geochemistry and provenance of the middle ordovician austin glen member normanskill formation and the taconian orogeny in new england the austin glen member of the upper middle ordovician normanskill formation is a sandstone shale ysch succession deposited in the foreland of the taconian orogen petrographic major and trace element and nd pb isotopic data provide substantial constraints on its provenance lack of k feldspar and paucity of plagioclase in addition to the dominance of sedimentary rock fragments indicate that the source was dominated by recycled sedimentary components major and trace element data support this conclusion and indicate that the provenance of both shales and sandstones was the same no evidence of an ophiolitic or volcanic component was observed interpretation of nd isotopic characteristics are complicated by a partial resetting of the nd isotope system at about the time of sedimentation but indicate that the provenance of the austin glen member had a long term history of light rare earth element lree enrichment average tdm 1a8 ga furthermore nd isotopic compositions are extremely homogeneous end 8a1 0a6 1 s d n 23 at 450 ma the approximate depositional age indicating either a single source or very well mixed sources 207pb 204pb ratios are variable but within the range of pb isotopic compositions typically described as grenvillian the range of 207pb 204pb is greater than expected for the range of 206pb 204pb and suggests an additional component of pb possibly introduced during diagenesis the immediate source of the austin glen member may have been the accretionary prism that developed as older sediments of the laurentian margin were scraped off the basin oor incorporated within the accretionary prism and shed into the basin no evidence indicating the arrival of an undifferentiated island arc or continental fragment during the taconian orogeny has been found the data acquired during this study can be explained almost exclusively by grenville province source components but with possible additional contributions from older laurentian terranes and late proterozoic rift volcanics that are not readily quanti ed but likely to have been minor accordingly we conclude that the taconian orogeny in new england involved either 1 a continental arc that involved exclusively laurentia 2 collision of a continental block with identical geochemical characteristics as laurentia or 3 essentially no detritus from any exotic colliding block island arc or continental fragment reached the foreland basin at the time of austin glen deposition

distribution of pb between sediments and pore water in woods lake adirondack state park new york u s a abstract interstitial water samples and sediments were collected from acidified woods lake ph 5 0 to evaluate pb profile stability and distribution between the solid and aqueous phases a simple equation was developed to describe the distribution coefficient for pb kdpb based on the sample moisture content and analyte concentrations in bulk sediment and pore water in woods lake sediment kdpb values ranged from 6 7 104to6 7 105ml g the affinity of pb for the solid phase was further demonstrated by inverting a sediment core and leaving it for 10 months in situ upon retrieval the pb profile was found to have remained intact over the same depth albeit inverted as in the surrounding sediment geochemical modeling using minteqa2 demonstrates that pb solids that may reasonably be expected to precipitate were all undersaturated by several orders of magnitude with respect to the interstitial water indicating that pb was sorbed to rather than precipitated in woods lake sediment

regional patterns and local variations of sediment distribution in the hudson river estuary abstract the hudson river benthic mapping project funded by the new york state department of environmental conservation resulted in a comprehensive data set consisting of high resolution multibeam bathymetry sidescan sonar and sub bottom data as well as over 400 sediment cores and 600 grab samples this detailed data set made it possible to study the regional pattern and the local variations of the sediment distribution in the hudson river estuary based on these data we describe the distribution of sediment texture and process related sedimentary environments for the whole 240 km long estuary together with along river variations of depth cross sectional area and grain size distribution we compare these parameters with changes in surrounding geology and tributary input and as a result divide the hudson river estuary in eight sections with distinct combinations of channel morphology bedrock type sediment texture and sediment dynamics the regional sediment distribution consists of marine sand dominated sediments near the ocean end of the estuary a large mud dominated central section and fluvial sand dominated sediments in the freshwater section of the hudson river estuary this regional trend is highly modified by small scale variations in the sediment distribution these local variations are controlled by changes in morphology bedrock and tributary input as well as by anthropogenic modifications of the estuary in some areas these local variations are larger than the overall trend in sediment distribution and control the actual sediment type as well as the condition of erosion and deposition in the estuary

effects of relative density in progressive sliding of tailings deposits insights from flume tests abstract we present a series of flume tests to observe the process of tailings slope failure when subjected to a concentrated water flow progressive flow slides were observed in a range of tailing deposits with varying relative densities in which hydraulic conductivity reduced with increasing relative density slope densification by compaction of very loose or loose tailings deposits can lead to a lower permeability generating excess pore pressure and subsequently reducing slope stability this is evident from the great number of acoustic emission signals before sudden failure and from a sharp increase in the surface displacement and internal displacement observed after excess pore pressure generation the variation of fluid pressure distribution results in successive sliding onset at the toe and progressing from the toe to the rear of the slope excess pore pressure generation is found to occur after rather than prior to sliding and it only occurs along the slip surface an optimal relative density of 0 35 was identified in which the slope failure changes from a sudden collapse to a progressive failure however the optimal relative density may vary with the height of the slope this research extends existing knowledge about behavior of tailings materials while the observed discrepancy between the failure mechanisms of slopes made of loose and dense deposits could provide insights for preventing failures of tailings dams

reconstructing depositional processes and history from reservoir stratigraphy englebright lake yuba river northern california 1 reservoirs provide the opportunity to link watershed history with its stratigraphic record we analyze sediment cores from a northern california reservoir in the context of hydrologic history watershed management and depositional processes observations of recent depositional patterns sediment transport calculations and 137cs geochronology support a conceptual model in which the reservoir delta progrades during floods of short duration days and is modified during prolonged weeks to months drawdowns that rework topset beds and transport sand from topsets to foresets sediment coarser than 0 25 0 5 mm deposits in foresets and topsets and finer material falls out of suspension as bottomset beds simple hydraulic calculations indicate that fine sand 0 063 0 5 mm is transported into the distal bottomset area only during floods the overall stratigraphy suggests that two phases of delta building occurred in the reservoir the first from dam construction in 1940 to 1970 was heavily influenced by annual prolonged 20 m drawdowns of the water level the second built on top of the first reflects sedimentation from 1970 to 2002 when the influence of drawdowns was less sedimentation rates in the central part of the reservoir have declined 25 since 1970 likely reflecting a combination of fewer large floods changes in watershed management and winnowing of stored hydraulic mining sediment

plutonium radiocesium and radiocobalt in sediments of the hudson river estuary abstract anthropogenic radionuclides have reached the hudson estuary as global fallout from nuclear weapons testing and through local releases from commercial nuclear reactors significant activities of 238 pu and 239 240 pu fallout derived 134 cs and 60 co reactor released and 137 cs derived from both sources have accumulated in the sediments throughout the estuary with the primary zone of accumulation near the downstream end of the system in new york harbor the estuary appears to have trapped nearly all of the 239 240 pu delivered as fallout and consequently ocean dumping of dredged harbor sediment is currently the primary means for the net transport of these nuclides to coastal waters in contrast only 10 30 of the 137 cs 134 cs and 60 co delivered to the estuary have been retained on the fine particles which accumulate at a rapid rate in the harbor the primary factors which have governed the distribution of anthropogenic radionuclides in hudson sediments are 1 spread of fine particles labeled with both fallout and reactor nuclides throughout the axis of the estuary 2 differences in timing of the peak fallout years 1962 1964 and years of maximum reactor releases 1971 1972 3 large variations in sediment accumulation rates ranging from a few millimeters per year or less to many tens of centimeters per year 4 appreciable desorption of 137 cs and 134 cs from particles at higher salinities and 5 possible enhanced desorption of 60 co at higher salinities relative to 134 cs and 137 cs which may be associated with the release of reduced manganese from the harbor sediments

ring shear tests on soil from the vaiont landslide slip surface the paper presents results from ring shear tests carried out on two samples from the slip surface of the vaiont landslide in north italy the tests were carried out at slow and fast rates of shearing in order to determine values of the coefficient of friction appropriate to static and dynamic aspects of the landslide both samples showed a significant loss of strength negative rate effect up to 60 below the slow residual strength when sheared at rates of shearing greater than 100 mm min the observed loss of strength may explain the high acquired velocity of the landslide or alternatively some combination of this and other mechanisms may have taken place le papier presente les resultats d essais de cisaillement par anneau effectues sur deux echantilions preleves sur la surface de cisaillement du glissement de terrain vaiont dans le nord de l italie les essais ont ete menes avec des vitesses de cisaillement lentes et rapides de maniere a pouvoir determiner les valeurs des coefficients de frotteme

lake sediment geochemistry reveals 1400 years of evolving extractive metallurgy at cerro de pasco peruvian andes the geochemical record preserved in lake sediments is a potentially powerful tool in archaeometallurgy here sediments from llamacocha a small lake in the central peruvian andes are used to reconstruct a 1400 year legacy of metal extraction from cerro de pasco once the largest silver mine in the world the earliest evidence for anthropogenic lead pb enrichment occurs ca a d 600 and is confi rmed by pb stable isotope ratios that match those of cerro de pasco ores early pb pollution is attributed to precolonial smelting for silver production which relied on galena based fl uxes following colonial control of the mine ca a d 1600 the switch to mercury hg amalgamation for winning silver resulted in atmospheric hg emissions as registered in llamacocha sediments both pb and hg deposition increased through the twentieth century attaining peak values in a d 1968 and 1942 respectively principal components analysis pca identifi es a gradient that differentiates anthropogenic from natural metals within the record confi rming that early smelting led to the volatilization of trace metals associated with local ore mineralogy these results represent the fi rst evidence for a major precolonial mining industry at cerro de pasco provide a chronological framework for evolving extractive technologies and are the fi rst to document widespread hg pollution associated with colonial hg amalgamation 80 w 70 w

lead and sulfur isotope microstratigraphy in galena crystals from mississippi valley type deposits the development of an analytical procedure for lead and sulfur isotope analysis by secondary ion microprobe mass spectrometry allowed us to provide in situ isotopic microanalyses of galena crystals we performed analyses across the growth zones of two crystals of galena from mississippi valley type ore deposits with a spatial resolution of 50 mu m and a spacing of 250 mu m these analyses show frequent variations for both lead and sulfur isotope compositions which occurred during the time of the crystal growth we can demonstrate that for both elements these variations involved changes in the sources of the brines which formed the ore deposits the comparison of lead and sulfur isotope behavior suggests that for the picher deposit lead and sulfur originated from common sources whereas for the buick mine deposit lead and sulfur had separate sources the two galenas exhibit rapid and frequent changes in isotopic composition this suggests numerous and discontinuous inputs of lead and sulfur to the ore deposits this model agrees well with a physical model for mississippi valley type deposits proposed by cathles and smith 1983 the isotopically different sources were probably different sedimentary layers and perhaps basement rocks in the same basin whose formation waters were channeled in preferred water conduits to the ore deposit location during the subsidence of the basin allowing mixing between the different sources to occur during the brines travel

metallogeny of structural zones grenville province northeastern north america abstract recent subdivision of the grenville province into northwestern central and southeastern tectonic zones provides a convenient basis for describing the tectonic affiliation of the contained mineral deposits the northwestern zone consists of reworked foreland lithologies southeast of the grenville front major deposits of metamorphosed superior type iron formations are present in metamorphosed kaniapiscau supergroup equivalents exposed at lower metamorphic grades in the labrador trough occurrences of volcanogenic massive sulphides abitibi group equivalents ni cu quartzite hosted u au and alkaline intrusion hosted ree s are of only mineralogical importance the central zone contains polydeformed gneisses that have been intruded by three ages of anorogenic anorthosite massifs circa 1 64 1 36 and 1 14 ga and associated charnockite magnerite complexes major magmatic ti fe lac allard and large low grade ni cu mcnickel deposits are associated with the younger anorthosite suite magmatic ni cu also occurs in differentiated metapyroxenite metaperidotite of uncertain age pegmatites are widespread but not commercially important the southeastern zone consists of the rocks of the central metasedimentary belt cmb and central granulite terrane cgt as well as rocks of the relatively unmetamorphosed wakeham supergroup initial deposition of volcanic and carbonate rocks occurred in the cmb between 1 28 and 1 24 ga and was followed by deposition of the flinton group 1 15 ga the rocks are overprinted by the elzeviran and ottawan orogenies 1 25 and 1 08 ga respectively volcanogenic zn pb ag au deposits and sedex marble hosted zn deposits occur widely in the layered rocks of the central metasedimentary belt deposition 1 28 ga small massive sulphide and shale hosted base metal occurrences and both oxide and sulphide iron formations are widespread near volcanic lithologies but are generally small or very low grade syngenetic magmatic deposits include subeconomic fe ti and ni cu deposits that are syntectonic with respect to the ottawan orogeny but others may be as old as elzeviran small magnetite rich skarn deposits are widespread with 2 major past producing deposits and are related to magmatic events accompanying the elzeviran orogeny gold and gold sulphosalt occurrences in grenville volcanic and carbonate lithologies and flinton group rocks of various types are not well constrained in age some are spatially associated with older elzeviran intrusions and have been genetically related to them others exhibit metamorphic textures but cut younger flinton group rocks while others appear to be completely post metamorphic extensive pegmatitic and related skarn and carbonate vein u mo ree occurrences may relate either to metamorphic or intrusive processes related to the ottawan orogeny in the cgt fe ti and ni cu occurrences associated with the younger anorogenic anorthosite massifs are similar to occurrences in the central zone large fluorite bearing magnetite iron deposits associated with alaskitic gneisses are interpreted as similar to the swedish kiruna type deposits following stabilization of the grenville craton rifting associated with the opening of iapetus in the latest proterozoic cambrian and again in the cretaceous resulted in the regional intrusion of alkaline complexes which included large nb and ree rich carbonatite intrusions in the cretaceous rift related faults became the sites of small fluorite barite galenastrontianite deposits over a wide area in the elzevir and frontenac terranes and in the charlevoix saguenay area of the central zone

anthropogenic versus natural control on trace element and sr nd pb isotope stratigraphy in peat sediments of southeast florida usa 1500 ad to present abstract analysis of a well dated peat core from blue cypress marsh bcm provides a detailed record of natural and anthropogenic factors that controlled the geochemical cycles of a number of trace elements in florida over the last five centuries the trace elements were divided into natural and anthropogenic groups using concentration trends from the bottom to the top of the core the natural group includes li sc cr co ga ge zr nb cs ba hf y ta th and ree rare earth elements these elements show similar concentrations throughout the core indicating that changes in human activities after european arrival in the new world did not affect their geochemical cycles the anthropogenic group includes pb cu zn v sb sn bi and cd upcore enrichment of these elements indicates enhancement by anthropogenic activities from the early 1500s to present fluxes of the anthropogenic metals to the marsh increased significantly with modern accumulation rates several fold e g v to hundreds of times e g zn greater than pre colonial rates the dominant input mechanism for trace elements from both groups to the marsh has been atmospheric deposition atmospheric input of a number of the elements including the anthropogenic metals was dominated by local sources during the last century for several elements long distant transport may be important for instance ree and nd isotopes provide evidence for long range atmospheric transport dominated by saharan dust the greatest increase in flux of the anthropogenic metals occurred during the 20th century and was caused by changes in the chemical composition of atmospheric deposition entering the marsh increased atmospheric inputs were a consequence of several anthropogenic activities including fossil fuel combustion coal and oil agricultural activities and quarrying and mining operations pb and v exhibit similar trends with peak accumulation rates in 1970 the principal anthropogenic source of v is oil combustion the decline in v accumulation after 1970 in the bcm peat corresponds to the introduction of low sulfur fuels and the change from heavy to distilled oils since the 1970s after the 1920s pb distribution in the peat follows closely the history of alkyl lead consumption in the us which peaked in the 1970s pb isotopes support this inference and furthermore record changes in the ore sources used to produce leaded gasoline idaho ores dominated the peat pb isotope record until the 1960s followed by pb from mississippi valley type deposits from the 1960s to the 1980s enhanced fluxes of cu zn cd sn sb bi and to some extent ni during the last century are likely also related to fossil fuel combustion local agricultural activities may also have influenced the geochemical cycles of cu and zn the peat record shows enhanced u accumulation during the last century possibly related to phosphate mining in western florida sr isotopes in the peat core also reflect anthropogenic influence the 87sr 86sr ratio decreases from natural background values in the basal part of the core to lower values in the upper part of the core the sr isotope shift is probably related to quarrying operations in florida and marks the first time an anthropogenic signal has been detected using the sr isotope record in a peat core

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

lead isotopic compositions of balmat ores and their genetic implications the lead isotopic compositions of galenas and composite ore concentrates from balmat new york state display a small but distinct range of values 206 pb 204 pb 16 72 16 96 which form linear trends on conventional pb pb data plots we believe these are mixing lines not isochrons the less radiogenic component of the ore lead appears to have been derived from surrounding or underlying grenville age sources but the more radiogenic source has not been identified the isotope data correlate with the stratigraphic positions of the ores suggesting that the original ores were sedimentary compositional variations also indicate the existence of two distinct phases or stages of mineralization corresponding to different sections of the stratigraphic sequence data for the edwards mine 206 pb 204 pb 16 58 lie on the same trends but fall outside the range for balmat ores suggesting that these ores were derived from similar sources but that they were formed during a third distinct phase of mineralization compositional variations in the fowler horsetail ores give clear evidence for movement and some mixing of ores during metamorphism and preliminary data for pure sphalerites suggest that other ores may also be remixed

lead isotope ratios in niagara escarpment rocks and galenas implications for primary and secondary sulphide deposition galenas occumng in vugs and veins in the dolomites of the eramosa goat island and gasport members of the middle silurian lockport formation in the niagara escarpment have a small but significant range in lead isotopic composition these differences are recorded in specimens from exposures in the niagara gorge in the east to the guelph quarry 100 km to the northwest the galena isotopic data fit linear trends on 207pb 204pb 206pb 204pb and 208pb 204pb 206pb 204pb plots within experimental error the most radiogenic ratios are anomalous giving model ages based on the growth curves of zartman and doe up to 200 ma younger than the most likely age of primary deposition of 300 ma sulphides currently being deposited from springs at the floor of the vinemount quarry have a lead isotopic composition similar to that of some of the galena in the overlying dolomites rocks from several of the formations exposed at this site contain lead only slightly more radiogenic than the most radiogenic galenas these results are consistent with the hypothesis of haynes and mostaghel that the modem sulphides result from local solution and redeposition of older sulphides previously published isotopic ratios for lead in the potassium feldspar constituents of 300 ma plutonic intrusives in the appalachians cluster around the least radiogenic galena ratios and suggest that the lead in the niagara peninsula galenas has been remobilized from rock units in the appalachian basin grenville crystalline basement rocks do not appear to have contributed significantly to this lead a single sample of galena from the eramosa member exposed in the ebel quarry in the michigan basin at the northwestern extension of the escarpment has 207pb 204pb and 206pb 204pb ratios that are substantially more radiogenic than those in any of the galenas from the niagara region of the appalachian basin and a 08pblz04pb ratio that lies significantly below the linear distribution defined by the niagara region data set we tentatively interpret this difference as reflecting derivation of the lead in the two basins from different crustal blocks

heterogeneous strain of a phyllite as revealed by porphyroblast matrix relationships abstract garnet porphyroblasts in a homogeneous phyllite specimen from the central norwegian caledonides provide insight into the distribution and type of strain which followed the garnet growth matrix schistosity is traceable through the porphyroblasts in the form of inclusions which allow the measurement of two parameters the flattening of the matrix schistosity around the porphyroblasts and an angle of rotation of the porphyroblasts relative to the matrix schistosity both parameters vary considerably as studied in a large thin section cut parallel to mineral lineation and perpendicular to schistosity accepting some simplifications and assumptions it seems necessary to consider the strain as composed of two components a noncoaxial strain component of a simple shear type and an approximately coaxial strain component both of which are heterogeneously developed on the scale of the thin section the shear planes of the simple shear type strain are likely to lie parallel or at a very small angle to the matrix schistosity the linear fabric of the phyllite seems to be a material expression of the coaxial strain component the 1 2 plane of the finite strain ellipsoid most probably varies in orientation across the thin section and is only by coincidence parallel to the almost constantly oriented matrix schistosity

landslide amplification by liquefaction of runout path material after the 2008 wenchuan m 8 0 earthquake china here we propose that an earthquake can trigger the failure of a landslide mass while simultaneously triggering liquefaction of runout path materials before the arrival of the landslide mass thus greatly increasing the size and mobility of an overriding landslide during the 2008 wenchuan earthquake about 60 000 landslides were triggered directly resulting in about 20 000 casualties while these landslides mainly originated from steep slopes some landslides with high mobility formed in colluvial valley deposits among these the most catastrophic was the xiejiadian landslide in pengzhou city which traveled hundreds of meters before coming to rest through field investigation and laboratory testing we conclude that this landslide primarily formed from colluvial deposits in the valley and secondarily from failure of slopes in granitic rock located uphill much of the granitic slope failure was deposited in the upper part of the travel path near the slide head the remainder was dispersed throughout the main landslide deposit superposition of deposits at the landslide toe indicates that landslide debris derived from colluvial soil was deposited first the deposits at the landslide toe displayed flow characteristics such as fine materials comprising basal layers and large boulders covering the deposit surface we hypothesize that the main part of the landslide resulted from seismogenic liquefaction of valley colluvium rather than from liquefaction potentially caused by undrained loading from the granitic slope failures impacting the colluvium to examine the likelihood that seismogenic liquefaction occurred we took samples from different areas of the landslide deposit and performed undrained cyclic shear tests on them in the laboratory the results showed that the sandy soils that comprise most of the deposit are highly liquefiable under seismic loading therefore we conclude that liquefaction of the colluvium in the valley during the earthquake was the main reason for this rapid 46 m s long runout 1 7 km landslide

the effects of normal and shear stress wave phasing on coseismic landslide displacement predictive models used to assess the magnitude of coseismic landslide strain accumulation in response to earthquake ground shaking typically consider slope parallel ground accelerations only and ignore both the influence of coseismic slope normal ground accelerations and the phase relationship between dynamic slope normal and slope parallel accelerations we present results of a laboratory study designed to assess the significance of the phase offset between slope normal and slope parallel cyclic stresses on the generation of coseismic landslide displacements using a dynamic back pressured shearbox that is capable of simulating variably phased slope normal and slope parallel dynamic loads we subjected sediment samples to a range of dynamic loading scenarios indicative of earthquake induced ground shaking we detail the variations in strain accumulation observed when slope normal and slope parallel stresses occur independently and simultaneously both in and out of phase using a range of dynamic stress amplitudes our results show that the instantaneous phasing of dynamic stresses is critical in determining the amount of coseismic landslide displacement which may vary by up to an order of magnitude based solely on wave phasing effects instantaneous strain rate is an exponential function of the distance normal to the mohr coulomb failure envelope in plots of shear stress against normal effective stress this distance is strongly controlled by the phase offset between dynamic normal and shear stresses our results demonstrate that conditions considered by conventional coseismic slope stability models can either overestimate or underestimate earthquake induced landslide displacement by up to an order of magnitude this has important implications for accurate assessment of coseismic landslide hazard

lead isotope zoning in galena an ion microprobe study of a galena crystal from the buick mine southeast missouri ion microprobe techniques have been used to determine the variations of pb isotope ratios within a single octahedral crystal of galena from the buick mine southeast missouri the crystal shows uniform concentric zonation of pb isotope ratios with a total variation of approximately 3 percent in 208 pb 206 pb and approximately 4 percent in 207 pb 206 pb and with the crystal margin being less radiogenic lower 206 204 than the core the range in the observed 208 pb 206 pb ratio is larger than that observed previously for bulk galena analyses from throughout the mine and is almost as large as the total variation reported for the whole southeast missouri ore district the ion probe results are demonstrated to be accurate to 0 1 0 2 percent by comparison with conventional mass spectrometric analyses performed on microsamples of the same crystal the ion probe technique holds promise for establishing a pb isotope chronostratigraphy for the ore bearing solutions which will be useful in delineating temporal and spatial aspects of the fluid circulation patterns

transport of industrial lead in snow through soil to stream water and groundwater determination of isotopic compositions and concentrations of pb in stream water groundwater soil and bed rock in a subalpine watershed combined with concentrations of ca na k mg fe and mn and mineralogical data show that 90 of the industrial pb in snow is trapped in a subunit of the upper 2 cm of soil this is composed of humus plus fe hydroxides and mn oxides where industrial pb mixes isotopically with pb already accumulated there from previous inputs of industrial pb and natural rock pb the 206 pb 207 pb ratio of pb in the upper 2 cm soil accumulation reservoir is different from that of industrial pb added from snow each year because it is a mixture of natural rock pb derived from weathering 20 which has a 206 pb 207 pb ratio different from industrial pb and because the 206 pb 207 pb ratio of industrial pb accumulated from atmospheric inputs during the past century 80 has changed considerably during that time during spring melt when streams are fed mostly by surface runoff pb in the surface soil accumulation reservoir is released back into the runoff and into streams at this time the proportion of industrial pb in mountain stream waters is that in the surface soil accumulation reservoir 80 concentrations and isotopic composition of pb in soil profiles and the relation between pb and organic matter concentration in soil indicate little or no industrial pb accumulates in the reservoir below 2 cm depths these data combined with measured proportions of ca and pb and 206 pb 207 pb ratios in groundwater indicate that most of the pb in aquifers at depth below 30 cm originates by weathering from natural rock pb although aquifers are charged by snow melt industrial pb is removed from the water as it percolates downward through the soil accumulation reservoir therefore during times when streams are fed mainly from these aquifers stream waters contain mainly natural rock pb and some industrial pb in colloids originally contained in snow melt concentrations of pb in stream waters tend to remain constant both throughout different seasons when rates of stream discharge change 20 fold and over the last decade when pb inputs from snow decreased 6 fold because pb in those waters originates from a fixed reservoir in the soil

mixing line isochrons a new interpretation of galena lead isotope data from southeastern british columbia ainsworth bluebell slocan and moyie camps mixing of lead from two different sources both of which follow simple growth curve lead evolution the more radiogenic source is thought to represent evolution of lead in the upper crustal continentally derived sedimentary rocks which host these deposits the two stage bluebell growth curve provides an estimate of the uranium poor lead source which may be the lower crust the upper mantle or a mixture of both mixing line isochrons drawn between these two curves at ages corresponding to the best estimates for the mineralization ages at these three mining camps closely fit the lead isotope data this supports the age estimates for all three camps and in particular substantiates a lower cambrian age for the original mineralization in the ainsworth and bluebell deposits mixing is assumed to take place at the time of mineralization and may be attributed to magmatic activity in the moyie and slocan camps applicability of the model to a large part of the omineca belt may be used to date both epigenetic and syngenetic or penecontemporaneous deposits of unknown age modified journal abstract

lead isotopic determination of historical sources of lead to lake erie north america abstract measurements of lead concentrations and stable lead isotopic compositions 204pb 206pb 207pb 208pb in sediment cores from lake erie document both temporal and spatial variations in lead sources to the lake these analyses track the history of lead contamination in the lake as well as the transport of particulate matter which governs the redistribution of particle reactive contaminants within the lake the isotopic compositions of the sediments reveal two sources of natural lead fluvial and shoreline bluff erosion and three primary sources of anthropogenic lead coal combustion gasoline additives and municipal waste water discharges to the lake lead concentrations and isotopic compositions of 210pb dated sediment cores record historical variations in the inputs from these sources the heterogeneous isotopic composition of the three basins of lake erie indicates that lead from municipal effluent is most prominent in the urbanized western region of the lake and that atmospheric deposition is most prominent in the more rural eastern areas calculations based on a 207 pb 206 pb vs 208 pb 206 pb linear mixing model show that as much as 70 of sediment in the central basin and 25 in the east basin originates from the west basin of lake erie these calculations attest to the interbasinal redistribution of particle reactive contaminants within the lake

the protocontinental nature and regional variability of the central metasedimentary belt of the grenville province lead isotope evidence the lead isotopic compositions of sulphide samples mainly galenas from a representative set of mineral deposits within the central metasedimentary belt of the grenville province have been determi

a probabilistic model for the persistence of early planar fabrics in polydeformed pelitic schists abstract although early planar fabrics are commonly preserved within microlithons in low grade pelites in higher grade amphibolite facies pelitic schists fabric regeneration often appears complete evidence for early fabrics may be preserved within porphyroblasts but within the matrix later deformation often appears to totally obliterate or reorient earlier fabrics however examination of several hundred dalradian pelites from connemara western ireland reveals that preservation of early fabrics is by no means uncommon relict matrix domains although volumetrically insignificant are remarkably persistent even when inferred later strains are very large and fabric regeneration appears at first sight complete deterministic plasticity theories are ill suited to the analysis of such an inhomogeneous material response and a probabilistic model is proposed instead it assumes that ductile polycrystal deformation is controlled by elementary flow units which can be activated once their associated stress barrier is overcome bulk flow propensity is related to the proportion of simultaneous activations and a measure of this is derived from the probabilistic interaction between a stress barrier spectrum and an internal stress spectrum the latter determined by the external loading and the details of internal stress transfer the spectra are modelled as gaussian distributions although the treatment is very general and could be adapted for other distributions using the time rate of change of activation probability it is predicted that initially fabric development will be rapid but will then slow down dramatically even though stress increases at a constant rate this highly non linear response suggests that early fabrics persist because they comprise unfavourable distributions of stress barriers which remain unregenerated at the time bulk stress is stabilized by steady state flow relict domains will however bear the highest stress and are potential upper bound palaeostress estimators some factors relevant to the micromechanical explanation of relict matrix domains are discussed

nd and pb isotope signatures on the southeastern south american upper margin implications for sediment transport and source rocks abstract neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the southeastern south american upper margin the sediments of the argentinian margin exhibit an average nd value of 1 9 indicating the influence of the andean rocks as sediment sources sediments from the rio de la plata estuary show an average nd value of 9 6 which is similar to that of the southern brazilian upper margin finally sediments of southeastern brazil which are associated with the transport of the brazil current exhibit an average nd of 13 0 the pb isotope signatures also confirm the differentiation of source rocks in the sedimentation of the study area in addition pb isotopes helped to establish the extent of the influence of the rio de la plata on the sedimentation of the southern brazilian margin in terms of pb isotopes the sediments from the rio de la plata estuary and southern brazil are more radiogenic than those of southeastern brazil and the argentinian margin

quantifying 20th century deposition in complex estuarine environment an example from the hudson river sediment processes in estuaries are controlled by the interaction of factors that include tides fresh water inputs bed morphology sediment supply and hydrodynamics the interaction of these factors strongly influences the pattern of sediment deposition the ability to quantify sediment deposition on a regional scale will improve the understanding of the underlying processes and provide valuable information for managing estuarine systems this paper describes our approach for obtaining the deposition pattern and quantifying the amount of 20th century impacted sediments in the haverstraw bay section of the hudson river estuary through the combination of high resolution seismic data and rapidly acquired geochemical information from numerous sediment cores we estimate that our study site experiences an average sediment accumulation rate of 3 mm y and that 75 000 t y or 10 of the annual total sediment input measured at the poughkeepsie ny gauging station usgs is stored in this reach of the hudson river on 100 y timescales a detailed analysis of the depositional pattern indicates that the accumulation rate varies considerably throughout the study area ranging from non depositional to 8 mm y our data also clearly indicate that the dredged channel in haverstraw bay is currently the main focus of deposition in this area

an experimental study to characterize the initiation of the seismic induced tsaoling rock avalanche abstract the tsaoling rock avalanche which had a sliding volume of 120 million m3 and a maximum thickness of 170 m was triggered by the chi chi earthquake in 1999 however the initiation mechanism has not been well understood because different friction models have been proposed to describe the triggering process using the newmark sliding model and numerical simulations in this study a new dynamic ring shear test with a maximum normal stress higher than 3400 kpa is applied as an alternative approach to investigate the initiation of the seismic induced rock avalanche along the wet sliding surface at the interface of the cholan sandstone and consolidated remold shale experimental results verify that the seismic stresses at the wet sliding surface touch the failure surface and generate significant cumulative shear displacements additionally the shear surface should have non linear failure criteria rather than the well known linear mohr coulomb failure criteria with a constant friction angle furthermore the initiation time of the tsaoling rock avalanche obtained from the dynamic ring shear test is strongly correlated with the available seismic signal interpretations and the interviews of witnesses who travelled with the sliding mass this is the first experiment clarifying the co seismic behavior of the sliding surface and the initiation of the tsaoling landslide during the chi chi earthquake additionally from the development of the ring shear test the integrations of high normal stress the wet sandstone shale interface and the dynamic test with seismic loadings greatly extend the use of ring shear tests to rock avalanches

sediment mixing and accumulation rate effects on radionuclide depth profiles in hudson estuary sediments measured anthropogenic radionuclide profiles in sediment cores from the hudson river estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment observed sup 134 cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide whereas the inputs of sup 137 cs and sup 239 240 pu to the estuary were complicated by runoff or erosion in upstream areas in addition to direct fallout from precipitation our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0 25 to 1 cm sup 2 yr or less in some areas of the harbor adjacent to new york city were fine particle accumulation rates are generally 3 cm yr and often as high as 10 to 20 cm yr sediment mixing rates as high as 10 cm sup 2 yr would have little effect on radionuclide peak distributions consequently anthropogenic radionuclide maximum activities in subsurface sediments of the hudson appear to be useful as time stratigraphic reference levels which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation

the development of shear zones in polycrystalline camphor urai j l and humphreys f j 1981 the development of shear zones in polycrystalline camphor in g s lister h j behr k weber and h j zwart editors the effect of deformation on rocks tectonophysics 78 677 685 thin polycrystalline specimens of rhombohedral camphor have been deformed in pure shear in the temperature range 283 343k the deformation processes dynamic recrystallization and the development of microstructure were followed by transmission polarized light microscopy when the stress distribution in the specimens was favourable shear zones were initiated the development of microstructure changed drastically above 310320k the shape of the dynamically recrystallized grains which was equiaxed below this temperature became strongly elongated this change probably due to the development of a marked anisotropy in grain boundary mobilities and the activation of new slip systems made the development of shear zones a more frequently occurring phenomenon above 310 320k

excess pore pressure and grain crushing of sands by means of undrained and naturally drained ring shear tests an investigation of excess pore pressure generation of a weathered granitic sand taken from the source area of a typical landslide caused as a result of liquefaction and a fine silica sand was conducted in which grain crushing within the shear zone of ring shear test specimens was examined as the key phenomenon of rapid long runout motion of landslides in order to investigate and explain the low average apparent friction angle mobilized in a liquidized landslide speed controlled ring shear tests were conducted under undrained conditions on weathered granitic sand specimens formed under a wide range of initial void ratios it was revealed that very small steady state shear resistances were obtained irrespective of the initial void ratios which can explain the low average apparent friction angle in addition two series of ring shear tests on weathered granitic and fine silica sands were conducted under naturally drained conditions by keeping the upper drain valve of the shear box open during the tests the first series of tests was performed under differing total normal stresses but at the same shear speed and the second series was conducted at differing shear speeds but under the same total normal stress in order to investigate and analyze excess pore pressure generation and dissipation within the shear zone that is associated with grain crushing permeability analyses were conducted by passing water through the sample box of the ring shear test apparatus before and after shearing in addition grain size distribution analyses of samples taken from the shear zone after shearing were carried out for the weathered granitic sand samples a significant change in bulk permeability and large amount of grain crushing were observed in these tests on the above soil a considerable reduction of shear resistance which increased proportionally to the total normal stress and shear speed were obtained it was observed that due to grain crushing finer grains that lowered the permeability of the soil in the shear zone were formed it is likely that the decrease in permeability facilitated the generation of high excess pore pressures by reducing the pore pressure dissipation rate from the shear zone thus flow behaviour was exhibited even under naturally drained conditions

undrained anisotropy of hostun rf loose sand new experimental investigations the undrained behaviour of loose and overconsolidated hostun rf sand in triaxial compression and extension tests is described the samples are isotropically or anisotropically overconsolidated along several constant effective stress ratio paths with various overconsolidation ratios ocr up to 24 to minimize the effect of variation of density on the observed undrained behaviour all tested samples are required to have a nearly identical void ratio before the final monotonic undrained shearing isotropically overconsolidated and normally consolidated samples exhibit the same phenomenon of partial static liquefaction but anisotropically overconsolidated specimens reveal a completely different undrained behaviour a common pseudoelastic response is observed for a given overconsolidation history this response is induced by recent stress history in terms of effective stress paths independent of the ocr during overconsolidation the initial gradient of the effective stress paths seems to depend solely on t

u pb dating of a remagnetized paleozoic limestone the upper ordovician trenton group of new york state is one of a number of appalachian limestones which yields paleomagnetic poles suggesting disturbance in the late paleozoic calcite fractions dissolved from samples of the trenton limestone define a 238u 206pb age of 454 8 ma mswd 12 8 in excellent agreement with 40ar 39 ar and u pb ages for the deposition of the underlying diecke bentonite this requires that the u pb system in the calcite has been preserved since deposition and early diagenesis if late paleozoic remagnetization of this limestone was induced by fluids these fluids did not interact with significant amounts of carbonate the apparent robustness of the u pb system and the large spread in values 18 17 118 8 offers potential precision of 1 ma in determining the paleozoic time scale

lead pollution resulting from roman gold extraction in northwestern spain roman mining and metallurgy left a detectable signal of lead pollution throughout europe northern africa and the middle east las medulas in northwestern iberia was the largest roman gold mine

the origin of a mississippi valley type deposit in the viburnum trend southeast missouri petrologic and isotopic studies of the base metal sulfide mineralization in the buick mine have established the following paragenesis an early stage of fine grained pyrite and marcasite replaced the dolostone host rock the iron disulfides and dolostone were replaced by sphalerite during the main stage of sphalerite precipitation delta 34 s sp 16 5 to 19 0ppm following the sphalerite two main stages of galena were precipitated a cuboctahedral stage delta 34 s gn 21 3 to 10 0ppm during which galena replaced dolostone and sphalerite and grew in vugs in the dolostone and in the sphalerite and a cubic stage delta 34 s gn 10 5 to 0 9ppm the two stages of galena precipitation were separated by a period during which the main stage of sphalerite and the cuboctahedral galena were partially dissolved and bladed marcasite delta 34 s mc 2 3 to 4 1ppm was precipitated and followed by a period of mild etching of the cubic galena minor amounts of pale sphalerite delta 34 s sp 14 0 to 16 5ppm were then precipitated white and colorless rhombs of dolomite were precipitated at the same time as some of the main stage of sphalerite the cubic galena and the pale sphalerite after the pale sphalerite was precipitated chalcopyrite quartz and siegenite were precipitated followed by calcite and finally kaolinite the paragenetic and textural data for both galena and sphalerite in the buick mine strongly suggest that these minerals were precipitated and dissolved repetitively during ore formation similar textural evidence for galena reported by other workers for different mines in the viburnum trend implies that repetitive precipitation and dissolution of galena was probably an important process during the formation of the entire viburnum trend fluid inclusions in late quartz crystals coprecipitated with chalcopyrite have filling and freezing temperatures within the ranges reported for sphalerite from other parts of the viburnum trend demonstrating that the ore forming solutions in the viburnum trend were probably at temperatures in the range 105 degrees to 141 degrees c assuming a maximum pressure correction of about 11 degrees c and were extremely saline containing about 4 0 to 5 0 molal chloride consideration of typical chemical analyses of fluid inclusions from other mississippi valley type deposits suggests that the maximum likely concentration of dissolved co 2 in the ore forming solutions was about 0 05 molal at these concentrations the ore forming solutions that travelled to the site of deposition could have had ph9s about two units less than neutral and still have been in equilibrium with dolomite or calcite the ranges of sulfur and lead isotopic compositions of galena from the buick mine are very similar to those established by earlier studies of the old lead belt and adjacent subdistricts however the correlation of isotopically lighter sulfur with more radiogenic lead is much stronger for the viburnum trend suggesting that galena was precipitated from many solutions each of which carried lead and sulfur together and had different lead and overall sulfur isotopic compositions the textural paragenetic and isotopic data for the buick mine cannot be easily explained either by a sulfate reduction model in which sulfate was reduced by organic matter or methane or mixing models in which base metals and reduced sulfur were transported separately to the site of deposition instead the data strongly support a reduced sulfur model for ore formation according to which the base metals were transported together with reduced sulfur as h 2 s in the same solutions to the sites of deposition the reduced sulfur model is also supported by a theoretical calculation of the solubilities of galena and sphalerite which demonstrate that low but economically significant concentrations of lead or zinc could have been transported as chloride complexes together with equivalent concentrations of reduced sulfur at temperatures of 100 degrees to 150 degrees c and ph9s of one to two units less than neutral and could have been precipitated by ph increases cooling or dilution at the sites of deposition

lead pb isotopes as a tracer of pb origin in yangtze river intertidal zone abstract in order to investigate the source of pb within the yangtze river intertidal zone studying pb isotope ratios is a likely approach because the ratios of these pb isotopes can be used to identify the natural or anthropogenic origin of pb in this study a total of 59 surface sediment samples 204 pb 206 pb 207 pb and 208 pb and found that the total pb concentrations varied from 18 3 to 44 1 mg kg 1 with an average concentration of 27 3 mg kg 1 the observed pb isotope ratios excluding one station near shanghai pudong airport which is significantly influenced by anthropogenic sources varied from 18 459 to 18 750 for 206 pb 204 pb 15 628 to 15 728 for 207 pb 204 pb and 38 715 to 39 213 for 208 pb 204 pb this study shows that pb found within the yangtze river intertidal zone sediments was mainly from the catchment in the yangtze river watershed significant pb pollution was not discerned in the yangtze river intertidal zone however pb contamination in some localized areas was suggested by pb enrichment factor ef

the interaction of deformation and metamorphism in slates abstract the distribution microchemistry and internal structure of phases present in a slate are reported and used as a basis for a discussion of the interaction between deformation and metamorphism in slates the study reveals details of the interactions between mechanical and chemical processes involved in slaty cleavage evolution evidence for the involvement of mechanical rotation solution and crystallisation recrystallisation and metamorphic reactions is presented and amalgamated into a model of cleavage development the model involves a synchronous variation in the type location and rate of cleavage evolution processes and a change in the importance of particular processes during the total history the early stages of cleavage development are dominated by mechanical rotation associated with crenulation and possibly accompanied by grain boundary sliding and solution processes later stages of cleavage evolution are more heterogeneous and occur by a complex interaction of deformation and metamorphic growth processes which are concentrated at the interfaces between domains generated earlier in the strain history the variations in grain chemistry and orientation together with changes in the strain rate or stress level are suggested to control the different deformation behaviour of different grains along these strain accommodation zones and to dictate whether grains bend kink dissolve recrystallise or react and undergo growth evidence for the involvement of reactions ranging from ionic exchange to crystallisation from solution and solid state reordering is presented and the influence of deformation on the location and rates of these reactions discussed approximately ten potential reactions are involved in the cleavage evolution of the slate studied the model presented incorporates these reactions into the deformation processes and accounts for the concentration of phengite and iron poor chlorites in to one microstructural domain and paragonite quartz and fe rich chlorites into the other domain two transformations appear to be fundamental in the slate studied 1 1 the transformation of illite to phengite 2 2 the transformation of fe rich chlorite to fe poor chlorites and both can be related to particular responses of grains to the reorientation processes at domain interfaces

lead isotope analyses of leached feldspars constraints on the early crustal history of the grenville orogen abstract lead isotopic data on leached k feldspars plagioclases and muscovite provide constraints on the premetamorphic evolution of the grenville orogen in ontario and new york a boundary between reworked archean crust to the northwest and new mantle derived crust generated during mid proterozoic times to the southeast is identified within the northern portion of the gneiss belt of ontario the identification of juvenile mid proterozoic crust at the southeastern margin of the orogen is consistent with previous investigations based on neodymium model ages however near the grenville front lead isotopes indicate the presence of reworked archean crust rather than primary early proterozoic crust postulated on the basis of neodymium model ages this discrepancy between the lead and neodymium isotopic terranes underscores the necessity of using a multidisciplinary approach to identify possible terrane boundaries only through a combination of the lead with neodymium isotopes is it possible to distinguish between crust that formed during a single major orogenic cycle and crust that represents a mixture of old with new mantle derived material the combined neodymium and lead data imply that the grenville orogen in ontario consists essentially of reworked archean crust and juvenile mantle derived material generated around 1 5 ga the grenville orogen involved archean crust that was depleted in thorium and uranium several hundred ma before high grade metamorphism at ca 1 1 ga such a depletion may have a significant impact on the geotherm achieved during orogeny and may explain the lower metamorphic thermal gradients observed for the gneiss belt

lead isotopes as particulate contaminant tracers and chronostratigraphic markers in lake sediments in northeastern north america abstract the utility of lead pb isotopes as tracers of particulate contamination and as chronostratigraphic markers was assessed in five lake sediment cores from the great lakes and southern ontario region the marker for smelting of highly radiogenic ores in the upper mississippi valley in the mid 19th century was seen in the pb isotopes in four lakes expanding the geographic range of this established marker into southern and central ontario this marker is useful for age dating sediments deposited in the 1800s in archives where it is present the estimated dates for this 1850 marker using other dating methods span a range of 57 years emphasizing the importance of the marker as a tie point for extrapolated dates in the 19th century lead isotopes identified leaded gasoline as an important source only in one lake in the second half of the 20th century its signal was not identified in all other lakes because the lakes were more affected by local and regional inputs lead isotopes combined with trace metal fluxes identified a potential marker for coal combustion or urban sources in the second half of the 20th century in southern ontario where these sources were significant enough to outweigh leaded gasoline input the effects of canadian mining and smelting activities were seen in the trace metal flux profiles of central ontario lakes however these activities were not visible in the pb isotopes likely due to mixing of several sources with similar pb isotopic signatures this study demonstrates the usefulness of combining lead isotopes and trace metal flux profiles for identifying markers of historical and modern particulate contamination sources especially in regions where several pollution sources exist

experimental study on the dynamic characteristics of low angle loess slope under the influence of long and short term effects of rainfall before earthquake abstract landslides on low angle slopes can be caused under the coupled effect of rainfall and earthquake in order to investigate the influence of duration of time between rainfall and earthquake on the scale and failure mode of landslides a low angle loess slope at lanzhou new area was adopted as a prototype and a large scale shaking table test was performed by using self designed artificial rainfall equipment 30 mm of rainfall 12 h before shaking and 20 mm rainfall immediately before shaking were exerted on the slope model to investigate the responses and determine the differences in the failure mode of the low angle slope under different rainfall cases to measure the dynamic response of the test model at each working condition 18 acceleration sensors 7 soil pressure sensors 10 pore water pressure sensors and optical measurement techniques were used the results show that the acceleration amplification effect increased with increasing intensity and the soil pressure increased with decreasing elevation under the long term effects of rainfall before earthquake but the value on the slope surface decreased under the short term effects of rainfall before earthquake the dynamic pore pressure value varied considerably between positive and negative and the maximum displacements at slope surface increased about 69 7 under the short term effects of rainfall before earthquake large displacements and deep cracks occurred on the surface of the slope mainly caused by the loess losing its strength and the large inertial force on the surface owing to the long term effect of rainfall before the earthquake the damage to the low angle slope was mainly caused by liquefaction and the loss of loess strength under the influence of short term rainfall before the earthquake the failure of the slope was soil flow which was similar to the sliding process of the yongguang village landslides finally we note that the effect of coupled effect on the low angle slope should be evaluated in future work from two aspects the intensity of rainfall and earthquake and the time when rainfall occurred before the earthquake

a new attenuation relation for peak horizontal acceleration of strong earthquake ground motion in japan abstract a new attenuation relation for peak horizontal acceleration applicable to the near source region in japan is developed the data base consists of 1372 horizontal components of peak ground acceleration from 28 earthquakes in japan and 15 earthquakes in the united states and other countries coefficients describing the decrease in acceleration with increasing distance found by most previous studies of japanese data are significantly smaller than those found by analyzing individual earthquakes this phenomenon is examined and found to result from use of general nonstratified multiple regression analyses the present analysis uses a two step stratified regression procedure and an attenuation model that accounts for geometrical spreading and anelastic attenuation but has magnitude independent shape at very short distances the resulting relation in japan is log 10 a 0 41 m log 10 r 0 032 10 0 41 m 0 0034 r 1 30 where a is the mean of the peak acceleration from two horizontal components at each site cm sec 2 r the shortest distance between site and fault rupture km and m the surface wave magnitude the median estimate of peak horizontal acceleration at the source region is 620 cm sec 2 independent of earthquake magnitude effects of four different ground condition rock hard medium and soft soils on the attenuation relation are also examined average peak horizontal accelerations for the rock and the soft soil sites are 60 and 140 per cent respectively of the value predicted from the equation

assessing the response of watersheds to catastrophic logging and possible secular global temperature change perturbations using sediment chemical chronologies abstract geochemical profiles of sediment cores from two oligotrophic lakes elk and mullett in northern lower michigan were studied to examine the response and recovery of watersheds to large scale logging that occurred between 1850 and 1920 specific questions addressed were can the impact of extensive clear cutting of forests be recognized in the sediment chemical chronologies can states of system stability be identified prior to the logging and are there indications that the systems are recovering and possibly returning to a stable state to answer these questions elements were put into four groups as proxies for watershed runoff or export e g al mg pollution e g pb cu redox e g fe as and productivity e g ca p it was observed that vertical patterns of all proxies were influenced by logging and the early increases in concentration of pollution proxies were due to increased watershed export not pollution system stability might be recognized by relatively symmetrical vertical patterns among all of the proxies or secular changes of slowly increasing or decreasing vertical concentration trajectories some pre logging trajectories were punctuated by episodes of slightly elevated concentrations that appear to be related to comparatively warmer periods during the little ice age iron and mn enrichments caused by increased watershed runoff might be misinterpreted as paleo redox horizons results are interpreted to indicate that 1 reference conditions may be better defined as the temporal trends among proxy groups and not individual concentrations 2 simply assuming pre 1800 conditions as a reference may not be appropriate 3 inter proxy group comparisons are needed to help for interpretations of intra proxy group patterns 4 the possible regime shift identified here might be expected for other ecosystems because of the intensity of human disturbances and secular changes and 5 without consideration of a possible regime shift recovery from logging is estimated to be on the order of 75 130 a but shorter if regime shifts are considered

post failure mobility of saturated sands in undrained load controlled ring shear tests the undrained shear behavior of soils with progress of shear displacement is essential to the understanding of liquefied slope failures with long travel distance in this paper using a newly devel

magnitudes and sources of precipitation and dry deposition fluxes of indestrial and natural leads to the north pacific at enewetak a total atmospheric pb input flux of 7 ng pb cm 2 yr 1 was measured in the north pacific easterlies at enewetak parameters used to measure this flux were ratio of dry deposition flux to precipitation flux pb 210 pb in precipitation and seawater 210 pb flux washout factor and pb concentrations in air rain and dry deposition deposits relations among these parameters established at enewetak were used to recompute and confirm previous estimates of lead fluxes to the oceans ng pb cm 2 yr 1 at the following locations north atlantic westerlies 170 north pacific westerlies 50 and south pacific easterlies 3 prehistoric lead output fluxes to sediments ng pb cm 2 yr 1 at these locations have been previously measured and were 4 enewetak 30 north atlantic westerlies 3 north pacific westerlies 4 south pacific easterlies these data show that the rates of atmospheric inputs of lead to the oceans vary directly with variations in rates of upwind emissions of industrial lead from urban complexes on land in the north pacific and north atlantic present rates of atmospheric lead inputs are 10 fold greater than prehistoric outputs in equatorial regions present inputs and past outputs are more nearly equal these observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans the average concentration of lead in marine air at enewetak is 170 pg m 3 and varies less than a factor of 2 from that mean one to 15 of this lead comes from seaspray while the remainder comes from sources on land about 90 of the seaspray lead is industrial while 80 to 99 of that originating from land sources is industrial concentrations of lead in rain at enewetak range from 6 to 63 pg g with a mean value of 28 the mean precipitation flux corrected for recycled lead in sea salts measured by four different methods was 6 ng pb cm 2 yr 1 while the net dry deposition flux measured on horizontal plastic plates was 0 6 ng pb cm 2 yr 1 the total dry deposition flux measured was 6 ng cm 2 yr 1 but 90 of this lead came from recycled seaspray lead isotope tracers show that japan is the major source of industrial lead at enewetak during the dry season while the united states is the major source during the wet season

residual shear strength variability as a primary control on movement of landslides reactivated by earthquake induced ground motion implications for coastal oregon u s most large seismogenic landslides are reactivations of preexisting landslides with basal shear zones in the residual strength condition residual shear strength often varies during rapid displacement but the response of residual shear zones to seismic loading is largely unknown we used a ring shear apparatus to perform simulated seismic loading tests constant displacement rate tests and tests during which shear stress was gradually varied on specimens from two landslides to improve understanding of coseismic landslide reactivation and to identify shear strength models valid for slow gravitational failure through rapid coseismic failure the landslides we studied represent many along the oregon u s coast seismic loading tests resulted in 1 catastrophic failure involving unbounded displacement when stresses represented those for the existing landslides and 2 limited to unbounded displacement when stresses represented those for hypothetical dormant landslides suggesting that coseismic landslide reactivation may be significant during future great earthquakes occurring near the oregon coast constant displacement rate tests indicated that shear strength decreased exponentially during the first few decimeters of displacement but increased logarithmically with increasing displacement rate when sheared at 0 001 cm s 1 or greater dynamic shear resistance estimated from shear strength models correlated well with stresses observed during seismic loading tests indicating that displacement rate and amount primarily controlled failure characteristics we developed a stress based approach to estimate coseismic landslide displacement that utilizes the variable shear strength model the approach produced results that compared favorably to observations made during seismic loading tests indicating its utility for application to landslides

late holocene sea and land level change on the u s southeastern atlantic coast abstract late holocene relative sea level rsl reconstructions can be used to estimate rates of land level subsidence or uplift change and therefore to modify global sea level projections for regional conditions these reconstructions also provide the long term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability to address a spatial absence of late holocene data in florida and georgia we reconstructed 1 3 m of rsl rise in northeastern florida usa during the past 2600 years using plant remains and foraminifera in a dated core of high salt marsh sediment the reconstruction was fused with tide gauge data from nearby fernandina beach which measured 1 91 0 26 mm year of rsl rise since 1900 ce the average rate of rsl rise prior to 1800 ce was 0 41 0 08 mm year assuming negligible change in global mean sea level from meltwater input removal and thermal expansion contraction this sea level history approximates net land level subsidence and geoid change principally from glacio isostatic adjustment historic rates of rise commenced at 1850 1890 ce and it is virtually certain p 0 99 that the average rate of 20th century rsl rise in northeastern florida was faster than during any of the preceding 26 centuries the linearity of rsl rise in florida is in contrast to the variability reconstructed at sites further north on the u s atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable rsl reconstructions comparison of the difference between reconstructed rates of late holocene rsl rise and historic trends measured by tide gauges indicates that 20th century sea level trends along the u s atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the greenland ice sheet

high resolution historical records from pettaquamscutt river basin sediments 2 pb isotopes reveal a potential new stratigraphic marker a high resolution record of pb deposition in rhode island over the past 250 yr was constructed using a sediment core from the anoxic pettaquamscutt river basin the sedimentary pb concentration record shows the well described maximum associated with leaded gasoline usage in the united states diminished pb variability during recorded periods of local industrial activity 1735 to 1847 supports the greater importance of regional atmospheric lead transport vs local inputs the pb isotopic composition at this site shows a clear maximum in anthropogenic 206 pb 207 pb in the mid 1800s similar peaks have also been observed in sediments from chesapeake bay and the great lakes suggesting a common source possible causes for this event include mining and smelting of pb ores in the upper mississippi valley district which accounted for almost all pb production in the united states in that period the timing of this event can provide an important stratigraphic marker for sediments deposited in the past 200 yr in the northeastern united states the downcore profile of anthropogenic 206 pb 207 pb provides a classic example of how changes in the mixture of ores for production of tetraethyl lead caused a regional scale shift in the sedimentary record and suggests that coal could have played a secondary role in pb emissions after 1920 copyright 2005 elsevier ltd

stable lead isotopes contaminant metals and radionuclides in upper hudson river sediment cores implications for improved time stratigraphy and transport processes radionuclide stable lead isotope and trace metal analyses on fine grained sediment cores collected along a 24 mile reach of the upper hudson river were used to establish temporal trends of contaminant loadings to establish stable lead isotopes as an additional stratigraphic tool and as tracers for resolving particle transport fluxes over periods of decades very large contaminant inputs of cd sb pb and cr were evident in the sediment record one potential large source for these metals was from a pigment manufacturing facility in glens falls ny the total range in stable lead isotope ratios observed in well dated cores from about 15 miles downstream of the potential metal inputs was large e g maximum difference in 206 pb 207 pb is 10 and characterized by four major shifts occurring in the 1950s 1960s 1970s and 1980s the temporal trend in 206 pb 207 pb has been used to establish precise dating of a sediment core from 24 miles further downstream the large magnitude and abrupt shifts in stable lead isotope ratios preserved in upper hudson sediment cores provide a way to significantly improve dating models based only on radionuclide analyses cadmium lead and antimony were identified as quite sensitive tracers of upper hudson sediments due to the magnitude of contamination and the lack of significant additional downstream sources of these contaminant metals metal measurements in a pair of sediment cores located 24 miles apart were used to constrain relative fluxes of sediment entering the river between the two coring locations with sediment sections deposited between the early 1960s and the late 1970s in these two cores suggesting that 3 4 times more sediment entered the river between the two coring sites than was transported from upstream these dilution factors agree very well with estimates based on suspended sediment measurements during a flood event in april 1994 and with estimates based on mechanistic model of suspended sediment transport between 1977 and 1992 d 2003 elsevier science b v all rights reserved

lead isotopes as tracers of lead pollution from various sources an example from northern sweden abstract the surface sediments in the central bothnian bay are contaminated with anthropogenic pb preindustrial concentrations range from 9 to 43 ppm but the surface sediments contain up to 158 ppm pb possible sources of the pb pollution are anthropogenic atmospheric pb where the main pb source is combustion of gasoline and ore from the laisvall mine which is processed in the smelter ronnskars verken on the coast of bothnian bay because the pb isotope composition of these possible sources are known an attempt was made to trace the origin of the anthropogenic pb in bothnian bay by studying the pb isotope composition of sediments the results show unequivocally that laisvall pb is not the source of the pollution the enrichment of pb in surface sediments is caused by atmospheric deposition of pb additives from gasoline lead emitted from ronnskarsverken is deposited relatively close to the smelter and has not reached central bothnian bay in traceable amounts

experimental study on the shearing behavior of saturated silty soils based on ring shear tests the shearing behavior of saturated silty soils has been examined extensively by performing undrained and partially drained the upper drainage valve of the shear box was open during shearing ring shear tests on mixtures of a sandy silt with different loess contents by performing tests at different initial void ratios the shear behavior of these silty soils at different initial void ratios is presented and discussed undrained shear test results showed that the liquefaction phenomena in ring shear tests were limited within the shear zone for a given void ratio or interfine void ratio both the peak and steady state shear strengths decreased with increase of loess content the partially drained shear tests revealed that a great reduction in the shear strength could result after the shear failure due to the buildup of excess pore water pressure within the shear zone the magnitude of reduction in shear strength after failure was affected by the initial void ratio the shear speed after failure as well as the loess content in the sample for a given void ratio or interfine void ratio with increase of loess content the drained peak shear strength became smaller while the brittleness index became greater it was also found that due to localized shearing the permeability of the soil within the shear box after drained shearing could be three orders of magnitude smaller than before shearing

lead in corals reconstruction of historical industrial fluxes to the surface ocean twentieth century environmental lead chronologies for the western north atlantic pacific and indian oceans have been reconstructed from annually banded scleractinian corals measurements of lattice bound pb in sequential coral bands reveal temporal changes in surface water pb concentrations and pb isotopic distributions perturbations are observable in all specimens studied attesting to global augmentation of environmental pb by industrialization in the western north atlantic pb perturbations have occurred in direct response to the american industrial revolution and the subsequent introduction and phasing out of alkyl pb additives in gasoline surface ocean conditions near bermuda may be reliably reconstructed from the coral data via a lead distribution coefficient of 2 3 for the species diploria strigosa based on210pb measurements a similar distribution coefficient may be characteristic of corals in general surface pb concentrations in the pre industrial sargasso sea were about 15 20 pm concentrations rose to near 90 pm by 1923 as a result of metals manufacture and fossil fuel combustion beginning in the late 1940 s increased utilization of leaded gasoline eventually led to a peak concentration of 240 pm in 1971 representing an approximate 15 fold increase over background surface ocean concentrations are presently declining rapidly 128 pm in 1984 as a result of curtailed alkyl pb usage lead isotopic shifts parallel the concentration record indicating that characteristic industrial and alkyl pb source signatures have not changed appreciably in time industrial releases recorded in the florida keys reflect a weaker source and evidence of recirculated pb 5 6 years old from the north atlantic subtropical gyre an inferred background concentration of 38 pm suggests influence of shelf and or resuspended inputs of pb to these coastal waters in remote areas of the south pacific and indian oceans industrial signals are fainter and the corals studied much younger than their atlantic counterparts contemporary pb concentrations implied by coral measurements assumingkd 2 3 are 40 50 pm for surface waters near tutuila and galapagos in the south pacific and 25 29 pm near mauritius in the indian ocean a single coral band from fiji 1920 5yr implies a pre industrial surface water concentration of 16 19 pm pb for the south pacific in view of reported surface water measurements and the north atlantic coral data the pacific coral extrapolations may be slightly high this could be a result of small variations inkd among different coral genera or incorporation of diagenetic pb by corals sampled in coastal environments

a new ring shear device for testing rocks under high normal stress and dynamic conditions abstract a new ring shear device was developed to investigate the sliding mechanism of earthquake triggered large rock avalanches the loading capacity of the new device is adequate to apply dynamic normal force and torque to a rock specimen to simulate the dynamic stress path of the sliding surface in an earthquake a rock sample taken from cholan formation at the tsaoling landslide site which was triggered by the 1999 chi chi earthquake was the primary test material investigated the failure conditions of the sliding surface and the effect of seismic inertial force on the sliding blocks are considered as the terms of this test the experimental results reveal that different cumulative shear displacements under different initial normal stresses the accumulated shear displacements with and without seismic inertial forces are 38 7 mm and 2 mm respectively the negative accumulated shear displacement indicates an abnormal sliding orientation that moved toward the top of the slope therefore the new ring shear device is a useful tool in realizing the dynamic behavior and shear mechanics of the sliding surface of an earthquake triggered large rock avalanche

changes of lead and barium with time in california off shore basin sediments during ancient times the natural deposition fluxes of lead which can be leached with dilute acid from sediments in santa barbara santa monica and san pedro basins offshore from the los angeles urban complex were about 0 7 0 1 and 0 2 g pb cm 2 yr respectively since there was little difference in biological productivity in surface waters of these basins it is proposed that clay is a major transport vehicle for sequestered soluble lead which then explains why the lead deposition flux within the santa barbara basin was so much larger compared to the other basins the fluxes of silicate mud in the basins in ancient times were about 92 19 and 30 mg cm 2 yr in santa barbara santa monica and san pedro basins respectively today deposition fluxes of acid soluble lead within these three basins are 3 to 9 fold greater being about 2 1 1 1 and 1 8 g pb cm 2 yr respectively partly in the form of directly deposited large sewage particles which account for none 2 3 and 3 4 of the total industrial lead deposition fluxes in the respective basins concentrations of leachable lead in varve dated sediment layers increase with time and isotopic compositions of these leads change in accordance with corresponding known changes of isotopic compositions of industrial lead in the los angeles atmosphere lead remaining in acid leached sediment residues originates from igneous and clay minerals exhibiting no change in concentration or isotopic composition since pre industrial times deposition fluxes of total barium in sediments among the three basins were proportional to mass deposition fluxes before 1950 in the same manner as for lead afterwards there are barium concentration maxima with time in both santa monica and san pedro basin sediments which are attributable to industrial sewage rather than to episodic erosion from barium rich sedimentary evaporite strata exposed locally along the shore an increase of barium concentrations in present day santa barbara basin sediments may reflect dispersal of barium rich drilling mud from local drilling operations

lead isotope variations across the central peruvian andes lead isotope values of ore and host rock samples from 18 deposits of nine mining districts in an andean transect between latitudes 9 degrees and 14 degrees s are reported the ore deposits discussed in this paper comprise a relatively narrow age span of about 200 m y upper triassic to early pliocene the lead isotope ratios from different ore deposits correlate closely with their geotectonic settings there is a systematic increase of radiogenic lead isotope ratios from west to east i e from ore deposits located near the coast in the lower cretaceous marginal basin of central peru to ore deposits in the carbonate platform at the margin of the brazilian shield for the coastal deposits ral condestable and los icas the lead may be mantle derived and was supplied via the casma volcanics the more radiogenic lead of the leonila graciela santa cecilia ores may be related to lateral facies variations within the marginal basin it is assumed that here a mantle derived component was mixed with a crustal component the lead isotope ratios from ore deposits in the western cordillera mainly indicate a contribution from the orogen reservoir leaching of the paleozoic basement is probably the main source igneous activity may have facilitated remobilization processes during younger tectonic and magmatic cycles mixing between upper crust and orogen reservoirs with participation of magmatic lead can explain the lead isotope ratios of the ore deposits in the atacocha district the lead isotope signature of the shalipayco ores is interpreted in relation to the permo triassic mitu volcanism leaching of permian rift related volcanics could be responsible for the less radiogenic lead in this deposit the ores of the san vicente deposit are characterized by highly radiogenic values and negative model ages typical of upper crustal leads in cratonic regions the ore lead of san vicente could have been derived by leaching clastic sediments derived from precambrian upper crust brazilian shield

strain variation between quartz grains of different crystallographic orientation in a naturally deformed metasiltstone abstract the shapes of isolated quartz grains in a metasiltstone from the fleurieu peninsula south australia vary markedly the amount of strain undergone by individual grains being strongly influenced by crystallographic orientation relative to the finite strain axes the least deformed grains have c axis orientations clustered about the principal strain directions that is they have orientations for which the resolved shear stress on the 0001 a and 1010 c slip systems would have been close to zero during coaxial deformation a simple theoretical approach suggests that the geometry of the bulk strain should influence the observed c axis fabric of these least deformed grains the fabrics should vary from a a pronounced maximum parallel to z with a subsiduary distribution in the xy plane for pure flattening strain through b fabrics with maxima parallel to x and z and a weak maximum parallel to y to c fabrics with a pronounced maximum parallel to x and a subsiduary distribution within the yz plane for pure constriction the most elongate quartz grains in the metasiltstone show a strong maximum of c axes parallel to the intermediate strain axis y this suggests predominant prismatic slip in a direction at a large angle to the c axis probably on 1010 a the bulk strain undergone by the specimen is an integral of the variable strains in the component minerals and the extremes the least deformed or the most elongate grains cannot be regarded as anomalous if a realistic strain estimate is to be obtained

isotopic record of lead pollution in lake sediments from the northeastern united states abstract although it is common knowledge that pb concentrations have increased in lake sediments in the northeastern united states over the last 150 years the processes responsible have been the subject of debate in this study differences in lead isotopic compositions and concentrations in sediment from large lakes lake erie ontario and michigan and small ones deep lake and lake andrus are used to infer temporal changes in the source s of anthropogenic pb in the great lakes region a natural background component of pb is present in sediment deposited prior to 1860 in lake erie and the other lakes as indicated from low pb concentrations and uniform lead isotopic compositions changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic pb superimposed on the natural component such as regional deforestation from 1860 1890 followed by coal combustion and ore smelting through 1930 combustion of leaded gasoline was the dominant anthropogenic pb source to the atmosphere and by inference to lake sediment from 1930 1980 temporal changes in lead isotopic compositions in lake sediment suggest that the source of the pb used in gasoline additives gradually changed from 1930 to present the best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased pb production from the viburnum trend deposits in missouri present in all lakes except ontario however the changes in lead isotopic compositions are much less variable than and do not parallel those calculated on the basis of annual united states mine production and imports rather anthropogenic recycling of pb as well as natural mixing processes during emission transport and deposition of pb in lake sediment control most of the variation in lead isotope ratios differences in lead isotopic ratios in lake michigan erie and deep lake sediment preserve regional differences in lead isotopic ratios from u s and canadian sources first noted in aerosols by sturges and barrie 1987 more localized sources of pb such as point discharges are needed to explain the results from lake ontario and andrus

effect of irrigation induced densification on the post failure behavior of loess flowslides occurring on the heifangtai area gansu china abstract irrigation resulted in serious ground settlement on the heifangtai terrace in china and also repeatedly triggered a lot of loess flowslides on the margin of the terrace to study the possible effect of resultant loess densification accompanying the ground settlement on the sliding behavior of these landslides we took loess samples from the source area of a landslide in the heifangtai terrace and performed a series of undrained ring shear tests to examine the undrained shear behaviors of these samples at differing initial void ratios results showed that all these tested samples exhibited purely contractive behavior throughout the entire undrained shearing process the loose samples suffered collapse failure behavior while those relatively denser samples experienced gradual increase in pore water pressure after the shear failure occurred the peak and steady state shear strengths increased as void ratio decreased however the brittleness index decreased with reduction of void ratio until a certain value after that it increased with further reduction of void ratio therefore we concluded that irrigation induced densification may have affected the occurrence and mobility of landslides occurring on the terrace margin of the heifangtai area

high resolution evaluation of recent bank accretion rate of the managed rhone a case study by multi proxy approach abstract we determined the sedimentation rates near a managed embankment on the lower rhone for the second half of the twentieth century this was carried out using a combination of chronological indicators 137 cs 241 am dendrochronology and archived data and sedimentological measurements a high resolution chronological sequence has emerged from these data sets the average annual sedimentation rate of 14 cm has increased progressively over the last 50 years and at a much faster rate than observed elsewhere on this river this is probably due to a combination of factors such as the size of the river abundance and coarse texture of the solid load and local impact of river engineering works we also studied hydrological and sedimentological characteristics for a number of flood events

an in situ optical investigation of the deformation behaviour of sodium nitrate an analogue for calcite abstract in situ observations have been made under the optical microscope of the deformation of thin polycrystalline specimens of sodium nitrate calcite structure at temperatures between 20 c 0 5 tm and 300 c 0 98 tm at low temperatures or high strain rates deformation twinning is observed between 20 c and 180 c inhomogeneous deformation together with dynamic recrystallisation by subgrain rotation results in a core and mantle microstructure at temperatures above 180 c rapid dynamic recrystallisation by grain boundary migration also occurs producing a coarse grained microstructure the results are interpreted in terms of impurity controlled grain boundary motion as proposed for halite and a strong similarity between the deformation behaviour of sodium nitrate and marble is noted

seismic loading impacts on excess pore water pressure maintain landslide triggered flowslides during the 2003 sanriku minami earthquake japan a flowslide was triggered on a slope of about 13 5o the displaced landslide mass developed into a flowslide and deposited on a horizontal rice paddy after traveling approximately 130 m to study the trigger and movement mechanisms of this landslide field investigation and laboratory ring shear tests were performed field investigation revealed that the landslide originated from a fill slope where a gully was buried for cultivation some decades ago and shallow ground water was present undrained monotonic and cyclic ring shear tests on a sample pyroclastic deposits taken from the source area revealed that the soil is highly liquefiable and its steady state shear strength can be little affected by overconsolidation using the seismic records of the earthquake probable seismic loadings on the sliding surface were synthesized and applied to the samples in ring shear tests which were performed under undrained or partially drained conditions the undrained and partially drained tests revealed that shear failure can be triggered by the introduction of seismic loading and formation of excess pore water pressure the generation of excess pore water pressure along with increase of shear displacement and the inhibited dissipation of excess pore water pressure due to the thickness of the saturated soil layer above the sliding surface probably enabled the continued post failure landsliding copyright 2008 john wiley sons ltd

undrained shear behavior of loess saturated with different concentrations of sodium chloride solution abstract a series of ring shear tests was conducted on saturated loess to investigate the effects of nacl concentration in pore water and desalinization on the shear behavior under undrained conditions the loess samples were taken from the ground surface of a frequently active landslide in china were saturated by de aired distilled water with different concentrations of nacl and then were sheared undrained after that the samples were retrieved remolded re set into the shear box and re saturated by passing through de aired distilled water such that the samples were desalinized and then were sheared undrained again through comparing the undrained shear behavior the effects of nacl in the pore water and desalinization on the undrained shear behavior of loess were examined the results showed that the variation of nacl concentration in pore water can strongly affect the shear behavior of saturated loess both the peak shear strength and steady state strength increased with increase of nacl concentration until a certain value after which they decreased with further increase of nacl concentration meanwhile the peak shear strength and steady state strength of the desalinized samples recovered to those of the original sample hence the effects of salinization are reversible these findings may be of practical importance to better understand the repeated occurrence of some irrigation induced loess landslides in china

sargipali galenas unusual lead isotope data from eastern india the sargipali sulphide deposit hosted by a sequence of metasediments of the precambrian gangpur series represents the stratiform and stratabound pb cu mineralization lead isotope analyses obtained from six galena samples of different forms and stratigraphical levels yielded a model pb age of 1665 ma which predates the episodes of deformation and metamorphism 850 ma as well as syn to late tectonic magmatism the model pb age on the contrary shows a relationship to the closing phase of the gangpur sedimentation 1700 ma in a shallow water marine environment the notable paucity of the interlayered volcanic rock in the deposit and its pb rich nature possibly point to its being the sedimentary exhalative sedex type documentary evidence for the pb component from the geological environment of the upper continental crust is revealed by an exceptionally high 238u 204pb and the slightly above average w 232th 238u values these indicate that the source rock was initially rich in u th pb concentration for the sargipali ore pb the parent is assumed to be late archean lower proterozoic soda granite

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