geological controls on gas saturation in the yanchuannan coalbed methane field southeastern ordos basin china abstract the paper investigates lateral variation of gas saturation and its geological controls of the no 2 coal seam in the permian shanxi formation based on coal samples from 21 exploration wells in the yanchuannan coalbed methane cbm field southeastern ordos basin china the data set reveals that gas saturation of the no 2 coal seam shows a high lateral variation from 32 44 to 89 69 and that there is an overall trend in gas saturation with depth overprinted by four other factors 1 influence of faults 2 secondary biogenic gas generation 3 local top seal conditions and 4 variations in coal properties the reverse faults f1 and f2 are effective barriers horizontally for the hydraulic communication and divide our study area into relatively closed and recharge zones gas saturation of the relatively closed zone is generally higher than that in the recharge zone in the recharge gas saturation increases generally along the flow pathway of groundwater with the exceptions of the areas affected by secondary biogenic gas the stable isotope compositions suggest that late stage biogenic methane was generated via co 2 reduction associated with meteoric water recharge which significantly contributes to higher gas saturation than expected meanwhile the biogenic gas generation was is restricted to shallow depths the apparent variations in local areas of lithology of the overlying stratum next to the coal seam suggest that the top seal conditions are deteriorative which can cause gas dissipation and reduce gas saturation remarkably integrally for the variations in coal properties gas saturation has a general positive relationship with coalification and weak negative correlations with moisture content and ash yield but the relationships lacks statistical significances gas saturation is not associated with coal maceral in the study area

devils hole nevada δ18o record extended to the mid holocene abstract the mid to late pleistocene devils hole 18 o record has been extended from 60 000 to 4500 yr ago the new 18 o time series in conjunction with the one previously published is shown to be a proxy of pacific ocean sea surface temperature sst off the coast of california during marine oxygen isotope stages mis 2 and 6 the devil hole and sst time series exhibit a steady warming that began 5000 to 10 000 yr prior to the last and penultimate deglaciations several possible proximate causes for this early warming are evaluated the magnitude of the peak 18 o or sst during the last interglacial lig is significantly greater 1 per mill and 2 to 3 c respectively than the peak value of these parameters for the holocene in contrast benthic 18 o records of ice volume show only a few tenths per mill difference in the peak value for these interglacials statistical analysis provides an estimate of the large shared information variation between the devils hole and eastern pacific sst time series from 41 to 2 n and enforces the concept of a common forcing among all of these records the extended devils hole record adds to evidence of the importance of uplands bordering the eastern pacific as a source of archives for reconstructing pacific climate variability

microbial controls on the origin and evolution of coal seam gases and production waters of the walloon subgroup surat basin australia abstract the walloon subgroup coal seam gas csg play in the surat basin queensland is australia s pre eminent onshore gas field concerted multi disciplinary research is underway investigating the distribution origin and composition of waters and gases in this dominantly microbial csg reservoir to guide both continued production and potential microbially enhanced coal bed methane mecom applications however prior to the present research a detailed study of co produced waters and gases from across the surat basin was not available in the public domain this study tested whether co produced water compositional and stable isotopic data show relationships with production gas stable isotope compositions to elucidate further evidence for microbial co2 reduction and explore the down dip geochemical evolution of walloon coal bed waters and gases a total of 41 wells were sampled with 50 water and 25 gas samples spanning the 3 major production areas of the surat basin detailed isotopic and hydrochemical analysis of these samples revealed distinct spatial trends between the different production locales water compositions were distinct for each of the production regions reflecting the different lithologies of adjacent recharge zones differing fluid rock interactions likely different microbial consortia and the extent of methanogenesis on the western side of the basin near roma waters were the freshest with the lowest median values for alkalinity 861 mg l and cl 588 mg l and a 13cdic of 14 2 on the eastern side of the basin the kogan nose waters were the most saline with the highest median values for na 1955 mg l cl 2280 mg l and 13cdic 20 0 also in the east in the present gas fairway the undulla nose waters had the highest median alkalinity 1841 mg l and were found to have a na excess median 1050 mg l and a lower than expected median 13cdic 14 0 co mingled produced methane carbon isotope values 13c 57 0 to 44 5 from both the upper juandah and lower taroom coal measures plot within the mixed thermogenic microbial genetic field by contrast deuterium isotopic difference 2h h2o ch4 values and cross plots of 2h h2o and 18o h2o suggest that microbially mediated co2 reduction is the dominant methane generation process in situ at a given depth the undulla nose waters in the east are more depleted in 2h and 18o than elsewhere in the surat basin which may suggest these samples have been more heavily impacted by water rock microbial reactions 14c values from the 3 production regions 0 115 to 1 769 pmc age 32 400 to 50 000 years before present b p suggest that walloon coals likely recharged in the last 50 000 years limit of radiocarbon dating consistent with these dates 2h h2o and 18o h2o values for the surat basin 2h 32 to 56 18o 5 9 to 9 0 echo the stable isotopic composition of meteoric waters during the initial part of the last glacial period in southeast queensland based on a strong correlation between 2h ch4 and 2h h2o we suggest that methane was generated since the late pleistocene pca analysis showed a degree of positive correlation between total alkalinity and both the 13cdic median 14 2 and 13c ch4 median 52 1 vectors that is consistent with finite reservoir effects the results inform ongoing studies of gas distribution and origins and mecom potential in the surat basin and underpin a broader study examining aquifer interactions

tims u series dating and stable isotopes of the last interglacial event in papua new guinea the extensive flight of uplifted reef terraces which occurs along the vitiaz strait on the northern flank of the huon peninsula in png papua new guinea contains a particularly good record of sea level changes in the last 250 ky the huon terraces were the target of an international expedition which took place in july august 1988 in particular we searched for suitable samples for u series dating in a reef complex designated as vii which is correlated with the last interglacial episode and high sea level stand this complex is composed of a barrier reef viib a lagoon and a fringing reef viia twelve corals from these terraces and two corals from the older reef complex viii were selected for analysis the petrography oxygen and carbon isotope compositions and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium 230 th 234 u ages of the corals with 99 aragonite having primary textures and which show u sr ratios around 0 4 10 3 and initial 234 u values close to that of present seawater appear to be reliable the most reliable ages from complex vii corals fall in two tight groups centered at 118 ky and 134 ky corals with 234 u t values higher than 160 and u sr ratios substantially lower than seawater are assumed to have undergone diagenetic alteration which appears to be common in this area the simplest model for sea level height for terrace vii is a continuous rise between 134 and 118 ky alternatively there may have been two periods of rapid sea level rise in contrast in the bahamas there is evidence that sea level remained rather constant over the time interval 132 to 120 ky the absence of ages between 132 and 120 ky in png could be the result of changes in the local tectonic uplift rates during that time or erosion that disrupted the continuous record in any event we find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation or as a test of climatic models the older ages reported here precede the milankovitch solar insolation peak at 128 ky and the younger ages are 10 ky after this peak if the present high precision data are correct then it will be necessary to reassess the validity of the milankovitch theory of climatic changes the fundamental issue which must now be resolved is a means of identifying coral samples that have not been disturbed by diagenetic processes

geochemistry of formation waters from the wolfcamp and cline shales insights into brine origin reservoir connectivity and fluid flow in the permian basin usa abstract despite being one of the most important oil producing provinces in the united states information on basinal hydrogeology and fluid flow in the permian basin of texas and new mexico is lacking the source and geochemistry of brines from the basin were investigated ordovician to guadalupian age reservoirs by combining previously published data from conventional reservoirs with geochemical results for 39 new produced water samples with a focus on those from shales salinity of the ca cl type brines in the basin generally increases with depth reaching a maximum in devonian median 154 g l reservoirs followed by decreases in salinity in the silurian median 77 g l and ordovician median 70 g l reservoirs isotopic data for b o h and sr and ion chemistry indicate three major types of water lower salinity fluids 100 g l isotopically heavy o and h water in leonardian permian to pennsylvanian reservoirs 2 3 2 km depth is evaporated late permian seawater water from the permian wolfcamp and pennsylvanian cline shales which are isotopically similar but lower in salinity and enriched in alkalis appear to have developed their composition due to post illitization diffusion into the shales samples from the cline shale are further enriched with nh 4 br i and isotopically light b sourced from the breakdown of marine kerogen in the unit lower salinity waters 3 km depth which plot near the modern local meteoric water line are distinct from the water in overlying reservoirs we propose that these deep meteoric waters are part of a newly identified hydrogeologic unit the deep basin meteoric aquifer system chemical isotopic and pressure data suggest that despite over pressuring in the wolfcamp shale there is little potential for vertical fluid migration to the surface environment via natural conduits

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

delayed triggering of the 1999 hector mine earthquake by viscoelastic stress transfer stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases1 2 3 4 5 the 1999 hector mine earthquake in southern california magnitude 7 1 occurred only 20 km from and 7 years after the 1992 landers earthquake magnitude 7 3 this suggests that the hector mine earthquake was triggered in some fashion by the earlier event but uncertainties in the slip distribution and rock friction properties associated with the landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the hector mine hypocentre with estimates varying from 1 4 bar ref 6 to 0 5 bar ref 7 more importantly coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events here we present the results of a three dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the landers earthquake using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the landers earthquake our calculations suggest that lower crustal or upper mantle flow can lead to postseismic stress increases of up to 1 2 bar at the location of the hector mine hypocentre during this time period contributing to the eventual occurrence of the 1999 hector mine earthquake these results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard8 9 10 11

viscoelastic flow in the lower crust after the 1992 landers california earthquake space geodesy showed that broad scale postseismic deformation occurred after the 1992 landers earthquake three dimensional modeling shows that afterslip can only explain one horizontal component of the postseismic deformation whereas viscoelastic flow can explain the horizontal and near vertical displacements the viscosity of a weak about 10 km thick layer in the lower crust beneath the rupture zone that controls the rebound is about 10 18 pascal seconds the viscoelastic behavior of the lower crust may help to explain the extensional structures observed in the basin and range province and it may be used for the analysis of earthquake hazard

empirical method for measuring seasonality in deep sea cores we present an extended 100 000 yr oxygen isotope record from the mid atlantic ridge at lat 45 n obtained by using coincident isotope values from both warm and cold water planktonic foraminifera in the same subsamples throughout the core these isotope values reflect paleotemperatures independent of assemblage tolerances our record indicates much stronger seasonal fluctuations than previously reported and these isotope values can be used to identify glacial and deglacial events more precisely although the possibility of this type of record had been suggested by work on recent foraminifera this is the first extended record of this kind

hydrogeologic factors affecting gas content distribution in coal beds gas content in coal is not fixed but changes when equilibrium conditions within the reservoir are disrupted therefore gas content distribution in coal varies laterally within individual coal beds vertically among coal beds in a single well and within thicker coal beds major hydrogeologic factors affecting gas content variability include gas generation coal properties and reservoir conditions gas generation affects gas content variability on a regional scale whereas coal properties influence gas content distribution on a regional and local scale reservoir conditions affect gas content more locally within specific fields or individual wells the potential for high gas content is controlled directly by the amount of thermogenic and secondary biogenic gases generated from the coal which in turn are controlled by burial history maceral composition and basin hydrodynamics variability in mineral matter ash and moisture content sorption behavior among macerals diffusion coefficients and permeability result in heterogeneous gas content distribution gas content decreases with decreasing pressure and temperature and coal beds become undersaturated with respect to methane during basin uplift and cooling gas content generally increases where conventional and hydrodynamic trapping of coal gases occur and may decrease in areas of active recharge with downward flow potential and or convergent flow where there is no mechanism for entrapment

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

source fault structure of the 2003 bam earthquake southeastern iran inferred from the aftershock distribution and its relation to the heavily damaged area existence of the arg e bam fault proposed 1 we investigate the hypocenter distribution of aftershocks of the december 26 2003 bam earthquake mw 6 5 by using a temporal seismic network the hypocenters distribute linearly over about 20 km in parallel with a line 3 5 km west of the geological bam fault and extend from the south of bam city to the heavily damaged area in the eastern part of the city including the historical mud brick citadel arg e bam based on the hypocenter distribution we propose a schematic 3 d structural model of a new fault that we have named the arg e bam fault we suggest that the bam earthquake occurred not in the bam fault but in the arg e bam fault bam city is located just above northern part of the arg e bam fault and also on the rupture propagation direction from the asperity this may be one of the main reasons why eastern part of bam city suffered the heaviest damage

horizontal stress anisotropy and effective stress as regulator of coal seam gas zonation in the sydney basin australia abstract coal seam gas zonation in the sydney basin nsw australia is related to basin hydrodynamics and hydrochemical facies evolution along the flow path from the subcrop to the basin center biogenic methane corresponds with meteoric water under hydrostatic pressure and persists down to the top of the geopressured zone 800 to 1000 m thermogenic gases including wet hydrocarbons can reach up to relatively shallow horizons of less than 500 600 m depth in the transition zone between the top of the geopressured and base of the hydrostatic zone a mixed water and gas regime prevails comprising brackish waters and gases of mixed biogenic thermogenic and inorganic origins including co 2 mechanisms for and the role of stress in the development of this layered hydrogeological and gas environment are investigated in this paper the inverse relationship between effective horizontal stress and permeability in coals through regulation of cleat volumes is well documented and there is evidence of regionally compartmentalized stress regimes with depth within the sydney and other eastern australian coal basins this regional stress regime can be overprinted by the effect of localized geological features it is hypothesized that the in situ stress regime plays an important role in the regulation of groundwater flow regimes and extents resulting in the development of the reported gas content and compositional zonation analysis of regional gas and stress data obtained from public and private databases as well as literature supports this hypothesis changes in gas concentration and composition with depth correspond with discernable variations in horizontal stress anisotropy gas contents generally increase with depth down to a peak gas horizon below which concentrations decrease this peak gas zone is coincident with a horizontal stress anisotropy change from moderately high to low levels associated with reverse to strike slip faulting conditions respectively the stress release zone also marks the top of the thermogenic gas zone identified by the first appearance of ethane in the vertical profile this zone also hosts gases of mixed origins biogenic thermogenic and inorganic co 2 and represents a mixed transitional groundwater flow environment the base of the mixed gas zone is the top of the geopressured only flow associated with thermogenic gases and is signaled by the return to high stress reverse faulting conditions below 850 900 m depth in the sydney basin

precise timing of the last interglacial period from mass spectrometric determination of thorium 230 in corals the development of mass spectrometric techniques for determination of 230 th abundance has made it possible to reduce analytical errors in 238 u 234 u 230 th dating of corals even with very small samples samples of 6 x 10 8 atoms of 230 th can be measured to an accuracy of 3 percent 2 and 3 x 10 10 atoms of 230 th can be measured to an accuracy of 0 2 percent the time range over which useful age data on corals can be obtained now ranges from about 50 to about 500 000 years for young corals this approach may be preferable to 14 c dating the precision with which the age of a coral can now be determined should make it possible to critically test the milankovitch hypothesis concerning pleistocene climate fluctuations analyses of a number of corals that grew during the last interglacial period yield ages of 122 000 to 130 000 years the ages coincide with or slightly postdate the summer solar insolation high at 65 n latitude which occurred 128 000 years ago this supports the idea that changes in pleistocene climate can be the result of variations in the distribution of solar insolation caused by changes in the geometry of the earth s orbit and rotation axis

new data on the pleistocene of mallorca abstract stratigraphic geomorphologic and isoleucine epimerization studies at 15 sites in mallorca define four aminozones a c e and f g of increasing age that are related to transgressive regressive marine cycles from the holocene to the mid pleistocene calibration of aminozone e glycymeris aile ile mean from all sites 0 41 0 03 n 38 is provided by a 129 7 ka u series coral age on cladocora caespitosa from son grauet of the younger aminozones a relates to the holocene transgression and aminozone c to a mid to late isotopic stage 5 event 90 15 ka revealed only by supralittoral eolianites assigning an age to the older poorly resolved aminozones f and g called f g in this case is uncertain without supporting radiometric data but an age of 180 ka can be assigned to these aminozone s f g based on a kinetic model and other examples in the mediterranean several deposits previously dated u series molluscs between 75 and 300 ka appear to belong to the last interglacial complex stage 5 and aminozone e a proposed revision of the positive sea level history of mallorca shows multiple minor oscillations during the major last interglacial cycle stage 5 and two mid pleistocene sea levels one lower than present and the other at about 14 m a s l

relationships between water and gas chemistry in mature coalbed methane reservoirs of the black warrior basin water and gas chemistry in coalbed methane reservoirs of the black warrior basin reflects a complex interplay among burial processes basin hydrodynamics thermogenesis and late stage microbial methanogenesis these factors are all important considerations for developing production and water management strategies produced water ranges from nearly potable sodium bicarbonate water to hypersaline sodium chloride brine the hydrodynamic framework of the basin is dominated by structurally controlled fresh water plumes that formed by meteoric recharge along the southeastern margin of the basin the produced water contains significant quantities of hydrocarbons and nitrogen compounds and the produced gas appears to be of mixed thermogenic biogenic origin late stage microbial methanogenesis began following unroofing of the basin and stable isotopes in the produced gas and in mineral cements indicate that late stage methanogenesis occurred along a co2 reduction metabolic pathway hydrocarbons as well as small amounts of nitrate in the formation water probably helped nourish the microbial consortia which were apparently active in fresh to hypersaline water the produced water contains nh4 and nh3 which correlate strongly with brine concentration and are interpreted to be derived from silicate minerals denitrification reactions may have generated some n2 which is the only major impurity in the coalbed gas carbon dioxide is a minor component of the produced gas but significant quantities are dissolved in the formation water degradation of organic compounds augmented by deionization of nh4 may have been the principal sources of hydrogen facilitating late stage co2 reduction

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

offset and evolution of the gowk fault s e iran a major intra continental strike slip system abstract we use drainage reconstructions to estimate long term offsets on the gowk fault an oblique right lateral strike slip fault in eastern iran on which there have been a number of recent large earthquakes a 3 km horizontal offset is inferred from well preserved geomorphology we further identify a total cumulative offset of 12 km which produces a simple reconstruction of geomorphology across the fault filling in pull apart basins restoring rivers to linear courses across the fault trace and aligning structural and bed rock features the probable age of the gowk fault and k ar dating of offset basalts north of the study region suggest an overall slip rate of 1 5 2 4 mm year this is small compared with the overall 10 20 mm year of shear expected between central iran and afghanistan and the deficit is likely to have been accommodated on other faults east of the gowk fault drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic profile that resembles an asymmetric saw tooth the geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components reflecting a probable ramp and flat structure in cross section this interpretation is consistent with evidence from the analysis of seismological radar and surface rupture data in recent earthquakes

fluid evolution in fracturing black shales appalachian basin opening mode veins in cores drilled from the mudrocks overlying and underlying the major silurian salt decollement in the appalachian plateau tioga and lawrence counties pennsylvania have mineralogic and isotopic compositions generally matching those of their host mudrocks suggesting opening and filling amid little cross stratal fluid motion calcite and most trace minerals probably entered the veins via dissolution reprecipitation from nearby host rock consistent with this interpretation are the observations that 1 trace minerals within the veins including quartz pyrite and dolomite are invariably also present within the layers hosting the veins with vein cement minerals generally reflecting the abundance and solubility of minerals in the host rock and 2 carbon and oxygen isotopic compositions of vein filling calcite are similar to those of calcite within the host rock with vein filling 18o slightly depleted and 13c slightly enriched modeling the fluid isotopic evolution assuming vein opening and filling amid immobile connate formation water accounts for these minor but systematic differences which are attributable to increasing temperature and hydrocarbon maturation an exception to the above trend is barite which despite its low solubility is systematically enriched in veins with respect to the host rock it is unclear whether barite precipitation resulted from the influx of external fluids perhaps deriving from silurian salt or from barium mobilized at depth from local clays or organic material

variable gas saturation in coalbed methane reservoirs of the black warrior basin implications for exploration and production abstract gas saturation is highly variable in carboniferous coalbed methane reservoirs of the black warrior basin usa and diverse geologic data derived from more than three decades of exploration and development provides insight into the origin of this variability and the consequences for production performance coalbed methane is produced from numerous thin 0 3 to 95 importantly this range of variation is commonly developed among closely spaced seams within the same well exploration has to date been successful where coal seams are in the thermogenic gas window geochemical evidence indicates that thermogenic gases have been altered by subsurface water movement and may have been augmented with late stage biogenic gases particularly in areas affected by fresh water recharge adsorption isotherms of coal samples in the black warrior basin typically have langmuir volume between 15 and 30 cm3 g and langmuir pressure between 2 and 6 mpa both langmuir pressure and langmuir volume correlate significantly with coal rank in deep normally pressured coal beds where reservoir pressure is substantially above langmuir pressure even a small degree of undersaturation can necessitate prolonged dewatering before a large reservoir volume can reach the critical desorption pressure permeability moreover decreases exponentially with depth which can make dewatering coal seams deeper than 800 m difficult where reservoir pressure is relatively low however isotherm geometry indicates that significantly undersaturated reservoirs can be near the critical desorption pressure consequently areas of underpressure favor high gas production along with minimal water production

last interglacial sea stands on barbados and an early anomalous deglaciation timed by differential uplift three major sea level maxima between 137 and 120 kyr b p are documented by surveys of pairs of wave cut notches and other features associated with the broadly defined last interglacial coral terrace on barbados regression analysis of elevation differences between notch pair members as a function of their uplift rates at seven sites yields the age difference between first and third sea stands and their eustatic sea level difference these results when combined with stratigraphic data from the bahamas bermuda and western australia and a chronology based on age limits of corals from the bahamas and western australia yield an endpoint age and eustatic low tide elevation of 136 7 kyr b p and 7 4 m respectively for the first sea stand 126 kyr b p and 5 6 m for the second and 120 5 kyr b p and 3 0 m for the third the first sea stand is the result of an anomalous deglaciation that was completed during low northern summer milankovitch insolation this is contrary to the milankovitch hypothesis that orbitally controlled insolation largely determines the variations of glacial ice volume it implies that internal factors within the earth s climate system can be much stronger than the effects of insolation variations

the appalachian ouachita connection paleozoic orogenic belt at the southern margin of north america late paleozoic orogenic belt structures exposed in the appalachian mountains of alabama and in the ouachita mountains of arkansas plunge from opposite directions beneath postorogenic mesozoic cenozoic strata in the mississippi embayment of the gulf coastal plain figure 1 the paleozoic stratigraphic sequence and details of structural style in the ouachita outcrops contrast strongly with those in the appalachian outcrops furthermore straight line projection of structural strike from the outcrops does not lead to a simple connection of structures beneath the coastal plain concealed by the coastal plain cover are answers to questions such as the following are the orogenic belts continuous discontinuous offset or intersecting how are along strike changes in stratigraphy and structural style expressed what is the sequence of tectonic evolution early attempts to interpret the subsurface relationships between the appalachian and ouachita structures were of necessity based on the first few scattered wells that were drilled through coastal plain strata into paleozoic rocks subsequent studies have enjoyed the availability of progressively more numerous deep wells and a growing accumulation of geophysical data various stages in the evolution of thought were outlined by king 1950 1961 1975 and by thomas 1973 1976 this review summarizes available subsurface data in a pre mesozoic paleogeologic

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

methanogenic pathways of coal bed gas in the powder river basin united states the geologic factor abstract coal bed gas of the tertiary fort union and wasatch formations in the powder river basin in wyoming and montana u s was interpreted as microbial in origin by previous studies based on limited data on the gas and water composition and isotopes associated with the coal beds to fully evaluate the microbial origin of the gas and mechanisms of methane generation additional data for 165 gas and water samples from 7 different coal bed methane bearing coal bed reservoirs were collected basinwide and correlated to the coal geology and stratigraphy the c1 c2 c3 ratio and vitrinite reflectance of coal and organic shale permitted differentiation between microbial gas and transitional thermogenic gas in the central part of the basin analyses of methane 13c and d carbon dioxide 13c and water d values indicate gas was generated primarily from microbial co2 reduction but with significant gas generated by microbial methyl type fermentation aceticlastic in some areas of the basin microbial co2 reduction occurs basinwide but is generally dominant in paleocene fort union formation coals in the central part of the basin whereas microbial methyl type fermentation is common along the northwest and east margins isotopically light methane 13c is distributed along the basin margins where d is also depleted indicating that both co2 reduction and methyl type fermentation pathways played major roles in gas generation but gas from the latter pathway overprinted gas from the former pathway more specifically along the northwest basin margin gas generation by methyl type fermentation may have been stimulated by late stage infiltration of groundwater recharge from clinker areas which flowed through highly fractured and faulted coal aquifers also groundwater recharge controlled a change in gas composition in the shallow eocene wasatch formation with the increase of nitrogen and decrease of methane composition of the coal bed gas other geologic factors such as burial thermal and maturation history lateral and vertical continuity and coalification of the coal beds also played a significant role in controlling methanogenic pathways and provided new perspectives on gas evolution and emplacement the early stage gas produced by co2 reduction has mixed with transitional thermogenic gas in the deeper central parts of the powder river basin to form old gas whereas along the basin margins the overprint of gas from methyl type fermentation represents new gas thus a clear understanding of these geologic factors is necessary to relate the microbiological biogeochemical and hydrological processes involved in the generation of coal bed gas

evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

water rock interaction and methanogenesis in formation water in the southeast huaibei coalfield china abstract the hydrogeochemical characteristics of aquifers in coal bearing strata can provide an important foundation for understanding the evolution of the aquifers and recognizing the formation process and occurrence of biogenic gas by analyzing the hydrogeochemical characteristics of water produced from the cenozoic the limestone and the coal strata aquifers and the coalbed gas wells this study focused on water rock interactions and methanogenesis in the formation water of the suzhou mining area huaibei coalfield china tectonically this is one of the most complex coalfields in china the dissolution of evaporites silicates and carbonates controlled the chemical composition of the formation water the cenozoic aquifers have a relatively stable water quality type and balanced ionic composition but more complex water rock interactions occur in the coal strata and the limestone aquifers extensive methanogenic activity and methanogenesis could be recognized by the meteoric water recharge positive 13 c signatures for dissolved inorganic carbon dic 15 4 26 2 lower sulfate concentrations

potential of sentinel 2 data for alteration extraction in coal bed methane reservoirs abstract this study illustrates the potential of alteration extraction in coal bed methane cbm reservoirs using the recently available sentinel 2 data this study then evaluates the capabilities for mapping the altered minerals and vegetation in the alteration mapping process we separately analyzed the key remote sensing signatures of altered minerals and geobotanical anomalies based on the hydrocarbon micro seepage theory the diagnostic spectral characteristics of irons clays and altered vegetation were concentrated and demonstrated the distribution of hydrocarbon micro seepage in the bare soil region the altered minerals including irons and clays were extracted through band math and principal component analysis pca methods in the vegetation area mapping the diagnostic spectral feature parameters such as the locations and slopes of three feature edges were calculated in addition the mapping accuracy was assessed based on the extraction results of hyperion data through full spectral profile matching method and the x ray diffraction xrd analysis results the results show that 1 compared with band math and pca methods the different extraction methods were suitable for different minerals 2 the extraction results of iron and clay minerals were most accurate 78 33 and 76 67 respectively with xrd analysis 3 the highest rate of change of the feature edge slope was up to 39 with a reference spectrum and 4 the distribution of alteration information was consistent with the hudi coal mining area in jincheng shanxi province the potential geological application of sentinel 2 data was revealed to identify the direction of cbm exploration in a large scale highly efficient convenient and inexpensive way

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the significance of fixed ammonium in palaeozoic sediments for the generation of nitrogen rich natural gases in the north german basin in contrast to predominantly hydrocarbon rich natural gases in the western part of the central european basin ceb accumulations of natural gases from the eastern part of the north german basin ngb are nitrogen rich with up to 90 n2 this study is focused on the behaviour of fixed ammonium in clay minerals of organic rich palaeozoic sediments in the eastern part of the ngb as a major source of nitrogen rich natural gases carboniferous shales have been investigated for a better understanding of nitrogen fixing during diagenesis storage during burial and release during devolatilization processes or fluid rock interactions the total nitrogen contents in the studied carboniferous shales of the ngb reach up to 2700 ppm with an inorganic fixed portion in the form of nh4 n of more than 60 the results of this study indicate an increasing proportion of the mineralogically fixed ammonium with increasing thermal maturity and storage up to catagenetic conditions the isotopic composition of fixed nh4 is relatively homogeneous in the majority of the shales and ranges from 1 to 3 5 in contrast samples from the basin centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in 15n up to 5 6 suggesting a release of nitrogen on a large scale calculation of nitrogen loss and isotopic fractionation indicate that more than 30 of nitrogen was released as ammonium probably as a consequence of fluid rock interaction with highly saline brines

a study of hydrogeology and its effect on coalbed methane enrichment in the southern junggar basin china this paper analyzes regional hydrogeological conditions and divides the study area into three hydrogeological types and seven hydrogeological units to investigate hydrogeology and its effect on coalbed methane cbm enrichment in the southern junggar basin china from this work it is found that the groundwater flow paths in the study area are the joint effects of south to north and west to east flows this study also shows that microbial gases are widely developed although the depth limit of microbial gas occurrence is still unclear in the study area microbial co2 reduction is the leading formation path in the study area except for the houxia region where fermentation is the formation mechanism the abnormally high co2 in stagnant zones i e water flow is slow and stagnant is mainly associated with methanogenesis whereas relatively low co2 microbial or thermogenic is present where water flow is active the average cbm content within the xishanyao formation changes within various hydrogeological units moreover the average cbm content within the badaowan formation of the same hydrogeological unit e g fukang suggests that the hydrogeological and cbm enrichment conditions are different within various structural types overall the hydrogeological conditions exert control on the gas content in the study area that is the gas content is high in stagnant zones finally influenced by supplemental microbial gases changes in the cbm oxidation zone are relatively complex in the study area the depth of which has no obvious correlation with hydrogeological conditions and changes significantly from west to east

influence of groundwater flowpaths residence times and nutrients on the extent of microbial methanogenesis in coal beds powder river basin usa water and natural gas samples were collected from coalbed methane wells and a surface coal mine in the powder river basin prb and analyzed for solute chemistry isotopes and gas composition to test hypotheses about the timing and source of recharge importance of nutrient influx and extent of microbial methanogenesis in coalbeds recharge to the wyodak anderson coal zone in the central portions of the prb appears to be from the southern basin margin based on 18o h2o values and hydraulic gradients coal zones along the eastern margin near the coal outcrop represent mixing between surface water and deeper circulating groundwater coalbeds along the northwestern basin margin may contain high elevation recharge from the bighorn mountains with flow patterns likely affected by local faults detectable 14c 0 39 to 4 13 pmc in coal waters throughout the prb indicates they were recharged 50 000 bp correlation of d ch4 and d h2o values suggests that methane has accumulated since the late pleistocene nutrient concentrations c n and p species are low throughout the prb and do not correlate to groundwater flowpaths or methanogenic pathways nutrients may be sourced from in situ leaching of coals carbon isotope values of ch4 and co2 likely indicate the extent of methanogenesis i e early versus late stage rather than the dominant metabolic pathway i e acetate fermentation versus co2 reduction coal gasses from the northwestern margin of the basin are isotopically depleted and suggest early stage methanogenesis where the reactant carbon reservoir has not been significantly fractionated due to relatively rapid groundwater flow coal gasses from the central basin and southeastern margin are isotopically enriched and suggest late stage methanogenesis where the reactant carbon reservoir has been significantly depleted likely due to longer groundwater residence times

production waters associated with the ferron coalbed methane fields central utah chemical and isotopic composition and volumes this study investigated the composition of water co produced with coalbed methane cbm from the upper cretaceous ferron sandstone member of the mancos shale in east central utah to better understand coalbed methane reservoirs the ferron coalbed methane play currently has more than 600 wells producing an average of 240 bbl day well water water samples collected from 28 wellheads in three fields buzzards bench drunkards wash and helper state of the northeast southwest trending play were analyzed for chemical and stable isotopic composition water produced from coalbed methane wells is a na cl hco3 type water from the drunkards wash field has the lowest total dissolved solids tds 6300 mg l increasing in value to the southeast and northeast in the helper state field about 6 miles northeast water has the highest total dissolved solids 43 000 mg l and major ion abundance indicates the possible influence of evaporite dissolution or mixing with a saline brine in the southern buzzards bench field water has variable total dissolved solids that are not correlated with depth or spatial distance significant differences in the relative compositions are present between the three fields implying varying origins of solutes and or different water rock interactions along multiple flow paths stable isotopic values of water from the ferron range from 0 9 to 11 4 18o and 32 to 90 2h and plot below the global meteoric water line gmwl on a line near but above values of present day meteoric water isotopic values of ferron water are consistent with modification of meteoric water along a flow path by mixing with an evolved seawater brine and or interaction with carbonate minerals analysis of isotopic values versus chloride conservative element and total dissolved solids concentrations indicates that recharge water in the buzzards bench area is distinct from recharge water in drunkards wash and is about 3 c warmer these variations in isotopes along with compositional variations imply that the ferron reservoir is heterogeneous and compartmentalized and that multiple flow paths may exist

geological and hydrological controls on the producibility of coalbed methane geological and hydrological comparison of two united states coalbed methane basins the prolific san juan basin and the marginally producing sand wash basin indicates that coal distribution and rank gas content permeability ground water flow and depositional and structural setting are critical controls on coalbed methane producibility a complex interplay and moreover a synergy amongst these controls determines high productivity this paper proposes a basin scale explanation for the prolific and marginal production in the two basins and that can be applied to evaluation of coalbed methane potential in coal basins worldwide high productivity is governed by 1 thick laterally continuous coals of high thermal maturity 2 basinward flow of ground water through coals of high rank and gas content orthogonally toward no flow boundaries regional hingelines fault systems facies changes and or discharge areas and 3 conventional trapping along those boundaries to provide additional gas beyond that sorbed on the coal surface

characterization of the origin of coalbed gases in southeastern illinois basin by compound specific carbon and hydrogen stable isotope ratios abstract coalbed gases and waters from exploratory and production gas wells in the southeastern illinois basin were sampled to assess geochemically the origin of coalbed gases with an emphasis on the springfield and seelyville coal members that are commercially targeted for coalbed methane production in indiana on line analyses of hydrocarbon gases methane to butanes c 1 c 2 c 3 n c 4 i c 4 and co 2 yielded gas concentrations plus d and 13 c values the low thermal maturity of indiana coals with vitrinite reflectance r 0 0 6 is in agreement with an overwhelmingly biogenic isotopic signature of coalbed gases containing 96 methane generated via bacterial co 2 reduction in contrast thermogenic gas was generated in the stratigraphically equivalent coal beds in western kentucky s rough creek graben zone where higher maturities of up to r 0 0 8 were reached owing to tectonic and hydrothermal activity no secondary biogenic methane was observed in more mature western kentucky coal beds where greater burial depth limits the recharge of meteoric water biogenic and thermogenic coalbed gases represent two end members that are compositionally and isotopically distinct microbial biodegradation of thermogenic c 2 hydrocarbon gases in indiana coal beds preferentially targets c 3 and introduces isotope fractionation whereby remaining c 3 is enriched in deuterium and 13 c

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

secarb co 2 injection test in mature coalbed methane reservoirs of the black warrior basin blue creek field alabama abstract the secarb black warrior field verification test employed a diverse suite of well testing and monitoring procedures designed to determine the injectivity capacity heterogeneity and performance of mature coalbed methane reservoirs a total of 3250 bbl of water and 252 t of co2 were injected into coal in a battery of slug tests these tests demonstrate that significant injectivity exists in black warrior coalbed methane reservoirs and that reservoir heterogeneity is a critical factor to consider when implementing co2 sequestration and co2 enhanced recovery programs the primary test well produces coalbed methane at wellhead pressures just above atmospheric and yet desorption testing indicates that less than 20 of the original gas in place has been recovered by primary production injection of co2 was conducted at sustained rates of about 90 t d of co2 reservoir pressure declined exponentially following the emplacement of each co2 slug slug and pressure buildup tests verify that permeability decreases exponentially with depth and also decreased during injection monitoring operations included multi zone pressure logging and gas sampling in deep observation wells and groundwater sampling in a shallow observation well results indicate that significant permeability anisotropy exists in each coal group in the black creek coal pressure response was greatest in the dominant natural fracture direction in the pratt coal group pressure response was dominated by hydrofractures co2 broke through to the observation wells only in the pratt coal group and only along the major fracture directions no significant flow of co2 out of zone was detected and no impact on shallow groundwater resources was identified

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

new evidence for two highstands of the sea during the last interglacial oxygen isotope substage 5e sedimentologic stratigraphic and geochronologic analyses of a previously undescribed carbonate section on oahu hawaii provide new evidence for two distinct sea level highstands on oahu during the last interglacial period oxygen isotope substage 5e whereas electron spin resonance and uranium series ages 122 8 ka to 152 25 ka and 115 10 ka to 160 15 ka respectively of in situ corals place the age of the deposits within substage 5e it is the unique sequence of strata found in these exposures that reveals the two transgressions a highstand lagoonal deposit of coral algal bafflestone is overlain by large seaward dipping slabs of beach rock the beachrock deposited during a mid 5e regression is in turn overlain by a second highstand lagoonal deposit this sequence was deposited in a broad shallow back reef embayment that was very sensitive to fluctuations in sea level elsewhere along much of the shoreline of oahu an in situ coral algal framestone waimanalo formation representing the initial 5e highstand is erosionally truncated on its upper surface this erosional unconformity represents the mid 5e lowstand and separates the framestone from overlying seaward dipping planar bedded grainstone and rudstone leahi formation that accumulated during the second 5e highstand

chaotic deposition by a giant wave molokai hawaii a coral basalt breccia conglomerate is exposed 60 m above present sea level and nearly 2 km inland from the present shoreline on the southwest side of east molokai volcano molokai the conglomerate is preserved mantling interfluves between gullies and forms a blanket like deposit 0 5 to 3 m thick no evidence of a wavecut terrace either within the blanket or at its upper or lower limits of exposure can be found no coral was found in growth position unsorted basalt clasts as large as boulder size are subrounded to angular randomly oriented and vary from 2 3 to 50 volume of the deposit the size of the largest basalt and coral fragments shows almost no systematic variation with elevation distance inland or lateral position parallel to the shore two indistinct rock units are present in a few places a lower carbonate rich unit that we interpret as an onwash facies and an upper basalt rich unit an offwash facies the carbonate rich onwash facies is dominated by biogenic debris especially fragments of coral and beach rock and gastropod and bivalve shells the offwash facies contains 40 to 90 basalt cobbles and boulders in a matrix of finely broken biogenic fragments where the distinct facies are lacking the proportion of basalt clasts increases crudely from the lower to the upper part of the conglomerate at a single place and from lower to higher elevation out crops where the deposit overlies a cinder cone several carbonate bearing elastic dikes extend from the conglomerate as much as 10 m down into the basalt cinders this deposit was apparently laid down by a giant wave that broke over an outer reef similar to the present fringing reef and advanced as a turbulent bore over the back reef flat picking up a slurry of carbonate rich debris and depositing it on the slopes inland as the wave advanced the offwash picked up loose basalt debris on its return flow u series dating of coral fragments indicates that the age of this deposit is 240 200 ka indicating the wave is distinct from that which produced a similar deposit on lanai about 100 ka this giant wave was most likely caused by one of the many large submarine landslides that have been identified on the lower slopes of the major hawaiian islands

stress transfer relations among the earthquakes that occurred in kerman province southern iran since 1981 summary we explore the possible stress triggering relationship of the m 6 4 earthquakes that occurred in kerman province southern iran since 1981 we calculated stress changes due to both coseismic sudden movement in the upper crust and the time dependent viscous relaxation of the lower crust and or upper mantle following the event four events of m 6 4 occurred between 1981 and 2005 on and close to the gowk fault show a clear coulomb stress load to failure relationship the 2003 m 6 5 bam earthquake however which occurred approximately 95 km sw of the closest gowk event shows a very weak stress relation to preceding earthquakes the coseismic static stress change at the hypocentre of the bam earthquake is quite small 0 006 bars the time dependent post seismic stress change could be 26 times larger or 7 times lower than that of coseismic static stress alone depending on the choice of viscoelastic crustal model and the effective coefficient of friction given the uncertainties in the viscoelastic earth models and the effective coefficient of friction we cannot confidently conclude that the 2003 bam event was brought closer to failure through coseismic or post seismic stress loading interestingly the southern gowk segment with a similar strike to that of the bam fault experienced a stress load of up to 8 3 bars between 1981 and 2003 and is yet to have a damaging earthquake

structural control of coalbed methane production in alabama abstract thin skinned structures are distributed throughout the alabama coalbed methane fields and these structures affect the production of gas and water from coal bearing strata extensional structures in deerlick creek and cedar cove fields include normal faults and hanging wall rollovers and area balancing indicates that these structures are detached in the pottsville formation compressional folds in gurnee and oak grove fields by comparison are interpreted to be detachment folds formed above decollements at different stratigraphic levels patterns of gas and water production reflect the structural style of each field and further indicate that folding and faulting have affected the distribution of permeability and the overall success of coalbed methane operations area balancing can be an effective way to characterize coalbed methane reservoirs in structurally complex regions because it constrains structural geometry and can be used to determine the distribution of layer parallel strain comparison of calculated requisite strain and borehole expansion data from calliper logs suggests that strain in coalbed methane reservoirs is predictable and can be expressed as fracturing and small scale faulting however refined methodology is needed to analyze heterogeneous strain distributions in discrete bed segments understanding temporal variation of production patterns in areas where gas and water production are influenced by map scale structure will further facilitate effective management of coalbed methane fields

comparison of fluid geochemistry and microbiology of multiple organic rich reservoirs in the illinois basin usa evidence for controls on methanogenesis and microbial transport abstract microbial methane in sedimentary basins comprises approximately 20 of global natural gas resources yet little is known about the environmental requirements and metabolic rates of these subsurface microbial communities the illinois basin located in the midcontinent of the united states is an ideal location to investigate hydrogeochemical factors controlling methanogenesis as microbial methane accumulations occur 1 in three organic rich reservoirs of different geologic ages and organic matter types upper devonian new albany shale up to 900 m depth pennsylvanian coals up to 600 m depth and quaternary glacial sediments shallow aquifers 2 across steep salinity gradients and 3 with variable concentrations of so 4 2 for all three organic rich reservoirs aqueous geochemical conditions are favorable for microbial methanogenesis with near neutral ph so 4 2 concentrations 80 c in nutrient poor environments necessitating the re introduction of microbes into the subsurface via groundwater transport

u series measurements in tyrrhenian deposits from mallorca further evidence for two last interglacial high sea levels in the balearic islands the campo de tiro type section for the tyrrhenian ecostratigraphic beds of the balearic islands shows four indurated littoral conglomerates and beach rocks unconformably superimposed the lower two units 1 and 2 are separated by a thin layer of reddish continental silts both contain a typical eutyrrhenian fauna whereas a neotyrrhenian fauna characterizes the overlying units 3 and 4 thu measurements by thermal ionisation mass spectrometry on mollusk shells from these deposits yielded ages of 135 ka unit 1 117 ka units 2 and 3 and a scatter of ages around 100 ka unit 4 the stratigraphic relationships and thu data indicate i that uranium was uptaken by mollusks shells but arca sp each time during a relatively short early diagenetic interval before cementation ensured a fair closure of the radioactive system ii two high sea stands characterized the last interglacial isotopic substage 5e of the balearic islands area iii the duration of this episode was 17 ka and iv the change in faunal assemblages and disconformity observed between units 2 and 3 are due to fluctuations in sea level and surface water conditions which occurred during the second high sea level episode of the last interglacial

high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial abstract u series ages using methods of thermal ionisation mass spectrometry tims are reported for last interglacial fossil reefs along the stable coastal margin of western australia thorium isotope ratios were measured with superior precision using methods of charge collection high levels of precision in the measurement of both uranium and thorium isotopes has reduced the age uncertainty due to analytical errors excluding the uncertainty in the decay constants by a factor of four over the precisions reported by many earlier tims workers uncertainties in 234u t determined from both 230th 238u and 234u 238u are also significantly smaller than previously reported allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified strict criteria were adopted to screen the new western australian data reliable ages range from 127 to 122 ka published tims observations from other localities have been assessed using the same strict criteria when these are combined with glacio hydro isostatic sea level models they indicate that the last interglacial period occurred from at least 130 to 117 ka however these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the last interglacial globally the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka in direct agreement with the narrow range in ages obtained from the western australian sites this may indicate that the last interglacial was of short duration extending from 127 to 122 ka only alternatively this interval may reflect a major reef building event in the middle of a longer duration 130 117 ka interglacial interval

coal reservoir saturation impact of temperature and pressure methane adsorption isotherms measured for a series of coals with varying rank at a wide range of temperatures and pressures allows the prediction of the change in sorption capacity as a function of tectonic history changes in sorption capacity in response to declining pressure and temperature associated with uplift may increase or decrease the capacity of the coal and if the coal is initially saturated result in excess gas or a deficiency of gas undersaturation assuming reasonable geothermal and pressure gradients our data indicate that the sorption capacity will generally decrease with uplift and associated exhumation suggesting that an initially gas saturated coal will desorb gas during uplift of the reservoir the desorbed gas would be available for migration and or potentially resaturation of an undersaturated coal our results argue against the generally accepted theory that undersaturation of coal reservoirs results from an increase in the sorption capacity with uplift except for coals at such high pressures that the isotherms are essentially flat or for very high pressure and geothermal gradients

geochemical analysis of atlantic rim water carbon county wyoming new applications for characterizing coalbed natural gas reservoirs coalbed natural gas cbng production typically requires the extraction of large volumes of water from target formations thereby influencing any associated reservoir systems we describe isotopic tracers that provide immediate data on the presence or absence of biogenic natural gas and the identify methane containing reservoirs are hydrologically confined isotopes of dissolved inorganic carbon and strontium along with water quality data were used to characterize the cbng reservoirs and hydrogeologic systems of wyoming s atlantic rim water was analyzed from a stream springs and cbng wells strontium isotopic composition and major ion geochemistry identify two groups of surface water samples muddy creek and mesaverde group spring samples are ca mg so4 type water with higher 87sr 86sr reflecting relatively young groundwater recharged from precipitation in the sierra madre groundwaters emitted from the lewis shale springs are na hco3 type waters with lower 87sr 86sr reflecting sulfate reduction and more extensive water rock interaction to distinguish coalbed waters methanogenically enriched was used from other natural waters enriched between 3 6 and 13 3 identified spring water that likely originates from mesaverde coalbed reservoirs strongly positive between 12 6 and 22 8 identified those coalbed reservoirs that are confined whereas lower between 0 0 and 9 9 identified wells within unconfined reservoir systems these results demonstrate that analysis provides immediate data to help identify atlantic rim groundwater sources hydraulic reservoir confinement springs associated with methanogenic coalbed reservoirs areas of peak methanogenic activity and to help assess gas potential and promote efficient cbng production

stable isotope geochemistry of coals humic kerogens and related natural gases isotope systematics are well defined for conventional sapropelic type i ii kerogens and their associated bacterial and thermogenic natural gas products these geochemical tools are used to estimate source type maturity and depositional environment and as a correlation technique in many cases the natural gas signatures in near surface samples and drill cuttings can be used to classify or predict a deeper lying source rock or reservoir corresponding interpretative schemes for coals type iii kerogens and their associated hydrocarbons are progressing quickly the shift in attention to humic sources is driven primarily by depletion of conventional oil and gas resources and the economic and societal requirements of coal and coal bed methane carbon hydrogen and nitrogen stable isotope variations can be large between different coals and humic kerogens these differences can often be recognized in their bulk 13corg dorg and 15norg values isotope signatures of coals can be diagnostic of several factors including deposit age type geographic location maturity and generation history however these characteristic isotopic variations are substantially better defined by the c h and n isotope ratios of the separate maceral groups such as vitrinite exinite and inertinite this new application of stable isotopes at the maceral and compound levels have great potential to improve the interpretative precision over conventional whole coal or bulk techniques hydrocarbon gases including coal gases derived from coals and humic kerogens can be distinguished from type i ii sources based on their molecular rations i e c1 c2 c3 and by comparing their stable isotope compositions especially 13cch4 and dch4 the 13cc2h6 can also be valuable but ethane is generally present in small amount 1 vol and requires

viscoelastic stress triggering of the 1999 hector mine earthquake by the 1992 landers earthquake the 1999 mw 7 1 hector mine earthquake occurred only 20 km from the 1992 mw 7 3 landers earthquake fault the close spacing between the two earthquakes suggests that the landers earthquake trigger the hector mine event based on an elastic half space model scientists from the usgs scec and cdmg 2000 have found a negative coulomb stress change at the hector mine hypocenter due to landers this negative stress change is inconsistent with the hypothesis of static stress triggering in this paper i show evidence of stress triggering of the hector mine earthquake by landers due to a process governed by viscoelastic flow in the lower crust this visoelastic flow has produced broad scale postseismic rebound observed by gps and insar measurements the result of this study is that viscoelastic flow has significantly modified the regional stress field in the mojave desert after the landers earthquake the evolving stress field including viscoelastic flow has gradually moved the coulomb stress change at the hector mine hypocenter to a positive level the increase in coulomb stress exceeded 1 bar right before the hector mine earthquake bringing the hector mine ruptures to the proximity of catastrophic failure

constraints on the age and duration of the last interglacial period and on sea level variations the relation between height and age of shorelines formed during the last interglacial period as revealed by coral reefs cannot be related directly to changes in ocean volume because of the effect of isostatic uplift in response to changes in ice sheet loading sea level changes at sites near the melting ice sheet such as bermuda and the caribbean islands differ from those along the australian margin modelling of these differences constrains the times of onset and termination of the last interglacial which are at variance with those deduced from oxygen isotope studies of deep sea cores

geochemical signature of formation waters associated with coalbed methane formation waters associated with coalbed methane have a common chemical character that can be an exploration tool regardless of formation lithology or age effectively devoid of sulfate calcium and magnesium the waters contain primarily sodium and bicarbonate and where influenced by water of marine association also contain chloride the distinct geochemical signature evolves through the processes of biochemical reduction of sulfate enrichment of bicarbonate and precipitation of calcium and magnesium cation exchange with clays may also deplete the dissolved calcium and magnesium but is not prerequisite low sulfate bicarbonate ratios characterize these waters and are also common but less pronounced with occurrences of conventional oil and gas waters rich in sulfate calcium and magnesium occur in many coalbed aquifers but are not found in association with methane users of total dissolved solids data should ensure that the values reflect adjustments of bicarbonate concentrations to simulate evaporation residues results that erroneously sum the entire bicarbonate content can be far too high in these bicarbonate rich waters thereby exacerbating the issues of disposal evaluations of prospects and choices of exploration targets can be enhanced by an added focus on the geochemical signature that should be expected in association with methane knowledge of the geochemical signature may also be useful in the commonly protracted testing of wells the appearance of high sulfate concentrations in water analyses can justify early curtailment of test pumping and can prompt the siting of subsequent drill holes farther from areas of recharge

hydrodynamics of coalbed methane reservoirs in the black warrior basin key to understanding reservoir performance and environmental issues abstract the black warrior basin of the southeastern united states hosts one of the world s most prolific and long lived coalbed methane plays and the wealth of experience in this basin provides insight into the relationships among basin hydrology production performance and environmental issues along the southeast margin of the basin meteoric recharge of reservoir coal beds exposed in an upturned fold limb exerts a strong control on water chemistry reservoir pressure and production performance fresh water plumes containing na hco3 waters with low tds content extend from the structurally upturned basin margin into the interior of the basin northwest of the plumes coal beds contain na cl waters with moderate to high tds content carbon isotope data from produced gas and mineral cements suggest that the fresh water plumes have been the site of significant bacterial activity and that the coalbed methane reservoirs contain a mixture of thermogenic and late stage biogenic gases water produced from the fresh water plumes may be disposed safely at the surface whereas underground injection has been used locally to dispose of highly saline water wells in areas that had normal hydrostatic reservoir pressure prior to development tend to produce large volumes of water and may take up to 4 a to reach peak gas production in contrast wells drilled in naturally underpressured areas distal to the fresh water plumes typically produce little water and achieve peak gas rates during the first year of production environmental debate has focused largely on issues associated with hydrologic communication between deep reservoir coal beds and shallow aquifers in the coalbed methane fields of the black warrior basin a broad range of geologic evidence suggests that flow is effectively confined within coal and that the thick intervals of marine shale separating coal zones limit cross formational flow

oxygen isotopes in meteoric calcite cements as indicators of continental paleoclimate because meteoric water 18 o values decrease with decreasing ambient temperature and increasing latitude 18 o values of meteoric calcite cement should exhibit a similar relation with paleolatitude and be an indicator of continental paleotemperatures to test this we compiled isotopic and paleolatitude data for 20 meteoric cements and nine speleothems ranging in age from devonian to modern and in paleolatitude from 3 5 to 83 mean 18 o values for meteoric cements and speleothems both show the same negative correlation with paleolatitude the 18 o vs latitude trend for these carbonates is almost identical to that predicted for modern inland environments but differs from the trend for coastal environments this suggests that the ground water controlling the ultimate composition of meteoric cement is derived predominantly from inland recharge if it is assumed that the modern meteoric water 18 o vs temperature relation is valid for the past and that insignificant evaporation occurred prior to carbonate precipitation then coastal and inland paleotemperatures can be calculated from the 18 o values of meteoric calcite 18 o mcl and seawater 18 o sw by using the equations t coastal 13 3 32 6 0 231 0 0613 18 o mcl 18 o sw and t inland 17 8 16 2 0 572 0 1233 18 o mcl 18 o sw where t is temperature in c calcite precipitated from coastal meteoric water at temperatures between 0 and 25 c will exhibit a narrow range in 18 o 6 to 4 where 18 o sw 0 the 18 o of calcite precipitated from inland meteoric water will be sensitive to paleotemperature ranging from 14 to 5 where 18 o sw 0 for temperatures of 0 to 25 c

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

geological and hydrological controls on the accumulation of coalbed methane within the no 3 coal seam of the southern qinshui basin abstract since 2006 the zhengzhuang zz block has been part of a commercial coalbed methane cbm production area in the southern qinshui basin which has become one of the most productive cbm areas in china however hydrogeological study of the migration gas and groundwater of the zz block has not been systematically launched this study focuses on geochemical analysis including quality analysis and stable isotope analyses for the water from the cbm production wells discusses the groundwater flow pathways and their influencing factors and evaluates the geological and hydrological controls on gas accumulation in the study area the results show that the produced waters produced with total dissolved solids tds values of 152 8 5389 49 mg l are typically fresh water and brackish water the water type is primarily bicarbonate and the dissolved ions are effectively devoid of sulfate calcium and magnesium with the low desulfurization coefficients of 0 24 5 63 the hydrochemical condition is conductive to cbm preservation the predominant flow of groundwater originates from the southwestern source which flows to the north basin center and then shifts to the east deep graben due to the drastic structural variation four hydrodynamic zones were distinguished through the differences in hydrodynamic conditions in the southwest zone i and the central zone ii the gas contents are relatively low 13 17 24 53 m 3 t despite the high thermal maturity r o max 3 31 3 97 however the stagnant zone iii in the north and the deep stagnant zone iv in the southeast show comparatively high gas content 16 5 31 44 m 3 t the complex geostructures act synergistically with the intense hydrodynamic activities for gas accumulation three cbm enrichment modes were distinguished hydrodynamic trapping at structure lows with high hydrostatic pressure conventional trap of impermeable boundary and hydraulic flushing and gas loss through the fault these investigations may serve for cbm exploration and development in the study area

mobility of continental mantle evidence from postseismic geodetic observations following the 1992 landers earthquake the crust around the rupture zone of the 1992 landers earthquake has continued to deform in the years following the earthquake at rates 3 times greater than pre earthquake rates we use a combination of global positioning system gps and synthetic aperture radar insar data collected during a 3 year epoch following the earthquake in order to investigate postseismic mechanisms responsible for the high transient velocities in order to maximize the potential signal from viscoelastic relaxation we evaluate and model postseismic relaxation following the first few months of documented accelerated deformation the combination of gps and insar data allows us to establish viscoelastic relaxation of the lower crust and upper mantle as the dominant postseismic process and to discriminate among possible viscoelastic models the data particularly require the presence of a highly ductile uppermost mantle beneath the central mojave domain with temperature between the wet and dry basalt solidus this is consistent with independent seismic and geochemical inferences of a regionally warm uppermost mantle further consideration of seismic velocity variations in conjunction with faulting patterns within the mojave desert suggests that the primary faulting characteristics of the mojave desert namely the pervasive late cenozoic deformation within the eastern california shear zone versus the near absence of faults in the western mojave domain are controlled by the rheology of the uppermost mantle

rapid fluctuations in sea level recorded at huon peninsula during the penultimate deglaciation about 140 000 years ago the breakup of large continental ice sheets initiated the last interglacial period sea level rose and peaked around 135 000 years ago about 14 meters below present levels a record of last interglacial sea levels between 116 000 years to 136 000 years ago is preserved at reef vii of the uplifted coral terraces of huon peninsula in papua new guinea however corals from a cave situated about 90 meters below the crest of reef vii are 130 000 2000 years old and appear to have grown in conditions that were 6 c cooler than those at present these observations imply a drop in sea level of 60 to 80 meters after 130 000 years sea level began rising again in response to the major insolation maximum at 126 000 to 128 000 years ago the early about 140 000 years ago start of the penultimate deglaciation well before the peak in insolation is consistent with the devils hole chronology

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

erosional modification of bahama escarpment the precipitous 28 to 40 bahama escarpment is characterized by abundant low energy restricted peritidal and lagoonal rocks and scarce high energy bank margin rocks of early and middle cretaceous age at depths of 2 000 m this indicates significant erosional modification of the slope all models of carbonate platforms have high energy facies at platform edges with low energy and restricted facies confined to platform interiors erosion has removed marginal deposits that constituted the original slope of the bahama platform and exposed peritidal and lagoonal facies rocks on the basis of widths of facies belts of middle cretaceous carbonate platforms in eastern mexico and of erosional benches apparent in seismic profiles across the bahama and blake escarpments an estimated 5 km of material has been eroded from the base of the escarpment greatest erosion occurred between the cenomanian and maastrichtian with additional erosion in the paleocene and oligocene as documented by tertiary and late cretaceous pelagic and forereef deposits that unconformably drape and fill fissures in the older shallow water rocks it is unclear whether erosion of the escarpment is occurring at present erosion of the slope deeper than 2 500 m is effected in part by spalling of joint blocks from shattered exposures jointing probably results from expansion of previously buried rocks exposed at the sea floor by erosion erosion of the bahama escarpment may have occurred by other processes acting in concert or individually at different times as well dissolution by corrosive water below the calcite compensation depth ccd and removal of sediments at the base of the slope by abyssal currents probably contributed most to erosional modification of the bahama escarpment bioerosion and jointing may aid dissolution by increasing surface area exposed to corrosive waters tectonic activity related to movements along fracture zone trends might have contributed locally to erosion of the bahama escarpment erosion of the bahama escarpment shallower than 2 500 m has been less extensive and apparently proceeds by slumping of large allochthonous blocks as indicated by the presence of an apparently intact eocene forereef deposit in the interval from 3 590 to 3 430 m off eleuthera island

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

south carolina interglacial sites and stage 5 sea levels abstract amino acid and other studies have been made on the 30 km pleistocene sections of the intracoastal waterway between myrtle beach and little river south carolina our ratios differentiate the long established waccamaw oldest canepatch and socastee formations the ratios from the four laboratories that have worked in this area agree very well and apparent conflicts with u series dates may merely reflect an abundance of reworked corals our amino acid correlations with u series coral dates in south carolina bermuda and the mediterranean all argue that the classical canepatch and its horry clay date from isotope stage 5e and not as has been implied from stage 7 9 11 or 13 excavations and erosion have increased position fixing problems along the waterway and canepatch amino acid ratios and u series dates 460 000 100 000 yr b p at icw5 may be from an older unit the canepatch shows the double marine transgression visible in many stage 5e deposits pollen shows that the second transgression occurred late in the interglaciation and stratigraphic studies show that it reached 14 m it therefore fits very well antarctic ice surge models of stage 5 sea level and climate the socastee adds to the evidence for one or more sea levels above 0 m late in stage 5

records of cosmogenic radionuclides 10be 26al and 36cl in corals first studies on coral erosion rates and potential of dating very old corals we present results of measurements of cosmogenic 10 be 26 al and 36 cl and the indigenous intrinsic concentrations of the stable elements be al and cl in 120 200 kyr old corals from barbados and puerto rico the concentration levels of these radionuclides in the corals lie in the range 10 4 to 10 8 atoms g a comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that i the radionuclides 26 al and 36 cl are derived from in situ cosmic ray interactions in the corals after their formation but that ii the radionuclide 10 be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals copyright 2005 elsevier ltd we discuss production rates and potential uses of cosmogenic radionuclides in corals and the implications of the measure ments reported here on the concentration of the cosmogenic radionuclides 10 be 26 al and 36 cl we show that the latter two radionuclides serve as gauges of coral terrace erosion rates whereas the cosmogenic 10 be is suitable for determining the ages of old corals of ages exceeding a few million years up to 10 myr the erosion rates of the corals range from 0 7 to 5 10 3 cm yr corresponding to an appreciable surface loss after aerial exposure 1 3 m since the last interglacial and 8m since the penultimate interglacial

origin of minerals in joint and cleat systems of the pottsville formation black warrior basin alabama implications for coalbed methane generation and production coalbed methane is produced from naturally fractured strata in the lower pennsylvanian pottsville formation in the eastern part of the black warrior basin alabama major fracture systems include orthogonal fractures which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and less commonly cleats in coal joint fill calcite postdates most pyrite and is a weakly ferroan coarse crystalline variety that formed during a period of uplift and erosion late in the burial history pyrite forms fine to coarse euhedral crystals that line joint walls or are complexly intergrown with calcite stable isotope data reveal large variations in the carbon isotope composition of joint and cleat fill calcite 10 3 to 24 3 peedee belemnite pdb but only a relatively narrow range in the oxygen isotope composition of this calcite 16 2 to 4 1 pdb negative carbon values can be attributed to 13c depleted co2 derived from the oxidation of organic matter and moderately to highly positive carbon values can be attributed to bacterial methanogenesis assuming crystallization temperatures of 2050c most joint and cleat fill calcite precipitated from fluids with 18o ratios ranging from about 11 to 2 standard mean ocean water smow uplift and unroofing since the mesozoic led to meteoric recharge of pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned southeastern margin of the basin influxes of fresh water into the basin via faults and coalbeds facilitated late stage bacterial methanogenesis which accounts for the high gas content in coal and the carbonate cementation of joints and cleats diagenetic and epigenetic minerals can affect the transmissivity and storage capacity of joints and cleats and they appear to contribute significantly to interwell heterogeneity in the pottsville formation in highly productive coalbed methane fields joint and cleat fill calcite have strongly positive 13c values whereas calcite fill has lower 13c values in fields that are shut in or abandoned petrographic analysis and stable isotope geochemistry of joint and cleat fill cements provide insight into coalbed methane reservoir quality and the nature and extent of reservoir compartmentalization which are important factors governing methane production

quaternary reef response to sea level and environmental change in the western atlantic the tropical subtropical western atlantic realm harbours abundant fringing reefs two major barrier reefs belize florida several atolls and large reef fringed carbonate platforms bahamas data from belize and south florida indicate that major barrier reefs were established during the high sea levels of the long and warm marine isotope stage 11 reefs formed during pleistocene sea level highstands whereas erosion non deposition and the formation of subaerial exposure surfaces prevailed during lowstands of sea level florida bahamas exposed reefs and platforms with siliciclastic hinterlands were characterized by deposition of clays and sands on fluvial plains belize elevated terraces and outcrops of reefs of the last interglacial of marine isotope stage 5e are evidence of higher than present sea level and temperature that sustained large reef fringed carbonate platforms and ramps in the florida bahamas region and central america belize mexico including ooid deposition in warm and shallow waters during the highstands of marine isotope stages 5c and 5a at sea levels several metres lower than today fringing reefs developed in parts of the caribbean for example in south florida outlier reefs data from the island of barbados support the contention that the postglacial sea level rise from about 120 m was rapid and punctuated by two meltwater pulses ia and ib which bracket the beginning and end of the younger dryas respectively after reflooding of shelves in the early holocene reefs developed preferentially on highs of the underlying karstified pleistocene limestone surface and on former river channel bars many reefs in the western atlantic region kept pace with holocene sea level rise whereas some were drowned reasons for reef drowning are debated and include sea level rise elevation of antecedent topography and deterioration of environmental conditions such as high nutrient input apart from sea level and antecedent topography factors such as exposure to waves and currents storms and sedimentation have controlled reef development the historical decline of acroporid corals in the caribbean realm has been attributed to cooling following the holocene thermal optimum however historical die offs of reef building corals and other reef organisms suggest that some if not all recent declines were unprecedented during the holocene rising temperatures decreasing carbonate saturation increased frequency of major storms high nutrient concentrations and sedimentation overfishing and disease certainly played a role in decline but systematic studies relating these environmental factors to holocene reef building are only in the early stages

thermogenic and secondary biogenic gases san juan basin colorado and new mexico implications for coalbed gas producibility the san juan basin is the most prolific coalbed gas basin in the world with 1992 production exceeding 440 gcf footnote 12 4 billion m3 resources of approximately 50 tcf 1 4 trillion m3 and proved reserves of over 6 tcf 170 billion m3 coalbed gas wells with the highest production initial potential greater than 10 mcf day or 0 28 million m3 day occur in the overpressured north central part of the basin hydrologic analysis indicates that overpressure in the fruitland formation is artesian in origin and represents repressuring that developed during the middle pliocene highly permeable laterally continuous coal beds override abandoned shoreline pictured cliffs sandstones and extend to the elevated recharge area in he northern basin to form a dynamic regionally interconnected aquifer system coal rank and basin hydrodynamics control the composition of fruitland coalbed gases which varies significantly across the basin chemically dry gases in the north central part of the basin coincide with meteoric recharge and regional overpressure the consistency of methane dgr13c values across the basin the presence of isotopically heavy carbon dioxide in coalbed gases and bicarbonate in formation waters and biodegraded n alkane distributions of some coal extracts indicate that coalbed gases in the north central basin are a mixture of thermogenic 25 50 secondary biogenic 15 30 and migrated thermogenic 12 60 gases migrated conventionally and hydrodynamically trapped gases in situ generated secondary biogenic gases and solution gases result in gas content that plot on or above the coal sorption isotherm bacteria transported basinward in groundwater flowing from the elevated northern basin margins metabolized wet gas components n alkanes and organic compounds in the coal and generated secondary biogenic methane and carbon dioxide subsequent to coalification uplift erosion and cooling these gases may be limited to basin margins where shallow depths and structural deformation result in higher permeability or may extend more than 35 mi 56 km basinward from the recharge zone the presence of appreciable secondary biogenic gas indicates an active dynamic flow system with overall permeability sufficient for high productivity basin hydrogeology reservoir heterogeneity location of permeability barriers no flow boundaries and the timing of biogenic gas generation and trap devel pment are critical for exploration and development of unconventional gas resources in organic rich rocks

postseismic rebound in fault step overs caused by pore fluid flow near field strain induced by large crustal earthquakes results in changes in pore fluid pressure that dissipate with time and produce surface deformation synthetic aperture radar sar interferometry revealed several centimeters of postseismic uplift in pull apart structures and subsidence in a compressive jog along the landers california 1992 earthquake surface rupture with a relaxation time of 270 45 days such a postseismic rebound may be explained by the transition of the poisson s ratio of the deformed volumes of rock from undrained to drained conditions as pore fluid flow allows pore pressure to return to hydrostatic equilibrium

evolution of marine terraces and sea level in the last interglacial cave hill barbados the uplifted marine terrace of last interglacial stage 5e age at cave hill barbados has been investigated with views toward terrace architecture developmental processes and sea level history methods include stratigraphic analysis of new deep exposures precise 230th geochronology and geomorphic mapping cave hill was central to earlier studies that led to important ideas on reef and terrace evolution but with which we find significant disagreement we present a new model of terrace evolution that emphasizes the role of marine erosion deposition of carbonate cover during the full eustatic cycle rather than only at highstand and principal reef development during transgression rather than at highstand by keep up rather than catch up growth the new model and geochronology contribute to an improved understanding of surficial processes during emergence of uplifting coral coasts and of global sea level changes in the last interglacial transgression in stage 5e at cave hill was accompanied by progressive marine erosion of a terrace floor and receding seacliff and deposition of a seaward thickening reefal wedge on the floor and above limestones of stage 6 and 7 ages the wedge contains a diachronous basal acropora palmata fringe reef this is overlain by an in place a cervicornis reef that aggraded progressively during sea level rise the transgressive phase took place between 136 ka or earlier and ca 128 ka during highstand between ca 127 and 120 ka the floor and seacliff continued to recede landward re gression began at or after ca 120 ka and sea level fell 37 m below the highstand level by ca 115 ka in stage 5c the seaward front of the last interglacial terrace was eroded landward an uncertain distance the sea level record at cave hill has implications for timing and constituent events of the penultimate glacial the last interglacial highstand and the fall in sea level at the transition from stage 5e to stage 5d shoreline angles which are isochronous linear geomorphic features are the most accurate markers of sustained highstand levels highstand levels and uplift rates interpreted from a palmata in barbados are less accurate and lower because the coral grew mainly in transgression the coral derived data therefore include uncertainties of depths of growth and collapse

microbial production and modification of gases in sedimentary basins a geochemical case study from a devonian shale gas play michigan basin an expanded data set for gases produced from the antrim shale a devonian black shale in the michigan basin united states has allowed for a detailed examination of the related chemical and isotopic compositional changes in the solid gas liquid systems that discriminate between microbial and thermogenic gas origin in the antrim shale economic microbial gas deposits are located near the basin margins where the shale has a relatively low thermal maturity and fresh water infiltrates the permeable fracture network the most compelling evidence for microbial generation is the correlation between deuterium in methane and coproduced water along the basin margins there is also a systematic enrichment in 13c of ethane and propane with decreasing concentrations that suggests microbial oxidation of these thermogenic gas components microbial oxidation accounts not only for the shift in 13c values for ethane but also in part for the geographic trend in gas composition as ethane and higher chain hydrocarbons are preferentially removed this oxidation is likely an anaerobic process involving a syntrophic relationship between methanogens and sulfate reducing bacteria the results of this study are integrated into a predictive model for microbial gas exploration based on key geochemical indicators that are present in both gas and coproduced water one unequivocal signature of microbial methanogenesis is the extremely positive carbon isotope values for both the dissolved inorganic carbon in the water and the coproduced co2 gas in contrast the 13c value of methane is of limited use in these reservoirs as the values typically fall between the commonly accepted fields for thermogenic and microbial gas in addition the confounding isotopic and compositional overprint of microbial oxidation increasing the values to typically thermogenic values may obscure the distinction between methanogenic and thermogenic gas

rapid determination of coalbed methane exploration target region utilizing hyperspectral remote sensing abstract this study reveals the common surface mineral characteristics over coalbed methane cbm enrichment regions from spaceborne hyperion images and the possibility of hyperspectral remote sensing for prospecting coalbed methane exploration target region with an inexpensive large scale rapid and convenient way for this study a typical scheme including bands removal atmospheric correction snr estimation minimum noise fraction mnf pixel purity index ppi and n dimensional visualization was applied on hyperion image in qinshui basin china to accurately extract mineral endmembers the endmember spectra of carbonate and clay mineral were identified based on the diagnostic absorption feature while no endmember of ferrous iron mineral was found the absorption feature parameters of carbonate absorption position and especially asymmetric factor and clay mineral absorption position left and right shoulder positions were quantitatively estimated which showed the endmember spectra of carbonate and clay mineral from hyperspectral images in this paper were correct in addition this study proposed an interesting research direction measuring the asymmetric absorption factor to facilitate the identification of carbonates furthermore spectral angle mapper sam and spectral feature fitting sff were used to map carbonates and clay minerals two assessment methods visual interpretation based on field spectra and x ray diffraction xrd analysis were utilized to evaluate the mapping accuracy which showed total agreements of 84 03 and 72 58 respectively the results in this paper suggested that both carbonates and clay minerals were rich while there was hardly any ferrous iron mineral on the surface of cbm enrichment regions in addition another similar experiment was carried out in ordos basin and also showed similar surface mineral characteristics on cbm enrichment region

deciphering the impact of sea level changes and tectonic movement on erosional sequence boundaries in carbonate successions a case study from tertiary strata on grand cayman and cayman brac british west indies abstract the stratigraphic architecture of carbonate successions that develop on geographically isolated islands reflects the balance between sea level highstands lowstands and tectonic activity this is readily apparent in the tertiary carbonate sequences on the cayman islands that are formed of the bluff group which includes the brac formation lower oligocene cayman formation middle miocene and pedro castle formation middle pliocene these strata are overlain by the pleistocene ironshore formation the unconformities that define the boundaries between these formations are variable because some developed during one cycle of past erosion others developed through two or more past erosional cycles and some are still developing today some unconformities like the one at the top of the cayman formation are geographically variable because they underwent different developmental histories in different areas the challenge with architectural complex successions like those on the cayman islands is that of deciphering the impact of sea level changes as opposed to tectonic influences during sea level lowstands the older carbonate successions were exposed on land and modified by surface and subsurface karst development at the same time marine erosional processes affected the coastal areas surface karst modification which commonly produced rugged topographies with erosional relief at least 62 m was controlled largely by rainfall runoff and stratal dip weathering on grand cayman at the end of the miocene for example produced a dish shaped topography with elevated peripheral rims in contrast uplift of the east end of cayman brac between the late pliocene 3 6 ma and 400 ka elevated the basal part of the cayman formation 33 m above sea level subsequent karst development which is still ongoing today removed most of the cayman formation on the eastern part of the island and produced peripheral rims that are higher than those on grand cayman during some lowstands like that between the late pliocene and 400 ka coeval coastal erosion led to the development of coastal benches that cut into the older carbonate strata the combination of karst development in the islands interiors and coastal erosion produced complex rugged topographies that strongly influenced patterns of deposition during the following highstand the complex stratigraphic architecture of the carbonate successions on the cayman islands reflects the variable impact of tectonics karst development and coastal erosion that was associated with each lowstand highstand cycle

duration and structure of the past four interglaciations reanalysis and additional dating of the devils hole 18o paleotemperature record confirm that the last interglaciation in the great basin the continental analog of marine isotopic substage 5e lasted 22 000 yr consistent with the vostok paleotemperature record which suggests a duration of 19 000 yr for this event in antarctica the three preceding interglaciations in the devils hole record analogs of marine isotopic substages 7e 9c and 11c range from 20 000 to 26 000 yr in duration a 20 000 yr duration for the last interglaciation is consistent with tims uranium series dated sea level high stands thus the widely held view that interglaciations were of 11 000 to 13 000 yr duration and constituted only about 10 of mid to late pleistocene climatic cycles needs reexamination the warmest portion of each interglaciation in the devils hole time series is marked by a 18o plateau signifying apparent climatic stability for periods of 10 000 to 15 000 yr duration

sensitivity of static stress calculations to the earthquake slip distribution 1 the apparent strong correlation between coulomb stress changes and the spatial distribution of aftershocks suggests the possibility of making near real time estimations of areas at risk of experiencing off fault aftershocks in order to do this in practice a number of issues must first be addressed including the extent to which the main shock slip must be known in detail before a meaningful stress map can be constructed here we investigate this issue by constructing a time ordered sequence of slip solutions for the landers earthquake computing coulomb stress changes for each solution and quantitatively comparing the stress field with the observed aftershocks by 1 resolving the coulomb stress change onto the aftershock nodal planes and calculating the percentage of events consistent with triggering and 2 constructing a two dimensional map of coulomb stress and computing the correlation coefficient between the positive and negative areas and the locations of the aftershocks we find that slip solutions based on empirical relations and either focal mechanism or moment tensor data produce stress fields inconsistent with the observed spatial distribution of aftershocks whereas slip solutions incorporating the correct rupture geometry but greatly simplified slip produce stress fields consistent with the aftershock distribution when very near fault events are excluded we further find that resolving stress perturbations onto earthquake nodal planes and computing the percentage of events experiencing positive coulomb stress provides a poor measure of success because of the limited range of structures on which events occur and the compatibility of the main shock stress field with these structures our results support the hypothesis that coulomb stress changes affect the spatial distribution of aftershocks and suggest that meaningful calculations of coulomb stress can be made as soon as an earthquake s rupture geometry is well constrained

bermuda sea level during the last interglacial bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of sea level fluctuation during the period 135 70 kyr has been reconstructed from 230th 234u dating of corals and speleothems amino acid racemization dating of molluscs and a reinterpretation of geological field relations during the past 5 yr bermuda has been the focus of an extensive geochronological programme which has included a detailed re examination of the geology to be reported elsewhere1 3 here we focus only on the latest interglacial sequence we use the stratigraphie nomenclature of land et al 4 but will present new age data and interpretations of geological relationships this information as it relates to the last interglacial period is given in tables 1 and 2 and summarized in fig 1 we show that during the last interglacial period sea level was only above its present level for a few thousand years at about 125 kyr when it stood at 4 to 6m at 105 and 85 kyr sea level rose to between 15 and 20 m as constrained by ages for submerged speleothems and eolianites at 95 kyr sea level in bermuda was at least 15 m below present level

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

time dependent distributed afterslip on and deep below the izmit earthquake rupture surface deformation transients measured with the global positioning system during the 87 days between the 17 august 1999 izmit earthquake and the 12 november 1999 duzce earthquake indicate rapidly decaying aseismic fault slip on and well below the coseismic rupture elastic model inversions for time dependent distributed fault slip using a network inversion filter approach show that afterslip was highest between and below the regions of maximum coseismic slip and propa gated downward to or even below the base of the crust maximum afterslip rates decayed from greater than 2 m yr immediately after the i zmit earthquake to about 1 2 m yr just prior to the duzce earthquake maximum afterslip occurred below the eastern karadere rupture segment and near the i zmit hypocenter afterslip in the upper 16 km decayed more rapidly than that below the seismogenic zone these observations are consistent with a phase of rapid aseismic fault slip concentrated near the base of the seismogenic zone continued loading from the rapid deep afterslip along the eastern rupture zone is a plausible mechanism that helped trigger the nearby mw 7 2 12 november duzce earthquake

temperature pressure conditions in coalbed methane reservoirs of the black warrior basin implications for carbon sequestration and enhanced coalbed methane recovery abstract sorption of gas onto coal is sensitive to pressure and temperature and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs more than 5000 wells have been drilled in the coalbed methane fields of the black warrior basin in west central alabama and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal bearing strata reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 f 27 52 c and geothermal gradient ranges from 6 0 to 19 9 f 1000 ft 10 9 36 2 c km geothermal gradient data have a strong central tendency about a mean of 9 0 f 1000 ft 16 4 c km hydrostatic pressure gradients in the coalbed methane fields range from normal 0 43 psi ft to extremely underpressured geothermal gradients within the coalbed methane fields are high enough that reservoirs never cross the gas liquid condensation line for carbon dioxide however reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft 756 m under normally pressured conditions all target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway although mature reservoirs are dewatered and thus are in the carbon dioxide gas window supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment coal can hold large quantities of carbon dioxide under supercritical conditions and supercritical isotherms indicate non langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals hence carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist

postseismic relaxation theory on the spherical earth abstract postseismic displacements and strains observed at the earth9s surface can be explained through the relaxation of a viscoelastic asthenosphere underlying a purely elastic crust a theory is presented for modeling the effects of postseismic relaxation on a spherically symmetric earth for an earthquake point source located in the upper elastic layer the displacement field is decomposed into its toroidal and spheroidal components a linear maxwell rheology in the viscoelastic layers is assumed enabling the use of the correspondence principle for the solutions of the equations of static equilibrium displacement and strain fields are then calculated using normal mode summation computational results are presented for two simple earthquake sources a strike slip fault and a uniaxial thrust fault the patterns of postseismic displacements and strains are found to depend strongly on both the earth model and earthquake source geometry in particular the elastic plate thickness asthenosphere thickness fault type and fault length each play a major role in determining the spatial pattern of postseismic relaxation effects asthenospheric viscosity controls the temporal pattern of relaxation

identification of microbial and thermogenic gas components from upper devonian black shale cores illinois and michigan basins differentiation of microbial versus thermogenic methane in coalbed and black shale accumulations can affect strategies for exploration and may influence the total gas content in a given area early identification of these processes from crushed core materials even before formation fluids and produced gas samples are available could permit a more efficient and cost effective exploration total gas contents and compositional and isotopic data from new albany shale core materials are presented which delineate regional occurrence of microbial thermogenic and mixed gas generation in the illinois basin these trends are consistent with those identified from detailed prior studies of produced gas and water chemistry from the same locations the most useful markers for microbial gas in crushed core gases are elevated co2 contents characterized by high values 5 core gas analyses from wells in which microbial gas is identified commonly have significantly more total gas absorbed than do core samples from wells producing gases solely of thermogenic origin these observations are independent of variations in sample depth and organic carbon content in a given core thus this integrated case study of core and produced gases in the illinois basin illustrates that the areas containing microbial gas in addition to early thermogenic gas may be more productive than pure thermogenic zones for these early to immature unconventional gas deposits