well hydraulics theory and data analysis of the constant head test in an unconfined aquifer with the skin effect 1 in a constant head test cht groundwater is withdrawn from a well that has a fixed drawdown accordingly the cht is particularly useful in aquifers of low transmissivity because the constant head well would not be dewatered owing to overpumping the problem of interest pertains to a cht in a homogeneous and anisotropic unconfined aquifer where water released by the water table decline is assumed to be instantaneous and the skin effect surrounding the constant head well is represented by a skin factor a two dimensional transient well hydraulics model is developed and its laplace domain solutions of aquifer drawdown and the constant head well discharge are determined it is found that the three distinct segments typically noted in the time drawdown history of a constant rate test crt are also characteristic of the temporal drawdown variation of the cht however the early time and late time asymptotes conform to the radial flow solution of a cht in confined aquifers as given by hantush 1964 under the late time radial flow conditions the asymptotic solution is in terms of an apparent storage coefficient equal to the sum of the storage coefficient and the specific yield and a specific mass balance relation exists among the constant head well discharge the discharge due to aquifer storage and the discharge resulted from the water table decline while aquifer drawdown and the constant head well discharge are under the influence of well skin their ratios are free from it a curve matching method using this ratio is developed to determine the horizontal and the vertical hydraulic conductivities the storage coefficient and the specific yield when the prescribed constant drawdown is not negligibly small in comparison to the initial saturated thickness aquifer drawdown in late times may be large and thus a drawdown correction is needed for data analysis it is found that the jacob correction for large drawdown of a crt can also be used for the late drawdown correction in a cht

improved forward and inverse analyses of saturated unsaturated flow toward a well in a compressible unconfined aquifer 1 we present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and or unsaturated zone we improve upon a previous such solution due to tartakovsky and neuman 2007 by 1 adopting a more flexible representation of unsaturated zone constitutive properties and 2 allowing the unsaturated zone to have finite thickness both solutions account for horizontal as well as vertical flows throughout the system we investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van genuchten mualem constitutive model use our solution to analyze drawdown data from a pumping test conducted by the u s geological survey at cape cod massachusetts and compare our estimates of van genuchten mualem parameters with laboratory values obtained for similar materials in the area

modeling slug tests in unconfined aquifers taking into account water table kinematics wellbore skin and inertial effects two models for slug tests conducted in unconfined aquifers are developed by a extending the unconfined kgs solution to oscillatory responses yielding a model referred to herein as the unified model and b replacing the constant head condition with the linearized kinematic condition at the water table the models can be used to analyze the full range of responses from highly oscillatory to overdamped the second model refered to as the moving water table mwt model is only applicable when effects of well bore skin are negligible the models are validated by comparison with published solutions and by application to a published case study of field tests conducted in wells without skin in an unconfined aquifer at the msea site in nebraska in this regard a the mwt model essentially yields the same results as the confined kgs model except very close to the water table and b the unified model yields slightly smaller aquifer k values relative to the mwt model at all positions in the well all model solutions yield comparable results when fitted to published field data obtained in an unconfined fluvial aquifer at the msea site in nebraska the unified model is fitted to field data collected in wells known to exhibit positive skin effects at the boise hydrogeophysical research site bhrs in boise idaho it is shown to yield hydraulic conductivity estimates of comparable magnitude to those obtained with the kgs model for overdamped responses and the springer gelhar model for oscillatory responses sensitivity of the mwt model to specific yield s y and hydraulic anisotropy j is evaluated and the results when plotted in log log space and with consideration of log scale time derivatives of the response indicate that these two parameters should be estimable from slug test data though challenges still remain

river stage tomography a new approach for characterizing groundwater basins received 19 june 2008 revised 16 february 2009 accepted 12 march 2009 published 9 may 2009 1 data from tomographic surveys make an inverse problem better posed in comparison to the data from a single excitation source a tomographic survey provides different coverages and perspectives of subsurface heterogeneity nonfully redundant information of the subsurface fusion of these pieces of information expands and enhances the capability of a conventional survey provides cross validation of inverse solutions and constrains inherently ill posed field scale inverse problems basin scale tomography requires energy sources of great strengths spatially and temporally varying natural stimuli are ideal energy sources for this purpose in this study we explore the possibility of using river stage variations for basin scale subsurface tomographic surveys specifically we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of the river stage in a hypothetical groundwater basin we then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image subsurface heterogeneity of the basin results of the numerical exercises are encouraging and provide insights into the proposed river stage tomography using naturally recurrent stimuli such as river stage variations for characterizing groundwater basins could be the future of geohydrology however it calls for implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface

three dimensional model of modern channel bend deposits 1 we present a three dimensional model of heterogeneous modern channel bend deposits developed through purely structure imitating interpolation kriging of hydraulic properties this model augmented with ground penetrating radar data and directional variograms agrees with detailed observations in similar modern environments and leads to a process based interpretation of the presented hydraulic conductivity structure integration of all available information permitted delineation and characterization of the modern streambed as a distinct hydrostratigraphic unit without coring or outcrop studies our results imply that the modern streambed is commonly oversimplified in available analytical and numerical models of groundwater surface water interactions where it is assumed to be homogeneous and isotropic and characterized by a constant width and thickness this three dimensional approach that integrates concepts and principles developed in sedimentology hydrogeology geophysics and geostatistics has potential implications on model development of stream aquifer systems

influence of aquifer heterogeneity and return flow on pumping test data interpretation abstract analytical solutions of drawdown in unconfined aquifers are widely applied for determining the specific yield s y and the horizontal and the vertical hydraulic conductivity k r and k z respectively in many previous studies estimates of s y and k z were observed to be highly variable and physically unrealistic this has been attributed to the conceptualization of flow above the declining water table and aquifer heterogeneity in the applied models we present the analysis of time drawdown data from a pumping test instrumented with depth differentiated observation piezometers arranged in clusters applying homogeneous anisotropic aquifer models in combination with nonlinear least squares parameter identification techniques the data were analyzed in different groups analysis of data from individual piezometer clusters and simultaneous analysis of the entire data set from all piezometer clusters global analysis from the cluster analyses estimates of s y and k z exhibit large variances and depart from a priori estimates inferred from the hydrostratigraphy parameter estimates from the global analysis do not fall within the parameter bounds minimum and maximum values defined by the cluster analyses while heterogeneity appears to be the important reason for large parameter variances we discuss the influence of rarely considered aquifer return flow on drawdown and the inconsistent results from the cluster and global analyses we corroborate our findings with data on hydraulic gradients slug test data and results from the application of a more realistic numerical flow model

variation in the eastern north pacific subtropical gyre california current system during the middle to late miocene as inferred from radiolarian assemblages abstract the california current has influenced the primary productivity along the california margin which plays a significant role in global carbon cycles although previous studies have explored the response of the california current to climate change since the pliocene comparatively little is known about that during the middle and late miocene when the paleoclimate changed significantly here we present variations of the california current based on new data of radiolarian fossil assemblages integrated with previously published data from the middle to late miocene and show that the california current was strengthened from 12 3 to 10 5 ma 9 0 to 8 2 ma and 7 2 to 6 9 ma at odp site 1021 the biogenic opal declined during periods of increased strength of the california current from the middle to late miocene at site 1021 in offshore area these data suggest that the biogenic opal decreased at site 1021 in offshore area due to the deep nutricline depth by the strengthened california current r mode cluster analyses divided into three major assemblages surface warm cool surface to thermocline and intermediate deep water taxa the pronounced faunal changes of radiolarian assemblages to the dominance of intermediate deep water taxa might reflect an initiation of the modern type california current system since ca 10 5 ma in the early late miocene due to the tectonic changes e g partial closing of tropical gateways and uplift of the himalaya and the rocky mountains and or significant high latitude cooling

a case history of field pumping tests in a deep gravel formation in the taipei basin taiwan 33 large diameter wells embedded in 2 m thick 63 m deep diaphragm walls were constructed to reduce both the uplift pressures and the groundwater inflow during the excavations as the actual thickness of the pumped aquifer is unknown the installed wells are regarded as partial penetration wells single well and multi well pumping tests were conducted in the deep gravel formation of taipei basin to derive the hydraulic parameters and to investigate the drawdown characteristics at both the construction and remote sites however the tidal effect on the drawdown of both the pumping well and nearby observation wells was found significant additionally wellbore storage skin and leakage need to be taken into account for deriving the hydraulic parameters hence a method to remove these five factors influencing the drawdown curve is developed which takes advantage from the late time characteristics of drawdown data and the early time behavior of drawdown some currently available semi log graphic techniques are therefore proven applicable for parameter determination validity of the proposed method is verified by the good agreement between the calculated and the measured drawdown of both the pumping well and observation well

flow to a horizontal well in an aquitard aquifer system a horizontal well is sometime installed in an aquifer beneath a water reservoir to get significant amount of groundwater with better quality an aquitard often separates the surface water body from the underneath aquifer previous studies in vertical wells related to this subject treated leakage from the aquitard as a volumetric source term in the governing equation of flow in the main aquifer a hypothesis termed hantush s approximation for partially penetrating wells in this study flow in the aquitard and aquifer is treated as two systems which are linked through the continuity of flux and head at the aquitard aquifer boundary in particular we treat leakage as a boundary at the aquitard aquifer interface not as a volumetric source the leakage induced by the pumping horizontal well depends on several parameters such as the aquitard thickness the vertical hydraulic conductivity of the aquitard the aquitard specific storage the well location and the well length in general we find that the solution based on the hantush s approximation to some extent deviates from that obtained based on the actual scenario of leakage through the interface during the transient flow condition particularly at the early time for steady state flow the hantush s approximation works reasonably well under realistic conditions of aquitard thickness and hydraulic conductivity as long as the aquitard thickness is relatively thick aquitard aquifer ratio greater than 0 001 this approximation also works reasonably well under realistic horizontal well length and well location as long as the well is not too close to the aquitard aquifer boundary q 2005 elsevier b v all rights reserved

pliocene pleistocene evolution of the north pacific ocean atmosphere system interpreted from fossil diatoms the relative abundance of diatom taxa in 216 core tops has been quantified and compared using cluster analysis with assemblages in six cores located beneath different water masses of the north pacific ocean all but one sequence span at least 1 5 m y early pleistocene to holocene and one extends to 2 6 ma the quantitative abundance of each taxon and the space time occurrence of each cluster are interpreted as tracers of oceanographic conditions in addition to high frequency glacial interglacial oscillations the records display rapid steplike changes at 2 4 ma 1 6 1 5 ma 1 0 ma 0 8 0 7 ma and 0 35 ma two secondary transitions recorded only in the northwestern cores occur at 2 0 ma and 1 1 ma we conclude that both the high frequency oscillations and the stepwise transitions reflect variations in extent of subarctic water masses under the influence of the siberian high pressure and aleutian low pressure atmospheric cells we further conclude that 1 the subarctic water mass has developed progressively and attained its modern structure only in the late pleistocene 2 some stages of this evolution may have occurred earlier in the eastern subarctic 3 the holocene is an atypical warm extreme so that the present is not a very good key to the past 4 there were several glaciations between 2 4 and 2 0 ma and 5 the subtropical gyre is more conservative than the subarctic gyre and major changes in the region have been due to forcing from the north we propose a conceptual model of oscillating metastable climatic modes maintained by internal feedback and suggest that steplike changes may occur when one set of boundary conditions is temporarily exceeded

a pliocene to recent history of the bering sea at site u1340a iodp expedition 323 fossil diatoms are the principal component of bering sea sediments and reflect the paleoceanographic history of the region diatom accumulation rates and relative abundances at international ocean discovery program iodp site u1340a are presented overall the total diatom productivity record from 4 9 ma to the present day reveals a fourfold reduction at circa 4 2 ma from 45 107 down to 11 107 valves g wet sediment signifying a major shift in the upwelling and or nutrient regime coinciding with the end of the late miocene early pliocene bloom identified in the eastern equatorial pacific and california margin further abrupt shifts in the diatom assemblage occur at 1 2 78 2 55 ma 2 2 0 1 8 ma and 3 1 0 0 88 ma 1 at 2 78 2 55 ma the appearance of sea ice related species marks the regional cooling associated with the expansion of northern hemisphere ice sheets subsequent development of stratified nutrient depleted waters and increased influence of western basin water masses most likely due to the suppressed inflow of the alaskan stream 2 rapid cooling between 2 0 and 1 8 ma indicates increased sea ice duration and or frequency this coupled with low sea level stands caused prolonged closure of the aleutian passes coupled with further increased western basin water inflow 3 the shift to 100 ka glacial interglacial cycles at the middle pleistocene transition 1 0 0 88 ma marked an increase in upwelling related species indicating enhanced surface water mixing these records confirm that the development and changing dynamics of sea ice in the bering sea played a major role in sub arctic ocean circulation and is an integral component of global climate change

closure of the isthmus of panama the near shore marine record of costa rica and western panama the final closure of the isthmus of panama at 3 5 ma divided the american tropical ocean into two separate and different oceanographic regions consequences for the marine biota were profound but hitherto correlation of the pacific and caribbean coastal sections has not been precise enough to track biologic patterns we present here a correlation of 31 sections from the pacific and caribbean coasts of costa rica and western panama using calcareous nannofossils and planktonic foraminifera at both the tops and bottoms of each formation we estimate that the caribbean section ranges from 8 2 ma to 1 7 ma and the pacific sequence from 3 6 ma to 1 7 ma these intervals bracket postulated dates for final closure of the isthmus and provide the first well dated record of middle and late pliocene faunas from the region the caribbean and pacific sections include very different environments of deposition yet there is sufficient overlap and diversity of habitats to permit meaningful biological comparisons on the caribbean side formations tied together by the overlap of the upper pliocene markers sphenolithus abies and pseudoemiliana lacunosa 3 5 ma to 3 6 ma range from very shallow to shallow inner shelf 200 m and upper slope 200 800 m the pacific coast sections were mostly deposited in a trench slope environment which is absent on the caribbean side these sections fortuitously include abundant thick intra formational slumps containing shallow water fauna more appropriate for biological comparison with the caribbean biota similarly the 1 9 ma to 1 5 ma interval well constrained by various taxa includes middle to outer shelf and inner shelf to upper slope deposits on the caribbean side and marginal marine to inner shelf deposits on the pacific coast using our new biostratigraphic framework to correlate previously poorly constrained mollusc collections we show that evolutionary divergence of the pacific and caribbean near shore marine faunas had occurred by 3 5 ma this strongly suggests that the isthmus was effectively closed by this time

semi analytical solution of flow to a well in an unconfined fractured aquifer system separated by an aquitard abstract semi analytical solutions are presented for flow to a well in an extensive homogeneous and anisotropic unconfined fractured aquifer system separated by an aquitard the pumping well is of infinitesimal radius and screened in either the overlying unconfined aquifer or the underlying fractured aquifer an existing linearization method was used to determine the watertable drainage the solution was obtained via laplace and hankel transforms with results calculated by numerical inversion the main findings are presented in the form of non dimensional drawdown time curves as well as scaled sensitivity dimensionless time curves the new solution permits determination of the influence of fractures matrix blocks and watertable drainage parameters on the aquifer drawdown the effect of the aquitard on the drawdown response of the overlying unconfined aquifer and the underlying fractured aquifer was also explored the results permit estimation of the unconfined and fractured aquifer hydraulic parameters via type curve matching or coupling of the solution with a parameter estimation code the solution can also be used to determine aquifer hydraulic properties from an optimal pumping test set up and duration

genes diversity and geologic process on the pacific coast abstract we examine the genetics of marine diversification along the west coast of north america in relation to the late neogene geology and climate of the region trophically important components of the diverse west coast fauna including kelp alcid birds e g auks puffins salmon rockfish abalone and cancer crabs appear to have radiated during peaks of upwelling primarily in the late miocene and in some cases secondarily in the pleistocene phylogeographic barriers associated with mio pliocene estuaries of the mid california coast the pliocene opening of the gulf of california tectonic and eustatic evolution of the california bight as well as the influence of pleistocene and holocene climate change on genetic structure are assessed in a geologic context comparisons to east coast and western freshwater systems as well as upwelling systems around the globe provide perspective for the survey

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

magnetostratigraphic biostratigraphic and stable isotope stratigraphy of an upper miocene drill core from the sale briqueterie northwestern morocco a high resolution chronology for the messinian stage we report a high resolution stable isotope carbonate magnetostratigraphic and biostratigraphic record from a 175 m drill core from the sale briqueterie which is part of the bou regreg section in northwestern morocco the sale drill core spans the interval from paleomagnetic chron c4n partim to c3r earliest gilbert which represents the time leading up to and including the isolation and desiccation of the mediterranean i e the messinian salinity crisis during chrons c3an and c3ar 6 935 to 5 894 ma the isotope and carbonate signals display quasi periodic variations with estimated periods of 40 and 100 kyr respectively we interpret the 40 kyr 18o variations as reflecting changes in global ice volume caused by obliquity induced changes 41 kyr in solar insolation in polar regions the 100 kyr carbonate variations probably represent long term modulation of the amplitude of the precessional cycle 21 kyr which is not resolved by our sampling frequency the cyclic nature of the oxygen isotope signal permits us to extend the isotope nomenclature of shackleton et al 1994a from stage tg24 in chron c3r earliest gilbert to stage c3ar 18o 18 at the base of chron c3ar 6 935 ma a major change in paleoceanographic conditions is recorded across the tortonian messinian boundary which we correlate to chron c3bn at 7 04 ma benthic foraminiferal 18o values increased by an average of 0 4 in two steps at 7 17 ma and 6 8 ma and 13c values decreased by 0 7 0 8 between 7 1 and 6 8 ma representing the late miocene carbon shift the first step in 18o values coincides with an inferred reversal in deep water circulation through the rifian corridor and the second correlates with the base of the tripoli formation and onset of crisis conditions in the mediterranean we suggest that the increase in 18o values represents at least in part an increase in global ice volume that lowered sea level and contributed to the establishment of a negative water budget in the mediterranean average 18o values remained high throughout most of chrons c3ar and c3an reaching maximum 18o values during isotope stages tg20 and 22 in chron c3r earliest gilbert the glacio eustatic falls associated with these events may have resulted in the complete isolation of the mediterranean from the world ocean shackleton et al 1994a following stage tg12 in the sale record there exists a trend toward progressively lower 18o values that may represent a series of marine transgressions that eventually reflooded the mediterranean and ended the salinity crisis

on the implementation of the surface conductance approach using a block centred surface subsurface hydrology model summary in physically based catchment hydrology models dynamic surface subsurface interactions are often represented using the surface conductance sc coupling approach guidance on sc parameterisation within block centred codes is limited and common practice is to express the sc coefficient as the quotient of the vertical saturated hydraulic conductivity and the half cell thickness of the uppermost layer this study evaluates the implementation of the sc approach utilising a popular block centred surface subsurface hydrology model modhms to simulate one dimensional infiltration experiments under hortonian conditions results show that defining the sc coefficient based on a half cell thickness of the uppermost subsurface cell inhibits accurate prediction of infiltration rates q e and the time to initiate surface runoff t ro for the adopted rainfall runoff scenario increasing the sc coefficient independently of the grid allows for accurate simulation of q e but not t ro the addition of a thin layer at the surface is shown to improve model accuracy substantially such that q e and t ro approach those obtained using an equivalent mesh centred model i e where the surface and upper subsurface nodes are coincident whilst the addition of a single thin layer in block centred codes allows improved prediction of surface subsurface interaction it does not provide a surrogate for fine discretisation throughout the subsurface that is necessary for accurate simulation of unsaturated zone flow this study offers guidance on the implementation of the sc approach in a block centred code and demonstrates the importance of systematic testing of parameters that are otherwise calibrated in physically based surface subsurface hydrology models

scale dependent parameterization of groundwater surface water interactions in a regional hydrogeological model abstract in regional hydrogeological models groundwater surface water interaction is generally represented with a cauchy boundary condition in which a conductance parameter governs the exchange flux rate in some models the conductance is controlled by the streambed properties since it has generally a lower hydraulic conductivity than the aquifer however depending on the specific system and the spatial discretization of the hydrogeological model aquifer conductance can be a limiting factor for groundwater surface water interactions the present study introduces a new expression to represent the aquifer conductance as a function of aquifer properties surface water network density and model discretization this expression is based on the dupuit forcheimer theory the ernst equation and vertical 2d numerical experiments at the field scale the main assumptions used to derive our formulation are the presence of a no flow boundary at the bottom of the hydrogeological model and the homogeneity of the aquifer the expression is evaluated using simulations with 3d hydrogeological models at different spatial resolutions and compared against previously published parameterization approaches the results show that the new expression outperforms the other approaches by capturing accurately both the grid size and the surface water network density dependency of the conductance which is caused by pressure head losses due to flow within the aquifer grid cell to the surface water without any additional numerical calculation moreover the proposed expression can be implemented directly in hydrogeological models thereby improving current approaches to represent groundwater surface water interactions in regional hydrogeological models

seismicity and earthquake hazard analysis of the teton yellowstone region wyoming abstract earthquakes of the teton yellowstone region represent a high level of seismicity in the intermountain west u s a that is associated with intraplate extension associated with the yellowstone hotspot including the nearby teton and hebgen lake faults the seismicity and the occurrence of high slip rate late quaternary faults in this region leads to a high level of seismic hazard that was evaluated using new earthquake catalogues determined from three dimensional 3 d seismic velocity models followed by the estimation of the probabilistic seismic hazard incorporating fault slip and background earthquake occurrence rates the 3 d p wave velocity structure of the teton region was determined using local earthquake data from the jackson lake seismic network that operated from 1986 2002 an earthquake catalog was then developed for 1986 2002 for the teton region using relocated hypocenters the resulting data revealed a seismically quiescent teton fault at m l local magnitude 3 with diffuse seismicity in the southern jackson hole valley area but notable seismicity eastward into the gros ventre range relocated yellowstone earthquakes determined by the same methods highlight a dominant e w zone of seismicity that extends from the aftershock area of the 1959 m s surface wave magnitude 7 5 hebgen lake montana earthquake along the north side of the 0 64 ma yellowstone caldera earthquakes are less frequent and shallow beneath the yellowstone caldera and notably occur along northward trending zones of activity sub parallel to the post caldera volcanic vents stress field orientations derived from inversion of focal mechanism data reveal dominant e w extension across the teton fault with a ne sw extension along the northern teton fault area and southern yellowstone the minimum stress axes directions then rotate to e w extension across the yellowstone caldera to n s extension northwest of the caldera and along the hebgen lake fault zone the combination of accurate hypocenters unified magnitudes and seismotectonic analysis helped refine the characterization of the background seismicity that was used as input into a probabilistic seismic hazards analysis our results reveals the highest seismic hazard is associated with the teton fault because of its high slip rate of approximately 1 3 mm yr compared to the highest rate of 1 4 mm yr in southern yellowstone on the mt sheridan fault this study demonstrates that the teton yellowstone area is among the regions highest seismic hazard in the western u s

comment on sensitivity analysis and determination of streambed leakance and aquifer hydraulic properties by xunhong chen and xi chen journal of hydrology 2003 vol 284 270 284 recently studies of the platte river watershed have gained significant attention from federal and nebraska usa state agencies due to the importance of groundwater surface water interactions under drought conditions using archive data from a 1983 pumping test chen and chen 2003 interpret the hydraulic properties of the alluvium and a streambed of the platte river near kearney nebraska and compare their data with results of other studies performed over the past several years three important inconsistencies of this article will be highlighted here 1 misuse of the analytical model of hunt 1999 2 departure of their results from previously published data and 3 unsatisfactory explanation of these anomalous results

ignimbrites of the eastern snake river plain evidence for major caldera forming eruptions the eastern snake river plain is a predominantly rhyolitic province analogous to the present day yellowstone plateau volcanic field but older and further evolved the widespread quaternary basaltic lavas that now blanket the eastern snake river plain appear to have erupted after major rhyolitic activity ceased and represent less than 20 of the total volume of volcanic rock near the north central margin of the plain the rhyolites show a general age progression that becomes younger northeastward toward yellowstone three major ignimbrite sheets comparable in magnitude to those of the yellowstone plateau field have been correlated on both sides of the eastern snake river plain from the arco and pocatello areas to margins of the yellowstone plateau these 4 3 to 6 5 ma old ignimbrites are referred to herein as the heise volcanic field studies of facies changes and lateral variations in the three major ignimbrites of the heise field permit identification of related calderas that are now buried beneath the plain petrologic studies suggest that although the ignimbrites overlap compositionaliy each was derived from an isotopicaliy distinct magma that contained a significant component of crustal material

the interaction between the unsaturated zone aquifer and stream during a period of groundwater withdrawal summary by combining laboratory and field experiments we study the release of water from above a falling water table and the implications this has on pumping test analysis and prediction of stream depletion undisturbed core samples from the field site were used in laboratory experiments to measure drainage responses to water table drawdown the responses can be sufficiently modeled by estimating the specific yield and five exponential time constants of a moench boulton type model of delayed drainage the average specific yield is thus estimated to 0 24 which is in agreement with previous small scale and large scale estimates in addition two pumping tests were conducted near the stream the drawdown analysis was made using a 3d numerical groundwater flow model facilitating use of the moench boulton type boundary condition at the water table the drawdown observations were fitted by calibrating two alternative models one simulating the release of water at the water table as instantaneous the other simulating the release of water as delayed comparing the calibration results for the two alternative models showed that they fit the drawdown observations nearly equally well and most estimated parameter values are realistic and nearly identical however estimation of the specific yield is found to be sensitive to whether drainage is modeled as instantaneous or as delayed in the first case the estimated specific yield is about half of the estimate from the core experiments and of the previous estimates in the second case the estimate 0 17 is in better agreement with core and previous estimates 0 24 the analysis indicates that relatively fast drainage and the existence of two drawdown dependent sources of groundwater recharge the storage and the stream complicates pumping test design to obtain unique parameter estimation the analysis supports that an essential factor in parameter estimation by pumping test analysis for at least some unconfined aquifers is the use of a model that accounts for time varying drainage from the vadose zone finally when predicting stream depletion beyond 1 day of pumping it is acceptable in the present case to use a model simulating drainage as instantaneous if unbiased parameter estimates are used

timing of late cenozoic tidewater glaciation in the far north pacific the onset of late cenozoic glacial events in the far north pacific ocean is recorded by ice rafted debris in the yakataga formation in the gulf of alaska the dating of these events is controversial ages based on molluscs suggest that initial late cenozoic tidewater glaciation occurred in the early middle miocene 15 16 ma previous work on planktic foraminifera indicates that this event is no older than late miocene probably latest miocene 5 6 ma resolution of this problem is important because the yakataga formation is the thickest most complete and best exposed repository of late cenozoic glaciomarine rocks in the northern hemisphere investigation of this record has broader implications for global temperature gradients paleoceanographic development of the far north pacific and northern hemisphere glacial history new planktic foraminiferal data from onshore and offshore yakataga formation sections in the gulf of alaska are compared to a regional depositional and chronostratigraphic framework in order to test whether the yakataga record is anomalous or consistent with the paleoclimatic record of the north pacific this comparison reconfirms that initial glaciomarine rocks of the yakataga formation are no older than late miocene new paleomagnetic data suggest that the base of the yakataga formation is within the lower gilbert polarity chron consistent with the planktic foraminiferal dating and k ar dates on glauconite correlation of the yakataga record to key offshore sections in the far north pacific deep sea drilling project dsdp sites 178 183 192 provides additional insights into the paleoclimatic significance of these rocks uplift of the alaska coastal ranges a necessary prelude to alpine glaciation occurred during late miocene time diatom biofacies dsdp sites 183 192 indicate warm middle miocene conditions climatic deterioration during the late middle and early late miocene time and initial tidewater glaciation between 5 0 and 6 7 ma a relatively warm mid pliocene interval succeeded this initial glaciation which was in turn followed by hemisphere scale glaciation beginning at 2 5 ma this second phase of yakataga glaciation may have begun as early as 3 0 3 5 ma glaciomarine rocks in the basal yakataga formation mark an important climatic event in the north pacific ocean they are latest miocene in age consistent with regional climatic information and not a middle miocene climatic anomaly

late miocene vegetational and climatic variations inferred from a pollen record in northwest wyoming a pollen stratigraphy from late miocene lacustrine strata teewinot formation in jackson hole wyoming permits analysis of vegetation and climate history over a time interval of less than 300 000 years with better temporal resolution of data than has been reported from terrestrial tertiary deposits the flora was essentially modern and six successive pollen assemblages indicate alternating dry and wet conditions the frequency of climatic change in this record is similar to that inferred from marine isotope records for both late tertiary and quaternary time

drastic change in the late pliocene subarctic pacific diatom community associated with the onset of the northern hemisphere glaciation abstract to date there is scarcely clear understanding of the detailed responses of the subarctic pacific phytoplankton communities to the significant climate transition across the initiation of the northern hemisphere glaciation nhg approximately 2 7 million years ago we present more highly resolved evidence of the rapid and drastic change in the phytoplankton biosphere using diatom as a tracer of environmental changes and based on quantitative assemblage analysis of two marine cores from oceanic regions of the north pacific subarctic gyre in the late pliocene subarctic pacific coscinodiscus marginatus and neodenticula kamtschatica were widely dominant but the flora rapidly and drastically shifted to one rich in neodenticula complex n koizumii n seminae at the onset of nhg perhaps due to intense changes in paleoceanographic conditions such as cooling and or a collapse of the previously nutrient regime in the region we also suggest that vertical pumping of biogenic matter by diatoms may have been more efficient in this region earlier than the onset of nhg after the nhg intensification the major primary productivity role in the subarctic pacific shifted from the c marginatus rich flora to the neodenticula complex the drastic decrease of biogenic opaline accumulation reportedly associated with the initiation of nhg would have resulted from not only a decrease of primary production but also from the change in diatom assemblages and consequent effects on their principal role in export flux

onset timing and slip history of the teton fault wyoming a multidisciplinary reevaluation the dramatic relief of the teton range in northwestern wyoming results from motion along the teton normal fault new apatite u th he ahe and fission track aft ages of samples collected in the footwall yield fundamental constraints on contrasting models of teton fault activity and consequent relative footwall uplift low elevation samples in the immediate footwall of the fault range from 12 5 to 6 5 ma ahe ages of samples from subvertical transects range from 57 8 to 6 5 ma rendezvous 54 0 to 6 8 ma grand and 20 5 to 7 1 ma moran with all three transects yielding an expected trend of decreasing age with decreasing elevation aft ages obtained from the three transects range from 55 4 to 45 7 ma rendezvous 43 2 to 13 3 ma grand and 38 0 to 11 7 ma moran inverse thermal history modeling indicates that the onset of relatively rapid cooling as a proxy for relative footwall uplift initiated first in the northern part of the range 15 13 ma and then migrated south as fault displacement continued 7 ma to present at rendezvous thus this work suggests that although the teton fault likely initiated due to basin and range extension this structure remains active normal fault displacement models also suggest a minimum of 6 km displacement for footwall uplift of 2 km if evaluated in the context of established normal fault length displacement relationships this yields a length of 180 km substantially longer than current estimates of teton fault length and putting the northern end of the fault well into and potentially beyond the bounds of yellowstone national park

effects of late neogene climatic cooling on north pacific radiolarian assemblages and oceanographic conditions abstract radiolarian census and abundance data were collected from three deep sea cores drilled by the ocean drilling program sites 884 887 and 1151 to investigate patterns of ecologic changes in space and time during the last 16 million years for the mid latitude to subarctic north pacific high concentrations of radiolarians occurred between 9 0 and 2 7 ma radiolarian species richness was highest in the early middle miocene at each site and gradually decreased up to about 7 ma coinciding with a well established global cooling trend a degree of overlap index calculated for radiolarian assemblages revealed 11 faunal change events of which 8 corresponded to global cooling events and expansions of polar ice sheets three of the faunal change events were observed within the peak of radiolarian accumulation rate and were ascribed to changes in primary productivity in the north pacific rather than global climatic changes our assemblage analyses revealed that north south differentiation in radiolarian assemblages in the northwestern pacific has existed since 16 ma and became more distinct via major steps at 6 8 ma and 2 7 ma coinciding with major glaciation events and that east west faunal contrasts in the subarctic region became obvious beginning at 11 7 ma and changed to a different mode around 6 8 ma the observed east west faunal differences possibly reflect east to west climate differences that were characterized by cooler temperatures in the east than the west during the late miocene 11 7 6 8 ma and then by the opposite temperature trend 6 8 ma recent a severe glaciation at 2 7 ma played a large role particularly in temporal changes in radiolarian accumulation rate and assemblage composition

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

response of deep ocean circulation to initiation of northern hemisphere glaciation 3 2 ma carbon isotopic records from benthic foraminifera are used to map patterns of deep ocean circulation between 3 and 2 million years ago the interval when significant northern hemisphere glaciation began the 18o and 13c data from four atlantic sites 552 607 610 and 704 and one pacific site 677 show that global cooling over this interval was associated with increased suppression of north atlantic deep water nadw formation however the relative strength of nadw production was always greater than is observed during late pleistocene glaciations when extreme decreases in nadw are observed in the deep north atlantic our data indicate that an increase in the equator to pole temperature gradient associated with the onset of northern hemisphere glaciation did not intensify deepwater production in the north atlantic but rather the opposite occurred this is not unexpected as it is the warm high salinity characteristic rather than the low temperature of thermocline waters that is critical to the deepwater formation process in this region today

pliocene pleistocene oxygen isotope record site 586 ontong java plateau abstract oceanographic changes in the western equatorial pacific during the past 6 ma are inferred from oxygen isotopic analyses of planktic and benthic foraminifera from ontong java plateau dsdp site 586 the taxa areglobigerinoides sacculifer pulleniatina cibicidoides wuellerstorfi andoridorsalis umbonatus cooling and ice buildup are indicated by an18o enrichment of 0 3 in the planktic species near 3 4 ma this shift apparently is compensated in the benthic data by a warming of the deep waters by between 1 and 2 c we suggest that the dominant source of upper deep water supply to the pacific changed from antarctic to north atlantic at that time the north atlantic derived water being warmer near 2 8 ma approximately the planktic foraminifera again record an enrichment in18o 18o 0 25 we suggest ice buildup in the northern hemisphere as the cause because of subsequent sharp increase in fluctuations of the 18o signal that is instability the enrichment is magnified in the benthic foraminifera 18o 0 5 by a cooling of the deep water by 1 5 at the time presumably signalling a glacial type reduction of north atlantic deep water nadw production episodic divergence between the signals ofg sacculifer andpulleniatina in the pleistocene apparently reflects periods of increased upwelling in the western equatorial pacific the amplitude of ice volume fluctuations cannot be reconstructed from 18o data alone unless there are constraints on temperature variations the increase in amplitude of fluctuation of the benthic and planktic signals during the pleistocene may be attributed either to an increase in maximum ice volume or to an increase in the fractionation of continental ice or a combination of both causes

analysis of pumping induced unsaturated regions beneath a perennial river 1 the presence of an unsaturated region beneath a streambed during groundwater pumping near streams can reduce the pumping capacity change flow paths and alter the types of biological transformations in the streambed sediments a three dimensional multiphase flow model of two horizontal collector wells along the russian river near forestville california was developed to investigate the impact of varying the ratio of the aquifer to streambed permeability on 1 the formation of an unsaturated region beneath the stream 2 the pumping capacity 3 stream water fluxes through the streambed and 4 stream water traveltimes to the collector wells the aquifer to streambed permeability ratio at which the unsaturated region was initially observed ranged from 10 to 100 the size of the unsaturated region beneath the streambed increased as the aquifer to streambed permeability ratio increased the simulations also indicated that for a particular aquifer permeability decreasing the streambed permeability by only a factor of 2 3 from the permeability where desaturation initially occurred resulted in reducing the pumping capacity in some cases the stream water fluxes increased as the streambed permeability decreased however the stream water residence times increased and the fraction of stream water that reached that the wells decreased as the streambed permeability decreased indicating that a higher streambed flux does not necessarily correlate to greater recharge of stream water around the wells

electrical and hydraulic vertical variability in channel sediments and its effects on streamflow depletion due to groundwater extraction summary the stratification of channel sediments and their vertical hydraulic conductivity kv are important hydrologic information in the analysis of stream aquifer interactions this paper describes the use of direct push technology to generate electrical conductivity ec logs and collect continuous sediment cores beneath river channels the techniques were applied to nine study sites along a 130 km reach of the platte river in southeast nebraska ec logs for the channel surface down to as much as 24 m below the channel surface indicate that the channel sediments in the western part of the reach consist predominantly of sand and gravel low kv silt clay layers occur in the rest of the reach these silt clay layers are either interbedded with sand and gravel or occur as a major unit within the channel sediments as a result the values of kv determined from the sediment cores can vary by four to five orders of magnitude in the same vertical profile of channel sediments at a number of sites the river channel is not lined by a low kv layer at the surface instead the kv values for the top part of channel sediments were consistently greater than kv values for sediments in deeper parts they show a decreasing tendency with the depth this paper also analyzes the effect of low kv layers within channel sediments on streamflow depletion induced by groundwater pumping simulation results suggest that the effectiveness of low kv layers on the calculation of streamflow depletion depends on their depth thickness vertical permeability the length along the channel and the width within the channel as well as the extension into the aquifer on both sides of the river a low kv layer present at the channel surface seems to be the most effective hydrologic feature in reducing the hydrologic connection of stream aquifer a 2008 elsevier b v all rights reserved

stream depletion rate and volume from groundwater pumping in wedge shape aquifers in river basins with several tributaries wells in alluvial valleys are often located near the wedge shaped confluence of two tributaries therefore stream depletion characteristics namely stream depletion rate sdr and stream depletion volume sdv induced by the pumping wells are distributed between two tributaries upstream from the confluence existing methods for the evaluation of stream depletion characteristics are applicable only for a wedge shaped aquifer with special or uncommon wedge angles or for steady state conditions in water resources management temporal stream depletion characteristics are important for the adjudication of water rights a new and practically important method for analytical evaluation of transient sdr and sdv is developed for a wedge shaped aquifer with arbitrary wedge angles results are obtained for each of two tributaries or the tributary segment lengths a simple expression for the sdr fraction that originates from each tributary is presented for long period of pumping after which 100 of the pumping rate is supplied by stream depletion the sensitivity analyses for different parameters are performed to examine their affects on the influence period of the total sdr and the results indicated that the sdr is sensitive to the angles of wedge shaped aquifer and the pumping well the results and sensitivity analysis presented in this study may provide useful information in the assessment of water balance or exploitation of river basins

diatom records in the quaternary marine sequences around the japanese islands abstract understanding the quaternary is a key to estimating what the earth s climate will be like in the future such studies demand high resolution analyses based on paleoclimatic proxy records of changing earth s orbital forcing and solar insolation that affect the climate system quaternary diatom biostratigraphy and paleoceanography have been well established based on the quaternary marine sequences obtained by piston coring and deep sea drilling around the japanese islands this paper firstly reviews the quaternary diatom datum levels that are directly tied to magnetic polarity and then the late pleistocene and holocene rhythmic fluctuations in td derived ssts c which correlate with the earth s orbital parameters and finally reveals the large and abrupt climatic changes that have occurred around the japanese islands on centennial to millennial time scales the main aim is to provide the results of td ssts c based on the late pliocene to pleistocene sequences from three holes obtained by deep sea drilling dsdp odp the main difference between td and twt is that twt gives 0 5 values to xt warm transitional taxa thalassiosira oestrupii is grouped with xt in twt but with warm water species in td differences between the twt and td ssts c curves at hole 436 are unremarkable the remarkable variations of paleo temperatures based on td ssts c show four conspicuous episodes which correspond to the double precession cycle of mis 11 in the japan sea the twt ratio remarkably decreases at 2 6 ma due to a large increase in cold water taxa and indicates the beginning of the glacial age defined as the pliocene pleistocene boundary both twt and td ssts c increase at 2 60 2 0 ma and coincide with the lithologic change from diatom bearing clay with few dark colored layers to fine grained sediments with distinct dark light colored cycles wavelet analysis of td ssts c at site 798 indicates a reversed saw tooth pattern of 48 to 24 ky periods during 1 2 0 7 ma and 24 to 12 ky periods during 0 7 0 ma resulting in a change from longer to shorter cycles these fluctuations correlate with the earth s orbital parameters and climatic changes on a millennial time scale

slipstream an early holocene slump and turbidite record from the frontal ridge of the cascadia accretionary wedge off western canada and paleoseismic implications slipstream slump a well preserved 3 km wide sedimentary failure from the frontal ridge of the cascadia accretionary wedge 85 km off vancouver island canada was sampled during canadian coast guar

capture zone between two streams summary we have investigated stream aquifer interaction with a single pumping well in an aquifer bounded by two parallel nearby streams this study presents steady state semi analytical solutions to calculate the fraction of water withdrawal from two streams potential theory is used to describe the capture zone between two streams when low permeability streambeds are not present steady state flow equations in the aquifer and two streambeds are solved following rigorous mass balance requirements if low permeability streambeds are present when the low permeability streambeds are not present and the regional flow exists between two streams this study finds that the maximal capture size without extracting water from the down gradient stream decreases with the normalized well location in an approximately linear fashion furthermore the normalized flux from the up gradient stream decreases with the normalized well location faster than the linear fashion when the low permeability streambeds exist and the regional flow is neglected the normalized flux across either streambed varies with the normalized well location in a linear function furthermore the magnitude of the slope of that function is nearly unity when the hydraulic conductance ratio of the two streambeds is one and is less than unity when the hydraulic conductance ratio of the two streambeds is either greater or smaller than one when the normalized well location with equal fluxes from two streams versus the hydraulic conductance ratio of the two streambeds are plotted semi logarithmically we observed a segmented curve including a steep segment at the beginning followed by a flat segment and a final steep segment

early and middle miocene stable isotopes implications for deepwater circulation and climate the middle miocene 18o increase represents a fundamental change in the ocean atmosphere system which like late pleistocene climates may be related to deepwater circulation patterns there has been some debate concerning the early to early middle miocene deepwater circulation patterns specifically recent discussions have focused on the relative roles of northern component water ncw production and warm saline deep water originating in the eastern tethys our time series and time slice reconstructions indicate that ncw and tethyan outflow water two relatively warm deepwater masses were produced from 20 to 16 ma ncw was produced again from 12 5 to 10 5 ma another feature of the early and middle miocene oceans was the presence of a high 13c intermediate water mass in the southern hemisphere which apparently originated in the southern ocean miocene climates appear to be related directly to deepwater circulation changes deep waters warmed in the early miocene by 3 c 20 to 16 ma and cooled by a similar amount during the middle miocene 18o increase 14 8 to 12 6 ma corresponding to the increase 20 ma and subsequent decrease 16 ma in the production of ncw and tethyan outflow water large 0 6 relatively rapid 0 5 m y 18o increases in both benthic and planktonic foraminifera i e the mi zones of miller et al 1991a and wright and miller 1992a were superimposed in the long term deepwater temperature changes they are interpreted as reflecting continental ice growth events seven of these m y glacial interglacial cycles have been recognized in the early to middle miocene two of these glacial interglacial cycles mi3 and mi4 combined with a 2 to 3 c decrease in deepwater temperatures to produce the middle miocene 18o shift

stream depletion predictions using pumping test data from a heterogeneous stream aquifer system a case study from the great plains usa abstract this uniquely designed study investigates a fundamental issue the feasibility of predicting stream depletion rates using linear uniform two dimensional models required input for these models includes the hydraulic parameter estimates of the aquifer and the stream aquifer interface which may be obtainable through pumping test data analysis this study utilizes pumping test data collected near the naturally meandering prairie creek platte river watershed nebraska usa drawdown data were obtained in eight piezometer clusters located on both sides of the stream each containing three piezometers screened at different aquifer depths parameter estimates and thus stream depletion predictions varied over a wide range large parameter variance and a low degree of goodness of fit between the calculated and measured data encountered during the analysis suggest deficiencies of the uniform aquifer models in describing significant physical processes this was also shown by additional field experiments that indicate lateral and vertical aquifer heterogeneity hydrogeological and sedimentological considerations of the meandering stream architecture point bar versus cut bank and the application of a linear piecewise homogeneous model yielded a higher degree of goodness of fit and higher confidence in stream depletion predictions aquifer heterogeneity appears to be the major reason for uncertainty in stream depletion predictions though other possible sources of uncertainty should be considered these include the model linearity the dupuit assumption the simplified representation of the stream aquifer interface the approximation of the stream as a straight line or a strip and the impact of regional groundwater flow

evolution of eastern pacific warm pool and upwelling processes since the middle miocene based on analysis of radiolarian assemblages response to indonesian and central american seaways a quantitative racholarian study at ocean drilling program site 1241 in the eastern tropical pacific enables us to reconstruct paleoceanographic changes that occurred since the latest middle miocene today this site is located just under the eastern pacific warm pool epwp based on the abundance variations of radiolarian characteristic species which are indicators of upwelling and thermocline changes it is suggested that three notable changes occurred at 10 6 9 8 and 4 2 ma in the region four distinct periods of oceanographic conditions bounded by these notable changes were characterized on the basis of the following 1 stratified seawater 12 0 to 10 6 ma 2 a shallowing of the thermocline and an increasing of upwelling 10 6 to 9 8 ma 3 significant inflow of warm water to the eastern tropical pacific caused by an intensified northern equatorial countercurrent necc resulting in the formation of epwp 9 8 to 4 2 ma and 4 the reduction of the epwp and the necc and an increase in upwelling 4 2 to 0 ma the timing of these paleoceanographic events indicated the strong relations with the opening and closing of the indonesian and central american panama seaways the reduction of the epwp this study and the deepening of the thermocline in western pacific at about 4 2 ma cannariato and ravelo 1997 chaisson and ravelo 2000 indicated a change from a state resembling el nino in the late miocene and the early pliocene time to a state resembling la nina by the late pliocene c 2009 elsevier b v all rights reserved

constant head test at a partially penetrating well in an aquifer aquitard system abstract an analytical model for describing pumping induced drawdown by constant head test at a partially penetrating well in a leaky confined aquifer is developed by treating the leakage of aquitard storage as an interface phenomenon rather than an volumetric effect which is the novel and never developed so far three different cases of remote lateral boundaries are considered in the model the new drawdown solution in laplace space is obtained and inverted into time domain solution utilizing the stehfest method the semi analytical solutions for well discharge are then obtained under three different cases analytical solutions in laplace and time domains are developed for calculating the total leakage rate and volume across the aquitard aquifer interface due to constant head test at a partially penetrating well in a leaky confined aquifer and such solutions are of great use for groundwater resource management based on the newly developed solutions the distribution of wellbore flowrate and aquitard leakage are explored and the sensitivity analysis is conducted to identify the most important controlling factor the sensitivity analysis shows that the wellbore flowrate and the drawdown in infinite case 1 finite case 2 and closed case 3 leaky confined aquifer systems are both sensitive to the variation of well partial penetration well radius and aquifer anisotropic ratio during the whole pumping period and they are most sensitive to the change of outer boundary distance at late time for case 3 the effect of the outer boundary on the drawdown or wellbore flowrate is more significant for a shorter outer boundary distance

carya as marker for tree refuges in southern italy boiano basin at the middle pleistocene abstract the carya genus a tree of the juglandaceae family has a restricted geographical distribution today mainly confined to north america and southeast asia and with a precise range of ecological requirements during the neogene carya had a wide distribution across the northern hemisphere however its habitat was reduced progressively in response to pliocene and quaternary climate changes in the early and middle pleistocene paleobotanical records carya is considered a relic which testifies to the final climatic deterioration of the pliocene and to the global effect of the quaternary climate cycles the lacustrine and fluvio palustrine sequence of boiano molise italy records the paleoenvironmental and climate changes since the middle pleistocene the chronological framework is based on several tephra layers related to known eruptions or directly dated and indicates that the basal deposits are older than 440 ka palynological study of the sedimentary filling highlights vegetation changes from oxygen isotopic stage ois 13 to 2 the boiano biotope characterized by a continuous edaphic and climatic humidity favored the persistence of hygrophilous tree taxa thus carya is present until the ois 9 which represents its latest occurrence in western europe the boiano basin could have been an ecological refuge for the middle pleistocene arboreal flora in fact the physiography of the basin certainly softened the impacts of climatic deterioration during glacial episodes therefore the late carya occurrence within the boiano palynological record in a time period when it is commonly supposed to be extinct from europe leads to a consideration of its ecological requirements as a tool for quaternary paleoenvironmental reconstructions and for identification of refuge areas

response to comment by h lough department of civil engineering university of canterbury christchurch new zealand on the paper stream depletion predictions using pumping test data from a heterogeneous stream aquifer system a case study from the gr we thank h lough for her interest in our data set and the attempt to re analyze our results kollet and zlotnik 2003 using the recent model by hunt 2003 we welcome others to share our unique data set of the pumping test from the prairie creek site nebraska usa nevertheless we believe that this particular attempt failed because h lough selected a wrong model of semi confined aquifer conditions for the interpretation of the pumping test data which was collected in an unconfined aquifer h lough based her selection on the three distinct drawdown segments observed during the test it is well known that geologically distinct aquifers can yield a three segment drawdown response under pumping conditions e g streltsova 1988 examples include unconfined aquifers e g neuman 1972 moench 1997 aquifers with double porosity or fractures e g barenblatt et al 1960 boulton and streltsova adams 1978 and semi confined aquifers in contact with aquitards e g cooley and case 1973 moench 1985 at the prairie creek site the aquifer is unconfined the interpretation of the pumping test data collected at the site using type curves that are valid for an aquifer aquitard system is a mistake in fact this approach illustrates a typical problem associated with more inverse modeling drastically different models can closely reproduce a system response and yield some parameter estimates although the models do not represent the real system adequately here the improper model yields some parameter estimates for an aquitard although the aquitard does not exist at the prairie creek test site we must also unequivocally state that the model by hunt 2003 is clearly formulated and correct for stream aquifer aquitard systems within the stated limitations pumping wells screened only in the lowest stratigraphic layer etc however the hunt 1999 or bzt butler et al 2001 models should be used for interpreting pumping tests near streams in non leaky aquifers as outlined in our study kollet and zlotnik 2003 the purpose of the comment by h lough is to examine three drawdown segments and results from kollet and zlotnik 2003 using a newer analytical model of stream aquifer interactions by hunt 2003 we will address the key issues of this comment in this paper less

unusual drawdown curves for a pumping test in an unconfined aquifer at lachenaie quebec field data and numerical modeling an unconfined aquifer was instrumented with monitoring wells over a surface area of about 100 m 100 m the aquifer is a sand deposit overlying a thick nonfissured layer of champlain sea clay the paper presents the results of a pumping test at a constant flow rate none of the curves of drawdown versus time presented the s shape of current theories however all drawdowns indicated that the aquifer was homogeneous the values for the specific yield were too low and varied with distance and time instead of being constant the theories for steady and unsteady states provided different values for the saturated hydraulic conductivity to understand the field behavior that differs from theoretical predictions the pumping test conditions were modeled numerically using a finite element method the transmissivity was derived from the dupuit equation and different curves for capillary retention and unsaturated permeability were examined the numerical drawdowns agree with the experimental drawdowns several nu

timing and development of the heise volcanic field snake river plain idaho western usa the snake river plain srp developed over the last 16 ma as a bimodal volcanic province in response to the southwest movement of the north american plate over a fixed melting anomaly volcanism along the srp is dominatedby eruptions of explosive high silica rhyolites and represents some of the largest eruptions known basaltic eruptions represent the final stages of volcanism forming a thin cap above voluminous rhyolitic deposits volcanism progressed generally from west to east along the plain episodically in successive volcanic fields comprised of nested caldera complexes with major caldera forming eruptions within a particular field separated by ca 0 5 1 ma similar to and in continuation with the present day yellowstone plateau volcanic field passage of the north american plate over the melting anomaly at a particular point in time and space was accompanied by uplift regional tectonism massive explosive eruptions and caldera subsidence and followed by basaltic volcanism and general subsidence the heise volcanic field in the eastern srp idaho represents an adjacent and slightly older field immediately to the southwest of the yellowstone plateau volcanic field five large volume 0 5 km 3 rhyolitic ignimbrites constitute a time stratigraphic framework of late miocene to early pliocene volcanism for the study region field relations and high precision 4 0 ar 3 9 ar age determinations establish that four of these regional ignimbrites were erupted from the heise volcanic field and form the framework of the heise group these are the blacktail creek tuff 6 62 0 03 ma walcott tuff 6 27 0 04 ma conant creek tuff 5 51 0 13 ma and kilgore tuff 4 45 0 05 ma all errors reported at 2a the fifth widespread ignimbrite in the region is the arbon valley tuff member of the star light formation 10 21 0 03 ma which erupted from a caldera source outside of the heise volcanic field these results establish the conant creek tuff as a distinct and widespread ignimbrite in the heise volcanic field eliminating former confusion resulting from previous discordant k ar and fission track dates new 4 0 ar 3 9 ar determinations when combined with geochemical lithologic geophysical and field data define the volcanic and tectonic history of the heise volcanic field and surrounding areas volcanic units erupted from the heise volcanic field also provide temporal control for tectonic events associated with late cenozoic extension in the snake range and with uplift of the teton range wyoming in the snake range movement of large 0 10 km 3 slide blocks of mississippian limestone exposed 50 km to the east of the heise field occurred between 6 3 and 5 5 ma and may have been catastrophically triggered by the caldera eruption of the 5 51 0 13 ma conant creek tuff this slide block movement of 300 vertical meters indicates that the snake range had significant relief by at least 5 5 ma in jackson hole the distribution of outflow facies of the 4 45 0 05 ma kilgore tuff related to eruption from the kilgore caldera in the heise volcanic field on the eastern srp indicates that the northern teton range was not a significant topographic feature at this time

late neogene changes in diatom sedimentation in the north pacific abstract during the late neogene north pacific diatom sedimentation underwent major changes in response to high latitude cooling and changes in surface and deep water circulation at 9 ma diatom mass accumulation rates mars increased in the nw pacific and off northeast japan possibly due to shoaling of the isthmus of panama which lead to an enrichment of nutrients in north pacific deep waters during the latest miocene diatom mars increased progressively off southem california 6 5 ma at high latitudes of the north pacific 6 2 ma and off northeastern japan 5 5 ma presumably in response to high latitude cooling at about 4 5 ma diatom sedimentation abruptly increased in the nw pacific but declined off japan and california coincident with the onset of a prolonged period of high latitude warmth enhanced upwelling of nutrient rich deep waters in the nw pacific probably stimulated diatom production there a major step in high latitude cooling at 2 7 ma caused a reversal of these mid pliocene diatom sedimentation patterns upwelling of deep nutrient rich waters waned at higher latitudes leading to a decline in diatom productivity while wind driven coastal upwelling increased off southern california and stimulated diatom growth

thermal plume transport from sand and gravel pits potential thermal impacts on cool water streams summary we investigated the potential thermal impacts from below water table aggregate extraction on a cool water stream supporting brook trout salvelinus fontinalis and cool water macroinvertebrates we monitored thermal plumes emanating from an aggregate pit through an unconfined glacial outwash aquifer our objectives were to complete a detailed assessment to quantify the persistence of thermal plumes in the subsurface and establish a framework for guiding these investigations as the growing demand for aggregate increases pressures to pursue extraction in ecologically sensitive areas during a 10 year period we measured ground and surface water temperatures in an outwash aquifer and cool water stream including two periods of intensive monitoring 22 months and 2 5 years focusing on plume movement from one aggregate pit we quantified the aquifer hydraulic conductivity k at the laboratory and field scale and characterized the effective thermal conductivity at an unprecedented level of detail the mean k s from the multi scale tests span two orders of magnitude 1 8 10 4 to 1 7 10 2 m s 1 and are related to the test support volume the saturated has a mean of 2 42 w m 1 k 1 ranges from 2 14 to 2 69 w m 1 k 1 and is correlated to stratigraphic units gravel sand and till the annual temperature amplitude in the pit is 10 c above up gradient ground water and our results show that alternating warm and cool plumes persist in the aquifer for 11 months and migrate up to 250 m down gradient the observed plume velocity 1 2 m d 1 lags the ground water velocity 2 8 m d 1 due to thermal retardation furthermore hydraulic conductivity is shown to vary with the scale of the test and ground water velocities estimated from pumping tests may overestimate thermal plume velocities while we focused on plume migration our results demonstrate that assessing impacts on the aquatic community requires an integrated multi disciplinary study this work can guide such assessments

oscillatory pumping wells in phreatic compressible and homogeneous aquifers oscillatory well pumping was proposed recently as a tool for hydraulic tomography periodic pumping at a few frequencies is carried out through vertical intervals along the pumping well and the periodic head is measured along a few piezometers the paper presents an analytical solution for the head field in an unconfined aquifer of finite depth under the common assumptions of a linearized water table condition different horizontal and vertical constant permeabilities constant specific storativity and water table drainable porosity and small well radius to length ratio the solution provides the expressions of the amplitude and phase of the head as a function of coordinates frequency and the problem parameters the solution simplifies to one pertaining to an upper constant head condition and a rigid aquifer for a wide range of the dimensionless frequency values

applicability of method to estimate transmissivity based on yield drawdown analysis in mountainous fractured rock aquifers a case study in taiwan abstract the observation of yield drawdown response in the course of pumping test as well as its derived application for aquifer characterization is an essential practice in a geotechnical investigation on the basis of that for providing a reasonable estimate of aquifer transmissivity on site a number of empirical models have therefore been proposed yet the majority of previous studies are conducted based on investigations at homogeneous alluvial plain very few particularly in the case of taiwan are carried out focusing on mountainous fractured rock aquifers aiming to address this problem the observation data of 53 pumping tests obtained from a multi years in situ geological investigation program are analyzed and the applicability of empirical log log linear relationship between t and q s is examined our analysis reveals that the yield drawdown responses derived from different geologic formations are quantitatively distinct and those empirical rules derived from the alluvial landform should be used with care when applying in mountainous fractured rock aquifers based on the analysis of statistical results in our study with a systematic investigation and clarification of the q s relationship in advance a satisfactory and cost effective solution is obtained

optimization of groundwater sampling approach under various hydrogeological conditions using a numerical simulation model abstract this study presents a numerical model based on field data to simulate groundwater flow in both the aquifer and the well bore for the low flow sampling method and the well volume sampling method the numerical model was calibrated to match well with field drawdown and calculated flow regime in the well was used to predict the variation of dissolved oxygen do concentration during the purging period the model was then used to analyze sampling representativeness and sampling time site characteristics such as aquifer hydraulic conductivity and sampling choices such as purging rate and screen length were found to be significant determinants of sampling representativeness and required sampling time results demonstrated that 1 do was the most useful water quality indicator in ensuring groundwater sampling representativeness in comparison with turbidity ph specific conductance oxidation reduction potential orp and temperature 2 it is not necessary to maintain a drawdown of less than 0 1 m when conducting low flow purging however a high purging rate in a low permeability aquifer may result in a dramatic decrease in sampling representativeness after an initial peak 3 the presence of a short screen length may result in greater drawdown and a longer sampling time for low flow purging overall the present study suggests that this new numerical model is suitable for describing groundwater flow during the sampling process and can be used to optimize sampling strategies under various hydrogeological conditions

reply to comment by h lough department of civil engineering university of canterbury christchurch new zealand on the paper stream depletion predictions using pumping test data from a heterogeneous stream aquifer system a case study from the great plains usa by s j kollet and v a zlotnik 281 96 114

hydrogeologic controls on disconnection between surface water and groundwater 1 understanding how changes in the groundwater table affect surface water resources is of fundamental importance in quantitative hydrology if the groundwater table below a stream is sufficiently deep changes in the groundwater table position effectively do not alter the infiltration rate this is referred to as a disconnected system previous authors noted that a low conductivity layer below the surface water body is a necessary but not sufficient criterion for disconnection to occur we develop a precise criterion that allows an assessment of whether surface water groundwater systems can disconnect or not we further demonstrate that a disconnected system can be conceptualized by a saturated groundwater mound and the development of a capillary zone above this mound this conceptualization is used to determine the critical water table position at the point where full disconnection is reached a comparison of this calculated critical water table position with a measurement of the water table depth in a borehole allows the assessment of the disconnection status a sensitivity analysis of this critical water table showed that for a given aquifer thickness and river width the depth to groundwater where the system disconnects is approximately proportional to the stream depth and the hydraulic conductivity of the streambed sediments and inversely proportional to the thickness of these sediments and the hydraulic conductivity of the aquifer the conceptualization also allows the disconnection problem to be analyzed using both variably saturated and fully saturated groundwater models and provides guidance for numerical and analytical approaches

pliocene and pleistocene paleoceanography in the western subarctic pacific based on diatom analyses of odp leg 145 hole 884b and iodp expedition 323 holes u1341b and u1343e abstract late pliocene pleistocene fossil diatom assemblages from ocean drilling program odp leg 145 hole 884b in the western subarctic pacific were investigated to improve the diatom biostratigraphy moreover the paleoceanographic records at hole 884b were compared with those in integrated ocean drilling program iodp expedition 323 holes u1341b and u1343e in the bering sea for the time interval of 2 5 0 ma in order to clarify the differences in the diatom assemblage fluctuations and the history of past ocean circulations around the subarctic pacific in hole 884b five diatom zones from the neodenticula koizumii neodenticula kamtschatica zone to the neodenticula seminae zone were identified the decreases in the relative abundance of temperate water species were recognized at ca 1 9 ma in hole u1343e ca 2 1 ma in holes 884b and u1341b the decreases of the temperate water species at these sites indicate that a widespread cooling event must have occurred over the subarctic pacific at 2 ma in addition the continuous low occurrences of the sea ice related species from around 2 ma onward which indicate the presence of sea ice were observed at sites 884 and u1341 we also point out that the age differences in decrease of temperate water species at the three sites i e delay in response of the temperate water species at site u1343 may be related to changes of seawater inflow from the north pacific to sites u1341 and u1343 and of the east kamchatka current from the bering sea to site 884

analysis of flow near a dug well in an unconfined aquifer a numerical analysis of flow to a dug well in an unconfined aquifer is made taking into account well storage elastic storage release gravity drainage anisotropy partial penetration vertical flow and seepage surface at the well face and treating the water table in the aquifer and water level in the well as unknown boundaries the pumped discharge is maintained constant the solution is obtained by a two level iterative scheme the effects of governing parameters on the drawdown development of seepage surface and contribution from aquifer flow to the total discharge are discussed the degree of anisotropy and partial penetration are found to be the parameters which affect the flow characteristics most significantly the effect of anisotropy on the development of seepage surface is very pronounced

spatial variations of holocene climatic change in the yellowstone region abstract the paleoecologic record of the northern rocky mountains shows considerable spatial variability which has been difficult to explain as a unified response to large scale changes in effective moisture or temperature through time comparison of past and present climatic patterns suggests that the spatial heterogeneity in the fossil record arises from a local response to the effects of greater summer solar radiation during the early holocene solar radiation directly determines evapotranspiration and indirectly controls the strength of the summer monsoon and the eastern pacific subtropical high pressure system the yellowstone region provides an example of an area where the indirect effects of solar radiation are manifest by the juxtaposition of two contrasting climatic regimes today and where these regimes were amplified during the early holocene fossil pollen data suggest that central and southern yellowstone the summer dry area became drier in the early holocene while northern yellowstone the summer wet area became wetter the boundary between regimes however is controlled by topography and has not changed significantly in the holocene the spatial variations of holocene vegetation and climatic changes in the northern rocky mountains may therefore be explained as a trade off between strengthened monsoonal circulation and a stronger subtropical high in the early holocene and the relative importance of these precipitation regimes on a topographically complex landscape

miocene deepwater oceanography a global synthesis of miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that miocene thermohaline circulation evolved through three regimes corresponding approximately to early middle and late miocene times there is evidence for major qualitative differences between the circulation of the modern ocean and the miocene ocean prior to 11 ma the 13c 12c ratios of the benthic foraminifera cibicidoides are interpreted in terms of water mass aging i e the progressive depletion of dissolved o2 and lowering of 13c values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans both isotopic and faunal data indicate that the early miocene regime from 22 to 15 ma was the most different from today s during that interval intermediate and deep waters of both the atlantic and the pacific oceans aged in a northward direction and the intermediate waters of the indian the south atlantic and the south pacific oceans were consistently the youngest in the global ocean we speculate that early miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water tethyan indian saline water from the tethys into the northern indian ocean the isotopic and faunal data suggest that flow from the tethyan region into the indian ocean diminished or terminated at about 14 ma isotopic and faunal data give no evidence for north atlantic deep water nadw formation prior to about 14 5 ma with the exception of a brief episode in the early miocene from 14 5 to 11 ma nadw formation was weak and circumpolar and antarctic water flooded the deep south atlantic and south pacific as the antarctic ice cap grew from about 10 ma to the end of the miocene thermohaline circulation resembled the modern circulation in many ways in latest miocene time 6 to 5 ma circulation patterns were very similar to today s except that nadw formation was greatly diminished the distribution pattern of siliceous oozes in miocene sediments is consistent with our proposed reconstruction of thermohaline circulation major changes which occurred in circulation during the middle miocene were probably related to the closing of the tethys and may have contributed to rapid middle miocene growth of the antarctic ice cap appendices 1 4 6 and 7 are available withentire article on microfiche order fromamerican geophysical union 2000 floridaavenue n w washington dc 20009 document 88p 002 5 00 payment mustaccompany order

paleoceanographic implications of miocene deep sea hiatuses miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages the subsequent changes in oceanic circulation and development of major antarctic glaciation the consequences and timing of these events can be observed in variations in the distribution of deep sea hiatuses sedimentation patterns and biogeographic distribution of planktic organisms the opening of the drake passage in the latest oligocene to early miocene 25 20 ma resulted in the establishment of the deep circumpolar current which led to thermal isolation of antarctica and increased global cooling this development was associated with a major turnover in planktic organisms resulting in the evolution of neogene assemblages and the eventual extinction of paleogene assemblages the erosive patterns of two widespread hiatuses ph 23 0 22 5 ma and nh 1 20 18 ma indicate that a deep circumequatorial circulation existed at this time characterized by a broad band of carbonate ooze deposition siliceous sedimentation was restricted to the north atlantic and a narrow band around antarctica a major reorganization in deep sea sedimentation and hiatus distribution patterns occurred near the early middle miocene boundary apparently resulting from changes in oceanic circulation beginning at this time deep sea erosion occurred throughout the caribbean hiatus nh 2 16 15 ma suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents and or intensification of the gulf stream sediment distribution patterns changed dramatically with the sudden appearance of siliceous ooze deposition in the marginal and east equatorial north pacific by 16 0 to 15 5 ma coincident with the decline of siliceous sedimentation in the north atlantic this silica switch may have been caused by the introduction of norwegian overflow water into the north atlantic acting as a barrier to outcropping of silica rich antarctic bottom water the main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13 5 to 12 5 ma hiatus nh 3 coincident with the establishment of a major east antarctic ice cap antarctic glaciation resulted in a broadening belt of siliceous ooze deposition around antarctica increased siliceous sedimentation in the marginal and east equatorial north pacific and indian oceans and further northward restriction of siliceous sediments in the north atlantic periodic cool climatic events were accompanied by lower eustatic sea levels and widespread deep sea erosion at 12 to 11 ma nh 4 10 to 9 ma nh 5 7 5 to 6 2 ma nh 6 and 5 2 to 4 7 ma nh 7

effect of volcanic dykes on coastal groundwater flow and saltwater intrusion a field scale multiphysics approach and parameter evaluation volcanic dykes are common discrete heterogeneities in aquifers however there is a lack of field examples of and methodologies for comprehensive in situ characterization of their properties with respect to groundwater flow and solute transport we have applied an integrated multi physics approach to quantify the effect of dolerite dykes on saltwater intrusion in a coastal sandstone aquifer the approach involved ground geophysical imaging passive magnetics and electrical resistivity tomography well hydraulic testing and tidal propagation analysis which provided constraints on the geometry of the dyke network the subsurface saltwater distribution and the sandstone hydrodynamic properties and connectivity a three dimensional variable density groundwater model coupled with a resistivity model was further calibrated using groundwater and geophysical observations a good agreement of model simulations with tide induced head fluctuations geophysically derived pore water salinities and measured apparent resistivities was obtained when dykes hydraulic conductivity storativity and effective porosity are respectively about three one and one orders of magnitude lower than the host aquifer the presence of the dykes results in barrier like alterations of groundwater flow and saltwater intrusion preferential flowpaths occur parallel to observed dyke orientations freshwater inflows from upland recharge areas concentrate on the land facing side of the dykes and saltwater penetration is higher on their sea facing side this has major implications for managing groundwater resources in dyke intruded aquifers including in coastal and island regions but also provides wider insights on preferential pathways of groundwater flow and transport in highly heterogeneous aquifer systems this article is protected by copyright all rights reserved

isotopic paleoceanography of the caribbean and east pacific role of panama uplift in late neogene time comparisons of carbon isotopic data on benthic foraminifera from deep sea drilling project sites 502 western caribbean and 503 eastern pacific indicate that the difference between the atlantic and the pacific in the per mil enrichment in carbon 13 of total dissolved carbon dioxide increased about 6 million years ago and again 3 million years ago when the difference reached the modern level 1 per mil comparisons of planktonic foraminiferal oxygen isotopic data for the caribbean and the pacific suggest that the salinity of caribbean surface waters began increasing 4 million years ago possibly in response to shoaling of the panama isthmus these results suggest that modern circulation patterns in the caribbean and eastern pacific developed by 3 million years ago in concert with changing tectonic climatic and biogeographic patterns

transient flow into a partially penetrating well during the constant head test in unconfined aquifers this study derives a semianalytical solution for drawdown distribution during a constant head test at a partially penetrating well in an unconfined aquifer the constant head condition is used to describe the boundary along the screen in addition a free surface condition is used to delineate the upper boundary of the unconfined aquifer the laplace domain solution is then derived using separation of variables and laplace transform this solution can be used to identify the aquifer parameters from the data of the constant head test when integrated with an optimization scheme or to investigate the effects of vertical flow caused by the partially penetrating well and free surface boundary in an unconfined aquifer

a concept of maximum stream depletion rate for leaky aquifers in alluvial valleys 1 existing analytical models for evaluating stream depletion by wells in alluvial aquifers are based on the assumption that stream depletion supplies 100 of groundwater withdrawals analysis of specific hydrostratigraphic conditions in leaky aquifers indicates that stream depletion may range from 0 to 100 a new concept of maximum stream depletion rate msdr is introduced and defined as a maximum fraction of the pumping rate contributed by the stream depletion several new analytical solutions indicate that the msdr is determined by aquifer hydrostratigraphic conditions geometry of recharge and discharge zones and locations of pumping wells

evolutionary changes in the biometry of the fossil radiolarian stichocorys peregrina lineage in the eastern equatorial and eastern north pacific abstract stichocorys peregrina riedel contributes to paleoceanography as a valuable stratigraphic tool for correlation of deep sea siliceous sediments in world oceans and as a paleoceanographic indicator this paper documents the evolutionary morphologic changes of the s peregrina lineage from the middle miocene to late pliocene in the eastern equatorial and eastern north pacific iodp site u1335 and odp site 887 respectively the size and shape changes show that there are at least two geographical variations in the s peregrina lineage in the eastern equatorial pacific two significant morphological shifts took place about 11 0 and 7 0 ma but the morphology remained relatively stable from 7 0 to 3 0 ma coincident with morphological changes in the s peregrina lineage were changes in biogenic productivity these changes suggest that there is a close correspondence between major paleoceanographic events in the late neogene and evolutionary changes of the s peregrina lineage in the low latitudes in the high latitudes the ratio of the third segment to fourth segment in width and height showed a maximum from 9 5 to 8 0 ma and decreased stepwise at about 8 0 and 6 5 ma however the radiolarian data in the high latitudes do not show a clear relationship between the paleoceanographic events and size variation of this lineage the evolutionary transition from stichocorys delmontensis to s peregrina can be used as a primary biostratigraphic marker in the low latitudes however it is not easy to use the evolutionary transition for biostratigraphic correlation and age determination in the high latitudes because there is no obvious change in the ratio of the third to fourth segment widths that can be used to distinguish s delmontensis from the descendant s peregrina

spatial patterns of atmospheric pollen transport in a montane region abstract annual pollen deposition pollen cm 2 yr 1 was sampled for 6 yr in the southern sierra nevada the owens valley and the inyo mountains of central california spatial pollen distributions were examined for anemophilous plants which are limited to growth sites 1 at high elevations on one or both mountain ranges 2 on lower mountain slopes and 3 on the owens valley floor pollen deposition values for high and low elevation plants changed by a factor of 5 to 10 between adjacent sample sites which straddle boundaries of the plant communities in which the source plants grow pollen deposition values were high and variable within communities in which the species grew pollen deposition beyond source populations was low and uniform despite great differences in distance of sites from pollen sources the step function that seems to characterize pollen distribution patterns implies that pollen from distant populations may be of little value in interpreting vegetation stability and change reflected by fossil pollen stratigraphy the physical isolation of pollen embedded in the local mountain valley wind system from that in the prevailing westerlies may explain part of the spatial distribution of the pollen

sangamonian and wisconsinan paleoenvironments in yellowstone national park pollen and plant macrofossil records from yellowstone national park if combined with dated glacial events provide a paleoenvironmental record of much of the last glacial interglacial cycle bull lake glaciation has been dated at 140 000 yr b p section ep 6 records a late glacial to full interglacial sequence which is correlated with the sangamonian interglacial and estimated to be 127 000 yr old at the peak warm period a prevailing pseudotsuga pinus flexilis pinus ponderosa forest suggests that climate was considerably warmer than any in the holocene section ep 5 is somewhat younger probably late sangamonian and shows a forest dominated by picea abies pseudotsuga and a haploxylon pinus slightly cooler conditions than those of the present are indicated the warmest phase of the grassy lake reservoir section is considered to be 82 000 yr old and records a warm interstadial cycle beginning with tundra the warming sequence is indicated by change to a picea abies pinus albicaulis forest and then to a pinus contorta forest the cycle ends with forest destruction and a return to open tundra and presumably cold conditions extremely low values of arboreal pollen indicate that tundra vegetation and cold conditions continued from 70 000 to 50 000 yr b p one cool and apparently short interstadial interrupted this extended period of tundra shortly after 68 000 b p when a very open parkland of picea abies pinus albicaulis appeared no records of environment are available between 50 000 and 30 000 yr b p the pinedale icecap apparently expanded 30 000 yr b p and lasted until 14 000 yr b p late glacial picea abies pinus albicaulis parklands gave way to pinus contorta forests that have prevailed with minor variation for 10 000 yr

possible regional tectonic controls on mammalian evolution in western north america abstract previous work has suggested that tectonically active regions act as speciation pumps for mammals and plant species but little is known about how fast or widespread tectonism must be in order to directly influence evolution here we use oxygen and hydrogen isotopic data from miocene sedimentary deposits to characterize the topographic evolution of the southern columbia plateau snake river plain and northern rocky mountain regions during the yellowstone hotspot passage with the ultimate goal of understanding whether topographic changes caused by the hotspot influenced mammalian evolution within those regions we conducted oxygen isotope analyses of 130 samples of lacustrine and paleosol carbonate from miocene stratigraphic sections that span much of the northern rocky mountain region and combined these data with previously published isotopic records collectively these isotopic data show that caldera formation associated with the yellowstone hotspot has modified regional topography and rearranged drainages along the track of the hotspot and that the hotspot has left a topographic depression in its wake we explore the extent to which these topographic changes influenced or are decoupled from diversity changes exhibited by the local mammal faunas and conclude that the passage of the hotspot and consequent surface uplift created rainshadows in the lee of high elevation calderas and or generated large volumes of volcanic materials influencing soils and vegetation collectively that may explain a possible rise in mammal diversity in the cp srp region at 14 ma coincident with a drop in diversity in the nrm it is still unclear however how different taphonomic pathways and sample standardization problems are influencing apparent diversity peaks at this temporal and geographic resolution

quantifying variable erosion rates to understand the coupling of surface processes in the teton range wyoming short term geomorphic processes fluvial glacial and hillslope erosion and long term exhumation control transient alpine landscapes long term measurements of exhumation are not sufficient to capture the processes driving transient responses associated with short term climatic oscillations because of high variability of individual processes across space and time this study compares the efficacy of different erosional agents to assess the importance of variability in tectonically active landscapes responding to fluctuations in quaternary climate we focus on the teton range where erosional mechanisms include hillslope glacial and fluvial processes erosion rates were quantified using sediment accumulation and cosmogenic dating bedrock and stream sediments results show that rates of erosion are highly variable with average short term rockfall rates 0 8 mm y occurring faster than either apparent basin averaged 0 2 mm y and long term ridge erosion rates 0 02 mm y examining erosion rates separately also demonstrates the coupling between glacial fluvial and hillslope processes apparent basin averaged erosion rates amalgamate valley wall and ridge erosion with stream and glacial rates climate oscillations drive the short term response of a single erosional process e g rockfalls or other mass wasting that may enhance or limit the erosional efficiency of other processes glacial or fluvial while the teton landscape may approach long term equilibrium stochastic processes and rapid response to short term climate change actively perpetuate the transient ruggedness of the topography

transient flow of water to a well in an unconfined aquifer applicability of some conceptual models currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term the parameter specific yield sy is assumed to dictate the total quantity of water that is derivable through the desaturation process it is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping in a model proposed in 1954 boulton empirically assumed that the drainable water associated with sy is released gradually at the water table as an exponential function of time this concept of boulton is similar to the notion of first order kinetics frequently used to handle chemical transformations boulton s model is considered by some to have no physical basis numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time dependent process which is mathematically more complex than a simple exponential relation although boulton did not provide a rational physical explanation his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone however the simple exponential approximation is not adequate to account for what is seemingly a complex process it appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time dependent drainage from above the water table with vertical components of flow in the saturated zone an additional assumption frequently made is that the well can be treated as a line source results from numerical experiments suggest that caution is in order before neglecting effects of well bore storage in interpreting data from tests on unconfined aquifers

aquitard effect on drawdown in water table aquifers 1 the effects of an aquitard on drawdown in an overlying unconfined aquifer can be represented by a drainage type term at the aquitard aquifer interface the functional form of this boundary condition is similar to the boulton neuman boundary condition used for water table aquifers except the kernel contains an inverse square root of time instead of a negative exponential type curves using the new boundary condition were obtained in semianalytical form examples for several representative conditions show that the effect of the underlying aquitard can contribute to the type curve at early and intermediate times but the effect becomes negligible at late times

boundary depletion rate and drawdown in leaky wedge shaped aquifers this study presents analytical solutions of the three dimensional groundwater flow to a well in leaky confined and leaky water table wedge shaped aquifers leaky wedge shaped aquifers with and without storage in the aquitard are considered and both transient and steady state drawdown solutions are derived unlike the previous solutions of the wedge shaped aquifers the leakages from aquitard are considered in these solutions and unlike similar previous work for leaky aquifers leakage from aquitards and from the water table are treated as the lower and upper boundary conditions a special form of finite fourier transforms is used to transform the z coordinate in deriving the solutions the leakage induced by a partially penetrating pumping well in a wedge shaped aquifer depends on aquitard hydraulic parameters the wedge shaped aquifer parameters as well as the pumping well parameters we calculate lateral boundary dimensionless flux at a representative line and investigate its sensitivity to the aquitard hydraulic parameters we also investigate the effects of wedge angle partial penetration screen location and piezometer location on the steady state dimensionless drawdown for different leakage parameters results of our study are presented in the form of dimensionless flux dimensionless time and dimensionless drawdown leakage parameter type curves the results are useful for evaluating the relative role of lateral wedge boundaries and leakage source on flow in wedge shaped aquifers this is very useful for water management problems and for assessing groundwater pollution the presented analytical solutions can also be used in parameter identification and in calculating stream depletion rate and volume copyright 2011 john wiley sons ltd

recognizing and modeling variable drawdown due to evapotranspiration in a semiarid riparian zone considering local differences in vegetation and distance from a river source 1 riparian zones in semiarid regions often exhibit high rates of evapotranspiration et in spite of low soil moisture content due to the presence of phreatophytic vegetation that is able to withdraw water from shallow aquifers this work seeks to better define the relationship between et the saturated zone and the river boundary by comparing observed water table drawdown records to analytically modeled drawdown in fully penetrating wells of an unconfined aquifer in response to daily et flux et at the boise hydrogeophysical research site bhrs a riparian zone in a temperate semiarid environment is calculated using a radiation based method to provide et values at four different wells with different vegetation densities analytically modeled drawdown response to et forcing shows that drawdown magnitude increases with increasing distance from the river edge even as the surficial et forcing remains constant this behavior is also observed in well hydrographs and shows the buffering effect that flow from the river has on drawdown in fully penetrating riparian wells in highly permeable unconfined aquifers relative contributions of river water to aquifer storage are calculated for et induced diurnal fluctuations of the water table at increasing distances from the river boundary failure to account for these spatial differences in drawdown related to the river source may explain some errors associated with estimating et from well hydrographs alone

three dimensional response to a partially penetration well pumping in a general anisotropic three layer aquifer system abstract three dimensional response to well pumping in a multilayer aquifer system with rigorous treatment of interfacial flow attracts great attention among the subsurface hydrologists because of its theoretical importance and practical merits in this study a general theory of three dimensional groundwater flow to a well of infinitesimal radius in an anisotropic three layer aquifer system is developed with a constant rate pumping in the lower layer and associated semi analytical solutions of drawdowns in individual layers are obtained this theory discards many previous assumptions for studying a multilayer aquifer system such as simplified flow configuration in the aquitard treatment of cross formation flow as a volumetric averaged term adding to the governing equations of aquifer flows and sometimes negligence of vertical flow components in the aquifers additionally this theory considers three types of commonly used top boundary conditions a water table with delayed gravity drainage boundary condition case 1 a constant head top boundary condition case 2 and a no flow top boundary condition case 3 the dimensionless drawdown solutions in laplace domain are obtained and inverted numerically to calculate the time domain solutions the solution encompasses existing solutions for a two layer or a single layer e g unconfined or confined aquifer system as subsets the developed solutions are tested extensively with a finite element numerical solution using comsol and other existing solutions and a sensitivity analysis is performed to prioritize the influences of different parameter groups the results of this study can be used to predict the pumping induced drawdown at any position with an observation well and to estimate the hydraulic parameters of the lower pumped layer and upper layer as well as the middle layer the developed theory provides a basis for other potential applications such as geotechnical engineering and groundwater management

plio pleistocene climatic transition and the lifting of the teton range wyoming abstract fine grained lacustrine riverine and ash fall sediments of the shooting iron formation whose late pliocene age is established by blancan gastropods and vertebrates yield a pollen flora that is essentially similar in composition to the modern pollen rain in the jackson hole area the pliocene assemblage suggests a climate like that of the jackson valley and foothills today these spectra also resemble a pliocene pollen flora from yellowstone park dated at 2 02 ma however the underlying miocene teewinot sediments differ by containing pollen of four exotic deciduous hardwoods tertiary relicts that suggest a summer moist climate unlike that of today the shooting iron sediments lie with an angular unconformity on and above the miocene lake sediments of the teewinot formation both of these deposits probably preceded the main uplift of the teton range based on the absence of precambrian clasts in the tertiary valley deposits because the pliocene floras were modern in aspect a plio pleistocene transition would be floristically imperceptible here the sequence denotes a protracted period of relative stability of climate during teewinot time and a shift in vegetational state summer wet trees drop out sometime between the latest miocene and latest pliocene the pliocene spectra suggest a dry cooler climate toward the end of shooting iron time

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage

revised ages for tuffs of the yellowstone plateau volcanic field assignment of the huckleberry ridge tuff to a new geomagnetic polarity event 40 ar 39 ar ages were determined on the three major ash flow tuffs of the yellowstone plateau volcanic field in the region of yellowstone national park in order to improve the precision of previously determined ages total fusion and incremental heating ages of sanidine yielded the following mean ages huckleberry ridge tuff 2 059 0 004 ma mesa falls tuff 1 285 0 004 ma and lava creek tuff 0 639 0 002 ma the huckleberry ridge tuff has a transitional magnetic direction and has previously been related to the reunion normal polarity subchron dating of the reunion event has been reviewed and its ages have been normalized to a common value for mineral standards the age of the huckleberry ridge tuff is significantly younger than lava flows of the reunion event on re union island supporting other evidence for a normal polarity event younger than the reunion event