marine crenarchaeotal membrane lipids in decapods implications for the tex86 paleothermometer pelagic crenarchaeota produce glycerol dibiphytanyl glycerol tetraethers gdgts as membrane lipids and the gdgt composition changes according to growth temperature this forms the basis of the tex86 paleotemperature proxy this ratio correlates with sea surface temperature sst despite the fact that crenarchaeota are distributed through the water column therefore there must be mechanisms that transport the surface signal to sediments such as repackaging in fecal pellets marine snow mass falls after phytoplankton blooms or daily migration to study gdgt transport we analyzed stomachs and intestines of atlantic and mediterranean decapods as they are one of the major megafaunal groups are easy to sample and occur in both pelagic and benthic environments gdgts were found in most decapods guts gdgt abundances are significantly lower in intestines but tex86 derived temperatures are not significantly different between stomachs and intestines 1oc suggesting that tex86 values are not altered during gut transit atlantic decapods show no difference in tex86 values between benthic detritivors and pelagic predators however mediterranean decapods show a substantial difference between macroplankton feeders and bentho pelagic predators this is probably related to the freshness of the material consumed tex86 derived temperatures in atlantic decapods are close to the sst around the time of sampling in agreement with stomach content analysis that shows fresh organic matter being ingested for mediterranean decapods tex86 temperatures are significantly higher than sst around the time of sampling this can be partly attributed to the large variability between decapod specimens and the low amounts of fresh material found in their stomachs

ring index a new strategy to evaluate the integrity of tex86 paleothermometry the tex86 tetraether index of 86 carbon atoms sea surface temperature proxy has been increasingly applied in the reconstruction of mesozoic and cenozoic ocean temperatures however the archaeal lipids that compose tex86 indices glycerol dialkyl glycerol tetraethers gdgts can derive from water column production terrestrial sources and or within sediments tex86 sea surface temperature estimates can also be influenced by non temperature factors such as growth phase and nutrient levels here we show that the weighted average of cyclopentane moieties known as the ring index ri can be used to determine if tex86 temperature estimates are influenced by non thermal factors and or deviate from modern analogues we demonstrate that ri and tex86 indices from the published global core top data set and mesocosm cultures are significantly correlated as predicted through the influence of temperature on lipid biochemistry we further show that when ri and tex86 indices in modern or ancient records deviate from the modern global tex86 ri relationship gdgt distributions are not solely controlled by environmental temperature and or tex86 based temperature reconstructions are questionable

holocene variability in sea surface temperature and sea ice extent in the northern bering sea a multiple biomarker study abstract the bering sea as a transition between the arctic and the pacific oceans plays an important role in global climate change and biogeochemical cycles here we examined a variety of biomarkers in a core br07 from the northern continental slope of the bering sea in order to reconstruct summer sea surface temperature sst and sea ice extent during the period 11 2 ka thousands of calendar years ago the tex 86 l derived sst gradually decreased ca 1 6 c from early to mid holocene 11 3 8 0 ka but did not show a cooling or warming trend afterwards our sst data do not support the hypothesis of a holocene seesaw in temperature between the north atlantic and the north pacific several algal biomarkers including ip 25 and its derived indicators for sea ice brassicasterol for diatoms and dinosterol for dinoflagellates suggest that the sea ice extent gradually increased from early to late holocene interrupted by rapid changes at ca 2 8 2 6 and 5 5 5 0 ka the synchronous evolution between ip 25 and sst indicates a strong coupling between sea ice cover and climate change in the holocene

reconstruction of sea surface temperature variations in the arabian sea over the last 23 kyr using organic proxies tex86 and u37k well established u37 0 based on long chain unsaturated ketones synthesized by haptophyte algae and the newly proposed tex86 derived from the membrane lipids of crenarchaeota comparison of niop905 and 74kl core top data with present day sst 0 10 m values indicates that both proxies yield temperatures similar to local annual mean ssts however tex86 and u37 0 sst down core records derived from the same cores differ in magnitude and phasing the alkenone sst record of niop905 shows small changes in sst 0 5 c over the last 23 kyr while that of core 74kl shows a 2 c increase from the last glacial maximum lgm 23 19 calendar cal kyr b p through the holocene the last 11 5 cal kyr b p synchronous with changes in the northern hemisphere in contrast the tex86 records of both cores show a large increase in sst from 22 23 c in the lgm to 28 30 c during termination i 19 11 5 cal kyr b p decreasing to present day annual means of 26 c a cold phase between 14 5 and 12 cal kyr b p that may correspond to the antarctic cold reversal is also observed this implies a southern hemisphere control on tropical sst reconstructed by the tex86 possibly related to sw monsoon our results suggest that the application of both tex86 and u37 0 give different but complementary information on sst developments in past marine environments

synthetic fluid inclusions in natural quartz iii determination of phase equilibrium properties in the system h2o nacl to 1000 c and 1500 bars phase equilibria in the system h2o nacl have been determined to 1000 c and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion free brazilian quartz in the presence of the two coexisting immiscible h2o nacl fluids at various temperatures and pressures petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present or mixtures of the two salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single homogeneous fluid phase results of the present study are consistent with previously published data on the h2o nacl system at lower temperatures and pressures and indicate that the two phase field extends well into the p t range of most shallow magmatic hydrothermal activity as a consequence chloride brines exsolved from many epizonal plutons during the process of second boiling should immediately separate into a high salinity liquid phase and a lower salinity vapor phase and produce coexisting halite bearing and vapor rich fluid inclusions this observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions particularly the porphyry copper deposits in which halite bearing and coexisting vapor rich inclusions are commonly associated with the earliest stages of magmatic hydrothermal activity

tex86 paleothermometer as an indication of bottom water temperature in the yellow sea the tex86 paleothermometer was applied for reconstructing sea surface temperature sst from glycerol dialkyl glycerol tetraethers gdgts in marine sediments it has become clear that gdgt producing archaea live throughout the water column with maximum concentration usually well below the surface mixed layer of the ocean why the tex86 parameter correlates well with sst remains poorly understood here we evaluate the fidelity of the tex86 thermometer using surface sediments and suspended particles from the yellow sea ys a shallow marginal sea between china and the korean peninsula the highest concentration of gdgts in the water column at a site a02 from the middle of the ys occurred in the bottom layer at 70 m this contrasts with phytoplankton lipids which were most abundant near the surface consistent with the maximum abundance of gdgts in bottom water tex86 values in surface sediments correlated better with mean annual bottom water temperature bwt r 2 0 81 than with mean

subtropical climate conditions and mangrove growth in arctic siberia during the early eocene the early eocene ca 56 47 8 ma was an interval of exceptional warmth with reduced pole to equator temperature gradients climate proxies indicate mean annual air temperatures mats and sea surface temperatures ssts exceeding 8 18 c and frost free mild winters in polar areas features that have proven difficult to reproduce with the most elaborate climate models a full appraisal of the early eocene polar climate has been however limited by possible seasonal biases associated with geochemical proxies and the lack of data from the vast eurasian arctic here we present multiproxy data from lower middle eocene coastal plain sediments of the new siberian islands russia showing that taxodioid cupressaceae palms and the mangrove avicennia grew in arctic siberia above 72 n under air temperatures averaging 16 21 c annually and 5 5 14 c in winter kaolinite contents are exceptionally high up to 60 of clay assemblages and comparable to those found in present day subtropical soils formed under high mean annual precipitation map 1000 mm and warm mat 15 c conditions the avicennia pollen records the northernmost mangrove growth ever documented and indicates early eocene ssts exceeding 13 c in winter and 18 c in summer considering the high map estimated for arctic siberia and other pan arctic landmasses we propose that the heat from warm river waters draining into the arctic might have amplified early eocene polar warmth our results provide the first climate constraints for the early eocene of arctic siberia and support the view that most climate models underestimate polar warming in greenhouse conditions

alkenone paleothermometry in the north atlantic a review and synthesis of surface sediment data and calibrations despite a clear correlation of alkenone unsaturation and sea surface temperatures sst throughout most parts of the ocean scatter of the regression for various calibration equations has been shown to increase significantly at low ssts in this study we combine previously published n 101 and new n 51 surface sediment data from the northern north atlantic to constrain uncertainties of alkenone paleothermometry at low ssts and to discuss possible sources of the increased scatter in the regression the correlation between alkenone unsaturation and ssts is strongest in particular at the cold end ssts 10 c when the tetra unsaturated alkenones c37 4 are included in the unsaturation index expressed as inline image and regressed against spring summer temperature surface ocean salinity and sea ice cover are not correlated with inline image per se however samples located in regions of permanent winter sea ice cover exhibit a significant warm bias deviation from the linear regression is posited to be related to a number of additional non exclusive factors such as advection of allochthonous material local temperature stratification and uncertainty in the absolute age of surface sediment samples assumed to be equivalent to modern conditions we conclude that alkenone unsaturation allows accurate reconstruction of sst records from many regions of the north atlantic if the factors confounding alkenone paleothermometry detailed here can be excluded

holocene subsurface temperature variability in the eastern antarctic continental margin 1 we reconstructed subsurface 45 200 m water depth temperature variability in the eastern antarctic continental margin during the late holocene using an archaeal lipid based temperature proxy tex86l our results reveal that subsurface temperature changes were probably positively coupled to the variability of warmer nutrient rich modified circumpolar deep water mcdw deep water of the antarctic circumpolar current intrusion onto the continental shelf the tex86lrecord in combination with previously published climatic records indicates that this coupling was probably related to the thermohaline circulation seasonal variability in sea ice extent sea temperature and wind associated with high frequency climate dynamics at low latitudes such as internal el nino southern oscillation enso this in turn suggests a linkage between centennial enso like variability at low latitudes and intrusion variability of mcdw into the eastern antarctic continental shelf which might have further impact on ice sheet evolution

magmatic chloride and metals in fluids tongonan geothermal field philippines the origin of solutes in high temperature geothermal systems has been discussed by ellis and mahon 1977 ellis 1979 giggenbach 1981 and henley and ellis 1983 ellis and mahon 1977 argued that chloride and elements such as li cs and as could derive from rocks during water rock interaction in a geothermal reservoir or directly from a single intrusion ellis 1979 states that chloride could come from sea water such as happens at the reykjanes area iceland from dissolution of evaporite beds e g red sea or salton sea from meteoric water convecting through the top of a magma chamber giggenbach 1981 suggests that magmatic hc1 gas converts to the less reactive product nacl at temperatures between 350 c and 400 c thus forming brines beneath high temperature geothermal systems henley and ellis 1983 conclude that a contribution of up to 10 magmatic fluid containing about 2 wt nac1 could account for all of the discharged chloride and 30 of the heat budget for a system like wairakei a magmatic source for chloride in the tongonan fluids is invoked here but the precise mechanism for the supply of chloride differs in detail from that described by the authors cited above the tongonan geothermal field is located on the island of leyte philippines the reservoir rocks consist of a miocene plutonic basement which is overlain by a 1 km thick pile of volcanic rocks the basement is composed of monzodiorites granodiorites granites gabbros monzogabbros and diorites while the volcanic rocks consist of andesite lavas and tuffaceous sediments interbedded with thin 10 m miocene limestone and shale beds relatively unaltered hornblende dacite dykes encountered in drill holes cut the volcanic series and are thought to be the only subsurface manifestation of a rhyolitic magma chamber which is crystallising at about 1 kbar water pressure or about 10 to 15 km depth scott 1988

southern ocean upwelling earth s obliquity and glacial interglacial atmospheric co2 change previous studies have suggested that during the late pleistocene ice ages surface deep exchange was somehow weakened in the southern ocean s antarctic zone which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages here high resolution diatom bound nitrogen isotope measurements from the indian sector of the antarctic zone reveal three modes of change in southern westerly wind driven upwelling each affecting atmospheric carbon dioxide two modes related to global climate and the bipolar seesaw have been proposed previously the third mode which arises from the meridional temperature gradient as affected by earth s obliquity axial tilt can explain the lag of atmospheric carbon dioxide behind climate during glacial inception and deglaciation this obliquity induced lag in turn makes carbon dioxide a delayed climate amplifier in the late pleistocene glacial cycles

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

isotopic imaging of surface water groundwater interactions sacramento valley california groundwater isotope data across the sacramento valley california establish two types of groundwater mining 1 overdraft of ancient groundwater with limited recharge by surface waters producing cones of depression 2 ancient groundwater withdrawal followed by rapid recharge of irrigation water reducing groundwater quality the first type occurs in the sacramento metropolitan area where meteoric runoff is unnaturally high and 40 years of pumping have depressed water levels to 25 m below sea level inducing recharge from losing reaches of the sacramento and american rivers lateral migration rates are quantified by the binary mixing between river water 18o 10 8 and natural groundwater 18o 7 0 the second type of mining occurs in agricultural regions to the west where 14c ages indicate that irrigation waters constitute more than 80 of modern recharge this recharge has several characteristics of evaporated irrigation water including 1 high 18o values to 6 0 that define closed contour patterns 2 elevated no3 concentrations to 100 ppm 3 low 14c ages of less than 500 years stable isotope contours augmented by 14c data provide dynamic recharge patterns in this profoundly disturbed giant alluvial aquifer on a large scale 100 km2 the lateral permeabilities of alluvial aquifers are essentially isotropic whereas on a smaller scale 25 km2 anisotropy is evident and isotope values can be geographically complex and seasonally transient groundwater flow patterns implied by the isotope data can differ substantially from steady state models based on head measurements

sea surface temperature records of termination 1 in the gulf of california challenges for seasonal and interannual analogues of tropical pacific climate change 1 centennial scale records of sea surface temperature and opal composition spanning the last glacial maximum and termination 1 circa 25 6 ka are presented here from guaymas basin in the gulf of california through the application of two organic geochemistry proxies the u37k index and the tex86h index we present evidence for rapid stepped changes in temperatures during deglaciation these occur in both temperature proxies at 13 ka 3 c increase in 270 years 10 0 ka 2 c decrease over 250 years and at 8 2 ka 3 c increase in 200 years an additional rapid warming step is also observed in tex86h at 11 5 ka in comparing the two temperature proxies and opal content we consider the potential for upwelling intensity to be recorded and link this millennial scale variability to shifting intertropical convergence zone position and variations in the strength of the subtropical high the onset of the deglacial warming from 17 to 18 ka is comparable to a southern hemisphere signal although the opal record mimics the ice rafting events of the north atlantic heinrich events neither the modern seasonal cycle nor el nino southern oscillation patterns provide valid analogues for the trends we observe in comparison with other regional records fully coupled climate model simulations confirm this result and in combination we question whether the seasonal or interannual climate variations of the modern climate are valid analogues for the glacial and deglacial tropical pacific

archaeal tetraether membrane lipid fluxes in the northeastern pacific and the arabian sea implications for tex86 paleothermometry the newly introduced temperature proxy the tetraether index of archaeal lipids with 86 carbon atoms tex86 is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraether gdgt lipids of marine crenarchaeota the composition of sedimentary gdgts used for tex86 paleothermometry is thought to reflect sea surface temperature sst however marine crenarchaeota occur ubiquitously in the world oceans over the entire depth range and not just in surface waters we analyzed the gdgt distribution in settling particulate organic matter collected in sediment traps from the northeastern pacific ocean and the arabian sea to investigate the seasonal and spatial distribution of the fluxes of crenarchaeotal gdgts and the origin of the tex86 signal transported to the sediment in both settings the tex86 measured at all trap deployment depths reflects sst in the arabian sea analysis of an annual time series showed that the sst estimate based on tex86 in the shallowest trap at 500 m followed the in situ sst with a 1 to 3 week time delay likely caused by the relatively low settling speed of sinking particles this revealed that the gdgt signal that reaches deeper water is derived from the upper water column rather than in situ production of gdgts the gdgt temperature signal in deeper traps at 1500 m and 3000 m did not show a seasonal cyclicity observed in the 500 m trap but rather reflected the annual mean sst this is probably due to a homogenization of the tex86 sst signal carried by particles as they ultimately reach the interior of the ocean our data confirm the use of tex86 as a temperature proxy of surface ocean waters

isotopic and trace element constraints on the origin and evolution of saline groundwaters from central missouri na ca cl groundwaters with salinities of 1 to 30 discharge from natural springs and artesian wells in mississippian carbonates and ordovician sandstones and carbonates in central missouri carbonate saturation and quartz supersaturation are maintained throughout the salinity range major and trace element and isotopic variations in the waters are used to place constraints on models for rock water interaction and regional hydrology the groundwaters have d values that range from 108 to 45 and 18 o values that range from 14 7 to 6 5 smow these data lie approximately along the meteoric water line ranging from values similar to local recharge in missouri to significantly lower values that are similar to 18 o and d for meteoric recharge in high altitude and high latitude regions of north america the more saline samples have the lowest 18 o and d contents a trend that is opposite to that observed in most other studies of saline waters the h o isotopic correlation and the range in salinity and several major and trace element concentrations in central missouri groundwaters are readily explained by a saline dilute water mixing model 87sr 86sr ratios for the groundwaters range from 0 7155 to 0 7161 these values are significantly higher than previously published values for 1 estimates of 87 sr 86 sr in phanerozoic seawater 0 7068 0 7092 and 2 carbonates of the mississippian burlington keokuk fm 0 7075 0 7105 through which some of the waters migrate as they pass to the surface nd 0 values in the groundwaters range from 10 9 to 8 1 and 147 sm 144 nd ratios range from 0 108 to 0 128 these values are similar to or lower than previously published analyses of carbonates and other authigenic phases from the burlington keokuk fm mean nd 0 7 8 0 8 1 mean 147 sm 144 nd 0 141 the h o sr and nd isotopic data and the results of model calculations preclude 1 models involving the modification of ancient seawater for the origin of the saline waters and 2 extensive interaction between the groundwaters and their host carbonates the waters apparently acquired their 18 o and d values as meteoric recharge and their 87sr 86sr and rare earth element signatures from extraformational crustal sources high 87 sr 86 sr low nd 0 low 147sm 144nd and largely preserved these isotopic signatures during subsequent migration through the carbonates chemical exchange via rock water interaction is required for isotopic exchange to occur therefore the present state of chemical equilibrium between the groundwaters and carbonate aquifer minerals may serve to limit rock water interaction and hence preserve the extraformational isotopic signatures in the waters the integration of geochemical isotopic and hydrologic data on a local and regional scale suggests a history for the central missouri groundwaters involving 1 meteoric recharge in the front range of colorado 2 dissolution of permian halite in the subsurface of kansas 3 interaction with predominantly silicate mineral assemblages in paleozoic strata and possibly precambrian basement with aquisition of crustal sr and ree signatures 4 dilution and migration to shallow aquifer levels in central missouri and 5 mixing with local meteoric recharge through mississippian carbonates with no significant change of the isotopic signatures acquired in stage 3

unusually low tex86 values in the transitional zone between pearl river estuary and coastal south china sea impact of changing archaeal community composition tex86 calculated based on the distribution of isoprenoid glycerol dialkyl glycerol tetraethers gdgts is used worldwide for paleotemperature reconstruction in marine and lacustrine environments recently however increasing evidence showed that tex86 could be affected by multiple environmental variables in this study tex86 was calculated for core and polar gdgts obtained from water column and surface sediments in the lower pearl river and its estuary together with previously published core gdgt data from the coastal and open south china sea scs a comparison was made between tex86 derived and satellite based surface water temperature which showed a tex86 temperature minimum that is considerably lower than winter satellite temperature in the transitional zone between the pearl river estuary and the coastal scs tex86 showed significantly positive correlation with gdgt 2 and gdgt 3 in this transitional zone indicating that they are the primary compounds for the tex86 bias toward cooler temperature lipid and molecular dna data both indicate that the variation in archaeal community composition rather than water depth or seasonality is likely the crucial factor causing the deviation of tex86 in the transitional area our study has implications for studies in ancient continental margins where unusually low tex86 temperatures may be observed in the geological record c 2015 elsevier b v all rights reserved

d 18o enriched waters of the coast range mountains northern california connate and ore forming fluids abstract d and 18o enriched waters of several weight percent salinity issue from hot and cold springs in franciscan complex and great valley sequence rocks in the northern coast range mountains of california although these waters have been described separately in the past and called metamorphic connate and serpentinizing fluids this study shows that the hot and cold springs are all fed by one source of water trapped cretaceous seawater modified by a variety of reactions the district is an example of the complexities of subsurface waters and their importance for our understanding of metamorphic fluid sources oil field waters and ore transport problems the subsurface waters have a range of 34s values including some near marine sulfate values 20 and 13c near marine calcite values 0 strontium isotopic signatures in the spring waters are derived from the great valley sequence 87 sr 86 sr values near 0 705 the most saline spring pool is lined with serpentine phases found together as a fine white precipitate and has a ph of 11 one portion of the subsurface water is heated and reduced it transports au ag sb as and hg to the surface gold grades of the hot spring precipitates range from less than 1 ppm to over 10 ppm these heated waters are chemically and isotopically similar to the fluids which formed au mineralization at the nearby mclaughlin gold mine the hot springs precipitate pyrite and native sulfur and are supersaturated with respect to calcite other springs are less saline and are oxidized cooler and diluted versions of the hot spring fluid they do not carry ore metals but they are supersaturated with respect to silica and calcite 3 he 4 he ratios of the springs gases are all above atmospheric values and indicate a possible magmatic component consistent with the presence of quaternary clear lake volcanics 129i data yield a minimum age of 60 80 ma for the source of the iodide in the waters consistent with the connate nature of the source fluid fehn et al 1992

temporal and spatial variation in tetraether membrane lipids of marine crenarchaeota in particulate organic matter implications for tex86 paleothermometry the tex86 is a new temperature proxy which is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraether gdgt lipids of the membranes of crenarchaeota that occur ubiquitously in oceans and shelf seas this proxy was calibrated by core top sediments but it is as yet not clear during which season and at which depth in the water column the gdgt signal used for tex86 paleothermometry is biosynthesized here we analyzed 200 particulate organic matter pom samples from 11 different marine settings for tex86 this revealed that the gdgts occur seasonally in surface waters and occur in higher abundances during the winter and spring months the depth distribution showed that gdgts generally appeared in higher amounts below 100 m depth in the water column however the tex86 values for waters below the photic zone 150 1500 m did not correlate with the in situ temperature but rather correlated linearly with surface temperature the tex86 for pom from the upper 100 m showed a linear correlation with in situ temperature which was nearly identical to the previously reported core top equation the correlation of all pom samples with surface temperature was also strikingly similar to the core top correlation these findings demonstrate that the gdgt signal which reaches the sediment is mainly derived from the upper 100 m of the water column this may be caused by the fact that gdgts from the photic zone are much more effectively transported to the sediment by grazing and repackaging in large particles than gdgts from deeper waters

coherent millennial scale patterns in u37k and tex86h temperature records during the penultimate interglacial to glacial cycle in the western mediterranean 1 the tex86h temperature proxy is a relatively new proxy based on crenarchaeotal lipids and has rarely been applied together with other temperature proxies in this study we applied the tex86h on a sediment core from the alboran sea western mediterranean core odp 977a covering the penultimate climate cycle that is from 244 to 130 ka and compared this with previously published sea surface temperatures derived from the u37k of alkenones of haptophyta and mg ca records of planktonic foraminifera the tex86h temperature record shows remarkably similar stadial interstadial patterns and abrupt temperature changes to those observed with the u37k palaeothermometer absolute tex86h temperature estimates are generally higher than those of u37k though this difference 3 c in 81 of the data points is mainly within the temperature calibration error for both proxies suggesting that crenarchaeota and haptophyta experienced similar temperature variations during occasional events 5 of the analyzed time span however the tex86h exhibits considerably higher absolute temperature estimates than the u37k comparison with mg ca records of planktonic foraminifera as well as other mediterranean tex86 and u37k records suggests that part of this divergence may be attributed to seasonal differences that is with tex86h reflecting mainly the warm summer season while u37k would show annual mean biases in the global calibration of both proxies or specific biases in the mediterranean are an alternative though less likely explanation despite differences between absolute tex86h and u37k temperatures the correlation between the two proxies r2 0 59 95 significance provides support for the occurrence of abrupt temperature variations in the western mediterranean during the penultimate interglacial to glacial cycle

modern organic carbon deposition in the laptev sea and the adjacent continental slope surface water productivity vs terrigenous input sediment samples from the laptev sea taken during the 1993 rv polarstern expedition ark ix 4 and the rv ivan kireyev expedition transdrift i were investigated for the amount and composition of their organic carbon fractions of major interest was the identification of different processes controlling organic carbon deposition i e terrigenous supply vs surface water productivity long chain unsaturated alkenones derived from prymnesiophytes and fatty acids derived from diatoms and dinoflagellates were analysed by means of gas chromatography and mass spectrometry first results on the distribution of these biomarkers in surface sediments indicate that the surface water productivity signal is well preserved in the sediment data this is shown by the distribution of the 16 1 n 7 and 20 5 n 3 fatty acids indicative for diatoms and the excellent correlation with the chlorophyll a concentrations in the surface water masses and the biogenic opal content and increased hydrogen indices of the sediments the high concentration of these unsaturated fatty acids in shallow water sediments shows the recent deposition of the organic material in deep sea sediments on the other hand the concentrations are low this decreased content is typical for phytoplankton material which has been degraded by microorganisms or autoxidation in general the alkenone concentrations are very low suggesting low production rates by prymnesiophytes only at one station from the lower continental margin influenced by the inflow of atlantic water masses were some higher amounts of alkenones determined long chain n alkanes as well as high c n ratios and low hydrogen indices indicate the importance of fluvial supply of terrigenous organic matter

merging late holocene molecular organic and foraminiferal based geochemical records of sea surface temperature in the gulf of mexico 1 a molecular organic geochemical proxy tex86 for sea surface temperature sst is compared with a foraminifera based sst proxy mg ca in a decadal resolution marine sedimentary record spanning the last 1000 years from the gulf of mexico we assess the relative strengths of the organic and inorganic paleoceanographic techniques for reconstructing high resolution sst variability during recent climate events including the little ice age lia and the medieval warm period mwp sst estimates based on the molecular organic proxy tex86 show a similar magnitude and pattern of sst variability to foraminiferal mg ca sst estimates but with some important differences for instance both proxies show a cooling 1 c 2 c of gulf of mexico ssts during the lia during the mwp however mg ca ssts are similar to near modern ssts while tex86 indicates ssts that were cooler than modern using the respective sst calibrations for each proxy results in tex86 sst estimates that are 2 c 4 c warmer than mg ca sst throughout the 1000 year record we interpret the tex86 sst as a summer weighted sst signal from the upper mixed layer whereas the mg ca sst better reflects the mean annual sst downcore differences in the sst estimates between the two proxies t tex86 mg ca are interpreted in the context of varying seasonality and or changing water column temperature gradients

synchronous tropical and polar temperature evolution in the eocene palaeoclimate reconstructions of periods with warm climates and high atmospheric co2 concentrations are crucial for developing better projections of future climate change deep ocean1 2 and high latitude3 palaeotemperature proxies demonstrate that the eocene epoch 56 to 34 million years ago encompasses the warmest interval of the past 66 million years followed by cooling towards the eventual establishment of ice caps on antarctica eocene polar warmth is well established so the main obstacle in quantifying the evolution of key climate parameters such as global average temperature change and its polar amplification is the lack of continuous high quality tropical temperature reconstructions here we present a continuous eocene equatorial sea surface temperature record based on biomarker palaeothermometry applied on atlantic ocean sediments we combine this record with the sparse existing data4 6 to construct a 26 million year multi proxy multi site stack of eocene tropical climate evolution we find that tropical and deep ocean temperatures changed in parallel under the influence of both long term climate trends and short lived events this is consistent with the hypothesis that greenhouse gas forcing7 8 rather than changes in ocean circulation9 10 was the main driver of eocene climate moreover we observe a strong linear relationship between tropical and deep ocean temperatures which implies a constant polar amplification factor throughout the generally ice free eocene quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29 26 23 and 19 degrees celsius in the early early middle late middle and late eocene respectively compared to the preindustrial temperature of 14 4 degrees celsius finally combining proxy and model based temperature estimates with available co2 reconstructions8 yields estimates of an eocene earth system sensitivity of 0 9 to 2 3 kelvin per watt per square metre at 68 per cent probability consistent with the high end of previous estimates11

how phyllosilicate mineral structure affects fault strength in mg rich fault systems the clay mineralogy of fault gouges has important implications for the frictional properties of faults often identified as a major factor contributing to profound fault weakness this work compares the frictional strength of a group of mg rich minerals common in the mg al si o compositional space talc saponite sepiolite and palygorskite by conducting triaxial frictional tests with water or argon as pore fluid the studied minerals are chemically similar but differ in their crystallographic structure results show that fibrous mg rich phyllosilicates are stronger than their planar equivalents frictional strength in this group of minerals is highly influenced by strength of the atomic bonds continuity of water layers within the crystals and interactions of mineral surfaces with water molecules all of which are dictated by crystal structure the formation and stability of the minerals studied are mainly controlled by small changes in pore fluid chemistry which can lead to significant differences in fault strength

constraining ecological and biological bias in planktonic foraminiferal mg ca and δ18occ a multispecies approach to proxy calibration testing 1 parallel stable isotope 18occ and mg ca measurements performed in three planktonic foraminifer species provide multiple perspectives on past temperature change and thus allow published calibrations for these geochemical proxies to be tested against each other the comparison of simultaneous temperature records as recorded by both the 18occ and mg ca signature of each species reveals very clearly the nonpassive character of foraminifera as proxy carriers and allows the systematic temperature response of 18occ and mg ca in different foraminifer species to be explored on the basis of their mg ca signatures neogloboquadrina pachyderma right globigerina bulloides and globigerinoides ruber white are each found to exhibit a specific and narrow range of temperature variability however the interspecies offsets in optimum temperature habitat that are suggested in this way are not expressed by similarly scaled 18occ offsets hence it is demonstrated that the temperature modes variations that are recorded by each species cannot be calibrated to mg ca and 18occ variations via a single pair of calibrations for all three species species specific 18occ and or mg ca temperature calibrations are required on the basis of the average 18occ and mg ca offsets observed between the three species it appears that many of the temperature calibrations that are currently proposed for both of these proxies are inconsistent the data presented here cannot provide species specific mg ca and 18occ temperature calibrations however they do provide a simple method for testing our calibrations in application and clearly indicate that further calibration work using paired mg ca and 18occ is required before the full potential of these proxies may be realized

biogeochemical controls on glycerol dialkyl glycerol tetraether lipid distributions in sediments characterized by diffusive methane flux the tex86 tetraether index of tetraethers consisting of 86 carbon atoms is a proxy for sea surface temperature sst based on the distribution of isoprenoidal glycerol dialkyl glycerol tetraether gdgt membrane lipids synthesized by marine pelagic thaumarchaeota one of the caveats of this proxy is the production of additional gdgts by sedimentary euryarchaeota involved in anaerobic oxidation of methane aom that occurs at deep sea methane seeps but is also widespread in many continental shelf settings here gdgt distributions are investigated through the sulfate methane transition zone smtz in aarhus bay denmark to examine the extent the tex86 proxy is compromised in such a continental shelf setting where aom is characterized by a diffusive rather than rapid advective methane flux both free extractable and non extractable lipid fractions were analyzed as it was expected that pelagic derived and sediment derived gdgts could become incorporated into the molecular and sedimentary matrix to a different extent the results show a large change of tex86 values mainly due to the relative high amounts of gdgt 2 produced by aom related archaea both in the free and non extractable lipid fractions this additional gdgt input renders calculation of ssts based on tex86 inappropriate at the smtz the aom related gdgt signature however did not persist into deeper sediments perhaps reflecting rapid remineralization of the gdgts at the smtz although the process of aom at aarhus bay might not be representative for all continental margin settings it illustrates that aom in a variety of settings not just cold seeps can influence sedimentary gdgt distributions

changes in sea ice cover and ice sheet extent at the yermak plateau during the last 160 ka reconstructions from biomarker records the yermak plateau is located north of svalbard at the entrance to the arctic ocean i e in an area highly sensitive to climate change a multi proxy approach was carried out on core ps92 039 2 to study glacial interglacial environmental changes at the northern barents sea margin during the last 160 ka the main emphasis was on the reconstruction of sea ice cover based on the sea ice proxy ip25 and the related phytoplankton sea ice index pip25 sea ice was present most of the time but showed significant temporal variability decisively affected by movements of the svalbard barents sea ice sheet for the first time we prove the occurrence of seasonal sea ice at the eastern yermak plateau during glacial intervals probably steered by a major northward advance of the ice sheet and the formation of a coastal polynya in front of it maximum accumulation of terrigenous organic carbon ip25 and the phytoplankton biomarkers brassicasterol dinosterol hbi iii can be correlated to distinct deglaciation events more severe but variable sea ice cover prevailed at the yermak plateau during interglacials the general proximity to the sea ice margin is further indicated by biomarker gdgt based sea surface temperatures below 2 5 c

an interlaboratory study of tex86 and bit analysis using high performance liquid chromatography mass spectrometry recently two new proxies based on the distribution of glycerol dialkyl glycerol tetraethers gdgts were proposed i e the tex86 proxy for sea surface temperature reconstructions and the bit index for reconstructing soil organic matter input to the ocean in this study fifteen laboratories participated in a round robin study of two sediment extracts with a range of tex86 and bit values to test the analytical reproducibility and repeatability in analyzing these proxies for tex86 the repeatability indicating intralaboratory variation was 0 028 and 0 017 for the two sediment extracts or 1 2 c when translated to temperature the reproducibility indicating among laboratory variation of tex86 measurements was substantially higher i e 0 050 and 0 067 or 3 4 c when translated to temperature the latter values are higher than those obtained in round robin studies of mg ca and u37 k paleothermometers suggesting the need to primarily improve compatibility between labs the repeatability of bit measurements for the sediment with substantial amounts of soil organic matter input was relatively small 0 029 but reproducibility was large 0 410 this large variance could not be attributed to specific equipment used or a particular data treatment we suggest that this may be caused by the large difference in the molecular weight in the gdgts used in the bit index i e crenarchaeol versus the branched gdgts potentially this difference gives rise to variable responses in the different mass spectrometers used calibration using authentic standards is needed to establish compatibility between labs performing bit measurements

glacial to holocene evolution of sea surface temperature and surface circulation in the subarctic northwest pacific and the western bering sea it has been proposed that north pacific sea surface temperature sst evolution was intimately linked to north atlantic climate oscillations during the last glacial interglacial transition however during the early deglaciation and the last glacial maximum the sst development in the subarctic northwest pacific and the bering sea is poorly constrained as most existing deglacial sst records are based on alkenone paleothermometry which is limited prior to 15 ka b p in the subarctic north pacific realm by applying the texl86 temperature proxy we obtain glacial holocene sst records for the marginal northwest pacific and the western bering sea our texl86 based records and existing alkenone data suggest that during the past 15 5 ka ssts in the northwest pacific and the western bering sea closely followed millennial scale climate fluctuations known from greenland ice cores indicating rapid atmospheric teleconnections with abrupt climate changes in the north atlantic our sst reconstructions indicate that in the western bering sea ssts drop significantly during heinrich stadial 1 hs1 similar to the known north atlantic climate history in contrast progressively rising sst in the northwest pacific is different to the north atlantic climate development during hs1 similarities between the northwest pacific sst and climate records from the gulf of alaska point to a stronger influence of alaskan stream waters connecting the eastern and western basin of the north pacific during this time during the holocene dissimilar climate trends point to reduced influence of the alaskan stream in the northwest pacific

distributions of bacterial and archaeal membrane lipids in surface sediments reflect differences in input and loss of terrestrial organic carbon along a cross shelf arctic transect enhanced climate warming affecting the arctic region could have a dramatic impact on the terrigenous organic carbon terroc stored in the eurasian permafrost and could increase the amount of oc remobilized to the arctic shelves an improved understanding of the fate of this remobilized soil oc is essential for better understanding of the consequences for the arctic and global carbon cycle in this study glycerol dialkyl glycerol tetraethers gdgts and bacteriohopanepolyols bhps in surface sediments along a 500 km cross shelf transect from the mouth of the kolyma river to the middle of the vast east siberian sea were analysed to assess their potential and that of the associated branched and isoprenoid tetraether bit and r 0 soil indices for tracing terroc in arctic systems both bhp and gdgt contributions indicated the greatest contribution of terroc close to the river mouth while the associated indices showed declining trends in an offshore direction supporting an increasing marine oc input and or a decrease in terroc however while the bhps indicated a dominance of terroc at the start of the transect the gdgts suggested a much larger almost 50 marine oc input at this point in addition the bit index displayed an exponential decline controlled mainly by a substantial contribution of marine gdgts while

cretaceous sea surface temperature evolution constraints from tex86 and planktonic foraminiferal oxygen isotopes it is well established that greenhouse conditions prevailed during the cretaceous period 145 66 ma determining the exact nature of the greenhouse gas forcing climatic warming and climate sensitivity remains however an active topic of research quantitative and qualitative geochemical and palaeontological proxies provide valuable observational constraints on cretaceous climate in particular reconstructions of cretaceous sea surface temperatures ssts have been revolutionised firstly by the recognition that clay rich sequences can host exceptionally preserved planktonic foraminifera allowing for reliable oxygen isotope analyses and secondly by the development of the organic palaeothermometer tex86 based on the distribution of marine archaeal membrane lipids here we provide a new compilation and synthesis of available planktonic foraminiferal 18o 18opl and tex86 sst proxy data for almost the entire cretaceous period the compilation uses ssts recalculated from published raw data allowing examination of the sensitivity of each proxy to the calculation method e g choice of calibration and places all data on a common timescale overall the compilation shows many similarities with trends present in individual records of cretaceous climate change for example both sst proxies and benthic foraminiferal 18o records indicate maximum warmth in the cenomanian turonian interval our reconstruction of the evolution of latitudinal temperature gradients low 48 palaeolatitudes reveals temporal changes in the valanginian aptian the low to higher mid latitudinal temperature gradient was weak decreasing from 10 17 c in the valanginian to 3 5 c in the aptian based on tex86 ssts in the cenomanian santonian reconstructed latitudinal temperature contrasts are also small relative to modern 14 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts compared with 20 c for the modern in the mid campanian to end maastrichtian latitudinal temperature gradients strengthened 19 21 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts with cooling occurring at low middle and higher palaeolatitude sites implying global surface ocean cooling and or changes in ocean heat transport in the late cretaceous these reconstructed long term trends are resilient regardless of the choice of proxy tex86 or 18opl or calibration this new cretaceous sst synthesis provides an up to date target for modelling studies investigating the mechanics of extreme climates

gold bearing hot spring systems of the northern coast ranges california gold mercury mineralization in the knoxville and sulphur creek districts of the coast ranges of northern california fits the emerging hot spring classification of epithermal ore deposits quartz and chalcedony veins which show hydrofracture texture are capped by subaerial sinter deposits all the deposits appear to be very young the mclaughlin deposit and the sulphur valley and elgin deposits contain hydrocarbons in their ore gold bearing quartz of the san quentin ore shoot of the mclaughlin deposit is isotopically heavy delta 18 o 24 ppm and appears to have formed near 150 degrees c from isotopically heavy waters such waters are presumed to have moved both hydrocarbons and precious metals to the surface sinter of the deposit hot springs composed of isotopically heavy fluids issue today from the centers of the sulphur valley and elgin deposits the hot spring fluids carry small concentrations of hydrocarbons and transport gold silver and mercury to the surface ag au weight ratios of the precipitates formed by the hot springs are about 1 8 gold grades of the hot spring precipitates range from 0 5 to more than 10 ppm the mean value for 20 samples is 3 3 ppm measurements show that the waters carry 1 ppb gold in solution thermodynamic calculations indicate the gold is probably present as a bisulfide complex the chemical and isotopic characteristics of the hot spring fluids appear to be similar to the fluids inferred to have formed the mclaughlin deposit in these two gold districts nonmeteoric waters are responsible for the formation of epithermal gold deposits a sedimentary or metasedimentary source for the ore forming fluids is indicated by chemical and isotopic data and is consistent with the local geology

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

glacial interglacial variability in atlantic meridional overturning circulation and thermocline adjustments in the tropical north atlantic article i nfo k 37 tex86 atlantic meridional overturning circulation thermocline changes in the strength of atlantic meridional overturning circulation amoc are known to have profound impacts on global climate coupled modelling studies have suggested that on annual to multi decadal time scales a slowdown of amoc causes a deepening of the thermocline in the tropical atlantic however this process has been poorly constrained by sedimentary geochemical records here we reconstruct surface u k 37 index and thermocline tex h 86 water temperatures from the guinea plateau margin eastern tropical atlantic over the last two glacial interglacial cycles 192 kyr these paleotemperature records show that periods of reduced amoc as indicated by the 13 c benthic foraminiferal record from the same core coincide with a reduction in the near surface vertical temperature gradient demonstrating for the first time that amoc induced tropical atlantic thermocline adjustment exists on longer millennial time scales modelling results support the interpretation of the geochemical records and show that thermocline adjustment is particularly pronounced in the eastern tropical atlantic thus variations in amoc strength appear to be an important driver of the thermocline structure in the tropical atlantic from annual to multi millennial time scales

isotope geochemistry of mercury in source rocks mineral deposits and spring deposits of the california coast ranges usa abstract we present here the first study of the isotopic composition of mercury in rocks ore deposits and active spring deposits from the california coast ranges a part of earth s crust with unusually extensive evidence of mercury mobility and enrichment the franciscan complex and great valley sequence which form the bedrock in the california coast ranges are intruded and overlain by tertiary volcanic rocks including the clear lake volcanic sequence these rocks contain two types of mercury deposits hot spring deposits that form at shallow depths the franciscan complex and great valley sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the clear lake volcanic field mean mercury isotopic compositions 202hg for all three rock units are similar although the range of values in franciscan complex rocks is greater than in either great valley or clear lake rocks hot spring and silica carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units although 202hg values for the mercury deposits have a greater variance than the country rocks precipitates from spring and geothermal waters in the area have similarly large variance and a mean 202hg value that is significantly lower than the ore deposits and rocks these observations indicate that there is little or no isotopic fractionation

temperature and stable isotope variations in different water masses from the alboran sea western mediterranean between 250 and 150 ka 1 mg ca sr ca and stable isotope measurements have been performed on tests from the planktonic foraminifers globigerinoides ruber white globigerina bulloides and neogloboquadrina pachyderma right coiling in samples from ocean drilling program site 977a in the alboran sea western mediterranean the evolution of different water masses between 250 and 150 ka is described warm substages were characterized by strong seasonality and thermal stratification of the water column by contrast less pronounced seasonality and basin stratification seem to prevail during cold substages several periods of stratification due to the low salinity of the upper water mass occurred during the formation of organic rich layers and also during a possible heinrich like event at 220 ka the three foraminifer species studied show a common and large shell sr ca variability in short timescales suggesting changes in the global ocean sr ca ratio as one of the main causes of variations in shell composition

core top calibration of the lipid based u37k and tex86 temperature proxies on the southern italian shelf sw adriatic sea gulf of taranto abstract the mediterranean sea is at the transition between temperate and tropical air masses and as such of importance for studying climate change the gulf of taranto and adjacent sw adriatic sea are at the heart of this region their sediments are excellently suited for generating high quality environmental records for the last millennia with a sub decadal resolution the quality of these records is dependent on a careful calibration of the transfer functions used to translate the sedimentary lipid signals to the local environment here we examine and calibrate the u 37 k and tex 86 lipid based temperature proxies in 48 surface sediments and relate these to ambient sea surface temperatures and other environmental data the u 37 k based temperatures in surface sediments reflect winter spring sea surface temperatures in agreement with other studies demonstrating maximum haptophyte production during the colder season the tex 86 based temperatures for the nearshore sites also reflect winter sea surface temperatures however at the most offshore sites they correspond to summer sea surface temperatures additional lipid and environmental data including the distribution of the bit index and remote sensed chlorophyll a suggest a shoreward increase of the impact of seasonal and spatial variability in nutrients and control of planktonic archaeal abundance by primary productivity particle loading in surface waters and or overprint by a cold biased terrestrial tex 86 signal as such the offshore tex 86 values seem to reflect a true summer signal to the effect that offshore u 37 k and tex 86 reconstruct winter and summer temperature respectively and hence provide information on the annual temperature amplitude

gaia s breath global methane exhalations abstract methane ch 4 is the most abundant organic compound in the earth s atmosphere where it acts as a greenhouse gas and thus has implications for global climate change the current atmospheric ch 4 budget however does not take into account geologically sourced ch 4 seepage geological sources of ch 4 include natural macro and micro seeps mud volcanoes and other miscellaneous sources such as gas hydrates magmatic volcanoes geothermal regions and mid ocean ridges macro seeps contribute 25 tg teragrams ch 4 yr to the atmosphere whereas micro seepage contributes perhaps 7 tg ch 4 yr mud volcanoes emit 5 tg ch 4 yr and miscellaneous sources emit 8 tg ch 4 yr to the atmosphere thus the total contribution to the atmosphere from geological sources is estimated to be 45 tg ch 4 yr which is significant to the atmospheric organic carbon cycle and should be included in any global inventory of atmospheric ch 4 we argue that the atmospheric ch 4 global inventory of the interplanetary panel on climate change must be adjusted in order to incorporate geologically sourced ch 4 from naturally occurring seepage

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

coupled sea surface temperature seawater δ18o reconstructions in the arabian sea at the millennial scale for the last 35 ka two sediment cores from the western 905 10 46 9 n 51 56 4 e water depth 1586 m and eastern sk17 15 15 n 72 58 e water depth 840 m arabian sea were used to study past sea surface temperatures sst and seawater 18o 18ow variations for the past 35 ka we used coupled mg ca 18o calcite variability in two planktonic foraminiferal species globigerinoides ruber which thrives throughout the year and globigerina bulloides which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing ssts in both areas based on mg ca in g ruber were 3 to 4 c lower during the last glacial maximum lgm 21 ka than today and the holocene period the sst records based on g bulloides also indicate general cooling down to 18 c in both areas ssts in the western arabian sea based on g bulloides were always lower than those based on g ruber indicating the presence of strong seasonal temperature contrast during the holocene and lgm we interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling sw monsoon and winter convective mixing ne monsoon in the western arabian sea in the eastern arabian sea g bulloides based ssts were slightly lower about 1 c than g ruber based ssts during the holocene indicating the almost absence of a seasonal temperature gradient similar to today however a large seasonal temperature contrast occurred during the lgm which favors the assumption that strong ne monsoon winds forced winter upwelling or convective mixing offshore goa sst and 18ow reconstructions reveal evidence of millennial scale cycles particularly in the eastern arabian sea here the stadial periods northern hemisphere cold periods such as younger dryas and heinrich events are marked by increasing ssts and salty sea surface conditions relative to those during the interstadial periods indeed the 18ow record shows evidence of low saline surface waters during interstadial periods indicating increased freshwater runoff from the western ghats as a consequence of enhanced sw monsoon intensity

a study of the alkenone tex86 and planktonic foraminifera in the benguela upwelling system implications for past sea surface temperature estimates suspended particulate matter from seawater and core top sediments were collected during 2003 meteor cruise m57 1 in january february from the continental margin off western south africa for analysis of alkenones glycerol dibiphytanyl glycerol tetraether gdgt lipids and planktonic foraminifera alkenone analysis of suspended particulates in seawater and core top sediments indicates that u37k temperatures were representative of annual mean sea surface temperature in contrast gdgt analysis suggests that tex86 temperatures are cold biased due to upward transports of gdgts produced below the mixed layer the analysis of plankton tow samples revealed that the 18o of globorotalia inflata in core top sediments could be biased toward lower temperatures due to subsurface calcification accordingly our study shows that each paleotemperature proxy may record different temperature signals in the benguela upwelling system emphasizing the general need to constrain potential biases in each proxy for better interpreting paleoclimate records

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

glacial cooling as inferred from marine temperature proxies texh86 and uk 37 knowledge of the magnitude of the last glacial maximum lgm cooling is a useful constraint for estimating the climate sensitivity used in projecting future climate change proxy comparison especially that between the alkenone based uk 37 and the archaeal tetraether based tex86 has been increasingly applied in paleoceanographic studies as a measure to better constrain proxy derived temperature estimates in this study we compile and compare published multiproxy uk 37 and texh86 records of glacial cooling measured on the same sediment cores in spite of the diversity in oceanographic and sedimentation settings spanned by the study sites we find that the texh86 derived mean tropical lgm cooling is approximately twice as strong as that suggested by the uk 37 and margo estimates the extent of proxy discrepancy varies with the application of various regional calibrations but the mean texh86 inferred cooling remains stronger than that inferred from uk 37 to understand the discrepancy between proxies we examine the seasonal and water column structure of lgm cooling simulated by state of the art climate models we find that the dissimilar magnitudes of proxy derived glacial cooling cannot be fully explained by proxies reflecting temperature of different seasons or different water depths if the recording season and depth are assumed to stay constant through time a hypothetical shift in recording season and or depth between the holocene and the lgm could in theory cause the proxy discrepancy but this hypothesis cannot be constrained due to a lack of information on lipid production and export in the water column during the lgm alternatively the systematic proxy discrepancy which persists across diverse oceanographic settings may imply that the commonly applied proxy calibrations for reconstructing past temperatures are fundamentally biased as evidenced by the improved consistency between uk 37 and texh86 based estimates of lgm cooling after we applied a global subsurface 0 200 m temperature calibration for texh86 it is plausible that the texh86 signal originates from deeper in the water column than typically assumed for the proxy calibration

contrasting lipid biomarker composition of terrestrial organic matter exported from across the eurasian arctic by the five great russian arctic rivers contrasting lipid biomarker composition of terrestrial organic matter exported from across the eurasian arctic by the five great russian arctic rivers

origins of archaeal tetraether lipids in sediments insights from radiocarbon analysis abstract understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers gdgts in marine sediments helps inform their use in paleoceanography compound specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect u 37 k paleotemperature reconstructions similar analyses are warranted to investigate how analogous processes affecting gdgts impact tex 86 paleotemperatures here we present radiocarbon measurements on individual gdgts from bermuda rise and santa monica basin sediments and discuss the results in the context of previous studies of co depositional alkenones and foraminifera the 14 c contents of gdgts and planktonic foraminifera in bermuda rise are very similar suggesting a local source and tex 86 derived temperatures agree more closely with foraminiferal temperatures than do u 37 k temperatures in contrast gdgts in santa monica basin are depleted in 14 c relative to both alkenones and foraminifera and tex 86 temperatures agree poorly with known surface water values we propose three possible factors that could explain these results i gdgts may be labile relative to alkenones during advective transport through oxic waters ii archaeal production deep in the water column may contribute 14 c depleted gdgts to sediments and iii some gdgts also may derive from sedimentary archaeal communities each of these three processes is likely to occur with varying relative importance depending on geographic location the latter two may help to explain why tex 86 temperature reconstructions from santa monica basin do not appear to reflect actual sea surface temperatures terrigenous gdgts are unlikely to be major contributors to bermuda rise or santa monica basin sediments based on values of the bit index the results also indicate that the crenarchaeol regioisomer is governed by processes different from other gdgts individual measurements of the crenarchaeol regioisomer are significantly depleted in 14 c relative to co occurring gdgts indicating an alternative origin for this compound that presently remains unknown re examination of the contribution of crenarchaeol regioisomer to the tex 86 index shows that it is a significant influence on the sensitivity of temperature reconstructions

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

descent toward the icehouse eocene sea surface cooling inferred from gdgt distributions the tex86 proxy based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids gdgts is increasingly used to reconstruct sea surface temperature sst during the eocene epoch 56 0 33 9 ma here we compile published tex86 records critically reevaluate them in light of new understandings in tex86 palaeothermometry and supplement them with new data in order to evaluate long term temperature trends in the eocene we investigate the effect of archaea other than marine thaumarchaeota upon tex86 values using the branched to isoprenoid tetraether index bit the abundance of gdgt 0 relative to crenarchaeol gdgt 0 and the methane index mi we also introduce a new ratio gdgtrs which may help identify red sea type gdgt distributions in the geological record using the offset between tex86h and tex86l h l and the ratio between gdgt 2 and gdgt 3 2 3 we evaluate different tex86 calibrations and present the first integrated sst compilation for the eocene 55 to 34 ma although the available data are still sparse some geographic trends can now be resolved in the high latitudes 55 there was substantial cooling during the eocene 6 c our compiled record also indicates tropical cooling of 2 5 c during the same interval using an ensemble of climate model simulations that span the eocene our results indicate that only a small percentage 10 of the reconstructed temperature change can be ascribed to ocean gateway reorganization or paleogeographic change collectively this indicates that atmospheric carbon dioxide pco2 was the likely driver of surface water cooling during the descent toward the icehouse

the sedimentary cycle of the boron isotopes abstract marine sediments contain two isotopically distinct components a non desorbable fraction with 11b between 4 3 and 2 8 per mil n 10 and a desorbable component with 11b between 13 9 and 15 8 per mil n 6 the adsorption coefficient k for the uptake of b from seawater by fluvial suspended material mississippi has an experimentally determined value of 1 54 0 05 the associated isotope fractionation factor is 0 974 0 003 empirical values for k determined from the analysis of marine sediments n 6 were between 3 and 4 the amount of b adsorbed onto fluvial suspended material during estuarine mixing is about 9 109 moles yr based on pore water data adsorption experiments and comparative size fraction analyses suspended sediments from the mississippi river vs bottom deposits from the delta there is no evidence for the incorporation of b into detrital sediments at low temperature however the high b content of bauer deep metalliferous sediments must be due to incorporation of seawater b during formation of authigenic silicates the 11b of these minerals is 2 3 per mil hydrothermally altered sediments from dsdp hole 477 guaymas basin gulf of california have variable b contents from 33 ppm similar to the unaltered detritus to 1 2 ppm in the recrystallized material the latter has 11b as low as 9 0 per mil substantially lower than the unaltered material hydrothermal solutions collected from vents adjacent to the hole have boron contents elevated by about a factor of 4 relative to seawater and 11b between 16 5 and 23 2 per mil the b mobilized from the sediments is isotopically fractionated with the fluids being preferentially enriched in the heavy isotope analysis of an oxisol profile developed over granite in the guyana shield showed that boron is partially mobilized during weathering with an isotopic offset of 2 5 per mil between bedrock and soil the observed enrichment of b in shales relative to igneous rocks does not occur during weathering or during exposure to seawater at low temperature incorporation occurs only during burial diagenesis at temperatures greater than about 60 c however the enrichments cannot be attained during a single cycle of primary weathering and burial but must be cumulative over many cycles

the source of halogens in geothermal fluids from the taupo volcanic zone north island new zealand abstract forty seven samples of deep geothermal well fluids and hot springs from 14 geothermal sites in the taupo volcanic zone tvz north island new zealand were analyzed for cl br and li concentrations and 37cl 7li 18o and d values the main purpose of this study was to identify the sources of salinity in the tvz fluids and to assess the processes that control stable chlorine isotopic fractionation in the geothermal waters the samples were obtained from deep wells in the mokai ohaaki wairakei rotokawa kawerau ngatamariki and tauhara geothermal fields and from the hot springs at rotorua waiotapu lake taupo waimangu waikite orakei korako and tokaanu two main meteoric recharge areas were identified in the central tvz one located to the ne with 18o and d values of 5 5 and 35 respectively and the other to the sw with a 18o value of 6 7 and d value of 43 water rock interactions in most of the geothermal fluids resulted in a 18o shift to more positive values up to 1 for mokai and over 3 for kawerau the 7li values range from 2 9 to 2 0 and suggest that the deep geothermal fluids have interacted with rocks with low 7li values the highest 7li values 1 4 in the reservoir fluids were found at kawerau where the low quartz content of the greywacke may result in the depletion of 6li the 37cl values of the samples ranged from 1 0 to 0 8 the 37cl values of 0 2 0 1 and 0 0 were measured in samples from orakei korako waiotapu and waimangu respectively and these are interpreted to have been affected by surface evaporation and distillation processes excluding these data most waters with high cl br ratios had positive 37cl values the cl br molar ratios in well samples ranged from 659 to 1664 and the 37cl values from 1 0 to 0 8 the hot springs had cl br molar ratios ranging from 858 to 1611and 37cl values from 0 8 to 0 7 overall the cl br molar ratios of the fluids are comparable with published data on basaltic magmas and these magmas are inferred to be the main source of halogens in the geothermal fluids however the geothermal fluids can be separated into two main groups one associated with rhyolitic magmas characterized by positive 37cl values and high cl br molar ratios and other related to andesitic magmas with negative 37cl values and lower cl br molar ratios we suggest therefore that the isotopic fractionation of the stable cl isotopes is related to the difference in water contents of andesitic and rhyolitic magmas and that the fluid phase is enriched in 37cl during magmatic evolution there is no evidence of isotopic fractionation during the transit of the geothermal fluids from the reservoir to the surface but evaporation and distillation processes at the surface can affect the 37cl values

holocene southern ocean surface temperature variability west of the antarctic peninsula the antarctic peninsula is currently one of the fastest warming locations on earth but its long term variability has remained unclear amelia shevenell and colleagues now use the tex86 proxy a palaeothermometer that tracks membrane lipids of the marine picoplankton crenarchaeota to show that a long term cooling of about 4 c occurred in waters near the tip of antarctic peninsula over the past 12 000 years this is consistent with orbitally controlled changes in insolation shorter term variability in temperature seems to have been strongly influenced by the position of the westerly winds this work suggests that the present influence of the el nino southern oscillation system on the antarctic peninsula is a relatively recent phenomenon dating to the late holocene the antarctic peninsula is currently one of the fastest warming locations on earth but its long term variability has remained unclear this study uses tex86 sea surface temperature proxy evidence to show that a long term cooling of about 3 4 c occurred in waters near the tip of the antarctic peninsula over the past 12 000 years consistent with orbitally controlled changes in insolation shorter term variability in temperature at the antarctic peninsula appears to have been strongly influenced by the position of westerly winds the present influence of the el nino southern oscillation system on the antarctic peninsula may have arisen only during the late holocene the disintegration of ice shelves reduced sea ice and glacier extent and shifting ecological zones observed around antarctica1 2 highlight the impact of recent atmospheric3 and oceanic warming4 on the cryosphere observations1 2 and models5 6 suggest that oceanic and atmospheric temperature variations at antarctica s margins affect global cryosphere stability ocean circulation sea levels and carbon cycling in particular recent climate changes on the antarctic peninsula have been dramatic yet the holocene climate variability of this region is largely unknown limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms here we show that surface ocean temperatures at the continental margin of the western antarctic peninsula cooled by 3 4 c over the past 12 000 years tracking the holocene decline of local 65 s spring insolation our results based on tex86 sea surface temperature sst proxy evidence from a marine sediment core indicate the importance of regional summer duration as a driver of antarctic seasonal sea ice fluctuations7 on millennial timescales abrupt sst fluctuations of 2 4 c coincide with globally recognized climate variability8 similarities between our ssts southern hemisphere westerly wind reconstructions9 and el nino southern oscillation variability10 indicate that present climate teleconnections between the tropical pacific ocean and the western antarctic peninsula11 strengthened late in the holocene epoch we conclude that during the holocene southern ocean temperatures at the western antarctic peninsula margin were tied to changes in the position of the westerlies which have a critical role in global carbon cycling9 12

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

129i and 36cl concentrations in waters of the eastern clear lake area california residence times and source ages of hydrothermal fluids abstract the clear lake area of northern california is the location of hot spring activity some of which is associated with the formation of au and hg deposits we measured 129 i i and 36 cl cl ratios in nine warm springs formation springs six cold springs with elevated levels of cl and i mineral springs and five springs of recent meteoric origin dating of the i in the formation waters indicated that sources of i in these waters are formations with minimum ages between 60 and 80 ma this age range is in good agreement with the ages of the franciscan complex and the great valley sequence the dominant formations in this area because the mineral waters are essentially formation waters diluted with meteoric water i in these waters is of the same origin residence times of the waters were calculated based on the build up of129i and 36cl as a consequence of the presence of u and th in the crust the residence time of the formation waters in the great valley sequence the location for most of these springs was probably not longer than 84 000 yr the concentrations found for 36cl and 129i in the mineral waters indicate that these waters have residence times of similar magnitude in formations such as the franciscan complex or the clear lake volcanics which have slightly higher levels of u and th than the great valley sequence

alkenone temperature anomalies in the brazil malvinas confluence area caused by lateral advection of suspended particulate material alkenone temperatures derived from suspended particulate organic material which was collected in austral summer 2001 from surface waters 5 m south of the brazil malvinas confluence deviate from measured temperatures by 4 to 7 c when uk 37 ratios are converted to temperature using the muller et al 1998 calibration and up to 3 c when using the calibration of conte et al 2006 in contrast alkenone temperatures determined from particulate material sampled north of the confluence reveal close correspondence to in situ temperatures or show slightly higher values we suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing malvinas current whereas the northern samples carry an uk 37 signal of tropical subtropical origin transported southward with the brazil current on the basis of surface ocean transport pathways and velocities simulated with the large scale geostrophic lsg ocean general circulation model we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents

the evaporation path of seawater and the coprecipitation of br and k with halite brines and salt were sampled at the morton bahamas solar salt production facility on great inagua island in the bahamas the brines were analyzed by ion chromatography to define more precisely than heretofore the evaporation path of seawater to the end of the halite facies at inagua calcium carbonate begins to precipitate at a brine concentration factor of 1 8 times that of seawater gypsum begins to precipitate at a brine concentration of 3 8 times seawater and halite at a concentration factor of 10 6 three of the most concentrated brines from inagua 40 times seawater were evaporated further in the laboratory magnesium sulfate first precipitated at brine concentrations about 70 times those of seawater and potassium bearing phases began to precipitate for these brines at concentrations greater than 90 times those of seawater the distribution of coefficients of br and k between brines and halite were determined by combining analytical data for the inagua brines with measurements of the br and k content of halites from inagua and of halite which had precipitated from inagua brines during storage the observed average value of dbr is 0 032 in good agreement with some of the previous measurements the measured values of dk are highly variable 0 001 to 0 021 dk for halite precipitated early in the halite facies is in the vicinity of 0 015

aging of marine organic matter during cross shelf lateral transport in the benguela upwelling system revealed by compound specific radiocarbon dating organic matter accumulation and burial on the namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers much of the material deposited in depo centers on the slope ultimately derives from the shelf supply of organic matter from the shelf involves selective transport of organic matter we studied these selective transport processes by analyzing the radiocarbon content of co occurring sediment fractions here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity phytoplankton derived alkenones membrane lipids of pelagic crenarchaeota crenarchaeol and calcareous microfossils of planktic foraminifera in core top and near surface sediment samples the samples were collected on the namibian margin along a shelf slope transect 85 to 1040 m at 24 s and from the upper slope depo center at 25 5 s in core top sediments alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth crenarchaeol while younger than alkenones also increased in age with distance offshore it was concluded that the observed ages were a consequence of cross shelf transport and associated aging of organic matter radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied pre aged material present in a sample highlighting the importance of nepheloid transport for the sedimentation of organic matter over the namibian margin

particle fluxes to the interior of the southern ocean in the western pacific sector along 170 w abstract an array of five bottom tethered moorings with 19 parflux time series sediment trap at three depths 1 and 2 km below the surface and 0 7 km above the sea floor was deployed in the western pacific sector of the southern ocean along 170 w the five stations were selected to sample settling particles in the main hydrological zones of the southern ocean the sampling period spanned 425 days november 28 1996 january 23 1998 and was divided into 13 or 21 synchronized time intervals a total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass tmf organic carbon carbonate biogenic silica and lithogenic particles the fluxes of biogenic material were higher than anticipated challenging the notion that the southern ocean is a low productivity region organic carbon fluxes at 1 km depth within the polar frontal zone and the antarctic zone were relatively uniform 1 7 2 3 g m 2 yr 1 and about twice the estimated ocean wide average ca 1 g m 2 yr 1 carbonate fluxes were also high and uniform between the subantarctic front and ca 64 s 11 13 g m 2 yr 1 a large fraction of the carbonate flux in the antarctic zone was due to the presence of pteropod shells coccoliths were found only to the north of the polar front and calcium carbonate became the dominant phase in the subantarctic zone in contrast carbonate particles were nearly absent near 64 s latitudinal variations in biogenic silica fluxes were substantial the large opal flux 57 g m 2 yr 1 measured in the antarctic zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the polar front unlike biogenic material fluxes of lithogenic particles were among the lowest measured in the open ocean 0 12 0 05 g m 2 yr 1 reflecting a very low dust input

constraining the applicability of organic paleotemperature proxies for the last 90 myrs abstract we evaluated changes in the distributions of long chain alkenones long chain diols and gdgts lipids commonly used for paleothermometry over the last 90 myrs for sediments deposited on the new jersey shelf the bass river site and assessed potential effects of different ancestral producers and diagenesis on their distributions and their impact on the associated temperature proxies as reported before the paleogene distributions of alkenones are generally similar to those in modern haptophytes but unusual alkenone distributions characterized by a dominant di unsaturated c40 alkenone are observed for late cretaceous sediments suggesting different ancestral source organisms for alkenones in this interval the isoprenoid gdgt distributions remained comparable to modern day distributions suggesting that tex86 can be applied up to ca 90 ma the miocene long chain diol distributions are similar to modern day distributions but the older sediments reveal unusual distributions dominated by the c28 1 12 and c26 1 13 diols suggesting different source organisms before 30 ma accordingly the ldi does not match other paleotemperature proxies suggesting its applicability might be compromised for sediments older than the miocene our results indicate that of the three proxies the tex86 seems to be the most applicable for deep time temperature reconstructions

temperature dependent variation in the distribution of tetraether membrane lipids of marine crenarchaeota implications for tex86 paleothermometry 1 recently a new geochemical temperature proxy the tex86 was introduced this proxy is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraethers gdgts of the membrane lipids of marine crenarchaeota which changes as a response to temperature however until now only sediment data have been used to establish this proxy and experimental work is missing we performed mesocosm studies with marine crenarchaeota incubated at temperatures ranging from 5 to 35 c and salinities of 27 and 35 to test the validity of the tex86 proxy growth of marine crenarchaeota in these mesocosms was evident from the substantial increase in the concentration of marine crenarchaeotal membrane lipids with amounts up to 3400 ng l with increasing temperature an increase in the number of cyclopentane moieties in the crenarchaeotal membrane lipids was observed different salinities did not show any effect on the gdgt distribution the tex86 showed a significant linear correlation to incubation temperature tex86 0 015 t 0 10 r2 0 79 this equation has a similar slope to the correlation obtained from core tops but differs in the intersection tex86 0 015 t 0 28 r2 0 92 this difference is mainly determined by the smaller amount of the regioisomer of crenarchaeol in the incubation series compared to core top samples these incubation experiments indicates that water temperature is indeed the major controlling factor for the membrane distribution of marine crenarchaeota and confirms that the tex86 proxy depends on a physiological response to regulate membrane fluidity

mantle helium in sacramento basin natural gas wells abstract helium isotope ratios in sacramento basin natural gas wells show a strong mantle signal the3he 4he ratios range from 0 11 times the atmospheric ratio 0 11 ra in the rio vista field to 2 75 ra in the moon bend field indicating that 1 to 34 of the helium is mantle derived 3he 4he versus ch4 4he ratios provide evidence of two component mixing between crustal and magmatic end members extrapolation of the linear regression line to ch4 4he 0 gives a hypothetical magmatic end member 3he 4he ratio of 3 84 ra half the typical mantle ratio this indicates that the magmatic end member may actually represent a mixture of mantle and crustal helium gases which deviate from the simple two component mixture can be explained by addition of pure methane radiogenic 4he or a high n2 he component with 3he 4he 0 6 ra to 1 0 ra the ch4 3he ratio of the magmatic end member remains poorly constrained 0 to 3 109 and one cannot rule out the possibility that a significant proportion of the methane in some fields may be of deep earth origin however fields with the highest 3he 4he ratios are associated with buried plio pleistocene intrusives which have up arched sediments to form hydrocarbon traps the methane in these fields may have been produced by rapid thermal alteration of the intruded sediment elsewhere the methane appears either to have migrated from deeply buried sediments in the western basin or to have been produced by local microbial activity

alteration of the oceanic crust implications for geochemical cycles of lithium and boron abstract fresh tholeiitic basalt glass has been reacted with seawater at 150 c water rock mass ratio of 10 and fresh diabase has been reacted with a na k ca cl fluid at 375 c water rock mass ratios of 1 2 and 5 to understand better the role of temperature basalt composition and water rock mass ratio on the direction and magnitude of b and li exchange during basalt alteration at 150 c slight but nevertheless significant amounts of b and li were removed from seawater and incorporated into a dominantly smectite alteration phase at 375 c however b and li were leached from basalt b behaved as a soluble element and attained concentrations in solution limited only by the b concentration in basalt and the water rock mass ratio li however was less mobile for example at water rock mass ratios of 1 2 and 5 the percent of li leached from basalt was 58 70 and 92 respectively this suggests some mineralogic control on li mobility during hydrothermal alteration of basalt especially at low water rock mass ratios in general these results as well as those for b are consistent with the temperature dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids based on the distribution and chemistry of products of seafloor weathering low 150 c and high temperature hydrothermal alteration of basalt and the chemistry of ridge crest hydrothermal fluids it was estimated that alteration of the oceanic crust is a li source for seawater this is not true for b however since the hot spring flux estimated for b is balanced by low temperature basalt alteration these data coupled with b and li flux estimates for other processes e g continental weathering clay mineral adsorption authigenic silicate formation and formation of siliceous skeletal material yield new insight into the b and li geochemical cycles calculations performed here indicate relatively good agreement between the magnitude of b and li sources and sinks the geochemical cycle of b however may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones serpentinites are conspicuously enriched in b and if the b source for these rocks is seawater then an additional b sink exists which must be integrated into the b geochemical cycle however until more data are available in terms of areal extent of serpentinization serpentite chemistry and isotopic composition the importance of b in these rocks with respect to the b geochemical cycle remains speculative at best

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

appraisal of tex86 and tex86l thermometries in subpolar and polar regions tex86 tetraether index of tetraethers consisting of 86 carbon atoms is a sea surface temperature sst proxy based on the distribution of archaeal isoprenoid glycerol dialkyl glycerol tetraethers gdgts in this study we appraise the applicability of tex86 and view the mathml sourcetex86l in subpolar and polar regions using surface sediments we present tex86 and view the mathml sourcetex86l data from 160 surface sediment samples collected in the arctic the southern ocean and the north pacific most of the sst estimates derived from both tex86 and view the mathml sourcetex86l are anomalously high in the arctic especially in the vicinity of siberian river mouths and the sea ice margin plausibly due to additional archaeal contributions linked to terrigenous input we found unusual gdgt distributions at five sites in the north pacific high gdgt 0 crenarchaeol and gdgt 2 crenarchaeol ratios at these sites suggest a substantial contribution of methanogenic and or methanotrophic archaea to the sedimentary gdgt pool here apart from these anomalous findings tex86 and view the mathml sourcetex86l values in the surface sediments from the southern ocean and the north pacific do usually vary with overlaying ssts in these regions the sedimentary tex86 sst relationship is similar to the global calibration and the derived temperature estimates agree well with overlaying annual mean ssts at the sites however there is a systematic offset between the regional view the mathml sourcetex86l sst relationships and the global calibration at these sites temperature estimates based on the global view the mathml sourcetex86l calibration are closer to summer ssts than annual mean ssts this finding suggests that in these subpolar settings a regional view the mathml sourcetex86l calibration may be a more suitable equation for temperature reconstruction than the global calibration

methane index a tetraether archaeal lipid biomarker indicator for detecting the instability of marine gas hydrates abstract gas hydrates represent one of the largest pools of readily exchangeable carbon on earth s surface releases of the greenhouse gas methane from hydrates are proposed to be responsible for climate change at numerous events in geological history many of these inferred events however were based on carbonate carbon isotopes which are susceptible to diagenetic alterations here we propose a molecular fossil proxy i e the methane index mi to detect and document the destabilization and dissociation of marine gas hydrates mi consists of the relative distribution of glycerol dibiphytanyl glycerol tetraethers gdgts the core membrane lipids of archaea the rational behind mi is that in hydrate impacted environments the pool of archaeal tetraether lipids is dominated by gdgt 1 2 and 3 due to the large contribution of signals from the methanotrophic archaeal community our study in the gulf of mexico cold seep sediments demonstrates a correlation between mi and the compound specific carbon isotope of gdgts which is strong evidence supporting the mi methane consumption relationship preliminary applications of mi in a number of hydrate impacted and or methane rich environments show diagnostic mi values corroborating the idea that mi may serve as a robust indicator for hydrate dissociation that is useful for studies of global carbon cycling and paleoclimate change

an interlaboratory study of tex86 and bit analysis of sediments extracts and standard mixtures two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers gdgts are the tex86 tetraether index of 86 carbon atoms paleothermometer for sea surface temperature reconstructions and the bit branched isoprenoid tetraether index for reconstructing soil organic matter input to the ocean an initial round robin study of two sediment extracts in which 15 laboratories participated showed relatively consistent tex86 values reproducibility 3 4 degrees c when translated to temperature but a large spread in bit measurements reproducibility 0 41 on a scale of 0 1 here we report results of a second round robin study with 35 laboratories in which three sediments one sediment extract and two mixtures of pure isolated gdgts were analyzed the results for tex86 and bit index showed improvement compared to the previous round robin study the reproducibility indicating interlaboratory variation of tex86 values ranged from 1 3 to 3 0 degrees c when translated to temperature these results are similar to those of other temperature proxies used in paleoceanography comparison of the results obtained from one of the three sediments showed that tex86 and bit indices are not significantly affected by interlaboratory differences in sediment extraction techniques bit values of the sediments and extracts were at the extremes of the index with values close to 0 or 1 and showed good reproducibility ranging from 0 013 to 0 042 however the measured bit values for the two gdgt mixtures with known molar ratios of crenarchaeol and branched gdgts had intermediate bit values and showed poor reproducibility and a large overestimation of the true i e molar based bit index the latter is likely due to among other factors the higher mass spectrometric response of branched gdgts compared to crenarchaeol which also varies among mass spectrometers correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of bit index measurements among laboratories as well as a substantially improved estimation of molar based bit values this suggests that standard mixtures should be used in order to obtain consistent and molar based bit values

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

major and rare gases at white island volcano new zealand origin and flux of volatiles analyses of fumarolic gases at white island new zealand are reported with special emphasis on rare gases he ne ar kr and xe normalization of major species to rare gases have lead to the identification of several sources air saturated meteoric or marine water a magma body the crust and or sediments when compared to mid ocean ridge discharges the white island gas discharge represents about 3 0 7 0 1 and 0 05 of the global water carbon sulfur and helium 3 discharges respectively this balance shows that except for 3he which derives from the mantle practically all rare gases water and carbon and part of sulfur derive from originally superficial sources

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

a radiocarbon based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments crenarchaeotal glycerol dibiphytanyl glycerol tetraether gdgt lipids and alkenones are two types of biomarkers derived from planktonic marine microorganisms which are used for reconstruction of sea surface temperature we determined the radiocarbon contents of the archaeal gdgt crenarchaeol and of alkenones isolated from continental margin sediments systematic differences were found between the two biomarkers with higher radiocarbon content in crenarchaeol than in the phytoplankton derived alkenones these differences can be explained by variable contributions of pre aged laterally advected material to the core sites crenarchaeol appears to be more efficiently degraded during transport in oxygen replete environments than alkenones whether this reflects the influence of chemical structure or mode of protection e g particle association is not known

boron lithium and nitrogen isotope geochemistry of nh4 illite clays in the fossil hydrothermal system of harghita bai east carpathians romania abstract coarse 2 0 0 2 m and fine boron in nh4 i s clays ranges from 513 to 1457 ppm and reached 1000 ppm in the k i nh4 k i the 11b measured in nh4 i s ranges from 12 6 to 22 4 0 3 and in k i nh4 k i is consistently 5 5 to 5 1 0 3 boron isotopes systematically become lighter in the nh4 i s series as temperature increased from 90 to 270 c low li content 1 to 8 ppm was found in illitic clay fractions the 7li shows negative values ranging from 8 6 to 12 3 0 8 for the coarser 2 0 0 2 m nh4 i s clays and from 4 3 to 14 1 1 for the finer the 11b of k i nh4 k i clays reflect a magmatic source whereas the nh4 i s series is consistent with the influx of isotopically light b waters derived from hydrothermal leaching of continental evaporites and or organic rich sediments the 7li signature measured on k i nh4 k i clays also support a magmatic fluid enriched in heavy li followed by precipitation of coarser nh4 i s from more recent sedimentary contributions of isotopically light li this interpretation is also supported by the 15n which reflect an influx of waters from an organic sediment origin the 15n of 14 6 0 6 measured on nh4 i s could be attributed to the presence of meteoric waters mixed with hydrothermal fluids the isotopic data obtained trace the mobility of magmatic and organic sedimentary components in the upper continental crust

holocene sea surface temperature variability in the chilean fjord region here we provide three new holocene 11 0 cal ka bp alkenone derived sea surface temperature sst records from the southernmost chilean fjord region 50 53 s sst estimates may be biased towards summer temperature in this region as revealed by a large set of surface sediments the holocene records show consistently warmer than present day ssts except for the past 0 6 cal ka bp however they do not exhibit an early holocene temperature optimum as registered further north off chile and in antarctica this may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea level stands enhanced advection of colder and fresher inner fjord waters and stronger westerly winds during the mid holocene pronounced short term variations of up to 2 5 c and a cooling centered at 5 cal ka bp which coincides with the first neoglacial glacier advance in the southern andes are recorded the latest holocene is characterized by two pronounced cold events centered at 0 6 and 0 25 cal ka bp i e during the little ice age these cold events have lower amplitudes in the offshore records suggesting an amplification of the sst signal in the inner fjords

an evaluation of 14c age relationships between co occurring foraminifera alkenones and total organic carbon in continental margin sediments 1 radiocarbon age relationships between co occurring planktic foraminifera alkenones and total organic carbon in sediments from the continental margins of southern chile northwest africa and the south china sea were compared with published results from the namibian margin age relationships between the sediment components are site specific and relatively constant over time similar to the namibian slope where alkenones have been reported to be 1000 4500 years older than co occurring foraminifera alkenones were significantly similar to 1000 years older than co occurring foraminifera in the chilean margin sediments in contrast alkenones and foraminifera were of similar age within 2 sigma error or better in the nw african and south china sea sediments total organic matter and alkenone ages were similar off namibia age difference toc alkenones 200 700 years chile 100 450 years and nw africa 360 770 years suggesting minor contributions of preaged terrigenous material in the south china sea total organic carbon is significantly 2000 3000 years older owing to greater inputs of preaged terrigenous material age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter physical characteristics of the depositional setting such as seafloor morphology shelf width and sediment composition may control the age of co occurring sediment components in particular offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions aging of organic matter is promoted by transport age offsets are correlated with organic richness suggesting that formation of organic aggregates is a key process

isoprenoid and branched gdgt based proxies for surface sediments from marine fjord and lake environments in chile abstract proxies based on glycerol dialkyl glycerol tetraether gdgt lipids from archaea isoprenoid gdgts and bacteria branched br gdgts in 33 surface sediments from marine fjord and lake systems between 25 s and 50 s in chile were analyzed the regional texh86 calibration obtained from the marine and fjord sediments and mean annual surface temperature t 59 6 texh86 33 0 r2 0 9 n 23 is statistically identical to the global ocean calibration based on suspended particulate material in terms of slope but not in terms of intercept the regional surface and subsurface texh86 calibrations were statistically different from the existing global ocean core top calibrations the tex86 calibration model based on most of the relatively large lakes studied here t 50 7 tex86 11 8 r2 0 9 n 5 is statistically identical to the global lake calibration the relatively high tex86 values from smaller lakes suggested an additional source for isoprenoid gdgts likely terrestrial or aquatic methanogenic archaea application of the soil calibrated mbt cbt methylation and cyclization of br gdgts respectively temperature proxy to the marine and fjord sediments resulted in an overestimation of continental mean annual air temperature maat suggesting in situ production of certain br gdgts in the water column or surface sediment for the lakes mbt cbt based surface air temperature estimates were 3 6 c below maat however temperature estimates from the lake specific mbt cbt global calibration were in good agreement with mean annual surface temperature for all the lakes the results highlight the need for testing local vs global calibrations of gdgt based proxies before their application for palaeoenvironmental reconstruction