estimation of quality factors from cmp records estimates of the quality q factor are commonly obtained from vertical seismic data or stacked surface seismic data this paper describes a method that allows q factor to be estimated directly from common midpoint cmp gathers absorption of the wavefield is dependent on three parameters frequency traveltime in the medium and medium q factor assuming that the amplitude spectrum of the seismic source signature may be modeled by that of a ricker wavelet we derive an analytical relation between q factor and seismic data peak frequency variation both along offset and vertical time direction the q factor is estimated from cmp gathers using a layer stripping approach

inverse q filter for seismic resolution enhancement a principal limitation on seismic resolution is the earth attenuation or q effect including the energy dissipation of high frequency wave components and the velocity dispersion that distorts seismic wavelets an inverse q filtering procedure attempts to remove the q effect to produce high resolution seismic data but some existing methods either reduce the s n ratio which limits spatial resolution or generate an illusory high resolution wavelet that contains no more subsurface information than the original low resolution data in this paper seismic inverse q filtering is implemented in a stabilized manner to produce high quality data in terms of resolution and s n ratio stabilization is applied to only the amplitude compensation operator of a full inverse q filter because its phase operator is unconditionally stable but the scheme neither amplifies nor suppresses high frequencies at late times where the data contain mostly ambient noise the latter property makes the process invertible differ

calibration of modern sedimentary δ2h plant wax water relationships in greenland lakes abstract sedimentary plant wax distributions and isotopic compositions are powerful widely applied paleoenvironmental proxies however there is conflicting evidence on the behavior of these proxies at high latitude sites where extreme climate and light conditions may uniquely influence plant physiology and growth here we present modern sedimentary n alkane and n alkanoic acid abundances and compound specific 2h and 13c isotope values from a 22 lake transect extending from northwest to southernmost greenland covering a large latitudinal and climatic gradient sedimentary plant waxes are similar in abundance and carbon isotopic composition across the transect suggesting no major differences in biologic sources there are strong correlations r 0 8 0 9 between 2h values of many long chain sedimentary waxes and those of modelled precipitation with n alkanes more tightly correlated to precipitation than n alkanoic acids data presented here also demonstrate that 2h values of mid chain sedimentary waxes do not strongly correlate to the 2h values of lake water when it decouples isotopically from precipitation i e in glacier fed and evaporatively enriched lakes this calls into question the common interpretation that mid chain sedimentary waxes can be ascribed to aquatic plants we contextualize our greenland data with an updated global dataset of 2h values of modern sedimentary waxes and precipitation this update adds 100 lakes from recently published literature to the seminal review presented by sachse et al 2012 this large new compilation suggests a global average apparent fractionation including arctic data between n c28 alkanoic acids and annual precipitation ec28 ann of 99 and between n c29 alkanes and annual precipitation ec29 ann of 121 the latter value is remarkably consistent with the value first reported by sachse et al 2012

temperature calibration and phylogenetically distinct distributions for freshwater alkenones evidence from northern alaskan lakes abstract alkenones are a class of unsaturated long chain ketone biomarkers that have been used to reconstruct sea surface temperature and more recently continental temperature by way of alkenone unsaturation indices e g u 37 k and u 37 k alkenones are frequently found in brackish and saline lakes however species effects confound temperature reconstructions when multiple alkenone producing species with different temperature responses are present interestingly available genetic data indicate that numerous freshwater lakes host a distinct phylotype of alkenone producing haptophyte algae the group i or greenland phylotype providing evidence that species effects may be diminished in freshwater lakes these findings encourage further investigation of alkenone paleotemperature proxies in freshwater systems here we investigated lakes from northern alaska n 35 and show that alkenones commonly occurred in freshwater lakes where they featured distinct distributions characterized by dominant c37 4 alkenones and a series of tri unsaturated alkenone isomers the distributions were characteristic of group i type alkenone distributions previously identified in greenland and north america our analysis of suspended particulate matter from toolik lake 68 38 n 149 36 w yielded the first in situ freshwater u 37 k calibration u 37 k 0 021 t 0 68 r2 0 85 n 52 rmse 1 37 c we explored the environmental significance of the tri unsaturated isomers using our northern alaskan lakes dataset in conjunction with new data from haptophyte cultures and canadian surface sediments our results show that these temperature sensitive isomers are biomarkers for the group i phylotype and indicators of multiple species effects together these findings highlight freshwater lakes as valuable targets for continental alkenone based paleotemperature reconstructions and demonstrate the significance of the recently discovered tri unsaturated isomers

multiple water isotope proxy reconstruction of extremely low last glacial temperatures in eastern beringia western arctic abstract precipitation isotopes are commonly used for paleothermometry in high latitude regions here we present multiple water isotope proxies from the same sedimentary context perennially frozen loess deposits in the klondike goldfields in central yukon canada representing parts of marine isotope stages mis 4 3 and 2 allowing us to uniquely corroborate fractionations and temperature conversions during these late pleistocene cold stages we include new and existing proxy data from relict wedge ice a direct archive for snowmelt relict pore ice an archive for bulk soil water integrating year round precipitation and hydrated volcanic glass shards and fossil plant waxes which are also thought to integrate year round precipitation but are subject to large fractionations in some cases our temperature estimates based on existing proxy data are much cooler than previously estimated due to our use of source water corrections for the glacial ocean new transfer functions calibrated specifically for northern north america d precip 3 1 c 1 t 155 and 18 o precip 0 41 c 1 t 20 2 and novel insights on the apparent net fractionation correction for eastern beringian steppe tundra plant waxes e wax precip 59 10 the snowmelt origin of wedge ice ensures a relatively constrained winter spring seasonality of contributing precipitation as supported by the consistency between water isotope measurements from late holocene wedge ice and modern winter spring precipitation wedge ice dating to the transitional mis 3 2 is isotopically depleted relative to modern spring winter precipitation by an amount that indicates a temperature depression of 14 5 c below modern the soil water origin of pore ice and other proxies integrating year round precipitation from soil water allows for a more variable precipitation seasonality the isotopic composition of modern pore ice is consistent with mean annual precipitation however the isotopic composition of pore ice during mis 3 2 converges on wedge ice values signalling an increase in the ratio of cold to warm season precipitation integrated by pore ice during glacial times possibly due to drier summers as supported by the fossil record and climate model simulations in the study region water isotope proxies integrating year round precipitation may overestimate annual temperature differences between today and recent cold stages due to transient precipitation seasonality as detected here and thus are best interpreted as upper bound estimates based on these proxies we estimate that annual temperatures during mis 4 3 2 and 2 were depressed below the modern climate to a maximum of 18 c 16 c and 21 c 4 5 c respectively our study highlights the value of multiple water isotope proxies towards understanding changes in precipitation seasonality and developing robust reconstructions of past climate and may be particularly important for studies of the major climate transformations over glacial interglacial timescales

coupling instrumental and geological records of sea level change evidence from southern new england of an increase in the rate of sea level rise in the late 19th century 1 we construct a high resolution relative sea level record for the past 700 years by dating basal salt marsh peat samples above a glacial erratic in an eastern connecticut salt marsh to test whether or not the apparent recent acceleration in the rate of sea level rise slr is coeval with climate warming the data reveal an average slr rate of 1 0 0 2 mm year from about 1300 to 1850 a d coupling of the regional tide gauge data 1856 to present with this marsh based record indicates that the nearly three fold increase in the regional rate of slr to modern levels likely occurred in the later half of the 19th century thus the timing of the observed slr rate increase is coincident with the onset of climate warming indicating a possible link between historic slr increases and recent temperature increases

effects of aridity and vegetation on plant wax δd in modern lake sediments we analyzed the deuterium composition of individual plant waxes in lake sediments from 28 watersheds that span a range of precipitation d h vegetation types and climates the apparent isotopic fractionation ea between plant wax n alkanes and precipitation differs with watershed ecosystem type and structure and decreases with increasing regional aridity as measured by enrichment of 2 h and 18 o associated with evaporation of lake waters the most negative ea values represent signatures least affected by aridity these values were 125 5 for tropical evergreen and dry forests 130 for a temperate broadleaf

chemical composition of dissolved organic matter draining permafrost soils abstract northern circumpolar permafrost soils contain roughly twice the amount of carbon stored in the atmosphere today but the majority of this soil organic carbon is perennially frozen climate warming in the arctic is thawing permafrost soils and mobilizing previously frozen dissolved organic matter dom from deeper soil layers to nearby surface waters previous studies have reported that ancient dom draining deeper layers of permafrost soils was more susceptible to degradation by aquatic bacteria compared to modern dom draining the shallow active layer of permafrost soils and have suggested that dom chemical composition may be an important control for the lability of dom to bacterial degradation however the compositional features that distinguish dom drained from different depths in permafrost soils are poorly characterized thus the objective of this study was to characterize the chemical composition of dom drained from different depths in permafrost soils and relate these compositional differences to its susceptibility to biological degradation dom was leached from the shallow organic mat and the deeper permafrost layer of soils within the imnavait creek watershed on the north slope of alaska dom draining both soil layers was characterized in triplicate by coupling ultra high resolution mass spectrometry 13c solid state nmr and optical spectroscopy methods with multi variate statistical analyses reproducibility of replicate mass spectra was high and compositional differences resulting from interfering species or isolation effects were significantly smaller than differences between dom drained from each soil layer all analyses indicated that dom leached from the shallower organic mat contained higher molecular weight more oxidized and more unsaturated aromatic species compared to dom leached from the deeper permafrost layer bacterial production rates and bacterial efficiencies were significantly higher for permafrost compared to organic mat dom however respiration rates were similar between dom sources increased release of permafrost dom from arctic soils to surface waters will change the chemical composition of dom and its lability to bacteria but this study suggests that these shifts in dom composition and lability may not increase the carbon dioxide produced by bacterial respiration of permafrost dom exported to arctic surface waters compared to dom currently draining the shallow active layer

hydrologic cycling over antarctica during the middle miocene warming global warmth 20 15 million years ago allowed vegetation to grow on formerly ice covered areas of antarctica leaf wax and pollen data show that this growth was supported by increased hydrologic activity over the antarctic coast derived from a local moisture source

pollen corrected leaf wax d h reconstructions of northeast african hydrological changes during the late miocene abstract plant leaf wax hydrogen isotope dwax reconstructions are increasingly being used to reconstruct hydrological change this approach is based upon the assumption that variations in hydroclimatic variables and in particular the isotopic composition of precipitation dp dominate dwax however modern calibration studies suggest that offsets between plant types may bias the dwax hydrological proxy at times of vegetation change in this study i pair leaf wax analyses with published pollen data to quantify this effect and construct the first vegetation corrected hydrogen isotopic evidence for precipitation dcorrp in marine sediments from deep sea drilling program site 231 in the gulf of aden spanning 11 4 3 8 ma late miocene and earliest pliocene i find 77 swings in dwax that correspond to pollen evidence for substantial vegetation change similarities between dp and dcorrp imply that the hydrological tracer is qualitatively robust to vegetation change however computed vegetation corrections can be as large as 31 indicating substantial quantitative uncertainty in the raw hydrological proxy the resulting dcorrp values quantify hydrological change and allow us to identify times considerably wetter than modern at 11 09 7 26 5 71 and 3 89 ma more generally this novel interpretative framework builds the foundations of improved quantitative paleohydrological reconstructions with the dwax proxy in contexts where vegetation change may bias the plant based proxy the vegetation corrected paleoprecipitation reconstruction dcorrp represents the best available estimate as proof of concept for an approach that i hope will be refined and more broadly applied

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

robust prestack q determination using surface seismic data part 1 method and synthetic examples the accurate determination of seismic attenuation or 1 q is useful for signal enhancement and reservoir characterization to arrive at the necessary accuracy however a number of issues must be addressed in the measurement technique specifically spectral interference from closely spaced reflections is a major concern in addition to the assumptions and errors associated with the raypath geometries of the reference and measured reflections we have developed a robust method for measuring attenuation from prestack surface seismic gathers that helps minimize these issues in our prestack q inversion technique the presence of spectral interference was first reduced by making use of a variable window time frequency transform to minimize the effects of the remaining interference we then made use of an inversion scheme operating simultaneously in the frequency and traveltime difference coordinates a by product of this inversion was a collection of the frequency independent amplitude changes which in the

mechanisms of decadal sea level variability in the eastern north atlantic and the mediterranean sea decadal sea level variations from tide gauge records along the western european coast and in the mediterranean sea commencing in the late 19th and early 20th centuries are examined relative to large scale atmospheric forcing recent studies have provided evidence for a link between sea level in the eastern north atlantic and atmospheric forcing however the nature of this relationship is still unclear here the outputs of a regional barotropic model and a nearly global baroclinic model are used in conjunction with wind stress and heat flux data to explore the physical mechanisms responsible for the observed sea level variability all tide gauge records show significant decadal variability up to 15 cm and are highly correlated with the nao and among themselves at decadal periods there is a coherent sea level signal that affects the eastern boundary of the north atlantic northward of 25 n and is limited to a narrow band of the order of a few hundred kilometers along the coast this band tends to become narrower towards higher latitudes we find that longshore wind and wave propagation along the boundary are the major contributors to coastal sea level variability but no significant contribution from mass redistribution linked to changes in the strength of the subtropical gyre is observed the mass component dominates sea level in the mediterranean and is mainly driven by mass exchanges with the atlantic which explains the correlation between both regions southward of 25 n sea level changes are mainly driven by heat advection through ekman fluxes

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

relative sea level change in west greenland during the last millennium relative sea level rsl data provide important long term century to millennial scale constraints on ice load history in greenland in this paper we present the results of a litho bio and chronostratigraphic study designed to reconstruct rsl during the last millennium from salt marsh deposits recovered from a field site near to the town of sisimiut west greenland the stratigraphy at three marshes typically records an upwards transition from freshwater to salt marsh deposits we use a quantitative transfer function and subjective model to reconstruct palaeomarsh elevation and changes in mean tide level mtl from 16 sediment profiles from these marshes these palaeomarsh elevations are placed in a chronological framework established by 18 radiocarbon dated index points both models yield similar results and show mtl rose from 0 60 0 20 m at c 600 cal a bp to reach 0 10 0 20 m at c 400 cal a bp after this time mtl remained close to present 0 20 m until the present day although low sedimentation rates limit the resolution of our reconstructions during this interval the initial rise in rsl can be explained by the dominance of non greenland processes notably the collapse of the laurentide forebulge over local greenland solid earth uplift caused by postglacial ice unloading this is despite some reloading of the crust that occurred during the neoglacial expansion of the greenland ice sheet in this part of west greenland the slow down in rsl at 400 cal a bp does not record either a change in the rate of laurentide forebulge collapse or a change in eustatic sea level we argue instead that this slow down records the effects of a sustained reduction in local greenland ice mass that persists over most of the past 400 years the latter interval is widely acknowledged as a period of generally cooler than present conditions associated with the later stages of the little ice age during this period field evidence suggests that in many areas the ice sheet had reached its maximum late holocene extent it is not obvious at this stage how to reconcile an expanding ice sheet with a reduction in ice load during this interval although we hypothesise it could reflect one or more of i a change in ice sheet dynamics ii reduced mass accumulation caused by cold and dry conditions and iii a lagged response to earlier periods of climate warming

contrasting records of sea level change in the eastern and western north atlantic during the last 300 years we present a new 300 year sea level reconstruction from a salt marsh on the isle of wight central english channel uk that we compare to other salt marsh and long tide gauge records to examine spatial and temporal variability in sea level change in the north atlantic our new reconstruction identifies an overall rise in relative sea level rsl of c 0 30 m since the start of the eighteenth century at a rate of 0 9 0 3 mmyr 1 error in variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset the reconstruction is broadly comparable to other tide gauge and salt marsh records from the european atlantic demonstrating coherence in sea level in this region over the last 150 300 years in contrast we identify significant differences in the rate and timing of rsl with records from the east coast of north america the absence of a strong late 19th early 20th century rsl acceleration contrasts with that recorded in salt marsh sediments along the eastern usa coastline in particular in a well dated and precise sea level reconstruction from north carolina this suggests that this part of the north carolina sea level record represents a regionally specific sea level acceleration this is significant because the north carolina record has been used as if it were globally representative within semi empirical parameterisations of past and future sea level change we conclude that regional scale differences of sea level change highlight the value of using several regionally representative rsl records when calibrating and testing semi empirical models of sea level against palaeo records this is because by using records that potentially over estimate sea level rise in the past such models risk over estimating sea level rise in the future

impacts of climate and vegetation change on carbon accumulation in a south central alaskan peatland assessed with novel organic geochemical techniques to constrain the effect of climate and peatland type on carbon accumulation we reconstructed these parameters from a holocene length core of a sphagnum dominated peatland near cordova ak usa we determined peat type using a combination of peat texture and density macrofossils distributions of leaf wax biomarkers and soil ph reconstructions based on distributions of branched glycerol dialkyl glycerol tetraether lipids brgdgts we produced an independent record of hydroclimate and temperature change using hydrogen isotope ratios of leaf wax biomarkers and distributions of brgdgts carbon accumulation rates were constrained with 14 ams 14c dates from identified macrofossils and ash free bulk density in the early holocene the site was a shallow pond with evidence for emergent macrophytes sphagnum and algae growing in a warm moist climate at 9 2 kyr 1 kyr 1000 cal yr bp the site became a sphagnum dominated bog under mid holocene warm evaporative climate conditions the site became sedge dominated as climate cooled and effective precipitation increased sphagnum was able to gain dominance abruptly at 3 5 kyr large changes in the vegetation assemblage and hydrology and climate are contemporaneous with significant changes in the rate of carbon accumulation carbon accumulated most rapidly when sphagnum dominated and effective moisture was high and most slowly when sedges were dominant and conditions were warmer and drier estimates of future climate change indicate warmer more evaporative conditions that in the past favored a sedge dominated environment suggesting that this peatland and those similar can contribute to a positive feedback to warming by transitioning to less efficient carbon sinks

comparison of soil derived tetraether membrane lipid distributions and plant wax δd compositions for reconstruction of canadian arctic temperatures abstract polar amplification of climate warming has received much attention as these rapidly rising temperatures have the potential to alter ecosystem function and biogeochemical cycles in particular carbon preserved in arctic tundra soil and permafrost may be especially vulnerable resulting in carbon cycle perturbations providing an additional positive feedback to climate change reliable methods for reconstructing past temperature changes in polar regions have been established from ice cores and marine sediments however techniques for the continental terrestrial environments are lacking but are imperative to examine polar amplification of climate warming here we compare two molecular methods for reconstructing continental annual mean air temperature mat for the canadian arctic based on the distribution of soil bacterial derived glycerol dialkyl glycerol tetraether gdgt membrane lipids mbt cbt proxy and the hydrogen isotopic composition d of plant wax derived n alkanes these two proxies were applied to both modern soil and paleosols collected from the yukon territory canada to evaluate both the accuracy of the reconstructed absolute temperatures as well as the relative change in temperature between the last glacial and the holocene branched gdgt based estimates using the recently revised mbt cbt calibration are overall higher by ca 6 c compared to the original calibration mat estimates for modern soils based on the original mbt cbt calibration are comparable with those based on the d of extracted c29 n alkanes and instrumental data however produced a 6 c higher temperature signal for the glacial paleosols therefore branched gdgt based temperature reconstructions for glacial soils in the high arctic may represent the higher temperatures at the time of soil formation when bacterial activity was optimal whereas d of c29 n alkane plant lipids appear to integrate an average annual signal when used in tandem these geochemical proxies may provide a more comprehensive method for reconstructing arctic paleoclimate

development of a foraminifera based transfer function in the basque marshes n spain implications for sea level studies in the bay of biscay abstract in order to reconstruct former sea level we have developed a foraminifera based transfer function using three models based on a modern dataset of 59 samples and 23 species obtained from four basque marshes in northern spain the relationship between observed and foraminifera predicted elevation illustrated the strong performance of the transfer function r 2 jack ranges from 0 74 to 0 81 these results indicated that precise reconstructions of former sea levels are possible error ranges from 0 11 to 0 19 m the transfer function was used to calibrate the foraminiferal assemblages collected from a 50 cm salt marsh core we placed the foraminifera based reconstructions into a temporal framework using 137 cs pb concentrations and 210 pb derived sediment accumulation rates the resulting relative sea level curve is in good agreement with regional tide gauge data both instrumental data and microfossil records suggest a rate of relative sea level rise of approximately 2 mm yr 1 for the 20th century

estimation of interval anisotropic attenuation from reflection data knowledge of interval attenuation can be highly beneficial in reservoir characterization and lithology discrimination we combine the spectral ratio method with velocity independent layer stripping to develop a technique for the estimation of the interval attenuation coefficient from reflection seismic data the layer stripping procedure is based on identifying the reflections from the top and bottom of the target layer that share the same ray segments in the overburden the algorithm is designed for heterogeneous arbitrarily anisotropic target layers but the overburden is assumed to be laterally homogeneous with a horizontal symmetry plane although no velocity information about the overburden is needed interpretation of the computed anisotropic attenuation coefficient involves the phase angle in the target layer tests on synthetic p wave data from layered transversely isotropic and orthorhombic media confirm the high accuracy of 2d and 3d versions of the algorithm we also demonstrate that the interval attenuation estimates are independent of the inhomogeneity angle of the incident and reflected waves

preservation of lipid hydrogen isotope ratios in miocene lacustrine sediments and plant fossils at clarkia northern idaho usa abstract we measured d h ratios of individual lipids isolated from plant fossils and water lain sediments from the miocene clarkia lacustrine deposit 15 20 ma in northern idaho usa in order to assess the preservation potential of lipid hydrogen isotope ratios distinct n alkyl lipid profiles in plant fossils platanus quercus salix and the sedimentary matrix demonstrate the high degree of lipid preservation as previously reported our data suggest that original hydrogen isotope ratios of carbon bound hydrogen in lipids may have been preserved after 15 20 million years of burial in the water lain lacustrine sediment because d values of individual lipids show large variations between different fossil genera and between fossils and sediments and hydrogen isotope values of fossil lipids differ by more than 123 from the associated sediment water these data are consistent with minimal isotopic exchange between carbon bound hydrogen in lipids and sediment water hydrogen our results validate the use of lipid hydrogen isotope ratios for paleoecological studies over an extended geological time period

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

the application of foraminifera to reconstruct the rate of 20th century sea level rise morbihan golfe brittany france abstract foraminiferal assemblages preserved within salt marsh sediment can provide an accurate and precise means to reconstruct relative sea level due to a strong relationship with elevation which can be quantified using a transfer function we collected a set of surface samples from two salt marshes in the morbihan golfe france to determine foraminiferal distribution patterns dominant taxa included jadammina macrescens trochammina inflata haplophragmoides spp and miliammina fusca we developed a foraminifera based transfer function using a modern training set of 36 samples and 23 species the strong relationship between observed and predicted values r 2 jack 0 7 indicated that foraminiferal distribution is primarily controlled by elevation with respect to the tidal frame and precise reconstructions of former sea level are possible rmsep jack 0 07 m the application of the transfer function to a short salt marsh core 0 32 m allowed the reconstruction of former sea levels which were placed in a chronological framework using short lived radionuclides 210 pb and 137 cs the agreement between the foraminifera based sea level curve and the brest tide gauge record confirms the reliability of transfer function estimates and the validity of this methodology to extend sea level reconstructions back into the pre instrumental period both instrumental and microfossil records suggest an acceleration of sea level rise during the 20th century

hydrogen isotopic compositions along a precipitation gradient of chinese loess plateau critical roles of precipitation evaporation and vegetation change as controls for leaf wax δd abstract the hydrogen isotopic compositions d of long chain plant leaf waxes can reflect changes of continental hydrology and thus have been increasingly utilized for paleoclimate reconstruction one of the unresolved major issues is whether variations of leaf wax d dwax signals along a precipitation gradient reflect changes of precipitation d precipitation amount and or evapo transpiration this ambiguity limits our interpretation of dwax in geological records as well as the quantitative reconstruction of paleohydrological variability here we systematically investigated d of soil water and waxes extracted from soil and plant leaves in the chinese loess plateau clp and its surrounding areas along a precipitation gradient with mean annual precipitation map varying from 140 mm to 676 mm the results showed that while the variation of modeled precipitation d has no significant correlation with map soil water d soil dwax and individual plant dwax exhibit negative correlations with map in relatively arid areas the d values of soil water and plant leaf waxes are significantly more positive due to much lower precipitation relative to evapo transpiration suggesting that effective precipitation p e ratio has played a crucial role in the d enrichment of soil and plant leaf waxes in this region while parallel decreasing trends in dwax are found along the increase of precipitation gradient among dominant plants including artemisia spp aster hispidus stipa bungeana and cleistogenes squarrosa in the region with similar slopes the large d offsets between plant groups suggest that plant type is an important factor in controlling plant hydrogen isotope fractionations our results indicate that dwax preserved in paleosols can be used to infer past conditions of water availability in arid and semi arid inland regions but with a mechanism that is different from the influence of amount effect in humid areas moreover vegetation changes should be constrained by independent paleobotanical data before monsoon related paleohydrology in the clp and its surrounding areas can be quantitatively reconstructed using the plant wax d proxy

hydrogen isotope ratios of lacustrine sedimentary n alkanes as proxies of tropical african hydrology insights from a calibration transect across cameroon abstract hydrogen isotope values d of sedimentary aquatic and terrestrial lipid biomarkers originating from algae bacteria and leaf wax have been used to record isotopic properties of ancient source water i e precipitation and or lake water in several mid and high latitude lacustrine environments in the tropics however where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes calibration studies for this proxy are not yet available to close this gap of knowledge we sampled surface sediments from 11 lakes in cameroon to identify those hydro climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers here we present a robust framework for the application of compound specific hydrogen isotopes in tropical africa our results show that the d values of the aquatic lipid biomarker n c17 alkane were not correlated with the d values of lake water carbon isotope measurements indicate that the n c17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis we demonstrate that the d values of the n c29 alkane were correlated with the d values of surface water i e river water and groundwater which on large spatial scales reflect the isotopic composition of mean annual precipitation such a relationship has been observed at higher latitudes supporting the robustness of the leaf wax lipid d proxy on a hemispheric spatial scale in contrast the d values of the n c31 alkane did not show such a relationship but instead were correlated with the evaporative lake water d values this result suggests distinct water sources for both leaf wax lipids most likely originating from two different groups of plants these new findings have important implications for the interpretation of long chain n alkane d records from ancient lake sediments in particular a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and or growth form of organisms and therefore the source of hydrogen used during lipid biosynthesis

sedimentary charcoal proxy records of fire in alaskan tundra ecosystems abstract extensive burning of arctic tundra landscapes in recent years has contradicted the conventional view that fire is a rare spatially limited disturbance in tundra these fires have been identified as harbingers of climate change despite our limited understanding of arctic fire frequency and climatic controls much of this understanding relies upon sedimentary charcoal based fire reconstructions yet the controls on sedimentary charcoal abundance need to be rigorously tested in tundra ecoregions we compile published charcoal based tundra fire reconstructions in alaska and compare them with historical limnological and spatial data to 1 evaluate the spatial and temporal characteristics of tundra fires 2 identify the primary controls of charcoal accumulation in lake sediments 3 assess the accuracy of peak analysis in identifying local

seismic attenuation tomography using the frequency shift method we present a method for estimating seismic attenuation based on frequency shift data in most natural materials seismic attenuation increases with frequency the high frequency components of the seismic signal are attenuated more rapidly than the low frequency components as waves propagate as a result the centroid of the signal s spectrum experiences a downshift during propagation under the assumption of a frequency independent q model this downshift is proportional to a path integral through the attenuation distribution and can be used as observed data to reconstruct the attenuation distribution tomographically the frequency shift method is applicable in any seismic survey geometry where the signal bandwidth is broad enough and the attenuation is high enough to cause noticeable losses of high frequencies during propagation in comparison to some other methods of estimating attenuation our frequency shift method is relatively insensitive to geometric spreading reflection and transmission effects source and receiver coupling and radiation patterns and instrument responses tests of crosswell attenuation tomography on 1 d and 2 d geological structures are presented

mccall glacier record of arctic climate change interpreting a northern alaska ice core with regional water isotopes abstract we explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the arctic paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions such as water isotopes therefore we measured periodic precipitation samples at toolik lake field station toolik in the northern foothills of the brooks range in the alaskan arctic to determine 18 o and 2 h we applied this multi decadal local precipitation 18 o temperature regression to 65 years of mccall glacier also in the brooks range ice core isotope measurements and found an increase in reconstructed temperatures over the late 20th and early 21st centuries we also show that the mccall glacier 18 o isotope record is negatively correlated with the winter bidecadal north pacific index npi climate oscillation mccall glacier deuterium excess d excess 2 h 8 18 o values display a bidecadal periodicity coherent with the npi and suggest shifts from more southwestern bering sea moisture sources with less sea ice lower d excess values to more northern arctic ocean moisture sources with more sea ice higher d excess values northern ice covered arctic ocean mccall glacier moisture sources are associated with weak aleutian low al circulation patterns and the southern moisture sources with strong al patterns ice core d excess values significantly decrease over the record coincident with warmer temperatures and a significant reduction in alaska sea ice concentration which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources a concept recently proposed by modeling studies and also present in greenland ice core d excess values during previous transitions to warm periods this study also shows the efficacy and importance of using ice cores from arctic valley glaciers in paleoclimate reconstructions

environmental controls on the 2h 1h values of terrestrial leaf waxes in the eastern canadian arctic the hydrogen isotope composition of plant waxes preserved in lacustrine sediments is a potentially valuable tool for reconstructing paleoenvironmental changes in the arctic however in contrast to

a major increase in winter snowfall during the middle holocene on western greenland caused by reduced sea ice in baffin bay and the labrador sea precipitation is predicted to increase in the arctic as temperature increases and sea ice retreats yet the mechanisms controlling precipitation in the arctic are poorly understood and quantified only by the short sparse instrumental record we use hydrogen isotope ratios 2h of lipid biomarkers in lake sediments from western greenland to reconstruct precipitation seasonality and summer temperature during the past 8 kyr aquatic biomarker 2h was 100 more negative from 6 to 4 ka than during the early and late holocene which we interpret to reflect increased winter snowfall the middle holocene also had high summer air temperature decreased early winter sea ice in baffin bay and the labrador sea and a strong warm west greenland current these results corroborate model predictions of winter snowfall increases caused by sea ice retreat and furthermore suggest that warm currents advecting more heat into the polar seas may enhance arctic evaporation and snowfall

comparable hydrogen isotopic fractionation of plant leaf wax n alkanoic acids in arid and humid subtropical ecosystems 1 leaf wax hydrogen isotope proxies have been widely used to reconstruct past hydrological changes however published reconstructions have given little consideration for the potentially variable hydrogen isotopic fractionation relative to precipitation ewax p under different climate and environmental settings chief among various potential factors controlling fractionation is relative humidity which is known to strongly affect oxygen isotopic ratios of plant cellulose but its effect on hydrogen isotopic fractionation of leaf waxes is still ambiguous analyses of lake surface sediments and individual modern plants have provided valuable information on the variability of ewax p but both approaches have significant limitations here we present an alternative method to obtain the integrated time resolved ecosystem level ewax p values by analyzing modern aerosol samples collected weekly from arid arizona lowlands and humid subtropical atlanta georgia environments during the main growth season because aerosol samples mainly reflect regional leaf wax resources the extreme contrast in the hydroclimate and associated vegetation assemblages between our study sites allows us to rigorously assess the impact of relative humidity and associated vegetation assemblages on leaf wax hydrogen isotopic fractionation we show there is only minor difference mostly 10 in the mean ewax p values in the two end member environments one possible explanation is that the positive isotopic effects of low relative humidity are offset by progressive replacement of trees with grasses that have a more negative apparent fractionation our results represent an important step toward quantitative interpretation of leaf wax hydrogen isotopic records

the past present and future evolution of hurst castle spit hampshire abstract previous models of the evolution of hurst castle spit over emphasised longshore growth at the expense of other processes particularly rise in sea level initially a pleistocene valley system was submerged creating a tidal strait the west solent between christchurch bay and the east solent this almost certainly caused a major hydrodynamic change transforming much of christchurch bay and the west solent from a low to a high tidal energy environment hurst castle spit and the shingles bank then began to form due to a combination of an easterly littoral drift offshore gravel movement due to the high tidal energy a rising sea level the transgression of hurst beach due to overwashing and the formation of recurves due to waves in the west solent the growth of the shingles bank due to offshore sediment movement from hurst castle spit was of particular importance because of its influence on the wave energy along hurst beach significant local supplies of shingle in the vicinity of hurst castle spit reworked from quatenary deposits were also of importance thus it is not a classic multi recurved spit and the transgressive segment hurst beach has much in common with barrier coastlines the same processes are continuing to shape hurst castle spit at present with the additional effects of human interference in the coastal sediment system the construction of sea defences at milford on sea in the period 1936 to 1968 has modified the sediment budget and hurst castle spit is experiencing a phase of rapid evolution maximum recession rates have increased from 1 5m a 1 1867 1968 to 3 5m a 1 1968 1982 it is difficult to quantify the exact role of sea level rise in the present evolution of hurst castle spit the future evolution of hurst castle spit will depend largely on man if there is no further interference which is highly unlikely the beach volume will continue to decline resulting in a further increase in the rate of recession ultimately a true tidal breach will probably form marking a new phase in the evolution of hurst castle spit and its environs however shingle renourishment or another coastal engineering solution will probably be undertaken the future rate of sea level rise will have important long term influences on all these options

glacial aridity in central indonesia coeval with intensified monsoon circulation abstract the last glacial maximum was cool and dry over the indo pacific warm pool ipwp a key region driving global oceanic atmospheric circulation both low and high latitude teleconnections with insolation ice sheets and sea level have been suggested to explain the pervasive aridity observed in paleoecological and geomorphic data however proxies tracking the h and o isotopic composition of rainfall e g speleothems sedimentary biomarkers suggest muted aridity or even wetter conditions than the present complicating interpretations of glacial ipwp climate here we use multiproxy reconstructions from lake sediments and modern rainfall isotopic measurements from central indonesia to show that contrary to the classical amount effect intensified australian indonesian monsoon circulation drove lighter h and o isotopic composition of ipwp rainfall during the lgm while at the same time dry conditions prevailed precipitation isotopes are particularly sensitive to the apparent increase in monsoon circulation and perhaps also decreased moisture residence time implied by our data explaining contrasts among proxy records while illuminating glacial ipwp atmospheric circulation a key target for climate models

the stable hydrogen isotopic composition of sedimentary plant waxes as quantitative proxy for rainfall in the west african sahel various studies have demonstrated that the stable hydrogen isotopic composition d of terrestrial leaf waxes tracks that of precipitation d precip both spatially across climate gradients and over a range of different timescales yet reconstructed estimates of d precip and corresponding rainfall typically remain largely qualitative due mainly to uncertainties in plant ecosystem net fractionation relative humidity and the stability of the amount effect through time here we present d values of the c 31 n alkane d wax from a marine sediment core offshore the northwest nw african sahel covering the past 100 years and overlapping with the instrumental record of rainfall we use this record to investigate whether accurate quantitative estimates of past rainfall can be derived from our d wax time series we infer the composition of vegetation c 3 c 4 within the continental catchment area by analysis of the stable carbon isotopic composition of the same compounds 13 c wax calculated a net ecosystem fractionation factor and corrected the d wax time series accordingly to derive d precip using the present day relationship between d precip and the amount of precipitation in the tropics we derive quantitative estimates of past precipitation amounts our data show that a vegetation composition can be inferred from 13 c wax b the calculated net ecosystem fractionation represents a reasonable estimate and c estimated total amounts of rainfall based on d wax correspond to instrumental records of rainfall our study has important implications for future studies aiming to reconstruct rainfall based on d wax the combined data presented here demonstrate that it is feasible to infer absolute rainfall amounts from sedimentary d wax in tandem with 13 c wax in specific depositional settings

sources and abundances of leaf waxes in aerosols in central europe abstract atmospheric transport is an understudied mechanism for leaf wax hydrogen isotope applications that contributes to mobilizing and depositing these compounds on the surface of the earth while previous efforts have identified the importance of atmospheric leaf wax deposition in remote marine locations the processes are not well constrained on land in temperate latitudes where lakes are common and sedimentary leaf wax hydrogen isotope values are an attractive tool for understanding past precipitation changes this work presents results from a field study that was conducted in 2010 and 2011 at hainich national park germany in order to evaluate the quantity and sources of leaf waxes in the atmosphere aerosols were sampled at approximately weekly intervals inside the forest canopy and n alkane distributions and hydrogen isotope values were compared with those from major tree species surrounding the sampling site despite sampling in what was expected to be a major production center the distribution and hydrogen isotope values of atmospheric n alkanes bore little resemblance to those of the local vegetation comparison with local meteorological data and to 10 day and 36 h back air mass trajectories indicated shifting effects of winds and temperature and that mesoscale transport processes were more important than long range mechanisms back trajectories also highlighted source effects with easterly winds coinciding with relatively lower leaf wax hydrogen isotope values from more continental regions these results suggest that leaf wax aerosols average over spatial scales that exceed typical surface catchment areas for small lake systems even in forested areas yet that the area over which these compounds are derived is still relatively regional depositional fluxes were also estimated in order to assess the potential importance of atmospheric transport to sedimentary archives although difficult to constrain these estimates suggest that atmospheric deposition may be non negligible for lake systems in cases where inputs from rivers or surface runoff are limited together these observations provide new insights on how leaf waxes from different sources are integrated during aeolian transport and the spatial scales over which these processes occur

quantitative assessment of precipitation seasonality and summer surface wetness using ombrotrophic sediments from an arctic norwegian peatland article i nfo article history received 18 april 2008 available online xxxx seasonality of precipitation is an important yet elusive climate parameter in paleoclimatological reconstructions this parameter can be inferred qualitatively from pollen and other paleoecological methods but is difficult to assess quantitatively here we have assessed seasonality of precipitation and summer surface wetness using compound specific hydrogen and carbon isotope ratios of vascular plant leaf waxes and sphagnum biomarkers extracted from the sediments of an ombrotrophic peatland bostad bog nordland norway our reconstructed precipitation seasonality and surface wetness are consistent with regional vegetation reconstructions during the early holocene 11 5 7 5 ka fennoscandia experienced a cool moist climate the middle holocene 7 5 5 5 ka was warm and dry transitioning towards cooler and wetter conditions from the mid holocene to the present changes in seasonality of precipitation during the holocene show significant coherence with changes in sea surface temperature in the norwegian sea with higher sst corresponding to greater percentage of winter precipitation both high sst in the norwegian sea and increased moisture delivery to northern europe during winter are correlated with a strong gradient between the subpolar low and subtropical high over the north atlantic positive north atlantic oscillation

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

estimation of q from surface seismic reflection data reliable estimates of the anelastic attenuation factor q are desirable for improved resolution through inverse q deconvolution and to facilitate amplitude analysis q is a useful petrophysical parameter itself yet q is rarely measured estimates must currently be made from borehole seismology this paper presents a simple technique for determining q from conventional surface seismic common midpoint cmp gathers it is essentially the classic spectral ratio method applied on a trace by trace basis to a designatured and nmo stretch corrected cmp gather the variation of apparent q versus offset qvo is extrapolated to give a zero offset q estimate studies on synthetics suggest that for reasonable data quality s n ratios better than 3 1 shallow 5 dips and stacking velocity accuracy 5 source to reflector average q is recoverable to within some 3 and q for a specific interval depending on its two way time thickness and depth is recoverable to 15 20 three case studies are reported first

the determination of the seismic quality factor q from vsp data a comparison of different computational methods1 ten methods for the computation of attenuation have been investigated namely amplitude decay analytical signal wavelet modelling phase modelling frequency modelling rise time pulse amplitude matching technique spectral modelling and spectral ratio in particular we have studied the reliability of each of these methods in estimating correct values of q using three synthetic vsp seismograms for plane p waves with different noise contents the investigations proved that no single method is generally superior rather some methods are more suitable than others in specific situations depending on recording noise or geology the analytical signal method has been demonstrated to be superior if true amplitude recordings are available otherwise spectral modelling or in the noise free case the spectral ratio method is optimal finally two field vsps in sediments are investigated only in the case of the highest quality vsp can significant information be deduced from the computed attenuation

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

the role of seasonality in abrupt climate change abstract a case is made that seasonality switches dominated by wintertime were instrumental in abrupt climate changes in the north atlantic region during the last glaciation and into the holocene the primary evidence comes from mismatches between mean annual temperatures from greenland ice cores in comparison with snowline changes in east greenland northern europe and north america the most likely explanation is a shutdown or reduction in strength of the conveyor this allows the spread of winter sea ice across the north atlantic thus causing the northern region to experience much colder winters because they mimic the greenland temperature rather than the snowline signal changes in the atlantic intertropical convergence zone and the asian monsoon may also share a winter linkage with greenland thus the paleoclimate record is consistent with the notion that a huge continental sector of the northern hemisphere stretching from greenland to asia was close to an extreme winter threshold during much of the last glaciation winter climate crossed this threshold repeatedly with marked changes in seasonality that may well have amplified and propagated a signal of abrupt change throughout the hemisphere and into the tropics

measurements of attenuation from vertical seismic profiles values of attenuation have been extracted from five detailed velocity surveys significant amounts of attenuation are observed in all five wells measured values of attenuation vary by a factor of 10 ranging from less than 0 1 to 0 9 db wavelength correlation of attenuation with lithology is good considering the resolution limits of the surveys one of the surveys was performed in west texas and the other four were carried out in the gulf coast area the total number of recording depths in each survey varied from 31 to 208 with downhole recordings taken every 10 or 20 ft over key stratigraphic zones in all five surveys a monitor geophone was placed near the well to check for source consistency our procedure for measuring attenuation involved constructing the spectral ratio between each downhole pulse and one particular reference pulse a value of cumulative attenuation ca was then extracted from each spectral ratio and plotted as a function of geophone depth this method allowed us to use many m

composition of lipids from coal deposits of the far east relations to vegetation and climate change during the cenozoic abstract twenty one samples of sub bituminous coal and 1 sample of coaly shale have been collected from different coal seams representing the cenozoic coal basins widely distributed in the region of primorye and sakhalin russia and ne china hunchun deposit the seams belong to lower miocene upper oligocene sineutesovsky oligocene upper eocene pavlovsky upper eocene ust davydovsky lower eocene uglovsky and upper paleocene kivdinsky local chronostratigraphic units terpenoid biomarker compositions indicate the contribution of conifers and angiosperms to peat formation the results are in agreement with paleobotanical data from sedimentary successions closely associated with the seams highlighting abundant conifers of the taxodioid cupressaceae and pinaceae families as well as betula alnus fagus and ulmus during cenozoic in the far east in contrast to previous findings about changes in peat forming vegetation in central europe the terpenoid biomarker ratios revealed increased contributions of angiosperms during the oligocene and gymnosperm domination during eocene and miocene the different evolution may be related to differences in temperature and precipitation distribution as well as in geomorphology and landscape evolution a positive relationship between the di di tri terpenoid biomarker ratios and 13c of oligocene samples indicates the role of varying gymnosperm angiosperm influences on the 13c of coal differences in vegetation and climate are most probably responsible for the different trends in 13c of terpenoid biomarkers over the cenozoic beside their general variation coupled to the evolution in 13c of atmospheric co2 lower 2h values of plant derived lipids during the oligocene were most probably caused by lower temperatures during coal formation this conclusion is supported by the results of recent paleobotanical studies yielding lower mean annual temperatures mat during the oligocene but comparable values for mean annual precipitation map during the eocene and oligocene in the primorye region pimarane type diterpenoids are significantly depleted in 2h the results are in agreement with previous studies identifying different sources of hydrogen and or different biosynthetic pathways during their formation

hydrogen isotope fractionation in leaf waxes in the alaskan arctic tundra abstract leaf wax hydrogen isotopes dwax are increasingly utilized in terrestrial paleoclimate research applications of this proxy must be grounded by studies of the modern controls on dwax including the ecophysiological controls on isotope fractionation at both the plant and landscape scales several calibration studies suggest a considerably smaller apparent fractionation between source water and waxes eapp at high latitudes relative to temperate or tropical locations with major implications for paleoclimatic interpretations of sedimentary dwax here we investigate apparent fractionation in the arctic by tracing the isotopic composition of leaf waxes from production in modern plants to deposition in lake sediments using isotopic observations of precipitation soil and plant waters living leaf waxes and waxes in sediment traps in the brooks range foothills of northern alaska we also analyze a lake surface sediment transect to compare present day vegetation assemblages to eapp at the watershed scale source water and eapp were determined for live specimens of eriophorum vaginatum cottongrass and betula nana dwarf birch two dominant tundra plants in the brooks range foothills the d of these plants xylem water closely tracks that of surface soil water and reflects a summer biased precipitation source leaf water is enriched by 23 15 relative to xylem water for e vaginatum and by 41 19 for b nana evapotranspiration modeling indicates that this leaf water enrichment is consistent with the evaporative enrichment expected under the climate conditions of northern alaska and that 24 h photosynthesis does not cause excessive leaf water isotope enrichment the eapp determined for our study species average 89 14 and 106 16 for b nana n alkanes and n acids respectively and 182 10 and 154 26 for e vaginatum n alkanes and n acids which are similar to the eapp of related species in temperate and tropical regions indicating that apparent fractionation is similar in arctic relative to other regions and there is no reduced fractionation in the arctic sediment trap data suggest that waxes are primarily transported into lakes from local watershed scale sources by overland flow during the spring freshet and so dwax within lakes depends on watershed scale differences in water isotope compositions and in plant ecophysiology as such the large difference between our study species suggests that the relative abundance of graminoids and shrubs is potentially an important control on dwax in lake sediments these inferences are supported by dwax data from surface sediments of 24 lakes where eapp relative to dxylem averages 128 13 and 130 8 for n acids and n alkanes respectively and co varies with vegetation type across watersheds these new determinations of plant source water seasonality and eapp for the arctic will improve the dwax paleoclimate proxy at high latitudes

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso