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

geochronology stratigraphy and geochemistry of cindery tuff in pliocene hominid bearing sediments of the middle awash ethiopia cindery tuff is a subalkaline rhyolitic air fall deposit that was probably produced by a mixed magma eruption it is a distinctive datable regional isochronous marker bed within the pliocene sediments of the middle awash district and is stratigraphically situated between two new fossil hominid discoveries based on 40ar 39ar analyses of plagioclase rhyolitic glass and basaltic glass as well as fission track analyses of zircons we estimate its age to be 3 8 4 0 myr this implies that associated hominid skull fragments are at least 3 9 myr old

an effect of dissolved nutrient concentrations on alkenone based temperature estimates the ratio of 37 carbon diunsaturated to diunsaturated and triunsaturated alkenones uk 37 produced by some haptophytes is widely used as a proxy for past sea surface temperatures however our isothermal culturing experiments with emiliania huxleyi clone ccmp372 show uk 37 values to also vary with nutrient availability and cell division rate these results provide a reasonable explanation for large isothermal variation in uk 37 values of single coccolithophorid strains grown in culture they also suggest that alkenone based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature

seasonal variability of the long chain alkenone flux and the effect on the u37k index in the norwegian sea a seasonally varying sedimentation pattern was observed for the alkenone flux measured with sediment traps in the northern north atlantic in the norwegian sea traps were set at 500 1000 and 3000 m the alkenone flux varied between 0 1 and 7 1 g m 2 d 1 and followed the seasonal pattern of the bulk parameters maximum fluxes occurred from mid october until mid november and were also high in may a surprising result was that considerably higher particle fluxes were observed at 3000 m for the alkenone flux the highest additional input of 250 was observed during the period when sediment resuspension was greatest in summer at the barents sea continental margin traps at 1840 and 1950 m the alkenone fluxes follow the sedimentation pattern of the bulk parameters with a less visible signal of distinct seasonality observed in the 1950 m trap the sedimentation of total alkenones varied between 0 8 and 144 g m 2 d 1 at 1840 m and between 0 5 and 31 0 g m 2 d 1 at 1950 m resuspension and lateral advection contributed significantly to measured fluxes in the two near bottom traps alkenone concentrations were determined in faecal pellets of appendicularia ostracods and euphausids from selected samples at the barents sea site the alkenone flux in pellets 4 to 24 of total was 5 to 6 times higher at 1950 m depth than at 1840 m and the major part 77 78 of the total flux of c37 3 reaching the near bottom trap at 1950 m was associated with faecal pellets of the meso zooplankton spatial and temporal variations of the u37k signals were observed indicating that the imprint in the alkenone signal depends on the origin and transport pathway of the organic material strong deviations occur in areas where nepheloid layers contribute particles of long residence times to the primary flux

the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

depth ranges of alkenone production in the central pacific ocean we report analytical results of long chain c 37 c 39 alkenones in the surface sediments taken along a latitudinal transect at 175 e from 48 n to 15 s unsaturation degree of c 37 alkenones u k 37 indicated that alkenone temperature is the highest about 28 3 c in the tropical pacific and decreases toward 48 n about 10 1 c although the latitudinal trend of the alkenone temperature is generally similar to that of the observed sea surface temperature of the surface mixed layer the former exhibits markedly lower values than the latter does in the midlatitude 35 19 n on the basis of the comparisons between water column temperatures and alkenone temperatures in the surface sediments we estimated that in the midlatitudes alkenones are produced in the thermocline waters whereas in the high 48 40 n and low 10 n 2 s latitudes they are produced in the surface mixed layer this result is supported by the depth distribution of emiliania huxleyi and gephyrocapsa oceanica along a 155 w transect in the central pacific the latitudinal distribution of the alkenone production layers estimated from u k 37 is found to be consistent with that of the nitrate suggesting that the depth of alkenone production is mainly controlled by the nutrient supply from deeper waters alkenones in the sediments exhibited relatively large abundances in 43 27 n with a maximum at 30 n which may be explained by high productivity of haptophyte algae in kuroshio extension

long chain alkenones and alkyl alkenoates as palaeotemperature indicators their production flux and early sedimentary diagenesis in the eastern north atlantic the production and fate of long chain alkenones and alkenoates was examined with regard to their use as palaeotemperature indicators alkenoate abundances were higher than previously reported for other regions and more strongly correlated with temperature than was alkenone unsaturation u37k suggesting biogeographical variability in alkenone and alkenoate production in surface waters we define the aa36 ratio to parameterize alkenoate abundance and present an empirical temperature calibration derived from our euphotic zone samples for use in the north atlantic t 17 35 25 12 u37k 26 73 aa36 93 90 u37k aa36 significant diagenetic losses of alkenones and alkenoates were found within the water column and near surface sediments in spite of diagenetic losses the temperature signal recorded by these compounds in the sediments remains largely unaltered and corresponds to the euphotic zone water temperature during the springtime period of maximum coccolithophorid production and flux rather than the average annual sea surface temperature

hydrological changes in the mediterranean sea over the last 30 000 years sea surface temperatures were reconstructed over the last 30 000 years from alkenone paleothermometry sst alk and planktonic foraminifera assemblages using the modern analog technique mat sst foram along two cores of the mediterranean sea md84 632 levantine basin and md04 2797 siculo tunisian strait oxygen isotope of planktonic foraminifera g bulloides for core md04 2797 and g ruber for core md84 632 were also determined sst alk in the levantine basin indicate colder values at the last glacial maximum lgm 14 c than earlier established from mat and a cooling amplitude of 6 7 c comparable to the central mediterranean sea climatic events such as the younger dryas yd and heinrich events 1 and 2 h1 and h2 were times of significant cooling in the two cores in the eastern basin values of local seawater oxygen isotope w indicate relatively saltier waters during the lgm and deglaciation than today with increasing w values higher salinity in the eastern basin and decreasing ones lower salinity in the central mediterranean sea during cold stadials the observed alterations of surface water properties t and w in the central and eastern mediterranean at the lgm are consistent with model experiments showing slightly lower evaporation in the mediterranean than today except for the eastern basin

freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the okhotsk sea across millennial scale cycles 1 we present records of phytoplankton produced alkenones down a long piston core which reveal changes of sea surface temperature sst and sea surface salinity sss in the southwestern okhotsk sea over the past 120 ka between 20 and 60 ka b p alkenone derived temperatures typically increased by 6 c 8 c from periods corresponding within a few hundred years to stadials to those corresponding to interstadials recorded in greenland ice cores the abundance of c37 4 alkenone relative to total c37 alkenones percent c37 4 a possible proxy for salinity indicated that during most low sss was associated with high sst the warm freshwater events might be related to 1 a decline in the supply of saline water entering the okhotsk sea through the soya strait 2 strengthening of the freshwater supply from the amur river and precipitation over the okhotsk sea associated mainly with increased asian summer monsoon activity and 3 the effect of melting sea ice these findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the pacific and the atlantic sides of the northern hemisphere

speleothem u th age constraints for the last glacial conditions in the apuan alps northwestern italy abstract during the quaternary several glaciations occurred in the mountain regions around the mediterranean and in recent years new ages have better constrained their timing however this is not the case for the apuan alps a high rainfall mountain chain adjacent to the mediterranean sea here in spite of the widespread evidence for glaciers the complete lack of geochronological information hinders our understanding of glaciation history in this paper we utilize speleothem ages to better constrain the timing of these glacial features we re examine 293 uranium thorium ages from 19 speleothems collected in five caves at different elevations after a period of very low growth between 160 and 132 ka the analysed speleothems grew almost continuously to 75 ka this period was followed by intermittent growth with lower deposition rate and presence of hiatuses until 12 5 12 ka this is consistent with an ice coverage persisting over the apuan alps inhibiting or interrupting the growth of speleothems via the limited availability of groundwater and the scarcity absence of soils this interval is much greater than the time interval that has previously been attributed to the existence of glaciers on the apuan alps which has been assumed to be restricted to marine isotope stage mis 2 instead ice cover probably also appeared in the apuan alps during mis 4 the phase of restarting of growth which may implies the definitive or substantial glacier melts seem to predate the holocene

alkenones alkenoates and organic matter in coastal environments of nw scotland assessment of potential application for sea level reconstruction reconstruction of late quaternary sea level history in areas of glacioisostatic uplift often relies on sediment archives from coastal isolation basins natural coastal rock depressions previously isolated from or connected to the sea at different times proxy indicators for marine brackish or lacustrine conditions combined with precise dating can constrain the time when the sea crossed the sill threshold and isolated or connected the basin the utility of isolation basins in investigations of sea level change is well known but investigations have been mostly limited to microfossil proxies the application of which can be limited by preservation and nonanalog problems here we investigate the potential of long chain alkenones alkenoates and bulk organic parameters toc corg n for reconstructing past sea level changes in isolation basins in nw scotland we analyze organic biomarkers and bulk parameters from both modern basins at different stages of isolation from the sea and fossil basins with sea level histories reconstructed from established proxies logit regression analysis was employed to find which of the biomarker metrics or bulk organic measurements could reliably characterize the sediment samples in terms of a marine brackish or isolated lacustrine origin the results suggested a good efficiency for the alkenone index c37 4 at predicting the depositional origin of the sediments this study suggests that alkenones could be used as a novel proxy for sea level change in fossil isolation basins especially when microfossil preservation is poor

groundwater dynamics and arsenic contamination in bangladesh although arsenic contaminated groundwater in bangladesh is a serious health issue little is known about the complex transient patterns of groundwater flow that flush solutes from aquifers and carry solutes into the subsurface hydrologic modeling results for our field site in the munshiganj district indicate that groundwater flow is vigorous flushing the aquifer over time scales of decades to a century and also transporting solute loads into the aquifer with recharge from ponds rivers and rice fields the combined hydrologic and biogeochemical results from our field site imply that the biogeochemistry of the aquifer system may not be in steady state and that the net effect of competing processes could either increase or decrease arsenic concentrations over the next decades modeling results suggest that irrigation has greatly changed the location timing and chemical content of recharge to the aquifer flushing water through the system more quickly and also cycling large fluxes of water through rice fields during the dry season that could mobilize arsenic from oxides in near surface sediments furthermore the hydrologic model reveals that ponds many of which have been excavated over the last 50 years now provide much of the groundwater recharge these ponds receive most of the waste from the villages and thus provide another potential source of organic carbon to the groundwater system

an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years eleven sediment samples taken downcore and representing the past 26 kyr of deposition at manop site c 0 57 2 n 138 57 3 w were analyzed for lipid biomarker composition biomarkers of both terrestrial and marine sources of organic carbon were identified in general concentration profiles for these biomarkers and for total organic carbon toc displayed three common stratigraphic features in the time series 1 a maximum within the surface sediment mixed layer 4 ka 2 a broad minimum extending throughout the interglacial deposit and 3 a deep pronounced maximum within the glacial deposit using the biomarker records a simple binary mixing model is described that assesses the proportion of terrestrial to marine toc in these sediments best estimates from this model suggest that 20 of the toc is land derived introduced by long range eolian transport and the remainder is derived from marine productivity the direct correlation between the records for terrestrial and marine toc with depth in this core fits an interpretation that primary productivity at site c has been controlled by wind driven upwelling at least over the last glacial interglacial cycle the biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr b p diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr

molecular records of twentieth century el nino events in laminated sediments from the santa barbara basin organic molecules preserved in sediments especially long chain alkenones can preserve and record evidence of past climate variations1 5 a dependence of alkenone distributions on temperature has been recognized in cultures of the unicellular coccolithophorid alga emiliania huxleyi1 6 which survives in sediments and water column participates6 through this dependence stratigraphic profiles of the degree of alkenone unsaturation expressed asuk37 values1 have been shown in several oceanic settings to reflect long term changes in sea surface temperatures associated with glacial interglacial cycles1 5 here we show that annual variations in alkenone unsaturation in laminated sediments from the santa barbara basin off the shore of california reveal increases in water temperatures which can be linked directly to the observed sequence of el nino events in the twentieth century7 the range and variations in water temperatures calculated from uk37 values 12 8 15 2 c using the relationship established from culture experiments6 8 broadly correspond to the annually averaged temperatures 11 3 15 2 c measured intermittently by the calcofi programme at 20 m depth between 1953 and 1984 these results show that in favourable settings alkenone unsaturation profiles can provide an annually resolved record of oceanic temperaturechanges and may constitute a valuable tool for describing and evaluating the history of global climate variability and change

deglacial changes in flow and frontal structure through the drake passage the oceanic gateways of the drake passage and the agulhas current are critical locations for the inflow of intermediate depth water masses to the atlantic which contribute to the shallow return flow that balances the export of deep water from the north atlantic the thermohaline properties of northward flowing intermediate water are ultimately determined by the inflow of water through oceanic gateways here we focus on the less well studied cold water route through the drake passage we present millennially resolved bottom current flow speed and sea surface temperature records downstream of the drake passage spanning the last 25 000 yr we find that prior to 15 ka bottom current flow speeds at sites in the drake passage region were dissimilar and there was a marked anti phasing between sea surface temperatures at sites upstream and downstream of the drake passage after 14 ka we observe a remarkable convergence of flow speeds coupled with a sea surface temperature phase change at sites upstream and downstream of drake passage we interpret this convergence as evidence for a significant southward shift of the sub antarctic front from a position north of drake passage this southward shift increased the through flow of water from the pacific likely reducing the density of atlantic intermediate water the timing of the southward shift in the sub antarctic front is synchronous with a major re invigoration of atlantic meridional overturning circulation with which we argue it may be linked

geochemical evidence for a large methane release during the last deglaciation from marmara sea sediments abstract recent methane inventories have revealed the potential impact of gas hydrates on the global carbon cycle and hence in climate change milkov 2004 however only a few studies have traced methane release in the geologic record here we show geochemical evidence for a large scale methane release at mid latitudes during the last deglaciation the sea of marmara an enclosed sea between the mediterranean and black seas is located in a tectonically active basin with gas hydrate expulsion and the formation of shallow gas hydrates since depths in the basin are shallower than 1100 m future global temperatures are expected to have a great influence in destabilizing methane clathrates among the suite of biomarkers we have focused on diplopterol and diploptene profiles in core md012430 retrieved from the central basin in the marmara sea our results indicate that during the last 15 000 years hopanoids showed important concentration variations with a pronounced peak during the deglaciation the lack of a relationship between diplopterol diploptene and phytoplanktonic biomarker concentrations as well as a depleted isotopic composition have linked the hopanoid maxima to methanotrophic activity suggesting that an intense methane release occurred at the onset of deglaciation in the marmara sea the vulnerability of the hydrate stability zone to changes in temperature and pressure under this range of shallow water depths as well as the relative timing of the hopanoid maxima and sea surface temperature rise points to thermal destabilization of hydrates as a trigger for methane release in the water column

ecological and environmental factors affecting alkenone distributions in seawater and sediments 1 the use of alkenones to estimate past sea surface temperatures has gained wide acceptance but there are still some issues that need to be resolved before alkenone proxies can be used confidently in all environmental settings a particular concern is defining what seawater temperature is recorded by the alkenone distributions preserved in sediments does it for example reflect a seasonal average or a snapshot of bloom conditions or some other combination of environmental effects this paper reviews some of the environmental and ecological factors that might affect alkenone distributions and in particular the influence of depth and seasonality on alkenone production in the water column

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

long chain alkenones and alkyl alkenoates in the coastal and pelagic sediments of the northwest north pacific with special reference to the reconstruction of emiliania huxleyi and gephyrocapsa oceanica ratios abstract long chain n c37 c39 alkenones and n c37 c38 alkyl alkenoates in marine sediments are derived mainly from two marine coccolithophorids emiliania huxleyi and gephyrocapsa oceanica laboratory cultured strains of e huxleyi strain eh2 and g oceanica strain go1 isolated from the great barrier reef and mutsu bay in northern japan 41 n 141 e respectively were cultured at 10 c 15 c 20 c 22 c 25 c 28 c and analyzed for c37 to c39 alkenones c36 methyl alkenoate fame and c36 ethyl alkenoate faee results obtained indicated significant differences in the alkenone and alkyl alkenoate profiles between these two algal species the ratios of faee to c37 alkenones ee k37 and c38 alkenones ee k38 in g oceanica were higher than those in e huxleyi and for both algal species these ratios showed strong negative nonlinear exponential correlations when plotted against the unsaturation index of c37 alkenones uk 37 using fitted equations for these relationships the relative abundance of e huxleyi and g oceanica in the sediment samples from the northwest north pacific and the coastal and inland waters of japan were estimated and compared with direct microscopic determinations e huxleyi comprised more than 80 of the sedimentary coccolith assemblage in the open ocean whereas g oceanica was exclusively dominant in the inland waters these results almost agreed with microscopic counts of these coccoliths occurring in the sediment samples in the light of these findings we suggest that there is a possibility that the relative abundance of e huxleyi and g oceanica in sediments may be estimated using nonlinear exponential calibrations based on ee k37 to uk 37 and ee k38 to uk 37 regressions

postdepositional oxic degradation of alkenones implications for the measurement of palaeo sea surface temperatures free and bound long chain alkenones c37 2 and c37 3 in oxidized and unoxidized sections of four organic matter rich pliocene and miocene madeira abyssal plain turbidites one from ocean drilling program site 951b and three from site 952a were analyzed to determine the effect of severe post depositional oxidation on the value of u37k the profiles of both alkenones across the redox boundary show a preferential degradation of the c37 3 compared to the c37 2 compound because of the high initial u37k values and the way of calculating the u37k this degradation hardly influences the u37k profiles however for lower u37k values measured selective degradation would increase u37k up to 0 17 units equivalent to 5 c for most of the u37k band width much smaller degradation already increases u37k beyond the analytical error 0 017 units consequently for interpreting the u37k record in terms of past sea surface temperatures selective degradation needs serious consideration

the role of north brazil current transport in the paleoclimate of the brazilian nordeste margin and paleoceanography of the western tropical atlantic during the late quaternary abstract reconstructions of surface paleoceanographic conditions of the western equatorial atlantic and past climates of the adjacent northeast brazilian the nordeste continental margin were undertaken by analyzing sediments from a piston core and associated gravity and box cores recovered from 3107 meter water depth at 0 20 n on the equatorial brazilian continental slope the record is dated by radiocarbon analysis and oxygen isotopic stratigraphy of planktonic foraminifers and spans from near modern to approximately 110 ka high resolution xrf analysis provides insight into the paleoclimate history of the nordeste during the last glacial interval several large amplitude and abrupt peaks are observed in the time series of ti ca and are usually accompanied by peaks of fe k together these record periods of increased precipitation and intense weathering on the adjacent continent and increased terrestrial sediment discharge from nordeste rivers into the atlantic within the limits of dating accuracy most ti ca peaks correlate with heinrich events in the north atlantic this record thus corroborates and extends back in time the previous record of arz et al 1998 determined on sediment cores from farther southeast along the nordeste margin stable oxygen isotopic analysis and mg ca paleothermometry on the near surface dwelling planktonic foraminiferal species globierinoides ruber find that mean sea surface temperature sst during glacial time 20 55 ka n 97 was 23 89 0 79 c and the mean sst during the late holocene 0 5 ka n 14 was 26 89 0 33 c ssts were 0 5 2 c higher and inferred sea surface salinities were lower during most of the periods of elevated ti ca thus as observed in previous studies the western equatorial atlantic was warm at least locally and the adjacent southern tropical continent was wet at the same time that the high latitude north atlantic was cold using the syntrace ccsm3 fully coupled climate model with transient forcing for the period 22 ka to present we find that decreased transport of the north brazil current co occurs with reduced atlantic meridional overturning circulation and colder than normal ssts in the north atlantic region these simulated conditions are invariably associated with significantly increased precipitation in the nordeste region

new insights into environmental controls on the occurrence and abundance of group i alkenones and their paleoclimate applications evidence from volcanic lakes of northeastern china abstract the distinctive long chain alkenones lcas produced by group i isochrysidales from freshwater and oligohaline lakes have great potential for quantitative paleotemperature reconstructions the widespread application of sedimentary group i lcas however is hampered by an incomplete understanding of the environmental controls on the occurrence of group i lcas in freshwater lakes the correspondence between group i lca concentrations and ph 6 2 8 5 in northern alaskan freshwater lakes longo et al 2016 suggests that group i isochrysidales may preferentially thrive in freshwater lakes with high ph here we systematically study lca distributions haptophyte specific 18s rdna sequences and concentrations of major ions and trace elements in 18 freshwater volcanic lakes in northeastern china with an extended ph range from 7 17 to 9 99 we find that 11 of the 18 lakes examined contain group i lcas and the corresponding dna sequences of their producers our dna results indicate that the dominant alkenone producer in all 11 lakes is closely related to the group i greenland otu 5 genotype with the exception of two anthropogenically impacted lakes where small numbers of group ii sequences are found statistical analyses indicate that the highest concentrations of group i lcas are found in oligotrophic freshwater lakes with ph ranging from 7 3 to 8 8 we find that elevated concentrations of certain trace elements may lead to the disappearance of group i lcas despite lake water falling within the optimal ph range together with previously published group i lca data from the temperature calibration in northern hemisphere freshwater lakes longo et al 2018 we find for the first time that group i r3b r3b c37 3b c38 3bet c37 3b values are most sensitive to winter temperature changes when mean winter temperature is higher than 20 c our results suggest that the freshwater volcanic lakes in northeastern china are highly valuable targets for paleotemperature reconstructions using group i lcas

long chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments long chain n c37 c39 alkenones and alkyl alkenoates are biological markers for sediment inputs of algae from the class prymnesiophyceae which includes the coccolithophorids these compounds have been recognized in many recent and ancient marine sediments but in only a few living algal species notably the ubiquitous coccolithophorid emiliania huxleyi the proven value of long chain alkenones in palaeotemperature assessment prompts an evaluation of their sedimentary record especially their correspondence with coccolithophorid fossils in ancient marine sediments synthesis of available micropalaeontological and molecular data suggests that morphologically related species of the genera crenalithus dictyococcites emiliania gephyrocapsa pseudoemiliania and reticulofenestra all belonging to the family gephyrocapsaceae were potential biological sources of alkenones and alkyl alkenoates in marine sediments deposited since the eocene 45 ma the occurrence of alkenones in cenomanian and albian sediments devoid of nannofossils may be presumed to reflect contributions from ancestors of the gephyrocapsaceae although an investigation of cretaceous samples containing both coccoliths and alkenones would provide further evidence of this proposed correspondence the combination of palaeontological and molecular chemotaxonomic information offers a novel approach to the evaluation of the phylogenetic lineages that link living and extinct algae

characteristics of alkenones synthesized by a bloom of emiliania huxleyi in the bering sea abstract we investigated the characteristics of the alkenones produced by a bloom of emiliania huxleyi in the eastern bering sea in 2000 alkenones were detected in surface waters between 57 n and 63 n where phosphate concentrations were low and the ammonium nitrate ratio was high the total alkenone content c37 2 c37 3 and c37 4 ranged from 22 0 to 349 g g 1 in suspended particles and from 0 109 to 1 42 g g 1 in surface sediments this suggests that a large proportion of the particulate alkenones synthesized in the surface water rapidly degraded within the water column and or at the water sediment interface of the bering shelf the change in the stable carbon isotopic composition 13c of c37 3 alkenone could not be explained only by variation in co2 aq in the surface water but also depended on the growth rate of e huxleyi the alkenone unsaturation index uk 37 was converted into an alkenone temperature with three equations prahl et al 1988 sikes et al 1997 muller et al 1998 sikes et al s 1997 equation gave the best correlation with the observed sea surface temperature sst in the eastern bering sea however some temperatures estimated by sikes et al s 1997 equation from the uk 37 varied from the observed sst possibly because of the rapidly changing rate of alkenone synthesis in the logarithmic growth stage or the low rate of alkenone synthesis when nutrients were limiting temperatures estimated from uk 37 in the surface sediments 6 8 8 2 c matched the observed sst in september 7 8 c but differed from the annual average sst of 4 to 5 c suggesting that most of the alkenone in the eastern bering sea was synthesized during limited periods for instance in september the relative amounts of c37 4 alkenone as proportions of the total alkenones referred to as c37 4 were high ranging from 18 3 to 41 4 low salinity water

alkenones and coccoliths in ice rafted debris during the last glacial maximum in the north atlantic implications for the use of uk37 as a sea surface temperature proxy the uk37 index has proven to be a robust proxy to estimate past sea surface temperatures ssts over a range of time scales but like any other proxy it has uncertainties for instance in reconstructions of the last glacial maximum lgm in the northern north atlantic uk37 indicates higher temperatures than those derived from foraminiferal proxies here we evaluate whether such warm glacial estimates are caused by the advection of reworked alkenones in ice rafted debris ird to deep sea sediments we have quantified both coccolith assemblages and alkenones in sediments from glaciogenic debris flows in the continental margins of the northern north atlantic and from a deep sea core from the reykjanes ridge certain debris flow deposits in the north atlantic were generated by the presence of massive ice sheets in the past and their associated ice streams such deposits are composed of the same materials that were present in the ird at the time they were generated we conclude that ice rafting from some locations was a transport pathway to the deep sea floor of reworked alkenones and pre quaternary coccolith species during glacial stages but that not all of the ird contained alkenones even when reworked coccoliths were present we speculate that the ratio of reworked coccoliths to alkenone concentration might be useful to infer whether significant reworked alkenone inputs from ird did occur at a particular site in the glacial north atlantic we also observe that alkenones in some of the debris flows contain a colder signal than estimated for lgm sediments in the northern north atlantic this is also clear in the deep sea core studied where the warmest intervals do not correspond to the intervals with large inputs of reworked coccoliths or ird we conclude that any possible bias to uk37 estimates associated with reworked alkenones is not necessarily towards higher values and that the high sst anomalies for the lgm are unlikely to be the result of a bias caused by ird inputs

magnetism of biotite crystals abstract we report mossbauer spectra magnetic hysteresis acquisition and demagnetization of isothermal remanent magnetization irm and low temperature irm warming curves of biotite crystals as well as a summary of domain observations on magnetic extracts the biotites are from 1 0 to 1 2 ga gneisses and 1 85 ga plutons of the grenville churchill and bear provinces canada most have paramagnetic susceptibilities in the range 0 45 1 2 10 3 si similar to reported values for iron rich biotites magnetite identified by its 120 k verwey transition is an inclusion in all the biotites sizes and domain states of inclusions correlate with magnetite content as measured by saturation magnetization ms the higher ms is the lower are the domain state indicators mrs ms mrs is saturation irm and coercive force hc added to a base population 0 003 0 1 of pseudo single domain psd grains with mrs ms from 0 1 to 0 3 and hc from 7 to 20 mt is 1 in two exceptional cases 7 and 14 of coarse grained multidomain md magnetite with much softer hysteresis properties the underlying psd magnetite fraction in biotites potentially retains useful paleomagnetic remanence in the more magnetic micas this stable fraction may be swamped by md magnetite with less stable behavior

the organic geochemistry of peru margin surface sediments i a comparison of the c37 alkenone and historical el nino records abstract the alkenone u k 37 paleothermometer has potential as a sedimentary marker for el nino southern oscillation enso events in the peru upwelling regime we assessed this potential by comparing the historical enso record with detailed u k 37 profiles for 210 pb dated cores from the peru margin oxygen minimum zone omz sediments with the greatest potential for holding a sedimentary u k 37 record of el nino events are sediments from the center of the omz sectioned at intervals the yearly sedimentation rate the u k 37 signals of individual el nino events were substantially attenuated in the sediments we examined and periods of frequent enso activity e g 1870 1891 were more readily identified than isolated enso events in periods of less frequent enso activity detailed depth profiles of the c 37 alkenones in a core from 253 m o 2 k 37 values for the five 2 mm sections from 0 1 cm suggests that the u k 37 may be unaffected by the alkenone loss correlation between the c 37 alkenone concentration profiles in two cores from 15 s collected nine years apart are consistent with the use of these compounds for molecular stratigraphy

interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high latitude locations alkenone sediment data from the nordic seas and north atlantic are compared to those from sikes et al 1997 for the southern ocean to evaluate further uk37 and uk37 as proxies to estimate cold temperatures 10 c and the effect of salinity and temperature in the relative abundance of 37 4 to the total abundance of c37 alkenones 37 4 uk37 and uk37 are found to be equally viable as proxies but there are significant regional differences in their cold temperature dependence the measurement of 37 4 in cores from the north atlantic region can be used to identify situations when uk37 is not a reliable paleothermometer variations in salinity are probably responsible for changes in the sedimentary record of 37 4 and a preliminary calibration has been obtained for 37 4 f salinity this new relationship should be further confirmed through field or laboratory experiments but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters

modifications of the c37 alkenone and alkenoate composition in the water column and sediment possible implications for sea surface temperature estimates in paleoceanography 1 the literature pertaining to c37 alkenone and c37 and c38 alkenoate production and diagenesis has been reviewed and evaluated for issues that might jeopardize their usefulness in paleotemperature estimation we also examined the use of the c37 alkenones as paleoproductivity indicators the stability of their 13c isotopic compositions and their incorporation into the nonsolvent extractable organic matter fraction biological transformation of organic matter by bacteria and zooplankton does not appear to cause significant changes to the ratio of c37 2 and c37 3 alkenones but there are major alterations in the relative composition of alkenoates studies of water column processes and postdepositional sedimentary changes indicate overall stability in the c37 2 c37 2 c37 3 ratio leading to effective preservation of the paleotemperature signal this is not the case for alkenoates and there also appear to be some doubts about the dependence between sea surface temperature and the sedimentary abundance of the c37 4 alkenone c37 alkenones may provide useful qualitative estimates of marine paleoproductivity although these compounds are apparently only derived from haptophycea changes in their quantitative composition might reflect changes in nutrient availability that on sedimentary timescales should also be generally significant of other algal species one caveat is that in highly productive upwelling systems productivity may be expressed mostly in diatom growth and thus not measurable by the c37 alkenones no changes in 13c c37 alkenone composition are observed upon zooplankton ingestion although this is expected from a theoretical perspective further studies are encouraged in order to fully assess the stability of the isotopic signal during c37 alkenone diagenesis finally alkenones bound in the nonextractable fraction of sedimentary organics have not been adequately studied and further work is required to clarify any possible correspondence with a temperature signal

high resolution alkenone sea surface temperature variability on the north icelandic shelf implications for nordic seas palaeoclimatic development during the holocene the palaeoceanography of the northern icelandic shelf for the holocene period was reconstructed from alkenone indices measured in core jr51 gc35 this contains a continuous record of holocene sedimentation spanning 0 10 2 cal kyr bp with a resolution of 20 yr cm we have identified a general holocene cooling trend that has superimposed millennial scale oscillations of 28c their timing is in close agreement with the timing of glacier advances in northern iceland for the later half of the holocene the alkenone sea surface temperature sst record from jr51 gc35 correlates with proxy data for the strength of nadw formation recorded in cores south of iceland this is interpreted as evidence of a close connection existing between north icelandic sea surface temperatures and the north atlantic meridonal overturning circulation the timing of the millennial scale sst variability in our core off north iceland is found to be out of phase or anti phased with the sst variability of a record in the eastern nordic seas md952011 this suggests that the evolution of holocene climate in the nordic seas was more complex than previously proposed and it is likely to be caused by differential responses of the irminger and norwegian currents and modulated by changes in atmospheric circulation analogous to the north atlantic oscillation

early diagenesis of lipid biomarker compounds in north atlantic sediments near surface sediments 0 45 mm depth interval from the iceland basin 59 n 21 w 3070 m water depth and biscay abyssal plain 48 n 17 w 4105 m water depth were sectioned at millimeter scale resolution to assess alterations in key lipid biomarkers during early diagenesis inventories g cm 2 in the topmost 45 mm of biomarkers from presumed terrestrial sources c20 linear n alkanes n alkanoic acids n alkanols and from phytoplankton sources phytosterols long chain alkenones and alkenoates were 1 5 4 times more abundant in the iceland basin core than in the biscay abyssal plain core indicating greater sedimentary inputs and or preservation at the iceland basin site biomarker concentrations varied significantly over millimeter scale depth intervals pronounced subsurface concentration maxima were present at both sites at the biscay abyssal plain site steep concentration gradients in the uppermost few mm of the sediment column indicate extensive diagenetic losses at or near the sediment water interface strong covariance was seen in the concentrations of various compounds within each class e g long chain n alkanes n alkanols n alkanoic acids and long chain alkenones and alkyl alkenoates indicating that individual compounds within each class are associated with the same organic matrix and have similar degradation and mixing rates thus biomarker indices for assessment of land derived inputs cpi c29 c31 acl and sea surface temperature ipt remain largely unaltered by early diagenetic processes in oxic abyssal sediments in spite of extensive bioturbation and degradative losses within the uppermost few centimeters of the sediment column

characterization on arsenic sorption and mobility of the sediments of chia nan plain where blackfoot disease occurred higher levels of arsenic in the aquifers of chia nan plain in southwestern taiwan were attributed to the cause of blackfoot disease in the area half a century ago although extensive studies were conducted on the occurrence speciation mobility and transport of arsenic in the region the relationship between arsenic adsorption by different aquifer materials and the concentration and speciation of arsenic in these aquifers was poorly delineated this study focused on characterization of sediments in the region as well as determination of relations between arsenic adsorption and other geochemical and clay mineralogical properties of the sediments the arsenic adsorption capacity was positively related to the clay minerals fe and mn contents in the sediments the higher arsenic adsorption capacity of the sediments served as a sink for the arsenic during its transport from the central mountains to the coast and as a source for its release under reduced environment and in the presence of humic substances

disentangling seasonal signals in holocene climate trends by satellite model proxy integration past sea surface temperatures ssts are routinely estimated from organic and inorganic remains of fossil phytoplankton or zooplankton organisms recovered from sea floor sediments potential seasonal biases of paleo proxies were intensely studied in the past however even for the two most commonly used paleo proxies for sst uk0 37 and mg ca ratios a clear global picture does not yet exist in the present study we combine holocene sst trends derived from uk0 37 and mg ca ratios with results from idealized climate model simulations forced by changes in the orbital conguration which represents the major climate driver over the last 10 kyrs such changes cause a spatio temporal redistribution of incoming solar radiation resulting in a modulation of amplitude and phasing of the seasonal cycle considering that the climate signal recorded by a plankton based paleo proxy may be aected by the seasonal productivity cycle of the respective organism we use the modern relationship between sst and marine net primary production npp both obtained from satellite observations to calculate a seasonality index si as an independent constraint to link modeled sst trends with proxy data although the climate model systematically underestimates holocene sst trends we find that seasonal productivity peaks of the phytoplankton based uk0 37 result in a preferential registering of the warm cold season in high low latitudes as it was expected from the si distribution the overall smoother trends from the zooplankton derived mg ca ssts suggest a more integrated signal over longer time averages which may also carry a seasonal bias but the spatial pattern is less clear based on our ndings careful multi proxy approaches can actually go beyond the reconstruction of average climate trends specifically allowing to resolve the evolution of seasonality

oceanographic considerations for the application of the alkenone based paleotemperature u37k index in the gulf of california abstract alkenone concentrations were determined in sediment trap samples and surficial sediments collected from guaymas basin gulf of california to investigate the factors that control the relationship between the u37k index and sst the results from the sediment trap study reveal a positive correlation r2 0 5 between alkenone fluxes and satellite avhrr sea surface temperature sst and a strong correlation r2 0 9 between u37k and sst over an annual temperature range of 20 c although sst and u37k are tightly coupled throughout two upwelling seasons the relationship deviates from the expression developed by prahl et al 1988 at temperatures higher than 26 c the possible reasons for this deviation are varied but include the observed changes in the coccolithophore species assemblage and the evolution of the thermocline during periods of high sst the seasonal pattern of alkenone fluxes higher fluxes during warm periods observed throughout the 1996 to 1997 study period causes a bias in the annually averaged u37k record resulting in temperature estimates that are 1 c higher than the annual avhrr sst average furthermore the u37k ratios obtained from core top sediments indicate an additional 2 c warm bias in the sedimentary record that may be related to the lateral inputs of alkenones from other regions of the gulf these results highlight the importance of oceanographic processes in determining the alkenone temperature signal that is preserved in sediments after accounting for such effects u37k ratios from a box core were used to reconstruct a sst record extending back to the 18th century for the guaymas basin these results indicate a steady 2 c warming of the surface waters of the gulf from early 1700s to the 1950s followed by a rapid apparent 1 c cooling between the 1950s and the 1980s

the alkenone temperature signal in western north atlantic surface waters abstract haptophyte algae derived long chain c 37 c 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the oceanic flux program bermuda atlantic time series ofp bats site in the western sargasso sea surface water temperatures at the site range annually from 19 to 29 c alkenone concentrations ranged from 1 in summer to 100 ng l 1 following the passage of storms highest seasonal concentrations occurred during the late winter and spring under stratified conditions alkenone concentrations in the surface mixed layer 0 20 m were generally 2 to 4 times higher than in the deep fluorescent maximum 75 110 m consistent with emiliania huxleyi concentration profiles haidar and thierstein 2001 and indicated that alkenone production primarily occurs within the upper euphotic zone in this region alkenone compound distributions and the temperature calibrations of c 37 and c 38 methyl and ethyl alkenone unsaturation u 37 k u 38me k and u 38et k respectively were remarkably similar to that observed in an e huxleyi strain previously isolated from the same area conte et al 1998 providing strong evidence that e huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are in many cases consistent with those of populations in the region of origin the bermuda calibration of u 37 k vs water temperature u 37 k 1 9835 0 2004t 0 0034t 2 r 2 0 95 n 91 is nonlinear and falls along the same trendline as euphotic zone particulates from warm 15 c waters of the eastern north atlantic conte and eglinton 1993 and mediterranean ternois et al 1997 the combined north atlantic temperature calibration u 37 k 1 1365 0 1257t 0 0018t 2 r 2 0 963 n 134 differs significantly from published coretop sediment calibrations rosell mele et al 1995 muller et al 1998 based on sea surface temperature maps levitus and boyer 1994 having a steeper slope at temperatures 24 c the reasons are not clearly apparent and manifest a need for detailed studies linking production patterns in surface waters with the signal arriving at the seafloor to fully understand the generation of the sedimentary signal

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

occurrence of extended chain length c41 and c42 alkenones in hypersaline lakes the chain length of long chain alkenones lcas in ocean and lake sediments commonly ranges from c 37 to c 39 alkenones c 40 are extremely rare c 41 and c 42 alkenones have only been reported in a cretaceous black shale cenomanian ca 95 ma from the blake bahama basin western north atlantic dsdp leg 76 site 534 the significance of these exceptionally long chain alkenones is however unclear we have conducted a systematic survey of lcas in surface sediments from 12 lakes with a wide range of salinity 0 7 146 3 g l from arid northwestern china they showed a general trend of increasing maximum chain length with increasing salinity in particular c 41 and c 42 lcas occurred only in the surface sediments of hypersaline lakes 113 6 146 3 g l but were absent from lakes with lower salinity indicating that these compounds may be produced by an unknown haptophyte species living in hypersaline environments c 2014 elsevier ltd all rights reserved

paleoenvironmental conditions for the development of calcareous nannofossil acme during the late miocene in the eastern equatorial pacific repeated monospecific coccolithophore dominance intervals acmes of specimens belonging to the noelaerhabdaceae family including the genus reticulofenestra and modern descendants emiliania and gephyrocapsa occurred during the neogene such acme was recognized during the late miocene 8 6 ma at a time of a major reorganization of nannofossil assemblages resulting in a worldwide temporary disappearance of larger forms of the genus reticulofenestra r pseudoumbilicus and the gradual recovery and dominance of its smaller forms 5 m in this study we present a multiproxy investigation of late miocene sediments from the east equatorial pacific integrated ocean drilling program site u1338 where small reticulofenestrid type placoliths with a closed central area known as small dictyococcites spp 3 m formed an acme we report on oxygen and carbon stable isotope records of multispecies planktic calcite and alkenone derived sea surface temperature our data indicate that during this 100 kyr long acme the east equatorial pacific thermocline remained deep and stable local surface stratification state fails to explain this acme and thus contradicts the model based hypothesis of a southern ocean high latitude nutrient control of the surface waters in the east equatorial pacific instead our findings suggest that external forcing such as an extended period of low eccentricity may have created favorable conditions for the small dictyococcites spp growth

pyritization of trace metals in anoxic marine sediments the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as h2s reactive fe pyrite content and salinity in controlling this process the areas studied included anoxic sulfidic sediments baffin bay a hypersaline coastal lagoon from texas and green canyon a hemipelagic oil seepage area anoxic nonsulfidic sediments with high sedimentation rates atchafalaya bay mississippi delta system hemipelagic anoxic nonsulfidic sediments with low sedimentation rates gulf of mexico shelf and slope and orca basin an euxinic hypersaline basin and organic rich marsh sediments atchafalaya bay results indicate that the degree of trace metal pyritization dtmp of all trace metals except cd increased with increasing degree of pyritization dop irrespective of the type of sedimentary environment involved however for as hg and mo the dtmpdop values were generally above the 1 1 ratio line whereas the transition metals co cu mn and ni displayed a close to linear increase in dtmp with dop and moderate incorporation into pyrite chromium and the class b metals pb and zn were also gradually incorporated into the pyrite phase but without reaching the dtmp levels exhibited by the transition metals cadmium was not incorporated to a significant extent these results are consistent with the chemical attributes of these different classes of trace elements availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of co cr cu and ni into pyrite in anoxicsulfidic fe poor and h2s rich environments

the prism pliocene palaeoclimate reconstruction time for a paradigm shift global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change but single temperature representations of the oceanic mixed layer for dat

physiological impacts on alkenone paleothermometry we conducted isothermal 15 c batch culture experiments with the coccolithophorid emiliania huxleyi strain nepcc 55a to evaluate the extent to which nutrient and light stress contribute to variability in the alkenone unsaturation index u37k alkenone content and composition were constant throughout exponential growth in both experiments when nutrients nitrate and orthophosphate were replete stationary phase nutrient starved cells continued to produce alkenones amassing concentrations alk 3 times higher than those dividing exponentially 1 5 2 pg cell 1 and the u37k of excess alkenone dropped by 0 11 units in contrast 5 days of continuous darkness resulted in a 75 decrease in cellular alk and a significant u37k increase 0 11 units given an established 0 034 unit c response for exponentially growing cells of this strain the observed range of u37k variability at 15 c corresponds to an uncertainty of 3 2 c in predicted growth temperature this level of variability matches that of the global u37k annual mean sea surface temperature calibration for surface marine sediments begging the question what is the physiological condition of alkenone producing cells exported to marine sediments comparison of our laboratory results for a strain of e huxleyi isolated from the subarctic pacific ocean with depth profiles for alkenones in surface waters from two contrasting sites in the northeast pacific ocean suggests that the answer to this question depends on the ocean regime considered a possibility with significant bearing on how stratigraphic u37k records in marine sediments are to be interpreted paleoceanographically

atlantic core top calibration of the u37k index as a sea surface palaeotemperature indicator abstract a field calibration of the uk index with sea surface temperature is discussed through analysis of an extensive suite of surface sediments n 109 from the northeastern atlantic 2 s 75 n values of u 37 k are compared with sea surface temperatures for overlying waters measured at different depths and seasons to obtain a correlation suitable for palaeotemperature reconstructions the best fit is obtained using surface 0 m temperatures corresponding to caloric winter and autumn months however the annual average spring and summer surface temperature equations also have high correlation coefficients and are also appropriate for climatic studies the results further validate the general applicability of the u 37 k as a climatic proxy because the calibration equations are valid over a wide range of surface water temperatures 0 28 c for different algal populations and are representative of the average contribution of alkenones to sediments as found in sediment cores

evidence for differential degradation of alkenones under contrasting bottom water oxygen conditions implication for paleotemperature reconstruction abstract the successful reconstruction of sea surface temperatures using alkenone paleothermometry u37k has relied on the premise that there is no significant differential degradation of alkenones with different states of unsaturation during diagenetic processes to test this assumption we conducted a comparative study of contemporary sediments in oxic and anoxic bottom waters from the santa monica basin offshore california long chain alkenones were quantified and sea surface temperature were calculated using the calibrated u37k t relationship of prahl et al 1988 our results show that temperature record from the oxic sediments is higher by as much as 4 c compared to those from time equivalent anoxic sediments as a result of differential degradation of long chain unsaturated alkenones and bioturbation mixing in the oxic sediments the differential degradation of c37 3 vs c37 2 alone could account for up to 2 5 c difference between these two records this finding has significant implication in the interpretation of paleo sea surface temperature data using alkenone paleothermometry

the influence of salinity on d h fractionation in alkenones from saline and hypersaline lakes in continental north america abstract we present a preliminary assessment of the hydrogen isotopic composition of individual alkenones c 37 39 di tri and tetra unsaturated methyl and ethyl ketones purified from surface lake sediment from sites spanning a range of salinities from 20 to 133 ppt combining these measurements with measurements of the hydrogen isotopic composition of modern lake water we estimate the magnitude of d h fractionation across our sample set and observe reduced sensitivity to salinity compared to observations from emiliania huxleyi and gephyrocapsa oceanica this lends support to the hypothesis that d h fractionation during biosynthesis is less sensitive to changes in salinity in alkenone producers from continental interior sites than in producers from open marine environments we also observe stronger correlations between the tetra unsaturated alkenone d values with water d values and associated values with salinity than we do for the di and tri unsaturated compounds and suggest that this may result from increased number of lacustrine haptophyte species producing the di and tri unsaturated as compared to the tetra unsaturated

c37 alkenone measurements of sea surface temperature in the gulf of lions nw mediterranean a study of the c37 alkenone compositions in suspended particulate matter in the northwestern mediterranean sea has shown a correspondence between uk 37 and sea surface temperature that significantly deviates from the general equation regularly observed in most marine world areas muller et al 1998 however the temperatures measured in the core top sediments using the general equation are in agreement with the annual average water column temperatures between 0 40 m depth these discrepancies suggest that despite the rather constant correlation between uk 37 and seawater temperature throughout the world oceans specific calibrations should be developed for each new area of application of the c37 alkenones for paleotemperature determination

aqueous and solid phase arsenic speciation in the sediments of a contaminated wetland and riverbed abstract mobility of as in the environment is controlled by its association with solid phases through adsorption and co precipitation to elucidate the mobilization potential of as deposited in wetland and riverbed sediments of the wells g h wetland in woburn ma as the result of decades of industrial activity as retention mechanisms were inferred from aqueous and solid phase geochemical measurements of sediment cores testing included a sequential extraction method designed for and standard tested with as phases and pe ph equilibrium modeling the uppermost sediments in the wells g h wetland contain elevated concentrations of both dissolved and solid phase as up to 2 000 g l and 15 000 g g respectively and a maximum concentration between 30 and 40 cm depth measurements obtained in this study suggested that as in the wetland sediments was predominantly adsorbed likely onto amorphous fe hydr oxide phases and mixed valence fe phases in the riverbed sediments however a relatively greater proportion of the solid as was associated with more reduced and crystalline phases and adsorbed as was more likely associated with al oxide or secondary reduced fe phases ph pe modeling of the fe as s system was consistent with observations the association of as with more oxidized phases in the wetland compared with the riverbed sediments may result from a combination of plant activities including evapotranspiration driven water table depression and or root oxygenation

depth and seasonality of alkenone production along the california margin inferred from a core top transect alkenone unsaturation indices uk 37 of marine sediment could prove particularly useful on organic rich continental margins where carbonate dissolution hampers the use of other paleoclimatic proxies mccaffrey et al 1990 kennedy and brassell 1992 forty core top samples of recent sediment from a latitudinal transect 23 40 n along the california margin yield uk 37 values that correlate linearly with modern mean annual sea surface temperatures ssts in the range of 12 23 c reproducibility of the unsaturation value in closely spaced cores is near analytical error uk 37 data define a relationship to temperature nearly identical to the prahl et al 1988 laboratory cultures of emiliania huxleyi the close agreement is particularly significant in light of the nannofossil composition of the sediments where the abundance of the coccolith taxon gephyrocapsa oceanica known to synthesize alkenones equals or exceeds that of e huxleyi comparison with seasonal temperature variations at different depths indicates that little if any alkenone production occurs at depths 30 m along the continental margin water depths 2 km sediments in more pelagic locations exhibit small but consistent biases toward winter and or subsurface production similar to previously reported sediment trap and core top data from the oregon margin prahl et al 1993 doose et al 1997

alkenone sea surface temperature in the southern ocean for the last two deglaciations a piston core taken from the tasman plateau in the southern ocean has been studied for organic compounds to reconstruct the late pleistocene marine environments here we report paleo sea surface temperature sst for the last two deglaciations using the unsaturation degree of alkenones u k 37 preserved in the marine sediments the u k 37 record indicates that the sst was at least 4 c lower than the present sst at the last glacial maximum lgm and the amplitude of paleo sst is at most 5 2 c from the penultimate glacial mis 6 to the last interglacial warm period the eemian our results also demonstrate that the eemian warm period in the southern ocean lasted only 3 000 years followed by a sharp cooling at around 120 kyr bp the sharp cooling in the southern ocean seemed to occur a few millennia 2 3 kyrs before the beginning of continental ice sheet growth

long chain alkenones in the early pliocene sicilian sediments trubi formation punta di maiata section implications for the alkenone paleothermometry abstract article history received 6 september 2010received in revised form 15 march 2011accepted 16 march 2011available online 23 march 2011keywords alkenoneearly pliocenereticulofenestridsmediterranean seasea surface temperature the u k 37 record and coccolithophorid remains in sediments from the early pliocene sicilian trubi formation punta di maiata have been estimated to assess the possible in uence of changes in the alkenone producingcoccolithophoridsontheu k 37 temperaturerelationship thesamplesweredominatedbysmallreticulofenestra r minutaandr minutula andthec 37 andc 38 methylandethylunsaturationratios u k 37 u k38me andu k38et weresimilar to those found in modern populations e huxleyi and g oceanica those results suggest that the earlypliocene small reticulofenetrids had a similar temperature sensitivity of u k 37 to thatfound in present day theseresults support the application of the u k 37 modern calibrations to reconstruct sst at least back in the pliocene 2011 published by elsevier b v

compositional heterogeneity of tephras from the 1980 eruptions of mount st helens samples collected at hourly intervals on may 18 19 1980 at three sites 200 km downwind from mount st helens have made possible a detailed reconstruction of the conditions that contribute to the compositional heterogeneity of mineral and glass components observed in distal tephra layers the air fall tephra deposited at the sites during the first 7 hours of the may 18 eruption is mostly coarse grained microlite rich nonjuvenile glass and feldspar grain size maxima in this initial tephra can be related to the cataclysmic blast at 0832 and a subsequent pulse of the eruption at 1200 juvenile microlite free glass increases in relative abundance at the sampling sites beginning at about 1900 such a change between nonjuvenile and juvenile tephra can be related to a 5 km increase in column height associated with the last major pulse of the eruption which occurred at 1700 at the volcano electron microprobe study of both microlite rich and microlite free pumice in the time series samples reveals significant compositional differences interstitial glass in nonjuvenile pumice deposited during the first few hours at the sampling sites is enriched in sio2 and k2o and depleted in tio2 feo and mgo relative to juvenile glass by comparison major element composition of the least evolved juvenile glass sampled during the last several hours of the eruption displays a slight trend toward less evolved composition least squares calculations suggest that the more evolved character of the nonjuvenile glass can be explained by greater fractional crystallization brought about by enhanced cooling in a cryptodome prior to eruption whereas the temporal changes observed in juvenile glass composition during the last several hours of the eruption suggest the presence of a small slightly zoned magma chamber at depth electron microprobe study of glass coated ilmenites magnetites and plagioclases provides the following estimates of the physical conditions in this reservoir 865 50 c ph2o 2 2 kbar and log o2 11 7 analyses of bulk pumice glass and selected mineral phases from may 25 june 12 july 22 and october 16 18 pumices erupted from mount st helens indicate that the bulk pumice magma compositions have become slightly more andesitic with time while mineral and co existing glass compositions have changed significantly in post may 18 eruptions with both being more highly evolved than those associated with the may 18 eruption an application of the magnetite ilmenite geothermometer to june 12 and july 22 samples indicates temperatures of 919 30 c and 930 50 c respectively least squares calculations suggest that such evolved post may 18 glass and mineral phases can be derived by fractional crystallization of a magma composition like bulk may 18 pumice into approximately 50 crystals and 50 residual liquid such partitioning between crystals and residual liquid appears to have occurred on the scale of centimeters and is interpreted as a consequence of accelerated crystallization under reduced water pressure

faunal and alkenone reconstructions of subtropical north atlantic surface hydrography and paleotemperature over the last 28 kyr two techniques for estimating past variations in sea surface temperature sst have been used to investigate climatic change in biogeochemical oceanic flux study bofs core 31k 19 n 20 w from the eastern subtropical atlantic high resolution sst records for the last 28 kyr have been produced using planktonic foraminiferal assemblages based on the imbrie kipp transfer function technique and the uk 37 index derived from abundances of c37 alkenones biosynthesized by prymnesiophyte algae modern observations suggest that these indices reflect particular hydrographic conditions in the upper ocean the uk 37 index corresponds to the temperature at the time of maximum coccolith productivity typically late spring early summer in the study area today whereas the faunal transfer function is calibrated for seasonal maximum and minimum temperatures in general the faunal and biomarker paleotemperature records display comparable sst variations during the last glacial and deglacial but although the overall trends are similar differences exist in the magnitude and timing of these temperature changes most notably the faunal twarm and uk 37 sst estimates diverge by 3 c between 8 ka and 6 ka and this offset persists through the late holocene this difference cannot be adequately explained by uncertainties associated with either the calibration data sets or fluctuating preservation levels we therefore propose that the deviation in sst estimates is linked to a switch in the seasonal timing of maximum coccolith production from the summer in the glacial ocean to the late spring early summer in the modern ocean our results suggest that a dual approach to sst estimation based on faunal and biomarker proxies can provide a valuable means of evaluating mixed layer and productivity changes associated with the movement of oceanographic frontal zones during the late quaternary

evidence for a holocene climatic optimum in the southwest pacific a multiproxy study the early holocene sea surface temperature sst gradient across the subtropical front stf to the east of new zealand was 2 c measured between core sites md97 2121 and md97 2120 considerably less than the 6 c modern gradient between the two core sites we document the surface ocean temperatures east and south of new zealand during the early and middle holocene to test and expand upon this reconstruction this new study samples a latitudinal transect of seven sediment cores from 37 s to 60 s in the southwest pacific from subtropical waters north of new zealand to polar waters in the southern ocean our compilation of sst proxies consists of 525 sst estimates from five different methods and includes 243 new data points we confirm that an early holocene warm peak in this region was mostly restricted to the area immediately south of the stf which resulted in a lower temperature gradient across the stf than in modern times however there is no change in holocene sst south of the polar front faunal assemblages suggest an early holocene meridional expansion of fauna characteristic of the modern subtropical front in the bounty gyre we suggest that such an expansion could be achieved by a reduced inflow of subantarctic surface water into the bounty gyre results from a modern analog matching platform called the past interpretation of climate tool pict suggest that the early holocene sst is most consistent with reduced westerly winds in the new zealand sector of the southern ocean

solid phases and desorption processes of arsenic within bangladesh sediments abstract arsenic is a contaminant in the groundwater of bangladesh and west bengal india where an estimated 57 million people may be drinking water with unsafe arsenic levels the source of arsenic appears to be natural solid phase arsenic in the sediments and various theories have been put forth regarding the modes of arsenic release ranging from the oxidative or reductive degradation of arsenic bearing solids to competitive ligand displacement by phosphate currently however reductive dissolution of fe iii hydr oxides and concomitant arsenic release is the most widely accepted explanation of high arsenic groundwater concentrations using micro x ray fluorescence elemental mapping and micro x ray absorption near edge structure spectroscopy we detect arsenic bearing sulfides in the aquifer sediments from our field site in munshiganj bangladesh reduction of fe and as in surface soil layers is apparent but fe iii hydr oxides are not detected in the holocene aquifer materials rapid abiotic desorption of arsenic from sediments is observed in batch experiments and positive controls with ferrihydrite dismiss the role of ferric hydr oxides in arsenic retention within the aquifer sediments based on our laboratory results we do not see evidence for ferric hydr oxide reductive dissolution at well depths in the holocene aquifer in contrast our data suggest that arsenic is only released via redox cycling in surface soils sediments and thus must then be transported to well depth through the sandy aquifer

high resolution alkenone palaeobarometry indicates relatively stable pco2 during the pliocene 3 3 to 2 8 ma temperature reconstructions indicate that the pliocene was approximately 3 c warmer globally than today and several recent reconstructions of pliocene atmospheric co2 indicate that it was above pre industrial levels and similar to those likely to be seen this century however many of these reconstructions have been of relatively low temporal resolution meaning that these records may have failed to capture variations associated with the 41 kyr glacial interglacial cycles thought to have operated in the pliocene here we present a new high temporal resolution alkenone carbon isotope based record of pco2 spanning 3 3 2 8 ma from ocean drilling program site 999 our record is of high enough resolution approx 19 kyr to resolve glacial interglacial changes beyond the intrinsic uncertainty of the proxy method the record suggests that pliocene co2 levels were relatively stable exhibiting variation less than 55 ppm we perform sensitivity studies to investigate the possible effect of changing sea surface temperature sst which highlights the importance of accurate and precise sst reconstructions for alkenone palaeobarometry but demonstrate that these uncertainties do not affect our conclusions of relatively stable pco2 levels during this interval

interhemispheric comparison of deglacial sea surface temperature patterns in atlantic eastern boundary currents abstract sediment core geob 1023 5 from the eastern south atlantic was investigated at high temporal resolution for variations of sea surface temperature sst during the past 22 kyr using the alkenone u k 37 method ssts increased by 3 5 c from about 18 c during the last ice age 21 2 cal kyr bp to about 21 5 c at 14 5 cal kyr bp this warming trend associated with the deglaciation phase was followed by a cooling event with lowest ssts near 20 c persisting for about 1000 years between 13 and 12 cal kyr bp the ssts then continued to increase to about 22 5 c at the holocene climatic optimum at 7 cal kyr bp and decreased again during the late holocene to a core top value of 19 8 c that is comparable to modern annual mean sst values when compared with alkenone sst records from the eastern north atlantic our sst record indicates continuous warming throughout the deglaciation phase in the benguela current while its northern counterpart the canary current experienced prominent cooling during heinrich event 1 h1 on the other hand for the time period corresponding to the younger dryas yd cooling event the benguela sst record exhibits a cold temperature interval that corresponds to that observed in the eastern north atlantic sst records this observation suggests that interhemispheric climate response in atlantic eastern boundary current systems was different with respect to the two abrupt climate events associated with termination i for the h1 the eastern south atlantic sst record strongly supports the hypothesis that an anti phase thermal behavior in south atlantic surface waters was forced by the slowdown of the north atlantic deep water formation during cold spells in the north atlantic in contrast the abrupt cooling in the eastern south atlantic coincident with the yd period was probably induced by more vigorous global atmospheric circulation enhancing the upwelling intensity in both eastern boundary current systems this atmospheric control may have overridden any effect caused by changes in thermohaline circulation on the south atlantic ssts during the yd which leads to the assumption that the thermohaline circulation was already much closer to its interglacial mode during the yd than during the h1

distributions of uk37 and uk37 in the surface waters and sediments of the nordic seas implications for paleoceanography in this paper we revise the application of the u and u indices as sea surface temperature sst proxies in the nordic seas in the summer of 1999 and 2000 we obtained samples of filtered particulate organic matter pom from surface waters 6 m depth of the nordic seas a number of samples were collected from polar waters with up to 80 of sea ice cover alkenones were detected in all of the major water masses of the nordic seas across a spectrum of sst values from 0 5 to 13 c and sss values from 29 6 to 35 6 psu concentrations of alkenones were similar in magnitude to those reported previously for the north atlantic and the southern ocean values of u from the new nordic seas pom data show no correlation with sst below 8 c in contrast below this temperature a linear correlation exists between u and regional sst supporting previous suggestions that overall u may be a more appropriate sst index for the region it must be noted however that u is calculated using the tetraunsaturated alkenone and the dominant control on this compound is not yet fully understood the new data highlight major differences between distributions of u and u in the water column pom and surficial sediments of the nordic seas we also examine the geographical dependence of the u versus sst relationship in the region s surficial sediments some areas are associated with unreliable sst estimates whereas in others the u versus sst relationship falls within the range of a global core top calibration it is suggested that the breakdown of the u sst relationship in some regions is due to ecological and sedimentological factors the latter relates to the extension of the habitats of alkenone producers in polar waters the former to the resuspension of sediments and laterally transported alkenone inputs this suggests that accurate alkenone derived sst estimates in the nordic seas are geographically constrained

alkenone distributions in the north atlantic and nordic sea surface waters 1 the c37 c39 alkenones were quantified in suspended particulate matter obtained from the surface waters of the north atlantic including the nordic seas over a temperature range of 4 20 c u37k values were linearly correlated to temperature over the entire range covered by our data set i e 4 20 c u37k 0 027t 0 036 r2 0 97 the compilation of water column data from the atlantic pacific and southern ocean and mediterranean sea suggests that the linear model may not be the best function for fitting u37k and in situ temperature values it also shows that suspended matter data from warm waters t 20 c are still needed to constrain the equation of the global curve high abundances of c37 4 were found in the coldest polar waters around 4 c c37 4 represented up to 35 a value that dropped to zero at temperatures above 10 c values of c37 4 were linearly correlated to temperature c37 4 3 7t 43 7 r2 0 50 and salinity c37 4 48 1s 1691 r2 0 78 further investigations from other oceanic basins are necessary to confirm these findings

temperature trends during the present and last interglacial periods a multi model data comparison though primarily driven by insolation changes associated with well known variations in earth s astronomical parameters the response of the climate system during interglacials includes a diversity of feedbacks involving the atmosphere ocean sea ice vegetation and land ice a thorough multi model data comparison is essential to assess the ability of climate models to resolve interglacial temperature trends and to help in understanding the recorded climatic signal and the underlying climate dynamics we present the first multi model data comparison of transient millennial scale temperature changes through two intervals of the present interglacial pig 8 1 2 ka and the last interglacial lig 123 116 2 ka periods we include temperature trends simulated by 9 different climate models alkenone based temperature reconstructions from 117 globally distributed locations about 45 of them within the lig and 12 ice core based temperature trends from greenland and antarctica 50 of them within the lig the definitions of these specific interglacial intervals enable a consistent inter comparison of the two intervals because both are characterised by minor changes in atmospheric greenhouse gas concentrations and more importantly by insolation trends that show clear similarities our analysis shows that in general the reconstructed pig and lig northern hemisphere mid to high latitude cooling compares well with multi model mean temperature trends for the warmest months and that these cooling trends reflect a linear response to the warmest month insolation decrease over the interglacial intervals the most notable exception is the strong lig cooling trend reconstructed from greenland ice cores that is not simulated by any of the models a striking model data mismatch is found for both the pig and the lig over large parts of the mid to high latitudes of the southern hemisphere where the data depicts negative temperature trends that are not in agreement with near zero trends in the simulations in this area the positive local summer insolation trend is counteracted in climate models by an enhancement of the southern ocean summer sea ice cover and or an increase in southern ocean upwelling if the general picture emerging from reconstructions is realistic then the model data mismatch in mid and high southern hemisphere latitudes implies that none of the models is able to resolve the correct balance of these feedbacks or alternatively that interglacial southern hemisphere temperature trends are driven by mechanisms which are not included in the transient simulations such as changes in the antarctic ice sheet or meltwater induced changes in the overturning circulation

northern and southern hemisphere controls on seasonal sea surface temperatures in the indian ocean during the last deglaciation 37 are consistently warmer than those derived from mg ca by 2 3 c except for the heinrich event 1 in addition the initial timing for the deglacial warming of alkenone sst started at 15 6 ka which lags behind that of mg ca temperatures by 2 5 kyr we argue that the discrepancy between the two sst proxies reflects seasonal differences between summer and winter rather than postdepositional processes or sedimentary biases the u k 37 sst record clearly mimics the deglacial sst trend recorded in the north atlantic region for the earlier part of the termination indicating that the early deglacial warming trend attributed to local summer temperatures was likely mediated by changes in the atlantic meridional overturning circulation at the onset of the deglaciation in contrast the glacial to interglacialsstpatternrecordedbyg rubermg ca probably reflectscoldseasonssts this indicates that the cold season ssts was likely mediated by climate changes in the southern hemisphere as it closely tracks the antarctic timing of deglaciation therefore our study reveals that the tropical southwestern indian ocean seasonal sst was closely linked to climate changes occurring in both hemispheres the austral summer and winter recorded by each proxy is further supported with seasonal sst trends modeled by atmosphere ocean general circulation models for our core site our interpretation that the alkenone and mg ca ssts are seasonally biased may also explain similar proxy mismatches observed in other tropical regions at the onset of the last termination

palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data abstract the high resolution stratigraphy of various marker compounds has been studied using gc hplc and gc ms in a 13 m gravity core recovered from the kane gap region eastern equatorial atlantic which provides a record of the glacial interglacial episodes over the last million years downhole variations in many presumed source specific components are observed e g in n alkanes from terrigenous land plants and dinosterol from dinoflagellates which may be due to perturbations or cyclicities resulting from climatic change fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial interglacial cycles recorded in the 18 o values for planktonic foraminifera thereby providing a potential organic geochemical measure of past climates these molecular abundance data can be linked to the palaeotemperature record following computer treatments using principal component and spectral analyses molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail for example through calcium carbonate dissolution

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

the importance of atmospheric input of terrestrial organic material to deep sea sediments the concentrations of lipids were determined in atmospheric particle gas and rain samples collected from the tropical north pacific to assess lipid sources transport mechanisms and fluxes to the ocean surface four lipid compound classes aliphatic hydrocarbons fatty alcohols fatty acid esters and salts all unequivocally show a terrestrial vascular plant source these aerosol lipids originate from wind erosion of asian and american soils and direct emission from vegetation the major fluxes result from rain rather than dry deposition these fluxes are large enough to have a major potential impact on the inventory of terrestrially derived lipid material found in deep sea sediments this has been showm for n alkanes fatty alcohols fatty acids total lipids and for organic carbon by comparing atmospheric and sediment trap fluxes with sediment accumulation rates it is suggested that some biogenic terrestrial material is more protected from degradation than marine derived material

primary signal ecological and environmental factors report from working group 2 alkenone based proxies are routinely used for paleoceanographic and climatologic reconstructions despite the fact that their calibration to environmental parameters is still a matter of debate significant differences are observed among culture calibrations using different strains of alkenone producers between regional field calibrations within the euphotic zone and between water column and core top based calibrations the reasons for these discrepancies are not well understood and call for further evaluation the possibility is raised that several aspects of genetics physiology and ecology of alkenone producing haptophytes may be responsible and suggestions of future research are proposed

comparison and implication of tex86 and u37k temperature records over the last 356kyr of odp site 1147 from the northern south china sea abstract proxy records from the south china sea scs have played an important role in understanding late quaternary scs environmental changes and the east asian monsoon eam variations but few long sea surface temperature sst records have been generated from the scs the recently established tex86 index provides an opportunity to generate long sst records especially for tropical oceans but the applicability and climatic interpretation of the tex86 index for the scs need further study we report and compare orbital scale resolution ca 5 3 kyr tex86 and u37k temperature records of the past 356 kyr for odp site 1147 from the northern scs both records display clear and similar glacial interglacial patterns the u37k sst fluctuated between 22 3 c and 28 3 c with a glacial interglacial difference of 4 5 c while the tex86 temperature fluctuated between 20 3 c and 25 4 c with a slightly smaller glacial interglacial difference of ca 4 c the tex86 temperature has been consistently lower than the u37k temperature over the past 356 kyr consistent with previous studies suggesting that the u37k index is a proxy for sst but the tex86 index is a proxy for subsurface temperature thus it is proposed that the temperature difference t between the u37k and tex86 records reflects mixed layer depth mld changes in the northern scs which fluctuated between 0 3 and 4 0 c with high values mostly during interglacials and lower values mostly during glacial stages mld changes in the northern scs are interpreted to be driven by eam changes with stronger winter monsoon resulting in a deeper mld and a smaller t thus the combination of u37k and tex86 records and their t can be used to reconstruct east asian winter monsoon variations as well as their influences on the hydrographic structure of the scs

a 4500 year reconstruction of sea surface temperature variability at decadal time scales off north iceland marine paleo records acquired at high temporal resolution provide critical data for testing numerical climate models and help to understand processes underlying ocean variability this study presents a unique 4500 year reconstruction of sea surface temperature sst obtained from alkenones in the north atlantic polar front area off north iceland at an average temporal resolution of 4 5 years spectral analysis of this signal shows dominant multidecadal oscillations which occurred with a stronger amplitude between 2500 and 4200 years bp hand in hand with fluctuations of bottom currents indicated by paleomagnetic proxies contemporaneous large excursions of the inter tropical convergence zone itcz are also recorded by the distant cariaco titanium time series suggesting a link with low latitude atlantic climate we speculate that the oscillations reflect changes of the meridional overturning circulation moc induced by increased enso activity

alkenones and alkenes in surface waters and sediments of the southern ocean implications for paleotemperature estimation in polar regions abstract the concentration of c37 c39 long chain alkenones and alkenes were determined in surface water and surface sediment samples from the subpolar waters of the southern ocean distributions of these compounds were similar in both sample sets indicating little differential degradation between or within compound classes the relative amounts of the tri to tetra unsaturated c37 alkenones increased with increasing temperature for temperatures below 6 c similar to the di and tri unsaturated c37 alkenones the c37 di tri and tetra unsaturated methyl alkenones are used in paleotemperature calculations via the u37k and the u37k ratios in these datasets the relative abundances of the c37 2 and the c37 3 alkenones as a proportion of the total c37 alkenones were opposite and strongly related to temperature the latter with more scatter but the abundance of the c37 4 alkenone showed no relationship with temperature the original definition of u37k includes the abundance of 37 4 in both the numerator and denominator and thus it is perhaps not surprising that there is considerable scatter in the values obtained for u37k at low temperatures of the two we suggest that u37k is the better parameter for use in paleotemperature estimations even in cold locations u37k values in the sediments fall on virtually the same regression line obtained for the water column samples of sikes and volkman 1993 indicating that their calibration is suitable for use in southern ocean sediments the comparison of water column data with sedimentary temperature estimates suggests that the alkenone distributions are dominated by contributions from the summer when the biomass of emiliania huxleyi and presumably flux to the sediment is expected to be high

combined coccolith foraminiferal and biomarker reconstruction of paleoceanographic conditions over the past 120 kyr in the northern north atlantic 59 n 23 w we present data for north atlantic core biogeochemical ocean flux study bofs 16k 59 n 23 w water depth 2370 m including coccolith flora 18o planktonic foraminiferal sea surface temperatures ssts by fa20 and simmax methods and alkenone based u37k and u37k ssts a good correlation exists between the abundances of cold water coccolith species and foraminifera and a broad correlation exists between coccolith and alkenone abundances except in the holocene reworked cretaceous coccoliths at the last glacial maximum are coincident with warm deviations of the u37k signal assessment of various calibrations of u37k and u37k with paleotemperature shows the inappropriateness of a global correlation we have produced a north atlantic u37k calibration on the basis of north atlantic data alone u37k 0 026t 0 186 which produces sst data for summer season at 0 m water depth comparable to the warm season foraminiferal ssts except during the intervals 26 36 58 65 and 100 120 ka when the alkenones indicate somewhat cooler surface waters

distribution of glycerol dialkyl glycerol tetraethers in soils from two environmental transects in the usa abstract glycerol dialkyl glycerol tetraethers gdgts of both archaeal and bacterial origin form the basis of new temperature proxies applicable to soil and lake and marine sediments in soil branched gdgts are prevalent and their abundance of methyl or cyclic groups has been calibrated to mean annual temperature mat using mbt and cbt indices however soil ph is also known to be an important variable controlling the distribution of branched gdgts precipitation amount helps control soil moisture as well as ph and soil moisture is a leading variable affecting microbial diversity and activity in soil we have evaluated the distribution of gdgts from two soil transects in the usa a dry western transect covering six western states and a wet east coast transect from maine to georgia in order to assess the effect of precipitation on the distribution of soil gdgts our results show distinctly different gdgt distributions across climatic regions with dry western soils characterized predominantly by thaumarchaeotal isoprenoid iso gdgts and as a consequence low bit index values 0 2 0 6 and moist temperate east coast transect soils expressing mostly branched br gdgts and higher bit values 0 9 1 the predominance of iso gdgts in the western soils is related to the degree of aeration which in turn is related to precipitation amount and also to soil ph we also observed a substantial increase in the offset between measured mat and mbt cbt based mat below an annual precipitation of 700 800 mm yr 1 implying an impact of precipitation amount on mbt cbt based temperature reconstruction the data suggest that while soil tetraethers work well as a temperature proxy in moist temperate regimes they do not produce reliable measurements of temperature in sediments sourced from areas with 1 precipitation moreover erosion of soils with low bit values into lacustrine or marginal marine environments will not be detected via the bit index which can potentially affect paleotemperature reconstruction from sediments and so provide erroneous estimates of soil carbon delivery bit index values also show a correlation with precipitation amount the abundance of iso gdgts in western transect soils allowed calculation of tex 86 values but no correlation was found between tex 86 calculated temperature and mean annual temperature

spatial and temporal offsets between proxy records in a sediment drift chronologies for late quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information a key premise is that microfossils and other indicators within a given sediment horizon are of equal age we show here that haptophyte derived alkenones isolated from bermuda rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera this temporal offset which is apparently due to lateral transport of alkenones on fine grained particles from the nova scotian margin markedly influences molecular estimates of sea surface temperatures more broadly the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments

flat meridional temperature gradient in the early eocene in the subsurface rather than surface ocean sea surface temperature estimates from the early eocene indicate an unusually flat meridional temperature gradient a re evaluation of the proxy used to derive these temperatures argues against this interpretation

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

seasonal sea ice cover during the warm pliocene evidence from the iceland sea odp site 907 abstract sea ice is a critical component in the arctic and global climate system yet little is known about its extent and variability during past warm intervals such as the pliocene 5 33 2 58 ma here we present the first multi proxy ip25 sterols alkenones palynology sea ice reconstructions for the late pliocene iceland sea odp site 907 our interpretation of a seasonal sea ice cover with occasional ice free intervals between 3 50 3 00 ma is supported by reconstructed alkenone based summer sea surface temperatures as evidenced from brassicasterol and dinosterol primary productivity was low between 3 50 and 3 00 ma and the site experienced generally oligotrophic conditions the east greenland current and east icelandic current may have transported sea ice into the iceland sea and or brought cooler and fresher waters favoring local sea ice formation between 3 00 and 2 40 ma the iceland sea is mainly sea ice free but seasonal sea ice occurred between 2 81 and 2 74 ma sea ice extending into the iceland sea at this time may have acted as a positive feedback for the build up of the greenland ice sheet gis which underwent a major expansion 2 75 ma thereafter most likely a stable sea ice edge developed close to greenland possibly changing together with the expansion and retreat of the gis and affecting the productivity in the iceland sea

a 5 million year comparison of mg ca and alkenone paleothermometers geochemical sea surface temperature sst proxies such as the magnesium to calcium ratio mg ca in foraminifera and the alkenone unsaturation index uk 37 are becoming widely used in pre pleistocene climate records this study quantitatively compares previously published mg ca and uk 37 data from ocean drilling program odp site 847 in the eastern equatorial pacific to assess the utility of these proxies to reconstruct tropical sst over the last 5 ma foraminiferal mg ca sst calibrations that include a dissolution correction are most appropriate at this location because they provide sst estimates for the youngest sample that are close to modern mean annual sst the long term trends in the two records are remarkably similar and confirm a 3 5 c cooling trend from the early pliocene warm period to the late pleistocene noted in previous work absolute temperature estimates are similar for both proxies when errors in the dissolution correction used to estimate sst from mg ca are taken into account comparing the two sst records at odp site 847 to other records in the region shows that the eastern equatorial pacific was 2 4 c warmer during the early pliocene compared to today

production and turnover rates of c37 alkenones in the eastern bering sea implication for the mechanism of a long duration of emiliania huxleyi bloom abstract production and turnover rates of c37 alkenones were determined by a 13c labeling technique during the emiliania huxleyi blooms in the eastern bering sea the production rates of c37 alkenones are variable in the surface water of the bering sea during emiliania huxleyi blooms ranging from 0 019 0 043 g l 1 day 1 for c37 2 and 0 057 0 16 for g l 1 day 1 c37 3 respectively the temperature difference dt between in situ temperature and uk 37 based temperature estimated by c37 alkenone unsaturation index uk 37 for seston is generally larger than the temperature difference between in situ temperature and pr uk 37 based temperature estimated by the unsaturation index of c37 alkenone production rate therefore the application of pr uk 37 determined by the 13c labeling can be suggested as a more accurate calibration of in situ temperature on the other hand the c37 alkenones concentration 3 1 g l 1 at br 10 middle shelf is 4 16 fold larger than the concentrations 0 19 0 77 g l 1 at other stations in addition the uk 37 based seawater temperature at br 10 4 0 c was much lower than the in situ temperature 7 5 c showing the largest seawater temperature difference dt this low temperature and high abundance of c37 alkenones may be the result of turbulent mixing like that caused by eddies on the continental slope area considering the existence of very low temperature and high ammonium concentration water in the water mass beneath the surface layer the uncoupling between the in situ temperature and uk 37 based seawater temperature in the middle of shelf area br 10 may indicate a link between the nutrient supply mechanism and the sustained emiliania huxleyi bloom from summer through autumn

the discrimination of pyroclastic deposits on the basis of the mossbauer spectra of their magnetites a preliminary test abstract magnetite fe3o4 has the spinel structure which has two cation sites which also contain vacancies the spinel structure is also stable over large deviations from stoichiometry fe3o4 has a phase transition at 120 k and physical properties at room temperature can be very different from those at liquid nitrogen temperature it is magnetic at room temperature and is thus easily separated magnetically from any mineral of which it is a component for these reasons it seems an ideal substance for fingerprinting minerals by mossbauer spectroscopy since it is capable of exhibiting large variations in its physical properties the room temperature mossbauer spectra of seven samples of magnetite extracted from volcanic ash were found to be sufficiently different that different sources could be distinguished by visual inspection a least squares analysis showed that the spectra could be composed of 3 relaxing six line patterns the ratios of the intensities of these patterns and ratios of their relaxation times gave 5 parameters which appear to characterize the different sources of the tephra one of these parameters appears to be a function of the temperature of crystallization of the magnetite

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