geochemical evidence for possible natural migration of marcellus formation brine to shallow aquifers in pennsylvania the debate surrounding the safety of shale gas development in the appalachian basin has generated increased awareness of drinking water quality in rural communities concerns include the potential for migration of stray gas metal rich formation brines and hydraulic fracturing and or flowback fluids to drinking water aquifers a critical question common to these environmental risks is the hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers we present geochemical evidence from northeastern pennsylvania showing that pathways unrelated to recent drilling activities exist in some locations between deep underlying formations and shallow drinking water aquifers integration of chemical data br cl na ba sr and li and isotopic ratios 87sr 86sr 2h h 18o 16o and 228ra 226ra from this and previous studies in 426 shallow groundwater samples and 83 northern appalachian brine samples suggest that mixing relationships between shallow ground water and a deep formation brine causes groundwater salinization in some locations the strong geochemical fingerprint in the salinized cl 20 mg l groundwater sampled from the alluvium catskill and lock haven aquifers suggests possible migration of marcellus brine through naturally occurring pathways the occurrences of saline water do not correlate with the location of shale gas wells and are consistent with reported data before rapid shale gas development in the region however the presence of these fluids suggests conductive pathways and specific geostructural and or hydrodynamic regimes in northeastern pennsylvania that are at increased risk for contamination of shallow drinking water resources particularly by fugitive gases because of natural hydraulic connections to deeper formations

iodine 129 87sr 86sr and trace elemental geochemistry of northern appalachian basin brines evidence for basinal scale fluid migration and clay mineral diagenesis evidence for basin scale brine migration and clay mineral diagenesis in the northern appalachian basin was investigated using elemental and isotope 129i i 87sr 86sr geochemistry of formation waters collected from the middle to upper devonian section of the northern basin margin in western new york northwest pennsylvania and eastern kentucky one sample from each of the mississippian berea sandstone and the silurian medina sandstone were analyzed for comparison measured iodine ratios range between 28 to 1 890 10 15 and are anomalously high compared to cosmogenic iodine sourced from devonian age organic matter iodine 129 in the waters was largely derived from fissiogenic sources the spontaneous fission of 238u to produce 129i with estimated 129i i values up to 270 10 15 which occur locally in the organic rich shales there are three water samples that have values of 490 10 15 860 10 15 and 1 890 10 15 which are above the range for local fissiogenic 129i and may be accounted for by topographically driven basin scale fluid flow through a regionally high fissiogenic source relatively large uranium occurrences lie along the structural front of the appalachian basin in the blue ridge province and are situated within hypothesized flow paths parallel to the main compressional direction of the alleghanian orogeny estimated 129i i values for these uranium occurrences are in excess of 55 000 10 15 the strontium isotope composition and sr concentration of brines display a mixing trend between a highly radiogenic end member 0 7210 with low sr 51 mg l and a non radiogenic 0 7100 high sr 4789 mg l end member potassium and boron concentrations are notably depleted relative to evaporated paleozoic seawater the hypothesized source of appalachian basin brines the k rb values of formation waters are depleted relative to seawater values but in some cases are well above values indicative of water rock reactions the sr isotopic composition k and b depletion and intermediate k rb ratios are consistent with smectite diagenesis and paleo temperatures that are likely greater than approximately 150 c these temperatures may be high given the burial history of the study area and support the flow of formation waters from deeper within the basin the combined isotopic and elemental results of formation waters provide compelling evidence for basin scale fluid migration in the northern appalachian basin and are consistent with previously published evidence documented from the rock record including clay mineral diagenesis and ore deposition

strontium isotope quantification of siderite brine and acid mine drainage contributions to abandoned gas well discharges in the appalachian plateau unplugged abandoned oil and gas wells in the appalachian region can serve as conduits for the movement of waters impacted by fossil fuel extraction strontium isotope and geochemical analysis indicate that artesian discharges of water with high total dissolved solids tds from a series of gas wells in western pennsylvania result from the infiltration of acidic low fe fe 10 mg l coal mine drainage amd into shallow siderite iron carbonate cemented sandstone aquifers the acidity from the amd promotes dissolution of the carbonate and metal and sulfate contaminated waters rise to the surface through compromised abandoned gas well casings strontium isotope mixing models suggest that neither upward migration of oil and gas brines from devonian reservoirs associated with the wells nor dissolution of abundant nodular siderite present in the mine spoil through which recharge water percolates contribute significantly to the artesian gas well discharges natural sr isotope composition can be a sensitive tool in the characterization of complex groundwater interactions and can be used to distinguish between inputs from deep and shallow contamination sources as well as between groundwater and mineralogically similar but stratigraphically distinct rock units this is of particular relevance to regions such as the appalachian basin where a legacy of coal oil and gas exploration is coupled with ongoing and future natural gas drilling into deep reservoirs

granite molybdenite systems stockwork molybdenite deposits in the western conterminous united states may be divided into two groups based on the chemistry of the source pluton granodiorite systems and granite systems these two groups show significant differences in age tectonic setting at time of formation and orebody geometry granite molybdenite systems develop in and adjacent to epizonal plutons that meet tuttle and bowen s 1958 definition of granite cenozoic source plutons for these systems were emplaced in the eastern rockies and great basin coincident with or just prior to regional extensional tectonism mineralization and alteration patterns in granite molybdenite systems generally conform to those described at the climax and henderson deposits major element data displayed on ab or q and a k f plots 1 can characterize potassic quartz sericite argillic and silicic alteration assemblages and lead to evaluation of the probable depth to mineralization in prospects observed alteration reflects hydrogen and alkali metasomatism in fluorine rich systems minor elements concentrated in granite molybdenite systems include be cs f li mo nb rb sn ta th u and w geophysical and geological evidence indicates that the cylindrical source plutons associated with known granite molybdenite systems are cupolas on the tops of batholiths suggesting a genetic link between batholiths and ore a granite molybdenite system appears to be the result of the following lithophile element concentration by convection aided thermogravitational diffusion in the upper part of a batholithic magma chamber transfer of the resulting high silica volatile rich magma from the roof zone of the batholith to a high level cylindrical cupola establishment of thermogravitational diffusion in the cupola causing further lithophile element concentration formation of potassic alteration and an ore shell as a result of volatile saturation resurgent boiling hydrofracturing and boiling and the evolution of peripheral alteration assemblages as meteoric waters enter the magmatic fluid plume above the cupola stacked orebodies represent discrete episodes of resurgent boiling hydrofracturing and mineralization computer assisted evaluation of major element analyses of igneous rocks using chemical criteria developed from known granite molybdenite systems may locate areas with a high exploration potential these techniques suggest that several late precambrian bimodal basaltrhyolite terrains in the eastern united states and canada have exploration potential for molybdenum

late quaternary sediment dating and quantification of lateral sediment redistribution applying230thex a study from the eastern atlantic sector of the southern ocean high resolution records of the natural radionuclide230th were measured in sediments from the eastern atlantic sector of the antarctic circumpolar current to obtain a detailed reconstruction of the sedimentation history of this key area for global climate change during the late quaternary high resolution dating rests on the assumption that the230thex flux to the sediments is constant short periods of drastically increased sediment accumulation rates up to a factor of 8 were determined in the sediments of the antarctic zone during the climate optima at the beginning of the holocene and the isotope stage 5e by comparing expected and measured accumulation rate of230thex lateral sediment redistribution was quantified and vertical particle rain rates originating from the surface water above were calculated we show that lateral contributions locally were up to 6 5 times higher than the vertical particle rain rates at other locations only 15 of the expected vertical particle rain rate were deposited

the strontium isotopic evolution of marcellus formation produced waters southwestern pennsylvania abstract the production of natural gas and natural gas liquids from unconventional tight shale formations involves hydraulic fracturing and subsequent removal of fluids co produced with the gas the chemistry of the returning fluid reflects the original composition of the injection water mobilized constituents in the shale formation and co mingled formation waters liberated by hydraulic fracturing produced water from unconventional gas wells tapping the middle devonian marcellus formation is characterized by high total dissolved solids tds including very high strontium concentrations in this study the strontium isotope composition 87 sr 86 sr was measured in produced waters from four horizontally drilled hydraulically fractured marcellus shale gas wells in southwestern pennsylvania sampled from the first day after commencement of flowback to as much as 27 months later the 87 sr 86 sr of the waters tended to change rapidly over the first few days of water return and then approached but did not reach a constant range of values from 0 7113 to 0 7114 which appears to be characteristic of this part of the marcellus play in contrast the concentration of sr rose more slowly and appeared to hit a steady state value up to 3000 mg l by the end of the first year taken together with results from earlier work these data suggest mixing between injected frac fluid and high tds formation water highly enriched in sr and isotopically relatively uniform throughout the marcellus shale gas play this brine could exist within porous lenses of organic matter in the shale in pre existing fractures within the shale and or originate from fluids that migrated from adjacent formations at some point during the post depositional history of the basin

antarctic sea ice and palaeoproductivity variation over the last 156 000 years in the indian sector of southern ocean abstract antarctic sea ice plays a vital role in global climate via its impact on ocean circulation biological productivity and co2 partitioning between the ocean and the atmosphere however very little is known about its past history especially in the southwestern indian sector of the southern ocean so we here provide new quantitative records of winter sea ice concentration wsic and duration wsid sea surface temperatures sst and productivity in sediment core sk 200 33 55 s 45 e from the permanently open ocean zone over the last 156 000 years the new records combined with regional records indicate that the hydrological structures migrated northward by a few degrees of latitude during all glacial periods with the southern antarctic circumpolar current front reaching the core site the antarctic polar front located at 46 s and the winter sea ice wsi probably extending to 49 s in contrast hydrological fronts and wsi edge migrated poleward by a couple of degrees of latitude during the early holocene and last interglacial comparison to sst and wsi records from different sectors of the so suggests higher amplitude variations in wsi in the atlantic sector as compared to the indian and western pacific sectors over the last glacial interglacial cycle which we attribute to the presence of the weddell gyre transporting far to the north the sea ice produced in the weddell sea the new records also suggest a drop in productivity in the pooz during glacial periods probably related to greater wsi extent and reduced growing season

modern distribution of diatoms in sediments from the george v coast antarctica abstract currently little information exists concerning high frequency climate change in the antarctic data that are essential to gaining a more complete understanding of global climate change sediments from the george v coast continental margin potentially contain a high resolution record of the late holocene the relatively high rate of sedimentation 3 mm year and the presence of laminated intervals which contain undisturbed sequences make these sediments valuable for future downcore work in order to utilize diatom assemblages as proxies of paleoclimatic and paleoceanographic parameters a preliminary study of the surface sediment distribution of diatoms from the george v coast continental margin was completed nitzschia curta van heurck hasle and nitzschia kerguelensis o meara hasle present great potential for tracking the holocene retreat of ice across the continental shelf of this region concentrations of n curta an ice related form decreases in an offshore direction whereas n kerguelensis an oceanic species associated with circumpolar flow displays an increase in sediments offshore the genus thalassiosira cleve displays a clear association with areas of open water primary production as has been noted in others parts of the antarctic downcore variability in relative abundance of this genus will be useful in understanding the history of sea ice versus open water production on the george v coast shelf in contrast the distribution of chaetoceros ehrenberg resting spores appears to be more complex but may be related to the position of the stationary ice edge associated with the annual minimal extent of sea ice finally an understanding of the downcore variability of thalassiothrix antarctica schimper ex karsten a species which is very abundant in the laminated sections of the sediment cores will have to rely on studies of its distribution in other areas of the antarctic as it is sparsely distributed along the george v coast today

geochemical evaluation of flowback brine from marcellus gas wells in pennsylvania usa large quantities of highly saline brine flow from gas wells in the marcellus formation after hydraulic stimulation fracking this study assesses the composition of these flowback waters from the marcellus shale in pennsylvania usa concentrations of most inorganic components of flowback water cl br na k ca mg sr ba ra fe mn total dissolved solids and others increase with time from a well after hydraulic stimulation based on results in several datasets reported here the greatest concentration of cl in flowback water is 151 000 mg l for total ra combined 226ra and 228ra in flowback the highest level reported is 6540 pci l flowback waters from hydraulic fracturing of marcellus wells resemble brines produced from conventional gas wells that tap into other paleozoic formations in the region the br cl ratio and other parameters indicate that both types of brine formed by the evaporation of seawater followed by dolomitization sulfate reduction and subsurface mixing with seawater and or freshwater trends and relationships in brine composition indicate that 1 increased salt concentration in flowback is not mainly caused by dissolution of salt or other minerals in rock units 2 the flowback waters represent a mixture of injection waters with highly concentrated in situ brines similar to those in the other formations and 3 these waters contain concentrations of ra and ba that are commonly hundreds of times the us drinking water standards

establishing baseline water quality for household wells within the marcellus shale gas region susquehanna county pennsylvania u s a abstract flowback fluids associated with hydraulic fracturing shale gas extraction are a potential source of contamination for shallow aquifers in the marcellus shale region of northeastern pennsylvania certified water tests have been used to establish baseline water chemistry of private drinking water wells this study investigates whether a single certified multiparameter water test is sufficient for establishing baseline water chemistry from which possible future contamination by flowback waters could be reliably recognized we analyzed the water chemistry major and minor inorganic elements and stable isotopic composition of multiple samples collected from lake spring and well water from 35 houses around fiddle lake susquehanna county pa that were collected over approximately a two year period statistical models estimated variance of results within and between households and tested for significant differences between means of our repeated measurements and prior certified water tests overall groundwater chemistry varies more spatially due to heterogeneity of minerals within the bedrock aquifer and due to varying inputs of road salt runoff from paved roads than it does temporally at a single location for wells located within road salt runoff zones na and cl concentrations although elevated are generally consistent through repeated measurements high acid neutralizing capacity anc and base cation concentrations in well water sourced from mineral weathering reactions and a uniform stable isotopic composition for well water suggests long flowpaths for groundwater that dampen seasonal variability of most elements exceptions occur for two wells within road salt runoff zones that show the greatest range of concentrations for na and cl suggesting that these wells have a faster pathway to surficial recharge additionally sampling protocols can induce variability for fe mn and pb making other elements identified in flowback fluids ba br ca cl mg na sr more dependable indicators of contamination although there is general concordance between our repeated measurements and the certified test results characterizing baseline chemistry is strengthened when results from multiple households are combined to establish regional upper baseline limits that will have a low probability of being exceeded by future samples unless conditions have changed

phase relations of peraluminous granitic rocks and their petrogenetic implications peraluminous granitic rocks are magmatic rocks that contain quartz po tassic feldspar and or sodic plagioclase and one or more aluminum rich minerals thus these rocks contain more aluminum than could be accom modated by feldspar in a cipw normative calculation and show normative corundum peraluminous granites are defined by their chemical nature but their recognition is often based on petrography this discrepancy thus may lead to inconsistency although peraluminous granitic rocks are com monly true granite streckeisen 1973 they range from tonalite to granite of special interest are strongly peraluminous as defi ned below granite granodiorite or in rare instances trondhjemite these rocks contain alumi nous minerals almandinic garnet cordierite tourmaline muscovite that are thought to be stable in silicate magmas only if these magmas are themselves peraluminous the origin of peraluminous granite and related intrusive rocks is of much current interest many of these form shallow level intrusions and they can reach enormous sizes examples are the batholiths in the lachlan fold belt in southeastern australia white chappell 1983 the cornub ian batholith in england exley stone 1966 the south mountain batholith in nova scotia mckenzie clarke 1975 the manaslu batho lith in the himalayas lefort 1981 much of the idaho batholith

chemical and isotopic tracers of the contribution of microbial gas in devonian organic rich shales and reservoir sandstones northern appalachian basin in this study the geochemistry and origin of natural gas and formation waters in devonian age organic rich shales and reservoir sandstones across the northern appalachian basin margin western new york eastern ohio northwestern pennsylvania and eastern kentucky were investigated additional samples were collected from mississippian berea sandstone silurian medina sandstone and ordovician trenton black river group oil and gas wells for comparison dissolved gases in shallow groundwaters in devonian organic rich shales along lake erie contain detectable ch4 0 01 50 55 mol with low 13c ch4 values 74 68 to 57 86 and no higher chain hydrocarbons characteristics typical of microbial gas nevertheless these groundwaters have only moderate alkalinity 1 14 8 72 meq kg and relatively low 13c values of dissolved inorganic c dic 24 8 to 0 6 suggesting that microbial methanogenesis is limited the majority of natural gases in devonian organic rich shales and sandstones at depth 168 m in the northern appalachian basin have a low ch4 to ethane and propane ratios 3 35 mol c1 c2 c3 and high 13c and d values of ch4 53 35 to 40 24 and 315 0 to 174 6 respectively which increase in depth reservoir age and thermal maturity the molecular and isotopic signature of these gases show that ch4 was generated via thermogenic processes despite this the geochemistry of co produced brines shows evidence for microbial activity high 13c values of dic 10 slightly elevated alkalinity up to 12 01 meq kg and low so4 values 1 mmole l in select devonian organic rich shale and sandstone formation water samples suggest the presence of methanogenesis while low 13c dic values 22 and relatively high so4 concentrations up to 12 31 mmole l in many brine samples point to so4 reduction which likely limits microbial ch4 generation in the appalachian basin together the formation water and gas results suggest that the vast majority of ch4 in the devonian organic rich shales and sandstones across the northern appalachian basin margin is thermogenic in origin small accumulations of microbial ch4 are present at shallow depths along lake erie and in western ny

last glacial maximum sea surface temperature and sea ice extent in the pacific sector of the southern ocean sea surface temperatures and sea ice extent are most critical variables to evaluate the southern ocean paleoceanographic evolution in relation to the development of the global carbon cycle atmospheric co2 and ocean atmosphere circulation here we present diatom transfer function based summer sea surface temperature ssst and winter sea ice wsi estimates from the pacific sector of the southern ocean to bridge a gap in information that has to date hampered a well established reconstruction of the last glacial southern ocean at circum antarctic scale we studied the last glacial maximum lgm at the epilog time slice 19 000e23 000 calendar years before present in 17 cores and consolidated our lgm picture of the pacific sector taking into account published data from its warmer regions our data display a distinct east west differentiation with a rather stable wsi edge north of the pacific antarctic ridge in the ross sea sector and a more variable wsi extent over the amundsen abyssal plain the zone of maximum cooling 4 k during the lgm is in the present subantarctic zone and bounded to its south by the 4 c isotherm the isotherm is in the ssst range prevailing at the modern antarctic polar front representing a circum antarctic feature and marks the northern edge of the glacial antarctic circum polar current acc the northward deflection of colder than modern surface waters along the south american continent led to a significant cooling of the glacial humboldt current surface waters 4e8 k which affected the temperature regimes as far north as tropical latitudes the glacial reduction of acc temperatures may also have resulted in significant cooling in the atlantic and indian southern ocean thus enhancing thermal differentiation of the southern ocean and antarctic continental cooling the comparison with numerical temperature and sea ice simulations yields discrepancies especially con cerning the estimates of the sea ice fields but some simulations reproduce well our proxy based tem perature data

petrogenesis of tourmaline granites and topaz granites the contribution of experimental data abstract fluorine and boron are generally only minor components of granitic rocks but may be found highly concentrated in certain tourmaline granites and topaz granites up to 1 wt b2o3 and 3 2 wt f respectively studies of various examples of these granite types which occur as small bodies emplaced at shallow levels p lithostatic textural and petrographic data indicate that the tourmaline and topaz granite magmas crystallized at low to moderate temperatures below 700 c and that a fluid phase may have been present during the crystallization interval both granites varieties are peraluminous co up to 5 characterized by the presence of white micas lithium micas or muscovite aluminium silicates and other al rich minerals garnet cordierite boron and fluorine are hosted by tourmaline schorl rich member of the schorl dravite series topaz and mica respectively these granites have low ca fe mg and ti contents each the crystallization of tourmaline granite and topaz granite magmas is discussed using experimental data derived from studies of granitic systems with added boron and fluorine both elements act as a flux enabling boron and fluorine enriched melts to persist to temperatures as low as 650 c at 1 kbar in addition the effect of increasing fluorine content displaces the minimum in q ab or at ph2o 1 kbar toward the albite apex plots of fluorine rich topaz granites coincide with this trend suggesting that the role of fluorine in magmatic processes may have affected the rock composition as well as crystallization temperatures boron rich granites plot near the low ph2o minima in qz ab or suggesting that boron has less of an influence on minimum melt compositions the low temperatures of crystallization permits phases such as muscovite or andalusite topaz and two alkali feldspars to crystallize directly from f and b enriched melts at low pressures in addition the limited available experimental data are used to compare the effects of fluorine and boron on major and trace element distribution during melt vapour interaction

late quaternary sea ice history in the indian sector of the southern ocean as recorded by diatom assemblages abstract a modern analog technique mat5201 31 has been applied to fossil diatom assemblages to provide down core estimates of february sea surface temperatures ssts and of sea ice duration over the past 220 000 years at 56 40 s 160 14 e at the core location sea ice progression lagged the sst drop by 1 ka at interglacial glacial transitions and sea ice retreat was almost synchronous to the sst increase at glacial interglacial terminations sea ice increased continuously during glacial periods to reach its maximum extent at the end of glacial times although ssts were almost constant during glacials this indicates that ssts are the major parameter determining the advance and retreat of sea ice at transitions but that the sea ice advance during glacial conditions may be related to positive feedbacks of the ice on albedo air temperature and meridional wind stress the strong correlation r 0 75 between sea ice duration at the core location and the vostok co2 record argues for a control of antarctic sea ice extent on atmospheric co2 concentration via the modification of the ocean to atmosphere gas balance

acidity salinity diagrams application to greisen and porphyry deposits to a first approximation alteration minerals in greisen and related fluorine rich porphyry deposits lie in the system k 2 o al 2 o 3 sio 2 h 2 o f 2 o sub 1 equilibria in this model system can be depicted on quartz and fluid saturated chemical potential diagrams whose axes are mu hf acidity where mu hf mu hcl mu sub fcl sub 1 and mu kf salinity where mu kf mu nacl mu sub kna sub 1 mu sub fcl sub 1 advantages of this approach are that it reflects the fact that the anion f unlike cl is incorporated in greisen minerals mainly topaz fluorite and micas and that mineral stabilities can be correlated with possible ore forming processes the most important of these processes is probably vapor phase separation from an aqueous brine or magma first or second boiling fluid inclusion studies have shown that boiling occurs in all porphyry and many but not all greisen deposits vapor phase separation from a magma pneumatolysis must similarly be responsible for the formation of greisenlike mineral assemblages in miarolitic topaz rhyolite lava flows and is presumably also responsible for the formation of gem pockets in more deeply seated pegmatites and granites the result of boiling is an increase in mu hf and a decrease in mu kf in the vapor phase and the opposite in the residual brine or magma in deep greisen veins the muscovite stability field is encountered between the k feldspar and topaz fields whereas in f rich relatively shallow porphyry deposits such as henderson colorado boiling causes aqueous fluids to pass directly from the k feldspar ore zone to the overlying topaz magnetite zone muscovite or f bearing mn fe garnet is only encountered farther out as the fluids are condensed neutralized and diluted by cooler meteoric waters when ca fe mn be w o 2 s 2 and co 2 are added to the greisen model system scheelite is shown to transform to wolframite with increasing mu hf and beryl to phenakite with increasing mu hf or mu kf biotite transforms to magnetite hematite siderite pyrite chlorite or fayalite beyond the k feldspar field its stability is enhanced by high mu hf and chlorite cordierite or mn fe garnet transform to an mn fe carbonate oxide or sulfide or biotite beyond the al silicate field the ca content of plagioclase coexisting with fluorite decreases with an increase in either mu hf or mu kf and thus provides an indicator of total fluorine in both acid and neutral species

diatom distribution in southern ocean surface sediments atlantic sector implications for paleoenvironmental reconstructions abstract a study of 230 surface sediment samples collected in the atlantic sector of the southern ocean between the southernmost weddell sea and the subtropical zone documents the modern distribution of diatoms revealing patterns of paleoenvironmental significance estimations of diatom valves per gram dry sediment display numbers of 50 200 106 in the zone of high opal burial located between the mean position of the winter sea ice edge and the polar front and maximum values of greater than 200 106 in the near shore sedimentary basins off the antarctic peninsula lowest diatom concentrations and assemblages strongly affected by dissolution were encountered in the weddell basin despite alteration of the diatom assemblages prior to their incorporation into the sediment record the biogeographic distribution and the abundance pattern of most of the 35 studied diatom species shows a close relationship with the surface hydrography water temperature these relationships can be used to estimate past surface water temperatures based on statistical treatments of the assemblages or on simple relations of species occurrences in the geological record another close link occurs between the distribution of sea ice and sea ice related diatoms

the biogeography of major diatom taxa in southern ocean sediments 2 open ocean related species diatoms from 228 southern ocean core top sediment samples were examined to determine the geographic distributions of 32 major diatom species taxa preserved in the sediments of three zonally distinct regions sea ice open ocean and the tropical subtropical in the first of three papers 14 species taxa occurring in the region where sea ice covers the ocean surface on an annual basis are geographically documented comparisons are drawn between the diatom abundances on the sea floor sea ice parameters annual duration and concentration in february and september and february sea surface temperature such parameters are commonly used in reconstructing past oceanographic conditions in the sea ice and open ocean zones analysis of the geographic patterns and sea surface parameter correlations reveals species specific distributions regulated primarily by sea ice coverage and sea surface temperature which support the use of diatom remains for the estimation of these past seasurface environmental parameters comparison with reliable accounts of the 14 species from the sediments or plankton also provides the first glimpses into species specific ecology and habitat linkages d 2005 elsevier b v all rights reserved

diatom distributions in northern north pacific surface sediments and their relationship to modern environmental variables abstract the quantitative analysis of diatom assemblages preserved in 52 samples from the bellingshausen and the amundsen seas provides the first comprehensive view on the distribution of diatoms in surface sediments of the eastern and central pacific sector of the southern ocean on a latitudinal transect along 120 w diatom valve accumulation rates ar reach maximum values 8 10 108 valves m 2 yr 1 in a zone extending over ca 900 km between the antarctic polar front and the maximum average winter sea ice extent and exceed those ars obtained from an eastern transect along 90 w by one order of magnitude lowest diatom concentrations 1 3 106 valves g 1 were encountered in sediments of the sea ice zone affected by winter and summer sea ice the accumulation rate pattern of the most abundant diatom fragilariopsis kerguelensis 50 abundance in 47 samples mirrors the pattern of the total diatom valve ar and the biogenic silica bsi ar making f kerguelensis the major contributor to the bsi preserved at the sea floor relative abundances of diatom species and species groups were statistically compared with a selection of environmental variables such as the mean summer sea surface temperature and salinity mean annual surface nutrient concentration nitrate phosphate silicon mean annual water column stratification mixed layer depth in summer and mean summer and winter sea ice concentrations polynomial canonical redundancy analysis rda revealed the biogeographic distribution of diatom species had the strongest relationship with summer sea surface temperature ssst out of the nine tested environmental variables this relationship accounted for 69 6 of the total variance of the diatom distribution with 29 7 explained by the first gradient significantly correlated to ssst with r2 0 941 and 15 6 explained by the second gradient correlated to both summer and winter sea ice and silicon concentration azpeitia tabularis hemidiscus cuneiformis and roperia tesselata were associated with warmer water conditions 4 c whereas fragilariopsis curta f separanda f rhombica and thalassiosira gracilis were correlated with cold ssst confirming these environmental relationships is crucial for the development of reference data sets used in quantitative estimations of palaeoclimatic and palaeoceanographic conditions with statistical methods this new data set represents the first modernised treatment of diatom remains from the se pacific ocean and generally supports the use of a circum polar database for the determination of summer sst sea ice and potentially biogenic silica distribution of the southern ocean back into the late quaternary

origin of brines salts and carbonate from shales of the marcellus formation evidence from geochemical and sr isotope study of sequentially extracted fluids fluids co produced with methane from hydraulically fractured organic rich shales of the marcellus formation usa are characterized by high total dissolved solids tds including elevated levels of ba sr and br to investigate the source and geologic history of these high tds fluids and their dissolved constituents we carried out a series of sequential extraction experiments on dry drilled cuttings extracted within below and above the marcellus shale from a well in tioga county new york state the experiments were designed to extract 1 water soluble components 2 exchangeable cations 3 carbonate minerals and 4 hydrochloric acid soluble constituents the geochemistry of the resultant leachates highlights the different geochemical reservoirs for extractable elements within the shale notably na and br were largely water soluble while ba was extracted primarily from exchangeable sites and ca and sr were found both in exchangeable sites and carbonate strontium isotope ratios measured on the leachates indicate that each of the element reservoirs has a distinct value measured 87sr 86sr ratios in the water soluble component are similar to those of marcellus produced water while the ion exchange reservoir yields lower ratios and carbonate sr is lower still approaching devonian silurian seawater values despite the isotopic similarity of water leachates and produced water the total water chemistry argues against generation of produced water by interaction of hydraulic fracturing fluid with dry shale the high tds produced water is most likely trapped formation water within and or adjacent to the shale that is released by hydraulic fracturing the formation water was affected by multiple processes possibly including basin scale tectonically driven fluid flow significant chemical and isotopic differences between marcellus shale produced water and overlying upper devonian lower mississippian produced waters suggests a hydrologic barrier has been maintained in parts of the appalachian basin since the late paleozoic

crystallisation of magmatic topaz and implications for nb ta w mineralisation in f rich silicic melts the ary bulak ongonite massif textural mineralogical and geochemical data on f rich rhyolite ongonite from the ary bulak massif of eastern transbaikalia help constrain the formation of magmatic topaz in these rocks topaz occurs as phenocrysts thus providing compelling evidence for crystallisation at the orthomagmatic stage cathodoluminescence images of topaz and quartz reveal growth textures with multiple truncation events in single grains indicative of a dynamic system that shifted from saturated to undersaturated conditions with respect to topaz and quartz electron microprobe and raman analyses of topaz indicate near pure f composition al2sio4f2 with very limited oh replacement laser ablation icp ms traverses revealed the presence of a large number of trace elements present at sub ppm to hundreds of ppm levels the chemical zoning of topaz records trace element fluctuations in the coexisting melt concentrations of some trace elements li ga nb ta and w are correlated with cathodoluminescence intensity thus suggesting that some of these elements act as cl activators in topaz the study of melt inclusions indicates that melts with different f contents were trapped at different stages during formation of quartz and topaz phenocrysts respectively electron microprobe analyses of glass in subhedral quartz hosted melt inclusions indicate f 1 2 wt whereas irregular shaped melt inclusions hosted in both topaz and quartz have f 9 wt cryolithionite na3li3al2f12 coexists with glass in irregular inclusions implying high li contents in the melt the very high f contents would have increased the solubility of nb ta and w in the melt thus allowing progressive concentration of these elements during magma evolution crystallisation of nb ta w oxides w ixiolite and tantalite columbite may have been triggered by separation of cryolithionite which would have caused f and li depletion and consequent drop in the solubility of these elements

new tools for the reconstruction of pleistocene antarctic sea ice abstract based on the quantitative analysis of diatom assemblages preserved in 274 surface sediment samples recovered in the pacific atlantic and western indian sectors of the southern ocean we have defined a new reference database for quantitative estimation of late middle pleistocene antarctic sea ice fields using the transfer function technique the detrended canonical analysis dca of the diatom data set points to a unimodal distribution of the diatom assemblages canonical correspondence analysis cca indicates that not only winter sea ice wsi but also summer sea surface temperature ssst represent the most prominent environmental variables that control the spatial species distribution to test the applicability of transfer functions for sea ice reconstruction in terms of concentration and occurrence probability we applied four different methods the imbrie and kipp method ikm the modern analog technique mat weighted averaging wa and weighted averaging partial least squares wapls using logarithm transformed diatom data and satellite derived 1981 2010 sea ice data as a reference the best performance for ikm results was obtained using a subset of 172 samples with 28 diatom taxa taxa groups quadratic regression and a three factor model ikm d172 28 3q resulting in root mean square errors of prediction rmsep of 7 27 and 11 4 for wsi and summer sea ice ssi concentration respectively mat estimates were calculated with different numbers of analogs 4 6 using a 274 sample 28 taxa reference data set mat d274 28 4an 6an resulting in rmsep ranging from 5 52 4an to 5 91 6an for wsi as well as 8 93 4an to 9 05 6an for ssi wa and wapls performed less well with the d274 data set compared to mat achieving wsi concentration rmsep of 9 91 with wa and 11 29 with wapls recommending the use of ikm and mat the application of ikm and mat to surface sediment data revealed strong relations to the satellite derived winter and summer sea ice field sea ice reconstructions performed on an atlantic and a pacific southern ocean sediment core both documenting sea ice variability over the past 150 000 yr mis 1 mis 6 resulted in similar glacial interglacial trends of ikm and mat based sea ice estimates on the average however ikm estimates display smaller wsi and slightly higher ssi concentration and probability at lower variability in comparison with mat this pattern is a result of different estimation techniques with integration of wsi and ssi signals in one single factor assemblage by applying ikm and selecting specific single samples thus keeping close to the original diatom database and included variability by mat in contrast to the estimation of wsi reconstructions of past ssi variability remain weaker combined with diatom based estimates the abundance and flux pattern of biogenic opal represents an additional indication for the wsi and ssi extent

quaternary surface water temperature estimations new diatom transfer functions for the southern ocean abstract here we present an improvement of paleotemperature reconstructions for the southern ocean by combining new diatom data from the pacific sector with published atlantic and indian sector reference data the statistical analysis of 336 surface sediment samples recovered from a wide area of southern ocean environments defines a supra regional reference data set for quantitative summer sea surface temperature ssst estimations in situ temperature measurements covering the time span from approx 1900 to 1991 were used as reference instead of more recent time series of satellite derived data possibly biased by ocean warming different transfer function tf models for the imbrie and kipp method ikm the modern analog technique mat weighted averaging wa and weighted averaging partial least squares wapls were tested best performance for ikm was obtained using the d336 set with 29 diatom taxa and three factors resulting in root mean square error of prediction rmsep of 0 833 c for ssst mat estimates were best with six analogs resulting in the lowest rmsep of 0 812 c wapls applied to d336 resulted in a rmsep of 0 782 c wa performed less well expressed by a rmsep of 0 974 c furthermore two subsets for the atlantic d151 and the pacific sectors d107 were applied with ikm to test for the advantages of localized tfs ikm d151 and ikm d107 performed comparably good as ikm d336 with rmsep of 0 71 c and 0 68 c respectively application of the augmented reference data sets on two pleistocene sediment records from the atlantic ps1768 8 and pacific ps58 271 1 sectors led to the best performance of ikm with d336 expressed by high overall communalities 0 75 and fewer ps1768 8 to no ps58 271 1 no analogs compared to the regional data sets proving ikm d336 to deal better with higher assemblage variability ssst estimates for both cores exhibit similar glacial interglacial patterns for all four applied d336 based tf methods with the best concordance between ikm and wapls

a biomarker perspective on dust productivity and sea surface temperature in the pacific sector of the southern ocean abstract in this study we present a new multiproxy data set of terrigenous input marine productivity and sea surface temperature sst from 52 surface sediment samples collected along e w transects in the pacific sector of the southern ocean allochthonous terrigenous input was characterized by the distribution of plant wax n alkanes and soil derived branched glycerol dialkyl glycerol tetraethers brgdgts 230th normalized burial of both compound groups were highest close to the potential sources in australia and new zealand and are strongly related to lithogenic contents 232th indicating common sources and transport detection of both long chain n alkanes and brgdgts at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110 w i e by prevailing westerly winds two independent organic sst proxies were used the u 37 k based on alkenones and the tex86 based on isoprenoid gdgts both u 37 k and tex86 indices show robust relationships with temperature over a temperature range between 0 5 and 20 c likely implying different seasonal and regional imprints on the temperature signal alkenone based temperature estimates best reflect modern summer sst in the study area when using the polar calibration of sikes et al 1997 in contrast tex86 derived temperatures may reflect a subsurface signal rather than surface 230th normalized burial of alkenones is highest close to the subtropical front and is positively related to the deposition of lithogenic material throughout the study area in contrast highest isogdgt burial south of the antarctic polar front may be largely controlled by diatom blooms and thus high opal fluxes during austral summer

the spatial structure of the 128 ka antarctic sea ice minimum we compare multi ice core data with 18o model output for the early last interglacial antarctic sea ice minimum the spatial pattern of 18o across antarctica is sensitive to the spatial pattern of sea ice retreat local sea ice retreat increases the proportion of winter precipitation depleting 18o at ice core sites however retreat also enriches 18o because of the reduced source to site distance for atmospheric vapor the joint overall effect is for 18o to increase as sea ice is reduced our data model comparison indicates a winter sea ice retreat of 67 59 and 43 relative to preindustrial in the atlantic indian and pacific sectors of the southern ocean a compilation of southern ocean sea ice proxy data provides weak support for this reconstruction however most published marine core sites are located too far north of the 128 000 years b p sea ice edge preventing independent corroboration for this sea ice reconstruction plain language summary the antarctic isotope and temperature maximum which occurred approximately 128 000 years before present b p during the warmer than present last interglacial period is associated with a major retreat of antarctic sea ice understanding the details of this major sea ice retreat is crucial in order to understand the sensitivity of the southern hemisphere sea ice system and to evaluate the performance of climate model simulations in response to future warming this work uses a multi ice and ocean core data model evaluation to assess the magnitude and spatial pattern of this sea ice retreat our results suggest that sea ice retreat was greatest in the atlantic and indian sectors of the southern ocean and less in the pacific sector these results may have had serious implications for the stability of marine terminating glaciers around the antarctic ice sheet and their contribution to the last interglacial sea level rise these results also support a hypothesized slowdown in northward ocean heat transport during the early last interglacial

last glacial holocene climate variability in the atlantic sector of the southern ocean abstract the southern ocean plays a major role in the glacial interglacial global carbon cycle however there is a substantial lack of information from its antarctic zone south of the polar front pf to understand key climate processes e g sea ice variability productivity changes co2 source region shifts of the southern westerly wind active in this region during the glacial interglacial transition due to the limited high resolution sediment records from this area to close this gap we investigated high resolution diatom records from a series of sediment cores from the atlantic and western indian sectors of the southern ocean between the modern pf and the winter sea ice wsi edge summer sea surface temperature ssst and sea ice information spanning the past 30 thousand years were derived from diatom transfer functions and indicators which augment comprehensive information on past surface ocean conditions and related ocean and atmospheric circulation as well as opal deposition these complementary lines of evidences also provide important environmental boundary conditions for climate simulations understanding the past climate development in the high latitudes southern ocean our reconstructions show that the last glacial lg sssts south of the modern pf are 1 3 c colder than modern conditions wsi expanded to the modern pf our data suggests effective carbon export in the antarctic zone during the lg deglacial two steps of warming support the bipolar seesaw mechanism antarctic zone is an important source region for the co2 deglacial increase the warming was more suppressed towards south due to continuous ice discharge from antarctica the sssts exceeded modern values during the early holocene optimum when wsi extent probably retreated south of its modern position the southern boundary of maximum opal deposition zone may have shifted to south of 55 s in the bouvet island area at this time the mid late holocene cooling with wsi re expanding to the bouvet island area probably related to enhanced cold water export by the weddell gyre from the developing cavity under the west antarctic ice shelf the cooling also suggests a northward shift of the southern westerly wind at least its southern boundary

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

highly branched isoprenoids reveal onset of deglaciation followed by dynamic sea ice conditions in the western amundsen sea antarctica abstract the amundsen sea drainage sector of the west antarctic ice sheet wais is widely regarded as a candidate for triggering potential wais collapse the grounded ice sheet drains into the amundsen sea embayment and is thereby buttressed by its fringing ice shelves which have thinned at an alarming rate satellite based observations additionally reveal a considerable long term decrease in sea ice cover in the amundsen sea over the last two decades although the long term significance of this trend is unclear due to the short instrumental record since the 1970s in this context investigations of past sea ice conditions are crucial for improving our understanding of the influence that sea ice variability has on the adjacent marine environment as well as any role it plays in modulating ice shelf and ice sheet dynamics in this study we apply novel organic geochemical biomarker techniques to a marine sediment core from the western amundsen sea shelf in order to provide a valuable long term perspective on sea ice conditions and the retreat of the getz ice shelf during the last deglaciation we analysed a specific biomarker lipid called ipso25 alongside a phytoplankton biomarker and sedimentological parameters and additionally applied diatom transfer functions for reconstructing palaeo sea ice coverage this multi proxy data set reveals a dynamic behaviour of the getz ice shelf and sea ice cover during the deglaciation following the last ice age with potential linkages to inter hemispheric seesaw climate patterns we further apply and evaluate the recently proposed pipso25 approach for semi quantitative sea ice reconstructions and discuss potential limitations

mineralogical constraints on the genesis of w nb ta mineralization in the laiziling granite xianghualing district south china abstract the laiziling granitic pluton located in the xianghualing district hunan province china comprises typical rare metal granites with a pronounced vertical lithological zonation this pluton includes three granitic phases comprising from base to top medium grained mg alkali feldspar granite fine grained fg alkali feldspar granite and albite granite here we report the results of textural and chemical analyses of w nb ta oxide minerals from the laiziling granitic pluton the chemical compositions of whole rock samples rock forming minerals and zircon have allowed us to identify the magmatic hydrothermal processes that operated during the formation and rare metal mineralization of the laiziling pluton the granites are slightly peraluminous to peraluminous highly evolved and fractionated as inferred from whole rock geochemical and mineralogical micas and zircon signatures all the micas in different granitic phases are classified into the zinnwaldite group li concentration in the primary micas 2 6 4 wt li 2 o and hf concentration 1 8 wt hfo 2 in the zircon increase for the base to the top granitic phases both alkali feldspar granites contain oxide mineral aggregates including columbite group minerals wolframoixiolite qitianlingite wolframite and cassiterite the columbite group minerals wolframite and cassiterite also occur as isolated grains within the albite granite the presence of the oxide minerals suggests that the w nb ta mineralization developed during the latter stages of the magmatic evolution related to fluids that were compositionally evolved from the granites the composition of the fluids controls the aggregate of the oxide minerals the wolframite and cassiterite that precipitated within the laiziling skarn type deposit are chemically different from those within the granite indicating a hydrothermal origin for the oxide minerals that formed as a result of pervasive alteration

fingerprinting marcellus shale waste products from pb isotope and trace metal perspectives abstract drill cuttings generated during unconventional natural gas extraction from the marcellus shale appalachian basin u s a generally contain a very large component of organic rich black shale because of extensive lateral drilling into this target unit in this study element concentrations and pb isotope ratios obtained from leached drill cuttings spanning 600 m of stratigraphic section were used to assess the potential for short and long term environmental impacts from marcellus shale waste materials in comparison with material from surrounding formations leachates of the units above below and within the marcellus shale yielded cl br ratios of 100 150 similar to produced water values leachates from oxidized and unoxidized drill cuttings from the marcellus shale contain distinct suites of elevated trace metal concentrations including cd cu mo ni sb u v and zn the most elevated mo ni sb u and v concentrations are found in leachates from the lower portion of the marcellus shale the section typically exploited for natural gas production in addition lower 207 pb 206 pb ratios within the lower marcellus shale 0 661 0 733 provide a distinctive fingerprint from formations above 0 822 0 846 and below 0 796 0 810 reflecting 206 pb produced as a result of in situ 238 u decay within this organic rich black shale trace metal concentrations from the marcellus shale leachates are similar to total metal concentrations from other black shales these metal concentrations can exceed screening levels recommended by the epa and thus have the potential to impact soil and water quality depending on cuttings disposal methods

fluorite stability in silicic magmas recent experimental evidence is used to assess the conditions under which fluorite forms an early crystallising phase in silicic magmas fluorite solubility primarily depends on the na k al balance in the coexisting silicic melt reaching a minimum in metaluminous melts it can display reaction relationships with topaz and titanite depending on changes in melt composition during crystallisation an empirical model of fluorite stability in ca poor peralkaline rhyolite melts is derived and applied to selected rocks text f text melt left text wt right left left text na text k text al right left 2 1110 3 text t left circ c right 1 5778 right right 2 789

morphometry of the diatom fragilariopsis kerguelensis from southern ocean sediment high throughput measurements show second morphotype occurring during glacials abstract fragilariopsis kerguelensis is one of the most abundant diatoms in the sediments of the southern ocean its morphometric features have been proposed as proxies based on links with for example iron availability sea surface temperature and glacial interglacial conditions we investigated morphometric changes in f kerguelensis valves in a well studied sediment core record focusing on transition periods between glacials and interglacials by applying a high throughput diatom imaging and morphometry workflow we found two clearly distinct morphotypes which were differentiated by their rectangularity one of them occurred preferentially in glacial samples whilst the other persisted throughout this indicates that their relative abundances depend on environmental conditions and thereby points to the possibility that paleo proxies based on f kerguelensis valve morphometric features might in the future benefit from differentiating these two morphotypes as an initial exploration of this idea we show that the abundance ratio of both morphotypes correlates well with paleo temperatures which had been reconstructed using independent data from the same core distinguishing between the two morphotypes only became possible by image analysis for precisely measuring diatom valve outlines and area highlighting the potential of such methods for diatom analyses

non pegmatitic deposits of beryllium mineralogy geology phase equilibria and origin non pegmatitic occurrences of be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest they currently provide the majority of the world s be ore and emeralds and they contain the greatest resource of these commodities of the approximately 100 be minerals known see chapter 1 by grew appendix a most occur in hydrothermal deposits or non pegmatitic igneous rocks where their distribution varies systematically with the setting and origin table 1 fig 1 view this table table 1 beryllium minerals in non pegmatitic deposits formulas use and occurrence 1 figure 1 chemography of the principal solid phases in the beo al2o3 sio2 h2o f2o 1 bash system with the projected positions of helvite group and alkali be silicates also shown are generalized fields for some of the major types natural of occurrences cf table 1 fig 4 see text for discussion beryllium minerals are best known from geologic systems associated with felsic magmatism they also occur in a variety of settings that lack evident igneous associations environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition genetically related igneous rocks are felsic and share low calcium and high f contents but are diverse in composition setting and origin compositions range from strongly peraluminous to peralkaline and can be silica undersaturated beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes table 2 summarizes the types and significance of major groups of occurrences by their lithologic associations figure 2 shows the global distribution of some important examples and regional belts for most types at least one example has been described in some detail and can be used to help evaluate general patterns however

identification and quantification of regional brine and road salt sources in watersheds along the new york pennsylvania border usa abstract the ecologically sensitive susquehanna river basin srb is an important recharge area and drinking water source for a large population in the northeastern united states seasonal road salt application the presence of regional brines at shallow depths and produced waters associated with active and legacy conventional upper devonian oil and gas wells could increase total dissolved solids tds in groundwater and streams this study focused on srb watersheds along the new york pennsylvania border in order to assess current water quality and to establish baseline geochemistry for ground and surface water in a region with potential for increased development of the marcellus shale and other unconventional shale gas units geochemical composition was determined for 300 stream samples collected from ten sites in four watersheds over variable seasonal flow conditions and for groundwater from over 500 drinking water wells in this region results indicate that many streams and groundwater wells in the study area have elevated tds levels that indicate pre existing contributions from saline sources dilution of these inputs with fresh water and the lack of low level trace element concentrations and isotopic composition in many water quality analyses highlight the need for alternate robust and sensitive chemical signatures comparison with cl br anion ratios and 87sr 86sr isotope ratios indicate that the ba sr mg ratio can be used to discriminate between road salt and regional brine in these cases and mixing models show that even small additions 0 1 0 01 of these contaminants can be detected with this cation ratio the ba sr mg ratio may be even more sensitive by an order of magnitude to incursions of marcellus shale produced water depending on the composition of marcellus produced waters in this region this study highlights the need for baseline sampling of freshwater reservoirs and the characterization of potential high tds sources at a local and regional scale

modeling fluid rock interaction during greisenization at the east kemptville tin deposit implications for mineralization interaction between a tin bearing greisenizing fluid and a leucogranitic rock was modeled in order to evaluate the possible role of alteration induced changes in fluid chemistry in cassiterite deposition the interaction was modeled using simple titration and multiple pass fluid flow models with the program chiller modified to permit calculations at 450 c and 4 0 kb the compositions of the mineralizing fluid and the unaltered leucogranite were based respectively on analyses of fluid inclusions and whole rock chemistry of samples from the east kemptville greisen hosted tin deposit nova scotia the starting fluid contained 4 85 m cl 3 7 m na 0 53 m fe and minor k si f and sn and was at a ph of 3 0 while the leucogranite contained 35 wt quartz 29 wt albite 19 wt muscovite and 17 wt k feldspar in both models the calculations show that with increasing alteration k feldspar was the first mineral consumed and that this was followed by replacement of albite by muscovite with further alteration muscovite was replaced by topaz and pyrrhotite and cassiterite precipitated in quartz topaz rocks in the most altered rocks only topaz and quartz are present these changes accurately reproduce those determined for natural samples at east kemptville however only the multiple pass fluid flow model predicts the changes in fluid inclusion composition the multiple pass fluid flow model quantified changes in fluid composition as a function of its interaction with the wall rock and thus enabled us to assess better the factors that controlled cassiterite precipitation important conclusions of the model are that the fluid and the rock equilibrated at each stage of the alteration and the water rock ratio remained constant across the alteration halo we further concluded that phases precipitated close to the vein in an earlier stage of the alteration were re dissolved with evolution of the mineralizing system in particular re dissolution of cassiterite caused an increase in the concentration of sncl in the fluid as a result cassiterite saturated at a lower ph and the chemical potential of sncl increased away from the vein this could in turn explain the low tin grades at east kemptville

application of modern analog technique to marine antarctic diatoms reconstruction of maximum sea ice extent at the last glacial maximum modern analog technique mat applied to antarctic diatoms is a new approach for quantitative sea ice paleoreconstructions in the southern ocean in a first step we show that mat is a better approach than the imbrie and kipp method to reconstruct the modern sea ice pattern we then use this approach to reconstruct sea ice presence in number of months per year during the last glacial maximum lgm at this time sea ice presence was greater than today leading to a shorter diatom growing season the maximum sea ice extent inferred from quantitative values of sea ice presence was located 5 8 north of its actual position leading to double the surface of modern winter sea ice this greater sea ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid latitude and high latitude climates it may also have reduced the amount of heat moisture and co2 from the ocean to the atmosphere thus participating in the lowering of atmospheric co2 during the lgm

quaternary surface water temperature estimations calibration of a diatom transfer function for the southern ocean the quantitative diatom analysis of 218 surface sediment samples recovered in the atlantic and western indian sector of the southern ocean is used to define a base of reference data for paleotemperature estimations from diatom assemblages using the imbrie and kipp transfer function method the criteria which justify the exclusion of samples and species out of the raw data set in order to define a reference database are outlined and discussed sensitivity tests with eight data sets were achieved evaluating the effects of overall dominance of single species different methods of species abundance ranking and no analog conditions e g eucampia antarctica on the estimated paleotemperatures the defined transfer functions were applied on a sediment core from the northern antarctic zone overall dominance of fragilariopsis kerguelensis in the diatom assemblages resulted in a close affinity between paleotemperature curve and relative abundance pattern of this species downcore logarithmic conversion of counting data applied with other ranking methods in order to compensate the dominance of f kerguelensis revealed the best statistical results a reliable diatom transfer function for future paleotemperature estimations is presented

the biogeography of major diatom taxa in southern ocean surface sediments 3 tropical subtropical species abstract this paper gives a modern circumscription of tropical subtropical diatoms regarding their relationship with sea surface temperatures sst and sea ice cover diatoms from 228 core top sediment samples collected from the southern ocean were studied to determine the geographic distribution of eight major diatom species taxa preserved in surface sediments generally located north of the subantarctic front the comparison of the relative contribution of diatom species with modern february sst and sea ice cover reveals species specific sedimentary distributions regulated both by water temperatures and sea ice conditions although selective preservation might have played some role their presence in surface and downcore sediments from the southern ocean are reliable indicators of high sst and poleward transport of waters from the tropical subtropical atlantic our work supports the use of diatom remains to reconstruct past variations of these environmental parameters via qualitative and transfer function approaches

late pliocene sea ice expansion and its influence on diatom species turnover in the southern ocean abstract fossil diatom records from the southern ocean are needed to clarify the detailed conditions under warmer than present global climate in the piacenzian stage 3 60 2 588 ma and to provide direct evidence of simultaneity between changes in environmental conditions and diatom species turnovers in this study fossil diatom records between 3 5 and 2 8 ma were investigated at two sites located along a latitudinal gradient within the indian sector of the southern ocean offshore from prydz bay and south east of the kerguelen plateau paleoceanographic changes were assessed from assemblage changes of extant diatom indicators fluctuations of their relative percentages were compared with those of extinct diatom species the diatom assemblage between 3 5 and 3 1 ma consisted of open ocean species which indicate warmer than present sst notable increases in sea ice associated species were identified at 3 3 ma and 3 1 ma at both sites our results suggest sea ice existence during short intervals of 3 3 ma and 3 1 2 8 ma at the studied area at both sites relative abundances of species which have first occurrences during the piacenzian increased at 3 2 3 1 ma conversely those of species which have last occurrences during the piacenzian decreased at the same period these diatom records show a correlation with cooling at 3 1 ma suggested from extant indicators and compositional changes in fossil diatoms from the southern ocean this comparison can provide insights into the environmental effects on diatom evolutionary acceleration which can help identify ecologies of extinct species

reconstruction of sea surface temperatures from assemblages of planktonic foraminifera multi technique approach based on geographically constrained calibration data sets and its application to glacial atlantic and pacific oceans abstract we present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts this approach is based on simultaneous application of a variety of transfer function techniques which are trained on geographically constrained calibration data sets it serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples allowing identification of adverse effects of no analog faunas and technique specific bias we have compiled new calibration data sets for the north n 862 and south n 321 atlantic and the pacific ocean n 1111 we show evidence that these data sets offer adequate coverage of the sea surface temperature sst and faunal variation range and that they are not affected by the presence of pre holocene samples and or calcite dissolution we have applied four transfer function techniques including artificial neural networks revised analog method and simmax with and without distance weighting on faunal counts in a last glacial maximum lgm data set for the atlantic ocean 748 samples in 167 cores based on the glamap 2000 compilation and a new data set for the pacific ocean 265 samples in 82 cores and show that three of these techniques provide adequate degree of independence for the advantage of a multi technique approach to be realised the application of our new approach to the glacial pacific lends support to the contraction and perhaps even a cooling of the western pacific warm pool and a substantial 3 c cooling of the eastern equatorial pacific and the eastern boundary currents our results do not provide conclusive evidence for lgm warming anywhere in the pacific the atlantic reconstruction shows a number of robust patterns including substantial cooling of eastern boundary currents with considerable advection of subpolar waters into the benguela current a cooling of the equatorial atlantic by 5 c and steep sst gradients in the mid latitude north atlantic the transfer function techniques generally agree that subtropical gyre areas in both hemispheres did not change significantly since the lgm although the ann technique produced glacial sst in the southern gyre 1 2 c warmer than today we have revisited the issue of sea ice occurrence in the nordic seas and using the distribution of subpolar species of planktonic foraminifera in glacial samples we conclude that the norwegian sea must have been ice free during the summer

multiple glacial maxima of similar extent at 20 45 ka on mt usborne east falkland south atlantic region abstract the pattern timing and origin of southern hemisphere climate change during the last glaciation remains a pressing problem with implications for the role of orbital forcing in ice age cycles here we present geomorphological and cosmogenic exposure age data from east falkland in the south atlantic region that show onset of glacial conditions by marine isotope stage 4 60 70 ka with expansion of ice to its maximum extent of the last glaciation at least seven geomorphological units marked by multiple crests on composite moraines indicate glacier expansion on mt usborne the highest peak of east falkland from 20 to 45 ka glaciers fluctuated on a millennial timescale with near maximum conditions being reached repeatedly overall ice extent appears to have shrunk slightly through time with evidence of glaciation at 20 ka preserved only in the highest elevation cirques this long glacial maximum is inconsistent both with local orbital control and orbital forcing as expressed in the traditional milankovitch hypothesis the timing of millennial glacier expansions occurred between northern hemisphere heinrich stadials and resembles that documented for new zealand glaciers suggesting at least a trans pacific expression we postulate that periodic recessions corresponded with southward expansion of the southern westerlies during heinrich stadials and warming air and ocean temperatures over the south atlantic region

an approach for assessing engineering risk from shale gas wells in the united states in response to a series of energy crises in the 1970s the united states government began investigating the potential of unconventional domestic sources of energy to offset imported oil hydraulic fracturing applied to vertical tight sand and coal bed methane wells achieved some degree of success during a period of high energy prices in the early 1980s but shale gas remained largely untapped until the late 1990s with the application of directional drilling a mature technology adapted from deepwater offshore platforms that allowed horizontal wells to penetrate kilometers of organic rich shale and staged hydraulic fracturing which created high permeability flowpaths from the horizontal wells into a much greater volume of the target formations than previous completion methods these new engineering techniques opened up vast unconventional natural gas and oil reserves but also raised concerns about potential environmental impacts these include short term and long term impacts to air and water quality from rig operations potential migration of gas fluids and chemicals through the ground and effects on small watersheds and landscapes from roads pads and other surface structures engineering risk assessment commonly uses integrated assessment models iams which define sources of risk from features events and processes the risk from each system element is assessed using high fidelity models output from these is simplified into reduced order models so that a large integrated site performance assessment can be run using the iam the technique has been applied to engineered systems in geologic settings for sequestering carbon dioxide and it is also applicable to shale gas albeit with some modifications of the various system elements preliminary findings indicate that shale gas well drilling and hydraulic fracturing techniques are generally safe when properly applied incident reports recorded by state environmental agencies suggest that human error resulting from the disregard of prescribed practices is the greatest cause of environmental incidents this can only be addressed through education regulations and enforcement

palaeotemperature estimation methods sensitivity test on two western equatorial pacific cores abstract this study examines three methods of estimating past sea surface temperature sst imbrie and kipp s transfer function method ikm the modern analogue technique mat and the weighted averaging method wam by testing a number of experimental transfer functions on two western equatorial pacific cores rc17 177 and erdc 93p it is shown that sst estimation is sensitive to the number of factors and to the selection of core top samples in the calibration the most plausible result was given by an equation which is calibrated from a restricted region which is sufficiently large to fully cover the potential range of down core sst estimates the mat gave spurious sst estimates probably due to the failure of the dissimilarity coefficient the wam persistently gave lower sst estimates than the ikm because of the averaging effect of the method but the sst time series estimated by the two methods show almost identical fluctuation patterns the tolerance weighting approach in the wam may be inappropriate because tolerances of different species may have different implications all the above methods are affected by the distribution of calibration samples

the reconstruction of late quaternary antarctic sea ice distribution the use of diatoms as a proxy for sea ice the study of annual diatom transfer from the southern ocean surface to the sea floor using time series sediment traps combined with the mapping of diatom assemblages from surface sediments results in the definition of a proxy for past variations of sea ice extent the application and robustness of the proposed proxy are demonstrated by the study of late pleistocene sediment cores recovered from different environmental regimes in the southern ocean relative amounts of the sea ice indicator diatoms fragilariopsis cylindrus and fragilariopsis curta of 3 in diatom assemblages preserved in sediments are representative of the presence of seasonal winter sea ice summer sea ice occurrence is signalled by a distinct drop in biogenic sedimentation rate as a result of strongly reduced biogenic export in the presence 3 of diatom assemblage of the deep temperature diatom fragilariopsis obliquecostata the spatial and temporal distribution pattern of the sea ice proxy indicates significant sea ice variations during marine isotope stages 1 and 5 in the present antarctic zone of the southern ocean during glacial maxima the antarctic winter sea ice was extended into the present polar front zone while the antarctic summer sea ice was most probably expanded into the area of the present winter sea ice edge during the short climatic optima at the onset of interglacial periods the winter sea ice extent was distinctly reduced

hydroxyl rich topaz in high pressure and ultrahigh pressure kyanite quartzites with retrograde woodhouseite from the sulu terrane eastern china hydroxyl rich topaz was recognized in thick kyanite quartzites from both high pressure hp and ultrahigh pressure uhp belts of the sulu terrane china these quartzites contain variable proportions of quartz kyanite and topaz with minor phengite pyrite and rutile some topaz grains from the uhp belt contain abundant inclusions of oriented kyanite whereas those from the hp belt are partially replaced by woodhouseite caal 3 po 4 so 4 oh 6 most topaz crystals contain 9 5 to 13 5 wt f 0 92 1 30 atoms per formula unit apfu indicating 35 55 substitution of f by oh such naturally occurring hydroxyl rich topaz has not been previously reported some topaz grains from the hp belt show distinct zoning 1 decreasing f content from narrow cores 13 3 16 5 wt to thick rims 9 5 wt or 2 oscillatory zoning 9 44 12 77 wt unit cell parameters of topaz show a positive linear correlation between the oh content and a and b as well as volume based on our petrologic data the experimentally determined curve of ky h 2 o topaz oh at very high pressures and calculated oh oh f isopleths of topaz at low pressures the topaz with x oh 0 35 from the uhp belt may have formed at p t conditions within the coesite stability field the p t condition of hp topaz is less well constrained its high x oh 0 40 0 55 may have been caused by lower metamorphic temperatures and higher initial x oh in comparison with uhp topaz hydroxyl rich topaz together with other hydrous minerals in uhp rocks may be important carriers of h 2 o to mantle depths of 100 200 km during continental subduction