the younger dryas termination and north atlantic deep water formation insights from climate model simulations and greenland ice cores results from the gisp2 and grip ice cores show that the termination of the younger dryas yd climate event in greenland was a large and extremely fast climate change a reinitiation of north atlantic deep water formation following a shutdown and its associated winter release of heat to the atmosphere has been suggested as the most likely cause of this climate transition to test this idea two general circulation model experiments using genesis have been completed for yd time 12 000 calendar years ago one with low heat flux in the nordic seas 10 w m deep water shutdown and one with high nordic sea heat flux 300 w m active deep water formation comparison of greenland climate differences between these experiments with the ice core records shows that when deep water is turned on much of the yd termination warming is achieved the increase in precipitation is underestimated because of a model tendency to overestimate summertime precipitation which obscures the dominantly wintertime response to the specified forcing the winter storm track shift toward greenland contributes much of the climate change at the yd termination

dynamic response of soil pile structure system subjected to lateral spreading shaking table test and parallel finite element simulation this paper investigates the dynamic response of soil pile structure interaction spsi system behind a quay wall in liquefiable soil and laterally spreading ground through both large scale shaking

paleometeorology high resolution northern hemisphere wintertime mid latitude dynamics during the last glacial maximum 1 hourly winter weather of the last glacial maximum lgm is simulated using the community climate model version 3 ccm3 on a globally resolved t170 75 km grid results are compared to a longer lgm climatological run with the same boundary conditions and monthly saves hourly scale animations are used to enhance interpretations the purpose of the study is to explore whether additional insights into ice age conditions can be gleaned by going beyond the standard employment of monthly average model statistics to infer ice age weather and climate results for both lgm runs indicate a decrease in north atlantic and increase in north pacific cyclogenesis storm trajectories react to the mechanical forcing of the laurentide ice sheet with pacific storms tracking over middle alaska and northern canada terminating in the labrador sea this result is coincident with other model results in also showing a significant reduction in greenland wintertime precipitation a response supported by ice core evidence higher temporal resolution puts in sharper focus the close tracking of pacific storms along the west coast of north america this response is consistent with increased poleward heat transport in the lgm climatological run and could help explain early glacial warming inferred in this region from proxy climate records additional analyses shows a large increase in central asian surface gustiness that support observational inferences that upper level winds associated with asian pacific storms transported asian dust to greenland during the lgm

transformation models for effective friction angle and relative density calibrated based on generic database of coarse grained soils this study compiles a generic database of seven parameters including relative density and friction angle for coarse grained soils from 176 studies covering a wide range of reconstituted and in situ coarse grained soils this database labeled as sand 7 2794 is dominated by data from laboratory reconstituted soils such as erksak hokksund monterey ottawa sacramento river ticino and tonegawa sands about 15 of the data points in the database are in situ samples obtained from tube sampling block sampling or ground freezing techniques the correlation behavior among some parameters in the database is consistent with existing transformation models in the literature mine tailings volcanic soils railroad ballast gravelly soils with significant cobble or boulder content and soils with high fines contents are removed from the database because they exhibit inconsistent behavior soils subjected to very high effective stresses are also removed from the database the generic database is adopted to

genetic relationship between granitic magmatism and w mineralization recorded in the nanling scientific drilling sp nlsd 2 in the pangushan w mining district south china abstract the nanling region in south china hosts numerous w dominated polymetallic deposits that are related to mesozoic granites although considerable amounts of age data have been obtained the genetic relationship between granitic magmatism and w mineralization remains unclear the nanling scientific drilling sp nlsd 2 in the pangushan w deposit has penetrated upper devonian sedimentary rocks 4 1 721 9 m sinian sedimentary rocks 721 9 1287 9 m and mesozoic granite 1287 9 2012 1 m the drill hole clearly reveals a zonation including exocontact w bearing quartz veins alkali autometasomatic zone and primary k feldspar granite the k feldspar granite at the depth of 1880 m and rocks of potassium autometasomatic zone at 1414 m and greisenized zone at 1288 m have magmatic zircon grains with u pb ages of 164 8 1 4 ma 161 7 1 6 ma and 153 8 1 2 ma respectively molybdenite re os ages of endocontact mineralization at the depths of 1302 m and 1291 m are 155 9 3 1 ma and 155 0 2 3 ma respectively muscovite ar ar ages of exocontact mineralization at the depths of 1050 and 885 m are 154 9 1 5 ma and 154 0 3 0 ma respectively and molybdenite re os age of exocontact quartz vein type mineralization at 860 m is 152 0 2 6 ma these new ages indicate that the granite emplacement potassium autometasomatism greisenization and w mineralization occurred at 164 8 ma 161 7 ma 153 8 ma and 155 9 152 ma respectively the w mineralization was approximately 9 13 myr younger than the hosting granite the whole rock and feldspar chemical compositions of k feldspar granite potassium autometasomatic zone greisenized zone and feldspar quartz veins indicate the sequence of metal transportation and concentration to form the zonation the granite crystallized from high k calcalkaline metaluminous to peraluminous highly differentiated magmas that were enriched in w and bi during crystallization the magmas underwent potassium autometasomatism caused by post magmatic fluids which were rich in k fe w and rare earth elements ree but poor in na and ca and formed the potassium autometasomatic zone the evolved post magmatic fluids became rich in k si ca ree and w but poor in na and fe and initiated greisenization to generate the greisenized zone which almost exhausted ca ree na and fe of the fluids the later crystallization of feldspar quartz veins exhausted k and caused the residual post magmatic fluids to be rich in si and w the fluids formed w bearing quartz veins with decreasing temperature and pressure the main reason for w enrichment in the hydrothermal fluids was due to the successive crystallization of minerals rather than autometasomatism

performance of embankments on liquefiable soils improved with dense granular columns observations from case histories and centrifuge experiments abstractdense granular columns dgcs are generally known to mitigate the liquefaction hazard through a combination of 1 installation induced ground densification 2 enhanced drainage and 3

out of the tropics the pacific great basin lakes and late pleistocene water cycle in the western united states the water cycle in the western united states changed dramatically over glacial cycles in the past 20 000 years higher precipitation caused desert lakes to form which have since dried out higher glacial precipitation has been hypothesized to result from a southward shift of pacific winter storm tracks we compared pacific ocean data to lake levels from the interior west and found that great basin lake high stands are older than coastal wet periods at the same latitude westerly storms were not the source of high precipitation instead air masses from the tropical pacific were transported northward bringing more precipitation into the great basin when coastal california was still dry the changing climate during the deglaciation altered precipitation source regions and strongly affected the regional water cycle

base stability of multi propped excavations in soft clay subjected to hydraulic uplift excavations in soft clay underlain with an aquifer may be destabilized by hydraulic uplift previous studies on this subject are based mainly on field observations dewatering from the aquifer is a

mechanics of lateral spreading observed in a full scale shake test this paper examines in detail the mechanics of lateral spreading observed in a full scale test of a sloping saturated fine sand deposit representative of liquefiable young alluvial and hydraulic fill sands in the field the test was conducted using a 6 m tall inclined laminar box shaken at the base at the end of shaking nearly the whole deposit was liquefied and the ground surface displacement had reached 32 cm the presented analysis of lateral spreading mechanics utilizes a unique set of lateral displacement results dh from three independent techniques one of these techniques motion tracking analysis of the experiment video recording is especially useful as it produced dh time histories for all laminar box rings and a complete picture of the lateral spreading initiation with an unprecedented degree of resolution in time and space a systematic study of the data identifies the progressive stages of initiation and accumulation of lateral spreading lateral spread contribution of various depth ranges and sliding zones their relation to the simultaneous pore pressure buildup and the soil shear strength response during sliding doi 10 1061 ascegt 1943 5606 0000409 ce database subject headings soil liquefaction residual strength hydraulic fill full scale tests lateral displacement author keywords liquefaction residual strength hydraulic fill full scale tests lateral displacement

simulated winter circulation types in the north atlantic and european region for preindustrial and glacial conditions 1 winter circulation types under preindustrial and glacial conditions are investigated and used to quantify their impact on precipitation the analysis is based on daily mean sea level pressure fields of a highly resolved atmospheric general circulation model and focuses on the north atlantic and european region we find that glacial circulation types are dominated by patterns with an east west pressure gradient which clearly differs from the predominantly zonal patterns for the recent past this is also evident in the frequency of occurrence of circulation types when projecting preindustrial circulation types onto the glacial simulations the elevation of the laurentide ice sheet is identified as a major cause for these differences in areas of strong precipitation signals in glacial times the changes in the frequencies of occurrence of the circulation types explain up to 60 of the total difference between preindustrial and glacial simulations

a new mechanism for decreasing north atlantic deep water production rates during the pleistocene geological data suggest that north atlantic deep water nadw production rates decreased during the pleistocene we apply a coupled ice mixed layer model for vertical overturn in the marginal ice zone hakkinen 1987a to propose an explanation for such a decrease the model predicts that prevailing wind direction is important in preconditioning of the water column along the marginal ice zone miz because it affects rates of upwelling and mixing of surface and subsurface waters processes that result in deep water formation at present prevailing wind directions during the winter in the greenland sea are northeasterly because ice has a larger drag coefficient than water ekman transport is greater under the ice than in open water this configuration causes divergence along the miz mixing of surface and subsurface waters and vertical overturn during the glacial maximum however the prevailing winds along the miz polar front were predominantly westerly modeling studies suggest that ice age changes in the prevailing winds would have significantly increased the depth of the mixed layer and decreased entrainment equal to mixing rates in agreement with geological data mixing changes due to westerly winds are greater than mixing changes due to a lower salinity layer under the present wind regime changes due to winds are so large that further changes in boundary conditions low salinity surface layer result in only minor additional reductions in vertical mixing still the maximum reduction occurs when the two processes are considered together a situation that may be applicable to the younger dryas event during the last deglaciation when a meltwater lid may have developed in the subpolar north atlantic our study suggests that wind induced changes in mixed layer depth along the miz represent a viable mechanism for decreasing past nadw production rates

effect of fines content and void ratio on the saturated hydraulic conductivity and undrained shear strength of sand silt mixtures the hydraulic conductivity represents an important indicator parameter in the generation and redistribution of excess pore pressure of sand silt mixture soil deposits during earthquakes this paper aims to determine the relationship between the undrained shear strength liquefaction resistance and the saturated hydraulic conductivity of the sand silt mixtures and how much they are affected by the percentage of low plastic fines finer than 0 074 mm and void ratio of the soil the results of flexible wall permeameter and undrained monotonic triaxial tests carried out on samples reconstituted from chlef river sand with 0 10 20 30 40 and 50 non plastic silt at an effective confining pressure of 100 kpa and two initial relative densities d r 20 91 are presented and discussed it was found that the undrained shear strength liquefaction resistance can be correlated to the fines content intergranular void ratio and saturated hydraulic conductivity the results obtained from this study reveal that the saturated hydraulic conductivity k sat of the sand mixed with 50 low plastic fines can be in average four orders of magnitude smaller than that of the clean sand the results show also that the global void ratio could not be used as a pertinent parameter to explain the undrained shear strength and saturated hydraulic conductivity response of the sand silt mixtures

soil pile response to blast induced lateral spreading ii analysis and assessment of the p y method this paper presents an assessment of the potential of using the p y analysis method for single piles and pile groups subjected to lateral spreading the computed responses were compared with the results from the full scale lateral spreading tests in japan as presented in the part i companion paper the responses of the single piles subjected to lateral spreading were determined by imposing the known free field soil movement profile to the winkler spring model the soil springs of nonliquefied soils used in this study were based upon standard p y springs whereas zero spring stiffness was used for liquefied soils for the case of pile groups they were modeled as an equivalent single pile with a rotational spring at the pile head to simulate effect of pile head restraint a decrease of soil spring stiffnesses using the p multiplier approach was used to account for pile group effects based on the results of analyses the computed responses of all sets of the test piles using a single set of baseline soil properties were in good agreement with the measured responses these results suggest that the p y analysis method may be used to estimate the behavior of piles subjected to lateral spreading

cyclic characterization of wave induced oscillatory and residual response of liquefiable seabed the paper presents a robust modeling method for a fully coupled effective stress analysis of the wave induced liquefaction scenarios based on the biot consolidation theory in this context emphasis is placed on the implementation of a well calibrated cyclic soil model and an empirical shear volume coupling equation which links the increment of volumetric strain per cycle of wave with the shear strain occurring during that particular cycle unlike most of the previous investigations using the amplitude of shear stress over the wave period or the phase resolved oscillatory shear stresses as the source term for calculating the residual pore pressure in this study the source term is related to the rate of plastic volumetric deformation and implemented into the biot consolidation equation to consider both generation and partial dissipation of excess pore pressure during wave propagation then the proposed modeling method is incorporated into a dynamic finite difference analysis procedure model calibrations are carried out in terms of individual soil element behavior and seabed response under progressive waves respectively overall good agreement demonstrates the reliability of the modeling method for the prediction of wave induced seabed response finally the paper highlights the potentials of proposed modeling framework to simulate the basic features of wave induced seabed response i e the coupling of progressive buildup of pore pressure and cyclic softening of soil skeleton by means of numerical examples the obtained results show that the cyclic behavior of liquefiable seabed under wave actions can be well captured by the proposed model

initiation and failure mechanism of base instability of excavations in clay triggered by hydraulic uplift excavations in clay overlying an aquifer may cause catastrophic basal failure due to hydraulic uplift although case histories with hydraulic uplift failures are reported worldwide from time to time the initiation and failure mechanism of the base instability are not well studied and understood to address these two issues dimensional analysis is firstly conducted to propose dimensionless groups dgs possibly relevant to this subject effects of these dgs on the initiation and failure mechanism of base instability are then investigated by carrying out a series of finite element analyses in which constitutive models and model parameters have been previously validated against centrifuge test results it is revealed that the initiation and failure mechanism of base instability due to hydraulic uplift is mainly governed by a ratio of excavation width over the thickness of soft clay inside excavation b d as excavation becomes narrower i e b d decreases the hydraulic pressure pi required to initi

the influence of continental ice sheets on the climate of an ice age the climate influence of the land ice that existed 18 000 years before present 18k b p is investigated by use of a general circulation model of the atmosphere coupled with a static mixed layer ocean simulated climates are obtained from two versions of the model one with the land ice distribution of the present and the other with that of 18k b p in the northern hemisphere the tropospheric flow field is strongly influenced by the laurentide ice sheet and features a split flow straddling the ice sheet with a strong jet stream forming the southern branch the northern branch of the flow brings very cold air over the north atlantic ocean where thick sea ice is maintained the distribution of sea surface temperature sst difference between the two experiments in the northern hemisphere resembles the difference between the sst at 18k b p and at present as estimated by the climap project 1981 the 18k b p ice sheets have very little influence upon atmospheric temperature and sst in the southern hemisphere this is because the interhemispheric heat transport hardly changes as the loss of heat energy due to the reflection of solar radiation by continental ice sheets in the northern hemisphere is almost completely counterbalanced by the in situ reduction of upward terrestrial radiation hydrologic changes in the model climate are also found with statistically significant decreases in soil moisture occurring in a zone located to the south of the ice sheets in north america and eurasia these findings are consistent with some geological evidence of regionally drier climates from the last glacial maximum

simulation of the climate of 18 000 years bp results for the north american north atlantic european sector and comparison with the geologic record of north america abstract the large ice sheets in north america and europe and the extensive sea ice cover in the north atlantic at the time of the last glacial maximum must have greatly modified the surface temperature patterns and in turn the location and intensity of the surface winds and jet streams a general circulation model was used to simulate the january and july patterns of temperature precipitation and wind for 18 ka bp boundary conditions for the model consisting of ice sheet location and height sea ice location and sea surface temperature were prescribed from climap 1981 the model results are illustrated and described for the north american north atlantic european sector the jet stream splits around the north american ice sheet and the southern branch strengthens considerably compared to present over the southern portion of the united states the sea ice margin of the north atlantic and the southern edge of the european ice sheet geologic evidence principally from north america of wind temperature and moisture conditions is assessed from sand dune and loess records estimates of snowline depression pollen records and lake level studies the geologic evidence is generally compatible with the model simulation

causes of reduced north atlantic storm activity in a cam3 simulation of the last glacial maximum abstract the aim of this paper is to determine how an atmosphere with enhanced mean state baroclinity can support weaker baroclinic wave activity than an atmosphere with weak mean state baroclinity as a case study a last glacial maximum lgm model simulation previously documented to have reduced baroclinic storm activity relative to the modern day climate simulated by the same model despite having an enhanced midlatitude temperature gradient is considered several candidate mechanisms are evaluated to explain this apparent paradox a linear stability analysis is first performed on the jet in the modern day and the lgm simulation the latter has relatively strong barotropic velocity shear it was found that the lgm mean state is more unstable to baroclinic disturbances than the modern day mean state although the three dimensional jet structure does stabilize the lgm jet relative to the eady growth rate next feature tracking was used to assess the storm track seeding and temporal growth of distur

a state dependent elasto plastic model for saturated and unsaturated soils a state dependent elasto plastic constitutive model for both saturated and unsaturated soils is presented in this paper the model which is developed under an extended critical state framework uses two independent stress state variables net normal stress and matric suction in addition the influence of a simplified non linear soil water characteristic curve on mechanical behaviour is incorporated in the model by using a bi linear function most importantly a state dependent dilatancy formulation is introduced to account for the effects of stress level or stress ratio internal state density and soil suction in this paper details of the model formulation and the determination of model parameters are described and reported by using the new model numerical simulations of triaxial tests have been carried out on both saturated and unsaturated fine grained sandy silt and coarse grained gravelly sand weathered soils the simulated triaxial tests include undrained shear tests on saturated specimens

downstream development and kona low genesis 1 a composite analysis of 43 kona lows in conjunction with a case study of a particularly damaging kona low indicate that downstream development is dynamically important to the subtropical cyclogenesis it takes the form of eastward propagating statistically significant upstream potential vorticity pv anomalies with accompanying meridional wind anomalies at the tropopause level prior to the formation of a kona low the downstream development culminates in the formation of a pv streamer a meridionally elongated stratospheric intrusion of high pv air into the troposphere associated with a breaking wave on the dynamical tropopause subsequently the streamer cuts off from the stratospheric reservoir of high pv and translates equatorward thereby providing a necessary dynamical forcing for the subtropical surface cyclogenesis

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

latest pleistocene to holocene hydroclimates from lake elsinore california abstract the hydroclimate of the southwestern united states us region changed abruptly during the latest pleistocene as the continental ice sheets over north america retreated from their most southerly extent to investigate the nature of this change we present a new record from lake elsinore located 36 km inland from the pacific ocean in southern california and evaluate it in the context of records across the coastal and interior southwest united states including northwest mexico the sediment core recovered from lake elsinore provides a continuous sequence with multi decadal resolution spanning 19 9 ka bp sedimentological and geochemical analyses reveal hydrologic variability in particular sand and carbonate components indicate abrupt changes at the oldest dryas od bolling allerod ba and younger dryas yd transitions consistent with the timing in greenland hydrogen isotope analyses of the c28 n alkanoic acids from plant leaf waxes dwax reveal a long term trend toward less negative values across 19 9 ka bp dwax values during the od suggest a north pacific moisture source for precipitation consistent with the dipping westerlies hypothesis we find no isotopic evidence for the north american monsoon reaching as far west as lake elsinore therefore we infer that wet dry changes in the coastal southwest were expressed through winter season precipitation consistent with modern climatology comparing lake elsinore to other southwest records notably cave of bells and fort stanton we find coincident timing of the major transitions od to ba ba to yd and hydrologic responses during the od and ba the hydrologic response however varied during the yd consistent with a dipole between the coastal and interior southwest the coherent pattern of hydrologic responses across the interior southwest us and northwest mexico during the od wet the ba drier and yd wet follows changes in the atlantic meridional overturning circulation presumably via its combined influence on north pacific winter storm tracks and the extent magnitude of the north american monsoon in contrast lake elsinore and the coastal southwest experiences a deglacial drying trend punctuated by abrupt change at the od to ba and ba to yd transitions this trend tracks rising greenhouse gases through the deglacial with an apparent southward shift in westerly moisture sources adjusting to the retreating ice sheet

a critical state constitutive model for liquefiable sand this paper presents a critical state constitutive model for sands over a wide range of void ratios and consolidation pressures in a triaxial plane a single set of parameters including a unique critical state line reached at large strain is also used in the model and differences in behavior in triaxial compression and extension are modeled by accounting for anisotropy at small and medium ranges of strain the model uses a capped yield surface ys which is characterized by its size and shape following evidence in past literature the stress ratio at the peak point of the capped ys of loose sands is approximated by the stress ratio measured at the peak point of their undrained effective stress path yielding parameters obtained using this stress ratio are also applied in modeling dense sand behavior and drained loading these parameters account for the effects of inherent anisotropy void ratio and confining pressure on yielding stresses and are readily determined from laboratory tests but further r

single pile under vertical vibrations in cohesionless soil the vertical response of a fixed head floating single pile embedded in sand is obtained experimentally under 1g conditions specifically pile head stiffnesses and axial strains generated along the

development of cyclic p y curves for laterally loaded pile based on t bar penetration tests in clay offshore pile foundations are always subjected to cyclic lateral loads which can result in the remolding and softening of the surrounding seabed soil cyclic t bar penetrometer testing provides a rapid and effective method for assessing the remolded shear strength it is widely believed that the soil strength degrades with the accumulation of plastic strain but the strain cannot be measured numerical analysis described in this paper shows that the accumulated plastic displacement of the t bar in a cyclic range of two diameters is approximately equal to its accumulated displacement by using t bar test data a cyclic degradation model based on the accumulated plastic displacement is developed to describe the soil strength degradation at a given depth furthermore an improved p y curve model based on the cyclic degradation model is proposed to estimate the lateral response of pile under cyclic loads the improved p y curve model was embedded into the opensees program to investigate the cyclic lateral

seismic performance of helical piles in dry sand from large scale shaking table tests recent earthquakes have highlighted the need for safe and efficient construction of earthquake resilient structures meanwhile helical piles are gaining popularity as a foundation not only for new

predicting the onset of static liquefaction of loose sand with fines abstractloose sandy soil subject to undrained shearing manifests deviatoric strain softening and such a behavior has been referred to as collapse static liquefaction or instability this paper uses the term instability and characterizes its triggering by the corresponding effective stress ratio referred to as the instability ratio is to capture the influence of fines on is the state parameter as originally proposed by been and jefferies was generalized to an equivalent granular state parameter this is achieved simply by replacing the void ratio e with the equivalent granular void ratio e the conversion from e to e was achieved by a predictive approach and backanalysis is not required it was hypothesized that provided the fines content is less than the threshold value is and at the start of undrained shearing can be described by a single relationship irrespective of the fines content two published databases and a series of undrained triaxial tests results are used to eva

the world class nanling metallogenic belt jiangxi china w and sn deposition at 160 ma followed by 30 m y of hydrothermal metal redistribution abstract the w sn maoping deposit and related w sn deposits from the world class nanling range in southeast china formed at ca 160 ma and experienced several phases of metal addition and metal redistribution between 160 and 130 ma isotopic dating of ore mineral wolframite of maoping demonstrates that w was deposited first during a hydrothermal event at ca 160 ma successive fluid episodes at ca 156 ma mo and sn rich fluid and 152 ma ree rich fluid resulted in the formation of ree and fe cu zn sulfide minerals a last fluid event occurring at ca 130 ma was responsible for the deposition of zr ree nb ta minerals that are attributed to magmatic fluids derived from unexposed magmatic bodies the three episodes of fluid circulation post dating w deposition resulted in partial to complete resetting of the isotopic systems mica wolframite xenotime which are conventionally used for dating such deposits we show that w and sn mineralization in the nanling range formed during a unique fluid event at ca 160 ma later fluid episodes redistributed the previously deposited metals and sequentially introduced additional metals including mo sn fe cu zn and zr ree nb ta direct dating of paragenetically well constrained minerals is therefore critical for determining the age and the duration of mineralizing processes and for characterizing the fluid evolution of magmatic hydrothermal systems as exemplified in the nanling range

chronology of expansion and contraction of four great basin lake systems during the past 35 000 years abstract during the past 35 000 years lake bonneville lake russell and lake searles underwent a major period of lake level change the lakes were at moderate levels or dry at the beginning of the period and seem to have achieved highstands between about 15 000 and 13 500 yr b p the rise of lake lahontan was gradual but not continuous in part because of topographic constraints intrabasin spill lake lahontan also had an oscillation in lake level at 15 500 yr b p radiocarbon age estimations for materials that were deposited in the lake basins indicate that lake bonneville rose more or less gradually from 32 000 yr b p and had major oscillations in level between 23 000 and 21 000 yr b p and between 15 250 and 14 500 yr b p lake russell and lake searles had several major oscillations in lake level between 35 000 and 14 000 yr b p the timing and exact magnitude of the oscillations are difficult to decipher but both lakes may have achieved multiple highstand states all four lakes may have had nearly synchronous recessions between about 14 000 and 13 500 yr b p after the recessions the lakes seem to have temporarily stabilized or experienced a minor increase in size between about 11 500 and 10 000 yr b p these data provide circumstantial evidence that the younger dryas event affected climate on at least a hemispheric scale during the holocene the four lakes remained at low levels and small oscillations in lake level occurred an important aspect of the lake level data is the accompanying expansion of lake surface area at the time of the last highstand lake bonneville and lake lahontan had surface areas about 10 times larger than their mean historical reconstructed areas whereas lake russell and lake searles had surface areas about 5 times larger than their mean historical reconstructed areas differences in the records of effective wetness may have been due to the locations of the basins relative to the position of the jetstream or they may have resulted from lake atmosphere feedback processes

northern hemisphere storm tracks in present day and last glacial maximum climate simulations a comparison of the european pmip models abstract extratropical weather systems are an essential feature of the midlatitude climate and global circulation at the last glacial maximum lgm the formation of regions of high transient activity referred to as storm tracks is strongly affected by the presence of large ice sheets over northern america and scandinavia and by differences in sea surface temperature sst distributions in the framework of the palaeoclimate modelling intercomparison project simulations of the lgm climate have been run with a wide range of atmospheric general circulation models agcms using the same set of boundary conditions allowing a valuable comparison between simulations of a climate very different from the present one in this study the authors focus on the storm track representation in the models and its relationship with the surface temperatures the mean flow and the precipitation storm tracks are described using transient eddy diagnostics such as mean sea level pressure variance and three dimensional

meta analysis of tropical surface temperatures during the last glacial maximum 1 the magnitude of tropical cooling during the last glacial maximum lgm has been the subject of uncertainty for over 25 years we use principles of metaanalysis as an objective approach to reconcile estimates from different proxies this approach treats each observation as a random estimate of the true mean and weights estimates by their reported precision we assigned global uncertainties to proxies and derived a new regional standard deviation for temperatures calculated from the sr ca ratio in tropical corals s 1 4 c using a bayesian spatial interpolation scheme we estimate a mean cooling of lgm tropical sea surface temperatures of 2 7 0 5c s and surface air temperatures of 5 4 0 3c s citation ballantyne a p m lavine t j crowley j liu and p b baker 2005 meta analysis of tropical surface temperatures during the last glacial maximum geophys res lett 32 l05712 doi 10 1029 2004gl021217

lateral spreading near deep foundations and influence of soil permeability a three dimensional finite element fe model is calibrated based on a large scale 1g shake table experiment in this experiment single piles were subjected to liquefaction induced lateral spreading the testing configuration experimental results and fe framework are presented and discussed the presence of piles in this fully saturated ground model caused a significant reduction in the extent of accumulated lateral soil deformation in this regard high shear strains additional to those in the free field occur as the soil moves around the piles in the downslope direction the associated shear induced tendency for dilation increases the effective confinement and reduces the resulting downslope deformations as such an fe parametric study is undertaken to investigate the effect of soil permeability on this observed liquefaction induced lateral response as the prescribed soil permeability increased in the silt sand range higher levels of ground lateral deformation occured albeit with a lower p

a centrifuge study of the seismic response of pile raft systems embedded in soft clay a series of centrifuge tests were performed on a 4 3 pile raft system embedded in soft kaolin clay to investigate the pile bending moment and raft acceleration response under seismic excitation

undrained behavior of silty sand and the role of isotropic and k0 consolidation abstractthe characteristic features of undrained behavior of a silty sand are investigated for a range of initial conditions e p for both isotropic consolidation ciu and k0 consolidation k0u

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

defining an appropriate steady state line for merriespruit gold tailings failure of the merriespruit gold tailings dam in 1994 in south africa was unusual in that never before had a gold tailings dam in south africa failed in such a catastrophic fashion conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading primarily because of the method of deposition which allows significant consolidation to occur due to sun drying this paper demonstrates that the concept of a steady state line which separates dilative from contractive behaviour upon undrained loading is applicable to merriespruit tailings four particle size distributions of merriespruit tailings were tested to determine the influence of the percent finer than 75 m on the position of the steady state line the tailings with the greater percentage of fines gave a steady state line that plotted above all the others which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low fines tailings samples

dynamic soil pile foundation structure interaction records and predictions the problem of soil pile foundation superstructure interaction is examined and a simple rational procedure to analyse the response of a structure supported on pile groups is presented this proced

liquefaction induced lateral spreading in near fault regions during the 1999 chi chi taiwan earthquake we document and analyze incidents of liquefaction induced lateral ground deformation at five sites located in the near fault region of the 1999 chi chi taiwan earthquake each of the lateral spreads involved cyclic mobility of young alluvial soils towards a free face at creek channels in each case the lateral spreading produced relatively modest lateral displacements approximately 10 200 cm in parts of the spreads not immediately adjacent to channel slopes for each site we present displacement vectors across the spread features which are based on mapping performed within three weeks of the earthquake we review the results of detailed subsurface exploration conducted at each site including cone penetration test soundings borings with standard penetration testing and laboratory index tests we back analyze the field displacements using recent empirical and semiempirical models and find that the models generally overestimate the observed ground displacements possible causes of the models overpr

seismic soil pile structure interaction experiments and analyses a dynamic beam on a nonlinear winkler foundation or dynamic p y analysis method for analyzing seismic soil pile structure interaction was evaluated against the results of a series of dynamic centrifuge model tests the centrifuge tests included two different single pile supported structures subjected to nine different earthquake events with peak accelerations ranging from 0 02 to 0 7g the soil profile consisted of soft clay overlying dense sand site response and dynamic p y analyses are described input parameters were selected based on existing engineering practices reasonably good agreement was obtained between calculated and recorded responses for both structural models in all earthquake events sensitivity of the results to dynamic p y model parameters and site response calculations are evaluated these results provide experimental support for the use of dynamic p y analysis methods in seismic soil pile structure interaction problems

p y plasticity model for nonlinear dynamic analysis of piles in liquefiable soil abstractliquefiable soil structure interaction material models are developed and implemented in the open source finite element modeling platform opensees inputs to the free end of the p y materials include the ground motion and mean effective stress time series from a free field soil column example simulations using a single p y element attached to a soil element demonstrate key features the models are then used to analyze centrifuge experiments of a single pile in a level liquefiable profile and a six pile group in a sloping liquefiable profile that resulted in lateral spreading measured displacements and mean effective stress time series are used as inputs to isolate the response of the material models from predictive uncertainties in free field ground motion and excess pore pressure the predicted pile response agrees reasonably well with measurements the cyclic mobility behavior of sand in undrained loading is shown to be an important mechanism affecting bending moments in the piles neglecting t

dynamic analysis for laterally loaded piles and dynamic p y curves pile foundations are often subjected to lateral dynamic loading due to forces on the supported structure in this study a simple two dimensional analysis was developed to accurately model the pile response to dynamic loads the proposed model incorporates the static p y curve approach where p is the static soil reaction and y is the pile deflection and the plane strain assumptions to represent the soil reactions within the frame of a winkler model the p y curves are used to relate pile deflections to the nonlinear soil reactions wave propagation and energy dissipation are also accounted for along with discontinuity conditions at the pile soil interface the inclusion of damping with the static unit transfer curves results in increased soil resistance thus producing dynamic p y curves the dynamic p y curves are a function of the static p y curve and velocity of the soil particles at a given depth and frequency of loading the proposed model was used to analyze the pile response to the lateral stat

evaluation of static liquefaction potential of silty sand slopes the mechanism of instability in granular soils is explained and its requirement as a forerunner to the liquefaction of level or sloping ground is described case histories support the observation t

an infrared microthermometric study of fluid inclusions in coexisting quartz and wolframite from late mesozoic tungsten deposits in the gannan metallogenic belt south china abstract numerous wolframite quartz vein type tungsten deposits are present in the gannan metallogenic belt south china including the piaotang and dangping deposits in the chong you yu ore cluster the dajishan deposit in the jiulianshan ore cluster and the pangushan deposit in the yushan ore cluster the ores generally consist of quartz and wolframite with variable amounts of base metal sulfides wolframite and quartz are intergrown but the genetic relationships between them are still ambiguous quartz contains two phase aqueous inclusions type i and two or three phase co 2 bearing inclusions type ii but wolframite only contains two phase aqueous inclusions type iw the homogenization temperatures for primary inclusions in wolframite are generally 40 to 100 c higher than those in quartz in a single deposit moreover there are variable amounts of co 2 in inclusions in quartz but no co 2 rich inclusions are identified in coexisting wolframite type i fluid inclusions in quartz from the piaotang deposit show that fluid mixing is predominant in the formation of quartz veins whereas fluid inclusions from the dangping deposit suggest that simple cooling is the primary factor quartz from the dajishan and pangushan deposits contains both type i and coexisting type ii inclusions indicating a process of fluid immiscibility the homogenization temperatures of two phase aqueous inclusions type iw in wolframite from all of these deposits show a clearly decreasing trend with constant salinities implying a simple cooling process hence simple cooling fluid mixing and fluid immiscibility take place in quartz but only simple cooling happens in wolframite our results show that the gangue and ore minerals from the late mesozoic tungsten deposits in the gannan metallogenic belt have different homogenization temperatures volatile compositions and fluid processes the gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown

magmatic evolution and w sn u nb ta mineralization of the mesozoic jiulongnao granitic complex nanling range south china abstract south china is famous for its large scale mineralization genetically related to widespread mesozoic granites the jiulongnao complex is one of the largest intrusions in southern jiangxi province and is closely associated with w dominated polymetallic mineralization the complex comprises four intrusive phases i iv phase i consists of medium to coarse grained biotite granite whereas medium to coarse grained porphyritic biotite granite and muscovite bearing granite comprise phase ii phase iii is composed of medium to fine grained porphyritic biotite granite and phase iv consists of medium to fine grained garnet and biotite bearing granite these intrusive phases have la icp ms zircon u pb ages of 160 9 0 6 ma 158 6 0 7 ma 157 0 1 5 ma and 154 1 1 2 ma respectively all of the granites are enriched in rb th u ta and pb and significantly depleted in eu ba nb sr p and ti they have ehf t and end t values ranging from 17 9 to 8 2 and 10 7 to 9 8 respectively with two stage hf model ages of 1 7 2 3 ga they are s type granites derived by partial melting of paleo proterozoic metasedimentary rocks the four phases have tzr of 746 760 c 712 802 c 798 810 c and 648 731 c respectively oxygen fugacities of phases i to iii display a decreasing trend but phase iv has much higher oxygen fugacity in its early stage which decreased in the late stage the four phases have different accessory mineral assemblages phase i is characterized by an assemblage of zircon apatite fergusonite thorite and uraninite whereas phase ii is rich in thorite uraninite ree bearing minerals e g monazite fergusonite and xenotime and fluorite monazite is the main accessory mineral in phase iii whereas phase iv contains a wide range of minerals including thorite uraninite nb ta bearing minerals e g fergusonite and pyrochlore cassiterite and rutile these mineral assemblages together with other geological and geochemical features suggest that w mineralization was genetically related to phases i ii and iv whereas u mineralization was most extensive in phase ii sn nb and ta mineralization was associated with the highly fractionated of magmas of phase iv

steering of westerly storms over western north america at the last glacial maximum the last glacial maximum hydroclimate over western north america differed from the modern climate a proxy model comparison suggests that the glacial storm track was squeezed and steered by atmospheric high pressure systems

components and mechanisms of hydrologic cycle changes over north america at the last glacial maximum abstractthis study examines the differences in the moisture budget over north america between the last glacial maximum lgm and modern climate as simulated by nine models from paleoclimate modell

numerical study of shear stress distribution for discrete columns in liquefiable soils abstractdiscrete columns such as stone and soil cement columns are often used to improve the liquefaction resistance of loose sandy ground potentially subjected to strong shaking the shear stress reduction in the loose ground resulting from the reinforcing effect of these stiffer discrete columns is often considered as a contributing mechanism for liquefaction mitigation current design practice often assumes that discrete columns and soil deform equally in pure shear i e shear strain compatible deformation in addition because the discrete column is stiffer than the soil it is assumed to attract higher shear stress thereby reducing the shear stress in the surrounding soil in this paper shear stress reduction in liquefiable soils and shear strain distribution between liquefiable soil and discrete columns along with the potential of development of tensile cracks is investigated using three dimensional linear elastic finite element analysis parametric analyses are performed for a range of geom

seismic response of end bearing piles a very simple analysis of dynamic soil pile supported mass interaction is presented as an aid to understanding pile foundations behaviour during earthquakes the equilibrium equations of the soil and pile movements during seismic motions are established and the response of the soil pile system is obtained as a function of the existing frequency for simplicity the analysis was based on winkler s model although the same procedure can be applied using a more refined model the effect of the supported mass is studied the natural frequency of the system is obtained and some practical design considerations are presented a method for considering group effects is also presented

shear displacement amplitude dependent pore pressure generation in undrained cyclic loading ring shear tests an energy approach by conducting a series of shear torque controlled stc and shear displacement controlled sdc ring shear tests under undrained conditions the effects of cyclic loading frequency shear displacement rate and overconsolidation ratio ocr on the pore pressure generation were examined and analyzed by means of an energy approach cyclic stc tests demonstrated that as the frequency of loading increased the shear energy wtotal as well as the total shear displacement ltotal until liquefaction substantially decreased while the number of cycles to liquefaction n increased with frequency nevertheless sdc tests showed that wtotal ltotal n did not vary with frequency this dependency of wtotal on the loading frequency in stc tests was inferred to be due to the different resultant shear displacement amplitude after shear failure but before liquefaction during cyclic shearing the results of stc tests on samples with different ocrs showed that all these three parameters of wtotal ltotal n incr

a coupled dynamic thermodynamic model of an ice ocean system in the marginal ice zone wind driven ice ocean processes in the marginal ice zone are studied when thermodynamics is included into a coupled ice ocean model the ocean is considered to be a two layer ocean where a fresh and cold freezing mixed layer is lying above the stagnant warm and saline lower layer the essential part of the thermodynamics is the entrainment between the mixed layer and the lower layer which is parameterized using the frictional velocity at the ocean surface a kraus turner type parameterization it is shown that upwelling at the ice edge which is generated by the difference in the air ice and air water surface stresses will give rise to a strong entrainment by bringing the pycnocline nearer to the surface furthermore the entrainment is negligible outside the areas affected by the ice edge upwelling when cooling at the top is included the heat and salt exchange are further enhanced in the upwelling areas because the entrainment depends inversely on the density difference between the layers new ice formation occurs in the area which is not affected by ice edge upwelling that is no entrainment of the warm lower layer fluid so the mixed layer temperature stays at the freezing point the ice growth will give rise to a large salt flux to the upper layer but the subsequent salinity change is not as large as that due to the entrainment of the lower layer fluid the mixed layer in the areas affected by the ice edge upwelling is only slightly less saline than the lower layer it is suggested that these high salinity mixed layer regions with a scale of a few rossby radii of deformation 10 km will overturn due to cooling possibly as a plume and may this contribute to the formation of deep water

the behavior of a compressible silty fine sand publications associated with sands are often limited to clean i e little fines content uniform uncemented silica or quartz sand on the other hand the importance of mineral content particle

effect of soil permeability on centrifuge modeling of pile response to lateral spreading this paper presents experimental results and analysis of six model centrifuge experiments conducted on the 150 g ton rensselaer polytechnic institute centrifuge to investigate the effect of soil permeability on the response of end bearing single piles and pile groups subjected to lateral spreading the models were tested in a laminar box and simulate a mild infinite slope with a liquefiable sand layer on top of a nonliquefiable layer three fine sand models consisting of a single pile a 3 1 pile group and a 2 2 pile group were tested first using water as pore fluid and then repeated using a viscous pore fluid hence simulating two sands of different permeability in the field the results were dramatically different with the three tests simulating a low permeability soil developing 3 6 times larger pile head displacements and bending moments at the end of shaking deformation observations of colored sand strips as well as measurements of sustained negative excess pore pressures near the foundations i

a numerical study into lateral cyclic nonlinear soil pile response pile foundations are generally designed to resist both axial and lateral loads under lateral cyclic loading the response of the pile foundation is affected by factors such as soil and pile yieldi

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

behavior of pile foundations in laterally spreading ground during centrifuge tests eight dynamic model tests were performed on a 9 m radius centrifuge to study the behavior of single piles and pile groups in liquefiable and laterally spreading ground pile diameters ranged from 0 36 to 1 45 m for single piles and from 0 73 to 1 17 m for pile groups the soil profile consisted of a gently sloping nonliquefied crust over liquefiable loose sand over dense sand each model was tested with a series of realistic earthquake motions with peak base accelerations ranging from 0 13 g to 1 00 g representative data that characterize the important aspects of soil pile interaction in liquefiable ground are presented dynamic soil pile and soil pile cap forces are backcalculated directions of lateral loading from the different soil layers are shown to depend on the mode of pile deflection relative to the soil which depends on the deformed shape of the soil profile the pile foundation stiffness and the magnitude of loads imposed by the nonliquefied crust procedures for estimating the total horizontal loads on embedded piles and pile caps i e passive loads plus friction along the base and sides are evaluated due to liquefaction of the sand layer beneath the crust the relative displacement between the pile cap and free field crust required to mobilize the peak horizontal loads is much larger than expected based on static pile cap load tests in nonliquefied soils

constraints on the magnitude and patterns of ocean cooling at the last glacial maximum observation based reconstructions of sea surface temperature from relatively stable periods in the past such as the last glacial maximum represent an important means of constraining climate sensitivity and evaluating model simulations1 the first quantitative global reconstruction of sea surface temperatures during the last glacial maximum was developed by the climate long range investigation mapping and prediction climap project in the 1970s and 1980s refs 2 3 since that time several shortcomings of that earlier effort have become apparent4 here we present an updated synthesis of sea surface temperatures during the last glacial maximum rigorously defined as the period between 23 and 19 thousand years before present from the multiproxy approach for the reconstruction of the glacial ocean surface margo project5 we integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins in contrast to the simulations of the last glacial maximum climate available at present6 7

tropical boundary layer equilibrium in the last ice age a radiative convective boundary layer model is used to assess the effect of changing sea surface temperature pressure wind speed and the energy export from the tropics on the boundary layer equilibrium equivalent potential temperature it remains difficult to reconcile the observations that during the last glacial maximum 18 000 yr bp the snowline on the tropical mountains fell 950 m while the tropical sea surface temperatures fell only 1 2 k

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

mitigation of liquefaction induced lateral deformation in a sloping stratum three dimensional numerical simulation finite element fe simulations are increasingly providing a versatile environment for conducting lateral ground deformation studies in this environment mitigation strategies may be assessed in order to achieve economical and effective solutions on the basis of a systematic parametric study three dimensional fe simulations are conducted to evaluate mitigation by the stone column sc and the pile pinning approaches mildly sloping saturated cohesionless strata are investigated under the action of an applied earthquake excitation for that purpose the open source computational platform opensees is employed through a robust user interface that simplifies the effort intensive pre and postprocessing phases the extent of deployed remediation and effect of the installed sc permeability are investigated the influence of mesh resolution is also addressed generally sc remediation was found to be effective in reducing the sand stratum lateral deformation for a similar stratum with permeability in the silt range sc remediation was highly ineffective in contrast pile pinning appeared to be equally effective for the sand and silt strata permeability scenarios overall the conducted study highlights the potential of computations for providing insights toward the process of defining a reliable remediation solution

geophysical investigations of the geology and structure of the pangushan tieshanlong tungsten ore field south jiangxi china evidence for site selection of the 2000 m nanling scientific drilling project sp nlsd 2 abstract the pangushan tieshanlong tungsten ore field located in the center of southern jiangxi province eastern nanling region contains many granitic plutons both exposed and concealed and hosts numerous tungsten polymetallic ore deposits despite many previous geological studies the deep geology and structure of the field are poorly known because few geophysical measurements have been undertaken in this study we carried out a variety of geophysical measurements including gravity magnetic field detection magnetotelluric sounding mt and high resolution seismic reflection to better outline the nature of the ore field and to aid in site selection for the 2000 m nanling scientific drilling project sp nlsd 2 to be carried out by the chinese sinoprobe program four granitic intrusives the tangcun pangushan huangsha and bai e plutons crop out independently at the surface but were found to be parts of a large batholith at depth the tangcun composite pluton which at the surface consists chiefly of caledonian granite and minor early yanshanian intrusive material was found to be chiefly early yanshanian granite concealed beneath the lower part of the caledonian granite the bai e pluton initially decreases in size with depth and then expands as it merges with the major batholith the pangushan and huangsha plutons are domes on the inferred batholith four granitic magma channels and a considerable number of faults have been identified due to its favorable geological conditions the top of the pangushan pluton is predicted to be the best candidate for ore prospecting it is basically a granite cupola with many cross cutting and parallel faults in addition it is characterized by a high gravity anomaly a high magnetic anomaly and locally a low electrical resistivity anomaly

cyclic loading response of loose air pluviated fraser river sand for validation of numerical models simulating centrifuge tests cyclic loading response of loose fraser river sand was investigated as input to numerical simulation of centrifuge physical models using constant volume direct simple shear tests conducted with a

simplified bnwf model for nonlinear seismic response analysis of offshore piles with nonlinear input ground motion analysis the seismic response of pile supported offshore structures is strongly affected by the nonlinear behavior of the supporting piles nonlinear response of the pile foundation is the most important so

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

temporal consistency between granite evolution and tungsten mineralization in huamei ao southern jiangxi province china evidence from precise zircon u pb molybdenite re os and muscovite 40ar 39ar isotope geochronology abstract the large huamei ao tungsten deposit with total wo 3 reserves of 67 400 tons at an average grade of 1 334 wo 3 is located in the convergent zone of the eastern nanling e w trending tectono magmatic belt and the western wuyishan nne ssw trending tectono magmatic belt in southern jiangxi province china the tungsten mineralization in this deposit is mainly found in quartz wolframite veins with most orebodies distributed at the outer contact zone between concealed late jurassic granitic stocks and sinian weakly metamorphosed sandstones and phyllites zircons collected from medium to fine grained biotite granite in a diamond drill hole at a sea level of ca 10 m yield a crystallization age of 159 9 1 2 ma through laser ablation multicollector inductively coupled plasma mass spectrometry la mc icp ms u pb dating molybdenite and muscovite that were both separated from quartz wolframite veins yield a re os isochron age of 158 5 3 3 ma and an 40 ar 39 ar weighted plateau age of 157 9 1 1 ma respectively these dates obtained via three independent geochronological techniques constrain the ore forming age of the huamei ao deposit and link the genesis of the ore and the underlying granite analyses of available high precision zircon u pb molybdenite re os and muscovite 40 ar 39 ar radiometric ages of major w sn deposits in southern jiangxi province indicate that there is no significant time interval between w sn mineralization and its intimately associated parent granite emplacement interval of 0 6 ma these deposits formed over three intervals during the mesozoic 240 210 170 150 and 130 90 ma with large scale w sn mineralization occurring mainly between 160 and 150 ma the majority of w sn deposits in this region are located in southern jiangxi and southern hunan provinces

high resolution climate simulation of the last glacial maximum the climate of the last glacial maximum lgm is simulated with a high resolution atmospheric general circulation model the ncar ccm3 at spectral truncation of t170 corresponding to a grid cell size of roughly 75 km the purpose of the study is to assess whether there are significant benefits from the higher resolution simulation compared to the lower resolution simulation associated with the role of topography the lgm simulations were forced with modified climap sea ice distribution and sea surface temperatures sst reduced by 1 c ice sheet topography reduced co2 and 21 000 bp orbital parameters the high resolution model captures modern climate reasonably well in particular the distribution of heavy precipitation in the tropical pacific for the ice age case surface temperature simulated by the high resolution model agrees better with those of proxy estimates than does the low resolution model despite the fact that tropical ssts were only 2 1 c less than the control run there are many lowland tropical land areas 4 6 c colder than present comparison of t170 model results with the best constrained proxy temperature estimates noble gas concentrations in groundwater now yield no significant differences between model and observations there are also significant upland temperature changes in the best resolved tropical mountain belt the andes we provisionally attribute this result in part as resulting from decreased lateral mixing between ocean and land in a model with more model grid cells a longstanding model data discrepancy therefore appears to be resolved without invoking any unusual model physics the response of the asian summer monsoon can also be more clearly linked to local geography in the high resolution model than in the low resolution model this distinction should enable more confident validation of climate proxy data with the high resolution model elsewhere an inferred salinity increase in the subtropical north atlantic may have significant implications for ocean circulation changes during the lgm a large part of the amazon and congo basins are simulated to be substantially drier in the ice age consistent with many but not all paleo data these results suggest that there are considerable benefits derived from high resolution model regarding regional climate responses and that observationalists can now compare their results with models that resolve geography at a resolution comparable to that which the proxy data represent

towards establishing criteria for identifying trigger mechanisms for soft sediment deformation a case study of late pleistocene lacustrine sands and clays onikobe and nakayamadaira basins northeastern japan five main deformation units discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment were selected for study within late pleistocene lacustrine sands and clays in the onikobe and nakayamadaira basins northeastern japan the deformed units show evidence of deformation by a variety of mechanisms including fluidization liquefaction brittle failure and cohesive flow driving forces are thought to be primarily reverse density gradient systems but also include gravitational body force shear stress and unequal loading the main trigger mechanisms are firstly earthquakes secondly overloading from volcanic sands and thirdly to a lesser extent subaqueous currents consideration is given to criteria that allow the trigger mechanism to be identified this study shows that the following criteria can be used to identify a seismic triggering agent i setting ii the extent of the deformation units iii absence of evidence relating to other potential trigger mechanisms and iv evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment conversely the following criteria while they are important in interpreting the driving force and deformation mechanism have no relevance to the trigger mechanism i sediment composition ii deformation structures being restricted to a single stratigraphic interval 1 m thick not necessarily correlatable over large areas and iii similarity to structures in the literature

geological characteristics and metallogenic epoch of pangushan w bi te ore deposit in yudu county jiangxi province the pangushan tungsten ore deposit is a large size wolframite quartz vein type w bi te ore deposit in the exocontact zone of the buried rock body within the eastern part of the nanling metallogenic belt the authors collected molybdenite samples from the w bearing quartz veins of different geological modes of occurrence re os isotopic dating yielded isochron ages of molybdenite 157 75 0 76 ma mswd 0 99 and 158 8 5 7 ma mswd 1 7 the ages indicate that these two mineralized veins belong to the same product and were formed in the same period i e early yanshanian the study also provides useful evidence that the ore deposit is the product of nanling ew trending tectonic magmatic belt

design of dsm grids for liquefaction remediation abstractdeep soil mixing dsm to form in ground shear walls has been used to remediate against the potential effects of earthquake induced liquefaction on many projects a grid pattern of soil cement walls act as a confined shear box which can provide additional shear stiffness and strength for sites to withstand liquefaction current design practice for dsm grids commonly relies on the strain compatibility assumption where the dsm walls and confined soil are assumed to experience the same shear strain in this paper the distributions of shear stresses and strains in liquefiable soil deposits treated with dsm grids are investigated using three dimensional linear elastic finite element analyses of unit cells parametric analyses are performed for a range of geometries relative stiffness ratios and dynamic loadings these linear elastic results provide a baseline against which future nonlinear modeling results can be compared but they are also sufficient for demonstrating that shear stress reductions

assessing climatic and nonclimatic forcing of pinedale glaciation and deglaciation in the western united states new 10 be surface exposure ages from adjacent valleys in the upper arkansas river basin colorado united states indicate that pinedale maxima culminated asynchronously at 22 4 1 4 19 2 0 2 17 8 0 6 and 15 8 0 4 ka but that deglaciation initiated synchronously between ca 16 and 15 ka these data are combined with published glacial chronologies across the western united states and indicate that although the ages of pinedale terminal moraines vary within individual ranges as well as regionally most western united states glaciers remained near their pinedale termini until ca 16 ka at which time widespread deglaciation commenced we hypothesize that the near synchronous demise of glaciers across the western u s between ca 15 and ca 13 ka was driven by the first major northern hemisphere warming following the last glacial maximum but that some differences in pinedale culmination ages can be explained by nonclimatic factors intrinsic to individual valleys these results suggest the need for caution in focusing exclusively on climate forcings to explain apparent asynchrony in pinedale maxima

undrained shear strength of soils under flow deformation the initial stress and density condition leading to flow deformation and the resultant undrained strength of clean and silty sands are examined based on the un drained triaxial tests the effective major stress at consolidation 1c is found to serve as a primary parameter in defining a series of characteristic state lines and undrained strength ratios the largest possible undrained strength ratio sus 1c under flow deformation was found not to differ largely among soils though the range of such initial density conditions differs the estimation of undrained strength would therefore be practically useful in determining the occurrence of flow deformation

kinematic pile bending during earthquakes analysis and field measurements the passage of seismic waves through the soil surrounding a pile imposes lateral displacements and curvatures on the pile thereby generating kinematic bending moments even in the absence of a su

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

collapse of the california current during glacial maxima linked to climate change on land time series of alkenone unsaturation indices gathered along the california margin reveal large 4 to 8 c glacial interglacial changes in sea surface temperature sst over the past 550 000 years interglacial times with ssts equal to or exceeding that of the holocene contain peak abundances in the pollen of redwood the distinctive component of the temperate rainforest of the northwest coast of california in the region now dominated by the california current ssts warmed 10 000 to 15 000 years in advance of deglaciation at each of the past five glacial maxima ssts did not rise in advance of deglaciation south of the modern california current front glacial warming along the california margin therefore is a regional signal of the weakening of the california current during times when large ice sheets reorganized wind systems over the north pacific both the timing and magnitude of the sst estimates suggest that the devils hole nevada calcite record represents regional but not global paleotemperatures and hence does not pose a fundamental challenge to the orbital milankovitch theory of the ice ages

cyclic liquefaction of loose gassy sand gas can be found in many soils but none more common than in seabed soils gas charged sediments are known to be widely distributed throughout the world s oceans numerous research programs have studied saturated soil response to cyclic loading however little is known about the behavior of gassy soils subjected to cyclic loading the response of loose gassy specimens subjected to cyclic loading was studied in a laboratory program triaxial tests were performed on specimens of reconstituted ottawa sand prepared to various gas contents and densities the specimens were consolidated and then sheared under undrained cyclic loading gas content was measured at the beginning and end of each test using time domain reflectometry the response of the gassy specimens has been shown to be influenced by the soil state and grain characteristics and the intensity duration and frequency of the cyclic loading the propensity of a soil to liquefy is represented by a cyclic resistance ratio defined as the cyclic stres

estimation of peak acceleration and bending moment for pile raft systems embedded in soft clay subjected to far field seismic excitation abstractan extensive suite of three dimensional finite element simulations was carried out to examine the response of pile raft soil systems under seismic excitation representative of far field eve

response in atmospheric circulation and sources of greenland precipitation to glacial boundary conditions the response in northern hemisphere atmospheric circulation and the resulting changes in moisture sources for greenland precipitation to glacial boundary conditions are studied in ncar s ccm3 atmospheric general circulation model fitted with a moisture tracking functionality we employ both the climap sst reconstruction and a modification thereto with reconstructions of glacial ice sheets and land masks the individual components of the boundary conditions are added first one at a time and finally together these steps show the atmospheric circulation to respond approximately linearly to the boundary condition changes and the full glacial change may thus be decomposed into contributions from sst and topography changes respectively we find that using the climap sst reconstruction leads to a shift from atlantic toward pacific source regions not found with the modified reconstruction having cooler tropics and less sea ice the occurrence of such a shift depends chiefly on the sst reconstruction and not on the existence of the large northern hemisphere glacial ice sheets the influence of these circulation changes on important factors for ice core interpretation such as precipitation seasonality condensation temperatures and source temperatures are assessed

p y curve and lateral response of piles in fully liquefied sands this paper provides a technique to assess the response of laterally loaded piles and associated p y curves in fully liquefied soils where p is the soil pile reaction and y is the pile deflection the technique accounts for the variation of water pressure in the liquefied soils around the pile and its impact on the shape of the p y curves and the pile lateral response a constitutive undrained stress strain model for fully liquefied saturated sands using the basic properties of sand is established to predict the post liquefaction varying resistance of liquefied sands at different levels of loading assuming fully undrained conditions the degradation in soil strength due to the free field excess pore water pressure uxs ff caused by an earthquake and resulting in full liquefaction is considered along with the near field excess pore water pressure uxs nf induced by lateral loading from the superstructure the presented procedure also accounts for the influence of the overburden pressure and sand densi

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos