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

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

the pacific meridional mode and the occurrence of tropical cyclones in the western north pacific abstractthis study investigates the association between the pacific meridional mode pmm and tropical cyclone tc activity in the western north pacific wnp it is found that the positive pmm phase favors the occurrence of tcs in the wnp while the negative pmm phase inhibits the occurrence of tcs there observed relationships are consistent with those from a long term preindustrial control experiment 1000 yr of a high resolution tc resolving geophysical fluid dynamics laboratory gfdl forecast oriented low ocean resolution flor coupled climate model the diagnostic relationship between the pmm and tcs in observations and the model is further supported by sensitivity experiments with flor the modulation of tc genesis by the pmm is primarily through the anomalous zonal vertical wind shear zvws changes in the wnp especially in the southeastern wnp the anomalous zvws can be attributed to the responses of the atmosphere to the anomalous warming in the northwestern part of the pmm pattern during th

large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

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

the multidecadal variability of the asymmetric mode of the boreal autumn hadley circulation and its link to the atlantic multidecadal oscillation abstractprevious studies show that the first principal mode of the variability of the seasonal mean hadley circulation hc is an equatorial asymmetric mode am with long term trend this study demonstrates that the variability of the boreal autumn september november son hc is also dominated by an am but with multidecadal variability the son am has ascending and descending branches located at approximately 20 n and 20 s respectively and explains about 40 of the total variance further analysis reveals that the am is closely linked to the atlantic multidecadal oscillation amo which is associated with a large cross equatorial sea surface temperature sst gradient and sea level pressure slp gradient the cross equatorial thermal contrast further induces an equatorial asymmetric hc anomaly numerical simulations conducted on an atmospheric general circulation model also suggest that amo associated sst anomalies can also induce a cross equatorial slp gradient and anomalous vertical shear of the

intensified interannual relationship between tropical cyclone genesis frequency over the northwest pacific and the sst gradient between the southwest pacific and the western pacific warm pool since the mid 1970s abstractthe sea surface temperature gradient sstg between the southwest pacific swp 40 20 s 160 e 170 w and the western pacific warm pool wwp 0 16 n 125 165 e in boreal spring was revealed to contribute significantly to the interannual variability of tropical cyclone tc genesis frequency over the western north pacific wnp since 1980 the present study extends the analysis back to 1951 results show that the interannual relationship between the sstg and wnp tc genesis frequency is statistically significant only after the mid 1970s while insignificant prior to 1974 further analyses show that the sstg is strongly negatively correlated with the sst anomaly ssta in the central pacific cp in the recent period while with the ssta in the equatorial eastern pacific ep in the prior period in the prior period the spring positive negative ep ssta induces an anticyclonic cyclonic circulation over the wnp this partly offsets the impact of the sstg anomaly on the atmospheric circulation ov

decadal changes in tropical cyclone activity over the western north pacific in the late 1990s a pronounced decadal change in tropical cyclone tc activity over the western north pacific wnp in the late 1990s was identified based on a comparison of the two epochs that occurred before and after the late 1990s the tc genesis number exhibited an evident decrease over the southern wnp s wnp 5 20 n 105 170 e and an increase over the northern wnp n wnp 20 25 n 115 155 e which partly corresponded to a significant northward migration in the seasonal mean latitudinal location of tc genesis i e from 17 2 n to 18 7 n after the late 1990s the northwestward moving track became the most dominant track mode accompanied by the weakening of both the westward moving track and the northeastward recurving track meanwhile the tc occurrence frequency tcf experienced evident increases over southeastern china and the okinawa islands while prominent decreases occurred over the south china sea the philippine sea japan and east of japan changes in the tcf were determined by tc genesis changes tc track shifts and variations in regional tc durations which were all ascribed to the decadal change in tropical indo pacific sea surface temperature the full picture on the decadal changes in the wnp tc activity revealed in this study may provide useful guidance for regional tc seasonal forecasts and future projections

interhemispheric thermal gradient and tropical pacific climate 1 we explore the impact of interhemispheric thermal gradients forcing on the tropical pacific ocean atmosphere climate in an intermediate coupled model the equatorial zonal sea surface temperature sst gradient strengthens with an increased northward interhemispheric thermal gradient the increase arising from earlier onset and later retreat of the seasonal cold tongue and intensification during the peak cold season when the mean interhemispheric thermal gradient is reversed the central equatorial pacific sst annual cycle abruptly reverses in phase with its cold season in mar may rather than sep nov while startling this response is consistent with a prevailing hypothesis that ties the cold tongue sst annual cycle phase to the hemispheric mean asymmetry of the intertropical convergence zone el nino southern oscillation activity is also sensitive to the interhemispheric thermal gradient with peak activity occurring when the mean gradient is small reducing rapidly as the mean gradient increases in either direction

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

air hydrate inclusions in fresh ice core one of the characteristic features of polar glacier ice is the abundance of air bubbles1 3 with increasing depth from the surface of the ice sheet the size of the bubbles generally decreases in response to the change of overburden pressure below a certain depth the bubbles start to shrink faster than expected and finally become invisible although not visible to the naked eye unit mass of the bubble free clear ice includes almost the same volume of air as unit mass of bubbly ice4 5 it is hypothesized that the air exists in the ice structure probably in the form of clathrate hydrates as suggested by miller6 7 but until now the location of the air has been unknown direct observations of air hydrate inclusions were carried out for the first time in fresh ice cores from dye 3 greenland when the ice structure surrounding air hydrate was melted an explosive transition occurred releasing a gas bubble into the melt cavity

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

impacts of tropical north atlantic sst on western north pacific landfalling tropical cyclones abstractthis study examines the impacts of tropical north atlantic tna sea surface temperature anomaly ssta on western north pacific wnp landfalling tropical cyclones tcs the authors find that tna ssta has significant negative correlations with the frequency of tcs making landfall in china vietnam the korean peninsula and japan and the entirety of east asia tna ssta influences the frequency of tc landfalls in these regions by regulating tc genesis location and frequency associated with modulated environmental conditions during cold tna sst years larger low level relative vorticity and weaker vertical wind shear lead to more tc formations over the south china sea scs and western philippine sea wps and larger low level relative vorticity higher midlevel relative humidity and weaker vertical wind shear result in more tc formations over the eastern part of wnp ewnp more tcs forming over different regions are important for more tc landfalls in vietnam mainly forming over the scs and w

interdecadal variation of tropical cyclone genesis and its relationship to the convective activities over the central pacific using the outgoing longwave radiation olr data from the national oceanic and atmospheric administration archives this paper analyzes the interdecadal variation of convective activities over the central pacific cp from july to october of 1979 2013 and its impact on tropical cyclone tc genesis in the western north pacific wnp concurrent with the interdecadal decrease of tc genesis the tropical convection underwent a significant interdecadal change in the late 1990s overall the first leading empirical orthogonal function mode of the tropical olr during july october turned from a zonal dipole pattern during 1979 1997 to a tripole pattern during 1998 2013 concomitant to this change the boreal part of the walker circulation shrank westward with its downdraft branch located over the cp the downward motion anomalies over the cp increased after the late 1990s as did the trade easterlies consistent with the cp convective activity anomalies the negative low level relative vorticity anomalies and upper level divergence anomalies positive vertical wind shear anomalies and anomalous abundant water vapor can be observed over the southeastern part of the wnp additionally the tropical depression td type waves associated with the cp convective activities are significantly different before and after the late 1990s before the late 1990s the off equatorial td type waves could be distinctly observed with clear transitions located along the wnp monsoon trough however these transitions were vague after the late 1990s therefore the convective activities over the cp may have played an important role in affecting the interdecadal change of tc genesis by affecting the genesis of td type waves

air clathrate crystals from the grip deep ice core greenland a number size and shape distribution study we performed microscopic observations and a statistical study of the number size and shape distribution of clathrates in the grip greenland ice core project deep ice core using 185 samples from a depth range of 1016 3014m spanning a period of 6 to 110 ka sp and encompassing the holocene wisconsin and eemian periods the number concentration of the clathrates varied considerably with climatic changes it was possible to detect the rapid climatic oscillations in the last glacial between 13 and 110 ka bp the dansgaard oeschger cycles in the number concentration profile of clathrates the mean volume of clathrates is less clearly influenced by climatic factors with a tendency towards greater volumes in warmer periods but also a growth of clathrates with depth could be detected this growth rate was calculated to be 3 1 x 10 12 cm 3 a 1 the amount of gases captured in the clathrates is estimated to be significantly smaller than the total amount of air determined by gas concentration measurements this points to diffusion processes of atmospheric gases within the ice matrix

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

raman tomography of natural air hydrates cryo raman tomography allows us for the first time to determine accurate morphologies and volumes of natural air hydrates in antarctic ice cores the measurements show complex growth structures that are not accounted for by the available models of hydrate formation

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

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

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

intensified impact of east indian ocean sst anomaly on tropical cyclone genesis frequency over the western north pacific abstracta recent finding is the significant impact of the sea surface temperature anomaly ssta over the east indian ocean eio on the genesis frequency of tropical cyclones tcs over the western north pacific wnp in this study it is shown that such an impact is significant only after the late 1970s the results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the eio ssta is positively correlated with the equatorial central pacific ssta and the latter produces an opposite atmospheric circulation response over the wnp to the former as a result the impact of the eio ssta on the tc genesis over the wnp is largely suppressed by the latter after the late 1970s the area coverage of the eio ssta is expanding this considerably enhances the large scale circulation response over the wnp to the eio ssta and significantly intensifies the impact of the eio ssta on tc genesis frequency over the wnp the results from this study have great implications for s

impacts of the boreal spring indo pacific warm pool hadley circulation on tropical cyclone activity over the western north pacific abstractthis study investigated the impacts of the interannual variability in the boreal spring regional hadley circulation over the indo pacific warm pool ipwp on the tropical cyclone tc activity over the western north pacific wnp the principal modes of the interannual variability in the ipwp hadley circulation were calculated using empirical orthogonal function eof analysis the leading mode eof 1 features cross equatorial southerly wind anomalies over the indian ocean and maritime continent and has an evident impact on wnp tc activity during summer in the summer following a positive phase of the eof 1 a cyclonic circulation anomaly with upward motion positive relative vorticity anomalies and weak sea level pressure dominates the wnp and this favors increased tc genesis however large positive vertical wind shear anomalies over the south china sea and philippine sea inhibit the tc intensification a positive wind sea surface temperature sst precipitation feedback was found to facili

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

contributions of sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone genesis frequency over the western north pacific abstractthis study attempts to evaluate quantitatively the contributions of sea surface temperature sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone tc

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

kinetics of conversion of air bubbles to air hydrate crystals in antarctic ice the depth dependence of bubble concentration at pressures above the transition to the air hydrate phase and the optical scattering length due to bubbles in deep ice at the south pole are modeled with diffusion growth data from the laboratory taking into account the dependence of age and temperature on depth in the ice the model fits the available data on bubbles in cores from vostok and byrd and on scattering length in deep ice at the south pole it explains why bubbles and air hydrate crystals coexist in deep ice over a range of depths as great as 800 meters and predicts that at depths below 1400 meters the amanda neutrino observatory at the south pole will operate unimpaired by light scattering from bubbles

possible linkage between the monsoon trough variability and the tropical cyclone activity over the western north pacific abstractthe present study investigates the influence of the monsoon trough mt on the interannual variability of tropical cyclone tc activity over the western north pacific during july november for the period 1979 2007 it is shown that the tc activity is closely related to the mt location during the years when the mt extends eastward retreats westward more less tcs form within the southeastern quadrant of the western north pacific such a relationship can be explained by the changes in large scale environmental factors associated with the movement of the mt an eastward extension of the mt coincides with warmed ocean surface enhanced convection increased relative humidity in the lower and midtroposphere reduced vertical shear of zonal wind intensified upper level divergence and low level anomalous cyclonic vorticity over the southeast quadrant of the western north pacific these conditions associated with the eastern extension of the mt are favorable for tc genesis while those associated w

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

modulation of tropical cyclogenesis location and frequency over the indo western north pacific by the intraseasonal indo western pacific convection oscillation during the boreal extended summer abstractthe influence of the intraseasonal indo western pacific convection oscillation ipco on tropical cyclone tc genesis location and frequency over the indo western north pacific wnp during the boreal extended summer may october is explored observational analysis shows that the impacts of the intraseasonal ipco on tcs over the indo wnp include an evident phase lock of tc genesis location and distinct differences in tc frequency in the wnp in the positive intraseasonal ipco phase the atmosphere gains heat through the release of latent heat in cumulus convective condensation and the anomalous cyclonic circulation weakens the western pacific subtropical high wpsh and enhances tc genesis thereby tending to produce many more tcs moreover the diminished wpsh and the westward shift of the centers of anomalous cyclonic circulations lock tc genesis locations to the west wnp and lower latitudes around 5 20 n especially in the south china sea the almost opposite situation occurs in a nega

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

the sst gradient between the southwestern pacific and the western pacific warm pool a new factor controlling the northwestern pacific tropical cyclone genesis frequency abstractthe sea surface temperature gradient sstg between the southwestern pacific ocean 40 20 s 160 e 170 w and the western pacific warm pool 0 16 n 125 165 e in boreal spring has been identified as a new factor that controls the interannual variability of tropical cyclone tc frequency over the western north pacific ocean wnp this sstg can explain 53 of the total variance of the wnp tc genesis frequency during the typhoon season for the period 1980 2011 the positive sstg anomaly produces an anomalous cross equatorial pressure gradient and thus anomalies in low level southward cross equatorial flow and tropical easterlies over the central western pacific the anomalous easterlies further produce local equatorial upwelling and seasonal cooling in the central pacific which in turn maintains the easterly anomalies throughout the typhoon season these dynamical thermodynamical effects induced by the positive sstg anomaly lead to a reduced low level cyclonic shear increased vertical wind sh

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

modulation of tropical cyclone tracks over the western north pacific by intra seasonal indo western pacific convection oscillation during the boreal extended summer this study investigates the effect of the intra seasonal indo western pacific convection oscillation ipco on tropical cyclone tc tracks over the western north pacific wnp during the boreal extended summer may october the number of west and northwest moving tc tracks is found to sharply increase over the wnp in the positive intra seasonal ipco phase recurving tracks have greater weight in the negative intra seasonal ipco phase possible physical mechanisms are further examined in terms of steering flow energy conversion and energy propagation when the intra seasonal ipco phase is positive the first order moment term of perturbation potential energy ppe1 converts into perturbation kinetic energy pke at lower latitudes the pressure trough spreads farther to the east meanwhile rossby waves emanating from the convective centers of the intra seasonal ipco over the wnp wavewnp and eeio waveeeio travel into the trough region thereby deepening the trough these features enhance the westward and northwestward steering flow between 20 n and about 30 n sharply increasing the number of straight west and northwest moving tc tracks over the wnp when the intra seasonal ipco is in a negative phase conversion from ppe1 to pke at lower latitudes is suppressed and the trough weakens more ppe1 converts to pke in the climatological western pacific subtropical high wpsh region and the wpsh is intensified moreover waveeeio intensifies the north south ridge of the wpsh over the southern indian peninsula meanwhile part wavewnp propagate northeastward these features favor northeastward motion of tcs over the wnp

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

contribution of the interdecadal pacific oscillation to the recent abrupt decrease in tropical cyclone genesis frequency over the western north pacific since 1998 abstractprevious studies have documented an abrupt decrease of tropical cyclone tc genesis frequency over the western north pacific wnp since 1998 in this study results from an objective clus

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