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

evidence for episodic cementation and diagenetic recording of seismic pumping events north coles levee california u s a abstract bands of calcite and dolomite cements alternating with zones of nearly carbonate free sand occur in the stevens sandston aat north coles levee san joaquin valley california temperatures calculated from o isotopes suggest that the calcite cement bands were emplaced episodically as a result of repeated injections of hot water from deeper in the section burial analysis suggests that these cements precipitated from 7 ma to the present over the temperature range of 45 to 95 c carbon isotope data suggest that the c in the cements is a mixture derived from two sources detrital shell material 13c pdb and co2 liberated from maturing kerogen 13c 24 plots of 13c vs time and depth of crystallization show that the cementation sequence was 1 dolomite cements possibly concretionary precipitated at depths a log of 13c vs calculated depth of crystallization correlates with the stratigraphic column at north coles levee if the correlation is valid the light 13 in each cement sample can be tied to its source a model based on this interpretation suggests that the early light c was derived from maturing kerogen in the kreyenhagen formation eocene as it passed through the oil window between 4 and 5 ma the subsequent passage of younger sediments with less organic material produced correspondingly smaller amounts of light co2 which was reflected in the relatively heavier c isotopes in the later cements it is suggested that the epidsodic injections of hot water carried dissolved gases and minerals principally calcite upward from rocks as deep as 2 3 km below the stevens sandstone and reprecipitated the calcite in more permeable zones in the rock degassing of co2 from rising pore waters likely triggered the precipitation and accounts for the relatively large volumes of cement the sibson model for seismic pumping of pore fluids is considered a likely explanation for the observed cementation

origin of inertinite rich coals of australian cratonic basins abstract the australian permian cratonic cooper and galilee basins contain extensive deposits of inertinite rich coals in contrast the contiguous foreland sydney and bowen basins are dominated by vitrinite rich coals inertinite in the cratonic basin coals is mainly botanically unstructured fragmentary inertodetrinite in the foreland basin coals semifusinite is the dominant inertinite maceral microlithotypes in the cratonic basin coals are characteristically finely banded sulfur and ash contents are low by world standards the cratonic basin coals accumulated in freshwater mires where low subsidence rates led to extensive oxidation of the peat subaerial and probably subaqueous oxidation took place due to water table fluctuations there is no evidence that these inertinite rich coals were formed from a unique flora or under climatic conditions different from vitrinite rich permian coals

stevens and earlier miocene turbidite sandstones southern san joaquin valley california a thick marine turbidite succession dominantly coarse sandstone underlies the southern part of the san joaquin valley sands are pebbly to fine grained commonly poorly sorted quartzose to arkosic and are interbedded with dark shales bearing deep water foraminifers graded bedding is common and with the depths of 2 000 to 6 000 ft 610 to 1 830 m implied by the fauna is taken to indicate a turbidity current origin for most of the sands the upper middle and lower miocene turbidite section was revealed by extensive coring at paloma and is similar to the more widespread and oil and gas productive upper miocene stevens sandstone the central basin stevens was deposited as channel sands on deep sea fans derived from several discrete troughs or canyons on the eastern and southeastern margin of the basin prior to their burial by prograding santa margarita sand sand channels and lobes in the bakersfield arch area were controlled locally by compaction structures the rising paloma anticline deflected stevens sands for a time and the very last sands were guided also by incipient folds on the outer bakersfield arch coarse stevens conglomerates and sands shed from the emergent temblor range were deflected by the buena vista hills elk hills and other anticlinal shoals and were deposited in intervening gaps as thick oil productive channel sands they merge with sands from the east side in flowing axially into the di tal northwestern basin facies recognized in the subsurface include a meander channel facies developed in the prograded muddy slope area upstream from the massive braided sand facies

geochemical cycles in sediments deposited on the slopes of the guaymas and carmen basins of the gulf of california over the last 180 years sediments deposited on the slopes of the guaymas and carmen basins in the central gulf of california were recovered in two box cores q mode factor analyses identified detrital clastic carbonate and redox associations in the elemental composition of these sediments the detrital clastic fraction appears to contain two source components a more mafic component presumably derived from the sierra madre occidental along the west coast of mexico and a more felsic component most likely derived from sedimentary rocks mostly sandstones of the colorado plateau and delivered by the colorado river the sediments also contain significant siliceous biogenic components and minor calcareous biogenic components but those components were not quantified in this study redox associations were identified in both cores based on relatively high concentrations of molybdenum which is indicative of deposition under conditions of sulfate reduction decreases in concentrations of molybdenum in younger sediments suggest that the bottom waters of the gulf have became more oxygenated over the last 100 years many geochemical components in both box cores exhibit distinct cyclicity with periodicities of 10 20 years the most striking are 20 year cycles in the more mafic components e g titanium particularly in sediments deposited during the 19th century in that century the titanium cycles are in very good agreement with warm phases of the pacific decadal oscillation implying that at times of greater influx of titanium rich

instantaneous outbursts in underground coal mines an overview and association with coal type instantaneous outbursts in underground coal mines have occurred in at least 16 countries involving both methane ch4 and carbon dioxide co2 the precise mechanisms of an instantaneous outburst are still unresolved but must consider the effects of stress gas content and physico mechanical properties of the coal other factors such as mining methods e g development heading into the coal seam and geological features e g coal seam disruptions from faulting can combine to exacerbate the problem prediction techniques continue to be unreliable and unexpected outburst incidents resulting in fatalities are a major concern for underground coal operations gas content thresholds of 9 m 3 t for ch4 and 6 m 3 t for co2 are used in the sydney basin to indicate outburst prone conditions but are reviewed on an individual mine basis and in mixed as situations data on the sorption behaviour of bowen basin coals from australia have provided an explanation for the conflicting results obtained by coal face desorption indices used for outburst proneness assessment a key factor appears to be different desorption rates displayed by banded coals which is supported by both laboratory and mine site investigations dull coal bands with high fusinite and semifusinite contents tend to display rapid desorption from solid coal for a given pressure drop the opposite is true for bright coal bands with high vitrinite contents and dull coal bands with high inertodetrinite contents consequently when face samples of dull fusinite or semifusinite rich coal of small particle size are taken for desorption testing much gas has already escaped and low readings result the converse applies for samples taken from coal bands with high vitrinite and or inertodetrinite contents in terms of outburst potential it is the bright vitrinite rich and the dull inertodetrinite rich sections of a coal seam that appear to be more outburst prone this is due to the ability of the solid coal to retain gas even after pressure reduction creating a gas content gradient across the coal face sufficient to initiate an outburst once the particle size of the coal is reduced rapid gas desorption can then take place c 1998 elsevier science

monterey formation porcelanite reservoirs of the elk hills field kern county california oil and gas production from monterey formation porcelanite at the elk hills field in california s san joaquin basin occurs from intervals that have quartz phase mineralogy however characteristics differ from chert and porcelanite reservoirs of the coastal california monterey formation in that matrix porosity is more typical of the opal ct phase petroleum storage is mostly in the matrix and natural fracture patterns are dominantly small scale several elk hills reservoirs located on two large anticlines produce from porcelanite the 29r ab and 31s d are the most productive porcelanite reservoirs each having cumulative oil production of about 40 million bbl although interbedded with siliceous shale sandstone and dolomite most of the porous reservoir rock is laminated porcelanite porosity averages between 20 and 25 and is evenly distributed throughout the porcelanite as extremely small pores ranging in size from 1 to 10 m matrix permeability averages 0 8 md but flow of oil and gas is enhanced through fractures parallel with and perpendicular to bedding higher than anticipated porosity may be in part due to migration of hydrocarbons into the porcelanite reservoirs while still in opal ct phase mineralogy the dissolution of opal ct and precipitation of quartz occurs in place and the resulting quartz phase mineral structure mimicks the porous opal ct framework

secondary biogenic coal seam gas reservoirs in new zealand a preliminary assessment of gas contents abstract four coal cores one from the huntly eocene two from the ohai cretaceous and one from the greymouth cretaceous coalfields were sampled and analysed in terms of gas content and coal properties the coals vary in rank from subbituminous b a huntly to subbituminous c a ohai and high volatile a bituminous greymouth average gas contents were 1 60 m 3 t s 0 2 in the huntly core 4 80 m 3 t s 0 8 in the ohai cores and 2 39 m 3 t s 0 8 in the greymouth core the ohai core not only contained more gas but also had the highest saturation 75 compared with the huntly 33 and greymouth 45 cores carbon isotopes indicate that the ohai gas is more mature containing higher 13 c isotopes values than either the huntly or greymouth gas samples this may indicate that the gas was derived from a mixed biogenic and thermogenic source the huntly and greymouth gases appear to be derived solely from a secondary biogenic by co 2 reduction source although the data set is limited preliminary analysis indicates that ash yield is the dominant control on gas volume in all samples where the ash yield was above 10 below 10 the amount of gas variation is unrelated to ash yield although organic content has some influence on gas volume associations are basin and or rank dependent in the huntly core total gas content and structured vitrinite increase together although this relationship does not appear for the other core data for the ohai sc3 core lost gas and fusinite are associated whereas gelovitrinite unstructured vitrinite correlates positively with residual gas for the greymouth data

upper miocene stevens sandstone san joaquin basin california reinterpretation of a petroliferous sand rich deep sea depositional system deep marine sands of the upper miocene stevens sandstone one of the most important hydrocarbon producing units in the united states were deposited by sediment gravity flows in the bakersfield arch area of the southern san joaquin basin the stevens sandstone historically has been considered to be a thick turbidite succession shed off the southern sierra nevada as four fans in a long lived submarine fan system fed in large part by several large submarine canyons access to previously unavailable proprietary two dimensional and three dimensional seismic data sets carefully calibrated by well log and core data permits a more complete understanding of the depositional architecture of this highly petroliferous deep marine depositional system we conclude that these units were deposited in a structurally controlled sand rich deep sea system which was fed by a delta system that lacked major submarine canyons the uppermost sand unit the upper stevens sandstone developed as a deep sea braid plain in the area of the present bakersfield arch within the braid plain curvilinear features detected on horizon slices through a three dimensional seismic data cube are interpreted as braided channel form deposits hydrocarbon production established along these linear trends may reflect improved reservoir quality localized by channel sedimentary processes

the record of triassic charcoal and other evidence for palaeo wildfires signal for atmospheric oxygen levels taphonomic biases or lack of fuel abstract as wildfires are today important sources of disturbance in many terrestrial ecosystems it is of great interest to understand how different environmental parameters and fire activity interacted during past periods of the earth history fossil charcoal inertinites and pyrogenic polycyclic aromatic hydrocarbons pahs represent the only direct evidence for the occurrence of such palaeo wildfires in the present study a review of published data together with new data on the occurrence of fossil charcoal for the permian and the triassic is presented for a long time it has been speculated that an assumed lack of evidence for palaeo wildfires during the triassic should be explained by a large drop in atmospheric oxygen concentration following or during the end permian mass extinction event preventing the occurrence of wildfires however evidence for palaeo wildfires is relatively common in many middle and late triassic strata whereas such evidence is almost totally lacking from early triassic sediments the interpretation of this charcoal gap or depression is difficult as many factors e g atmospheric oxygen concentration taphonomical biases lack of sediments suitable for the preservation of macroscopic charcoal lack of fuel and ignorance of scientists may have influenced not only the production but also the preservation and recovery of evidence for palaeo wildfires during this period thus it is not clear whether this early triassic charcoal gap can also be seen as evidence for an assumed wildfire gap or not without any doubt further investigations on the early triassic record of charcoal and other evidence for palaeo wildfires will be necessary before this problem can be solved in fact it can be expected that the number of published records of early triassic evidence for palaeo wildfires will increase in the future as more and more scientist working on sediments of this age may become aware of the interest in fires from this time this will certainly make it possible to give a much better picture of the temporal and regional distribution of wildfires during this period in the future

the stratigraphic distribution of inertinite abstract the paper presents the results of an investigation into the stratigraphic distribution of inertinite in humic coals ranging from the silurian to the neogene periods this range equals the time span during which both land plants and atmospheric oxygen evolved the survey is based on a literature study of inertinite in coals covering a variety of depositional environments and climates in all continents the inertinite percentages listed in this paper have been arranged in stratigraphic order they are the mean values based on mineral free whole coal compilations maceral compositions listed in the literature for individual subsections have been averaged to represent complete coal seams beds although this might not have been always possible due to some ambiguity in the published record moreover not all of the published and unpublished information could be used because of poor sample description obscure geographic origin or insufficient stratigraphic information the results show that there have been times in the geological past e g during the late permian in which coals were particularly rich in inertinite compared with other times e g during much of the late tertiary in which many coals contained very little inertinite occasionally such primary global trends were modulated by a diffuse distribution of inertinite percentages that correspond to differences in climate depositional settings e g active orogenic margins versus tectonically inactive shelf margins and other local or regional variations although various mechanisms for the generation of inertinite have been proposed in the past the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal this points to secular variations in the atmospheric oxygen content as an explanation for the global changes in the inertinite distribution while differential subsidence and climatically influenced reaction rates governed regional and local variations in inertinite percentages

middle miocene tectonic uplift of southern san joaquin basin california calculations of the tectonic component of the subsidence history of california s southern san joaquin basin indicate 200 400 m of abrupt tectonic uplift during the relizian about 15 ma this uplift can be explained as an isostatic response to the movement of thin young lithosphere south of the subducted mendocino fracture zone to a position under the basin the calculated uplift cannot be a result of extension and subsidence caused by instability of the mendocino triple junction but earlier early miocene subsidence of the basin may have resulted from triple junction related extension marine strata deposited in the san joaquin basin during the middle miocene are rich sources of petroleum so the inferred uplift and facies shifts may have important implications for ex loration

evidence for meteoric recharge in the san joaquin basin california provided by isotope and trace element chemistry of calcite abstract calcite cements were analysed petrographically and geochemically to document patterns of meteoric recharge into marine sandstones in the san joaquin basin california calcite cements in shallow marine sandstones in the eastern basin are pure 96 mol ca 32 and 18 o pdb 18 o and point counted volumes of 26 27 appear 5 m apart the purity of low temperature calcite 8 10 9 m 3 and rates of locally variable dissolution reactions and calcite crystallization exceeded the flushing rates of reservoirs if meteoric recharge began shortly after the deposition of marine shelf sandstones approximately 23 ma then calcite cements record downdip infiltration at an average rate of 1 mm year less than some recorded rates of gravity driven flow

thermal history of rocks in southern san joaquin valley california evidence from fission track analysis the theory of the fission track method and its application to sedimentary basin analysis is illustrated by a case study in the southern san joaquin valley california fission tracks provide a powerful tool for studying the thermal history of sedimentary basins because the two minerals most commonly used in fission track studies apatite and zircon occur as detrital constituents in many sedimentary rocks and their annealing temperatures span the main temperature range for oil generation fission tracks also provide information on the sedimentation record and provenance of rocks in a basin we have used fission track analysis to study the thermal and depositional history of the subsurface tertiary sedimentary rocks on both sides of the active white wolf reverse fault in the southern san joaquin valley the distinctly different thermal histories of the rocks in the two structural blocks are clearly reflected in the apatite fission track data which suggest that rocks in the rapidly subsiding basin northwest of the fault have been near their present temperature for only about 1 m y compared with about 10 m y for rocks southeast of the fault these estimates of heating time agree with previous estimates for these rocks zircon fission track data indicate that the tertiary sediments were derived from parent rocks of more than one age however from at least the eocene to late miocene or pliocene the major sediment source was rocks related to the youngest sierra nevada mesozoic intrusive complexes which are presently exposed east and south of the southern san joaquin valley

organic petrology geochemistry gas content and gas composition of middle pennsylvanian age coal beds in the eastern interior illinois basin implications for cbm development and carbon sequestration abstract fifty four samples of coal and organic rich roof shale strata were collected as part of a coal bed methane exploration program following canister desorption to document gas contents the samples were analyzed by geochemical and petrographic methods coal samples were found to have moderate ash yields avg 13 5 dry basis and high total sulfur contents avg 4 3 dry basis the average gas content was 1 91 m3 ton petrographically the coals were dominated by vitrinite macerals avg 81 6 mmf especially telovitrinite by comparison liptinite avg 7 1 mmf and inertinite macerals avg 11 3 mmf were minor in occurrence coal samples ranged from high volatile c to high volatile a bituminous in rank avg ro maximum 0 76 shale samples had higher ash yields avg 76 1 dry basis though total sulfur contents were comparable to the coal samples avg 4 2 dry basis gas contents were lower than the corresponding coal samples avg 0 65 m3 ton petrographically the shale samples contained decreased amounts of vitrinite avg 25 6 mmf and higher amounts of liptinite avg 45 4 mmf and inertinite avg 29 0 mmf macerals relative to the coal samples gas obtained from coal and shale beds in the illinois basin was relatively pure high ch4 content limited data also indicated that illinois basin coals have the ability to adsorb fairly significant amounts of co2 this suggests that co2 injection to enhance methane production ecbm and or to sequester co2 may have some potential mineralization in the coals could negatively impact cbm production but it was found that the majority of the mineralization was present in the roof strata

40ar 39ar age spectrum analysis of detrital microclines from the southern san joaquin basin california an approach to determining the thermal evolution of sedimentary basins abstract detrital microcline grains from sedimentary strata preserve a record of thermal evolution in the temperature range 100 to 200 c which can be revealed by40ar 39ar age spectrum analysis microcline separates from deep drill hole intersections with eocene to miocene sediments in the basin and tejon blocks of the southern san joaquin valley california analysed by the age spectrum approach show radiogenic40ar 40ar gradients that record both the slow cooling of the uplifting sediment source 65 ma ago and a recent thermal event this information in conjunction with the observation of fission track annealing in the coexisting apatites allows estimation of the temperature time conditions of this thermal event at about 140 c for 200 ka present and paleotemperature data is in accord with heating related to several kilometers of pleistocene sediment deposition heat flow calculations suggest that this recent subsidence has depressed the thermal gradient from about 30 c km 1 to the present apparent gradient of 24 c km 1 40ar 39ar analysis of detrital microcline crystals yields thermochronological information in the temperature time range of petroleum maturation and provides this technique with potential as both a useful exploration tool and as a means of probing the fundamental geodynamic processes of basin evolution

the burning of gondwana permian fires on the southern continent a palaeobotanical approach abstract fossil charcoal has widely been accepted as a direct indicator for the occurrence of palaeo wildfires in upper palaeozoic sediments of euramerica and cathaysia records of these remains are relatively common and regionally and stratigraphically more or less homogeneously distributed in terrestrial sequences on the other hand just a few records have been published for the permian of gondwana and only recently has it been demonstrated that macroscopic charcoals are also common here most permian macroscopic charcoal from gondwana is gymnospermous and has been reported from coal bearing strata macroscopic charcoal occurrences are spread out in different sequences and also in distinct stratigraphic intervals in the permian e g parana basin sakmarian artinskian of brazil karoo basin artinskian of south africa damodar basin lopingian of india and dead sea area changhsingian of jordan they range from peri glacial post glacial to warm temperate climatic systems throughout the permian macro and micro charcoal occurrences are compared to inertinite incidences to support the pyrogenic origin for these coal macerals and to provide an up to date overview on the known evidences of permian wildfires on gondwana in space and time

tectonic depositional and diagenetic history of monterey formation miocene central san joaquin basin california the miocene monterey formation in the central san joaquin basin of california consists of biogenic siliceous rocks with a significant terrigenous clastic component correlation of electric logs in conjunction with analysis of outcrop sections core samples and paleontologic data suggests that deposition of the monterey was controlled by an interplay of basin geometry san andreas related tectonics fluctuations in sea level and changes in climate the basin is bounded on the east by the sierran magmatic arc complex and on the west by the san andreas fault during the late saucesian through early mohnian 20 10 ma the basin was reshaped by tectonism related to the migrating mendocino triple junction creating a broad gently sloping shelf to the east that cut off the supply of clastics to the central basin with the subsequent evolution of the san andreas fault the salinian block was emplaced along the western basin margin restricting the seaway and permitting low oxygen nutrient rich waters to occupy the basin as a result laminated organic rich fine grained pelagic to hemipelagic sediments of the monterey formation were deposited a warmer climate during saucesian through luisian time with less intensive upwelling le to more calcareous less siliceous sedimentation a cooling trend during late miocene time 10 5 ma increased upwelling activity diatom productivity in the water column and deposition of diatomaceous debris although turbidites accumulated on the basin floor and terrigenous clastics were deposited on the eastern shelf relatively undiluted diatomaceous deposits developed on outer shelves and slopes atop anticlinal banks generated by wrench tectonism and in some areas of the basin floor a mid mohnian eustatic sea level rise caused fine grained deposition to extend onto the eastern shelf slightly later a mid late mohnian period of exceptionally cool temperatures resulted in the most extensive development of upwelling related siliceous sediments throughout the basin with diagenesis these deposits formed the siliceous shales and porcelanites of the monterey formation high sedimentation rates coincident with a eustatic drop in sea level led to clastic progradation in latest miocene time as the basin filled analysis of organic matter from cores of the monterey formation shows that kerogen type reflects overall sedimentation trends samples from northern and eastern areas contain abundant terrestrial organic matter whereas samples from western areas mostly contain marine kerogens source potential is thus strongly influenced by geographic locality as well as lithology maturity of kerogen was assessed using vitrinite reflectance thermal alteration indices and pyrolysis techniques the latter two appear to be the more reliable indicators of organic matter maturity in the monterey formation of the san joaquin valley although much of the monterey formation in the study area may be thermally immature portions are probably generating hydrocarbons today in deep synclinal areas

influence of chemical properties on ch4 adsorption capacity of anthracite derived from southern sichuan basin china abstract this study aimed to determine the effects of high rank coal chemical properties on ch4 adsorption capacity a total of 24 core samples of anthracite from 11 coalbed methane wells in southern sichuan basin china were examined systemically using maceral analysis proximate and ultimate analyses total sulfur content test and ch4 isotherm adsorption experiment results show that vitrinite group macerals are the most abundant maceral group followed by inertinite and inorganic mineral matter of these coals vitrinite and inertinite rich coals have the similar average langmuir volume under dry ash free basis vldaf and no positive or negative correlation was found between vldaf and vitrinite and inertinite content in addition there is a weakly negative relationship between inorganic mineral matter and ch4 adsorption capacity effects of coal elements by ultimate analysis such as c element and the atomic ratios of h c o c and n c on ch4 adsorption capacity were studied ch4 adsorption capacity has positive correlation with c element content h c atomic ratio and n c atomic ratio respectively but negative with o c atomic ratio effects of four proximate analysis parameters moisture ash fixed carbon and volatile matter content on ch4 adsorption capacity were also studied moisture ash and volatile matter content negatively affect ch4 adsorption respectively and fixed carbon content has exactly the opposite effect principle component regression analyses for the set of elements and proximate analysis parameters show that c o ash and fixed carbon content are the important influence factors on ch4 adsorption capacity

evolution of the southern san joaquin basin and mid tertiary transitional tectonics central california a cenozoic tectonic and sedimentary history is proposed for the southern san joaquin basin ssjb and tehachapi mountains that evolved adjacent to the plate margin off central california seismic reflection borehole field biostratigraphic and paleomagnetic data are integrated into geologic and fault structure maps cross sections and geohistory plots and are analyzed with previous work in the region to develop a model relating the sequence timing and distribution of complex tectonically linked events the largely buried structures and strata in the ssjb preserve an unusually complete record of the mid tertiary transition from convergent to transform plate boundary as well as the regional transition to contraction during the pliocene significant structural relief existing across both extensional and contractile features is preserved in the subsurface and an active fold thrust belt propagates basinward along the margin of the u shaped tejon embayment the cenozoic evolution of the ssjb reflects the regional deformation of central california as different tectonic events followed each other along the adjacent north american plate margin five oligocene miocene basin phases are identified in the ssjb 1 late oligocene early miocene extensional subsidence with high and low angle normal faulting accompanied by volcanism and deposition of coarse syntectonic conglomerates 2 middle miocene uplift 3 later mid miocene transtensional subsidence to lower bathyal depths 4 alternating subsidence and uplift until the late miocene and 5 flexural subsidence due to pliocene to recent contraction reconstructions of mid tertiary california place the southern san joaquin tehachapi extensional terrane as a paleotectonic block located between the western mojave terrane then to the east and the western california terrane then to the south and west regional extension occurred during a long transition period between convergent and transform boundaries along the north american plate margin significant slip along the san andreas transform postdates this extensional event its origin apparently coincided with a regional middle miocene uplift event indicating that the san andreas fault is younger than previously supposed the tertiary ssjb has subsided due to extension transtension crustal tilting and thrust related loading the maricopa subbasin floor is likely composed of ensimatic and mafic rocks like those along the west side of the sierra nevada and locally has subsided beyond 12 km in contrast the relatively stable tejon embayment underlain by sierran crystalline crust achieved its maximum subsidence in the miocene since pliocene time the ssjb has filled and continued to deepen after the basin was tectonically shut off from the pacific ocean

lignite cleat studies from the first middle polish first lusatian lignite seam in central poland abstract some miocene lignite seams are characterized by the presence of natural discontinuities so called cleats most often they are opening mode fractures consisting of two orthogonal sets face and butt both almost perpendicular to the bedding this paper determines distributions of cleat orientation spacing and aperture from the first group of the middle polish first lusatian lignite seams mpls 1 which has been exploited inter alia in the jo win iib and kazimierz n opencast mines in central poland all observations and measurements were conducted at macroscopic scale the cleats mean orientations are ne sw and nw se dipping at a high angle 75 the first set of fractures refers to the face cleats and the second one to the butt cleats the spacing of face cleats is from 10 0 to 17 2 cm averaging 12 65 cm and the spacing of butt cleats is from 9 3 to 24 3 cm averaging 13 75 cm on the other hand aperture measurements of these cleats range from 0 2 to 1 9 cm averaging 0 68 cm and from 0 1 to 1 5 cm averaging 0 42 cm respectively the obtained results clearly indicate that face cleat orientations nw se are strictly parallel to the elongation of the main tectonic structures in the study area their origin may be explained in at least two ways that is by tectonic folding the maximum principal stress 1 was horizontal or by salt diapirism the maximum principal stress 1 was vertical in both cases the intermediate principal stress 2 was parallel to the face cleat strikes namely nw se although the well developed butt cleats in the context of regional geology provide additional evidence for the creation of an orthogonal system of fractures cleats in the cover of salt structures thus the nw se direction is characteristic of both the extent of the main tectonic units in central poland and the face cleat orientation in mpls 1

meso and microporosity characteristics of miocene lignite and subbituminous coals in the kinik coalfield soma basin w turkey abstract three miocene age coal seams a lower seam km2 subbituminous a middle seam km3 subbituminous and an upper seam kp1 lignite in the kinik coalfield located in the southwesternmost part of the soma basin in western turkey and factors controlling mesoporosity and microporosity characteristics were investigated using low pressure n2 and co2 adsorption techniques respectively in addition this study is also aimed to compare controlling factors on meso and microporosity characteristics of soma basin and late carboniferous zonguldak and late miocene pliocene dombayova basins it is found that distinct differences with regard to meso and microporosity exist among the three seams km2 km3 and kp1 investigated in the kinik coalfield specifically samples from kp1 have greater mesopore surface areas and volumes than those from km3 in addition samples from the upper part of km2 have significantly lower mesopore surface area and volume than from the lower part of this seam and from km3 and kp1 samples from the lower part of km2 have higher meso and micropore surface area and volume values than km3 and kp1 samples the increase in mesopore surface area and volume along with the increase in ash yield toward the lower part of km2 suggests that mesoporosity characteristics in this seam appear to be controlled mainly by mineral matter content the results of this study show that meso and micropore surface area and volume of miocene subbituminous coal km2 in kinik and eynez coalfields of the soma basin have higher values than lignite from the dombayova basin and bituminous coal from the zonguldak basin the differences in mesopore characteristics between the soma and the zonguldak basins could be related to differences in rank in addition the mesoporosity of coal seams in the dombayova basin is more similar to seams in the zonguldak basin these conflicting data suggest that rank might not be a controlling factor on the meso and micropore characteristics of the basins investigated in this paper nevertheless the common presence of structured huminite macerals in the soma basin seems to have caused relatively higher microporosity surface area and volume values whereas the common presence of illite particularly in the lower parts of km2 resulted in higher values of mesopore surface area and volume in the soma basin samples consequently maceral and mineralogical compositions of the studied turkish coals seem to exert major controls on meso and micropore characteristics

charging of elk hills reservoirs as determined by oil geochemistry crude oils from miocene and pliocene reservoirs from the elk hills field in california s san joaquin basin were analyzed for stable carbon isotopes and biomarkers cluster analysis of geochemical variables defines five principal oil families all derived from different organic rich facies of the miocene monterey formation carbon isotope analysis indicates no contribution from the basin s other major source rock the eocene kreyenhagen formation oil families show a strong correspondence to stratigraphic intervals oils from pre monterey reservoirs were probably generated from the lowermost organic rich facies of the monterey and are the most thermally mature upper miocene stevens zone turbidite reservoirs contain oils of various thermal maturity stages but mature light ends are abundant and are likely generated from the floors of the adjacent subbasins located north and south of elk hills the relatively minor presence of low thermal maturity biomarkers that are typically characteristic of monterey oils may indicate that stevens traps did not form until after the source intervals were at a higher level of thermal maturity all oils in stevens porcelanite reservoirs contain a higher concentration of low maturity biomarkers which may indicate derivation from more localized areas on the flanks of the elk hills anticlines the shallow pliocene oils have suffered biodegradation to different degrees and the lowest api gravities occur on the flanks of the anticline the carbon isotopic composition of these oils suggests yet another monterey source facies that charged the pliocene reservoirs and is not simply the result of vertical leakage from the older miocene reservoirs john e zumberge has been vice president and cofounder of geomark research in houston since 1991 he was manager of geochemical and geological research for cities service occidental general manager for ruska laboratories and director of geochemical services for core laboratories he has global experience in petroleum geochemistry focusing on crude oil biomarkers he obtained a b s degree in chemistry from the university of michigan and a ph d in organic geochemistry from the university of arizona judy a russell is a senior geological advisor for occidental and works on worldwide exploration and production with an emphasis on the integration of geochemistry she has extensive experience in many of occidental s projects in latin america far east the united states and the middle east she has a b s degree from phillips university and an m s degree from the new mexico institute of mining and technology stephen anthony reid is a senior geological advisor for occidental and works on international exploration with an emphasis on deep water projects he has extensive experience in california s san joaquin basin including the elk hills field where he conducted studies on stevens turbidite and monterey porcelanite reservoirs he has b s and m s degrees from california state university northridge

study on coalbed methane accumulation characteristics and favorable areas in the binchang area southwestern ordos basin china article the binchang area of southwestern ordos basin is one of the most promising areas for low rank coalbed methane cbm in china this work investigates the jurassic yanan formation coal and cbm geology and accumulation characteristics of cbm in the southwestern ordos basin based on data from 46 wells and labo ratory measurements of 14 coal samples from 7 mines the results show that coal rank in the binchang area is mainly sub bituminous a and high volatile c bituminous 0 46 0 73 ro coals are dominated by inertinite 14 7 85 6 less abundant are vitrinite 8 5 77 7 and liptinite 1 5 15 2 minerals are found only in small amounts 0 4 8 3 permeability is between 0 04 and 25 3 md and porosity ranges from 2 4 to 20 1 most coal pores are less than 100 nm in diameter making them favorable for gas adsorption but unfavorable for gas permeability pore morphology is represented mainly by micro and mesopores with a well connected and ink bottle shaped narrow throat and wide body morphology these coals are charac terized by a high adsorption volume of more than 3 0 10 3

tectono eustatic controls on reservoir compartmentalisation and quality an example from the upper miocene of the san joaquin basin california abstract systematic changes in stratigraphic architecture and reservoir quality of upper miocene stevens sandstones at north and south coles levee fields san joaquin basin reflect tectono eustatic controls on deposition two depositional sequences 330 500 m thick are present in the coles levee stevens the upper sequence contains sandstones deposited by sediment gravity flows in water depths of 300 500 m backstepping retrogradational reservoir compartments in this sequence overlie vertically stacked to prograding compartments although the backsteps are the better reservoirs with higher permeabilities and porosities the vertically stacked to prograding compartments are volumetrically more important curiously the upper stevens section is sand rich 60 80 ss on structural highs that were also palaeotopographic highs thicker sections with less and characterise the flanks these sand distributions are anomalous since sediment gravity flows preferentially deposit in bathymetric lows apparently the flanks of stevens palaeohighs subsided faster than the crests consequently accomodation increases were greatest on the flanks and resulted in aggradation with preservation of section less accommodation on the crests resulted in progradation with erosion and reworking through lobe switching processes some sand reached all parts of the depocenter subsequent progradation with erosion of shale interbeds and attendant reworking by density currents created sand rich sections in slowly subsiding areas crests concurrent aggradation preserved shale interbeds and created shale dominated sections in rapidly subsiding areas flanks greater compaction of thicker shale dominated flanks equalised thicknesses of flank and crest sections thus the reservoir architecture represents the integrated effects of compensation lobe switching accommodation subsidence sea level and compaction

relations between coal petrology and gas content in the upper newlands seam central queensland australia the upper newlands seam in the northern bowen basin queensland australia consists of six benches a f that have different petrographic assemblages benches c and e contain relatively abundant inertodetrinite and mineral matter as well as anomalously high reflectance values these characteristics support a largely allochthonous detrital origin for the c and e benches fractures and cleats in the seam show a consistent orientation of northeast southwest for face cleats and a wide range of orientations for fractures cleat systems are well developed in bright bands with poor continuity in the dull coal both maceral content and cleat character are suggested to influence gas drainage in the upper newlands seam a pronounced positive correlation between vitrinite abundance and gas desorption data suggests more efficient drainage from benches with abundant vitrinite conversely inertinite rich benches are suggested to have less efficient drainage and possibly retain gas within pore spaces which could increase the outburst potential of the coal c 2001 elsevier science bn all rights reserved

diagenetic carbonate in miocene sandstone reservoir san joaquin basin california stevens arkosic sandstones deposited about 7 ma in a deep marine environment form the north coles levee reservoir dolomite and calcite cements occur as zones averaging 1 ft thick and having less than 300 ft of lateral continuity based on dgr18o measurements and estimated pore fluids between 0 and 2 8 the dolomite formed at 30 40 c an early calcite cement formed at 50 60 c and a late pore filling and plagioclase replacing calcite formed at 70 80 c corresponding to these temperature estimates dolomite formed in the zone of methanogenesis dgr13c 4 to 8 and calcites in the zone of decarboxylation dgr13c 3 to 12 dolomite has between 4 and 12 mole fe and calcites contain up to 8 mole o fe mg mn with a characteristic fe mn mg ratio of about 3 1 the latest calcite is the most ca rich due in part to ca sourced from plagioclase dissolution calcite cements in nonmarine sections have markedly high mn contents to 5 mole compared with the marine section at north coles levee the volume of cement systematically decreases from about 40 20 over the cementation temperature interval suggesting progressive compaction of the sandstones present day mean porosity of the reservoir 15 appears to be largely a result of mechanical compaction a very late dolomite cement with high fe content 13 mole and light carbon dgr13c 14 is found in the cleavage flakes of crushed biotite the dolomite is calculated to have formed from a fluid with a dgr18o of 0 9 at present reservoir temperatures of 105 c suggesting precipitation in the past 20 years during release of the gas cap and injection of isotopically light water calcite also forms thick scales in production tubing primarily as a result of pressure drops from 4 900 to 400 psi in the tubing string the calcites have high mg contents 7 mole due to the composition of the injection water calculated distribution coefficients for fe and mn are similar to published values but mg is two times higher than published values at 90 c similar results are obtained for late calcite cements a time temperature plot for north coles levee constrains the timing of dolomite cementation between 5 and 6 ma and the calcite cementation between 4 and 2 5 ma plagioclase dissolution and hydrocarbon emplacement occurred within the past few million years suggesting that the presence of the hydrocarbons and associated byproducts of kerogen maturation enhance porosity despite the narrow window for diagenesis minimum fluid fluxes of only 0 02 cm3 yr per 100 cm3 rock are required to account for the volume of dissolved plagioclase

quaternary reactivation of the kern canyon fault system southern sierra nevada california the kern canyon fault the longest fault in the southern sierra nevada is an active structure and has been reactivated at discrete times over the past 100 m y in response to changing lithospheric stresses after initiation as a cretaceous transpressional structure the kern canyon fault transitioned into a dextral strike slip shear zone that remained active as it was exhumed into the brittle regime during regional late cretaceous uplift of the sierra nevada batholith the kern canyon fault was reactivated during miocene regional extension as part of a transfer zone between two differentially extending domains in the southern sierra nevada subsequent normal displacement along the fault began in pliocene time new evidence for fault activity which continued into late quaternary time includes its current geomorphic expression as a series of meters high west side up scarps that crop out discontinuously along the fault s 130 km length relocated focal mechanisms of modern earthquakes confirm ongoing normal faulting and geodetic measure ments suggest that the sierra nevada is uplifting relative to the adjacent valleys this evidence for recent activity overturns a long held view that the kern canyon fault has been in active for more than 3 5 m y its reactivation indicates that deformation repeatedly localized along a pre existing crustal weakness a cretaceous shear zone we propose that a system of inter related normal faults including the kern canyon fault is responding to mantle lithosphere removal beneath the southern sierra nevada region the location of the active kern canyon fault within the sierra nevada great valley microplate indicates that deformation is occurring within the microplate

diagenetic mass transport in the southern san joaquin basin california u s a implications from the strontium isotopic composition of modern pore fluids abstract three types of chemically and isotopically distinct pore fluids from the southern san joaquin basin previously recognized by j b fisher and j r boles also have distinctive 87 sr 86 sr ratios and sr concentrations meteoric fluids have stable isotopic compositions which lie on or near the meteoric water line and low chlorinities sr concentrations are between 0 01 and 2 6 mg l 1 and 87 sr 86 sr ratios range from 0 7061 to 0 7078 diagenetically modified connate marine fluids have d and 18o values more positive than 35 and 0 respectively and have chlorinities generally comparable to seawater sr concentration are much higher than the meteoric group 16 198 mg l 1 although the 87 sr 86 sr ratios 0 7070 0 7081 are not distinctive mixed meteoric modified connate fluids have d 18o and chlorinity intermediate between the meteoric and modified connate groups sr concentrations are also intermediate between 16 and 22 mg l 1 but 87 sr 86 sr ratios 0 7080 0 7087 are generally more radiogenic than either the meteoric or modified connate groups all of the fluids have 87 sr 86 sr ratios comparable to or lower than tertiary seawater alteration of detrital plagioclase is the probable origin of the low isotopic ratios mass balance calculations based on the sr data suggest that essentially no transport of sr occurred during diagenesis of sandstones containing modified connate pore fluids while large amounts of sr have been transported out of meteoric reservoirs by fluid flow the chemically anomalous mixed meteoric modified connate fluids contain the most radiogenic strontium in the basin these fluids are spatially associated with major faults and may represent clay mineral dehydration waters which have been transported upward from greater depth these results suggest that the three types of fluids identified by fisher and boles represent three distinct mass transport regimes a largely stagnant deep basin system containing modified connate pore fluids an actively recharging meteoric system along the basin flanks and a third system restricted to the southern basin which may be characterized by largescale cross formational fluid flow rather than dilution by meteoric waters