coagulation and transport of sediments in the gironde estuary the distribution of suspended particle size and concentration were measured along the gironde estuary france from the river seaward to the ocean the suspended particle size and volume concentration were measured using in situ holography and onboard optical techniques utilizing special procedures in order to avoid floc breakage sediments discharged by the rivers coagulate upon encountering the very low salinities 0 2 of the upper estuary confirmed with laboratory experiments and are then transported and deposited by currents in the remainder of the estuary this coagulation coupled with estuarine circulation produces a turbidity maximum which is offset between the surface and bottom waters the floc size maximum is oceanward of the turbidity maximum and is likewise offset along the estuary by about 30 km the estuary can be subdivided into the following zones 1 coagulation 2 hydrodynamic landward of the null point and 3 hydrodynamic seaward of the null point initial coagulation appears to be completed in coagulation zone 1 and particles are transported and settled with very little floc breakage and recoagulation in zones 2 and 3 only the floc settling velocities coupled with estuarine circulation control the concentration and size distributions of flocs in the water column and eventually control the deposition of sediments

flood ebb tidal asymmetry in a shallow sandy estuary and the impact on net sand transport flood ebb tidal dominance plays a pivotal role in estuarine sediment transport the dyfi estuary mid wales uk is used as a case study together with an idealized trumpet shaped estuary morphology to illustrate key processes giving rise to flood ebb dominance observations made in the main entrance channel to the dyfi indicate that the system is presently ebb dominant with regard to both the relatively long duration of the ebb tide and also the faster ebb velocities predictions made across the mouth of the estuary using the telemac modelling system suggest further that the net sand transport presently occurs out of the estuary in contrast due to the varying distribution of channels and flats within the estuary the tidal flow in the upper estuary is flood asymmetric and here the net transport is up estuary flood versus ebb dominance is shown to be attributable to the relative extent of the channels and sandflats in relation to the mean water level an attempt is made to develop a simple metric to determine present day transport pathways within an estuary in response to its cross channel flow asymmetries

the effects of channels and shoals on exchange between the chesapeake bay and the adjacent ocean the role of bathymetric changes in determining the transport of water and salt in the lower chesapeake bay lcb was investigated using high resolution acoustic doppler current profiler adcp and conductivity temperature depth profiles a cross channel transect was repeated eight times during neap tides on october 6 7 1993 which illustrated the lateral structure of the longitudinal and transverse flow fields and the intratidal variations in the flow structure across the lcb amplitude and phase of the m2 tidal component as well as the mean flow velocity were calculated using least squares fitting at every point of a uniform grid obtained from the adcp data the results differ from the classical two layer pattern of estuarine circulation modified by coriolis effects but are consistent with recent hydrographic observations semidiurnal flow was highest over the navigational channels and lateral gradients were strongest in regions of sharp bathymetric changes the phase lag of the semidiurnal flow also showed lateral and vertical gradients that represented advances at the bottom with respect to the surface and over the shoals in relation to the channels the section of the water column measured indicated a mean outflow of 0 7 104 m3 s and a mean inflow of 1 3 104 m3 s the apparent gain of water by the estuary during the period of observation can be explained by meteorologically forced net barotropic inflow the depth averaged mean longitudinal flow consisted of inflow in the navigational channels and outflow over the shoals the mean transverse flow showed near surface convergence over the channels we propose a possible explanation for the observed flow and density structure as follows the barotropic and baroclinic forcing interact with the bathymetry to extend the inflow from the bottom to the surface thereby inducing a transverse circulation that yields near surface convergence over the channels

impact of rock fabric on water imbibition and salt diffusion in gas shales abstract understanding water uptake of gas shales is critical for designing fracturing and treatment fluids previous imbibition experiments on unconfined gas shales have led to several key observations the water uptake of dry shales is higher than their oil uptake furthermore water imbibition results in sample expansion and microfracture induction this study provides additional experimental data to understand the effects of rock fabric complex pore network clay swelling and osmotic potential on imbibition behavior we systematically measure and compare the imbibition rates of deionized water and oil into wet dry and confined unconfined rock samples from different shale members of the horn river basin we also measure the ion diffusion rate from shale into water during imbibition experiments the results show that initial water saturation decreases the water uptake of shale samples however it has no effect on oil imbibition rates the liquid imbibition and ion diffusion rates along the lamination are higher than those against the lamination the results also suggest that confining the shale samples decreases the water imbibition rate parallel to the lamination however it has a negligible effect on water uptake perpendicular to the lamination furthermore confining does not significantly affect the ion diffusion rates the comparative study suggests that for both confined and unconfined samples water uptake is higher than oil uptake however previous experiments on crushed shale samples show that the oil uptake of crushed packs is higher than their water uptake xu and dehghanpour 2014 the data suggest that the connected pore network of the intact samples is water wet while the majority of rock including poorly connected pores is oil wet this argument is backed by bse images and complete spreading of oil on fresh break surfaces of the rock

late quaternary evolution of coastal sand barriers port stephens myall lakes area central new south wales australia abstract the geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of newcastle new south wales n s w australia in order to determine modes of deposition and the degree to which marine and estuarine deposits can be correlated and dated each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur in four of the bays dual sand barriers comprising an inner barrier and an outer barrier provide the framework for correlation between embayments six stages are recognized in the deposition of late quaternary sediments in this area i pre last interglacial involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes ii last interglacial stage during which inner barriers were formed iii last glacial reworking of barrier and dune sands by westerly winds iv postglacial marine transgression during which the outer barriers were initiated v mid holocene stage following cessation of sea level rise ca 6000 6500 yr b p on this coast and involving progradation of outer barriers in some embayments and vi late holocene episodic eolian reworking of dune complexes and outer barriers the relatively high wave and wind energy as well as the tectonic setting of the central n s w coast results in somewhat different geomorphic histories from barrier island coasts in north america and europe

laboratory measurement of water imbibition into low permeability welded tuff abstract laboratory imbibition and vapor diffusion experiments were developed and conducted to measure accurately water imbibition and vapor condensation into welded tuff of low permeability automatically recorded balance readings were used to quantify the uptake of water into rock cores by imbibition and or vapor condensation the total uptake of water was checked against independent weighings of the sample before and after each experiment as water was imbibed into the sample and evaporated from the reservoir the buoyant force on the sample decreased balance readings corrected for the buoyancy effect agreed very well with independently measured total uptake sorptivity was calculated from the slope of a plot of corrected cumulative imbibition versus square root of time vapor condensation can provide a significant contribution to the water uptake into cores during imbibition experiments rock cores were coated with epoxy on the sides and covered on the top except for a small hole that allowed air to escape to minimize the vapor condensation contribution comparison of the sorptivity values between different core treatments shows that a consistent fraction about 20 of water uptake actually enters the core by vapor condensation overall methods for separating the confounding effects of buoyant force change and vapor condensation result in more accurate measurement of sorptivity as exhibited by the consistent and reproducible results of triplicate measurements these methods for buoyancy and vapor condensation correction are expected to be very useful for measuring imbibition rates on a wide range of porous materials especially very low permeability materials

lateral variability of subtidal flow at the mid reaches of a macrotidal estuary transverse variations of tidal and subtidal flow were investigated in a macrotidal and convergent estuary this was accomplished by combining data analysis of current velocities and water density with numerical modeling at the mid reaches of the gironde estuary france nonlinear mechanisms responsible for overtide generation and hence subtidal flows were found to vary across the estuary and from neap to spring tides subtidal flows were driven by a combination of internal asymmetry tidal advective accelerations nonlinear effects of water level variations quadratic friction and river discharge the quarter diurnal overtide band d4 in the flow was generated by internal asymmetry and tidal advective accelerations during neap tide the ratio of quarter diurnal to squared semidiurnal bands d4 d22 was largest 0 3 in sections of the channel showing subtidal outflow river discharge increased from neap to spring tides causing a subsequent increase of seaward subtidal currents during spring tide d4 was generated by tidal advective accelerations and quadratic friction combined with river discharge rather than by internal asymmetry the sixth diurnal overtide d6 in the flow was comparable to d4 for both neap and spring tides largest d6 d23 ratios were found in the shallowest cross channel locations during both neap and spring tides

mechanical anisotropy in the woodford shale permian basin origin magnitude and scale the rock mechanical properties of shales are critical to how they perform as reservoirs determining both their tendency to develop natural fractures and their response to hydraulic stimulation these mechanical properties are in turn manifestations of composition fabric and porosity and fluid saturations such properties also dictate the seismic response of shales as well as their signature on many well logs it has long been recognized or perhaps assumed that shales are relatively homogeneous in the plane parallel to bedding and relatively heterogeneous in the direction perpendicular to bedding

thermal maturity of woodford shale gas and oil plays oklahoma usa abstract being a hydrocarbon source rock and having a brittle silica rich lithologic character makes the woodford shale late devonian to early mississippian an important oil and gas shale in oklahoma since 2004 woodford shale plays have expanded from producing primarily thermogenic methane in one geologic province to producing thermogenic methane condensate oil and biogenic methane in four geologic provinces at thermal maturities from mature 0 5 vitrinite reflectance ro to post mature 2 to 3 ro condensate is produced at a thermal maturity up to 1 67 ro oil is produced from naturally fractured silica rich shale biogenic methane is produced in shallow

experimental investigations on the geometry and connectivity of pore space in organic rich wufeng and longmaxi shales abstract the nano scale pore systems of organic rich shale reservoirs were investigated from upper ordovician wufeng and lower silurian longmaxi formations in southeast sichuan basin these two formations are the most important target plays of shale gas development in china the purpose of this article is to assess the geometry and connectivity of multi scale pore systems and to reveal the nature and complexity of pore structure for these over mature gas shales to achieve these objective total organic carbon mineralogy image analyses by focused ion beam sem low pressure nitrogen adsorption mercury injection capillary pressure micp and spontaneous fluid deionized di water and n decane imbibition were performed most of the visible pores from sem work in wufeng and longmaxi shales are within nm and m size regimes and belong to organic matter om pores the shapes of om pore in longmaxi samples are elliptical bubble like irregular or rounded wufeng pores are mainly irregular linear and faveolated even though two shales have small depth difference as well as similar thermal maturity kerogen type and toc content nano scale pores in longmaxi are mainly associated with narrow platelike or slitlike pores with pore size of 3 50 nm while inkbottle pores are dominant in wufeng samples and over 88 of the pore volume is contributed by pores with diameter

play analysis and leading edge oil reservoir development methods in the permian basin increased recovery through advanced technologies the permian basin of west texas and southeast new mexico remains an important oil producing province accounting for 17 of united states production 327 million bbl in 2002 with a resource base of such size increased understanding of reservoir geology and improved use of enhanced recovery practices in the basin can have a substantial impact on united states oil production thirty two oil plays covering both the texas and new mexico portions of the permian basin were defined on the basis of reservoir stratigraphy lithology depositional environment and structural and tectonic setting one thousand three hundred and thirty nine significant sized reservoirs cumulative production of 1 million bbl 1 59 105 m3 of oil through 2000 were assigned to a geologic play cumulative production from these reservoirs was 28 9 billion bbl 4 59 109 m3 or 95 of the basin s total examples of successful reservoir development practices are listed by play because methods demonstrated to work well in one reservoir should be applicable to other reservoirs in the play the permian basin is dominantly a carbonate province carbonate reservoirs account for 75 of total oil production clastics 14 mixed clastics and carbonates 8 and chert 3 the plays having the largest cumulative production are the northwest shelf san andres platform carbonate play 4 0 billion bbl 6 31 108 m3 the leonard restricted platform carbonate play 3 3 billion bbl 5 25 108 m3 the pennsylvanian and lower permian horseshoe atoll carbonate play 2 7 billion bbl 4 29 108 m3 and the san andres platform carbonate play 2 2 billion bbl 3 42 108 m3 the permian system dominates production accounting for 73 of cumulative production followed by the pennsylvanian 13 and the ordovician 6 the estimated remaining reserves from that component of the resource base that is already discovered and producing is 3 25 billion bbl 5 17 108 m3

the sedimentology stratigraphy and paleoenvironmental significance of a late pleistocene alluvial fill central coastal areas of western australia a late pleistocene alluvial fill termed the red alluvium occurs in a number of drainage basins in the geraldton region of the central coastal areas of western australia measured sections were established and analysed for lithofacies characteristics 14c dates and the stratigraphic position of the alluvial fill provide an age bracket for the unit of 40000 yrs b p and 120000 yrs b p the details of the various lithofacies indicate a paleoenvironmental setting conducive to the development of a braided stream regime with predominantly bed load channels and a high rate of sediment supply channel switching and overbank deposition were an integral part of the channel regime soil forming intervals were long enough to produce argillic horizons and carbonate segregations by pedogenetic processes

pore throat sizes in sandstones tight sandstones and shales pore throat sizes in siliciclastic rocks form a continuum from the submillimeter to the nanometer scale that continuum is documented in this article using previously published data on the pore and pore throat sizes of conventional reservoir rocks tight gas sandstones and shales for measures of central tendency mean mode median pore throatsizes diameters are generally greater than2 mm in conventionalreservoir rocks range from about 2 to 0 03 mm in tight gas sandstones and rangefrom0 1to0 005 mminshales hydrocarbonmolecules asphaltenes ring structures paraffins and methane form another continuum ranging from 100 a 0 01 mm for asphaltenes to 3 8 a 0 00038 mm for methane the pore throat size continuum provides a useful perspective for considering 1 the emplacement of petroleum in consolidated siliciclastics and 2 fluid flow through fine grained source rocks now being exploited as reservoirs

determining the causes of pleistocene stream aggradation in the central coastal areas of western australia summary late pleistocene stream aggradation was widespread in the moresby ranges western australia the general geomorphological characteristics of the drainage basins and the details of the sedimentology paleohydraulics suggest that stream aggradation was due to sediment yields exceeding stream capacity however from a consideration of the mechanics of stream aggradation it is demonstrated that stream aggradation was a response to both sediment supply and base level controls with both processes operating against a background of high sediment yields the study demonstrates that it can be relatively straightforward to establish the causes of stream aggradation

experimental investigations of the wettability of clays and shales 1 wettability in argillaceous materials is poorly understood yet it is critical to hydrocarbon recovery in clay rich reservoirs and capillary seal capacity in both caprocks and fault gouges the hydrophobic or hydrophilic nature of clay bearing soils and sediments also controls to a large degree the movement of spilled nonaqueous phase liquids in the subsurface and the options available for remediation of these pollutants in this paper the wettability of hydrocarbons contacting shales in their natural state and the tendencies for wettability alteration were examined water wet oil wet and mixed wet shales from wells in australia were investigated and were compared with simplified model shales single and mixed minerals artificially treated in crude oil the intact natural shale samples preserved with their original water content were characterized petrophysically by dielectric spectroscopy and nuclear magnetic resonance plus scanning electron optical and fluorescence microscopy wettability alteration was studied using spontaneous imbibition pigment extraction and the sessile drop method for contact angle measurement the mineralogy and chemical compositions of the shales were determined by standard methods by studying pure minerals and natural shales in parallel a correlation between the petrophysical properties and wetting behavior was observed these correlations may potentially be used to assess wettability in downhole measurements

a note on tidal asymmetry in the severn estuary a one dimensional non linear numerical model is used to investigate the tidally averaged frictional stress and set up of water level due to tidal asymmetry in the severn estuary these quantities depend on the overtides in the region a linearized model of the overtides is applied to calculations of the m4 currents in order to delineate the mechanisms responsible for their generation the relative importance of individual non linear mechanisms to the tidally averaged stress and set up is determined these mechanisms are interactions between tidal flow and changes in depth or breadth over a cross section frictional interaction between the tidal flow and stokes drift interaction between the tidal fluctuations in water depth and frictional retardation and non linear advection

a sequence stratigraphic framework for the upper devonian woodford shale permian basin west texas criteria for recognizing stratigraphic sequences are well established on continental margins but more challenging to apply in basinal settings we report an investigation of the upper devonian woodford shale permian basin west texas based on a set of four long cores identifying sea level cycles and stratigraphic sequences in an organic rich shale the woodford shale is dominated by organic rich mudstone sharply overlain by a bioturbated organic poor mudstone that is consistent with a second order eustatic sea level fall interbedded with the organic rich mudstone are carbonate beds chert beds and radiolarian laminae all interpreted as sediment gravity flow deposits bundles of interbedded mudstone and carbonate beds alternate with intervals of organic rich mudstone and thin radiolaria rich laminae defining a 5 10 m 16 33 ft thick third order cyclicity the former are interpreted to represent highstand systems tracts whereas the latter are interpreted as representing falling stage lowstand and transgressive systems tracts carbonate beds predominate in the lower woodford section associated with highstand shedding at a second order scale chert beds predominate in the upper woodford section responding to the second order lowstand additional variability is introduced by geographic position wells nearest the western margin of the basin have the greatest concentration of carbonate beds caused by proximity to a carbonate platform a well near the southern margin has the greatest concentration of chert beds resulting from shedding of biogenic silica from a southern source a well in the basin center has little chert and carbonate here third order sea level cycles were primarily reflected in the stratigraphic distribution of radiolarian rich laminae

pore structure wettability and spontaneous imbibition of woodford shale permian basin west texas abstract even after more than 30 years of exploration and production low total recovery of shale gas

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

minor and trace element and re os chemistry of the upper devonian woodford shale permian basin west texas insights into metal abundance and basin processes the trace and minor element and re os geochemistry of the upper devonian woodford shale are analyzed in order to characterize elemental abundances to identify associations among trace elements and to constrain paleoceanographic conditions and depositional processes this organic carbon rich mudstone in the permian basin west texas is a major source of hydrocarbons in the basin and is coeval with many other upper devonian shales in north america the woodford lacks enrichment in many trace metals only mo u s and se are significantly enriched other redox sensitive elements are depleted or similar to average shale composition including pb bi cr ti cu zn co and v elements associated with granitic sources such as rare earths th ce and tio2 are also depleted relative to average shale this appears to be related to be a source control a strong basin reservoir effect is noted among several redox sensitive elements including mo cu and ni which largely accounts for the depletion dilution by biogenic silica had an additional effect on metal concentrations multivariate factors analysis identified associations between elements including groupings of rare earth elements elements enriched in granitic crust silica varying antithetically with elements in carbonate minerals organic carbon mo and u v phosphate fe and s noteworthy among the results are the different behavior of redox sensitive elements suggesting different precipitation mechanisms or varying dependence on reservoir effects a strong redox effect is noted in the toc ptot ratio at approximately the frasnian famennian boundary indicating an abrupt transition to an anoxic column boundary that coincides with a short term significant fall in sea level this suggests that anoxia was induced by isolation of the basin from the global ocean however with the exception of the uppermost famennian initial 187os 188os values determined from re os geochronology for the permian basin are similar to correlative sections of the appalachian and peace river basins of north american and the rhenohercynian basin of europe this indicates that although the permian basin became restricted during the upper devonian and early mississippian ocean connectivity remained between regional and global basins

wettability of mississippian barnett shale samples at different depths investigations from directional spontaneous imbibition because of its significant impact on relative permeability capillary pressure stimulation methods and ultimate recovery the wettability of reservoir rocks is a critical factor of the petroleum recovery process however characterizing the wettability of shale with extremely low matrix permeabilities is a challenging task because of the dominant presence of nanopores in shale and high heterogeneity of shale compositions at multiple scales from spontaneous imbibition behavior that uses two types of imbibing fluid water and n decane the present study examines the wettability characteristics of gas window barnett shale samples taken from four different depths of texas united 1 blakely core in wise county in texas imbibition experiments were conducted in two directions parallel and transverse to the lamination of the samples a scaling method was used to analyze imbibition data and observed imbibition behaviors were interpreted to infer the different wettability conditions of four samples with different mineralogy total organic carbon content and pore throat size distribution our results show that wettability significantly affects fluid imbibition behavior and that four tested samples can be divided into three wettability categories more water wet mixed wet and more oil wet overall the variable wettability of barnett samples will affect hydrocarbon storage distribution and production

tidal bore dynamics in funnel shaped estuaries the formation and dynamics of tidal bores in funnel shaped estuaries is investigated from both a global tidal wave scaling analysis and new quantitative field observations we show that tidal bore occurrence in convergent estuaries can be estimated from a dimensionless scaling parameter characterizing the relative intensity of nonlinear friction versus local inertia in the momentum equation a detailed analysis of tidal bore formation and secondary wave structure is presented from a unique long term database observations of more than 200 tides acquired during four campaigns in the two main french tidal bore estuaries the seine and gironde garonne estuaries we describe the effect of freshwater discharge on the global tidal wave transformation at the estuarine scale and on local tidal bore occurrence in the upper estuary our field data suggest that the tidal bore intensity is mainly governed by the dimensionless tidal range which characterizes the local tidal wave nonlinearity we also show that the secondary wavefield associated with tidal bore propagating in natural estuaries differs significantly from those associated to undular bores in rectangular channels in particular we observe an abrupt decrease of the whelp steepness when the froude number goes below 1 1 this secondary field transition can explain why tidal bore occurrence in worldwide estuaries is certainly underestimated

a prescriptive model of stratification induced by freshwater runoff abstract stratification induced by freshwater buoyancy input constitutes a key determinant of the environment both in estuaries and adjacent regions of freshwater influence rofis predicting the development and breakdown of estuarine stratification is inherently more difficult than the prediction of thermal stratification because the buoyancy input is localized at the lateral boundaries rather than being uniformly distributed over the surface the primary processes responsible for controlling water column stability have been identified in a previous paper simpson et al 1990 estuaries 12 125 132 as i the estuarine circulation driven by horizontal density gradients ii stirring by tidal and wind stresses and iii straining of the density field by tidal shear these processes are incorporated in a prescriptive model of the time evolution of stratification which utilizes analytical solutions for the tidal and density current profiles specifies the mixing in terms of energy conditions previously used in the heating stirring models and assumes a horizontal density gradient which is invariant with depth the behaviour of this simple model is described and compared with recent time series observations of the variability of stratification in a tidally energetic rofi which indicate the presence of strong semi diurnal and semi monthly cycles in water column stability the model reproduces the main qualitative features of the observations but is restricted as a predictive tool by the constant density gradient assumption and the omission of the interaction between the tidal and density driven flows the inclusion of this latter interaction which occurs via the frictional stresses and the control of eddy viscosity by stratification and the turbulent energy intensity requires a dynamically active model which specifies the feedback processes in terms of an appropriate closure scheme

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

a study of non linear tidal propagation in shallow inlet estuarine systems part i observations the offshore tide becomes strongly distorted as it propagates into shallow estuarine systems observations of sea surface elevation and horizontal currents over periods ranging from three days to one year at nine stations within nauset inlet estuary document the non linear interaction of the off shore equilibrium tidal constituents despite strong frictional attenuation within the estuary the overtides and compound tides of m2 s2 and n2 in particular reach significant amplitude resulting in strong tidal distortion high frequency forced constituents in sea surface are phase locked consistently leading the forcing tides by 60 70 resulting in a persistent distortion where falling tide is longer than rising tide forced constituents in currents are more nearly in phase with equilibrium constituents producing flood currents which are shorter but more intense than ebb currents a compound fortnightly tide msf modulates the mean water level such that lowest tides occur during neap phase instead of spring phase this fortnightly tide can be contaminated by storm surge changing the phase characteristics of this constituent implications of the overtides compound tides and lower frequency tides on near bed suspended and dissolved material transport are profound