an 15 000 year record of el nino driven alluviation in southwestern ecuador debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the pacific ocean in ecuador these storm induced events were dated by radiocarbon and the age of laminae that are less than 200 years old matches the historic record of el nino events from about 15 000 to about 7000 calendar years before the present the periodicity of clastic deposition is greater than or equal to 15 years thereafter there is a progressive increase in frequency to periodicities of 2 to 8 5 years this is the modern el nino periodicity which was established about 5000 calendar years before the present this may reflect the onset of a steeper zonal sea surface temperature gradient which was driven by enhanced trade winds

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

identification of tsunami deposits using a combination of radiometric dating and oxygen isotope profiles of articulated bivalves abstract four tsunami deposits deposits i iv have been identified on ishigaki island southwest japan the youngest tsunami deposit deposit i was caused by the meiwa tsunami which occurred on 24 april 1771 ce as described in reliable historical documents two well preserved specimens of articulated marine bivalve were collected from the youngest tsunami deposit deposit i and an additional two from the second youngest tsunami deposit deposit ii 920 620 cal yr bp the shells were tightly closed and empty inside no encrusting epifauna or evidence of erosion was observed on the inner or outer shell surfaces in each tsunami deposit the 14c ages of the shells are nearly identical the mode of occurrence and coincidence of ages mean that these shells were transported and buried alive by tsunamis we analyzed the oxygen isotope 18o profiles of these bivalves to determine the seasons of their death which provides clues to the seasonal timing of tsunamis tsunami deposits i and ii were formed during spring and fall respectively the former supports the proposal that tsunami deposit i was caused by the 1771 meiwa tsunami and provides regional radiocarbon reservoir age for the late 1700s the latter provides a chronological constraint on the identification of tsunami deposit ii thus a combination of radiometric dating and 18o profiles of articulated bivalves derived from tsunami deposits provides important chronologic constraints for examining paleo tsunami events

effect of ray and speed perturbations on ionospheric tomography by over the horizon radar a new method most recent methods in ionospheric tomography are based on the inversion of the total electron content measured by ground based gps receivers as a consequence of the high frequency of the gps signal and the absence of horizontal raypaths the electron density structure is mainly reconstructed in the f2 region 300 km where the ionosphere reaches the maximum of ionization and is not sensitive to the lower ionospheric structure we propose here a new tomographic method of the lower ionosphere based on the full inversion of over the horizon oth radar data previous studies using oth radar for ionospheric tomography inverted only the leading edge echo curve of backscatter ionograms the major advantage of our methodology is taking into account numerically and jointly the effect that the electron density perturbations induce not only in the speed of electromagnetic waves but also on the raypath geometry this last point is extremely critical for oth radar inversions as the emitted signal propagates through the ionosphere between a fixed starting point the radar and an unknown end point on the earth surface where the signal is backscattered we detail our ionospheric tomography method with the aid of benchmark tests having proved the necessity to take into account both effects simultaneously we apply our method to real data this is the first time that the effect of the raypath deflection has been quantified and that the ionospheric plasma density has been estimated over the entirety of europe with an oth radar

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

stable isotope fractionation in benthic foraminifera from the peruvian continental margin abstract stable isotope ratios of the carbonate tests of benthic foraminifera are now widely used to reconstruct past changes in ocean circulation and chemistry such studies depend on the accuracy with which changing environmental conditions are recorded and preserved in the tests of foraminifera found in deep sea deposits assessment of this aspect of the method is best accomplished through rigorous study of modern core tops collected from a wide range of depths and bottom water temperatures stable isotope analyses of eighteen taxa of benthic foraminifera from surface sediments of the peru continental margin indicate that most foraminifera are slightly depleted in 18o relative to the benthic foram uvigerina peregrina for at least five taxa we observed subparallel 18 o temperature relationships with slopes nearly equal to that predicted by shackleton 1974 for uvigerina for seven taxa isotopic analysis of six size fractions in the range 210 590 mm reveals that with the exception of u peregrina variation between different size classes for each species is small for 18 o and for 13 c a slight inverse correlation between foraminiferal 18o and 13c content implies a complex interplay of biological and environmental factors which control isotopic composition

giant bivalves tridacna gigas as recorders of enso variability we compare monthly resolved oxygen isotope records derived from a giant bivalve shell tridacna gigas and massive parkes corals collected along the northern coast of papua new guinea this intercomparison study demonstrates that delta o 18 profiles obtained from these different aragonite secreting organisms collected from within a 30 km range are correlated in great detail and record the timing and amplitude of seasonal and interannual enso related variations in sea surface temperature sst and water isotopic composition which is closely related to rainfall furthermore the t gigas record is shown to be close to isotopic equilibrium with the local sea water in contrast to the corals which are approximately 4 parts per thousand offset these results reveal that living and fossil t gigas clam shells have the potential to yield reliable records of past changes in seasonality and enso variability as well as mean climate conditions in particular since the non porous shells are generally more resistant to diagenesis than coral skeletons they may provide robust estimates of past tropical climate for periods and locations where unaltered corals are absent crown copyright c 2011 published by elsevier b v all rights reserved

investigating δ 18 o of turbo sarmaticus l 1758 as an indicator of sea surface temperatures abstract the large marine gastropod turbo sarmaticus was and still is an important food item for coastal foragers along the south coast of south africa opercula of this species are well preserved in both holocene and pleistocene archaeological sites offering the opportunity to reconstruct past sea surface temperatures from 18o of shell carbonate over much of the last glacial cycle we have analysed 18o and 13c in 16 opercula and one shell of modern animals collected alive from an area with good sst records in order to explore how reliably this species records water temperature through the year and to investigate possible vital effects that may influence the isotope record we find that t sarmaticus deposits aragonite in both operculum and shell in oxygen isotopic equilibrium with seawater operculum 18o values of this species reliably reflect water temperatures between c 14 and 24 c although they do not always capture temperature extremes especially in winter likely due to slower growth under stressful growth conditions these thresholds probably alter according to factors such as variations in nutrient supply the averaged maximum and minimum values across the set of sixteen serially sampled opercula very closely approximate the temperatures of the warmest and coolest months and therefore provide a good measure of the seasonal temperature range and of mean annual sst 18o of edge increments can to some extent be used to indicate season of collection within the broad categories of warmer cooler seasons

ligamental increments of the mid holocene pacific oyster crassostrea gigas are reliable independent proxies for seasonality in the western bohai sea china abstract modern living and mid holocene shells of crassostrea gigas from the western bohai sea in china were subjected to sclerochronological analysis with the aim of determining whether their concave bottoms and growth breaks on resilifer surfaces as well as corresponding translucent growth bands visible in cross section have seasonal significance an additional aim was to obtain ontogenetic information from mid holocene fossil shells we compared 18 o and 13 c profiles compiled with high and low sampling resolution for the same shell in order to test the consistency of the results and identify a suitable sampling strategy for future sclerochronological studies the results show that concave bottoms on the resilifer surface and corresponding translucent growth bands in cross section formed during the cold season these features are appropriate indicators of annual growth increments in fossil c gigas shells moreover growth breaks located near convex tops indicate annual growth increments for that part of the shell which grew when the organism was sexually mature therefore spawning related growth breaks and alternating winter freeze shocks concave bottoms are excellent morphological features in determining annual growth increments consequently the life span growth rate and timing of spawning and death can be determined from the increments of ligament growth of these fossil oyster shells for future sclerochronological studies an adaptive micro sampling strategy could be used for different increments of ligament growth that represent different seasons such a strategy would be more efficient in providing reliable insights into growth history of shells with variable growth rates of annual increments

controls on δ18o and δ13c profiles within the aragonite bivalve arctica islandica the geochemistry of arctica islandica shells provides an opportunity to reconstruct intra annual resolution climate records in temperate latitudes and the annual banding allows close temporal constraint stable isotope analyses of carbon and oxygen from an arctica islandica live collected at 6 m depth from irvine bay uk are presented seawater temperature ranges reconstructed from shell 18o agree within error with instrumental sea surface temperature measurements the saw tooth profile of the seasonal 18o signal compared with the sinusoidal seawater temperature indicates that shell accretion rate is not constant throughout the year modelling the expected 18o profile from water temperature salinity and shell growth rate suggest that a islandica at this site has significant variation in the shell extension rate during the year material deposited during shell damage shows a positive shift in 18o a strong ontogenetic effect is seen in 13c and damage to the shell is associated with a significa

growth patterns of the topshell phorcus lineatus da costa 1778 in northern iberia deduced from shell sclerochronology abstract combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns respectively recent investigations have shown that the gastropod phorcus lineatus da costa 1778 forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies in contrast the shell growth patterns of this species have received virtually no attention despite providing information on the rate and timing of shell growth that is crucial for correctly interpreting environmental proxies derived from shell geochemistry in this paper we compare microgrowth patterns and isotopic profiles of four modern individuals of the gastropod p lineatus from northern iberia to determine the timing and periodicity of subannual growth markers within the shells results of this sclerochronological study showed the presence of two types of growth lines increments i large scale accretionary units formed with variable periodicity and ii small scale accretionary units formed by micro growth lines and increments determined by semidiurnal tidal cycles results suggest that shells grew uninterruptedly during early ontogeny however older specimens exhibited growth cessation slowdown during summer and winter spring therefore shell growth rate is not only controlled by environmental conditions but also by ontogenetic age and or endogenous rhythms a high correlation was found between seawater temperature derived from shell oxygen isotopes and instrumental seawater temperature r2 0 88 0 98 p values

a high resolution δ18o record of modern tridacna gigas bivalve and its paleoenvironmental implications abstract the lack of monthly resolved paleoenvironmental records beyond the instrumental era hinders our full understanding of global climate dynamics tridacna gigas shells have a large potential to quantitatively document the variability of the ocean surface environment on time scales from daily to interannual in the past while the applicability of the geochemical proxies of tridacna gigas needs to be quantitively investigated here we establish a chronology for a tridacna gigas shell from the southern south china sea scs by identifying daily growth laminae using a laser scanning confocal microscope lscm our high resolution tridacna gigas shell 18oshell record throughout 1989 2013 shows a high correlation with changes in local precipitation and the index of el nino southern oscillations enso on the interannual time scale together with observed sea surface temperature sst we calculated seawater 18o 18osw and derived sea surface salinity sss change in the southern scs based on the tridacna gigas shell 18o record our salinity budget calculation results suggest that the sss variability in the southern scs is predominantly affected by the vertical mixing and sea surface freshwater flux our study reveals that the tridacna gigas shell is an ideal archive for high resolution and quantitative paleoenvironmental reconstructions in tropical ocean regions thus providing a new window to explore paleoenvironmental changes on annual and interannual time scales

high benthic methane flux in low sulfate oceans evidence from carbon isotopes in late cretaceous antarctic bivalves abstract the shell material of marine benthic bivalves provides a sensitive archive of water chemistry immediately above the sediment water interface which in turn is affected by sedimentary geochemistry and redox reactions sulfate has a major controlling effect on sedimentary carbon cycling particularly the processes of methane production and oxidation with lower concentrations of sulfate likely resulting in an increase in sedimentary methane production whilst it is accepted that ocean sulfate varied markedly across the phanerozoic evidence of changes in methane production in sediments has so far been lacking there is potential for the oxidation products of sedimentary methane to be preserved and detected in marine fossils here we present the results of high resolution carbonate isotope records from two taxa of well preserved shallow infaunal bivalve lahillia and cucullaea collected from the marine shelf succession across the cretaceous paleogene k pg boundary in seymour island antarctica the succession has pre existing subtle indications of more abundant methane and the time period is characterized by much lower marine sulfate concentrations than modern these shell carbonate carbon isotope records vary widely at one extreme shells have typical average values and small ranges compatible with a contemporaneous marine dissolved inorganic carbon dic source and modern style sedimentary carbon cycling at the other the shells have large amplitude annual cycles of carbon isotopic variability of up to 23 8 within a single year of growth and shell carbonate 13 c compositions as negative as 34 shells with these increased ranges and unusually negative values are found at discrete intervals and across both bivalve taxa the contribution of methane required to explain the most negative carbonate carbon isotopic values in the bivalve shells is extremely high between 30 to 85 of bottom water dic based on mass balance calculations records of organic carbon isotopes from the same succession remained between 26 1 and 21 7 throughout suggesting that methane influence was restricted to bottom waters a lack of authigenic carbonate in the section indicates that methane oxidation progressed aerobically and may have provided a significant driver for transient bottom water de oxygenation where methane addition is indicated the seasonal sensitivity precludes control by methane hydrates we argue that these data represent the increased importance and sensitivity of methanogenesis in the sediments enabled by lower ocean sulfate concentrations during the late cretaceous the tendency towards a more dynamic role for marine methane production and oxidation is likely to apply to other times of low marine sulfate in earth s history

delta o 18 of fissurella maxima as a proxy for reconstructing early holocene sea surface temperatures in the coastal atacama desert 25 degrees s abstract fissurella maxima is a keyhole limpet that is abundant and well preserved in archaeological shell midden sites along the coast of chile making it an appropriate species to use for reconstructions of past sea surface temperature sst in the present study we evaluate the potential of f maxima shells as a proxy of sst by analysing 18o of modern shells collected alive from the atacama desert area of taltal 25 s and archaeological shells from two early holocene rockshelter sites 224a and paposo norte 9 reconstructed sst from modern f maxima shells were related to sst obtained from in situ thermometers supporting the use of this mollusc species as a paleotemperature archive mean sst reconstructed from early holocene archaeological shells 14 13 c was 2 86 c cooler than mean temperature recorded in modern shells 16 99 c mean sst reconstructed from modern shells was 1 04 c warmer than the mean temperature of in situ thermometers 15 95 c hence the paleo sst data from archaeological sites 224a and paposo norte 9 enrich the early holocene nearshore paleoceanographic scenario of the pacific coast of south america with mean sst cooler than present day sst our results validate the use of f maxima shells as a sst proxy and contribute to a better understanding of the latitudinal distribution of the coastal upwelling regime during the early holocene temporal changes in the structure of the humboldt current along the holocene and its influence on human adaptation through the prehistory of south america

interdecadal variation in the extent of south pacific tropical waters during the younger dryas event during the younger dryas event about 12 000 years ago the northern hemisphere cooled by between 2 and 10 degrees c refs 1 2 whereas east antarctica experienced warming but the spatial signature of the event in the southern mid latitudes and tropics is less well known as records are sparse and inconclusive here we present high resolution analyses of skeletal sr ca and 18o 16o ratios for a giant fossil diploastrea heliopora coral that was preserved in growth position on the raised reef terraces of espiritu santo island vanuatu in the southwestern tropical pacific ocean our data indicate that sea surface temperatures in vanuatu were on average 4 5 1 3 degrees c cooler during the younger dryas event than today with a significant interdecadal modulation the amplified annual cycle of sea surface temperatures relative to today indicates that cooling was caused by the compression of tropical waters towards the equator the positive correlation in our record between the oxygen isotope ratios of sea water and sea surface temperatures suggests that the south pacific convergence zone which brings 18o depleted precipitation to the area today was not active during the younger dryas period

environmental controls on the stable isotopic composition of mercenaria mercenaria potential application to paleoenvironmental studies 1 we have investigated the environmental controls of seasonally resolved records of oxygen and carbon isotopes of modern mercenaria mercenaria bivalves collected live from five coastal sites along the east coast of north america seasonal profiles of 18o and 13c obtained by subsampling the incremental growth layers of aragonite were compared with in situ historical records of temperature and salinity we show that m mercenaria 18o profiles track accurately the seasonal variations of water temperature and that variations in growth rates do not affect the shell 18o values growth rates are strongly reduced or interrupted below water temperatures ranging from 8 to 10 c implying that only bivalves sampled in tropical areas track the full amplitude of seasonal variations although further measurements of water 18o and a better understanding of seasonal variations of the water 18o salinity relationships are necessary mercenaria mercenaria bivalves appear to precipitate their shell close to isotopic equilibrium whereas the amplitude of the seasonal profiles of 18o reflects variations in water temperature the annual average 18o decreases with latitude reflecting the trend of rainfall and riverwater 18o with latitude over the northern american continent

ridge formation and de spinning of iapetus via an impact generated satellite abstract we present a scenario for building the equatorial ridge and de spinning iapetus through an impact generated disk and satellite this impact puts debris into orbit forming a ring inside the roche limit and a satellite outside this satellite rapidly pushes the ring material down to the surface of iapetus and then itself tidally evolves outward thereby helping to de spin iapetus this scenario can de spin iapetus an order of magnitude faster than when tides due to saturn act alone almost independently of its interior geophysical evolution eventually the satellite is stripped from its orbit by saturn the range of satellite and impactor masses required is compatible with the estimated impact history of iapetus

thermally anomalous holocene molluscan assemblages from coastal peru evidence for paleographic not climatic change abstract holocene marine mollusks many in situ are found in great numbers on anemergent coastal plain north of the rio santa on the north central coast of peru samples of the mollusks were collected identified and grouped into assemblages of recurring species the surficial sedimentology and geomorphology of the coastal plain were studied to determine the paleoecological significance of the molluscan shells many of which belong to species now restricted to a biogeographically transitional zone north of bayovar peru 200 km north of the study of the area radiocarbon dates mostly obtained from shells in natural deposits and middens were used to track the holocene development of the coastline the warm water mollusks lived within a shallow lagoon of about 29 km2 between 4300 6500 yr b p free tidal exchange with the pacific ocean was impeded by partially drowned beach ridges within the lagoon and by a barrier forming beach ridge that joined the mainland with an offshore island contemporaneus in situ cold water faunas were discovered at the mouth of the lagoon and in washover deposits landward of the barrier beach ridge the association of contemporaneous and adjacent assemblages of warm water and cold water mollusks shows that the thermally anomalous molluscan assemblage tama at santa is a consequence of local coastal paleographyy not regional or global mid holocene climate change

shell sclerochronology and stable isotopes of the bivalve anomalocardia flexuosa linnaeus 1767 from southern brazil implications for environmental and archaeological studies abstract this study presents the first stable isotopic and sclerochronological calibration of the bivalve anomalocardia flexuosa linnaeus 1767 in relation to environmental variables in a subtropical coastal area of southern brazil we investigate incremental shell growth patterns and 18o and 13c values of modern specimens collected alive from the laguna lagoonal system lls shells of anomalocardia flexuosa are also one of the main biological components of pre columbian archaeological shell mounds and middens distributed along the brazilian coastline we therefore selected archaeological specimens from a local late holocene shell mound cabecuda to compare their stable carbon and oxygen isotope values with those of modern specimens shell growth increments 18o and 13c values respond to a complex of environmental conditions involving for example the effects of temperature and salinity the isotopic information extracted from archaeological specimens from cabecuda shell midden in the lls indirectly indicates that environmental conditions during the late holocene were different from present day in particular intra shell 18o and 13c values of archaeological shells reveal a stronger marine influence at 3 ka cal bp which is in contrast to the seasonal freshwater seawater balance that currently prevails at the lls

otolith δ18o record of mid holocene sea surface temperatures in peru peruvian sea catfish galeichthys peruvianus sagittal otoliths preserve a record of modern and mid holocene sea surface temperatures ssts oxygen isotope profiles in otoliths excavated from ostra 6010 90 years before the present yr b p 8 degrees 55 s indicate that summer ssts were approximately 3 degrees c warmer than those of the present siches otoliths 6450 110 yr b p 4 degrees 40 s recorded mean annual temperatures approximately 3 degrees to 4 degrees c warmer than were measured under modern conditions trophic level and population diversity and equitability data from these faunal assemblages and other peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the peru chile current intensified after approximately 5000 yr b p

comment on otolith δ18o record of mid holocene sea surface temperatures in peru andrus et al 1 1 asserted that oxygen isotope profiles from modern and mid holocene otoliths of the peruvian sea catfish galeichthys peruvianus and diversity indices derived from midden collections of fish bones provide evidence for warmer sea surface temperatures ssts they further

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

new views of tropical paleoclimates from corals abstract corals offer a rich archive of past climate variability in tropical ocean regions where instrumental data are limited and where our knowledge of multi decadal climate sensitivity is incomplete in the eastern equatorial pacific coral isotopic records track variations in enso related changes in sea surface temperature further west corals record variability in sea surface temperature and rainfall that accompanies zonal displacement of the indonesian low during enso events these multi century records reveal previously unrecognised enso variability on time scales of decades to centuries outside the enso sensitive equatorial pacific long term trends towards recent warmer wetter conditions suggest the tropics respond to global forcings new coral paleothermometers indicate that surface ocean temperatures in the tropical southwestern pacific were depressed by 4 6 c during the younger dryas climatic event and rose episodically during the next 4000 yr high temporal resolution measurements of sr ca and 18 o in corals provide information about the surface ocean hydrologic balance and can resolve the seasonal balance between precipitation and evaporation radiocarbon measurements in corals coupled with ocean circulation models may be used to reconstruct near surface ocean circulation past mixing rates and the distribution of fossil fuel co2 in the upper ocean most recently seasonal to interannual variations in the radiocarbon of corals from the equatorial pacific have been linked to the redistribution of surface waters associated with the enso

pliocene climate and seasonality in north atlantic shelf seas this paper reviews north atlantic shelf seas palaeoclimate during the interval 4 3 ma prior to and incorporating the mid pliocene warm period ca 3 29 2 97 ma fossil assemblages and stable isotope data demonstrate northwards extension of subtropical faunas along the coast of the carolinas virginia yorktown and duplin formations relative to the present day suggesting a more vigorous florida current with reduced seasonality and warm water extending north of cape hatteras reconstructed annual range for virginia 12 30 c this interpretation supports conceptual models of increased meridional heat transport for the pliocene sea temperatures for florida lower pinecrest beds were similar to or slightly cooler than summers 25 27 c today and were probably influenced by seasonal upwelling of cold deep water reduced seasonality is also apparent in the coralline crag formation of the southern north sea with ostracods suggesting winter sea temperatures of 10 c modern 4 c however estimates from pliocene bivalves 3 6 16 6 c are similar to or cooler than the present day this mixed signal is problematic given warmer seas in the carolinas virginia and climate model and oceanographic data that show warmer seas in the mid pliocene eastern north atlantic this may be because the coralline crag formation was deposited prior to peak mid pliocene warmth

shell sclerochronology and stable oxygen isotope ratios from the limpet patella depressa pennant 1777 implications for palaeoclimate reconstruction and archaeology in northern spain abstract stable oxygen isotope ratios of mollusc shells 18oshell offer the possibility to reconstruct coastal resource exploitation patterns and changes in the oceanographic conditions of direct relevance to past human populations this method relies on the fact that shell carbonate is deposited by molluscs in equilibrium with their surrounding environment and actualistic investigation of modern specimens is needed to ensure that selected species can be used as accurate palaeoclimate indicators the limpet patella depressa pennant 1777 is one of the most common mollusc species found in holocene archaeological assemblages along the atlantic coast of europe however this taxon has not to date been tested as a seawater palaeothermometer here we explore the ability of p depressa to be used as an environmental recorder in this littoral region specifically in northern iberia where we obtained live collected specimens throughout the year we undertook sclerochronological investigations combining observations of incremental shell growth patterns with 18oshell values carbonate samples were taken on i the ventral margins of shells collected alive year round in order to test for isotopic equilibrium and ii along the axis of maximum shell growth of four modern specimens to decipher the shell growth pattern of this species isotopic data showed that calcium carbonate is precipitated in predictable isotopic disequilibrium with the ambient seawater r2 0 95 p

mollusc and brachiopod skeletal hard parts intricate archives of their marine environment the biogenic carbonate hard parts of fossil bivalves cephalopods and brachiopods are among the most widely exploited marine archives of phanerozoic environmental and climate dynamics research the advent of novel analytical tools has led many workers to explore non traditional geochemical and petrographic proxies and work performed in neighbouring disciplines sheds light on the complex biomineralization strategies applied by these organisms these considerations form a strong motivation to review the potential and problems related to the compilation and interpretation of proxy data from bivalve cephalopod and brachiopod hard parts from the viewpoint of the sedimentologist and palaeoceanographer specific focus is on the complex biomineralization pathways of a given dissolved ion or food particle from its aquatic environment via the digestion and biomineralization apparatus in molluscs and brachiopods and its incorporation into a biomineral given that molluscs and brachiopods do not secrete their hard parts from seawater but rather from their mantle and periostracum this paper evaluates differences and similarities of seawater versus that of body fluids cephalopods bivalves and brachiopods exert a strong biological control on biomineralization that to some degree may buffer their shell geochemistry against secular changes in seawater chemistry disordered amorphous calcium carbonate precursor phases later transformed to crystalline biominerals may be significant in carbonate archive research due to expected geochemical offset relative to the direct precipitation of stable phases a reasonable level of understanding of the related mechanisms is thus crucial for those who use these skeletal hard parts as archives of the palaeo environment the impact of what is commonly referred to as biological factors on the geochemistry of mollusc and brachiopod hard parts is explored for conventional isotope systems such as carbon oxygen strontium and traditionally used element to calcium ratios in particular the often used 13ccarb or the mg ca and sr ca elemental proxies are fraught with problems an interesting new research field represents the analysis calibration and application of non traditional proxies to mollusc and brachiopod hard parts examples include the carbonate clumped isotope 47 approach and the analysis of the isotopes of ca mg n li s or element to ca ratios such as li ca or b ca and rare earth elements based on considerations discussed here a series of do s and don ts in mollusc and brachiopod archive research are proposed and suggestions for future work are presented in essence the suggestions proposed here include experimental work also field experiments making use of recent archive organisms or where possible a reasonable recent analogue in the case of extinct groups moreover the detailed understanding of the architecture of mollusc and brachiopod hard parts and their ultra structures must guide sampling strategies for geochemical analyses where feasible a detailed understanding of the diagenetic pathways and the application of multi proxy and multi archive approaches should form the foundation of fossil carbonate archive research the uncritical compilation of large data sets from various carbonate shelled organisms collected at different locations is not encouraged

a multiaxial growth analysis of stable isotopes in the modern shell of saxidomus gigantea implications for sclerochronology studies 1 stable isotope ratios of two modern saxidomus gigantea specimens from namu british columbia are presented to show intraspecimen and interspecimen isotopic variation isotopic profiles 13cshell 18oshell were generated along the axis of maximum growth the profiles show that analogous seasonal variation is recorded in 18oshell however significant variability is recorded in 13cshell we suggest this is caused by differences in metabolic activity between individuals intrashell variability along a growth horizon shows good reproducibility in 13cshell but significant variability in 18oshell especially at the sinistral margin a multiaxial growth analysis generated several profiles from a single valve similar seasonal variations are recorded in 18oshell along all axes 13cshell show significantly less covariation possibly related to internal metabolic activity this study highlights that 18oshell profiles generated from any portion of the shell can be used to evaluate seasonal fluctuations and may be excellent to evaluate types and rates of shell growth

reconstructing past upwelling intensity and the seasonal dynamics of primary productivity along the peruvian coastline from mollusk shell stable isotopes 1 we present here a potential new method to evaluate past variations of the mean intensity of peruvian coastal upwelling and of the seasonal timing of phytoplankton blooms this method uses a combination of the monthly carbon and oxygen isotopic signals preserved in fossil mollusk shells and a series of corrections to extract the variations of the dissolved inorganic carbon dic 13c based on the analysis of five shell samples 85 shells in total from the southern peruvian coast we suggest that the mean coastal upwelling intensity can be determined from a linear relationship between average values of corrected shell 13c and 18o this new potential proxy would bring additional independent information valuable to interpret paleoproductivity changes reconstructed from marine sediment of the nearby continental shelf results obtained on fossil samples from the middle holocene show an increase in upwelling intensity during this period associated to a spatial reorganization of upwelling centers along the south peruvian coast at the seasonal scale corrected shell 13c enrichment indicates a phytoplankton bloom seasonal timing of phytoplankton blooms can be estimated by the lag with the annual temperature cycle reproduced by shell 18o monthly variations the results obtained with two modern shell samples indicate phytoplankton blooms occurring during summer and fall consistently with in situ productivity observations our method relies on revisited assumptions about the influence of temperature and metabolism in mollusk shell 13c we further discussed the validity of these assumptions and the potential implications for the interpretation of similar data sets

reconstructing el nino southern oscillation activity and ocean temperature seasonality from short lived marine mollusk shells from peru abstract a critical need exists for quantitative reconstructions of long term el nino southern oscillation enso variability in the eastern tropical pacific presented here is a method to quantitatively estimate past changes 1 in the seasonal amplitude of sea surface temperature sst in the peruvian coastal upwelling system and 2 in the amplitude of enso related interannual variability in the eastern tropical pacific the seasonal amplitude of sst t along the length of the peruvian coast is strongly correlated with the nino1 2 index we show that the frequency distribution of t values provided by a modern sample of 13 mesodesma donacium shells faithfully reflects modern enso variability at the regional scale including the range of anomalies from la nina to moderate el nino events but excludes extreme warm anomalies because of high shell mortality we propose to use the frequency distribution of enso anomalies in paleoclimate studies for comparisons between shell records coral records and gcm simulations reconstruction uncertainties can be quantified using monte carlo simulations the method presented here opens new perspectives for quantitative paleo enso reconstructions in the eastern pacific since it may be applied with any mollusk species from peru provided at least one annual cycle of sst is faithfully recorded by shell 18 o

oxygen isotope fractionation in marine aragonite of coralline sponges oxygen isotope values of the extant caribbean coralline sponge ceratoporella nicholsoni are compared with published temperatures and 18o of water calculated from salinities the measured values from aragonitic sponge skeletons have a mean offset of 1 0 0 1 from calculated calcite equilibrium values aragonite calcite 1 0010 this is in good agreement with published values from synthetic aragonite they further agree with published near equilibrium oxygen isotope values of temperate and cold water molluscs and foraminifera extrapolated to the temperature range of the coralline sponges these results and the mode of skeleton formation of ceratoporella nicholsoni suggest that these sponges precipitate aragonite close to isotopic equilibrium the temperature dependence of oxygen isotopic fractionation between the aragonite of ceratoporella nicholsoni and water is only roughly constrained by the available data due to the narrow temperature range of the caribbean reef sites however as the data suggest oxygen isotopic equilibrium we can calculate a well constrained temperature equation combining temperate and cold water equilibrium values from molluscs and foraminifera with our sponge data full size image 1 k and full size image 1 k

upwelling signals in radiocarbon from early 20th century peruvian bay scallop argopecten purpuratus shells abstract we quantified 14c 18o and 13c cycles along ontogeny within four bay scallop argopecten purpuratus shells collected from callao bay salaverry and sechura bay peru following the 1907 1908 non el nino years and the 1925 1926 el nino 14c and 13c generally covary 14c and 18o vary inversely simultaneous decreases in 14c and increases in 18o in non el nino shells are followed by constant 14c and gradually decreasing 18o which we interpret as evidence for discrete marine upwelling events followed by warming of the initially cold upwelled water upwelling changes from el nino events are detectable with difficulty in mollusk shell 14c

the shell of the queen scallop aequipecten opercularis l as a promising tool for palaeoenvironmental reconstruction evidence and reasons for equilibrium stable isotope incorporation abstract the queen scallop aequipecten opercularis has been an important part of the marine fauna of the northeast atlantic region since the miocene and is a suitable candidate for palaeoenvironmental studies using stable isotopes modern shells were investigated to determine if carbonate is precipitated in isotopic equilibrium in this species and to confirm that growth continues through the year specimens of a opercularis were cultured under monitored semi natural conditions over an autumn winter period and the analyses of these specimens were supplemented with isotope data from preserved indigenous north sea specimens the results indicated that the cultured specimens grew in relatively low temperatures that oxygen isotopes of shell exterior carbonate were precipitated in isotopic equilibrium and that a large proportion of the ambient temperature range was recorded in shell carbonate the indigenous north sea specimens exhibited a good correspondence to predicted oxygen isotope values for summer the isotopic record related to winter was however somewhat truncated due to growth decelerations in the specimens carbon isotopes of shell exterior carbonate were calculated as being derived primarily from external sources and showed comparatively little influence from metabolically derived carbon this suggests that carbon isotopes were at least close to equilibrium with ambient waters the limited incorporation of metabolic products suggests that a opercularis would be a good monitor of changing carbon isotope ratios in seawater dissolved inorganic carbon the occurrence of equilibrium shell precipitation is explained using a pteriomorph shell calcification model which proposes that transport of ions through the periostracum caused the composition of the extrapallial fluid to be effectively the same as seawater carbonate secretion is therefore not influenced significantly by biological vital effects

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

the fidelity of oxygen and strontium isotope values from shallow shelf settings implications for temperature and age reconstructions abstract the oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age respectively while open ocean samples are the standard source for these measures shelf settings can also provide detailed records however the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions such as freshwater influx confound regional and global signals here we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment data are derived from mollusc shells collected from a stratigraphically restricted transgressive unit in the early eocene 55 ma of the us gulf coastal plain gcp lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region whereas more typically marine facies predominated elsewhere isotopic composition varies predictably with paleoenvironmental setting shells from the estuary have 18o values and 87sr 86sr ratios that reflect high freshwater input specimens in the eastern gcp however from within and between outcrops separated by up to 400 km all yield similar results serial microsampling reveals congruence not only in mean 18o values but also in winter and summer extremes estimated paleotemperatures mean annual temperature of 26 c agree well with proxy and model evidence for the early eocene and the gcp and 87sr 86sr ratios are consistent with the established early eocene seawater ratio the fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry

a 25 000 year tropical climate history from bolivian ice cores ice cores that were recovered from the summit of sajama mountain in bolivia provide carbon 14 dated tropical records and extend to the late glacial stage lgs oxygen isotopic ratios of the ice decreased 5 4 per mil between the early holocene and the last glacial maximum which is consistent with values from other ice cores the abrupt onset and termination of a younger dryas type event suggest atmospheric processes as the probable drivers regional accumulation increased during the lgs during deglaciation and over the past 3000 years which is concurrent with higher water levels in regional paleolakes unlike polar cores sajama glacial ice contains eight times less dust than the holocene ice which reflects wetter conditions and extensive snow cover

el nino variability in the coastal desert of southern peru during the mid holocene abstract fourteen organic rich sedimentary layers in the deposits at quebrada de los burros in coastal southern peru tacna department lie between two debris flow units interpreted to result from el nino events at 8980 cal yr b p and after 3380 cal yr b p respectively the accumulation of the fine grained and low energy sediments of this deposit during the mid holocene is incompatible with the occurrence of el nino events in this region as these would produce catastrophic flood deposits the occurrence of organic rich sediments and evidence of an enhancement of upwelling strength at this time imply the existence of a permanent water supply resulting from an increased condensation of fog at mid altitudes these results suggest a lower intensity and perhaps a lower frequency of occurrence of the el nino phenomenon during the mid holocene it is precisely during this period that the most important human settlements are found at this site probably indicating the presence of reliable supply of fresh water the chronologies for wetlands in the central south altiplano are out of phase with those indicating increased soil moisture episodes on the coast implying a long term difference in climate between these two regions

high resolution windows into early holocene climate srca coral records from the huon peninsula high precision measurements of srca ratios are reported for porites corals from the uplifted holocene coral terraces at huon peninsula papua new guinea the early holocene porites have u th mass spectrometric ages of 8920 60 yr and 7370 50 yr and 234u t values of 145 2 similar to modern seawater the srca coral records provide 5 6 year high resolution near weekly time windows into early holocene sea surface temperatures seasonal temperature fluctuations are generally in the range of 1 c with occasional excursions of 2 c which may indicate the more frequent recurrence of very strong enso el nino southern oscillation events mean annual srca temperatures of 24 2 1 1 c and 22 9 0 8 c have been obtained which are 2 3 c cooler than that exhibited by a modern porites these results indicate that during the early holocene the equatorial western pacific ocean was at least several degrees cooler than present day temperatures this is consistent with late glacial coral records from the caribbean that indicate lower 6 c sea surface temperatures for the equatorial oceans the huon peninsula corals also indicate that ssts were several degrees cooler than those in the caribbean during the early holocene thus although the northern hemisphere summer radiation maximum occurred at 10 ka there appears to have been a significant lag in the response of the equatorial western pacific ocean to this warming cooler early holocene sea surface temperatures in the western pacific may have been due to changing patterns of ocean atmosphere circulation resulting from the exposure of large areas of continental shelf in the southeast asia region a consequence of lower glacial sea levels it is likely that ocean temperatures in the huon peninsula were influenced by the opening at 7 ka of the torres strait that now separates new guinea from the australian mainland

h2o2 treatment of recent coral aragonite oxygen and carbon isotopic implications coral skeletons contain relatively little organic material and inorganically precipitated carbonate cement although these quantities are enough to bias geochemical measurements preliminary treatment is therefore often necessary to remove these materials hydrogen peroxide seems to be the most efficient reagent this strong oxidant destroys organic matter and its acid ph promotes dissolution of carbonate cements that precipitate after the coral skeleton has formed we tested the isotopic effects both on 18o 16o and 13c 12c ratios of such a chemical treatment on coral aragonite we demonstrate that only one treatment is necessary to eliminate different contents without alteration of coral aragonite and we verified that there is no isotopic exchange between the oxygen atoms from cac03 and h2o2 we measured carbon and oxygen isotopic compositions from samples that cover 2 5 years of coral growth and that were split in two ways untreated and h2o2 treated the h2o2 treated subsamples reveal a clear seasonal oscillation that is not evident in the untreated isotopic record therefore hydrogen peroxide treatment should be systematically carried out before isotopic analyses in order to perform palaeoclimatic reconstructions

stable isotope aspects of modern molluscs brachiopods and marine cements from cool water carbonates lacepede shelf south australia the isotopic composition of some modern gastropods bivalves and brachiopods from the lacepede shelf of south australia were investigated to determine the isotopic equilibrium and dis equilibrium states of biogenic and non biogenic inorganic carbonates and to understand the kinetic and metabolic isotopic effects on precipitating carbonates and the isotopic fractionation between these different carbonates and dissolved bicarbonate seawater and high mg calcite hmc marine cements from different depths were also analyzed to determine equilibrium isotopic composition this study shows that the shells of some cool water gastropods and bivalves precipitate in isotopic equilibrium with their ambient waters while brachiopod shells show 18o values heavier than equilibrium values and coralline algae and ahermatypic corals exhibit significant metabolic and kinetic effects the isotopic equilibrium precipitation seen in these biogenic carbonates results from lower precipitation rates that are in turn caused by the lower bottom temperatures in this area

late pleistocene monsoon variability in northwest thailand an oxygen isotope sequence from the bivalve margaritanopsis laosensis excavated in mae hong son province abstract long continuous records of late quaternary environmental change are rare in southeast asia yet they are crucial for understanding the nature of early human dispersal and occupation in the australasian region we present a new record of palaeomonsoon activity extending back to 35 000 bp years before the present based on the analysis of oxygen isotope ratios 18 o in the freshwater bivalve margaritanopsis laosensis excavated from the tham lod and ban rai rockshelters in mae hong son province northwest thailand long term changes in the m laosensis 18 o record reflect changes in the 18 o of the river water in which these organisms grew and correlate well with changes in speleothem 18 o records of east asian monsoon rainfall from hulu cave and dongge cave in china the new northwest thailand 18 o sequence indicates wetter and relatively unstable climatic conditions from 35 000 to 20 000 bp followed by drier conditions from 20 000 to 11 500 bp a period of peak aridity occurred around 15 600 bp during heinrich event 1 suggesting that the intertropical convergence zone shifted southward when the north atlantic region cooled however there is little evidence for the younger dryas event at 12 800 11 500 bp after 9 800 bp precipitation increased substantially and climatic variability declined our findings provide an improved baseline against which to gauge interactions between early humans and climate change in southeast asia for example there was no significant change in the prehistoric flake stone technology used at tham lod and ban rai despite the bivalve 18 o evidence for substantial climate change in the region also the climatic impact of the younger dryas event appears to have been less intense in northwest thailand compared to the cooling and drying observed in china and may explain why agriculture made a relatively late appearance in thailand possibly involving migrants from china

ecological and paleoenvironmental information using stable isotope profiles from living and fossil molluscs stable oxygen and carbon isotopic profiles from recent specimens of spisula solidissima and placopecten magellanicus collected off the virginia coast are used to calibrate annual temperature controlled cycles in the 18o profile and shell growth characteristics the amplitude of the annual 18o cycles decreases with increasing water depth and may be used as a relative depth indicator the isotopic of profiles of two fossil specimens of pleistocene spisula are very similar in amplitude and character to modern analogues and verify the formation of annual growth increments in these fossil specimens offsets between the 18o profiles of the fossil and modern specimens are related to known temperature and ice volume effects during the late pleistocene and support the utility of mollusc isotope records as a stratigraphic tool carbon isotopic profiles from all specimens show light values in the spring and or fall associated with seasonal phytoplankton productivity offsets in the carbon isotopic composition between infaunal and epifaunal species may be related to sediment porewater geochemistry and oxidation of organic matter trends toward lighter 13c values through ontogeny suggest the effects of metabolic changes from a fast growing juvenile into a slower growing sexually mature adult anomalies in both the oxygen and carbon isotopic profiles identify the formation of minor shell growth increments as corresponding to hydrographic perturbations and to winter cold temperatures

exploring the calcium isotope signature of arctica islandica as an environmental proxy using laboratory and field cultured specimens abstract the calcium isotope composition 44 40ca of the aragonitic bivalve arctica islandica grown in laboratory and field cultures was investigated in terms of environmental and biological controls to explore its potential as a palaeoceanographic proxy while we found no significant effect of salinity on ca isotope fractionation the relationship between 44ca 40ca ratios of a islandica and temperature was best explained by a generalised additive model which describes the temperature versus ca isotope relationship as a nonlinear second degree polynomial with an optimum temperature of 15 c since 44ca 40ca ratios clearly increase with increasing temperature up to 15 c the temperature versus ca isotope relation can be approximated through a linear fit up to 15 c the slope of this linear temperature dependent ca isotope fractionation resembles previous calibrations of inorganic and biogenic aragonites providing insights into fractionation processes during bivalve biomineralization our findings suggest that the observed biologically induced ca isotope fractionation occurs when ca is transported from seawater to the site of mineralization most likely during the passage through the epithelial mantle the observed evidence for strong vital effects indicates limited use of ca isotopes in a islandica as a temperature proxy

conus shell δ13c values as proxies for δ13cdic in tropical waters abstract we use time series 18o and 13c data from seawater and live collected conus shells from panama s pacific coast to test the fidelity of the gastropod s 13c values as a proxy for the 13c of marine dissolved inorganic carbon dic and the potential of 18o 13c correlations in shell profiles for resolving relative magnitudes of seasonal upwelling and freshening water samples were collected from march 2011 to august 2012 from naos island marine laboratory and conus specimens were collected from nearby veracruz beach in july 2013 in general patterns corresponded with seasonal changes in rainfall and upwelling on the pacific coast of panama during the long rainy season the upwelling signal is absent and seawater salinity 18o and 13cdic all decline during the dry season the upwelling signal increases and runoff declines increasing salinity 18o and 13cdic values shell 13c values strongly correlate with measured 13cdic values but are lower than expected equilibrium for aragonite by approximately 2 reflecting the incorporation of light metabolic c the co dependences of 18o and 13c provide reliable indicators of upwelling negative correlation and freshening positive correlation for nearshore environments allowing for the study of historical climate change and upwelling based on beach collected museum specimens

stable isotope fractionation between mollusc shells and marine waters from martinique island abstract forty nine aragonitic and calcitic shells from 14 species of marine tropical molluscs bivalvia gastropoda polyplacophora and ambient waters from martinique have been analyzed for their carbon and oxygen isotope compositions mineralogy of shells was systematically determined by raman spectroscopy that reveals composite shell structures and early processes of diagenetic alteration in mangrove brackish waters result from the mixing between 89 1 of seawater and 11 1 of freshwater a hydrological budget quantified by both oxygen isotope and salinity mass balance calculations mollusc shells from the mangrove environment s 31 18 o 0 5 are characterized by mean 13 c values 1 2 lower than those 2 6 living in the open sea s 35 18 o 1 these low carbon isotope compositions result from the oxidation of organic matter into bicarbonate ions used in the building of mollusc shells the oxygen isotope compositions of the studied mollusc species are mainly controlled by the temperature and composition of seawater whereas the role of the so called vital effects is negligible contrasting with carbon isotopes variability in the 18 o values among and within species of mollusc shells is very low 1 0 15 for a given littoral environment using ambient temperatures of seawater 28 30 c oxygen isotope fractionations between all studied living species and environmental waters match those extrapolated from the fractionation equation established for molluscs by grossman and ku chem geol isot geosci sect 59 1986 59 in the range 3 20 c by analyzing calcite and aragonite layers from the same shell or by comparing shells from different species living in the same environment there is no evidence that oxygen isotope fractionation between aragonite and water differs from that between calcite and water on the basis of these results we conclude that the oxygen isotope compositions of shells from most fossil mollusc species are suitable to estimate past seawater temperatures at any paleolatitude

stable isotope vital effects in coccolith calcite uncertainties about the origin of the many disequilibrium or vital effects in a variety of calcifying organisms and whether these effects are constant or variable have hampered paleoceanographic application of carbon and oxygen isotopic ratios unraveling the source of these effects will improve paleoceanographic applications and may provide new information on changes in cell physiology and ecology culture of eight species of coccolithophorids a dominant marine phytoplankton group reveals a 5 array of disequilibrium or vital effects in both the carbon and oxygen isotopic composition of coccolith calcite in moderate light and nutrient replete cultures oxygen isotopic fractionation and carbon isotopic fractionation correlates directly with cell division rates and correlates inversely with cell size across a range of species however when growth rates of a single species are increased or decreased by higher or lower light levels 18o is relatively invariant likewise growth rate variations as a function of temperature do not influence coccolith 18o the slope of the 18o vs temperature relation in cultures of both gephyrocapsa oceanica and helicosphaera carteri is the same as for abiogenic carbonates this suggests a constant species specific isotopic fractionation which does not vary with cell physiology the constancy of vital effects suggests that coccolith stable isotopes will provide reliable phase for paleoceanographic reconstruction of temperature and seawater chemistry as long as monospecific fractions are analyzed or changes in nannofossil assemblages are accounted for with species specific correction factors we suspect that the cell size and its constraints on the rate of co2 diffusion relative to c fixation may be the first order influence on coccolith stable isotope vital effects a quantitative model of this process may provide important constraints on mechanisms of carbon acquisition of coccolithophorids in both modern and extinct species

ice elevation near the west antarctic ice sheet divide during the last glaciation 1 interior ice elevations of the west antarctic ice sheet wais during the last glaciation which can serve as benchmarks for ice sheet models are largely unconstrained here we report past ice elevation data from the ohio range located near the wais divide and the onset region of the mercer ice stream cosmogenic exposure ages of glacial erratics that record a wais highstand 125 m above the present surface date to 11 5 ka the deglacial chronology prohibits an interior wais contribution to meltwater pulse 1a our observational data of ice elevation changes compare well with predictions of a thermomechanical icesheet model that incorporates very low basal shear stress downstream of the present day grounding line we conclude that ice streams in the ross sea embayment had thin lowslope profiles during the last glaciation and interior wais ice elevations during this period were several hundred meters lower than previous reconstructions citation ackert r p jr s mukhopadhyay b r parizek and h w borns 2007 ice elevation near the west antarctic ice sheet divide during the last glaciation geophys res lett 34 l21506 doi 10 1029 2007gl031412

climatic and environmental changes during the middle to late holocene in southern south america a sclerochronological approach using the bivalve retrotapes exalbidus dillwyn from the beagle channel abstract little is known about the effects of holocene climate variability on marine environments and their biota in southern south america fossil shells of the aragonitic bivalve retrotapes exalbidus dillwyn offer the possibility of investigating climate variability and particularly the seasonal dynamics of sea water temperature in the beagle channel during different parts of the middle to late holocene we compared three specimens of different geological age determined by 14 c i e 5190 bp 3839 bp and 431 bp these shells respectively refer to a cooling period at ca 5000 bp a climate optimum at ca 4000 bp and a further cooling at ca 500 bp all three shells showed clear annual growth bands with a distinct intra annual 18 o cycle 18 o ranges clearly indicate higher summer temperatures in the 3839 bp shell 1 53 1 16 compared with the 5190 bp shell 1 29 0 72 and the 431 bp shell 1 55 0 44 which correspond to maximum ssts of 17 73 c 9 61 c and 10 81 c respectively apparently r exalbidus shells are suitable bioarchives that allow comparing seasonal patterns through the holocene thus constituting another proxy for evaluating paleoclimatic and paleoenvironmental changes in this region

variation in holocene el nino frequencies climate records and cultural consequences in ancient peru analysis of mollusks from archaeological sites on the north and central coasts of peru indicates that between ca 5800 and 3200 2800 cal yr b p el nino events were less frequent than today with modern rapid recurrence intervals achieved only after that time for several millennia prior to 5 8 ka el nino events had been absent or very different from today the phenomena called el nino have had severe consequences for the modern and colonial historically recorded inhabitants of peru and el nino events also influenced prehistoric cultural development the onset of el nino events at 5 8 ka correlates temporally with the beginning of monumental temple construction on the peruvian coast and the increase in el nino frequency after 3 2 2 8 ka correlates with the abandonment of monumental temples in the same region

composition of stable isotopes in geoduck panopea abrupta shells a preliminary assessment of annual and seasonal paleoceanographic changes in the northeast pacific abstract we tested the suitability of using panopea abrupta geoduck shells to evaluate changes in both annual and seasonal sea surface temperature geoducks are long lived and deposit annual growth increments within their shell each winter making them potentially excellent paleoceanographic archives shells were sampled by thin section from the hinge plate region where the first 20 30 years of growth provide relatively wide annual increments suitable for sampling for isotopic analysis the geoducks used in this study were collected in ad 2000 from west of protection island located at the eastern end of the strait of juan de fuca the isotopic record is compared to the historic instrumental record as well as the thickness of geoduck growth increment measurements which were also correlated with water temperature strom a francis r c mantua n j miles e l peterson d l 2004 north pacific climate recorded in growth rings of geoduck clams a new tool for paleoenvironmental reconstruction geophysical research letters 31 p lo6206 doi 10 1029 2004gl019440 the annual average oxygen isotopic values from two geoduck clams whose first years of growth correspond to the early historic instrumental record ad 1920 appear to be recording trends in sea surface temperature intra annual sampling of annual growth increments indicates that the shells also appear to be recording seasonal changes in sea surface temperature preliminary analysis of carbon isotopic data on both the annual and seasonal timescales indicate the potential for assessing productivity changes in ambient seawater

seasonal climatic fluctuations in the late triassic tropics high resolution oxygen isotope records from aragonitic bivalve shells cassian formation northern italy abstract three megalodontoid bivalves from the upper triassic cassian formation n italy dolomites were sampled for 13 c and 18 o sclerochronology n 270 with more than 1000 described invertebrate species the cassian formation has one of the best records of an early mesozoic tropical fauna in addition the cassian formation is one of the very few triassic occurrences with original aragonite preservation with all studied shells consisting of pristine aragonite the presence of aragonite and crossed lamellar as well as fibrous prismatic shell microstructures shown for the first time for triassic megalodontoids suggests absence or minimal impact of diagenetic alteration the 13 c values range from 3 6 to 5 8 and show a distinct cyclicity in two studied shells whereas a third shell shows no obvious cyclicity in one bivalve specimen the cycles are somewhat offset from 18 o cycles and in the other specimen 18 o and 13 c curves are inversely correlated seasonal variation in freshwater runoff including nutrient input and subsequent changes in plankton productivity during dry and wet seasons may explain 13 c cyclicity 18 o values show a pronounced cyclicity within each of the studied shells varying from 3 6 to 1 4 the variations in 18 o suggest a pronounced seasonality in late triassic tropical shallow waters of the western tethys with inferred seasonal temperature changes ranging from 24 to 32 c influx of fresh water during the rainy seasons mega monsoon or upwelling might also explain part of the variation in 18 o the presented data suggest that the diverse cassian fauna lived under conditions characterized by warm sea surface waters with a pronounced seasonality similar conditions are reported for some modern tropical settings

reconstructing the duration of the west african monsoon season from growth patterns and isotopic signals of shells of anadara senilis saloum delta senegal abstract long term reconstructions of the seasonality of the west african monsoon are limited by the lack of seasonally resolved paleoclimate archives in this region we present an application based on the growth patterns and monthly resolved 18o profiles of anadara senilis bivalve shells to quantitatively estimate the duration of the rainy and dry seasons in the hypersaline saloum delta senegal fortnightly growth patterns are used to estimate changes of the growth rate and to place the shell isotope record into a temporal context based on fortnightly growth patterns and sharply declining 18o values the duration of the rainy season was estimated as an illustrative example we quantitatively estimated the duration of two rainy seasons and two dry seasons that occurred about 1500 years ago from a fossil shell of the dioron boumak archaeological site to the nearest month this precision can be statistically improved by the analysis of a larger shell number or by higher resolution isotope sampling our results open the possibility of using large fossil shell accumulations in the saloum delta for quantitative studies of the long term variability of the west african monsoon seasonality

stable isotopes and sclerochronology of the bivalve mesodesma donacium potential application to peruvian paleoceanographic reconstructions reconstructing the past enso el nino southern oscillation interannual variability requires very high resolution sea surface temperature sst proxies in order to compensate for the lack of coral archive in the eastern pacific cold tongue we studied the potentiality of the bivalve species mesodesma donacium as a sst tracer for the peruvian coast biomineralisation cycles and growth line formation in the shells are shown to be controlled by tides the sclerochronology based on fortnightly cycles allowed us to compare local sst data with high resolution shell records as a result of the high correlation between sst and aragonite delta 18 o we calculated a linear sst fractionation relationship for the 14 20 degrees c range t degrees c 17 41 1 15 3 66 0 16 delta 18 o arag pdb delta 18 o wat smow the difference from the commonly used grossman and ku 1986 grossman e l ku t l 1986 oxygen and carbon fractionation in biogenic aragonite temperature effect chemical geology 59 59 74 equation suggests the potential existence of a species dependence of vital effect within bivalves this preliminary equation allows monthly scale sst reconstructions with a 1 5 degrees c precision using m donacium archaeological shells from southern peru giving potential insights into the problem of past enso behaviour c 2005 elsevier b v all rights reserved

a 38 000 year record of floods and debris flows in the ilo region of southern peru and its relation to el nino events and great earthquakes abstract previous work throughout the ilo region of south coastal peru has documented the existence of flood and debris flow deposits produced by two el nino events evidently much more severe than any in recent history these two events have been dated to ca ad 1300 1400 and ad 1607 08 the late pleistocene to holocene record of older sedimentary deposits in this region is dominated by flood and debris flow deposits of similar scale these older deposits have been described and dated from three coastal alluvial fan sites these deposits which are as old as 38 200 years are dominated by massive debris flow deposits several tens of cm thick typically composed of cobble and boulder sized clasts in a matrix of silty sand with characteristics indicating generation by heavy rainfall in an arid environment twenty two radiocarbon dates and a single infrared stimulated luminescence date show that particularly severe el nino events occurred throughout the late pleistocene and two of three divisions of the holocene with significantly different frequencies the period of greatest activity was during the early holocene when at least six such events took place during a period of ca 3600 years beginning near the end of the younger dryas ca 12 000 years ago one of these events produced a debris flow that may have caused abandonment of the paleo indian site at quebrada tacahuay one of the oldest on the andean coast no severe events took place during the middle holocene between ca 8400 and 5300 years ago when a wide variety of other paleoclimate proxy records indicate that the el nino southern oscillation regime was particularly weak since ca 5300 years ago four of these severe events have taken place the late pleistocene sequence is constrained by only two dates which indicate that at least ten severe events took place between ca 38 200 and 12 900 years ago mechanisms probably responsible for generating these large scale deposits include 1 mega ninos that produced anomalously heavy rainfall along most or all of the central andean coast 2 el ninos that occurred shortly after great earthquakes that produced large amounts of sediment or 3 el ninos that produced anomalously heavy local rainfall the existence of these large scale deposits in the ilo region implies a level of hazard much higher than indicated by the historical record alone

strong el nino events during the early holocene stable isotope evidence from peruvian sea shells intrashell oxygen and carbon stable isotope profiles 18o 13c were established for mesodesma donacium shells from the preceramic archaeological site quebrada de los burros in coastal southern peru to reconstruct the sea surface temperature sst variations and to estimate changes of the el nino southem oscillation enso interannual variability from the early holocene to the present very strong oxygen isotopic excursions attributed to el nino events are evident in three shells dated between 9 and 7 9 ka this indicates that short and strong warm events were breaking the mean cooler surface conditions 2 3 c cooler compared with today ssts in relation with an intense upwelling system at 4 8 ka slightly lower mean sst cooler than today by 0 7 c and a reduced seasonality confirms the previous hypothesis of a weak enso variability at this period

shell midden sclerochronology abstract sclerochronological analysis of shell midden faunal remains offers a unique opportunity to study climate and environmental change in relation to human activity middens exist near most aquatic habitats almost worldwide for much of the late pleistocene and holocene they afford good preservation of accretionary calcium carbonate remains such as mollusk shells and fish otoliths in comparatively well dated contexts as such midden samples are a source of sequential proxy records of past climate and environmental conditions and may provide detailed pictures of human environment interaction however midden samples present several challenges to the development and application of sclerochronological proxies including unique taphonomic concerns here these challenges are outlined within descriptions of the major applications of midden sclerochronology archeological concerns including season of capture reconstructing the history of anthropogenic environmental impacts and paleoclimate environment proxy reconstructions

daily growth and tidal rhythms in miocene and modern giant clams revealed via ultra high resolution la icpms analysis a novel methodological approach towards improved sclerochemistry abstract we present a novel approach for ultra high resolution laser ablation inductively coupled plasma mass spectrometry la icpms analysis which not only allows us to clearly resolve tridacna giant clam shells daily element ca variability preserved within microscopically visible growth increments is resolved by utilizing the combined capabilities of a rotating rectangular aperture spot size on target 4 50 m the rapid signal washout of a laurin two volume laser ablation cell and slow compositional profiling 1 5 m s striking co variation between oscillating cycles in b ca mg ca sr ca and ba ca is discernible yet also tantalizingly sub daily shifts between these element ca ratios can be observed in comparison to a lower resolution seasonally resolved 18 o mg ca record warter et al 2015 the 10 20 m element ca cycles are determined to be daily in origin and a further 14 15 day cyclicity is superimposed on the daily cycles the latter is interpreted to reflect miocene tidal periodicity changes in pixel intensity during thin section observation associated with micro and macroscopically visible low and high density bands have been quantified via image processing analysis this reveals close correspondence to the measured trace elemental cyclicity indicating a coupling between the geochemical composition of the shell and the incremental growth pattern a comparison between the elemental and image processing results reveals that ultra high resolution la icpms analysis surpasses the latter in detecting environmental rhythms including daily and tidal cycles highly resolved la icpms analysis is a viable alternative to nanosims and opens up routine investigation of long term deep time paleoenvironmental records at daily resolution

an aquaculture based method for calibrated bivalve isotope paleothermometry to quantify species specific relationships between bivalve carbonate isotope geochemistry 18oc and water conditions temperature and salinity related to water isotopic composition 18ow an aquaculture based methodology was developed and applied to mytilus edulis blue mussel the four by three factorial design consisted of four circulating temperature baths 7 11 15 and 19 c and three salinity ranges 23 28 and 32 parts per thousand ppt monitored for 18ow weekly in mid july of 2003 4800 juvenile mussels were collected in salt bay damariscotta maine and were placed in each configuration the size distribution of harvested mussels based on 105 specimens ranged from 10 9 mm to 29 5 mm with a mean size of 19 8 mm the mussels were grown in controlled conditions for up to 8 5 months and a paleotemperature relationship based on juvenile m edulis from maine was developed from animals harvested at months 4 5 and 8 5 this relationship t c 16 19 0 14 4 69 0 21 18oc vpbd 18ow vsmow 0 17 0 13 18oc vpbd 18ow vsmow 2 r2 0 99 n 105 p 0 0001 is nearly identical to the kim and o neil 1997 abiogenic calcite equation over the entire temperature range 7 19 c and it closely resembles the commonly used paleotemperature equations of epstein et al 1953 and horibe and oba 1972 further the comparison of the m edulis paleotemperature equation with the kim and o neil 1997 equilibrium based equation indicates that m edulis specimens used in this study precipitated their shell in isotopic equilibrium with ambient water within the experimental uncertainties of both studies the aquaculture based methodology described here allows similar species specific isotope paleothermometer calibrations to be performed with other bivalve species and thus provides improved quantitative paleoenvironmental reconstructions

seasonality in the north sea during the allerod and late medieval climate optimum using bivalve sclerochronology seasonal temperature patterns may have changed through time in response to current global warming however the temporal resolution of available proxy records is not sufficient to quantify paleotemperature seasonality prior to anthropogenic forcing of the climate in the present study we reconstructed seasonal and inter annual temperature patterns of the north sea during the last 140 years the allerod interglacial and the late medieval climate optimum using sclerochronological and 18oaragonite data from bivalve shells arctica islandica on average the climate during 1278 1353 ad was ca 1 1 c colder and seasonality was ca 60 less than today during the allerod long term temperatures remained about 3 2 c below present values and absolute summer and winter anomalies were ca 4 and 2 7 c respectively however seasonality was statistically indistinguishable from today long term average temperatures compare well with existing data for the late medieval and allerod but detailed information on seasonality during the studied time intervals has never been presented before our data also demonstrated that annual instrumental and 18oaragonite derived temperatures did not always match this difference is explained by 1 nao driven salinity changes which influence the temperature estimation from 18oaragonite and 2 food driven changes in growth rates portions of the shell that formed more rapidly are overrepresented in carbonate samples our study indicated that individual bivalve shells can open discrete near century long ultra high resolution windows into the climate past such information can be vital for testing and verifying numerical climate models

palynological evidence for increased aridity on the central chilean coast during the holocene abstract the late quaternary vegetation of the semiarid coast of central chile is inferred from the palynological analysis of profiles from quereo 31 55 s and quintero 32 47 s prior to 11 400 yr b p wet conditions are suggested by the abundance of pollen indicators of swamp and aquatic taxa such as cyperaceae and myriophyllum and by the presence of traces of arboreal pollen since ca 10 000 yr b p a trend toward increasingly drier conditions is implied by the almost complete absence of arboreal and aquatic taxa and a general decrease in the diversity of the semiarid shrubland indicators from 3000 yr b p onward the pollen records show the reappearance of swamp and aquatic taxa presumably associated with wetter conditions which led to recolonization by forest taxa at 1720 yr b p in quintero the drier climate detected along the semiarid coast of central chile during most of the holocene extended inland to the andean foot hills within the present mediterranean type climate zone of chile and also affected the distribution of the winter deciduous nothofagus forests and the northern boundary of the temperate rain forests

eurhomalea exalbida bivalvia a reliable recorder of climate in southern south america abstract due to the lack of suitable high resolution archives regional and continental scale climate dynamics of southern south america are not well understood shells of the long lived shallow marine bivalve mollusk eurhomalea exalbida dillwyn are likely to contain information on the past water temperatures as yet however no rigorous calibration study has been presented so that growth history traits and the reliability of shell oxygen isotope based temperature estimates remain unknown shell growth patterns and oxygen isotope ratios of four young specimens of e exalbida from the falkland islands southwest atlantic were analyzed and cross calibrated with environmental parameters results indicate that e exalbida likely captured the full seasonal temperature amplitude in its shell annual growth line formation occurred between fall and early winter the most remarkable finding however was that e exalbida formed its shell with an offset of 0 48 to 1 91 from expected oxygen isotopic equilibrium with the ambient water if this remained unnoticed paleotemperature estimates would overestimate actual water temperatures by 2 1 8 3 c with increasing ontogenetic age the discrepancy between measured and reconstructed temperatures increases exponentially irrespective of the seasonally varying shell growth rates we attribute this finding to a ph increase in the extrapallial fluid during ontogeny favoring a dominance of the isotopically lighter carbonate ions over isotopically heavier bicarbonate ions when this disequilibrium fractionation effect is taken into account e exalbida can serve as a high resolution paleoclimate archive for mid to high latitudes of southern south america providing quantifiable temperature estimates even from single fossil specimens