seasonal and interannual variation of coccolithophore fluxes and species composition in sediment traps north of gran canaria 29 n 15 w abstract coccolithophore flux variations in sediment traps of the time series station estoc european station for time series in the ocean canary islands located 60 nm north of gran canaria were recorded from april 1993 to december 1996 the 20 cup particle traps were deployed at 1000 and 3000 m below sea surface and sampling intervals ranged from eight days to three weeks coccolith and coccosphere fluxes at both trap depths were characterized by a strong seasonality at 1000 m maximum coccolith fluxes were reached during spring from march to april 1995 and from february to march 1996 highest coccolith fluxes of 4538 106 coccoliths m 2 d 1 occurred at the beginning of march 1996 whereas lowest values of 19 8 106 coccoliths m 2 d 1 were recorded in june 1994 total coccosphere fluxes were constantly low during most of the investigated time interval and showed only high values during the main sedimentation phases from january to march 1995 up to 6 2 106 spheres m 2 d 1 and in march 1996 36 4 106 spheres m 2 d 1 at 3000 m water depth the sedimentation pattern was rather similar to the pattern observed at 1000 m maximum coccolith and coccosphere fluxes were also reached during spring time in february 1994 8200 106 and 15 6 10 6 m 2 d 1 respectively and in march 1996 8114 106 and 32 3 10 6 m 2 d 1 respectively however total coccolith flux peaks at 3000 m were about 2 4 times higher compared to the upper traps probably due to horizontal advection from phytoplankton material from north of the study site this effect also influenced the coccolith caco3 flux estimates mean calculated coccolith caco3 fluxes ranged between 3 9 mg m 2 d 1 for the upper traps 1995 1996 and 9 9 mg m 2 d 1 for the lower traps 1996 coccoliths contributed for about 8 78 of the measured total caco3 fluxes the coccolithophore assemblages were dominated by emiliania huxleyi florisphaera profunda and gephyrocapsa ericsonii during the entire sampling period whereas all other species together generally contributed less than 40 to the total assemblages variability of species compositions at either trap depth was very low indicating similar seasonal flux patterns of the different species

long chain alkenone patterns in the baltic sea an ocean freshwater transition two different patterns of long chain alkenones are found in surficial sediments of the baltic sea which is the largest brackish water body on earth one pattern occurs in surficial sediments from the western baltic sea where surface water salinitiy is in excess of 7 7 psu it corresponds to the pattern produced by the marine coccolithophorid emiliania huxleyi with a suite of c37 di to tetra unsaturated methyl ketones and c38 di and tri unsaturated methyl and ethyl ketones a second pattern resembling that found in lake sediments in lacking c38 methyl ketones and having distinctly higher c37 4 methyl ketone concentrations dominates in surficial sediments of the eastern and northern baltic sea where salinities are lower than 7 7 psu correspondence of sea surface temperature sst estimates from the u37 and u379 indices using marine calibrations with mean sst in the euphotic zone from july august the main haptophyte growth season is poor thus these indices are not applicable as sedimentary thermometers in surficial sediments of the baltic sea the different patterns may either reflect the salinity dependent occurrence of specific alkenone producers or changes in the alkenone biosynthesis due to physiological stress caused by salinity variations furthermore advection of saline and oxygenated north sea water may transport marine algal material characterized by a marine e huxleyi like alkenone pattern into the western baltic sea thus covering the signature of the local alkenone producers with a baltic sea pattern copyright 2000 elsevier science ltd

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

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

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

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

dna and lipid molecular stratigraphic records of haptophyte succession in the black sea during the holocene abstract previous studies suggest that the coccolithophorid haptophyte emiliania huxleyi entered the black sea 3400 yrs ago and since then a coccolith ooze defined as unit i has developed unit i sediments contain long chain alkenones derived from e huxleyi whereas the alkenone distribution of the deeper coccolith free sapropel unit ii is rather unusual alkenone derived past sea surface temperature sst estimates suggest a large difference between unit ii and unit i which is likely a result of unusual biological precursors of the alkenones in unit ii here we report a high resolution stratigraphic analysis of ancient haptophyte dna to establish the holocene succession of haptophytes as sources of the alkenones in the black sea haptophytes related to brackish isochrysis spp were the initial sources of alkenones and appeared immediately after the onset of sapropel deposition 7550 yrs before present a bp as salinity increased isochrysis related haptophytes were slowly replaced by a complex suite of e huxleyi strains as sources of alkenones our paleogenetic data showed that e huxleyi colonized the black sea shortly after the onset of sapropel deposition 4000 yrs earlier than previously recognized based on their preserved coccoliths e huxleyi strains were the most likely source of the previously reported abundant and unusual c36 di unsaturated black sea alkenone strong haptophyte species and strain specific effects were observed on the level of unsaturation of alkenones which resulted in spurious alkenone derived sst estimates before 5250 a bp in contrast from 5250 a bp onwards a relatively stable haptophyte assemblage dominated by a different suite of e huxleyi strains yielded robust alkenone sst values and indicated a gradual cooling from 19 c to 15 c at the top of the record 450 a bp

sea surface temperatures of the western arabian sea during the last deglaciation 1 in this study we present a sea surface temperature sst record from the western arabian sea for the last 20 000 years we produced centennial scale d 18 o and mg ca sst time series of core niop929 with focus on the glacial interglacial transition the western arabian sea is influenced by the seasonal ne and sw monsoon wind systems lowest ssts occur during the sw monsoon season because of upwelling of cold water and highest ssts can be found in the low productivity intermonsoon season the mg ca based temperature record reflects the integrated sst of the sw and ne monsoon seasons the results show a glacial interglacial sst difference of 2c which is corroborated by findings from other arabian sea cores at 19 ka b p a yet undescribed warm event of several hundred years duration is found which is also reflected in the d 18 o record a second centennial scale high sst low d 18 o event is observed at 17 ka b p this event forms the onset of the stepwise yet persistent trend toward holocene temperatures highest mg ca derived ssts in the niop929 record occurred between 13 and 10 ka b p interglacial sst is 24c indicating influence of upwelling the onset of arabian sea warming occurs when the north atlantic is experiencing minimum temperatures the rapid temperature variations at 19 17 and 13 ka b p are difficult to explain with monsoon changes alone and are most likely also linked to regional hydrographic changes such as trade wind induced variations in warm water advection

in situ measurement of velocity stress sensitivity using crosswell continuous active source seismic monitoring abstractthe ability to characterize time varying reservoir properties such as the state of stress has fundamental implications in subsurface engineering relevant to geologic sequestration of co2 stress variation here in the form of changes in pore fluid pressure is one factor known to affect seismic velocity induced variations in velocity have been used in seismic studies to determine and monitor changes in the stress state previous studies conducted to determine velocity stress sensitivity at reservoir conditions rely primarily on laboratory measurements of core samples or theoretical relationships we have developed a novel field scale experiment designed to study the in situ relationship between pore fluid pressure and seismic velocity using a crosswell continuous active source seismic monitoring cassm system at the cranfield mississippi co2 sequestration field site we actively monitored seismic response for five days with a temporal resolution of 5 min the target was a 26 m thick inject

crustal strains in the japanese islands as deduced from dense gps array data from the nationwide continuous gps network operated by the geographical survey institute of japan were used to estimate crustal strains in the japanese islands we used horizontal velocity vectors at 610 sites for the period april 1996 to march 1997 and employed the least squares prediction method to interpolate the velocities to a uniform 7km 7km grid over japan the gridded velocities were then differentiated in space to calculate principal components of strains results clearly portray tectonic strainings of the japanese islands in one year 1 dilatational strains show that the japanese islands are under a compressive strain regime induced by the subducting oceanic plates 2 distribution of high maximum shear strains coincides with the regions of crustal activities and 3 principal axes of the strains indicate influences of e w and nw se compression due to the converging oceanic plates north south extension in kyushu is also visible

efficacy of δ18o data from pliocene planktonic foraminifer calcite for spatial sea surface temperature reconstruction comparison with a fully coupled ocean atmosphere gcm and fossil assemblage data for the mid pliocene sea surface temperature sst estimates using the 18o composition of fossil planktonic foraminifer calcite within the time slice 3 12 to 3 05 ma pliocene kaena subchron c2an1r are assessed for nine atlantic ocean sites these are compared with sst estimates from fossil assemblages for the time slab 3 29 2 97 ma and with estimates from a fully coupled ocean atmosphere general circulation model gcm for the same time interval most sst estimates derived from the 18o data indicate a cooler ocean surface than at present through the latitudinal range 69 25 n to 46 88 s at some sites the temperature difference is greater than 5 c cooler than at present this contrasts with sst estimates from fossil assemblages that give warmer than present temperatures at mid to high latitudes and similar temperatures in the tropics and with the gcm which predicts ssts warmer than at present across all latitudes for this time interval difficulties interpreting the ecology of fossil foraminifer assemblages and inaccurate estimates of mid pliocene seawater 18o composition 18osw at some sites may partly produce the temperature discrepancy between isotope based and fossil based sst estimates but do not adequately explain the cool signal of the former we interpret the cool sst estimates from the 18o data to be the product of a calcite formed at a level deep within or below the ocean mixed layer during the life cycle of the foraminifera b secondary calcite with higher 18o formed in the planktonic foraminifer tests in sea bottom pore waters although these effects differ between sites secular and temporal oceanographic trends are preserved in the primary calcite formed in the mixed layer near the ocean surface witnessed by the latitudinal variation in estimated ssts reconstructing accurate mid pliocene ssts with much of the existing published oxygen isotope data probably requires a detailed re assessment of taphonomy particularly at tropical sites this study also indicates that methods for estimating atlantic pliocene 18osw need to be refined

auto correlation analysis of coda waves from local earthquakes for detecting temporal changes in shallow subsurface structures the 2011 tohoku oki japan earthquake for monitoring temporal changes in subsurface structures i propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers which probably contain more body waves than surface waves use of coda waves requires earthquakes resulting in decreased time resolution for monitoring nonetheless it may be possible to monitor subsurface structures in sufficient time resolutions in regions with high seismicity in studying the 2011 tohoku oki japan earthquake mw 9 0 for which velocity changes have been previously reported i try to validate the method kik net stations in northern honshu are used in this analysis for each moderate earthquake normalized auto correlation functions of surface records are stacked with respect to time windows in the s wave coda aligning the stacked normalized auto correlation functions with time i search for changes in phases arrival times the phases at lag times of 1 s are studied because changes at shallow depths are focused temporal variations in the arrival times are measured at the stations based on the stretching method clear phase delays are found to be associated with the mainshock and to gradually recover with time the amounts of the phase delays are 10 on average with the maximum of about 50 at some stations the deconvolution analysis using surface and subsurface records at the same stations is conducted for validation the results show the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths the auto correlation analysis seems to have an accuracy of about several percent which is much larger than methods using earthquake doublets and borehole array data so this analysis might be applicable in detecting larger changes in spite of these disadvantages this analysis is still attractive because it can be applied to many records on the surface in regions where no boreholes are available

biological and optical properties of mesoscale coccolithophore blooms in the gulf of maine two coccolithophore blooms in the gulf of maine were studied in 1988 and 1989 each bloom was about 50 000 km in area and confined to the top 20 m of the water column maximal cell concentrations were 2 000 cells ml and coccolith densities of 3 x lo5 ml were observed the coccolith cell ratio was highest in the bloom center region of most intense reflectance and lowest at the bloom periphery an indication of varying organic vs inorganic c production chlorophyll concentrations were generally low within the bloom and no relation could be observed between major nutrients and coccolithophore abundance backscattered light was profoundly affected by coccolith density and was slightly wavelength dependent we calculated total backscattering as well as backscattering bh caused exclusively by coccoliths and derived the algorithm relating coccolith density to backscattering although cells were efficient light absorbers coccoliths showed negligible light absorption diffuse attenuation was lowest in the green and blue green part of the visible spectrum at the center of the bloom coccoliths contributed 75 of the backscattering signal and 50 of the beam attenuation signal the most accurate way to estimate coccolith concentrations via remote sensing is to measure water leaving radiance in the green wavebands the coccolithophore emiliania huxleyi lohm hay et al mohler class prymnesiophyceae is thought to be the most abuni present address lockheed engineering and sciences p o box 58561 houston texas 77258 acknowledgments many thanks to capt donald bradford and the crew of the rv argo maine for ship handling and help with sampling shiptime for leg 1 of the 1988 cruise was provided by charles s yentsch howard gordon provided the light scattering photometer as well as the software for calculating total backscattering robert evans and jody splain arranged for the transfer of avhrr data from miami to bigelow lab janet campbell and thor aarup analyzed the satellite data during the cruise and relayed the information to the ship stephen groom calculated the visible band reflectance from the avhrr data jeffrey brown tracy skinner and albert chapin were instrumental in completing many measurements at sea and in the laboratory dave townsend coordinated the ctd measurements elin haugen and r r l guillard provided an inverted microscope for the 1988 cruise christodant calcifying organism on earth westbroek et al 1985 of all coccolithophore species e huxleyi is numerically dominant and can be found from tropical to subarctic regions of the atlantic extending into waters with temperatures o c off spitsbergen furthermore it is the only coccolithophore species that is regularly abundant in neritic continental shelf seas including the gulf of maine marshall 1984 the distributions of this species and others in the surface waters tend to match those in the sedpher garside ran the nutrient analyses patricia matrai and kay kilpatrick provided logistical support for the 1989 cruise aline rodrigues digitized the light scattering data for input into the software program the comments of h gordon as well as two anonymous reviewers improved the manuscript the office of naval research ocean optics program and the national science foundation biological oceanography program supported this work this is bigelow laboratory contribution 9 1003

calculation of coccolith volume and its use in calibration of carbonate flux estimates abstract estimates of coccolith volume help in determining total coccolith carbonate fluxes and the relative contributions of various coccolith species it is argued here that the best approach to deriving such coccolith volumes is to calculate shape factors k s for each species separately based on reconstruction of cross profiles and to determine mean sizes from measurement of size variation in the sample of interest then volume k s l 3 values of k s are given for the most important extant coccolith species based on reconstruction of cross sections followed by calculation of a volume of rotation using an iterative routine implemented in an image analysis package substantial errors ca 50 are inevitable in such calculations but the resultant data are nonetheless of value coccolith assemblages from north atlantic 47 n 20 w jgofs 1989 sediment trap samples are analysed as a test case calculated coccolith pic fluxes constitute 30 80 of the chemically determined total pic fluxes

in situ observations of velocity changes in response to tidal deformation from analysis of the high frequency ambient wavefield we report systematic seismic velocity variations in response to tidal deformation measurements are made on correlation functions of the ambient seismic wavefield at 2 8 hz recorded by a dense array at the site of the pinon flat observatory southern california the key observation is the dependence of the response on the component of wave motion and coda lapse time measurements on the vertical correlation component indicate reduced wave speeds during periods of volumetric compression whereas data from horizontal components show the opposite behavior compatible with previous observations these effects are amplified by the directional sensitivities of the different surface wave types constituting the early coda of vertical and horizontal correlation components to the anisotropic behavior of the compliant layer the decrease of the velocity volumetric strain sensitivity s with indicates that this response is constrained to shallow depths the observed velocity dependence on strain implies nonlinear behavior but conclusions regarding elasticity are more ambiguous the anisotropic response is possibly associated with inelastic dilatancy of the unconsolidated low velocity material above the granitic basement however equal polarity of vertical component velocity changes and deformation in the vertical direction indicate that a nonlinear poisson effect is similarly compatible with the observed response pattern peak relative velocity changes at small are 0 03 which translates into an absolute velocity strain sensitivity of s 5 10 3 and a stress sensitivity of 0 5 mpa 1 the potentially evolving velocity strain sensitivity of crustal and fault zone materials can be studied with the method introduced here

sea surface temperature and productivity records for the past 240 kyr in the arabian sea abstract deep sea sediments of two cores from the western ty93 929 p and the southeastern md900963 arabian sea were used to study the variations of the indian monsoon during previous climatic cycles core ty93 929 p was located between the sw monsoon driven upwelling centres off somalia and oman which are characterized by large seasonal sea surface temperature sst and particle flux changes by contrast core md900963 was situated near the maldives platform an equatorial ocean site with a rather small sst seasonality less than 2 c for both cores we have reconstructed sst variations by means of the unsaturation ratio of c37 alkenones which is compared with the 18o records established on planktonic foraminifera in general the sst records follow the 18o variations with an sst maximum during oxygen isotope stage 5 5 the last interglacial at about 120 130 kyr and a broad sst minimum during isotope stage 4 and 3 3 approximately 40 50 kyr the sst difference between the holocene and the last glacial maximum lgm is of the order of 2 c in both cores the ssts during isotope stage 6 are distinctly higher by 1 2 c than the cold sst minima during the last glacial cycle lgm and stage 3 to reconstruct qualitatively the past productivity variations for the two cores we used the concentrations and fluxes of alkenones and organic carbon together with a productivity index based on coccolith species florisphaera profunda relative abundance within each core there is a general agreement between the different palaeoproductivity proxies in the southeastern arabian sea core md900963 glacial stages correspond to relatively high productivity whereas warm interstadials coincide with low productivity all time series of productivity proxies are dominated by a cyclicity of about 21 23 kyr which corresponds to the insolation precessional cycle a hypothesis could be that the ne monsoon winds were stronger during the glacial stages which induced deepening of the surface mixed layer and injection of nutrients to the euphotic zone by contrast the records are more complicated in the upwelling region of the western arabian sea core ty93 929 p this is partly due to large changes in the sedimentation rates which were higher during specific periods isotope stages 6 5 4 5 2 3 and 2 unlike core md900963 no simple relationship emerges from the comparison between the 18o stratigraphy and productivity records the greater complexity observed for core ty93 929 p could be the result of the superimposition of different patterns of productivity fluctuations for the two monsoon seasons the sw monsoon being enhanced during interglacial periods whereas the ne monsoon was increased during glacial intervals a similar line of reasoning also could help explain the sst records by the superimposition of variations of three components global atmospheric temperature and sw and ne monsoon dynamics

aeolian cliff top deposits and buried soils in the white river badlands south dakota usa aeolian deposits in the north american great plains are important sources of holocene palaeo environmental records although there are extensive studies on loess and dune records in the region little is known about records in aeolian cliff top deposits these are common on table mesa edges in the white river badlands these sediments typically have loam and sandy loam textures with dominantly very fine sand 0 5 1 organic carbon and 0 5 5 caco3 some of these aeolian deposits are atypically coarse and contain granules and fine pebbles buried soils within these deposits are weakly developed with a c and a ac c profiles beneath these are buried soils with varying degrees of pedogenic development formed in fluvial aeolian or colluvial deposits thickness and number of buried soils vary however late holocene soils from several localities have ages of approximately 1300 2500 and 3700 14c yrs bp the 1300 14c yr bp soil is cumulic with a thicker and lighter a horizon soils beneath the cliff top dep

alkenone distributions and hydrogen isotope ratios show changes in haptophyte species and source water in the holocene baltic sea the baltic sea a dynamic marginal marine basin experienced a number of large changes in salinity during the holocene as a result of fluctuations in global and local sea level related to melting of glacial ice sheets and subsequent isostatic rebound these changes likely had pronounced effects on the species composition of haptophytes a common phytoplankton group found in the baltic sea this dynamic environment provides the ideal setting to study how species change impacts distribution and hydrogen isotope ratios of long chain alkenones h c37 haptophyte specific biomarkers here we analyzed the aforementioned parameters in holocene sediments covering the contrasting hydrological phases of the baltic sea alkenone distributions changed with different baltic sea salinity phases suggesting that species shifts coincide with salinity change h c37 values show two major shifts one in the middle of the freshwater ancylus lake phase 10 6 to 7 7 ka and a second at the transition from the brackish littorina sea phase 7 2 to 3 ka into the fresher modern baltic 3 ka to the present the first shift represents a significant enrichment of 50 which cannot be explained by salinity or species changes only at this time the isotopically depleted ice sheets had melted and only the relatively enriched freshwater source remained the second shift coincident with a change in distribution is likely caused by a change in species composition alone these findings show that hydrogen isotope ratios of long chain alkenones combined with their relative distribution can be used to reconstruct changes in source water

alkenones in cretaceous black shales blake bahama basin western north atlantic abstract we here report the discovery of unusual distributions of long chain alkenones c37 c42 in two cretaceous black shales from the blake bahama basin western north atlantic these sediments are cenomanian c 95 ma and mid albian c 105 ma in age thus significantly extending the geological range of these compounds the precise source of these lipids is as yet unknown although they may derive from an ancient ancestor of emiliania huxleyi

temperature dependency of long chain alkenone distributions in recent to fossil limnic sediments and in lake waters distribution patterns of c37 and c38 polyunsaturated long chain alkenones lcas serve as proxies for the determination of paleotemperatures for marine surface waters we studied recent subrecent and late glacial holocene sediments from germany austria russia and the u s to test for a correspondence between lca distribution and surface water temperature in limnic systems previously reports of lca occurrence were restricted to sediments of 6 wide distributed freshwater and alkaline lakes in this study 13 of 27 investigated lakes contained lcas in surface sediments with concentrations varying between 12 to 205 g g toc late glacial to holocene sediment sequences from lake steisslingen and lake wummsee germany lake pichozero russia and brush lake u s a contained abundant lcas with averaged concentrations of 33 to 7536 g g toc for the first time we observed the occurrence of lcas within in the water column of oligotrophic lake stechlin ne germany alkenones were restricted to the zone of maximum chlorophyll concentration within the water column indicating that lcas have a biosynthetic origin and can be attributed to phototrophic micro algae attempts to identify the producing organism however were not successful culture experiments allow various phytoplankton to be excluded as producers alkenone producing algae are evidently of small size hindering microscopical identification lcas commonly occur in high concentrations in late glacial sediments mainly during the cold period of the younger dryas whereas the holocene usually is devoid of polyunsaturated alkenones the episodic occurrence of lcas restricts their utility as proxies for continuous geological records furthermore lack of microscopical verification and the episodic distribution allow for different producers of unsaturated alkenones in recent and late glacial sediments an empirical relationship between lca distribution and temperature was observed in fossil sediments from lake steisslingen there is a good correspondence between uk37 and the temperature controlled 18o isotope ratio of lake chalk comparison of lca patterns obtained from the uppermost centimetres of lake sediments with averaged summer surface water temperatures of the lakes studied demonstrates a trend of covariance r2 uk 37 0 90 uk37 0 67 n 9 hence the same mechanism that causes temperature dependence of lca patterns in marine systems might be effective in limnic settings identification of alkenone producers and their culture under controlled temperature are still mandatory before lcas can be routinely applied as paleotemperature proxy in limnic systems

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

marine paleoclimatic proxies a shift from qualitative to quantitative estimation of seawater parameters abstract understanding past climate during contrasting boundary conditions can help in assessing imminent climate changes marine sediments offer a vast archive of past climate various indirect methods called proxies are used to infer principal climate parameters like temperature salinity productivity monsoon intensity ocean circulation seawater ph and others from the marine sediments the relationship between a climate parameter and marine paleoclimate proxy may vary from region to region additionally the marine proxies are often affected by more than one climate parameter thus making it difficult to assess the change in any particular parameter from a single proxy diagenetic alteration can also significantly affect the parameter proxy relationship a growing emphasis now is on quantifying changes in key climatic parameters in the past proxies for quantitative estimation of seawater temperature runoff sea level and ph are now fairly well established similar robust quantitative proxies for dissolved oxygen concentration and productivity are however still being developed additionally the uncertainty associated with quantitative estimation of past climate has to be reduced therefore continuous efforts are being made to develop novel paleoclimate proxies and to evaluate existing proxies in different regions of the world oceans

precessional forcing of nutricline dynamics in the equatorial atlantic climate control of nutricline depth in the equatorial atlantic can be monitored by variations in the abundance of the phytoplankton species florisphaera profunda a conceptual model based on in situ evidence associates high abundances of f profunda with a deep nutricline and low abundances with a shallow nutricline a 200 000 year record of f profunda relative abundances obtained from a deep sea core sited beneath the region of maximum equatorial divergence at 10 w has 52 percent of its variance centered on the 23 000 year precessional band cross spectral analysis between the signals of f profunda and sea surface temperature independently derived from zooplankton species shows their 23 000 year cycles to be coherent and nearly in phase abundance minima of f profunda coincide with times of december perihelion whereas abundance maxima coincide with june perihelion these relations indicate that nutricline dynamics in the divergence region of the equatorial atlantic are controlled by variations in the tropical easterlies forced by the precessional component of orbital insolation on time scales greater than 10 000 years

environmental controls on long chain alkenone occurrence and compositional patterns in lacustrine sediments northwestern china abstract long chain alkenones occur widely in lacustrine settings and their compositions are potential proxies for reconstructing terrestrial paleoclimatological and paleoenvironmental changes however factors influencing their occurrence abundance compositional pattern and unsaturation indices are not well understood here we investigated the alkenones in surface sediments from 19 lakes in northwestern china as well as potential environmental factors of the lakes 12 contain long chain alkenones 3 have the isomeric c 37 3 alkenone and 3 have very low abundance of alkenones our results show that salinity has a substantial influence on the occurrence concentration and compositional pattern most of the compositions are dominated by tri unsaturated compounds with c 38 methyl ketones absent the predominance of c 37 4 and the occurrence of a c 37 3 isomer are suggested to be responses to low salinity as both are only found in the three alkenone containing freshwater lakes the proportion of c 37 4 varies by up to 50 and shows a negative relationship with salinity within the surveyed region an arched relationship of alkenone content and salinity is apparent with no or very low contents of alkenones in freshwater salinity 100 g l environments the u 37 k index is suggested to be a better terrestrial temperature proxy than u 37 k as u 37 k values from lakes containing elevated alkenone content are all within the ranges of published u 37 k temperature calibrations and u 37 k values show a weak positive relationship with salinity

no analog planktonic foraminiferal faunas in the glacial southern south china sea implications for the magnitude of glacial cooling in the western pacific warm pool sea surface temperature sst estimates in the sediment core md01 2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern south china sea scs during the last glacial maximum lgm relative to modern temperatures these results are in contrast to substantial cooling of 2 5 c inferred by geochemical uk 37 mg ca ratios and terrestrial proxies from the western tropical pacific region using multivariate statistics we show that the glacial southern scs harboured unique planktonic foraminiferal assemblages that have no modern analogs analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from mg ca data but that this signal is subdued by superimposed variations in the relative abundance of pulleniatina obliquiloculata and neogloboquadrina pachyderma dextral these species occur in glacial samples at proportions that are not observed in the calibration data set the glacial high abundance of n pachyderma dextral are interpreted to reflect a seasonal winter inflow of cold surface water from the northeast via the bashi strait due to the combined effects of an intensified winter monsoon a southward shift of the polar front and the eastward migration of the kuroshio current in contrast processes controlling the high relative abundances of p obliquiloculata during the lgm may be unique to the southern scs we propose a scenario involving a stronger winter mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow dwelling warm indicators to establish larger populations during the lgm our results indicate that a no analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical mg ca ratios alkenone unsaturation index marine proxies is a more likely scenario

culturing of the first 37 4 predominant lacustrine haptophyte geochemical biochemical and genetic implications long chain alkenones lcas are potential biomarkers for quantitative paleotemperature reconstructions from lacustrine environments however progress in this area has been hindered because the conditions necessary for the growth of haptophytes responsible for alkenone distributions in lake sediments the predominance of c37 4 lca are not known here we report the first enrichment culturing of a novel haptophyte phylotype hap a from lake george nd that produces predominantly c37 4 lca hap a was enriched from its resting phase collected from deep sediments rather than from water column samples in contrast enrichments from near surface water yielded a different haptophyte phylotype hap b closely related to chrysotila lamellosa and pseudoisochrysis paradoxa which does not display c37 4 lca predominance similar enrichments have been reported previously the lca profile in sediments resembles that of enrichments containing hap a suggesting that hap a is the dominant alkenone producer of the sedimentary lcas in enrichments increased lighting appeared to be crucial for triggering alkenone production both u37k and u38k indices show a promising positive relationship with temperature for hap a in enrichments but the offset from the environmental calibration suggests that other factors e g the growth stage or nutrients may influence the absolute u37k value based on 18s rrna gene analyses several lakes from the northern great plains as well as pyramid lake nv and tso ur tibetan plateau china contain the same two haptophyte phylotypes analysis of surface sediment from the great plains lakes show the hap a type lca distribution whereas pyramid and tso ur show the hap b type distribution waters of the great plain lakes are dominated by sulfate ions whereas those pyramid and tso ur are dominated by carbonate ions suggesting that the sulfate to carbonate ratio may be a determining factor for the dominance of the hap a and hap b phylotypes in natural settings

biomarkers for aerobic methanotrophy in the water column of the stratified gotland deep baltic sea filter samples from the oxic zone and suboxic zone of the physically stratified water column and sediment samples of the gotland deep baltic sea were analyzed for bacteriohopanepolyol bhp and phospholipid fatty acid plfa concentrations in total eight bhps were identified with the greatest diversity in the suboxic zone there 35 aminobacteriohopane 31 32 33 34 tetrol aminotetrol and 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol whose concentrations decreased concurrently from the lower to the upper suboxic zone indicated type i methanotrophic bacteria and thus aerobic oxidation of methane the presence and activity of type i aerobic methanotrophic bacteria was further supported by the presence of 13c depleted plfas specifically 16 1 8c and 16 1 5c 13c as low as 41 2 however the relative amount of methanotroph specific compounds was low aminopentol 0 2 of total bhps 16 1 8c ca 0 5 of total plfas suggesting a minor contribution of aerobic methanotrophic bacteria to the particulate organic matter the distinctive bhp pattern in the suboxic zone including aerobic methanotroph biomarkers and a tentative marker for a pelagic redoxcline putative 22s isomer of the ubiquitous 22r bacteriohopanetetrol bht was mirrored in the sediment samples our data indicate that a major portion of the sedimentary hopanoids of the gotland deep is sourced from the suboxic part of the water column via an effective but unknown transport mechanism

hydrogen isotopes in individual alkenones from the chesapeake bay estuary hydrogen isotope ratios of individual alkenones from haptophyte algae were measured in suspended particles and surface sediment from the chesapeake bay cb estuary eastern usa in order to determine their relationship to water dd values and salinity dd values of four alkenones mec37 2 mec37 3 etc38 2 etc38 3 from particles and sediments were between 165 and 221 and increased linearly r 2 0 7 0 9 with water dd values from the head to the mouth of the bay individual alkenones were depleted in deuterium by 156 188 relative to water the mec37 alkenones were consistently enriched by 12 relative to the etc38 alkenones and the di unsaturated alkenones of both varieties were consistently enriched by 20 relative to the tri unsaturated alkenones all of the increase in alkenone dd values could be accounted for by the water dd increase consequently no net change in alkenone water d h fractionation occurred as a result of the salinity increase from 10 to 29 this observation is at odds with results from culture studies with alkenone producing marine coccolithophorids and from two field studies one with a dinoflagellate sterol in the cb and one with a wide variety of lipids in saline ponds on christmas island that indicate a decline in d h fractionation with increasing salinity why d h fractionation in alkenones in the cb showed no dependence on salinity while d h fractionation in cb dinsoterol decreased by 1 per unit increase in salinity remains to be determined two hypotheses we consider to be valid are that i the assemblage of alkenone producing haptophytes changes along the bay and each species has a different sensitivity to salinity such that no apparent trend in aalkenone water occurs along the salinity gradient and ii greater osmoregulation capacity in coastal haptophytes may result in a diminished sensitivity of alkenone water d h fractionation to salinity changes

increased seasonality during the intensification of northern hemisphere glaciation at the pliocene pleistocene boundary 2 6 ma abstract near the pliocene pleistocene neogene quaternary boundary during marine isotope stage mis 104 at around 2 6 ma the intensification of northern hemisphere glaciation inhg was marked by a southward shift of the north atlantic current and arctic front and a concurrent drop in sea surface temperature sst in the mid latitudes of the north atlantic here we evaluate two mg ca based sea surface temperature reconstructions for the 2 78 2 52 ma interval using the planktonic foraminifera globigerina bulloides and globigerinoides ruber white sensu stricto as the biotic carriers sstbul and sstrub and a reconstruction based on the alkenone saturation index sstalk the mg ca based sst estimates begin to diverge from one another significantly during mis g3 2 66 ma culminating during mis 104 2 60 ma and remaining distinctly different for the remaining 80 kyr of the studied interval the magnitude of this divergence sstrub bul is caused mainly by a decrease in sstbul with sstrub remaining relatively constant we attribute this difference to a drop in sst during the early spring blooming season of g bulloides that was less pronounced during the late summer blooming season of g ruber using sstrub bul as a seasonality indicator we show that seasonality increased significantly owing to a drop in early spring temperatures from mis 104 onwards and peaked during glacial episodes maximum seasonality occurred during mis 104 in coincidence with a major expansion of the circum atlantic ice sheets particularly the north american ice sheet this expansion appears to have had a critical influence on global climate and especially seasonality

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

seismic evidence of nonlinear crustal deformation during a large slow slip event in mexico repeated cross correlations of ambient seismic noise indicate a long term seismic velocity change associated with the 2006 m7 5 slow slip event sse in the guerrero region mexico because the sse does not radiate seismic waves the measured velocity change cannot be associated with the response of superficial soil layers to strong shaking as observed for regular earthquakes the perturbation observed maximized at periods between 7 s and 17 s which correspond to surface waves with sensitivity to the upper and middle crust the amplitude of the relative velocity change 10 3 was much larger than the volumetric deformation 10 6 at the depths probed 5 20 km moreover the time dependence of the velocity perturbation indicated that it was related to the strain rate rather than the strain itself this suggests that during strong slow slip events the deformation of the overlying crust shows significant nonlinear elastic behavior

a natural pyrolysis experiment hopanes from hopanoic acids abstract the formation or generation of hopanes are important processes during both the natural heating of organic rich sediments and laboratory pyrolysis experiments molecular maturity parameters as well as the amounts ng g rock of the c31 hopanes and c30 c32 hopanoic acids were quantified in a jurassic silty shale horizon isle of skye scotland as a function of distance from an igneous intrusion the maturity profiles of the homohopanes and the hopanoic acids are comparable there is also a correlation between the decreasing amounts of c30 c32 hopanoic acids and concomitant increases in c29 c31 hopanes suggesting that free hopanoic acids could be one potential source of hopanes in this particular horizon other possible sources could include hopanoic acids that are bound into the macromolecular fraction

paleoceanography of the mid pleistocene the fossil record of the pleistocene calcareous nannoplankton indicates that during the mid pleistocene 0 93 1 25 my occurred an episode of overwhelming dominance of smallgephyrocapsa during this episode normally abundant large size specimens of this genus mainlygephyrocapsa oceanica were virtually excluded from the phytoplankton of tropical and subtropical oceans the best modern analog of this dominantly smallgephyrocapsa assemblage is the subpolaremiliania huxleyi assemblage which implies that nutrient content was significantly greater and water temperature was lower in the photic water column of the tropical oceans than they are today increased equatorial upwelling in the oceans on a scale much greater than today may explain the above pattern to achieve such broad equatorial upwelling there must be a source and a drive for cold dense water the arctic ocean which was probably seasonally free of ice during this interval of the mid pleistocene is capable of providing the requisite source as well as a drive for the inferred equatorial upwelling the energy balance of a predominantly ice free arctic ocean requires an approximately three to seven fold increase of hydrospheric heat transport from the north atlantic to the arctic ocean which dictates a corresponding or even greater increase in the volume of warm water entering the arctic ocean at the surface and cold dense water exiting at depth to the north atlantic such enhanced dense water formation in the arctic ocean could drive the intensified equatorial upwelling implied by the smallgephyrocapsa dominance interval if the above scenario is correct then the climate of the earth s northern hemisphere during the mid pleistocene may have been very different from the younger pleistocene climate one manifestation of this difference may be the mid pleistocene shift in climatic cycle periodicity from 40 ky to 100 ky another important aspect is that the enhanced greenhouse effect expected during the next century because of an increase of atmospheric co2 is thought to lead directly to melting of the arctic ocean ice cover and of the greenland ice sheet thus the greenhouse arctic ocean and its attendant ocean circulation would resemble the inferred mid pleistocene conditions

pleistocene wind system in eastern austria and its impact on landscape evolution abstract during cold periods in the quaternary the intracontinental pannonian basin was part of the european periglacial zone and aeolian erosion had a profound effect in shaping the landscape geomorphologically most effective winds were channelled between the alps and carpathians and entered the pannonian basin from the nw to assess the nature of meteorological conditions producing these winds field studies were carried out in the foreland of the basin entrance in eastern austria as a result we report on the first bedrock ventifacts from austria and aeolian sand occurrence in the bohemian massif through a compilation of published data and field work the distribution of ventifacts was mapped and appears to be controlled primarily by available lithologies palaeo wind directions were identified using mesoforms of bedrock ventifacts especially flutes the acquired air flow directions are accordant with the orientation of erosional landforms on soft sediments and form a coherent system with westerly to north westerly winds in the west which turn towards the entrance of the pannonian basin in the east there are no directions referring to the direct influence of katabatic winds produced on the ice sheet instead the wind system must have been driven by synoptic scale patterns like the polar front the narrow distribution of wind directions suggests that the low altitude air flow system was relatively stable even without a funnelling topography as in the pannonian basin though the alps could have acted to deflect the winds osl data from the bohemian massif indicate aeolian sand movement during the late pleistocene the results provide data for aeolian transport studies among them for loess provenance analyses and can be used as input for climate models

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

photosynthetic fractionation of 13c and concentrations of dissolved co2 in the central equatorial pacific during the last 255 000 years carbon isotopically based estimates of co2 levels have been generated from a record of the photosynthetic fractionation of 13c is equivalent to epsilon p in a central equatorial pacific sediment core that spans the last approximately 255 ka contents of 13c in phytoplanktonic biomass were determined by analysis of c37 alkadienones these compounds are exclusive products of prymnesiophyte algae which at present grow most abundantly at depths of 70 90 m in the central equatorial pacific a record of the isotopic composition of dissolved co2 was constructed from isotopic analyses of the planktonic foraminifera neogloboquadrina dutertrei which calcifies at 70 90 m in the same region values of epsilon p derived by comparison of the organic and inorganic delta values were transformed to yield concentrations of dissolved co2 is equivalent to c e based on a new site specific calibration of the relationship between epsilon p and c e the calibration was based on reassessment of existing epsilon p versus c e data which support a physiologically based model in which epsilon p is inversely related to c e values of pco2 the partial pressure of co2 that would be in equilibrium with the estimated concentrations of dissolved co2 were calculated using henry s law and the temperature determined from the alkenone unsaturation index u k 37 uncertainties in these values arise mainly from uncertainties about the appropriateness particularly over time of the site specific relationship between epsilon p and 1 c e these are discussed in detail and it is concluded that the observed record of epsilon p most probably reflects significant variations in delta pco2 the ocean atmosphere disequilibrium which appears to have ranged from approximately 110 microatmospheres during glacial intervals ocean atmosphere to approximately 60 microatmospheres during interglacials fluxes of co2 to the atmosphere would thus have been significantly larger during glacial intervals if this were characteristic of large areas of the equatorial pacific then greater glacial sinks for the equatorially evaded co2 must have existed elsewhere statistical analysis of air sea pco2 differences and other parameters revealed significant p 0 01 inverse correlations of delta pco2 with sea surface temperature and with the mass accumulation rate of opal the former suggests response to the strength of upwelling the latter may indicate either drawdown of co2 by siliceous phytoplankton or variation of co2 si oh 4 ratios in upwelling waters

alkenone distribution impacts the hydrogen isotopic composition of the c37 2 and c37 3 alkan 2 ones in emiliania huxleyi the hydrogen isotopic composition delta d of long chain alkenones derived from haptophyte algae has recently been applied as paleo sea surface salinity proxy but this application has been complicated by reported differences in delta d of individual c 37 alkenones of up to 45 parts per thousand here we show that this difference in d h ratios is the result of the desaturation of the c 37 2 alkenone to form the c 37 3 alkenone and related to the relative abundance of the individual alkenones and therefore the u 37 k for the purpose of reconstructing paleo sea surface salinities it is recommended to determine the delta d of combined rather than individual c 37 alkenones

controls on alkenone unsaturation ratios along the salinity gradient between the open ocean and the baltic sea abstract alkenone unsaturation ratios of sedimentary lipids are used as a geochemical proxy for sea surface temperatures and interest is growing in their potential as indicators of different water masses and possibly of salinity we analyzed the abundance of unsaturated c37 to c38 ketones in lipid extracts of 57 surface sediment 0 1 cm samples along a salinity gradient from 8 to 33 psu in the transition from the skagerrak to the baltic sea nw europe in addition to surface sediments we analyzed alkenones in suspended particulate matter at 13 stations over a gradient in salinity from 25 to 33 psu during a bloom of the coccolithophore emiliania huxleyi alkenones were detected in all samples suspended matter and sediment with variable contributions of the tetra unsaturated c37 alkenone compound c37 4 range from 2 to 10 of total c37 alkenone content comparing the alkenone unsaturation index u37k and c37 4 data to climatological sea surface temperature and sea surface salinity data sets revealed that sst estimated from u37k of saline end members samples from the skagerrak is in the general range of modern sst during bloom periods of haptophytes at salinities below 30 psu c37 4 increases to above 5 and the unsaturation ratios cease to be related to climatological annual or seasonal sea surface temperatures on the other hand the c37 4 appears to be inversely and significantly correlated to salinity highest c37 4 proportions in the inner baltic sea are caused by an unidentified organism but in the transition area at salinities down to 10 psu the producer apparently is e huxleyi the suspended matter data together with those from the water column support the hypothesis of changing biosynthesis of alkenones under salt stress by the coccolithophore e huxleyi but constrain the maximum of c37 4 attributable to salt stress to 10 of all c37 alkenones

calcareous nannoplankton in surface sediments of the east china sea abstract twenty eight species of coccoliths were identified in surface sediments of the east china sea the species composition of the coccolith assemblages is similar to that of the north pacific water mass but differs from the latter by a greater dominance of emiliania huxleyi and gephyrocapsa oceanica together making up over 90 specimens the coccolith species composition shows considerable differences between the continental shelf and the okinawa trough areas reflecting different water masses on the other hand the coccolith content in sediments is apparently controlled largely by the deposition rate of terrigenous material

extended hopanoids in peat environments abstract detailed results are presented for the distributions of triterpenoid alkanes acids and alcohols of the hopane family in ten samples of peat from three environments and of contributing organisms in the case of lyne of skene scotland extended hopanoids of the and configuration appear at the very earliest stage of diagenesis such environments appear to be characterised by particular distributions of c 32 hopanoid acids and alcohols and a high preponderance of the c 31 hopane

seismic wave velocity changes and stress build up in the crust of the kanto tokai region we show there are large temporal p wave velocity changes in the crust of the kanto tokai region in japan from repeated observations of explosions we find that the variation is the response of the crustal rocks to two components of stress change the tidal stress and the secular stress accumulation the inferred annual rate of fractional velocity change year caused by the stress accumulation in the upper crust is of the order of 10 3 year the results indicate that the build up of stress in the crust can be monitored by precise observations of seismic wave velocities

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

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

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 and coccolithophorid species changes in late quaternary sediments from the walvis ridge implications for the alkenone paleotemperature method abstract sea surface temperatures ssts derived from the alkenone u37 record of quaternary sediments may be subject to bias if algae with different temperature sensitivities have contributed to the sedimentary alkenone record the alkenone derived sst records are usually based on a u37 temperature relationship which was measured in culture experiments using the coccolithophorid emiliania huxleyi f g prahl l a muehlhausen and d l zahnle 1988 further evaluation of long chain alkenones as indicators of paleoceanographic conditions geochim cosmochim acta 52 2303 2310 to assess possible effects of past species changes on the u37 temperature signal we have analysed long chain alkenones and coccolithophorids in a late quaternary sediment core from the walvis ridge and compared the results to sst estimates extracted from the 18o record of the planktonic foraminifer globigerinoides ruber alkenones and isotopes were determined over the entire 400 kyr core record while the coccolithophorid study was confined to the last 200 kyr when the most pronounced changes in alkenone content occurred throughout oxygen isotope stages 6 and 5 species of the genus gephyrocapsa were the predominating coccolithophorids e huxleyi began to increase systematically in relative abundance since the stage 5 4 transition became dominant over gephyrocapsa spp during stage 3 and reached the highest abundances in the holocene carbon normalized alkenone concentrations are inversely related to the relative abundances of e huxleyi and directly related to that of gephyrocapsa spp suggesting that species of this genus were the principal alkenone contributors to the sediments nevertheless sst values obtained from the u37 temperature relationship for e huxleyi compare favourably to the isotope derived temperatures the recently reported u37 temperature relationship for a single strain of gephyrocapsa oceanica j k volkman s m barrett s i blackburn and e l sikes 1995 alkenones in gephyrocapsa oceanica implications for studies of paleoclimate geochim cosmochim acta 59 513 520 produces unrealistically high sst values indicating that the temperature response of the examined strain is not typical for the genus gephyrocapsa this is supported by the c37 c38 alkenone ratios of the sediments which are comparable to average ratios reported for e huxleyi but significantly higher than for the g oceanica strain most notably the general accordance of the alkenone characteristics between sediments and e huxleyi persists through stages 8 to 5 and even in times that predate the first appearance of this species 268 ka h r thierstein k r geitzenauer and b molfino 1977 global synchroneity of late quaternary coccolith datum levels validation by oxygen isotopes geology 5 400 404 our results suggest that u37 temperature relationships based on e huxleyi produce reasonable paleo sst estimates even for late quaternary periods when this species was scarce or absent because other alkenone synthesizing algae e g of the genus gephyrocapsa responded similarly to temperature changes

application of carboxylic acid biomarkers as indicators of biodegradation and migration of crude oils from the maracaibo basin western venezuela abstract the acid fractions of 15 crude oils of different degrees of maturity biodegradation and origin from the maracaibo basin western venezuela were analyzed by high resolution gas chromatography mass spectrometry gc ms to determine their usefulness as indicators of biodegradation and oil migration acyclic as well as tri and pentacyclic hopanoic monocarboxylic acids were identified and quantified for this purpose the total acidity as well as the ratio of tricyclic to pentacyclic acids were good parameters of biodegradation in these oils when used in conjunction they differentiated mixed oils biodegraded with non biograded and early generated oils from others contrary to previous reports hopanoic acids has were found to be morre resistant to biodegradation than their alkane counterparts the isomeric distribution of the has as well as the carbon preference index cpi and the c 28 c 18 ratio of the n acids were found to be useful in determining the migration histories of the oils

coccolithophore fluxes in the norwegian greenland sea seasonality and assemblage alterations abstract coccolithophore fluxes were investigated by sediment trap studies at two well separated oceanographic sites in the norwegian and greenland seas from 1990 to 1992 each trap mooring comprised traps at 500 and 1000 m water depth and 300 m above the seafloor both sites were characterized by a strong seasonality in coccolithophore fluxes in the norwegian sea fluxes were about 10 to 20 times higher than in the greenland sea maximum fluxes 13 106 ind m 2d 1 for the norwegian sea and 2 4 106 ind m 2d 1 for the greenland sea were reached during high sedimentation phases in late summer and autumn the settling assemblages represented already highly altered remnants of the former living communities dominant species were emiliania huxleyi in the norwegian sea and coccolithus pelagicus in the greenland sea despite severe alterations the coccolithophore assemblages of each site were characterized by a distinct signature reflecting the local oceanography the settling assemblages underwent only minor alterations during sinking from 500 to 1000 m water depth by contrast resuspension and lateral advection within an extensive bottom nepheloid layer strongly influenced the assemblages of the deep sediment traps 300 m above the seafloor wiping out the distinct seasonality in coccolithophore fluxes and diminishing the differences in assemblage compositions between the two sites

late miocene atmospheric co2 concentrations and the expansion of c4 grasses the global expansion of c4 grasslands in the late miocene has been attributed to a large scale decrease in atmospheric carbon dioxide co2 concentrations this triggering mechanism is controversial in part because of a lack of direct evidence for change in the partial pressure of co2 pco2 and because other factors are also important determinants in controlling plant type distributions alkenone based pco2 estimates for the late miocene indicate that pco2 increased from 14 to 9 million years ago and stabilized at preindustrial values by 9 million years ago the estimates presented here provide no evidence for major changes in pco2 during the late miocene thus c4 plant expansion was likely driven by additional factors possibly a tectonically related episode of enhanced low latitude aridity or changes in seasonal precipitation patterns on a global scale or both

dynamics of a holocene cliff top dune along mountain river northwest territories canada abstract the dynamics of a cliff top dune system located at the foot of the mackenzie mountains was reconstructed by radiocarbon dating and tree ring analysis of forest paleosols in eolian sediments the first evidence of eolian activity dates to ca 3000 yr b p when the breaching of a bedrock sill initiated the erosion of glaciofluvial deposits that resulted in the exposure of a 75 m high cliff of erodible sediment sandy sediment eroded from the cliff by katabatic winds from the mackenzie mountains buried a mature forest growing on alluvial sediments despite a minor eolian event between 750 and 860 cal yr a d dune development began ca 1100 cal yr a d and has been marked by two major sedimentation periods between ca 1100 cal yr a d and 1460 a d and from 1865 to present detailed analysis of tree morbidity and mortality indicates that the dune progressed at an average rate of 78 cm yr for the last century dune dynamics are directly related to slope activity that controls the episodic nature of sediment availability and to the katabatic wind regime comparison of the dune dynamics and paleoclimatic data suggest a possible influence of warm climate on eolian activity

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

mid chain diols and keto ols in se atlantic sediments a new tool for tracing past sea surface water masses abstract long mid chain diols and keto ols in se atlantic surface sediments have been studied in relation to the properties of the overlying surface waters the strongest change in compound composition occurs over the angola benguela front 14 16 s south of the front 1 13 and 1 14 diols notably the 1 14c 28 and 1 13c 30 homologs increase relative to 1 15 diols the 1 13c 30 keto ol is almost absent north of the front these changes probably reflect differences in sea surface temperature persistence of stratification and upwelling at opposite sides of the front elevated relative abundances of the 1 15c 32 diol and 1 15c 32 keto ol below the congo river plume 6 s may be outflow related which should be tested on other river plumes lower relative abundances of 1 15 diols close to walvis bay might relate to a higher upwelling intensity compared to the other sites investigated the applicability of the observed surface patterns is tested down core for the penultimate deglaciation the temporal changes in diol and keto ol composition not only have their spatial counterpart in the se atlantic surface sediments they are also readily interpretable on the basis of the modern diol and keto ol assemblages as well as the palaeoenvironmental reconstructions based on other proxies

development of a cliff top dune indicated by particle size and geochemical characteristics rubjerg knude denmark particle size and geochemical data have been used to investigate the development of a large cliff top dune at rubjerg knude located on the western coast of jutland denmark textural parameters and geochemical ratios provided useful indicators of the dune sediment provenance and mode of evolution of the dune the dune sediments themselves showed no significant spatial particle size trends and reflect a number of processes including grainfall wind ripple migration and avalanching grainflow which formed a high proportion of the deposits on both the stoss and lee sides of the present dune fine grainfall sediments which have accumulated to form a sandplain in the lee of the dune show fining and improved sorting with distance and extend more than 2 km downwind of the dune crest comparison of the textural and geochemical data from rubjerg knude and other locations on the jutland coast indicates that although there is a contribution of sand to the dune from local marine sources the main source of sand to the cliff top dune and sand plain sediments has been provided by the wind erosion of the underlying cliffs which are composed of weichselian age sandy glaciofluvial and glaciolacustrine deposits optically stimulated luminescence dating indicated an apparent age for the sand at the base of 274 14 years if this date is reliable it suggests that accumulation of the aeolian sand in this area began within approximately the last 300 years map and photographic evidence indicate that the modern high dune only began to form after 1885 apparently associated with an acceleration in the rate of coastal cliff retreat

climatic influences on the paleogene evolution of alkenones application of the alkenone paleotemperature proxy uk 37 for marine sediments is typically constrained by three factors i an absence of alkatrienones in sediments deposited where ocean temperatures exceed 28 c ii loss of alkenones in thermally altered sediments and iii poor preservation of alkenone signals due to oxidative degradation in addition there appears to be a temporal limit on the occurrence of alkatrienones which are conspicuously absent in all alkenone containing sediments from the early aptian to the immediate aftermath of the early eocene climatic optimum eeco when they first appeared in arctic ocean sediments compilation of reported and previously unpublished alkenone distributions for the paleogene coupled with assessment of co occurring calcareous nannoplankton genera within the noelaerhabdaceae provide evidence that evolutionary developments in alkenone occurrences include biosynthetic responses likely triggered by climate change the timing of emergence of alkatrienones post eeco and their subsequent appearance at all latitudes during the middle eocene accompanies expansion of the calcareous nannoplankton genus reticulofenestra coincident with significant climate driven changes in oceanic conditions including i modification of trophic structure associated with weakened thermal stratification ii higher productivity facilitated by enhanced nutrient influx and iii changes in seasonality initially at high latitudes related to greater latitudinal temperature gradients collectively these changes would serve to favor eurythermal eurytrophic algae like reticulofenestra with a biomechanism to store energy through production of lipid bodies rich in alkenones during episodes of higher nutrient availability this ability likely enhanced the viability of this marine haptophyte when nutrients were limiting ultimately ensuring its evolutionary success

late quaternary aeolian dunes on the presently humid blue mountains eastern australia abstract sand dunes on the newnes plateau 1000 m a s l west of sydney were active during the last glacial maximum the scattered sand dunes are forested under the modern humid temperate climate regime dune types range from parabolic to transverse lee dunes and sand sheets or patches all point to the presence of conditions marginal for aeolian activity made possible through wind acceleration on windward slopes ready sand supply from the weathered sandstone of the plateau and sparse vegetation cover modern climate envelopes of sand dune activity in australia predict that unrealistically drier conditions are necessary to allow wind transport at this site only additional impediments to plant growth such as lower temperature and lower atmospheric carbon dioxide concentrations appear to allow the necessary conditions for dune formation these observations and conclusions extend our understanding of the extremes of the lgm climate in humid eastern australia confirming that the widespread treeless vegetation was also sparse even in areas that today have annual rainfall above 1000 mm

the fate of coccoliths at 48 n 21 w northeastern atlantic abstract as part of the joint global ocean flux study program jgofs north atlantic bloom experiment nabe coccolithophore fluxes were recorded over one year period from april 1989 to april 1990 three vertically moored sediment traps synchronized on a 14 day interval were deployed at 48 n 21 w at three water depths at 1 2 and 3 7 km sea floor at 4 4 km we present the results on the vertical variability of coccolith and coccosphere fluxes through the water column calcium carbonate was the largest component of the total mass flux followed by particulate organic matter and opal coccolith and coccosphere seasonal fluxes followed the seasonality of the biogeochemical particle fluxes at all three depths with maxima occurring during the spring particle bloom the decrease in correlation between coccosphere and coccolith fluxes with depth from r 0 98 at 1 km depth to 0 60 at 3 7 km depth documents that disaggregation of the coccospheres occurs during settling in the deeper part of the water column between 1 and 3 7 km water depth annual coccosphere and coccolith fluxes were 1 5 108 and 0 9 10 11 m 2 year 1 respectively at 1 km depth or 3 1 108 and 1 4 10 11 m 2 year 1 including the spring 1990 episode for the 3 7 km trap the corresponding values were 0 5 108 and 1 1 1011 0 6 108 and 1 1 1011 including the partially recorded spring 1990 episode the slight increase in coccolith numbers with water depth can be explained by coccosphere disintegration and lateral influx nevertheless selective dissolution of delicate coccolith species from 1 to 3 7 km water depth occurs e g relative abundances of oolithothus fragilis coccoliths decrease from 3 at 1 km to less than 0 5 at 3 7 km water depth emiliania huxleyi gephyrocapsa muellerae calcidiscus leptoporus and coccolithus pelagicus constitute from 65 at 1 km depth to 95 at 3 7 km depth of the total coccolith assemblages the same four coccolith taxa dominate the fossil assemblages in the underlying surface sediments selective dissolution continues in the sediments most notably the abundance of the solution resistant species c leptoporus increases from 10 to 15 in the trap samples to 15 40 in the sediments annual flux of calcium carbonate in sediment trap samples accounts for about 60 of the total annual mass flux with the coccolith fraction m being about 45 of the annual carbonate flux mean value of 41 at 1 km and 50 at 3 7 km water depth the correlation between the m caco 3 and the calculated coccolithophore and calcisphere caco3 fluxes decreases with depth r 0 92 at 1 km and r 0 86 at 3 7 km indicating that partial dissolution and fragmentation of the delicate less calcified coccolithophore and planktic foraminifera species occurs during settling this fine fragmentation of biogenic caco3 can contribute to the m fraction causing the decrease of correlation with the calculated caco3 fluxes being based only on the flux of intact coccoliths and calcispheres

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

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

a continuous record of holocene eolian activity in west greenland eolian landforms are widespread alongside proglacial valley sandurs in west greenland and comprise low relief sand sheets climbing dunes and upland loess sedimentary facies mainly reflect distance to outwash source zones and the influence of vegetation cover the sediments show stratification types typical for poorly to moderately vegetated sand sheets alternately laminated silt peat sequences and unstratified loess twenty five accelerator mass spectrometry 14c dates provide the basis for the chronostratigraphy of the inland eolian deposits 14c dates from interstratified sand sheets suggest that the bulk of eolian sands were deposited prior to 3400 cal yr b p and after 550 cal yr b p this two phase formation for the inland dunes most likely reflects local changes in proglacial floodplain development and meltwater rerouting associated with a significant recession of the greenland ice sheet during the mid holocene climate optimum subsequent floodplain regeneration and renewed sand sheet formation after 550 cal yr b p followed when the ice margin readvanced to its present position in contrast atmospheric deposition of regionally derived silt in upland peat mires has been continuous since at least 4750 cal yr b p silt influx data demonstrate a strongly episodic history of the intensity of eolian activity over the past five millennia which tentatively reflects alternating periods of winter aridity associated with the variable incursion of maritime air masses over the interior ice free areas of west greenland

coccolithophores in the equatorial atlantic ocean response to seasonal and late quaternary surface water variability abstract the present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial atlantic data from a range of different samples from the plankton surface sediments as well as sediment cores are shown and compared with each other in general the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns cell densities reached a maximum of up to 300 103 coccospheres l in the upwelling area of the equatorial atlantic here emiliania huxleyi is the dominant species with relatively high cell numbers whereas umbellosphaera irregularis and umbellosphaera tenuis are characteristic for oligotrophic surface waters although they are observed in high relative abundances these species only occur in low absolute numbers the lower photic zone is dominated by high abundances and considerable cell numbers of florisphaera profunda the geographical distribution pattern of coccoliths in surface sediments reflects the conditions of the overlying surface water masses however abundances of the oligotrophic species umbellosphaera irregularis and umbellosphaera tenuis are strongly diminished causing an increase in relative abundance of the lower photic zone taxa florisphaera profunda and gladiolithus flabellatus during the past 140 000 years the surface water circulation of the equatorial atlantic has changed drastically as can be seen from changes in the coccolithophore species composition absolute coccolith numbers as well as coccolith accumulation rates significant increases in coccolith numbers and accumulation rates is observed in the southern equatorial atlantic during the last glacial interval oxygen isotope stages 2 4 which we attribute to enhanced upwelling intensities and advection of cool nutrient rich waters at this site in the western equatorial atlantic we observe an opposite trend with decreasing numbers of coccoliths during glacial periods which probably is caused by a deepening of the thermocline

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

sedimentary alkenone distributions reflect salinity changes in the baltic sea over the holocene the baltic sea has had a complex salinity history since the last deglaciation here we show how distributions of alkenones and their d values varied with past fluctuations in salinity in the baltic sea over the holocene by examining a holocene record 11 2 0 1 cal kyr bp from the arkona basin major changes in the alkenone distribution i e changes in the fractional abundance of the c37 4 me alkenone the c38 2 et alkenone and a c36 2 me alkenone the latter which has not been reported in the baltic sea previously correlated with known changes in salinity both alkenone distributions and hydrogen isotopic composition suggest a shift in haptophyte species composition from lacustrine to brackish type haptophytes around 7 7 7 2 cal kyr bp corresponding with a salinity change that occurred when the connection between the basin and the north sea was re established a similar salinity change occurred in the black sea previously published alkenone distributions and their d values from the black sea were used to reconstruct holocene changes in surface water salinity and hence it was shown that the unusual c36 2 alkenone dominates the alkenone distribution at salinities of 2 8 ppt g kg this information was used to corroborate the interpretations made about salinity changes from the data presented for the baltic sea low and variable salinity waters in the baltic sea over the holocene have led to a variable alkenone producing haptophyte community composition including low salinity adapted species hindering the use of the unsaturation ratios of long chain alkenones for sea surface temperature reconstruction however these alkenone based indices are potentially useful for studying variations in salinity regionally as well as in the past

preservation and diagenesis of hopanoids in recent lacustrine sediments of priest pot england abstract absolute concentrations of various bio and geohopanoids have been determined in a 24 cm long core from anoxic recent sediments of priest pot a small highly productive lake in the english lake district samples were soxtherm extracted derivatised by methods targeted at specific hopanoid groups and quantified by gc ms periodic acid sodium borohydride treatment was used to cleave the side chains of highly functionalised hopanoids producing products more amenable to our detection methods biohopanoids are extremely abundant totalling up to 3000 g g dry sediment particularly those with composite or highly penta and hexa functionalised side chains suggesting that these are important precursors to sedimentary hopanoids in priest pot downcore biohopanoid abundance profiles show a general diagenetic decline with a marked dip at 5 8 cm which we interpret as a change in bacterial input since this is most marked in the composite hopanoids rather than bacteriohopanetetrol we suggest that these two hopanoid groups have at least partly different sources and may thus have potential as environmental markers the geohopanoids are also abundant totalling up to 1700 g g dry sediment being dominated by the and bishomohopanoic acids and bishomohopanol and hop 17 21 ene downcore plots show no apparent conversion of free bio to geohopanoids with depth which suggests that incorporation into kerogen may be commencing at an early diagenetic stage in the sediments

coccolithophore export production species composition and coccolith caco3 fluxes in the ne atlantic and abstract coccolithophores were examined in two sediment traps deployed for one year april 1989 to april 1990 at approximately 1 km water depth in the subtropical ne atlantic at 34 n 21 w station nabe 34 and in the temperate ne atlantic 48 n 21 w station nabe 48 as part of the jgofs north atlantic bloom experiment nabe at both stations maximum coccolith and coccosphere fluxes were recorded during local spring bloom periods the average coccolith and coccosphere fluxes at nabe 34 were 1 12 10 9 m 2 d 1 and 4 90 10 6 m 2 d 1 respectively at this station coccoliths from 51 taxa were identified a marked seasonal change was noticed in relative abundances of emiliania huxleyi and deep photic zone species e huxleyi dominated during spring while in late autumn the coccolith assemblage was dominated by florisphaera profunda and the coccosphere assemblage by g flabellatus and algirosphaera spp emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assemblages with 69 and 64 respectively at nabe 48 the average daily fluxes were significantly lower with 3 88 10 8 coccoliths m 2 d 1 and 8 45 10 5 coccospheres m 2 d 1 and only 36 taxa were recorded in the trap samples emiliania huxleyi was the dominant species in the coccolith assemblage throughout the year with 72 and showed maximum fluxes during spring 1990 coccolithus pelagicus exhibited a distinct seasonal pattern with maximum fluxes in early june 1989 probably related to the development of a mesoscale cyclonic eddy in the vicinity of the trap site holococcolithophore fluxes were highest during maximum sea surface temperatures in summer the coccosphere assemblage was dominated by gephyrocapsa spp syracosphaera spp and e huxleyi estimated caco3 fluxes of coccoliths coccospheres and calcareous dinophytes were compared with the caco3 content in the fine m fraction the annual mass estimated caco3 flux of coccoliths and coccospheres was 5 1 g m 2 yr at nabe 34 and 2 7 g m 2 yr at nabe 48 and that of calcareous dinophytes 0 9 and 0 1 g m 2 yr respectively these summed mass estimated values contributed on average only 55 at nabe 34 and 60 at nabe 48 to the fine fraction caco3

alkenone distribution in lake van sediment over the last 270 ka influence of temperature and haptophyte species composition abstract fossil long chain alkenones have been used for several decades to reconstruct past ocean surface water temperatures and gained recent interest as a paleotemperature proxy for continental lake settings however factors besides temperature can affect alkenone distributions in haptophyte algae and alkenone compositions can differ between haptophyte species alkenone biosynthesizing haptophyte algae are genetically much more diverse in lakes than in the marine realm and species level variations in alkenone compositions could have implications for alkenone paleothermometry here we performed a paired analysis of alkenone distributions and haptophyte species compositions using ancient dna in up to 270 ka old sediments of lake van in turkey to reveal a possible species effect on fossil alkenone distributions and paleotemperature estimates the same predominant haptophyte in lake van today prevailed also since the last 100 ka however a calibration of alkenone paleotemperature especially in the oldest analyzed intervals is complicated due to a more complex haptophyte species composition predominated by a haptophyte lvhap 6 which is phylogenetically different from sequences recovered from currently existing lakes including lake van and from haptophyte species existing in culture the predominance of lvhap 6 coincided with the presence of alkenone mec38 3 and relatively high mec37 3 4 2 4 and mec38 4 5 ratios 3 0 uk37 index values in the sediment core over the last 270 ka reflect relative changes in past temperature and are additionally linked to haptophyte species composition a sustained period of high salinity as indicated by pore water salinity measurements could potentially have triggered the succession of haptophytes as sources of alkenones in lake van

using repeated sources to quantitatively determine temporal change of medium properties theory and an example 1 we develop a theory of using difference wavefields of repeated sources to locate and quantify temporal medium change and apply the theory to locate temporal change of seismic properties beneath the japan subduction zone using repeated earthquakes our theory states the difference wavefields of two repeated sources in a temporally changed medium can be equivalently treated as wavefields propagating from conceptual sources with their location at the place of temporal change and their strengths equal to the product of magnitude of medium property change and magnitude of the initial wavefields from the repeated sources when the medium change extends to a finite region the conceptual sources become volumetric sources distributed over the region of the medium change and propagating in the direction of the initial wave the conceptualization establishes a theoretical framework for possible applications of using difference wavefields to locate and quantify temporal medium changes in geological sciences ultrasonic experiments civil engineering and medical imaging we search repeating earthquakes occurring in the japan subduction zone formulate an empirical procedure to extract the difference wavefields between repeating earthquakes and determine temporal change of seismic properties using a back projection method we locate the temporal change of seismic properties beneath the japan subduction zone to be at 37 2 n 142 e and estimate the magnitude of the conceptual body force associated with the temporal change to be 1 15 1010n or as a reference a 0 87 density change for an assumed volume of temporal change of 103 km3

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

time dependent seismic tomography summary of methods for measuring temporal changes in seismic wave speeds in the earth seismic tomography is among those that offer the highest spatial resolution 3 d tomographic methods are commonly applied in this context by inverting seismic wave arrival time data sets from different epochs independently and assuming that differences in the derived structures represent real temporal variations this assumption is dangerous because the results of independent inversions would differ even if the structure in the earth did not change due to observational errors and differences in the seismic ray distributions the latter effect may be especially severe when data sets include earthquake swarms or aftershock sequences and may produce the appearance of correlation between structural changes and seismicity when the wave speeds are actually temporally invariant a better approach which makes it possible to assess what changes are truly required by the data is to invert multiple data sets simultaneously minimizing the difference between models for different epochs as well as the rms arrival time residuals this problem leads in the case of two epochs to a system of normal equations whose order is twice as great as for a single epoch the direct solution of this system would require twice as much memory and four times as much computational effort as would independent inversions we present an algorithm tomo4d that takes advantage of the structure and sparseness of the system to obtain the solution with essentially no more effort than independent inversions require

long chain alkenones in baltic sea surface sediments new insights abstract c 37 alkenones produced by certain haptophytes of the isochrysidales are valuable sedimentary biomarkers used to estimate sea surface temperature sst in the open ocean however in coastal seas the role of salinity gradients on alkenone producing species and sst estimates is poorly known alkenones were analyzed in surface sediments from the marine skagerrak region and the entire brackish baltic sea three types of alkenone distribution patterns were identified type a distribution which resembles the distribution in emiliania huxleyi type b distribution which is similar to ruttnera lamellosa isochrysis galbana and pseudoisochrysis paradoxa distributions although these haptophytes are absent from the baltic sea and type c distribution which is also found in worldwide lake sediments these types of distribution are apparent in the percentage of c 37 4 alkenone c 37 4 which is significantly negatively correlated to sea surface salinity sss the distribution of alkenones very likely results from distinct alkenone producing haptophytes whose spatial distribution is ultimately related to sss as supported by the hydrogen isotope fractionation between alkenones and water u 37 k and u 37 k correlate more significantly than u 37 k with both sst and sss probably due to the superimposed effect of changing alkenone producing species the application of u 37 k and u 37 k as sst proxies results in unrealistic holocene temperature records for the southern baltic sea but c 37 4 as a sss proxy reveals reasonable salinity changes interestingly a c 32 hopanoic acid was found abundantly as the methyl ester in the ketone fractions and may represent a marker for cyano bacterial biomass in the baltic sea

salinity changes in the central baltic sea nw europe over the last 10000 years we attempt a reconstruction of salinity levels of the central baltic sea based on diatom assemblages the isotopic composition of organic matter and sedimentological expression of anoxia over the last 10 000 years we use the data to investigate the dependence of salinity levels on climate evolution and isostasy changes in salinity of surface and deep waters were most pronounced from 8400 to approximately 5000 cal bp density stratification between salty deep and fresher surface waters caused the frequent development of anoxic conditions and deposition of laminated sediments on large parts of the sea floor in the central baltic sea and dramatic changes in organic carbon accumulation rates from 5000 to 3100 cal bp the salinity of the basin decreased oxygenation of deep sea floors was improved and fertility of the sea surface was significantly reduced this is reflected by low accumulation rates of organic carbon in bioturbated sediments since 2800 cal bp salinity rose again and anoxic periods were more common even though the major steps in environmental evolution in the baltic sea coincide with known patterns of climatic change of the north atlantic realm over the last 10 000 years we find no conclusive evidence for synchronous changes or linear responses on submillennial timescales however we note that major variations in our salinity records agree with temporal patterns of reconstructed summer warmth and winter precipitation in southern scandinavia both types of record suggest that climate in the mid holocene was far from stable our data also confirm that climate evolution over the late holocene had significant impact on environmental conditions in the baltic sea

plankton in the norwegian greenland sea from living communities to sediment assemblages an actualistic approach a synoptic study is carried out to reconstruct the development of the plankton community in the late quaternary in the norwegian greenland sea it comprises quantitative analyses of coccolithophores dinoflagellate cysts diatoms and radiolarians an actualistic approach is applied to evaluate the different fossil records of these plankton groups the preliminary results of the current investigation are reported here

phylogenetic diversity and evolutionary relatedness of alkenone producing haptophyte algae in lakes implications for continental paleotemperature reconstructions alkenones have been found in an increasing number of lakes around the world making them a promising new tool for continental paleoclimate reconstruction however individual lakes may harbor different species of haptophyte algae with different sensitivities to temperature variations thus presenting a significant challenge to the use of lacustrine alkenones for paleotemperature reconstructions to explore the extent of lacustrine haptophyte diversity we conducted the first comprehensive phylogenetic and geochemical survey of lacustrine alkenone producers we sampled 15 alkenone containing lake surface sediments from a variety of geographic locales and inferred identities of environmental sequences using 18s ribosomal rna rrna gene based phylogenies for two lakes brayaso in southwest greenland and tso ur on the tibetan plateau we also analyzed both surface and downcore sediments to characterize haptophyte populations through time in parallel with phylogenetic analyses we determined the alkenone distributions including c37 c38 ratios and the presence absence of c38 methyl ketones and c40 compounds in all the samples the resulting alkenone profiles from this study do not all align with traditional marine versus coastal lacustrine alkenone profiles additionally our genetic data indicate the presence of multiple haptophyte species from a single lake sediment sample these distinct haptophyte populations could not be discerned from the alkenone profiles alone these results show that alkenone profiles are not a reliable way to assess the haptophyte algae in lakes and that dna fingerprinting is a preferred approach for species identification although closely related haptophyte species or subspecies may not warrant different temperature calibrations our results emphasize the importance of genetic data for inferring haptophyte identities and eventually selecting alkenone temperature calibrations for paleoclimate reconstructions

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