenor pahang malaysia abstract the eastern chenor pahang area of the penyu basin contains an untapped potential in part due to poor knowledge of its organic facies characteristics the sedimentary succession of eastern chenor pahang area is dominated by fine to coarse grained sandstone occurring in association with oil shale and mudstone in a predominantly fining upward sequence detailed geochemical and petrographic characterization was carried out on oil shale and mudstone samples to evaluate the origin and type of organic matter om as well as the paleoenvironmental conditions and organic richness of the paleogene sedimentary succession the facies are only enriched in total organic carbon toc potential hydrocarbon yield s2 and extractible organic matter eom the types of organic matter are important index reflecting the potential of the source rock s based on elemental ratios the analyzed samples are shown to contain types i and ii kerogens this finding is supported by the high hydrogen index hi of 300 mg hc g toc and the presence of abundant liptinitic materials biomarker signatures n alkanes n c25 high c29 c30 17 h hopane ratios 0 8 3 3 and high c29 steranes 49 78 low total sulfur and v v ni ratio suggest a predominantly terrestrial source input with some contribution from aquatic microorganisms as indicated by the common occurrence of amorphous organic matter combining this results with n alkane patterns kerogen types and organic petrography predominance of c29 sterane probably indicates a contribution of aquatic organisms such as green and brown algae consistent with botrycoccus braunii race a and pediastrum contribution and some influence of higher plants om integration of biomarker studies with bulk geochemical and petrographic analysis suggests that the analyzed samples were deposited under suboxic conditions in a fresh water lacustrine environment this finding is corroborated by the ratios of pristane phytane v ni and sr br high bioproductivity and a stratified fresh water column with suboxic bottom water condition enhanced om preservation in the analyzed mudstone and shale facies the high om content in these samples maybe related to the fine grained matrix of the mud rocks and the paleoclimate in the area

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

steady state concepts and static liquefaction of silty sands the results from an experimental study on silty sands are presented and evaluated in view of the framework of critical state or steady state soil mechanics drained and undrained compression tests were performed on nevada sand containing nonplastic silt the drained and undrained steady state lines diverged this divergence was caused by the tendency for static liquefaction at low pressures results from undrained tests with different initial void ratios produced different steady state lines unique steady state lines may therefore not always exist for silty sands denser specimens liquefied at low confining pressures while looser specimens at higher confining pressures showed stable behavior thus a unique relation between void ratio and confining pressure namely the steady state line may not represent the behavior of loose silty sands this occurs because silty sands exhibit reverse behavior characteristics more dilative behavior is observed with increasing confining pressure under undrained shearing load and deformation control testing was performed to evaluate the effect of strain rate compressibility was examined as an alternative measure of liquefaction potential

anisotropy and shear velocity heterogeneities in the upper mantle long period surface waves are used to map lateral heterogeneities of velocity and anisotropy in the upper mantle the dispersion curves are expanded in spherical harmonics up to degree 6 and inverted to find the depth structure the data are corrected for the effect of surface layers and both love and rayleigh waves are used shear wave velocity and shear polarization anisotropy can be resolved down to a depth of about 450 km the shear wave velocity distribution to 200 km depth correlates with surface tectonics except in a few anomalous regions below that depth the correlation vanishes cold subducted material shows up weakly at 350 km as fast s wave anomalies in the transition region a large scale pattern appears with fast mantle in the south atlantic s anisotropy at 200 km can resolve uprising or downwelling currents under some ridges and subduction zones the pacific shows a nw se fabric

mapping convection in the mantle long period 100 250 sec love and rayleigh waves are used to map heterogeneity and azimuthal anisotropy in the upper mantle spherical harmonic descriptions of anisotropy up to l m 3 and 2 are derived azimuthal anisotropy obtains values as high as 1 there is good correlation of fast rayleigh wave directions with upper mantle return flow directions derived from kinematic considerations this is consistent with the a axis of olivine being aligned in the flow direction the main differences between the flow models and the rayleigh wave azimuthal variation maps occur in the vicinity of hotspots hawaii for example appears to perturb the return flow there is strong correlation of the geoid and surface wave velocity at l 4 and 5 slow regions at this scale are associated with geoid highs and high heat flow consistent with upwelling convective flow or with isostatically compensated regions of low density the correlation of azimuthal anisotropy with upper mantle return flow directions rather than with plate directions suggests that part of the return flow is in the upper mantle and this in turn implies a low viscosity channel

source rock characteristics depositional setting and hydrocarbon generation potential of cretaceous coals and organic rich mudstones from gombe formation gongola sub basin northern benue trough ne nigeria abstract the ongoing exploration activities at the maiganga coal mine uncover some missing gaps in the stratigraphy of the late cretaceous gombe formation therefore there is a need to further investigate this sequence including the organic facies variations and distributions of the coals mudstones and sandy shaly sediments in the gombe sandstone formation gongola sub basin northern benue trough of northeastern nigeria geochemical and petrographic methods were used to assess the organic matter source input paleodepositional conditions thermal maturity and hydrocarbon generation potential of the analysed maiganga and yaya ngari samples field observations showed four coal seams interbedded with mudstones and shales deposited in coarsening upward sequence of a deltaic environment evaluation based on the source rock analyses sra reveals that maiganga sedimentary facies is dominated by terrestrial source input of type iii kerogen this is supported by the biomarker study suggesting land plant origin for the organic matter with minor lacustrine and marine influences in maiganga that grades into predominantly mixed organic matter input of a transitional terrestrial to marine environment in the yaya ngari area this shows a progressive movement towards marine source input paleodepositional conditions of organic matters were sub oxic to oxic in maiganga while the mixed organic matters in yaya ngari were deposited in sub oxic conditions based on organic petrology and bitumen extraction data the maiganga coal was distinctly observed to be immature of pre oil generation window while the yaya ngari is in early oil generation window these analysed sediments are mainly gas prone based on the dominance of type iii kerogen although the presence of type ii iii kerogen supported by relatively higher hi may indicate gas oil potential for the maiganga coal on the other hand type iv kerogen dominated the yaya ngari samples this suggests that these shales are gas prone or do not possess any hydrocarbon generation potential as indicated by the very low hi values

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

the 3 d shear wave structure in the mantle by overtone waveform inversion ii inversion of x waves r waves and g waves summary the 3 d upper mantle structure from the surface of the earth to a depth of about 1000 km is obtained by inverting waveforms of fundamental and higher mode surface waves minor and major arc waves of r waves g waves and x waves higher mode wave packets are used as basic data two features of the solution seem fairly robust one is the shallow structure in the upper few hundred kilometres which is strongly correlated with the age of the crust the second feature is the deep fast velocity anomaly near the western pacific indonesia philippines and mariana region and its antipodal region of south america both of which are subduction zones which forms a strong l 2 pattern simple slab models with 100 km thicknesses of 10 per cent faster velocity material do not explain such large scale fast velocity anomalies this may indicate large scale deformation of the 670 km discontinuity piling up of slabs in the upper mantle or thickening lithosphere in the lower mantle or large horizontal motions of subducted material these results are stable whether an earth model 1066a or prem is used as a starting model

unusual biological marker geochemistry of oils and possible source rocks offshore beaufort mackenzie delta canada abstract tertiary oils and source rocks from the offshore beaufort mackenzie delta have been examined for their biological marker content the triterpane and sterane distributions suggest a predominant land plant contribution to the oils the oils range in maturity from extremely immature to moderately mature 18 h oleanne is a major triterpane of the oils together with probable bisnorlupanes and an excellent correlation is observed in the concentration of these components in individual oils an excellent correlation is also observed between the concentration of bisnorlupanes and oil maturity based on sterna and triterpane maturation parameters suggesting that the decrease in relative concentration of these components with increasing maturity is a result of progressive dilution by hydrocarbons generated by the cracking of kerogen only one formation in cores taken from the delta has been found to contain bisnorlupanes and were present they are the dominant hydrocarbons of the branched cyclic fraction

structure and evolution of lithospheric slab beneath the sunda arc indonesia tomographic imaging reveals seismic anomalies beneath the sunda island arc indonesia that suggest that the lithospheric slab penetrates to a depth of at least 1500 kilometers the sunda slab forms the eastern end of a deep anomaly associated with the past subduction of the plate underlying the mesozoic tethys ocean in accord with previous studies the lithospheric slab was imaged as a continuous feature from the surface to the lower mantle below java with a local deflection where the slab continues into the lower mantle the deep slab seems to be detached from the upper mantle slab beneath sumatra this complex slab structure is related to the tertiary evolution of southeastern asia and the indian ocean region

surface wave tomography for southeastern asia using iris farm and jisnet data abstract previous seismic studies for southeastern asia around indonesia have used global seismic data and thus included few regional broadband seismic stations to better understand seismic structure of this area we temporarily deployed japan indonesia seismic network jisnet which was composed of 23 broadband seismic stations in central to western indonesia since 1998 under the super plume project of japan in this study we analyse regional jisnet data and global incorporated research institute of seismology iris fast archive recovery method farm data in order to obtain detailed images of 3d s wave velocity vs of this area we use vertical component lp seismograms of farm data recorded from 1989 to 1993 13471 seismograms and vertical component of broadband jisnet data recorded from 1998 to 2000 1782 seismograms we select seismic events with body wave magnitudes greater than 5 5 and take hypocenters and centroid moment tensor solutions from the harvard cmt catalogue phase velocity anomalies of fundamental mode rayleigh waves period from 34 to 197 s relative to preliminary reference earth model prem are determined by measuring phase differences between the synthetic waveforms and the observations global distribution of rayleigh wave phase velocities are determined by block inversions using damped least squares with a finer block size of 5 5 for the indonesia region than the surrounding area firstly we compare the results obtained from the inversion using the farm data alone called farm inversion and those from the inversion using both the farm and the jisnet data called jisnet farm inversion for the fundamental rayleigh waves of short periods phase velocities obtained from the jisnet farm inversion show greater degrees of negative anomaly throughout indonesia than those from the farm inversion the clearest difference is seen for the region around kalimantan and java slower phase velocities of less than 1 relative to prem at periods of about 70 s are obtained by the farm inversion whereas including jisnet data requires lower phase velocity anomalies of 2 5 secondly we compare the resolution kernels of both data set around java sumatra kalimantan and sulawesi the resolution of the jisnet farm inversion is substantially better than that of the farm data alone with the peaks of resolution kernels up to five times as high as those for the farm inversion the best resolution improvement is obtained for west kalimantan to java sea thirdly we invert the phase velocity perturbations for the modes to obtain the upper mantle 3d s wave velocity vs structure of the study area the jisnet farm inversion tends to give larger up to four times negative vs anomalies when compared with the farm inversion the vs heterogeneities concentrate in the uppermost mantle shallower than 200 km throughout indonesia beneath sumatra java and kalimantan the uppermost 100 km of the mantle is slower than prem by about 2 3 a prominent high vs anomaly 2 4 around the depths from 100 to 200 km extends from northern australia through the banda sea to east sulawesi and halmahera the subducted indian plate is visible as a nearly 1 high vs anomaly

organic geochemistry of the lower suban coal seam south sumatra basin indonesia palaeoecological and thermal metamorphism implications abstract hydrocarbons extracted from the tertiary age coals from the lower suban seam south sumatra basin indonesia have been investigated using gas chromatography gc and combined gas chromatography mass spectrometry gc ms low rank vitrinite huminite reflectance 0 41 0 45 coals from the tambang air laya mine represent different maceral assemblages of an ideal succession of ombrogenous palaeo peat development in a vertical section high rank coals vitrinite reflectance 1 42 5 18 from the suban mine have been thermally metamorphosed by an andesitic intrusion variations in the distributions of n alkanes isoprenoids and saturated and aromatic biomarkers in the low rank coals reflect variations in local source input and palaeomire conditions terpenoid biomarkers such as cadinane and eudesmane type sesquiterpenoids and oleanane and ursane type triterpenoids indicate the predominance of angiosperm plants in the palaeomire particularly dipterocarpaceae the distribution of hopanoids is affected by the organic facies of the coal and their maturity and correlates with the palaeomire evolution as derived from petrological studies close to the igneous intrusion rapid thermal stress has destroyed most of the biomarkers but variations in n alkane distributions attributable to palaeomire conditions remain reversals in the trends for molecular parameters based on aliphatic hydrocarbons n alkane distribution and pristane phytane ratio and aromatic hydrocarbons methyl phenanthrenes with coal rank are observed

anisotropic models of the upper mantle long period rayleigh wave and love wave dispersion data particularly for oceanic areas have not been simultaneously satisfied by an isotropic structure in this paper available phase and group velocity data are inverted by a procedure which includes the effects of transverse anisotropy anelastic dispersion sphericity and gravity we assume that the surface wave data represents an azimuthal average of actual velocities thus we can treat the mantle as transversely isotropic the resulting models for average earth average ocean and oceanic regions divided according to the age of the ocean floor are quite different from previous results which ignore the above effects the models show a low velocity zone with age dependent anisotropy and velocities higher than derived in previous surface wave studies the correspondence between the anisotropy variation with age and a physical model based on flow aligned olivine is suggestive for most of the earth sh sv in the vicinity of the low velocity zone neat the east pacific rise however sv sh at depth consistent with ascending flow anisotropy is as important as temperature in causing radial and lateral variations in velocity the models have a high velocity nearly isotropic layer at the top of the mantle that thickens with age this layer defines the lid or seismic lithosphere in the pacific the lid thickens with age to a maximum thickness of 50 km this thickness is comparable to the thickness of the elastic lithosphere the lid thickness is thinner than derived using isotropic or pseudo isotropic procedures a new model for average earth is obtained which includes a thin lid this model extends the fit of a prem type model to shorter period surface waves

anomalous heat flow and geoid across the cape verde rise evidence for dynamic support from a thermal plume in the mantle summary we describe results from 200 heat flow measurements across the cape verde rise in the north atlantic they show that the heat flow through normal 125 myr old crust is 45 5 3 4mwm 2 close to the prediction for a lithospheric plate model heat flow increases towards the centre of the rise reaching a maximum of 16 4 mw m 2 above the normal oceanic value the concommitant geoid anomaly at the centre of the rise is 7 6 0 3 m and the depth anomaly is 1900 200 m the anomalous heat flow geoid and bathymetric values are used to constrain a variety of theoretical models of hot spot mechanisms lithospheric reheating models alone whether involving transient or sustained thinning of the lithosphere fail to model the broad heat flow anomaly and the long duration of uplift and volcanism observed on the cape verde rise axisymmetric convection models provide a better fit to the observed data and suggest that the swell is a consequence primarily of dynamic uplift generated by an ascending thermal plume in the underlying mantle uplift caused by expansion of the solid lithosphere is of smaller importance the observed geoid bathymetry and heat flow anomalies are reproduced well using convection models with upper mantle viscosities of 2 4 times 1020 pa s and a coefficient of thermal expansion in the range 2 0 2 5 times 10 5 k 1 the effect of melting in the ascending plume is to buffer the heat flow anomalies in the case of the cape verde rise partial melting is minimal but its effect on other hotspots will be to limit observed heat flow anomalies at the surface to less than 20 25 mw m 2

rayleigh wave attenuation and its variation across the atlantic ocean summary fundamental mode rayleigh walies generated by several earthquakes situated on great circle paths traversing pairs of seismograph stations in american and european coastal regions and on atlantic islands have been analysed to obtain anelastic attenuation coefficients group and phase velocities and specific quality factors at periods between 15 and 100s inversions of the dispersion and attenuation data have yielded shear velocity and shear wave internal friction qj models of the upper mantle for regions of varying age in the atlantic ocean the attenuation coefficients and internal friction values can be related to the age of the atlantic ocean floor older regions being characterized by lower internal friction or higher q values a lowq zone is prominent in the upper mantle of all regions less than 65 myr in age but is poorly developed in older regions in contrast to the attenuation results no systematic variations of rayleigh or shear velocities with age can be resolved using the dispersion data of this study a comparison of internal friction models beneath the atlantic with those beneath the pacific indicates that for regions of similar age internal friction is smaller or q larger beneath the atlantic than beneath the pacific especially in the younger regions immediately contiguous with the ridges in particular the upper mantle low velocity low q zone is less prominent beneath the atlantic the fact that spreading rates of the lithospheric plates are also smaller in the atlantic suggests that internal friction and the rate of long term creep in the mantle are closely related

benue trough and benue chain it is suggested that the benue trough may have been initiated by the extension of the equatorial oceanic fracture zones onto the continent during the early stages of the separation of africa and south america a transcurrent movement along deep seated faults of the basement is responsible for the structure of the trough after a period of extension characterized by the sedimentary infilling of the trough and igneous activity the trough is turned into a chain through a short phase of compression a discrete pattern of en echelon folds and the strain pattern deduced from the analysis of large scale and microfracturing correspond to a n s to n160 e direction of compression coupled to a sinistral transcurrent movement along a ne sw direction the difference in age of the folding phase in the northern and southern parts of the chain indicates a diachronous nature for this tectonic event in relation to the wrench regime the tertiary evolution of the trough marked by a tensional regime resulting in an e w extension is to be related to the cameroon volcanic line

waveform inversion of mantle love waves the born seismogram approach summary normal mode theory extended to the slightly laterally heterogeneous earth by the first order born approximation is applied to the waveform inversion of mantle love wave 200 500 s for the earth s lateral heterogeneity at l 2 and a spherically symmetric anelasticity q structure the data are from the global digital seismograph network gdsn the l 2 pattern is very similar to the results of other studies that used either different methods such as phase velocity measurements and multiplet location measurements or a different data set such as mantle rayleigh waves from different instruments the results are carefully analysed for variance reduction and are most naturally explained by heterogeneity in the upper 420 km because of the poor resolution of the data set for the deep interior however a fairly large heterogeneity in the transition zones of the order of up to 3 5 per cent in shear wave velocity is allowed it is noteworthy that love waves of this period range cannot constrain the structure below 420 km and thus any model presented by similar studies below this depth are likely to be constrained by rayleigh waves spheroidal modes only the calculated modal q values for the obtained q model fall within the error bars of the observations the result demonstrates the discrepancy of rayleigh wave q and love wave q and indicates that care must be taken when both rayleigh and love wave data including amplitude information are inverted simultaneously anomalous amplitude inversions of g2 and g3 for example are observed for some source receiver pairs this is due to multipathing effects one example near the epicentral region which is modelled by the obtained l 2 heterogeneity is shown

organic geochemical characteristics and oil generating potential of the upper jurassic safer shale sediments in the marib shabowah basin western yemen the organic rich safer shales exposed in the north central part of onshore marib shabowah basin are evaluated and their depositional environments are interpreted total organic carbon contents toc of the shales range from 1 02 16 8 wt and yield hydrogen index hi values ranging from 130 to 820 mg hc g toc consistent with mainly type ii with minor contributions from type i and mixed types ii iii kerogens the safer shale samples have vitrinite reflectance values in the range of 0 5 1 0 ro indicating early mature to peak mature stage for oil generation tmax values range from 429 438 c which are in reasonably good agreement with vitrinite reflectance data kerogen microscopy shows that the safer shales are characterized by high amounts of organic matter consisting predominantly of yellow fluorescing amorphous organic matter and alginite of marine origin this is supported by their high content of hydrogen rich type ii and i oil prone kerogen the biomarker distributions of the upper jurassic safer extracts are characterized by dominant low to medium molecular weight compounds n c14 to n c20 low pr ph ratio 1 0 high phytane n c18 ratios 0 82 2 68 and predominant regular sterane c27 all biomarker parameters clearly indicate that the organic matter was derived from marine algal inputs and deposited under anoxic reducing conditions hypersaline conditions also prevailed during deposition of these sediments as indicated by the presence of gammacerane

worldwide distribution of group velocity of mantle rayleigh waves as determined by spherical harmonic inversion we have determined the worldwide distribution of group velocity of mantle rayleigh waves for periods between 100 and 300 sec without assuming any regionalization group slowness 1 u is expressed by spherical harmonics and the coefficients up to angular order 7 have been determined from travel times of rayleigh waves by a least squares method from these u has been synthesized since we cannot obtain information about the odd terms of the expansion from one circuit measurements around the world we have used group velocities of mainly r 2 and r 3 the overall pattern of u for periods between 100 and 200 sec is consistent with results of previous pure path and regional studies group velocities for tectonically active regions are low and those of the shields and the northwestern pacific are high

discussion of evaluation of static liquefaction potential of silty sand slopes 1 1appears in the canadian geotechnical journal 48 2 247 264 doi 10 1139 t10 063

upper mantle shear velocity beneath eastern australia from inversion of waveforms from skippy portable arrays in 1993 the research school of earth sciences of the australian national university commenced a nationwide seismometry project skippy for a comprehensive study of the upper mantle beneath the australian continent we applied a waveform inversion technique to broad band data recorded while the skippy portable arrays were positioned in eastern australia in order to construct a 3 d model of shear velocity in the upper mantle and transition zone beneath eastern australia and the adjacent oceanic regions the skippy data were augmented by data from the permanent seismological observatories in the region the first step of the waveform inversion used involved the matching of the waveforms of fundamental and higher mode rayleigh waves with waveforms synthesized from radially stratified models in the second stage the linear constraints on radial variations in shear velocity were combined in a tomographic inversion for aspherical variations in shear velocity the preferred model reduces the data variance by 90 per cent owing to the dense data coverage structural features with dimensions larger than 250 km laterally and 50 km vertically are resolved the major structural features inferred from the tomographic images are 1 a substantial increase in the thickness of the high velocity lid from the oceanic region to the phanerozoic continental and proterozoic continental regions 2 a pronounced low velocity zone centred at 140 km depth beneath the part of eastern australia often referred to as the tasman fold belt which confirms previous inferences from rayleigh wave dispersion curves 3 a prominent zone of low wave speeds beneath the eastern margin of the continent that coincides with locations of cenozoic volcanism and regions of enhanced heat flow 4 deep low wave speed anomalies beneath both the coral and tasman seas and 5 localized high wave speed perturbations in the mantle transition zone 410 660 km depth beneath eastern australia in particular beneath the new england fold belt and the mount isa block from the images we infer that the eastern boundary of the precambrian shields does not coincide with a sharp seismic contrast unless this boundary is located further to the east than is commonly assumed the structure of the upper mantle and transition zone beneath eastern australia as inferred from the images is more complex than that beneath the precambrian cratons of central and western australia which could be due to subduction beneath the eastern continental margin prior to opening of the tasman sea if correct this interpretation would imply that part of the upper mantle has moved along laterally with the lithosphere during the relatively fast northward motion of the plane

geometric effects of global lateral heterogeneity on long period surface wave propagation long period rayleigh waves from iranian earthquakes have large amplitude asymmetries between minor arc and major arc arrivals e g r 2 and r 3 at digital stations in the azimuth range n20 w to n60 e these asymmetries are as large as a factor of 2 at a period of 256 s and persist to periods greater than 300 s in some cases the entire rayleigh wave group arrival spanning periods from 100 to 300 s is either uniformly enhanced in amplitude or diminished to such a degree that the group arrival appears to be missing the amplitude anomalies are generally not accompanied by significant phase anomalies the irregular azimuthal distribution of the amplitude asymmetries and their occurrence for events with different focal mechanisms and epicentral separations of several hundred kilometers preclude an explanation of these observations by source complexity events in the mediterranean and nepal do not produce similar amplitude asymmetries at the same stations the anomalies are thus most likely due to focusing and defocusing propagation effects as a preliminary investigation of the effects of lateral heterogeneity of upper mantle velocity structure on long period surface wave amplitudes surface wave ray tracing calculations are performed using recently proposed global phase velocity distributions dramatic deviations from great circle paths are predicted for long propagation paths e g r 3 the particular spatial distribution of lateral velocity gradients around a given source location determines whether substantial amplitude asymmetries will be observed between minor arc and major arc arrivals and whether these will persist for sequential great circle orbits the 200 s period amplitude asymmetry observed at kip for the iranian source region r 2 4 r 3 is well predicted by the ray tracing results the absence of this anomaly for the other source regions is also predicted other observed anomalies are not all well predicted but it is clear that geometric effects can contribute significantly to the observed variations of rayleigh and love wave amplitudes this is the probable explanation for the instability of q estimates made from surface waves other source regions producing large surface wave amplitude anomalies include japan and southeastern alaska

striated conical structures and related fractures in bituminous coal of the southern canadian rocky mountains abstract striated structures many of which are conical in form are common mesoscopic features in bituminous and semi anthracite coals of the southern canadian rocky mountains the structures are planar conical to pyramidal in outline and are characterized by striae which radiate from a common apex and bifurcate or horsetail to form secondary structures on the master surface they are up to 20 cm in length 4 cm in width and have apical angles varying from 10 to 50 the striated structures occur at numerous localities in both highly sheared and relatively unsheared coal seams the conical striated structures closely resemble some shatter cones developed in fine grained rocks whereas the planar striated structures are somewhat similar to chevron structured hackle marked joints the pyramidal structures are apparently unique to coal all three types of structures are considered to be the result of brittle shear fracture based on their occurrence orientation and morphology the apparently restricted occurrence of the structures to coal is likely a function of the homogeneity and low tensile and compressive strength of bituminous and semi anthracite coals possibly augmented by high inter and or intra particle gas pressure resulting from devolatization of the coal during progressive coalification

crust and upper mantle structure and its tectonic implications in the south china sea and adjacent regions abstract we present a 3d s velocity model for the crust and upper mantle of the south china sea and the surrounding regions constrained from the analysis of over 12 000 of fundamental rayleigh wave dispersion curves between 10 s and 150 s periods the lateral resolution was found to vary from 2 to 4 with the increasing period over the study region a robust scheme of debayle and sambridge allowed us to conduct the tomographic inversion efficiently for massive datasets group velocity maps varying with period show lateral heterogeneities well related to the geological and tectonic features in the study region the 3d s velocity model was constructed from the 1d structure inversion of the tomographic group velocity dispersion curves at each node the obtained average crustal structure is similar to the prem model while the average mantle velocity is typically lower than the global average the complicated 3d structures reveal three prominent features correlated with geological divisions sea basin regions island and arc regions and continental regions the derived crustal and lithospheric thicknesses range from 15 to 50 km and from 60 to 140 km respectively with the thinnest in the south china sea the thickest in eastern tibet and the yangtze block and the medium in the south china fold belt indochina and island arc regions our results further confirm that 1 a mesozoic subduction zone which is interpreted as the tectonic weak zone during the paleogene exists along the south china margin 2 the influence of the indochina extrusion along the red river fault is limited for the south china sea region 3 there is a slab remnant of the proto south china sea beneath borneo new findings suggest that the mesozoic subduction zone should be built into any evolution model for the region as well as the other two major tectonic boundaries of the red river fault and proto south china sea subduction zone

measurements of mantle wave velocities and inversion for lateral heterogeneities and anisotropy 3 inversion lateral heterogeneity in the earth s upper mantle is investigated by inverting dispersion curves of long period surface waves 100 330 s models for seven different tectonic regions are derived by inversion of regionalized great circle phase velocity measurements from our previous studies we also obtain a representation of upper mantle heterogeneities with no a priori regionalization from the inversion of the degree 6 spherical harmonic expansion of phase and group velocities the data are from the observation of about 200 paths for love waves and 250 paths for rayleigh waves for both the regionalized and the spherical harmonic inversions corrections are applied to take into account lateral variations in crustal thickness and other shallow parameters these corrections are found to be important especially at low spherical harmonic order the trench region and fast velocities down to 250 km under shields below 200 km under the oceans both s velocity and s anisotropy support a model of small scale convection in which cold blobs detach from the bottom of the lithosphere when its age is large enough the spherical harmonic models clearly demonstrate a posteriori the relation between surface tectonics and s velocity heterogeneities in the first 250 km all shields are fast most ridges are slow below 300 km a belt of fast mantle follows the pacific subduction zones however at greater depths large scale heterogeneities that seem to bear no relationship to surface tectonics are observed the most prominent feature at 450 km is a fast velocity region under the south atlantic ocean smaller scale heterogeneities that are not related to surface tectonics are also mapped at shallower depths an anomalously slow region centered in the south central pacific is possibly linked to intense hot spot activity a very fast region southeast of south america may be related to subduction of old pacific plate between 200 and 400 km a belt of sv sh anisotropy follows part of the ridge and subduction systems indicating vertical mantle flow in these regions the spherical harmonic results open new horizons for the understanding of convection in the mantle perspectives for the improvement of the models presented are discussed

dynamically supported geoid highs over hotspots observation and theory hotspots are associated with long wavelength geoid highs an association that is even stronger when the geoid highs associated with subduction zones are removed we quantify these associations by expanding the hotspot distribution in spherical harmonics and calculating correlation coefficients as a function of harmonic degree the hotspot distribution spectrum is nearly white except for peaks at degrees 2 and 6 it is correlated positively with the slab residual geoid for degrees 2 6 with low seismic velocity in the lower mantle at degree 2 and with low seismic velocity in the upper mantle at degree 6 we test fluid mechanical models for hotspots including lithospheric delamination and hot plumes by calculating their predicted dynamic geoid responses and comparing them to the observations these models include the effects of temperature dependent rheology our preferred hotspot model based on observations of the geoid and seismic tomography has plumes preferentially occurring in regions of large scale background temperature highs in a mantle which has a substantial viscosity increase with depth although other models are possible alternatively strong plumes in the lower mantle may neck down and attenuate in the upper mantle due to changes in plume viscosity the major low density anomalies causing the geoid highs associated with plumes appear to be in the lower mantle we hypothesize that cold lower mantle underlying the complementary geoid lows is due to deeply subducted oceanic lithosphere and that hotspot plumes tend to be excluded from these cold regions of the mantle

static liquefaction of very loose sands discussion the study presented in this paper has provided further evidence to indicate that natural sands particularly those con taining fines or shells do not behave in the same way as clean sands however one of the conclusions made by the authors that is that the resistance to liquefaction increases with the effective confining stress may need further discus sion it is a common observation for a number of sands that the liquefaction behaviour of very loose sand is very sensitive to the void ratio after consolidation i e before undrained shearing figure d1 presents the effective stress paths of two undrained tests on loose sand cu3 and cu6 conducted under the same effective confining stress but on specimens with different post consolidation void ratios ec the ec for test cu3 is 0 962 and for test cu6 is 1 023 the difference in void ratios is only 0 061 however liquefaction occurs in test cu6 but not in test cu3 as seen in fig d1 the sand used is a granular fill material dredged from the sea it has a mean grain diameter of 0 3 mm it contains very little fines 0 4 but a high shell content of 14 one more example is given in fig d2 in which the results of two undrained tests on loose sand are compared the ec values of the two tests are 0 838 for test 6 and 0 849 for test 7 the difference in void ratios is 0 011 with this small difference in ec test 7 exhibits steady state behaviour and test 6 limit steady behaviour the basic properties of the sand used can be found in chu 1995 it can be seen from fig 5 for nevada sand and fig 7 for ottawa sand of the discussed paper that the e c value of each test at different confining stress is different and the higher the confining stress the smaller the e c the maximum difference in e c in these tests is 0 038 if the authors were to compare the liquefaction behaviour for tests with the same or nearly the same e c value the conclusion that the resistance to liquefaction increases with effective confining stress may have been different it should be pointed that it is the post consolidation void ratio e c that is used to establish the steady state behaviour i e castro 1969

the organic geochemistry of the eocene oligocene black shales from the lunpola basin central tibet abstract this paper reports on the depositional paleoenvironment and the potential hydrocarbons of the eocene oligocene black shales from the dingqinghu and niubao formations in the lunpola basin central tibet nineteen samples from two outcrop profiles were analysed the contents of the total organic carbon toc and sulphur were measured other analyses included rock eval pyrolysis solvent extraction and gas chromatography mass spectrometer gc ms the results indicated that the shales from the dingqinghu and niubao formations are thermally immature the pyrolysis data show that the shales contain type i organic matter and that lacustrine algal are the main organic matter sources the low pristane to phytane ratios and the high gammacerane indices indicate that the shales were deposited in a reducing stratified and hypersaline palaeo lake which is consistent with the climate information provided by the development history of palaeo lakes from the eocene to the oligocene epochs

mapping the lower mantle determination of lateral heterogeneity in p velocity up to degree and order 6 the data from the international seismological centre bulletins for the years 1964 1979 are used to derive a three dimensional model of lateral variations of the p velocity in the lower mantle unlike previous studies in which such perturbations were represented by a blocklike parameterization we seek the solution in the form r k 0k l 0l m 0l k r kalm cos m kblm sin m plm cos some 500 000 travel time residuals for teleseismic distances from 5000 earthquakes are used in an iterative procedure to derive the coefficients a and b the maximum k and l used are 4 and 6 respectively in each iteration in addition to solving for the three dimensional structure we also relocate all the earthquakes perturb the average travel time curve and determine station corrections for over 1000 stations particular attention is given to the problem of weighting the individual observations in order to avoid as much as possible the bias due to the uneven distribution of sources and receivers the resulting model shows a high level of perturbations just below the 670 km discontinuity and just above the core mantle boundary where the maximum perturbations reach 1 1 5 of the average velocity even for this highly smoothed model at a depth of 2000 km the rms perturbations are some 3 to 4 times lower than at either of the two boundaries the model predicts well the large scale pattern of observed travel time residuals for various source regions except for the distinct effects of the subduction zones the most striking large scale three dimensional feature of the model is a ring of high velocities circumscribing the pacific basin within a depth range from 1000 km to the core mantle boundary if the proportionality between perturbations in the velocity and temperature is assumed the derived pattern of anomalies could be consistent with a two boundary layer model of convection in the lower mantle some caution however should be exercised in interpreting the results near the 670 km discontinuity where the resolving power of our data set is limited by the lack of adequate control of the upper mantle structure at the same time a significant global increase in the level of perturbations in the lowermost mantle is established beyond question the results of dziewonski et al 1977 on the correlation between the equivalent geoid and the observed geoid for the angular order numbers 2 and 3 is confirmed but there is no significant correlation for degrees from 4 to 6 these calculations are made for the rigid earth richards and hager this issue show that introduction of finite viscosity can change the sign of a geoid anomaly in addition recent studies of lateral variations in the shear velocity reveal the presence of large scale anomalies in the upper mantle thus while the inferences made here with respect to the origin of the gravest orders of the geopotential field are not conclusive they point the way in which results from seismology can be used to address some of the basic questions of geodynamics

the upper mantle degree 2 constraints and inferences from global mantle wave attenuation measurements we present the results of an analysis of global lateral variations in anelasticity of the upper mantle as measured from very long period rayleigh waves observed on the geoscope network four consecutive wave trains are used on each record to eliminate uncertainty on the amplitude at the source and to take into account in a linear manner focussing effects due to lateral variations in elastic parameters local estimates of attenuation are obtained using an inversion method based on the introduction of a correlation length as an alternative to spherical harmonics expansion comparison of phase velocity and attenuation maps obtained at various periods shows a strong correlation of high q and high velocity regions respectively low q and low velocity both for great circle and minor arc data at periods around 200 s the detailed analysis of the degree 2 pattern well resolved in the attenuation maps around this period shows that it originates in the depth range 250 500 km and indicates that of the upper mantle degree 2 pattern observed in shear velocity is likely to be of thermal origin possibly related to the topmost part of the large scale convective system corrections for dispersion due to anelastic attenuation in degree 2 lead to significant decrease of corresponding lateral variations in shear velocity and a better agreement in phase and amplitude of the upper mantle degree 2 pattern with that observed in the geoid this study shows that it is important to consider correcting presently available upper mantle tomographic models for the effects of intrinsic attenuation at long periods before performing any comparison with short period data or other geophysical parameters

oleanane parameter verification by quantitative study of the biomarker occurrence in sediments of the niger delta abstract the variation of the absolute concentration of oleananes in three selevted sedimentary columns of the tertiary niger delta is paralleled by the corresponding oleanane parameter op profile thereby confirming that the latter can be utilized for estimating the relative contribution of terrigenous organic matter it is shown that op features a dynamic range especially at the oil generative window ogw and can precisely delimit the top of the ogw which for the niger delta is shown to coincide approximately with the 80 c isotherm and ro 0 55 this study provides the first direct evidence of the inadequacy of vitrinite reflectance as a maturity parameter for type iii kerogen furthermore based on the new findings an alternative model for oleanene oleanane interconversions in the geosphere is proposed

microfacies and petroleum properties of coals as revealed by a study of north sea jurassic coals abstract the influence of the composition and microstructural aspects of coal microfacies on petroleum properties were investigated in light of petrographic and geochemical studies the first study concerns a collection of north sea jurassic coals of various maceral compositions the second study is a pyrolysis gas chromatography study on pure microlithotypes from a similar french jurassic coal the results show that hydrocarbon potential is logically increased by a high content in liptinite but more often in hydrogen rich vitrinite in the same way the hydrocarbon potential is reduced by a high inertinite content mainly due to pre sedimentary oxidation of the original biomass but also due to early diagenetic processes that lead especially to the formation of micrinite or to post sedimentary alterations these trends indicate that total hydrocarbon potential is increased by an autochthonous origin of the organic matter that was deposited in a relatively closed paleoenvironment and thus protected from detrital and organo detrital inputs finally the oil potential of humic coals as determined by open pyrolysis gas chromatographic studies as related to the weight of rock is similar to classical source rocks the structural aspects of the coal microfacies which probably play a role in the release of oil from coal seams in natural conditions are also discussed

global love wave phase velocity variation and its significance to plate tectonics abstract global love wave phase velocity variation was constructed for periods between 80 and 200 s by using approximately 9000 paths from 971 earthquakes with m 5 5 the data set was from gdsn and geoscope networks between 1980 and 1987 we examined both the spherical harmonic expansion method and the block parameterization method with a simple constant damping parameter approach synthetic tests showed that more accurate results were obtained by the block parameterization method than by the spherical harmonic expansion method we adopted the block inversion method with a nearly equal area block 5 5 near the equator discretization the general pattern of the resulting maps were consistent with previous global and local studies with a discretization of 5 by 5 the maps were detailed enough to test some plate tectonic models for the pacific atlantic and indian oceans surface wave velocities increased smoothly to plate ages older than 100 ma simple forward modeling showed that seismic phase velocity variation with a continuous thickening of lithosphere up to about 150 ma fits the present observation disagreeing with the model deduced from the heat flow and ocean depth data which change variations at about 60 80 ma the seismic phase velocity variations in different oceans showed systematic differences at younger ages and convergence beyond 100 ma the difference at younger ages implies a failure of scaling derived from a simple thermal boundary layer model for oceanic plates age seismic phase velocity relationships on each side of ridges were also examined and asymmetric velocity variations were found which suggests differences in thermal states from one side of the ridge to the other in order to further examine the thermal state of the lithosphere average age phase velocity relations were established for each ocean and subtracted from phase velocity variation maps the results indicated broad low velocity regions in the south pacific super swell region the south and west indian ocean and high velocity regions east of the east pacific rise and in the north to northeast indian ocean the results reflect the asymmetry of phase velocity variation about ridges there is some correlation between hot spot locations and low velocity anomalies but additional large scale thermal anomalies exist under old oceanic plate

three dimensional modelling of upper mantle structure under the pacific ocean and surrounding area summary long period 75 250 s fundamental mode love and rayleigh waves are inverted for the seismic velocity variations in the upper mantle under the pacific ocean and surrounding area the data are inverted to map the regional variation of phase velocity and then the velocity structure of the upper mantle no a priori regionalization is used in this study and the lateral heterogeneity is expanded horizontally into blocks lo x 10 to estimate the reliability of the velocity distribution we have calculated the resolving kernels in the central nw ne and sw regions the resolving kernels have fairly sharp peaks in the se region however resolution is not so good the results show good correlation with surface tectonics in the velocity map shields and ridges are the major features in the depth interval 50 100km anomalies associated with the east pacific rise and the shields persist to 300 km at 400 and 500 km high velocity anomalies appear under the eastern and southern pacific ridges and a low velocity anomaly appears beneath australia the present study provides better resolution than previous studies because of the better path coverage for example a large low velocity anomaly emerges under hawaii down to the depth of 200 km for sh velocity the horizontal extent of this anomaly is comparable to the sue of the hawaiian swell this feature supports that the hawaii hotspot is an isolated truly anomalous feature in the pacific ocean

petrographic and geochemical characterization of the upper cretaceous coal and mudstones of gombe formation gongola sub basin northern benue trough nigeria implication for organic matter preservation paleodepositional environment and tectonic settings abstract under exploration of the upper cretaceous petroleum systems in the northern benue trough nigeria has been attributed largely to lack of subsurface samples and non integration of organic and inorganic geochemical methods recent access to surface sampling from maiganga coalfield revealed a need for detailed evaluation of the sedimentary facies types for better understanding of the hydrocarbon potential of the area detailed maceral point count py gc chnso as well as major oxides and trace element icp ms analysis were used to characterize the gombe formation coals and the mudstones for determination of the organic matter origin preservation paleodepositional environment tectonic setting and paleoclimatic condition during sedimentation evaluation based on the maceral composition tpi gi values plot of trace elements v versus ni and sedimentary succession suggest deposition of predominantly terrigenous organic matter 45 to 73 huminite maceral in an upper deltaic setting for the maiganga facies the maceral analysis associated with py gc studies indicates that the sedimentary facies of gombe formation have potential to generate liquid hydrocarbon this can be estimated from an average of 21 50 liptinite content and the ternary plot of the py gc pyrolysate m p xylene n octene and phenol suggesting presence of type ii and type ii iii kerogen within the basin assessment of the paleodepositional environment based on the trace elements composition indicates a moderate stratified water column and salinity within a relatively sub oxic to oxic conditions during sedimentation the major oxide composition as well as the binary plots of sio2 versus al2o3 k2o na2o and log sio2 versus k2o na2o for the shales and mudstones revealed a predominance of semi arid to slightly humid warm paleoclimatic conditions and a passive continental margin setting this is in accordance with the cretaceous tectonic events of the west and central africa which affected the petroleum system in the entire benue trough

the three dimensional shear wave structure in the mantle by overtone waveform inversion i radial seismogram inversion summary the three dimensional 3 d shear wave structure of the mantle down to the depth of about 900 km is obtained by inverting waveforms of radial component seismograms radial component seismograms contain large amplitude overtone signals which circle the earth as wave packets and are sometimes called x1 x2 x3 we use data which contain r1 x1 and x2 and filtered between 2 and 10mhz it is shown that unless each seismogram is weighted all seismograms are not fitted uniformly only data from large earthquakes are fitted and the final velocity anomalies are biased by the small number of large earthquake data resolution is good at shallow depths becomes worse in the intermediate depth range between about 400 and 500 km and then becomes better at greater depth ranges 600 900km even though we use only spheroidal mode data velocity anomalies in the shallow structure show excellent correlation with the age of the surface rocks of the earth in the deeper regions between about 600 and 900km south america shows a fast velocity anomaly which may indicate the slab penetration beyond 700 km there another region which shows a fast velocity anomaly is the mariana trench but other subduction regions do not show such features

organic geochemical characteristics of crude oils from the masila basin eastern yemen the masila basin is an important hydrocarbon province in yemen but the origin of hydrocarbons and their generation history are not fully understood in this regard 10 crude oils from different petroleum reservoir sections in the masila basin were characterized by a variety of biomarker and non biomarker parameters using gc gc ms and stable carbon isotope techniques oils from the masila basin display pristane phytane pr ph ratios ranging from 1 7 to 2 0 low sulfur content high c35 homohopane index relatively high c27 sterane concentrations and relatively high tricyclic terpanes suggesting a marine clay source rock that was deposited in mildly anoxic to suboxic conditions with dominantly algal organic matter c29 20s 20s 20r steranes and bb bb aa sterane ratios indicate that the masila oils have reached peak oil window maturity another related feature of these oils is the absence of 18a h oleanane which suggests a source age older than cretaceous the carbon isotope compositions are similar to those of the potential source rocks which range from 25 4 to 28 3 indicating a marine environment the new data presented in this paper suggest that the masila oils constitute one oil family and that the oil originated from the upper jurassic madbi source rock in the basin