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

low pressure granulite facies metamorphism in the larsemann hills area east antarctica petrology and tectonic implications for the evolution of the prydz bay area thermobarometric studies on various granulite facies areas along the prydz bay coast east antarctica 73 79 e 68 70 s show that at around 1100 ma during a late proterozoic orogeny the rocks of the larsemann hills suffered a lower pressure metamorphic peak than the surrounding areas along the prydz bay coast the rocks affected by this event include parts of the vestfold hills block plus all of the rauer group the larsemann hills and the munro kerr mountains the dykes in the south west corner of the vestfold hills were recrystallized during this event with little deformation at temperatures not quite as high as in the areas further south west 650 c 6 5 kbar collerson et al 1983 the rauer group was metamorphosed at 800 c and 7 5 kbar harley 1987a the larsemann hills at 750 c and 4 5 kbar and the munro kerr mountains probably at around 850 c and 5 kbar retrograde equilibration in the different areas occurred during decompression to about 10 km depth in all areas followed by isobaric cooling at this depth this paper shows that the peak metamorphism in the larsemann hills occurred at a pressure which is too low to have been the consequence of thermal relaxation of overthickened crust with normal mantle heat flow although other areas in prydz bay were metamorphosed at sufficiently high pressures so that their decompression paths are not inconsistent with a continental collision model the inferred pre metamorphic peak histories and the requirement of consistency with the larsemann hills make it unlikely that collision followed by erosion driven decompression is an appropriate model we suggest that the thermal regime of the crust in the larsemann hills region was controlled by a perturbation in the asthenosphere with magma invasion of the crust we suggest that the 500 ma event represented in prydz bay by granitic outcrops at landing bluff and by several k ar ages from the larsemann hills area was responsible for the final excavation of the terrane

enso reconstructions over the past 60 ka using giant clams tridacna sp from papua new guinea we present 12 seasonally resolved delta o 18 profiles of giant clams tridacna sp from the huon peninsula papua new guinea spanning discrete periods of time 9 38 years over the past 60 ka the interannual anomaly time series of these shells are used to reconstruct interannual variability which can predominantly be attributed in the modern climate to the el nino southern oscillation enso in this region we have found a significant reduction in interannual delta o 18 variance during the early holocene whereas during marine isotope stage 3 there were at least some periods with variance not significantly different to the twentieth century we show that enso variability seen during the late twentieth century is rare but not unprecedented within glacial climates

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

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

metamorphism and granite genesis in the hidaka metamorphic belt hokkaido japan the main zone of the hidaka metamorphic belt is an uplifted crustal section of island arc type the crust was formed during early tertiary time as a result of collision between two arc trench systems of cretaceous age the crustal metamorphic sequence is divided into four metamorphic zones i iv in which zone iv is in the granulite facies a detailed study of the evolution of the hidaka belt based on a revised p t t analysis of the metamorphic rocks notably a newly found staurolite bearing granulite confirms a prograde isobaric heating path after a supposed event of tectonic thickening of accretionary sedimentary and oceanic crustal rocks during the peak metamorphic event c 53 ma the regional geothermal gradient attained 33 40 c km 1 and the highest p t condition obtained from the lowest part of the granulite unit is 830 c 7 kbar in this part xh2o of gt opx cd gneiss is about 0 15 and that of gt cd bt gneiss is 0 4 the p t xh2o condition of the granulite unit is well within a field where fluid present partial melting of pelitic and greywacke metamorphic rocks takes place this is in harmony with the restitic nature of the gt opx cd gneiss in the lowest part of the granulite unit the possibility that partial melting took place in the main zone is significant for the genesis of the peraluminous s type granitic rocks within it the s type granitic rocks in this zone are opx gt bt tonalite in the granulite zone gt cd bt tonalite in the amphibolite zone and cd bt mus tonalite in the bt mus gneiss zone the mineralogical and chemical nature of these strongly peraluminous tonalitic rocks permit them to be regarded as having been derived from s type granitic magma generated by crustal anatexis of pelitic metamorphic rocks in deeper crust

mediterranean sea surface radiocarbon reservoir age changes since the last glacial maximum sea surface reservoir ages must be known to establish a common chronological framework for marine continental and cryospheric paleoproxies and are crucial for understanding ocean continent climatic relationships and the paleoventilation of the ocean radiocarbon dates of planktonic foraminifera and tephra contemporaneously deposited over mediterranean marine and terrestrial regions reveal that the reservoir ages were similar to the modern one 400 years during most of the past 18 000 carbon 14 years however reservoir ages increased by a factor of 2 at the beginning of the last deglaciation this is attributed to changes of the north atlantic thermohaline circulation during the massive ice discharge event heinrich 1

millennial scale variability in antarctic ice sheet discharge during the last deglaciation two well dated high resolution records of iceberg rafted debris are presented that document variability in antarctic ice sheet discharge during the last deglaciation global sea levels have risen by more than 100 metres since the last glacial maximum around 20 000 years ago with several meltwater pulses of several metres or more in the most dramatic of these meltwater pulse 1a sea level rose by about 16 metres at 14 600 years ago this magnitude of sea level rise strongly suggests major antarctica contributions but to date there has been no firm physical evidence now michael weber and colleagues present a record of iceberg rafted debris from the scotia sea and show clear signals of pulsed iceberg release from antarctica as early as 19 000 years ago the largest iceberg release occurred during meltwater pulse 1a providing the long sought confirmation of antarctic contributions to this major jump in sea level rise our understanding of the deglacial evolution of the antarctic ice sheet ais following the last glacial maximum 26 000 19 000 years ago 1 is based largely on a few well dated but temporally and geographically restricted terrestrial and shallow marine sequences2 3 4 this sparseness limits our understanding of the dominant feedbacks between the ais southern hemisphere climate and global sea level marine records of iceberg rafted debris ibrd provide a nearly continuous signal of ice sheet dynamics and variability ibrd records from the north atlantic ocean have been widely used to reconstruct variability in northern hemisphere ice sheets5 but comparable records from the southern ocean of the ais are lacking because of the low resolution and large dating uncertainties in existing sediment cores here we present two well dated high resolution ibrd records that capture a spatially integrated signal of ais variability during the last deglaciation we document eight events of increased iceberg flux from various parts of the ais between 20 000 and 9 000 years ago in marked contrast to previous scenarios which identified the main ais retreat as occurring after meltwater pulse 1a3 6 7 8 and continuing into the late holocene epoch the highest ibrd flux occurred 14 600 years ago providing the first direct evidence for an antarctic contribution to meltwater pulse 1a climate model simulations with ais freshwater forcing identify a positive feedback between poleward transport of circumpolar deep water subsurface warming and ais melt suggesting that small perturbations to the ice sheet can be substantially enhanced providing a possible mechanism for rapid sea level rise

contrasting seismic reflectivity of the lower crust and uppermost mantle between ne japan and sw japan as illustrated by petrophysical analyses of mafic and ultramafic xenoliths 1 petrophysical analyses of mafic and ultramafic xenoliths reveal large contrasts in acoustic impedance between the lower crustal rocks and uppermost mantle rocks both beneath ichinomegata crater in ne japan and beneath oki dogo island in sw japan in contrast to minor contrasts in acoustic impedance both among the lower crustal rocks and among the uppermost mantle rocks beneath ichinomegata crater relatively large contrasts in acoustic impedance are present beneath oki dogo island between granulite and olivine gabbro in the lower crustal rocks as well as between plagioclase bearing wehrlite and other cumulus peridotites in the uppermost mantle rocks based on the existing petrologic models of the lower crust and uppermost mantle beneath ichinomegata crater and oki dogo island we then constructed model structures of the lower crust and uppermost mantle beneath these two areas composed of units with randomly arranged 100 m thick foliation parallel horizontal layers of xenolith samples and used these model structures to examine the seismic reflectivity beneath these two areas the results suggest the presence of strong seismic reflectors between the lower crust and the uppermost mantle in both areas although no other recognizable seismic reflector is expected beneath ichinomegata crater many seismic reflectors due to the above contrasts in acoustic impedance are expected both in the lower crust and in the uppermost mantle beneath oki dogo island thus a remarkable contrast in seismic reflectivity in the lower crust and uppermost mantle is likely present between these two areas as well as between ne japan and sw japan

the hidaka shear zone hokkaido japan genesis during a right lateral strike slip movement the mesozoic structure of hokkaido which is characterized by a wide spread ophiolite sequence unconformably overlain by a cretaceous flysch sequence is cut by a north south trending metamorphic belt the hidaka belt this contribution aims to demonstrate that the hidaka belt is a wide right lateral strike slip shear zone the movement is contemporaneous with the metamorphism and the magmatism of oligo miocene time

crustal structure and tectonics of the hidaka collision zone hokkaido japan revealed by vibroseis seismic reflection and gravity surveys abstract this study is the first integrated geological and geophysical investigation of the hidaka collision zone in southern central hokkaido japan which shows complex collision tectonics with a westward vergence the hidaka collision zone consists of the idon nappu belt ib the poroshiri ophiolite belt pob and the hidaka metamorphic belt hmb with the hidaka belt from west to east the pob metamorphosed ophiolites is overthrust by the hmb steeply eastward dipping palaeo arc crust along the hidaka main thrust hmt and in turn thrusts over the idon nappu belt melanges along the hidaka western thrust hwt seismic reflection and gravity surveys along a 20 km long traverse across the southern hidaka mountains revealed hitherto unknown crustal structures of the collision zone such as listric thrusts back thrusts frontal thrust and fold structures and duplex structures the main findings are as follows 1 the hmt which dips steeply at the surface is a listric fault dipping gently at a depth of 7 km beneath the eastern end of the hmb and cutting across the lithological boundaries and schistosity of the hidaka metamorphic rocks 2 a second reflector is detected 1 km below the hmt reflector the intervening part between these two reflectors is inferred to be the pob which is only little exposed at the surface this inference is supported by the high positive bouguer anomalies along the hidaka mountains 3 the shallow portion of the ib at the front of the collision zone has a number of nne dipping reflectors indicative of imbricated fold and thrust structures 4 subhorizontal reflectors at a depth of 14 km are recognized intermittently at both sides of the seismic profile these reflectors may correspond to the velocity boundary 5 9 6 6 km s previously obtained from seismic refraction profiling in the northern hidaka mountains 5 these crustal structures as well as the back thrust found in the eastern end of the traverse represent characteristics of collisional tectonics resulting from the two collisional events since the early tertiary

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

tertiary deep crustal ultrametamorphism in the hidaka metamorphic belt northern japan the main zone of the hidaka metamorphic belt is an imbricate stack of crustal material derived from an island arc in which a sequence of units with increasing metamorphic grade from low to high structural levels is exposed the basal part of the metamorphic sequence underwent granulite facies metamorphism with peak p t conditions of 7kbar 870 c in this zone pelitic granulite includes leucosomes which consist mainly of orthopyroxene plagioclase quartz to test whether the leucosome was derived by partial melting of the surrounding pelite melting experiments of the pelitic granulite were carried out for water saturated and dry systems at 7 kbar and 850 c the chemical composition of the leucosome produced during these runs shows a peraluminous s type tonalitic affinity and is located very close to the tie line between the average melts produced in water saturated systems and the average composition of the residual orthopyroxene plagioclase this therefore suggests that the lecosome in pelitic granulite was formed by incipient anatexis at close to the highest p t condition of the main zone the age of the crustal anatexis is determined by the rb sr whole rock isochron method for garnet cordierite biotite gneiss host rock garnet orthopyroxene cordierite gneiss restite and s type tonalite melt this gives an age of 56 0 ma with an initial 87sr 86sr ratio of 0 705711 the s type tonalite magmas that form large intrusive masses in the main zone were probably generated by crustal anatexis in deeper parts of the crust at the same time late palaeocene

decompressional coronas and symplectites in granulites of the musgrave complex central australia abstract in granulite facies metapelitic rocks in the musgrave complex central australia reaction between s1 garnet and sillimanite involves the development in s2 of both garnet cordierite hercynitic spinel biotite and hercynitic spinel cordierite sillimanite biotite the s2 assemblages occur either in coronas and symplectites mainly around garnet or in rocks in which s2 is more strongly developed as recrystallized assemblages ignoring the presence of biotite and ilmenite the mineral textures can be accounted for qualitatively by a consideration of the model system feo mgo al2o3 sio2 fmas the textural relationships accord with decompression accompanying the change from s1 to s2 however since biotite and ilmenite are involved in the assemblages the parageneses are better accounted for in terms of equilibria in the expanded model system k2o feo mgo al2o3 sio2 h2 tio2 fe2o3 kfmashto i e afm tio2 fe2o3 the coronas reflect the tectonic unroofing of at least part of the musgrave complex from peak s1 conditions of about 8 kbar to s2 conditions of about 4 kbar

development of an inshore fringing coral reef using textural compositional and stratigraphic data from magnetic island great barrier reef australia the stratigraphy of fringing coral reef environments and platforms provides unique insights into reef development and evolution this study used twelve sediment cores from three transects across a reef flat in nelly bay magnetic island ne australia to examine its development over the holocene the maximum thickness of the holocene reefal material based on seismic and bore log data was around 5 m and comparable to other fringing reefs in the great barrier reef gbr six different sedimentary facies were identified in the cores and two coincided with reef accretion the lower muddy sand with coral rubble and the upper siliciclastic sand with coral rubble radiocarbon and u series dates show that the nelly bay fringing reef initiated around 6300 yr bp on a gently sloping unconsolidated or weakly cemented pleistocene alluvial sedimentary facies the ages of four massive coral heads range between 5790 and 6290 calibrated c 14 yr bp were almost contemporaneous with reefal initiation indicating that conditions were favourable for reef growth around this time vertical accretion rates for the nelly bay fringing reef were on average about 0 5 mm yr over the last 6000 yr although rates were as high as 5 mm yr during initiation average lateral accretion rates varied from 98 to 120 mm yr which are comparable to rates of other fringing reefs in the region the age structure of the lower muddy sedimentary facies was consistent with the classic seaward prograding model of fringing reef development in contrast the upper siliciclastic sand with coral rubble facies was much younger in age 1100 yr bp than the models and appears to represent an erosional unconformity between the upper and lower reefal facies possibly linked to late holocene sea level fall this younger facies extends laterally across the reef flat and has no obvious prograding symmetry our integrated approach using multi proxy analyses of sediment cores from the nelly bay reef flat highlights the complex development of this reef which include changes in coral composition and rubble preservation reef evolution in response to sea level change and changes in reef accretion rates

tropical warming in the timor sea led deglacial antarctic warming and atmospheric co2 rise by more than 500 yr on the basis of the radiocarbon c 14 plateau tuning method a new age model for timor sea core md01 2378 was established it revealed a precise centennial scale phasing of climate events in the ocean cryo and atmosphere during the last deglacial and provides important new insights into causal linkages controlling events of global climate change at site md01 2378 reservoir ages of surface waters dropped from 1600 yr prior to 20 cal ka to 250 500 yr after 18 8 cal ka this evidence is crucial for generating a high resolution age model for deglacial events in the indo pacific warm pool sea surface temperatures sst started to change near 18 8 cal ka that is similar to 500 yr after the start of presumably northern hemispheric deglacial melt and sea level rise as shown by the benthic foraminiferal oxygen isotope ratio delta o 18 however the sst rise occurred 500 1000 yr prior to the onset of deglacial antarctic warming and the first major rise in atmospheric carbon dioxide at about 18 ka the increase in sst may partly reflect reduced seasonal upwelling of cold subsurface waters along the eastern margin of the indian ocean which is reflected by a doubling of the thermal gradient between the sea surface and the thermocline a halving of chlorin productivity from 19 to 18 5 cal ka and in particular by the strong decrease in surface water reservoir ages two significant increases in deglacial timor sea surface salinities from 19 to 18 5 and 15 5 to 14 5 cal ka may partly reflect the deglacial increase in the distance of local river mouths partly an inter hemispheric millennial scale see saw in tropical monsoon intensity possibly linked to a deglacial increase in the dominance of pacific el nino regimes over heinrich stadial 1 c 2010 elsevier b v all rights reserved

radiocarbon as a thermocline proxy for the eastern equatorial pacific an ocean model is used to test the idea that sea surface delta 14 c behaves as a thermocline proxy in the eastern equatorial pacific the orca2 model which includes delta 14 c as a passive tracer has been forced with reanalysis fluxes over 1948 1999 and the output is compared with a previously reported galapagos delta 14 c record the model reproduces the abrupt increase in the seasonally minimum delta 14 c in 1976 77 found in the data this increase is associated with neither a shift of thermocline depth over the nino3 region nor a change in the relative proportion of northern southern source waters rather it is due to a decrease in the sub antarctic mode water samw component of the upwelling water thereby representing a decrease in entrainment of water from below the base of the directly ventilated thermocline

arsenic speciation in sinter mineralization from a hydrothermal channel of el tatio geothermal field chile summary el tatio geothermal field is the principal natural source of arsenic for the loa river the main surface water resource in the hyper arid atacama desert antofagasta region northern chile prior investigations by bulk x ray absorption spectroscopy have identified hydrous ferric oxides as the principal arsenic containing phase in sinter material from el tatio suggesting sorption as the main mechanism for arsenic scavenging by the solid phases of these hot spring environments here we examine siliceous sinter material sampled from a hydrothermal channel using synchrotron based x ray micro probe techniques including as and fe k x ray fluorescence xrf as k edge x ray absorption near edge structure xanes and x ray diffraction xrd least squares linear fitting of xanes spectra shows that arsenic is predominantly present as arsenate sorbed on hydrous ferric oxides 63 molar proportion but we also identify nodular arsenide micro mineralizations 37 molar proportion similar to loellingite feas 2 not previously detected during bulk scale analysis of the sinter material presence of arsenide mineralizations indicates development of anoxic environments on the surface of the siliceous sinter and suggests a more complex biogeochemistry for arsenic than previously observed for circum neutral ph brine hot spring environments

stability in the south pacific surface marine 14c reservoir over the last 750 years evidence from american samoa the southern cook islands and the marquesas abstract although minor climatic and sea level changes have been documented for the south pacific during the late holocene our understanding of the consequent impact of these changes on the marine 14 c reservoir and therefore the 14 c content of shellfish is limited ultimately this has implications for documenting the chronology of human movement and adaptation in this region in this paper we compare marine reservoir r data obtained from tightly controlled archaeological proveniences with known age pre ad 1950 shells from the southern cook islands american samoa and marquesas islands results indicate that there has been no significant change in the near shore marine reservoir in these three locations over the last ca 750 years furthermore known age pre ad 1950 shell samples provide more precise r values for use in sample calibration than archaeological paired shell charcoal samples this is attributed in part to the limitations of assigning provenance and age to material from archaeological sites on the basis of these results we conclude that the known age pre ad 1950 shell derived r values can be used to calibrate shell 14 c results from deposits of late holocene age

oceanic climate and circulation changes during the past four centuries from radiocarbon in corals we analyzed radiocarbon in annual coral bands from the galapagos islands in the tropical east pacific to understand natural variability of past ocean circulation associated with climate change variability was observed on el nino timescales 3 7 years as well as at decadal and multi decadal periods low radiocarbon levels persisted for ten years during the early 1600s and for sixteen years during the early 1800s both coincident with periods of high volcanic aerosol loading in the atmosphere from massive eruptions intensification of tropical circulation at this time may be linked to climatically controlled changes in the structure of the tropical thermocline that is responsible for delivering cool upwelled waters to the tropical east pacific

changes in north atlantic radiocarbon reservoir ages during the allerod and younger dryas estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late quaternary climate we radiocarbon dated marine shells and terrestrial plant remains deposited in two bays on norway s west coast between 11 000 and 14 000 years ago a time of large and abrupt climatic changes that included the younger dryas yd cold episode the radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early yd stabilized for 900 years and dropped by 300 years within a century across the yd holocene transition

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

distribution of radiogenic heat generation in the arc s crust of the hokkaido island japan radiogenic heat generation was measured for rocks collected in the vertical section of the crust of the arc exposed in the hokkaido island japan measured heat generation value of metasediments is nearly constant of 1 0 w m and independent of the metamorphic grade using the measured heat generation value together with the published heat generation data of a granitic body emplaced in this section vertical profile of heat generation in the crust is constructed the estimated heat generation profile shows steep decrease with depth but is not lower than a value of 1 0 w m in the upper crust in the lower crust metabasites are dominant and heat generation value is one order of magnitude lower than that in the upper crust surface heat flow derived from the crustal heat generation is estimated to be 25 mw m when the crustal heat generation is considered temperature at the bottom of the crust estimated from surface heat flow becomes 300 c lower this temperature difference corresponds to the viscosity variation of more than three orders of magnitude which is important for understanding lithosphere dynamics

garnet orthopyroxene plagioclase quartz barometry refinement and application to the english river subprovince and the minnesota river valley recent experimental theoretical and thermodynamic studies permit better calibration of two reactions for geobarometry grossular pyrope quartz anorthite enstatite grossular almandine quartz anorthite ferrosilite if both reactions are applied using the same thermodynamic data and activity models they should yield the same pressure for a given garnet pyroxene plagioclase quartz assemblage application to a variety of high grade terrains generally yielded excellent results however poor results have been obtained for high fe rocks which can be traced to errors in activity models for garnet and or pyroxene either a two site ideal mixing model for orthopyroxene cf wood and banno 1973 underestimates enstatite activity for high fe orthopyroxenes or the ganguly and saxena 1984 model overestimates pyrope activity in low mg garnets

atmospheric 14c variations derived from tree rings during the early younger dryas abstract atmospheric radiocarbon variations over the younger dryas interval from 13 000 to 11 600 cal yr bp are of immense scientific interest because they reveal crucial information about the linkages between climate ocean circulation and the carbon cycle however no direct and reliable atmospheric 14c records based on tree rings for the entire younger dryas have been available in this paper we present 1 high precision 14c measurements on the extension of absolute tree ring chronology from 12 400 to 12 560 cal yr bp and 2 high precision high resolution atmospheric 14c record derived from a 617 yr long tree ring chronology of huon pine from tasmania australia spanning the early younger dryas the new tree ring 14c records bridge the current gap in european tree ring radiocarbon chronologies during the early younger dryas linking the floating lateglacial pine record to the absolute tree ring timescale a continuous and reliable atmospheric 14c record for the past 14 000 cal yr bp including the younger dryas is now available the new records indicate that the abrupt rise in atmospheric 14c associated with the younger dryas onset occurs at 12 760 cal yr bp 240 yrs later than that recorded in cariaco varves with a smaller magnitude of 40 followed by several centennial 14c variations of 20 25 comparing the tree ring 14c to marine derived 14c and modelled 14c based on ice core 10be fluxes we conclude that changes in ocean circulation were mainly responsible for the younger dryas onset while a combination of changes in ocean circulation and 14c production rate were responsible for atmospheric 14c variations for the remainder of the younger dryas

fe mg mixing in cordierite constraints from natural data and implications for cordierite garnet geothermometry in granulites from chemicaldata on 108 pairs of naturally occurring garnet and cordierite the interchange energy of fe mg mixing in cordierite wo and the free energy change of the exchange equilibrium feralrsiro t t zmgraiosiro y mgralrsiro yzferalosiro in the temperature range of 700 850 c have been extracted using standard methods of linear regression analysis the input thermochemical parameters for multicomponent camg fe mn garnet solid solutions are based on the updated and revised values after ganguly and saxena 1984 e g wr 2500 cal w w 3000 cal calculated on the basis of one third formula unit on the basis of the derived values at 710 760 800 and 850 c fe mg mixing in cordierite has been approximated to a symmetric regular solution the fe mg substitution shows positive deviation from ideality in cordierite with tzi 1 9 34 4 54kj mol of divalent cation the values derived for the free energy of mixing at xi d xi ds 0 5 are 3 26 kj at 700 c and 4 39 kl at 900 c the ag value in joules for the above equilibrium can be expressed as 15079 8 552 incorporating these parameters the geothermometric expression for the exchange equilibrium is

prograde and anatectic reactions in the deep arc crust exposed in the hidaka metamorphic belt hokkaido japan abstract the hidaka metamorphic belt is a tilted crustal assembly of a magmatic arc exposing two third of a total thickness of the arc crust the igneous activities and metamorphism took place during the eocene in a tectonically stacked and thickened accretionary prism of the latest cretaceous to earliest tertiary age the lower part of the exposed section consists mainly of mafic rocks with thin intercalations of pelitic and psammitic rocks metamorphosed under amphibolite and granulite and granulite facies while the upper part consists almost of pelitic and psammitic rocks metamorphosed under amphibolite and greenschist facies which are gradually changed to very weakly metamorphosed sedimentary rocks toward the top of the section reexamination of prograde metamorphism of pelitic granulite facies rocks confirmed a path of increasing temperature with a constant pressure or with slight decrease of pressure associated with moderate shearing norite and diorite veining as a part of mafic intrusives were followed to give rise to the peak metamorphism associating incipient anatexis of pelitic and psammitic gneisses in the basal part of the exposed section due to the anatexis small leucocratic patches or viens are formed with orthopyroxene and cordierite as residual phases cutting strong foliations of biotite with garnet and cordierite porphyroblasts the mafic intrusives played an important role in the metamorphic evolution in the deep part of the hidaka crust

low reservoir ages for the surface ocean from mid holocene florida corals the 14 c reservoir age of the surface ocean was determined for two holocene periods 4908 4955 and 3008 3066 calendar cal b p using u th dated corals from biscayne national park florida united states we found that the average reservoir ages for these two time periods 294 33 and 291 27 years respectively were lower than the average value between a d 1600 and 1900 390 60 years from corals it appears that the surface ocean was closer to isotopic equilibrium with co 2 in the atmosphere during these two time periods than it was during recent times seasonal 18 o measurements from the younger coral are similar to modern values suggesting that mixing with open ocean waters was indeed occurring during this coral s lifetime likely explanations for the lower reservoir age include increased stratification of the surface ocean or increased 14 c values of subsurface waters that mix into the surface our results imply that a more correct reservoir age correction for radiocarbon measurements of marine samples in this location from the time periods 3040 and 4930 cal years b p is 292 30 years less than the canonical value of 404 20 years

low pressure granulite facies metapelitic assemblages and corona textures from macrobertson land east antarctica the importance of fe2o3and tio2in accounting for spinel bearing assemblages low pressure granulite facies metasedimentary gneisses exposed in macrobertson land east antarctica include hercynitic spinel bearing metapelitic gneisses peak metamorphic mineral assemblages include spinel rutile ilmenite sillimanite garnet spinel ilmenite sillimanite garnet cordierite ortho pyroxene magnetite ilmenite garnet spinel cordierite biotite ilmenite and orthopyroxene cordierite biotite each with quartz k feldspar and melt the presence of garnet biotite and cordierite orthopyroxene bearing assemblages implies crossing tie lines in afm projection for the k2o feo mgo al2o3 sio2 h2o kfmash system this apparent contradiction and the presence of spinel rutile and ilmenite in the assemblages is acounted for by using the kfmash tio2 o2 system i e afm tio2 fe2o3 we derive a petrogenetic grid for this system applicable to low pressure granulite facies metamorphic conditions retrograde assemblages are interpreted from corona textures on hercynitic spinel and fe ti oxides the relative positions of the peak and retrograde metamorphic assemblages on the petrogenetic grid suggest that corona development occurred during essentially isobaric cooling

magmatic sulfide formation by reduction of oxidized arc basalt the hidaka metamorphic belt in southeastern hokkaido japan provides insights into how magmatic sulfide deposits may form through magma mixing deep within arcs here a near complete cross section of arc crust is exposed with large mafic igneous complexes preserved at deeper levels magmatic sulfide mineralization occurs within the opirarukaomappu gabbroic complex ogc which preserves a record of crustal contamination of mafic magmas via assimilation and magma mixing involving introduction of crust derived tonalite assimilation fractional crystallization modelling suggests that the gabbro evolved through a combination of approximately 10 wt mixing and 14 wt fractional crystallization magmatic sulfides and associated gabbros diorites and tonalites at this locality contain graphite with carbon isotope signatures consistent with derivation from the surrounding partially melted carbonaceous shales this indicates that crust derived carbon was added to the mafic magma through the magma mixing and assimilation process sulfur isotope data suggest that sulfur was also added from crustal sources during assimilation and magma mixing the relationships observed in the ogc suggest that intrusion of basalt into a segment of deep arc crust drove partial melting of carbonaceous metamorphic rocks producing graphite bearing felsic magmas with high reducing potential redox budget modelling shows that mixing of only small proportions of these magmas is sufficient to lower the oxidation state of oxidized basaltic magmas enough to induce sulfide saturation and consequent exsolution of immiscible sulfide melt magmatic sulfide deposits are likely to form by this reduction induced sulfide saturation mechanism deep within other arcs where magma mixing is thought to be common

abrupt shift in subsurface temperatures in the tropical pacific associated with changes in el nino radiocarbon 14c content of surface waters inferred from a coral record from the galapagos islands increased abruptly during the upwelling season july through september after the el nino event of 1976 sea surface temperatures ssts associated with the upwelling season also shifted after 1976 the synchroneity of the shift in both 14c and sst implies that the vertical thermal structure of the eastern tropical pacific changed in 1976 this change may be responsible for the increase in frequency and intensity of el nino events since 1976

holocene changes in the position and intensity of the southern westerly wind belt the position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature during the austral winter the belt expands northward and the wind intensity in the core decreases conversely during the summer the belt contracts and the intensity within the core is strengthened reconstructions of the westerly winds since the last glacial maximum however have suggested that changes at a single site reflected shifts throughout the entire southern wind belt 1 4 here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12 500 yr from sites along the windward side of the andes precipitation at the sites located in the present core and northern margin of the westerlies is driven almost entirely by the wind belt 5 and can be used to reconstruct its intensity rather than varying coherently throughout the holocene epoch we find a distinct anti phasing of wind strength between the core and northern margin over multi millennial timescales during the early holocene the core westerlies were strong whereas the northern margin westerlies were weak we observe the opposite pattern in the late holocene as this variation resembles modern seasonal variability we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern south pacific ocean chile is ideally located to reconstruct past variability of the southern westerly wind belt sww as the sww almost entirely controls precipitation on the western side of the andes in southern south america with an extreme northsouth

variability of surface ocean radiocarbon and stable isotopes in the southwestern pacific we present high precision radiocarbon 14c results and stable isotope 18o and 13c records for a coral from heron island 23 s 152 e and new stable isotope 18o and 13c records for annual coral bands from abraham reef 22 s 153 e in the southern great barrier reef studied earlier druffel and griffin 1993 these tracers provide unique information on the regional water mass history and together these data allow us to constrain the variability of circulation in the upper pacific over the past four centuries first we observe decreases in 18o of coral from abraham reef and heron island indicating an increase in sea surface temperature and or a decrease in surface salinity since 1850 second the small suess effect value 14c decrease from 1880 to 1955 due mostly to fossil fuel co2 observed previously at abraham reef druffel and griffin 1993 is confirmed in the measurements reported here from the heron island coral this value is low compared to those observed in other areas of the ocean druffel 1997 druffel and linick 1978 nozaki et al 1978 between 1880 and 1955 third we report alterations in the correlation between el nino events and the occurrence of low 14c which is indicative of long term change s in circulation in the sw pacific the 14c shifts reported here are not large but even small temporal changes in prebomb 14c suggest that important changes in the large scale state of the ocean have occurred such as a temporal change in circulation

large variations of surface ocean radiocarbon evidence of circulation changes in the southwestern pacific radiocarbon 14c and stable isotope 18o and 13c records are presented for biannual samples from a 323 year banded coral series collected from the southern great barrier reef australia the high precision 14c record contains variations on an interannual timescale that are particularly large between a d 1680 and 1730 by comparison with tree ring 14c records stuiver and quay 1980 m stuiver personal communication 1992 it is clear that these shifts were not caused by changes in the 14c of atmospheric co2 changes in vertical mixing and large scale advective changes involving source waters to the western coral sea region are likely processes that could account for these large 14c variations most low 14c values for the period a d 1635 1875 coincide with el nino southern oscillation enso events as reported by quinn et al 1987 for the eastern tropical pacific however enso does not explain all of the variations especially during 1875 1920 when 14c values remained high cross spectral analysis of the early half of the 14c and 18o records a d 1635 1795 reveals that the 6 year period is coherent this coherency is not present in the latter half a d 1797 1957 of the isotope records these data support the concept of century timescale changes in the nature of enso as it is manifest in the southwestern pacific our coral record shows no evidence of a suess effect the lowering of 14c from late 1800s through 1955 due mainly to co2 input from fossil fuel burning this is coincident with the change we observe in the nature of enso and is further evidence that a long term change in mixing of upper waters occurred in this region

tracking the extent of the south pacific convergence zone since the early 1600s 1 the south pacific convergence zone spcz is the largest and most persistent spur of the intertropical convergence zone at the southeastern edge of the spcz near 170 w and 15 20 s a surface ocean salinity frontal zone exists that separates fresher western pacific warm pool water from saltier and cooler waters in the east this salinity front is known to shift east and west with the phase of the el nino southern oscillation we have generated subannually resolved and replicated coral oxygen isotopic time series from fiji 17 s 179 e and rarotonga 21 5 s 160 w that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front and eastern extent of the spcz has shifted east west through 10 to 20 of longitude three times during this interval the most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the spcz since the mid 1800s the expansion of the spcz implies a gradual change in the south pacific to more la nina like long term mean conditions this observation is consistent with the ocean thermostat mechanism for the pacific coupled ocean atmosphere system whereby exogenous heating of the atmosphere would result in greater warming in the western pacific and a greater east west surface temperature gradient components 8034 words 7 figures 2 tables

temperatures of granulite facies metamorphism constraints from experimental phase equilibria and thermobarometry corrected for retrograde exchange this study assesses temperatures of formation of common granulites by combining experimental constraints on the p t stability of granulite facies mineral associations with a garnet orthopyroxene grt opx thermobarometry scheme based on al solubility in opx corrected for late fe mg exchange we applied this scheme to 414 granulites of mafic intermediate and aluminous bulk compositions our findings suggest that granulites are much hotter than traditionally assumed and that the p t conditions of the amphibolite granulite transition portrayed in current petrology textbooks are significant underestimates by over 100 c for aluminous and intermediate granulites mean corrected temperatures based on our method are 890 17 and 841 11 c respectively uncertainties reported as 95 confidence limits on the mean consistent with minimum temperatures for orthopyroxene production by fluid absent partial melting in these bulk compositions in contrast mean temperatures based on grt opx fe mg exchange equilibria using the same thermodynamic data are 732 22 and 723 11 c respectively well below the minimum temperatures for opx stability for mafic granulites the mean corrected temperature using our method is 816 12 c similar to the mean temperature of 793 13 c from fe mg exchange reasons for the differences between the mafic granulites and aluminous intermediate granulites are unclear but may be due to the lower al concentrations in opx in the mafic rocks and possible deficiencies in the thermodynamic modelling of these low concentrations we discuss a number of well known granulite terrains in the context of our findings including the adirondacks the acadian granulites of new england the incipient charnockites of southern india and sri lanka and the kerala khondalite belt our findings carry implications for thermotectonic models of granulite formation a computer program to perform our thermobarometry calculations rclc is available from the journal of petrology website at http www petrology oupjournals org or from the authors at http www geo ucalgary ca pattison drm pattison rclc htm

a large drop in atmospheric 14c 12c and reduced melting in the younger dryas documented with 230th ages of corals paired carbon 14 14 c and thorium 230 230 th ages were determined on fossil corals from the huon peninsula papua new guinea the ages were used to calibrate part of the 14 c time scale and to estimate rates of sea level rise during the last deglaciation an abrupt offset between the 14 c and 230 th ages suggests that the atmospheric 14 c 12 c ratio dropped by 15 percent during the latter part of and after the younger dryas yd this prominent drop coincides with greatly reduced rates of sea level rise reduction of melting because of cooler conditions during the yd may have caused an increase in the rate of ocean ventilation which caused the atmospheric 14 c 12 c ratio to fall the record of sea level rise also shows that globally averaged rates of melting were relatively high at the beginning of the yd thus these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the mississippi to the st lawrence river triggered the yd event

mylonitic deformation of gabbro in the lower crust a case study from the pankenushi gabbro in the hidaka metamorphic belt of central hokkaido japan abstract the mylonitization of the pankenushi gabbro in the hidaka metamorphic belt of central hokkaido japan occurred along its western margin at 600 mpa and 660 700 c through dynamic recrystallization of plagioclase and a retrograde reaction from granulite facies to amphibolite facies orthopyroxene clinopyroxene plagioclase h2o hornblende quartz the reaction produced a fine grained 100 m polymineralic aggregate composed of orthopyroxene clinopyroxene quartz hornblende biotite and ilmenite into which strain is localized the dynamic recrystallization of plagioclase occurred by grain boundary migration and produced a monomineralic aggregate of grains whose crystallographic orientations are mostly unrelated to those of porphyroclasts the monomineralic plagioclase aggregates and the fine grained polymineralic aggregates are interlayered and define the mylonitic foliation while the latter is also mixed into the former by grain boundary sliding to form a rather homogeneous polymineralic matrix in ultramylonites however in both mylonite and ultramylonite plagioclase aggregates form a stress supporting framework and therefore controlled the rock rheology crystal plastic deformation of pyroxenes and plagioclase with dominant 100 001 and 001 1 2 1 1 0 slip systems respectively produced distinct shape and crystallographic preferred orientations of pyroxene porphyroclasts and dynamically recrystallized plagioclase grains in both mylonite and ultramylonite euhedral to subhedral growth of hornblende in pyroxene porphyroclast tails during the reaction and its subsequent rigid rotation in the fine grained polymineralic aggregate or matrix produced clear shape and crystallographic preferred orientations of hornblende grains in both mylonite and ultramylonite in contrast the dominant grain boundary sliding of pyroxene and quartz grains in the fine grained polymineralic aggregate of the mylonite resulted in their very weak shape and crystallographic preferred orientations in the fine grained polymineralic matrix of the ultramylonite however pyroxene and quartz grains became scattered and isolated in the plagioclase aggregate so that they were crystal plastically deformed leading to stronger shape and crystallographic preferred orientations than those seen in the mylonite

radiocarbon in corals from the cocos keeling islands and implications for indian ocean circulation annual bands of a porites coral from the cocos keeling islands eastern indian ocean were analysed by radiocarbon for 1955 1985 ad a rapid oceanic response of the site to bomb c is found with a maximum c value of 132 in 1975 this value is considerably higher than those for the northwestern indian ocean suggesting that surface waters reaching cocos are not derived from the arabian sea instead c values for cocos and those for watamu kenya agree well over most of the study interval suggesting that the south equatorial current carries c elevated water rather than c depleted water westward across the indian ocean this implies that oceanic upwelling in the northwestern indian ocean is spatially confined with little contribution to the upper limb of the global thermohaline circulation copyright 2005 by the american geophysical union

speleothem derived asian summer monsoon variations in central china 54 46 ka the oxygen isotope signature delta o 18 of stalagmite si3 collected from shizi cave in north east sichuan province provides an asian summer monsoon asm record in central china for the period 54 46 ka the si3 delta o 18 record clearly shows a negative delta o 18 excursion centred around 49 4 ka which was reported in hulu cave in east china but not identified in the speleothem records from south west china as a whole this record displays a higher coherence with the two hulu records from east china than with the speleothem delta o 18 records from south west china suggesting that at 54 46 ka central china was influenced more by the east asian summer monsoon than by the indian summer monsoon it also displays a significant negative delta o 18 excursion at 47 5 46 6 ka which is not clearly documented in two other speleothem delta o 18 records previously reported from south west china this suggests that details of the greenland interstadial 12 warrant further investigations in future in monsoonal china the si3 delta o 18 record displays more significant centennial scale variations than the other four speleothem delta o 18 records from east and south west china which may be due to the fact that the study site is closer to the north west boundary of the asm and more sensitive to variations of the asm than east and south west china copyright c 2011 john wiley sons ltd

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

high precision u series ages of transported coral blocks on heron reef southern great barrier reef and storm activity during the past century transported coral blocks scattered on reef flats have previously been identified as useful proxies for past storm occurrences high precision tims u series dating and detailed field observations of 110 coral samples collected from 102 individual transported coral colonies coral blocks and 4 transported sections of reef matrix reef blocks from the northern side of heron reef southern great barrier reef indicate that 1 the youngest age of corals attached to reef blocks may represent the age of possible past storm occurrence providing a proxy for historical storm reconstruction 2 most ages of dated storm transported coral and reef blocks match well relatively with known cyclone and storm events further supporting that they are good indicators of past storm events and 3 age distribution and relative probability frequency analysis of the dated coral and reef blocks suggest that there have been eight broad periods of storm occurrence since 1900 ad 1904 1909 1914 1916 1935 1941 1945 1960 1965 1967 1976 1977 1983 1988 and 2001 2007 roughly showing decadal variations the coral based storm reconstruction therefore extended the database of past storm occurrences around heron reef area these findings suggest that coral reefs in the southern great barrier reef are frequently influenced by periods of high storm activity and show strong resilience to natural disturbances over the past century additionally our results show for the first time that the blue skeletal coral heliopora coerulea order helioporacae has u concentrations of only 0 12 to 0 30 ppm similar to 5 10 that of common reef building corals with white skeletons order scleractinia which may be a unique chemical signature of the only living species of the helioporidae family c 2012 elsevier b v all rights reserved

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

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

timing and duration of the last interglacial inferred from high resolution u series chronology of stalagmite growth in southern hemisphere high precision th 230 u 238 ages for a stalagmite from newdegate cave in southern tasmania australia define a rare record of precipitation between 100 and 155 ka before the present the fastest stalagmite growth occurred between 129 2 1 6 and 122 1 2 0 ka similar to 61 5 mm ka coinciding with a time of prolific coral growth from western australia 128 122 ka this is the first high resolution continental record in the southern hemisphere that can be compared and correlated with the marine record such correlation shows that in southern australia the onset of full interglacial sea level and the initiation of highest precipitation on land were synchronous the stalagmite growth rate between 129 2 and 142 2 ka similar to 5 9 mm ka was lower than that between 142 2 and 154 5 ka similar to 18 7 mm ka implying drier conditions during the penultimate deglaciation despite rising temperature and sea level this asymmetrical precipitation pattern is caused by latitudinal movement of subtropical highs and an associated westerly circulation in response to a changing equator to pole temperature gradient both marine and continental records in australia strongly suggest that the insolation maximum between 126 and 128 ka at 65 degreesn was directly responsible for the maintenance of full last interglacial conditions although the triggers that initiated penultimate deglaciation at similar to 142 ka remain unsolved c 2001 elsevier science b v all rights reserved

reduced ventilation and enhanced magnitude of the deep pacific carbon pool during the last glacial period it has been proposed that the ventilation of the deep pacific carbon pool was not significantly reduced during the last glacial period posing a problem for canonical theories of glacial interglacial co2 change however using radiocarbon dates of marine tephra deposited off new zealand we show that deep 2000 m 2000 m and shallow sub surface ocean atmosphere 14c age offsets i e reservoir or ventilation ages in the southwest pacific increased by 1089 and 337 yrs respectively reaching 2689 and 1037 yrs during the late glacial a comparison with other radiocarbon data from the southern high latitudes suggests that broadly similar changes were experienced right across the southern ocean if like today the southern ocean was the main source of water to the glacial ocean interior these observations would imply a significant change in the global radiocarbon inventory during the last glacial period possibly equivalent to an increase in the average radiocarbon age 2 km 2 km of 700 yrs 700 yrs simple mass balance arguments and numerical model sensitivity tests suggest that such a change in the ocean s mean radiocarbon age would have had a major impact on the marine carbon inventory and atmospheric co2 possibly accounting for nearly half of the glacial interglacial co2 change if confirmed these findings would underline the special role of high latitude shallow sub surface mixing and air sea gas exchange in regulating atmospheric co2 during the late pleistocene

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

holocene changes in eastern tropical pacific climate inferred from a galapagos lake sediment record abstract paleoclimate records from the tropical pacific suggest the early to mid holocene was a period of reduced el nino southern oscillation enso variability with a transition to modern increased enso frequency occurring some time in the last few thousand years however the nature and timing of this shift remains uncertain due to the discontinuous nature and or coarse resolution of many enso proxies as well as a lack of agreement between previously published records a new continuous climate record from el junco crater lake in the galapagos islands reveals several abrupt changes in lake level and precipitation through the holocene hydroclimatic model simulations suggest that el junco lake level responds sensitively to increases in precipitation associated with el nino events rising during wet el nino events and falling during the intervening dry periods grain size data from el junco sediment cores indicate past lake level variability likely associated with changing seasonal precipitation and enso frequency the grain size data suggest increased precipitation intensity prior to 9000 120 cal years bp and after 4200 130 cal years bp as well as a two step increase in precipitation at 3200 160 and 2000 100 cal years bp maximum holocene precipitation and inferred enso variability occurred between 2000 100 and 1500 70 cal years bp during the same period that six other independent proxy records suggest higher enso frequency and longer stronger el nino events decreasing sediment carbon nitrogen c n ratios in el junco sediments indicate rising lake levels from the early holocene to present corroborating the grain size data the inferred increase in precipitation at 4200 130 cal years bp and at 2000 100 cal years bp coincides with decreasing southwest asian and east asian monsoon intensity suggesting tropical pacific climate and the asian monsoon were interconnected systems at centennial to millennial timescales during the holocene a weakening trend in the asian monsoon and the trend toward wetter conditions at el junco also coincide with a trend toward cooler and drier conditions inferred from cariaco basin sediment proxies from the mid holocene to present suggesting the migration of the intertropical convergence zone itcz likely influenced hydrological changes in both the eastern tropical pacific and the asian monsoon region during the holocene

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

post glacial evolution of the indo pacific warm pool and el nino southern oscillation recent research has revealed new insights into the temperature size and variability of the indo pacific warm pool ipwp and the nature of the el nino southern oscillation enso since the last glacial maximum lgm sea surface temperature sst reconstructions from foraminiferal mg ca alkenone and revised coral sr ca palaeothermometry agree that ssts in the ipwp during the lgm were similar to 3degreesc cooler than at present in the central portion of the ipwf the rapid post glacial rise in sst led the deglaciation by similar to 3000 years to produce near modern ssts by the early holocene in contrast further west and north post glacial shifts in ssts in the south china and sulu seas are synchronous with abrupt climate changes in the north atlantic new evidence for the nature of the little ice age in the tropics has been obtained from a 420 year record of coral sr ca and 6180 from the great barrier reef australia this indicates that ssts and salinity were higher in the 18th century than in the 20th century the results suggest that the tropical pacific played a role as a source region of water vapour during the global expansion of little ice age glaciers the onset of modern enso periodicities is identified by palaeo enso records throughout the tropical pacific region similar to 5000 years ago with an abrupt increase in enso magnitude similar to 3000 years ago individual enso events recorded by corals reveal that the precipitation response to el nino temperature anomalies was subdued in the mid holocene the apparent non linear onset of enso in the late holocene appears to reflect abruptly enhanced interaction between the southern oscillation and the pacific intertropical convergence zone comparisons of precipitation variability recorded by great barrier reef corals with enso indices for the last 350 years confirms that non stationarity of enso teleconnections is a natural characteristic of modern climate c 2003 elsevier ltd and inqua all rights reserved

mechanisms of mid holocene precipitation change in the south pacific convergence zone abstractthe variability of the south pacific convergence zone spcz during the mid holocene is investigated using models archived in the paleoclimate modelling intercomparison project phase ii pmip2 database relative to preindustrial conditions mid holocene top of atmosphere insolation was relatively lower during austral summer december february djf which is the season when the spcz is at its peak intensity in response to this perturbation the pmip2 models simulate a displacement of the spcz to the southwest this spcz shift is associated with a sea surface temperature sst dipole with increased rainfall collocated with warm sst anomalies decomposing the djf precipitation changes in terms of a diagnostic moisture budget indicates that the spcz shift is balanced to leading order by a change in the mean moisture convergence changes to the broad area of upper level negative zonal stretching deformation where transient eddies can become trapped and subsequently generate deep convection suppo

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