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

geochemistry of peruvian near surface sediments sixteen short sediment cores were recovered from the upper edge ueo within wo and below bo the oxygen minimum zone omz off peru during cruise 147 of r v sonne solids were analyzed for major trace elements total organic carbon total inorganic carbon total sulfur the stable sulfur isotope composition 34 s of pyrite and sulfate reduction rates srr pore waters were analyzed for dissolved sulfate sulfide and 34 s of sulfate in all cores highest srr were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and or diffusion of sulfate from bottom water 34 s of dissolved sulfate showed only minor downcore increases strong 32 s enrichments in sedimentary pyrite to 48 vs v cdt are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction manganese and co are significantly depleted in peruvian upwelling sediments most likely due to mobilization from particles settling through the omz whereas release of both elements from reducing sediments only seems to occur in near coastal sites cadmium mo and re are exceptionally enriched in wo sediments 600 m water depth high re and moderate cd and mo enrichments are seen in bo sediments 600 m water depth re mo ratios indicate anoxic and suboxic conditions for wo and bo sediments respectively cadmium and mo downcore profiles suggest considerable contribution to ueo wo sediments by a biodetrital phase whereas re presumably accumulates via diffusion across the sediment water interface to precipitation depth uranium is distinctly enriched in wo sediments due to sulfidic conditions and in some bo sediments due to phosphorites silver transfer to suboxic bo sediments is likely governed by diatomaceous matter input whereas in anoxic wo sediments ag is presumably trapped due to sulfide precipitation cadmium cu zn ni cr ag and t1 predominantly accumulate via biogenic pre concentration in plankton remains rhenium sb as v u and mo are enriched in accordance with seawater te availability lead and bi enrichment in ueo surface sediments is likely contributed by anthropogenic activity mining accumulation rates of toc cd mo u and v from peruvian and namibian sediments exceed those from the oman margin and gulf of california due to enhanced preservation off peru and namibia copyright 2004 elsevier ltd

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

the organic geochemistry of peru margin surface sediments ii paleoenvironmental implications of hydrocarbon and alcohol profiles we assess the utility of sedimentary hydrocarbons and alcohols as indicators of short term changes in depositional conditions in the coastal peruvian upwelling regime at 15 s the distribution of 35 lipids n alkanes n alkanols hopanols keto ols lycopane phytol stenols stanols sterenes and tetrahymanol in a l m dated core from 253 m water depth are interpreted by 1 a principal components analysis and 2 a consideration of individual source specific biomarkers profiles of odd carbon number n alkanes c25 c33 and even carbon number n alkanols c24 c28 reflect changes in the contribution of terrigenous sediment relative to marine sediment during deposition as indicated by the correlations between these lipids and inorganic indicators of terrigenous clastic debris the n alkane carbon preference index cpi provides a less sensitive record of fluctuations in the terrestrial input than the concentration profiles of the individual n alkanes and n alkanols and these lipids are not well correlated with the historical el nino record the similarity of all the stenol profiles measured and the lack of concordance between these profiles and inorganic indicators of terrigenous input suggest that any fluctuations in the abundance of higher plant stenols are obscured by the larger marine contribution of these compounds similarities between the profiles of total organic carbon toc and cholestanol cholesterol are consistent with stenol hydrogenation being influenced by the sediment redox conditions

molecular stratigraphy of the santa barbara basin comparison with historical records of annual climate change abstract the molecular record of 20th century climatic variability in laminated sediments of the santa barbara basin has been compiled distributions and abundance profiles of alkenones and selected sterols reveal annual oscillations in sea surface temperatures and phytoplankton productivity positive excursions in alkenone temperature profiles coincide with all major 20th century el nino events recording oceanic warming downcore abundance profiles for dinosterol brassicasterol cholesterol and alkenones reflect productivity trends in phytoplankton and illustrate the comparative resilience of their molecular records series of subsurface concentration maxima for dinosterol a dinoflagellate derived sterol appear synchronous with regional historical reports of dinoflagellate blooms

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

coupled north atlantic slope water forcing on gulf of maine temperatures over the past millennium to investigate ocean variability during the last millennium in the western gulf of maine gom we collected a 142 year old living bivalve arctica islandica l in 2004 and three fossil a islandica shells calibrated 14cams 1030 78 ad 1320 45 ad 1357 40 ad for stable isotope and growth increment analysis a statistically significant relationship exists between modern gom temperature records shell isotope derived 30 m r 0 79 p 0 007 prince 5 50 m r 0 72 p 0 019 boothbay harbor sst r 0 76 p 0 011 and labrador current lc transport data from the eastern newfoundland slope during 1993 2003 in all cases as lc transport increased gom water temperatures decreased the following year decadal trends in the north atlantic oscillation nao and the atlantic multidecadal oscillation amo influence gom water temperatures in the most recent period with water temperatures decreasing during nao and amo negative modes most likely linked to lc transport and gulf stream interaction mean shell derived isotopic changes 18oc during the last 1 000 years were 0 47 and likely reflect a 1 2 c cooling from 1000 ad to present based on these results we suggest that observed cooling in the gom during the last millennium was due to increased transport and or cooling of the lc and decreased gulf stream influence on the gom

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

geochemical implications of the lipid composition of thioploca spp from the peru upwelling region 15 s thioploca a genus of colorless sulphur oxidizing filamentous bacteria constitutes as much as 80 of the biomass in dysaerobic surface sediments o2 0 1 ml l bottom water in the coastal upwelling regimes of peru and chile the lipid composition of thioploca collected from sediments from the oxygen minimum zone in the peru upwelling region near 15 s is presented here and we provide the first assessment of the influence of thioploca on organic compound distributions in upwelling regime sediments since marine species of thioploca have been found only in dysaerobic surface sediments of upwelling regimes biomarkers for this organism may be useful in identifying similar depositional conditions in the sedimentary record thioploca dry was found to be 3 8 4 1 wt lipid three fatty acids cis 16 1 9 16 0 and cis 18 1 11 accounted for 69 72 of this lipid hydroxy fatty acids hopanoids and hydrocarbons were conspicuously absent from the thioploca the thioploca was found to contain cyclolaudenol a c31 sterol with an unusual structure diagenetic alteration products of this sterol may serve as markers for thioploca input to sedimentary organic matter and hence as markers for paleo upwelling depositional environments in the sedimentary record

accumulation and biological mixing of peru margin sediments abstract rates of sediment accumulation and biological particle mixing in eight cores from the peru shelf have been estimated by application of uranium series disequilibrium techniques and radiocarbon dating activities of 210pb 226ra 234th and 238u have been determined in closely spaced intervals in each sediment core biological particle mixing coefficients were determined via a two box advection diffusion steady state mixing model based on the distribution profiles of excess 210pb and in some cases excess 234th activities the sedimentation rates estimated were in the order of a few millimeters yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen minimum zone estimated biological mixing coefficients were in the order of 100 101 cm2 yr 1 for the surface mixed layer and 10 1 100 cm2 yr 1 for the layer below sediment slumping appears to have affected the 210pb distribution of two or three of our cores

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

composition of organic matter in subducted and unsubducted sediments off the nicoya peninsula costa rica odp leg 170 sites 1039 and 1040 investigation of sediment samples from sites 1039 and 1040 odp leg 170 drilled oa the nicoya peninsula costa rica by organic geochemical and organic petrological methods has revealed that subduction has only little influence on the composition of the sedimentary organic matter organic carbon contents reached 1 5 in the pleistocene samples but miocene and pliocene sediments had an average organic carbon content of less than 0 5 organic carbon sulfur ratios are generally below 2 8 reflecting an intense sulfate reduction in the uppermost sediments which was enhanced by sulfate supply both from sea water and deeper strata microscopical examinations indicate that the organic matter is mainly derived from marine sources a small amount of terrigenous organic matter is however present as well according to n alkane and fatty acid distributions the alkenone unsaturation index u k 0 37 shows only a slight decrease during the miocene and pliocene and stronger variations in the pleistocene probably indicating more stable sea surface temperatures during the miocene and pliocene variations in the pleistocene can possibly be related to glacial interglacial changes 2000 elsevier science ltd all rights reserved

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

an alkenone u 37 k quasi annual sea surface temperature record a d 1440 to 1940 using varved sediments from the santa barbara basin abstract analyses for c37 alkenones u37k and total organic carbon toc in a varved core from the depocenter of the santa barbara basin 34 13 5 n 120 01 w 590 m water depth have been made on an approximately 1 2 year basis from a d 1440 to 1940 the u37k based sea surface temperature sst record oscillates around 15 5 c with an amplitude of less than 3 c at approximately interannual decadal and centennial frequencies historical el nino southern oscillation enso events are matched only partially by warmer u37k ssts three records our sst a published pacific coral 18o and a published tree ring temperature anomaly from the california valleys show no evidence of colder temperatures during the little ice age ca 1500 to 1840 a d significantly there is a strong centennial scale cyclicity in the u37k sst record which approaches 1 c in amplitude toc burial and alkenone fluxes are largely controlled by sedimentation rate as expressed in varve thickness

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

biogeochemistry of lipids in surface sediments of the peru upwelling area at 15 s abstract organic carbon lycopane a monoene of 2 6 10 trimethyl 7 3 methyl butyl dodecane c37 alkenones and 20 5 and 22 6 polyunsaturated fatty acid concentrations in two box cores from the peru continental margin area at 15 s in 90 and 268 m water depth have depth profiles that are synchronous and appear to indicate an historical record of fluctuating higher productivity lower productivity enso periods the u37k ratio calculated using c37 2 and c37 3 alkenones in the 268 m water depth core in the center of the upwelling zone varies with depth in the core in a manner consistent with the u37k functioning as an historical recorder of euphotic zone temperature concentrations and cpi for n alkanes c25 c31 are reported for both cores a c27 anthrasteroid has been identified and quantified in the 268 m water depth core

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

sea surface temperature reconstruction for the middle okinawa trough during the last glacial interglacial cycle using c37 unsaturated alkenones c 37 unsaturated alkenones were analyzed on a core retrieved from the middle okinawa trough the calculated u 37 k displays a trend generally parallel with those of the oxygen isotopic compositions of two planktonic foraminiferal species neogloboquadrina dutertrei and globigerinoides sacculifer suggesting that in this region sst has varied in phase with global ice volume change since the last glacial interglacial cycle the u 37 k derived sst ranged from ca 24 0 to 27 5 degrees c with the highest value 27 5 degrees c occurring in marine isotope stage 5 and the lowest similar to 24 0 degrees c in marine isotope stage 2 this trend is consistent with the continental records from the east asian monsoon domain and the marine records from the equatorial pacific the deglacial increase of the u 37 k derived sst is similar to 2 4 degrees c from the last glacial maximum to the holocene c 2007 elsevier b v all rights reserved

the lipid chemistry of an interfacial sediment from the peru continental shelf fatty acids alcohols aliphatic ketones and hydrocarbons a sample of the sediment water column interface which lies on the continental shelf under the peru upwelling regime has been examined for fatty acids fatty alcohols ketones and hydrocarbons fatty acids were the most abundant compound class ranging from c12 c24 with 16 0 as the major component 765 5 g g dry sediment the alcohols were dominated by 3 7 11 15 tetramethylhexadeca 2 en ol phytol with even chain n alcohols in the range c14 c20 the ketones consisted of c37 c39 di and tri unsaturated alken 2 ones and alken 3 ones both alkanes and alkenes were present in the hydrocarbon fraction the alkanes ranging from c13 c20 and comprising both straight chain and isoprenoid compounds the alkenes consisting of isomeric pairs of c25 branched trienes and tetraenes the data indicate that the organic content has been contributed very largely from marine sources probably mainly from phytoplankton and bacteria showing little terrigenous influence the presence of labile compounds such as polyunsaturated fatty acids with two to six double bonds implies that the sediment has undergone very little diagenetic alteration and the lipids are probably largely unchanged from the state in which they actually reached the sediment they may therefore serve as a useful baseline in assessing diagenesis in older sediments where diagenetic transformations are more advanced

alkenone temperature and carbon isotope records temporal resolution offsets and regionality 1 over the last decade the number of paleoceanographic studies presenting and discussing alkenone derived sea surface temperature sst records and carbon isotope ratios of alkenones 13calkenones has increased rapidly this short review paper summarizes the state of knowledge about sst variability determined by alkenone paleothermometry in sediment trap studies and investigations of marine sediments for timescales of single to millions of years in particular from the evaluation of quaternary records characteristic temperature pattern have emerged that mismatch with sst curves estimated by other methods e g foraminiferal stable oxygen isotopes and transfer functions in future studies the spatial distribution of such variance patterns typically observed in alkenone sst curves should be checked in order to better understand their meaning for ocean circulation changes and a possible relationship to global climate change on the other hand certain physical and biological processes have the potential to put the reliability of alkenone sst curves into question accordingly examples for possible effects of bioturbational mixing lateral transport of remote alkenones diagnetic alteration and degradation of alkenone composition biogeographic and temporal diversity changes in alkenone producing algae as well as the influence of changes in salinity and nutrient conditions on the alkenone paleotemperature signal are briefly mentioned highlighting the need for more detailed future studies on these issues finally a short summary on the status of the use of the 13calkenones signal as a proxy for past variations in the carbon dioxide pressure pco2 in ocean surface waters and related problems is given

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

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

el nino southern oscillation events recorded in the stratigraphy of the tropical quelccaya ice cap peru snow accumulation measured during 1982 1983 on the quelccaya ice cap peru was 70 percent of the average from 1975 through 1983 inspection of 19 years 1964 through 1983 of accumulation measured near the summit of quelccaya reveals a substantial decrease 30 percent in association with the last five el nino southern oscillation enso occurrences in the equatorial pacific the enso phenomenon is now recognized as a global event arising from large scale interactions between the ocean and the atmosphere understanding this extreme event with the goal of prediction requires a record of past occurrences the quelccaya ice cap which contains 1500 years of annually accumulated ice layers may provide a long and detailed record of the most extreme enso events

increased sensitivity of the plio pleistocene northwest pacific to obliquity forcing abstract insolation driven changes in poleward heat transport and changes in greenhouse gas concentrations can explain aspects of the rise of obliquity paced climate variability during the pliocene pleistocene transition based on an alkenone based sea surface temperature sst reconstruction of the kuroshio current extension kce we propose here that emergence of this region as the primary locus of ocean atmosphere heat transfer in the pacific ocean promoted northern hemisphere glaciation nhg our record shows that with intensification of nhg at 2 7 ma the kce cooled 2 4 c during glacial intervals likely in nh winter spring these high amplitude 41 kyr sst cycles slightly lead o 18 variations ruling out global ice volume changes as the primary cause the lead of sst over o 18 cycles matches the phasing between these two proxies observed in the tropics supporting changes in co2 concentrations as a unifying mechanism of ocean surface temperature change however the amplitude of the kce sst cycle is twice that of the tropical records pointing to an additional regional process we infer that cooling of the north pacific sea surface by the east asian winter monsoon and associated westerlies intensified during glacial intervals this transfer of heat and moisture from the ocean to the atmosphere potentially furthered glacial formation by accelerating snow fall in north america therefore these results might also support a role for tropical extratropical heat balance in enhancing glacial growth via the obliquity pacing

germanium silicon fractionation in a river influenced continental margin the northern gulf of mexico abstract in this study we have sampled the water column and sediments of the gulf of mexico to investigate the effects of high riverine terrigenous load and sediment redox conditions on the cycling of ge and si water column ge si ratios across the gulf of mexico continental shelf range from 1 9 to 25 mol mol which is elevated compared to the global ocean value of 0 7 mol mol the ge enrichment in the gulf of mexico seawater is primarily due to anthropogenic contamination of the mississippi river which is the main ge and si source to the area and to a smaller extent due to discrimination against ge during biogenic silica bsi production ge si 1 2 1 8 mol mol especially by radiolarians and siliceous sponges ge si 0 6 1 1 mol mol most sediment pore waters ge si 0 3 4 5 mol mol and sediment incubation experiments benthic flux ge si 0 9 1 2 mol mol indicate precipitation of authigenic phases that sequester ge from pore waters non opal sink this process appears to be independent of oxidation reduction reactions and suggests that authigenic aluminosilicate formation reverse weathering may be the dominant ge sink in marine sediments compilation of previously published data shows that in continental margins non opal ge burial flux is controlled by bsi supply while in open ocean sediments it is 10 100 times lower and most likely limited by the supply of lithogenic material we provide a measurement based estimate of the global non opal ge burial flux as 4 32 mmol yr 1 encompassing the 2 16 mmol yr 1 needed to keep the global marine ge cycle at steady state

carotenoid diagenesis in recent marine sediments i the peru continental shelf 15 s 75 w abstract we report here the distribution of carotenoids in peru marine surface sediments including partial identification of 37 pigments 33 of which have not been previously reported to occur in marine sediments our analysis demonstrates that zooplanktonic crustacea diatoms dinoflagellates cryptomonads purple nonsulfur photosynthetic bacteria and unidentified species of photosynthetic bacteria are contributors to sedimentary organic matter fucoxanthin fucoxanthinol diadinoxanthin peridinin and peridininol the principal carotenoids of diatoms and dinoflagellates observed in sediment traps are nearly absent from our sample even though these phytoplankton are the primary source of organic matter we attribute this to the presence of 5 6 epoxides in these pigments a feature which causes rapid cleavage of the polyene and fragmentation to low molecular weight compounds

microbial degradation of the marine prymnesiophyte emiliania huxleyi under oxic and anoxic conditions as a model for early diagenesis long chain alkadienes alkenones and alkyl alkenoates to investigate the effect of bacterial diagenesis on the distributions of algal lipids the marine haptophyte emiliania huxleyi was incubated with estuarine sediment slurries under defined conditions oxic sulfate reducing and methanogenic rapid initial degradation of lipids corresponded to increased bacterial populations both of which subsequently declined under oxic conditions the algal c31 dienes were rapidly and completely degraded within 178 days extensive degradation of the characteristic c37 methyl alkenones occurred under all conditions up to 85 under oxic conditions however the u37k index remained essentially constant except for a slight increase at the longest oxic incubation time under anoxic conditions the alkyl alkenoates were preferentially degraded relative to the alkenones and changes in the aa36 index occurred these results demonstrate that lipids are part of the labile organic matter however they were generally degraded at multiple rates which slowed during incubation resulting in their partial preservation hence laboratory experiments conducted over only short periods cannot predict the preservation potential of lipid components furthermore preservation differed between sulfate reducing and methanogenic conditions so the roles of anaerobic processes need to be considered individually with regard to oxic vs anoxic preservation

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

comparison of mg ca and alkenone based sea surface temperature estimates in the fresh water influenced gulf of guinea eastern equatorial atlantic this study presents a comparison of sea surface temperature sst estimates based on mg ca ratios of globigerinoides ruber and alkenone unsaturation index u37 k in core sediment recovered from the gulf of guinea eastern equatorial atlantic mg ca and u37 k based sst estimates yield fairly comparable results for the time interval 21 000 14 500 years and for the late holocene the early and middle holocene however are largely characterized by a discrepant trend with warm mg ca and cold u37 k based sst estimates this discrepant sst trend is accompanied by low sea surface salinity estimates high riverine runoff and biogenic sediment which is characterized by high biogenic opal content low carbonate content and relatively low alkenone concentration we hypothesize that the discrepancy in the reconstructed ssts during the middle and early holocene presumably suggests a period of elevated riverine input of dissolved silica and dominantly siliceous phytoplankton bloom in a low saline and warm surface water while alkenone producers were likely prevalent in a season of cold sst and low riverine silica input this study suggests that changes in the local hydrography and nutrient input have strong influence on the u37 k based sst estimate that may be unraveled by combining different sst proxies

assessment of sea surface temperature at 42 n in the california current over the last 30 000 years assessment of changes in surface ocean conditions in particular sea surface temperature sst is essential to understand long term changes in climate especially in regions where continental climate is strongly influenced by oceanographic processes to evaluate changes in sst in the northeast pacific we have analyzed long chain alkenones of prymnesiophyte origin at 38 depths in a piston and associated trigger core collected beneath the contemporary core of the california current system at 42 n 270 km off the coast of oregon california the samples span 30 000 years of deposition at this location unsaturation patterns u37k in the alkenone series display a statistically significant difference p 0 001 between interglacial 0 44 0 02 n 11 and glacial 0 29 0 04 n 20 intervals of the cores detailed examination of other compositional features of the c37 c38 c39 alkenone series and a related c36 alkenoate series measured downcore suggests the published u37k temperature calibration u37k 0 034 t 0 039 defined for cultures of a strain of emiliania huxleyi isolated from the subarctic pacific provides best estimates of winter sst at our study site this inference is purely statistical and does not imply however that the phytoplankton source of these biomarkers is most productive in winter or at the ocean surface the temperature record for u37k implies 1 an 4 c shift occurred in winter sst from 7 5 1 1 c at the last glacial maximum to 11 7 0 7 c in the present interglacial period and 2 this warming trend was confined to the time frame 14 10 ka within the glacial to interglacial transition period these conclusions are corroborated entirely by results from an independent sst transformation of radiolarian species assemblage data obtained from the same core materials

western arabian sea sst during the penultimate interglacial a comparison of u37k and mg ca paleothermometry millennial scale records of planktonic foraminiferal mg ca bulk sediment u37 k and planktonic foraminiferal 18o are presented across the last two deglaciations in sediment core niop929 from the arabian sea mg ca derived temperature variability during the penultimate and last deglacial periods falls within the range of modern day arabian sea temperatures which are influenced by monsoon driven upwelling the u37 k derived temperatures in mis 5e are similar to modern intermonsoon values and are on average 3 5 c higher than the mg ca temperatures in the same period mis 5e u37 k and mg ca temperatures are 1 5 c warmer than during the holocene while the u37 k mg ca temperature difference was about twice as large during mis 5e this is surprising as nowadays both proxy carriers have a very similar seasonal and depth distribution partial explanations for the mis 5e u37 k mg ca temperature offset include carbonate dissolution the change in dominant alkenone producing species and possibly lateral advection of alkenone bearing material and a change in seasonal or depth distribution of proxy carriers our findings suggest that 1 mg ca of g ruber documents seawater temperature in the same way during both studied deglaciations as in the present with respect to e g season and depth and 2 u37 k based temperatures from mis 5 or older represent neither upwelling sst nor annual average sst as it does in the present and the holocene but a higher temperature despite alkenone production mainly occurring in the upwelling season further we report that at the onset of the deglacial warming the mg ca record leads the u37 k record by 4 ka of which a maximum of 2 ka may be explained by postdepositional processes deglacial warming in both temperature records leads the deglacial decrease in the 18o profile and mg ca based temperature returns to lower values before 18o has reached minimum interglacial values this indicates a substantial lead in arabian sea warming relative to global ice melting

climatic changes in the upwelling region off cap blanc nw africa over the last 70 kyear a multi biomarker approach abstract molecular statigraphic records of core su94 11k 21 n 18 w 1200 m water depth were reconstructed for organic carbon oc carbonates alkenones n alkanols and sterols over the last 70 ky to study past changes of production and paleoceanographic conditions in the coastal upwelling of northwest africa u k 37 derived sea surface temperatures sst show a 2 5 c warming during the last deglaciation surprisingly they also indicate that during the last glacial period between 24 and 15 kyear sst rose by 1 c it can be seen from the values of marine and terrigenous biomarker mass accumulation rates mar that this time interval was also the period of lowest marine production and dust supply suggesting a major change in the north east trade winds system this situation would have lasted until the onset of the deglaciation from which upwelling progressively intensified to produce highest marine biomarker mar at the holocene our data also show a reduced terrigenous supply in late holocene sediments that may reflect lower emission rates from the vegetation and or changes in the wind conditions

variations in the content and composition of organic matter in sediments underlying active upwelling regimes a study from odp legs 108 112 and 117

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

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

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

uranium series and ams 14c studies of modern phosphatic pellets from peru shelf muds recent sediments and separated phosphate pellets 125 500 m in diameter from the peru shelf have been analyzed for uranium decay series isotopes and 14c in order to determine age relationships and mineralization rates uranium series ages of pellets separated from one box core are significantly higher than ams radiocarbon ages determined for the same pellets these differences appear to be a consequence of mixing of an older generation of pellets with ones which are more recently formed postdepositional adsorption of reactive elements such as thorium and protactinium onto pellet surfaces may also contribute to the observed discordancy with radiocarbon ages sediment radiocarbon and 210pb sediment results as well as some trends in the uranium series data suggest that high concentrations of phosphate pellets have accumulated in some peru shelf sediments without extensive reworking individual pellets apparently form very quickly on time scales of a few years estimated authigenic uptake rates of phosphorus into pellets ranges from 0 5 to 9 40 mol p cm 2 yr 1 somewhat higher than rates measured for nodules from the same area this is consistent with observations that pelletal morphologies predominate over nodular forms within ancient phosphorite deposits

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

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

diverse late stage crystallization and storage conditions in melt domains from the youngest toba tuff revealed by age and compositional heterogeneity in the last increment of accessory phase growth the chemical record contained within the final increment of growth on crystals is utilized to reveal the dynamics and timescales of magma assembly and storage before eruption of the cataclysmic 2800 km3 youngest toba tuff ytt indonesia in situ u th disequilibrium dates and trace element concentrations were obtained via secondary ionization mass spectrometry sims on unsectioned and unpolished faces of individual zircon and allanite crystals the six high silica 73 wt sio2 pumices from which crystals were derived are among the more evolved and lower crystallinity 25 wt pumices from the ytt eruption and likely represent the melt dominated portion of the magma system discrete sims measurement cycles were coupled with statistical treatments to detect zircon and allanite surface zoning domains at the 1 m scale coupled r melts and accessory phase saturation modeling indicates that at the granite ternary minimum or eutectoid conditions that define this portion of the ytt zircon and allanite crystallization is dependent on and proportionate to major phase crystallization and is more limited than at pre eutectoid conditions a lower proportion of near eruption zircon surface ages in the comparatively cool and wet ytt relative to other hotter and drier voluminous silicic eruptions could reflect the influence of eutectoid storage conditions on magmatic responses to remobilization related magmatic recharge

euxinia and primary production in late cretaceous eastern equatorial atlantic surface waters fostered orbitally driven formation of marine black shales 1 oceanic anoxic events oae in the cretaceous represent major perturbations in the global climate and ocean system characterized by widespread deposition of organic carbon in the ocean the causes and effects of these events are poorly constrained mainly because of the lack of high resolution marine records here we report the distribution of molecular markers from a millennial scale record of coniacian santonian black shale oae 3 from ocean drilling program site 959 in the deep ivorian basin in the eastern equatorial atlantic highly branched isoprenoids and alkenone derived organic compounds indicate that diatoms and calcareous nanoplankton were important primary producers changes in redox sensitive trace metal accumulation and biomarkers of green sulfur bacteria provide evidence for extreme variations in redox conditions with intervals of lower photic zone euxinia pze accordingly oxygen in the coniacian santonian tropical atlantic was absent as during the cenomanian turonian boundary oae 2 but over more restricted geographic area and more limited time intervals we hypothesize that pze was a common phenomenon typical in large areas of tropical continental margins these conditions fostered sequestration of atmospheric co2 and thus helped cause the positive excursion in 13c of carbonate documented in higher latitude marine records

the lycopane c31 n alkane ratio as a proxy to assess palaeoxicity during sediment deposition abstract recently two of us schulte et al earth planet sci lett 173 1999 205 221 advocated the use of the c 35 c 31 n alkane ratio to reconstruct past variations in the intensity of the oxygen minimum zone omz in the northeastern arabian sea new analyses of arabian sea surface sediments and re analysis of previously investigated sediments indicate however that the marked increase of the c 35 c 31 n alkane ratio in surface sediments from within the omz is due to enhanced preservation of lycopane which on some stationary phases in gas chromatography co elutes with the n c 35 alkane under anoxic conditions re examination of published data farrington et al org geochem 13 1988 607 617 on surface sediments from the peru upwelling region also revealed a marked preservation of lycopane and thus a higher abundance relative to terrestrial n alkanes under anoxic conditions within the omz thus the lycopane c 31 n alkane ratio can be interpreted as an oxicity proxy an overview of literature data indicates that lycopane is indeed often abundant in sediments which were deposited under anoxic conditions the carbon isotopic composition of lycopane and its response to the perturbation of the global carbon cycle during the cenomanian turonian oceanic anoxic event suggests that lycopane is derived from a marine photoautotroph although its biological source has yet to be identified

proceedings of a workshop on alkenone based paleoceanographic indicators 1 the papers in this theme derive from a workshop on alkenone based paleoceanographic indicators held at the j erik jonsson center of the national academy of sciences in woods hole massachusetts october 3 6 1999 the papers fall into two groups position papers prepared in advance of the workshop by the leaders of six different working groups and reports prepared during and after the workshop by rapporteurs and members of the working groups their publication here is intended to provide a record of the discussions and thus to serve to the paleoceanographic community an overview of the conference and its participants is also provided

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

transuranic nuclides in two coastal marine sediments off peru the fluxes of plutonium isotopes as well as their depth profiles are similar for northern and southern hemispheric varved sediments taken off western american coasts the inventories are in excess of the values predicted for atmospheric fallout in these anoxic sediments there is a general increase in concentration from depths to the near surface these observations are explainable on the bases that anoxic deposits have a substantially higher retentivity of sedimented materials compared to that of their bioturbated oxic counterparts and that there are inputs of resuspended materials previously deposited in the marine environment the 241am distributions are explained by ingrowth from 241pu assuming a substantial input of the parent from the u s thermonuclear tests during the 1950 s and the immobilization of both pu and am in the deposits

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

an alluvial record of el nino events from northern coastal peru overbank flood deposits of northern coastal peru provide the potential for the development of a late quaternary chronology of el nino events alluvial deposits from the 1982 1983 el nino event are the basis for establishing a type el nino deposit sedimentary structures suggesting depositional processes range from sheet flows to debris flows with sheet flood deposits being the most common the 1982 1983 deposits are characterized by a 50 to 100 cm thick basal gravel overlain by a 10 to 100 cm thick sand bed grading into a 1 to 10 cm thick silty sand bed and capped by a very thin layer of silt or clay the surface of the deposit commonly displays the original shear flow lines crosscut by postdepositional mud cracks and footprints human and animal stacked sequences of flood deposits are present in pleistocene and holocene alluvial fill suggesting that el nino type events likely occurred throughout the late quaternary a relative chronology of the deposits is developed based on terrace and soil stratigraphy and on the degree of preservation of surficial features a minimum of 15 el nino events occurred during the holocene a minimum of 21 events occurred during the late pleistocene timing of the holocene events is bracketed by isochrons derived from the archaeologic stratigraphy corrected radiocarbon ages from included detrital wood provide the following absolute dates for el nino events 1720 60 a d 1460 20 a d 1380 140 a d error overlaps with the a d 1460 event these may represent a single event and 1230 60 b c

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

diphytanyl glycerol ether distributions in sediments of the orca basin abstract archaebacterially produced diphytanyl glycerol ether dpge was examined in core sediments from the orca basin an anoxic hypersaline basin in the northwestern gulf of mexico to observe its spatial variability and potential origin a differential extraction protocol was employed to quantify the isopranyl glycerol ethers associated with unbound intermediate bound and kerogen bound lipid fractions archaebacterial lipids were evident at all depths for the unbound and intermediate bound fractions concentrations of dpge ranged from 0 51 to 2 91 g g dry sediment at the surface and showed secondary maxima deeper in basin sediments intermediate bound dpge concentrations exhibited an inverse relationship to unbound dpge concentrations kerogen bound dpge concentrations were normally below detection limits earlier studies describing the general homogeneity of lipid components within the overlying brine and at the brine seawater interface suggest that the large scale sedimentary dpge variations observed in this study result from spatial and temporal variations in in situ production by methanogenic or extremely halophilic archaebacteria

biomarker stratigraphic records over the last 150 kyears off the nw african coast at 25 n terrigenous and marine biomarkers were investigated in a core oa northwest africa in the northeast atlantic 25n 16w 1445 m depth to assess changes in the sedimentation pattern of organic carbon oc over the last 150 kyears alkenone derived temperatures recorded a warming of 4 5c during the last deglaciation n alkanol mass accumulation rates mar fluctuated in parallel with northeast trade winds netw intensity oc and sterol mar both increased during glacial times indicating enhanced fertility of the ocean in response to intensified netw alkenone oc ratios were higher by a factor of two over stages 4 6 than stages 1 3 thus reflecting distinct coccolithophorid inputs this transition coincides with a major change of alkenone producers inferred from coccolith counts 2000 elsevier science ltd all rights reserved

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

carotenoid diagenesis in recent marine sediments ii degradation of fucoxanthin to loliolide abstract the quantitative distributions of loliolide and the major phytoplankton carotenoids fucoxanthin diadinochrome diatoxanthin and carotene in two cores of anoxic marine sediment recovered from the peru continental shelf are reported our results demonstrate that the rapid degradation of carotenoids in sediments is not a result of their high degree of unsaturation as has been previously suggested instead carotenoids exhibit a wide range of degradation rates that are proportional to the ability of specific pigments to form unstable bicyclic furanoxides carotenoid furanoxides undergo subsequent fragmentation to loliolide isololiolide dihydroactinidiolide and other as yet undetermined low molecular weight products this degradation pathway accounts for the relative rates of removal for specific carotenoids fucoxanthin fucoxanthinol diadinoxanthin diatoxanthin carotene the distribution of carotenoids reported by wpatts and maxwell 1977 and c ardoso et al 1978 in ancient sediments the occurrence of novel carotenoid transformation products in surface sediments reported by r pidout et al 1984 and the distribution of loliolides in recent sediments recovered from the namibian shelf reported by k plok et al 1984a b we predict that loliolide and isololiolide will inherit a specific stereochemistry from their carotenoid precursors but that dihydroactinidiolide will be racemic for every mole of fucoxanthin degraded in peru sediments 0 7 1 1 mole of loliolide is produced summation of fucoxanthin and loliolide at each subsurface horizon yields an estimate of the total deposition of fucoxanthin at t 0 throughout the 0 20 cm depth of our samples this parameter is remarkably constant to 16 individual horizons exhibit excursions which may reflect changes in surface productivity extrapolation of our measurements to deeper sediments may therefore be of some value in deciphering questions on environmental conditions of deposition and paleoproductivity

distribution of magma beneath the toba caldera complex north sumatra indonesia constrained by three dimensional p wave velocities seismicity and gravity data 1 we estimate the one and three dimensional p wave velocity structure beneath the toba caldera complex a 30 100 km topographic depression in north sumatra using arrival time data of local earthquakes recorded by a 40 station seismic network that operated for 4 months inversions reveal the presence of p velocities up to 37 below normal that likely map the distribution of magma within this subduction related volcanic system considered the world s largest in the upper 10 km of crust the largest low velocity region underlies the southern two thirds of the depression and coincides with a gravity low centered over the resurgent dome a smaller volume of low velocities is observed in the upper crust under the north end of the depression separating the two regions is a zone of locally high velocities indicating that the shallow subcaldera magma system is composed of two separate reservoirs not a single one that extends the entire length of the caldera complex above each low velocity region is a postcollapse volcano that erupted mostly mafic lavas after the last major caldera collapse 74 kyr ago a low velocity column below one of these volcanoes can be traced into the uppermost mantle and corresponds with a planar distribution of low frequency earthquakes in the 20 to 40 km depth range the low frequency earthquakes apparently record the migration of melt in the mafic roots of this large volume crustal magma system

laminated sediments from the central peruvian continental slope a 500 year record of upwelling system productivity terrestrial runoff and redox conditions sedimentological studies including x ray digital analyses mineralogy inorganic contents and organic geochemistry on cores of laminated sediments accumulated in the oxygen minimum zone of the central peruvian margin reveal variable oceanographic and climate conditions during the last 500 yr coherent upcore variations in sedimentological and geochemical markers in box cores taken off pisco b0405 6 and callao b0405 13 indicate that variability in the climate proxies examined has regional significance most noteworthy is a large shift in proxies at 1820 ad as determined by 210pb and 14c radiometric dating this shift is characterized by an increase in total organic carbon toc in parallel with an abrupt increase in the enrichment factor for molybdenum mo indicating a regional intensification of redox conditions at least at the sediment water interface in addition there was lower terrestrial input of quartz feldspar and clays to the margin based on these results we interpret that during several centuries prior to 1820 which corresponds to the little ice age lia the northern humboldt current region was less productive and experienced higher terrestrial input related to more humid conditions on the continent these conditions were probably caused by a southward displacement of the inter tropical convergence zone and the subtropical high pressure cell during the lia since 1870 increases in toc and terrigenous mineral fluxes suggest an increase of wind driven upwelling and higher productivity these conditions continued to intensify during the late 20th century as shown by instrumental records of wind forcing

systematic pattern in u37k temperature residuals for surface sediments from high latitude and other oceanographic settings abstract twenty seven multicores collected in late summer 2004 from coastal and inland marine sites throughout se alaska 55 to 61 n were analyzed for c 37 to c 39 alkenones of specific haptophyte origin this biomarker signal detected in core top sediments from 20 of the sites was quantitatively most significant in organic carbon and biogenic silica rich sediments deposited south of icy strait 58 n along the outer coastline of baranof and prince of wales islands u 37 k based water temperature estimates derived using a standard calibration equation u 37 k 0 034t 0 039 were uniform throughout the study area averaging 11 9 1 0 c a value 4 c warmer than mean annual sst masst for the region epoxides indicative of selective alkenone degradation by an aerobic bacterial process were also detected and quantified in all sediments containing alkenones semi quantitative accounting of the impact that compound selective degradation can impose on alkenone unsaturation patterns indicates the standard u 37 k based temperature estimates could be too warm by a variable amount 0 7 2 4 c depending upon the site with an overall average of 1 4 c even after adjustment for this potential diagenetic warming effect estimates still best match summer and not masst in this subarctic region re examination of alkenone signatures preserved in sediment from the north atlantic and on the continental margin located south of 45 s along the chilean coast indicates the apparent summer signal in u 37 k derived sst estimates is not unique to se alaskan sediments but rather a common finding when alkenone thermometry is applied to sediments from high latitude environments examination of model residuals from analysis of surface sediment samples collected at lower latitude settings along the west coast of the americas also identifies other sites where significant biogeographic patterns seem apparent and viable oceanographic explanations can be offered

the impact of alkenone degradation on uk 37 paleothermometry a model derived assessment the u37k proxy for past sea surface temperature sst is based on the unsaturation ratio of c37 alkenones it is considered a diagenetically robust proxy but biases have been invoked because the index can be altered by preferential degradation of the c37 3 alkenone resulting in higher reconstructed sst however alkenone degradation rate constants are poorly constrained making it difficult to evaluate the plausibility of such a bias therefore we quantitatively assessed the effect of 1 different alkenone degradation rate constants 2 differential degradation factors between di and tri unsaturated c37 alkenones 3 and initial u37k values on the u37k paleothermometer for two depositional environments shelf and upper slope by means of a reaction transport model rtm rtm results reveal that preferential degradation of c37 3 can potentially alter the original signal of the u37k paleothermometer but sst biases sst are largely within u37k calibration error sst 1 5 c are associated with marked downcore decreases in alkenone concentration consequently we caution against the interpretation of u37k indices when extensive degradation results in very low alkenone concentrations 5 ng g 1

late quaternary high resolution biomarker and other sedimentary climate proxies in a northeast atlantic core we studied variations in terrigenous input and sea surface temperature over the last 208 ka using a multiproxy approach involving direct comparison of terrigenous and marine molecular biomarker foraminiferal abundance and other sedimentological data for the same horizons in a single northeast atlantic core core t88 9p 48 23 n 25 05 w 3193 m water depth 790 cm core length with a well resolved 18o stratigraphy the abundances of three land derived long chain compound classes the n alkanes c27 c29 and c31 the n alkanoic acids c24 c26 and c28 and the n alkanols c24 c26 and c28 show glacial interglacial related changes in the past 208 ka which generally parallel the weight percent noncarbonate the abundances of these three compound classes are higher in glacial than in interglacial sediments such changes are consistent with the expected higher dust inputs during glaciations as well as enhanced advection of particulate matter in current systems ice rafted debris heinrich events may also contribute to the terrigenous biomarker record the sea surface temperature sst signals derived from the alkenone unsaturation index uk 37 give an average sst during interglacial periods of 13 c which is about 3 4 c higher than the average glacial sst estimate the uk 37 derived sst values dropped markedly in some heinrich layers while sometimes leading the onset of the layer the percent neogloboquadrina pachyderma s which is another frequently used qualitative temperature proxy generally shows maxima coinciding with the layers our results show that most heinrich layers were produced during times of intensely cold waters in the eastern north atlantic they demonstrate that sufficient alkenones are present in the sediments for alkenone stratigraphy to be used as a tool for the assessment of short term variations in sea surface temperatures even in these oligotrophic north atlantic waters

el nino events and their relation to the southern oscillation 1925 1986 relationships among sea surface temperatures ssts at the coast of peru and offshore river discharge in northern peru and sea level pressure at darwin australia during the period 1925 1986 are investigated using time series plots frequency distributions and a simple statistical analysis it is shown that ssts undergo a larger seasonal cycle offshore than at the coast exhibit more interannual variability during the warm than the cool season are positively skewed during much of the year and exhibit greatest month to month persistence during the cool season many but not all episodes of above normal coastal ssts are accompanied by enhanced river discharge in northern peru comparison of the darwin pressure and coastal sst records during the past 60 years shows that el nino events episodes of above normal ssts along the coast of peru have occurred both in advance of and subsequent to major negative swings of the southern oscillation and associated climatic changes in the central equatorial pacific in addition el nino events and negative swings of the southern oscillation have occurred separately hence el nino and the southern oscillation are more loosely coupled than other studies would imply

peruvian sediments as recorders of an evolving hiatus for the last 22 thousand years highlights review of sediment archives from the peruvian margin since the lgm focus on the evolutionary feature of the hiatus found in archives modern analogue for current dominated environments for paleo reconstructions new results for erosional potential of the non linear internal waves nliws abstract the peruvian continental margin is characterized by the presence of one of the strongest and most distinct oxygen minimum zones omzs in today s oceans therefore it has long been in the focus of oceanographic and geological investigations observations indicate that omzs are expanding in relation with currently changing climate to advance understanding of the temporal evolution of omzs and climate change complete paleoceanographic and palaeoclimatological reconstructions are needed however the development of paleoenvironmental scenarios for the period since the last glacial maximum at this region was hampered by a ubiquitous hiatus and short term interruptions of the stratigraphical record in the present study we combined the stratigraphical information from 31 sediment cores from the peruvian margin located between 3 and 18 s and water depths of 90 to 1300 m within and below today s omz in order to determine the extent of the hiatus and assess the responsible mechanisms a widespread unconformity and related erosional features omission surfaces and phosphorites were observed in sediment cores from the area south of 7 s depicting a prograding feature on the continental slope from south to north during the deglaciation combining recent oceanographic and sedimentological observations it is inferred that tide topography interaction and resulting non linear internal waves nliws shape the slope by erosion carry sediments upslope or downslope and leave widespread phosphoritic lag sediments while the peru chile undercurrent pcuc transports the resuspended sediments southward causing non deposition this exceptional sedimentary regime makes the peruvian margin a modern analogue for such environments overall our compilation of downcore records showed that enhanced bottom currents due to tide topography interaction were progressively evolving and affected a wider area with the onset of the last deglaciation elevated tidal amplitudes and variability of mid depth water masses i e density changes and hydrodynamics in relation with changing climate were potential reasons of this evolving feature of erosion and reworking additionally erosion and non deposition was observed widest and even was encountered on the continental shelf during the early holocene potentially indicating a strong phase of the pcuc mirroring today s el nino like conditions

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

historical oceanographic events reflected in13c 12c ratio of total organic carbon in laminated santa barbara basin sediment an 1844 1987 time series of carbon stable isotope ratios from dated sedimentary total organic carbon toc from the center of the santa barbara basin sbb is compared with historical climate and oceanographic records four isotopically distinct biogeochemical sources of toc are important phytoplankton derived marine biomass macroalgal biomass from kelp forests terrigenous biomass mainly flushed into the sbb via river discharge and redeposited fossil organic carbon the significance of the latter two sources is largely limited to a few unusual flood and oil spill events whereas the combination of 13c depleted phytoplankton and 13c enriched macroalgal biomass appears to be responsible for most of the isotopic variance of the marine coastal biomass as recorded in sedimentary toc the isotopic response of marine organic carbon in sediments records strong el nino southern oscillation enso and the frequently associated severe storm and wave events in sbb varved sediments the plausible major isotopic mechanisms are 1 increased physical liberation of 13c enriched kelp carbon from locally abundant giant kelp macrocystis spp forests during times of physical and environmental stress and 2 decreased productivity of 13c depleted phytoplankton during enso events

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites