middle miocene ocean climate transition high resolution oxygen and carbon isotopic records from deep sea drilling project site 588a southwest pacific high resolution stable isotopic records are presented for the epi benthic foraminifer cibicidoides the inferred shallow dwelling planktonic globigerinoides quadrilobatus and the inferred deep dwelling planktonic globoquadrina dehiscens from the middle miocene 16 12 ma of deep sea drilling project site 588a lord howe rise southwest pacific high resolution multiple species oxygen and carbon isotopic data define the timing and character of the well known middle miocene climatic oceanographic transition with a resolution comparable to quaternary records the benthic foraminiferal 18o record is marked by several large fluctuations from 16 to 14 8 ma followed by a series of rapid 50 kyr 18o increases that suggest a new state of the ocean climate system after 14 8 ma the total middle miocene benthic oxygen isotopic increase of 1 2 is largely incorporated in two steps an increase of 0 8 from 14 5 to 14 0 ma and a second increase of 0 7 from 13 45 to 12 45 ma each step is comprised of a series of marked 18o increases indicative of rapid east antarctic ice sheet growth and contemporaneous deepwater cooling a strong covariance of 0 7 between the benthic and deep dwelling planktonic species from 14 5 to 14 0 ma including a rapid increase from 14 1 to 14 05 ma suggests a 0 7 increase in the 18o composition of seawater 18osw because of east antarctic ice sheet growth comparison of the 18o record of gs quadrilobatus suggests that surface waters warmed at this site by 3 c from 14 1 to 13 6 ma carbon isotopic time series for each species generally covary throughout the early to middle miocene interval 16 12 ma confirming that 13c variations in this interval largely represent reservoir changes high resolution 13c data allow improved resolution of the latter five of six 13c maxima within the well known early to middle miocene carbon isotopic excursion the monterey carbon isotopic excursion from 17 0 to 13 5 ma this is useful for global correlation the last of these maxima ends with a 1 decrease centered from 13 9 to 13 7 ma 300 kyr after the 18o increase considered to reflect east antarctic ice growth covariance between benthic 18o and 13c from 16 to 13 8 ma suggests a sensitive relation between global carbon cycling and the ocean climate system prior to 13 8 ma episodic increases in organic carbon burial may have contributed to deep sea benthic 13c maxima and synchronous global cooling the positive relationship ended at 13 8 ma indicative of changing relations between global carbon cycling and the ocean climate system brought on by the increased stability of the east antarctic ice sheet after a major growth phase from 14 5 to 14 0 ma

pacific ocean and cenozoic evolution of climate 1 the pacific ocean has played a major role in climate evolution throughout the cenozoic 65 0 ma it is a fundamental component of global heat transport and circulation the dominant locus of primary productivity and consequently the largest reservoir for carbon exchange between the oceans and the atmosphere a satisfactory understanding of the cenozoic evolutionary history of the pacific and its impact on global climate is currently data limited nevertheless the large dynamic range of cenozoic conditions sets the stage to greatly expand our understanding of global climate and biogeochemical cycles past earth experiments are particularly useful to understand interactions between climate and geosystems under different greenhouse gas loads we highlight in this review four important problems in which the pacific played a major role the effect of changing geographic boundary conditions on ocean circulation interactions between the carbon cycle and climate the pacific ocean s influence on north american climate and its water cycle and the gradual evolution of climate systems

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

paleogene deepwater mass composition of the tropical pacific and implications for thermohaline circulation in a greenhouse world 1 the pacific ocean likely exerted the greatest marine influence on climate during the greenhouse interval of the paleogene the first step toward assessing the role of pacific deepwater circulation in global heat transport is a comprehensive reconstruction of deepwater mass composition and circulation patterns we present new deepwater mass nd isotope data from odp leg 199 sites 1215 1217 1219 and 1221 to augment the existing coverage provided by ferromanganese crust and fossil fish debris data the new data corroborate the notion that the pacific ocean operated in a bimodal pattern with deepwater sources in both the southern ocean and north pacific for much of the early to middle paleogene in addition the data indicate that there was little to no influence of atlantic waters on the deepwater composition of the tropical pacific the available deepwater nd isotope data provide refined constraints on the geographic and depth range of influence of both a southern ocean and north pacific deepwater mass from 65 to 45 ma the deep tropical pacific was the mixing location of deep waters sourced from the southern ocean and the north pacific the southern ocean deepwater mass extended from 1800 m to abyssal depths until 53 6 ma it circulated northward in the western pacific at least as far as the paleolocation of fe mn crust cld01 5 n paleolatitude and in the eastern portion of the pacific as far as site 1215 10 n paleolatitude a north pacific deepwater mass extended from at least 2400 m to 2900 m water depth from 65 to 54 ma south to shatsky rise paleolatitude 10 15 n and possibly as far as site 1215 700 km to the south of shatsky rise sites 1209 and 1211

geostatistical modeling of the gas emission zone and its in place gas content for pittsburgh seam mines using sequential gaussian simulation determination of the size of the gas emission zone the locations of gas sources within and especially the amount of gas retained in those zones is one of the most important steps for designing a successful methane control strategy and an efficient ventilation system in longwall coal mining the formation of the gas emission zone and the potential amount of gas in place gip that might be available for migration into a mine are factors of local geology and rock properties that usually show spatial variability in continuity and may also show geometric anisotropy geostatistical methods are used here for modeling and prediction of gas amounts and for assessing their associated uncertainty in gas emission zones of longwall mines for methane control this study used core data obtained from 276 vertical exploration boreholes drilled from the surface to the bottom of the pittsburgh coal seam in a mining district in the northern appalachian basin after identifying important coal and non coal layers for the gas emission zone univariate statistical and semivariogram analyses were conducted for data from different formations to define the distribution and continuity of various attributes sequential simulations performed stochastic assessment of these attributes such as gas content strata thickness and strata displacement these analyses were followed by calculations of gas in place and their uncertainties in the pittsburgh seam caved zone and fractured zone of longwall mines in this mining district grid blanking was used to isolate the volume over the actual panels from the entire modeled district and to calculate gas amounts that were directly related to the emissions in longwall mines results indicated that gas in place in the pittsburgh seam in the caved zone and in the fractured zone as well as displacements in major rock units showed spatial correlations that could be modeled and estimated using geostatistical methods this study showed that gip volumes may change up to 3 mmscf per acre and in a multi panel district may total 9 bcf of methane within the gas emission zone therefore ventilation and gas capture systems should be designed accordingly in addition rock displacements within the gas emission zone are spatially distributed from an engineering and practical point of view spatial distributions of gip and distributions of rock displacements should be correlated with in mine emissions and gob gas venthole productions

os isotope chemostratigraphy applied to organic rich marine sediments from the eocene oligocene transition on the west african margin odp site 959 1 the known temporal relationship between the benthic foraminiferal 18o record and the marine os isotope record is used to reinterpret the absolute chronology and paleoceanographic context of an episode of organic carbon burial on the west african margin ocean drilling program odp site 959 although organic rich sediments require significant corrections for in situ decay of 187re to 187os these results demonstrate the utility of the marine os isotope record for chemostratigraphic correlation of organic rich sediments that are devoid of age diagnostic microfossils with pelagic carbonate sequences revision of the odp site 959 chronology shifts the age assignment of an interval of biosiliceous organic rich sediment deposition from the oligocene to the late eocene and earliest oligocene likely culminating with the first major glaciation of the oligocene oi1 we speculate that enhanced organic carbon burial over much of the west african margin may have contributed to drawdown of atmospheric carbon dioxide before and during the oi1 event and suggest that os isotope chemostratigraphy provides a valuable tool for further exploring this possibility

paleogene calcite compensation depth in the eastern subtropical pacific answers and questions 1 ocean drilling program leg 199 drilled a north south transect across the eocene paleoequator in the eastern pacific permitting reconstruction the calcite compensation depth ccd since earliest eocene time the ccd was relatively shallow near the early eocene pacific equator 3200 m and unlike modern latitudinal ccd gradients deepened to the north to 3600 m paleolatitude 10 n at 41 ma the ccd underwent a brief sharp transient deepening of 700 m then remained shallow until the eocene oligocene boundary at the e o boundary the ccd deepened by 1200 m in less than 300 kyr this rapid deepening served to more than double the area of seafloor subject to caco3 deposition sea level fall associated with ice volume buildup and ensuing shelf basin fractionation is unlikely to be the sole cause of the increased deep ocean caco3 burial rather a sudden rapid increase in the amount of ca entering the ocean appears necessary to explain the observations

coal bed reservoir simulation with geostatistical property realizations for simultaneous multi well production history matching a case study from illinois basin indiana usa abstract coal seam degasification is a means to recover energy from the methane gas retained in coal and is also a supplementary measure to ventilation which is proven to be one of the most effective ways to reduce methane emissions to a safe level in coal mines reservoir simulation is probably the most effective way to assess the coal seam as a gas reservoir and thereby its fluid storage and flow related properties this objective is achieved by taking advantage of history matching of wellbore production reservoir simulation with multi well history matching is a tedious process as important coal properties that affect wells production characteristics are spatially variable across the seam the common practice is to change various properties at the well blocks during the history matching process and assume that they are uniform across the domain of interest this process however often does not produce realistic and effective results for well or coal reservoir management in this work a multi level approach to coal bed reservoir simulation is demonstrated for a group of coalbed methane wells in the illinois basin producing from the seelyville coal member of the linton formation of the carbondale group pennsylvanian in indiana this approach includes in order gas and water deliverability analyses of wells geostatistical simulation and co simulation and coal bed reservoir simulation it is shown that a reservoir model which utilizes the geostatistical maps of important coal properties is effective for simultaneous history matching of all wells and eliminates the need for guessing and changing values of coal properties at and around individual well blocks this methodology also provides realistic distributions of reservoir parameters and how they change during gas depletion and thus aids in coal seam and coal gas management

latest eocene early oligocene climate change and southern ocean fertility inferences from sediment accumulation and stable isotope data abstract the earliest oligocene 33 5 ma is marked by a major step in the long term transition from an ice free to glaciated world the transition characterized by both cooling and ice sheet growth triggered a transient but extreme glacial period designated oi 1 high resolution isotope records suggest that oi 1 lasted for roughly 400 000 yr the duration of magnetochron 13n before partially abating and that it was accompanied by an ocean wide carbon isotope anomaly of 0 75 one hypothesis relates the carbon isotope anomaly to enhanced export production brought about by climate induced intensification of wind stress and upwelling particularly in the southern ocean to understand how this climatic event affected export production in the southern ocean biogenic silica opal and carbonate accumulation rates were computed for the sub polar indian ocean using deep sea cores from odp site 744 kerguelen plateau our findings suggest that net productivity in this region increased by several fold in response to the oi 1 glaciation in addition calcareous primary producers dominant in the late eocene were partially replaced by opaline organisms suggesting a trend toward seasonally greater surface divergence and upwelling in this sector of the southern ocean we attribute these changes to intensification of atmospheric oceanic circulation brought about by high latitude cooling and the appearance of a full scale continental ice sheet on east antarctica higher terrigenous sediment accumulation rates support the idea that wind induced changes in regional productivity were augmented by an increased supply of glacial dust and debris that provided limiting micro nutrients e g iron rich dust particles we speculate that the rapid changes in biogenic sediment accumulation in the southern ocean and other upwelling dominated regions contributed to the ocean wide positive carbon isotope anomaly by temporarily increasing the burial rate of organic carbon relative to carbonate carbon the changes in burial rates in turn may have produced a positive feedback on climate by briefly drawing down atmospheric pco2

probabilistic modeling using bivariate normal distributions for identification of flow and displacement intervals in longwall overburden abstract gob gas ventholes ggv are used to control methane emissions in longwall mines by capturing it within the overlying fractured strata before it enters the work environment in order for ggvs to effectively capture more methane and less mine air the length of the slotted sections and their proximity to top of the coal bed should be designed based on the potential gas sources and their locations as well as the displacements in the overburden that will create potential flow paths for the gas in this paper an approach to determine the conditional probabilities of depth displacement depth flow percentage depth formation and depth gas content of the formations was developed using bivariate normal distributions the flow percentage displacement and formation data as a function of distance from coal bed used in this study were obtained from a series of borehole experiments contracted by the former us bureau of mines as part of a research project each of these parameters was tested for normality and was modeled using bivariate normal distributions to determine all tail probabilities in addition the probability of coal bed gas content as a function of depth was determined using the same techniques the tail probabilities at various depths were used to calculate conditional probabilities for each of the parameters the conditional probabilities predicted for various values of the critical parameters can be used with the measurements of flow and methane percentage at gob gas ventholes to optimize their performance

tertiary oxygen isotope synthesis sea level history and continental margin erosion tertiary benthic and planktonic foraminiferal oxygen isotope records are correlated to a standard geomagnetic polarity time scale making use of improved chronostratigraphic control and additional oligocene isotope data synchronous changes in both benthic and planktonic 18o values which occurred in the oligocene to miocene 36 5 2 ma are interpreted in part to represent ice growth and decay the inferred ice growth events correlate with erosion on passive continental margins as interpreted from seismic and chronostratigraphic records this association is consistent with a link between oligocene to miocene erosional events and rapid 15 m m y glacioeustatic lowerings of about 50 m high benthic foraminiferal 18o values suggest the presence of continental ice sheets during much of the oligocene to recent 36 0 ma substantially ice free conditions probably existed throughout the paleocene and eocene 66 36 ma the mechanisms and rates of sea level change apparently were different between the early and late tertiary with glacioeustatic changes restricted to the past 36 m y pre oligocene erosion on passive continental margins was caused by eustatic lowerings resulting from global spreading rate changes we apply a model which suggests that large areas of the continental shelves were subaerially exposed during such tectonoeustatic lowstands stimulating slope failure and submarine erosion the different mechanisms and rates of eustatic change may have caused contrasting erosional patterns between the early and late tertiary on passive continental margins this speculation needs to be confirmed by examination of data from several passive margins

thresholds for cenozoic bipolar glaciation the long standing view of earth s cenozoic glacial history calls for the first continental scale glaciation of antarctica in the earliest oligocene epoch 33 6 million years ago1 followed by the onset of northern hemispheric glacial cycles in the late pliocene epoch about 31 million years later2 the pivotal early oligocene event is characterized by a rapid shift of 1 5 parts per thousand in deep sea benthic oxygen isotope values3 oi 1 within a few hundred thousand years4 reflecting a combination of terrestrial ice growth and deep sea cooling the apparent absence of contemporaneous cooling in deep sea mg ca records4 5 6 however has been argued to reflect the growth of more ice than can be accommodated on antarctica this combined with new evidence of continental cooling7 and ice rafted debris8 9 in the northern hemisphere during this period raises the possibility that oi 1 represents a precursory bipolar glaciation here we test this hypothesis using an isotope capable global climate ice sheet model that accommodates both the long term decline of cenozoic atmospheric co2 levels10 11 and the effects of orbital forcing12 we show that the co2 threshold below which glaciation occurs in the northern hemisphere 280 p p m v is much lower than that for antarctica 750 p p m v therefore the growth of ice sheets in the northern hemisphere immediately following antarctic glaciation would have required rapid co2 drawdown within the oi 1 timeframe to levels lower than those estimated by geochemical proxies10 11 and carbon cycle models13 14 instead of bipolar glaciation we find that oi 1 is best explained by antarctic glaciation alone combined with deep sea cooling of up to 4 c and antarctic ice that is less isotopically depleted 30 to 35 than previously suggested15 16 proxy co2 estimates remain above our model s northern hemispheric glaciation threshold of 280 p p m v until 25 myr ago but have been near or below that level ever since10 11 this implies that episodic northern hemispheric ice sheets have been possible some 20 million years earlier than currently assumed although still much later than oi 1 and could explain some of the variability in miocene sea level records

control of gas emissions in underground coal mines abstract a high level of knowledge is now available in the extremely relevant field of underground gas emissions from coal mines however there are still tasks seeking improved solutions such as prediction of gas emissions choice of the most suitable panel design extension of predrainage systems further optimization of postdrainage systems options for the control of gas emissions during retreat mining operations and prevention of gas outbursts research results on these most important topics are presented and critically evaluated methods to predict gas emissions for disturbed and undisturbed longwall faces are presented prediction of the worked seam gas emission and the gas emission from headings are also mentioned but not examined in detail the ventilation requirements are derived from the prediction results and in combination with gas drainage the best distribution of available air currents is planned the drainage of the gas from the worked coal seam also referred to as predrainage can be performed without application of suction only by over or underworking the seam but in cases where this simple method is not applicable or not effective enough inseam boreholes are needed to which suction is applied for a relatively long time the reason for this is the low permeability of deep coal seams in europe the main influences on the efficiency of the different degasing methods are explained conventional gas drainage employing cross measure boreholes is still capable of improvement in terms of drilling and equipment as well as the geometrical borehole parameters and the operation of the overall system improved control of gas emissions at the return end of retreating faces can be achieved by installation of gas drainage systems based on drainage roadways or with long and large diameter boreholes the back return method can be operated safely only with great difficulty if at all another method is lean gas drainage from the goaf the gas outburst situation in germany is characterized by events predominantly in the form of nonclassical outbursts categorized as sudden liberation of significant quantities of gas recent research results in this field led to a classification of these phenomena into five categories for which suitable early detection and prevention measures are mentioned

the stability of methane capture boreholes around a long wall coal panel this paper describes the application of computational modelling to the prediction of the stability of methane drainage boreholes during the extraction life of an active long wall coal panel within a united kingdom coal mine the modelling was undertaken to investigate the affects that changes in the roof geology and roadway support system may have on the deformation and closure of the gas drainage boreholes drilled from the tailgate across the goaf of an active long wall panel the paper also outlines the development of an analytical model to estimate the bending deformation axial strain and the rupture of borehole casing due to rock shear this model was used in conjunction with the geomechanical strata models to predict the distance behind the face line at which excessive borehole deformation and closure would occur this method was used to evaluate the optimum roadway support system and spacing between boreholes to maintain effective borehole drainage subject to the range of geological conditions encountered during the panel retreat a good correlation was obtained between the model predictions and the geomechanical and gas drainage data measured at a uk colliery

10be and ba concentrations in west african sediments trace productivity in the past particle reactive elements are scavenged to a higher degree at ocean margins than in the open ocean due to higher fluxes of biogenic and terrigenous particles in order to determine the influence of these processes on the depositional fluxes of10be and barium we have performed high resolution measurements on sediment core geob 1008 3 from the congo fan because the core is dominated by terrigenous matter supplied by the congo river it has a high average mass accumulation rate of 6 5 cm kyr biogenic10be and ba concentrations were calculated from total concentrations by subtracting the terrigenous components of10be and ba which are assumed to be proportional to the flux of al2o3 the meanba al weight ratio of the terrigenous component was determined to be 0 0045 the unusualy high terrigenous10be concentrations of 9 1 109 atoms g al2o3 are either due to input of particles with high10be content by the congo river or due to scavenging of oceanic10be by riverine particles the maxima of biogenic10be and ba concentrations coincide with maxima of the paleoproductivity rates time series analysis of the10be and of ba concentration profiles reveals a strong dominance of the precessional period of 24 kyr which also controls the rates of paleoproductivity in this core during the maxima of productivity the flux of biogenic ba is enhanced to a larger extent than that of biogenic10be applying a model for coastal scavenging we ascribe the observed higher sensitivity of ba to biogenic particle fluxes to the fact that the ocean residence time of ba is approximately 10 times longer than that of10be

middle eocene to early oligocene paleoceanography from agulhas ridge southern ocean ocean drilling program leg 177 site 1090 1 the agulhas ridge off the tip of africa between the atlantic and indian oceans is ideally located to capture the evolution of paleogene early neogene circulation patterns associated with global cooling multiproxy records of productivity biogenic barium baex opal caco3 mass accumulation rates mars nutrient and organic carbon burial reactive phosphorus pr mars and redox state of deep waters u enrichment from ocean drilling program odp site 1090 reflect hydrographic shifts in this region between the middle eocene and early oligocene 39 33 ma several peaks in increased export productivity and burial of organic matter occurred within the late eocene 36 5 34 and 33 7 ma which along with surface hydrologic conditions favoring opaline organisms over calcareous organisms could have aided in the draw down of pco2 to a threshold level that facilitated large ice sheet development on antarctica in the earliest oligocene our multiproxy approach illustrates the importance of vertical as well as spatial hydrographic reorganization in amplifying or driving climatic cooling of the middle eocene to early oligocene by facilitating increases in the relative or absolute burial of organic carbon

optimum and robust 3d facies interpolation strategies in a heterogeneous coal zone tertiary as pontes basin nw spain coal exploration and mining in extensively drilled and sampled coal zones can benefit from 3d statistical facies interpolation starting from closely spaced core descriptions and using interpolation methods a 3d optimum and robust facies distribution model was obtained for a thick heterogeneous coal zone deposited in the non marine as pontes basin oligocene early miocene nw spain several grid layering styles interpolation methods truncated inverse squared distance weighting truncated kriging truncated kriging with an areal trend indicator inverse squared distance weighting indicator kriging and indicator kriging with an areal trend and searching conditions were compared facies interpolation strategies were evaluated using visual comparison and cross validation moreover robustness of the resultant facies distribution with respect to variations in interpolation method input parameters was verified by taking into account several scenarios of uncertainty the resultant 3d facies reconstruction improves the understanding of the distribution and geometry of the coal facies furthermore since some coal quality properties e g calorific value or sulphur percentage display a good statistical correspondence with facies predicting the distribution of these properties using the reconstructed facies distribution as a template proved to be a powerful approach yielding more accurate and realistic reconstructions of these properties in the coal zone

high resolution record of export production in the eastern equatorial pacific across the eocene oligocene transition and relationships to global climatic records 1 understanding changes in export production through time provides insight into the response of the biological pump to global climate change particularly during periods of rapid climate change in this study we consider what role changes in export production may have had on carbon sequestration and how this may have contributed to the onset of the eocene oligocene transition eot in addition we consider if these export production variations are dominantly controlled by orbitally driven climate variability to accomplish these objectives we report changes in export production in the eastern equatorial pacific eep from site u1333 across the eot reconstructed from a high resolution record of marine barite accumulation rates bar bar fluctuations suggest synchronous declines in export production associated with the two step increases in oxygen isotopes that define the transition the reduction in productivity across the eot suggests that the biological pump did not contribute to carbon sequestration and the cooling over this transition we also report a previously undocumented peak in eep export productivity before the eot onset this peak is consistent with export production proxies from the southern ocean potentially implying a global driver for this precursor event we propose that this enhanced export production and the associated carbon sequestration in the late eocene may have contributed to the pco2 drawdown at the onset of antarctic glaciation

the ocean circulation in the southern hemisphere and its climatic impacts in the eocene abstract opening of southern ocean gateways may have had a controlling influence on the evolution of global climate the largest step in the history of cenozoic climate from an eocene greenhouse toward the modern glaciated state is correlated with opening of a deep water connection between the southern indian and southern pacific oceans this study synthesizes results from previous work assesses the possibility that ocean heat transport was much greater than modern during the globally warm eocene and explores the sensitivity of polar climate to large changes in ocean heat transport the magnitudes of these sensitivities are compared with those due to greenhouse gas concentration changes we find that ocean heat transport was unlikely to have been sufficiently greater than modern during the eocene to explain the change in the climate specifically in order to have significantly affected antarctic climate ocean heat transport changes would have had to change by an order of magnitude much greater than the largest change produced in our simulations in coupled climate model simulations changes in co2 concentrations from 1120 to 560 ppm supported by proxy records lead to significant antarctic responses in the absence of ocean heat transport changes the results show that antarctic snow accumulation is primarily controlled by changes in summer temperature not precipitation and that snow did not remain on antarctica during summer months in eocene even at low greenhouse gas concentrations greenhouse gas concentration changes and subsequent processes such as ice albedo and weathering feedbacks were more likely to have been the primary cause of antarctic glaciation than ocean heat transport changes

reservoir rock properties of coal measure strata of the lower monongahela group greene county southwestern pennsylvania from methane control and production perspectives abstract the methane emission rate into an underground mine environment from overburden strata during longwall mining is impacted by reservoir and geomechanical characteristics of the coal measure rocks in the overlying strata as well as the presence of any coal seam the reservoir characteristics and how they change during mining potentially affect the performance of gob gas ventholes which consequently impacts the efficiency of methane control in the mining environment this study presents reservoir and elastic properties of coal measure rocks in the lower monongahela group in greene county southwestern pennsylvania of the northern appalachian basin since the source of methane in this region from underground mining is located between the sewickley coal and the pittsburgh coal a specific emphasis was given to this interval core analyses were performed in the laboratory to determine rock porosity and permeability geophysical logging data gamma density sonic obtained from two exploration boreholes were used for evaluating formation boundaries shale contents log porosities and geomechanical properties of formations permeability was also calculated using density log data and empirical equations and compared with laboratory measurements and slug tests performed in isolated intervals of boreholes the results presented in this study can be used as data sources for reservoir studies related to the production and control of methane

using borehole geophysical data as soft information in indicator kriging for coal quality estimation abstract mineral resources estimation comprises basically two stages i data collection analysis and validation and ii the estimate of the grades and tonnes of the deposit the most often applied method for obtaining geological data during mineral exploration is rotary drilling with total core recovery high drilling costs make borehole geophysical logging attractive to obtain the maximum possible information from each borehole helping to understand ore intersections grades variability and extension of the deposit and its continuity in this paper borehole geophysical logging was used to enhance the sampling survey and to derive grades indirectly without lab analysis with a certain amount of uncertainty soft indicator kriging ik was selected to estimate coal quality by combining hard data from drill holes and soft data from geophysical logging correlation the method showed to be adequate to incorporate the uncertainty associated with the geophysical derived grade values the results were compared to the conventional procedures using grades determined via core analysis and ordinary kriging borehole geophysical logging proved to be essential to define the features of ore deposit and soft ik provided results with acceptable precision and accuracy if compared to the model provided by ordinary kriging and hard data

a direct link between the china loess and marine δ 18 o records aeolian flux to the north pacific most studies of quaternary climates conducted during the past 150 years have focused on glacial sequences and for the past 25 years marine sediments have provided significant further understanding of glacial and interglacial palaeoclimates an important goal of palaeoclimatology however to link the well known detailed continental records to marine records of similar resolution has yet to be realized the classic loess sequences of china provide an apparently continuous record of continental climate over the past 2 4 million years1 2 the oxygen isotope 18o timescale developed from the marine record3 gives us a global chrono stratigraphy of late pleistocene climates previously it has been suggested in studies of the aeolian component in pelagic sediments that it may be possible to link these two records directly by finding a suitable core from the north west pacific downwind from china4 5 here we report the results of such an effort for core v21 146 fig 1 and tie the last 500 000 years of the chinese loess soil sequence directly to the 18o timescale and in so doing refine the dating of regional loess and soil horizons

a geostatistical approach to predicting sulfur content in the pittsburgh coal bed abstract the us geological survey usgs is completing a national assessment of coal resources in the five top coal producing regions in the us point located data provide measurements on coal thickness and sulfur content the sample data and their geologic interpretation represent the most regionally complete and up to date assessment of what is known about top producing us coal beds the sample data are analyzed using a combination of geologic and geographic information system gis models to estimate tonnages and qualities of the coal beds traditionally gis practitioners use contouring to represent geographical patterns of similar data values the tonnage and grade of coal resources are then assessed by using the contour lines as references for interpolation an assessment taken to this point is only indicative of resource quantity and quality data users may benefit from a statistical approach that would allow them to better understand the uncertainty and limitations of the sample data to develop a quantitative approach geostatistics were applied to the data on coal sulfur content from samples taken in the pittsburgh coal bed located in the eastern us in the southwestern part of the state of pennsylvania and in adjoining areas in the states of ohio and west virginia geostatistical methods that account for regional and local trends were applied to blocks 2 7 mi 4 3 km on a side the data and geostatistics support conclusions concerning the average sulfur content and its degree of reliability at regional and economic block scale over the large contiguous part of the pittsburgh outcrop but not to a mine scale to validate the method a comparison was made with the sulfur contents in sample data taken from 53 coal mines located in the study area the comparison showed a high degree of similarity between the sulfur content in the mine samples and the sulfur content represented by the geostatistically derived contours

integration of vertical and in seam horizontal well production analyses with stochastic geostatistical algorithms to estimate pre mining methane drainage efficiency from coal seams blue creek seam alabama coal seam degasification and its efficiency are directly related to the safety of coal mining degasification activities in the black warrior basin started in the early 1980s by using vertical boreholes although the blue creek seam which is part of the mary lee coal group has been the main seam of interest for coal mining vertical wellbores have also been completed in the pratt mary lee and black creek coal groups of the upper pottsville formation to degasify multiple seams currently the blue creek seam is further degasified 2 3 years in advance of mining using in seam horizontal boreholes to ensure safe mining the studied location in this work is located between tuscaloosa and jefferson counties in alabama and was degasified using 81 vertical boreholes some of which are still active when the current long mine expanded its operation into this area in 2009 horizontal boreholes were also drilled in advance of mining for further degasification of only the blue creek seam to ensure a safe and a productive operation this paper presents an integrated study and a methodology to combine history matching results from vertical boreholes with production modeling of horizontal boreholes using geostatistical simulation to evaluate spatial effectiveness of in seam boreholes in reducing gas in place gip results in this study showed that in seam wells boreholes had an estimated effective drainage area of 2050 acres with cumulative production of 604 mmscf methane during 2 years of operation with horizontal borehole production gip in the blue creek seam decreased from an average of 1 52 mmscf to 1 23 mmscf per acre it was also shown that effective gas flow capacity which was independently modeled using vertical borehole data affected horizontal borehole production gip and effective gas flow capacity of coal seam gas were also used to predict remaining gas potential for the blue creek seam

coal exploration modelling using geostatistics in jharia coalfield india abstract jharia coalfield located in dhanbad district of the jharkhand state is one of the most important gondwana coalfields in india in terms of its prime coking quality of coal and its vast coal resources various agencies had carried out exploration in the jharia coalfield that led to generation of a huge exploration database however no exploration modelling had been carried out using geostatistics in this context the present paper has attempted to derive geostatistical models of coal seams using the exploration data of ten select coal seams with respect to various proximate coal constituents and seam thickness that were made available to the authors by bharat coaking coal limited dhanbad geostatistical structural modelling through semi variography resulted into quantification of spatial relationship of coal quality parameters together with seam thickness block wise quality estimation employing ordinary kriging technique provided improved estimates associated with error of estimation quantified by the magnitude of kriging variance the uncertainty maps generated using kriging variances are of aid in identifying areas of high uncertainty that decide on further sampling to improve the accuracy of estimation simulated annealing algorithm has been applied to carry out geostatistical imaging of a representative coal seam the technique provided a means to heterogeneity modelling of coal seams and its advantage over the kriged estimates smoothing effect is highlighted integration of these geostatistical model parameters with the geology of jharia coalfield aids in characterization of the coal depositional environment

a comparison between excess barium and barite as indicators of carbon export 1 since dymond et al 1992 proposed the paleoproductivity algorithm based on bio ba which relies on a strong correlation between ba and organic carbon fluxes in sediment traps this proxy has been applied in many paleoproductivity studies barite the main carrier of particulate barium in the water column and the phase associated with carbon export has also been suggested as a reliable paleoproductivity proxy in some locations we demonstrate that baexcess total barium minus the fraction associated with terrigenous material frequently overestimates babarite barium associated with the mineral barite most likely due to the inclusion of barium from phases other than barite and terrigenous silicates e g carbonate organic matter opal fe mn oxides and hydroxides a comparison between overlying oceanic carbon export and carbon export derived from baexcess shows that the dymond et al 1992 algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14 c and chlorophyll a measurements of primary production this relationship varies by ocean basin but with the application of the appropriate f ratio to 14 c and chlorophyll a primary production estimates the plot of babarite accumulation and carbon export for the equatorial pacific atlantic and southern ocean converges to a global relationship that can be used to reconstruct paleo carbon export index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 4825 oceanography biological and chemical geochemistry keywords paleoproductivity barite export production excess barium marine sediments citation eagle m a paytan k r arrigo g van dijken and r w murray a comparison between excess barium and barite as indicators of carbon export paleoceanography 18 1 1021 doi 10 1029 2002pa000793 2003

reservoir simulation based modeling for characterizing longwall methane emissions and gob gas venthole production abstract longwall mining alters the fluid flow related reservoir properties of the rocks overlying and underlying an extracted panel due to fracturing and relaxation of the strata these mining related disturbances create new pressure depletion zones and new flow paths for gas migration and may cause unexpected or uncontrolled migration of gas into the underground workplace one common technique to control methane emissions in longwall mines is to drill vertical gob gas ventholes into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment thus it is important to optimize the well parameters e g the borehole diameter and the length and position of the slotted casing interval relative to the fractured gas bearing zones this paper presents the development and results of a comprehensive dynamic three dimensional reservoir model of a typical multi panel pittsburgh coalbed longwall mine the alteration of permeability fields in and above the panels as a result of the mining induced disturbances has been estimated from mechanical modeling of the overlying rock mass model calibration was performed through history matching the gas production from gob gas ventholes in the study area results presented in this paper include a simulation of gas flow patterns from the gas bearing zones in the overlying strata to the mine environment as well as the influence of completion practices on optimizing gas production from gob gas ventholes

evolution of atlantic thermohaline circulation early oligocene onset of deep water production in the north atlantic the flow of deep water masses is a key component of heat transport in the modern climate system yet the role of deep ocean heat transport during periods of extreme warmth is poorly understood the present mode of meridional overturning circulation is characterized by deep water formation in both the north atlantic and the southern ocean however a different mode of meridional overturning circulation operated during the extreme greenhouse warmth of the early cenozoic during which time the southern ocean was the dominant region of deep water formation the combination of general global cooling and tectonic evolution of the atlantic basins over the past 55 m y ultimately led to the development of a mode of overturning circulation characterized by both southern ocean and north atlantic deep water sources the change in deep water circulation mode may in turn have affected global climate however unraveling the causes and consequences of this transition requires a better understanding of the timing of the transition new nd isotope data from the southeastern atlantic ocean indicate that the initial transition to a bipolar mode of deep water circulation occurred in the early oligocene ca 33 ma the likely cause of significant deep water production in the north atlantic was tectonic deepening of the sill separating the greenland norwegian sea from the north atlantic

analyses of geological and hydrodynamic controls on methane emissions experienced in a lower kittanning coal mine this paper presents a study assessing potential factors and migration paths of methane emissions experienced in a room and pillar mine in lower kittanning coal indiana county pennsylvania methane emissions were not excessive at idle mining areas but significant methane was measured during coal mining and loading although methane concentrations in the mine did not exceed 1 limit during operation due to the presence of adequate dilution airflow the source of methane and its migration into the mine was still a concern in the course of this study structural and depositional properties of the area were evaluated to assess complexity and sealing capacity of roof rocks composition gas content and permeability of lower kittanning coal results of flotation tests and geochemistry of groundwater obtained from observation boreholes were studied to understand the properties of coal and potential effects of old abandoned mines within the same area these data were combined with the data obtained from exploration boreholes such as depths elevations thicknesses ash content and heat value of coal univariate statistical and principal component analyses pca as well as geostatistical simulations and co simulations were performed on various spatial attributes to reveal interrelationships and to establish area wide distributions these studies helped in analyzing groundwater quality and determining gas in place gip of the lower kittanning seam furthermore groundwater level and head on the lower kittanning coal were modeled and flow gradients within the study area were examined modeling results were interpreted with the structural geology of the allegheny group of formations above the lower kittanning coal to understand the potential source of gas and its migration paths analyses suggested that the source of methane was likely the overlying seams such as the middle and upper kittanning coals and freeport seams of the allegheny group simulated ground water water elevations gradients of groundwater flow and the presence of recharge and discharge locations at very close proximity to the mine indicated that methane likely was carried with groundwater towards the mine entries existing fractures within the overlying strata and their orientation due to the geologic conditions of the area and activation of slickensides between shale and sandstones due to differential compaction during mining were interpreted as the potential flow paths

preservation of palaeoproterozoic early svecofennian structures in the orijarvi area sw finland evidence for polyphase strain partitioning abstract the predominantly migmatitic palaeoproterozoic uusimaa belt preserves early lower grade svecofennian structures in the orijarvi area in sw finland this study aims at explaining the deformational history responsible for its preservation and also at defining the age of the early svecofennian deformation detailed structural analysis reveals that the preservation was enabled by polyphase strain partitioning which initiated during the early svecofennian d2 deformation 1875 ma ago as revealed by ion microprobe u pb data on zircons from granodioritic and intermediate syn d2 intrusive dykes the d2 structures were low strain upright folds at high crustal levels and sub horizontal high strain folds at deeper crustal levels the sub horizontal d2 structures were refolded into upright folds during the subsequent late svecofennian d3 deformation whereas the upright d2 structures behaved as almost rigid blocks that caused strain partitioning into high strain zones along the block margins this accounts for the low cumulative strain in specific parts of the orijarvi area further strain partitioning during d4 caused reverse dip slip movements along regional scale shear zones crustal depth controlled the metamorphic grade during d2 when local migmatisation took place at deep crustal levels later metamorphic overprint during d3 deformation is evident from post d2 growth of sillimanite and a second generation of andalusite similarities in the structural patterns between the orijarvi area and the tampere vammala area 100 km to the north suggest that irrespective of the age of the later overprint subsequent deformation was localised along the margins of the early formed upright domains while the low grade rocks within the domains were preserved

investigation of longwall goaf gas flows and borehole drainage performance by cfd simulation abstract to reduce methane emissions into the workings of a longwall panel the mechanisms of gas emissions and migration within the longwall goaf must first be understood additionally high performance drainage boreholes must be designed many variables affect the goaf gas flow and borehole drainage efficiency namely the gas release characteristics of gas sources the heights of caved and fractured zones of the goaf the location of the drainage borehole and the position of the effective drainage section the portion of the perforated case and the uncased open hole this paper illustrates how these variables influence the goaf gas flow patterns and borehole performances through cfd simulations a permeability model and a gas release curve which reflect observations from experiments geomechanical modellings mine site monitoring and borehole drainage data were constructed for the mining disturbed strata and incorporated into the cfd model the cfd model was calibrated with the actual drainage data from the surface boreholes at a coal mine simulation results show that the gas drainage velocities around the perimeter of the panel goaf are higher than in the central goaf which is consistent with the overlying annular fracture zone model established from csiro previous research boreholes located within the annular area drew methane at a higher flow rate than those located in the central area leading to a significant reduction of methane emissions to the ventilation system goaf geometry with higher caved and fractured zones has lower pressure and methane concentration but higher gas flow velocity the location of the effective drainage section of the borehole has significant influence on drainage performance boreholes with the bottom end located in the lower region of the fractured zone 20 m above the roof can draw more methane than those located in the upper region of the fractured zone 70 m above the roof and those located in the caved zone 2 m above the roof

eocene oligocene ocean de acidification linked to antarctic glaciation by sea level fall one of the most dramatic perturbations to the earth system during the past 100 million years was the rapid onset of antarctic glaciation near the eocene oligocene boundary some 34 million years ago this climate transition was accompanied by a deepening of the calcite compensation depth the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution but the mechanism linking glaciation to the deepening of calcite compensation depth remains unclear merico et al use a global biogeochemical box model to test competing hypotheses put forward to explain the eocene oligocene transition they find that only shelf to deep sea carbonate partitioning can explain the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor this work sheds new light on the mechanisms linking glaciation and ocean acidity change during this important climate transition a global biogeochemical box model is used to test competing hypotheses put forward to explain the eocene oligocene transition it is found that only shelf to deep sea carbonate partitioning is capable of explaining the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor this work sheds new light on the mechanisms linking glaciation and ocean acidity change across the climate transition of the cenozoic one of the most dramatic perturbations to the earth system during the past 100 million years was the rapid onset of antarctic glaciation near the eocene oligocene epoch boundary1 2 3 34 million years ago this climate transition was accompanied3 by a deepening of the calcite compensation depth the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution changes in the global carbon cycle4 rather than changes in continental configuration5 have recently been proposed as the most likely root cause of antarctic glaciation but the mechanism linking glaciation to the deepening of calcite compensation depth remains unclear here we use a global biogeochemical box model to test competing hypotheses put forward to explain the eocene oligocene transition we find that of the candidate hypotheses only shelf to deep sea carbonate partitioning is capable of explaining the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor in our simulations glacioeustatic sea level fall associated with the growth of antarctic ice sheets permanently reduces global calcium carbonate accumulation on the continental shelves leading to an increase in pelagic burial via permanent deepening of the calcite compensation depth at the same time fresh limestones are exposed to erosion thus temporarily increasing global river inputs of dissolved carbonate and increasing seawater 13c our work sheds new light on the mechanisms linking glaciation and ocean acidity change across arguably the most important climate transition of the cenozoic era

identifying spatial heterogeneity of coal resource quality in a multilayer coal deposit by multivariate geostatistics this study presents a new geostatistical approach to characterization of the geometry and quality of a multilayer coal deposit using the data of seam thickness as a geometric property and the contents of ash sodium total sulphur and the heating value as quality properties a coal deposit in east kalimantan borneo indonesia which has a synclinal geological structure was chosen as the study site semivariogram analysis clarified the strong dependence of heating value on ash content in the top and bottom parts of each seam and the existence of a strong correlation with sodium content over the sub seams in the same location the correlations between the geometry and quality of the seams were generally weak a linear coregionalization model was used to derive the spatial correlation coefficients of two variables at each scale component from the single and cross semivariogram matrices because the data were correlated spatially in the same seam or over different seams multivariate techniques ordinary cokriging and factorial cokriging were mainly used and the resultant spatial estimates were compared to those derived using a univariate technique ordinary kriging a factorial cokriging was effective to decompose the spatial correlation structures with different scales another important characteristic was that the sodium content shows distinct segregation the low zones are concentrated near the boundary of the sedimentary basin while the high zones are concentrated in the central part the main component of sodium originates from the abundance of saline water therefore it can be inferred that seawater had stronger effects on the coal depositional process in the central basin than in the border part the geostatistical modeling results suggest that the thicknesses of all the major seams were controlled by the syncline structure while the coal qualities chiefly were originated from the coal depositional and diagenetic processes

deep water temperature carbonate ion and ice volume changes across the eocene oligocene climate transition 1 paired benthic foraminiferal stable isotope and mg ca data are used to estimate bottom water temperature bwt and ice volume changes associated with the eocene oligocene transition eot the largest global climate event of the past 50 myr we utilized odp sites 1090 and 1265 in the south atlantic to assess seawater 18o w antarctic ice volume and sea level changes across the eot 33 8 33 54 ma we also use benthic 13c data to reconstruct the sources of the deep water masses in this region during the eot our data together with previously published records indicate that a pulse of northern component water influenced the south atlantic immediately prior to and following the eot benthic 18o records show a 0 5 increase at 33 8 ma eot 1 that represents a 2 c cooling and a small 10 m eustatic fall that is followed by a 1 0 increase associated with oi 1 the expected cooling of deep waters at oi 1 33 54 ma is not apparent in our mg ca records we suggest the cooling is masked by coeval changes in the carbonate saturation state co32 which affect the mg ca data to account for this the bwt ice volume and w estimates are corrected for a change in the co32 of deep waters on the basis of recently published work corrected bwt at sites 1090 and 1265 show a 1 5 c cooling coincident with oi 1 and an average w increase of 0 75 the increase in ice volume during oi 1 resulted in a 70 m drop in global sea level and the development of an antarctic ice sheet that was near modern size or slightly larger

methodology for quantifying uncertainty in coal assessments with an application to a texas lignite deposit a common practice for characterizing uncertainty in coal resource assessments has been the itemization of tonnage at the mining unit level and the classification of such units according to distance to drilling holes distance criteria such as those used in u s geological survey circular 891 are still widely used for public disclosure a major deficiency of distance methods is that they do not provide a quantitative measure of uncertainty additionally relying on distance between data points alone does not take into consideration other factors known to have an influence on uncertainty such as spatial correlation type of probability distribution followed by the data geological discontinuities and boundary of the deposit several geostatistical methods have been combined to formulate a quantitative characterization for appraising uncertainty drill hole datasets ranging from widespread exploration drilling to detailed development drilling from a lignite deposit in texas were used to illustrate the modeling the results show that distance to the nearest drill hole is almost completely unrelated to uncertainty which confirms the inadequacy of characterizing uncertainty based solely on a simple classification of resources by distance classes the more complex statistical methods used in this study quantify uncertainty and show good agreement between confidence intervals in the uncertainty predictions and data from additional drilling

missing organic carbon in eocene marine sediments is metabolism the biological feedback that maintains end member climates 1 ocean chemistry is affected by pco2 in the atmosphere by increasing the dissolution of solid calcium carbonate and elevating the dissolved inorganic carbon concentrations in seawater positive feedbacks between the ocean and atmosphere can maintain high atmospheric pco2 and affect global climate we report evidence for changes in the oceanic carbon cycle from the first high quality organic carbon corg data set of eocene sediments beneath the equatorial pacific upwelling region leg 199 of the ocean drilling program eocene corg mass accumulation rates mars are 10 times lower than holocene rates even though expected corg mars estimated from biogenic barium mars an indicator of biological production equal or exceed modern fluxes what happened to the missing corg recent advances in ecology and biochemical kinetics show that the metabolism of nearly all animals marine and terrestrial is positively correlated by first principles to environmental temperatures the approximately 10 c abyssal temperature difference from eocene to holocene should have radically reduced pelagic corg burial as we observe we propose that higher basal metabolism and nutrient utilization recycling rates in the eocene water column and surface sediments precluded corg sediment burial in the pelagic ocean increased rates of metabolism nutrient utilization and lowered corg sedimentation caused by increased temperature may have acted as a biological feedback to maintain high atmospheric pco2 and hothouse climates conversely these same parameters would reverse sign to maintain low pco2 when temperatures decrease thereby maintaining icehouse conditions during cold climate regimes

reconciling longwall gob gas reservoirs and venthole production performances using multiple rate drawdown well test analysis abstract longwall mining is an underground mining method during which a mechanical shearer progressively mines a large block of coal called a panel in an extensive area during this operation the roof of the coal seam is supported only temporarily with hydraulic supports that protect the workers and the equipment on the coal face as the coal is extracted the supports automatically advance and the roof strata cave behind the supports caving results in fracturing and relaxation of the overlying strata which is called gob due its highly fractured nature gob contains many flow paths for gas migration thus if the overlying strata contain gassy sandstones or sandstone channels gas shales or thinner coal seams which are not suitable for mining then the mining induced changes can cause unexpected or uncontrolled gas migration into the underground workplace vertical gob gas ventholes ggv are drilled into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment thus it is important first to understand the properties of the gas reservoir created by mining disturbances and second to optimize the well parameters and placement accordingly in this paper the production rate pressure behaviors of six ggvs drilled over three adjacent panels were analyzed by using conventional multi rate drawdown analysis techniques the analyses were performed for infinite acting and pseudo steady state flow models which may be applicable during panel mining dm and after mining am production periods of ggvs these phases were analyzed separately since the reservoir properties due to dynamic subsidence boundary conditions and gas capacity of the gob reservoir may change between these two stages the results suggest that conventional well test analysis techniques can be applicable to highly complex gob reservoirs and ggvs to determine parameters such as skin permeability radius of investigation flow efficiency and damage ratio the insights obtained from well test analyses can be used for a better understanding of the gob and for designing more effective gob gas venthole systems

paleoproductivity nutrient burial climate change and the carbon cycle in the western equatorial atlantic across the eocene oligocene boundary paleoproductivity nutrient burial and carbon cycling were investigated across the eocene oligocene e o boundary begin to end 36 9 32 7 ma at 40 kyr resolution timescale of shackleton et al 1999 at ocean drilling program site 925 on the ceara rise in the western equatorial atlantic 3040 m present water depth 748 26 850 70 mbsf downcore bulk sediment records of biogenic barium total reactive phosphorus biogenic silica and calcium carbonate are interpreted to represent export production net nutrient burial biogenic opal production and inorganic carbon burial respectively the global positive excursion in 13c subsequent to the e o boundary is recorded at site 925 export production appears to have been externally forced by orbital parameters at eccentricity frequencies during the study interval based on spectral analysis of the biogenic barium and reactive phosphorus records biogenic silica production or preservation increased after the eocene oligocene boundary to a higher baseline although overall productivity and nutrient burial did not increase based on barium and reactive phosphorus records thus although absolute production did not increase at this site a shift in relative abundance of siliceous versus carbonate productivity may have resulted in a change in relative organic carbon burial this may have contributed to the positive excursion in global oceanic 13c subsequent to the eocene oligocene boundary although the silica maximum persists after the carbon isotope excursion ends

eocene oligocene transition in the southern ocean history of water mass circulation and biological productivity high resolution records of carbon and oxygen isotopes and benthic foraminiferal accumulation rates for the eocene oligocene section at ocean drilling program site 689 maud rise weddell sea paleodepth about 1500 m were used to infer variations in paleoproductivity in relation to changes in climate and ventilation of the deeper water column the benthic foraminiferal abundance and isotope records show short term fluctuations at periodicities of 100 and 400 ka implying orbitally driven climatic variations both records suggest that intermediate depth water chemistry and primary productivity changed in response to climate during the eocene productivity increased during cold periods and during cold to warm transitions possibly as a result of increased upwelling of nutrient rich waters in the oligocene in contrast productivity maxima occurred during intervals of low d18o values presumably warmer periods when a proto polar front moved to the south of the location of site 689 this profound transition in climate productivity patterns occurred around 37 ma coeval with rapid changes toward increasing variability of the oxygen and carbon isotope and benthic abundance records and toward larger amplitude d18o fluctuations therefore we infer that at this time temperature fluctuations increased and a proto polar front formed in conjunction with the first distinct pulsations in size of the antarctic ice sheet we speculate that this major change might have resulted from an initial opening of the drake passage at 37 ma at least for surface and intermediate water circulation

coalbed methane resource potential and current prospects in pennsylvania abstract coalbed methane gas content analyses from exploratory coal cores and existing data indicate that gas content generally increases with increasing depth and rank the coal beds studied are from the main bituminous field of pennsylvania which currently contains 24 coalbed methane pools and the northern and southern anthracite coal fields they range from the middle pennsylvanian allegheny group to the late pennsylvanian early permian dunkard group previous us bureau of mines studies revealed gas contents from 0 4 to 13 8 cm 3 g at depths of 99 to 432 m for the bituminous coal beds of the allegheny group more recent core data from the allegheny group yielded gas contents from 2 2 to 8 9 cm 3 g at depths from 167 to 387 m in the anthracite region of eastern pennsylvania the little data that are available show that gas content is anomalously high or low gas yields from test holes in eastern pennsylvania are low with or without artificial stimulation mainly due to the lack of a good cleat system overall estimates of coalbed methane resources indicate there may be 1 7 tm 3 61 tcf of gas in place contained in the northern appalachian coal basin the amount of technically recoverable coalbed methane resources is projected by the us geological survey national oil and gas resource assessment team us geological survey national oil and gas resource assessment team 1996 1995 national assessment of united states oil and gas resources results methodology and supporting data us geological survey digital data series dds 30 cd rom denver co 80 pp and lyons lyons p c 1997 central northern appalachian coalbed methane flow grows oil and gas journal 95 27 76 79 at 0 3 tm 3 11 48 tcf this includes portions of pennsylvania ohio west virginia and a small part of maryland consequently a mapping investigation was conducted to evaluate the regional geology of the bituminous coal bearing intervals in southwestern pennsylvania and its influence on coalbed methane potential phase i of this study involved the entire pennsylvanian coal bearing interval of southwestern pennsylvania phase ii focused on a stratigraphic delineation and evaluation of allegheny group coal beds and associated sandstones several prospective coal beds and associated facies relationships with channel fill sandstones were determined possible non coal scenarios for coalbed methane include erosional contacts between coal beds and overlying channel fill sandstones and areas of stacked channel fill sandstones repetitive sequences of coal accumulation are stacked commonly with shale interburden and are also potential coalbed methane targets additional pennsylvania geological survey drilling coalbed methane sampling occurred in armstrong beaver cambria greene lawrence somerset and washington counties raw coalbed methane desorption data tables graphical displays of gas contents versus depth thickness and time and average composition and heating values from coal beds of the allegheny group to the dunkard group are available at the pennsylvania geological survey further information on cross sections isopleth maps isopach maps raw drillhole data and ownership issues can also be obtained from the same source

timing and climatic consequences of the opening of drake passage age estimates for the opening of drake passage range from 49 to 17 million years ago ma complicating interpretations of the relationship between ocean circulation and global cooling secular variations of neodymium isotope ratios at agulhas ridge southern ocean atlantic sector suggest an influx of shallow pacific seawater approximately 41 ma the timing of this connection and the subsequent deepening of the passage coincide with increased biological productivity and abrupt climate reversals circulation productivity linkages are proposed as a mechanism for declining atmospheric carbon dioxide these results also indicate that drake passage opened before the tasmanian gateway implying the late eocene establishment of a complete circum antarctic pathway

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

a comparison of multiple proxies for export production in the equatorial pacific 1 several commonly used paleoproductivity proxies were compared to evaluate the validity of assumptions and limitations associated with each proxy export production fluxes cexport over glacial interglacial timescales were calculated from previously developed proxy specific algorithms at ttn013 pc72 and ttn013 pc114 both located in the equatorial pacific comparison of data from the same core intervals yields conflicting results despite calibrations based on the same core top samples the periodicity of marine barite excess ba and excess al based cexport records is similar the relative magnitude of cexport when calculated using excess ba and algorithms based on sediment trap data is significantly different than records based on core top calibrations particularly during glacial intervals at both sites bulk sedimentary al ti and ba ti ratios covary however these ratios do not correspond with the downcore records of their respective excess concentrations and their accumulation rates or with contemporaneous records based on marine barite excess ba and excess al accumulation although downcore records based on sediment mass accumulation rates may be compromised by sediment focusing this process cannot explain all the differences observed among the various data sets presented here this implies that some or all of these proxies do not exclusively respond to changes in export production the contradictions among these data highlight the importance of addressing inconsistencies among paleoproxies and re examining assumptions imbedded in proxy fundamentals prior to applying paleoproductivity proxies and interpreting paleoceanographic records

orbitally induced climate and geochemical variability across the oligocene miocene boundary to assess the influence of orbital scale variations on late oligocene to early miocene climate and ocean chemistry high resolution 5 kyr benthic foraminiferal carbon and oxygen isotope and percent coarse fraction time series were constructed for ocean drilling program site 929 on ceara rise in the western equatorial atlantic these time series exhibit pervasive low to high frequency variability across a 5 myr interval 20 5 25 4 ma the records also reveal several large scale secular variations including two positive 1 6 oxygen isotope excursions at 22 95 and 21 1 ma suggestive of large but brief glacial maxima mi 1 and mi 1a events of miller et al 1991 and a long term cyclical increase in the carbon isotopic composition of seawater shift of 1 52 that reaches a maximum coincident with peak 18o values at 22 95 ma lower resolution 25 kyr records constructed from benthic and planktonic foraminifera as well as bulk carbonate at a shallower site on ceara rise site 926 for the period 21 7 24 9 ma covary with site 929 18o values reflecting changes in antarctic ice volume likewise covariance among carbon isotopic records of bulk sediment benthic and planktonic foraminifera suggest that the low frequency cycles 400 kyr and long term increase in 13c values represent changes in the mean carbon composition of seawater co2 the time series presented here constitute the longest most continuous and highest resolution records of pre pliocene climate and oceanography to date the site 929 carbon and oxygen isotope power spectra show significant concentrations of variance at 400 100 and 41 kyr demonstrating that orbitally induced oscillations have been a normal characteristic of the global climate system since at least the oligocene including periods of equable climate and times with no apparent northern component water production

impact of geological modeling processes on spatial coalbed methane resource estimation spatial coalbed methane cbm resource estimation is based on spatial distributions of coal coal adsorbed gas content and coal density however the spatial distribution of gas content can be generated via two different geological modeling processes 1 the gas content distribution is generated by geological modeling based on the interpreted gas content at boreholes 2 distributions of gas content related logs or coal properties are generated firstly then the gas content distribution is calculated based on the spatial distributions of logs or coal properties by the relationship between the gas content and logs or coal properties this paper presents a study to compare the impact of these two processes on cbm resource estimation for coal seam no 3 cs 3 in southeast qinshui basin china well logs from 22 wells laboratory data from five wells and well tops from 131 wells for cs 3 are used in log interpretation and geological modeling the simple kriging sk is used to build the structural model and the coal distribution weighted and unweighted omni directional variograms for structural residual and coal thickness are calculated using an in house program logs of gamma ray gr and density den or rhob are distributed in 3d by using sequential gaussian simulation sgs with sk algorithm artificial neural network ann is used to build the relationship of the measured raw gas content rgc gas content in raw coal basis with the logs of gr den and measured depth md then the rgc is distributed in 3d by the two geological modeling processes cbm resources are calculated in 3d based on the cells volume coal density and rgc results show that rgc increases with an increase in burial depth total cbm resources for the study area calculated by these two processes are similar for cs 3 but the distribution probability of high gas content is highly different which is important for locating wells