winding down the chicxulub impact the transition between impact and normal marine sedimentation near ground zero abstract the chicxulub impact led to the formation of a 200 km wide by 1 km deep crater on mexico s yucatan peninsula over a period of hours after the impact the ocean re entered and covered the impact basin beneath several hundred meters of water a suite of impactites were deposited across the crater during crater formation and by the resurge tsunami and seiche events that followed international ocean discovery program international continental scientific drilling program expedition 364 drilled into the peak ring of the chicxulub crater and recovered 130 m of impact deposits and a 75 cm thick fine grained carbonate rich transitional unit above which normal marine sedimentation resumed here we describe the results of analyses of the uppermost impact breccia suevite and the transitional unit which suggests a gradual waning of energy recorded by this local k pg boundary sequence the dominant depositional motif in the upper suevite and the transitional unit is of rapid sedimentation characterized by graded bedding local cross bedding and evidence of oscillatory currents the lower transitional unit records the change from deposition of dominantly sand sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward the middle part of the transitional unit is interrupted by a 20 cm thick soft sediment slump overlain by graded and oscillatory current cross laminated beds the uppermost transitional unit is also soft sediment deformed contains trace fossils and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors the transitional unit as with similar deposits in other marine target impact craters records the final phases of impact related sedimentation prior to resumption of normal marine conditions petrographic and stable isotopic analyses of carbon from organic matter provide insight into post impact processes 13corg values are between terrestrial and marine end members with fluctuations of 1 3 timing of deposition of the transitional unit is complicated to ascertain the repetitive normally graded laminae both below and above the soft sediment deformed interval record rapid deposition from currents driven by tsunami and seiches processes that likely operated for weeks to potentially years post impact due to subsequent continental margin collapse events highly siderophile element enrichment at the top of the unit is likely from fine grained ejecta that circulated in the atmosphere for several years prior to settling the transitional unit is thus an exquisite record of the final phases of impact related sedimentation related to one of the most consequential events in earth history

quantitative reconstruction of middle and late eocene paleoclimate based on palynological records from the huadian basin northeastern china evidence for monsoonal influence on oil shale formation abstract the eocene was an interval of climate evolution when the extreme high temperatures of the earliest cenozoic gave way to a global cooling trend fine grained lacustrine sediments of eocene age from northeastern china represent an excellent archive to study long term environmental and climatic changes at high resolution the huadian basin is a cenozoic fault bounded basin in jilin province northeastern china though small in area it contains numerous oil shale and coal bearing layers which provide an abundant middle to late eocene palynoflora eighty five palynomorph genera and one hundred palynomorph species were identified in the huadian formation allowing to distinguish 4 palynozones the nearest living relatives of the recovered palynomorph taxa suggest the presence of subtropical evergreen and deciduous broad leaved forests during deposition of the huadian formation using the coexistence approach ca we calculated seven paleoclimatic parameters which indicate a subtropical warm and humid climate with a mean annual temperature above 13 6 c and a mean annual precipitation of at least 887 mm however the climate became cooler and drier during the transition from the lower oil shale member to the upper carbonaceous shale member palaeoclimatic data from the various middle and late eocene basins of northeastern china i e the huadian fushun yilan hunchun and jishu basins were compared with data from north american and european basins middle eocene climate in the northern hemisphere was generally warm and humid and the mean annual temperature and precipitation in northeastern china were similar to those in north america though slightly lower than those of europe similar trends in temperature and precipitation on different continents support the existence of a global mid eocene cooling event this paper is the first systematic study of middle to late eocene seasonality in the huadian basin our results show an apparent differentiation in both temperature and precipitation between summer and winter supporting the view that the east asian monsoon was established in northeastern china already during the middle to late eocene this middle and late eocene monsoon was likely driven by the development of pacific trade winds and an alternating seasonal high and low pressure system over siberia the climatic changes observed in our dataset especially the precipitation changes appear to have played an important role in controlling oil shale formation in the huadian basin a warmer and more humid climate with abundant precipitation and high subsidence rates formed a deeper huadian depositional lake high productivity and stable stratification provided the abundant organic matter and favorable preservation conditions necessary for oil shale accumulation

initiation of dilute and concentrated pyroclastic currents from collapsing mixtures and origin of their proximal deposits numerical solution of the time dependent conservation equations for mass momentum specific internal energy and granular temperature in flows involving gas particle mixtures is used to explore the initiation of pyroclastic currents from collapsing mixtures such as during fountaining eruptions one objective is to determine when a depth averaged granular flow model or a box model for dilute currents is most applicable for hazards modeling of pyroclastic currents produced by column collapse a second objective is to gain insight into the formation of proximal breccia facies of ignimbrites collapsing gas particle mixtures impacting a flat surface are modeled with mixtures of coarse particles that are poorly coupled with the gas phase and well coupled fine particles resulting lateral flows are sensitive to the impact speed overall particle concentration and proportions of fine and coarse particles for total particle concentrations of around 1 vol an impacting mixture consisting of at least 50 coarse particles relative to fines will tend to form a concentrated lateral underflow which can be approximated by a depth averaged granular flow model for hazard assessment purposes starting from the impact zone low total particle concentrations e g total concentrations of 0 1 vol tend to produce dilute lateral flows that could be simplified to box model approaches for dilute pyroclastic currents larger total particle concentrations in impacting mixtures 10 vol produce granular underflows if they have any coarse particles but these can be complicated by mach number effects for intermediate concentrations of the impacting mixture a rough threshold for development of a concentrated underflow versus a dilute only current is based upon the flux per unit area of coarse particles to the impact and their stokes numbers in general some knowledge of the eruption column fountain conditions is required in order to make an informed decision as to which hazards modeling approach is most applicable for a given scenario modeling indicates that proximal breccias are related to influxes of coarse wall rock material into an eruptive mixture which increase both the total particle concentration and the proportion of coarse dense clasts in the mixture that subsequently collapses and impacts the ground the breccias record concentration of dominantly coarse clasts immediately upon impact and formation of concentrated flows that propagate laterally while expelled fines and gas flow rapidly overhead as dilute currents lateral and vertical heterogeneity in proximal deposits likely record rapid time and space variations in avalanches of material into eruptive vents and the occurrence of breccia hummocks might record the temporary positions of impact zones

formation of high grade ignimbrites part ii a pyroclastic suspension current model with implications also for low grade ignimbrites analogue experiments in part i led to the conclusion that pyroclastic flows depositing very high grade ignimbrite move as dilute suspension currents in the thermo fluid dynamical model developed the degree of cooling of expanded turbulent pyroclastic flows dynamically evolves in response to entrainment of air and mass loss to sedimentation initial conditions of the currents are derived from column collapse modeling for magmas with an initial h2o content of 1 3 wt erupting through circular vents and caldera ring fissures the flows spread either longitudinally or radially from source up to a runout distance that increases with higher mass flux but decreases with higher gas content temperature bottom slope and coarser initial grain size progressive dilution by entrainment and sedimentation causes pyroclastic currents to transform into buoyant ash plumes at the runout distance the ash plumes reach stratospheric heights and distribute 30 80 of the erupted material as widespread co ignimbrite ash pyroclastic suspension currents with initial mass fluxes of 107 1012 kg s can spread for tens of kilometers with only limited cooling although they move as supercritical strongly entraining currents for the eruption conditions considered here with increasing eruption mass flux cooling during passage through the fountain diminishes while cooling during flow transport increases the net effect is that eruption temperature exerts the prime control on emplacement temperature pyroclastic suspension currents can form welded ignimbrite across their entire extent if eruption temperature is to 1 3 tmw the minimum welding temperature high eruption rates a large fraction of fine ash and a ring fissure vent favor the formation of extensive high grade ignimbrite for very hot eruptions producing sticky partially molten pyroclasts analysis of particle aggregation systematics shows that factors favoring longer runout also favor more efficient aggregation which reduces runout as a result very high grade ignimbrites cannot spread more than a few tens of kilometers from their source in cooler pyroclastic currents particles do not aggregate and the sedimentation process may involve re entrainment of particles which potentially leads to more extensive cooling and longer runout such effects however are only significant when net erosion of substrate occurs model results can be employed to estimate mass flux and duration of ignimbrite eruptions from measured ignimbrite masses and aspect ratios the model also provides an alternative explanation of the observed decrease in h lratios with ignimbrite mass

high resolution astrochronological record for the paleocene oligocene 66 23 ma from the rapidly subsiding bohai bay basin northeastern china abstract the paleogene succession of the bohai bay basin bbb a highly productive petroleum basin in northeastern china with predominantly lacustrine fill is poorly dated at present here we generated an internal astronomical time scale ats for the paleogene strata of the bohai bay basin dongying depression jiyang subbasin using multitaper method mtm spectral analysis of high resolution gamma ray logs this ats which extends from 66 to 23 ma is anchored to the standard geologic time scale by calibration to the paleogene neogene boundary 23 03 ma at the top of dongying formation based on this ats we recalibrated the ages of biozones rifting episodes and paleoclimate stages within the bbb the recalibrated ages of rifting episodes and related fluctuations in sedimentation rates exhibit a close relationship to secular variation in production rates of pacific oceanic plateaus and spreading rates of the southeast indian ridge confirming that the subsidence history of the bbb was significantly influenced by subduction of the pacific plate along the eastern margin of asia and by collision of the indian and eurasian plates age recalibration also facilitated re evaluation of the relationship of sedimentation in the bohai bay basin to the paleogene climate history of east asia e g confirming a cooling and drying trend throughout the eocene

simulation of block and ash flows and ash cloud surges of the 2010 eruption of merapi volcano with a two layer model a new depth averaged model has been developed for the simulation of both concentrated and dilute pyroclastic currents and their interactions the capability of the model to reproduce a real event is tested for the first time with two well studied eruptive phases of the 2010 eruption of merapi volcano indonesia we show that the model is able to reproduce quite accurately the dynamics of the currents and the characteristics of the deposits thickness extent volume and trajectory the model needs to be tested on other well studied eruptions and the equations could be refined but this new approach is a promising tool for the understanding of pyroclastic currents and for a better prediction of volcanic hazards

a multi proxy geochemical investigation of the early paleocene danian continental palaeoclimate at the fontllonga 3 site south central pyrenees spain chronologically well constrained non marine deposits across the cretaceous tertiary boundary ktb are exceptionally rare the fontllonga section tremp formation south central pyrenees lleida spain constitutes one of these rare global records stable isotope 18oco3 and 13c analyses have been performed on the carbonate fraction of 29 samples from diverse skeletal micro remains charophyte gyrogonites gastropod shells ostracod valves and isolated skeletal remains of lepisosteids and pycnodonts from the earliest danian site fontllonga 3 a mean ba ca water palaeotemperature of 28 0 6 7 c has been obtained from the ganoine of 25 lepisosteid scales this mean palaeotemperature is comparable with the temperature tolerance range for extant relatives of fossil osteoglossiform fish found at fontllonga 3 which require a temperature range of 24 35 c mean annual temperature 27 30 c to survive using the temperature range provided by the ba ca palaeothermometer 21 3 34 7 c it is possible to determine 18owater values from the isotopic content of charophyte gyrogonites gastropod shells ostracod valves and fish remains mean 18oco3 5 00 0 21 18owater values of between 4 01 and 0 95 vsmow are calculated which when combined with la yb n versus la sm n plots are in good agreement with the sedimentary interpretation of the site as an estuarine environment based upon a comparison with modern day meteorical conditions these isotopic values are relatively high for subtropical freshwaters suggesting a low precipitation rate amount effect high evaporation rate and or long residence time when combined with other isotopic palaeobotanical and mineralogical studies carried out in the pyrenean and tethys realms this first geochemical study of an early paleocene site is consistent with there being a subtropical seasonally dry climate in the south central pyrenees at this time

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

a mechanical model for merapi type pyroclastic flow abstract a numerical simulation model of merapi type pyroclastic flow for predicting a potential hazardous area is given and its applicability is examined by numerically reproducing actual phenomena that occurred in 1991 at unzen volcano kyushu japan merapi type pyroclastic flow arises from collapse of the lava dome whereby large lava blocks are crushed into smaller particles during movement down the steep slope the early stage of flow it may be called the debris avalanche stage in which the dominant particles are coarser than about 1 mm in diameter is considered as a grain granular flow in an inertial grain flow particle collision stress plays an important role in the mechanism of flow and the effect of gas emitted from the lava blocks is minimal most of the particles composing the inertial grain flow deposit over a comparatively short range on steep slope due to marked resistance within the flow the remainder which is composed of mainly fine particles smaller than 1 mm continues to run down by a support of the upward flow of gas ejected from the material itself thereby the resistance to flow becomes small thus the pyroclastic flow stage in a narrow sense appears the main body of the pyroclastic flow is composed of lower insufficiently fluidized layer bottom layer and upper fluidized layer in which the entire weight of the particles is supported by the upward gas flow sometimes the fluidized layer cannot exist if gas emission is insufficient as the slope down which the pyroclastic flow moves becomes milder downstream the bottom layer deposits some solids because the driving force due to gravity within this layer becomes smaller than the resistance due to inter particle contact then a part of the fluidized layer if exists changes to a part of the bottom layer because of the shortage of the upward gas flow that is caused by deposition of the gas emitting particles upstream thus the entire main body stops when it arrives at a gently sloping area smaller particles and gas escape from the main body generating a hot ash cloud layer above the main body the hot ash cloud layer can travel independent of the main body but its development or attenuation depend on the conditions of the supply of particles and gas from the main body when the hot ash cloud lacks the supply of particles and gas due to the stopping of the main body upstream or by its swerving from the course of the main body it becomes soon weakened and stops the entrainment of ambient air the escape of air and ash from the upper boundary as a buoyant plume and the particle settling also affect the behaviors of the hot ash cloud fundamental mechanics of the grain granular flow stage the pyroclastic flow stage and the transition from the former to the latter stages are discussed theoretically and experimentally and mathematical formulae describing the phenomena are obtained these one dimensional equations are extended to fit the planar two dimensional system behaviors of the main body as well as the hot ash cloud are simulated using the obtained system of equations the results of simulation are very satisfactory in comparison to the actual phenomena

paleoenvironment of the eocene coal seam in the fushun basin ne china implications from petrography and organic geochemistry abstract the fushun basin in northeast china is a strike slip basin filled with coal bearing eocene sediments the basin fill includes from base to top volcaniclastic rocks a 20 to 145 m thick coal seam lower eocene guchengzi formation and lacustrine oil shale up to 300 m thick jijuntun formation the sub bituminous coal of the guchengzi formation famous for the amber inclusions is exploited in the largest opencast coal and oil shale mine in asia in the present contribution the depositional environment and the thermal history of the guchengzi formation are investigated based on macro and micropetrographic data bulk geochemical parameters biomarker analysis stable isotope geochemistry and vitrinite reflectance measurements according to our interpretation accumulation of the low sulfur coal commenced in a low lying mire near a shallow lake subsequently low ash coal was deposited either in a low lying mire protected from clastic influx or in a raised mire finally high subsidence rates typical for strike slip basins caused the flooding of the mire and terminated peat accumulation pristane phytane ratios suggest a gradual change from oxic to less oxic conditions during the drowning phase of the seam organic rich shales accumulated in the newly formed freshwater lake and resulted in the deposition of the overlying oil shale bearing jijuntun formation the coal is rich in liptinite macerals especially sporinite gymnosperms dominated the paleovegetation of the mire something that is also reflected by the frequent occurrence of resinite and amber and their biomarker composition the coal reached the sub bituminous or even the high volatile bituminous stage despite the limited burial depth simple 1d models suggest that this is a result of high heat flow rather than of deep burial and erosion the hydrogen rich coal is oil prone

lidar derived morphology of the 1993 lascar pyroclastic flow deposits and implication for flow dynamics and rheology abstract pumice flows are potentially destructive volcanic events that derive from eruption column collapse and whose dynamics are poorly understood the challenges in studying these flows include the lack of constraints on the dynamics kinematics and initial conditions that control their emplacement we present a morphological study of the distal deposits lobes of the pumice flows resulting from the 1993 eruption at lascar chile the surface geometry of the lobes was measured in detail using a lidar device which allowed for detailed characterisation of their morphology consisting of central channel and lateral levees and terminal frontal snout in particular we find that the ratio of channel levee height as a function of the ratio of the distance between levees total width of the lobe has a characteristic curve for these pumice flow lobes our analysis of several of the lascar pumice lobe deposits south east sector identified several dimensionless groups of the available parameters which when compared against published results from both experimental and numerical investigations allowed us to constrain crucial kinematic and dynamic information on the terminal phase of the pumice flows notably we estimate the velocity of the terminal phase of pumice flows to be 5 10 m s froude numbers of 1 5 2 are comparable with values found for experimental granular flows height width aspect ratios for the levee channel section of the pumice lobes are similar to those for experimental flows although these same aspect ratios for the snout are much larger for the natural deposits than their small scale analogues finally we discuss the possible emplacement dynamics of the terminal lascar 1993 pumice flows a pseudo reynolds number based on the velocity estimation is found to be up to 100 times larger for the pumice flows than experimental scale flows this suggests that the flow retarding frictional forces for large scale flows are relatively unimportant compared to flows at smaller scales mechanical effects such as fluidisation mobilisation of material lying on the slopes over which they propagate and lubrication due to polydispersivity could provide an explanation for their ability to propagate on shallow slopes 6 11

eocene monsoon prevalence over china a paleobotanical perspective abstract proxy based quantitative estimates of eocene climates can be made from marine isotope records for ocean conditions or fossil plants for terrestrial environment however our understanding about eocene terrestrial climates is derived mainly from north america and europe and little is known about east asia previous qualitative paleoclimate studies briefly revealed three climatic regimes across china during the eocene with a planetary wind dominated subtropical to tropical arid zone in the central part i e the subtropical highs which was flanked by the subtropical climate zone in the north and tropical climate zone in the south but such a pattern of paleoclimatic zonation still requires a test from quantitative study based on analyses of 66 plant assemblages carefully selected from 37 fossil sites throughout china we here report the first large scale quantitative climatic results and discuss the eocene climatic patterns in china our results demonstrate that the eocene monsoonal climate must have been more or less developed over china judging from the presence of apparent seasonality of both temperature and precipitation revealed by our quantitative estimation this appears not to support the previously claimed eocene planetary wind dominated climate system at least in the region of eastern china in addition the research indicates that with a slight declining trend of mat during the eocene the winter temperature substantially dropped in tropical southern china during the middle to late eocene interval this might be related to the development of a weak eocene kuroshio current in the southwestern pacific and or a significantly enhanced paleo winter monsoon from siberia

climatic change during the palaeocene to eocene based on fossil plants from fushun china abstract by applying the coexistence approach ca to palynological data from the laohutai lizigou guchengzi jijuntun and xilutian formations in fushun northeastern china a quantitative reconstruction of the palaeocene to eocene climate is made during that time mean annual temperature changed from 11 3 to 21 c mean annual precipitation from 654 to 1540 mm mean temperature of the warmest month from 19 4 to 28 2 c mean temperature of the coldest month from 3 6 to 13 9 c mean annual range of temperature from 12 8 to 23 5 c mean maximum monthly precipitation from 175 to 354 mm and mean minimum monthly precipitation from 8 to 27 mm all the parameters in the five formations indicate a subtropical climate this situation is different from the current climate at the same site a mid temperate and continental monsoon climate with a mean annual temperature of 6 6 c and a mean annual precipitation of 804 mm in addition the climatic parameters obtained from megafossil data only found in the jijuntun formation were analyzed and approximate those from the palynological data the parameters from the palynological data support the view that the palaeogene climate of northeast asia and north america was similar but unlike that of europe

interaction between permafrost and infrastructure along the qinghai tibet railway detected via jointly analysis of c and l band small baseline sar interferometry abstract the qinghai tibet railway qtr is the highest and longest plateau linear structure in the world the embankment is prone to instability primarily due to the freezing and thawing of the permafrost overlying active layer the infrastructure construction changes environmental conditions and in turn has influenced permafrost evolutions in this study we have investigated the feasibility of extracting surface motions in permafrost regions by means of satellite sar interferometry the relationship between surface deformation permafrost active layer and other environmental conditions were further analyzed in total 19 l band alos palsar slc images acquired from 21 june 2007 to 30 december 2010 and 38 c band envisat asar slc images acquired from 18 november 2004 to 17 december 2009 were employed to cover the beiluhe experimental site qinghai china a hybrid persistent scatterer interferometry model based on interferometric point target analysis ipta and small baseline strategy was firstly developed for surface motion estimation minimizing the seasonal decorrelation effect then the results from c and l band data were analyzed and compared based on a statistical calibration model ground leveling data acquired from fenghuo mount tunnel front with a one month interval were used for insar derived results validation revealing good agreement in displacement rates as well as time series the qtr has been in operation since 2006 our study has observed distinct surface motions along the embankment primarily in the range of 20 to 20 mm yr implying the necessity of continued satellite based surveillance along the qtr

a new perspective on origin of the east sea intermediate water observations of argo floats abstract the east sea intermediate water esiw defined as the salinity minimum in the east sea hereafter es sea of japan is examined with respect to its overall characteristics and its low salinity origin using historical argo float data from 1999 to 2015 our findings suggest that the esiw is formed in the western japan basin 40 42 n 130 133 e especially west of the north korean front in north korean waters where strong negative surface wind stress curl resides in wintertime the core esiw near the formation site has temperatures of 3 4 c and less than 33 98 psu salinity warmer and fresher than that in the southern part of the es in order to trace the origin of the warmer and fresher water at the sea surface in winter we analyzed the data in three different ways 1 spatial distribution of surface water properties using monthly climatology from the argo float data 2 seasonal variation of heat and salt contents at the formation site and 3 backtracking of surface drifter trajectories based on these analyses it is likely that the warmer and fresher surface water properties found in the esiw formation site are attributed to the low salinity surface water advected from the southern part of the es in autumn

organic matter accumulation in the oil shale and coal bearing huadian basin eocene ne china abstract the huadian basin located in northeastern china is a fault controlled basin filled by eocene non marine sediments assigned to the huadian formation the formation is subdivided from bottom to top into three members pyrite member oil shale member and carbonaceous shale member using bulk geochemical data from borehole hd3 and core descriptions from a high number of wells the factors controlling organic matter accumulation have been evaluated the organic matter content of the pyrite member is relatively low average toc 0 9 wt mudstones deposited in shallow lacustrine environments contain between 1 and 2 wt toc max 6 wt and a kerogen type ii hi 400 600 mg hc g toc an arid climate prevented the accumulation of thick coal the overlying oil shale member contains 13 oil shale layers which are mined underground the oil shale member has been interpreted as a 3rd order sequence significant differences exist between oil shales deposited in different systems tracts 2 m thick coaly oil shale of low quality oil yield 3 5 wt developed in the lowstand systems tract oil shale up to 7 m thick of moderate quality oil yield 4 1 8 0 wt was deposited during the transgressive systems tract tst thinner the carbonaceous shale member representing the balanced fill to overfilled stage of basin evolution hosts economic coal seams which are occasionally accompanied by shallow lacustrine shales with abundant hydrogen rich organic matter otherwise non coal layers are typically low in organic matter average toc 0 9 wt in contrast to the huadian basin a very thick coal seam overlain by a single oil shale layer more than 100 m thick developed in the eocene fushun basin this indicates major differences in the evolution of basins with similar tectonic setting and age

changes in atmospheric co2 concentrations and climate from the late eocene to early miocene palaeobotanical reconstruction based on fossil floras from saxony germany abstract in the present study proxy data concerning changes in atmospheric co2 and climatic conditions from the late eocene to the early miocene were acquired by applying palaeobotanical methods fossil floras from 10 well documented locations in saxony germany were investigated with respect to 1 stomatal density index of fossil leaves from three different taxa eotrigonobalanus furcinervis laurophyllum pseudoprinceps and laurophyllum acutimontanum 2 the coexistence approach ca based on nearest living relatives nlr and 3 leaf margin analysis lma whereas the results of approach 1 indicate changes in atmospheric co2 concentration approaches 2 and 3 provide climate data the results of the analysis of stomatal parameters indicate that the atmospheric co2 concentration was higher during the late eocene than during the early oligocene and increased towards the late oligocene a lower atmospheric pco2 level after the late eocene is also suggested by an increase in marine palaeoproductivity at this time from the late oligocene onwards no changes in atmospheric co2 concentration can be detected with the present data for the considered sites the results of the coexistence approach and of the leaf margin analysis document a significant cooling event from the late eocene to the early oligocene the pco2 decrease from the late eocene to the early oligocene indicated by the stomatal data raised in this study was thus coupled to a temperature decrease which is reflected by the present datasets from the early oligocene onwards however no further fundamental climate change can be inferred for the considered locations the pco2 increase from the early oligocene to the late oligocene which is indicated by the present data is thus not accompanied by a climate change at the considered sites a warming event during the late oligocene is however recorded by marine climate archives according to the present data no change in pco2 occurred during the cooling event at the oligocene miocene boundary which is also indicated by marine data the quality and validity of stomatal parameters as sensors for atmospheric co2 concentration are discussed

characterization of depositional conditions for lacustrine oil shales in the eocene jijuntun formation fushun basin ne china abstract the strike slip fushun basin hosts a lacustrine oil shale interval of ca 50 300 m in the eocene lutetian jijuntun formation the oil shale deposits consist of the lower lean oil shale unit losu and the upper rich oil shale unit rosu in outcrop areas the identified depositional cycles of ca 8 10 m and 5 8 m in thickness record the stacking of massive and non laminated oil shales in the losu and fine and coarse laminated oil shales in the rosu respectively depositional conditions in the paleo jijuntun lakes were synoptically reconstructed based on sedimentary features trace element and organic geochemical proxies oxic to suboxic fresh water conditions were prevailing in the paleo jijuntun lakes during deposition of the losu and then evolved into oxygen deficient fresh to mildly brackish water conditions during deposition of the rosu as revealed by the concentrations of redox and salinity sensitive trace elements e g v ni v cr ni co and sr ba ratios and boron content in the oil shales warm to cool and humid to arid climate represented by e g sr cu and rb sr ratios could result in the deepening of water column from ca 20 30 m to ca 100 m and saline stratification superposed on pre existing thermal stratification in the paleo jijuntun lakes a systematical decrease approximately one order of magnitude in the concentrations of most trace elements except for boron and co in the coaly oil shale in the lowermost losu relative to those in the other oil shales in the jijuntun formation indicates the significant change of organic matter om input from higher plant especially coaly materials to aquatic plankton this is partly consistent with the variations of om input from terrestrial higher plant and aquatic organisms type ii kerogen in the losu to lacustrine algae type i kerogen in the rosu as revealed by biomarkers the slight to significant enrichment or depletion of few trace elements i e mn and mo in these immature to low mature oil shale deposits may be associated with low to moderate productivities of aquatic plankton and or incompletely oxygen free conditions in the paleo jijuntun lakes

stratified flow in pyroclastic surges stratified flow theory is applied to pyroclatic surges in an effort to gain insight into transport dynamics during explosive eruptions particle transport is assumed to be by turbulent suspension and calculations contained herein show that this is likely for many cases including the 18 may 1980 blast at mount st helens the discussion centers on the rouse number pn which represents a ratio of particle settling velocity to scale of turbulence the brunt vaisala frequency n which is the maximum possible frequency of internal waves the froude number fr representing the ratio of inertial forces to gravitational forces and the richardson number ri a ratio of buoyant restoring forces to turbulent mixing forces the velocity or flow power dependence of bed form wavelength in surge deposits is related to a velocity dependence of wavelength of internal waves in the turbulent surge this produces a decrease in dune wavelength with increasing distance from vent migration direction of bed forms is related tofr as it is defined for a continuously stratified flow proximal to distal facies variations in surge deposits reflect increasingpn andri as the flows move away from their sources this produces the progression from sandwave to massive to planar facies with increasing distance from vent where the long axis of topography is at low angles to the flow direction massive facies in topographic lows may from concurrently with sandwave facies on highs due to the higher particle concentration in the lows where long axis of topography is at high angles to flow direction denser lower parts of the surge may be dammed or blocked blocked material tends to form massive flows that may move down slope independent of the overriding surge a model incorporating turbulent transport stratified flow and time evolution of pyroclastic surges is proposed for deposits which have been attributed to both pyroclastic flow and pyroclastic surge transport by various workers during the initial high energy waxing phase of the eruptive event pn is sufficiently low that only coarse but poorly sorted material is deposited to form relatively coarse bottom layers as the event wanes remaining finer material is deposited through a thin bed load to produce overlying bedded and cross bedded veneer deposits throughout most of the event blocking occurs to produce relatively thick and massive deposits in valley bottoms

particle fallout thermal disequilibrium and volcanic plumes we develop a model of a volcanic eruption column that includes the effects of fallout of pyroclasts and thermal disequilibrium we show that clast fallout with no thermal disequilibrium has only a small effect upon the column however disequilibrium changes column behaviour significantly and can even induce collapse our results may explain the lower plume heights and less widely dispersed fallout of cone forming eruptions contrasted with sheet forming eruptions the model also predicts that the transition from the gas thrust to the convective region in a column results in an inflection in dispersal curves that some features of the stratigraphy common to many fall deposits may result from column velocity structure and that there may exist a region near the volcanic vent in which maximum pyroclast size does not decrease significantly with distance

major and trace elements in mid eocene lacustrine oil shales of the fushun basin ne china concentration features and paleolimnological implications abstract mid eocene tectonic subsidence of the pull apart fushun basin ne china accommodated an up to 300 m thick oil shale succession within the lacustrine jijuntun formation lutetian based on sedimentary records and bulk element geochemistry accumulation of this oil shale succession is modeled to evaluate the principal controls on enrichment patterns of organic matter om and trace metals in lacustrine organic facies the jijuntun formation consisting primarily of massive oil shale and interbedded siltstone and sandstone that grade rapidly upward into well laminated oil shale records an overall evolution from lacustrine deltaic facies associations to profundal facies associations sedimentological characteristics of the oil shale succession display a gradual change of moderately overfilled to balanced fill lake fill mode consistent with the up section drop in siliciclastic inputs reflected by detrital proxies like decreased si al and k na ratios variations in the sedimentary fill states are accompanied by increasing hydrographic restriction of the jijuntun paleo lake in agreement with low mo toc consistently

predicting the geometry of channelized deep sea turbidites analytical relationships between the dynamic properties of a deposit forming turbidity current propagating across a sea floor with small slope and the geometry of the resulting deposit have been confirmed experimentally for a wide range of particle sizes initial concentrations and volumes of the driving suspension these simple expressions provide a basis for inferring the dynamics of natural flows from their deposits we surmise that the turbidity current responsible for depositing the black shell turbidite in the northwestern atlantic ocean had an initial sediment concentration on the order of 100 g of silt per litre and a volume on the order of 1000 km 3

geological implications and applications of high velocity two phase flow experiments abstract beds of solid particles under high pressure have been suddenly decompressed the resulting high speed two phase flows develop a highly inhomogeneous character with interpenetrating regions of high and low particle concentration the flow is highly turbulent with large velocity and density fluctuations the flows approach homogeneity only when highly expanded with low particle concentrations

computer simulations of pyroclastic flows from dome collapse we present a method of simulating both the avalanche and surge components of pyroclastic flows generated by lava collapsing from a growing pelean dome this is used to successfully model the pyroclastic flows generated on 12 may 1996 by the soufriere hills volcano montserrat in simulating the avalanche component we use a simple 3 fold parameterisation of flow acceleration for which we choose values using an inverse method the surge component is simulated by a 1d hydraulic balance of sedimentation of clasts and entrainment of air away from the avalanche source we show how multiple simulations based on uncertainty of the starting conditions and parameters specifically location and size mass flux could be used to map hazard zones

surface deformation detected by alos palsar small baseline sar interferometry over permafrost environment of beiluhe section tibet plateau china abstract the evolution of permafrost and the active layer is highly related to biological diversity and climate change because of its feedback effects involving water and carbon storage in this study we firstly examined the relationship of active layer variation geomorphological processes and anthropogenic activities by means of small baseline synthetic aperture radar interferometry in beiluhe hoh xil natural reserve in tibet plateau tp china 3 5 yr observation span of l band alos palsar data june 2007 to december 2010 was used the estimated surface displacements primarily in the range of 20 mm yr 1 to 20 mm yr 1 and time series implied evolution of the active layer and permafrost beneath the motion trend along slopes was complicated due to the geomorphological processes and thus interdisciplinary interpretations were needed anthropogenic influences on this frail permafrost environment were significant as evident from the remarkable surface settlement along the embankment of qinghai tibet railway it is crucial and necessary to monitor this permafrost plateau owing to the consequences arising from a combination of factors related to climate change geo hazard prediction nature conservation and regional sustainable development

deposition of coal and oil shale in ne china the eocene huadian basin compared to the coeval fushun basin abstract the huadian and fushun basins located along the dunmi fault zone ne china are filled with non marine coal and oil shale bearing sediments of eocene age despite similar tectonic setting the habitat of coal and oil shale differs significantly during this study the depositional environment of organic rich sediments in the huadian basin and factors controlling differences between both basins were investigated early in the history of the huadian basin thin coaly and bituminous mudstones accumulated in shallow lake environments pyrite member water depth increased during deposition of the oil shale member but did not exceed a few tens of meters preventing stable water column stratification moreover deposition of fan delta sediments interrupted accumulation of fine grained rocks nevertheless algal blooms and oxygen depleted conditions resulted in accumulation of 13 thin high subsidence rates in the fushun basin favored deposition of thick coal during the transgressive stage and of oil shale in a deep lake in contrast minor subsidence in the huadian basin resulted in a lake with moderate water depth and deposition of several oil shale layers with varying quality in this basin economic coal developed only during the regressive stage

mobility of a large volume pyroclastic flow emplacement of the campanian ignimbrite italy abstract the trachytic campanian ignimbrite originally exposed over a 30 000 km 2 area around naples italy is the product of a highly energetic gas rich eruption the deposit lies in valleys and isolated watersheds and in its medial and distal extent to the south north and east of naples the campanian pyroclastic current encountered mountains exceeding 1000 meters anisotropy of magnetic susceptibility ams measurements indicate that the campanian pyroclastic current the transport system traveled radially outward from the phlegrean fields area but the ignimbrite forming flow the deposition system that developed from the base of the transport system moved downslope from mountainsides to valleys including slopes facing the eruption source and flowed down drainage systems from intermontane basins the campanian pyroclastic current flowed 35 km over the water of the bay of naples to deposit 43 m of ignimbrite on the south shore and also overtopped a 685 1000 m high ridge of the sorrento peninsula to deposit more on the other side the distribution of the ignimbrite and the measured flow directions suggest that the campanian pyroclastic current moved across the landscape as an expanded and therefore turbulent decompressing flow rather than as a high density nonturbulent sheet like current moving over mountains by momentum acquired by eruption column collapse strong expansion is corroborated by shard morphology that indicates derivation from highly inflated pumice and suggests vesicles must have been at least 80 by volume of the original magma

early palaeocene palaeoclimatic inferences from fossil floras of the western interior usa abstract twenty one early palaeocene floral assemblages were collected from a variety of alluvial depositional environments from sites in the williston powder river and raton basins of the western interior of the usa leaf fossils were assigned to morphotypes and their physiognomy was quantified for palaeoclimatic analysis two methods were used climate leaf analysis multi variate program clamp and leaf margin analysis lma temperature estimates and trends derived from clamp and lma indicate that early palaeocene palaeotemperatures decreased from the latest cretaceous particularly in northern areas of north america climatic zones shifted southwards from their latest cretaceous positions resulting in a steepened north south temperature gradient and decreased equability in the early palaeocene sub tropical conditions prevailed as far north as the raton basin with the 20 c mean annual temperature isotherm megathermal mesothermal boundary located at approximately 45 n palaeolatitude the 13 c mean annual temperature isotherm mesothermal microthermal boundary was located at approximately 55 n palaeolatitude to the south of the williston basin clamp estimates indicate that precipitation increased significantly in all areas sampled directly after the k t boundary event especially in the southern rockies precipitation levels decreased somewhat after this initial peak but remained high throughout the early palaeocene evidence from this and other studies suggests that seasonality increased from the latest cretaceous into the palaeocene and was most pronounced in central and northerly areas of the north american continent

paleoweathering and paleoenvironmental change recorded in lacustrine sediments of the early to middle eocene in fushun basin northeast china deciphering the long term interaction among continental silicate weathering global climate and atmospheric co2 concentrations is helpful in understanding the mechanisms of the cenozoic climate change and accessing the future climatic and environmental response to anthropogenic carbon emissions the eocene which is characterized by the early eocene climatic optimum eeco and the following global cooling represents an ideal test case here we generate geochemical data of the eocene lacustrine sediments from the fushun basin northeast china to explore the regional climatic response to the global climate change the chemical index of alteration cia and plagioclase index of alteration pia consistently show a gradual long term decrease indicating a climatic transition from warm and humid to relatively cold and arid during the eocene in the fushun basin this climatic trend is broadly coincident with the global cooling and decreasing co2 concentration implying that the regional climate is closely correlated with the global climate change over geological time scales additionally the extreme silicate weathering and high lake productivity as reflected by relatively positive 13c values of lacustrine organic matter are associated with the eeco this consistency may demonstrate that enhanced continental weathering and lake productivity had served as effective sinks to lower atmospheric co2 across the eeco collectively our new geochemical data add supporting evidence for a long term close coupling among continental silicate weathering climate and global carbon cycle during the eocene

settling behaviour of concentrated dispersions and some volcanological applications abstract experiments have been carried out on the settling of non aggregating poorly sorted aqueous dispersions laced with lowdensity particles in order to gain insight into the sedimentation behaviour of volcaniclastic flows which contain pumice two poorly sorted dispersions of silicon carbide particles with continuous size distributions were studied plastic beads were added as a light component experiments were carried out at solids concentrations between 10 and 60 vol dispersions of low concentration generated normally graded deposits in which particles of different densities were in approximate hydraulic equivalence above a critical concentration 45 to 60 depending on the grain size distribution particle segregation was suppressed and the dispersion settled to form a virtually ungraded bed hindered settling at intermediate concentrations generated normally graded deposits with elutriation pipes floating rafts of plastic and capping layers of fines elutriated by escaping pore fluid buoyancy forces resulted in strong hydraulic inequivalence between light and dense components in the deposits from intermediate concentrations two mechanisms of elutriation pipe growth were observed at intermediate concentrations pipes grew progressively upwards in the deposit as the latter aggraded whereas at high concentrations they nucleated and grew uniformly throughout the whole dispersion elutriation pipes form readily during sedimentation of some poorly sorted aqueous dispersions the presence of elutriation pipes cannot be used alone to distinguish between deposits of epiclastic and pyroclastic flows reverse grading of pumice pumice rafts elutriation pipes and layers of elutriated fines should characterise deposits from pumice rich submarine mass flows despite differences in the fluid phase the experiments also have implications for fluidization mechanisms in pyroclastic flows hindered settling of a concentrated poorly sorted dispersion is a type of self fluidization in which the sedimentation of large particles causes a sufficiently strong vertical fluid flux to fluidize or elutriate smaller ones hindered settling is intrinsic to all pyroclastic flows as they spread out and deflate across the landscape and may reinforce other gas sources as an effective fluidization mechanism during emplacement of type 2 and type 3 ignimbrites and of coignimbrite lag breccias

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

modeling dense pyroclastic basal flows from collapsing columns 1 a two layer model for the formation of dense pyroclastic basal flows from dilute collapsing volcanic eruption columns is presented the collapsing dilute current is described by depth averaged isothermal continuum conservation equations the dense basal flow is modelled as a granular avalanche of constant density simulations demonstrate that pyroclastic flow formation and behavior is dependent upon slope conditions when the dilute part of the current has lost most of its mass the dilute current runout increases with decreasing particle size and increasing initial column height if the dilute current has transferred its mass to the dense basal flow on volcanic slopes with inclination angle greater than the friction angle of the basal flow then the basal flow will continue to propagate until frictional forces bring it to rest if the dilute current terminates on lower angled slopes frictional forces dominate the basal flow preventing further front propagation

a model for generation of ash clouds by pyroclastic flows with application to the 1980 eruptions at mount st helens washington pyroclastic flows are defined as consisting of a dense basal avalanche underlying a turbulent ash cloud the generation of ash clouds by the basal avalanche is commonly assumed to be closely related either to fluidization mechanisms within the avalanche or to airflow flow front interactions these mechanisms carry ash upward from the basal avalanche into the ash cloud in currents of gas or air but so far no mechanisms have been proposed to keep the ash in turbulent suspension in the ash cloud here i consider the ash cloud turbulence that is generated in two ways by temperature differences between the basal avalanche and overriding air and by the motions of the blocks lapilli and ash on the outer surface of the basal avalanche this turbulence would carry ash from saltation into turbulent suspension at the base of the ash cloud and this transition would simultaneously occur from the upper surface and front of the basal avalanche this approach quantifies one type of airflow flow front interaction the analysis incorporates studies of heat and mass transfer from rough surfaces during high reynolds number flow equations for conservation of mass momentum heat energy and ash particle concentration are formulated and presented in integral form model results show that for typical avalanche velocities and temperatues temperature differences between the basal avalanche and the surrounding air are insignificant in generating the initial turbulence within the ash cloud instead the initial distribution of particle sizes in the ash cloud is controlled by the turbulence generated by the saltating cascading particles in the basal avalanche study of the morphology of observed ash clouds suggests that thermally driven convection often becomes significant hundreds of meters or more behind the flow front and this may result from deposition of significant quantities of ash from the ash cloud onto the basal avalanche the variations in ash cloud heights morphologies and particle sizes that are predicted by this model are consistent with published observations of small pyroclastic flows at mount st helens in 1980

dynamics of co ignimbrite plumes generated from pyroclastic flows of mount st helens 7 august 1980 four co ignimbrite plumes were generated along the flow path of the pyroclastic flow of 7 august 1980 at mount st helens three of the plumes were generated in discrete pulses which can be linked to changes in slope along the channel one plume was generated at the mouth of the channel where the flow decelerated markedly as it moved onto the lower slopes of the pumice plain plume generation here may be triggered by enhanced mixing due to a hydraulic jump associated with an abrupt slope change measurements of plume ascent velocity and width show that the co ignimbrite plumes increased in velocity with height the plumes have initial velocities of 1 2 m s two of the plumes reached a velocity maximum 4 6 and 8 8 m s respectively at heights of 270 and 315 m above the flow and thereafter decelerated the other plumes reached velocities of 6 2 and 13 m s the four plumes become systematically less energetic downstream as measured by their ascent rates which can be interpreted as a consequence of decreasing interaction of the pyroclastic flow front with the atmosphere theoretical models of both co ignimbrite plumes and discrete co ignimbrite clouds assume that there is no initial momentum and both are able to predict the observed acceleration stage the rising plumes mix with and heat air and sediment out particles causing their buoyancy to increase theoretical models agree well with observations and suggest that the initial motion of the ascending material is best described as a discrete thermal cloud which expands as it entrains air whereas the subsequent motion of the head may become influenced by material supplied from the following plume the models agree well with observations for an initial temperature of the ash and air mixture in the range of 500 600 k which is in turn consistent with the measured initial ash temperature of around 920 k ash masses of 3 4 105 to 1 8 106 kg are estimated

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

a fast calibrated model for pyroclastic density currents kinematics and hazard abstract multiphase flow models represent valuable tools for the study of the complex non equilibrium dynamics of pyroclastic density currents particle sedimentation flow stratification and rheological changes depending on the flow regime interaction with topographic obstacles turbulent air entrainment buoyancy reversal and other complex features of pyroclastic currents can be simulated in two and three dimensions by exploiting efficient numerical solvers and the improved computational capability of modern supercomputers however numerical simulations of polydisperse gas particle mixtures are quite computationally expensive so that their use in hazard assessment studies where there is the need of evaluating the probability of hazardous actions over hundreds of possible scenarios is still challenging to this aim a simplified integral box model can be used under the appropriate hypotheses to describe the kinematics of pyroclastic density currents over a flat topography their scaling properties and their depositional features in this work multiphase flow simulations are used to evaluate integral model approximations to calibrate its free parameters and to assess the influence of the input data on the results two dimensional numerical simulations describe the generation and decoupling of a dense basal layer formed by progressive particle sedimentation from the dilute transport system in the boussinesq regime i e for solid mass fractions below about 0 1 the current froude number i e the ratio between the current inertia and buoyancy does not strongly depend on initial conditions and it is consistent to that measured in laboratory experiments i e between 1 05 and 1 2 for higher density ratios solid mass fraction in the range 0 1 0 9 but still in a relatively dilute regime particle volume fraction lower than 0 01 numerical simulations demonstrate that the box model is still applicable but the froude number depends on the reduced gravity when the box model is opportunely calibrated with the numerical simulation results the prediction of the flow runout is fairly accurate and the model predicts a rapid non linear decay of the flow kinetic energy or dynamic pressure with the distance from the source the capability of pdc to overcome topographic obstacles can thus be analysed in the framework of the energy conoid approach in which the predicted kinetic energy of the flow front is compared with the potential energy jump associated with the elevated topography to derive a condition for blocking model results show that although preferable to the energy cone the energy conoid approach still has some serious limitations mostly associated with the behaviour of the flow head implications of these outcomes are discussed in the context of probabilistic hazard assessment studies in which a calibrated box model can be used as a fast pyroclastic density current emulator for monte carlo simulations

problems with an in vent column collapse model for the emplacement of massive volcaniclastic kimberlite a discussion of in vent column collapse as an alternative model for massive volcaniclastic kimberlite emplacement an example from the fox kimberlite ekati diamond mine nwt canada by porritt et al j volcanol geotherm res 174 90 102

a two layer model for the evolution and propagation of dense and dilute regions of pyroclastic currents we present calculations of a simplified two layer pyroclastic flow model which incorporates different physics to represent the dense and dilute regions of column collapse pyroclastic density currents the two layers evolve separately but are coupled through mass exchange as suspended ash in the dilute cloud settles into the underlying dense basal layer the runout distance of the upper dilute current and the associated runout time are found to increase with increasing initial column height and decreasing particle size likewise steeper slopes increase the propagation velocity and thus the runout distance the independent runout distance of the basal flow exhibits opposite behaviour to that of the parent dilute current increasing with decreasing initial column height and increasing particle size observed runout distances can be calculated for basal flows using a coulomb friction law but deposit morphology is not well reproduced and is more realistic when an empirical slope dependent sedimentation rate is included dominant flow behaviour is controlled by the rate of mass transfer from the parent suspension current into the dense underflow tall column collapses which contain fine grained particles transfer their mass slowly to the dense basal flow and are well described by dilute cloud assumptions however for short columns containing coarse grains the particulate mass is rapidly transferred from the collapsing dilute current into the basal flow the bulk of the pyroclastic current material propagates as a concentrated suspension for the majority of its travel distance and is better described by the physics of granular avalanches

paleogene temperature gradient seasonal variation and climate evolution of northeast china abstract continental paleogene climates have been well studied in europe and north america but very little is known from asia because paleoclimatic results have only been reported from particular geological intervals here based on 29 plant assemblages from 8 well age controlled fossiliferous sites we quantitatively reconstruct the climates through most of the paleogene of northeast china and discuss related seasonal variations our results demonstrate that the mean annual temperature mat gradient was fairly shallow 0 27 c 1 latitude during the paleocene throughout this region in the eocene seasonality was high in the region indicated by marked differences in both temperature and precipitation between winters and summers of the sites the paleo east asian monsoon must have had intensified at least in the late mid eocene shown by apparent differences in annual precipitation distribution at all the sites regarding the paleogene climatic evolution of northeast china our quantitative results suggest that mat overall declined from warm in the paleocene and eocene to moderate in the oligocene generally consistent with the trend of marine records but with some distinctions two significant cooling events are recognized in the early and mid eocene with mat 3 4 c and 3 8 c lower and winter temperature 5 8 c and 4 7 c lower respectively in similar magnitudes to corresponding variations in europe and north america furthermore the present results show that mat rebounded in the late mid eocene and then decreased until the oligocene a similar pattern demonstrated in europe during the mid eocene to oligocene interval

a two layer depth averaged model for both the dilute and the concentrated parts of pyroclastic currents pyroclastic currents are very destructive and their complex behavior makes the related hazards difficult to predict a new numerical model has been developed to simulate the emplacement of both the concentrated and the dilute parts of pyroclastic currents using two coupled depth averaged approaches interaction laws allow the concentrated current pyroclastic flow to generate a dilute current pyroclastic surge and inversely the dilute current to form a concentrated current or a deposit the density of the concentrated current is assumed to be constant during emplacement whereas the density of the dilute current changes depending on the particle supply from the concentrated current and the mass lost through sedimentation the model is explored theoretically using simplified geometries as a proxies for natural source conditions and topographies it reproduces the relationships observed in the field between the surge genesis and the topography the increase in surge production in constricted valleys the decoupling between the concentrated and the dilute currents and the formation of surge derived concentrated flows the strong non linear link between the surge genesis and the velocity of the concentrated flow beneath it could explain the sudden occurrence of powerful and destructive surges and the difficulty of predicting this occurrence a companion paper compares the results of the model with the field data for the eruption of merapi in 2010 kelfoun et al submitted and demonstrates that the approach is able to reproduce the natural emplacement of the concentrated and the dilute pyroclastic currents studied with good accuracy

depositional environment of oil shale within the eocene jijuntun formation in the fushun basin ne china abstract the non marine fushun basin in ne china is a fault controlled basin filled with eocene sediments it hosts the largest opencast coal and oil shale mine in asia a single thick oil shale layer overlying sub bituminous coal occurs within the middle eocene jijuntun formation based on mineralogy inorganic and organic geochemistry organic petrography stable isotope geochemistry and vitrinite reflectance measurements the depositional environment and the oil shale potential of the oil shale bearing succession were investigated the jijuntun formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale respectively the thick oil shale layer of the jijuntun formation developed under long lasting stable conditions in a deep freshwater lake after drowning of a swamp the organic matter in the lower unit is characterized by landplant derived macerals the sediments containing a type ii kerogen hi 400 mghc gtoc were deposited during warm and humid conditions lacustrine organisms predominant in the upper unit are forming kerogen type i hi 700 mghc gtoc high bioproductivity and excellent preservation conditions resulted in high toc contents up to 23 6 wt in the upper unit the organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake without significant changes in bottom water salinity mid eocene cooling during deposition of the upper unit of the jijuntun formation is reflected by clay mineral composition a hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate rich xilutian formation individual geochemical parameters in the fushun basin have to be used with caution e g the maturity proxy tmax is affected by kerogen type the redox proxy pr ph ratio is probably biased by different sources of isoprenoids this demonstrates the importance of multi proxy studies

reversing buoyancy in turbidity currents developing a hypothesis for flow transformation and for deposit facies and architecture a turbidity current that contains fresher or otherwise less dense water than its surroundings may initially be denser than the ambient and propagate as a bottom hugging flow but later reverse in buoyancy as its bulk density decreases through sedimentation to become lower than that of the ambient seawater it is proposed that this reversal in buoyancy may be a significant mechanism controlling the structure and facies of turbiditic deposits buoyancy reversal followed by lofting may directly affect the relative distribution of fine and coarse material in the deposit while buoyancy reversal itself may mediate the transformation between dilute and highly concentrated suspension flows particularly in distal regions and thus lead to the formation of complex turbiditic beds in particular the generation of distal co genetic debrites may be expected similar transformations occur within dilute pyroclastic density currents where a mobile basal concentrated flow termed a surge derived pyroclastic flow develops through rapid sedimentation from the suspended load of the overlying surge the physical mechanisms involved in these processes are discussed leading to the proposal of some associated facies models these are compared with field data from the northern apennines with some striking similarities being noted as well as some differences on the basis of this discussion some directions are suggested for future experimental and modelling work on the topic

erosion transport and segregation of pumice and lithic clasts in pyroclastic flows inferred from ignimbrite at lascar volcano chile abstract investigations have been made on the distribution of pumice and lithic clasts in the lithic rich soncor ignimbrite 26 5 ka and the 1993 pumice flow deposits of lascar volcano chile the soncor ignimbrite shows three main lithofacies which grade into one another coarse lithic breccias range from matrix poor stratified varieties irregular shaped sheets and elongate hummocks in proximal environments to breccia lenses with pumiceous ignimbrite matrix massive lithic rich facies comprise the bulk of the ignimbrite pumice rich facies are bimodal with abundant large pumice clasts often with reverse grading rare lithic clasts and occur distally and on high ground adjacent to deep proximal valleys in the 1993 pyroclastic flow deposits lithic rich facies are deposited on slopes up to 14 whereas pumice rich facies are deposited only on slopes

volatile contents of obsidian clasts in tephra from the taupo volcanic zone new zealand implications to eruptive processes obsidian clasts in 6500 20 000 year old rhyolitic tephra deposits from the taupo volcanic zone new zealand contain variable h2o 0 2 2 5 wt and ci 0 12 0 18 wt contents these are elevated compared to degassed obsidian from rhyolitic domes 0 1 wt h2o2 0 1 wt cl which quenched at the surface major and trace element compositions of obsidian from tephra deposits suggest that they are co genetic with associated pumice the clear glassy appearance of the obsidian their high h2o release temperatures and 18o of 7 show that the water is magmatic and was not absorbed into the obsidian after tephra deposition based on analysis of melt inclusions recent primary taupo volcanic zone rhyolitic magmas contain 4 3 wt h2o and 0 18 wt cl the obsidian in the tephra deposits therefore represents partially degassed quenched primary magma water and cl contents correlate in the obsidian suggesting that the magmatic cl partitioned into a h2o rich fluid phase during eruptive degassing the partitioning of cl between the water rich vapor phase and the residual magma can be modelled as open system rayleigh fractionation using a pre eruptive h2o content of 4 3 wt and burnham s 1979 water solubility model the pressure and depth of initial vesiculation of the taupo magma is calculated to occur at about 0 9 kbar or 3 5 km depth initial fragmentation assumed to occur at a vapor melt ratio of 3 1 began at 0 1 kbar or 500 m depth obsidian in most tephra deposits contains less than 1 wt h2o and are calculated to have formed at 0 1 kbar or 500 m depth therefore some obsidian in these tephra deposits may have formed from fragmented magma the variable water contents of obsidian fragments in a single deposit indicates that quenching occurred over a range of depths this and the strong alignment of microphenocrysts in obsidian suggests that fragmented magma was welded onto the conduit walls during eruption cooled to form obsidian then incorporated into the tephra the 2000 year old hatepe phreatoplinian tephra contains many obsidian fragments with 2 wt h2o the meteoric water which caused this eruption to be phreatomagmatic may have caused obsidian to quench at unusually great depths resulting in higher h2o contents

testing the climatic estimates from different palaeobotanical methods an example from the middle miocene shanwang flora of china the miocene shanwang biota from eastern china contains exceptionally well preserved plant fossils with abundant leaf fossils and palynomorphs co occurring at several levels in the sedimentary succession this has provided an ideal opportunity to undertake detailed comparative quantitative palaeoclimate reconstruction based on both mega and microfloral assemblages using various approaches namely the coexistence approach coa leaf margin analysis lma and climate leaf analysis multivariate programme clamp by applying these approaches to the same dataset and using multiple fossil assemblages from different levels we are able to compare results from the different methods of climate prediction clamp and lma give consistently lower temperature mean annual temperature mat predictions than the coa taking errors into account all methods indicate no overall climate change through the sequence studied results from coa show overall agreement in the palaeoclimate parameters obtained using both pollen and leaf datasets indicating a high degree of internal consistency with this method

fabrics facies and flow through a large volume ignimbrite pampa de oxaya chile the miocene oxaya formation exposed along the western andean slope in northern chile represents one of the largest ignimbrite provinces on earth in this study magnetic fabric data were acquired from a 1 km long core drilled vertically through a single cooling unit of the oxaya formation the ca 22 ma cardones ignimbrite samples for magnetic analysis were obtained every 20 m from the fine grained matrix of the core detailed measurements of the variation in bulk magnetic properties including natural remanent magnetization nrm susceptibility and anisotropy of magnetic susceptibility ams were used to monitor changes in magnetic mineralogy as well as changes in the strength and orientation of the magnetic fabric throughout the flow ams ellipsoid orientation and shape reflect rapid deposition from a concentrated granular fluidized flow and constrain both the location of the source caldera for this catastrophic eruption and processes of transport and deposition in this large volume ignimbrite after utilizing the magnetic remanence to correct for rotation about the core axis well grouped and imbricated petrofabric orientations reveal a well defined sw 247 transport direction down a proto western andean slope indicating syn or post welding flow and confirming the deformed lauca caldera as the likely source of the eruption systematic variations in fabric shape t and intensity p with depth reveal a predominately oblate fabric toward the top and base of the flow and predominately prolate fabrics in the center these vertical changes in fabric reveal that this massive apparently homogeneous deposit has a systematic layering this layering reflects depth dependent temperature variations temporal changes in the flow boundary zone during deposition and post depositional processes

runout and fine sediment deposits of axisymmetric turbidity currents we develop a model that describes the runout behavior and resulting deposit of a radially spreading suspension driven gravity current on a surface of negligible slope our analysis considers the separate cases of constant volume and constant flux sources it incorporates expressions for the conservation of volume a froude number condition at the current front and the evolution of the driving suspension due to settling of particles to the underlying bed the model captures the key features of a range of experimental observations the analysis also provides important scaling relationships between the geometry of a deposit and the source conditions for the deposit forming flow as well as explicit expressions for flow speed and deposit thickness as functions of radial distance from the source among the results of our study we find that in the absence of information regarding flow history the geometries of relatively well sorted deposits generated by flows with source conditions of constant volume or constant flux are virtually indistinguishable the results of our analysis can be used by geologists in the interpretation of some geologically important gravity surge deposits using our analytical results we consider three previously studied radially symmetric turbidites of the hispaniola caicos basin in the western atlantic ocean from gross geometry and grain size of the turbidites alone we estimate for the respective deposit forming events that upon entry into the basin the initial sediment concentrations were approximately 3 by volume and the total volumes were roughly between 30 km 3 and 100 kn1 3 each of the suspension driven flows is inferred to have spread into the basin with a characteristic speed of 3 5 m s 1 and reached its ultimate runout length of about 60 75 km while laying down a deposit over a period of about 10 12 hours

early miocene vegetation and climate in weichang district north china abstract the early miocene palynological assemblage of guangfayong gfy in the weichang district hebei province china has been studied it consists of 48 palynomorphs belonging to 39 families with pollen and spores belonging to angiosperms 28 9 gymnosperms 59 9 ferns 10 8 and other elements 0 5 based on the palynological assemblages of gfy and wuluogong wlg another locality in the weichang district the early miocene vegetation of the weichang district was characterized by a mixed temperate forest of conifers e g pinus picea tsuga and broad leaved trees e g betula alnus with some subtropical plants e g carya the palaeoclimatic parameters of guangfayong were obtained by applying the coexistence approach the mean annual temperature from 7 8 to 14 9 c the difference of temperature between the coldest and warmest months from 14 2 to 23 c the mean temperature of the coldest month from 3 to 5 9 c the mean temperature of the warmest month from 23 5 to 25 4 c the mean annual precipitation from 658 7 to 1389 4 mm the minimum monthly precipitation from 7 6 to 16 4 mm and the maximum monthly precipitation from 161 4 to 205 9 mm it suggests a warm temperate to subtropical climate in weichang district similar to that of present day zhaojue city sichuan province in the yangtze river valley when the palaeoclimatic parameters were compared with those of middle miocene shanwang basin it would seem that the temperature and precipitation were a little higher in the middle miocene of eastern china however if the latitudinal temperature gradient at that time is considered the median temperature values of gfy of early miocene and shanwang of mid miocene were similar

radial flow to a partially penetrating well with storage in an anisotropic confined aquifer summary drawdowns generated by extracting water from large diameter e g water supply well are affected by wellbore storage we present an analytical solution in laplace transformed space for drawdown in a uniform anisotropic aquifer caused by withdrawing water at a constant rate from partially penetrating well with storage the solution is back transformed into the time domain numerically when the pumping well is fully penetrating our solution reduces to that of papadopulos and cooper 1967 hantush 1964 when the pumping well has no wellbore storage theis 1935 when both conditions are fulfilled and yang 2006 when the pumping well is partially penetrating has finite radius but lacks storage newly developed solution is then used to explore graphically the effects of partial penetration wellbore storage and anisotropy on time evolutions of drawdown in the pumping well and in observation wells we concluded after validating the developed analytical solution using synthetic pumping test

modelling pyroclastic density currents from a subplinian eruption at la soufriere de guadeloupe west indies france we have used a three dimensional non equilibrium multiphase flow numerical model to simulate subplinian eruption scenarios at la soufriere de guadeloupe lesser antilles france initial and boundary conditions for computer simulations were set on the basis of independent estimates of eruption source parameters i e mass eruption rate volatile content temperature grain size distribution from a field reconstruction of the 1530 ce subplinian eruption this event is here taken as a reference scenario for hazard assessment at la soufriere de guadeloupe a parametric study on eruption source parameters allowed us to quantify their influence on the simulated dynamics and in particular the increase of the percentage of column collapse and pyroclastic density current pdc intensity at constant mass eruption rate with variable vent diameter numerical results enabled us to quantify the effects of the proximal morphology on distributing the collapsing mass around the volcano and into deep and long valleys and to estimate the areas invaded by pdcs their associated temperature and dynamic pressure significant impact temperature 300 c and dynamic pressure 1 kpa in the inhabited region around the volcano is expected for fully collapsing conditions and mass eruption rates 2 107 kg s we thus combine this spatial distribution of temperature and dynamic pressure with an objective consideration of model related uncertainty to produce preliminary pdc hazard maps for the reference scenario in such a representation we identify three areas of varying degree of susceptibility to invasion by pdcs very likely to be invaded and highly impacted susceptible to invasion and moderately impacted and unlikely to be invaded or marginally impacted the study also raises some key questions about the use of deterministic scenario simulations for hazard assessment where probability distributions and uncertainties are difficult to estimate use of high performance computing techniques will in part allow us to overcome such difficulties but the problem remains open in a scientific context where validation of numerical models is still necessarily an incomplete and ongoing process nevertheless our findings provide an important contribution to the quantitative assessment of volcanic hazard and risk at la soufriere de guadeloupe particularly in the context of the current unrest of the volcano and the need to prepare for a possible future reawakening of the volcano that could culminate in a magmatic explosive eruption supplementary information the online version of this article 10 1007 s00445 020 01411 6 contains supplementary material which is available to authorized users

transport and deposition of a pyroclastic surge across an area of high relief the 18 may 1980 eruption of mount st helens washington the 08 32 pdt 18 may 1980 mount st helens eruption began as an explosion blast that produced a laterally flowing pyro clastic current blast surge it moved outward in a 180 arc at supersonic speeds and then slowed to subsonic speeds supersonic flow severely eroded the ground and produced a ground layer formerly layer a0 above the ground layer lies the deposit derived from the blast surge the blast surge deposits formed in three continuous and concurrent stages the first stage was movement of the transport system that is the blast surge carrying fragments most of the distance from the vent the next two stages involved the depositional system this system developed from rapidly accumulating sediment by gravity segregation at the base of the blast surge two stages of sediment gravity flows with independent flow regimes formed sequentially in rapid succession from the moving blast surge each moved downhill due to gravity independently of the generating blast surge that was driven by explosive expansion units repeated in some sections are deposits derived from divergent and crossing surge lobes caused by irregular topography locally ponded massive deposits in valleys and depressions formed from gas rich pyroclastic flows and originated in two ways 1 topographic blocking by steep volcano facing slopes blocking includes diversion or damming of the lower elevation high density part of the blast surge that could not surmount high ridges 2 also occurring to form valley ponds was drainage of just deposited or almost deposited material from steep slopes 30 35 moving downhill in all slope directions into separate valleys or depressions distances traveled by the blast surge and rates at which coarsest fragments decrease laterally are related to the topographic grain surge runout was farther where flow directions paralleled topographic trends and least where trends were at right angles to the flow obstacle interference depositional patterns thinning thickening rapid fine to coarse facies changes caused a spread in median diameter values that are as great in local areas near the volcano as they are over the width of the devastated region

emplacement of the taupo ignimbrite by a dilute turbulent flow an ignimbrite is a pumice rich deposit that records the passage of a ground hugging ash flow a pyroclastic flow generated by the collapse of a volcanic eruption column1 geologists study such deposits to reconstruct the parent eruptions and to predict the consequences of future eruptions the 1 800 yr old taupo ignimbrite of new zealand has been interpreted to represent en masse emplacement by an avalanche like flow with a volumetric solids concentration in excess of 30 ref 2 the evidence for this is equivocal however and here we propose the alternative view that the deposit was emplaced by a relatively dilute and turbulent density current3 we present an isothermal hydraulic model the results of which taken together with existing observations suggest that the total flow rate of solids and gas was about 40km3s 1 for around 15 minutes this intense flux resulted in a flow which had a near vent solids concentration of 0 3 by volume was about 1 km thick and travelled outward from the vent with a typical speed of 200 ms 1 in view of the good agreement between predicted and observed radial trends in the taupo deposit we suggest that the origin of other ignimbrites with similar characteristics should be reconsidered

comment on radial flow to a partially penetrating well with storage in an anisotropic confined aquifer by phoolendra k mishra velimir v vesselinov and shlomo p neuman journal of hydrology 448 449 2012 255 259

the run out distance of large scale pyroclastic density currents a two layer depth averaged model abstract we have developed a new two layer pyroclastic density current pdc model that considers the effects of the entrainment and thermal expansion of ambient air in the upper dilute layer in order to investigate the dominant factors controlling the run out distance of large scale pdcs numerical simulations show a dilute current spreading radially from the collapsing eruption column edge and forming a thin dense basal current through particle settling i e a two layer pdc forms forward propagation of the two layer pdc stops owing to lift off of the dilute current and or deposition of the dense current and eventually the two layer pdc converges to a steady state our parametric study classifies the flow patterns of steady state two layer pdcs into one of two flow regimes according to the relative magnitude of the run out distances of the dilute and dense currents this relative magnitude critically depends on the ratio of the deposition speed at the base of the dense current d to the speed of particles settling from the dilute current to the dense current ws the run out distance of the whole two layer pdc is determined by that of the dilute current when d ws is large 4 10 3 otherwise when d ws is small 4 10 3 the run out distance of the dense basal current exceeds that of the dilute current the former increases as d ws decreases the run out distance of the dilute current is too short to explain some of the long run out distances of pdcs observed in the field e g the 1991 pinatubo and 2014 kelud eruptions it is suggested that the dense current traveling beyond the lift off point of the parent dilute current plays a significant role in the emplacement of pdcs with such long run out distances

late paleocene early eocene climate changes in southwestern wyoming paleobotanical analysis the warmest global temperatures of the cenozoic era occurred in early eocene time following a warming trend that started in late paleocene time the greater green river basin of southwestern wyoming is one of the best areas in the rocky mountains for paleobotanical investigation of the paleocene eocene climatic transition intensive sampling has resulted in the recovery of an estimated 189 species of plant macrofossils from the tiffanian clarkforkian wasatchian and bridgerian land mammal ages the leaf morphologies and taxonomic affinities of these fossils were used in combination with other indicators to evaluate paleocene eocene climates following cool humid conditions in the tiffanian the clarkforkian was humid and subtropical and several plant families with modern tropical affinities appeared however as in the tiffanian clarkforkian floras had low diversity and were dominated by a single species in the birch family mean annual temperature mat rose from an estimated 12 c in the tiffanian to 19 c in the clarkforkian while mean annual precipitation map for the tiffanian and clarkforkian is estimated to have been 130 150 cm little fossil plant material is preserved from the latest clarkforkian or the earliest wasatchian which is thought to have contained an interval of cooling and drying followed by renewed warming by the middle wasatchian the time of the cenozoic thermal maximum the inferred mat was about 21 c and the map was near 140 cm a second influx of plant families with tropical affinities appeared in the area and diversity increased significantly but most plant families known from the clarkforkian persisted species turnover from the clarkforkian to the wasatchian was greater than 80 a second turnover of more than 80 of species but not families from the wasatchian to the early bridgerian accompanied drying and increased seasonality of precipitation the early bridgerian mat is inferred to have been near 20 c and the map to have been about 80 cm except for the tiffanian and possibly portions of the early wasatchian paleoclimates during the study interval were predominantly frost free although the moderating influence of the green river lake system has been suggested as a possible explanation for mild eocene winters in wyoming this study shows that virtually frostfree climates existed in the area prior to and independent of significant lake development

the taupo eruption new zealand i general aspects the ca a d 186 taupo eruption was the latest eruption at the taupo volcanic centre occurring from a vent at horomatangi reefs now submerged beneath lake taupo in the central north island of new zealand minor initial phreatomagmatic activity was followed by the dry vent 6 km 3 hatepe plinian outburst large amounts of water then entered the vent during the 2 5 km 3 hatepe phreatoplinian ash phase eventually stopping the eruption though large amounts of water continued to be ejected from the vent area causing gullying of the ash deposits after a break of several hours to weeks phreatoplinian activity resumed generating the 1 3 km 3 rotongaio ash notable for its fine grainsize and for containing significant quantities of non or poorly vesicular juvenile material the vent area then became dry again and eruption rates and power markedly increased into the 23 km 3 taupo ultraplinian phase which is the most powerful plinian outburst yet documented synchronous with this ultraplinian activity lesser volumes of non to partially welded ignimbrite were generated by diversion of ejecta from or partial collapse of the eruption column the rapid rate of magma withdraw al during this phase removed support from the vent area to trigger local vent collapse and initiate the catastrophic eruption of the ca 30 km 3 taupo ignimbrite finally after some years lava was extruded on to the floor of the reformed lake taupo and floating fragments derived from the lava carapace were driven ashore the known eruption volume is more than 65 km 3 while additional volumes are represented by primary material now beneath lake taupo and layer 3 to the ignim brite phases a total volume of more than 105 km 3 is likely equivalent to more than 35 km 3 of magma plus more than 3 km 3 of lithic debris airfall deposits more than 10 cm thick blanketed 30000 km 2 of land east of the vent while ignimbrite covers a near circular area of 20000 km 2 widespread and locally severe ground shaking occurred during but mostly after the eruption associated with subsidence in the lake taupo basin secondary deposits are abundant above and extending beyond the taupo ignimbrite consisting of the products of surface water interacting with the still hot ignimbrite and subsequent water reworking of the light pumiceous materials the complexity and size of this eruption preclude accurate forecasting of the size nature and return period of the inevitable next eruption from the taupo volcanic centre

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