iron control of past productivity in the coastal upwelling system off the atacama desert chile 1 biogenic opal and organic carbon vertical rain rates in sediment cores reveal a strong cyclicity in the productivity of the upwelling system off presently arid northern chile during the last 100 000 years changes in productivity are found to be in phase with the precessional cycle 20 000 years and with inputs of iron from the continent during austral summer insolation maxima increased precipitation and river runoff in the region appear to have brought high inputs of iron mainly from the andes to the coastal ocean enhancing primary productivity there we interpret our results as providing evidence for iron control of past productivity in this upwelling system and for a tight link between productivity and orbital forcing at midlatitudes

chronological and geoarchaeological investigations on an anthropogenic shell accumulation layer in the longotoma dune field central chile abstract along the chilean peruvian coast numerous archaeological sites associated with shell accumulations provide evidence for the role of coastal environments as a natural corridor for the human occupation of south america in particular the semi arid coastline of northern central chile 33 27 s is a key area for investigating the relationship between human occupation history and past climate changes as palaeoenvironmental studies record important climatic fluctuations in the area throughout the holocene in this study we present a consistent chronology of an anthropogenic shell accumulation layer and an associated palaeosol found in the stratigraphy of palaeodunes in the longotoma dune system northern central chile 32 24 s 71 23 w infrared stimulated luminescence irsl dating of feldspars is used for the first time in this context to establish the chronological framework together with radiocarbon dating the consistency between irsl and radiocarbon ages demonstrates the potential of irsl techniques for studies in comparable settings and at similar time scales where optically stimulated luminescence osl dating of quartz is problematic the chronostratigraphical results i allow to infer different phases of dune activity as well as an intermittent period of interdunal soil formation at the end of the 6th millennium bp when the cultural layer and the palaeosol formed ii allocate an age range of 4500 3500 a to alluvial deposits below the modern dune corridor and thereby iii give further evidence for the presence of archaic coastal hunter gatherer populations in the la ligua bay and in northern central chile

rainfall response to orbital and millennial forcing in northern peru over the last 18 ka we present a high resolution marine record of sediment input from the guayas river ecuador that reflects changes in precipitation along western equatorial south america during the last 18ka we use log ti ca derived from x ray fluorescence xrf to document terrigenous input from riverine runoff that integrates rainfall from the guayas river catchment we find that rainfall induced riverine runoff has increased during the holocene and decreased during the last deglaciation superimposed on those long term trends we find that rainfall was probably slightly increased during the younger dryas while the heinrich event 1 was marked by an extreme load of terrigenous input probably reflecting one of the wettest period over the time interval studied when we compare our results to other deglacial to holocene rainfall records located across the tropical south american continent different modes of variability become apparent the records of rainfall variability imply that changes in the hydrological cycle at orbital and sub orbital timescales were different from western to eastern south america orbital forcing caused an antiphase behavior in rainfall trends between eastern and western equatorial south america in contrast millennial scale rainfall changes remotely connected to the north atlantic climate variability led to homogenously wetter conditions over eastern and western equatorial south america during north atlantic cold spells these results may provide helpful diagnostics for testing the regional rainfall sensitivity in climate models and help to refine rainfall projections in south america for the next century

the last 7500 cal yr b p of westerly rainfall in central chile inferred from a high resolution pollen record from laguna aculeo 34 s abstract we report multiproxy analyses of a sediment core obtained from laguna aculeo that spans the past 7500 years laguna aculeo 33 50 s 70 55 w is one of the few natural inland lakes located in the mediterranean zone of central chile near the northern margin of the influence of the southern westerlies the record shows elevated pollen counts of halophytes and seasonally drying of the lake basin prior to 5700 cal yr b p indicating severe aridity and warmer than present conditions this was followed by the establishment of a fresh water lake along with an increase in arboreal and herbaceous plant diversity between 5700 and 3200 cal yr b p an intensification of this trend started at 3200 cal yr b p along with the abrupt decrease of halophytes until 100 cal yr b p within this humid period pollen accumulation rates show large amplitude fluctuations coeval with numerous turbidite layers suggesting a highly variable and torrential rainfall pattern this intense and variable precipitation regime is probably associated with the el nino southern oscillation enso phenomenon we suggest that the modern mediterranean climate of central chile was established at 3200 cal yr b p paleovegetation and paleolimnological changes starting at 100 cal yr b p correlate with documented human activity surrounding the lake

last deglacial sea surface temperature evolution in the southeast pacific compared to climate changes on the south american continent abstract applying the alkenone method we estimated sea surface temperatures ssts for the past 33 kyr in two marine sediment cores recovered from the continental slope off mid latitude chile the sst record shows an increase of 6 7 c from the last ice age lia to the holocene climatic optimum while the temperature contrast between lia and modern temperatures is only about 3 4 c the timing and magnitude of the last deglacial warming in the ocean correspond to those observed in south american continental records according to our sst record the existence of a younger dryas equivalent cooling in the southeast pacific is much more uncertain than for the continental climate changes a warming step of about 2 5 c observed between 8 and 7 5 cal kyr bp may have been linked to the early to mid holocene climatic transition 8 2 7 8 cal kyr bp also described from equatorial africa and antarctica in principal variations in the latitudinal position of the southern pacific westerlies are considered to be responsible for sst changes in the peru chile current off mid latitude chile

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

characteristics and formation of eastern south pacific intermediate water 1 newly gathered hydrographic data from the eastern south pacific is combined with other high quality data mainly woce to reassess the properties and boundaries of the eastern south pacific intermediate water espiw to date the espiw has been only poorly described the espiw core is found off central and northern chile between the coast and 90 w and 20 38 s located at 50 400 m of depth its temperature varies between 11 13 c salinity ranges from 34 1 34 3 and its sigma t lies between 25 75 26 25 kgm 3 espiw spreads with the subtropical gyre circulation and can be traced to at least 150 w formed through the process of subduction southeastward of the wind driven gyre circulation the espiw communicates surface properties of the waters off central chile to tropical latitudes

accounting for the marine reservoir effect in radiocarbon calibration abstract the radiocarbon dating method is supported by highly refined calibration data empirically obtained from environmental archives nevertheless marine calibration remains problematic due to the spatiotemporally variable marine reservoir effect mre the currently accepted curve for radiocarbon calibration in the ocean is a global curve partly derived by numerical modelling from its atmospheric counterpart as such this curve cannot account for the effects of local phenomena strongly correlated with 14c signatures in seawater e g ocean dynamics and continental input although the radiocarbon community has suggested the use of regional calibration curves that would better represent the heterogeneous ocean reservoir a reasonable method for their construction has not yet been proposed we directly address this longstanding issue in radiocarbon research by exploring the output of a model for the temporal evolution of the mre the limitations of this model are inherited by our method and this hinders the use of the regional curves derived here in many regions of the world ocean nevertheless the approach described in this paper remains valid regardless of the chosen model and our preliminary results show that with the future development of accurate and highly resolved models for the mre this method may be a promising alternative to the use of r values in the process of marine calibration

sun ocean nuclear bombs and fossil fuels radiocarbon variations and implications for high resolution dating radiocarbon or 14c is a radiometric dating method ideally suited for providing a chronological framework in archaeology and geosciences for timescales spanning the last 50 000 years 14c is easily detectable in most common natural organic materials and has a half life 5 730 40 years relevant to these timescales 14c produced from large scale detonations of nuclear bombs between the 1950s and the early 1960s can be used for dating modern organic materials formed after the 1950s often these studies demand high resolution chronology to resolve ages within a few decades to less than a few years despite developments in modern high precision 14c analytical methods the applicability of 14c in high resolution chronology is limited by short term variations in atmospheric 14c in the past this article reviews the roles of the principal natural drivers e g solar magnetic activity and ocean circulation and the anthropogenic perturbations e g fossil fuel co2 and 14c from nuclear and thermonuclear bombs

changes in biological productivity and ocean climatic fluctuations during the last 1 5 kyr in the humboldt ecosystem off northern chile 27 s a multiproxy approach abstract a sedimentary box core biac072014 collected in a coastal environment in the humboldt current ecosystem hce inglesa bay 27 s northern chile was used to reconstruct the changes in biological productivity and ocean climate fluctuations during the last 1 5 kyr via geochemical mineralogical and micropaleontological analyses from 510 ce to 930 ce el nino like conditions prevailed while during the medieval climate anomaly mca 950 ce to 1450 ce la nina like conditions predominated this pattern might have resulted from weakening strengthening of the walker cell contraction expansion of the south pacific sub tropical high spsh and a predominance of warm cold phases of the pacific decadal oscillation pdo between 1820 ce and the present inglesa bay experienced a reduction in the oxygen minimum zone omz intensity and biological productivity an increase in the detritic input and a decrease in sea surface temperature sst despite the regional intensification and secular cooling 14 s and 27 s of coastal upwelling the similarity between the reduction in biological productivity and omz intensity in this region and that in the central zone of chile 36 s suggests that inglesa bay acts a transition zone in relation to the oceanographic behaviour of the hce the reduction in the omz intensity and biological productivity during the last 200 years could be explained by greater subsurface ventilation in intermediate depths due to more northward displacement of the subduction region of the eastern south pacific intermediate water espiw near 30 s in response to the strengthening of the circulation of the subtropical gyre the coastal cooling observed in the northern section of hce during the current warm period suggests that it is not possible to demonstrate that el nino like conditions promoted the reduction in biological productivity and omz intensity in inglesa bay

mid and late holocene limnogeology of laguna del negro francisco northern chile and its palaeoclimatic implications lacustrine sediments from the high elevation endorheic saline lake negro francisco 27 28 s 69 14 w 4125 m provide a detailed mid and late holocene environmental history of the southern chilean altiplano mineralogy chemical composition and sedimentary facies analyses of the deposits confirm the regional significance of mid holocene aridity between 6000 and 3800 bp precipitation rates were signifi cantly lower than the c 250 mm yr 1 of today fully arid conditions were interrupted by short term moist spells with an average return period of about 200 years effective moisture increased after 3800 bp and peaked between 3000 and 2600 bp and between 2200 and 1800 bp in two phases with conditions more humid than today comparison with regional palaeodata suggest that these two late holocene humid spells were most likely related to pacific moisture sources salinity levels increased again in laguna del negro francisco after 1800 bp the onset of modern climatic conditions was a stepwise nonlinear proce

old radiocarbon ages in the southwest pacific ocean during the last glacial period and deglaciation marine radiocarbon 14c dates are widely used for dating oceanic events and as tracers of ocean circulation essential components for understanding ocean climate interactions past ocean ventilation rates have been determined by the difference between radiocarbon ages of deep water and surface water reservoirs but the apparent age of surface waters currently approximately 400 years in the tropics and approximately 1 200 years in antarctic waters might not be constant through time as has been assumed in radiocarbon chronologies and palaeoclimate studies here we present independent estimates of surface water and deep water reservoir ages in the new zealand region since the last glacial period using volcanic ejecta tephras deposited in both marine and terrestrial sediments as stratigraphic markers compared to present day values surface reservoir ages from 11 900 14c years ago were twice as large 800 years and during glacial times were five times as large 2 000 years contradicting the assumption of constant surface age furthermore the ages of glacial deep water reservoirs were much older 3 000 5 000 years the increase in surface to deep water age differences in the glacial southern ocean suggests that there was decreased ocean ventilation during this period

the geochronological potential of isoleucine epimerisation in cassowary and megapode eggshells from archaeological sites abstract our research demonstrates that the extent of isoleucine epimerisation a i in fragments of avian eggshells provides geochronological information in archaeological contexts in the archaeological sequence of hay cave northern queensland australia there is an excellent correspondence between the a i values of australian brush turkey alectura lathami eggshells n 99 and independent geochronological control n 16 radiocarbon ages including 4 on eggshell calcite the a i values identify three phases of deposition during the holocene at hay cave in contrast to the alectura eggshell a i values a poor correspondence was observed between the a i values of cassowary casuarius eggshells from toe n 35 and kria caves n 23 ayamaru plateau papua and the depths from which the specimens were recovered in these stratified sequences given coherent archaeofauna trends and radiocarbon chronologies n 8 and 2 eggshell calcite radiocarbon ages at toe and kria respectively with respect to depth the variable a i values are not explicable in terms of mixing rather the variability is most likely due to exposure of the eggshells to the high temperatures of campfires despite the variability eggshells with relatively low a i values amongst specimens recovered from similar depths and therefore presumably least influenced by high temperatures exhibit a gradual increase in a i with respect to depth as expected in a stratified deposit from this observation it is suggested that the identification of heated eggshells will increase confidence in geochronological information provided by a i these studies illustrate the complications that arise from campfire induced acceleration of amino acid racemisation and emphasise that although this phenomenon is common it is not universally encountered in archaeological contexts

variability of 14c reservoir age and air sea flux of co2 in the peru chile upwelling region during the past 12 000 years abstract the variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo environmental archives we report here new radiocarbon reservoir ages r from the central coast of chile 32 s for the holocene period and compare these values to existing reservoir age reconstructions from southern peru and northern chile late holocene r values show little variability from central chile to peru prior to 6000 cal yr bp however r values were markedly increased in southern peru and northern chile while similar or slightly lower than modern r values were observed in central chile this extended dataset suggests that the early holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern chile this change in the marine reservoir ages indicates that the early holocene air sea flux of co2 could have been up to five times more intense than in the late holocene in the peruvian upwelling while slightly reduced in central chile our results show that oceanic circulation changes in the humboldt system during the holocene have substantially modified the air sea carbon flux in this region

from the use of space to territorialisation during the early holocene in taltal coastal atacama desert chile in this paper we present recent data on early holocene human occupations from taltal in the coast of the atacama desert we focus on evidences of mobility and subsistence economy discussing the data in terms of a concept of territoriality adapted from cultural geographers working with hunting gathering societies we attempt to show that the huentelauquen cultural complex usually considered the earliest evidence of human occupation in the coast of northern chile exhibits an already consolidated territorialisation process we question whether it represents the earliest phases of the peopling process or if such evidence are still lacking at a regional level we try to go beyond the characterization of huentelauquen cultural complex as an early maritime adaptation understanding it as the earliest socio territorial identity known to date for the arid coast of northern chile

high resolution planktic foraminiferal record of the last 13 300 years from the upwelling area off chile abstract a high resolution sedimentary record spanning the last deglacial and holocene periods was obtained by studying the deep sea sediment core gik 17748 2 retrieved from 2545 m water depth in the valparaiso basin chilean continental slope southeast pacific 32 45 00 s 72 02 00 w ams 14 c measurements and oxygen isotope analyses of the planktic foraminifera species globigerina bulloides and neogloboquadrina pachyderma dex indicate an age of 13 3 ams 14 c kyr b p at the base of the core 383 cm and sedimentation rates ranging between 9 and 92 cm kyr foraminiferal assemblages and accumulation rates were analysed in order to investigate variations in paleoceanography and paleoproductivity in the southern peru chile current during the last 13 kyr changes in foraminiferal assemblages indicate a sequence of three major hydrographic regimes at the site of the core 1 deglacial sediments are characterised by variable faunal compositions generally reflecting strong upwelling and high productivity 2 during the early and middle holocene upwelling and thus productivity decreased as indicated by an elevated relative abundance of n pachyderma dex and the importance of the subtropical surface water of the peru chile countercurrent increased as indicated by higher relative amounts of n dutertrei 3 for the last 3 kyr variable faunal assemblages indicate variable competing environmental conditions characterised on one hand by increased upwelling reflected by an elevated relative abundance of n pachyderma sin and on the other hand by warmer conditions deduced from a higher relative abundance of n dutertrei probably due to more frequent and more intense el nino events in addition hints for slightly cooler conditions between 11 4 and 10 7 kyr b p might be related to a younger dryas event in this region

the use of land snail shells in paleoenvironmental reconstruction fossil land snail shells constitute a valuable source of paleoenvironmental information for the quaternary they can be dated by a variety of methods including radiocarbon amino acid racemization and epimerization and perhaps also thu and esr the vast majority of paleoenvironmental studies based on land snail shells have examined the faunal composition of fossil assemblages from which a variety of paleoenvironmental characteristics such as biome temperature and moisture conditions have been reconstructed still there are a number of problems involved in using this approach and these are discussed shell morphology has occasionally been used to reconstruct such factors as rainfall and temperature stable isotope studies on quaternary land snails include analysis of 18o values of organic matter in the shells to reconstruct c4 plant distributions from which rainfall amounts can be inferred and analysis of 18o values of shell carbonate from which trends in the oxygen isotope composition of rainfall can be reconstructed stable carbon isotopes of shell carbonate have also been studied but their interpretation is not clear amino acid epimerization analysis dalloisoleucinel isoleucine ratios of land snail shells has been used for estimation of paleotemperatures some potential uses of land snail shells for paleoenvironmental reconstruction include the study of stable isotopes of h and n periodic growth lines and deposits of pedogenic carbonates on the shells

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

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

high resolution marine record of climatic change in mid latitude chile during the last 28 000 years based on terrigenous sediment parameters abstract marine sediment cores from the continental slope off mid latitude chile 33 s were studied with regard to grain size distributions and clay mineral composition the data provide a 28 000 yr14c accelerator mass spectrometry dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland these variations can be interpreted in terms of the paleoclimatic evolution of mid latitude chile and are compared to existing terrestrial records glacial climates 28 000 18 000 cal yr b p were generally cold humid with a cold semiarid interval between 26 000 and 22 000 cal yr b p the deglaciation was characterized by a trend toward more arid conditions during the middle holocene 8000 4000 cal yr b p comparatively stable climatic conditions prevailed with increased aridity in the coastal range the late holocene 4000 0 cal yr b p was marked by more variable paleoclimates with generally more humid conditions variations of rainfall in mid latitude chile are most likely controlled by shifts of the latitudinal position of the southern westerlies compared to the holocene the southern westerly wind belt was located significantly farther north during the last glacial maximum less important variations of the latitudinal position of the southern westerlies also occurred on shorter time scales

radiocarbon evidence for mid late holocene changes in southwest pacific ocean circulation variability in the southwest sw pacific ocean circulation is influenced by the changes in the south pacific subtropical gyre and its western boundary current the east australian current eac the eac plays a significant role in transporting warm well ventilated nutrient poor waters to more temperate higher latitudes recent climate changes associated with eac intensification have led to anomalous warming in the south tasman with implications for marine ecosystems and environment a clear understanding of the significance of these changes requires knowledge of past natural variability here we have reconstructed a 4500 year record of regional sea surface radiocarbon reservoir ages r and local reservoir effects r our results reveal the centennial scale variability over the last 4500 years with r ranges as large as 390 14c yr older r 410 14c yr between 1610 to 1860 a d in our record corresponding to the little ice age suggests a weaker influence of the eac in the south tasman between 4000 and 1900 cal years b p r and r were significantly younger than the modern with values of 170 and 130 14c yr respectively indicating increased eac transport of tropical waters into the south tasman we propose that the large r variability was influenced by strong and abrupt el nino events which punctuated the muted el nino southern oscillation enso period in the mid late holocene and enabled increased westward flow of gyre waters into the sw pacific the strengthening of the eac extension appears to have been a response to the precession modulated enso southern annular mode interactions

oxygen isotope composition of living land snail shells data from italy sixty seven shells of living land snails were selected from 31 different localities across italy to investigate the relationships between their oxygen isotopic composition 18os and the mean value of local rainfall 18op despite the difficulty for some localities to correctly estimate the oxygen isotopic composition of local rainfall a good relationship was found this indicates that the oxygen isotopic composition of environmental water used by the snails is in italy strictly related to that of the local meteoric precipitation however the relationship found is substantially different from that previous established for central europe indicating that regional climatic conditions are important in defining the final isotopic composition of land snail shells moreover these equations may not hold for different climatic conditions existing during for instance glacial and interglacial periods the data also show that isotopic differences among species are relatively narrow and that they may depend on ecological factors i e style of life rather than any clearly identifiable different vital offset

deglacial to holocene ocean temperatures in the humboldt current system as indicated by alkenone paleothermometry the response of the humboldt current system to future global warming is uncertain here we reconstruct alkenone derived near surface temperatures from multiple cores along the peruvian coast to infer the driving mechanisms of upwelling changes for the last 20 kyr our records show a deglacial warming consistent with antarctic ice core temperatures and a mid holocene cooling which in combination with other paleoceanographic records suggest a strengthening of upwelling conditions this cooling during the globally warm mid holocene is consistent with an intensification of the walker circulation and the south eastern pacific subtropical anticyclone indicative of la nina like conditions in the tropical pacific surprisingly oxygen contents in the subsurface increased and productivity was low during the mid holocene which are at odds with la nina like conditions this suggests that the humboldt current system reacts in multiple ways to a warmer world and may even include a reversal in the present day subsurface deoxygenation

reply to comments on implications of a late glacial pollen record for the glacial and climatic history of the fraser lowland british columbia a parks canada western canada service centre 300 300 west georgia street vancouver bc canada v6b 6b4 b school of resource and environmental management simon fraser university burnaby bc canada v5a 1s6 c department of biological sciences simon fraser university burnaby bc canada v5a 1s6 d department of earth sciences simon fraser university burnaby bc canada v5a 1s6 e geological survey of canada 101 605 robson street vancouver bc canada v6b 5j3

deglacial changes in ocean circulation from an extended radiocarbon calibration temporal variations in the atmospheric concentration of radiocarbon sometimes result in radiocarbon based age estimates of biogenic material that do not agree with true calendar age this problem is particularly severe beyond the limit of the high resolution radiocarbon calibration based on tree ring data which stretches back only to1 2 about 11 8 kyr before present bp near the termination of the younger dryas cold period if a wide range of palaeoclimate records are to be exploited for better understanding the rates and patterns of environmental change during the last deglaciation extending the well calibrated radiocarbon timescale back further in time is crucial several studies attempting such an extension using uranium thorium dated corals3 4 5 and laminae counts in varved sediments6 7 8 9 show conflicting results here we use radiocarbon data from varved sediments in the cariaco basin in the southern caribbean sea to construct an accurate and continuous radiocarbon calibration for the period 9 to 14 5 kyr bp nearly 3 000 years beyond the tree ring based calibration a simple model compared to the calculated atmospheric radiocarbon concentration and palaeoclimate data from the same sediment core suggests that north atlantic deep water formation shut down during the younger dryas period but was gradually replaced by an alternative mode of convection possibly via the formation of north atlantic intermediate water

timing and extent of allerod and younger dryas age ca 12 500 10 000 14c yr b p oscillations of the cordilleran ice sheet in the fraser lowland western north america the use of shaded digital topographic models to visualizes suites of topographic features stratigraphy and field mapping reveals newly recognized multiple moraines associated with oscillations of the remnants of the cordilleran ice sheet in the fraser lowland along the western washington british columbia border morphologic features show the extent of ice represented by sumas drift ca 11 600 10 000 14c yr b p following ca 3000 yr of retreat from the glacial maximum fraser glaciation positions 80 km south of seattle and in the strait of juan de fuca the paleogeography of the ice margin and timing of ice retreat during the sumas stade is reconstructed and bracketed by 70 radiocarbon dates 24 on marine shells 46 on wood and peat which are secured by morphologic and stratigraphic evidence four topographically distinct phases of the sumas deglaciation model are suggested phase si 11 600 11 400 14c yr b p outermost drift scattered remnants of ice contact deposits phase sii 11 600 11 400 14c yr b p glacier readvance building prominent moraine followed by glacier retreat phase siii 10 980 10 250 14c yr b p glacier readvance building of multiple moraines followed by glacier retreat phase siv 10 250 10 000 14c yr b p glacier readvance building of inner moraine followed by glacier retreat

using archaeological shell middens as a proxy for past local coastal upwelling in northern chile abstract shell middens large heaps of refuse materials that are often interspersed with burials hearths and other cultural features provide important data regarding the lifestyles of past coastal and maritime dwellers despite the abundance of organic materials radiocarbon ages from shell middens can be a challenge to interpret because marine shells are depleted in radiocarbon with respect to their contemporaneous atmosphere known as the reservoir effect r this issue is particularly problematic in regions like the coastal atacama desert where the upwelling of subsurface radiocarbon depleted waters creates a shell local reservoir effect r with a time variable intrinsic uncertainty here we review and discuss how the dating of diverse materials from these deposits including the shells themselves can reveal large shifts between the terrestrial atmospheric and marine carbon cycles furthermore a chronology of such shifts can be used as a proxy of upwelling intensity and to help establish the duration of strong versus weak local upwelling episodes to test and evaluate these ideas we present a chronology of r and r variations from a 2 m shell midden sequence from caleta vitor in northern chile that spans the middle holocene which remains underrepresented by regional r values the 2000 y sequence of caleta vitor located onshore from a major upwelling center displays dramatic shifts in radiocarbon reservoir effects which we hypothesize are linked to strong changes in the intensity of local upwelling further replication of such archaeomalacological records will be key for not only solving methodological problems regarding the dating of coastal sites but can provide further insights into the evolving terrestrial and marine carbon cycles and how these relate to past climate change

radiocarbon age calibration at archaeological sites of coastal massachusetts and vicinity abstract radiocarbon ages of 15 paired marine and terrestrial archaeological samples along with 10 marine samples of known historic age from massachusetts maine connecticut and new york provide data for studying the reservoir effect on these coasts the marine calibration method of stuiver pearson braziunas 1986 proves effective at correcting the ages of shells from boston harbor cape cod and nan ucket island massachusetts and several samples from maine and long island sounc however some shells from long island sound and the lower hudson and merrimack rivers exhibit very large reservoir ages fluvial discharges carrying old terrestrial carbon can explain these large variations although oceanic upwelling cannot be ruled out

the southern westerlies in central chile holocene precipitation estimates based on a water balance model for laguna aculeo 33 50 s central chile 32 35 s lies at the northern border of strong influence of the westerly circulation belt westerlies and is therefore characterized by a steep precipitation gradient in this region quantitative reconstructions of holocene precipitation are scarce hence the present study estimates precipitation changes based on lake level fluctuations of laguna aculeo 33 50 s 70 54 w the lake level curve has been reconstructed using a multi proxy study of lake sediments lake level changes have been simulated using a simple water balance model as a result palaeo precipitation could be estimated uncertainties concerning the input parameters and past conditions have limitated the precision of precipitation estimates the results suggest that during the beginning of the holocene when the lake level 1 5 m was low precipitation was 200 mm year before 8000 cal yr bp the lake frequently dried out between 8000 and 6000 cal yr bp precipitation appeared to be higher 150 300 mm year and after about 6000 cal yr bp precipitation increased dramatically 350 450 mm year around 3000 cal yr bp modern lake level and precipitation 450 550 mm year were generally established the dry conditions during the early and mid holocene are in good agreement with other records from central chile and northern patagonia the westerlies were probably deflected southward by the southeast pacific subtropical high pressure cell during the mid and early holocene subsequently the increase in moisture in central chile during the late holocene appears to be strongly related to intensified westerly activity and probably also to increased el nino activity

sedimentary facies and high resolution primary production inferences from laminated diatomacous sediments off northern chile 23 s the oceanographic conditions at the mejillones bay 23 s are strongly influenced by an important wind driven upwelling cell of the humboldt current system hcs as well as by the presence of the oxygen minimum zone omz in this region laminated diatomaceous sediments in this bay were analysed using different qualitative and quantitative techniques on the sediment cores 33c and 32b to interpret the main physical ocean climate factors driving sedimentation processes the composition of these sediments is dominated by the high concentration of resting spores of the genus chaetoceros sp which denotes the strong influence of the upwelling events and primary production on hemipelagic sedimentation processes within the basin the laminae characterized by thickness ranging from 1 mm to several cm are associated with changes in density porosity due to the different concentration and composition of phytoplankton remains and organic matter dark laminae are generally characterized by higher concentration of chaetoceros r s toc organic matter carbonates and lithic minerals with respect to the adjacent lighter laminae representing periods of strong upwelling events high primary production rates and intensified hypoxia contrarily relatively lighter laminae are characterized by diminished concentration of chaetoceros r s and relative increases of the concentration of centric and pennate diatoms producing a more porous sediment some of these light laminae could be associated with short lived major oceanographic enso like events the variability of the sedimentary fluxes observed in both cores represents mostly ocean climate trends at decadal interdecadal and secular time periods the secular trends of the sedimentary fluxes suggest an intensification of the upwelling events and primary production from the second half of the 19th century as well as intensified processes during the 20th century these changes seem to occur contemporaneously with ocean climate variations in the southwestern tropical pacific ocean suggesting a major basin scale climate change during this period

enso tropical extratropical climate teleconnections and mechanisms for holocene debris flows along the hyperarid coast of western south america 17 24 s abstract el nino the warm phase of the enso cycle involves ocean climate anomalies in the tropical pacific ocean and in the extratropics which frequently result in heavy rainfall episodes along the equatorial and subtropical regions of western south america here we investigate meteorological mechanisms producing heavy rains floods and debris flows along the less known hyperarid coasts of southern peru and northern chile to evaluate the paleoclimate significance of holocene debris flow deposits our results reveal that heavy rainfall over the coast of southernmost peru occurs either during austral summer at the mature stage of el nino in connection with warmer sea surface temperatures and anomalous jet streams off northern chile or during the previous austral winter spring associated with equatorward shifted pacific south america psa atmospheric teleconnection patterns at antofagasta in northern chile such events occur almost exclusively in the latter season when deeper psa related anomaly poles extend their influence equatorwards beyond central chile during non el nino conditions short lived heavy rainfall episodes in southernmost peru can be associated with similar albeit weaker or less persistent circulation anomalies in addition to that a seasonally enhanced low level southerly flow provides orographic uplift rainfall favourable conditions by the andes at the 18 s coastal bend ultimately the trigger for rainfall events in all seasons and phases of the enso cycle was invariably connected with mid troposphere wave disturbances from mid latitudes the chronostratigraphy of debris flow deposits from both areas and its comparison with other paleoclimate records at the western side of the andes suggests that the enso related teleconnection patterns operated only during the second half of the holocene supporting an onset of modern el nino manifestations at 5300 5500 cal bp and increased frequency of major events during recent times we suggest that several debris flows dated between 12 900 and 8400 cal bp in southernmost peru previously interpreted as an indication of strong el nino events were associated with short and intense heavy rainfall episodes similar to those described here during the late winter spring season in non el nino conditions concomitant with stronger low level southerlies strengthened south eastern pacific subtropical anticyclone and intensified coastal upwelling

late quaternary precessional cycles of terrigenous sediment input off the norte chico chile 27 5 s and palaeoclimatic implications abstract the palaeoclimatic conditions during the last glacial maximum lgm of southern south america and especially latitudinal shifts of the southern westerly wind belt are still discussed controversially longer palaeoclimatic records covering the late quaternary are rare a particularly sensitive area to late quaternary climatic changes is the norte chico northern chile because of its extreme climatic gradients small shifts of the present climatic zonation could cause significant variations of the terrestrial sedimentary environment which would be recorded in marine terrigenous sediments to unveil the history of shifting climatic zones in northern chile we present a sedimentological study of a marine sediment core geob 3375 1 from the continental slope off the norte chico 27 5 s sedimentological investigations include bulk and silt grain size determinations by sieving atterberg separation and detailed sedigraph analyses additionally clay mineralogical parameters were obtained by x ray diffraction methods the 14c dated core covering the time span from approximately 10 000 to 120 000 cal yr b p consists of hemipelagic sediments terrigenous sedimentological parameters reveal a strong cyclicity which is interpreted in terms of variations of sediment provenance modifications of the terrestrial weathering regimes and modes of sediment input to the ocean these interpretations imply cyclic variations between comparatively arid climates and more humid conditions with seasonal precipitation for northern chile 27 5 s through the late quaternary the cyclicity of the terrigenous sediment parameters is strongly dominated by precessional cycles for the palaeoclimatic signal this means that more humid conditions coincide with maxima of the precession index as e g during the lgm higher seasonal precipitation for this part of chile is most likely derived from frontal winter rain of the southern westerlies thus the data presented here favour not only an equatorward shift of this atmospheric circulation system during the lgm but also precession controlled latitudinal movements throughout the late quaternary precessional forcing of latitudinal movements of the westerly atmospheric circulation system may be conceivable through teleconnections to the northern hemisphere monsoonal system in the atlantic ocean region

surface sediment distribution along the chilean continental slope related to upwelling and productivity abstract the coastal upwelling system of the peru chile current belongs to the most productive regions in the world oceans in spite of this remarkable fact only very little is known about the sediment distribution in its southern part off the coast of chile to increase the knowledge about this region a multiparameter study of the surface sediment distribution along the chilean continental slope between 27 and 42 s has been carried out detailed analyses of sedimentary data toc and carbonate contents 13corg 15n of the species composition of planktic foraminifera and of the stable isotope composition of the two planktic foraminifera species neogloboquadrina pachyderma dex and globigerina bulloides reveal a close relation to environmental conditions in the region the pattern of a southward increase of surface water productivity known from satellite data is closely reflected in the organic carbon and 15n data information about the water mass distribution especially about varying influences of upwelling waters and warmer subtropical surface waters can be derived from the species composition of the planktic foraminifera while the stable isotope data provide additional clues about water mass characteristics high productivity along the chilean margin north of 40 s is sustained by coastal upwelling while further to the south advection of nutrients with the antarctic circumpolar current and a significant riverine input fuel the highest productivity found in the study area this data set will provide the base for future paleoclimatic and paleoceanographic reconstructions of the southeast pacific region

late quaternary rapid climate change in northern chile analyses of terrigenous sediments from the chilean continental slope off the southern border of the atacama desert 27 5 s focusing on illite crystallinity and the fe al ratio of the sediments reveal a high frequency variability of the position of the southern westerlies which is very similar to the coeval short term climatic events known from greenland ice cores and from north atlantic sediments besides showing dominantly precession driven variability in precipitation over the andes these analyses also reveal rapid changes in weathering intensity along the chilean coastal range during the last 80 000 years these rapid changes occur at much shorter timescales than the 19 100 kyr orbital forcing of the milankovitch cycles

major hydrological regime change along the semiarid western coast of south america during the early holocene water availability in the semiarid western coast of chile 30 32 s is conditioned by high interannual precipitation variability reflecting the transition between arid subtropical and moist mid latitude climates in the southeastern pacific ocean a paleoclimate reconstruction based on the latest pleistocene holocene geological record from the quebrada santa julia archeological site in chile 31 50 s and on modern meteorological mechanisms producing alluvial episodes in this region indicates a major change in the rainfall regime shortly after 8600 cal yr bp this together with other paleoclimate proxies along the west coast of south america 34 14 s suggests la nina like conditions 13 000 8600 cal yr bp based on sedimentological and geomorphologic evidence we hypothesized that the absence of heavy rainfall events in northern chile and the new hydrological regime that prevailed ca 8600 5700 cal yr bp in north central chile resulted from an increase in the large scale westerly flow over central chile as expected in near neutral enso conditions this atmospheric circulation anomaly is compatible with an equatorward shift of the influence of the southeast pacific subtropical anticyclone relative to the early holocene prior to the onset of modern enso variability

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

comments on implications of a late glacial pollen record for the glacial and climatic history of the fraser lowland british columbia by pellatt et al 2002

implications of a late glacial pollen record for the glacial and climatic history of the fraser lowland british columbia abstract late glacial sediments at mike lake in the fraser lowland of southwestern british columbia shed light on the timing and significance of the younger dryas and sumas events on the west coast of canada five pollen zones span the period from about 11 700 to 9700 radiocarbon years before present yr bp or 13 700 to 11 200 calibrated calendar years before present cal bp climate during this interval is inferred to have ranged from cool continental to warm and dry changes in pollen assemblages lithology and loss on ignition in mike lake sediments deposited prior to 11 000 yr bp 13 000 cal bp may signal the sumas glacial advance which has been dated elsewhere in the fraser lowland to this time palynologic and sedimentological data indicate that there was much climatic and ecological variability in southwestern british columbia during the younger dryas chronozone detrended correspondence analysis of modern pollen from lake sediment surface samples collected throughout british columbia is used to compare mike lake fossil pollen assemblages to modern vegetation zones the inferred vegetation assemblage during most of the younger dryas chronozone indicates a progressively warming climate with a cool interval between 10 400 and 10 000 yr bp the pollen assemblage in this interval is similar to that of present subalpine forests on the west coast of canada the cooling coincides with the later part of the younger dryas chronozone and occurred too late to be the driving mechanism for the final sumas advance which peaked around 11 300 14c yr bp 13 200 cal bp

cross stratigraphies from a seismically active mud lens off peru indicate horizontal extensions of laminae missing sequences and a need for multiple cores for high resolution records abstract marine laminated sediments in dysoxic areas of the ocean floor are an excellent archive for high resolution climate reconstructions while the existence of discontinuities produced by natural events such as underwater landslides slumps strong bottom currents and or bioturbation is usually acknowledged for long records the extent of their influence on high resolution sequences is usually not considered in the present work we show strong evidence for multiple stratigraphic discontinuities in different gravity and box cores retrieved off pisco peru covering the last 600 years chronostratigraphies are largely based on cross correlation of distinct sedimentary structures determined by x ray image analysis and validated using 210 pb 241 am and 14 c profiles as well as proxy records the cross correlation of distinct stratigraphic layers allows for chronostratigraphic tie points and clearly shows that some sedimentary sequences are continuous across scales of tens of kilometers indicating that regional processes often determine laminae formation some differences in laminae thickness were found among cores which could be explained by different sedimentation rates spatially variable deposition of diatom blooms changes in silica dissolution and partial deposition erosion caused by bottom currents using multiple stratigraphic tie points provides clear evidence for laminated sequences present in some cores to be missing in other cores moreover instantaneous depositions from upslope were identified in all the cores disrupting the continuity of the sediment records these discontinuities instantaneous deposits and missing sequences may be due to slumps possibly triggered by earthquakes and or erosion by strong bottom currents in spite of the missing sequences in some cores a continuous composite record of the last six centuries was reconstructed from spliced sequences of the different cores which provides a well constrained temporal framework to develop further high resolution proxies in this region the present work shows that paleoreconstructions developed from single cores particularly in areas with strong seismic activity and or strong bottom currents are subject to both temporal gaps and instantaneous depositions from upslope both of which could be misinterpreted as abrupt climate changes or anomalous climate events we stress the need for multiple cores to determine the stratigraphic continuity and chronologies for high resolution records

paleodeviations of radiocarbon marine reservoir values for the northeast pacific differences in the radiocarbon ages of coeval marine shells and wood from emergent glaciomarine sediments in the fraser lowland of southwestern british columbia and northwest washington indicate that a total marine radiocarbon reservoir value of 1 1 1 k y is applicable in the region this is 40 greater 300 yr than the 800 yr value currently used to correct the ages of both modern and late pleistocene marine shells from this area the glaciomarine sediments were deposited rapidly between ca 12 5 and 11 5 1 4 c k y b p paleodeviations of the marine reservoir value may illustrate that rapid environmental changes occurred during the last glacial to interglacial transition these variations are thought to have been caused by changes in both deep and surface ocean circulation and by variations in the production of atmospheric radiocarbon 1 4 c these findings may indicate a rapid reordering of oceanic atmospheric circulation in the region

high and low latitude climate control on the position of the southern peru chile current during the holocene 1 we reconstructed changes of temperature salinity and productivity within the southern peru chile current during the last 8000 years from a high resolution sediment core recovered at 41 s using alkenones isotope ratios of planktic foraminifera biogenic opal and organic carbon paleotemperatures and paleosalinities reached maximum values at 5500 years ago and thereafter declined to modern values whereas paleoproductivity continuously increased throughout the last 8000 years we ascribe these long term holocene trends primarily to latitudinal shifts of the antarctic circumpolar current acc the concurrence with shifts in the position of the southern westerlies points to a common response of atmospheric and oceanographic circulation patterns off southern chile millennial to centennial scale fluctuations of paleotemperatures and paleosalinities on the other hand lag displacements in the position of the southern westerlies but reveal a significant correlation to short term temperature changes in antarctica indicating a high latitude control of the acc at these timescales

radiocarbon age of last glacial pacific deep water one of the most important projects envisaged ever since the possibility emerged of making tandem accelerator mass spectrometric radiocarbon determinations has been that of investigating changes in the radiocarbon age of the deep ocean1 initial attempts to achieve this2 were thwarted by difficulties imposed by bioturbation because these workers used core v28 238 with an accumulation rate of only 1 5 cm kyr 1 thus emphasizing the need to work in a core with a higher accumulation rate working in the glacial section of core tr163 31b with an accumulation of 10 cm kyr 1 we show here that the ventilation age of pacific deep water was about 500 years greater in last glacial times than it is today

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

antarctic timing of surface water changes off chile and patagonian ice sheet response marine sediments from the chilean continental margin are used to infer millennial scale changes in southeast pacific surface ocean water properties and patagonian ice sheet extent since the last glacial period our data show a clear antarctic timing of sea surface temperature changes which appear systematically linked to meridional displacements in sea ice westerly winds and the circumpolar current system proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore but reveal a variable glacier response time of up to 1000 years which may explain some of the current discrepancies among terrestrial records in southern south america

paleoproductivity in the southern peru chile current through the last 33 000 yr abstract based on a multiparameter approach including organic carbon biogenic opal carbonate and the species composition of planktic foraminifera this paper provides the first qualitative assessment of the history of paleoproductivity on glacial interglacial time scales in the southern peru chile current pcc off chile which belongs to the least studied parts of the world ocean during the last glacial maximum lgm highest relative paleoproductivity of the last 33 kyr indicated by high accumulation rates of organic carbon biogenic opal and carbonate has been found contrasted by lowest values during the early and middle holocene this shift from high to low productivity is accompanied by a major change in the species composition of planktic foraminifera from a dominance of neogloboquadrina pachyderma sin to the dominance of n pachyderma dex the temporal pattern of paleoproductivity off chile is very similar to the history of the continental paleoclimate in the region which is supposed to be driven by the position of the southern westerlies this observation points to a functional relationship between the position of the southern westerlies and the history of paleoproductivity off chile assuming that atmospheric and oceanographic circulation are closely linked a northward displacement of the antarctic circumpolar current during the lgm in line with the northward movement of the southern westerlies would bring the main nutrient source closer to our core sites resulting in increased productivity however based on the available data it is not clear if the higher productivity in the southern pcc during the lgm reflects generally higher productivity during this time or only a regional displacement of the main productivity centers

anchovy population and ocean climatic fluctuations in the humboldt current system during the last 700 years and their implications a marine sedimentary record collected from 87 m water depth in a coastal environment of the humboldt current system mejillones bay 23 s northern chile was used to reconstruct the past 700 years of ocean climatic conditions and to study the influence of any changes on anchovy population dynamics we analyzed quartz organic carbon total nitrogen alkenones and fish scales four stratigraphic units in the sediment column correspond with fluctuations in these and other proxies low scale deposition rate sdr values from 1330 to 1420 suggest a low abundance of anchovy in this coastal environment three subsequent cycles of ca 170 years each showed an increase and decrease of anchovy populations which is in agreement with changes in the wind regime sea surface temperature and primary productivity since ca 1840 marked fluctuations of sdr have been observed probably as a consequence of the onset of a different oceanographic regime characterized by intensified southern winds and upwelling colder surface waters higher primary productivity and enhanced la nina like interdecadal variability an increase of the anchovy population was observed until halfway through the 20th century followed by a decrease even though water temperature decreased and primary productivity increased this situation is likely the consequence of the increased fishery activity that developed in this zone during the last 60 years after analyzing the results obtained for anchovy sdr we can determine that there is a relation between the abundance of this species and phases of the pacific decadal oscillation pdo in which an increase in the sdr coincides with a pdo cold phase while a decline coincides with a warm phase fast fourier transformation analysis applied to the time series obtained from the mejillones sediment core and to the north atlantic oscillation nao the pdo and the solar irradiance index time series shows three different decadal cycles 80 100 years 61 75 years and 45 48 years approximately furthermore the results of this study suggest that both the pdo and the nao and the biogeochemical markers of mejillones exhibit periodicities that fall within the 80 to 100 year gleissberg solar cycle indicating that global solar radiation plays a key role in the local ocean climatic processes and confirming teleconnection linkages between widely separated regions

radiocarbon dating reservoir effects and calibration abstract we summarize how radiocarbon measurements are made using accelerator mass spectrometry we also discuss some complications inherent in the radiocarbon dating method when calibrating radiocarbon dates to calendar dates for example measurements of radiocarbon 14c in some types of materials are complicated by a reservoir effect caused by an apparent age of the source reservoir that differs from the contemporary atmospheric surface 14c value in other cases mobile carbon sources in nature can produce mixed sources of carbon we explore these effects and discuss their possible implications for 14c measurements and how we can deal with them

preliminary estimates for the radiocarbon age of deep water in the glacial ocean radiocarbon ages for benthic and planktonic foraminifera from the late glacial sections of two atlantic and two pacific cores are reported the differences for benthic planktonic pairs suggest that the radiocarbon age for deep atlantic water was somewhat larger than today s i e 600 250 as opposed to 400 years and that the radiocarbon age for deep pacific water was also slightly larger than today s 2100 400 as opposed to 1600 years our results suggest that during glacial time the deep pacific was as it is today significantly depleted in radiocarbon relative to the deep atlantic as many questions remain unanswered regarding the reliability of this approach these conclusions must be considered to be preliminary

differences in radiocarbon age between shell and charcoal from a holocene shellmound in northern california abstract the west berkeley shellmound the oldest well dated archaeological site in the san francisco bay region contains shell and charcoal ranging in age from ca 1200 to 5700 cal yr b p radiocarbon ages of marine shell and charcoal collected from fifteen stratigraphic levels in the west berkeley shellmound suggest changes in the 14 c content of san francisco bay surface waters relative to the atmosphere the oceanic reservoir age over the past 5000 yr the reservoir age of san francisco bay waters fluctuated between 870 and 170 14 c yr over the past 5000 yr with the lowest values occurring 2900 to 3800 cal yr b p and the highest values between 1200 and 2000 cal yr b p changes in the radiocarbon reservoir age may be due to changes in the strength of seasonal wind driven upwelling off coastal california where upwelling brings 14 c depleted waters to the surface the period of lowest r values at 3500 to 3900 cal yr b p is coincident with relatively low salinity in san francisco bay indicating high freshwater inflow and wet climate in california based on lake level records the period of high r values 1200 2000 cal yr b p is coincident with one of the driest periods in california during the late holocene these data suggest a link between coastal upwelling and precipitation over central california the age of the top of west berkeley mound and several other mounds in the san francisco bay region 1100 to 1300 cal yr b p coincides with a prolonged dry period in california and low river inflow to san francisco bay perhaps the sites were abandoned because of the drought

pleistocene holocene environmental change in the canary archipelago as inferred from the stable isotope composition of land snail shells abstract the isotopic composition of land snail shells was analyzed to investigate environmental changes in the eastern canary islands 28 29 n over the last 50 ka shell 13c values range from 8 9 to 3 8 at various times during the glacial interval 15 to 50 ka moving average shell 13c values were 3 higher than today suggesting a larger proportion of c4 plants at those periods shell 18o values range from 1 9 to 4 5 with moving average 18o values exhibiting a noisy but long term increase from 0 1 at 50 ka to 1 6 1 8 during the lgm 15 22 ka subsequently the moving average 18o values range from 0 0 at 12 ka to 0 9 at present calculations using a published snail flux balance model for 18o constrained by regional temperatures and ocean 18o values suggest that relative humidity at the times of snail activity fluctuated but exhibited a long term decline over the last 50 ka eventually resulting in the current semiarid conditions of the eastern canary islands consistent with the aridification process in the nearby sahara thus low latitude oceanic island land snail shells may be isotopic archives of glacial to interglacial and tropical subtropical environmental change

younger dryas readvance in squamish river valley southern coast mountains british columbia abstract stratigraphy and landforms in the brohm creek basin and lowermost mamquam river valley provide evidence for a readvance of a valley glacier in the southern coast mountains of british columbia during the younger dryas interval at brohm creek till containing wood 10 500 and 10 700 14 c yr old ca 12 500 12 900 cal yr old overlies an ice contact terrace that is correlative with similar terraces at the mouth of mamquam river 11 km to the south and 900 m lower in elevation a line linking the two sites has a slope of 5 which is similar to slopes of termini of present day valley glaciers in the southern coast mountains we used these observations to reconstruct the younger dryas glacier in squamish valley at the head of howe sound the glacier deflected landslide debris derived from steep slopes at the head of cheekye river basin on the west flank of mt garibaldi southward to an ice marginal lake at the mouth of mamquam river foreset bedded sediments in the core of a large fan at the mouth of cheekye river indicate the glacier terminus had retreated up squamish valley beyond cheekye and mamquam rivers by 10 200 14 c yr bp 11 900 cal yr old radiocarbon ages on the oldest postglacial sediments in a kettle on the landslide debris show that stagnant ice in the study area had melted before 10 000 14 c yr bp 11 500 cal yr bp the readvance of the squamish valley glacier during the younger dryas chronozone was probably driven by a regional climate reversal

abrupt increase in the coastal uplift and earthquake rate since 40 ka at the northern chile seismic gap in the central andes abstract over long term geological scales the position and vertical movements of the coast are considered to be among the most important effects resulting from first order plate tectonics interactions in the subduction zones however the relationship between short term vertical deformation driven by earthquakes and long term coastal uplift in the andean subduction contact of northern chile has not been thoroughly elucidated to date based on precise radiocarbon dating and geomorphological analysis of littoral deposits in the mejillones peninsula at the southern edge of the major northern chile seismic gap we report a drastic increase in coastal uplift since marine isotope stage 3 mis 3 with uplift rates one order of magnitude more rapid than previously in the late pleistocene geomorphological evidence supplied by holocene littoral deposits and marine terraces shows that this tectonic regime could be operating at present together with new geodetic data following the 2007 mw7 7 tocopilla event these observations indicate that coastal uplift results from cumulative coseismic vertical displacement with low subsequent interseismic subsidence recovery driven by both deep moderate and large megathrust earthquakes we suggest that the accelerated coastal uprising and earthquake rate over the past 44 ka demonstrated in this work results from changes involving the entire subduction contact between the nazca and south american plates in northern chile

southern westerlies during the holocene deduced from geomorphological and pedological studies in the norte chico northern chile 27 33 s abstract in the norte chico precipitation is controlled by atmospheric perturbations and frontal systems associated with the belt of westerly wind circulation the holocene climatic history of the region can be reconstructed from geomorphic and pedologic investigations in comparison to modern climatic conditions increased influence of the westerlies is deduced for the time periods prior to 7300 yr b p between 5000 3700 yr b p 3000 1800 yr b p and around 270 yr b p it remains uncertain whether the increased influence of the westerlies was the consequence of northward shifts of the westerlies as a whole of a meridional expansion of the westerly belt or only of intensity changes of the atmospheric dynamics almost synchronous with changes in the westerlies the coastal fogs in the region were apparently reduced or the fog belt in the coastal range was elevated probably due to a weakened upwelling and warmer water conditions in the eastern pacific in general the climate of the norte chico has become more variable since 5000 yr b p especially since 3000 yr b p with frequent changes of the geoecological conditions

ice age vegetation and climate of subtropical chile abstract vegetation and climate of subtropical chile over the past 50 000 yr are reconstructed from pollen spores and other microfossils contained in a 10 7 m section of lacustrine deposits of laguna de tagua tagua 34 30 s 71 10 w controlled by 14 radiocarbon age determinations five pollen assemblages covering stratigraphic zones in the section represent plants on the upland and species inhabiting the lake basin surface pollen spectra from 58 stations approximately 30 40 s form an adjunct for interpreting past vegetation and climate from the fossil record temperature semi humid woodland of southern beech nothofagus dombeyi type and podocarp prumnopitys andina was apparently established about laguna de tagua tagua during the pleistocene contrasting existing semi arid broad sclerophyllous vegetation the woodland was extensive about the lake at the time of the last glacial maximum 25 000 14 000 yr b p and earlier 43 000 34 000 yr b p pollen from the families chenopodiaceae and amaranthaceae which characterize intervals of the pleistocene centered around 33 000 and 43 000 yr b p and the holocene suggests intervening episodes of relative aridity lake level fluctuations appear to follow the late quaternary climatic pattern implied by pollen assemblage data water in the lake was relatively high during development of southern beech podocarp woodland whereas during intervals of chenopod amaranth dominance lake levels were comparatively low excess precipitation over evaporation which during the pleistocene favored development of woodland of beech and podocarp is attributed to greater storm frequency conditions were apparently governed by strengthening of atmospheric circulation in the belt of southern westerly winds in the late glacial the temperate and more humid ice age climate with limited seasonality underwent transition to a subtropical semi arid mediterranean type that identifies the postglacial fluctuations in intensity of the southern westerlies marked by latitudinal movement of the polar front can account for past vegetation changes at laguna de tagua tagua

the north atlantic atmosphere sea surface 14c gradient during the younger dryas climatic event abstract we attempt to quantify the 14c difference between the atmosphere and the north atlantic surface during a prominent climatic period of the last deglaciation the younger dryas event yd our working hypothesis is that the north atlantic may have experienced a measurable change in 14c reservoir age due to large changes of the polar front position and variations in the mode and rate of north atlantic deep water nadw production we dated contemporaneous samples of terrestrial plant remains and sea surface carbonates in order to evaluate the past atmosphere sea surface 14c gradient we selected terrestrial vegetal macrofossils and planktonic foraminifera neogloboquadrina pachyderma left coiling mixed with the same volcanic tephra the vedde ash bed which occurred during the yd and which can be recognized in north european lake sediments and north atlantic deep sea sediments based on ams ages from two norwegian sites we obtained about 10 300 yr bp for the atmospheric 14c age of the volcanic eruption foraminifera from four north atlantic deep sea cores selected for their high sedimentation rates 10 cm kyr 1 were dated by ams 21 samples for each core the raw 14c ages assigned to the ash layer peak is significantly older than the 14c age obtained on land part of this discrepancy is due to bioturbation which is shown by numerical modelling nevertheless after correction of a bioturbation bias the mean 14c age obtained on the planktonic foraminifera is still about 11 000 11 100 yr bp the atmosphere sea surface 14c difference was roughly 700 800 yr during the yd whereas today it is 400 500 yr a reduced advection of surface waters to the north atlantic and the presence of sea ice are identified as potential causes of the high 14c reservoir age during the yd

early to mid holocene aridity in central chile and the southern westerlies the laguna aculeo record 34 s abstract central chile 32 35 s lies at the northern border of strong westerly influence and thus exhibits a steep precipitation gradient therefore the palaeoclimatic archives in the region are suitable for detecting past moisture changes the study of laguna aculeo 33 50 s 70 54 w presents a multiproxy holocene lake record including sedimentology geochemistry mineralogy pollen diatoms and radiocarbon dating 17 dates results indicate an arid early to mid holocene period about 9500 5700 cal yr b p after 5700 cal yr b p effective moisture increased progressively and around 3200 cal yr b p modern humid conditions were established numerous intercalated clastic layers reflect flood deposition during rainy winters a fluvial unit was deposited shortly before 9000 cal yr b p subsequently flood events were absent until 5700 but have become frequent since 3200 cal yr b p the frequency of flood layers possibly points to weak or no el nino activity during the early and mid holocene with a subsequent increase during the late holocene during the early and mid holocene the westerlies were probably blocked and hence deflected southward by the subtropical high pressure cell higher precipitation during the last 3200 yr seems strongly related to a weakened subtropical high pressure cell with intensified westerlies and possibly increased el nino activity

geo archaeological records of large holocene tsunamis along the hyperarid coastal atacama desert in the major northern chile seismic gap abstract the coastal atacama desert is exposed to strong earthquakes and giant tsunamis associated with the subduction of the nazca plate beneath the south american plate nevertheless historical and geological records of tsunamis and paleotsunamis in this region are scarce taltal 25 4 s is located at the southern edge of the hyperarid atacama desert within a major historical 1000 km long megathrust seismic gap in northern chile where the most recent large tsunamigenic earthquakes occurred in 1877 ce and 1922 ce rupturing its northern and southern segments respectively by multiproxy geological and archaeological analyses from pits and trenches we report distinctive strata of reworked archaeological material as well as sedimentary layers that we interpret as being produced by tsunami run up and or backwash deposition we identified two large holocene paleotsunamis dated close to 4000 cal yrs bp and younger than 863 199 ce 1087 cal years bp by comparing the run ups of the last historical tsunamis with our minimum run up estimates from the geo archaeological record we conclude that the impact of these holocene paleotsunamis was larger than any known historical event suggesting the need to re evaluate local regional and pacific basin scale tsunami hazard assessments

evidence for younger dryas age cooling on the north pacific coast of america abstract a review of the palynological evidence from the olympic peninsula of washington state north to the alaska panhandle strongly supports the existence of a climatic oscillation similar in timing and effect to the younger dryas cooling 11 10 ka bp of europe and eastern north america the evidence includes many late glacial pollen peaks of mountain hemlock tsuga mertensiana an indicator of cool and moist climate reversals from forest to non arboreal vegetation and paleoclimate analysis using pollen climate transfer functions on the queen charlotte islands evidence of cooler ocean waters based on fossil foraminifera in cores from the continental shelf also supports an interpretation of a younger dryas age climatic reversal on the other hand geological evidence of glacier readvances during the younger dryas chronozone is weak and poorly dated although more and better constrained ams dates are needed to confirm the timing of the pacific northwest cold oscillation results so far point to maximum cooling and increased moisture between ca 10 7 10 ka bp followed by rapid warming in the early holocene additional late glacial sites need to be investigated in detail to confirm the geographical pattern of vegetation and climate change during this interval which is best expressed in hypermaritime and maritime climate regions similar to the younger dryas event around the north atlantic these results suggest that the search for causal mechanisms to drive the younger dryas cooling cannot be limited to events in the north atlantic region but should focus on possible hemispheric or global processes

differences between mono generic and mixed diatom silicon isotope compositions trace present and past nutrient utilisation off peru in this study we combine for the first time silicon si isotope compositions of small mixed diatom species 30sibsio2 and of large handpicked mono generic i e genus coscinodiscus diatom samples 30sicoscino with diatom assemblages extracted from marine sediments in the peruvian upwelling region in order to constrain present and past silicate utilisation the extension of a previous core top data set from the peruvian shelf demonstrates that 30sicoscino values record near complete si utilisation as these are similar to the isotopic composition of the subsurface source waters feeding the upwelling in contrast the 30sibsio2 of small mixed diatom species increase southward along the shelf as well as towards the shore we attribute highest 30sibsio2 values partly to transient iron limitation but primarily to the gradual increase of si isotope fractionation within the seasonal diatom succession which are mainly recorded by small diatom species during intense bloom events in contrast lower 30sibsio2 values are related to initial si isotope utilisation during periods of weak upwelling when low si oh 4 concentrations do not permit intense blooms and small diatom species record substantially lower 30si signatures as such we propose that the intensity of the upwelling can be deduced from the offset between 30sibsio2 and 30sicoscino 30sicoscino bsio2 which is low for strong upwelling conditions and high for prevailing weak upwelling we apply the information extracted from surface sediments to generate a record of the present day main upwelling region covering the past 17 700 years and find that this location has also been characterized by a persistent offset 30sicoscino bsio2 by comparison with the diatom assemblages we show that the coastal upwelling system changed markedly between weak and strong upwelling conditions in addition our model calculations to quantify species specific si isotope fractionation effects based on the diatom assemblages indicate an overall minor influence that cannot explain the high amplitude in the measured 30sibsio2 record

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

marine reservoir age variability and water mass distribution in the iceland sea abstract lateglacial and holocene tephra markers from icelandic source volcanoes have been identified in five sediment cores from the north icelandic shelf and correlated with tephra layers in reference soil sections in north iceland and the grip ice core land sea correlation of tephra markers that have been radiocarbon dated with terrestrial material or dated by documentary evidence provides a tool for monitoring reservoir age variability in the region age models developed for the shelf sediments north of iceland based on offshore tephrochronology on one hand and on calibrated ams 14c datings of marine molluscs on the other display major deviations during the last 4500 years the inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations the observed reservoir ages are generally considerably higher by up to 450 years than the standard model ocean it is postulated that the intervals with increased and variable marine reservoir age reflect incursions of arctic water masses derived from the east greenland current to the iceland sea and the north icelandic shelf

large variations in the holocene marine radiocarbon reservoir effect reflect ocean circulation and climatic changes accurate radiocarbon dating of marine samples requires knowledge of the marine radiocarbon reservoir effect this effect for a particular site region is generally assumed constant through time when calibrating marine 14c ages however recent studies have shown large temporal variations of several hundred to a couple of thousand years in this effect for a number of regions during the late quaternary and holocene here we report marine radiocarbon reservoir correction r r for heron reef and moreton bay in southwestern sw pacific for the last 8 ka derived from 14c analysis of 230th dated corals most of our r r for the last 5 4 ka agree well with their modern value but large r r variability of 410 yr from trough to peak with possible decadal centennial fluctuations is evident for the period 5 4 8 ka the latter time interval also has significant variations with similar features in previously published r r values for other sites in the pacific including southern peru northern chile in southeastern se pacific the south china sea vanuatu and papua new guinea with the largest magnitude of 920 yr from se pacific the mechanisms for these large r r variations across the pacific during the mid holocene are complex processes involving 1 changes in the quantity and 14c content of upwelled waters in tropical east pacific tep frequency and intensity of ocean upwelling in the tep and contribution of subantarctic mode water to the upwelled waters which is influenced by the intensity and position of southern westerly winds and 2 variations in ocean circulation associated with climate change la nina el nino conditions intensity of easterly trade winds positions of the intertropical convergence zone and the south pacific convergence zone which control the spreading of the older upwelled surface waters in the tep to the western sites our results imply the need for employing temporal changes in r r values instead of constant modern values for age calibration of holocene marine samples not only for the sw pacific sites but also for other tropical and subtropical sites in the pacific

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

temporal variability in the holocene marine radiocarbon reservoir effect for the tropical and south pacific understanding the marine radiocarbon reservoir effect i e marine radiocarbon reservoir age r and or correction r is important for the construction of robust radiocarbon chronologies for marine archives for various research areas including archaeology palaeoecology paleoceanography quaternary research and climate change studies in this study we examined temporal r variability for the south china sea scs and the great barrier reef gbr during the past 8 1 ka based on 14c analysis of 230th dated corals results show large r variations of 410 yr and 490 yr for the scs and the northern gbr for 5 5 8 1 ka and 5 5 7 ka respectively and a smaller r variability of 200 yr for the scs for 2 3 5 ka our data together with those previously published for the tropical and south pacific indicate that variability in ocean upwelling bringing old subsurface waters to the surface and or changes in the sources or 14c level of the upwelled waters are responsible for seeing large r variations in coastal areas along the eastern pacific and the tropical east pacific tep of several hundred to a thousand years mostly during the early to middle holocene r variations in the central and western pacific of several and a couple of hundred years during the middle and late holocene respectively might be due to variability in pacific wide ocean circulation associated with climatic changes controlling the spread of upwelled waters from the tep to the west this mechanism together with local regional effects such as changes in ocean upwelling in the scs resulting from east asian monsoon variability and changes in upwelling and or horizontal advection in the northern gbr associated with variability in the el nino southern oscillation might be responsible for the observed r variations in these areas the results of our study also indicate the need for regional marine radiocarbon calibration curves for improved radiocarbon dating of marine samples as the observed holocene r values for the tropical and south pacific are not fully reproduced by a recent modelling work using a 3d ocean model which takes into account climate change effects ocean circulation changes were included in the model for the period of 11 5 50 cal kyr bp but possibly not considered or not well represented for the holocene which might explain the differences between the observed and modelled r values

retention of hunter gatherer economies among maritime foragers from caleta vitor northern chile during the late holocene evidence from stable carbon and nitrogen isotopic analysis of skeletal remains abstract on the basis of stable carbon and nitrogen isotope analysis of human remains this paper provides evidence for the retention of hunter gatherer economies among coastal inhabitants in northern chile during the late holocene at the same time that inland populations were adopting agricultural economies coastal diets from the caleta vitor region of the atacama desert were dominated by marine based foods predominantly from upper trophic levels the focus on reliable marine food resources is interpreted as a risk minimisation strategy in this marginal arid environment although these coastal hunter gatherers adopted other goods and traditions from agricultural populations their participation in this larger interregional exchange network did not affect their basic subsistence economies associated new radiocarbon dates from the site are also discussed skeletal remains and artefacts associated with the caleta vitor shell middens generally originate from sites with dates ranging from c 9000 476 bp however the human remains that are the subject of this research cover the time period c 4000 476 bp

comments on marine and limnic radiocarbon reservoir corrections for studies of late and postglacial environments in georgia basin and puget lowland british columbia canada and washington usa by hutchinson et al 2004 quaternary research 61 193 203

midges and palaeotemperature reconstruction the north american experience abstract the development of midge based palaeoclimatology in north america is reviewed with a focus on lateglacial and holocene climatic change although relatively few sites have been studied midge inferred palaeotemperatures reveal detailed records of lateglacial climate oscillations and more subtle holocene temperature changes holocene climate changes are often at or near the detection limit using current palaeotemperature inference models interference from other environmental variables including water depth and oxygen concentration changes are discussed as well as the challenges inherent to developing better models the isotopic signature of chitin preserved in midge head capsules has opened new avenues for midge palaeotemperature inference through coordinated research efforts national and international collaborations will provide opportunities to reconstruct holocene palaeoclimate at continental and hemispheric scales

reduced deep ocean ventilation in the southern pacific ocean during the last glaciation persisted into the deglaciation abstract marine radiocarbon 14c is widely used to trace ocean circulation and the 14c levels of interior ocean water masses can provide insight into atmosphere ocean exchange of co2 the since the last glaciation using tephras as stratigraphic tie points with which to estimate past atmospheric 14c we reconstructed a series of deep radiocarbon ages for several time slices from the last glaciation through the deglaciation and holocene in the southwestern pacific glacial ventilation ages were much greater in magnitude than modern and had a strong mid depth 14c minimum centered on 2500 m glacial radiocarbon ages of intermediate depth waters 600 1200 m were 800 to 1600 14c years about twice modern and persisted through the early deglaciation notably in the glaciation shallower depths were significantly more enriched in 14c than waters between 1600 and 3800 m which were 4000 to 6200 14c years or about 3 5 times older than modern abyssal waters deeper than 4000 m were also more 14c rich than the overlying deep water with radiocarbon ages of 1800 2300 14c years this was similar to modern values in the early deglaciation 14c depleted waters were flushed from shallower depths first and replaced with progressively younger waters such that by 18 ka the deep to intermediate age difference was reduced by half and by 14 ka a modern type 14c profile for deep ocean water masses was in place our results 1 confirm a deep 14c depleted water mass during the lgm and early deglaciation and 2 constrain the extent of this old water in the southern pacific as between 1600 m and 3800 m the availability of atmospheric ages from tephras reveals that the presence of older surface reservoir ages in the glaciation caused the estimation of ventilation ages from simple benthic planktonic offsets to significantly underestimate the depletion of 14c in deep waters this may have had a role in masking the large change in reservoir ages since the glaciation when using benthic planktonic reservoir age estimates

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

marine radiocarbon reservoir effect along the northern chile southern peru coast 14 24 s throughout the holocene abstract through an extensive sampling and dating of pairs of associated shells and charcoal fragments combined with reanalysis of all the available previous data we reconstruct the evolution throughout the holocene of the regional marine radiocarbon reservoir effect r values along the northern chile southern peru area 14 24 s after elimination of the cases in which the terrestrial component yielded older ages than the marine shells to which they were associated the study is based upon data from 47 pairs of associated marine and terrestrial material our results suggest major changes in both the magnitude and variability range of r during the whole holocene period 1 between 10 400 and 6840 cal yr bp high values 511 278 yr probably result from a strengthened se pacific subtropical anticyclone and shoaling of equatorial subsurface waters during intensified upwelling events 2 between 5180 and 1160 cal yr bp lower values 226 98 yr may reflect a major influence of subtropical water and diminished coastal upwelling processes 3 during the last thousand years high values between 355 105 and 253 207 yr indicate an increased influence of 14 c depleted water masses and of enso for the early twentieth century a r value of 253 207 yr was calculated

226ra in barite absolute dating of holocene southern ocean sediments and reconstruction of sea surface reservoir ages absolute dating of marine sediments is necessary to achieve reliable correlations of paleoclimate records the 2 2 6 ra decay in barite separated from a deep sea core of the southern ocean was used to determine absolute ages for the holocene epoch comparison with 1 4 c ages measured on planktic foraminifers provides the first past sea surface reservoir ages in the antarctic zone of the southern ocean throughout the middle to late holocene our results indicate a reservoir age of ca 1100 yr comparable to modern estimates a significantly higher reservoir age ca 1900 yr is obtained for the early holocene which suggests a major change in the southern ocean circulation at that time