geochemical evolution of clay pore water as an indicator for palaeoenvironmental variability in the hebei plain northern china in order to elaborate geochemical evolution of clay pore water cpw and associated palaeoenvironment in hengshui where there is shallow saline water in the area of hebei plain a borehole with a depth of 130 m was drilled in august 2013 in hengshui city q4 sediments occurred above 35 m and q3 mainly at depth of 130 35 m sediment particle size geochemistry and deuterium and oxygen isotopes of cpw were analyzed the cpw was generally of meteoric origin and was influenced by evaporation total dissolved solids tds in pore water were high which was mainly controlled by na mg2 so4 2 and cl ratios of rna rca of cpw were mostly larger than 1 indicating the missing of ca2 as a result of evaporation and cation exchange at depths of 20 10 m ratios of rna rcl were larger than 1 reflecting the accumulation of na during the continent salinization process the tds and 18o values of cpw above 6 m demonstrated that cpw was primarily affected by human irrigation as well as by atmospheric precipitation the mean 18o values of cpw were 11 5 12 1 and 10 6 at depths of 130 90 65 29 and 23 0 m respectively which were lower than the 18o values of groundwater at depths of 90 65 m 9 8 and 29 23 m 8 2 the depletion in 18o of cpw suggested that the cpw saved the palaeoenvironment media at depths below 6 m the 18o of cpw indicated that the temperature decreased at the depths from 130 to 90 m and the climate became colder at depths of 65 29 m but evolved to be warm in holocene at depths of 23 0 m

trends of sr and nd isotopes through time near the japan sea in northeastern japan nd and sr isotopic analyses were made on selected volcanic rocks of known stratigraphic age from a limited area in the green tuff region northeastern japan and in adjacent areas two ultramafic inclusions from ichinomegata were also analyzed the volcanic rocks range in age from 27 to 6 ma and vary in e nd from 0 9 to 5 7 and in e sr from 14 1 to 16 3 the isotopic data plot generally along the region of the mantle array when plotted against time the isotopic ratios are found to be a regular function of geologic age the results indicate that 1 the volcanic rocks in the area are part of a related sequence or evolutionary pattern over a time period of 27 ma 2 the evolutionary pattern goes from an initially enriched source to that of a very depleted source the shift in isotopic composition appears to reflect the ongoing lining of magma conduits or the decreasing extraction of lower crustal contributions with increasing infiltration of oceanic magma types in an environment where the crust is thinning based on the geotectonic development of this area due to the back arc spreading of the japan sea we identify two different stages the pre opening stage 15 ma and the post opening stage 15 ma the volcanic rocks of the pre opening stage are characterized by an enriched isotopic signature and those of the post opening era by a depleted signature the host rocks of the kuroko ore deposit lie within this evolutionary trend and contain a substantial amount of continentally derived materials processed through an oceanic environment in general we infer that the degree of continental crust involvement is high during the pre opening stages of a back arc basin when it is associated with a rifted continental mass

paleomagnetic evidence for the miocene counter clockwise rotation of northeast japan rifting process of the japan arc paleomagnetic results have been obtained from more than 700 oriented samples in igneous rocks of cretaceous to miocene age from northeast japan the remanent magnetizations of welded tuffs with age between 32 ma and 21 ma old from 17 widely distributed sampling sites in northeast japan are fairly well grouped with a mean ofd 41 2 i 56 5 95 7 2 the remanent magnetization of welded tuffs of 14 ma and 11 ma from 4 sites shows a northerly direction d 11 7 i 60 5 95 15 3 these data imply that northeast japan was apparently subjected to a counter clockwise rotation through 47 14 about a vertical axis on the representative point of northeast japan 141 e 39 n during the past 21 ma comparing with the period of the clockwise rotation of southwest japan the differential rotation between northeast japan and southwest japan is concluded to have occurred concurrently during the period between 21 ma and 12 ma a rifting model of the japan arc is proposed northeast japan rotated counter clockwise through 50 about a northern pivot at 146 e 44 n while southwest japan rotated clockwise through 54 about a southern pivot at 129 e 34 n the differential rotation about different rotation pivots gives rise to the opening of a diamond shaped back arc basin the japan sea

nd and sr isotope systematics of miocene to holocene volcanic rocks from southwest japan volcanism since the opening of the japan sea isotope nd and sr and geochemical data for twelve volcanic rocks from the shimane oki san in region of southwest japan give some insight into the miocene recent volcanic history of southern japan since rifting from the asian mainland the oldest rocks examined dolerites and ushikiri formation were erupted during the opening of the japan sea at about 15 ma and comprise arc tholeiites derived from a depleted source end 0 esr 0 interpreted in terms of a depleted mantle source modified by a slab derived fluid volcanics of oki dozen island in the japan sea are alkalic derived from an enriched mantle plume isotopically distinct from nearly oki dogo island eruption of the calc alkaline wakurayama andesite early pliocene and both arc and within plate type basalts 1 ma show that magmas were tapped from a variety of sources taking into account plate tectonics and seismic data the subduction influence until the quaternary was the pacific plate with philippines sea plate subduction affecting quaternary and younger volcanics

seasonal and spatial variations of 17oexcess and dexcess in antarctic precipitation insights from an intermediate complexity isotope model an intermediate complexity isotope model icm is used to investigate the sensitivity of water isotope ratios in precipitation including 17oexcess to climate variations in the southern hemisphere the icm is forced with boundary conditions from seasonal ncep doe ii reanalysis data perturbations to the surface temperature and humidity fields are used to investigate the isotopic sensitivity the response of 17oexcess to a uniform temperature change is insignificant over the ocean while there is a large magnitude response over the ice sheet particularly in east antarctica a decrease of ocean surface relative humidity produces increased 17oexcess and dexcess with a coherent response over both the ocean and antarctica for interior east antarctica the model simulates a seasonal cycle in 17oexcess that is positively correlated with 18o and of large magnitude 50 per meg consistent with the observations from vostok the seasonal cycle in 17oexcess for interior west antarctica is predicted to be considerably smaller in magnitude 12 per meg and is negatively correlated with 18o consistent with new data from a firn core near the west antarctic ice sheet divide site over the ocean the icm predicts much smaller seasonal cycles in 17oexcess oceanic source changes i e humidity are insufficient to explain the amplitude of the simulated seasonal cycle over the antarctic continent spatial differences in the seasonal response of 17oexcess to local temperature reflect the balance of equilibrium and kinetic fractionation during snow formation

understanding the 17o excess glacial interglacial variations in vostok precipitation combined measurements of delta o 18 delta o 17 and delta d in ice cores leading to d excess and o 17 excess are expected to provide new constraints on the water cycle and past climates we explore different processes both in the source regions and during the poleward transport that could explain the o 17 excess increase by 20 per meg observed from the last glacial maximum lgm to early holocene eh at the vostok station using a single column model over tropical and subtropical oceans we show that the relative humidity at the surface is the main factor controlling o 17 excess in source regions then using a rayleigh type model we show that the o 17 excess signal from the source region is preserved in the polar snowfall contrary to d excess evaporative recharge over mid and high latitudes and delta o 18 seasonality in polar regions can also affect the vostok o 17 excess but cannot account for most of the 20 per meg deglacial increase from lgm to eh on the other hand a decrease of the relative humidity at the surface rh s by 8 to 22 would explain the observed change in o 17 excess such a change would not necessarily be incompatible with a nearly unchanged boundary layer relative humidity if the surface thermodynamic disequilibrium decreased by 4 degrees c such a change in rh s would affect source and polar temperatures reconstructions from delta o 18 and d excess measurements strengthening the interest of o 17 excess measurements to better constrain such changes

provenance of paleozoic mesozoic sedimentary rocks in the inner zone of southwest japan an evaluation based on nd model ages abstract nd model ages using depleted mantle tdm values for the sedimentary rocks in the inner zone of the sw japan and western area of tanakura tectonic line in the ne japan allow classification into five categories 2 6 2 45 2 3 2 05 1 9 1 55 1 45 1 25 and 1 2 0 85 ga the provenance of each terrane belt district is interpreted on the basis of the tdms 147sm 144nd vs 143nd 144nd relation nd isotopic evolution of the source rocks in east china and u pb zircon ages the provenance of 2 6 1 8 ga rocks which are reported from hida oki and renge belts and kamiaso conglomerates is inferred to be the sino korean craton skc the 2 3 1 55 ga rocks mostly from ryoke mino and ashio belts are originally related with the skc and or yangtze craton yc the provenances of the sedimentary rocks with 1 45 0 85 ga from the suo belt higo and some districts in the mino and ashio belts are different from the skc and yc especially the higo with 1 2 0 85 ga is considered as a fragment of collision zone in east china akiyoshi belt probably belongs to the youngest age category of 1 2 0 85 ga some metasedimentary rocks from the ryoke belt have extremely high 147sm 144nd and 143nd 144nd ratios whose main components are probably derived from mafic igneous rocks within the ryoke belt itself and from the adjacent tamba belt

site information and initial results from deep ice drilling on law dome antarctica the aim of deep ice drilling on law dome antarctica has been to exploit the special characteristics of law dome summit i e low temperature and high accumulation near an ice divide to obtain a high resolution ice core for climatic environmental studies of the holocene and the last glacial maximum lgm drilling was completed in february 1993 when basal ice containing small fragments of rock was reached at a depth of 1196 m accurate ice dating obtained by counting annual layers revealed by fine detail 18 o peroxide and electrical conductivity measurements is continuous down to 399 m corresponding to a date of ad 1304 sulphate concentration measurements made around depths where conductivity tracing indicates volcanic fallout allow confirmation of the dating for agung in 1963 and tambora in 1815 or estimates of the eruption date from the ice dating for the kuwae vanuatu eruption 1457 the lower part of the core is dated by extrapolating the layer counting using a simple model of the ice flow at the lgm ice fabric measurements show a large decrease 250 to 14 mm 2 in crystal size and a narrow maximum in c axis verticality the main zone of strong single pole fabrics however is located higher up in a broad zone around 900 m oxygen isotope 18 o measurements show holocene ice down to 1113 m the lgm at 1133 m and warm 18 o about the same as holocene ice near the base of the ice sheet the lgm holocene 18 o shift of 7 0 only 1 larger than for vostok indicates that law dome remained an independent ice cap and was not overridden by the inland ice sheet in the glacial

water isotopes in precipitation data model comparison for present day and past climates abstract variations of hdo and h2 18 o concentrations are observed in precipitation both on a geographical and on a temporal basis these variations resulting from successive isotopic fractionation processes at each phase change of water during its atmospheric cycle are well documented through the iaea wmo network isotope concentrations are in middle and high latitudes linearly related to the annual mean temperature at the precipitation site paleoclimatologists have used this relationship to infer paleotemperatures from isotope paleodata extractable from ice cores deep groundwater and other such sources for this application to be valid however the spatial relationship must also hold in time at a given location as the location undergoes a series of climatic changes progress in water isotope modeling aimed at examining and evaluating this assumption has been recently reviewed jouzel et al 1997 with a focus on polar regions and more specifically on greenland we extend this review in comparing the results of two different isotopic agcms nasa giss and echam and in examining with a more global perspective the validity of the above assumption i e the equivalence of the spatial and temporal isotope temperature relationships these results confirm the dominating role of local temperature changes on the paleo isotope signal in most regions however the exact calibration of this valuable paleothermometer is biased by for example the seasonality of precipitation and other factors we forced the two models by the climatic boundary conditions of the mild holocene at 6 kyr bp which only slightly differs from today s climate the isotope response on this weak forcing is quite heterogeneous the only robust common response is the intensification of the hydrological cycle in low latitudes and therefore isotopically more depleted precipitation in the tropics and subtropics we also examine recent progress made in modeling the relationship between the conditions prevailing in moisture source regions for precipitation and the deuterium excess of that precipitation

spatial variations of sr and nd isotope ratios of cretaceous paleogene granitoid rocks southwest japan arc cretaceous paleogene granitoid rocks and contemporaneous volcanic rocks are widely distributed in the inner zone of southwest japan this intense intermediate to felsic magmatism is considered to have taken place on the eastern margin of the eurasian continent before the southwest japan arc drifted away from the continent in the middle miocene resulting in the opening of the japan sea the granitoid rocks show regional variations in terms of their radiometric age petrography sr nd and o isotope ratios based on sr and nd isotope ratios granitoid rocks can be divided into three zones south transitional and north between the median tectonic line and the japan sea granitoid rocks and associated gabbros of the north zone have low initial sr isotope ratios 0 7048 to 0 7068 and high initial end values 3 to 2 2 whereas granitoid rocks and gabbros from the south zone have high initial sr isotope ratios 0 7070 to 0 7088 and low initial end values 3 0to 8 0 most granitoid rocks from the transitional zone have sr and nd isotope ratios that lie between those of the north and south zones although there is some overlap contamination of magmas by upper crust cannot explain this geographical variation in sr and nd isotopes instead the regional variation is attributed to compositionally different magma sources probably upper mantle and lower crust beneath the north and south zones this is supported by the sr and nd isotopic ratios of upper mantle and lower crustal xenoliths included in cenozoic volcanic rocks in the north and south zones these ratios are similar to those of the granitoid rocks in the respective zones it is suggested that a micro continent or island arc consisting of continental crust was underthrust beneath the south zone before or during the cretaceous resulting in compositionally distinct sources for granitoid rocks of the north and south zones the large variation observed in sr and nd isotope ratios for transitional zone granitoid rocks is explained by variable proportions of the two different crustal and upper mantle components

calibrating the ice core paleothermometer using seasonality high resolution oxygen isotope measurements on the dome summit south dss ice core from law dome antarctica provide a seasonal profile that is sufficiently stable and undistorted by biases in accumulation to permit comparison with measured temperature seasonality this comparison yields an isotope temperature relation with a gradient d dt of 0 44 0 02 c and provides a new method for exploring the isotope temperature relationship at high accumulation sites if applied to the observed isotope record from the dss core which extends through the last glacial and beyond this calibration suggests that at its coldest the last glaciation was 13 c colder than present at this site after correcting for elevation change this finding compares with a temperature difference of 8 c computed by using the local spatially derived calibration

timing of rotational motion of southwest japan inferred from paleomagnetism abstract paleomagnetic field directions for the period younger than 35 ma are obtained from igneous rocks distributed in the san in district inner zone of southwest japan the remanent magnetization of samples between 30 and 35 ma old are fairly well grouped with a mean direction of d 65 9 i 48 6 and 95 6 5 this result establishes that southwest japan rotated clockwise 56 12 during the past 30 m y a declination value of about 60 is observed in the rocks of 28 ma d 52 2 i 33 5 and 21 ma d 69 9 i 49 5 comparing this with results from dacitic rocks with an age of 15 ma in other areas of southwest japan suggests that rotational motion did not occur possibly until 15 ma these results require that the rotation of southwest japan occurred just after the shikoku basin had been created

measuring stable isotopes of hydrogen and oxygen in ice by means of laser spectrometry the bolling transition in the dye 3 south greenland ice core we report on the first application of a new technique in ice core research based on direct absorption infrared laser spectrometry ls for measuring h 2 o 17 and o 18 isotope ratios the data are used to calculate the deuterium excess d defined as delta 2 h 8delta 18 o for a section of the dye 3 south greenland deep ice core around the bolling transition 14 500 bp the precision of ls is slightly better than that of most traditional methods for deuterium but not for the oxygen isotopes the ability to measure delta 17 o is new and is used here to improve the precision of the delta 18 o determination still the final precision for delta 18 o remains inferior to traditional isotope ratio mass spectrometry irms therefore deuterium excess was calculated from a combination of the ls and irms isotope determinations

paleo climate of the boise area idaho from the last glacial maximum to the present based on groundwater δ2h and δ18o compositions abstract a 30 ka paleo climate record of the boise area idaho usa has been delineated using groundwater stable isotopic compositions groundwater ages are modern cold batholith 5 15 ka thermal batholith 10 20 ka frontal fault and 20 30 ka snake river plain thermal the stable isotopic composition of groundwaters have been used as a surrogate for the stable isotopic composition of precipitation using 2h and 18o compositions local groundwater lines lgwl s were defined for each system each lgwl has been evaluated with defined slopes of 6 94 and 8 respectively and resulting deuterium excess values d were found for each groundwater system for each slope time dependent changes in moisture source humidity and temperature and boise area recharge temperatures calculated from stable isotopic data and the deuterium excess factors agree with previous paleo climate studies results indicate that from the last glacial maximum to the present time the humidity over the ocean moisture source increased by 9 sea surface temperature at the moisture source increased 6 7 c and local boise temperature increased by 4 5 c a greater increase of temperature at the moisture source as compared to the boise area may impart be due to a shift in the moisture source area

cold conditions in antarctica during the little ice age implications for abrupt climate change mechanisms abstract the little ice age lia is one of the most prominent climate shifts in the past 5000 yrs it has been suggested that the lia might be the most recent of the dansgaard oeschger events which are better known as abrupt large scale climate oscillations during the last glacial period if the case then according to broecker 2000a 2000b antarctica should have warmed during the lia when the northern hemisphere was cold here we present new data from the ross sea antarctica that indicates surface temperatures were 2 c colder during the lia with colder sea surface temperatures in the southern ocean and or increased sea ice extent stronger katabatic winds and decreased snow accumulation whilst we find there was large spatial and temporal variability overall antarctica was cooler and stormier during the lia although temperatures have warmed since the termination of the lia atmospheric circulation strength has remained at the same elevated level we conclude that the lia was either caused by alternative forcings or that the sea saw mechanism operates differently during warm periods

rifting of kyushu japan based on the fault controlled concurrent eruption of oceanic island basalt type and island arc type lavas the tectonic environment of kyushu japan is affected both by the subduction of the philippine sea plate and by the extensional tectonics related to rifting of okinawa trough at the eastern margin of the eurasia plate we found that the sendai fault zone acts as a channel for concurrent eruption of oceanic island basalt oib type and island arc ia type basaltic rocks propagating west to east in the sendai region of southern kyushu the location of the sendai fault zone is likely to correspond to the left lateral shear zone in southern kyushu as inferred by gps earth observation network a similar magmatic association is present in the beppu shimabara bs graben system in central kyushu the associate magmas of oib type rocks in kyushu can be classified into typical em ii like and their intermediate oib type magmas in addition to morb like oib type magma in 87sr 86sr nb y systematics typical oib type and intermediate oib type magmas are erupted within the sendai fault zone and bs graben system respectively the former is characterized by highest nb y but low 87sr 86sr similar to morb like oib type magma erupted in northern kyushu and the latter has intermediate nb y and 87sr 86sr between typical and em ii like oib type magmas almost all the ia type rocks within the sendai fault zone are generated from parental ia type magma in kyushu and characterized by weak crustal assimilation having the lowest 87sr 86sr similar to typical oib type magma but the highest 143nd 144nd of arc magmas in kyushu the ages of both types of basaltic rocks within the sendai fault zone range from 1 6 to 0 01 ma clearly younger than those of andesitic rocks on northern and southern outsides of the fault zone and become younger from west to east initial formation of the fault zone has been induced by the counterclockwise rotation of southern kyushu during the last 2 ma as well as the bs graben system kyushu has continued to be split into three parts by the sendai fault zone and bs graben during the quaternary northern central and southern zones their initial formation ages are likely to be linked to the initial rifting age of the middle okinawa trough back arc basin

a 700 year record of atmospheric circulation developed from the law dome ice core east antarctica 1 a 700 year high resolution multivariate ice core record from dome summit south dss 66 46 s 112 48 e 1370 m law dome is used to investigate sea level pressure slp variability in the region of east antarctica empirical orthogonal function eof analysis reveals that the first eof ldeof1 of the combined glaciochemical oxygen isotope ratio and accumulation rate record from dss represents most of the variability in sea salt seen in the record ldeof1 is positively correlated at least 95 confidence level to instrumental june mean slp across most of east antarctica over the last 700 years ldeof1 levels at law dome were the highest during the nineteenth century suggesting an increase in intensification of winter circulation during this period the law dome dss oxygen isotope ratio series also indicates that the nineteenth century had the coldest winters of any century in the record in contrast ldeof1 levels were the lowest at law dome during the eighteenth century suggesting a significant shift in the patterns and or intensity of east antarctic atmospheric circulation between the eighteenth and the nineteenth centuries the ldeof1 sea salt record is characterized by significant decadal scale variability with a strong 25 year periodic structure

the grip deuterium excess record abstract ice cores from greenland and antarctica are ideal archives for retrieving long time series of deuterium excess d d 8 18 o a parameter influenced by conditions prevailing in the oceanic regions which provide moisture for polar snow the central greenland grip deuterium excess record has recently been interpreted in terms of oceanic source temperatures both for the holocene and for the last glacial period this approach being less straightforward for the latter period because of changes in the precipitation seasonality between glacial and interglacial periods this article examines why a conventional or sea surface temperature interpretation of the grip excess record seems inconsistent with inferred site and source temperature changes in addition the grip excess record is extended back into the penultimate glacial period and we assess its geographic significance through a comparison with existing dye 3 and north grip data we examine why low d 18o slopes observed during glacial times are associated with low deuterium excess values similarities between the greenland grip and antarctic vostok excess records are discussed in terms of potential links with insolation and insolation gradient changes finally the isotope records in specific do events are examined in light of intruiging differences between the isotope ratios d or 18o and the excess records that may result from a feedback mechanism linked with freshwater oceanic input

migration effects on the composition of hydrocarbon accumulations in the oml 67 70 areas of the niger delta systematic changes in gas oil ratios in the oml 67 70 area joint venture acreage of the niger delta nigeria illustrate the effects of hydrocarbon migration on the compositional changes observed in the accumulations over large depth intervals one interpretation is that the reservoirs are currently both filling and leaking hydrocarbons indicating that trap styles affect the migration pathways in this region of the niger delta the accumulations are more liquid prone with depth based on the bubble point of the fluids in the reservoir applying these results to regional exploration opportunities indicates that fluid contacts in the normally pressured section are controlled by leaking seals class iii traps the potential exists for pressure controlled filled to spill traps class ii traps in the overpressured section where a high quality seal impedes the vertical flux of hydrocarbon fluids although these conclusions apply to a specific portion of the niger delta combining the concept of trap style with compositional changes resulting from migration processes is useful in identifying new play concepts and opportunities in other regions of the world

three dimensional seismic structure beneath southwest japan the subducting philippine sea plate abstract a three dimensional seismic structure beneath southwest japan has been investigated in detail by applying an inversion method this analysis clearly reveals the present and possibly the past subduction of the philippine sea plate beneath southwest japan beneath the izu peninsula the philippine sea plate does not appear to subduct but collides against the continental asian plate here and its thickness appears thinnest at most about 30 km from the tokai to the shikoku regions the high velocity zone corresponds well to the zone of subcrustal earthquakes down to a depth of about 60 70 km indicating that the subduction of the present philippine sea plate does not reach below this depth here however a small high velocity portion appears at depths between 100 km and 150 km beneath a part of the kinki region and probably extends to the chugoku region where no corresponding seismic activities exist these high velocities might be an indication of the remnants of the past subduction of the philippine sea plate in the kyushu region the high velocity zone continues down to a depth of about 150 km or even to 200 km in the southern part corresponding to a steeply inclined seismic zone the philippine sea plate in this region appears to be thicker than in regions east of the kyushu palau ridge it was also found that there exist narrow low velocity zones intervening within the philippine sea plate where two aseismic ridges the kyushu palau and shichito iwojima ridges extend northwards and the nankai trough shows warping these low velocity zones give support to the buoyant subduction hypothesis it also appears that lateral heterogeneities existing within and around the subducting plate are closely related to the mode of rupture of large earthquakes occurring around there

geochemical indications of provenance change as recorded in miocene shales opening of the japan sea san in region southwest japan abstract shales from the san in region southwest japan exhibit geochemical patterns that record provenance change during the opening of the japan sea four formations the koura josoji ushikiri and furue are described the basal koura formation is non marine while those overlying are marine the koura formation shows variation from basic to silicic composition due to fluvial transportation of source rocks with lower cia chemical index of alteration than those of the josoji formation the source material of the koura formation is mainly felsic possibly plutonic rocks as shown by cr zr y ni systematics and similar to ebi granitic rocks of the hida continental massif in sio 2 tio 2 al 2 o 3 tio 2 ratios the josoji formation is enriched in sio 2 from high biogenic productivity ti zr and cr zr y ni ratios of the josoji formation suggest that basalt to andesite were significant lithologies in the source region provenance change from the koura to the josoji formations was possibly related to the transgression caused by the first opening of the japan sea where sediments were derived from deeply weathered material in the wider source areas the ushikiri formation shows mainly intermediate composition and is characterized by relatively higher ca and sr this is indicative of uplift of the paleogene igneous rocks in the source areas with intermediate volcanic activity probably related to the second opening event the furue formation has similar composition to the ushikiri formation but with comparatively higher cia suggesting another episode of deeper source area weathering and well mixed source material the results are consistent with published geological interpretations of the area and show that the geochemistry of shales from active margins is a useful tool for examining the development of such margins locally derived shales retain source composition variability and signatures while those deposited in deeper basins show more consistent chemistry closer to paas composition

nd and sr isotopic study of volcanic rocks from japan two older granitic rocks and some selected quaternary volcanic rocks from the japanese islands were analyzed in a reconnaissance study for the purpose of examining the relationships between nd and sr isotopic abundances and the megatectonic structure around the japanese islands model ages of 0 9 ae were determined by the nd and sr methods on a paleozoic gneiss which confirms that a relatively ancient acidic basement exists in the japanese islands the nd and sr isotopic data show that the cretaceous granodiorite is the result of partial melting of older crust the nd of tholeiitic rocks from the izu arc gives e nd ranging from 8 3 to 9 3 and with the corresponding e sr from 14 5 to 18 5 these results are identical to those found for the mariana arc these values are distinctly lower than typical morb by around 1 2 eu this difference in e nd between arcs and morb is attributed to the contribution of oceanic sediments to the partial melts produced during subduction of oceanic crust the hakone volcano is clearly confirmed as belonging to an oceanic source by nd isotopic results e sr e nd values of the volcanics from a section along the fossa magna show a clear indication that they are a blend of oceanic mantle material and continental crustal material the crustal component clearly increases in going from south to north volcanics across the northeast japan arc also show a distinct correlation of e sr e nd related to the position relative to the active subduction zone but with the opposite trend these relationships of the present isotopic pattern and the zonal arrangement relative to the subduction zone suggest the former existence of a local spreading center in the japan sea in general there appear to be regular isotopic relationships between the izu mariana oceanic island arc and the continental island arc of japan which indicates that partially melted or assimilated older continental basement is admixed with young rising oceanic arc magmas

a reconstruction of extratropical indo pacific sea level pressure patterns during the medieval climate anomaly subtropical and extratropical proxy records of wind field sea level pressure slp temperature and hydrological anomalies from south africa australia new zealand patagonian south america and antarctica were used to reconstruct the indo pacific extratropical southern hemisphere sea level pressure anomaly slpa fields for the medieval climate anomaly mca 700 1350 ce and transition to the little ice age lia 1350 1450 ce the multivariate array of proxy data were simultaneously evaluated against global climate model output in order to identify climate state analogues that are most consistent with the majority of proxy data the mean slp and slp anomaly patterns derived from these analogues illustrate the evolution of low frequency changes in the extratropics the indo pacific extratropical mean climate state was dominated by a strong tropical interaction with antarctica emanating from 1 the eastern indian and south west pacific regions prior to 1100 ce then 2 the eastern pacific evolving to the central pacific la nina like pattern interacting with a ve sam to 1300 ce a relatively abrupt shift to ve sam and the central pacific el nino like pattern occurred at 1300 a poleward equatorward shift in the subtropical ridge occurred during the mca mca lia transition the hadley cell expansion in the australian and southwest pacific region together with the poleward shift of the zonal westerlies is contemporaneous with previously reported hadley cell expansion in the north pacific and atlantic regions and suggests that bipolar climate symmetry was a feature of the mca

early ordovician continental break up in variscan europe ndsr isotope and trace element evidence from bimodal igneous associations of the southern massif central france abstract the high grade marvejols group and the low grade albigeois cevennes sedimentary sequence contain bimodal igneous rocks of early ordovician age which are representative of a widespread thermal event in the european variscides comparison of their nd sr isotope and trace element characteristics provides additional evidence for their origin in an ensialic extensional setting as an alternative to the back arc model proposed by previous authors we propose that these associations record a continental break up episode unrelated to contemporaneous subduction in this model the widespread early paleozoic bimodal magmatism marks the birth of a mid european oceanic arm we propose that the break up was controlled by both transtensional processes and mantle plume activity high grade associations such as the marvejols group and low grade bimodal associations such as the albigeois cevennes might be regarded as representing opposite rifted passive margins the northern marvejols type margin was involved in a late ordovician silurian subduction like process with hp ht metamorphism in contrast the southern albigeois cevennes margin remained largely unaffected possibly as part of the overriding plate of the subduction zone pseudo calc alkaline signatures unrelated to subduction processes may occur in magmatic rocks associated with continental break up episodes in this case negative nb anomalies are produced by the addition of crustal components enriched in th and lree relative to nb this inferred alternative origin of nb anomalies has important bearing on the paleogeodynamic settings based on geochemical data

snow precipitation at four ice core sites in east antarctica provenance seasonality and blocking factors snow precipitation is the primary mass input to the antarctic ice sheet and is one of the most direct climatic indicators with important implications for paleo climatic reconstruction from ice cores provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites dome c law dome talos dome and taylor dome in east ant arctica were analysed with air mass back trajectories cal culated using the lagrangian model and the mean composite data for precipitation geopotential height and wind speed field data from the european centre for med ium range weather forecast from 1980 to 2001 on an annual basis back trajectories showed that the atlantic indian and ross pacific oceans were the main provenances of precipitation in wilkes land 80 and victoria land 40 respectively whereas the greatest influence of the ice sheet was on the interior near the vostok site 80 and in the southwest ross sea 50 an effect that decreased towards the coast and along the antarctic slope victoria land received snowfall atypically with respect to other antarctica areas in terms of pathway eastern instead of western seasonality summer instead of winter and velocity old air age geopotential height patterns at 500 hpa at low 10 days and high 2 6 days frequen cies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the tasman sea eastern indian ocean at higher latitudes 60 70s than normal this could be considered part of an atmospheric blocking event with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low frequency positive anomalies

asymmetries in the moisture origin of antarctic precipitation the seasonality of moisture sources for precipitation in antarctica is studied with a lagrangian moisture source diagnostic moisture origin for precipitation in antarctica has strongly asymmetric properties which are related to the antarctic topography seasonal sea ice coverage and the land ocean contrasts in the mid latitudes of the southern hemisphere the highest altitudes of the east antarctic ice shield where major ice cores have been drilled have mean source latitudes of 45 40 s year round this finding contrasts to results from previous lagrangian studies which detected a more southerly moisture origin due to too short trajectories now results from lagrangian moisture source diagnostics are consistent with findings from general circulation models with tagged tracers thus both approaches can serve as a common benchmark for the interpretation of moisture source indicators based on stable isotopes such as deuterium excess in antarctic ice cores

neocene stress field of the japanese arcs and its relation to igneous activity abstract the neogene stress field in the southern part of northeast japan and the eastern part of southwest japan was restored with special reference to its time scale based mainly on k ar ages and strike directions of dike swarms the present study indicates the changes of stress field at about 22 ma b p 15 ma b p 12 ma b p and 8 ma b p in the southern part of northeast japan and at about 15 ma b p in the eastern part of southwest japan the stress changes are also thought to have occurred at about 12 ma b p 9 ma b p and 1 ma b p in the eastern part of southwest japan these results imply that some common causes generated the stress changes in both northeast and southwest japan at about 15 ma b p 12 ma b p and 8 9 ma b p major igneous activity in the japanese arcs seems likely to have taken place almost at same times as the stress changes the history of volcanic activity in the northwest pacific region during the miocene also shows the temporal correlation with the change of the stress regime the tectonic evolution in subduction zones therefore appears to be characterized by the synchronism of stress changes and intensive igneous activity

recent southern indian ocean climate variability inferred from a law dome ice core new insights for the interpretation of coastal antarctic isotopic records stable isotopes in water have been measured along a very high accumulation ice core from law dome on the east antarctic coast these enable a detailed comparison of the isotopic records over sixty years 1934 1992 with local antarctic station data and remote meteorological observations atmospheric reanalyses and sea surface temperature estimates on a seasonal to inter annual time scale using both observations and isotopic atmospheric general circulation model gcm results we quantify the relationships between stable isotopes 18o d and deuterium excess d d 8 18o with site and source temperature at seasonal and decadal time scales showing the large imprint of source conditions on law dome isotopes these calibrations provide new insights for the quantitative interpretation of temporal isotopic fluctuations from coastal antarctic ice cores an abrupt change in the local meridional atmospheric circulation is clearly identified from law dome deuterium excess during the 1970s and analysed using gcm simulations

modeling the isotopic composition of antarctic snow using backward trajectories simulation of snow pit records 1 the quantitative interpretation of isotope records d 18 o dd and d excess in ice cores can benefit from a comparison of observed meteorology with associated isotope variability for this reason we studied four isotope records from snow pits in western dronning maud land dml antarctica covering the period 1998 2001 timing and magnitude of snowfall events on these locations were monitored using sonic height rangers for the distinguished snowfall events we evaluated the isotopic composition of the moisture during transport by combining backward trajectory calculations with isotopic modeling using a rayleigh type distillation model mcim the initial isotope ratio of the moisture was determined frommonthlymeanisotopefields fromageneralcirculation model echam4 the trajectory analysis showed that the southern atlantic ocean is the major moisture sourceforprecipitationindml modelingresultsalongthetrajectoriesrevealedthatmostof the isotopic depletion occurred during the last day of the transport finally a diffusion model was applied to describe the diffusion in the firn layer such that the modeled isotopes couldbecomparedwiththeobservedisotoperecords theresultingmodeledisotopeprofiles were mostly in good agreement with the observed seasonal variability in the snow however at low temperatures especially on the antarctic interior magnitude of the total distillation was underestimated regarding the d excess parameter our results show a large influence of advection height on the final value of d excess in precipitation this in turn points to the importance of the vertical structure of d excess over the oceanic source region which obscures the classical interpretation of this parameter in terms of temperature and relative humidity in the moisture source region

a seasonal deuterium excess signal at law dome coastal eastern antarctica a southern ocean signature the snow isotopic composition 18o and d of two shallow cores from the high accumulation summit region of law dome east antarctica was measured at monthly resolution over the 1980 1992 period while the 18o or d signals clearly reflect the local temperature cycle the deuterium excess d d 8 18o is shifted with respect to 18o cycle by a 4 months lag interpretation of this phase lag is investigated using both an atmospheric general circulation model agcm which includes the water isotopic cycles and a simple isotopic model which better describes the microphysical processes within the cloud using this dual approach we show that the seasonality of 18o and d at law dome summit results from a combination of the southern ocean temperature cycle shifted by 2 3 months with respect to the local insolation and seasonal moisture origin changes due to a strong contribution of the local ocean when ice free both approaches are consistent with a dominant temperate to subtropical moisture origin we thus demonstrate from our present day subseasonal study that the record of d in the dome summit south dss deep ice core represents a potential tool for identifying changes in southern ocean temperatures and or sea ice cover at the scale of the past thousand years

atmospheric influence on the deuterium excess signal in polar firn implications for ice core interpretation the seasonal deuterium excess signal of fresh snow samples from neumayer station coastal dronning maud land antarctica was studied to investigate the relationship between deuterium excess and precipitation origin an isotope model was combined with a trajectory model to determine the relative influence of different moisture sources on the mean annual course of the deuterium excess focusing on the phase lag between d 18 o and excess d whereas the annual course of d 18 o always shows an austral summer maximum which clearly depends on local temperature and the annual course of moisture source area parameters the deuterium excess of the fresh snow samples shows maximum values already in spring there can be many different reasons for the time lag between d 18 o and deuterium excess in an ice core including post depositional processes and changes in the moisture source of precipitation the use of fresh snow samples enabled us to exclude post depositional processes and study solely the influence of precipitation origin changes in the moisture source connected to systematic changes in the general atmospheric circulation can have a strong influence on the phase lag between deuterium excess and d 18 o which has to be taken into account for climatic interpretation of stable isotope profiles from ice cores

variations of 17o 16o and 18o 16o in meteoric waters the variations of d 17 o and d 18 o in recent meteoric waters and in ice cores have proven to be an important tool for investigating the present and past hydrologic cycle in order to close significant information gaps in the present distribution ofd 17 o and d 18 o of meteoric water we have run precise measurements with respect to vsmow on samples distributed globally from low to high latitudes based on the new and existing data we present the global meteoric water line gmwl ford 17 o andd 18 o as ln d 17 o 1 0 528 ln d 18 o 1 0 000033 r 2 0 99999 in addition to meteoric water we carried out the first measurements of seawater from the pacific and atlantic oceans with respect to vsmow the obtained results show that the slope of the trend line ln d 17 o 1 vs ln d 18 o 1 of seawater samples is 0 528 the same as for meteoric water but the regression intercept is 5 per meg thus the positive intercept in the gmwl indicates an excess of 17 o in meteoric waters with respect to the ocean an excess or depletion of 17 o in water is defined as 17 o excess ln d 17 o 1 0 528 d 18 o 1 most meteoric water samples have positive 17 o excess of varying magnitudes with an average of 37 per meg with respect to vsmow we explain how these positive values originate from evaporation of sea water into marine air which is undersaturated in water vapor and how subsequent increase of 17 o excess occurs when atmospheric vapor condenses to form liquid and solid precipitation we also clarify the effect of excessive evaporation on 17 o excess finally based on the new results on 17 o excess of seawater we recalculated the relationship of d 17 o vs d 18 o in vapor diffusion in air as 18 adiff 1 0096

opening mode of the japan sea inferred from the palaeomagnetism of the japan arc the western edge of the pacific plate is marked by a chain of back arc basins stretching from the aleutians through japan and the philippines to new zealand most of the basins lie behind volcanic island arcs far from continents and are the result of extension of the oceanic lithosphere1 but the japan sea is bounded on one side by continental crust the sikhote alin and korean peninsula of the asian continent and on the other by an active arc with continental fragments it can thus be said to be associated more with continental rifting1 4 than with oceanic processes we report here palaeomagnetic data from the japan arc which indicate that since the early miocene north east japan has rotated counter clockwise through 47 around a vertical axis while south west japan has rotated clockwise through 56 refs 5 8 we attribute this differential rotation which took place concurrently between 21 and 11 myr ago to the back arc opening of the japan sea8 with a double door mode that is there are two fan shaped spreading basins facing each other such a fan shaped opening is probably peculiar to the geological phenomenon of rifting of a continental fragment from thick continental lithosphere

climatic and glaciological information inferred from air content measurements of a law dome east antarctica ice core the total air content v of ice has been measured along the dome summit south dss core from law dome east antarctica the main features of this record are the very well preserved sub annual fluctuations of v down to at least 900 m depth and the significant increase of the v values during the last deglaciation the sub annual variations reflect changes in close off porosity and we interpret the v seasonal peaks as tracers of depth hoar layers for the longer time scale the large v fluctuations observed are interpreted in terms of elevation and or close off porosity changes under different assumptions we analyze the possible influence of a different global pressure field and or a change in seasonal temperature and precipitation cycles during the last glacial period our estimates of surface elevation changes derived from the v data are then compared with independent reconstructions of past elevations

contemporaneous ascent of within plate type and island arc type magmas in the beppu shimabara graben system kyushu island japan abstract within plate wp type and island arc ia type magmas have erupted in north kyushu and south kyushu respectively during quaternary time the former is related to the eastern end of the east asian extensional province and the latter to the subduction zone of the philippine sea plate the beppu shimabara graben system in the central part of kyushu island is located in the area of overlap between them quaternary volcanic rock samples from the graben system can be chemically classified as wp and ia types by their multi element patterns and positions on a zr nb y discrimination diagram rocks of both type and of similar ages occur throughout the graben system furthermore the rocks of wp type give systematically higher 87sr 86sr ratios 0 7048 0 7049 than those of the associated ia type around 0 7040 the relations between 87sr 86sr and nb y ratios of the former are clearly distinguished from those of the latter these results demonstrate that this graben system is characterized by the contemporaneous ascents of wp and ia type magmas to the same quaternary volcanic areas such rivalrous ascents of wp and ia type magmas seem to be a common feature of magmatism associated with graben in extensional provinces related to subduction zones of island arcs and their boundary areas

whole rock geochemistry and sr isotopic compositions of phanerozoic sedimentary rocks in the inner zone of the southwest japan arc abstract pre cretaceous metasedimentary rocks occurring in the inner zone of the southwest japan arc can be divided into three major groups namely high p t metamorphic renge and suo belts low p t metamorphic hida oki ryoke and higo belts and accretionary terranes akiyoshi maizuru mino tamba and ashio belts major and trace element compositions of most of the sedimentary rocks are typical of relatively mature sedimentary rocks although abundances of ferromagnesian elements also suggest the presence of a significant mafic to intermediate igneous component the sedimentary rocks with older nd model ages 2 0 ga have high esr values and major and trace element geochemical signatures typical of mature sediments whereas those with younger model ages

paleoposition of southwest japan at 16 ma implication from paleomagnetism of the miocene ichishi group abstract new paleomagnetic data from shallow marine sediments of the ichishi group suggest a clockwise tectonic rotation of southwest japan in the middle miocene samples have been collected from mud or tuff layers at 17 sites stability of remanent magnetization has been examined by using alternating field and thermal demagnetization the polarity sequence composed of four normal and seven reversed polarity sites is correlated to polarity epoch 16 15 2 17 6 ma based on micropaleontological assignment of the upper ichishi group to blow s zone n8 the mean paleomagnetic direction of the 11 sites shows an anomalous declination toward the northeast this result suggests that southwest japan was subjected to a clockwise rotation through 45 since 16 ma the clockwise rotation can be explained by the drift of southwest japan associated with the spreading of the japan sea during the middle miocene

holocene temperature variations inferred from antarctic ice cores we have reconstructed temperature changes over the past 15 000 years from ice core data in antarctica we used measurements of the d h isotope ratio in ice as a proxy of temperature for central sites vostok dome c and komsomolskaya as well as coastal sites d47 d15 and d10 first we examined the dating of each core and built up a common temporal framework for the ensemble of the data secondly we addressed the problem of inferring small amplitude temperature fluctuations from the isotope data in the light of noise generating mechanisms involved in snow deposition temperature was reconstructed so as to minimize distortion created by the sampling of ice cores in the field the seven ice cores studied yield an average temperature curve which can be put in perspective with nearby paleoclimatic records the early holocene experienced climates warmer than today by 1 2 c the late holocene period shows more discernible shorter duration temperature fluctuations superimposed on a fairly stable base line temperature

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

deuterium excess in an east antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum a continuous deuterium excess profile d d 8 18o was obtained from the dome c ice core spanning 32 000 yr it exhibits significant variations over this period in particular d was 4 5 lower around 18 000 yr bp than over the past 7 500 yr interpreted as reflecting higher relative humidity estimated 90 over the oceanic areas providing moisture for antarctic precipitation

seasonality in late holocene climate from ice core records high resolution ice core 18o data from a site with well preserved seasonal cycles are used to extract seasonal temperature trends over the last 700 years with an effective resolution of a few mont

extreme snow metamorphism in the allan hills antarctica as an analogue for glacial conditions with implications for stable isotope composition understanding physical processes in near zero accumulation areas can help us to better understand polar ice core records particularly during periods when accumulation rates were lower than today we report measurements from a 5 m firn core from the allan hills antarctica which include physical properties using computer tomography stable isotope ratios d and 18 o and 210 pb activity the core shows a highly metamorphosed firn with homogeneous and stable structure but with discrete layers near the surface the observed firn structure is caused by a combination of unique depositional and post depositional processes the irregular d and 18 o signal does not follow the stratigraphic sequence and implies post depositional modification caused by microscopic pressure gradients in the firn that can result from either forced ventilation over rough surfaces in the presence of wind or alternating temperature gradients between the firn and the atmosphere our results also indicate impact snow deposition under high winds and with a high initial density and air exchange between the atmosphere and the snowpack 210 pb activity below 0 3 m falls below the detection limit implying that most of the core is more than 100 years old we conclude that the allan hills record provides a unique opportunity to investigate important processes that would have affected ice core records from glacial periods

a late medieval warm period in the southern ocean as a delayed response to external forcing on the basis of long simulations performed with a three dimensional climate model we propose an interhemispheric climate lag mechanism involving the long term memory of deepwater masses warm anomalies formed in the north atlantic when warm conditions prevail at surface are transported by the deep ocean circulation towards the southern ocean there the heat is released because of large scale upwelling maintaining warm conditions and inducing a lagged response of about 150 years compared to the northern hemisphere model results and observations covering the first half of the second millenium suggest a delay between the temperature evolution in the northern hemisphere and in the southern ocean the mechanism described here provides a reasonable hypothesis to explain such an interhemipsheric lag

nd sr systematics of the setouchi volcanic rocks southwest japan a clue to the origin of orogenic andesite abstract twenty three volcanic rocks from the setouchi volcanic belt southwest japan were analyzed for nd and sr isotopic compositions for the purpose of examining the genetic relationships among the basalt high magnesium andesite hma and evolved porphyritic andesite the andesites have higher 87 sr 86 sr 0 70487 0 70537 and lower 143 nd 144 nd 0 512509 0 512731 than the basalts i e 0 70408 0 70468 and 0 512691 0 512830 respectively this result confirms earlier conclusions obtained from petrologic study that the andesites cannot be fractionation products of basaltic magma but that the andesitic and basaltic magmas were generated independently on the basis of melting experiments for hma and basalt it is inferred that there is an isotopically stratified mantle beneath southwest japan evolved porphyritic andesites have essentially identical sr and nd isotopic ratios to hma and can be derived by fractionation of primary andesitic magma a model to produce orogenic andesite is proposed on petrologic experimental and isotopic bases

a study of clay pore water and sporopollens for characterizing paleoenvironments in the hebei plain northern china abstract we developed a clay pore water cpw isotopic method for tracing paleoenvironments characterized by sporopollens the thick clayey layers have the advantage of preserving pore water regardless of whether the water is inherent in the clayey layers or not therefore the clayey layers are a suitable target from which paleoenvironmental information can be extracted sediment sporopollens as well as cpw deuterium and oxygen isotopes were investigated in drilling cores obtained from a 130 m borehole at a field site in hengshui in the north china plain our interpretation of 18 o in cpw was consistent with sporopollens climate indices indicating that cpw was an effective proxy for obtaining paleoenvironmental information sporopollens species were abundant in the cores but the quantity of each species was low furthermore mean annual temperature and precipitation curves were established using a pollen climatic response surface model the results indicated two warm humid periods 5 2 0 m 22 6 11 m and one cold dry period 8 8 6 4 m in the holocene as well as two warm humid periods 90 6 83 m 110 6 108 2 m and three cold dry periods approximately 40 m 66 4 56 8 m approximately 100 m in the late pleistocene data derived from the sporopollens and cpw cumulatively elucidate the environmental change in northern china

glacial interglacial changes in ocean surface conditions in the southern hemisphere the stable isotope signatures of oxygen and hydrogen in the water of preserved ice and snow are both widely used to infer local temperatures of past environments a derived quantity based on these two signatures the deuterium excess 1 provides additional palaeoclimatic information2 3 4 as this parameter depends on the meteorological and oceanic characteristics of the water s source regions in particular their temperature2 3 and relative humidity4 published studies mainly focus on records from the past 40 000 years here we present a deuterium excess history obtained from ice cores from vostok east antarctica spanning the full glacial interglacial cycle of the past 150 000 years the deuterium excess record shows a strong anticorrelation with the earth s orbital obliquity 41 000 year periodicity and values are markedly higher during the cold stage 5d following the last interglacial than during the other cold stages we interpret the relationship with obliquity as resulting from changes in the latitudinal insolation gradient affecting ocean surface conditions and thus the delivery of moisture to the polar region we argue that the high 5d values relative to other cold stages are driven by relatively less moisture delivered from high latitudes and more from low latitudes the deuterium excess in antarctic precipitation thus provides long term spatially integrated information on ocean surface conditions and ocean atmosphere circulations in the southern hemisphere

water isotopes as tools to document oceanic sources of precipitation the isotopic composition of precipitation in deuterium oxygen 18 and oxygen 17 depends on the climatic conditions prevailing in the oceanic regions where it originates mainly the sea surface temperature and the relative humidity of air this dependency applies to present day precipitation but also to past records which are extracted for example from polar ice cores in turn coisotopic measurements of deuterium and oxygen 18 offer the possibility to retrieve information about the oceanic origin of modern precipitation as well as about past changes in sea surface temperature and relative humidity of air this interpretation of isotopic measurements has largely relied on simple rayleigh type isotopic models and is complemented by lagrangian back trajectory analysis of moisture sources it is now complemented by isotopic general circulation models igcm in which the origin of precipitation can be tagged we shortly review published results documenting this link between the oceanic sources of precipitation and their isotopic composition we then present experiments performed with two different igcms the giss model ii and the lmdz model we focus our study on marine water vapor and its contribution to precipitation over antarctica and over the andean region of south america we show how igcm experiments allow us to relate climatic conditions prevailing in the oceanic source of precipitation to its isotopic composition such experiments support at least qualitatively the current interpretation of ice core isotopic data in terms of changes in sea surface temperature additionally we discuss recent studies clearly showing the added value of oxygen 17 measurements key points link between the isotopic content of precipitation and its oceanic origin application of this method to polar ice cores andean precipitation potential of combining deuterium excess and oxygen 17 excess 2013 american geophysical union all rights reserved

peroxide concentrations in the dome summit south ice core law dome antarctica measurements of h2o2 concentrations have been made at intervals along the full length of the dome summit south dss ice core from law dome antarctica these results show mean peroxide concentrations of approximately 37 parts per billion by mass over the past 4 kyr and a tendency for concentrations to decrease with age the rate of h2o2 decay in antarctic ice appears slower than in greenland ice and the pattern of measurements suggests an abrupt increase in concentration during the emergence from the last glacial into the holocene there is some evidence for a recent increase in h2o2 but the data so far are not conclusive detailed examination of the timing of the seasonality in h2o2 and 18o shows that peroxide extrema occur very near the solstices these seasonal curves have been used to derive atmospheric seasonal h2o2 curves based on possible air snow partitioning models these show a broad low in atmospheric concentration with a sharp peak which is again very near the summer solstice

holocene climate variability in antarctica based on 11 ice core isotopic records a comparison is made of the holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east antarctica vostok dome b plateau remote komsomolskaia dome c taylor dome dominion range d47 km105 and law dome and west antarctica byrd with temporal resolution from 20 to 50 yr the long term trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations all the records confirm the widespread antarctic early holocene optimum between 11 500 and 9000 yr in the ross sea sector a secondary optimum is identified between 7000 and 5000 yr whereas all eastern antarctic sites show a late optimum between 6000 and 3000 yr superimposed on the long time trend all the records exhibit 9 aperiodic millennial scale oscillations climatic optima show a reduced pacing between warm events typically 800 yr whereas cooler periods are associated with less frequent warm events pacing 1200 yr

deuterium excess record in a southern tibetan ice core and its potential climatic implications a 55 m long ice core drilled close to bedrock from mt noijin kangsang on the southern tibetan plateau in summer 2007 was annually dated covering the period of 1864 2006 ad the stable isotope ratios 18o and d of the ice core were measured and thereby the deuterium excess d was calculated by d d 8 18o for the individual ice samples results show that the d values of the ice samples were predominantly controlled by the moisture sources the significant increasing trend of annual mean d values along the ice core is mainly related to the rapid warming of the tropical indian ocean although the tendency is subjected to the modulation by the western derived moisture the decreasing indian monsoon precipitation on the southern tibetan plateau physically linked with the increasing tropical indian ocean sst reduced the share of monsoon precipitation in the annual total accumulation making an additional contribution to the significant increase of annual mean d in the noijin kangsang ice core with high values during the past 143 years

synoptic variability in the ross sea region antarctica as seen from back trajectory modeling and ice core analysis 1 synoptic variability in the ross sea region antarctica over the last thirty years is investigated using back trajectory modeling and cluster analysis we identify two dominant air mass trajectory clusters oceanic west antarctic and continental east antarctic our analysis shows that the oceanic west antarctic trajectories have an annual cycle similar to the semiannual oscillation and on average peak in frequency during april while continental east antarctic trajectories reach their annual maximum during december we demonstrate a causal association between the el nino southern oscillation enso and the frequency of oceanic west antarctic trajectories originating from the ross sea and amundsen sea regions in contrast we find that the southern annular mode sam has little influence on the trajectory cluster frequencies we then develop proxy records for synoptic variability using a shallow firn core from gawn ice piedmont in southern victoria land continental east antarctic trajectory frequency correlates with concentrations of nitrate no3 which is sourced from stratospheric air masses descending over the antarctic interior at seasonal to inter annual scales the frequency of oceanic west antarctic trajectory clusters strongly correlate with deuterium excess which is sensitive to changes in relative humidity and sea surface temperature in the ross and amundsen seas inter annual variability in the frequency of oceanic west antarctic trajectories is discussed with respect to enso and changes in sst and sea ice extent

the origin of present day antarctic precipitation from surface snow deuterium excess data the deuterium excess d is defined as a linear combination of the d h and 18 o 16 o ratios in natural waters we present an interpretation of deuterium excess data in surface antarctic snow using an isotopic model to derive information on the origin of present day antarctic precipitation the data come from near the coast d47 adelie land and from inland south pole 1000 km from the sea the one dimensional isotopic model belongs to the rayleigh family but fully accounts for mixed cloud processes between 0 c and 30 c modeling d in polar snowfalls meets the problem of a large sensitivity to the saturation conditions prevailing at snow formation therefore we decided to tune the saturation in the model in order to yield realistic mean d values but we use the seasonal phase of d versus which is less sensitive to the saturation conditions as an independent validation of the model predictions both inland and near the coast our model can simulate the observed phase between d and in snow with moisture of subtropical origin 40 20 s although we do not treat specifically storm precipitation near the coast this study indicates that the observed phase between d and brings up a new validation of isotopic models it supports a distant vapor source for large scale precipitation delivered to the antarctic continent

crustal structure of south western honshu japan and the nature of the mohorovicic discontinuity summary two record sections have been prepared for a series of explosions near lake biwa south western honshu japan the record sections cover both the array stations and the network of microearthquake stations that are distributed throughout the area this enabled us to detect for the first time in the japanese islands the phase reflected at the mohorovicic discontinuity until now the weakness and obscurity of the phase has made it difficult to detect we were able to overcome this problem by processing the seismograms to enhance the phase our work leads us to propose that the surface of the mohorovic discontinuity may be divided into pieces by a number of deep faults while a thin layer of ultrabasic rock in the lower crust may account for the weakness of the signal

strontium isotopic characteristics of arc volcanic rocks at the initial stage of subduction in western japan abstract in western japan the philippine sea plate subducts northwestward from the ryukyu trench and the nankai trough to form two volcanic arcs the ryukyu and southwest japan arcs respectively these arcs are thought to be in the initial stage of subduction because microearthquake data show that the subducting slab extends only a short distance from the trenches in the southwest japan arc volcanoes are aligned parallel to the nankai trough although the leading edge of the subducted slab does not reach under the volcanic arc to the south the subducted slab reaches just under the ryukyu volcanic arc we determined 87sr 86sr ratios and rb and sr contents for 39 volcanic rock samples from 14 quaternary volcanoes of both arcs and summarized the spatial distribution of the ratios the ranges of 87sr 86sr ratios of volcanic rocks from the ryukyu and southwest japan arcs are 0 7040 0 7069 and 0 7035 0 7066 respectively in the ryukyu arc the regional variation in 87sr 86sr ratios of volcanic rocks is hidden under the wide scatter of ratios of different volcanic rocks from each one volcano in the southwest japan arc the ratios of volcanic rocks from volcanoes on the volcanic front vary in the along arc direction 0 7040 0 7048 for the western part 0 7035 0 7039 for the central part and 0 7048 0 7066 for the eastern part the across arc variations in the ratios are different from place to place these isotopic features suggest the absence of slab derived components in the source mantle and reflect the heterogeneous nature of 87sr 86sr ratios in the upper mantle modified by crustal processes this coincides with the seismological observation that the subducting philippine sea slab does not reach under the volcanic arc at all

temperature accumulation and ice sheet elevation in central greenland through the last deglacial transition we present a combined heat and ice flow model constrained by measurements of temperature in the greenland ice sheet project 2 gisp2 borehole and by the gisp2 18o record and depth age scale which determines a history of temperature accumulation rate and ice sheet elevation for the past 50 000 years in central greenland important results are that the temperature increase from average glacial to holocene conditions was large approximately 15 c with a 20 c warming from late glacial to holocene that the average accumulation rate during the last glacial maximum between 15 and 30 kyr b p was 5 5 to 7 cm yr 1 approximately 25 of the modern accumulation rate that long term 500 1000 years averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the holocene and that the greenland ice sheet probably thickened during the deglacial transition the inverse correlation of accumulation rate and temperature in the mid and late holocene suggests that the greenland ice sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature the elevation history of the ice sheet is poorly constrained by the model and independent evidence is needed we also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins this was approximately 1900 years for central greenland during deglaciation

zonal structure of cenozoic basalts related to mantle upwelling in southwest japan cenozoic olivine bearing basaltic rocks in the central chugoku district form eight provinces each 20 to 30 km in diameter these provinces can be grouped into three zones almost parallel to the elongation of the sw japan arc based on geological and petrological characteristics the san yo zone the closest to the nankai trough is characterized by a small amount of alkaline basalt in the sekiryo zone intermediate zone transitional basalt is dominant the san in zone along the japan sea coast is characterized by subalkaline basalt and a large amount of andesitic rocks the eruption volume of these volcanics exponentially increases toward the back arc side less than 1 km3 to more than 100 km3 chemical compositions of relatively undifferentiated basalts show systematic across arc variations sio2 and al2o3increase and feo mgo and cao decrease toward the back arc side 44 to 54 13 to 18 11 to 6 13 to 7 and 12 to 8 wt at feo mgo 0 85 respectively melting experiments on the basalt h2o co2 systems show that the pressure and temperature of magma segregation decrease toward the back arc side 17 19 kbar and 1340 1320 c to 8 kbar and 1250 c and the coexisting phases change from a spinel lherzolite assemblage to a harzburgite assemblage these pt conditions define a trend which can be interpreted as a pt path for adiabatic upwelling of the mantle material consequently the observed volcanism and zonation may have been caused by upwelling of a plume from a deep part of the mantle

paleogeographic reconstruction and origin of the philippine sea abstract our reconstruction of the philippine sea suggests that it formed by two distinct episodes of back arc spreading each of which resulted from seaward retreat of the trench in the first episode the protoizu bonin trench retreated northward and the west philippine basin formed behind the northern half of the palau kyushu ridge in the second episode the izu mariana trench retreated eastward and the shikoku and parece vela basins formed behind it during the last 17 ma the philippine sea basin has been moving northwestward with respect to eurasia shifting the ttt triple junction off central japan westward by about 50 km the motion of the philippine sea with respect to eurasia at the triple junction changed from north northwestward to west northwestward 10 5 ma ago for the period before 17 ma ago we construct two models retreating trench model and anchored slab model the izu bonin trench migrated from south to northeast rotating in a clock wise sense since 48 ma ago in the retreating trench model in the anchored slab model the trench has been fixed with respect to eurasian margin since 43 ma ago we prefer the retreating trench model because the deformation of the plate boundary along the eastern margin of eurasia during 30 17 ma ago is much simpler for this model than for the anchored slab model furthermore rotations of the bonin mariana islands are consistent with those predicted from the retreating trench model the 48 ma ages of the northern part of the palau kyushu ridge and of chichi jima of the bonin islands indicate that there was subduction beneath the northern half of the ridge beginning at least 48 ma ago from this and the subparallelism in trend between the northern part of the palau kyushu ridge and the central basin ridge we propose that the major part of the west philippine basin formed by back arc spreading in a n s direction behind the northern part of the palau kyushu ridge the pacific plate was moving northward with respect to hot spots from 48 to 43 ma ago which implies that the pacific plate is not likely to have been subducting beneath the west philippine basin during this time we speculate that another plate existed south of the pacific plate and thai it was subducting beneath both tile west philippine basin and australia the annihilation of this plate might he a cause for the sudden change of the pacific plate motion at 43 ma ago