a unique lacustrine mixed dolomitic clastic sequence for tight oil reservoir within the middle permian lucaogou formation of the junggar basin nw china reservoir characteristics and origin abstract the middle permian lucaogou formation in the jimusaer sag of the southeastern junggar basin nw china was the site of a recent discovery of a giant tight oil reservoir this reservoir is unusual as it is hosted by lacustrine mixed dolomitic clastic rocks significantly differing from other tight reservoirs that are generally hosted by marine lacustrine siliciclastic calcitic sequences here we improve our understanding of this relatively new type of tight oil reservoir by presenting the results of a preliminarily investigation into the basic characteristics and origin of this reservoir using field petrological geophysical including seismic and logging and geochemical data field and well core observations indicate that the lucaogou formation is a sequence of mixed carbonate mainly dolomites and terrigenous clastic mainly feldspars sediments that were deposited in a highly saline environment the formation is divided into upper and lower cycles based on lithological variations between coarse and fine grained rocks in particular dolomites and siltstones are interbedded with organic rich mudstones in the lower part of each cycle whereas the upper part of each cycle contains few dolomites and siltstones tight oil accumulations are generally present in the lower part of each cycle and dolomites and dolomite bearing rocks are the main reservoir rocks in these cycles including sandy dolomite dolarenite dolomicrite and a few dolomitic siltstones optical microscope back scattered electron and scanning electron microscope imaging indicate that the main oil reservoir spaces are secondary pores that were generated by the dissolution of clastics and dolomite by highly acidic and corrosive hydrocarbon related fluids

formation mechanism and tectonic significance of millipede microstructures in the nw himalaya abstract this article focuses on the origin and tectonic significance of millipede inclusion trail microstructures preserved within garnet porphyroblasts of typical barrovian type schist from the swat region of the himalayas in pakistan two possible kinematic models are assessed envisaging bulk coaxial shortening and progressive simple shear 3d microstructural analysis of three samples hosting the millipedes reveals a poly phase deformation history that produced three suborthogonal foliations called sx sy sz successive inclusion of sx and sy in garnet porphyroblasts produced two sets of millipedes with distinctive subvertical and subhorizontal orientations respectively this kinematic reconstruction is supported further with a numerical simulation using finite difference code of millipede formation in a spherical porphyroblast subjected to a superposition of two orthogonal shortening directions measurements of inclusion trail curvature axes or fia foliation intersection inflexion axes in porphyroblasts in 61 additional samples from the study area which contain straight sigmoidal or spiral inclusion trails reflect two principle orogenic episodes during the first episode fias developed with wnw ese set 1 and e w set 2 trends associated with thrusting and collision tectonics a younger fia set 3 with nne ssw trend developed as a result of subsequent bulk e w crustal shortening and associated regional scale folding sigmoidal or straight inclusion trails defining this fia set can be correlated with the millipede microstructures based on their similar trends and timing relative to matrix fabrics these results are consistent with the meso and macro scale structures in the region and significant in terms of establishing relative timing of formation of different structures in the region well developed preferred vertical and horizontal orientations of both sigmoidal and millipede inclusion trails imply that their development involved limited or no relative rotations between porphyroblasts sigmoidal trails formed in zones where bulk shearing caused progressively reoriented matrix foliations around stable garnets while millipedes formed simultaneously in local coaxial strain pods

properties origin and nomenclature of rodlets of the inertinite maceral group in coals of the central appalachian basin u s a abstract resin rodlets sclerenchyma strands and woody splinters which are collectively called rodlets were studied by chemical optical petrographic and scanning electron microscopic sem techniques a study was made of such rodlets from the bituminous coal beds of the central appalachian basin pennsylvanian upper carboniferous of the united states comparisons were made with rodlets from coal beds of the illinois basin the southern anthracite field of pennsylvania the st rose coal field of nova scotia and european and other coal fields in order to determine their physical and chemical properties a detailed study was made of the rodlets from the pomeroy coal bed high volatile a bituminous coal monongahela formation upper pennsylvanian of kanawha county west virginia the origin of the rodlets was determined by a comparative analysis of a medullosan seed fern stem from the herrin no 6 coal bed high volatile c bituminous coal carbondale formation from washington county illinois rodlets are commonly concentrated in fusain or carbominerite layers or lenses in bituminous coal beds of the central appalachian basin most of the rodlets examined in our study were probably derived from medullosan seed ferns the three types of rodlets are distinguished on the basis of cellularity morphology and fracture the resin rodlets studied by us are noncellular and appear to be similar in properties and origin to those found in coal beds of the middle and upper pennsylvanian of the illinois basin the resin rodlets extracted from the pomeroy coal bed exhibit high relief and high reflectance when polished and viewed in reflected light they are opaque in transmitted light in cross section the resin rodlets are oval to round and have diameters ranging from 60 to 450 m many are solid but some have vesicles canals or cavities which are commonly filled with clay probably kaolinite typically they have distinct fracture patterns kerfs in longitudinal and cross sections and many are characterized by dense probably oxidized rims the orientation and amounts of void space and mineralization of resin rodlets in coal have resulted in much confusion in their recognition and classification the resin rodlets are petrographically recognized as sclerotinites of the inertinite maceral group we here propose that resin rodlets be assigned to the maceral variety of sclerotinites termed resino sclerotinite because of their presumable resinous origin other investigators have confused some fusinitized resin rodlets with fungal masses which have different morphological properties and which probably have different chemical properties we here propose that such fungal masses be assigned to the maceral variety of sclerotinites termed fungo sclerotinite the sclerenchyma strands examined in our study are cellular thick walled and crescent shaped in cross section they exhibit high reflectance and high relief and belong to semifusinite and fusinite of the inertinite maceral group sclerenchyma strands are commonly associated with resin canals in medullosa and related seed fern genera which are common in coal balls of the illinois basin we here propose adoption of the maceral varietal terms sclerenchymo fusinite and sclerenchymo semifusinite for these bodies the woody splinters in the pomeroy coal bed are cellular and thin walled and have scattered pits as much as a few microns in diameter they are dark brown to black in transmitted light and commonly have a lower reflectance than the resino sclerotinite and sclerenchymo fusinite of the pomeroy coal the woody splinters belong to semifusinite and fusinite of the inertinite maceral group the maceral varietal terms xylemo semifusinite and xylemo fusinite are here proposed for these bodies elemental chemical data for the resin rodlets of the pomeroy coal bed of the central appalachian basin indicate that resin rodlets have significantly lower atomic h c and o c ratios than do sclerenchyma strands and woody splinters the lower atomic h c and o c ratios of the resin rodlets correlate with the highest reflectance in the coal ball medullosan seed fern stem from the herrin no 6 coal bed of the illinois basin the reflectances of the resin rodlets woody splinters and sclerenchyma strands are similar and comparable to those of associated vitrinite in the coal ball stem and in the attached coal however resin rodlets and sclerenchyma strands in the attached coal have significantly higher reflectances similar to those of the pomeroy coal

a numerical study of strike slip bend formation with application to the salton sea pull apart basin how stepovers of strike slip faults connect to form bends is a question important for understanding the formation of push up ranges restraining bends and pull apart basins releasing bends we investigated the basic mechanics of this process in a simple three dimensional viscoelastoplastic finite element model our model predicts localized plastic strain within stepovers that may eventually lead to the formation of strike slip bends major parameters controlling strain localization include the relative fault strength geometry of the fault system and the plasticity model assumed using the drucker prager plasticity model in which the plastic yield strength of the crust depends on both shear and normal stresses our results show that a releasing bend is easier to develop than a restraining bend under similar conditions these results may help explain the formation of the salton sea pull apart basin in southern california 0 5 0 1 ma ago when the stepover between the imperial fault and the san andreas fault was connected by the brawley seismic zone

upper permian lacustrine oil shales southern junggar basin northwest china upper permian organic rich lacustrine mudstones oil shales that crop out in the southern junggar basin rank among the richest and thickest petroleum source rock intervals in the world with maximum toc values reaching 34 and rock eval pyrolytic yields s 2 up to 200 kg hc t rock lacustrine sedimentary facies define an overall transgressive regressive cycle of approximately 2000 m gross thickness which includes approximately 800 m of source rocks averaging 4 1 toc and 26 2 kg hc t rock basinal facies comprise silicic organic rich laminated lacustrine mudstones and interbedded siltstones organic matter contained in the mudstones ranges in composition from type i to type iii basinal facies were deposited in a deep oxygen deficient stratified lake lake margi facies consist of nonlaminated siliciclastic mudstones rippled dolomitic siltstones and sandstones and minor limestones maximum toc values are approximately 6 desiccation cracks are common in the marginal facies but evaporite minerals are rare or absent biomarker correlation parameters measured from rock extracts exhibit significant stratigraphic variability but strongly support the hypothesis that upper permian lacustrine oil shales charge the giant karamay field in the northwestern junggar basin karamay oils are characterized by high relative abundances of beta carotane this characteristic is restricted to desiccated facies in the outcrop sections however we therefore propose that an abundance of beta carotane indicates elevated environmental salinities during deposition of the oil shales orographic precipitation induced by a paleo tian shan range may have provided fresh water to the southern areas of the basin while more evaporative conditions prevailed to the north outcrop oil seeps confirm that the outcrop sections have attained sufficient thermal maturity to generate oil t max values range from 431 to 451 degrees c vitrinite reflectances range from 0 73 to 0 88 and sterane isomerization ratios range from 0 30 to 0 48 20s 20s 20r matoil registered trademark computer modeling of burial history and thermal maturity of the outcrop sections indicates that approximately 4 5 km of triassic jurassic cover was needed to bring the oil shales to their current maturity the major phase of hydrocarbon generation in this area appears to have preceded the creation of traps by neogene thrusting which may account for the lack of discoveries in the southern junggar basin most of the oil discovered so far is trapped in structures which originated duri g the late paleozoic or mesozoic

depositional environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china abstract the non marine santanghu basin in northwest china hosts one of the richest and thickest permian lacustrine source rock intervals in the world conventional oil in jurassic sandstone reservoirs and tight oil in the tuffaceous permian tiaohu formation were sourced from mudrocks in the underlying second member of lucaogou formation which also have tight oil potential proved by recent commercial discoveries based on inorganic and organic geochemistry organic petrography and stable isotope geochemistry the depositional environment and the tight oil potential of the second member of permian lucaogou formation were investigated the data imply a gradual evolution of the depositional environment from a stratified saline to a freshwater lake the succession can be subdivided into a lower middle and an upper unit each characterized by decreasing water salinity high bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria water column stratification accelerated the activity of methanothrophs as indicated by low 13c values of hopanes biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of prasinophytae compared to other algae with decreasing salinity enhanced terrigenous organic matter input appeared during periods of high freshwater inflow low total organic carbon toc contents in the lower unit are most likely caused by rapid sedimentation rate high bioproductivity and excellent preservation conditions resulted in high toc contents in the middle unit terrigenous organic matter input increased together with fresh water inflow in the upper unit resulting in high toc values during periods of possibly low sedimentation rates in a deep water column the samples of the second member exhibit a good to very good potential to generate conventional oil high toc and extractable organic matter yields together with the thickness of the fine grained sediments show that the middle and upper units of the second member of lucaogou formation hold significant tight oil potential mineralogical composition of this dolomite rich shale with respect to abundance of brittle minerals including quartz and carbonates and rare clay testifies a good tight oil potential

a seismic refraction survey of the imperial valley region california the u s geological survey conducted an extensive seismic refraction survey in the imperial valley region of california in 1979 the imperial valley is located in the salton trough an active rift between the pacific and north american plates forty shots fired at seven shot points were recorded by 100 portable seismic instruments at typical spacing of 0 5 1 km more than 1300 recording locations were occupied and more than 3000 usable seismograms were obtained we analyzed five profiles using a standard ray tracing program constructed a contour map of reduced travel times from our most widely recorded shot point and modeled an existing gravity profile across the salton trough results are itemized 1 all models have in common a sedimentary layer vp 1 8 5 0 km s a transition zone vp 5 0 5 65 km s a basement vp 5 65 km s in the imperial valley 5 9 km s on the bordering mesas and subbasement vp 7 2 km s 2 the sedimentary layer ranges in thickness along the axis of the salton trough from 3 7 km salton sea to 4 8 km u s mexican border on the bordering mesas it is quite variable in thickness 3 the transition zone is about 1 km thick in most places in the imperial valley there are no marked velocity discontinuities in this zone between the sedimentary layer and basement on the bordering mesas however there is a discontinuity at the top of this zone 4 there are apparently two types of basement on the bordering mesas basement is crystalline igneous and metamorphic rocks in the imperial valley basement is mostly lower greenshist facies sedimentary rocks based primarily on the smooth transition in character from sediment to basement arrivals the low value of basement velocity and the fact that deep 4 km wells in the valley penetrate only the upper part of the known cenozoic stratigraphic column for the salton trough 5 the subbasement or intermediate crustal layer ranges in depth along the axis of the salton trough from 16 km salton sea to 10 km u s mexican border gravity modeling requires that this layer deepen and or pinch out beneath the bordering mesas and mountain ranges based on its high velocity and the presence of intrusive basaltic rocks in the sedimentary section in the imperial valley the subbasement is thought to be a mafic intrusive complex similar to oceanic middle crust 6 several structures are seen that affect basement transition zone and deeper parts of the sedimentary layer they include a scarp along the imperial fault as much as 1 km down to the northeast and a scarp passing roughly along the topographic boundary between the imperial valley and the bordering mesa to the west as much as 3 km down to the east we interpret the latter scarp to be the suture or rift boundary between the older crystalline basement on the mesa and the younger metasedimentary basement in the imperial valley 7 on a contour map of reduced travel time from our most widely recorded shot point subtle patches of early arrivals among otherwise late arrivals in the central imperial valley correlate well with known geothermal resource areas having reservoir temperatures of more than 150 c apparently the salton trough is a location where new crust is being generated as the rift opens mafic intrusive rocks fill it from below as sedimentary rocks fill it from above rifting and intrusion produce high heat flow that metamorphoses the sedimentary rocks to shallow depth metasedimentary basement in the imperial valley and thus consolidates the new crust

organic petrology of source rocks history and state of the art abstract the development of organic source rock petrology depended on the methods applied a procedure derived from coal petrology is the study of polished sections of the untreated rock under incident light this method combined with the fluorescence techniques is best suited to characterize and identify the discrete organic matter macerals and permits the most reliabble maturity measurements on the basis of vitrinite reflectance and of various fluorescence parameters another common method treats the rock with acids and studies strew slides of organic matter concentrates this destroys the natural texture of the rock and often some of the individual macerals as well but on the other hand it allows recognition of extremely fine particles which are not resolvable in polished sections maturity studies based on maceral colour changes as observed in strew slides are rapid and practical although they are rather subjective the relative merits of the various methods are discussed the individual organic constituents as seen in the whole rock and in organic matter concentrates are described and illustrated in two colour plates some classification systems are compared in tabular form finally the history of microscopic observations and measurements with respect to the generation of petroleum like substances in coal is briefly reviewed

computer simulations of california tectonics confirm very low strength of major faults recent improvements in the technique of modeling fault networks with thin plate finite elements yield full convergence of the solutions without any compromise in the representation of the frictional rheology of the upper crust or the transition to dislocation creep in the lower crust we apply these techniques to model the california region incorporating all faults with estimated slip rate over 1 mm yr as well as variations in elevation heat flow and crustal thickness velocity boundary conditions on the model sides are based on the nuvel 1 plate model and an approximation of deformation in the great basin the frictional and dislocation creep rheologic constants of the crust are calibrated to reproduce the observed variations in the maximum depth of seismicity which occurs at model temperatures of 350 410 c this leaves two free parameters the time averaged coefficient of friction on faults and the apparent activation energy for creep in the lower crust these parameters are systematically varied in three sets of 10 81 and 64 experiments respectively the predictions of each model are tested against three published data sets a set of 79 geologic limits on average slip rate on faults a set of 221 principal stress directions and a set of 841 secular rates of geodetic baselines both trilateration and vlbi very long baseline interferometry the patterns of model scores indicate that the time averaged friction coefficient of major faults is only 0 17 0 25 or only 20 30 of the value 0 85 that is assumed for the friction in the intervening blocks the laser trilateration data taken alone would indicate a preference for a high stress model but this model is one with very little fault slip and seismicity which can be rejected on other grounds in the final three parameter set of 64 models we test whether the anomalous weakness of faults is uniform or proportional to net slip with slip dependent weakening there is a general reduction in prediction errors which supports the hypothesis the geologic data and geodetic data agree in implying that fault weakness that is friction of 0 17 is general with an additional 30 slip dependent weakening of the san andreas to friction of 0 12 or 14 of normal the stress data however are fit best if all weakness is slip dependent effectively only the san andreas is weak thus the hypothesis that all weakening is slip dependent should not be rejected the best models predict all available data with rms root mean square mismatch of as little as 3 mm yr 6 of the relative plate velocity so their predictions may be useful for seismic hazard estimation at least along faults where no data are available this study extends the finding of very low friction from subduction zones where it was previously documented to a dominantly strike slip system in which underthrusting of wet sediment is not widespread return of previously subducted water from the mantle and its chemical or physical binding in fine grained gouge are possible explanations for the very low friction

petroleum generation and expulsion characteristics of lower and middle jurassic source rocks on the southern margin of junggar basin northwest china implications for unconventional gas potential jurassic strata along the southern margin of junggar basin are important petroleum system elements for exploration in northwest china the lower and middle jurassic source rock effectiveness has been questioned as exploration progresses deeper into the basin these source rocks are very thick and are distributed widely they contain a high total organic carbon composed predominantly of type iii kerogen with some type ii kerogen our evaluation of source rock petroleum generation characteristics and expulsion history including one dimensional basin modeling indicates that jurassic source rocks are gas prone at deeper depths they reached peak oil generation during the early cretaceous and began to generate gas in the late cretaceous gas generation peaked in the paleogene neogene source rock shales and coals reached petroleum expulsion thresholds at thermal maturities of 0 8 and 0 75 vitrinite reflectance respectively when the petroleum expulsion efficiency was 40 the petroleum generated and exp

organic petrology in the service of archaeology abstract the techniques of organic petrology have been used to study the nature and provenance of 81 ornaments ranging in age from the celtic dated as late hallstatt early la tene tims 500 300 b c to roman 1st 4th century a d periods which have been recovered from graves and settlements in germany and switzerland the ornaments were mainly black or dark brown armlets but also included beads buttons and medallions the most commonly used source material was jet 22 objects which is derived from bituminized drift woods found in liassic oil shale probably mainly of english provenance eleven objects were made from carboniferous cannel coal and four from boghead coal both of unknown geographic provenance only one object proved to be made from posidonia shale a liassic oil shale from southern germany the identification of two distinctive sapropelites used mainly for the production of armlets is of particular interest these sapropelites are the schwarte from the top of the kounova seam stephanian of northern bohemia 15 objects and the kimmeridge coal of dorset england 19 objects the recognition of these organic materials was made possible by the study of fresh rock samples all the armlets made from schwarte were excavated in the celtic oppidum at manching in southern germany the armlets made from kimmeridge coal were found in celtic and roman graves these discoveries suggest the existence of early trade routes crossing the english channel and passing south to switzerland probably along the river rhine a very few armlets were made from dark tuff probably of bohemian origin black glass or dark brown bone these materials were probably all used as substitutes for jet and or sapropelites it is interesting to note that all these dark armlets were thought to possess magic properties which may explain their frequency

organic geochemistry and elements distribution in dahuangshan oil shale southern junggar basin origin of organic matter and depositional environment abstract the dahuangshan oil shale located in the northern bogda mountain on the southern margin of the junggar basin was deposited in a late permian lacustrine environment a combined investigation of element and organic geochemistry was performed to define the source rock potential the paleoenvironment and source of the organic matter thick sequences of oil shales with an average thickness of 638 m were deposited in lucaogou formation which mainly consists of oil shale argillaceous dolomite silty claystone tuff limestone and dolomitic marl a spot of plant stem fossils and abundance of pyrite crystals fishtail and fish skeleton can also be found there analyzed oil shale samples from dahuangshan area are characterized by high total organic carbon toc contents 5 6 34 75 s2 22 65 199 25 mg hc g rock hydrogen index hi 359 1068 mg hc g toc and oil yield 4 9 26 6 indicating the oil shales have excellent source rock potential tmax values 433 453 c show an early to medium maturation stage of organic matter which is supported by organic geochemical maturation parameters all of the obtained kerogen types are types ii and i with oil prone source rock potential dahuangshan oil shale samples are rich in sio2 68 59 followed by al2o3 10 18 and fe2o3 5 43 compared with average shale and north american shale composite nasc analyzed oil shale samples are obviously enriched in p 0 71 there is a significant correlation between al2o3 and fe2o3 mgo k2o mno cu ba co and ni for their association with clay minerals besides the significant correlations between fe2o3 and mno co and ni are considered to result from their similarity on geochemical behavior all selected oil shales are characterized by distinctly sloping light rare earth elements lree trends lan smn 2 70 5 95 accompanied by flat heavy rare earth elements hree trends with distinct eu negative anomalies 0 60 0 73 two slightly different patterns of rees in the oil shale samples are distinguished by the difference in ce depletion and nd anomaly in addition dahuangshan oil shale samples are characterized by short to middle chain n alkanes low carbon preference index cpi values 0 93 1 24 single peak composed of nc20 or nc22 low pr ph 0 41 0 91 relatively high homohop index 0 061 0 99 and high concentrations of c27 sterane indicating reducing deep water and moderate saline environment with prevalent contribution of algae and microorganisms to organic matter accumulation

sedimentation and crustal recycling along an active oblique rift margin salton trough and northern gulf of california transtensional basins embedded in the san andreas fault system of southern california united states and northwestern mexico are fi lled with sediment derived from the colorado river which drains a large area of the western u s interior the sediment is rapidly buried heated and mingled with intrusions in the deep basins to form a new generation of recycled crust along the active plate boundary using a range of values for total basin depth relative volume of mantle derived intrusions and composition of early rift deposits the volume of colorado river derived sediment in the basins is bracketed between 2 2 and 3 4 10 5 km 3 similar to the volume of rock that likely was eroded from the colorado river catchment over the past 5 6 m y the volumetric rate of crustal growth by sedimentation is 80 130 km 3 m y km comparable to growth rates in subductionrelated island arcs and slow seafl oor spreading centers sedimentary and basinal processes thus play a major role in crustal evolution and recycling in this setting and may be important at other rifted margins where a large river system is captured following tectonic collapse of a prerift orogenic highland

genetic classification of petroleum systems our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories 1 charge factor supercharged normally charged or undercharged 2 migration drainage style vertically drained or laterally drained and 3 entrapment style high impedance or low impedance the charge factor is estimated on the basis of the richness and volumetrics of mature source rocks the source potential index spi which combines source rock richness and thickness into a single parameter is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity in extensively explored basins a positive correlation exists between the magnitude of spi and basin wide petroleum reserves the migration drainage style is determined from the structural and stratigraphic framework of a basin vertical migration drainage which occurs mainly through faults and fracture systems breaching a seal is characteristic of petroleum systems contained within rift basins deltaic sequences salt dome provinces wrench basins and fold and thrust belts in contrast lateral migration drainage is dominant wherever stratigraphically continuous seal reservoir doublets extend over a very large area in a tectonically stable province e g commonly foreland or intracratonic platform basins recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the hydrocarbon kitchens the entrapment style which is also dependent on the structural framework and the presence and effectiveness of seals describes the degree of resistance i e impedance working against dispersion of the petroleum charge application of these working concepts should help to significantly reduce geologic risk particularly in new ventures type exploration

quantification of loss of calcite pyrite and organic matter due to weathering of toarcian black shales and effects on kerogen and bitumen characteristics abstract comparison of geochemical data on posidonia shale early toarcian from a shallow unweathered core and from adjacent weathered exposures of the same fades was performed results revealed that quantitatively the most affected petrographic constituent is pyrite and that organic matter and carbonate were also altered by weathering due to this process of weathering the bulk composition of organic matter especially the molecular composition of soluble organic matter and the fluorescence colour of organic particles are changed estimates of weathering rates reveal that the annual release of sulphur and organic carbon from black shales may significantly add to anthropogenic pollution

sem petrography of eastern mediterranean sapropels analogue data for assessing organic matter in oil and gas shales abstract examination of organic matter hosted pore systems in unconventional reservoir rocks has drawn attention to the appearance of sedimentary organic matter om as seen in high resolution sem images field emission sem imaging of eastern mediterranean sapropels pliocene pleistocene age from ocean drilling program drill sites was performed on samples prepared by ar ion cross section polishing the immaturity of marine kerogen in these rocks allows inspection of petrographic textures without overprints related to thermal maturation hydrocarbon generation kerogen in these samples includes discrete particles that in some cases contain primary intragranular pores the most abundant organic matter is in the form of microns thick flaky or stringy material largely nonporous and internally amorphous and lacking the well defined shapes of discrete particles this dominant om has behaved in a highly ductile manner in compaction and is now highly pervaded into intergranular spaces between silt and clay size grains a portion of the larger mineral hosted pores remain open unfilled by ductile om minor nanometer scale pores of uncertain origin occur in the dominant om silt and clay size mineral crystals are distributed in organic matter of most types and it is difficult to fully ascertain if the om mineral mixing has occurred during compaction versus during aggregation during gravity settling marine snow sedimentation or through sediment accumulation in om rich microbial mats results indicate that sediments rich in marine kerogen are subject to substantial compactional porosity loss in early burial these observations of marine detrital organic matter in its early diagenetic state provide a useful baseline for interpretation of petrographic features in more mature om rich mudrocks it is clear that petrographic discrimination of diagenetically generated organic matter bitumen and related om types from ductile dispersed amorphous detrital om kerogen using sem data will be challenging in the absence of compositional information

inception of the eastern california shear zone and evolution of the pacific north american plate boundary from kinematics to geodynamics 1 the san andreas fault saf is the transform boundary between the pacific and the north american plates yet up to 25 of the relative plate motion is now accommodated by the eastern california shear zone ecsz here we investigate the inception of the ecsz and its geodynamic interactions with the saf using a 3 d viscoelastoplastic finite element model for a given fault configuration of the plate boundary zone the model simulates long term slip on the faults and plastic strain outside the faults our results show that the formation of the big bend of the saf around 5 12 ma impeded fault slip and localized strain along the ecsz causing its inception development of the ecsz was further enhanced by the activation of the garlock fault gf and lithospheric weakening caused by the encroachment of the basin and range extension similarly the san jacinto fault sjf in southern california developed along a belt of localized strain which resulted from the formation of the restraining bend along the san bernardino mountains segment of the saf 2 myr ago once activated the sjf reduced slip on both the southern saf and the ecsz across the mojave desert these results indicate causative relationship between the saf and the ecsz the inception of the ecsz and other young faults is the consequence of the evolving saf plate boundary zone that continuously adjusts itself to accommodate the relative plate motion

coal petrology and the origin of coal macerals a way ahead the development of coal petrology and the establishment of a nomenclatural system have proved of major use both for the industrial utilization of coal and for the development of a broad understanding of coal formation and diagenesis the development over the past 30 years however of nomenclature that includes aspects of plant origin and process is a retrograde step e g pyrofusinite degradofusinite and funginite equally problematic is the use of prescriptive formulae to indicate coal origins this paper reviews some of the problems involved with coal petrology as it is usually practiced in addition new advances in organic geochemical techniques have led to a fuller understanding of the relationship of plants and coal macerals recent research on the origin of coal macerals is presented and there is a discussion of the problems and challenges facing coal petrologists a holistic approach to studies of the origin of coal and coal macerals which includes not only petrographic but also chemical and biological studies is advocated d 2002 elsevier science b v all rights reserved

carbon isotope analysis of fossil wood and dispersed organic matter from the terrestrial wealden facies of hautrage mons basin belgium pedogenic nodules calcitic shells dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon isotope chemostratigraphy up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon isotope chemostratigraphy in terrestrial settings the 235 m thick wealden facies sediments of the danube bouchon quarry at hautrage hautrage clays formation mons basin belgium encompass dark to grey clays and sands rich in organic matter and coalified charcoalified fragments of fossil wood deposited in an alluvial plain during middle barremian to earliest aptian we measured and compared the carbon isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon delta c 13 doc and fossil wood delta c 13 wood collected in the same geological level in the whole succession the averages of delta c 13 doc and delta c 13 wood have a significant difference of about 0 9 the delta c 13 wood is usually heavier than the delta c 13 doc which is consistent with measurements on different constituents of modern trees branches versus leaves and tissues in one single stratigraphic level the variability of delta c 13 wood is much higher up to 7 3 parts per thousand than that of delta c 13 doc 0 4 parts per thousand four main causes may explain these results firstly the delta c 13 doc averages the isotopic signal of different compounds and tissues such as leaves seeds cuticles as they become mixed and dispersed the delta c 13 wood reflects the carbon isotope ratio of a small part only of one single tree which is a complex system with delta c 13 variations over a range of 4 parts per thousand secondly there is strong delta c 13 variability between different species of plants in hautrage several gymnosperm genera were collected including podocarpoxylon taxodioxylon brachyoxylon and thujoxylon and numerous fern taxa thirdly coalification and charcoalification can affect the delta c 13 of the doc and the various kinds of woods in a different way fourthly the wood fragments may be reworked several times from more ancient geological levels especially in the alluvial plain environment of hautrage where thick levels of fluviatile coarse sand deposits are observed however in the whole succession both delta c 13 wood and delta c 13 doc curves show similar trends this suggests that carbon isotope curves on fossil wood can be matched to carbon isotope curves on doc for the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession whenever possible both control of the wood taxa and estimation of degree of char coalification are however recommended in one single level charcoal has more stable delta c 13 wood values than delta c 13 wood of coalified fragments the delta c 13 positive trend can be due to several causes including global pco 2 variations and or regional changes and or local environmental conditions in the alluvial plain if global the dating of the hautrage succession may be refined to the late early barremian early late barremian by matching palynological and carbon isotope chemostratigraphical data c 010 elsevier b v all rights reserved

upper permian lacustrine organic facies evolution southern junggar basin nw china abstract the jingjingzigou lucaogou and hongyanchi formations of the southern junggar basin together comprise over 1000 m of organic rich lacustrine facies they record an overall evolution from relatively shallow evaporative lakes to freshwater lakes associated with fluvial systems the jingjingzigou formation is characterized by low toc and hi and biomarker features such as abundant carotane consistent with a specialized saline or hypersaline biota biomarker distributions in jingjingzigou formation extracts most closely resemble oils from the giant karamay oilfield the lucaogou formation represents one of the richest and thickest lacustrine source rock intervals in the world yet it contradicts conventional lacustrine source rock models in at least two important aspects first deposition occurred at middle paleolatitudes 39 43 n rather than in the tropics second limited nutrient supply in a drainage basin dominated by intermediate volcanic rocks appears to have caused low to moderate primary productivities stable salinity stratification and low inorganic sedimentation rates in a deep lake nonetheless resulted in deposits with up to 20 toc and hi near 800 the overlying hongyanchi formation has 1 5 toc but low hi and was deposited in freshwater oxic to sub oxic lakes

intact microbial fossils in the permian lucaogou formation oil shale junggar basin nw china abstract the permian lucaogou formation was deposited in a deep stratified lake with good preservation of the organic matter in the sediments likely due to anoxic bottom waters the lucaogou formation oil shale contains excellent source rocks with high toc contents 12 4 32 9 wt and high hi values 547 869 mg hc g toc the maceral compositions of the oil shales are dominated by lamalginite with some higher plant debris spherical structures about 75 150 m in diameter having yellow fluorescence were observed in the shale edx sem showed that these contained c o p and ca two kinds of well preserved microbial fossils with different morphology were found in these spherical structures using a confocal laser scanning microscope and sem ellipsoidal cells 1 1 5 m long and 0 5 1 m wide occurred inside the spherical structure whereas microspherical cells occur within the outer layers through excluding modern contaminants and endolithic microbes we propose that these microbial fossils are indigenous and syngenetic with oil shale deposition their close physical association in the sediments suggests a symbiotic relationship hydrocarbon extracts of these oil shales have relatively depleted carbon isotopic signatures which is suggestive of methane oxidation this was confirmed by analysis of abundant c 29 and c 30 17 21 h hopanes which show distinctly negative 13 c values typical of those found in methanotrophs several possibilities are presented for the identity of these microorganisms but it is not yet possible to state unequivocally that they are related to methane production and consumption

organic petrology of fukang permian lucaogou formation oil shales at the northern foot of bogda mountain junggar basin china abstract the fukang oil shale zone located in the northern bogda mountain on the southern margin of the junggar basin was deposited in a deep lacustrine environment permian lucaogou formation shale samples collected from six measured outcrop profiles were characterized using organic petrographic and geochemical techniques the macerals can be divided into four groups bituminite liptinite vitrinite and fusinite oil shales are different from coal by their lower content of vitrinite and fusinite but generally high content of bituminite and liptinite all samples containing sufficient hydrogen rich organic matter types i and ii are considered to have a high potential for oil generation the organic matter was deposited in a clastic algal dominated deep water environment and it mainly consists of unstructured bituminite and mineral bituminous groundmass the oil shales with a sapropelitic constituent content lower than 5 5 to 15 15 to 25 and over 25 correspond to non oil shale low quality medium quality and high quality oil shales in industrial grade respectively approximately 65 of the samples belong to sapropel containing shales with an oil yield between 3 5 and 10 which are low quality and medium quality oil shales the total maceral content can be used as an auxiliary index to classify the industrial grade of oil shales oil yields of 3 5 5 and 10 correspond to total organic matter contents of 7 8 9 8 and 17 5 respectively

dispersed organic matter from silurian shales of the barrandian basin czech republic optical properties chemical composition and thermal maturity abstract samples of lower silurian liten and kopanina formations dark shales from the barrandian basin czech republic were examined using reflected light microscopy fourier transform infrared spectroscopy ft ir and gas chromatography mass spectrometry gc ms the samples contained uniform assemblage of organic material that included dominant graptolites chitinozoa bitumens and minor anthracite to meta anthracite rank particle of unknown origin two types of graptolite morphologies were recognized a nongranular blocky type and a granular type bitumen is also common in these rocks and forms discrete oval bodies resembling droplets or angular particles with granular internal fabrics the thermal maturity of the sediments was examined by measuring random reflectance of organic particles the variations in graptolite reflectance in between three localities in the western part of the basin were relatively minor suggesting a similar level of diagenetic transformation the values range from 0 78 to 1 53 rr the reflectance of graptolites was correlated with the reflectance of chitinozoa and bitumen and also indirectly with illite crystallinity data which indicates thermal maturation levels in the high temperature part of the oil window to the onset of wet gas condensate zone mature petroleum that commonly impregnates veins crosscutting the sequence further supports a maturation level within the oil window graptolite and bitumen reflectance values markedly elevated above the regional diagenetic background were found in several centimeter wide contact zones immediately adjacent to basalt sills that locally penetrate the silurian strata as shown by computer modeling heating in the range of 600 800 c which lasted only several years was sufficient to promote an increase in reflectance up to 2 2 5 rr in the contact samples with increasing thermal stress the graptolite periderm undergoes progressive optical and structural changes being gradually converted into a highly condensed aromatic residuum structurally and chemically similar to highly matured kerogen on a basin wide scale however the overall impact of basalt intrusions on organic maturity of enclosing shales was minimal

middle permian environmental changes and shale oil potential evidenced by high resolution organic petrology geochemistry and mineral composition of the sediments in the santanghu basin northwest china abstract shales in the middle permian lucaogou formation have been considered as one of the most important unconventional reservoirs in nw china due to their excellent shale oil and tight oil potential based on the data of previous organic geochemical studies the overall evolution of the ecosystem in the lake water conditions and organic matter sources have been outlined here we present the results of the mineralogical and organic petrological examinations and the rock eval pyrolysis on samples of a fine grained mixed carbonate clastic sedimentary succession from the santanghu basin providing new detailed insights into paleoenvironmental evolution and lake level changes in addition shale oil potential was further evaluated on this oil prone shale analytical results from a total of 196 shale samples from the second member of the lucaogou formation collected from one newly drilled core indicate algal microbial sources of organic matter classified by rock eval pyrolysis as type i kerogen samples characterized by lower hydrogen index hi values type ii kerogen contain increased contributions of terrigenous organic matter evidenced by enhanced inertinite and vitrinite contents vertical variations in mineralogical and bulk geochemical composition reflect an evolution from a saline anoxic to a deep freshwater lake two environmental changes subdivided the sequence into three units the boundary between the lower unit i and the middle unit ii is characterized by the drastic decrease of smectite and k feldspar contents and a sharp increase in total organic carbon toc content the upper unit iii is distinguished by high toc s ratios based on variations in petrography and carbon isotopes of hopanes the middle unit ii can be further subdivided into two parts reflecting changes in water level of the lake all the periods of high water level are characterized by higher lamalginite contents 40 vol and higher hi values than those obtained from sediments deposited during periods of shallower water levels deposition in a shallow lake is evidenced by increased dolomite and decreased lamaginite contents lake level fluctuations indicated by mineralogical and geochemical parameters are associated with changes in organic matter sources leading to the great variability in mineral content organic petrography and hydrocarbon generation potential high toc and brittle minerals contents micro nanopores system and large thickness of the shale show that the lucaogou formation holds a significant shale oil potential in areas where oil window maturity is reached

three dimensional models of deformation near strike slip faults we use three dimensional elastic models to help guide the kinematic interpretation of crustal deformation associated with strike slip faults deformation of the brittle upper crust in the vicinity of strike slip fault systems is modeled with the assumption that upper crustal deformation is driven by the relative plate motion in the upper mantle the driving motion is represented by displacement that is spectied on the bottom of a 15km thick elastic upper crust everywhere except in a zone of finite width in the vicinity of the faults which we term the shear zone stress free basal boundary conditions are specified within the shear zone the basal driving displacement is either pure strike slip or strike slip with a small oblique component and the geometry of the fault system includes a single fault several parallel faults and overlapping en echelon faults we examine the variations in deformation due to changes in the width of the shear zone and due to changes in the shear strength of the faults in models with weak faults the width of the shear zone has a considerable effect on the surficial extent and amplitude i c1 j l c i rl l b blhi aill i srizcxi ld 3 rr ij i n flail 3il i dilitiiiat df ti ijtluii clicili c i i zor tz a j t s ii acmes strong fault lnnlds havs lnore luc tlixd dxz a ac tip of tne faults and the deformation is partly distributed outside the fault zone the dimensions of large basins along strike slip faults such as the rukwa and dead sea basins and the absence of uplift around pull apart basins fit models with weak faults better than models with strong faults our models also suggest that the length to width ratio of pull apart basins depends on the width of the shear zone and the shear strength of the faults and is not constant as previously suggested we show that pure strike slip motion can produce tectonic features such as elongate half grabens along a single fault rotated blocks at the ends of parallel faults or extension perpendicular to overlapping en echelon faults which can be misinterprete d to indicate a regional component of extension zones of subsidence or uplift can become wider than expected for transform plate boundaries when a minor component of oblique motion is added to a system of parallel strike slip faults

mineralogy and geochemistry of a late permian coal in the dafang coalfield guizhou china influence from siliceous and iron rich calcic hydrothermal fluids abstract this paper describes the influence of siliceous and iron rich calcic low temperature hydrothermal fluids lthf on the mineralogy and geochemistry of the late permian no 11 coal anthracitic r r 2 85 in the dafang coalfield in northwestern guizhou province china the no 11 coal has high contents of vein ankerite 10 2 vol and vein quartz 11 4 vol with formation temperatures of 85 and 180 c respectively indicating that vein ankerite and vein quartz were derived from low temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes the vein quartz appears to have formed earlier than vein ankerite did and at least three distinct stages of ankerite formation with different ca sr and fe mn ratios were observed the two types of mineral veins are sources of different suites of major and trace metals scanning electron microscope and sequential extraction studies show that in addition to fe mg and ca vein ankerite is the dominant source of mn cu ni pb and zn in the coal and the contents of these five elements are as high as 0 09 and 74 0 33 6 185 and 289 g g respectively in contrast vein quartz is the main carrier mineral for platinum group elements pges pd pt and ir in the coal and the contents of pd pt and ir are 1 57 0 15 and 0 007 g g respectively sequential extraction showed a high pge content in the silicate fraction up to 10 4 g g pd 1 23 g g pt and 0 05 g g ir respectively it is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the no 11 coal in the dafang coalfield guizhou result from the influx of calcic and siliceous low temperature hydrothermal fluids

evolution of porosity and pore types in organic rich calcareous lower toarcian posidonia shale low and high resolution petrographic studies have been combined with mineralogical toc rockeval and porosity data to investigate controls on the evolution of porosity in stratigraphically equivalent immature oil window and gas window samples from the lower toarcian posidonia shale formation a series of 26 samples from three boreholes wickensen harderode and haddessen in the hils syncline was investigated the main primary components of the shales are microfossiferous calcite 30 50 clay minerals 20 30 and type ii organic matter toc 7 15 hi 630 720 mg gc in immature samples characteristic sub centimetric light and dark lamination reflects rapid changes in the relative supply of these components total porosities decrease from 10 to 14 at ro 0 5 to 3 5 at ro 0 9 and then increase to 9 12 at ro 1 45 these maturity related porosity changes can be explained by a the primary composition of the shales b carbonate diagenesis c compaction and d the maturation micro migration local trapping and gasification of heterogeneous organic phases calcite undergoes dissolution and reprecipitation reactions throughout the maturation sequence pores quantifiable in sem ca 50 nm account for 14 25 of total porosity at ro 0 5 sem visible macropores1 are associated mainly with biogenic calcite at this maturity clays and organic matter are not visibly porous but nevertheless hold most of the shale porosity porosity loss into the oil window reflects a compaction b carbonate cementation and c perhaps the swelling of kerogen by retained oil in addition porosity is occluded by a range of bituminous phases especially in microfossil macropores and microfractures in the gas window mineral hosted porosity is still the primary form of macroporosity most commonly observed at the organic inorganic interface increasing porosity into the gas window also coincides with the formation of isolated spongy and complex meso and macropores within organic particles related to thermal cracking and gas generation this intraorganic porosity is highly heterogeneous point counted macroporosity of individual organic particles ranges from 0 to 40 with 65 of organic particles containing no macropores we suggest that this reflects the physicochemical heterogeneity of the organic phases plus the variable mechanical protection afforded by the mineral matrix to allow macroporosity to be retained the development of organic macroporosity cannot alone account for the porosity increase observed from oil to gas window major contributions also come from the increased volume of organic micro and meso porosity and perhaps by kerogen shrinkage

geochemical and mineralogical anomalies of the late permian coal in the zhijin coalfield of southwest china and their volcanic origin abstract this paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the zhijin coalfield in western guizhou province china our studies reveal that the no 9 coal seam in the zhijin coalfield has very high content of fe 4 34 cu 369 90 g g u 49 6 g g mo 63 10 g g zn 33 97 g g and zr 841 80 g g the studies have also found that elements such as fe and cu do not occur as sulfides in this coal seam in sharp contrast to many other coal seams in china the geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash in addition to normal macerals and minerals in coal a volcanic influenced material vim derived from volcanic ash detrital material of terrigenous origin and organic matter was identified under polarized light reflectance microscopy and scanning electron microscopy equipped with energy dispersive x ray edx analyzer the volcanic influenced material is the main carrier of the above elements in this coal six types of the volcanic influenced material vim 1 vim 2 vim 3 vim 4 vim 5 and vim 6 are further distinguished on the basis of their structures and compositions to the best of our knowledge this is the first report that presents a detailed classification of coal components with a high content of volcanic ash

geochemistry of the shitoumei oil shale in the santanghu basin northwest china implications for paleoclimate conditions weathering provenance and tectonic setting abstract thick sequences of organic rich lacustrine oil shale were deposited in the middle permian lucaogou formation of the junggar basin and the santanghu basin the mineralogy and major trace and rare earth element geochemistry of the oil shales and mudstones collected from the lucaogou formation are discussed the chondrite normalized patterns of the studied samples show lree enrichments hree deficits and generally negative eu anomalies and positive ce anomalies the paleoclimate indictor c value varies between 0 08 and 0 62 reflecting generally arid to subhumid conditions in addition low rb sr with a mean value of 0 14 and high sr cu with a mean value of 33 22 values indicate that arid conditions prevailed during the deposition of the lucaogou formation sr ba ratios 0 31 7 73 of the studied samples suggest a paleoenvironment with variable salinity the salinity of the lake is controlled by climate variations freshwater replenishment seawater intrusion and redox conditions the studied oil shales in the lucaogou formation are mainly derived from a felsic dacite and rhyolite to intermediate andesite source that formed in the early permian and mixed with small amounts of basic rocks basalt volcanic eruptions provided the source rocks for the lucaogou formation the chemical index of alteration cia the plagioclase index of alternation pia and an a cn k ternary diagram indicate that the parent rocks of the oil shale experienced weak to moderate chemical weathering

characteristics of selected petroleum source rocks xianjiang uygur autonomous region northwest china 1 the sedimentary basins of xinjiang uygur autonomous region china are moderately to poorly explored for petroleum volumetric adequacy of petroleum source rocks is a critical exploration risk in these basins particularly because source rock data are limited this study provides new source rock data and speculatively assesses the source rock potential of xinjiang basins the junggar zhungaer basin the best explored of the xinjiang basins and containing a giant oil field is underlain in many areas by an upper permian lacustrine oil shale sequence remarkable for its organic richness and oil source quality depending on its position in the basin the permian section ranges from immature to overmature and is inferred to be the principal source of oil in the basin upper triassic middle jurassic coal measures including lacustrine rocks constitute a secondary source rock sequence in the basin the smaller intermontane turpan tulufan basin contains a very similar upper triassic middle jurassic sequence which where sufficiently buried probably comprises the only significant oil source sequence in the basin the vast tarim talimu basin offers the greatest variety of potential source rocks of all xinjiang basins but remains the least well documented from limited but geologically planned and focused sampling cambrian carboniferous and permian strata are not considered major oil contributors in the dominantly shallow marine paleozoic section of the northern tarim basin only ordovician black shales appear to have significant potential the upper triassic middle jurassic sequence of the northern tarim basin is similar to that of the junggar and turpan basins a section rich in coal and lacustrine shale that constitutes another potentially significant oil source due to the size stratigraphic packaging and structural relief of the northern tarim basin paleozoic and mesozoic potential il source beds range from immature to overmature

depositional model for a salinized lacustrine basin the permian lucaogou formation jimsar sag junggar basin nw china abstract fine grained sedimentary rocks are well developed in a salinized lacustrine basin in the junggar basin china understanding the sedimentary characteristics and process of these fine grained sediments is essential to find the exploration target for tight oil in this study the sedimentary characteristics and forming mechanism of fine grained sediments in the permian lucaogou formation within the jimsar sag were investigated based on core and thin section observation sem combined with xrd and geochemical data and eleven lithofacies were identified including 1 brecciated dolomitic mudstone 2 intraclastic conglomerate 3 mixed siliciclastic and intraclastic grainstone 4 dolomitic siltstone 5 carbonate packstone and grainstone 6 dolomitic mudstone 7 laminated algae bearing tuffaceous mudstone 8 massive tuffaceous mudstone 9 turbidite dolomitic mudstone to siltstone 10 pebbled sandstone and 11 green mudstone and siltstone the organic constituents in the fine grained sedimentary rocks include sapropelic exinite vitrinite inertinite and secondary macerals which are dominated by unstructured algae and asphaltene the fine grained sedimentary rocks are characterized by high frequency cycles composed of three successive facies associations profundal littoral sublittoral and palustrine which recorded distinct lacustrine expansion and contraction developed mud cracks paleosols and vertical dissolution fractures in the fine grained sedimentary rocks indicate that these facies recorded the depositional process in an ephemeral to perennial lake in an arid climate fluvio deltaic and aeolian transport were main modes for transporting the siliciclastic component that ultimately accumulated in a subaqueous and subaerial environment the dolomite in the littoral zone might develop with the evaporitic concentration of the lake water during the early diagenetic stage the depositional processes in the profundal zone included suspension and turbidity currents multiphase volcanic activities affected the lithofacies and prompted the accumulation of organic matter understating the depositional process of the fine grained sedimentary rocks in the lucaogou formation in the jimsar sag is helpful to understand the depositional environment in the salinized lacustrine basin in the junggar basin

mineralogy and organic petrology of oil shales in the sangkarewang formation ombilin basin west sumatra indonesia abstract the ombilin basin is filled by late eocene to early oligocene marginal fan deposits brani formation and lacustrine shales sangkarewang formation unconformably overlain by a late oligocene to early miocene fluvial sequence sawahlunto and sawahtambang formations and capped by an early to mid miocene marine sequence ombilin formation significant oil shale deposits occur in the sangkarewang formation intercalated with thin laminated greenish grey calcareous sandstones x ray diffraction shows that the sediments consist mainly of quartz feldspar carbonates and a range of clay minerals together in some cases with minor proportions of sulphides evaporites and zeolites feldspar and non kaolinite clay minerals decrease up the sequence relative to kaolinite suggesting a changing sediment source as the basin was filled calcite thought to be mainly of authigenic origin is also more abundant in the middle and upper parts of the sequence the organic matter in the oil shales of the sequence is dominated by liptinite macerals particularly alginite mainly lamalginite and sporinite cutinite also occurs in some samples along with resinite and traces of bituminite the dominance of lamalginite in the liptinite components suggests that the material can be described as a lamosite samples from the sangkarewang formation have vitrinite reflectance values ranging between 0 37 and 0 55 these are markedly lower than the vitrinite reflectance for coal from the overlying sawahlunto formation 0 68 possibly due to suppression associated with the abundant liptinite in the oil shales fischer assay data on outcrop samples indicate that the oil yield is related to the organic carbon content correlations with xrd data show that with one exception the oil yield and organic carbon can also be correlated directly to the abundance of carbonate calcite and inversely to the abundance of quartz plus feldspar this suggests that the abundance of algal material in the lake sediments was preferentially associated with carbonate deposition high yields of oil are noted in some samples as a percentage of the organic carbon content this may indicate that partial generation of hydrocarbons from the material has already taken place in association with thermal maturation of the sangkarewang succession

fluorescence spectral analysis of resinite macerals from coals of the hanna formation wyoming u s a abstract flourescence spectral analysis indicates that resinite macerals from tertiary hanna formation coals hanna coal field southcentral wyoming u s a can be separated into five distinct groups the first resinite group fluoresces a a medium green in blue light its average spectral maximum occurs at or below 440 mm with a red green quotient of 0 22 the second resinite group fluoresces yellow green with an average spectral maximum of 500 nm and a red green quotient of 0 53 the third resinite group displays a yellow fluorescence having an average spectral maximum of 580 nm and a red green quotient of 0 86 the fourth resinite group fluorescence orange brown having an average spectral maximum of 610 nm and a red green quotient of 1 20 these four groups mostly occur as primary globular resinites exhibiting scratches and fractures indicating that they are brittle solid substances primary cell filling and secondary fracture filling resinites also occur in these four groups the fifth group only occurs as a secondary void filling material and lacks evidence of br of brittle properties it fluoresces a reddish brown has a spectral maximum at 690 nm and a red green quotient of 1 54 the fifth group has properties resembling exsudatinite the five resinite groups can be separated on the basis of their nine spectral properties alone without qualitative petrographic interpretation the relative quantities of the five resinite groups vary among hanna formation coals the origins of these five resinite groups are probably related to their botanical properties and pre and post depossitional conditions overall hanna formation resinites have petrographic characteristics similar to other north american resinites however only four resinite groups have been distinguished in in certain coals from utah and new mexico u s a and western canada

cannel coals implications for classification and terminology abstract cannel coals are tough massive coals with a dull luster that break with an even compact grain and conchoidal cross fractures historically cannel coals were of significant economic and social importance during the early industrialization of the usa they were the source for a sophisticated petrochemical industry and a fuel source for heating gas making coke making and oil generation petrographic data proximate analysis and ultimate analysis data were obtained for 68 cannel coals from kentucky to decide how well the cannel coals fit the generally accepted definitions of a cannel coal four maceral assemblages were found sporinite with abundant medium grained vitrinite and inertinite sporinite with abundant fine grained vitrinite and inertinite of which micrinite is abundant bituminite may be present alginite with abundant fine grained vitrinite and inertinite and alginite and bituminite with minor vitrinite and inertinite volatile matter and h c ratios are highest for those samples with abundant liptinite with a sample from breckenridge having the highest value of each five samples were analyzed by the rock eval method the s2 and hi indices show that the coals would make excellent source rocks discrepancies between the values for the five samples are related to maceral composition and there may be a good correlation between source rock potential and importance as a feedstock for synthetic crude oil production in the 1800s the maceral composition of the microlithotypes is related to the environment of deposition coal composed of assemblage i formed in humic peat swamps in which unusually large numbers of spores were introduced possibly because of unusual climatically controlled reproductive cycles coals composed of assemblages ii to iv formed as sapropelic coals in lakes at some stage of peat swamp development

organic petrology and geochemistry of mudrocks from the lacustrine lucaogou formation santanghu basin northwest china application to lake basin evolution abstract exploration for tight oil in the frontier santanghu basin of northwest china has resulted in recent commercial discoveries sourced from the lacustrine upper permian lucaogou formation already considered a world class source rock in the junggar basin to the west here we apply an integrated analytical program to carbonate dominated mudrocks from the lucaogou formation in santanghu basin to document the nature of organic matter om in the context of an evolving lake system the organic rich samples toc 2 8 11 4 wt n 10 were widely spaced from an 200 m cored section interpreted from textural and mineralogical evidence to document transition from a lower under filled to an overlying balanced filled lake organic matter is dominated by moderate to strongly fluorescent amorphous material with type i geochemical signature hi values 510 755 n 10 occurring in a continuum from lamellar stringers 10 20 m thick some 1 mm in length possible microbial mat preserved only in lower under filled section to finely disseminated amorphous groundmass intimately intermixed with mineral matrix biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a complex microbial consortium a unicellular prasinophyte green alga similar to tasmanites in marine rocks is present as discrete flattened discs 50 100 m in diameter type iii om including vitrinite some fluorescent and inertinite also is abundant solid bitumen indicating local kerogen conversion fills voids and occurs throughout the cored section vitrinite reflectance values are 0 47 0 58 consistent with strong om fluorescence but may be suppressed other proxies e g biomarker parameters indicate the lucaogou formation is in the early oil window at this location on average slightly more amorphous om and telalginite are present in the lower section consistent with a shallow stratified saline environment with low sediment dilution more inertinite is present in the upper section indicating greater terrestrial influx and consistent with higher quartz and plagioclase content dominantly authigenic chalcedony and albite laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing also indicating stratified water column conditions a decrease upsection in authigenic dolomite with reciprocal increase of ankerite siderite is consistent with decreasing salinity as is an overall decrease in gammacerane index values these observations suggest evolution from a shallow stratified evaporative saline setting to a deeper stratified freshwater basin with higher water input during lucaogou deposition the evolution from an under filled to balance filled lake in santanghu basin is similar to lucaogou deposition in junggar basin suggesting similar tectonic and climatic controls paleoclimate interpretations from other researchers in this area suggested an evolution from semi arid to humid conditions during the roadian we interpret that the evolution from an under filled to balanced filled lake seen in our data is in response to climate change and may represent increased groundwater delivery to the santanghu basin

mineralogy and geochemistry of boehmite rich coals new insights from the haerwusu surface mine jungar coalfield inner mongolia china abstract boehmite rich coal of pennsylvanian age was discovered earlier at the heidaigou surface mine jungar coalfield inner mongolia china this paper reports new results on 29 bench samples of the no 6 coal from a drill core from the adjacent haerwusu surface mine and provides new insights into the origin of the minerals and elements present the results show that the proportion of inertinite in the no 6 coal is higher than in other late paleozoic coals in northern china based on mineral proportions boehmite to kaolinite ratio and major element concentrations in the coal benches of the drill core the no 6 coal may be divided into five sections i to v major minerals in sections i and v are kaolinite sections ii and iv are mainly kaolinite with a trace of boehmite and section iii is high in boehmite the boehmite is derived from bauxite in the weathered surface benxi formation in the sediment source region the no 6 coal is rich in al2o3 8 89 tio2 0 47 li 116 g g f 286 g g ga 18 g g se 6 1 g g sr 350 g g zr 268 g g rees 172 g g pb 30 g g and th 17 g g the elements are classified into five associations by cluster analysis i e groups a b c d and e group a ash sio2 al2o3 na2o li and group b ree sc in y k2o rb zr hf cs u p2o5 sr ba ge are strongly correlated with ash yield and mainly have an inorganic affinity the elements that are negatively or less strongly correlated with ash yield with exceptions of fe2o3 be v and ni are grouped in the remaining three associations group c se pb hg th tio2 bi nb ta cd sn group d co mo tl be ni sb mgo re ga w zn v cr f cu and group e s as cao mno fe2o3 aluminum is mainly distributed in boehmite followed by kaolinite the high correlation coefficients of the li ash li al2o3 and li sio2 pairs indicate that li is related to the aluminosilicates in the coal the boehmite rich coal is high in gallium and f which occur in boehmite and the organic matter selenium and pb are mainly in epigenetic clausthalite fillings in fractures the abundant rare earth elements in the coal benches were supplied from two sources the bauxite on the weathered surface of the benxi formation and from adjacent partings by groundwater leaching during diagenesis the light rare earth elements lrees are more easily leached from the partings and incorporated into the organic matter than the heavy rees leading to a higher ratio of lrees to hrees in the coal benches than in the overlying partings