oceanographic and eustatic control of carbonate platform evolution and sequence stratigraphy on the cretaceous valanginian campanian passive margin northern gulf of mexico an integrated sequence stratigraphic study based on outcrop core and wireline log data documents the combined impact of cretaceous eustacy and oceanic anoxic events on carbonate shelf morphology and facies distributions in the northern gulf of mexico the diverse facies and abundant data of the comanche platform serve as a nearly complete global reference section and provide a sensitive record of external processes affecting cretaceous platform development regional cross sections across the shoreline to shelf margin profile provide a detailed record of mixed carbonate siliciclastic strata for the hauterivian to lower campanian stages ca 136 to 80 ma the study window on the slowly subsiding passive margin allows the stratigraphic response to external forcing mechanisms to be isolated from regional structural processes three second order supersequences comprised of eight composite sequences are recognized in the valanginian barremian the aptian albian and the cenomanian campanian the valanginian barremian supersequence transitioned from a siliciclastic ramp to carbonate rimmed shelf and is a product of glacial ice accumulation and melting as well as variable rates of mid ocean ridge volcanism the aptian albian supersequence chronicles the drowning and recovery of the platform surrounding oceanic anoxic events 1a and 1b the cenomanian campanian supersequence similarly documents shelf drowning following oceanic anoxic event 1d after which the platform evolved to a deep subtidal system consisting of anoxic dysoxic shale and chalk in the time surrounding oceanic anoxic event 2 each period of oceanic anoxia is associated with composite sequence maximum flooding termination of carbonate shelf sedimentation and deposition of condensed shale units in distally steepened ramp profiles composite sequences unaffected by oceanic anoxic events consist of aggradational to progradational shelves with an abundance of grain dominated facies and shallow subtidal to intertidal environments because they are products of eustacy and global oceanographic processes the three supersequences and most composite sequences defined in the south texas passive margin are recognizable in other carbonate platforms and published eustatic sea level curves

depositional controls on sediment body architecture in the eagle ford boquillas system insights from outcrops in west texas united states a detailed sedimentological study of the middle eagle ford boquillas outcrop analog of subsurface producing strata units was conducted on numerous roads cut along us highway 90 in val verde county and on outcrops in big bend national park brewster county texas using field based petrographical and high resolution image capture methods light detection and ranging and gigapans this study demonstrates that vertical and lateral facies distribution is controlled by the interaction of sediment productivity under the influence of bottom currents below storm wave base vertical cyclicity is the result of alternating periods of lower primary productivity and relatively low sediment accumulation rates globigerinid argillaceous wackestones and shorter periods of high primary productivity and higher accumulation rates pelagic grainstones driven by the absence or presence of iron from volcanic ash deposition lateral variations are controlled by the deposition and reworking of pelagic sediment under the influence of below storm wave base bottom currents pelagic grainstones accumulated in the form of isolated barchanoid hydraulic dunes sand ridges coalesced sand ridges and sand sheets and less commonly as continuous beds detailed measurements show that pelagic grainstones have no more than 50 continuity and ash beds have 72 continuity application of sequence stratigraphic principles needs to be done with caution because the deeper water depositional setting is affected not by sediment input from a shallow water benthic carbonate factory but by pelagic sediment from the open marine environment subject to bottom current reworking packages of strata may be more reliable for longer distance correlations

mantle convection with longest wavelength thermal heterogeneity in a 3 d spherical model degree one or two 1 the formation of longest wavelength mantle convection in the sluggish lid regime is investigated using a three dimensional spherical model the bottom rayleigh number is fixed at 107 considering temperature dependent rheology degree one dominant thermal convection occurs for both purely basal heating and mixed i e basal and internal heating modes for the purely basal heating mode degree one convection occurs when the viscosity contrast due to temperature dependent rheology is 103 104 in both boussinesq and extended boussinesq fluids however with extended boussinesq fluid degree one convection may only occur in the basal heating mode in the mixed heating mode degree one convection shifts to one with high degree modes presumably because of enhanced viscous dissipation in the highly viscous lid over up downwelling plumes the geophysically relevant degree two convection with sheet like downwellings is not observed in this study the inclusion of visco plastic rheology in the top part of the mantle breaks down degree one convection

geomorphic indices and longitudinal profile of the daba shan northeastern sichuan basin evidence for the late cenozoic eastward growth of the tibetan plateau abstract the daba shan orocline is located in the northeastern sichuan basin and has undergone foreland propagation and distinct surface uplift owing to the eastward expansion of the tibetan plateau since the late cenozoic in order to describe and quantify the earth surface processes respond to deep geological mechanisms and to detect the kind of tectonic deformation in the daba shan area during the late cenozoic various geomorphic indices were analyzed for study area the obtained results are 1 the northeast of the hanzhong basin the hannan micang massifs along the chengkou fangxian fault and the shennongjia massif exhibit intense tectonic activity 2 the spatial patterns of the channel steepness indices indicate that the western segment of the northern daba shan fenghuang shan and paotaizi region have higher uplift rates than the eastern 3 the longitudinal profile analysis revealed that the landscape evolution of the shennongjia massif is in a transient state with an uplift amplitude of 1700 1900 m since the end of the paleogene 25 ma and an average uplift rate of 0 072 0 004 mm a the paleochannel reconstruction indicate an incision of 900 1000 m since the late neogene 3 0 3 4 ma with the average uplift rate being 0 3 0 03 mm a 4 three tectonic deformation zones can be distinguished in the daba shan from west to east the shortening deformation strike slip deformation and vertical uplift zones these observations suggest that the eastward growth of the tibetan plateau has affected the daba shan area and shaped the modern landscape

slab pull mantle convection and pangaean assembly and dispersal two global scale mantle convection cells presently exist on earth centred on upwelling zones in the south pacific ocean and northeast africa one cell panthalassan contains only oceanic plates the other pangaean contains all the continental plates they have remained fixed relative to one another for 400 ma a transverse rheic tethyian subduction system splits the pangaean cell poloidal plate motion in the oceanic cell reflects circumferential pull of panthalassan slabs but toroidal flow in the pangaean cell reflected by vortex type motion of continents toward the altaids of central east asia throughout the phanerozoic has resulted from the competing slab pull forces of both cells the combined slab pull effects from both cells also controlled pangaean assembly and dispersal assembly occurred during palaeozoic clockwise toroidal motion in the pangaean cell when gondwana was pulled into pangaea by the ne trending rheic subduction zone forming the appalachian variscide altaid chain pangaean dispersal occurred when the rheic trench re aligned in the jurassic to form the nw trending tethyside subduction system which pulled east gondwanan fragments in the opposite direction to form the cimmerian himalayan alpine chain this re alignment also generated a new set of indian mid ocean ridge systems which dissected east gondwana and facilitated breakup 100 200 myr long phanerozoic wilson cycles reflect rifting and northerly migration of gondwanan fragments across the pangaean cell into the rheic tethyian trench pangaean dispersal was amplified by retreat of the panthalassan slab away from europe and africa which generated mantle counterflow currents capable of pulling the americas westward to create the atlantic ocean thermal blanketing beneath pangaea and related hotspot activity were part of a complex feedback mechanism that established the breakup pattern but slab retreat is considered to have been the main driving force the size and longevity of the two cells organised and maintained by long lived slab pull forces favours deep mantle convection as the dominant circulation process during the phanerozoic

decoupling of the carbon cycle during ocean anoxic event 2 the cenomanian to turonian boundary transition ca 95 93 ma represents one of the most profound global perturbations in the carbon cycle of the past 140 m y this interval is characterized by widespread deposition of organic rich fine grained sediment marked by a globally recognized positive carbon isotope excursion cie reflecting the widespread removal of 12 c enriched organic matter in marine sediments under global anoxic greenhouse conditions however the exact timing and trigger of this inferred global phenomenon termed oceanic anoxic event 2 oae 2 is still debated with recent studies showing diachroneity between the deposition of the organic rich sediment and the cie and conflicting interpretations on detailed redox analyses in several of these inferred anoxic settings here we present the first evidence for widespread and persistent oxygenation during oae 2 based primarily on the distribution of redox sensitive trace metals and biota preserved in sedimentary rocks from the western interior seaway of north america our data indicate anoxic euxinic conditions in the mid to late cenomanian but improved bottom water oxygenation prior to and during the cie trace metal enrichments support large volumes of mafic volcanism possibly from the high arctic large igneous province halip which occur within the middle of the cie indicating that the emplacement of lips was not the primary trigger of the cenomanian turonian cie the apparent paradox of an oxygenated phase within oae 2 suggests a much more complex carbon cycle during these global perturbations than previously thought these findings have important implications for greenhouse carbon cycle changes over time scales of 0 1 10 m y

coccolith sr ca as a new indicator of coccolithophorid calcification and growth rate 1 polyspecific coccolith separates from core top sediments in the eastern equatorial pacific show variations of 15 in sr ca ratios across the equatorial upwelling zone with sr ca highest at the equator and decreasing off axis these variations cannot be due to changes in the sr ca of seawater which varies by less than 2 in the surface ocean variations in sr ca of coccolith sediments are similar to variations in primary productivity and alkenone estimated coccolithophorid growth rates in overlying surface waters and to caco3 rain rates measured in sediment traps because of these relationships and because calcification rate exerts a strong control on sr ca in abiogenic calcites we suggest that the observed sr ca variations in coccoliths may be strongly controlled by coccolithophorid growth and calcification rates although temperature may also influence coccolith sr ca to a lesser degree changes in dissolution intensity and coccolith assemblages appear to exert a minor influence if any on coccolith sr ca in these sediment core tops if further work confirms relationships between coccolith sr ca and coccolithophorid productivity sr ca records of past changes in coccolithophorid productivity may be useful in reconstructing past variations in the rain ratio of organic to carbonate carbon an important control on deep ocean ph and partitioning of co2 between the atmosphere and ocean in addition coccolith sr ca might provide an independent record of past changes in coccolithophorid growth rates which in combination with data on the carbon isotopic fractionation in coccolithophorid organic matter may permit more reliable calculations of past dissolved co2 in the surface ocean

hyperspectral mapping of mineral assemblages associated with gold mineralization in the central pilbara western australia the indee district located in the central pilbara tectonic zone of the north pilbara terrain in western australia contains archean lode gold deposits and epithermal gold systems hydrothermal alteration assemblages associated with these deposits contain the minerals pyrophyllite white mica chlorite and tourmaline known prospects are surrounded by flat areas of poorly exposed calcretized bedrock calcretes rock float and sandy soils two adjacent lines of airborne hyperspectral data hymap were acquired to produce mineral abundance maps these data were processed to correct for atmospheric and illumination conditions and then calibrated to reflectance data using field spectra this analysis successfully mapped the distribution of pyrophyllite white mica mg chlorite fe chlorite calcite dolomite kaolinite tourmaline hematite and goethite alteration assemblages associated with the camel 2 deposit which is located along the mallina shear zone were found to be characterized by pyrophyllite and al rich white mica the latter having an aloh absorption feature at 2 194 m in contrast alteration assemblages associated with epithermal deposits south of the mallina shear zone are characterized by al poor white mica with a longer wavelength absorption feature at 2 210 m the shift reflecting the change in al chemistry tschermak substitution tourmaline is also present near the epithermal like deposits suggesting that it may be an integral part of these systems fe chlorite is associated with both the mesothermal and epithermal systems but is also pervasive as a regional metamorphic mineral regolith related carbonates are common throughout the area and their compositions are determined by the hyperspectral processing mineral abundance images were verified by pima portable infrared mineral analyser analysis of ground samples and assays of rocks in previously unknown areas of pyrophyllite and white mica confirmed the presence of anomalous gold these results show that mineral maps and compositional information derived from hyperspectral analysis are extremely valuable for exploration even in poorly exposed regolith dominated districts such as indee

the cenomanian turonian eagle ford group of south texas insights on timing and paleoceanographic conditions from geochemistry and micropaleontologic analyses abstract the interbedded organic rich marls and limestones of the eagle ford group of south texas were deposited on the shelf of the central texas platform during the upper cenomanian through the turonian micropaleontological analyses of thin sections and residue samples from subsurface cores taken in atascosa and karnes counties yielded 13 biostratigraphic datums which were integrated with calcareous nannofossil datums stable carbon isotopic and bulk inorganic geochemical analysis to gain an understanding of the paleoceanographic conditions of the study area and their relationship to regional and global events the paired thin section residue sampling was necessitated by poor recovery of planktonic foraminifera in washed samples which were however abundant in most thin sections lower eagle ford marls were deposited under euxinic conditions produced by a stratified water column periodic enhanced water column mixing increased oxygen levels and surface water primary productivity which promoted calcite diagenesis and generation of limestones containing calcispheres and radiolaria an oxygenated bottom water mass entered the basin in the uppermost cenomanian prior to the onset of oceanic anoxic event oae 2 causing a spike in benthic foraminiferal diversity and decreasing preservation of organic matter although the lower portion of the upper eagle ford is age equivalent to oae2 as indicated by positive shift in 13corg it contains less organic matter and evidence of more oxygen than the lower eagle ford so deposition of the eagle ford black shales is not contemporaneous to oae2

origin of limestone marlstone cycles astronomic forcing of organic rich sedimentary rocks from the cenomanian to early coniacian of the cretaceous western interior seaway usa abstract we present an integrated multidisciplinary study of limestone marlstone couplets from a continuously cored section including parts of the upper buda limestone the entire eagle ford group boquillas formation and lower austin chalk from the shell iona 1 research borehole texas usa which provides a 8 million year myr distal clastic sediment starved intrashelf basin record of the early cenomanian to the earliest coniacian stages results show that despite variable yet minimal diagenetic overprints several unambiguous primary environmental signals are preserved and support greater water mass ventilation and current activity promoting increased silica carbonate productivity during the deposition of limestone beds compared to deposition of marlstone beds which reflect greater organic matter productivity and preservation furthermore our astronomical analyses demonstrate that the limestone marlstone couplets in the iona 1 core reflect climatic forcing driven by solar insolation resulting from integrated milankovitch periodicities in particular we propose that obliquity and precession forcing on the latitudinal distribution of solar insolation may have been responsible for the observed lithological and environmental variations through the cenomanian turonian and coniacian in this mid latitude epicontinental sea setting our data also suggests that rhythmic lithological alternations deposited in greenhouse periods in general may simply reflect climate driven cycles related to earth sun dynamics without the need to invoke significant sea level variations

low degree mantle convection with strongly temperature and depth dependent viscosity in a three dimensional spherical shell 1 a series of numerical simulations of thermal convection of boussinesq fluid with infinite prandtl number with rayleigh number 10 7 and with the strongly temperature and depth dependent viscosity in a three dimensional spherical shell is carried out to study the mantle convection of single plate terrestrial planets like venus or mars without an earth like plate tectonics the strongly temperature dependent viscosity the viscosity contrast across the shell is 10 5 makes the convection under stagnant lid short wavelength structures numerous cylindrical upwelling plumes are developed because of the secondary downwelling plumes arising from the bottom of lid this convection pattern is inconsistent with that inferred from the geodesic observation of the venus or mars additional effect of the stratified viscosity at the upper lower mantle the viscosity contrast is varied from 30 to 300 are investigated it is found that the combination of the strongly temperature and depth dependent viscosity causes long wavelength structures of convection in which the spherical harmonic degree l is dominant at 1 4 the geoid anomaly calculated by the simulated convections shows a long wavelength structure which is compared with observations the degree one l 1 convection like the martian mantle is realized in the wide range of viscosity contrast from 30 to 100 when the viscosity is continuously increased with depth at the lower mantle

short wavelength infrared swir spectral analysis of hydrothermal alteration zones associated with base metal sulfide deposits at rosebery and western tharsis tasmania and highway reward queensland spectral analysis of rock samples by short wavelength infrared swir analysis using the portable infrared mineral analyzer pima spectrometer is a relatively new field method with applications in mineral exploration the technique allows rapid field based identification of hydrothermal alteration minerals and delineation of alteration zones variations in mineral composition crystallinity and relative abundance may also be determined phyllosilicates including white mica and chlorite are particularly amenable to short wavelength infrared analysis these are prominent alteration minerals in the felsic volcanic rocks in the mount read volcanics tasmania and the mount windsor subprovince north queensland they have regional distributions as diagenetic and metamorphic products and exist locally in alteration zones associated with volcanic hosted sulfide deposits a geochemical and spectral investigation of white micas in the least altered rocks in the mount read volcanics has shown considerable background compositional variations the white micas range from phengite to moderately sodic muscovite and swir spectral measurements provide reliable estimates of their compositions chlorites also have a broad compositional range in these rocks however swir spectral analysis has proven to be unreliable in determining chlorite composition in samples where chlorite exists in low proportions relative to white mica or in mixed assemblages with epidote white micas in footwall alteration zones of the rosebery stratiform zn pb deposit tasmania are variably phengitic similar to those in regional background volcanics a unit of relatively unaltered volcaniclastic sandstone in the rosebery hanging wall sequence contains anomalous sodic muscovite in proximity to ore lenses white micas associated with the disseminated to massive pyritic cu au deposits at western tharsis tasmania and highway reward north queensland range in composition from phengite to slightly sodic muscovite in these symmetrically zoned alteration systems white micas grade in composition from phengite in peripheral zones to slightly sodic muscovite in proximal zones near ore in all three cases the white mica compositional variation is a vector to ore that is effectively measured by swir spectrometry with particular application in prospect scale exploration chlorite compositions at rosebery are not strictly spatially related to ore but tend to be most magnesian in zones of high chlorite abundance in the outer alteration zone at western tharsis there is a faint proximal trend to iron rich chlorites however it does not represent a well defined vector to ore in either case attempts at quantitative estimation of the relative abundance of white mica and chlorite in mixed samples by spectral analysis have produced results that are imprecise in comparison to geochemically derived estimates the data scatter relates to the low proportions of chlorite in the majority of the samples analyzed resulting in weak chlorite absorptions better results may be obtainable in specific alteration or lithostratigraphic domains by use of customized spectral unmixing software this investigation has shown that pima based swir spectrometry is a potent field method of mapping compositional variations in white micas that represent empirical vectors to at least some types of volcanic hosted sulfide deposits it has also highlighted its effectiveness in field identification of megascopically difficult or indeterminate alteration minerals such as pyrophyllite zunyite and topaz which may have genetic implications and exploration significance

high resolution stratigraphy and facies architecture of the upper cretaceous cenomanian turonian eagle ford group central texas rock based studies of the eagle ford group of central texas demonstrate that mudrock deposition is more complicated than previously supposed x ray diffraction x ray fluorescence total organic carbon toc and log data collected from eight cores and two outcrops demonstrate that bottom current reworking and planktonic productivity are primary depositional controls acting independently from eustatic forcing central texas eagle ford facies include 1 massive argillaceous mudrock 2 massive foraminiferal calcareous mudrock 3 laminated calcareous foraminiferal lime mudstone 4 laminated foraminiferal wackestone 5 cross laminated foraminiferal packstone grainstone 6 massive bentonitic claystone and 7 nodular foraminiferal packstone grainstone high degrees of lateral facies variability characterized by pinching and swelling of units lateral facies changes truncations and locally restricted units are observed even at small lateral scales 50 ft 15 m at 10 mi 16 km and greater lateral spacings core and geochemical data significantly underestimate intraformational facies variability approximately 73 of units can be successfully correlated across a distance of 500 ft 152 m 35 are traceable across 1 mi 1 6 km and only 16 of beds are correlative across 10 mi 16 km geochemical proxies enrichment in molybdenum and other trace elements indicate that maximum anoxia occurred within the bouldin member despite being composed of the most calcareous and high energy facies comparison of total gamma ray gr logs to computed gr logs is requisite because gr alone may provide misleading determination of facies toc content depositional environment and sequence stratigraphic implications

core mantle boundary topography estimated from numerical simulations of instantaneous mantle flow core mantle boundary cmb topography is estimated from numerical simulations of instantaneous mantle flow in a three dimensional spherical shell geometry density anomaly models of the earth s mantle are derived from geodynamic models constrained principally by seismic tomography results to account for the small 1 5 km cmb topographic relief inferred from recent seismological results lateral viscosity variations in the mantle compositionally dense piles in the deep mantle and a low viscosity d layer are all required for the numerical models low viscosity subducting slabs in the lower mantle serve to reduce the topographic amplitude below high velocity regions i e the circum pacific belt the existence of dense piles may cause the local topographic depressions even below low velocity regions i e the south pacific and atlantic africa regions

high resolution hyperspectral based continuous mineralogical and total organic carbon analysis of the eagle ford group and associated formations in south texas hyperspectral sensing is used to generate mineral maps of a fine grained vertical eagle ford group cored section and underlying buda limestone and del rio formation in south texas this technology produces a map that shows the distribution of minerals on the core surface three different cameras within the hyperspectral core imaging system were used to image a 99 1 m 325 ft core a 1 line scan camera which produces a high resolution red green blue 120 m natural color photograph of the dry core from the visible light spectrum 2 short wave infrared swir spectrometer 300 500 m resolution and 3 long wave infrared lwir spectrometer 300 500 m resolution in 2016 the introduction of a new high resolution lwir spectrometer made it possible to identify minerals in cores that were not detected by previous swir systems high resolution hyperspectral imaging technology using both the swir and lwir spectra provides a significant step toward quantifying mineralogy and total organic carbon hyperspectral imaging is a powerful tool for studying textural and fabric relationships because it detects and highlights the major mineralogical changes that occur between depositional beds and among depositional features calcite compositional variations and cyclicity appear to be closely related the sr rich calcite appears to indicate a smaller allochem size dominance as well as the slower sedimentation rates that are required for nannofossils to settle from suspension finally the observed diagnostic cyclicity of the lower eagle ford can be related to coccolithophore productivity

dip related changes in stratigraphic architecture and associated sedimentological and geochemical variability in the upper cretaceous eagle ford group in south texas a detailed rock based investigation of three upper cretaceous eagle ford group cores situated behind at and downdip of the lower cretaceous stuart city paleoreef shelf margin in south texas was conducted to understand stratigraphic sedimentological and geochemical relationships across this buried shelf margin an understanding of how the eagle ford group lithofacies vary across the paleoreef shelf margin is currently lacking we therefore examined a dip section of three cores across the antecedent shelf margin and delineated seven eagle ford lithofacies 1 massive argillaceous mudstone 2 massive to laminated foraminiferal lime wackestone 3 radiolarian and foraminiferal dolomitic to lime packstone 4 massive to bioturbated skeletal lime wackestone 5 laminated foraminiferal lime packstone 6 laminated inoceramid and foraminiferal lime grainstone and 7 massive to bioturbated claystone a basinward decrease in calcite from 60 to 48 is accompanied by an increase in clay minerals from 12 to 20 the low relief raised rim of the older buried stuart city paleoshelf margin may have acted as a barrier dividing the eagle ford group into two sedimentological systems 1 a restricted drowned shelf to the north and 2 an open marine basinal setting to the south the lower to upper cenomanian eagle ford strata on the drowned shelf are cyclic and enriched in molybdenum suggesting anoxic to euxinic water masses the anoxic open marine basinward strata are less cyclical and have a lower molybdenum compared with the drowned shelf content ash beds and gravity flow deposits are rare south of the margin a depositional model was constructed of the lower and upper eagle ford formations

coccolith strontium to calcium ratios in emiliania huxleyi the dependence on seawater strontium and calcium concentrations in recent studies the sr ca ratio of coccolithophore calcite was used as a proxy for past coccolithophore growth and calcification rates since sr and ca concentrations in seawater have not remained constant through time interpretation of sr ca data from the coccolith dominated sedimentary record requires knowledge about the incorporation of seawater sr into coccolith calcite during coccolithogenesis here we show that sr ca of emiliania huxleyi coccoliths is linearly related to seawater sr ca meaning that the sr exchange coefficient does not change with changing seawater sr ca the exchange coefficient for sr in this study 0 39 is close to values presented in the literature and is high compared with values obtained by inorganic precipitation experiments this suggests a strong effect of cell physiology on biogenic calcite precipitation in coccolithophores we present a conceptual model based on the transmembrane transport of sr and ca which explains the offset

shale microfacies eagle ford group cenomanian turonian north central texas outcrops and subsurface equivalents abstract the eagle ford group is a mixed siliciclastic carbonate unit that records a late cretaceous cenomanian to turonian transgression a major condensed interval cycle 2 5 of the uza 2 supercycle occurs within the eagle ford shale eagle ford strata are overlain disconformably by the austin chalk the austin eagle ford contact represents the turonian coniacian boundary 89 ma the cenomanian turonian 92 ma boundary occurs within the eagle ford group regionally eagle ford strata consist of two major depositional units a lower transgressive unit dominated by dark well laminated shales exhibiting only minor evidence of bioturbation and an upper regressive unit consisting of thinly interstratified high frequency cycles shales limestones and carbonaceous quartzose siltstones petrographic characterization of shales from eagle ford outcrops near austin waco and dallas texas and subsurface equivalents in a core getty 1 j t wilson from lasalle county texas reveals six microfacies 1 pyritic shales 2 phosphatic shales 3 bentonitic shales 4 fossiliferous shales 5 silty quartzose shales and 6 bituminous claystone and shales transgressive eagle ford shales consist mainly of microfacies 1 4 and 6 the eagle ford condensed interval consists of microfacies 1 2 and 3 and highstand eagle ford shales are comprised of microfacies 4 and 5 eagle ford microfacies exhibit distinctive sedimentological aspects and have source rock characteristics that vary systematically within a sequence stratigraphic framework transgressive eagle ford shales occurring below the condensed interval have optimum oil prone source potential whereas overlying regressive shales are gas prone transgressive and condensed eagle ford strata represent poorly oxygenated low energy below storm wave base marine paleoenvironments of deposition in contrast overlying regressive eagle ford lithofacies accumulated in higher energy above storm wave base well oxygenated shallow marine paleoenvironments

seismostratigraphy and thermal structure of earth s core mantle boundary region we used three dimensional inverse scattering of core reflected shear waves for large scale high resolution exploration of earth9s deep interior d and detected multiple piecewise continuous interfaces in the lowermost layer d beneath central and north america with thermodynamic properties of phase transitions in mantle silicates we interpret the images and estimate in situ temperatures a widespread wave speed increase at 150 to 300 kilometers above the coremantle boundary is consistent with a transition from perovskite to postperovskite internal d stratification may be due to multiple phase boundary crossings and a deep wave speed reduction may mark the base of a postperovskite lens about 2300 kilometers wide and 250 kilometers thick the core mantle boundary temperature is estimated at 3950 200 kelvin beneath central america a site of deep subduction the d is relatively cold t 700 100 kelvin accounting for a factor of two uncertainty in thermal conductivity core heat flux is 80 to 160 milliwatts per square meter mw m 2 into the coldest d region and 35 to 70 mw m 2 away from it combined with estimates from the central pacific this suggests a global average of 50 to 100 mw m 2 and a total heat loss of 7 5 to 15 terawatts

the quantification and application of handheld energy dispersive x ray fluorescence ed xrf in mudrock chemostratigraphy and geochemistry abstract traditionally analytical techniques such as wavelength dispersive x ray fluorescence wd xrf inductively coupled plasma icp and mass spectrometry icp ms instrumental neutron activation analysis inaa or stationary bench top energy dispersive x ray fluorescence ed xrf have been used to generate quantitative geochemical results however a more efficient means of data collection using portable ed xrf instrumentation now allows the investigator to acquire rapid non destructive quantitative measurements on drill core and clean flat rock surfaces in addition to pressed powder pellets typically used in wd xrf analysis similar to traditional xrf methods quantification using the handheld ed xrf requires a matrix specific calibration unfortunately very few internationally accepted mudrock or shale reference materials exist and their elemental ranges provide inadequate coverage for the geochemical diversity of mudrocks in order to return reliable calibrated results a unique set of reference materials has been developed that incorporates a wide range of mudrock elemental compositions the current method provides elemental calibrations for major elements heavier than sodium and the following trace elements ba v cr ni cu zn rb sr y zr nb mo th and u a comparison of handheld energy dispersive and wavelength dispersive x ray fluorescence ed xrf and wd xrf results from pressed powder pellets of mississippian age barnett shale of north central texas usa is presented in order to evaluate the reliability of the reference calibration and the quantification of unknown samples using two different instrument platforms it will be demonstrated that calibrated results from the handheld ed xrf effectively define chemostratigraphic changes in real time as a consequence quantified results can be used immediately to assess changes in bulk mineralogy paleo redox conditions and to link down core geochemical changes to stratigraphic sedimentological and paleoenvironmental observations